bluuebunny/crossref_metadata_2025 huggingface dataset:
Color–color diagrams as tools for assessment of the variable absorption in high mass X-ray binaries
Authors: Grinberg V. , Nowak M. A. , Hell N.
Published: October 2020

High mass X-ray binaries hold the promise of allowing us to understand the structure of the winds of their supermassive companion stars by using the emission from the compact object as a backlight to evaluate the variable absorption in the structured stellar wind. The wind along the line of sight can change on timescales as short as minutes and below. However, such short timescales are not available for the direct measurement of absorption through X-ray spectroscopy with the current generation of X-ray telescopes. In this paper, we demonstrate the usability of color–color diagrams for assessing the variable absorption in wind accreting high mass X-ray binary systems. We employ partial covering models to describe the spectral shape of high mass X-ray binaries and assess the implication of different absorbers and their variability on the shape of color–color tracks. We show that in taking into account, the ionization of the absorber, and in particular accounting for the variation of ionization with absorption depth, is crucial to describe the observed behavior well.
New approach to study HTS bulk behavior for a fully superconducting motor design
Authors: Bouchekhou Hocine , Allag Hicham , Mekideche Mohamed Rachid , Lévêque Jean , Gueraiche Larbi
Published: October 2020

The originality of this work is to applied Amperian Approach for modelling HTS bulk especially in electrical motor applications. This approach has proven its efficiency in electrical materials having a constant conductivity. For HTS materials, the resistivity change brutally and have a non linear comportment through any external magnetic field variations. To success the modelisation, we have to create an iterative procedure. All simulation steps are based on the power law model for computing resistivity and current densities adding the fixed point method for non linear iterations. The majority of our results concern the current densities in the HTS bulk rotor with different critical currents constatations under mgnetic field created by three phase coils of the proposed superconducting synchronous motor (SSM) prototype. Some results are consolidated by numerical way using flux 2D software.
Molecular characterization ofCryptosporidiumspp. from patients with diarrhoea in Lusaka, Zambia
Authors: Mulunda Namwiinga Rozaria , Hayashida Kyoko , Yamagishi Junya , Sianongo Sandie , Munsaka Gilbert , Sugimoto Chihiro , Mutengo Mable Mwale
Published: October 2020

Cryptosporidiumis a major etiological agent of diarrhoeal diseases among children and immune-compromised individuals in sub-Saharan African countries. We conducted a study to determine the prevalence and genetic characteristics ofCryptosporidiumspp. in stool samples from patients with diarrhoea who presented at the University Teaching Hospital in Lusaka, Zambia.Cryptosporidiumspecies and subtypes from 71 microscopically confirmed cryptosporidiosis stool samples collected between 2017 and 2019 were determined by polymerase chain reaction followed by partial sequencing of the small subunit rRNA and 60-kDa glycoprotein (gp60) gene. Additionally, data for the period between 2014 and 2019 were reviewed and analysed for cryptosporidiosis seasonal and age distribution.Cryptosporidiumwas more prevalent in the rainy season. The highest number of cases was reported among the 1–4 year age group. By sequence analysis of the 71 positive isolates,Cryptosporidium hominis(n= 42; 59.2%),C. parvum(n= 27; 38%),C. felis(n= 1; 1.4%), andC. meleagridis(n= 1; 1.4%) were identified. FourC. hominissubtype families (Ia, Ib, Id, and Ie) and threeC. parvumsubtype families (IIc, IIe, and IIs) were identified. The most frequent subtypes were IeA11G3T3 (n= 20; 28.2%), IIcA5G3 (n= 12; 16.9%), IIeA12G1 (n= 11; 15.5%) and IaA30R3 (n= 10; 14.1%). The observed species/subtypes ofC. hominisandC. parvumindicated that the infection was mainly transmitted through the anthroponotic route. The identification ofC. felisandC. meleagridissuggests that an atypical zoonotic transmission cycle also exists.
Hemmnisse und Verbesserungspotenziale bei der Diagnose und der Therapie asylsuchender Tuberkulosepatienten in Deutschland: Ergebnisse einer qualitativen Untersuchung
Authors: Stadtmüller Sven , Menold Natalja , Schröder Jette , Ehlers Stefan
Published: October 2020

Seit 2014 ist die Zahl der Neuerkrankungen an Tuberkulose (TB) in Deutschland
um rund 20% angestiegen. Diese Entwicklung fällt mit einer
hohen Zuwanderung von Asylsuchenden zusammen, die z. T. aus Ländern
stammen, in denen die TB deutlich weiter verbreitet ist als hierzulande. Vor
diesem Hintergrund setzt sich der vorliegende Beitrag zum Ziel, Hemmnisse
bei der Diagnose und der Therapie asylsuchender TB-Patienten in Deutschland
zu identifizieren und zu erklären. Zugleich sollen
Verbesserungspotenziale in diesen Bereichen aufgezeigt werden. Als
Datengrundlage dienen 14 leitfadengestützte, problemzentrierte
Interviews mit Ärzten und Bediensteten des öffentlichen
Gesundheitswesens, die als Experten die Versorgerseite
repräsentieren. Auf der einen Seite bringen strukturelle Faktoren
die von den Experten benannten Hemmnisse hervor. So führt bspw. der
eingeschränkte Zugang zur Gesundheitsversorgung zu einer
verspäteten Diagnose, da Asylsuchende hierdurch später (oder
gar nicht) zum Arzt gehen. Entsprechend wird eine flächendeckende
Einführung einer elektronischen Gesundheitskarte vorgeschlagen. Auf
der anderen Seite spielen individuelle bzw. kulturelle Faktoren eine
wichtige Rolle. Hierzu zählen z. B. Sprachbarrieren, welche
die Anamnese (und damit die Diagnose), v. a. aber die Aufklärung des
Patienten erschweren und damit den Therapieerfolg gefährden. Zudem
resultiert aus der fehlenden Vertrautheit von Asylsuchenden mit dem
deutschen Gesundheitssystem die Gefahr einer Therapieunterbrechung.
Schulungsprogramme nach dem „train the trainer“-Konzept und
die Etablierung eines „Lotsen“, der asylsuchende
TB-Patienten durch das deutsche Gesundheitssystem navigiert, könnten
diese Probleme lindern.
Association Between Vitamin D and Uric Acid in Adults: A Systematic
Review and Meta-Analysis
Authors: Isnuwardana Ronny , Bijukchhe Sanjeev , Thadanipon Kunlawat , Ingsathit Atiporn , Thakkinstian Ammarin
Published: October 2020

Association between vitamin D and uric acid is complex and might be
bidirectional. Our study aimed to determine the bidirectional association
between vitamin D and uric acid in adults. Using MEDLINE via PubMed and Scopus,
we systematically searched for observational or interventional studies in
adults, which assessed the association between serum vitamin D and serum uric
acid, extracted the data, and conducted analysis by direct and network
meta-analysis. The present review included 32 studies, of which 21 had vitamin D
as outcome and 11 had uric acid as outcome. Meta-analysis showed a significant
pooled beta coefficient of serum uric acid level on serum 25(OH)D level from 3
studies of 0.512 (95% confidence interval: 0.199, 0.825) and a
significant pooled odds ratio between vitamin D deficiency and hyperuricemia of
1.496 (1.141, 1.963). The pooled mean difference of serum 25(OH)D between groups
with hyperuricemia and normouricemia was non-significant at 0.138
(−0.430, 0.707) ng/ml, and the pooled mean difference of serum
uric acid between categories of 25(OH)D were also non-significant at 0.072
(−0.153, 0.298) mg/dl between deficiency and normal, 0.038
(−0.216, 0.292) mg/dl between insufficiency and normal, and
0.034 (−0.216, 0.283) mg/dl between deficiency and
insufficiency. In conclusion, increasing serum uric acid might be associated
with increasing 25(OH)D level, while vitamin D deficiency is associated with
hyperuricemia. These reverse relationships should be further evaluated in a
longitudinal study.
Intensivmedizin und COVID-19
Authors: Roedl Kevin , Kluge Stefan , Wichmann Dominic
Published: October 2020

Im Dezember 2019 kam es zur Ausbreitung von SARS-CoV-2, welches zu einer weltweiten Pandemie führte. Neben den Einschränkungen im täglichen Alltag sah sich die Medizin mit bisher nicht dagewesenen Problemen konfrontiert. In einigen Ländern führte ein rasanter Anstieg an SARS-CoV-2 bzw. Erkrankungen mit COVID-19 zu einer Überforderung der Gesundheitssysteme, unter anderem aufgrund eines Mangels an Intensivbetten und Beatmungsgeräten. In der Intensivmedizin bestanden initial große Unsicherheiten bezüglich des Einsatzes von nichtinvasiven Beatmungsformen aufgrund der potenziellen Aerosolbelastung. Ca. 5 % der infizierten Patienten mussten zur weiteren Therapie auf die Intensivstation aufgenommen werden, im Regelfall aufgrund einer schweren Pneumonie. Es kann sich im Verlauf der Erkrankung das Vollbild eines akuten Lungenversagens ausbilden, welches mit einer hohen Mortalität vergesellschaftet ist. Da es sich bei COVID-19 um eine gänzlich unerforschte virale Erkrankung handelt, war die Erforschung der Todesursache und die Charakterisierung von Organschäden sehr wichtig. Mehrere Obduktionsstudien konnten zeigen, dass es bei Patienten mit COVID-19 zu einem vermehrten Auftreten von venösen und arteriellen Thrombosen kommt. Neben klassischen Lungenembolien kommt es auch zur Ausbildung von Mikrothromben in der pulmonalen Endstrombahn. Zudem ließ sich eine Neoangiogenese nachweisen, die bisher im Rahmen des diffusen Alveolarschadens bei pathologischen Untersuchungen noch nicht beschrieben wurde.
COVID-19 und das Herz
Authors: Westermann Dirk , Lindner Diana , Blankenberg Stefan
Published: October 2020

Bei Patienten mit COVID-19 sind Herzbeteiligungen relativ häufig. Dabei ist eine Erhöhung des Troponins als Ausdruck der kardialen Beteiligung am häufigsten zu sehen. Doch auch Arrhythmien und Herzinfarkte aufgrund von systemischen Thrombosen sind als Folgen der COVID-19-Erkrankung beschrieben.

Durch eine Autopsie-Studie konnten wir zeigen, dass das Herz (neben anderen Organen) ebenfalls durch SARS-CoV-2 infiziert werden kann. Das führt zu einer Veränderung in der Expression von inflammatorischen Botenstoffen, aber nicht zu einer Myokarditis im Sinne einer Einwanderung von Entzündungszellen in das Herzgewebe. Damit ist eine direkte Beteiligung des Herzens unter COVID-19 nachgewiesen. Ob aber diese Mitbeteiligung zu einem langfristigen Schaden führt, ist noch völlig unklar und kann nur durch weitere Studien nachgewiesen werden.
COVID-19 – eine vaskuläre Systemerkrankung
Authors: Werlein Christopher , Braubach Peter , Schmidt Vincent , Dickgreber Nicolas J. , Märkl Bruno , Laenger Florian , Jonigk Danny
Published: October 2020

Die aktuelle COVID-19-Pandemie verzeichnet mittlerweile über 18 Millionen Erkrankte und 680 000 Todesfälle weltweit. Für die hohe Variabilität sowohl der Schweregrade des klinischen Verlaufs als auch der Organmanifestationen fanden sich zunächst keine pathophysiologisch zufriedenstellenden Erklärungen. Bei schweren Krankheitsverläufen steht in der Regel eine pulmonale Symptomatik im Vordergrund, meist unter dem Bild eines „acute respiratory distress syndrome“ (ARDS). Darüber hinaus zeigen sich jedoch in unterschiedlicher Häufigkeit Organmanifestationen in Haut, Herz, Nieren, Gehirn und anderen viszeralen Organen, die v. a. durch eine Perfusionsstörung durch direkte oder indirekte Gefäßwandschädigung zu erklären sind. Daher wird COVID-19 als vaskuläre Multisystemerkrankung aufgefasst. Vor dem Hintergrund der multiplen Organmanifestationen sind klinisch-pathologische Obduktionen eine wichtige Grundlage der Entschlüsselung der Pathomechanismen von COVID-19 und auch ein Instrument zur Generierung und Hinterfragung innovativer Therapieansätze.
Catalytic Asymmetric Synthesis of P-Stereogenic Phosphines: Beyond Precious Metals
Authors: Glueck David S.
Published: October 2020

Metal-catalyzed asymmetric synthesis of P-stereogenic phosphines is a potentially useful approach to a class of chiral ligands with valuable applications in asymmetric catalysis. We introduced this idea with chiral platinum and palladium catalysts, exploiting rapid pyramidal inversion in diastereomeric metal–phosphido complexes (ML*(PRR′)) to control phosphorus stereochemistry. This Account summarizes our attempts to develop related synthetic methods using earth-abundant metals, especially copper, in which weaker metal–ligand bonds and faster substitution processes were expected to result in more active catalysts. Indeed, precious metals were not required. Without any transition metals at all, we exploited related P-epimerization processes to prepare enantiomerically pure phosphiranes and secondary phosphine oxides (SPOs) from commercially available chiral epoxides.

1 Introduction

2 Copper-Catalyzed Phosphine Alkylation

3 Copper-Catalyzed Tandem Phosphine Alkylation/Arylation

4 Nickel-Catalyzed Phosphine Alkylation

5 Proton-Mediated P-Epimerization in Synthesis of Chiral Phosphiranes

6 Diastereoselective Synthesis of P-Stereogenic Secondary Phosphine Oxides (SPOs) from (+)-Limonene Oxide

7 Conclusions
Potassium tert-Butoxide Mediated Reductive C–P Cross-Coupling of Arylvinyl Sulfides through C–S Bond Cleavage
Authors: Zeng Qingle , Feng Jie , Zhang Qiaoling , Li Fuhai , Yang Lu , Kuchukulla Ratnakar Reddy
Published: October 2020

A transition-metal-free t-BuOK-mediated reductive C–P cross-coupling reaction of arylvinyl sulfides with diarylphosphine oxides through C–S bond cleavage has been developed. This protocol not only permits the synthesis of diaryl(2-arylethyl)phosphine oxides, but also achieves an unprecedented construction of a C–P bond through C–S bond cleavage and reduction of a C–C double bond in one pot.
Self-interaction correction, electrostatic, and structural influences on time-dependent density functional theory excitations of bacteriochlorophylls from the light-harvesting complex 2
Authors: Kehrer Juliana , Richter Rian , Foerster Johannes M. , Schelter Ingo , Kümmel Stephan
Published: October 2020

First-principles calculations offer the chance to obtain a microscopic understanding of light-harvesting processes. Time-dependent density functional theory can have the computational efficiency to allow for such calculations. However, the (semi-)local exchange-correlation approximations that are computationally most efficient fail to describe charge-transfer excitations reliably. We here investigate whether the inexpensive average density self-interaction correction (ADSIC) remedies the problem. For the systems that we study, ADSIC is even more prone to the charge-transfer problem than the local density approximation. We further explore the recently reported finding that the electrostatic potential associated with the chromophores’ protein environment in the light-harvesting complex 2 beneficially shifts spurious excitations. We find a great sensitivity on the chromophores’ atomistic structure in this problem. Geometries obtained from classical molecular dynamics are more strongly affected by the spurious charge-transfer problem than the ones obtained from crystallography or density functional theory. For crystal structure geometries and density-functional theory optimized ones, our calculations confirm that the electrostatic potential shifts the spurious excitations out of the energetic range that is most relevant for electronic coupling.
Assessing observability of chaotic systems using Delay Differential Analysis
Authors: Gonzalez Christopher E. , Lainscsek Claudia , Sejnowski Terrence J. , Letellier Christophe
Published: October 2020

Observability can determine which recorded variables of a given system are optimal for discriminating its different states. Quantifying observability requires knowledge of the equations governing the dynamics. These equations are often unknown when experimental data are considered. Consequently, we propose an approach for numerically assessing observability using Delay Differential Analysis (DDA). Given a time series, DDA uses a delay differential equation for approximating the measured data. The lower the least squares error between the predicted and recorded data, the higher the observability. We thus rank the variables of several chaotic systems according to their corresponding least square error to assess observability. The performance of our approach is evaluated by comparison with the ranking provided by the symbolic observability coefficients as well as with two other data-based approaches using reservoir computing and singular value decomposition of the reconstructed space. We investigate the robustness of our approach against noise contamination.
Picosecond solid-state generator with a peak power of 50 GW
Authors: Alichkin E. A. , Pedos M. S. , Ponomarev A. V. , Rukin S. N. , Timoshenkov S. P. , Karelin S. Y.
Published: October 2020

This article describes a picosecond solid-state pulsed system, where the input pulse from the generator with a semiconductor opening switch (SOS) is amplified in power and decreases in duration by ferrite gyromagnetic lines. The lines operate in the Magnetic Compression Line (MCL) mode, which occurs at close values of the input pulse duration and the period of the oscillations generated in the line. The energy compression system contains three successive stages—MCL1–MCL3 lines. For an input pulse power of 6 GW (490 kV, 40 Ω) and a duration of 7 ns, pulses of 54 GW (1.62 MV, 48 Ω) and a duration of 170 ps have been achieved at the MCL3 output. Compared to the parameters of the input pulse, the voltage rise rate has been increased ∼130 times up to 14.8 MV/ns, and the power rise rate has been increased ∼350 times up to 0.7 TW/ns. A numerical simulation of the MCL3 line operation in which the maximum electric and magnetic fields are realized (>2 MV/cm and >500 kA/m, respectively) has been carried out. The inner structure of the process of power amplification during the electromagnetic wave passage along the line has been demonstrated. First, the front of the input pulse is sharpened, and then, after the excitation of the oscillations, the process of power amplification begins, followed by the pulse amplitude reaching the saturation region.
Correlation between bonding, vacancy migration mechanisms, and creep in model binary and ternary hcp-Mg solid solutions
Authors: Paranjape Priyanvada , Srinivasan S. G. , Choudhuri Deep
Published: October 2020

High temperature creep deformation of hcp-Mg alloys is dominated by dislocation climb driven by out-of-plane (OOP) vacancy migration. Past experiments and atomistic simulations have indicated that Zn addition reduces vacancy migration tendencies and improves creep resistance. Here, we have compared in-plane (IP) and out-of-plane (OOP) vacancy migration mechanisms in binary Mg–X (Ca, Y, and Gd) and ternary Mg–X (Ca, Y, and Gd)–Zn alloys using density functional theory based first principles computations. Irrespective of Zn addition, the migration barrier for OOP diffusion was consistently higher than IP in our prototype binary and ternary alloys. The presence of Zn in ternary systems, however, substantially increases the OOP activation barrier relative to binary alloys. The higher OOP barrier in Mg–X–Zn was attributed to favorable local relaxation, enhanced charge localization, higher interplanar bond stiffness, and greater s orbital electron occupancy in the peak saddle state. Combined, these factors restrict non-conservative dislocation climb by impeding out-of-plane vacancy movement and improve the creep resistance of ternary Mg–X (Ca, Y, and Gd)–Zn alloys.
Targeted free energy estimation via learned mappings
Authors: Wirnsberger Peter , Ballard Andrew J. , Papamakarios George , Abercrombie Stuart , Racanière Sébastien , Pritzel Alexander , Jimenez Rezende Danilo , Blundell Charles
Published: October 2020

Free energy perturbation (FEP) was proposed by Zwanzig [J. Chem. Phys. 22, 1420 (1954)] more than six decades ago as a method to estimate free energy differences and has since inspired a huge body of related methods that use it as an integral building block. Being an importance sampling based estimator, however, FEP suffers from a severe limitation: the requirement of sufficient overlap between distributions. One strategy to mitigate this problem, called Targeted FEP, uses a high-dimensional mapping in configuration space to increase the overlap of the underlying distributions. Despite its potential, this method has attracted only limited attention due to the formidable challenge of formulating a tractable mapping. Here, we cast Targeted FEP as a machine learning problem in which the mapping is parameterized as a neural network that is optimized so as to increase the overlap. We develop a new model architecture that respects permutational and periodic symmetries often encountered in atomistic simulations and test our method on a fully periodic solvation system. We demonstrate that our method leads to a substantial variance reduction in free energy estimates when compared against baselines, without requiring any additional data.
Spline moment models for the one-dimensional Boltzmann–Bhatnagar–Gross–Krook equation
Authors: Koellermeier Julian , Scholz Ullika
Published: October 2020

We introduce Spline Moment Equations (SMEs) for kinetic equations using a new weighted spline ansatz of the distribution function and investigate the ansatz, the model, and its performance by simulating the one-dimensional Boltzmann–Bhatnagar–Gross–Krook equation. The new basis is composed of weighted constrained splines for the approximation of distribution functions that preserves mass, momentum, and energy. This basis is then used to derive moment equations using a Galerkin approach for a shifted and scaled Boltzmann–Bhatnagar–Gross–Krook equation, to allow for an accurate and efficient discretization in velocity space with an adaptive grid. The equations are given in a compact analytical form, and we show that the hyperbolicity properties are similar to the well-known Grad moment model. The model is investigated numerically using the shock tube, the symmetric two-beam test, and a stationary shock structure test case. All tests reveal the good approximation properties of the new SME model when the parameters of the spline basis functions are chosen properly. The new SME model outperforms existing moment models and results in a smaller error while using a small number of variables for efficient computations.
Comparison of intermolecular energy transfer from vibrationally excited benzene in mixed nitrogen–benzene baths at 140 K and 300 K
Authors: Ahamed Sk. Samir , Kim Hyunsik , Paul Amit K. , West Niclas A. , Winner Joshua D. , Donzis Diego A. , North Simon W. , Hase William L.
Published: October 2020

Gas phase intermolecular energy transfer (IET) is a fundamental component of accurately explaining the behavior of gas phase systems in which the internal energy of particular modes of molecules is greatly out of equilibrium. In this work, chemical dynamics simulations of mixed benzene/N2 baths with one highly vibrationally excited benzene molecule (Bz*) are compared to experimental results at 140 K. Two mixed bath models are considered. In one, the bath consists of 190 N2 and 10 Bz, whereas in the other bath, 396 N2 and 4 Bz are utilized. The results are compared to results from 300 K simulations and experiments, revealing that Bz*–Bz vibration–vibration IET efficiency increased at low temperatures consistent with longer lived “chattering” collisions at lower temperatures. In the simulations, at the Bz* excitation energy of 150 kcal/mol, the averaged energy transferred per collision, ⟨ΔEc⟩, for Bz*–Bz collisions is found to be ∼2.4 times larger in 140 K than in 300 K bath, whereas this value is ∼1.3 times lower for Bz*–N2 collisions. The overall ⟨ΔEc⟩, for all collisions, is found to be almost two times larger at 140 K compared to the one obtained from the 300 K bath. Such an enhancement of IET efficiency at 140 K is qualitatively consistent with the experimental observation. However, the possible reasons for not attaining a quantitative agreement are discussed. These results imply that the bath temperature and molecular composition as well as the magnitude of vibrational energy of a highly vibrationally excited molecule can shift the overall timescale of rethermalization.
Contact welding strength measurement for metal electrode materials conducting inrush electrical current
Authors: Ren Wanbin , Zhang Xu
Published: October 2020

Contact welding is considered the major failure mechanism for electromechanical switch applications. There has been increasing demand to research the measurement method to characterize the anti-welding ability of metal electrode materials. In this paper, the contact welding phenomenon of closed electrodes is made to reoccur by using our novel designed test rig. The welding strength and welding area of typical electrode materials, including silver, copper, silver tin oxide, and silver nickel alloy, are explicitly measured and compared. In addition, the effects of electrical current and mechanical load force on welding strength and welding trace are presented. The calculation method of the threshold welding current is introduced for elastic contact situation in low current switching devices.
Stacking the MoS2/GeSe2 vertical van der Waals heterostructure for memory device
Authors: Yao Jiadong , Liu Yali , Guo Wenxuan , Niu Xinyue , Li Mengge , Wu Xiaoxiang , Yu Ying , Yan Xiaoyuan , Xing Boran , Zhang Shucheng , Sha Jian , Wang Yewu
Published: October 2020

Recently, two-dimensional materials have shown great potential in the application of memories due to their atomic thickness and excellent electrical properties. Furthermore, van der Waals heterostructures consisting a variety of two-dimensional materials provide more possibilities for memory research. Here, we design a simple memory device based on the molybdenum disulfide/germanium diselenide (MoS2/GeSe2) van der Waals heterostructure, which exhibits a large memory window of about 10 V in the gate range of ±10 V. Its ratio of program/erase current reaches over 102 and remains after more than 2 × 103 s and 103 cycles, showing good stability and reliability. Compared to conventional floating gate memory, the device based on this structure provides promising advantages in the reduction of the device size and simplification of manufacturing.
Structural transition and recovery of Ge implanted
β
-Ga2O3
Authors: Anber Elaf A. , Foley Daniel , Lang Andrew C. , Nathaniel James , Hart James L. , Tadjer Marko J. , Hobart Karl D. , Pearton Stephen , Taheri Mitra L.
Published: October 2020

Ion implantation-induced effects were studied in Ge implanted β-Ga2O3 with the fluence and energy of 3 × 1013 cm−2/60 keV, 5 × 1013 cm−2/100 keV, and 7 × 1013 cm−2/200 keV using analytical electron microscopy via scanning/transmission electron microscopy, electron energy loss spectroscopy, and precession electron diffraction via TopSpin. Imaging shows an isolated band of damage after Ge implantation, which extends ∼130 nm from the sample surface and corresponds to the projected range of the ions. Electron diffraction demonstrates that the entirety of the damage band is the κ phase, indicating an implantation-induced phase transition from β to κ-Ga2O3. Post-implantation annealing at 1150 °C for 60 s under the O2 atmosphere led to a back transformation of κ to β; however, an ∼17 nm damage zone remained at the sample surface. Despite the back transformation from κ to β with annealing, O K-edge spectra show changes in the fine structure between the pristine, implanted, and implanted-annealed samples, and topspin strain analysis shows a change in strain between the two samples. These data indicate differences in the electronic/chemical structure, where the change of the oxygen environment extended beyond the implantation zone (∼130 nm) due to the diffusion of Ge into the bulk material, which, in turn, causes a tensile strain of 0.5%. This work provides a foundation for understanding of the effects of ion implantation on defect/phase evolution in β-Ga2O3 and the related recovery mechanism, opening a window toward building a reliable device for targeted applications.
Large scale structures of turbulent flows in the atmospheric surface layer with and without sand
Authors: Wang Guohua , Gu Haihua , Zheng Xiaojing
Published: October 2020

Field measurements at the Qingtu Lake Observation Array site were performed to explore the features of large scale structures relevant to very large scale motions (VLSMs) and large scale motions (LSMs) in the atmospheric surface layer during dust weather events. The three velocity components, PM10 concentrations (particles with size less than 10 μm), and sand saltation fluxes at different heights were measured synchronously. By comparing with the results in clean-air flows, the influences of sand particles on the VLSMs were investigated. The present results indicate that the streamwise turbulent kinetic energy across all scales is enhanced in the sand-laden flows. However, the energy enhancement of small-scale motions is more pronounced than that of large scale structures, resulting in a decreased energy fraction of the large scale structures in the sand-laden flows. The inclination angles of the large scale structures are found to increase with sand concentration, owing to the decreased velocity gradient. The streamwise length scale of large scale structures and the size of the most energetic turbulent structures are found to be unchanged in the sand-laden flows relative to those in the clean-air flows. This is the study on the particle-laden wall turbulence at the largest Reynolds number to date, and the results demonstrate that the dispersed tiny particles in very dilute particle–gas flows can affect the turbulence even for the large scale structures.
Diffusiophoretic separation of colloids in microfluidic flows
Authors: Shin Sangwoo
Published: October 2020

In this review, we cover recent advances in microfluidic colloid separation enabled by diffusiophoresis. Diffusiophoresis describes the motion of colloidal particles induced by local chemical gradients. Despite its long history, it is only recently that diffusiophoresis has gained a renewed interest in the scientific community. Such a resurgence is, in part, due to the recognition that diffusiophoresis may enable useful applications that are otherwise difficult to achieve or can be augmented by it. One example is continuous colloid separation, which requires the control of particle motion relative to the flow. This review aims to provide a fundamental understanding of diffusiophoretic separation along with a survey of the recent literature on diffusiophoretic colloid separation in microfluidic flows in both cross-gradient and counter-gradient settings.
Photon-avalanche-like upconversion in NdAl3(BO3)4 nanoparticles excited at 1064 nm
Authors: da Silva Jefferson F. , da Silva Rodrigo F. , Santos Emanuel P. , Maia Lauro J. Q. , Moura André L.
Published: October 2020

We report efficient nonresonant ground-state excitation at 1064 nm of trivalent neodymium (Nd3+) ions in stoichiometric neodymium aluminum borate NdAl3(BO3)4 nanoparticles, which are crystalline and, besides the large content of Nd3+ ions, present excellent photoluminescence properties. Upconversion (UC) emission was observed, and the energy pathways were identified starting from multi-phonon assisted ground-state absorption (4I9/2 → 4F3/2) and excited-state absorption (4I11/2 → 4F3/2) with the population of the 4I11/2 level by thermal coupling with the ground state. The excited state 4I11/2 is also populated by relaxations of the Nd3+ ions at upper-lying levels. Cross-relaxation between two Nd3+ ions (4F3/2, 4I9/2) → (4I15/2, 4I15/2) with subsequent phonon emission leads to two ions at the 4I11/2 level, with every iteration triggering a photon-avalanche-like emission, which greatly enhances the efficiency of the UC emissions. Ladder thermal excitation 4F3/2 → (4F5/2, 2H9/2) → (4F7/2, 4S3/2) → 4F9/2 was achieved, and the ground-state relaxation from these levels provided emission at 880 nm, 810 nm, 750 nm, and 690 nm, respectively. Energy transfer UC (Auger) between Nd3+ ions at the 4F3/2 level allowed the population of (2G3/2, 4G7/2) from which relaxations to the 4I9/2, 4I11/2, and 4I13/2 states provided emissions around 536 nm, 600 nm, and 660 nm, respectively. Associated with the nonradiative relaxations, we observed the heating of the nanoparticles (22 °C–240 °C) with subsequent thermal enhancement of the frequency UC emissions due to population redistribution between the coupled energy levels of the Nd3+ ions. The present results have potential applications in super-resolution imaging and nanothermometry.
Tetrahedral framework nucleic acids as an advanced drug delivery system for oligonucleotide drugs
Authors: Liu Yuhao , Liu Zhiqiang , Cui Weitong , Li Yanjing , Qin Xin , Zhang Mei , Lin Yunfeng
Published: October 2020

Nucleic acid therapy has played a promising role in the treatment of many diseases, such as cancer, infections, immune diseases, and neurodegenerative diseases. However, its application is still limited mainly because of poor cell-entry performance and low resistance to in vivo degradation. Tetrahedral framework nucleic acids (tFNAs) have shown potential in delivering low-molecular-weight drugs owing to their stability, biocompatibility, cell-entry performance, and flexible drug-loading ability. In particular, tFNAs can successfully deliver oligonucleotide drugs with improved effects and co-deliver oligonucleotide drugs with other drugs for synergistic effects. In this review, the recent progress on tFNA-based delivery of oligonucleotide drugs is outlined by single delivery systems—through sequence extension and complementation, and co-delivery systems—through multiple sequence extension, drug–DNA interactions, and specific binding. Furthermore, the current limitations and future developments of tFNA-based delivery of oligonucleotide drugs are discussed.
Charge trapping by iodine ions in photorefractive Sn2P2S6 crystals
Authors: Scherrer E. M. , Giles N. C. , Dodson T. E. R. , Grabar A. A. , Evans D. R. , Basun S. A. , Slagle J. E. , Halliburton L. E.
Published: October 2020

Electron paramagnetic resonance (EPR) is used to establish the role of iodine as an electron trap in tin hypothiodiphosphate (Sn2P2S6) crystals. Iodine ions are unintentionally incorporated when the crystals are grown by the chemical-vapor-transport method with SnI4 as the transport agent. The Sn2P2S6 crystals consist of Sn2+ ions and (P2S6)4− anionic groups. During growth, an iodine ion replaces a phosphorus in a few of the anionic groups, thus forming (IPS6)4− molecular ions. Following an exposure at low temperature to 633 nm laser light, these (IPS6)4− ions trap an electron and convert to EPR-active (IPS6)5− groups with S = 1/2. A concentration near 1.1 × 1017 cm−3 is produced. The EPR spectrum from the (IPS6)5− ions has well-resolved structure resulting from large hyperfine interactions with the 127I and 31P nuclei. Analysis of the angular dependence of the spectrum gives principal values of 1.9795, 2.0123, and 2.0581 for the g matrix, 232 MHz, 263 MHz, and 663 MHz for the 127I hyperfine matrix, and 1507 MHz, 1803 MHz, and 1997 MHz for the 31P hyperfine matrix. Results from quantum-chemistry modeling (unrestricted Hartree–Fock/second-order Møller–Plesset perturbation theory) support the (IPS6)5− assignment for the EPR spectrum. The transient two-beam coupling gain can be improved in these photorefractive Sn2P2S6 crystals by better controlling the point defects that trap charge.
Extreme anomalous centrifugal distortion in methylene
Authors: Coudert Laurent H.
Published: October 2020

A new treatment is presented to account for the extreme anomalous centrifugal distortion displayed by the open-shell methylene radical. This new treatment is based on a four-dimensional approach in which both the overall rotation and the large amplitude bending mode are treated simultaneously. It accounts for the spin–rotation and spin–spin fine couplings, assumed to depend on the large amplitude bending coordinate, as well as for the hyperfine coupling. The new treatment is tested analyzing the available high-resolution data. 336 transitions, involving the ground and first excited vibrational states of the bending mode, are reproduced with a unitless standard deviation of 1.3, using 42 molecular constants. Compared to a previous analysis [S. Brünken et al., J. Chem. Phys. 123, 164315 (2005)], the present analysis is more satisfactory as it accounts for a larger dataset and the ratio of the number of data to the number of varied constants is larger. The present theoretical treatment also allows us to retrieve the bending potential and the main kinetic energy term.
Plasma modification of vanadium oxynitride surfaces: Characterization by in situ XPS experiments and DFT calculations
Authors: Osonkie A. , Lee V. , Chukwunenye P. , Cundari T. , Kelber J.
Published: October 2020

Plasma modification of transition metal nitride/oxynitride (MOxNy) surfaces for enhanced surface properties is highly desirable, given the scalability of such methods and limitations of thermal treatments. In situ x-ray excited photoelectron spectroscopy demonstrates that the O2 plasma oxidation of VOxNy films generates non-lattice N1s surface features with binding energies near 396.5 eV, which are associated with the nitrogen reduction reaction activity but not observed upon thermal oxidation. The NH3 plasma generates N1s surface features near 400.5 eV binding energy. The O2+NH3 plasma generates both types of N1s features. Annealing in UHV to <1000 K reverses plasma-induced changes to N1s spectra. Density functional theory (DFT) calculations integrated with the experiments indicate that the plasma-induced N1s features at ∼396.5 eV and 400.5 eV are V≡N: and V—NH2 sites, respectively, with significantly lower thermal stabilities than lattice N sites. These results provide practical insight regarding the plasma modification of MOxNy surfaces for important applications.
Solid oxide fuel cells based on ceramic membranes with mixed conductivity: improving efficiency
Authors: Pikalova Elena Yu. , Kalinina Elena G.
Published: October 2020

Modern approaches to increasing the efficiency of solid-oxide fuel cells (SOFCs) based on electrolytic membranes with mixed conductivity are considered. These approaches are based on material-science concepts (expansion of the electrolytic domain boundary due to the doping of basic oxides and development of various composite materials) and various technological solutions (application of electron-blocking layers on the anode and cathode sides, rational selection of the electrolyte thickness, and optimization of the electrolyte and electrode structures by synthesizing heterostructures). The methods of mathematical modelling of devices with an electrolytic membrane having mixed conductivity are analyzed in order to determine the most efficient design and optimal operation conditions for SOFCs. The application of nanocomposite electrolytes with a core – shell structure and salt composites is considered. Data on new design solutions — single-layer and single-chamber SOFCs — are presented. The prospects of the proposed approaches are evaluated.

The bibliography includes 384 references.
Nonstoichiometry, structure and properties of nanocrystalline oxides, carbides and sulfides
Authors: Valeeva Albina A. , Rempel Andrey A. , Rempel Svetlana V. , Sadovnikov Stanislav I. , Gusev Aleksandr I.
Published: October 2020

The results of recent experimental studies of the influence of the size of oxide, carbide and sulfide nanoparticles on changes in their nonstoichiometry are analyzed and generalized. In relation to intrinsically nonstoichiometric titanium oxides and niobium and vanadium carbides, on the one hand, and stoichiometric silver sulfides, on the other hand, it is shown that a decrease in the particle size to the nano scale has a strong impact on the chemical composition of nanocrystalline compounds, viz., it leads to the occurrence of or increase in nonstoichiometry. A conclusion is drawn that interplay between the particle size and nonstoichiometry is common to all solid nanocrystalline substances and should be taken into account in studies on the synthesis, structure and properties of these systems.

The bibliography includes 260 references.
Widely accessible 3D printing technologies in chemistry, biochemistry and pharmaceutics: applications, materials and prospects
Authors: Gordeev Evgeniy G. , Ananikov Valentine P.
Published: October 2020

Representative examples of the application of 3D printing in organic synthesis, biochemistry, biotechnology, analytical chemistry, pharmaceutics and chemical education are considered. It is shown that additive technologies open up new prospects for the development of these fields of science. The characteristics of widely used 3D printing methods (fused deposition modelling and stereolithography) are discussed in the context of chemical applications. It is noted that the key feature of these methods is the wide accessibility of technologies and materials.

The bibliography includes 498 references.
Reconciling the climate and ozone response to the 1257 CE Mount Samalas eruption
Authors: Wade David C. , Vidal Céline M. , Abraham N. Luke , Dhomse Sandip , Griffiths Paul T. , Keeble James , Mann Graham , Marshall Lauren , Schmidt Anja , Archibald Alexander T.
Published: October 2020

Significance

The Mount Samalas eruption in 1257, one of the largest explosive volcanic eruptions in the Common Era, has proven a complex case for climate models which have generally overestimated the climate response compared with proxy data. Here we perform Earth system model simulations of the impacts of the Mount Samalas eruption using a range of

SO

2

and halogen emission scenarios. Reported halogen emissions are considerable from the eruption, but using our model simulations and reconstructed climate response we can rule out all but minor halogen emissions reaching the stratosphere. Including a minor fraction of the halogen inventory reaching the stratosphere captures the observed “muted” climate response but results in significant ozone depletion with implications for ultraviolet exposure and human health.
Contractile pericytes determine the direction of blood flow at capillary junctions
Authors: Gonzales Albert L. , Klug Nicholas R. , Moshkforoush Arash , Lee Jane C. , Lee Frank K. , Shui Bo , Tsoukias Nikolaos M. , Kotlikoff Michael I. , Hill-Eubanks David , Nelson Mark T.
Published: October 2020

Significance

Capillaries—the most abundant vessels in the circulatory system—deliver O
2
and nutrients to all cells of the body. In the brain and retina, capillaries also act as a sensory web that detects neuronal activity. Here, we demonstrate that pericytes localized at capillary junctions in a postarteriole transitional region possess unique properties, notably including contractility, that enable them to dynamically manipulate capillary branch diameters and exert fine control over the distribution of blood within the capillary network. In so doing, these contractile junctional pericytes fine tune the delivery of O
2
and nutrients and thus serve to meet the specific needs of neurons. Given these unique properties, pericytes represent a therapeutic target for cardiovascular and neurodegenerative diseases.
Poxvirus-encoded TNF receptor homolog dampens inflammation and protects from uncontrolled lung pathology during respiratory infection
Authors: Al Rumaih Zahrah , Tuazon Kels Ma. Junaliah , Ng Esther , Pandey Pratikshya , Pontejo Sergio M. , Alejo Alí , Alcamí Antonio , Chaudhri Geeta , Karupiah Gunasegaran
Published: October 2020

Significance

Viruses have coevolved with their hosts and developed strategies to dampen, evade, or subvert the host immune response to provide an advantage to the virus. We show that ectromelia virus (ECTV) encodes a TNF receptor (TNFR) homolog, which provides an advantage to the host and virus by dampening TNF levels and inflammation. Infection of ECTV-resistant mice with a mutant virus lacking viral TNFR (vTNFR) caused significant lung pathology and death due to secretion of excessive levels of TNF and other inflammatory cytokines. In vitro, recombinant vTNFR from ECTV and other orthopoxviruses bound to membrane-associated TNF and down-regulated inflammatory gene expression through reverse signaling. vTNFR benefits the host by enabling survival, potentially facilitating virus spread, which should advantage the virus.
Large and seasonally varying biospheric CO
2
fluxes in the Los Angeles megacity revealed by atmospheric radiocarbon
Authors: Miller John B. , Lehman Scott J. , Verhulst Kristal R. , Miller Charles E. , Duren Riley M. , Yadav Vineet , Newman Sally , Sloop Christopher D.
Published: October 2020

Significance

Megacities contribute significantly to national and global CO
2
emissions and are an increasingly important element of emissions mitigation efforts. Atmospheric monitoring helps to characterize urban emissions, but CO
2
measurements alone cannot distinguish between biogenic and fossil fuel contributions to observed CO
2
enhancements. We use measurements of CO
2
and the fossil fuel tracer
14
CO
2
to demonstrate that even for highly urbanized and arid environments such as Los Angeles, the managed urban biosphere contributes significantly to the local carbon budget. These findings highlight the need to understand and quantify urban biospheric CO
2
in order to more accurately measure and track fossil fuel–CO
2
emissions and the impact of urban greening campaigns, as needed to evaluate and optimize emissions mitigation strategies.
Effect of border policy on exposure and vulnerability to climate change
Authors: Benveniste Hélène , Oppenheimer Michael , Fleurbaey Marc
Published: October 2020

Significance

Migration is increasingly presented as an adaptation solution to climate change. When populations move, they change their level of exposure and vulnerability to climate change impacts. We analyze how different border policies might affect people’s exposure and vulnerability. We propose a substantial methodological innovation by including explicit migration and remittance dynamics in one of the models typically used to compute climate change damages. We find that restrictive border policy can increase exposure and vulnerability, by trapping people in areas where they find themselves more exposed and vulnerable than where they would otherwise migrate.
Nucleus accumbens cytoarchitecture predicts weight gain in children
Authors: Rapuano Kristina M. , Laurent Jennifer S. , Hagler Donald J. , Hatton Sean N. , Thompson Wesley K. , Jernigan Terry L. , Dale Anders M. , Casey B. J. , Watts Richard
Published: October 2020

Significance

As the prevalence of pediatric obesity continues to rise, determining neurobiological mechanisms underlying longitudinal childhood weight gain is critically important for informing early intervention and prevention strategies. We use an MRI technique to probe nucleus accumbens (NAcc) tissue microstructure and predict waist circumference after 1 y. We find that increased cell density in the NAcc is strongly associated with obesity in a large cohort of children and predicts future weight gain independent of waist circumference at baseline. These results extend animal studies showing a vicious cycle in which diet-induced neuroinflammation leads to disruption of the brain’s reward circuitry and subsequently promotes further unhealthy eating and weight gain.
Coupling stabilizers open KV1-type potassium channels
Authors: Silverå Ejneby Malin , Wallner Björn , Elinder Fredrik
Published: October 2020

Significance

Voltage-gated ion channels are transmembrane pores responsible for the generation and transmission of nervous impulses. They are also obvious targets for pharmaceutical drugs against neurological diseases. A challenge is to develop compounds that target a specific ion channel. Here, we report on the discovery of a large family of compounds that specifically open one subfamily of potassium channels. These compounds act on the linker between the channel’s voltage sensor and gate to keep the channel open. These findings open up an avenue for the development of ion-channel modulators.