Home  About us  Contact
 

Processing Scheme (processing + scheme)

Distribution by Scientific Domains
Physics and Astronomy25%

Selected Abstracts

An image fiber based fluorescent probe with associated signal processing scheme for biomedical diagnostics

LASER PHYSICS LETTERS, Issue 10 2008
M. Vaishakh
Abstract A dual-modality image fiber based fluorescent probe that can be used for depth sensitive imaging and suppression of fluorescent emissions with nanosecond lifetime difference is proposed and illustrated in this paper. The system can give high optical sectioning and employs an algorithm for obtaining phase sensitive images. The system can find main application in in vivo biomedical diagnostics for detecting biochemical changes for distinguishing malignant tissue from healthy tissue. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Processing approaches of AlGaN/GaN Metal Insulator Semiconductor Hetero Field Effect Transistors (MISHFET) on Si (111) substrates

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009
Martin Eickelkamp
Abstract We report on the fabrication of AlGaN/GaN MISHFETs using SiO2 and SiN as gate dielectrics. In particular, two different passivation procedures are investigated with respect to the resulting electrical properties. A fluorine based ICP etch step, as used here to remove the gate dielectric prior to passivation layer deposition, is shown to deteriorate the sheet carrier concentration and mobility. Depositing the passivation layer upon the gate dielectric, on the other hand, slightly decreases the sheet resistance as compared to a conventional HFET. Gate diode characteristics reveal significant reduction of gate leakage currents in both, reverse and forward biasing regions, of 1-2 and up to 6 orders of magnitude, respectively. All devices exhibit more pronounced current collapse compared to a conventional passivated HFET. In addition, a clear depencency on the processing scheme is observed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Controlling the properties of single-polymer composites by surface melting of the reinforcing fibers,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10-12 2002
D. M. Rein
Abstract All-thermoplastic single-polymer composites are materials in which both the reinforcing fibrous phase and the matrix between them are made of the same thermoplastic polymer. Excellent bonding is achieved by mutual entanglement macromolecules due to controlled surface melting of the fibers. This results in a uniform structure of a single chemical entity. The physical properties of the consolidated material, such as modulus and coefficient of thermal expansion (CTE), can be controlled by the extent of melting effected in the process, which determines the fiber/matrix ratio. The fabrication technology utilizes oriented polymer fibers in various forms: unidirectional lay-up, woven fabric or chopped fibers/non-woven felt. The key element in the processing scheme is the control of the fibers' melting temperature by hydrostatic pressure. The fibers are heated under high pressure to a temperature that is below their melting point at the high pressure but above the melting temperature at some lower pressure. Reduction of pressure for controlled time results in melting of the fibers, which starts at the fiber surface. This surface melting under controlled pressure followed by crystallization produces the consolidated structure. We illustrate and describe this process using fibers of ultra-high-molecular-weight polyethylene (UHMWPE), showing the effect of the processing conditions on the flexural modulus, fiber/matrix ratio, and CTE in plane and in the thickness direction. These properties are relevant to the use of such composites as substrates for microwave antennae. Copyright © 2003 John Wiley & Sons, Ltd. [source]

A novel purification strategy for retrovirus gene therapy vectors using heparin affinity chromatography

BIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005
Marķa de las Mercedes Segura
Abstract Membrane separation and chromatographic technologies are regarded as an attractive alternative to conventional academic small-scale ultracentrifugation procedures used for retrovirus purification. However, despite the increasing demands for purified retroviral vector preparations, new chromatography adsorbents with high specificity for the virus have not been reported. Heparin affinity chromatography is presented here as a novel convenient tool for retrovirus purification. The ability of bioactive retroviral particles to specifically bind to heparin ligands immobilized on a chromatographic gel is shown. A purification factor of 63 with a recovery of 61% of functional retroparticles was achieved using this single step. Tentacle heparin affinity supports captured retroviral particles more efficiently than conventional heparin affinity chromatography supports with which a lower recovery was obtained (18%). Intact, infective retroviral particles were recovered by elution with low salt concentrations (350 mM NaCl). Mild conditions for retrovirus elution from chromatographic columns are required to preserve virus infectivity. VSV-G pseudotyped retroviruses have shown to be very sensitive to high ionic strength, losing 50% of their activity and showing membrane damage after a short exposure to 1M NaCl. We also report a complete scaleable downstream processing scheme for the purification of MoMLV-derived vectors that involves sequential microfiltration and ultra/diafiltration steps for virus clarification and concentration respectively, followed by fractionation by heparin affinity chromatography and final polishing by size-exclusion chromatography. Overall, by using this strategy, a 38% yield of infective particles can be achieved with a final purification factor of 2,000. © 2005 Wiley Periodicals, Inc. [source]

Using pulsed gradient spin echo NMR for chemical mixture analysis: How to obtain optimum results

CONCEPTS IN MAGNETIC RESONANCE, Issue 4 2002
Brian Antalek
Abstract Pulsed gradient spin echo NMR is a powerful technique for measuring diffusion coefficients. When coupled with appropriate data processing schemes, the technique becomes an exceptionally valuable tool for mixture analysis, the separation of which is based on the molecular size. Extremely fine differentiation may be possible in the diffusion dimension but only with high-quality data. For fully resolved resonances, components with diffusion coefficients that differ by less than 2% may be distinguished in mixtures. For highly overlapped resonances, the resolved spectra of pure components with diffusion coefficients that differ by less than 30% may be obtained. In order to achieve the best possible data quality one must be aware of the primary sources of artifacts and incorporate the necessary means to alleviate them. The origin of these artifacts are described, along with the methods necessary to observe them. Practical solutions are presented. Examples are shown that demonstrate the effects of the artifacts on the acquired data set. Many mixture analysis problems may be addressed with conventional high resolution pulsed field gradient probe technology delivering less than 0.5 T m,1 (50 G cm,1). © 2002 Wiley Periodicals, Inc. Concepts Magn Reson 14: 225,258, 2002. [source]

Nonlinear signal processing schemes for OFDM modulations within conventional or LINC transmitter structures

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2008
Rui Dinis
This paper considers two classes of digital signal processing schemes, recently proposed by the authors, both combining a nonlinear operation in the time domain with a linear operation in the frequency domain, so as to reduce the envelope fluctuations and allow good power/bandwidth tradeoffs with Orthogonal Frequency Division Multiplexing (OFDM) transmission. These classes can be adopted within both conventional and two-branch, LInear amplification with Nonlinear Components (LINC) transmitter structures . The paper addresses the statistical characterisation of the transmitted frequency-domain blocks, so as to evaluate performances by analytical means, in a unified manner. A set of numerical results, which have been obtained with the help of this analytical method, is presented and discussed. These results allow a comparison between the two classes of signal processing schemes, namely for nonlinear operations of the ,clipping' type, when a conventional transmitter structure is employed. They also allow an accurate evaluation of the phase and gain imbalance effects in the two-branch power amplification case. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A Framework of Massively Parallel Analysis of Regional Earthquake Activities

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009
Huai ZHANG
Abstract: Recent rapid progress in cyberinfrastructure in geosciences is providing seismologists an enormous boost for addressing multi-physical phenomena of regional seismic activities. The inherent nature of their multi-scale properties, from temporal to spatial spaces, makes it inevitably to be solved using large-scale computations and distributed parallel data processing schemes. Under such circumstance, using the advanced numerical algorithms and unstructured mesh generation technologies become the obstacles for modern seismologists. The main objective of this paper is to present a framework, which includes a parallel finite element simulation and distributed data infrastructure, to address the novel algorithms, state-of-the-art modeling and their implementation in regional seismicgenic systems. We also discuss and implement this framework to analyze the strong earthquake evolution processes in the Sichuan-Yunnan region. This study is the key to long-term seismic risk by estimates, providing a platform for predictive large-scale numerical simulation modeling of regional earthquake activities. [source]