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2013年8月2日星期五

New type of protein modification may play a role in cancer and diabetes

"It appears to be an intrinsic feedback mechanism in glucose metabolism, but I suspect that its other functions throughout the cell will prove at least as interesting when they are more fully elucidated," said Benjamin F. Cravatt, chair of the Department of Chemical Physiology and member of the Skaggs Institute for Chemical Physiology at TSRI.

Cravatt and his postdoctoral fellow Raymond E. Moellering reported the finding in the August 2, 2013 issue of the journal Science.

In Search of New Protein Modifiers

The Cravatt laboratory has long studied the natural chemical modifications that can change the functions of proteins "on the fly," switching their biological activities on or off or otherwise altering them. The better known of these modifications include phosphorylation, the addition of a small molecule known as a phosphate group, and acetylation, the addition of an acetyl group.

In search of new protein modifiers, Cravatt and Moellering, whose postdoctoral fellowship is sponsored in part by the Howard Hughes Medical Institute and the Damon Runyon Cancer Research Foundation, decided to investigate a small molecule known as 1,3-bisphosphoglycerate (1,3-BPG). The molecule's chemical makeup suggested that it might readily react with some proteins to form semipermanent, function-altering modifications. 1,3-BPG is one of the main "intermediate" molecules produced during glycolysis, which is a core metabolic pathway that converts glucose to cellular fuel.

"1,3-BPG's intrinsic reactivity seemed odd to us, considering that it is such a central metabolite," remembered Moellering.

Moellering's initial test-tube experiments showed that 1,3-BPG does indeed react with certain lysine amino acids to modify GAPDH, the enzyme that mediates the production of 1,3-BPG. "That gave us the first indication that this reaction does happen, and that we should therefore start looking for it in cells," he said.

A Role in Glucose Metabolism

After devising new methods to detect this unique lysine modification in human cell cultures, Moellering soon found it -- on other glucose-metabolizing enzymes, as well as on proteins seemingly unrelated to glucose metabolism.

"With every step we took, the project became more interesting, because we were finding signs that this reaction occurs frequently in cells and in animal tissues, and in unexpected cellular locations, too," Moellering said.

He detected the signature of the new lysine modification not only on proteins in the main volume of the cell (the cytosol), but also in the DNA-containing cell nucleus and even on the cell's membrane compartments.

"It appears that wherever GAPDH goes within cells, it is capable of catalyzing the localized production of 1,3-BPG, which in turn reacts with nearby proteins to modify their structure and function," said Cravatt.

Moellering found that when 1,3-BPG's lysine modification occurs on glucose-metabolizing enzymes, it tends to inhibit their activities, causing a slowdown of central glucose processing and a consequent buildup of certain glucose metabolites in the processing pathway. Moellering and Cravatt suspect that these overabundant metabolites may end up being shunted into other cellular processes besides basic fuel-making -- processes that contribute to the synthesis of new molecules and even cell proliferation.

Moellering also discovered that 1,3-BPG and the modification it makes on proteins become more prevalent as glucose levels rise. Within the context of glucose metabolism, 1,3-BPG's modification thus seems to act as a "very old, maybe ancient feedback mechanism for regulating that central metabolic pathway," Moellering said.

Looking Ahead

The abnormal processing of glucose within cells features in a number of major diseases including cancer and diabetes. "Cancer cells, for example, bring in as much as 20 times more glucose than non-cancerous cells of the same type," Moellering noted. He now wants to find out whether 1,3-BPG is part of the problem in such cells. At abnormally high levels, it conceivably could help force glucose metabolism toward the runaway cell proliferation that is a hallmark of cancer.

Cravatt and Moellering also want to learn more about what 1,3-BPG's lysine modification does in the nuclei and membrane compartments of cells, where they found evidence of it. "We suspect that it works to connect glucose metabolism to other pathways, perhaps as a kind of signaling mechanism," said Moellering.

Already Moellering has uncovered evidence that there are enzymes that work to reverse 1,3-BPG's modification of lysines -- which underscores the likelihood that this modification represents a fundamental, dynamic mechanism in cells. "We'd like to discover which enzymes catalyze the removal of the modification," said Cravatt, "because then, in principle, we could use inhibitors of these enzymes to control the levels of the modification and get a better understanding of its biological functions as well as the conditions under which it occurs."

Funding for the study, "Functional Lysine Modification by an Intrinsically Reactive Primary Glycolytic Metabolite," was provided by the National Institutes of Health (CA087660), the Skaggs Institute for Chemical Biology at TSRI and the Damon Runyon Cancer Research Foundation.

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As climate, disease links become clearer, study highlights need to forecast future shifts

Aug. 1, 2013 — Climate change is affecting the spread of infectious diseases worldwide, according to an international team of leading disease ecologists, with serious impacts to human health and biodiversity conservation. Writing in the journal Science, they propose that modeling the way disease systems respond to climate variables could help public health officials and environmental managers predict and mitigate the spread of lethal diseases.

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The issue of climate change and disease has provoked intense debate over the past decade, particularly in the case of diseases that affect humans, according to the University of Georgia's Sonia Altizer, who is the study's lead author.

"For a lot of human diseases, responses to climate change depend on the wealth of nations, healthcare infrastructure and the ability to take mitigating measures against disease," said Altizer, an associate professor in the UGA Odum School of Ecology. "The climate signal, in many cases, is hard to tease apart from other factors like vector control and vaccine and drug availability."

Climate warming already is causing changes in diseases affecting wildlife and agricultural ecosystems, she said. "In many cases, we're seeing an increase in disease and parasitism. But the impact of climate change on these disease relationships depends on the physiology of the organisms involved, the location on the globe and the structure of ecological communities."

At the organism level, climate change can alter the physiology of both hosts and parasites. Some of the clearest examples are found in the Arctic, where temperatures are rising rapidly, resulting in faster developing parasites. A lungworm that affects muskoxen, for instance, can now be transmitted over a longer period each summer, making it a serious problem for the populations it infects.

"The Arctic is like a 'canary in the global coal mine,'" said co-author Susan Kutz of the University of Calgary and Canadian Cooperative Wildlife Health Centre.

"Climate warming in the Arctic is occurring more rapidly than elsewhere, threatening the health and sustainability of Arctic plants and animals, which are adapted to a harsh and highly seasonal environment and are vulnerable to invasions by 'southern' species -- both animals and parasites."

A changing climate also is affecting entire plant and animal communities. This is particularly evident in tropical marine environments such as the world's coral reef ecosystems. In places like the Caribbean, warmer water temperatures have stressed corals and facilitated infections by pathogenic fungi and bacteria. When corals -- the framework builders of the ecosystem -- succumb, the myriad of species that depend on them are also at risk.

"Biodiversity loss is a well-established consequence of climate change," said coauthor Richard Ostfeld of the Cary Institute of Ecosystem Studies. "In a number of infectious disease systems, such as Lyme disease and West Nile virus, biodiversity loss is tied to greater pathogen transmission and increased human risk. Moving forward, we need models that are sensitive to both direct and indirect effects of climate change on infectious disease."

Where human health is concerned, there is not only the direct risk from pathogens like dengue, malaria and cholera, all of which are linked to warmer temperatures, but indirect risks from threats to agricultural systems and game species crucial for subsistence and cultural activities.

"Earth's changing climate and the global spread of infectious diseases are threatening human health, agriculture and wildlife. Solving these problems requires a comprehensive approach that unites scientists from biology, the geosciences and the social sciences," said Sam Scheiner, National Science Foundation program director for the joint NSF-National Institutes of Health Ecology and Evolution of Infectious Diseases Program.

The study was funded in part by the National Science Foundation.

"We need to transcend simple arguments about which is more important -- climate change or socioeconomics -- and ask just how much harder will it be to control diseases as the climate warms?" Ostfeld said. "Will it be possible at all in developing countries?"

To respond to that challenge, Altizer and her colleagues -- Kutz, Ostfeld, Pieter T. J. Johnson of the University of Colorado Boulder and C. Drew Harvell of Cornell University -- laid out an agenda for future research and action.

One recommendation is to expand data about the physiological responses hosts and parasites have to temperature changes to help develop early warning systems.

"We'd like to be able to predict, for example, that if the climate warms by a certain amount, then in a particular host-parasite system we might see an increase from one to two transmission cycles per year," Altizer said. "But we'd also like to try to tie these predictions to actions that might be taken."

Such forecasting is well established in crop disease management and has been used to both preventatively close coral reefs and target areas at risk of malaria outbreaks.

"We face a tough task in the oceans, where disease outbreaks can be out of sight and undetected," Harvell said. "Because some coral disease outbreaks are predictable from warming events, we are developing forecasting programs to help us respond before the outbreak begins."

The researchers also pointed out that certain human communities, such as those of indigenous peoples in the Arctic, could be disproportionately impacted by climate-disease interactions.

"A better understanding of the impacts of parasitism on wildlife health, and an ability to make accurate predictions of future wildlife sustainability, is particularly important to aboriginal people across the Arctic who depend on wildlife as a source of food, income and a focus of cultural activities," Kutz said.

Johnson continued, "Because disease represents the product of multiple interacting species, including hosts, pathogens and other members of the food web, forecasting responses to ongoing climate shifts is a tremendous challenge," he said. "Given the rising importance of infectious diseases not only for human health but also wildlife conservation, it's also a challenge for which we are in sore need of a solution. We hope our work contributes to that."

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New water splitting technique efficiently produces hydrogen fuel

The CU-Boulder team has devised a solar-thermal system in which sunlight could be concentrated by a vast array of mirrors onto a single point atop a central tower up to several hundred feet tall. The tower would gather heat generated by the mirror system to roughly 2,500 degrees Fahrenheit (1,350 Celsius), then deliver it into a reactor containing chemical compounds known as metal oxides, said CU-Boulder Professor Alan Weimer, research group leader.

As a metal oxide compound heats up, it releases oxygen atoms, changing its material composition and causing the newly formed compound to seek out new oxygen atoms, said Weimer. The team showed that the addition of steam to the system -- which could be produced by boiling water in the reactor with the concentrated sunlight beamed to the tower -- would cause oxygen from the water molecules to adhere to the surface of the metal oxide, freeing up hydrogen molecules for collection as hydrogen gas.

"We have designed something here that is very different from other methods and frankly something that nobody thought was possible before," said Weimer of the chemical and biological engineering department. "Splitting water with sunlight is the Holy Grail of a sustainable hydrogen economy."

A paper on the subject was published in the Aug. 2 issue of Science. The team included co-lead authors Weimer and Associate Professor Charles Musgrave, first author and doctoral student Christopher Muhich, postdoctoral researcher Janna Martinek, undergraduate Kayla Weston, former CU graduate student Paul Lichty, former CU postdoctoral researcher Xinhua Liang and former CU researcher Brian Evanko.

One of the key differences between the CU method and other methods developed to split water is the ability to conduct two chemical reactions at the same temperature, said Musgrave, also of the chemical and biological engineering department. While there are no working models, conventional theory holds that producing hydrogen through the metal oxide process requires heating the reactor to a high temperature to remove oxygen, then cooling it to a low temperature before injecting steam to re-oxidize the compound in order to release hydrogen gas for collection.

"The more conventional approaches require the control of both the switching of the temperature in the reactor from a hot to a cool state and the introduction of steam into the system," said Musgrave. "One of the big innovations in our system is that there is no swing in the temperature. The whole process is driven by either turning a steam valve on or off."

"Just like you would use a magnifying glass to start a fire, we can concentrate sunlight until it is really hot and use it to drive these chemical reactions," said Muhich. "While we can easily heat it up to more than 1,350 degrees Celsius, we want to heat it to the lowest temperature possible for these chemical reactions to still occur. Hotter temperatures can cause rapid thermal expansion and contraction, potentially causing damage to both the chemical materials and to the reactors themselves."

In addition, the two-step conventional idea for water splitting also wastes both time and heat, said Weimer, also a faculty member at CU-Boulder's BioFrontiers Institute. "There are only so many hours of sunlight in a day," he said.

The research was supported by the National Science Foundation and by the U.S. Department of Energy.

With the new CU-Boulder method, the amount of hydrogen produced for fuel cells or for storage is entirely dependent on the amount of metal oxide -- which is made up of a combination of iron, cobalt, aluminum and oxygen -- and how much steam is introduced into the system. One of the designs proposed by the team is to build reactor tubes roughly a foot in diameter and several feet long, fill them with the metal oxide material and stack them on top of each other. A working system to produce a significant amount of hydrogen gas would require a number of the tall towers to gather concentrated sunlight from several acres of mirrors surrounding each tower.

Weimer said the new design began percolating within the team about two years ago. "When we saw that we could use this simpler, more effective method, it required a change in our thinking," said Weimer. "We had to develop a theory to explain it and make it believable and understandable to other scientists and engineers."

Despite the discovery, the commercialization of such a solar-thermal reactor is likely years away. "With the price of natural gas so low, there is no incentive to burn clean energy," said Weimer, also the executive director of the Colorado Center for Biorefining and Biofuels, or C2B2. "There would have to be a substantial monetary penalty for putting carbon into the atmosphere, or the price of fossil fuels would have to go way up."

C2B2 is an arm of the Colorado Energy Research Collaboratory involving CU-Boulder, the Colorado School of Mines, Colorado State University and the National Renewable Energy Laboratory in Golden. The collaboratory works with industry partners, public agencies and other institutions to commercialize renewable energy technologies, support economic growth in the state and nation and educate the future workforce.

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Extreme wildfires in Western U.S. likely fueled by climate change

These erratic fires are harder to contain and often result in catastrophic damage and loss of property and life. Although not analyzed in the study, the recent Arizona wildfire that began with a lightning strike and killed 19 firefighters appeared to be such an unpredictable, fast-spreading blaze, according to a state report.

The MSU-led study, which appears in the Journal of Applied Meteorology and Climatology, predicts the trend will continue in the western United States.

"Our findings suggest that future lower atmospheric conditions may favor larger and more extreme wildfires, posing an additional challenge to fire and forest management," said Lifeng Luo, MSU assistant professor of geography and lead author on the study.

The researchers analyzed current and future climate patterns projected by multiple regional climate models and their effect on the spread of fire in a mountainous region that includes Arizona, Idaho, Nevada, New Mexico, Utah and Wyoming. The study focused on August, the most active month for wildfires in the western United States.

August 2012 saw 3.6 million acres burn in the region, the most of any August since 2000. However, there were only 6,948 fires in August 2012 -- the second fewest in that 12-year timeframe -- meaning the fires were much larger.

Large wildfires are mainly driven by natural factors including the availability of fuel (vegetation), precipitation, wind and the location of lightning strikes. In particular, the researchers found that exceptionally dry and unstable conditions in the earth's lower atmosphere will continue contributing to "erratic and extreme fire behavior."

"Global climate change may have a significant impact on these factors, thus affecting potential wildfire activity across many parts of the world," the study says.

Co-authors include Ying Tang and Shiyuan Zhong from MSU, and Xindu Bian and Warren Heilman from the USDA Forest Service.

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Existing cropland could feed four billion more by dropping biofuels and animal feed

Aug. 1, 2013 — The world's croplands could feed 4 billion more people than they do now just by shifting from producing animal feed and biofuels to producing exclusively food for human consumption, according to new research from the Institute on the Environment at the University of Minnesota.

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Even a smaller, partial shift from crop-intensive livestock such as feedlot beef to food animals such as chicken or pork could increase agricultural efficiency and provide food for millions, the study says.

"We essentially have uncovered an astoundingly abundant supply of food for a hungry world, hidden in plain sight in the farmlands we already cultivate," says graduate research assistant Emily Cassidy, lead author of the paper published in Environmental Research Letters. "Depending on the extent to which farmers and consumers are willing to change current practices, existing croplands could feed millions or even billions more people."

Demand for crops is expected to double by 2050 as population grows and increasing affluence boosts meat consumption. Meat takes a particularly big toll on food security because it takes up to 30 crop calories to produce a single calorie of meat. In addition, crops are increasingly being used for biofuels rather than food production. This study sought to quantify the benefit to food security that would accrue if some or all of the lands used to produce animal feed and fuel were reallocated to directly produce food for people.

To get at that question, Cassidy and colleagues first mapped the extent and productivity of 41 major crops between 1997 and 2003, adjusting numbers for imports and exports and calculating conversion efficiencies of animal feed using U.S. Department of Agriculture data. The researchers assumed humans need an average of 2,700 calories per day, and grazing lands and animals were not included in the study. Among the team's findings:

Only 12 percent of crop calories used for animal feed end up as calories consumed by humans.
Only 55 percent of crop calories worldwide directly nourish people.
Growing food exclusively for direct human consumption could boost available food calories up to 70 percent
U.S. agriculture alone could feed an additional 1 billion people by shifting crop calories to direct human consumption.
When calculated on the basis of protein rather than calories, results were similar. For instance, of all plant protein produced, 49 percent ends up in human diets.

In addition to the global findings, the research team looked at allocation of crop calories in four key countries: India, China, Brazil and the U.S. They found that while India allocates 90 percent of calories to feeding people, the other three allocate 58 percent, 45 percent, and 27 percent, respectively.

Noting the major cultural and economic dimensions involved, the researchers acknowledged that while a complete shift from animal to plant-based diets may not be feasible, even a partial shift would benefit food security. Quantifying the impact of various strategies, they found that a shift from crop-intensive beef to pork and chicken could feed an additional 357 million people, and a shift to nonmeat diets that include eggs and milk could feed an additional 815 million people.

The researchers emphasized that they are not making diet prescriptions or recommendations, just pointing out opportunities for gains in food production. They noted that humans can completely meet protein needs with plant-based diets, but that crop systems would need to shift (e.g., toward more production of protein-rich legumes) to meet human dietary needs.

"The good news is that we already produce enough calories to feed a few billion more people," Cassidy says. "As our planet gets more crowded or we experience disasters like droughts and pests, we can find ways of using existing croplands more efficiently."

In addition to her role as Global Landscapes Initiative graduate research assistant with the Institute on the Environment, Cassidy is a graduate student in the Natural Resources Science and Management program in the University of Minnesota's College of Food, Agriculture and Natural Resource Sciences.

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The when and where of the Y: Research on Y chromosomes uncovers new clues about human ancestry

But even though we all trace our family lineage to a few common ancestors, scientists still don't know exactly when and how those few ancestors started to give rise to the incredible diversity of today's population.

A brand-new finding, made using advanced analysis of DNA from all over the world, sheds new light on this mystery. By studying the DNA sequence of Y chromosomes of men from many different populations, scientists have determined that their male most recent common ancestor (MRCA) lived sometime between 120,000 and 156,000 years ago.

It's the first time the human ancestry has been traced back through the male line by sequencing the DNA of many entire Y chromosomes.

And, it agrees reasonably well with previous findings about our female most recent common ancestor, made by studying DNA carried down through the human race's female line. Such studies used DNA from mitochrondria -- structures inside cells -- and placed that time of the most recent common ancestor between 99,000 and 148,000 years ago. That agreement makes the new finding especially significant:

The research was done by a team of scientists from Stanford University, the University of Michigan Medical School, Stony Brook University, and their colleagues, and is published in the journal Science.

The team hopes their work will lead to further research on Y chromosomes as vehicles for studying human history -- and tracing male lineages back to the common "Adam" ancestors.

Jeffrey Kidd, Ph.D., an Assistant Professor of Human Genetics and Computational Medicine & Bioinformatics who worked on the new study, notes that only recently has it become possible to sequence Y chromosomes, because of technical limitations of previous approaches.

The new paper details how the team was able to make reliable measurements of the sequence variation along the Y chromosome -- which is handed down only from father to son without exchanging, or recombining, genetic material with other chromosomes.

Kidd notes that this initial paper on Y chromosome sequence diversity provides important first evidence that the male most recent common ancestor did not live more recently than the female most recent common ancestor.

"We're interested in understanding the historical relationships between many different human populations, and the migration patterns that have led to the peopling of the world," he says. "We hope that others will make use of this approach and sequence additional chromosomes of interest that are related to the peopling of specific places."

The study involved Y chromosomes obtained through the Human Genome Diversity Project, and from other sources. It included chromosomes from 69 men in several populations in sub-Saharan Africa, and from Siberia, Cambodia, Pakistan, Algeria and Mexico.

The great migrations of our ancestors out of Africa, across Asian and Europe and into the Americas all helped shape today's populations -- as did more recent forces related to colonialism and ever-growing global mobility.

Genetic studies such as this one may help anthropologists understand those migrations -- and their timing -- even better by giving them a genetic "clock" to use when studying today's humans, or potentially DNA extracted from ancient bones. It may also help scientists understand the great genetic diversity seen across Africa, and the evolution process that led to modern humans.

The reconciliation of the timing of "Adam" and "Eve," however, may be this study's most important immediate implication.

"This has been a conundrum in human genetics for a long time," said Carlos D. Bustamante, PhD, a professor of genetics at Stanford and senior author of the study. "Previous research has indicated that the male MRCA lived much more recently than the female MRCA. But now our research shows that there's no discrepancy. In fact, if anything, the Y chromosome may be a bit older."

In addition to Kidd and Bustamante, the research team includes U-M's Elzbieta Sliwerska, Stanford's G. David Poznik, Brenna M. Henn, Muh-Ching Yee, Ghia M. Euskirchen, Alice A. Lin, Michael Snyder, and Peter A. Underhill, and Lluis Quintana-Murci from Institut Pasteur in Paris.

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Climate change occurring ten times faster than at any time in past 65 million years

Aug. 1, 2013 — The planet is undergoing one of the largest changes in climate since the dinosaurs went extinct. But what might be even more troubling for humans, plants and animals is the speed of the change. Stanford climate scientists warn that the likely rate of change over the next century will be at least 10 times quicker than any climate shift in the past 65 million years.

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If the trend continues at its current rapid pace, it will place significant stress on terrestrial ecosystems around the world, and many species will need to make behavioral, evolutionary or geographic adaptations to survive.

Although some of the changes the planet will experience in the next few decades are already "baked into the system," how different the climate looks at the end of the 21st century will depend largely on how humans respond.

The findings come from a review of climate research by Noah Diffenbaugh, an associate professor of environmental Earth system science, and Chris Field, a professor of biology and of environmental Earth system science and the director of the Department of Global Ecology at the Carnegie Institution. The work is part of a special report on climate change in the current issue of Science.

Diffenbaugh and Field, both senior fellows at the Stanford Woods Institute for the Environment, conducted the targeted but broad review of scientific literature on aspects of climate change that can affect ecosystems, and investigated how recent observations and projections for the next century compare to past events in Earth's history.

For instance, the planet experienced a 5 degree Celsius hike in temperature 20,000 years ago, as Earth emerged from the last ice age. This is a change comparable to the high-end of the projections for warming over the 20th and 21st centuries.

The geologic record shows that, 20,000 years ago, as the ice sheet that covered much of North America receded northward, plants and animals recolonized areas that had been under ice. As the climate continued to warm, those plants and animals moved northward, to cooler climes.

"We know from past changes that ecosystems have responded to a few degrees of global temperature change over thousands of years," said Diffenbaugh. "But the unprecedented trajectory that we're on now is forcing that change to occur over decades. That's orders of magnitude faster, and we're already seeing that some species are challenged by that rate of change."

Some of the strongest evidence for how the global climate system responds to high levels of carbon dioxide comes from paleoclimate studies. Fifty-five million years ago, carbon dioxide in the atmosphere was elevated to a level comparable to today. The Arctic Ocean did not have ice in the summer, and nearby land was warm enough to support alligators and palm trees.

"There are two key differences for ecosystems in the coming decades compared with the geologic past," Diffenbaugh said. "One is the rapid pace of modern climate change. The other is that today there are multiple human stressors that were not present 55 million years ago, such as urbanization and air and water pollution."

Record-setting heat

Diffenbaugh and Field also reviewed results from two-dozen climate models to describe possible climate outcomes from present day to the end of the century. In general, extreme weather events, such as heat waves and heavy rainfall, are expected to become more severe and more frequent.

For example, the researchers note that, with continued emissions of greenhouse gases at the high end of the scenarios, annual temperatures over North America, Europe and East Asia will increase 2-4 degrees C by 2046-2065. With that amount of warming, the hottest summer of the last 20 years is expected to occur every other year, or even more frequently.

By the end of the century, should the current emissions of greenhouse gases remain unchecked, temperatures over the northern hemisphere will tip 5-6 degrees C warmer than today's averages. In this case, the hottest summer of the last 20 years becomes the new annual norm.

"It's not easy to intuit the exact impact from annual temperatures warming by 6 C," Diffenbaugh said. "But this would present a novel climate for most land areas. Given the impacts those kinds of seasons currently have on terrestrial forests, agriculture and human health, we'll likely see substantial stress from severely hot conditions."

The scientists also projected the velocity of climate change, defined as the distance per year that species of plants and animals would need to migrate to live in annual temperatures similar to current conditions. Around the world, including much of the United States, species face needing to move toward the poles or higher in the mountains by at least one kilometer per year. Many parts of the world face much larger changes.

The human element

Some climate changes will be unavoidable, because humans have already emitted greenhouse gases into the atmosphere, and the atmosphere and oceans have already been heated.

"There is already some inertia in place," Diffenbaugh said. "If every new power plant or factory in the world produced zero emissions, we'd still see impact from the existing infrastructure, and from gases already released."

The more dramatic changes that could occur by the end of the century, however, are not written in stone. There are many human variables at play that could slow the pace and magnitude of change -- or accelerate it.

Consider the 2.5 billion people who lack access to modern energy resources. This energy poverty means they lack fundamental benefits for illumination, cooking and transportation, and they're more susceptible to extreme weather disasters. Increased energy access will improve their quality of life -- and in some cases their chances of survival -- but will increase global energy consumption and possibly hasten warming.

Diffenbaugh said that the range of climate projections offered in the report can inform decision-makers about the risks that different levels of climate change pose for ecosystems.

"There's no question that a climate in which every summer is hotter than the hottest of the last 20 years poses real risks for ecosystems across the globe," Diffenbaugh said. "However, there are opportunities to decrease those risks, while also ensuring access to the benefits of energy consumption."

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When galaxies switch off: Hubble's COSMOS survey solves 'quenched' galaxy mystery

Until now, these small, snuffed-out galaxies were thought to grow into the larger quenched galaxies we see nearby.

As these galaxies are no longer forming new stars, they were thought to grow by colliding and merging with other smaller quenched galaxies some five to ten times less massive. However, these mergers would require many such small galaxies floating around for the quenched population to snack on -- which we do not see.

Until recently it had not been possible to explore a sufficient number of quenched galaxies, but now a team of astronomers has used observations from the Hubble COSMOS survey to identify and count these switched-off galaxies throughout the last eight billion years of cosmic history.

"The apparent puffing up of quenched galaxies has been one of the biggest puzzles about galaxy evolution for many years," says Marcella Carollo of ETH Zurich, Switzerland, lead author on a new paper exploring these galaxies. "No single collection of images has been large enough to enable us to study very large numbers of galaxies in exactly the same way -- until Hubble's COSMOS," adds co-author Nick Scoville of Caltech, USA.

The team used the large set of COSMOS images, alongside additional observations from the Canada-France-Hawaii Telescope and the Subaru Telescope, both in Hawaii, USA, to peer back to when the Universe was less than half its present age. These observations mapped an area in the sky almost nine times that of the full Moon.

The quenched galaxies seen at these times are small and compact -- and surprisingly, it seems they stay that way. Rather than puffing up and growing via mergers over time, these small galaxies mostly keep the size they had when their star formation switched off. So why do we see these galaxies apparently growing larger over time?

"We found that a large number of the bigger galaxies instead switch off at later times, joining their smaller quenched siblings and giving the mistaken impression of individual galaxy growth over time," says co-author Simon Lilly, also of ETH Zurich. "It's like saying that the increase in the average apartment size in a city is not due to the addition of new rooms to old buildings, but rather to the construction of new, larger apartments," adds co- author Alvio Renzini of INAF Padua Observatory, Italy.

This tells us a lot about how galaxies have evolved over the last eight billion years of the Universe's history. It was already known that actively star-forming galaxies were smaller in the early Universe, explaining why they were smaller when their star formation first switched off.

"COSMOS provided us with simply the best set of observations for this sort of work -- it lets us study very large numbers of galaxies in exactly the same way, which hasn't been possible before," adds co-author Peter Capak, also of Caltech. "Our study offers a surprisingly simple and obvious explanation to this puzzle. Whenever we see simplicity in nature amidst apparent complexity, it's very satisfying," concludes Carollo.

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Look where 3D printing can get you headlights Led Luminaries

2013/08/01

07aug13BlogLamp.jpg

Not sure if this bicycle light has been made or is just excellent rendering of a CAD design.

Either way, the case it ready to be made in a 3D printer, and shows how straightforward making a prototype could be.

More information on Thingiverse.

Bet those heatsinks get warm after a while.

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