Search results for " ACTIVATION"
showing 10 items of 1535 documents
Determination of gold in two Egyptian gold ores using instrumental neutron activation analysis
2003
Abstract The applicability of thermal neutron activation analysis for the determination of gold and other elements in two Egyptian gold ores has been studied. Ten samples collected from El Sukari and Atud in the Eastern Desert-Egypt have been analyzed. The samples were properly prepared together with their standards and simultaneously irradiated in a neutron flux of the order 7×10 11 n/cm 2 s using the TRIGA research reactor at Mainz. Short-term (1 and 5 m) irradiation in the pneumatic system was also used for detection of the elements with shorter half-lives. After activation, the samples were subjected to γ -ray spectrometry using a high-purity germanium detection system and computerize…
Determination of macro, micro nutrient and trace element concentrations in Indian medicinal and vegetable leaves using instrumental neutron activatio…
1999
Abstract Leafy samples often used as medicine in the Indian Ayurvedic system and vegetables were analyzed for 20 elements (As, Ba, Br, Ca, Ce, Cr, Cs, Co, Eu, Fe, K, La, Na, Rb, Sb, Sc, Sm, Sr, Th, Zn) by employing Instrumental Neutron Activation Analysis (INAA). The samples were irradiated at the 100 kW TRIGA-MAINZ nuclear reactor and the induced activities were counted by gamma ray spectrometry using an efficiency calibrated high resolution High Purity Germanium (HPGe) detector. The concentration of the elements in the medicinal and vegetable leaves and their biological effects on human beings are discussed.
Fast determination of impurities in metallurgical grade silicon for photovoltaics by instrumental neutron activation analysis
2010
Standard wafer solar cells are made of near-semiconductor quality silicon. This high quality material makes up a significant part of the total costs of a solar module. Therefore, new concepts with less expensive so called solar grade silicon directly based on physiochemically upgraded metallurgical grade silicon are investigated. Metallurgical grade silicon contains large amounts of impurities, mainly transition metals like Fe, Cr, Mn, and Co, which degrade the minority carrier lifetime and thus the solar cell efficiency. A major reduction of the transition metal content occurs during the unidirectional crystallization due to the low segregation coefficient between the solid and liquid phas…
Evidences of cannabinoids-induced modulation of paroxysmal events in an experimental model of partial epilepsy in the rat
2010
Different studies have been shown a clear anticonvulsant activity exerted by cannabinoids (CB) through the CB1 receptor activation. The purpose of this study was to evaluate, in an in vivo experimental model of temporal lobe epilepsy (maximal dentate gyrus activation - MDA) in the rat, the protective effect of (R)-(+)-[2,3-Dihydro-5-methyl-3-(4-morpholinylmethyl) pyrrolo[1,2,3-de]-1,4-benzoxazin-6-Yl]-1-naphthalenylmethanone (WIN 55,212-2, CB agonist) alone or in combination with N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251, selective CB1 antagonist). Pre-treatment with AM251 (1 mg kg-1, 30 min interval) dramatically reduced the signif…
Effcts of Dextran Sulphate (Dxs) on Lymphocyte Localization in Complement-Deficient Mice: Evidence that the Fifth Component of Complement is not Impl…
1984
AbstractThe effects of subcutaneously or intraperitoneally administered dextran sulphate (DXS) (5nmg/kg) on the subseguent 1 h localization of intravenously injected radiolabelled lymph node cells was investigated in complement deficient mice which lack C5.DXS proved to be equally as potent in depressing cell localizzation in deficient as compared to normal mice. These findings. indicate that the terminal complement components are not, essential for DXS activity.
Regulatory effects of polyamines on membrane-bound acetylcholinesterase
1974
The effects of putrescene, spermidine and spermine on membrane-bound acetylcholinesterase from human erythrocyte ‘ghosts’ and the solubilized enzyme of the electric organ of the electric eel were studied by kinetic methods. Measurements were made by using a photometric method which made it possible to record the enzyme reaction in the steady-state phase. Substrate-concentration-dependent activation and inhibition of acetylcholinesterase by polyamines is similar to that by Na+, K+, Ca2+, Mg2+ and certain quaternary and bisquaternary amines. The kinetics suggest an allosteric reaction mechanism. On the basis of the kinetic results a role for the polyamines as modulators of synaptic acetylchol…
Metal- and Reagent-Free Electrochemical Synthesis of Alkyl Arylsulfonates in a Multi-Component Reaction.
2020
Abstract This work presents the first electrochemical preparation of alkyl arylsulfonates by direct anodic oxidation of electron‐rich arenes. The reaction mechanism features a multi‐component reaction consisting of electron‐rich arenes, an alcohol of choice and excess SO2 in an acetonitrile‐HFIP reaction mixture. In‐situ formed monoalkyl sulfites are considered as key intermediates with bifunctional purpose. Firstly, this species functions as nucleophile and secondly, excellent conductivity is provided. Several primary and secondary alcohols and electron‐rich arenes are implemented in this reaction to form the alkyl arylsulfonates in yields up to 73 % with exquisite selectivity. Boron‐doped…
Activation of mitogen-activated protein kinase by the bradykinin B2receptor is independent of receptor phosphorylation and phosphorylation-triggered …
1999
Recent evidence suggests that serine/threonine phosphorylation and internalization of beta2-adrenergic receptors play critical roles in signalling to the mitogen-activated protein kinase cascade. To investigate whether this represents a general mechanism employed by G protein-coupled receptors, we studied the requirement of these processes in the activation of mitogen-activated protein kinase by G alpha(q)-coupled bradykinin B2 receptors. Mutant B2 receptors impaired in receptor phosphorylation and internalization are fully capable to activate mitogen-activated protein kinase. Bradykinin-induced long-term effects on mitogenic signalling monitored by measuring the transcriptional activity of…
The Ability of Variant Peptides to Reverse the Nonresponsiveness of T Lymphocytes to the Wild-Type Sequence p53264–272 Epitope
2002
Abstract Recently, we observed that CTL specific for the wild-type (wt) sequence p53264–272 peptide could only be expanded ex vivo from PBMC of a subset of the HLA-A2.1+ normal donors or cancer patients tested. Surprisingly, the tumors of the responsive patients expressed normal levels of wt p53 and could be considered unlikely to present this epitope. In contrast, tumors of nonresponsive patients accumulated mutant p53 and were more likely to present this epitope. We sought to increase the responsive rate to the wt p53264–272 peptide of PBMC obtained from normal donors and patients by identifying more immunogenic variants of this peptide. Two such variants were generated by amino acid exch…
Human leucocyte antigen-A2 restricted and Mycobacterium tuberculosis 19-kDa antigen-specific CD8+ T-cell responses are oligoclonal and exhibit a T-ce…
2001
CD8+ T cells can be grouped into two different types of secretory T lymphocytes, based on the cytokine-secretion pattern upon antigen exposure: those with a T-cell cytotoxic type 1 response (Tc1), which secrete interferon-gamma (IFN-gamma), or those with a T-cell cytotoxic type 2 response, which secrete interleukin (IL)-4 and IL-10. We examined the CD8+ T-cell response directed against an immunodominant human leucocyte antigen (HLA)-A2-presented peptide derived from a 19-kDa Mycobacterium tuberculosis-associated antigen. T cells were examined by functional analysis and by T-cell receptor (TCR) complementarity-determining region 3 (CDR3)-spectratyping, which defines the complexity of a T-cel…