The chemistry of Venus' atmosphere

A model for the Venus atmosphere involving photochemistry of oxygen, hydrogen, chlorine and sulfur species is presented. Sulfur reaction schemes and hydrogen and chlorine reaction schemes were included. The impact of sulfur on the oxygen budget and the subsequent production of H2SO4 molecules for the Venus cloud deck were explored. A major new reaction scheme for production of H2SO4 molecules involving sulfur and oxygen chemistry was established shown to dominate over the odd hydrogen scheme proposed earlier. The efficiency of the scheme in formation of H2SO4 is only about 50%, with the remaining sulfur residing in SO2 molecules. The calculated downward flux of H2SO4 may be sufficient to maintain a steady state sulfuric acid cloud if the resident time of H2SO4 droplets in the cloud is as long as a few years. If however, the resident time is half a year or shorter, additional chemistry capable of more efficient conversion of SO2 to SO3 is required

Harmonically Trapped Four-Boson System

Four identical spinless bosons with purely attractive two-body short-range interactions and repulsive three-body interactions under external spherically symmetric harmonic confinement are considered. The repulsive three-body potential prevents the formation of deeply-bound states with molecular character. The low-energy spectrum with vanishing orbital angular momentum and positive parity for infinitely large two-body $s$-wave scattering length is analyzed in detail. Using the three-body contact, states are classified as universal, quasi-universal, or strongly non-universal. Connections with the zero-range interaction model are discussed. The energy spectrum is mapped out as a function of the two-body $s$-wave scattering length $a_s$, $a_s>0$. In the weakly- to medium-strongly-interacting regime, one of the states approaches the energy obtained for a hard core interaction model. This state is identified as the energetically lowest-lying "BEC state". Structural properties are also presented.Comment: 6 figure

Minimal hepatic toxicity of Onyx-015: spatial restriction of coxsackie-adenoviral receptor in normal liver.

We administered an adenoviral vector, Onyx-015, into the hepatic artery of patients with metastatic colorectal cancer involving the liver. Thirty-five patients enrolled in this multi-institutional phase I/II trial received up to eight arterial infusions of up to 2 x 10(12) viral particles. Hepatic toxicity was the primary dose-limiting toxicity observed in preclinical models. However, nearly 200 infusions of this adenoviral vector were administered directly into the hepatic artery without significant toxicity. Therefore, we undertook this analysis to determine the impact of repeated adenoviral exposure on hepatic function. Seventeen patients were treated at our institution, providing a detailed data set on the changes in hepatic function following repeated exposure to adenovirus. No changes in hepatic function occurred with the first treatment of Onyx-015 among these patients. Transient increases in transaminase levels occurred in one patient starting with the second infusion and transient increases in bilirubin was observed in two patients starting with the fifth treatment. These changes occurred too early to be explained by viral-mediated lysis of hepatocytes. In addition, viremia was observed starting 3-5 days after the viral infusion in half of the patient, but was not associated with hepatic toxicity. To further understand the basis for the minimal hepatic toxicity of adenoviral vectors, we evaluated the replication of adenovirus in primary hepatocytes and tumor cells in culture and the expression of the coxsackie-adenoviral receptor (CAR) in normal liver and colon cancer metastatic to the liver. We found that adenovirus replicates poorly in primary hepatocytes but replicates efficiently in tumors including tumors derived from hepatocytes. In addition, we found that CAR is localized at junctions between hepatocytes and is inaccessible to hepatic blood flow. CAR is not expressed on tumor vasculature but is expressed on tumor cells. Spatial restriction of CAR to the intercellular space in normal liver and diminished replication of adenovirus in hepatocytes may explain the minimal toxicity observed following repeated hepatic artery infusions with Onyx-015

On the relative merits of three-point integration rules for six-node triangles

There exist two three-point integration rules for triangular elements. Both rules are precise up to the second order and used for evaluating the six-node triangles. While one of rules has its sampling stations inside the triangle, that of the other coincide with the edge nodes. Though the former is commonly employed, it will be seen in this short paper that latter is indeed more favourable in view of element accuracy. © 1997 Elsevier Science B.V.postprin

A simple assumed strain method for enhancing the accuracy of the cubic triangular C degree plate bending element

The conventional cubic triangular Mindlin/Reissner plate bending element, DISP10, is in general too stiff. To reduce the element stiffness, three of the strain sampling points are shifted from the integration stations to the element corners so as to reduce the number of shear constraints in the global level. The strain field is then obtained by interpolation. In this way, the constraint ratio of the element increases from 1.125 to 1.5 which is exactly equal to a postulated optimal value. However, the element does not appear to be more accurate than its conventional counterpart. While keeping the constraint ratio and interpolation pivots unchanged, two different ways of refining the sampled strains at the element corners are attempted and the pertinent elements are consistently more accurate than DISP10postprin

A quadratic assumed natural strain curved triangular shell element

In this paper, a six-node triangular C 0 curved shell element is developed by the assumed natural or covariant strain (ANS) method. All the sampled natural strains are optimal with respect to the derivative of a prescribed cubic field in a subparametric element. Numerical examinations reveal that the element shows no sign of locking, passes all the patch tests and yields satisfactory accuracy. © 1999 Elsevier Science S.A. All rights reserved.postprin

Assumed strain and hybrid destabilized ten-node C0 triangular shell elements

The conventional ten-node C0 triangular shell element is in general too stiff. In this paper, several less stiff formulations are proposed. To reduce the transverse shear stiffness, the assumed strain method is adopted. On the other hand, both assumed strain method and hybrid destabilization are employed for softening the membrane stiffness. The improvement is validated by popular numerical problems.postprin

Myocardial fibrosis in stroke survivors

Stroke survivors are most likely to die of cardiac death, yet few undergo comprehensive cardiac assessment to look for reversible causes. Myocardial fibrosis (MF) is not only the hallmark of cardiomyopathy, but also a substrate for sudden cardiac death, ventricular tachyarrhythmia and heart failure. Procollagen carboxyl-terminal telopeptide (PICP) was found to be a marker of MF. The relationship between PICP and cardiac abnormalities in stroke survivors is unknown. We recently showed that MF in stroke survivors can be treated by spironolactone and amiloride in a randomised placebo-controlled cross-over study with reduction in PICP levels and QTc [1]

Voltage modulated electro-luminescence spectroscopy and negative capacitance - the role of sub-bandgap states in light emitting devices

Voltage modulated electroluminescence spectra and low frequency ({\leq} 100 kHz) impedance characteristics of electroluminescent diodes are studied. Voltage modulated light emission tracks the onset of observed negative capacitance at a forward bias level for each modulation frequency. Active participation of sub-bandgap defect states in minority carrier recombination dynamics is sought to explain the results. Negative capacitance is understood as a necessary dielectric response to compensate any irreversible transient changes in the minority carrier reservoir due to radiative recombinations mediated by slowly responding sub-bandgap defects. Experimentally measured variations of the in-phase component of modulated electroluminescence spectra with forward bias levels and modulation frequencies support the dynamic influence of these states in the radiative recombination process. Predominant negative sign of the in-phase component of voltage modulated electroluminescence signal further confirms the bi-molecular nature of light emission. We also discuss how these states can actually affect the net density of minority carriers available for radiative recombination. Results indicate that these sub-bandgap states can suppress external quantum efficiency of such devices under high frequency operation commonly used in optical communication.Comment: 21 pages, 4 sets of figure

Transition finite element families for adaptive analysis of axisymmetric elasticity problems

In this paper, four transition element families that comprise five- to seven-node quadrilateral elements are developed based on the hybrid-stress and enhanced assumed strain (EAS) formulations for adaptive analyses of axisymmetric elasticity problems. For members in the first hybrid-stress family, a quasi-linear stress field with ten equilibrating stress modes is derived and employed. To study the effect of including more stress modes in the assumed stress field, another family with two additional stress modes is implemented. On the other hand, two EAS element families are constructed with respect to the incompatible displacement modes of two existing incompatible displacement transition element families. Several numerical examples are exercised. It can be seen that the first hybrid-stress family is the most accurate one among the proposed families. Moreover, the EAS families are close to the respective incompatible families in accuracy yet the former families are not only more efficient in computation but also more concise in formulation. © 2010 Elsevier B.V. All rights reserved.postprin