See my KQED Quest blog on Dr. Mina Bissell’s pivotal breast cancer research at Lawrence Berkeley National Lab. She will be part of a free public lecture, Science at the Theater: Health Detectives. It will be held on April 23 at 7 pm at the Berkeley Repertory Theater.
The stereotypical image of a scientist looks something like Albert Einstein, an older white man with either wild hair or almost none. The media often reinforces this image of a “mad scientist” in a white lab coat. But in reality, scientists are just a diverse group of people that mostly look and act like everyone else.
This scientist stereotype has been informally studied by at least two major scientific laboratories, Fermilab and the Pacific Northwest National Laboratory. About 12 years ago, a group of seventh graders came for a regular field trip to Fermilab. Few young people have ever knowingly met a scientist. So Fermilab had these students draw and describe what they thought a scientist looked like, both before and after going on the tour. While at Fermilab, the students met a diverse selection of real life scientists, including speaking in small groups with a typical white male, a young female and an African American male physicist. Before their field trip, the students mostly drew the stereotypical white man wearing a lab coat. However, their drawings after the tour were much more diverse and casually dressed.
Such studies have inspired a small group of people to demonstrate what a scientist is really like. Also inspired by Science Online 2012, they recently created a website where scientists can post a photograph and short description of themselves. Their hope is to challenge the stereotypical perception of a scientist. If you are a scientist and interested in joining their efforts, you can easily submit your photograph to be uploaded on their “This Is What A Scientist Looks Like” home page. However, I hope everyone enjoys the ever-expanding collection of photographs.
A journal article, just published in Applied Physics Letters, details a major breakthrough for experiments at SLAC’s Linac Coherent Light Source (LCLS).
LCLS delivers intense ultrashort x-ray pulses that can be used to study the motion of atoms as they respond to external triggers, such as an optical laser. In these “pump-probe” experiments, the optical laser “pump” pulse starts a reaction in the material, while the x-ray “probe” pulse investigates the state of the material after a defined time delay. A sequence of x-ray pulses, with different time delays between the laser and x-ray pulses, is used to “film” the reaction in the material.
LCLS ultrafast x-ray pulses basically act like high-speed flashes of a camera strobe, allowing scientists to capture images with a “shutter speed” of less than 100 femtoseconds – the time it takes light to travel the width of a human hair.
In order to be able to “film” optically-induced ultrafast processes, however, scientists need more than just ultrashort x-ray and laser pulses. They also need to synchronize the x-ray pulses to the optical laser pulses with almost femtosecond accuracy, in order to have snapshots with good time resolution (“sharp focus”). This is a major challenge, since the main laser system for the x-ray free electron laser is a kilometer away from the optical laser and experiment.
State-of-the-art synchronization is performed at LCLS by accurately measuring the arrival times of the electron bunches (and corresponding x-ray pulses) relative to the radiofrequency that drives the accelerator, since the optical laser is locked to this reference radiofrequency. The best time resolution so far achieved with this approach is 280 fs (full width at half maximum, FWHM).
Recently, scientists at the LCLS Atomic, Molecular and Optical Science Instrument (AMO) dramatically improved the time resolution for their pump-probe experiments. Their new synchronization strategy is to directly measure the relative arrival time of both the x-ray and optical laser pulses at the experiment on a shot-by-shot basis. They do this by introducing into the x-ray beam what they call a cross-correlator, which is mounted downstream of the main experiment.
AMO scientists split their laser beam, sending it to both a pump-probe experiment and the cross-correlator (with a time delay). In the cross-correlator, the laser beam is reflected off a Si3N4 thin film. The spot of the laser pulse is then imaged with a long-distance microscope on a CCD camera. X-ray pulses also hit the same surface of the Si3N4 film, quasi-instantaneously changing the surface reflectivity.
The x-ray pulse very briefly changes the surface reflectivity. By imaging and measuring the position of this reflectivity change with the reflected laser, AMO scientists can directly measure the relative arrival time of the x-ray and optical laser pulses at their experiment. The scientists then use this pulse arrival time information from the cross-correlator to correct their corresponding experimental data on a shot-by-shot basis.
The AMO team demonstrated their improved time resolution with a nitrogen pump-probe experiment. With the time information from the cross-correlator, they were able to decrease the time resolution of their nitrogen experiment down to only 50 fs (FWHM). That’s almost down to the theoretical limit, allowing scientists to investigate all sorts of new ultrafast science.
Scientists often talk about their work only with other scientists within their specialized research field. As a result, they spend years learning to speak in a technical dialect full of acronyms and jargon that is difficult for others to understand.
If the person off the street can’t understand you, does that mean that you’re incredibly smart and well educated? Actually, in my opinion it means the opposite. If you really understand something, then you should be able to explain it to anyone. You shouldn’t have to rely on jargon or math. And you should also be able to explain why the concept is relevant to “real” life.
So, my challenge for this science blog is to communicate about science using plain English. I spend much of my time at work writing dry technical publications, reports and grants. This is my attempt to talk in a more conversational way about science news.
The following posts are from my previous science blog named “A Scientist’s Viewpoint” (http://scientistviewpoint.tumblr.com/). After taking a hiatus from science blogging, I am switching over to this new WordPress platform. For convenience and completeness, I have transferred the contents of my old Tumblr blog to this one.
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.”
— Richard Feynman
Girls have always gone through puberty at varying ages. When I was 11 years old, I looked like a flat-chested scrawny little girl. Meanwhile, my best friend Judy at that age looked like a grown woman, basically the same as when she graduated from high school. This was a real problem for large-chested Judy because older men frequently hit on her, probably having no idea that she was only 11 years old and unprepared to cope with their advances.
Early maturation in girls is associated with lower self-esteem, less favorable body image, and greater rates of eating problems, depression, suicide attempts and risky behavior. Beyond the emotional issues, girls that go through puberty early are also at higher risk for some medical problems such as breast cancer, endometrial cancer, pre-diabetes and elevated blood pressure. These emotional and health concerns appear to worsen as the age of puberty onset lowers.
Although the timing of puberty always varies between different girls, the average age when girls enter puberty has fallen in the past two decades. A lot of reports and controversy have surrounded this finding, starting with a study published in 1997 in Pediatrics. Why this is happening is not fully understood. Ongoing studies are trying to determine whether this trend is continuing or whether the age of puberty onset for girls has stabilized.
The results of a new study on the timing of breast development in girls were just reported in Pediatrics by a research team led by Dr. Frank Biro, director of adolescent medicine at Cincinnati Children’s Hospital Medical Center. Dr. Biro and his colleagues studied 1239 girls ages 6 to 8 who were recruited from 3 diverse sites: East Harlem in New York, Cincinnati metropolitan area, and San Francisco Bay Area. The recruited group was 34% white, 31% black, 30% Hispanic, and 5% Asian. The data came from interviews with caregivers and physical examinations of the girls. Great care was taken to ensure that the examinations were performed by only well-trained certified staff, using identical well-established guidelines for determining the onset of puberty.
The researchers found that more girls are starting puberty at the age of 7 or 8 than previously reported 10 to 30 years earlier. At 7 years, 10.4% of white, 23.4% of black, and 14.9% of Hispanic girls had enough breast development to indicate the beginning of puberty. At 8 years, 18.3% of white, 42.9% of black and 30.9% of Hispanic girls had sufficient breast development. In comparison, the 1997 study found only 5% of white girls and 15.4% of black girls to have entered puberty at the age of 7.
So the new study shows that the age of entering puberty is continuing to fall for young girls, especially white girls. However, black and Hispanic girls still mature at younger ages than white girls. The cause of this concerning trend is not fully understood. Increased rates of obesity are thought to play a significant role, because body fat can produce sex hormones. Environmental chemicals are also suspected, since they might mimic effects of estrogen and speed up puberty, but this is still under study. Genetics may also play a role.
Breast Cancer and the Environmental Research Centers (BCERC) were established in 2003 as a consortium to study some of these issues, in partnership with the National Institute of Environmental Health Science (NIEHS) and National Cancer Institute (NCI). As Dr. Biro summarizes, “I think we need to think about the stuff we’re exposing our bodies to and the bodies of our kids. This is a wake-up call, and I think we need to pay attention to it.”
“I’d put my money on the sun and solar energy. What a source of power! I hope we don’t have to wait until oil and coal run out before we tackle that.”
—Thomas Edison, in conversation with Henry Ford (1931)
Everyone loves the idea of solar power — heating and cooling your home using the sun as a clean, free source of power. It sounds like the ultimate way to lower your carbon foot print! However, solar cells are expensive and typically only about 15% efficient, as I discussed in an earlier blog.
In order to make solar power more practical on a wide scale, a lot of research is underway to increase solar power efficiency. Stanford researchers have just reported a significant breakthrough in such solar power research, as described in their new paper in Nature Materials. They have developed a novel solar technology that uses both the light and heat of the sun to generate electricity. This new technology could double solar power efficiency and make it more affordable.
When most people think of solar power, they think of rooftop solar panels. These sort of solar panels (or arrays of photovoltaic solar cells) use expensive semiconductor materials to convert photons of light into electricity. The photons from sunlight are absorbed by the semiconductor material, so the energy from the photons is given to the electrons in the semiconductor. The energy given to an electron can “excite” it from the valence band to the conduction band, where it is free to move around within the semiconductor to produce electricity. Solar panels basically convert solar energy into direct current electricity. However, these types of solar panels aren’t very efficient. If an excited photon doesn’t absorb enough energy, then it can’t make it to the conduction band to produce electricity. On the other hand, if an excited photon absorbs more energy than needed (to make it to the conduction band) then the excess energy is lost as heat. In silicon solar panels, half of the solar energy that hits the solar panel is lost due to these two processes. Ideally you would like to somehow harvest the energy that is lost as heat, in order to make solar cells more efficient.
Solar power can also be generated by a thermionic energy convertor, which directly converts heat into electricity. A thermionic converter produces electricity by causing a heat-induced flow of electrons from a hot cathode across a vacuum gap to a cooler anode. However, only a small fraction of the electrons gain sufficient thermal energy to generate this kind of electricity, and very high temperatures are needed for efficient thermionic conversion.
The Stanford researchers have recently developed a new process that exploits the benefits of both solar and thermal cell conversion. The research was led by Nicholas Melosh, as a joint venture of Stanford and SLAC National Accelerator Laboratory. Melosh’s group coated a piece of semiconducting material with a thin layer of metal cesium, demonstrating that this allowed the material to use both light and heat to generate electricity. This new PETE (photon-enhanced thermionic emission) device used the same basic architecture as a thermionic converter except with this special semiconductor as the cathode.
Although the physical process of this PETE device is different than the standard solar cell mechanisms, the new device gives a similar response at very high temperatures. In fact, the PETE device is most efficient at over 200 C. This means that PETE devices won’t replace rooftop solar panels, since they require higher temperatures to be efficient. Instead, they could be used in combination with solar concentrators as part of a large scale solar power plant, for instance in the Mojave Desert.
Melosh’s initial “proof of concept” research was performed with the semiconductor galium nitride to demonstrate that the new energy conversion process works, but galium nitride isn’t suitable for solar applications. They plan to extend their research to other semiconductors, such as gallium arsenide which is commonly used in household electronics. Based on theoretical calculations, they expect to develop PETE devices that operate with a 50 percent efficiency at temperatures exceeding 200 C. They hope to design the new PETE devices so they can be easily incorporated into existing solar power plants, significantly increasing the efficiency of solar power to make it competitive with oil.
“That’s the whole problem with science. You’ve got a bunch of empiricists trying to describe things of unimaginable wonder.”
— Calvin (and Hobbes)
Scientists Talk Funny 