bluuebunny/crossref_metadata_2025 huggingface dataset:
17 000%/W second-harmonic conversion efficiency in single-crystalline aluminum nitride microresonators
Authors: Bruch Alexander W. , Liu Xianwen , Guo Xiang , Surya Joshua B. , Gong Zheng , Zhang Liang , Wang Junxi , Yan Jianchang , Tang Hong X.
Published: September 2018

High quality factor optical microcavities have been employed in a variety of material systems to enhance nonlinear optical interactions. While single-crystalline aluminum nitride microresonators have recently emerged as a low loss platform for integrated nonlinear optics such as four wave mixing and Raman lasing, few studies have investigated this material for second-harmonic generation. In this letter, we demonstrate an optimized fabrication of dually resonant phase-matched ring resonators from epitaxial aluminum nitride thin films. An unprecendented second-harmonic generation efficiency of 17 000%/W is obtained in the low power regime, and pump depletion is observed at a relatively low input power of 3.5 mW. This poses epitaxial aluminum nitride as the highest efficiency second-harmonic generator among current integrated platforms.
Investigation of magnetic dipole-dipole interaction using magnetic density on solid oxygen based on first-principles approach
Authors: Obata Masao , Christivana Mega , Oda Tatsuki
Published: September 2018

We have developed the computational method to estimate magnetic dipole-dipole interaction energy including magnetic spin density on three-dimensional materials, in the framework of density functional theory. We investigated the stable spin direction in oxygen molecule and α- and δ-phases of solid oxygen. Our method gave the result that the magnetic dipole-dipole interaction of realistic spin density distribution provides the stable magnetic moments perpendicular to the molecular axis, in contrary to the simple expectation from the isolated-spin moment model of the oxygen molecule. The reason has been explained by the spin density distribution of oxygen molecule and magnetic dipole field. Moreover, the result of magnetic anisotropy energy was found to be consistent with the experimental ones.
Crucial role of fragmented and isolated defects in persistent relaxation of deeply supercooled water
Authors: Saito Shinji , Bagchi Biman , Ohmine Iwao
Published: September 2018

Properties of water have been well elucidated for temperatures above ∼230 K and yet mysteries remain in the deeply supercooled region. By performing extensive molecular dynamics simulations on this supercooled region, we find that structural and dynamical instabilities are hidden in the experimentally inaccessible region between 235 K and 150 K. We find a hitherto undiscovered fragmentation from 220 K to 190 K, which is the breakup of large clusters consisting of molecules with a locally distorted tetrahedral structure into small pieces with one or two isolated defects. The fragmentation leads to considerable changes in the relaxation dynamics of water. We reveal a crucial role of specific three-coordinated defects in slow but persistent structural relaxation. The presence of relaxation due to these specific defects makes the water glass transition temperature Tg (=136 K) extremely low and explains why the Tg of water is ∼1/2 of the melting temperature Tm, much lower than the commonly obeyed 2/3 rule of Tg/Tm.
A coherent derivation of the Ewald summation for arbitrary orders of multipoles: The self-terms
Authors: Stamm Benjamin , Lagardère Louis , Polack Étienne , Maday Yvon , Piquemal Jean-Philip
Published: September 2018

In this work, we provide the mathematical elements we think essential for a proper understanding of the calculus of the electrostatic energy of point-multipoles of arbitrary order under periodic boundary conditions. The emphasis is put on the expressions of the so-called self-parts of the Ewald summation where different expressions can be found in the literature. Indeed, such expressions are of prime importance in the context of new generation polarizable force field where the self-field appears in the polarization equations. We provide a general framework, where the idea of the Ewald splitting is applied to the electric potential and, subsequently, all other quantities such as the electric field, the energy, and the forces are derived consistently thereof. Mathematical well-posedness is shown for all these contributions for any order of multipolar distribution.
Flexoelectricity in antiferroelectrics
Authors: Vales-Castro P. , Roleder Krystian , Zhao Lei , Li Jing-Feng , Kajewski Dariusz , Catalan Gustau
Published: September 2018

Flexoelectricity (coupling between polarization and strain gradients) is a property of all dielectric materials that has been theoretically known for decades, but only relatively recently it has begun to attract experimental attention. As a consequence, there are still entire families of materials whose flexoelectric performance is unknown. Such is the case of antiferroelectrics: materials with an antiparallel but switchable arrangement of dipoles. These materials are expected to be flexoelectrically relevant because it has been hypothesised that flexoelectricity could be linked to the origin of their antiferroelectricity. In this work, we have measured the flexoelectricity of two different antiferroelectrics (PbZrO3 and AgNbO3) as a function of temperature, up to and beyond their Curie temperature. Although their flexocoupling shows a sharp peak at the antiferroelectric phase transition, neither flexoelectricity nor the flexocoupling coefficients are anomalously high, suggesting that it is unlikely that flexoelectricity causes antiferroelectricity.
Dispersion in two-dimensional periodic channels with discontinuous profiles
Authors: Mangeat M. , Guérin T. , Dean D. S.
Published: September 2018

The effective diffusivity of Brownian tracer particles confined in periodic micro-channels is smaller than the microscopic diffusivity due to entropic trapping. Here, we study diffusion in two-dimensional periodic channels whose cross section presents singular points, such as abrupt changes of radius or the presence of thin walls, with openings, delimiting periodic compartments composing the channel. Dispersion in such systems is analyzed using the Fick-Jacobs (FJ) approximation. This approximation assumes a much faster equilibration in the lateral than in the axial direction, along which the dispersion is measured. If the characteristic width a of the channel is much smaller than the period L of the channel, i.e., ε = a/L is small, this assumption is clearly valid for Brownian particles. For discontinuous channels, the FJ approximation is only valid at the lowest order in ε and provides a rough, though on occasions rather accurate, estimate of the effective diffusivity. Here we provide formulas for the effective diffusivity in discontinuous channels that are asymptotically exact at the next-to-leading order in ε. Each discontinuity leads to a reduction of the effective diffusivity. We show that our theory is consistent with the picture of effective trapping rates associated with each discontinuity, for which our theory provides explicit and asymptotically exact formulas. Our analytical predictions are confirmed by numerical analysis. Our results provide a precise quantification of the kinetic entropic barriers associated with profile singularities.
Dynamic behavior of droplets under interfacial jamming of nanoparticles
Authors: Li Xiaoguang , Wang Yiqi , Yang Yao , Wang Senhao , Zang Duyang , Geng Xingguo
Published: September 2018

Interfacial particle jamming can lock a droplet in a non-spherical shape; however, the effects of jamming on the dynamic behaviors of droplets are not well known. In this paper, droplet impact dynamics are studied on a mechanically weak superhydrophobic surface whose outer nanoparticles were detached by an impinging droplet and jammed at the droplet surface during retraction. The number and coverage of jammed particles were increased by increasing the impinging velocity, and unusual parachute-like shapes appeared at the rebounding moments for polyethylene oxide (PEO) droplets. Also, oscillation prohibition, bounce damping, and final deformation of the PEO droplets were each enhanced with increased velocity. The critical impinging velocity for the final deformation was much smaller than that required to generate complete droplet coverage, indicating that considerable local jamming was sufficient for generating droplet deformation. Local jamming was difficult to achieve during impact when droplet viscosity was low, as in the case of pure water, because particles were well dispersed under high surface flowability.
Performance of quantum-dot-based tunnel-injection lasers: A theoretical analysis
Authors: Lorke M. , Michael S. , Cepok M. , Jahnke F.
Published: September 2018

Tunnel-injection lasers promise advantages in the modulation bandwidth and temperature stability in comparison with conventional laser designs. In this paper, we present results of a microscopic theory for laser properties of tunnel-injection devices and a comparison with a conventional quantum-dot laser structure. In general, the modulation bandwidth of semiconductor lasers is affected by the steady-state occupations of electrons and holes via the presence of spectral hole burning. For tunnel-injection lasers with InGaAs quantum dot emitting at an telecom wavelength of 155 μm, we demonstrate that the absence of spectral hole burning favors this concept over conventional quantum-dot based lasers.
Acoustic nonlinearity parameter induced by extended dislocations
Authors: Gao Xiang , Qu Jianmin
Published: September 2018

Excess acoustic nonlinearity is a signature of microstructural defects on a propagating ultrasound. By measuring the excess acoustic nonlinearity parameter, defect characteristics can be inferred nondestructively through ultrasonic techniques. To this end, proper models are needed to relate the excess acoustic nonlinearity parameter with defect characteristics. In this study, an analytical model for extended dislocations is developed that relates the excess acoustic nonlinearity parameter with characteristics of the extended dislocation including dislocation density, stacking fault energy, and equilibrium distance between the two partial dislocations that form the extended dislocation. According to this model, the excess acoustic nonlinearity parameter induced by extended dislocations consists of a stress-independent term and a stress-dependent term. Both terms are scaled with (Lchar/b)n, where Lchar is the equilibrium distance between the two partials, b is the magnitude of Burgers vector, and n is 3 and 4 for the stress-independent and stress-dependent terms, respectively. The model will be useful for interpreting results from ultrasonic nondestructive evaluation of material defects.
Ge2Pt hut clusters: A substrate for germanene
Authors: van Bremen Rik , Bampoulis Pantelis , Aprojanz Johannes , Smithers Mark , Poelsema Bene , Tegenkamp Christoph , Zandvliet Harold J. W.
Published: September 2018

The formation and structure of Ge2Pt clusters was studied in order to understand their germanene termination layer. The Ge2Pt clusters are formed by depositing a few layers of Pt on a Ge(110) surface. Annealing at temperatures above 1043 K results in eutectic Ge-Pt droplets that etch grooves on the surface in the [11¯0] direction. Upon cooling down, they solidify and decompose into a Ge2Pt phase and a pure Ge phase. Electron diffraction reveals that the hut-shaped clusters have their (001) plane oriented parallel to the Ge(110) surface and their (100) plane facing in the Ge[11¯0] direction. The facets of the Ge2Pt hut clusters have been determined to be the {101} and {011} planes. The germanene layers which cover these facets are commensurate with the {101} and {011} facets of the Ge2Pt substrate.
Apply surface wettability gradient to non-wetting capillary: A simulation study on spontaneous droplet flow
Authors: Zhang Dingni , Shangguan Qianqian , Wang Yuxiang
Published: September 2018

The present work simulates a concept about how to drive droplet flowing through non-wetting (hydrophobic) capillaries without any external force by using many-body dissipative particle dynamics. By decorating the capillary segments with wettability gradients, a droplet with proper radius can be absorbed by the non-wetting capillaries and then constantly flow through the capillary. The simulation results show the droplet can keep flowing through the whole capillaries under certain wettability gradients and the flow velocity also depends on the degree of the wettability gradients. The average wettability of the whole capillary is also essential for the continuous flowing, higher non-wetting capillaries can still keep the flowing with low wettability gradients due to less surface adhesion. A strategy on how to achieve longer flow pathway is also presented. It is also find that unbalanced uptake of droplet via lateral heterogeneous surfaces cannot stir the inside flow of the droplet. The simulation results could inspire the new design of microfluidics in which the transportation of droplet is an important aspect.
Deep level transient spectroscopy study of heavy ion implantation induced defects in silicon
Authors: Lew C. T.-K. , Johnson B. C. , McCallum J. C.
Published: September 2018

Defects introduced by low fluence arsenic, antimony, erbium, and bismuth ion implantation have been investigated as a function of annealing temperature using deep level transient spectroscopy (DLTS) and Laplace-DLTS. The defects produced by heavy ion implantation are stable up to higher temperatures than those introduced by electron irradiation and low mass ions. This result is attributed to the enhanced defect interactions that take place in the dense collision cascades created by heavy ion implantation. As a consequence, broadened DLTS features are apparent, especially after annealing. Using high energy resolution Laplace-DLTS, the well-known singly charged divacancy and vacancy-donor pair are accompanied by additional apparent defect signals. This shows that Laplace-DLTS is highly sensitive to the type of damage present, and extreme care must be exercised for reliable Arrhenius analysis.
Effect of shock breakout pressure on material ejection from tin surface under unsupported shocks
Authors: Liu WenBin , He An-Min , Wang Pei
Published: September 2018

We perform smoothed particle hydrodynamics (SPH) simulations to study the material ejection from a grooved tin surface under unsupported shocks with different shock breakout pressures. It is found that melting has a substantial impact on both of the ejection morphology and spatial density distributions of ejecta. However, the failure depth of material approximates the width of the unsupported shock wave, independent of the shock breakout pressure.
The role of time-lag in the surface discharge inception under positive repetitive pulse voltage
Authors: Fu Pengyu , Zhao Zhibin , Li Xuebao , Cui Xiang , Yang Zhuodong
Published: September 2018

Polyetheretherketone is used in the packaging of high voltage power electronics as a frame material, and the surface discharge behaviors of polyetheretherketone are the main concerns for the packaging design. Pulse width modulation voltage, which shows a variable duty cycle, is applied to polyetheretherketone at working conditions. The surface discharge behaviors of polyetheretherketone under a positive repetitive pulse voltage of 50 Hz with different duty cycles were investigated in this paper. It is generally considered that the surface discharge inception is mainly related to electric field distribution; however, the pulse width of voltage could significantly affect the surface discharge inception characteristics. In this study, the surface discharge inception voltage, time-integrated streamer images, and cumulative surface discharge patterns under a positive repetitive pulse voltage of 50 Hz were obtained. It was found that the surface discharge inception voltage decreased with the increase in the duty cycle. This relationship was explained by the role of time-lag. Time-lag distribution analysis was performed, and the time-lag distribution was mainly determined by stochastic time-lag. The mean stochastic time-lag was obtained by the Laue plot, and the relationship between the mean stochastic time-lag and applied voltage could be well fitted by the inverse power law. Furthermore, the relationship between the surface discharge inception voltage and duty cycle could be exactly fitted by the inverse power law, which was derived from the relationship between the stochastic mean time-lag and applied voltage. The closely related relationships demonstrate that time-lag plays a critical role in the surface discharge inception at different duty cycles.
Continuously variable atomic structure in monatomic metallic glasses through active icosahedral dynamics below glass transition temperature
Authors: Xu Donghua , Chen Fangzheng
Published: September 2018

As a ubiquitous structural feature in metallic glasses, icosahedral clusters are known to be arrested below the glass transition temperature (Tg), and correspondingly, the atomic structure of a solid metallic glass is generally fixed, even though interatomic spacing varies slightly with temperature. Here, we report our discovery from large molecular dynamics simulations that icosahedral clusters in monoatomic metallic glasses (e.g., Ta, V) are capable of adapting their population and geometry to changing temperature in a wide range spanning more than 1000° below Tg. This enables variation of the atomic structure of the metallic glasses directly in the solid state and provides an opportunity to tailor the materials' performance in functional devices, despite precautions needed to avoid undesired crystallization. The surprising discovery of active icosahedral dynamics far below Tg has important implications for the physical understanding of glassy metallic systems.
Long-range dispersion C6 coefficient for SF6 dimer: Experimental and theoretical study
Authors: Tatarenko Kira A. , Lazarev Alexander V. , Bokhan Denis , Trubnikov Dmitrii N. , Perera Ajith
Published: September 2018

The long-range dispersion C6 coefficient for the SF6 dimer is experimentally measured using a technique that uses the expansion of a supersonic pulse jet into a vacuum. A dynamic model of the jet enables us to correlate the position of the maximal peak in the time-of-flight spectrum with the initial conditions of the experiment and the parameters of the intermolecular interaction potential. Due to the low temperature of the jet target, the C6 coefficient can be extracted directly from the experimental results. Theoretical calculation of the C6 dispersion coefficient is also performed by using linearly approximated explicitly correlated coupled-cluster singles and doubles (CCSD(F12)) method with the subsequent utilization of the Casimir-Polder formula. Good agreement of experimental and theoretical results confirms the reliability of results.
Quantitative analysis of the reduction kinetics of a Pt(II) precursor in the context of Pt nanocrystal synthesis
Authors: Zhou Shan , Yang Tung-Han , Zhao Ming , Xia Younan
Published: September 2018

In this letter, we report a quantitative analysis of how a Pt(II) precursor is reduced to atoms at different temperatures for the formation of Pt nanocrystals with different morphologies and sizes. Our results suggest that in the early stage of a synthesis, the Pt(II) precursor is reduced to atoms exclusively in the solution phase, followed by homogeneous nucleation to generate nuclei and then seeds. At a relatively low reaction temperature such as 22°C, the growth of the seeds is dominated by autocatalytic surface reduction that involves the adsorption and then reduction of the Pt(II) precursor on the surface of the just-formed seeds. This particular growth pathway results in relatively large assemblies of Pt nanocrystals. When the reaction temperature is increased to 100°C, the dominant reduction pathway will be switched from surface to solution phase, producing much smaller assemblies of Pt nanocrystals. Our results also demonstrate that a similar trend applies to the seed-mediated growth of Pt nanocrystals in the presence of Pd nanocubes.
Femtosecond stimulated Raman line shapes: Dependence on resonance conditions of pump and probe pulses
Authors: Chen Cheng , Zhu Liang-dong , Fang Chong
Published: September 2018

Resonance enhancement has been increasingly employed in the emergent femtosecond stimulated Raman spectroscopy (FSRS) to selectively monitor molecular structure and dynamics with improved spectral and temporal resolutions and signal-to-noise ratios. Such joint efforts by the technique- and application-oriented scientists and engineers have laid the foundation for exploiting the tunable FSRS methodology to investigate a great variety of photosensitive systems and elucidate the underlying functional mechanisms on molecular time scales. During spectral analysis, peak line shapes remain a major concern with an intricate dependence on resonance conditions. Here, we present a comprehensive study of line shapes by tuning the Raman pump wavelength from red to blue side of the ground-state absorption band of the fluorescent dye rhodamine 6G in solution. Distinct line shape patterns in Stokes and anti-Stokes FSRS as well as from the low to high-frequency modes highlight the competition between multiple third-order and higher-order nonlinear pathways, governed by different resonance conditions achieved by Raman pump and probe pulses. In particular, the resonance condition of probe wavelength is revealed to play an important role in generating circular line shape changes through oppositely phased dispersion via hot luminescence (HL) pathways. Meanwhile, on-resonance conditions of the Raman pump could promote excited-state vibrational modes which are broadened and red-shifted from the coincident ground-state vibrational modes, posing challenges for spectral analysis. Certain strategies in tuning the Raman pump and probe to characteristic regions across an electronic transition band are discussed to improve the FSRS usability and versatility as a powerful structural dynamics toolset to advance chemical, physical, materials, and biological sciences.
Au10(TBBT)10: The beginning and the end of Aun(TBBT)m nanoclusters
Authors: Zeng Chen-jie , Zhou Meng , Gayathri Chakicherla , Gil Roberto R. , Sfeir Matthew Y. , Jin Rongchao
Published: September 2018

Gold(I) thiolate compounds (i.e. AuI-SR) are important precursors for the synthesis of atomically precise Aun(SR)m nanoclusters. However, the nature of the AuI-SR precursor remains elusive. Here, we report that the Au10(TBBT)10 complex is a universal precursor for the synthesis of Aun(TBBT)m nanoclusters (where TBBT=4-tertbutylbenzenethiol/thiolate). Interestingly, the Au10(TBBT)10 complex is also found to be re-generated through extended etching of the Aun(SR)m nanoclusters with excess of TBBT thiol and O2. The formation of well-defined Au10(TBBT)10 complex, instead of polymeric AuI-SR, is attributed to the bulkiness of the TBBT thiol. Through 1D and 2D NMR characterization, the structure of Au10(TBBT)10 is correlated with the previously reported X-ray structure, which contains two inter-penetrated Au5(TBBT)5 rings. The photophysical property of Au10(TBBT)10complex is further probed by femtosecond transient absorption spectroscopy. The accessibility of the precise Au10(TBBT)10 precursor improves the efficiency of the synthesis of the Aun(TBBT)m nanoclusters and is expected to further facilitate excellent control and understanding of the reaction mechanisms of nanocluster synthesis.
Energy partition, nutritional energy requirements and methane production in F1 Holstein × Gyr bulls, using the respirometric technique
Authors: Ferreira A. L. , Borges A. L. C. C. , Mourão R. C. , Silva R. R. , Duque A. C. A. , Silva J. S. , Souza A. S. , Gonçalves L. C. , Carvalho P. H. A.
Published: September 2018

The nutritional energy requirements of animals for maintenance and weight gain, such as the energy partition of the diet, were determined in different feeding plans. Fifteen F1 Holstein × Gyr, non-castrated male bovines with a mean initial liveweight of 302 kg were used. The diets were corn silage and concentrate, formulated to enable gains of 100, 500 and 900 g/day, called low, medium and high weight gains, respectively. Tests of digestibility and metabolism were conducted to determine energy losses through faeces, urine and methane emissions. Heat production was determined using respirometry chamber. Net energy for maintenance was calculated as the antilogarithm of the intercept of the regression of the logarithm of the heat production, as a function of the metabolisable energy intake. Retained energy was obtained by subtracting the heat production from the metabolisable energy intake. With the increased consumption of dry matter, there was an increase in faecal and urinary energy loss. Retained energy increased linearly with the metabolisable energy intake. The net energy for gain in the diet did not differ among the treatments, such as the efficiency of use of metabolisable energy for weight gain kg (0.34). The net energy for maintenance was 312 kJ/kg LW0.75, and the metabolisable energy for maintenance was 523 kJ/kg LW0.75. The daily methane production (g/day) increased with the dry matter level and the daily loss represented 5.31% of the gross energy consumption.
Gastropod communities associated with different morphologies of the intertidal seaweed Hormosira banksii
Authors: Gemelli F. , Johnson C. R. , Wright J. T.
Published: September 2018

Hormosira banksii is an important intertidal habitat-forming seaweed in southern Australia that shows large variation in morphology. We examined the relationship between morphological variation in Hormosira and associated gastropod community structure, abundance and diversity in Tasmania, southern Australia. We sampled both Hormosira and gastropods from sites in two habitats (coast and estuary), two times (February–March and October–November) at two regions (northern and eastern Tasmania). There were distinct Hormosira morphs on the north coast (small individuals), east coast (intermediate sized individuals) and in estuaries (large individuals). Multivariate analysis showed that gastropod communities varied among the different algal morphologies, and suggest an influence of morphological traits, specifically thallus length, vesicle number and size, on the distribution patterns of gastropod species. Despite the finding of distinct gastropod communities associated with the different Hormosira morphs, because the different morphs occur in different locations with different physical conditions, we cannot unequivocally attribute the differences in gastropod communities to seaweed morphology per se. Nonetheless, our results confirm that H. banksii is an important foundation species in the intertidal zone and suggest a habitat-specific effect of algal morphological traits on gastropods.
Princess PrEP program: the first key population-led model to deliver pre-exposure prophylaxis to key populations by key populations in Thailand
Authors: Phanuphak Nittaya , Sungsing Thanthip , Jantarapakde Jureeporn , Pengnonyang Supabhorn , Trachunthong Deondara , Mingkwanrungruang Pravit , Sirisakyot Waraporn , Phiayura Pattareeya , Seekaew Pich , Panpet Phubet , Meekrua Phathranis , Praweprai Nanthika , Suwan Fonthip , Sangtong Supakarn , Brutrat Pornpichit , Wongsri Tashada , Na Nakorn Panus Rattakittvijun , Mills Stephen , Avery Matthew , Vannakit Ravipa , Phanuphak Praphan
Published: September 2018

Background No data are available on the feasibility of pre-exposure prophylaxis (PrEP) delivered by trained key population (KP) community health workers. Herein we report data from the KP-led Princess PrEP program serving men who have sex with men (MSM) and transgender women (TGW) in Thailand. Methods: From January 2016 to December 2017, trained MSM and TGW community health workers delivered same-day PrEP service in community health centres, allowing clients to receive one PrEP bottle to start on the day of HIV-negative testing. Visits were scheduled at Months 1 and 3, and every 3 months thereafter. Uptake, retention and adherence to PrEP services and changes in risk behaviours over time are reported. Results: Of 1467 MSM and 230 TGW who started PrEP, 44.1% had had condomless sex in the past 3 months. At Months 1, 3, 6, 9 and 12, retention was 74.2%, 64.0%, 56.2%, 46.7% and 43.9% respectively (lower in TGW than MSM at all visits; P<0.001), with adherence to at least four PrEP pills per week self-reported by 97.4%, 96.8%, 96.5%, 97.5% and 99.5% of respondents respectively (no difference between MSM and TGW). Logistic regression analysis identified age >25 years, being MSM and having at least a Bachelors degree significantly increased retention. Condomless sex did not change over the 12-month period (from 47.2% to 45.2%; P=0.20). New syphilis was diagnosed in 4.9% and 3.0% of PrEP clients at Months 6 and 12 (cf. 7.0% at baseline; P=0.007). Among PrEP adherers and non-adherers, there were one and six HIV cases of seroconversion respectively, which resulted in corresponding HIV incidence rates (95% confidence interval) of 0.27 (0.04–1.90) and 1.36 (0.61–3.02) per 100 person-years. Conclusion: Our KP-led PrEP program successfully delivered PrEP to MSM and TGW. Innovative retention supports are needed, especially for TGW and those who are young or with lower education levels. To scale-up and sustain KP-led PrEP programs, strong endorsement from international and national guidelines is necessary.
Mechanism of drug extrusion by brain endothelial cells via lysosomal drug trapping and disposal by neutrophils
Authors: Noack Andreas , Gericke Birthe , von Köckritz-Blickwede Maren , Menze Arne , Noack Sandra , Gerhauser Ingo , Osten Felix , Naim Hassan Y. , Löscher Wolfgang
Published: September 2018

Significance

Located at the apical (blood-facing) site of brain capillary endothelial cells that form the blood–brain barrier (BBB), the efflux transporter P-glycoprotein (Pgp) restricts the brain entry of various lipophilic xenobiotics, which contributes to BBB function. Pgp may become saturated if exposed to too-high drug concentrations. Here, we demonstrate a second-line defense mechanism in human brain capillary endothelial cells—that is, Pgp-mediated intracellular lysosomal drug trapping. Furthermore, we describe a mechanism of drug disposal at the BBB, which is shedding of lysosomal Pgp/substrate complexes at the apical membrane of human and porcine BBB endothelial cells and subsequent phagocytosis by neutrophils. Thus, we have discovered a fascinating mechanism of how Pgp might contribute to brain protection.
Dawn and photoperiod sensing by phytochrome A
Authors: Seaton Daniel D. , Toledo-Ortiz Gabriela , Ganpudi Ashwin , Kubota Akane , Imaizumi Takato , Halliday Karen J.
Published: September 2018

Significance

The changing seasons subject plants to a variety of challenging environments. To deal with this, many plants have mechanisms for inferring the season by measuring the duration of daylight in a day. A number of well-known seasonal responses such as flowering are responsive to daylength or photoperiod. Here, we describe how the photoreceptor protein phytochrome A senses short photoperiods. This arises from its accumulation during long nights, as happens during winter, and subsequent activation by light at dawn. As a result of this response, the abundance of red anthocyanin pigments is increased in short photoperiods. Thus, we describe a mechanism underlying a seasonal phenotype in an important model plant species.
Siglec-7 engagement by GBS β-protein suppresses pyroptotic cell death of natural killer cells
Authors: Fong Jerry J. , Tsai Chih-Ming , Saha Sudeshna , Nizet Victor , Varki Ajit , Bui Jack D.
Published: September 2018

Significance

Direct interactions between natural killer (NK) cells and bacteria are rarely observed, and the consequences of these interactions not well understood. We show that human NK cells exposed to the bacterium group BStreptococcus(GBS) undergo pyroptosis, a type of inflammatory cell death. By releasing inflammatory mediators, pyroptosis is thought to be a way for sentinels to die and alert the immune system of infection. Interestingly, we also found that GBS has a protein that binds to Siglec-7, an inhibitory molecule on NK cells. Siglec-7 inhibits pyroptosis and silences the sentinel activity of NK cells by preventing the release of inflammatory molecules. These studies suggest that a human pathogen can silence the sentinel by specific interaction with a Siglec protein.
Single-molecule analysis of endogenous β-actin mRNA trafficking reveals a mechanism for compartmentalized mRNA localization in axons
Authors: Turner-Bridger Benita , Jakobs Maximillian , Muresan Leila , Wong Hovy Ho-Wai , Franze Kristian , Harris William A. , Holt Christine E.
Published: September 2018

Significance

De novo protein synthesis in neuronal axons plays important roles in neural circuit formation, maintenance, and disease. Key to the selectivity of axonal protein synthesis is whether an mRNA is present at the right place to be translated, but the mechanisms behind axonal mRNA localization remain poorly understood. In this work, we quantitatively analyze the link between axonal β-actin mRNA trafficking and its localization patterns. By developing a single-molecule approach to live-image β-actin mRNAs in axons, we explore the biophysical drivers behind β-actin mRNA motion and uncover a mechanism for generating increased density at the axon tip by differences in motor protein-driven transport speeds. These results provide mechanistic insight into the control of local translation through mRNA trafficking.
Beyond the classical thermodynamic contributions to hydrogen atom abstraction reactivity
Authors: Bím Daniel , Maldonado-Domínguez Mauricio , Rulíšek Lubomír , Srnec Martin
Published: September 2018

Significance

Hydrogen atom abstraction reactivity is a key property of many important biological and synthetic compounds that depends on their proton-coupled reduction potentials. These potentials quantify the ability of species to acquire an electron and proton pair. Intuitively, a species with a higher proton-coupled reduction potential abstracts hydrogen atoms more easily, which translates into a lower reaction barrier. Beyond this classical thermodynamic effect on reactivity, we discovered a significant contribution arising from a factor reflecting propensity for (a)synchronicity in concerted H
+
/e
−
transfers, which stems directly from the reduction potentials and acidity constants of reactants and products. We show that the most synchronous hydrogen atom abstractions tend to pass over the highest barriers, as exemplified by computations on Fe
IV
O oxidants.
BRCA1-IRIS promotes human tumor progression through PTEN blockade and HIF-1α activation
Authors: Li Andrew G. , Murphy Elizabeth C. , Culhane Aedin C. , Powell Emily , Wang Hua , Bronson Roderick T. , Von Thanh , Giobbie-Hurder Anita , Gelman Rebecca S. , Briggs Kimberly J. , Piwnica-Worms Helen , Zhao Jean J. , Kung Andrew L. , Kaelin William G. , Livingston David M.
Published: September 2018

Significance

Spontaneous overexpression of endogenous IRIS, an alternatively spliced product of the tumor suppressor gene
BRCA1
, allows it to function as an oncoprotein that stimulates a potentially lethal outcome, i.e. metastasis of human cancer cells to tissues served, in part, by the arterial circulation. It does so by suppressing phosphatase and tensin homolog (PTEN) mRNA synthesis, thereby stabilizing and activating HIF-1α in normoxic cells. Thus, this study provides a strong rationale for exploring the therapeutic value of interfering with spontaneously overexpressed IRIS function in multiple types of tumors that can naturally overexpress it.
Genetically defined cellular correlates of the baseline brain MRI signal
Authors: Wen Jie , Goyal Manu S. , Astafiev Serguei V. , Raichle Marcus E. , Yablonskiy Dmitriy A.
Published: September 2018

Significance

Understanding the structure and function of the human brain at a cellular level is a fundamental aim of neuroscience. Tremendous progress has been made in recent years based on different in vivo and ex vivo approaches, including major advances in brain MRI. However, uncertainties remain in determining how brain MRI measurements relate to the brain’s underlying cellular composition. In this paper we use a recently developed MRI technique, quantitative gradient recalled echo (qGRE), and information on gene profiles in the human brain available from the Allen Human Brain Atlas. We demonstrate that qGRE and related MRI techniques can be used to probe the underlying cellular composition of the human brain in vivo.
Optimal protection againstSalmonellainfection requires noncirculating memory
Authors: Benoun Joseph M. , Peres Newton G. , Wang Nancy , Pham Oanh H. , Rudisill Victoria L. , Fogassy Zachary N. , Whitney Paul G. , Fernandez-Ruiz Daniel , Gebhardt Thomas , Pham Quynh-Mai , Puddington Lynn , Bedoui Sammy , Strugnell Richard A. , McSorley Stephen J.
Published: September 2018

Significance

Effective vaccination againstSalmonellainfection requires the generation of memory T cells that can be reactivated upon exposure to bacteria in a natural setting. It is unclear whether immunity requires memory T cells that continuously patrol blood, lymphatics, and tissues, whether noncirculating T cells are important, or both. We demonstrate the generation of circulating and noncirculating memory pools after immunization. However, naive mice that previously shared a blood supply with vaccinated partners received recirculating memory T cells, but did not have T cell memory with characteristics of tissue residence, resulting in a failure to acquire robust protective immunity. Thus, noncirculating tissue-resident memory T cells are vital for effective protection againstSalmonella.
Corepressor SMRT is required to maintain Hox transcriptional memory during somitogenesis
Authors: Hong Suk-Hyun , Fang Sungsoon , Lu Benson C. , Nofsinger Russell , Kawakami Yasuhiko , Castro Glenda L. , Yin Yunqiang , Lin Chengqi , Yu Ruth T. , Downes Michael , Izpisúa Belmonte Juan Carlos , Shilatifard Ali , Evans Ronald M.
Published: September 2018

Significance

Retinoic acid (RA) is an important transcriptional regulator during both vertebrate and invertebrate body pattern formation. The Homeobox (Hox) gene family is activated by a gradient of RA formed along the length of the embryo at specific time points during fetal development. Generation of a genetically modified mouse harboring mutations in the SMRT repressor demonstrated that SMRT-dependent repression of retinoic acid receptor (RAR) is critical to establish and maintain the somitic Hox code and segmental identity during fetal development via epigenetic marking of target loci.
On the control of the proton current in the voltage-gated proton channel Hv1
Authors: Lee Myungjin , Bai Chen , Feliks Mikolaj , Alhadeff Raphael , Warshel Arieh
Published: September 2018

Significance

Voltage activation of proton transport is an important mechanism that plays a key role in fundamental biological processes, yet the detailed control of such processes is far from clear. Here we investigate the voltage-activated proton channel Hv1 to explore the structure/function basis of its activation by combining empirical valence bond and electrostatic calculations. Our study provides a detailed description of the exquisite use of an ionizable aspartic acid residue and arginine residues in controlling the crucial selectivity of the proton transport through the channel. This type of mechanism is likely to have implications for the action of other related systems.
Earth’s outgoing longwave radiation linear due to H2O greenhouse effect
Authors: Koll Daniel D. B. , Cronin Timothy W.
Published: September 2018

Significance

Earth’s climate is set by a balance between incoming solar and outgoing infrared radiation. The physical processes that influence this balance are complex and nonlinear, yet models and satellite measurements counterintuitively show that Earth’s infrared radiation is simply a linear function of surface temperature. Here we explain why: Linearity is due to the cancellation of two nonlinear processes and always arises in an atmosphere dominated by a condensable greenhouse gas. Our work explains a fundamental property of Earth’s climate and has implications for climate change as well as the climates of extrasolar planets with exotic greenhouse gases.
Distinct modes of derepression of an
Arabidopsis
immune receptor complex by two different bacterial effectors
Authors: Ma Yan , Guo Hailong , Hu Lanxi , Martinez Paula Pons , Moschou Panagiotis N. , Cevik Volkan , Ding Pingtao , Duxbury Zane , Sarris Panagiotis F. , Jones Jonathan D. G.
Published: September 2018

Significance

Plants and animals carry intracellular nucleotide-binding leucine-rich repeat (NLR) immune receptors. How NLR receptors activate defense on perceiving pathogen molecules is poorly understood, especially in plants. Some NLRs function in pairs, with one NLR carrying a domain that mimics a pathogen effector target. Effector action on this domain activates the second “helper” NLR. In the
Arabidopsis
RPS4 and RRS1 pair, RRS1 carries a WRKY transcription factor domain targeted by bacterial effectors AvrRps4 and PopP2. We monitored conformational changes in RPS4–RRS1 during activation and developed a “molecular padlock” to reversibly restrict such changes. This revealed domains within RRS1 required to keep the RRS1–RPS4 complex inactive prior to effector detection, and specific domain–domain interactions whose disruption or modification contributes to defense activation.
Multiscale wavelet decomposition of time-resolved X-ray diffraction signals in cyclohexadiene
Authors: Osipov Vladimir Al. , Kowalewski Markus , Mukamel Shaul
Published: September 2018

Significance

Free electron laser sources of ultrafast X-ray pulses can record movies of chemical reactions by measuring snapshots of the charge density along the reaction path on the femtosecond timescale. Only a few valence electrons typically participate in chemical bond breaking and forming. To separate the valence electron density from the strong background of highly localized core electrons we use a wavelet transform, a powerful tool for filtering, and scaling analysis of signals. The wavelet-processed signal from the cyclohexadiene molecule reported here clearly reveals the valence electron rearrangements in the early steps of the photoinduced pericyclic ring opening reaction, which are not resolved in the bare signal. This multiscale analysis of charge densities should be extremely valuable for disentangling complex reaction pathways.
Cold exposure causes cell death by depolarization-mediated Ca2+overload in a chill-susceptible insect
Authors: Bayley Jeppe Seamus , Winther Christian Bak , Andersen Mads Kuhlmann , Grønkjær Camilla , Nielsen Ole Bækgaard , Pedersen Thomas Holm , Overgaard Johannes
Published: September 2018

Significance

Insects comprise the largest class of animals and include numerous species of direct importance to humans, including pests and pollinators. Cold tolerance is arguably among the most important traits determining the distribution of insects. Hypothermia has been proposed to induce cell injury directly by promoting membrane phase transitions resulting in cell leak. Additionally, hypothermia induces hemolymph hyperkalemia, and it has been proposed that hypothermia induces injury indirectly through the resulting depolarization by inducing Ca2+influx promoting apoptosis/necrosis. Here we show that depolarization is a principal mechanism for hypothermic cell injury. Furthermore, we show that intracellular Ca2+increases upon depolarization and that this increase must flux through Ca2+channels in the membrane to accumulate and induce injury.
Effect of simultaneous addition of ferroniobium and ferrotitanium on properties of hardfacing
Authors: Liu Dashuang , Wu Mingfang , Long Weimin , Li Leijun , Wei Ping
Published: September 2018

The slag-free self-shielded flux-cored wire with simultaneous addition of ferroniobium (Fe-Nb) and ferrotitanium (Fe-Ti) was developed to fabricate the iron-based hardfacing alloys. The transfer coefficients of Nb and titanium of slag-free self-shielded flux-cored wire were 91.2 and 63.8%, respectively. The changes in microstructures indicate that Nb and Ti addition shifted the carbon concentration in the remaining liquid to one corresponding to the near eutectic state owing to the formation of (Nb, Ti)C which consumed carbon. The wear loss of the hardfacing alloy with 18 wt-% Fe-Nb and 6 wt-% Fe-Ti addition was the smallest among all the alloys owing to the formation of reinforced uniform quadrangle-shaped (Nb, Ti)C carbides in the refined microstructure and the highest hardness.
In situ analysis of the strain evolution during welding using low transformation temperature filler materials
Authors: Dixneit Jonny , Vollert Florian , Kromm Arne , Gibmeier Jens , Hannemann Andreas , Fischer Torben , Kannengiesser Thomas
Published: September 2018

Compared to conventional welding consumables using low transformation temperature (LTT) filler materials is an innovative method to mitigate tensile residual stresses due to delayed martensite transformation of the weld. For the effective usage of LTT filler materials, a deeper understanding of the complex processes that lead to the final residual stress state during multi-pass welding is necessary. Transformation kinetics and the strain evolution of multi-pass welds during welding were investigated in situ at the beamline HEMS@PETRAIII, Germany. Compared to conventional welds, the total strain was reduced and compression strain was achieved when using LTT filler materials. For an optimal use of the LTT effect in the root of multi-pass welds, the alloying concept must be adapted taking care of dilution.
Understanding co-production as a new public governance tool
Authors: Sorrentino Maddalena , Sicilia Mariafrancesca , Howlett Michael
Published: September 2018

Co-production has become a buzzword for both scholars and practitioners in the past decade. This introduction to the thematic issue ‘Co-production: Implementation problems, new technologies and new designs’ unpacks the concept of co-production and illustrates how it has been operationalized on the ground in diverse country-specific contexts. To facilitate the analysis, we make a distinction between ‘traditional’ and ‘non-traditional’ forms of co-production, even though the practice has not really been around long enough to have established a tradition in the true sense of the word. However, these two distinct forms of co-production are highly useful conceptual lenses through which to view the finer details and nuances, to identify the enabling conditions and to foreshadow the governance challenges, but also to highlight the innovating role co-production plays in forging public services and public policies. Thanks to the rich and varied ways in which the contributors have approached this central topic; the thematic issue enables the research and practice to more fully appreciate the ins and outs of co-production and suggests the most promising directions for future study.
The lipid bilayer membrane and its protein constituents
Authors: Robertson Janice L.
Published: September 2018

In 1918, the year the Journal of General Physiology was founded, there was little understanding of the structure of the cell membrane. It was evident that cells had invisible barriers separating the cytoplasm from the external solution. However, it would take decades before lipid bilayers were identified as the essential constituent of membranes. It would take even longer before it was accepted that there existed hydrophobic proteins that were embedded within the membrane and that these proteins were responsible for selective permeability in cells. With a combination of intuitive experiments and quantitative thinking, the last century of cell membrane research has led us to a molecular understanding of the structure of the membrane, as well as many of the proteins embedded within. Now, research is turning toward a physical understanding of the reactions of membrane proteins and lipids in this unique and incredibly complex solvent environment.