High birefringence photonic crystal fiber with a complex unit cell of asymmetric elliptical air hole cladding

High birefringence induced by elliptical air hole photonic crystal fibers (EHPCFs) is analyzed numerically using the finite-element method. Statistical correlations between the birefringence and the various parameters are obtained. We found that the complex elliptical air hole is better than that of a circular one to obtain high birefringence in photonic crystal fibers. Our suggested structures can considerably enhance the birefringence in EHPCFs and show that the birefringence can be as high as 1.1294 x 10(-2), which is higher than the birefringence obtained from conventional step-index fiber (5 x 10(-4)), circular air holes PCF (3.7 x 10(-3)), and elliptical hollow PCF (2.35 x 10(-3)).     

Evaluation of dose equivalent by the electronic personal dosemeter for neutron 'Saphydose-N' at different workplaces of nuclear facilities

This paper presents the results of measurements made with the electronic personal neutron Saphydose-N during the four campaigns of the European contract EVIDOS (EValuation of Individual DOSimetry in mixed neutron and photon radiation fields). These measurements were performed at Institute for Radiological Protection and Nuclear Safety (IRSN) in France (C0), at the Krümmel Nuclear Power Plant in Germany (C1), at the VENUS Research Reactor and the Belgonucléaire fuel processing plant in Belgium (C2) and at the Ringhals Nuclear Power Plant in Sweden (C3). The results for Saphydose-N are compared with reference values for dose equivalent.     

Charge-trapping effects caused by ammonia in carbon nanotubes

Hysteretic behaviors caused by low-concentration ammonia gas are found in single-walled carbon nanotube based field-effect transistors. The transfer curves are found to shift towards negative gate voltage when the gate voltage is swept forwardly upon introducing ammonia. In contrast, no significant change in the transfer curves is observed for the backward sweeping of the gate voltage. This phenomenon is repeatable even after the devices are annealed in dry air at 200 degrees C for 2 hrs. Our findings can be interpreted in terms of additional charge traps induced by the adsorbed ammonia molecules. The observed hysteretic behavior enables the devices to work as memory cells, in which the carbon nanotube field-effect transistors act as readout and ammonia molecules play roles of charge storage.     

A novel sliding-mode observer for indirect position sensing ofswitched reluctance motor drives

A switched reluctance motor (SRM) drive generally requires a rotor position sensor for commutation and current control. However, the use of this position sensor increases both cost and size of the motor drive and causes limitations for industrial applications. In this paper, a novel indirect position sensing technique, namely, the sliding-mode observer, is proposed for SRM drives. The corresponding design approach and operating performance are provided to illustrate the fast convergence and high robustness of the observer against disturbances and variations     

Shear Yielding in Blown Oriented Polystyrene Films

Control over orientation is important for polystyrene (PS) films since it can affect brittleness in these materials. These authors discuss how the film morphology can be varied by orientation processing in amorphous bubble‐blown PS films and how it influences the properties and performance of the film. The Figure shows the film morphology resulting from straining along the transverse direction of the blown bubble.     

Free vibrations of stiffened coupled shear walls

This paper presents the free vibration analysis of stiffened coupled shear walls based on a discrete–continuous approach. The stiffened system is reinforced by an additional stiffening beam at some level of the structure. This induces additional axial forces, and thus reduces the bending moments in the walls, as well as helping to reduce the lateral deflection. The effect of the stiffening beam on the free vibration characteristics of coupled shear walls is studied, and numerical investigations show that the natural frequencies of vibration can be significantly increased. The optimal position for the stiffening beam to increase as far as possible the first natural frequency of vibration is also presented. © 1998 John Wiley & Sons, Ltd.     

Preparation of SBS-g-VP copolymer membrane by UV radiation without degassing

The solvent-cast film of styrene-butadiene-styrene triblock copolymer (SBS) was prepared, and the grafting of 4-vinyl pyridine (VP) to the SBS membrane was induced by ultraviolet radiation without degassing to obtain the SBS-g-VP copolymer membrane. The chemical composition of the graft copolymer membrane was studied by infrared spectroscopy. In addition to those absorption peaks associated with pure SBS, the SBS-g-VP graft copolymer also showed a peak of absorption at 820 cm⁻¹, which appeared in the spectra of homopolyvinylpyridine. The degree of grafting and the mechanical properties of SBS and SBS-g-VP were measured. Contact angle, water content, and protein absorption of fibrinogen and albumin experiments were also performed to evaluate the blood biocompatibility of the SBS-g-VP membrane. It was found that the degree of grafting exhibited an approximate linear increase with VP concentration at 0°C. The degree of grafting increased sharply with VP concentration above 30% v/v at 10°C. The degree of grafting increased with VP concentration and then leveled off when the temperature was at 30°C. The rate of grafting followed Arrhenius law. The activation energy obtained was 3.25 kcal/mol. PolyVP has a glass transition temperature (T_g) at about 240°C, and hence, it performes as a hard rigid plastic at room temperature. Therefore, the SBS-g-VP graft copolymer showed the plastic performance with increasing degree of grafting. The surface tension of SBS-g-VP was determined by using Kaelble's equation and the contact angle data. It was found that the surface tension and water content of SBS-g-VP membrane increased, whereas the contact angle decreased with grafting degree. Albumin and fibrinogen adsorption increased with time and reached a steady-state level after 20 and 40 min, respectively. The maximum desorption appeared in 30 min for albumin, but it took more time to reach maximum desorption for fibrinogen. The amount of protein adsorption decreased with the increasing of grafting degree, and the amount of protein adsorption eventually leveled off. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 109–116, 1997     

Cyanobacteria,Cyanotoxins, and Neurodegenerative Diseases: Dangerous Liaisons

The prevalence of neurodegenerative disease (ND) is increasing, partly owing to extensions in lifespan, with a larger percentage of members living to an older age, but the ND aetiology and pathogenesis are not fully understood, and effective treatments are still lacking. Neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis are generally thought to progress as a consequence of genetic susceptibility and environmental influences. Up to now, several environmental triggers have been associated with NDs, and recent studies suggest that some cyanotoxins, produced by cyanobacteria and acting through a variety of molecular mechanisms, are highly neurotoxic, although their roles in neuropathy and particularly in NDs are still controversial. In this review, we summarize the most relevant and recent evidence that points at cyanotoxins as environmental triggers in NDs development.     

Real-time monitoring of morphological changes in living cells by electronic cell sensor arrays: an approach to study G protein-coupled receptors

G protein-coupled receptors (GPCRs) constitute important targets for drug discovery against a wide range of ailments including cancer, inflammatory, and cardiovascular diseases. Efforts are underway to screen selective modulators of GPCRs and also to deorphanize GPCRs with unidentified natural ligands. Most GPCR-based cellular screens depend on labeling or recombinant expression of receptor or reporter proteins, which may not capture the true physiology or pharmacology of the GPCRs. In this paper, we describe a noninvasive and label-free assay for GPCRs that can be used with both engineered and nonengineered cell lines. The assay is based on using cell-electrode impedance to measure minute changes in cellular morphology as a result of ligand-dependent GPCR activation. We have used this technology to assay the functional activation of GPCRs coupled to different signaling pathways and have compared it to standard assays. We have used pharmacological modulators of GPCR signaling pathways to demonstrate the specificity of impedance-based measurements. Our data indicate that cell-electrode impedance measurements offer a convenient, sensitive, and quantitative method for assessing GPCR function. Moreover, the noninvasive nature of the readout offers the added advantage of performing multiple treatments in the same well to study events such as desensitization and receptor cross-talk.     

Design and fabrication of diffusive solar cell window

A diffusive solar cell window was designed and fabricated with uniformly distributed nanocomposite particles in a light diffusive plate that was sandwiched between two glass layers. The entire composite construction transfers light radiation to solar cells at the edge of the windows. It is based on a new combination of existing technologies because of it uses mature, mass-produced components - solar cells - as well as nanocomposite particles that are embedded inside the light-guide plate. They are integrated using an inexpensive and widely used method for making building windows. The result is an inexpensive, strong, stable, view quality-preserving solar energy-harvesting window that has no close competition. The diffusive solar cell window does not suffer from aging, and products that are made using diffusive solar cell window technology will be new entries to the solar power generation window market.