showing 36 of ~574560 from 574555 documents
Theoretical prediction of the electronic properties of silicon fullerenes
1994
Summary form only given. High symmetry silicon clusters present currently intense interest because of the possibility they present properties similar to those displayed by fullerenes. Thermodynamic studies have shown that the buckminsterfullerene structure of Si6o is much more stable than other suggested structures. We present here a detailed investigation of the structure and electronic properties of silicon cluster analogous to fullerenes. We have made use of AMI method to obtain reliable geometrical parameters. The calculated valence effective Hamiltonian (VEH) electronic structures are used to predict ionization potentials, electron affinities, HOMO-LUMO energy gaps and first allowed tr…
Quasisymmetric maps and string theory
1994
Externalismo, escepticismo y el principio iterativo del conocimiento
1994
EN la epistemología de este siglo ha sido tradicional mantener las tres equivalencias o simetrías siguientes relativas a la atribución de conocimiento: 1) 'Saber' y 'saber que se sabe' son equivalentes. 2) Los criterios para la atribución de conocimiento en primera y tercera persona son idénticos. 3) 'Saber algo' y 'saber que algo es verdad' son lo mismo. Las dos primeras están íntimamente relacionadas y la introducción de la perspectiva 'externalista' acerca de la justificación de nuestras creencias ha implicado, o al menosposibilitado, su declive.En el presente trabajo me propongo argumentar que es foconsistente negar las dos primeras equivalencias a las que hemos aludido mientras se mant…
SEssion 06 Morphogenesisin vitro
1994
Acute Effects of Tumor Necrosis Factor-α or Lymphotoxin on Oxygenation and Bioenergetic Status in Experimental Tumors
1994
Recombinant human tumor necrosis factor-α (rhTNF-α) exerts direct cytolytic and cytostatic effects on tumor cells in vitro (Fiers,1991).In vivo,indirect actions on the tumor microvasculature have been described, such as the formation of fibrin thrombi (Nawroth et al.,1988),which cause stasis and damage of tumor microvessels with subsequent hemorrhagic necrosis.
A finite size scaling study of the five-dimensional Ising model
1994
For systems above the marginal dimension d*, where mean field theory starts to become valid, such as Ising models in d = 5 for which d* = 4, hyperscaling is invalid and hence it was suggested that finite size scaling is not ruled by the correlation length ξ (∝ |t| −1/2 in Landau theory, t being the distance from the critical point) but by a “thermodynamic length” l (∝ |t| −2/d). Early simulation work by Binder et al. using nearest neighbor hypercubic L5 lattices with L ⩽ 7 yielded some evidence for this prediction, but the renormalized coupling constant gL = −3 + 〈M4〉/〈M2〉2 at Tc was gL ≈ −1.0 instead of the prediction of Brezin and Zinn-Justin, gL(Tc) = −3 + Γ4(1/4)/(8 π2) ≈ −0.812. In the…
Oxidative dehydrogenation of propane and n-butane on V-Mg based catalysts
1994
Abstract The catalytic properties of vanadium supported catalysts for the oxidative dehydrogenation of propane and n-butane has been studied. Natural Sepiolite and magnesium oxalate were used as starting support materials. Large differences in the type of crystalline phases were detected on the calcined catalysts depending on the vanadium content and nature of the support. The active and selective sites for the oxidative dehydrogenation of propane and n-butane, are related with isolated V 5+ with atetrahedral coordination. The presence of vanadium species with coordination higher than 4 negatively influence the selectivity to dehydrogenation products.
Trashumancia aragonesa en el reino de Valencia (s. XVI y XVII)
1994
El carlismo latente: desposesión agraria y protesta campesina en Castellón
1994
Synthese von 2-alkoxysubstituierten Oligo- und Poly(1,4-phenylenethenylen)en und 2-Arylbenzo[b]furanen mit Hilfe der Siegrist-Reaktion
1994
Synthesis of 2-Alkoxy Substituted Oligo- and Poly(1,4-phenyleneethylene)s and 2-Arylbenzo[b]furanes by Applying the Siegrist Reaction Alkylation of 2-hydroxy-4-methylbenzaldehyde (1) yields the 2-alkoxy-4-methylbenzaldehydes (2a-l) which can be easily transformed to the Schiff bases 3a-l. The intermolecular self-condensation in a strongly alkaline medium leads to the oligo- and poly(1,4-phenyleneethenylene)s (4a-i) with an outstanding regular constitution and overall (E)-configuration. The terminal N-arylamino group can be cleaved by hydrolysis generating the compounds 5a-i. An intramolecular condensation forming the benzo[b]furanes 6j,k is observed for 3j,k – due to the activated OCH2 grou…
Surface glycoproteins in copepods: potential signals for mate recognition
1994
The mechanism male copepods use to recognize mates is not well understood. Both chemical and mechanical cues have been implicated, but the relative importance of these is not known. This lack of knowledge is despite the belief that mate recognition has a critical role in maintaining reproductive isolation of many species and influences the direction of evolution. Glycoproteins are used as mating signals by a number of aquatic organisms including rotifers, ciliates, and algae. We have developed techniques for selectively probing surface glycoproteins in zooplankton using fluorescently labeled lectins. We examined surface glycoproteins on the urosomes of several species of marine and freshwat…
Cyclosporin A resistance of herpes simplex virus-induced "fusion from within" as a phenotypical marker of mutations in the Syn 3 locus of the glycopr…
1994
We here report research in which nine strains of Herpes simplex virus (HSV) with fusing activity were investigated in order to establish precise phenotypical markers of mutations in the carboxy terminus of glycoprotein B (gB). The gene region encoding the carboxy terminus of gB was isolated, then cloned, and finally sequenced. Our investigation showed that seven strains have different mutations in the syn 3 locus. We observed no base difference in the gB gene region encoding the carboxy terminus of gB of two other strains. Strains with a mutation in the carboxy terminus of gB induced fusion from within (FFWI) in the presence of Cyclosporin A (CyA) at a concentration up to 150 µM. There are …
Blood flow and metabolic microenvironment of brain tumors
1994
Summarizing thesein vivo data in the context of brain tumor therapy, the following aspects are of particular importance: Low and heterogeneous tumor blood flow may — in addition to the limiting effects of the blood-brain barrier — result in compromised delivery of drugs from blood to the tissue. Low tumor pO2 reduces sensitivity to standard radiation and ‘O2-dependent’ anticancer drugs. Treatment efficacy may be further altered by changes of tumor pH. Particularly acidosis can decrease radiation sensitivity and modulate the cytotoxicity of anticancer drugs. In the following presentations, these aspects will be discussed regardingin vivo data obtained with positron emission tomography.
La terapia adiuvante nelle pazienti affette da carcinoma mammario con linfonodi ascellari negativi. Attuale ruolo dei fattori prognostici nella condo…
1994
Conversación y conversación cotidiana: Sobre una confusión de niveles
1994
Lo que pretendemos en este trabajo es señalar la distinción de niveles que resulta necesaria para una delimitación operativa de la conversación como objeto de la pragmática, pues lo que normalmente se define como tal es en realidad un tipo de conversación, generalmente la conversación cotidiana. Analizaremos por eso distintos intentos de definición, y clasificaciones o tipologías en las que es evidente la mezcla de criterios pragmáticos y sociales, lo que, dicho de otra forma, puede asimilarse a perspectivas 'internas' o lingüísticas, y 'externas' o sociolingüísticas. Veremos que la conversación, desde el punto de vista pragmático (es decir, el 'hacer' conversacional), se define tan sólo po…
Les installations agricoles de l'Âge du Fer en Ile-de-France : colloque.
1994
ill.
Del delirio melancólico a la serenidad reflexiva: el escepticismo humeano y la condición humana
1994
Este artículo analiza el escepticismo humeano.
Management of Renal Angiomyolipoma: A Report of 14 Cases and Review of the Literature
1994
14 patients with renal angiomyolipoma are presented. Two of them had tuberous sclerosis (TS) with synchronous bilateral and multiple tumors. Two other patients without TS also had multiple tumors in 1 kidney. More than half the patients were symptomatic (n = 8), 2 of them with spontaneous rupture of the tumor. Misdiagnosis, spontaneous rupture and tumor growth can be prevented by utilizing conservative, organ-sparing techniques. In cases of solitary kidneys with large and/or hemorrhagic angiomyolipoma, superselective arterial embolization is indicated.
Les inégalités sociales à l'école : quel calendrier, quels mécanismes ?
1994
International audience; L'analyse de la genèse des différences de carrières scolaires met en valeur de manière fine l'importance de la classe de CP - inégale selon l'origine sociale - et le rôle central du collège dans l'accentuation des inégalités sociales de réussite. Elle révèle également que, à résultats scolaires comparables, la moitié environ des différenciations sociales d'orientation tient à des différences dans les ambitions et la demande familiale. Quelles réflexions peut suggérer cette recherche pour l'amélioration des procédures d'orientation et l'action dans le domaine pédagogique (BCD, ZEP, remédiation psychopédagogique ... ) ?
La décomposition canonique et la cointégration
1994
This paper has introduced state space models for cointegrated time series. In doing so, the notion of cointegration is slightly generalized. We develop the notion of dynamic aggregation link with error correction model and common trends.
Criminalité et folie
1994
La pequeña y mediana empresa ante el ordenamiento jurídico-laboral
1994
La cronologia dels estils ceràmics neolítics a Catalunya i la datació de C14 de la Timba del Barenys (Riudoms, Tarragona)
1994
Session 22 other topics
1994
Two-Length-Scale Structure in Some Computer-Generated Aggregates Grown by Diffusion-Limited Aggregation
1994
AbstractThe properties of some aggregates “grown” on a computer by diffusion-limited aggregation have been investigated. Calculations showed that the intensity of the small-angle x-ray and neutron scattering from the aggregates was proportional to q−D for qL ≫ 1, where D > 0, L is a length that characterizes the large-scale structure of the aggregate, q = 4πλ−1 sin(θ/2), γ is the wavelength, and θ is the scattering angle. The magnitude of the exponent D was appreciably smaller than the fractal dimensions that many simulations have shown to be typical of the mass fractal aggregates grown by diffusion-limited aggregation. The calculations suggest that the aggregates have structure on two d…
On Rough Sets in Topological Boolean Algebras
1994
We have focused on rough sets in topological Boolean algebras. Our main ideas on rough sets are taken from concepts of Pawlak [4] and certain generalizations of his constructions which were offered by Wiweger [7]. One of the most important results of this note is a characterization of the rough sets determined by regular open and regular closed elements.
Ubiquitin and ubiquitination in cells from the marine sponge Geodia cydonium.
1994
Marine sponges, e.g. Geodia cydonium, have been intensively used to investigate the biochemical and molecular biological basis of cell-cell- and cell-matrix adhesion. It has been shown that a family of galactose-specific lectins, which are present in the extracellular space of G. cydonium, is a main component involved in cell-matrix adhesion in the sponge system. In the present study it is outlined that the purified 16-kDa lectin-1 binds to a 67-kDa membrane-associated protein. This lectin-binding protein undergoes mono- and diubiquitination after incubation of dissociated sponge cells with the homologous aggregation factor (AF), a molecule involved in cell-cell adhesion. The gene coding fo…
España 1990: modernismo, anarquismo y fin de siglo
1994
Estructuras de reconocimiento y de serialidad ritual: el modelo melodrama en los films de David Wark Griffith (1918-1921)
1994
La Parte Primera aborda los problemas de orden teórico y epistemológico: la noción de melodrama en su dimensión diacrónica; la caracterización de lo melodramático en base a una serie de estructuras de reconocimiento -iconográficas, espaciales, actanciales, narrativas y musicales-; el estudio del problema del melodrama como género; finalmente, el examen del lugar de Griffith en la historia del cine y de su tradicional adscripción al "cine clásico". La Parte Segunda consiste en un estudio del corpus de films propuesto, con un examen de las condiciones de producción, distribución y exhibición del periodo; el análisis del nivel profílmico y compositivo; del montaje y los sistemas espacial y tem…
Crimes et châtiments (17e et 18e siècles)
1994
International audience
El tesoro de Rosas
1994
Conflictos jurídicos a raíz de la expulsión de los moriscos de España
1994
Anomalous time decay of transient nutations in S = 1/2 spin systems
1994
La decroissance temporelle des signaux de nutation transitoire a ete etudiee experimentalement a la frequence micro-onde sur des systemes de spin 1/2 (centres E' dans la silice and [AlO 4 ] o dans le quartz). Ces signaux decroissent exponentiellement mais avec une vitesse plus grande que la valeur habituellement donnee par les equations de Bloch. On trouve une dependence lineaire de cette vitesse avec la frequence de Rabi. Aucun interpretation pour le moment n'explique veritablement ce comportement anormal
Baltijas reņģes nārsta vietu un embrionālās attīstības raksturojums Rīgas jūras līcī
1994
Advisor: L. Duškina
Latvijas upes: nosaukumi un ģeogrāfiskais izvietojums (ar kartoshēmu)
1994
Titullapā izdošanas gads uzrādīts kļūdaini 1993.