Cationic poly(lactide-co-glycolide) nanoparticles as efficient in vivo gene transfection agents

Poly(lactide-co-glycolide) (PLGA), a biocompatible and biodegradable polyester co-polymer of PLA and PGA, has been recognized for its ability to deliver genes. However, gene delivery by PLGA nanoparticles is limited by their negative charge and their poor transport through mucosal barriers. In this study, PLGA nanoparticles were surface modified with cationic chitosan in an effort to improve their gene delivery capability. PLGA nanoparticles were synthesized by emulsion-diffusion-evaporation technique using PVA-chitosan (PLGA1) or PVA-chitosan-PEG (PLGA2) blend as stabilizers. This method is reproducible and produces nanoparticles with hydrodynamic diameter <200 nm. The nanoparticles were characterized by zetasizer, photon correlation spectroscopy and atomic force microscopy. A549 epithelial cells were transfected in vitro with PLGA particles complexed with a reporter plasmid encoding green fluorescent protein. PLGA particles transferred EGFP gene, but were less efficient than the lipofectamine control. The nanoparticles were also tested for their ability to transport across the nasal mucosa in vivo in mice. The results show that both PLGA1 and PLGA2 facilitate gene delivery and expression in vivo with increased efficiency and without causing inflammation, as measured by IL-6. Together, these results indicate that chitosan-modified PLGA nanoparticles have greater potential as gene carriers.     

Real-time detection of nucleic acid interactions by total internal reflection fluorescence

This paper describes the development of an optical readout system for the real-time analysis of fluorescent-labeled DNA microarrays is described. The system is targeted toward research applications in genomics, agriculture, and life sciences, where the end-point detection of state-of-the-art readout systems does not provide sufficient information on the hybridization process. The hybridization progress of molecules from the liquid phase in a flow cell to immobilized oligonucleotides on a transducer surface can be observed. The excitation of fluorochromes is realized by a semiconductor laser, and the fluorescence emission is collected by a cooled CCD camera. Quantitative data can be extracted from the images for analysis of the microarray. For the signal transduction, the principle of total internal reflection is used. With a multiple internal reflection arrangement, the sensor chip was adapted to the standard microscope slide format and a homogeneous evanescent illumination of the active area of the sensor surface was achieved. An application measurement was carried out with this readout system. The hybridization of Cy5-labeled 30-mer single-stranded oligonucleotides to fully complementary immobilized strands was observed in real time. A kinetic analysis was demonstrated with the recorded data. Melting curves of a 140-mer PCR product from a hemochromatosis patient sample hybridized to immobilized wild-type mutant 15- and 17-mer oligonucleotides were recorded and single-point mutations could be detected.     

Transient Modeling and Analysis of Pulse-Width Modulated Z-Source Inverter

The newly proposed Z-Source inverter has been proven in the literature to exhibit both steady-state voltage buck and boost capabilities using a unique LC impedance network coupled between the power source and converter circuit. This paper now presents transient modeling and analysis of a voltage-type Z-source inverter. These aspects are found to be challenging and they need to be carefully investigated before attempting to design advanced control algorithms for controlling the Z-source inverter. Through detailed analysis, the paper identifies several phenomena on the dc and ac-sides of the inverter, which would result in the inverter having a non-minimum-phase transient response. The dc-side phenomenon is associated with the Z-source impedance network, which is shown through small-signal and signal-flow-graph analyses to be having a right-half-plane zero in its control-to-output transfer function. Also, the ac-side phenomenon is shown through space vector analysis to depend on the time intervals of inverter states used for reconstructing the desired inverter output voltage. Based on the ac vectorial analysis, a method for improving the inverter transient response is also presented. Last, simulation results obtained using a switching-functional model and experimental results obtained using a laboratory prototype are presented for validating the described theoretical concepts     

GaAs/AIGaAs laser arrays with and without proton isolation

Abstract

Two types of GaAs/AIGaAs laser arrays, each consisting of five emitters and suitable for high power operations, have been fabricated and tested. They are easily fabricated, have high yield and deliver high power. The first array structure was fabricated using proton implantation to define the active lasing channels. Damage introduced by proton bombardment provides both electrical and optical confinement for the lasing channels. We have investigated the effect of heat treatment on the performance of these lasers and have found that the heat treated samples had a lower threshold current and higher quantum efficiency. For 400 μm long devices, with uncoated facets, we have measured a threshold current of 200 mA and a peak power of 231 mW/facet. The highest external quantum efficiency is 60%. We have also fabricated laser arrays with a simple, self‐aligned, index guided ridge waveguide structures. We have obtain a pulsed output power of up to 551 mW/facet with a quantum efficiency of 37.4%. The typical threshold current is 370 mA.     

Enhancement of the water repellency durability of the fabrics treated by fluorinated nanocopolymer emulsions

The fluorinated copolymer emulsions containing different monomers with the reactive groups were successfully prepared at our lab, using emulsion polymerization technique. The water repellency and the durability for the fabrics treated by fluorinated water repellents after 30 and 50 washes were measured and compared. Actually, the combination of the comonomers containing blocked isocyanate or other reactive groups after copolymerization would increase the durability of the water repellency. In addition, the blocked isocyanate crosslinking agent (Jintexguard FCN) does, indeed, substantially increase the durability also. It clearly indicates that the copolymer emulsion prepared by the reaction of fluorinated acrylate, cyclohexyl methacrylate, and 3‐chloro‐2‐hydroxy‐propyl methacrylate(Topolene M) with monomers containing blocked isocyanate group(Jintexan BIA) showed very good durability. More importantly, the combination of this copolymer and Jintexguard FCN will significantly provide excellent water repellency and durability after 50 washes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2451–2457, 2007     

Visualizing performance debugging

The authors examine a special software development environment called the Parallel Programming and Instrumentation Environment (PIE). PIE is designed to develop performance-efficient parallel and sequential computations. Following an explanation of PIE's general theory and features, PIE's visualization tools are used to isolate and repair the parallelism problem of an eight-process computation. Two more difficult examples using PIE are discussed. Some of the issues involved in correctly presenting visual information, such as the features users ask for and what can be done about a performance monitor's perturbation of computations, are addressed     

30 years of adaptive neural networks: perceptron, Madaline, andbackpropagation

Fundamental developments in feedforward artificial neural networks from the past thirty years are reviewed. The history, origination, operating characteristics, and basic theory of several supervised neural-network training algorithms (including the perceptron rule, the least-mean-square algorithm, three Madaline rules, and the backpropagation technique) are described. The concept underlying these iterative adaptation algorithms is the minimal disturbance principle, which suggests that during training it is advisable to inject new information into a network in a manner that disturbs stored information to the smallest extent possible. The two principal kinds of online rules that have developed for altering the weights of a network are examined for both single-threshold elements and multielement networks. They are error-correction rules, which alter the weights of a network to correct error in the output response to the present input pattern, and gradient rules, which alter the weights of a network during each pattern presentation by gradient descent with the objective of reducing mean-square error (averaged over all training patterns)     

未经改性的聚丙烯纤维织物的染色

描述了德国邓肯道夫纺织化学与化学纤维研究所开发的对未经改性的聚丙烯纤维织物还原染色的新工艺.该工艺的关键是在还原染料染色前利用等离子技术对PP纤维进行预处理.用还原染料染PP纤维,除了获得较深的颜色和优异的色牢度性能外,这一工艺的显著特点还在于它摒弃了还原剂,如保险粉.染料的固色在高温蒸箱或利用热定型工艺可连续完成.     

Development of a PCR assay for the detection of nifH and nifD genes in indigenous photosynthetic bacteria

Molybdenum (Mo) nitrogenases consist of two components: dinitrogenase reductase (encoded by nifH) and the dinitrogenase or MoFe protein (encoded by nifDK). Nitrogenase enzyme of photosynthetic bacteria is responsible for hydrogen production. Therefore, primers were designed for the nitrogenase gene only. In this study, two primers (ND and NH) were designed after comparative genomic analysis of nifH and nifD gene sequences from public databases. The designed primers were used for the amplification of nifH and nifD genes to detect nitrogenase genes in photosynthetic bacteria. Initial detection was done using a monoplex Polymerase Chain Reactions (PCRs) followed by optimization of the PCR protocols. Subsequently, a duplex PCR was designed for amplification and detection of nifH and nifD genes in indigenous photosynthetic bacteria. Evaluation of the duplex PCR on six samples isolated from Palm Oil Mill Effluent (POME) showed that only four isolates contained both the nifH and nifD genes, indicating that these isolates were potential hydrogen-producing bacteria. PCR detection provides a rapid and efficient pre-identification of potential photosynthetic bacterial hydrogen producers.