Memory traces

The question of where and how memories are stored in the brain is one of the most intriguing in neuroscience. Answers to this question are just starting to emerge, as reported here.

That research dealt with short-term memory in honeybees. It showed that the memory trace involves synchronized neural activity lasting for several minutes. The activity was in clusters of neurons known as glomeruli in the bee's antenna lobe. This area is considered to be the equivalent of the olfactory bulb in vertebrates (which handles the sense of smell).

Now there are additional results involving longer-term memory in fruit flies.

Memory follows dynamic pattern involving many cells in brain

Memory formation follows a dynamic pattern, allowing for retrieval from different areas of the brain, depending on when an organism needs to remember, said a researcher at Baylor College of Medicine.

That is what Dr. Ron L. Davis, professor of molecular and cellular biology at BCM, theorizes, based on his most recent report on the topic that finds a memory trace in Drosophila or fruit flies is formed in a pair of neurons called the dorsal pair medial neurons, but only 30 minutes after the fact and only through the mediation of a gene called, ironically, amnesiac.

The really interesting thing is that the trace of a specific memory does not appear to remain in one place, but instead seems to move around:

The finding belies the commonly held precept that a memory is formed in the same way that data are stored in a computer - always in the same place.

"It's not as if we are forming memories that are then being written to a "hard disk" area of the brain, and it's there and recalled from the same location at any time after learning," said Davis. "We now think that different areas of the brain have dominion over small intervals of time after training. One area might have dominion and then another."

Tags: memory trace, neuroscience

Global warming could halt ocean circulation

It's looking more and more as though one of the more unwelcome consequences of global warming may come to pass by 2100 -- the paradoxical possibility of much colder termperatures in Europe and the northeastern U. S.

Weakening of ocean's circulation could actually cool things down

Things get worse if the north Atlantic water is swamped by fresh water from rain, continental rivers or melting glaciers, especially from the Greenland ice cap. Fresh water dilutes the salty ocean, making it less dense and even more buoyant. In a worst-case scenario, the north Atlantic water is so warm and buoyant that it can't sink at all, as if it were an inflated balloon floating atop a swimming pool.

When that happens, the oceanic heat-transport system stalls or totally breaks down. Like a blood clot in a vein, the buoyant water blocks the oceanic circulation, preventing new warm tropical water from flowing north, and Europe's average temperature drops by several degrees.

How likely is this to happen? Some researchers think it's a lot more probable than recently believed:

Global warming could halt ocean circulation, with harmful results

Absent any climate policy, scientists have found a 70 percent chance of shutting down the thermohaline circulation in the North Atlantic Ocean over the next 200 years, with a 45 percent probability of this occurring in this century. The likelihood decreases with mitigation, but even the most rigorous immediate climate policy would still leave a 25 percent chance of a thermohaline collapse.

“This is a dangerous, human-induced climate change,” said Michael Schlesinger, a professor of atmospheric sciences at the University of Illinois at Urbana-Champaign. “The shutdown of the thermohaline circulation has been characterized as a high-consequence, low-probability event. Our analysis, including the uncertainties in the problem, indicates it is a high-consequence, high-probability event.”

Tags: global warming, thermohaline collapse, earth science, climate change

How do galaxies grow?

It's certainly a golden age for research in astrophysics and cosmology. This is largely a result of all the new observational technology -- a number of very powerful ground-based telescopes in addition to Hubble and other space-based instruments.

One area in which new results are appearing frequently is the question of how galaxies form and evolve. See here, for example.

One topic that is rapidly becoming clearer is the question of how large galaxies come about. They aren't born fully grown, nor do they grow gradually. Basically, large galaxies come about through cannibalism.

Galaxy Collisions Dominate the Local Universe

New Haven, Conn. — More than half of the largest galaxies in the nearby universe have collided and merged with another galaxy in the past two billion years, according to a Yale astronomer in a study using hundreds of images from two of the deepest sky surveys ever conducted.

The idea of large galaxies being assembled primarily by mergers rather than evolving by themselves in isolation has grown to dominate cosmological thinking.

One apparent problem with this idea is that there are many large galaxies which appear to be quite old. (See here.) However, there are ways to deal with this:

[A] troubling inconsistency within this general theory has been that the most massive galaxies appear to be the oldest, leaving minimal time since the Big Bang for the mergers to have occurred.

“Our study found these common massive galaxies do form by mergers. It is just that the mergers happen quickly, and the features that reveal the mergers are very faint and therefore difficult to detect,” said Pieter van Dokkum, assistant professor of astronomy at Yale University, and sole author of the paper appearing in the December 2005 issue of the Astronomical Journal.

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Additional information

Supplemental material about the research

Galaxies become monsters by repeated mergers

More Often Than Not, Massive Galaxies Form by Mergers

Tags: galaxies, astrophysics, cosmology

ID now means "It's Dead"

Well, we can hope so, anyhow.

For a summary of the wholesale fraud that "intelligent design" proponents in Dover, PA were attempting, see

"Evolution Teaches Nothing But Lies," And Other Dover Facts

The Dover Defendants, as well as the entire ID community, are exposed now as the religious zealots they are. No more hiding behind "scientific" theories or claims of benign motives. No, Judge Jones has ripped off their shroud and exposed them as irrational, conniving, manipulative people with no respect for that venerable principle of separation of church and state.

His opinion leaves no doubt that ID is creationism. Moreover, with a great recitation of ID's history, he proves that the "ID movement" is a calculated attempt to relabel creationism in order to bypass the establishment clause. In short, Judge Jones has exposed ID for what it is: a sham by religious fundamentalists to obliterate the separation between church and state.

Permian-Triassic mass extinction

About 252 million years ago, at the end of the Permian geologic period (and the beginning of the Triassic), more than 90% of marine organisms and about 70% of terrestrial vertebrate species went extinct. This Permian-Triassic extinction event is the most extensive instance of mass extinction that is known -- considerably more severe than the Cretaceous-Tertiary extinction event (KT event) of 65.5 million years ago that wiped out the dinosaurs.

There is even more uncertainty about what caused the PT event than there is about the later KT extinction. Hypotheses include:

• an impact event (similar to the currently favored explanation of the KT event) that could have led to either immediate superheating of the atmosphere causing widespread fires, and/or a subsequent "nuclear winter effect" due to lingering particulates that caused drastic cooling
  
• large-scale gasification of methane hydrate in the oceans, producing quantities of methane gas that led to a greenhouse effect and a 5°C average rise in global temperatures
  
• volcanic eruptions, probabaly in the Siberian Traps, that would have produced acid rains, greenhouse gasses, temperature fluctuations, and eventually severe depletion of oxygen dissolved in the oceans
  
• other possibilities, such as a nearby supernova, or perhaps a combination of several of these possibilities
  

Recently reported research argues for the explanation involving volcanism:

No safe ground for life to stand on during world's largest mass extinction

[A]nalysis of a unique set of molecules found in rocks taken from the Dolomites in Italy has enabled scientists to build up a picture of what actually happened. The molecules are the remains of polysaccharides, large sugar-based structures common in plants and soil, and they tell the story of the extinction.

The molecules date from the same time as a major volcanic eruption that caused the greatest ever outpouring of basalt lava over vast swathes of land in present day Siberia.

The researchers believe that the volcanic gases from the eruption, which would have depleted earth's protective ozone layer and acidified the land and sea, killed rooted vegetation. This meant that soil was no longer retained and it washed into the surrounding oceans.

The chemistry of the rocks reveals that although the sugar molecules were found in marine sediments, they derived from land, supporting the theory that massive soil erosion caused them to end up in the sea.

Soil materials in the oceans would have blocked out light and soaked up oxygen. Analysis of rock chemistry suggests that after the soil crisis on land, the marine ecosystem succumbed to the stresses of environmental change and oceanic life faltered, completing a global catastrophe.

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Another account: Geologists Link the "Great Dying" to Volcanism

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Tags: mass extinctions, permian-triassic mass extinction, earth science

Interview with Chris Mooney

I wrote about Mooney's book, The Republican War on Science, here. By now I expect the book is pretty well known among people who care about political distortions and abuses of science. Those who've read the book, as well as those who haven't, may be interested in this interview that just appeared: The War on Science.

Mooney talks about how he came to write the book, and various scientific issues that have been made politically controversial, such as evolution, stem cells, the Plan B contraceptive, mercury pollution, and global warming.

Tags: republican war on science, chris mooney

Tidal dwarf galaxies

Not all galaxies in the universe are as large or as distinctive in appearance as the majestic spirals such as our own Milky Way or the Andromeda galaxy (M31). Many, known as dwarf galaxies, are small and shapeless, with perhaps 1/1000 the mass of the Milky Way. Some of these formed soon after the big bang and have changed little since then. Others may have formed much later as a byproduct of collisions between much larger galaxies. These are known as tidal dwarf galaxies.

Is there any way to tell which is which?

Cornell astronomers investigate cosmic forces that produce new galaxies

To understand which dwarf galaxies are tidal in origin and how those galaxies differ from primordial dwarf galaxies, Cornell researcher Sarah Higdon and her colleagues studied a system called NGC 5291, which is 200 million light years from Earth and stretches a distance roughly four times the span of the Milky Way. At the system's center are two colliding galaxies; behind them trail a string of much smaller dwarfs.

By looking for signs of strong star-forming activity, the researchers found that it was taking place mainly in the cast-off tidal dwarfs, rather than in the colliding galaxies themselves. This enabled them to recognize characteristic properties of the tidal dwarfs:

the team found that the tidal dwarfs show strong emission from organic compounds, found in crude petroleum, burnt toast and (more relevantly) stellar nurseries, known as PAHs -- for polycyclic aromatic hydrocarbons. And for the first time, the researchers detected warm molecular hydrogen -- another indicator of star formation, and one that has never before been directly measured in tidal dwarf galaxies.

Tags: dwarf galaxies, galaxies, astronomy, cosmology, star formation

Why caffeine works

Coffee's effects revealed in brain scans

Coffee improves short-term memory and speeds up reaction times by acting on the brain’s prefrontal cortex, according to a new study.

Researchers used functional magnetic resonance imaging (fMRI) to determine how coffee activates different areas of the brain in 15 volunteers.

“Caffeine modulates a higher brain function through its effects on distinct areas of the brain,” explains Florian Koppelstätter, who carried out the research with colleagues at the Medical University at Innsbruck, Austria.

What areas specifically?

“The group all showed activation of the working memory part of the brain," Koppelstätter explains. "But those who received caffeine had significantly greater activation in parts of the prefrontal lobe, known as the anterior cingulate and the anterior cingulate gyrus. These areas are involved in 'executive memory', attention, concentration, planning and monitoring."

There must be more to the effect of caffeine than that. Most of us know, for instance, that a common symptom of withdrawal from caffeine is headaches. What's with that? Adenosine recoptors?

Caffeine is known to influence adenosine receptors which are found throughout the brain on nerve cells and blood vessels. It is thought that the drug inhibits these receptors and that this excites the nerve cells in the brain. “This may be the mechanism involved,” suggests Koppelstätter.

Another story on this: The tall and the short of why caffeine works
Press release: Coffee Jump-starts Short-term Memory

Tags: caffeine, health, neuroscience

Science at Daily Kos

A political blog (the most heavily-trafficked one of all, it appears) seems an unlikely place to find serious science discussion. But Kos seems to have it.

Today, contributor DarkSyde put up a poll asking what science topics people would like to read about. The answers are interesting.

DarkSyde himself has already written a lot on the site that's of interest. He also contributes at Unscrewing the Inscrutable.

Planetary nebula M2-9

M2-9 with Adaptive Optics

Color composite adaptive optics image of the planetary nebula M2-9 using the ALTAIR adaptive optics system on Gemini North. This image reveals remarkable details in the dynamic gas outflows from a dying star. It is thought that our Sun might meet a similar fate in 4-5 billion years once its hydrogen nuclear fuel becomes scarce and instabilities expel gas into space. The concentric shells of gas are still a mystery to astronomers and these data will help to understand the complexities surrounding this beautiful object.

M2-9 -- Click for 640×640 image

More information: Stunning photo previews the death of our Sun

More evidence for dark energy

Back here we provided an overview of the topic of dark energy and some of the evidence for its existence.

Recently announced research results from a project known as the Supernovae Legacy Survey (SNLS) have now provided additional evidence for dark energy, and suggested that it is more likely that the dark energy is due to Einstein's cosmological constant than to an even more exotic possibility known as quintessence.

Was Einstein's 'biggest blunder' a stellar success?

The genius of Albert Einstein, who added a “cosmological constant” to his equation for the expansion of the universe but later retracted it, may be vindicated by new research.

The enigmatic dark energy that drives the accelerating expansion of the universe behaves just like Einstein's famed cosmological constant, according to the Supernova Legacy Survey (SNLS), an international team of researchers in France and Canada that collaborated with large telescope observers at Oxford, Caltech and Berkeley. Their observations reveal that the dark energy behaves like Einstein’s cosmological constant to a precision of 10 per cent.

“The significance is huge,” said Professor Ray Carlberg of the Department of Astronomy and Astrophysics at U of T. “Our observation is at odds with a number of theoretical ideas about the nature of dark energy that predict that it should change as the universe expands, and as far as we can see, it doesn’t.”

The basic difference between dark energy in the form of a cosmological constant or of quintessence is that the former yields a constant acceleration, while the latter produces ever increasing acceleration. The latter scenario is sometimes called the "big rip" because eventually it would cause even atoms, neutrons, and protons to burst apart.

By measuring the spectra of light from distant supernovae of a special type (known as Type 1a), it is possible to determine both the distance to a supernova and its velocity relative to Earth. Whether the acceleration of the universe's expansion is constant or increasing can be deduced from this data. The evidence is that the acceleration is constant, which rules out quintessence.

Further, when the acceleration data is combined with measurements of the cosmic microwave background (called "baryon acoustic oscillation"), it is possible to determine that the dark energy makes up about 75% of the total matter and energy in the universe.

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Additional resources:

Einstein's Dark Energy Accelerates the Universe -- Particle Physics and Astronomy Research Council press release

First results describing the nature of dark energy -- press release from the journal Astronomy & Astrophysics

Gemini's Nod-&-Shuffle Provides Critical Deep Spectroscopic Data for Supernova Legacy Survey -- contains a more technical description of the SNLS results

New Study of Supernovae May Absolve Einstein of Self-confessed "Biggest Blunder" -- Keck Observatory press release

The Supernova Legacy Survey: measurement of Ω_M, Ω_Λ and w from the first year data set -- original paper (PDF)

Canada-France-Hawaii Telescope Legacy Survey

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Tags: dark energy

Stem cells may reverse cancer

We noted here how stem cells may be implicated in the onset of cancer. Even more surprisingly, stem cells may be able to reverse cancer.

Stem Cell Microenvironment Reverses Malignant Melanoma

Northwestern University researchers have demonstrated how the microenvironments of two human embryonic stem cell (hESC) lines (federally approved) induced metastatic melanoma cells to revert to a normal, skin cell-like type with the ability to form colonies similar to hESCs. The researchers also showed that these melanoma cells were less invasive following culture on the microenvironments of hESCs.

"Our observations highlight the potential utility of isolating the factors within the hESC microenvironment responsible for influencing tumor cell fate and reversing the cancerous properties of metastatic tumor cells, such as melanoma," said Mary J. C. Hendrix, in whose laboratories at Children's Memorial Research Center the experiments were conducted.

Tags: stem cells, cancer

Excess cell signaling and cancer

Global Signaling Study Suggests Cancer Link To Protein Promiscuity

When found at abnormally high concentrations, two proteins implicated in many human cancers have the potential to spur indiscriminate biochemical signaling inside cells, chemists at Harvard University have found. Their finding may expand scientists' current understanding of oncogenesis -- that cancer arises when an oncoprotein becomes overactive, ramping up the biochemical pathways that it normally activates -- suggesting that an important additional mechanism could be the inappropriate activation of numerous secondary pathways.

"Our data offer a new way to think about cancer, adding to the current paradigm," says Gavin MacBeath, an assistant professor of chemistry and chemical biology in Harvard's Faculty of Arts and Sciences and co-author of a paper published in the journal Nature. "We present the hypothesis that an important component of oncogenesis is the ability of proteins to turn on alternative, secondary signaling pathways when overexpressed, rather than simply upregulating primary pathways."

Tags: cancer, oncogenesis

Stem cells may trigger bone cancer

Our bodies normally contain many types of stem cells, which are essential for generating many other types of cells, such as bone, blood, and skin. But by their very nature, since stem cells can turn into other types of body cells, there have been suspicions that stem cells may (although quite rarely) also become cancer cells.

Scientists say stem cells may trigger bone cancer

Stem cells may cause some forms of bone cancer, University of Florida scientists report.

The researchers are the first to identify a population of cells with characteristics of adult and embryonic stem cells in cultures derived from biopsies of patients’ bone tumors. They describe their findings in this month’s issue of the medical journal Neoplasia.

“We’re saying the cell of origin of these tumors may be very, very primitive,” said Dr. C. Parker Gibbs, an associate professor of orthopaedic oncology and a member of the UF Shands Cancer Center. Gibbs collaborated with several UF scientists, including Dennis A. Steindler, director of UF’s McKnight Brain Institute.

Researchers elsewhere already have implicated stem cells in the development of leukemia, and Steindler’s lab previously discovered stem-like cells in brain cancer. Others have identified these same cells in some breast cancers.

Tags: stem cells, cancer

Earliest Animals Had Human-like Genes

Earliest Animals Had Human-like Genes

Species evolve at very different rates, and the evolutionary line that produced humans seems to be among the slowest. The result, according to a new study by scientists at the European Molecular Biology Laboratory [EMBL], is that our species has retained characteristics of a very ancient ancestor that have been lost in more quickly-evolving animals.

What was surprising was this:

The genes of animals usually contain extra bits of DNA sequence, called introns – information which has to be removed as cells create new molecules. The number of introns in genes, however, varies greatly among animals. While humans have many introns in their genes, common animal models such as flies have fewer. From an evolutionary perspective, it was long assumed that the simpler fly genes would be more ancient. The current study reveals the opposite: early animals already had a lot of introns, and quickly-evolving species like insects have lost most of them.

Early Earth likely had continents

The conventional view has been that continents and other conditions similar to what we have today did not develop until the planet was 500 million years old, about 4 billion years ago. Since there is some evidence of the existence of life when Earth was 600 to 700 million years old, life would have had to arise very quickly. But now it appears that the first continents may have appeared much earlier:

Early Earth Likely Had Continents And Was Habitable, Says New Study

A surprising new study by an international team of researchers has concluded Earth's continents most likely were in place soon after the planet was formed, overturning a long-held theory that the early planet was either moon-like or dominated by oceans.

The team came to the conclusion following an analysis of a rare metal element known as hafnium in ancient minerals from the Jack Hills in Western Australia, thought to be among the oldest rocks on Earth. Hafnium is found in association with zircon crystals in the Jack Hills rocks, which date to almost 4.4 billion years ago.

More details from another press release:

There was no such thing as hell on Earth

The research, published in the latest edition of Science, follows on from results by Professor Harrison and his colleagues published earlier this year that confirmed that our planet was also likely to have had oceans during most of the Hadean.

“A new picture of early Earth is emerging,” Professor Harrison said. “We have evidence that the Earth’s early surface supported water – the key ingredient in making our planet habitable. We have evidence that this water interacted with continent-forming magmas throughout the Hadean.

“And now we have evidence that massive amounts of continental crust were produced almost immediately upon Earth formation. The Hadean Earth may have looked much like it does today rather than our imagined view of a desiccated world devoid of continents.”

The dating was accomplished by measuring percentages of different isotopes of hafnium in the zircons.

[H]afnium isotope variations produced by the radioactive decay of an isotope of lutetium indicate many of these ancient zircons formed in a continental setting within about 100 million years of Earth formation.

“The evidence points to almost immediate development of continent followed by its rapid recycling back into the mantle via a process akin to modern plate tectonics,” according to Professor Harrison.

Tags: Hadeon eon

First evidence of a living memory trace

What is a memory, physically, as it resides in the brain? Looks like there's progress finding out:

Scientists find first evidence of a living memory trace

An international team of scientists for the first time has detected a memory trace in a living animal after it has encountered a single, new stimulus. The research, done with honeybees sensing new odors, allows neuroscientists to peer within the living brain and explore short-term memory as never before, according to scientist Roberto Fernández Galán, a leading author on the report who is currently a postdoctoral research associate at Carnegie Mellon University.

What was it, exactly, that they found?

"Our findings show that an odor produces a memory trace of synchronized neural activity that lasts several minutes after a bee initially senses it," said Galán. "This is the first time anyone has revealed a short-term, stimulus-specific neural pulse within the living brain that occurs after exposure to a previously unknown stimulus."

Tags: memory, memory trace

Videoconferencing on steroids

It's hard to say how long the idea of a "telephone" that could carry visual images as well as voices has been around, but experimental implementations of videophones have existed since the early 1960s. Nevertheless, even today ordinary people are unable to buy such a thing that works over existing telephone lines.

But we're getting a lot closer. Elaborate (and expensive) implementations of a slight generalization of the idea, in the form of videoconferencing, have been done since the late 1960s. The idea here is to tie together TV cameras and video screens over some sort of connection with sufficiently high bandwidth that make it possible to hold virtual meetings among a number of people which approximate the experience of being in the same room. The approximations are getting better and better, and are available to any group -- mainly businesses -- that can afford them.

Thanks to the Internet and cheap personal computers -- using inexpensive video cams and broadband network connections -- the functional equivalents of videophones are finally available to the general public. Even if such video chats are not yet quite as simple to use as ordinary telephones. But with the rapid spread of voice over IP just about to happen, we're almost there.

The experience of using such a system is still not quite like being in the same room with others. For instance, one has to look into a camera to give the other person the illusion of eye contact, and in the process losing one's own subjective feeling of eye contact. And there remain problems of latency and lack of smooth motion in less expensive systems.

But things are getting pretty good at the high end:

Together across a continent: Bridging time and place with 'Shared Spaces'

"Modern videoconferencing hasn't worked well as it doesn't allow you to interrupt one another and has never managed to support the quality of interaction that people experience in real life. We wanted to change that," says John Roston, director of Instructional Multimedia Services at McGill University.

"Our technology provides a life-size, high-definition view on a large panoramic screen, which gives users the impression that they're talking to people in the same room with a window between them," adds Professor Jeremy Cooperstock of the Department of Electrical and Computer Engineering.

It's interesting to think about how such systems will impact our lives when they become generally available. For instance, it will become posible to have regular virtual visits with friends and relatives anywhere in the world (subject to time zone differences). We will be able to schedule an evening (or morning, or afternoon) with people we like who live across a continent or an ocean as easily as we do now with friends in the next town. Even easier, in one important respect, as there will be no time wasted in travel. (More bad news for the airlines.)

Will we finally shuck off our thralldom to the boob tube if real, live people we like are as accessible as the latest TV sitcom characters? (The advertising industry will be further devastated.) Or, on the downside, will we discover that our friends and relatives actually aren't as interesting as fictional characters on TV?

In another direction, what will happen with colleges and universities when it becomes possible to "sell" individual lectures by expert faculty members to students anywhere in the world? Will institutions of higher education prosper, or will they flounder as their best faculty go freelance and earn a lot more without the overhead expenses of physical campuses and administrative staffs? Will domestic educators and educational institutions suffer in the same way as other service businesses when their jobs are outsourced to India? What new mechanisms will evolve to certify that students in such a very "open university" have mastered the contents of a particular course?

It's going to be really interesting to watch what actually develops as basic -- and eventually more advanced -- forms of teleimmersion become widespread.

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Update, December 18, 2005 -- Story about a presently-available videoconferencing system: Videoconference system creates boardroom illusion

Tags: videoconference, video chat, teleimmersion

Evolution books

Here's a great reading list of evolution books for young and old from Pharyngula - An updated book list for evolutionists.

And if that's not enough to fill your wish list or your gift list, here are some more books on biology amd medicine for your holiday shopping pleasure: Holiday Reading: Science Books

String theory vs. intelligent design

What's the most controversial scientific theory today?

Quite possibly it's superstring theory. What about the theory of evolution? Or global warming? Nope. They are hardly controversial at all scientifically, and only controversial outside of science because of their political or philosophical ramifications.

While there are still many open questions and details yet to be worked out in evolution and global warming, the scientific evidence for both is now very strong, and growing stronger all the time.

The evidence for superstring theory, on the other hand, is non-existent, and that is generally accepted, even by supporters of the theory. Why, then, does it even have supporters? Because of its elegance and its potential to answer the deepest questions of physics, especially: What is the relation between quantum theory and general relativity?

One of the original developers of string theory, Leonard Susskind, has a new book coming out: The Cosmic Landscape : String Theory and the Illusion of Intelligent Design. Ironically (perhaps), as the title suggests, there are interesting parallels between string theory and the totally unscientific nonsense known as "intelligent design". These parallels involve closely related and controversial topics, including the "anthropic principle" and Susskind's notion of "the landscape".

Here is one nontechnical overview of some of these topics: String Theory Versus Intelligent Design by Kenneth Silber (via Luboš Motl's reference frame).

There's a heck of a lot more material to present on these topics... This is an ongoing story that probably isn't going to lead to a conclusion anytime soon.

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References:

Superstringtheory.com - the "official" string theory Web site

Superstring theory - a history and overview

Is string theory even wrong? - a critical view

Leonard Susskind on "the landscape" - article at Edge

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Tags: superstrings, superstring theory, landscape, anthropic principle

Most detailed image of the Crab Nebula

Most detailed image of the Crab Nebula

The Crab Nebula is a six-light-year-wide expanding remnant of a star’s supernova explosion. Japanese and Chinese astronomers witnessed this violent event nearly 1,000 years ago in 1054.

The filaments are the tattered remains of the star and consist mostly of hydrogen. The rapidly spinning neutron star embedded in the centre of the nebula, only barely visible in this Hubble image, is the dynamo powering the nebula’s eerie interior bluish glow. The blue light comes from electrons whirling at nearly the speed of light around magnetic field lines from the neutron star. The neutron star, like a lighthouse, ejects twin beams of radiation that appear to pulse 30 times a second due to the neutron star's rotation. A neutron star is the crushed ultra-dense core of the exploded star.

Crab Nebula -- click for 1280×1280 image

Tags: Crab Nebula

RNA splicing occurs in nerve-cell dendrites

A single gene is capable of directing the production of a number of different proteins. This is because each gene consists of regions ("exons") that code for amino acids that make up a protein, and other regions ("introns") that do not. Initially a gene is transcribed into RNA. But before this RNA is used to construct a protein, the introns are removed in a process called "splicing". Exons may be removed, as well, before the final messenger RNA is complete. Variant forms of the messenger RNA result depending on which exons are removed.

Normally this splicing process occurs in the nucleus of a cell. But new research shows that it can also occur in the parts of nerve cells known as "dendrites", which receive incoming signals from other nerve cells. It may be that the production of variant proteins from a single gene affects the strength of connections between nerve cells, and hence is involved in the processes of learning and memory.

RNA splicing occurs in nerve-cell dendrites

Protein diversity is a key aspect to the complexity of the central nervous system. Proteins are the workhorses of the cell and are generally responsible for insuring that cells function properly. When proteins interact with one another they can elicit specific physiological responses, including the generation and maintenance of memories. Changing protein identity, as can occur with splicing, can change the ability of the protein to interact with other proteins and therefore potentially change such physiological processes. With the dendrite being the initial site in the neuron where learning is thought to occur, the ability to create a diversity of mRNAs, through local splicing, and subsequent protein translation may permit exquisitely sensitive control of these cellular functions.

Tags: RNA splicing

Did More Endorphins Make Us Human?

We may be getting closer to understanding some of the evolutionary changes that occurred between humans and our last common ancestor with chimpanzees. Surprisingly, it could involve changes in gene regulation, rather than in genes themselves. And even more surprisingly, one of the genes involved seems to be one for an opium-like protein.

"Perception" gene tracked humanity's evolution, scientists say

BLOOMINGTON, Ind. -- A gene thought to influence perception and susceptibility to drug dependence is expressed more readily in human beings than in other primates, and this difference coincides with the evolution of our species, say scientists at Indiana University Bloomington and three other academic institutions. Their report appears in the December issue of Public Library of Science Biology.

The gene encodes prodynorphin, an opium-like protein implicated in the anticipation and experience of pain, social attachment and bonding, as well as learning and memory.

"Humans have the ability to turn on this gene more easily and more intensely than other primates," said IU Bloomington computational biologist Matthew Hahn, who did the brunt of the population genetics work for the paper. "Given its function, we believe regulation of this gene was likely important in the evolution of modern humans' mental capacity."

Another news story on this: Did More Endorphins Make Us Human? (may require registration)

Gravitational waves

Nice BBC article:

Science to ride gravitational waves

The real aim is to have a new means of studying the Universe - to trace its exotic phenomena in detail in a way that does not rely on light.

"The analogy I like is this: imagine being able to see the world but you are deaf, and then suddenly someone gives you the ability to hear things as well - you get an extra dimension of perception," explains Professor Bernard Schutz from the Albert Einstein Institute and Cardiff University.

"Up until now we've only been able to see the Universe with our telescopes, but with gravitational waves we will be able to hear it as well; and that's going to convey a different type of information.

"Most of the Universe cannot emit electromagnetic waves - we will never see it with light. But we can see it, or parts of it, with gravitational waves."

Tags: gravitational waves