A Variationally Consistent Time Modelling of Elastic-Plastic Constitutive Equations

1991

A general energy-based time discretization method for evolutive analysis is presented. Most known time integration procedures (mid-point rule, backward difference, etc.) are shown to be particular cases of it. For space continuous systems, a sequence of weighted boundary value problems of deformation-theory plasticity are obtained, each characterizable by a number of variational principles useful for finite element discretization.

Acid—base properties of azo dyes in the presence of surfactants

1991

Abstract The changes in the acid—base properties of an azo dye produced by the presence of surfactants, at surfactant concentrations below and above the CMC, are quantitatively described using a simple model and spectrophotometric and potentiometric measurements. The azo dye formed by aniline and N -(1-naphthyl)-ethylenediamine, and the surfactants sodium dodecyl sulphate, Triton X-100 and N -cetylpyridinium chloride (NCPC) are used. The protonation constants of the free and surfactant-bound dye species, the binding constant of the protonated and unprotonated forms of the dye, and the average aggregation number of the dye—NCPC aggregates are evaluated.

Die Messung des freien Speichel-Cortisols vor und nach intravenöser Stimulation mit Corticotropin-Releasing Hormon. Der Einfluß basaler Cortisolspieg…

1991

La propuesta de Eurigania (P. Lille de Estesícoro)

1991

Los autores, tras hacer una edición y traducción, llevan a cabo un análisis detallado que confirma lo que sabíamos de Estesícoro, ratificando con ello su autoría, y que muestra la importancia de este fragmento para el conocimiento del tratamiento literario del mito tebano; así algunas de sus variantes, considera- das tradicionalmente modificaciones de los tragediógrafos, las hallamos ya en él, mientras que otras ven reforzada su consideración de innovación. También muestra el análisis el compromiso del poeta con la sociedad al hacerse eco de los problemas de sucesión en el obcog.

On the numerical solution of the distributed parameter identification problem

1991

A new error estimate is derived for the numerical identification of a distributed parameter a(x) in a two point boundary value problem, for the case that the finite element method and the fit-to-data output-least-squares technique are used for the identifications. With a special weighted norm, we get a pointwise estimate. Prom the error estimate and also from the numerical tests, we find that if we decrease the mesh size, the maximum error between the identified parameter and the true parameter will increase. In order to improve the accuracy, higher order finite element spaces should be used in the approximations.

SISTEMA COMPUTERIZZATO PER L'ACQUISIZIONE DI GRANDEZZE ELETTRICHE

1991

Formal theory for two-particle channels

1991

The general formalism has been developed over many years by various authors. One starting point is the work of de Swart (DSw 59) who has considered electric multipoles in the long-wave-length limit using the Siegert theorem and as magnetic contribution only the dipole spin-flip transition. The T-matrix is then expanded in terms of reduced multipole amplitudes. This approach has been generalized by Donnachie (Don 62a) and Partovi (Par 64) by including higher electric and magnetic multipoles. Furthermore, the electric multipoles are not restricted to the long-wave-length limit and the additional terms besides the Siegert operators (see section 4.1) are included. Using techniques from angular …

Katalizatory cyrkonowe zawierające ligandy alkoksylowe do polimeryzacji olefin

1991

Osteomielitis vertebral cervical como complicación de cirugía faríngea: a propósito de un caso

1991

Se presenta un caso de un a enferma de 59 años, diabética, afecta de un a osteomielitis vertebral cervical por Candida Albicans. La vía de infección fué la persistencia durante varios meses de unos tutores, colocados tras la resección de un a estenosis nasofaríngea , que impactaban sobre la cara anterior de la vértebra C3. El desarrollo insidioso y la ausencia de un cuadro clínico específico fué la causa del retraso diagnóstico. A 5 9 yea r ol d woma n wit h diabete s mellitu s presente d a cervica l vertebra l osteomyelitis du e t o Candid a Albicans. Th e chroni c implantatio n o f dilatio n tube s followin g th e resectio n o f a nasopharyngea l stenosis wa s th e mod e o f infection . T…

Importancia de la embolización preoperatoria en el tratamiento del quiste óseo aneurismático: Presentación de un caso clínico

1991

Se describe el tratamiento de un quiste óseo aneurismático localizado en el raquis dorsal, en un niño de 8 años de edad. El quiste óseo aneurismático es una lesión benigna y a menudo extremadamente vascular. En la columna puede causar extensa destrucción ósea y compromiso de las estructuras neurales. Se demuestra el valor de la embolización preoperatoria reduciendo la vascularización y permitiendo su extirpación quirúrgica total. I n this report, th e managemen t o f a n aneurysma l bon e cyst i n th e thoraci c spin e o f an 8 year s ol d bo y is described . Aneurysma l bon e is a histologicall y benig n lesio n tha t is ofte n extremel y vascular . I n th e spine , it ca n caus e extensiv…

Computational stability of an initially radial solution of a growth/dissolution problem in a nonradial implementation

1991

We consider a free boundary problem modelling the growth/dissolution of a crystal. The aim is to investigate the following question: Does the solution to the crystal growth problem posed in two dimensions with radially symmetric initial and boundary condition evolve as a radially symmetric solution?

Running time to recognize nonregular languages by 2-way probabilistic automata

1991

R. Freivalds proved that the language {0m1m} can be recognized by 2-way probabilistic finite automata (2pfa) with arbitrarily high probability 1-ɛ. A.G.Greenberg and A.Weiss proved that no 2pfa can recognize this language in expected time \(T(n) = c^\circ{(n)}\). For arbitrary languages C.Dwork and L.Stockmeyer showed somewhat less: if a language L is recognized by a 2pfa in expected time \(T(n) = c^{n^\circ{(1)} }\), then L is regular. First, we improve this theorem replacing the expected time by the time with probability 1-ɛ. On the other hand, time bound by C.Dwork and L.Stockmeyer cannot be improved: for arbitrary k≥2 we exhibit a specific nonregular language that can be recognized by 2…

Wielonienasycone kwasy tłuszczowe zawarte w rybich tłuszczach a miażdżyca

1991

Profesors Bruno Rolovs: biobibliogrāfiskais rādītājs

1991

Biobibliogrāfiskajā rādītājā ietverti fizikas un matemātikas zinātņu doktora profesora Bruno Rolova publicētie darbi no 1958.gada līdz 1990.gadam, kā ari literatūra par viņu.

La condrodiastasis como técnica de alargamiento óseo

1991

Las técnicas de alargamiento óseo, en sus diferentes formas, son bien conocidas y utilizadas en la práctica ortopédica. La introducción de los fijadores axiales por una parte y la posibilidad de dinamización por otra, ha simplificaso este tipo de tratamientos y se han reducido las complicaciones. La escuela de la Universidad de Verona ha sido responsable, en gran medida, no sólo del diseño del Fijador Axial Dinámico (DAF) sino de la sistematización de la donominada callotaxis (1). En la edad infantil esos mismo cirujanos italianos han introducido otros sistemas de alargamiento actuando en la zona epifisaria y no en la diafisaria como otras técnicas clásicas. Nos referimos a la llamada condr…

Lacunary Bifurcation of Multiple Solutions of Nonlinear Eigenvalue Problems

1991

In order to describe the type of nonlinear eigenvalue problems we are going to discuss, consider a densely defined closed linear operator T in a real Hilbert space H and let H1 be the Hilbert space which consists of the domain of T together with the graph norm. Also, let H 1 * be the dual space of H1 and denote the dual operator corresponding to T: H1 → H by T’:H → H 1 * . Since H1 is dense in H, we may view H as a subspace of H1, and then the scalar product (·,·) on H and the dual pairing on H1 × H 1 * coincide on H1 × H.

Protecting Groups

1991

There is hardly any area of preparative organic chemistry in which the proper use of protecting groups is not a prerequisite for the successful achievement of the goals aimed at. For this reason such blocking functions have been developed for nearly 100 years by numerous researchers from all disciplines of organic chemistry, and consequently solutions to the existing problems have been devised, making use of various synthetic transformations. It was Fischer who, among his many important contributions to chemistry, first realized that the application of protecting functions is often a necessity for a successful synthesis. Thus, he introduced the isopropylidene ketal in carbohydrate chemistry…

Etude cinétique de la réduction dans l'hydrogène d'oxydes spinelles de cobalt faiblement substitués par le chrome

1991

La reduction par l'hydrogene a 250 °C des oxydes spinelles Co3-x Crx O4 (0 ≤ x ≤ 0,5) a ete etudiee dans des conditions de regime chimique en fonction du taux de subtitution en chrome, x, d'une part, et de variations du protocole experimental d'autre part. La phase CoO pure ou substituee par Cr est formee intermediairement. Les cinetiques respectives de la reduction du spinelle en CoO et la reduction de CoO en metal sont modifiees par des changements mineurs du protocole experimental. On observe un changement graduel de regime cinetique du type lineaire au type parabolique avec l'augmentation du taux de chrome: le taux limite suppose de solubilite du chrome dans CoO separe deux domaines dif…

Man-made garbage pollution on the Mediterranean coastline

1991

Abstract Measurements of persistent litter on 13 beaches in Spain, Italy (Sicily), Turkey, Cyprus and Israel between 1988 and 1989 show that plastic items are the most abundant in the litter composition, followed by wood, metal and glass items. Remnants of fishing gear are rather rare. It appears that the quantity of litter on a beach is inversely related to its geographical distance to a population center and directly related to the number of visitors frequenting it. Seasonal fluctuations in coastal litter are caused by storm waves which wash the litter landward, leaving the beach clean during winter, and by bathers who pollute it during summer. Based on the nature of the garbage, there ar…

Nueva inscripción romana de Segorbe (El Alto Palancia)

1991

La inscripción objeto de la presente noticia fue recuperada en el mes de enero de 1992, en el transcurso de las excavaciones de urgencia realizadas en el Convento de los Jerónimos de Nuestra Señora de la Esperanza. Dicho convento se localiza a unos 4 km. de Segorbe en dirección NW, dentro de su término municipal, a 39º 52' OS' de latitud N y 3º 10' 55' de longitud E del meridiano de Madrid, Hoja 640 (Segorbe) del I.G.C. Escala 1: 50.000. Ocupa la ladera este de una suave colina, el monte de la Esperanza, a cuyos pies surge el manantial que abastece a las poblaciones de Segorbe, Altura y Navajas.

Infinite lie groups of point transformations leaving invariant the linear equation which describes in the hodograph plane the isentropic one-dimensio…

1991

Abstract The group analysis of the hodograph equation which is equivalent to the non-linear system of one-dimensional isentropic gas dynamics reveals the existence of infinite groups of symmetry in correspondence with particular pressure laws. These turn out to be polytropes with selected indices, as is expected, as well as a new type of pressure. In all these cases the hodograph equation can be transformed, by a suitable change of variables, into the wave equationψ ζ = 0.

Mitterrand defiende una confederación europea basada en la democracia

1991

De l'isoproturon au dff, une question de site d'action

1991

National audience

Dossier de demande d'habilitation à diriger les recherches

1991

78 ref. *INRA Station de Recherches sur les Arômes BP 86510 21065 Dijon cedex (FRA) Diffusion du document : INRA Station de Recherches sur les Arômes BP 86510 21065 Dijon cedex (FRA); National audience

El potencial regional de innovación del sector industrial : el caso español

1991

Tratamiento quirúrgico de las fracturas de la diáfisis humeral

1991

Se analizan las indicaciones del tratamiento quirúrgico de las fracturas de la diáfisis humeral y las ventajas e inconvenientes de las diferentes técnicas de osteosíntesis. Después de objetivar la gravedad de las fracturas con la clasificación de Nicoll, se practica un estudio comparativo de los resultados obtenidos, entre una serie de 79 casos tratados con la técnica de Hackethal y otra serie de 25 casos tratados mediante osteosíntesis con placa atornillada, relacionando el tiempo medio de consolidación con el tipo de trazo de fractura, localización del trazo y presencia de conminución en el foco de fractura. Se estudia asimismo la relación entre el tiempo medio de consolidación y el grado…

DSC Studies and Stability of Frozen Foods

1991

This paper discusses the role played by the “WLF decrease in viscosity” above the temperature of the glass transition (Tg) in the temperature dependence of the stability of frozen foods. In the first part, the complex features observed before the melting endotherm on DSC/DTA thermograms of sugar-water solutions are examined; they are suggested to be representative of a glass transition associated with enthalpy relaxation. In the second part, the values of Tg for some complex foods are discussed. It is shown that ice melting adds an important contribution to the WLF effect on the decrease of the viscosity of the freeze-concentrated phase. The temperature dependence of the deterioration proce…

Clinical Syndromes, Pathogenesis, and Differential Diagnosis

1991

The temporal sequence of signs and symptoms in patients with cerebral ischemia provides important information for the analysis of underlying pathophysiologic mechanisms and in the search for a major hemodynamic or embolic cause. The signs reported and symptoms assessed are useful for localization of the ischemic region of the brain and identification of the affected vascular territories. Even in the case of a typical clinical picture the clinical findings alone are often insufficient for unequivocal anatomic and pathologic identification, however important they may be in the choice of diagnostic and therapeutic measures. In the first few hours after cerebral ischemia, determining the progno…

On the Rational Homogeneous Manifold Structure of the Similarity Orbits of Jordan Elements in Operator Algebras

1991

Considering a topological algebra B with unit e, an open group of invertible elements B −1 and continuous inversion (e. g. B = Banach algebra, B = C∞(Ω, M n (ℂ)) (Ω smooth manifold), B = special algebras of pseudo-differential operators), we are going to define the set of Jordan elements J ⊂ B (such that J = Set of Jordan operators if B = L(H), H Hilbert space) and to construct rational local cross sections for the operation mapping $$ {B^{ - 1}} \mathrel\backepsilon g \mapsto gJ{g^{ - 1}} $$ of B −1 on the similarity orbit S(J):= {gJg −1: g Є B −1}, J Є J.

Reflux nephropathy: a clinico-pathological study of 16 cases.

1991

The pathologic features of 16 nephrectomy specimens obtained from patients with a radiological diagnosis of reflux nephropathy were analyzed. Chronic pyelonephritis was diagnosed in 7 cases, renal dysplasia in 5 and segmental atrophy in 4. Clear correlations between pathologic pictures and pathogenic mechanisms involved in the development of renal lesions in kidneys with reflux are difficult to establish. These results show, however, that 'reflux nephropathy' is a broad term, which encompasses both congenital and acquired renal lesions.

Post-transcriptional analysis of rat mitochondrial D-3-hydroxybutyrate dehydrogenase control through development and physiological stages.

1991

Abstract The nuclear encoded mitochondrial D -3-hydroxybutyrate dehydrogenase (BDH) is synthesized in the cytosal as a larger precursor. This membrane enzyme which requires lecithin for activity plays an essential role in energy metabolism as a ketone bodies-converting enzyme. A cDNA clone of the rat liver enzyme encompassing an antigenic determinant peptide has been isolated after immunoscreening of a λ gt11 expression library. The nucleotide sequence of this 279-base cDNA insert contains a single open reading frame of 93 amino-acids, which represents about a third of the mature enzyme. Amino-acid sequence analysis predicts a hydrophobic stretch of 29 amino-acids long which probably functi…

La crise des universités francophones en Afrique sub-saharienne

1991

International audience; Les responsables des universités francophones en Afrique subsaharienne sont confrontés à un cruel dilemne : au fil des années, leur budget leur permet de moins en moins d'assurer un fonctionnement décent de leur établissement, d'où une baisse de la qualité des diplômés et de la recherche ; dans le même temps, un certain nombre d'études montrent que les coûts unitaires y sont trop élevés, que l'enseignement supérieur reçoit une proportion trop forte des crédits d'éducation et que la cure d'amaigrissement de leur budget doit être prolongée et accentuée. L'objectif de cet article est d'abord de confirmer, par des données, les énoncés de ces deux diagnostics apparemment …

Electrophilic Aromatic Substitution. VonR. Taylor. Wiley, Chichester 1990. XVI, 513 S., geb. £ 85.00 — ISBN 0-471-92482-2

1991

Clustering Algorithms for MRI

1991

Magnetic Resonance Imaging (MRI) plays a relevant role in the design of systems for computer assisted diagnosis. MR-images are multi-dimensional in nature; physicians have to combine several perceptual information images to perform the tissue classification needed for diagnosis. Automatic clustering methods help to discriminate relevant features and to perform a preliminary segmentation of the image; it can guide the final manual classification of body-tissues. Three clustering techniques and their integration in a MRI-system are described. Their performance and accuracy was evaluated on synthetic and real image-data. A comparison of our approach with the tissue-classification done by a rad…

Lipid and Apoprotein Profile in Renal Transplant Recipients

1991

Lipid and apoprotein profiles of renal transplant recipients were compared with that of a group of uremic patients on hemodialytic treatment. Total cholesterol, HDL-cholesterol, apo AI and apo B were higher and triglycerides, apo CII, apo CIII and apo E lower in renal transplant patients. Type IIa and IIb were the prevalent phenotypes in renal transplant recipients.

Configuration optimale des aires de marché et coûts de transport

1991

La théorie des Places Centrales étudiée par LÖSCH (4) et CHRISTALLER (5) a pour objet l'examen et la construction d'un paysage hiérarchisé. Celui-ci est basé sur un système d'aires de marché qui possèdent des configurations précises (hexagonales et carrées principalement). En fait raire de marché correspond à la zone d'influence d'un offreur. LÖSCH (4, p 130) a supposé que la libre entrée de firmes indépendantes localisées sur une plaine où sont situés des demandeurs équidistants entraine une transformation des aires circulaires en aires hexagonales et ainsi une maximisation du nombre de firmes par unité d'aire. HARTWICK (2) examine analytiquement le théorème de LÖSCH concernant les aires d…