bluuebunny/crossref_metadata_2025 huggingface dataset:
Eine Frage der Zeit und Dosierung – intraarterielle Chemotherapie beim Oropharynxkarzinom
Authors: Aigner Karl Reinhard , Selak Emir , Gailhofer Sabine , Aigner Kornelia
Published: October 2020

Einleitung Patienten mit Kopf-Hals-Tumoren erreichen durch die Standardtherapie gute Ansprechraten. Die Lebensqualität ist aber unter Radiochemotherapie oft sehr beeinträchtigt und Hauptgrund der hohen Suizidrate. In dieser Studie wird über die Behandlung von fortgeschrittenen Oropharynxkarzinomen des Stadiums IV mit intraarterieller Kurzzeit-Chemotherapie berichtet.

Methoden 55 Patienten mit progredienten, inzwischen inoperablen Oropharynxkarzinomen des Stadiums IVA (n = 44), IVB (n = 4) und IVC (n = 7) wurden mit intraarterieller Kurzzeit-Chemotherapie (IAC) behandelt. Die IAC wurde niedrigdosiert entweder über einen Angiokatheter oder einen implantierten intraarteriellen Portkatheter über einen Zeitraum von 7–12 Minuten infundiert. Ausgeprägte Tumormassen, eine hohe Anzahl an metastasierten Lymphknoten oder Lungenmetastasen wurden mit zusätzlicher isolierter Thoraxperfusion behandelt.

Ergebnis Unterschiedliche Überlebenszeiten wurden erreicht, je nach Vorbehandlung der Patienten. Die 1-, 2- und 3-Jahres-Überlebensraten lagen bei 76 %, 54 % und 35 % für nicht vorbestrahlte Tumoren und bei 40 %, 7 % und 7 % für vorbestrahlte Tumoren. Besonders gute Überlebenszeiten hatte die Untergruppe der zuvor behandelten, aber nicht bestrahlten Patienten mit Rezidiven (n = 8), welche eine mediane Überlebenszeit von 33,5 Monaten erreichten. Demgegenüber betrug die mediane Überlebenszeit der Patienten mit bestrahlten und rezidivierten Tumoren 8,2 Monate. Tracheostomien und Ernährungssonden wurden in allen Fällen vermieden.

Diskussion Randomisierte klinische Studien sind nötig, um die Ergebnisse zu belegen. Die Gabe von kleinen Dosierungen in das begrenzte Volumen der Tumorregion erzeugt hohe Konzentrationen am Wirkort und damit eine verstärkte Wirkung.
Iron-Catalyzed Tandem Radical Addition/Cyclization: Highly Efficient Access to Methylated Quinoline-2,4-diones
Authors: Liu Ji-Kai , Sun Huan , Jiang Yue , Lu Ming-Kun , Li Yun-Yun , Li Li
Published: October 2020

A visible-light-induced and iron-catalyzed oxidative radical addition/cyclization cascade reaction of N-(o-cyanoaryl)acrylamides with dimethyl sulfoxide has been developed. The method exhibits a wide substrate scope and an excellent functional-group tolerance, thus providing an efficient and convenient access to a variety of methylated quinoline-2,4-diones.
An Acute Spinal Intradural Hematoma after an Extraforaminal Wiltse Approach: A Case Report and Review of the Literature
Authors: Raymaekers Vincent , Beck Tobias , Goebel Svenja , Janssens Femke , Van den Branden Lien , Menovsky Tomas , Plazier Mark
Published: October 2020

A nontraumatic spontaneous spinal acute subdural hematoma (sSDH) is a rare complication after spinal surgery. Although an sSDH is often associated with anticoagulation therapy, vascular malformations, or lumbar puncture, the pathogenesis of nontraumatic spontaneous sSDH remains unclear. We present the case of an intradural hematoma after an extraforaminal surgery through the Wiltse approach for an extraforaminal disk herniation at L5/S1. This 58-year-old woman experienced hypoesthesia and progressive motor dysfunction in the left leg several hours postoperation. Urgent magnetic resonance imaging revealed an intradural hematoma at the L1/L2 to L2/L3 level in the ventral dural sac proximal to the surgical level. Surgical decompression was performed. There was no evidence of trauma, coagulopathy, or anticoagulation therapy. To our knowledge, this case is the first to report an acute sSDH proximal to the surgery level after an extraforaminal spinal surgery through the Wiltse approach for an extraforaminal disk herniation. It illustrates that attentive postoperative neurologic monitoring, even in the absence of intraoperative irregularities, remains important to diagnose and treat this complication at the early stage.
A Case Series of Penile Skin Grafting in Children
Authors: Qiu Lin , Zhang Xuan , Liu Yan , Fu Yuexian , Yuan Xingang
Published: October 2020

Pediatric penile skin grafting is rarely performed. We present a case series of four pediatric patients receiving skin grafting due to the loss of penile skin. The four boys were followed up for 1 to 5 years. One full-thickness skin graft and three split-thickness skin grafts (STSGs) survived well with low Vancouver scar scale scores. One boy gradually developed lymphedema of the distal foreskin and underwent a second preputioplasty. He presented with normal erectile function and did not experience any pain. We propose thick STSGs as the most appropriate choice for pediatric penile skin reconstruction. Lymphedema of the foreskin is an important long-term complication of penile skin grafting.
Convalescent Plasma Therapy for COVID-19: Current Status and Future Directions
Authors: Seshan Jayanth , Dube Surya K. , Rajagopalan Vanitha , Panda Pragyan S. , Rath Girija P.
Published: October 2020

The ongoing pandemic of coronavirus disease 2019 (COVID-19) has triggered a global health crisis probably due to a lack of a reliable cure till date. Several clinical trials are ongoing, but initial results have not been overly promising. Convalescent plasma (CP), which refers to plasma collected from individuals recovered from an illness and developed antibodies against the pathogen, is also being proposed as a therapeutic option for COVID-19 treatment in severe cases to achieve short-term immunity against the virus. Use of CP is not new, and it has been used in various outbreaks over the past century, ranging from the Spanish influenza outbreak in 1918 to the recent Middle East respiratory syndrome (MERS). However, data available on its use in COVID-19 patients is limited. Use of CP so far is restricted to a “rescue therapy” and needs further trials to assess its possible use in other situations (prevention, postexposure prophylaxis) and patient populations (considering age and comorbid illnesses). In this review, we will try to summarize the current status of use of CP for COVID-19 and ongoing trials in India and elsewhere and will discuss the possible avenues for its use in future.
COVID-19 Perceptional Disparity Among Dental Healthcare Personnel at King Faisal University: Applying Health Belief Model
Authors: Nasir Elwalid Fadul , Elhag Ahmed Khalid , Almahdi Hatim Mohammed
Published: October 2020

Objectives In Saudi Arabia, more than 100, 000 cases of COVID-19 have been reported, and more than 4,000 in Al Hofuf to date. Dental healthcare personnel are at a higher risk of COVID-19 due to their exposure to saliva, blood, and aerosol/droplet during their daily practice. Their perceptions of COVID-19 drive their behaviors.

Materials and Methods A cross-sectional online survey to assess COVID-19 related perceptions and possible disparities between them.

Statistical analysis Data were analyzed using the Statistical Package for the Social Science, version 23 (IBM SPSS). Descriptive analyses were performed using frequencies and percentages for categorical variables, mean and (± SD) for numerical variables. Bivariate analyses were assessed using t-test and one-way ANOVA, with a 95% confidence interval (CI).

Results With a response of 75% (150), results showed that there were perceptional disparities: students and technical staff perceived more barriers to preventive measures compared to faculties with a mean difference of (−0.145 SD ± 0.580, p = 0.802, CI −1.29 / 1.00 and −2.433, SD ± 0.94, p = 0.010), respectively. This was also shown in threat perception with a mean difference of (2.525, SE ± 0.917, CI 0.71/4.34, p = 0. 0.007). Students perceived more threat than clerks did with a mean difference of (1.281, SE ± 0.569, CI − 0.16 / 2.41, p = 0.026), while clerks perceived less threat than the technical staff with a mean difference of (−2.790, SE ± 0.860, CI −4.49 /−1.09, p = 0.001).

Conclusions There was a clear disparity in the perceptions among the different categories of participants. More emphasis on the training and preparedness of the dental healthcare personnel is required.
Laparoscopic Partial Splenectomy Assisted by Fluorescence in a 13-Year-Old Girl
Authors: Bada-Bosch Isabel , Mata David Peláez , de la Torre Manuel , Ordóñez Javier , Blanco María Dolores , de Agustin Juan
Published: October 2020

Partial splenectomy allows preserving immune function in benign splenic lesions such as epidermoid cysts. Determining the plane of resection and perfusion of the spleen remnant can be difficult, especially in centrally located lesions. We present a 13-year-old girl with a symptomatic splenic cyst of 6 cm in diameter located next to the splenic hilum. Laparoscopic partial splenectomy was performed through a 10-mm umbilical approach and three accessory 5-mm ports. Intraoperative intravenous injection of indocyanine green (ICG) at 0.2 mg/kg guided the careful dissection of the splenic hilum and checked the spleen perfusion once the upper arterial branch was clamped. The subsequent wash-out of the ICG allowed inspection of the peripheral vascular return of the splenic remnant through polar veins. Surgery was uneventful with minimal blood loss. Follow-up ultrasound scan revealed a well-perfused small splenic remnant with no signs of recurrence.

Laparoscopic partial splenectomy is feasible in benign splenic tumors, especially in those cases of peripheral location. Fluorescence facilitates the safe dissection of the splenic hilum, the visualization of the transection plane of the spleen and the perfusion of the remnant in cases of anatomically and technically complicated partial splenectomies.
Experience and Technique for Zenker's Diverticulum Per Oral Endoscopic Myotomy: Z-POEM
Authors: Podgaetz Eitan , Konda Vani
Published: October 2020

Objective With the advent of minimally invasive surgery, incisionless surgery, and third-space endoscopy, the treatment for Zenker's diverticulum has also moved toward less invasive techniques

Methods New incisionless per oral techniques can be applied for cricopharyngeal myotomy in Zenker's diverticulum.

Results Five patients underwent Zenker's diverticulum per oral endoscopic myotomy (Z-POEM) without complications, minimal discomfort, and narcotic consumption, with complete resolution of their symptoms by history and Eckardt scores.

Conclusions Z-POEM is performed entirely endoscopically with very little associated pain or complication rates, with short-term follow-up having excellent functional and symptomatic results.
Presenting Characteristics, Treatment Patterns, and Outcomes among Patients with Venous Thromboembolism during Hospitalization for COVID-19
Authors: Fernández-Capitán Carmen , Barba Raquel , Díaz-Pedroche María del Carmen , Sigüenza Patricia , Demelo-Rodriguez Pablo , Siniscalchi Carmine , Pedrajas José María , Farfán-Sedano Ana I. , Olivera Pavel Eduardo , Gómez-Cuervo Covadonga , Llamas Pilar , Villares Paula , Sanchez Olivier , López-Reyes Raquel , Catella Judith , Bikdeli Behnood , Weinberg Ido , Tafur Alfonso J. , Jiménez David , Monreal Manuel
Published: October 2020

Venous thromboembolism (VTE) is common in patients with coronavirus disease-2019 (COVID-19). However, limited data exist on patient characteristics, treatments, and outcomes. To describe the clinical characteristics, treatment patterns, and short-term outcomes of patients diagnosed with VTE during hospitalization for COVID-19. This is a prospective multinational study of patients with incident VTE during the course of hospitalization for COVID-19. Data were obtained from the Registro Informatizado de la Enfermedad TromboEmbólica (RIETE) registry. All-cause mortality, VTE recurrences, and major bleeding during the first 10 days were separately investigated for patients in hospital wards versus those in intensive care units (ICUs). As of May 03, 2020, a total number of 455 patients were diagnosed with VTE (83% pulmonary embolism, 17% isolated deep vein thrombosis) during their hospital stay; 71% were male, the median age was 65 (interquartile range, 55–74) years. Most patients (68%) were hospitalized in medical wards, and 145 in ICUs. Three hundred and seventeen (88%; 95% confidence interval [CI]: 84–91%) patients were receiving thromboprophylaxis at the time of VTE diagnosis. Most patients (88%) received therapeutic low-molecular-weight heparin, and 15 (3.6%) received reperfusion therapies. Among 420 patients with complete 10-day follow-up, 51 (12%; 95% CI: 9.3–15%) died, no patient recurred, and 12 (2.9%; 95% CI: 1.6–4.8%) experienced major bleeding. The 10-day mortality rate was 9.1% (95% CI: 6.1–13%) among patients in hospital wards and 19% (95% CI: 13–26%) among those in ICUs. This study provides characteristics and early outcomes of patients diagnosed with acute VTE during hospitalization for COVID-19. Additional studies are needed to identify the optimal strategies to prevent VTE and to mitigate adverse outcomes associated.
Burned Ear Reconstruction Using the Combination of an Expanded Postauricular Scar Skin Flap and a Postauricular Fascial Flap
Authors: Guo Peipei , Pan Bo , Jiang Haiyue , Yang Qinghua , Lin Lin
Published: October 2020

The external ear is highly vulnerable to burn injury due to its location and thin integument. Reconstruction of the external ear after burns is a major challenge to undertake, and surgeons face many problems, including excessive scar tissue, poor blood supply, a paucity of available skin, and a high infection rate, when designing an operative plan for patients with postburn auricular deformity. In this article, the authors describe their experience of using an expanded postauricular scar flap combined with a postauricular fascial flap as the coverage for the framework for subtotal and total ear reconstruction in 27 burned patients. Four patients developed expander exposure and two developed framework exposure, which were resolved with good results after further repair. After an average follow-up time of 6 months, all of the patients experienced very good cosmetic outcomes, high satisfaction, and low morbidity.
Polymerase chain reaction thermal cycling using the programmed tilt displacements of capillary tubes
Authors: Abid Hassan Ali , Lin Eric Shen , Ong Jian Wern , Minifie Tristan , Song Zhixiong , Liew Oi Wah , Ng Tuck Wah
Published: October 2020

A thermal cycling method, whereby capillary tubes holding polymerase chain reactions are subjected to programmed tilt displacements so that they are moved using gravity over three spatial regions (I, II, and III) kept at different constant temperatures to facilitate deoxyribonucleic acid (DNA) denaturation, annealing, and extension, is described. At tilt speeds in excess of 0.2 rad/s, the standard deviation of static coefficient of friction values was below 0.03, indicating in sync movement of multiple capillary tubes over the holding platform. The travel time during the acceleration phase and under constant velocity between adjacent regions (I to II and II to III) and distant regions (III to I) was 0.03 s and 0.31 s, respectively. The deviations in temperature did not exceed 0.05 °C from the average at the prescribed denaturing, annealing, and extension temperatures applied. DNA amplification was determined by optical readings, the fluorescence signal was found to increase twofold after 30 thermal cycles, and 1.16 × 106 DNA copies/μl could be detected. The approach also overcomes problems associated with thermal inertia, sample adhesion, sample blockage, and handling of the reaction vessels encountered in the other thermal cycling schemes used.
Collective Thomson scattering in non-equilibrium laser produced two-stream plasmas
Authors: Sakai K. , Isayama S. , Bolouki N. , Habibi M. S. , Liu Y. L. , Hsieh Y. H. , Chu H. H. , Wang J. , Chen S. H. , Morita T. , Tomita K. , Yamazaki R. , Sakawa Y. , Matsukiyo S. , Kuramitsu Y.
Published: October 2020

We investigate collective Thomson scattering (CTS) in two-stream non-equilibrium plasmas analytically, numerically, and experimentally. In laboratory astrophysics, CTS is a unique tool to obtain local plasma diagnostics. While the standard CTS theory assumes plasmas to be linear, stationary, isotropic, and equilibrium, they are often nonlinear, non-stationary, anisotropic, and non-equilibrium in high energy phenomena relevant to laboratory astrophysics. We theoretically calculate and numerically simulate the CTS spectra in two-stream plasmas as a typical example of a non-equilibrium system in space and astrophysical plasmas. The simulation results show the feasibility to diagnose two-stream instability directly via CTS measurements. To confirm the non-equilibrium CTS analysis, we have developed an experimental system with a high repetition rate tabletop laser for laboratory astrophysics.
Comment on “Quantum time and spatial localization: An analysis of the Hegerfeldt paradox” [J. Math. Phys. 41, 6093 (2000)]
Authors: Taillebois E. R. F. , Avelar A. T.
Published: October 2020

Von Zuben [J. Math. Phys. 41, 6093 (2000)] proposed a resolution to spatial localization problems related to Hegerfeldt’s paradox. To do so, he applied Dirac’s formalism to a free spinless massive particle to introduce a new perspective in which this paradox could be interpreted as an apparent phenomenon. However, although being a physically interesting proposal, here we show that its main result was obtained using an incomplete basis for the physical Hilbert space, the correction of which invalidates the proposed resolution.
Wireless differential resonance frequency pressure sensor: Circuital model and prototype validation
Authors: Achury-Florian Alvaro , Ramirez Fernando , Unigarro-Calpa Edgar , Ramon Eloi , Segura-Quijano Fredy E. , Arciniegas Alejandro
Published: October 2020

This article presents a pressure sensor composed of a set of three Archimedean spiral inductors. One of them is below the other two concentric spirals, where the upper coils are over a flexible membrane. When external pressure is applied over the sensor, the membrane deforms and changes the distance between the lower spirals and the upper inside coil, the capacitance, and its resonance frequency. However, once the sensor is in contact with a conductive medium, a change in the effective permittivity surrounding the sensor takes place reshaping the resonant frequencies. To improve the sensor response, we introduce a reader resonator sensor system. We present the comparative response of the system as a prototype, an analytical model, and a finite element model (FEM). The prototype system is fabricated using a photolithographic process for the elements of the sensor over a polymethylsiloxane and glass substrate, while the reader is fabricated over a FR4 substrate. COMSOL Multiphysics is used for the FEM simulation of the system to evaluate its behavior. The analytical model involves the integration of techniques to obtain the effective permittivity for each element plane and a coupled magnetic resonance to represent the interaction of the parts. We obtain a correspondence between the resonances of the different elements, with a maximum displacement frequency of 240 MHz for the proposed model, and 80 MHz in the FEM case related to the implemented prototype. The accuracy of this model allows a fast analysis to improve the design of this type of topology without high computational processing.
Amplitude-modulated resonant accelerometer employing parametric pump
Authors: Zhang Hemin , Chen Dongyang , Pandit Milind , Sun Jiangkun , Zhao Chun , Seshia Ashwin
Published: October 2020

This paper demonstrates a resonant accelerometer employing weakly coupled resonators for inertial force transduction. An ultra-low virtual mode coupling is established by employing the parametric pump in the coupled resonators to enhance the parametric sensitivity. This paper proposes that the amplitude of the driven resonator can be used for monitoring the input acceleration in a limited linear range around the veering point. In addition to the high-sensitivity improvement, the measurement complexity is also considerably reduced compared to the previous amplitude ratio readout sensors. The sensitivity is adjustable by changing the parametric pumping amplitude. The experimental results show that the noise power spectral density is ∼230 ng/√Hz, which is the best reported noise floor for resonant accelerometers based on weakly coupled resonators.
Multiband enhanced second-harmonic generation via plasmon hybridization
Authors: Shen Shaoxin , Yang Weimin , Shan Jiejie , Sun Guoya , Shih Tien-Mo , Zhou Yongliang , Yang Zhilin
Published: October 2020

Boosting nonlinear frequency-conversion efficiencies in hybrid metal–dielectric nanostructures generally requires the enhancement of optical fields that interact constructively with nonlinear dielectrics. Inevitably for localized surface plasmons, spectra subject to this enhancement tend to span narrowly. As a result, because of the spectral mismatch of resonant modes at frequencies participating in nonlinear optical processes, strong nonlinear signal generations endure the disadvantage of rapid degradations. Here, we experimentally design a multiband enhanced second-harmonic generation platform of three-dimensional metal–dielectric-metal nanocavities that consist of thin ZnO films integrated with silver mushroom arrays. Varying geometric parameters, we demonstrate that the introduction of ZnO materials in intracavity regions enables us to modulate fundamental-frequency-related resonant modes, resulting in strong coupling induced plasmon hybridization between localized and propagating surface plasmons. Meanwhile, ZnO materials can also serve as an efficient nonlinear dielectric, which provides a potential to obtain a well-defined coherent interplay between hybridized resonant modes and nonlinear susceptibilities of dielectric materials at multi-frequency. Finally, not only is the conversion efficiency of ZnO materials increased by almost two orders of magnitude with respect to hybrid un-pattered systems at several wavelengths over a 100-nm spectral range but also a hybrid plasmon-light coupling scheme in three-dimensional nanostructures can be developed.
Design of a compact short pulse positron source based on laser plasma accelerators
Authors: Xie C. Z. , Xiao C. F. , Xu Z. Y. , Liu J. X. , Gong Z. , Lu H. G. , Huang S. L. , Chen M. , Xu T. Q. , Wang K. D. , Yan X. Q. , Lu H. Y.
Published: October 2020

Compact short pulse positron source in the energy range of a few tens of MeV driven by laser plasma accelerator is a promising tool for many applications, such as materials science and source of colliders. A collection and transmission system based on laser plasma accelerators is proposed to intensify and narrow the beam divergence for positrons generated from converters. The system is composed of a converter, a collimator, a solenoid, quadrupoles, and a slit in the exit. Numerical simulations were performed to demonstrate the feasibility and robustness of the design. The designed system can work in the center energy range from 15 to 40 MeV within ±10% energy spread (FWHM) and greatly improve the quality of collected positron beams with a divergence of around 50 mrad.
Kinetics and free energy of ligand dissociation using weighted ensemble milestoning
Authors: Ray Dhiman , Gokey Trevor , Mobley David L. , Andricioaei Ioan
Published: October 2020

We consider the recently developed weighted ensemble milestoning (WEM) scheme [D. Ray and I. Andricioaei, J. Chem. Phys. 152, 234114 (2020)] and test its capability of simulating ligand–receptor dissociation dynamics. We performed WEM simulations on the following host–guest systems: Na+/Cl− ion pair and 4-hydroxy-2-butanone ligand with FK506 binding protein. As a proof of principle, we show that the WEM formalism reproduces the Na+/Cl− ion pair dissociation timescale and the free energy profile obtained from long conventional MD simulation. To increase the accuracy of WEM calculations applied to kinetics and thermodynamics in protein–ligand binding, we introduced a modified WEM scheme called weighted ensemble milestoning with restraint release (WEM-RR), which can increase the number of starting points per milestone without adding additional computational cost. WEM-RR calculations obtained a ligand residence time and binding free energy in agreement with experimental and previous computational results. Moreover, using the milestoning framework, the binding time and rate constants, dissociation constants, and committor probabilities could also be calculated at a low computational cost. We also present an analytical approach for estimating the association rate constant (kon) when binding is primarily diffusion driven. We show that the WEM method can efficiently calculate multiple experimental observables describing ligand–receptor binding/unbinding and is a promising candidate for computer-aided inhibitor design.
Velocity and mass density of the ejecta produced from sinusoidal grooves in laser shock-loaded tin
Authors: Prudhomme G. , de Rességuier T. , Roland C. , Sollier A. , Lescoute E. , Loison D. , Brambrink E.
Published: October 2020

When a shock wave of several tens of GPa breaks out at a free surface, a material is ejected ahead of this surface. The amount and velocity of such ejecta depend on the breakout pressure, state of the released material (solid, liquid, or mixed), whether the shockwave is supported or unsupported, and the initial geometrical perturbation (or roughness) of the free surface. If surface defects consist of small grooves, pits, or scratches, material ejection occurs in the form of jets breaking up into tiny particles (so-called microjetting), with jet tip velocities up to several times higher than the free surface velocity. The laser-based experiments presented in this paper focus on microjetting in shock-melted tin with periodic surface perturbations. Several complementary diagnostics are combined to measure the velocity and mass of ejecta during the early stages of the jetting process. One relevant advancement is the use of ps-laser x-ray radiography to probe the density of the ejecta in distinct jets a few tens of μm-wide. The effects of the depth and wavelength of the initial perturbation are investigated in both linear and near-linear growth regimes. The results are compared with predictions derived from the Richtmyer–Meshkov Instability theory.
Tailoring impact debris dispersion using intact or fragmented thermite projectiles
Authors: Ryan Bratton K. , Hill Kevin J. , Woodruff Connor , Cagle Colton , Pantoya Michelle L. , Abraham Joseph , Wei Liang , Dube Pascal
Published: October 2020

A high-velocity impact-ignition testing system was used to study the dynamic response of brittle thermite projectiles impacting an inert steel target at velocities of 850 and 1200 m/s. The projectiles included consolidated aluminum and bismuth trioxide that were launched by a propellant driven gun into a catch chamber equipped with high-speed imaging diagnostics. The projectiles passed through a break-screen at the entrance to the chamber and either fragmented upon penetrating the break-screen or remained intact prior to impacting the steel target. In all cases, the projectiles pulverized upon impact, and a reacting debris cloud spreads through the catch chamber. At lower impact velocities, the fragmented and intact projectiles produced similar flame spreading rates of 217–255 m/s. At higher impact velocities, the intact projectile produced the slowest average flame spreading rate of 179 m/s because debris rebounding was limited by the length of the projectile and the resulting debris field was highly consolidated in the radial direction. In contrast, the fragmented projectile rebounded into a well dispersed debris cloud with the highest, 353 m/s, flame spreading rate. A kinetic energy flux threshold was proposed as a means for describing the shift in observed debris dispersion and flame spreading rates. A reactivity model was developed based on particle burn times using a computational fluid dynamics code that incorporated heat transfer and particle combustion in a multiphase environment to understand how the particle size influenced flame spreading. Results from the model show a trade-off between faster reactivity and increased drag inhibiting movement for smaller particle debris.
Stochastic scattering theory for excitation-induced dephasing: Comparison to the Anderson–Kubo lineshape
Authors: Li Hao , Srimath Kandada Ajay Ram , Silva Carlos , Bittner Eric R.
Published: October 2020

In this paper, we present a quantum stochastic model for spectroscopic lineshapes in the presence of a co-evolving and non-stationary background population of excitations. Starting from a field theory description for interacting bosonic excitons, we derive a reduced model whereby optical excitons are coupled to an incoherent background via scattering as mediated by their screened Coulomb coupling. The Heisenberg equations of motion for the optical excitons are then driven by an auxiliary stochastic population variable, which we take to be the solution of an Ornstein–Uhlenbeck process. Itô’s lemma then allows us to easily construct and evaluate correlation functions and response functions. Focusing on the linear response, we compare our model to the classic Anderson–Kubo model. While similar in motivation, there are differences in the predicted lineshapes, notably in terms of asymmetry, and variation with the increasing background population.
Accelerating the evaluation of inspiral–merger–ringdown waveforms with adapted grids
Authors: García-Quirós Cecilio , Husa Sascha , Mateu-Lucena Maite , Borchers Angela
Published: October 2020

This paper presents an algorithm to accelerate the evaluation of inspiral–merger–ringdown waveform models for gravitational wave data analysis. While the idea can also be applied in the time domain, here we focus on the frequency domain, which is most typically used to reduce computational cost in gravitational wave data analysis. Our work extends the idea of multibanding Vinciguerra S et al (2017 Class. Quantum Grav.
34 115006), which has been developed to accelerate frequency domain waveforms, to include the merger and ringdown and spherical harmonics beyond the dominant quadrupole spherical harmonic. The original method of Vinciguerra S et al (2017 Class. Quantum Grav.
34 115006) is based on a heuristic algorithm based on the inspiral to de-refine the equi-spaced frequency grid used for data analysis where a coarser grid is sufficient for accurate evaluation of a waveform model. Here we use a different criterion, based on the local interpolation error, which is more flexible and can easily be adapted to general waveforms, if their phenomenology is understood. We discuss our implementation in the LIGO Algorithms Library (The LIGO Scientific Collaboration 2015 https://lsc-group.phys.uwm.edu/daswg/projects/lalsuite.html) for the IMRPhenomXHM García Quirós C et al (2020 arXiv:2001.10914) frequency domain model, and report the acceleration in different parts of the parameter space of compact binary systems.
On the radiation gauge for spin-1 perturbations in Kerr–Newman spacetime
Authors: Hollands Stefan , Toomani Vahid
Published: October 2020

We extend previous work (2020 Class. Quantum Grav.
37 075001) to the case of Maxwell’s equations with a source. Our work shows how to construct a vector potential for the Maxwell field on the Kerr–Newman background in a radiation gauge. The vector potential has a ‘reconstructed’ term obtained from a Hertz potential solving Teukolsky’s equation with a source, and a ‘correction’ term which is obtainable by a simple integration along outgoing principal null rays. The singularity structure of our vector potential is discussed in the case of a point particle source.
Chandrasekhar-like transformations for electromagnetic and scalar waves in Schwarzschild spacetime
Authors: Nakajima Hiroaki , Lin Wenbin
Published: October 2020

In this note we present the Chandrasekhar-like transformations for the electromagnetic waves and the scalar waves in Schwarzschild spacetime, which are simpler than those known before.
Simulating waves and macroscopic phonons
Authors: Girwidz R V
Published: October 2020

Wave phenomena are fundamental for many branches of physics, not only for mechanics. Thus, students at university level should become familiar with the underlying theory, and especially with solutions of the wave equation. This paper refers to a multimedia program for PCs, tablets or smartphones, and introduces and discusses several animated illustrations. The introduced program can illustrate the power of the wave equation. Basic wave phenomena can be computed with numerical methods. The finite difference method which is used can be lead back to fundamental assumptions of physics. Yet, this numerical method is capable of calculating a great variety of wave phenomena. Several examples can demonstrate the power of this numerical procedure. Phenomena like the propagation of circular waves diverging from a point source, Huygens’s elementary waves, superposition of waves, reflexion, refraction and transmission at the interface between different media, scattering, interference phenomena, as well as dispersion and the Doppler effect can be studied in animated visualisations. This opens up a variety of teaching and learning strategies, e.g. the single concept principle and the inverted classroom concept, and the modelling of partial differential equations (the wave equation as well as the heat equation) can be supported. The conceptual approach is described here; an empirical study about learning will be a next step.
Identification and thermal stability of point defects in neutron-irradiated hexagonal boron nitride (h-BN)
Authors: Toledo J R , Krambrock K
Published: October 2020

Point defects in wide-bandgap semiconductors, such as hexagonal boron nitride (h-BN), have driven enormous amounts of research due to their interesting optical properties such as quantum emission at room temperature. Defect engineering by particle irradiation is a very interesting strategy for producing quantum emitters in a controlled way. The identification of most point defects is done by electron paramagnetic resonance and related advanced techniques. Following our recent works, we present new data about point defects produced by neutron irradiation at room temperature and investigate their thermal stability in crystalline, flake and ultrafine h-BN powder. Our experimental data indicate the formation of the nitrogen antisite defect next to a nitrogen vacancy in its neutral charge state, (NBVN)0, with spin S= 1/2 in all types of h-BN showing strong axial hyperfine interaction (A
|| ≈ 95 MHz and A
⊥ ≈ 5 MHz). It is thermally stable up to ~600 ºC, which is similar to the disappearance of the negative charged boron vacancy,

V

B

−

. In addition, after neutron irradiation of h-BN powder samples, a spin S= 1/2 point defect is observed presenting an axial superhyperfine interaction with two equivalent nitrogen nuclei (14N, I = 1, 99.68%), which we tentatively assign to the CNVB defect. It is thermally stable up to ~850 ºC. Another, yet-unidentified S = 1/2 center acts as a charge compensating defect at specific annealing temperatures. Our experimental results are compared and discussed with theoretical models available in the literature.
Assisted laser impedance spectroscopy to probe breast cancer cells
Authors: Mesa F , Paez-Sierra B A , Romero A , Botero P , Ramírez-Clavijo S
Published: October 2020

Confidence and integrity are critical in the physical and chemical analyses of tissues and living cells. However, many of the probes targeting biological markers for confocal spectroscopy affect cells’ molecular identity. Hence, we combined photonics with electrical analysis in an assisted laser impedance spectroscopy facility and applied it to characterize two breast cancer cell lines (BT-474 and MCF-7) and lymphocytes (as a normal control). The setup comprised a sample holder with a ∼15 000 cell capacity fitted with two isolated conducting electrodes arranged concentrically and connected to an impedance analyser with a 20 Hz–1 MHz sweeping frequency. Capacitive transconductance measurements showed bands at 3491, 3494 and 3470 Hz corresponding to the BT-474, MCF-7, and lymphocytes, respectively. Under photonic stimulation by a 532 nm laser, these dark reference bands shifted to 3518, 3566 and 3674 Hz, respectively, reflecting optical transitions favouring ionic transport in the cells. Based on the experimental Nyquist diagrams and taking into account the roughness nature of the cell membrane, a constant phase element (CPE) was introduced in the circuit. The CPE was explained through a fractional parameter, α, based on fractional calculus. Results showed that, under photonic stimulation, α is less than ½, and the minimum change of series and membrane resistances are about 28.95% and 58.88%, respectively.
Partitioning interatomic force constants for first-principles phonon calculations: applications to NaCl, PbTiO3, monolayer CrI3, and twisted bilayer graphene
Authors: Lee Chi-Cheng , Hsu Chin-En , Hsueh Hung-Chung
Published: October 2020

First-principles phonon calculations have been widely performed for studying vibrational properties of condensed matter, where the dynamical matrix is commonly constructed via supercell force-constant calculations or the linear response approach. With different manners, a supercell can be introduced in both methods. Unless the supercell is large enough, the interpolated phonon property highly depends on the shape and size of the supercell and the imposed periodicity could give unphysical results that can be easily overlooked. Along this line, we discuss how a traditional method can be used to partition the force constants at the supercell boundary and then propose a more flexible method based on the translational symmetry and interatomic distances. The partition method is also compatible with the mixed-space approach for describing LO–TO splitting. We have applied the proposed partition method to NaCl, PbTiO3, monolayer CrI3, and twisted bilayer graphene, where we show how the method can deliver reasonable results. The proper partition is especially important for studying moderate-size systems with low symmetry, such as two-dimensional materials on substrates, and useful for the implementation of phonon calculations in first-principles packages using atomic basis functions, where symmetry operations are usually not applied owing to the suitability for large-scale calculations.
The effects of sub-bandgap transitions and the defect density of states on the photocurrent response of a single ZnO-coated silica nanospring
Authors: Wojcik Peter M , Bastatas Lyndon D , Rajabi Negar , Bakharev Pavel V , McIlroy David N
Published: October 2020

The electrical and optoelectronic properties of nanometer-sized ZnO structures are highly influenced by its native point defects. Understanding and controlling these defects are essential for the development of high-performance ZnO-based devices. Here, an electrical device consisting of a polycrystalline ZnO-coated silica nanospring was fabricated and used to characterize the electrical and photoconductive properties of the ZnO layer using near-UV (405 nm) and sub-bandgap (532 and 633 nm) excitation sources. We observe a photocurrent response with all three wavelengths and notably with 532 nm green illumination, which is the energy associated with deep oxygen vacancies. The polycrystalline ZnO-coated silica nanospring exhibits a high responsivity of 1740 A W−1 with the 405 nm excitation source. Physical models are presented to describe the photocurrent rise and decay behavior of each excitation source where we suggest that the rise and decay characteristics are highly dependent on the energy of the excitation source and the trapping of electrons and holes in intermediate defect levels in the bandgap. The energy levels of the trap depths were determined from the photoconductive decay data and are matched to the reported energy levels of singly and doubly ionized oxygen vacancies. A phenomenological model to describe the dependence of the saturation photocurrent on excitation intensity is presented in order to understand the characteristics of the observed breaks in the slopes of the saturation photocurrent versus excitation intensity profile.
Graphene-facilitated synthesized vertically aligned hexagonal boron nitride nanowalls and their gas adsorption properties
Authors: Sun Xiaoyan , Li Dongdong , Gao Wei , Yin Hong
Published: October 2020

The capability of hexagonal boron nitride (h-BN) to adsorb gas atoms may stimulate various promising applications in environment remediation and energy storage, while the interactivity with gas molecules yet remains challenging due to its inherent chemical inertness. In this article, we report a feasible and effective route for the scalable synthesis of vertically aligned h-BN nanowalls assisted by reduced graphene oxide (rGO) without metallic catalysts. The average thickness of the fine h-BN nanowalls is few-atomic layers about 3.7 nm, that grow on the large substrate-like flakes transformed from the pristine rGO. The hierarchical h-BN nanowalls exhibit an enhanced gas adsorption performance, not only through physisorption owing to the synergistic combination of different porous geometries, but also through chemisorption via the open edge groups. Moreover, it demonstrates a significantly enhanced adsorption of CO2 over CH4 as compared to the h-BN nanosheets with similar sizes. Density functional theory calculations reveal that the –OH edge groups can effectively increase the adsorption capability towards CO2, accompanied by a shortened adsorption distance when the gas molecule is energetically stabilized. The wetting characteristics of h-BN nanowalls was further examined by contact angle goniometry.
Microdosimetry of a therapeutic proton beam with a mini-TEPC and a MicroPlus-Bridge detector for RBE assessment
Authors: Conte V , Agosteo S , Bianchi A , Bolst D , Bortot D , Catalano R , Cirrone G A P , Colautti P , Cuttone G , Guatelli S , James B , Mazzucconi D , Rosenfeld A B , Selva A , Tran L , Petringa G
Published: October 2020

Proton beams are widely used worldwide to treat localized tumours, the lower entrance dose and no exit dose, thus sparing surrounding normal tissues, being the main advantage of this treatment modality compared to conventional photon techniques. Clinical proton beam therapy treatment planning is based on the use of a general relative biological effectiveness (RBE) of 1.1 along the whole beam penetration depth, without taking into account the documented increase in RBE at the end of the depth dose profile, in the Bragg peak and beyond. However, an inaccurate estimation of the RBE can cause both underdose or overdose, in particular it can cause the unfavourable situation of underdosing the tumour and overdosing the normal tissue just beyond the tumour, which limits the treatment success and increases the risk of complications. In view of a more precise dose delivery that takes into account the variation of RBE, experimental microdosimetry offers valuable tools for the quality assurance of LET or RBE-based treatment planning systems. The purpose of this work is to compare the response of two different microdosimetry systems: the mini-TEPC and the MicroPlus-Bridge detector. Microdosimetric spectra were measured across the 62 MeV spread out Bragg peak of CATANA with the mini-TEPC and with the Bridge microdosimeter. The frequency and dose distributions of lineal energy were compared and the different contributions to the spectra were analysed, discussing the effects of different site sizes and chord length distributions. The shape of the lineal energy distributions measured with the two detectors are markedly different, due to the different water-equivalent sizes of the sensitive volumes: 0.85 μm for the TEPC and 17.3 μm for the silicon detector. When the Loncol’s biological weighting function is applied to calculate the microdosimetric assessment of the RBE, both detectors lead to results that are consistent with biological survival data for glioma U87 cells. Both the mini-TEPC and the MicroPlus-Bridge detector can be used to assess the RBE variation of a 62 MeV modulated proton beam along its penetration depth. The microdosimetric assessment of the RBE based on the Loncol’s weighting function is in good agreement with radiobiological results when the 10% biological uncertainty is taken into account.
Contact resistance assessment and high-frequency performance projection of black phosphorus field-effect transistor technologies
Authors: Valdez-Sandoval Leslie , Ramirez-Garcia Eloy , Jiménez David , Pacheco-Sanchez Anibal
Published: October 2020

In this work, an evaluation of the contact quality of black phosphorus field-effect transistors from different technologies previously reported is performed by means of an efficient and reliable contact resistance extraction methodology based on individual device practical characteristics. A good agreement is achieved between the extracted values with the Y-function method used here and reference values obtained with other methods considering internal values as well as with more expensive methods involving fabricated test structures. The method enables a direct evaluation of different steps in the same technology and it embraces the temperature dependence of the contact characteristics. Channel phenomena have no impact on the extracted contact resistance values. High-frequency performance projections are obtained for fabricated devices based on the extracted contact resistance.
Rapid threshold switching dynamics of co-sputtered chalcogenide Ge15Te85 device for selector application
Authors: Sengottaiyan Rathinavelu , Saxena Nishant , Shukla Krishna Dayal , Manivannan Anbarasu
Published: October 2020

Threshold switching is a unique characteristic feature in amorphous chalcogenide materials that establishes stable and fast switching between a high resistance OFF state and a conductive ON state in the amorphous phase, envisaging the electronic nature of two-terminal ovonic threshold switch (OTS) selectors in vertically stackable cross-point memory arrays. In this paper, we demonstrate voltage-dependent nanosecond threshold switching dynamics and stable OFF–ON transitions of co-sputtered thin Ge15Te85 film devices using ultrafast time-resolved current–voltage measurements. The time-resolved measurement of device current upon the application of voltage pulse reveals a stable threshold switching and OFF–ON transient characteristics of OTS devices and the measured delay time is found to decrease to few nanoseconds upon increasing the amplitude of the applied voltage pulse and such OTS characteristics are found to be stable even above 60% of the high value of threshold voltage. These experimental results found to be consistent with analytical solutions and also demonstrate a systematic trend in the voltage dependent switching properties enabling ultrafast threshold switching characteristics suitable towards designing reliable and stable OTS selector devices.
A model for photothermal conversion of graphene-filled nanocomposites under NIR irradiation
Authors: Li Fang , Wang Lanlan , Tian Hongyan , Zhang Haiyu , Lin Yongshui
Published: October 2020

Graphene, acted as an excellent photothermal inorganic filler in photothermal smart composites, has triggered the fast increasing research upsurge in biomedical imaging, photothermal therapy, photothermal driving and so on recently. Many studies have shown that a low mass loading graphene nanosheets (GNSs) in a matrix can provide the nanocomposite with high photothermal conversion efficiency in the near-infrared (NIR) region due to its strong NIR adsorption and high thermal conductivity. Aiming to indicate the photothermal conversion mechanism, we present an analytical approach based on the Maxwell electromagnetic wave theory, thermodynamics method and effective medium approximation. The influence mechanism of graphene concentration and size, light intensity of NIR irradiation, interfacial thermal resistance between graphene and matrix on the photothermal conversion are all explained in this paper.