Showing papers by "Oak Ridge National Laboratory published in 1974"

Computer simulation of atomic-displacement cascades in solids in the binary-collision approximation

Abstract: A comprehensive computer program has been developed for the simulation of atomic-displacement cascades in a variety of crystalline solids, using the binary-collision approximation to contruct the projectile trajectories. The atomic scattering is governed by the Moli\'ere potential.Impact-parameter-dependent inelastic losses are included using Firsov's theory. Thermal vibrations of the target atoms and crystal surfaces may be included. Permanent displacement of lattice atoms may be based on either an energy-threshold criterion or a Frenkel-pair-separation criterion. An extensive series of calculations has been made for cascades in the simple metals Cu, Fe, and Au, to test the effects on the results of many of the model parameters. When a displacement-threshold energy is used, the number of Frenkel pairs is found to be a linear function of that part of the primary recoil energy which remains as the kinetic energy of atoms. This result is independent of target temperature, of the presence or absence of inelastic energy losses, and of various details of the model. In contrast, when a separation criterion is used, the number of defects increases less rapidly than linearly. This effect is caused by increased recombination in the highly disturbed tracks of the energetic recoils. Agreement between theoretical and experimental estimates of the radiation damage produced by neutron irradiation of Cu is substantially improved in the latter model.

Spheroid Chromatin Units (ν Bodies)

Abstract: Linear arrays of spherical chromatin particles (nu bodies) about 70 angstroms in diameter have been observed in preparations of isolated eukaryotic nuclei swollen in water, centrifuged onto carbon films, and positively or negatively stained. These bodies have been found in isolated rat thymus, rat liver, and chicken erythrocyte nuclei. Favorable views also reveal connecting strands about 15 angstroms wide between adjacent particles.

Acidity measurements at elevated temperatures. VII. Dissociation of water

Abstract: The self-dissociation of water has been studied over the temperature range from 0 to 300°C and in KCl media from 0.02m to 2.7m. Also, isothermal pressure coefficients of the dissociation quotients have been obtained in these same media up to 250°C. A potentiometric method employing a hydrogen electrode concentration cell with flowing solutions was employed. The estimated accuracy of logQw values up to 250°C is 0.02 log units and at 300°C is 0.04 log units. Smoothing functions have been found which fit these data along with the precise potentiometric data of Harned and co-workers at low temperatures, the existing calorimetric data up to 55°C and the recent conductimetric measurements of pure water up to 271°C by Bignoldet al., within about 1.5 times the estimated errors. Thermodynamic quantities for the dissociation reaction have been tabulated for rounded values of temperature and ionic strength at the saturation pressure of water. The isothermal pressure coefficients of log Qw varies approximately linearly with the square root of the ionic strength. This and the dependence of logKw on the density of the water is consistent with the assumption that the molal volumes of aqueous ions vary linearly with the compressibility coefficient of water. The heat for the dissociation reaction at infinite dilution is also shown to be strongly dependent on density.

Secondary-electron emission spectroscopy and the observation of high-energy excited states in graphite: Theory and experiment

Abstract: Fine structure in the energy distribution of secondary electrons "back-scattered" from a graphite crystal surface is resolved and shown to be consequence of inelastic electron-electron scattering in which the dominant process is the population of final states above the vacuum level by electron-hole pair production via screened-Coulombic interaction between the incident primary electrons and the valence electrons in the solid. The scattering theory of Kane is applicable and emphasizes that features due to one-electron density of final states should be resolvable in experimental secondary-electron-emission spectra of crystals. Experimental results are presented, which provide strong support for this view. Previous measurements on graphite have been extended and weak secondary-electron-emission structure, resolved in the second derivative of the energy-distribution spectrum, is reported for kinetic energies, $10\ensuremath{\lesssim}{E}_{\mathrm{kin}}\ensuremath{\lesssim}40$ eV. Maxima are observed at 16.2, 22.2, 29.2, 31.2, 36.2, and 40.7 \ifmmode\pm\else\textpm\fi{} 0.5 eV above the Fermi energy. Details are presented of a first-principles high-energy band-structure calculation of graphite extending over a 80-eV energy range. The observed spectral features correlate closely with final-density-of-states maxima as predicted by the theory.

Amphibian Vitellogenin: Properties, Hormonal Regulation of Hepatic Synthesis and Ovarian Uptake, and Conversion to Yolk Proteins

Abstract: Amphibian vitellogenin is a sex-limited protein found in the serum of normal females but not that of males. Its appearance can be induced in males, females, and hypophysectomized animals by estrogens, particularly estradiol-17rβ. The natural source of estradiol-17rβ is the ovary, and ovarian synthesis is markedly stimulated by gonadotropin(s). The pituitary is the natural source of gonadotropin(s), and hypophysectomy invariably leads to ovarian regression. Pituitary secretion in turn appears to depend primarily upon food supply rather than other environmental factors. The liver is the site of vitellogenin synthesis, and its induction by estrogen may involve both transcriptional and translational control mechanisms. Estrogen induction of unprimed liver (in which no vitellogenin synthesis occurs) may involve a cell differentiation or division phenomenon and has not yet been achieved in vitro. Estrogen induction of primed liver (in which a basal level of vitellogenin synthesis takes place) appears to be primarily a modulation phenomenon and can be duplicated to some extent in vitro. The secretion of vitellogenin by liver parenchymal cell is as yet poorly understood. Available evidence indicates that synthesis, phosphorylation, and lipid addition are closely linked events, and that approximately 2 hr are required for the newly synthesized peptide chain to be secreted from the liver. Serum vitellogenin is sequestered by the ovary, and specifically by the vitellogenic oocyte, by a micropinocytotic process. The uptake of vitellogenin is highly selective, is stimulated by gonadotropin(s), and may involve attachment to receptor sites on the oocyte membrane. Once incorporated into the oocyte, vitellogenin is converted within yolk platelets into the yolk proteins lipovitellin and phosvitin, for which it seems to be the sole source. The conversion process appears to involve a proteolytic cleavage of the vitellogenin peptides into those that make up lipovitellin and phosvitin.

Estrogen-induced synthesis of yolk proteins in roosters

Abstract: synopsis. Vitellogenin is the serum precursor of the yolk proteins a-lipovitellin, j8-lipovitellin, and phosvitin. The precursor can be dissociated to produce the yolk proteins only by proteolytic enzymatic action, to which it is very susceptible. Denaturation in sodium dodecyl sulfate, combined with reduction of disulfide bridges and blocking of thiols, yields a complex with a moiecuiar weight of 200,000 to 250,000. a-Lipovitellin contains three polypeptides, with moiecuiar weights of about 135,000, 105,000, and 40,000, and j3-lipovitellin is composed of two polypeptide chains with moiecuiar weights of 135,000 and 30,000. The 40,000 subunit of a-lipovitellin and both /3-lipovitellin subunits are phosphopeptides. We tested RNA isolated from the liver of estrogen-treated roosters for mRNA activity in a cell-free reticulocyte system. The vitellogenin mRNA has a sedimentation coefficient great? er than 285 and thus contains enough information to code for a long polypeptide chain. Estrogen administration to roosters induces the appearance of vitellogenin and a lowdensity lipoprotein, the syntheses of which are not coordinated. The course of vitellogenin synthesis was calculated from accumulation and turnover data, and it was found that from about 25 hr after estradiol-17)8 administration the rate of vitellogenin synthesis increases linearly for several days, paralleling an increase in vitellogenin-synthesizing polysomes. Thus, we estimate a constant translation rate of about 8 amino acids per ribosome per sec. A "memory" effect is observed when a second hormone dose is given some time after the vitellogenin induced by the first dose has disappeared from the blood. After the second dose vitellogenin synthesis is detected sooner, and its initial increase is more rapid, than after the first dose. Although the synthesis of vitellogenin starts 3 to 4 hr after the second as well as after the first injection, the rate of synthesis after the first injection increases much more slowly during the first 15 hr than during the subsequent period of linear accumulation, whereas after the second injection the linear increase in the rate of synthesis begins im? mediately after the lag period of 3 to 4 hr. The "memory" effect is undiminished even 50 days after the first hormone dose; thus, the causative factor either is very stable or is synthesized in great excess during the first stimulation. When the second injection is given during the descending part of the turnover curve, an increase in vitellogenin synthesis is observed within 3.5 hr. There are thus at least three different effects of estradiol; (i) the "memory" effect, which probably is due to'commitment or differentiation of vitellogenin-synthesizing cells; (ii) the effect that causes the committed cells to give full response after the 3- to 4-hr lag period; and (iii) the effect that causes the immediate response. To explain these results we suggest that committed cells can synthesize vitellogenin mRNA only during a certain period of the cell cycle.

Photoionization of neon between 100 and 2000 eV: Single and multiple processes, angular distributions, and subshell cross sections

Abstract: All aspects of photoionization in the soft-x-ray region are taken into account, and a complete partitioning of the photoionization cross section of neon is given in terms of single-electron processes in $2p$, $2s$, and $1s$ subshells and multiple-electron processes involving these subshells. The various processes, including their angular dependences, are identified and studied by the technique of photoelectron spectrometry. The partition relies solely on experimental evidence. Absolute subshell cross sections for the emission of a single electron are compared with current theoretical predictions: The single-particle, frozen-structure model (Cooper, 1962) that uses the Herman-Skillman potential overestimated ${\ensuremath{\sigma}}_{2p}$ by up to 15%, ${\ensuremath{\sigma}}_{2s}$ by (25-35)%, and ${\ensuremath{\sigma}}_{1s}$ by about 20%; the random-phase-approximation-with-exchange model (Amusia, 1972) that includes multielectron correlation and uses Hartree-Fock wave functions predictions correctly ${\ensuremath{\sigma}}_{2s}$ at $110lh\ensuremath{ u}l220$ eV, where comparative data exist. The absolute cross section for double ionization in the $L$ shell is 5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}20}$ ${\mathrm{cm}}^{2}$ at $h\ensuremath{ u}=278$ eV as compared with the theoretical value of 4 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}20}$ ${\mathrm{cm}}^{2}$. The energy dependence of simultaneous excitation and ionization processes in the $L$ shell is reported. A finite threshold value is observed and a plateau at higher energy is indicated. For $h\ensuremath{ u}g130$ eV, $\ensuremath{\epsilon}l,{n}^{\ensuremath{'}}{l}^{\ensuremath{'}}$ transitions are found to be most probable in which the continuum electron changes its angular momentum, $\ensuremath{\Delta}l=\ifmmode\pm\else\textpm\fi{}1$, and the excited electron retains its momentum, $\ensuremath{\Delta}l=0$, namely $2{p}^{6}\ensuremath{\rightarrow}2{p}^{4}\ensuremath{\epsilon}d,np$. Anisotropy parameters $\ensuremath{\beta}$ for $2p$ electrons agree well with theoretical results; however an unexplained maximum near $\ensuremath{\theta}={0}^{\ensuremath{\circ}}$ at $h\ensuremath{ u}g1$ keV is found for the angular distributions of $2p$ photoelectrons.

Lattice dynamics of cadmium telluride

Abstract: The phonon dispersion relation of CdTe at 300 \ifmmode^\circ\else\textdegree\fi{}K has been measured for the [100], [111], and [110] directions of propagation using neutron inelastic scattering. The CdTe single crystal was grown from the melt with Cd present as $^{114}\mathrm{Cd}$ to reduce the neutron absorption of the specimen. The results have been fitted to a 14-parameter shell model that represents both the neutron data and other measured properties well when the non-neutron data are included in the fit. The present results, along with earlier measurements on $\ensuremath{\alpha}\ensuremath{-}\mathrm{Sn}$ and InSb, complete the isoelectronic sequence $\ensuremath{\alpha}\ensuremath{-}\mathrm{Sn}\ensuremath{\rightarrow}\mathrm{InSb}\ensuremath{\rightarrow}\mathrm{CdTe}$. The systematic trends in the lattice dynamics of this series of semiconductors (which is characterized by increasing band gap and ionicity) are brought out by comparison of frequency distributions calculated from the shell-model fits.

Model of Fish Biomass Dynamics

Abstract: A model of fish biomass dynamics is developed based on principles of physiology, population biology, and trophic ecology. The model is designed to incorporate measurable parameters for simulating seasonal changes in a natural population. All parameters were implemented for the bluegill (Lepomis macrochirus) and simulation results compared with independently derived laboratory and field data. Applications of the model to thermal enrichment problems are given as an example of future potential uses.

Inelastic Resonance Emission of X Rays: Anomalous Scattering Associated with Anomalous Dispersion

Abstract: An inelastic resonance scattering of monochromatic Cu $K\ensuremath{\alpha}$ x rays incident on various targets is observed when an absorption edge of the target is just above the energy of the incident x rays. This frequency-dependent and angular-independent inelastic scattering is interpreted with the x-ray scattering theory of anomalous dispersion. Conservation-of-intensity arguments allow a comparison of the observed inelastic intensity with the real part of the anomalous dispersion corrections to the coherent atomic scattering factors for x rays.

Effects of interstitial oxygen on the superconductivity of niobium

Abstract: Superconductivity in niobium-oxygen body-centered-cubic solid-solution alloys (oxygen content 0.024-3.50 at.%) was studied by calorimetric, magnetic, and resistive measurement techniques. These measurements included low-temperature-specific-heat capacity, superconducting-normal transition temperature ${T}_{c}$, direct-current magnetization, and electrical resistivity, as well as x-ray lattice parameter, microhardness, and optical metallography to characterize the samples. Oxygen in solid solution lowers the ${T}_{c}$ of niobium. In contrast to the prediction of DeSorbo, we found that $\ensuremath{\gamma}$, the electronic coefficient of low-temperature-specific-heat capacity, also decreases with oxygen concentration. Our data indicated that the "band-structure" electronic density of states at the Fermi level ${N}_{\mathrm{bs}}(0)$ and the electron-phonon coupling constant $\ensuremath{\lambda}$ both decrease with oxygen content. Therefore, both the density of electronic states and the phonon spectrum may be controlling the magnitude of ${T}_{c}$ in the niobium-oxygen system. Additional superconducting parameters were calculated for the niobium-oxygen alloys from our calorimetric, magnetic, and resistive data. The Ginzburg-Landau parameter ${\ensuremath{\kappa}}_{\mathrm{GL}}$ was found to increase from less than 1.0 for essentially pure Nb to about 10 for the Nb-3.5-at.%-O alloy. Calculated values of ${H}_{c2}(4.2 \mathrm{K})$ versus atomic-percent oxygen exhibit a maximum at 2-at.% oxygen which was observed experimentally.

Preferential DNA repair in human cells.

Abstract: EXCISION repair plays a vital role in the recovery of human cells from ultraviolet irradiation1, but it does not remove all lesions from DNA, even when they are as potent as cyclobutane pyrimidine dimers. In fact, only about 50% to 75% of the dimers produced by low fluences of ultraviolet light are excised and the remainder persist in the DNA for at least 24 to 48 h2–4. We have investigated why some but not all dimers are excised. Our conclusion is that dimers, and possibly other ultraviolet photoproducts, persist in tracts of DNA which are rendered refractory to excision repair by a ‘mask’ of protein.

Autogenous immunity to endogenous RNA tumor virus. Identification of antibody reactivity to select viral antigens.

Abstract: The viral antigenic determinants recognized in an autogenous immune response in mice against their endogenous C-type virus have been identified by SDS-polyacrylamide gel electrophoresis of immune precipitates between various sera and H(3)-labeled intact or disrupted AKR leukemia virus. Normal B6C3F(1) [(C57BL/6 x C3H/Anf)F(1)] serum reacts with viral envelope antigens having mol wt of approximately 68,000, 43,000, and 17,000. In addition, minor reactions with viral antigens having mol wts of approximately 19,000 and 15,000 are demonstrable. The 68,000 and 43,000 mol wt antigens can be labeled with [(3)H]glucosamine and may correspond to the major viral envelope antigens M(2) and M(1), respectively. The antigens recognized by autogenous immune sera do not differ with respect to age of the animal, nor are they significantly different in sera from various strains of mice (BALB/c, C57BL/6, and C3H/Anf). These results suggest that the age-asociated and strain variations in the autogenous immune response, as determined by radioimmune precipitation assays against intact virus, are due to quantitative and qualitative alterations of antibody levels against common antigens.

Phosphoric acid dissociation equilibria in aqueous solutions to 300°C

Abstract: The dissociation equilibria of phosphoric acid were studied potentiometrically using a hydrogen-electrode concentration cell to 300°C at KCl concentrations up to 1.0m. Least-squares analysis of data atP(V) concentration of 0.008 and 0.045m indicate the absence of significant amounts of polyphosphates up to 200°C.P(V) data at concentrations less than 0.01m extending to 300°C were analyzed in terms of the species H n PO 4 (−3) . The equilibrium quotients expressed for neutralization reactions have been fitted with a nine-parameter expression for the first stepwise neutralization and 11 parameters for the second. Fewer data were obtained for the third neutralization since the HPO2− becomes a strong base above about 150°C in water. Thermodyanamic parameters have been derived for these equilibria, and comparisons have been drawn with other similar data recently reported. There is evidence from the salt effects that the extent of association of HPO4 2− or H2PO 4 − with K+ is not great in 1m KCl.

The Permeation of Hydrogen Isotopes Through Structural Metals at Low Pressures and Through Metals with Oxide Film Barriers

Abstract: The permeation and the pressure dependence of the permeation of hydrogen isotopes through metals and oxidized metals were studied at temperatures from 300 to 800°C and at pressures of 10-3 Torr to ...

Nitrosocarbaryl as a Potent Mutagen of Environmental Significance

Abstract: THE widespread accumulation of environmental pollutants has led to concern over their long-range effects on living organisms. Although many herbicides, pesticides, and food additives have no deterimental effect on experimental animals, the possible chemical interaction of these compounds with each other or with natural elements of the environment to produce biologically active compounds has rarely been considered. We have found that the combination of a food additive, sodium nitrite, with a commonly used pesticide, carbaryl, results in the formation in acid solution of a new mutagen of considerable potency, nitrosocarbaryl (NC). A study of the reactions leading to formation of mutagens and carcinogens from several types of pesticides and herbicides is reported elsewhere1. We present here an examination of the mutagenicity of NC in two bacterial systems, Escherichia coli and Haemophilus influenzae.

Neutral-beam injection into a tokamak, part I: fast-ion spatial distribution for tangential injection

Abstract: The production processes and spatial distribution of fast ions resulting from tangential injection of a diffuse neutral beam into a tokamak are discussed. The spatial distribution of fast ions for various injection trajectories and absorption mean free paths are calculated and discussed in detail. Maximum beam absorption for a parabolic density profile is shown to occur for injection roughly halfway between the inner wall of the torus and the magnetic axis; however, since this maximum is near unity and only weakly dependent on the injection trajectory, this is not the most important possible optimization. Since the drift orbit surface area over which the fast ions are distributed is roughly proportional to the distance from the magnetic axis, the fast ion density is found to be strongly peaked at the magnetic axis for present experiments where the absorption mean free path λ is comparable to the plasma radius a. This geometric peaking effect is strong enough to overcome the exponential beam attenuation and cause the fast-ion density and consequent beam energy deposition to be peaked at the plasma centre as long as λ0 a/4. Charge exchange of the fast ions with neutrals in the plasma can deplete the fast-ion population, particularly near the plasma edge. When charge exchange is an important loss mechanism, beam injection nearly tangent to the magnetic axis is found to maximize the beam effectiveness in heating.

Acetaminophen Metabolism in Man, as Determined by High-Resolution Liquid Chromatography

Abstract: Acetaminophen is a commonly used analgesic, available without prescription. Several of its metabolites have heretofore been isolated from physiologic fluids and analytically characterized. In general, the separation methods are complicated, usually requiring extensive sample pretreatment, and do not measure the individual conjugated metabolites. High-resolution anionexchange separation of urinary samples from subjects receiving acetaminophen reveals eight chromatographic peaks, representing seven metabolites and the free drug itself. Metabolites separated include 2-methoxyacetaminophen, its glucuronide and sulfate conjugates, the sulfate conjugate of 2-hydroxyacetaminophen, the glucuronide and sulfate conjugates of acetaminophen, S -(5-acetamido-2-hydroxyphenyl)cysteine, and S -(5-acetamido-2-glucuronosidophenyl)cysteine. Urinary and serum concentrations of the drug and its seven metabolites were determined by high-resolution liquid chromatography as a function of time after two clinically normal men ingested 1950 mg of the drug. Concentrations in urine and serum are compared, and estimated urinary excretion rates are reported for all metabolites except S -(5-acetamido-2-hydroxyphenyl)cysteine. Serum concentrations of the glucuronide were higher than concentrations of the free drug 2 h after the drug was ingested, indicating that solvent-extraction procedures for serum will yield low estimates of total drug unless hydrolysis precedes the extraction step.