Showing papers by "Oak Ridge National Laboratory published in 1976"
TL;DR: In this paper, the authors investigated the role of predation in the adaptive significance of vertical migration among zooplankton in both Gatun Lake in Panama and Fuller Pond in Connecticut.
Abstract: Field data and laboratory feeding experiments support the hypothesis that predation can be an important factor in the adaptive significance of vertical migration among zooplankton. In both Gatun Lake in Panama and Fuller Pond in Connecticut the diel vertical migration patterns of prey populations assume distributions which result in lessened predation by the dominant lake planktivores. It is concluded that such patterns of vertical migration will result when prey populations are under intense, selective pressures from visually dependent predators.
699 citations
TL;DR: In this paper, a compilation of optical-model parameters determined by fitting elastic-scattering angular distributions for various incident particles including heavy ions is presented, including parameters from previous compilations back to 1954 and from an extensive literature search in the leading journals and publications up to June 1975.
662 citations
TL;DR: In this article, the authors used the binary collision cascade simulation program MARLOWE to study the reflection of 10 eV to 20 keV H, T and He atoms from amorphous Al, Cu, Nb and Au.
581 citations
TL;DR: In this article, it was shown that the shape of large, random clusters near the critical percolation concentration is such that their mean boundary is proportional to their mean bulk, and that the dimension of the boundary is the same as that of the bulk.
Abstract: It is shown that the shape of the large, random clusters, near the critical percolation concentration ${c}_{0}$, is such that their mean boundary $〈b〉$ is proportional to their mean bulk $〈n〉$ and this is illustrated by an argument which shows that the dimension of the boundary is the same as that of the bulk. The resulting ratio $\frac{〈b〉}{〈n〉}$ is simply related to the critical concentration ${c}_{0}$. The detailed results of a Monte Carlo calculation, previously reported, are given for $cl{c}_{0}$ on a simple square lattice; they yield an empirical formula for the probability distribution $\mathcal{P}(n,b)$, for finding a cluster of size $n$ and boundary $b$, that is proportional to a Gaussian in $\frac{b}{n}$, which is independent of concentration and which narrows to a $\ensuremath{\delta}$ function at $\frac{b}{n}={\ensuremath{\alpha}}_{0}$, $n\ensuremath{\rightarrow}\ensuremath{\infty}$. The asymptotic behavior of the Gaussian form gives the critical exponents $\ensuremath{\beta}=0.19\ifmmode\pm\else\textpm\fi{}0.16$, and $\ensuremath{\gamma}=2.34\ifmmode\pm\else\textpm\fi{}0.3$, and ${\ensuremath{\alpha}}_{0}$, gives the critical concentration ${c}_{0}=0.587\ifmmode\pm\else\textpm\fi{}0.14$, in agreement with previous determinations.
294 citations
TL;DR: Evidence from the laboratory indicates that brief exposure to the potent phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA), stimulates DNA synthesis and ODC activity in mouse epidermal cell cultures.
Abstract: TUMOUR-PROMOTING agents have been defined by their ability to promote tumour formation on carcinogen-initiated mouse skin. The most potent of these agents are the diesters of phorbol which are the active components of croton oil, the classic promoting substance. Phorbol esters can be chemically modified in a number of positions to form molecules with a wide range of promoter potency1. Such modifications have been useful in determining structure-function relationships2. A good correlation exists between the ability of phorbol esters to promote epidermal tumours and their ability to stimulate epidermal macro-molecular synthesis in vivo3,4. In particular, all tumour promoters stimulate synthesis of epidermal DNA, although not all chemicals which induce hyperplasia are promoters1. Recently O'Brien et al.5 suggested that the degree of induction of ornithine decarboxylase (ODC) activity in mouse skin after application of promoting and non-promoting compounds correlates well with their promoting potency. Evidence from our laboratory indicates that brief exposure to the potent phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA), stimulates DNA synthesis and ODC activity in mouse epidermal cell cultures (S.H.Y., T.B., E.P., D. Michael, K. Elgjo and H.H., to be published, and U.L. and S.H.Y., to be published). Using such a culture system, we have examined a series of phorbol esters to test the correlation of promoter potency in vivo with the stimulation of DNA synthesis and ODC activity in vitro.
251 citations
TL;DR: In this article, the effect of ordinary viscosity on nuclear fission was studied by solving clasical equations of motion for the time evolution of fissioning nuclei. And the collective potential energy was calculated both by means of the usual liquid-drop model and by a modified liquid drop model that takes into account the lowering in the nuclear macroscopic energy due to the finite range of the nuclear force.
Abstract: We study the effect of ordinary viscosity on nuclear fission by solving clasical equations of motion for the time evolution of fissioning nuclei. The collective potential energy is calculated both by means of the usual liquid-drop model and by means of a modified liquid-drop model that takes into account the lowering in the nuclear macroscopic energy due to the finite range of the nuclear force. The collective kinetic energy is calculated for incompressible, nearly irrotational hydrodynamical flow by use of the Werner-Wheeler method. The Rayleigh dissipation function, which describes the transfer of energy of collective motion into internal excitation energy, is calculated under the assumption that nuclear dissipation arises from individual two-body collisions. Prior to scission the nuclear shape is specified in terms of smoothly joined portions of three quadratic surfaces of revolution. After scission the fission fragments are represented by two spheroids with collinear symmetry axes. In addition to slowing the system down and converting some of the collective energy into internal energy, two-body viscosity hinders the formation of a neck. This leads to a more elongated scission configuration and consequently to a smaller final fission-fragment kinetic energy. From a comparison of calculated and experimental most probable fission-fragment kinetic energies for nuclei throughout the periodic table, we determine that at high excitation energies the average value of the viscosity coefficient $\ensuremath{\mu}$ is $\ensuremath{\mu}=0.015\ifmmode\pm\else\textpm\fi{}0.005 \mathrm{TP}=9\ifmmode\pm\else\textpm\fi{}3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}$ MeV s/${\mathrm{fm}}^{3}$, provided that nuclear dissipation arises from two-body collisions. This is about 30% of the value that is required to critically damp the quadrupole oscillations of idealized heavy actinide nuclei.NUCLEAR REACTIONS, FISSION Calculated dependence of most probable fission-fragment kinetic energies on viscosity and compared with experimental values. Liquid-drop model, hydrodynamical model, nuclear potential energy of deformation, nuclear inertia, nuclear dissipation, numerical solution of classical equations of motion for fissioning nuclei.
251 citations
TL;DR: A major concern to environmentalists, health physicists and radioecologists is the fate of 137Cs released to the environment from existing light-water power stations (estimated annual discharge of 137C as liquid effluent exceeds 2.0 Ci per yr per power station) and future nuclear fuel reprocessing facilities.
Abstract: A MAJOR concern to environmentalists, health physicists and radioecologists is the fate of 137Cs released to the environment from existing light-water power stations (estimated annual discharge of 137Cs as liquid effluent exceeds 2.0 Ci per yr per power station) and future nuclear fuel reprocessing facilities1. Its long half life (30 yr) and its ability to be readily assimilated into body tissues make it potentially one of the most hazardous radionuclides for man. Numerous investigations into the fate of 137Cs in terrestrial environments have revealed that soils exhibit a marked capacity to retain 137Cs; thus soils act as a ‘sink’ for 137Cs released to the environment2,3, and sediments retain 137Cs in a similar fashion in aquatic environments4,5.
189 citations
TL;DR: In this article, correlations between concentrations of nitrogen, phosphorus, magnesium, calcium and potassium across a variety of species, which seem to be based on biochemical similarities between elements in cell metabolism, were reported.
Abstract: INTEREST in the cycling of the elements through ecosystems has increased in recent years, and numerous plant species have been analysed. It can be assumed that elements do not cycle independently in vegetation because they are involved in the basic structure and function of cells, which have similar biochemical pathways. Thus concentrations of different elements must be correlated. Little attention has been given to the relationships between concentrations of elements within or across a variety of species. This is undoubtedly because the chemical composition of individuals within a species may vary considerably from one site to another1. The ratio of different elements may be relatively unaffected by this geographic variation because natural vegetation can absorb and accumulate nutrients selectively2 maintaining a balance of intracellular concentrations to optimise metabolism, protein synthesis and tissue production. If concentrations of elements were correlated across a variety of species from different sites, this would indicate a relatively constant ratio between concentrations of elements among plant cells. I report here correlations between concentrations of nitrogen, phosphorus, magnesium, calcium and potassium, across a variety of species, which seem to be based on biochemical similarities between elements in cell metabolism.
139 citations
TL;DR: The results suggest that the initial stimulus in response to acute thrombocytopenia acts primarily on diploid precursors, programming them to mature into a population of megakaryocytes with an average ploidy approximately one level greater than in normal rats and a proportionate increase in cell size.
128 citations
TL;DR: The character of rate constants for a dissociation occurring near threshold on an attractive potential-energy surface is discussed in this article, where application is made to the attachment of electrons to SF6 and CCl4, and to the autoionization of SF6-.
127 citations
TL;DR: In this article, the authors calculate several quantities of physical interest for an arbitrarily shaped diffuse-surface nuclear density distribution that is made diffuse by folding a short-range function over a uniform sharp-surface distribution of given shape.
Abstract: We calculate several quantities of physical interest for an arbitrarily shaped diffuse-surface nuclear density distribution that is made diffuse by folding a short-range function over a uniform sharp-surface distribution of given shape. The quantities calculated include the moment of inertia about an arbitrary axis, generalized multipole moments, Coulomb and nuclear potentials, and Coulomb and nuclear energies. The expressions that are obtained in terms of volume integrals are converted into surface integrals by use of single and double divergence relations; these techniques are discussed for general functions. All of our methods and some of our results apply to arbitrary folding functions, although for definiteness most of our results are specialized to the case of a Yukawa folding function. The diffuseness of the nuclear surface increases the moment of inertia of light nuclei substantially, which increases the critical angular momentum at which compound nuclei can no longer be formed. The diffuseness correction to the Coulomb energy contains a term that is proportional to the surface area; this term increases the effective surface energy by approximately 2% for light nuclei and by approximately 1% for heavy nuclei.NUCLEAR STRUCTURE Calculated quantities of physical interest for arbitrarily shaped diffuse-surface nuclear density distribution. Moment of inertia, generalized multipole moments, Coulomb and nuclear potentials, Coulomb and nuclear energies, Yukawa folding function, single and double divergence relations, applications to nuclear fission and heavy-ion reactions.
TL;DR: The results are interpreted as indicating that failure of repair is not a causal event in the failure of late passage cells to divide, but that as cells age the ability to do the many coordinated steps in repair declines.
TL;DR: The skin tumor initiating abilities of both K-region and non-K-region epoxides of benzo(a)pyrene(BP) were determined in mice using a two-stage system of tumorigenesis suggesting that it may be a proximate carcinogen.
TL;DR: In this article, the authors analyzed microscopic crystalline monazite inclusions showing giant halo formation in biotite mica by the method of proton-induced x-ray emission.
Abstract: Microscopic crystalline monazite inclusions showing giant halo formation in biotite mica have been analyzed by the method of proton-induced x-ray emission. The observed x-ray energy spectra are best explained by the presence of a number of superheavy elements. (AIP)
TL;DR: Human red cells were equilibrated for 30 min at 20degreesC in buffered saline containing 2 M glycerol and then frozen to --196degreesS/min, confirming previous observations of Meryman in human red cells and indicating the sensitivity to slow warming presumably reflects the recrystallization of intracellular ice.
TL;DR: In this article, a semi-empirical method based on the Pariser-Parr-Pople approximation to the Hartree-Pock equation was used to calculate energy levels for conjugated systems containing C, N, and O atoms.
Abstract: Energy levels have been calculated for some conjugated systems containing C, N, and O atoms using a semi-empiricalmethod based upon a variableβ-γ modification of the Pariser-Parr-Pople approximation to the Hartree-Pock equation. Koopmans' theorem is used to relate the calculated energy of the lowest vacant molecular orbital, ɛLVMO, to the adiabatic electron affinity of a molecule. The approach is identical to that used previously by Kunii and Kuroda [13]. An excellent correlation is found between electron affinities deduced from recent beam experiments and ɛLVMO. This relationship is used to predict electron affinities for over 100 other organic molecules. In addition, excited state energies for negative ions are calculated, and good agreement is found with the available experimental data. Bound excited states are also predicted for some organics which contain the =C(CN)2 substructure. The additive contribution of group substitutions to the electron affinity is discussed for the case of CN substitutions to ethylene, benzene, and naphthalene.
TL;DR: Comparison of neutron irradiation with acute gamma irradiation showed that tumors were induced more effectively with neutrons than with gamma rays, particularly at low doses, while the need for examination of the basis of such relationships are discussed.
Abstract: The influence of dose and dose rate on tumorigenicity after neutron irradiation was investigated in female RFM mice exposed to various doses of neutrons at dose rates of 5 and 25 rad/min or 1 rad/day. Comparison of neutron irradiation with acute gamma irradiation showed that tumors were induced more effectively with neutrons than with gamma rays, particularly at low doses. Linear relationships were obtained at both dose rates for thymic lymphoma induction after neutron irradiation, while a dose-squared relationship was obtained for gamma rays. At low doses little dose-rate dependence was seen with neutrons, while at the highest doses the low dose rate was more effective. An increased incidence of lung adenomas was seen after neutron irradiation with doses as low as 20 rad, while the incidence after gamma-ray irradiation decreased with increased dose except at approximately 300 rad. In spite of the apparent sensitivity, the neutron dose--response curve for lung tumors was not linear. Neutron irradiation at low dose rates appeared to induce thymic lymphomas and possibly lung adenomas more efficiently than irradiation at high dose rates, but was less effective than high dose rates in inducing ovarian and pituitary tumors. Both the importance of a more complete understandingmore » of dose and dose-rate relationships (particularly in the low dose range) and the need for examination of the basis of such relationships are discussed.« less
TL;DR: The reproductive performance of 152 grade Hereford cows that were 14 to 15 years of age at either death or slaughter resulted in an observed mean of 9.3 calves and a calculated mean lifetime reproductive capacity of 10.4 calves, and Cystic corpus luteum was the apparent principal cause of infertility.
Abstract: The reproductive performance of 152 grade Hereford cows that were 14 to 15 years of age at either death or slaughter resulted in an observed mean of 9.3 +- 0.3 calves and a calculated mean lifetime reproductive capacity of 10.4 calves. The median was 10 calves and the modal number was 12. As dictated by the criterion ''failure to bear a calf during two successive years,'' 15 years was the age at which over 50 percent of the herd became infertile. Ovaries from 69 fertile and 78 infertile cows were serially sectioned and microscopically examined; the groups did not differ in total germ-cell endowment (P greater than 0.05), and fertile significantly exceeded infertile only in number of growing follicles (P less than 0.01). No intergroup difference occurred in either number or quality of vesicular follicles. The mean germ-cell endowment of 14- to 15-year-old cows was 24 +- 3 thousand (N = 147). Cystic corpus luteum was the apparent principal cause of infertility.
TL;DR: In this article, the density of states of Pd-H for H/Pd between 0 and 1 was calculated and the superconductivity of such compounds was discussed and a recent theory of Papaconstantopoulos and Klein was found to be reasonable.
Abstract: Results of a CPA calculation of the density of states of Pd-H for H/Pd between 0 and 1 are reported The superconductivity of such compounds is discussed and a recent theory of Papaconstantopoulos and Klein is found to be reasonable 15 references
Alcatel-Lucent1, University of Chicago2, Clemson University3, Rochester Institute of Technology4, Cleveland State University5, DuPont6, University of Illinois at Urbana–Champaign7, IBM8, Johns Hopkins University9, American Cyanamid10, Monsanto11, National Institute of Standards and Technology12, University of Texas at Dallas13, Oak Ridge National Laboratory14, Université Paris-Saclay15
TL;DR: In this article, TTF-TCNQ was measured along the $b$ axis of tetrathiafulvalenium-tetracyanoquinodimethanide (TTF-TTE) to provide a comprehensive summary including approximately 600 samples studied at 18 different laboratories.
Abstract: New measurements of electrical conductivity along the $b$ axis of tetrathiafulvalenium-tetracyanoquinodimethanide (TTF-TCNQ) are combined with published results to provide a comprehensive summary including approximately 600 samples studied at 18 different laboratories The magnitudes of these measured conductivities do not necessitate the assumption of superconducting fluctuations or any other collective state in which the conductivity exceeds the limitations of single-particle scattering Since an adequate theory of the limitations of single-particle scattering for TTF-TCNQ does not exist at present, experiment alone does not rule out the possibility that collective effects may somewhat enhance or suppress the conductivity
TL;DR: It is shown that this defined nutrient medium, referred to as DNOM, can maintain certain morphological and functional characteristics of oocytes for periods up to 3 weeks.
Abstract: A procedure is described for the isolation and culture of large numbers of follicle cell-freeXenopus laevis oocytes in all stages of development. The isolation procedure involves the incubation of pieces of ovary in a calcium-free solution OR2 containing 0.2% collagenase. A defined nutrient medium for the maintenance of the oocytes in vitro is presented. It is shown that this medium, referred to as DNOM, can maintain certain morphological and functional characteristics of oocytes for periods up to 3 weeks.
TL;DR: The susceptibility of rats to pulmonary carcinogens is increased in the absence of vitamin A intake even when considerable amounts of Vitamin A are stored in the liver and deficiency symptoms are absent.
Abstract: The susceptibility of rats to pulmonary carcinogens is increased in the absence of vitamin A intake even when considerable amounts (0.4 nmole/mg) of vitamin A are stored in the liver and deficiency symptoms are absent. This was demonstrated in studies on the induction of metaplastic lung nodules by intratracheally administered 3-methylcholanthrene. Only moderate amounts of all-trans-retinyl acetate in the diet (7.6 nmole/g of diet) were required to prevent the development of this state of enhanced susceptibility. A further increase in intake of retinoids (by intragastric administration of either all-trans-retinyl acetate or 13-cis-retinoic acid) provided no additional protection against the effects of carcinogen.
TL;DR: In this article, a high-volatile bituminous coal (HVab) was examined by means of transmis sion electron microscopy in a highvoltage electron microscope (1 MeV).
TL;DR: The sensitivity of detection of in vivo DNA repair in the germ cells of male mice makes such a system a useful adjunct to other genetic tests for studying chemical mutagenesis in mammals.
Abstract: In vivo DNA repair occurring in early spermatid stages of the mouse has been studied with four mutagens that are chemical homologs: MMS, EMS, PMS and IMS. Using the well-studied sequence of events that occurs during spermatogenesis and spermiogenesis in the mouse, and administering testicular injections of [3H]dT, repair in early spermatids was measured by the unscheduled incorporation of [3H]dT into these germ cells which were recovered from the caudal epididymides 16 days after chemical treatment. Purification of the caudal sperm DNA at this time verified that the [3H]dT was incorporated into the DNA. For each chemical mutagen a study was made on the level of DNA repair occurring in early spermatids as a function of the administered, in vivo dose. Within experimental errors, all four chemicals produced a linear increase in DNA repair in early spermatids with increasing dose. Only the highest dose of MMS (100 mg/kg) produced a greater repair response than expected for a linear curve. At equimolar doses the most effective chemical in inducing DNA repair was MMS, followed by EMS, IMS and PMS. When testicular injections of [3H]dT were given at the same time as the intraperitoneal injections of the mutagens, the amount of unscheduled incorporation of [3H]dT into the DNA of early spermatids was maximized. Since [3H]dT has been shown to be available for incorporation into germ-cell DNA for only ∼ 1 h after injection, all four mutagens must reach the DNA of early spermatids and begin producing “repairable” lesions within 1 h after treatment. The amount of DNA repair occurring at later times after chemical treatment of early spermatids was studied by testicular injections of [3H]dT 1 2 , 1, 2 and 3 days after chemical treatment. Repair was still occurring in the early spermatids at 3 days post-treatment; this repair is most likely a manifestation of the finite rate of the repair process rather than resulting from newly alkylated DNA. For MMS and EMS there was a rapid decrease in the level of DNA repair in the first 1 2 day following treatment. This was followed by a much slower, exponential decrease in the level of repair out to 3 days post-treatment. The curves suggest that the amount of repair is proportional to the number of repairable lesions still present in the DNA. For PMS and IMS the level of repair decreases rapidly in the first 1 2 day after treatment and thereafter remains relatively constant through 3 days post-treatment. With all four mutagens, DNA repair in early spermatids was detectable at doses 5 to 10 times lower than those required to observe other genetic end points such as dominant lethals, translocations and specific-locus mutations in any germ-cell stage. The sensitivity of detection of in vivo DNA repair in the germ cells of male mice makes such a system a useful adjunct to other genetic test for studying chemical mutagenesis in mammals.
TL;DR: In this article, a statistical model is described and employed to calculate inverse mean free paths and stopping powers for electrons of energies from a few eV to 10 keV above the Fermi level in Al, Si, Ni, Cu, Ag and Au.
Abstract: A statistical model is described and employed to calculate inverse mean free paths and stopping powers for electrons of energies from a few eV to 10 keV above the Fermi level in Al, Si, Ni, Cu, Ag, and Au. Brief tables of mean free paths and stopping powers for these solids are presented. In some cases graphical displays of inverse mean free paths and stopping powers are also included. The calculations based on this model are discussed and compared with previous work.
TL;DR: Chimpanzees chronically infected with hepatitis-B virus showed transient changes in several markers of infection when treated with the interferon inducer polyriboinosinic-polyribocytidylic acid-poly-l-lysine carboxymethyl cellulose, and defective (D.N.A.A.-polymerase-negative) Dane particles increased in titre transiently during treatment; these may play a role in the modulation of hepatitis- B virus infection.
TL;DR: Preliminary experimental results and an empirical mathematical model of the tapered bed indicate that bed stability is associated with a decreasing velocity and void‐fraction profile up the bed and the pressure drop across the bed decreases with increasing flow rates.
Abstract: Reactor systems based on tapered fluidized beds are being developed for aqueous bioprocesses in which adhering microorganisms or immobilized active biological fractions are used. The use of a fluidized bed prevents biomass buildup, accommodates particulates in the feed stream, is compatible with gas sparging, and allows easy removal or addition of the active materials. The tapered reactor tends to stabilize the fluidized bed, thus allowing a much wider range of operating conditions. Preliminary experimental results and an empirical mathematical model of the tapered bed indicate that bed stability is associated with a decreasing velocity and void-fraction profile up the bed and the pressure drop across the bed decreases with increasing flow rates. The tapered fluidized bed bioreactor is being evaluated for use in the enzymatic production of hydrogen, microbiological denitrification, and microbiological degradation of coal conversion aqueous waste streams. The enzyme catalyzed conversion of lactose to glucose and galactose was used in the evaluation of the reactor concept.
TL;DR: In this paper, a compilation of 72 published thermochemical cycles for the production of hydrogen from water is presented, and a review of the most modern concepts for the hydrogen production from water can be found.
TL;DR: A causal role for defective storage and release of endogenous serotonin as the basis for the bleeding tendency in beige mice is suggested, acting either independently or synergistically with impaired release of adenine nucleotides.
Abstract: Beige mice have been observed to bleed excessively from small wounds. Platelets obtained from these mice were deficient in adenine nucleotides and serotonin and in vivo uptake of labeled serotonin was impaired. Heterozygotes of beige and C57BL/6 mice have adenine nucleotide and serotonin levels comparable to control and do not manifest a bleeding tendency, consistent with the recessive mode of inheritance of the beige mouse syndrome. Morphologic confirmation of the observed biochemical defects was obtained by the demonstration that serotonin storage organelles were not observed in electron photomicrographs of beige mouse platelets. The demonstration that small doses of serotonin were effective in reversing the bleeding tendency in beige mice suggested a causal role for defective storage and release of endogenous serotonin as the basis for the bleeding tendency, acting either independently or synergistically with impaired release of adenine nucleotides.
TL;DR: In this paper, a semiquantitative model is presented which treats the phenomenon in terms of quantum mechanical phase interference between pairs of near-resonant quasimolecular levels.
Abstract: Measurements have been performed of the dependence on scattering angle and target orientation of the oscillatory structure recently observed in low-energy ion scattering from surfaces. Wide variation is exhibited in the behavior of oscillation maxima as a function of scattering angle depending on the target species studied. A semiquantitative model is presented which treats the phenomenon in terms of quantum mechanical phase interference between pairs of near-resonant quasimolecular levels.