Showing papers by "Oak Ridge National Laboratory published in 1980"
TL;DR: In this article, it was shown that the averaged Green's-function formulation of the Bloch spectral density function leads to manifestly unphysical results and that no manipulation of the expression can eliminate this behavior.
Abstract: It is demonstrated that the expression that has hitherto been used for calculating the Bloch spectral-density function ${A}^{B}(E,\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}})$ in the Korringa-Kohn-Rostoker coherent-potential-approximation theory of alloys leads to manifestly unphysical results. No manipulation of the expression can eliminate this behavior. We develop an averaged Green's-function formulation and from it derive a new expression for ${A}^{B}(E,\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}})$ which does not contain unphysical features. The earlier expression for ${A}^{B}(E,\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}})$ was suggested as plausible on the basis that it is a spectral decomposition of the Lloyd formula. Expressions for many other properties of alloys have been obtained by manipulations of the Lloyd formula, and it is now clear that all such expressions must be considered suspect. It is shown by numerical and algebraic comparisons that some of the expressions obtained in this way are equivalent to the ones obtained from a Green's function, while others are not. In addition to studying these questions, the averaged Green's-function formulation developed in this paper is shown to furnish an interesting new way to approach many problems in alloy theory. The method is described in such a way that the aspects of the formulation that arise from the single-site approximation can be distinguished from those that depend on a specific choice for the effective scatterer.
406 citations
TL;DR: Although mezerein by itself is a weak promoter and mimics TPA in many biochemical and morphological effects it is a potent second-stage promoter in a two-stage promotion regimen, the results suggest that 4-O-methyl-TPA had weak activity as a first-stage promoters.
Abstract: The effects of nonpromoting and weakly promoting diterpenes on skin tumor promotion by 12-O-tetradecanoylphorbol 13-acetate (TPA) were investigated When phorbol and phorbol 12,13-diacetate (both nonpromoting) were given simultaneously with TPA after 7,12-dimethylbenz[a]-anthracene (DMBA) initiation in female mice, they had no effect on TPA promotion However, the nonpromoter 4-O-methyl-TPA and the weak promoter mezerein were found to inhibit TPA promotion in a dose-dependent manner when given simultaneously with TPA Because mezerein was found to be an effective inhibitor of TPA promotion when given simultaneously and because it induces many biological responses similar to those to TPA, the capacity of mezerein to act as an incomplete promoter in a two-stage promotion protocol was also investigated Twice-weekly applications of 1,2, or 5 μg of TPA for 2 weeks after DMBA initiation produced 0, 0, and 05 papilloma per mouse, respectively, at 20 weeks When the twice-weekly applications of TPA for 2 weeks were followed by twice-weekly treatments with 2 μg of mezerein for 18 weeks, the number of papillomas per mouse was 22, 35, and 90, respectively Twice-weekly applications of 2 μg of TPA for 2 weeks followed by twice-weekly treatments with 1, 2, or 4 μg of mezerein for 18 weeks produced 21, 35, and 68 papillomas per mouse, respectively, in DMBA-treated mice Twice-weekly doses as high as 40 μg of 4-O-methyl-TPA were not effective in producing tumors when given after a limited treatment with TPA; however, 4-O-methyl-TPA had weak activity as a first-stage promoter The results suggest that although mezerein by itself is a weak promoter and mimics TPA in many biochemical and morphological effects it is a potent second-stage promoter in a two-stage promotion regimen
340 citations
TL;DR: The effects of cadmium on nucleic acids and proteins are examined for a number of specific cases to illustrate the variety of interactions that are well recognized and to demonstrate the utility of soft metal ions as reagents and probes for examining the relationship of structure and function in these macromolecules.
339 citations
TL;DR: In this paper, the authors investigated the resilience of food web energy models and nutrient cycling models and showed that resilience increases as the flux of energy through the food web per unit amount of energy in the steady state web increases.
Abstract: The resilience, defined here as the speed with which a system returns to equilibrium state following a perturbation, is investigated for both food web energy models and nutrient cycling models. Previous simulation studies of food web energy models have shown that resilience increases as the flux of energy through the food web per unit amount of energy in the steady state web increases. Studies of nutrient cycling models have shown that resilience increases as the mean number of cycles that nutrient (or other mineral) atoms make before leaving the system decreases. In the present study these conclusions are verified analytically for general ecosystem models. The behavior of resilience in food web energy models and nutrient cycling models is a reflection of the time that a given unit, whether of energy or matter, spends in the steady state system. The shorter this residence time is, the more resilient the system is.
256 citations
Book•
01 Jan 1980TL;DR: In this paper, the shape and size of an object and its other properties are inferred by interpreting their measurements on the scattered light, which can be used to learn about the shape, size, and other properties of the object.
Abstract: When we wish to observe an object, we usually illuminate it with a beam of light. The light is then reflected, refracted, diffracted, absorbed, in various ways. By interpreting our measurements on the scattered light, we learn about the shape and size of the object and its other properties. For example, we may learn whether the object is transparent or opaque; if the former, we may measure its refractive index, if the latter, we can find its absorptivity, and so on. If we study further by using monochromatic light, we find these various properties vary with the wavelength (in particular, we may find the object is coloured; i.e. it preferentially scatters light of a particular wavelength). In some cases we may find more than just scattering or absorption of the light. The object may continue to re-emit light after the incident beam is removed (phosphorescence), it may emit radiation of a different wavelength from that used to illuminate it (fluorescence) or it may emit radiation of a different kind (e.g. electrons in the photo effect).
247 citations
TL;DR: In this paper, the role of metabolic activation in Chemical-Induced Lung Injury was discussed and a detailed review of the biochemical mechanism of lung injury was presented. But this paper focused on lung injury.
Abstract: (1980). Biochemical Mechanisms in Chemical-Induced Lung Injury: Roles of Metabolic Activation. CRC Critical Reviews in Toxicology: Vol. 7, No. 2, pp. 103-176.
239 citations
TL;DR: In this paper, the cross-sections of the corresponding Fermi and Gamow-Teller matrix elements extracted from ε-decay measurements were found to be proportional to the squares of corresponding matrix elements.
Abstract: After simple corrections for distortion effects, 120-MeV, 0\ifmmode^\circ\else\textdegree\fi{} ($p, n$) cross sections are found to be proportional to the squares of the corresponding Fermi and Gamow-Teller matrix elements extracted from $\ensuremath{\beta}$-decay measurements. It is suggested that this proportionality can be used to extract Gamow-Teller matrix elements for transitions inaccessible to $\ensuremath{\beta}$ decay.
229 citations
TL;DR: Fly ash specimens from four power plants in the Tennessee Valley Authority system have been separated into three matrices: glass, mullite-quartz, and magnetic spinel, revealing the magnetic component of fly ash is ferrite.
Abstract: Fly ash specimens from four power plants in the Tennessee Valley Authority system have been separated into three matrices: glass, mullite-quartz, and magnetic spinel. Chemical species of trace elements are defined to a large extent by the matrices that contain them. The magnetic component of fly ash is ferrite. The mullite-quartz phase is relatively pure and can be recovered as a resource.
221 citations
TL;DR: A photomicroscopic method has been use to determine the kinetics of water loss at various constant temperatures from fertilized and unfertilized mouse ova.
Abstract: A photomicroscopic method has been use to determine the kinetics of water loss at various constant temperatures from fertilized and unfertilized mouse ova. Ova were transferred into hypertonic saline solutions, photographed, and their volumes calculated from their cross-sectional areas as a function of time after transfer. Curves describing the observed water loss have been compared to those calculated using a programmed version of the classical water permeability equation. The hydraulic conductivity,L
p
, was determined by changing its value in the calculation until the majority of the observed cell volumes fell on or very close to the calculated curve of volume vs. time. In this way, fertilized and unfertilized ova were found to have respective hydraulic conductivities of 0.43 and 0.44 μm3/μm2-min-atm at 20°C and respective activation energies for water permeability of 13.0 and 14.5 kcal/mol.
216 citations
TL;DR: The binding of cis(c)- and trans(t)-Pt(NH3)2Cl2 to DNA at platinum/DNA-nucleotide ratios (Ri) of 0.1 or less has been studied by means of radioactive 195mPt-labeled compounds, suggesting that both compounds should bind to DNA under biological conditions.
204 citations
TL;DR: In this article, the solubility of amorphous silica was measured at 25°C in ten separate sets of aqueous salt solutions, and the extent of decrease differed greatly from a 6% decrease in a solution saturated with NaHCO 3 to a 95.7% decrease with CaCl 2, depending upon the cation in the order Mg 2+, Ca 2+ > Li + > Na + > K +.
TL;DR: It was found that slight differences in the degree of dispersal of initial sizes of individuals were probably more important in influencing the population dynamics than alternative food availability or other factors.
TL;DR: In this article, the effects of site manipulations on soil leaching rates were analyzed in a site in Washington State, and the authors showed that the importance of accounting for bicarbonate transformations following site manipulation was highlighted.
TL;DR: In this paper, the Gamow-Teller matrix elements are extracted and a large part of the expected strength is found, and three giant resonances are interpreted as the $T = 4$ and $T=5$ components of the Gamew-Tller strength and an $E 1$ resonance.
Abstract: Neutron spectra from $^{90}\mathrm{Zr}(p, n)^{90}\mathrm{Nb}$ at ${E}_{p}=120$ MeV are measured in the angular range 0\ifmmode^\circ\else\textdegree\fi{}-25\ifmmode^\circ\else\textdegree\fi{}. Three giant resonances are seen and are interpreted as the $T=4$ and $T=5$ components of the Gamow-Teller strength and an $E1$ resonance. Gamow-Teller matrix elements are extracted, and a large part of the expected strength is found.
TL;DR: The binding of HMG 14 (or 17) to nucleosome cores produces two major additional bands on non-aturing polyacrylamide gels, which alters the relative densities of the end-labeled DNA fragmen as mentioned in this paper.
Abstract: The binding of HMG 14 (or 17) to nucleosome cores produces two major additional bands on nondenaturing polyacrylamide gels. Bound HMG 14 alters the relative densities of the end-labeled DNA fragmen...
TL;DR: In this paper, the authors explore the quantal energy spectrum of the Henon-Heiles Hamiltonian system and find both avoided crossings and crossings of the eigenvalues of the energy spectrum.
Abstract: Several aspects of the quantal energy spectrum are explored for the Henon–Heiles Hamiltonian system: a striking and initially unexpected continuation of sequences of eigenvalues from the quasiperiodic to the stochastic regime, the origin of large second differences Delta2Ei of eigenvalues arising from variation of a parameter, the comparison of classical and quantal spectra, and a comparison of the "classical" and quantal number of states. In the study of the second differences we find both "crossings" and "avoided crossings" of the eigenvalues. We discuss the importance of overlapping avoided crossings as a basis for a possible theory of "quantum stochasticity".
TL;DR: In this teleostean species, multiple vitellogenin polypeptides are apparently processed into multiple yolk protein polypePTides within the growing oocyte.
Abstract: 1. 1. A chromatographic procedure for isolating intact, highly purified vitellogenin from the plasma of the goldfish, Carassius auratus, is described. 2. 2. Vitellogenin is normally present in the plasma of females during the breeding season, but is not found in males; however, estradiol-17β induces the appearance of vitellogenin in male plasma. 3. 3. Native (dimeric_ goldfish vitellogenin has a molecular weight of about 380,000 and contains 15.4% protein-nitrogen and 0.79% protein-phosphorus; amino acid profiles were compared for vitellogenins from goldfish, Salmo gairdneri and Xenopus laevis. 4. 4. At least three polypeptides, ranging in molecular weight from 140,000 to 147,000, were identified by sodium dodecyl sulfate-gel electrophoresis of vitellogenin; native (dimeric) vitellogen is comprised of two such polypeptides together with approx 20% lipid. 5. 5. Native goldfish yolk protein consists of a lipovitellin and a phosvitin fraction; the former yields one class of at least two large polypeptides ( mol. wt = 105,000 and 110,000 ) and another class of up to four small polypeptides ( mol. wt = 19,000–25,000 ) on sodium dodecyl sulfate-gel electrophoresis, while the phosvitin fraction yields at least two polypeptides ( mol. wt = 7600 and 14,500 ) on Sephadex-gel filtration. 6. 6. In this teleostean species, multiple vitellogenin polypeptides are apparently processed into multiple yolk protein polypeptides within the growing oocyte.
TL;DR: Glycerol uptake calculated indirectly from the volume changes of the ova agreed well with that measured directly by labeled glycerol uptake, and it was found that the zona pellucida fertilized and unfertilized ova did not detectably impede the permeation by Glycerol.
Abstract: The coefficients of permeability to glycerol, Pglyc, and their temperature-dependence were determined from volume changes of fertilized and unfertilized mouse ova under hyperosmotic conditions. Fertilization caused a significant increase in the value of Pglyc. Unfertilized ova exhibited Pglyc values of 1 X 10(-5), 2 X 10(-6), and 5 X 10(-7) cm/min at approximately 20 degrees C, and approximately 12 degrees C, and approximately 3 degrees C, respectively. Fertilized ova exhibited Pglyc values of 3.4 X 10(-5), 1.3 X 10(-5), and 4.7 X 10(-6) cm/min at apoproximately 20 degrees C, 12 degrees C, and approximately 3 degrees C, respectively. The activation energy of glycerol permeation into fertilized and unfertilized ova was calculated to be 18.7 and 28.4 kcal/mol, respectively. Fertilization caused a rather dramatic increase in glycerol permeability, the major extent of which occurred within about 3 hours after fertilization. Pglyc was also measured at approximately 20 degrees C by isotope uptake. Glycerol uptake calculated indirectly from the volume changes of the ova agreed well with that measured directly by labeled glycerol uptake. It was also found that the zona pellucida fertilized and unfertilized ova did not detectably impede the permeation by glycerol.
TL;DR: The G2 results suggest that ara-C inhibits the repair of damage that leads to the formation of exchange aberrations in unstimulated human lymphocytes, and a possible mechanism for the induction of chromosomeAberrations by X-rays is offered.
Abstract: The yield of X-ray-induced chromosome aberrations in unstimulated human lymphocytes is greatly enhanced when the cells are incubated with cytosine arabinoside (ara-C) after irradiation. There is an increase in aberration yield with increasing time of incubation in ara-C (1, 2 or 3 h). When G 2 cells are X-irradiated and incubated with ara-C until fixation, the deletion yields are considerably increased, but no interchanges are observed. In the absence of ara-C, 0.29 interchanges per cell were observed. The G 2 results suggest that ara-C inhibits the repair of damage that leads to the formation of exchange aberations. The increase in yield in unstimulated lymphocytes is interpreted to be due to an accumulation of strand breaks caused by ara-C inhibition of repair; when the inhibition is reversed with deoxycytidine, these breaks can interact to form aberrations. A possible mechanism for the induction of chromosome aberrations by X-rays is offered on the basis of these results.
TL;DR: In this article, general sensitivity theory is presented for treating problems characterized by systems of nonlinear equations with nonlinear responses, and the concept of the Frechet derivative is shown to be fundamen...
Abstract: General sensitivity theory is presented for treating problems characterized by systems of nonlinear equations with nonlinear responses. The concept of the Frechet derivative is shown to be fundamen...
TL;DR: In this article, it was shown that the electron temperature in a tokamak scales linearly with electron-cyclotron-heating power, and that the central electron temperature increases from 850 to 1250 eV.
Abstract: Results are reported of electron-cyclotron-heating experiments in which 80 kW of microwave power from a 35-GHz gyrotron is injected into a tokamak with large single-pass absorption. For 10-ms microwave pulses, incident from the high-field side of the torus, the central electron temperature increases from 850 to 1250 eV, in agreement with empirical transport-code calculations. For the first time it is demonstrated that electron temperature in a tokamak scales linearly with electron-cyclotron-heating power.
TL;DR: Results provide additional evidence for the importance of dark basal keratinocytes in stage I of promotion and indicate that most of the other biochemical and morphological responses normally associated with promotion (such as polyamines) are actually associated with stage II of promotion.
Abstract: The effects of fluocinolone acetonide (FA), retinoic acid (RA), and tosylphenylalanine chloromethyl ketone (TPCK) on two-stage promotion after 7,12-dimethylbenz[a]-anthracene (DMBA) initiation in female Sencar mice were investigated. The two-stage promotion protocol was achieved by twice weekly applications of 2 microgram of 12-O-tetradecanoylphorbol 13-acetate (TPA) for 2 weeks (stage I) followed by twice weekly applications of mezerein for 18 weeks (stage II). Separately stage I and II do not cause any tumors to develop after DMBA initiation. FA was found to be a potent inhibitor of stages I and II but to a greater degree for stage I than for stage II. RA was ineffective in stage I but was a potent inhibitor of stage II; TPCK specifically inhibited stage I but not stage II. FA and TPCK effectively counteract the appearance of the dark basal keratinocytes, whereas RA has no effect. These results provide additional evidence for the importance of dark basal keratinocytes in stage I of promotion and indicate that most of the other biochemical and morphological responses normally associated with promotion (such as polyamines) are actually associated with stage II of promotion.
TL;DR: In this paper, a method of solution of the static Hartree-Fock problem is proposed based on the extension of the method of solving the time-dependent Hartree Fock problem to imaginary time.
TL;DR: These results provide direct evidence that a previously described inducible repair activity in E. coli acts by demethylating O6-methylguanine at the DNA level, as shown by the appearance of 3H-labeled deoxyguanosine in hydrolysates of the recovered DNA.
01 Jun 1980
TL;DR: Evidence is presented that mutant larvae of Drosophila melanogaster are a mutant form of the crystal cells, a type of larval hemocyte with characteristic paracrystalline inclusions, and that these crystal cells store phenolic substrates and are the source of the hemolymph phenol oxidase activity in the larva of D. melanogasters.
Abstract: Black cells (Bc, 2-80.6±) mutant larvae ofDrosophila melanogaster have pigmented cells in the hemolymph and lymph glands. In this report we present evidence that these melanized cells are a mutant form of the crystal cells, a type of larval hemocyte with characteristic paracrystalline inclusions.Bc larvae lack crystal cells. Furthermore, the distribution pattern of black cells inBc larvae parallels that of experimentally-blackened crystal cells in normal larvae (phenocopy).InBc/Bc zygotes black cells appear during mid embryonic development but inBc +/Bc zygotes pigmented cells are not found until late in the first larval instar.Crystal cells are present in the heterozygous larvae until this time, and paracrystalline inclusions can be seen in some of the cells undergoing melanization in these larvae.The rate of phenol oxidase activity inBc +/Bc larval cell-free extracts is less than half that ofBc +/Bc +extracts whereas enzyme activity is undetectable inBc/Bc larvae. We propose that theBc +gene product is required for maintaining the integrity of the paracrystalline inclusions; inBc/Bc larvae either the product is absent or nonfunctional so an effective contact between substrate and enzyme results in melanization of the cells.Phenol oxidase itself is either destroyed or consumed in the melanization process accounting for the absence of enzyme activity inBc/Bc larvae. These studies confirm that the crystal cells store phenolic substrates and are the source of the hemolymph phenol oxidase activity in the larva ofD. melanogaster.
TL;DR: High-resolution chromatographic and spectroscopic analysis of alkaline subfractions enriched in mutagenic activity show the causative agents to be polycyclic aromatic primary amines, which may be responsible for the increased biological activity of coal- and shale-derived petroleum substitutes relative to petroleum.
TL;DR: In this article, the spin dynamics of the transition-metal ferromagnets nickel and iron are investigated within the framework of the itinerant theory of magnetism, which is developed in terms of a generalized random-phase approximation which incorporates the band and wave-vector dependence of relevant interaction matrix elements.
Abstract: The spin dynamics of the transition-metal ferromagnets nickel and iron are investigated within the framework of the itinerant theory of magnetism. The theory is developed in terms of a generalized random-phase approximation which incorporates the band and wave-vector dependence of relevant interaction matrix elements. In contrast to constant-matrix-element approximations, this formalism generates band- and wave-vector-dependent splitting of the energy bands, possible ''optical'' spin-wave modes, and a different interpretation of the spin-wave disappearance phenomena. First-principles numerical calculations of the neutron scattering intensity based on this model have been found to be in excellent agreement with experiments. Recent neutron scattering experiments have also verified the existence of an ''optical'' spin-wave branch predicted by this theory.
Abstract: Monochromatized synchrotron radiation near the photoionization threshold was used to produce the (2p/sub 3/2/) vacancy state in atomic Xe. Deexcitation of the state through L/sub 3/-M/sub 4/M/sub 5/(/sup 1/G/sub 4/) Auger-electron emission was measured. The 5d spectator-electron Auger satellite was observed. The satellite energy exhibits linear dispersion. The observed width of the /sup 1/G diagram line decreases by approx. 40% when the exciting photon energy reaches the vicinity of the Xe L/sub 3/ binding energy. This radiationless process can thus be construed as the Auger analog of the x-ray resonant Raman effect. The /sup 1/G diagram line is shifted by -+3 eV due to post-collision interaction; this shift varies with excitation energy.
TL;DR: In this article, the 208 Pb(p, n) 208 Bi reaction has been studied at E p =120 and 160 MeV, and the GT resonance is found to be concentrated in disagreement with a recent theoretical suggestion that it is highly fragmented in heavy nuclei, but in good agreement with an earlier calculation.