Showing papers by "Argonne National Laboratory published in 1977"
TL;DR: In this article, the Hartree and Thomas-Fermi calculations for infinite and semi-infinite symmetric nuclear matter are made for Cubic and quartic scalar meson self-interactions.
931 citations
TL;DR: A one parameter family of variable metric updates is developed by considering a fundamental decomposition of the Hessian that underlies Variable Metric Algorithms and considers particular choices of the parameter.
Abstract: We develop a one parameter family of variable metric updates by considering a fundamental decomposition of the Hessian that underlies Variable Metric Algorithms. The relationship with other Variable Metric Updates is discussed. Considerations based on the condition of the Hessian inverse approximation indicate particular choices of the parameter and these are discussed in the second half of this paper.
333 citations
TL;DR: Free Nambu strings in space-time are the two-dimensional sheet analog of one-dimensional curves which are timelike or spacelike geodesics as mentioned in this paper. But this is not the case for null geodesic strings.
Abstract: Free Nambu strings in space-time are the two-dimensional sheet analog of one-dimensional curves which are timelike or spacelike geodesics. It is pointed out that there is also a sheet analog of one-dimensional curves which are null geodesics.
297 citations
262 citations
TL;DR: In this paper, Al can substitute for Ni in LaNi5 with dramatic results in lowering decomposition pressures without impairing the kinetics or the hydrogen carrying capacities, and the important new result is that Al substitutions allow a wide range of decomposition pressure to be spanned in continuous fashion.
Abstract: METAL alloys which reversibly absorb and desorb hydrogen are being used or considered for a variety of energy applications1,2. Alloys of general composition AB5 are prime candidates because of their good hydrogen absorption/desorption kinetics and large hydrogen storage capacity. The LaNi5–H2 system, in particular, has been extensively investigated. In many applications, however, materials are required whose plateau pressures are different from those of LaNi5H6,7. The desorption pressure of LaNi5H6,7 may be modified by substitutions either of La or Ni with other elements. Previous work3 has shown that 20% substitutions of Ni by a variety of transition metals can lower plateau pressures by a factor of ∼4. We report here that Al can substitute for Ni in LaNi5 with dramatic results in lowering decomposition pressures without impairing the kinetics or the hydrogen carrying capacities. The important new result is that Al substitutions allow a wide range of decomposition pressure to be spanned in continuous fashion. In the range 0–20% Al, the plateau pressures of the LaNi5–LaNi4 Al hydride system are reduced by a factor of ∼ 300.
224 citations
01 Jan 1977
TL;DR: Photochemical possibilities of natural components of the cell suggest that efficient mechanisms for the partial prevention or repair of resultant damage from exposure to solar radiation must exist for biological entities to survive regular exposure to natural sunlight.
Abstract: Ultraviolet (UV) radiation* of wavelengths longer than 295 nm from sunlight is a ubiquitous part of the natural environment of most organisms. Although beneficial and possibly beneficial aspects of sunlight have long been recognized and studied (Daniels, 1974; Wurtman, 1975), harmful effects, except for sunburn, have received relatively little attention until recently. Photochemical possibilities of natural components of the cell suggest that efficient mechanisms for the partial prevention or repair of resultant damage from exposure to solar radiation must exist for biological entities to survive regular exposure to natural sunlight. Recent work has identified DNA lesions induced by near-UV radiation (Section 2.4). Furthermore, mechanisms of protection and repair of near-UV-induced lesions have been reported (Sections 2.3 and 2.6).
209 citations
TL;DR: In this paper, degradation techniques, including pyrolysis, depolymerization, and oxidation, were used to study the insoluble polymer from the Murchison C2 chondrite.
206 citations
TL;DR: Glycine and taurine conjugates of 5beta-cholanic acids have been synthesized using improved procedures based on the peptide coupling reagent, N-ethoxycarbonyl-2-eth oxygen-1,2-dihydroquinoline in yields higher than 90%.
198 citations
TL;DR: In this article, a deformed singleparticle potential mode with residual interactions was applied to an analysis of states in odd-mass nuclides with $Ag228$, and configuration assignments were presented for many levels.
Abstract: A deformed single-particle potential mode, with residual interactions, is applied to an analysis of states in odd-mass nuclides with $Ag228$, and configuration assignments are presented for many levels. The systematics of energy level spacings throughout the actinides are studied, and the values of the nuclear deformation parameters that are appropriate to these nuclides are discussed. Tables of occupation probabilities and single-particle matrix elements are provided to facilitate the comparison of future measurements with theoretical expectations.
144 citations
TL;DR: The results suggest that the dissimilar tumorigenic-enhancing abilities of BHT and phenobarbitone may result from differences in the effects of these agents on biochemical processes related to liver growth.
144 citations
TL;DR: A mechanism is proposed for the suppression of nitrate uptake rate by ammonium through feedback control of the nitrate permease system and/or the Nitrate reductase enzyme system, postulated to be regulated by the level of total amino acids in the cell.
Abstract: The effect of ambient ammonium concentration on the nitrate uptake rate of marine phytoplankton was investigated. These studies consisted of laboratory experiments using unialgal species and field experiments using natural phytoplankton communities. In laboratory experiments, ammonium suppressed the uptake rates of nitrate and nitrite. Approximately 30 min were required for ammonium to exhibit its fully inhibitory effect on nitrate uptake. At high ammonium concentration (>3 μg-at/l), a residual nitrate uptake rate of approximately 0.006 h-1 was observed. When the ambient ammonium concentration was reduced to a value less than 1 μg-at/l, the suppressed nitrate uptake rate subsequently attained a value comparable to that observed before the addition of ammonium. A range of 25 to 60% reduction in the nitrate uptake rate of natural phytoplankton communities was observed at ambient ammonium concentrations of ∼1.0 μg-at/l. A mechanism is proposed for the suppression of nitrate uptake rate by ammonium through feedback control of the nitrate permease system and/or the nitrate reductase enzyme system. The feedback control is postulated to be regulated by the level of total amino acids in the cell.
TL;DR: The role of pulsed spallation neutron sources for slow neutron spectroscopy is sketched in this paper, and the effect of moderator-reflectors, which enhance the slow neutron beam current at low energies, are examined.
TL;DR: In this article, a fully-consistent numerical-basis-set linear-combination-of-atomic-orbitals calculation of the electronic structure of Ti${\mathrm{S}}_{2}$ is reported using the method described previously.
Abstract: A fully-self-consistent numerical-basis-set linear-combination-of-atomic-orbitals calculation of the electronic structure of Ti${\mathrm{S}}_{2}$ is reported using the method described previously. The calculated band structure differs considerably from those previously obtained by non-self-consistent muffin-tin models. Comparison with experiment shows that the calculated optical properties for energies below 16 eV and the various characteristics of the valence and conduction bands agree very well with optical-absorption and electron-energy-loss data as well as with photoemission, x-ray absorption, and appearance-potential spectra. A small indirect gap (0.2-0.3 eV) occurs at the points $M$ and $L$ in the Brillouin zone with a larger direct gap (0.8 eV) at $\ensuremath{\Gamma}$. We suggest that the characteristic semi-metallic large $g$ value observed experimentally originates from a near coincidence of the band gap with the enhanced spin-orbit splitting which is consistent with the soft-x-ray data and our band model. The bonding mechanism in Ti${\mathrm{S}}_{2}$ is discussed in detail; it is shown by a direct calculation of the self-consistent charge density and the transverse effective charge that the system is predominantly covalent with small static ionic character and large dynamic ionicity. In contrast with muffin-tin $X\ensuremath{\alpha}$ models, the bonding is found to be largely due to Ti $4s4p$ to S $3p$ bonds and a much weaker Ti $3d$ to S $3p$ bond. The effects of muffin-tin approximation and self-consistency are discussed in detail. Extrapolation of these results to the case of Ti${\mathrm{Se}}_{2}$ is made and the possible origin of its charge-density wave is discussed.
TL;DR: In this paper, the current status of the theory of yield strength was assessed at a workshop at Argonne National Laboratory (ANL) from May 29 to June 1, 1976, where six half-day sessions were held, each concentrating on one problem area, which was reported on by one or two speakers.
TL;DR: No evidence for a direct role of deoxycholate in the pathogenesis of cholesterol cholelithiasis was obtained in these studies, but biliary bile acid composition and biliary lipid secretion did not change in any consistent manner.
TL;DR: Polarized spectra of evaporated thin films of glass have been recorded before and after annealing at the glass transition temperature and compared with the corresponding spectrum of the bulk glass as discussed by the authors.
Abstract: Polarized spectra of evaporated thin films of ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$ glass have been recorded before and after annealing at the glass transition temperature and compared with the corresponding spectrum of the bulk glass. The spectra of virgin films consist of several sharp molecular bands superposed on a networklike continuum which is characteristic of the bulk glass, whereas annealed films yield only the bulk glass spectrum albeit with some indication of residual nonstoichiometry. These results are direct evidence that irreversible thermostructural transformations (or equivalent photostructural transformations) in evaporated ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$ films proceed through polymerization of a metastable molecular glass as suggested by deNeufville, Moss, and Ovshinsky. The polarized Raman spectra of the vapors over ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$ liquid have been obtained and indicate the presence of serveral gaseous molecular species. The molecular constituency of the evaporated amorphous film is also complex but distinct from that of the vapor, an indication that deposition itself introduces some structural alterations.
TL;DR: In this paper, a self-consistent numerical basis set (non-muffin-tin) linear-combination-of-atomic-orbitals (LDF) method was used to model the ionic ionic solid LiF.
Abstract: The band structure, charge density, x-ray scattering factor (and their behavior under pressure), equilibrium lattice constant, and cohesive energy of the prototype ionic solid LiF were determined using our recently developed self-consistent numerical basis set (non-muffin-tin) linear-combination-of-atomic-orbitals method, within the local-density formalism (LDF). The details of the bonding and the effects of exchange and correlation on the electronic structure are discussed with reference to the conventional picture of ionic bonding. Remarkably good agreement is found with the observed data for the ground-state properties of the system. Contrary to the results of previous band studies, the conventional band-structure approach to excitation energies (i.e., identifying them with the band eigenvalue differences) is found to fail completely in accounting for the observed data in the entire x-ray and optical spectral region when fully self-consistent solutions of the LDF one-particle equation with no further approximation to the crystal potential are obtained. It is found that in the presence of some spatial localization of the initial or final crystal states, the spurious self-interaction terms, as well as the polarization and orbital relaxation self-energy effects are of a similar order of magnitude as the Koopmans'-like interband terms. In order to treat these effects within the LDF self-consistently, we describe the excitation processes as transitions involving point-defect-like states in the solid calculated by a supercell method in which the excitation energies are determined as total-energy differences between (separately calculated) excited- and ground-state configurations. The excited state is represented as a superlattice of locally excited sites using large (8-and 16-atom) unit cells, each containing a single excited site. We find, in the self-consistency limit, that a small but finite degree of spatial localization of the excited states exists even for valence excitations, inducing thereby self-interaction as well as self-energy relaxation and polarization effects. The LDF model is found to account very well for both interband and exciton transitions over the entire spectral region (12-695 eV) and to yield definite predictions regarding the exciton bandwidths and series limits.
TL;DR: In this article, the relativistic 4f-electron wave functions are more expanded in space, as a result of the core contraction, than the Hartree-Fock wave functions, and the net effect of the spin orbit and mass correction term on the scattering of neutrons, implicitly included in the relatvistic formulation of the scattering amplitude, is such that the neutron senses a current density more expanded than predicted by nonrelativistic calculations.
Abstract: Magnetic form factors have been obtained from Dirac-Fock calculations for all the rare-earth tripositive ions. In addition to using relativistic 4f wave functions, the coupling of the neutron magnetic moment to the current density has been treated consistently using a relativistic formulation for the scattering amplitude. For each rare-earth ion we evaluated the odd magnetic multipoles, of order less or equal to seven, which are needed for the evaluation of the magnetic scattering amplitude in most cases of experimental interest. We find that in all cases the magnetic form factor decreases faster with increasing scattering angle than predicted by nonrelativistic calculations. This is because (i) the relativistic 4f-electron wave functions are more expanded in space as a result of the relativistic core contraction than the Hartree-Fock wave functions and (ii) the net effect of the spin orbit and mass correction term on the scattering of neutrons, implicitly included in our relativistic formulation of the scattering amplitude, is such that the neutron senses a current density more expanded in space than predicted by nonrelativistic calculations. (AIP)
TL;DR: The melting, eutectic, peritectic, solidus, and liquidus temperatures in the system Zr-O have been measured directly by a simple optical pyrometric technique requiring only a few hundred milligrams of sample.
Abstract: The melting, eutectic, peritectic, solidus, and liquidus temperatures in the system Zr-O have been measured directly by a simple optical pyrometric technique requiring only a few hundred milligrams of sample. The saturation solubility of oxygen in α-Zr(s) between 1270° and 1980°C and the lower phase boundary of the ZrO2–α phase between 1900° and 2400°C have been measured by an isopiestic equilibration method. The oxygen solubility limit in α-Zr(s) agrees well with previous low-temperature studies and reaches a maximum solubility of 35°1 at.% O at the eutectic temperature, 2065°°5°C. The maximum melting temperature of α-Zr(ss) is 2130°°10°C and corresponds to a composition of 25°1 at.% O. Both of these temperatures are approximately 150° higher than previously reported. Liquidus compositions above the eutectic temperature were obtained via mass spectrometry from the kinetic behavior of the liquid solution-ZrO2–x(s) mixture as it approached equilibrium at 2125°°5°C. The lower phase boundary or solidus of the ZrO2–x phase departs appreciably from ideal stoichiometry above 1900°C and smoothly reaches its most reduced composition, 61 at.% (ZrO1.56), near 2300°C. The solidus is retrograde at higher temperatures. The melting temperature of the stoichiometric dioxide is 2710°°15°C.
TL;DR: In this article, a detailed description of an experiment which studies the interactions of muon-type neutrinos in hydrogen and deuterium is given, where the neutrino energy spectrum peaks at 0.5 GeV and has a tail extending to 6 GeV, and the shape and intensity of the flux is determined using measurements of pion yields from beryllium.
Abstract: This paper gives a detailed description of an experiment which studies the interactions of muon-type neutrinos in hydrogen and deuterium. The experiment was performed at the Zero Gradient Synchrotron using the wide-band neutrino beam incident on the Argonne 12-foot bubble chamber filled with hydrogen and deuterium. The neutrino energy spectrum peaks at 0.5 GeV and has a tail extending to 6 GeV. The shape and intensity of the flux is determined using measurements of pion yields from beryllium. The produced pions are focused by one or (for the latter part of the experiment) two magnetic horns. A total of 364000 pictures were taken with a hydrogen filling of the bubble chamber and 903 000 with a deuterium filling. The scanning and other analyses of the events are described. The most abundant reaction occurs off neutrons and is quasi-elastic scattering $\ensuremath{
u}d\ensuremath{\rightarrow}{\ensuremath{\mu}}^{\ensuremath{-}}p{p}_{s}$. The separation of these events from background channels is discussed. The total and differential cross sections are analyzed to obtain the axial-vector form factor of the nucleon. Our result, expressed in terms of a dipole form factor, gives an axial-vector mass of 0.95\ifmmode\pm\else\textpm\fi{}0.09 GeV. A comparison is made to previous measurements using neutrino beams, and also to determinations based upon threshold pion electroproduction experiments. In addition, the data are used to measure the weak vector form factor and so check the conserved-vector-current hypothesis.
TL;DR: In this article, the authors extended positive parity states of 11 B to the region of the giant E1 resonance with a complete non-spurious 1ℏ.ω basis.
TL;DR: Eddy-correlation measurements of the vertical flux of particles in the size range of 0.05-0.1 μm indicate that the deposition velocity at 5 m above a moderately rough surface varies from 1.0- 0.1 cm s −1 in light winds as discussed by the authors.
TL;DR: An algorithm which generates conjugate search directions and maintains finite termination, when applied to quadratic functions, without requiring that line searches be exact is developed.
Abstract: We develop an algorithm which generates conjugate search directions and maintains finite termination, when applied to quadratic functions, without requiring that line searches be exact The technique requiresO(n) storage, wheren is the dimension of the problem Results when the algorithm is applied to a number of standard test problems are included
TL;DR: The demonstration that large amounts of bile acid continue to be excreted during therapy suggests that interruption ofmore of the enterohepatic circulation continues and that deficiencies of the intraluminal phase may persist during enzyme therapy in this disease.
TL;DR: In this article, the authors derived the equations for steady-state nucleation from the rates of growth and decay of clusters with emphasis on a clear distinction between thermodynamic quantities and inherently kinetic quantities, and showed that the emission rates of molecules from embryos can be related to the equilibrium size distribution of clusters in a saturated vapor.
TL;DR: The reflectivities at 80 K of chalcopyrite semiconductors were measured in the energy range from 2 to 26 eV using sychrotron radiation in this paper.
Abstract: The reflectivities at 80 K of the chalcopyrite semiconductors CuGa${\mathrm{S}}_{2}$, CuAl${\mathrm{S}}_{2}$, CuIn${\mathrm{Se}}_{2}$, AgIn${\mathrm{Se}}_{2}$, ZnGe${\mathrm{P}}_{2}$, and ZnGe${\mathrm{As}}_{2}$ were measured in the energy range from 2 to 26 eV using sychrotron radiation. Occupied and unoccupied electronic states are described with the aid of the sharp reflectivity features from $d$ levels and of the electronic spectrum from an ESCA spectrometer.
TL;DR: In this article, the second-order decay rate of the HO2 signal was found to increase by up to a factor of ⋍2.5 in the presence of small amounts of added H2O or NH3.
Abstract: Electron pulse radiolysis at ⋍298°K of 2 atm H2 containing 5 torr O2 produces HO2 free radical whose disappearance by reaction (1), HO2 + HO2 →H2O2 + O2, is monitored by kinetic spectrophotometry at 230.5 nm. Using a literature value for the HO2 absorption cross section, the values k1 = 2.5×10−12 cm3/molec·sec, which is in reasonable agreement with two earlier studies, and G(H) G(HO2) ⋍13 are obtained. In the presence of small amounts of added H2O or NH3, the observed second-order decay rate of the HO2 signal is found to increase by up to a factor of ⋍2.5. A proposed kinetic model quantitatively explains these data in terms of the formation of previously unpostulated 1:1 complexes, HO2 + H2O ⇋ HO2·H2O (4a) and HO2 + NH3⇋ HO2·NH3 (4b), which are more reactive than uncomplexed HO2 toward a second uncomplexed HO2 radical. The following equilibrium constants, which agree with independent theoretical calculations on these complexes, are derived from the data: 2×10−20≲K4a≲6.3 × 10−19 cm3/molec at 295°K and K4b = 3.4 × 10−18 cm3/molec at 298°K. Several deuterium isotope effects are also reported, including kH/kD = 2.8 for reaction (1). The atmospheric significance of these results is pointed out.
TL;DR: The composition and sequence of this region are similar to those of the short-lived hydrophobic amino-terminal precursor segments of certain other proteins, especially myeloma immunoglobulin light chains and pancreatic zymogens.
TL;DR: In this paper, the normal state electrical resistances of several high-layer superconductors were measured and it was shown that the resistances are linear functions of the temperature from 20 K to 40 K.
Abstract: We report new measurements of the normal-state electrical resistances of several high-${T}_{c}$ (\ensuremath{\sim} 20 K) $A\ensuremath{-}15$ structure superconductors. It is found that the resistances are linear functions of ${T}^{2}$ from ${T}_{c}$ to 40 K. Analysis of available lattice heat-capacity data on the same materials shows that it also varies as ${T}^{2}$ over the same temperature interval. These observations suggest that the ${T}^{2}$ resistivity is due to electron-phonon scattering. This interpretation is supported by the results of a model calculation for the temperature dependence of the resistivity and the lattice-heat capacity of ${\mathrm{Nb}}_{3}$Sn.
TL;DR: 1 (t‐Butyl‐amino‐3‐ol‐2‐propyl) oximino‐9 fluorene is a new β2‐adrenoceptor blocking agent with a pA2 of 9.23 ± 0.25 on isolated trachea.
Abstract: 1 (t-Butyl-amino-3-ol-2-propyl) oximino-9 fluorene is a new beta2-adrenoceptor blocking agent with a pA2 of 9.23+/-0.25 on isolated trachea. 2 It provokes hypertension in normotensive rats and does not prevent arterial hypertension in SHR rats, although it does prevent the renin secretion normally induced by isoprenaline infusion.