Day: 02/14/2012

World’s most efficient nanoplasmonic solar cells developed.

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In a boon for the local solar industry, a team of researchers from Swinburne University of Technology and Suntech Power Holdings have developed the world’s most efficient broadband nanoplasmonic solar cells.

In a paper published in Nano Letters, the researchers describe how they have manufactured thin film solar cells with an absolute efficiency of 8.1 per cent.

The research was conducted under the auspices of the Victoria-Suntech Advanced Solar Facility (VSASF) at Swinburne. The group is working to dramatically increase the efficiency of thin film solar technology.

According to Swinburne Professor Min Gu, Director of the VSASF, thin film cells have attracted enormous research interest as a cheap alternative to bulk crystalline silicon cells. However, the significantly reduced thickness of their silicon layer makes it more difficult for them to absorb sunlight.

“Light trapping technology is of paramount importance to increase the performance of thin film solar cells and make them competitive with silicon cells,” Professor Gu said. “One of the main potential applications of the technology will be to cover conventional glass, enabling buildings and skyscrapers to be powered entirely by sunlight.”

The VSASF group has been improving thin film cell efficiency by embedding gold and silver nanoparticles into the cells. This increases the wavelength range of the absorbed light, improving the conversion of photons into electrons.

In their most efficient cells yet, the researchers went one step further, using what are known as nucleated or ‘bumpy’ nanoparticles.

Senior Research Fellow at Swinburne Dr Baohua Jia said: “The broadband plasmonic effect is an exciting discovery of the team. It is truly a collaborative outcome between Swinburne and Suntech over the last 12 months.”

Dr Jia believes that this new technology will have an important impact on the solar industry. “What we have found is that nanoparticles that have an uneven surface scatter light even further into a broadband wavelength range. This leads to greater absorption, and therefore improves the cell’s overall efficiency.

Professor Gu applauded the quick timeframe in which the research group has been able to achieve 8.1 per cent total efficiency, however he believes there is still considerable scope to improve the cells and transform the way the world sources energy.

“We are on a rapid upwards trajectory with our research and development. With our current rate of progress we expect to achieve 10 per cent efficiency by mid 2012,” he said. “We are well on track to reach the VSASF’s target to develop solar cells that are twice as efficient and run at half the cost of those currently available.”

Professor Gu said that another advantage of the group’s approach is that nanoparticle integration is inexpensive and easy to upscale and therefore can easily be transferred to the production line.

“We have been using Suntech solar cells from the outset, so it should be very straightforward to integrate the technology into mass manufacturing. We expect these cells to be commercially available by 2017.”

Suntech CEO Dr Zhengrong Shi said: “Our team has achieved an impressive milestone with the world record for the most efficient broadband nanoplasmonic thin-film cell. This is an important step in demonstrating the potential of nanotechnology in leading the next generation of solar cells.”

Source:Nano letters

 

Study brings diagnostics for viruses a step closer to reality.

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Scientists have developed a technique which could form the basis of a non-invasive diagnostic for Adenovirus – the virus responsible for a large number of common illnesses.

The biosensor technology developed by researchers at the University of Leeds can not only detect the presence of the virus, it can also identify the individual strain and the number of virus particles present.

The study underpinning this research is published on Feb. 15 in the journal Biosensors & Bioelectronics.

Currently, testing for viruses is complicated, time consuming and requires specialist preparation of samples to identify virus DNA. Using this new technique, testing for viruses could be much quicker, simpler and ultimately less costly. For patients, this sort of diagnostic would mean faster treatment.

“This is a significant leap forward in testing for viruses,” says Professor Paul Millner of the University’s Faculty of Biological Sciences, who supervised the study. “For the first time we’ve been able to test for the presence of a whole virus, rather than having to seek out its genetic material, and the first time the number of virus particles has been counted using a lab-on-a-chip device. These are both exciting developments.”

Adenovirus is a common virus found in vertebrates and causes many illnesses, from the common cold through to gastroenteritis. People with strong immune systems are not badly affected by the virus, but for those with a compromised or immature immune system – such as small children or HIV sufferers– it can have fatal consequences.

The new technique uses antibodies attached to an electrical sensor. By measuring the sensor’s electrical changes, researchers were able to identify how many virus particles were present, and determine the type of virus dependent on its response.

“There’s a long way to go before the technology might reach a doctor’s surgery, but we’ve proven the concept,” says Rebecca Caygill, the PhD student behind the study. “We now need to increase the sensitivity of the test and optimise the different stages of the process so that we can consider scaling it up for clinical trials.”

Source:Physics.org

X-rays reveal why sea urchins are no easy prey.

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The team of scientists was led by Helmut Cölfen from the University of Konstanz (Germany) and comprised scientists from the universities of Beijing, Bristol, Leeds, Potsdam, the German Federal Centre for Materials Research (BAM) in Berlin, the CNRS in Orsay, the Max-Planck Institute of Colloids and Interfaces in Potsdam and the European Synchrotron Radiation Facility (ESRF) in Grenoble.

The team found the answer to a well-known problem: the hard-to-break spines of sea urchins consist of lime (calcium carbonate), a material which in crystalline form is hard but brittle. In geological deposits, lime usually forms calcite crystals that have very different properties to sea urchin spines as they break easily along their cleavage planes. However, it is known from X-ray analysis that the spines consist of calcite crystals. When they are broken, on the other hand, they do not produce the plane cleavage surfaces of single crystals but a rough fracture surface corresponding more to a glass or a ceramic material.

Helmut Cölfen built an international network of institutes specialising in materials characterisation to tackle this problem with electron microscopy, X-ray diffraction, nano-analysis and other methods.

The use of different X-ray scattering techniques at the ESRF was instrumental to reveal that sea urchin spines are actually built like walls of nanometre-sized bricks of calcite crystals which are aligned in parallel. The bricks are glued together with a mortar of non-crystalline lime. Such a composite arrangement efficiently absorbs shocks and collisions, as it confers elasticity to the material. “It was a real challenge to separately characterise the crystalline and non-crystalline parts of the spines, because the individual structures are extremely small. We had to combine two very different techniques using thin X-ray beams, one optimised for nanocrystals and the other for amorphous structures”, says Aurélien Gourrier of the CNRS and ESRF.

The researchers determined that 92% of the spines consist of crystalline calcite and 8% of amorphous lime. The disordered lime is in turn made of 99.9% calcium carbonate into which a tiny amount of protein is mixed (0.1%). At a disordered layer thickness of one or two nanometres around the calcite crystals, the amorphous lime ensures that the sting can only be broken with difficulty. This work is the first detailed structural proof of biological mesocrystals. The newly discovered structure solves a decades-long debate on the nature of the sea urchin spine – thanks to the mesocrystalline structure, it combines the properties of thin calcite nanocrystals and of the disordered chalk layer surrounding them.

The large internal surface area of the nature-made mesocrystals can inspire the design of, for example, new materials that are thin and hardly breakable and at the same time environmentally friendly in production and use. “It is fascinating that nature can turn fragile materials through structuring into high-performance composite materials, that manufacturing has not managed to produce so far,” says Helmut Cölfen on the global quest to learn from biominerals. His group at the University of Konstanz is already in collaboration with two major international companies on projects dedicated to the manufacture of future high performance concrete.

Source:Physics.org

 

New nano-material combinations produce leap in infrared technology.

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Arizona State University researchers are finding ways to improve infrared photodetector technology that is critical to national defense and security systems, as well as used increasingly in commercial applications and consumer products.

A significant advance is reported in a recent article in the journal Applied Physics Letters. It details discovery of how infrared photodetection can be done more effectively by using certain materials arranged in specific patterns in atomic-scale structures.

It’s being accomplished by using multiple ultrathin layers of the materials that are only several nanometers thick. Crystals are formed in each layer. These layered structures are then combined to form what are termed “superlattices.”

Photodetectors made of different crystals absorb different wavelengths of light and convert them into an electrical signal. The conversion efficiency achieved by these crystals determines a photodectector’s sensitivity and the quality of detection it provides, explains electrical engineer Yong-Hang Zhang.

The unique property of the superlattices is that their detection wavelengths can be broadly tuned by changing the design and composition of the layered structures. The precise arrangements of the nanoscale materials in superlattice structures helps to enhance the sensitivity of infrared detectors, Zhang says.

Zhang is a professor in the School of Electrical, Computer and Energy Engineering, one of ASU’s Ira A. Fulton Schools of Engineering. He is leading the work on infrared technology research in ASU’s Center for Photonics Innovation.

Additional research in this area is being supported by a grant from the Air Force Office of Scientific Research and a new Multidisciplinary University Research Initiative (MURI) program established by the U.S. Army Research Office. ASU is a partner in the program led by the University of Illinois at Urbana-Champaign.

The MURI program is enabling Zhang’s group to accelerate its work by teaming with David Smith, a professor in the Department of Physics in ASU’s College of Liberal Arts and Sciences, and Shane Johnson, a senior research scientist in the ASU’s engineering schools.

The team is using a combination of indium arsenide and indium arsenide antimonide to build the superlattice structures. The combination allows devices to generate photo electrons necessary to provide infrared signal detection and imaging, says Elizabeth Steenbergen, an electrical engineering doctoral student who performed experiments on the supperlattice materials with collaborators at the Army Research Lab.

“In a photodetector, light creates electrons. Electrons emerge from the photodetector as electrical current. We read the magnitude of this current to measure infrared light intensity,” she says.

“In this chain, we want all of the electrons to be collected from the detector as efficiently as possible. But sometimes these electrons get lost inside the device and are never collected,” says team member Orkun Cellek, an electrical engineering postdoctoral research associate.

Zhang says the team’s use of the new materials is reducing this loss of optically excited electrons, which increases the electrons’ carrier lifetime by more than 10 times what has been achieved by other combinations of materials traditionally used in the technology. Carrier lifetime is a key parameter that has limited detector efficiency in the past.

Another advantage is that infrared photodetectors made from these superlattice materials don’t need as much cooling. Such devices are cooled as a way of reducing the amount of unwanted current inside the devices that can “bury” electrical signals, Zhang says.

The need for less cooling reduces the amount of power needed to operate the photodetectors, which will make the devices more reliable and the systems more cost effective.

Researchers say improvements can still be made in the layering designs of the intricate superlattice structures and in developing device designs that will allow the new combinations of materials to work most effectively.

The advances promise to improve everything from guided weaponry and sophisticated surveillance systems to industrial and home security systems, the use of infrared detection for medical imaging and as a road-safety tool for driving at night or during sand storms or heavy fog.

“You would be able to see things ahead of you on the road much better than with any headlights,” Cellek says.

Source:Physics.org

New record for world’s smallest atomic valentine.

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Their tiny heart measures approximately 5 nm x 3.5 nm, a significant downsizing of the 8-nm heart from 2010.

The nanosized valentine is too small to be seen by the human eye or even with an optical microscope since it’s smaller than a visible wavelength of light. PhD student Alina Bruma, under the supervision of Dr. Ziyou Li, took a few images of the heart last weekend using a JEOL 2100F electron microscope, which uses electrons rather than photons to produce images. The scientists work at the university’s Nanoscale Physics Research Laboratory, which is headed by Prof. Richard Palmer.

As Li explained, the “bumps” that make up the heart are made of palladium (Pd) atoms and gold (Au) atoms, which are arranged on an amorphous carbon film. The different colors are false colors produced by imaging software. The key to making the nanoparticles form the heart shape was heating the nanoparticles, which causes a structure transformation.

“The spontaneously formed nanoparticles at room temperature tend to have irregular structures,” Li told PhysOrg.com. “Upon heating to 200-300 °C (473-573 K), marked structure transforms occur, resulting in more ordered and regular alloyed nanoparticles.”

By controlling the annealling temperature and the order of the atoms, the researchers can control how the nanoparticles are chemically arranged. They added that, due to improved control of the heating, this year’s valentine is also more stable than the one from two years ago. As might be expected, these abilities come in handy for making other things besides tiny hearts.

“The ability to control the structure of nanoalloys may one day lead to new materials with novel properties, having potential applications in areas such as catalysis and optical devices,” Li said.

Source: University of Birmingham Nanoscale Physics Research Laboratory

Clinical utility of array comparative genomic hybridisation for prenatal diagnosis: a cohort study of 3171 pregnancies

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Objective  To evaluate the clinical value of prenatal array comparative genomic hybridisation (CGH) in screening for submicroscopic genomic imbalances.

Design  Cross-sectional study.

Setting  Tertiary referral centre.

Population  From June 2008 to February 2011, 3171 fetuses underwent prenatal array CGH testing and karyotyping at the National Taiwan University Hospital. Indications for invasive prenatal diagnosis included abnormal karyotype, abnormal ultrasound, advanced maternal age and parental anxiety.

Methods  In all, 2497 fetuses were screened with 1-Mb resolution bacterial artificial chromosome array-based CGH, and 674 fetuses with 60-K oligonucleotide array-based CGH. Multiplex ligation-dependent probe amplification, fluorescence in situ hybridization, or 105-K oligonucleotide array CGH provided further confirmation.

Main outcome measure  Copy number variations identified by array CGH.

Results  Array CGH detected numerical chromosome anomalies in 37 (1.2%) fetuses, microdeletion/duplication in 34 (1.1%) fetuses, large deletion/duplication in 13 (0.4%) fetuses, benign copy number changes in 13 (0.4%) fetuses and variation of unknown clinical significance in five (0.2%) fetuses. Array CGH was effective in identifying submicroscopic genomic imbalance in fetuses with de novo balance translocations (2/17, 1.8%), supernumerary marker chromosomes (3/6, 50%), and abnormal prenatal ultrasound findings (33/194, 17.0%). Array CGH detected microdeletions/duplications in 12 fetuses with normal karyotype.

Conclusion  Prenatal array CGH is effective in screening for submicroscopic genomic imbalance. Array CGH may add 8.2% to the diagnostic field, compared with conventional karyotyping, for fetuses with abnormal ultrasound results, and is particularly useful in fetuses with karyotypic balanced translocation or marker chromosomes. There is a 0.52% baseline risk of submicroscopic genomic imbalance, even in women with an uneventful prenatal examination.

Source:BJOG

Boceprevir Interacts with Boosted HIV Protease Inhibitors.

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The interaction could reduce the effectiveness of both drugs.

In a “Dear Healthcare Professional” letter dated February 6, 2012, the maker of the hepatitis C virus (HCV) protease inhibitor boceprevir warned providers that coadministering the drug with a ritonavir-boosted HIV protease inhibitor might reduce the effectiveness of both drugs. The warning is based on the results of a pharmacokinetic study in which concomitant administration of boceprevir with ritonavir-boosted darunavir, lopinavir/ritonavir, or ritonavir-boosted atazanavir led to reduced plasma concentrations of the HIV protease inhibitors. Furthermore, lopinavir/ritonavir and ritonavir-boosted darunavir substantially lowered boceprevir levels.

According to the letter, patients who are already taking boceprevir with a boosted HIV protease inhibitor should be monitored closely for HCV treatment response and for potential HCV and HIV virologic rebound.

Comment: Previous studies demonstrated clinically significant interactions between the HCV protease inhibitor telaprevir and boosted HIV protease inhibitors, but boceprevir was supposed to be better in this regard. Efficacy looked promising in a trial of peginterferon/ribavirin + boceprevir among HIV/HCV-coinfected patients, most of whom were receiving boosted HIV protease inhibitors . However, the study was small (64 patients in the boceprevir arm), and in hindsight, perhaps the slower-than-expected HCV RNA reduction had a pharmacokinetic explanation.

For now, the bottom line is that there really is no optimal HCV protease inhibitor for HIV/HCV-coinfected patients, especially those on a boosted HIV protease inhibitor. The good news is that there are numerous HCV drugs in the late stages of development, so many coinfected patients may be stable enough to defer treatment for now. Of course, these new agents will also need evaluation in this difficult-to-treat population.

Source: Journal Watch HIV/AIDS Clinical Care

 

Dementia Often Missed When Primary Care Clinicians Rely on Symptoms.

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About a quarter of elderly patients without signs of cognitive impairment fail invited cognitive screens in primary care settings, according to a study in the Journal of the American Geriatrics Society. U.S. Preventive Services Task Force guidelines say there is insufficient information to make a recommendation on such screening.

Veterans Affairs researchers offered screening to some 8000 veterans aged 70 and older without signs of cognitive impairment. About one quarter failed the 3-minute screening with Mini-Cog during the course of a routine primary care visit. In that group, those who agreed to further screening had impairment confirmed over 90% of the time.

The authors note that their approach identified cognitive impairment in roughly 10% of patients, versus 4% with traditional clinical discovery based on patients’ symptoms.

The authors say that screening should be considered for all older adults, despite the lack of effective treatment. Such early warnings, they say, could avoid problems with driving, financial mismanagement, and social isolation.

Source:Journal of the American Geriatrics Society

Flu Season Off to Slow Start .

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Flu season has finally begun in the U.S., according to one measure used by the CDC.

For the first time this season, the proportion of respiratory specimens that tested positive for influenza nationally reached 10.5% for the week ending February 4. Passing the 10% mark is one indication that flu season has begun.

Other markers of influenza activity are also off to a slow start this year, the CDC reports, but the agency says it expects activity to pick up. To date, the circulating viruses have been well matched to this year’s influenza vaccine.

Source:CDC