Ionophore-mediated uptake of ciprofloxacin and vincristine into large unilamellar vesicles exhibiting transmembrane ion gradients

A new method, based on the ion-translocating properties of the ionophores nigericin and A23187, is described for loading large unilamellar vesicles (LUVs) with the drugs vincristine and ciprofloxacin. LUVs composed of distearoylphosphatidylcholine/cholesterol (DSPC/Chol) (55:45 mol/mol) or sphingomyelin (SPM)/Chol (55:45 mol/mol) exhibiting a transmembrane salt gradient (for example, internal solution 300 mM MnSO4 or K2SO4; external solution 300 mM sucrose) are incubated in the presence of drug and, for experiments involving divalent cations, the chelator EDTA. The addition of ionophore couples the outward movement of the entrapped cation to the inward movement of protons, thus acidifying the vesicle interior. External drugs that are weak bases can be taken up in response to this induced transmembrane pH gradient. It is shown that both nigericin and A23187 facilitate the rapid uptake of vincristine and ciprofloxacin, with entrapment levels approaching 100% and excellent retention in vitro. Following drug loading, the ionophores can be removed by gel exclusion chromatography, dialysis, or treatment with biobeads. In vitro leakage assays (addition of 50% mouse serum) and in vivo pharmacokinetic studies (in mice) reveal that the A23187/Mn2+ system exhibits superior drug retention over the nigericin/K+ system, and compares favorably with vesicles loaded by the standard DeltapH or amine methods. The unique features of this methodology and possible benefits are discussed.     

Emotional Devaluation of Distracting Patterns and Faces: A Consequence of Attentional Inhibition During Visual Search?

Visual search has been studied extensively, yet little is known about how its constituent processes affect subsequent emotional evaluation of searched-for and searched-through items. In 3 experiments, the authors asked observers to locate a colored pattern or tinted face in an array of other patterns or faces. Shortly thereafter, either the target or a distractor was rated on an emotional scale (patterns, cheerfulness; faces, trustworthiness). In general, distractors were rated more negatively than targets. Moreover, distractors presented near the target during search were rated significantly more negatively than those presented far from the target. Target-distractor proximity affected distractor ratings following both simple-feature and difficult-conjunction search, even when items appeared at different locations during evaluation than during search and when faces previously tinted during search were presented in grayscale at evaluation. An attentional inhibition account is offered to explain these effects of attention on emotional evaluation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microstructure and Hydrogen-Induced Failure Mechanisms in Fe and Ni Alloy Weldments

The microstructure and fracture morphology of AISI 8630-IN625 and ASTM A182-F22-IN625 dissimilar metal weld interfaces were compared and contrasted as a function of postweld heat treatment (PWHT) duration. For both systems, the microstructure along the weld interface consisted of a coarse grain heat-affected zone in the Fe-base metal followed by discontinuous martensitic partially mixed zones and a continuous partially mixed zone on the Ni side of the fusion line. Within the partially mixed zone on the Ni side, there exists a 200-nm-wide transition zone within a 20-??m-wide planar solidification region followed by a cellular dendritic region with Nb-Mo?Crich carbides decorating the dendrite boundaries. Although there were differences in the volume of the partially mixed zones, the major difference in the metal weld interfaces was the presence of M₇C₃ precipitates in the planar solidification region, which had formed in AISI 8630-IN625 but not in ASTM A182-F22-IN625. These precipitates make the weldment more susceptible to hydrogen embrittlement and provide a low energy fracture path between the discontinuous partially mixed zones.     

The effect of laser surface texturing on transitions in lubrication regimes during unidirectional sliding contact

Laser surface texturing (LST) is an emerging effective method for improving the tribological performance of friction units lubricated with oil. In LST technology, a pulsating laser beam is used to create thousands of arranged microdimples on a surface by a material ablation process. These dimples generate hydrodynamic pressure between oil-lubricated parallel sliding surfaces. The impact of LST on lubricating-regime transitions was investigated in this study. Tribological experiments were conducted with a pin-on-disk apparatus at sliding speeds in the range of 0.015–0.75 m/s and nominal contact pressures that ranged from 0.16 to 1.6 MPa. Two oils with different viscosities (54.8 and 124.7 cSt at 40 °C) were used as lubricants. The test results showed that laser texturing expanded the contact parameters in terms of load and speed for hydrodynamic lubrication, as indicated by friction transitions on the Stribeck curve. The beneficial effects of laser surface texturing are more pronounced at higher speeds and loads and with higher viscosity oil.     

Low-temperature epitaxy of silicon by electron beam evaporation

In this paper we report on homoepitaxial growth of thin Si films at substrate temperatures T_s = 500-650 °C under non-ultra-high vacuum conditions by using electron beam evaporation. Si films were grown at high deposition rates on monocrystalline Si wafers with (100), (110) and (111) orientations. The ultra-violet visible reflectance spectra of the films show a dependence on T_s and on the substrate orientation. To determine the structural quality of the films in more detail Secco etch experiments were carried out. No etch pits were found on the films grown on (100) oriented wafers. However, on films grown on (110) and (111) oriented wafers different types of etch pits could be detected. Films were also grown on polycrystalline silicon (poly-Si) seed layers prepared by an Aluminum-Induced Crystallisation (AIC) process on glass substrates. Electron Backscattering Diffraction (EBSD) shows that the film growth proceeds epitaxially on the grains of the seed layer. But a considerably higher density of extended defects is revealed by Secco etch experiments.     

X-Rays as a Tool for Investigation of Scuffing and Boundary Lubrication

A suite of X-ray-based techniques has been adopted for the investigation of scuffing and other tribological failure modes. Depth-profiled X-ray diffraction, reflectivity, and fluorescence are being used to gather information on additive reaction film thickness, roughness, and electron density, presence and distribution of additive elements within those layers, identification of crystalline phases in the reaction film and subsurface material, and degree and depth of deformation. The differences between the samples and equipment used in development of this approach, and the production mechanical parts and laboratory X-ray systems, are discussed, with emphasis on application of the approach in industry.     

Physical and tribological properties of diamond films grown in argoncarbon plasmas

Nanocrystalline diamond films have been deposited using a microwave plasma consisting of argon, 2–10% hydrogen and a carbon precursor such as C₆₀ or CH₄. It was found that it is possible to grow the diamond phase with both carbon precursors, although the hydrogen concentration in the plasma was 1–2 orders of magnitude lower than normally required in the absence of the argon. Auger electron spectroscopy, X-ray diffraction measurements and transmission electron microscopy indicate the films are predominantly composed of diamond. Surface roughness, as determined by atomic force microscopy and scanning electron microscopy indicate the nanocrystalline films grown in low hydrogen content plasmas are exceptionally smooth (30–50 nm rms) to thicknesses of 10 m. The smooth nanocrystalline films result in low friction coefficients (μ = 0.04–0.06) and low average wear rates as determined by ball-on-disk measurements.     

Zinc content of ZDDP films formed thermally and mechanically

Reaction films of zinc dialkyl dithiophosphate (ZDDP) were formed on flats of polished steel, and the Zn content of the films was determined. Films formed thermally were compared to those formed mechanically in reciprocating wear; both types were formed by using lubricants with a range of ZDDP concentrations. Grazing-incidence X-ray fluorescence was used to quantify the areal density of Zn and to verify that the measured fluorescence was due to a reaction film and not from debris or the bulk oil. The amount of Zn in the films generally rose with increasing ZDDP concentration, but films formed thermally were found to contain more Zn than those formed mechanically. Several possible explanations for this difference have been discussed.     

Immunologic bullous diseases: blisters without a precipitating event

Although the overall incidence of immunologic bullous diseases is comparatively low, they are nonetheless potentially lethal dermatologic disorders that occur most commonly in individuals age 55 and older. Thus familiarity with the signs, symptoms, and treatments will be valuable to the primary care physician. For bullous diseases in general, the challenge is to differentiate between those arising from immunologic rather than exogenous causes, such as drug-induced or drug-triggered pemphigus. Treatment goals include screening for associated malignancies, managing the lesions, and minimizing the morbidity and mortality associated with the disease. Collaboration with a dermatologist can aid in achieving these objectives.