Department of Atomic Energy

Abstract The effect of combined hydrostatic pressure, P, and of uniaxial tension, [sgrave], on the rupture time of polycrystalline copper wire in the temperature range 400° to 500°c has been determined. All the specimens broke by intergranular fracture, due to the growth of voids along grain boundaries. Preliminary experiments indicated that the voids grow by the addition of vacancies under the action of the applied stress. A theory has been developed assuming that failure results from the growth of void nuclei on the grain boundary, which requires that the activation energy for failure is that of grain boundary diffusion and that the rupture time, tr, depends only on ([sgrave]-P). The experiments show that the activation energy is close to the expected value, and provided that [sgrave] is constant tr agrees with theory. Changes in [sgrave], when ([sgrave] - P) is constant, affect tr appreciably, and the results suggest that many of the void nuclei are stress induced.

Abstract A new method is described for setting up the effective potential for electrons in non-transition metals, including liquid metals and alloys. It is based on a model potential fitted to the spectroscopically measured energy levels of the free ions. The potential between the atomic cores is obtained from the dielectric screening calculation of Cohen and Phillips (1961) with some refinements. The method is tested on the band structures of the (solid) alkali metals. The Fermi surfaces of K, Rb and Cs are found to be considerably less distorted than calculated by Ham (1962), and thus in better agreement with experiment.

Abstract Formulae are obtained for the concentration in a poorly diffusing half space bisected by a thin well-diffusing slab, at different times after the edge of the half-space has been suddenly raised from zero to unit concentration. This represents a simplified model for studying 'grain boundary' diffusion of one metal into another. The problem also has obvious application to the study of heat flow in a poorly conducting solid with a metallic fin.

We show how to use known constant elements in a Jacobian matrix to reduce the work required to estimate the remaining elements by finite differences.

The flow produced by an infinite rotating disk when the fluid at infinity is in a state of solid rotation is investigated numerically. When the fluid at infinity is rotating in the same sense as the disk, physically acceptable solutions exist in all cases. When the fluid at infinity is rotating in the opposite sense to that of the disk, the only physically acceptable solutions appear to be those in which there is a uniform suction present acting through the disk.

The traditional view that mental disorders are distinct, categorical disorders has been challenged by evidence that disorders are highly comorbid and exist on a continuum (e.g., Caspi et al., 2014; Tackett et al., 2013). The first objective of this study was to use structural equation modeling to model the structure of psychopathology in an adolescent community-based sample (N = 2,144) including conduct disorder, attention-deficit/hyperactivity disorder (ADHD), oppositional-defiant disorder (ODD), obsessive-compulsive disorder, eating disorders, substance use, anxiety, depression, phobias, and other emotional symptoms, assessed at 16 years. The second objective was to identify common personality and cognitive correlates of psychopathology, assessed at 14 years. Results showed that psychopathology at 16 years fit 2 bifactor models equally well: (a) a bifactor model, reflecting a general psychopathology factor, as well as specific externalizing (representing mainly substance misuse and low ADHD) and internalizing factors; and (b) a bifactor model with a general psychopathology factor and 3 specific externalizing (representing mainly ADHD and ODD), substance use and internalizing factors. The general psychopathology factor was related to high disinhibition/impulsivity, low agreeableness, high neuroticism and hopelessness, high delay-discounting, poor response inhibition and low performance IQ. Substance use was specifically related to high novelty-seeking, sensation-seeking, extraversion, high verbal IQ, and risk-taking. Internalizing psychopathology was specifically related to high neuroticism, hopelessness and anxiety-sensitivity, low novelty-seeking and extraversion, and an attentional bias toward negatively valenced verbal stimuli. Findings reveal several nonspecific or transdiagnostic personality and cognitive factors that may be targeted in new interventions to potentially prevent the development of multiple psychopathologies. (PsycINFO Database Record

Abstract It is a feature of many atomic diffusion jump mechanisms that successive jumps of an atom are "correlated" in the sense that the direction of a jump is not completely at random but is influenced to some extent by the direction of the preceding jump or jumps. General formulae are derived for the diffusion coefficient which take account of this correlation. The theory is applied to a calculation of the diffusion coefficient of solute atoms by the Johnson mechanism.

I. INTRODUCTION I. INTRODUCTION Chemical speciation may be defined as the determination of the individual concentrations of the various chemical forms of an element which together make up the total concentration of that element in a sample. The next decade will certainly see a blossoming of interest from chemists, biochemists, and biologists in techniques for chemical speciation. This is because it is becoming more and more apparent that both bioavailability and toxicity are critically dependent on the chemical form of the substance under test. Measurement of the total concentration of a nutrient or a trace element provides very little information about the bioavailability of the substance, since many vitamins and essential elements are now known to exist in a variety of chemical forms, the assimilability of which vary greatly.1–3 For example, niacin and folic acid exist in some foods in bound forms which are unavailable to many species,4 and the same is true of a whole range of essential metals, including iron, zinc, cobalt, and chromium. For man, the most assimilable form of iron is heme iron from meat. Inorganic iron salts and simple organic complexes are far less available. The group of chromium-amino-acid complexes known as the glucose tolerance factor1.5 provides most of the usable chromium, while cobalamin (vitamin B12) is the only essential chemical form of cobalt.6 It has also been suggested that zinc-amino-acid complexes are more available than inorganic zinc.2.7 Analysis of a diet for total iron, chromium, cobalt, or zinc, without some information about their chemical forms, is therefore almost worthless because a nutritional deficiency of these elements could exist despite their widespread distribution.

Existing expressions for the density of vibrational energy levels of polyatomic molecules are inadequate and/or very difficult to evaluate. Simple, approximate expressions, which are sufficiently accurate for most applications, are obtained for the density of vibrational energy levels, its integrals and the density of vibrational/rotational energy levels. Both harmonic and anharmonic vibrations are considered.

ABSTRACT Chhaochharia and Grinstein estimate that CEO pay decreases 17% more in firms that were not compliant with the recent NYSE/Nasdaq board independence requirement than in firms that were compliant. We document that 74% of this magnitude is attributable to two outliers of 865 sample firms. In addition, we find that the compensation committee independence requirement increases CEO total pay, particularly in the presence of effective shareholder monitoring. Our evidence casts doubt on the effectiveness of independent directors in constraining CEO pay as suggested by the managerial power hypothesis.

Natural scientists are being encouraged by environmental and developmental agencies to define and operationalize the concept of sustainability in a “scientific” manner. Such an approach is fraught with dangers because values, opinions, and social influences are an inextricable part of science, especially applied science. Natural scientists’ attempts to define sustainability, particularly to decide what should be sustained, cannot therefore be value‐neutral. They simply end up shifting value judgments to different levels by choosing either a single obvious objective, an arbitrary range of objectives, or an arbitrary method of aggregating different preferences. This lack of self‐reflectiveness on the part of scientists has important consequences for the direction of research and its political implications. Natural scientists should heed lessons from earlier cases of scientists’ involvement in policy and redefine the terms of reference before shouldering their social burden. The dilemma of pursuing objective science in a value‐loaded and socially charged discourse can be resolved by properly understanding the role of analysis and by pursuing a socially grounded pluralistic approach to problem definition and research methodology.

THE role of human exposure to radiation in the genesis of leukemia has been recognized since 1925. In recent times many authors have reported cases of leukemia occurring in irradiated persons.1 2 3 4 5 6 7 8 9 10 11 12 13 14 Several reports of the Atomic Bomb Casualty Commission have verified the development of leukemia at an excessive rate in the survivors of the atomic bombings.15 16 17 18 19 20 21 22 23 24 25 The literature on the relation of ionizing radiation to leukemia has been summarized in the past by others26 27 28 and most recently by Miller.29 The previous findings of the Commission have demonstrated an excess of leukemia developing in those more proximal to the hypocenter at . . .

By chromatography on a silicic acid column, artificial lipid mixtures and plasma lipids have been separated into fractions composed mainly of the following groups: sterol esters, triglycerides, sterols, fatty acids and phospholipids. By this tech-nic eleostearic acid is found exclusively in the triglyceride fraction after having been fed as the methyl ester.

Abstract A model for describing the clustering of interstitial atoms in graphite is set forth, based on chemical reaction rate theory. Vacancies and interstitials are assumed to be homogeneously generated by the neutron flux. The interstitials are allowed to move freely between the layer planes whilst the vacancies are considered to be stationary. Two types of nucleation are considered: (1) homogeneous nucleation when one unbound interstitial meets another unbound interstitial, (2) heterogeneous nucleation when one unbound interstitial encounters another interstitial atom bound already to a boron atom. It is shown that heterogeneous nucleation may be taken into account in the reaction rate theory by reducing the velocity of the interstitials by an amount which corresponds to the time they spend bound to an impurity. Differential equations are formulated to allow for the variation of loop density and average loop radius with time. Numerical and asymptotic solutions are obtained and fitted to data obtained from electron microscope observations (Kelly and Mayer 1969); the theory predicts that the loop density is proportional to the square root of the impurity concentration and that the loop radius is inversely proportional to the sixth root of the impurity concentration, provided the interstitial velocity is ‘impurity controlled’.

(1962). Neutron scattering studies of liquid diffusion. Advances in Physics: Vol. 11, No. 43, pp. 203-232.

Summary The modifications produced in the Rayleigh-Jeffreys theory of slow thermal convection by magneto-hydrodynamic effects in a conducting fluid placed in a magnetic field are examined. Even for a non-viscous fluid, a critical temperature gradient β0 must be exceeded in order that convection occur. In this, the place of viscosity η occurring in the Rayleigh-Jeffreys formula is taken by a quantity η H depending on the conductivity of the fluid, the magnetic field strength H and depth of fluid d, thus η H= (4/27)(d 2/π2)(σμ 2H2/c 2). If the fluid is viscous a multiple of the normal viscosity depending on H must be added to η H. An estimate of the critical gradient is made tor somewhat artificial boundary conditions and it is found large enough to be experimentally detectable. The applicability of Jeffreys' method of marginal stability is discussed and the nature of possible oscillations investigated.

The absorption of palmitic acid-1-C/sup 14/ by ascites tumor cells was studied in vitro. Palmitate was metabolized more rapidly from its albumin complex than from buffer alone, but the albumin carrier was not absorbed or metabolized. Cyanide-inhibited cells absorbed palmitate from ihe medium but did noi metabolize it. The process of absorption was thus revealed as a distribution of fatty acid between the medium and the inert cell surface probably followed by an active transfer of the fatty acid into the cell for oxidation. (auth)

Ionic micelles in aqueous solution usually grow in size on addition of the electrolytes. This paper deals with the understanding of the reasons for different growths of micelles for different electrolytes. In this connection, small-angle neutron scattering (SANS) experiments on aqueous micellar solutions of ionic surfactants cetyltrimethylammonium chloride (CTAC) and sodium dodecyl sulphate (SDS) in presence of various alkali-metal halide electrolytes are reported. The measurements have been carried out from 0.1 M CTAC for varying concentrations of $\mathrm{KBr}(=0.0,0.03,0.05,0.07,$ and 0.1 M) and $\mathrm{KCl}(=0.0,0.05,0.1,0.3,0.5,0.7,$ and 1.0 M). It is found that micelles grow on addition of KBr, but their size is constant over a wide range of KCl concentration. When compared with similar data on CTAB micellar solutions, these data suggest that the differences in the micellar growths in the above systems are not connected with the common ion effect. To examine the effect of size and hydration behavior of ions of the electrolytes on the micellar growth, SANS measurements from SDS micellar solutions have been carried out in presence of alkali halide electrolytes $(AX,A=\mathrm{Na},\mathrm{K},\mathrm{Cs}$ and $X=\mathrm{Cl},\mathrm{Br},\mathrm{I})$ for the fixed concentrations of surfactant (= 0.3 M) and the electrolyte (= 0.1 M). It is found that micellar growth strongly depends on the counterions and there is negligible effect of the coions. The growth is more when the counterion hydration is smaller.

Applying first principles electronic structure calculations and molecular dynamics (MD) simulations we have studied the structural stability, hydrogen adsorption capability and hydrogen desorption kinetics of Y-decorated single walled carbon nanotube (SWCNT). We have predicted that a single Y atom attached on SWCNT can physisorb up to six hydrogen molecules which is not reported so far. Our MD simulations with four Y atoms placed at the alternate hexagons of SWCNT showed no clustering effect of Y atoms at room temperature and also we found that the system is stable even at higher temperature (700 K). For the first time we showed that 100% desorption at comparatively lower temperature can be achieved in a transition metal-decorated SWCNT system. Therefore the Y-decorated SWCNT has the potential to become a promising hydrogen storage device.

Abstract The spatial distribution of electronic charge is calculated exactly for three simple cases. These are the perfect lattice, perfect lattice with a single vacancy and perfect lattice with a single substitutional impurity. The potential is assumed to be of muffin tin form. The results are similar in appearance to the equations for the Kohn-Rostoker band structure calculations and appear ideally suited to numerical computation. Examples are given to illustrate the results. These are rather simple, but two interesting conclusions can be drawn: the charge at a vacancy is not directly proportional to the density of states of the host lattice and an impurity can cause two bound states to appear from a narrow band.