Constantine Alexander's blog

Transparent solar cells for windows that generate electricity

On the left is a piece of glass plate, and on the right is the transparent solar cell. Credit: Rui Zhu, Ph.D

Scientists are reporting development of a new transparent solar cell, an advance toward giving windows in homes and other buildings the ability to generate electricity while still allowing people to see outside. Their report appears in the journal ACS Nano.

Yang Yang, Rui Zhu, Paul S. Weiss and colleagues explain that there has been intense world-wide interest in so-called polymer solar cells (PSCs), which are made from plastic-like materials. PSCs are lightweight and flexible and can be produced in high volume at low cost. That interest extends to producing transparent PSCs. However, previous versions of transparent PSCs have had many disadvantages, which the team set out to correct.

They describe a new kind of PSC that produces energy by absorbing mainly infrared light, not visible light, making the cells 66 percent transparent to the human eye. They made the device from a photoactive plastic that converts infrared light into an electrical current. Another breakthrough is the transparent conductor made of a mixture of silver nanowire and titanium dioxide nanoparticles, which was able to replace the opaque metal electrode used in the past. This composite electrode also allowed the solar cell to be fabricated economically by solution processing. The authors suggest the panels could be used in smart windows or portable electronics.

The authors acknowledge funding from the Engineering School of UCLA, the Office of Naval Research and the Kavli Foundation. The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 164,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.

Contact: Michael Bernstein
m_bernstein@acs.org
202-872-6042
American Chemical Society

 

 

Tropical climate in the Antarctic

Palm trees once thrived on today's icy coasts 52 million years ago

		It is difficult to believe that 50 million years ago palm trees thrived on today' s icy coasts of Antarctica. Credit: Etienne Classen, Integrated Ocean Drilling Program

Given the predicted rise in global temperatures in the coming decades, climate scientists are particularly interested in warm periods that occurred in the geological past. Knowledge of past episodes of global warmth can be used to better understand the relationship between climate change, variations in atmospheric carbon dioxide and the reaction of Earth's biosphere. An international team led by scientists from the Goethe University and the Biodiversity and Climate Research Centre in Frankfurt, Germany, has discovered an intense warming phase around 52 million years ago in drill cores obtained from the seafloor near Antarctica — a region that is especially important in climate research. The study published in the journal Nature shows that tropical vegetation, including palms and relatives of today's tropical Baobab trees, was growing on the coast of Antarctica 52 million years ago. These results highlight the extreme contrast between modern and past climatic conditions on Antarctica and the extent of global warmth during periods of elevated atmospheric carbon dioxide levels.

Around 52 million years ago, the concentration of the greenhouse gas carbon dioxide (CO2) in the atmosphere was more than twice as high as today. "If the current CO2 emissions continue unabated due to the burning of fossil fuels, CO2 concentrations in the atmosphere, as they existed in the distant past, are likely to be achieved within a few hundred years", explains Prof. Jörg Pross, a paleoclimatologist at the Goethe University and member of the Biodiversity and Climate Research Centre (BiK-F) in Frankfurt, Germany. "By studying naturally occurring climate warming periods in the geological past, our knowledge of the mechanisms and processes in the climate system increases. This contributes enormously to improving our understanding of current human-induced global warming."

Computer models indicate that future climate warming will be particularly pronounced in high-latitude regions, i.e., near the poles. Until now, however, it has been unclear how Antarctic terrestrial ecosystems responded in the geological past to a greenhouse climate with high atmospheric CO2 concentrations.

The scientists working with Prof. Pross analysed rock samples from drill cores on the seabed, which were obtained off the coast of Wilkes Land, Antarctica, as part of the Integrated Ocean Drilling Program (IODP). The rock samples are between 53 and 46 million years old and contain fossil pollen and spores that are known to originate from the Antarctic coastal region. The researchers were thus able to reconstruct the local vegetation on Antarctica and, accordingly, interpret the presence of tropical and subtropical rainforests covering the coastal region 52 million years ago.

In an area where the Antarctic ice sheet borders the Southern Ocean today, frost-sensitive and warmth-loving plants such as palms and the ancestors of today's baobab trees flourished 52 million years ago. The scientists' evaluations show that the winter temperatures on the Wilkes Land coast of Antarctica were warmer than 10 degrees Celsius at that time, despite three months of polar night. The continental interior, however, was noticeably cooler, with the climate supporting the growth of temperate rainforests characterized by southern beech and Araucaria trees of the type common in New Zealand today. Additional evidence of extremely mild temperatures was provided by analysis of organic compounds that were produced by soil bacteria populating the soils along the Antarctic coast.

		The scientists used the drillship JOIDES Resolution to recover sediment cores off the Antarctic coast. Drilling reached a depth of more than 1,000 m below the sea floor. Credit: Rob Dunbar, Stanford University

These new findings from Antarctica also imply that the temperature difference between the low latitudes and high southern latitudes during the greenhouse phase 52 million years ago was significantly smaller than previously thought. "The CO2 content of the atmosphere as assumed for that time interval is not enough on its own to explain the almost tropical conditions in the Antarctic", says Pross. "Another important factor was the transfer of heat via warm ocean currents that reached Antarctica." When the warm ocean current collapsed and the Antarctic coast came under the influence of cooler ocean currents, the tropical rainforests including palms and Baobab relatives also disappeared.

Paper:

Pross, J., Contreras, L., Bijl, P.K., Greenwood, D.R., Bohaty, S.M., Schouten, S., Bendle, J.A., Röhl, U., Tauxe, L., Raine, J.I., Huck, C.E., van de Flierdt, T., Jamieson, S.S.R., Stickley, C.E., van de Schootbrugge, B., Escutia, C., Brinkhuis, H., IODP Expedition 318 Scientists (2012): Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch. Nature, DOI: 10.1038/nature11300.

The Goethe University, with its strong research focus, is based in Frankfurt, Europe's financial metropolis. It was founded 94 years ago by Frankfurt citizens and is now one of Germany's ten largest universities. On January 1, 2008 it returned to its historical roots as a university financed by foundations, guaranteeing it an exceptional degree of autonomy. And the historical ensemble of buildigns designed by Julius Poelzig back in the 1920s in Frankfurt's Westend is now the hub of what, when complete, will be Germany's most beautiful campus - the construction work will cost a total of about EUR 600 million. Since 2000, over 50 new foundation-financed professorships and visiting professorships have been established, meaning the Goethe University is again the trailblazers in Germany, and has been well up with leaders for three consecutive issues of the CHE's three research ranking table and the German Academic Excellence Initiative.

Contact: Prof. Jörg Pross
joerg.pross@em.uni-frankfurt.de
49-069-798-40181
Goethe University Frankfurt

 

 

Earth's oceans and ecosystems still absorbing about half the greenhouse gases emitted by people

		As carbon emissions by human activities have increased (purple), some carbon has stayed in the atmosphere (red) and some has been absorbed by natural “sinks” on land and in the oceans (blue). Natural sinks, including land ecosystems and the oceans, remove about half of the carbon emitted by human activities back out of the atmosphere. Note: The graph depicts carbon accumulation, which is proportional to carbon dioxide accumulation. Credit: NOAA Illustration

Earth's oceans, forests and other ecosystems continue to soak up about half the carbon dioxide emitted into the atmosphere by human activities, even as those emissions have increased, according to a study by University of Colorado and NOAA scientists to be published August 2 in the journal Nature.

The scientists analyzed 50 years of global carbon dioxide (CO2) measurements and found that the processes by which the planet's oceans and ecosystems absorb the greenhouse gas are not yet at capacity.

"Globally, these carbon dioxide 'sinks' have roughly kept pace with emissions from human activities, continuing to draw about half of the emitted CO2 back out of the atmosphere. However, we do not expect this to continue indefinitely," said NOAA's Pieter Tans, a climate researcher with NOAA's Earth System Research Laboratory in Boulder, Colo., and co-author of the study. The University of Colorado's Ashley Ballantyne is lead author.

		Earth's oceans, forests and other ecosystems soak up about half the greenhouse gas carbon dioxide emitted into the atmosphere by fossil fuel burning and other human activities, according to a new University of Colorado and NOAA study published in Nature. Credit: Will von Dauster, NOAA

Carbon dioxide is emitted into the atmosphere mainly by fossil fuel combustion but also by forest fires and some natural processes. The gas can also be pulled out of the atmosphere into the tissues of growing plants or absorbed by the waters of Earth's oceans. A series of recent studies suggested that natural sinks of carbon dioxide might no longer be keeping up with the increasing rate of emissions. If that were to happen, it would cause a faster-than-expected rise in atmospheric carbon dioxide and projected climate change impacts.

Ballantyne, Tans and their colleagues saw no faster-than-expected rise, however. Their estimate showed that overall, oceans and natural ecosystems continue to pull about half of people's carbon dioxide emissions out of the atmosphere. Since emissions of CO2 have increased substantially since 1960, Ballantyne said, "Earth is taking up twice as much CO2 today as it was 50 years ago."

The rest continues to accumulate in the atmosphere, where it is likely to accelerate global warming.

		Earth's oceans, forests and other ecosystems remove about half the greenhouse gas carbon dioxide emitted by fossil fuel burning and other human activities; The rest continues to accumulate in the atmosphere, causing warming, according to a new University of Colorado and NOAA study published in Nature. Credit: Will von Dauster, NOAA

This new global analysis makes it clear that scientists do not yet understand well enough the processes by which ecosystems of the world are removing CO2 from the atmosphere, or the relative importance of possible sinks: regrowing forests on different continents, for example, or changing absorption of carbon dioxide by various ocean regions.

"Since we don't know why or where this process is happening, we cannot count on it," Tans said. "We need to identify what's going on here, so that we can improve our projections of future CO2 levels and how climate change will progress in the future."

Tans, Ballantyne and colleagues at the University of Colorado, including the Cooperative Institute for Research in Environmental Sciences, dissected the long-term records of CO2 levels measured by NOAA and the Scripps Institution of Oceanography at remote sites around the world, including the top of a mountain in Hawaii and the South Pole. Those CO2 levels reflect global averages of the greenhouse gas, which are affected by natural cycles as well as people's activities.

The researchers also scrutinized national and international inventories or bookkeeping estimates of CO2 emissions by people and compared those to the increasing atmospheric levels of the gas.

"The uptake of carbon dioxide by the oceans and by ecosystems is expected to slow down gradually," Tans said. Oceans, for example, are already becoming more acidic as they absorb about a quarter of the carbon dioxide pumped into the air by human activities. "As the oceans acidify, we know it becomes harder to stuff even more CO2 into the oceans," Tans said. "We just don't see a letup, globally, yet.

NOAA's mission is to understand and predict changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources.

Relevant Links:

• NOAA Earth System Research Laboratory Global Monitoring Division
• Carbon dioxide data and trends
• The Carbon Cycle

Contact: Katy Human
katy.g.human@noaa.gov
303-497-4747
NOAA Headquarters

 

 

Cut emissions further or face risks of high air pollution, study shows

Most of the world's population will be subject to degraded air quality in 2050 if man-made emissions continue as usual. In this 'business-as-usual' scenario, the average world citizen 40 years from now will experience similar air pollution to that of today's average East Asian citizen. These conclusions are those of a study published today in Atmospheric Chemistry and Physics, an Open Access journal of the European Geosciences Union (EGU).

Air pollution is a major health risk that may worsen with increasing industrial activity. At present, urban outdoor air pollution causes 1.3 million estimated deaths per year worldwide, according to the World Health Organisation [1].

"Strong actions and further effective legislation are essential to avoid the drastic deterioration of air quality, which can have severe effects on human health," concludes the team of scientists, led by Andrea Pozzer of the Abdus Salam International Centre for Theoretical Physics in Italy (now at the Max Planck Institute of Chemistry in Germany), in the new paper.

The researchers studied the impact of man-made emissions on air quality, assuming past emission trends continue and no additional climate change and air pollution reduction measures (beyond what is in place since 2005) are implemented. They point out that, while pessimistic, the global emissions trends indicate such continuation.

"At present the post-Kyoto climate negotiations are progressing slowly, and it is unclear how air quality policies will develop globally," explains co-author Greet Janssens-Maenhout of the European Commission Joint Research Centre in Italy. "In regions with economic growth, it might be less effective to implement emission-reduction measures due to strong growth in activities in particular sectors; in countries suffering from the economic downturn, implementing expensive air-quality measures could prove difficult in coming years," she adds.

"We show that further legislation to control and reduce man-made emissions is needed, in particular for eastern China and northern India, to avoid hot-spots of elevated air pollution," says Pozzer. Combined with the fact that these are regions of high population density, elevated air pollution here would mean that air quality would worsen significantly for the average world citizen in 2050.

Air pollution would also increase in Europe and North America, but to a much lesser extent than in Asia, due to the effect of mitigation policies that have been in place for over two decades.

Pozzer and his colleagues estimated air quality in 2005, 2010, 2025 and 2050 using an atmospheric chemistry model. "The model uses basic mathematical formulation to predict the meteorology and the chemical composition of the atmosphere," Pozzer explains. "In practice, it is a software used to forecast – or hindcast, for past years – the status of the atmosphere at specific times."

The results show that in 2025 and 2050, under the business-as-usual scenario studied, East Asia will be exposed to high levels of pollutants, such as nitrogen dioxide, sulphur dioxide and fine particulate matter (PM2.5) [2]. Northern India and the Arabian Gulf region, on the other hand, will suffer a marked increase in ozone levels.

The analysis now published is the first to include all five major air pollutants know to negatively impact human health: PM2.5, nitrogen dioxide, sulphur dioxide, ozone, and carbon monoxide. The scientists considered pollutants released through human activity, as well as those occurring naturally such as desert dust, sea spray, or volcanic emissions.

Taking all pollutants into account, eastern China, northern India, the Middle East, and North Africa are projected to have the world's poorest air quality in the future. In the latter locations this is due to a combination of natural desert dust and man-induced ozone. The effect of anthropogenic pollution emissions are predicted to be most harmful in East and South Asia, where air pollution is projected to triple compared to current levels.

The study aimed to compare the influence of man-made emissions on air quality in different regions, and show how no-further legislation to reduce emissions can result in drastic deterioration of air quality worldwide compared to the present day situation.

1. World Health Organisation (WHO) 'Air quality and health' fact sheet (September 2011) 
2. PM2.5 refers to pollutant particles less than 2.5 micrometers in aerodynamic size, or about a quarter of the size of a cloud droplet. According to the WHO, "PM affects more people than any other pollutant." PM2.5 is more dangerous than particulate matter of larger size because these particles can reach the smallest of airways and interfere with gas exchange in the lungs. 

Contact: Andrea Pozzer
andrea.pozzer@mpic.de
49-613-130-54600
European Geosciences Union

 

 

Rewarding work for butterflies

Insects learn faster when they are rewarded with nectar

Credit: Constantine Alexander. All Rights Reserved

Butterflies learn faster when a flower is rewarding than when it is not, and females have the edge over males when it comes to speed of learning with rewards. These are the findings of a new study, by Dr. Ikuo Kandori and Takafumi Yamaki from Kinki University in Japan. Their work, published online in Springer's journal Naturwissenschaften - The Science of Nature, is the first to investigate and compare the speed at which insects learn from both rewarding and non-rewarding experiences.

Learning is a fundamental mechanism for adjusting behavior to environmental change. In insects, there are three main types of learning: reward learning where insects develop a positive association between visual and/or olfactory cues and resources such as nectar; aversive learning where insects associate visual and/or olfactory cues with negative stimuli such as salt, shock and toxins; and non-reward learning where they associate the cues with the absence of rewards. To date, very few studies have explored non-reward learning in pollinator insects, including the butterfly Byasa alcinous.

In a series of four experiments, Kandori and Yamaki examined both the reward (nectar present) and non-reward (no nectar) learning abilities of the butterfly while foraging among artificial flowers of different colors. They also compared the reward and non-reward learning speeds.

They found that the butterfly learned to associate flower color, not only with the presence of nectar, but also with the absence of nectar. This demonstrates that the butterfly used both reward and non-reward learning while foraging on the flowers. In addition, the butterfly learned quicker via reward learning than it did via non-reward learning; and females learned faster than males.

These authors conclude: "Byasa alcinous can find rewarding flower species more efficiently via both reward and non-reward learning. Insects may initially visit a certain flower by innate preference. If this flower is rewarding, they quickly increase their focus on that flower species through reward learning. If the flower species is unrewarding and common, frequent visits to that flower species enhances non-reward learning to avoid that flower species. The butterfly can then identify new rewarding flower species with a reduced loss of energy and time, if it avoids foraging on such abundant, innately attractive but unrewarding flower species."

Reference: Kandori I & Yamaki T (2012). Reward and non-reward learning of flower colours in the butterfly Byasa alcinous (Lepidoptera: Papilionoidae). Naturwissenschaften – The Science of Nature; DOI 10.1007/s00114-012-0952-y

Contact: Joan Robinson
joan.robinson@springer.com
49-622-148-78130
Springer