Conductive-probe atomic force microscopy characterization of silicon nanowire

The electrical conduction properties of lateral and vertical silicon nanowires (SiNWs) were investigated using a conductive-probe atomic force microscopy (AFM). Horizontal SiNWs, which were synthesized by the in-plane solid-liquid-solid technique, are randomly deployed into an undoped hydrogenated amorphous silicon layer. Local current mapping shows that the wires have internal microstructures. The local current-voltage measurements on these horizontal wires reveal a power law behavior indicating several transport regimes based on space-charge limited conduction which can be assisted by traps in the high-bias regime (> 1 V). Vertical phosphorus-doped SiNWs were grown by chemical vapor deposition using a gold catalyst-driving vapor-liquid-solid process on higly n-type silicon substrates. The effect of phosphorus doping on the local contact resistance between the AFM tip and the SiNW was put in evidence, and the SiNWs resistivity was estimated.     

Methods derived from nonlinear dynamics for analysing heart rate variability

Methods from nonlinear dynamics (NLD) have shown new insights into heart rate (HR) variability changes under various physiological and pathological conditions, providing additional prognostic information and complementing traditional time- and frequency-domain analyses. In this review, some of the most prominent indices of nonlinear and fractal dynamics are summarized and their algorithmic implementations and applications in clinical trials are discussed. Several of those indices have been proven to be of diagnostic relevance or have contributed to risk stratification. In particular, techniques based on mono- and multifractal analyses and symbolic dynamics have been successfully applied to clinical studies. Further advances in HR variability analysis are expected through multidimensional and multivariate assessments. Today, the question is no longer about whether or not methods from NLD should be applied; however, it is relevant to ask which of the methods should be selected and under which basic and standardized conditions should they be applied.     

A Mutant D‐Fructose‐6‐Phosphate Aldolase (Ala129Ser) with Improved Affinity towards Dihydroxyacetone for the Synthesis of Polyhydroxylated Compounds

A mutant of D ‐fructose‐6‐phosphate aldolase (FSA) of Escherichia coli, FSA A129S, with improved catalytic efficiency towards dihydroxyacetone (DHA), the donor substrate in aldol addition reactions, was explored for synthetic applications. The k_cat/K_M value for DHA was 17‐fold higher with FSA A129S than that with FSA wild type (FSA wt). On the other hand, for hydroxyacetone as donor substrate FSA A129S was found to be 3.5‐fold less efficient than FSA wt. Furthermore, FSA A129S also accepted glycolaldehyde (GA) as donor substrate with 3.3‐fold lower affinity than FSA wt. This differential selectivity of both FSA wt and FSA A129S for GA makes them complementary biocatalysts allowing a control over donor and acceptor roles, which is particularly useful in carboligation multi‐step cascade synthesis of polyhydroxylated complex compounds. Production of the mutant protein was also improved for its convenient use in synthesis. Several carbohydrates and nitrocyclitols were efficiently prepared, demonstrating the versatile potential of FSA A129S as biocatalyst in organic synthesis.     

Development of a novel portable-size PEMFC short stack with electrodeposited Pt hydrogen diffusion anodes

This paper presents, for the first time, a five-cell polymer electrolyte membrane fuel cell (PEMFC) short stack with electrodeposited hydrogen diffusion anodes. The anodes were manufactured by means of galvanostatic pulse electrodeposition and the cathodes by air-brushing. Nafion^® 212 was employed as a solid polymer electrolyte membrane in all cases. The short stack, whose cells had an active geometric area of 14 cm², was assembled and tested under different operating conditions. A peak power of about 11 W was obtained at 50 °C and atmospheric pressure using hydrogen and air feed, whereas a smaller value of 8.6 W was obtained from a five-cell short PEMFC stack with conventional hydrogen diffusion anodes under the same operating conditions. The better performance of the cells described in this paper has been assigned to the higher utilization of the platinum in the electrodeposited anodes compared to the conventional ones.     

Integration of a molten carbonate fuel cell with a direct exhaust absorption chiller

A high market value exists for an integrated high-temperature fuel cell-absorption chiller product throughout the world. While high-temperature, molten carbonate fuel cells are being commercially deployed with combined heat and power (CHP) and absorption chillers are being commercially deployed with heat engines, the energy efficiency and environmental attributes of an integrated high-temperature fuel cell-absorption chiller product are singularly attractive for the emerging distributed generation (DG) combined cooling, heating, and power (CCHP) market. This study addresses the potential of cooling production by recovering and porting the thermal energy from the exhaust gas of a high-temperature fuel cell (HTFC) to a thermally activated absorption chiller. To assess the practical opportunity of serving an early DG-CCHP market, a commercially available direct fired double-effect absorption chiller is selected that closely matches the exhaust flow and temperature of a commercially available HTFC. Both components are individually modeled, and the models are then coupled to evaluate the potential of a DG-CCHP system. Simulation results show that a commercial molten carbonate fuel cell generating 300 kW of electricity can be effectively coupled with a commercial 40 refrigeration ton (RT) absorption chiller. While the match between the two “off the shelf” units is close and the simulation results are encouraging, the match is not ideal. In particular, the fuel cell exhaust gas temperature is higher than the inlet temperature specified for the chiller and the exhaust flow rate is not sufficient to achieve the potential heat recovery within the chiller heat exchanger. To address these challenges, the study evaluates two strategies: (1) blending the fuel cell exhaust gas with ambient air, and (2) mixing the fuel cell exhaust gases with a fraction of the chiller exhaust gas. Both cases are shown to be viable and result in a temperature drop and flow rate increase of the gases before the chiller inlet. The results show that no risk of cold end corrosion within the chiller heat exchanger exists. In addition, crystallization is not an issue during system operation. Accounting for the electricity and the cooling produced and disregarding the remaining thermal energy, the second strategy is preferred and yields an overall estimated efficiency of 71.7%.     

Optogenetics Comes of Age: Novel Inhibitory Light‐Gated Anionic Channels Allow Efficient Silencing of Neural Function

Optogenetics, the developing field of research that uses light‐switchable biochemical tools in a sophisticated technological approach to monitor or control neural function, is rapidly evolving with the discovery and development of novel microbial rhodopsins. Light‐absorbing membrane proteins, as tools for brain research, are promoting new applications within the discipline of optogenetics. Light‐gated rhodopsin ion channels with better intrinsic light sensitivity and improved resolution are needed to overcome some of the current limitations of existing molecules. The recent discovery of light‐gated inhibitory anion channels opens new opportunities for studying physiological neural processes and, at the same time, represent a powerful approach for elucidating the mechanisms of neurological and mental disorders that could benefit from this approach.     

Absorbing photonic crystals for silicon thin-film solar cells: Design,fabrication and experimental investigation

In this paper, we present the integration of an absorbing photonic crystal within a thin-film photovoltaic solar cell. Optical simulations performed on a complete solar cell revealed that patterning the hydrogenated amorphous silicon active layer as a 2D photonic crystal membrane enabled to increase its integrated absorption by 28 % between 300 and 720 nm, comparing to a similar but unpatterned stack. In order to fabricate such promising cells, we developed a high throughput process based on holographic lithography and reactive ion etching. The influences of the parameters taking part in those processes on the obtained patterns are discussed. Optical measurements performed on the resulting “photonized” solar cell structures underline the regularity of the 2D pattern and a significant absorption increase above 550 nm, similarly to what is observed on the simulated absorption spectra. Moreover, our patterned cells are found to be robust with regards to the angle of incidence of the light.     

Influence of carbon nanotubes structures embedded in UHMWPE on bacterial adherence

Because of their intrinsic properties, carbon nanotubes (CNTs) have been suggested for biomedical applications. We studied the anti-adherent performance of two ultra-high-molecular-weight polyethylene (UHMWPE) surfaces which contains 3% multi-wall CNT variant (MWCNT): Nanocyl/UHMWPE and Arc/UHMWPE. These surfaces were obtained by hot pressure forming after mechanical mixture. Additional nanoindentation studies were performed and hardness and stiffness were determined. Mechanical properties of the MWCNT/UHMWPE composites were also compared to raw UHMWPE and correlated with their anti-adherent performance. Comparing with UHMWPE, Nanocyl/UHMWPE was the least adherent surface. Bacterial adherence was also significantly reduced in Arc/UHMWPE for four strains.     

Small-angle synchrotron study of liquid crystalline poly[oxybis(trimethylene) p,p′-bibenzoate]

Summary Small-angle synchrotron experiments have been performed in two samples of poly[oxybis(trimethylene) p,p-bibenzoate], PDTMB. Owing to the very slow transformation of the mesophase of this polymer into the crystal, only the liquid crystalline phase is present in a PDTMB sample quenched from the melt, while about 30% crystallinity is found in the annealed specimen. The results indicate that the layer spacing peak for the mesophase is very close to a crystal diffraction. This seems to be a general fact in thermotropic polybibenzoates. Moreover, no long spacing has been detected in the quenched sample. On the contrary, the annealed specimen exhibits a long spacing centered at about 16 nm, corresponding to a rather small crystal thickness.