bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytic expressions for the steady-state current with finite extended reservoirs
Authors: Zwolak Michael
Published: December 2020

Open-system simulations of quantum transport provide a platform for the study of true steady states, Floquet states, and the role of temperature, time dynamics, and fluctuations, among other physical processes. They are rapidly gaining traction, especially techniques that revolve around “extended reservoirs,” a collection of a finite number of degrees of freedom with relaxation that maintains a bias or temperature gradient, and have appeared under various guises (e.g., the extended or mesoscopic reservoir, auxiliary master equation, and driven Liouville–von Neumann approaches). Yet, there are still a number of open questions regarding the behavior and convergence of these techniques. Here, we derive general analytical solutions, and associated asymptotic analyses, for the steady-state current driven by finite reservoirs with proportional coupling to the system/junction. In doing so, we present a simplified and unified derivation of the non-interacting and many-body steady-state currents through arbitrary junctions, including outside of proportional coupling. We conjecture that the analytic solution for proportional coupling is the most general of its form for isomodal relaxation (i.e., relaxing proportional coupling will remove the ability to find compact, general analytical expressions for finite reservoirs). These results should be of broad utility in diagnosing the behavior and implementation of extended reservoir and related approaches, including the convergence to the Landauer limit (for non-interacting systems) and the Meir–Wingreen formula (for many-body systems).
Vacuum characterization of a compact room-temperature trapped ion system
Authors: Aikyo Yuhi , Vrijsen Geert , Noel Thomas W. , Kato Alexander , Ivory Megan K. , Kim Jungsang
Published: December 2020

We present the design and vacuum performance of a compact room-temperature trapped ion system for quantum computing, consisting of an ultra-high vacuum (UHV) package, a micro-fabricated surface trap, and a small form-factor ion pump. The system is designed to maximize mechanical stability and robustness by minimizing the system size and weight. The internal volume of the UHV package is only ≈2 cm3, a significant reduction in comparison with conventional vacuum chambers used in trapped ion experiments. We demonstrate trapping of 174Yb+ ions in this system and characterize the vacuum level in the UHV package by monitoring both the rates of ion hopping in a double-well potential and ion chain reordering events. The calculated pressure in this vacuum package is ≈2.2×1011 Torr, which is sufficient for the majority of current trapped ion experiments.
Superconducting tunnel junction fabrication on three-dimensional topography based on direct laser writing
Authors: Heiskanen Samuli , Maasilta Ilari J.
Published: December 2020

Superconducting junctions are widely used in a multitude of applications ranging from quantum information science and sensing to solid-state cooling. Traditionally, such devices must be fabricated on flat substrates using standard lithographic techniques. In this study, we demonstrate a highly versatile method that allows for superconducting junctions to be fabricated on a more complex topography. It is based on maskless direct laser writing and two-photon lithography, which allows writing in 3D space. We show that high-quality normal metal–insulator–superconductor tunnel junctions can be fabricated on top of a 20-μm-tall three-dimensional topography. Combined with conformal resist coating methods, this technique could allow sub-micron device fabrication on almost any type of topography in the future.
High aspect ratio transition edge sensors for x-ray spectrometry
Authors: de Wit M. , Gottardi L. , Taralli E. , Nagayoshi K. , Ridder M. L. , Akamatsu H. , Bruijn M. P. , D’Andrea M. , van der Kuur J. , Ravensberg K. , Vaccaro D. , Visser S. , Gao J. R. , den Herder J.-W. A.
Published: December 2020

We are developing large Transition Edge Sensor (TES) arrays in combination with a frequency domain multiplexing readout for the next generation of X-ray space observatories. For operation under an AC-bias, the TESs have to be carefully designed and optimized. In particular, the use of high aspect ratio devices will help us to mitigate non-ideal behavior due to the weak-link effect. In this paper, we present a full characterization of a TES array containing five different device geometries, with aspect ratios (width:length) ranging from 1:2 up to 1:6. The complex impedance of all geometries is measured in different bias configurations to study the evolution of the small-signal limit superconducting transition parameters α and β, as well as the excess noise. We show that high aspect ratio devices with properly tuned critical temperatures (around 90 mK) can achieve excellent energy resolution, with an array average of 2.03±0.17 eV at 5.9 keV and a best achieved resolution of 1.63±0.17 eV. This demonstrates that AC-biased TESs can achieve a very competitive performance compared to DC-biased TESs. The results have motivated a push to even more extreme device geometries currently in development.
A perovskite retinomorphic sensor
Authors: Trujillo Herrera Cinthya , Labram John G.
Published: December 2020

Designed to outperform conventional computers when performing machine-learning tasks, neuromorphic computation is the principle whereby certain aspects of the human brain are replicated in hardware. While great progress has been made in this field in recent years, almost all input signals provided to neuromorphic processors are still designed for traditional (von Neumann) computer architectures. Here, we show that a simple photosensitive capacitor will inherently reproduce certain aspects of biological retinas. We found that capacitors based on metal halide perovskites will output a brief voltage spike in response to changes in incident light intensity, but output zero voltage under constant illumination. Such a sensor is not only optimized for use with spiking neuromorphic processors but also anticipated to have broad appeal from fields such as light detection and ranging, autonomous vehicles, facile recognition, navigation, and robotics.
Effect of sneezing on the flow around a face shield
Authors: Akagi Fujio , Haraga Isao , Inage Shin-ichi , Akiyoshi Kozaburo
Published: December 2020

A flow analysis around a face shield was performed to examine the risk of virus infection when a medical worker wearing a face shield is exposed to a patient’s sneeze from the front. We ensured a space between the shield surface and the face of the human model to imitate the most popularly used face shields. In the present simulation, a large eddy simulation was conducted to simulate the vortex structure generated by the sneezing flow near the face shield. It was confirmed that the airflow in the space between the face shield and the face was observed to vary with human respiration. The high-velocity flow created by sneezing or coughing generates vortex ring structures, which gradually become unstable and deform in three dimensions. Vortex rings reach the top and bottom edges of the shield and form a high-velocity entrainment flow. It is suggested that vortex rings capture small-sized particles, i.e., sneezing droplets and aerosols, and transport them to the top and bottom edges of the face shield because vortex rings have the ability to transport microparticles. It was also confirmed that some particles (in this simulation, 4.4% of the released droplets) entered the inside of the face shield and reached the vicinity of the nose. This indicates that a medical worker wearing a face shield may inhale the transported droplets or aerosol if the time when the vortex rings reach the face shield is synchronized with the inhalation period of breathing.
Analytic investigation of combined effects of anisotropic thermal transport and energetic particles on stability of resistive plasma resistive wall mode
Authors: Bai Xue , Liu Yueqiang , Hao Guangzhou
Published: December 2020

The combined effects of anisotropic thermal transport and trapped energetic particles (EPs) on the stability of the resistive plasma resistive wall mode (RPRWM) are investigated by an energy-principle based analytical model. The results qualitatively confirm that of a recent toroidal modeling study [Bai et al., Phys. Plasmas 27, 072502 (2020)], in which the thermal transport can stabilize the RPPWM depending on the parameters of both the plasma equilibrium and energetic particles. The analytical model predicts a complete stabilization of the RPRWM in highly resistive plasmas, at sufficiently high EPs' pressure, and finite plasma flow. The stabilizing effect of thermal transport originates from its enhancement of energy dissipations associated with both the resistive layer and the trapped energetic particles.
Microfluidic-based approaches for COVID-19 diagnosis
Authors: Mu Hsuan-Yu , Lu Yu-Lun , Hsiao Tzu-Hung , Huang Jen-Huang
Published: December 2020

Novel coronavirus, COVID-19, erupted in Wuhan, China, in 2019 and has now spread to almost all countries in the world. Until the end of November 2020, there were over 50 × 106 people diagnosed with COVID-19 worldwide and it caused at least 1 × 106 deaths. These numbers are still increasing. To control the spread of the pandemic and to choose a suitable treatment plan, a fast, accurate, effective, and ready-to-use diagnostic method has become an important prerequisite. In this Review, we introduce the principles of multiple off-site and on-site detection methods for virus diagnosis, including qPCR-based, ELISA-based, CRISPR-based methods, etc. All of these methods have been successfully implanted on the microfluidic platform for rapid screening. We also summarize currently available diagnostic methods for the detection of SARS, MERS, and COVID-19. Some of them not only can be used to analyze the SARS and MERS but also have the potential for COVID-19 detection after modifications. Finally, we hope that understanding of current microfluidic-based detection approaches can help physicians and researchers to develop advanced, rapid, and appropriate clinical detection techniques that reduce the financial expenditure of the society, accelerate the examination process, increase the accuracy of diagnosis, and eventually suppress the worldwide pandemic.
Mechanism of surface freezing of alkanes
Authors: Modak Viraj P. , Wyslouzil Barbara E. , Singer Sherwin J.
Published: December 2020

Using molecular dynamics simulation of octane (C8) and nonadecane (C19), we probe the mechanism of n-alkane surface freezing, the appearance of a crystalline monolayer above the liquid at a temperature Tsf above the bulk freezing point Tf. Formation of a crystalline monolayer occurs robustly in these systems. When Tf > Tsf, the surface frozen phase is metastable with respect to the solid but persists for long periods for study in simulations. Surface freezing of both C8 and C19 is driven by significant energy-lowering when alkane chains become ordered along the surface normal, and we elucidate the origins of this phenomenon. The degree of configurational disorder in the surface frozen layer relative to the solid is much larger for C8 compared to C19. From the Gibbsian viewpoint, we extract the excess energy and entropy of the liquid and surface frozen phases. We also consider the surface frozen layer as an intervening third phase, the viewpoint taken in previous theoretical analyses. Here, we find significantly increased entropy of the surface frozen phase of C8 associated with configurational disorder, while the energy and entropy of the surface frozen phase of C19 are marginally different from the bulk solid. Finally, by combining our previously determined solid–vapor surface free energies of C8 and C19 with liquid–vapor surface tensions from this work, we eliminate wetting as a possible mechanism for C8 surface freezing, but it remains a possibility for C19. We analyze the molecular structure of the liquid, surface frozen, and solid surfaces and discuss its relevance to thermodynamic properties.
Investigation of the symmetry-breaking instability in a T-mixer with circular cross section
Authors: Chicchiero Claudio , Siconolfi Lorenzo , Camarri Simone
Published: December 2020

This paper investigates the laminar flow inside a T-mixer composed of three pipes with a circular cross section. The flow enters the mixer symmetrically from the two aligned pipes and leaves the device from the third pipe. In similar devices, but involving rectangular channels instead of pipes, an important regime for mixing has been identified, denoted as engulfment. Despite the symmetries of the flow and of the geometry, engulfment is an asymmetric steady regime, which is observed above a critical value (Rec) of the flow Reynolds number. Conversely, for Reynolds numbers lower than Rec, the flow regime is steady and symmetric, and it is usually denoted as the vortex regime. In this paper, both the vortex and the engulfment regimes are identified for the considered geometry, and they are characterized in detail by dedicated direct numerical simulations (DNSs). Despite an apparent similitude with the behavior of T-mixers employing rectangular channels, which are the most investigated T-mixers in the literature, substantial differences are observed and highlighted here concerning both regimes, i.e., the vortex and the engulfment ones, and concerning transition between the two. Global stability analysis is finally used in synergy with DNS to investigate the onset of the engulfment regime, which is shown to be related to a symmetry-breaking bifurcation of the vortex regime.
Simulation of shock induced vapor condensation flows in the Lennard-Jones fluid by microscopic and continuum models
Authors: Frezzotti A. , Barbante P.
Published: December 2020

The vapor condensation onto a thin liquid film, induced by the reflection of a weak shock wave, is studied by molecular dynamics atomistic simulations of a simple Lennard-Jones fluid. Molecular dynamics results provide reference flowfields for two models. The first one adopts a hybrid continuum-kinetic description in which the liquid phase is described by hydrodynamic equations, whereas the vapor is described by the Boltzmann equation. The structureless liquid–vapor interface is replaced by a classical kinetic boundary condition. The second model is based on the diffuse interface full continuum description of the Lennard-Jones fluid liquid, vapor, and interface regions. For both models, the required fluid thermodynamic and transport properties have been prescribed according to those of the Lennard-Jones fluid. Not unexpectedly, the results show that the continuum-kinetic model provides a good description of molecular dynamics results when the vapor is close to ideal conditions, increasingly deviating from reference data when the vapor non-ideality increases. The opposite behavior is found for the diffuse interface model. It is observed that flow conditions exist where both models fail to provide a reasonably accurate description of reference flow properties.
Reduced-cost supercell approach for computing accurate phonon density of states in organic crystals
Authors: Cook Cameron , Beran Gregory J. O.
Published: December 2020

Phonon contributions to organic crystal structures and thermochemical properties can be significant, but computing a well-converged phonon density of states with lattice dynamics and periodic density functional theory (DFT) is often computationally expensive due to the need for large supercells. Using semi-empirical methods like density functional tight binding (DFTB) instead of DFT can reduce the computational costs dramatically, albeit with noticeable reductions in accuracy. This work proposes approximating the phonon density of states via a relatively inexpensive DFTB supercell treatment of the phonon dispersion that is then corrected by shifting the individual phonon modes according to the difference between the DFT and DFTB phonon frequencies at the Γ-point. The acoustic modes are then computed at the DFT level from the elastic constants. In several small-molecule crystal test cases, this combined approach reproduces DFT thermochemistry with kJ/mol accuracy and 1–2 orders of magnitude less computational effort. Finally, this approach is applied to computing the free energy differences between the five crystal polymorphs of oxalyl dihydrazide.
Is Australia’s clinician scientist capacity appropriate for addressing the next pandemic?
Authors: Eley Diann S. , O’Leary Shaun P. , Young Adrienne , Buttrum Peter
Published: December 2020

Australia’s clinical research communities responded quickly to COVID-19. Similarly, research funding to address the pandemic was appropriately fast-tracked and knowledge promptly disseminated. This swift and purposeful research response is encouraging and reflects thorough and meticulous training of the academic workforce; in particular the clinician scientist. Clinician scientists have formal clinical and research qualifications (primarily PhD), and are at the forefront of translating knowledge into health care. Yet in reality, advances in medical research are not rapid. Scientific discovery results from the long-term accumulation of knowledge. The drivers of this knowledge are often PhD students who provide new lines of clinical inquiry coupled with the advanced training of early- and mid-career researchers who sustain discovery through a clinician scientist workforce. A crucial point during these COVID-19 times is that this initial investment in training must be nurtured and maintained. Without this investment, the loss of a future generation of potential discoveries and a vibrant scientific workforce to safeguard us from future global health threats is at risk. This risk includes the modest gains achieved by increasing female and minority representation in STEM and the clinician scientist workforce. COVID-19 has presented serious concerns to Australia’s health and economy. This perspective is central to these concerns and urges investment in the continuity of training and maintaining a sustainable clinician scientist workforce sufficient to address current and future pandemics, alongside continuing discoveries to improve the health of Australians.
Colorimetric Aptasensor for Testosterone Detection Based on Aggregation of Gold Nanoparticles Induced by Cationic Surfactant
Authors: Pan Chaoqiang , Qiu Jianmin , Wang Lumei , Yan Zhiyu , Huang Weiwen , Zhang Dongwei , Zhan Xuejia , Shen Guoqing
Published: December 2020

This paper proposes a colorimetric aptasensor for the detection of testosterone (TES) in environmental water, using TES-specific aptamer (apT5) as a sensing probe, gold nanoparticles (AuNPs) as indicator, and hexadecyltrimethylammonium bromide (CTAB) as inducer, respectively. Based on competition between TES and CTAB for apT5, the aptamer can form an aptamer–TES complex, leaving CTAB free to aggregate AuNPs in the presence of TES. Dispersed and aggregated AuNPs have different absorption wavelengths and the signal of absorption intensity is associated with the concentration of TES, so TES can be detected quantitatively based on the signal absorption intensity. This sensitive aptasensor for TES detection has a wide linear range (R=0.998) from 1.91–800nM and a limit of detection (LOD) of 1.91nM. In addition, this aptasensor has high selectivity over some interferents. The method detects TES in tap water samples with recoveries in the range of 98.9–102.6% (RSD ≤ 7.35%). This biosensor presents a good and potential application to rapidly detect TES in actual environmental water samples.
Growth patterns and yield of maize (Zea mays) hybrids as affected by nitrogen rate and sowing date in southern Brazil
Authors: Coelho Antonio Eduardo , Sangoi Luis , Balbinot Junior Alvadi Antonio , Fioreze Samuel Luiz , Berghetti Juliano , Kuneski Hugo François , Leolato Lucieli Santini , Martins Júnior Marcos Cardoso
Published: December 2020

Sowing date and nitrogen (N) fertilisation modify the morpho-physiological characteristics of maize (Zea mays L.) plants, which can alter the yield. The aim of this study was to analyse the effects of sowing date and N rate on the growth-pattern characteristics of maize hybrids with contrasting cycles, and the subsequent relationship with grain yield. Two experiments were set up in Santa Catarina State, southern Brazil. Two maize hybrids (AG9025, super-early cycle; P30F53, early cycle), two sowing periods (early spring and late spring), and four rates of topdressed N (0, 150, 300 and 450 kg N ha−1) were tested. Plant height, leaf area index (LAI), and relative chlorophyll content (RCC) were evaluated. The increment in N rate increased plant height at the silking stage for early spring sowing, and had no effect for late spring sowing. Higher N rates increased plant height of P30F53 and did not affect plant height of AG9025. Increasing the N rate enhanced LAI and RCC at silking more sharply when maize was sown in early spring. Higher N rates resulted in increased RCC during grain-filling, as well as maintenance of LAI, factors that were strongly associated with grain yield, especially for early spring sowing with hybrid P30F53. This research shows that the use of increasing N rates is an adequate management strategy to increase maize grain yield when the crop is sown in early spring. When applied at this sowing time, N has greater effect on the elevation of LAI and RCC and their maintenance during grain filling.
Predawn leaf conductance depends on previous day irradiance but is not related to growth in aspen saplings grown under artificially manipulated air humidity
Authors: Kupper Priit , Kaasik Ants , Kukumägi Mai , Rohula-Okunev Gristin , Rusalepp Linda , Sõber Anu
Published: December 2020

Recent studies have suggested that predawn stomatal opening may enhance early-morning photosynthesis (A) and improve the relative growth rate of trees. However, the causality between night-time stomatal conductance, A, and tree growth is disputable because stomatal opening in darkness can be mediated by previous day photosynthate loads and might be a consequence of growth-related processes like dark respiration (R). To identify linkages between night-time leaf conductance (gl_night), A, R, and tree growth, we conducted an experiment in hybrid aspen saplings grown under different air relative humidity (RH) conditions and previous day irradiance level (IR_pday). Predawn leaf conductance (gl_predawn) depended on RH, IR_pday and R (P < 0.05), whereas early-morning gross A (Agross_PAR500) depended on IR_pday and gl_predawn (P < 0.001). Daytime net A was positively related to Agross_PAR500 and leaf [N] (P < 0.05). Tree diameter and height increment correlated positively with gl at the beginning and middle of the night (P < 0.05) but not before dawn. Although our results demonstrate that gl_night was related to tree growth, the relationship was not determined by R. The linkage between gl_predawn and Agross_PAR500 was modified by IR_pday, indicating that daily CO2 assimilation probably provides feedback for stomatal opening before dawn.
Guanine, a high-capacity and rapid-turnover nitrogen reserve in microalgal cells
Authors: Mojzeš Peter , Gao Lu , Ismagulova Tatiana , Pilátová Jana , Moudříková Šárka , Gorelova Olga , Solovchenko Alexei , Nedbal Ladislav , Salih Anya
Published: December 2020

Significance

Vast areas of the oceans are N limited, and how microalgae can flourish in these N-poor waters is still not known. Furthermore, mechanisms and sites of N uptake and storage have not been fully determined. We show that crystalline guanine (C
5
H
5
N
5
O) is an important N storage form for phytoplankton and for symbiotic dinoflagellates of corals. The widespread occurrence of guanine reserves among taxonomically distant microalgal species suggests an early evolutionary origin of its function as N storage. Crystalline guanine appears to be a multifunctional biochemical with an important role in the N cycle that remains to be elucidated. In particular, a better knowledge of N-storage metabolism is necessary to understand the impact of eutrophication on coral-symbiont interaction.
A long noncoding RNA,
LncMyoD
, modulates chromatin accessibility to regulate muscle stem cell myogenic lineage progression
Authors: Dong Anqi , Preusch Christopher B. , So Wai-Kin , Lin Kangning , Luan Shaoyuan , Yi Ran , Wong Joyce W. , Wu Zhenguo , Cheung Tom H.
Published: December 2020

Significance

Epigenetic regulations control the accessibility of transcription factors to their target regions. Modulation of chromatin accessibility determines which transcripts to be expressed and therefore, defines cell identity. Chromatin modulation during cell fate determination involves a complex regulatory network, yet the comprehensive view remains to be explored. Here, we provide a global view of chromatin accessibility during muscle stem cell activation. We identified a long noncoding RNA (lncRNA),
LncMyoD
, which regulates lineage determination and progression through modulating chromatin accessibility. Functional analysis showed that loss of
LncMyoD
strongly impairs reprogramming of fibroblasts into myogenic lineage and causes defects in muscle stem cell differentiation. Our findings provide an epigenetic mechanism for the regulation of muscle stem cell myogenic lineage progression by an lncRNA.
The interrelationship between the face and vocal tract configuration during audiovisual speech
Authors: Scholes Chris , Skipper Jeremy I. , Johnston Alan
Published: December 2020

Significance

Speech perception is improved when we are able to see the person who is speaking, but how visual speech cues are used to improve speech perception is currently unclear. Brain imaging has revealed that regions responsible for motor control are active during the perception of speech, opening up the possibility that visual cues are mapped onto an internal representation of the vocal tract. Here, we show that there is sufficient information in the configuration of the face to recover the vocal tract configuration and that the key areas responsible for driving the correspondence vary in accordance with the articulation required to form the acoustic signal at the appropriate point in a sentence.
The importance of “year zero” in interdisciplinary studies of climate and history
Authors: Büntgen Ulf , Oppenheimer Clive
Published: December 2020

The mathematical aberration of the Gregorian chronology’s missing “year zero” retains enduring potential to sow confusion in studies of paleoclimatology and environmental ancient history. The possibility of dating error is especially high when pre-Common Era proxy evidence from tree rings, ice cores, radiocarbon dates, and documentary sources is integrated. This calls for renewed vigilance, with systematic reference to astronomical time (including year zero) or, at the very least, clarification of the dating scheme(s) employed in individual studies.
Case assignment in Spanish nominalizations
Authors: Leal Tania , Renaud Jeffrey
Published: December 2020

Spanish nominalizations, structures in which a
determiner precedes an infinitive (el susurrar de
Mario “Mario’s whispering”), present a syntactic
contradiction in which a verb exists within a Determiner Phrase
(DP). Speakers attest two types: nominalizations co-occurring with
nominal modifiers (e.g., adjectives, genitive case for argument
expression) and those whose modifiers are verbal (adverbs,
nominative/accusative arguments). Absent cartographic approaches
(Cinque, 2002)
predetermining the order of functional heads, the point in the
derivation at which verbal categories transition into nominal ones,
and this transition’s effect on case assignment, are thus far
unanswered empirical questions. Using a self-paced reading task, we
adopt Alexiadou et al.’s
(2011) proposal to experimentally determine the cases
available in each nominalization type. Results show that speakers
process nominal nominalizations as expected but may allow for the
possibility of adverbial adjunction, as suggested by Ramírez (2003). We propose
that this data reveals the value of empirically testing syntactic
proposals.
Dual competence in dual language learners
Authors: Satterfield Teresa
Published: December 2020

This chapter focuses on grammatical variability
in object clitic placement (omission and clitic climbing) and
morphology (gender and number) in child heritage Spanish.
Implementing Wexler’s
(2003) Clitic Acquisition Theory (CAT), original corpus
data from 60 U.S. Spanish heritage speakers (SHS), ages 4–7, are
analyzed and compared to previous research on adult L1/L2/child L1
and bilingual acquisition on clitic expression and acceptability
judgments. Results show SHS at all proficiency levels produce
clitics to some degree; however compared to Wexler (2003) and subsequent CAT studies,
SHS demonstrate ongoing clitic optionality. A high percentage of
this variability is grammatical: for instance, no substantial
difference in SHS frequencies for proclisis or enclisis occurs. In
the spirit of L2 work by Slabakova, Rothman and Kempchinsky (2011), the
Underlying and Surface Competence (Duffield, 2003) is tested as a
generative-based account of variability in more mature child
grammars, complementing CAT. The dual competence model provides a
finer-grained snapshot of ‘adult-like’ Spanish clitic expression in
children.
The mitotic exit network regulates the spatiotemporal activity of Cdc42 to maintain cell size
Authors: Gihana Gabriel M. , Cross-Najafi Arthur A. , Lacefield Soni
Published: December 2020

During G1 in budding yeast, the Cdc42 GTPase establishes a polar front, along which actin is recruited to direct secretion for bud formation. Cdc42 localizes at the bud cortex and then redistributes between mother and daughter in anaphase. The molecular mechanisms that terminate Cdc42 bud-localized activity during mitosis are poorly understood. We demonstrate that the activity of the Cdc14 phosphatase, released through the mitotic exit network, is required for Cdc42 redistribution between mother and bud. Induced Cdc14 nucleolar release results in premature Cdc42 redistribution between mother and bud. Inhibition of Cdc14 causes persistence of Cdc42 bud localization, which perturbs normal cell size and spindle positioning. Bem3, a Cdc42 GAP, binds Cdc14 and is dephosphorylated at late anaphase in a Cdc14-dependent manner. We propose that Cdc14 dephosphorylates and activates Bem3 to allow Cdc42 inactivation and redistribution. Our results uncover a mechanism through which Cdc14 regulates the spatiotemporal activity of Cdc42 to maintain normal cell size at cytokinesis.
Sterol and oxysterol synthases near the ciliary base activate the Hedgehog pathway
Authors: Findakly Sarah , Daggubati Vikas , Garcia Galo , LaStella Sydney A. , Choudhury Abrar , Tran Cecilia , Li Amy , Tong Pakteema , Garcia Jason Q. , Puri Natasha , Reiter Jeremy F. , Xu Libin , Raleigh David R.
Published: December 2020

Vertebrate Hedgehog signals are transduced through the primary cilium, a specialized lipid microdomain that is required for Smoothened activation. Cilia-associated sterol and oxysterol lipids bind to Smoothened to activate the Hedgehog pathway, but how ciliary lipids are regulated is incompletely understood. Here we identified DHCR7, an enzyme that produces cholesterol, activates the Hedgehog pathway, and localizes near the ciliary base. We found that Hedgehog stimulation negatively regulates DHCR7 activity and removes DHCR7 from the ciliary microenvironment, suggesting that DHCR7 primes cilia for Hedgehog pathway activation. In contrast, we found that Hedgehog stimulation positively regulates the oxysterol synthase CYP7A1, which accumulates near the ciliary base and produces oxysterols that promote Hedgehog signaling in response to pathway activation. Our results reveal that enzymes involved in lipid biosynthesis in the ciliary microenvironment promote Hedgehog signaling, shedding light on how ciliary lipids are established and regulated to transduce Hedgehog signals.
Double layer from least action principle
Authors: Berezin V A , Dokuchaev V I , Eroshenko Yu N , Smirnov A L
Published: December 2020

We derived the equations for the double layers in quadratic gravity, using solely the least action principle. The advantage of our approach is that, in the process of calculation, the δ′-function does not appear at all, and the δ-functions appear for a moment and are mutually canceled prior to integration. We revealed the peculiar structure of the obtained equations, namely, that the surface energy–momentum tensor of the matter fields (constituents of the thin shells) does not play a role in the determination of the trajectory of the double layer. Also, we suggested that the space-like double layers may provide us with the adequate description of the creation of the Universe from the black hole singularity. The related topics, including the Gauss–Bonnet term and F(R)-theories, are shortly discussed.
Sparsity of Hawking radiation in D + 1 space-time dimensions for massless and massive particles
Authors: Schuster Sebastian
Published: December 2020

Hawking radiation from an evaporating black hole has often been compared to black body radiation. However, this comparison misses an important feature of Hawking radiation: its low density of states. This can be captured in an easy to calculate, heuristic, and semi-analytic measure called ‘sparsity’. In this note we shall present both the concept of sparsities and its application to D + 1-dimensional Tangherlini black holes and their evaporation. In particular, we shall also publish for the first time sparsity expressions taking into account in closed form effects of non-zero particle mass. We will also see how this comparatively simple method reproduces results of (massless) Hawking radiation in higher dimensions and how different spins contribute to the total radiation in this context.
Colossal dielectric permittivity and high energy storage efficiency in barium strontium titanate ceramics co-doped with bismuth and lithium
Authors: Alkathy Mahmoud S , Raju K C James , Eiras J A
Published: December 2020

The development of energy storage devices in lead-free perovskite materials is critically important in addressing the environmental issues of perovskite lead. In this article, for the first time, lead-free (Ba0.60Sr0.40)(1−x)(Bi,Li)
x
TiO3, abbreviated as (BST6:BLx%); (0%⩽ x ⩽ 8%) ceramics, have been successively synthesized via the conventional solid-state reaction method. The structural evolution, dielectric and energy storage properties, as functions of co-doping levels, were systematically studied by x-ray diffraction, x-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy, scanning electron microscopy, impedance analyzer, and a Radiant Precision Premier II Analyzer. It was found that a small amount of co-dopants induced a colossal permittivity (CP) (over 105) with low loss (<0.1), a maximum energy storage density of 0.3856 J cm−3 with a BDS of ∼100 kV cm−1, and an efficiency of over 90%. The defects and chemical state of the elements contained in the material’s surface were investigated using XPS. In conjunction with the results of XPS and complex impedance studies, the mechanism of massive permittivity was interpreted based on a defect-dipole model. We believe that BST6:BLx% ceramics, as CP and high energy storage efficiency materials, might be considered a promising candidate for high energy storage applications.
Current-driven skyrmion movement in a curved nanotrack
Authors: Cai Na , Liu Yan
Published: December 2020

We report the results of complex studies concerning skyrmion motion in U-shaped and V-shaped nano-tracks simulated with MuMax3. The Thiele equation was used for description of skyrmion velocity components. It was shown that both size and velocity of a skyrmion vary depending on its position in the system, featuring distinct values for the straight and curved branches of the track. The degree of velocity variation can be effectively controlled by geometry of the track (including track width and its curvature radius) as well as the density of the driving current applied to the system.
Tunable edge enhancement by higher-order spiral Fresnel incoherent correlation holography system
Authors: Bu Yuanzhuang , Wang Xi , Li Yu , Du Yanli , Gong Qiaoxia , Zheng Guangchao , Ma Fengying
Published: December 2020

Tunable edge enhancement can selectively emphasize the edge features of objects. We demonstrate a higher-order spiral Fresnel incoherent correlation holography system to realize isotropic edge enhancement with tunable width. The spatial light modulator is space-division multiplexed by a conventional lens and a spiral lens with a series of higher-order Laguerre–Gaussian phases. The effects of the radial quantum number p and the angular quantum number l on the spatial filtering are theoretically discussed, as well as confirmed by simulations and experiments. Reconstruction images of resolution target, hairs and label-free onion cells all show obvious tunable edge enhancement effects, which makes the edge information easier to be identified. Furthermore, double-edge enhancement is also detected for the first time.
Decoupling between metal–insulator transition and structural phase transition in an interface-engineered VO2
Authors: Ji Yanda , Cheng Lei , Li Ning , Yuan Ye , Liang Weizheng , Yang Hao
Published: December 2020

The coupling between the metal–insulator transition (MIT) and the structural phase transition (SPT) in VO2 has been at the center of discussion for several decades, while the underlying mechanisms of electron–lattice or electron–electron interactions remain an open question. Until recently, the equilibrium state VO2 is believed to be a non-standard Mott–Hubbard system, i.e., both of the two interactions cooperatively work on MIT, indicating the association between MIT and SPT. However, due to the pronounced contribution of strain in strongly correlated systems, it is desirable to explore the correspondence in an interface-engineered VO2. Herein, we investigate the carrier dynamics in the VO2 films with anomalous MIT on the basis of time-resolved transient differential reflectivity measurements. Unexpectedly, MIT is decoupled from SPT, in sharp contrast with the case of strain-free VO2 films: MIT is triggered by bandgap recombination below 75 °C during heating, while intense SPT-induced signal appears separately between 70 °C and 100 °C. The decoupling between MIT and SPT provides insights into the interfacial interactions in VO2 thin films.
Controlling soft vortex matter: edge effects on vortex configurations and partial vortices in a superconducting type-II/type-I bilayer
Authors: Córdoba-Camacho W Y , da Silva R M , Barba-Ortega J , Albino Aguiar J
Published: December 2020

We demonstrate that the presence of edges in a superconducting film made of a type-I/type-II bilayer stabilizes type-II/type-I hybrid (inter-type) flux patterns, as vortex clusters, chains, and gel phase. These patterns are very sensitive to primary parameters such as applied magnetic field, layer coupling, and temperature. Thus, the magnetization versus temperature curves, M(T), for many values of coupling were used to estimate the strength of the layer couplings, and also as a guide for obtaining sequentially the flux patterns. We also show that the effect of the borders on the unrestricted states is to shift them to states of higher density, since they introduce extra compression on the vortex matter. For a low layer coupling regime, we observe an unusual magnetic response where few partial vortices (partial in a sense they miss the contribution of the type I part), repelling each other and bounded to the surfaces, populate one layer leaving the other empty. We expect that the predicted flux configurations can stimulate experimentalists in trying to observe them by direct imaging techniques.
Non-hydrostatic pressure-dependent structural and transport properties of BiCuSeO and BiCuSO single crystals
Authors: Lv Yang-Yang , Zhou Yonghui , Xu Lu , Luo Yecheng , Zhang Yan-Yan , Cao Lin , Zhou Jian , Chen Y B , Yao Shu-Hua , Zhang Shan-Tao , Yang Zhaorong , Chen Yan-Feng
Published: December 2020

High-pressure experiments usually expect a hydrostatic condition, in which the physical properties of materials can be easily understood by theoretical simulations. Unfortunately, non-hydrostatic effect is inevitable in experiments due to the solidification of the pressure transmitting media under high pressure. Resultantly, non-hydrostaticity affects the accuracy of the experimental data and sometimes even leads to false phenomena. Since the non-hydrostatic effect is extrinsic, it is quite hard to analyze quantitatively. Here, we have conducted high pressure experiments on the layered BiCuXO (X = S and Se) single crystals and quantitatively analyzed their pronounced non-hydrostatic effect by high throughput first-principles calculations and experimental Raman spectra. Our experiments find that the BiCuXO single crystals sustain the tetragonal structure up to 55 GPa (maximum pressure in our experiment). However, their pressure-dependent Raman shift and electric resistance show anomalous behaviors. Through optimization of thousands of crystal structures in the high throughput first-principles calculations, we have obtained the evolution of the lattice constants under external pressures, which clearly substantiates the non-hydrostatical pressure exerted in BiCuXO crystals. Our work indicates that the high throughput first-principles calculations could be a handy method to investigate the non-hydrostatic effect on the structural and electronic properties of materials in high pressure experiments.
Spontaneous Raman scattering at trace gas concentrations with a pressurized external multipass cavity
Authors: Velez Juan S Gomez , Muller Andreas
Published: December 2020

A setup is described with which the spontaneous Raman scattering rate from pressurized gas samples is greatly enhanced inside a near-concentric optical cavity. The pump source is a high power multimode semiconductor laser diode that receives optical feedback from the cavity by way of a volume Bragg grating, resulting in a linewidth of 80 pm and circulating power close to 100 W. Under pressurization (up to 8 bar) a limit of detection below 100 parts-per-billion was obtained for gaseous hydrogen, measured in ambient air and in breath. Furthermore, isotopic trace detection is demonstrated by headspace measurements of semiheavy water.
Non-null interferometers for irregular surface measurement with system modeling
Authors: Zang Zhongming , Xu Zhaorui , Peng Shaojing , Zhang Huxiang , Chen Nan , Liu Chong , Yan Tianliang , Liu Dong
Published: December 2020

A design method of non-null interferometers is proposed in this paper for measuring irregular surfaces such as optical aspherics, freeform surfaces and droplet surfaces. With system modeling and raytracing, the improved reverse optimization reconstruction method is employed to correct the retrace error and obtain the accurate shape of the test part with all frequency information. To simplify the model in the raytracing program, an imaging lens images the desired interferogram at a certain plane on the detector and, therefore, only the test arm needs to be modeled. The imaging error of an interferogram, which can be reduced by the partial compensation system (PCS), is analyzed, and the design of the PCS is also demonstrated. Two cases with different optical layouts show the feasibility and the versatility of our method.
Crystallinity and photocatalytic properties of BiVO4/halloysite nanotubes hybrid catalysts for sunlight-driven decomposition of dyes from aqueous solution
Authors: Sun Qing , Zhao Yingjie , Qin Feng , Zhang Jian , Wang Bin , Ye Huijian , Sheng Jiawei
Published: December 2020

The BiVO4/HNTs hybrid photocatalysts were synthesized by liquid phase precipitation using natural halloysite nanotubes (HNTs) as supporter and Bi(NO3)·5H2O as resource of Bi. XRD, scanning electron microscopy (SEM), transmission electron microscopy, HRTEM, x-ray photo electron spectroscopy and UV–Vis DRS were used to characterize the samples prepared at different calcination temperatures, and the effects of crystallization, Brunauer–Emmett–Teller specific surface area and morphological structure on the photoactivity were investigated. Results reveal that increasing calcination temperature can accelerate the transition of BiVO4 from tetragonal to monoclinic and also decrease the surface area of BiVO4/HNTs. The SEM results showed that BiVO4 was successfully coated on HNTs surface with ellipsoid or near rod like morphology, and the obtained BiVO4/HNTs had regular nanotube morphology. HRTEM results showed that, the regular fringe spacing of the lattice planes are about 0.474 and 0.364 nm, which is consistent with the (110) and (200) plane of the monoclinic and tetragonal BiVO4, confirming the exiting of mixed crystal structure in BiVO4/HNTs. BiVO4 with tetragonal phase (80.02%) and monoclinic phase (19.98%) mixed crystal is loaded on the surface of HNTs with calcinations at 400 °C for 2 h. The structure and Si (Al)–O bond of HNTs can be obviously changed over the calcination temperature of 400 °C. The effect of calcination temperature on photocatalytic reactivity of samples was investigated by degradation of dyes (MB, MO and RhB) under simulated solar light. And the sample calcined at 400 °C with the better mixed crystalline structure and larger specific surface area exhibits significant activity with the removal rate of MB and RhB up to 100% within 4 h. The degradation of MB follows the first order kinetic model. BiVO4/HNTs photocatalysts with the band gap of 2.34 eV has higher photocatalytic reaction rate and better sedimentation performance than Degussa P25. The photocatalytic degradation efficiency of BiVO4/HNTs for MB was no significant reduction after four times recycles.
Atomic-scale constituting stable interface for improved LiNi0.6Mn0.2Co0.2O2 cathodes of lithium-ion batteries
Authors: Wang Xin , Cai Jiyu , Liu Yongqiang , Han Xiaoxiao , Ren Yang , Li Jianlin , Liu Yuzi , Meng Xiangbo
Published: December 2020

Ascribed to their higher capacity and lower cost compared to conventional LiCoO2, the Ni-rich layered LiNi0.6Mn0.2Co0.2O2 (NMC622) is now considered as one promising cathode for lithium-ion batteries (LIBs). However, it still suffers from some evident performance degradation, especially under high cutoff voltages (i.e., >4.3 V versus Li/Li+). The performance degradation typically is exhibited as capacity fading and voltage drop, mainly originating from an instable interface between the NMC622 and electrolyte as well as the evolution of the NMC structure. To improve the interfacial and structural stability of NMC cathodes, herein we deposited an ultrathin layer of Al2O3 coatings (<5 nm) conformally over NMC622 composite electrodes directly using atomic layer deposition (ALD). It was found that, under different upper cutoff voltages (4.3, 4.5, and 4.7 V), the ALD Al2O3 coatings enable enhanced performance of NMC622 cathodes with better cyclability and higher capacity. Particularly, the beneficial effects of the ALD Al2O3 coatings are more remarkable at higher upper cutoff voltages (4.5 and 4.7 V). Furthermore, the ALD coatings can significantly improve the rate capability of NMC622. To this end, we utilized a suite of characterization tools and performed a series of electrochemical tests to clarify the effects of the ALD Al2O3 coatings. This study revealed that the beneficial effects of the Al2O3 ALD coatings are multiple: (i) serving as an artificial layer of solid electrolyte interphase to mitigate undesirable interfacial reactions; (ii) acting as a physical barrier to inhibit metal dissolution of NMC; and (iii) forming a reinforced networked overcoating to boost the mechanical integrity of NMC cathodes. This study is favorable for designing high-performance NMC cathodes.