bluuebunny/crossref_metadata_2025 huggingface dataset:
Shockwave generation by electrical explosion of cylindrical wire arrays in hydrogen peroxide/water solutions
Authors: Rososhek A. , Efimov S. , Maler D. , Virozub A. , Krasik Ya. E.
Published: June 2020

We report the results of experiments investigating the implosion of a shock generated by the electrical explosion of a cylindrical aluminum wire array immersed in a >80% hydrogen peroxide/water solution. This solution was chosen as an additional energy source to the supplied electrical energy to generate the imploding flow with higher velocity. The experiments were conducted using a generator with the stored energy of ∼4.8 kJ, delivering to the array a ≤280 kA current rising during ∼1 μs. The backlighted images of the imploding shocks were recorded using a streak camera. Using different diameter wires, the explosion of arrays, characterized by critically damped and under-damped discharges, was studied. The experiments revealed that an array explosion in a 92% H2O2/H2O solution results in the second strong shock generated after the peak of the deposited electrical power, a solid indication of H2O2 detonation. This second shock converges ∼40% faster than the first strong shock generated by the wire explosion. One-dimensional hydrodynamic simulations of the shock convergence in H2O2/H2O solutions support this proposition.
Investigation on boundary schemes in lattice Boltzmann simulations of boiling heat transfer involving curved surfaces
Authors: Yu Y. , Li Q. , Wen Z. X. , Huang R. Z.
Published: June 2020

The lattice Boltzmann (LB) method has been applied to simulate boiling heat transfer in recent years. However, the existing studies are mostly focused on boiling on flat surfaces or structured surfaces with square pillars/cavities, and very few LB studies have been made regarding boiling on curved surfaces. In order to clarify the issues involved in the curved boundary implementation for boiling simulations, we numerically investigate the performances of two LB boundary schemes in simulating boiling on curved surfaces. One is the halfway bounce-back scheme, which is very popular in the LB community because of its easy implementation, and the other is a curved boundary scheme. Numerical results clearly show that the halfway bounce-back scheme leads to “artificial” nucleation sites in simulating boiling on curved surfaces because of its staircase approximation. A curved boundary scheme can overcome such a drawback, but it yields serious mass leakage. Hence, a mass-conservation correction should be enforced to the curved boundary scheme so as to eliminate the mass leakage in boiling simulations. The present study indicates that the halfway bounce-back scheme is not suitable for the LB simulations of boiling involving curved surfaces, while the curved LB boundary schemes must be combined with a mass-conservation correction when applied to simulate boiling on curved surfaces.
Ab initio potential energy surface and microwave spectrum of the NH3–N2 van der Waals complex
Authors: Surin Leonid A. , Tarabukin Ivan V. , Hermanns Marius , Heyne Bettina , Schlemmer Stephan , Kalugina Yulia N. , van der Avoird Ad
Published: June 2020

We present a five-dimensional intermolecular potential energy surface (PES) of the NH3–N2 complex, bound state calculations, and new microwave (MW) measurements that provide information on the structure of this complex and a critical test of the potential. Ab initio calculations were carried out using the explicitly correlated coupled cluster [CCSD(T)-F12a] approach with the augmented correlation-consistent aug-cc-pVTZ basis set. The global minimum of the PES corresponds to a configuration in which the angle between the NH3 symmetry axis and the intermolecular axis is 58.7° with the N atom of the NH3 unit closest to the N2 unit, which is nearly parallel to the NH3 symmetry axis. The intermolecular distance is 7.01 a0, and the binding energy De is 250.6 cm–1. The bound rovibrational levels of the four nuclear spin isomers of the complex, which are formed when ortho/para (o/p)-NH3 combines with (o/p)-N2, were calculated on this intermolecular potential surface. The computed dissociation energies D0 are 144.91 cm−1, 146.50 cm−1, 152.29 cm−1, and 154.64 cm−1 for (o)-NH3–(o)-N2, (o)-NH3–(p)-N2, (p)-NH3–(o)-N2, and (p)-NH3–(p)-N2, respectively. Guided by these calculations, the pure rotational transitions of the NH3–N2 van der Waals complex were observed in the frequency range of 13–27 GHz using the chirped-pulse Fourier-transform MW technique. A complicated hyperfine structure due to three quadrupole 14N nuclei was partly resolved and examined for all four nuclear spin isomers of the complex. Newly obtained data definitively established the K values (the projection of the angular momentum J on the intermolecular axis) for the lowest states of the different NH3–N2 nuclear spin isomers.
STEM imaging artifacts with three-fold astigmatism in monolayer transition metal dichalcogenides
Authors: Hong Jinhua , Koshino Masanori , Xu Hua , Feng Qingliang , Suenaga Kazu
Published: June 2020

Aberration-corrected scanning transmission electron microscopy has been demonstrated as a versatile tool to probe the atomic defects and local electronic states in 2D materials. However, the residual aberration of the probe may give rise to considerable deviations from the perfect imaging, especially in polyphase transition metal dichalcogenides. Here, we clarify the misleading imaging artifact of opposite subdomains in monolayer MoS2 through both image simulations and experimental in-plane rotation series. This non-honeycomb imaging artifact turns out to be caused by both probe residual threefold astigmatism and local sample tilt or fluctuation. Our results suggest that the direct STEM imaging should be cautiously treated to achieve accurate phase assignment.
Can a toilet promote virus transmission? From a fluid dynamics perspective
Authors: Li Yun-yun , Wang Ji-Xiang , Chen Xi
Published: June 2020

Currently, a novel coronavirus named “SARS-CoV-2” is spreading rapidly across the world, causing a public health crisis, economic losses, and panic. Fecal–oral transmission is a common transmission route for many viruses, including SARS-CoV-2. Blocking the path of fecal–oral transmission, which occurs commonly in toilet usage, is of fundamental importance in suppressing the spread of viruses. However, to date, efforts at improving sanitary safety in toilet use have been insufficient. It is clear from daily experience that flushing a toilet generates strong turbulence within the bowl. Will this flushing-induced turbulent flow expel aerosol particles containing viruses out of the bowl? This paper adopts computational fluid dynamics to explore and visualize the characteristics of fluid flow during toilet flushing and the influence of flushing on the spread of virus aerosol particles. The volume-of-fluid (VOF) model is used to simulate two common flushing processes (single-inlet flushing and annular flushing), and the VOF–discrete phase model (DPM) method is used to model the trajectories of aerosol particles during flushing. The simulation results are alarming in that massive upward transport of virus particles is observed, with 40%–60% of particles reaching above the toilet seat, leading to large-scale virus spread. Suggestions concerning safer toilet use and recommendations for a better toilet design are also provided.
On respiratory droplets and face masks
Authors: Dbouk Talib , Drikakis Dimitris
Published: June 2020

Face mask filters—textile, surgical, or respiratory—are widely used in an effort to limit the spread of airborne viral infections. Our understanding of the droplet dynamics around a face mask filter, including the droplet containment and leakage from and passing through the cover, is incomplete. We present a fluid dynamics study of the transmission of respiratory droplets through and around a face mask filter. By employing multiphase computational fluid dynamics in a fully coupled Eulerian–Lagrangian framework, we investigate the droplet dynamics induced by a mild coughing incident and examine the fluid dynamics phenomena affecting the mask efficiency. The model takes into account turbulent dispersion forces, droplet phase-change, evaporation, and breakup in addition to the droplet–droplet and droplet–air interactions. The model mimics real events by using data, which closely resemble cough experiments. The study shows that the criteria employed for assessing the face mask performance must be modified to take into account the penetration dynamics of airborne droplet transmission, the fluid dynamics leakage around the filter, and reduction of efficiency during cough cycles. A new criterion for calculating more accurately the mask efficiency by taking into account the penetration dynamics is proposed. We show that the use of masks will reduce the airborne droplet transmission and will also protect the wearer from the droplets expelled from other subjects. However, many droplets still spread around and away from the cover, cumulatively, during cough cycles. Therefore, the use of a mask does not provide complete protection, and social distancing remains important during a pandemic. The implications of the reduced mask efficiency and respiratory droplet transmission away from the mask are even more critical for healthcare workers. The results of this study provide evidence of droplet transmission prevention by face masks, which can guide their use and further improvement.
Corrigendum to: Estimation of surface dead fine fuel moisture using automated fuel moisture sticks across a range of forests worldwide
Authors: Cawson Jane G. , Nyman Petter , Schunk Christian , Sheridan Gary J. , Duff Thomas J. , Gibos Kelsy , Bovill William D. , Conedera Marco , Pezzatti Gianni B. , Menzel Annette
Published: June 2020

Field measurements of surface dead fine fuel moisture content (FFMC) are integral to wildfire management, but conventional measurement techniques are limited. Automated fuel sticks offer a potential solution, providing a standardised, continuous and real-time measure of fuel moisture. As such, they are used as an analogue for surface dead fine fuel but their performance in this context has not been widely evaluated. We assessed the ability of automated fuel sticks to predict surface dead FFMC across a range of forest types. We combined concurrent moisture measurements of the fuel stick and surface dead fine fuel from 27 sites (570 samples), representing nine broad forest fuel categories. We found a moderate linear relationship between surface dead FFMC and fuel stick moisture for all data combined (R2=0.54), with fuel stick moisture averaging 3-fold lower than surface dead FFMC. Relationships were typically stronger for individual forest fuel categories (median R2=0.70; range=0.55–0.87), suggesting the sticks require fuel-specific calibration for use as an analogue of surface dead fine fuel. Future research could identify fuel properties that will enable more generalised calibration functions.
Quantifying how sources of uncertainty in combustible biomass propagate to prediction of wildland fire emissions
Authors: Kennedy Maureen C. , Prichard Susan J. , McKenzie Donald , French Nancy H. F.
Published: June 2020

Smoke emissions from wildland fires contribute to concentrations of atmospheric particulate matter and greenhouse gases, influencing public health and climate. Prediction of emissions is critical for smoke management to mitigate the effects on visibility and air quality. Models that predict emissions require estimates of the amount of combustible biomass. When measurements are unavailable, fuel maps may be used to define the inputs for models. Mapped products are based on averages that poorly represent the inherent variability of wildland fuels, but that variability is an important source of uncertainty in predicting emissions. We evaluated the sensitivity of emissions estimates to wildland fuel biomass variability using two models commonly used to predict emissions: Consume and the First Order Fire Effects Model (FOFEM). Flaming emissions were consistently most sensitive to litter loading (Sobol index 0.426–0.742). Smouldering emissions were most often sensitive to duff loading (Sobol 0.655–0.704) under the extreme environmental scenario. Under the moderate environmental scenario, FOFEM-predicted smouldering emissions were similarly sensitive to sound and rotten coarse woody debris (CWD) and duff fuel components (Sobol 0.193–0.376). High variability in loading propagated to wide prediction intervals for emissions. Direct measurements of litter, duff and coarse wood should be prioritised to reduce overall uncertainty.
How canyons evolve by incision into bedrock: Rainbow Canyon, Death Valley National Park, United States
Authors: Zhang Li , Li Tiejian , Wang Guangqian , Kwang Jeffrey S. , Nittrouer Jeffrey A. , Fu Xudong , Parker Gary
Published: June 2020

Incising rivers may be confined by low-slope, erodible hillslopes or steep, resistant sidewalls. In the latter case, the system forms a canyon. We present a morphodynamic model that includes the essential elements of a canyon incising into a plateau, including 1) abrasion-driven channel incision, 2) migration of a canyon-head knickpoint, 3) sediment feed from an alluvial channel upstream of the knickpoint, and 4) production of sediment by sidewall collapse. We calculate incision in terms of collision of clasts with the bed. We calculate knickpoint migration using a moving-boundary formulation that allows a slope discontinuity where the channel head meets an alluvial plateau feeder channel. Rather than modeling sidewall collapse events, we model long-term behavior using a constant sidewall slope as the channel incises. Our morphodynamic model specifically applies to canyon, rather than river–hillslope evolution. We implement it for Rainbow Canyon, CA. Salient results are as follows: 1) Sediment supply from collapsing canyon sidewalls can be substantially larger than that supplied from the feeder channel on the plateau. 2) For any given quasi-equilibrium canyon bedrock slope, two conjugate slopes are possible for the alluvial channel upstream, with the lower of the two corresponding to a substantially lower knickpoint migration rate and higher preservation potential. 3) Knickpoint migration occurs at a substantially faster time scale than regrading of the bedrock channel itself, underlying the significance of disequilibrium processes. Although implemented for constant climactic conditions, the model warrants extension to long-term climate variation.
Protein folding from heterogeneous unfolded state revealed by time-resolved X-ray solution scattering
Authors: Kim Tae Wu , Lee Sang Jin , Jo Junbeom , Kim Jong Goo , Ki Hosung , Kim Chang Woo , Cho Kwang Hyun , Choi Jungkweon , Lee Jae Hyuk , Wulff Michael , Rhee Young Min , Ihee Hyotcherl
Published: June 2020

Significance

Protein undergoes a folding pathway to find a three-dimensional structure that expresses its biological function in a living cell. From vast theoretical studies, the funnel-like free-energy landscape has been recognized as a prominent scheme to describe protein folding, but it has been unclear how the dynamic behavior of protein folding is linked to conformational heterogeneity. Here we employ the time-resolved X-ray scattering method combined with systematic structural analysis to track the folding of cytochrome c. The kinetics and structural changes obtained from the data reveal that various protein conformations in the unfolded state take the complex folding pathways, resulting in the stretched exponential kinetics. This study may provide structural insights into fundamental principles governing protein folding.
An energy landscape approach to locomotor transitions in complex 3D terrain
Authors: Othayoth Ratan , Thoms George , Li Chen
Published: June 2020

Significance

Effective locomotion in nature happens by transitioning across multiple modes (e.g., walk, run, climb). Using laboratory experiments on a model system, we demonstrate that an energy landscape approach helps understand how multipathway transitions across locomotor modes in complex 3D terrain statistically emerge from physical interaction. Animals’ and robots’ locomotor modes are attracted to basins of a potential energy landscape. They can use kinetic energy fluctuation from oscillatory self-propulsion to cross potential energy barriers, escaping from one basin and reaching another to make locomotor transitions. Our first-principle energy landscape approach is the beginning of a statistical physics theory of locomotor transitions in complex terrain. It will help understand and predict how animals, and how robots should, move through the real world.
Molecular motor crossing the frontier of classical to quantum tunneling motion
Authors: Stolz Samuel , Gröning Oliver , Prinz Jan , Brune Harald , Widmer Roland
Published: June 2020

Significance

Conversion of undirected energy input into directed motion on molecular scales is the basis for controlled movements in living organisms. In this context, fundamental insights can be obtained by investigating artificial molecular machines under well-defined conditions. We devised the currently smallest, atomically precise molecular machine, whose rotor (C
2
H
2
) consists of just four atoms and whose functioning we have tracked employing scanning tunneling microscopy (STM). Unlike all other reported surface-anchored rotors, ours is characterized by an extremely high degree of directionality which is independent of STM-tip condition or position, therefore solely defined by the chiral support. Owing to its ultrasmall size, our rotor’s operation crosses the well-established classical to an unanticipated quantum tunneling kinetic regime without loss in directionality.
Power-law distribution of degree–degree distance: A better representation of the scale-free property of complex networks
Authors: Zhou Bin , Meng Xiangyi , Stanley H. Eugene
Published: June 2020

Significance

It is hard to decide if a real-world complex network is scale free, as it has never reached an agreement on how to confirm whether the network exhibits statistically favored power-law distributions. Here, we define a fundamental property—the degree–degree distance—possessed by each link, the distribution of which usually exhibits a stronger power law than the degree distribution of a finite-size network as indicated by empirical and statistical studies. A bidirectional preferential selection model is introduced to explain and reproduce this finding, which implies that being scale free as a property should not be defined by apparent statistics but determined by the underlying mechanism. We conclude that power-law degree–degree distance distribution better represents the scale-free property.
Thyroid hormone receptors mediate two distinct mechanisms of long-wavelength vision
Authors: Volkov Leo I. , Kim-Han Jeong Sook , Saunders Lauren M. , Poria Deepak , Hughes Andrew E. O. , Kefalov Vladimir J. , Parichy David M. , Corbo Joseph C.
Published: June 2020

Thyroid hormone (TH) signaling plays an important role in the regulation of long-wavelength vision in vertebrates. In the retina,
thyroid hormone receptor β
(
thrb
) is required for expression of long-wavelength-sensitive opsin (
lws
) in red cone photoreceptors, while in retinal pigment epithelium (RPE), TH regulates expression of a cytochrome P450 enzyme,
cyp27c1
, that converts vitamin A
1
into vitamin A
2
to produce a red-shifted chromophore. To better understand how TH controls these processes, we analyzed the phenotype of zebrafish with mutations in the three known TH nuclear receptor transcription factors (
thraa
,
thrab
,
and thrb
). We found that no single TH nuclear receptor is required for TH-mediated induction of
cyp27c1
but that deletion of all three (
thraa

−/−

;thrab

−/−

;thrb

−/−

) completely abrogates its induction and the resulting conversion of A
1
- to A
2
-based retinoids. In the retina, loss of
thrb
resulted in an absence of red cones at both larval and adult stages without disruption of the underlying cone mosaic. RNA-sequencing analysis revealed significant down-regulation of only five genes in adult
thrb

−/−

retina, of which three (
lws1
,
lws2
, and
miR-726
) occur in a single syntenic cluster. In the
thrb

−/−

retina, retinal progenitors destined to become red cones were transfated into ultraviolet (UV) cones and horizontal cells. Taken together, our findings demonstrate cooperative regulation of
cyp27c1
by TH receptors and a requirement for
thrb
in red cone fate determination. Thus, TH signaling coordinately regulates both spectral sensitivity and sensory plasticity.
Structure-guided engineering of the affinity and specificity of CARs against Tn-glycopeptides
Authors: Sharma Preeti , Marada Venkata V. V. R. , Cai Qi , Kizerwetter Monika , He Yanran , Wolf Steven P. , Schreiber Karin , Clausen Henrik , Schreiber Hans , Kranz David M.
Published: June 2020

Significance

CAR T cells have shown significant promise in treating hematopoietic cancers but challenges remain, including antigen loss and identification of targets in solid tumors. Aberrant O-linked glycosylation in solid cancers is common, often resulting in expression of cell-surface neoantigens. We used directed evolution to engineer the binding site of an antibody so variants reacted more broadly with tumor-specific glycoprotein epitopes containing Tn (GalNAc-O-S/T). As CARs, these variants showed improved broader activity against mouse and human cancer cells with dysregulated O-glycosylation. Even cancer cells without MUC1, the most studied cancer-associated glycoantigen, were recognized by the engineered CARs. Cancer-specific recognition was retained due to Tn-antigen requirement, but broader activity against the glycoprotein backbone provides opportunities for potent use with minimal antigen-loss escape.
Scaling up behavioral science interventions in online education
Authors: Kizilcec René F. , Reich Justin , Yeomans Michael , Dann Christoph , Brunskill Emma , Lopez Glenn , Turkay Selen , Williams Joseph Jay , Tingley Dustin
Published: June 2020

Significance

Low persistence in educational programs is a major obstacle to social mobility. Scientists have proposed many scalable interventions to support students learning online. In one of the largest international field experiments in education, we iteratively tested established behavioral science interventions and found small benefits depending on individual and contextual characteristics. Forecasting intervention efficacy using state-of-the-art methods yields limited improvements. Online education provides unprecedented access to learning opportunities, as evidenced by its role during the 2020 coronavirus pandemic, but adequately supporting diverse students will require more than a light-touch intervention. Our findings encourage funding agencies and researchers conducting large-scale field trials to consider dynamic investigations to uncover and design for contextual heterogeneity to complement static investigations of overall effects.
Changes in firearm mortality following the implementation of state laws regulating firearm access and use
Authors: Schell Terry L. , Cefalu Matthew , Griffin Beth Ann , Smart Rosanna , Morral Andrew R.
Published: June 2020

Significance

Many US states have tried to regulate firearm storage and use to reduce the 39,000 firearms-related deaths that occur each year. Looking at three classes of laws that regulate children’s access to firearms, the carrying of a concealed firearm, and the use of a firearm in self-defense, we found that state laws restricting firearm storage and use are associated with a subsequent 11% decrease in the firearms-related death rate. In a hypothetical situation in which there are 39,000 firearms deaths nationally under the permissive combination of these three laws, we expect 4,475 (80% CI, 1,761 to 6,949) more deaths nationally than under the restrictive combination of these laws.
Mechanisms of lipid preservation in archaeological clay ceramics revealed by mass spectrometry imaging
Authors: Hammann Simon , Scurr David J. , Alexander Morgan R. , Cramp Lucy J. E.
Published: June 2020

Traces of lipids, absorbed and preserved for millennia within the inorganic matrix of ceramic vessels, act as molecular fossils and provide manifold information about past people’s subsistence, diet, and rituals. It is widely assumed that lipids become preserved after adsorption into nano- to micrometer-sized pores, but to this day the distribution of these lipids in the ceramics was virtually unknown, which severely limits our understanding about the process of lipid preservation. Here we use secondary ion mass spectrometry (SIMS) imaging for direct
in situ
analysis of lipids absorbed in 700- to 2,000-y-old archaeological pottery. After sectioning from larger sherds, wall cross-sections of smaller fragments were used for SIMS analysis. Lipids were found in relatively large zones of 5- to 400-µm diameter, which does not support the notion of absorption only into individual nanometer-scale pores but indicates that more macroscopic structures in the ceramics are involved in lipid preservation as well. Furthermore, lipids were found concentrated on calcium carbonate inclusions in the ceramics, which suggests that precipitation of fatty acids as calcium salts is an important aspect of lipid preservation in archaeological samples. This has important implications for analytical methods based on extraction of lipids from archaeological ceramics and needs to be considered to maximize the yield and available information from each unique sample.
The social context of nearest neighbors shapes educational attainment regardless of class origin
Authors: Hedefalk Finn , Dribe Martin
Published: June 2020

We study the association between sociospatial neighborhood conditions throughout childhood and educational attainment in adulthood. Using unique longitudinal microdata for a medium-sized Swedish town, we geocode its population at the address level, 1939 to 1967, and link individuals to national registers, 1968 to 2015. Thus, we adopt a long-term perspective on the importance of nearby neighbors during a period when higher education expanded. Applying a method for estimating individual neighborhoods at the address level, we analyze the association between the geographically weighted social class of the nearest 6 to 100 childhood neighbors (ages 2 to 17), and the likelihood of obtaining a university degree by age 40, controlling for both family social class and school districts. We show that even when growing up in a town with relatively low economic inequality, the social class of the nearest same-age neighbors in childhood was associated with educational attainment, and that the associations were similar regardless of class origin. Growing up in low-class neighborhoods lowered educational attainment; growing up in high-class neighborhoods increased attainment. Social class and neighborhoods reinforced each other, implying that high-class children clustered with each other had much higher odds of obtaining a university degree than low-class children from low-class neighborhoods. Thus, even if all groups benefited from the great expansion of free higher education in Sweden (1960s to 1970s), the large inequalities between the classes and neighborhoods remained unchanged throughout the period. These findings show the importance of an advantageous background, both regarding the immediate family and the networks of nearby people of the same age.
Novel genetic features of human and mouse Purkinje cell differentiation defined by comparative transcriptomics
Authors: Buchholz David E. , Carroll Thomas S. , Kocabas Arif , Zhu Xiaodong , Behesti Hourinaz , Faust Phyllis L. , Stalbow Lauren , Fang Yin , Hatten Mary E.
Published: June 2020

Comparative transcriptomics between differentiating human pluripotent stem cells (hPSCs) and developing mouse neurons offers a powerful approach to compare genetic and epigenetic pathways in human and mouse neurons. To analyze human Purkinje cell (PC) differentiation, we optimized a protocol to generate human pluripotent stem cell-derived Purkinje cells (hPSC-PCs) that formed synapses when cultured with mouse cerebellar glia and granule cells and fired large calcium currents, measured with the genetically encoded calcium indicator jRGECO1a. To directly compare global gene expression of hPSC-PCs with developing mouse PCs, we used translating ribosomal affinity purification (TRAP). As a first step, we used
Tg(Pcp2-L10a-Egfp)
TRAP mice to profile actively transcribed genes in developing postnatal mouse PCs and used metagene projection to identify the most salient patterns of PC gene expression over time. We then created a transgenic
Pcp2
-
L10a-Egfp
TRAP hPSC line to profile gene expression in differentiating hPSC-PCs, finding that the key gene expression pathways of differentiated hPSC-PCs most closely matched those of late juvenile mouse PCs (P21). Comparative bioinformatics identified classical PC gene signatures as well as novel mitochondrial and autophagy gene pathways during the differentiation of both mouse and human PCs. In addition, we identified genes expressed in hPSC-PCs but not mouse PCs and confirmed protein expression of a novel human PC gene, CD40LG, expressed in both hPSC-PCs and native human cerebellar tissue. This study therefore provides a direct comparison of hPSC-PC and mouse PC gene expression and a robust method for generating differentiated hPSC-PCs with human-specific gene expression for modeling developmental and degenerative cerebellar disorders.
Infrared spectroscopy of neutral water clusters at finite temperature: Evidence for a noncyclic pentamer
Authors: Zhang Bingbing , Yu Yong , Zhang Yang-Yang , Jiang Shukang , Li Qinming , Hu Han-Shi , Li Gang , Zhao Zhi , Wang Chong , Xie Hua , Zhang Weiqing , Dai Dongxu , Wu Guorong , Zhang Dong H. , Jiang Ling , Li Jun , Yang Xueming
Published: June 2020

Significance

Spectroscopic investigation of neutral water clusters is critical in understanding the structures and properties of condensed-phase water. Because of the difficulty for size selection of neutral clusters in general, infrared spectroscopic study of structural evolution of confinement-free, neutral water clusters has been a grand challenge. In this work, we exploit recently developed, hybrid instruments that integrate infrared spectroscopy with a tunable vacuum ultraviolet free-electron laser to capture structural evolution of water clusters. Striking spectral change in the OH stretch region is observed from water tetramer to penta- and hexamer, due to appearance of three-dimensional hydrogen-bonding networks. The technique has the potential to obtain the infrared spectra of size-selected neutral clusters and to access their rich structural landscape.
Spontaneous formation of geysers at only one pole on Enceladus’s ice shell
Authors: Kang Wanying , Flierl Glenn
Published: June 2020

The ice shell on Enceladus, an icy moon of Saturn, exhibits strong asymmetry between the northern and southern hemispheres, with all known geysers concentrated over the south pole, even though the expected pattern of tidal forced deformation should be symmetric between the north and south poles. Using an idealized ice-evolution model, we demonstrate that this asymmetry may form spontaneously, without any noticeable a priori asymmetry (such as a giant impact or a monopole structure of geological activity), in contrast to previous studies. Infinitesimal asymmetry in the ice shell thickness due to random perturbations are found to be able to grow indefinitely, ending up significantly thinning the ice shell at one of the poles, thereby allowing fracture formation there. Necessary conditions to trigger this hemispheric symmetry-breaking mechanism are found analytically. A rule of thumb we find is that, for Galilean and Saturnian icy moons, the ice shell can undergo hemispheric symmetry breaking only if the mean shell thickness is around 10 to 30 km.
Identification of a chemical fingerprint linking the undeclared 2017 release of
106
Ru to advanced nuclear fuel reprocessing
Authors: Cooke Michael W. , Botti Adrian , Zok Dorian , Steinhauser Georg , Ungar Kurt R.
Published: June 2020

Significance

In the fall of 2017, a massive, undeclared release of
106
Ru occurred that was detected across Eurasia. To conclusively address the nature of the release, we have used carefully selected and established chemical transformations to reveal a chemical fingerprint for the
106
Ru contaminant that is uniquely consistent with specific methodology employed in the reprocessing of spent nuclear fuel. In view of international attention and investigation to date, this chemical fingerprint is the first direct evidence to this effect. This work serves, by example, as a potentially valuable addition to the field of nuclear forensics, considering that it is the only means to extract historical information from a radiopure contaminant in the absence of stable elemental anomalies.
Brain networks underlying vulnerability and resilience to drug addiction
Authors: Ersche Karen D. , Meng Chun , Ziauddeen Hisham , Stochl Jan , Williams Guy B. , Bullmore Edward T. , Robbins Trevor W.
Published: June 2020

Regular drug use can lead to addiction, but not everyone who takes drugs makes this transition. How exactly drugs of abuse interact with individual vulnerability is not fully understood, nor is it clear how individuals defy the risks associated with drugs or addiction vulnerability. We used resting-state functional MRI (fMRI) in 162 participants to characterize risk- and resilience-related changes in corticostriatal functional circuits in individuals exposed to stimulant drugs both with and without clinically diagnosed drug addiction, siblings of addicted individuals, and control volunteers. The likelihood of developing addiction, whether due to familial vulnerability or drug use, was associated with significant hypoconnectivity in orbitofrontal and ventromedial prefrontal cortical-striatal circuits—pathways critically implicated in goal-directed decision-making. By contrast, resilience against a diagnosis of substance use disorder was associated with hyperconnectivity in two networks involving 1) the lateral prefrontal cortex and medial caudate nucleus and 2) the supplementary motor area, superior medial frontal cortex, and putamen—brain circuits respectively implicated in top-down inhibitory control and the regulation of habits. These findings point toward a predisposing vulnerability in the causation of addiction, related to impaired goal-directed actions, as well as countervailing resilience systems implicated in behavioral regulation, and may inform novel strategies for therapeutic and preventative interventions.
A high-coverage Neandertal genome from Chagyrskaya Cave
Authors: Mafessoni Fabrizio , Grote Steffi , de Filippo Cesare , Slon Viviane , Kolobova Kseniya A. , Viola Bence , Markin Sergey V. , Chintalapati Manjusha , Peyrégne Stephane , Skov Laurits , Skoglund Pontus , Krivoshapkin Andrey I. , Derevianko Anatoly P. , Meyer Matthias , Kelso Janet , Peter Benjamin , Prüfer Kay , Pääbo Svante
Published: June 2020

We sequenced the genome of a Neandertal from Chagyrskaya Cave in the Altai Mountains, Russia, to 27-fold genomic coverage. We show that this Neandertal was a female and that she was more related to Neandertals in western Eurasia [Prüfer et al., Science 358, 655–658 (2017); Hajdinjak et al., Nature 555, 652–656 (2018)] than to Neandertals who lived earlier in Denisova Cave [Prüfer et al., Nature 505, 43–49 (2014)], which is located about 100 km away. About 12.9% of the Chagyrskaya genome is spanned by homozygous regions that are between 2.5 and 10 centiMorgans (cM) long. This is consistent with the fact that Siberian Neandertals lived in relatively isolated populations of less than 60 individuals. In contrast, a Neandertal from Europe, a Denisovan from the Altai Mountains, and ancient modern humans seem to have lived in populations of larger sizes. The availability of three Neandertal genomes of high quality allows a view of genetic features that were unique to Neandertals and that are likely to have been at high frequency among them. We find that genes highly expressed in the striatum in the basal ganglia of the brain carry more amino-acid-changing substitutions than genes expressed elsewhere in the brain, suggesting that the striatum may have evolved unique functions in Neandertals.
Text form and grammatical changes in Medieval French
Authors: Simonenko Alexandra , Crabbé Benoît , Prévost Sophie
Published: June 2020

This paper presents a treebank-based study of the effect the text form (prose vs. verse) has on the course of two grammatical
changes in Medieval French: the loss of null subjects and the loss of OV word order. By means of statistical analysis, we
demonstrate that naive estimates of the spread of overt subjects and VO orders give the impression that there is a significant
difference between the rates of development in prose vs. verse. By contrast, estimates based on an abstract grammar competition
model which distinguishes between grammar-ambiguous surface forms (overt personal subjects, null subjects in coordination
contexts) and grammar-unambiguous surface forms (overt expletive subjects, null subjects in non-coordination contexts) show
prose-verse parallelism, prose having an earlier change onset, in line with traditional intuitions. At a more general level, these
results suggest that the product of the interaction of a particular grammar with universal pragmatic laws is constant, which can
be observed if the factors responsible for variation in grammatical choices are controlled for.
How and why people are impolite in danmu?
Authors: Wang Jiayi
Published: June 2020

This study explores how and why people are impolite in danmu. Danmu refers to anonymous
comments overlaid on videos uploaded to video-sharing sites. Although there is wide recognition that impoliteness prevails in
danmu, the questions of how and why people are impolite in this context have rarely been investigated. This study
addresses this lacuna of research. Using both an analysis of comments identified as impolite by participants and an analysis of focus group
interview data, this research identified seven impoliteness strategies, covering both conventionalised formulae and implicational
impoliteness. By applying uses and gratifications theory, this study identified five uses and gratifications for performing impoliteness in
danmu: social interaction, entertainment, relaxation, expression of (usually differing) opinions and finding connections.
The dialectic of resonance and opposition that emerged from the data helped explain why impolite comments tended not to be perceived as
inappropriate in danmu. Thus, this study contributes to the emerging research on impoliteness in social media.
Revisitation of time delay interferometry combinations that suppress laser noise in LISA
Authors: Muratore Martina , Vetrugno Daniele , Vitale Stefano
Published: June 2020

With the purpose of understanding how time delay interferometry (TDI) combinations can best be used for the characterization of LISA instrumental noise, we revisit their laser frequency noise cancellation properties. We have developed an algorithm to search for all possible combinations that suppress noise at the same level as the X, Y and Z classical combinations. The algorithm calculates delays using symbolic formulas that explicitly include velocities and accelerations of satellites up to the relevant order. In addition, once a combination has been identified, delays are verified by solving numerically the relevant equations using Keplerian orbits and Shapiro delay corrections. We find that the number of combinations that suppress the noise is larger than what was reported in the literature. In particular we find that some combinations that were thought to only partly suppress the noise, in reality do suppress it at the same level of accuracy as the basic X, Y and Z combinations.
Thermal boundary resistance of direct van der Waals bonded GaN-on-diamond
Authors: Waller William M , Pomeroy James W , Field Daniel , Smith Edmund J W , May Paul W , Kuball Martin
Published: June 2020

Carbide forming interlayers, such as amorphous silicon nitride, are typically used for GaN-on-diamond heterogenous integration. This interlayer has a low thermal conductivity, introducing an additional extrinsic interfacial thermal resistance. It may therefore be advantageous to omit this layer, directly bonding GaN-to-diamond (van der Waals bond). However, weakly bonded interfaces are known to increase the intrinsic thermal boundary resistance. An adapted acoustic mismatch model has been implemented to assess which bonding approach is the most optimal for low thermal resistance GaN-on-diamond. A high thermal boundary resistance of 200 m2 K GW−1 is predicted for weakly bonded GaN-to-diamond interfaces, which is close to the measured value of 220 ± 70 m2 K GW−1, and ∼7× higher than values measured when a 10’s nm-thick SiN interlayer is included. Covalently bonded interfaces are therefore critical for achieving low thermal resistance GaN-on-diamond.
Condensed matter physics in time crystals
Authors: Guo Lingzhen , Liang Pengfei
Published: June 2020

Time crystals are physical systems whose time translation symmetry is spontaneously broken. Although the spontaneous breaking of continuous time-translation symmetry in static systems is proved impossible for the equilibrium state, the discrete time-translation symmetry in periodically driven (Floquet) systems is allowed to be spontaneously broken, resulting in the so-called Floquet or discrete time crystals. While most works so far searching for time crystals focus on the symmetry breaking process and the possible stabilising mechanisms, the many-body physics from the interplay of symmetry-broken states, which we call the condensed matter physics in time crystals, is not fully explored yet. This review aims to summarise the very preliminary results in this new research field with an analogous structure of condensed matter theory in solids. The whole theory is built on a hidden symmetry in time crystals, i.e., the phase space lattice symmetry, which allows us to develop the band theory, topology and strongly correlated models in phase space lattice. In the end, we outline the possible topics and directions for the future research.
Lorentz-violating type-II Dirac fermions in full-Heusler compounds XMg2Ag (X = Pr, Nd, Sm)
Authors: Meng Weizhen , Zhang Xiaoming , Liu Ying , Dai Xuefang , Liu Guodong
Published: June 2020

Lorentz-violating type-II Dirac fermion, as a new type of quasiparticles beyond the high-energy physics, has received intense attention recently. However, excellent candidate materials which contain sufficiently more type-II Dirac points near the Fermi level are still in scarcity. Here, we report a family of existing full-Heusler compounds, namely XMg2Ag (X = Pr, Nd, Sm), can serve as excellent Lorentz-violating type-II Dirac semimetals. We find they show several symmetry-protected nodal loops and triply degenerate nodal points (TDNPs) when spin–orbit coupling (SOC) is not considered. These fermions show clear nontrivial surface states. When SOC is included, the TDNPs transform into type-II Dirac points, characterized by Fermi arc surface states. The type-II DPs are protected by the C
4v
symmetry in the Γ–X path. Comparing with other type-II Dirac semimetals, XMg2Ag compounds have additional advantages including: (i) they contain as much as three pairs of type-II Dirac points; (ii) all the Dirac points locate very close to the Fermi level. These advantages make XMg2Ag compounds are suitable for studying the novel properties of type-II Dirac fermions in future experiments.
Weyl fermions in ferromagnetic high-temperature phase of K2Cr8O16
Authors: Zhao J Z , Jin Y J , Wang R , Xia B W , Xu H
Published: June 2020

By combining first-principles calculations and symmetry arguments, we propose that the half-metallic phase of K2Cr8O16 presents ferromagnetic Weyl fermions. In particular, K2Cr8O16 possesses two pairs of Weyl nodes, which originate from two groups of nodal lines connected by the mirror reflection symmetry. We show that the non-trivial topological properties of K2Cr8O16 come from the partially occupied t2g states of Cr, and we also demonstrate that such exotic topological feature is robust. The topological surface states and corresponding Fermi arcs are revealed. As K2Cr8O16 is a realistic and widely studied material, our results suggest that K2Cr8O16 is an ideal candidate for studying ferromagnetic Weyl fermions. In addition, K2Cr8O16 possesses several interesting phenomena, such as the co-existence of charge density wave and Weyl fermions, even pairs of FM Weyl points, and tunable distribution of Weyl points, which will attract intensive attentions in this field.
Quasi-fine-grained uncertainty relations
Authors: Xiao Yunlong , Xiang Yu , He Qiongyi , Sanders Barry C
Published: June 2020

Nonlocality, which is the key feature of quantum theory, has been linked with the uncertainty principle by fine-grained uncertainty relations, by considering combinations of outcomes for different measurements. However, this approach assumes that information about the system to be fine-grained is local, and does not present an explicitly computable bound. Here, we generalize above approach to general quasi-fine-grained uncertainty relations (QFGURs) which applies in the presence of quantum memory and provides conspicuously computable bounds to quantitatively link the uncertainty to entanglement and Einstein–Podolsky–Rosen (EPR) steering, respectively. Moreover, our QFGURs provide a framework to unify three important forms of uncertainty relations, i.e., universal uncertainty relations, the uncertainty principle in the presence of quantum memory, and fine-grained uncertainty relation. This result gives a direct significance to uncertainty principle, and allows us to determine whether a quantum measurement exhibits typical quantum correlations, meanwhile, it reveals a fundamental connection between basic elements of quantum theory, specifically, uncertainty measures, combined outcomes for different measurements, quantum memory, entanglement and EPR steering.
Natural Rubber Modified Asphalt
Authors: Mustafa Kamal Mazlina , Arifin Hadithon Kamarul , Abu Bakar Rohani
Published: June 2020

The asphalt binder is modified using natural rubber (NR) based on cup lump to improve its performance and service life due to intense load and weather induced stress. A source of PG 60-70 asphalt was used for preparing a natural rubber modified asphalt, (NRMA). The rheological characteristics of the NRMA was analyzed using dynamic shear rheometer (DSR) according to Superpave test protocol. The presence of the NR also was investigated by thermogravimetric analysis (TGA) and Fouirier infra-red spectroscopy (FTIR). Results showed that the conventional properties of the base bitumen such as penetration, softening point, and temperature susceptibility improved with addition of NR. The DSR analysis exhibited that the presence of elastic NR within the bitumen network increases the viscosity, stiffness and reduces temperature susceptibility which consequently enhances the rutting property.