Perturbative treatment of triple excitations in coupled‐cluster calculations of nuclear magnetic shielding constants

1996

A theory for the calculation of nuclear magnetic shielding constants at the coupled‐cluster singles and doubles level augmented by a perturbative correction for connected triple excitations (CCSD(T)) has been developed and implemented. The approach, which is based on the gauge‐including atomic orbital (GIAO) ansatz, is illustrated by several numerical examples. These include a comparison of CCSD(T) and other highly correlated methods with full configuration interaction for the BH molecule, and a systematic comparison with experiment for HF, H2O,NH3, CH4, N2, CO, HCN, and F2. The results demonstrate the importance of triple excitations in establishing quantitative accuracy. Finally, the abil…

A study of coronene?coronene association using atom?atom pair potentials

1996

A study of the coronene—coronene association using different interaction potentials based on an atom-atom pair potential proposed by Fraga has been performed. The interaction potentials employed differ in the way the electrostatic and/or dispersion contributions are computed. The influence of both contributions on the geometries predicted for the coronene dimer is discussed in order to analyze the effectiveness of the different interaction potentials. The stationary points found in each interaction energy hypersurface are characterized by calculating the Hessian eigenvalues. Results are discussed in the light of those previously reported for the benzene dimer. Stacked-displaced structures a…

Ab initio study of lithiated N-methylpyridones

1996

Interpolation of non-abelian lattice gauge fields

1996

We propose a method for interpolating non-abelian lattice gauge fields to the continuum, or to a finer lattice, which satisfies the properties of (i) transverse continuity, (ii) (lattice) rotation and translation covariance, (iii) gauge covariance, (iv) locality. These are the properties required for use in our earlier proposal for non-perturbative formulation and simulation of chiral gauge theories.

The effect of random matter density perturbations on the MSW solution to the solar neutrino problem

1996

We consider the implications of solar matter density random noise upon resonant neutrino conversion. The evolution equation describing MSW-like conversion is derived in the framework of the Schr\"odinger approach. We study quantitatively their effect upon both large and small mixing angle MSW solutions to the solar neutrino problem. This is carried out both for the active-active $\nu_e \ra \nu_{\mu,\tau}$ as well as active-sterile $\nu_e \ra \nu_s$ conversion channels. We find that the small mixing MSW solution is much more stable (especially in $\Delta m^2$) than the large mixing solution. The possible existence of solar matter density noise at the few percent level could be tested at futu…

Elastic pion scattering on the deuteron in a multiple scattering model

1996

Pion elastic scattering on deuterium is studied in the KMT multiple scattering approach developed in momentum space. Using a Paris wave function and the same methods and approximations as commonly used in pion scattering on heavier nuclei excellent agreement with differential cross section data is obtained for a wide range of pion energies. Only for $T_{\pi}>250$ MeV and very backward angles, discrepancies appear that are reminiscent of disagreements in pion scattering on $^3$He, $^3$H, and $^4$He. At low energies the second order corrections have been included. Polarization observables are studied in detail. While tensor analyzing powers are well reproduced, vector analyzing powers exhibit…

Double beta decay in left-right symmetric models

1996

Left-right symmetric models provide a natural framework for neutrinoless double beta ($\znbb$) decay. In the analysis of $\znbb$ decay in left-right symmetric models, however, it is usually assumed that all neutrinos are light. On the other hand, heavy {\it right-handed} neutrinos appear quite naturally in left-right symmetric models and should therefore not be neglected. Assuming the existence of at least one right-handed heavy neutrino, absence of $\znbb$ decay of $^{76}$Ge currently provides the following limits on the mass and mixing angle of right-handed W-bosons: $m_{W_R}\ge 1.1 $ TeV and $\tan(\zeta) \le 4.7 \times 10^{-3}$ for a particular value of the effective right-handed neutrin…

Paramagnetic Cobalt and Nickel Derivatives of Alcaligenes denitrificans Azurin and Its M121Q Mutant. A 1H NMR Study

1996

Using cobalt or nickel to replace copper in native azurin allows one to fingerprint the metal coordination site of the protein. The metal sites of wild type Alcaligenes denitrificans azurin and its M121Q mutant are clearly distinguishable through the paramagnetic 1H NMR spectra of the Ni(II) and Co(II) derivatives. In the wild type azurin, Gly45 coordinates to nickel or cobalt, while Met121 appears as a weak metal ligand. On the contrary, in the M121Q azurin mutant, the metal exhibits a clear preference for the Gln121, which coordinates through the side chain carbonyl oxygen, and Gly45 is not a ligand. Changes in the isotropic shifts and relaxation properties of signals from the Cys112, His…

A Monte Carlo study of diffusion in "living polymers"

1996

We report the first numeric experiments on diffusion in living polymers (polymers that can break and recombine reversibly, and are characterized by an exponential molecular weight distribution). In the simulation we use a modification of the bond fluctuation model which is known to reproduce the correct Rouse dynamics of polymer chains. The diffusion coefficient D reveals a Rouse-type behaviour D ∝ 1/L, where L is the average chain length of the polydisperse system. We also find a D ∝ exp [ − V/2kBT] dependence on the bond energy V, whereas at constant temperature the diffusion coefficient turns out to be inversely proportional, D ∝ ρ−1, to the monomer density of the system ρ in agreement w…

A Controlled Trial of Two Acellular Vaccines and One Whole-Cell Vaccine against Pertussis

1996

Background Concern about both safety and efficacy has made the use of whole-cell pertussis vaccines controversial. In some European countries, including Italy, the rate of vaccination against pertussis is low. Methods We conducted a double-blind trial in Italy in which infants were randomly assigned to vaccination at two, four, and six months of age with an acellular pertussis vaccine together with diphtheria and tetanus toxoids (DTP); a DTP vaccine containing whole-cell pertussis (manufactured by Connaught Laboratories); or diphtheria and tetanus toxoids without pertussis (DT). The acellular DTP vaccine was either one containing filamentous hemagglutinin, pertactin, and pertussis toxin ina…

Protective effect of O6-methylguanine-DNA methyltransferase (MGMT) on the cytotoxic and recombinogenic activity of different antineoplastic drugs

1996

The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) removes alkyl groups from the O6 position of guanine in DNA and thus may protect cells against genotoxic effects of agents inducing this lesion. To analyze quantitatively the level of protection mediated by MGMT against antineoplastic drugs, we determined the cytotoxic and recombinogenic (sister-chromatid exchange inducing) effects of various chemotherapeutic agents in a pair of isogenic Chinese hamster cell lines deficient and proficient for MGMT, generated upon transfection with human MGMT cDNA. Furthermore, we compared the responses of the human cell lines HeLa MR (MGMT deficient) and HeLa S3 (MGMT proficient) to the va…

An improved cosmological bound on the tau-neutrino mass

1996

We consider the influence of non-equilibrium electronic neutrinos (and anti-neutrinos) on the neutron-to-proton ratio. These neutrinos would come from massive $\nu_\tau$ annihilations $\bar \nu_\tau \nu_\tau \rightarrow \bar \nu_e \nu_e$. For sufficiently large $\nu_\tau$ masses this new effect would strongly enhance the (n/p)-ratio, leading to a very stringent bound on the $\nu_\tau$ mass, even adopting a rather weak upper bound on the effective number on neutrino species during nucleosynthesis.

Nachweis der spezifischen Proteinadsorption an Chelatorlipidmonoschichten mit FT-IR-Spektroskopie an der Wasser/Luft-Grenzfläche

1996

Multiple Sialyl-Lewisx-N-Glycopeptide: Effektive Liganden für E-Selectin

1996

Stability ofS50100n50Deduced from Excited States inC4899d51

1996

Excited states of neutron deficient nuclei close to Sn-100 were investigated in an in-beam spectroscopic experiment using the NORDBALL detector array. Excited states in Cd-99 were identified for the first time. The measured half-life of an isomeric state in Cd-99 indicates that the stability with respect to quadrupole shape changes is as large in Sn-100 as for other heavy doubly magic nuclei.

A General and Efficient Method for the Monohydroxylation of Alkanes

1996

Low-energy fission investigated in reactions of 750 AMeV 238U-ions with Pb and Be targets

1996

Charge distributions of fragments from low energy nuclear fission are investigated in reactions of highly fissile238U projectiles at relativistic energies (750 A·MeV) with a heavy (Pb) and a light (Be) target. The fully stripped fission fragments are separated by the Fragment Separator (FRS). Their high kinetic energies in the laboratory system allow the identification of all atomic numbers by using Multiple-Sampling Ionization Chambers (MUSIC). The elemental distributions of fragments observed at larger magnetic rigidities than the238U projectiles show asymmetric break-up and odd-even effects. They indicate a low energy fission process, induced mainly by dissociation in the electro-magneti…

Microscopic theory of colloid formation in solids under irradiation

1996

Results of the first-principles study of diffusion-controlled aggregation of Frenkel defects-interstitial atoms-under irradiation of solids are presented. Conditions of the efficient radiation-induced aggregation of vacancies and interstitials are studied and the scenario of this process is presented.

Low temperature optical spectroscopy of low-spin ferric hemeproteins

1996

We report the Soret absorption spectra (500-350 nm) of the cyanomet derivatives of human hemoglobin and horse myoglobin, in the temperature range 300-20 K and in two different solvents (65% v/v glycerol-water or 65% v/v ethylene glycol-water). In order to obtain information on stereodynamic properties of active site of the two hemeproteins, we perform an analysis of the band profiles within the framework of electron-vibrations coupling. This approach enables us to single out the various contributions to the spectral bandwidth, such as those arising from non-radiative decay of the excited electronic state (homogeneous broadening) and from the coupling of the electronic transition i) with hig…

Immunophenotypical comparison of Gaucher's and pseudo-Gaucher cells.

1996

An immunohistochemical study on bone marrow biopsies and spleens of patients with Gaucher's disease and chronic myeloid leukemia was performed to investigate the immunophenotype of Gaucher's cells and pseudo-Gaucher cells. A panel of antibodies was used which were reactive on paraffin-embedded tissues and directed against different hematopoietic lineage cells. Gaucher's cells and pseudo-Gaucher cells expressed a very similar immunophenotype and displayed an intense reaction for the monocytic antibodies tested, thus confirming their common origin and that they belong to the same system. The expression of HLA-DR antigens was much stronger in Gaucher's than in pseudo-Gaucher cells. This last f…

Copper(II) and nickel(II) chelates with dihydrogen Trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetate(2−) ion (H2CDTA2−). Synthesis, XRD structure a…

1996

Abstract Stoichiometric reactions of metal hydroxycarbonates with the acid trans -1,2-cyclohexanediaminotetraacetic acid (H 4 CDTA) in water under reduced pressure yielded [Cu(H 2 CDTA)]·H 2 O ( I ) and [Ni(H 2 CDTA) (H 2 O)]·4H 2 O ( II ). Both compounds were characterized by TG-DTA analysis, spectral properties (IR, reflectance and RSE) and X-ray diffraction. In I the copper(II) atom exhibits a distorted square-base coordination (type 4+1) by chelation of one H 2 CDTA 2− ligand through two N and two O (carboxylate) at the square base and one O (carboxylic) at the apex of the coordination polyhedron; a second carboxymethyl group of H 2 CDTA 2− remains free. In II the H 2 CDTA 2− chelating …

Vergleichende dimerisierung der enantiomere von Oct-1-in-3-ol mit chiralen rhodium-phosphan-komplexen

1996

Abstract Three optically active phosphanes ([(S)-2-methylbutyl]3−nP[phenyl]n(n = 0, 1, 2), were tested as ligands in rhodium(I) complexes to form catalysts for the enantioselective dimerisation of (R)- and (S)-oct-1-yn-3-ol. The catalytic reaction provides enantioselectivity for this type of CC bond formation. For reactions at 45–75°C and depending on the P-ligand used the rates vary for both enantiomers from 6:1 to 50:1 in favour of the (S)-octynol.

Primary plasmacytoma of the skin.

1996

Primary plasmacytoma of the skin without evidence of bone marrow plasmacytosis is a rare disorder belonging to the heterogenous spectrum of plasma cell neoplasms. With immunohistochemical techniques, differentiation from benign plasma cell aggregates can be accomplished by demonstrating the monoclonality of tumor cells. We describe a patient in whom a solitary primary cutaneous plasmacytoma developed on the left thigh. Immunohistochemically, plasma cells showed restriction of immunoglobulin lambda-chain expression. Underlying multiple myeloma was excluded by serum protein and immunoglobulin electrophoresis, roentgenographic skeletal survey, and bone marrow biopsy. The tumor responded well t…

Quantum chemical simulations of the optical properties and diffusion of electron centres in mgo crystals

1996

Semiempirical quantum chemical simulations have been undertaken to obtain the self-consistent atomic and electronic structure of the two basic electron defects in MgO crystals: F+ and F centres (one and two electrons trapped by an 0 vacancy, V,). The calculated absorption and luminescence energies agree well with the experimental data; the excited states of both defects are found to be essentially delocalised over nearest-neighbour cations. The activation energy for diffusion is found to increase monotonically in a series V, --f F+ --f F centre (2.50 eV, 2.72 eV and 3.13 eV, respectively).

Hormonal regulation of S-adenosylmethionine synthase transcripts in pea ovaries

1996

Two cDNA clones coding for S-adenosyl-L-methionine synthase (SAMs, EC 2.5.1.6) have been isolated from a cDNA library of gibberellic acid-treated unpollinated pea ovaries. Both cDNAs were sequenced showing a high degree of identity but coding for different SAMs polypeptides. The presence of two SAMs genes in pea was further confirmed by Southern analysis. Expression of the SAMs genes in the pea plant was found at different levels in vegetative and reproductive tissues. We characterized the expression levels of SAMs genes during the development or senescence of pea ovaries. Northern analysis showed that transcription of SAMs genes in parthenocarpic fruits was upregulated by auxins in the sam…

Cationic lipide mediated transfer of c-abl and bcr antisense oligonucleotides to immature normal myeloid cells: Uptake, biological effects and modula…

1996

Uptake and biochemical and biological effects of antisense oligodeoxynucleotides (ODN) specific for c-abl and bcr genes were studied in normal immature myeloid cells. CD34-positive cells were purified by positive and negative selection and cultured in liquid culture for 7 days. These cells were then incubated with ODNs, either alone or in combination with cationic lipids. The uptake of ODNs was enhanced by the use of cationic lipids. In addition, very low concentrations of ODNs in combination with cationic lipids were capable of specifically inhibiting the expression of the c-abl gene. In contrast, no effects were seen on the expression of bcr. However, despite the effective blocking of c-a…

Proteolytic Processing ofBacillus thuringiensisCryIIIA Toxin and Specific Binding to Brush-Border Membrane Vesicles ofLeptinotarsa decemlineata(Color…

1996

Abstract The mode of action of Bacillus thuringiensis insecticidal proteins in lepidopteran insects is known to involve five steps: ingestion, solubilization, protease activation, binding to midgut membrane receptors, and disruption of the intestinal membrane. Two of these steps, protease activation and binding to midgut membrane receptors, have been analyzed in the major potato pest, the coleoptera Leptinotarsa decemlineata (Colorado potato beetle). Unlike recently proposed, after treatment of the coleopteran-specific B. thuringiensis toxin CryIIIA with gut content from the Colorado potato beetle, a 42-kDa processing polypeptide has been identified. The study of binding to midgut membrane …

The active center of superoxide dismutase from Propionibacterium shermanii

1996

A self-consistent description of the EPR spectra and of the Mossbauer spectra of the natural superoxide dismutase from Propionibacterium shermanii with ferric iron as an active centre is presented. The spectra were measured at pH 6.5, 7.8 and 9.4. The theoretical approach is based on the use of the complete crystal field Hamiltonian for the high-spin ferric complexes with due regard for the terms of the fourth power of the electronic spin. It is shown that a SOD molecule can exist in two conformations. The low-pH conformation has predominantly trigonal symmetry, while the high-pH conformation has the symmetry close to the «extreme rhombic». This interpretation is in full agreement with EXAF…

Acid tolerance inLeuconostoc oenos. Isolation and characterization of an acid-resistant mutant

1996

The acid tolerance ofLeuconostoc oenos was examined in cells surviving at pH 2.6, which is lower than the acid limit of growth (about pH 3.0). Acid-adapted cells survived better than non-adapted cells. Tolerance to acid stress was found to be dependent upon the adaptive pH. Acid resistance was increased by an order of magnitude for cultures adapted to a pH of about 2.9. Inhibiting protein synthesis with chloramphenicol prior to acid shock revealed that acid adaptation may involve two separate systems, one of which appears to be independent of protein synthesis. The acid-resistant mutant LoV8413, isolated during a long-term survival screen at pH 2.6, was found to be able to grow in acidic me…

Physiological and Molecular Characteristics of Elicitin-Induced Systemic Acquired Resistance in Tobacco

1996

Elicitins are low molecular weight proteins secreted by all Phytophthora species analyzed so far. Application of the purified proteins to tobacco Nicotiana tabacum leads to the induction of resistance to subsequent inoculations with the black shank-causing agent, Phytophthora parasitica var nicotianae. In this paper, we describe the systemic characteristics of elicitin-induced acquired resistance in tobacco. Elicitin application is followed by the rapid translocation of the protein in the plant. The basic elicitin, cryptogein, induces necrosis formation in the leaves, which results from accumulation of the protein in these organs. Necrosis does not seem to be essential for the establishment…

Differential Effects of Nonhydroxylated Flavonoids as Inducers of Cytochrome P450 1A and 2B Isozymes in Rat Liver

1996

Flavanone, flavone, and tangeretin differentially affected the activities of cytochrome P540 1A and 2B isozymes in rat liver. Flavone and, to a lesser extent, tangeretin, increased activities of ethoxyresorufin O-deethylase, methoxyresorufin O-demethylase, and pentoxyresorufin O-dealkylase (PROD), whereas flavanone mainly enhanced PROD activity. Immunoblot analysis indicated that flavone and tangeretin increased cytochrome P450 1A1, 1A2, and 2B1,2 forms, whereas flavanone only enhanced the cytochrome P450 2B isozymes. Northern blot study showed that flavone and tangeretin increased the level of the cytochrome P450 1A2 mRNAs. The concentration of the other mRNAs were slightly or not affected…

Ac field dependence of the susceptibility of Bi2Sr2CaCu2O8 thin films at low dc fields

1996

We have measured the ac field dependence of the ac susceptibility of 400 nm thick Bi2212 thin films at low dc fields 0 ≤μ0Ha ≤ 1 mT in transverse geometry. We show that at reduced temperaturest≤0.85 the ac field dependence can be described by the non-linear Bean model after Brandt as in Y123 thin films. Att>0.85, however, we observe a decrease of the energy dissipation and shielding capability. The critical current density at zero dc field is given byjc−4×1010(1−(T/Tc))2.8±0.1 A/m2.

A new shape-oriented classification method for UV/VIS-spectra

1996

A new shape-oriented classification method is described. It is shown, how shapes of UV/VIS-spectra can be classified and coded and how a classification technique can be used to improve database search operations for pre-selections or even shape-oriented identifications.

The influence of Albunex on the pulmonary circulation in patients with pulmonary hypertension or left heart failure.

1996

To determine the safety of the ultrasound contrast agent Albunex, its influence on right and left heart haemodynamics in patients with pulmonary artery hypertension or left heart failure was assessed after intravenous injection. Patients with a left ventricular ejection fraction smaller than 40% or a systolic pulmonary artery pressure greater than 40 mmHg received 0.08 and 0.22 ml.kg -1 Albunex and 10 ml albumin in random order during right heart catheterization and transthoracic echocardiography. Right atrial, systolic and diastolic pulmonary artery and capillary wedge pressures were measured at 3 min and 5 min and cardiac output at 5 min after the intravenous injection of Albunex and cont…

Lp-Spaces as Quasi *-Algebras

1996

Abstract The Banach space L p ( X , μ), for X a compact Hausdorff measure space, is considered as a special kind of quasi *-algebra (called CQ*-algebra) over the C*-algebra C ( X ) of continuous functions on X . It is shown that, for p ≥2, ( L p ( X , μ),  C ( X )) is *-semisimple (in a generalized sense). Some consequences of this fact are derived.

The surface modification of polymers to modulate endothelial cell growth

1996

The effect of nitrogen ion implantation or ion-assisted film deposition on the growth of human endothelial cells in vitro on a substrate has been studied. It was shown that the largest change occurs when TiO2 films were reactively sputtered onto the substrates, while the most passive surface was reactively sputtered SiO2. SEM pictures of the cells adhering to the various treated surfaces show that the cells were healthy. Future studies on the effect of alloy films and their oxides and nitrides are proposed.