A vector radiative transfer model for coupled atmosphere and ocean systems with a rough interface

We report on an exact vector (polarized) radiative transfer (VRT) model for coupled atmosphere and ocean systems. This VRT model is based on the successive order of scattering (SOS) method, which virtually takes all the multiple scattering processes into account, including atmospheric scattering, oceanic scattering, reflection and transmission through the rough ocean surface. The isotropic Cox–Munk wave model is used to derive the ref and transmission matrices for the rough ocean surface. Shadowing effects are included by the shadowing function. We validated the SOS results by comparing them with those calculated by two independent codes based on the doubling/adding and Monte Carlo methods. Two error analyses related to the ocean color remote sensing are performed in the coupled atmosphere and ocean systems. One is the scalar error caused by ignoring the polarization in the whole system. The other is the error introduced by ignoring the polarization of the light transmitted through the ocean interface. Both errors are significant for the cases studied. This code fits for the next generation of ocean color study because it converges fast for absorbing medium as, for instance, ocean.     

Molecular simulation study of water mobility in aerosol-OT reverse micelles

In this work, we present results from molecular dynamics simulations on the single-molecule relaxation of water within reverse micelles (RMs) of different sizes formed by the surfactant aerosol-OT (AOT, sodium bis(2-ethylhexyl)sulfosuccinate) in isooctane. Results are presented for RM water content w(0) = [H(2)O]/[AOT] in the range from 2.0 to 7.5. We show that translational diffusion of water within the RM can, to a good approximation, be decoupled from the translation of the RM through the isooctane solvent. Water translational mobility within the RM is restricted by the water pool dimensions, and thus, the water mean-squared displacements (MSDs) level off in time. Comparison with models of diffusion in confined geometries shows that a version of the Gaussian confinement model with a biexponential decay of correlations provides a good fit to the MSDs, while a model of free diffusion within a sphere agrees less well with simulation results. We find that the local diffusivity is considerably reduced in the interfacial region, especially as w(0) decreases. Molecular orientational relaxation is monitored by examining the behavior of OH and dipole vectors. For both vectors, orientational relaxation slows down close to the interface and as w(0) decreases. For the OH vector, reorientation is strongly affected by the presence of charged species at the RM interface and these effects are especially pronounced for water molecules hydrogen-bonded to surfactant sites that serve as hydrogen-bond acceptors. For the dipole vector, orientational relaxation near the interface slows down more than that for the OH vector due mainly to the influence of ion-dipole interactions with the sodium counterions. We investigate water OH and dipole reorientation mechanisms by studying the w(0) and interfacial shell dependence of orientational time correlations for different Legendre polynomial orders.     

Water/hydrocarbon interfaces: effect of hydrocarbon branching on single-molecule relaxation

Water/hydrocarbon interfaces are studied using molecular dynamics simulations in order to understand the effect of hydrocarbon branching on the dynamics of the system at and away from the interface. A recently proposed procedure for studying the intrinsic structure of the interface in such systems is utilized, and dynamics are probed in the usual laboratory frame as well as the intrinsic frame. The use of these two frames of reference leads to insight into the effect of capillary waves at the interface on dynamics. The systems were partitioned into zones with a width of 5 A, and a number of quantities of dynamical relevance, namely, the residence times, mean squared displacements, the velocity auto correlation functions, and orientational time correlations for molecules of both phases, were calculated in the laboratory and intrinsic frames at and away from the interface. For the aqueous phase, translational motion is found to be (a) diffusive at long times and not anomalous as in proteins or micelles, (b) faster at the interface than in the bulk, and (c) faster upon reduction of the effect of capillary waves. The rotational motion of water is (a) more anisotropic at the interface than in the bulk and (b) dependent on the orientation of the covalent O-H bond with respect to the plane of the interface. The effect of hydrocarbon branching on aqueous dynamics was found to be small, a result similar to the effect on the interfacial water structure. The hydrocarbon phase shows a larger variation for all dynamical probes, a trend consistent with their interfacial structure.     

A MULTITHERAPY RESISTANCE FACTOR FROM MELANOMA REVEALS THAT KILLING BY NEAR UV IS DIFFERENT FROM GENOTOXIC AGENTS

A diffusible multitherapy resistance factor (MTRF) is produced by Cloudman S91 melanoma cells in vitro. The MTRF decreases sensitivity of the target cell line, S91/amel, to γ-irradiation, UVC (200–280nm) and mitomycin C (MMC). In the present study, we demonstrate that MTRF also increases the survival of S91/amel after exposure to actinomycin D (AMD) and vinblastine (VBL). The MTRF is thus effective when target cells have been exposed to five genotoxic agents that act by different mechanisms. It does not alter the response to the same five agents of the S91/13 producer cells, which are presumably saturated with the factor. The factor has no effect on the survival of S91/amel cells that have been exposed to lethal doses of near monochromatic UVB (280–320nm) or UVA (320–400nm) or to polychromatic FS20 lamps. The lack of effectiveness of MTRF after cells have been exposed to near (300–400nm) UV radiation indicates that in this wavelength range, S91 melanoma cells are killed by mechanisms that are different from the lethal effects of the five genotoxic agents (γ-irradiation, UVC, MMC, AMD and VBL) to which the target cells demonstrate a response.     

Venous cavernoma at 8 Tesla MRI

Cavernous angiomas or cavernomas are vascular malformations, which may be associated with risk of bleeding episodes. We present a case report comparing high resolution 8 Tesla gradient echo (GE) imaging with routine fast spin echo (FSE) at 1.5 Tesla in a patient with venous cavernoma. A 55-year-old male with a history of hemorrhagic stroke was studied using high-resolution 8 Tesla magnetic resonance imaging (MRI) system, which revealed venous cavernoma (9 x 8.6 mm) in the left parietal region and visualized adjacent microvascular supply. Signal loss was prominent in the cavernoma region compared to surrounding brain tissue, and signal intensity declined by factor 7.3 +/- 2.4 (679 +/- 62%) on GE images at 8 Tesla. Cavernoma was not apparent on routine T(2)-weighted FSE images at 1.5 Tesla MRI. This case report indicates that GE images at 8 Tesla can be useful for evaluation of vascular pathologies and microvasculature.     

Water-hydrocarbon interfaces: effect of hydrocarbon branching on interfacial structure

Molecular dynamics simulation are performed for the water/hydrocarbon system to study the effect of hydrocarbon branching on interfacial properties. The following two series of hydrocarbons are considered: (1) n-pentane, 2-methyl pentane, and 2,2,4-trimethyl pentane (constant chain length) and (2) n-octane, 2-methyl heptane, and 2,2,4-trimethyl pentane (constant molecular mass). With a simple algorithm for identification of surface sites and mapping nonsurface sites to these surface sites, intrinsic profiles were constructed with respect to the surface layer. Intrinsic density profiles for water and hydrocarbons with respect to the hydrocarbon and water surface, respectively, resemble density profiles of liquids in the presence of a wall. Order parameters were used to study orientation of molecules with respect to the surface normal and the hydrogen bond network was characterized in terms of the number of hydrogen bonds per water molecule and percentage of hydrogen bonded molecules in the first coordination shell. The corresponding intrinsic profiles were obtained. The O-H bond for surface water was found to have two preferential orientations, pointing toward the hydrocarbon phase and parallel to the interface. Hydrocarbon molecules in series 1 orient along the interface with the more branched molecule better aligned. For molecules in series 2, the larger molecular length reduces the alignment of molecules along the interface.     

Electronic structure calculations in liquid and amorphous metals

We review the theoretical methods employed to describe electronic states in structurally disordered metallic systems. Substantial progress has been made in this area using techniques based on multiple scattering theory. We focus on the way in which X-ray and neutron scattering data enter the calculation of the average electronic spectrum. Applications to molten Cu and amorphous NiP alloys are discussed.     

Synthesis,Molecular Docking and Potential Antioxidant Activity of Di/Trisubstituted Pyridazinone Derivatives

A number of pyridazinone derivatives bearing substituted benzylidene and heterocyclic/aromatic rings at 4^th and 6^th positions, respectively were synthesized in good to moderate yields and screened for antioxidant activity. Antioxidant activity of pyridazinone derivatives was evaluated by using several in vitro radical scavenging methods such as 1,1‐diphenylpicrylhydrazyl (DPPH), hydrogen peroxide (H₂O₂), nitric oxide (NO), reducing power, and metal chelating assay etc. Molegro virtual docker software was used to study the binding affinity of the title compounds with the xanthine oxidoreductase enzyme. Amongst the tested compounds, 5a, 5d, 5g & 5j were found to exhibit excellent antioxidant activity at par with the positive control, ascorbic acid. The molecular docking studies of these compounds demonstrated a good selectivity profile with xanthine oxidoreductase receptors. A preliminary study of the structural‐activity relationship showed that the presence of electron withdrawing group and heterocyclic ring on pyridazinone nucleus are associated with the best potency and selectivity profile. It could be proposed that xanthine oxidoreductase receptor may be involved in observed antioxidant activity of pyridazinone derivatives bearing aromatic ring and benzylidene substituents and thus the synthesized compounds are worthy of further exploration.     

INFLUENCE OF FLUOROCARBON EMULSIONS ON PORPHYRIN-SENSITISED OXIDATION OF HISTIDINE

The influence of fluorocarbon emulsions on the efficiency of photosensitized oxidation of histidine in solution has been studied, using haematoporphyrin and dihaematoporphyrin derivatives as sensitisers. It is shown that the fluorocarbon emulsions at low concentrations efficiently disaggregate porphyrins, and thereby enhance photosensitised oxidation. The high solubility of oxygen in fluorocarbon emulsions maintains solution oxygen tension, optimising photooxidative damage. It is suggested that fluorocarbon emulsions might find a role in photodynamic therapy, both as carriers for sensitising dyes, and also to maintain tissue oxygenation in hypoxic regions of solid tumours.     

DYE-SENSITIZED DESTABILIZATION OF LIPOSOMES BEARING PHOTOOXIDIZABLE LIPID HEAD GROUPS

Abstract— Liposomes were prepared from mixtures of dipalmitoyl-i.-α-phosphatidylcholine and up to 40% mol:mol of N-stearoyl-L-histidine (NSH) in the presencc or the hydrophobic sensitizer DHE. In the dark such liposomes are stable and retain entrapped salts. On photolysis with visible light, liposomes leak trapped ions at NSH concentrations greater than 10% mol:mol. Up to 15% mol:mol NSH concentration leakage is seen only during the illumination period, whereas at higher concentration the liposomes continue to leak contents after illumination and fuse to form larger structures. Photolysis of the liposomes is accompanied by oxygen uptake in proportion to the NSH concentration within the bilayer. Photocontrol of liposome permeability through oxidation of membrane additives such as NSH offers a potential means for controlled drug delivery and might he useful as an adjunct to photodynamic therapy.