showing 36 of ~574560 from 574555 documents
Transmission Electron Microscopy of GroEL, GroES, and the Symmetrical GroEL/ES Complex
1994
Two new 2-D crystal forms of the Escherichia coli chaperone GroEL (cpn60) 2 x 7-mer have been produced using the negative staining-carbon film (NS-CF) technique. These 2-D crystals, which contain the cylindrical GroEL in side-on and end-on orientations, both possess p21 symmetry, with two molecules in the respective unit cells. The crystallographically averaged images correlate well with those obtained by other authors from single particle analysis of GroEL and our own previous crystallographic analysis. 2-D crystallization of the smaller chaperone GroES (cpn10) 7-mer has also been achieved using the NS-CF technique. Crystallographically averaged images of GroES single particle images indic…
London equation of state for a quantum-hard-sphere system
1994
The London analytical interpolation equation between zero and packing densities for the ground-state energy of a many-boson hard-sphere system is corrected for the reduced mass of a pair of particles in a ``sphere-of-influence'' picture. It is thus brought into good agreement with computer simulations and with experimental results extrapolated out to close packing.
Photoinduced electron transfer in molecular organizates at the gas-water interface
1994
Abstract The influence of the molecular geometry is of fundamental importance for a better understanding of the photoinduced electron transfer mechanism. Because of their typical molecular structures, cyclophane rings have proved to be suitable for this purpose as electron acceptor molecules adsorbed under an amphiphile monolayer. We used a pyrene-labelled phospholipid derivative both as molecular anchor for the cyclophane ring and electron donor molecule. The co-spreading technique was used to prepare the complex monolayers. Surface pressure and surface potential measurements have indicated similar monolayer behaviour as with dimyristoylphosphatidic acid as anchor molecule, leading to the …
Cycloadditionen von 2H ‐Benzo[ b ]thiet und Verbindungen mit kumulierten Doppelbindungen
1994
Cycloaddition Reactions of 2H-Benzo[b]thiete and Compounds with Cumulated Double Bonds o-Thiobenzoquinone methide (2), generated by thermal ring opening of 2H-benzo[b]thiete (1), reacts with allene 3, ketene imine 7, the carbodiimides 9a-c, and the N-sulfinylamines 11a-c in highly specific [8π + 2π] cycloaddition processes to form novel types of heterocyclic systems 4, 8, 10a-c, and 12a-c with exocyclic double bonds. The 1:1 adduct 4 can add a further molecule of allene to yield the spiro compounds 5 and 6.
«Dígales que mi vida ha sido maravillosa»: ética y existencia en L. Wittgenstein
1994
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1994
Giraffid remains from several Neogene localities from the Temel Basin (Spain) are stu died. The material belongs to the following sites: Masia de la Roma and Masia del Barbo (Vallesian); Masada del Valle 2 (Turolian); La Gloria 4 and La Calera (Alfambrian). Fos sils recently obtained are described, with special emphasis on the Pliocene taxa that were previously unrecorded in this basin. The presence of Decennatheriumpachecoi in the Va llesian and Birgerbohlinia schaubi in the Turolian is specified here. In order to make a dis tinction between both species two characteristics can be pointed out among the rest: the postcranial skeleton of Decennatherium is more slender than the one of Bir…
Etude des composés volatils de produits alimentaires par couplage "headspace-chromatographie gazeuse-spectrométrie de masse"
1994
National audience
Neutrino Magnetic Moment and the Process $\nu e \rightarrow \nu e \gamma$
1994
The contribution of a neutrino magnetic moment $\mu_{\nu}$ to the cross section of the process $\nu e^{-}\rightarrow \nu e^{-} \gamma $ has been calculated and compared with the Standard Electroweak one. The radiative process allows to reach low enough values of $Q^2$ without the need to operate at very small energies of recoil electrons. Regions in the phase space which are more favourable to set bounds on $\mu_{\nu}$ are suggested.
Cytotoxic necrotizing factor type 2 produced by virulent Escherichia coli modifies the small GTP-binding proteins Rho involved in assembly of actin s…
1994
Cytotoxic necrotizing factor type 2 (CNF2) produced by Escherichia coli strains isolated from intestinal and extraintestinal infections is a dermonecrotic toxin of 110 kDa. We cloned the CNF2 gene from a large plasmid carried by an Escherichia coli strain isolated from a lamb with septicemia. Hydropathy analysis of the deduced amino acid sequence revealed a largely hydrophilic protein with two potential hydrophobic transmembrane domains. The N-terminal half of CNF2 showed striking homology (27% identity and 80% conserved residues) to the N-terminal portion of Pasteurella multocida toxin. Methylamine protection experiments and immunofluorescence studies suggested that CNF2 enters the cytosol…
New Supernova Constraints on active-sterile neutrino conversions
1994
We consider active-sterile neutrino conversions in a supernova in the presence of random magnetic field domains. For large enough fields the magnetization of the medium may enhance the active to sterile neutrino conversion rates. Neglecting neutrino transition magnetic moments we show that for KeV neutrino mass squared differences these limits may overcome those that would apply in the isotropic case.
Characterization of Acylating and Deacylating Activities of an Extracellular Phospholipase A2 in a Water-Restricted Environment
1994
The behavior of porcine pancreatic phospholipase A2 (ppPLA2) in monophasic low-water media has been explored, for the first time, in a systematic manner. It has been investigated how a number of variables can modulate both acylating and deacylating activities of the enzyme, and several interesting, unexpected results are presented. Among the most relevant, when placing ppPLA2 in the water-restricted environment, are the following: (i) it displays a remarkable alteration of its specificity toward the substrate polar head relative to all-water medium; (ii) it is quite severely inhibited by lysophosphatidylcholine (LPC), which has important implications, particularly concerning its acylation a…
RP-HPLC für Anwender. (Reihe: Die Praxis der instrumentellen Analytik, Reihenherausgeber: U. Gruber und W. Klein.) Von W. Gottwald. VCH Verlagsgesell…
1994
Spin Dynamics of the Half-Integer-Spin Quasi-One-Dimensional Heisenberg Antiferromagnet CsMnI3
1994
Magnetic excitations of CsMnI 3 , a quasi-one-dimensional Heisenberg antiferromagnet with S =5/2, have been measured by means of inelastic neutron scattering. Magnetic excitations in the low temperature phase are in good agreement with the predictions of the conventional linear spin-wave theory. In particular, in accordance with the linear spin-wave theory, we found three separate modes at Q =(0, 0, 1) instead of a threefold degenerate mode as seen in CsNiCl 3 ( S =1). It confirms that the spin dynamics of the integer spin value system are very different from those of the half-integer spin value system, even in their three-dimensionally ordered phase. Magnetic excitations in the intermediat…
Les ossements d'animaux et l'interprétation des sites d'habitats gaulois
1994
International audience
Les restes animaux du site des Bonnettes (Pas-de-Calais)
1994
International audience
RV coefficient and statis: useful multivariate statistical methods for sensory evaluation
1994
National audience
Wavelet-like orthonormal bases for the lowest Landau level
1994
As a first step in the description of a two-dimensional electron gas in a magnetic field, such as encountered in the fractional quantum Hall effect, we discuss a general procedure for constructing an orthonormal basis for the lowest Landau level, starting from an arbitrary orthonormal basis in L2(R). We discuss in detail two relevant examples coming from wavelet analysis, the Haar and the Littlewood-Paley bases.
Résolution des contraintes géométriques
1994
National audience; La modélisation par contraintes définit les objets géométriques (typiquement, en 2D, les points, droites, cercles, coniques, etc) par les contraintes qu'ils doivent vérifier (distances, angles, tangences, incidences, etc. entre paires d'objets). L'exposé tente de faire le point sur les diverses méthodes proposées à ce jour pour la résolution des contraintes, en 2D ou en 3D. Les méthodes algébriques transforment les contraintes en un système d'équations, et recourent ensuite à des méthodes numériques (relaxation, Newton-Raphson) [4] ou symboliques (bases de Grobner, méthode de Wu et Ritt) [5,3]. Les méthodes géométriques décomposent le système de contraintes en problèmes g…
Effective kink-kink interaction in a one-dimensional model mediated by phonon exchange
1994
The general 1D double-well model with anharmonic interaction is considered in the displacive limit. Expansion of the Hamiltonian around a multikink state results in a phonon-kink Hamiltonian. It is shown that at rather low temperatures and short wave lengths the phonon-kink interaction can be treated in Born approximation, leading to a decomposition of the multikink-phonon Hamiltionian. Elimination of the phonons results in an effective potential for the kink-kink interaction, which corresponds to the one-dimensional analog of the RKKY interaction. This long-range interaction is inherent only for models with anharmonic on-site potentials and not in case of a double-parabola model.
TOPOLOGICAL QUANTUM DOUBLE
1994
Following a preceding paper showing how the introduction of a t.v.s. topology on quantum groups led to a remarkable unification and rigidification of the different definitions, we adapt here, in the same way, the definition of quantum double. This topological double is dualizable and reflexive (even for infinite dimensional algebras). In a simple case we show, considering the double as the "zero class" of an extension theory, the uniqueness of the double structure as a quasi-Hopf algebra. A la suite d'un précédent article montrant comment l'introduction d'une topologie d'e.v.t. sur les groupes quantiques permet une unification et une rigidification remarquables des différentes définitions,…
Clumsiness in Adolescence: Educational, Motor, and Social Outcomes of Motor Delay Detected at 5 Years
1994
This paper reports the follow-up at age 15 of a group of children who were diagnosed at age 5 as having delayed motor development. The group of children who were clumsy and the control group still differed in motor performance 10 years later: 46% of the members of the early motor delay group were classified as different from the control group on motor and perceptual tasks. The remainder made up an intermediate group that could not be clearly distinguished from the other groups. Adolescents with stable motor problems had fewer social hobbies and pastimes and had lower academic ambitions for their future than the controls, although the lower academic ambitions also reflect their lower academi…
Guinean and sahelian rainfall anomaly indices at annual and monthly scales (1933-1990)
1994
The annual and monthly rainfall variability in north tropical Africa are analysed by principal component analysis in order to detect the main coherent modes. The Sahel constitutes the first mode, although it is divided close to 1O"W into an Atlantic section and a Continental section. The Guinean zone is less coherent, and is divided into distinct modes. The subequatorial area never formed a distinct mode. Rainfall variability for the coherent areas is constructed from rainfall anomaly indices (RAI), based on the coherent areas, and a rainfall typology taking into account the spatial pattern of the rainfall anomaly fields and the intensity of the anomaly. Their evolution (mainly since 1950) …
Die Renaissance der Elektronenmikroskopie. Transmissions-Elektronenmikroskop mit Energiefilter für biologische Proben
1994
Seit Entwicklung der Transmissions-Elektronenmikroskopie durch Ernst Ruska und Max Knoll im Jahre 1931 ist das Auflosungsvermogen der Elektronenmikroskope bis zum atomaren Bereich gesteigert worden, und auch dickere Praparate oder ganze Zellen konnen jetzt durch Erhohung der Beschleunigungsspannung durchstrahlt werden (high voltage electron microscopy). Eine wesentliche Verbesserung in der Anwendung des Transmissions-Elektronenmikroskops (TEM) uber das deskriptive Niveau der Feinstruktur-Analyse hinaus wird durch die Ausstattung der Mikroskope mit analytischen Zusatzgeraten erreicht, wie beispielsweise durch die Rontgen-Mikroanalyse (energy dispersive X-ray analysis − EDX) oder die Elektron…
HIGH-PRECISION MONTE CARLO DETERMINATION OF α/ν IN THE 3D CLASSICAL HEISENBERG MODEL
1994
To study the role of topological defects in the three-dimensional classical Heisenberg model we have simulated this model on simple cubic lattices of size up to 803, using the single-cluster Monte Carlo update. Analysing the specific-heat data of these simulations, we obtain a very accurate estimate for the ratio of the specific-heat exponent with the correlation-length exponent, α/ν, from a usual finite-size scaling analysis at the critical coupling Kc. Moreover, by fitting the energy at Kc, we reduce the error estimates by another factor of two, and get a value of α/ν, which is comparable in accuracy to best field theoretic estimates.
Condensed phases in monolayers of a triple-chain lecithin on water
1994
Abstract A triple-chain phospholipid monolayer at the air-water interface is investigated by means of grazing incidence X-ray diffraction (GID). Analysis of the diffraction spot profiles parallel and perpendicular to the surface yields different ordered phases. On increasing the lateral pressure at different temperatures the hydrocarbon chains form tilted phases with a tilt toward the nearest neighbors and eventually a hexagonal lattice with vertical chain orientation.
Automated image analysis DNA cytometry in testicular cancer
1994
The value of automated DNA cytometry for differentiation of testis cancer was evaluated in 54 seminomas, 13 HCG-positive seminomas, and 48 embryonal carcinomas. Slices of paraffin embedded tissue were enzymatically digested and stained with Feulgen SITS after fixation on glass slides. Automated DNA cytometry was performed with a Modular Image Analysis Computer (MIAC). DNA histogram phenotpye and computed DNA indices were correlated with the different tumor types. The ratio of hypertriploid to hypotriploid increased from HCG-positive seminoma over embryonal carcinoma to seminoma. The following mathematical DNA indices were found to correlate with tumor type: mean ploidy, 2c deviation index, …
Indagine Clinico Epidemiologica su 132 Nati da Gravidanze Multiple
1994
AbstractL'epidemiologia delle gravidanze multiple si è notevolemente modificata nel corso degli ultimi due decenni in virtù del perfezionamento e della diffusione delle tecniche di riproduzione assistita. L'utilizzazione di induttori farmacologici della ovulazione (specie le gonadotropine ed il citrato di clomifene) e l'impianto in utero di più embrioni fecondati in vitro, sono fattori che maggiormente hanno contribuito a fare impennare verso l'alto il numero di nati da gravidanze plurigemine. L'incidenza di parti trigemini, ad esempio, considerata gli inizi degli anni '70 di circa 1:10,000 parti, oggi si è elevata sino ad 1:3,500 circa.Presentiamo i dati relativi a 132 soggetti nati da gra…
Influence of Mannaproteins from Yeast on the Aroma Intensity of a Model Wine
1994
Abstract The influence of mannaproteins released from yeast cell walls during alcoholic fermentation on the volatility of aroma substances was investigated in a model wine. After the characterization of macromolecules (substrates), two techniques have been used to study the interactions with aroma compounds: headspace analysis and an equilibrium dialysis method. The assumed effects of these macromolecules from yeasts on the fixation of volatile compounds were demonstrated. The physico-chemical interactions between aroma substances and mannaproteins depended on the nature of volatile compounds. Protein concentration in substrates was an important factor in their binding capacity. The retenti…
The Hunting of the MR Model
1994
We consider experimental signatures of the standard model's minimal supersymmetric extension with a continuous $U(1)_R$ symmetry (MR model). We focus on the ability of existing and planned electron-positron colliders to probe this model and to distinguish it from both the standard model and the standard model's minimal supersymmetric extension with a discrete $R$-parity.
Randomised controlled study with cyproterone acetate (100 mg/die) versus Pygeum africanum (200 mg/die) in benign prostatic hypertrophy
1994
A multi-centre comparative study was carried out on 143 patients with benign prostatic hypertrophy and reduced or no sexual activity. 74 patients were treated with a low dose of CPA (100 mg a day) and 69 with PYG (200 mg a day), administered orally and assigned randomly. The patients were evaluated at 4,12 and 24 weeks. Results showed a significant statistical difference in favour of the CPA treatment for almost all parameters (flow, post-micturitional residue, symptomatological score). There was a decrease in prostate volume, equal to 19.3% compared to the initial values, only in those patients treated with CPA who completed the treatment. Considerable improvement in nicturia and micturit…
Central obesity and hypertension. Relationship between fasting serum insulin, plasma renin activity, and diastolic blood pressure in young obese subj…
1994
This study was designed to evaluate the role of fasting serum insulin and plasma renin activity in obesity-induced hypertension. In view of this, plasma catecholamines, fasting serum insulin (IRI), urinary sodium excretion (NaU), plasma renin activity (PRA), and plasma aldosterone (PA) levels were assessed in young (age less than 40 years) normotensive (n = 27) and hypertensive (n = 14) subjects with central obesity and in lean normotensives (n = 20). Central obesity was evaluated by waist-to-hip ratio (WHR) according to the indication of the Italian Consensus Conference of Obesity. PRA, PA, IRI, and plasma norepinephrine levels were significantly (P < .05) higher in both obese groups than …
Isolation and characterization of yeast monomorphic mutants of Candida albicans.
1994
A method was devised for the isolation of yeast monomorphic (LEV) mutants of Candida albicans. By this procedure, about 20 stable yeast-like mutants were isolated after mutagenesis with ethyl methane sulfonate. The growth rate of the mutants in different carbon sources, both fermentable and not, was indistinguishable from that of the parental strain, but they were unable to grow as mycelial forms after application of any of the common effective inducers, i.e., heat shock, pH alterations, proline addition, or use of GlcNAc as the carbon source. Studies performed with one selected strain demonstrated that it had severe alterations in the chemical composition of the cell wall, mainly in the le…
Reaction kinetics in dense two-dimensional polymer solutions : an excimer probe study
1994
We report measurements of the time dependent reaction rate of excimer formation in two-dimensional solutions of a polymerized amphiphile with partially pyrene-labelled chains in monolayers at the air-water-interface. We find a time dependent reaction rate for excimer formation obeying a power law r(t) ∞ t -β . The exponent β has a value of 0.22±0.12. This value is consistent with β=1/4, as has been predicted for bimolecular diffusion-controlled reactions in two-dimensional polymer melts by de Gennes. The measurements demonstrate the usefulness of the excimer technique to explore polymer dynamics
Textures in hexatic films of nonchiral liquid crystals: Symmetry breaking and modulated phases
1994
Novel modulated textures, such as stripes and multiarmed star defects, have been observed in freely suspended films of nonchiral liquid crystals just below the smectic-$C$ to hexatic phase transition. Detailed studies using depolarized reflection microscopy suggest that the stripes are locally chiral surface splay domains of the smectic-$L$ phase, a tilted hexatic not previously identified in thermotropic liquid crystals. Line defects which form additional domain walls in the hexatic lattice lead to characteristic modulations of the basic one-dimensional stripe pattern. Inside thick circular islands, for example, stripes form circumferentially and the lines form centered 12-armed stars, res…
The Role the Static Maximization Approach Plays in Neoclassical Analyses
1994
This is an article on the methodology of economic thought. The critical assessment of the neoclassical research programme contained here basically comes from the contributions of J.M. Buchanan, Nobel prize winner in Economics 1986. These comments are aimed at pointing out the role that the static maximization approach plays in neoclassical analyses since L. Robbins and P. Samuelson’s influential contributions came about after World War II. Just to complement this basic purpose, I present in section 4 the alternative methodological foundations J.M. Buchanan proposes and uses to replace the static maximization approach when building public choice analyses and I sketch in section 5 several pe…