bluuebunny/crossref_metadata_2025 huggingface dataset:
A PdCu nanoalloy catalyst for preferential CO oxidation in the presence of hydrogen
Authors: Khobragade Rohini , Dahake Pranali , Labhsetwar Nitin , Saravanan Govindachetty
Published: February 2021

Alloy PdCu nanoparticles for CO oxidation in the presence and absence of hydrogen.
Correction: PLGA protein nanocarriers with tailor-made fluorescence/MRI/PET imaging modalities
Authors: Zhang Yajie , García-Gabilondo Miguel , Grayston Alba , Feiner Irene V. J. , Anton-Sales Irene , Loiola Rodrigo A. , Llop Jordi , Ramos-Cabrer Pedro , Barba Ignasi , Garcia-Dorado David , Gosselet Fabien , Rosell Anna , Roig Anna
Published: February 2021

Correction for ‘PLGA protein nanocarriers with tailor-made fluorescence/MRI/PET imaging modalities’ by Yajie Zhang et al., Nanoscale, 2020, 12, 4988–5002, DOI: 10.1039/c9nr10620k.
The Effect of Cognition on the Aided Benefit in Terms of Speech Understanding and Listening Effort Obtained With Digital Hearing Aids: A Systematic Review
Authors: Kestens Katrien , Degeest Sofie , Keppler Hannah
Published: February 2021

Purpose

Hearing aids are the primary rehabilitation devices used to compensate for presbycusis, though large intersubject variability in hearing aid benefit has been reported. This systematic review aimed to investigate how intersubject differences in cognition could influence the aided benefit for speech understanding and listening effort with bilateral digital hearing aids.

Method

Articles were selected through systematic searches in MEDLINE, Embase, Central, and reference lists. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed.

Results

The initial search resulted in 1,092 unique hits, of which 16 were included. The effect of cognition on the aided benefit in terms of speech understanding and listening effort was examined in 12 and four studies, respectively. The aided speech and listening effort benefit obtained from hearing aid use in general or from a specific digital feature (i.e., microphone directionality, noise reduction, amplitude compression, and frequency compression) was associated with four cognitive functions (i.e., working memory, processing speed, selective attention, and executive functions).

Conclusions

Hearing aid users with poorer cognitive functioning derived more aided benefit in terms of speech understanding from hearing aid settings facilitating the matching process between the incoming auditory signal and representations stored in long-term memory. However, since the number of included studies was limited, this trend should be interpreted with caution.

Supplemental Material

https://doi.org/10.23641/asha.13626509
Medialization Laryngoplasty: A Review for Speech-Language Pathologists
Authors: Wilson Azure , Kimball Emily E. , Sayce Lea , Luo Haoxiang , Khosla Sid M. , Rousseau Bernard
Published: February 2021

Purpose

The purpose of this study is to familiarize speech-language-pathologists with the current state of the science regarding medialization laryngoplasty in the treatment of voice disorders, with emphasis on current evidence-based practice, voice outcomes, and future directions for research.

Method

A literature review was performed in PubMed and Embase using the keywords
vocal fold/cord
and
laryngoplasty, thyroplasty, augmentation,
or
laryngeal framework
. Articles published between 2010 and 2020 were reviewed for data about clinical applications, technical approach, voice-related outcomes, and basic science or clinical innovations with the potential to improve patient care. A synthesis of data was performed from articles meeting the outlined search criteria.

Conclusions

As key members in the multidisciplinary care of voice disorders, speech-language pathologists need to be informed of current research in medialization laryngoplasty, a procedure commonly used for patients with glottic insufficiency. Advances in anesthetic technique, office-based procedures, and the development of materials with increased bio-tolerability over the past decade have led to innovations in treatment and improved patient outcomes. Recent applications of computational and bioengineering approaches have the potential to provide new directions in the refinement of currently available techniques and the improvement of patient-based treatment outcomes.
The impact of mass-transfer physics on the observable properties of field binary black hole populations
Authors: Bavera Simone S. , Fragos Tassos , Zevin Michael , Berry Christopher P. L. , Marchant Pablo , Andrews Jeff J. , Coughlin Scott , Dotter Aaron , Kovlakas Konstantinos , Misra Devina , Serra-Perez Juan G. , Qin Ying , Rocha Kyle A. , Román-Garza Jaime , Tran Nam H. , Zapartas Emmanouil
Published: February 2021

We study the impact of mass-transfer physics on the observable properties of binary black hole populations that formed through isolated binary evolution. We used the POSYDON framework to combine detailed MESA binary simulations with the COSMIC population synthesis tool to obtain an accurate estimate of merging binary black hole observables with a specific focus on the spins of the black holes. We investigate the impact of mass-accretion efficiency onto compact objects and common-envelope efficiency on the observed distributions of the effective inspiral spin parameter χeff, chirp mass Mchirp, and binary mass ratio q. We find that low common envelope efficiency translates to tighter orbits following the common envelope and therefore more tidally spun up second-born black holes. However, these systems have short merger timescales and are only marginally detectable by current gravitational-wave detectors as they form and merge at high redshifts (z ∼ 2), outside current detector horizons. Assuming Eddington-limited accretion efficiency and that the first-born black hole is formed with a negligible spin, we find that all non-zero χeff systems in the detectable population can come only from the common envelope channel as the stable mass-transfer channel cannot shrink the orbits enough for efficient tidal spin-up to take place. We find that the local rate density (z ≃ 0.01) for the common envelope channel is in the range of ∼17–113 Gpc−3 yr−1, considering a range of αCE ∈ [0.2, 5.0], while for the stable mass transfer channel the rate density is ∼25 Gpc−3 yr−1. The latter drops by two orders of magnitude if the mass accretion onto the black hole is not Eddington limited because conservative mass transfer does not shrink the orbit as efficiently as non-conservative mass transfer does. Finally, using GWTC-2 events, we constrained the lower bound of branching fraction from other formation channels in the detected population to be ∼0.2. Assuming all remaining events to be formed through either stable mass transfer or common envelope channels, we find moderate to strong evidence in favour of models with inefficient common envelopes.
Revisiting the mass- and radius–luminosity relations for FGK main-sequence stars
Authors: Fernandes João , Gafeira Ricardo , Andersen Johannes
Published: February 2021

Context. Scaling relations are very useful tools for estimating unknown stellar quantities. Within this framework, eclipsing binaries are ideal for this goal because their mass and radius are known with a very good level of accuracy, leading to improved constraints on the models.

Aims. We aim to provide empirical relations for the mass and radius as function of luminosity, metallicity, and age. We investigate, in particular, the impact of metallicity and age on those relations.

Methods. We used a multi-dimensional fit approach based on the data from DEBCat, an updated catalogue of eclipsing binary observations such as mass, radius, luminosity, effective temperature, gravity, and metallicity. We used the PARAM web interface for the Bayesian estimation of stellar parameters, along with the stellar evolutionary code MESA to estimate the binary age, assuming a coeval hypothesis for both members.

Results. We derived the mass and radius–luminosity–metallicity–age relations using 56 stars, with metallicity and mass in the range −0.34 < [Fe/H] < 0.27 and 0.66 < M/M⊙ < 1.8. With that, the observed mass and radius are reproduced with an accuracy of 3.5% and 5.9%, respectively, which is consistent with the other results in literature.

Conclusions. We conclude that including the age in such relations increases the quality of the fit, particularly in terms of the mass, as compared to the radius. On the other hand, as otherss authors have noted, we observed an higher dispersion on the mass relation than in that of the radius. We propose that this is due to a stellar age effect.
In der Praxis Praxisanleitung ermöglichen
Authors: Brand-Hörsting Birgit
Published: February 2021

Am 1. Januar 2020 ist das neue Pflegeberufegesetz in Kraft getreten. Auf dieser Grundlage wird die generalistische Ausbildung in den Pflegeschulen umgesetzt. Die Folgen für die Praxisanleitung sind weitreichend und fordern ein radikales Umdenken – auch im Pflegemanagement.
Praktisch anleiten
Authors: Gerhard-Mehl Anja
Published: February 2021

Vor über vier Jahren wurden in Kassel bereits die Weichen für eine umfassende Weiterentwicklung der praktischen Anleitung mit der Pflegedirektion und der Akademie für Bildung der Gesundheit Nordhessen ausgearbeitet.
Sag uns wann, wir sagen wo!
Authors: Erle Lynn
Published: February 2021

Um auf der einen Seite einen verlässlichen Dienstplan zu gewährleisten und auf der anderen den Mitarbeitern – etwa Müttern – geregelte Arbeitszeiten anbieten zu können, hat das Klinikum Wolfsburg einen FlexiPool ins Leben gerufen.
ABO Blood Group and Inhibitor Risk in Severe Hemophilia A Patients: A Study from the Italian Association of Hemophilia Centers
Authors: Franchini Massimo , Coppola Antonio , Santoro Cristina , De Cristofaro Raimondo , Barillari Giovanni , Giordano Paola , Gresele Paolo , Lassandro Giuseppe , Napolitano Mariasanta , Lucchini Giuseppe , Luciani Matteo , Ferretti Antonietta , Baldacci Erminia , Riccardi Federica , Santoro Rita Carlotta , Pasca Samantha , Zanon Ezio , Tagliaferri Annarita
Published: February 2021

Considering the profound influence exerted by the ABO blood group system on hemostasis, mainly through the von Willebrand factor and factor VIII (FVIII) complex, we have conducted a study evaluating the possible role of blood type on the risk of inhibitor development in hemophilia A. A total of 287 consecutive Caucasian patients with severe hemophilia A (202 without FVIII inhibitors and 85 with FVIII inhibitors) followed at seven Italian Hemophilia Treatment Centers belonging to the Italian Association of Hemophilia Centers (AICE) were included in the study. A higher prevalence of O blood group was detected in patients without inhibitors as compared in inhibitor patients (55 vs. 30.6%; p < 0.001). Among the other variables analyzed (age, F8 mutation, type and intensity of treatment and treatment regimen), F8 mutation class (high-risk vs. low-risk), and treatment regimen (on-demand vs. prophylaxis) were significantly correlated with inhibitor development. However, on a multivariate analysis, only the effects of F8 mutation and ABO blood type were independent of other covariates, being that non-O blood type is associated with a 2.89-fold increased risk of inhibitor development. In conclusion, our study supports the protective effect of O blood type on inhibitor risk in severely affected hemophilia A patients.
Nonlinear kinetic simulation study of the ion–ion streaming instability in single- and multi-ion species plasmas
Authors: Chapman T. , Winjum B. J. , Berger R. L. , Dimits A. , Banks J. W. , Brunner S. , Joseph I. , Ghosh D.
Published: February 2021

The nonlinear evolution of the ion–ion streaming instability (IISI) is studied using numerical techniques novel to this problem that afford direct insight into the evolution of the particle distributions of each species. During the linear phase of the instability, we demonstrate quantitative agreement with linear kinetic theory. Subsequently, the electrostatic field generated by the IISI causes ring-like velocity distributions of ions to form that are both heated and slowed to varying degrees relative to their initial flows. Due to variation in the trapping conditions for ion species of differing charge-to-mass ratio, when flows of multiple species interact, the nonlinear evolution of each species can be starkly different: we show a case where a lighter ion species is completely stopped by a heavier ion species via the IISI alone (i.e., without collisions) and, for the first time, demonstrate how the IISI can introduce a relative flow between ion species that initially have the same flow velocities, thereby separating them.
Spatial coupling of gyrokinetic simulations, a generalized scheme based on first-principles
Authors: Dominski J. , Cheng J. , Merlo G. , Carey V. , Hager R. , Ricketson L. , Choi J. , Ethier S. , Germaschewski K. , Ku S. , Mollen A. , Podhorszki N. , Pugmire D. , Suchyta E. , Trivedi P. , Wang R. , Chang C. S. , Hittinger J. , Jenko F. , Klasky S. , Parker S. E. , Bhattacharjee A.
Published: February 2021

We present a scheme that spatially couples two gyrokinetic codes using first-principles. Coupled equations are presented and a necessary and sufficient condition for ensuring accuracy is derived. This new scheme couples both the field and the particle distribution function. The coupling of the distribution function is only performed once every few time-steps, using a five-dimensional (5D) grid to communicate the distribution function between the two codes. This 5D grid interface enables the coupling of different types of codes and models, such as particle and continuum codes, or delta-f and total-f models. Transferring information from the 5D grid to the marker particle weights is achieved using a new resampling technique. Demonstration of the coupling scheme is shown using two XGC gyrokinetic simulations for both the core and edge. We also apply the coupling scheme to two continuum simulations for a one-dimensional advection–diffusion problem.
Constructing a new predictive scaling formula for ITER's divertor heat-load width informed by a simulation-anchored machine learning
Authors: Chang C. S. , Ku S. , Hager R. , Churchill R. M. , Hughes J. , Köchl F. , Loarte A. , Parail V. , Pitts R. A.
Published: February 2021

Understanding and predicting divertor heat-load width λq is a critically important problem for an easier and more robust operation of ITER with high fusion gain. Previous predictive simulation data for λq using the extreme-scale edge gyrokinetic code XGC1 [S. Ku et al., Phys. Plasmas 25, 056107 (2018)] in the electrostatic limit under attached divertor plasma conditions in three major US tokamaks [C. S. Chang et al., Nucl. Fusion 57, 116023 (2017)] reproduced the Eich and Goldston attached-divertor formula results [formula #14 in T. Eich et al., Nucl. Fusion 53, 093031 (2013) and R. J. Goldston, Nucl. Fusion 52, 013009 (2012)] and furthermore predicted over six times wider λq than the maximal Eich and Goldston formula predictions on a full-power (Q = 10) scenario ITER plasma. After adding data from further predictive simulations on a highest current JET and highest-current Alcator C-Mod, a machine learning program is used to identify a new scaling formula for λq as a simple modification to the Eich formula #14, which reproduces the Eich scaling formula for the present tokamaks and which embraces the wide λqXGC for the full-current Q = 10 ITER plasma. The new formula is then successfully tested on three more ITER plasmas: two corresponding to long burning scenarios with Q = 5 and one at low plasma current to be explored in the initial phases of ITER operation. The new physics that gives rise to the wider λqXGC is identified to be the weakly collisional, trapped-electron-mode turbulence across the magnetic separatrix, which is known to be an efficient transporter of the electron heat and mass. Electromagnetic turbulence and high-collisionality effects on the new formula are the next study topics for XGC1.
Tunable optical and electrical properties of thermal and plasma-enhanced atomic layer deposited Si-rich SixTi1−xO2 thin films
Authors: Biswas Jayeeta , Bajaj Geetika , Tyagi Astha , Goradia Prerna , Lodha Saurabh
Published: February 2021

Ternary dielectrics with varying composition formed by alloying two binary oxides can enable tunable optical and electrical properties for advanced technological applications. Atomic layer deposition (ALD) gives precise control over ternary dielectric composition through the ability to finely tune the precursor pulsing ratio. This work presents ALD development of Si-rich SixTi1−xO2 dielectrics with varying composition (x), along with spectroscopic and electrical characterization of their properties. Stoichiometry of the SixTi1−xO2 films was determined using X-ray photoelectron spectroscopy. Their composition-dependent refractive index, energy bandgap, and reflectance show promise for diverse optical applications ranging from anti-reflective coatings in photovoltaics to optical waveguides. This work also reports a first comparative study of SixTi1−xO2 films prepared by thermal (T-) and plasma-enhanced (PE-) ALD with varying Si composition and deposition temperatures. Deposition rates of 0.67–0.92 Å/cycle were obtained for SixTi1−xO2 films with x = 0.5–0.91 deposited using PE-ALD at 250 °C, which were higher than that of T-ALD at 200 °C (0.42–0.05 Å/cycle). PE-ALD also exhibited a high deposition rate of 0.81 Å/cycle for SixTi1−xO2 film with x = 0.91 at a low growth temperature of 150 °C. The PE-ALD Si-rich silica–titania films show substantially lower (100×) leakage current densities than the thermally deposited films, along with higher breakdown fields for decreasing deposition temperature. A dielectric constant as low as ∼5 was achieved for PE-ALD SixTi1−xO2 films with high Si (x = 0.91) content.
Polarized Raman scattering in micrometer-sized crystals of triclinic vanadium dioxide
Authors: Shvets Petr , Maksimova Ksenia , Goikhman Alexander
Published: February 2021

Triclinic vanadium dioxide VO2 (T) films were produced using cathodic arc deposition. Under certain conditions, the film growth on sapphire substrates Al2O3 (001) is associated with the formation of triclinic monocrystals with lateral sizes of several tens of micrometers. Borders between different crystallites can be determined by Raman mapping analysis. X-ray diffraction measurements revealed that the micrometer-sized monocrystals had two different orientations—epitaxial (002) and non-epitaxial (201). The film was studied by polarized micro-Raman spectroscopy, which can be used to determine the orientation of any single crystallite. The Raman tensor elements of the VO2 (T) phase were determined, and it was shown that though crystallographically triclinic VO2 cell could be fitted by monoclinic one with a high degree of precision, such monoclinic approximation was not valid in terms of Raman spectroscopy. Contrary to the two types of phonons expected for the monoclinic crystal [having five nonzero (four independent) or four nonzero (two independent) Raman tensor elements], all phonons in VO2 (T) have nine (six independent) generally nonzero tensor components.
Dust-acoustic wave electrostatic and self-gravitational potentials in an opposite polarity dusty plasma system
Authors: Mannan Abdul , De Nicola Sergio , Fedele Renato , Mamun A. A.
Published: February 2021

An opposite polarity dusty plasma system (containing inertial positive as well as negative dust species and inertialess singly charged ion species) is considered. The nature of the electrostatic and self-gravitational potential structures (associated with the dust-acoustic waves) is identified by the numerical analysis of two coupled second-order nonlinear differential equations. The latter are Poisson’s equations for electrostatic and self-gravitational potentials, where the positive and negative dust number densities (determined from their continuity and momentum equations) and the ion number density (determined from the Boltzmann law) are substituted. It is observed that the plasma system under consideration supports the dust-acoustic solitary structures associated with the positive as well as negative self-gravitational potentials but only with the positive electrostatic potential. The basic features of the electrostatic and self-gravitational solitary potential structures are studied. It is also found that the amplitude of the electrostatic and self-gravitational solitary potential structures decreases with the increase in the positive dust number density. The effects of other different dusty plasma parameters on these solitary potential structures are also identified. The applications of this investigation in some space and laboratory dusty plasma systems are pinpointed.
Sustainable and superior polymeric piezoelectric nanogenerator for sensing human body vibration, air flow, and water wave
Authors: Rajak Ujjwal , Khatun Farha , Biswas Prosenjit , Thakur Pradip
Published: February 2021

A simple, lightweight, cost-effective, bio-compatible, and highly sensitive piezoelectric nanogenerator has been sketched in a sustainable manner using naturally available clay, i.e., kaolinite doped poly(vinylidene fluoride) film. The developed nanogenerator is able to produce electrical signals by capturing a very small mechanical signal of our living systems. Very low mechanical impulse due to human body vibration, air flow, and water wave has been well adsorbed by our fabricated piezoelectric nanogenerator to generate electrical output signals. The device generates output voltages (peak to peak) of ∼1.4 V, 325 mV, and 230 mV under human body vibration, air flow, and water wave, respectively. Moreover, under gentle finger impartation (force, ∼12.5 N), the device can generate an open circuit voltage of ∼45 V and a short circuit current of ∼2.9 μA. The results remain almost same for a long tested time duration (∼12 months). The power density is calculated to be 43.5 mW/cm3. A capacitor (∼1 μF) is charged up to ∼2.8 V within 18 s, and several LEDs are lightened using our device as an energy supplier.
An estimation of the axial structure of surface-wave produced plasma column
Authors: Kovačević Milan S. , Kuzmanović Ljubica , Milošević Marko M. , Djordjevich Alexandar
Published: February 2021

An analytical expression to predict the axial distribution of electron density along the surface-wave sustained plasma column has been derived. The model is based on the square root approximation of the dispersion relation that gives a linear roll-off of electron density distribution in the plasma column. The point is to use a more tractable analytical approximation of dispersion relation of surface waves. An expression of attenuation coefficient, which includes the collisional loss, has been applied in studying the structure of the surface-wave produced plasma column. The derived attenuation model predicts a linear axial attenuation of electron density, as well as a nonlinear relation between the glass permittivity dependent frequency sensitivity and the wavenumber. The nonlinearity arises from non-negligible dielectric thickness. This result is consistent with early Aliev's results of the electron density profile, which correspond to the volume collisional absorption regime of surface wave sustained plasmas. The combined effects of surface-wave amplitude attenuation due to collisions and frequency dependence of group velocity cause an axial decrease in the surface wave axial power flux as the wave moves away from the launcher. A short analysis of the sensitivity of the normalized frequency to the permittivity of the glass based on the quasistatic approximation of the dispersion relation of surface waves is given.
Target heating in femtosecond laser–plasma interactions: Quantitative analysis of experimental data
Authors: Nardi Eran , Zinamon Zeev , Stambulchik Evgeny , Zastrau Ulf , Kroupp Eyal , Uschmann Ingo , Paulus Gerhard G. , Maron Yitzhak
Published: February 2021

We study electron heating and stopping power in warm dense matter as formed in interactions of sub-picosecond high-intensity lasers with solid bulk targets. In such interactions, an intense beam of forward moving relativistic electrons is created, inducing a compensating return current and generating characteristic Kα x-ray radiation along the propagation path. The theoretical calculations presented here are inspired by, and tested against, a previously published study that provides bulk-temperature and absolutely calibrated Kα radial profiles. By using Monte Carlo simulations, the experimental data allow for inferring the flux of the relativistic electrons, which is a crucial input for the target heating calculations. For the latter, a “rigid beam” model is employed, describing the central, nearly homogeneous, part of the target. The comparison with the experiment shows a fairly good agreement. For the conditions analyzed, we find that the effect of the return current is dominant both in the target heating and in the beam stopping.
Enhanced logical chaotic resonance
Authors: Yao Yuangen , Ma Jun , Gui Rong , Cheng Guanghui
Published: February 2021

It was demonstrated recently that logical chaotic resonance (LCR) can be observed in a bistable system. In other words, the system can operate robustly as a specific logic gate in an optimal window of chaotic signal intensity. Here, we report that the size of the optimal window of chaotic signal intensity can be remarkably extended by exploiting the constructive interaction of chaotic signal and periodic force, as well as coupling, in a coupled bistable system. In addition, medium-frequency periodic force and an increasing system size can also lead to an improvement in the response speed of logic devices. The results are corroborated by circuit experiments. Taken together, a reliable and rapid-response logic operation can be realized based on periodic force- and array-enhanced LCR.
Linearized dynamical system for extended magnetohydrodynamics in terms of Lagrangian displacement fields and isovortical perturbations
Authors: Hirota M.
Published: February 2021

Linear stability theory for extended magnetohydrodynamics (XMHD), which incorporates the Hall and electron-inertia effects into MHD, is developed by introducing Lagrangian displacement fields for ions and electrons. For simplicity, incompressible and dissipationless XMHD is assumed in this work, since the present consideration is greatly inspired by an analogy with incompressible ideal fluid. The governing equations for the Lagrangian displacement fields are written as a gyroscopic dynamical system, to which the well-established canonical Hamiltonian theory is ready to apply. This linear perturbation can be further restricted to the isovortical one in the same manner as ideal fluid, which is more generally understood as dynamically accessible perturbation in a constrained Hamiltonian system. In XMHD, there are two isovortical constraints corresponding to the two canonical vorticities for ions and electrons. It is shown that the Frieman–Rotenberg equation for ideal MHD is reproduced by not only neglecting the Hall and electron-inertia effects but also imposing one of the two isovortical constraints. As an application, a new stability condition for static equilibria of inertial MHD is derived.
Change in vibrational entropy with change in protein volume estimated with mode Grüneisen parameters
Authors: Reid Korey M. , Yu Xin , Leitner David M.
Published: February 2021

For a small adjustment in average volume, due to a change in state of a protein or other macromolecule at constant temperature, the change in vibrational entropy is related to the mode Grüneisen parameters, which relate shifts in frequency to a small volume change. We report here values of mode Grüneisen parameters computed for two hydrated proteins, cytochrome c and myoglobin, which exhibit trends with mode frequency resembling those of glassy systems. We use the mode Grüneisen parameters to relate volumetric thermal expansion to previously computed values of the isothermal compressibility for several proteins. We also estimate changes in vibrational entropy resulting from the change in volume upon ligand bonding of myoglobin and the homodimeric hemoglobin from Scapharca inaequivalvis (HbI). We compare estimates of the change in entropy upon ligation obtained in terms of mode Grüneisen parameters with the results of normal mode analysis for myoglobin and earlier molecular dynamics simulations of HbI. The results illustrate how small changes in average volume can yield changes in entropy that contribute to ligand binding and allostery.
Quantum and quasiclassical dynamical simulations for the Ar2H+ on a new global analytical potential energy surface
Authors: Koner Debasish
Published: February 2021

A new analytical potential energy surface (PES) has been constructed for the Ar2H+ system from a dataset consisting of a large number of ab initio energies computed using the coupled-cluster singles, doubles and perturbative triples method and aug-cc-pVQZ basis set. The long-range interaction is added to the diatomic potentials using a standard long range expansion form to better describe the asymptotic regions. The vibrational states for the most stable structures of the Ar2H+ system have been calculated, and few low lying states are assigned to quantum numbers. Reactive scattering studies have been performed for the Ar + Ar′H+ → Ar′ + ArH+ proton exchange reaction on the newly generated PES. Reaction probability, cross sections, and rate constants are calculated for the Ar + Ar′H+(v = 0, j = 0) collisions within 0.01 eV–0.6 eV of relative translational energy using exact quantum dynamical simulations as well as quasiclassical trajectory (QCT) calculations. The effect of vibrational excitation of the reactants is also explored for the reaction. State averaged rate constants are calculated for the proton exchange reaction at different temperatures using the QCT method. The mechanistic pathways for the reaction are understood by analyzing the quasiclassical trajectories.
Theoretical insights into the thermal reduction of N2 to NH3 over a single metal atom incorporated nitrogen-doped graphene
Authors: Fang Zhongpu , Wang Qi , Li Yanli , Li Yi , Huang Shuping , Lin Wei , Chen Wenkai , Zhang Yongfan
Published: February 2021

Density functional theory calculations have been performed to study the reaction mechanism of N2 thermal reduction (N2TR) over a single metal atom incorporated nitrogen-doped graphene. Our results reveal that the type of metal atoms and their coordination environments have a significant effect on the catalytic activity of N2TR. Regarding CoN4- and FeN4-embedded graphene sheets that the metal atom is fourfold coordinated, they are inactive for N2TR owing to the poor stability of the adsorbed H2 and N2 molecules. In contrast, if the monodisperse metal atom is surrounded by three N atoms, namely, CoN3/G and FeN3/G show activity toward N2TR, and catalytic conversion of N2 into ammonia is achieved through the associative mechanism rather than the dissociative mechanism. Further investigations show that the synthesis of NH3 over the two surfaces is mainly through the formation of an NHNH* intermediate; however, the detailed reaction mechanisms are sensitive to the type of metal atom introduced into N-doped graphene. Based on the calculated kinetic barriers, FeN3/G exhibits a better catalytic activity for N2TR. The superior performance of FeN3/G can be attributed to the fact that this surface prefers a high spin-polarized state during the whole process of N2TR, while the non-spin polarized state is predicted as the ground state for most of the elementary steps of N2-fixation over CoN3/G. The present study provides theoretical insights into developing graphene-based single atom catalysts with a high activity toward ammonia synthesis through N2TR.
Impact of the degree of dehydrogenation in ethanol C–C bond cleavage on Ir(100)
Authors: Wu Ruitao , Wiegand Kaitlyn R. , Wang Lichang
Published: February 2021

A lack of comprehensive studies of the C–C bond cleavage in organic molecules hampers the rational design of catalysts for many applications, such as in fuel cells and steam reforming technologies. Employing ethanol on Ir(100) as an example, we studied 14 C–C bond cleavages of various species involved in the ethanol oxidation reaction using density functional theory calculations and used the degree of dehydrogenation (DoDH) of the reactant species as a variable to correlate the C–C bond cleavage barrier and reaction energy. This correlation method was also applied to the dehydrogenation reactions of ethanol on various catalysts, and great insight was obtained. The results show that the C–C cleavage barrier generally decreases with DoDH, with a local minimum around 33.3% DoDH. For reactants having more than 50% DoDH, the C–C cleavage is more ready to take place than the dehydrogenation and can occur at room temperature. Furthermore, the O atom in the reactive species plays a critical role in lowering the C–C bond cleavage barrier. The results provide necessary inputs for kinetic studies of ethanol reactions under operando conditions, where a reaction network beyond the minimum energy pathway is needed. The results will also serve as a benchmark for future studies of the ethanol C–C cleavage on other facets of Ir catalysts or on different catalysts. Furthermore, this work demonstrates that the proposed method opens up a new and effective way of correlating catalytic activities for the C–C bond cleavage involving long-chain alkanes and alcohols.
Defect effect on the performance of nonpolar GaN-based ultraviolet photodetectors
Authors: Yang Yuhui , Wang Wenliang , Zheng Yulin , You Jiawen , Huang Siyu , Wu Kefeng , Kong Deqi , Luo Zhengtang , Chen Hong , Li Guoqiang
Published: February 2021

The anisotropy of GaN(11-20) makes it possible to fabricate polarized ultraviolet (UV) photodetectors (PDs) for applications in fields such as remote sensing and airborne astronomical navigation. The defect density has a significant effect on the performance of GaN(11-20)-based UV PDs. However, the mechanism through which different defects and their densities affect the performance of these devices is unclear. Therefore, in this work, we investigated the mechanisms of the screw or mixed dislocation, edge dislocation, and basal stacking fault (BSF) densities affecting the dark current, responsivity, and response time of GaN (11-20)-based PDs, respectively. We observed that the screw or mixed dislocation increased the dark current mainly through reducing the Schottky barrier height and forming leakage current, whereas the edge dislocation and BSF decreased the responsivity by reducing the electron mobility. Furthermore, all the three types of defects increased the response time through forming traps to recombine the holes with electrons and thus delaying the escape of carriers. These results are highly significant for developing nonpolar GaN-based UV PDs.
Finite-temperature dynamical and static properties of Nd magnets studied by an atomistic modeling
Authors: Nishino Masamichi , Uysal Ismail Enes , Hinokihara Taichi , Miyashita Seiji
Published: February 2021

We investigate static and dynamical properties of the Nd permanent magnet, Nd2Fe14B, using a recently developed atomistic model. We show the temperature dependence of magnetizations and domain wall profiles by a Monte Carlo method. With the use of the stochastic Landau-Lifshitz-Gilbert method, we present an unusual temperature dependence of the ferromagnetic resonance frequency. By introducing a statistical method which extends the limitation of the simulation time, we estimate the coercive force of a single grain. We also show the surface anisotropy effect of Nd atoms on the coercive force and nucleation and pinning fields in a prototype hard-soft-hard magnet model.
Network motifs involving both competition and facilitation predict biodiversity in alpine plant communities
Authors: Losapio Gianalberto , Schöb Christian , Staniczenko Phillip P. A. , Carrara Francesco , Palamara Gian Marco , De Moraes Consuelo M. , Mescher Mark C. , Brooker Rob W. , Butterfield Bradley J. , Callaway Ragan M. , Cavieres Lohengrin A. , Kikvidze Zaal , Lortie Christopher J. , Michalet Richard , Pugnaire Francisco I. , Bascompte Jordi
Published: February 2021

Significance

Biodiversity is driven by complex associations among species, but ecologists often look only at competitive or facilitative interactions either independently or only for few species at a time. Using a large dataset of mountain ecosystems encompassing more than 2,000 species across the globe, we analyze the prevalence and importance of both positive and negative associations among plants. Our findings indicate that facilitation and competition between plant species must be studied together in order to explain biodiversity change.
Mechanism and ultrasensitivity in Hedgehog signaling revealed by Patched1 disease mutations
Authors: Petrov Kostadin , de Almeida Magalhaes Taciani , Salic Adrian
Published: February 2021

Significance

The Hedgehog signaling pathway is fundamental in animal development, controlling the size, morphology, and differentiation of tissues and organs. How Hedgehog signaling is evolutionarily tuned to produce different outputs is poorly understood. We use cell biology, mathematical modeling, and analysis of mutations causing birth defects to demonstrate that ultrasensitivity is a key signal-processing feature of the Hedgehog pathway, which can lead to different outputs. We explain ultrasensitivity by a mathematical model of Hedgehog signaling whereby the tumor-suppressor membrane protein Patched catalyzes the deactivation of the GPCR-like transducer Smoothened in primary cilia. The Sonic Hedgehog ligand binds and inhibits Patched, causing switch-like Smoothened activation. Our results clarify the regulation of the Patched–Smoothened module in normal signaling and in disease.
A machine learning-based framework for modeling transcription elongation
Authors: Feng Peiyuan , Xiao An , Fang Meng , Wan Fangping , Li Shuya , Lang Peng , Zhao Dan , Zeng Jianyang
Published: February 2021

Significance

Although plenty of studies have identified the RNA polymerase II (Pol II) pausing events in eukaryotes and demonstrated the regulatory roles of such events in gene expression and RNA processing, there was no study that systematically modeled the global landscape of Pol II pausing in the whole genome. Here, we have developed a deep learning framework that can accurately predict the Pol II pausing events from the contextual DNA sequences. Through applying our powerful computational approach to predict the pausing tendencies on interested regions in the human genome, we provided useful insights into understanding the relations between Pol II pausing events and alternative splicing, transcription factors, histone modifications, and DNA methylation.
SOX9-COL9A3–dependent regulation of choroid plexus epithelial polarity governs blood–cerebrospinal fluid barrier integrity
Authors: Vong Keng Ioi , Ma Tsz Ching , Li Baiying , Leung Thomas Chun Ning , Nong Wenyan , Ngai Sai Ming , Hui Jerome Ho Lam , Jiang Liwen , Kwan Kin Ming
Published: February 2021

Significance

Tight regulation of the brain microenvironment is fundamental to proper neurologic function. The restriction of molecule entry into the central nervous system from the brain vascular endothelium has been well studied; however, far less is known about the molecular events that control permeability across the choroid plexus (CP) epithelium at the interface between the systemic circulation and cerebrospinal fluid (CSF). Our study establishes an essential role for SOX9 in the regulation of CP permeability. SOX9 induces the transcription of
Col9a3
, which mediates the microtubule dynamics necessary for orienting cell polarity and thereby assembling epithelial tight junctions. Our findings lay the groundwork for the manipulation of blood–CSF barrier permeability and expand our understanding of epithelial tissue integrity.
A high-resolution record of early Paleozoic climate
Authors: Goldberg Samuel L. , Present Theodore M. , Finnegan Seth , Bergmann Kristin D.
Published: February 2021

Significance

The Cambrian–Ordovician (541 million to 443 million y ago) climate record is poorly constrained due to the sparsity of carbonate fossils typically used for temperature reconstructions. We demonstrate that the abundant carbonate sediments from this time can preserve isotopic compositions and trends similar to those of fossil material and combine sediment records into a high-resolution proxy record of Late Cambrian and Ordovician climate. Examination of this record in the context of evolutionary and tectonic changes demonstrates that Earth’s climate was tightly coupled to tectonic and volcanic activity and played a strong role in biodiversity trends during the time of early animal evolution.
Lipopeptide-mediated bacterial interaction enables cooperative predator defense
Authors: Zhang Shuaibing , Mukherji Ruchira , Chowdhury Somak , Reimer Lisa , Stallforth Pierre
Published: February 2021

Significance

Natural products are important mediators in interacting microbial communities. Here, we show that bacteria can defend themselves against a common predator by teaming up. This form of cooperative defense relies on the production of a linear lipopeptide by a
Pseudomonas
species, which induces the production of peptidases and proteases in a
Paenibacillus
species. These enzymes degrade the lipopeptide into fragments which are highly toxic to the amoebal predator. Investigating microbial interactions enables identification of novel chemical entities with potent biological functions.
Expression attenuation as a mechanism of robustness against gene duplication
Authors: Ascencio Diana , Diss Guillaume , Gagnon-Arsenault Isabelle , Dubé Alexandre K. , DeLuna Alexander , Landry Christian R.
Published: February 2021

Significance

Many studies have focused on the mechanisms of long-term retention of gene duplicates, such as the gain of functions or reciprocal losses. However, such changes are more likely to occur if the duplicates are maintained for a long period. This time span will be short if duplication is immediately deleterious. We measured the distribution of fitness effects of gene duplication for 899 genes in budding yeast. We find that gene duplication is more likely to be deleterious than beneficial. However, contrary to previous models, in general, gene duplication does not affect fitness by altering the organization of protein complexes. We show that expression attenuation may protect complexes from the effects of gene duplication.
The feeding system of
Tiktaalik roseae
: an intermediate between suction feeding and biting
Authors: Lemberg Justin B. , Daeschler Edward B. , Shubin Neil H.
Published: February 2021

Significance

The water-to-land transition is a major event in vertebrate history, involving significant changes to feeding structures and mechanics. In water, fish often use suction-feeding to capture prey, but this feeding strategy is not possible on land. Therefore, it has been traditionally believed that the invasion of land involved a shift from suction-based prey capture to mechanisms based on biting and snapping. Computed tomography analysis of
Tiktaalik roseae
, a key intermediate in tetrapod evolution, compared with extant analogs (gars and polypterids), reveals a rigid skull, capable of biting, with joint morphologies suggestive of cranial kinesis and suction generation. An intermediate condition that utilizes both feeding strategies helps explain some of the key morphological changes in cranial anatomy during the water-to-land transition.
Determinism and contingencies shaped the evolution of mitochondrial protein import
Authors: Rout Samuel , Oeljeklaus Silke , Makki Abhijith , Tachezy Jan , Warscheid Bettina , Schneider André
Published: February 2021

Significance

All mitochondria import most of their proteins from the cytosol. Even though the targeting signals of imported proteins are well conserved within eukaryotes, this is not the case for the mitochondrial outer membrane receptors that recognize these signals. Here we compare the substrate preferences of protein import receptors from the parasitic protozoansTrypanosoma bruceiandTrichomonas vaginalis, as well as from yeast. Using biochemical and proteomic analysis, combined with complementation experiments, we show that evolutionarily unrelated receptors can share the same substrate preferences. Moreover, we provide evidence that receptors sharing the same domain structure and topology can have different substrate specificity. In summary, our study illustrates how determinism and contingencies have shaped the evolution of mitochondrial import receptors.
In situ magnetic identification of giant, needle-shaped magnetofossils in Paleocene–Eocene Thermal Maximum sediments
Authors: Wagner Courtney L. , Egli Ramon , Lascu Ioan , Lippert Peter C. , Livi Kenneth J. T. , Sears Helen B.
Published: February 2021

Significance

Giant magnetofossils are the preserved remains of iron-biomineralizing organisms that have so far been identified only in sediments deposited during ancient greenhouse climates. Giant magnetofossils have no modern analog, but their association with abrupt global warming events links them to environmental disturbances. Thus, giant magnetofossils may encode information about nutrient availability and water stratification in ancient aquatic environments. Identification of giant magnetofossils has previously required destructive extraction techniques. We show that giant, needle-shaped magnetofossils have distinct magnetic signatures. Our results provide a nondestructive method for identifying giant magnetofossil assemblages in bulk sediments, which will help test their significance with respect to environmental change.
Social penumbras predict political attitudes
Authors: Gelman Andrew , Margalit Yotam
Published: February 2021

Significance

The political influence of a group is typically explained in terms of its size, geographic concentration, or the wealth and power of the group’s members. This article introduces another dimension, the penumbra, defined as the set of individuals in the population who are personally familiar with someone in that group. Distinct from the concept of an individual’s social network, penumbra refers to the circle of close contacts and acquaintances of a given social group. Using original panel data, the article provides a systematic study of various groups’ penumbras, focusing on politically relevant characteristics of the penumbras (e.g., size, geographic concentration, sociodemographics). Furthermore, we show the connection between changes in penumbra membership and public attitudes on policies related to the group.
Amygdala-hippocampal innervation modulates stress-induced depressive-like behaviors through AMPA receptors
Authors: Ma Hui , Li Chenyang , Wang Jinpeng , Zhang Xiaochen , Li Mingyue , Zhang Rong , Huang Zhuo , Zhang Yong
Published: February 2021

Significance

Basal lateral amygdala and ventral CA1 are critical sites during chronic stress-induced depression. Here we demonstrated that AMPARs mediated weakening of pBLA-vCA1 innervation in mice subjected to CUMS. Stimulation of pBLA-vCA1 innervation via chemogenetics or administration of cannabidiol (CBD) could reverse synaptosomal AMPAR decrease and alleviate CUMS-induced depressive-like behaviors. These findings highlighted the importance of AMPARs and the pBLA-vCA1 innervation in an animal model of depression and revealed the potential for CBD in major depression treatment.