Efficient Polarization Research Articles

Multiwavelength Stellar Polarimetry of the Filamentary Cloud IC5146. I. Dust Properties

Abstract We present optical and near-infrared stellar polarization observations toward the dark filamentary clouds associated with IC5146. The data allow us to investigate the dust properties (this paper) and the magnetic field structure (Paper II). A total of 2022 background stars were detected in the R c , , H, and/or K bands to mag. The ratio of the polarization percentage at different wavelengths provides an estimate of , the wavelength of the peak polarization, which is an indicator of the small-size cutoff of the grain size distribution. The grain size distribution seems to significantly change at mag, where both the average and dispersion of decrease. In addition, we found μm for mag, which is larger than the ∼0.55 μm in the general interstellar medium (ISM), suggesting that grain growth has already started in low-A V regions. Our data also reveal that polarization efficiency ( ) decreases with A V as a power law in the R c , , and K bands with indices of −0.71 ± 0.10, −1.23 ± 0.10, and −0.53 ± 0.09. However, H-band data show a power index change; the PE varies with A V steeply (index of −0.95 ± 0.30) when mag, but softly (index of −0.25 ± 0.06) for greater A V values. The soft decay of PE in high-A V regions is consistent with the radiative alignment torque model, suggesting that our data trace the magnetic field to mag. Furthermore, the breakpoint found in the H band is similar to that for A V , where we found the dispersion significantly decreased. Therefore, the flat PE–A V in high-A V regions implies that the power-index changes result from additional grain growth.

Star-shaped oligothiophene-functionalized truxene materials as stationary phases for capillary gas chromatography

This work reports oligothiophene-functionalized truxene-based stationary phases (TTT, TDT and TFT) with a unique star-shaped π-conjugated architecture for gas chromatographic (GC) separations. They exhibited medium polarity and column efficiency of 3340–3760 plates/m determined by naphthalene at 120°C. Among them, the TTT stationary phase displayed advantageous resolving capability over the TDT and TFT phases for a wide ranging analytes from apolar to polar, particularly for structural and positional isomers, including alcohols, phenols, halogenated and alkylated benzenes and naphthalenes. Moreover, the TTT column exhibited good thermal stability and repeatability with relative standard deviation (RSD) values of 0.02%–0.07% for run-to-run, 0.10%–0.53% for day-to-day and 2.1%–2.9% for column-to-column, respectively. In addition, it was applied for the determination of isomer impurities in real samples, proving its good potential for practical GC analysis.

Analysis of ultra-compact TE to TM polarization rotator in InGaAsP and SOI technologies

This article describes full analysis of a novel transverse electric (TE) to transverse magnetic (TM) polarization rotator based on mode interference utilizing finite element method. The core, substrate, and cladding of the polarization rotator are in the hybrid technology of InGaAsP and SiO2 materials. Effect of several parameters such as core's refractive index, width to height ratio of the polarization rotator, and incident light's wavelength on polarization conversion length, polarization efficiency, polarization extinction ratio, and rotation angle were investigated. Simulation results revealed that the rotation length was less than 1μm, while the polarization conversion efficiency of 90%, polarization extinction ratio of 15dB, and maximum rotation angle of 85° at 1.55μm wavelength can be achieved.

New derivatives of (E,E)-azomethines: Design, quantum chemical modeling, spectroscopic (FT-IR, UV/Vis, polarization) studies, synthesis and their applications: Experimental and theoretical investigations

In present work, Polarization, Excited States, FT-IR, 1H, 13C NMR, Trans–Cis (E → Z) Isomerization Properties and Anisotropy of Thermal and Electrical Conductivity of the three new Azomethines dyes such as: 4-((E)-((4-((E)-phenyldiazenyl)phenyl)imino)methyl)benzoic acid (I), 5-phenyl-N-(pyrimidin-2-yl)isoxazole-3-carboxamide (II) and (Z)-1-(4-((E)-((4-phenylcyclopenta-1,4-dien-1-yl)methylene)amino)phenyl)ethanone oxime (III) in the presence of polyvinyl alcohol (PVA) matrix were studied. The absorption spectrum of the I, II and III in dimethylformamide (DMF) solution was calculated. The nature of absorption peaks of the dyes in the UV/Vis spectral regions was interpreted. The molecular HOMO-LUMO, excitation energies and oscillator strengths for E and Z isomers of the I, II and III have also been calculated and presented. Optical Properties of the PVA-films containing these new synthesized dyes have investigated. Polarizing Efficiency (PE) of obtained PVA-film is 97–98% at Stretching Degree (Rs) 3.5. Anisotropy of thermal and electrical conductivity of the PVA-films containing the title compounds was also measured and discussed.

Superconformal Cobalt Fill through the Use of Sacrificial Oxidants

As interconnect dimensions continue to decrease, the extendibility of conventional copper damascene processing becomes increasingly problematic. Small feature openings can lead to agglomeration of the thin seed that is required to avoid pinch-off, and this can then lead to poor nucleation during the electrodeposition process. Electromigration performance also suffers from the decrease in line dimensions. In addition, the increase in line resistance with shrinking dimensions means that the barrier is consuming valuable space within the feature. To address these extendibility issues, alternative metals, such as cobalt, are being actively explored. Conventional damascene electroplating utilizes a combination of organic additives, namely, a suppressor, an accelerator, and a leveler, to achieve superconformal fill of interconnects. An alternative mechanism for superconformal cobalt fill is presented here. This mechanism, the Differential Current Efficiency Fill (DCEF) mechanism, utilizes sacrificial oxidants to achieve void-free superconformal fill. In the DCEF mechanism, the presence of a sacrificial oxidant promotes a difference in metal deposition rate between the field and the feature bottom. Addition of a single suppressor-type additive may assist in driving the plating rate differential. By appropriately selecting the sacrificial oxidant, the waveform, and the rotation rate, void-free superconformal fill can be achieved. Figure 1 shows an example of the superconformal cobalt fill that can be achieved. Here, the rate and degree of fill are modulated by changing the rotation rate during the electrodeposition. Electrochemical polarization and current efficiency experiments are useful in determining appropriate process conditions, and these data will also be discussed. The DCEF mechanism presents a new approach to achieving superconformal fill and will be important in extending electroplating to increasingly smaller interconnect dimensions. While the DCEF mechanism has been shown to work for superconformal cobalt fill, the concept may be applicable to other metals as well. Figure 1: Superconformal cobalt fill: 1mA/cm2 240s, varied rotation rate Figure 1

Sistema sensor com câmera USB para uso em experimentos de polarização da luz

Este trabalho apresenta um sistema sensor para uso em laboratórios de ensino, composto por uma câmera USB e um software desenvolvido e disponibilizado pelos autores. O sistema sensor é adequado para o estudo de fenômenos associados à propriedade de polarização da luz, tendo sido testado em experimentos realizados para verificar a Lei de Malus e a eficiência espectral de polarizadores. São apresentados detalhes da montagem experimental, na qual a luz de uma lanterna de LED usada como fonte luminosa no visível é projetada numa tela branca após passar por dois polarizadores. A imagem projetada na tela é captada pela câmera e o software fornece a intensidade luminosa relativa da luz. Com o uso de dois polarizadores lineares tipo H rotatórios, ajustes lineares da Lei de Malus aos dados de intensidade da luz transmitida apresentaram coeficientes de correlação R maiores do que 0,9988. A eficiência dos polarizadores em diferentes regiões do espectro eletromagnético visível foi analisada com o auxílio de filtros de cor inseridos à montagem experimental. O sistema também foi empregado na avaliação da estabilidade temporal da intensidade do LED de luz branca.

Dynamic Nuclear Polarization Efficiency Increased by Very Fast Magic Angle Spinning.

Dynamic nuclear polarization (DNP) has recently emerged as a tool to enhance the sensitivity of solid-state NMR experiments. However, so far high enhancements (>100) are limited to relatively low magnetic fields, and DNP at fields higher than 9.4 T significantly drops in efficiency. Here we report solid-state Overhauser effect DNP enhancements of over 100 at 18.8 T. This is achieved through the unexpected discovery that enhancements increase rapidly with increasing magic angle spinning (MAS) rates. The measurements are made using 1,3-bisdiphenylene-2-phenylallyl dissolved in o-terphenyl at 40 kHz MAS. We introduce a source–sink diffusion model for polarization transfer which is capable of explaining the experimental observations. The advantage of this approach is demonstrated on mesoporous alumina with the acquisition of well-resolved DNP surface-enhanced 27Al cross-polarization spectra.

Through-mask electrochemical machining of hole arrays on molybdenum sheets

Molybdenum is an important modern industrial material. It is widely used in high-energy and high-heat environments due to its high melting point and thermal conductivity, as well as its low thermal expansion coefficient. Hole arrays on molybdenum sheets are commonly used in industry, with applications in ion plating equipment, projection electron microscopes, cryo-electron microscopy, and electron guns. However, fabrication of these arrays on molybdenum sheets is very difficult due to high opening ratio limitations, deformation of thin sheets, and the mechanical properties of the metal. Therefore, high-efficiency, high-precision fabrication of hole arrays on molybdenum sheets has emerged as a focus of research. Through-mask electrochemical machining (TMECM) is an effective method of fabricating hole-type components. This paper describes a method of fabricating hole arrays on a sheet using a TMECM process in a neutral NaNO3 solution. Polarization and current efficiency curves were measured for molybdenum in a NaNO3 solution to identify its electrochemical characteristics in the electrolyte. The results show that molybdenum dissolves well in NaNO3 solutions and exhibits good surface erosion uniformity. Furthermore, it does not produce obvious protuberances, dimples, or stress cracks. The experimental results indicate that hole arrays can be fabricated on molybdenum sheets with relatively high precision via a TMECM process with appropriate processing parameters. The aperture deviation was less than 0.05 mm, and the roundness deviation of the holes was less than 9.8 μm.

Photoaligned Nanorod Enhancement Films with Polarized Emission for Liquid‐Crystal‐Display Applications

Semiconductor nanorods (NR) emit polarized light, which is expected to bring manifold benefits, in terms of brightness and color enhancement, for modern liquid-crystal displays (LCD). In this regard, photoaligned nanorod enhancement films (NREF) for color and polarization conversion for LCD backlights are introduced here. The photoinduced anchoring forces, by the photoalignment layer, stimulate well-ordered self-assembly of NR in the thin polymer films. Green and red emitting NR with a quantum yield of ≈80% are aligned unidirectionally and in-plane, showing a polarization ratio of >7:1 and a degree of polarization of >0.81. The photoalignment technique facilitates the fabrication of mixed and multiple stacked NREF for LCDs, which improves the color gamut and polarization efficiency, and is thus expected to increase the optical efficiency of conventional LCDs by ≈60%.

Effect of magnetic field on spin-dependent hole transport through a type-I Cd1-xMnxTe/CdTe double barrier heterostrucutre

We study the effect of the magnetic field on the spin-dependent hole transport through a diluted magnetic semiconductor double barrier heterostrucutre such as Cd1-x Mn x Te/CdTe. Using the transfer matrix, the barrier transparency, polarization efficiency and tunneling lifetime of a light hole and a heavy hole are calculated. The spin separation is found out and is observed that it is the same for both the light and the heavy hole. The heavy hole takes more time to travel in the heterostrucutre than the light hole. The effect of the magnetic field influences the tunneling lifetime. The results give the basic idea about the spin-dependent transport of light and heavy holes.

Simulation and optimization of a new focusing polarizing bender for the diffuse neutrons scattering spectrometer DNS at MLZ

We present the concept and the results of the simulations of a new polarizer for the diffuse neutron scattering spectrometer DNS at MLZ. The concept of the polarizer is based on the idea of a bender made from the stack of the silicon wafers with a double-side supermirror polarizing coating and absorbing spacers in between. Owing to its compact design, such a system provides more free space for the arrangement of other instrument components. To reduce activation of the polarizer in the high intensity neutron beam of the DNS spectrometer we plan to use the Fe/Si supermirrors instead of currently used FeCoV/Ti:N ones. Using the VITESS simulation package we have performed simulations for horizontally focusing polarizing benders with different geometries in the combination with the double-focusing crystal monochromator of DNS. Neutron transmission and polarization efficiency as well as the effects of the focusing for convergent conventional C-benders and S-benders have been analyzed both for wedge-like and plane-parallel convergent geometries of the channels. The results of these simulations and the advantages/disadvantages of the various configurations are discussed.

Spin-analyzed SANS for soft matter applications

The small angle neutron scattering (SANS) of nearly Q-independent nuclear spin-incoherent scattering from hydrogen present in most soft matter and biology samples may raise an issue in structure determination in certain soft matter applications. This is true at high wave vector transfer Q where coherent scattering is much weaker than the nearly Q-independent spin-incoherent scattering background. Polarization analysis is capable of separating coherent scattering from spin-incoherent scattering, hence potentially removing the nearly Q-independent background. Here we demonstrate SANS polarization analysis in conjunction with the time-of-flight technique for separation of coherent and nuclear spin-incoherent scattering for a sample of silver behenate back-filled with light water. We describe a complete procedure for SANS polarization analysis for separating coherent from incoherent scattering for soft matter samples that show inelastic scattering. Polarization efficiency correction and subsequent separation of the coherent and incoherent scattering have been done with and without a time-of-flight technique for direct comparisons. In addition, we have accounted for the effect of multiple scattering from light water to determine the contribution of nuclear spin-incoherent scattering in both the spin flip channel and non-spin flip channel when performing SANS polarization analysis. We discuss the possible gain in the signal-to-noise ratio for the measured coherent scattering signal using polarization analysis with the time-of-flight technique compared with routine unpolarized SANS measurements.

Submicron silica as high−capacity lithium storage material with superior cycling performance

Submicron silica (SiO2) is prepared via directly milling bulk SiO2, which is the major constituent of the abundant sand on the earth. The electrochemical lithium storage performance of SiO2 is found to be strongly associated with the ball milling treatment. The reversible capacity of SiO2 gradually increases from 163 to 803mAhg−1 as the milling time is extended from 0 to 72h. For the SiO2 milled for 24h, it exhibits excellent cycling performance with a discharge capacity of 602mAhg−1 over 150 cycles, corresponding to the capacity retention of 99.8% relative to the 2nd cycle. The different particle sizes distribution and electrochemical activity of SiO2 are responsible for the effect of ball milling on its electrochemical lithium storage performance such as reversible capacity, cycling stability, electrode polarization and initial Coulombic efficiency.

Local surface plasmon enhanced polarization and internal quantum efficiency of deep ultraviolet emissions from AlGaN-based quantum wells

We report the enhancement of the polarization and internal quantum efficiency (IQE) of deep-UV LEDs by evaporating Al nanoparticles on the device surface to induce localized surface plasmons (LSPs). The deep-UV LEDs polarization is improved due to part of TM emission turns into TE emission through LSPs coupling. The significantly enhanced IQE is attributed to LSPs coupling, which suppress the participation of delocalized and dissociated excitons to non-radiative recombination process.

Frequency‐Swept Integrated Solid Effect

AbstractThe efficiency of continuous wave dynamic nuclear polarization (DNP) experiments decreases at the high magnetic fields used in contemporary high‐resolution NMR applications. To recover the expected signal enhancements from DNP, we explored time domain experiments such as NOVEL which matches the electron Rabi frequency to the nuclear Larmor frequency to mediate polarization transfer. However, satisfying this matching condition at high frequencies is technically demanding. As an alternative we report here frequency‐swept integrated solid effect (FS‐ISE) experiments that allow low power sweeps of the exciting microwave frequencies to constructively integrate the negative and positive polarizations of the solid effect, thereby producing a polarization efficiency comparable to (±10 % difference) NOVEL. Finally, the microwave frequency modulation results in field profiles that exhibit new features that we coin the “stretched” solid effect.

Frequency-Swept Integrated Solid Effect.

The efficiency of continuous wave dynamic nuclear polarization (DNP) experiments decreases at the high magnetic fields used in contemporary high-resolution NMR applications. To recover the expected signal enhancements from DNP, we explored time domain experiments such as NOVEL which matches the electron Rabi frequency to the nuclear Larmor frequency to mediate polarization transfer. However, satisfying this matching condition at high frequencies is technically demanding. As an alternative we report here frequency-swept integrated solid effect (FS-ISE) experiments that allow low power sweeps of the exciting microwave frequencies to constructively integrate the negative and positive polarizations of the solid effect, thereby producing a polarization efficiency comparable to (±10 % difference) NOVEL. Finally, the microwave frequency modulation results in field profiles that exhibit new features that we coin the "stretched" solid effect.

Efficient assignment and NMR analysis of an intact virus using sequential side-chain correlations and DNP sensitization

An experimental strategy has been developed to increase the efficiency of dynamic nuclear polarization (DNP) in solid-state NMR studies. The method makes assignments simpler, faster, and more reliable via sequential correlations of both side-chain and Cα resonances. The approach is particularly suited to complex biomolecules and systems with significant chemical-shift degeneracy. It was designed to overcome the spectral congestion and line broadening that occur due to sample freezing at the cryogenic temperatures required for DNP. Nonuniform sampling (NUS) is incorporated to achieve time-efficient collection of multidimensional data. Additionally, fast (25 kHz) magic-angle spinning (MAS) provides optimal sensitivity and resolution. Data collected in <1 wk produced a virtually complete de novo assignment of the coat protein of Pf1 virus. The peak positions and linewidths for samples near 100 K are perturbed relative to those near 273 K. These temperature-induced perturbations are strongly correlated with hydration surfaces.

Wind-farm simulation over moderately complex terrain

A comparison between three independent software to estimate the power production and the flow field in a wind farm is conducted, validating them against SCADA (Supervisory, Control And Data Acquisition) data. The three software were ORFEUS, WindSim and WAsP: ORFEUS and WAsP are linearised solvers, while WindSim is fully nonlinear. A wake model (namely a prescribed velocity deficit associated to the turbines) is used by WAsP, while ORFEUS and WindSim use the actuator-disc method to account for the turbines presence. The comparison indicates that ORFEUS and WAsP perform slightly better than WindSim in the assessment of the polar efficiency. The wakes simulated with ORFEUS appear more persistent than the ones of WindSim, which uses a two-equation closure model for the turbulence effects.

Grain size effect and microstructure influence on the energy storage properties of fine‐grained BaTiO3‐based ceramics

AbstractThe dependence of energy storage properties on grain size was investigated in BaTiO3‐based ferroelectric ceramics. Modified BaTiO3 ceramics with different grain size were fabricated by two‐step sintering method from BaTiO3 powders doped with Al2O3 and SiO2 by aqueous chemical coating. For samples doped with ZnO sintering aid in addition to Al2O3‐SiO2, the density and breakdown strength increased significantly. In general, samples with smaller grains have lower polarization but higher energy storage efficiency. Al2O3‐SiO2‐ZnO‐doped samples with average grain size of 118±2 nm have an energy density of 0.83±0.04 J/cm3. Obvious segregation of doping elements in second phase and grain boundary was observed by TEM‐EDS. Impedance spectroscopy further explains the relationship between microstructure and properties. Compared to common energy storage ceramics, the grain size of this low‐cost ceramics sintered at relatively low temperature is small, and the pilot scale production has been well completed. All these features make the utilization in multilayer devices and industrial mass production possible. In addition, the obtained rules are helpful in further development of energy storage ceramics.

High resolution neutron Larmor diffraction using superconducting magnetic Wollaston prisms

The neutron Larmor diffraction technique has been implemented using superconducting magnetic Wollaston prisms in both single-arm and double-arm configurations. Successful measurements of the coefficient of thermal expansion of a single-crystal copper sample demonstrates that the method works as expected. The experiment involves a new method of tuning by varying the magnetic field configurations in the device and the tuning results agree well with previous measurements. The difference between single-arm and double-arm configurations has been investigated experimentally. We conclude that this measurement benchmarks the applications of magnetic Wollaston prisms in Larmor diffraction and shows in principle that the setup can be used for inelastic phonon line-width measurements. The achievable resolution for Larmor diffraction is comparable to that using Neutron Resonance Spin Echo (NRSE) coils. The use of superconducting materials in the prisms allows high neutron polarization and transmission efficiency to be achieved.