showing 36 of ~574560 from 574555 documents
Pion induced pion production on deuterium: A Quasifree process
1992
Abstract A detailed experimental analysis of the π+d → π+π−pp in-plane coincidence data first presented by Rui et al. is compared to an expanded version of the Oset and Vicente-Vacas model for pion-induced pion production on a free nucleon. This extended model averages over Fermi motion to describe the assumed quasifree nature of the process occurring on the deuteron and includes nine additional diagrams to account for the N ∗ → N (ππ) p-wave reaction channels. Experimental effects such as pion energy loss in the target and in the detectors, pion decay and muon detection are investigated and incorporated into the comparison of experimental data and theory. Inclusion of Fermi motion was foun…
Automated Determination of Fluvoxamine in Plasma by Column-Switching High-Performance Liquid Chromatography
1992
Abstract A column-switching system with high-performance liquid-chromatographic separation and ultraviolet detection is described for automated determination of fluvoxamine in human plasma or serum. Samples were injected and the drug was retained in a clean-up column [20 x 4.6 mm (i.d.)] filled with C8 reversed-phase material (10-micron particles). After unwanted material was washed out, the drug was eluted and separated with an analytical chromatography column, 4.6 x 250 mm (i.d.), filled with Nucleosil 100 CN (5-micron particles) with an acetonitrile:methanol:0.01 mol/L phosphate buffer eluent (188:578:235 by vol) at a flow rate of 1.5 mL/min for < 20 min and detected by spectromet…
“The View from Without: Madness and the Other in the Narrators of ‘The Tell-Tale Heart’ and ‘The Cask of Amontillado.’”
1992
International audience
Dynamic Stark effect action on optical pumping of atoms in an external magnetic field
1992
Abstract The influence of the dynamic Stark effect on the optical pumping of atoms in a magnetic field, using the broad band approximation, is examined. It is demonstrated that the dynamic Stark effect can lead to a nonlinear effect on the light intensity conversion of alignment produced by linearly polarized light in the orientation of the angular momentum of atoms.
Environmental factors affecting monogeneans parasitic on freshwater fishes
1992
The environmental factors that act on fish parasites have received increasing attention in recent years. The effects of changing environmental conditions on parasite communities can provide valuable information on the effects of pollution on the ecosystem as a whole. This, of course, demands that we have a detailed knowledge o f parasite communities and the mechanisms acting upon them in a variety of natural conditions. Here, Mari Koskivaaro looks at those environmental factors that affect monogeneans parasitic on freshwater fishes.
Hyperfine structure andg-factor measurements in ion traps
1992
We report about measurements on ground-state hyperfine splitting constants of stable Eu+ isotopes in radio frequency ion traps and experiments on the electronicg-factor of Ba+ in a Penning trap. From the precision of both measurements, which ranges between 3·10−6 and 5·10−7, we conclude that precise determination of the differential Bohr-Weisskopf effect in chains of isotopes will be possible in the near future.
Genetic, cytogenetic and developmental analysis of the Drosophila melanogaster tumor suppressor gene lethal(2)tumorous imaginal discs (l(2)tid)
1992
Abstract Three of the twenty recessive-lethal tumor suppressor genes of Drosophila cause imaginal disc tumors in the homozygously mutated state. One of these is the lethal(2)tumorous imaginal discs (l(2)tid) gene. Histo-logical preparations show the tumorous imaginal disc epithelium to consist of a mosaic of cells in monolayer and cells in clumped arrangement. In contrast, the wild-type imaginal disc epithelium is comprised exclusively of cells in monolayer arrangement. Mutant imaginal disc tissue pieces implanted into ready-to-pupariate wild-type larvae fail to differentiate. Implantation of l(2)tid imaginal disc tissue pieces in vivo into wild-type adult flies revealed a lethal, tumorous …
Nalidixic acid-resistant V79 cells with reduced DNA topoisomerase II activity and amplification prone phenotype
1992
Spontaneously nalidixic acid-resistant lines (NAr lines) were selected from a V79 Chinese hamster cell line and phenotypically characterized. NAr lines showed an increased doubling time, a higher number of spontaneous SCE, and more interestingly, decreased DNA topoisomerase II activity. These lines were also cross-resistant to the eukaryotic topoisomerase II inhibitors etoposide and adriamycin, but showed the same level of sensitivity as the parental line to the DNA topoisomerase I inhibitor camptothecin. NAr lines were cross-resistant to other drugs, such as PALA, MTX and MPA, resistance to which has been shown to arise by amplification of the target genes. This last feature, together with…
Suprasellar Granular Cell Tumor
1992
A case of a suprasellar granular cell tumor, approximately 1.5 cm in diameter, in a 68-year-old woman is described. Diagnosis was established postoperatively by histopathological examination of the tumor tissue. The preoperative computed tomographic scan revealed a slightly hyperdense suprasellar mass with strong contrast enhancement. There was no evidence of calcification. The T1-weighted image on magnetic resonance imaging scan showed an isointense tumor with non-homogeneous enhancement after intravenous gadolinium diethylene-triamine-pentaacetic acid. In the proton-weighted image, the suprasellar mass presented a non-homogeneously enhanced signal. A non-homogeneous signal reduction was s…
Impaired neuromuscular transmission during partial inhibition of acetycholinest-erase: The of stimulus-induced antiromic backfiring in the generation…
1992
Neuromuscular transmission was studied in the rat phrenic nerve-hemidiaphragm preparation with acetylcholinesterase (AChE) partially inactivated. Enzyme inhibition resulted in (1) increased single-twitch tension of the diaphragm; (2) compound muscle action potential (CMAP) containing repetitive discharges; (3) stimulus-induced antidromic backfiring (SIAB) seen in the phrenic nerve; and (4) repetitive nerve stimulation (RNS) eliciting a decrement-increment (D-I) phenomenon (i.e., amplitude reduction maximal with the second CMAP). Using a high-calcium and low-magnesium solution, SIAB and the decrement of the second CMAP during RNS were intensified, whereas closely spaced trains and (+)-tubocu…
π+π− coincidence measurement in the 4He(π+, π+π−) reaction at Tπ+ = 280 MeV
1992
Abstract The pion induced pion production (π, 2π) reaction on deuterium has been studied at an incident pion energy of 280 MeV. The outgoing pions were detected in coincidence and the measured four-fold cross sections were compared with a πN → ππ N microscopic model, and, upon integration, with the available experimental total cross sections from the same reaction on H and 2 H. Finally, the results were directly compared with recent data from the 16 O(π + , π + π − ) reaction at the same incident energy.
Studies on the effects of Ca2++ and Co++ on the swimming behavior of the blind Mexican cave fish
1992
The hypothesis that the blind cave fish (Astyanax hubbsi) adjusts the level of stimulation to its lateral line system (LLS) by varying its own velocity was examined. When the sensitivity of the LLS sense organs was reduced by lowering the Ca2+ concentration in the water or by adding Co2+ the fish compensated for this by swimming at a higher velocity.
A simple technique for estimating surface temperature by means of a thermal infrared radiometer
1992
Abstract In this Letter we present a simple technique for estimating surface temperatures from data obtained by means of a thermal infrared radiometer. The technique is based simply on the use of a table and a graph, from which cmissivity and atmospheric effects are easily evaluated. The accuracy is better than a tenth of a degree when emissivity and atmospheric radiance arc known.
The lipid composition, fluidity, and Mg2+-ATPase activity of rice (Oryza sativa L. cv. Bahia) shoot plasma membranes: effects of ABA and GA3
1992
Six-day-old rice plants (Oryza sativa L., cv Bahia) were grown for 5 days more in nutrient solution culture containing 10−5 M abscisic acid (ABA) or gibberellic acid (GA3) (treated plants). Plasma membrane (PM) vesicles were isolated from the shoots of treated or control plants, and ATPase hydrolytic and proton-pumping activity, fluidity, and free sterol and phospholipid composition were determined. Both treatments resulted in modified plant growth and increases in PM fluidity. The ATPase hydrolytic activity was decreased by 25% of control values with ABA treatment and by 35% with GA3. Both treatments reduced proton-pumping by 23%. GA3 treatment reduced the relative amount (%) of stigmaster…
Excitons in SiO2: a review
1992
Abstract In this paper, excitonic properties of crystalline and glassy SiO 2 are reviewed. Experimental spectroscopic data (optical absorption and reflection spectra, as well as spectra of luminescence and its excitation), luminescence decay kinetics at different temperatures, and photoelectric properties — photoconductivity and photoelectron emission — were used to determine excitons in SiO 2 . Information on migration of excitons was obtained on the basis of energy transport to impurity luminescence centers, the latter being detectors of quasiparticles. Determination of excitonic properties in glassy SiO 2 was based on the comparison of the observed phenomena in crystalline and glassy mat…
Synthesis and characterization of NdNiO3 prepared by low temperature methods
1992
Abstract NdNiO3 has been prepared with an orthorhombic perovskite structure by a low temperature and low oxygen pressure method starting from a nickel(III) oxide precursor, β-NiO(OH). The compound LaNiO3 has also been obtained by this method. This chemical-precursor-based synthesis overcomes problems related to the use of high oxygen pressures in the synthesis.
Spectrophotometric determination of promazine with an oxidative column in FIA manifolds
1992
Abstract A simple flow-injection spectrophotometric method for the determination of promazine is described. The two proposed procedures are based on the oxidation of analyte with a manganese dioxide column. Concentrations of promazine in the ranges 2–20 and 1–6 are determined with a relative standard deviation of 1.0%. The injection rates are 62 and 80 samples h −1 , respectively. The influence of foreign species and the determination of promazine in a pharmaceutical formulation are also reported.
Immunological detection of phenylalanine hydroxylase protein in Drosophila melanogaster.
1992
A monoclonal antibody raised against monkey liver phenylalanine hydroxylase (PAH) has been used to detect this protein in Drosophila melanogaster. A cross-reacting material (CRM) band of apparent molecular mass 50-52 kDa, equivalent to that deduced for the Drosophila melanogaster PAH protein based on the pah gene cDNA sequence, has been detected. This CRM was analysed throughout development and showed an equivalent pattern to that reported for PAH activity in this insect, with maxima at pupariation and at pharate adult formation. Distribution of this CRM in larval tissues, the haemolymph and the adult body is mainly restricted to the larval fat body and the adult head. Demonstration of this…
Oscillator realization of the q-deformed anti-de Sitter algebra
1992
Abstract We construct a realization of the q-deformed anti-de Sitter algebra in terms of two q-oscillators. We use the standard Drinfel'd-Jimbo prescription for the q-deformation of the Chevalley basis which we express in terms of q-oscillators. We also discuss the anti-de Sitter radius R → ∞ limit and the structure of the first so (3, 2)q Casimir operator.
Covariant phase space quantization of the Jackiw-Teitelboim model of two-dimensional gravity
1992
Abstract On the basis of the covariant phase space formulation of field theory we analyze the Jackiw-Teitelboim model of two-dimensional gravity on a cylinder. We compute explicitly the symplectic structure showing that the (reduced) phase space is the cotangent bundle of the space of conjugacy classes of the PSL(2, R ) group. This makes it possible to quantize the theory exactly. The Hilbert space is given by the character functions of the PSL (2, R ) group. As a byproduct, this implies the complete equivalence with the PSL (2, R )-topological gravity model.
Further monotonicity and convexity properties of the zeros of cylinder functions
1992
AbstractLet cvk be the kth positive zero of the cylinder function Cv(x,α)=Jv(x) cos α−Yv sin α, 0⩽α<π, where Jv(x) and Yv(x) are the Bessel functions of the first and the second kind, respectively. We prove that the function v(d2cvkddv2+δ)cvk increases with v⩾0 for suitable values of δ and k−απ⩾ 0.7070… . From this result under the same conditions we deduce, among other things, that cvk+12δv2 is convex as a function of v⩾0. Moreover, we show some monotonicity properties of the function c2vkv. Our results improve known results.
Structure ofSb118nucleus
1992
{gamma}, {gamma}{gamma}-coincidence, internal conversion electron, and {gamma}-ray angular distribution spectra of the {sup 118}Sn({ital p},{ital n}{gamma}){sup 118}Sb reaction were measured at different bombarding proton energies between 5.5 and 7.5 MeV. {gamma}, {gamma}{gamma}-coincidence, and internal conversion electron spectra of the {sup 115}In ({alpha},{ital n}{gamma}){sup 118}Sb reaction were also measured at {ital E}{sub {alpha}}=14.5 MeV. Ge(HP), Ge(Li), Ge(LEPS) {gamma}-ray detectors, as well as a superconducting magnetic lens electron spectrometer (with Si(Li) detectors), were used in the experiments. About 210 (including {similar to}130 new) {gamma} rays have been assigned to {…
An ethological analysis of the effects of diazepam and nitrazepam on the responses of female mice to anosmic males encountered in a novel arena
1992
The effects of acutely administered benzodiazepines have largely been validated in male animals, in spite of the fact that the majority of anti-anxiety drugs are prescribed for female patients. A study was carried out assessing the potential of female mice in the testing of the anxiolytic properties of drugs. Three doses (0.5, 1.0 and 2.0mg/kg) of the benzodiazepines diazepam and nitrazepam were given to individually-housed female Swiss mice before dyadic encounters with anosmic, group-housed males. Videotape analysis of the encounters, using an ethopharmacological technique, revealed suppressive effects of diazepam (1.0 and 2.0mg/kg) and nitrazepam (all doses) on avoidance/flee, confirming…
Venom gland and reservoir morphology in the Doryctinae and related braconid wasps (Insecta, Hymenoptera, Braconidae)
1992
Detailed venom reservoir and venom gland intima morphology has been investigated in reprsentatives of 84 genera and 10 subfamilies of Braconidae with particular reference to the Doryctinac, basal cyclostomes and related groups including the Opiinae, Alysiinae and Rogadinae sens. lat. Several new phylogenetically significant characters are described and illustrated. Extcnsivc secretory ductules on the primary venom duct is suggested as a synapomorphy for the subfamilies Braconinac, Doryctinae, Opiinae, Alysiinae and Gnamptodontinae. The presence of two separate venom gland insertions and their position beyond the spiral sculpture of the reservoir are suggested as synapomorphies for the subfa…
Chromatographic and mass spectrometric characteristics of 20-dihydroaldosterone.
1992
The 20 alpha-reduced derivative of aldosterone, 20 alpha-dihydroaldosterone, was needed as reference compound in order to continue the studies on 18-hydroxylation in the Y-1 adrenal cell line. It was obtained by reduction of aldosterone with sodium borohydride. Analysis of the products of the reaction as methoxime trimethylsilyl (MO-TMS) derivatives by gas chromatography (GC) and GC-mass spectrometry (GC-MS) showed three possible forms of the compound. Their identification was confirmed by comparison with the products obtained by stereospecific reduction of aldosterone using 3 alpha,20 beta-hydroxysteroid dehydrogenase. Chromatographic behavior and mass spectra are given for the three forms…
The relaxant effects of cromakalim (BRL 34915) on human isolated airway smooth muscle
1992
Cromakalim (BRL 34915) is a potassium channel opener with therapeutic potential as a bronchodilator in asthma. Cromakalim (0.1–30 μmol/l) inhibited the spontaneous tone of human isolated bronchi n a concentration-related manner being nearly as effective as isoprenaline or theophylline. The order of relaxant potencies (expressed as -log10 IC50 mol/l; mean ±SEM) was isoprenaline (7.29 ± 0.27; n = 8) > cromakalim (5.89 ± 0.12; n = 7) > theophylline (4.07 ±0.13; n = 10). In human bronchi where tone had been raised by addition of histamine (0.1 mmol/l), acetylcholine (0.1 mmol/l) or leukotriene D4 (LTD4, 0.1 μmol/l), the relaxant effect of cromakalim was substantially reduced. Cromakalim suppres…
Abduction nystagmus in internuclear ophthalmoplegia
1992
Direct current electro-oculography revealed abduction nystagmus with hypermetric abduction saccades in 35 of 64 patients with unilateral and 55 of 66 patients with bilateral internuclear ophthalmoplegia. Slowing of abduction saccades occurred in 27 unilateral cases, mainly ipsilateral to the paretic eye, and in 36 bilateral cases. Abduction nystagmus with hypermetric abduction saccades of normal velocity is explained by an increased phasic innervation adjusted to adduction paresis. Slowed abduction saccades are attributed to impaired inhibition of the medial rectus muscle. Superposition of impaired medial rectus inhibition and increased phasic innervation best explains abduction nystagmus w…
The two-loop three-point functions. General massive cases
1992
Abstract We present a calculation of the two-loop three-point scalar functions for the two overlapping topologies. These are the master functions for the ladder and the crossed ladder graphs. We also present a method for the extraction of possible (on-shell) mass singularities.
Changes in the Constitution of Thylakoid Membranes in Spruce Needles During an Open‐top Chamber Experiment
1992
The goal of the presented paper was to study the emission effects of natural air pollutants on the protein complexes of the thylakoid membrane. The tests were carried out in the frame of a long-term experiment in which spruce trees kept in open-top chambers with unfiltered ambient-air were compared to spruce trees in chambers with purified-air. The reaction centres of photosystem I (P-700), cytochrome f, cytochrome b-563, cytochrome b-559, as well as the oxidation speed of the antennae chlorophylls were quantified. The concentrations of the cytochromes f and b-563 indicate a marked annual rhythm with decreased concentrations during the summer months. The spruce trees in chambers with ambien…
Resumen cronoestratigráfico de las rocas ígneas de Costa Rica basado en dataciones radiométricas
1992
Resume El presente trabajo recopila los resultados de aproximadamente 160 dataciones radiometricas K-Ar y U-Th que se han realizado en Costa Rica en los ultimos 20 anos. Con base en estas dataciones y en relaciones estratigraficas se establecio un cuadro cronoestratigrafico sobre la evolucion del magmatismo desde el Mesozoico hasta el presente. Las rocas igneas del Jurasico hasta el Oligoceno se caracterizan por su tendencia toleitica. A partir del Mioceno tardio predominan rocas de la serie calcoalcalina y la actividad volcanica culmina en el Pleistoceno con la erupcion de grandes volumenes de ignimbritas en la parte norte y central de Costa Rica y la edificacion de los estratovolcanes de …
Allocortical neurofibrillary changes in progressive supranuclear palsy.
1992
Silver techniques for intraneuronal cytoskeleton abnormalities (neurofibrillary tangles and neuropil threads) and extracellular A4-amyloid deposits were used to examine lesions of the cerebral cortex in six cases of progressive supranuclear palsy (three were mentally unimpaired and three showed moderate degrees of dementia). Deposits of A4-amyloid protein occurred in small numbers or were absent. Neurofibrillary tangles and neuropil threads were present in all cases and were largely confined to the allocortex. A characteristic pattern of changes was found in the entorhinal cortex. The three mentally unimpaired individuals had mild cortical changes virtually confined to the transentorhinal r…
DETERMINATION OF TWELVE TRACE ELEMENTS IN TWENTY-SEVEN AND TEN MAJOR ELEMENTS IN TWENTY-THREE GEOCHEMICAL REFERENCE SAMPLES BY X-RAY FLUORESCENCE SPE…
1992
This study reports the results of twelve trace elements in twenty-seven International geochemical reference samples (IGRS) (15 from Japan, 7 from South Africa, 4 from France and 1 from U.S.A.). Similarly, ten major elements were also determined in twenty-three GRS (15 from Japan, 5 from South Africa, 2 from France and 1 from U.S.A.). Whenever possible, the results are compared with literature values for these GRS.
Isolation, sequence analysis and characterization of cDNA clones coding for the C chain of mouse C1q. Sequence similarity of complement subcomponent …
1992
A mouse macrophage lambda gt11 cDNA library was screened using a genomic DNA clone coding for the C-chain gene of human C1q. Approximately 600,000 recombinant phage plaques were hybridized with peroxidase-labeled human C-chain probe and detected by enhanced chemiluminescence. Five positive clones were obtained. The size of the full-length cDNA is 1019 bp. The sequence identity of the nucleotide sequence with human C1q C chain is 79%, the identity of the deduced amino acid sequences is 73%. The mouse C1q C chain exhibits the same structural features as the human C chain, e.g. conservation of the cysteine residues. Like the mouse A chain, the mouse C chain has an RGD sequence that may be reco…
A qualitative model of the HIV vital cycle
1992
Qualitative modelling is a recent artificial intelligence approach to physical system modelling. This approach has been successfully applied in several fields. On the basis of an analysis and qualitative modelling of cell growth, we reckon that a qualitative model of the vital cycle of HIV can be proposed, including the phases in which HIV can be attacked. The actions of antiviral drugs can also be qualitatively modelled, provided their action mechanism is known, even only in a broad sense.
Sesquiterpene lactones and lignans from Centaurea species
1992
Abstract The aerial parts of Centaurea calcitrapa yielded cnicin, cnicin 4′-acetate, melitensin, a related elemanolide, the two new germacranolides 11α,13- and 11β,13-dihydrosalonitenolide, and the lignans arctigenin, pinoresinol and 7′( S )-hydroxyarctigenin. The latter compound is described for the first time as a natural product. The aerial parts of Centaurea pabotii yielded 11,13-dihydrodeacylcynaropicrin, aguerin A and a new guaianolide related to cynaropicrin.
Isolation, Identification, and Chemical Synthesis of 6α-Hydroxyraumacline: A Novel Alkaloid from CultivatedRauwolfia serpentinaCells
1992
From RAUWOLFIA SERPENTINA cells cultivated in the presence of ajmaline ( 2) the new indole alkaloid, 6alpha-hydroxyraumacline ( 1), was isolated. This alkaloid also occurs in significant amounts in the nutrition medium. A simple chemical synthesis of 1 was developed starting from ajmaline ( 2).