The economic benefits of taking cover-cropping to the next level are important because the benefits will convince more corn, wheat and soybean growers in the Northeast and Mid-Atlantic regions to adopt the practice, the researchers said. Those cash crops are grown over large acreages mainly to feed livestock such as dairy and beef cows, hogs, and poultry.

“Cover crops are one of the main tools we have for reducing nutrients in the waters of the Chesapeake Bay — they have the potential to be agricultural nitrogen regulators that reduce leaching through soils and then deliver nitrogen to subsequent cash crops,” said Jason Kaye, professor of soil biogeochemistry. His research group in Penn State’s College of Agricultural Sciences has been studying cover-crop species for nearly a decade.

Yet regulating nitrogen in this way has proven difficult, because cover-crop species excel at either reducing nitrogen leaching or increasing nitrogen supply to cash crops, but they fail to excel at both simultaneously. Researchers tested mixed-species cover-crop stands to see if they could balance the nitrogen-fixing and nitrogen-scavenging capabilities of individual species.

They tested six cover-crop monocultures and four mixtures for their effects on nitrogen cycling in an organically managed maize-soybean-wheat feed-grain rotation at Penn State’s Russell E. Larson Agricultural Research Center. For three years, researchers used a suite of integrated approaches to quantify soil nitrogen dynamics and measure plant nitrogen uptake.

In the study, all cover-crop species — including legume monocultures — reduced nitrogen leaching compared to fallow plots. Cereal rye monocultures reduced nitrogen leaching by 90 percent, relative to fallow plots. Notably, mixtures with a low-seeding rate of rye did almost as well. Austrian winter-pea monocultures increased nitrogen uptake in cash crops the most, relative to fallow. Conversely, rye monocultures decreased nitrogen uptake, relative to fallow.

The research’s results, published this month in PLOS One, show clearly that cover-crop species selection and mixture design can substantially mitigate tradeoffs between nitrogen retention and nitrogen supply to cash crops, providing a powerful tool for managing nitrogen in cropping systems, Kaye pointed out.

“The mixtures were all very good at reducing pollution, but their impact on yields was limited,” he said. “Mixtures that performed best are the ones that had a higher proportion of legumes and mixed in a little bit of the grasses such as rye. Mixtures that include cereal rye dramatically decreased pollution because grasses establish root biomass that holds nitrogen and provides microbial activity in the soil.”

The process in which cover crops keep nutrients out of streams, protecting the bay, and pass along nitrogen to cash crops is straightforward. Kaye noted that in the fall after a cash crop is harvested, there is nitrogen in the soil that could go to the Chesapeake. A cover crop can take up that nitrogen and then, when the cover crop is killed in the spring, the nitrogen in the tissues of the cover crop are decomposed by microorganisms in the soil and passed on to the next cash crop, increasing yields.

The research findings may hold timely significance for Pennsylvania organic feed-grain producers, Kaye believes. Cover crops are especially important in organic systems in which tillage is used to manage and kill weeds and cover crops. In those situations, reducing erosion in disturbed soil is critical.

“Organic agriculture is growing very quickly in Pennsylvania,” he said. “One example is that Bell & Evans recently expanded organic poultry operations in the state. So, farmers potentially have a new and expanding market for feed grains that are grown organically. Incorporating cover-crop mixtures into their rotations will help them be more productive without increasing nutrient pollution.”

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Materials provided by Penn State. Original written by Jeff Mulhollem. Note: Content may be edited for style and length.

Now MIT engineers have flipped the picture of the standard polymer insulator, by fabricating thin polymer films that conduct heat — an ability normally associated with metals. In experiments, they found the films, which are thinner than plastic wrap, conduct heat better than many metals, including steel and ceramic.

The team’s results, published in the journal Nature Communications, may spur the development of polymer insulators as lightweight, flexible, and corrosion-resistant alternatives to traditional metal heat conductors, for applications ranging from heat dissipating materials in laptops and cellphones, to cooling elements in cars and refrigerators.

“We think this result is a step to stimulate the field,” says Gang Chen, the Carl Richard Soderberg Professor of Power Engineering at MIT, and a senior co-author on the paper. “Our bigger vision is, these properties of polymers can create new applications and perhaps new industries, and may replace metals as heat exchangers.”

Chen’s co-authors include lead author Yanfei Xu, along with Daniel Kraemer, Bai Song, Jiawei Zhou, James Loomis, Jianjian Wang, Migda Li, Hadi Ghasemi, Xiaopeng Huang, and Xiaobo Li from MIT, and Zhang Jiang of Argonne National Laboratory.

In 2010, the team reported success in fabricating thin fibers of polyethylene that were 300 times more thermally conductive than normal polyethylene, and about as conductive as most metals. Their results, published in Nature Nanotechnology, drew the attention of various industries, including manufacturers of heat exchangers, computer core processors, and even race cars.

It soon became clear that, in order for polymer conductors to work for any of these applications, the materials would have to be scaled up from ultrathin fibers (a single fiber measured one-hundredth of the diameter of a human hair) to more manageable films.

“At that time we said, rather than a single fiber, we can try to make a sheet,” Chen says. “It turns out it was a very arduous process.”

The researchers not only had to come up with a way to fabricate heat-conducting sheets of polymer, but they also had to custom-build an apparatus to test the material’s heat conduction, as well as develop computer codes to analyze images of the material’s microscopic structures.

In the end, the team was able to fabricate thin films of conducting polymer, starting with a commercial polyethylene powder. Normally, the microscopic structure of polyethylene and most polymers resembles a spaghetti-like tangle of molecular chains. Heat has a difficult time flowing through this jumbled mess, which explains a polymer’s intrinsic insulating properties.

Xu and her colleagues looked for ways to untangle polyethylene’s molecular knots, to form parallel chains along which heat can better conduct. To do this, they dissolved polyethylene powder in a solution that prompted the coiled chains to expand and untangle. A custom-built flow system further untangled the molecular chains, and spit out the solution onto a liquid-nitrogen-cooled plate to form a thick film, which was then placed on a roll-to-roll drawing machine that heated and stretched the film until it was thinner than plastic wrap.

The team then built an apparatus to test the film’s heat conduction. While most polymers conduct heat at around 0.1 to 0.5 watts per meter per kelvin, Xu found the new polyethylene film measured around 60 watts per meter per kelvin. (Diamond, the best heat-conducting material, comes in at around 2,000 watts per meter per kelvin, while ceramic measures about 30, and steel, around 15.) As it turns out, the team’s film is two orders of magnitude more thermally conductive than most polymers, and also more conductive than steel and ceramics.

To understand why these engineered polyethylene films have such an unusually high thermal conductivity, the team conducted X-ray scattering experiments at the U.S. Department of Energy’s Advanced Photon Source (APS) at the Argonne National Laboratory.

“These experiments, at one of the world’s most bright synchrotron X-ray facilities, allow us to see the nanoscopic details within the individual fibers that make up the stretched film,” Jiang says.

By imaging the ultrathin films, the researchers observed that the films exhibiting better heat conduction consisted of nanofibers with less randomly coiled chains, versus those in common polymers, which resemble tangled spaghetti. Their observations could help researchers engineer polymer microstructures to efficiently conduct heat.

“This dream work came true in the end,” Xu says.

Going forward, the researchers are looking for ways to make even better polymer heat conductors, by both adjusting the fabrication process and experimenting with different types of polymers.

Zhou points out that the team’s polyethylene film conducts heat only along the length of the fibers that make up the film. Such a unidirectional heat conductor could be useful in carrying heat away in a specified direction, inside devices such as laptops and other electronics. But ideally, he says the film should dissipate heat more effectively in any direction.

“If we have an isotropic polymer with good heat conductivity, then we can easily blend this material into a composite, and we can potentially replace a lot of conductive materials,” Zhou says. “So we’re looking into better heat conduction in all three dimensions.”

Young age per se is not a reason to give more intensive treatment highlighted Lambertini: “Women under 40 years of age tend to be diagnosed with more aggressive breast cancer types — for example their tumours are more likely to be triple negative and HER2 positive. Despite this, survival and local recurrence rates are similar to those of the general population of breast cancer patients provided they receive appropriate treatment.”

The aggressiveness of the tumour

The aggressiveness of tumours is illustrated in a study from Portugal in 207 patients under 35 years. (2) Of all breast cancers, 5% occur in women under 35, making it the most common cancer in women of this age group. Regarding tumour subtypes, 20% were triple negative, 28% HER2 positive, and 4% luminal A versus 67% luminal B, confirming the higher percentages of more aggressive tumour subtypes in young women. After a median follow-up of 53.5 months, 85% of women were alive, 26 patients had developed metastases and three a local recurrence.

Study author Dr. Ines F. Eiriz, of the Hospital Prof. Doutor Fernando Fonseca, Amadora, Portugal, said: “Disease-free survival was longest in women with hormone receptor positive tumours, followed by those with HER2 positive disease, and lastly those with triple negative breast cancer. The median survival of patients without metastases was 130 months compared to 37 months for those with metastatic disease.” (3)

The recurrence of the tumour

A Swiss study looking at breast cancer recurrence in 359 women aged 50 years or younger, showed that during a median follow-up of 45.6 months, 14 patients developed local recurrence, six developed distant metastases, and nine developed both. (4) The median time to recurrence was 31 months. The three- and five-year risks for local recurrence were 4.7% and 9.5%, respectively. Rates of disease free survival were 94.3% and 91.2% at three and five years, respectively. The rate of overall survival at five years was 93%.

Study author Dr. Simona Cima, of the IOSI — Oncology Institute of Southern Switzerland, Bellinzona, Switzerland, said: “Most recurrences in these patients were local rather than metastatic. Our study is ongoing, and the next step is to identify predictors of local recurrence. For example, we will examine the likelihood of local recurrence according to HER2 and triple negative status.”

Lambertini said: “It’s not true that being diagnosed with breast cancer at a young age means poorer survival or higher chances of the cancer coming back, and these studies further confirm that. Proper guideline-recommended treatments should be given to all breast cancer patients regardless of their age. Special attention should be paid in these women on the potential side effects of anticancer therapies including the risk of infertility.”

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Materials provided by European Society for Medical Oncology. Note: Content may be edited for style and length.