Showing papers by "Lawrence Berkeley National Laboratory published in 1973"
TL;DR: A simple and convenient approximation for the multiphoton energy transfer processes which accompany the scattering of a charged particle by a scattering potential in the presence of a strong external electromagnetic field was obtained in this article.
Abstract: A simple and convenient approximation is obtained for the multiphoton energy-transfer processes which accompany the scattering of a charged particle by a scattering potential in the presence of a strong external electromagnetic field. It is expressed in terms of the differential elastic-scattering cross section combined with known functions, and is valid when the scattering potential is weak or when the wave frequency is small. A detailed form of the classical limit is obtained.
499 citations
TL;DR: Evidence indicates that cycloheximide impairs acquisition and anisomycin is an effective, nontoxic inhibitor of cerebral protein synthesis and as amnestic agents in mice.
211 citations
01 Jan 1973
TL;DR: In this paper, phase equilibria were studied for ternary systems of Zr, C, and the transition metals Re, Ru, Os, Rh, Ir, Pd, Pt, Ag, and Au.
Abstract: The Engel theory of metals predicts unusually high thermodynamic stability for certain classes of alloys of transition metals for which generalized Lewis-acid-base interactions are possible. To test these predictions, phase equilibria were studied for ternary systems of Zr, C, and the transition metals Re, Ru, Os, Rh, Ir, Pd, Pt, Ag, and Au. Similar literature data for Nb, Ta, Hf, Th, Y, Ce, Er, and Pu with Re, Ru, Rh, Ir, Pt, and Au were evaluated. Thermodynamic data for the carbides of Zr, Hf, Th, Nb, Ta, U, and Y were critically evaluated, tabulated for 1200 to 2300 K, and used to fix the Gibbs energies of formation in kcal/g-atom of alloy, or their limits, for the binary phases of the above metals. In addition, for Zr, activity coefficients and excess Gibbs energies are tabulated. The predicted high stabilities for alloys of Rh, Ir, Pd, and Pt are confirmed with excess Gibbs energies ranging to —100 kcal/g-atom and activity coefficients as low as 10-12 for zirconium or hafnium in dilute solutions of platinum at 1800 K. Some of the properties of these unusually stable compounds have been measured.
164 citations
TL;DR: By using the techniques of wavelength-modulation spectroscopy, this paper measured the reflectivity of PbTe, PbSe, and PbS from 1.5 to 6 eV and independently calculated the band structure, frequency-dependent dielectric function, density of states, and derivative reflectivity spectrum for all three compounds.
Abstract: By using the techniques of wavelength-modulation spectroscopy, we have measured the reflectivity $R(\ensuremath{\omega})$ and the derivative of the reflectivity, $\frac{(\frac{1}{R})dR}{d\ensuremath{\omega}}$, for PbTe, PbSe, and PbS from 1.5 to 6 eV. We have independently calculated the band structure, frequency-dependent dielectric function, density of states, and derivative reflectivity spectrum for all three compounds by the empirical pseudopotential method.
148 citations
TL;DR: In this article, it was shown that molecular ordering in the isotropic phase of MBBA can be induced by an intense laser field and the ordering relaxation time as a function of temperature.
Abstract: We have shown by measuring the field-induced refractive index that molecular ordering in the isotropic phase of $p$-methoxy benzylidene $p\ensuremath{-}n$-butylaniline (MBBA) can be induced by an intense laser field. We have also measured directly the ordering relaxation time as a function of temperature. The results are compared with the predictions of the Landau---de Gennes model.
133 citations
TL;DR: In this article, the authors used Rayleigh interference optics to measure the diffusion coefficient of binary solutions in a vertical cell closed at the ends (restricted diffusion) of isothermal diffusion.
Abstract: Diffusion coefficients of binary solutions can be measured accurately by observation at long times of isothermal diffusion in a vertical cell closed at the ends (restricted diffusion). The present analysis, which accounts for the effects of solvent flux and variable solution properties, demonstrates that the experiment yields a well-defined, differential diffusion coefficient, even in concentrated solutions.
Observation is effected by Rayleigh interference optics, and results for aqueous potassium chloride solutions confirm the accuracy of the method.
121 citations
TL;DR: In this paper, the valence bands of crystalline and amorphous As, Sb, and Bi have been measured and compared with band-structure calculations for the crystalline materials.
Abstract: X-ray photoelectron spectra (XPS) of the valence bands of crystalline and amorphous As, Sb, and Bi have been measured The results are compared with band-structure calculations for the crystalline materials A splitting, $\ensuremath{\Delta}E$, of the "$s$-like" peak for the crystalline phase disappears in the amorphous phase and the "$p$-like" peak is shifted towards higher energies This similarity to tetrahedrally coordinated covalent semiconductors is explained by describing the semimetals as layers of distorted covalently bonded hexagonal rings This generalizes the "even-odd" ring effect previously observed in group-IV semiconductors to the $A7$ lattice of As, Sb, and Bi The relation of $\ensuremath{\Delta}E$ to the interatomic distance is described by a universal curve, which applies to the group-V semimetals as well as group-IV semiconductors
107 citations
TL;DR: In this paper, the LBL-SLAC 82-in. hydrogen bubble chamber was exposed to a linearly polarized photon beam at 2.8, 4.7, and 9.3 GeV.
Abstract: We present results on vector-meson photoproduction via $\ensuremath{\gamma}p\ensuremath{\rightarrow}\mathrm{Vp}$ in the LBL-SLAC 82-in. hydrogen bubble chamber exposed to a linearly polarized photon beam at 2.8, 4.7, and 9.3 GeV. We find ${\ensuremath{\rho}}^{0}$ production to have the characteristics of a diffractive process, i.e., a cross section decreasing slowly with energy and a differential cross section with slope of \ensuremath{\sim} 6.5 ${\mathrm{GeV}}^{\ensuremath{-}2}$. Within errors the ${\ensuremath{\rho}}^{0}$ production amplitudes are entirely due to natural-parity exchange. $s$-channel helicity is conserved to a high degree in the $\ensuremath{\gamma}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}$ transition. We find evidence for small helicity-flip amplitudes for $\ensuremath{\pi}\ensuremath{\pi}$ pairs in the ${\ensuremath{\rho}}^{0}$ region. Photoproduction of $\ensuremath{\omega}$ mesons is separated into its natural- (${\ensuremath{\sigma}}^{N}$) and unnatural- (${\ensuremath{\sigma}}^{U}$) parity-exchange contributions. The ${E}_{\ensuremath{\gamma}}$ and $t$ dependence and the spin density matrix of the unnatural-parity-exchange contribution are consistent with a one-pion-exchange process. The natural-parity-exchange part has characteristics similar to ${\ensuremath{\rho}}^{0}$ production. At 9.3 GeV the ratio of $\ensuremath{\sigma}({\ensuremath{\rho}}^{0})$ to ${\ensuremath{\sigma}}^{N}(\ensuremath{\omega})$ is \ensuremath{\sim} 7. The slope of the $\ensuremath{\varphi}$ differential cross section is \ensuremath{\sim} 4.5 ${\mathrm{GeV}}^{\ensuremath{-}2}$, smaller than that of ${\ensuremath{\rho}}^{0}$ and $\ensuremath{\omega}$ production. Natural-parity exchange is the main contributor to $\ensuremath{\varphi}$ production. No evidence for higher-mass vector mesons is found in $\ensuremath{\pi}\ensuremath{\pi}$, $\ensuremath{\pi}\ensuremath{\pi}\ensuremath{\pi}$, or $K\overline{K}$ final states. The $s$ and $t$ dependences of Compton scattering as calculated from $\ensuremath{\rho}$, $\ensuremath{\omega}$, and $\ensuremath{\varphi}$ photoproduction using vector-meson dominance agree with experiment, but the predicted Compton cross section is too small by a factor of 2.
103 citations
TL;DR: In this paper, a short-range disorder model was proposed to explain both the amorphous density of states and the amomorphous ∆-epsilon spectrum of the diamond, wurtzite, Si-III (BC-8) and geodesic structures.
Abstract: We present calculations of the band structures and the imaginary part of the dielectric function ${\ensuremath{\epsilon}}_{2}$ as a function of energy for Ge and Si in the diamond, wurtzite, Si-III (BC-8) and Ge-III (ST-12) structures using the empirical pseudopotential method. In particular we have obtained the symmetries of wave functions along important symmetry directions and identified the major contributions to the optical structure. A further study is made into the optical properties of amorphous Ge and Si using our short-range-disorder model. We find that, unlike long-range-disorder models, short-range disorder can explain both the amorphous density of states and the amorphous ${\ensuremath{\epsilon}}_{2}$. In particular we find that the ${\ensuremath{\epsilon}}_{2}$ spectrum has the same form as an averaged matrix element as a function of frequency.
72 citations
TL;DR: In the absence of chemical reactions with the substrate, the degree of ordering depends on the heats of adsorption, Δ H ads, and the activation energies for surface diffusion, Δ E D ∗ as mentioned in this paper.
65 citations
TL;DR: In this article, the potential energy curves for the 1 Σg+, 3 Σu+, and 5 ǫ+ states which arise from two triplet metastable helium atoms (1s 2s 3S) have been calculated by a large configuration interaction expansion.
Abstract: Potential energy curves for the 1 Σg+, 3 Σu+, and 5 Σg+ states which arise from two triplet metastable helium atoms (1s 2s 3S) have been calculated by a large configuration interaction expansion. From the potential curves for the 1 Σg+ and 3 Σu+ autoionizing states, cross section for Penning and associative ionization have been calculated; the total ionization cross section for thermal energy (0.026 eV) collisions, for example, is computed to be 94 A2. In this low energy region the orbiting model is seen to be adequate for determining the total ionization cross section, but not the more specific cross sections.
TL;DR: In this paper, the rotary echoes and rotary echo trains have been detected for molecules in their excited triplet states by monitoring the microwave-induced modulation of the phosphorescence, and the results suggest that nuclear and electron spins in ground and excited states, acoustic phenomena in molecular solids, energy transfer, spin exchange, nuclear polarization, and a wide variety of additional processes can be optically detected.
Abstract: Electron spin locking, rotary echoes, and rotary echo trains have been detected for molecules in their excited triplet states by monitoring the microwave-induced modulation of the phosphorescence. The preliminary results of these studies suggest that nuclear and electron spins in ground and excited states, acoustic phenomena in molecular solids, energy transfer, spin-exchange, nuclear polarization, and a wide variety of additional processes can be optically detected, measuring as few as ${10}^{4}$ spins.
TL;DR: In this paper, the resonance enhancement of five Raman lines of Cu 2 O has been measured in the vicinity of the blue and indigo excitons, and the experimental results show qualitative agreement with the theoretical predictions.
TL;DR: Results indicate that the major, if not the sole, morphine degradative pathway involves an initial demethylation to normorphine, which is subsequently degraded to non-alkaloidal metabolites.
TL;DR: In this article, various modifications to the electromagnetic delay lines used for wire chamber readout are described, which consist of changing the cross-section of the lines, decreasing the eddy current losses, the dielectric losses, and increasing the characteristic impedance.
TL;DR: The LBL SuperHilac as discussed by the authors was used as an injector for the LBL Bevatron to produce high energy, high intensity beams of a variety of heavy-ions.
Abstract: An economical means for the production of high energy, high intensity beams of a variety of heavy-ions is to utilize the existing LBL SuperHilac as an injector for the existing LBL Bevatron. Particle energies from 0.25 to 2.6 GeV/nucleon will be realized. The description of this facility, which will be in operation in late 1973, includes the general arrangements, the modest changes to each accelerator, beam transport line design, and a new bio-medical experimental area.
TL;DR: A new relatively long-lived isotope of element 102 has been produced through the bombardment of 248 Cm with 18 O ions at both Oak Ridge and Berkeley as discussed by the authors, and a total half-life of 58 ± 5 min was computed from the combined data of both laboratories.
TL;DR: In this article, a low-frequency intermolecular Raman mode at ∼ 24 cm−1 was observed in the solid phase of two related smectic A compounds.
TL;DR: In this paper, the forward angle elastic scattering may be described by strongly absorbing potentials and the backward rise of the cross sections in both the elastic and inelastic transitions can be explained by a four nucleon transfer12C(16O,12C)16O.
Abstract: Angular distributions of the reactions12C(16O,16O)12C and12C(16O,12C)16O have been measured in the angular range of θ
CM
=10 °–60 ° at 65 and 80 MeV to ground states and excited states of both final nuclei. An optical model withl-dependent imaginary potential gives no consistent description of the elastic scattering data. It is shown, however, that the forward angle elastic scattering may be described by strongly absorbing potentials and that the backward rise of the cross sections in both the elastic and inelastic transitions can be explained by a four nucleon transfer12C(16O,12C)16O.
TL;DR: In this article, the effect of non-axisymmetric perturbations on the magnetic surfaces of a levitron is investigated and a Hamiltonian theory is developed for predicting the formation of both primary and secondary magnetic islands for the main resonances.
Abstract: The effect of non-axisymmetric perturbations on the magnetic surfaces of a levitron is investigated. A Hamiltonian theory is developed for predicting the formation of both primary and secondary magnetic islands for the main resonances. Numerical calculations are made for a range of levitron parameters and compared with results of the Hamiltonian theory. Good agreement is obtained both for island width and for local rotational transform of the islands. A simple criterion for island destruction and the consequent stochasticity of the field lines agrees well with numerical results. A ring tilt of 0.5 degree is found to destroy the magnetic surfaces in the neighbourhood of the main resonances (i = ?, 2?).
TL;DR: In this paper, the authors calculated the solar intensity as a function of wavelength and the instantaneous rates (molecules cm−3 sec−1) for each Chapman reaction and for each of several reactions of the oxides of nitrogen.
Abstract: Starting with the average actual distribution of ozone (Dutsch [15]) and temperature in the stratosphere, we have calculated the solar intensity as a function of wavelength and the instantaneous rates (molecules cm−3 sec−1) for each Chapman reaction and for each of several reactions of the oxides of nitrogen. The calculation is similar to that ofBrewer andWilson [5]. These reaction rates were calculated independently in each volume element in spherical polar coordinates defined by ΔR=1 km from zero to 50, δϑ=5° latitude, and δo=15° longitude (thus including day and night conditions). Calculations were made for two times: summer-winter (January 15) and spring-fall (March 22). As input data we take observed solar intensities (Ackerman [1]) and observed, critically evaluated. constants for elementary chemical and photochemical reactions; no adjustable parameters are employed. (These are not ‘photochemical equilibrium’ calculations.) According to the Chapman model, the instantaneous, integrated, world-wide rate of formation of ozone from sunlight is about five times faster than the rate of ozone destruction, and locally (lower tropical stratosphere) the rate of ozone formation exceeds the rate of destruction by a factors as great as 1000. The global rates of increase of ozone are more than 50 times faster thanBrewer andWilson's [5] estimate of the average annual transfer rate of ozone to the troposphere. The rate constants of the Chapman reactions are believed to be well-enough known that it is highly improbable that these discrepancies are, due to erroneous rate constants. It is concluded that something else besides neutral oxygen species is very important in stratospheric ozone photochemistry. The inclusion of a uniform concentration of the oxides of nitrogen (NOx as, NO and NO2) averaging 6.6×10−9 mole fraction gives a balance between global ozone formation and destruction rates. The inclusion of a uniform mole fraction of NOx at 28×10−9 also gives a global balance. These calculations support the hypethesis (Crutzen [10],Johnston [24]) that the oxides of nitrogen are the most important factor in the global, natural ozone balance. Several authors have recently evaluated the natural source strength of NOx in the stratosphere; the projected fleets of supersonic transports would constitute an artificial source of NOx about equal to the natural value, thus promising more or less to double an active natural stratospheric ingredient.
TL;DR: In this article, the authors measured the wavelength modulation spectra (1/R ) d R /d E of GaSe, GaS, GaSe 0.2 S 0.8, and GaSe0.8 S 0.2 at 5, 77 and 300 K between 2 and 6 eV.
TL;DR: In this paper, a simultaneous measurement has been made of analyzing powers and cross sections of protons scattered elastically from Si between 17 and 29 MeV, and an optical model analysis shows an anomalous non-monotonic behavior of the spin orbit potential in this energy region.
TL;DR: In this article, the authors report the observation of enhanced and long-lived 13 C nuclear spin echoes in solids, which can be used to determine limiting natural resolution and lineshapes due to the randomly distributed 13 C spins coupled via dipolar interactions.
TL;DR: In this paper, the energy band structure, reflectivity, modulated reflectivity and imaginary part of the frequency dependent dielectric function are calculated for InAs and InSb using the empirical pseudopotential method.
TL;DR: In this paper, the authors investigated the effect of interference conductance on the I(o)-V(o) curve and the heights of steps induced by rf radiations.
Abstract: : Calculations of static I(o)-V(o) curves, and of the heights of steps induced by rf radiations, have been carried out for current biased Josephson junctions with both a phase-independent quasiparticle conductance G(o) and a phase-dependent quasiparticle pair 'interference' conductance G(1) cos(phi). Little or no effect of the term in G1cos(phi) is found for junctions with zero capacitance. It thus appears that this term can be neglected in many practical applications of weak links. (Author)
01 Apr 1973
TL;DR: The 6.2-keV gamma translion of Ta-181 (T1/2 = 6.8 μs) has been shown to have great promise for high-resolution Mossbauer studies of hyperfine interactions as mentioned in this paper.
Abstract: In attempting to improve the resolution of the Mossbauer method considerable attention has been devoted to the few potential Mossbauer resonances with lifetimes in the microsecond region [1–4]. It has been shown recently, that in particular the 6.2-keV gamma transltion of Ta-181 (T1/2 = 6.8 μs) warrants great promise for high-resolution Mossbauer studies of hyperfine interactions. This is true for magnetic-dipole and electric-quadrupole hyperfine interactions as well as for isomer shifts [5–12].
TL;DR: In this article, the performance of a multiwire proportional chamber filled with Xenon (93% Xe, 7% C02) to a pressure of 60 psi absolute was described.
Abstract: We describe the performance of a multiwire proportional chamber filled with Xenon (93% Xe, 7% C02) to a pressure of 60 psi absolute. The readout is by the electromagnetic delay line method. Measurements taken at 60 keV and 140 keV show that 1 mm and 2 mm lead grid patterns can be resolved. MTF curves are given for both these energies and the projected performance for clinical work with 99Tc is described.
Journal Article•
TL;DR: It is shown that Phycomyces grown in the dark lack normal geotropic responses: pre-exposure to light is necessary for the synthesis of structures responsible for geotropism.
Abstract: Part I. Migration and Diffusion of Graviceptors: The physical action of gravitational and inertial forces on graviceptors is considered. The motion of graviceptors as influenced by physical dimensions, density, electric charge, composition of the suspending medium and flow variables is demonstrated. Part II. Observations on Geotropism in Phycomyces blakesleeanus: Mutants of Phycomyces blakesleeanus exhibit strikingly different rates of geotropic response. It is shown that Phycomyces grown in the dark lack normal geotropic responses: pre-exposure to light is necessary for the synthesis of structures responsible for geotropism. A physical model is presented that may account for some of the geotropic phenomena observed in Phycomyces.
TL;DR: A set of programs running under a multiprogramming batch operating system on the CDC 6600 which provide remote users with a time sharing service which is known as the People's Time Sharing System (PTSS), and the performance of the system, and user reaction to it are described.
Abstract: A set of programs running under a multiprogramming batch operating system on the CDC 6600 which provide remote users with a time sharing service is described. The basis for the system is the ability of a user program to create job control statements during execution, thereby tricking the operating system into treating it as an ordinary batch job. The text editor and the interactive debugging facilities are described. The performance of the system, known as the People's Time Sharing System (PTSS), and user reaction to it are also described.
(This work was supported by the U.S. Atomic Energy Commission.)