1,720,993 research outputs found
Feasibility Study of the Use of Operational Amplifiers as Forward Gain Stages in Charge Preamplifiers and Shaping Filters for Radiation Detectors
Full text linkDifferent application fields require the development of charge preamplifiers to be coupled with dedicated radiation detectors. In view of fast prototyping and targeting a medium number of readout channels, there are several advantages to the use of operational amplifiers (OpAmps) for the forward gain stage of charge preamplifiers and shaping filters. In this article, we present the feasibility study, design, and qualification of an OpAmp-based, charge preamplifier suited to equip a smart rad-hard detection system for the diagnostics and tagging of radioactive ion beams (RIBs) at high intensities (106 pps or higher). This article illustrates the conception and design of the fast readout system and presents a detailed analysis and qualification of its performance
Characterization of the glycosidic linkage by infraed and Raman spectroscopy in the CH stretching region: a,a-trehalose and a,a-trehalose-2,3,4,6,6-d10
No full textEffects of Sulfation on Antithrombin-Thrombin/Factor Xa Interactions in Semisynthetic Low-Molecular Weight Heparins
No full textMost of the biological effects of heparin and low molecular weight (LMW) heparins are related to their ability to bind to many different proteins. To gain insight into structure-activity relationships, we investigated quantitatively the interactions of a series of sulfated LMW heparins of similar molecular weights (deriving from statistical desulfation of a supersulfated heparin) with the target-enzymes human antithrombin III (AT) and thrombin (T). In addition, we analyzed the activation process of the protease inhibitor against T and factor Xa (Xa).
A non-linear correlation between strength of the AT-heparin complex and the sulfation degree of the LMW heparins was observed, whereas only a modest modulation of T binding to heparin occurred. The efficiency of the heparin derivatives in activating AT towards the proteases is generally high for derivatives exhibiting a low dissociation constant. Only the supersulfated LMW heparin shows a serpine activation ability higher than expected from the affinity studies.
These results indicate that chemical modification of sulfation pattern of LMW-heparin can be used to efficiently modulate binding affinity and activity towards biological targets
Interactions of low-molecular-weight semi-synthetic sulfated heparins with human leukocyte elastase and human Cathepsin G
No full textSemi-synthetic low-molecular-weight heparin samples (LMWHs), having homogeneous
degree of polymerization and saccharide backbone, but differing in the number and location
of sulfate groups, were investigated in their ability to interfere with the pharmacologically
relevant targets human leukocyte elastase (EL) and human Cathepsin G (CatG). Spectroscopic
studies were performed for a quantitative evaluation of the enzyme-inhibitor dissociation
constant, Ki, and of the IC50 values for the inhibition of cleavage of target peptide
sequences. Both proteases are inhibited by the tested polysaccharides through a mixed
hyperbolic binding process. A non-linear relationship was found between degree of sulfation
and binding affinity or enzyme inhibition properties, showing a composite correlation
between heparin charge density and interference with EL/CatG activity
Effects of Ca2+ ions on the interactions between antithrombin III and factor Xa mediated by variously-sulfated semi-synthetic low-molecular-weight heparins
No full textA homogeneous set of low-molecular weight heparins, chemically modified to yield different degrees of sulfation (SD), were investigated in their ability of interfering with the Antithrombin III (AT III)-Factor Xa (FXa) interaction process in the presence/absence of physiological concentrations of calcium ions. The heparin-AT III dissociation constants were not appreciably affected by the presence of the metal ion, whereas the catalytic process was strongly dependent upon Ca2+. Our data suggest that AT III binding to heparin represents the main factor driving the FXa inhibition process. In addition, the presence of the metal ion is likely to mask favorable AT III- heparin ionic contacts occurring with the highly sulfated material. These results help in assessing proper structure-activity relationships for glycosaminoglycans, a multi-target family of biologically active compounds
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Characterization of the chemical-structure of sulfated glycosaminoglycans after enzymatic digestion - application of liquid-chromatography mass-spectrometry with an atmospheric-pressure interface
No full textPneumatically assisted electrospray was demonstrated to be a powerful ionization source for the analysis of oligosaccharides. A mass spectrometer was interfaced to an HPLC system, using this interface, to determine oligosaccharides from the enzymatic digestion of heparin separated on a reversed-phase column. To set up the technique, and particularly to clarify the ionization process, purified disaccharides, from enzymatic digestion of chondroitin sulphates, were measured. The use of a suitable counter ion in the mobile phase, tetrapropylammonium (TPA), to optimize the HPLC separation, gave, with sulphated di- and oligosaccharides, adducts [M + nTPA - (n + m)H]m-, which were unexpectedly stable to fragmentation; molecular ions [M - (n + 1)H]n-, in the presence of the counter ion, were observed only with desulphated or monosulphated disaccharides. The stability of the adducts and the use of a deuterated ion-pair reagent permitted an exact evaluation of the molecular masses of disaccharides and oligosaccharides of unknown structure. Spectra obtained in the absence of the counter ion contained singly or multiply charged molecular ions and fragmentation ions mainly from loss of the sulphate groups; under these ionization conditions the exact mass determination and interpretation of the spectra were difficult. After removal of the counter ion, tandem mass spectra could be obtained with some interesting data for the characterization of these molecules. Complete spectral analyses were performed with amounts of samples of 50 mug but, using microbore columns, one twentieth of this amount may give good spectra
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
