Tag Archives: environmental

New device could provide electrical power source from walking and other ambient motions:MIT Research

Harnessing the energy of small bending motions
New device could provide electrical power source from walking and other ambient motions.

By David Chandler


 

CAMBRIDGE, Mass.–For many applications such as biomedical, mechanical, or environmental monitoring devices, harnessing the energy of small motions could provide a small but virtually unlimited power supply. While a number of approaches have been attempted, researchers at MIT have now developed a completely new method based on electrochemical principles, which could be capable of harvesting energy from a broader range of natural motions and activities, including walking.

The new system, based on the slight bending of a sandwich of metal and polymer sheets, is described in the journal Nature Communications, in a paper by MIT professor Ju Li, graduate students Sangtae Kim and Soon Ju Choi, and four others.

Most previously designed devices for harnessing small motions have been based on the triboelectric effect (essentially friction, like rubbing a balloon against a wool sweater) or piezoelectrics (crystals that produce a small voltage when bent or compressed). These work well for high-frequency sources of motion such as those produced by the vibrations of machinery. But for typical human-scale motions such as walking or exercising, such systems have limits.

“When you put in an impulse” to such traditional materials, “they respond very well, in microseconds. But this doesn’t match the timescale of most human activities,” says Li, who is the Battelle Energy Alliance Professor in Nuclear Science and Engineering and professor of materials science and engineering. “Also, these devices have high electrical impedance and bending rigidity and can be quite expensive,” he says.

Simple and flexible

By contrast, the new system uses technology similar to that in lithium ion batteries, so it could likely be produced inexpensively at large scale, Li says. In addition, these devices would be inherently flexible, making them more compatible with wearable technology and less likely to break under mechanical stress.

While piezoelectric materials are based on a purely physical process, the new system is electrochemical, like a battery or a fuel cell. It uses two thin sheets of lithium alloys as electrodes, separated by a layer of porous polymer soaked with liquid electrolyte that is efficient at transporting lithium ions between the metal plates. But unlike a rechargeable battery, which takes in electricity, stores it, and then releases it, this system takes in mechanical energy and puts out electricity.

When bent even a slight amount, the layered composite produces a pressure difference that squeezes lithium ions through the polymer (like the reverse osmosis process used in water desalination). It also produces a counteracting voltage and an electrical current in the external circuit between the two electrodes, which can be then used directly to power other devices.

Because it requires only a small amount of bending to produce a voltage, such a device could simply have a tiny weight attached to one end to cause the metal to bend as a result of ordinary movements, when strapped to an arm or leg during everyday activities. Unlike batteries and solar cells, the output from the new system comes in the form of alternating current (AC), with the flow moving first in one direction and then the other as the material bends first one way and then back.

This device converts mechanical to electrical energy; therefore, “it is not limited by the second law of thermodynamics,” Li says, which sets an upper limit on the theoretically possible efficiency. “So in principle, [the efficiency] could be 100 percent,” he says. In this first-generation device developed to demonstrate the electrochemomechanical working principle, he says, “the best we can hope for is about 15 percent” efficiency. But the system could easily be manufactured in any desired size and is amenable to industrial manufacturing process.

Test of time

The test devices maintain their properties through many cycles of bending and unbending, Li reports, with little reduction in performance after 1,500 cycles. “It’s a very stable system,” he says.

Previously, the phenomenon underlying the new device “was considered a parasitic effect in the battery community,” according to Li, and voltage put into the battery could sometimes induce bending. “We do just the opposite,” Li says, putting in the stress and getting a voltage as output. Besides being a potential energy source, he says, this could also be a complementary diagnostic tool in electrochemistry. “It’s a good way to evaluate damage mechanisms in batteries, a way to understand battery materials better,” he says.

In addition to harnessing daily motion to power wearable devices, the new system might also be useful as an actuator with biomedical applications, or used for embedded stress sensors in settings such as roads, bridges, keyboards, or other structures, the researchers suggest.

The team also included postdoc Kejie Zhao (now assistant professor at Purdue University) and visiting graduate student Giorgia Gobbi , and Hui Yang and Sulin Zhang at Penn State. The work was supported by the National Science Foundation, the MIT MADMEC Contest, the Samsung Scholarship Foundation, and the Kwanjeong Educational Foundation.

Source: MIT News Office

Persian Gulf could experience deadly heat: MIT Study

Detailed climate simulation shows a threshold of survivability could be crossed without mitigation measures.

By David Chandler


 

CAMBRIDGE, Mass.–Within this century, parts of the Persian Gulf region could be hit with unprecedented events of deadly heat as a result of climate change, according to a study of high-resolution climate models.

The research reveals details of a business-as-usual scenario for greenhouse gas emissions, but also shows that curbing emissions could forestall these deadly temperature extremes.

The study, published today in the journal Nature Climate Change, was carried out by Elfatih Eltahir, a professor of civil and environmental engineering at MIT, and Jeremy Pal PhD ’01 at Loyola Marymount University. They conclude that conditions in the Persian Gulf region, including its shallow water and intense sun, make it “a specific regional hotspot where climate change, in absence of significant mitigation, is likely to severely impact human habitability in the future.”

Running high-resolution versions of standard climate models, Eltahir and Pal found that many major cities in the region could exceed a tipping point for human survival, even in shaded and well-ventilated spaces. Eltahir says this threshold “has, as far as we know … never been reported for any location on Earth.”

That tipping point involves a measurement called the “wet-bulb temperature” that combines temperature and humidity, reflecting conditions the human body could maintain without artificial cooling. That threshold for survival for more than six unprotected hours is 35 degrees Celsius, or about 95 degrees Fahrenheit, according to recently published research. (The equivalent number in the National Weather Service’s more commonly used “heat index” would be about 165 F.)

This limit was almost reached this summer, at the end of an extreme, weeklong heat wave in the region: On July 31, the wet-bulb temperature in Bandahr Mashrahr, Iran, hit 34.6 C — just a fraction below the threshold, for an hour or less.

But the severe danger to human health and life occurs when such temperatures are sustained for several hours, Eltahir says — which the models show would occur several times in a 30-year period toward the end of the century under the business-as-usual scenario used as a benchmark by the Intergovernmental Panel on Climate Change.

The Persian Gulf region is especially vulnerable, the researchers say, because of a combination of low elevations, clear sky, water body that increases heat absorption, and the shallowness of the Persian Gulf itself, which produces high water temperatures that lead to strong evaporation and very high humidity.

The models show that by the latter part of this century, major cities such as Doha, Qatar, Abu Dhabi, and Dubai in the United Arab Emirates, and Bandar Abbas, Iran, could exceed the 35 C threshold several times over a 30-year period. What’s more, Eltahir says, hot summer conditions that now occur once every 20 days or so “will characterize the usual summer day in the future.”

While the other side of the Arabian Peninsula, adjacent to the Red Sea, would see less extreme heat, the projections show that dangerous extremes are also likely there, reaching wet-bulb temperatures of 32 to 34 C. This could be a particular concern, the authors note, because the annual Hajj, or annual Islamic pilgrimage to Mecca — when as many as 2 million pilgrims take part in rituals that include standing outdoors for a full day of prayer — sometimes occurs during these hot months.

While many in the Persian Gulf’s wealthier states might be able to adapt to new climate extremes, poorer areas, such as Yemen, might be less able to cope with such extremes, the authors say.

The research was supported by the Kuwait Foundation for the Advancement of Science.

Source: MIT News Office

Climate change requires new conservation models, Stanford scientists say

In a world transformed by climate change and human activity, Stanford scientists say that conserving biodiversity and protecting species will require an interdisciplinary combination of ecological and social research methods.

By Ker Than

A threatened tree species in Alaska could serve as a model for integrating ecological and social research methods in efforts to safeguard species that are vulnerable to climate change effects and human activity.

In a new Stanford-led study, published online this week in the journal Biological Conservation, scientists assessed the health of yellow cedar, a culturally and commercially valuable tree throughout coastal Alaska that is experiencing climate change-induced dieback.

In an era when climate change touches every part of the globe, the traditional conservation approach of setting aside lands to protect biodiversity is no longer sufficient to protect species, said the study’s first author, Lauren Oakes, a research associate at Stanford University.

“A lot of that kind of conservation planning was intended to preserve historic conditions, which, for example, might be defined by the population of a species 50 years ago or specific ecological characteristics when a park was established,” said Oakes, who is a recent PhD graduate of the Emmett Interdisciplinary Program in Environment and Resources (E-IPER) at Stanford’s School of Earth, Energy, & Environmental Sciences.

But as the effects of climate change become increasingly apparent around the world, resource managers are beginning to recognize that “adaptive management” strategies are needed that account for how climate change affects species now and in the future.

Similarly, because climate change effects will vary across regions, new management interventions must consider not only local laws, policies and regulations, but also local peoples’ knowledge about climate change impacts and their perceptions about new management strategies. For yellow cedar, new strategies could include assisting migration of the species to places where it may be more likely to survive or increasing protection of the tree from direct uses, such as harvesting.

Gathering these perspectives requires an interdisciplinary social-ecological approach, said study leader Eric Lambin, the George and Setsuko Ishiyama Provostial Professor in the School of Earth, Energy, & Environmental Sciences.

“The impact of climate change on ecosystems is not just a biophysical issue. Various actors depend on these ecosystems and on the services they provide for their livelihoods,” said Lambin, who is also  a senior fellow at the Stanford Woods Institute for the Environment.

“Moreover, as the geographic distribution of species is shifting due to climate change, new areas that are currently under human use will need to be managed for biodiversity conservation. Any feasible management solution needs to integrate the ecological and social dimensions of this challenge.”

Gauging yellow cedar health

The scientists used aerial surveys to map the distribution of yellow cedar in Alaska’s Glacier Bay National Park and Preserve (GLBA) and collected data about the trees’ health and environmental conditions from 18 randomly selected plots inside the park and just south of the park on designated wilderness lands.

“Some of the plots were really challenging to access,” Oakes said. “We would get dropped off by boat for 10 to 15 days at a time, travel by kayak on the outer coast, and hike each day through thick forests to reach the sites. We’d wake up at 6 a.m. and it wouldn’t be until 11 a.m. that we reached the sites and actually started the day’s work of measuring trees.”

The field surveys revealed that yellow cedars inside of GLBA were relatively healthy and unstressed compared to trees outside the park, to the south. Results also showed reduced crowns and browned foliage in yellow cedar trees at sites outside the park, indicating early signs of the dieback progressing toward the park.

Additionally, modeling by study co-authors Paul Hennon, David D’Amore, and Dustin Wittwer at the USDA Forest Service suggested the dieback is expected to emerge inside GLBA in the future. As the region warms, reductions in snow cover, which helps insulate the tree’s shallow roots, leave the roots vulnerable to sudden springtime cold events.

Merging disciplines

In addition to collecting data about the trees themselves with a team of research assistants, Oakes conducted interviews with 45 local residents and land managers to understand their perceptions about climate change-induced yellow cedar dieback; whether or not they thought humans should intervene to protect the species in GLBA; and what forms those interventions should take.

One unexpected and interesting pattern that emerged from the interviews is that those participants who perceived protected areas as “separate” from nature commonly expressed strong opposition to intervention inside protected areas, like GLBA. In contrast, those who thought of humans as being “a part of” protected areas viewed intervention more favorably.

“Native Alaskans told me stories of going to yellow cedar trees to walk with their ancestors,” Oakes said. “There were other interview participants who said they’d go to a yellow cedar tree every day just to be in the presence of one.”

These people tended to support new kinds of interventions because they believed humans were inherently part of the system and they derived many intangible values, like spiritual or recreational values, from the trees. In contrast, those who perceived protected areas as “natural” and separate from humans were more likely to oppose new interventions in the protected areas.

Lambin said he was not surprised to see this pattern for individuals because people’s choices are informed by their values. “It was less expected for land managers who occupy an official role,” he added. “We often think about an organization and its missions, but forget that day-to-day decisions are made by people who carry their own value systems and perceptions of risks.”

The insights provided by combining ecological and social techniques could inform decisions about when, where, and how to adapt conservation practices in a changing climate, said study co-author Nicole Ardoin, an assistant professor at Stanford’s Graduate School of Education and a center fellow at the Woods Institute.

“Some initial steps in southeast Alaska might include improving tree monitoring in protected areas and increasing collaboration among the agencies that oversee managed and protected lands, as well as working with local community members to better understand how they value these species,” Ardoin said.

The team members said they believe their interdisciplinary approach is applicable to other climate-sensitive ecosystems and species, ranging from redwood forests in California to wild herbivore species in African savannas, and especially those that are currently surrounded by human activities.

“In a human-dominated planet, such studies will have to become the norm,” Lambin said. “Humans are part of these land systems that are rapidly transforming.”

This study was done in partnership with the U.S. Forest Service Pacific Northwest Research Station. It was funded with support from the George W. Wright Climate Change Fellowship; the Morrison Institute for Population and Resource Studies and the School of Earth, Energy & Environmental Sciences at Stanford University; the Wilderness Society Gloria Barron Fellowship; the National Forest Foundation; and U.S. Forest Service Pacific Northwest Research Station and Forest Health Protection.

For more Stanford experts on climate change and other topics, visit Stanford Experts.

Source : Stanford News


Ant-Man possible? Scientists shrink ants to study mechanisms that control DNA expression

By shrinking ants to sizes smaller than exist in nature, biologists present a useful model for understanding how environmental factors can influence DNA expression to create a range of outcomes.

This may not be exactly what the Marvel’s Ant-Man story has but still close enough to be amazing! 

BY BJORN CAREY


In the pages of Marvel comic books, Ant-Man manipulates fictional subatomic particles in order to shrink and fight crime as one of Earth’s mightiest heroes.

In real life, a team of biologists has now achieved similar shrinking results by manipulating ants’ DNA. The work won’t produce any superpowers, but it presents a useful model for understanding how environmental factors can influence DNA expression to create a range of outcomes in a population.

The work is published online in the journal Nature Communications. Sebastian Alvarado, a postdoctoral fellow at Stanford, conducted the research as a graduate student at McGill University, working alongside fellow graduate student Rajendhran Rajakumar, and professors Ehab Abouheif and Moshe Szyf, all of McGill.

 

Video : Stanford researcher explains the science behind Ant-Man

The experiment was designed as a means to study variation in quantitative traits. These are individual qualities, such as height or body weight, that can naturally vary across a defined range in a population. This variation is usually driven by the degree that environmental or other factors influence the expression of a particular gene, which makes ants an excellent test model.

In an ant colony, queens, workers and soldiers share similar genetics. But early in ant development, social, nutritional and chemical cues cause some genes to be more active, ultimately creating a wide range of body sizes, each specialized to a different task in the colony.

Many of these changes are controlled by DNA methylation, a process in which molecules are added to sections of DNA sequences. These additions affect how the DNA is interpreted and expressed, thus influencing an organism’s development or behavior.

“A lot of growth and development and sizing mechanisms that exist across the animal kingdom are found to be regulated by the same DNA methylation processes,” Alvarado said.

In the experiment, Alvarado and his colleagues at McGill exposed ant larvae to drugs that either increased or decreased the amount of DNA methylation. In doing so, they created ants that were larger within a caste and even significantly smaller than what exists in a natural population.

They then traced this size change to a specific growth factor gene, and found that across the population, varying degrees of DNA methylation to that gene directly corresponded to body size. A 20 percent modification in DNA methylation yielded a 20 percent change in body size, for example.

“This helps explain at a molecular level how continuums exist between two very discrete variables,” said Alvarado, who is now a member of biology Professor Russell Fernald’s lab at Stanford. “We can now look at diversity within a population by considering what expressions exist in between these variables and the actual molecular mechanism that controls that difference.”

Drawing a stronger connection between how environment and genetic factors influence DNA expression, Alvarado said, could have payoff in mapping the genetic basis of diseases and understanding evolutionary changes.

Source: Stanford News