showing 36 of ~574560 from 574555 documents
Simulación y verificación empírica de las propiedades de la activación
1991
Study of the Density and Temperature Dependences of the Vibrational Raman Transition in Compressed Liquid N2
1991
0021-9606; Accurate values of linewidth and line shift in the isotropic vibrational Raman spectrum of compressed liquid N2 have been obtained by using inverse Raman spectroscopy. Experiments have been performed for eight isotherms, from the normal boiling point to the critical point temperatures of N2, the number density varying between the value on the coexistence line, and the maximum value of 2.1 x 10^22 cm-3. Minima of the linewidth have been observed above 86 K, showing the increasing influence of vibration-rotation coupling (motional narrowing) competing with the broadening due to pure vibrational dephasing. Moreover, for the first time, maxima of the red line shifts have been found, …
Intracrystalline Diffusion of Benzene in Ga-Silicate
1991
Abstract The sorption kinetics of benzene in large Ga-MFI crystals was investigated under constant volume- variable pressure conditions. A complete analysis of the uptake curves has been performed using solution of a nonlinear Volterra equation which describes the interaction of uptake process with the apparatus. Within the time scale of uptake measurements (10 3 -10 4 s) the uptake curves were found to be consistent with the solution of the second Fick's law. Corrected diffusion coefficients were found to be essentially independent of loading within the loading range investigated and in contrast to the system benzene-HNaZSM-5 [1,2] their temperature dependence is much stronger.
Introducción a La necesidad de revisión de la izquierda de J. Habermas
1991
En una entrevista concedida recientemente en la que se le critica el presunto gran formato, lo pretencioso, lo decimonónico de su teoría, Habermas hace unas aclaraciones que pueden contribuir a entender de dónde proviene la riqueza teórica a la vez que concreción de los trabajos y entrevistas recogidos en este libro. «Nunca –viene a decir Habermas- he considerado posible el tipo de teoría que se practicó en la tradición a que me remito, siempre consideré absurdo el intento de absorber y superar por arriba la pluralidad de discursos; mi trabajo diario tiene un aspecto bien distinto. Me interesan los problemas concretos, los problemas en cierto modo ya "diseccionados", que surgen en contextos…
Regiospecific oxidation of polycyclic aromatic dihydrodiols by rat liver dihydrodiol dehydrogenase
1991
Rat liver dihydrodiol dehydrogenase (DDH, E.C. 1.3.1.20) has recently been shown to oxidize the highly carcinogenic benz[a]anthracene-3,4- dihydrodiol in an NADP(+)-dependent reaction to its corresponding catechol. The present study is a systematic investigation of the substrate specificity of the purified enzyme towards synthetic trans-dihydrodiol metabolites of phenanthrene, benz[a]anthracene, chrysene, dibenz[a, h]anthracene and benzo[a]pyrene. DDH exhibited a remarkable regiospecificity of enzymatic catalysis with regard to the site of the dihydrodiol moiety of the parent hydrocarbon. M-region- and, with lower efficiency, bay-region dihydrodiols were found to be good substrates of the e…
La gran Europa
1991
Se trata de la versión no publicada del texto "La Gran Europa". Se desconoce si finalmente fue publicado.
La fabrication d'une fibule celtique
1991
International audience
High-Frequency Rotational Angioplasty
1991
In 19 patients with significant coronary artery disease, PTCR was used instead of PTCA. The PTCR was successful in all patients, but in nine patients additional PTCA was successfully performed. Coronary luminal narrowing could be reduced from 78 ± 19% to 32 ± 14% after rotablation and by combined treatment to 21 ± 14%. Only in one patient did coronary dissection occur; the patient was sent to surgery and had an uneventful outcome. No vessel perforation was observed. In one patient peripheral diagonal branch occlusion occurred. All vessels were open according to 24-control coronary angiography. Restenosis (>70% stenosis) occurred in 4/15 patients controlled after 6 months, mainly in those wi…
Caste differentiation in Isoptera: basic features, role of pheromones
1991
The polymorphism of termites, essentially phenotypic, results from alternative orientations during individual development, triggered by hormones and neurohormones. The hormonal equilibrium is itself modulated by several influences, both from the outer world and the society. Among the latter, the primer pheromones seem especially important in the regulation (either by stimulation or inhibition) of the separate castes.
Hartmann: The Historicity of Cultural Data
1991
Interactions of the mitochondrial membrane rat liver d-3-hydroxybutyrate dehydrogenase with glass beads during adsorption chromatography
1991
D-3-Hydroxybutyrate dehydrogenase (BDH) is an NAD(+)-dependent dehydrogenase of the mitochondrial inner membrane involved in the energetic balance between the liver and peripheral organs in mammals. It allows the conversion of ketone bodies (acetoacetate and D-3-hydroxybutyrate) and it is one of the best documented lipid-requiring enzymes with a dependence on lecithins. After release of proteins from the membrane by phospholipase A2 treatment of salt-treated mitochondria, the rat liver enzyme is absorbed on controlled-pore glass beads. After batch washing, the enzyme, devoid of lipids (apoBDH), is specifically eluted at pH 8.05-8.15 with a 0.1 M Tris-1 M LiBr buffer under reducing condition…
Zirconolite-bearing ultra-potassic veins in a mantle-xenolith from Mt. Melbourne Volcanic Field, Victoria Land, Antarctica
1991
One mantle xenolith from a basanite host of the Mt. Melbourne Volcanic Field (Ross Sea Rift) is extraordinary in containing veins filled with leucite, plagioclase, clinopyroxene, nepheline, Mg-ilmenite, apatite, titaniferous mica, and the rare mineral zirconolite. These veins show extensive reaction with the dunitic or lherzolitic host (olivine+spinel+orthopyroxene+clinopyroxene). The reaction areas contain skeletal olivine and diopside crystals, plagioclase, phlogopite, aluminous spinel and ilmenite in a fine grained groundmass of aluminous spinel, clinopyroxene, olivine, plagioclase and interstitial leucite. The vein composition estimated from modal abundances and microprobe analyses is a…
Computer Simulations for Polymer Dynamics
1991
In this paper we review recent work on the dynamics of polymeric systems using computer simulation methods. For a two-dimensional polymer melt, we show that the chains segregate and the dynamics can be described very well by the Rouse model. This simulation was carried out using the bond fluctuation Monte Carlo method. For three-dimensional (3d) melts and for the study of hydrodynamic effects, we use a molecular dynamics simulation. For 3d melts our results strongly support the concept of reptation. A detailed comparison to experiment shows that we can predict the time and length scales for the onset of reptation for a variety of polymeric liquids. For a single chain, we find the expected h…
Revisión taxonómica del género fumana en la Península Ibérica y las Islas Baleares
1991
El estudio tiene dos motivos: en primer lugar, el género tiene uno de sus centros de especiación en el Mediterráneo Occidental. Además las especies encuadradas en él se encuentran ampliamente distribuidas, al menos en la mitad oriental de la Península Ibérica y en las Islas Baleares. En base a los datos obtenidos ha sido fundamentado el tratamiento taxonómico propuesto.
Народное хозяйство: Проблемы становления рыночной экономики Латвии
1991
В сборнике рассматриваются как общеметодологические проблемы использования экономических регуляторов и их воздействия на развитие рынка, так и проблемы формирования рыночных отношений в отдельных отраслях народного хозяйсства.
Karyotype analysis, nucleolus organizer regions and C-banding pattern of Eisenia foetida (oligochaeta, lumbricidae)
1991
The diploid number 2n=22 and haploid number n=11 found for Eisenia foetida from Palermo, Italy, confirm earlier data for this species from other localities. Analyses of silver-stained and C-banded mitotic and meiotic chromosomes suggest that a single chromosome pair has active NORs which correspond with C-positive regions. The occurrence of nucleolus activity during spermatogenesis of E. foetida is ascertained.
Recent Developments in Heterogeneous Photoreactor Modelling
1991
A selection of recently proposed heterogeneous photoreactors is presented. In some cases efforts have been made for the formulation of models able to describe the photoreactor behaviour with regard to the absorption of radiation. Examples of proposals of both novel photoreactor and models are critically reviewed.
[Post-translational regulation of N-glycosylated proteins expression in human intestinal cells in culture].
1991
International audience; HT-29 cells derived from a human colonic adenocarcinoma, can express a typical intestinal differentiation. Undifferentiated HT-29 cells accumulate N-linked glycoproteins substituted with unprocessed carbohydrate chains before to degrade them. Conversely, carbohydrate chains of N-linked glycoproteins are classically processed in differentiated HT-29 cells. The instability of N-linked glycoproteins in undifferentiated HT-29 cells is due to their rapid delivery from the endoplasmic reticulum to a compartment with lysosomal characteristics. This catabolitic pathway involves a bypass of the Golgi apparatus.
Precipitaciones mediterráneas y movimientos de masa en margas de los valles de Alcoi
1991
Se realiza una evaluación espacio-temporal de las precipitaciones (anuales, tandas máximas de varios días de duración y máximas en 24 h) que preceden y acompañan a movimientos de ladera en un ambiente típicamente mediterráneo. A partir de casos observados (LA ROCA 1991b) se distinguen dos tipos de precipitación (volumen, intensidad, duración), que, a grandes rasgos, van asociados a diferentes morfogénesis por movimientos de ladera: a) tandas de lluvias muy intensas (> 200 mm), tras una prolongada y / o intensa sequía, responsable de la apertura de profundas grietas de retracción, asociadas a movimientos superficiales localizados. b) tandas menos intensas ( 1000 mm), acompañadas de movimient…
Photocatalytic degradation of nitrophenols in aqueous titanium dioxide dispersion
1991
Abstract The results are reported of an investigation into the photodegradation of nitrophenol isomers carried out in aqueous titania (anatase) dispersions under various experimental conditions. We investigated the influence of various parameters on the photodegradation rate, such as the concentrations of the catalyst, dissolved oxygen and organic compound, and the presence of various anions in the dispersion. A plausible explanation is proposed for the influence of these parameters, both mechanistic and kinetic factors being accounted for. Gas chromatography and mass spectrometry were used as analytical methods in order to determine intermediate products. Spectroscopic methods (UV-vis and …
Славянская филология: Имя и глагол в исторической перспективе
1991
Сборник посвящен актуальным вопросам развития именных и глагольных форм и категорий, рассмотренных в широкой исторической перспективе - от праславянского периода до наших дней.
Условия референтной определенности слова
1991
На материале германских, романских, а также латышского языков в сборнике рассматриваются регулярные семантические отношения и структурные условия функционирования единиц языка всех уровней: фонетического, морфологического, синтаксического.
Chiral gamma-lactones from Fusarium poae: enentiomeric ratios and sensory differentiation of cis-6-gamma-dodecenolactone enantiomers
1991
Chiral gamma-lactones from Fusarium poae: enentiomeric ratios and sensory differentiation of cis-6-gamma-dodecenolactone enantiomers
El gobernador en la Hispania romana
1991
EL ARTICULO EXAMINA LAS PROCEDENCIAS DEL CARGO DE GOBERNADOR Y SUS DISTINTAS PECULIARIDADES. POR OTRA PARTE LAS COMPETENCIAS, DETENIENDONOS EN LO MILITAR, JURIDICO, ADMINISTRACION, OBRAS PUBICAS, ETC. Y CONSECUENCIAS QUE ELLO CONLLEVARA. ASIMISMO SE EXPONEN LAS RESPONSABILIDADES, SUS LAXITUDES, ASI COMO DIVERSOS CASOS CONCRETOS EN QUE NO SE DARA ESTA LAXITUD POR UNA SERIE DE CIRCUNSTANCIAS. (A)
Surfactant Association: Recent Theoretical and Experimental Developments
1991
A theoretical model describing the association of ionic surfactants into rod-shaped micelles is combined with an approximate formula for the viscosity increase induced by rod-shaped aggregates. It is shown that most of the thermodynamic parameters of the association model can be obtained from viscosity measurements. The approach is applied to micellar solutions of hexadecylpyridinium salts. The pronounced effect of counter-ion concentration on the growth of rod-shaped micelles can be attributed to a slightly higher degree of counter-ion association in the cylindrical part than in the end portions. An attempt is made to explain the finding that the degree of counter-ion association is virtua…
A new method for measurements of insoluble submicron particles in water
1991
Abstract A new method was developed to determine the size distribution of insoluble particles in e.g., fog water in the particle size range 50 nm p nm. First the water was nebulized and than the droplets dried to form residual aerosol particles. Using a Tandem Differential Mobility Analyser (TDMA), soluble and insoluble particles were separated. The system was calibrated with monodisperse latex particles to determine the loss factor for insoluble particles.
Measurement of α from the structure of particle clusters produced in hadronic Z decays
1991
Abstract Using 106 000 hadronic events obtained with the ALEPH detector at LEP at energies close to the Z resonance peak, the strong coupling constant αs is measured by an analysis of energy-energy correlations (EEC) and the global event shape variables thrust, C-parameter and oblateness. It is shown that the theoretical uncertainties can be significantly reduced if the final state particles are first combined in clusters using a minimum scaled invariant mass cut, Ycut, before these variables are computed. The combined result from all shape variables of pre-clustered events is αs(MZ2 = 0.117±0.005 for a renormalization scale μ= 1 2 M Z . For μ values between MZ and the b-quark mass, the res…
La qualità del recupero edilizio. Criteri per la formulazione di un metodo di verifica degli interventi attuati
1991
Enseigner la Révolution à partir des archives
1991
Contribution à une nouvelle économie de la santé : asymétries d'information et régulation en médecine ambulatoire
1991
Le fonctionnement de la médecine ambulatoire est analysé à travers la spécification de relations d'agence complexes qui s'instaurent entre les différents acteurs : le malade, le médecin, l'assurance, la tutelle. Après une approche conceptuelle et normative qui distingue relations d'agence "parfaites" et "imparfaites", l'accent est mis deux relations : la relation assurance-principal et assuré-agent sur le marché de l'assurance maladie, et la relation patient-principal et médecin-agent sur le marché des soins médicaux. Les "effets pervers" inhérents à l'asymétrie d'information sont étudiés en terme de sélection adverse et de risque moral. L'hypothèse d'une démarche induite par l'offre, consé…
Epifisiolisis de la extremidad superior del fémur en un adulto asociada a craneofaringioma
1991
Se presenta un caso de epifisiolisis de la extremidad superior del fémur en un paciente de 22 años, asociado a un hipopituitarismo de origen tumoral (Craneofaringioma). Se estudia la asociación entre epifisiolisis de la extremidad superior del fémur y transtornos endocrinos. We report an adult male, 22 years old, with slipping of the uppe r femoral epiphysis, afected by hypopituitarism due to intracranial tumour (Craniopharingyoma). The clinical assocition betwee n slipped uppe r femoral epiphysis and endocrine disease is studied.
Pollination: An Integrating Factor of Biocenoses
1991
A survey is given of the ecological constraints which affect the process of pollen transfer — and hence the gene flow — within a biocenosis. Wind pollination (anemophily) plays a dominant role in species-poor communities only. The quantity of zoophilous species increases equator-ward to up to 100 % and so does the degree of integration in animal-plant interactions. Biotic pollination is pinpointed. Manifoldness and specifity of methods reduce pollen waste and mispollinations. Saturated ecosystems dispose of a complete set of pollination syndromes and the respective pollinator guilds, narrow niche widths, a high percentage of eutropic flowers, shorter flowering times, and a temporal and spat…
Electromagnetically Generated Extracorporeal Shock Wave Lithotripsy and Adjuvant Combined Oral Litholysis for Therapy of Symptomatic Gallbladder Ston…
1991
A prospective study was conducted to evaluate effectivity, problems and adverse effects of extracorporeal shock wave lithotripsy (ESWL) using a newly developed electromagnetic biliary lithotriptor (Lithostar Plus, Siemens, Erlangen, FRG) for the treatment of selected patients presenting with symptomatic cholecystolithiasis. In addition to generally accepted criteria for the selection of patients, gallbladder contractility was established and pigment stones were excluded by computed tomography (CT). 80 out of 486 patients (63 females, 17 males, mean age 36, range 17-76 years) were selected for ESWL using a standardized diagnostic program. 62 out of 80 patients participating in the study had …
Cesareo novelliere
1991
Approche quantitative, approche qualitative : une opposition à dépasser ?
1991
International audience; Dans le contexte français de la recherche en éducation, la dichotomie entre approche qualitative et approche quantitative apparait singulièrement marquée. C'est la pertinence de cette dichotomie que nous entendons discuter ici.