Blood Vessels: the Pied Piper for Growing Nerve Cells
Researchers at Johns Hopkins have discovered that blood vessels in the head can guide growing facial nerve cells with blood pressure controlling proteins. The findings, which suggest that blood vessels throughout the body might have the same power of persuasion over many nerves, are published this week in Nature.
“We’re excited to have stumbled across another family of proteins that can tell a growing nerve which way to grow,” says David Ginty, Ph.D., a professor of neuroscience at Hopkins and investigator of the Howard Hughes Medical Institute. “But the really interesting thing is that the nerves appear to use blood vessels as guideposts to direct their growth in one of several possible directions.”
The research team studied in mice a group of about 15,000 nerve cells known as the superior cervical ganglia, or SCG, which extend projections that innervate various structures in the head including the eyes, mouth and salivary glands. The SCG sits in a Y-like branching point of the blood vessel in the neck that supplies the head with blood, the carotid artery. In the developing embryo, nerve projections grow out of the SCG and grow along one of the two branches of the carotid artery; the nerves that grow along the internal carotid innervate the eyes and mouth among other head structures, and those that grow along the external carotid innervate the salivary glands.
To figure out how nerve cells “choose” to grow along the external carotid artery to innervate the salivary glands, the team looked for genes that appear to be preferentially turned on in the external carotid, and off in the internal carotid. Says Ginty, “There’s only two directions they can go and we wanted to know if they choose their direction or if the decision to go one way or the other is random.”
They found one gene that is expressed preferentially in the external carotid, a gene that makes the blood pressure regulating protein, endothelin, active. “It comes as no surprise that something critical for regulating the cardiovascular system in the adult also is used for directing nerve growth in the developing embryo,” says Ginty. “The genome is limited and nature has figured out a way to use things over and over again for unrelated functions.”
Further examination of the arteries in mouse embryos confirmed that endothelin is found only in the external carotid. To confirm that the nerve cell projections grow toward endothelin, the researchers removed SCGs and grew each one next to an endothelin-soaked bead. Checking on them three days later, the team found that nerves from the SCGs had grown towards the beads. To be certain that endothelin directs nerve growth in the living animal, the researchers then looked in mice that had the endothelin gene removed. Sure enough, these mice had no nerves growing along their external carotid arteries.
The team then wondered if all growing nerves in the SCG can respond to endothelin. So they looked for the endothelin receptors in SCG nerves and found only a subset of SCG nerves make endothelin receptors and concluded that those nerves somehow already had been chosen to respond to the endothelin made by the external carotid.
“How do these nerve cells know which target organ they’re supposed to innervate when they all come from the same progenitor?” asks Ginty. “This is what we’re going to study next.”
The research was funded by the National Institutes of Health and the Howard Hughes Medical Institute.
Authors on the paper are Takako Makita and Ginty of Hopkins; Henry Sucov of the University of Southern California; Cheryl Gariepy of the University of Michigan; and Masashi Yanagisawa of the University of Texas Southwestern Medical Center.
Saturday, April 12, 2008
“Black Gold Agriculture” May Revolutionize Farming, Curb Global Warming
Fifteen hundred years ago, tribes people from the central Amazon basin mixed their soil with charcoal derived from animal bone and tree bark. Today, at the site of this charcoal deposit, scientists have found some of the richest, most fertile soil in the world. Now this ancient, remarkably simple farming technique seems far ahead of the curve, holding promise as a carbon-negative strategy to rein in world hunger as well as greenhouse gases.
At the 235th national meeting of the American Chemical Society, scientists report that charcoal derived from heated biomass has an unprecedented ability to improve the fertility of soil — one that surpasses compost, animal manure, and other well-known soil conditioners.
They also suggest that this so-called “biochar” profoundly enhances the natural carbon seizing ability of soil. Dubbed “black gold agriculture,” scientists say this “revolutionary” farming technique can provide a cheap, straight-forward strategy to reduce greenhouse gases by trapping them in charcoal-laced soil.
“Charcoal fertilization can permanently increase soil organic matter content and improve soil quality, persisting in soil for hundreds to thousands of years,” Mingxin Guo, Ph.D., and colleagues report. In what they describe as a “new and pioneering” ACS report — the first systematic investigation of soil improvement by charcoal fertilization — Guo found that soils receiving charcoal produced from organic wastes were much looser, absorbed significantly more water and nutrients and produced higher crop biomass. The authors, with Delaware State University, say “the results demonstrate that charcoal amendment is a revolutionary approach for long-term soil quality improvement.”
Soil deterioration from depletion of organic matter is an increasingly serious global problem that contributes to hunger and malnutrition. Often a result of unsustainable farming, overuse of chemical fertilizers and drought, the main weapons to combat the problem —compost, animal manure and crop debris — decompose rapidly.
“Earth’s soil is the largest terrestrial pool of carbon,” Guo said. “In other words, most of the earth’s carbon is fixed in soil.” But if this soil is intensively cultivated by tillage and chemical fertilization, organic matter in soil will be quickly decomposed into carbon dioxide by soil microbes and released into the atmosphere, leaving the soil compacted and nutrient-poor.
Applying raw organic materials to soil only provides a temporary solution, since the applied organic matter decomposes quickly. Converting this unutilized raw material into biochar, a non-toxic and stable fertilizer, could keep carbon in the soil and out of the atmosphere, says Guo.
“Speaking in terms of fertility and productivity, the soil quality will be improved. It is a long-term effect. After you apply it once, it will be there for hundreds of years,” according to Guo. With its porous structure and high nutrient- and water-holding capabilities, biochar could become an extremely attractive option for commercial farmers and home gardeners looking for long-term soil improvement.
The researchers planted winter wheat in pots of soil in a greenhouse. Some pots were amended with two percent biochar, generated from readily available ingredients like tree leaves, corn stalk and wood chips. The other pots contained ordinary soil.
The biochar-infused soil showed vastly improved germination and growing rates compared to regular soil. Guo says that even a one-percent charcoal treatment would lead to improved crop yield.
Guo is “positive” that this ground-breaking farming technique can help feed countries with poor soil quality. “We hope this technology will be extended worldwide,” says Guo.
“The production of current arable land could be significantly improved to provide more food and fiber for the growing populations. We want to call it the second agricultural revolution, or black gold revolution!”
He suggests that charcoal production has been practiced for at least 3000 years. But until now, nobody realized that this charcoal could improve soil fertility until archaeologists stumbled on the aforementioned Amazonian soil several years ago.
Biochar production is straightforward, involving a heating process known as pyrolysis. First, organic residue such as tree leaves and wood chips is packed into a metal container and sealed. Then, through a small hole on top, the container is heated and the material burns. The raw organic matter is transformed into black charcoal. Smokes generated during pyrolysis can also be collected and cooled down to form bio-oil, a renewable energy source, says Guo.
In lieu of patenting biochar, Guo says he is most interested in extending the technology into practice as soon as possible. To that end, his colleagues at Delaware State University are investigating a standardized production procedure for biochar. They also foresee long-term field studies are needed to validate and demonstrate the technology. Guo noted that downsides of biochar include transportation costs resulting from its bulk mass and a need to develop new tools to spread the granular fertilizer over large tracts of farmland.
The researchers are about to embark on a five-year study on the effect of “black gold” on spinach, green peppers, tomatoes and other crops. They seek the long-term effects of biochar fertilization on soil carbon changes, crop productivity and its effect of the soil microorganism community.
“Through this long-term work, we will show to people that biochar fertilization will significantly change our current conventional farming concepts,” says Guo.
The American Chemical Society — the world’s largest scientific society — is a nonprofit organization chartered by the U.S. Congress and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.
Fifteen hundred years ago, tribes people from the central Amazon basin mixed their soil with charcoal derived from animal bone and tree bark. Today, at the site of this charcoal deposit, scientists have found some of the richest, most fertile soil in the world. Now this ancient, remarkably simple farming technique seems far ahead of the curve, holding promise as a carbon-negative strategy to rein in world hunger as well as greenhouse gases.
At the 235th national meeting of the American Chemical Society, scientists report that charcoal derived from heated biomass has an unprecedented ability to improve the fertility of soil — one that surpasses compost, animal manure, and other well-known soil conditioners.
They also suggest that this so-called “biochar” profoundly enhances the natural carbon seizing ability of soil. Dubbed “black gold agriculture,” scientists say this “revolutionary” farming technique can provide a cheap, straight-forward strategy to reduce greenhouse gases by trapping them in charcoal-laced soil.
“Charcoal fertilization can permanently increase soil organic matter content and improve soil quality, persisting in soil for hundreds to thousands of years,” Mingxin Guo, Ph.D., and colleagues report. In what they describe as a “new and pioneering” ACS report — the first systematic investigation of soil improvement by charcoal fertilization — Guo found that soils receiving charcoal produced from organic wastes were much looser, absorbed significantly more water and nutrients and produced higher crop biomass. The authors, with Delaware State University, say “the results demonstrate that charcoal amendment is a revolutionary approach for long-term soil quality improvement.”
Soil deterioration from depletion of organic matter is an increasingly serious global problem that contributes to hunger and malnutrition. Often a result of unsustainable farming, overuse of chemical fertilizers and drought, the main weapons to combat the problem —compost, animal manure and crop debris — decompose rapidly.
“Earth’s soil is the largest terrestrial pool of carbon,” Guo said. “In other words, most of the earth’s carbon is fixed in soil.” But if this soil is intensively cultivated by tillage and chemical fertilization, organic matter in soil will be quickly decomposed into carbon dioxide by soil microbes and released into the atmosphere, leaving the soil compacted and nutrient-poor.
Applying raw organic materials to soil only provides a temporary solution, since the applied organic matter decomposes quickly. Converting this unutilized raw material into biochar, a non-toxic and stable fertilizer, could keep carbon in the soil and out of the atmosphere, says Guo.
“Speaking in terms of fertility and productivity, the soil quality will be improved. It is a long-term effect. After you apply it once, it will be there for hundreds of years,” according to Guo. With its porous structure and high nutrient- and water-holding capabilities, biochar could become an extremely attractive option for commercial farmers and home gardeners looking for long-term soil improvement.
The researchers planted winter wheat in pots of soil in a greenhouse. Some pots were amended with two percent biochar, generated from readily available ingredients like tree leaves, corn stalk and wood chips. The other pots contained ordinary soil.
The biochar-infused soil showed vastly improved germination and growing rates compared to regular soil. Guo says that even a one-percent charcoal treatment would lead to improved crop yield.
Guo is “positive” that this ground-breaking farming technique can help feed countries with poor soil quality. “We hope this technology will be extended worldwide,” says Guo.
“The production of current arable land could be significantly improved to provide more food and fiber for the growing populations. We want to call it the second agricultural revolution, or black gold revolution!”
He suggests that charcoal production has been practiced for at least 3000 years. But until now, nobody realized that this charcoal could improve soil fertility until archaeologists stumbled on the aforementioned Amazonian soil several years ago.
Biochar production is straightforward, involving a heating process known as pyrolysis. First, organic residue such as tree leaves and wood chips is packed into a metal container and sealed. Then, through a small hole on top, the container is heated and the material burns. The raw organic matter is transformed into black charcoal. Smokes generated during pyrolysis can also be collected and cooled down to form bio-oil, a renewable energy source, says Guo.
In lieu of patenting biochar, Guo says he is most interested in extending the technology into practice as soon as possible. To that end, his colleagues at Delaware State University are investigating a standardized production procedure for biochar. They also foresee long-term field studies are needed to validate and demonstrate the technology. Guo noted that downsides of biochar include transportation costs resulting from its bulk mass and a need to develop new tools to spread the granular fertilizer over large tracts of farmland.
The researchers are about to embark on a five-year study on the effect of “black gold” on spinach, green peppers, tomatoes and other crops. They seek the long-term effects of biochar fertilization on soil carbon changes, crop productivity and its effect of the soil microorganism community.
“Through this long-term work, we will show to people that biochar fertilization will significantly change our current conventional farming concepts,” says Guo.
The American Chemical Society — the world’s largest scientific society — is a nonprofit organization chartered by the U.S. Congress and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.
Dr. Mom Was Right — and Wrong — About Washing Fruits and Vegetables
Washing fresh fruits and vegetables before eating may reduce the risk of food poisoning and those awful episodes of vomiting and diarrhea. But according to new research, described today at the 235th national meeting of the American Chemical Society, washing alone — even with chlorine disinfectants — may not be enough.
Studies show that certain disease-causing microbes are masters at playing hide-and-go seek with such chemical sanitizers. These bacteria can make their way inside the leaves of lettuce, spinach and other vegetables and fruit, where surface treatments cannot reach. In addition, microbes can organize themselves into tightly knit communities called biofilms that coat fruits and vegetables and protect the bacteria from harm. This kind of bacterial community can harbor multiple versions of infectious, disease-causing bacteria, such as Salmonella and E. coli.
Now, new findings from scientists at the U.S. Department of Agriculture suggest that irradiation, a food treatment currently being reviewed by the FDA, can effectively kill internalized pathogens that are beyond the reach of conventional chemical sanitizers.
Irradiation exposes food to a source of electron beams, creating positive and negative charges. It disrupts the genetic material of living cells, inactivating parasites and destroying pathogens and insects in food, including E. coli and Salmonella.
Using this technique on fresh and fresh-cut fruits and vegetables could provide a reliable way to reduce the numbers of foodborne illnesses reported each year in the United States, says Brendan A. Niemira, Ph.D., a microbiologist with the USDA's Agricultural Research Service in Wyndmoor, Pa., who directed the study.
“When bacteria are protected — whether they’re inside a leaf or inside a biofilm — they’re not going to be as easy to kill,” Niemira says. “This is the first study to look at the use of irradiation on bacteria that reside inside the inner spaces of a leaf or buried within a biofilm.”
The quantity of fresh fruits and vegetables in the United States has increased every year in the last decade. Unfortunately, the increase in consumption has been accompanied with an increase in the number of outbreaks and recalls due to contamination with human pathogens such as E. coli. Fresh fruits and vegetables carry the potential risk of contamination because they are generally grown in open fields with potential exposure to pathogens from soil, irrigation water, manure, wildlife or other sources.
“The spinach outbreak in the fall of 2006, in particular, raised questions about how these organisms survived the various treatments that are applied – the rinses and the washes and things,” Niemira says.
At the time, research had already demonstrated that pathogens like Salmonella and E. coli can be drawn into fruits after they've formed, and can migrate into them during fruit growth and maturation if the plant is exposed to them during pollination or in the irrigation water. But questions remained as to whether a penetrating process such as irradiation could kill a pest located inside a leaf.
To see how internalized sources of bacteria responded to various treatments, Niemira and his colleagues devised a way to pull bacteria into the leaves of leafy green vegetables. The scientists cut leaves of romaine lettuce and baby spinach into pieces and submerged them in a cocktail mixture of E. coli. The bacteria was pushed inside the leaves with a vacuum perfusion process. The leaves were then treated with either a three-minute water wash, a three-minute chemical treatment or irradiation.
After treatment, the leaves were suspended in a neutral buffer solution and crushed to recover and count the internalized bacteria. The study showed that washing with plain water was not effective at reducing the levels of the pathogen on either spinach or lettuce. The chemical treatment, a sodium hypochlorite solution, did not result in significant reductions of E. coli cells in spinach leaves, and an gave less than 90 percent reduction of E. coli in the romaine lettuce samples.
Ionizing radiation, in contrast, significantly reduced the pathogen population in both the spinach and the lettuce leaves. The level of kill was dependent on the dose applied, with reductions of 99.99 percent on romaine lettuce and 99.9 percent on spinach at the highest dose tested.
The researchers then conducted lab tests with biofilms to see how well different strains of Salmonella and E. coli, which were buried inside the biofilms, stood up to irradiation.
The biofilms that contained Salmonella tended to die more easily with irradiation, while those that were infected with E. coli were a bit more resistant, Niemira says.
“In the most resistant cases, we saw a difference of a few percent, but it was nothing at all compared to the resistance you might see if you were using a chemical treatment,” he says.
The scientists now are conducting studies of biofilms on leafy green vegetables to better gauge how irradiation might work on plants in the field.
Niemira says it’s still not clear if human pathogens can actually increase in population within plant tissues, or if they merely persist.
“This is an important question, because if the pathogens don't reproduce effectively within these protected spaces and stay below minimally infective population sizes, then the risk they pose to consumers is less,” he says. “If they are able to reproduce inside, then they may increase to more dangerous levels.”
Though some activist groups continue to speak against irradiation, consumer confidence in the application has grown steadily through the years as studies have shown its effectiveness in reducing pathogens that cause foodborne illnesses, says Christine Bruhn, Ph.D., who focuses on consumer issues in food safety and quality at the University of California at Davis.
“Sixty to 90 percent of consumers indicate that they would buy irradiated food when told of the benefits of the process and the endorsement of health authorities,” Bruhn says.
She and Niemira have submitted a proposal to the USDA to further explore the applications of irradiation in leafy greens and to gauge consumer acceptance of this application.
Note for reporters’ use only: For full information about the New Orleans meeting, including access to abstracts of more than 9,000 scientific papers and hundreds of non-technical summaries, visit http://www.eurekalert.org/acsmeet.php.
The paper on this research, AGFD 136, will be presented at 9:00 a.m., Thursday, April 10, 2008, in the Marriott Convention Center, Blaine Kern E, during the symposium, "Intentional and Unintentional Contaminants of Food and Feed."
Brendan A Niemira, Ph.D., is a microbiologist with the USDA's Agricultural Research Service in Wyndmoor, Pa.
ALL PAPERS ARE EMBARGOED UNTIL DATE AND TIME OF PRESENTATION, UNLESS OTHERWISE NOTED
AGFD 136
Inactivation of microbial contaminants in fresh produce
Program Selection: Division of Agricultural & Food Chemistry
Topic Selection: Intentional and Unintentional Contaminants of Food and Feed: Potential Strategies to Prevent Contamination of Food
Abstract
With the microbial safety of fresh produce of increasing concern, conventional sanitizing treatments need to be supplemented with effective new interventions to inactivate human pathogens. Our research group investigates physical and chemical treatments such as hot water pasteurization, gaseous chlorine dioxide, cold plasma and irradiation. Research in biological controls deals with the use of single or multiple isolates of antagonistic bacteria for inhibiting the outgrowth of bacterial human pathogens. Related research in microbial ecology determines how pathogen biofilm formation and interactions with native microflora may alter the efficacy of applied treatments and interventions. This presentation will summarize the advances made in these areas, as well as research results on the process of scaling up effective interventions from laboratory scale to pilot plant scale, including the critical process of evaluating the effects of the various interventions on sensory and nutritional quality attributes, yield, physiology, and shelf-life.
Thursday, April 10, 2008
New Method Rapidly Produces Low-Cost Biofuels from Wood, Grass
George Huber of the University of Massachusetts Amherst has received a $400,000 CAREER grant from the National Science Foundation to pursue his revolutionary new method for making biofuels, or “green gasoline,” from wood or grasses, a process that would be much less expensive than conventional gasoline or ethanol made from corn.
Results of Huber’s research were published in the April 2008 issue of ChemSusChem, a publication devoted to environmentally-sound chemistry.
“We’ve proven this method on a small scale in the lab,” says Huber, a professor of chemical engineering. “But we need to make further improvements and prove it on a large scale before it’s going to be economically viable.”
Huber is a nationally recognized expert on biofuels, which are sustainable fuels made from plant materials. In June 2007, he chaired a workshop in Washington, D.C., for the National Science Foundation and the U. S. Department of Energy titled “Breaking the Chemical & Engineering Barriers to Lignocellulosic Biofuels,” which was attended by 71 top experts from academia, industry and governmental agencies.
Huber’s method is for making biofuels from cellulose, the non-edible portion of plant biomass and a major component of grasses and wood. At $10 to $30 per barrel of oil energy equivalent, cellulosic biomass is significantly cheaper than crude oil. The U.S. could potentially produce 1.3 billion dry tons of cellulosic biomass per year, which has the energy content of four billion barrels of crude oil. That’s more than half of the seven billion barrels of crude oil consumed in our country each year. What’s more, biomass as an energy crop could increase the national farm income by $3 to $6 billion per year.
Huber is addressing the lack of an economical process for converting cellulose into liquid biofuels, which is the main roadblock for their mass production. Every conventional conversion method takes several steps, with each step making the whole process more expensive and less feasible. For example, ethanol production from cellulosic biomass currently involves multiple steps, including pretreatment, enzymatic or acid hydrolysis, fermentation, and distillation. Other processes for making biofuels have been hamstrung by similar multi-step methods.
Huber has come up with a technique for producing his “green gasoline” from biomass in one simple step by placing solid biomass feedstocks such as wood in a reactor, which is basically a high-tech still for thermal conversion of feedstock to gasoline. He heats the feedstock by a technique known as catalytic fast pyrolysis, which means the rapid heating of the biomass to between 400 and 600 degrees centigrade, followed by quick cooling. By adding zeolite catalysts to this process, gasoline range hydrocarbons can be directly produced from cellulose within sixty seconds.
“This is a big improvement because it’s all done in one single step, instead of several stages,” explains Huber. “Also, because of the high temperatures we use in the process, the residence time in our reactor is two to 60 seconds. With cellulosic ethanol, your residence time is five to ten days, which means you have to have a huge reactor costing much more money. So we estimate that building a facility to use our process would be much less expensive.”
Using the current cost of wood in Massachusetts, which is $40 per dry ton, as an example of the feedstock he can use in this process, Huber estimates that a gallon of green gasoline can be produced with his method for between $1 and $1.70, depending on how much he can improve the catalytic conversion in his process through standard engineering techniques.
Huber has already demonstrated that this process will work on a small scale in his lab. Now he has to design a reactor and catalysts that are specifically geared for his process. Huber just received a $30,000 grant from the UMass Amherst Office of Commercial Ventures and Intellectual Property, as funded by the UMass president’s office, to develop a prototype reactor to demonstrate green gasoline production on a large scale.
Huber has been working with three other professors at UMass Amherst including Phillip R. Westmoreland, a chemical engineer and expert on fast pyrolisis who has been helping to design the reactor, and William C. Conner, a chemical engineer with expertise in zeolite catalysts. The third researcher is Scott Auerbach, a theoretical chemist from the UMass Amherst chemistry department.
George Huber of the University of Massachusetts Amherst has received a $400,000 CAREER grant from the National Science Foundation to pursue his revolutionary new method for making biofuels, or “green gasoline,” from wood or grasses, a process that would be much less expensive than conventional gasoline or ethanol made from corn.
Results of Huber’s research were published in the April 2008 issue of ChemSusChem, a publication devoted to environmentally-sound chemistry.
“We’ve proven this method on a small scale in the lab,” says Huber, a professor of chemical engineering. “But we need to make further improvements and prove it on a large scale before it’s going to be economically viable.”
Huber is a nationally recognized expert on biofuels, which are sustainable fuels made from plant materials. In June 2007, he chaired a workshop in Washington, D.C., for the National Science Foundation and the U. S. Department of Energy titled “Breaking the Chemical & Engineering Barriers to Lignocellulosic Biofuels,” which was attended by 71 top experts from academia, industry and governmental agencies.
Huber’s method is for making biofuels from cellulose, the non-edible portion of plant biomass and a major component of grasses and wood. At $10 to $30 per barrel of oil energy equivalent, cellulosic biomass is significantly cheaper than crude oil. The U.S. could potentially produce 1.3 billion dry tons of cellulosic biomass per year, which has the energy content of four billion barrels of crude oil. That’s more than half of the seven billion barrels of crude oil consumed in our country each year. What’s more, biomass as an energy crop could increase the national farm income by $3 to $6 billion per year.
Huber is addressing the lack of an economical process for converting cellulose into liquid biofuels, which is the main roadblock for their mass production. Every conventional conversion method takes several steps, with each step making the whole process more expensive and less feasible. For example, ethanol production from cellulosic biomass currently involves multiple steps, including pretreatment, enzymatic or acid hydrolysis, fermentation, and distillation. Other processes for making biofuels have been hamstrung by similar multi-step methods.
Huber has come up with a technique for producing his “green gasoline” from biomass in one simple step by placing solid biomass feedstocks such as wood in a reactor, which is basically a high-tech still for thermal conversion of feedstock to gasoline. He heats the feedstock by a technique known as catalytic fast pyrolysis, which means the rapid heating of the biomass to between 400 and 600 degrees centigrade, followed by quick cooling. By adding zeolite catalysts to this process, gasoline range hydrocarbons can be directly produced from cellulose within sixty seconds.
“This is a big improvement because it’s all done in one single step, instead of several stages,” explains Huber. “Also, because of the high temperatures we use in the process, the residence time in our reactor is two to 60 seconds. With cellulosic ethanol, your residence time is five to ten days, which means you have to have a huge reactor costing much more money. So we estimate that building a facility to use our process would be much less expensive.”
Using the current cost of wood in Massachusetts, which is $40 per dry ton, as an example of the feedstock he can use in this process, Huber estimates that a gallon of green gasoline can be produced with his method for between $1 and $1.70, depending on how much he can improve the catalytic conversion in his process through standard engineering techniques.
Huber has already demonstrated that this process will work on a small scale in his lab. Now he has to design a reactor and catalysts that are specifically geared for his process. Huber just received a $30,000 grant from the UMass Amherst Office of Commercial Ventures and Intellectual Property, as funded by the UMass president’s office, to develop a prototype reactor to demonstrate green gasoline production on a large scale.
Huber has been working with three other professors at UMass Amherst including Phillip R. Westmoreland, a chemical engineer and expert on fast pyrolisis who has been helping to design the reactor, and William C. Conner, a chemical engineer with expertise in zeolite catalysts. The third researcher is Scott Auerbach, a theoretical chemist from the UMass Amherst chemistry department.
Scientists, Collaborators Create First Superinsulator
Superinsulation may sound like a marketing gimmick for a drafty attic or winter coat. But it is actually a newly-discovered fundamental state of matter created by scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory in collaboration with several European institutions. This discovery both opens new directions of inquiry in condensed matter physics and breaks ground for a new generation of microelectronics.
Led by Argonne senior scientist Valerii Vinokur and Russian scientist Tatyana Baturina, an international team of scientists from Argonne, Germany, Russia and Belgium fashioned a thin film of titanium nitride with they then chilled to near absolute zero. When they tried to pass a current through the material, the researchers noticed that its resistance suddenly increased by a factor of 100,000 once the temperature dropped below a certain threshold. The same sudden change also occurred when the researchers decreased the external magnetic field.
"Titanium nitride films as well as films prepared from some other materials can be either superconductors or insulators depending on the thickness of the film. If you take the film which is just on the insulating side of the transition and decrease the temperature or magnetic field, then the film all of a sudden becomes a superinsulator," Vinokur said.
Like superconductors, which have applications in many different areas of physics, from accelerators to magnetic levitation (maglev) trains to MRI machines, superinsulators could eventually find their way into a number of products, including circuits, sensors and battery shields.
If, for example, a battery is left exposed to the air, the charge will eventually drain from it in a matter of days or weeks because the air is not a perfect insulator, according to Vinokur. "If you pass a current through a superconductor, then it will carry the current forever; conversely, if you have a superinsulator, then it will hold a charge forever," he said.
Additionally, scientists could eventually form superinsulators that would encapsulate superconducting wires, creating an optimally efficient electrical pathway with almost no energy lost as heat. A miniature version of these superinsulated superconducting wires could find their way into more efficient electrical circuits.
Titanium nitride's sudden transition to a superinsulator occurs because the electrons in the material join together in twosomes called Cooper pairs. When these Cooper pairs of electrons join together in long chains, they enable the unrestricted motion of electrons and the easy flow of current, creating a superconductor. In superinsulators, however, the Cooper pairs stay separate from each other, forming self-locking roadblocks. "In superinsulators, Cooper pairs avoid each other, creating enormous electric forces that oppose penetration of the current into the material,” Vinokur said. "It's exactly the opposite of the superconductor," he added.
The theory behind the experiment stemmed from Argonne's Materials Theory Institute, which Vinokur organized six years ago in the laboratory's Materials Science Division. The MTI hosts a handful of visiting scholars from around the world who then perform cutting-edge research on the most pressing questions in condensed matter physics. Upon completion of their tenure at Argonne, these scientists return to their home institutions but continue to collaborate on the joint projects. The MTI attracts the world's best condensed matter scientists, including Russian "experimental star" Tatyana Baturina, who, according to Vinokur, "became a driving force in our work on superinsulators."
Scientists from the Institute of Semiconductor Physics in Novosibirsk, Russia, Regensburg and Bochum Universities in Germany and IMEC in Leuven, Belgium also participated in the research.
About Argonne
Argonne National Laboratory brings the world’s brightest scientists and engineers together to find exciting and creative new solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. (NewsWise)
Superinsulation may sound like a marketing gimmick for a drafty attic or winter coat. But it is actually a newly-discovered fundamental state of matter created by scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory in collaboration with several European institutions. This discovery both opens new directions of inquiry in condensed matter physics and breaks ground for a new generation of microelectronics.
Led by Argonne senior scientist Valerii Vinokur and Russian scientist Tatyana Baturina, an international team of scientists from Argonne, Germany, Russia and Belgium fashioned a thin film of titanium nitride with they then chilled to near absolute zero. When they tried to pass a current through the material, the researchers noticed that its resistance suddenly increased by a factor of 100,000 once the temperature dropped below a certain threshold. The same sudden change also occurred when the researchers decreased the external magnetic field.
"Titanium nitride films as well as films prepared from some other materials can be either superconductors or insulators depending on the thickness of the film. If you take the film which is just on the insulating side of the transition and decrease the temperature or magnetic field, then the film all of a sudden becomes a superinsulator," Vinokur said.
Like superconductors, which have applications in many different areas of physics, from accelerators to magnetic levitation (maglev) trains to MRI machines, superinsulators could eventually find their way into a number of products, including circuits, sensors and battery shields.
If, for example, a battery is left exposed to the air, the charge will eventually drain from it in a matter of days or weeks because the air is not a perfect insulator, according to Vinokur. "If you pass a current through a superconductor, then it will carry the current forever; conversely, if you have a superinsulator, then it will hold a charge forever," he said.
Additionally, scientists could eventually form superinsulators that would encapsulate superconducting wires, creating an optimally efficient electrical pathway with almost no energy lost as heat. A miniature version of these superinsulated superconducting wires could find their way into more efficient electrical circuits.
Titanium nitride's sudden transition to a superinsulator occurs because the electrons in the material join together in twosomes called Cooper pairs. When these Cooper pairs of electrons join together in long chains, they enable the unrestricted motion of electrons and the easy flow of current, creating a superconductor. In superinsulators, however, the Cooper pairs stay separate from each other, forming self-locking roadblocks. "In superinsulators, Cooper pairs avoid each other, creating enormous electric forces that oppose penetration of the current into the material,” Vinokur said. "It's exactly the opposite of the superconductor," he added.
The theory behind the experiment stemmed from Argonne's Materials Theory Institute, which Vinokur organized six years ago in the laboratory's Materials Science Division. The MTI hosts a handful of visiting scholars from around the world who then perform cutting-edge research on the most pressing questions in condensed matter physics. Upon completion of their tenure at Argonne, these scientists return to their home institutions but continue to collaborate on the joint projects. The MTI attracts the world's best condensed matter scientists, including Russian "experimental star" Tatyana Baturina, who, according to Vinokur, "became a driving force in our work on superinsulators."
Scientists from the Institute of Semiconductor Physics in Novosibirsk, Russia, Regensburg and Bochum Universities in Germany and IMEC in Leuven, Belgium also participated in the research.
About Argonne
Argonne National Laboratory brings the world’s brightest scientists and engineers together to find exciting and creative new solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. (NewsWise)
Monday, April 07, 2008
p53 hampers energy metabolism in cancer cells
The tumour suppressor p53 can limit tumour development by inhibiting aerobic glycolysis reports a paper.
Cancer cells normally shift their metabolism to aerobic glycolysis - the conversion of glucose to lactic acid in the presence of oxygen - which confers an advantage in sustaining tumour growth.
p53 activity is lost in over half of human tumours; its primary role is to eliminate cells that have undergone oncogenic transformation by inducing cell growth arrest or programmed cell death. Nobuyuki Tanaka and colleagues found, by looking at p53-deficient primary fibroblasts, that loss of p53 leads to higher glucose metabolism, and demonstrated that this requires de-repression of the transcription factor NF-kB and one of its target genes called GLUT3.
This work reveals an additional function of p53 in restricting cell proliferation through suppression of NF-kB, which is important for maintaining normal levels of glucose metabolism and cell growth.
Author contact:
Nobuyuki Tanaka (Nippon Medical School, Kawasaki-shi, Japan)
Tel: +81 44 733 1860; E-mail: nobuta@nms.ac.jp
The tumour suppressor p53 can limit tumour development by inhibiting aerobic glycolysis reports a paper.
Cancer cells normally shift their metabolism to aerobic glycolysis - the conversion of glucose to lactic acid in the presence of oxygen - which confers an advantage in sustaining tumour growth.
p53 activity is lost in over half of human tumours; its primary role is to eliminate cells that have undergone oncogenic transformation by inducing cell growth arrest or programmed cell death. Nobuyuki Tanaka and colleagues found, by looking at p53-deficient primary fibroblasts, that loss of p53 leads to higher glucose metabolism, and demonstrated that this requires de-repression of the transcription factor NF-kB and one of its target genes called GLUT3.
This work reveals an additional function of p53 in restricting cell proliferation through suppression of NF-kB, which is important for maintaining normal levels of glucose metabolism and cell growth.
Author contact:
Nobuyuki Tanaka (Nippon Medical School, Kawasaki-shi, Japan)
Tel: +81 44 733 1860; E-mail: nobuta@nms.ac.jp
Common genetic variants influencing adult height
Scientists have discovered dozens of common genetic variants influencing adult human height.
Recently, two independent studies reported that common variants near two genes, HMGA2 and GDF5, are associated with variation in human height in the general population. Using substantially larger sample sizes, three groups now report the discovery of dozens of additional variants influencing adult height.
The newly discovered variants explain up to 4% of normal height variation in populations of European ancestry. Individuals carrying predominantly ‘tall’ versions of these variants are, on average, 5 cm taller than individuals carrying only a few of the ‘tall’ variants.
Many of the height-associated variants reside near genes known or suspected to have a role in skeletal development. Others reside near genes that control how cells grow and divide.
Height is considered a classic complex trait with a strong heritable component. Therefore, understanding the genetic basis of this model trait may shed light on the genetic architecture of other traits, including those influencing risk of common diseases.
Author contacts:
Timothy Frayling (Peninsula Medical School, Exeter, UK)
Tel: +44 1392 262935; E-mail: tim.frayling@pms.ac.uk
Kari Stefansson (deCODE Genetics, Reykjavik, Iceland)
Tel: +354 570 1900; E-mail: kstefans@decode.is
Joel Hirschhorn (Broad Institute of Harvard and MIT, Cambridge, MA, USA)
Tel: +1 617 919 2129; E-mail: joelh@broad.mit.edu
Scientists have discovered dozens of common genetic variants influencing adult human height.
Recently, two independent studies reported that common variants near two genes, HMGA2 and GDF5, are associated with variation in human height in the general population. Using substantially larger sample sizes, three groups now report the discovery of dozens of additional variants influencing adult height.
The newly discovered variants explain up to 4% of normal height variation in populations of European ancestry. Individuals carrying predominantly ‘tall’ versions of these variants are, on average, 5 cm taller than individuals carrying only a few of the ‘tall’ variants.
Many of the height-associated variants reside near genes known or suspected to have a role in skeletal development. Others reside near genes that control how cells grow and divide.
Height is considered a classic complex trait with a strong heritable component. Therefore, understanding the genetic basis of this model trait may shed light on the genetic architecture of other traits, including those influencing risk of common diseases.
Author contacts:
Timothy Frayling (Peninsula Medical School, Exeter, UK)
Tel: +44 1392 262935; E-mail: tim.frayling@pms.ac.uk
Kari Stefansson (deCODE Genetics, Reykjavik, Iceland)
Tel: +354 570 1900; E-mail: kstefans@decode.is
Joel Hirschhorn (Broad Institute of Harvard and MIT, Cambridge, MA, USA)
Tel: +1 617 919 2129; E-mail: joelh@broad.mit.edu
Host-to-graft disease spread in Parkinson disease?
Cell transplants have long been proposed as a possible therapy for Parkinson disease, but a series of reports suggest that the pathology may spread from the host to the transplants.
Parkinson disease results from the abnormal aggregation of a protein known as alpha-synuclein and the degeneration of the substantia nigra, a dopamine-releasing region of the midbrain. Therapies for the disease aiming at replacing the lost cells have given hope and, in the 1990s, clinical trials transplanting dopaminergic fetal brain tissue into the brains of patients with Parkinson took place.
Two independent groups led by Patrik Brundin and by Jeffrey Kordower report that the transplanted tissue in some subjects shows evidence of alpha-synuclein aggregates. This observation is striking because the grafts were too young to develop this on their own, and the fetal tissue had been placed into the striatum, a brain region that receives input from the substantia nigra but does not develop alpha-synuclein aggregates in Parkinson disease. So, in these subjects, the disease seems to have spread from the host to the graft.
But not all studies agree. A third study, led by Ole Isacson, failed to show Parkinson-like pathology in the transplants from a different set of similar subjects, finding instead a large proportion of serotonergic, and not only dopaminergic, neurons within the grafts.
As current efforts to develop cell-replacement therapies focus on the use of stem cells to generate substantia nigra-like dopaminergic neurons, the findings of these three groups on long-term transplant recipients add a level of complexity to the idea of curing Parkinson disease with grafted tissue.
Author contacts:
Patrik Brundin (Wallenberg Neuroscience Center, Lund, Sweden)
Tel: +46 46 222 05 63; E-mail: patrik.brundin@med.lu.se
Jeffrey Kordower (Rush University Medical Center, Chicago, IL, USA)
Tel.: +1 312 563 3570; E-mail: jkordowe@rush.edu
Ole Isacson (Harvard Medical School/McLean Hospital, Belmont, MA, USA)
Tel: +1 617 855 3283; E-mail: isacson@hms.harvard.edu
Cell transplants have long been proposed as a possible therapy for Parkinson disease, but a series of reports suggest that the pathology may spread from the host to the transplants.
Parkinson disease results from the abnormal aggregation of a protein known as alpha-synuclein and the degeneration of the substantia nigra, a dopamine-releasing region of the midbrain. Therapies for the disease aiming at replacing the lost cells have given hope and, in the 1990s, clinical trials transplanting dopaminergic fetal brain tissue into the brains of patients with Parkinson took place.
Two independent groups led by Patrik Brundin and by Jeffrey Kordower report that the transplanted tissue in some subjects shows evidence of alpha-synuclein aggregates. This observation is striking because the grafts were too young to develop this on their own, and the fetal tissue had been placed into the striatum, a brain region that receives input from the substantia nigra but does not develop alpha-synuclein aggregates in Parkinson disease. So, in these subjects, the disease seems to have spread from the host to the graft.
But not all studies agree. A third study, led by Ole Isacson, failed to show Parkinson-like pathology in the transplants from a different set of similar subjects, finding instead a large proportion of serotonergic, and not only dopaminergic, neurons within the grafts.
As current efforts to develop cell-replacement therapies focus on the use of stem cells to generate substantia nigra-like dopaminergic neurons, the findings of these three groups on long-term transplant recipients add a level of complexity to the idea of curing Parkinson disease with grafted tissue.
Author contacts:
Patrik Brundin (Wallenberg Neuroscience Center, Lund, Sweden)
Tel: +46 46 222 05 63; E-mail: patrik.brundin@med.lu.se
Jeffrey Kordower (Rush University Medical Center, Chicago, IL, USA)
Tel.: +1 312 563 3570; E-mail: jkordowe@rush.edu
Ole Isacson (Harvard Medical School/McLean Hospital, Belmont, MA, USA)
Tel: +1 617 855 3283; E-mail: isacson@hms.harvard.edu
Coastal pollution could produce an unhealthy chemical cocktail
The reaction of chemical compounds in the pollution from cities and ships with sea salt aerosols from the ocean could affect air quality in coastal areas where the two meet, according to a research. A team measured high levels of nitryl chloride, an active halogen implicated in ground-level ozone production, in industrially polluted air along the southeast coast of the US, implying that ozone pollution could be particularly high where industrial combustion products meet the ocean, as in many megacities around the world.
James Roberts and colleagues measured unexpectedly high levels of nitryl chloride in ship exhaust plumes along the southeast coast of the US. They show that this chemical compound is produced during the night by the reaction of the nitrogen oxides in polluted air from ships or cities with the chlorine from sea salt. With the help of the morning sunlight, nitryl oxide is rapidly split into a reactive radical that can produce ozone in combination with suitable atmospheric compounds, and nitrogen oxides. (researchsea)
Author contact:
James Roberts (National Oceanic and Atmospheric Administration, Boulder, CO, USA)
Tel: +1 303 497 3982, E-mail: James.M.Roberts@noaa.gov
The reaction of chemical compounds in the pollution from cities and ships with sea salt aerosols from the ocean could affect air quality in coastal areas where the two meet, according to a research. A team measured high levels of nitryl chloride, an active halogen implicated in ground-level ozone production, in industrially polluted air along the southeast coast of the US, implying that ozone pollution could be particularly high where industrial combustion products meet the ocean, as in many megacities around the world.
James Roberts and colleagues measured unexpectedly high levels of nitryl chloride in ship exhaust plumes along the southeast coast of the US. They show that this chemical compound is produced during the night by the reaction of the nitrogen oxides in polluted air from ships or cities with the chlorine from sea salt. With the help of the morning sunlight, nitryl oxide is rapidly split into a reactive radical that can produce ozone in combination with suitable atmospheric compounds, and nitrogen oxides. (researchsea)
Author contact:
James Roberts (National Oceanic and Atmospheric Administration, Boulder, CO, USA)
Tel: +1 303 497 3982, E-mail: James.M.Roberts@noaa.gov
Thursday, April 03, 2008
Algae Could One Day be Major Hydrogen Fuel Source
As gas prices continue to soar to record highs, motorists are crying out for an alternative that won’t cramp their pocketbooks.
Scientists at U.S. Department of Energy’s Argonne National Laboratory are answering that call by working to chemically manipulate algae for production of the next generation of renewable fuels – hydrogen gas.
“We believe there is a fundamental advantage in looking at the production of hydrogen by photosynthesis as a renewable fuel,” senior chemist David Tiede said. “Right now, ethanol is being produced from corn, but generating ethanol from corn is a thermodynamically much more inefficient process.”
Some varieties of algae, a kind of unicellular plant, contain an enzyme called hydrogenase that can create small amounts of hydrogen gas. Tiede said many believe this is used by Nature as a way to get rid of excess reducing equivalents that are produced under high light conditions, but there is little benefit to the plant.
Tiede and his group are trying to find a way to take the part of the enzyme that creates the gas and introduce it into the photosynthesis process.
The result would be a large amount of hydrogen gas, possibly on par with the amount of oxygen created.
“Biology can do it, but it’s making it do it at 5-10 percent yield that’s the problem,” Tiede said. “What we would like to do is take that catalyst out of hydrogenase and put into the photosynthetic protein framework. We are fortunate to have Professor Thomas Rauchfuss as a collaborator from the University of Illinois at Champaign-Urbana who is an expert on the synthesis of hydrogenase active site mimics.”
Algae has several benefits over corn in fuel production. It can be grown in a closed system almost anywhere including deserts or even rooftops, and there is no competition for food or fertile soil. Algae is also easier to harvest because it has no roots or fruit and grows dispersed in water.
“If you have terrestrial plants like corn, you are restricted to where you could grow them,” Tiede said. “There is a problem now with biofuel crops competing with food crops because they are both using the same space. Algae provides an alternative, which can be grown in a closed photobioreactor analogous to a microbial fermentor that you could move any place.”
Tiede admitted the research is its beginning phases, but he is confident in his team and their research goals. The next step is to create a way to attach the catalytic enzyme to the molecule.
Funding for the research was provided by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.
Argonne National Laboratory brings the world's brightest scientists and engineers together to find exciting and creative new solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.
As gas prices continue to soar to record highs, motorists are crying out for an alternative that won’t cramp their pocketbooks.
Scientists at U.S. Department of Energy’s Argonne National Laboratory are answering that call by working to chemically manipulate algae for production of the next generation of renewable fuels – hydrogen gas.
“We believe there is a fundamental advantage in looking at the production of hydrogen by photosynthesis as a renewable fuel,” senior chemist David Tiede said. “Right now, ethanol is being produced from corn, but generating ethanol from corn is a thermodynamically much more inefficient process.”
Some varieties of algae, a kind of unicellular plant, contain an enzyme called hydrogenase that can create small amounts of hydrogen gas. Tiede said many believe this is used by Nature as a way to get rid of excess reducing equivalents that are produced under high light conditions, but there is little benefit to the plant.
Tiede and his group are trying to find a way to take the part of the enzyme that creates the gas and introduce it into the photosynthesis process.
The result would be a large amount of hydrogen gas, possibly on par with the amount of oxygen created.
“Biology can do it, but it’s making it do it at 5-10 percent yield that’s the problem,” Tiede said. “What we would like to do is take that catalyst out of hydrogenase and put into the photosynthetic protein framework. We are fortunate to have Professor Thomas Rauchfuss as a collaborator from the University of Illinois at Champaign-Urbana who is an expert on the synthesis of hydrogenase active site mimics.”
Algae has several benefits over corn in fuel production. It can be grown in a closed system almost anywhere including deserts or even rooftops, and there is no competition for food or fertile soil. Algae is also easier to harvest because it has no roots or fruit and grows dispersed in water.
“If you have terrestrial plants like corn, you are restricted to where you could grow them,” Tiede said. “There is a problem now with biofuel crops competing with food crops because they are both using the same space. Algae provides an alternative, which can be grown in a closed photobioreactor analogous to a microbial fermentor that you could move any place.”
Tiede admitted the research is its beginning phases, but he is confident in his team and their research goals. The next step is to create a way to attach the catalytic enzyme to the molecule.
Funding for the research was provided by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.
Argonne National Laboratory brings the world's brightest scientists and engineers together to find exciting and creative new solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.
Astronomers Find Suspected Medium-Size Black Hole in Omega Centauri
A well-known star cluster that glitters with the light of millions of stars may have a mysterious dark object tugging at its core. Astronomers have found evidence for a medium-size black hole at the core of Omega Centauri, one of the largest and most massive globular star clusters orbiting our Milky Way Galaxy.
The intermediate-mass black hole is estimated to be roughly 40,000 times the mass of the Sun. The black hole was discovered with NASA's Hubble Space Telescope and Gemini Observatory on Cerro Pachon in Chile. The ancient cluster is located 17,000 light-years from Earth.
Globular clusters are gravitationally bound swarms of typically up to a million stars. There are more than 200 globular clusters in our Milky Way Galaxy.
"This result shows that there is a continuous range of masses for black holes, from supermassive, to intermediate, to small, stellar types," explained astronomer Eva Noyola of the Max-Planck Institute for Extraterrestrial Physics in Garching, Germany, and leader of the team that made the discovery.
"This finding also is important because the theory of formation for supermassive black holes requires seed black holes that are exactly in the mass range of the one we found. Such seeds have not been identified so far. If these types of intermediate-mass black holes happen to be common in star clusters, then they can provide numerous seeds for the formation of the supermassive black holes."
Astronomers have debated the existence of moderately sized black holes because they have not found strong evidence for them, and there is no widely accepted mechanism for how they could form. They have ample evidence that small black holes of a few solar masses are produced when giant stars die. There is similar evidence that supermassive black holes weighing the equivalent of millions to billions of solar masses sit at the heart of many galaxies, including our Milky Way.
"Before this observation, we had only one example of an intermediate-mass black hole in the globular cluster G1, in the nearby Andromeda Galaxy," said astronomer Karl Gebhardt of the University of Texas at Austin and a member of the team that made the discovery.
Noyola and Gebhardt used Hubble and Gemini to gather evidence for the black hole. Hubble's Advanced Camera for Surveys showed how the stars are bunching up near the center of Omega Centauri, as seen in the gradual increase in starlight near the center. Measuring the speed of the stars swirling near the cluster's center with the Gemini Observatory, the astronomers found that the stars closer to the core are moving faster than the stars farther away. The measurement implies that some unseen matter at the core is tugging on stars near it.
By comparing these results with standard models, the astronomers determined that the most likely cause of this accelerating stellar traffic jam is the gravitational pull of a massive, dense object, the astronomers explained. They also used models to calculate the black hole's mass.
Although the presence of an intermediate-mass black hole is the most likely reason for the stellar speedway near the cluster's center, the astronomers said they have considered a couple of other possible causes.
In the first scenario, the traffic jam of stars near the center is due to a collection of burned-out stars such as white dwarfs or neutron stars. Another possibility is that stars in the center of Omega Centauri have elongated orbits that would make the stars closest to the center appear to speed up.
"For both alternative scenarios it is very hard to get stars to behave that way, either the burned-out stars really bunched up in the center or many stars with very elongated orbits," Noyola explained. "The normal evolution of a star cluster like Omega Centauri should not end up with stars behaving in those ways. But even if we assume that either scenario did happen somehow, both configurations are expected to be very short lived. A clump of burned-out stars, for example, are expected to move farther away from the center quickly. The stars with elongated orbits are expected to become circular very quickly."
Many astronomers regard Omega Centauri as an unusual globular cluster because of its enormous size and mass. In fact, the 12 billion year old cluster has long been suspected of being the stripped-down core of a dwarf galaxy that had been shredded of most of its stars long ago. A previous Hubble survey of supermassive black holes and their host galaxies showed a correlation between the mass of a black hole and that of its host. Astronomers estimated that the mass of the suspected Omega Centauri dwarf galaxy was roughly 10 million solar masses. If lower-mass galaxies obey the same rule, then the mass of Omega Centauri does match that of its black hole.
Noyola and Gebhardt will use the European Southern Observatory's Very Large Telescope in Paranal, Chile to conduct follow-up observations of the velocity of the stars near the cluster's center to confirm the discovery.
The finding will appear in the April 10 issue of The Astrophysical Journal.
A well-known star cluster that glitters with the light of millions of stars may have a mysterious dark object tugging at its core. Astronomers have found evidence for a medium-size black hole at the core of Omega Centauri, one of the largest and most massive globular star clusters orbiting our Milky Way Galaxy.
The intermediate-mass black hole is estimated to be roughly 40,000 times the mass of the Sun. The black hole was discovered with NASA's Hubble Space Telescope and Gemini Observatory on Cerro Pachon in Chile. The ancient cluster is located 17,000 light-years from Earth.
Globular clusters are gravitationally bound swarms of typically up to a million stars. There are more than 200 globular clusters in our Milky Way Galaxy.
"This result shows that there is a continuous range of masses for black holes, from supermassive, to intermediate, to small, stellar types," explained astronomer Eva Noyola of the Max-Planck Institute for Extraterrestrial Physics in Garching, Germany, and leader of the team that made the discovery.
"This finding also is important because the theory of formation for supermassive black holes requires seed black holes that are exactly in the mass range of the one we found. Such seeds have not been identified so far. If these types of intermediate-mass black holes happen to be common in star clusters, then they can provide numerous seeds for the formation of the supermassive black holes."
Astronomers have debated the existence of moderately sized black holes because they have not found strong evidence for them, and there is no widely accepted mechanism for how they could form. They have ample evidence that small black holes of a few solar masses are produced when giant stars die. There is similar evidence that supermassive black holes weighing the equivalent of millions to billions of solar masses sit at the heart of many galaxies, including our Milky Way.
"Before this observation, we had only one example of an intermediate-mass black hole in the globular cluster G1, in the nearby Andromeda Galaxy," said astronomer Karl Gebhardt of the University of Texas at Austin and a member of the team that made the discovery.
Noyola and Gebhardt used Hubble and Gemini to gather evidence for the black hole. Hubble's Advanced Camera for Surveys showed how the stars are bunching up near the center of Omega Centauri, as seen in the gradual increase in starlight near the center. Measuring the speed of the stars swirling near the cluster's center with the Gemini Observatory, the astronomers found that the stars closer to the core are moving faster than the stars farther away. The measurement implies that some unseen matter at the core is tugging on stars near it.
By comparing these results with standard models, the astronomers determined that the most likely cause of this accelerating stellar traffic jam is the gravitational pull of a massive, dense object, the astronomers explained. They also used models to calculate the black hole's mass.
Although the presence of an intermediate-mass black hole is the most likely reason for the stellar speedway near the cluster's center, the astronomers said they have considered a couple of other possible causes.
In the first scenario, the traffic jam of stars near the center is due to a collection of burned-out stars such as white dwarfs or neutron stars. Another possibility is that stars in the center of Omega Centauri have elongated orbits that would make the stars closest to the center appear to speed up.
"For both alternative scenarios it is very hard to get stars to behave that way, either the burned-out stars really bunched up in the center or many stars with very elongated orbits," Noyola explained. "The normal evolution of a star cluster like Omega Centauri should not end up with stars behaving in those ways. But even if we assume that either scenario did happen somehow, both configurations are expected to be very short lived. A clump of burned-out stars, for example, are expected to move farther away from the center quickly. The stars with elongated orbits are expected to become circular very quickly."
Many astronomers regard Omega Centauri as an unusual globular cluster because of its enormous size and mass. In fact, the 12 billion year old cluster has long been suspected of being the stripped-down core of a dwarf galaxy that had been shredded of most of its stars long ago. A previous Hubble survey of supermassive black holes and their host galaxies showed a correlation between the mass of a black hole and that of its host. Astronomers estimated that the mass of the suspected Omega Centauri dwarf galaxy was roughly 10 million solar masses. If lower-mass galaxies obey the same rule, then the mass of Omega Centauri does match that of its black hole.
Noyola and Gebhardt will use the European Southern Observatory's Very Large Telescope in Paranal, Chile to conduct follow-up observations of the velocity of the stars near the cluster's center to confirm the discovery.
The finding will appear in the April 10 issue of The Astrophysical Journal.
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