Science news, education and opinions in plain English
Author: Jennifer Huber
As a Ph.D. physicist and research scientist at the Lawrence Berkeley National Laboratory, I gained extensive experience in medical imaging and technical writing. Now, I am a full-time freelance science writer, editor and science-writing instructor. I've lived in the San Francisco Bay Area most of my life and I frequently enjoy the eclectic cultural, culinary and outdoor activities available in the area.
Courtesy of jdxyw's photostream via Creative Commons
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.
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.”
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.
It seems like more and more food boasts that it is gluten-free on the packaging. Is this just another food fad being pushed by marketing agencies? Or is there a real medical need for a gluten-free diet?
Gluten is a protein present in wheat, barley, and rye that can be found in foods like bread, pasta, cake, cereal and beer. Gluten is also added as a stabilizing agent to some unexpected foods like ketchup and ice cream. Maintaining a gluten-free diet can be difficult and expensive, so most people on this restricted diet have Celiac disease.
Over 2 million people in the United States have Celiac disease, or 1 in 133 Americans. Celiac disease is a common genetic disorder in which a person has an autoimmune response to gluten. Symptoms can vary widely, but common symptoms include diarrhea, bloating, and abdominal pain. These symptoms are caused by the person’s immune system mistaking the gluten as a hostile organism. As the immune system attacks the gluten, the small intestines are inflamed and damaged. Currently people with Celiac disease have to rely on a lifelong gluten-free diet.
However, researchers have recently discovered the cause of this immune reaction, as reported in the peer-reviewed journal Science Translational Medicine. A large study was performed by scientists from Australia, the UK and Italy. These researchers recruited 226 volunteers with Celiac disease (age range 19-70 years, average age 50 years, 73% women) and a control group with similar characteristics. Prior to participating in the study, the volunteers with Celiac disease had been strictly gluten-free for at least 3 months and the normal controls for 1 month.
During the study, the volunteers ate foods with gluten — barley risotto, slices of wheat bread, rye muffins, or a combination of these over three days. Eating these foods induced an immune response in the volunteers, causing their bodies to produce gluten-specific T cells (a type of white blood cells that are important in the immune system). Blood samples were taken for each volunteer at the time of the first “grain eating challenge” and 6 days later. Researchers then performed complicated laboratory analysis of these T cells from the blood samples.
The researchers identified three key substances (specific peptides) in the gluten that caused most of the immune response. These key substances were found in all three grains — wheat, barley and rye. Effects of other gluten substances were found to be negligible in comparison.
This breakthrough in understanding Celiac disease should lead to new treatments, such as immunotherapy. In immunotherapy, a person is repeatedly exposed to toxins that cause an immune response, eventually causing the body to tolerate the toxins. This technique is commonly used to reduce allergic reactions — e.g., to grasses or pets. The researchers are now designing and testing an immunotherapy for Celiac disease, based on using the three identified key substances in gluten as the toxins. This new therapy is now being tested as a phase 1 clinical trial. Hopefully some day soon people that suffer from Celiac disease will be free of a gluten-free diet.
I’m one of those grocery shoppers that turns the package around to check the ingredients, before I buy anything for the first time. Checking food packages is relatively easy, because I expect only recognizable simple ingredients. As Michael Pollan says, would my Great Grandmother recognize this as food? However, what about sunscreen? You don’t really expect to know all the ingredients in sunscreen, so how can you tell if it is safe to use?
The Environmental Working Group has done extensive research to evaluate the effectiveness and safety of over 500 sunscreens currently on the market, so you don’t have to. Their fourth annual “2010 Sunscreen Guide” lists the best and worst sunscreens, and it allows you to look up information on your sunscreen. It is worth a look to make sure your current sunscreen isn’t on the “Hall of Shame” list. The Environmental Working Group also provides a lot of detailed information about sunscreen ingredients that can be damaging to your body.
This year there is concern over the large number of sunscreens with exaggerated SPF claims. There are substantially more sunscreens with high-SPF ratings in 2010, with one in six products claiming higher than SPF 50. The FDA believes that these higher ratings are “inherently misleading.” Many of these high-SPF sunscreens provide little protection from UVA radiation, the type of sunlight that doesn’t cause sunburns but does cause other skin damage and cancer. Scientists are worried that the high-SPF products will encourage people to stay out in the sun too long, increasing their risk of sun damage.
In general, most people do not use enough sunscreen to get the real benefit of the SPF rating promised on the bottle. According to the Environmental Working Group, “people typically use about a quarter of the recommended amount.” When under-applied, the typical effectiveness of SPF 100 to 15 sunscreens actually drops down to perform like SPF 3.2 to 2.
This year there is also significant concern over retinyl palmitate, which is a form of vitamin A that is found in 41 percent of sunscreens. Vitamin A is an anti-oxidant that slows aging, so it is commonly used in lotions. This may be a safe ingredient for night creams. However, a recent FDA study found that vitamin A results in the growth of cancerous tumors when used on skin that is exposed to sunlight. The National Toxicology Program is studying whether vitamin A exposed to sunlight forms free radicals that can damage DNA. Although these research studies are preliminary, the Environmental Working Group recommends that you avoid sunscreens with vitamin A (any form of retinyl or retinol).
You also need to be careful of products with hormone-disrupting compounds, such as oxybenzone which is found in about 60 percent of beach and sport sunscreens. Oxybenzone readily penetrates the skin and enters the bloodstream. This results in increased production of free radicals that may cause cancer and other health issues. The Centers for Disease Control and Prevention have found that 97 percent of Americans tested had oxybenzone in their bodies, and additional research is underway to better understand how this affects our health. So oxybenzone is considered one of the main toxic ingredients to avoid in sunscreens.
All these troubling facts may tempt you to give up on wearing sunscreen altogether. However, public health agencies still recommend using sunscreen, just not as a your first line of defense. Hats, clothing and shade are the most reliable sun protection. When that isn’t enough, then use the Environmental Working Group’s Sunscreen Guide to help you select a a relatively safe sunscreen.
I was surprised to find that my two favorite sunscreens, Neutrogena Sensitive Skin Sunblock and Alba Botanica Facial Sunblack, only rated a 4 out of 10 with “moderate” health concerns and UVA protection. So I’m also trying out some of the recommended sunscreens (rated 0-2) in search of a new favorite.
Scientists Talk Funny 