bluuebunny/crossref_metadata_2025 huggingface dataset:
Perceived Age in Patients Exposed to Distinct UV Indexes: A Systematic Review
Authors: Avila Francisco R. , Carter Rickey E. , McLeod Christopher J. , Bruce Charles J. , Giardi Davide , Guliyeva Gunel , Torres-Guzman Ricardo A. , Maita Karla C. , Forte Antonio J.
Published: December 2022

Photodamage is caused by chronic sun exposure and ultraviolet radiation and presents as wrinkles, sagging, and pigmented spots. An increase in the ultraviolet index can increase a person's perceived age by worsening skin photodamage. However, since the ultraviolet index varies considerably between geographical regions, perceived age might vary substantially among them. This review aims to describe the differences in chronological and perceived age in regions of the world with different ultraviolet indexes. A literature search of three databases was conducted for studies analyzing perceived age and its relationship to sun exposure. Ultraviolet indexes from the included studies were retrieved from the National Weather Service and the Tropospheric Emission Monitoring Internet Service. Out of 104 studies, seven fulfilled the inclusion criteria. Overall, 3,352 patients were evaluated for perceived age. All studies found that patients with the highest daily sun exposures had the highest perceived ages for their chronological age (p < 0.05). People with high sun exposure behaviors living in regions with high ultraviolet indexes will look significantly older than same-aged peers living in lower ultraviolet index regions.
Direct energy conversion using Ni/SiC Schottky junction in 237Np and 241Am gamma ray regions
Authors: Fukuda Tatsuo , Kobata Masaaki , Shobu Takahisa , Yoshii Kenji , Kamiya Junichiro , Iwamoto Yosuke , Makino Takahiro , Yamazaki Yuichi , Ohshima Takeshi , Shirai Yasuhiro , Yaita Tsuyoshi
Published: December 2022

Direct energy conversion has been investigated using Ni/SiC Schottky junctions with the irradiation of monochromatized synchrotron x rays mimicking the gamma rays of 237Np (30 keV) and 241Am (60 keV). Through current–voltage measurements, electrical energies were obtained for both types of gamma rays. The energy conversion efficiencies based on absorbed energy were found to be ∼1.6%, which is comparable to other previously described semiconducting systems. This result raises the prospect of energy recovery from nuclear wastes utilizing the present system, judging from the radiation tolerant nature of SiC. Additionally, we found different conversion efficiencies between the two samples during the same process. This could be explained using hard x-ray photoelectron spectroscopy and secondary ion mass spectroscopy measurements, suggesting the creation of Ni–Si compounds at the interface in the sample with poor performance. Hence, such combined measurements are useful to provide data that electrical measurements cannot provide us.
Unveiling the strain and structural ferroelectric phase transition induced by temperature in lead titanate perovskite modified with 40% of calcium
Authors: Ribeiro Galão Larissa , Garcia Ducinei , Estrada Flávia Regina
Published: December 2022

Structurally correlated ferroelectric phase transitions induced by temperature are reported for the solid solution Pb0.6Ca0.4TiO3 compound. Such phase transitions were analyzed by considering different parameters, such as lattice parameters, microstrain, dielectric properties, and thermal analysis. Synchrotron x-ray diffraction and Rietveld refinement studies revealed a tetragonal symmetry from room temperature up to ∼550 K and uniaxial microstrain from room temperature to ∼400 K. The first thermally driven phase transition observed was from displacive ferroelectric tetragonal symmetry to another non-displacive tetragonal symmetry. The next phase transition was from the tetragonal to cubic. The electric permittivity as a function of temperature for frequency from 1 kHz to 1 MHz and the differential scanning calorimetry report features typical of ferroelectric–paraelectric phase transition only around 400 K, and no other abrupt change in properties is observed at 550 K, indicating the sequence of first- and then second-order phase transition.
Simultaneous measurement of fine pattern shape and overall shape by a nano-profiler
Authors: Miyawaki Takashi , Endo Katsuyoshi
Published: December 2022

Improving the optical performance and functions of mirrors and lenses requires manufacturing pattern shapes such as those of microlens arrays. In this context, various measuring devices have been developed to accurately measure the depth of shapes with a microscopic interferometer. However, with an interferometer, the number of pixels of a light-receiving element, such as a charge-coupled device, is limited; furthermore, when measuring a pattern shape, the measurement field of view becomes narrow. Thus, measuring a wide range of shapes is not possible. By contrast, if the device can arbitrarily increase the number of measurement points, such as in the case of a three-dimensional measuring machine, in principle, a pattern shape can be measured, while ensuring the measurement capability for a wide range of shapes; however, in this case, the measurement time increases. A nano-profiler previously developed by the authors can measure the shape and slope angle distribution of a surface with a laser beam. In this study, the measurement program was changed to realize continuous high-speed scanning at 1 kHz, and the number of measurement points was increased to verify the compatibility between fine pattern shape measurements and diverse shape measurements. The results measured by the nano-profiler were compared with those obtained using microscopic and Fizeau-type interferometers, which can measure the pattern and overall shapes, respectively. In comparison, the difference in pattern depth and overall shape was 2.1 and 2.9 nm PV, respectively.
Apparatuses for verifying the precision of gravimeters with lifting spherical source masses
Authors: Mao Qiangbing , Xu Hao , Cheng Yuan , Liu Ruiqi , Huang Tong , Huang Jiaojiao , Li Qing
Published: December 2022

Two apparatuses with lifting spherical source masses are built and used to verify the precision of gravimeters. The 333-kg source mass produces a maximum acceleration of 200 nm/s2 with an uncertainty of 0.31 nm/s2, which corresponds to a relative uncertainty of 0.16%. After evaluating the temperature effect, drift of the gravimeter, the atmospheric effect, and the tidal effect, a combined uncertainty of 1 nm/s2 is obtained. One CG6 gravimeter is tested using two apparatuses, the measured accelerations agree with the theoretical values within the error range. Differential measurement with two CG6 gravimeters on one apparatus is performed, which provides a common-mode rejection of the effects due to ambient noise, such as the gravity tide, atmospheric effect, and drift. The difference in acceleration measured by the two gravimeters is determined to be 199 ± 6 nm/s2, which agrees well with the value 200 ± 1 nm/s2 obtained by using apparatus II. Our apparatuses provide a verification of the precision of gravimeters with an uncertainty of 1 nm/s2, which is one of the lowest uncertainties reached so far. The determination of geometrical metrology and mass distribution and detailed error analysis are presented. The methods on error analysis as well as differential measurement used in our work are helpful for gravity measurement.
A coarse-grain reactive model of RDX: Molecular resolution at the μm scale
Authors: Lee Brian H. , Sakano Michael N. , Larentzos James P. , Brennan John K. , Strachan Alejandro
Published: December 2022

Predictive models for the thermal, chemical, and mechanical response of high explosives at extreme conditions are important for investigating their performance and safety. We introduce a particle-based, reactive model of 1,3,5-trinitro-1,3,5-triazinane (RDX) with molecular resolution utilizing generalized energy-conserving dissipative particle dynamics with reactions. The model is parameterized with respect to the data from atomistic molecular dynamics simulations as well as from quantum mechanical calculations, thus bridging atomic processes to the mesoscales, including microstructures and defects. It accurately captures the response of RDX under a range of thermal loading conditions compared to atomistic simulations. In addition, the Hugoniot response of the CG model in the overdriven regime reasonably matches atomistic simulations and experiments. Exploiting the model’s high computational efficiency, we investigate mesoscale systems involving millions of molecules and characterize size-dependent criticality of hotspots in RDX. The combination of accuracy and computational efficiency of our reactive model provides a tool for investigation of mesoscale phenomena, such as the role of microstructures and defects in the shock-to-deflagration transition, through particle-based simulation.
Quantitative phase imaging of biological cells using lensless inline holographic microscopy through sparsity-assisted iterative phase retrieval algorithm
Authors: Galande Ashwini S. , Gurram Hanu Phani Ram , Kamireddy Aruna Priya , Venkatapuram Vijaya Sree , Hasan Qurratulain , John Renu
Published: December 2022

The twin image-free phase reconstruction is still a challenge with single-shot inline holographic systems. Existing solutions mostly are based on the inverse problem approaches or alternating projections. However, there exists a trade-off between phase retrieval and twin image elimination. Recent studies have introduced a hybrid method involving both the approaches to mitigate this trade-off. Following these works, we propose a single-shot sparsity-assisted iterative phase retrieval approach that applies a sparsity constraint in the object domain and formulates phase retrieval as a minimization problem. We demonstrate lensless digital inline holographic microscopy for imaging transparent and weakly scattering biological samples over a large field-of-view of ∼29mm2. The proposed method achieves high fidelity phase reconstruction with faster convergence compared to the existing single-shot phase retrieval methods. We further demonstrate the phase quantification of label-free biological samples, such as cervical cells and RBCs, to highlight the potential of our technique in clinical applications.
A joint calibration technique for improving measurement accuracy of voltage and current probes during synchronous operation for RF-based plasma devices
Authors: Mahreen  , Ganguli A. , Gajula Veda Prakash , Kar Satyananda , Sahu Debaprasad
Published: December 2022

This paper presents a joint calibration scheme for voltage (V) and current (I) probes that helps accurately resolve the voltage–current phase differences even when the difference is very close to 90°. The latter has been a major issue with V–I probes when used with miniature RF plasma devices such as the atmospheric pressure plasma jet (APPJ). Since the impedance of such miniature devices is predominantly capacitive, the phase difference between the voltage and current signals is very nearly 90°. It turns out, however, that when V–I probes are used with such devices without joint calibration, these frequently yield phase shifts over 90°. Also, since the power absorption is proportional to the resistive part of the impedance, it becomes very sensitive to the phase difference when it is close to ≈90°. Thus, it is important to be able to accurately resolve the phases. Post-calibration, V–I probes would be indispensable for the electrical characterization of APPJs for determining the average RF power Pav, plasma impedance Zp, etc. Typical post-calibration V–I data yield Zp ≈ 93.6 − j 1139 Ω (81.5 − j 1173 Ω) at Pav ≈9.8W (≈7.7W) for helium (argon) gas.
Transport properties of magneto-excitations in integer and fractional quantum Hall insulators
Authors: Gorbunov A. V. , Larionov A. V. , Kulik L. V. , Timofeev V. B.
Published: December 2022

Using a high-resolution optical system, we visualize and compare the real-space transport of the dense ensembles of photoexcitations in integer and fractional quantum Hall insulators at the filling factors ν=2 and ν=1/3. We analyze the correlation between the transport properties and spatial coherence of these ensembles.
Elastic and inelastic low-energy electron scattering from pyridine
Authors: Su He , Cheng Xinlu , Cooper Bridgette , Tennyson Jonathan , Zhang Hong
Published: December 2022

A comprehensive investigation of elastic and inelastic electron scattering from molecular pyridine is reported using the ab initio R-matrix method with the static exchange plus polarization and close-coupling approximations for incident energies up to 10 eV. The two well-known low-lying 1 2B1 and 1 2A2 shape resonances as well as a 2 2B1 mixed-character resonance compare well with the theoretical and experimental results. We also detect five core-excited resonances (1 2A1, 1 2B2, 3 2B1, 2 2A2, and 4 2B1), which lie above the first electronic excitation threshold. The total elastic cross sections and momentum transfer cross sections agree reasonably with previous reference data. Comparisons of the differential elastic cross sections of pyridine with those measured for benzene, pyrazine, and pyrimidine show remarkable agreement at scattering angles above 40° but behave differently for forward scattering below 40° below 6 eV, due to the dominant effect of the permanent dipole moment on the differential cross section in the low energy region with narrow scattering angles. Inelastic electronic excitation cross sections are presented, showing the influence of core-excited resonances below the ionization threshold for the first time.
Maximum density perspectives on the stability of Brinkman porous convection in a vertical channel
Authors: Nagamani K. V. , Shankar B. M. , Shivakumara I. S.
Published: December 2022

The stability of parallel buoyant flow is studied in a vertical layer of Brinkman porous medium possessing a density maximum in its interior with quadratic density law. The vertical boundaries are considered to be rigid and maintained at different uniform temperatures. The similarities and differences between the linear and quadratic density-temperature relationships on the base flow, stability features of fluid flow, and the mode of instability are underlined. If the flow is governed by classical Darcy's law, then it is proved analytically that the base flow remains unconditionally stable irrespective of how the density varies with temperature. On the contrary, the change in the density-temperature relationship affects the stability of base flow when the flow is governed by either unsteady Darcy's law or the Brinkman-extended Darcy law and for these cases, the eigenvalue problem is solved numerically. For the unsteady Darcy flow model, instability occurs through the traveling-wave mode in a certain range of Darcy–Prandtl number for the quadratic density law yet the base flow is always stable if the density law is linear. The nature of the density-temperature relationship and the magnitude of governing parameters combine together in influencing the instability of fluid flow in the Brinkman regime. The possibility of otherwise stabilization of the base flow becoming unstable with the change in the density-temperature relationship from linear to quadratic for the same values of governing parameters is identified. These intricacies are discussed in detail by computing the critical stability parameters for different values of the Darcy–Prandtl number and the Darcy number.
Mechanical stability of (Li,Na,K)NbO3-based multilayered piezoceramics with Ag/Pd inner electrodes
Authors: Nishiyama Hiroshi , Ito Ryo , Aizawa Tomoya , Goto Takayuki , Shimizu Hiroyuki
Published: December 2022

Lead-free (Li,Na,K)NbO3-based multilayered piezoceramics with Ag0.9Pd0.1 inner electrodes were prepared, and their large-signal piezoelectric properties under combined electrical and mechanical loadings were characterized at room temperature. The piezoelectric constant d33∗(=SMax/EMax) of the multilayer was 96 pm/V with an applied unipolar field of 5 kV/mm under zero stress. More importantly, a favorable stress stability of d33∗ was observed, with a slight variation ≤8% of SMax, when the uniaxial stress was increased from −5 to −80 MPa. Further investigations of temperature-dependent x-ray diffraction, permittivity, and an energy-dispersive x-ray spectrometer revealed that the mechanical stability of d33∗ was due to a shift in phase transition temperature caused by a solid solution of the Ag inner electrode to the A-site of (Li,Na,K)NbO3 piezoceramics.
Strong strain-dependent phonon hydrodynamic window in bilayer graphene
Authors: Zeng Bowen , Ding Zhong-Ke , Pan Hui , Luo Nannan , Zeng Jiang , Tang Li-Ming , Chen Ke-Qiu
Published: December 2022

Phonon hydrodynamics, a collective motion of phonons, has recently attracted renewed attention since its temperature window has been greatly extended in layered materials. The exploration of phonon hydrodynamics bears importance in understanding phonon collective behavior, and its window is crucial for determining the phonon transport regime and engineering the heat transport. Thus, strategies for continuous tuning of the hydrodynamic window are needed, but it remains a challenge. In this work, we demonstrate that the phonon hydrodynamic window in bilayer graphene can be strongly altered by the strain based on theoretical calculations. In particular, the phonon hydrodynamics can be observed at 60 K in unstrained bilayer graphene, while only 0.25% strain can reduce this temperature to 28 K. This strong strain dependence not only provides an efficient way of modulating the phonon collective behavior but also renders a possibility of strain-induced transition of phonon transport regime.
Compression and interpenetration of adsorption-active brushes
Authors: Ivanova Anna S. , Polotsky Alexey A. , Skvortsov Alexander M. , Klushin Leonid I. , Schmid Friederike
Published: December 2022

Compression and interpenetration of two opposing polymer brushes formed by end-grafted adsorption-active chains are studied by the numerical self-consistent field approach and by analytical theory. For sufficiently strong polymer–surface attraction, a fraction of chains in the adsorption-active brush condenses into a near-surface layer, while the remaining ones form the outer brush with reduced effective grafting density. Analysis shows that the normal pressure in adsorption-active brushes can be understood in terms of the effective grafting density concept although the pressure at small separations is affected by the presence of the dense adsorbed phase. We propose a simple theory modification that accounts for this effect. We also formulate a procedure for extracting the value of the effective grafting density directly from the pressure vs separation curves by inverting the equation of state. In contrast to the normal pressure, the interpenetration of the two opposing adsorption-active brushes demonstrates a much more intricate behavior. At weak to moderate compressions, the effective grafting density concept works well but fails spectacularly at small interbrush separations. We identify two interpenetration regimes for adsorption-active brushes: (i) at separations larger than the ideal Gaussian coil size N1/2, the overlap of the two brushes is concentrated in the mid-plane region, in the same way as in brushes grafted onto non-attractive surfaces; (ii) at separations less than N1/2, the brush overlap is strongly enhanced in the wall regions where the attractive interaction plays an important role both in generating the dense layer for the “proper” brush and in attracting the “foreign” chains.
Using small angle x-ray scattering to examine the aggregation mechanism in silica nanoparticle-based ambigels for improved optical clarity
Authors: Kashanchi Glareh N. , King Sophia C. , Ju Susan E. , Dashti Ali , Martinez Ricardo , Lin Yu-Keng , Wall Vivian , McNeil Patricia E. , Marszewski Michal , Pilon Laurent , Tolbert Sarah H.
Published: December 2022

Silica-based aerogels are a promising low-cost solution for improving the insulation efficiency of single-pane windows and reducing the energy consumption required for space heating and cooling. Two key material properties required are high porosity and small pore sizes, which lead to low thermal conductivity and high optical transparency, respectively. However, porosity and pore size are generally directly linked, where high porosity materials also have large pore sizes. This is unfavorable as large pores scatter light, resulting in reduced transmittance in the visible regime. In this work, we utilized preformed silica colloids to explore methods for reducing pore size while maintaining high porosity. The use of preformed colloids allows us to isolate the effect of solution conditions on porous gel network formation by eliminating simultaneous nanoparticle growth and aggregation found when using typical sol–gel molecular-based silica precursors. Specifically, we used in situ synchrotron-based small-angle x-ray scattering during gel formation to better understand how pH, concentration, and colloid size affect particle aggregation and pore structure. Ex situ characterization of dried gels demonstrates that peak pore widths can be reduced from 15 to 13 nm, accompanied by a narrowing of the overall pore size distribution, while maintaining porosities of 70%–80%. Optical transparency is found to increase with decreasing pore sizes while low thermal conductivities ranging from 95 +/− 13 mW/m K are maintained. Mechanical performance was found to depend primarily on effective density and did not show a significant dependence on solution conditions. Overall, our results provide insights into methods to preserve high porosity in nanoparticle-based aerogels while improving optical transparency.
Tip vortices shed by a hydrofoil in the wake of a marine propeller
Authors: Posa A.
Published: December 2022

Large-eddy simulations on a grid consisting of 3.8 billion points are reported, dealing with a system composed of a propeller and a downstream semi-infinite hydrofoil, mimicking a propeller–rudder system typical of surface ships. The analysis is focused on the tip vortices shed by the hydrofoil across four values of incidence angle. The results of the simulations highlight the generation of two vortices, from the pressure and suction edges of the tip of the hydrofoil, respectively, with the former more intense than the latter. They promote higher turbulence levels and pressure fluctuations at the tip of the suction side of the hydrofoil and especially at its bottom end, while the pressure side is almost unaffected. For large incidence angles, they join in the near wake of the system into a single streamwise-oriented structure. This dominates the wake signature. It is a location of minima of pressure and maxima of turbulence, which affect performance in terms of cavitation and noise. Large levels of turbulent kinetic energy are also achieved in the region of shear of this vortex with the tip vortices shed by the propeller and coming from the pressure side of the hydrofoil, rolling around the vortex from the tip of the hydrofoil. In contrast, at no incidence or for small angles, the wake of the system is dominated by the shear layer shed from the trailing edge of the hydrofoil and by the hub and tip vortices populating the wake of the propeller.
Analytic gradients for local density fitting Hartree–Fock and Kohn–Sham methods
Authors: Csóka József , Kállay Mihály
Published: December 2022

We present analytic gradients for local density fitting Hartree–Fock (HF) and hybrid Kohn–Sham (KS) density functional methods. Due to the non-variational nature of the local fitting algorithm, the method of Lagrange multipliers is used to avoid the solution of the coupled perturbed HF and KS equations. We propose efficient algorithms for the solution of the arising Z-vector equations and the gradient calculation that preserve the third-order scaling and low memory requirement of the original local fitting algorithm. In order to demonstrate the speed and accuracy of our implementation, gradient calculations and geometry optimizations are presented for various molecular systems. Our results show that significant speedups can be achieved compared to conventional density fitting calculations without sacrificing accuracy.
Calculation of tunneling current across trapezoidal potential barrier in a scanning tunneling microscope
Authors: Dessai Malati , Kulkarni Arun V.
Published: December 2022

Accurate calculation of the tunneling currents in a scanning tunneling microscope (STM) is needed for developing image processing algorithms that convert raw data of the STM into surface topographic images. In this paper, an accurate calculation of the tunneling current for several tip–sample distances, bias voltages, and tips of a hyperboloidal shape with several radii of curvature is carried out. The main features of this calculation are the following. Non-WKB exact solutions to the trapezoidal (linear) potential in the barrier region are used to calculate the tunneling probabilities. Pauli blocking effects on both forward and reverse current densities are introduced. Finite temperature (viz. 300K) calculation in which electrons belonging to a narrow band of energy about the Fermi level contribute to tunneling is carried out. Integration over a field line method is used to obtain tunneling currents for the nonplanar hyperboloidal shaped tips, using the expressions obtained in the paper, for planar model current densities. An estimate of the lateral resolution is introduced. Earlier works do not consider all these aspects together in a single calculation. Tunneling currents are found to increase rapidly with increasing bias voltage and decrease exponentially with increasing tip–sample distances. Airy function determined currents are a more accurate function of a tip–sample distance than the WKB determined currents. Pauli effects are found to not always reduce currents from their non-Pauli values. The lateral resolution is found to be degraded for blunter tips, larger bias voltages, and larger tip–sample distances.
On the intensity of light scattered by molecular liquids—Comparison of experiment and quantum chemical calculations
Authors: Pabst Florian , Blochowicz Thomas
Published: December 2022

The intensity of light scattered by liquids has been studied for over a century since the valuable microscopic information about the molecules can be obtained, such as the anisotropy of the molecular polarizability tensor or preferred orientations of neighboring molecules. However, in modern dynamic light scattering experiments, the scattering intensity is usually disregarded, unlike in dielectric spectroscopy, which can be considered as a complementary experimental method, where the dielectric strength is routinely evaluated. The reason lies partly on the fact that the exact form of the equations relating the macroscopically measured light scattering intensity to the microscopic properties of the molecules is debated in the literature. Therefore, as a first step, we compare anisotropy parameters from the literature, calculated from light scattering intensities using different equations, with quantum chemical calculations for over 150 medium-sized molecules. This allows us to identify a consistent form of equations. In a second part, we turn to the depolarized light scattering spectra of 13 van der Waals liquids and some mixtures thereof, recorded with a combination of Tandem–Fabry–Perót and Raman spectroscopies, giving direct access to the reorientational dynamics of the molecules. We discuss how the strength of the structural α-relaxation is connected to the anisotropy parameter, what implication this has for the shape of the α-relaxation, how the components of a mixture—also for the case of ionic liquids—can be identified in this way, and how orientational correlation parameters can be extracted. Additionally, we point out for the example of n-alkanes that for highly flexible molecules, the reorientational motion might not be the decisive source of the depolarized scattered light. We also show that light scattering might serve as a sensitive tool to check the accuracy of a conformer ensemble obtained by quantum chemical calculations.
Tumor-derived OBP2A promotes prostate cancer castration resistance
Authors: Jeong Ji-Hak , Zhong Shangwei , Li Fuzhuo , Huang Changhao , Chen Xueyan , Liu Qingqing , Peng Shoujiao , Park HaJeung , Lee You Mie , Dhillon Jasreman , Luo Jun-Li
Published: December 2022

Androgen deprivation therapy (ADT) is a systemic therapy for advanced prostate cancer (PCa); although most patients initially respond to ADT, almost all cancers eventually develop castration-resistant PCa (CRPC). Currently, most research focuses on castration-resistant tumors, and the role of tumors in remission is almost completely ignored. Here, we report that odorant-binding protein (OBP2A) released from tumors in remission during ADT catches survival factors, such as CXCL15/IL8, to promote PCa cell androgen-independent growth and enhance the infiltration of myeloid-derived suppressor cells (MDSCs) into tumor microenvironment, leading to the emergence of castration resistance. OBP2A knockdown significantly inhibits CRPC and metastatic CRPC development and improves therapeutic efficacy of CTLA-4/PD-1 antibodies. Treatment with OBP2A-binding ligand α-pinene interrupts the function of OBP2A and suppresses CRPC development. Furthermore, α-pinene–conjugated doxorubicin/docetaxel can be specifically delivered to tumors, resulting in improved anticancer efficacy. Thus, our studies establish a novel concept for the emergence of PCa castration resistance and provide new therapeutic strategies for advanced PCa.
Photothermal effects on optical bistability and second-order sidebands in a cavity
Authors: Lv Jiang , Bi Jie , Xu Yifan , Li Tieping , Chen Hongyun
Published: December 2022

We theoretically study the optical bistability and second-order sideband generation (SSG) in an optical cavity having photothermal effect in our paper. Using the perturbation method, we give an explicit analytical expression for SSG, showing a conversion efficiency of over 30

%

. With change in the system parameters, our numerical method shows that the transparency window of the photothermal induced transparency and the SSG can be significantly enhanced by the photothermal effects. Our obtained results in this study can provide a reference to develop a new way in all-optical switching and precision measurement.
Backward scattering impact on the photoionization time delay of asymmetric molecules
Authors: Chen Xi , Cao Wei , Zhan BiFu , Lu Peixiang
Published: December 2022

The time delays in photoionization of asymmetric diatomic molecules are numerically investigated using the technique of reconstruction of attosecond beating by interference of two-photon transitions (RABBITTs). Our results show that two different oscillatory structures appear in the molecular photoionization time delays as the photoelectron energy changes, and the contribution of these two oscillations to the time delays varies with the nuclear distance. By using an analytical interference model, we demonstrate that one oscillation is traced back to the two-center interference and the other originates from the photoelectrons backward scattering. With the increases of internuclear distance, the backward scattering impact on the time delays is gradually distinct in a particular direction of the photoionization. The amplitude of the backward scattering induced oscillation decreases when the photoelectron energy increases. Furthermore, the stereo RABBITT time delays display a distinct downshift as the increases of asymmetry degree of molecule, which is attributed to the increasing depth of the additional Coulomb potential experienced by the ionized electron.
Multispectral tunable symmetry-protected bound states in the continuum in all-dielectric split-ring resonator metasurfaces
Authors: Sharma Shubhanshi , Lahiri Basudev , Varshney Shailendra
Published: December 2022

Symmetry incompatible bound states in the continuum (BICs) are the non-radiating states that remain decoupled from the radiation continuum due to the symmetry mismatch. However, it has always been challenging to observe multiple symmetry-protected BICs in single resonator dielectric metasurfaces. This work reports multiple symmetry-protected BICs for both linear polarizations in all-dielectric metasurfaces made up of split-ring resonators (SRRs). Intensive numerical simulations predict that SRR can support a high-quality factor (Q) of 106 for standalone and with substrate in presence of asymmetry. However, for a realistic and practical scenario, a Q-factor of

≈

8000 for standalone structures is achieved, which reduces by a factor of 1.25 in the presence of silica substrate. Even if the out-of-plane asymmetry is introduced either in the geometry or variation in the angle of incidence, BICs are transformed into quasi-BICs possessing Fano resonance. Eigenmode and multipole decomposition analysis confirm multiple BIC resonances; notable dominant contributions are from magnetic dipole, toroidal dipole, and electric and magnetic quadrupoles. Integrating monolayer graphene adds tunability to the metasurface, where distinct quasi-BIC modes can be employed to facilitate an excellent switching.
Investigation of deep transfer learning for cross-turbine diagnosis of wind turbine faults
Authors: Xie Ping , Zhang Xingmin , Jiang Guoqian , Cui Jian , He Qun
Published: December 2022

Data-driven fault diagnosis of wind turbines has gained popularity, and various deep learning models have been developed accordingly with massive amounts of data and achieved an excellent diagnosis performance. However, most existing deep learning models require a similar distribution of both training and testing data, thus the trained model cannot generalize new wind turbines with different data distributions. In addition, there are insufficient fault data in practice, and therefore the cost of training a new model from scratch is extremely high. To solve these problems, a cross-turbine fault diagnosis method based on deep transfer learning is proposed for wind turbines with the available supervisory control and data acquisition (SCADA) data. To better capture the spatial features of SCADA data, a deep multi-scale residual attention convolutional neural network (DMRACNN) is first designed. Then, the distribution differences between the source and target domain data are aligned at feature level. Specifically, we investigate the transfer performance of four different domain adaptation metrics. We evaluate our proposed method using SCADA data from two wind turbines to compare the diagnostic performance of four basic networks combined with four transfer metrics. Compared with traditional deep learning methods, our proposed DMRACNN achieved significant performance improvements. A cross-validation experiment using two turbines demonstrates the strong generalization ability of the proposed method.
Analysis of uncertainties in the measurement of the space charge distribution in dielectrics
Authors: Pan Jiaping , Cao Zebin , Zheng Feihu , Zhang Yewen
Published: December 2022

The results obtained from the commonly used space charge distribution measurement methods are frequently apparent and one-dimensional results of a localized area; moreover, random errors can be caused by various factors. In this work, three factors—sample thickness uniformity, pressure wave intensity uniformity, and space charge distribution uniformity—that may cause measurement uncertainties are examined. The analysis and evaluation of the experimental data are affected by the measurement uncertainties, which are particularly noticeable in experiments on semiconductive electrode-flat polyethylene samples that use the laser-induced pressure propagation method. These factors are investigated separately using several auxiliary experiments, including laser beam spot energy distribution measurements and space charge distribution measurements, at different measurement positions on the same uniform sample. A clear and intelligible model is developed to discuss the influence of these factors on the uncertainties in the space charge distribution measurement in dielectrics.
Minimizing susceptibility-induced BOLD sensitivity loss in multi-band accelerated fMRI using point spread function mapping and gradient reversal
Authors: In Myung-Ho , Kang Daehun , Jo Hang Joon , Yarach Uten , Meyer Nolan K , Trzasko Joshua D , Huston John , Bernstein Matt A , Shu Yunhong
Published: December 2022

Objective. Interleaved reverse-gradient fMRI (RG-fMRI) with a point-spread-function (PSF) mapping-based distortion correction scheme has the potential to minimize signal loss in echo-planar-imaging (EPI). In this work, the RG-fMRI is further improved by imaging protocol optimization and application of reverse Fourier acquisition. Approach. Multi-band imaging was adapted for RG-fMRI to improve the temporal and spatial resolution. To better understand signal dropouts in forward and reverse EPIs, a simple theoretical relationship between echo shift and geometric distortion was derived and validated by the reliable measurements using PSF mapping method. After examining practical imaging protocols for RG-fMRI in three subjects on both a conventional whole-body and a high-performance compact 3 T, the results were compared and the feasibility to further improve the RG-fMRI scheme were explored. High-resolution breath-holding RG-fMRI was conducted with nine subjects on the compact 3 T and the fMRI reliability improvement in high susceptibility brain regions was demonstrated. Finally, reverse Fourier acquisition was applied to RG-fMRI, and its benefit was assessed by a simulation study based on the breath-holding RG-fMRI data. Main results. The temporal and spatial resolution of the multi-band RG-fMRI became feasible for whole-brain fMRI. Echo shift measurements from PSF mapping well estimated signal dropout effects in the EPI pair and were useful to further improve the RG-fMRI scheme. Breath-holding RG-fMRI demonstrated improved fMRI reliability in high susceptibility brain regions. Reverse partial Fourier acquisition omitting the late echoes could further improve the temporal or spatial resolution for RG-fMRI without noticeable signal degradation and spatial resolution loss. Significance. With the improved imaging scheme, RG-fMRI could reliably investigate the functional mechanisms of the human brain in the temporal and frontal areas suffering from susceptibility-induced functional sensitivity loss.
Markerless motion tracking with simultaneous MV and kV imaging in spine SBRT treatment—a feasibility study
Authors: Cai Weixing , Fan Qiyong , Li Feifei , He Xiuxiu , Zhang Pengpeng , Cervino Laura , Li Xiang , Li Tianfang
Published: December 2022

Objective. Motion tracking with simultaneous MV-kV imaging has distinct advantages over single kV systems. This research is a feasibility study of utilizing this technique for spine stereotactic body radiotherapy (SBRT) through phantom and patient studies. Approach. A clinical spine SBRT plan was developed using 6xFFF beams and nine sliding-window IMRT fields. The plan was delivered to a chest phantom on a linear accelerator. Simultaneous MV-kV image pairs were acquired during beam delivery. KV images were triggered at predefined intervals, and synthetic MV images showing enlarged MLC apertures were created by combining multiple raw MV frames with corrections for scattering and intensity variation. Digitally reconstructed radiograph (DRR) templates were generated using high-resolution CBCT reconstructions (isotropic voxel size (0.243 mm)3) as the reference for 2D–2D matching. 3D shifts were calculated from triangulation of kV-to-DRR and MV-to-DRR registrations. To evaluate tracking accuracy, detected shifts were compared to known phantom shifts as introduced before treatment. The patient study included a T-spine patient and an L-spine patient. Patient datasets were retrospectively analyzed to demonstrate the performance in clinical settings. Main results. The treatment plan was delivered to the phantom in five scenarios: no shift, 2 mm shift in one of the longitudinal, lateral and vertical directions, and 2 mm shift in all the three directions. The calculated 3D shifts agreed well with the actual couch shifts, and overall, the uncertainty of 3D detection is estimated to be 0.3 mm. The patient study revealed that with clinical patient image quality, the calculated 3D motion agreed with the post-treatment cone beam CT. It is feasible to automate both kV-to-DRR and MV-to-DRR registrations using a mutual information-based method, and the difference from manual registration is generally less than 0.3 mm. Significance. The MV-kV imaging-based markerless motion tracking technique was validated through a feasibility study. It is a step forward toward effective motion tracking and accurate delivery for spinal SBRT.
Feasibility of using a dual isocentre technique for treating cervical cancer on the 1.5 T MR-Linac
Authors: Chuter Robert W , Brewster Frank , Retout Louise , Cree Anthea , Aktürk Nesrin , Hales Rosie , Benson Rebecca , Hoskin Peter , McWilliam Alan
Published: December 2022

Objective. Patients treated for cervical cancer exhibit large inter and intra-fraction anatomical changes. The Unity MR-Linac (MRL) can image these patients with MR prior to and during treatment which enables daily plan adaptation. However, the MRL has a limited treatment field in the sup/inf direction of 22 cm which can restrict the treatment of patients who require longer treatment fields. Here we explore potential adaptive workflows in combination with a dual isocentre approach, to widen the range of cervix patients that can benefit from this treatment. Approach. Ten cervical cancer patients were retrospectively planned with a dual isocentre technique to deliver 45 Gy in 25 fractions. 5 node-negative and 5 node-positive patients were planned using the EMBRACE II protocol. A 2 cm overlap region between the two isocentres was positioned entirely in the nodal region. A treatment workflow was simulated to account for inter-fraction anatomical change. Isocentre shifts of 3 and 6 mm were applied to investigate the effect of intra-fraction motion. Main results. Dual isocentre adapted plans ensured significantly better coverage than non-adapted (recalculated) plans with a larger benefit seen for the node-negative cases. The difference to the reference plan for the V4275 cGy to the ITV was −0.8 cGy and −8.2 cGy for the adapted and recalculated plans respectively. Movements superiorly did not affect the coverage of the ITV by more than 1%, but shifting it inferiorly caused the ITV coverage on the plan to reduce by ∼2.4% per mm. Significance. A dual isocentre technique for cervical cancer treatments and adaptive workflows have been demonstrated to recover the required plan quality for inter-fraction changes. This illustrates the feasibility of a dual isocentre technique for the MRL.
Joint motion estimation and penalized image reconstruction algorithm with anatomical priors for gated TOF-PET/CT
Authors: Tsai Yu-Jung , Liu Chi
Published: December 2022

The presence of respiratory motion not only degrades the reconstructed image but also limits the utilization of anatomical priors in emission tomography. In this study, we explore the potential application of a joint motion estimation and penalized image reconstruction algorithm using anatomical priors in gated time-of-flight positron emission tomography/computed tomography (PET/CT). The algorithm is able to warp both the activity image and the attenuation map to align them with the measured data with the facilitation of anatomical information contained in the attenuation map. Five patient datasets, three acquired in single-bed position and two acquired in whole-body continuous-bed-motion mode, are included. For each patient, the attenuation map is derived from a breath-hold CT. The Parallel Levels Sets (PLS) is chosen as a representative anatomical prior. In addition to demonstrating the reliability of the estimated motion and the benefits of incorporating anatomical prior, preliminary results also indicate that the algorithm shows the potential to reconstruct an activity image in the space corresponding to that of the attenuation map, which could be applied to address the potential misalignment issue in applications involving multiple PET acquisitions but a single CT.
Dynamics of frustrated tunneling ionization driven by inhomogeneous laser fields
Authors: Xu Jingkun , Zhou Yueming , Li Yingbin , Liu Aihua , Chen Yongkun , Ma Xiaomeng , Huang Xiang , Liu Kunlong , Zhang Qingbin , Li Min , Yu Benhai , Lu Peixiang
Published: December 2022

We theoretically investigated frustrated tunneling ionization (FTI) driven by spatially inhomogeneous strong laser fields induced by surface plasmon resonance within a bow-tie metal nanostructure. The results show that the FTI probability and the principal quantum number distribution exhibit similar oscillatory behavior as a function of the pulse duration. Our analysis reveals that the periodic defocusing and refocusing of the electron spatial distribution due to the inhomogeneous laser field is responsible for the oscillatory structures. In addition, the initial tunneling coordinates and the angular momentum distributions of the FTI events and theirs pulse duration dependence are also explored. Moreover, our results show that the frequency of the oscillatory structures depends sensitively on the electron quiver amplitude and the inhomogeneity strength. Thus, the electron quiver amplitude and the size of the gap between bow-tie nanostructure are useful and efficient knobs for controlling the yield and properties of exited Rydberg states.
Resonant Kushi-comb-like multi-frequency radiation of oscillating two-color soliton molecules
Authors: Melchert O , Willms S , Oreshnikov I , Yulin A , Morgner U , Babushkin I , Demircan A
Published: December 2022

Nonlinear waveguides with two distinct domains of anomalous dispersion can support the formation of molecule-like two-color pulse compounds. They consist of two tightly bound subpulses with frequency loci separated by a vast frequency gap. Perturbing such a two-color pulse compound triggers periodic amplitude and width variations, reminiscent of molecular vibrations. With increasing strength of perturbation, the dynamics of the pulse compound changes from harmonic to nonlinear oscillations. The periodic amplitude variations enable coupling of the pulse compound to dispersive waves, resulting in the resonant emission of multi-frequency radiation. We demonstrate that the location of the resonances can be precisely predicted by phase-matching conditions. If the pulse compound consists of a pair of identical subpulses, inherent symmetries lead to degeneracies in the resonance spectrum. Weak perturbations lift existing degeneracies and cause a splitting of the resonance lines into multiple lines. Strong perturbations result in more complex emission spectra, characterized by well separated spectral bands caused by resonant Cherenkov radiation and additional four-wave mixing processes.
Spectral probing of an extremely compressed femtosecond wave packet in calcium fluoride
Authors: Geints I Y , Kompanets V O , Melnikov A A , Chekalin S V , Dormidonov A E , Kandidov V P
Published: December 2022

We use time-resolved spectral probing to study the dynamics of transformation of the optical properties of a nonlinear medium during formation and propagation of an extremely compressed mid-IR femtosecond wave packet in calcium fluoride. Broadening, attenuation and distortion of the probe pulse spectrum have been experimentally observed varying the delay time of the probe pulse relative to the pump. By solving the unidirectional pulse propagation equation that describes propagation and filamentation of a pump pulse in a calcium fluoride crystal we determine temporal changes of the refractive index and absorption coefficient induced by an extremely compressed wave packet. A mechanism of the observed broadening and breakup of the probe pulse spectrum is proposed.