bluuebunny/crossref_metadata_2025 huggingface dataset:
Comprehensive review on control strategies of parallel‐interfaced voltage source inverters for distributed power generation system
Authors: Sinha Akanksha , Chandra Jana Kartick
Published: June 2020

The distributed power generation system (DPGS) with renewable energy sources is gaining popularity over conventional sources of energy. Although the renewable sources of energy are available in abundance and are eco‐friendly, yet, they have intermittent nature. As a result, renewable energy‐based DPGS face difficulty in power transfer during adverse atmospheric conditions. Also, if the interfacing unit is a single inverter, its switches have to withstand a large amount of heat and handle a high value of current. Henceforth, to ensure uninterrupted supply and reduce voltage stress on switches, the power inverters need to be connected in parallel. This study presents various current and power‐sharing control strategies of parallel‐interfaced voltage source inverters with a common AC bus. A detailed classification and analysis of wired and wireless (droop) controllers for parallel‐connected voltage source inverters have been done. Moreover, the recent trends and improvements in traditional droop controllers are presented. Finally, a comparative analysis among the various wired and wireless controllers is done, listing their advantages and limitations.
Adaptive fast protection technique for uncompensated/compensated double‐circuit transmission lines connected to large‐scale wind farms
Authors: Saber Ahmed
Published: June 2020

The penetration of large‐scale offshore wind farms in power grids has a negative effect on the operation of the conventional distance relays. In this study, a new protection technique is presented for uncompensated/compensated double‐circuit transmission lines utilising one‐end current measurements. The proposed protection technique does not require any information regarding the transmission line parameters, wind farms, or the compensation devices. In addition, the errors in phasor estimation due to the generated sub‐harmonics and inter‐harmonics by the wind generators are avoided as the current samples are directly used. Comprehensive studies are implemented on PSCAD/EMTDC software considering numerous cases of external and internal faults. In addition, the double‐circuit transmission line is modelled using the frequency‐dependent phase model and the mutual‐coupling between both circuits are considered. The recorded results confirm the high efficacy of the proposed protection technique with respect to fault type, fault location, and fault resistance.
Energy assessment and monitoring of a novel photovoltaic‐thermal collector designed for solar‐assisted heat pump systems
Authors: Leonforte Fabrizio , Del Pero Claudio , Aste Niccolò , Miglioli Alessandro , Croci Lorenzo , Besagni Giorgio
Published: June 2020

Hybrid photovoltaic‐thermal (PVT) collectors have been widely investigated in recent decades since they ensure higher performances and compactness with respect to the two sub‐components. In this study, a novel covered PVT water collector, specifically designed to be coupled with heat pumps, is presented. The PV‐cells are directly laminated on the aluminium roll‐bond absorber without the usual front glass layer, while a glass cover is added after the lamination, creating an air gap with the PV‐absorber laminate. The novel collector has electrical features similar to those of uncovered PVTs, in which the front glass layer is laminated in contact with PV‐cells and even better performances than a traditional covered collector, which has a second glass cover on top. The electric performances of the PVT, operated in stand‐alone mode and solar‐assisted mode, were monitored and compared with a traditional PV module, obtaining interesting results in both conditions. In particular, the novel PVT showed comparable and even better electric performances than the traditional PV when combined with the heat pump, thanks to PV‐cells active cooling. The work proves that the proposed manufacturing technique could lead to a new generation of hybrid collectors, which may achieve competitive performances when integrated with heat pumps.
The NLRP3 Inflammasome in Alcoholic and Nonalcoholic Steatohepatitis
Authors: Knorr Jana , Wree Alexander , Tacke Frank , Feldstein Ariel E.
Published: June 2020

Nonalcoholic steatohepatitis (NASH) and alcoholic hepatitis (ASH) are advanced forms of fatty liver diseases that are associated with a high morbidity and mortality worldwide. Patients with ASH or NASH are more susceptible to the progression of fibrosis and cirrhosis up to the development of hepatocellular carcinoma. Currently, there are limited medical therapies available. Accompanied by the asymptomatic disease progression, the demand for liver transplants is high. This review provides an overview about the growing evidence for a central role of NLR family pyrin domain containing 3 (NLRP3) inflammasome, a multiprotein complex that acts as a central driver of inflammation via activation of caspase 1, maturation and release of pro-inflammatory cytokines including interleukin-1β, and trigger of inflammatory pyroptotic cell death in both NASH and ASH. We also discuss potential therapeutic approaches targeting NLRP3 inflammasome and related upstream and downstream pathways to develop prognostic biomarkers and medical treatments for both liver diseases.
Hepatobiliary Differentiation: Principles from Embryonic Liver Development
Authors: Freeburg Scott H. , Goessling Wolfram
Published: June 2020

Hepatocytes and biliary epithelial cells (BECs), the two endodermal cell types of the liver, originate from progenitor cells called hepatoblasts. Based principally on in vitro data, hepatoblasts are thought to be bipotent stem cells with the potential to produce both hepatocytes and BECs. However, robust in vivo evidence for this model has only recently emerged. We examine the molecular mechanisms that stimulate hepatoblast differentiation into hepatocytes or BECs. In the absence of extrinsic cues, the default fate of hepatoblasts is hepatocyte differentiation. Inductive cues from the hepatic portal vein, however, initiate transcription factor expression in hepatoblasts, driving biliary specification. Defining the mechanisms of hepatobiliary differentiation provides important insights into congenital disorders, such as Alagille syndrome, and may help to better characterize the poorly understood hepatic lineage relationships observed during regeneration from liver injury.
Revision Total Hip Arthroplasty in Osteogenesis Imperfecta
Authors: Schoof Lauren H. , Duenes Matthew L. , Feng James E. , Long William J. , Schwarzkopf Ran
Published: June 2020

Osteogenesis imperfecta (OI) is a rare group of connective tissue disorders commonly associated with bone fragility, deformity, and fractures, leading to instability and early osteoarthritis. Current advancements in the medical and surgical management of OI have extended the life span of these patients, resulting in an increased need for joint arthroplasty to help maintain quality of life. However, surgery among this patient population is technically challenging and comes with a high burden of revision. In this report, we present a case of revision total hip arthroplasty in a patient with OI and review important considerations to help ensure proper preoperative planning and correct precautions to minimize complications and decrease implant failure.
Nonlinear current–voltage characteristics in electron doped YBCO superconductor below the critical temperature
Authors: Sk T. , Ghosh Ajay Kumar
Published: June 2020

Below the critical temperature, several Ce substituted YBa2Cu3O7−δ superconductors exhibit nonlinear current–voltage (IV) characteristics. We have extracted an exponent following the idea of the Kosterlitz–Thouless transition using IV over a wide range of temperatures around the critical temperature. The superfluid phase stiffness has been extracted within the framework of the Ambegaokar–Halperin–Nelson–Siggia theory. In a combined plot of the superfluid density and resistivity as a function of temperature, we observe that the superfluid density varies widely corresponding to the zero resistive states. The shift of the temperature corresponding to the crossing point with the electron doping level has been found to be very strong.
Multistable metamaterial on elastic foundation enables tunable morphology for elastic wave control
Authors: Ramakrishnan Vinod , Frazier M. J.
Published: June 2020

We present a strategy for continuously and reversibly tuning the propagation of elastic waves in one-dimensional systems without need for persistent external stimulation. The general approach places a bistable metamaterial on an elastic substrate which is subsequently deformed via prescribed boundary displacements. The internal substrate deformation, which is shaped by a prescribed spatial variation in elasticity, is reflected in the overlaying metamaterial and facilitates the reconfiguration of bistable elements over isolated regions. As each configuration is associated with a unique stiffness, these regions represent an adjustable, meso-scale morphology amenable to tuning elastic waves. The essential bistability is characterized by an asymmetric, double-welled equipotential energy function and is developed by mechanical rather than phenomenological means. The asymmetry provides for the unique, configuration-specific (stable) equilibrium stiffnesses; the equipotential promotes reversibility (i.e., no one configuration is energetically preferred). From a uniform metamaterial-substrate system, we demonstrate the utility of our strategy by producing a waveguide with shifting passband and a metamaterial with variable unit cell morphology.
Water exchange in magnesium’s hydration shells impacts biological processes
Authors: Bandari Anashe
Published: June 2020

The dynamics is important to a variety of biological phenomena, and transition path sampling provides an alternative path to study the process that is out of reach for all-atom simulations.
Vortex induced vibrations of wind turbine blades: Influence of the tip geometry
Authors: Horcas S. G. , Barlas T. , Zahle F. , Sørensen N. N.
Published: June 2020

The present investigation used numerical simulations to study the vortex induced vibrations (VIVs) of a 96 m long wind turbine blade. The results of this baseline shape were compared with four additional geometry variants featuring different tip extensions. The geometry of the tip extensions was generated through the variation of two design parameters: the dihedral angle bending the blade out of the rotor plane and the sweep angle bending the blade in the rotor plane. The applied numerical methods relied on a fluid structure interaction (FSI) approach, coupling a computational fluid dynamics solver with a multi-body structural solver. The methodology followed for locating VIV regions was based on the variation of the inclination angle. This variable was defined as the angle between the freestream velocity and the blade axis, being 0° when these vectors were normal and positive when a velocity component from tip to root was introduced. For the baseline geometry, the FSI simulations predicted significant blade vibrations for inclination angles between 47.5° and 60° with a maximum peak-to-peak amplitude of 2.3 m. The installation of the different tip extensions on the blade geometry was found to significantly modify the inclination angles where VIV was observed. In particular, the simulations of three of the tip designs showed a shifting of several degrees for the point where the maximum vibrations were recorded. For the specific tip geometry where only the sweep angle was taken into account, a total mitigation of the VIV was observed.
Synchronization of thermoacoustic quasiperiodic oscillation by periodic external force
Authors: Sato M. , Hyodo H. , Biwa T. , Delage R.
Published: June 2020

Quasiperiodic oscillations can occur in nonequilibrium systems where two or more frequency components are generated simultaneously. Many studies have explored the synchronization of periodic and chaotic oscillations; however, the synchronization of quasiperiodic oscillations has not received much attention. This study experimentally documents forced synchronization of the quasiperiodic state and the internally locked state of a thermoacoustic oscillator system. This system consists of a gas-filled resonance tube with a nonuniform cross-sectional area. The thermoacoustic oscillator was designed and built in such a way that nonlinear interactions between the fundamental acoustic oscillation mode and the third mode of the gas column are controlled by a temperature difference that is locally created in the resonance tube. Bifurcation diagrams were mapped out by changing the forcing strength and frequency. Separated Arnold tongues were found and both modes were entrained to the external force through complete synchronization. A saddle-node bifurcation was observed in the route from partial to complete synchronization when the forcing strength was relatively weak. However, a Hopf (torus-death) bifurcation was observed when the forcing was relatively strong. In the internally locked state, the bifurcation occurred after the internal locking was broken down by the external force.
Thermoelectric porous MOF based hybrid materials
Authors: Redel Engelbert , Baumgart Helmut
Published: June 2020

Porous hybrid materials and MOF (Metal–Organic-Framework) films represent modern designer materials that exhibit many requirements of a near ideal and tunable future thermoelectric (TE) material. In contrast to traditional semiconducting bulk TE materials, porous hybrid MOF templates can be used to overcome some of the constraints of physics in bulk TE materials. These porous hybrid systems are amenable for simulation and modeling to design novel optimized electron-crystal phonon-glass materials with potentially very high ZT (figure of merit) numbers. Porous MOF and hybrid materials possess an ultra-low thermal conductivity, which can be further modulated by phonon engineering within their complex porous and hierarchical architecture to advance the TE figure of merit (ZT). This Perspective review discusses recent results of MOF TE materials and provides a future outlook and the vision to the search for the next generation TE porous hybrid and MOF materials, which could be part of the green renewable energy revolution with novel materials of sustainably high ZT values.
Bacterial chemotaxis in thin fluid layers with free surface
Authors: Ivančić Filip , Sheu Tony W. H. , Solovchuk Maxim
Published: June 2020

Thin fluid layers are common natural habitats for various species of aerobic bacteria. Collective behaviors in bacterial colonies caused by chemotaxis can form complex bioconvection patterns, which often work in favor of the colony’s survival and growth. The connection between the biology of bacterial aerotaxis and the physics of buoyancy effects caused by non-uniform suspension density is numerically investigated for a suspension of oxytactic bacteria placed in the Petri dish. The upper surface is free and open to the atmosphere, and through it oxygen diffuses into the suspension. Surface tension and dynamic contact line are incorporated into the mathematical and numerical models. A comparison has been made between dynamic free surface and fixed free surface models, and differences have been revealed. The parametric study in the case of dynamic free surface has been performed, and the non-linear dynamics of the phenomenon has been investigated. Resulting from upward aerotaxis and downward gravitational force, Rayleigh–Taylor-like instabilities develop between layers of different densities in the suspension. Bacterial plume patterns and their dynamics, such as sinking, merging, and birth of new plumes, characterize the phenomenon for particular intervals of dimensionless parameters. Accordingly, categorization of the phenomenon based on bacterial plume evolution has been made, and significant intervals of dimensionless parameters have been extracted.
Plasmonic hot electrons for sensing, photodetection, and solar energy applications: A perspective
Authors: Tang Haibin , Chen Chih-Jung , Huang Zhulin , Bright Joeseph , Meng Guowen , Liu Ru-Shi , Wu Nianqiang
Published: June 2020

In plasmonic metals, surface plasmon resonance decays and generates hot electrons and hot holes through non-radiative Landau damping. These hot carriers are highly energetic, which can be modulated by the plasmonic material, size, shape, and surrounding dielectric medium. A plasmonic metal nanostructure, which can absorb incident light in an extended spectral range and transfer the absorbed light energy to adjacent molecules or semiconductors, functions as a “plasmonic photosensitizer.” This article deals with the generation, emission, transfer, and energetics of plasmonic hot carriers. It also describes the mechanisms of hot electron transfer from the plasmonic metal to the surface adsorbates or to the adjacent semiconductors. In addition, this article highlights the applications of plasmonic hot electrons in photodetectors, photocatalysts, photoelectrochemical cells, photovoltaics, biosensors, and chemical sensors. It discusses the applications and the design principles of plasmonic materials and devices.
Predicting the dynamic behavior of the mechanical properties of platinum with machine learning
Authors: Chapman James , Ramprasad Rampi
Published: June 2020

Over the last few decades, computational tools have been instrumental in understanding the behavior of materials at the nano-meter length scale. Until recently, these tools have been dominated by two levels of theory: quantum mechanics (QM) based methods and semi-empirical/classical methods. The former are time-intensive but accurate and versatile, while the latter methods are fast but are significantly limited in veracity, versatility, and transferability. Recently, machine learning (ML) methods have shown the potential to bridge the gap between these two chasms due to their (i) low cost, (ii) accuracy, (iii) transferability, and (iv) ability to be iteratively improved. In this work, we further extend the scope of ML for atomistic simulations by capturing the temperature dependence of the mechanical and structural properties of bulk platinum through molecular dynamics simulations. We compare our results directly with experiments, showcasing that ML methods can be used to accurately capture large-scale materials phenomena that are out of reach of QM calculations. We also compare our predictions with those of a reliable embedded atom method potential. We conclude this work by discussing how ML methods can be used to push the boundaries of nano-scale materials research by bridging the gap between QM and experimental methods.
Plasmon-enhanced high order harmonic generation of open-ended finite-sized carbon nanotubes: The effects of incident field’s intensity and frequency and the interference between the incident and scattered fields
Authors: Sun Jin , Ding ZongLin , Yu YuanQin , Liang WanZhen
Published: June 2020

The nonlinear optical properties of hybrid systems composed of a silver nanosphere and an open-ended finite-sized armchair single-walled carbon nanotube (SWCNT) are systematically investigated by the hybrid time-dependent Hartree–Fock (TDHF)/finite difference time domain (FDTD) approach, which combines the real-time TDHF approach for the molecular electronic dynamics with the classical computational electrodynamics approach, the FDTD, for solving Maxwell’s equations. The high order harmonic generation (HHG) spectra of SWCNTs are studied as a function of the intensity (I0) and frequency (ω0) of the incident field, and SWCNTs length as well. It is found that the near field generated by a Ag nanoparticle has an overall enhancement to the molecular HHG in all the energy range, and it extends the HHG spectra to high energy. The inhomogeneity of the near field results in the appearance of even-order harmonics, and their corresponding spectral intensities are sensitive to ω0, therefore the near field’s gradient. When ω0 is far away from the frequency of plasmon resonance of the silver nanosphere (ωc), the interference between the incident and scattering light beams extends the spectral range and makes the HHG spectra more sensitive to I0, while at ω0 = ωc, the impact of the interference on the spectra is negligible.
Reduced order modeling-based discrete unified gas kinetic scheme for rarefied gas flows
Authors: Zhao Xiang , Wu Chen , Chen Zhen , Yang Liming , Shu Chang
Published: June 2020

Boltzmann solvers face significant difficulty in simulating rarefied flows at high Knudsen numbers. In this flow regime, the gas distribution function is widely scattered and highly concentrated with a very steep slope in the particle velocity space. In order to capture the feature of such a flow, the Boltzmann solvers such as the Discrete Unified Gas Kinetic Scheme (DUGKS) discretize the particle velocity space with a very fine mesh (many discrete particle velocities) using the Discrete Velocity Method (DVM) due to which the load for computation becomes unendurable. In this paper, a Reduced Order Modeling (ROM) method is used to generate a reduced discrete velocity space for the DUGKS. More specifically, the discrete empirical interpolation method [S. Chaturantabut and D. C. Sorensen, SIAM J. Sci. Comput. 32, 2737–2764 (2010)] is used to select the dominant nodes in the original discrete velocity space to form a reduced discrete velocity space, which represents important dynamical characteristics. In this way, most grid points in the discrete velocity space, which are of negligible importance on the integration, are removed in practical computation, which yields a significant improvement in computational efficiency. The proposed ROM approach is not limited to a specific DVM-based solver. For illustration, in this paper, we developed the Reduced Order Modeling-based Discrete Unified Gas Kinetic Scheme (ROM-DUGKS) by applying the reduced velocity space to the conventional DUGKS. Validations are performed in both low-speed and hypersonic rarefied flows at various Knudsen numbers. The results show that the ROM-DUGKS is much more efficient than the original DUGKS while still maintaining high accuracy. This significant improvement in computational efficiency will unleash the potential of the DVM-based solvers such as the DUGKS for practical applications to rarefied flow problems.
Numerical calculation of free-energy barriers for entangled polymer nucleation
Authors: Tang Xiaoliang , Tian Fucheng , Xu Tingyu , Li Liangbin , Reinhardt Aleks
Published: June 2020

The crystallization of entangled polymers from their melt is investigated using computer simulation with a coarse-grained model. Using hybrid Monte Carlo simulations enables us to probe the behavior of long polymer chains. We identify solid-like beads with a centrosymmetry local order parameter and compute the nucleation free-energy barrier at relatively high supercooling with adaptive-bias windowed umbrella sampling. Our results demonstrate that the critical nucleus sizes and the heights of free-energy barriers do not significantly depend on the molecular weight of the polymer; however, the nucleation rate decreases with the increase in molecular weight. Moreover, an analysis of the composition of the critical nucleus suggests that intra-molecular growth of the nucleated cluster does not contribute significantly to crystallization for this system.
Direct measurement of interfacial Dzyaloshinskii–Moriya interaction at the MoS2/Ni80Fe20 interface
Authors: Kumar Akash , Chaurasiya Avinash Kumar , Chowdhury Niru , Mondal Amrit Kumar , Bansal Rajni , Barvat Arun , Khanna Suraj P. , Pal Prabir , Chaudhary Sujeet , Barman Anjan , Muduli P. K.
Published: June 2020

We report on a direct measurement of sizable interfacial Dzyaloshinskii–Moriya interaction (iDMI) at the interface of two-dimensional transition metal dichalcogenide (2D-TMD), MoS2 and Ni80Fe20 (Py), using Brillouin light scattering spectroscopy. A clear asymmetry in spin-wave dispersion is measured in MoS2/Py/Ta, while no such asymmetry is detected in the reference Py/Ta system. A linear scaling of the DMI constant with the inverse of Py thickness indicates the interfacial origin of the observed DMI. We further observe an enhancement of DMI constant in a three to four layer MoS2/Py system (by 56%) as compared to that in two layer MoS2/Py, which is caused by a higher density of MoO3 defect species in the case of three to four layer MoS2. The results open possibilities of spin–orbitronic applications utilizing the 2D-TMD-based heterostructures.
Progress in quantum-dot single photon sources for quantum information technologies: A broad spectrum overview
Authors: Arakawa Yasuhiko , Holmes Mark J.
Published: June 2020

Semiconductor quantum dots (QDs) of various material systems are being heavily researched for the development of solid state single photon emitters, which are required for optical quantum computing and related technologies such as quantum key distribution and quantum metrology. In this review article, we give a broad spectrum overview of the QD-based single photon emitters developed to date, from the telecommunication bands in the IR to the deep UV.
Observation of the elusive “oxygen-in” OCS dimer
Authors: Miller Isaac , Faulkner Ty , Saunier John , Raston Paul L.
Published: June 2020

The carbonyl sulfide (OCS) dimer serves as a prototype system for studying intermolecular forces between nonsymmetrical linear polyatomic molecules. Here, we performed a laser spectroscopic investigation of OCS dimers embedded in helium nanodroplets and found rovibrational bands corresponding to the non-polar “sulfur-in” and parallel polar dimers that have been extensively characterized in the gas phase, as well as a new non-polar “oxygen-in” dimer that has long been predicted by theory. Frequency alternations in the rotational branches along with the absence of a Stark effect provided important clues as to its assignment.
Large non-saturating shift of the torsional resonance in a doubly clamped magnetoelastic resonator
Authors: Staruch Margo , Matis Bernard R. , Baldwin Jeffrey W. , Bennett Steven P. , van 't Erve Olaf , Lofland Sam , Bussmann Konrad , Finkel Peter
Published: June 2020

The magnetic field dependence of the resonance frequencies of Co1−xFex thin film microfabricated resonators was examined for fields applied in the plane of the film. Remarkably, the observed resonance frequency shift with an applied magnetic field did not saturate even up to fields of nearly 2 T. A minimized mechanical and magnetic free energy model of clamped–clamped resonators revealed that for a two-dimensional structure, both bending and torsional modes are allowed, but would have have very different resonance shift behavior with the applied field. A post-anneal of the structure confirms this case by increasing the stress-induced anisotropy of CoFe, which selectively enhances the contribution of the torsional mode and creates the non-saturating field-induced frequency shift. By using the resonance shift in this device in a potential magnetic field sensing paradigm, such a non-saturating torsional mode may be useful for applications such as nuclear magnetic resonance or MRI, which specifically requires sensitive detection of small fluctuations in high magnetic fields.
Milestoning with wind: Exploring the impact of a biasing potential in exact calculation of kinetics
Authors: Wang Hao , Elber Ron
Published: June 2020

We consider the algorithm wind-assisted reweighted Milestoning of Grazioli and Andricioaei [J. Chem. Phys 149(8), 084103 (2018)], expand it, and assess its performance. We derive exact expressions for underdamped and overdamped Langevin dynamics and examine its efficiency for a simple model system (Mueller’s potential) and for bond breaking in solution. The use of a biasing force (wind) significantly enhances the sampling of otherwise rare trajectories but also introduces an exponential weight to the trajectories that significantly impact the value of the statistics. In our examples, computing averages and standard deviations are not better using wind compared to straightforward Milestoning. However, the biasing force is useful for highly steep energy landscapes. On these landscapes, the probability of sampling straightforward Milestoning trajectories, which overcome the barrier, is low and the biasing force enables the observations of these rare events.
Aperiodic electro-optic time lens for spectral manipulation of single-photon pulses
Authors: Sośnicki F. , Mikołajczyk M. , Golestani A. , Karpiński M.
Published: June 2020

Electro-optic time lenses are promising experimental components for photonic spectral-temporal processing of quantum information. We report a stable method to realize an electro-optic time lens, which relies on the amplification of an electronic response of a fast photodiode. The method does not require a repetitive clock and may be applied to aperiodic optical signals. We experimentally demonstrate the approach using single-photon pulses, and directly verify its aperiodicity. The approach will enable the construction of complex electro-optic temporal optical systems.
Experimental investigation of turbulent flow in a two-pass channel with different U-shaped bends
Authors: Liu Runzhou , Li Haiwang , You Ruquan , Tao Zhi
Published: June 2020

Time-resolved particle image velocimetry is used to study internal flow field characteristics in U-shaped channels of square cross section and different structures of the bend section. The Reynolds number based on the hydraulic diameter of the channel is 8888, 13 333, or 17 777. The mean flow and Reynolds stress are considered, and proper orthogonal decomposition (POD) is used to investigate the flow characteristics. A series of important conclusions are drawn from the results. For the main flow, the structure of the bend section has an obvious influence on the flow field characteristics. The size and number of vortices in the corner area are significantly reduced because the increase in the Reynolds number makes the impact of the influx stronger. It can be seen from the clear differences in the Reynolds stress for different bend sections that the fluctuations caused by the mixing of the main flow and the vortices are significantly stronger than those at the boundary. The flow in the bend section is complex, there is a relatively high proportion of turbulent kinetic energy in the low-order modes, and there is an obvious stripe-like structure in the bend section of the channel in which the bend has both inner and outer circular walls, which matches the velocity field from the POD.
Physiological changes associated with enhanced cold resistance during maize (Zea mays) germination and seedling growth in response to exogenous calcium
Authors: Zhang Qian , Liu Yongxi , Yu Qiaoqiao , Ma Yue , Gu Wanrong , Yang Deguang
Published: June 2020

Maize (Zea mays L.) is one of the most important crops worldwide. However, low temperature limits seed germination and seedling growth of maize, which can in turn affect grain yield. The calcium ion (Ca2+) is the second messenger involved in the response to environmental-stimuli-induced signal transduction networks. The underlying physiological mechanisms related to the effects of exogenous Ca2+ treatment of different maize cultivars under low temperature are unclear. We selected two inbred lines, cold-sensitive cv. C546 and cold-tolerant cv. Y478, for studying the effects of Ca2+ on seed germination, photosynthesis, antioxidant enzymes and the osmotic regulation of seedling resistance to low temperature. The optimal concentration of CaCl2 was 80 mmol L–1, which significantly improved the germination percentage at temperatures <10°C. Application of CaCl2 at this concentration under cold stress mitigated the degree of membrane injury and improved the antioxidant enzyme system through reduced relative electrolyte conductivity and malondialdehyde content, increased the soluble protein content, and enhanced superoxide dismutase and peroxidase activity. CaCl2 also significantly increased chlorophyll fluorescence indicators (Fv/Fo, Fv/Fm) and the photosynthetic rate. We conclude that exogenous CaCl2 at a concentration of 80 mmol L–1 protects the function and structure of the membrane and photosystems, improves antioxidant enzyme activity and increases osmotic regulatory substances under cold stress. These results improve our understanding of the mechanisms of Ca2+ and contribute to the development of cold-tolerant maize varieties.
The ventral striatum dissociates information expectation, reward anticipation, and reward receipt
Authors: Filimon Flavia , Nelson Jonathan D. , Sejnowski Terrence J. , Sereno Martin I. , Cottrell Garrison W.
Published: June 2020

Do dopaminergic reward structures represent the expected utility of information similarly to a reward? Optimal experimental design models from Bayesian decision theory and statistics have proposed a theoretical framework for quantifying the expected value of information that might result from a query. In particular, this formulation quantifies the value of information before the answer to that query is known, in situations where payoffs are unknown and the goal is purely epistemic: That is, to increase knowledge about the state of the world. Whether and how such a theoretical quantity is represented in the brain is unknown. Here we use an event-related functional MRI (fMRI) task design to disentangle information expectation, information revelation and categorization outcome anticipation, and response-contingent reward processing in a visual probabilistic categorization task. We identify a neural signature corresponding to the expectation of information, involving the left lateral ventral striatum. Moreover, we show a temporal dissociation in the activation of different reward-related regions, including the nucleus accumbens, medial prefrontal cortex, and orbitofrontal cortex, during information expectation versus reward-related processing.
Mentorship and protégé success in STEM fields
Authors: Ma Yifang , Mukherjee Satyam , Uzzi Brian
Published: June 2020

Significance

Mentorship is arguably a scientist’s most significant collaborative relationship; yet of all collaborations, comparatively little research exists on the link between mentorship and protégé success. Using new large-scale data from the genealogical and performance records of 10s of thousands of scientists worldwide from 1960 to the present, we found that mentorship is associated with diverse forms of protégé success, significantly increasing protégés’ chances of producing celebrated research, being inducted into the National Academy of Science, and achieving superstardom. Paradoxically, protégés achieve their highest impact when they display intellectual independence from their mentors. Protégés do their best work when they break from their mentor’s research topics and coauthor no more than a small portion of their overall research with their mentors.
Fair payments for effective environmental conservation
Authors: Loft Lasse , Gehrig Stefan , Salk Carl , Rommel Jens
Published: June 2020

Global efforts for biodiversity protection and land use-based greenhouse gas mitigation call for increases in the effectiveness and efficiency of environmental conservation. Incentive-based policy instruments are key tools for meeting these goals, yet their effectiveness might be undermined by such factors as social norms regarding whether payments are considered fair. We investigated the causal link between equity and conservation effort with a randomized real-effort experiment in forest conservation with 443 land users near a tropical forest national park in the Vietnamese Central Annamites, a global biodiversity hotspot. The experiment introduced unjustified payment inequality based on luck, in contradiction of local fairness norms that were measured through responses to vignettes. Payment inequality was perceived as less fair than payment equality. In agreement with our preregistered hypotheses, participants who were disadvantaged by unequal payments exerted significantly less conservation effort than other participants receiving the same payment under an equal distribution. No effect was observed for participants advantaged by inequality. Thus, equity effects on effort can have consequences for the effectiveness and efficiency of incentive-based conservation instruments. Furthermore, we show that women exerted substantially more conservation effort than men, and that increasing payment size unexpectedly reduced effort. This emphasizes the need to consider social comparisons, local equity norms, and gender in environmental policies using monetary incentives to motivate behavioral change.
Nearest-neighbor parameters for predicting DNA duplex stability in diverse molecular crowding conditions
Authors: Ghosh Saptarshi , Takahashi Shuntaro , Ohyama Tatsuya , Endoh Tamaki , Tateishi-Karimata Hisae , Sugimoto Naoki
Published: June 2020

Significance

The intracellular environment is occupied by a high concentration of various types of biomolecules that lead to a situation known as molecular crowding, which affects important biological reactions such as replication and transcription by altering the stability of nucleic acids. Because intracellular crowded conditions are heterogeneous, a general method is needed to predict the stability of nucleic acids in such conditions. Here, we predicted the stability of DNA duplexes under crowded conditions induced by a large amount of a cosolute at a physiological salt concentration using the nearest-neighbor model. We also extended the parameters for predicting DNA stability under conditions imposed by different cosolutes that mimicked a localized intracellular crowded region.
Human XPG nuclease structure, assembly, and activities with insights for neurodegeneration and cancer from pathogenic mutations
Authors: Tsutakawa Susan E. , Sarker Altaf H. , Ng Clifford , Arvai Andrew S. , Shin David S. , Shih Brian , Jiang Shuai , Thwin Aye C. , Tsai Miaw-Sheue , Willcox Alexandra , Her Mai Zong , Trego Kelly S. , Raetz Alan G. , Rosenberg Daniel , Bacolla Albino , Hammel Michal , Griffith Jack D. , Cooper Priscilla K. , Tainer John A.
Published: June 2020

Xeroderma pigmentosum group G (XPG) protein is both a functional partner in multiple DNA damage responses (DDR) and a pathway coordinator and structure-specific endonuclease in nucleotide excision repair (NER). Different mutations in the XPG gene
ERCC5
lead to either of two distinct human diseases: Cancer-prone xeroderma pigmentosum (XP-G) or the fatal neurodevelopmental disorder Cockayne syndrome (XP-G/CS). To address the enigmatic structural mechanism for these differing disease phenotypes and for XPG’s role in multiple DDRs, here we determined the crystal structure of human XPG catalytic domain (XPGcat), revealing XPG-specific features for its activities and regulation. Furthermore, XPG DNA binding elements conserved with FEN1 superfamily members enable insights on DNA interactions. Notably, all but one of the known pathogenic point mutations map to XPGcat, and both XP-G and XP-G/CS mutations destabilize XPG and reduce its cellular protein levels. Mapping the distinct mutation classes provides structure-based predictions for disease phenotypes: Residues mutated in XP-G are positioned to reduce local stability and NER activity, whereas residues mutated in XP-G/CS have implied long-range structural defects that would likely disrupt stability of the whole protein, and thus interfere with its functional interactions. Combined data from crystallography, biochemistry, small angle X-ray scattering, and electron microscopy unveil an XPG homodimer that binds, unstacks, and sculpts duplex DNA at internal unpaired regions (bubbles) into strongly bent structures, and suggest how XPG complexes may bind both NER bubble junctions and replication forks. Collective results support XPG scaffolding and DNA sculpting functions in multiple DDR processes to maintain genome stability.
Distortion matrix approach for ultrasound imaging of random scattering media
Authors: Lambert William , Cobus Laura A. , Frappart Thomas , Fink Mathias , Aubry Alexandre
Published: June 2020

Focusing waves inside inhomogeneous media is a fundamental problem for imaging. Spatial variations of wave velocity can strongly distort propagating wave fronts and degrade image quality. Adaptive focusing can compensate for such aberration but is only effective over a restricted field of view. Here, we introduce a full-field approach to wave imaging based on the concept of the distortion matrix. This operator essentially connects any focal point inside the medium with the distortion that a wave front, emitted from that point, experiences due to heterogeneities. A time-reversal analysis of the distortion matrix enables the estimation of the transmission matrix that links each sensor and image voxel. Phase aberrations can then be unscrambled for any point, providing a full-field image of the medium with diffraction-limited resolution. Importantly, this process is particularly efficient in random scattering media, where traditional approaches such as adaptive focusing fail. Here, we first present an experimental proof of concept on a tissue-mimicking phantom and then, apply the method to in vivo imaging of human soft tissues. While introduced here in the context of acoustics, this approach can also be extended to optical microscopy, radar, or seismic imaging.
Stimuli-responsive composite biopolymer actuators with selective spatial deformation behavior
Authors: Wang Yushu , Huang Wenwen , Wang Yu , Mu Xuan , Ling Shengjie , Yu Haipeng , Chen Wenshuai , Guo Chengchen , Watson Matthew C. , Yu Yingjie , Black Lauren D. , Li Meng , Omenetto Fiorenzo G. , Li Chunmei , Kaplan David L.
Published: June 2020

Significance

The majority of deformable actuators rely on synthetic materials with stimuli-responsive properties to execute the system, limiting their use in vivo. We designed and built a new class of bionic actuator entirely out of biocompatible and biodegradable materials. Stimuli-responsive genetically engineered silk–elastin-like proteins (SELPs) and cellulose nanofibers (CNFs) are combined to fabricate an actuator system that could effectively respond to physical and chemical stimuli. Programmable and reversible deformations in response to the stimuli have been achieved with this actuator. The SELP/CNF actuator provides an option for fields such as in vivo biomedical soft robotics and biomimetic devices where biocompatibility, biodegradability, biomedical signals recognition, and durability are desired.
Parallel RNA and DNA analysis after deep sequencing (PRDD-seq) reveals cell type-specific lineage patterns in human brain
Authors: Huang August Yue , Li Pengpeng , Rodin Rachel E. , Kim Sonia N. , Dou Yanmei , Kenny Connor J. , Akula Shyam K. , Hodge Rebecca D. , Bakken Trygve E. , Miller Jeremy A. , Lein Ed S. , Park Peter J. , Lee Eunjung Alice , Walsh Christopher A.
Published: June 2020

Elucidating the lineage relationships among different cell types is key to understanding human brain development. Here we developed parallel RNA and DNA analysis after deep sequencing (PRDD-seq), which combines RNA analysis of neuronal cell types with analysis of nested spontaneous DNA somatic mutations as cell lineage markers, identified from joint analysis of single-cell and bulk DNA sequencing by single-cell MosaicHunter (scMH). PRDD-seq enables simultaneous reconstruction of neuronal cell type, cell lineage, and sequential neuronal formation (“birthdate”) in postmortem human cerebral cortex. Analysis of two human brains showed remarkable quantitative details that relate mutation mosaic frequency to clonal patterns, confirming an early divergence of precursors for excitatory and inhibitory neurons, and an “inside-out” layer formation of excitatory neurons as seen in other species. In addition our analysis allows an estimate of excitatory neuron-restricted precursors (about 10) that generate the excitatory neurons within a cortical column. Inhibitory neurons showed complex, subtype-specific patterns of neurogenesis, including some patterns of development conserved relative to mouse, but also some aspects of primate cortical interneuron development not seen in mouse. PRDD-seq can be broadly applied to characterize cell identity and lineage from diverse archival samples with single-cell resolution and in potentially any developmental or disease condition.
Genomic determinants of pathogenicity in SARS-CoV-2 and other human coronaviruses
Authors: Gussow Ayal B. , Auslander Noam , Faure Guilhem , Wolf Yuri I. , Zhang Feng , Koonin Eugene V.
Published: June 2020

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses an immediate, major threat to public health across the globe. Here we report an in-depth molecular analysis to reconstruct the evolutionary origins of the enhanced pathogenicity of SARS-CoV-2 and other coronaviruses that are severe human pathogens. Using integrated comparative genomics and machine learning techniques, we identify key genomic features that differentiate SARS-CoV-2 and the viruses behind the two previous deadly coronavirus outbreaks, SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV), from less pathogenic coronaviruses. These features include enhancement of the nuclear localization signals in the nucleocapsid protein and distinct inserts in the spike glycoprotein that appear to be associated with high case fatality rate of these coronaviruses as well as the host switch from animals to humans. The identified features could be crucial contributors to coronavirus pathogenicity and possible targets for diagnostics, prognostication, and interventions.
Identifying airborne transmission as the dominant route for the spread of COVID-19
Authors: Zhang Renyi , Li Yixin , Zhang Annie L. , Wang Yuan , Molina Mario J.
Published: June 2020

Various mitigation measures have been implemented to fight the coronavirus disease 2019 (COVID-19) pandemic, including widely adopted social distancing and mandated face covering. However, assessing the effectiveness of those intervention practices hinges on the understanding of virus transmission, which remains uncertain. Here we show that airborne transmission is highly virulent and represents the dominant route to spread the disease. By analyzing the trend and mitigation measures in Wuhan, China, Italy, and New York City, from January 23 to May 9, 2020, we illustrate that the impacts of mitigation measures are discernable from the trends of the pandemic. Our analysis reveals that the difference with and without mandated face covering represents the determinant in shaping the pandemic trends in the three epicenters. This protective measure alone significantly reduced the number of infections, that is, by over 78,000 in Italy from April 6 to May 9 and over 66,000 in New York City from April 17 to May 9. Other mitigation measures, such as social distancing implemented in the United States, are insufficient by themselves in protecting the public. We conclude that wearing of face masks in public corresponds to the most effective means to prevent interhuman transmission, and this inexpensive practice, in conjunction with simultaneous social distancing, quarantine, and contact tracing, represents the most likely fighting opportunity to stop the COVID-19 pandemic. Our work also highlights the fact that sound science is essential in decision-making for the current and future public health pandemics.