bluuebunny/crossref_metadata_2025 huggingface dataset:
A first principle comparative study of the ionic diffusivity in LiAlO2 and NaAlO2 polymorphs for solid-state battery applications
Authors: Bianchini F. , Fjellvåg H. , Vajeeston P.
Published: March 2018

DFT-based modelling of the ionic diffusion in LiAlO2 and NaAlO2 rationalises the larger mobility of sodium under ambient conditions.
Hydrodeoxygenation of guaiacol over bimetallic Fe-alloyed (Ni, Pt) surfaces: reaction mechanism, transition-state scaling relations and descriptor for predicting C–O bond scission reactivity
Authors: Liu Xiaoyang , An Wei , Wang Yixing , Turner C. Heath , Resasco Daniel E.
Published: March 2018

Small means big: DFT-calculated C–O bond length of adsorbed intermediates can serve as a good descriptor for predicting the C–O bond scission reactivity of phenolics over metal catalysts.
Carbonylation of dimethyl ether over Co-HMOR
Authors: Ma Meng , Zhan Ensheng , Huang Xiumin , Ta Na , Xiong Zhiping , Bai Luyi , Shen Wenjie
Published: March 2018

Incorporation of Co2+ into the framework of HMOR significantly enhanced the activity for the carbonylation of dimethyl ether to methyl acetate.
Vanadyl dithiolate single molecule transistors: the next spintronic frontier?
Authors: Cardona-Serra S. , Gaita-Ariño A.
Published: March 2018

The combination of a cutting-edge project of rational design of molecular spin qubits and a series of experiments in molecular spintronics for quantum computing are reviewed and discussed.
Layered rare-earth hydroxide (LRH, R = Tb, Y) composites with fluorescein: delamination, tunable luminescence and application in chemosensoring for detecting Fe(iii) ions
Authors: Su Feifei , Guo Rong , Yu Zihuan , Li Jian , Liang Zupei , Shi Keren , Ma Shulan , Sun Genban , Li Huifeng
Published: March 2018

The delaminated FLN/OS-LRH (R = Tb, Y) composites exhibit tunable luminescence and excellent luminescence chemosensoring for the detection of Fe3+.
Pronounced effect of pore dimension of silica support on Pd-catalyzed Suzuki coupling reaction under ambient conditions
Authors: Das Trisha , Uyama Hiroshi , Nandi Mahasweta
Published: March 2018

The pore size of the mesoporous silica support affects the reactivity of heterogeneous palladium catalysts in the Suzuki reaction under ambient conditions, which is leveled at higher temperature.
Arsenic for high-capacity lithium- and sodium-ion batteries
Authors: Lim Young Rok , Shojaei Fazel , Park Kidong , Jung Chan Su , Park Jeunghee , Cho Won Il , Kang Hong Seok
Published: March 2018

We report experiments and theoretical calculations on arsenic as a promising alternative to graphite anode materials in lithium- and sodium-ion batteries.
Improved vaccine-induced immune responses via a ROS-triggered nanoparticle-based antigen delivery system
Authors: Liang Xiaoyu , Duan Jianwei , Li Xuanling , Zhu Xiaowei , Chen Youlu , Wang Xiaoli , Sun Hongfan , Kong Deling , Li Chen , Yang Jing
Published: March 2018

A ROS-triggered nanoparticle-based antigen delivery system that could be employed to promote in vivo efficacy of vaccine-induced immune responses.
Graphene growth by molecular beam epitaxy: an interplay between desorption, diffusion and intercalation of elemental C species on islands
Authors: Presel Francesco , Tetlow Holly , Bignardi Luca , Lacovig Paolo , Tache Cristian A. , Lizzit Silvano , Kantorovich Lev , Baraldi Alessandro
Published: March 2018

A real-time XPS investigation of single- and multi-layer graphene growth on Ir (111).
The adsorption of silicon on an iridium surface ruling out silicene growth
Authors: Satta Mauro , Lacovig Paolo , Apostol Nicoleta , Dalmiglio Matteo , Orlando Fabrizio , Bignardi Luca , Bana Harsh , Travaglia Elisabetta , Baraldi Alessandro , Lizzit Silvano , Larciprete Rosanna
Published: March 2018

We followed the adsorption of Si on the Ir(111) surface via high resolution core level photoelectron spectroscopy, starting from the clean metal surface up to a coverage exceeding one monolayer.
Tailored dimensionality to regulate the phase stability of inorganic cesium lead iodide perovskites
Authors: Li Faming , Pei Yunhe , Xiao Fei , Zeng Tixian , Yang Zhou , Xu Jinjiang , Sun Jie , Peng Bo , Liu Mingzhen
Published: March 2018

Stable quasi-2D CsxPEA1−xPbI3 perovskites were fabricated through incorporating large cations. The optimal film remained stable in the α-phase up to 250 °C.
Boron-passivated surface Fe(iv) defects in hematite for highly efficient water oxidation
Authors: Lan Huiwen , Wei Aimin , Zheng Hechuang , Sun Xuhui , Zhong Jun
Published: March 2018

Surface Fe(iv) defects in hematite are for the first time identified and passivated by surface boron-termination for efficient solar water oxidation.
Metallic CuCo2S4 nanosheets of atomic thickness as efficient bifunctional electrocatalysts for portable, flexible Zn-air batteries
Authors: Li Yuxuan , Yin Jie , An Li , Lu Min , Sun Ke , Zhao Yong-Qing , Cheng Fangyi , Xi Pinxian
Published: March 2018

A portable, flexible Zn-air battery using CuCo2S4 NSs as the air-cathode displays a high open circuit voltage and strong rechargeable capacity due to the excellent reversible oxygen catalytic performance of metallic CuCo2S4 NSs of atomic thickness with abundant defects.
Regioselective construction of 1,3-diaryl tetrahydroindazolones via the three-component reaction of 1,3-cyclohexanediones, β-nitrostyrenes and arylhydrazines
Authors: Wang Ting , Qing Xushun , Dai Chenlu , Su Zhenjie , Wang Cunde
Published: March 2018

1,5,6,7-Tetrahydro-4H-indazol-4-one derivatives were synthesized effectively via the regioselective three-component reactions of substituted β-nitrostyrenes, 1,3-cyclohexanediones and phenylhydrazines.
Converting natural rubber waste into ring-opening metathesis polymers with oligo-1,4-cis-isoprene sidechains
Authors: Abbas Mudassar , Neubauer Maximilian , Slugovc Christian
Published: March 2018

Cross-metathesis with acrylates is used as the key-step to recycle natural rubber waste.
A review of transition-metal boride/phosphide-based materials for catalytic hydrogen generation from hydrolysis of boron-hydrides
Authors: Sun Hongming , Meng Jing , Jiao Lifang , Cheng Fangyi , Chen Jun
Published: March 2018

Efficient hydrogen generation and storage is an essential prerequisite of a future hydrogen economy.
Catalytic activity of Pd/hydrophilic phosphine ligand in the interface of an aqueous-phase Cu-free Sonogashira coupling
Authors: Rizkin Benjamin A. , Hartman Ryan L.
Published: March 2018

The reaction mechanism and the catalytic lifecycle of a biphasic Sonogashira coupling was studied by microfluidics coupled to Raman spectroscopy.
A high throughput screening method for the nano-crystallization of salts of organic cations
Authors: Nievergelt Philipp P. , Babor Martin , Čejka Jan , Spingler Bernhard
Published: March 2018

96 nano-crystallization trials can be done with just (sub)-milligram amounts of an organic salt to directly yield single crystal structures.
Li2S/carbon nanocomposite strips from a low-temperature conversion of Li2SO4 as high-performance lithium–sulfur cathodes
Authors: Ye Fangmin , Noh Hyungjun , Lee Jinhong , Lee Hongkyung , Kim Hee-Tak
Published: March 2018

A Li2S/carbon nanocomposite strip cathode derived from Li2SO4/poly(vinyl alcohol) nanocomposite strips at a record low temperature shows an excellent electrochemical performance.
New strategies based on microfluidics for the synthesis of metal–organic frameworks and their membranes
Authors: Echaide-Górriz Carlos , Clément Coralie , Cacho-Bailo Fernando , Téllez Carlos , Coronas Joaquín
Published: March 2018

The microfluidics approach allows not only the continuous production of metal–organic frameworks (MOFs) but also an accurate reaction parameter control in their synthesis.
Pharmacognostic and pharmacological evaluation ofEulaliopsis binataplant extracts by measuringin vitro/in vivosafety profile and anti-microbial potential
Authors: Kumar Vinod , Sharma Arun K. , Rajput Satyendra K. , Pal Mahesh , Dhiman Neerupma
Published: March 2018

Present investigation emphasizes the pharmacognostic and phytochemical screening ofEulaliopsis binataextracts as well as their toxicological profile and anti-bacterial potential.
Reprise d’un traitement implantaire
Authors: LECLERQ Philippe , MARTINEZ Jean-François , BRÜSH Michael
Published: March 2018

La mise en place d’implants dentaires doit
obéir à un certain nombre de règles concernant
à la fois leur chirurgie, mais également
la prothèse, les prothèses de recouvrement ayant
un pronostic plus défavorable que les prothèses
fixées. Lorsque ces règles sont transgressées,
le résultat est souvent médiocre, obligeant
à une reprise du traitement. Dans ces cas,
un protocole très strict doit être suivi, concernant
essentiellement les délais de cicatrisation
qui vont permettre, malgré un allongement
de la durée du travail, d’assurer chaque étape
du traitement.

La reprise exposée dans cet article
va essentiellement insister sur ces différentes
étapes.
The Effect of Metformin on Serum Gonadotropin Levels in Postmenopausal Women with Diabetes and Prediabetes: A Pilot Study
Authors: Krysiak Robert , Szkróbka Witold , Okopień Bogusław
Published: March 2018

Background Metformin was found to decrease serum levels of prolactin and thyrotropin. The aim of this study was to investigate the effect of this drug on hypothalamic-pituitary-ovarian axis activity in postmenopausal women with recently diagnosed and untreated glucose metabolism abnormalities.

Methods The study included three matched groups of postmenopausal women: patients with type 2 diabetes (group A, n=16), women with prediabetes (group B, n=14), and individuals with normal glucose metabolism (group C, n=14). Women with diabetes were then treated with high-dose metformin (3 g daily), while women with prediabetes received moderate doses of this agent (1.7 g daily). Glucose homeostasis markers, as well as serum levels of FSH, LH, thyrotropin, prolactin, estradiol and creatinine were measured at baseline and after 16 weeks of metformin treatment.

Results In both groups of metformin-treated women, the drug improved glucose homeostasis. High-dose metformin treatment reduced circulating levels of FSH and tended to reduce serum levels of LH, and these effects correlated with an improvement in insulin sensitivity. No changes in gonadotropin levels were observed in prediabetic women receiving moderate doses of metformin. Serum levels of thyrotropin, prolactin and estradiol, as well as the estimated glomerular filtration rate remained at a similar level throughout the study.

Conclusions Our study shows that the effect of metformin on hypothalamic-pituitary-ovarian axis activity in postmenopausal women depends on its dose and the magnitude of insulin resistance.
Klinische Basisuntersuchung des Kniegelenkes
Authors: Roessler Philip , Wirtz Dieter , Friedrich Max
Published: March 2018

Zielsetzung Die erfolgreiche Behandlung von Kniegelenkserkrankungen erfordert eine exakte Diagnose. Neben einer differenzierten Anamneseerhebung stellt die klinische Untersuchung dabei den wichtigsten Bestandteil in der Diagnostik von Kniegelenkserkrankungen dar.

Methode Das vorliegende Video erklärt die gängigen Provokationstests und Funktionsprüfungen, die in der Basisuntersuchung des Kniegelenkes zum Einsatz kommen. Neben der generellen Inspektion und Palpation liegt der Fokus hierbei auf den einzelnen Regionen Patella, Menisken, Kreuzbändern und Kollateralbändern.

Schlussfolgerung Der vorliegende Basisuntersuchungsgang ermöglicht eine strukturierte Herangehensweise an klinische Problemstellungen und kann, ergänzt um weitere spezifische und individuelle Tests eine gute Grundlage für die Diagnostik von Kniegelenkserkrankungen darstellen.
Germany since 1789
Authors: Williamson David G.
Published: March 2018

This essential text provides a clear and engaging introduction to the history of modern Germany. The updated and expanded new edition now takes the story back to 1789 and brings it right up to the present day, adopting a controversy-led approach throughout. Visual evidence, maps, documents and key event boxes support the text and aid learning.
The Political Economy of Housing Development in Africa
Authors: Bah El-hadj M. , Faye Issa , Geh Zekebweliwai F.
Published: March 2018

This chapter discusses some of the problems impeding the demand and supply of housing in Africa. Governance issues such as poor land governance and administration, corruption, inadequate housing policies and infrastructure development, as well as problems of housing affordability, are examined in this chapter.
The Construction Cost Conundrum in Africa
Authors: Bah El-hadj M. , Faye Issa , Geh Zekebweliwai F.
Published: March 2018

The chapter focuses on the underlying factors explaining high construction costs in Africa and possible solutions for lowering costs. A value chain analysis shows that the rising prices of building materials, large shares of imports, and inefficiencies in the construction process are the main factors that lead to the high costs of housing construction in Africa. The chapter emphasizes the need to consider the broader development objectives in the choice of solutions aimed at lowering construction costs, in order to increase housing affordability in Africa. Taking an industrial approach, using labor-intensive technologies including local technologies, improving efficiency and reducing waste, producing building materials locally, densifying, and increasing the availability of skills are viable avenues for reducing construction costs and increasing housing supply.
The Way Forward: A Stakeholder Analysis
Authors: Bah El-hadj M. , Faye Issa , Geh Zekebweliwai F.
Published: March 2018

The authors draw on key lessons learned from other emerging countries to explore possible and alternative solutions to housing Africa’s population. The chapter provides policy suggestions to the myriad stakeholders involved in Africa’s housing market. These include innovative ways to reduce the risk in housing finance transactions, in order to encourage the private sector to serve low-income households; the enhancement of tenure security and property rights; the use of low-cost and labor-intensive construction techniques; and the adoption of enabling strategies for slum upgrading and prevention.
Rate-induced tipping from periodic attractors: Partial tipping and connecting orbits
Authors: Alkhayuon Hassan M. , Ashwin Peter
Published: March 2018

We consider how breakdown of the quasistatic approximation for attractors can lead to rate-induced tipping, where a qualitative change in tracking/tipping behaviour of trajectories can be characterised in terms of a critical rate. Associated with rate-induced tipping (where tracking of a branch of quasistatic attractors breaks down), we find a new phenomenon for attractors that are not simply equilibria: partial tipping of the pullback attractor where certain phases of the periodic attractor tip and others track the quasistatic attractor. For a specific model system with a parameter shift between two asymptotically autonomous systems with periodic attractors, we characterise thresholds of rate-induced tipping to partial and total tipping. We show these thresholds can be found in terms of certain periodic-to-periodic and periodic-to-equilibrium connections that we determine using Lin's method for an augmented system.
Investigation of proton spin relaxation in water with dispersed silicon nanoparticles for potential magnetic resonance imaging applications
Authors: Kargina Yu. V. , Gongalsky M. B. , Perepukhov A. M. , Gippius A. A. , Minnekhanov A. A. , Zvereva E. A. , Maximychev A. V. , Timoshenko V. Yu.
Published: March 2018

Porous and nonporous silicon (Si) nanoparticles (NPs) prepared by ball-milling of electrochemically etched porous Si layers and crystalline Si wafers were studied as potential agents for enhancement of the proton spin relaxation in aqueous media. While nonporous Si NPs did not significantly influence the spin relaxation, the porous ones resulted in strong shortening of the transverse relaxation times. In order to investigate an effect of the electron spin density in porous Si NPs on the proton spin relaxation, we use thermal annealing of the NPs in vacuum or in air. The transverse relaxation rate of about 0.5 l/(g s) was achieved for microporous Si NPs, which were thermally annealing in vacuum to obtain the electron spin density of the order of 1017 g−1. The transverse relaxation rate was found to be almost proportional to the concentration of porous Si NPs in the range from 0.1 to 20 g/l. The obtained results are discussed in view of possible biomedical applications of Si NPs as contrast agents for magnetic resonance imaging.
High-efficiency optical terahertz modulation of aligned Ag nanowires on a Si substrate
Authors: Lee Gyuseok , Maeng Inhee , Kang Chul , Oh Myoung-Kyu , Kee Chul-Sik
Published: March 2018

High-efficiency optical modulation of a terahertz pulse transmitted through aligned silver nanowires on a silicon substrate is demonstrated. Without optical excitation, the terahertz pulses mostly pass through the silver nanowires. However, an optically excited sample significantly modulates the transmittance compared with an excited silicon substrate. The enhanced modulation efficiency is explained by the redistribution effect of photo-carriers due to the nanowires. The simple structure of metal nanowires on a semiconductor substrate could be useful in implementing optically tunable terahertz wave modulators.
Experiments and models of MHD jets and their relevance to astrophysics and solar physics
Authors: Bellan Paul M.
Published: March 2018

Magnetohydrodynamic (MHD)-driven jets involve poloidal and toroidal magnetic fields, finite pressure gradients, and unbalanced forces. The mechanism driving these jets is first discussed qualitatively by decomposing the magnetic force into a curvature and a gradient component. The mechanism is then considered quantitatively by consideration of all terms in the three components of the MHD equation of motion and in addition, the implications of Ampere's law, Faraday's law, the ideal Ohm's law, and the equation of continuity. The analysis shows that jets are self-collimating with the tip of the jet moving more slowly than the main column of the jet so there is a continuous stagnation near the tip in the jet frame. Experiments supporting these conclusions are discussed and it is shown how this mechanism relates to jets in astrophysical and solar corona contexts.
Deep level defects in Ge-doped (010) β-Ga2O3 layers grown by plasma-assisted molecular beam epitaxy
Authors: Farzana Esmat , Ahmadi Elaheh , Speck James S. , Arehart Aaron R. , Ringel Steven A.
Published: March 2018

Deep level defects were characterized in Ge-doped (010) β-Ga2O3 layers grown by plasma-assisted molecular beam epitaxy (PAMBE) using deep level optical spectroscopy (DLOS) and deep level transient (thermal) spectroscopy (DLTS) applied to Ni/β-Ga2O3:Ge (010) Schottky diodes that displayed Schottky barrier heights of 1.50 eV. DLOS revealed states at EC − 2.00 eV, EC − 3.25 eV, and EC − 4.37 eV with concentrations on the order of 1016 cm−3, and a lower concentration level at EC − 1.27 eV. In contrast to these states within the middle and lower parts of the bandgap probed by DLOS, DLTS measurements revealed much lower concentrations of states within the upper bandgap region at EC − 0.1 – 0.2 eV and EC − 0.98 eV. There was no evidence of the commonly observed trap state at ∼EC − 0.82 eV that has been reported to dominate the DLTS spectrum in substrate materials synthesized by melt-based growth methods such as edge defined film fed growth (EFG) and Czochralski methods [Zhang et al., Appl. Phys. Lett. 108, 052105 (2016) and Irmscher et al., J. Appl. Phys. 110, 063720 (2011)]. This strong sensitivity of defect incorporation on crystal growth method and conditions is unsurprising, which for PAMBE-grown β-Ga2O3:Ge manifests as a relatively “clean” upper part of the bandgap. However, the states at ∼EC − 0.98 eV, EC − 2.00 eV, and EC − 4.37 eV are reminiscent of similar findings from these earlier results on EFG-grown materials, suggesting that possible common sources might also be present irrespective of growth method.
A numerical study on the non-Boussinesq effect in the natural convection in horizontal annulus
Authors: Zhang Yu , Cao Yuhui
Published: March 2018

In the present study, the non-Boussinesq effect in the thermal convection in an air-filled horizontal concentric annulus is studied numerically by using the variable property-based lattice Boltzmann flux solver (VPLBFS), with the radial temperature difference ratio of 1.0, the radius ratio of 2.0, and the Rayleigh number in the range 104 ≤ Ra ≤ 106. Several solutions are obtained by using the standard form or simplified versions of the VPLBFS, including the real solution with the total variation in fluid properties considered, named as the variable property solution (VPS), the constant property solution (CPS) based on the Boussinesq approximation, the solution with variable dynamic viscosity (VVS), the solution based on the partial Boussinesq approximation (PBAS), the solution with variable thermal conductivity (VCS) and the solution with variable fluid density (VDS). The discrepancy between these solutions is analyzed to illuminate the influence of the non-Boussinesq effects induced by partial or total variation in fluid properties on flow instability behaviors and heat transfer characteristics. The present study reveals the complicated flow instability behavior under non-Boussinesq conditions and its tight association with heat transfer characteristics. Also, it demonstrates the necessity of considering the integral effect of the total variation in fluid properties and highlights the essential role of the fluid density variation.
Study of flow over object problems by a nodal discontinuous Galerkin-lattice Boltzmann method
Authors: Wu Jie , Shen Meng , Liu Chen
Published: March 2018

The flow over object problems are studied by a nodal discontinuous Galerkin-lattice Boltzmann method (NDG-LBM) in this work. Different from the standard lattice Boltzmann method, the current method applies the nodal discontinuous Galerkin method into the streaming process in LBM to solve the resultant pure convection equation, in which the spatial discretization is completed on unstructured grids and the low-storage explicit Runge-Kutta scheme is used for time marching. The present method then overcomes the disadvantage of standard LBM for depending on the uniform meshes. Moreover, the collision process in the LBM is completed by using the multiple-relaxation-time scheme. After the validation of the NDG-LBM by simulating the lid-driven cavity flow, the simulations of flows over a fixed circular cylinder, a stationary airfoil and rotating-stationary cylinders are performed. Good agreement of present results with previous results is achieved, which indicates that the current NDG-LBM is accurate and effective for flow over object problems.
Frequency and temperature dependent dielectric properties of TiO2-V2O5 nanocomposites
Authors: Ray Apurba , Roy Atanu , De Sayan , Chatterjee Souvik , Das Sachindranath
Published: March 2018

In this manuscript, we have reported the crystal structure, dielectric response, and transport phenomenon of TiO2-V2O5 nanocomposites. The nanocomposites were synthesized using a sol-gel technique having different molar ratios of Ti:V (10:10, 10:15, and 10:20). The phase composition and the morphology have been studied using X-ray diffraction and field emission scanning electron microscope, respectively. The impedance spectroscopy studies of the three samples over a wide range of temperature (50 K–300 K) have been extensively described using the internal barrier layer capacitor model. It is based on the contribution of domain and domain boundary, relaxations of the materials, which are the main crucial factors for the enhancement of the dielectric response. The frequency dependent ac conductivity of the ceramics strongly obeys the well-known Jonscher's power law, and it has been clearly explained using the theory of jump relaxation model. The temperature dependent bulk conductivity is fairly recognized to the variable-range hopping of localized polarons. The co-existence of mixed valence state of Ti ions (Ti3+ and Ti4+) in the sample significantly contributes to the change of dielectric property. The overall study of dielectric response explains that the dielectric constant and the dielectric loss are strongly dependent on temperature and frequency and decrease with an increase of frequency as well as temperature.
Gaussian field model for polar fluids as a function of density and polarization: Toward a model for water
Authors: Berthoumieux H.
Published: March 2018

This work is concerned with a simple model for a polar fluid, a Gaussian field model based on the excess density and on the polarization. It is a convenient framework to implement the dielectric properties of correlated liquids that stem from nanometric correlations between molecules. It allows us to study the effects of coupling terms between density and polarization on the structure of the fluid. Despite the simplicity of such a model, it can capture some interesting features of the response functions of water such as the quasi-resonant longitudinal dielectric susceptibility or the presence of two maxima in the structure factor. Explicit models of water generate high computational cost and implicit models sometimes fail to properly treat the electrostatic interactions. A Gaussian field theory could therefore be an interesting alternative to describe water.
Anomalous dynamic arrest of non-interacting spheres (“polymer”) diluted in a hard-sphere (“colloid”) liquid
Authors: Lázaro-Lázaro E. , Moreno-Razo J. A. , Medina-Noyola M.
Published: March 2018

Upon compression, the equilibrium hard-sphere liquid [pair potential uHS(r)] freezes at a packing fraction ϕf = 0.494 or, if crystallization is prevented, becomes metastable up to its glass transition at ϕg ≈ 0.58. Throughout the fluid regime (ϕ < ϕg), we are, thus, certain that this model liquid does not exhibit any form of kinetic arrest. If, however, a small portion of these spheres (packing fraction ϕ2 ≪ ϕ) happen to ignore each other [u22(r) = 0] but do not ignore the remaining “normal” hard spheres [u12(r) = u21(r) = u11(r) = uHS(r)], whose packing fraction is thus ϕ1 = ϕ − ϕ2, they run the risk of becoming dynamically arrested before they demix from the “normal” particles. This unexpected and counterintuitive scenario was first theoretically predicted and then confirmed by simulations.
Learning free energy landscapes using artificial neural networks
Authors: Sidky Hythem , Whitmer Jonathan K.
Published: March 2018

Existing adaptive bias techniques, which seek to estimate free energies and physical properties from molecular simulations, are limited by their reliance on fixed kernels or basis sets which hinder their ability to efficiently conform to varied free energy landscapes. Further, user-specified parameters are in general non-intuitive yet significantly affect the convergence rate and accuracy of the free energy estimate. Here we propose a novel method, wherein artificial neural networks (ANNs) are used to develop an adaptive biasing potential which learns free energy landscapes. We demonstrate that this method is capable of rapidly adapting to complex free energy landscapes and is not prone to boundary or oscillation problems. The method is made robust to hyperparameters and overfitting through Bayesian regularization which penalizes network weights and auto-regulates the number of effective parameters in the network. ANN sampling represents a promising innovative approach which can resolve complex free energy landscapes in less time than conventional approaches while requiring minimal user input.
Quantum mechanical tunneling in the automerization of cyclobutadiene
Authors: Schoonmaker R. , Lancaster T. , Clark S. J.
Published: March 2018

Cyclobutadiene has a four-membered carbon ring with two double bonds, but this highly strained molecular configuration is almost square and, via a coordinated motion, the nuclei quantum mechanically tunnels through the high-energy square state to a configuration equivalent to the initial configuration under a 90° rotation. This results in a square ground state, comprising a superposition of two molecular configurations, that is driven by quantum tunneling. Using a quantum mechanical model, and an effective nuclear potential from density functional theory, we calculate the vibrational energy spectrum and the accompanying wavefunctions. We use the wavefunctions to identify the motions of the molecule and detail how different motions can enhance or suppress the tunneling rate. This is relevant for kinematics of tunneling-driven reactions, and we discuss these implications. We are also able to provide a qualitative account of how the molecule will respond to an external perturbation and how this may enhance or suppress infra-red-active vibrational transitions.
Photodissociation dynamics in the first absorption band of pyrrole. II. Photofragment distributions for the 1A2(πσ*)←X̃1A1(ππ) transition
Authors: Picconi David , Grebenshchikov Sergy Yu.
Published: March 2018

The analysis of the total kinetic energy release (TKER) of the photofragments pyrrolyl + H-atom formed in the photodissociation of pyrrole in the low-lying state 1A2(πσ*) is presented. The TKER distributions contain complementary and often more precise information on the fragmentation process than the broad diffuse absorption spectra. The distributions are calculated quantum mechanically for the diabatic state 1A2(πσ*) either isolated or coupled to the ground electronic state at an exit channel conical intersection. The calculations use the novel ab initio quasi-diabatic potential energy matrix constructed in the work of Picconi and Grebenshchikov [J. Chem. Phys. 148, 104103 (2018)]. The approximate overlap integral-based adiabatic mapping approach is introduced with which the quantum mechanical TKER distributions can be efficiently and accurately reproduced. Finally, the calculated TKERs are compared with the experimental results. The main features of the measured vibrationally resolved distributions are reproduced, and the spectral peaks are assigned and interpreted in detail.
Controlling the electric charge of gold nanoplatelets on an insulator by field emission nc-AFM
Authors: Baris Bulent , Alchaar Mohanad , Prasad Janak , Gauthier Sébastien , Dujardin Erik , Martrou David
Published: March 2018

Charging of 2D Au nanoplatelets deposited on an insulating SiO2 substrate to or from the tip of a non-contact atomic force microscope (nc-AFM) is demonstrated. Charge transfer is controlled by monitoring the resonance frequency shift Δf(V) during the bias voltage ramp V applied to the tip-back electrode junction. The onset of charge transfer is revealed by a transition from a capacitive parabolic behavior to a constant Δf(V) region for both polarities. An analytical model, based on charging by electron field emission, shows that the field-emitted current saturates shortly after the onset of the charging, due to the limiting effect of the charge-induced rise of the Au platelet potential. The value of this current plateau depends only on the rate of the bias voltage ramp and on the value of the platelet/SiO2/back electrode capacitance. This analysis is confirmed by numerical simulations based on a virtual nc-AFM model that faithfully matches the experimental data. Our charging protocol could be used to tune the potential of the platelets at the single charge level.
An efficient solution to the decoherence enhanced trivial crossing problem in surface hopping
Authors: Bai Xin , Qiu Jing , Wang Linjun
Published: March 2018

We provide an in-depth investigation of the time interval convergence when both trivial crossing and decoherence corrections are applied to Tully’s fewest switches surface hopping (FSSH) algorithm. Using one force-based and one energy-based decoherence strategies as examples, we show decoherence corrections intrinsically enhance the trivial crossing problem. We propose a restricted decoherence (RD) strategy and incorporate it into the self-consistent (SC) fewest switches surface hopping algorithm [L. Wang and O. V. Prezhdo, J. Phys. Chem. Lett. 5, 713 (2014)]. The resulting SC-FSSH-RD approach is applied to general Hamiltonians with different electronic couplings and electron-phonon couplings to mimic charge transport in tens to hundreds of molecules. In all cases, SC-FSSH-RD allows us to use a large time interval of 0.1 fs for convergence and the simulation time is reduced by over one order of magnitude. Both the band and hopping mechanisms of charge transport have been captured perfectly. SC-FSSH-RD makes surface hops in the adiabatic representation and can be implemented in both diabatic and locally diabatic representations for wave function propagation. SC-FSSH-RD can potentially describe general nonadiabatic dynamics of electrons and excitons in organics and other materials.
Influence of dense plasma on the energy levels and transition properties in highly charged ions
Authors: Chen Zhan-Bin , Hu Hong-Wei , Ma Kun , Liu Xiao-Bin , Guo Xue-Ling , Li Shuang , Zhu Bo-Hong , Huang Lian , Wang Kai
Published: March 2018

The studies of the influence of plasma environments on the level structures and transition properties for highly charged ions are presented. For the relativistic treatment, we implemented the multiconfiguration Dirac-Fock method incorporating the ion sphere (IS) model potential, in which the plasma screening is taken into account as a modified interaction potential between the electron and the nucleus. For the nonrelativistic treatment, analytical solutions of the Schrödinger equation with two types of the IS screened potential are proposed. The Ritz variation method is used with hydrogenic wave function as a trial wave function that contains two unknown variational parameters. Bound energies are derived from an energy equation, and the variational parameters are obtained from the minimisation condition of the expectation value of the energy. Numerical results for hydrogen-like ions in dense plasmas are presented as examples. A detailed analysis of the influence of relativistic effects on the energy levels and transition properties is also reported. Our results are compared with available results in the literature showing a good quantitative agreement.
Thermally assisted nanosecond laser generation of ferric nanoparticles
Authors: Kurselis K. , Kozheshkurt V. , Kiyan R. , Chichkov B. , Sajti L.
Published: March 2018

A technique to increase nanosecond laser based production of ferric nanoparticles by elevating temperature of the iron target and controlling its surface exposure to oxygen is reported. High power near-infrared laser ablation of the iron target heated up to 600 °C enhances the particle generation efficiency by more than tenfold exceeding 6 μg/J. Temporal and thermal dependencies of the particle generation process indicate correlation of this enhancement with the oxidative processes that take place on the iron surface during the per spot interpulse delay. Nanoparticles, produced using the heat-assisted ablation technique, are examined using scanning electron and transmission electron microscopy confirming the presence of 1–100 nm nanoparticles with an exponential size distribution that contain multiple randomly oriented magnetite nanocrystallites. The described process enables the application of high power lasers and facilitates precise, uniform, and controllable direct deposition of ferric nanoparticle coatings at the industry-relevant rates.
Long-range fluctuations and multifractality in connectivity density time series of a wind speed monitoring network
Authors: Laib Mohamed , Telesca Luciano , Kanevski Mikhail
Published: March 2018

This paper studies the daily connectivity time series of a wind speed-monitoring network using multifractal detrended fluctuation analysis. It investigates the long-range fluctuation and multifractality in the residuals of the connectivity time series. Our findings reveal that the daily connectivity of the correlation-based network is persistent for any correlation threshold. Further, the multifractality degree is higher for larger absolute values of the correlation threshold.
High-efficiency water-loaded microwave antenna in ultra-high-frequency band
Authors: Gong Zilun , Bartone Chris , Yang Fuyi , Yao Jie
Published: March 2018

High-index dielectrics are widely used in microwave antennas to control the radiation characteristics. Liquid water, with a high dielectric index at microwave frequency, is an interesting material to achieving tunable functionalities. Here, we demonstrate a water-loaded microwave antenna system that has high loss-tolerance and wideband tunability enabled by fluidity. Our simulation and experimental results show that the resonance frequency can be effectively tuned by the size of loading water. Furthermore, the antenna systems with water loading can achieve high radiation efficiency (>90%) in the ultra-high-frequency (0.3–3 GHz) band. This work brings about opportunities in realistic tunable microwave antenna designs enabled by liquid.
Japan, the new “El Dorado” of solar PV?
Authors: Bermudez Veronica
Published: March 2018

Japan intends to increase the share of photovoltaic (PV) energy in its mix of electricity production from 4.5% today to 12% by 2030. However, as a result of Feed-in-Tariff (FIT) reductions and limited grid access for new projects, Japan's PV demand shrank by 23% year-over-year in 2016 and another 10% in 2017. Even so, in terms of the cost and pace of deployment, solar PV has grown much more quickly than expected in Japan, similar to what has occurred in other markets in the past (for example, the Spanish market between 2000 and 2008). Due to this fast growth, the generation cost of solar PV appears high in Japan compared with international benchmarks, something that can damage future market development.
Single-molecule peptide fingerprinting
Authors: van Ginkel Jetty , Filius Mike , Szczepaniak Malwina , Tulinski Pawel , Meyer Anne S. , Joo Chirlmin
Published: March 2018

Significance

Protein sequencing remains a challenge for small samples. A sensitive sequencing technology will create the opportunity for single-cell proteomics and real-time screening for on-site medical diagnostics. To resolve protein identity, we previously developed a computational algorithm that analyzes the ordered sequence of only two types of amino acids within a protein species. Through modification of a biological nanomachine, here, we developed single-molecule fluorescence technology to linearize protein molecules and to read signals from labeled amino acids in an ordered manner. This proof of concept of single-molecule fingerprinting will open the door to single-molecule protein sequencing and pave the road toward the development of a new, fast, and reliable diagnostic tool.
The preregistration revolution
Authors: Nosek Brian A. , Ebersole Charles R. , DeHaven Alexander C. , Mellor David T.
Published: March 2018

Progress in science relies in part on generating hypotheses with existing observations and testing hypotheses with new observations. This distinction between postdiction and prediction is appreciated conceptually but is not respected in practice. Mistaking generation of postdictions with testing of predictions reduces the credibility of research findings. However, ordinary biases in human reasoning, such as hindsight bias, make it hard to avoid this mistake. An effective solution is to define the research questions and analysis plan before observing the research outcomes—a process called preregistration. Preregistration distinguishes analyses and outcomes that result from predictions from those that result from postdictions. A variety of practical strategies are available to make the best possible use of preregistration in circumstances that fall short of the ideal application, such as when the data are preexisting. Services are now available for preregistration across all disciplines, facilitating a rapid increase in the practice. Widespread adoption of preregistration will increase distinctiveness between hypothesis generation and hypothesis testing and will improve the credibility of research findings.
Training replicable predictors in multiple studies
Authors: Patil Prasad , Parmigiani Giovanni
Published: March 2018

This article considers replicability of the performance of predictors across studies. We suggest a general approach to investigating this issue, based on ensembles of prediction models trained on different studies. We quantify how the common practice of training on a single study accounts in part for the observed challenges in replicability of prediction performance. We also investigate whether ensembles of predictors trained on multiple studies can be combined, using unique criteria, to design robust ensemble learners trained upfront to incorporate replicability into different contexts and populations.
Metastudies for robust tests of theory
Authors: Baribault Beth , Donkin Chris , Little Daniel R. , Trueblood Jennifer S. , Oravecz Zita , van Ravenzwaaij Don , White Corey N. , De Boeck Paul , Vandekerckhove Joachim
Published: March 2018

We describe and demonstrate an empirical strategy useful for discovering and replicating empirical effects in psychological science. The method involves the design of a metastudy, in which many independent experimental variables—that may be moderators of an empirical effect—are indiscriminately randomized. Radical randomization yields rich datasets that can be used to test the robustness of an empirical claim to some of the vagaries and idiosyncrasies of experimental protocols and enhances the generalizability of these claims. The strategy is made feasible by advances in hierarchical Bayesian modeling that allow for the pooling of information across unlike experiments and designs and is proposed here as a gold standard for replication research and exploratory research. The practical feasibility of the strategy is demonstrated with a replication of a study on subliminal priming.
Enhancing primary reports of randomized controlled trials: Three most common challenges and suggested solutions
Authors: Li Guowei , Bhatt Meha , Wang Mei , Mbuagbaw Lawrence , Samaan Zainab , Thabane Lehana
Published: March 2018

Evidence from a well-designed randomized controlled trial (RCT) is generally considered to be the gold standard that can inform clinical practice and guide decision-making. However, several deficiencies in the reporting of RCTs have frequently been identified, including incomplete, selective, and biased or inconsistent reporting. Such suboptimal reporting may lead to irreproducible results, substantial waste of resources, impaired study validity, erosion of public trust in science, and a high risk of research misconduct. In this article, we present an overview of the reporting of RCTs in the biomedical literature with a focus on the three most common reporting problems: (
i
) lack of adherence to reporting guidelines, (
ii
) inconsistencies between trial protocols or registrations and full reports, and (
iii
) inconsistencies between abstracts and their corresponding full reports. Unsatisfactory levels of adherence to guidelines and frequent inconsistencies between protocols or registrations and full reports, and between abstracts and full reports, were consistently found in various biomedical research fields. A variety of factors were found to be associated with these reporting challenges. Improved reporting can build public trust and credibility of science, save resources, and enhance the ethical integrity of research. Therefore, joint efforts from the various sectors of the biomedical community (researchers, journal editors and reviewers, educators, healthcare providers, and other research consumers) are needed to reduce and reverse the current suboptimal state of RCT reporting in the literature.
An empirical analysis of journal policy effectiveness for computational reproducibility
Authors: Stodden Victoria , Seiler Jennifer , Ma Zhaokun
Published: March 2018

A key component of scientific communication is sufficient information for other researchers in the field to reproduce published findings. For computational and data-enabled research, this has often been interpreted to mean making available the raw data from which results were generated, the computer code that generated the findings, and any additional information needed such as workflows and input parameters. Many journals are revising author guidelines to include data and code availability. This work evaluates the effectiveness of journal policy that requires the data and code necessary for reproducibility be made available postpublication by the authors upon request. We assess the effectiveness of such a policy by (
i
) requesting data and code from authors and (
ii
) attempting replication of the published findings. We chose a random sample of 204 scientific papers published in the journal
Science
after the implementation of their policy in February 2011. We found that we were able to obtain artifacts from 44% of our sample and were able to reproduce the findings for 26%. We find this policy—author remission of data and code postpublication upon request—an improvement over no policy, but currently insufficient for reproducibility.
CD96 expression determines the inflammatory potential of IL-9–producing Th9 cells
Authors: Stanko Katarina , Iwert Christina , Appelt Christine , Vogt Katrin , Schumann Julia , Strunk Franziska Janina , Ahrlich Stefanie , Schlickeiser Stephan , Romagnani Chiara , Jürchott Karsten , Meisel Christian , Willimsky Gerald , Kühl Anja A. , Sawitzki Birgit
Published: March 2018

Significance

T helper type (Th) 9 cells demonstrate both pro- and antiinflammatory properties, pointing to a functional heterogeneity not examined so far. Applying single cell gene expression analysis of alloreactive Th9 cells, we revealed the existence of two major subsets, CD96highand CD96lowTh9 cells, with strongly opposing inflammatory and, especially, colitis-inducing potential. Mechanistically, we found that CD96 controls cytokine and colitis-inducing potential of Th9 cells, providing strong evidence for an inhibitory role of CD96 in controlling CD4+T-cell effector functions. Thus, interfering with CD96-mediated immune inhibition would be a promising approach in preventing Th9-mediated diseases, such as ulcerative colitis, or reinforcement of Th9-mediated immune control of tumors and infections.
Substrate recognition and mechanism revealed by ligand-bound polyphosphate kinase 2 structures
Authors: Parnell Alice E. , Mordhorst Silja , Kemper Florian , Giurrandino Mariacarmela , Prince Josh P. , Schwarzer Nikola J. , Hofer Alexandre , Wohlwend Daniel , Jessen Henning J. , Gerhardt Stefan , Einsle Oliver , Oyston Petra C. F. , Andexer Jennifer N. , Roach Peter L.
Published: March 2018

Significance

Polyphosphate kinases (PPKs) are involved in many metabolic processes in bacteria, including pathogenic species. As these enzymes are not present in animals, they are a prime target for the development of novel antibiotics. The detailed knowledge of the mechanism of action and structure–function relationships of these enzymes is of utmost importance for the identification and design of new pharmaceutically active compounds and the rational improvement of lead structures. In addition, PPKs use inexpensive and stable polyphosphate as a phosphate donor and phosphorylate nucleoside 5′-mono- as well as 5′-diphosphates. This makes them of special interest for application in ATP regeneration systems, which can be efficiently coupled to ATP-consuming enzymes in environmentally friendly and sustainable biotechnological processes.