Preparation of crystalline beta barium borate thin films on Sr2+-doped alpha barium borate substrates by liquid phase epitaxy

Thin films of beta barium borate have been prepared by liquid phase epitaxy on Si2+-doped alpha-BaB2O4 (alpha-BBO, the high temperature phase of barium berate) (001) and (110) substrates. The results of X-ray diffraction indicate that the films show highly (001) preferred orientation on (001)-oriented substrates while the films grown on (110) substrates are textured with (140) orientation. The crystallinity of these films was found to depend on growth temperature, rotation rate, dip time and orientation of substrate. Growth conditions were optimized to grow films with (001) orientation on (001) substrates reproducibly. The films show second harmonic generation of 400 nm light upon irradiation with 800 nm Ti: Sapphire femtosecond laser light. (c) 2005 Elsevier B.V. All rights reserved.

Growth and characterization of ZnO films on (0 0 1), (1 0 0) and (0 1 0) LiGaO2 substrates

ZnO films were fabricated on LiGaO2 (0 0 1), (10 0) and (0 10) planes by RF magnetron sputtering. The structural, morphological and optical properties of as-grown ZnO films were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectra and photoluminescence (PL) spectra. It is found that the orientation of ZnO films is strongly dependent on the substrate plane. [0 0 0 11, [1 (1) over bar 00] and [11 (2) over bar0] oriented ZnO films are deposited on LiGaO2 (001), (100) and (010), respectively. AFM shows the (0001) ZnO film consists of well-aligned regular hexagonal grains. Raman spectra reveal a tensile stress in the (0 0 0 1) ZnO film and a compressive stress in (110 0) and (112 0) ZnO films. PL spectra of all ZnO films exhibit only a near-band-edge UV emission peak. (C) 2008 Elsevier B.V. All rights reserved.

Enhancement of near-band-edge photoluminescence of ZnO thin films in sandwich configuration at room temperature

ZnO/ITO/ZnO sandwich structure films were fabricated. The effects of buffer layer on the structure and optical properties of ZnO films were investigated by x-ray diffraction (XRD), photoluminescence, optical transmittance, and absorption measurements. XRD spectra indicate that a buffer layer has the effects of lowering the grain orientation of ZnO films and increasing the residual stresses in the films. The near-band-edge emissions of ZnO films deposited on both single indium tin oxide (ITO) buffer and ITO/ZnO double buffers are significantly enhanced compared with that deposited on a bare substrate due to the quantum confinement effect. (C) 2006 American Institute of Physics.

Use of stereo camera systems for assessment of rockfish abundance in untrawlable areas and for recording pollock behavior during midwater trawls

We describe the application of two types of stereo camera systems in fisheries research, including the design, calibration, analysis techniques, and precision of the data obtained with these systems. The first is a stereo video system deployed by using a quick-responding winch with a live feed to provide species- and size- composition data adequate to produce acoustically based biomass estimates of rockfish. This system was tested on the eastern Bering Sea slope where rockfish were measured. Rockfish sizes were similar to those sampled with a bottom trawl and the relative error in multiple measurements of the same rockfish in multiple still-frame images was small. Measurement errors of up to 5.5% were found on a calibration target of known size. The second system consisted of a pair of still-image digital cameras mounted inside a midwater trawl. Processing of the stereo images allowed fish length, fish orientation in relation to the camera platform, and relative distance of the fish to the trawl netting to be determined. The video system was useful for surveying fish in Alaska, but it could also be used broadly in other situations where it is difficult to obtain species-composition or size-composition information. Likewise, the still-image system could be used for fisheries research to obtain data on size, position, and orientation of fish.

Patterns of orographic uplift in the Sierra Nevada and their relationship to upper-level atmospheric circulation

We examine monthly and seasonal patterns of precipitation across various elevations of the eastern Central Valley of California and the Sierra Nevada. A measure of the strength of the orographic effect called the “precipitation ratio” is calculated, and we separate months into four groups based on being wet or dry and having low or high precipitation ratios. Using monthly maps of mean 700-mb height anomalies, we describe the northern hemisphere mid-tropospheric circulation patterns associated with each of the four groups. Wet months are associated with negative height anomalies over the eastern Pacific, as expected. However, the orientation of the trough is different for years with high and low precipitation ratios. Wet months with high ratios typically have circulation patterns factoring a west-southwest to east-northeast storm track from around the Hawaiian Islands to the Pacific Northwest of the United States. Wet months with low precipitation ratios are associated with a trough centered near the Aleutians and a northwest to southeast storm track. Dry months are marked by anticyclones in the Pacific, but this feature is more localized to the eastern Pacific for months with low precipitation ratios than for those with high ratios. Using precipitation gauge and snow course data from the American River and Truckee-Tahoe basins, we determined that the strength of the orographic effect on a seasonal basis is spatially coherent at low and high elevations and on opposite sides of the Sierra Nevada crestline.

Multiple grasp-specific representations of tool dynamics mediate skillful manipulation.

Skillful tool use requires knowledge of the dynamic properties of tools in order to specify the mapping between applied force and tool motion. Importantly, this mapping depends on the orientation of the tool in the hand. Here we investigate the representation of dynamics during skillful manipulation of a tool that can be grasped at different orientations. We ask whether the motor system uses a single general representation of dynamics for all grasp contexts or whether it uses multiple grasp-specific representations. Using a novel robotic interface, subjects rotated a virtual tool whose orientation relative to the hand could be varied. Subjects could immediately anticipate the force direction for each orientation of the tool based on its visual geometry, and, with experience, they learned to parameterize the force magnitude. Surprisingly, this parameterization of force magnitude showed limited generalization when the orientation of the tool changed. Had subjects parameterized a single general representation, full generalization would be expected. Thus, our results suggest that object dynamics are captured by multiple representations, each of which encodes the mapping associated with a specific grasp context. We suggest that the concept of grasp-specific representations may provide a unifying framework for interpreting previous results related to dynamics learning.

Effect of elastic stresses on free oscillations in ferroelectric liquid crystals

It is shown experimentally that an elastic mechanical stress in a crystal structure is a necessary factor for the appearance of free oscillations of the director of a ferroelectric liquid crystal. Such a mechanical stress arises as a result of internal textural perturbations in the presence of regions with a different orientation of the director or is produced by external pressure applied to one of the cell plates in the appropriate direction. © 1999 American Institute of Physics.

Characterization of nano-composite M-2411/Y-123 thin films by electron backscatter diffraction and in-field critical current measurements

Thin films of nano-composite Y-Ba-Cu-O (YBCO) superconductors containing nano-sized, non-superconducting particles of Y2Ba 4CuMOx (M-2411 with M = Ag and Nb) have been prepared by the PLD technique. Electron backscatter diffraction (EBSD) has been used to analyze the crystallographic orientation of nano-particles embedded in the film microstructure. The superconducting YBa2Cu3O7 (Y-123) phase matrix is textured with a dominant (001) orientation for all samples, whereas the M-2411 phase exhibits a random orientation. Angular critical current measurements at various temperature (T) and applied magnetic field (B) have been performed on thin films containing different concentration of the M-2411 second phase. An increase in critical current density J c at T < 77 K and B < 6 T is observed for samples with low concentration of the second phase (2 mol % M-2411). Films containing 5 mol % Ag-2411 exhibit lower Jc than pure Y-123 thin films at all fields and temperatures. Samples with 5 mol % Nb-2411 show higher Jc(B) than phase pure Y-123 thin films for T < 77 K. © 2010 IOP Publishing Ltd.

Reaction of fishes to the underwater A.C. field

A comparative study on the effect of A.C. field on Puntius ticto, Heteropneustis fossilis and Tilapta mossambica was carried out using a slowly rising field intensity. Well defined reactions appeared in the species of fish with slight specific variations, depending on their orientation in the electrical field, on reaching the field intensity to specific value. These reactions can be distinguished as first reaction, when the fish perceive the surrounding field, jerky swimming when parallel to the current lines (longitudinal oscillotaxis), the static position finally adopted by the fish sooner or latter depending on the potential gradient (transverse oscillotaxis), and a state of muscular rigidity (tetanus). After switching off the current, a hypnotic condition prevailed in the treated fishes before returning to their normal swimming condition. The orientation of fish body in the field had an important bearing on the behaviour reactions and current thresholds necessary for those reactions. Initial reaction, jerky swimming between electrodes and hypnosis after stoppage of current appeared in fishes earlier when the fish body was in parallel to the current lines, whereas fishes responded to transverse oscillotaxis quickly when perpendicular to current lines.

Response of fishes to the underwater D.C. field

Response to external electric field (D. C.) of three different varieties of fish namely Puntius ticto, Heteropneustis fossilis and Tilapia mossambica having different anatomical and behavioural characteristics were studied. Clearly distinguished reactions occurred one after another m all the varieties of fish with the increase in field intensity with minor specific variations. These reactions can be broadly classified into initial start (first reaction), forced swimming (galvanotaxis), slackening of body muscle (galvanonarcosis) and state of muscular rigidity (tetanus). The orientation of the organism (projection of nervous element) to the surrounding field has been found to have important bearing on the behaviour reactions. Clearly differentiated anodic taxis and true narcosis set in when fish body axis was parallel to the lines of current conduction. But with greater angle between the body axis and the current lines, fish did not show well marked reactions. Fish body, when perpendicular to current lines responded for anodic curvature and off balance swimming followed by tetanus.

Benefits of current percolation in superconducting coated conductors

The critical currents of coated conductors fabricated by metal-organic deposition (MOD) on rolling-assisted biaxially textured substrates (RABiTS) and by pulsed laser deposition (PLD) on ion-beam assisted deposition (IBAD) templates have been measured as a function of magnetic field orientation and compared to films grown on single crystal substrates. By varying the orientation of magnetic field applied in the plane of the film, we are able to determine the extent to which current flow in each type of conductor is percolative. Standard MOD/RABiTS conductors have also been compared to samples whose grain boundaries have been doped by diffusing Ca from an overlayer. We find that undoped MOD/RABiTS tapes have a less anisotropic in-plane field dependence than PLD/IBAD tapes and that the uniformity of critical current as a function of in-plane field angle is greater for MOD/RABiTS samples doped with Ca. (C) 2005 American Institute of Physics.

Analysis of the energies of the triple base triplets

Sixty-four sets of three-dimensional models of DNA triplex base triplets (TBT) were built up based on codons by homologous modeling method and their energies were minimized. According to sequence of TBT and orientation of the third ODN strand third, the energies of monomers and water-K+-TBT ternary complexes of TBT were analyzed. The results showed: (i) The energies of the symmetric parallel monomers are generally lower than those of the symmetric anti-parallel monomers of TBT, but the energies of the symmetric parallel ternary complexes are higher than those of the symmetric anti-parallel ternary complexes of TBT. (ii) No matter TBTs are monomers or ternary complexes, the energies of asymmetric parallel TBTs are generally lower than those of the asymmetric anti-parallel ones. (iii) Although the energies of the parallel TBTs are correlated with those of the anti-parallel ones, the energy differences are significant between them. The results here suggest the sequences of TBTs and the orientations of the third ODN strands are two of the key factors that can influence the formation and stability of TBT. (C) 2002 Elsevier Science B.V. All rights reserved.

Characterize dynamic conformational space of human CCR5 extracellular domain by molecular modeling and molecular dynamics simulation

The chemokine receptor CCR5 is the receptor for several chemokines and major coreceptor for R5 human immunodeficiency virus type-1 strains entry into cell. Three-dimensional models of CCR5 were built by using homology modeling approach and 1 ns molecular dynamics (MD) simulation, because studies of site-directed mutagenesis and chimeric receptors have indicated that the N-terminus (Nt) and extracellular loops (ECLs) of CCR5 are important for ligands binding and viral fusion and entry, special attention was focused on disulfide bond function, conformational flexibility, hydrogen bonding, electrostatic interactions, and solvent-accessible surface area of Nt and ECLs of this protein part. We found that the extracellular segments of CCR5 formed a well-packet globular domain with complex interactions occurred between them in a majority of time of MID simulation, but Nt region could protrude from this domain sometimes. The disulfide bond Cys20-Cys269 is essential in controlling specific orientation of Nt region and maintaining conformational integrity of extracellular domain. RMS comparison analysis between conformers revealed the ECL1 of CCR5 stays relative rigid, whereas the ECL2 and Nt are rather flexible. Solvent-accessible surface area calculations indicated that the charged residues within Nt and ECL2 are often exposed to solvent. Integrating these results with available experimental data, a two-step gp120-CCR5 binding mechanism was proposed. The dynamic interaction of CCR5 extracellular domain with gp120 was emphasized. (C) 2004 Elsevier B.V. All rights reserved.

Statistics and dynamics of turbulence-flame alignment in premixed combustion

The geometric alignment of turbulent strain-rate structures with premixed flames greatly influences the results of the turbulence-flame interaction. Here, the statistics and dynamics of this alignment are experimentally investigated in turbulent premixed Bunsen flames using high-repetition-rate stereoscopic particle image velocimetry. In all cases, the statistics showed that the most extensive principal strain-rate associated with the turbulence preferentially aligned such that it was more perpendicular than parallel to the flame surface normal direction. The mean turbulence-flame alignment differed between the flames, with the stronger flames (higher laminar flame speed) exhibiting stronger preferential alignment. Furthermore, the preferential alignment was greatest on the reactant side of the mean flame brush. To understand these differences, individual structures of fluid-dynamic strain-rate were tracked through time in a Lagrangian manner (i.e., by following the fluid elements). It was found that the flame surface affected the orientation of the turbulence structures, with the majority of structures rotating as they approached the flame such that their most extensive principal strain-rate was perpendicular to the flame normal. The maximum change in turbulent structure orientation was found to decrease with the strength of the structure, increase with the strength of the flame, and exhibit similar trends when the structure strength and flame strength were represented by a Karlovitz number. The mean change in orientation decreased from the unburnt to burnt side of the flame brush and appears to be influenced by the overall flame shape. © 2011 The Combustion Institute.

The structure of turbulent stratified and premixed methane/air flames I: Non-swirling flows

A series of flames in a turbulent methane/air stratified swirl burner is presented. The degree of stratification and swirl are systematically varied to generate a matrix of experimental conditions, allowing their separate and combined effects to be investigated. Non-swirling flows are considered in the present paper, and the effects of swirl are considered in a companion paper (Part II). A mean equivalence ratio of φ=0.75 is used, with φ for the highest level of stratification spanning 0.375-1.125. The burner features a central bluff-body to aid flame stabilization, and the influence of the induced recirculation zone is also considered. The current work focuses on non-swirling flows where two-component particle image velocimetry (PIV) measurements are sufficient to characterize the main features of the flow field. Scalar data obtained from Rayleigh/Raman/CO laser induced fluorescence (CO-LIF) line measurements at 103μm resolution allow the behavior of key combustion species-CH 4, CO 2, CO, H 2, H 2O and O 2-to be probed within the instantaneous flame front. Simultaneous cross-planar OH-PLIF is used to determine the orientation of the instantaneous flame normal in the scalar measurement window, allowing gradients in temperature and progress variable to be angle corrected to their three dimensional values. The relationship between curvature and flame thickness is investigated using the OH-PLIF images, as well as the effect of stratification on curvature.The main findings are that the behavior of the key combustion species in temperature space is well captured on the mean by laminar flame calculations regardless of the level of stratification. H 2 and CO are significant exceptions, both appearing at elevated levels in the stratified flames. Values for surface density function and by extension thermal scalar dissipation rate are found to be substantially lower than laminar values, as the thickening of the flame due to turbulence dominates the effect of increased strain. These findings hold for both premixed and stratified flames. The current series of flames is proposed as an interesting if challenging set of test cases for existing and emerging turbulent flame models, and data are available on request. © 2012 The Combustion Institute.