bluuebunny/crossref_metadata_2025 huggingface dataset:
Room temperature semiconductor detectors for nuclear security
Authors: Johns Paul M. , Nino Juan C.
Published: July 2019

Preventing radioactive sources from being used for harmful purposes is a global challenge. A requirement for solving the challenge is developing radiation detectors that are efficient, sensitive, and practical. Room temperature semiconductor detectors (RTSDs) are an important class of gamma-ray sensors because they can generate high-resolution gamma-ray spectra at ambient operating temperatures. A number of diverse and stringent requirements must be met for semiconducting materials to serve as sensors in RTSD spectrometers, which limits the number of candidates of interest that receive attention and undergo focused research and development efforts. Despite this, the development of new compounds for sensors in RTSDs is a thriving research field, and a number of materials with stunning potential as RTSD materials have emerged within the last decade. In this perspective, the state of the art in RTSD materials is examined, and emerging semiconducting compounds are reviewed. The highly developed CdTe, CdZnTe, HgI2, and TlBr are first discussed to highlight the potential that can emerge from RTSD compounds in advanced stages of technological development. Thereafter, emerging compounds are reviewed by class from chalcogenides, iodides and chalcohalides, and organic-inorganic hybrid compounds. This work provides both a compilation of the physical and electronic properties of the emerging RTSD candidates and a perspective on the importance of material properties for the future of compounds that can transform the field of radiation detection science.
Linear response of a Hall magnetic drift wave for verification of Hall MHD algorithms
Authors: Farmer W. A. , Ellison C. L. , Hammer J. H.
Published: July 2019

Numerical implementations of Hall magnetohydrodynamics (Hall MHD) can be challenging due to the nonlinear multidimensional nature of the Hall term. Here, a model problem is presented that couples the hydrodynamic motion of the plasma to Hall MHD evolution of the magnetic field. The Hall MHD equations are linearized about unperturbed solutions in both cylindrical and Cartesian coordinates in two dimensions. The magnetic field is assumed to lie in the ignorable direction, and the linear response about the unperturbed solution is considered. The resulting ordinary differential equation is used to numerically compute the eigenfunctions and eigenfrequencies of the mode. The resulting eigenfunctions do not make the local wave approximation but are instead global solutions that depend on the spatial dependence of the unperturbed Alfvén speed. Hall MHD simulations are then performed in the Ares multiphysics code and shown to agree with the predicted phase velocities of the wave, and the simulated solutions are shown to numerically converge to the semianalytic modes. By varying the background density of the plasma (and correspondingly, the ion inertial length), the importance of Hall physics can be varied. This allows the test problem to transition from the classical MHD limit to the extreme Hall MHD limit. This problem is a useful tool for the verification of Hall MHD routines implemented in various codes, and the robustness of a routine can be tested in regimes in which Hall physics is dominant.
Precipitation patterns driven by gravity current
Authors: Pótári Gábor , Tóth Ágota , Horváth Dezső
Published: July 2019

A precipitation reaction can be driven by a gravity current that spreads on the bottom as a denser fluid is injected into an initially stagnant liquid. Supersaturation and nucleation are restricted to locations where the two liquids come into contact; hence, the flow pattern governs the spatial distribution of the final product. In this numerical study, we quantitatively characterize the flow associated with the gravity current prior to the onset of nucleation and distinguish three zones where the coupling of transport processes with the reaction can take place depending on their time scales. A scaling law associated with the region of Rayleigh–Taylor instability behind the tip of the gravity current is also determined.
An ab initio molecular dynamics study of benzene in water at supercritical conditions: Structure, dynamics, and polarity of hydration shell water and the solute
Authors: Choudhary Ashu , Chandra Amalendu
Published: July 2019

Anisotropic structure and dynamics of the hydration shell of a benzene solute in supercritical water are investigated by means of ab initio molecular dynamics simulations. The polarity and structural distortion of the benzene solute in supercritical water are also investigated in this study. Calculations are done at 673 K for three different densities of the solvent. The simulations are carried out using the Becke-Lee-Yang-Parr (BLYP) and also the Becke-Lee-Yang-Parr functional including dispersion corrections of Grimme (BYLP-D). The structural anisotropy is found to exist even at supercritical conditions as elucidated by the radial distribution functions of different conical regions and also by angular and spatial distribution functions. The benzene–water πH-bond and also the water–water hydrogen bonds are found to exist even at the supercritical temperature of 673 K. However, the numbers of these hydrogen bonds are reduced substantially with a decrease in water density. The water molecules in the axial region of benzene are found to be preferably oriented with one OH vector pointing toward the benzene ring, whereas the water molecules located in the equatorial region are found to orient their dipoles mostly parallel to the ring plane. The orientational distributions, however, are found to be rather broad at the supercritical temperature due to thermal fluctuations. Although the water molecules have faster dynamics at these supercritical conditions, a slight difference is observed in the dynamics of the solvation shell and bulk molecules. The conformational flexibility of the ring is found to be enhanced which causes an increase in polarity of the benzene solute in water under supercritical conditions.
Physical properties of group 14 semiconductor alloys in orthorhombic phase
Authors: Fan Qingyang , Xu Jie , Zhang Wenzhu , Song Yanxing , Yun Sining
Published: July 2019

The structural properties, electronic band structures, mechanical anisotropy, and the stability of Si, SiGe, Ge, GeSn, and Sn in the Cmca phase are comprehensively investigated in this paper. Si, Ge, and Sn, when in the Cmca phase, are dynamically, thermodynamically, and mechanically stable. Firstly, two novel semiconductor materials with direct bandgap are proposed in this paper. When Ge atoms and Sn atoms are combined into compounds with the Cmca phase at a stoichiometric ratio of 1:1, the bandgap is 0.48 eV, and Sn in the Cmca phase is also a direct bandgap semiconductor material with a bandgap of 0.41 eV. In addition, the mechanical anisotropy of Si, SiGe, Ge, GeSn, and Sn in the Cmca phase and SiGe and GeSn in the F4¯3m phase is systematically studied, investigating the bulk modulus, shear modulus, Young's modulus, and Poisson's ratio. Young's modulus of SiGe and GeSn in the Cmca phase exhibits the largest mechanical anisotropy in (111) and (001) planes. In the F4¯3m phase, the mechanical anisotropy is smaller than that of SiGe and GeSn, except for in the (111) plane, due to the (111) plane of SiGe and GeSn, in the F4¯3m phase, being mechanically isotropic.
Non-Markovian stochastic Schrödinger equation in k-space toward the calculation of carrier dynamics in organic semiconductors
Authors: Lian Man , Wang Yu-Chen , Ke Yaling , Zhao Yi
Published: July 2019

A non-Markovian stochastic Schrödinger equation developed in our former work [Y. Ke and Y. Zhao, J. Chem. Phys. 147, 184103 (2017)] is extended to the reciprocal (k-) space to calculate the carrier dynamics in organic semiconductors with both local and nonlocal carrier-phonon interactions taken into account. The validity of this approach is examined by comparing with numerically exact benchmark results. As an application, the carrier mobilities are calculated within a one-dimensional periodic lattice model. The results reveal an inversion in the magnitude of the mobility as the nonlocal carrier-phonon interaction varies from weak to strong strengths, indicating a transition of the transport mechanism. This is also demonstrated by a variation in the temperature dependence of the mobility. In addition, a transient localization diffusive behavior caused by intramolecular vibrations is also found.
Properties of plasma sterilizer using non-thermal atmospheric-pressure biocompatible plasma
Authors: Park Jang Sick , Han Ihn , Choi Eun Ha
Published: July 2019

Non-thermal atmospheric-pressure biocompatible plasma (NBP) has diverse functions such as surface treatment, and cleaning and decomposing organic matter. Few commercially available devices use plasma to sterilize and disinfect the air and surfaces. We commercialize a new plasma sterilizer that can eradicate viruses, bacteria, etc., using NBP with a compact setup. The hydroxyl (OH) radical species concentration inside the dielectric-barrier discharge (DBD) is estimated from the equation reduced by R. Sankaranarayanan, which is approximately 9.78 × 1015 cm−3. The new plasma sterilizer with water droplets developed in this work exhibits excellent sterilization properties, with the OH radical concentration being approximately 30 times higher than that obtained in other types of atmospheric-pressure DBD devices in air saturated with vapor.
The optimal Stokes-Brinkman coupling for two-dimensional transverse flows in dual-scale fibrous porous media using the effective Navier slip approach
Authors: Lu Jin Gang , Woo Nam Sub , Hwang Wook Ryol
Published: July 2019

Optimal values of the effective viscosity and the stress jump coefficient in the Stokes-Brinkman model with continuous and jump stress conditions, respectively, have been accurately characterized and then applied to solve various two-dimensional transverse dual-scale flows in fibrous porous media. In this work, the effective viscosity and the stress jump coefficient are determined such that the interfacial slip velocity can be identified to that in the effective Navier-slip description and therefore it naturally facilitates the accurate prediction of the slip velocity and its gradient (stress) at the fluid/porous interface along with the velocity fields in both the porous media and the pure fluid domain. With these optimal values of the effective viscosity and the stress jump coefficient, the Stokes-Brinkman coupling can be employed to accurately describe the dual-scale porous flow at low computational cost, which may provide an effective computational framework in investigating particle deposition/filtration and void transports within composites.
Synthesis of endohedral-fullerenes using laser ablation plasma from solid material and vaporized fullerenes
Authors: Itagaki H. , Fujiwara Y. , Minowa Y. , Ikehara Y. , Kaneko T. , Okazaki T. , Iizumi Y. , Kim J. , Sakakita H.
Published: July 2019

We have recently developed a technique to synthesize endohedral fullerenes that involves the collision of vaporized fullerenes and plasma particles produced following the laser ablation of a solid material. Using this technique, we synthesized N@C60 using a boron nitride rod as the source of the plasma particles. Optical emission measurements showed that the kinetic energy of N+ ions could be controlled from 20 to 65 eV by changing the energy of the incident laser beam. The synthesis of N@C60 was performed with a N+ kinetic energy of 65 eV, a C60 vaporizing temperature of 800 °C, and a total reaction time of one hour. By optimizing the kinetic energy for producing the encapsulated particles, we were able to synthesis N@C60 with a purity of 4.52 x 10−3%. The purity of our material was two orders of magnitude higher than that achieved using alternative physical synthetic methods that use solid materials, such as arc discharge and co-evaporation methods.
Surfactant-aided dispersion of carbon nanomaterials in aqueous solution
Authors: Borode Adeola O. , Ahmed Noor A. , Olubambi Peter A.
Published: July 2019

Carbon nanomaterials such as graphene and carbon nanotubes possess great thermophysical properties which make them very good candidates for heat transfer application. However, the major challenge of these nanomaterials is their tendency to agglomerate and bundle together when dispersed in base fluids. This study reviews the homogeneous dispersion of these nanomaterials in aqueous solution with the aid of surfactants. The different surfactants and their characterization methods for stable dispersion of carbon nanomaterials have been examined. The influence of surfactants on the thermophysical and rheological properties of carbon-based nanofluids was also highlighted. The usefulness of noncovalent functionalization using surfactants is due to its ability to efficiently unbundle carbon nanomaterials and sustain homogeneity of the nanofluids without compromising the integrity of their structure. Sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfate (SDBS), Gum Arabic (GA), Triton X-100, and cetyltrimethylammonium bromide (CTAB) are the commonly used surfactants. Unlike SDS, SDBS, and CTAB, GA does not foam when agitated. Various authors have investigated the stability of carbon-based nanofluids. Both physical and chemical techniques have been used to stabilize nanofluids. Mixed surfactants were found to stably disperse nanomaterials at lower concentrations compared to individual surfactants. However, limited studies exist for long term stability of carbon-based nanofluids.
Nonlocal quantum erasure of phase objects
Authors: Gao Lu , Zhang Yingwen , Cohen Eliahu , Elitzur Avshalom C. , Karimi Ebrahim
Published: July 2019

Franson interference is a fourth order interference effect which, unlike the better known Hong-Ou-Mandel interference, does not require the entangled photon pairs to be present at the same space-time location for interference to occur—it is nonlocal. Here, we use a modified Franson interferometer to experimentally demonstrate the nonlocal erasure and correction of an image of a phase-object taken through coincidence imaging. This nonlocal quantum erasure technique can have several potential applications such as phase corrections in quantum imaging and microscopy and also user authentication of two foreign distant parties.
Adaptive inverse ray-tracing for accurate and efficient modeling of cross beam energy transfer in hydrodynamics simulations
Authors: Colaïtis A. , Follett R. K. , Palastro J. P. , Igumenschev I. , Goncharov V.
Published: July 2019

Integrated hydrodynamics simulations of inertial confinement fusion rely on reduced physics models. To reproduce experimental trends, these models often feature tuning parameters, but this comes with a risk: the over-tuning of one model can hide physics inadequacies in another. The ray-based models of cross-beam-energy transfer (CBET) represent this risk. Here, we present an accurate and efficient model of CBET suitable for inline implementation in 3D hydrodynamics simulations. Inverse Ray Tracing (IRT) is used to compute the ray field in a 3D permittivity profile described on an unstructured tetrahedral mesh using the Inline Field Reconstruction and Interaction using Inverse Tracing framework. CBET is accounted for through perturbations to the permittivity associated with ion acoustic waves driven by the overlapped fields. Large gradients in the permittivity are resolved by coupling the IRT to a recursive Adaptive Mesh Refinement (AMR) algorithm. The use of AMR also allows for the resolution of caustics, with accurate field reconstruction performed using the Etalon integral method. Comparisons of the model with wave-based solutions from the Laser Plasma Simulation Environment demonstrate its ability to control energy conservation and gain convergence through the AMR depth only, without the use of ad hoc physical models or artificial tuning parameters.
Stochastic resolution of identity second-order Matsubara Green’s function theory
Authors: Takeshita Tyler Y. , Dou Wenjie , Smith Daniel G. A. , de Jong Wibe A. , Baer Roi , Neuhauser Daniel , Rabani Eran
Published: July 2019

We develop a stochastic resolution of identity representation to the second-order Matsubara Green’s function (sRI-GF2) theory. Using a stochastic resolution of the Coulomb integrals, the second order Born self-energy in GF2 is decoupled and reduced to matrix products/contractions, which reduces the computational cost from O(N5) to O(N3) (with N being the number of atomic orbitals). The current approach can be viewed as an extension to our previous work on stochastic resolution of identity second order Møller-Plesset perturbation theory [T. Y. Takeshita et al., J. Chem. Theory Comput. 13, 4605 (2017)] and offers an alternative to previous stochastic GF2 formulations [D. Neuhauser et al., J. Chem. Theory Comput. 13, 5396 (2017)]. We show that sRI-GF2 recovers the deterministic GF2 results for small systems, is computationally faster than deterministic GF2 for N > 80, and is a practical approach to describe weak correlations in systems with 103 electrons and more.
Time and frequency resolved transient-absorption and stimulated-Raman signals of stochastic light
Authors: Osipov V. Al. , Asban S. , Mukamel S.
Published: July 2019

Covariance spectroscopy signals based on the transmission of broadband stochastic probe light undergoing a nonlinear optical process with matter are studied. The resulting signal depends on intensity correlation functions of the probe pulse. Application is made to transient absorption and stimulated Raman signals, where an ultraviolet pump and a delayed stochastically modulated infrared or optical Raman probe are used for monitoring vibrational excitations. We show that the stochastic properties of light can be exploited to circumvent the limitations on the joint temporal and spectral resolution of the signal. We study a model system with a time-dependent frequency and show that the dynamical information can be fully extracted from the covariance signal. This information is heavily suppressed upon averaging of noisy signals and practically inaccessible in conventional stimulated Raman measurements.
Positive temperature dependence of time-dependent breakdown of GaN-on-Si E-mode HEMTs under positive gate stress
Authors: Masin F. , Meneghini M. , Canato E. , De Santi C. , Stockman A. , Zanoni E. , Moens P. , Meneghesso G.
Published: July 2019

We report an extensive analysis of the time-dependent breakdown of E-mode GaN-on-Si power HEMTs subjected to positive gate stress and demonstrate that TTF (time-to-failure) has a positive temperature dependence. The analyzed devices have a p-type gate; large (60 A) power transistors were subjected to positive stress at different voltages and temperatures ranging from 25 °C to 250 °C. The original results collected in this paper demonstrate that (i) constant voltage stress induces a gradual decrease in gate leakage current, which is ascribed to hole-trapping in Mg-acceptors located at the p-GaN/AlGaN interface; (ii) this trapping process becomes less pronounced at high temperatures, due to a faster detrapping from the shallow Mg-related traps; (iii) the devices stressed at the same voltage and different temperatures show a similar initial gate leakage, due to the fact that in the analyzed regime, gate conduction is dominated by Fowler-Nordheim tunneling, a field-related, rather than thermally activated, process; (iv) the time-to-failure has a positive temperature dependence. The latter result is explained by considering that time-dependent breakdown occurs due to the accumulation of positive charges at the p-GaN/AlGaN interface, which results in an increased injection of 2DEG electrons into the p-GaN layer, where they are accelerated by the electric field. High temperatures favor the detrapping of holes, thus reducing this process and leading to a better stability.
Pushered single shell implosions for mix and radiation trapping studies using high-Z layers on National Ignition Facility
Authors: Dewald E. L. , Pino J. E. , Tipton R. E. , Salmonson J. D. , Ralph J. , Hartouni E. , Khan S. F. , Hatarik R. , Young C. V. , Thorn D. , Smalyuk V. A. , Sacks R. , Nikroo A. , Rice N. , MacLaren S. A. , Prisbrey S. , Remington B. A. , Graziani F.
Published: July 2019

Pushered Single Shells (PSSs) are an alternative approach to Inertial Confinement Fusion implosions that employ high-Z materials in the innermost capsule layer (pusher) as a means to enhance radiation trapping and lower core ignition requirements. However, adding high-Z materials can also increase losses due to mix, provide extra tamping, and make the capsule emission opaque to x-ray diagnostics. The first PSS implosions performed on the National Ignition Facility use plastic ablators with a germanium (Ge) dopant as a high-Z surrogate in the pusher to isolate the effects of high-Z mix and radiation trapping without changing tamping. Using a 2-shock laser pulse, the PSS implosions are designed and symmetrized to reach 3.7 keV core temperatures. A low concentration (2.8%) Ge dopant is added to the innermost layer, and the resulting effects on mix and x-ray opacity are observed. The method of separated reactants is used to infer information about mixing between the deuterated plastic pusher and the capsule fill gas (25% tritium) from the resulting nuclear DT reactions. Radiation transport is studied via capsule emission x-ray spectroscopy and imaging. Both nuclear and x-ray data corroborate the hypothesis that the addition of Ge strongly affects the mix region through radiation losses but has a minimal effect on the core and the warm, unmixed regions. Simulations using diffusive and turbulent mix models agree qualitatively with data, but quantitative agreement may require hybrid mix models that can model the transitional regime between turbulence and diffusion. Simulations matching the observables show increased core radiation trapping when Ge is added.
Mathematical foundations of an ultra coarse-grained slip link model
Authors: Shanbhag Sachin
Published: July 2019

The master equation underlying ecoSLM, an ultra-coarse-grained slip link model, is presented. In the absence of constraint release, the equilibrium and dynamic properties of the discrete master equation for large chains are found to be virtually identical to the continuous Fokker-Planck equation for Brownian particles diffusing in a potential. A single-chain microscopic model with repulsion between adjacent slip links is described. It is approximately consistent with the quadratic fluctuation potential used in ecoSLM. Mapping ecoSLM with fine-grained slip link models or experiments requires specification of an effective friction as a function of molecular weight. Methods to accomplish this are discussed. Collectively, the mathematical framework described provides an interface for fine-grained slip link models to potentially use ecoSLM for extreme coarse-graining.
Simulation of solid propellant microstructures by combining the collective rearrangement method with the discrete element method
Authors: Xiao Liqun , Fu Xiaolong , Fan Xuezhong , Li Jizhen , Xie Wanli
Published: July 2019

The polydisperse particulate components in solid propellant are incompact and randomly packed, which determines the microstructural features of the propellants. A packing method, combining the discrete element method (DEM) and collective rearrangement method, was applied to model propellant microstructures. The validity of this method was investigated by comparing the calculated and experimental properties of the monodisperse, bidisperse, and polydisperse random close packed sphere systems. The propellant models were generated using a stepwise approach, and their homogeneity, local randomness, and long-range pattern were analyzed. A statistical study of aluminum (Al) particle distribution was also conducted. The results indicated that this packing method can effectively determine the microscopic characteristics of random close packed monodisperse spheres. The maximum packing fraction of bidisperse and polydisperse spheres had similar trends to those reported in experimental studies and using other packing algorithms. In addition, this method was capable of generating non-compacted propellant structures with uniformly distributed polydisperse particles. The radial distribution functions (RDFs) for Al-Al particles provided information about the Al distribution, but this was mainly related to the size and content of the large particle components.
Deformation and failure characteristics of weathered granite under uniaxial compression
Authors: Zhang Lingfan , Yang Duoxing , Chen Zhonghui
Published: July 2019

In this paper, we have examined the crack formation of weathered granite by monitoring acoustic emissions (AE) under uniaxial compression. Except for the uniaxial compressive strength (UCS), the thresholds have been determined for crack closure, crack initiation and crack damage, respectively. Moreover, the relationship has been preliminarily established between the AE energy and the rock damage variable. Compared to the deformation and failure characteristics of unweathered granite, the uniaxial compression strength and the elastic modulus of weathered granite are significantly decreased. Additionally, the acoustic emissions are consistently observed in the stage of original crack closure and loading-induced crack initiation followed by crack formation. The crack volumetric strain is an indicator for the crack closure and crack initiation, while the bulk volume strain is an indicator to the crack damage threshold. In elastic phase, AE signals are mainly caused by the micro-damage, while in plastic phase, AE signals are attributed to the plastic deformation. The AE cumulative parameter curves describe the damage evolution process, including the damage initiation and damage development for the weathered granite. The b-value of AE accompanying rock-fracturing is estimated, and oscillates between 1.0 and 1.7 on a long-term decreasing background, indicating a close correlation with the alternate occurrence of clustering. Of particular interest is that the two PZTs are appropriate for monitoring acoustic emissions under uniaxial compression.
A coordinate system invariant formulation for space-charge limited current in vacuum
Authors: Darr Adam M. , Garner Allen L.
Published: July 2019

While space-charge limited emission current density Jcr is calculated exactly for one-dimensional (1D) planar geometry, 1D cylindrical and spherical geometries require approximations such as the Langmuir-Blodgett (LB) equations or nonphysical assumptions. Using variational calculus (VC), we derive a differential equation from first principles to calculate Jcr for any geometry. This yields exact, closed-form analytical solutions for 1D coaxial cylindrical and concentric spherical geometries that approach LB for sufficiently close cathode (Rc) and anode (Ra) radii. VC agrees better with simulations in cylindrical geometry than LB at Rc/Ra = 0.5. The analytical VC solutions also demonstrate the asymptotic behavior for Jcr. For cylindrical geometry, Jcr ∝ 1/Rc2 as Rc/Ra approaches zero or infinity. For spherical geometry, Jcr ∝ 1/Rc2 as Rc/Ra → 0 and Jcr ∝ Ra2/Rc4 as Rc/Ra → ∞.
Strategies for Red-Shifting Type I Photoinitiators: Internal Electric Fields versus Lewis Acids versus Increasing Conjugation
Authors: Hill Nicholas S. , Coote Michelle L.
Published: July 2019

Time-dependent density functional theory calculations were performed on derivatives of Irgacure 2959, a water-soluble, acetophenone-type photoinitiator, in order to assess the relative merits and drawbacks of three distinct ways of modifying its photochemistry: Lewis acid complexation, changing the amount of conjugation in the molecule, and application of an internal electric field through inclusion of a remote charged functional group. The effectiveness of each of the three methods was evaluated against the magnitude of the change in energy of the excited states. Internal electric fields were shown to provide the best method for targeting specific excited states in a controlled and rational manner. The other strategies also had significant effects but it was more difficult to independently target different transitions. Nonetheless, for the specific case of Irgacure 2959, we predict that its complexation with Mg2+ ions in a range of solvents will both red-shift the initiator’s absorbance while improving its efficiency and it is thus a promising candidate for testing as a visible light photoinitiator.
Migratory fishes in Myanmar rivers and wetlands: challenges for sustainable development between irrigation water control infrastructure and sustainable inland capture fisheries
Authors: Conallin John C. , Baumgartner Lee J. , Lunn Zau , Akester Michael , Win Nyunt , Tun Nyi Nyi , Nyunt Maung Maung Moe , Swe Aye Myint , Chan Nyein , Cowx Ian G.
Published: July 2019

Irrigated agriculture and maintaining inland capture fisheries are both essential for food and nutrition security in Myanmar. However, irrigated agriculture through water control infrastructure, such as sluices or barrages, weirs and regulators, creates physical barriers that block migration routes of important fish species. Blocking of fish migration routes, leading to a degradation of inland capture fisheries, will undermine Myanmar’s efforts to develop sustainably and meet the sustainable development goals (SDGs), particularly SDG 2 (Zero Hunger), and the sustainability targets within the national Myanmar Sustainable Development Plans, as well as its Agricultural Development Strategy and Investment Plan. Despite the ambitious international and national targets, there is no explicit policy or legislation and no examples of where fish have been considered in the development or operation of irrigation infrastructure in Myanmar. Solutions are needed that provide opportunities to achieve multi-objective outcomes within irrigation infrastructure and water use. This can be achieved by increasing cross-sectoral collaboration in irrigation projects, improving capacity, increasing research within country by experts and providing technical solutions to aid in better management and mitigation options. This paper explores the various components of policy and governance, institutional and educational capacity and technical and management-based practices needed to plan and integrate better migratory fish and technical needs within irrigated agricultural infrastructure in Myanmar.
Effects of the peer metagenomic environment on smoking behavior
Authors: Sotoudeh Ramina , Harris Kathleen Mullan , Conley Dalton
Published: July 2019

Recent scholarship suggests that the genomes of those around us affect our own phenotypes. Much of the empirical evidence for such “metagenomic” effects comes from animal studies, where the socio-genetic environment can be easily manipulated. Among humans, it is more difficult to identify such effects given the nonrandom distribution of genes and environments. Here we leverage the as-if-random distribution of grade-mates’ genomes conditional on school-level variation in a nationally representative sample. Specifically, we evaluate whether one’s peers’ genetic propensity to smoke affects one’s own smoking behavior net of one’s own genotype. Results show that peer genetic propensity to smoke has a substantial effect on an individual’s smoking outcome. This is true not only when the peer group includes direct friends, and therefore where the individual plays an active role in shaping the metagenomic context but also when the peer group includes all grade-mates and thus in cases where the individual does not select the metagenomic environment. We explore these effects further and show that a small minority with high genetic risk to smoke (‘bad apples’) can greatly affect the smoking behavior of an entire grade. The methodology used in this paper offers a potential solution to many of the challenges inherent in estimating peer effects in nonexperimental settings and can be utilized to study a wide range of outcomes with a genetic basis. On a policy level, our results suggest that efforts to reduce adolescent smoking should take into account metagenomic effects, especially bad apples, within social networks.
Infants expect leaders to right wrongs
Authors: Stavans Maayan , Baillargeon Renée
Published: July 2019

Significance

Social scientists have proposed that expectations about leadership-based power asymmetries have gradually evolved over the course of human history. Some of these expectations concern leaders’ responsibilities to their followers. In particular, leaders are expected to intervene in within-group transgressions and confront the wrongdoers. In violation-of-expectation experiments, we examined whether 17-mo-old infants would share this expectation about leaders. When a fairness transgression occurred among a group of bear puppets, infants expected a leader to intervene and rectify this transgression, but they held no particular expectation for intervention from a nonleader. Thus, consistent with claims that abstract expectations about leaders’ responsibilities are part of the human endowment, our findings indicate that such expectations are already present by the second year of life.
Reappraising academic and social adversity improves middle school students’ academic achievement, behavior, and well-being
Authors: Borman Geoffrey D. , Rozek Christopher S. , Pyne Jaymes , Hanselman Paul
Published: July 2019

Significance

Without social and emotional support, adolescent students who have recently made the difficult transition to middle school experience decreased social belonging, waning academic performance, and increased risk of dropping out. This randomized field trial, conducted at scale across a Midwestern school district, reveals how a psychologically precise intervention for students supported transitioning sixth graders. Intervention materials taught students that middle school adversity is common, short-lived, and due to external, temporary causes rather than personal inadequacies. As a result, students realized improved social and psychological well-being, fewer absences and disciplinary infractions, and higher grade point averages. Implemented at scale, this intervention holds potential to help to address the widespread academic underperformance by the nation’s transitioning middle school students.
Ethnic networks can foster the economic integration of refugees
Authors: Martén Linna , Hainmueller Jens , Hangartner Dominik
Published: July 2019

There is widespread concern in Europe and other refugee-receiving continents that living in an enclave of coethnics hinders refugees’ economic and social integration. Several European governments have adopted policies to geographically disperse refugees. While many theoretical arguments and descriptive studies analyze the impact of spatially concentrated ethnic networks on immigrant integration, there is limited causal evidence that sheds light on the efficacy of these policies. We provide evidence by studying the economic integration of refugees in Switzerland, where some refugees are assigned to live in a specific location upon arrival and, by law, are not permitted to relocate during the first 5 y. Leveraging this exogenous placement mechanism, we find that refugees assigned to locations with many conationals are more likely to enter the labor market. This benefit is most pronounced about 3 y after arrival and weakens somewhat with longer residency. In addition, we find that, among refugees employed by the same company, a high proportion share nationality, ethnicity, or language, which suggests that ethnic residential networks transmit information about employment opportunities. Together, these findings contribute to our understanding of the importance of ethnic networks for facilitating refugee integration, and they have implications for the design of refugee allocation policies.
High-speed AFM reveals subsecond dynamics of cardiac thin filaments upon Ca
2+
activation and heavy meromyosin binding
Authors: Matusovsky Oleg S. , Mansson Alf , Persson Malin , Cheng Yu-Shu , Rassier Dilson E.
Published: July 2019

Significance

The advent of high-speed atomic force microscopy (HS-AFM) changed the field of biology considerably. HS-AFM is the only method where in situ dynamics of biological samples and imaging can be coupled with a spatial resolution of 1 to 5 nm in the horizontal direction. Unlike electron or cryo-electron microscopy, HS-AFM does not require fixation or freezing of the samples, and has the ability to derive kinetic parameters by recording the live movements of single-molecule dynamics. In this paper, we used HS-AFM to investigate directly the mechanisms of cardiac muscle activation. We visualized the muscle regulatory tropomyosin–troponin complex movements during activation by calcium or myosin (motor that drives contraction), and the structural transitions that happen during these events.
Radiokrypton unveils dual moisture sources of a deep desert aquifer
Authors: Yokochi Reika , Ram Roi , Zappala Jake C. , Jiang Wei , Adar Eilon , Bernier Ryan , Burg Avihu , Dayan Uri , Lu Zheng-Tian , Mueller Peter , Purtschert Roland , Yechieli Yoseph
Published: July 2019

Significance

Paleoprecipitation records and subsurface water storage properties are essential data ingredients for accurate hydroclimate and water balance projections. Although both types of data could be extracted from groundwater, their application over long timescales had been limited by the lack of appropriate chronometers. We used a long-lived radiokrypton isotope and identified two distinct moisture source contributions to a deep desert aquifer from low eccentricity periods, one recent and the other 360 ky ago. The groundwater recharge periods show the sensitivity of the moisture transport processes to orbital forcing, whereas the long storage reflects subsurface flow attenuation exerted by faults. Krypton-81 enables groundwater to serve as a direct record of paleoprecipitation over land and of subsurface water storage for the past 1,300 ky.
How Kaposi’s sarcoma-associated herpesvirus stably transforms peripheral B cells towards lymphomagenesis
Authors: Faure Aurélia , Hayes Mitch , Sugden Bill
Published: July 2019

Primary effusion lymphomas (PELs) are causally associated with Kaposi’s sarcoma-associated herpesvirus (KSHV) and 86% of PELs are coinfected with Epstein–Barr virus (EBV). Understanding how PELs develop has been impaired by the difficulty of infecting B cells with KSHV in vitro, and the inability of KSHV to transform them. We show that EBV supports an optimal coinfection of 2.5% of peripheral B cells by KSHV. This coinfection requires 1 or more transforming genes of EBV but not entry into KSHV’s lytic cycle. We demonstrate that dually infected B cells are stably transformed in vitro and show that while both viruses can be maintained, different cells exhibit distinct, transformed properties. Transformed cells that grow to predominate in a culture express increased levels of most KSHV genes and differentially express a subset of cellular genes, as do bona fide PEL cells. These dually infected peripheral B cells are thus both stably transformed and allow in vitro molecular dissection of early steps in the progression to lymphomagenesis.
Personal infidelity and professional conduct in 4 settings
Authors: Griffin John M. , Kruger Samuel , Maturana Gonzalo
Published: July 2019

Significance

The relative importance of personal traits compared with context for predicting behavior is a long-standing issue in psychology. This debate plays out in a practical way every time an employer, voter, or other decision maker has to infer expected professional conduct based on observed personal behavior. Despite its theoretical and practical importance, there is little academic consensus on this question. We fill this void with evidence connecting personal infidelity to professional behavior in 4 different settings.
Dynamic colocalization of 2 simultaneously active
VSG
expression sites within a single expression-site body in
Trypanosoma brucei
Authors: Budzak James , Kerry Louise E. , Aristodemou Aris , Hall Belinda S. , Witmer Kathrin , Kushwaha Manish , Davies Carys , Povelones Megan L. , McDonald Jacquelyn R. , Sur Aakash , Myler Peter J. , Rudenko Gloria
Published: July 2019

Significance

The African trypanosome
Trypanosoma brucei
expresses a single variant surface glycoprotein (VSG) gene from one of multiple VSG expression sites (ESs) in a stringent monoallelic fashion. The counting mechanism behind this restriction is poorly understood. Unusually for a eukaryote, the active ES is transcribed by RNA polymerase I (Pol I) within a unique Pol I body called the expression-site body (ESB). We have demonstrated the importance of the ESB in restricting the singular expression of VSG. We have generated double-expresser trypanosomes, which simultaneously express 2 ESs at the same time in an unstable dynamic fashion. These cells predominantly contain 1 ESB, and, surprisingly, simultaneous transcription of the 2 ESs is observed only when they are both colocalized within it.
Histone acetylation recruits the SWR1 complex to regulate active DNA demethylation in
Arabidopsis
Authors: Nie Wen-Feng , Lei Mingguang , Zhang Mingxuan , Tang Kai , Huang Huan , Zhang Cuijun , Miki Daisuke , Liu Pan , Yang Yu , Wang Xingang , Zhang Heng , Lang Zhaobo , Liu Na , Xu Xuechen , Yelagandula Ramesh , Zhang Huiming , Wang Zhidan , Chai Xiaoqiang , Andreucci Andrea , Yu Jing-Quan , Berger Frederic , Lozano-Duran Rosa , Zhu Jian-Kang
Published: July 2019

Active DNA demethylation is critical for controlling the DNA methylomes in plants and mammals. However, little is known about how DNA demethylases are recruited to target loci, and the involvement of chromatin marks in this process. Here, we identify 2 components of the SWR1 chromatin-remodeling complex, PIE1 and ARP6, as required for ROS1-mediated DNA demethylation, and discover 2 SWR1-associated bromodomain-containing proteins, AtMBD9 and nuclear protein X1 (NPX1). AtMBD9 and NPX1 recognize histone acetylation marks established by increased DNA methylation 1 (IDM1), a known regulator of DNA demethylation, redundantly facilitating H2A.Z deposition at IDM1 target loci. We show that at some genomic regions, H2A.Z and DNA methylation marks coexist, and H2A.Z physically interacts with ROS1 to regulate DNA demethylation and antisilencing. Our results unveil a mechanism through which DNA demethylases can be recruited to specific target loci exhibiting particular histone marks, providing a conceptual framework to understand how chromatin marks regulate DNA demethylation.
Energy conversion via metal nanolayers
Authors: Boamah Mavis D. , Lozier Emilie H. , Kim Jeongmin , Ohno Paul E. , Walker Catherine E. , Miller Thomas F. , Geiger Franz M.
Published: July 2019

Significance

This work reports kinetic:electrical energy transduction using nanolayers formed in a single step from Earth-abundant elements. The method utilizes large-area physical vapor deposition onto rigid or flexible substrates that can be readily scaled to arbitrarily large areas. In addition to flowing aqueous droplets across the nanolayers, current is shown to be created either with linear flow of salinity gradients or with oscillatory flow of a constant salinity. The operational requirement of having to move a dynamically changing electrical double layer (a “gate”) across the nanostructure identified in prior approaches is confirmed for the structures and augmented by a need for electron transfer within the thermal oxide nanooverlayers terminating the metals. The simplicity of the approach allows for rapid implementation.
Structural basis for GPCR-independent activation of heterotrimeric Gi proteins
Authors: Kalogriopoulos Nicholas A. , Rees Steven D. , Ngo Tony , Kopcho Noah J. , Ilatovskiy Andrey V. , Sun Nina , Komives Elizabeth A. , Chang Geoffrey , Ghosh Pradipta , Kufareva Irina
Published: July 2019

Heterotrimeric G proteins are key molecular switches that control cell behavior. The canonical activation of G proteins by agonist-occupied G protein-coupled receptors (GPCRs) has recently been elucidated from the structural perspective. In contrast, the structural basis for GPCR-independent G protein activation by a novel family of guanine-nucleotide exchange modulators (GEMs) remains unknown. Here, we present a 2.0-Å crystal structure of Gαi in complex with the GEM motif of GIV/Girdin. Nucleotide exchange assays, molecular dynamics simulations, and hydrogen–deuterium exchange experiments demonstrate that GEM binding to the conformational switch II causes structural changes that allosterically propagate to the hydrophobic core of the Gαi GTPase domain. Rearrangement of the hydrophobic core appears to be a common mechanism by which GPCRs and GEMs activate G proteins, although with different efficiency. Atomic-level insights presented here will aid structure-based efforts to selectively target the noncanonical G protein activation.
In vitro 0N4R tau fibrils contain a monomorphic β-sheet core enclosed by dynamically heterogeneous fuzzy coat segments
Authors: Dregni Aurelio J. , Mandala Venkata S. , Wu Haifan , Elkins Matthew R. , Wang Harrison K. , Hung Ivan , DeGrado William F. , Hong Mei
Published: July 2019

Significance

The microtubule-binding protein tau misfolds into filamentous aggregates in many neurodegenerative diseases. Understanding the structure and dynamics of tau fibrils is important for designing anti-tau inhibitors. Patient-brain-derived tau fibrils have been shown to adopt disease-specific molecular conformations, but in vitro heparin-fibrillized tau was recently proposed to exhibit significant structural polymorphism. Using solid-state NMR, we show that the β-sheet core of heparin-fibrillized 0N4R tau adopts a single molecular conformation that encompasses the second and third microtubule-binding repeats, and both cysteine residues in the protein are involved in side-chain packing with other β-sheet residues. Extensive characterization of the protein dynamics indicates that these tau fibrils are heterogeneously dynamic, and the first and fourth microtubule-binding repeats are semirigid while retaining β-sheet character.
Anomalous relaxation and the high-temperature structure factor of XXZ spin chains
Authors: Gopalakrishnan Sarang , Vasseur Romain , Ware Brayden
Published: July 2019

Significance

The XXZ model is a canonical model of quantum magnetism. In one dimension, this model is integrable and has ballistically moving quasiparticles; thus, energy spreads ballistically, but, surprisingly, spin transport can be diffusive or superdiffusive. Here, we show that spin transport is even richer in the presence of a magnetic field: Some fraction of the spin moves out ballistically, but the dynamical spin-structure factor decays with an anomalous, continuously varying exponent. A hitherto-unnoticed phase transition takes place at finite fields, separating ballistic from subballistic decay of local correlations. We analytically derive these results using generalized hydrodynamics and support our findings numerically. These anomalous exponents can readily be measured via the frequency and wavevector dependence of the spin conductivity.