bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time-dependent methods for calculating thermal rate coefficients using flux correlation functions
Authors: Thachuk Mark , Schatz George C. 
Published: July 2002

In this paper we study numerical methods for calculating thermal rate coefficients using flux correlation functions, with the goal of determining optimal methods for producing values with a specified accuracy. In all cases we employ grid based methods for solving the time-dependent Schrödinger equation in one mathematical dimension for a simple barrier potential function. The solutions are used to determine the propagator matrix elements needed to evaluate the flux correlation functions. Within this framework, we examine (1) several time-dependent methods for propagating the wave packets, (2) several procedures for evaluating the action of the Hamiltonian on the wave function, (3) the choice of complex time contours for evaluating the rate coefficient expression, (4) alternatives for estimating the initial short-time evolution of the wave packet (which starts as a δ function), (5) quadrature methods for evaluating the spatial and time integrals appearing in the flux correlation function, and (6) special numerical strategies which can dramatically improve the accuracy of the calculation, particularly at low temperatures. We find that several methods yield rate coefficients accurate to 1% or 0.1% using about the same computational effort.
These include (a) split-operator time propagators combined with fast-Fourier-transform evaluations of the wave-function derivatives, and (b) the Chebyshev time propagator combined with either an eleventh-order finite-difference or fifth-order spline evaluation of the wave-function derivatives. These finite-difference and spline methods can also be used competitively with the split-operator approach provided that a Crank–Nicholson approximation is utilized in evaluating the action of the kinetic-energy propagator. It was also found that inaccuracies in estimating the initial short-time behavior of the wave function could limit the effectiveness of the more accurate methods. A multigrid approach based on the split-operator/Fourier transform method is developed for treating this, and provides results with sufficient accuracy. However, for some choices of grid parameters this initialization process determines the overall computational efficiency of the calculation, independent of the numerical efficiency of methods used after the initialization.
Power spectra as a diagnostic tool in probing statistical/nonstatistical behavior in unimolecular reactions
Authors: Chang Xiaoyen Y. , Sewell Thomas D. , Raff Lionel M. , Thompson Donald L. 
Published: July 2002

The possibility of utilizing different types of power spectra obtained from classical trajectories as a diagnostic tool to identify the presence of nonstatistical dynamics is explored by using the unimolecular bond-fission reactions of 1,2-difluoroethane and the 2-chloroethyl radical as test cases. In previous studies, the reaction rates for these systems were calculated by using a variational transition-state theory and classical trajectory methods. A comparison of the results showed that 1,2-difluoroethane is a nonstatistical system, while the 2-chloroethyl radical behaves statistically. Power spectra for these two systems have been generated under various conditions. The characteristics of these spectra are as follows: (1) The spectra for the 2-chloroethyl radical are always broader and more coupled to other modes than is the case for 1,2-difluoroethane. This is true even at very low levels of excitation. (2) When an internal energy near or above the dissociation threshold is initially partitioned into a local C–H stretching mode, the power spectra for 1,2-difluoroethane broaden somewhat, but discrete and somewhat isolated bands are still clearly evident.
In contrast, the analogous power spectra for the 2-chloroethyl radical exhibit a near complete absence of isolated bands. The general appearance of the spectrum suggests a very high level of mode-to-mode coupling, large intramolecular vibrational energy redistribution (IVR) rates, and global statistical behavior. (3) The appearance of the power spectrum for the 2-chloroethyl radical is unaltered regardless of whether the initial C–H excitation is in the CH2 or the CH2Cl group. This result also suggests statistical behavior. These results are interpreted to mean that power spectra may be used as a diagnostic tool to assess the statistical character of a system. The presence of a diffuse spectrum exhibiting a nearly complete loss of isolated structures indicates that the dissociation dynamics of the molecule will be well described by statistical theories. If, however, the power spectrum maintains its discrete, isolated character, as is the case for 1,2-difluoroethane, the opposite conclusion is suggested. Since power spectra are very easily computed, this diagnostic method may prove to be useful.
The role of surface corrugation in direct translationally activated dissociative adsorption
Authors: Xia Li-Qun , Engstrom J. R. 
Published: July 2002

Recent experimental results concerning reactive scattering in the hyperthermal kinetic energy regime can be described by energy scaling relationships Ei cosn θi, where n&lt;2, and Ei and θi are the incident kinetic energy and incident angle, respectively. Such power law scaling arguments are empirical, the results of which cannot easily be related to the fundamental parameters that describe the gas–surface interaction. We present a detailed and thorough analysis where the role of surface corrugation in determining the coupling between incident kinetic energy and incident angle in these translationally activated systems is considered explicitly. The key features of the analysis involve the assumption that the kinetic energy directed along the local surface normal (E⊥) controls the reaction probability (SR), and that by averaging this quantity over the unit cell, one obtains the appropriate energy scaling relationship. The major advantage associated with the proposed analysis is that one need not assume a functional form concerning how the reaction probability depends on kinetic energy, i.e., SR(E⊥).
Our analysis demonstrates that in the absence of shadowing, a single ‘‘universal’’ scaling function exists EiΘ(θi), which is given by the expression Θ(θi)=(1−Δ)cos2 θi+3Δ sin2 θi, where Δ is a corrugation parameter (0≤Δ≤1) and only in-plane corrugation has been considered. Shadowing plays an important role at sufficiently large corrugation amplitudes and/or sufficiently large angles of incidence. Specifically, it leads to more complex scaling functions, which depend on the shape of the surface corrugation, for which several examples have been considered. Both local minima and local maxima can be observed for Θ(θi) as a function of incident angle. Two factors can introduce errors in the analysis, namely, the presence of nonlinearities, and the effects of nonuniform surface reactivity, and illustrative examples are considered. The model accounts well for recent experimental results concerning the dissociation of silanes on silicon surfaces, and alkanes on a corrugated platinum surface. It is probable that other systems involving reactive scattering in the hyperthermal kinetic energy regime may also be described well employing this analysis.
High resolution spectroscopy of the He79Br2 van der Waals molecule: An experimental and theoretical study
Authors: Jahn Douglas G. , Barney William S. , Cabalo Jerry , Clement Simon G. , Rohrbacher Andreas , Slotterback Timothy J. , Williams Jason , Janda Kenneth C. , Halberstadt Nadine 
Published: July 2002

The structure, dissociation dynamics, and intermolecular potential energy surfaces of the He79Br2 van der Waals molecule have been studied using high resolution, two color, pump–probe laser induced fluorescence spectroscopy and three dimensional quantum mechanical calculations. A conical nozzle produces higher centerline cluster densities than a standard nozzle, and allows data collection further downstream from the nozzle. This yields improved signal to noise ratios and lower Doppler widths. He79Br2 is found to have a T-shaped average geometry with He to Br2 center-of-mass distances of 3.98 Å and 4.11 Å for the X and B states, respectively, somewhat longer than previously reported. Spectra were also obtained for excitation to excited bending levels of the van der Waals coordinate. However, these spectra have yet to be rotationally assigned. Vibrational predissociation line widths for the B state of He79Br2 have been measured for three new vibrational levels and range from 0.036 cm−1 for B, v′=8 to 0.062 cm−1 for B, v′=12.
These values are somewhat larger than was expected based on previous HeBr2 linewidth measurements for higher vibrational levels. Forms for the potential energy surface that have previously been used to simulate the spectra of HeCl2 have been applied to the HeBr2 data. For the HeBr2 X state, two potentials are tested. First, a slightly anisotropic, one center Morse–Spline–van der Waals potential with angle dependent parameters is used. Second a much more anisotropic potential obtained from ab initio calculations is tested. The more anisotropic potential produces a significantly better fit to the data. The B state potential is constructed using Morse atom–atom potentials for the short range part of the He–Br interaction. This simple potential is sufficient to fit the main excitation band, but does not yield a fit to spectra involving vibrationally excited van der Waals modes.
Z extensions to the RHMAPPER package.
Authors: Soderlund C , Lau T , Deloukas P 
Published: July 2002

Abstract
MOTIVATION: Extensions have been made to the RHMAPPER-1.1 package. One set of extensions computes the totally linked markers and uses the results as input to the salient RHMAPPER functions. The second set of extensions uses TKperl to provide an interactive interface for ease of querying the database and displaying maps. AVAILABILITY: The extensions can be obtained via ftp.sanger.ac.uk/pub/zmapper. Supplementary information: The User's Manual can be viewed from http:/www.sanger.ac.uk/Users/cari/Z.shtml. CONTACT: cari@sanger.ac.uk
Solution structure of a K+‐channel blocker from the scorpion Tityus cambridgei
Authors: Wang Iren , Wu Shih‐Hsiung , Chang Hsueh‐Kai , Shieh Ru‐Chi , Yu Hui‐Ming , Chen Chinpan 
Published: July 2002

AbstractA new K+‐channel blocking peptide identified from the scorpion venom of Tityus cambridgei (Tc1) is composed of 23 amino acid residues linked with three disulfide bridges. Tc1 is the shortest known toxin from scorpion venom that recognizes the Shaker B K+ channels and the voltage‐dependent K+ channels in the brain. Synthetic Tc1 was produced using solid‐phase synthesis, and its activity was found to be the same as that of native Tc1. The pairings of three disulfide bridges in the synthetic Tc1 were identified by NMR experiments. The NMR solution structures of Tc1 were determined by simulated annealing and energy‐minimization calculations using the X‐PLOR program. The results showed that Tc1 contains an α‐helix and a 310‐helix at N‐terminal Gly4–Lys10 and a double‐stranded β‐sheet at Gly13–Ile16 and Arg19–Tyr23, with a type I′ β‐turn at Asn17–Gly18. Superposition of each structure with the best structure yielded an average root mean square deviation of 0.26 ± 0.05 Å for the backbone atoms and of 1.40 ± 0.23 Å for heavy atoms in residues 2 to 23. The three‐dimensional structure of Tc1 was compared with two structurally and functionally related scorpion toxins, charybdotoxin (ChTx) and noxiustoxin (NTx). We concluded that the C‐terminal structure is the most important region for the blocking activity of voltage‐gated (Kv‐type) channels for scorpion K+‐channel blockers. We also found that some of the residues in the larger scorpion K+‐channel blockers (31 to 40 amino acids) are not involved in K+‐channel blocking activity.
Fluorescence correlation spectroscopy as a method for assessment of interactions between phage displaying antibodies and soluble antigen
Authors: Lagerkvist Ann Catrin , Földes‐Papp Zeno , Persson Mats A.A. , Rigler Rudolf 
Published: July 2002

AbstractPhage display is widely used for expression of combinatorial libraries, not least for protein engineering purposes. Precise selection at the single molecule level will provide an improved tool for generating proteins with complex and distinct properties from large molecular libraries. To establish such an improved selection system, we here report the detection of specific interactions between phage with displayed antibody fragments and fluorescently labeled soluble antigen based on Fluorescence Correlation Spectroscopy (FCS). Our novel strategy comprises the use of two separate fluorochromes for detection of the phage–antigen complex, either with labeled antiphage antibody or using a labeled antigen. As a model system, we studied a human monoclonal antibody to the hepatitis‐C virus (HCV) envelope protein E2 and its cognate antigen (rE2 or rE1/E2). We could thus assess the specific interactions and determine the fraction of specific versus background phage (26% specific phage). Aggregation of these particular antigens made it difficult to reliably utilize the full potential of cross‐correlation studies using the two labels simultaneously. However, with true monomeric proteins, this will certainly be possible, offering a great advantage in a safer and highly specific detection system.
Variation between Antiferromagnetism and Ferrimagnetism in NiPS3 by Electron Doping
Authors: Mi Mengjuan , Zheng Xingwen , Wang Shilei , Zhou Yang , Yu Lixuan , Xiao Han , Song Houning , Shen Bing , Li Fangsen , Bai Lihui , Chen Yanxue , Wang Shanpeng , Liu Xiaohui , Wang Yilin 
Published: May 2022

AbstractTo electrically control magnetic properties of material is promising toward spintronic applications, where the investigation of carrier doping effects on antiferromagnetic (AFM) materials remains challenging due to their zero net magnetization. In this work, the authors find electron doping dependent variation of magnetic orders of a 2D AFM insulator NiPS3, where doping concentration is tuned by intercalating various organic cations into the van der Waals gaps of NiPS3 without introduction of defects and impurity phases. The doped NiPS3 shows an AFM‐ferrimagnetic (FIM) transition at a doping level of 0.2–0.5 electrons/cell and a FIM‐AFM transition at a doping level of ≥0.6 electrons/cell. The authors propose that the found phenomenon is due to competition between Stoner exchange dominated inter‐chain ferromagnetic order and super‐exchange dominated AFM order at different doping level. The studies provide a viable way to exploit correlation between electronic structures and magnetic properties of 2D magnetic materials for realization of magnetoelectric effect.
Donor Functionalization Tuning the N‐Type Performance of Donor–Acceptor Copolymers for Aqueous‐Based Electrochemical Devices
Authors: Cong Shengyu , Chen Junxin , Wang Lewen , Lan Liuyuan , Wang Yazhou , Dai Haojie , Liao Hailiang , Zhou Yecheng , Yu Yaping , Duan Jiayao , Li Zhengke , McCulloch Iain , Yue Wan 
Published: May 2022

AbstractIn this work, three n‐type donor–acceptor copolymers consisting of glycolated naphthalene tetracarboxylicdiimide (gNDI) coupled with variable donating companion moieties are reported. Using 2,2′‐bis(3,4‐ethylenedioxy)bithiophene, 2,​2′‐​bithiophene, 3,3′‐difluoro‐2,2′‐bithiophene (FBT), the donating strength of the donor units is systematically functionalized. These copolymers are used as a platform for aqueous‐based electrochemical devices, including energy‐storage devices, electrochromic devices (ECDs), and organic electrochemical transistors (OECTs). It is found that the electrochemical redox stability and electron mobility of copolymers are significantly improved via weakening the electron‐donating strength of donor units. gNDI coupling with FBT (gNDI‐FBT) exhibits a charge‐storage capacity exceeding 190 Fg−1, which is the highest value reported to date for NDI‐based polymer electrodes in aqueous media. For ECDs, gNDI‐FBT remains 100% of initial electrochromism contrast (∆%T = 20%) up to 1200 s. In addition, gNDI‐FBT outperforms its two analogs in OECTs, including lower threshold voltage (0.19 V), faster response time (45.5 ms), and higher volumetric capacitance (197 F cm−3). Moreover, gNDI‐FBT with fluorine atoms leads to the bipolarons delocalization along the polymer backbone and favorable molecular packing for ion–electron transport. Through such weak donor functionalization strategy, this work provides ways for n‐type copolymers tuning to access desirable performance metrics in optical, electrochemical, and bioelectronic applications.
Quasiplanar Heterojunction All‐Polymer Solar Cells: A Dual Approach to Stability
Authors: Cao Congcong , Wang Hengtao , Qiu Dongsheng , Zhao Tingxing , Zhu Yulin , Lai Xue , Pu Mingrui , Li Yan , Li Heng , Chen Hui , He Feng 
Published: May 2022

AbstractIn addition to efficiency, stability is another key factor in developing organic solar cells. The quasiplanar heterojunction (Q‐PHJ) structure, combining two pure layers as major and tiny nanoscale bulk heterojunction (BHJ) at interface, demonstrates superior device stability compared with BHJ devices. In this contribution, the polymer donor, PBQx‐H‐TF, and configurationally defined polymeric acceptor, PBTIC‐γ‐TSe are synthesized and used to fabricate bilayer devices by orthogonal solvents, the corresponding Q‐PHJ all‐polymer solar cells (all‐PSCs) deliver reliable stability with high efficiency. An encouraging PCE of 15.77% is achieved, which is the highest one among Q‐PHJ all‐PSCs with real‐bilayer structure. There is a major improvement over the 13.91% PCE in the BHJ device, and the carrier transport performance is improved substantially following the reduction of recombination in the Q‐PHJ all‐PSCs. Benefiting from the bilayer morphology, the stability of Q‐PHJ all‐PSCs has been greatly enhanced over that of the BHJ devices. The charge recombination process is also more serious in the aging BHJ compared with the aging Q‐PHJ all‐PSCs. This work inspires the application of Q‐PHJ in the preparation of high‐efficient all‐PSCs, but also provides guidance on the improvement of device stability from a dual approach of material and device engineering aspects.
Photoinduced Contraction Fibers and Photoswitchable Adhesives Generated by Stretchable Supramolecular Gel
Authors: Li Jinjie , Wang He , Liu Binxiu , Chen Jianzhuang , Gu Jinlou , Lin Shaoliang 
Published: May 2022

AbstractDynamically crosslinked supramolecular networks have emerged in the last decades as extremely stretchable and self‐healing materials thanks to the energy dissipation in weak and reversible interactions. Stretchable materials with tunable properties represent an effort to develop a charming class of smart devices. Once stretched, however, these materials’ properties are usually fixed due to strain‐induced crystallization (SIC), hindering their practical applications. Here, photoinduced contraction smart fibers and photoswitchable adhesives are generated from a dynamic supramolecular gel network, the SIC in which can be disrupted by UV irradiation to release the prestored strain energy. The dynamic sliding of azo‐bridged bipedal host molecules along the polymer chains renders the extreme stretchability of supramolecular gel under stretching forces. The oriented crystalline microdomains or crystallites through SIC upon stretching serve as physical crosslinks to store the contractile energy of fibers and improve the adhesion force of adhesives, and then are disoriented induced by trans‐to‐cis isomerization of azobenzene mesogens to release the prestored strain energy, resulting in such contraction of fibers and reduction of adhesion strength of adhesives. This work provides inspiration for exploring the structure–property relationship of supramolecular networks and transforming their clear potential to fabricate more remarkable synthetic smart materials.
Wirelessly Powered 3D Printed Hierarchical Biohybrid Robots with Multiscale Mechanical Properties
Authors: Tetsuka Hiroyuki , Pirrami Lorenzo , Wang Ting , Demarchi Danilo , Shin Su Ryon 
Published: May 2022

AbstractThe integration of flexible and stretchable electronics into biohybrid soft robotics can spur the development of new approaches for fabricating biohybrid soft machines, thus enabling a wide variety of innovative applications. Inspired by flexible and stretchable wireless‐based bioelectronic devices, untethered biohybrid soft robots are developed that can execute swimming motions, which are remotely controllable by the wireless transmission of electrical power into a cell simulator. To this end, wirelessly‐powered, stretchable, and lightweight cell stimulators are designed to be integrated into muscle bodies without impeding the robots’ underwater swimming abilities. The cell stimulators function by generating controlled monophasic pulses of up to ≈9 V in biological environments. By differentiating induced pluripotent stem cell‐derived cardiomyocytes directly on the cell stimulators using an accordion‐inspired, three‐dimensional (3D) printing construct, the native myofiber architecture are replicated with comparable robustness and enhanced contractibility. Wirelessly modulated electrical frequencies enables the control of speed and direction of the biohybrid soft robots. A maximum locomotion speed of ≈580 µm s−1 is achieved in robots possessing a large body size by adjusting the pacing frequency. This innovative approach will provide a platform for building untethered and biohybrid systems for various biomedical applications.
A Flexible, Transparent, Ultralow Detection Limit Capacitive Pressure Sensor
Authors: Zammali Marouen , Liu Sijun , Yu Wei 
Published: May 2022

AbstractThe capacitive pressure sensor (CPS) with low detection limit and high sensitivity is crucial for the future development of electronic skins. Although introducing surface microstructures on dielectric layer may improve the sensitivity of CPS in some extent, it leads to a limited pressure‐response range due to the poor structural compressibility. Moreover, such microstructures deteriorate the transparency and flexibility of the final sensor and require costly microfabrication methods. Herein, a low‐cost high performance pressure sensor is developed by integrating the high permittivity and soft dielectric gel with the mechanically comparable ionic conductor. The device shows an unprecedented detection limit of 0.2 Pa, a high sensitivity of 4.2 kPa−1 in the low‐pressure regime of <1.2 kPa, and a fast response time of 13 ms. This ultralow detection limit allows for the efficient and accurate detection of weak pressure signals from acoustic waves to pulse and air‐flow, exhibiting promising application potentials in voice recognition, screening of cardiovascular diseases, and diagnosis of gas leakage. Furthermore, the combination of ionic conductor and dielectric gel also endows the capacitive pressure sensor with remarkable transparency, mechanical stability, and durability even under extreme environments. This study proposes a novel perspective for development of flexible and transparent electronic skins.