The intensive terahertz electroluminescence induced by Bloch oscillations in SiC natural superlattices

We report on efficient terahertz (THz) emission from high-electric-field-biased SiC structures with a natural superlattice at liquid helium temperatures. The emission spectrum demonstrates a single line, the maximum of which shifts linearly with increases in bias field. We attribute this emission to steady-state Bloch oscillations of electrons in the SiC natural superlattice. The properties of the THz emission agree fairly with the parameters of the Bloch oscillator regime, which have been proven by high-field electron transport studies of SiC structures with natural superlattices.     

Performance anomalies in boundary data structures

A Δ-shaped data structure that is more compact and efficient under certain conditions than existing ones is proposed. The method has excellent storage efficiency (6E, with E being the total number of edges) and provides improved access time in a virtual memory environment. The discussion covers previous work, virtual memory and databases, determining record access costs, constant-time data schemes, multiple entities, and implementation methods     

Luminescence properties of poly‐ (phenylene vinylene) derivatives

BACKGROUND: Conjugated polymers, especially those of the poly(phenylene vinylene) (PPV) family, are promising candidates as emission material in light‐emitting devices. The aim of this work was to investigate the dependence of the luminescence properties of PPV‐based derivatives on their polymer structure, especially side groups. RESULTS: Three PPV derivatives, BEHPPV, MEHPPV and MEHSPPV, were synthesised and characterised by photoluminescence (PL) and cathodoluminescence (CL) spectroscopies in the temperature range 10–300 K. PL and CL spectra of the polymers exhibit similar luminescence peaks, which undergo a blue shift with increasing temperature. The shift in wavelength is accompanied by variations in the relative intensities of emission peaks. Both BEHPPV and MEHPPV display emission characteristics of the PPV backbone, but the peak of MEHPPV shifts to a longer wavelength in comparison with the corresponding peak of BEHPPV at the same temperature. The luminescence spectra of MEHSPPV, which has a sulfanyl incorporated in the side chain, are considerably different from those of the two other derivatives. CONCLUSIONS: The results demonstrate that the luminescence properties depend strongly on the chain conformations of the conjugated backbone, which are affected by polymer side chains. Copyright © 2007 Society of Chemical Industry     

Inhibition of thymidine uptake by staphylococci, a new method for the investigation of phagocytosis

A radioassay employing (3H) thymidine, to measure inhibition of growth of Staphylococcus aures by human phagocytes is presented. The principle of this new method is that viable and dividing staphylococci take up thymidine more rapidly than white cells, so that whereas in control cultures containing staphylococci alone high counts per minute (cpm) are obtained within 90 min of incubation in test cultures both leucocytes and plasma from 25 normal subjects reduced the cpm, following ingestion and killing of staphylococci.     

Petrological control on engineering properties of carbonate rocks in arid regions

Bulletin of Engineering Geology and the Environment - Petrological features of carbonate rocks that exert control on their mechanical and physical properties are examined in the study presented...     

Development of meloxicam in situ implant formulation by quality by design principle

Objective: The focus of this study was to develop and optimize in situ implant formulation of meloxicam by quality by design (QbD) principle for long-term management of musculoskeletal inflammatory disorders.

Methods: The formulation was optimized by Box–Behnken design with polylactide-co-glycolide (PLGA) level (X₁), N-methyl pyrrolidone level (X₂) and PLGA intrinsic viscosity (X₃) as the independent variables and initial burst release of drug (Y₁), cumulative release (Y₂), and dissolution efficiency (Y₃) as the dependent variables. The formulation was physicochemically characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and powder X-ray diffraction (PXRD). Pharmacokinetic studies of the optimized formulation were performed on Sprague--Dawley rats.

Results: Y₁ was significantly affected by X₂ and X₃. Y₂ was affected by X₁ and X₃ while Y₃ was affected by all three independent variables employed in the formulations. Responses for the optimized formulation were in close agreement with the values predicted by the model. SEM photomicrographs indicated uniform gel formulation. No chemical interaction between the components of formulation was observed by FT-IR and meloxicam was found to be present in the amorphous form in the gel matrix as revealed by PXRD. The maximum plasma concentration (C_max), time to achieve C_max and area under plasma concentration curve were significantly different from those of the solution formulation used as the control. Plasma concentration of meloxicam was maintained above its IC₅₀ concentration required for COX-2 inhibition for 23 days.

Conclusion: Meloxicam in situ implant may provide long-term management of inflammatory conditions with improved patient compliance and better therapeutic index.     

Design and optimization of ultra-wideband planar multilayer absorber based on long-carbon fiber-loaded composites

Journal of Materials Science - This article presents a strategy for designing optimal microwave planar multilayer absorbers based on epoxy foam composites loaded with carbon fibers of...     

Network-status aware quality adaptation algorithm for improving real-time video streaming over the internet

Multimedia Tools and Applications - Video streaming over Internet has been gaining momentum and several quality adaptation schemes have been reported to improve quality of the streamed videos. Most...     

Particle/cell separation on microfluidic platforms based on centrifugation effect: a review

Particle/cell separation in heterogeneous mixtures including biological samples is a standard sample preparation step for various biomedical assays. A wide range of microfluidic-based methods have been proposed for particle/cell sorting and isolation. Two promising microfluidic platforms for this task are microfluidic chips and centrifugal microfluidic disks. In this review, we focus on particle/cell isolation methods that are based on liquid centrifugation phenomena. Under this category, we reviewed particle/cell sorting methods which have been performed on centrifugal microfluidic platforms, and inertial microfluidic platforms that contain spiral channels and multi-orifice channels. All of these platforms implement a form of centrifuge-based particle/cell separation: either physical platform centrifugation in the case of centrifugal microfluidic platforms or liquid centrifugation due to Dean drag force in the case of inertial microfluidics. Centrifugal microfluidic platforms are suitable for cases where the preparation step of a raw sample is required to be integrated on the same platform. However, the limited available space on the platform is the main disadvantage, especially when high sample volume is required. On the other hand, inertial microfluidics (spiral and multi-orifice) showed various advantages such as simple design and fabrication, the ability to process large sample volume, high throughput, high recovery rate, and the ability for multiplexing for improved performance. However, the utilization of syringe pump can reduce the portability options of the platform. In conclusion, the requirement of each application should be carefully considered prior to platform selection.