Thin Screen Research Articles

Phytochemical and Antioxidant studies on Stem Bark of Aubrevillea kerstingii

Antioxidants are believed to play a role in preventing the development of some chronic diseases. Medicinal plants with antioxidant activity have continuously been utilized both in traditional and contemporary medicine for management of free radical related diseases. There is need to search for medicinal plants with antioxidant potentials and to isolate compounds responsible for the activity. The aim of this research was to carry out the phytochemical and antioxidant studies on stem bark extract of Aubrevillea kerstingii. The powdered stem bark of Aubrevillea kerstingii (1.5kg) was extracted with n-hexane, ethyl acetate and methanol using sequential maceration. Qualitative screening for antioxidant activity was carried out using thin layer chromatographic TLC autographic screening on pre-coated silica plate. The determination of 2,2-diphenyl-1- picrylhydrazyl (DPPH) radical scavenging activity of the 3 stem bark extracts was carried out according to a standard method. The ethyl acetate extract (5g) was pre-adsorbed on silica gel and loaded into a column pre-packed with 100g silica gel (60-120 Merck). The extract was eluted with n-hexane: ethyl acetate in a gradient elution starting from n-hexane (100%) to ethyl acetate methanol (90:10). The DPPH scavenging activity of the extracts revealed a concentration dependent increase in free radical scavenging activity. The n-hexane, ethyl acetate and methanol extracts showed IC50 values of 98.58μg/ml, 36.79μg/ml and 49.27μg/ml respectively compared with ascorbic acid which had IC50 of 17.89μg/ml. The isolated compound was identified as oleanolic acid using NMR. The 1H-NMR and13C-NMR spectra obtained in CDCl3 with NMR spectrometer showed chemical shifts characteristic of oleanolic acid. The methanol extract and ethyl acetate extracts showed significant antioxidant activity. Oleanolic acid isolated from the ethyl acetate extract may be responsible for the antioxidant activity.

Wave optics simulations of plane-wave propagation in non-Kolmogorov turbulence

We derive limits for wave optics simulations of plane wave propagation in non-Kolmogorov turbulence using the split-step method and thin phase screens. These limits are used to inform two simulation campaigns where the relationship between volume turbulence strength and normalized intensity variance for various non-Kolmogorov power-laws. We find that simulations of smaller power laws are limited turbulence strengths with Rytov numbers of 7 when the simulation side-length sampling rate is 8192. Under these same conditions it is possible to simulate volume turbulence strength out to Rytov numbers of 12 for Kolmogorov power-laws and higher. We show that the peak scintillation and Rytov number where peak scintillation occur increases monotonically with power-law. Also, that if turbulence strength is fixed, the relationship between scintillation index and power-law depends on the operating regime. In weak turbulence the relationship is negative, and it is positive in stronger turbulence. This work also emphasizes the importance of properly scaling turbulence strength with comparing results with different power-laws and the influence and importance of defining inner and outer scales in these simulations.

The Effect of Brand Image and Price Perception on Asus Laptop Purchase Decision

This study is to find out factors that influence brand image as the refelection of the associations in the mind of consumer who buy laptop especially Asus in some local store. This study is also to examine the effect of the image variable brand (X1) and price perception variable (X2) on purchasing decisions (Y) which was carried out on the Consumers of the Risky Media Computer Store who once bought an ASUS brand laptop. There is two hypothesis on this study, H1:Brand image has a positive effect on laptop purchasing decisions ASUS brand at Computer Risky Media Store, H2: Price perception has a positive effect on purchasing decisions ASUS brand laptop at Risky Media Computer Store. In this study using techniques in taking sample using the Accidental Sampling method, which is sampling technique based on chance, that is, anyone who coincidentally met a researcher and was deemed suitable to be used as a data source, which is the consumers of Risky Media Computer Stores who have been bought an Asus Laptop. Total 105 respondents were asking through questionnaire and direct interview in the shop to get specified information. Based on the results of this study, it is found that Brand Image contributes to purchasing decisions on Asus Laptops and also that price perception contributes to purchasing decisions on Asus laptops, it means that Asus laptops are expected to provide attractiveness by turning Asus laptops into entertainment media such as watching streaming and other browsers. With thin screen edges, it provides an exciting visual experience because the screen feels wider. This laptop also has dual loudspeakers that are loud and clear. Keywords: Brand Image; Price Perception; Purchase Decision; Marketing Management

Orbital Dynamics and Extreme Scattering Event Properties from Long-term Scintillation Observations of PSR J1603−7202

We model long-term variations in the scintillation of binary pulsar PSR J1603−7202, observed by the 64 m Parkes radio telescope (Murriyang) between 2004 and 2016. We find that the time variation in the scintillation arc curvature is well-modeled by scattering from an anisotropic thin screen of plasma between the Earth and the pulsar. Using our scintillation model, we measure the inclination angle and longitude of ascending node of the orbit, yielding a significant improvement over the constraints from pulsar timing. From our measurement of the inclination angle, we place a lower bound on the mass of J1603−7202's companion of ≳0.5 M ⊙ assuming a pulsar mass of ≳1.2 M ⊙. We find that the scintillation arcs are most pronounced when the electron column density along the line of sight is increased, and that arcs are present during a known extreme scattering event. We measure the distance to the interstellar plasma and its velocity, and we discuss some structures seen in individual scintillation arcs within the context of our model.

Interstellar Scintillation of PSR J2048−1616

Abstract We report on the interstellar scintillation from pulsar J2048−1616 for the first time at 732, 1369, and 3100 MHz observed with the Parkes 64 m radio telescope. Dynamic spectra are obtained and diffractive parameters are derived from two-dimensional autocorrelation analyses. The frequency dependencies of the observed diffractive scintillation timescale and decorrelation bandwidth indicate that the electron density fluctuations in the interstellar medium (ISM) do not follow the Kolmogorov spectrum. The secondary spectra are calculated by forming the Fourier power spectra of the corresponding dynamic spectra. Prominent parabolic arcs are revealed in the secondary spectra at three frequencies, which indicate that they originated from scattering by a thin screen. The scattering screen is approximately located centrally between the pulsar and Earth assuming that the ISM is stationary.

Phytochemical Profile and Antibacterial Photodynamic Activity of Centella asiatica L. (Apiaceae), Citrus grandis L. (Rutaceae) and Zanthoxylum gilletii De Wild. (Rutaceae) Leaves Extracts

Aims: The objective of this study was to determine the phytochemical profile of Centella asiatica, Citrus grandis and Zanthoxylum gilletii leaves, in solution and the thin layer chromatography chemical screening and to evaluate the antibacterial photodynamic activity of the species extracts.
 Materials and Methods: The search of the secondary metabolites in solution and by thin layer chromatography, the alkaloids and polyphenols extraction were carried out using standard protocols.
 The antibacterial photodynamic activity was performed using microdilution method in solution and solid culture media.
 Results: Centella asiatica and Citrus grandis showed the same phytochemical profile, with the presence of alkaloids, terpenoids, steroids and polyphenols such as: flavonoids, free quinones, anthocyanins, leuco-anthocyanins and tannins. Zanthoxylum gilletii extract showed similar profile with the absence of anthocyanins and leucoanthocyanins. The polyphenolic extracts of both Centella asiatica and Citrus grandis leaves were active against Staphylococcus aureus and Escherichia coli after one and two hours of solar exposition, respectively. Whereas for Zanthoxylum gilletii extract, one hour was sufficient to completely destroy both bacterial strains.
 Conclusion: Polyphenolic extracts from Centella asiatica, Citrus grandis and Zanthoxylum gilletii leaves showed a photodynamic effect on Escherichia coli and Staphylococcus aureus.

Ga and Ti co-doped In2O3 films for flexible amorphous transparent conducting oxides

We designed Ga and Ti co-doped In2O3 (IGTO) films to use as a flexible and transparent amorphous conducting oxide electrode in thin film heaters (TFHs) and flexible touch screen panels (FTSPs) for automobiles. The properties of the IGTO electrodes deposited on cyclic olefin copolymer (COP) at room temperature were investigated as a function of the O2/(Ar + O2) flow ratio, to confirm the best sputtering condition for transparent and flexible electrode. Depending on the oxygen flow ratio, the IGTO/COP electrodes showed sheet resistance of (39.3 – 1.57) × 104 Ohm/sq, an average transmittance of (84.90 – 87.12) % at visible wavelength area, and a surface roughness of (0.95 – 3.23) nm. In addition, IGTO/COP samples exhibited good mechanical flexibility with critical bending radius of 3 mm, which is enough to be used as FTSPs. From the previously mentioned results, we found the amorphous IGTO/COP to be a promising flexible and transparent electrode for curved TFHs and FTSPs. The flexible IGTO/COP TFHs demonstrated a saturated temperature of 78.6 °C when applied with low operating direct current (DC) of 8 V, due to its low sheet resistance. In addition, the IGTO/COP FTSPs showed very stable touch sensitivity, even at a bent state. We found that the optimized IGTO/COP is a promising flexible and transparent electrode for next-generation automobiles.

Opaque pixel mask with a broadband absorbing metasurface: application to infrared detectors.

We present an imager architecture comprising dark and active pixels allowing the simultaneous measurement of photonic and dark current, which is of particular interest for low-photon-flux astronomical applications. The principle of operation relies on both the total opacity of a thin metallic screen of sufficient area and the anti-reflective properties of well-designed resonant metal-dielectric gratings made on the same screen. The concept is exemplified in the context of cooled HgCdTe hybrid detectors, at short- and long-wave infrared ranges.

Lensing from small-scale travelling ionospheric disturbances observed using LOFAR

Observations made using the LOw-Frequency ARray (LOFAR) between 10:15 and 11:48 UT on the 15th of September 2018 over a bandwidth of approximately 25–65 MHz contain discrete pseudo-periodic features of ionospheric origin. These features occur within a period of approximately 10 min and collectively last roughly an hour. They are strongly frequency dependent, broadening significantly in time towards the lower frequencies, and show an overlaid pattern of diffraction fringes. By modelling the ionosphere as a thin phase screen containing a wave-like disturbance, we are able to replicate the observations, suggesting that they are associated with small-scale travelling ionospheric disturbances (TIDs). This modelling indicates that the features observed here require a compact radio source at a low elevation and that the TID or TIDs in question have a wavelength <~30 km. Several features suggest the presence of deviations from an idealised sinusoidal wave form. These results demonstrate LOFAR’s capability to identify and characterise small-scale ionospheric structures.

Editor’s Page

Editor’s Page Stephanie G’Schwind and Donald Revell As we approach the third year of the pandemic—an ongoing interruption, suspension, cessation—some of us have been struggling a bit with our sense of time: Did we do that last year or was it the year before . . . The months seem to flow one into the next, often without the usual demarcations of events or celebrations or rituals we use as guideposts in remembering where we’ve been, when we’ve been, and thus how we’ve been. In Ariel Katz’s story “Disaster Management,” in which a young couple labors through the hurts and silences of their foundering relationship, our narrator describes that period of her life as a “seasonless year.” It’s a fitting phrase not just for these times but for the stories and essays in this issue, which locate themselves in states of disorientation and uncertain borders. A young woman grieving the death of her twin brother, in Maggie Pahos’s “Rhinoceros Ridge,” seeks refuge in travel, in “the winding roads that don’t tell you where you are—that let you forget.” In Courtney Sender’s deeply haunting “Prayer for Being Kissed,” a man survives execution but longs to die on his own terms, existing briefly, perhaps messianically, among the dead in the space between life and death. And in Caroline Schmidt’s “Nocturne,” a woman with suicidal tendencies examines her life—and all the things that keep her from ending it—and concludes: “What all these interruptions added up to was my life.” Shze-Hui Tjoa relates the splitting of her self, as a young piano prodigy, into body and mind, then the way “life comes, pulsing, to the thin screen between this world and the next” in her essay “The Story of Body.” Helena de Bres’s “Elevation” invites us into a transcendent meditation on the elevator: “its own enclosed world, set at some distance from the rest of civilization.” And in “Great Fortune,” Mike Broida reflects on the nature of luck, fortune, and fate as he looks back on an accident, considering for a moment a near possible world in which a car did not collide with his bicycle. These are disorienting times: we are learning to adjust to a new normal, to observe ever-shifting boundaries between what is safe and not safe, to live in the now but have hope for the then. In the meantime, we can ground ourselves in story, in poetry, in these pages. Welcome to the spring issue. [End Page 1] Spring is meant to be a season of delightful impatience, an eager anxiety to get on with the business of blossoming and becoming. In my college days, the nearer spring approached, the farther and farther back in the lecture halls I would sit, trying to catch the first green fragrance through the door. And then would come a day when, although the lecture was beautifully devoted to a beautiful poem by Yeats, I could bear it no more, and out the door I went, delighted. But in this third springtime of a global pandemic, we are all of us suffering impatience of a very different sort. Nearness has become claustrophobic. Familiarity has become a presentiment of rage. What, if anything, can speak to this terrible, this almost insupportable impatience? Only the quiet remembrance of things Permanent, things Eternal, such as springtime. I direct you toward James Longenbach’s “The Interpreter,” and especially to the lines “Right above our heads / New stars are born. / New words occur. . . .” Poetry is an impatience clothed in life’s permanence. Look to Ethel Rackin’s “Something like Life” to find a “great show of light coming through.” In poetry, words are the transparent garment of permanence. Or, as Sarah Crossland would have it, in “The Silent City,” “bluebirds / singing there beneath the ice.” We are not captives. Word by word, a captivating springtime makes us free. [End Page 2] Copyright © 2022 Center for Literary Publishing

Калориметрические исследования СВЧ ионного двигателя

The authors continue their work in the field of calorimetric studies of the parameters of an accelerated ionized gas jet of prototypes of microwave ion micro-thrusters with an energy consumption of up to 10 watts. This paper presents an improved calorimetric method. The introduction into the design of a heat receiver in the form of a thin screen makes it possible to allocate the thermal component formed by the passage of an electric current through the plasma in the accelerating gap. Calorimetric studies of the prototype with a two-electrode accelerating system are carried out at the same accelerating voltages and power of the microwave generator and different mass gas flow rates. It is shown that at a nitrogen consumption of 5,668•10–9 kg/s, the velocity of the mixed jet (neutral gas with ionized component) of the gas was 63,75 m/s, the jet thrust is 0,36 μN. With a nitrogen consumption of 1,611•10–8 kg/s, the speed of the mixed gas jet was 47,9 m/s, the jet thrust was 0,77 μN.

Short communication extraction and phytochemical analysis of Hyptis spicigera leaves

Plants are recognized in the pharmaceutical industry for their broad structural diversity as well as their wide range of pharmacological activities, which is due to their biologically active compounds known as phytochemicals. The present study reports the extraction, thin layer chromatography and screening of phytochemical constituent of Hyptis spicigera leaves. The thin layer chromatography of the leave extract shows 11 bands with Rf values of 0.03, 0.06, 0.09, 0.12, 0.17, 0.19, 0.20, 0.23 and 0.31 respectively. Qualitative phytochemical screening showed the presence of alkaloids, flavonoids, steroids, emodins, and cardiac glycoside while phenols, tannins, terpenoids, tri terpenoids and anthraquinones were absent. The presences of these phytochemicals showed that Hyptis spicigera leaves may be useful for medicinal purpose.

Mathematical modeling of monochromatic acoustic wave diffraction on a system of bodies and on flat screens

Some problems of diffraction of a monochromatic acoustic wave on surfaces of complex shapes are considered. To solve such problems, an approach is applied, in which the problem is reduced to a boundary hypersingular integral equation, where the integral is understood in the sense of a finite value according to Hadamard. Such approach allows solving diffraction problems both on solid objects and on thin screens. To solve the integral equation, the method of piecewise constant approximations and collocations, developed in the previous works of the author, is used. In the present study, examples of modeling the diffraction of an acoustic wave by bodies with partial filling are given. It is shown how the filling of bodies influences the acoustic pressure field, and the field direction patterns are given. An example of applying this approach to solving the problem of sound propagation in an urban area is also given: the diffraction of an acoustic wave from a point source on a system of buildings is considered. The presented results demonstrate that this method allows constructing reflected fields and analyze their characteristics on surfaces of complex shapes.

Diffraction as scattering under the Born approximation.

Light diffraction at an aperture is a basic problem that has generated a tremendous amount of interest in optics. Some of the most significant diffraction results are the Fresnel-Kirchhoff and Rayleigh-Sommerfeld formulas. These theories are based on solving the wave equation using Green's theorem and result in slightly different expressions depending on the particular boundary conditions employed. In this paper, we show that the diffraction by a thin screen, which includes apertures, gratings, transparencies etc, can be treated more generally as a particular case of scattering. Furthermore, applying the first order Born approximation to 2D objects, we obtain a general diffraction formula, without angular approximations. Finally, our result, which contains no obliquity factor, is consistent with the 3D theory of scattering. We discuss several common approximations and place our results in the context of existing theories.

Cerebral aneurysm flow diverter modeled as a thin inhomogeneous porous medium in hemodynamic simulations

Rapid and accurate simulation of cerebral aneurysm flow modifications by flow diverters (FDs) can help improving patient-specific intervention and predicting treatment outcome. However, when FD devices are explicitly represented in computational fluid dynamics (CFD) simulations, flow around the stent wires must be resolved, leading to high computational cost. Classic porous medium (PM) methods can reduce computational expense but cannot capture the inhomogeneous FD wire distribution once implanted on a cerebral artery and thus cannot accurately model the post-stenting aneurysmal flow. We report a novel approach that models the FD flow modification as a thin inhomogeneous porous medium (iPM). It improves over the classic PM approaches in two ways. First, the FD is more appropriately treated as a thin screen, which is more accurate than the classic 3D-PM-based Darcy–Forchheimer relation. Second, pressure drop is calculated cell-by-cell using the local FD geometric parameters across an inhomogeneous PM. We applied the iPM technique to simulating the post-stenting hemodynamics of three patient-specific aneurysms. To test its accuracy and speed, we compared the results from the iPM technique against CFD simulations with explicit FD devices. The iPM CFD ran 500% faster than the explicit CFD while achieving 94%–99% accuracy; thus, iPM is a promising clinical bedside modeling tool to assist endovascular interventions with FD and stents.

Numerical Simulation of Millimeter Wave Scattering by Foam Covered Flat Sea-surface modelled as Sequences of Thin Phase Scattering Screens

Numerical Simulation of Millimeter Wave Scattering by Foam Covered Flat Sea-surface modelled as Sequences of Thin Phase Scattering Screens

Nonnegative principal component analysis in thin layer fingerprint screening: A case of Gentiana extracts from in vitro cultures

Twenty-one species of Gentiana L. were successfully grown in vitro in the same conditions and 72 samples of various cultures of these species (root, shoots, cotyledon callus, hypocotyl callus, and root callus) were obtained. The investigated species were as follows: G. affinis, G. andrewsii, G. bhutanica, G. burseri, G. cachemirica, G. capitata, G. crassicaulis, G. dahurica, G. decumbens, G. freyniana, G. frigida, G. gelida, G. grossheimii, G. kurroo, G. macrophylla, G. paradoxa, G. robusta, G. scabra, G. septemfida, G. siphonantha, and G. tianschanica. The obtained samples were extracted with methanol–acetone–water (3:1:1) mixture, evaporated to dryness, and subjected to TLC on silica gel with mobile phase ethyl acetate–methanol–water (8:2:2) in sandwich mode. Data fusion of two densitometric modes: extinction at 254 nm and fluorescence at 312 nm (emission above 370 nm) were used as a fingerprint of each sample. Densitograms were denoised, subjected to baseline removal, warped, and analyzed with principal component analysis (PCA), hierarchical cluster analysis and—the novel proposal—nonnegative PCA. This allowed to split negatively intercorrelated fingerprint features to subsequent principal components (PCs), which increases the number of PCs required to see the same information, but these PCs are much more informative.

Thermal performance enhancement of vapor chamber with modified thin screen mesh wick by laser etching

In order to cope with high heat flux of miniaturized electronic devices in narrow space, vapor chamber has been developed towards ultra-thin thickness. In this study, a novel design of thin screen mesh with superhydrophilic micro structure was firstly proposed to enhance the thermal performance of thin vapor chamber (TVC). A layer of 0.12 mm thick screen mesh was employed as evaporator wick. The central area of the thin wick above heat input region was treated by laser etching to form superhydrophilic micro structure for improving capillary capability and providing nucleation sites. The upper sheet without wick was stamped to form support columns for preventing deformation and providing axial thermal conduction passage. Three TVCs (70 × 70 × 1.5 mm3) with various laser-etching area ratio (LEAR) of 0%, 66.6% and 83.3% were fabricated to study thermal performance of the novel TVCs. The results indicated that the novel evaporator mesh wick could remarkably enhance thermal performance of the TVCs. With LEAR increasing from 0% to 83.3%, the lowest thermal resistance RVC of TVC dropped from 0.431 K/W to 0.328 K/W, i.e. decreased 23.9%, and the maximum heat transfer capacity increased from 100 W to 120W, i.e. increased 20%.

Evaluating the applicability of a screen diffraction approximation to local volcano infrasound

Atmospheric acoustic waves from volcanoes at infrasonic frequencies (0.01–20 Hz) can be used to estimate source parameters for hazard modeling, but signals are often distorted by wavefield interactions with topography, even at local recording distances (<15 km). We present new developments toward a simple empirical approach to estimate attenuation by topographic diffraction at reduced computational cost. We investigate the applicability of a thin screen diffraction relationship developed by Maekawa [1968, doi: https://doi.org/10.1016/0003-682X(68)90020- 0]. We use a 2D axisymmetric finite-difference method to show that this relationship accurately predicts power losses for infrasound diffraction over an idealized kilometer-scale screen; thus validating the scaling to infrasonic wavelengths. However, the Maekawa relationship overestimates attenuation for realistic volcano topography (using Sakurajima Volcano as an example). The attenuating effect of diffraction may be counteracted by constructive interference of multiple reflections along concave volcano slopes. We conclude that the Maekawa relationship is insufficient as formulated for volcano infrasound, and suggest modifications that may improve the prediction capability.

Monitoring electron energies during FLASH irradiations

When relativistic electrons are used to irradiate tissues, such as during FLASH pre-clinical irradiations, the electron beam energy is one of the critical parameters that determine the dose distribution. Moreover, during such irradiations, linear accelerators (linacs) usually operate with significant beam loading, where a small change in the accelerator output current can lead to beam energy reduction. Optimisation of the tuning of the accelerator’s radio frequency system is often required. We describe here a robust, easy-to-use device for non-interceptive monitoring of potential variations in the electron beam energy during every linac macro-pulse of an irradiation run. Our approach monitors the accelerated electron fringe beam using two unbiased aluminium annular charge collection plates, positioned in the beam path and with apertures (5 cm in diameter) for the central beam. These plates are complemented by two thin annular screening plates to eliminate crosstalk and equalise the capacitances of the charge collection plates. The ratio of the charge picked up on the downstream collection plate to the sum of charges picked up on the both plates is sensitive to the beam energy and to changes in the energy spectrum shape. The energy sensitivity range is optimised to the investigated beam by the choice of thickness of the first plate. We present simulation and measurement data using electrons generated by a nominal 6 MeV energy linac as well as information on the design, the practical implementation and the use of this monitor.