Search Results - (Author, Cooperation:P. Henri)

2018-07-04

Nature Publishing Group (NPG)

2041-1723

Biology

Chemistry and Pharmacology

Natural Sciences in General

Physics

2015-01-24

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

0001-9720

Ethnic Sciences

Political Science

Sociology

2018-03-06

Hindawi

2090-1968

2090-1976

Energy, Environment Protection, Nuclear Power Engineering

1089-7674

AIP Digital Archive

Physics

The coaxial plasma accelerator is a simple, compact, and mechanically robust device that utilizes the Lorentz J×B force to accelerate plasma to high velocity. Originally developed in the 1950s for the purpose of providing energetic plasmas for fusion energy experiments, coaxial plasma accelerators are presently being investigated as an environmentally sound and economical means of materials processing and advanced manufacturing. While commercial applications of this technology are already on line, future commercial applications will require improving accelerator reproducibility and efficiency, better controlling the accelerated plasma flow velocity or energy, and better controlling the distribution of directed energy or power on target. In this paper, the magnetohydrodynamic flow physics of magnetically nozzled plasma accelerators is presented with a view to achieving the accelerator control necessary for future industrial applications. Included is a fundamental description of plasma production, acceleration, and flow in a magnetic nozzle. © 1998 American Institute of Physics.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

Bias errors introduced by systems designed to measure low-frequency transients negate zero-mean assumptions on the measurement noise. On-line signal processing methods that require accurate low-frequency information can be adversely affected by bias errors. On-line integration of dynamic signals is a classical example of a process that is unstable in the presence of bias errors. Accurately integrated quantities (like velocity and displacement), from easily measured quantities (like acceleration), can inform control systems and reduce on-line computational burdens. This article introduces a feedback stabilization method for a hybrid digital-analog integrator. The analytical performance of this integrator is compared to a filtered analog integrator in the time and frequency domains. For wide-band random signals, the analog circuit performs well with respect to linearity and hysteresis, but does less well for long-period signals. A stabilized hybrid analog-digital integrator has exceptional accuracy when integrating long-period signals, but produces phase and bias errors when integrating wide-band signals. The integrators examined in this study are unconditionally stable and robust to bias on the input, internal bias currents in the operational amplifiers, and finite slew rates of the components. © 1998 American Institute of Physics.

Electronic Resource

0008-6215

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

1574-6968

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Abstract Ribotyping was investigated as a means of distinguishing ten different serotyped reference strains and seven epidemiologically unrelated isolates of Mycobacterium avium - Mycobacterium intracellulare using a labelled 16S rDNA probe. Thirteen restriction enzymes were screened towards an accurate discrimination of strins. Two selected restriction enzymes (SacI and ClaI) enabled us to classify the 17 strains into ten ribotypes with an index of discrimination of 0.897. Typeability and reproductibility of the method reached 100%. The patterns obtained exhibited polymorphism of RE fragments within and outside the 16S rRNA gene and may be useful for epidemiological studies.

Electronic Resource

1573-4978

Springer Online Journal Archives 1860-2000

Biology

Abstract The dissociation of free ribosomes at elevated concentrations of KCl is dependent on hydrostatic pressure. The pressure necessary for the dissociation is determined for KCl concentrations ranging from 0.1–0.4 m. It varies between 425 kg cm-2 at 0.1 m and 10 kg cm-2 at 0.4 m. The partial dissociation of complex ribosomes in KCl is dependent on hydrostatic pressure in the same way as the complete dissociation of free ribosomes. Therefore, it is concluded that mRNA and peptidyl-tRNA do not contribute to the stability of the ribosome under these conditions.

Electronic Resource

1573-4978

growth factor ; oncogene ; regulation

Springer Online Journal Archives 1860-2000

Biology

Abstract PDGF is an important polypeptide growth factor that plays an essential role during early vertebrate development and is associated with tissue repair and wound healing in the adult vertebrate. Moreover, PDGF is thought to play a role in a variety of pathological phenomena, such as cancer, fibrosis and atherosclerosis. PDGF is expressed as a dimer of A and/or B chains, the precursors of which are encoded by two single copy genes. Although the PDGF genes are expressed coordinately in a number of cell types, they are independently expressed in a majority of cell types. The expression of either PDGF gene can be affected by very diverse extracellular stimuli and the type of response is dependent on the cell type that is exposed to the stimulus. Expression of the PDGF chains can be modulated at every imaginable level: by regulating accessibility of the transcription start site, by varying the transcription initiation rate, by using alternative transcription start sites, by alternative splicing, by using alternative polyadenylation signals, by varying mRNA decay rates, by regulating efficiency of translation, by protein modification, and by regulating secretion. Even upon secretion, the activity of PDGF can be modulated by non-specific or specific PDGF-binding proteins. This review provides an overview of the cell types in which the PDGF genes are expressed, of the factors that are known to affect the expression of PDGF, and of the various levels at which the expression of PDGF genes can be regulated.

Electronic Resource

1573-4978

Springer Online Journal Archives 1860-2000

Biology

Abstract A reaction stimulated by elongation factor 2 (EF-2) is necessary for the formation of the initial peptide-bond in poly(U)-directed peptide synthesis on yeast ribosomal subunits. The stimulation is inhibited by fusidic acid or diphtheria toxin together with NAD. It is assumed that the reaction of EF-2 represents translocation: in the presence of EF-2 almost twice the amount of N-acetyl-phenylalanyl-tRNA is bound to ribosomes and moreover, upon addition of puromycin a considerable stimulation of N-acetyl-phenylalanyl-puromycin formation is found. Contradictory data in the literature on this subject may be due to nonenzymatic translocation caused by a high monovalent cation concentration in the ribosome preparations or to an unspecific method for the extraction of N-acetyl-phenylalanyl-puromycin.

Electronic Resource

0021-9304

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Medicine

Technology

In order to elucidate the general patterns of intermacromolecular surface interactions that may be involved in hemocompatibility phenomena, monolayers of representative macromolecules on an octadecylsilylated glass surface were exposed to solutions of other macromolecules, and the changes in interfacial composition were characterized by zeta potential-pH titration curves, as measured by alternating flow streaming current analysis and, in some cases, by radiotracer labeling. Experiments with poly(vinylpyrrolidone) (PVP), a blood-compatible linear polymer; bovine serum albumin (BSA), a representative serum protein; whole human serum (HS), a complex mixture of proteins; and erythrocyte surface glycoprotein (GP), an extended-chain macromolecular amphiphile, showed the following: (1) Penetration of the original monolayer occured within 24 hr in 9 of the 12 possible cases; it did not occur for BSA or HS monolayers exposed to PVP, and probably not for PVP exposed to GP. (2) In all cases, penetration was accompanied by no more than partial displacement of the original monolayer, thereby generating a mixed monolayer. Each of the six possible binary mixed monolayers could be obtained by at least one of the two possible mixing sequences. (3) In the three binary systems containing BSA, the formation of the mixed monolayer could be related to increased adsorption in the two-component system. (4) The two components of the mixed monolayers were not equally distributed across their thicknesses: thus, the outer surfaces of the PVP-BSA and (at neutral pH) the PVP-HS mixed monolayers contained only PVP; that of the BSA-HS mixtures only HS. In the PVP-HS, and probably the GP-BSA and GP-HS mixed monolayers, the composition of the outer surface appeared pH-dependent. The resultant zeta potential versus pH profiles in the latter two cases resembled those of intact blood cells.The results suggest that neither the compact monolayers of globular proteins nor the diffuse monolayers of randomly coiled water-soluble polymers can, by their prior adsorption on a synthetic surface, prevent the subsequent adsorption of other globular macromolecules. It is possible that the randomly coiled polymers may impede the adhesion of platelets to the substrate since the results indicate that the adsorption of such polymers causes a displacement of the shear plane.

5 Ill.

Electronic Resource