Ion-induced nucleation. II. Polarizable multipolar molecules

Density functional theory is applied to ion-induced nucleation of polarizable multipolar molecules. The asymmetric nature of the ion-molecule interaction is shown to cause the sign preference in ion-induced nucleation. When the ion-molecule interaction is weak, the observed sign preference is consistent with that of the bare ion-molecule interaction potential and decreases with increasing supersaturation. However, as the ion-molecule interaction becomes stronger, the sign preference in the reversible work exhibits some nontrivial behavior. For molecular parameters applicable for CS2 and CH4, the predicted values of the reversible work of nucleation depend on the sign of the ion charge, yielding a difference in the nucleation rate by factors of 10 to 10^(2) and 10 to 10^(5), respectively

Ion-induced nucleation: A density functional approach

Density functional theory is applied to ion-induced nucleation of dipolar molecules. The predicted reversible work shows a sign preference, resulting in a difference in the nucleation rate by a factor of 10–10^2, for realistic values of model parameters. The sign effect is found to decrease systematically as the supersaturation is increased. The asymmetry of a molecule is shown to be directly responsible for the sign preference in ion-induced nucleation

Binary nucleation of sulfuric acid-water: Monte Carlo simulation

We have developed a classical mechanical model for the H2SO4/H2O binary system. Monte Carlo simulation was performed in a mixed ensemble, in which the number of sulfuric acid molecules is fixed while that of water molecules is allowed to fluctuate. Simulation in this ensemble is computationally efficient compared to conventional canonical simulation, both in sampling very different configurations of clusters relevant in nucleation and in evaluating the free energy of cluster formation. The simulation yields molecular level information, such as the shape of the clusters and the dissociation behavior of the acid molecule in the cluster. Our results indicate that the clusters are highly nonspherical as a result of the anisotropic intermolecular interactions and that a cluster with a given number of acid molecules has several very different conformations, which are close in free energy and hence equally relevant in nucleation. The dissociation behavior of H2SO4 in a cluster differs markedly from that in bulk solution and depends sensitively on the assumed value of the free energy f(hb) of the dissociation reaction H2SO4+H2O-HSO4-. H3O+. In a small cluster, no dissociation is observed. As the cluster size becomes larger, the probability of having an HSO4-. H3O+ ion pair increases. However, in clusters relevant in nucleation, the resulting ion pairs remain in contact; about 240 water molecules are required to observe behavior that resembles that in bulk solution. If a larger value of f(hb) is assumed to reflect its uncertainty, the probability of dissociation becomes negligible. A reversible work surface obtained for a condition typical of vapor to liquid nucleation suggests that the rate-limiting step of new particle formation is a binary collision of two hydrated sulfuric acid molecules. The ion pairs formed by dissociation play a key role in stabilizing the resulting cluster. The reversible work surface is sensitive to the assumed value of f(hb), thus pointing to the need for an accurate estimate of the quantity either by ab initio calculations or experiments

Humidity effects on adhesion of nickel-zinc ferrite in elastic contact with magnetic tape and itself

The effects of humidity on the adhesion of Ni-Zn ferrite and magnetic tape in elastic contact with a Ni-Zn ferrite hemispherical pin in moist nitrogen were studied. Adhesion was independent of normal load in dry, humid, and saturated nitrogen. Ferrites adhere to ferrites in a saturated atmosphere primarily from the surface tension effects of a thin film of water adsorbed on the ferrite surfaces. The surface tension of the water film calculated from the adhesion results was 48 times 0.00001 to 56 times 0.00001 N/cm; the accepted value for water is 72.7 x 0.00001 N/cm. The adhesion of ferrite-ferrite contacts increased gradually with increases in relative humidity to 80 percent, but rose rapidly above 80 percent. The adhesion at saturation was 30 times or more greater than that below 80 percent relative humidity. Although the adhesion of magnetic tape - ferrite contacts remained low below 40 percent relative humidity and the effect of humidity was small, the adhesion increased considerably with increasing relative humidity above 40 percent. The changes in adhesion of elastic contacts were reversible on humidifying and dehumidifying

Octet and Decuplet Baryons in a Confining and Covariant Diquark-Quark Model

We treat baryons as bound states of scalar or axialvector diquarks and a constituent quark which interact through quark exchange. We obtain fully four-dimensional wave functions for both octet and decuplet baryons as solutions of the corresponding Bethe-Salpeter equation. Applications currently under investigation are: electromagnetic and strong form factors and strangeness production processes.Comment: 4 pages, 1 figure; talk given by R. Alkofer at PANIC 9

Association between Choroidal Characteristics and Systemic Severity in Amyloidosis

PURPOSE: This study aimed to describe the choroidal features of ocular amyloidosis using multimodal imaging, to correlate these findings with systemic involvement, and to propose a choroidal grading system. METHODS: Eleven patients with systemic amyloidosis were reviewed retrospectively. Each case was assigned a grade according to the severity of choroidal findings as determined by both enhanced depth imaging optical coherence tomography and indocyanine green angiography. The severity of systemic amyloidosis was then correlated with the choroidal involvement. RESULTS: On indocyanine green angiography, all patients exhibited hyperfluorescent spots in the late stage and were classified according to preexisting criteria. On enhanced depth imaging optical coherence tomography, hyperreflective foci were seen in the choriocapillaris and Sattler's layer in Grade 1, partial loss of Sattler's layer was additionally seen in Grade 2, and a dense hyperreflective Haller's layer was seen in Grade 3. Choroidal grading scores were significantly correlated with the systemic severity score (P = 0.0014, Pearson's correlation coefficient; ρ = 0.83). CONCLUSION: With ocular amyloidosis, evaluation of choroidal characteristics using multimodal imaging may serve as a biomarker for systemic involvement

Study of relativistic bound states for scalar theories in Bethe-Salpeter and Dyson-Schwinger formalism

The Bethe-Salpeter equation for Wick-Cutkosky like models is solved in dressed ladder approximation. The bare vertex truncation of the Dyson-Schwinger equations for propagators is combined with the dressed ladder Bethe-Salpeter equation for the scalar S-wave bound state amplitudes. With the help of spectral representation the results are obtained directly in Minkowski space. We give a new analytic formula for the resulting equation simplifying the numerical treatment. The bare ladder approximation of Bethe-Salpeter equation is compared with the one with dressed ladder. The elastic electromagnetic form factors is calculated within the relativistic impulse approximation.Comment: 30 pages, 10 figures, accepted for publication in Phys. Rev.

Consideration for Affects of an XOR in a Random Number Generator Using Ring Oscillators

A cloud service to offer entropy has been paid much attention to. As one of the entropy sources, a physical random number generator is used as a true random number generator, relying on its irreproducibility. This paper focuses on a physical random number generator using a field-programmable gate array as an entropy source by employing ring oscillator circuits as a representative true random number generator. This paper investigates the effects of an XOR gate in the oscillation circuit by observing the output signal period. It aims to reveal the relationship between inputs and the output through the XOR gate in the target generator. The authors conduct two experiments to consider the relevance. It is confirmed that combining two ring oscillators with an XOR gate increases the complexity of the output cycle. In addition, verification using state transitions showed that the probability of the state transitions was evenly distributed by increasing the number of ring oscillator circuits

Primary extrauterine endometrial stromal sarcoma: response to hormone therapy

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