bluuebunny/crossref_metadata_2025 huggingface dataset:
miR-25 inhibits sepsis-induced cardiomyocyte apoptosis by targetting PTEN
Authors: Yao Yulong , Sun Fangyuan , Lei Ming
Published: February 2018

To investigate the regulatory mechanism of miR-25 in sepsis-induced cardiomyocyte apoptosis. Rats models of sepsis were established by cecal ligation and puncture (CLP). Lipopolysaccharide (LPS)-induced cardiomyocyte was used as an in vitro model of sepsis. The expressions of miR-25, tensin homolog deleted on chromosome 10 (PTEN), Toll-like receptors 4 (TLR4), and p-p65 were analyzed by quantitative real-time PCR (qRT-PCR) and Western blot, respectively. The levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were detected by ELISA. Cell apoptosis was detected by terminal deoxynucleotidyl transferase-mediated d-UTP nick end labeling (TUNEL) assay. The relationship between miR-25 and PTEN was measured by luciferase reporter assays. MiR-25 expression in serum of CLP rats and LPS-induced cardiomyocyte was decreased, while the contents of TNF-α and IL-6 were increased. Moreover, the expressions of PTEN, TLR4, and p-p65 in LPS-induced cardiomyocyte were significantly increased. Overexpression of miR-25 increased the survival rate of rats, inhibited LPS-increased cardiomyocyte apoptosis, reversed the increased expression of PTEN, TLR4, p-p65, TNF-α, and IL-6 induced by LPS. The luciferase assay demonstrated that PTEN was a target of miR-25. Additionally, pcDNA-PTEN reversed the inhibitory effect of miR-25 mimic on cardiomyocyte apoptosis, while TAK-242 (TLR-4 inhibitor) countered this effect. miR-25 reduced LPS-induced cardiomyocyte apoptosis by down-regulating PTEN/TLR4/NF-κB axis.
Quantification of hepatic perfusion and hepatocyte function with dynamic gadoxetic acid-enhanced MRI in patients with chronic liver disease
Authors: Leporq Benjamin , Daire Jean-Luc , Pastor Catherine M. , Deltenre Pierre , Sempoux Christine , Schmidt Sabine , Van Beers Bernard E.
Published: February 2018

The purpose of the present study was to develop and perform initial validation of dynamic MRI enhanced with gadoxetic acid as hepatobiliary contrast agent to quantify hepatic perfusion and hepatocyte function in patients with chronic liver disease. Free-breathing, dynamic gadoxetic acid-enhanced MRI was performed at 3.0 T using a 3D time-resolved angiography sequence with stochastic trajectories during 38 min. A dual-input three-compartment model was developed to derive hepatic perfusion and hepatocyte function parameters. Method feasibility was assessed in 23 patients with biopsy-proven chronic liver disease. Parameter analysis could be performed in 21 patients (91%). The hepatocyte function parameters were more discriminant than the perfusion parameters to differentiate between patients with minimal fibrosis (METAVIR F0–F1), intermediate fibrosis (F2–F3) and cirrhosis (F4). The areas under the receiver operating characteristic curves (ROCs) to diagnose significant fibrosis (METAVIR F ≥ 2) were: 0.95 (95% CI: 0.87–1; P<0.001) for biliary efflux, 0.88 (95% CI: 0.73–1; P<0.01) for sinusoidal backflux, 0.81 (95% CI: 0.61–1; P<0.05) for hepatocyte uptake fraction and 0.75 (95% CI: 0.54–1; P<0.05) for hepatic perfusion index (HPI), respectively. These initial results in patients with chronic liver diseases show that simultaneous quantification of hepatic perfusion and hepatocyte function is feasible with free breathing dynamic gadoxetic acid-enhanced MRI. Hepatocyte function parameters may be relevant to assess liver fibrosis severity.
Reading Behind the Lines: The Factors Affecting the Text Reception Threshold in Hearing Aid Users
Authors: Zekveld Adriana A. , Pronk Marieke , Danielsson Henrik , Rönnberg Jerker
Published: February 2018

Purpose

The visual Text Reception Threshold (TRT) test (Zekveld et al., 2007) has been designed to assess modality-general factors relevant for speech perception in noise. In the last decade, the test has been adopted in audiology labs worldwide. The 1st aim of this study was to examine which factors best predict interindividual differences in the TRT. Second, we aimed to assess the relationships between the TRT and the speech reception thresholds (SRTs) estimated in various conditions.

Method

First, we reviewed studies reporting relationships between the TRT and the auditory and/or cognitive factors and formulated specific hypotheses regarding the TRT predictors. These hypotheses were tested using a prediction model applied to a rich data set of 180 hearing aid users. In separate association models, we tested the relationships between the TRT and the various SRTs and subjective hearing difficulties, while taking into account potential confounding variables.

Results

The results of the prediction model indicate that the TRT is predicted by the ability to fill in missing words in incomplete sentences, by lexical access speed, and by working memory capacity. Furthermore, in line with previous studies, a moderate association between higher age, poorer pure-tone hearing acuity, and poorer TRTs was observed. Better TRTs were associated with better SRTs for the correct perception of 50% of Hagerman matrix sentences in a 4-talker babble, as well as with better subjective ratings of speech perception. Age and pure-tone hearing thresholds significantly confounded these associations. The associations of the TRT with SRTs estimated in other conditions and with subjective qualities of hearing were not statistically significant when adjusting for age and pure-tone average.

Conclusions

We conclude that the abilities tapped into by the TRT test include processes relevant for speeded lexical decision making when completing partly masked sentences and that these processes require working memory capacity. Furthermore, the TRT is associated with the SRT of hearing aid users as estimated in a challenging condition that includes informational masking and with experienced difficulties with speech perception in daily-life conditions. The current results underline the value of using the TRT test in studies involving speech perception and aid in the interpretation of findings acquired using the test.
Detection of multiple micro‐drones via cadence velocity diagram analysis
Authors: Zhang Wenyu , Li Gang
Published: February 2018

Many studies have demonstrated the capability of radar micro‐Doppler signature for classifying micro‐drones. However, most existing works on radar classification of drones are based on the assumption that the received signal is only reflected from a single drone. When multiple drones are present simultaneously, the existing methods of drone classification fail due to the superimposition of the micro‐Doppler features of multiple drones. In this Letter, a method for detection of multiple drones is proposed. First the time–frequency spectrogram is converted into the cadence‐velocity diagram (CVD), which expresses how the curves in the time‐frequency‐domain repeat. Then the cadence frequency spectrum (CFS), as the basis vector of the training data from each class, of the CVD is extracted. Finally, the K‐means classifier is used to recognise the component of multiple micro‐drones based on the CFS. The experimental results on real radar data demonstrate that the proposed method is capable of dealing with multiple drones with satisfactory classification accuracy.
Synthesis of thinned planar arrays with two‐fold redundancy for microwave interferometric radiometers
Authors: Hu Fei , Zhu Dong , Peng Xiaohui , Tang Peiwen
Published: February 2018

The synthesis of thinned planar arrays with two‐fold redundancy in microwave interferometric radiometers (MIRs) is discussed. Based on (double) difference bases, a deterministic method is proposed for constructing two‐fold redundancy planar arrays (TFRPAs). The resulting TFRPAs sample the spatial frequencies at least twice within a given baseline coverage, which contributes to the reliability of MIR systems. A comparative study with two typical TFRPAs (i.e. the open‐ended ‘Cross’ and the closed ‘’ array configurations) is carried out, concerning array sampling efficiency in the spatial frequency domain. The numerical examples are presented to demonstrate the effectiveness of the proposed synthesis method.
Sensor fusion‐based precise obstacle localisation for automatic parking systems
Authors: Suhr J.K. , Jung H.G.
Published: February 2018

A precise obstacle localisation method for automatic parking systems is proposed. The proposed method improves the obstacle localisation accuracy by fusing only the sensors already installed on mass‐produced vehicles. This method finds the initial obstacle location using ultrasonic sensors. On the basis of the initial obstacle location, it detects the obstacle's vertical outlines using images provided by an around view monitor system while the ego‐vehicle is moving. The sequentially detected vertical outlines are combined based on the ego‐vehicle positions estimated by built‐in motion sensors. Finally, the obstacle location is refined by calculating the intersection point of the combined vertical outlines. In experiments, the proposed method was quantitatively evaluated and outperformed the previous method.
Full‐order sliding mode control for finite‐time attitude tracking of rigid spacecraft
Authors: Song Zhuoyue , Duan Chao , Su Housheng , Hu Jinchang
Published: February 2018

This study addresses an attitude tracking problem for a rigid spacecraft with bounded external disturbances. Attitude dynamics of the rigid spacecraft is modelled by a unit quaternion for global representation. Based on this representation, a novel continuous controller is proposed based on the full‐order terminal sliding mode method. The finite‐time stability of the closed‐loop system is assured by Lyapunov and homogeneous finite‐time stability theorems. Moreover, the singularity term in the terminal sliding surface is compensated by an identical item in the feedback control law, and this makes the closed‐loop system trajectories converge to the equilibrium in finite‐time, and hence a high precision is obtained. Finally, simulation results are presented to illustrate the effectiveness of the proposed controller.
Static output‐feedback synchronisation of multi‐agent systems: a secure and unified approach
Authors: Modares Hamidreza , Moghadam Rohollah , Lewis Frank L. , Davoudi Ali
Published: February 2018

In this study, a unified distributed static output‐feedback (OPFB) control protocol is presented for multi‐agent systems. The proposed approach is unified in the sense that it is applicable to both homogeneous and heterogeneous multi‐agent systems. Despite its importance, distributed OPFB control design is not considered for heterogeneous systems in the literature. Moreover, as will be shown, existing static OPFB controllers for homogeneous systems are vulnerable to attacks on sensors and actuators. More precisely, it is shown that a compromised agent can make an intact agent turn away from the leader if there is a directed path of any length from the compromised agent to the intact agent. To overcome these shortcomings, a distributed OPFB controller is presented which is (i) applicable to both homogeneous and heterogeneous systems, and (ii) is resilient against attacks on sensors and actuators. The proposed framework prevents attacks on sensors and actuators from propagating across the network and, thus, guarantees synchronisation of intact agents to the leader. To further improve the resiliency and guarantee synchronisation of even compromised agents, a disturbance compensator is designed. A significant advantage of this approach is that no assumption on topological connectivity and the number of agents under attack is required.
Hierarchical optimisation strategy in microgrid based on the consensus of multi‐agent system
Authors: Hao Ran , Jiang Ziqing , Ai Qian , Yu Zhiwen , Zhu Yuchao
Published: February 2018

To improve the automation level of distributed generation, a hierarchical optimisation strategy is proposed in this study. The strategy consists of day‐ahead dispatch and scheduling implementation by power control. The energy management framework about the multi‐agent system is also designed. Given the collaborative gaming process between microgrid and distributed network, a day‐ahead dispatch is used to minimise the general expenses. Moreover, considering security constraints, the secondary control strategy is proposed to realise the precise control of the active power, which is adaptive to voltage inconsistency. Besides, the consensus algorithm is utilised to trace the dispatch target of tie‐line power by monitoring power deviation at the point of common coupling. Finally, a series of simulation verifies the effectiveness of the method proposed. The influence of communication delay is also discussed.
Application of universal neutral reactor in shunt compensated transmission lines: feasibility study
Authors: Jafarian Peyman , Eskandari Hamid , Sanaye‐Pasand Majid
Published: February 2018

Single‐phase neutral reactors are used in shunt compensated transmission lines (TLs) to accelerate the extinction of the secondary arc through suppression of the arc current. Application of similar shunt reactors with the same capacities is prevalent in the transmission systems. Using the traditional method, however, for each TL, a specially designed neutral reactor is needed that could be in some cases extremely large and practically infeasible. This study investigates the feasibility of application of a properly designed neutral reactor, which is independent of the line length. This solution only depends on the ratio of positive‐ and zero‐sequence capacitances of the line as well as the shunt reactor inductance. Accordingly, for all TLs at the same voltage level equipped with shunt reactors of the same capacities, the proposed neutral reactance would be almost identical which helps to minimise the cost and design complexity. Meanwhile, the required insulation level would be kept sufficiently small for any compensation degree. Based on the steady‐state analysis and time‐domain simulations conducted using the electromagnetic transient program, it is shown that for the majority of TLs, it is possible to extinguish the secondary arc within an acceptable short period of time by applying the proposed neutral reactor.
Low‐voltage ride through control strategy of virtual synchronous generator based on the analysis of excitation state
Authors: Shi Kai , Ye Haihan , Xu Peifeng , Zhao Dean , Jiao Long
Published: February 2018

Virtual synchronous generator (VSG) possesses the advantage of friendly interaction with power grid by simulating synchronous generator characteristics. However, its low‐voltage ride through (LVRT) capability is insufficient. The excessive output current of VSG easily causes wind turbines to break away from the power grid, which will exacerbate the negative impact of grid fault. Thus, a new LVRT control strategy is proposed based on the analysis of excitation state for VSG. The droop characteristic, reactive power loop and active power loop of the VSG are improved, respectively, by specifically analysing the response characteristics of VSG. Moreover, the additional current loop is redesigned to assist the system operating in the under excitation state and suppress unbalanced currents without changing the original VSG characteristics. Furthermore, a new orientation method is adopted to accelerate the transient process and achieve better transient performance. It is worth noting that the proposed control strategy does not need switch control algorithm with smooth handoff algorithm under grid fault, and it can deal with both symmetric and asymmetric grid voltage drop problems at the same time. The correctness and feasibility of proposed scheme are verified by rigorous theoretical deduction and complete simulation verification.
Open‐end transformer‐based power tap for interconnection of AC/DC micro‐grids
Authors: Liu Yang , Zheng Jiehui , Shi Kai , Jiang Lin , Ni Kai , Wu Qinghua
Published: February 2018

This study proposes an open‐end transformer‐based power tap (OETPT) for the interconnection of the alternating current sub‐grid and the direct current sub‐grid of a hybrid micro‐grid. Two topologies, topology‐A and topology‐B, were designed for OETPT, in which the primary or secondary windings of the transformer of OETPT are grounded, respectively. Steady‐state and dynamic models were developed for OETPT, based on which a vector control system was designed for the coordinated control of OETPT with topology‐A and topology‐B, respectively. OETPT achieves the decoupled control of the active and reactive powers. Simulation studies and experimental validations were undertaken to manifest the coordinated power flow control performance of OETPT with topology‐A and topology‐B, respectively.
Ideal current‐based distributed control to compensate line impedance in DC microgrid
Authors: Islam Shirazul , Agarwal Shyam , Shyam A.B. , Ingle Anoop , Thomas Soumya , Anand Sandeep , Sahoo Soumya Ranjan
Published: February 2018

To achieve proportional power sharing among similar sources in DC microgrid, droop controllers are used. However, due to interconnecting cable impedances, power shared by the sources deviate from their desired values. To alleviate this problem, techniques utilising shift in droop characteristics and/or modification in droop gain are suggested in literature. Methods which use both of them offer better performance due to higher degree of freedom in control. However, these methods utilise distributed proportional‐integral control, which leads to winding‐up phenomenon. To address this problem, a distributed secondary controller using full communication is proposed. The current of each source is shared with other sources using low‐bandwidth communication. Using this information, each source calculates the ideal value of current to be supplied, which is then used to update its droop gain. To improve the average system voltage, shifting of droop characteristics is incorporated. Detailed small signal model of the proposed controller is developed. Effect of communication delay on the performance of the proposed controller is analysed using the characteristic equation of the system. To evaluate the performance of the proposed scheme, detailed simulation studies are carried out. A scaled down laboratory prototype is developed to determine the viability of the proposed controller.
SE adjustment of planar mesh screen by fine‐tuning metal thickness
Authors: Corredores Yonathan , Castel Xavier , Besnier Philippe , Dupeyrat Cyril , Foutrel Patrice
Published: February 2018

The study presents the thickness effect of mesh metal films printed onto glass substrate on the shielding effectiveness (SE) of such transparent screens. Currently, standards in microelectronic technology use a metal film thickness of between ∼100 nm and few micrometres, depending on the available deposition and implementation techniques. This study demonstrates that the thickness of mesh metal films is a key parameter which needs to be adjusted precisely. A theoretical model based on SE, complex impedance and optical transparency has been developed for this purpose. At microwaves, a relevant selection of the metal thickness values from 0.1 to 2 µm changes the SE at low frequency (from 36 to 40 dB at 2 GHz, respectively) while maintaining it constantly at a higher frequency (close to 20 dB at 18 GHz). The optical transparency of such mesh screens is kept constant over the entire visible light spectrum (78%). Experimental data are in complete agreement with the theoretical values.
Existence for dislocation-free finite plasticity
Authors: Stefanelli Ulisse
Published: February 2018

This note addresses finite plasticity under the constraint that plastic deformations are compatible. In this case, the total elastoplastic deformation of the medium is decomposed asy=ye○yp, where the plastic deformationypis defined on the fixed reference configuration and the elastic deformationyeis a mapping from the varying intermediate configurationyp(Ω). Correspondingly, the energy of the medium features both Lagrangian (plastic, loads) and not Lagrangian contributions (elastic).

We present a variational formulation of the static elastoplastic problem in this setting and show that a solution is attained in a suitable class of admissible deformations. Possible extensions of the result, especially in the direction of quasistatic evolutions, are also discussed.
Foreword to the special issue dedicated to the sixteenth “Journées Montoises d’Informatique Théorique”
Authors: Charlier Émilie , Leroy Julien , Rigo Michel
Published: February 2018

This volume of Theoretical Informatics and Applications is dedicated to the sixteenth “Journées Montoises d’Informatique Théorique” (Mons Theoretical Computer Science Days).
Increased Total Hip Arthroplasty Utilization, Osteoarthritis Diagnoses, and Comorbidity Burden in Patients Younger Than the Age of 65 Years: National Inpatient Trends 1998 to 2013
Authors: Brigati David , Navale Suparna , Schiltz Nicholas , Bozic Kevin
Published: February 2018

Primary total hip arthroplasty (THA) in patients younger than the age of 65 years demands long-term success to minimize lifetime revision surgery risks. Age at implantation, etiology of arthrosis, and comorbidity burden all have associations with revision risk. This study uses Nationwide Inpatient Sample (NIS) data between 1998 and 2013 to (1) report the annual utilization of THA in patients age 18 to 99 years divided into age groups, (2) determine trends in primary diagnoses, and (3) explore Elixhauser comorbidity burden trends. The authors reviewed 5,174,020 THA cases from the NIS. Cases were divided into age groups: 18 to 24, 25 to 34, 35 to 44, 45 to 54, 55 to 64, and 65 to 99 years. The annual utilization rate, primary diagnoses, and average count of Elixhauser comorbidities were plotted. Mann–Kendall's nonparametric tests determined significance with p < 0.05. The mean utilization of primary THA in patients aged 18 to 64 years was 57 cases per 105 persons (cpp). The incidence of utilization increased rapidly in patients age 55 to 64 years (123–240 cpp, p < 0.001) and age 45 to 54 years (46–100 cpp, p < 0.001). The predominant diagnoses were osteoarthritis increasing from 65 to 83% (p < 0.001), avascular necrosis decreasing from 17 to 7% (p < 0.001), and trauma decreasing from 11 to 6% (p < 0.001). The average count of Elixhauser comorbidities increased in all age groups from a minimum of 58% (1.2–1.9, p < 0.001) in patients age 55 to 64 years to a maximum of 200% (0.4–1.2, p = 0.003) in patients age 18 to 24 years. Increases in primary THA utilization are occurring disproportionately among patients age 45 to 64 years. The trends in etiologies and comorbidities show mixed anticipated effects on the risks for revision. Increased osteoarthritis diagnoses may be favorable as the etiology with the longest relative implant survival. However, increasing comorbidities may unfavorably heighten the risks of revision. Primary THA utilization is increasing for patients younger than the age of 65 years with osteoarthritis and rising comorbidity burdens. Current national administrative databases add valuable insights to large THA trends, but lack the granularity to fully characterize the causes behind revisions of primary THA.
Complex Pelvic Reconstruction using Patient-Specific Instrumentation and a 3D-Printed Custom Implant following Tumor Resection
Authors: Hennessy David , Anderson Megan , Lozano-Calderón Santiago
Published: February 2018

Resection of a periacetabular sarcoma is a difficult surgical problem due to the complex bony and soft tissue anatomy. The challenge of pelvic tumor resection lies in achieving clear margins while also reconstructing the defect with a durable construct. Limb salvage surgery involving these types of tumors, as well as other tumors of the pelvis, has made great progress recently due to remarkable technological innovation in the field of computer-assisted surgery and custom implant design. In this study, the authors review the case of a 9-year-old child with an osteosarcoma arising from the proximal femur with local spread into the hip joint and a skip metastasis in the ipsilateral acetabulum. They undertook limb-sparing extra-articular resection of the sarcoma with a reconstruction consisting of a 3D-custom printed pelvic implant and a proximal femur extendible prosthesis. The resection of the pelvis was performed with patient-specific cutting guides, rather than computer-assisted navigation. The resection resulted in a clear margin and the patient has had no evidence of local recurrence. These patient-specific guides closely matched the planned resection in terms of orientation in the pelvis, which allowed for straightforward implantation of the custom prosthesis at the time of surgery. The result has been a durable reconstruction that has produced an excellent functional outcome for this patient.
Role of the boundary in feather bud formation on one-dimensional bioengineered skin
Authors: Ishida Kentaro , Mitsui Toshiyuki
Published: February 2018

The role of a boundary in pattern formation from a homogenous state in Turing's reaction–diffusion equations is important, particularly when the domain size is comparable to the pattern scale. Such experimental conditions may be achieved for in vitro regeneration of ectodermal appendages such as feathers, via reconstruction of embryonic single cells. This procedure can eliminate a predefined genetic map, such as the midline of chick feather bud formation, leaving uniformly distributed identical cells as a bioengineered skin. Here, the self-organizing nature of multiple feather bud formation was examined in bioengineered 1D-skin samples. Primal formation of feather buds occurred at a fixed length from the skin edge. This formation was numerically recapitulated by a standard two-component reaction-diffusion model, suggesting that the boundary effect caused this observation. The proper boundary conditions were nonstandard, either mixed Dirichlet–Neumann or partial-flux. In addition, the model implies imperfect or hindered bud formation as well as nearly equal distances between buds. In contrast, experimental observations indicated that the skin curvature, which was not included in our model, also strongly affected bud formation. Thus, bioengineered skin may provide an ideal template for modeling a self-organized process from a homogenous state. This study will examine the possible diffusion activities of activator or inhibitor molecular candidates and mechanical activities during cell aggregation, which will advance our understanding of skin appendage regeneration from pluripotent or embryonic stem cells.
Electroforming free controlled bipolar resistive switching in Al/CoFe2O4/FTO device with self-compliance effect
Authors: Munjal Sandeep , Khare Neeraj
Published: February 2018

Controlled bipolar resistive switching (BRS) has been observed in nanostructured CoFe2O4 (CFO) films using an Al (aluminum)/CoFe2O4/FTO (fluorine-doped tin oxide) device. The fabricated device shows electroforming-free uniform BRS with two clearly distinguished and stable resistance states without any application of compliance current, with a resistance ratio of the high resistance state (HRS) and the low resistance state (LRS) of >102. Small switching voltage (<1 volt) and lower current in both the resistance states confirm the fabrication of a low power consumption device. In the LRS, the conduction mechanism was found to be Ohmic in nature, while the high-resistance state (HRS/OFF state) was governed by the space charge-limited conduction mechanism, which indicates the presence of an interfacial layer with an imperfect microstructure near the top Al/CFO interface. The device shows nonvolatile behavior with good endurance properties, an acceptable resistance ratio, uniform resistive switching due to stable, less random filament formation/rupture, and a control over the resistive switching properties by choosing different stop voltages, which makes the device suitable for its application in future nonvolatile resistive random access memory.
A Hamilton–Jacobi theory for implicit differential systems
Authors: Esen Oğul , de León Manuel , Sardón Cristina
Published: February 2018

In this paper, we propose a geometric Hamilton-Jacobi theory for systems of implicit differential equations. In particular, we are interested in implicit Hamiltonian systems, described in terms of Lagrangian submanifolds of TT*Q generated by Morse families. The implicit character implies the nonexistence of a Hamiltonian function describing the dynamics. This fact is here amended by a generating family of Morse functions which plays the role of a Hamiltonian. A Hamilton–Jacobi equation is obtained with the aid of this generating family of functions. To conclude, we apply our results to singular Lagrangians by employing the construction of special symplectic structures.
Multidimensional effects on proton acceleration using high-power intense laser pulses
Authors: Xiao K. D. , Zhou C. T. , Jiang K. , Yang Y. C. , Li R. , Zhang H. , Qiao B. , Huang T. W. , Cao J. M. , Cai T. X. , Yu M. Y. , Ruan S. C. , He X. T.
Published: February 2018

Dimensional effects in particle-in-cell (PIC) simulation of target normal sheath acceleration (TNSA) of protons are considered. As the spatial divergence of the laser-accelerated hot sheath electrons and the resulting space-charge electric field on the target backside depend on the spatial dimension, the maximum energy of the accelerated protons obtained from three-dimensional (3D) simulations is usually much less than that from two-dimensional (2D) simulations. By closely examining the TNSA of protons in 2D and 3D PIC simulations, we deduce an empirical ratio between the maximum proton energies obtained from the 2D and 3D simulations. This ratio may be useful for estimating the maximum proton energy in realistic (3D) TNSA from the results of the corresponding 2D simulation. It is also shown that the scaling law also applies to TNSA from structured targets.
Enhancing relativistic electron beam propagation through the use of graded resistivity guides
Authors: Alraddadi R. A. B. , Robinson A. P. L. , Pasley J. , Woolsey N. C.
Published: February 2018

We show, using three dimensional hybrid particle-in-cell simulations, that fast electron transport is improved in a resistive guide when using a linear decreasing gradient in the resistivity between the guide and substrate. We observe increased heating-at-depth along the guide and significantly reduced heating inhomogeneity. These improvements result from an increase in the width of the collimating magnetic field, improving fast electron confinement and limiting the growth of magnetic fields in the interior of the guide.
Noninvasive estimation of assist pressure for direct mechanical ventricular actuation
Authors: An Dawei , Yang Ming , Gu Xiaotong , Meng Fan , Yang Tianyue , Lin Shujing
Published: February 2018

Direct mechanical ventricular actuation is effective to reestablish the ventricular function with non-blood contact. Due to the energy loss within the driveline of the direct cardiac compression device, it is necessary to acquire the accurate value of assist pressure acting on the heart surface. To avoid myocardial trauma induced by invasive sensors, the noninvasive estimation method is developed and the experimental device is designed to measure the sample data for fitting the estimation models. By examining the goodness of fit numerically and graphically, the polynomial model presents the best behavior among the four alternative models. Meanwhile, to verify the effect of the noninvasive estimation, the simplified lumped parameter model is utilized to calculate the pre-support and the post-support left ventricular pressure. Furthermore, by adjusting the driving pressure beyond the range of the sample data, the assist pressure is estimated with the similar waveform and the post-support left ventricular pressure approaches the value of the adult healthy heart, indicating the good generalization ability of the noninvasive estimation method.
Magnetic properties and structural characterization of layered (Cr0.5Mn0.5)2AuC synthesized by thermally induced substitutional reaction in (Cr0.5Mn0.5)2GaC
Authors: Lai Chung-Chuan , Tao Quanzheng , Fashandi Hossein , Wiedwald Ulf , Salikhov Ruslan , Farle Michael , Petruhins Andrejs , Lu Jun , Hultman Lars , Eklund Per , Rosen Johanna
Published: February 2018

The magnetic properties of the new phase (Cr0.5Mn0.5)2AuC are compared to the known MAX-phase (Cr0.5Mn0.5)2GaC, where the former was synthesized by thermally induced substitution reaction of Au for Ga in (Cr0.5Mn0.5)2GaC. The reaction introduced a lattice expansion of ∼3% along the c-axis, an enhancement of the coercive field from 30 mT to 140 mT, and a reduction of the Curie temperature and the saturation magnetization. Still, (Cr0.5Mn0.5)2AuC displays similar features in the magnetic field- and temperature-dependent magnetization curves as previously reported magnetic MAX phases, e.g., (Cr0.5Mn0.5)2GaC and (Mo0.5Mn0.5)2GaC. The work suggests a pathway for tuning the magnetic properties of MAX phases.
Combinatorial approach to the representation of the Schur-Weyl duality in one-dimensional spin systems
Authors: Jakubczyk Dorota , Jakubczyk Paweł
Published: February 2018

We propose combinatorial approach to the representation of Schur-Weyl duality in physical systems on the example of one-dimensional spin chains. Exploiting the Robinson-Schensted-Knuth algorithm, we perform decomposition of the dual group representations into irreducible representations in a fully combinatorial way. As representation space, we choose the Hilbert space of the spin chains, but this approach can be easily generalized to an arbitrary physical system where the Schur-Weyl duality works.
Efficient CH3NH3PbI3 perovskite/fullerene planar heterojunction hybrid solar cells with oxidized Ni/Au/Cu transparent electrode
Authors: Lai Wei-Chih , Lin Kun-Wei , Guo Tzung-Fang , Chen Peter , Liao Yuan-Yu
Published: February 2018

We demonstrated the performance of inverted CH3NH3PbI3 perovskite-based solar cells (SCs) with a thermally oxidized nickel/gold/copper (Ni/Au/Cu) trilayer transparent electrode. Oxidized Ni/Au/Cu is a high transparent layer and has less resistance than the oxidized Ni/Au layer. Like the oxidized Ni/Au layer, oxidized Ni and Cu in oxidized Ni/Au/Cu could perform as a hole transport layer of the perovskite-based SCs. It leads to improved perovskite SC performance on an open circuit voltage of 1.01 V, a short circuit current density of 14.36 mA/cm2, a fill factor of 76.7%, and a power conversion efficiency (η%) of 11.1%. The η% of perovskite SCs with oxidized Ni (10 nm)/Au (6 nm)/Cu (1 nm) improved by approximately 10% compared with that of perovskite SCs with oxidized Ni/Au.
Enhanced water collection through a periodic array of tiny holes in dropwise condensation
Authors: Song Kyungjun , Kim Gyeonghee , Oh Sunjong , Lim Hyuneui
Published: February 2018

This paper introduces a simple method of water collection by increasing the coalescence effects in dropwise condensation with the use of microscale holes. The tiny holes modified the surface free energy states of the droplets on the plate, yielding a surface free energy barrier between the flat solid surface and the holes. The spatial difference in the surface free energy of the droplets enabled the droplets to move toward the adjacent droplets, thus increasing the possibility of coalescence. The water collection experiments were performed using a Peltier-based cooling system at 2 °C inside a chamber at 30 °C and 70% humidity. The results demonstrated that the perforated plates without any additional treatment provided the water collection rate of up to 22.64 L/m2 day, which shows an increase of 30% compared to that demonstrated by the bare plate. By comparing the experimental results for the surface of filmwise condensation, it was proved that the dominant water collecting improvement results from the increased coalescence effects. This simple technique can enhance the performance of systems exposed to water condensation, including water collection, heat-transfer, and dehumidifying systems.
Precision measurement of the quantized anomalous Hall resistance at zero magnetic field
Authors: Götz Martin , Fijalkowski Kajetan M. , Pesel Eckart , Hartl Matthias , Schreyeck Steffen , Winnerlein Martin , Grauer Stefan , Scherer Hansjörg , Brunner Karl , Gould Charles , Ahlers Franz J. , Molenkamp Laurens W.
Published: February 2018

In the quantum anomalous Hall effect, the edge states of a ferromagnetically doped topological insulator exhibit quantized Hall resistance and dissipationless transport at zero magnetic field. Up to now, however, the resistance was experimentally assessed using standard transport measurement techniques which are difficult to trace to the von-Klitzing constant RK with high precision. Here, we present a metrologically comprehensive measurement, including a full uncertainty budget, of the resistance quantization of V-doped (Bi,Sb)2Te3 devices without the external magnetic field. For the deviation of the quantized anomalous Hall resistance from RK, we determined a value of 0.17 ± 0.25 ppm, the smallest and most precise value reported to date. This is a step towards realization of a practical zero-field quantum resistance standard which in combination with the Josephson effect could provide the universal quantum units standard in the future.
Charge transport and electron-hole asymmetry in low-mobility graphene/hexagonal boron nitride heterostructures
Authors: Li Jiayu , Lin Li , Huang Guang-Yao , Kang N. , Zhang Jincan , Peng Hailin , Liu Zhongfan , Xu H. Q.
Published: February 2018

Graphene/hexagonal boron nitride (G/h-BN) heterostructures offer an excellent platform for developing nanoelectronic devices and for exploring correlated states in graphene under modulation by a periodic superlattice potential. Here, we report on transport measurements of nearly 0°-twisted G/h-BN heterostructures. The heterostructures investigated are prepared by dry transfer and thermally annealing processes and are in the low mobility regime (approximately 3000 cm2 V−1 s−1 at 1.9 K). The replica Dirac spectra and Hofstadter butterfly spectra are observed on the hole transport side, but not on the electron transport side, of the heterostructures. We associate the observed electron-hole asymmetry with the presence of a large difference between the opened gaps in the conduction and valence bands and a strong enhancement in the interband contribution to the conductivity on the electron transport side in the low-mobility G/h-BN heterostructures. We also show that the gaps opened at the central Dirac point and the hole-branch secondary Dirac point are large, suggesting the presence of strong graphene-substrate interaction and electron-electron interaction in our G/h-BN heterostructures. Our results provide additional helpful insight into the transport mechanism in G/h-BN heterostructures.
Neoclassical transport benchmark of global full-f gyrokinetic simulation in stellarator configurations
Authors: Matsuoka Seikichi , Idomura Yasuhiro , Satake Shinsuke
Published: February 2018

A global full-f gyrokinetic simulation code, GT5D, is extended to incorporate stellarator equilibria, provided by a widely used three-dimensional equilibrium code, VMEC [S. P. Hirshman and O. Betancourt, J. Comput. Phys. 96, 99 (1991)]. An interface code is newly developed, in which the so-called VMEC coordinates are transformed into the coordinates of GT5D. The following benchmark calculations in a typical LHD equilibrium are carried out for the numerical verification of GT5D in stellarator configurations. First, zonal flow damping tests are performed, and good agreement in the residual levels with an analytical theory is confirmed. Second, the neoclassical transport and the ambipolar radial electric field computed by a global δf neoclassical transport code, FORTEC-3D [S. Satake et al., Plasma Fusion Res. 3, S1062 (2008)], are successfully reproduced.
Determination of the spin orbit coupling and crystal field splitting in wurtzite InP by polarization resolved photoluminescence
Authors: Chauvin Nicolas , Mavel Amaury , Jaffal Ali , Patriarche Gilles , Gendry Michel
Published: February 2018

Excitation photoluminescence spectroscopy is usually used to extract the crystal field splitting (ΔCR) and spin orbit coupling (ΔSO) parameters of wurtzite (Wz) InP nanowires (NWs). However, the equations expressing the valence band splitting are symmetric with respect to these two parameters, and a choice ΔCR > ΔSO or ΔCR < ΔSO has to be taken into account in order to assign the numerical values. To solve this issue, polarization resolved micro-photoluminescence was performed on vertically aligned and untapered Wz InP NWs grown on silicon. The experimental results combined with a theoretical model and finite difference time domain calculations allow us to conclude that ΔCR > ΔSO in Wz InP.
Numerical and experimental analysis of the sedimentation of spherical colloidal suspensions under centrifugal force
Authors: Antonopoulou Evangelia , Rohmann-Shaw Connor F. , Sykes Thomas C. , Cayre Olivier J. , Hunter Timothy N. , Jimack Peter K.
Published: February 2018

Understanding the sedimentation behaviour of colloidal suspensions is crucial in determining their stability. Since sedimentation rates are often very slow, centrifugation is used to expedite sedimentation experiments. The effect of centrifugal acceleration on sedimentation behaviour is not fully understood. Furthermore, in sedimentation models, interparticle interactions are usually omitted by using the hard-sphere assumption. This work proposes a one-dimensional model for sedimentation using an effective maximum volume fraction, with an extension for sedimentation under centrifugal force. A numerical implementation of the model using an adaptive finite difference solver is described. Experiments with silica suspensions are carried out using an analytical centrifuge. The model is shown to be a good fit with experimental data for 480 nm spherical silica, with the effects of centrifugation at 705 rpm studied. A conversion of data to Earth gravity conditions is proposed, which is shown to recover Earth gravity sedimentation rates well. This work suggests that the effective maximum volume fraction accurately captures interparticle interactions and provides insights into the effect of centrifugation on sedimentation.
Enhanced mobility in vertically scaled N-polar high-electron-mobility transistors using GaN/InGaN composite channels
Authors: Li Haoran , Wienecke Steven , Romanczyk Brian , Ahmadi Elaheh , Guidry Matthew , Zheng Xun , Keller Stacia , Mishra Umesh K.
Published: February 2018

A GaN/InGaN composite channel design for vertically scaled N-polar high-electron-mobility transistor (HEMT) structures is proposed and demonstrated by metal-organic chemical vapor deposition. In a conventional N-polar HEMT structure, as the channel thickness (tch) decreases, the sheet charge density (ns) decreases, the electric field in the channel increases, and the centroid of the two-dimensional electron gas (2DEG) moves towards the back-barrier/channel interface, resulting in stronger scattering and lower electron mobility (μ). In this study, a thin InGaN layer was introduced in-between the channel and the AlGaN cap to increase the 2DEG density and reduce the electric field in the channel and therefore increase the electron mobility. The dependence of μ on the InGaN thickness (tInGaN) and the indium composition (xIn) was investigated for different channel thicknesses. With optimized tInGaN and xIn, significant improvements in electron mobility were observed. For a 6 nm channel HEMT structure, the electron mobility increased from 606 to 1141 cm2/(V·s) when the 6 nm thick pure GaN channel was replaced by the 4 nm GaN/2 nm In0.1Ga0.9N composite channel.
Magnetic propulsion of microspheres at liquid-glass interfaces
Authors: Helgesen Geir
Published: February 2018

Bio-coated, magnetic microspheres have many applications in biotechnology and medical technology as a tool to separate and extract cells or molecules in a water solution by applying external strong magnetic field gradients. However, magnetic microspheres with or without attached cargo can also be separated in the liquid solution if they are exposed to alternating or rotating, relatively weak magnetic fields. Microspheres that have a higher density than the liquid will approach the bottom surface of the sample cell, and then a combination of viscous and surface frictional forces can propel the magnetic microspheres along the surface in a direction perpendicular to the axis of field rotation. Experiments demonstrating this type of magnetic propulsion are shown, and the forces active in the process are discussed. The motion of particles inside sample cells that were tilted relative to the horizontal direction was studied, and the variation of propulsion velocity as a function of tilt angle was used to find the values of different viscous and mechanical parameters of motion. Propulsion speeds of up to 5 μm/s were observed and were found to be caused by a partly rolling and partly slipping motion of rotating microspheres with a slipping coefficient near 0.6.
Multi-scale transport in the DIII-D ITER baseline scenario with direct electron heating and projection to ITER
Authors: Grierson B. A. , Staebler G. M. , Solomon W. M. , McKee G. R. , Holland C. , Austin M. , Marinoni A. , Schmitz L. , Pinsker R. I. ,   DIII-D Team
Published: February 2018

Multi-scale fluctuations measured by turbulence diagnostics spanning long and short wavelength spatial scales impact energy confinement and the scale-lengths of plasma kinetic profiles in the DIII-D ITER baseline scenario with direct electron heating. Contrasting discharge phases with ECH + neutral beam injection (NBI) and NBI only at similar rotation reveal higher energy confinement and lower fluctuations when only NBI heating is used. Modeling of the core transport with TGYRO using the TGLF turbulent transport model and NEO neoclassical transport reproduces the experimental profile changes upon application of direct electron heating and indicates that multi-scale transport mechanisms are responsible for changes in the temperature and density profiles. Intermediate and high-k fluctuations appear responsible for the enhanced electron thermal flux, and intermediate-k electron modes produce an inward particle pinch that increases the inverse density scale length. Projection to ITER is performed with TGLF and indicates a density profile that has a finite scale length due to intermediate-k electron modes at low collisionality and increases the fusion gain. For a range of E×B shear, the dominant mechanism that increases fusion performance is suppression of outward low-k particle flux and increased density peaking.
The influence of polarizability and charge transfer on specific ion effects in the dynamics of aqueous salt solutions
Authors: Nguyen Mary , Rick Steven W.
Published: February 2018

The diffusion rates for water molecules in salt solutions depend on the identity of the ions, as well as their concentration. Among the alkali metal ions, cesium and potassium increase and sodium strongly decreases the diffusion constant of water. The origin of the difference can be understood by examining the simulation results using different potential models. In this work, aqueous solutions of salts are simulated with a variety of models. Commonly used non-polarizable models, which otherwise reproduce many experimental properties, do not capture the trend in the diffusion constant, while models which include polarization and/or charge transfer interactions do. For the non-polarizable models, the diffusion constant decreases too strongly with salt concentration. The changes in the water diffusion constant with increasing salt concentration match the diffusion constant of the ion. The ion diffusion constant is dependent on the residence time for water in the ion solvation shell. The non-polarizable models over-estimate the residence time, relative to the translational diffusion constant and so tend to under-estimate the ion and water diffusion constants.