Syndactyly (from Greek συν- = "together" plus δακτυλος = "finger") is a condition where two or more digits are fused together. It occurs normally in some mammals, such as the siamang, but is an unusual condition in humans.
Classification
Syndactyly can be simple or complex.
* In simple syndactyly, adjacent fingers or toes are joined by soft tissue.
* In complex syndactyly, the bones of adjacent digits are fused. The kangaroo exhibits complex syndactyly.
Syndactyly can be complete or incomplete.
* In complete syndactyly, the skin is joined all the way to the tip of the finger
* In incomplete syndactyly, the skin is only joined part of the distance to the fingertip.
Complicated syndactyly occurs as part of a syndrome (such as Apert's syndrome) and typically involves more digits and with complex syndactyly.
Fenestrated syndactyly means the skin is joined for most of the digit but in a proximal area there is gap in the syndactyly with normal skin. This type of syndactyly is found in amniotic band syndrome.
Simple syndactyly can be full or partial, and is present at birth (congenital). In early human fetal development, webbing (syndactyly) of the toes and fingers is normal. At about 16 weeks of gestation, apoptosis takes place and an enzyme dissolves the tissue between the fingers and toes, and the webbing disappears. In some fetuses, this process does not occur completely between all fingers or toes and some residual webbing remains.
Treatment
Timing
Syndactyly of the border digits (thumb/ index finger or ring/ small fingers) is treated at early age to prevent the larger digit from curving towards the smaller digit with growth. Typically, syndactyly of these digits is treated at 6 months of age. The treatment of syndactyly of the other digits is elective and is more commonly performed when the digits have grown, at 18– 24 months of age.
Techniques
Because the circumference of the conjoined fingers is smaller than the circumference of the 2 separated fingers, there is not enough skin to cover both digits once they are separated at the time of surgery. Therefore, the surgeon must bring new skin into the area at the time of surgery. This is most commonly done with a skin graft (from groin or anterior elbow). Skin can also be utilized from the back of the hand by mobilizing it (called a "graftless" syndactyly correction).
Complications
The most common problem with syndactyly correction is creeping of the skin towards the fingertip over time. This is likely due to tension at the site of the repair between the digits. Additional surgery may be required to correct this. One critique of using skin grafts is that the grafts darken in the years after surgery and become more noticeable. Also, if the skin grafts are harvested from the groin area, the skin may grow hair. Finally, the fingers may deviate after surgery. This is most commonly seen in complex syndactyly (when there has been a bony joining of the fingers).
Tuesday, June 30, 2009
Apoptosis
Apoptosis (pronounced /ˌæpəpˈtoʊsɨs/,[1] ăpˈəp-tō'sĭs, ăpˈə-tō'sĭs[2]) is the process of programmed cell death (PCD) that may occur in multicellular organisms. Programmed cell death involves a series of biochemical events leading to a characteristic cell morphology and death, in more specific terms, a series of biochemical events that lead to a variety of morphological changes, including blebbing, changes to the cell membrane such as loss of membrane asymmetry and attachment, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation (1-4). (See also Apoptosis DNA fragmentation.) Processes of disposal of cellular debris whose results do not damage the organism differentiate apoptosis from necrosis.
Histologic cross section of embryonic foot of mouse (Mus musculus) in 15.5 day of its development. There are still cells between fingers. (Full development of mouse lasts 27 days.) (Compare this image with image of leg of mouse.)
Fully developed foot of mouse has separate fingers.
In contrast to necrosis, which is a form of traumatic cell death that results from acute cellular injury, apoptosis, in general, confers advantages during an organism's life cycle. For example, the differentiation of fingers and toes in a developing human embryo occurs because cells between the fingers apoptose; the result is that the digits are separate. Between 50 billion and 70 billion cells die each day due to apoptosis in the average human adult. For an average child between the ages of 8 and 14, approximately 20 billion to 30 billion cells die a day. In a year, this amounts to the proliferation and subsequent destruction of a mass of cells equal to an individual's body weight.
Research on apoptosis has increased substantially since the early 1990s. In addition to its importance as a biological phenomenon, defective apoptotic processes have been implicated in an extensive variety of diseases. Excessive apoptosis causes hypotrophy, such as in ischemic damage, whereas an insufficient amount results in uncontrolled cell proliferation, such as cancer.
Histologic cross section of embryonic foot of mouse (Mus musculus) in 15.5 day of its development. There are still cells between fingers. (Full development of mouse lasts 27 days.) (Compare this image with image of leg of mouse.)
Fully developed foot of mouse has separate fingers.
In contrast to necrosis, which is a form of traumatic cell death that results from acute cellular injury, apoptosis, in general, confers advantages during an organism's life cycle. For example, the differentiation of fingers and toes in a developing human embryo occurs because cells between the fingers apoptose; the result is that the digits are separate. Between 50 billion and 70 billion cells die each day due to apoptosis in the average human adult. For an average child between the ages of 8 and 14, approximately 20 billion to 30 billion cells die a day. In a year, this amounts to the proliferation and subsequent destruction of a mass of cells equal to an individual's body weight.
Research on apoptosis has increased substantially since the early 1990s. In addition to its importance as a biological phenomenon, defective apoptotic processes have been implicated in an extensive variety of diseases. Excessive apoptosis causes hypotrophy, such as in ischemic damage, whereas an insufficient amount results in uncontrolled cell proliferation, such as cancer.
Friday, June 26, 2009
The 24 Hour Day
Why 24 Hours?
We're so used to the fact that there are 24 hours in a day that we don't stop to ask why. Why 24? Why not a nice round number like 20? Or perhaps 10?
Early hours were not even constant! The period of time between sunrise and sunset was simply divided by twelve, so the length of an hour would depend on the time of year as well as where you were on the planet. The decision to use equal length hours is usually credited to the Greek astronomer Hipparchus.
Nobody knows for sure why we have 24 hours - of whatever length - in a day. Here are a few theories:
Mathematics
My favourite theory is that 24 was simply a useful number. The day was divided into 24 hours for much the same reason as the old British pound was divided into 240 pennies: it made division easier.
24 can be divided easily by 2,3,4,6,8 and 12. So dividing a full day into three shifts is easy - eight hours each. On board ship there are six watches - so each is four hours long. If you want to buy someone's time for a quarter of a day (excluding the night), that's three hours of pay. Try doing that with a day made up of ten hours!
Finger Counting
A popular theory is that the Sumerians counted in base twelve rather than in the base ten we use today. This is said to have been done using the fingers.
If you look at the fingers - not the thumb - of one hand you will see that (for most people) each contains three segments. Three segments on each of four fingers gives twelve. The thumb can then be used to point to a particular segment and indicate a number.
So, twelve segments on each hand, one hand for day and the other for night - and we have a possible origin of the 24 hour day.
The Zodiac
The more mystically inclined like to think that the 24 hours figure comes from astrology and other such fields. The zodiac contains twelve signs and the number twelve has been considered important by many civilisations. So it would be natural to assign twelve hours to the night and twelve to the day.
Which Theory is Right?
We don't know which - if any - of the above theories is right. There's no reason that they can't all be.
It's entirely possible that the decision of the Sumerians to use a base 12 counting system was at least in part due to the utility of the number. Had nine been more useful than twelve, for example, then they could have ignored the little finger.
As for the zodiac, that could have simply been divided into twelve signs because the number twelve was already important.
So it's possible that all these factors merged together to give us the 24 hour day.
We're so used to the fact that there are 24 hours in a day that we don't stop to ask why. Why 24? Why not a nice round number like 20? Or perhaps 10?
Early hours were not even constant! The period of time between sunrise and sunset was simply divided by twelve, so the length of an hour would depend on the time of year as well as where you were on the planet. The decision to use equal length hours is usually credited to the Greek astronomer Hipparchus.
Nobody knows for sure why we have 24 hours - of whatever length - in a day. Here are a few theories:
Mathematics
My favourite theory is that 24 was simply a useful number. The day was divided into 24 hours for much the same reason as the old British pound was divided into 240 pennies: it made division easier.
24 can be divided easily by 2,3,4,6,8 and 12. So dividing a full day into three shifts is easy - eight hours each. On board ship there are six watches - so each is four hours long. If you want to buy someone's time for a quarter of a day (excluding the night), that's three hours of pay. Try doing that with a day made up of ten hours!
Finger Counting
A popular theory is that the Sumerians counted in base twelve rather than in the base ten we use today. This is said to have been done using the fingers.
If you look at the fingers - not the thumb - of one hand you will see that (for most people) each contains three segments. Three segments on each of four fingers gives twelve. The thumb can then be used to point to a particular segment and indicate a number.
So, twelve segments on each hand, one hand for day and the other for night - and we have a possible origin of the 24 hour day.
The Zodiac
The more mystically inclined like to think that the 24 hours figure comes from astrology and other such fields. The zodiac contains twelve signs and the number twelve has been considered important by many civilisations. So it would be natural to assign twelve hours to the night and twelve to the day.
Which Theory is Right?
We don't know which - if any - of the above theories is right. There's no reason that they can't all be.
It's entirely possible that the decision of the Sumerians to use a base 12 counting system was at least in part due to the utility of the number. Had nine been more useful than twelve, for example, then they could have ignored the little finger.
As for the zodiac, that could have simply been divided into twelve signs because the number twelve was already important.
So it's possible that all these factors merged together to give us the 24 hour day.
What Is Time?
the concept of time is self-evident. An hour consists of a certain number of minutes, a day of hours and a year of days. But we rarely think about the fundamental nature of time.
Time is passing non-stop, and we follow it with clocks and calendars. Yet we cannot study it with a microscope or experiment with it. And it still keeps passing. We just cannot say what exactly happens when time passes.
Time is represented through change, such as the circular motion of the moon around the earth. The passing of time is indeed closely connected to the concept of space.
According to the general theory of relativity, space, or the universe, emerged in the Big Bang some 13.7 billion years ago. Before that, all matter was packed into an extremely tiny dot. That dot also contained the matter that later came to be the sun, the earth and the moon – the heavenly bodies that tell us about the passing of time.
Before the Big Band, there was no space or time.
“In the theory of relativity, the concept of time begins with the Big Bang the same way as parallels of latitude begin at the North Pole. You cannot go further north than the North Pole,” says Kari Enqvist, Professor of Cosmology.
One of the most peculiar qualities of time is the fact that it is measured by motion and it also becomes evident through motion.
According to the general theory of relativity, the development of space may result in the collapse of the universe. All matter would shrink into a tiny dot again, which would end the concept of time as we know it.
“Latest observations, however, do not support the idea of collapse, rather inter-galactic distances grow at a rapid pace,” Enqvist says.
Time is passing non-stop, and we follow it with clocks and calendars. Yet we cannot study it with a microscope or experiment with it. And it still keeps passing. We just cannot say what exactly happens when time passes.
Time is represented through change, such as the circular motion of the moon around the earth. The passing of time is indeed closely connected to the concept of space.
According to the general theory of relativity, space, or the universe, emerged in the Big Bang some 13.7 billion years ago. Before that, all matter was packed into an extremely tiny dot. That dot also contained the matter that later came to be the sun, the earth and the moon – the heavenly bodies that tell us about the passing of time.
Before the Big Band, there was no space or time.
“In the theory of relativity, the concept of time begins with the Big Bang the same way as parallels of latitude begin at the North Pole. You cannot go further north than the North Pole,” says Kari Enqvist, Professor of Cosmology.
One of the most peculiar qualities of time is the fact that it is measured by motion and it also becomes evident through motion.
According to the general theory of relativity, the development of space may result in the collapse of the universe. All matter would shrink into a tiny dot again, which would end the concept of time as we know it.
“Latest observations, however, do not support the idea of collapse, rather inter-galactic distances grow at a rapid pace,” Enqvist says.
Saturday, June 20, 2009
Streptococcus mutans
Streptococcus mutans is a Gram-positive, facultatively anaerobic bacterium commonly found in the human oral cavity and is a significant contributor to tooth decay.The microbe was first described by Clarke in 1924.
Role in tooth decay
Early colonizers of the tooth surface are mainly Neisseria spp. and streptococci, including S. mutans. The growth and metabolism of these pioneer species changes local environmental conditions (e.g. Eh, pH, coaggregation, substrate availability), thereby enabling more fastidious organisms to further colonize after them, forming dental plaque.[4] Along with S. sobrinus, S. mutans plays a major role in tooth decay, metabolizing sucrose to lactic acid.[2] The acidic environment created in the mouth by this process is what causes the highly mineralized tooth enamel to be vulnerable to decay. S. mutans is one of a few specialized organisms equipped with receptors that help for better adhesion to the surface of teeth. Sucrose is utilized by S. mutans to produce a sticky, extracellular, dextran-based polysaccharide that allows them to cohere to each other forming plaque. S. mutans produces dextran via the enzyme dextransucrase (a hexosyltransferase) using sucrose as a substrate in the following reaction:
n sucrose → (glucose)n + n fructose
Sucrose is the only sugar that S. mutans can use to form this sticky polysaccharide.
Conversely, many other sugars—glucose, fructose, lactose—can be digested by S. mutans, but they produce lactic acid as an end product. It is the combination of plaque and acid that leads to dental decay.[5] Due to the role the S. mutans plays in tooth decay, there have been many attempts to make a vaccine for the organism. So far, such vaccines have not been successful in humans.[6] Recently, proteins involved in the colonization of teeth by S. mutans have been shown to produce antibodies that inhibit the cariogenic process.[7]
Role in tooth decay
Early colonizers of the tooth surface are mainly Neisseria spp. and streptococci, including S. mutans. The growth and metabolism of these pioneer species changes local environmental conditions (e.g. Eh, pH, coaggregation, substrate availability), thereby enabling more fastidious organisms to further colonize after them, forming dental plaque.[4] Along with S. sobrinus, S. mutans plays a major role in tooth decay, metabolizing sucrose to lactic acid.[2] The acidic environment created in the mouth by this process is what causes the highly mineralized tooth enamel to be vulnerable to decay. S. mutans is one of a few specialized organisms equipped with receptors that help for better adhesion to the surface of teeth. Sucrose is utilized by S. mutans to produce a sticky, extracellular, dextran-based polysaccharide that allows them to cohere to each other forming plaque. S. mutans produces dextran via the enzyme dextransucrase (a hexosyltransferase) using sucrose as a substrate in the following reaction:
n sucrose → (glucose)n + n fructose
Sucrose is the only sugar that S. mutans can use to form this sticky polysaccharide.
Conversely, many other sugars—glucose, fructose, lactose—can be digested by S. mutans, but they produce lactic acid as an end product. It is the combination of plaque and acid that leads to dental decay.[5] Due to the role the S. mutans plays in tooth decay, there have been many attempts to make a vaccine for the organism. So far, such vaccines have not been successful in humans.[6] Recently, proteins involved in the colonization of teeth by S. mutans have been shown to produce antibodies that inhibit the cariogenic process.[7]
MINAMATA DISEASE
Minamata disease was first discovered in Minamata city in Kumamoto prefecture, Japan in 1956. It was caused by the release of methyl mercury in the industrial wastewater from the Chisso Corporation's chemical factory, which continued from 1932 to 1968. This highly toxic chemical bioaccumulated in shellfish and fish in Minamata Bay and the Shiranui Sea, which when eaten by the local populace resulted in mercury poisoning. While cat, dog, pig and human deaths continued over more than 30 years, the government and company did little to prevent the pollution.
As of March 2001, 2,265 victims had been officially recognised (1,784 of whom had died)[1] and over 10,000 had received financial compensation from Chisso.[2] Lawsuits and claims for compensation continue to this day.
A second outbreak of Minamata disease occurred in Niigata Prefecture in 1965. Both the original Minamata disease and Niigata Minamata disease are considered two of the Four Big Pollution Diseases of Japan.
Researchers from Kumamoto University also began to focus on the cause of the strange disease. They found that the victims, often members of the same family, were clustered in fishing hamlets along the shore of Minamata Bay. The staple food of victims was invariably fish and shellfish from Minamata Bay. The cats in the local area, who tended to eat scraps from the family table, had died with symptoms similar to those now discovered in humans. This led the researchers to believe that the outbreak was caused by some kind of food poisoning, with contaminated fish and shellfish the prime suspects.
On November 4 the research group announced its initial findings: "Minamata disease is rather considered to be poisoning by a heavy metal... presumably it enters the human body mainly through fish and shellfish.
As soon as the investigation identified a heavy metal as the causal substance, the wastewater from the Chisso plant was immediately suspected as the origin. The company's own tests revealed that its wastewater contained many heavy metals in concentrations sufficiently high to bring about serious environmental degradation including lead, mercury, manganese, arsenic, selenium, thallium and copper. Identifying which particular poison was responsible for the disease proved to be extremely difficult and time consuming. During the years 1957 and 1958, many different theories were proposed by different researchers. Initially manganese was thought to be the causal substance due to the high concentrations found in fish and the organs of the deceased. Thallium, selenium and a multiple contaminant theory were also proposed but it was not until March 1958, when visiting British neurologist Douglas McAlpine suggested that Minamata symptoms resembled those of organic mercury poisoning, that the focus of the investigation centered on mercury.
In February 1959, the mercury distribution in Minamata Bay was investigated. The results shocked the researchers involved. Large quantities of mercury were detected in fish, shellfish and sludge from the bay. The highest concentrations centred around the Chisso factory wastewater canal in Hyakken Harbour and decreased going out to sea, clearly identifying the plant as the source of contamination. At the mouth of the wastewater canal a figure of 2 kg of mercury per ton of sediment was measured: a level which would be economically viable to mine. Indeed, Chisso did later set up a subsidiary to reclaim and sell the mercury recovered from the sludge.[10]
Hair samples were taken from the victims of the disease and also from the Minamata population in general. In patients the maximum mercury level recorded was 705 ppm (parts per million), indicating very heavy exposure and in non-symptomatic Minamata residents the level was 191 ppm. This compared to an average level of 4 ppm for people living outside the Minamata area.[10]
On November 12, 1959 the Ministry of Health and Welfare's Minamata Food Poisoning Subcommittee published its results:
"Minamata disease is a poisoning disease that affects mainly the central nervous system and is caused by the consumption of large quantities of fish and shellfish living in Minamata Bay and its surroundings, the major causative agent being some sort of organic mercury compound.
Local doctors and medical officials had noticed for a long time an abnormally high frequency of cerebral palsy and other infantile disorders in the Minamata area. In 1961 a number of medical professionals including Masazumi Harada (later to receive an honour from the United Nations for his body of work on Minamata disease) set about re-examining children diagnosed with cerebral palsy. The symptoms of the children closely mirrored those of adult Minamata disease patients but many of their mothers did not exhibit symptoms. The fact that these children had been born after the initial outbreak and had never been fed contaminated fish also led their mothers to believe they were not victims. At the time the medical establishment believed the placenta would protect the foetus from toxins in the bloodstream, which is indeed the case with most chemicals. What was not known at the time was that exactly the opposite is the case with methylmercury: the placenta removes it from the mother's bloodstream and concentrates the chemical in the foetus.
After several years of study and the autopsies of two children, the doctors announced that these children were suffering from an as yet unrecognised congenital form of Minamata disease. The certification committee convened on 29 November 1962 and agreed that the two dead children and the 16 children still alive should be certified as patients, and therefore liable for "sympathy" payments from Chisso, in line with the 1959 agreement.
Minamata disease remains an important issue in contemporary Japanese society. Lawsuits against Chisso and the prefectural and national governments are still continuing and many regard the government responses to date as inadequate.[33]
A memorial service was held at the Minamata Disease Municipal Museum on 1 May 2006 to mark 50 years since the official discovery of the disease. Despite bad weather the service was attended by over 600 people, including Chisso chairman Shunkichi Goto and Environment Minister Yuriko Koike.[34]
As of March 2001, 2,265 victims had been officially recognised (1,784 of whom had died)[1] and over 10,000 had received financial compensation from Chisso.[2] Lawsuits and claims for compensation continue to this day.
A second outbreak of Minamata disease occurred in Niigata Prefecture in 1965. Both the original Minamata disease and Niigata Minamata disease are considered two of the Four Big Pollution Diseases of Japan.
Researchers from Kumamoto University also began to focus on the cause of the strange disease. They found that the victims, often members of the same family, were clustered in fishing hamlets along the shore of Minamata Bay. The staple food of victims was invariably fish and shellfish from Minamata Bay. The cats in the local area, who tended to eat scraps from the family table, had died with symptoms similar to those now discovered in humans. This led the researchers to believe that the outbreak was caused by some kind of food poisoning, with contaminated fish and shellfish the prime suspects.
On November 4 the research group announced its initial findings: "Minamata disease is rather considered to be poisoning by a heavy metal... presumably it enters the human body mainly through fish and shellfish.
As soon as the investigation identified a heavy metal as the causal substance, the wastewater from the Chisso plant was immediately suspected as the origin. The company's own tests revealed that its wastewater contained many heavy metals in concentrations sufficiently high to bring about serious environmental degradation including lead, mercury, manganese, arsenic, selenium, thallium and copper. Identifying which particular poison was responsible for the disease proved to be extremely difficult and time consuming. During the years 1957 and 1958, many different theories were proposed by different researchers. Initially manganese was thought to be the causal substance due to the high concentrations found in fish and the organs of the deceased. Thallium, selenium and a multiple contaminant theory were also proposed but it was not until March 1958, when visiting British neurologist Douglas McAlpine suggested that Minamata symptoms resembled those of organic mercury poisoning, that the focus of the investigation centered on mercury.
In February 1959, the mercury distribution in Minamata Bay was investigated. The results shocked the researchers involved. Large quantities of mercury were detected in fish, shellfish and sludge from the bay. The highest concentrations centred around the Chisso factory wastewater canal in Hyakken Harbour and decreased going out to sea, clearly identifying the plant as the source of contamination. At the mouth of the wastewater canal a figure of 2 kg of mercury per ton of sediment was measured: a level which would be economically viable to mine. Indeed, Chisso did later set up a subsidiary to reclaim and sell the mercury recovered from the sludge.[10]
Hair samples were taken from the victims of the disease and also from the Minamata population in general. In patients the maximum mercury level recorded was 705 ppm (parts per million), indicating very heavy exposure and in non-symptomatic Minamata residents the level was 191 ppm. This compared to an average level of 4 ppm for people living outside the Minamata area.[10]
On November 12, 1959 the Ministry of Health and Welfare's Minamata Food Poisoning Subcommittee published its results:
"Minamata disease is a poisoning disease that affects mainly the central nervous system and is caused by the consumption of large quantities of fish and shellfish living in Minamata Bay and its surroundings, the major causative agent being some sort of organic mercury compound.
Local doctors and medical officials had noticed for a long time an abnormally high frequency of cerebral palsy and other infantile disorders in the Minamata area. In 1961 a number of medical professionals including Masazumi Harada (later to receive an honour from the United Nations for his body of work on Minamata disease) set about re-examining children diagnosed with cerebral palsy. The symptoms of the children closely mirrored those of adult Minamata disease patients but many of their mothers did not exhibit symptoms. The fact that these children had been born after the initial outbreak and had never been fed contaminated fish also led their mothers to believe they were not victims. At the time the medical establishment believed the placenta would protect the foetus from toxins in the bloodstream, which is indeed the case with most chemicals. What was not known at the time was that exactly the opposite is the case with methylmercury: the placenta removes it from the mother's bloodstream and concentrates the chemical in the foetus.
After several years of study and the autopsies of two children, the doctors announced that these children were suffering from an as yet unrecognised congenital form of Minamata disease. The certification committee convened on 29 November 1962 and agreed that the two dead children and the 16 children still alive should be certified as patients, and therefore liable for "sympathy" payments from Chisso, in line with the 1959 agreement.
Minamata disease remains an important issue in contemporary Japanese society. Lawsuits against Chisso and the prefectural and national governments are still continuing and many regard the government responses to date as inadequate.[33]
A memorial service was held at the Minamata Disease Municipal Museum on 1 May 2006 to mark 50 years since the official discovery of the disease. Despite bad weather the service was attended by over 600 people, including Chisso chairman Shunkichi Goto and Environment Minister Yuriko Koike.[34]
Tuesday, June 16, 2009
DARWIN'S THEORY OF EVOLUTION
Darwin's Theory of Evolution - The Premise
Darwin's Theory of Evolution is the widely held notion that all life is related and has descended from a common ancestor: the birds and the bananas, the fishes and the flowers -- all related. Darwin's general theory presumes the development of life from non-life and stresses a purely naturalistic (undirected) "descent with modification". That is, complex creatures evolve from more simplistic ancestors naturally over time. In a nutshell, as random genetic mutations occur within an organism's genetic code, the beneficial mutations are preserved because they aid survival -- a process known as "natural selection." These beneficial mutations are passed on to the next generation. Over time, beneficial mutations accumulate and the result is an entirely different organism (not just a variation of the original, but an entirely different creature).
Darwin's Theory of Evolution - Natural Selection
While Darwin's Theory of Evolution is a relatively young archetype, the evolutionary worldview itself is as old as antiquity. Ancient Greek philosophers such as Anaximander postulated the development of life from non-life and the evolutionary descent of man from animal. Charles Darwin simply brought something new to the old philosophy -- a plausible mechanism called "natural selection." Natural selection acts to preserve and accumulate minor advantageous genetic mutations. Suppose a member of a species developed a functional advantage (it grew wings and learned to fly). Its offspring would inherit that advantage and pass it on to their offspring. The inferior (disadvantaged) members of the same species would gradually die out, leaving only the superior (advantaged) members of the species. Natural selection is the preservation of a functional advantage that enables a species to compete better in the wild. Natural selection is the naturalistic equivalent to domestic breeding. Over the centuries, human breeders have produced dramatic changes in domestic animal populations by selecting individuals to breed. Breeders eliminate undesirable traits gradually over time. Similarly, natural selection eliminates inferior species gradually over time.
Darwin's Theory of Evolution - Slowly But Surely...
Darwin's Theory of Evolution is a slow gradual process. Darwin wrote, "…Natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by short and sure, though slow steps." [1] Thus, Darwin conceded that, "If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down." [2] Such a complex organ would be known as an "irreducibly complex system". An irreducibly complex system is one composed of multiple parts, all of which are necessary for the system to function. If even one part is missing, the entire system will fail to function. Every individual part is integral. [3] Thus, such a system could not have evolved slowly, piece by piece. The common mousetrap is an everyday non-biological example of irreducible complexity. It is composed of five basic parts: a catch (to hold the bait), a powerful spring, a thin rod called "the hammer," a holding bar to secure the hammer in place, and a platform to mount the trap. If any one of these parts is missing, the mechanism will not work. Each individual part is integral. The mousetrap is irreducibly complex. [4]
Darwin's Theory of Evolution - A Theory In Crisis
Darwin's Theory of Evolution is a theory in crisis in light of the tremendous advances we've made in molecular biology, biochemistry and genetics over the past fifty years. We now know that there are in fact tens of thousands of irreducibly complex systems on the cellular level. Specified complexity pervades the microscopic biological world. Molecular biologist Michael Denton wrote, "Although the tiniest bacterial cells are incredibly small, weighing less than 10-12 grams, each is in effect a veritable micro-miniaturized factory containing thousands of exquisitely designed pieces of intricate molecular machinery, made up altogether of one hundred thousand million atoms, far more complicated than any machinery built by man and absolutely without parallel in the non-living world." [5]
And we don't need a microscope to observe irreducible complexity. The eye, the ear and the heart are all examples of irreducible complexity, though they were not recognized as such in Darwin's day. Nevertheless, Darwin confessed, "To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree." [6]
Footnotes:
1. Charles Darwin, "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life," 1859, p. 162.
2. Ibid. p. 158.
3. Michael Behe, "Darwin's Black Box," 1996.
4. "Unlocking the Mystery of Life," documentary by Illustra Media, 2002.
5. Michael Denton, "Evolution: A Theory in Crisis," 1986, p. 250.
6. Charles Darwin, "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life," 1859, p. 155.
Darwin's Theory of Evolution is the widely held notion that all life is related and has descended from a common ancestor: the birds and the bananas, the fishes and the flowers -- all related. Darwin's general theory presumes the development of life from non-life and stresses a purely naturalistic (undirected) "descent with modification". That is, complex creatures evolve from more simplistic ancestors naturally over time. In a nutshell, as random genetic mutations occur within an organism's genetic code, the beneficial mutations are preserved because they aid survival -- a process known as "natural selection." These beneficial mutations are passed on to the next generation. Over time, beneficial mutations accumulate and the result is an entirely different organism (not just a variation of the original, but an entirely different creature).
Darwin's Theory of Evolution - Natural Selection
While Darwin's Theory of Evolution is a relatively young archetype, the evolutionary worldview itself is as old as antiquity. Ancient Greek philosophers such as Anaximander postulated the development of life from non-life and the evolutionary descent of man from animal. Charles Darwin simply brought something new to the old philosophy -- a plausible mechanism called "natural selection." Natural selection acts to preserve and accumulate minor advantageous genetic mutations. Suppose a member of a species developed a functional advantage (it grew wings and learned to fly). Its offspring would inherit that advantage and pass it on to their offspring. The inferior (disadvantaged) members of the same species would gradually die out, leaving only the superior (advantaged) members of the species. Natural selection is the preservation of a functional advantage that enables a species to compete better in the wild. Natural selection is the naturalistic equivalent to domestic breeding. Over the centuries, human breeders have produced dramatic changes in domestic animal populations by selecting individuals to breed. Breeders eliminate undesirable traits gradually over time. Similarly, natural selection eliminates inferior species gradually over time.
Darwin's Theory of Evolution - Slowly But Surely...
Darwin's Theory of Evolution is a slow gradual process. Darwin wrote, "…Natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by short and sure, though slow steps." [1] Thus, Darwin conceded that, "If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down." [2] Such a complex organ would be known as an "irreducibly complex system". An irreducibly complex system is one composed of multiple parts, all of which are necessary for the system to function. If even one part is missing, the entire system will fail to function. Every individual part is integral. [3] Thus, such a system could not have evolved slowly, piece by piece. The common mousetrap is an everyday non-biological example of irreducible complexity. It is composed of five basic parts: a catch (to hold the bait), a powerful spring, a thin rod called "the hammer," a holding bar to secure the hammer in place, and a platform to mount the trap. If any one of these parts is missing, the mechanism will not work. Each individual part is integral. The mousetrap is irreducibly complex. [4]
Darwin's Theory of Evolution - A Theory In Crisis
Darwin's Theory of Evolution is a theory in crisis in light of the tremendous advances we've made in molecular biology, biochemistry and genetics over the past fifty years. We now know that there are in fact tens of thousands of irreducibly complex systems on the cellular level. Specified complexity pervades the microscopic biological world. Molecular biologist Michael Denton wrote, "Although the tiniest bacterial cells are incredibly small, weighing less than 10-12 grams, each is in effect a veritable micro-miniaturized factory containing thousands of exquisitely designed pieces of intricate molecular machinery, made up altogether of one hundred thousand million atoms, far more complicated than any machinery built by man and absolutely without parallel in the non-living world." [5]
And we don't need a microscope to observe irreducible complexity. The eye, the ear and the heart are all examples of irreducible complexity, though they were not recognized as such in Darwin's day. Nevertheless, Darwin confessed, "To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree." [6]
Footnotes:
1. Charles Darwin, "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life," 1859, p. 162.
2. Ibid. p. 158.
3. Michael Behe, "Darwin's Black Box," 1996.
4. "Unlocking the Mystery of Life," documentary by Illustra Media, 2002.
5. Michael Denton, "Evolution: A Theory in Crisis," 1986, p. 250.
6. Charles Darwin, "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life," 1859, p. 155.
INFLUENZA
Influenza is a viral infection that affects mainly the nose, throat, bronchi and, occasionally, lungs. Infection usually lasts for about a week, and is characterized by sudden onset of high fever, aching muscles, headache and severe malaise, non-productive cough, sore throat and rhinitis.
The virus is transmitted easily from person to person via droplets and small particles produced when infected people cough or sneeze. Influenza tends to spread rapidly in seasonal epidemics.
Most infected people recover within one to two weeks without requiring medical treatment. However, in the very young, the elderly, and those with other serious medical conditions, infection can lead to severe complications of the underlying condition, pneumonia and death.
The virus is transmitted easily from person to person via droplets and small particles produced when infected people cough or sneeze. Influenza tends to spread rapidly in seasonal epidemics.
Most infected people recover within one to two weeks without requiring medical treatment. However, in the very young, the elderly, and those with other serious medical conditions, infection can lead to severe complications of the underlying condition, pneumonia and death.
The N1H1 Swine Flu pandemic scare is good or bad
Is the 2009 H1N1 pandemic scare good for us? Definitely.
The bad thing is that people became sick or died because of the flu, yet there are a few good things that came from this recent scare.
First, to put in in perspective, according to the Center for Disease Control, 36,000 people die in the US annually from influenza, mostly resulting from secondary problems of pneumonia and respiratory illnesses you can get when you are weak from the flu. For another comparison, Just under 40,000 people die from automobile accidents every year in the United Stated.
So what are the good things?
1. It made everyone more aware of basic hygiene like washing your hands, coughing on your sleeve/arm/tissue instead of your hand and promoted the use of hand sanitizers in buildings. Will these things stop it, no. But they will help to reduce the transmission. Every time you do these things, you are blocking the path of transmission and lowering everyone’s risk.
2. It made everyone dust off, or even develop, their Pandemic Management Plans. It probably made many Facility Managers realize that these plans are a guideline only - you still need good flexible planning since you can’t account for everything that will happen and flexibility is the key. As Sir Winston Churchill once said, “Plans are of little importance, but planning is essential.”
3. It made tenants and occupants think about how they will deal with a pandemic and forced them to interface with the Facility Management professionals to discuss and plan what will happen. By doing more visible things like hand sanitizers, we have raised the awareness and Facility Management’s importance in their planning process. In order for us to plan, they need to tell us what their plans are first, so we can react to their needs, rather than guessing.
4. It reminded us in a gentle way that we need to be prepared and learn more about it, including sharing approaches, and that our local, national and global institutions and associations need to work together to manage future pandemics.
But now isn’t the time to relax. You need to be constantly ready for the next time.
If you are interested in more detailed info about the flu, I suggest you check out http://en.wikipedia.org/wiki/Influenza
The bad thing is that people became sick or died because of the flu, yet there are a few good things that came from this recent scare.
First, to put in in perspective, according to the Center for Disease Control, 36,000 people die in the US annually from influenza, mostly resulting from secondary problems of pneumonia and respiratory illnesses you can get when you are weak from the flu. For another comparison, Just under 40,000 people die from automobile accidents every year in the United Stated.
So what are the good things?
1. It made everyone more aware of basic hygiene like washing your hands, coughing on your sleeve/arm/tissue instead of your hand and promoted the use of hand sanitizers in buildings. Will these things stop it, no. But they will help to reduce the transmission. Every time you do these things, you are blocking the path of transmission and lowering everyone’s risk.
2. It made everyone dust off, or even develop, their Pandemic Management Plans. It probably made many Facility Managers realize that these plans are a guideline only - you still need good flexible planning since you can’t account for everything that will happen and flexibility is the key. As Sir Winston Churchill once said, “Plans are of little importance, but planning is essential.”
3. It made tenants and occupants think about how they will deal with a pandemic and forced them to interface with the Facility Management professionals to discuss and plan what will happen. By doing more visible things like hand sanitizers, we have raised the awareness and Facility Management’s importance in their planning process. In order for us to plan, they need to tell us what their plans are first, so we can react to their needs, rather than guessing.
4. It reminded us in a gentle way that we need to be prepared and learn more about it, including sharing approaches, and that our local, national and global institutions and associations need to work together to manage future pandemics.
But now isn’t the time to relax. You need to be constantly ready for the next time.
If you are interested in more detailed info about the flu, I suggest you check out http://en.wikipedia.org/wiki/Influenza
Monday, June 15, 2009
GLOBAL WARMING
what is global warming?
Global warming is the observed and projected increases in the average temperature of Earth's atmosphere and oceans. The Earth's average temperature rose about 0.6° Celsius (1.1° Fahrenheit) in the 20th century.
Cause of global warming
Almost 100% of the observed temperature increase over the last 50 years has been due to the increase in the atmosphere of greenhouse gas concentrations like water vapour, carbon dioxide (CO2), methane and ozone. Greenhouse gases are those gases that contribute to the greenhouse effect (see below). The largest contributing source of greenhouse gas is the burning of fossil fuels leading to the emission of carbon dioxide.
The greenhouse effect
When sunlight reaches Earth's surface some is absorbed and warms the earth and most of the rest is radiated back to the atmosphere at a longer wavelength than the sun light. Some of these longer wavelengths are absorbed by greenhouse gases in the atmosphere before they are lost to space. The absorption of this longwave radiant energy warms the atmosphere. These greenhouse gases act like a mirror and reflect back to the Earth some of the heat energy which would otherwise be lost to space. The reflecting back of heat energy by the atmosphere is called the "greenhouse effect".
The major natural greenhouse gases are water vapor, which causes about 36-70% of the greenhouse effect on Earth (not including clouds); carbon dioxide CO2, which causes 9-26%; methane, which causes 4-9%, and ozone, which causes 3-7%. It is not possible to state that a certain gas causes a certain percentage of the greenhouse effect, because the influences of the various gases are not additive. Other greenhouse gases include, but are not limited to, nitrous oxide, sulfur hexafluoride, hydrofluorocarbons, perfluorocarbons and chlorofluorocarbons.
Global warming causes by greenhouse effect
Greenhouse gases in the atmosphere (see above) act like a mirror and reflect back to the Earth a part of the heat radiation, which would otherwise be lost to space. The higher the concentration of green house gases like carbon dioxide in the atmosphere, the more heat energy is being reflected back to the Earth. The emission of carbon dioxide into the environment mainly from burning of fossil fuels (oil, gas, petrol, kerosene, etc.) has been increased dramatically over the past 50 years.
The increase of greenhouse gas concentration (mainly carbon dioxide) led to a substantial warming of the earth and the sea, called global warming. In other words: The increase in the man-made emission of greenhouse gases is the cause for global warming.
Effects of global warming
There are two major effects of global warming:
Increase of temperature on the earth by about 3° to 5° C (34° to 41° Fahrenheit) by the year 2100.
2) Rise of sea levels by at least 25 meters (82 feet) by the year 2100.
Increasing global temperatures are causing a broad range of changes. Sea levels are rising due to thermal expansion of the ocean, in addition to melting of land ice. Amounts and patterns of precipitation are changing. The total annual power of hurricanes has already increased markedly since 1975 because their average intensity and average duration have increased (in addition, there has been a high correlation of hurricane power with tropical sea-surface temperature).
Changes in temperature and precipitation patterns increase the frequency, duration, and intensity of other extreme weather events, such as floods, droughts, heat waves, and tornadoes. Other effects of global warming include higher or lower agricultural yields, further glacial retreat, reduced summer stream flows, species extinctions. As a further effect of global warming, diseases like malaria are returning into areas where they have been extinguished earlier.
Although global warming is affecting the number and magnitude of these events, it is difficult to connect specific events to global warming. Although most studies focus on the period up to 2100, warming is expected to continue past then because carbon dioxide (chemical symbol CO2) has an estimated atmospheric lifetime of 50 to 200 years. For a summary of the predictions for the future increase in temperature up to 2100.
Proposed Global Warming Preventative Measures
If human activities are causing global warming, it must be possible for humans to stop those harmful activities. Currently, efforts to curb global warming are dismally weak. The famous Kyoto protocol is little more than an empty gesture, setting its aims so low as to be almost meaningless. Also, most environmental activists spend most of their time pleading for individual action such as using fuel-efficient cars and energy-efficient appliances, riding a bike, planting a tree, etc. Of course, these activities do reduce emissions, but in themselves they have little significant. In terms of trying to provide a good example, these individual measures may be admirable, but the only real solutions to greenhouse gas emissions lie in drastic changes.
Fossil fuel use must be phased out and replaced with renewable, non-polluting energy sources. Chemicals such as aerosols, CFCs, halons, etc must stop being produced altogether. Massive deforestation and pollution of crucial carbon sinks, such as the rainforests and oceans, must be halted, and if possible, reversed. The implications of this are certainly dramatic. Many things currently taken for granted will have to be altered, though preventing global warming does not necessarily mean sacrificing comfort and freedom. It may be bad for the energy and automobile companies, but for the masses, there is little which could be more of a threat to comfort and freedom than environmental catastrophe.
Unfortunately, it is easy to say what needs to be done, but difficult to do it. Control of the forces listed above is not directly in our hands. These things must be changed indirectly, by writing letters to newspapers and government officials, backing that up with demonstrations, boycotts, spreading of
education to others, etc. Worldwide demands for clean energy, clean transportation, and clean industry, as well as protection of vital carbon sinks, must be made. Specific solutions will not be listed here, simply because simple solutions are not available for this problem. As has been stated, global warming is an extremely complex issue, and therefore, requires an extremely complex solution, not only in terms of individual responsibility, but in international corporate and state practices as well. Sweeping reform of wasteful and polluting practices is the only way to make a difference.
Those who deny the threat of global warming, or at least see it as far-off and relatively manageable, scoff at such drastic measures, but for those who believe there is even a remote chance of global warming reaching catastrophic levels, these drastic measures are truly the only way of being sure the current trends are halted.
Mars Exploration Rover
NASA's Mars Exploration Rover (MER) Mission is an ongoing robotic mission of exploring Mars, that began in 2003 with the sending of two rovers — MER-A Spirit and MER-B Opportunity — to explore the Martian surface and geology.
Primary among the mission's scientific objectives is to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars. The mission is part of NASA's Mars Exploration Program which includes three previous successful landers: the two Viking landers in 1976 and Pathfinder in 1997.
The total cost of building, launching, landing and operating the rovers on the surface for the initial 90 Martian-day primary mission was US$820 million.[1] Since the rovers have continued to function for over five years after landing they have received five mission extensions with the fifth mission extension, which was granted in October 2007, being until the end of 2009.[1][2] The total cost of the first four mission extensions was $104 million and the fifth mission extension is expected to cost at least $20 million.[1] In July of 2007, Martian dust storms blocked sunlight to the rovers and threatened the ability of the craft to gather energy through their solar panels, causing engineers to fear that one or both of them might be permanently disabled. However, the dust storms lifted, allowing them to resume operations.[3]
In recognition of the vast amount of scientific information amassed by both rovers, two asteroids have been named in their honor: 37452 Spirit and 39382 Opportunity.
The mission is managed for NASA by the Jet Propulsion Laboratory, which designed, built and is operating the rovers.
Objectives.
The scientific objectives of the Mars Exploration Rover mission are to:
*Search for and characterize a variety of rocks and soils that hold clues to past water activity. In particular, samples sought will include those that have minerals deposited by water-related processes such as precipitation, evaporation, sedimentary cementation or hydrothermal activity.
* Determine the distribution and composition of minerals, rocks, and soils surrounding the landing sites.
* Determine what geologic processes have shaped the local terrain and influenced the chemistry. Such processes could include water or wind erosion, sedimentation, hydrothermal mechanisms, volcanism, and cratering.
* Perform calibration and validation of surface observations made by Mars Reconnaissance Orbiter instruments. This will help determine the accuracy and effectiveness of various instruments that survey Martian geology from orbit.
* Search for iron-containing minerals, identify and quantify relative amounts of specific mineral types that contain water or were formed in water, such as iron-bearing carbonates.
* Characterize the mineralogy and textures of rocks and soils and determine the processes that created them.
* Search for geological clues to the environmental conditions that existed when liquid water was present.
* Assess whether those environments were conducive to life.
During the next two decades, NASA will conduct several missions to address whether life ever arose on Mars. The search begins with determining whether the Martian environment was ever suitable for life. Life, as we understand it, requires water, so the history of water on Mars is critical to finding out if the martian environment was ever conducive to life. Although the Mars Exploration Rovers do not have the ability to detect life directly, they are offering very important information on the habitability of the environment in the planet's history.
Naming of Spirit and Opportunity.
The Spirit and Opportunity rovers were named through a student essay competition. The winning entry was by Sofi Collis, a third-grade Russian-American student from Arizona.
I used to live in an orphanage. It was dark and cold and lonely. At night, I looked up at the sparkly sky and felt better. I dreamed I could fly there. In America, I can make all my dreams come true. Thank you for the 'Spirit' and the 'Opportunity.'
— Sofi Collis, age 9
Prior to this, during the development and building of the rovers, they were known as MER-1 (Opportunity) and MER-2 (Spirit). Internally NASA also uses the mission designations MER-A (Spirit) and MER-B (Opportunity) based on the order of landing on Mars (Spirit first then Opportunity).
Thursday, June 11, 2009
Supercomputer's Model of Human Contact Simulates Swine Flu
An extravagantly detailed computer model of the U.S. population is taking a crack at understanding the H1N1 ”swine flu” outbreak. The model, built by researchers at Virginia Polytechnic Institute and State University, in Blacksburg, Va., is composed of realistic representations of the major ways that people in the United States come into contact with one another—in other words, real-world social networks. Last Thursday, the U.S. Department of Defense began using the model to provide recommendations to the Department of Health and Human Services, according to the Virginia Tech engineers.
In the model, called EpiSimdemics, real cities are represented as groups of artificial people whose demographic attributes match data from the last census and land-use databases. By seeding the model with a handful of infected individuals in a manner that mirrors the real cases—say, 45 teenagers in one part of New York City—the model can run hundreds of simulations to illustrate possible future infection patterns across a population of between 50 million and 60 million in nine regions, according to Madhav Marathe, a deputy director of Virginia Tech’s Network Dynamics and Simulation Science Laboratory (NDSSL). In one experiment, for example, the model was asked to determine the impact of school closures on flu transmissions.
The major innovation of EpiSimdemics is the ease with which it allows users to manipulate a wide array of variables in the simulations. ”We’ve built a tool that lets [public health officials] design experiments on how interventions will affect outcomes,” says Christopher Barrett, the director of NDSSL, which is in charge of the project. The tool is essentially an interface that hides the high-performance computing platform that runs the model, enabling public officials and health experts to tap into the university’s computing power without requiring any technical expertise.
One question that the model may help answer in the upcoming months is whether to release an H1N1 vaccine, assuming one is developed while the flu is still active. ”Suppose the current outbreak goes away in the summertime,” says Stephen Eubank, a physicist on the project. ”There are going to be a lot of questions about what to do with the vaccine if it’s ready by the fall.” The model can bring to light the full range of possible outcomes from a vaccine intervention, including changes in the flu’s virulence and the number of people who might become infected under different scenarios.
Another use is to help understand the impact of antiviral medicines. The use of antivirals places a specific type of pressure on a virus, which could cause a more virulent strain to evolve. Public health officials may need to decide whether to try to aggressively snuff out the strain with antivirals. The alternative, if the H1N1 virus proves not to be particularly virulent, is to hope that the strain dies out on its own.
An active research direction for the Virginia Tech team involves modeling the impact of sequestering a small group of critical individuals, such as transportation workers and people in the power industry, to limit the economic impact of disease outbreaks. Recent systems engineering research shows that the U.S. freight-rail system is particularly vulnerable to a flu pandemic.
In the model, called EpiSimdemics, real cities are represented as groups of artificial people whose demographic attributes match data from the last census and land-use databases. By seeding the model with a handful of infected individuals in a manner that mirrors the real cases—say, 45 teenagers in one part of New York City—the model can run hundreds of simulations to illustrate possible future infection patterns across a population of between 50 million and 60 million in nine regions, according to Madhav Marathe, a deputy director of Virginia Tech’s Network Dynamics and Simulation Science Laboratory (NDSSL). In one experiment, for example, the model was asked to determine the impact of school closures on flu transmissions.
The major innovation of EpiSimdemics is the ease with which it allows users to manipulate a wide array of variables in the simulations. ”We’ve built a tool that lets [public health officials] design experiments on how interventions will affect outcomes,” says Christopher Barrett, the director of NDSSL, which is in charge of the project. The tool is essentially an interface that hides the high-performance computing platform that runs the model, enabling public officials and health experts to tap into the university’s computing power without requiring any technical expertise.
One question that the model may help answer in the upcoming months is whether to release an H1N1 vaccine, assuming one is developed while the flu is still active. ”Suppose the current outbreak goes away in the summertime,” says Stephen Eubank, a physicist on the project. ”There are going to be a lot of questions about what to do with the vaccine if it’s ready by the fall.” The model can bring to light the full range of possible outcomes from a vaccine intervention, including changes in the flu’s virulence and the number of people who might become infected under different scenarios.
Another use is to help understand the impact of antiviral medicines. The use of antivirals places a specific type of pressure on a virus, which could cause a more virulent strain to evolve. Public health officials may need to decide whether to try to aggressively snuff out the strain with antivirals. The alternative, if the H1N1 virus proves not to be particularly virulent, is to hope that the strain dies out on its own.
An active research direction for the Virginia Tech team involves modeling the impact of sequestering a small group of critical individuals, such as transportation workers and people in the power industry, to limit the economic impact of disease outbreaks. Recent systems engineering research shows that the U.S. freight-rail system is particularly vulnerable to a flu pandemic.
THE UPSIDE OF MALARIA
Think your job's tedious? Try beheading 100 mosquitoes an hour.
Gently, no smushing allowed. Malaria parasites lurk in these mosquitoes' salivary glands, and a small company on the outskirts of the nation's capital needs them unharmed for a dramatic test -- attempting the first live vaccine to fight malaria.
Mutant mosquitoes, too, might help one day. Their eyes glow green under a special microscope, a sign that the University of Maryland's genetic engineering has taken hold: These bugs should become super malaria incubators, a bid to eventually get more of the vaccine's key ingredient per mosquito.
If the two experiments sound far-fetched, consider: A global push is on to eradicate this ancient scourge, and increasingly scientists are exploring how to use the mosquito itself to help -- not just with the vaccine research but also, conversely, by breeding insects that are less able to spread malaria.
"It's really gene therapy for insects," says Dr. David O'Brochta, who heads the Maryland university's novel laboratory and, with government funding, is creating both bug types.
It's a change in philosophy, and O'Brochta cautions that it's far from clear that any of the mosquito research will pan out.
A vaccine made of living malaria parasites "was considered laughable five to seven years ago," says Dr. Stephen Hoffman, CEO of Rockville, Md.-based Sanaria Inc.
In the Navy in the 1990s, Hoffman irradiated malaria-carrying mosquitoes to weaken the parasites inside them, and he and 13 colleagues subjected themselves to more than 1,000 bites. Usually malaria parasites race to the liver and multiply before invading the bloodstream to sicken. These weakened parasites instead sat harmlessly in the liver, unable to multiply but triggering the immune system to fend off later infections. All but one of the people in Hoffman's test, himself included, were immune when bitten by regular malaria-infected mosquitoes over the next 10 months.
The question was how to turn that protection into a long-lasting shot. Critics said "it couldn't possibly be made," Hoffman recalls. "We were dismissed by 99 percent of the people in the malaria field."
Yet two weeks ago, with the Food and Drug Administration's OK, the first of about 100 U.S. volunteers started receiving test doses of Sanaria's vaccine, in a first-stage safety study.
In O'Brochta's lab, Robert Harrell peers through a microscope and jabs a mosquito egg -- so small it takes a clump of them to resemble specks of dirt -- with a hair-thin glass needle. He's aiming new DNA near a spot that should develop into reproductive organs, so the resulting mutant mosquito can pass its new trait to next generations.
Inheritance is a hurdle: Of the mutants that survive to adulthood, only about 2 percent of their progeny remain genetically modified.
In a humid insectary that resembles a walk-in safe, O'Brochta pulls out a bucket swarming with Anopheles gambiae, the species that drives malaria in Africa. Deprived of human blood in the lab, these mosquitoes will suck on a sedated mouse for food. (The lab mouse, which loses a little blood, then gets a two-week vacation -- and no, mosquitoes don't make mice itch.)
But in the wild, this particular species hunts people like a bloodhound, so a malaria-resistance gene would have to spread a lot faster through mosquito populations to work. How to speed that spread is O'Brochta's main focus.
The flip side of his research brings us back to Sanaria.
It takes 3,000 mosquitoes to make a batch of the experimental vaccine, says Sanaria entomologist Adam Richman. In an FDA-sanctioned "clean room," workers dunk frozen mosquitoes in alcohol, killing them but not the stunned parasites inside. Then, peering through a microscope, the workers carefully pull each mosquito's head from its body. Out pops an almost translucent glob, the glands, ready for purification.
The company's eventual goal: a mosquito that can harbor 200,000 sporozoites, the immature parasites, twice the typical amount. In his nearby university lab, that's what O'Brochta is trying to create by switching off a gene that protects the bug when it eats malaria-infected human blood.
"No one has ever made transgenic mosquitoes with this gene knocked out," he says. "We want to cripple its immune system so when it takes an infected meal, it gets infected at very high levels.
Gently, no smushing allowed. Malaria parasites lurk in these mosquitoes' salivary glands, and a small company on the outskirts of the nation's capital needs them unharmed for a dramatic test -- attempting the first live vaccine to fight malaria.
Mutant mosquitoes, too, might help one day. Their eyes glow green under a special microscope, a sign that the University of Maryland's genetic engineering has taken hold: These bugs should become super malaria incubators, a bid to eventually get more of the vaccine's key ingredient per mosquito.
If the two experiments sound far-fetched, consider: A global push is on to eradicate this ancient scourge, and increasingly scientists are exploring how to use the mosquito itself to help -- not just with the vaccine research but also, conversely, by breeding insects that are less able to spread malaria.
"It's really gene therapy for insects," says Dr. David O'Brochta, who heads the Maryland university's novel laboratory and, with government funding, is creating both bug types.
It's a change in philosophy, and O'Brochta cautions that it's far from clear that any of the mosquito research will pan out.
A vaccine made of living malaria parasites "was considered laughable five to seven years ago," says Dr. Stephen Hoffman, CEO of Rockville, Md.-based Sanaria Inc.
In the Navy in the 1990s, Hoffman irradiated malaria-carrying mosquitoes to weaken the parasites inside them, and he and 13 colleagues subjected themselves to more than 1,000 bites. Usually malaria parasites race to the liver and multiply before invading the bloodstream to sicken. These weakened parasites instead sat harmlessly in the liver, unable to multiply but triggering the immune system to fend off later infections. All but one of the people in Hoffman's test, himself included, were immune when bitten by regular malaria-infected mosquitoes over the next 10 months.
The question was how to turn that protection into a long-lasting shot. Critics said "it couldn't possibly be made," Hoffman recalls. "We were dismissed by 99 percent of the people in the malaria field."
Yet two weeks ago, with the Food and Drug Administration's OK, the first of about 100 U.S. volunteers started receiving test doses of Sanaria's vaccine, in a first-stage safety study.
In O'Brochta's lab, Robert Harrell peers through a microscope and jabs a mosquito egg -- so small it takes a clump of them to resemble specks of dirt -- with a hair-thin glass needle. He's aiming new DNA near a spot that should develop into reproductive organs, so the resulting mutant mosquito can pass its new trait to next generations.
Inheritance is a hurdle: Of the mutants that survive to adulthood, only about 2 percent of their progeny remain genetically modified.
In a humid insectary that resembles a walk-in safe, O'Brochta pulls out a bucket swarming with Anopheles gambiae, the species that drives malaria in Africa. Deprived of human blood in the lab, these mosquitoes will suck on a sedated mouse for food. (The lab mouse, which loses a little blood, then gets a two-week vacation -- and no, mosquitoes don't make mice itch.)
But in the wild, this particular species hunts people like a bloodhound, so a malaria-resistance gene would have to spread a lot faster through mosquito populations to work. How to speed that spread is O'Brochta's main focus.
The flip side of his research brings us back to Sanaria.
It takes 3,000 mosquitoes to make a batch of the experimental vaccine, says Sanaria entomologist Adam Richman. In an FDA-sanctioned "clean room," workers dunk frozen mosquitoes in alcohol, killing them but not the stunned parasites inside. Then, peering through a microscope, the workers carefully pull each mosquito's head from its body. Out pops an almost translucent glob, the glands, ready for purification.
The company's eventual goal: a mosquito that can harbor 200,000 sporozoites, the immature parasites, twice the typical amount. In his nearby university lab, that's what O'Brochta is trying to create by switching off a gene that protects the bug when it eats malaria-infected human blood.
"No one has ever made transgenic mosquitoes with this gene knocked out," he says. "We want to cripple its immune system so when it takes an infected meal, it gets infected at very high levels.
Tuesday, June 9, 2009
school level biology
SECTION-A
1. A potted plant otherwise kept in sunlight, is shifted to monochromatic red light (wave length 700nm). Will the rate of photosynthesis increase, decrease or remain the same? (1 mark)
2. Name two non-iron products of the breakdown of haemoglobin. (1 mark)
3. Flowers that bloom at night are usually small and white but give out a strong scent. Why do they do so ? (1 mark)
4. Rearrange the following levels in their correct organisational sequence : Landscape, Organism, Community, Population Ecosystem, Biosphere. (1 mark)
5. During a meristem culture some explants were kept in culture medium containing more of auxins than cytokinins. Which organ of the plant is expected to differentiate from the callus? (1 mark)
SECTION-B
6. Name the enzyme that catalyses carboxylation as well as oxygenation reaction. In which cell organelle, is this enzyme found and in what way, is that organelle different in the mesophyll and bundle sheath cells? (2 marks)
7. How do the potassium, chloride and malate ions help in opening the stomata ? (2 marks)
8. Two green potted plants were kept separately inside oxygen free bell jars, one in sunlight and the other in dark. Which of the two plants will survive for longer period and why? (2 marks)
9. A student unknowingly crushed a cockroach under his shoes. Finding that no red fluid comparable to vertebrate blood came out, he was curious to know whether the cockroaches are at any disadvantage. How will you satisfy his curiosity? (2 marks)
10. Show by a series of diagrams the manner of regeneration in a hydra if it is cut into two pieces transversely at the middle. (2 marks)
OR
Show by a series of diagrams the manner of transverse binary fission in Planaria. ( 2 marks)
11. In extreme summer and winter, certain animals like frogs and lizards abandon active life. This is popularity called summer sleep and winter sleep respectively. (2 marks)
(i) What are the technical terms for summer sleep and winter sleep?
(ii) State any two changes in the body that occur during the above-mentioned dormant states.
12. State the relationship between biotic potential and environmental resistance. (2 marks)
13. Define parthenogenesis. Give one example of parthenogenesis from plants and one from animals. (2 marks)
14.What is meant by active immunity and passive immunity? (2 marks)
15. A person was born without thymus gland but otherwise normal. Mention any four ways in which the person is likely to suffer due to its absence. (2 marks)
SECTION-C
16. Mr. ‘X’ hardly fell sick when young. As he aged and grew older he started contracting many infectious diseases. (3 marks)
(i) Name the theory of ageing which explains the above mentioned change.
(ii)What causes susceptibility to infections in old age?
17. How many pairs of ribs are found in the humans? How do you categorise these on the basis of their attachment ? Explain. (3 marks)
18. Stomach is the right place in the alimentary canal where hydrochloric acid is secreted in the gastric juice. Describe any three points to justify this statement. (3 marks)
19. Suppose for some reason ATP falls deficient in a nerve fibre, how will it affect the conduction of nerve impulse through it? (3 marks)
20. Giving an example of CAM plants, explain the process of Crassulacean Acid Metabolism. What is its advantage? (3 marks)
OR
Starting from Glycolate produced in the chloroplast, explain the various steps of photorespiratory pathway that take place in the two other organelles up to the formation of PGA back in the chloroplast. (3 marks)
21. Differentiate between morula and blastocyst as stages in human embryonic development. Which of these stages gets implanted in the uterine wall and about how many days after fertilization? (3 marks)
22. Name the three major Biomes and state the kind of climax vegetation found in each of them. (3 marks)
23. Name and define the environment-related terms for the following: (3 marks)
(i) Pertaining to the fact that DDT accumulated in a three step food chain will be maximum in the secondary consumer.
(ii) Pertaining to causing algal bloom.
24. List and briefly describe any three diagnostic techniques by images based on the use of ‘X’-rays. (3 marks)
25. In regard to transplant of organs, what are isograft, allograft and xenograft? (3 marks)
SECTION-D
26. Name any two C4 plants. Specify how the C4 photosynthetic pathway increases C02 concentration in bundle sheath cells of such plants and explain what is the need of increasing C02 concentration. (5 marks)
OR
(a) Name two organisms whose symbiotic association leads to nitrogen fixation in root nodules. (2 marks)
(b) Describe the steps in the formation of root nodules and name the two plant harmones that promote cell division for nodule formation. Which two physiological processes provide the FAD and ATP required for fixation of atmospheric nitrogen? (3 marks)
27. Decribe the structure of immunoglobin or Ig/antibody. Draw a diagram showing the formation of antigen-antibody complex and label the parts. (5 marks)
OR
(a) Define the following : (3 marks)
(i) a protoplast
(ii) a somatic hybrid
(iii) an allopolyploid
(b) With the help of diagrams, describe the formation of a somatic hybrid cell. (2 marks)
28. Differentiate between osmoregulators and osmoconformers. How will you categorise humans, hagfish, and camel under these categories? Mention any four points how camel regulates the water content of its body. (5 marks)
OR
Trace the events in a muscle fibre from the time it receives the impulse through the neuromuscular junction up to the contractile response. (5 marks)
1. A potted plant otherwise kept in sunlight, is shifted to monochromatic red light (wave length 700nm). Will the rate of photosynthesis increase, decrease or remain the same? (1 mark)
2. Name two non-iron products of the breakdown of haemoglobin. (1 mark)
3. Flowers that bloom at night are usually small and white but give out a strong scent. Why do they do so ? (1 mark)
4. Rearrange the following levels in their correct organisational sequence : Landscape, Organism, Community, Population Ecosystem, Biosphere. (1 mark)
5. During a meristem culture some explants were kept in culture medium containing more of auxins than cytokinins. Which organ of the plant is expected to differentiate from the callus? (1 mark)
SECTION-B
6. Name the enzyme that catalyses carboxylation as well as oxygenation reaction. In which cell organelle, is this enzyme found and in what way, is that organelle different in the mesophyll and bundle sheath cells? (2 marks)
7. How do the potassium, chloride and malate ions help in opening the stomata ? (2 marks)
8. Two green potted plants were kept separately inside oxygen free bell jars, one in sunlight and the other in dark. Which of the two plants will survive for longer period and why? (2 marks)
9. A student unknowingly crushed a cockroach under his shoes. Finding that no red fluid comparable to vertebrate blood came out, he was curious to know whether the cockroaches are at any disadvantage. How will you satisfy his curiosity? (2 marks)
10. Show by a series of diagrams the manner of regeneration in a hydra if it is cut into two pieces transversely at the middle. (2 marks)
OR
Show by a series of diagrams the manner of transverse binary fission in Planaria. ( 2 marks)
11. In extreme summer and winter, certain animals like frogs and lizards abandon active life. This is popularity called summer sleep and winter sleep respectively. (2 marks)
(i) What are the technical terms for summer sleep and winter sleep?
(ii) State any two changes in the body that occur during the above-mentioned dormant states.
12. State the relationship between biotic potential and environmental resistance. (2 marks)
13. Define parthenogenesis. Give one example of parthenogenesis from plants and one from animals. (2 marks)
14.What is meant by active immunity and passive immunity? (2 marks)
15. A person was born without thymus gland but otherwise normal. Mention any four ways in which the person is likely to suffer due to its absence. (2 marks)
SECTION-C
16. Mr. ‘X’ hardly fell sick when young. As he aged and grew older he started contracting many infectious diseases. (3 marks)
(i) Name the theory of ageing which explains the above mentioned change.
(ii)What causes susceptibility to infections in old age?
17. How many pairs of ribs are found in the humans? How do you categorise these on the basis of their attachment ? Explain. (3 marks)
18. Stomach is the right place in the alimentary canal where hydrochloric acid is secreted in the gastric juice. Describe any three points to justify this statement. (3 marks)
19. Suppose for some reason ATP falls deficient in a nerve fibre, how will it affect the conduction of nerve impulse through it? (3 marks)
20. Giving an example of CAM plants, explain the process of Crassulacean Acid Metabolism. What is its advantage? (3 marks)
OR
Starting from Glycolate produced in the chloroplast, explain the various steps of photorespiratory pathway that take place in the two other organelles up to the formation of PGA back in the chloroplast. (3 marks)
21. Differentiate between morula and blastocyst as stages in human embryonic development. Which of these stages gets implanted in the uterine wall and about how many days after fertilization? (3 marks)
22. Name the three major Biomes and state the kind of climax vegetation found in each of them. (3 marks)
23. Name and define the environment-related terms for the following: (3 marks)
(i) Pertaining to the fact that DDT accumulated in a three step food chain will be maximum in the secondary consumer.
(ii) Pertaining to causing algal bloom.
24. List and briefly describe any three diagnostic techniques by images based on the use of ‘X’-rays. (3 marks)
25. In regard to transplant of organs, what are isograft, allograft and xenograft? (3 marks)
SECTION-D
26. Name any two C4 plants. Specify how the C4 photosynthetic pathway increases C02 concentration in bundle sheath cells of such plants and explain what is the need of increasing C02 concentration. (5 marks)
OR
(a) Name two organisms whose symbiotic association leads to nitrogen fixation in root nodules. (2 marks)
(b) Describe the steps in the formation of root nodules and name the two plant harmones that promote cell division for nodule formation. Which two physiological processes provide the FAD and ATP required for fixation of atmospheric nitrogen? (3 marks)
27. Decribe the structure of immunoglobin or Ig/antibody. Draw a diagram showing the formation of antigen-antibody complex and label the parts. (5 marks)
OR
(a) Define the following : (3 marks)
(i) a protoplast
(ii) a somatic hybrid
(iii) an allopolyploid
(b) With the help of diagrams, describe the formation of a somatic hybrid cell. (2 marks)
28. Differentiate between osmoregulators and osmoconformers. How will you categorise humans, hagfish, and camel under these categories? Mention any four points how camel regulates the water content of its body. (5 marks)
OR
Trace the events in a muscle fibre from the time it receives the impulse through the neuromuscular junction up to the contractile response. (5 marks)
important questions of biology (k10)
Biology
Q. 1. Describe the path of ascent of sap due to transpiration pull.What were the objections raised against this theory and how was it rectified. [6]
Q. 2. Describe cytochrome pump theory for active absorption of minerals. [5]
Q. 3. Describe the life cycle of filarial parasite. [6]
Q. 4. Describe the basic postulates of the Neo Darwinians. [6]
Q. 5. Describe Cardiac Cycle. [6]
Q. 6. Describe the histological structure of various digestive glands. [6]
Q. 7. Give an account of the Tunica Corpus Theory. [3]
Q. 8. What are Darwin’s finches.What important conclusion was drawn from their studies. [5]
Q. 9. Describe Miller Urey’s Experiment. [5]
Q. 10 Describe the process of hybridization. [6]
Q. 11. Write in detail about CT Scan and MRI? Which is safer and why. [8]
Q. 12. Describe Calvin Cycle with schematic representation. [7]
Q. 13. Give the functions of auxins. [3]
Q. 14. What is counter current mechanism.Explain in brief . [4]
Q. 15. Describe the various organs of male reproductive system. [8]
Q. 16. Explain sliding filament theory and the chemical events during muscle contraction. [6]
Q. 17. What are the advantages of using bio-fertilisers [2]
Q. 18. Give an account of process of urine formation and its hormonal control. [6]
Q. 19. State Cope’s Law. [2]
Q. 1. Describe the path of ascent of sap due to transpiration pull.What were the objections raised against this theory and how was it rectified. [6]
Q. 2. Describe cytochrome pump theory for active absorption of minerals. [5]
Q. 3. Describe the life cycle of filarial parasite. [6]
Q. 4. Describe the basic postulates of the Neo Darwinians. [6]
Q. 5. Describe Cardiac Cycle. [6]
Q. 6. Describe the histological structure of various digestive glands. [6]
Q. 7. Give an account of the Tunica Corpus Theory. [3]
Q. 8. What are Darwin’s finches.What important conclusion was drawn from their studies. [5]
Q. 9. Describe Miller Urey’s Experiment. [5]
Q. 10 Describe the process of hybridization. [6]
Q. 11. Write in detail about CT Scan and MRI? Which is safer and why. [8]
Q. 12. Describe Calvin Cycle with schematic representation. [7]
Q. 13. Give the functions of auxins. [3]
Q. 14. What is counter current mechanism.Explain in brief . [4]
Q. 15. Describe the various organs of male reproductive system. [8]
Q. 16. Explain sliding filament theory and the chemical events during muscle contraction. [6]
Q. 17. What are the advantages of using bio-fertilisers [2]
Q. 18. Give an account of process of urine formation and its hormonal control. [6]
Q. 19. State Cope’s Law. [2]
anatomical planes in humans.
General usage
Three basic reference planes are used in zoological anatomy.
* A sagittal plane, being a plane parallel to the sagittal suture, divides the body into sinister and dexter (left and right) portions.
o The midsagittal or median plane is in the mid line; i.e. it would pass through mid line structures such as the navel or spine, and all other sagittal planes (also referred to as parasagittal planes) are parallel to it. Median can also refer to the midsagittal plane of other structures, such as a digit.
* A coronal or frontal plane divides the body into dorsal and ventral (back and front, or posterior and anterior) portions.
* A transverse plane, also known as an axial plane or cross-section, divides the body into cranial and caudal (head and tail) portions.
For post-embryonic humans a coronal plane is vertical and a transverse plane is horizontal, but for embryos and quadrupeds a coronal plane is horizontal and a transverse plane is vertical.
When describing anatomical motion, these planes describe the axis along which an action is performed. So by moving through the transverse plane, movement travels from head to toe. For example, if a person jumped directly up and then down, their body would be moving through the transverse plane in the coronal and sagittal planes.
Some of these terms come from Latin. Sagittal means "like an arrow", a reference to the position of the spine which naturally divides the body into right and left equal halves, the exact meaning of the term "midsagittal", or to the shape of the sagittal suture, which defines the sagittal plane and is shaped like an arrow.
A longitudinal plane is any plane perpendicular to the transverse plane. The coronal plane and the sagittal plane are examples of longitudinal planes.
[edit] Usage in human anatomy
Sometimes the orientation of certain planes needs to be distinguished, for instance in medical imaging techniques such as sonography, CT scans, MRI scans, or PET scans. One imagines a human in the anatomical position, and an X-Y-Z coordinate system with the X-axis going from front to back, the Y-axis going from left to right, and the Z-axis going from up to down. The X-axis axis is always forward (Tait-Bryan angles) and the right-hand rule applies.
* A transverse (also known as axial or horizontal) plane is an X-Y plane, parallel to the ground, which (in humans) separates the superior from the inferior, or put another way, the head from the feet.
* A coronal (also known as frontal) plane is an X-Z plane, perpendicular to the ground, which (in humans) separates the anterior from the posterior, the front from the back, the ventral from the dorsal.
* A sagittal (also known as median) plane is an Y-Z plane, perpendicular to the ground, which separates left from right. The midsagittal plane is the specific sagittal plane that is exactly in the middle of the body.
The axes and the sagittal plane are the same for bipeds and quadrupeds, but the orientation of the coronal and transverse planes switch. The axes on particular pieces of equipment may or may not correspond to axes of the body, especially since the body and the equipment may be in different relative orientations.
Occasionally, in medicine, abdominal organs may be described with reference to the trans-pyloric plane which is a transverse plane passing through the pylorus.
[edit] Anatomical planes in animal brains
In discussing the neuroanatomy of animals, particularly rodents used in neuroscience research, the convention has been to name the sections of the brain according to the homologous human sections. Hence, what is technically a transverse section with respect to the body of a rat (dividing anterior from posterior) may often be referred to in rat neuroanatomical coordinates as a coronal section, and likewise a coronal section with respect to the body (i.e. dividing ventral from dorsal) in a rat brain is referred to as transverse. This preserves the comparison with the human brain which is rotated with respect to the body axis by 90 degrees in the ventral direction. It does mean that the planes of the rat brain are not necessarily the same as those of the body.
[edit] Surface and other landmarks in humans
In humans, reference may be made to landmarks which are on the skin or visible underneath. As with planes, lines and points are imaginary. Examples include:
* The mid-axillary line, a line running vertically down the surface of the body passing through the apex of the axilla (armpit). Parallel are the anterior axillary line, which passes through the anterior axillary skinfold, and the posterior axillary line, which passes through the posterior axillary skinfold.
* The mid-clavicular line, a line running vertically down the surface of the body passing through the midpoint of the clavicle.
* The mid-pupillary line, a line running vertically down the face through the midpoint of the pupil when looking directly forwards.
* The mid-inguinal point, a point midway between the anterior superior iliac spine and the pubic symphysis.
o mid-point of inguinal ligament = mid-point between anterior superior iliac spine and pubic tubercle
* Tuffier's line, which is a transverse line passing across the lumbar spine between the posterior iliac crests.
* Mid-ventral line, the intersection between the ventral skin and the median plane.
Additionally, reference may be made to structures at specific levels of the spine (e.g. the 4th cervical vertebra, abbreviated "C4"), or the rib cage (e.g. the 5th intercostal space).
Monday, June 8, 2009
MCQ'S FOR CLASS X STUDENTS
SAMPLE PAPER - 1
Section A
- When light travels from glass to air,
(a) no change occurs
(b) it moves away from the normal
(c) it moves towards the normal
(d) none of these- Refractive index depends on the following factors except
(a) nature of material of medium
(b) density of medium
(c) angle of incidence
(d) colour or wavelength of light- Mirages are observed in deserts due to the phenomenon of
(a) interference of light
(b) scattering of light
(c) dispersion of light
(d) total internal reflection- Ohm's law is valid for
(a) all conductors
(b) only metallic conductors
(c) all elements
(d) none of these- The SI unit of resistivity is
(a) ohm
(b) ohm metre square
(c) ohm metre
(d) ohm/metre- In this circuit the volt meter will read
(a) 24 V
(b) 25 V
(c) 30 V
(d)35 V- In the following circuit the ammeter will read
(a)5A
(b)0.5A
(c)1 A
(d)0.1A- When an object is placed at 2F in front of a cocave mirror, then its image is formed at
(a) F
(b) 2F
(c) infinity
(d) between F and 2 F- A convex lens is
(a) thicker at the middle than at the edges
(b) thicker at the edges than at the middle
(c)plane everywhere
(d) uniform for one half and non uniform thickness at the other half- A substance is behaving as a convex lens in air and concave lens in water, then its refractive index is :
(a) smaller than air
(b) greater than both water and air
(c)greater than air but less than water
(d) almost equal to that of water- In an acid soulution, the pH is
(a) greater than p(OH)
(b) leass than p(OH)
(c)equal to p(OH)
(d) none of these- Which of the following solutions of equal cncentration will have lowest pH?
(a) HCl
(b)H2SO4
(c) NaOH
(d)HNO3- Methyl Orange is suitable for titrating
(a)A weak acid with a weak base
(b)A strong base with a weak base
(c)A weak base with a strong acid
(d) none of these- pH of lime water is
(a)7
(b)more than 7
(c)less than 7
(d)zero
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