Parallel Bands Research Articles

Isobutane Infrared Bands: Partial Rotational Assignments, ab Initio Calculations, and Local Mode Analysis.

High-resolution infrared spectra of the symmetric top isobutane CH(CH3)3 were assigned with the help of ab initio calculations. The strong parallel band ν5(a1) with an origin at 1396.54741(76) cm-1 and the ν4(a1) mode, the CH2 scissors, at 1478.20363(41) cm-1 were rotationally analyzed. The bands in the C-H stretching region were assigned with the help of an anharmonic calculation and a local mode analysis.

Linear Dichroism Conversion in Quasi-1D Perovskite Chalcogenide.

Anisotropic photonic materials with linear dichroism are crucial components in many sensing, imaging, and communication applications. Such materials play an important role as polarizers, filters, and waveplates in photonic devices and circuits. Conventional crystalline materials with optical anisotropy typically show unidirectional linear dichroism over a broad wavelength range. The linear dichroism conversion phenomenon has not been observed in crystalline materials. The investigation of the unique linear dichroism conversion phenomenon in quasi-1D hexagonal perovskite chalcogenide BaTiS3 is reported. This material shows a record level of optical anisotropy within the visible wavelength range. In contrast to conventional anisotropic optical materials, the linear dichroism polarity in BaTiS3 makes an orthogonal change at an optical wavelength corresponding to the photon energy of 1.78 eV. First-principles calculations reveal that this anomalous linear dichroism conversion behavior originates from the different selection rules of the parallel energy bands in the BaTiS3 material. Wavelength-dependent polarized Raman spectroscopy further confirms this phenomenon. Such a material, with linear dichroism conversion properties, could facilitate the sensing and control of the energy and polarization of light, and lead to novel photonic devices such as polarization-wavelength selective detectors and lasers for multispectral imaging, sensing, and optical communication applications.

K+ and Cl\u2212 channels/transporters independently fine-tune photosynthesis in plants

In variable light environments, plants adjust light use in photosynthetic electron transport and photoprotective dissipation in the thylakoid membrane. In this respect, roles of the K+/H+ antiporter KEA3, the Cl− channel/transporter CLCe and the voltage-dependent Cl− channel VCCN1 have been unraveled in Arabidopsis thaliana. Here we report that they independently adjust photosynthesis on the basis of analyses using single and higher order loss-of-function mutants. In short experiments of photosynthetic response on transition from dark to low light, we reveal a sequential functioning of VCCN1 and CLCe in the activation of photoprotection and of KEA3 in its downregulation to a low steady state while adjusting the electron transport. On transition from low to high light, VCCN1 accelerates the activation of photoprotection, whereas KEA3 slows it down on transition from high to low light. Based on parallel electrochromic band shift measurements, the mechanism behind is that VCCN1 builds up a pH gradient across the thylakoid membrane, whereas KEA3 dissipates this gradient, which affects photoprotection. CLCe regulates photosynthesis by a pH-independent mechanism likely involving Cl− homeostasis. Nevertheless, all genotypes grow well in alternating high and low light. Taken together, the three studied ion channels/transporters function independently in adjusting photosynthesis to the light environment.

SAR-Mode Altimetry Observations of Internal Solitary Waves in the Tropical Ocean Part 2: A Method of Detection

It is demonstrated that the synthetic aperture radar altimeter (SRAL) on board of the Sentinel-3A can detect short-period internal solitary waves (ISWs) with scales of the order of a kilometer. A variety of signatures owing to the surface manifestations of the ISWs are apparent in the SRAL Level-2 products over the ocean. These signatures are identified in several geophysical parameters, such as radar backscatter ( σ 0 ) and sea level anomaly (SLA). Radar backscatter is the primary parameter in which ISWs can be identified owing to the measurable sea surface roughness perturbations in the along-track direction resulting from the sharpened SRAL footprint. The SRAL footprint is sufficiently small (300 m in the along-track direction) to capture radar power fluctuations over successive wave crests and troughs, which produce rough and slick surface patterns arrayed in parallel bands with scales of a few kilometers along-track. Furthermore, it was possible to calculate the mean square slope ( s 2 ¯ ) for the dual-band (Ku and C bands) altimeter of Sentinel-3, which made the ISW signatures unambiguously identified because of the large s 2 ¯ variations in exact synergy with ocean and land color instrument (OLCI) images. Hence, the detection method is validated in cloud-free sun glint OLCI images. It is shown that both σ 0 and SLA yield realistic estimates for routine observation of ISWs with the SRAL. The detection method that is used relies on the parameter s 2 ¯ which is calculated from σ 0 . This is a significant improvement from previous observations recently reported for conventional pulse-limited altimeters (Jason-2). An algorithm is developed to be used in any ocean region. Wavelets were applied for a first analysis of the s 2 ¯ variations because ISWs can be readily identified in high-frequency signals. Other geophysical parameters such as SLA were used to exclude phenomena that are unlikely to be ISWs.

Optical filter for smart windows with angle-selective light transmission

A grating optical filter for a smart window is presented, which provides dynamic control of the daylight and solar energy indoors throughout the year without human intervention and without the use of daylight-redirecting devices. Thin-layer gratings of alternating directionally transmissive and nontransmissive parallel bands on both surfaces of a window are arranged at an angle to the horizontal, taking into account the Sun’s trajectory relative to the window. The methods for calculating the optimal geometric parameters and angular characteristics of the filter for minimizing the light transmission for a specific date and time of day at a given latitude and longitude of the building and the azimuth of the window are described. A numerical simulation of the light transmission is performed, and the results are confirmed experimentally.

OpenCL을 사용한 Intel FPGA SoC 기반 실시간 병렬 다상분해 주파수 대역압축 및 복원 알고리즘

OpenCL을 사용한 Intel FPGA SoC 기반 실시간 병렬 다상분해 주파수 대역압축 및 복원 알고리즘

Infrared bands of CS2 dimer and trimer at 4.5 μm.

We report observation of new infrared bands of (CS2)2 and (CS2)3 in the region of the CS2 ν1 + ν3 combination band (at 4.5 µm) using a quantum cascade laser. The complexes are formed in a pulsed supersonic slit-jet expansion of a gas mixture of carbon disulfide in helium. We have previously shown that the most stable isomer of (CS2)2 is a cross-shaped structure with D2d symmetry and that for (CS2)3 is a barrel-shaped structure with D3 symmetry. The dimer has one doubly degenerate infrared-active band in the ν1 + ν3 region of the CS2 monomer. This band is observed to have a rather small vibrational shift of -0.844 cm-1. We expect one parallel and one perpendicular infrared-active band for the trimer but observe two parallel bands and one perpendicular band. Much larger vibrational shifts of -8.953 cm-1 for the perpendicular band and -8.845 cm-1 and +16.681 cm-1 for the parallel bands are observed. Vibrational shifts and possible vibrational assignments, in the case of the parallel bands of the trimer, are discussed using group theoretical arguments.

Chemical pressure effect on the optical conductivity of the nodal-line semimetals ZrSiY(Y=S,Se,Te) and ZrGeY(Y=S,Te)

ZrSiS is a nodal-line semimetal, whose electronic band structure contains a diamond-shaped line of Dirac nodes. We carried out a comparative study on the optical conductivity of ZrSiS and related compounds ZrSiSe, ZrSiTe, ZrGeS, and ZrGeTe by reflectivity measurements over a broad frequency range combined with density functional theory calculations. The optical conductivity exhibits a distinct U shape, ending at a sharp peak at around 10000~cm$^{-1}$ for all studied compounds, except for ZrSiTe. The U shape of the optical conductivity is due to transitions between the linearly dispersing bands crossing each other along the nodal line. The sharp high-energy peak is related to transitions between almost parallel bands, and its energy position depends on the interlayer bonding correlated with the $c$/$a$ ratio, which can be tuned by either chemical or external pressure. For ZrSiTe, another pair of crossing bands appears in the vicinity of the Fermi level, corrugating the nodal-line electronic structure and leading to the observed difference in optical conductivity. The findings suggest that the Dirac physics in Zr$XY$ compounds with $X$=Si, Ge and $Y$=S, Se, Te is closely connected to the interlayer bonding.

Semi-empirical calculation of 12CH3D-H2 broadening coefficients and their temperature-dependence exponents for rovibrational lines in parallel bands

Hydrogen-broadening coefficients and their temperature-dependence exponents for 12CH3D (J, K) lines in the parallel (ΔK = 0) ν3 band are computed by a semi-empirical method employing analytical Anderson-type expressions with a few-parameter correction factor introduced to account for various deviations from Anderson's theory approximations. On the basis of experimentally observed J-dependences of line widths, this correction factor is taken in the traditional two-parameter form, and the parameters are determined from fits on some room-temperature measurements. After validation by comparison with available experimental data, the calculations are done for extended ranges of rotational quantum numbers (0 ≤ J ≤ 70, 0 ≤ K ≤ 20) typically requested for spectroscopic databases. To get the temperature-dependence exponents, computations with the room-temperature parameters’ values are repeated for various temperatures in the room-temperature containing range 200–400 K recommended for HITRAN and least-squares fit procedures are applied. Detailed P-Q-R-line lists are provided. With negligible vibrational dependence of CH3D line widths, these data can be also employed for other A1-type bands.

Studying a Flexible Polyurethane Elastomer with Improved Impact-Resistant Performance.

A flexible polyurethane elastomer (PUE) is studied, and the improved impact-resistant performance is revealed. Compressive stress–strain curves over a wide loading rate range were derived. Under static loading, the rubbery-like characteristics are demonstrated, which are flexible and hyperelastic, to process a large strain of about 60% followed by full recovery upon unloading. Under high-rate loadingcompared with the mechanical data of polyurethane elastomer (PUE) and polyurea (PUA) materials in the literature. Orderly parallel deformation bands were formed from carrying a large strain. The fibrils were found between deformation bands for enhancing the yield/plateau stress. A considerable plastic zone ahead of propagating crack with numerous crazes and microcracks was produced for realizing the dynamic strain energy absorption. This work presents a scientific innovation for developing outstanding impact-resistant polyurethane elastomers for transparent protection engineering.

Accommodating constraints for modeling of biosonar processing by big brown bats

Constraints on modeling of wideband FM biosonar are acoustic (small targets return discrete replicas of the incident sound from individual component parts), auditory (inner-ear transduction segments broadcasts and echoes into numerous, parallel bandpass channels with integration-times of ~350 μs), neural (processing retains parallel frequency bands throughout the auditory pathway that use single spikes to mark frequencies), and perceptual (bats nevertheless perceive true delays of individual glint reflections, not just spectral coloration). The bat’s target model is geometric, registering the glints binaurally along the range axis. However, because closely-spaced glints are represented by their mutual interference, not by separate acoustic reflections, the ripples have to be transposed from an interference pattern back into glint delay estimates. Auditory cortical neurons selective for specific patterns of ripple come to register instead the underlying time separation of the glint reflections. The developing SCAT model of wideband FM biosonar incorporates a network for glint delay transformation that also offers a route for clutter suppression by contrasting dispersed, unfocused clutter images with tightly focused target images in range and azimuth space. The feedforward inhibition of this network preserves real-time operation for target reconstruction as well as for guidance in clutter. [Work supported by ONR.]

Slow Cooling of High‐Energy C Excitons Is Limited by Intervalley‐Transfer in Monolayer MoS2

AbstractHigh‐energy C exciton in 2D transition metal dichalcogenides with strong photon absorption can be utilized prospectively in light‐harvesting and opto‐electric devices. Here, a detailed study on C exciton dynamics in monolayer MoS2 is presented by femtosecond transient absorption (TA) spectroscopy. In the experiment, the C exciton with unique parallel band structure exhibits a slow process within tens of picoseconds (≈10–50 ps) as well as a fast process within several picoseconds (≈1–6 ps) instead of previous reported ultrafast cooling (<500 fs) process. From TA spectroscopy, the experimental results confirmed that the relatively slow cooling of C exciton is mainly limited by the rates of intervalley transfer rather than Pauli blocking effect from band‐edge excitons. The timescale of intervalley transfer is longer than that of intraband relaxation of C exciton, therefore, leading to the slow cooling of C exciton. Moreover, intervalley transfer time are estimated with two processes of 5.1 ± 0.6 ps and 69.5 ± 8 ps when the pump fluence is ≈127 µJ cm−2. This work provides further understanding of the ultrafast dynamics of C exciton in monolayer MoS2 and opens new opportunities for opto‐electric related applications.

Band structure and carrier effective masses of boron arsenide: Effects of quasiparticle and spin-orbit coupling corrections

We determine the fundamental electronic and optical properties of the high-thermal-conductivity III–V semiconductor boron arsenide (BAs) using density functional and many body perturbation theory including quasiparticle and spin-orbit coupling corrections. We find that the fundamental bandgap is indirect with a value of 2.049 eV, while the minimum direct gap has a value of 4.135 eV. We calculate the carrier effective masses and report smaller values for the holes than the electrons, indicating higher hole mobility and easier p-type doping. The small difference between the static and high frequency dielectric constants indicates that BAs is only weakly ionic. We also observe that the imaginary part of the dielectric function exhibits a strong absorption peak, which corresponds to parallel bands in the band structure. Our estimated exciton binding energy of 43 meV indicates that excitons are relatively stable against thermal dissociation at room temperature. Our work provides theoretical insights into the fundamental electronic properties of BAs to guide experimental characterization and device applications.

Application of the GALDIT method combined with geostatistics at the Bouteldja aquifer (Algeria)

This paper aims to spatially characterize the marine intrusion in the case of the Bouteldja main aquifer using the GALDIT method coupled with a geostatistical approach. The latter was used to compensate the weakness of GALDIT method for not considering the spatial variability of the studied variables. Using a field data set of the Bouteldja aquifer, the semi-variograms of four continuous important variables (hydraulic conductivity A, groundwater level L, thickness T and sea water intrusion I) were studied and modeled. The obtained structures were mainly composed of spherical models with a small nugget effect, except the I variable which has shown a perfectly continuous Gaussian model with zero nugget effect, arguing that the marine intrusion is seriously present and continuous. These individual results were also mapped by kriging and the intrusion easily shown on the field. However, the GALDIT computation and mapping did not confirm the found intrusion. It has merely shown a medium to low vulnerability in narrow and parallel bands close to the shore area. This work has shown that the GALDIT method used solely, without a geostatistical approach, would lead to a misinterpretation of the vulnerability of a main aquifer to saline intrusion.

Strong exciton regulation of Raman scattering in monolayer MoS2

The weakly screened electron-hole interactions in an atomically thin semiconductor not only downshift its excitation spectrum from a quasiparticle one, but also redistribute excitation energies and wave-function characters with profound effects on the diverse modes of the material response, including the exciton-phonon scattering processes accessible to resonant Raman measurements. Here, we develop a first-principles framework to calculate frequency-dependent resonant Raman intensities that includes excitonic effects and goes beyond the Placzek approximation. We show how excitonic effects in ${\mathrm{MoS}}_{2}$ strongly regulate Raman scattering amplitudes and thereby explain the puzzling near absence of a resonant Raman response around the $A$ and $B$ excitons (band-edge excitations which produce very strong signals in optical absorption), and also the pronounced strength of the resonant Raman response from the $C$ exciton (a higher-energy excitation arising from parallel valence and conduction bands). Furthermore, this efficient perturbative approach reduces the number of $GW$ plus Bethe-Salpeter-equation calculations from two per Raman mode (in finite displacement) to one for all modes and affords a natural extension to higher-order resonant Raman processes.

Microstructure and mechanical property evolutions of CuNi10Fe1.8Mn1 alloy tube produced by HCCM horizontal continuous casting during drawing and its deformation mechanism

Heating-cooling combined mold (HCCM) horizontal continuous casting was used to produce Ф70 mm × 3.5 mm CuNi10Fe1.8Mn1 alloy tubes. The as-cast tube had good surface quality, strong axial columnar grains and high elongation to failure of 45%, and can be directly drawn without surface treatment. The maximum cumulative cold deformation amount reached 94%. For the small deformation amount (<46%), dislocation sliding was main deformation mechanism, numerous dislocation cells formed and microregion crystal rotation in grains happened. When the deformation amount was 76%, shear deformation extent increased and many parallel shear bands formed in gains. With increasing the deformation amount to 92%, a large number of shear bands in different directions formed and the intersecting of shear bands induced displacement of 100–200 nm themselves, which formed wave-shaped deformation structures. With increasing the deformation amount, the tensile strength and hardness of the tube increased from 235 MPa and 86 HV of the as-cast tube to 585 MPa and 168 HV of 94% deformation amount, but the elongation to failure reduced to 6.6%. The process of HCCM horizontal continuous casting→drawing can work as a new compact method to produce thin-walled cupronickel alloy tube.

Fibrolamellar Carcinoma: A Concise Review.

Fibrolamellar carcinoma is a rare primary hepatocellular malignancy arising in noncirrhotic livers of young individuals. Patients commonly present with a large solitary liver mass and nonspecific symptoms. Characteristic histologic features include large polygonal cells with oncocytic cytoplasm and prominent nucleoli separated into trabeculae and cords by dense parallel bands of collagen. Important differential diagnoses include classical hepatocellular carcinoma and intrahepatic cholangiocarcinoma, which may be distinguished by a judicious panel of immunohistochemical studies, including cytokeratin 7, CD68, and hepatocyte paraffin 1 (HepPar-1). In addition, fibrolamellar carcinomas are characterized by activation of protein kinase A. Prognosis of fibrolamellar carcinoma is similar to classical hepatocellular carcinoma occurring in the absence of liver cirrhosis and is strongly correlated with tumor resectability. Other treatment options include liver transplant, chemotherapy, and hepatic artery embolization. In this article, we review the clinical features, gross and microscopic pathology, molecular genetics, differential diagnosis, treatment, and prognosis of this rare and interesting tumor.

Mechanical properties and Hall-Petch relationship of the extruded Mg-Zn-Y alloys with different volume fractions of icosahedral phase

The effect of the volume fraction (0.6–8.4%) of the icosahedral phase (I-phase) on the microstructure, texture and mechanical properties of extruded Mg-Zn-Y alloys was examined. During extrusion, the eutectic and divorced eutectic I-phase in the cast microstructures was broken into small particles, and the particles were dispersed along the extrusion direction, forming parallel particle bands. The broken I-phase particles promoted grain refinement via a particle-stimulated nucleation mechanism and led to basal texture weakening through dynamic recrystallization. The work hardening rate increased with an increase in the volume fraction of I-phase. However, the strength decreased with an increase in the volume fraction of I-phase due to the texture softening effect. To incorporate the texture softening effect into the Hall-Petch relation, a modified Hall-Petch equation, which simultaneously considers the effects of grain size and texture on strength, was developed using the Schmid factors for basal slip. The proposed equation predicts smaller Hall-Petch slope, friction stress and yield strength with easier activation of basal slip, agreeing with the experimental observations.

On the role of the collinear dislocation interaction in deformation patterning and laminate formation in single crystal plasticity

We investigate the reasons for severe deformation patterning observed in crystal plasticity simulations of an fcc nickel single crystal with initial near-Copper orientation deformed in plane strain compression. The resulting strain partitioning in the form of alternating parallel bands initiates at a very early loading stage, i.e. <0.5% global strain, and sharpens with ongoing deformation. At an applied average strain of 5.5%, the local strains finally deviate by half an order of magnitude in different regions of the initially homogeneous single crystal. We show that this microstructure lamination is the result of a complex interplay between available deformation systems, strain hardening, kinematics, and deformation energetics. Moreover, the boundary conditions play an important role as under the applied load two slip systems—which are collinear with respect to each other—have the same highest Schmid factor and therefore are preferentially activated. During strain hardening, the strong collinear interaction strength causes—depending on the initial deviation from the nominal orientation—the selection of a single prevalent slip system in clearly delimited regions. This behavior is explained by the lower global deformation energy in comparison to a homogeneous double slip behavior. We also reveal that the observed deformation pattern forms only for dislocation interaction strength values in the range predicted by discrete dislocation dynamic simulations.

SAR Mode Altimetry Observations of Internal Solitary Waves in the Tropical Ocean Part 1: Case Studies

It is well known that internal waves (IWs) of tidal frequency (i.e., internal tides) are successfully detected in sea surface height (SSH) by satellite altimetry. Shorter period internal solitary waves (ISWs), whose periods (and spatial scales) are an order of magnitude smaller than tidal internal waves, have been generally assumed too small to be detected with conventional altimeters. This is because conventional (pulse-limited) radar altimeter footprints are somewhat larger than or of similar size, at best, as the typical wavelengths of the ISWs. Here we demonstrate that the synthetic aperture radar altimeter (SRAL) on board the Sentinel-3A can detect short-period ISWs. A variety of signatures owing to the surface manifestations of the ISWs are apparent in the SRAL Level-2 products over the ocean. These signatures are identified in several geophysical parameters, such as radar backscatter (sigma0), sea level anomaly (SLA), and significant wave height (SWH). Radar backscatter is the primary parameter in which ISWs can be identified owing to the measurable sea surface roughness perturbations in the along-track sharpened SRAL footprint. The SRAL footprint is sufficiently small to capture radar power fluctuations over successive wave crests and troughs, which produce rough and slick surface patterns arrayed in parallel bands with scales of a few kilometers. The ISW signatures are unambiguously identified in the SRAL because of the exact synergy with OLCI (Ocean Land Colour Imager) images, which in cloud-free conditions allow clear identification of the ISWs in the sunglint OLCI images. We show that both sigma0 and SLA yield realistic estimates for routine observation of ISWs with the SRAL, which is a significant improvement from previous observations recently reported for conventional pulse-limited altimeters (Jason-2). Several case studies of ISW signatures are interpreted in light of our knowledge of radar backscatter in the internal wave field. An analysis is presented for the tropical Atlantic Ocean off the Amazon shelf to infer the frequency of the phenomena, being consistent with previous satellite observations in the study region.