Cesarean sections declined in the seven years following 1989, when U.S. birth certificates first recorded methods of delivery. But recently they have spiked. Proposed explanations include an increase in multiple births and in the number of women more likely to have a C-section, such as those who are older, overweight or diabetic. — Brie Finegold
Percent of births delivered by cesarean section in: 2004: 29.1 1996: 20.7 1989: 22.8
Percent increase in twin births, 1990 to 2003: 37.1
Fraction of women in 2003 who gained prepregnancy weight beyond recommended guidelines: 1/3
Percent increase in mothers with diabetes, 1990 to 2003: 40
Percent change in birth rate from 1990 to 2003 for women ages: 20 to 24: -12 35 to 39: 38 40 to 44: 58
SOURCES: Division of Vital Statistics, Centers for Disease Control and Prevention; Institute of Medicine (weight guidelines)
Along with rising prices at the pump, the cost of some petroleum-based chemicals used in plastics manufacturing has skyrocketed. Accordingly, researchers have sought to improve a process for turning fructose, a common plant sugar, into 5-hydroxymethylfur-furan (HMF), an alternative, nonpetroleum precursor for chemicals such as polyesters. The reaction occurs in water, which creates several unwanted compounds. To obtain pure HMF, chemists have had to redissolve it in a solvent that is hard to boil away, making the process costly and inefficient. A group from the University of Wisconsin-Madison doubled the reaction's overall yield, to 80 percent, by adding a series of compounds to suppress the reactions that create by-products. Moreover, the additives increase HMF's affinity for a solvent that boils at a low temperature, making the final product easier to obtain. Distill the essentials from the June 30 Science. —JR Minkel
"Men, like planets, have both a visible and an invisible history," wrote George Eliot. Actually, most planets have only an invisible history—we know them only through their indirect influences on the things we do see. Astronomers have yet to make a direct image of a true planet outside our solar system. Michael Liu of the University of Hawaii and his colleagues are now starting the most ambitious search so far, combining a new coronagraph (which masks out the host star), a high-sensitivity adaptive optics system (which de-twinkles the light), and a spectral subtraction technique that wrings out the remaining stellar glare by focusing on emission from methane (which sunlike stars, being too hot, do not contain). A Jupiter-size world in a Jupiterlike orbit around a young star would show up. Not only would direct images reveal bodies that indirect ones do not, they would show much more detail, including atmospheric composition and perhaps even potential signs of life. — George Musser
Psychedelic mushrooms have for millennia been said to trigger mystical experiences. The most rigorous scientific experiment with the hallucinogen, and the first in 40 years, proved capable of producing mystical states in the laboratory safely. Scientists at Johns Hopkins University selected 36 spiritually active volunteers, who might interpret the experiences best, and disqualified potential subjects who had a family or personal risk for psychosis or bipolar disorder. One third of volunteers given psilocybin, the mushroom's active compound, described it as the most spiritually meaningful experience of their lives, and about two thirds rated it in their top five. Some side effects occurred: A third admitted significant fear in the hours following their dose, and some felt momentary paranoia. Two months later 79 percent reported moderately or greatly increased well-being or life satisfaction compared with those given a placebo. Further research could lead to therapies against pain, depression or addiction, experts commented online July 12 in Psycho-pharmacology. — Charles Q. Choi
36 SCIENTIFIC AMERICAN SEPTEMBER 2006
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Support for the Stick gar O.4 Jv O.2-
STICK SAVE: A report affirms previous conclusions about past temperatures. Colors represent data provided by various sources, such as ice cores, tree rings and historical documents.
STICK SAVE: A report affirms previous conclusions about past temperatures. Colors represent data provided by various sources, such as ice cores, tree rings and historical documents.
■ Prion infections, such as mad cow disease, may incubate without symptoms for years. A technique that amplifies tiny amounts of prions in the blood successfully diagnosed infected hamsters within 20 days after exposure to prions and three months before symptoms appeared. Science, July 7
■ A radar system emits signals that appear as noise to other devices, thus enabling it to escape detection. Properly tuned, the stealth radar can also image objects behind walls.
Ohio State University announcement, June 26
■ Abnormal amygdalas may be the root of autism. A postmortem accounting reveals that adult autistic males have about 1.5 million (12 percent) fewer neurons in that brain region, important for memory and emotion.
Journal of Neuroscience, July 19
■ The ability to empathize does not appear to be restricted to primates. Mice became more sensitive to pain after having seen cage mates in some distress.
Science, June 30
Scientists connected with a 2001 report by the Intergovernmental Panel on Climate Change (IPCC) found in an analysis of Northern Hemisphere temperatures over the past millennium, a sharp rise starting around 1900. Their "hockey stick" graph and conclusion that human activity caused this sudden warming drew fire from politicians and critics. The National Research Council now lends support to the hockey stick. It finds that tree rings, ice cores and other evidence suggest with a high level of confidence that the last decades of the 20th century were warmer than any comparable span in the past four centuries. And like the IPCC work, its report, released June 22, expressed OPTICS less certainty in temperature reconstructions going back a millennium because of the scarcity of precisely dated evidence before the 17th century. The council noted that the available data did suggest that many locations were hotter in the past 25 years than during any other quarter-century period since the 10th century. — Charles Q. Choi
Petroleum alternatives include renewable fuels such as biodiesel, derived primarily from soybeans, and ethanol, distilled mostly from corn grain. In the first comprehensive analysis of the energy gains and environmental impact of both fuels, University of Minnesota researchers determined biodiesel to be the better choice. Ethanol from corn grain produces 25 percent more energy than all the energy people invested in it, whereas biodiesel from soybeans returns 93 percent more. Compared with fossil fuels, ethanol produces 12 percent fewer greenhouse gas emissions, whereas biodiesel produces 41 percent fewer. Soybeans also generate significantly less nitrogen, phosphorus and pesticide pollution. Dedicating all current U.S. corn and soybean production to biofuels, however, would meet only 12 percent of gasoline demand and 6 percent of diesel demand. Prairie grass may provide larger biofuel supplies with greater environmental benefits, the scientists reported online July 12 via the Proceedings of the National Academy of Sciences USA. — Charles Q. Choi
Digital cameras may soon get disabled via security systems that temporarily blind them. The process exploits a property of the image sensors used by digital cameras— namely, that they are retroreflective, sending light back directly to its origin rather than scattering it. Researchers at the Georgia Institute of Technology developed a prototype that uses light beams and cameras to scan areas for retroreflective dots matching sensors in shape. It then flashes a beam directly at those sensors, overwhelming them. Future versions might use infrared lasers at low, safe energy levels instead of light beams.
The camera-neutralizing technology could thwart clandestine photography or tackle the $3 -billion-a-year problem of movie piracy. It would prove ineffective against conventional film cameras, however, or single-lens reflex digital cameras, which use folding mirrors that mask their sensors except when a photograph is actually taken.
38 SCIENTIFIC AMERICAN SEPTEMBER 2006
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Fake, Mistake, Replicate
A court of law may determine the meaning of replication in science By MICHAEL SHERMER
In the rough-and-tumble world of science, disputes are usually settled in time, as a convergence of evidence accumulates in favor of one hypothesis over another. Until now.
On April 10 economist John R. Lott, Jr., formerly of the American Enterprise Institute, filed a defamation lawsuit against economist Steven D. Levitt of the University of Chicago and HarperCollins, the publisher of Levitt's 2005 book, Freakonomics. At issue is what Levitt meant when he wrote that scholars could not "replicate" Lott's results, referring to Lott's 1998 book, More Guns, Less Crime. Lott employed a sophisticated statistical analysis on data from state-level variation in "carry and conceal" laws, finding that states that passed laws permitting citizens to carry concealed weapons saw statistically significant declines in robbery, rape and homicide compared with states that did not pass such laws.
As is typical with such politically charged research, considerable controversy followed publication of Lott's book, with a flurry of conference presentations and journal papers, some of which replicated his results and some of which did not. For example, in a series of papers published in the Stanford Law Review (available at http://papers. ssrn.com), Lott and his critics debated the evidence.
In Freakonomics, Levitt proffered his own theory for the source of the 1990s crime decline—Roe v. Wade. According to Levitt, children born into impoverished and adverse environments are more likely to land in jail as adults. After Roe v. Wade, millions of poor single women had abortions instead of future potential criminals; 20 years later the set of potential offenders had shrunk, along with the crime rate. Levitt employed a comparative statistical analysis to show that the five states that legalized abortion at least two years before Roe v. Wade witnessed a crime decline earlier than the other 45 states. Further, those states with the highest abortion rates in the 1970s experienced the greatest fall in crime in the 1990s.
One factor that Levitt dismissed is Lott's, in a single passage in the middle of a 30-page chapter: "Lott's admittedly intriguing hypothesis doesn't seem to be true. When other scholars have tried to replicate his results, they found that right-to-carry laws simply don't bring down crime."
According to Lott's legal complaint, "the term 'replicate' has an objective and factual meaning": that other scholars "have analyzed the identical data that Lott analyzed and analyzed it the way Lott did in order to determine whether they can reach the same result." When Levitt said that they could not, he was "alleging that Lott falsified his results."
I asked Levitt what he meant by "replicate." He replied: "I used the term in the same way that most scientists do—substantiate results." Substantiate, not duplicate. Did he mean to imply that Lott falsified his results? "No, I did not." In fact, others have accused Lott of falsifying his data, so I asked Lott why he is suing Levitt. "Having some virtually unheard-of people making allegations on the Internet is one thing," Lott declared. "Having claims made in a book published by an economics professor and printed by a reputable book publisher, already with sales exceeding a million copies, is something entirely different. In addition, Levitt is well known, and his claims unfortunately carry some weight. I have had numerous people ask me after reading Freakonomics whether it is really true that others have been unable to replicate my research."
"Replicate" is a verb that depends on the sentence's object. "Replicate methodology" might capture Lott's meaning, but "replicate results" means testing the conclusion of the methodology, in this case that having more guns in society results in less crime. The problem is that such analyses are so complicated that the failure to replicate more likely indicates modeling mistakes made during the original research or in the replication process rather than fakery.
Mr. Lott, tear down this legal wall and let us return to doing science without lawyers. Replicating results means testing hypotheses—not merely duplicating methodologies—and this central tenet of science can only flourish in an atmosphere of open peer review. ®
Michael Shermer is publisher of Skeptic (www.skeptic.com) and author of Science Friction.
Replicating results means testing hypotheses.
Lower Fertility: A Wise Investment
Plans that encourage voluntary, steep reductions in the fertility rates of poor nations pay dividends in sustainability for everyone By JEFFREY D. SACHS
The world faces looming ecological threats from the incredible stresses that global economic activity places on our major ecosystems. True, rapid population growth is not the main driver today of these threats. Pride of place goes to the high and rising rates of resource use per person rather than to the rise in the sheer number of people. Even if the total population were to stabilize at today's level of 6.5 billion, the pressures of rising per capita resource use would continue to mount. With the rich countries living at roughly $30,000 per person and the world's average income at around $10,000 per person, simply having the poor catch up with the income levels of the rich would triple global economic throughput, with all the attendant environmental consequences.
Yet the continued rapid population growth in many poor countries will markedly exacerbate the environmental stresses. Under current demographic trends, the United Nations forecasts a rise in the population to around nine billion as of 2050, another 2.5 billion people. They will arrive in the poor regions but aspire to the income and consumption levels of the rest of the world. If the economic aspirations of the newly added population are fulfilled, the environmental pressures will be mind-boggling. If those aspirations are not fulfilled, the political pressures will be similarly mind-boggling.
For the poor countries, the benefits of lowering fertility are apparent. High fertility rates are leading to extreme local environmental pressures—water stress, land degradation, over-hunting and overfishing, falling farm sizes, deforestation and other habitat destruction—thereby worsening the grave economic challenges these lands face. High fertility also represents a disaster for the added children themselves, who suffer from profound underinvestments in education, health and nutrition and are thus far more likely to grow up impoverished. In short, a move to lower fertility rates will mean healthier children, much faster growth in living standards and reduced environmental stressors.
Reducing fertility rates in the poorest countries would also be among the smartest investments that the rich countries could make for their own future well-being. Fifty percent of the projected population increase by 2050 will fall within Africa and the Middle East, the planet's most politically and socially unstable regions. That development could well mean another generation of underemployed and frustrated young men, more violence because of joblessness and resource scarcity, more pressures for international migration, and more ideological battles with Europe and the U.S. The global ecological toll could be just as disastrous, because rapid population growth would be taking place in many of the world's "biodiversity hot spots."
Disappointingly, the Bush administration has turned its back on fertility control in poor countries—despite overwhelming evidence that fast, voluntary and highly beneficial transitions to low fertility rates are possible. Such transitions can be promoted through a sensible four-part strategy. First, promote child survival. When parents have the expectation that their children will survive, they choose to have fewer children. Second, promote girls' education and gender equality. Girls in school marry later, and empowered young women enter the labor force and choose to have fewer children. Third, promote the availability of contraception and family planning, especially for the poor who cannot afford such services on their own. Fourth, raise productivity on the farm. Income-earning mothers rear fewer children.
These four steps can reduce fertility rates quickly and dramatically from, say, five or more children per fertile woman to three or fewer within 10 to 15 years, as has occurred in Iran, Tunisia and Algeria. Many African leaders are waking up to this imperative, realizing that their nations cannot surmount their deep economic woes with populations that double every generation. If we in the rich countries would rise to help with this vital task, we would find eager local partners. ®
An expanded version of this essay is available online at www. sciam. com/ontheweb
Jeffrey D. Sachs is director of the Earth Institute at Columbia University and of the U.N. Millennium Project.
Four steps can reduce fertility rates dramatically within 15 years.
The Net's Real Security Problem
The deepest threats to online security are the weaknesses in the fundamental protocols that run the Internet By TOM LEIGHTON
Even casually savvy computer users these days know to beware of security threats such as viruses, worms, Trojan horses and other malicious bits of code. What few in the public realize, however, is that the Internet is vulnerable to much deeper levels of fraud that exploit fundamental security gaps in the network protocols themselves. These attacks represent a growing menace to personal, corporate and national security that the federal government needs to address urgently.
Consider the defenselessness of the domain name system (DNS), the Internet's version of 411 information. When you type a "www."-style name into your browser software, the browser converts it to an IP address, a string of digits that is the equivalent of a phone number. It does so by contacting a local name server, typically operated by your Internet service provider. Unlike telephone numbers, however, which may be valid indefinitely, IP addresses are valid only for a few seconds, hours or days.
If a local name server receives a request for an expired DNS name, it in turn queries a hierarchy of other servers, keying its request to two 16-bit identification codes— one for a transaction ID and one for a port number. Unfortunately, the port number is often predictable, so a cyberthief can very likely match both numbers by creating a relatively small number of answers (say, 65,536).
The cyberthief can then ask a local name server for the IP address for XYZ Bank's home page and learn when it will expire. At the moment of expiration, he again asks for the bank's address and immediately sends out the 65,536 answers that list his own computer's IP address as that of the bank. Under the DNS protocol, the local name server simply accepts the first answer that matches its codes; it does not check where the answer came from, and it ignores any additional replies.
So if our hacker gets his answers in first, the local name server will direct customers seeking XYZ Bank to the hacker's computer. Assuming that the hacker runs a convincing imitation of the bank's sign-in page on his computer, custom ers will not realize that they are handing their confidential information over to a fake.
Similar flaws plague some other critical network protocols as well. Such vulnerabilities imperil more than individuals and commercial institutions. Secure installations in the government and the military can be compromised this way, too. And indeed, there have been cases in which these loopholes did allow data to be stolen and records to be altered.
How did we come to be in such a mess? Today's protocols descend from ones developed 35 years ago, when the Internet was still a research network. There was no need to safeguard the network against malicious entities. Since then, the Internet has opened up and grown explosively, but we have not developed inherently stronger security.
Doing so would be a formidable challenge. For instance, techniques for authenticating that messages come from the proper parties are well developed, but those technologies are not necessarily fast enough to be embedded in all the routers on the Internet without bringing traffic to a crawl. Even worse, Internet users can be tricked into thinking they are protected by such measures while divulging confidential information to a cyberthief. For these reasons and more, in its February 2005 report the President's Information Technology Advisory Committee (of which I was a member) strongly recommended increased federal funding for basic research into cybersecurity.
Cybersecurity needs immediate, sustained attention. The longer we wait to fix the problem, the more we will pay in losses from cybercrime and the greater our exposure to a major attack on our IT infrastructure. ®
An extended version of this essay is available online at www.sciam.com/ontheweb
Tom Leighton is co-founder and chief scientist of Akamai Technologies, Inc., and professor of applied mathematics at the Massachusetts Institute of Technology.
Today's protocols descend from when the Internet was still just a research network.
□ New reports pile up each month about the perils of climate change, including threats to marine life, increases in wildfires, even more virulent poison ivy.
□ Implementing initiatives to stem global warming will prove more of a challenge than the Manhattan Project.
□ Leading thinkers detail their ideas in the articles that follow for deploying energy technologies to decarbonize the planet.
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The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.