Space–time VMS computation of wind-turbine rotor and tower aerodynamics

We present the space–time variational multiscale (ST-VMS) computation of wind-turbine rotor and tower aerodynamics. The rotor geometry is that of the NREL 5MW offshore baseline wind turbine. We compute with a given wind speed and a specified rotor speed. The computation is challenging because of the large Reynolds numbers and rotating turbulent flows, and computing the correct torque requires an accurate and meticulous numerical approach. The presence of the tower increases the computational challenge because of the fast, rotational relative motion between the rotor and tower. The ST-VMS method is the residual-based VMS version of the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) method, and is also called “DSD/SST-VMST” method (i.e., the version with the VMS turbulence model). In calculating the stabilization parameters embedded in the method, we are using a new element length definition for the diffusion-dominated limit. The DSD/SST method, which was introduced as a general-purpose moving-mesh method for computation of flows with moving interfaces, requires a mesh update method. Mesh update typically consists of moving the mesh for as long as possible and remeshing as needed. In the computations reported here, NURBS basis functions are used for the temporal representation of the rotor motion, enabling us to represent the circular paths associated with that motion exactly and specify a constant angular velocity corresponding to the invariant speeds along those paths. In addition, temporal NURBS basis functions are used in representation of the motion and deformation of the volume meshes computed and also in remeshing. We name this “ST/NURBS Mesh Update Method (STNMUM).” The STNMUM increases computational efficiency in terms of computer time and storage, and computational flexibility in terms of being able to change the time-step size of the computation. We use layers of thin elements near the blade surfaces, which undergo rigid-body motion with the rotor. We compare the results from computations with and without tower, and we also compare using NURBS and linear finite element basis functions in temporal representation of the mesh motion.     

Protective effect of K(ATP) openers in ischemic rat hearts treated with a potassium cardioplegic solution

ATP-sensitive potassium channel (KATP) openers directly protect ischemic myocardium, which may make them useful for treating patients undergoing cardiopulmonary bypass, but whether high-potassium-containing cardioplegic solutions would inhibit their protective effects is not clear. We determined whether additional protection greater than that provided by cardioplegia could be found for KATP openers. We studied the effect of 10 microM cromakalim or BMS-180448 pretreatment (10 min before cardioplegia) on severity of ischemia in isolated rat hearts given normothermic or cold St. Thomas' cardioplegic solution (16 mM K+). After cardioplegic arrest, the hearts were subjected to 30-min (normothermic) or 150-min (hypothermic) global ischemia, each followed by 30-min reperfusion. The cardioplegic solutions significantly protected the hearts, as measured by increased time to onset of contracture, enhanced recovery of function, and reduced lactate dehydrogenase (LDH) release. Cromakalim and BMS-180448 both further significantly increased time to contracture in both normothermic and hypothermic arrested hearts; this was accompanied by enhanced recovery of reperfusion contractile function and reduced cumulative LDH release. This additional protective effect of the K ATP openers was abolished by glyburide. Because administration of the K ATP openers only with the cardioplegic solution (1 min before global ischemia) was not efficacious, >1-min pretreatment apparently is necessary. K ATP openers provide additional protection to that afforded by cold or normothermic potassium cardioplegia in rat heart, although the timing of treatment may be crucial.     

Effects of crack cocaine on neurocognitive function

Because crack cocaine appears to have a preferential effect on the metabolic and electrophysiological activity of the frontal and temporal regions of the brain (Pascual-Leone et al., 1991a, 1991b; Volkow, 1992), we hypothesized that cognitive measures of those regions would be impaired in crack cocaine users relative to measures in normal volunteers. We used logistic regression to determine the relationship of cocaine usage to neuropsychological test performance. We compared 38 patients with an average of 3.6 (SD = 2.5) years of crack cocaine use and 24.5 (SD = 28.1) days of abstinence to 54 normal volunteers on a battery of neuropsychological tests. Statistical adjustments were made for the effects of age, education, socioeconomic class, and level of depression. Our findings were mixed with regard to purported measures of executive/frontal functioning, with worse performance associated with cocaine usage on the Booklet Categories Test, but better performance associated on others (number of categories on the Wisconsin Card Sorting Test, Controlled Oral Word Association). Cocaine usage was associated with impairment on measures of spatial, but not verbal memory, confrontation naming, and Trail-making Test, Part B, a measure of perceptual-motor speed and cognitive flexibility. In summary, it appears that continuous crack cocaine use produces a dissociative pattern in neuropsychological test performance with improvement on some measures, but deterioration on others. The permanence of these effects remains to be determined with longitudinal studies.     

Some cultural characteristics of Branhamella ovis isolated from the conjunctival sac of sheep

The colonial morphology and other cultural characteristics of Branhamella ovis were studied. The current investigation showed that colonies could be designated R (rough) and S (smooth) dependent on their appearance on agar. The colonial variants were apparently stable and each produced distinct types of pitting when grown on agar. A CAMP-like reaction was also shown to be a characteristic of B. ovis.     

SIMS depth profiling of multilayer metal-oxide thin films — improved accuracy using a xenon primary ion

Multilayer thin films containing silver and copper, sandwiched in a metal oxide, have been depth profiled by secondary ion mass spectrometry (SIMS) using primary ions of differing mass, energy and chemical reactivity. These results were compared for accuracy with those obtained by Rutherford backscattering spectrometry (RBS). The use of O₂⁺ or O^? as primary ions resulted in severe distortion of the silver ion intensity distribution in the SIMS profile of a ZnO/Ag/ZnO thin film on glass; O₂⁺ bombardment at energies from 3–10 keV resulted in the detection of silver at the glass interface, while the use of O^? caused the silver to be detected closer to the outer surface than expected from RBS results. Primary beams of Ar⁺ and Xe⁺ gave progressively more accurate results for the Zn/Ag/Zn distribution; Xe⁺ at 5.0 keV energy produced profiles that agreed within 10% of RBS-derived values. The same beam conditions, used to profile a double silver layer in ZnO, resulted in some discrepancy in the position of the inner layer, compared to RBS results, and this was attributed to an enhanced sputter rate in the oxide under the outside metal film. Depth profiling of TiO₂/Cu/TiO₂ films with oxygen also resulted in significant distortion of the perceived position of the metal layer, and this was again significantly improved using Xe⁺ primary ions of 6–9 keV energy. The distorting effects of oxygen bombardment can be understood in terms of a migration of metal ions in an electrostatic field created by a charged surface. Ionization of the metallic layer is enhanced by the use of oxygen. By contrast, the use of rare gases reduces the production of ions from the metallic layer which can migrate prior to the onset of sputtering.     

An increase in cytosolic protease activity during liver preservation. Inhibition by glutathione and glycine

Degradative cytosolic proteolysis contributes to cell injury following ATP depletion. Although ATP depletion is a salient feature of ischemic liver storage for transplantation, information regarding cytosolic protease activity during liver storage is lacking. Thus our aim was to measure liver cytosolic protease activity following ischemic storage. A progressive increase in total cytosolic protease activity was observed over time at both 37 degrees C and 4 degrees C, but the increase was greater at 37 degrees C. Total cellular proteolysis was also temperature-dependent during anoxia (37 degrees C > 4 degrees C), demonstrating a physiologic correlation between cellular proteolysis and measurements of cytosolic protease activity. The stimulation of total cytosolic protease activity was due to an increase in metallo- and aspartate protease activity. Of particular interest, glutathione (GSH) inhibited both metalloprotease and aspartate protease activity from cytosol of stored livers. Glycine, the carboxyl-terminal amino acid of GSH, also inhibited both metalloprotease and aspartate protease activity. In addition to being an antioxidant, GSH may exert its protective effects during organ preservation by inhibiting cytosolic proteases--perhaps via its glycine moiety. These experiments support the hypothesis that degradative proteolysis contributes to liver injury during organ preservation.