Transparent Regions Research Articles

Tectonic development of the northeastern Tibetan Plateau as constrained by high-resolution deep seismic-reflection data

A 180-km-long, high-resolution seismic-reflection survey that imaged the entire crust and the uppermost mantle lithosphere was conducted across the northeastern Tibetan Plateau. This work had three aims: (1) to examine whether the left-slip Haiyuan and Tianjing faults defining the margin of NE Tibet are crustal- or lithospheric-scale structures, (2) to determine whether seismic fabrics are consistent with middle- and/or lower-crustal channel flow, and (3) to establish the minimum amount of Cenozoic shortening strain in the region. Analysis of our newly obtained seismic-reflection data suggests that the left-slip Haiyuan and Tianjing faults have multiple strands and cut through the upper and middle crust. The faults likely terminate at a low-angle detachment shear zone in the lower crust, because the flat Moho directly below the projected traces of the faults is continuous. The seismic image displays subvertical zones of highly reflective sequences containing parallel and subhorizontal reflectors that are truncated by seismically transparent regions with irregular shape. The transparent regions in the middle crust are traceable to the seismically transparent lower crust and are interpreted as early Paleozoic plutons emplaced during the construction of the Qilian arc in the region. The presence of the undisturbed subvertical contacts between zones of highly reflective and seismically transparent regions rules out the occurrence of channel flow in the middle crust, as this process would require through-going subhorizontal reflectors bounding the channel above and below. The lack of continuous reflectors longer than a few kilometers in the lower crust makes a laminar mode of channel flow unfavorable, but lateral lower-crustal flow could have occurred via small-scale ductile deformation involving folding (less than a few kilometers in wavelength and amplitude). Integrating surface geology and the seismic data, we find that the upper crust along a segment of the seismic surveying line experienced up to 46% crustal shortening postdating the Cretaceous and is thus interpreted as entirely accumulated in the Cenozoic. If the estimated shortening strain is representative across northeastern Tibet, its magnitude is sufficient to explain the current elevation of the region without an appeal for additional contributing factors such as channel flow and/or a thermal event in the upper mantle.

Na8Lu2(CO3)6F2 and Na3Lu(CO3)2F2: Rare Earth Fluoride Carbonates as Deep-UV Nonlinear Optical Materials

Two nonlinear optical fluoride carbonate crystals (Na8Lu2(CO3)6F2 and Na3Lu(CO3)2F2) have been synthesized under subcritical hydrothermal condition. Both crystals crystallize in the noncentrosymmetric space group Cc (No. 9). The structure of Na8Lu2(CO3)6F2 with high density of [CO3] groups is described as 1D [Na5Lu(CO3)2F2] chains connected by [CO3] triangles, forming an intricate three-dimensional framework. Lu3+ and Na+ cations are alternatively ordered and disordered in the cavities of the 3D network. The structure of Na3Lu(CO3)2F2 is built up from the [NaLu(CO3)2F2] layers which are separated by other Na+ cations. The [CO3] anionic groups arrange approximately coparallel to the plane. The second harmonic generation (SHG) measurement indicates that Na8Lu2(CO3)6F2 and Na3Lu(CO3)2F2 have large SHG responses that are approximately 4.29 and 4.21 times KH2PO4 (KDP), respectively. The responses are also phase-matchable in the visible region. In addition, it exhibits wide transparent regions ranging from UV to near IR with a short UV cutoff edge (<200 nm), which suggests that the new compounds are promising as deep-UV NLO materials.

Syntheses, Structures, and Nonlinear Optical Properties of Quaternary Chalcogenides: Pb4Ga4GeQ12 (Q = S, Se)

Two noncentrosymmetric isostructural compounds Pb4Ga4GeQ12 (Q = S, Se) with their own structure type have been synthesized by solid-state reactions at high temperature. They crystallize in the tetragonal space group P42(1)c (No. 114) with a = 12.673(2) Å and c = 6.128(2) Å, and a = 13.064(7) Å and c = 6.310(5) Å, respectively, and Z = 2. The major structure motif features a three-dimensional framework constructed by chains of GaQ4 tetrahedra that are interconnected by separated GeQ4 tetrahedra at regular intervals. Interestingly, such a [Ga4GeQ12](8-) framework is flexible to allow the addition of Ag(+) or Li(+) to occupy the embedded A- or B-type of vacancies to generate the previously reported [AgGa5Q12](7-) or [LiGa5Q12](7-) interstitial compounds without symmetry breaking. The title compounds (Q = S, Se) have optical band gaps of 2.35 and 1.91 eV, respectively, and wide IR transparent regions of 0.80-22.5 and 0.75-22.5 μm, respectively. Significantly, the powder Pb4Ga4GeSe12 sample exhibits a strong second-harmonic-generation (SHG) response that is ∼2 times that of the benchmark AgGaS2 at a laser radiation of 2.05 μm with a non phase-matchable behavior. The calculated d36 coefficient agrees well with the experimental observation. The density functional theory (DFT) calculations suggest that the SHG response originates from the electronic transitions from Se 4p states to Pb 6p, Ga 4p, and Ge 4p states.

Optical characterization of As–S thin films induced by plasma immersion O− ion implantation

In this study, optical constants of different thicknesses of stoichiometric composition As40S60 obtained from transmission spectra were investigated. The effect of exposure to oxygen plasma immersion ion implantation (O−-PIII) on the optical constants of the same samples of different thicknesses was also investigated. It is observed that the O−-PIII treatment can effectively improve the transmission spectra of the samples, particularly in medium and transparent regions; therefore the refractive index decreases. In addition, the optical band gap Egopt was determined before and after PIII from the absorption coefficient values using Tauc's procedure, i.e. from the relationship α hν = K(hν - Egopt )2 where K is a constant. The O−-PIII causes an increase in the energy gap of stoichiometric composition As40S60.

Generation of coherent phonons in a CdTe single crystal using an ultrafast two-phonon laser-excitation process.

The detection-energy dependence of a coherent phonon in a (001) CdTe crystal, generated by ultrashort laser pulses with the center energy transparent or opaque to the sample, is investigated using a spectrally resolved pump-probe method. At the excitation in the transparent region, the detection-energy dependence of the phonon amplitude has two peaks at the energy shifted by one times the phonon energy of CdTe from the center energy of the probe pulses. On the other hand, the amplitude in the opaque region shows two peaks at the energy shifted by about two times the phonon energy. This difference occurs even though the observed energies of the coherent phonons in both regions are the same as that of the longitudinal optical phonon of CdTe. The energy shifts in the detection-energy dependence imply that the emission and absorption of one phonon and two phonons in the transparent and opaque regions, respectively, are implicated in coherent phonon generation. In this study, the detection-energy dependence is examined from the viewpoint of the third-order nonlinear susceptibility based on the impulsive stimulated Raman scattering process under nonresonant and resonant conditions.

Transparency Effect in the Emergence of Monopolies in Social Networks

A power law degree distribution is displayed in many complex networks. However, in most real social and economic networks, deviation from power-law behavior is observed. Such networks also have giant hubs far from the tail of the power law distribution. We propose a model based on information 'transparency' (i.e. how much information is visible to others), which can explain the power structure in societies with non-transparency in information delivery. The emergence of very high degree nodes is explained as a direct result of censorship. Based on these assumptions, we define four distinct transparency regions: perfectly non-transparent, low transparent, perfectly transparent regions and regions where information is exaggerated. We observe the emergence of some very high degree nodes in low transparency networks. We show that the low transparency networks are more vulnerable to attack and the controllability of low transparent networks is more difficult than for the others. Also, the low transparency networks have a smaller mean path length and higher clustering coefficients than the other regions.

Development And Characterization Of Green Tea Loaded Microemulsion For Vaginal Infections

Natural products are important sources for new drug development. Though antibiotic therapies are first line of treatment for vaginal infections but prolonged use results in various side effects, hence there is a need to develop alternative therapies based upon natural products. Green tea powder (GTP) has been reported to exhibit anti-microbial activity and has synergistic effect with some antibiotics. Conversely, the role of GTP against vaginal infections has not been explored extensively. GTP is safe even at high doses but exhibits poor oral bioavailability. Encapsulation of GTP in a microemulsion (ME) vehicle would protect it against degradation. Aim of this study is to formulate GTP loaded MEs for vaginal application and to assess its efficacy against various vaginal pathogens. UV analysis of the GTP was done and solubility studies in various oils, surfactants and cosurfactants were carried out to select various phases of MEs. Titrations were carried out with various oil:Smix ratios and the data obtained was used to plot pseudo-ternary phase diagrams. The emulsion regions which corresponded to particle less, transparent regions and within GRAS limits were subjected to thermodynamic stability studies. Droplet size of thermodynamically stable MEs was found to be in nanometre range. Escherichia coli and Staphylococcus epidermidis were found to be sensitive to GTP and its ME via disc diffusion assay.

Optical constants of vacuum annealed radio frequency (RF) magnetron sputtered zinc oxide thin films

Zinc oxide thin films were deposited by radio frequency magnetron sputtering. The films were annealed in vacuum at temperatures of 400, 600, and 800°C. The influence of annealing on the structural, chemical, and optical properties of the films was investigated. From a structural point of view, the films were highly oriented, with columnar microstructure. Chemical analysis indicated that the films were sub-stoichiometric, and that the concentration of oxygen vacancies was enhanced upon annealing. The films were highly transparent in the visible and near-infrared spectral regions. Transparency was reduced as the annealing temperature was increased. The refractive index and extinction coefficient, in the transparent regions of the films, were derived from transmittance measurements. The refractive index manifested variation that was affected by crystallite size, roughness and defect concentration. The extinction coefficient of the as-deposited films and those annealed at 400°C was negligible. However, the films annealed at 600 or 800°C had much larger values of the extinction coefficient due to increased absorption or scattering. The absorption coefficient and optical band gap of the films were derived from spectrophotometric measurements. The absorption coefficient showed progressive increase with the annealing temperature. However, the band gap did not show significant variation.

Crystal growth of [formula omitted] solid solutions by zone melting technique

Mixtures (1−x)LiGdF4+xLiLuF4 (0.50≤x≤0.75) were melted and submitted to one zone melting cycle under a reactive HF atmosphere, aiming the study of the crystal growth of LiGd1−xLuxF4 solid solutions. Phase identification and compositional studies of the ingots were performed by scanning electron microscopy, energy dispersive X-ray spectrometry, and X-ray powder diffraction. Transparent regions of the bar related to the formation of LiGd1−xLuxF4 solid solutions were found to be enlarged proportionally to the initial amount of Lu in the mixtures. Gd segregates to the end of the ingot.

Cadmium-rare earth oxyborates Cd4ReO(BO3)3 (Re = Y, Gd, Lu): congruently melting compounds with large SHG responses

A new series of cadmium–rare earth (Re) oxyborates Cd4ReO(BO3)3 (Re = Y, Gd, Lu) have been synthesized through high-temperature solid-state reactions in platinum crucibles. In their crystal structures, ReO6 (Re = Y, Gd, Lu) and CdOn (n = 6, 8) are distorted polyhedra interconnected via shared edges and corners in a 3D framework with tunnels along the c-axis, where all B atoms are located. BO3 planar triangles lie approximately parallel to the (001) plane. The combination of triangular BO3 groups with π-conjugated systems and the d10 Cd2+ cation with polar displacement produces large SHG responses. Second harmonic generation (SHG) measurements indicate that Cd4YO(BO3)3, Cd4GdO(BO3)3, and Cd4LuO(BO3)3 feature large SHG responses that are approximately 5.2, 5.0, and 5.3 × KH2PO4 (KDP), respectively. They are all phase matchable nonlinear optical materials that have wide transparent regions ranging from UV to near IR. These title compounds melt congruently, suggesting that the Cd4ReO(BO3)3 (Re = Y, Gd, Lu) complexes are very promising NLO materials. Their electronic structures and optical properties were analyzed by using the Vienna ab initio theoretical method.

COMPACT BASE STATION ANTENNAS USING METAMATERIALS

The paper deals with the modelling, practical implementa- tion and characterization of a directional antenna controllable through 360 - in the (2{2.5GHz) frequency band. The antenna is composed of a central omnidirectional broadband monopole feed surrounded by a metamaterial made of one or two controllable layers of metallic strips printed on a dielectric substrate, which can be electrically continuous or discontinuous. Following the electrical state of these strips, the metamaterial can be re∞ective or transparent. Then by controlling the distribution of re∞ective and transparent regions of the latter metama- terial around the central feed, a directional emission having an angular beamwidth lower or equal to 60 - and controllable through 360 - is pro- duced in the UMTS and WIFI frequency bands, demonstrating the wideband operation of this antenna.

The Role of Water Vapour in Earth’s Energy Flows

Water vapour modulates energy flows in Earth's climate system through transfer of latent heat by evaporation and condensation and by modifying the flows of radiative energy both in the longwave and shortwave portions of the electromagnetic spectrum. This article summarizes the role of water vapour in Earth's energy flows with particular emphasis on (1) the powerful thermodynamic constraint of the Clausius Clapeyron equation, (2) dynamical controls on humidity above the boundary layer (or free-troposphere), (3) uncertainty in continuum absorption in the relatively transparent window regions of the radiative spectrum and (4) implications for changes in the atmospheric hydrological cycle.

Spatial structure and stability of coupled Alfvén and drift compressional modes in non-uniform magnetosphere: Gyrokinetic treatment

The spatial structure and stability properties of the coupled Alfvén and drift compressional modes in a space plasma are studied in a gyrokinetic framework in a model taking into account field-line curvature and plasma and magnetic field inhomogeneity across the magnetic shells. The perturbation is found to be localized in two transparent regions, the Alfvén and drift compressional transparent regions, where the wave vector radial component squared is positive. Both regions are bounded by the resonance and cut-off surfaces, where the wave vector radial component turns into infinity and zero, respectively. An existence of the drift compressional resonance is one of the most important results of this work. It is argued that on the surface of this resonance the longitudinal and azimuthal components of the wave's magnetic field have a pole and logarithmic singularities, respectively. The instability conditions and expressions for the growth rate of the coupled modes have been obtained. In the Alfvénic transparent region, an instability occurs in the presence of the negative plasma temperature gradient. This instability does not lead to a non-stationary wave behavior: all the energy gained from the resonance particles was finally absorbed owing to any dissipation process. In a drift compressional transparent region, a necessary condition for the instability is the growth of the temperature with the radial coordinate. The growth rate is almost independent of the radial coordinate, which means that the wave energy gained from the particles cannot disappear. It will lead to an ever increasing wave amplitude, and no stationary picture for the unstable drift compressional mode is possible.

Water Vapor Continuum Absorption in the Microwave

The accurate modeling of continuum absorption is crucial for the so-called window regions of the spectrum, the relatively transparent regions between lines. The window regions in the microwave are of critical importance for Earth remote sensing and data assimilation. Presented in this paper is an evaluation of the widely used Mlawer, Tobin, Clough, Kneizys, and Davis (MT_CKD) water vapor continuum model in the microwave region, performed using measurements from ground-based radiometers operated by the Department of Energy's Atmospheric Radiation Measurement Program at sites in Oklahoma, USA, and the Black Forest, Germany. The radiometers used were the Radiometrics 23.8/31.4-GHz microwave radiometers (MWRs), the Radiometer Physics GmbH 90/150-GHz MWR at high frequencies (MWRHF), and the Radiometrics 183 GHz G-band vapor radiometer profiler (GVRP). Radiometer measurements were compared with brightness temperatures calculated using radiosonde temperature and humidity profiles input to the monochromatic radiative transfer model (MonoRTM), which uses the MT_CKD continuum model. Measurements at 23.8 GHz were used to correct for biases in the total precipitable water vapor (PWV) from the radiosondes. The long-term 31.4 GHz data set, with a range of PWV values spanning from 0.15 to 5 cm, allowed the separation of uncertainties in the self- and foreign-broadened components of the water vapor continuum. The MT_CKD model has been updated in the microwave region to provide improved agreement with the measurements. MonoRTM has been updated accordingly. The results for the different instruments and frequencies were consistent, providing high confidence in the continuum updates. The estimated uncertainties on the updated continuum coefficients in MT_CKD are 4% on the foreign-broadened water vapor continuum and 4% on the self-broadened water vapor continuum.

Visibility-aware direct volume rendering

Direct volume rendering (DVR) is a powerful visualization technique which allcvs users to effectively explore and study volumetric datasets. Different transparency settings can be flexibly assigned to different structures such that some valuable information can be revealed in direct volume rendered images (DVRIs). However, end-users often feel that some risks are always associated with DVR because they do not know whether any important information is missing from the transparent regions of DVRIs. In this paper, we investigate how to semi-automatically ger erate a set of DVRIs and also an animation which can reveal information missed in the original DVRIs and meanwhile satisy some image quality criteria such as coherence. A complete framework is developed to tackle various problems related to the generation and quality evaluation of visibility-aware DVRIs and animations. Our technique can reduce the risk of using direct volume rendering and thus boost the confidence of users in volume rendering systems.

Visibility-Aware Direct Volume Rendering

Direct volume rendering (DVR) is a powerful visualization technique which allows users to effectively explore and study volumetric datasets. Different transparency settings can be flexibly assigned to different structures such that some valuable information can be revealed in direct volume rendered images (DVRIs). However, end-users often feel that some risks are always associated with DVR because they do not know whether any important information is missing from the transparent regions of DVRIs. In this paper, we investigate how to semi-automatically generate a set of DVRIs and also an animation which can reveal information missed in the original DVRIs and meanwhile satisfy some image quality criteria such as coherence. A complete framework is developed to tackle various problems related to the generation and quality evaluation of visibility-aware DVRIs and animations. Our technique can reduce the risk of using direct volume rendering and thus boost the confidence of users in volume rendering systems.

Effect of temperature on the build-up and post hydrothermal processing of hydrogen-bonded PVPON/PAA film

Hydrogen-bonded films were prepared by layer-by-layer (LBL) assembly of poly(vinylpyrrolidone) (PVPON) and poly(acrylic acid) (PAA). The effect of temperature on the build-up and post hydrothermal process was studied in detail. It was found that the film's cloudiness was sensitive to the fabrication temperature. Below 20 °C the film was cloudy, while above 25 °C it was transparent. The temperature region from 20–25 °C was a mixed zone, transiting from cloudy to transparent. The thickness growth exhibited different temperature dependencies in the cloudy and transparent temperature regions. In the cloudy temperature region it was 5–6 nm °C−1 per cycle while in the transparent temperature region it was as high as 15–16 nm °C−1. At 50 °C, the film thickness increment of a single deposition step reached to ∼600 nm, which was considered as one of the fastest growth rates in LBL assembly. The post hydrothermal processing of the film was performed in acidic water (pH = 2.0) at temperatures higher than the build-up temperature. As the hydrothermal processing temperature elevated to 90 °C, the Fabry-Perot fringes gradually disappeared and a morphology full of pits formed, like the film that was prepared by layer-by-layer assembly at 50 °C.

Integrated microbioreactor for culture and analysis of bacteria, algae and yeast

We introduce a micro-scale bioreactor for automated culture and density analysis of microorganisms. The microbioreactor is powered by digital microfluidics (DMF) and because it is used with bacteria, algae and yeast, we call it the BAY microbioreactor. Previous miniaturized bioreactors have relied on microchannels which often require valves, mixers and complex optical systems. In contrast, the BAY microbioreactor is capable of culturing microorganisms in distinct droplets on a format compatible with conventional bench-top analyzers without the use of valves, mixers or pumps. Bacteria, algae and yeast were grown for up to 5days with automated semi-continuous mixing and temperature control. Cell densities were determined by measuring absorbances through transparent regions of the devices, and growth profiles were shown to be comparable to those generated in conventional, macro-scale systems. Cell growth and density measurements were integrated in the microbioreactor with a fluorescent viability assay and transformation of bacteria with a fluorescent reporter gene. These results suggest that DMF may be a useful new tool in automated culture and analysis of microorganisms for a wide range of applications.

Effects of glycerol content and film thickness on the properties of vital wheat gluten films cast at pH 4 and 11

AbstractThis study deals with the optical properties and plasticizer migration properties of vital wheat gluten (WG) films cast at pH 4 and 11. The films contained initially 8, 16, and 25 wt % glycerol and were aged at 23°C and 50% relative humidity for at least 17 weeks on a paper support to simulate a situation where a paper packaging is laminated with an oxygen barrier film of WG. The films, having target thicknesses of 50 and 250 μm, were characterized visually and with ultraviolet/visible and infrared spectroscopy; the mass loss was measured by gravimetry or by a glycerol‐specific gas chromatography method. The thin films produced at pH 4 were, in general, more heterogeneous than those produced at pH 11. The thin pH 4 films consisted of transparent regions surrounding beige glycerol‐rich regions, the former probably rich in gliadin and the latter rich in glutenin. This, together with less Maillard browning, meant that the thin pH 4 films, in contrast to the more homogeneous (beige) thin pH 11 films, showed good contact clarity. The variations in glycerol content did not significantly change the optical properties of the films. All the films showed a significant loss of glycerol to the paper support but, after almost 9 months, the thick pH 11 film containing initially 25 wt % glycerol was still very flexible and, despite a better contact to the paper, had a higher residual glycerol content than the pH 4 film, which was also more brittle. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Perceptual preferences in depth stratification of transparent layers: Photometric and non-photometric factors

In three experiments, using a two-alternative forced-choice task, we obtained depth judgments of displays containing transparent regions. The regions varied in lightness, size, and animation. Observers nearly always strongly preferred one certain depth ordering among the regions, even though their lightness conditions were expected to give rise to ambiguity among possible orderings. This expectation was based on the contrast polarity model, which expects ambiguity in the absence of contrast polarity reversal. The expectation was founded also on a stronger condition based on the transmittance anchoring principle, which gives preference to the largest lightness contrast between regions. In the absence of contrast polarity reversal and in conditions of balanced regional contrast, preferences were shown to depend on additional conditions of contrast between two respective regions and their overlap. Depth ordering judgment seems to be based on a critical decision threshold, independently of the coordinate system used to specify lightness. We also investigated the role of non-photometric factors such as motion and relative size, and concluded that these variables can modulate depth ordering judgments in transparency.