Natural and Synthetic Polymers as Inhibitors of Drug Efflux Pumps

Inhibition of efflux pumps is an emerging approach in cancer therapy and drug delivery. Since it has been discovered that polymeric pharmaceutical excipients such as Tweens® or Pluronics® can inhibit efflux pumps, various other polymers have been investigated regarding their potential efflux pump inhibitory activity. Among them are polysaccharides, polyethylene glycols and derivatives, amphiphilic block copolymers, dendrimers and thiolated polymers. In the current review article, natural and synthetic polymers that are capable of inhibiting efflux pumps as well as their application in cancer therapy and drug delivery are discussed

International Space Station Radiation Shielding Model Development

The projected radiation levels within the International Space Station (ISS) have been criticized by the Aerospace Safety Advisory Panel in their report to the NASA Administrator. Methods for optimal reconfiguration and augmentation of the ISS shielding are now being developed. The initial steps are to develop reconfigurable and realistic radiation shield models of the ISS modules, develop computational procedures for the highly anisotropic radiation environment, and implement parametric and organizational optimization procedures. The targets of the redesign process are the crew quarters where the astronauts sleep and determining the effects of ISS shadow shielding of an astronaut in a spacesuit. The ISS model as developed will be reconfigurable to follow the ISS. Swapping internal equipment rack assemblies via location mapping tables will be one option for shield optimization. Lightweight shield augmentation materials will be optimally fit to crew quarter areas using parametric optimization procedures to minimize the augmentation shield mass. The optimization process is being integrated into the Intelligence Synthesis Environment's (ISE's) immersive simulation facility at the Langley Research Center and will rely on High Performance Computing and Communication (HPCC) for rapid evaluation of shield parameter gradients

Active multispectral reflection fingerprinting of persistent chemical agents

Remote detection of toxic chemicals of very low vapour pressure deposited on surfaces in form of liquid films, droplets or powder is a capability that is needed to protect operators and equipment in chemical warfare scenarios and in industrial environments. Infrared spectroscopy is a suitable means to support this requirement. Available instruments based on passive emission spectroscopy have difficulties in discriminating the infrared emission spectrum of the surface background from that of the contamination. Separation of background and contamination is eased by illuminating the surface with a spectrally tuneable light source and by analyzing the reflectivity spectrum. The project AMURFOCAL (Active Multispectral Reflection Fingerprinting of Persistent Chemical Agents) has the research topic of stand-off detection and identification of chemical warfare agents (CWAs) with amplified quantum cascade laser technology in the long-wave infrared spectral range. The project was conducted under the Joint Investment Programme (JIP) on CBRN protection funded through the European Defence Agency (EDA). The AMURFOCAL instrument comprises a spectrally narrow tuneable light source with a broadband infrared detectorand chemometric data analysis software. The light source combines an external cavity quantum cascade laser (EC-QCL) with an optical parametric amplifier (OPA) to boost the peak output power of a short laser pulse tuneable over the infrared fingerprint region. The laser beam is focused onto a target at a distance between 10 and 20 m. A 3D data cube is registered by tuning the wavelength of the laser emission while recording the received signal scattered off the target using a multi-element infrared detector. A particular chemical is identified through the extraction of its characteristics pectral fingerprint out of the measured data. The paper describes the AMURFOCAL instrument, its functional units, and its principles of operation

On-wafer RF stress and trapping kinetics of Fe-doped AlGaN/GaN HEMTs

In this paper, we investigate the trapping effects, of iron doped AlGaN/GaN HEMTs, before and after on-wafer 24 hour RF stress test. First, we study the trap centers responsible of the current collapse at different on-state bias and temperature conditions. Second, we investigate 24 hour RF stress effect on the trapping kinetics. By filling traps under off-state condition with high drain-source voltage, we have identified two prominent traps labelled E 1 and E 2 with activation energies of 0.7 eV and 0.6 eV under the conduction band, respectively. An increase of the amplitude of the trap centers E 1 and E 2 by 22.9% and 15.8% respectively is noticed during the RF stress. This result suggests that the degradation observed during RF stress might have induced a density increase of the traps involved in the E 1 and E 2 trap signatures responsible on the current collapse

Microwave-accelerated O-alkylation of carboxylic acids with O-alkylisoureas

Microwave-assisted O-alkylations of several carboxylic acids have been performed with three different O-alkylisoureas. All reactions are significantly faster compared to conventionally heated reactions, while retaining high chemoselectivity. The combination of microwave technology with the use of the solid-supported isourea 3 enables the synthetic chemist to obtain the pure methyl esters starting from the corresponding acids in less than an hour