Self-Irradiation Cascade Simulations in Plutonium Metal: Model Behavior at High Energy

The Modified Embedded Atom Method model for Pu metal is revised so that it more accurately captures the behavior of the Ziegler-Biersack-Littmark model of ion-ion interactions. Two revision are tested with somewhat different stiffnesses in the 2-1000 eV range. The revised models show higher damage levels at 20 KeV than an earlier model, suggesting that the behavior of the models above 100 eV is dominating damage production, at least in the earlier stages of the cascade. Work was performed at Los Alamos National Laboratory under the auspices of the US Department of Energy, under contract DE-AC52-06NA25396.     

Atomistic simulations of Ga atom ordering in Pu 5 at. % Ga alloys

We employ molecular dynamics and Monte Carlo (MC) methods to simulate the rearrangement of Ga atoms from a randomly distributed Pu-Ga alloy and study the resultant effect on thermodynamic properties. The results show that all of the first neighbor Ga-Ga bonds are removed at all temperatures considered (200, 400 and 600 K) while the number of 2NN and 3NN bonds increase, and the number of 4NN bonds decreases. These results imply that Ga atoms develop strong short range ordering in the solid solution. The ordering causes an enthalpy decrease about ~3–4 meV/atom for different temperatures in the 5 at. % Ga alloy. This energy change is clearly important in the calculation of the Pu-Ga phase diagram. In addition, MC calculations at 200 K show pronounced Ga segregation.     

Collision cascades in pure <Emphasis Type="Italic">δ</Emphasis>-plutonium

Molecular dynamics simulations of the formation and annealing of large collision cascades in delta-phase plutonium are presented. The defect evolution is followed with time up to 2 ns. Simulations are performed with the MEAM potential at three different temperatures; at 600 K where the pure delta phase is thermodynamically stable; at 300 K where the delta phase can only be maintained in a metastable state with minor additions of gallium or aluminum; and at 180 K where plutonium should transform to the alpha phase. It is found in all three cases that the atomic structure within the cascade evolves through a glass-like state. At 600 K, this structure recovers very slowly; at 300 K it persist up to 2 ns with no discernable trend to recover eventually; and at 180 K the amorphous structure initiated by the collision cascade spreads through the entire crystal and converts it to a glass-like structure.     

Simulation of ion-track ranges in uranium oxide

Direct comparisons between statistically sound simulations of ion-tracks and published experimental measurements of range densities of iodine implants in uranium dioxide have been made with implant energies in the range of 100–800 keV. Our simulations are conducted with REED-MD (Rare Event Enhanced Domain-following Molecular Dynamics) in order to account for the materials structure in both single crystalline and polycrystalline samples. We find excellent agreement between REED-MD results and experiments for polycrystalline target materials.     

Nanoscale Plasticity at Grain Boundaries in Face-centered Cubic Copper Under Shock Loading

We investigate the responses of four representative grain boundaries in face-centered cubic Cu bicrystals to shock compression as a function of the loading direction. Two loading directions are considered, either parallel or perpendicular to the grain boundary plane, representing the extremes that a polycrystalline sample will ordinarily experience under the uniaxial strain conditions of planar shock loading. Using molecular dynamics simulations, we demonstrate that the deformation processes during shock compression of the same boundary are altered measurably by changing the loading direction. The Majority of the differences in the nanoscale deformation processes were related to the activation of varying slip systems in the same boundary under the two loading conditions. This change in deformation processes, and hence the plastic response, might eventually affect the failure stress for a grain boundary.     

Emulsified anterior chamber silicone oil and glaucoma

PURPOSE: This retrospective study was undertaken to assess the occurrence of postoperative anterior chamber emulsified silicone oil after intravitreal instillation and to examine the relation between such emulsification and new postoperative glaucoma. METHODS: Forty-eight consecutive eyes received intravitreal silicone oil, were followed for at least 1 year, and were evaluated postoperatively by gonioscopy on at least one occasion. Eight eyes received 1000 cs oil, and 40 eyes received 5000 cs oil from which low molecular weight contaminants were removed. All aphakic and pseudophakic eyes received an inferior iridectomy. Oil was removed in 19% of eyes during follow-up. RESULTS: Fifty-six percent of eyes manifested anterior chamber emulsified oil postoperatively. The oil was typically identified only on gonioscopy. This complication developed in 50% of eyes receiving 1000 cs oil and 58% of eyes receiving highly homogeneous 5000 cs oil. Of the 48 eyes, new postoperative glaucoma best explained by interval angle oil emulsification developed in 5 (10%). CONCLUSION: Anterior chamber oil emulsification occurred frequently, despite inferior peripheral iridectomy in aphakic or pseudophakic eyes and the use of highly purified, higher viscosity oil in 83% of eyes. In this series, new glaucoma in the setting of angle oil emulsification only developed in 10% of eyes. The glaucoma was managed medically in four of five patients.     

Parental expressed emotion and affective style in an adolescent sample at risk for schizophrenia spectrum disorders.

Investigated the correspondence between interview-assessed parental emotional attitudes toward a particular offspring (expressed emotion; EE) and parental affective behavior manifested in direct family interactions for 52 14–19 yr old disturbed but nonpsychotic adolescents. Individual parents who expressed an excessive number of critical comments during the interview (high EE) manifested significantly more mild and harsh criticisms in direct interactions with their offspring than did low-EE parents. A more complex relationship emerged between attitudes and behavior when both parents' emotional attitudes were considered simultaneously. When both parents were high EE, they expressed high levels of mild and harsh criticisms in direct interactions with their offspring. Parental affective behavior in families with only 1 high-EE parent was characterized by high levels of mild criticisms but low levels of harsh criticisms. When both parents were low EE, they manifested few mild or harsh criticisms in direct interactions. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parental expressed emotion and psychophysiological reactivity in an adolescent sample at risk for schizophrenia spectrum disorders.

The correspondence between interview-assessed parental emotional attitudes toward a particular offspring (expressed emotion [EE]) and the psychophysiological reactivity of both parents and their children during a series of direct family interactions was investigated for a sample of 52 disturbed but nonpsychotic adolescents (aged 14–29 yrs). Parents who expressed an excessive number of critical comments during the interview were designated as high EE, and the remainder were designated as low EE. Both high-EE parents and their adolescent offspring became significantly more psychophysiologically reactive as the 1st of 2 family confrontations in which they participated progressed. Adolescents also showed greater arousal when anticipating interactions with a high-EE parent when that parent was first in the experimental sequence. These results are combined with those of a previous study by the authors and J. A. Doane (see record 1984-06985-001) to support the notion that the EE measure is marking clearly defined family emotional climates that appear to be related to the subsequent onset of schizophrenia spectrum disorders in this adolescent sample. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Consilient Psychoanalysis.

The concept of consilience, that is, the fundamental unity of knowledge across disciplines, is applied to the field of psychoanalysis. Whereas practitioners in other disciplines, especially the natural sciences, strive for consilience, psychoanalysis as a discipline is found to be frequently lacking in consilience. Implications for paradigm change, metatheory, and evidence-based practice are discussed, and it is suggested that all psychoanalytic theories should be evaluated for their degree of consilience so as to make the discipline as robust and well integrated with knowledge in other disciplines as possible. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tumor necrosis factor release by human monocytes stimulated with platelet-activating factor

Platelet-activating factor (PAF) is a low molecular weight phospholipid which enhances human monocyte cytotoxicity for tumor cells. In the current studies, the capacity of PAF to stimulate release of tumor necrosis factor α (TNFα) by human monocytes was assessed. PAF induced maximal TNFα synthesis 2–3 hr after monocyte stimulation as assessed by dot blotting of cell-associated TNFα using polyclonal anti-TNF antibody. Maximal net release of TNFα occurred 5–16 hr after monocyte stimulation, as assessed by a specific ELISA. Dose-response studies revealed that a maximal two- to three-fold increase in release of TNFα occurs at 10–100 pM PAF. LysoPAF and the optical isomer of PAF did not stimulate release of TNFα, suggesting that stimulation is mediated by specific PAF receptors. Scatchard analysis of [³H]PAF binding to monocyte membranes revealed 651±495 binding sites/monocyte with a Kd of 4.7±4.2×10⁻¹⁰M. PAF is a structurally unique activator of monocytes whose interactions with TNFα and other cytokines may be critical to host defense against tumors. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.