bluuebunny/crossref_metadata_2025 huggingface dataset:
Doubling Recruitment of Pediatric Low-grade Glioma within Two Decades
does not change Outcome – Report from the German LGG
Studies
Authors: Gnekow Astrid Katharina , Kandels Daniela , Pietsch Torsten , Bison Brigitte , Warmuth-Metz Monika , Thomale Ulrich W. , Kortmann Rolf-D. , Timmermann Beate , Driever Pablo Hernàiz , Witt Olaf , Schmidt René , Spix Claudia
Published: May 2021

Background Successive multicenter studies for pediatric low-grade glioma
(LGG) in Germany were accompanied by a doubling of annual recruitment over 2
decades. We investigated whether this increase conveyed a change of
epidemiologic characteristics or survival.

Methods and results Participating centers reported 4634 patients with the
radiologic/histologic diagnosis of LGG (1996–2018), rising from
109 to 278/year. Relating these numbers to all pediatric CNS tumors
registered at the German Childhood Cancer Registry, the LGG fraction and annual
crude incidence rates increased (32% to 51%; 0.94 to
2.12/100,000 children/adolescents<15 years). The
consecutive LGG studies recruited 899 (HIT-LGG 1996), 1592 (SIOP-LGG 2004), and
1836 (LGG-registry) patients with similar distribution of tumor-sites,
histology, and dissemination. 5-year overall survival was
96%-98% at median observation time of 8.1 years. Acknowledging
unequal follow-up periods, 589/899 (66%), 1089/1582
(69%), and 1387/1836 (76%) patients remained under
observation, while 1252/4317 received adjuvant treatment with decreasing
frequency of front-line radiotherapy from 16% to 5%.

Conclusion Pediatric LGG incidence rates in Germany are now comparable to
other European countries. The rise in patient numbers followed implementation of
standard-of-care treatment protocols, but did not result in relevant changes of
epidemiologic or clinical parameters or survival. Shifts in patient distribution
between treatment arms reflect growing acceptance of the LGG therapy
algorithm.
Synthesis of Highly Functionalized 4-Amino-2-(trifluoromethyl)-1H-pyrroles
Authors: Zanatta Nilo , Zachow Lucimara L. , Mittersteiner Mateus , Aquino Estefania C. , Bonacorso Helio G. , Martins Marcos A. P.
Published: May 2021

In this work, the reactivity of 5-bromo-1,1,1-trifluoro-4-methoxypent-3-en-2-one toward primary aliphatic amines was studied. The reaction was found to be extremely selective to synthesize a series of 1-alkyl-4-(aminoalkyl)-2-(trifluoromethyl)-1H-pyrroles (13 examples, up to 90% yield) and a series of highly functionalized β-enaminones (6 examples, up to 78% yield), with only the amount of amine and the reaction conditions needing to be controlled. The structure of the products was unambiguously determined by single crystal X-ray diffraction and 2D NMR experiments.
Synthesis of Cyclic Phosphinates by Microwave-Assisted Ionic-Liquid-Promoted Alcoholysis
Authors: Keglevich György , Harsági Nikoletta , Kiss Nóra Zsuzsa , Drahos László
Published: May 2021

A series of 1-alkoxy-3-methyl- and 3,4-dimethyl-3-phospholene 1-oxides, as well as 1-alkoxy-3-methylphospholane 1-oxides were prepared in good yields by the microwave (MW)-assisted [bmim][PF6]-catalyzed transesterification of the corresponding methyl or ethyl esters. The alcoholyses studied represent another case, where MW irradiation has had a crucial role on the course of the reaction. The method developed is an alternative possibility to other esterifications starting from the corresponding phosphinic chlorides and acids.
Recent Advances in Metal-Nanoparticle-Catalyzed Coupling Reactions Assisted by Microwave Irradiation
Authors: Arisawa Mitsuhiro , Sako Makoto
Published: May 2021

Transition-metal-catalyzed coupling reactions are among some of the most important processes in synthetic chemistry as they are reliable tools for carbon–carbon and carbon–heteroatom bond formation. This short review focuses on recent advances in microwave-assisted­ coupling reactions using transition-metal-nanoparticle catalysts.

1 Introduction

2 Microwave-Assisted Coupling Reactions in Polar Solvents

3 Microwave-Assisted Coupling Reactions in Nonpolar Solvents

4 Conclusion
Risk of Bleeding during Implant Surgery in Patients Taking Antithrombotics: A Systematic Review
Authors: Miziara Luciano Nascimento Braga , Sendyk Wilson Roberto , Ortega Karem López , Gallottini Marina , Sendyk Daniel Isaac , Martins Fabiana
Published: May 2021

The objective of this systematic review is to assess the risk of postoperative bleeding in oral surgery for implant placement in individuals taking antithrombotics (i.e., anticoagulants and/or antiplatelet agents). A literature search was performed in PubMed (MEDLINE), Web of Science, Scopus, and EMBASE databases for articles published until August 2020, with no date restriction, and manually completed. We included prospective clinical studies that provided information regarding the presence of an experimental group (i.e., implant placement), a control group (patients not under treatment with antithrombotics), and a well-established protocol for evaluating bleeding. Meta-analysis determined the risk of bleeding during the placement of implants in antithrombotic-treated patients. Of the 756 potentially eligible articles, 5 were included in the analysis with 4 ranked as high and 1 as medium quality. Antithrombotic treatment comprised the following drug classes: (1) anticoagulants: vitamin K antagonists, (2) nonvitamin K antagonist oral anticoagulants, (3) low-molecular-weight heparin, and (4) antiplatelet agents (not specified). The results suggest that the risk of bleeding is not substantially higher in antithrombotic-treated patients (odds ratio = 2.19; 95% confidence interval: 0.88–5.44, p = 0.09) compared with nontreated patients. This systematic review suggests that the absolute risk is low and there is no need to discontinue or alter the dose of the antithrombotic treatment for implant placement surgery.
The Historical Role of the Plastic Surgeon in Spine Reconstruction
Authors: Do Annie , Davis Matthew J. , Abu-Ghname Amjed , Winocour Sebastian J. , Reece Edward M. , Holmes Scott , Xu David S. , Ropper Alexander E. , Hansen Scott L.
Published: May 2021

Wound complications occur in up to 19% of patients undergoing complex spine surgery. The role of the plastic surgeon in complex and redo spine surgery is important and evolving. Classically, plastic surgeons have been involved in the management of patients who develop wound complications following surgery. This involves reconstruction of posterior trunk defects with locoregional fasciocutaneous, muscle, and free tissue transfers. There has also been an increasing role for plastic surgeons to become involved in prophylactic closures of complex and/or redo spine surgeries for high-risk populations. Identification of patients with comorbidities and likelihood for multiple reoperations who are prophylactically treated with complex closure with or without local muscle flaps could significantly decrease the postoperative wound complications.
Failures in Thoracic Spinal Fusions and Their Management
Authors: Prablek Marc , McGinnis John , Winocour Sebastian J. , Reece Edward M. , Kakarla Udaya K. , Raber Michael , Ropper Alexander E. , Xu David S.
Published: May 2021

Instrumented fixation and fusion of the thoracic spine present distinct challenges and complications including pseudarthrosis and junctional kyphosis. When complications arise, morbidity to the patient can be significant, involving neurologic injury, failure of instrumentation constructs, as well as iatrogenic spinal deformity. Causes of fusion failure are multifactorial, and incompletely understood. Most likely, a diverse set of biomechanical and biologic factors are at the heart of failures. Revision surgery for thoracic fusion failures is complex and often requires revision or extension of instrumentation, and frequently necessitates complex soft tissue manipulation to manage index level injury or to augment the changes of fusion.
Vascularized Scapular Bone Grafting: Indications, Techniques, Clinical Outcomes, and Alternatives
Authors: Reece Edward M. , O'Neill Rebecca C. , Davis Matthew J. , Abu-Ghname Amjed , Ropper Alexander E. , Bohl Michael , Xu David S. , Winocour Sebastian J.
Published: May 2021

Spinal fusion can be challenging to obtain in patients with complex spinal pathology. Medial scapular vascularized bone grafts (S-VBGs) are a novel approach to supplement cervicothoracic arthrodesis in patients at high risk of failed spinal fusion. In this article, we discuss the benefits of using VBGs compared with both nonvascularized bone grafts and free vascularized bone flaps and the surgical technique, feasibility, and limitations specific to the S-VBG.
Imaging of electrostatic field vector distribution
Authors: Tsuchiya M.
Published: May 2021

This paper reports on the visualization of a two-dimensional distribution of electrostatic field vectors around an electrified object using the electric field imager (EFIM) device. The EFIM device is made of a virtually connected pair of plate electrodes in parallel and in proximity, between which an electronic circuit for detection and optical indication is embedded. The EFIM device is not only accurately sensitive to the electrostatic field but also possessed of agility and mobility together with directivity and noninvasiveness. It was successfully demonstrated that electrostatic field vectors were visualized quantitatively, and their spatial distributions were mapped in combination with rather simple, mobile, and low-cost equipment. The advantages and disadvantages of the EFIM visualization scheme are discussed together with the future prospect of the EFIM device.
System-on-chip upgrade of millimeter-wave imaging diagnostics for fusion plasma
Authors: Zhu Y. , Yu J.-H. , Yu G. , Ye Y. , Chen Y. , Tobias B. , Diallo A. , Kramer G. , Ren Y. , Tang W. , Dong G. , Churchill R. , Domier C. W. , Li X. , Luo C. , Chen M. , Luhmann N. C.
Published: May 2021

Monolithic, millimeter wave “system-on-chip” technology has been employed in chip heterodyne radiometers in a newly developed Electron Cyclotron Emission Imaging (ECEI) system on the DIII-D tokamak for 2D electron temperature and fluctuation diagnostics. The system employs 20 horn-waveguide receiver modules each with customized W-band (75–110 GHz) monolithic microwave integrated circuit chips comprising a W-band low noise amplifier, a balanced mixer, a ×2 local oscillator (LO) frequency doubler, and two intermediate frequency amplifier stages in each module. Compared to previous quasi-optical ECEI arrays with Schottky mixer diodes mounted on planar antennas, the upgraded W-band array exhibits >30 dB additional gain and 20× improvement in noise temperature; an internal eight times multiplier chain is used to provide LO coupling, thereby eliminating the need for quasi-optical coupling. The horn-waveguide shielding housing avoids out-of-band noise interference on each module. The upgraded ECEI system plays an important role for absolute electron temperature and fluctuation measurements for edge and core region transport physics studies. An F-band receiver chip (up to 140 GHz) is under development for additional fusion facilities with a higher toroidal magnetic field. Visualization diagnostics provide multi-scale and multi-dimensional data in plasma profile evolution. A significant aspect of imaging measurement is focusing on artificial intelligence for science applications.
Feasibility of nuclide-identified imaging based on the back-streaming white neutron beam at the China Spallation Neutron Source
Authors: Tian Binbin , Jing Hantao , Wang Sheng , Li Qiang , Gao Xiaolong , Yang Xiaoyun
Published: May 2021

Back-streaming neutrons through the incoming proton channel at the spallation target station of the China Spallation Neutron Source have been studied as a white neutron source (Back-n). We report a physical study on white neutron imaging based on the Back-n beamline. The wide neutron energy spectrum spanning from 1 eV to 100 MeV was very suitable for nuclide-identified imaging as well as measurements of nuclear data and other applications. We calculated the back-streaming white neutron energy spectrum using the Monte Carlo N-Particle code. A comparison of the results of calculation with those of the FLUktuierende KAskade code and experimental measurements were carried out. The energy resolution of the Back-n beam was close to 5% depending on the neutron energy and the modes of operation, and its spatial resolution could attain the order of tens of micrometers.
Realization of a transition between type-I and type-II Dirac semimetals in monolayers
Authors: Xie Yuee , Kang Yujiao , Li Siwen , Yan Xiaohong , Chen Yuanping
Published: May 2021

The phase transition between type-I and type-II Dirac semimetals will reveal a series of significant physical properties because of their completely distinct electronic, optical, and magnetic properties. However, no mechanism and materials have been proposed to realize the transition to date. Here, we propose that the transition can be realized in two-dimensional (2D) materials consisting of zigzag chains by tuning external strains. The origination of the transition is that some orbital interactions in zigzag chains vary drastically with structural deformation, which changes dispersions of the corresponding bands. Two 2D nanosheets, monolayer phosphorous nitride and AsN, are searched out to confirm the mechanism by using first-principles calculations. They are intrinsic type-I or type-II Dirac materials and transit to another type of Dirac materials by external strains. In addition, a possible routine is proposed to synthesize the new 2D structures.
Molecular dynamics simulations reveal statistics and microscopic mechanisms of water permeation in membrane-embedded artificial water channel nanoconstructs
Authors: Hardiagon Arthur , Murail Samuel , Huang Li-Bo , van der Lee Arie , Sterpone Fabio , Barboiu Mihail , Baaden Marc
Published: May 2021

Understanding water transport mechanisms at the nanoscale level remains a challenge for theoretical chemical physics. Major advances in chemical synthesis have allowed us to discover new artificial water channels, rivaling with or even surpassing water conductance and selectivity of natural protein channels. In order to interpret experimental features and understand microscopic determinants for performance improvements, numerical approaches based on all-atom molecular dynamics simulations and enhanced sampling methods have been proposed. In this study, we quantify the influence of microscopic observables, such as channel radius and hydrogen bond connectivity, and of meso-scale features, such as the size of self-assembly blocks, on the permeation rate of a self-assembled nanocrystal-like artificial water channel. Although the absolute permeation rate extrapolated from these simulations is overestimated by one order of magnitude compared to the experimental measurement, the detailed analysis of several observed conductive patterns in large assemblies opens new pathways to scalable membranes with enhanced water conductance for the future design.
Electrical properties and deep trap spectra in Ga2O3 films grown by halide vapor phase epitaxy on p-type diamond substrates
Authors: Polyakov Alexander Y. , Nikolaev Vladimir I. , Tarelkin Sergey A. , Pechnikov Alexei I. , Stepanov Sergey I. , Nikolaev Andrey E. , Shchemerov Ivan V. , Yakimov Eugene B. , Luparev Nikolay V. , Kuznetsov Mikhail S. , Vasilev Anton A. , Kochkova Anastasiya I. , Voronova Marina I. , Scheglov Mikhail P. , Kim Jihyun , Pearton Stephen J.
Published: May 2021

Films of Ga2O3 were grown by Halide Vapor Phase Epitaxy (HVPE) on bulk heavily B-doped (001)-oriented diamond substrates using thin interlayers of Al2O3 deposited by HVPE or AlN/AlGaN deposited by metalorganic chemical vapor deposition. The growth with AlN/AlGaN was dominated by the formation of a highly conducting ɛ-phase with poor crystalline quality. For these samples, excessive leakage of Schottky diodes and of the Ga2O3/diamond heterojunction prevented meaningful electrical characterization. The film grown with the Al2O3 interlayer was mainly composed of (−201) β-Ga2O3 with an admixture of the ɛ-phase. The film had a low density of residual shallow donors, 5 × 1015 cm−3, with deep electron traps spectra consisting of the well documented centers for β-Ga2O3 near Ec 0.27, Ec 0.7, and Ec 1 eV, all of which are often ascribed to native defects or their complexes. The electrical properties of heterojunctions were mostly determined by the properties of the Ga2O3 films. Both Schottky diodes and heterojunctions showed measurable photosensitivity for 259 nm wavelength excitation, but very low photocurrent for near-UV (365 nm wavelength excitation).
Self-powered proton detectors based on GaN core–shell p–n microwires
Authors: Verheij D. , Peres M. , Cardoso S. , Alves L. C. , Alves E. , Durand C. , Eymery J. , Fernandes J. , Lorenz K.
Published: May 2021

Self-powered particle detectors have the potential to offer exceptional flexibility and compactness in applications where size limits and low power consumption are key requisites. Here, we report on the fabrication and characterization of radiation sensors based on GaN core/shell p–n junction microwires working without externally applied bias. With their small size, high resistance to radiation, and high crystalline quality, GaN microwires constitute highly interesting building blocks for radiation-hard devices. Through microfabrication steps, single-wire devices were processed that show a leakage current as low as 1 pA in reverse bias. Irradiation with both UV light and 2 MeV protons results in photo/ionocurrent signals several orders of magnitude above the dark current and response times below 30 ms. The sensor also showed a good resistance to radiation. Although we observed a small increase in the leakage current after a prolonged proton irradiation, the measured transient ionocurrent signal remains stable during irradiation with a total proton fluence of at least 1×1016 protons/cm2.
A Lagrangian probability-density-function model for turbulent particle-laden channel flow in the dense regime
Authors: Innocenti Alessio , Fox Rodney O. , Chibbaro Sergio
Published: May 2021

Modeling particle-laden turbulent flows at high volume fractions requires accounting for the coupling between phases. The latter is often a sensitive point, and proper closure of the exchange and production terms due to the presence of particles is not straightforward. In the present work, a Lagrangian probability-density-function model developed for homogeneous cluster-induced turbulence is extended to a channel flow. The key features are consistent two-way coupling and the decomposition of the particle velocity into spatially correlated and uncorrelated components, which is crucial for dense flows and which allows dealing with collisions from a statistical point of view. A numerical scheme for the coupled solution of the stochastic differential equations for the particles and a Reynolds-stress model for the fluid is developed. Tests with tracer particles without two-way coupling are done to assess the validity and the consistency of the numerical scheme. Finally, two sets of numerical simulations with particles with different diameters in a turbulent channel flow at a shear Reynolds of Reτ=300 are reported. The effect of two-way coupling by varying the mass loading of the dispersed phase in the mass-loading range φ= 0–2 is analyzed, and the results are compared to previous Eulerian–Lagrangian and Eulerian–Eulerian direct-numerical simulation (DNS) studies. Mean velocities and turbulent kinetic energy show good agreement with DNS, especially regarding the trend with respect to mass loading. Consistent with prior work, increased mass loading causes a drastic reduction of turbulent kinetic energy in the range φ= 0–2.
Spin-state smectics in spin crossover materials
Authors: Cruddas J. , Ruzzi G. , Powell B. J.
Published: May 2021

We show that a simple two-dimensional model of spin crossover materials gives rise to spin-state smectic phases where the pattern of high-spin (HS) and low-spin (LS) metal centers spontaneously breaks rotational symmetry and translational symmetry in one direction only. The spin-state smectics are distinct thermodynamic phases and give rise to plateaus in the fraction of HS metal centers. Smectic order leads to lines of Bragg peaks in the x-ray and neutron scattering structure factors. We identify two smectic phases and show that both are ordered in one direction, but disordered in the other, and hence that their residual entropy scales with the linear dimension of the system. This is intermediate to spin-state ices (examples of “spin-state liquids”) where the residual entropy scales with the system volume, and antiferroelastic ordered phases (examples of “spin-state crystals”) where the residual entropy is independent of the size of the system.
Assessment of effectiveness of optimum physical distancing phenomena for COVID-19
Authors: Chea Branson , Bolt Andre , Agelin-Chaab Martin , Dincer Ibrahim
Published: May 2021

Currently, COVID-19 is a global pandemic that scientists and engineers around the world are aiming to understand further through rigorous testing and observation. This paper aims to provide safe distance recommendations among individuals and minimize the spread of COVID-19, as well as examine the efficacy of face coverings as a tool to slow the spread of respiratory droplets. These studies are conducted using computational fluid dynamics analyses, where the infected person breathes, coughs, and sneezes at various distances and environmental wind conditions and while wearing a face-covering (mask or face shield). In cases where there were no wind conditions, the breathing and coughing simulations display 1–2 m physical distancing to be effective. However, when sneezing was introduced, the physical distancing recommendation of 2 m was deemed not effective; instead, a distance of 2.8 m and greater was found to be more effective in reducing the exposure to respiratory droplets. The evaluation of environmental wind conditions necessitated an increase in physical distancing measures in all cases. The case where breathing was measured with a gentle breeze resulted in a physical distancing recommendation of 1.1 m, while coughing caused a change from the previous recommendation of 2 m to a distance of 4.5 m or greater. Sneezing in the presence of a gentle breeze was deemed to be the most impactful, with a recommendation for physical distancing of 5.8 m or more. It was determined that face coverings can potentially provide protection to an uninfected person in static air conditions. However, the uninfected person's protection can be compromised even in gentle wind conditions.
Modulation of the solution-cathode glow-discharge and solution-anode glow discharge using a rotating magnetic field
Authors: Hazel Nicholas , Orejas Jaime , Ray Steven
Published: May 2021

The effects of an external magnetic field on the solution-cathode glow-discharge (SCGD) and solution-anode glow-discharge (SAGD) are investigated. The SCGD is atmospheric-pressure glow discharge sustained between a metal pin and a liquid cathode electrode in the ambient atmosphere, and it is often used for trace elemental analysis by atomic emission spectroscopy. Here, the SCGD is modified to allow an external permanent magnetic field to be applied, either in a static orientation or as a rotating field, as a means of stabilizing the SCGD plasma and modulating atomic emission from the discharge. The effect of the external magnetic field on the physical structure, electrical characteristics, and spectroscopic response of the SCGD and SAGD are investigated. A rotating external magnetic field was found to change both SAGD and SCGD structure and spatial emission pattern. Analytical figures of merit are examined, and a lock-in amplifier is used to discriminate analytical atomic emission from background emission, improving limits of detection.
Maximum spreading and energy analysis of ellipsoidal impact droplets
Authors: Zhang Xuan , Ji Bingqiang , Liu Xin , Ding Siyu , Wu Xiaomin , Min Jingchun
Published: May 2021

Droplet impacts on solid surfaces are ubiquitous in nature and industry. Before impact, the droplet shape may be affected by gravity, shear flow, and the electric and magnetic fields, inducing non-spherical droplets. However, most previous studies focused on the impact dynamics of spherical droplets. In this study, we conduct experiments, simulations, and theoretical analyses to investigate the impact behaviors of ellipsoidal water droplets whose symmetry axis is perpendicular to the surface. In particular, we explore the maximum spreading and energy evolution during impact. A numerical model adopting the Volume of Fluid method and Kistler's dynamic contact angle model achieves good agreement with the experimental results for both the temporal droplet profile and spreading factor. The effects of Weber number, contact angle, and aspect ratio on the impact dynamics are systematically investigated, and the outcomes show that both the maximum spreading time and factor enlarge with the increasing aspect ratio. Their relations approximately follow the 2/3-power and 1/6-power laws, respectively. Reducing the aspect ratio enhances the viscous dissipation during impact. Based on the theoretical analyses of above results, we modify the viscous dissipation in the conventional energy balance model to include the effects of aspect ratio on the maximum spreading factor. The modified theoretical model reduces the deviations from −23%–51% to −5%–25% and elucidates the scaling law between the maximum spreading factor and aspect ratio. This work deepens our understanding of the interaction between non-spherical impact droplets and surfaces and may contribute to associated applications.
Coupled vibration-dissociation time-histories and rate measurements in shock-heated, nondilute O2 and O2–Ar mixtures from 6000 to 14 000 K
Authors: Streicher Jesse W. , Krish Ajay , Hanson Ronald K.
Published: May 2021

Validation of high-fidelity models for high-temperature hypersonic flows requires high-accuracy kinetics data for oxygen (O2) reactions, including time-histories and rate parameter measurements. Consequently, shock-tube experiments with ultraviolet (UV) laser absorption were performed to measure quantum-state-specific time-histories and coupled vibration-dissociation (CVDV) rate parameters in shock-heated, nondilute O2 and oxygen–argon (O2–Ar) mixtures. Experiments probed mixtures of 20% O2–Ar, 50% O2–Ar, and 100% O2 for initial post-reflected-shock conditions from 6000 to 14 000 K and 26–210 Torr. Two UV lasers—one continuous-wave laser and one pulsed laser—measured absorbance time-histories from the fifth and sixth vibrational levels of the electronic ground state of O2, respectively. The absorbance time-histories subsequently yielded time-histories for vibrational temperature (Tv) from the absorbance ratio, translational/rotational temperature (Ttr) from energy conservation, total O2 number density (nO2) from the individual absorbances, and vibrational-state-specific number density (nv″) from the Boltzmann population fractions. These state-specific temperature and number density time-histories demonstrate the low uncertainty necessary for high-temperature model validation and provide data to higher temperature than previous experiments. Additional analysis of the temperature and number density time-histories allowed inference of rate parameters in the Marrone and Treanor CVDV model, including vibrational relaxation time (τO2−O2), average vibrational energy loss (ε), vibrational coupling factor (Z), and dissociation rate constants (kdO2−O2 and kdO2−O). The results for each of these five parameters show reasonable consistency across the range of temperatures, pressures, and mixtures and generally agree with a modified Marrone and Treanor model by Chaudhry et al. [“Implementation of a chemical kinetics model for hypersonic flows in air for high-performance CFD,” in Proceedings of AIAA Scitech Forum (2020)]. Finally, the results for τO2−O2, kdO2−O2, and kdO2−O exhibit much lower scatter than previous experimental studies.
Theoretical insights into the cineole-based deep eutectic solvents
Authors: Rozas Sara , Alomari Noor , Atilhan Mert , Aparicio Santiago
Published: May 2021

Deep eutectic solvents based on cineole as hydrogen bond acceptors and organic acids (succinic, malic, and lactic) as hydrogen bond donors are studied using a theoretical approach. The nature, strength, and extension of hydrogen bonding are analyzed, thus quantifying this prevailing interaction and its role in the fluid properties. Density functional theory was used to study small molecular clusters, and the topological characterization of the intermolecular forces was carried out using atoms in a molecule theory. Classical molecular dynamics simulations were considered to study nanoscopic bulk liquid properties and their relationship with relevant macroscopic properties such as density or thermal expansion. The reported results provide the characterization of environmentally friendly deep eutectic solvents and show the suitability of cineole for developing these sustainable materials.
Real-time dynamics of strongly correlated fermions using auxiliary field quantum Monte Carlo
Authors: Church Matthew S. , Rubenstein Brenda M.
Published: May 2021

Spurred by recent technological advances, there is a growing demand for computational methods that can accurately predict the dynamics of correlated electrons. Such methods can provide much-needed theoretical insights into the electron dynamics probed via time-resolved spectroscopy experiments and observed in non-equilibrium ultracold atom experiments. In this article, we develop and benchmark a numerically exact Auxiliary Field Quantum Monte Carlo (AFQMC) method for modeling the dynamics of correlated electrons in real time. AFQMC has become a powerful method for predicting the ground state and finite temperature properties of strongly correlated systems mostly by employing constraints to control the sign problem. Our initial goal in this work is to determine how well AFQMC generalizes to real-time electron dynamics problems without constraints. By modeling the repulsive Hubbard model on different lattices and with differing initial electronic configurations, we show that real-time AFQMC is capable of accurately capturing long-lived electronic coherences beyond the reach of mean field techniques. While the times to which we can meaningfully model decrease with increasing correlation strength and system size as a result of the exponential growth of the dynamical phase problem, we show that our technique can model the short-time behavior of strongly correlated systems to very high accuracy. Crucially, we find that importance sampling, combined with a novel adaptive active space sampling technique, can substantially lengthen the times to which we can simulate. These results establish real-time AFQMC as a viable technique for modeling the dynamics of correlated electron systems and serve as a basis for future sampling advances that will further mitigate the dynamical phase problem.
Complex optical conductivity of Bi2Se3 thin film: Approaching two-dimensional limit
Authors: Fang Mingsheng , Wang Zhenyu , Gu Honggang , Song Baokun , Guo Zhengfeng , Zhu Jinlong , Chen Xiuguo , Zhang Chuanwei , Jiang Hao , Liu Shiyuan
Published: May 2021

Two-dimensional Bi2Se3 thin films have attracted widespread attention as an ideal platform of high-performance optoelectronic applications. Understanding the intrinsic optical/electronic properties of Bi2Se3 thin films is vital for Bi2Se3-based optoelectronic applications. Here, the complex optical conductivities of a series of Bi2Se3 thin films with a varying number of quintuple layers are investigated by combining spectroscopic ellipsometry with the classical slab model over a broad spectral range of 0.73–6.43 eV. Results show that the zero-cross point of the imaginary complex optical conductivity exhibits a blueshift trend due to the enhanced coupling between the surface states as the thickness of Bi2Se3 thin film approaches the two-dimensional limit. Five feature peaks (A–E) are identified in the complex optical conductivity spectra, and their center energies exhibit interesting thickness dependencies, which are mainly attributed to the increased surface state gap due to the finite-size effects when the Bi2Se3 thin film gradually approaches the two-dimensional limit. Our work not only gives insights into the tunable optical properties of Bi2Se3 thin films but also reveals its intrinsic physical origin, which are essential and imperative for accurate modeling and design of Bi2Se3-based optoelectronic devices.
Structure of cholinium glycinate biocompatible ionic liquid at graphite electrode interface
Authors: Gupta Aditya , Dhattarwal Harender S. , Kashyap Hemant K.
Published: May 2021

We use constant potential molecular dynamics simulations to investigate the interfacial structure of the cholinium glycinate biocompatible ionic liquid (bio-IL) sandwiched between graphite electrodes with varying potential differences. Through number density profiles, we observe that the cation and anion densities oscillate up to ∼1.5 nm from the nearest electrode. The range of these oscillations does not change significantly with increasing electrode potential. However, the amplitudes of the cation (anion) density oscillations show a notable increase with increasing potential at the negative (positive) electrode. At higher potential differences, the bulkier N(CH3)3CH2 group of cholinium cations ([Ch]+) overcomes the steric barrier and comes closer to the negative electrode as compared to oxygen atom (O[Ch]+). We observe an increase in the interaction between O[Ch]+ and the positive electrode with a decrease in the distance between them on increasing the potential difference. We also observe hydrogen bonding between the hydroxyl group of [Ch]+ cations and oxygens of glycinate anions through the simulated tangential radial distribution function. Orientational order parameter analysis shows that the cation (anion) prefers to align parallel to the negative (positive) electrode at higher applied potential differences. Charge density profiles show a positive charge density peak near the positive electrode at all the potential differences because of the presence of partially positive charged hydrogen atoms of cations and anions. The differential capacitance (Cd) of the bio-IL shows two constant regimes, one for each electrode. The magnitude of these Cd values clearly suggests potential application of such bio-ILs as promising battery electrolytes.
Quantifying the spin mixing conductance of EuO/W heterostructures by spin Hall magnetoresistance experiments
Authors: Rosenberger Paul , Opel Matthias , Geprägs Stephan , Huebl Hans , Gross Rudolf , Müller Martina , Althammer Matthias
Published: May 2021

The spin Hall magnetoresistance (SMR) allows to investigate the magnetic textures of magnetically ordered insulators in heterostructures with normal metals by magnetotransport experiments. We here report the observation of the SMR in in situ prepared ferromagnetic EuO/W thin film bilayers with magnetically and chemically well-defined interfaces. We characterize the magnetoresistance effects utilizing angle-dependent and field-dependent magnetotransport measurements as a function of temperature. Applying the established SMR model, we derive and quantify the real and imaginary parts of the complex spin mixing interface conductance. We find that the imaginary part is by one order of magnitude larger than the real part. Both decrease with increasing temperature. This reduction is in agreement with thermal fluctuations in the ferromagnet.
Direct observation of x-ray excited optical luminescence from a Re6 metal cluster in true aqueous solution: The missing link between material characterization and in vivo applications
Authors: Stass Dmitri V. , Vorotnikova Natalya A. , Shestopalov Michael A.
Published: May 2021

Phosphorescent octahedral metal cluster complexes are highly attractive in terms of biomedical applications, particularly in the area of luminescent diagnostics and photodynamic therapy (PDT). The ability of clusters to be excited by x-radiation followed by red/near infrared emission makes them a new promising class of photosensitizers for deep-PDT. This work demonstrates a direct observation of x-ray-excited optical luminescence of hexanuclear clusters, by example of rhenium cluster complex Na4[{Re6Se8}(CN)6], in a true aqueous solution. The article also describes point-by-point the details and pitfalls of studying cluster radioluminescence in aqueous solution.
Rigorous investigation of the Navier–Stokes momentum equations and correlation tensors
Authors: Öz Yahya
Published: May 2021

An analytical solution to the Navier–Stokes momentum equations for a compressible flow with volume and small shear viscosities as well as external friction is presented while the dynamic viscosity is set to zero. The demonstrated methodology holds in d dimensions. However, in this study, the three-dimensional case is considered in detail. The analytical solution blows up at finite times T, which is determined by a cubic relation if the initial flow velocity is not divergence-free. The existence of T is a necessary and sufficient condition for implementing a singularity. Nonetheless, for external friction μe>T−1, all analytical expressions are smooth while the averaged expressions are smooth for all times.
The influence of palladium on the hydrogenation of acetylene on Ag(111)
Authors: Molina David L. , Muir Mark , Abdel-Rahman Mohammed K. , Trenary Michael
Published: May 2021

We have used reflection absorption infrared spectroscopy (RAIRS) and temperature programmed reaction (TPR) to study the selective hydrogenation of acetylene on both a clean Ag(111) surface and on a Pd/Ag(111) single-atom-alloy surface. The partial hydrogenation of acetylene to ethylene is an important catalytic process that is often carried out using PdAg alloys. It is challenging to study the reaction with ultrahigh vacuum techniques because H2 does not dissociate on Ag(111), and while H2 will dissociate at Pd sites, H-atom spillover from Pd to Ag sites does not generally occur. We bypassed the H2 dissociation step by exposing the surfaces to atomic hydrogen generated by the hot filament of an ion gauge. We find that hydrogen atoms react with acetylene to produce adsorbed ethylene at 85 K, the lowest temperature studied. This is revealed by the appearance of a RAIRS peak at 950 cm−1 due to the out-of-plane wagging mode of adsorbed ethylene when acetylene is exposed to a surface on which H atoms are pre-adsorbed. The formation of both ethylene and ethane are detected with TPR, but no acetylene coupling products, such as benzene, were found. From quantitative analysis of the TPR results, the percent conversion and selectivities to ethylene and ethane were determined. Low coverages of Pd enhance the conversion but do so mainly by increasing ethane formation.
Fragmentation of propionitrile (CH3CH2CN) by low energy electrons
Authors: Pelc A. , Ribar Valah A. , Huber S. E. , Marciszuk K. , Denifl S.
Published: May 2021

Propionitrile (CH3CH2CN, PN) is a molecule relevant for interstellar chemistry. There is credible evidence that anions, molecules, and radicals that may originate from PN could also be involved in the formation of more complex organic compounds. In the present investigation, dissociative electron attachment to CH3CH2CN has been studied in a crossed electron–molecular beam experiment in the electron energy range of about 0–15 eV. In the experiment, seven anionic species were detected: C3H4N−, C3H3N−, C3H2N−, C2H2N−, C2HN−, C2N−, and CN−. The anion formation is most efficient for CN− and anions originating from the dehydrogenation of the parent molecule. A discussion of possible reaction channels for all measured negative ions is provided. The experimental results are compared with calculations of thermochemical thresholds of the detected anions.
Controlling detachment residue via magnetic repulsion force
Authors: Jamali M. , Mehta K. S. , Holweger H. , Amrei M. M. , Tafreshi H. V.
Published: May 2021

This work demonstrates the possibility of using a magnetic repulsion force to reduce the volume of the residue that remains on a surface after detachment of a ferrofluid droplet. This technique provides a means for controlling the detachment residue by controlling the spatial strength of the magnetic field used for droplet detachment. The experimental technique developed in this work can help us to improve our understanding of the underlying physics of droplet adhesion to a surface and the mechanics of residue formation during droplet detachment.
Atomistic-scale investigations of hyperthermal oxygen–graphene interactions via reactive molecular dynamics simulation: The gas effect
Authors: Cui Zhiliang , Yao Guice , Zhao Jin , Zhang Jun , Wen Dongsheng
Published: May 2021

Hyperthermal atomic oxygen (AO) bombardment to thermal protection system surface has been identified to impact the aerodynamic heating significantly, due to complex chemical reactions at the gas–solid interface, e.g., surface catalysis recombination, oxidation, and ablation. Previous investigations have focused on the surface effects of the AO collision process, while the influence of impacting gas characteristics remains unclear under various non-equilibrium aerodynamic conditions. This work conducts a reactive molecular dynamics (RMD) study of AO collisions over graphene surface, by considering the incoming gas at different translational energies (0.1 ≤ Ek ≤ 10 eV), incident angles (θ = 15°, 30°, 45°, 60°, 75°, and 90°), and O/O2 ratios (χO2 = 0.00, 0.25, 0.50, 0.75, and 1.00). The RMD results indicate that for AO normal incidence, the predominant reactive products of O2, CO, and CO2 molecules are produced due to the synergistic catalytic recombination and surface ablation reaction effects. A maximum recombination performance is identified around 5-eV AO incidence. For off-normal AO incidence, the recombination coefficient increases with the increase in incidence angle from 15° to 60° due to the larger perpendicular components of translational energy and then decreases smoothly. With the increase in O2 mole fraction, the surface reflection probabilities increase, which result in the decrease in both catalytic recombination and ablation activities. Via revealing the atomistic-scale mechanism of gas effects on the surface under hypersonic non-equilibrium conditions, this work sheds light for the future design and optimization of thermal protection materials.
Review of Scientific Instruments New Products
Authors: Mandelis Andreas
Published: May 2021

In order to supplement manufacturers’ information, this department will welcome the submission by our readers of brief communications reporting measurements on the physical properties of materials, which supersede earlier data or suggest new research applications.
Scale-free movement patterns in termites emerge from social interactions and preferential attachments
Authors: Paiva Leticia R. , Marins Alessandra , Cristaldo Paulo F. , Ribeiro Danilo Miranda , Alves Sidiney G. , Reynolds Andy M. , DeSouza Og , Miramontes Octavio
Published: May 2021

Significance

When searching for food or conspecifics with whom to interact or merely meandering in a Petri dish, termites perform small displacements interspersed with a few long strides. This is known as Lévy walk, a pervasive movement pattern in animals. The extent to which this pattern is modifiable by the context is still under debate. We show that Lévy walks emerge from collective actions, being modified as the density of individuals in the group changes and absent when individuals interact with inert obstacles. Moreover, our data suggest strongly that preferential attachments, a phenomenon not reported previously, and favorite interactions with a limited number of acquaintances are responsible for the generation of Lévy movement patterns in these social insects.
Death rates at specific life stages mold the sex gap in life expectancy
Authors: Zarulli Virginia , Kashnitsky Ilya , Vaupel James W.
Published: May 2021

Significance

Female life expectancy exceeds male life expectancy. Males at ages 15 to 40 die at rates that are often three times female levels, but this excess mortality is not the main cause of the life expectancy gap. Few deaths occur at younger adult ages compared with mortality after age 60 or, historically, among newborns. Our demographic analysis shows that, up through the early decades of the 20th century, the life expectancy gap largely resulted from excess deaths of infant boys. Afterward, higher mortality among men 60+ became crucial. The higher mortality of males at ages 15 to 40 has played a modest role.
Air quality–related health damages of food
Authors: Domingo Nina G. G. , Balasubramanian Srinidhi , Thakrar Sumil K. , Clark Michael A. , Adams Peter J. , Marshall Julian D. , Muller Nicholas Z. , Pandis Spyros N. , Polasky Stephen , Robinson Allen L. , Tessum Christopher W. , Tilman David , Tschofen Peter , Hill Jason D.
Published: May 2021

Significance

Poor air quality is the largest environmental health risk in the United States and worldwide, and agriculture is a major source of air pollution. Nevertheless, air quality has been largely absent from discussions about the health and environmental impacts of food. We estimate the air quality–related health impacts of agriculture in the United States, finding that 80% of the 15,900 annual deaths that result from food-related fine particulate matter (PM
2.5
) pollution are attributable to animal-based foods. By estimating these impacts and exploring how to reduce them, this work fills a critical knowledge gap. Our results are relevant to food producers, processors, and distributors, and to policymakers and members of the public interested in minimizing the negative consequences of food.
Continuous learning of emergent behavior in robotic matter
Authors: Oliveri Giorgio , van Laake Lucas C. , Carissimo Cesare , Miette Clara , Overvelde Johannes T. B.
Published: May 2021

Significance

In the last century, robots have been revolutionizing our lives, augmenting human actions with greater precision and repeatability. Unfortunately, most robotic systems can only operate in controlled environments. While increasing the complexity of the centralized controller is an instinctive direction to enable robots that are capable of autonomously adapting to their environment, there are ample examples in nature where adaptivity emerges from simpler decentralized processes. Here we perform experiments and simulations on a modular and scalable robotic platform in which each unit is stochastically updating its own behavior to explore requirements needed for a decentralized learning strategy capable of achieving locomotion in a continuously changing environment or when undergoing damage.
TSG101 negatively regulates mitochondrial biogenesis in axons
Authors: Lin Tzu-Huai , Bis-Brewer Dana M. , Sheehan Amy E. , Townsend Louise N. , Maddison Daniel C. , Züchner Stephan , Smith Gaynor A. , Freeman Marc R.
Published: May 2021

Significance

Mitochondrial dysfunction has been associated with many age-dependent neurodegenerative disorders such as Parkinson’s and Alzheimer’s disease, yet understanding how a neuron maintains a pool of functional mitochondria in sufficient density and location throughout axons in vivo still remains enigmatic. Through an unbiased in vivo forward genetic screen, we identified an endosomal sorting complexes required for transport component, TSG101, as a modulator of mitochondrial number and size in neurons and provide evidence to place TSG101 as a negative regulator of mitochondrial biogenesis. We further find that TSG101 does not contribute to Parkin/Pink1-mediated mitophagy and discovered that macroautophagy regulators ATG1 and ATG6 are dispensable in axonal mitochondrial number regulation. Through in vivo screening, it is possible to unravel translatable mechanisms of axonal mitochondrial maintenance.