Wednesday, June 30, 2010

Lost Cities of the Amazon - “Nature Folk”

The most famous person to go looking for lost civilizations in the southern Amazon was Percy Harrison Fawcett. The British adventurer scoured what he called the “uncharted jungles” for an ancient city, Atlantis in the Amazon, replete with stone pyramids, cobbled streets and alphabetic writing. His tales inspired Conan Doyle’s The Lost World and perhaps the Indiana Jones movies. David Grann’s gripping recent book, The Lost City of Z, retraced Fawcett’s path before his disappearance in the Xingu in 1925.

Actually, five German expeditions had already visited the Xinguano people and lands. In 1894 Karl von den Steinen’s book Unter den Naturvölkern Zentral Brasiliens, which described the earliest expeditions, became an instant classic in the fl edgling discipline of anthropology. The book set the tone for 20th-century studies of Amazonian peoples as small, isolated groups living in a delicate balance with the tropical forest: “nature folk.” Later anthropologists often viewed the forest environment as uniformly inimical to agriculture; the soil’s poor fertility seemed to preclude large settlements or dense regional populations. By this reasoning, the Amazon of the past must have looked much like the Amazon in recent times.

But this view began to erode in the 1970s as scholars revisited early European accounts of the region, which talked not of small tribes but of dense populations. As Charles Mann’s best-selling book 1491 has eloquently described, the Americas were heavily populated on the eve of the European landings, and the Amazon was no exception. Gaspar de Carvajal, the missionary who chronicled the first Spanish expedition down the river, noted fortifi ed towns, broad, well-kept roads and large numbers of people. Carvajal wrote on June 25, 1542:

We went among some islands which we thought uninhabited, but after we got to be in among them, so numerous were the settlements which came into sight … that we grieved ... and, when they saw us, there came out to meet us on the river over two hundred pirogues [canoes], that each one carries twenty or thirty Indians and some forty . . . they were colorfully decorated with various emblems, and they had with them many trumpets and drums . . . and on land a marvelous thing to see were the squadron formations that were in the villages, all playing instruments and dancing about, manifesting great joy upon seeing that we were passing beyond their villages.

Archaeological research in several areas along the Amazon River, such as Marajó Island at the mouth of the river and sites near the modern cities of Santarém and Manaus, has confirmed these accounts. These societies interacted in far-flung systems of trade. Less is known about the southern peripheries of the Amazon, but recent work in Llanos de Mojos in lowland Bolivia and in the Brazilian state of Acre suggests that they, too, supported complex societies. In 1720 Brazilian frontiersman António Pires de Campos described a densely settled landscape in the headwaters of the Tapajós River, just west of the Xingu:

These people exist in such vast quantity, that it is not possible to count their settlements or villages, [and] many times in one day’s march one passes ten or twelve villages, and in each one of them there are ten to thirty houses, and in these houses there are some that are thirty to forty paces across . . . even their roads they make very straight and wide, and they keep them so clean that one finds not even a fallen leaf. . . .

Source of Information : Scientific American October 2009

Tuesday, June 29, 2010

Lost Cities of the Amazon

The Amazon tropical forest is not as wild as it looks

When Brazil established the Xingu Indigenous Park in 1961, the reserve was far from modern civilization, nestled deep in the southern reaches of the vast Amazon forest. When I first went to live with the Kuikuro, one of the reserve’s principal indigenous groups, in 1992, the park’s boundaries were still largely hidden in thick forest, little more than lines on a map. Today the park is surrounded by a patchwork of farmland, its borders often marked by a wall of trees. For many outsiders, this towering green threshold is a portal, like the massive gates of Jurassic Park, between the present—the dynamic modern world of soy fields, irrigation systems and 18-wheelers—and the past, a timeless world of primordial nature and society.

Long before taking center stage in the world’s environmental crisis as the giant green jewel of global ecology, the Amazon held a special place in the Western imagination. Mere mention of its name conjures images of dripping, vegetationchoked jungles; cryptic, colorful and often dangerous wildlife; endlessly convoluted river networks; and Stone Age tribes. To Westerners, Amazonian peoples are quintessential simple societies, small groups that merely make do with what nature provides. They have complex knowledge about the natural world but lack the hallmarks of civilization: centralized government, urban settlements and economic production beyond subsistence. In 1690 John Locke famously proclaimed, “In the beginning all the World was America.” More than three centuries later the Amazon still grips the popular imagination as nature at its purest, home to native peoples who, in the words of Rolling Stone editor Sean Woods in October 2007, preserve “a way of life unchanged since the dawn of time.”

Looks can be deceiving. Hidden under the forest canopy are the remnants of a complex pre-Columbian society. Working with the Kuikuro, I have excavated a network of ancestral towns, villages and roads that once supported a population perhaps 20 times its present size. Huge swaths of forest have grown over the ancient settlements, gardens, fields and orchards, which fell into disuse when epidemics brought by European explorers and colonists decimated the native peoples. The region’s rich biodiversity reflects past human intervention. By developing a mix of land uses, soil-enrichment techniques and long crop rotation cycles, the ancestors of the Kuikuro thrived in the Amazon despite its infertile natural soils. Their accomplishments could inform efforts to reconcile the environmental and development goals of this region and other parts of the Amazon.

To most people, the Amazon forest is the quintessential case of pure nature slowly being destroyed as humans intrude. In fact, what seems pristine has itself been shaped by humans. In some areas the forest is secondary growth that took hold when native peoples were wiped out by their encounters with Europeans. The author and his colleagues have found extensive pre-Columbian ruins. Communities had a self-similar or fractal structure in which houses, settlements and clusters of settlements were organized in similar ways. Thus, the history of the Amazon is rather more interesting than usually thought. The environmental challenge is not only to preserve unspoiled wilderness but also to recover the techniques of sustainable farming and forestry that the ancestors of the region’s present inhabitants developed.

Source of Information : Scientific American October 2009

Monday, June 28, 2010

Prospects for enhancers

Drugmakers have plans to counter various forms of dementia, ranging from that found in alzheimer’s disease to the common memory loss that occurs with aging (age-associated memory impairment). These compounds, a selection of which are included here and many of which have yet to reach late-stage clinical trials, might eventually be used by healthy people who want to improve mental functioning, although questions remain about how safe or effective they would be for people without a cognitive deficit.

Drug Class: Nicotinic acetylcholine receptor activators. Either increase levels of the neurotransmitter acetylcholine in the synapse of a neuron, or the drugs themselves take the place of acetylcholine in the synapse to activate the nicotinic acetylcholine receptor, enhancing attention, memory and other facets of cognition. Developer: Abbott, CoMentis, EnVivo, Targacept/AstraZeneca and Xytis.

Drug Class: Ampakines. Act on AMPA receptors to strengthen neuronal responses to the neurotransmitter glutamate, activity that should facilitate the laying down of long-term memories. Developer: Cortex Pharmaceuticals; Eli Lilly, GlaxoSmithKline/ Neurosearch, Organon, Pfizer and Servier.

Drug Class: Phosphodiesterase (PDE) Inhibitors. One type of PDE blocker enables a signaling molecule, cyclic AMP, to remain active longer in brain neurons, thereby enhancing the activity of a protein called CREB that is important to long-term memory. Developer: Helicon Therapeutics, Hoffmann–La Roche and Merck.

Drug Class: Antihistamines. Block a histamine receptor called the H3 receptor, thereby improving wakefulness, attention and cognition. One drug that interacts with the H1 receptor, developed as a treatment for hay fever in Russia, has entered late-stage clinical trials as an enhancer. Developer: GlaxoSmithKline, Johnson & Johnson and Medivation/Pfi zer.

Source of Information : Scientific American October 2009

Sunday, June 27, 2010

Turbocharging the Brain - The Always-On Drug

The checkered legacy of amphetamines prompted neuroscientists and physicians to hail the arrival of modafi nil as a wakefulness-promoting agent with a seemingly more favorable side effect and abuse profile than the amphetamines. The ability of modafi nil (introduced in the U.S. in 1998) to allow people to work long stretches without the need for breaks has turned it into a lifestyle drug for the jet-lagged who attempt to live in four time zones at once.

Jamais Cascio, an associate of the Institute for the Future in Palo Alto, Calif., obtained a prescription for modafi nil from his physician after hearing about it from friends who traveled a lot. On trips overseas, he noticed that it made him feel not only more awake but also sharper. “The perceived increased cognitive focus and clarity was very much of a surprise, but it was a very pleasant surprise,” says Cascio, who has mentioned the drug in some articles he has written. “My experience was not that I’d become a superbrain.
It was more an experience of more easily slipping into a state of cognitive flow, a state of being able to work without distraction.”

Testing has confi rmed some of Cascio’s impressions. In 2003 Sahakian and Robbins found that 60 rested, healthy male volunteers did better on a few neuropsychological measures, such as recall of numerical sequences, but results were unchanged on others. Investigators elsewhere have also found benefi ts for the drug, although, as Cascio noted, it will not make a dunce into a genius. None of these studies, moreover, has tested effects on cognition over extended periods.

Unregulated availability of either modafi nil or methylphenidate also remains unlikely because the drugs tend to affect individuals in different ways. Users with lower IQs appear to derive a large performance boost from modafi nil, whereas those with more innate ability show little or no benefit. With methylphenidate, those having poor working memory improved when tested; those having a naturally higher memory capacity showed much smaller benefits.

As with amphetamines, modafi nil did not emerge from a basic understanding of the underlying biology of how the brain works. Present research shows, however, that the drug seems to involve multiple neurotransmitters, the chemicals that trigger the firing of specific clusters of neurons. The drug’s exact mechanism remains to be elucidated. But recently Nora D. Volkow, director of the National Institute on Drug Abuse, and her colleagues discovered that one of those neurotransmitters is dopamine, the same chemical that is boosted by amphetamines and that imbues those drugs with their addiction potential. “It appears that methylphenidate and modafi nil are very similar in what they’re doing to the dopamine system in the brain, contrary to what was believed,” says Volkow, although she adds that it is not practical to smoke or ingest modafi nil to produce a strong high, so the possibility of abuse is lower. Another roadblock to wider use appeared in 2006, when the FDA rejected the drug as a treatment for ADHD in children because of reports about serious skin rashes.

Repackaging old attention-boosting drugs as cognitive enhancers for students, executives and software programmers may produce only marginal benefits over consuming a double espresso. The question of what exactly is an enhancer has prompted the convening of a group within the American College of Neuropsychopharmacology to discuss the standards that any drug should meet to be classified as a cognitive booster. Ultimately, enhancement drugs may come from another sphere of research. Insights into how we translate a baby’s image or a friend’s name into lasting memories has laid the groundwork for new drugs specifically designed to achieve better functioning in people with Alzheimer’s or other dementias.

Optimism about a new generation of pharmaceuticals derives in part from advances in basic research into the biochemical processes underlying memory formation. More than 30 types of gene-altered mice have demonstrated the ability to both acquire information and store it in longterm memory better than the average mouse. “This is the first time in the history of neuroscience that we have the backbone of the molecular and cellular biology of memory,” says Alcino J. Silva, a neurobiologist at the University of California,
Los Angeles. “What this means for society is that for the fi rst time we can use it to start changing how we learn and remember.”

But truly effective memory drugs are probably a long way off, in part because of the scientific challenges. Most of the 200 gene mutations introduced into mice by researchers worldwide caused deficits. Silva remembers one mouse in his laboratory that illustrated the possible tradeoffs that researchers will confront during development of a cognitive enhancer. The animals learned faster than normal, unaltered mice but were unable to complete an elaborate puzzle administered by the investigators. “If you taught them something simple, they acquired it fast, but for anything more complicated, they couldn’t acquire it,” Silva says. He estimates that it may take decades before drugs from this research are routinely used.

The logistical challenges are daunting as well. Several of the fi rst companies to enter the fray, including ones founded by leading academics, have faltered. In 2004 Science magazine cited four new firms—Sention, Cortex Pharmaceuticals, Memory Pharmaceuticals and Helicon Therapeutics—as exemplars of a trend. Sention went out of business. Cortex is ailing and desperately seeking a partner. Last year Hoffmann–
La Roche purchased at a penny-stock price (less than $1) Memory, co-founded by Nobelist Kandel, after it had experienced layoffs and a number of failed clinical trials. Helicon has survived because of the largesse of billionaire Kenneth Dart, the Styrofoam cup magnate, who was enticed by the prospect of memory drugs—the company has been developing a drug that would modulate a pathway related to glutamate, a neurotransmitter that triggers an intricate cellular signaling path related to the formation of longterm memories.

A sister company, Dart NeuroScience, now handles development of new drug candidates, leaving the job of conducting clinical trials to Helicon. So far Helicon has received more than $100 million in funding but has yet to reach latestage clinical trials for any of its drug candidates. “The way I like to explain this to audiences when I give talks is that when Helicon was formed I thought that I was making memory enhancers for my parents and I had no gray hair,” says Tim Tully, Helicon’s chief scientific officer, who co-founded the company when he was at Cold Spring Harbor Laboratory. “They’re now dead, I’m fully gray, and I’m fully cognizant of the fact that this is a race for me not them.”

Tully, 55, adds that he does not foresee his creations ever becoming the next Viagra or Prozac. “What the media loves to totally ignore is the side-effect potential and jump right to the wild speculation of this as a lifestyle drug,” Tully says. “And I think it’s just missing the mark. The reality is that if you’ve got a debilitating form of memory impairment these drugs may be helpful, but they’re probably going to be too dangerous for anyone else.”

Despite these cautionary tales, drugmakers continue trying to develop cognitive enhancers for Alzheimer’s and other dementias. Among the compounds under consideration are ones that alter the effects of neurotransmitters other than glutamate — including receptors switched on by the nicotine in tobacco (though not the one linked to addiction). One of the reasons that people smoke is because nicotine helps to sharpen attention.

Lessons learned from drugs developed for dementia could lead to agents that ease the milder cognitive problems associated with normal aging, assuming these compounds do not arrive burdened with intolerable side effects. If sufficiently benign, these pills could find their way into college dorms or executive suites. “Within the pharmaceutical fi eld, people recognize that a successful cognitive enhancer could be the bestselling pharmaceutical of all time,” says Peter B. Reiner, a professor of neuroethics at the University of British Columbia.

Source of Information : Scientific American October 2009

Saturday, June 26, 2010

Turbocharging the Brain - A Checkered History

The notion that existing drugs might enhance cognition in the healthy dates back for the better part of a century and has produced ambiguous results. Chemist Gordon Alles introduced am phetamine for medical use in 1929, a synthetic drug chemically similar to the Chinese herb ephedrine. (Alles also devised the drug Ecstasy, another amphetamine.) Various forms were dispensed on both sides during World War II to keep soldiers awake and alert and to bolster courage. The Germans and Japanese ingested methamphetamine, while the British and Americans used Benzedrine, a similar drug to Adderall.

Scientists soon wanted to know whether the perceived benefit in performance was genuine. Psychological assessments by both British and Americans during the 1940s found that users self-rated their performance highly on tests that measured reading speed, multiplication and other factors. But their test scores, in most tasks, were no better than those earned by subjects who ingested caffeine. Performance, in fact, could decline on more complex tasks. “Because of their mood-elevating effects, amphetamines tend to make us feel we are performing especially well, when in fact we are not,” says Nicolas Rasmussen, a historian of science at University of New South Wales in Sydney and author of the book On Speed (New York University Press, 2008). “In simplistic lab tests assessing performance on boring tasks, they boost scores by increasing diligence, but that’s not the same as taking a law school exam or flying in combat.”

Methylphenidate, a close chemical relative of the amphetamines, emerged in 1956 as a supposedly milder and gentler form of stimulant (“the happy medium in psychomotor stimulation,” in the words of the drugmaker), but both its biochemical and psychological effects are similar when adjusted for dose. The halcyon era for amphetamines occurred nearly 40 years ago. U.S. consumption reached as much as 10 billion pills in the late 1960s before the Food and Drug Administration clamped down and labeled them as controlled substances that required a special prescription. Neuroscientist Michael S. Gazzaniga of the University of California, Santa Barbara, one of the authors of the Nature commentary, remembers his father sending him Benzedrine for studying when he was in college in the early 1960s.

In the mid-1990s the growing use of methylphenidate for treatment of ADHD prompted researchers to deploy novel brain-imaging techniques and sophisticated neuropsychological tests to examine effects of the drug in healthy subjects, supplying a baseline for comparison with patients with ADHD and other neuropsychiatric disorders. A 1997 paper in Psychopharmacology by Barbara Sahakian, Trevor Robbins and their colleagues at the University of Cambridge showed that methylphenidate improved cognitive performance on several measures (spatial working memory and planning, in particular) in a group of rested, healthy young males but not on others, including attention and verbal fluency. As testing progressed, the volunteers seemed to make more errors in their responses, perhaps because of impulsivity induced by effects of the drug.

The same researchers found little cognitive benefit in healthy elderly males. And in 2005 a group at the University of Florida Medical School at Gainesville could not turn up any cognitive boost from the drug among 20 sleepdeprived medical students. Another impediment to methylphenidate ever being placed alongside NoDoz and other caffeine pills is its potential for causing cardiac arrhythmias and for abuse as a recreational drug. Addiction is rare with normal dosing. But in the 1970s methylphenidate users routinely became addicted after inhaling or injecting the drug that they called “West Coast.”

Source of Information : Scientific American October 2009

Friday, June 25, 2010

Turbocharging the Brain - Ethical Dissonance

Arguments about safety, fairness and coercion aside, demand is indeed high for cognitive enhancers that are otherwise prescribed for conditions such as ADHD. Based on government data gathered in 2007, more than 1.6 million people in the U.S. had used prescription stimulants nonmedically during the previous 12 months. Legal medicines in this category include methylphenidate (Ritalin), the amphetamine Adderall, and modafi nil (Provigil). On some campuses, one quarter of students have reported using the drugs. And an informal on line reader survey by Nature last year showed 20 percent of 1,427 respondents from 60 countries polled about their own use said they had used either methylphenidate, modafi nil or beta blockers (the last for stage fright). Overall, a need for improved concentration was the reason cited most frequently. People often manage to ac quire the drugs on the Internet or from doctors, who can prescribe medicines approved for one purpose to treat something else (drugmakers, however, cannot legally promote such “off label” uses).

Ingestion of these chemicals will likely grow along with an aging population and an increasingly globalized economy. “If you’re a 65-yearold living in Boston and your retirement savings have decreased dramatically and you have to stay on the job market and compete with a 23-yearold in Mumbai to stay alert and stay effective, you may feel pressured to turn to these compounds,” says Zack Lynch, executive director of the Neurotechnology Industry Organization.

The recent push for ethical guidelines, of course, presumes that these drugs are better than placebos and do in fact improve some aspect of cognition, be it attention, memory or “executive function” (planning and abstract reasoning, for instance). Given that assumption, many argue, it behooves ethicists to consider the ramifi cations of the popularity of these drugs. Such logic led in 2002 to a new academic discipline, neuroethics, meant in part to address the moral and social questions raised by cognition-enhancing drugs and devices (brain implants and the like).

Taking a highly provocative stand, a group of ethicists and neuroscientists published a commentary in Nature last year raising the prospect of a shift away from the notion of drugs as a treatment primarily for illness. The article suggested the possibility of making psychostimulants widely available to the able-minded to improve performance in the classroom or the boardroom, provided the drugs are judged to be safe and effective enough for healthy people. Citing research demonstrating the benefits of these drugs on memory and various forms of mental processing, the investigators equated pharmaceutical enhancement with “education, good health habits, and information technology— ways that our uniquely innovative species tries to improve itself.”

Six months later one of the article’s authors, John Harris, a bioethicist at the University of Manchester in England, went further in an opinion piece in the British Medical Journal. Harris, editor of the Journal of Medical Ethics and a book called Enhancing Evolution, noted that if methylphenidate is judged safe enough to be used in children, it should be considered sufficiently innocuous for consumption by adults interested in turbocharging their brains. In a later interview, Harris said he foresaw a gradual loosening of restrictions, and if no safety problems arise, the drug (a controlled substance in the U.S.) could ultimately become an over-the-counter purchase, like aspirin.

These musings have not gone unchallenged. Other researchers and ethicists have questioned whether drugs that modulate mental processes will ever have a safety profi le that will justify their being dispensed in the same fashion as a nonprescription painkiller or coffee or tea.

“People say that cognitive enhancement is just like improving vision by wearing glasses,” says James Swanson, a researcher at the University of California, Irvine, who was involved with clinical trials for both Adderall and modafi nil for ADHD. “I don’t think people understand the risks that occur when you have a large number of people accessing these drugs. Some small percentage will likely become addicted, and some people may actually see mental performance decline. That’s the reason I’m opposed to their general use.” Along these lines, the British Home Office, the interior ministry, is awaiting a report from an advisory panel on whether the potential harm from nonmedical use of enhancers requires new regulations.

Other scientists assert that the debate may be moot because improving smarts might not be possible through any means but the tedious exercise of cramming for a calculus exam. Some who have tried to develop drugs to reverse the memory loss of dementia doubt whether enhancement of the healthy is anything but a remote possibility. “I would not worry much about implications of cognitive enhancers in the healthy, because there are no cognitive enhancers to worry about,” says Rusiko Bourtchouladze, author of a popular book about the science of memory and a researcher who contributed to the work that led to a Nobel Prize for Eric R. Kandel in 2000. “To talk about cognitive enhancement, it’s too, too early, and these drugs may not arrive even in our lifetime. There’s too much noise about this.”

In this view, the complex mix of chemical signals, enzymes and proteins that collaborate to form a memory creates a self-regulating balance that resists tinkering unless disrupted by disease. The decline in thought processes and sense of identity that comes with dementia might be addressable by compensating for losses of key chemicals and might merit the risk of untoward side effects from drug intervention. But upsetting the fragile stasis in the healthy could produce unintended consequences: as just one example, any improvement in long-term memory (the place where recollections of childhood and last year’s vacation reside) could be countered by diminished capacity for working memory (the mental scratch pad where your brain stores a telephone number temporarily).

Some critics of those who argue over the ethics of neuroenhancement attribute the current flap to what they call “speculative ethics.” This tendency also besets nanotechnology and other technological endeavors in which ethicists, scientists and policy makers are diverted by discussions of the social implications of technologies yet to be invented, be they smart pills or nanorobots run amok. “A signifi cant part of the debate on human enhancement ... suffers from inflated expectations and technology hype,” notes Maartje Schermer of Erasmus University Rotterdam and her colleagues in the journal Neuroethics.

Source of Information : Scientific American October 2009

Brain boosters. Really?

The scientific literature and popular press commonly cite the medicines below approved for neurological disorders—as having potential to improve mental functioning in unimpaired people. The evidence is decidedly mixed, however, and even if the drugs do prove helpful, their risks may keep the agents from gaining approval by regulators for marketing to healthy individuals.

Methylphenidate (Ritalin, Concerta and others) and amphetamines (Adderall and others). Stimulants used for treatment of attention-deficit hyperactivity disorder (ADHD) and narcolepsy (uncontrollable sleep spells). Increase cognitive performance on certain tasks under conditions of fatigue; may improve planning and one type of working memory; appear to increase functioning on dull, repetitive tasks. Could worsen performance in a subset of users or on complex tasks; cardiovascular complications and seizures, hallucinations and addiction.

Modafinil (Provigil). Newer-generation stimulant for narcolepsy and excessive sleepiness because of shift work or obstructive sleep apnea. Appear to augment mental focus and better performance on a limited set of cognitive measures, such as recall of long strings of numbers. May have a higher potential for addiction than originally thought; may cause serious skin rashes.

Donepezil (Aricept). Treatment for the cognitive defi cits of Alzheimer’s disease; increases the neurotransmitter acetylcholine to improve cognition. Might aid in learning or memory, but overall results are equivocal; may take several weeks to work and is not as widely used off-label as the drugs above. Could cause a slight deterioration in cognitive performance in healthy individuals.

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Source of Information : Scientific American October 2009

Thursday, June 24, 2010

Turbocharging the Brain

Will a pill at breakfast improve concentration and memory—and will it do so without long-term detriment to your health?

The symbol H+ is the code sign used by some futurists to denote an enhanced version of humanity. The plus version of the human race would deploy a mix of advanced technologies, including stem cells, robotics, cognitionenhancing drugs, and the like, to overcome basic mental and physical limitations. The notion of enhancing mental functions by gulping down a pill that improves attention, memory and planning—the very foundations of cognition—is no longer just a fantasy shared by futurists. The 1990s, proclaimed the decade of the brain by President George H. W. Bush, has been followed by what might be labeled “the decade of the better brain.”

Obsession with cognitive enhancers is evidenced in news articles hailing the arrival of what are variously called smart drugs, neuroenhancers, nootropics or even “Viagra for the brain.” From this perspective, an era of enhancement has already arrived. College students routinely borrow a few pills from a friend’s Ritalin prescription to pull an all-nighter. Software programmers on deadline or executives trying to maintain a mental edge gobble down modafinil, a newer generation of pick-me-ups. Devotees swear that the drugs do more than induce the wakefulness of a caramel macchiato, providing instead the laserlike focus needed to absorb the nuances of organic chemistry or explain the esoteric of collateralized debt obligations.

An era of enhancement may also be advanced by scientists and drugmakers laboring to translate research on the molecular basis of cognition into pharmaceuticals meant specifically to improve mental performance—mainly for people suffering from dementias. But a drug that works for Alzheimer’s or Parkinson’s patients might inevitably be prescribed by physicians far more broadly in an aging population with milder impairments. Widely publicized debates over the ethics of enhancement have reinforced the sense that pills able to improve cognition will one day be available to us all.

Academic and news articles have asked whether cognitive enhancers already give some students an unfair advantage when taking college entrance line if they required ingestion of these chemicals to meet a company’s production deadlines.

But even as articles are published on the “boss turns pusher,” doubts have arisen about the reality of drugs for strengthening brainpower. Do current drugs developed for attention problems or excessive sleepiness really allow a student to do better on an exam or an executive to perform flawlessly under sharp questioning from a board of directors? Will any drug that fiddles with basic brain functions ever be safe enough to be placed on pharmacy shelves alongside nonprescription pain relievers and antacids? All these questions are now provoking heated deliberations among neuroscientists, physicians and ethicists.

Key Conce pts
College students and executives ingest stimulant drugs to enhance routine mental performance, although the compounds were never approved for that purpose.

Some ethicists and neuroscientists have raised the prospect of making these drugs widely available for enhancement of healthy people who do not suffer from dementia.

Questions remain about whether any drug that tinkers with basic mental functioning will be sufficiently safe and effective to be consumed like coffee or tea

Source of Information : Scientific American October 2009

Wednesday, June 23, 2010

The Way the Wind Blows

The wind power industry requires stiff gusts. Global warming may not deliver

This summer scientists published the first study that comprehensively explored the effect of climate change on wind speeds in the U.S. The report was not encouraging. Three decades’ worth of data seemed to point to a future where global warming lowers wind speeds enough to handicap the nascent wind industry. But the real story, like so much in climate science, is far more complex.

The study of decreased wind speeds came from a team led by Sara Pryor, professor and chair of the atmospheric science program at Indiana University. It examined wind speed data from hundreds of locations across the U.S. The team attempted to correct for any change in instrument position (such as what would happen if an airport places its anemometer atop a new control tower) and calculated for each site the average annual wind speed. Pryor and her colleagues found that in most of the U.S. wind speeds appear to be waning, in many locations by more than 1 percent a year.

The decline has the potential to be especially pernicious because turbines are exponentially sensitive to changes in wind speed. If the wind blows just 15 percent faster, a turbine will produce 50 percent more power. Conversely, a drop in average wind speed will significantly reduce the power output. Most of the locations that showed the most prominent decreases in wind speeds are strung along a corridor stretching from Texas to the Great Lakes that is home to 60 percent of the nation’s installed wind power.

Yet the situation may not be as dire as the data imply. Direct observations of wind speeds are inherently problematic. Anemometers are far less accurate and consistent than thermometers, Pryor says. In addition, almost all the locations used in the study are close to fast-growing urban areas that can alter wind patterns in unpredictable ways. And unlike temperature measurements, which in some locations stretch back 150 years, relatively accurate and widespread wind measurements began only in the 1970s—hardly enough time to pluck a subtle trend out of noisy data.

Because direct measurements of wind speeds are so unruly, Pryor’s team also tracked indirect measurements. These come from surface temperature and pressure records as well as balloon and satellite surveys. Computers crunch the data to produce a rich series of atmospheric portraits— a way to measure wind speeds without measuring the wind. This “reanalysis” data showed no change. Says Pryor: “If you have a mechanism causing your wind speeds to change”—global warming, for instance—“it should be evident in both the observations and in the reanalysis data.” If only one out of the two shows an effect, no one can say for sure what is going on.

For the wind industry, the most important change would be to peak wind speeds, because a turbine delivers most of its power only once the wind blows faster than about 25 miles per hour. Although the conclusions are preliminary, global climate models suggest that in the Northern Hemisphere, storm tracks should migrate northward, bringing more gusty storms to higher latitudes. “The northern part of the U.S. into Canada may see an increase” in peak wind speeds, Pryor says, “whereas the southern regions may see a decline.”

Yet any decline should still leave wind farms with plenty to work with. A recent study by Xi Lu of Harvard University calculates that wind power in the U.S. could potentially generate 16 times the nation’s current electricity production. The study limits potential wind farm locations to rural, nonforested sites (both on land and offshore) with high wind speeds. Worldwide, wind energy under the same constraints could supply at least 40 times the current electricity consumption.

According to Ryan Wiser, a staff scientist at Lawrence Berkeley National Laboratory and author of an upcoming special report on renewable energy and climate change by the Intergovernmental Panel on Climate Change, Lu’s study simply confirms that “there is absolutely no resource constraint for wind in the U.S.” Or, as Pryor puts it, “there may be regional winners and losers, but the winds are going to continue to blow.”

Source of Information : Scientific American October 2009

Tuesday, June 22, 2010

Not Set in Stone (or Ice)

A new model for comet production revises the theory of their origins BY JOHN MATSON

The chunks of ice and dust that make their home in the Oort cloud, far beyond the orbit of Pluto, sometimes become dislodged and head into the solar system as streaky comets. Some disruptions, caused by passing stars and other interactions with the Milky Way galaxy, are severe enough to send Oort comets into orbits that buzz or even collide with Earth. New simulations have revealed a novel mechanism for their entry into our part of the solar system, a method that also suggests that comet showers may not have been strongly involved in major extinctions on Earth.

Comet dynamics depend heavily on Jupiter and Saturn: their huge gravitational fields tend to keep objects away from Earth. Comets that manage to skirt Jupiter and Saturn, the conventional thinking goes, had to have originated in the outer reaches of the Oort cloud, where perturbations from outside the solar system can be felt most strongly and are writ large across vast cometary orbits that take hundreds of years to complete. Only during comet showers caused by close stellar passages, the theory holds, have extreme gravitational disruptions brought inner Oort cloud comets into the mix.

A computer simulation by Nathan Kaib and Thomas Quinn, both at the University of Washington, have upended this thinking. They have found that the comets that manage to cross the Jupiter-Saturn barrier do in fact originate in large numbers in the inner Oort cloud, even in the absence of a large disruption causing a comet shower. Specifically, they found that the relatively nearby objects of the inner Oort cloud can be kicked into the reaches of the outer cloud via interactions with the massive planets. Those newly far-flung comets, suddenly enjoying a longer orbit and greater gravitational perturbations from interstellar space, can find their orbits so changed that, by the time they pass through the planetary region again, they slip past the gas giants. “They can basically hop over the Jupiter-Saturn barrier,” Kaib says.

Kaib and Quinn estimate that more than half of the comets we observe streaking in from the Oort cloud reach our neighborhood via this route, and other researchers agree the simulation appears valid. “This mechanism, this dynamical path, as we call it, could work and could be a significant contributor,” says Paul Weissman, a senior research scientist at the NASA Jet Propulsion Laboratory.

The new research presents a route for comet production “that goes some way” toward resolving discrepancies between the standard model and the observations, says Scott Tremaine, an astrophysicist at the Institute for Advanced Study in Princeton, N.J. “One of the issues is that [the conventional view of] the cometary formation process is so inefficient; in order to produce the number of comets that we see, you’d need a really massive protoplanetary disk, one that appears to be incompatible with our best estimates from other sources,” Tremaine says.

Kaib and Quinn used their newfound mechanism, as well as the number of observed comets, to estimate an upper limit on how much material could be in the inner Oort cloud. They then produced a statistical model of how many comets would have hit Earth in comet showers in the past several hundred million years. Their conclusion: large cometary showers were few and hence probably did not cause more than one extinction event.

Using cometary dynamics to unwind the extinction history on Earth will likely meet with some controversy. Weissman notes that the extinction implications of Kaib and Quinn’s analysis would involve comet showers, not comets in general, and that even a diminished profile of showers does not rule out the role of comets in extinctions. One big strike, rather than a shower of small ones, is all that’s needed to trigger extinctions, he points out.

Source of Information : Scientific American October 2009

Monday, June 21, 2010

Hunting a Croc Killer

Mass deaths of South Africa’s Nile crocodiles puzzle biologists BY NAOMI LUBICK

Carcasses of adult crocodiles do not usually signal the return of winter in South Africa, but mass death seems to be becoming the harbinger of the season. Rangers at the Kruger National Park have found Nile crocodiles floating in the Olifants River or bloated and decaying along its banks. Investigators are rushing to figure out the cause and worry that the deaths might be signaling the presence of toxins or pathogens that could threaten not only the croc population but also the livelihoods of the people living near the river.

The Olifants River runs several hundred kilometers through three South African provinces and into Mozambique. It supplies water to industrial agriculture operations that send food to Europe and to the local rural communities, which also depend on those waters for fishing and farming.

The first sign of croc trouble in the river came in the winter of 2008, when rangers collected 170 dead individuals, sometimes at a rate of 20 bodies a week. A survey at the end of this May showed nearly 400 crocs living in the park’s gorge, down from at least 1,000 in 2008. So far, as of August 7, rangers and scientists have found 23 carcasses.

After slicing open some of the crocodile corpses last year, researchers determined some kind of pansteatitis—an inflammation of adipose tissue—was killing the animals. Specifically, their tails were swollen with the hardened, enlarged fat deposits, which had stiffened and immobilized the crocodiles and left them unable to hunt. Samples of the fat showed the deposits had oxidized to bright yellow.

The disease may not be limited to crocs. Scientists found the same kinds of fat deposits in fish in the Olifants River. And in the river’s gorge just upstream from Massingir Dam in Mozambique, which also has seen croc declines, birds were absent, raising the possibility that they, too, have succumbed to the same agent.

But the cause behind the strange fattening remains a mystery. In June a team led by Henk Bouwman of North-West University, Potchefstroom Campus, in South Africa reported test results from crocodile tissues at two European chemistry meetings. “Everything is there,” Bouwman says, referring to the detection of DDT, PCBs, dioxins and brominated flame retardants, “but nothing is screaming, ‘it’s me, it’s me, it’s me.’ ”

One possibility could be related to dinoflagellates and cyanobacteria found upstream in the catchment, which might be releasing toxins similar to those that cause red tides in marine environments, says Peter Ashton, a water resources specialist at the Council for Scientific and Industrial Research in South Africa and the University of Pretoria.

“It never is a quick, easy solution” in which it takes one test to find a culprit, explains Danny Govender, a disease ecologist for South African National Parks. She notes that samples taken from live crocs in 2007 showed that the fat of some crocodiles was beginning to harden. Along with Bouwman, she hypothesizes that all these toxins, found below harmful levels individually, could be acting together in a deadly brew.

Govender cites changes to the river’s ecosystem that stem from infrastructure outside the park, including hundreds of coal-mining operations upstream, where crocodiles have disappeared almost completely, and a dam downstream of the gorge. For the first time in the two decades since it was built, the dam’s reservoir was full last year, slowing down the Olifants’s flow through the crocodiles’ gorge. Govender wonders if the slowed water enabled toxins to build up along the crocodiles’ stretch of the river. Indeed, hydrogen sulfide, ammonia and other compounds from river sediments probably caused massive fish deaths in July, scientists have concluded, and crocs eating these contaminated fish could have been affected.

Even if researchers find the culprits, the impacts could reach further than suspected. “We really underestimated [the number of dead] crocodiles from last year’s count,” Govender adds, noting that their bodies could have been eaten by other crocs or sunk to the bottom of the river. “I suspect we’re losing a lot of breeding females,” whose carcasses are smaller and more easily scavenged. If that is the case, she says, the gorge’s crocodile population may not ever recover, even if scientists can pinpoint the cause of the die-off.

As for the people who depend on the Olifants River, “I don’t know what to tell them,” Bouwman says. His colleague Henrik Kylin of Swedish University of Agricultural Sciences in Uppsala wants to go into Mozambique to test fish there, and possibly people, to see if the croc killer kills more than just crocs.

Source of Information : Scientific American October 2009

Sunday, June 20, 2010

Tasting the Light

Device lets the visually impaired “see” with their tongues BY MANDY KENDRICK

The late neuroscientist Paul Bach-y-Rita hypothesized in the 1960s that “we see with our brains not our eyes.” Now a noninvasive device trades on that thinking and aims to partially restore the experience of seeing for the visually impaired by relying on the nerves on the tongue’s surface to send light signals to the brain.

First demonstrated in 2003 by neuroscientists at Middleton, Wis.–based Wicab (a company co-founded by Bachy-Rita), the device could finally be ready for sale at the end of the year. Called BrainPort, it tries to substitute for the two million optic nerves that transmit visual signals from the retina to the brain’s primary visual cortex. Visual data are collected through a small digital video camera mounted on the center of sunglasses worn by the user. Bypassing the eyes, the data go to a handheld base unit, which houses such features as zoom control and light settings as well as a central processing unit (CPU), which converts digital signals into electrical pulses.

From the CPU, the signals are sent to the tongue via a “lollipop,” an electrode array about nine square centimeters that sits directly on the tongue, which seems to be an ideal organ for sensing electric current. (Saliva is also a good conductor.) Moreover, the tongue’s nerve fibers are densely packed and are closer to the surface relative to other touch organs. The surfaces of fingers, for example, are covered with a layer of dead cells called the stratum corneum.

Each electrode on the lollipop corresponds to a set of pixels. White pixels yield a strong electrical pulse, whereas black pixels translate into no signal. The nerves at the tongue surface receive the incoming electrical signals, which feel a little like Pop Rocks or champagne bubbles to the user.

Typically within 15 minutes of using the device, blind people can begin interpreting spatial information via BrainPort, says William Seiple, research director at the nonprofit vision health care and research organization Lighthouse International. The electrodes spatially correlate with the pixels so that if the camera detects light fixtures in the middle of a dark hallway, electrical stimulations will occur along the center of the tongue. “It becomes a task of learning, no different than learning to ride a bike,” says Wicab neuroscientist Aimee Arnoldussen, adding that the “process is similar to how a baby learns to see. Things may be strange at first, but over time they become familiar.”

Seiple works with four patients who are training with Brain- Port once a week. He notes that his patients have learned how to quickly find doorways and elevator buttons, read letters and numbers, and pick out cups and forks at the dinner table without having to fumble around. “At first, I was amazed at what the device could do,” he says. “One guy started to cry when he saw his first letter.” The researchers have yet to figure out if the electrical information is transferred to the brain’s visual cortex, where sight information is normally sent, or to its somato sensory cortex, where touch data from the tongue are interpreted.

To develop criteria for monitoring the progress of artificial sight, optometrist Amy Nau of the University of Pittsburgh Medical Center’s Eye Center will further test BrainPort, along with other devices such as retinal and cortical implant chips. “We can’t just throw up an eye chart. We have to take a step back and describe the rudimentary precepts that these people are getting,” she says. Nau is particularly interested in BrainPort because it is noninvasive, unlike implants.

“Many people who have acquired blindness are desperate to get their vision back,” she points out. According to the National Institutes of Health, at least one million Americans older than 40 are legally blind, with vision that is 20/200 or worse or that has a field of view of less than 20 degrees. Adult vision loss costs the country about $51.4 billion a year.

Although sensory substitution techniques cannot fully restore sight, they do provide the information necessary for spatial orientation. Wicab had planned to submit BrainPort to the U.S. Food and Drug Administration for approval at the end of August, says Robert Beckman, president and chief executive officer of the company. He notes that the device could be approved for market by the end of 2009 for about $10,000 a machine.

Source of Information : Scientific American October 2009

Saturday, June 19, 2010

Nuclear Architecture

Positions inside the cell nucleus exert biological effects BY MELINDA WENNER

For decades the cell nucleus has been a black box of biology—scientists have understood little about its structure or the way it operates. But thanks in part to new visualization technologies; biologists have recently begun probing the architecture of the nucleus in real time. And they are discovering that this architecture appears to change as we age or fall ill or as our needs shift. In fact, the structure of nuclear components—chromosomes, RNA, protein complexes and other small bodies—could be as biologically important as the components themselves.

It is not surprising that the nucleus is carefully organized. The human genome’s 3.2 billion DNA base pairs have to be compacted 400,000-fold to fit within the tiny space—yet genes must also interact with one another there and with the machinery that transcribes them into proteins. Nuclear structure has historically been difficult to study because scientists had to rely on electron microscopy or antibody stains, which show cellular components only at single points in time. In the 1990s, however, biologists started using green fluorescent protein to observe nuclear components in living cells in real time, much like a movie. “A picture is worth 1,000 words, and I always like to say a movie is worth one million words,” says David L. Spector, a cell biologist at Cold Spring Harbor Laboratory.

One of first things biologists noticed was that genes reside in different parts of the nucleus depending on their activity. Chromosomal regions containing silent genes localize to condensed DNA regions in the outer periphery, whereas active genes stay in the roomier nuclear center, perhaps because there they can more easily share the transcription resources. But “like most things in biology, people have found exceptions,” notes Tom Misteli, a cell biologist at the National Cancer Institute. Sometimes active genes are on the periphery, and vice versa.

Chromosomes position themselves carefully relative to one another, too. Mouse olfactory cells contain the genes for 1,300 types of smell receptors, but only one of the genes turns on in each cell. In a 2006 paper researchers used fluorescent tags to show that a receptor gene becomes expressed only if it comes into physical contact with a specific part of chromosome 14. The idea is that “these two chromosomes come together in three-dimensional space, they kiss, and that’s how you get your regulation” of genetic activity, Misteli says. Chromosome “kissing” also appears to play a role in determining which X chromosome gets turned off in female cells, because only one copy is usually active.

Changes to nuclear structure can affect cellular function in dramatic ways. In April biologists Thomas Cremer and Boris Joffeof the Ludwig-Maximilians University in Munich noticed that the architecture of retina rod nuclei is inverted in nocturnal mice—condensed DNA sits at the center, with less condensed regions in the periphery. They had no idea why but eventually “came to the incredible idea that it might be related to vision,” Joffe says. The researchers compared the retinal nuclei of 38 species and found that those of nocturnal and crepuscular species—animals active at dusk or dawn featured the inverted structure, whereas diurnal species had the more traditional layout. The inverted architecture seems to minimize light scattering, which allows them to see better in the dark, Joffe says, but it is unclear why.

Aging and disease are also associated with changes to nuclear architecture. Generally, as cells age, stores of condensed DNA at the nuclear periphery start migrating inward. In a study in the Journal of Cell Biology in 2008, Misteli and his colleagues identified four cancer-related genes that change positions when breast cells become cancerous. Structure can also influence risk; when chromosomes get too close to one another, cancer-causing chromosomal translocations occur more often. And bizarrely, the X chromosome moves closer to the center after epileptic seizures.

No one knows whether these kinds of changes to nuclear structure trigger aging and disease or result from them, or both. In any case, it is clear “that if you mess around with the [nuclear] architecture, you can get disease,” Misteli says. It might one day be possible to diagnose diseases and age-related problems simply by looking at nuclear snapshots, he adds.

Perhaps the biggest remaining mystery is how the nucleus gets organized in the first place. Do molecular scaffolds tether nuclear constituents in a deterministic way, or does genome activity affect positioning in a probabilistic manner? Evidence supports both theories, and Spector posits that RNA may play an important role. This past March he and his colleagues identified an RNA that helps to structure nuclear compartments called paraspeckles. Undoubtedly, the mechanisms controlling nuclear organization will prove to be varied and complex. As Spector puts it: “Things in biology tend to not be in black and white.”

Source of Information : Scientific American October 2009

Friday, June 18, 2010

The Blood Factory

Learning that your bones are made of living tissue may surprise you, but your bones have even more going on. This time, however, the party’s on the inside.

To understand what takes place, you need to realize that bones aren’t solid all the way through. Instead, your bones have a hard outer layer and a honeycombed inner layer that’s laced with tiny holes. This combination gives bones an interesting characteristic—they’re both impressively strong and surprisingly light. In fact, for their weight, bones are one of the strongest materials on earth.

Furthermore, many bones have a hollow cavity packed with jelly-like bone marrow. Bone marrow comes in two flavors: yellow marrow, which simply stores fat, and red marrow, which creates new blood cells. Thanks to the red marrow, your bones are nonstop assembly lines, churning out more than 100 billion blood cells every day—important work indeed. In fact, a bone somewhere in your body created every blood cell that’s circulating in your body right now.

Clearly your bones deserve more respect than they usually get. So the next time you see a skull and crossbones slapped on a bottle of lethal toiletbowl cleaner, take a moment to reflect on your bones and their life-giving role as your body’s bottomless blood bank.

Yellow marrow is found in the middle of long bones, like those in your legs. Red marrow is found primarily in flatter bones, like your hip bones, breast bone, skull, and shoulder blades.

Bone marrow doubles as a supremely nutritious food delicacy (at least when it’s from some other creature’s bones). Packed with protein and unsaturated fat, it’s a key ingredient in Vietnamese pho soup and the highlight of Italian osso bucco (braised veal shanks). Some anthropologists even believe that marrow was a staple in the diet of our distant ancestors. The theory is that these early humans were inept hunters who rarely caught a good meal—so they spent most of their mealtime cracking open the bones that more capable predators left behind.

Source of Information : Oreilly - Your Body Missing Manual

Thursday, June 17, 2010

What exactly is solar energy ?

Solar power is radiant energy that's produced by the sun. Every single day the sun radiates, or sends out, a huge quantity of energy. The sun radiates more energy in one second than people have used since the beginning of time!

The energy of the Sun derives from within the sun itself. Like other stars, the sun is really a big ball of gases––mostly hydrogen and helium atoms.

The hydrogen atoms in the sun’s core combine to form helium and generate energy in a process called nuclear fusion.

During nuclear fusion, the sun’s extremely high pressure and temperature cause hydrogen atoms to come apart and their nuclei (the central cores of the atoms) to fuse or combine. Four hydrogen nuclei fuse to become one helium atom. But the helium atom contains less mass than the four hydrogen atoms that fused. Some matter is lost during nuclear fusion. The lost matter is emitted into space as radiant energy.

It requires countless years for the energy in the sun’s core to make its way to the solar surface, after which somewhat over eight minutes to travel the 93 million miles to earth. The solar energy travels to the earth at a speed of 186,000 miles per second, the speed of light.

Only a small portion of the power radiated by the sun into space strikes our planet, one part in two billion. Yet this amount of energy is enormous. On a daily basis enough energy strikes the usa to supply the nation’s energy needs for one and a half years!

Where does all of this energy go?

About 15 percent of the sun’s energy that hits the earth is reflected back to space. Another 30 percent is used to evaporate water, which, lifted into the atmosphere, produces rainfall. Solar energy is also absorbed by plants, the land, and the oceans. The rest could be employed to supply our energy needs.

Who invented solar energy ?

Humans have harnessed solar power for centuries. As early as the 7th century B.C., people used simple magnifying glasses to concentrate the light of the sun into beams so hot they would cause wood to catch fire. More than a century ago in France, a scientist used heat from a solar collector to make steam to drive a steam engine. In the beginning of this century, scientists and engineers began researching ways to use solar energy in earnest. One important development was a remarkably efficient solar boiler introduced by Charles Greeley Abbott, an american astrophysicist, in 1936.

The solar hot water heater gained popularity at this time in Florida, California, and the Southwest. The industry started in the early 1920s and was in full swing prior to The second world war. This growth lasted prior to the mid-1950s when low-cost gas had become the primary fuel for heating American homes.

The public and world governments remained largely indifferent to the possibilities of solar power prior to the oil shortages of the1970s. Today, people use solar technology to heat buildings and water and also to generate electricity.

How we use solar power today ?

Solar power is employed in a number of different ways, of course. There are 2 simple forms of solar energy:

* Solar thermal energy collects the sun's warmth through 1 of 2 means: in water or in an anti-freeze (glycol) mixture.

* Solar photovoltaic energy converts the sun's radiation to usable electricity.

Let us discuss the five most practical and popular techniques solar power can be used:

1. Small portable solar photovoltaic systems. We see these used everywhere, from calculators to solar garden tools. Portable units can be utilized for everything from RV appliances while single panel systems can be used traffic signs and remote monitoring stations.

2. Solar pool heating. Running water in direct circulation systems via a solar collector is a very practical solution to heat water for your pool or hot tub.

3. Thermal glycol energy to heat water. In this method (indirect circulation), glycol is heated by sunshine and the heat is then transferred to water in a warm water tank. This technique of collecting the sun's energy is more practical now than ever before. In areas as far north as Edmonton, Alberta, solar thermal to heat water is economically sound. It can pay for itself in 3 years or less.

4. Integrating solar photovoltaic energy into your home or business power. In many parts of the world, solar photovoltaics is an economically feasible solution to supplement the power of your home. In Japan, photovoltaics are competitive with other types of power. In america alone, new incentive programs make this form of solar technology ever more viable in many states. An increasingly popular and practical method of integrating solar energy into the power of your home or business is through the use of building integrated solar photovoltaics.

5. Large independent photovoltaic systems. For those who have enough sun power at your site, you might be able to go off grid. It's also possible to integrate or hybridize your solar energy system with wind power or other kinds of sustainable energy to stay 'off the grid.'

How do Photovoltaic panels work ?

Silicon is mounted beneath non-reflective glass to create photovoltaic panels. These panels collect photons from the sun, converting them into DC electric power. The power created then flows into an inverter. The inverter transforms the energy into basic voltage and AC electric power.

Solar cells are prepared with particular materials called semiconductors like silicon, which is presently the most generally used. When light hits the Photovoltaic cell, a specific share of it is absorbed inside the semiconductor material. This means that the energy of the absorbed light is given to the semiconductor.

The energy unfastens the electrons, permitting them to run freely. Pv cells also have one or more electric fields that act to compel electrons unfastened by light absorption to flow in a specific direction. This flow of electrons is a current, and by introducing metal links on the top and bottom of the -Photovoltaic cell, the current can be drawn to use it externally.

What are the positives and negatives of solar energy ?

Solar Pro Arguments

- Heating our homes with oil or propane or using electricity from power plants running with fossil fuels is a reason behind climatic change and climate disruption. Solar power, on the other hand, is clean and environmentally-friendly.

- Solar hot-water heaters require little maintenance, and their initial investment can be recovered within a relatively small amount of time.

- Solar hot-water heaters can work in almost any climate, even just in very cold ones. Simply choose the right system for your climate: drainback, thermosyphon, batch-ICS, etc.

- Maintenance costs of solar powered systems are minimal and the warranties large.

- Financial incentives (USA, Canada, European states…) can reduce the cost of the initial investment in solar technologies. The U.S. government, for example, offers tax credits for solar systems certified by by the SRCC (Solar Rating and Certification Corporation), which amount to 30 percent of the investment (2009-2016 period).

Solar Cons Arguments

- The initial investment in Solar Water heaters or in Photovoltaic Electric Systems is greater than that required by conventional electric and gas heaters systems.

- The payback period of solar PV-electric systems is high, as well as those of solar space heating or solar cooling (only the solar domestic hot water heating payback is short or relatively short).

- Solar water heating do not support a direct in conjunction with radiators (including baseboard ones).

- Some air cooling (solar space heating and the solar cooling systems) are very pricey, and rather untested technologies: solar air-con isn't, till now, a truly economical option.

- The efficiency of solar powered systems is rather dependent on sunlight resources. It's in colder climates, where heating or electricity needs are higher, that the efficiency is smaller.

Who am i ? - Barbara Young writes on solar RV panels in her personal hobby website Her efforts are dedicated to helping people save energy using solar power to lower CO2 emissions and energy dependency.

Wednesday, June 16, 2010

Bone Health

Remodeling presents another potential problem. When your body restructures your bones, it uses one set of cells to break down bone matter and another to rebuild it. If the wrecking crew starts working more quickly than the repair crew (which, after all, has the more difficult job), the whole process weakens your bones. Left unchecked, this leads to brittle bones and a dangerous condition known as osteoporosis.

Osteoporosis is a dismayingly common condition in the over-50 crowd. It’s particularly common in women after menopause, because the change in hormones affects the body’s rate of bone construction. Osteoporosis usually develops without symptoms until your bones are severely weakened, at which point you can fracture them from seemingly benign events, like a negligible fall, a minor bump, or even an ordinary strain like coughing.

Osteoporosis has the potential to greatly reduce the quality of life in your later years. However, it’s highly preventable if you follow the right steps throughout your life. Here are the cornerstones of good bone health:

• Exercise. Like the rest of your body, your bones need to be used. In fact, they grow denser and stronger in the areas you stress most. Weight-bearing exercise is best for bone health (see page 77), but even aerobic exercise (running, jumping, hip-hop dancing) helps, because these activities strain your bones with a force equal to several times your weight.

• Calcium. It’s a critical nutrient early in life, when your bones are growing. It’s also essential later in life to ensure that your body doesn’t open up your bone checking account and make a calcium withdrawal. Adults from the ages of 19 to 50 should strive for at least 1,000 milligrams of calcium per day. At the same time, make sure you’re getting enough vitamin D, because it aids in calcium absorption.

• Smoking. Avoid it. (No surprise there.)

• Testing. If you’re concerned about the health of your bones, you can take a simple, safe test that scans your body with a low-dose x-ray. The results will tell you if you’re suffering from the early stages of osteoporosis. In addition, the test will give you a benchmark against which you can compare future results to see how your bones change over time.

The easiest way to get your calcium is from skim milk, which supplies about 300 milligrams per glass. Other calcium-rich foods include cheese, yogurt, and fortified cereal. Some vegetables, nuts, legumes, and fruits provide smaller amounts of calcium—usually closer to 100 milligrams per serving. (You can read a detailed calcium food ranking at Avoid mixing calcium-rich foods with caffeine, because it impedes calcium absorption. Finally, if you don’t think you can consistently get the calcium you need from your diet, or you’re at particular risk for osteoporosis, see your doctor for advice on taking a calcium supplement.

Source of Information : Oreilly - Your Body Missing Manual

Monday, June 14, 2010

Living Bone

If you’re like most people, you think about bones as the dry, stiff specimens you see holding up dinosaur heads in museums or keeping turkey legs together on Thanksgiving. But the bones in your body are a world away from these fossilized and cooked leftovers. They’re still tough and impressively resilient, but they’re built of healthy, living tissue, just like all the other parts of your body. That’s why children can grow taller month after month, and why your body can restore a cracked bone to its original strength. On the darker side of things, that’s also why bones are susceptible to cancer.

You might assume that bones bother changing themselves only at certain times in your life—for example, as you grow through childhood or recover from an injury. But even if you’re an adult with pristine bones, your body is constantly busy breaking them down and rebuilding them in a process called remodeling (which, happily, doesn’t involve unreliable contractors or flighty home decorators).

To perform this ongoing regeneration, your body dissolves small patches of bone one bit at a time, and then fills the resulting holes with new material (sort of like an industrious road-repair crew). Remodeling serves three purposes. First, it fixes microscopic cracks in your bones. Second, it rebalances the strength of your bones, toughening up the parts that you strain most often. And third, it manages your body’s level of important minerals, like calcium.

For example, if you have extra calcium circulating in your blood, your body incorporates it into newly laid-down bone. But if your body is short of calcium, it reclaims the mineral from the chewed-out bone matter as it remodels, and contributes less calcium to the newly patched-up bit. This presents a problem, because without those hard minerals, your bones won’t have their full and proper strength. That’s why a low-calcium diet puts you at increased risk of developing fragile bones.

Remodeling is slow work—in fact, it takes months to fill a single hole. However, you have roughly a million independent repair crews working throughout your body, and together they do enough work to give you a new skeleton every decade of your life.

Source of Information : Oreilly - Your Body Missing Manual

Saturday, June 12, 2010

The Benefits of Bones

The purpose of your skeleton seems simple enough. After all, if you didn’t have one, you’d be as saggy as a beanbag chair and a lot less fun. But as you’ll discover, your skeleton isn’t just a handy place to hang your body. It’s actually a hard-working team member that helps you out in several ways:

• Protection. Your bones provide rigid pieces of body armor that protect your critical squishy parts. The best examples of this defense are your skull (which wraps your brain in a non-removable helmet), your spinal column (which sheaths the central highway of your nervous system), and your breastbone and rib cage (which deflect damage away from internal organs like your heart and lungs).

• Movement. As you saw in Chapter 3, your muscles are your body’s real movers and shakers. But muscles need to act on something to produce movement, and that “something” is your bones. Your muscles pull them like the levers of an intricate machine.

• Storage. Your bones are a reservoir of minerals like calcium, which your nervous system and muscles need to function. For example, if your blood doesn’t have a bare minimum of calcium, calcium will gradually leech out of your bones and into your blood. Some bones also store a last-ditch deposit of fat, which they keep in their hollow core.

• Production. As you’ll see in the next section, bones don’t just lie there lifelessly. They house a busy factory that creates blood cells.

Men and women have subtly different skeletons. On average, women have narrower shoulders, shorter arms, and wider hips than men, so women are less suited to actions like throwing and running, but have better stability and a lower center of gravity. There are also a number of subtle differences between male and female skulls. Women’s skulls, for example, tend to be less angular, and they have a less pronounced, softer chin. In a random face-recognition test, most people can quickly separate the women from the men.

Blood cells are tiny cells that circulate in your bloodstream. They play several essential roles. Red blood cells carry life-sustaining oxygen throughout your body. White blood cells produce antibodies that battle infection. Platelets create clots that prevent your blood from leaking out of damaged skin. Without any one of these players, you’d be in serious trouble.

Source of Information : Oreilly - Your Body Missing Manual

Thursday, June 10, 2010

Even Better Strength Training

The six strength-training exercises in this chapter are a great start. But if you’ve outgrown them, or if you want more guidance, there are plenty of resources to turn to. Here are some excellent options:

• Explore the Web. There are plenty of books and videos that dissect popular exercises, but the Web is the unchallenged champion of free and comprehensive workout information. An excellent start is the sprawling exercise and fitness pages on—dip your toe in at The Mayo Clinic provides a smaller set of articles and some helpful videos at

• Find a gym. Everyone can benefit from a well-stocked gym with like-minded fitness buffs and a supportive staff. You need to shop around to find one that suits you. Keep in mind that the obvious criteria (price and location) aren’t the only factors. To make sure you’ll feel comfortable, check out the crowd (Lycraclad treadmill bunnies? Macho men grunting like bulls?). And make sure you can make use of the most important gym benefit—the help of a personal trainer.

• Personal trainer. You don’t need to have one on staff. A monthly consultation is enough to help you test your fitness level (and see how it changes over time), devise a workout regimen that suits you, and get pointers to demystify tricky exercises. If you’re ready to invest in this experience, make sure you go to a personal trainer that has a degree in health science and certification from an internationally recognized organization, such as the NSCA (National Strength and Conditioning Association).

Source of Information : Oreilly - Your Body Missing Manual

Tuesday, June 8, 2010

Strength Exercises - Push-Ups

Although push-ups seem old-fashioned, they’re a surprisingly practical compound exercise that requires no extra equipment. Importantly, pushups don’t just tax the muscles in your arms and chest, they also require muscles throughout your body to stabilize your motion. And if you’re one of the many new exercisers who can’t complete a single push-up, there are two practical variations you can start with: wall push-ups and bent-knee push-ups (shown in the picture here).

Here’s how to do a classic push-up:

1. Lie chest-down on an exercise mat. Put your hands, palms down, on either side of your body at shoulder level. Keep your feet together, toes down.

2. Straighten your arms to push yourself up, breathing out. Keep your back straight,
your abdominal muscles tight, and your toes on the floor.

3. Pause, then lower yourself until your chest nearly touches the floor, breathing in. If you can, push yourself back up and continue with another repetition.

If a standard push-up is too hard (as it is for many), start with a bent-knee push-up. Before you begin, while you’re lying face-down, bend your legs into a right angle and lift your feet off the ground. (You can watch a demonstration at If that’s still too taxing, try a wall push-up. First, stand and face a wall. Then, lean against the wall and place your hands on either side at shoulder level. Finally, push against the wall. It’s essentially the same exercise, except now gravity is on your side.

Source of Information : Oreilly - Your Body Missing Manual

Sunday, June 6, 2010

Strength Exercises - Abdominal Crunch

What would the world be like without this exercise? It’s a modified sit-up that’s every gym teacher’s favorite torture tool and the first line of defense against a paunchy midriff. It’s also far friendlier to back muscles, which can be strained by improper sit-ups.

Technically, the abdominal crunch isn’t a weight-bearing exercise. It’s often called a “core-strength” exercise because it exercises the core set of abdominal and back muscles that promote good posture and reduce your risk of injury. But because you don’t choose the heftiness of the weight you’re lifting when performing an abdominal crunch, you need to deviate from the standard 8/14 rule.

That doesn’t mean you should stomach-crunch the day away. As you become a skilled cruncher, you should strive to perform two or three sets of 25 or fewer crunches. The goal is most decidedly not to perform as many crunches as you can. If you can breeze through 50 without a care in the world, you need to get fanatical about good form, find ways to intensify your effort, or switch to a more difficult variation (such as doing abdominal crunches on an exercise ball).

Here’s how to perform a basic crunch:

1. Lie down flat on your back. Bend your knees, keep your feet flat on the floor and hip-width apart, and place your hands across your chest.

2. As you breathe out, contract your abdominal muscles as tightly as you can, and slowly raise your head and shoulders just a few inches off the floor.

3. Hold your raised position for a few seconds, breathing in and out continually, and contract your stomach as hard as you can.

4. Slowly lower back down, but don’t relax all the way. This is a key point to getting the most out of a crunch—if you simply drop your body back down under the effect of gravity, you’ll lose half the benefit of the exercise.

To get the best results out of your abdominal crunch, concentrate on making sure that your abdominal muscles are doing all the work. Resist the urge to push with your feet, pull up with your arms, or lead with your chin. You can watch a basic instructional video at

Source of Information : Oreilly - Your Body Missing Manual