bluuebunny/crossref_metadata_2025 huggingface dataset:
Bimetallic superalkali substitution in the CsPbBr3 perovskite: Pseudocubic phases and tunable bandgap
Authors: Sikorska Celina , Gaston Nicola
Published: October 2021

Perovskites attract attention as efficient light absorbers for solar cells due to their high-power conversion efficiency (up to 24%). The high photoelectric conversion efficiency is greatly affected by a suitable band structure. Cation substitution can be an effective approach to tune the electronic band structure of lead halide perovskites. In this work, superalkali cations were introduced to replace the Cs+ cation in the CsPbBr3 material. The bimetallic superalkalis (LiMg, NaMg, LiCa, and NaCa) were inserted since they are structurally simple systems and have a strong tendency to lose one electron to achieve a closed-shell cation. The cation substitution in the lead halide perovskite leads to changes in the shape of both valence and conduction bands compared to CsPbBr3. Introducing superalkali cations produces extra electronic states close to the Fermi level, which arise from the formation of alkali earth metal states at the top of the valence band. Our first-principles computations reveal that bimetallic superalkali substitution decreases the bandgap of the perovskite. The bandgaps of MgLi–PbBr3 (1.35 eV) and MgNa–PbBr3 (1.06 eV) are lower than the bandgap of CsPbBr3 (2.48 eV) and within the optimal bandgap (i.e., 1.1–1.4 eV) for single-junction solar cells. Thus, the MgLi–PbBr3 and MgNa–PbBr3 inorganic perovskites are promising candidates for high-efficiency solar cells.
Phase diagram for nanodroplet impact on solid surfaces
Authors: Ma Qiang , Wang Yi-Feng , Wang Yi-Bo , He Xin , Zheng Shao-Fei , Yang Yan-Ru , Wang Xiao-Dong , Lee Duu-Jong
Published: October 2021

The impact dynamics of water nanodroplets on flat solid surfaces was studied by molecular dynamics simulations over a wide range of Weber numbers (We) and surface wettability (θ0), where θ0 is the Young contact angle. A phase diagram in the parameter space of We vs θ0 was established accommodating eight impact outcomes noted in the final stage of impact, with three of them, holes rebound, partial-rebound splash, and rebound splash, for the first time being identified and reported. The eight impact outcomes were classified into three categories, i.e., non-bouncing, bouncing, and splash. The results show that the splash is triggered only when Wecr > 140. The boundaries separating bouncing from non-bouncing were determined based on the phase diagram. When θ0 > 160°, the boundary is described as Wecr = a ≪ 1; when 110° < θ0 < 160°, the boundary depends on both We and θ0, with a larger We required to trigger bouncing on a less hydrophobic surface, expressed as Wecr = b + ccosθ0; when θ0 < 110°, bouncing never takes place, and hence, the boundary is determined only by the critical contact angle, expressed as θ0,cr = 110°. Here, a, b, and c are constants.
Magnetic properties manipulation of CrTe2 bilayer through strain and self-intercalation
Authors: Li Qiu-Qiu , Li Si , Wu Dan , Ding Zhong-Ke , Cao Xuan-Hao , Huang Lin , Pan Hui , Li Bo , Chen Ke-Qiu , Duan Xi-Dong
Published: October 2021

Two-dimensional van der Waals magnetic crystals have been attracting significant research interest in recent years, and the manipulation of their magnetism is important for understanding their physical property and achieving their actual applications. Here, we systematically studied the manipulation of magnetic properties of a CrTe2 bilayer through in-plane strain and self-intercalation. We found that the magnetic ground state of the CrTe2 bilayer varies from intralayer antiferromagnetic coupling to ferromagnetic coupling and then to interlayer antiferromagnetic coupling when the strain changes from −6% to 4%, which should result from the coupling between intralayer Cr atoms tuned from direct Cr–Cr exchange to indirect Cr–Te–Cr superexchange. The magnetic easy axis of the CrTe2 bilayer varies from the in-plane to the out-of-plane owing to the change of pz orbital occupation from Te atoms near the Fermi level. Moreover, the magnetic ground states of different Cr-intercalated concentrations for the CrTe2 bilayer are all ferromagnetic, and the magnetic easy axis is in-plane, which are different from the intrinsic one. Our results indicate that the magnetic property of the CrTe2 bilayer is sensitive to the in-plane strain and self-intercalation, which provides important guidance for the further magnetic manipulation of the CrTe2 bilayer in theoretical research and application of magnetic strain sensors and spin transistors.
Intersystem crossing and internal conversion dynamics with GAIMS-TeraChem: Excited state relaxation in 2-cyclopentenone
Authors: Mukherjee Saikat , Varganov Sergey A.
Published: October 2021

Excited states relaxation in complex molecules often involves two types of nonradiative transitions, internal conversion (IC) and intersystem crossing (ISC). In the situations when the timescales of IC and ISC are comparable, an interplay between these two types of transitions can lead to complex nonadiabatic dynamics on multiple electronic states of different characters and spin multiplicities. We demonstrate that the generalized ab initio multiple spawning (GAIMS) method interfaced with the fast graphics processing unit-based TeraChem electronic structure code can be used to model such nonadiabatic dynamics involving both the IC and ISC transitions in molecules of moderate size. We carried out 1500 fs GAIMS simulations leading to the creation of up to 2500 trajectory basis functions to study the excited states relaxation in 2-cyclopentenone. After a vertical excitation from the ground state to the bright S2 state, the molecule quickly relaxes to the S1 state via conical intersection. The following relaxation proceeds along two competing pathways: one involves IC to the ground state, and the other is dominated by ISC to the low-lying triplet states. The time constants describing the population transfer between the six lowest singlet and triplet states predicted by the GAIMS dynamics are in good agreement with the characteristic times of IC and ISC obtained from the analysis of the time-resolved photoelectron spectrum.
Molecular beam epitaxy of phase-pure antiperovskite Sr3SnO thin films
Authors: Wu Wangzhou , Combs Nicholas G. , Stemmer Susanne
Published: October 2021

The antiperovskite oxide Sr3SnO has attracted substantial interest due to its topologically non-trivial band structure. Sr-deficient Sr3-xSnO can become superconducting, making it a candidate intrinsic topological superconductor. Here, we show that epitaxial, phase-pure Sr3-xSnO films can be synthesized by molecular beam epitaxy (MBE) using solid Sr and SnO2 sources. We show that Sn-rich growth conditions result in a large amount of a Sn-rich impurity phase, which is challenging to detect in x-ray diffraction. Carrier densities and the amount of the impurity phase change systematically with the growth conditions, indicating that MBE provides excellent control over the films' stoichiometry. We discuss the electrical properties, including quantum interference phenomena, which support the topological nature of the films.
A simple generalization of the energy gap law for nonradiative processes
Authors: Jang Seogjoo J.
Published: October 2021

For more than 50 years, an elegant energy gap (EG) law developed by Englman and Jortner [Mol. Phys. 18, 145 (1970)] has served as a key theory to understand and model the nearly exponential dependence of nonradiative transition rates on the difference of energy between the initial and final states. This work revisits the theory, clarifies the key assumptions involved in the rate expression, and provides a generalization for the cases where the effects of temperature dependence and low-frequency modes cannot be ignored. For a specific example where the low-frequency vibrational and/or solvation responses can be modeled as an Ohmic spectral density, a simple generalization of the EG law is provided. Test calculations demonstrate that this generalized EG law brings significant improvement over the original EG law. Both the original and generalized EG laws are also compared with the stationary phase approximations developed for electron transfer theory, which suggests the possibility of a simple interpolation formula valid for any value of EG.
Multiple Dirac states in two-dimensional topological half-metallic CrB2C2
Authors: Zhang Bingwen , Chen Xuejiao , Wang Jun
Published: October 2021

Recently, Dirac states in two dimensional materials have drawn great attention because of its desirable transport properties. In this paper, we predicted a two-dimensional hexagonal CrB2C2, which exhibits stable mechanical and thermal properties. Young's modulus of CrB2C2 is 485.67  N/m, which is comparable with that of graphene. In addition, CrB2C2 is half-metallic, and the ferromagnetic Curie temperature is about 1500  K, which is far above room temperature. A CrB2C2 nanosheet exhibits multiple Dirac states in the spin minority channel and forms compensated electron-hole pockets. The Fermi velocity of two different Dirac states is about 4.18×105 and 3.42×105  m/s. In the electronic band structure, the Dirac state at the K point is weakly gapped by 0.38  meV under a spin orbital interaction, while the other one could be topological nontrivially gapped by 37.4  meV, and the bottom Dirac band exhibits a nonzero Chern number at about 0.25  eV above the Fermi energy.
Ultrafast stimulated resonance Raman signatures of lithium polysulfides for shuttling effect characterization: An ab initio study
Authors: Ren Hao , Wang Zhengjie , Guo Sibei , Guo Wenyue , Tian Guangjun , Tian Baoling
Published: October 2021

The shuttling effect is a crucial obstacle to the practical deployment of lithium sulfur batteries (LSBs). This can be ascribed to the generation of lithium polysulfide (LiPS) redox intermediates that are soluble in the electrolyte. The detailed mechanism of the shuttling, including the chemical structures responsible for the loss of effective mass and the dynamics/kinetics of the redox reactions, are not clear so far. To obtain this microscopic information, characterization techniques with high spatial and temporal resolutions are required. Here, we propose that resonance Raman spectroscopy combined with ultrafast broadband pulses is a powerful tool to reveal the mechanism of the shuttling effect. By combining the chemical bond level spatial resolution of resonance Raman and the femtosecond scale temporal resolution of the ultrafast pulses, this novel technique holds the potential of capturing the spectroscopic fingerprints of the LiPS intermediates during the working stages of LSBs. Using ab initio simulations, we show that, in addition to the excitation energy selective enhancement, resonance Raman signals of different LiPS intermediates are also characteristic and distinguishable. These results will facilitate the real-time in situ monitoring of LiPS species and reveal the underlying mechanism of the shuttling effect.
Ballistic transport in sub-10 nm monolayer planar GaN transistors for high-performance and low-power applications
Authors: Wang Boyu , Ning Jing , Zhang Jincheng , Wang Dong , Yang Xinyi , Jia Yanqing , Zhang Chi , Zeng Yu , Hao Yue
Published: October 2021

With the constant scaling down of transistors, “More Moore” has put forward requirements for channel materials. Two-dimensional materials are considered as potential next-generation channel materials due to their unique physical properties. Herein, we study the ballistic transport characteristics of sub-10 nm monolayer (ML) planar GaN metal–oxide–semiconductor field-effect transistors (MOSFETs) based on density functional theory and the non-equilibrium Green's function method. The calculation results indicate that n-type ML planar GaN MOSFETs with gate lengths not less than 5 nm exhibit excellent subthreshold characteristics, fast switching speeds, and low switching energies, and the corresponding parameters (off-current, on-current, delay time, and power-delay product) can simultaneously meet the requirements of the International Roadmap for Devices and Systems for the 2028 horizon for high-performance and low-power applications. Therefore, ML planar GaN is predicted to be a reliable next-generation channel material to extend Moore's law.
Rotational dynamics and transitions between Λ-type doubling of NO induced by an intense two-color laser field
Authors: Nakamura Kenta , Fukahori Shinichi , Hasegawa Hirokazu
Published: October 2021

We numerically investigate the rotational dynamics of NO in the electronic ground X2Π state induced by an intense two-color laser field (10 TW/cm2) as a function of pulse duration (0.3–25 ps). In the short pulse duration of less than 12 ps, rotational Raman excitation is effectively induced and results in molecular orientation. On the contrary, when the pulse duration is longer than 15 ps, the rotational excitation is suppressed. In addition to the rotational excitation, we find that transitions between Λ-type doubling are induced. Significantly, the maximum coherent wave packet between Λ-type doubling in J = 0.5 is generated using the pulse duration of 19.8 ps. The wave packet changes to the eigenstates of Λ = +1 or −1 alternatively, where Λ is the projection of the electronic orbital angular momentum on the N–O axis, which is regarded as the unidirectional rotation of an unpaired 2π electron around the N–O axis in a space-fixed frame as well as in a molecule-fixed frame. The experimental method to observe the alternation of the rotational direction of the electron around the N–O axis is proposed.
Spectroscopic study of the tunneling dynamics in N2-water observed in the O–D stretch region
Authors: Glorieux R. , Lauzin C. , Barclay A. J. , Herman M. , Moazzen-Ahmadi N.
Published: October 2021

The O–D stretch rovibrational spectra of N2–D2O and N2–DOH were measured and analyzed. A combination band involving the in-plane N2 bending vibration was also observed. These bands were recorded using a pulsed-slit supersonic jet expansion and a mid-infrared tunable optical parametric oscillator. The spectra were analyzed by considering the feasible tunneling motions, and transitions were fitted to independent asymmetric rotors for each tunneling state. The rotational constants of the four tunneling components of N2–D2O were retrieved for the excited vibrational states. A two order of magnitude increase in the tunneling splittings is observed for the asymmetric O–D stretch (ν3 in D2O) excitation compared to the symmetric stretch (ν1 in D2O) and to the ground vibrational state. This last finding indicates that the ν3 vibrational state is likely perturbed by a combination state that includes ν1. Finally, the observation of a local perturbation in the ν3 vibrational band, affecting the positions of few rovibrational levels, provides an experimental lower limit of the dissociation energy of the complex, D0 > 120 cm−1.
Grazing strategies for resilience of ryegrass (
Authors: Tozer Katherine , Müller Karin , Craven Anthony , Cameron Catherine
Published: October 2021

Perennial ryegrass (Lolium perenne L.) is a widely sown pasture species in temperate regions. Under heat and moisture-deficit stress, its production is suppressed and tiller mortality increases, particularly when plants are simultaneously exposed to other stresses such as intense defoliation. We investigated the effects of extended grazing exclusion periods in spring and summer on herbage and soils of rotationally grazed, perennial ryegrass-dominant pastures at a summer-wet site and a summer-dry site in sheep and beef hill country in New Zealand. Treatments comprised ‘grazed’ (conventional rotational grazing), ‘early opening’ (grazing exclusion from mid-spring to mid-summer to allow perennial ryegrass to flower), and ‘deferred grazing’ (grazing exclusion from mid-spring to late summer to allow perennial ryegrass to flower and set seed). At both sites, deferred grazing increased perennial ryegrass tiller density and total vegetation cover, and reduced the abundance of broadleaf species and Pseudopithomyces chartarum spores for up to 15 months after exclusion compared with the grazed control. Herbage production was reduced during the deferred period but there was a growth surge thereafter so that herbage production over the study period was similar in the deferred and grazed treatments. Pasture nutritive values were lower in the deferred than the grazed treatment during the exclusion period but were similar in all treatments by the end of the following winter. In the autumn after deferring, seedlings contributed ~50% of the perennial ryegrass tillers present at the summer-dry site but only ~10% at the summer-wet site, where regrowth tillering of existing plants contributed a high proportion of the perennial ryegrass tillers present. Overall, early opening had few effects on the pasture, whereas deferred grazing had numerous positive effects on the pasture but only short-term effects on soil quality.
Salt precipitation and evaporative flux on sandy soil with saline groundwater under different evaporation demand conditions
Authors: Li Xinhu , Shi Fengzhi
Published: October 2021

Context Salt precipitation and its influence on evaporation have been widely studied in recent years. However, the evolution process of salt precipitation and evaporative flux is poorly understood under various evaporation demand (ED) rate condition, which is defined as the evaporation rate of distilled water from soil under constant radiation conditions. Aims and methods This study investigated the evolution of salt crust and evaporative flux on sand soil columns with fixed saline groundwater at a depth of 20 cm under four ED conditions (29.5, 21.5, 9.0 and 4.0 mm day−1). Key results Evaporation rate significantly decreased in all treatments because the salt crust was elevated and salt domes formed, but the salt patterns of salt precipitation and evaporation exhibited significant differences between different EDs. The homogeneous fine powder crystals precipitated under relatively high ED conditions (29.5 and 21.5 mm day−1), and tended to aggregate and form an elevated salt crust in the initial period of salt precipitation. Consequently, it resulted in a sharp decrease in evaporation during the initial period of salt precipitation. In contrast, discrete and large crystals observed under low ED conditions (9.0 and 4.0 mm day−1), resulted in a stable evaporation stage during the initial period of salt precipitation. The highest relative evaporation rate was observed under the lowest ED condition when the evaporation rate reached stability, which was attributed to the formation of small and discrete salt domes, indicating that both the upward and lateral growth of salt precipitation were influenced by ED. Conclusions and implications The physics of salt crust formation needs to be considered in understanding how salt precipitates on the soil surface.
Double-observer distance sampling improves the accuracy of density estimates for a threatened arboreal mammal
Authors: Cripps Jemma K. , Nelson Jenny L. , Scroggie Michael P. , Durkin Louise K. , Ramsey David S. L. , Lumsden Linda F.
Published: October 2021

Abstract Context Determining population size or density is often fundamental for wildlife conservation. For nocturnal species, indices are commonly used in place of abundance estimates, with spotlighting indices (e.g. sighting rate per km) being prevalent. Distance sampling is a collection of techniques that provide estimates of wildlife abundance from line-transect data, by correcting raw counts for imperfect detection. These methods have rarely been used to assess the abundance of nocturnal arboreal mammals. Aims To develop and evaluate a method for estimating the abundance and density of nocturnal arboreal mammals using double-observer distance sampling, and to apply the approach to a survey of the southern greater glider (Petauroides volans) in the Strathbogie Ranges, Victoria, Australia. Methods Two observers, 15–20 min apart, surveyed 25 randomly located 500 m transects, and recorded greater gliders using spotlights and binoculars. Densities and abundances were derived from the line-transect data by using mark–recapture distance sampling (MRDS) models and were compared with conventional distance sampling analysis (CDS). Key results Using the double-observer approach, we estimated an overall density of 0.96 gliders ha−1 (95% CI 0.60–1.50), giving a population estimate of 24 575 greater gliders across the Strathbogie Ranges (25 865 ha, 95% CI 15 620–38 661). The corresponding estimates for the study area derived using CDS applied to either both observers’ observations or to the first observer’s observations only, were 87% and 53% respectively, of the MRDS estimate. The analysis confirmed that the probability of detection of gliders along the transect line was less than one, justifying the use of the double-observer method to obtain accurate estimates of abundance. Conclusions The low detectability of greater gliders means that uncorrected spotlight counts will underestimate abundance, as will CDS. The double-observer method corrects for the negative bias associated with raw counts, enabling more accurate estimation of abundance for survey, monitoring and management purposes. Implications We recommend that double-observer distance sampling is adopted as a standard technique for estimating the abundance of greater gliders. The double-observer method potentially has wider relevance for assessing population size of other arboreal mammals, providing the assumptions of the approach can be met.
People are more tolerant of inequality when it is expressed in terms of individuals rather than groups at the top
Authors: Walker Jesse , Tepper Stephanie J. , Gilovich Thomas
Published: October 2021

Significance

Economic inequality in the developed world has increased substantially over the past several decades. During the COVID-19 pandemic, billionaires saw their wealth increase while many people struggled to meet basic needs. Redistributive policies like wealth and inheritance taxes would reduce this inequality, but broad public support for these policies is elusive. This research finds that the wealth of successful individuals may reduce support for redistribution because people are more likely to believe that the wealth of individuals, rather than groups, at the top is well earned. These findings suggest that the way inequality is presented—with either groups or individuals at the top—affects people’s attributions for how wealth is earned and their tolerance of growing inequality.
Molecular insights into mechanisms of GPCR hijacking by
Staphylococcus aureus
Authors: Grison Claire M. , Lambey Paul , Jeannot Sylvain , Del Nero Elise , Fontanel Simon , Peysson Fanny , Heuninck Joyce , Sounier Rémy , Durroux Thierry , Leyrat Cédric , Granier Sébastien , Bechara Cherine
Published: October 2021

Significance

Bicomponent leukotoxins represent a promiscuous group among the virulence factors secreted by
Staphylococcus aureus
that help the pathogen to develop and evade the host immune system. These toxins specifically recognize host G protein–coupled receptors (GPCRs) in an unknown molecular mechanism and functional effects on the receptor’s biology. Here, using HlgA and HlgB, we identify atypical chemokine receptor 1 (ACKR1) as a receptor for HlgB and demonstrate that toxins compete with the ACKR1 natural ligand. Furthermore, we find that binding of leukotoxins leads to an allosteric conformational change in the ACKR1 intracellular part and interferes with receptor architecture, a process that was correlated with a destabilization of receptor−G protein interaction in living cells. Overall, our findings lay the ground for the development of antimicrobials by shielding leukotoxin−GPCR interactions.
Neural mechanisms of deliberate dishonesty: Dissociating deliberation from other control processes during dishonest behaviors
Authors: Sai Liyang , Bellucci Gabriele , Wang Chongxiang , Fu Genyue , Camilleri Julia A. , Eickhoff Simon B. , Krueger Frank
Published: October 2021

Numerous studies have sought proof of whether people are genuinely honest by testing whether cognitive control mechanisms are recruited during honest and dishonest behaviors. The underlying assumption is: Deliberate behaviors require cognitive control to inhibit intuitive responses. However, cognitive control during honest and dishonest behaviors can be required for other reasons than deliberation. Across 58 neuroimaging studies (1,176 subjects), we investigated different forms of honest and dishonest behaviors and demonstrated that many brain regions previously implicated in dishonesty may reflect more general cognitive mechanisms. We argue that the motivational/volitional dimension is central to deliberation and provide evidence that motivated dishonest behaviors recruit the perigenual anterior cingulate cortex. This work questions the view that cognitive control is a hallmark of dishonesty.
Ultrafast synthesis of hard carbon anodes for sodium-ion batteries
Authors: Zhen Yichao , Chen Yang , Li Feng , Guo Zhenyu , Hong Zhensheng , Titirici Maria-Magdalena
Published: October 2021

Significance

Hard carbon (HC) is one of the most promising anode materials for alkali metal-ion batteries, which is generally prepared by annealing in a tubular furnace with a low heating rate and long duration at a target temperature. Herein, we report an innovating sintering method to quickly fabricate HC even within one minute and ultrafast heating rate by multifield-regulated spark plasma sintering (SPS) technology. This is a universal way to the rapid preparation of various HCs from different carbon precursors. Notably, HCs prepared from SPS possess significantly lower oxygen contents and higher electronic conductivity than the traditional sintering way due to the remarkably accelerated pyrolysis reaction, leading to excellent electrochemical Na-ion storage performance.
Capronia normandinae
. [Descriptions of Fungi and Bacteria].
Authors: Cannon P. F. , Minter D. W.
Published: October 2021

A description is provided for
Capronia normandinae
. Some information on its morphological characteristics, associated organisms and substrata, dispersal and transmission, habitats and conservation status is given, along with details of its geographical distribution (Asia (Papua-New Guinea), Atlantic Ocean (Portugal, Madeira), Australasia (New Zealand), Europe (France, Ireland, Norway, Portugal, Spain, UK), South America (Argentina, Chile, Colombia, Ecuador)).
Capronia pilosella
. [Descriptions of Fungi and Bacteria].
Authors: Cannon P. F. , Minter D. W.
Published: October 2021

A description is provided for
Capronia pilosella
, found on unidentified, very rotten wood. Some information on its morphological characteristics, associated organisms and substrata, dispersal and transmission, habitats and economic impacts is given, along with details of its geographical distribution (Asia (China, Xinjiang Autonomous Region, Taiwan), Australasia (Australia, Australian Capital Territory, New South Wales, Northern Territory, South Australia, Tasmania, Victoria, New Zealand), Europe (Austria, Belgium, Croatia, Czech Republic, Denmark, Finland, France, Germany, Ireland, Netherlands, Norway, Spain, Sweden, Switzerland, Ukraine, UK), North America (Canada, Ontario, Prince Edward Island, USA, Idaho, Indiana, Iowa, Missouri, New Hampshire, New Jersey, New York), Pacific Ocean (Fiji), South America (Argentina, Brazil, Amazonas)).
The molecular evolution of function in the CFTR chloride channel
Authors: Infield Daniel T. , Strickland Kerry M. , Gaggar Amit , McCarty Nael A.
Published: October 2021

The ATP-binding cassette (ABC) transporter superfamily includes many proteins of clinical relevance, with genes expressed in all domains of life. Although most members use the energy of ATP binding and hydrolysis to accomplish the active import or export of various substrates across membranes, the cystic fibrosis transmembrane conductance regulator (CFTR) is the only known animal ABC transporter that functions primarily as an ion channel. Defects in CFTR, which is closely related to ABCC subfamily members that bear function as bona fide transporters, underlie the lethal genetic disease cystic fibrosis. This article seeks to integrate structural, functional, and genomic data to begin to answer the critical question of how the function of CFTR evolved to exhibit regulated channel activity. We highlight several examples wherein preexisting features in ABCC transporters were functionally leveraged as is, or altered by molecular evolution, to ultimately support channel function. This includes features that may underlie (1) construction of an anionic channel pore from an anionic substrate transport pathway, (2) establishment and tuning of phosphoregulation, and (3) optimization of channel function by specialized ligand–channel interactions. We also discuss how divergence and conservation may help elucidate the pharmacology of important CFTR modulators.
A CLT for dependent random variables with an application to an infinite system of interacting diffusion processes
Authors: Chen Le , Khoshnevisan Davar , Nualart David , Pu Fei
Published: October 2021

We present a central limit theorem for stationary random fields that are short-range dependent and asymptotically independent. As an application, we present a central limit theorem for an infinite family of interacting Itô-type diffusion processes.
Determinantal formulas with major indices
Authors: McConville Thomas , Robertson Donald , Smyth Clifford
Published: October 2021

We give an elementary proof of a major index determinant formula discovered by Krattenthaler and first proved by Thibon using noncommutative symmetric functions. We do so by proving a factorization of an element in the group ring of the symmetric group. By applying similar methods to the groups of signed permutations and colored permutations, we prove determinantal formulas in these groups as conjectured by Krattenthaler.
Robust electoral violence prevention: An example from Ghana
Authors: Bekoe Dorina A , Burchard Stephanie M
Published: October 2021

Existing electoral violence prevention programming does not sufficiently account for the incentives that compel political actors to use violence. When Nana Addo Dankwa Akufo-Addo defeated Ghana’s incumbent President, John Dramani Mahama, in December 2016, the transition was lauded for its orderliness and credited with furthering Ghana’s democratization. Many attributed the peaceful transfer of power to significant reforms undertaken by the electoral commission and the democratic values internalized by the candidates. However, we find that the reforms and personal attributes of the political actors were inadequate for resolving impasses that could have worsened the electoral environment. Our analysis reveals that interventions to prevent electoral violence must mitigate political actors’ incentives to use or tolerate violence in furtherance of their objectives. In Ghana, we find that back channel negotiations—coupled with identifying potential hotspots, early monitoring and observation, and conflict resolution mechanisms—created a robust electoral violence prevention framework that reduced tensions and produced a relatively peaceful political transition. Our findings advance existing theories and practices for preventing electoral violence, which emphasize capacity building, institutional reforms, and other technical approaches to managing elections. We conclude that directly engaging political actors is a critical component of preventing electoral violence in Africa.
Family dynamics reveal that female house mice preferentially breed in their maternal community
Authors: Evans Julian C , Lindholm Anna K , König Barbara
Published: October 2021

Whether females breed in their natal group is an important factor in the evolution of extended families in animal sociality. Breeding in natal groups comes with costs and benefits, depending on group size and presence of older relatives, including mothers. Studying the consequences of breeding in the natal versus another group provides insight into the decisions and trade-offs governing the formation and structure of family groups. We investigated the family dynamics of a population of free-ranging commensal house mice. Using dynamic community detection on long-term datasets, we determined which females first bred in their natal group. We then looked at how this influenced breeding success. We found most females (77%) exhibited strong philopatry, breeding in their natal groups. Breeding elsewhere was only somewhat predictable at very large and very small group sizes. Despite their philopatric preference, breeding elsewhere made no difference in how quickly and successfully a female bred. However, presence of their mother did lead females to breed sooner when born during high breeding activity, when competition over reproduction is high. Based on these results, potential loss of reproductive success from leaving the natal group does not seem to be the main driver of philopatry in female house mice. The effect of the presence of mothers suggests that benefiting from established social connections promotes breeding in the natal group. Mothers providing benefits also implies a lack of conflict between generations, which will be important for the development of stable social groups.
A point cloud-based deep learning strategy for protein–ligand binding affinity prediction
Authors: Wang Yeji , Wu Shuo , Duan Yanwen , Huang Yong
Published: October 2021

There is great interest to develop artificial intelligence-based protein–ligand binding affinity models due to their immense applications in drug discovery. In this paper, PointNet and PointTransformer, two pointwise multi-layer perceptrons have been applied for protein–ligand binding affinity prediction for the first time. Three-dimensional point clouds could be rapidly generated from PDBbind-2016 with 3772 and 11 327 individual point clouds derived from the refined or/and general sets, respectively. These point clouds (the refined or the extended set) were used to train PointNet or PointTransformer, resulting in protein–ligand binding affinity prediction models with Pearson correlation coefficients R = 0.795 or 0.833 from the extended data set, respectively, based on the CASF-2016 benchmark test. The analysis of parameters suggests that the two deep learning models were capable to learn many interactions between proteins and their ligands, and some key atoms for the interactions could be visualized. The protein–ligand interaction features learned by PointTransformer could be further adapted for the XGBoost-based machine learning algorithm, resulting in prediction models with an average Rp of 0.827, which is on par with state-of-the-art machine learning models. These results suggest that the point clouds derived from PDBbind data sets are useful to evaluate the performance of 3D point clouds-centered deep learning algorithms, which could learn atomic features of protein–ligand interactions from natural evolution or medicinal chemistry and thus have wide applications in chemistry and biology.
iProbiotics: a machine learning platform for rapid identification of probiotic properties from whole-genome primary sequences
Authors: Sun Yu , Li Haicheng , Zheng Lei , Li Jinzhao , Hong Yan , Liang Pengfei , Kwok Lai-Yu , Zuo Yongchun , Zhang Wenyi , Zhang Heping
Published: October 2021

Lactic acid bacteria consortia are commonly present in food, and some of these bacteria possess probiotic properties. However, discovery and experimental validation of probiotics require extensive time and effort. Therefore, it is of great interest to develop effective screening methods for identifying probiotics. Advances in sequencing technology have generated massive genomic data, enabling us to create a machine learning-based platform for such purpose in this work. This study first selected a comprehensive probiotics genome dataset from the probiotic database (PROBIO) and literature surveys. Then, k-mer (from 2 to 8) compositional analysis was performed, revealing diverse oligonucleotide composition in strain genomes and apparently more probiotic (P-) features in probiotic genomes than non-probiotic genomes. To reduce noise and improve computational efficiency, 87 376 k-mers were refined by an incremental feature selection (IFS) method, and the model achieved the maximum accuracy level at 184 core features, with a high prediction accuracy (97.77%) and area under the curve (98.00%). Functional genomic analysis using annotations from gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and Rapid Annotation using Subsystem Technology (RAST) databases, as well as analysis of genes associated with host gastrointestinal survival/settlement, carbohydrate utilization, drug resistance and virulence factors, revealed that the distribution of P-features was biased toward genes/pathways related to probiotic function. Our results suggest that the role of probiotics is not determined by a single gene, but by a combination of k-mer genomic components, providing new insights into the identification and underlying mechanisms of probiotics. This work created a novel and free online bioinformatic tool, iProbiotics, which would facilitate rapid screening for probiotics.
Automated left ventricular dimension assessment using artificial intelligence
Authors: Stowell C , Howard J , Cole G , Ananthan K , Demetrescu C , Pearce K , Rajani R , Sehmi J , Vimalesvaran K , Kanaganayagam S , Ghosh A , Chambers J , Rana B , Francis D , Shun-Shin M
Published: October 2021

Background and purpose

Artificial intelligence (AI) has the potential to greatly improve efficiency and reproducibility of quantification in echocardiography, but to gain widespread use it must both meet expert standards of excellence and have a transparent methodology. We developed an online platform to enable multiple collaborators to annotate medical images for training and validating neural networks.

Methods

Using our online collaborative platform 9 expert echocardiographers labelled 2056 images that comprised the training dataset. They labelled the four points from where the standard parasternal long axis (PLAX) measurements (interventricular septum, posterior wall, left ventricular dimension) would be made. Using these labelled images we trained a 2d convolutional neural network to replicate these labels. Separately, we curated an external validation dataset of the systolic and diastolic frames of 100 PLAX acquisitions. Each of these images were labelled twice by 13 different experts, and the average of the 26 measurements was taken as the consensus standard.

We then compared the individual experts and the AI measurements on the external validation dataset to the consensus standard, and calculated the precision standard deviation (SD) of the signed differences from the consensus standard.

Results

For diastolic septum thickness, the AI had a precision SD of 1.8 mm (ICC 0.81; 95% CI 0.73 to 0.97), compared with 2.0 mm for the individual experts (ICC 0.64; 95% CI 0.57 to 0.72). For diastolic posterior wall thickness, the AI had a precision SD 1.4 mm (ICC 0.54; 95% CI 0.38 to 0.66), and the individual experts 2.2 mm (ICC 0.37; 95% CI 0.29 to 0.46).

The AI's precision SD for left ventricular internal dimension was 3.5 mm (ICC 0.93, 95% CI 0.90 to 0.94), and for individual experts was 4.4mm (ICC 0.82, 95% CI 0.78 to 0.95). Both the experts and AI performed better in diastole than systole (precision SD AI 2.5mm vs 4.3mm, p<0.0001; experts 3.3mm vs 5.3mm, p<0.0001).

Conclusions

AI trained by a group of echocardiography experts was able to perform PLAX measurements which matched the reference standard more closely than any individual expert's own measurements.

This open, collaborative approach may be a model for the development of AI that is explainable to, and trusted by clinicians.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NIHR Imperil BRC ITMATDr Howard was additionally funded by Wellcome. Online collaborative platformResults of AI and experts
Association between cardiac pathology and outcomes of patients with COVID-19 using a hand-held ultrasound
Authors: Dadon Z , Levi N , Orlev A , Belman D , Alpert E A , Steinmetz Y , Wolak A , Glikson M , Gottlieb S , Butnaru A
Published: October 2021

Background

The association between COVID-19 infection and the cardiovascular system has been well described. Strict precautions limit the use of formal echocardiography in this setting. Information on the importance of the utilization of a hand-held point-of-care cardiac ultrasound (POCCUS) for cardiac evaluation in these patients is scarce.

Objective

To investigate the utilization of hand-held echocardiography in COVID-19 hospitalized patients and the association between cardiac pathologies and outcomes.

Methods

Consecutive patients diagnosed with COVID-19 underwent POCCUS evaluation using a hand-held ultrasound within 24 hours of admission at our institute, throughout March-May 2020. According to the POCCUS results, the patients were divided into two groups: 'Normal' and 'Abnormal' (including left or right ventricular dysfunction or enlargement, or moderate/severe valvular regurgitation/stenosis).

Results

Among 102 patients, 26 (25.5%) had an abnormal POCCUS study. They were older, with more co-morbidities, cardiovascular disease history, chronic medical therapy, and more severe presenting symptoms, as compared to the group with a normal echocardiography exam. Individual and composite endpoints (advanced ventilatory support, acute decompensated heart failure, shock, or death) are presented in Table 1. Multivariate logistic regression analysis adjusting for pertinent variables revealed that abnormal echocardiography at presentation was independently associated with the composite endpoint OR=4.63 (95% CI 1.51–14.15, p=0.007).

Conclusions

Abnormal echocardiography results in COVID-19 infection settings are associated with a higher burden of medical comorbidities and independently predict major adverse endpoints. Hand-held POCCUS at presentation can be utilized as an important tool for risk stratification for hospitalized COVID-19 patients.

Funding Acknowledgement

Type of funding sources: Private hospital(s). Main funding source(s): SZMC Scientific
Echocardiographic markers of mortality at 60 days in patients with COVID-19 in the intensive care unit
Authors: Sprockel J , Rincon J M , Rondon M , Bejarano M , Castellanos N , Santofimio Z , Cardenas H M , Hernandez D , Parra J E , Diaztagle J J
Published: October 2021

Introduction

Coronavirus disease (COVID)-19 predominantly produces its effects through lung damage, but an important component of multi-organ dysfunction is cardiac involvement. We have few reports that inform about the behavior of echocardiographic images of patients with the most severe forms of the disease.

Purpose

The present work aims to identify prognostic markers for 60-day mortality in patients hospitalized in intensive care based on echocardiographic findings.

Methodology

A single-center retrospective cohort was conducted. Hospitalized patients were included in one of the nine intensive care units for COVID-19 confirmed by RT-PCR from May to October 2020. Patients with previous conditions that determined a limitation of the therapeutic effort, those who died before 24 hours and pregnant women were excluded. Portable echocardiograms were performed by two expert cardiologists following the recommendations for isolation and personal protection. The time to death was evaluated as outcome. A Cox proportional hazards model was constructed, HR and 95% confidence intervals with their p values. The study was approved by the institutional ethics committee.

Results

Of 326 patients included, 153 patients had an echocardiogram. The mean age was 60.7 years, 47 (30.7%) were female and 67 (44.7%) had positive troponin. 91 patients (59.5%) not survive, the mean long of stay was 8.4 (SD: 4.2) days. 111 (72.5%) had shock, 128 (83.7%) severe ARDS (PaO2 / FiO2 <100 mmHg), 142 (92.8%) required invasive ventilatory support, and 86 (56.2%) acute kidney injury. 27 (17.6%) patients had acute pulmonary embolism, 16 (10.4%) acute myocardial infarction and 9 (5.9%) myocarditis. The mean right ventricular ejection fraction was 37%, TAPSE was decreased in 16 cases (10.4%). 41 cases (26.8%) had right diastolic dysfunction. 34/48 (71%) cases had pulmonary hypertension. The average LVEF was 59.3% and 74 (48.4%) had some left ventricular diastolic dysfunction. 12 (7.8%) had left ventricular segmental wall motion abnormality and 16 (10.4%) had pericardial effusion. Univariate analysis identified TAPSE, PSAP, acute cor pulmonale and right ventricular dilatation as variables related to the outcome of mortality. The multivariate Cox model (Table 2) documented that acute cor pulmonale with a HR of 12.8 (95% CI 3.51 - 46.63, p<0.001) and right ventricular dilation with a HR of 4, 87 (95% CI 1.36–17.46, P 0.016) were associated with mortality.

Conclusions

In patients hospitalized in the intensive care unit for COVID-19, acute cor pulmonale and right ventricular dilatation behaved as independent predictors of in-hospital death.

Funding Acknowledgement

Type of funding sources: None. Table 1. Baselines characteristicsTable 2. Multivariate analisys
Independent predictors of major cardiovascular events as quantitatively assessed by coronary CT-angiography: a long-term follow-up analysis
Authors: Bittner D , Roesner C , Kilian T , Goeller M , Dey D , Raaz-Schrauder D , Achenbach S , Marwan M
Published: October 2021

Introduction

Quantitative CT coronary angiography using semi-automated software provides detailed information about plaque volume and high-risk plaque characteristics, beyond traditional measures like diameter stenosis. We assessed the potential value of plaque quantity and morphology to independently predict MACE in a cohort with long-term follow up.

Methods

In this secondary analysis of 301 symptomatic patients undergoing coronary CTA at baseline, total plaque volume (TPV), non-calcified- (NCPV), calcified- (CPV) and vulnerable coronary plaque volume (in mm3), diameter stenosis (in %) and remodeling index were quantified using semi-automated software (Autoplaque version 2.5, Cedars-Sinai Medical Center, Los Angeles, CA). Patients were followed for major cardiovascular events (MACE), defined as a composite of cardiovascular death, myocardial infarction and coronary revascularization. Optimal thresholds for each quantitative CTA measure were computed using CART-algorithm (Classification and Regression Trees).

Results

Complete follow-up was available for 234 (78%) patients. The mean age was 59±10 years. Over a median follow-up of 10.7 years, the composite outcome occurred in 34 (15%) patients (5 patients with cardiovascular death, 6 with myocardial infarction, 26 with revascularization). Patients experiencing MACE had more frequently hypertension (p=0.03) and a higher Framingham risk score (p=0.002). Survival anaylsis using cox proportional hazard ratios showed significant univariate associations between MACE and TPV (HR 5.16; 95% CI 1.58–16.89; p=0.007), NCPV (HR 4.83; 95% CI 1.45–15.81; p=0.009), CPV (HR 2.86; 95% CI 1.39–5.86; p=0.004), vulnerable plaque volume (HR 3.35; 95% CI 1.52–7.41; p=0.003), diameter stenosis (HR 5.19; 95% CI 2.64–10.22; p<0.001) and remodeling index (HR 4.24; 95% CI 2.03–8.86; p<0.001). In multivariable cox regression analysis diameter stenosis (HR 3.70; 95% CI 1.72–7.93; p=0.001) and remodeling index (HR 2.69; 95% CI 1.19–6.09; p=0.018) remained significant independent predictors of MACE, adjusted for Framingham risk score (HR 2.56; 95% CI 1.26–5.22; p=0.010), however plaque volume and plaque subcomponents did not.

Conclusion

On long term follow-up, remodeling index and coronary diameter stenosis obtained by quantitative coronary CT angiography independently predicted MACE on multivariable assessment. More comprehensive plaque assessment algorithms including plaque volume as well as plaque subcomponents were significantly associated with MACE in univariate, but not multivariate analysis after adjustment for diameter stenosis and remodeling index.

Funding Acknowledgement

Type of funding sources: None.