Showing papers by "Lawrence Berkeley National Laboratory published in 1980"
TL;DR: An exact stochastic simulation of the Schroedinger equation for charged Bosons and Fermions was used to calculate the correlation energies, to locate the transitions to their respective crystal phases at zero temperature within 10%, and to establish the stability at intermediate densities of a ferromagnetic fluid of electrons.
Abstract: An exact stochastic simulation of the Schroedinger equation for charged Bosons and Fermions was used to calculate the correlation energies, to locate the transitions to their respective crystal phases at zero temperature within 10%, and to establish the stability at intermediate densities of a ferromagnetic fluid of electrons.
10,743 citations
TL;DR: A hypothesis is suggested which accounts for the extinctions and the iridium observations, and the chemical composition of the boundary clay, which is thought to come from the stratospheric dust, is markedly different from that of clay mixed with the Cretaceous and Tertiary limestones, which are chemically similar to each other.
Abstract: Direct physical evidence is presented for an unusual event at exactly the time of extinctions in the planktonic realm. Deep-sea limestones exposed in Italy, Denmark, and New Zealand indicate iridium increases of about 30, 160, and 20 times, respectively, above the background level at precisely the time of the Cretaceous-Tertiary extinctions, 65 million years ago. Reasons are given that this iridium is of extraterrestrial origin, but did not come from a nearby supernova. A hypothesis is set forth which accounts for the extinctions and the iridium observations. One prediction of this hypothesis is verified, that the chemical composition of the boundary clay, which is thought to come from the stratospheric dust, is markedly different from that of clay mixed with the chemically similar Cretaceous and Tertiary limestones.
3,357 citations
TL;DR: In this article, a special emphasis is put on quadrupoles because of their frequent use and because the aperture fields achievable (1.2-1.4 T) are rather large.
1,470 citations
TL;DR: In this paper, a laser-Doppler velocimeter (LDV) study of velocity profiles in the laminar boundary layer adjacent to a heated flat plate revealed that the seed particles used for the LDV measurements were driven away from the plate surface by thermophoretic forces, causing a particle free region within the boundary layer of approximately one half the boundary-layer thickness.
Abstract: A laser-Doppler velocimeter (LDV) study of velocity profiles in the laminar boundary layer adjacent to a heated flat plate revealed that the seed particles used for the LDV measurements were driven away from the plate surface by thermophoretic forces, causing a particle-free region within the boundary layer of approximately one half the boundary-layer thickness. Measurements of the thickness of this region were compared with particle trajectories calculated according to several theories for the thermophoretic force. It was found that the theory of Brock, with an improved value for the thermal slip coefficient, gave the best agreement with experiment for low Knudsen numbers, λ/R = O(10−1), where λ is the mean free path and R the particle radius.Data obtained by other experimenters over a wider range of Knudsen numbers are compared, and a fitting formula for the thermophoretic force useful over the entire range 0 [les ] λ/R [les ] ∞ is proposed which agrees within 20% or less with the majority of the available data.
1,372 citations
194 citations
TL;DR: The geometric properties of polygranular microstructures of the Johnson-Mehl cellular types have been studied through computer simulation as mentioned in this paper, and their geometric features have been characterized through a combination of analytic and computer simulation studies.
159 citations
TL;DR: The spring freshet increases density stratification in Chesapeake Bay and minimizes oxygen transfer from the surface to the deep layer so that waters below 10 m depth experience oxygen depletion which may lead to anoxia during June to September.
Abstract: The spring freshet increases density stratification in Chesapeake Bay and minimizes oxygen transfer from the surface to the deep layer so that waters below 10 m depth experience oxygen depletion which may lead to anoxia during June to September. Respiration in the water of the deep layer is the major factor contributing to oxygen depletion. Benthic respiration seems secondary. Organic matter from the previous year which has settled into the deep layer during winter provides most of the oxygen demand but some new production in the surface layer may sink and thus supplement the organic matter accumulated in the deep layer.
154 citations
TL;DR: In this article, the He(I) and He(II) spectra of some decamethylmetallocenes {M(η-C5Me5)2}, where Mg, V, Cr, Mn, Fe, Co, Ni and Ru, were reported.
145 citations
TL;DR: In this paper, the theoretical basis for a technique to fabricate nonaxisymmetric mirrors is developed for a mirror blank that would have the effect of elastically deforming a desired surface into a sphere, and upon release of the applied stress, the spherical surface deforms into the desired one.
Abstract: The theoretical basis is developed for a technique to fabricate nonaxisymmetric mirrors. Stresses are applied to a mirror blank that would have the effect of elastically deforming a desired surface into a sphere. A sphere is then polished into the blank, and upon release of the applied stress, the spherical surface deforms into the desired one. The method can be applied iteratively, so arbitrary accuracy should be possible. Calculations of the stresses and deformations are carried out in detail for an off-axis section of a paraboloid. For a very general class of surfaces, it is sufficient to only impose appropriate stresses at the edge of the blank plus a uniform pressure on the back.
126 citations
TL;DR: In this paper, the electronic structure of the reconstructed Si(001) surface is studied using the self-consistent pseudopotential method. And the authors confirm that the asymmetric-dimer model results in a semiconducting surface in agreement with experiment.
Abstract: The electronic structure of the (2 \ifmmode\times\else\texttimes\fi{} 1) reconstructed Si(001) surface is studied using the self-consistent pseudopotential method. The calculation is based on the asymmetric-dimer model recently proposed by Chadi using the tight-binding method. The present calculation confirms that the asymmetric-dimer model results in a semiconducting surface in agreement with experiment. The density of states is calculated, and it compares favorably with experiment. A study of the charge distributions and the energy dispersions of surface states allows us to determine the character of individual surface states. By doing comparative calculations of the total energy of the symmetric and asymmetric dimers, we conclude that the latter is more stable because of exchange-correlation energy contributions.
124 citations
TL;DR: In this paper, some design guidelines for improving strength-toughness combinations in medium car-bon structural steels are critically reviewed, and quaternary alloy development based on Fe/Cr/C steels with Mn or Ni additions for improved properties is described.
Abstract: Some design guidelines for improving strength-toughness combinations in medium car-bon structural steels are critically reviewed. From this, quaternary alloy development based on Fe/Cr/C steels with Mn or Ni additions for improved properties is described. Transmission electron microscopy and X-ray analysis reveal increasing amounts of retained austenite in these alloys with Mn content up to 2 wt pct and Ni additions at 5 wt pct after quenching from 1100°C. A corresponding improvement in toughness properties is also found. Grain refining results in a further increase in the amount of retained austenite. In addition, the excellent combinations of strength and toughness in these quaternary alloys are attributed to the production of dislocated lath martensite from a homogeneous austenite phase free from undissolved alloy carbides. The question of thermal instability of retained austenite following tempering is considered in detail and it is shown that the decomposition of retained austenite is closely related to the ease of nucleation and growth of cementite. Thus, graphitizing alloying elements such as Ni are beneficial in postponing the decomposition of retained austenite.
TL;DR: In this article, the Enzyme and Microbial Technology FERMENTATION OF PENTOSE SUGARS TO ETHANOL and other NEUTRAL PRODUCTS by MICROORGANISMS S. L. Rosenberg and S. S. Rosenberg RECEIVED LAWRENCE BERKELEY LABORATORY lARclt I980 LIBRARY ANL DOCUMENTS SECTIO*» January 1980 Two-WEEK LOAN COPY This is a Library Circulating Copy which may be borrowed for two weeks.
TL;DR: In this article, the first non-trivial QCD corrections to the quark-quark scattering process which contributes to the production of hadrons at large p T in hadron-hadron collisions were computed.
TL;DR: In this article, a model for relativistic nuclear collisions is studied on the basis of a conventional multiple-collision model, where the input is the differential cross sections for kaon production in elementary baryon-baryon collisions, estimated in a simple model.
TL;DR: A peak in the pK-+ and pK+- invariant mass spectra at 2.2850 is observed in this article, which is associated with the lowest lying charmed baryon (c).
Abstract: A peak in the pK-+ and p»K+- invariant-mass spectra at 2.2850.006 GeV/c2 is observed, which is associated with the lowest-lying charmed baryon (c). A cross section times branching ratio of 0.0370.012 nb at Ec.m.=5.2 GeV is measured with a substantial fraction of the events produced with an equal recoiling mass. New measurements of inclusive p and cross sections are also presented, allowing an estimate of the branching ratio B(c+pK-+)=0.0220.010. © 1980 The American Physical Society.
TL;DR: It is suggested that the patient had a primary neuronal tumor, whose neurosecretory activity promoted the development of the growth hormone secreting pituitary adenoma causing acromegaly.
Abstract: A hypothalamic neuronal hamartoma associated with a sparsely granulated growth hormone cell adenoma of the pituitary and acromegaly is reported. It is suggested that the patient had a primary neuronal tumor, whose neurosecretory activity promoted the development of the growth hormone secreting pituitary adenoma causing acromegaly.
TL;DR: Under the conditions of this study in which diet and weight were controlled, exercise conditioning did not elevate HDL-cholesterol levels, and data are consistent with the concept that exercise conditioning may affect HDL via alterations in body weight.
TL;DR: In this article, an attempt was made to detect the growing chains by their reaction with an olefin, an approach suggested by recent experiments with metal complexes containing alkylidene or alkyls ligands.
TL;DR: Proton emission in relativistic nuclear collisions is examined for events of low and high multiplicity, corresponding to large and small impact parameters in this paper, where the authors show that central collisions of equal-size nuclei are dominated by the formation and decay of a fireball system.
Abstract: Proton emission in relativistic nuclear collisions is examined for events of low and high multiplicity, corresponding to large and small impact parameters. Peripheral reactions exhibit distributions of protons in agreement with spectator-participant decay modes. Central collisions of equal-size nuclei are dominated by the formation and decay of a fireball system. Central collisions of light projectiles with heavy targets exhibit an enhancement in sideward emission which is predicted by recent hydrodynamical calculations.
TL;DR: In this paper, a search for nu-bar/sub e/ from multiplicative but not additive muon conservation was performed on a six-ton Cherenkov counter filled with H/sub 2/O (D/sub O) to look for the branching ratio.
Abstract: This paper reports on a search for nu-bar/sub e/ from ..mu../sup +/ ..-->.. e/sup +/nu-bar/sub e/..nu../sub ..mu../, allowed by multiplicative but not additive muon conservation, and for ..nu../sub e/ from ..mu../sup +/ ..-->.. e/sup +/..nu../sub e/nu-bar/sub ..mu../, allowed by both. Neutrinos from the Clinton P. Anderson Meson Physics Facility have been used, together with a six-ton Cherenkov counter filled with H/sub 2/O (D/sub 2/O) to look for ..nu../sub p/p ..-->.. ne/sup +/(..nu../sub e/d ..-->.. ppe/sup -/). The branching ratio (..mu../sup +/ ..-->.. e/sup +/..nu../sub e/..nu../sub ..mu../)/..mu../sup +/ ..-->.. all) =-0.001 +- 0.040 is in excellent agreement with the additive law. The cross section .. ppe/sup -/) >= (0.52 +- 0.18) x 10/sup -4/ cm/sup 2/ agrees with theory.
TL;DR: In this paper, a thermal treatment which combines grain refinement with an intercritical temper (the 2BT treatment) was used to achieve a promising combination of strength and toughness in a nickel-free ferritic steel of nominal composition Fe-5Mn-0.2Mo- 0.04C at temperatures as low as -196 °C.
Abstract: It is shown that a thermal treatment which combines grain refinement with an intercritical temper (the 2BT treatment) may be used to achieve a promising combination of strength and toughness in a nickel-free ferritic steel of nominal composition Fe-5Mn-0.2Mo-0.04C at temperatures as low as -196 °C. The properties achieved are attributed to a symbiotic influence between the grain refinement treatment and the introduction of thermally stable retained austenite during intercritical tempering, a conclusion supported by a comparison of the results to those obtained with simpler heat treatments. The influence of carbon, manganese, and nickel additions to the base compositions are studied. An increase in carbon content above 0.04 wt pct causes a deterioration in toughness, as does an increase in manganese to 8 wt pct. An addition of 1 to 3 wt pct nickel is beneficial giving an increase in alloy strength at -196 °C without loss of toughness.
TL;DR: In this article, the electronic structure of interfaces, in which one of the constituents is a semiconductor, is discussed, and a discussion of clean-surface properties of semiconductors is given as the background, since many concepts developed for the "semiconductor-vacuum interface" are needed to describe the semiconductor-solid cases.
Abstract: Publisher Summary This chapter focuses on the electronic structure of interfaces, in which one of the constituents is a semiconductor. Emphasis is placed on the studies of semiconductor-metal and semiconductor-semiconductor interfaces. Some discussion of the clean-surface properties of semiconductors is given as the background, since many concepts developed for the “semiconductor-vacuum interface” are needed to describe the semiconductor-solid cases. The purpose of the discussion on clean surfaces was to present a background for the description of the interface research that followed, and hence in no way reflected the vast amount of effort being applied in this area. The interdependence of the study of clean surfaces and solid-solid interfaces is large, and it is important for the researchers in these areas to be aware of developments in both the areas. The current calculations on clean surfaces have focused on the properties of surface states. These states have been observed experimentally and their properties have been studied for a number of surfaces.
TL;DR: In this paper, the authors studied the oxidation of the Rh(111) surface using low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and thermal desorption mass spectrograph (TDS).
TL;DR: In this article, the static properties of multichain systems are investigated by a "reptation" Monte Carlo algorithm, where all beads interact via a repulsive (shifted) Lennard-Jones potential.
Abstract: The static properties of continuum, multichain systems are investigated by a ’’reptation’’ Monte Carlo algorithm. All beads interact via a repulsive (shifted) Lennard‐Jones potential. In addition, nearest neighbors along chains are linked by a quasiharmonic potential which permits limited pair extensions. Chain lengths of 5, 10, 20, 32, 50, and 70 beads have been studied. Studies at densities of 0.1, 0.3, and 0.5 demonstrate that chain dimensions are compressed as the concentration is increased. Both the mean square end‐to‐end distance, 〈R2〉, and the mean square radius of gyration, 〈S2〉, have a power law dependence upon l‐1, the number of bonds, with exponent approximately 1.16 for ρ=0.1 and 1.07 for ρ=0.3 and 0.5. 〈R2〉 and 〈S2〉 scale with density as ρ−γ where γ∼−0.22±0.02 for long chains, in reasonable agreement with the scaling prediction of −0.25. The asphericity ratios, the pair correlation functions of the center of masses, and the extent of chain overlaps indicate the nonideal behavior of these systems.
TL;DR: In this article, a general synthesis and preliminary physical and chemical properties of biscarbyne clusters were described by a conceptually most simple route, the direct cleavage of alkynes.
Abstract: We describe a general synthesis and preliminary physical and chemical properties of biscarbyne clusters prepared by a conceptually most simple route, the direct cleavage of alkynes.
TL;DR: In this article, absorption and extended-fine-structure studies on the carbon $K$ edge in micro-crystalline, poly-crystaline, and oriented crystalline (monochromator) graphite were performed.
Abstract: We report absorption and extended-fine-structure studies on the carbon $K$ edge in microcrystalline, polycrystalline, and oriented crystalline (monochromator) graphite. On the basis of a density-of-states analysis, strong excitonic effects about the core hole are inferred. The fine structure at the absorption edge is found to differ for the three materials. This is explained by the orientational dependence of the polarization selection rules for electric dipole transitions from an $s$ core to $\ensuremath{\sigma}$ and $\ensuremath{\pi}$ conduction-band states. The extended x-ray fine structure (EXAFS) above the edge exhibits similar oscillations for the bulk crystalline samples (polycrystalline and monochromator graphite), but considerably weaker structure is observed for the microcrystalline sample. A Fourier analysis of the oscillations yields the nearest-neighbor shell separations. Finally, it is shown that the intensity modulations caused by carbon contamination on optical Au and Pt mirror surfaces that are exposed to high-intensity synchrotron radiation closely resemble those above the C $K$ edge in bulk crystalline graphite. This indicates the formation of graphitic overlayers on such mirrors even under ultrahigh-vacuum (1 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$ Torr) conditions. These findings furthermore demonstrate the feasibility of EXAFS studies of adsorbates on surfaces by monitoring the (totally) reflected radiation off the substrate.
TL;DR: In this paper, total and annihilation cross sections for p-barp and p-bard have been measured over the momentum range 355-1066 MeV/c at closely spaced momenta and with good energy resolution.
Abstract: Total and annihilation cross sections for p-barp and p-bard have been measured over the momentum range 355--1066 MeV/c at closely spaced momenta and with good energy resolution. No evidence is seen for the narrow structure reported by other experiments in the vicinity of 500 MeV/c. The present measurements indicate a broader enhancement in this region, which, if interpreted as a resonance, would have a height of approx. 3 mb and a width of approx. 20 MeV. This structure appears only in the p-barp data.
TL;DR: In this paper, the chloride complexation of element 104 and compared it to that of the actinides and Hf, Cm, and Fm was investigated and the results showed that in 12 M HCl solutions, the chloride complexes with element 104 were clearly stronger than those of the trivalent actinide and is quite similar to Hf.
TL;DR: The first observation of far-infrared molecular line emission from the interstellar medium is reported in this paper, which implies that the region is optically thin in these lines and that much of the carbon is in the form of CO.
Abstract: The first observation of far-infrared molecular line emission from the interstellar medium is reported. Strong emission from the J = 21-20 and J = 22-21 rotational transitions of carbon monoxide was detected in the Kleinmann-Low/shocked H2 region of the Orion Molecular Cloud. The results imply that the region is optically thin in these lines and that much of the carbon is in the form of CO. This work also represents the first use of an antimony-doped germanium photoconductor in an astronomical application.