In a new paper, North Carolina State University researchers Orlin Velev and Hyung-Jun Koo show that creating solar cell devices with channels that mimic organic vascular systems can effectively reinvigorate solar cells whose performance deteriorates due to degradation by the sun’s ultraviolet rays.... Read more »
Koo HJ, & Velev OD. (2013) Regenerable photovoltaic devices with a hydrogel-embedded microvascular network. Scientific reports, 2357. PMID: 23912814
A plastic solar cell—a type of flexible solar cell made with polymers—is a relatively new design that currently suffers from a lack of efficiency compared to its major competitors, conventional cells made of silicon. To increase performance, scientists are looking for new materials that will enhance the flow of electricity through the solar cell. Several groups expected to achieve good results by redesigning pliant polymers of plastic into orderly, silicon-like crystals, but the flow of electricity did not improve.... Read more »
Noriega R, Rivnay J, Vandewal K, Koch FP, Stingelin N, Smith P, Toney MF, & Salleo A. (2013) A general relationship between disorder, aggregation and charge transport in conjugated polymers. Nature materials. PMID: 23913173
Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled to a temperature of hundreds of degrees below zero. Warmed beyond those frigid conditions, the materials cross a critical temperature threshold and the superconductivity breaks down. But high-temperature superconductors (HTS)—warmer, but still subzero—may have untapped potential because their underlying mechanism remains a mystery. Unlocking that unknown HTS source and engineering new superconductor configurations could drive that critical temperature high enough to revolutionize energy technology.... Read more »
J. Wu,O. Pelleg, G. Logvenov, A.T. Bollinger, Y-J. Sun, G.S. Boebinger, M. Vanević, Z. Radović, I. Božović. (2013) Anomalous independence of interface superconductivity from carrier density. Nature Materials. DOI: 10.1038/nmat3719
Jewel wasps show us how new communication systems may have come to be. Photo by M.E. Clark at Wikimedia Commons.Finding and attracting a mate is tricky business for most species. It can be quite helpful then to have a species-specific signal that is sent and received by members of your own species, but not perceived as well by predators. Chemical signals (those we perceive through smell and taste) are among the most diverse and specific signals produced in the animal kingdom, so they make good candidates for these species-specific mating signals. Sex pheromones are chemical compounds released by an animal that attract animals of the same species but opposite sex. They are often so specific that other species can’t smell them at all, which makes them useful as a secret communication line for just that species. But this specificity raises an intriguing question: What develops first: the ability to make the pheromone or the ability to perceive it? This week I tell the story of how jewel wasps shed light on this chicken-or-the-egg problem at Accumulating Glitches. Check it out here. And to learn more, check these out: 1. Lassance, J., & Löfstedt, C. (2013). Chemical communication: A jewel sheds light on signal evolution Current Biology, 29 (3) DOI: 10.1016/j.cub.2013.03.0552. Niehuis, O., Buellesbach, J., Gibson, J.D., Pothmann, D., Hanner, C., Mutti, N.S., Judson, A.K., Gadau, J., Ruther, J., & Schmitt, T. (2013). Behavioural and genetic analyses of Nasonia shed light on the evolution of sex pheromones Nature, 494, 345-348 DOI: 10.1038/nature11838 ... Read more »
Lassance, J., & Löfstedt, C. (2013) Chemical communication: A jewel sheds light on signal evolution. Current Biology, 29(3). DOI: 10.1016/j.cub.2013.03.055
Niehuis, O., Buellesbach, J., Gibson, J.D., Pothmann, D., Hanner, C., Mutti, N.S., Judson, A.K., Gadau, J., Ruther, J., & Schmitt, T. (2013) Behavioural and genetic analyses of Nasonia shed light on the evolution of sex pheromones. Nature, 345-348. DOI: 10.1038/nature11838
Researchers at the University of Colorado Boulder have developed what they say is a radically new technique that uses the power of sunlight to efficiently split water into its components of hydrogen and oxygen, paving the way for the broad use of hydrogen as a clean, green fuel.... Read more »
Muhich CL, Evanko BW, Weston KC, Lichty P, Liang X, Martinek J, Musgrave CB, & Weimer AW. (2013) Efficient generation of H2 by splitting water with an isothermal redox cycle. Science (New York, N.Y.), 341(6145), 540-2. PMID: 23908235
Monash University researchers have brought next generation energy storage closer with an engineering first—a graphene-based device that is compact, yet lasts as long as a conventional battery.... Read more »
Yang X, Cheng C, Wang Y, Qiu L, & Li D. (2013) Liquid-mediated dense integration of graphene materials for compact capacitive energy storage. Science (New York, N.Y.), 341(6145), 534-7. PMID: 23908233
Researchers in the University of Minnesota’s College of Science and Engineering and the National Renewable Energy Laboratory in Golden, Colorado, have discovered a novel method for producing “electronic ink” using nonthermal plasma.... Read more »
Wheeler LM, Neale NR, Chen T, & Kortshagen UR. (2013) Hypervalent surface interactions for colloidal stability and doping of silicon nanocrystals. Nature communications, 2197. PMID: 23893292
Could you ever imagine that one day testing a protein in your tiny sample would be so easy, just like performing a pregnancy strip test at home. Yes, this is made possible by a group of chemists from Johannes Gutenberg University Mainz (JGU). They have developed a new method for multiple protein analysis that is, in principle, capable of identifying hundreds or even thousands of different proteins.... Read more »
Rosman C, Prasad J, Neiser A, Henkel A, Edgar J, & Sönnichsen C. (2013) Multiplexed Plasmon Sensor for Rapid Label-Free Analyte Detection. Nano letters. PMID: 23789876
Using a simple solar cell and a photo anode made of a metal oxide bismuth vanadate, scientists at the Delft University of Technology (TU Delft) in the Netherlands have successfully stored nearly five percent of solar energy chemically in the form of hydrogen.... Read more »
Fatwa F. Abdi, Lihao Han, Arno H. M. Smets, Miro Zeman, Bernard Dam, Roel van de Krol. (2013) Efficient solar water splitting by enhanced charge separation in a bismuth vanadate-silicon tandem photoelectrode. Nature Communications. DOI: 10.1038/ncomms3195
Recently, I came across an exciting new development in a Nature publication and couldn’t resist teasing my Twitter followers with…
... Read more »
Spiess C, Merchant M, Huang A, Zheng Z, Yang NY, Peng J, Ellerman D, Shatz W, Reilly D, Yansura DG.... (2013) Bispecific antibodies with natural architecture produced by co-culture of bacteria expressing two distinct half-antibodies. Nature biotechnology. PMID: 23831709
A possible way to harvest and use atmospheric carbon dioxide to make high performance diesel fuel has been proposed by a team of scientists with the U.S. Department of Energy (DOE)’s Joint BioEnergy Institute (JBEI).... Read more »
Müller J, Maceachran D, Burd H, Sathitsuksanoh N, Bi C, Yeh YC, Lee TS, Hillson NJ, Chhabra SR, Singer SW.... (2013) Engineering of Ralstonia eutropha H16 for Autotrophic and Heterotrophic Production of Methyl Ketones. Applied and environmental microbiology, 79(14), 4433-9. PMID: 23686271
Today's Google Doodle honours pioneering British biophysicist and x-ray crystallographer, Rosalind Franklin... Read more »
Researchers at Stanford have created a record-thin, record-efficient light-absorbing material. According to the results of the study published in the current online edition of the journal Nano Letters, this nanosize structure, thousands of times thinner than an ordinary sheet of paper, could significantly lower the costs and improve the efficiency of solar cells.... Read more »
Hägglund C, Zeltzer G, Ruiz R, Thomann I, Lee HB, Brongersma ML, & Bent SF. (2013) Self-Assembly Based Plasmonic Arrays Tuned by Atomic Layer Deposition for Extreme Visible Light Absorption. Nano letters. PMID: 23805835
A team of researchers at the Monash University under the Australian Research Council (ARC) Center of Excellence for Electromaterials Science (ACES) has developed an ionic liquid-based thermoelectrochemical cell that converts heat (temperature differences) directly into electrical energy.... Read more »
Theodore J. Abraham, Douglas R. MacFarlanea, Jennifer M. Pringleb. (2013) High Seebeck coefficient redox ionic liquid electrolytes for thermal energy harvesting. Energy . DOI: 10.1039/c3ee41608a
Researchers at CRANN, Ireland’s first purpose-built research institute whose purpose is to perform nanoscience research, based at Trinity College Dublin (TCD), have developed a new method of splitting water into hydrogen and oxygen.... Read more »
Doyle RL, Godwin IJ, Brandon MP, & Lyons ME. (2013) Redox and electrochemical water splitting catalytic properties of hydrated metal oxide modified electrodes. Physical chemistry chemical physics : PCCP. PMID: 23652494
At the end of the last Ice Age, as the world began to warm, a swath of the North Pacific Ocean came to life. During a brief pulse of biological productivity 14,000 years ago, this stretch of the sea teemed with phytoplankton, amoeba-like foraminifera and other tiny creatures, who thrived in large numbers until the productivity ended—as mysteriously as it began—just a few hundred years later.
(further reading on TK's page)... Read more »
Before settling down to have chicks of its own, a young adult loon shops around. It visits different lakes, swimming in them to test the water. Finally it chooses a home. Rather than selecting the best neighborhood in which to raise its young, though, the loon seems to pick a place that feels comfortably like where it grew up. If it's not the best place to raise kids, too bad.
Walter Piper, a biologist at Chapman University in California, has been chasing loons in Wisconsin for more than two decades. "It might seem like self-flagellation," he admits. Loons are a difficult study species, in that they tend to dive straight down into the water when a human approaches. Piper and his colleagues followed the aquatic birds between 1991 and 2012, snagging them with fishing nets and banding their young, and were able to build a detailed, multi-generation history of bird real estate decisions.
Common loons (Gavia immer) grow up in nests on the water tended by two parents. When they reach adulthood, they migrate over the winter and then return to make their own homes for breeding. The study area in Wisconsin is dotted with small glacial lakes, and breeding pairs of loons often claim an entire one of these lakes as their own territory.
When it comes time to choose an adult home, young loons that are thinking of the children ought to choose large lakes with a high pH; these have been shown to produce larger numbers of healthier chicks. Yet the adults don't always pick those prime locations.
The researchers tracked the movements of their loon subjects, as well as various qualities of the lakes they moved between: shape, depth, clarity of the water, and so on. They also ran computer simulations to see where loons might end up if they chose their new habitats randomly. Instead, they found that loons tended to choose lakes that were similar to where they grew up, both in the pH of the water and in overall size.
How do house-hunting loons find lakes with the qualities they care about? Piper says loons are adept at judging the size of a lake from the air, since they're big birds that need a lot of "runway" to take off from. If they land in a too-small body of water, they'll get trapped there. As for pH, he acknowledges, "We do not see loons using pH meters or pH paper." But the types of fish, insects and so on that live in a lake correlate to its acidity or alkalinity. This mix of prey species is probably one thing loons are judging when they shop around for a home.
Piper thinks loons must benefit from choosing lakes that are more like where they were raised, even if these aren't the lakes that produce the most chicks right away. Perhaps by choosing someplace similar to their old hunting grounds, they make it easier to find food. This might allow the loons to survive for more years, ultimately making up for their original disadvantage in number of chicks.
"Our finding shows that animals sometimes DO NOT pick the habitat that promises greatest reproductive success," Piper says. He thinks other scientists studying how animals choose homes should focus more on parents, rather than their offspring.
And when loon chicks complain about their habitat, their parents can tell them, "Back in my day we lived on a tiny lake and we liked it! There were even these people chasing us around with fishing nets..."
Image: by Ano Lobb (via Wikimedia Commons)
Piper WH, Palmer MW, Banfield N, & Meyer MW (2013). Can settlement in natal-like habitat explain maladaptive habitat selection? Proceedings. Biological sciences / The Royal Society, 280 (1765) PMID: 23804619
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Piper WH, Palmer MW, Banfield N, & Meyer MW. (2013) Can settlement in natal-like habitat explain maladaptive habitat selection?. Proceedings. Biological sciences / The Royal Society, 280(1765), 20130979. PMID: 23804619
Dye-sensitized solar cells (DSSCs) have many advantages over their silicon-based counterparts. They offer transparency, flexibility and high power conversion efficiencies under cloudy and artificial light conditions.... Read more »
Jin Hyuck Heo, Sang Hyuk Im, Jun Hong Noh, Tarak N. Mandal, Choong-Sun Lim, Jeong Ah Chang, Yong Hui Lee, Hi-jung Kim, Arpita Sarkar, Md. K. Nazeeruddin, Michael Grätzel . (2013) Efficient inorganic–organic hybrid heterojunction solar cells containing perovskite compound and polymeric hole conductors. Nature Photonics, 486-491. DOI: 10.1038/nphoton.2013.80
Popular bath salt drug shown to be highly addictive.
Researchers at the Scripps Research Institute (TSRI) in La Jolla, California, appear to have hammered the last nail into the coffin for the common “bath salt” drug known as MDPV. We can now say with a high degree of certainty that, based on animal models, we know that 3,4-methylenedioxypyrovalerone is addictive—perhaps more strongly addictive than methamphetamine, although such comparisons are always perilous. However, principal investigator Michael A. Taffe, an associate professor at TSRI, said in a prepared release that the research group “observed that rats will press a lever more often to get a single infusion of MPDV than they will for meth, across a fairly wide dose range.”
Like methamphetamine, MDPV works by stalling the uptake of dopamine, it also has effects on noradrenaline and serotonin. As cathinone derivatives, MPDV and mephedrone are related to the stimulant drug khat, which is used like cocaine in northeastern Africa. In earlier research at Scripps under Dr. Taffe, investigators found that lab rats would intravenously self-administer mephedrone and behave in a manner similar to the effects produced when the rats were on methamphetamine. In a paper for Drug and Alcohol Dependence, the Taffe Lab concluded that “the potential for compulsive use of mephedrone in humans is likely quite high, particularly in comparison with MDMA.”
Now the researchers have zeroed in on the effects of the dirty pharmacology represented by MDPV, the other primary ingredient in many bath salt mixtures. In a new study by Michael Taffe, Tobin J. Dickerson, Shawn M. Aarde, and others, to be published in the August issue of Neuropharmacology, the investigators found that MDPV was a more potent attraction than meth for rats allowed to self-administer the drugs. Very little lab data exists for MDPV, and this study was among the first to directly compare the effect of MDPV to methamphetamine in an animal experiment.
It took some time to tease out the behavioral clues—the cognitive, thermoregulatory, and potentially addictive effects of the drug—but MDPV’s strong affinities with speed can no longer be ignored. The researchers saw the same types of repetitive activities seen in animals on meth, such as excessive grooming, tooth grinding, and skin picking. Lead author Shawn Aarde said in a prepared statement that “one stereotyped behavior that we often observed was a rat repeatedly licking the clear plastic walls of its operant chamber—a behavior that was sometimes uninterruptable.”
MDPV, in the jargon of such experiments, had “greater reward value” than methamphetamine. Which is saying something, given the well-publicized addictive threat of speed. When the group boosted the number of lever presses needed for another infusion of MDPV or METH, “we observed that rats emitted about 60 presses on average for a dose of meth but up to about 600 for MDPV—some rats would even emit 3,000 lever presses for a single hit of MDPV,” said Aarde in a press release. “If you consider these lever presses a measure of how much a rat will work to get a drug infusion, then these rats worked more than 10 times harder to get MDPV.”
Excuse me, did he say as many as three thousand bar presses for another bump of intravenous MDPV? He did. Overall, the rats self-administered more MDPV than methamphetamine. In the paper itself, the authors write that “compared with METH, the effect of MDPV on drug-reinforced behavior was of greater potency (more responding under lowest dose under fixed-ratio schedule) and greater efficacy (more responding under optimal dose under a progressive ratio schedule)…”
The conclusion? MDPV’s “abuse liability” may be greater than that of standard methamphetamine. Which is another excellent piece of evidence for approaching the world of new synthetic psychoactives with great caution.
Aarde S.M., Huang P.K., Creehan K.M., Dickerson T.J. & Taffe M.A. (2013). The novel recreational drug 3,4-methylenedioxypyrovalerone (MDPV) is a potent psychomotor stimulant: Self-administration and locomotor activity in rats, Neuropharmacology, 71 130-140. DOI: 10.1016/j.neuropharm.2013.04.003 ... Read more »
Aarde S.M., Huang P.K., Creehan K.M., Dickerson T.J., & Taffe M.A. (2013) The novel recreational drug 3,4-methylenedioxypyrovalerone (MDPV) is a potent psychomotor stimulant: Self-administration and locomotor activity in rats. Neuropharmacology, 130-140. DOI: 10.1016/j.neuropharm.2013.04.003
Parallel tempering is one of my favourite sampling algorithms to improve MCMC mixing times. This algorithm seems to be used exclusively on distributed memory architectures using MPI and remains unexploited on shared memory architectures such as our office computers, which have up to eight cores. I’ve written parallel tempering algorithms in MPI and Rmpi but never in OpenMP. It turns out that the latter has substantial advantages. I guess when people think of parallel tempering they think of processors communicating with each other via MPI and swapping parameters directly. If you are on a shared memory device, however, you can have processor A simply write to a shared array and have processor B read therefrom, which really saves a lot of aggro fiddling around with message numbers, blocking/non-blocking calls and deadlocks etc. Moreover, with OpenMP you can spawn more threads than you have processors, which translates to more parallel MCMC chains in the present context, whereas this becomes troublesome with MPI due to the danger of deadlocks. OpenMP is also much easier to use than MPI, with one line you can fork a serial thread into a desired and hardware-independent number of parallel threads.... Read more »
Earl David J., & Deem Michael W. (2005) Parallel tempering: Theory, applications, and new perspectives. Physical Chemistry Chemical Physics, 7(23), 3910. DOI: 10.1039/b509983h
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