Ultra-high material-quality silicon pillars on glass

We investigated a unique crystalline silicon structure-silicon pillars-formed by melt crystallization using millisecond-long single-pulse pulses of 110-GHz radiation of amorphous Si thin films deposited on glass by hot-wire chemical vapor deposition. With many microscopy techniques, we found that these pillars usually contain 1-4 randomly oriented grains with growth direction and grain boundaries perpendicular to the substrate surface. The grains in the Si pillars have ultra-high crystalline quality with grain sizes up to 20 m. We attribute the formation mechanism of the Si pillars to the extremely high heating/cooling rates of Si on a glass substrate using millimeter-wave radiation and the important roles played by wetting and capping layers during the annealing process. Such understandings may enable us to prepare ultra-high-quality, large-grained poly-Si on inexpensive foreign substrates at large scale and low cost. © 2010 IEEE.published_or_final_versionThe 35th IEEE Photovoltaic Specialists Conference (PVSC 2010), Honolulu, HI., 20-25 June 2010. In Proceedings of 35th PVSC, 2010, p. 002176-00217

Cannabidiol activates PINK1-Parkin-dependent mitophagy and mitochondrial-derived vesicles

The PINK1/Parkin pathway plays an important role in maintaining a healthy pool of mitochondria. Activation of this pathway can lead to apoptosis, mitophagy, or mitochondrial-derived vesicle formation, depending on the nature of mitochondrial damage. The signaling by which PINK/Parkin activation leads to these different mitochondrial outcomes remains understudied. Here we present evidence that cannabidiol (CBD) activates the PINK1-Parkin pathway in a unique manner. CBD stimulates PINK1-dependent Parkin mitochondrial recruitment similarly to other well-studied Parkin activators but with a distinctive shift in the temporal dynamics and mitochondrial fates. The mitochondrial permeability transition pore inhibitor cyclosporine A exclusively diminished the CBD-induced PINK1/Parkin activation and its associated mitochondrial effects. Unexpectedly, CBD treatment also induced elevated production of mitochondrial-derived vesicles (MDV), a potential quality control mechanism that may help repair partial damaged mitochondria. Our results suggest that CBD may engage the PINK1-Parkin pathway to produce MDV and repair mitochondrial lesions via mitochondrial permeability transition pore opening. This work uncovered a novel link between CBD and PINK1/Parkin-dependent MDV production in mitochondrial health regulation

Substituent Effects on the Photodeprotection Reactions of Selected Ketoprofen Derivatives in Phosphate Buffered Aqueous Solutions

published_or_final_versio

Evaluating performance of multiple RRTs

This paper presents experimental results evaluating the performance of a new multiple Rapidly-exploring Random Tree (RRT) algorithm. RRTs are randomised planners especially adept at solving difficult, high-dimensional path planning problems. However, environments with low-connectivity due to the presence of obstacles can severely affect convergence. Multiple RRTs have been proposed as a means of addressing this issue, however, this approach can adversely affect computational efficiency. This paper introduces a new and simple method which takes advantage of the benefits of multiple trees, whilst ensuring the computational burden of maintaining them is minimised. Results indicate that multiple RRTs are able to reduce the logarithmic complexity of the search, most notably in environments with high obstacle densities. © 2008 IEEE

Multi-view Vehicle Detection based on Part Model with Active Learning

© 2018 IEEE. Nowadays, most ofthe vehicle detection methods aim to detect only single-view vehicles, and the performance is easily affected by partial occlusion. Therefore, a novel multi-view vehicle detection system is proposed to solve the problem of partial occlusion. The proposed system is divided into two steps: Background filtering and part model. Background filtering step is used to filter out trees, sky and other road background objects. In the part model step, each of the part models is trained by samples collected by using the proposed active learning algorithm. This paper validates the performance of the background filtering method and the part model algorithm in multi-view car detection. The performance of the proposed method outperforms previously proposed methods

Excitonic quantum confinement modified optical conductivity of monolayer and few-layered MoS2

2016-2017 > Academic research: refereed > Publication in refereed journal201804_a bcmaVersion of RecordPublishe

Electron transport and band structure in phosphorus-doped polycrystalline silicon films

We study transport mechanisms, effective mass, and band structure by measuring the resistivity, Hall, and Seebeck and Nernst coefficients in heavily phosphorus-doped polycrystalline silicon films made by thermal crystallization of amorphous silicon. We observe a change in transport mechanism which results in an increase in electron mobility from 10% to 80% of the single-crystal silicon mobility as the carrier concentration increases from 1019 to 1020 cm-3. Our measurements of effective mass at the Fermi level indicate that as the carrier concentration increases, there is a shift from impurity-band transport to conduction-band transport, and that the electron effective mass is lower in the impurity band than in the conduction band of Si. The shift to conduction-band transport improves electron mobility with carrier density by improving intragrain carrier mean free path lengths and relaxation times. © 2009 American Institute of Physics.published_or_final_versio

Improving on nature's shortcomings: evolving a lipase for increased lipolytic activity, expression and thermostability.

An enzyme must be soluble, stable, active and easy to produce to be useful in industrial applications. Not all enzymes possess these attributes. We set out to determine how many changes are required to convert an enzyme with poor properties into one that has useful properties. Lipase Lip3 from Drosophila melanogaster had been previously optimised for expression in Escherichia coli. The expression levels were good, but Lip3 was mainly insoluble with poor activity. Directed evolution was used to identify variants with enhanced activity along with improved solubility. Five variants and the wild-type (wt) enzyme were purified and characterised. The yield of the wt enzyme was just 2.2 mg/L of culture, while a variant, produced under the same conditions, gave 351 mg. The improvement of activity of the best variant was 200 times higher than that of the wt when the crude lysates were analysed using pNP-C8, but with purified protein, the improvement observed was 1.5 times higher. This means that most of the increase of activity is due to increase in solubility and stability. All the purified variants showed increased thermal stability compared with the wt enzyme that had a T1/2 of 37°C, while the mutant with P291L of 42.2°C and the mutant R7_47D with five mutations had a value of 52.9°C, corresponding to an improvement of 16°C. The improved variants had between five and nine changes compared with the wt enzyme. There were four changes that were found in all 30 final round variants for which sequences were obtained; three of these changes were found in the substrate-binding domain

Evolving a lipase for hydrolysis of natural triglycerides along with enhanced tolerance towards a protease and surfactants

In the accompanying paper, we described evolving a lipase to the point where variants were soluble, stable and capable of degrading C8 TAG and C8 esters. These variants were tested for their ability to survive in an environment that might be encountered in a washing machine. Unfortunately, they were inactivated both by treatment with a protease used in laundry detergents and by very low concentrations of sodium dodecyl sulfate (SDS). In addition, all the variants had very low levels of activity with triglycerides with long aliphatic chains and with naturally occurring oils, like olive oil. Directed evolution was used to select variants with enhanced properties. In the first 10 rounds of evolution, the primary screen was selected for variants capable of hydrolyzing olive oil whereas the secondary screen was selected for enhanced tolerance towards a protease and SDS. In the final six rounds of evolution, the primary and secondary screens identified variants that retained activity after treatment with SDS. Sixteen cycles of evolution gave variants with greatly enhanced lipolytic activity on substrates that had both long (C16 and C18) as well as short (C3 and C8) chains. We found variants that were stable for more than 3 hours in protease concentrations that rapidly degrade the wild-type enzyme. Enhanced tolerance towards SDS was found in variants that could break down naturally occurring lipid and resist protease attack. The amino acid changes that gave enhanced properties were concentrated in the cap domain responsible for substrate binding

Influence of the Earth on the background and the sensitivity of the GRM and ECLAIRs instruments aboard the Chinese-French mission SVOM

SVOM (Space-based multi-band astronomical Variable Object Monitor) is a future Chinese-French satellite mission which is dedicated to Gamma-Ray Burst (GRB) studies. Its anti-solar pointing strategy makes the Earth cross the field of view of its payload every orbit. In this paper, we present the variations of the gamma-ray background of the two high energy instruments aboard SVOM, the Gamma-Ray Monitor (GRM) and ECLAIRs, as a function of the Earth position. We conclude with an estimate of the Earth influence on their sensitivity and their GRB detection capability.Comment: 24 pages, 15 figures, accepted for publication in Experimental Astronom