Research Blogging - Physics - English

Once upon a time there was a star

2012-05-25T15:14:59Z

Why do we think that Population III stars exist? The term “Population III” could be assigned to two types of stars: “1) the ones which form out of the pristine gas left over after cosmological nucleosynthesis and generated the first metals; and 2) the ones which have been hypothesized to provide the dark matter in galactic halos” – Carr. The first type definitely exists, since we have metals in our disposal, and we know that elements heavier than H and He could only be generated through stellar nucleosynthesis. The second type, however, not necessarily exist, because first galactic halos could also be made of some ancient pre-atomic particles. I am going to discuss the first type of Population III stars. Note that both types of Population III stars might have formed during the first phase of galaxy formation or even before first galaxies were formed....

ResearchBlogging.org, & Bromm V. and Larson R. (2009) The First Stars in the Universe . Scientific American. info:/

Bromm, V. (2010) The Very First Stars: Formation and Reionization of the Universe. Proceedings of the International Astronomical Union, 5(S265), 27. DOI: 10.1017/S1743921310000116

Stacy, A., Greif, T., & Bromm, V. (2010) The first stars: formation of binaries and small multiple systems. Monthly Notices of the Royal Astronomical Society, 403(1), 45-60. DOI: 10.1111/j.1365-2966.2009.16113.x

Let the Buyer Beware

2012-05-22T13:26:00Z

"Modern societies are complex systems" may be the understatement of the year. Obvious or not, however, it must be stated when attempting to model even some minuscule aspect of such a society. Take, for instance......

Tiago P. Peixoto, & Stefan Bornholdt. (2012) No Need for Conspiracy: Self-Organized Cartel Formation in a Modified Trust Game. Physical Review Letters, 108(21), 218702. info:/10.1103/PhysRevLett.108.218702

Too good to be true? Stopping myopia progression by controlling peripheral refraction.

2012-05-17T03:47:26Z

New lights on optical methods to control myopia progression are not very promising... learn more....

Jaeken, B., & Artal, P. (2012) Optical quality of emmetropic and myopic eyes in the periphery measured with high angular resolution. Investigative Ophthalmology . DOI: 10.1167/iovs.11-8993

why we’d want to make some more antimatter

2012-05-16T17:05:00Z

Maybe the investors behind Planetary Resources should consider creating antimatter instead of building fuel depots on asteroids they want to mine since all they'd need to do to guarantee unimaginable profits is just a single gram of the stuff. Granted, the collider they'd have to build to smash ions until they decay into positrons and [...]...

Ronan Keane, & Wei-Ming Zhang. (2012) Beamed Core Antimatter Propulsion: Engine Design and Optimization. n/a. arXiv: 1205.2281v1

Nature’s Hand in Climate Change

2012-05-15T11:00:00Z

The heat wave throughout most of North America in the beginning of April had bought climate change into my mind. Was the heat wave caused by climate change? Likely not, I can’t imagine the effect of climate change happening so abruptly. But it made me think about what really causes climate change on this lovely blue planet of ours?...

J. Wilkinson. (2012) The Sun and Earth’s Climate . New Eyes on the Sun, , 201-217. info:/

Mufti, S., & Shah, G. (2011) Solar-geomagnetic activity influence on Earth's climate. Journal of Atmospheric and Solar-Terrestrial Physics, 73(13), 1607-1615. DOI: 10.1016/j.jastp.2010.12.012

Lockwood, M. (2011) Solar physics: Shining a light on solar impacts. Nature Climate Change, 1(2), 98-99. DOI: 10.1038/nclimate1096

Oreskes, N. (2004) BEYOND THE IVORY TOWER: The Scientific Consensus on Climate Change. Science, 306(5702), 1686-1686. DOI: 10.1126/science.1103618

Rivera, . (2012) Discovery of the Major Mechanism of Global Warming and Climate Change. Journal of Basic and Applied Sciences, 8(1). DOI: 10.6000/1927-5129.2012.08.01.29

Scanning The Acidic Brain

2012-05-10T13:35:37Z

According to University of Iowa researchers Vincent A. Magnotta and colleagues, any neuroscientist with an MRI scanner could soon be able to measure the acidity (pH) of the human brain in great detail: Detecting activity-evoked pH changes in human brain. If it works out, it would open up a whole new dimension of neuroimaging - and might be able to answer some of the biggest questions in the field.The method relies on measuring T1 relaxation in the rotating frame (T1ρ). Essentially, it's about the rate at which protons are swapped between water molecules and proteins. That rate is known to depend on pH.Anyway. It certainly looks impressive. Using a standard 3 Tesla MRI scanner, they were able to image the whole brain once every 6.6 seconds - only slightly slower than conventional fMRI measurements of brain activity, where 2 or 3 seconds is more usual. The spatial resolution was comparable to fMRI.Here's how it did on some bottles of jelly -Then they moved onto mouse brains (the differences are smaller here)...And finally they scanned some people. They were able to detect the (very small) pH changes caused by hyperventilation, which raises pH, and breathing air enriched in carbon dioxide, which lowers it.Lovely pictures I'm sure you agree, and it's a very clever methodology from a technical point of view. But what will it mean for neuroscience?Well, for one thing, it might be able to help resolve some of the debates over what conventional fMRI is actually measuring. For example, some neuroscientists believe that many (seemingly) interesting fMRI results may actually be (at least partially) reflections of subtle changes in breathing rate. Measuring acidity, an indirect proxy for breathing, could start to answer such questions.The main question though is, what are we going to call the new method? "T1ρ MRI"... not a terribly catchy name.Maybe MRalkalI?Magnotta, V., Heo, H., Dlouhy, B., Dahdaleh, N., Follmer, R., Thedens, D., Welsh, M., and Wemmie, J. (2012). Detecting activity-evoked pH changes in human brain Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1205902109...

Magnotta, V., Heo, H., Dlouhy, B., Dahdaleh, N., Follmer, R., Thedens, D., Welsh, M., & Wemmie, J. (2012) Detecting activity-evoked pH changes in human brain. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.1205902109

Why a Sperm Cell Is Like a Roomba

2012-05-08T10:07:02Z

A sperm cell, much like an expensive robotic vacuum cleaner, is a minimally intelligent body on a mission. Both the Roomba and the male gamete have to navigate a walled space without much idea where they're going or why. And although it won't clean your floors on the way, the sperm cell uses some of the same strategy as the robot vacuum. To discover the set of rules that sperm cells steer by, researchers used--what else?--sperm mazes. Led by fluid dynamics researcher Petr Denissenko at the University of Warwick, a group of scientists in the United Kingdom built hair-thin tunnels in various shapes. Then they sent human sperm into the curving or zigzagging tunnels. A camera watched through a glass wall on each channel to see what paths the tiny explorers took. In a narrow tunnel, frantically swimming sperm soon come up against a wall. Then, the camera showed, they follow that wall, seeming to keep their heads against it as they swim. (This same trick will get you out of a corn maze if you're lost, though you might want to keep a hand on the wall instead of your head.) Wall-following is also one of the rules used by a Roomba. In the case of the robot, it ensures that the edges of the room and the base of the sofa get clean. In the case of sperm, wall-following keeps them moving in one direction as they trace the twists and folds of a fallopian tube. But sperm aren't experts. When the wall takes a sharp turn away from them, sperm often don't notice; they simply shoot off in the direction they were already swimming. Luckily, they'll find another wall soon. "There are no large open spaces in the reproductive tract," Denissenko says. Not all sperm are equally spacey about following walls. When the path bends, some follow it better than others. If future research finds a connection between wall-following skill and sperm success--are better navigators also better fertilizers?--then fertility doctors might be able to sort out the best sperm using mazes. Knowing the rules that sperm swim by also means doctors can coax all of them to travel in the same direction. Denissenko and his coauthors built another maze, shaped like a wreath of grapes, that herds sperm into U-turns until they're all swimming one way. Roombas use other rules that sperm don't. For example, a Roomba knows to avoid cliffs, a hazard human sperm are unlikely to encounter since there are no staircases inside a human. Sperm have their own rule too: When they collide with each other, they swim off in different directions. Is this a trick for getting out of traffic? And how do sperm cells know they've hit a fellow swimmer, rather than a wall? Scientists aren't sure yet. "Understanding the role of collisions is really on my to-do list now," Denissenko says. Like cat-harassing robots, humans' own little automatons rely on a few simple algorithms to do their job. It's nice to see that these seemingly clueless cells know a thing or two. Now if only they'd take on some household chores. Denissenko, P., Kantsler, V., Smith, D., & Kirkman-Brown, J. (2012). Human spermatozoa migration in microchannels reveals boundary-following navigation Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1202934109 Image: IBRoomba/Flickr...

Denissenko, P., Kantsler, V., Smith, D., & Kirkman-Brown, J. (2012) Human spermatozoa migration in microchannels reveals boundary-following navigation. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.1202934109

Science in superheroes

2012-05-07T21:28:31Z

The magic of the movies mean almost anything can happen. You can time travel, control objects with your mind, or even heal yourself no matter how serious your injuries are. But did you know that filmmakers often consult scientists and engineers for their input in movies? Dr. Jim Kakalios, a professor at the University of [...]...

Lynne Robinson. (2012) The Super Materials of the Super Heroes. JOM, 64(1), 13-19. DOI: 10.1007/s11837-012-0256-x

What PhD's Want To Be When They Grow Up

2012-05-07T12:23:03Z

Almost everyone who goes to grad school in physics does so thinking that they will one become a tenured professor at a large university. And anyone who has been around a physics graduate program for a while knows that for most of us that is simply not going to happen. A recent book by Paula Stephan entitled "How Economics Shapes Science" shows that 23% of physics PhD's hold tenure-track appointments 6 years after their PhD, which means that less than one-quarter of those that survive grad school will get to be a professor in the way they imagined when they started. That's a dismal way to look at grad school, but I've made a strong assumption in the preceding paragraph that some of you probably already noticed. I assumed that every grad student wants to have a tenure-track position at a large research university. It turns out that what grad students want is far more diverse than that, and that it changes over the course of the average student's grad school experience. A recent study by a pair of management experts looked at exactly those questions and the results are fascinating. I recommend reading the entire paper as it's very well-written and accessible, but here at the two points that I found most interesting. First, they showed that even when asked to disregard the likelihood of actually getting a job in one of six areas, only 37% of beginning grad students in physics rated a tenure-track faculty position at a research university as "highly desirable" and that the percentage of students with that opinion didn't change over the course of grad school. Note that the percentages can add up to more than 100% because respondents could indicate multiple areas as "highly desirable". This indicates that new physics PhD's are not facing 1-in-4 odds of getting a tenure-track position, but rather that the odds are more like 1-in-2, assuming that there was little overlap between those that liked the "faculty-research" and "faculty-teaching" options. The second highlight is the way that students' opinions of the six career paths change over the course of grad school. They tracked what percentage of students rated each career path at the end of their graduate careers versus their ratings when they entered grad school. This shows that the faculty options were the two that took the biggest hits, meaning that a significant fraction of grad students realized that they didn't really want to be professors after getting effectively apprenticed to one for 5-7 years. Presumably replacing that career goal are fields like R&D at start-up firms and government labs, which saw the biggest increases in attractiveness. I find it very encouraging that most grad students realize that there are good things to do with a PhD in physics other than become your adviser, and that grad school actually does help open minds to other options. Sauermann, H., & Roach, M. (2012). Science PhD Career Preferences: Levels, Changes, and Advisor Encouragement PLoS ONE, 7 (5) DOI: 10.1371/journal.pone.0036307...

Sauermann, H., & Roach, M. (2012) Science PhD Career Preferences: Levels, Changes, and Advisor Encouragement. PLoS ONE, 7(5). DOI: 10.1371/journal.pone.0036307

High-risk research can’t be kept secret forever

2012-05-03T07:50:59Z

Should scientific journals publish high-risk scientific research that could in the wrong hands be disastrous for us all? Although it might be sensible to keep certain results secret for a while, I argue that eventually it does not make sense to withhold results in the long-term. What is this all about? Yesterday saw the publication [...]...

Imai, M., Watanabe, T., Hatta, M., Das, S., Ozawa, M., Shinya, K., Zhong, G., Hanson, A., Katsura, H., Watanabe, S.... (2012) Experimental adaptation of an influenza H5 HA confers respiratory droplet transmission to a reassortant H5 HA/H1N1 virus in ferrets. Nature. DOI: 10.1038/nature10831

Editorial. (2012) Publishing risky research. Nature. DOI: 10.1038/485005a