bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase
Authors: Wolf R. C. , Alonso A. , Äkäslompolo S. , Baldzuhn J. , Beurskens M. , Beidler C. D. , Biedermann C. , Bosch H.-S. , Bozhenkov S. , Brakel R. , Braune H. , Brezinsek S. , Brunner K.-J. , Damm H. , Dinklage A. , Drewelow P. , Effenberg F. , Feng Y. , Ford O. , Fuchert G. , Gao Y. , Geiger J. , Grulke O. , Harder N. , Hartmann D. , Helander P. , Heinemann B. , Hirsch M. , Höfel U. , Hopf C. , Ida K. , Isobe M. , Jakubowski M. W. , Kazakov Y. O. , Killer C. , Klinger T. , Knauer J. , König R. , Krychowiak M. , Langenberg A. , Laqua H. P. , Lazerson S. , McNeely P. , Marsen S. , Marushchenko N. , Nocentini R. , Ogawa K. , Orozco G. , Osakabe M. , Otte M. , Pablant N. , Pasch E. , Pavone A. , Porkolab M. , Puig Sitjes A. , Rahbarnia K. , Riedl R. , Rust N. , Scott E. , Schilling J. , Schroeder R. , Stange T. , von Stechow A. , Strumberger E. , Sunn Pedersen T. , Svensson J. , Thomson H. , Turkin Y. , Vano L. , Wauters T. , Wurden G. , Yoshinuma M. , Zanini M. , Zhang D. ,   the Wendelstein 7-X Team
Published: August 2019

Wendelstein 7-X is the first comprehensively optimized stellarator aiming at good confinement with plasma parameters relevant to a future stellarator power plant. Plasma operation started in 2015 using a limiter configuration. After installing an uncooled magnetic island divertor, extending the energy limit from 4 to 80 MJ, operation continued in 2017. For this phase, the electron cyclotron resonance heating (ECRH) capability was extended to 7 MW, and hydrogen pellet injection was implemented. The enhancements resulted in the highest triple product (6.5 × 1019 keV m−3 s) achieved in a stellarator until now. Plasma conditions [Te(0) ≈ Ti(0) ≈ 3.8 keV, τE > 200 ms] already were in the stellarator reactor-relevant ion-root plasma transport regime. Stable operation above the 2nd harmonic ECRH X-mode cutoff was demonstrated, which is instrumental for achieving high plasma densities in Wendelstein 7-X. Further important developments include the confirmation of low intrinsic error fields, the observation of current-drive induced instabilities, and first fast ion heating and confinement experiments. The efficacy of the magnetic island divertor was instrumental in achieving high performance in Wendelstein 7-X. Symmetrization of the heat loads between the ten divertor modules could be achieved by external resonant magnetic fields. Full divertor power detachment facilitated the extension of high power plasmas significantly beyond the energy limit of 80 MJ.
Experimental determination of impact ionization coefficients of electrons and holes in gallium nitride using homojunction structures
Authors: Ji Dong , Ercan Burcu , Chowdhury Srabanti
Published: August 2019

In this study, we experimentally determined the impact ionization coefficients of GaN using homoepitaxially grown p-n diodes with avalanche capability. The extracted hole impact ionization coefficient is obtained as β(E) = 4.39 × 106 exp (−1.8 × 107/E) cm−1, and the electron impact ionization coefficient is obtained as α(E) = 2.11 × 109 exp (−3.689 × 107/E) cm−1. This study also presents the temperature dependence of impact ionization coefficients in GaN. The results presented in this experimental study are an important contribution to the database on the material properties of GaN, which will enable more accurate prediction of the avalanche in GaN devices.
On the generation of vorticity and hydrodynamics of vortex ring during liquid drop impingement
Authors: Behera Manas Ranjan , Dasgupta Anirvan , Chakraborty Sudipto
Published: August 2019

In this work, we investigate the phenomenon of vortex generation and formation of a vortex ring when a liquid drop impinges on a miscible liquid surface. Although the formation of a vortex ring for this system has been studied for more than a century, little is known about its exact mechanism of generation and how its hydrodynamics is related to the shape of the drop. This is due to the complexity involved in the conversion of the initially generated vorticity into a vortex ring. To cast light on this intriguing phenomenon, time-resolved high-speed imaging with high magnification is used. This allows us to probe deeper into the vortex generation process and study the formation of the ring. We make a comprehensive study of the effect of drop impingement height and drop shape at the time of impact on the vortex generation and the hydrodynamics of the ring. The effect of crater evolution on the hydrodynamics of the vortex ring is studied in terms of its diameter and translational velocity. By examining the role of the shape of the crater on vortex ring penetration, we answer the question why the most penetrating vortex rings are generated by a prolate shaped drop.
Analysis of inner fold and bulge defects on J55 steel for oil casing pipe
Authors: Li Bosi , Zhu Hangyu , Xue Zhengliang , Qin Zhengfeng , Sun Jian
Published: August 2019

Typical macroscopic and microscopic morphologies of inner fold and bulge defects of J55 oil casing pipe are observed, and inclusions and the metallographic structure near these defects are detected to obtain an understanding of the defect formation mechanisms. The results show that the main inclusions near the origin of bulge defects are CaO·Al2O3 and MgO·Al2O3, with a similar inclusion composition being found in the inner fold layer. Brittle nonmetallic inclusions are the main causes of bulge and inner fold defects. Microcracks are formed owing to relative sliding between the inclusions and the metal matrix during the rolling process, and further extension of these microcracks then leads to the creation of bulge defects under sizing stress. Inner fold defects are formed from bulge defects owing to recompression and breaking of the latter as the plug exits from the pipe. It can therefore be concluded that the fundamental measures to avoid bulge and inner fold defects in oil casing pipe should be optimization of the deoxidization process and improvements in steel cleanliness.
High-performance high electron mobility transistors with GaN/InGaN composite channel and superlattice back barrier
Authors: Zhang Yachao , Guo Rui , Xu Shengrui , Zhang Jincheng , Zhao Shenglei , Wang Haiyong , Hu Qiang , Zhang Chunfu , Hao Yue
Published: August 2019

A heterostructure with a GaN/InGaN composite channel and superlattice back barrier is proposed, and high-performance high electron mobility transistors (HEMTs) are achieved on it. The carriers in the GaN/InGaN composite channel are well confined in the “U-pattern” potential well, which simultaneously possess high mobility, high density, and superior confinement. As a result, the output current density and linearity of the HEMTs are enhanced. Moreover, the GaN/InGaN superlattice back barrier effectively suppresses the buffer leakage, resulting in the significant improvement in the breakdown performance of the devices. The results in this work demonstrate the great promise of the devices with the GaN/InGaN composite channel and superlattice back barrier for next generation high power and wideband electronic applications.
Direct measurement of the surface energy of single-walled carbon nanotubes through atomic force microscopy
Authors: Li Hu , Liu Jiangwei , Papadakis Raffaello
Published: August 2019

Surface energy in nanomaterials is an essential parameter demonstrating a key role in their surface interactions and their functionalization aptitude. In this work, a new and facile methodology based on atomic force microscopy for the measurement of the surface energy of single-walled carbon nanotubes (SWCNTs) is reported. The proposed approach starts with the calibration based on a well-studied material, graphite, and the precision of the technique is confirmed by the measurement of the surface energy of multiwalled carbon nanotubes. Our measurements show that SWCNTs display a surface energy of 52.8 mJ/m2, which is in very good agreement with theoretical predictions of the measured property. Our experimental approach is essentially applicable to other nano-objects in contrast to conventional wet angle methods which are currently employed mainly in bulk materials.
Radiative and non-radiative decay kinetics of (CdSe)N (N = 3 and 4) clusters
Authors: Xie Yujuan , Yu Shengping , Zhang Li , Du Ning , Yang Mingli
Published: August 2019

Photoluminescence intermittency in semiconductor quantum dots (QDs) has limited their applications in single QD process. Understanding the origin of intermittency and its correlation with microstructure is crucial for the design and preparation of QDs with high fluorescence quantum yield. The small-sized (CdSe)3 and (CdSe)4 clusters provide a typical model for studying the effect of size, structure, surface defect, etc., on the radiative and nonradiative rates of II–VI QDs. The rate constants of radiative and nonradiative processes, kr and knr, are computed for the model systems using first-principles calculations, Marcus theory, and Fermi’s golden rule. Although kr and knr vary in a complicated way from cluster to cluster, their correlation with the geometrical and electronic properties of ground- and excited-state structures are revealed. Structure distortion in excitation, spatial overlap between the Kohn-Sham orbitals occupied by excited electron, reorganization energy, Huang-Rhys factor of dominant vibrational modes, as well as the unsaturation of surface atoms exert influences on kr and knr. Moreover, these quantities correlate with each other and their roles may change in the radiative/nonradiative process. While some quantities, such as reorganization energy and atomic unsaturation, have been used solely to estimate the photoluminescence yield, a combination of these factors is suggested to give reliable predictions. In addition, our calculations indicate that kr and knr can be tuned by designing the QDs with specific geometrical and electronic structures.
Correlation between zonal flow shearing and entropy transfer rates in toroidal ion temperature gradient turbulence
Authors: Miura T. , Watanabe T.-H. , Maeyama S. , Nakata M.
Published: August 2019

The transfer rate of the entropy variable in the wavenumber space perpendicular to the equilibrium magnetic field is evaluated by means of the gyrokinetic simulations of the toroidal ion temperature gradient turbulence. Fluctuations of the perturbed gyrocenter distribution function of the linearly unstable mode are transferred to those with higher radial wavenumbers through interactions with zonal flows driven by turbulence. The entropy transfer rate coincides with the zonal flow shearing rate in cases with weak ion temperature gradient where the zonal flows effectively regulate the turbulent transport. The obtained result verifies a correlation between the entropy transfer and the zonal flow shearing processes.
Effects of interionic non-hard sphere neutral interaction and solvent crowding on differential capacitance curve of electrical double layer
Authors: Zhou S.
Published: August 2019

By using classical density functional theory, we study the effects of interionic nonhard sphere neutral interaction (NHSNI) and solvent crowding on curve of differential electrical capacitance (Cd) vs surface charge strength |σ| of an electrical double layer (EDL) formed inside a cylindrical pore electrode. Main new findings are summarized as follows. (i) Increasing the intercounterion neutral attractive interaction helps in raising the Cd − |σ| curve and vice versa; the lowering or enhancing effect continues until rather high |σ|, such as |σ| = 1 C m−2. (ii) Attractive NHSNI between coion and counterion lowers the Cd − |σ| curve and vice versa; the lowering or enhancing effect quickly becomes very weak with |σ|. (iii) The lowering or enhancing effect strength of the intercounterion NHSNI potential range is negatively correlated with the bulk electrolyte concentration, whereas the correlation becomes positive for the potential range of the NHSNI between coion and counterion. (iv) Whether the bulk concentration is high or low, one stronger intercounterion attractive NHSNI tends to induce one more obvious peak of the Cd − |σ| curve at higher |σ|; only after this peak, the intercounterion NHSNI does not influence the Cd − |σ| curve obviously. However, the peak does not come with one intercounterion repulsive NHSNI and any kind of NHSNI between coion and counterion. (v) The solvent crowding induced by its granularity generally raises the Cd curve when |σ| is low and moderate, but the enhancing effect tends to become unobservable with further rising of |σ|. The above findings are explained reasonably by analyzing the ions local distributions in the EDL, their adsorption capacities, and the peak of change rate of the total ion adsorption capacity with |σ|.
A computational phase field study of conducting channel formation in dielectric thin films: A view toward the physical origins of resistive switching
Authors: Sevic John F. , Kobayashi Nobuhiko P.
Published: August 2019

A phase field method is used to computationally study conducting channel morphology of resistive switching thin film structures. Our approach successfully predicts the formation of conducting channels in typical dielectric thin film structures, comparable to a range of resistive switches, offering an alternative computational formulation based on metastable states treated at the atomic scale. In contrast to previous resistive switching thin film models, our formulation makes no a priori assumptions on conducting channel morphology and its fundamental transport mechanisms. Our method produces conducting channel morphology consistent with available experimental observations.
Magnetic properties of isolated skyrmion under the in-plane magnetic field and anisotropy gradient
Authors: Xia Haiyan , Song Chengkun , Wang Jinshuai , Jin Chendong , Ma Yunxu , Zhang Chunlei , Wang Jianbo , Liu Qingfang
Published: August 2019

The basic magnetic properties of isolated skyrmions in thin films are fundamental to understanding the physics of magnetic skyrmions and their applications in potential spintronic devices. Here, we study the static and dynamic magnetic properties of isolated skyrmions under an in-plane magnetic field and a magnetic anisotropy gradient using micromagnetic simulations. The results demonstrate that the rotational symmetry of skyrmions is broken under the in-plane field. The radius and domain wall width of the isolated skyrmion exhibits the dependence of the external stimuli. Furthermore, the skyrmion velocity can be effectively modulated by the anisotropy gradient as well as the in-plane field. An analysis model is also derived. This work may provide guidance for the design of next-generation spintronic devices.
Remarkable p-type activation of heavily doped diamond accomplished by boron ion implantation at room temperature and subsequent annealing at relatively low temperatures of 1150 and 1300 °C
Authors: Seki Yuhei , Hoshino Yasushi , Nakata Jyoji
Published: August 2019

Highly efficient impurity doping in diamond by ion implantation has been a crucial issue in the field of semiconductor fabrication for several decades. We investigated the electrical properties of heavily B-doped type IIa diamond introduced by ion implantation at room temperature with a shallow and flat impurity concentration of 3.6 × 1019 cm−3 (∼200 ppm) from the surface to ∼130 nm depth, followed by thermal annealing at 1150 and 1300 °C. The activation of the implanted acceptor B was a maximum of 80% for the sample into which B ions were implanted at room temperature followed by 1150 °C annealing. The hole concentration and Hall mobility at room temperature were realized to be higher than 1 × 1014 cm−3 and 110 cm2 V−1 s−1, respectively. We confirmed p-type conductivity and typical activation energy of acceptor B at wide temperatures from −100 to 800 °C for the prepared samples. It was consequently revealed from this study that at least room temperature B-implantation followed by above 1150 °C annealing is sufficiently effective for the electrical activation of B doped in high quality diamond.
Solvent-free synthesis of organometallic halides CH3NH3PbI3 and (CH3NH3)3Bi2I9 and their thermoelectric transport properties
Authors: Long Xiang , Pan Zhenyu , Zhang Zhuolei , Urban Jeffrey J. , Wang Heng
Published: August 2019

Organometallic halides are great candidates for optoelectronics. As an important family of semiconductors, understanding their thermoelectric transport properties is also important. This has been a challenging task as many of such compounds are highly intrinsic. In this work, we synthesized two halides, CH3NH3PbI3 and (CH3NH3)3Bi2I9, using a solvent-free method. We found an extraordinarily high Seebeck coefficient of +2600 ± 200 μV/K in (CH3NH3)3Bi2I9. For CH3NH3PbI3, our synthesis method led to a negative Seebeck coefficient of −1350 ± 50 μV/K, in contrast to positive values observed in solvent synthesized samples. We also found the thermal conductivity of CH3NH3PbI3 to be 0.38 W/m K, largely independent of temperature from 300 K to 450 K, despite a tetragonal-to-cubic phase transition. (CH3NH3)3Bi2I9 has an even lower thermal conductivity of 0.21 W/m K (also temperature independent) which is due to its soft phonon dispersion and weak bonds.
High frequency voltage-induced ferromagnetic resonance in magnetic tunnel junctions
Authors: Skowroński Witold , Łazarski Stanisław , Mojsiejuk Jakub , Chęciński Jakub , Frankowski Marek , Nozaki Takayuki , Yakushiji Kay , Yuasa Shinji
Published: August 2019

Voltage-induced ferromagnetic resonance (V-FMR) in magnetic tunnel junctions (MTJs) with a W buffer is investigated. Perpendicular magnetic anisotropy (PMA) energy is controlled by both the thickness of a CoFeB free layer deposited directly on the W buffer and a post-annealing process at different temperatures. The PMA energy and the magnetization damping are determined by analyzing field-dependent FMR signals in different field geometries. An optimized MTJ structure enabled the excitation of V-FMR at frequencies exceeding 30 GHz. The macrospin modeling is used to analyze the field- and angular-dependence of the V-FMR signal and to support experimental magnetization damping extraction.
Depth dependent ferroelectric to incommensurate/commensurate antiferroelectric phase transition in epitaxial lanthanum modified lead zirconate titanate thin films
Authors: Gao Min , Tang Xiao , Dai Steve , Li Jiefang , Viehland D.
Published: August 2019

Transmission electron microscopy was used to investigate the coexistence of ferroelectricity (FE) and antiferroelectricity (AFE) in (001) and (011) (Pb0.97, La0.02) (Zr0.95, Ti0.05) O3 (PLZT) epitaxial thin films. The depth resolved selected area electron diffraction (SAED) results revealed that the AFE phase was located in the near interface region, whereas the FE phase was found in the near surface region. A thickness dependent lattice parameter distribution was calculated using the SAED data, and a decrease in the c/a ratio was found to correlate with the transition from AFE to FE stability. Additionally, commensurate and incommensurate modulations in AFE PLZT were identified based on the observation of various superlattice reflections.
DFT study of Au self-diffusion on Au(001) in the presence of a Cl adlayer
Authors: Dávila López Alexandra Celinda , Pehlke Eckhard
Published: August 2019

The atomic-scale mechanism of self-diffusion on coinage metal surfaces has been investigated by density functional theory calculations before. However, the detailed role of the co-adsorbed anions and of the electrochemical interface is not yet fully understood. We present diffusion paths of a Au adatom on c(2 × 2)-Cl and c(2×22)R45◦-Cl Au(001) surfaces. In the case of the fully Cl covered Au(001) surfaces, the diffusion energy barriers are ≥0.44 eV. In the presence of a neighboring Cl vacancy, the diffusion barriers are drastically reduced to about half of the value for the fully Cl covered surface. Thus, Au self-diffusion is promoted by Cl vacancies. A first estimate for the effect of water on the diffusion energy barrier of the Cl vacancy is derived by calculating the interaction of configurations along the diffusion path with a water layer.
Can pure polymer liquids be represented at two different resolutions simultaneously?
Authors: Dinpajooh M. , Guenza M. G.
Published: August 2019

Given that the physical properties of polymeric liquids extend on a wide range of length scales, it is computationally convenient to represent them by coarse-grained descriptions at various granularities to investigate local and global properties simultaneously. We use the Integral Equation Coarse-Graining (IECG) theory for a mixture of two species with various resolutions representing polyethylene polymeric liquids and derive interacting potentials that ensure consistencies of relevant thermodynamical and structural properties. These properties are in agreement with the corresponding atomistic resolution description. The composition, temperature, and density dependences of such mixed resolution potentials are investigated numerically and analytically. In the limit of long polymer chains, where Markovian statistics is obeyed, the potentials are analytically solved and decay with characteristic scaling exponents that depend on the mixture composition and CG resolution of the two components. The implications of the effective IECG potentials are also discussed for multiresolution simulation approaches.
New device demonstrates potential for long-time fusion plasma
Authors: Lim Alane
Published: August 2019

A stellarator built by an international team of researchers demonstrate reduced plasma energy losses and optimized fusion confinement performance.
Changes in environmental salinity during the life of Pangasius krempfi in the Mekong Delta (Vietnam) estimated from otolith Sr : Ca ratios
Authors: Tran Ngan T. , Labonne Maylis , Hoang Huy D. , Panfili Jacques
Published: August 2019

Pangasius krempfi is a commercially important catfish in the Mekong River and is believed to migrate along the Mekong River basin. To verify this migration, elemental concentrations were measured in the water and in otoliths to infer the salinity of the water through the fish’s lifetime. In 2017, eight element concentrations were measured along the Mekong Delta using solution-based inductively coupled plasma mass spectrometry (ICP-MS). Concentrations of Sr, Li and Rb were strongly and positively correlated with salinity. Otoliths were taken from P. krempfi caught in the brackish waters of the lower Mekong Delta and seven element:Ca ratios were measured from the core to the otolith edge using laser ablation ICP-MS. The Sr:Ca, Ba:Ca, P:Ca and Mn:Ca ratios varied through the lifetime of the fish, but only Sr:Ca was suitable for estimating ambient salinity. The Sr:Ca profiles in otoliths were analysed and significantly correlated between individuals, with all fish hatched in water with very low levels of salinity, indicating a single freshwater spawning ground, and then living in waters with higher salinity, with two types of migration behaviour. Some individuals may return to low-salinity waters when older. These conclusions were supported by the Ba:Ca and Mn:Ca ratios. These migration patterns may have implications for fishery management.
Element composition of shark vertebrae shows promise as a natural tag
Authors: Pistevos J. C. A. , Reis-Santos P. , Izzo C. , Gillanders B. M.
Published: August 2019

Reconstructing movements and environmental histories of sharks may be possible by using the element composition of vertebrae, but unlocking such possibilities requires an understanding of the effects of extrinsic and intrinsic factors on element composition. We assessed water temperature and pH effects (independently and in combination) on vertebral chemistry of Port Jackson sharks while accounting for intrinsic factors (condition and sex) using indoor aquaria and outdoor mesocosm environments, where the latter may better reflect natural field conditions. We analysed eight element:Ca ratios (7Li, 8B, 24Mg, 55Mn, 65Cu, 88Sr, 138Ba and 238U) by laser ablation inductively coupled plasma mass spectrometry and found positive temperature-dependant responses for multiple elements, including B:Ca, Mn:Ca, Sr:Ca and Ba:Ca (r2=0.43, 0.22, 0.60 and 0.35 respectively), whereas pH had a minor effect on vertebral Mg:Ca and Li:Ca (r2=0.10 and 0.31 respectively). As shown for teleost otoliths, condition affected element composition (Mn:Ca), suggesting potential physiological influences on element uptake. The suitability of vertebral chemistry as a natural tag appears to be element specific, and likely governed by a suite of potentially codependent extrinsic and intrinsic factors. Overall, variations in vertebrae chemistry show promise to reconstruct movements and habitat use of cartilaginous fishes. Yet, further research is required to understand the ubiquitous nature of the findings presented here.
Impacts of climate change on future air quality and human health in China
Authors: Hong Chaopeng , Zhang Qiang , Zhang Yang , Davis Steven J. , Tong Dan , Zheng Yixuan , Liu Zhu , Guan Dabo , He Kebin , Schellnhuber Hans Joachim
Published: August 2019

Significance

More intense extreme events are projected under future climate change. However, the impacts of climate extremes on future air quality and associated health implications are not well recognized and are rarely quantified in China, with an enormous health burden from air pollution. Here, we estimate the climate-driven air pollution mortality in China and find that future climate change is likely to exacerbate air pollution mortality, largely influenced by the more intense extreme events such as stagnation events and heat waves. Our analysis provides quantitative assessments and insights regarding the links between climate extremes, future air quality, and public health, suggesting that extreme weather events may be an important mechanism by which climate change will affect air quality, and especially fine particulate matter.
Biomass losses resulting from insect and disease invasions in US forests
Authors: Fei Songlin , Morin Randall S. , Oswalt Christopher M. , Liebhold Andrew M.
Published: August 2019

Worldwide, forests are increasingly affected by nonnative insects and diseases, some of which cause substantial tree mortality. Forests in the United States have been invaded by a particularly large number (>450) of tree-feeding pest species. While information exists about the ecological impacts of certain pests, region-wide assessments of the composite ecosystem impacts of all species are limited. Here we analyze 92,978 forest plots distributed across the conterminous United States to estimate biomass loss associated with elevated mortality rates caused by the 15 most damaging nonnative forest pests. We find that these species combined caused an additional (i.e., above background levels) tree mortality rate of 5.53 TgC per year. Compensation, in the form of increased growth and recruitment of nonhost species, was not detectable when measured across entire invaded ranges but does occur several decades following pest invasions. In addition, 41.1% of the total live forest biomass in the conterminous United States is at risk of future loss from these 15 pests. These results indicate that forest pest invasions, driven primarily by globalization, represent a huge risk to US forests and have significant impacts on carbon dynamics.
Regulation of photoprotection gene expression in
Chlamydomonas
by a putative E3 ubiquitin ligase complex and a homolog of CONSTANS
Authors: Gabilly Stéphane T. , Baker Christopher R. , Wakao Setsuko , Crisanto Thien , Guan Katharine , Bi Ke , Guiet Elodie , Guadagno Carmela R. , Niyogi Krishna K.
Published: August 2019

Photosynthetic organisms use nonphotochemical quenching (NPQ) mechanisms to dissipate excess absorbed light energy and protect themselves from photooxidation. In the model green alga
Chlamydomonas reinhardtii
, the capacity for rapidly reversible NPQ (qE) is induced by high light, blue light, and UV light via increased expression of
LHCSR
and
PSBS
genes that are necessary for qE. Here, we used a forward genetics approach to identify SPA1 and CUL4, components of a putative green algal E3 ubiquitin ligase complex, as critical factors in a signaling pathway that controls light-regulated expression of the
LHCSR
and
PSBS
genes in
C. reinhardtii
. The
spa1
and
cul4
mutants accumulate increased levels of LHCSR1 and PSBS proteins in high light, and unlike the wild type, they express LHCSR1 and exhibit qE capacity even when grown in low light. The
spa1-1
mutation resulted in constitutively high expression of
LHCSR
and
PSBS
RNAs in both low light and high light. The qE and gene expression phenotypes of
spa1-1
are blocked by mutation of CrCO, a B-box Zn-finger transcription factor that is a homolog of CONSTANS, which controls flowering time in plants. CONSTANS-like
cis
-regulatory sequences were identified proximal to the qE genes, consistent with CrCO acting as a direct activator of qE gene expression. We conclude that SPA1 and CUL4 are components of a conserved E3 ubiquitin ligase that acts upstream of CrCO, whose regulatory function is wired differently in
C. reinhardtii
to control qE capacity via
cis
-regulatory CrCO-binding sites at key photoprotection genes.
Race influences professional investors’ financial judgments
Authors: Lyons-Padilla Sarah , Markus Hazel Rose , Monk Ashby , Radhakrishna Sid , Shah Radhika , Dodson Norris A. “Daryn” , Eberhardt Jennifer L.
Published: August 2019

Significance

We find evidence of racial bias in the investment decisions of asset allocators, who manage money for governments, universities, charities, foundations, and companies. This bias could contribute to stark racial disparities in institutional investing. In general, asset allocators have trouble gauging the competence of racially diverse teams. At stronger performance levels, asset allocators rate White-led funds more favorably than they do Black-led funds. At weaker performance levels, asset allocators actually prefer Black-led teams to White-led teams. However, asset allocators are unlikely to invest in weaker funds, diverse or otherwise. These results suggest that beyond racial disparities in the pipeline, there are additional systemic racial disparities in how investors evaluate funds and allocate money.
Prebiotic amino acids bind to and stabilize prebiotic fatty acid membranes
Authors: Cornell Caitlin E. , Black Roy A. , Xue Mengjun , Litz Helen E. , Ramsay Andrew , Gordon Moshe , Mileant Alexander , Cohen Zachary R. , Williams James A. , Lee Kelly K. , Drobny Gary P. , Keller Sarah L.
Published: August 2019

Significance

How did the first cells on Earth arise? In a minimal cell, a membrane separates proteins and RNA from the surrounding aqueous environment. Cell-like membranes spontaneously assemble from simple prebiotic surfactants called fatty acids. However, fatty acid membranes are unstable in solutions containing salts that were likely present in environments of the early Earth. We find that amino acids, the building blocks of proteins, bind to fatty acid membranes and stabilize them against salts. Moreover, enhanced stabilization persists after dilution as would occur when a dehydrated pool refills with water—a likely setting for the emergence of cells. In addition to explaining how the first membranes were stabilized, our findings answer how key components of the first cells colocalized.
Alternative promoters drive human cytomegalovirus reactivation from latency
Authors: Collins-McMillen Donna , Rak Mike , Buehler Jason C. , Igarashi-Hayes Suzu , Kamil Jeremy P. , Moorman Nathaniel J. , Goodrum Felicia
Published: August 2019

Significance

Cytomegalovirus is a herpesvirus that persists latently for the host’s lifetime, with periodic reactivation that can cause life threatening disease in individuals with inadequate immunity. Understanding the mechanisms by which the virus reactivates is critical to controlling reactivation and disease. For decades, reactivation of viral gene expression and replication has been presumed to be driven from de-repression of the major immediate early promoter (MIEP). We show that viral reactivation depends on alternative promoter elements within the major immediate early gene locus while the MIEP largely remains silent during reactivation. This finding represents a major paradigm shift, demonstrating the use of alternative promoters to drive virus reactivation in a context-dependent manner.
Mutation of external glutamate residue reveals a new intermediate transport state and anion binding site in a CLC Cl
−
/H
+
antiporter
Authors: Park Kunwoong , Lee Byoung-Cheol , Lim Hyun-Ho
Published: August 2019

The CLC family of proteins are involved in a variety of physiological processes to control cellular chloride concentration. Two distinct classes of CLC proteins, Cl
−
channels and Cl
−
/H
+
antiporters, have been functionally and structurally investigated over the last several decades. Previous studies have suggested that the conformational heterogeneity of the critical glutamate residue, Glu
ex
, could explain the transport cycle of CLC-type Cl
−
/H
+
antiporters. However, the presence of multiple conformations (
Up
,
Middle
, and
Down
) of the Glu
ex
has been suggested from combined structural snapshots of 2 different CLC antiporters: CLC-ec1 from
Escherichia coli
and cmCLC from a thermophilic red alga,
Cyanidioschyzon merolae
. Thus, we aimed to investigate further the heterogeneity of Glu
ex
-conformations in CLC-ec1, the most deeply studied CLC antiporter, at both functional and structural levels. Here, we show that the crystal structures of the Glu
ex
mutant E148D and wild-type CLC-ec1 with varying anion concentrations suggest a structural intermediate, the “
Midlow
” conformation. We also found that an extra anion can be located above the external Cl
−
-binding site in the E148D mutant when the anion concentration is high. Moreover, we observed that a carboxylate in solution can occupy either the external or central Cl
−
-binding site in the ungated E148A mutant using an anomalously detectable short carboxylic acid, bromoacetate. These results lend credibility to the idea that the Glu
ex
can take at least 3 distinct conformational states during the transport cycle of a single CLC antiporter.
High stretchability, strength, and toughness of living cells enabled by hyperelastic vimentin intermediate filaments
Authors: Hu Jiliang , Li Yiwei , Hao Yukun , Zheng Tianqi , Gupta Satish K. , Parada German Alberto , Wu Huayin , Lin Shaoting , Wang Shida , Zhao Xuanhe , Goldman Robert D. , Cai Shengqiang , Guo Ming
Published: August 2019

Significance

Intermediate filaments (IFs) remain the least understood with respect to their functions in mammalian cells even though they have been related to many devastating human diseases. Here we use optical tweezers to perform micromechanical measurements in living cells and in IF enriched cytoskeletons devoid of actin and microtubules. We identify that cytoskeletal vimentin IFs (VIFs) provide cells with a hyperelastic rubber-like network that regulates the essential mechanical properties of mammalian cells including stretchability, strength, resilience, and toughness. We show that VIFs maintain cell integrity and viability under conditions involving extreme deformations. We further show that the stretchy VIF network can effectively disperse locally induced mechanical stress to larger regions within individual cells, enabling the dissipation of energy throughout a cell.
Histone H4 induces platelet ballooning and microparticle release during trauma hemorrhage
Authors: Vulliamy Paul , Gillespie Scarlett , Armstrong Paul C. , Allan Harriet E. , Warner Timothy D. , Brohi Karim
Published: August 2019

Significance

Membrane ballooning is a fundamental mechanism by which platelets contribute to thrombin generation. However, this process has not previously been described in human disease. In this study, we demonstrated the presence of ballooning procoagulant platelets free in the circulation of critically injured humans, a phenomenon which results in systemic generation of thrombin and contributes to an acute coagulopathy. The surfaces of ballooning platelets were decorated with the damage-associated molecular pattern histone H4, and exposure of healthy platelets to histone caused membrane disruption and recapitulated the phenotypic changes in injured patients. These findings provide a description of platelet ballooning contributing to human disease and identify histone release from injured tissues as a driver of the procoagulant ballooning process.
HuR counteracts miR-330 to promote STAT3 translation during inflammation-induced muscle wasting
Authors: Mubaid Souad , Ma Jennifer F. , Omer Amr , Ashour Kholoud , Lian Xian J. , Sanchez Brenda J. , Robinson Samantha , Cammas Anne , Dormoy-Raclet Virginie , Di Marco Sergio , Chittur Sridar V. , Tenenbaum Scott A. , Gallouzi Imed-Eddine
Published: August 2019

Significance

Proinflammatory diseases, such as cancer, AIDS, and chronic obstructive pulmonary diseases, are often associated with a progressive loss of skeletal muscle tissue, a syndrome also known as cachexia. Cytokines trigger muscle loss by activating downstream effector pathways, including the ones driven by STAT3 protein. Although high levels of STAT3 protein are required for the onset of muscle wasting, the mechanisms modulating STAT3 expression in cachectic muscles remain elusive. Here we identify the RNA-binding protein HuR and its ability to interfere with miR-330 action as a key promoter of
STAT3
mRNA translation. Our work identifies the competition between HuR and miR-330 as a mechanism that could be targeted to design novel anticachexia therapies.
Mapping the effects of drought on child stunting
Authors: Cooper Matthew W. , Brown Molly E. , Hochrainer-Stigler Stefan , Pflug Georg , McCallum Ian , Fritz Steffen , Silva Julie , Zvoleff Alexander
Published: August 2019

Significance

We use geolocated child nutrition data from 53 developing countries to show that minor to severe droughts as well as severe periods of extreme rainfall are related to child stunting. We then explore how various geographic factors mitigate or amplify the effect of drought on child heights. Finally, we combine global data on these factors to map where child stunting is currently vulnerable to drought, finding that arid low-income countries with poor governance and political instability are where drought could have the largest effect on child stunting.
Characterization of glutamyl-tRNA–dependent dehydratases using nonreactive substrate mimics
Authors: Bothwell Ian R. , Cogan Dillon P. , Kim Terry , Reinhardt Christopher J. , van der Donk Wilfred A. , Nair Satish K.
Published: August 2019

The peptide natural product nisin has been used as a food preservative for 6 decades with minimal development of resistance. Nisin contains the unusual amino acids dehydroalanine and dehydrobutyrine, which are posttranslationally installed by class I lanthipeptide dehydratases (LanBs) on a linear peptide substrate through an unusual glutamyl-tRNA–dependent dehydration of Ser and Thr. To date, little is known about how LanBs catalyze the transfer of glutamate from charged tRNA
Glu
to the peptide substrate, or how they carry out the subsequent elimination of the peptide-glutamyl adducts to afford dehydro amino acids. Here, we describe the synthesis of inert analogs that mimic substrate glutamyl-tRNA
Glu
and the glutamylated peptide intermediate, and determine the crystal structures of 2 LanBs in complex with each of these compounds. Mutational studies were used to characterize the function of the glutamylation and glutamate elimination active-site residues identified through the structural analysis. These combined studies provide insights into the mechanisms of substrate recognition, glutamylation, and glutamate elimination by LanBs to effect a net dehydration reaction of Ser and Thr.
Complex dynamics under tension in a high-efficiency frameshift stimulatory structure
Authors: Halma Matthew T. J. , Ritchie Dustin B. , Cappellano Tonia R. , Neupane Krishna , Woodside Michael T.
Published: August 2019

Significance

Programmed ribosomal frameshifting (PRF) is important to many viruses, but how structures in mRNA stimulate PRF remains uncertain. By studying a frameshift signal stimulating very high PRF in West Nile virus (WNV), we identify features that differ from other structures stimulating more modest PRF levels. Using single-molecule force spectroscopy to mimic the effects of tension applied to the RNA by the ribosome during translation, we find that the WNV frameshift signal exhibits exceptionally heterogeneous conformational dynamics, forming several different pseudoknots and multiple combinations of hairpins, all connected on 2 mutually exclusive pathways. This work supports a role for conformational heterogeneity in PRF, suggesting that dynamic fluctuations rather than static properties play a key role in stimulating PRF efficiently.
Ballistic thermal phonons traversing nanocrystalline domains in oriented polyethylene
Authors: Robbins Andrew B. , Drakopoulos Stavros X. , Martin-Fabiani Ignacio , Ronca Sara , Minnich Austin J.
Published: August 2019

Thermally conductive polymer crystals are of both fundamental and practical interest for their high thermal conductivity that exceeds that of many metals. In particular, polyethylene fibers and oriented films with uniaxial thermal conductivity exceeding 50

W
⋅

m

−
1

⋅

K

−
1

have been reported recently, stimulating interest into the underlying microscopic thermal transport processes. While ab initio calculations have provided insight into microscopic phonon properties for perfect crystals, such properties of actual samples have remained experimentally inaccessible. Here, we report the direct observation of thermal phonons with mean free paths up to 200 nm in semicrystalline polyethylene films using transient grating spectroscopy. Many of the mean free paths substantially exceed the crystalline domain sizes measured using small-angle X-ray scattering, indicating that thermal phonons propagate ballistically within and across the nanocrystalline domains; those transmitting across domain boundaries contribute nearly one-third of the thermal conductivity. Our work provides a direct determination of thermal phonon propagation lengths in molecular solids, yielding insights into the microscopic origins of their high thermal conductivity.
Upregulation of reduced folate carrier by vitamin D enhances brain folate uptake in mice lacking folate receptor alpha
Authors: Alam Camille , Aufreiter Susanne , Georgiou Constantine J. , Hoque Md. Tozammel , Finnell Richard H. , O’Connor Deborah L. , Goldman I. David , Bendayan Reina
Published: August 2019

Significance

Folates are critical for brain development and function. Abnormalities in brain folate transport have been implicated in a number of childhood neurodevelopmental disorders, including cerebral folate deficiency syndrome, hereditary folate malabsorption, and autism spectrum disorders. These disorders have devastating effects in young children, and current therapeutic approaches are not sufficiently effective. In this study, we demonstrate that functional expression of the folate transporter, reduced folate carrier, at the blood–brain barrier and its upregulation by the vitamin D nuclear receptor can remarkably increase folate transport to the brain. These findings provide a strategy for enhancing brain folate delivery for the treatment of neurometabolic disorders caused by folate transport defects.
Transient enhancement of p53 activity protects from radiation-induced gastrointestinal toxicity
Authors: Pant Vinod , Xiong Shunbin , Wasylishen Amanda R. , Larsson Connie A. , Aryal Neeraj K. , Chau Gilda , Tailor Ramesh C. , Lozano Guillermina
Published: August 2019

Significance

Gastrointestinal (GI) failure is a serious dose-limiting side effect observed in patients undergoing lower-abdominal radiotherapy with no approved protective measure/cure. Here, we show that increased p53-induced p21 activity protects against radiation-induced GI toxicity in a genetically engineered mouse model. This radioprotection can be recapitulated in wild-type mice by pretreating them with RG7112, a pharmacological compound that enhances p53 activity by disrupting p53–Mdm2 interaction. These results signify that transient enhancement of wild-type p53 activity by pharmacological means could be exploited as a potential prophylactic strategy to alleviate GI toxicity issues in patients undergoing radiotherapy in the clinic.
Learning active sensing strategies using a sensory brain–machine interface
Authors: Richardson Andrew G. , Ghenbot Yohannes , Liu Xilin , Hao Han , Rinehart Cole , DeLuccia Sam , Torres Maldonado Solymar , Boyek Gregory , Zhang Milin , Aflatouni Firooz , Van der Spiegel Jan , Lucas Timothy H.
Published: August 2019

Significance

Our sensory experience is governed by sensor properties (e.g., eye photoreceptors) and corresponding motor strategies to sample the environment (e.g., eye movements). With injury, aging, or new task constraints, existing strategies can become incompatible with perceptual demands. Using a brain–machine interface paradigm in rats, we studied how motor strategies are adapted to new sensory inputs to accomplish a difficult searching task. We show that the strategies can be dynamically regulated through experience to optimally extract task-relevant sensory information.
Gulp1 controls Eph/ephrin trogocytosis and is important for cell rearrangements during development
Authors: Gong Jingyi , Gaitanos Thomas N. , Luu Olivia , Huang Yunyun , Gaitanos Louise , Lindner Jana , Winklbauer Rudolf , Klein Rüdiger
Published: August 2019

Trogocytosis, in which cells nibble away parts of neighboring cells, is an intercellular cannibalism process conserved from protozoa to mammals. Its underlying molecular mechanisms are not well understood and are likely distinct from phagocytosis, a process that clears entire cells. Bi-directional contact repulsion induced by Eph/ephrin signaling involves transfer of membrane patches and full-length Eph/ephrin protein complexes between opposing cells, resembling trogocytosis. Here, we show that the phagocytic adaptor protein Gulp1 regulates EphB/ephrinB trogocytosis to achieve efficient cell rearrangements of cultured cells and during embryonic development. Gulp1 mediates trogocytosis bi-directionally by dynamic engagement with EphB/ephrinB protein clusters in cooperation with the Rac-specific guanine nucleotide exchange factor Tiam2. Ultimately, Gulp1’s presence at the Eph/ephrin cluster is a prerequisite for recruiting the endocytic GTPase dynamin. These results suggest that EphB/ephrinB trogocytosis, unlike other trogocytosis events, uses a phagocytosis-like mechanism to achieve efficient membrane scission and engulfment.
Triple arginines as molecular determinants for pentameric assembly of the intracellular domain of 5-HT3A receptors
Authors: Pandhare Akash , Pirayesh Elham , Stuebler Antonia G. , Jansen Michaela
Published: August 2019

Serotonin type 3 receptors (5-HT3Rs) are cation-conducting pentameric ligand-gated ion channels and members of the Cys-loop superfamily in eukaryotes. 5-HT3Rs are found in the peripheral and central nervous system, and they are targets for drugs used to treat anxiety, drug dependence, and schizophrenia, as well as chemotherapy-induced and postoperative nausea and emesis. Decades of research of Cys-loop receptors have identified motifs in both the extracellular and transmembrane domains that mediate pentameric assembly. Those efforts have largely ignored the most diverse domain of these channels, the intracellular domain (ICD). Here we identify molecular determinants within the ICD of serotonin type 3A (5-HT3A) subunits for pentameric assembly by first identifying the segments contributing to pentamerization using deletion constructs of, and finally by making defined amino acid substitutions within, an isolated soluble ICD. Our work provides direct experimental evidence for the contribution of three intracellular arginines, previously implicated in governing the low conductance of 5-HT3ARs, in structural features such as pentameric assembly.