bluuebunny/crossref_metadata_2025 huggingface dataset:
Robotic Excision of Choledochal Cyst with Hepaticoduodenostomy (HD): Report of HD Technique, Initial Experience, and Early Outcome
Authors: Nazki Saalim , Kanojia Ravi Prakash , Bawa Monika , Binu Vineet , Lal Sadhna , Sood Ashwani , Samujh Ram
Published: July 2020

Introduction Minimal access surgical approach to choledochal cyst (CC) is becoming a standard of care in pediatric age group. Robotic-assisted excision of CC is increasingly being practiced at centers which have access to the system. We present our experience and technique of hepaticoduodenostomy (HD). Over all initial experience, short-term outcomes and complications are also presented and discussed.

Materials and Methods Patients with CC and undergoing robotic excision were retrospectively studied. Patients with active cholangitis, liver dysfunction, and perforated CC were excluded for robotic procedures. All included patients were preoperatively evaluated as per the defined protocol. They underwent excision of CC with HD. The duodenal anastomosis was done after limited mobilization and emphasis was laid on anastomosing the distal D2 part to the common hepatic duct. This prevents bile reflux into stomach. The follow-up evaluation was done for these patients. Hepatobiliary iminodiacetic acid (HIDA) scan for duodenogastric reflux (DGR) was done only if patients reported symptoms related to it.

Results A total of 19 patients (10 females) were studied. The mean age was 84 months. Type 1b was present in 12 patients and the rest were type IVb. Complete cyst excision with HD was done in all patients except conversion to open in one patient. The mean surgical time was 170 ± 40 minutes with console time of 140 ± 20 minutes. Median follow-up duration is 2.5 years (range: 3.5–0.5 years). HIDA scan was done in five patients who had reported epigastric pain. Of these five, one patient had a positive DGR. He is on conservative management.

Conclusion Robot-assisted CC excision with HD is feasible as proven by the outcome of 19 patients presented in this series. HD is to be done away from pylorus in distal part of down curving D2. This particular step prevents DGR and is the most important point of technique in doing HD. The presented series is the first report of robotic excision of CC with HD. The robot is a facilitator for complex and difficult operations as CC excision and HD.
Ethical, Social, and Economic Challenges in Managing a Child with Dravet Syndrome in a Developing Country
Authors: Gulati Sheffali , Sinha Rahul , Madaan Priyanka
Published: July 2020

Epilepsy is a chronic neurological disorder with a significant impact on sociocultural and economic aspects. The management of epilepsy in low-middle income countries (LMICs) is influenced by many factors such as disease burden, poverty, educational status, the reflection of the disease as a social stigma, diverse religious beliefs, and treatment expense. Despite the improvement in educational and social parameters, the stigmatization of the disease is still evident in many LMICs. The associated comorbidities and neurodevelopmental disorders further add to the cost and stigmatization. The pediatric neurologists/epileptologists in LMICs are encountered by distinctive ethical, social, and economic dilemmas during the patient care and management of epilepsy. This article discusses the various ethical dilemmas in a child with Dravet syndrome in a developing country.
Reliability sensitivity analysis based on stress–strength model of bearing with random parameters
Authors: Cheng Hongchuan , Zhang Yimin , Lu Wenjia , Yang Zhou
Published: July 2020

On the basis of the stress–strength model of the ball bearing with random parameters, the reliability sensitivity of the raceway strength is examined. The basic parameters are regarded as random variables subject to normal distribution. The Latin hypercube sampling method is adopted to obtain the samples, which are brought into the bearing model to obtain the corresponding maximum orthogonal shear stress. The explicit expression of shear stress was obtained by genetic algorithm-back propagation neural network fitting, and the limit-state equation is established in combination with the yield limit of bearing materials. First, this study analyzes the sensitivity of the maximum shear stress with respect to various parameters and obtains the effect of parameters on shear stress at various rotational speeds. Then, based on the stress–strength state equation, the strength reliability is obtained by using the improved first-order second-moment method, which is verified by Monte Carlo simulation. Finally, the reliability sensitivity with respect to the mean and standard variance of random variables is analyzed. This research can provide theoretical guidance for the design, production, and use of bearings.
Super-resolution surface slope metrology of x-ray mirrors
Authors: Yashchuk Valeriy V. , Rochester Simon , Lacey Ian , Babin Sergey
Published: July 2020

We present experimental, analytical, and numerical methods developed for reconstruction (deconvolution) of one-dimensional (1D) surface slope profiles over the spatial frequency range where the raw data are significantly perturbed due to the limited resolution of the measurement instrument. We characterize the spatial resolution properties of a profiler with the instrument’s transfer function (ITF). To precisely measure the ITF, we apply a recently developed method utilizing test surfaces with 1D linear chirped height profiles of constant slope amplitude. Based on the results of the ITF calibration, we determine parameters of an analytical model for the ITF that is used in the original reconstruction software. Here, we treat surface slope metrology data obtained with the Optical Surface Measuring System (OSMS), using as a sensor an electronic autocollimator (AC) ELCOMAT-3000. The spatial resolution of the OSMS is limited by the size of the AC light-beam-collimating aperture. For the purposes of this investigation, the OSMS is equipped with a circular aperture with a diameter of 2.5 mm. This is a typical arrangement of most AC-based slope profilers developed for surface slope metrology of state-of-the-art x-ray mirrors. Using the example of surface slope metrology of two state-of-the-art elliptically shaped x-ray focusing mirrors, we demonstrate that the developed data reconstruction procedure allows us to significantly improve the accuracy of surface slope metrology with the OSMS over the spatial wavelength range from ∼1.6 mm to 7 mm. Thus, the amplitude of the quasi-periodic error characteristic of the deterministic polishing process used appears to be higher by a factor of ∼2 than is apparent from the rough metrology data. Underestimation of the surface slope errors in this spatial wavelength range can lead to serious errors in the expected performance of x-ray mirrors in synchrotron beamlines, especially at modern light sources utilizing coherent x rays, where the perturbations can lead to increased speckle-like intensity variation.
Lagrangian chaos in steady three-dimensional lid-driven cavity flow
Authors: Romanò Francesco , Türkbay Tuǧçe , Kuhlmann Hendrik C.
Published: July 2020

Steady three-dimensional flows in lid-driven cavities are investigated numerically using a high-order spectral-element solver for the incompressible Navier–Stokes equations. The focus is placed on critical points in the flow field, critical limit cycles, their heteroclinic connections, and on the existence, shape, and dependence on the Reynolds number of Kolmogorov–Arnold–Moser (KAM) tori. In finite-length cuboidal cavities at small Reynolds numbers, a thin layer of chaotic streamlines covers all walls. As the Reynolds number is increased, the chaotic layer widens and the complementary KAM tori shrink, eventually undergoing resonances, until they vanish. Accurate data for the location of closed streamlines and of KAM tori are provided, both of which reach very close to the moving lid. For steady periodic Taylor–Görtler vortices in spanwise infinitely extended cavities with a square cross section, chaotic streamlines occupy a large part of the flow domain immediately after the onset of Taylor–Görtler vortices. As the Reynolds number increases, the remaining KAM tori vanish from the Taylor–Görtler vortices, while KAM tori grow in the central region further away from the solid walls.
Feasibility analysis of a modular uniform magnetic field coil
Authors: Jin Yinxi , Pan Donghua , Sun Zhiyin , Zou Zhilong , Li Liyi
Published: July 2020

In this paper, a feasibility analysis of a modular uniform magnetic field coil is provided. The modular uniform magnetic field coil consists of n2 square coil units. By adjusting the number of coil units or the current in the coil units, different sizes and patterns of uniform magnetic field coils can be easily formed to meet different experimental requirements. An analytical model of the modular uniform magnetic field coil considering the gap between coil units is first developed based on the Biot–Savart law and the superposition principle, and the analytical model is verified by the 3D finite element method. Then, the characteristics of the modular uniform magnetic field coil are analyzed and compared with the traditional Helmholtz coil, demonstrating the advantages of the proposed magnetic field coil. These advantages precisely verify the original intention of the modular uniform magnetic field coil proposed in this paper. Finally, a robustness analysis of the modular magnetic field coil is performed, including the effects of gap between coil units and assembly misalignment on the performance of the modular uniform magnetic field coil.
Development of x-ray reflectivity measurement system under N2 to prevent surface contamination
Authors: Azuma Yasushi , Kurokawa Akira
Published: July 2020

In this study, a method to prevent surface contamination on an SiO2 film/Si substrate system was used to improve thickness determination by x-ray reflectometry (XRR). XRR profiles can be significantly affected by the growth of a surface contamination layer, originating from the organic matter present in the measurement environment. An N2 spray method that enables XRR measurement under high-purity N2 has been developed to keep the surface free of contaminants. The method was adopted due to its high applicability to an existing XRR instrument and the ease of system construction. The system mainly consists of an outlet for N2 spray that is positioned in front of the sample and an N2 gas purifier. The high-purity N2 is sprayed on the sample until the measurements are complete. It was revealed that the measured XRR profiles were stable for 115 h, and the evaluated thicknesses were obtained with high reproducibility (±0.05 nm for 10 nm thickness) by adopting the analysis model for clean surfaces.
Screech characteristics of under-expanded high aspect ratio elliptic jet
Authors: Rao A. Nageswara , Kushari Abhijit , Chandra Mandal Alakesh
Published: July 2020

Screeching behavior and the closure mechanism of a feedback loop for the flapping mode in under-expanded supersonic jet are investigated by schlieren imaging and near-field acoustic measurements for a high aspect ratio elliptic nozzle. Near-field measurements revealed a single screech frequency for the measured Mach number range. The cross spectrum of pressure signals shows that the upstream propagating wave is out of phase, which was identified as the asymmetric flapping mode. The proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) methods were applied to the time-resolved schlieren data to extract the coherent information associated with screech and its harmonics. The first three spatial POD modes reveal the periodic flapping of the jet and the asymmetric upstream propagation of acoustic waves. POD modes 4 and 5 identify the flow structures and acoustic wave patterns associated with the harmonics of the fundamental screech tone. The spatial DMD mode corresponds to the frequency of ∼10 kHz and exhibits the radial distortion of the jet shear layer and the acoustic radiation pattern. The interaction of the acoustic waves with the jet shear layer indicates that the upstream-traveling guided jet mode is responsible for closing the feedback loop of the flapping mode.
Defect–defect magnetic coupling in Gd doped GaN epitaxial films: A polarization selective magneto-photoluminescence study
Authors: Chakrabarti Poulab , Saroj Rajendra K. , Sarkar Preetha , Deb Swarup , Dhar S.
Published: July 2020

Here, we have carried out a magnetic field dependent polarization selective photoluminescence (PL) study at 1.5 K on Gd-doped GaN epitaxial layers grown on c-SiC substrates, where the incorporation of Gd has been found to generate three types of defects, which results in bound excitonic features in low temperature PL spectra. The study reveals that the external magnetic field dependence of the spin-flip scattering rates for the three excitonic features shows an increasing tendency of saturation at high fields as the density of these defects increases in these layers. This suggests that the signals must be stemming from defects which are ferromagnetically coupled with each other. This is further confirmed by the study carried out on a GaN sample co-doped with Si and Gd, where defects are found to be ferromagnetically coupled, while the Si-donors do not.
Exact sampling of polymer conformations using Brownian bridges
Authors: Wang Shiyan , Ramkrishna Doraiswami , Narsimhan Vivek
Published: July 2020

The equilibrium conformation of a polymer molecule in an external field is often used in field theories to calculate macroscopic polymer properties of melts and solutions. We use a mathematical method called a Brownian bridge to exactly sample continuous polymer chains to end in a given state. We show that one can systematically develop such processes to sample specific polymer topologies, to confine polymers in a given geometry for its entire path, to efficiently generate high-probability conformations by excluding small Boltzmann weights, or to simulate rare events in a rugged energy landscape. This formalism can improve the polymer sampling efficiency significantly compared to traditional methods (e.g., Monte Carlo or Rosenbluth).
Improving double-ended transition state searches for soft-matter systems
Authors: Röder K. , Wales D. J.
Published: July 2020

Transitions between different stable configurations of biomolecules are important in understanding disease mechanisms, structure–function relations, and novel molecular-scale engineering. The corresponding pathways can be characterized efficiently using geometry optimization schemes based on double-ended transition state searches. An interpolation is first constructed between the known states and then refined, yielding a band that contains transition state candidates. Here, we analyze an example where various interpolation schemes lead to bands with a single step transition, but the correct pathway actually proceeds via an intervening, low-energy minimum. We compare a number of different interpolation schemes for this problem. We systematically alter the number of discrete images in the interpolations and the spring constants used in the optimization and test two schemes for adjusting the spring constants and image distribution, resulting in a total of 2760 different connection attempts. Our results confirm that optimized bands are not necessarily a good description of the transition pathways in themselves, and further refinement to actually converge transition states and establish their connectivity is required. We see an improvement in the optimized bands if we employ the adjustment of spring constants with doubly-nudged elastic band and a smaller improvement from the image redistribution. The example we consider is representative of numerous cases we have encountered in a wide variety of molecular and condensed matter systems.
Wilhelmy equation revisited: A lightweight method to measure liquid–vapor, solid–liquid, and solid–vapor interfacial tensions from a single molecular dynamics simulation
Authors: Imaizumi Yuta , Omori Takeshi , Kusudo Hiroki , Bistafa Carlos , Yamaguchi Yasutaka
Published: July 2020

We have given theoretical expressions for the forces exerted on a so-called Wilhelmy plate, which we modeled as a quasi-2D flat and smooth solid plate immersed in a liquid pool of a simple liquid. All forces given by the theory, the local forces on the top, the contact line, and the bottom of the plate as well as the total force, showed an excellent agreement with the MD simulation results. The force expressions were derived by a purely mechanical approach, which is exact and ensures the force balance on the control volumes arbitrarily set in the system, and are valid as long as the solid–liquid (SL) and solid–vapor (SV) interactions can be described by mean-fields. In addition, we revealed that the local forces around the bottom and top of the solid plate can be related to the SL and SV interfacial tensions γSL and γSV, and this was verified through the comparison with the SL and SV works of adhesion obtained by the thermodynamic integration (TI). From these results, it has been confirmed that γSL and γSV as well as the liquid–vapor interfacial tension γLV can be extracted from a single equilibrium MD simulation without the computationally demanding calculation of the local stress distributions and the TI.
2D graphene oxide liquid crystal for real-world applications: Energy, environment, and antimicrobial
Authors: Yun Taeyeong , Jeong Geong Hwa , Padmajan Sasikala Suchithra , Kim Sang Ouk
Published: July 2020

The wonder material, graphene, is now on the stage from academic research to real-world industrial application. Graphene oxide (GO), an oxygenated form of monolayer graphene platelet, is playing a crucial role for the large-scale production of minimal layer stacked graphene. Effective purification of GO by removing acidic and ionic impurities is the essential step for high dispersibility and long-term colloidal stability, endowing graphene oxide liquid crystal (GOLC) formation. GOLC can be readily utilized not only for the production of high quality graphene platelets but also in the straightforward design of multi-dimensional architectures, including 1D, 2D, and 3D, for the functional graphene-based material fabrication. Motivated from the inexpensive raw material and inherently scalable solution process, GOLC-based materials offer an idealized platform for the practical balance between material performance and economic cost. Herein, recent progress and future prospective associated with the commercialization of 2D GOLC-based materials are highlighted, specifically concerning the recent energy, environmental, and pandemic issues. Relevant crucial advantages and perspectives are reviewed for practical applications, including supercapcitors, membrane, molecular adsorption, and antimicrobial material.
Origin of reverse leakage current path in edge-defined film-fed growth (001)
β
-Ga2O3 Schottky barrier diodes observed by high-sensitive emission microscopy
Authors: Sdoeung Sayleap , Sasaki Kohei , Kawasaki Katsumi , Hirabayashi Jun , Kuramata Akito , Oishi Toshiyuki , Kasu Makoto
Published: July 2020

We utilized ultra-high sensitive emission microscopy to investigate the origin of reverse leakage current of edge-defined film-fed grown (001) β-Ga2O3 Schottky barrier diodes. In the emission patterns, we observed a partially appearing void, having a typical width and depth of 300 and 83 nm, respectively, with a base angle of 75°, below the Schottky barrier contact on the β-Ga2O3 surface. Simulations show that the electric field at the bottom of the void reached 9 × 106 V/cm at a reverse bias of −60 V and in the case of an ideally flat surface 3.1 × 106 V/cm. This indicates that the reverse leakage current originates from an electric field concentration in the partially appearing voids on the surface. On the other hand, we have confirmed that there is no clear relationship between the leakage current path and the dislocations observed by synchrotron x-ray topography.
Chemical renormalization of the paraelectric–ferroelectric phase transition in PbTiO3-BiB0.5′B0.5″O3 solid solutions with tetragonal symmetry
Authors: Mihailova B. , Bayarjargal L. , Margaritescu I. , Datta K. , Chen J.
Published: July 2020

The effect of the type of B-site substituent on the development of the ferroelectric state in the tetragonal part of the composition-temperature (x-T) diagram of (1-x)PbTiO3-xBiB0.5′B0.5″O3 solid solutions is analyzed by applying the second harmonic generation (SHG) method and Raman spectroscopy to three compounds with B0.5′B0.5″ = Mg0.5Ti0.5, Ni0.5Ti0.5, and Ni0.5Zr0.5, having nearly the same tolerance factor and unit-cell tetragonality, at temperatures up to ∼1000 K. The results reveal the importance of B-site divalent dopants with an isotropic electron configuration for the enhancement of local symmetry breaking at the A site and a consequent increase in the Curie temperature at small x, regardless of the macroscopic tetragonality with respect to PbTiO3.
Nonmonotonic adsorption behavior of semiflexible polymers
Authors: Jiang Jian
Published: July 2020

We study the adsorption behavior of semiflexible polymer chains with finite concentrations onto a structureless, planar, and impenetrable surface using polymer density functional theory based on a discretization of the Kratky–Porod wormlike chain model. Adsorption characteristics are investigated at different attractive interactions between the surface and polymers of various intrinsic stiffnesses. We analyze the density distributions in the vicinity of the surface and find, in the adsorption regime (when the surface attraction is strong: ϵw≳ϵwc, where ϵwc is the critical surface potential of adsorption transition), a nonmonotonic adsorption behavior for polymer chains with various intrinsic stiffnesses: the adsorption amount first decreases and then increases with the intrinsic stiffness, and the minimum adsorption amount (as well as the maximum critical surface potential of adsorption transition) occurs at lp ∼ Δ (Δ and lp are the attractive range of surface potential and persistence length, respectively), while in the depletion regime (ϵw≪ϵwc), the depletion depth and range are increased monotonically with the intrinsic stiffness. Furthermore, we find βϵwc∼lp/Δ−0.185 for lp ⋗ Δ and βϵwc∼lp/Δ0.366 for lp < Δ.
Observation of high-pressure bcc phase of titanium at 243 GPa
Authors: Akahama Yuichi , Kawaguchi Saori , Hirao Naohisa , Ohishi Yasuo
Published: July 2020

In this study, the pressure-induced phase transition of the 3d transition metal titanium (Ti) has been investigated at pressures up to 290 GPa at room temperature using an x-ray diffraction technique with a micro-beam. From the analysis of powder x-ray diffraction patterns, the high-pressure δ phase (orthorhombic, Cmcm) was found to transform to the β phase (body-centered cubic: bcc, Im3m) at 243 GPa. Although the volume reduction at this phase transition was less than 1%, the coexistence of the δ phase suggests that the transition is of the first order. The isothermal bulk modulus at zero pressure, B0, and the pressure derivative of B0, B0′, were estimated to be 125(2) GPa and 3.46(6) GPa, respectively, by least squares fitting to the Vinet equation of state based on the P–V data of the δ and β phases. This transition to the bcc phase verified predictions from theoretical studies and demonstrated the systematics of the pressure-induced structural phase transition in transition metals.
Machine learning substitutional defect formation energies in ABO3 perovskites
Authors: Sharma Vinit , Kumar Pankaj , Dev Pratibha , Pilania Ghanshyam
Published: July 2020

Perovskite oxides are a promising material platform for use in a wide range of technological applications including electronics, sensors, fuel cells, and catalysis. This is owing to the extraordinary tunability of their physical and chemical properties via defect engineering. The feasibility and the stability of a defect, such as a substitutional dopant, in the host lattice is usually obtained via experiments and/or through detailed quantum mechanical calculations. Both of these conventional routes are expensive and time consuming. An alternative is a data-driven machine learning (ML)-based approach. In this work, we have applied ML techniques to identify the factors that influence defect formation energy, which is an important measure of the stability of the defects, in perovskite oxides. Using 13 elemental properties as features and random forest regression, we demonstrate a systematic approach to down-selecting from the larger set of features to those that are important, establishing a framework for accurate predictions of the defect formation energy. We quantitatively show that the most important factors that control the dopant stability are the dopant ionic size, heat of formation, effective tolerance factor, and oxidation state. Our work reveals previously unknown correlations, chemical trends, and the interplay between stability and underlying chemistries. Hence, these results showcase the efficacy of ML tools in identifying and quantifying different feature-dependencies and provide a promising route toward dopant selection in the perovskites. We have developed a framework that itself is general and can be potentially applied to other material classes.
The quantum-Ehrenfest method with the inclusion of an IR pulse: Application to electron dynamics of the allene radical cation
Authors: Tran Thierry , Jenkins Andrew J. , Worth Graham A. , Robb Michael A.
Published: July 2020

We describe the implementation of a laser control pulse in the quantum-Ehrenfest method, a molecular quantum dynamics method that solves the time-dependent Schrödinger equation for both electrons and nuclei. The oscillating electric field–dipole interaction is incorporated directly in the one-electron Hamiltonian of the electronic structure part of the algorithm. We then use the coupled electron-nuclear dynamics of the π-system in the allene radical cation (•CH2=C=CH2)+ as a simple model of a pump–control experiment. We start (pump) with a two-state superposition of two cationic states. The resulting electron dynamics corresponds to the rapid oscillation of the unpaired electron between the two terminal methylenes. This electron dynamics is, in turn, coupled to the torsional motion of the terminal methylenes. There is a conical intersection at 90° twist, where the electron dynamics collapses because the adiabatic states become degenerate. After passing the conical intersection, the electron dynamics revives. The IR pulse (control) in our simulations is timed to have its maximum at the conical intersection. Our simulations show that the effect of the (control) pulse is to change the electron dynamics at the conical intersection and, as a consequence, the concomitant nuclear dynamics, which is dominated by the change in the torsional angle.
Consistent description of ion-specificity in bulk and at interfaces by solvent implicit simulations and mean-field theory
Authors: dos Santos Alexandre P. , Uematsu Yuki , Rathert Alexander , Loche Philip , Netz Roland R.
Published: July 2020

Solvent-implicit Monte Carlo (MC) simulations and mean-field theory are used to predict activity coefficients and excess interfacial tensions for NaF, NaCl, NaI, KF, KCl, and KI solutions in good agreement with experimental data over the entire experimentally available concentration range. The effective ionic diameters of the solvent-implicit simulation model are obtained by fits to experimental activity coefficient data. The experimental activity coefficients at high salt concentrations are only reproduced if the ion-specific concentration-dependent decrement of the dielectric constant is included. The dielectric-constant dependent contribution of the single-ion solvation free energy to the activity coefficient is significant and is included. To account for the ion-specific excess interfacial tension of salt solutions, in addition to non-ideal solution effects and the salt-concentration-dependent dielectric decrement, an ion-specific ion–interface interaction must be included. This ion–interface interaction, which acts in addition to the dielectric image-charge repulsion, is modeled as a box potential, is considerably more long-ranged than the ion radius, and is repulsive for all ions considered except iodide, in agreement with previous findings and arguments. By comparing different models that include or exclude bulk non-ideal solution behavior, dielectric decrement effects, and ion–interface interaction potentials, we demonstrate how bulk and interfacial ion-specific effects couple and partially compensate each other. Our MC simulations, which correctly include ionic correlations and interfacial dielectric image-charge repulsion, are used to determine effective ion–surface interaction potentials that can be used in a modified Poisson–Boltzmann theory.
Ultrasonic tunable focusing by a stretchable phase-reversal Fresnel zone plate
Authors: Xia Xiangxiang , Li Yongchuan , Cai Feiyan , Zhou Hui , Ma Teng , Zheng Hairong
Published: July 2020

This paper reports a stretchable silicone phase-reversal (PR) Fresnel zone plate (FZP) that can focus ultrasonic energy at different focal lengths with a high transmission coefficient in water. Unlike a traditional FZP that creates focused by constructive interference of waves diffracted through open annular zones in an opaque screen, the silicone PR-FZP takes advantage of all the zones of the FZP contribute to the focal area by adding phase compensation regions instead of opaque regions. More interestingly, the silicone PR-FZP can be stretched, and the focal length increases gradually with the unchanged full width at half maximum as the PR-FZP is stretched. The aforementioned performance aspects are verified in both experiments and simulations. The proposed stretchable PR-FZP with a tunable focal length has potential applications in the broad field of ultrasonics, such as ultrasonic imaging and ultrasound neuromodulation.
Sneezing and asymptomatic virus transmission
Authors: Busco Giacomo , Yang Se Ro , Seo Joseph , Hassan Yassin A.
Published: July 2020

The novel coronavirus disease (COVID-19) spread pattern continues to show that geographical barriers alone cannot contain a virus. Asymptomatic carriers play a critical role in the nature of this virus quickly escalating into a global pandemic. Asymptomatic carriers may transmit the virus unintentionally through sporadic sneezing. A novel Computational Fluid Dynamics (CFD) approach has been proposed with a realistic modeling of a human sneeze achieved by the combination of state-of-the-art experimental and numerical methods. This modeling approach may be suitable for future engineering analyses aimed at reshaping public spaces and common areas, with the main objective to accurately predict the spread of aerosol and droplets that may contain pathogens. This study shows that the biomechanics of a human sneeze, including complex muscle contractions and relaxations, can be accurately modeled by the angular head motion and the dynamic pressure response during sneezing. These have been considered as the human factors and were implemented in the CFD simulation by imposing a momentum source term to the coupled Eulerian–Lagrangian momentum equations. The momentum source was modeled by the measured dynamic pressure response in conjunction with the angular head motion. This approach eliminated the need to create an ad hoc set of inlet boundary conditions. With this proposed technique, it is easier to add multiple fixed and/or moving sources of sneezes in complex computational domains. Additionally, extensive sensitivity analyses based on different environmental conditions were performed, and their impact was described in terms of potential virus spread.
Machine learning classification can reduce false positives in structure-based virtual screening
Authors: Adeshina Yusuf O. , Deeds Eric J. , Karanicolas John
Published: July 2020

Significance

Many potential drug targets have been identified, but development of chemical probes to validate these targets has lagged behind. Computational screening holds promise for providing chemical tools to do so but has long been plagued by high false-positive rates: Many compounds ranked highly against a given target protein do not actually show activity. Machine learning approaches have not solved this problem, which we hypothesize is because models were not trained on sufficiently compelling “decoys.” By addressing this through a unique training strategy, we show that more effective virtual screening is attainable. We expect this insight to enable improved performance across diverse virtual screening pipelines, thus helping to provide chemical probes for new potential drug targets as they are discovered.
A cocrystal structure of dengue capsid protein in complex of inhibitor
Authors: Xia Hongjie , Xie Xuping , Zou Jing , Noble Christian G. , Russell William K. , Holthauzen Luis Marcelo F. , Choi Kyung H. , White Mark A. , Shi Pei-Yong
Published: July 2020

Significance

DENV represents the most important mosquito-borne viral pathogen in humans. Although one dengue vaccine has been approved for clinical use, its efficacies against serotypes 1 and 2 remain to be improved. No effective anti-DENV therapy is available for patient treatment. In this study, we solved the cocrystal structure of the DENV-2 capsid protein in complex with an inhibitor that preferentially inhibits serotype 2 (not the other three serotypes) in vitro and in vivo. Mechanistically, the compound is incorporated into virions by inducing capsid tetramerization. Such inhibitor-containing virions are defective in nucleocapsid uncoating when infecting new cells. Our results have also uncovered the resistance mechanism and provided a high-resolution structure for rational design of capsid inhibitors with pan-serotype DENV activity.
Interferon-stimulated gene 15 accelerates replication fork progression inducing chromosomal breakage
Authors: Raso Maria Chiara , Djoric Nikola , Walser Franziska , Hess Sandra , Schmid Fabian Marc , Burger Sibylle , Knobeloch Klaus-Peter , Penengo Lorenza
Published: July 2020

DNA replication is highly regulated by the ubiquitin system, which plays key roles upon stress. The ubiquitin-like modifier ISG15 (interferon-stimulated gene 15) is induced by interferons, bacterial and viral infection, and DNA damage, but it is also constitutively expressed in many types of cancer, although its role in tumorigenesis is still largely elusive. Here, we show that ISG15 localizes at the replication forks, in complex with PCNA and the nascent DNA, where it regulates DNA synthesis. Indeed, high levels of ISG15, intrinsic or induced by interferon-β, accelerate DNA replication fork progression, resulting in extensive DNA damage and chromosomal aberrations. This effect is largely independent of ISG15 conjugation and relies on ISG15 functional interaction with the DNA helicase RECQ1, which promotes restart of stalled replication forks. Additionally, elevated ISG15 levels sensitize cells to cancer chemotherapeutic treatments. We propose that ISG15 up-regulation exposes cells to replication stress, impacting genome stability and response to genotoxic drugs.
Lorentzian Snyder spacetimes and their Galilei and Carroll limits from projective geometry
Authors: Ballesteros Angel , Gubitosi Giulia , Herranz Francisco J
Published: July 2020

We show that the Lorentzian Snyder models, together with their Galilei and Carroll limiting cases, can be rigorously constructed through the projective geometry description of Lorentzian, Galilean and Carrollian spaces with nonvanishing constant curvature. The projective coordinates of such curved spaces take the role of momenta, while translation generators over the same spaces are identified with noncommutative spacetime coordinates. In this way, one obtains a deformed phase space algebra, which fully characterizes the Snyder model and is invariant under boosts and rotations of the relevant kinematical symmetries. While the momentum space of the Lorentzian Snyder models is given by certain projective coordinates on (anti-)de Sitter spaces, we discover that the momentum space of the Galilean (Carrollian) Snyder models is given by certain projective coordinates on curved Carroll (Newton–Hooke) spaces. This exchange between the Galilei and Carroll limits emerging in the transition from the geometric picture to the phase space picture is traced back to an interchange of the role of coordinates and translation operators. As a physically relevant feature, we find that in Galilean Snyder spacetimes the time coordinate does not commute with space coordinates, in contrast with previous proposals for non-relativistic Snyder models, which assume that time and space decouple in the non-relativistic limit c → ∞. This remnant mixing between space and time in the non-relativistic limit is a quite general Planck-scale effect found in several quantum spacetime models.
Rydberg–Stark deceleration and trapping of helium in magnetic fields
Authors: Žeško Matija , Tkáč Ondřej , Agner Josef A , Schmutz Hansjürg , Merkt Frédéric
Published: July 2020

Triplet (S = 1) He Rydberg atoms in supersonic beams with an initial velocity of 350 m s−1 have been decelerated to zero velocity and loaded into an off-axis electric trap in the presence and absence of magnetic fields. Comparing the deceleration efficiencies and the radiative decay of the population of trapped He Rydberg atoms to the (1s)1(2s)1
3S1 metastable level in the two sets of deceleration and trapping experiments revealed that the effects of magnetic fields up to 30 mT are negligible provided that a background dc electric field is maintained in the decelerator. A magnetic quadrupole trap of 30 mT depth corresponds to a He temperature of about 40 mK. The results thus represent an important step towards achieving high densities of cold paramagnetic samples following successive cycles of Rydberg–Stark deceleration, trapping, and radiative decay in overlaid electric and magnetic traps.
Theoretical model and analysis of an electromagnetic vibration energy harvester with nonlinear damping and stiffness based on 3D MEMS coils
Authors: Tao Zhi , Wu Hanxiao , Li Haiwang , Li Hanqing , Xu Tiantong , Sun Jiamian , Wang Wenbin
Published: July 2020

This paper presents a micro electromagnetic vibration energy harvester (VEH) that uses complementary metal-oxide-semiconductorcompatible 3D micro-electromechanical system coils and a ferromagnetic core to improve efficiency and output power. A systematic model is proposed to describe the nonlinear electromagnetic damping coefficient and nonlinear attraction between the magnet and the ferromagnetic core. The nonlinear model agrees well with the finite element calculation results. Then, a vibration model is established by considering nonlinear stiffness and damping coefficient to obtain the dynamic characteristics and output performance of the system. Furthermore, a numerical method is conducted to systematically investigate the influence of air gap and initial magnet offset under different excitation amplitudes. The simulation results indicate that with a smaller air gap, the output power is higher. Moreover, there is an optimal initial magnet offset in relation to the air gap to maximise the output power of the system. These conclusions and analysis models can be generalised and can be used as a guidance for the designs of similar structural devices. The results also show that the structure proposed in this study can significantly enhance the energy harvesting performance compared with published data of conventional VEHs.
Dynamics of the relativistic electron spin in an electromagnetic field
Authors: Mondal Ritwik , Oppeneer Peter M
Published: July 2020

A relativistic spin operator cannot be uniquely defined within relativistic quantum mechanics. Previously, different proper relativistic spin operators have been proposed, such as spin operators of the Foldy–Wouthuysen and Pryce type, that both commute with the free-particle Dirac Hamiltonian and represent constants of motion. Here we consider the dynamics of a relativistic electron spin in an external electromagnetic field. We use two different Hamiltonians to derive the corresponding spin dynamics. These two are: (a) the Dirac Hamiltonian in the presence of an external field, and (b) the semirelativistic expansion of the same. Considering the Foldy–Wouthuysen and Pryce spin operators we show that these lead to different spin dynamics in an external electromagnetic field, which offers possibilities to distinguish their action. We find that the dynamics of both spin operators involve spin-dependent and spin-independent terms, however, the Foldy–Wouthuysen spin dynamics additionally accounts for the relativistic particle-antiparticle coupling. We conclude that the Pryce spin operator provides a suitable description of the relativistic spin dynamics in a weak-to-intermediate external field, whereas the Foldy–Wouthuysen spin operator is more suitable in the strong field regime.
Stable and high-performance piezoelectric sensor via CVD grown WS2
Authors: Kim Junyoung , Lee Eunho , Mehta Gayatri , Choi Wonbong
Published: July 2020

Piezoelectric materials are widely used as electromechanical couples for a variety of sensors and actuators in nanoscale electronic devices. The majority of piezoelectric devices display lateral patterning of counter electrodes beside active materials such as two-dimensional transition metal dichalcogenides (2D TMDs). As a result, their piezoelectric output response is strongly dependent on the lattice orientation of the 2D TMD crystal structure, limiting their piezoelectric properties. To overcome this issue, we fabricated a vertical sandwich design of a piezoelectric sensor with a conformal contact to enhance the overall piezoelectric performance. In addition, we enhanced the piezoelectric properties of 2D WS2 by carrying out a unique solvent-vapor annealing process to produce a sulfur-deficient WS2(1-x) structure that yielded a 3-fold higher piezoelectric response voltage (96.74 mV) than did pristine WS2 to a 3 kPa compression. Our device was also found to be stable: it retained its piezoelectric performance even after a month in an ambient atmospheric condition. Our study has revealed a facile methodology for fabricating large-scale piezoelectric devices using an asymmetrically engineered 2D WS2 structure.
An inclined beam at rest on a ball or cylinder
Authors: Cross Rod
Published: July 2020

A well known physics problem is to calculate the friction forces required to support a ladder
against a wall. A more tractable problem is to calculate the friction forces needed to support
an inclined beam on a ball or a cylinder. In the latter case there are three rather than two
points of sliding support. Measurements and calculations are presented to show that a ball can
support an inclined beam without slipping, provided the incline angle is not too large.
Scaling laws for direct laser acceleration in a radiation-reaction dominated regime
Authors: Jirka M , Vranic M , Grismayer T , Silva L O
Published: July 2020

We study electron acceleration within a sub-critical plasma channel irradiated by an ultra-intense laser pulse (a
0 > 100 or I > 1022 W cm−2). In this regime, radiation reaction significantly alters the electron dynamics. This has an effect not only on the maximum attainable electron energy but also on the phase-matching process between betatron motion and electron oscillations in the laser field. Our study encompasses analytical description, test-particle calculations and two-dimensional particle-in-cell simulations. We show single-stage electron acceleration to multi-GeV energies within a 0.5 mm-long channel and provide guidelines how to obtain energies beyond 10 GeV using optimal initial configurations. We present the required conditions in a form of explicit analytical scaling laws that can be applied to plan the future electron acceleration experiments.
Oscillation of S5 helix under different temperatures in determination of the open probability of TRPV1 channel*
Authors: Li Tie , Li Jun-Wei , Pang Chun-Li , An Hailong , Geng Yi-Zhao , Wang Jing-Qin
Published: July 2020

Transient receptor potential vanilloid subtype 1 (TRPV1) is a polymodel sensory receptor and can be activated by moderate temperature (≥ 43 °C). Though extensive researches on the heat-activation mechanism revealed some key elements that participate in the heat-sensation pathway, the detailed thermal-gating mechanism of TRPV1 is still unclear. We investigate the heat-activation process of TRPV1 channel using the molecular dynamics simulation method at different temperatures. It is found that the favored state of the supposed upper gate of TRPV1 cannot form constriction to ion permeation. Oscillation of S5 helix originated from thermal fluctuation and forming/breaking of two key hydrogen bonds can transmit to S6 helix through the hydrophobic contact between S5 and S6 helix. We propose that this is the pathway from heat sensor of TRPV1 to the opening of the lower gate. The heat-activation mechanism of TRPV1 presented in this work can help further functional study of TRPV1 channel.
Flattening is flattering: The revolutionizing 2D electronic systems*
Authors: Dong Baojuan , Yang Teng , Han Zheng
Published: July 2020

Two-dimensional (2D) crystals are known to have no bulk but only surfaces and edges, thus leading to unprecedented properties thanks to the quantum confinements. For half a century, the compression of z-dimension has been attempted through ultra-thin films by such as molecular beam epitaxy. However, the revisiting of thin films becomes popular again, in another fashion of the isolation of freestanding 2D layers out of van der Waals (vdW) bulk compounds. To date, nearly two decades after the nativity of the great graphene venture, researchers are still fascinated about flattening, into the atomic limit, all kinds of crystals, whether or not they are vdW. In this introductive review, we will summarize some recent experimental progresses on 2D electronic systems, and briefly discuss their revolutionizing capabilities for the implementation of future nanostructures and nanoelectronics.
Acetone sensors for non-invasive diagnosis of diabetes based on metal–oxide–semiconductor materials
Authors: Li Yujie , Zhang Min , Zhang Haiming
Published: July 2020

In recent years, clinical studies have found that acetone concentration in exhaled breath can be taken as a characteristic marker of diabetes. Metal–oxide–semiconductor (MOS) materials are widely used in acetone gas sensors due to their low cost, high sensitivity, fast response/recovery time, and easy integration. This paper reviews recent progress in acetone sensors based on MOS materials for diabetes diagnosis. The methods of improving the performance of acetone sensor have been explored for comparison, especially in high humidity conditions. We summarize the current excellent methods of preparations of sensors based on MOSs and hope to provide some help for the progress of acetone sensors in the diagnosis of diabetes.