bluuebunny/crossref_metadata_2025 huggingface dataset:
Multifunctional semiconducting polymer dots for imaging, detection, and photo-killing of bacteria
Authors: Wan Yi , Zheng Laibao , Sun Yan , Zhang Dun
Published: May 2014

Multifunctional semiconducting polymer dots, which can detect bacteria with high sensitivity and selectively kill pathogens.
Self-assembly of guanosine and deoxy-guanosine into hydrogels: monovalent cation guided modulation of gelation, morphology and self-healing properties
Authors: Adhikari Bimalendu , Shah Afzal , Kraatz Heinz-Bernhard
Published: May 2014

The gelation, morphological, fluorescence and thixotropic properties of the purine nucleoside based hydrogels were found to modulate with metal ions.
A hybrid resist hemispherical-pit array layer for light trapping in thin film silicon solar cells via UV nanoimprint lithography
Authors: Wangyang Peihua , Gan Yanchang , Wang Qingkang , Jiang Xuesong
Published: May 2014

Micromorph tandem solar cells coated with a HP array layer were fabricated by UV NIL. The HP array layer could reduce the average reflectance of the solar cells from 7.7% to 1.8%. And a relative improvement of efficiency of up to 4.1% is observed as compared to the bare solar cells.
Fluorine-free blue phosphorescent emitters for efficient phosphorescent organic light emitting diodes
Authors: Lee Jieun , Oh Hankook , Kim Jinho , Park Ki-Min , Yook Kyoung Soo , Lee Jun Yeob , Kang Youngjin
Published: May 2014

Two blue phosphorescent Ir(iii) compounds with a main fluorine-free bipyridine ligand have been synthesized.
Nd2O3/Au nanocomposites: upconversion broadband emission and enhancement under near-infrared light excitation
Authors: Chen Xu , Xu Wen , Zhu Yongsheng , Zhou Pingwei , Cui Shaobo , Tao Li , Xu Lin , Song Hongwei
Published: May 2014

In the present work, the novel Nd2O3/Au nanocomposites were successfully prepared by a co-precipitation process, which realized the upconversion broadband emission and enhancement under near infrared light excitation.
Coaching Care Partners Who Support Loved Ones With MCI
Authors: Mills Kerry , Brush Jennifer
Published: May 2014

Speech-language pathologists can play a critical role in providing education and intervention to prevent social withdrawal, prevent premature disability, and maximize cognitive functioning in persons with MCI. The purpose of this article is to describe positive, solution-focused educational program that speech-language pathologists can implement with family care partners to improve relationships and provide quality care for someone living with MCI.
Mild Cognitive Impairment: A Framework for Intervention
Authors: McCullough Kim
Published: May 2014

SLPs have an important role in identification of individuals with Mild Cognitive Impairment (MCI) and their treatment. A rapidly growing body of literature suggests that individuals with MCI can benefit from intervention. The underlying principles for intervention and the key components of successful cognitive interventions will be reviewed.
Critical output‐capacitor ESR for stability of V2 controlled buck converter in CCM and DCM
Authors: Zhou Guohua , He Shengzong , Zhang Xi , Zhong Shu
Published: May 2014

It has been reported that subharmonic instability exists in the V2 controlled buck converter in continuous conduction mode (CCM) when the duty ratio is above 0.5 (D > 0.5) and no stability issue exists in discontinuous conduction mode (DCM) when 0 < D < 1. However, the CCM and DCM instabilities will appear in the safe duty ratio range when the equivalent series resistance (ESR) of the output capacitor is below a critical value. The critical output‐capacitor ESR for the stabiiity of a V2 controlled buck converter in CCM and DCM is investigated by using the discrete‐time model and verified by circuit simulations.
Interference‐free wireless power transfer system for biomedical implants using multi‐coil approach
Authors: RamRakhyani A.K. , Lazzi G.
Published: May 2014

Low‐frequency (1–20 MHz) inductive coupling is a leading technique to power biomedical implants wirelessly. Even though these are non‐radiating systems, the external and the implant coils can cause sufficient radiated electric field to exceed the federal standards for communication. A multi‐coil‐based wireless power transfer (WPT) technique is developed to selectively control the currents in the external and implant coils to reduce the radiated electric field. A four‐coil WPT system, which can achieve more than 37% reduction in the radiated electric field as compared with a two‐coil WPT system with the same dimensions and design constraints, is implemented and used to demonstrate the effectiveness of the proposed approach.
Video transmission over IEEE 802.11ac downlink multi‐user: max–min fair link adaptation strategy
Authors: Khavasi Ali A. , Aajami Mojtaba , Park Hae‐Ryeon , Suk Jung‐Bong
Published: May 2014

By exploiting the inherent nature of the H.264 encoded video streams, a practically optimal scheme that is devised to address the video‐cognizant link adaptation problem in the IEEE 802.11ac downlink multi‐user (DL‐MU) is proposed. To maximise the received video quality of the downlink users, it selects and allocates the modulation and coding scheme and power in a manner of minimising the expected video distortion caused by transmission failures. The objectives and constraints are set such that the users gain max–min fair opportunities to perceive, at least, the required video quality. The proposed scheme is analysed, and its efficiency is validated by experiments with respect to fairness and video quality compared with the video‐oblivious methods.
Efficient scene‐based method for real‐time non‐uniformity correction of infrared video sequences
Authors: Liang Chaobing , Sang Hongshi , Shen Xubang
Published: May 2014

A method combing simple linear and nonlinear filters is proposed for real‐time ‘non‐uniformity correction’ of infrared video sequences, which suppresses ‘ghosting’ artefacts due to both lack of motion and strong edges. In this ‘least mean square’ (LMS)‐based method, a mean filter is used first, when the ‘fixed pattern noise’ (FPN) level is high, taking advantage of its noise smoothing capability. When the FPN level drops to a low level, a sigma filter is used instead to reduce edge smearing. The sigma filter is also used to detect abnormal pixels like dead pixels and pixels contaminated by impulse noise, in addition to adaptive adjustment of the learning rate, with no extra cost. Experiments with simulated data and real infrared sequences show that the proposed method outperforms several other LMS methods. It is of the same computational complexity as Scribner's method, which makes it a good candidate for real‐time hardware implementation.
Performance analysis of amplify–decode‐and‐forward multihop binary phase‐shift keying/free‐space optical systems using avalanche photodiode receivers over atmospheric turbulence channels
Authors: Pham Thanh V. , Pham Anh T.
Published: May 2014

This study studies the performance of multihop free‐space optical systems using the subcarrier binary phase‐shift keying modulation over atmospheric turbulence channels. The authors propose a modified relaying strategy, termed ‘amplify–decode‐and‐forward’, realised by using avalanche photodiode (APD) receivers. The outage probability of the proposed system is analytically derived considering the atmospheric turbulence and the receiver noise, including APD shot noise and thermal noise. The analytical results are verified by Monte Carlo simulations, and a good agreement between the analytical and simulation results is confirmed. In the authors’ analysis, they quantitatively discuss the impact of turbulence strength, number of relay nodes, relaying configuration, system bit rate and receiver parameters on the system outage probability. In addition, the optimal value of APD gain for achieving the lowest outage probability in different cases of relaying configuration, number of relays and receiver parameters is also discussed.
Precoder designs for jointly suppressing out‐of‐band emission and peak‐to‐average power ratio in an orthogonal frequency division multiplexing system
Authors: Fang Juan , Lu I‐Tai
Published: May 2014

High peak‐to‐average‐ratio (PAPR) and large out‐of‐band emission (OOBE) are the two main shortcomings of orthogonal frequency division multiplexing (OFDM) signals for cognitive radios. Among all the existing techniques, it has been shown that precoding is an effective way for either reducing the PAPR or suppressing the OOBE. However, no work has focused on designing an effective precoding approach to reduce the PAPR and suppress the OOBE simultaneously. In this study, three new precoding approaches that can jointly suppress OOBE and reduce PAPR simultaneously are presented. The simulation results show that, firstly, all the three proposed precoding approaches can achieve the same power spectral density performance as the typical OOBE‐suppression precoding approach with the same spectral efficiency. Secondly, their PAPR performances are only slightly worse than the typical PAPR‐reduction precoding approach with a similar computational complexity. Finally, two of the three proposed precoding approaches do not cause any bit error rate (BER) performance degradation with respect to the conventional OFDM system. The abilities to suppress OOBE and PAPR jointly and to maintain the good BER performance make two of the three proposed approaches very favourable for practical applications.
Analytical evaluation of femtocell deployment in cellular networks using fractional frequency reuse
Authors: Wang Fei , Wang Weidong
Published: May 2014

Although deploying femtocells over traditional cellular networks has been considered as an effective way to improve the coverage and the capacity of the wireless networks, the consequent interference arising from an intercell and a crosstier limits the performance. The authors propose a spectrum allocation scheme for the femtocells and the macrocells based on a fractional frequency reuse (FFR) strategy to mitigate the interference. They adopt a hybrid model where the macrocells form a hexagonal grid whereas the femtocell base stations (FBSs) form a spatial Poisson point process (PPP) to model the two‐tier network. Instead of relying on the purely numerical simulations, they give an analytical evaluation of the performance of the mobile users according to their spatial locations. The optimal spectrum allocation is required to maximise the long term expected network throughput with the quality of service (QoS) constraints. Simulations are presented to validate the accuracy of the author's analysis and figure out the relationship between the network throughput and the density of the femtocells and the radius of the interior region of a macrocell, which can be guidelines in practical system design.
Low‐complexity ad‐hoc non‐linearities for blind multiuser detection of long‐code code‐division multiple access signals and asymptotic performance evaluation
Authors: Saberali Sayed Mohammad , Amindavar Hamidreza
Published: May 2014

In this study, monomials with odd integer powers are proposed for blind multiuser detection of code‐division multiple access signals with long spreading codes, in the near–far situation. The performance of the new non‐linear detectors are substantiated asymptotically and confirmed via simulations. It is demonstrated that the proposed non‐linear detectors significantly outperform the matched filter detector in the block fading and Ricean fading channels, at the cost of a small increase in computational complexity. The optimum integer power value for the block fading channel with a limited interferer level, the Ricean channel with a given K factor and asynchronous channel is determined. The proposed multiuser detectors are blind in the sense that they require neither training nor the spreading code of the interferers. The detectors also do not require long convergence time for decision making in contrast to conventional blind multiuser detectors.
Blind sequence‐length estimation of low‐SNR cyclostationary sequences
Authors: Vlok Jacobus David , Olivier Jan Corné
Published: May 2014

Several existing direct‐sequence spread spectrum (DSSS) detection and estimation algorithms assume prior knowledge of the symbol period or sequence length, although very few sequence‐length estimation techniques are available in the literature. This study presents two techniques to estimate the sequence length of a baseband DSSS signal affected by additive white Gaussian noise. The first technique is based on a known autocorrelation technique which is used as reference, and the second technique is based on principal component analysis. Theoretical analysis and computer simulation show that the second technique can correctly estimate the sequence length at a lower signal‐to‐noise ratio than the first technique. The techniques presented in this study can estimate the sequence length blindly which can then be fed to semi‐blind detection and estimation algorithms.
Optimisation of layer rate and wavelength allocation based on network coding for multirate optical multicast
Authors: Liu Huanlin , Hu Ting , Chen Yong , Chen Qianbin , Xie Yunhui
Published: May 2014

Layered multicast, one of the multirate multicast, is effective in optimising network throughput for heterogeneous WDM (wavelength division multiplexed) networks. Compared with single layer multicast, layered multicast can achieve the maximal network throughput, making each layer multicast member receive the data with its maximal capacity. However, how to optimise each layer rate for multirate multicast network is a classical NP‐hard problem. In this study, the authors propose a layer rate optimal allocation algorithm based on network coding (NC‐LROA) to get the optical multicast network maximal throughput and to reduce wavelength number required by multicast. In the NC‐LROA algorithm, the multicast layered rate is optimised with the heuristic algorithm, which runs to reachable network maximal throughput rather than the minimal value in each destination node's maximal flow. The authors use the network coding to compress the transmitting information among wavelength channels, which have high links sharing degree so as to improve wavelength utilisation. The high sharing degree links have the priority to assign wavelength bandwidth in the inter‐layer multicast routing. Simulation results show that the proposed algorithm can, by optimising the layer rate, get network maximal throughput and at the same time reduce the wavelength bandwidth consumption for the optical multicast network.
Adaptive schemes and analysis for blind beamforming with insufficient cyclic prefix in single carrier‐frequency division multiple access systems
Authors: Fu Kuo‐Ching , Huang Shiuan‐Wei , Chen Yung‐Fang
Published: May 2014

When the duration of the cyclic prefix (CP) is shorter than that of the channel impulse response in single carrier‐frequency division multiple access systems, inter‐symbol interference and inter‐carrier interference will degrade the system performance. Previously, one solution of this problem while considering the effect of carrier frequency offsets (CFOs) and the co‐channel interference is a blind received beamforming scheme based on eigenanalysis in a batch mode. As the capability in suppressing the multipath signal with the delay larger than the CP length has not previously been analysed theoretically for the scheme, the theoretical analysis regarding the capability in suppressing the long‐delayed multipath signal is provided in this study. The analysis provided in this study is also utilised to design an adaptive processing scheme. The adaptive algorithm is developed to find the beamforming weight vector updated on a per symbol basis without using reference signals. The proposed adaptive algorithm reduces the computational complexity of and shows competitive performance under the insufficient CP, the CFOs, the co‐channel interference and the time‐varying scenarios. The simulation results reveal that the proposed adaptive algorithm provides better performance than the previously proposed algorithm.
Outage performance of dual branch diversity techniques in broadband fixed wireless access networks
Authors: Kourogiorgas Charilaos I. , Panagopoulos Athanasios D.
Published: May 2014

New physical–mathematical models for the calculation of the outage probability of the maximal ratio combining and selection combining dual branch spatial diversity schemes for broadband fixed wireless access networks operating above 10 GHz are presented. At these frequency bands and considering line‐of‐sight conditions, rain attenuation is the dominant fading mechanism, which should be taken into account in the radio communications system design. The models are based on bivariate inverse Gaussian (IG) distribution and on the adoption of a spatial correlation coefficient for the convergent terrestrial wireless links. IG distribution has been shown that models accurately the rain attenuation fading for both temperate and tropical climatic regions. The models are validated with numerical results and some useful conclusions are drawn.
Video face recognition via combination of real‐time local features and temporal–spatial cues
Authors: Gou Gaopeng , Huang Di , Wang Yunhong
Published: May 2014

Video‐based face recognition has attracted much attention and made great progress in the past decade. However, it still encounters two main problems, which are efficiently representing faces in frames and sufficiently exploiting temporal–spatial constraints between frames. The authors investigate the existing real‐time features for face description, and compare their performance. Moreover, a novel approach is proposed to model temporal–spatial information which is then combined with real‐time features to further enforce the consistent constraints between frames to improve the recognition performance. The experiments are validated on three video face databases and the results demonstrate that temporal–spatial cues combined with the most powerful real‐time features largely improve the recognition rate.
Appearance‐based approach for complete human jaw shape reconstruction
Authors: Elhabian Shireen Y. , Farag Aly A.
Published: May 2014

Precise knowledge of the 3D shape of clinical crowns is crucial for the treatment of malocclusion problems as well as several endodontic procedures. While computed tomography would present such information, it is believed there is no threshold radiation dose below which it is considered safe. In this study, the authors propose an appearance based approach which allows for the reconstruction of plausible human jaw 3D models given a single optical image with unknown illumination. Appearance bases are analytically constructed using the frequency‐based representation of the irradiance equation while incorporating prior information about natural illumination and teeth reflectance. The inherent relation between the photometric information and the underlying 3D shape is formulated as a statistical model where the coupled effect of illumination and reflectance is modelled using the Helmholtz hemispherical harmonics‐based irradiance harmonics whereas the principle component regression is deployed to carry out the estimation of 3D shapes. The authors' approach relaxes limiting assumptions of conventional shape‐from‐shading approaches while being able to reconstruct tooth occlusal surface with challenging conditions, such as scattered specular spots and significant changes in colour and albedo characteristics resulting from tooth filling. Vis‐à‐vis dental applications, the results demonstrate a significant increase in accuracy in favour of the proposed approach.
Survey of single‐target visual tracking methods based on online learning
Authors: Liu Qi , Zhao Xiaoguang , Hou Zengguang
Published: May 2014

Visual tracking is a popular and challenging topic in computer vision and robotics. Owing to changes in the appearance of the target and complicated variations that may occur in various scenes, online learning scheme is necessary for advanced visual tracking framework to adopt. This paper briefly introduces the challenges and applications of visual tracking and focuses on discussing the state‐of‐the‐art online‐learning‐based tracking methods by category. We provide detail descriptions of representative methods in each category, and examine their pros and cons. Moreover, several most representative algorithms are implemented to provide quantitative reference. At last, we outline several trends for future visual tracking research.
Ternary contextualised histogram pattern for curve matching
Authors: Shanshan Zhi , Hongmin Liu , Zhiheng Wang
Published: May 2014

This study presents a novel texture descriptor for curve matching, called ternary contextualised histogram pattern (TCHP), which is based on the intensity order histogram and local ternary homogeneity patterns. Local ternary homogeneity patterns are firstly adopted to represent the texture features of the curve's neighbourhood, which ensures the robustness and distinctiveness of the descriptor. The proposed TCHP is constructed by three steps: firstly, the curve support region without assigning a dominant orientation is determined and then partitioned into several ordinal bins according to the intensity permutation; then, ternary contextualised histogram (TCH) feature of each point is generated by computing the statistics of the predefined ternary homogeneity patterns; finally, TCHP is achieved by accumulating the TCHs of points in each order bin. Experiments show TCHP can effectively characterise the texture features of the curve's neighbourhood and performs robust to image rotation, viewpoint change and illumination change.
Histogram of gradient phases: a new local descriptor for face recognition
Authors: Su Ching‐Yao , Yang Jar‐Ferr
Published: May 2014

Gradient‐based local descriptors have received more attention these years and have been successfully used in many applications such as human detection and face recognition. The advantages of the local descriptors are the resistance to the local geometric and photometric errors and the robustness to the expression variations. In this paper, the authors propose a new local descriptor called the histogram of gradient phases (HGP), which has some intriguing properties compared with the existing local descriptors such as the histogram of orientated gradients and DAISY for face recognition under the unconstrained conditions. In contrast with the histogram of the oriented gradient descriptor, the orientation histogram is computed from the estimated gradient phase distributions instead of weighting the votes of the gradient magnitudes. In this paper, the phase distributions are estimated by means of the gradient phases and the variances are decided by the estimated gradient signal‐to‐noise ratios of the pixels in a local region. The HGP descriptor which takes the confidence of the gradient phase into account is more discriminative and less sensitive to the normalisation process than most local descriptors, which significantly degrade without a proper normalisation. The simulation results show that the proposed HGP descriptor achieves a better performance and is more robust than the existing local descriptors.
Partially occluded pedestrian classification using histogram of oriented gradients and local weighted linear kernel support vector machine
Authors: Aly Saleh
Published: May 2014

One of the main challenges in pedestrian classification is partial occlusion. This study presents a new method for pedestrian classification with partial occlusion handling. The proposed method involves a set of part‐based classifiers trained on histogram of oriented gradients features derived from non‐occluded pedestrian data set. The score of each part classifier is then employed to weight features used to train a second stage full‐body classifier. The full‐body classifier based on local weighted linear kernel support vector machine is trained using both non‐occluded and artificially generated partial occlusion pedestrian dataset. The new kernel allows to significantly focus on the non‐occluded parts and reduce the impact of the occluded ones. Experimental results on real‐world dataset, with both partially occluded and non‐occluded data, show high performance of the proposed method compared with other state‐of‐the‐art methods.
Positron emission tracking of individual particles in particle-laden rimming flow
Authors: Denissenko P. , Guyez E. , Thomas P. J. , Parker D. J. , Seville J. P. K.
Published: May 2014

The motion of a single tracer particle in particle-laden rimming flows is investigated experimentally by means of Positron Emission Particle Tracking (PEPT). Semi-dilute suspensions, with a volume fraction of 8% of heavy particles are considered. The trajectory of the tracer particle is monitored for several thousand cylinder revolutions and related to the optically recorded drift of the large-scale granular segregation bands developing in the cylinder. Results of the data analysis provide first insights into the relation between behaviour of individual particles and the spatiotemporal dynamics displayed by the macroscopic particle-segregation patterns.
Contrasting physics in wire array z pinch sources of 1-20 keV emission on the Z facility
Authors: Ampleford D. J. , Jones B. , Jennings C. A. , Hansen S. B. , Cuneo M. E. , Harvey-Thompson A. J. , Rochau G. A. , Coverdale C. A. , Laspe A. R. , Flanagan T. M. , Moore N. W. , Sinars D. B. , Lamppa D. C. , Harding E. C. , Thornhill J. W. , Giuliani J. L. , Chong Y.-K. , Apruzese J. P. , Velikovich A. L. , Dasgupta A. , Ouart N. , Sygar W. A. , Savage M. E. , Moore J. K. , Focia R. , Wagoner T. C. , Killebrew K. L. , Edens A. D. , Dunham G. S. , Jones M. C. , Lake P. W. , Nielsen D. S. , Wu M. , Carlson A. L. , Kernahan M. D. , Ball C. R. , Scharberg R. D. , Mulville T. D. , Breden E. W. , Speas C. S. , Olivas G. , Sullivan M. A. , York A. J. , Justus D. W. , Cisneros J. C. , Strizic T. , Reneker J. , Cleveland M. , Vigil M. P. , Robertson G. , Sandoval D. , Cox C. , Maurer A. J. , Graham D. A. , Huynh N. B. , Toledo S. , Molina L. P. , Lopez M. R. , Long F. W. , McKee G. R. , Porter J. L. , Herrmann M. C.
Published: May 2014

Imploding wire arrays on the 20 MA Z generator have recently provided some of the most powerful and energetic laboratory sources of multi-keV photons, including ∼375 kJ of Al K-shell emission (hν ∼ 1–2 keV), ∼80 kJ of stainless steel K-shell emission (hν ∼ 5–9 keV) and a kJ-level of Mo K-shell emission (hν ∼ 17 keV). While the global implosion dynamics of these different wire arrays are very similar, the physical process that dominates the emission from these x-ray sources fall into three broad categories. Al wire arrays produce a column of plasma with densities up to ∼3 × 1021 ions/cm3, where opacity inhibits the escape of K-shell photons. Significant structure from instabilities can reduce the density and increase the surface area, therefore increase the K-shell emission. In contrast, stainless steel wire arrays operate in a regime where achieving a high pinch temperature (achieved by thermalizing a high implosion kinetic energy) is critical and, while opacity is present, it has less impact on the pinch emissivity. At higher photon energies, line emission associated with inner shell ionization due to energetic electrons becomes important.
High-power, high-intensity laser propagation and interactions
Authors: Sprangle Phillip , Hafizi Bahman
Published: May 2014

This paper presents overviews of a number of processes and applications associated with high-power, high-intensity lasers, and their interactions. These processes and applications include: free electron lasers, backward Raman amplification, atmospheric propagation of laser pulses, laser driven acceleration, atmospheric lasing, and remote detection of radioactivity. The interrelated physical mechanisms in the various processes are discussed.
Charge noise analysis of metal oxide semiconductor dual-gate Si/SiGe quantum point contacts
Authors: Kamioka J. , Kodera T. , Takeda K. , Obata T. , Tarucha S. , Oda S.
Published: May 2014

The frequency dependence of conductance noise through a gate-defined quantum point contact fabricated on a Si/SiGe modulation doped wafer is characterized. The 1/f2 noise, which is characteristic of random telegraph noise, is reduced by application of a negative bias on the global top gate to reduce the local gate voltage. Direct leakage from the large global gate voltage also causes random telegraph noise, and therefore, there is a suitable point to operate quantum dot measurement.
Thermal conductivity of silicon nanomeshes: Effects of porosity and roughness
Authors: Wolf Stefanie , Neophytou Neophytos , Kosina Hans
Published: May 2014

We theoretically investigate thermal conductivity in silicon nanomeshes using Monte Carlo simulations of phonon transport. Silicon membranes of 100 nm thickness with randomly located pores of 50 nm diameter are considered. The effects of material porosity and pore surface roughness are examined. Nanomesh porosity is found to have a strong detrimental effect on thermal conductivity. At room temperature, a porosity of 50% results in ∼80% reduction in thermal conductivity. Boundary roughness scattering further degrades thermal conductivity, but its effect is weaker. Thermal transport can additionally be affected by the specific arrangement of the pores along the transport direction.
Mono-textured nanocrystalline thin films with pronounced stress-gradients: On the role of grain boundaries in the stress evolution
Authors: Daniel R. , Jäger E. , Todt J. , Sartory B. , Mitterer C. , Keckes J.
Published: May 2014

The origins of residual stress gradients in nanocrystalline thin films, especially the role of grain size and texture gradients, are still not fully understood. In this work, the stress evolution in exemplary nanocrystalline TiN thin films with one and two fiber texture components as well as in homogeneous amorphous SiOx films is analyzed using wafer curvature as well as laboratory and synchrotron cross-sectional nanobeam X-ray diffraction techniques. The stress evolution across the film thickness is attributed to the evolutionary nature of microstructural development at the individual growth stages. While the effect of the smooth crystallographic texture changes during growth is only of minor importance, as this does not significantly affect the dominant stress formation mechanisms, the change in the grain size accompanied by a change of the volume fraction of grain boundaries plays a decisive role in the stress development across the film thickness. This is demonstrated on the monotextured thin films, where the residual stresses scale with the apparent grain size. These findings are validated also by the investigations of stress profiles in homogeneous amorphous SiOx films exhibiting no grain boundaries.
Novel signal inversion of laser beam induced current for femtosecond-laser-drilling-induced junction on vacancy-doped p-type HgCdTe
Authors: Qiu W. C. , Cheng X. A. , Wang R. , Xu Z. J. , Jiang T.
Published: May 2014

In this paper, experimental results of temperature-dependent signal inversion of laser beam induced current (LBIC) for femtosecond-laser-drilling-induced junction on vacancy-doped p-type HgCdTe are reported. LBIC characterization shows that the traps induced by femtosecond laser drilling are sensitive to temperature. Theoretical models for trap-related p-n junction transformation are proposed and demonstrated using numerical simulations. The simulations are in good agreement with the experimental results. The effects of traps and mixed conduction are possibly the main reasons that result in the novel signal inversion of LBIC microscope at room temperature. The research results provide a theoretical guide for practical applications of large-scale array HgCdTe infrared photovoltaic detectors formed by femtosecond laser drilling, which may act as a potential new method for fabricating HgCdTe photodiodes.
Exchange bias in phase-segregated Nd2/3Ca1/3MnO3 as a function of temperature and cooling magnetic fields
Authors: Fertman Elena , Dolya Sergiy , Desnenko Vladimir , Pozhar L. A. , Kajňaková Marcela , Feher Alexander
Published: May 2014

Exchange bias (EB) phenomena have been observed in Nd2/3Ca1/3MnO3 colossal magnetoresistance perovskite below the Curie temperature TC ∼ 70 K and attributed to an antiferromagnetic–ferromagnetic (FM) spontaneous phase segregated state of this compound. Field cooled magnetic hysteresis loops exhibit shifts toward negative direction of the magnetic field axis. The values of exchange field HEB and coercivity HC are found to be strongly dependent of temperature and strength of the cooling magnetic field Hcool. These effects are attributed to evolution of the FM phase content and a size of FM clusters. A contribution to the total magnetization of the system due to the FM phase has been evaluated. The exchange bias effect decreases with increasing temperature up to TC and vanishes above this temperature with disappearance of FM phase. Relaxation of a non-equilibrium magnetic state of the compound manifests itself through a training effect also observed while studying EB in Nd2/3Ca1/3MnO3.
Metallic filament formation by aligned oxygen vacancies in ZnO-based resistive switches
Authors: Gu Tingkun
Published: May 2014

The electronic structure of ZnO with defects of oxygen vacancies were investigated by using first-principles methods. Some structure models were constructed in order to investigate the effects of the distribution of oxygen vacancies on the electronic properties of ZnO. By analyzing the calculated results, we found that only the aligned oxygen vacancies can form the conducting channel in ZnO, and the transformation of the oxygen vacancy from charged state to neutral state is consistent with the energetics rule of the forming aligned oxygen vacancies. As for the heterojunction of Pt/ZnO/Pt, the oxygen vacancies near the interface of Pt/ZnO depress the local Schottky barrier effectively, and the aligned oxygen vacancies in ZnO form a conducting filament connecting two Pt electrodes. The metallic filament formation in Pt/ZnO/Pt resistive switching cells should be closely related to the carrier injection from Pt electrode into ZnO and the arrangement of oxygen vacancies in ZnO slab.
Modifying the characteristics of carbon nanotubes grown on metallic substrates for ultracapacitor applications
Authors: Jenicek D. P. , McCarthy A. , Kassakian J. G.
Published: May 2014

This paper reports the design, fabrication, and testing of carbon nanotube (CNT)-based ultracapacitor electrodes and provides quantitative results, showing that total electrode surface area—and, correspondingly, the total cell capacitance—is highly sensitive to the amount of catalyst material deposited prior to CNT growth. We deposit between 0.6 and 1.0 nm of iron catalyst on metallic (tungsten) substrates and synthesized vertically aligned CNT forests directly by thermal chemical vapor deposition. A capacitance maximum is observed with electrodes prepared with 0.8 nm of catalyst. Geometrical arguments based on average CNT diameter and areal density are used to corroborate this result. The CNTs' differential capacitance is found to be independent of their areal density, mean diameter, length, and the amount of catalyst used to grow them.
InvestigatingJatrophaprunings as a feedstock for producing fermentable sugars and chemical treatment for process optimization
Authors: Kumar Ravindra , Satlewal Alok , Sharma Sandeep , Kagdiyal Vivekanand , Gupta Ravi P. , Tuli Deepak K. , Malhotra Ravinder K.
Published: May 2014

Jatropha curcas has been considered as a material of choice in India for the production of bio-diesel and a very large area has been planted in India. For better growth, Jatropha plants need extensive pruning once a year, and the pruning of a healthy two year old plant on an average gives about 4–6 kg of lignocellulosic material (LCM). Jatropha prunings can be available in significant amount on annual basis. These prunings have no other use and this material has potential to be an economical and suitable LCM for conversion to fermentable sugars, as these contain considerable amount of holocellulose. In this study, acid pretreatment of Jatropha pruning was carried out using dilute sulfuric acid. A wide range of variables, i.e., acid concentrations from 2.50% to 10.0%, temperature from 120 to 180 °C, and reaction time of 5–45 min were studied. Three response factors, namely, maximum xylose release, minimum inhibitors, and maximum enzymatic digestibility, were optimized by application Taguchi design. Pretreatment efficiency was determined by enzymatic saccharification and physico-chemical properties of both native and pretreated biomass analyzed using scanning electron microscopy and Fourier transform infrared spectroscopy. This study provides insights into the intricacies involved in conversion of this biomass to fermentable sugars. These studies indicate that Jatropha prunings can be converted economically into ethanol and can provide additional support to Jatropha based bio-diesel programme.
Phase transition from fcc to bcc structure of the Cu-clusters during nanocrystallization of Fe85.2Si1B9P4Cu0.8 soft magnetic alloy
Authors: Nishijima Masahiko , Matsuura Makoto , Takenaka Kana , Takeuchi Akira , Ofuchi Hironori , Makino Akihiro
Published: May 2014

A role of Cu on the nanocrystallization of an Fe85.2Si1B9P4Cu0.8 alloy was investigated by X-ray absorption fine structure (XAFS) and transmission electron microscopy (TEM). The Cu K-edge XAFS results show that local structure around Cu is disordered for the as-quenched sample whereas it changes to fcc-like structure at 613 K. The fcc Cu-clusters are, however, thermodynamically unstable and begin to transform into bcc structure at 638 K. An explicit bcc structure is observed for the sample annealed at 693 K for 600 s in which TEM observation shows that precipitated bcc-Fe crystallites with ∼12 nm are homogeneously distributed. The bcc structure of the Cu-clusters transforms into the fcc-type again at 973 K, which can be explained by the TEM observations; Cu segregates at grain boundaries between bcc-Fe crystallites and Fe3(B,P) compounds. Combining the XAFS results with the TEM observations, the structure transition of the Cu-clusters from fcc to bcc is highly correlated with the preliminary precipitation of the bcc-Fe which takes place prior to the onset of the first crystallization temperature, Tx1 = 707 K. Thermodynamic analysis suggests that an interfacial energy density γ between an fcc-Cu cluster and bcc-Fe matrix dominates at a certain case over the structural energy between fcc and bcc Cu, ΔGfcc − bcc, which causes phase transition of the Cu clusters from fcc to bcc structure.
Study of charge-carrier relaxation in a disordered organic semiconductor by simulating impedance spectroscopy
Authors: Mesta M. , Cottaar J. , Coehoorn R. , Bobbert P. A.
Published: May 2014

Impedance spectroscopy is a very sensitive probe of nonstationary charge transport governed by charge-carrier relaxation in devices of disordered organic semiconductors. We simulate impedance spectroscopy measurements of hole-only devices of a polyfluorene-based disordered organic semiconductor by solving a time-dependent three-dimensional master equation for the occupational probabilities of transport sites in the semiconductor. We focus on the capacitance-voltage characteristics at different frequencies. In order to obtain good agreement with the measured characteristics, we have to assume a lower strength of a Gaussian energy disorder than obtained from best fits to the stationary current density-voltage characteristics. This lower disorder strength is in agreement with dark-injection studies of nonstationary charge transport on the same devices. The results add to solving the puzzle of reconciling nonstationary with stationary charge-transport studies of disordered organic semiconductors.
Graphene in ohmic contact for both n-GaN and p-GaN
Authors: Zhong Haijian , Liu Zhenghui , Shi Lin , Xu Gengzhao , Fan Yingmin , Huang Zengli , Wang Jianfeng , Ren Guoqiang , Xu Ke
Published: May 2014

The wrinkles of single layer graphene contacted with either n-GaN or p-GaN were found both forming ohmic contacts investigated by conductive atomic force microscopy. The local I–V results show that some of the graphene wrinkles act as high-conductive channels and exhibiting ohmic behaviors compared with the flat regions with Schottky characteristics. We have studied the effects of the graphene wrinkles using density-functional-theory calculations. It is found that the standing and folded wrinkles with zigzag or armchair directions have a tendency to decrease or increase the local work function, respectively, pushing the local Fermi level towards n- or p-type GaN and thus improving the transport properties. These results can benefit recent topical researches and applications for graphene as electrode material integrated in various semiconductor devices.
Occurrence and core-envelope structure of 1–4× Earth-size planets around Sun-like stars
Authors: Marcy Geoffrey W. , Weiss Lauren M. , Petigura Erik A. , Isaacson Howard , Howard Andrew W. , Buchhave Lars A.
Published: May 2014

Significance

Among the nearly 4,000 planets known around other stars, the most common are 1–4× the size of Earth. A quarter of Sun-like stars have such planets orbiting within half an Earth’s orbital distance of them, and more surely orbit farther out. Measurements of density show that the smallest planets are mostly rocky while the bigger ones have rocky cores fluffed out with hydrogen and helium gas, and likely water, befitting the term ‘‘mini-Neptunes.’’ The division between these two regimes is near 1.5
R
⊕
. Considering exoplanet hospitality, 11% of Sun-like stars have a planet of 1–2× the size of Earth that receives between 1.0–4.0× the incident stellar light that our Earth enjoys. However, we remain ignorant of the origins of, and existence of, exobiology, leaving the location of the habitable zone uncertain.
Unitary step of gliding machinery in
Mycoplasma mobile
Authors: Kinosita Yoshiaki , Nakane Daisuke , Sugawa Mitsuhiro , Masaike Tomoko , Mizutani Kana , Miyata Makoto , Nishizaka Takayuki
Published: May 2014

Significance

The mechanism of movement of bacteria shows extensive diversity, and some bacteria glide on the substrate surface via an unknown process.
Mycoplasma mobile
is one of the fastest, exhibiting smooth gliding movement with a speed of 2.0–4.5 µm/s. By applying the modified in vitro ghost model of
Mycoplasma mobile
to high precision colocalization microscopy, steps of the regular size, ∼70 nm, were detected for the first time in bacteria, to our knowledge. The binding target of the gliding machinery, sialylated oligosaccharides, was expected to be randomly oriented on the surface and, thus, our results suggest that the machinery can drive the steps with a cycle of attachment and detachment even if there is no periodic structure on the substrate.
Navigability of interconnected networks under random failures
Authors: De Domenico Manlio , Solé-Ribalta Albert , Gómez Sergio , Arenas Alex
Published: May 2014

Significance

Network theory has been exploited in the last decades to deepen our comprehension of complex systems. However, real-world complex systems exhibit multiple levels of relationships and require modeling by interconnected networks, characterizing interactions on several levels simultaneously. Questions such as “what is the efficiency of exploration of a city using the multiple transportation layers, like subway and bus?” and “what is its resilience to failures?” have to be answered using the multiplex framework. Here, we introduce fundamental mechanisms to perform such exploration, using random walks on multilayer networks, and we show how the topological structure, together with the navigation strategy, influences the efficiency in exploring the whole structure.
From confluent human iPS cells to self-forming neural retina and retinal pigmented epithelium
Authors: Reichman Sacha , Terray Angélique , Slembrouck Amélie , Nanteau Céline , Orieux Gaël , Habeler Walter , Nandrot Emeline F. , Sahel José-Alain , Monville Christelle , Goureau Olivier
Published: May 2014

Significance

Human induced pluripotent stem cells (hiPSCs) could be used as an unlimited source of retinal cells for the treatment of retinal degenerative diseases. The production of retinal cells from hiPSCs for personalized therapeutic approaches must comply with certain criteria, such as safety, efficiency, reproducibility, and low production cost. Here, we report a simple and scalable retinal differentiation process for the generation of retinal pigmented epithelial cells and neural retinal tissues containing retinal progenitor cells. These progenitors can be differentiated into all retinal cell types, including retinal ganglion cells and precursors of photoreceptors, which could find important applications in regenerative medicine. This method also provides an accessible in vitro model to investigate mechanisms involved in human retinogenesis and retinal diseases.
Investigation of triterpene synthesis and regulation in oats reveals a role for β-amyrin in determining root epidermal cell patterning
Authors: Kemen Ariane C. , Honkanen Suvi , Melton Rachel E. , Findlay Kim C. , Mugford Sam T. , Hayashi Keiko , Haralampidis Kosmas , Rosser Susan J. , Osbourn Anne
Published: May 2014

Significance

Sterols and triterpenes are complex molecules that are synthesized from the isoprenoid pathway. The functions of sterols in plants have been studied extensively, but the role of triterpenes is less well understood. Here we investigate triterpene synthesis and regulation in diploid oat. We show that the genes for triterpene synthesis are regulated by an ancient root development process that is conserved across diverse plants. We further show that mutants in which the metabolism of the most common plant triterpene, β-amyrin, is blocked undergo a change early in the development of the root epidermis that leads to a “superhairy” root phenotype. Our findings shed light on triterpene synthesis and provide evidence for a role for the simple triterpene β-amyrin in plant development.
Shear stress-dependent regulation of apical endocytosis in renal proximal tubule cells mediated by primary cilia
Authors: Raghavan Venkatesan , Rbaibi Youssef , Pastor-Soler Núria M. , Carattino Marcelo D. , Weisz Ora A.
Published: May 2014

Significance

The proximal tubule (PT) of the kidney is the primary site for reabsorption of ions, solutes, and filtered low molecular weight proteins. PT cells rapidly modulate ion transport capacity in response to the fluid shear stress (FSS) that accompanies changes in glomerular filtration rate. We report here that PT cells also adjust their capacity for endocytosis in response to FSS. Apical endocytosis of the megalin–cubilin ligand albumin and of fluid phase markers is markedly increased upon exposure to FSS. Moreover, Ca
2+
signaling mediated by the primary cilia on PT cells is required for this response. These studies define a novel pathway in PT cells that plays an essential role in maintaining kidney function.
Dietary history contributes to enterotype-like clustering and functional metagenomic content in the intestinal microbiome of wild mice
Authors: Wang Jun , Linnenbrink Miriam , Künzel Sven , Fernandes Ricardo , Nadeau Marie-Josée , Rosenstiel Philip , Baines John F.
Published: May 2014

Significance

Recent investigation of several mammalian hosts suggests that their intestinal bacterial communities display evidence of clusters characterized by differences in specific bacterial taxa, a concept referred to as enterotypes. By performing stable isotope analysis of environmental samples, monitoring communities during dietary shifts, and collecting functional metagenomic sequence data, we provide novel insight into the origins and dynamics of enterotype-like community clustering in wild house mice. Two clusters are present in wild mice, one associated with higher plant-derived and another with animal-derived food intake, which can shift within a period of 1 wk. Remarkably, these clusters display shared characteristics with those present in humans, chimpanzees, and laboratory mice, suggesting ancient shared traits among mammalian bacterial communities.