Showing papers by "United States Department of Energy published in 1984"

Universal features of the equation of state of metals

Abstract: The zero-temperature equation of state of metals, in the absence of phase transitions, is shown to be accurately predicted from zero-pressure data. Upon appropriate scaling of experimental pressure-volume data a simple universal relation is found. These results provide further experimental confirmation of the recent observation that the total-binding-energy---versus---separation relations for metals obey a universal scaling relation. Important to our results is a parameter $\ensuremath{\eta}$, which is a measure of the anharmonicity of a crystal. This parameter is shown to be essential in predicting the equation of state. A simple formula is given which predicts the zero-temperature derivative of the bulk modulus with respect to pressure.

A review of the genetic effects of ethyl methanesulfonate.

Abstract: Ethyl methanesulfonate (EMS) is a monofunctional ethylating agent that has been found to be mutagenic in a wide variety of genetic test systems from viruses to mammals. It has also been shown to be carcinogenic in mammals. Alkylation of cellular, nucleophilic sites by EMS occurs via a mixed SN1/SN2 reaction mechanism. While ethylation of DNA occurs principally at nitrogen positions in the bases, because of the partial SN1 character of the reaction, EMS is also able to produce significant levels of alkylation at oxygens such as the O6 of guanine and in the DNA phosphate groups. Genetic data obtained using microorganisms suggest that EMS may produce both GC to AT and AT to GC transition mutations. There is also some evidence that EMS can cause base-pair insertions or deletions as well as more extensive intragenic deletions. In higher organisms, there is clear-cut evidence that EMS is able to break chromosomes, although the mechanisms involved are not well understood. An often cited hypothesis is that DNA bases ethylated by EMS (mostly the N-7 position of guanine) gradually hydrolyze from the deoxyribose on the DNA backbone leaving behind an apurinic (or possibly an apyrimidinic) site that is unstable and can lead to single-strand breakage of the DNA. Data also exist that suggest that ethylation of some chromosomal proteins in mouse spermatids by EMS may be an important factor in causing chromosome breakage.

Vibrational frequencies via total-energy calculations. Applications to transition metals

Abstract: The important longitudinal ($\frac{2}{3},\frac{2}{3},\frac{2}{3}$) vibrational modes in Mo, Nb, and bcc Zr as well as the $H$- point modes in Mo and Nb have been studied using the frozen-phonon approach. These entirely first-principles calculations involve the precise evaluation of the total crystalline energy as a function of lattice displacement and yield calculated phonon frequencies to within a few percent of the experimental values. Anharmonic terms are readily obtained and are found to be very important for causing the tendency toward the $\ensuremath{\omega}$-phase instability in bcc Zr. The charge densities and single-particle energies obtained in the course of the calculations allow a detailed analysis of the electronic response to lattice distortions and the mechanisms causing phonon anomalies. The calculations also provide first-principles benchmarks at a few wave vectors where the validity of phenomenological models can be tested or their parameters determined.

Testing of chemicals for genetic activity with Saccharomyces cerevisiae: a report of the U.S. Environmental Protection Agency Gene-Tox Program.

Abstract: The yeast Saccharomyces cerevisiae is a unicellular fungus that can be cultured as a stable haploid or a stable diploid . Diploid cultures can be induced to undergo meiosis in a synchronous fashion under well-defined conditions. Consequently, yeasts can be used to study genetic effects both in mitotic and in meiotic cells. Haploid strains have been used to study the induction of point mutations. In addition to point mutation induction, diploid strains have been used for studying mitotic recombination, which is the expression of the cellular repair activities induced by inflicted damage. Chromosomal malsegregation in mitotic and meiotic cells can also be studied in appropriately marked strains. Yeast has a considerable potential for endogenous activation, provided the tests are performed with appropriate cells. Exogenous activation has been achieved with S9 rodent liver in test tubes as well as in the host-mediated assay, where cells are injected into rodents. Yeast cells can be recovered from various organs and tested for induced genetic effects. The most commonly used genetic end point has been mitotic recombination either as mitotic crossing-over or mitotic gene conversion. A number of different strains are used by different authors. This also applies to haploid strains used for monitoring induction of point mutations. Mitotic chromosome malsegregation has been studied mainly with strain D6 and meiotic malsegregation with strain DIS13 . Data were available on tests with 492 chemicals, of which 249 were positive, as reported in 173 articles or reports. The genetic test/carcinogenicity accuracy was 0.74, based on the carcinogen listing established in the Gene-Tox Program. The yeast tests supplement the bacterial tests for detecting agents that act via radical formation, antibacterial drugs, and other chemicals interfering with chromosome segregation and recombination processes.

Scaling relations in the equation of state, thermal expansion, and melting of metals

Abstract: A simple and yet quite accurate prediction of volume as a function of pressure for metals and alloys is presented. Thermal expansion coefficients and melting temperatures are predicted by simple, analytic expressions and results compare favorably with experiment for a broad range of metals. All of these predictions are made possible by the discovery of universality in binding energy relations for metals.

Flux-line-cutting and flux-pinning losses in type-II superconductors in rotating magnetic fields

Abstract: A general critical-state theory, including the effects of both flux-line cutting and flux pinning, is proposed for calculations of hysteresis in type-II superconductors in parallel applied magnetic fields that vary in both magnitude and direction. In this theory, if the magnitude of the electrical-current-density component perpendicular to the magnetic induction $\stackrel{\ensuremath{\rightarrow}}{\mathrm{B}}$ exceeds the corresponding critical value ${J}_{c\ensuremath{\perp}}$, depinning occurs, and an electric field component ${E}_{\ensuremath{\perp}}$ perpendicular to $\stackrel{\ensuremath{\rightarrow}}{\mathrm{B}}$ appears; if the magnitude of the current-density component parallel to $\stackrel{\ensuremath{\rightarrow}}{\mathrm{B}}$ exceeds the corresponding critical value ${J}_{c\ensuremath{\parallel}}$, flux-line cutting occurs, and an electric field component ${E}_{\ensuremath{\parallel}}$ parallel to $\stackrel{\ensuremath{\rightarrow}}{\mathrm{B}}$ appears. Model calculations are performed to solve for the electrodynamic response of a slab subjected to a parallel, constant magnetic field whose direction undergoes either continuous rotation or periodic oscillation. The relation of the theory to the pioneering experiments of LeBlanc and co-workers is discussed.

Reduction of reabsorption effects in scintillators by employing solutes with large Stokes shifts

Abstract: In a radiation or high energy particle responsive system useful as a scintillator, and comprising, a first component which interacts with said radiation or high energy particle to emit photons in a certain first wavelength range; and at least one additional solute component which absorbs the photons in said first wavelength range and thereupon emits photons in another wavelength range higher than said first range; an improvement is provided wherein at least one of said components absorbs substantially no photons in said wavelength range in which it emits photons, due to a large Stokes shift caused by an excited state intramolecular rearrangement.

Dielectronic satellite spectra of hydrogenlike titanium (Ti xxii)

Abstract: High resolution spectra of the Ly ..cap alpha../sub 1/ and Ly ..cap alpha../sub 2/ lines of hydrogenlike titanium, TiXXII, and the associated dielectronic satellites which are due to transitions 1snl-2pnl with n greater than or equal to 2, have been observed from tokamak discharges with auxiliary ion cyclotron heating (ICRH) with central electron temperatures of 2 keV and central electron densities of 8 x 10/sup 13/ cm/sup -3/ on the Princeton Large Torus (PLT). The data have been used for a detailed comparison with theoretical predictions based on the Z - expansion method and Hartree - Fock calculations. The results obtained with the Z - expansion method are in excellent agreement with the observed spectral data except for minor discrepancies between the theoretical and experimental wavelengths of 0.0003 A for the n = 2 satellites and of 0.0001 A for the separation of the Ly ..cap alpha../sub 1/ and Ly ..cap alpha../sub 2/ lines. Very good agreement with the experimental data is also obtained for the results from the Hartree - Fock calculations though somewhat larger discrepancies (approx. = 0.0009 A) exist between experimental and theoretical wavelengths which are systematically too small. The observed spectra are used for diagnosis ofmore » the central ion and electron temperatures of the PLT discharges and for a measurement of the dielectronic recombination rate coefficient of TiXXII.« less

A theoretical study of deuterium isotope effects in the reactions H2 + CH3 and H + CH4

Abstract: This paper presents ab initio potential surface parameters and transition state theory (TST) rate constants for the reaction H/sub 2/ + CH/sub 3/ ..-->.. H + CH/sub 4/, its reverse, and all the deuterium isotopic counterparts associated with it and its reverse. The potential surface parameters are derived from accurate POLCI calculations and include vibrational frequencies, moments of inertia, and other quantities for CH/sub 3/, H/sub 2/, CH/sub 4/, and the H-H-CH/sub 3/ saddle point. TST rate constants are calculated from standard expressions and the Wigner tunneling correction. For H/sub 2/ + CH/sub 3/ and H/sub 2/ + CD/sub 3/, agreement of the rate constant with experiment is good over a broad temperature range, suggesting that the calculated 10.7 kcal/mol barrier is accurate to within about 0.5 kcal/mol barrier. Agreement with experiment for H + CH/sub 4/ using the calculated 13.5 kcal/mol reverse reaction barrier is poorer; a 12.5 kcal/mol barrier is found to provide a more reasonable estimate of the true barrier. The analysis of isotope effects in the H + CH/sub 4/ reaction is restricted to examining the branching ratios between H and D atom abstraction in the reaction of H with the mixed species CH/sub 3/D, CH/submore » 2/D/sub 2/, and CHD/sub 3/. A combination of reaction path multiplicity, favorable zero point energy shifts, and a greater likelihood of tunneling causes H atom abstraction to predominate over D atom abstraction in H + CH/sub 3/D and H + CH/sub 2/D/sub 2/, but for H + CHD/sub 3/, it was found that the H atom and D atom abstraction rate constants cross near 700 K, with H atom abstraction dominating at low temperatures and D atom at high. 9 figures, 7 tables.« less

High-resolution photoemission study of γ- and α-cerium

Abstract: High-resolution photoemission studies on the ..cap alpha.. and ..gamma.. phases of cerium show changes in the binding energies of the two 4f-related features. The location of the two 4f-related features in the ..gamma.. phase are at -0.2 and -2.0 eV, while in the ..cap alpha.. phase these features are located at the Fermi level and -2.1 eV. These results are a direct test of the theories proposed to explain the presence of the two features.

Formaldehyde and hepatotoxicity: a review.

Abstract: Exposure to formaldehyde appears to be associated with hepatoxicity in many species, including humans, following injection, ingestion, or inhalation. Macroscopic, microscopic, and biochemical manifestations in the liver include alterations in weight, centrilobular vacuolization, focal cellular necrosis, and increased alkaline phosphatase concentrations. Time-related changes in the pattern of the effects are suggested as one goes from acute exposure by inhalation at greater concentrations to repeated exposure at lesser concentrations. Although the hepatic changes are generally not extensive and can be reversible following acute exposure, the potential exists for them to progressively become more serious with repeated exposures. There are several possible mechanisms for the toxicity. Depending on the route of exposure could include direct effects on hepatocytes and/or indirect effects through the circulatory and immune systems. The catabolism of formaldehyde includes conversion to CO2 by reactions involving glutathione. Many hepatotoxic chemicals require glutathione for detoxification. Formaldehyde may then have the potential to cause additive toxicity with such chemicals in some circumstances.

Measurement of phonon densities of states for pure and hydrogenated amorphous silicon

Abstract: Vibrational spectra for a-Si and a-SiH/sub 0.12/ have been measured by inelastic neutron scattering, directly yielding the phonon density of states for the former material, and the partial phonon density of states for H vibrations for the latter. The relevance of these results to the interpretation of infrared and Raman spectra is discussed.

Flow cytometer measurement of binding assays

Abstract: A method of measuring the result of a binding assay that does not require separation of fluorescent smaller particles is disclosed. In a competitive binding assay the smaller fluorescent particles coated with antigen compete with antigen in the sample being analyzed for available binding sites on larger particles. In a sandwich assay, the smaller, fluorescent spheres coated with antibody attach themselves to molecules containing antigen that are attached to larger spheres coated with the same antibody. The separation of unattached, fluorescent smaller particles is made unnecessary by only counting the fluorescent events triggered by the laser of a flow cytometer when the event is caused by a particle with a light scatter measurement within a certain range corresponding to the presence of larger particles.

Structural study of surface tungstate in WO3 ? Al2O3: Effects of Hydration and 18O Exchange

Abstract: The Raman spectra of a series of WO3AI2O3 catalysts containing 1-30 wt-% of WO3 were investigated with respect to the effect of O2 calcination and H2OD2O exposure. These studies showed that the frequencies of bands due to surface tungstate species can be shifted reversibly by as much as 6% of their values during alternate O2 calcination and H2O exposure cycles. The exchange of 18O for l6O in the surface tungstate was also investigated with Raman spectroscopy and ion-scattering spectrometry. The results were used to assign Raman bands to fundamental vibrations of the surface tungstate and to propose a mechanism of interaction between H2O and the surface tungstate that hitherto has not been addressed for WO3AI2O3.

High-resolution, low-temperature, photoemission-studies of heavy-fermion systems - ube-13 and upt-3

Abstract: High-resolution (0.13 eV) photoemission measurements performed at low temperatures (\ensuremath{\approx} 20 K) show that a sharp feature (measured width \ensuremath{\simeq} 0.15 eV at full width at half maximum) exists at the Fermi edge in the electronic structures of U${\mathrm{Be}}_{13}$ and U${\mathrm{Pt}}_{3}$. In U${\mathrm{Be}}_{13}$ the feature shows some temperature dependence.

Method of precisely modifying predetermined surface layers of a workpiece by cluster ion impact therewith

Abstract: A method of precisely modifying a selected area of a workpiece by producing a beam of charged cluster ions that is narrowly mass selected to a predetermined mean size of cluster ions within a range of 25 to 106 atoms per cluster ion, and accelerated in a beam to a critical velocity. The accelerated beam is used to impact a selected area of an outer surface of the workpiece at a preselected rate of impacts of cluster ions/cm2 /sec. in order to effect a precise modification in that selected area of the workpiece.

First-principles investigation of metal-hydrogen interactions in NbH

Abstract: First-principles total-energy calculations have been performed for NbH in the $\ensuremath{\beta}$- and $\ensuremath{\gamma}$- phase structures. Lattice constants, bulk moduli, and heats of formation as well as the frequencies and second harmonics of the optical vibrations of hydrogen and deuterium in the lattice have been calculated and found to be in excellent agreement with experiment. Our calculated electronic densities of states resolve the discrepancy between previous band calculations and photoemission experiments.

Hydraulic mining method

Abstract: A method of hydraulically mining an underground pitched mineral vein comprising drilling a vertical borehole through the earth's lithosphere into the vein and drilling a slant borehole along the footwall of the vein to intersect the vertical borehole. Material is removed from the mineral vein by directing a high pressure water jet thereagainst. The resulting slurry of mineral fragments and water flows along the slant borehole into the lower end of the vertical borehole from where it is pumped upwardly through the vertical borehole to the surface.

Evidence of deposition of anthropogenic pollutants in remote Rocky mountain lakes

Abstract: Thirteen trace elements, the PAH fluoranthene and PCBs were measured in the sediments of four remote high altitude lakes in Rocky Mountain National Park. PCBs were found in the sediments of all four lakes providing substantial evidence of anthropogenic inputs, most likely through atmospheric transport. The results were less certain, but still suggestive as to the anthropogenic origins for the elements As, Cd, Pb, and Sb and the PAH fluoranthene. Several of these elements, as well as fluoranthene and the PCBs, were found to be elevated in surface sediments compared to samples taken at greater depths, inferring that loadings of these substances into Rocky Mountain National Park region have increased with time.

Mutation tests in Neurospora crassa. A report of the U.S. Environmental Protection Agency Gene-Tox Program.

Abstract: Many mutation tests have been developed in Neurospora crassa during the almost 40 years of its use in mutation research These tests detect two major classes of mutation: gene mutation and meiotic nondisjunction Within the first class, forward- and reverse-mutation tests have been used The forward-mutation tests include those that detect mutations at many loci and at specific loci Both kinds of forward-mutation tests have been done in homokaryons ( n ) and heterokaryons ( n + n ′) From the publications that were not rejected by our pre-established criteria, data were extracted for 166 chemicals that had been tested for mutagenicity Only 6 of the 166 chemicals have been tested in one or more gene mutation test and the meiotic nondisjunction test; these 6 chemicals were positive in the first and negative in the second Of the 102 chemicals tested in one or more gene mutation tests, 94 were positive and 8 were negative Of the 70 chemicals tested in the meiotic nondisjunction test, 7 were positive and 63 were negative Two tests, the ad-3 ) forward-mutation test and the meiotic nondisjunction test, have been used most frequently These two tests are especially important for hazard evaluation, because each detects a class of mutations that is likely to be deleterious or lethal in the F 1 - disomics by the meiotic nondisjunction test and multilocus deletions by the ad-3 forward-mutation test in heterokaryons Generally, direct-acting chemicals are mutagenic in the gene mutation tests, but few chemicals that required metabolic activation have been tested Only 31 of the 166 chemicals tested in N crassa have been tested for carcinogenicity Among these chemicals, there is a good association between mutagenicity in gene mutation tests and carcinogenicity but a poorer association between meiotic nondisjunction and carcinogenicity; however, only a small number of chemicals has been tested in the meiotic nondisjunction test Further use and development of certain mutation tests in N crassa are desirable