bluuebunny/crossref_metadata_2025 huggingface dataset:
Co-adsorption of peptide amphiphile V6K and conventional surfactants SDS and C12TAB at the solid/water interface
Authors: Jayawardane Dharana , Pan Fang , Lu Jian R. , Zhao Xiubo
Published: August 2015

A practical route for short peptide amphiphiles to enter the real world of applications is through formulation with conventional surfactants. This study reports the co-adsorption of the surfactant-like peptide, V6K, with conventional anionic and cationic surfactants at the solid/water interface.
In vitro assembly of a viral envelope
Authors: Miles Penny , Cassidy Peter , Donlon Lynn , Yarkoni Orr , Frankel Daniel
Published: August 2015

HIV glycoproteins distort lipid vesicles suggesting a capsid is necessary for virion stability these glycoproteins can also assemble into molecular wires.
Universal scaling of crowding-induced DNA mobility is coupled with topology-dependent molecular compaction and elongation
Authors: Gorczyca Stephanie M. , Chapman Cole D. , Robertson-Anderson Rae M.
Published: August 2015

Universal scaling of crowding-induced DNA mobility is coupled with entropically-driven compaction of rings and elongation of linear chains.
A conductive selenized polyacrylonitrile cathode material for re-chargeable lithium batteries with long cycle life
Authors: Guo Jing , Wen Zhaoyin , Wang Qingsong , Jin Jun , Ma Guoqiang
Published: August 2015

Selenized polyacrylonitrile behaves as a new kind of conductive polymer cathode material for lithium batteries, in which not only selenium but also nitrogen groups participate in the reversible discharge/charge reactions and exhibits excellent prolonged cycling performance as well as remarkable fast-discharge/charge capability.
Enhanced photocatalytic H2-evolution by immobilizing CdS nanocrystals on ultrathin Co0.85Se/RGO–PEI nanosheets
Authors: Cao Shuang , Chen Yong , Kang Lei , Lin Zheshuai , Fu Wen-Fu
Published: August 2015

A novel noble-metal-free photocatalytic H2-production system was constructed by immobilizing CdS nanocrystals on ultrathin Co0.85Se/graphene nanosheets and achieved a dramatically enhanced H2-evolution performance.
Effectively promoting wound healing with cellulose/gelatin sponges constructed directly from a cellulose solution
Authors: Pei Ying , Ye Dongdong , Zhao Qi , Wang Xueying , Zhang Chun , Huang Weihua , Zhang Nu , Liu Shiqing , Zhang Lina
Published: August 2015

The cellulose sponges loading gelatin and bFGF as wound dressing were constructed directly from the cellulose solution via a green and cost-effective pathway, which effectively promoted wound healing.
Cationic surface modification of gold nanoparticles for enhanced cellular uptake and X-ray radiation therapy
Authors: Wang Chaoming , Sun An , Qiao Yong , Zhang Peipei , Ma Liyuan , Su Ming
Published: August 2015

Gold nanoparticles with cationic surface modification can enhance X-ray radiation therapy by enhancing cellular uptake.
Physical cues of cell culture materials lead the direction of differentiation lineages of pluripotent stem cells
Authors: Higuchi Akon , Ling Qing-Dong , Kumar S. Suresh , Chang Yung , Alarfaj Abdullah A. , Munusamy Murugan A. , Murugan Kadarkarai , Hsu Shih-Tien , Umezawa Akihiro
Published: August 2015

Differentiation methods of hPSCs into specific cell lineages. Differentiation of hPSCsviaEB formation (types AB, A–D) or without EB formation (types E–H).
Recent advances in gold nanoparticle-based bioengineering applications
Authors: Kim Eun Young , Kumar Dinesh , Khang Gilson , Lim Dong-Kwon
Published: August 2015

The recently developed gold nanoparticle-based bioengineering technologies for biosensors,in vitroandin vivobioimaging, drug delivery systems for improved therapeutics and tissue engineering are discussed.
Design of a versatile nanocomposite for ‘seeing’ drug release and action behavior
Authors: Zhang Yu , Shen Tingting , Deng Xia , Ma Yufei , Wang Lina , Peng Yong , Wu Jiang , Zhang Zhijun , Liu Weisheng , Tang Yu
Published: August 2015

To design a new method for ‘seeing’ drug release and action behavior, we combined a rare-earth complex with a magnetic-core-coated phenyl mesoporous silica nanoparticles matrix, taking advantage of the drug coordination for real-time monitoring.
Gene silencing of the pro-inflammatory cytokine TNF-α with siRNA delivered by calcium phosphate nanoparticles, quantified by different methods
Authors: Neuhaus Bernhard , Frede Annika , Westendorf Astrid Maria , Epple Matthias
Published: August 2015

The expression of the proinflammatory cytokine TNF-α was efficiently downregulated with nanoparticles, opening a way to combat inflammatory reactions.
Not your familiar two dimensional transition metal disulfide: structural and electronic properties of the PdS2monolayer
Authors: Wang Yu , Li Yafei , Chen Zhongfang
Published: August 2015

The PdS2monolayer has distinguished structural properties from other transition metal disulfides, and also has rather high carrier mobilities. It is semiconducting with a moderate indirect band gap, which could be effectively tuned by applying a tensile strain.
Tunable luminescent Eu2+-doped dicalcium silicate polymorphs regulated by crystal engineering
Authors: Mao Zhiyong , Lu Zhijuan , Chen Jingjing , Fahlman Bradley D. , Wang Dajian
Published: August 2015

Tunable luminescent Eu2+-doped dicalcium silicate phosphors are demonstrated based on crystal-phase engineering and crystal-site engineering approaches.
Dielectric, piezoelectric, and elastic properties of K0.8Na0.2NbO3 single crystals
Authors: Tian Hao , Hu Chengpeng , Meng Xiangda , Zhou Zhongxiang , Shi Guang
Published: August 2015

Photographs of the orientation dependence of the piezoelectric constant d33 and K0.8Na0.2NbO3 single crystals grown via the TSSG method.
Peroxiredoxin 6 triggers melanoma cell growth by increasing arachidonic acid-dependent lipid signalling
Authors: Schmitt Alexandra , Schmitz Werner , Hufnagel Anita , Schartl Manfred , Meierjohann Svenja
Published: August 2015

Tumour cells are reported to display an imbalance in the levels of ROS (reactive oxygen species). Frequently, elevated ROS production goes along with compensatory up-regulation of antioxidant enzymes. Accordingly, we found in a previous study that protein levels of several peroxiredoxins, including PRDX6 (peroxiredoxin 6), are highly elevated in experimentally induced melanomas. In the present study, we investigated the functional role of PRDX6 in human melanoma cells. PRDX6 is a bifunctional enzyme, which harbours iPLA2 (Ca2+-independent phospholipase A2) activity in addition to its peroxidase function. Our results show that PRDX6 is strongly expressed in most melanoma cells and its expression levels are maintained in a post-transcriptional manner, particularly by EGFR (epidermal growth factor receptor)-dependent signalling. PRDX6 enhances cell viability mainly by enhancing proliferation, which goes along with activation of Src family kinases. Interestingly, we were able to show that the phospholipase activity of the enzyme mediates the pro-proliferative effect of PRDX6. We identified AA (arachidonic acid) as a crucial effector of PRDX6-dependent proliferation and inducer of Src family kinase activation. These results support further the biological importance of the emerging field of lipid signalling in melanoma and highlight the particular functional relevance of PRDX6-dependent phospholipase activity.
Doxorubicin inhibits E. coli division by interacting at a novel site in FtsZ
Authors: Panda Pragnya , Taviti Ashoka Chary , Satpati Suresh , Kar Mitali Madhusmita , Dixit Anshuman , Beuria Tushar Kant
Published: August 2015

The increase in antibiotic resistance has become a major health concern in recent times. It is therefore essential to identify novel antibacterial targets as well as discover and develop new antibacterial agents. FtsZ, a highly conserved bacterial protein, is responsible for the initiation of cell division in bacteria. The functions of FtsZ inside cells are tightly regulated and any perturbation in its functions leads to inhibition of bacterial division. Recent reports indicate that small molecules targeting the functions of FtsZ may be used as leads to develop new antibacterial agents. To identify small molecules targeting FtsZ and inhibiting bacterial division, we screened a U.S. FDA (Food and Drug Administration)-approved drug library of 800 molecules using an independent computational, biochemical and microbial approach. From this screen, we identified doxorubicin, an anthracycline molecule that inhibits Escherichia coli division and forms filamentous cells. A fluorescence-binding assay shows that doxorubicin interacts strongly with FtsZ. A detailed biochemical analysis demonstrated that doxorubicin inhibits FtsZ assembly and its GTPase activity through binding to a site other than the GTP-binding site. Furthermore, using molecular docking, we identified a probable doxorubicin-binding site in FtsZ. A number of single amino acid mutations at the identified binding site in FtsZ resulted in a severalfold decrease in the affinity of FtsZ for doxorubicin, indicating the importance of this site for doxorubicin interaction. The present study suggests the presence of a novel binding site in FtsZ that interacts with the small molecules and can be targeted for the screening and development of new antibacterial agents.
Brain tumour classification using two‐tier classifier with adaptive segmentation technique
Authors: Anitha V. , Murugavalli S.
Published: August 2015

A brain tumour is a mass of tissue that is structured by a gradual addition of anomalous cells and it is important to classify brain tumours from the magnetic resonance imaging (MRI) for treatment. Human investigation is the routine technique for brain MRI tumour detection and tumours classification. Interpretation of images is based on organised and explicit classification of brain MRI and also various techniques have been proposed. Information identified with anatomical structures and potential abnormal tissues which are noteworthy to treat are given by brain tumour segmentation on MRI, the proposed system uses the adaptive pillar K‐means algorithm for successful segmentation and the classification methodology is done by the two‐tier classification approach. In the proposed system, at first the self‐organising map neural network trains the features extracted from the discrete wavelet transform blend wavelets and the resultant filter factors are consequently trained by the K‐nearest neighbour and the testing process is also accomplished in two stages. The proposed two‐tier classification system classifies the brain tumours in double training process which gives preferable performance over the traditional classification method. The proposed system has been validated with the support of real data sets and the experimental results showed enhanced performance.
Integrated self‐calibration of single axis motion for three‐dimensional reconstruction of roots
Authors: Kumar Pankaj , Miklavcic Stanley J.
Published: August 2015

In this study, the authors present an integrated approach for recovering both the intrinsic and extrinsic parameters of a camera from the silhouettes and feature point tracking of an object in a turntable image sequence. Their motivation in taking the integrated approach is to solve the problem of obtaining the Euclidean three‐dimensional (3D) reconstruction of cereal roots growing in gellan gum or objects immersed in water and imaged under turntable motion. The problem of self‐calibration by previous approaches is especially difficult in this case as the initialisation of the rotation axis from the bi‐tangent lines to the surface of revolution is not feasible. The conics projected from the circular trajectories of root tips are highly eccentric. Their approach is to initialise the axis of rotation ls from the centre of the conics fitted to feature point trajectory. An estimate of ls is then iteratively estimated by minimising an error function in estimating the harmonic homology introduced by the surface of symmetry. They compare the results of their approach to those of the maximum‐likelihood estimation‐based approach to conic fitting of point feature trajectories. They show results of real 3D reconstruction of roots, which are detailed enough for phenotypic analysis and are better both quantitatively and qualitatively than those using just feature point tracking.
Compact descriptor for local feature using dominating centre‐symmetric local binary pattern
Authors: Li Yingying , Tan Jieqing , Zhong Jinqin , Chen Qiang
Published: August 2015

The authors propose a terse texture feature, called the dominant centre‐symmetric local binary pattern (DCSLBP), which has similar distinctiveness and half dimension compared against original centre‐symmetric local binary pattern (CS‐LBP). On the basis of DCSLBP histogram and an improved construction, a compact descriptor for local feature is presented. To assess the proposed descriptor with the state‐of‐the‐art in performance and dimension, the authors extend it to two variants with different dimensions using the existing method. These descriptors are compared with scale‐invariant feature transform (SIFT), multisupport region rotation and intensity monotonic invariant descriptor (MRRID), orthagonal combination local binary pattern (OC‐LBP) in interest region matching and in the application of object recognition. The experiments demonstrate the proposed descriptor's compactness and robustness to various image transformations, especially to large illumination change.
Solution of optimal reactive power dispatch by chaotic krill herd algorithm
Authors: Mukherjee Aparajita , Mukherjee Vivekananda
Published: August 2015

This study presents an efficient and reliable evolutionary‐based approach, termed as chaotic krill herd algorithm (CKHA), to solve the optimal reactive power dispatch (ORPD) problem of power system. In the proposed CKHA, various chaotic maps are considered to improve the performance of the basic KHA. The performance of the proposed CKHA is examined and tested, successfully, on standard IEEE‐30 and IEEE‐57 bus test power systems for the solution of ORPD problem in which control of bus voltages, tap position of transformers and reactive power sources are involved. The objective function considered is either minimisation of active power transmission loss or that of total voltage deviation or enhancement of voltage stability index. The results offered by the proposed CKHA are compared with those offered by other evolutionary optimisation techniques surfaced in the recent state‐of‐the‐art literature. Simulation results indicate that the proposed CKHA yields superior solution over the other recently surfaced popular techniques in terms of effectiveness and convergence speed.
Automatic generation control of multi‐unit multi‐area deregulated power system using a novel quasi‐oppositional harmony search algorithm
Authors: Shiva Chandan Kumar , Mukherjee Vivekananda
Published: August 2015

This initiative work deals with the automatic generation control (AGC) of multi‐unit multi‐area power system in the prospective of deregulated power environment owing to load following issues. In present outlook, a deregulated four‐area power system having eight generation companies and eight distribution companies is treated as a plant model. The concerned objective is to intensify the bilateral behaviour and investigate the system AGC performance. In the state of deregulation, the influence of a novel quasi‐oppositional harmony search (QOHS) algorithm based Sugeno fuzzy‐logic (SFL) technique is proposed as an AGC optimisation task by showing its consequences on bilateral policy/dynamics. In the entire work, the proposed QOHS based SFL technique is incorporated for the tuning of on‐line, off‐nominal controller gains. The salient advantage of this control strategy is to provide good dynamic responses over a wide range of system parametric variations. The observations are based on the three deregulated cases which, generally, takes place in deregulated power market. The presented simulation results show that the proposed QOHS based SFL is a promising optimisation technique in the field of deregulated AGC study.
Two‐stage constant false alarm rate detection for distributed multiple‐input–multiple‐output radar
Authors: Hu Qinzhen , Su Hongtao , Zhou Shenghua , Liu Ziwei , Yang Yang , Liu Jun
Published: August 2015

In this study, the authors consider a two‐stage constant false alarm rate (TS‐CFAR) detection problem in a distributed multiple‐input–multiple‐output radar. This study is motivated by the fact that the clutter plus noise power and the signal to clutter plus noise ratio may be both unknown in practice. Two TS‐CFAR detectors are proposed, that is, TS generalised likelihood ratio test detector and TS adaptive matched filter detector. Each of the proposed detectors has two thresholds: the first one called local threshold controls the communication rate and the second one called global threshold adjusts the global probability of false alarm. It is proved that both of the proposed detectors have CFAR property. Numerical results illustrate that the two proposed detectors have good detection performance at a low communication rate.
Rotary bending fatigue properties of Inconel 718 alloys by ultrasonic nanocrystal surface modification technique
Authors: Kim Jun‐Hyong , Suh Chang‐Min , Amanov Auezhan , Kim Hak‐Doo , Pyun Young‐Sik
Published: August 2015

This study investigates the influence of ultrasonic nanocrystal surface modification (UNSM) technique on fatigue properties of SAE AMS 5662 (solution treatment) of Inconel 718 alloys. The fatigue properties of the specimens were investigated using a rotary bending fatigue tester. Results revealed that the UNSM‐treated specimens showed longer fatigue life in comparison with those of the untreated specimens. The improvement in fatigue life of the UNSM‐treated specimens is attributed mainly to the induced compressive residual stress, increased hardness, reduced roughness and refined grains at the top surface. Fractured surfaces were analysed using a scanning electron microscopy (SEM) in order to give insight into the effectiveness of UNSM technique on fracture mechanisms and fatigue life.
Facile fabrication of nitrogen‐doped zinc oxide nanoparticles with enhanced photocatalytic performance
Authors: Yi‐hao Tang , Hang Zheng , Yin Wang , Ming‐hui Ding , Guo Jin , Bin Zhang
Published: August 2015

Nitrogen (N)‐doped zinc oxide (ZnO) particles were successfully synthesised by a simple and economical ammonia‐assisted hydrothermal method. The samples were characterised by X‐ray diffraction, scanning electron microscopy, X‐ray photoelectron spectroscopy and ultraviolet–vis diffuse reflectance. It was found that N‐doped ZnO exhibited higher photocatalytic activity than commercial Degussa P25 towards the liquid‐phase degradation of Rhodamine B and methylene blue under simulation of solar light. The authors attribute these results to enhanced visible‐light absorption ability and efficient separation of photogenerated carriers. The authors hope that this study provides valuable information on the design of specific ZnO photocatalytic materials for further industrial application.
Modeling Graves’ Orbitopathy in Experimental Graves’ Disease
Authors: Moshkelgosha S. , Berchner-Pfannschmidt U. , Eckstein A. , Banga J. P.
Published: August 2015

Graves’ orbitopathy (GO), also known as thyroid eye disease is an inflammatory disease of the orbital tissue of the eye that arises as a consequence of autoimmune thyroid disease. The central feature of the disease is the production of antibodies to the thyrotropin hormone receptor (TSHR) that modulate the function of the receptor leading to autoimmune hyperthyroidism and GO. Over the years, all viable preclinical models of Graves’ disease have been incomplete and singularly failed to progress in the treatment of orbital complications. A new mouse model of GO based upon immunogenic presentation of human TSHR A-subunit plasmid by close field electroporation is shown to lead to induction of prolonged functional antibodies to TSHR resulting in chronic disease with subsequent progression to GO. The stable preclinical GO model exhibited pathologies reminiscent of human disease characterized by orbital remodeling by inflammation and adipogenesis. Inflammatory lesions characterized by CD3+ T cells and macrophages were localized in the orbital muscle tissue. This was accompanied by extensive adipogenesis of orbital fat in some immune animals. Surprisingly, other signs of orbital involvement were reminiscent of eyelid inflammation involving chemosis, with dilated and congested orbital blood vessels. More recently, the model is replicated in the author’s independent laboratories. The pre-clinical model will provide the basis to study the pathogenic and regulatory roles of immune T and B cells and their subpopulations to understand the initiation, pathophysiology, and progression of GO.
A fibre based triature interferometer for measuring rapidly evolving, ablatively driven plasma densities
Authors: Macdonald J. , Bland S. N. , Threadgold J.
Published: August 2015

We report on the first use of a fibre interferometer incorporating triature analysis for measuring rapidly evolving plasma densities of ne ∼ 1013/cm3 and above, such as those produced by simple coaxial plasma guns. The resultant system is extremely portable, easy to field in experiments, relatively cheap to produce, and—with the exception of a small open area in which the plasma is sampled—safe in operation as all laser light is enclosed.
Introducing a price variation limiter mechanism into a behavioral financial market model
Authors: Naimzada Ahmad , Pireddu Marina
Published: August 2015

In the present paper, we consider a nonlinear financial market model in which, in order to decrease the complexity of the dynamics and to achieve price stabilization, we introduce a price variation limiter mechanism, which in each period bounds the price variation so that the current price is forced to belong to a certain interval determined by the price realization in the previous period. More precisely, we introduce such mechanism into a financial market model in which the price dynamics are described by a sigmoidal price adjustment mechanism characterized by the presence of two asymptotes that bound the price variation and thus the dynamics. We show that the presence of our asymptotes prevents divergence and negativity issues. Moreover, we prove that the basins of attraction are complicated only under suitable conditions on the parameters and that chaos arises just when the price limiters are loose enough. On the other hand, for some suitable parameter configurations, we detect multistability phenomena characterized by the presence of up to three coexisting attractors.
Detection efficiency of microchannel plates for e− and π− in the momentum range from 17.5 to 345 MeV/c
Authors: Tulej M. , Meyer S. , Lüthi M. , Lasi D. , Galli A. , Desorgher L. , Hajdas W. , Karlsson S. , Kalla L. , Wurz P.
Published: August 2015

High-energy e– and π– were measured by the multichannel plate (MCP) detector at the PiM1 beam line of the High Intensity Proton Accelerator Facilities located at the Paul Scherrer Institute, Villigen, Switzerland. The measurements provide the absolute detection efficiencies for these particles: 5.8% ± 0.5% for electrons in the beam momenta range 17.5–300 MeV/c and 6.0% ± 1.3% for pions in the beam momenta range 172–345 MeV/c. The pulse height distribution determined from the measurements is close to an exponential function with negative exponent, indicating that the particles penetrated the MCP material before producing the signal somewhere inside the channel. Low charge extraction and nominal gains of the MCP detector observed in this study are consistent with the proposed mechanism of the signal formation by penetrating radiation. A very similar MCP ion detector will be used in the Neutral Ion Mass (NIM) spectrometer designed for the JUICE mission of European Space Agency (ESA) to the Jupiter system, to perform measurements of the chemical composition of the Galilean moon exospheres. The detection efficiency for penetrating radiation determined in the present studies is important for the optimisation of the radiation shielding of the NIM detector against the high-rate and high-energy electrons trapped in Jupiter’s magnetic field. Furthermore, the current studies indicate that MCP detectors can be useful to measure high-energy particle beams at high temporal resolution.
Dispersion, spatial growth rate, and start current of a Cherenkov free-electron laser with negative-index material
Authors: Wang Yuanyuan , Wei Yanyu , Li Dazhi , Takano Keisuke , Nakajima Makoto , Jiang Xuebing , Tang Xianfeng , Shi Xianbao , Gong Yubin , Feng Jinjun , Miyamoto Shuji
Published: August 2015

We present an analysis of a Cherenkov free-electron laser based on a single slab made from negative-index materials. In this system, a flat electron beam with finite thickness travelling close to the surface of the slab interacts with the copropagating electromagnetic surface mode. The dispersion equation for a finitely thick slab is worked out and solved numerically to study the dispersion relation of surface modes supported by negative-index materials, and the calculations are in good agreement with the simulation results from a finite difference time domain code. We find that under suitable conditions there is inherent feedback in such a scheme due to the characteristics of negative-index materials, which means that the system can oscillate without external reflectors when the beam current exceeds a threshold value, i.e., start current. Using the hydrodynamic approach, we setup coupled equations for this system, and solve these equations analytically in the small signal regime to obtain formulas for the spatial growth rate and start current.
A thermodynamical analysis of rf current drive with fast electrons
Authors: Bizarro João P. S.
Published: August 2015

The problem of rf current drive (CD) by pushing fast electrons with high-parallel-phase-velocity waves, such as lower-hybrid (LH) or electron-cyclotron (EC) waves, is revisited using the first and second laws, the former to retrieve the well-known one-dimensional (1D) steady-state CD efficiency, and the latter to calculate a lower bound for the rate of entropy production when approaching steady state. The laws of thermodynamics are written in a form that explicitly takes care of frictional dissipation and are thus applied to a population of fast electrons evolving under the influence of a dc electric field, rf waves, and collisions while in contact with a thermal, Maxwellian reservoir with a well-defined temperature. Besides the laws of macroscopic thermodynamics, there is recourse to basic elements of kinetic theory only, being assumed a residual dc electric field and a strong rf drive, capable of sustaining in the resonant region, where waves interact with electrons, a raised fast-electron tail distribution, which becomes an essentially flat plateau in the case of the 1D theory for LHCD. Within the 1D model, particularly suited for LHCD as it solely retains fast-electron dynamics in velocity space parallel to the ambient magnetic field, an H theorem for rf CD is also derived, which is written in different forms, and additional physics is recovered, such as the synergy between the dc and rf power sources, including the rf-induced hot conductivity, as well as the equation for electron-bulk heating. As much as possible 1D results are extended to 2D, to account for ECCD by also considering fast-electron velocity-space dynamics in the direction perpendicular to the magnetic field, which leads to a detailed discussion on how the definition of an rf-induced conductivity may depend on whether one works at constant rf current or power. Moreover, working out the collisional dissipated power and entropy-production rate written in terms of the fast-electron distribution, it is shown that the well-known formula for the steady-state CD efficiency, usually obtained from the first law in the form of power balance between the external sources and collisional losses, emerges as a lower bound for that CD figure of merit, in what can be interpreted as an instance of the second law.
Invited Article: A compact optically coherent fiber frequency comb
Authors: Sinclair L. C. , Deschênes J.-D. , Sonderhouse L. , Swann W. C. , Khader I. H. , Baumann E. , Newbury N. R. , Coddington I.
Published: August 2015

We describe the design, fabrication, and performance of a self-referenced, optically coherent frequency comb. The system robustness is derived from a combination of an optics package based on polarization-maintaining fiber, saturable absorbers for mode-locking, high signal-to-noise ratio (SNR) detection of the control signals, and digital feedback control for frequency stabilization. The output is phase-coherent over a 1-2 μm octave-spanning spectrum with a pulse repetition rate of ∼200 MHz and a residual pulse-to-pulse timing jitter <3 fs well within the requirements of most frequency-comb applications. Digital control enables phase coherent operation for over 90 h, critical for phase-sensitive applications such as timekeeping. We show that this phase-slip free operation follows the fundamental limit set by the SNR of the control signals. Performance metrics from three nearly identical combs are presented. This laptop-sized comb should enable a wide-range of applications beyond the laboratory.
Kinetic theory of weak turbulence in magnetized plasmas: Perpendicular propagation
Authors: Yoon Peter H.
Published: August 2015

The present paper formulates a weak turbulence theory in which electromagnetic perturbations are assumed to propagate in directions perpendicular to the ambient magnetic field. By assuming that all wave vectors lie in one direction transverse to the ambient magnetic field, the linear solution and second-order nonlinear solutions to the equation for the perturbed distribution function are obtained. Nonlinear perturbed current from the second-order nonlinearity is derived in general form, but the limiting situation of cold plasma temperature is taken in order to derive an explicit nonlinear wave kinetic equation that describes three-wave decay/coalescence interactions among X and Z modes. A potential application of the present formalism is also discussed.
On squares of representations of compact Lie algebras
Authors: Zeier Robert , Zimborás Zoltán
Published: August 2015

We study how tensor products of representations decompose when restricted from a compact Lie algebra to one of its subalgebras. In particular, we are interested in tensor squares which are tensor products of a representation with itself. We show in a classification-free manner that the sum of multiplicities and the sum of squares of multiplicities in the corresponding decomposition of a tensor square into irreducible representations has to strictly grow when restricted from a compact semisimple Lie algebra to a proper subalgebra. For this purpose, relevant details on tensor products of representations are compiled from the literature. Since the sum of squares of multiplicities is equal to the dimension of the commutant of the tensor-square representation, it can be determined by linear-algebra computations in a scenario where an a priori unknown Lie algebra is given by a set of generators which might not be a linear basis. Hence, our results offer a test to decide if a subalgebra of a compact semisimple Lie algebra is a proper one without calculating the relevant Lie closures, which can be naturally applied in the field of controlled quantum systems.
An ultra-low noise optical head for liquid environment atomic force microscopy
Authors: Schlesinger I. , Kuchuk K. , Sivan U.
Published: August 2015

The design considerations and eventual performance of a new, ultra-low noise optical head for dynamic atomic force microscopy (AFM) are presented. The head, designed specifically for the study of hydration layers and ion organization next to solid surfaces and biomolecules, displays an integrated tip-sample distance noise below 3 pm. The sensitivity of the optical beam deflection sensor, operating at frequencies up to 8.6 MHz (3 dB roll-off), is typically below 10 fm/Hz, enabling utilization of high frequency cantilevers of low thermal noise for fundamental and higher mode imaging. Exceptional signal stability and low optical noise are achieved by replacing the commonly used laser diode with a helium-neon laser. An integral photothermal excitation of the cantilever produces pure harmonic oscillations, minimizing the generation of higher cantilever modes and deleterious sound waves characterizing the commonly used excitation by a piezoelectric crystal. The optical head is designed to fit on top of the widespread Multimode® (Bruker) piezo-tube and accommodate its commercial liquid cell. The performance of the new AFM head is demonstrated by atomic resolution imaging of a muscovite mica surface in aqueous solution.
Growth of optical-quality anthracene crystals doped with dibenzoterrylene for controlled single photon production
Authors: Major Kyle D. , Lien Yu-Hung , Polisseni Claudio , Grandi Samuele , Kho Kiang Wei , Clark Alex S. , Hwang J. , Hinds E. A.
Published: August 2015

Dibenzoterrylene (DBT) molecules within a crystalline anthracene matrix show promise as quantum emitters for controlled, single photon production. We present the design and construction of a chamber in which we reproducibly grow doped anthracene crystals of optical quality that are several mm across and a few μm thick. We demonstrate control of the DBT concentration over the range 6–300 parts per trillion and show that these DBT molecules are stable single-photon emitters. We interpret our data with a simple model that provides some information on the vapour pressure of DBT.
Structural singularities in GexTe100−x films
Authors: Piarristeguy A. A. , Micoulaut M. , Escalier R. , Jóvári P. , Kaban I. , van Eijk J. , Luckas J. , Ravindren S. , Boolchand P. , Pradel A.
Published: August 2015

Structural and calorimetric investigation of GexTe100−x films over wide range of concentration 10 < x < 50 led to evidence two structural singularities at x ∼ 22 at. % and x ∼ 33-35 at. %. Analysis of bond distribution, bond variability, and glass thermal stability led to conclude to the origin of the first singularity being the flexible/rigid transition proposed in the framework of rigidity model and the origin of the second one being the disappearance of the undercooled region resulting in amorphous materials with statistical distributions of bonds. While the first singularity signs the onset of the Ge–Ge homopolar bonds, the second is related to compositions where enhanced Ge–Ge correlations at intermediate lengthscales (7.7 Å) are observed. These two threshold compositions correspond to recently reported resistance drift threshold compositions, an important support for models pointing the breaking of homopolar Ge–Ge bonds as the main phenomenon behind the ageing of phase change materials.
Proton transport in ice at 30–140 K: Effects of porosity
Authors: Bu Caixia , Baragiola Raúl A.
Published: August 2015

We examined the role of porosity, a crucial characteristic of amorphous solid water (ASW), on electrostatic charging and discharging of ASW films with 500 eV He+ and Xe+ ions, by measuring the surface potentials with a Kelvin probe. When a charged ASW film is heated, its surface potential decreases sharply, at temperatures that depend on the maximum temperature the film was once subject to. This sharp decrease of the surface potential is not due to a large thermally induced increase of the dielectric constant ε as proposed in other studies, since measurements of ε yielded a value of ∼3 below ∼100 K. Rather, the potential drop can be explained by the transport of the surface charge to the substrate, which depends on film porosity. We propose that the charge migrates along the walls of the pores within the ASW film, facilitated by the thermally induced reorientation of the incompletely coordinated molecules on the pore walls.
Development of a novel type of hybrid non-symmetric flexure hinges
Authors: Wang Rongqi , Zhou Xiaoqin , Zhu Zhiwei , Liu Qiang
Published: August 2015

A novel type of hybrid non-symmetric flexure hinges (NSFHs) is developed for higher motion precision in this paper, then the finite beam based matrix modeling (FBMM) method is employed to describe elastic deformation behaviors, model compliance matrix, and define non-dimensional precision factors of the hybrid NSFHs. Influences of the dimensional parameters on the dominant compliances and motion accuracies of the NSFHs are analytically investigated based on the FBMM models, while an asymmetry ratio is introduced and its influences on performances of the NSFHs are well revealed. Moreover, making comparisons of the main performances between the proposed NSFHs and symmetric flexure hinges, the obtained results indicate that the hybrid NSFHs can greatly improve the motion accuracy and suppress the adverse inherent motions. Finally, performances of the NSFHs and modeling accuracies are investigated by experimental tests, and making comparison with other flexure hinges.
Communication: Observation of local-bender eigenstates in acetylene
Authors: Steeves Adam H. , Park G. Barratt , Bechtel Hans A. , Baraban Joshua H. , Field Robert W.
Published: August 2015

We report the observation of eigenstates that embody large-amplitude, local-bending vibrational motion in acetylene by stimulated emission pumping spectroscopy via vibrational levels of the S1 state involving excitation in the non-totally symmetric bending modes. The Nb = 14 level, lying at 8971.69 cm−1 (J = 0), is assigned on the basis of degeneracy due to dynamical symmetry breaking in the local-mode limit. The level pattern for the Nb = 16 level, lying at 10 218.9 cm−1, is consistent with expectations for increased separation of ℓ = 0 and 2 vibrational angular momentum components. Increasingly poor agreement between our observations and the predicted positions of these levels highlights the failure of currently available normal mode effective Hamiltonian models to extrapolate to regions of the potential energy surface involving large-amplitude displacement along the acetylene ⇌ vinylidene isomerization coordinate.
Constrained optimal control of a point absorber wave energy converter with linear generator
Authors: Wang Liguo , Engström Jens , Göteman Malin , Isberg Jan
Published: August 2015

This paper investigates a method for optimal control of a point absorbing wave energy converter by considering the constraints on motions and forces in the time domain. The problem is converted to an optimization problem with the cost function being convex quadratic and the constraints being nonlinear. The influence of the constraints on the converter is studied, and the results are compared with uncontrolled cases and established theoretical bounds. Since this method is based on the knowledge of the future sea state or the excitation force, the influence of the prediction horizon is indicated. The resulting performance of the wave energy converter under different regular waves shows that this method leads to a substantial increase in conversion efficiency.
Assessment of maximum power point tracking techniques for photovoltaic system applications
Authors: Farahat Mohamed A. , Enany Mohamed A. , Nasr Ahmed
Published: August 2015

Photovoltaic (PV) energy is one of the most important renewable energies because it is clean, requires very little maintenance. However, the relatively high costs and low conversion efficiency are still the major challenge to a larger and faster spread of PV systems. Therefore, the maximum power point tracker (MPPT) is essential in a PV system for maximizing the conversion efficiency of the solar array. Because of the nonlinear behavior of the PV systems, various techniques of the MPPT are employed in order to continuously operate the solar array at their MPP, despite the unavoidable changes in solar irradiance and temperature. This paper presents an assessment of five widely used MPPT techniques. These techniques are simulated in Matlab/Simulink environment in order to provide a comparison in terms of sensors required, ease of implementation, efficiency, the dynamic response of the PV system to variations in temperature and irradiance, and their appropriateness for the different applications of PV system. This can be used as a reference for future research related to the PV power generation.
The piezoelectronic stress transduction switch for very large-scale integration, low voltage sensor computation, and radio frequency applications
Authors: Magdău I.-B. , Liu X.-H. , Kuroda M. A. , Shaw T. M. , Crain J. , Solomon P. M. , Newns D. M. , Martyna G. J.
Published: August 2015

The piezoelectronic transduction switch is a device with potential as a post–CMOS transistor due to its predicted multi-GHz, low voltage performance on the VLSI-scale. However, the operating principle of the switch has wider applicability. We use theory and simulation to optimize the device across a wide range of length scales and application spaces and to understand the physics underlying its behavior. We show that the four-terminal VLSI-scale switch can operate at a line voltage of 115 mV while as a low voltage-large area device, ≈200 mV operation at clock speeds of ≈2 GHz can be achieved with a desirable 104 On/Off ratio—ideal for on–board computing in sensors. At yet larger scales, the device is predicted to operate as a fast (≈250 ps) radio frequency (RF) switch exhibiting high cyclability, low On resistance and low Off capacitance, resulting in a robust switch with a RF figure of merit of ≈4 fs. These performance benchmarks cannot be approached with CMOS which has reached fundamental limits. In detail, a combination of finite element modeling and ab initio calculations enables prediction of switching voltages for a given design. A multivariate search method then establishes a set of physics-based design rules, discovering the key factors for each application. The results demonstrate that the piezoelectronic transduction switch can offer fast, low power applications spanning several domains of the information technology infrastructure.
Signatures of nonthermal melting
Authors: Zier Tobias , Zijlstra Eeuwe S. , Kalitsov Alan , Theodonis Ioannis , Garcia Martin E.
Published: August 2015

Intense ultrashort laser pulses can melt crystals in less than a picosecond but, in spite of over thirty years of active research, for many materials it is not known to what extent thermal and nonthermal microscopic processes cause this ultrafast phenomenon. Here, we perform ab-initio molecular-dynamics simulations of silicon on a laser-excited potential-energy surface, exclusively revealing nonthermal signatures of laser-induced melting. From our simulated atomic trajectories, we compute the decay of five structure factors and the time-dependent structure function. We demonstrate how these quantities provide criteria to distinguish predominantly nonthermal from thermal melting.
Microfluidic sorting of protein nanocrystals by size for X-ray free-electron laser diffraction
Authors: Abdallah Bahige G. , Zatsepin Nadia A. , Roy-Chowdhury Shatabdi , Coe Jesse , Conrad Chelsie E. , Dörner Katerina , Sierra Raymond G. , Stevenson Hilary P. , Camacho-Alanis Fernanda , Grant Thomas D. , Nelson Garrett , James Daniel , Calero Guillermo , Wachter Rebekka M. , Spence John C. H. , Weierstall Uwe , Fromme Petra , Ros Alexandra
Published: August 2015

The advent and application of the X-ray free-electron laser (XFEL) has uncovered the structures of proteins that could not previously be solved using traditional crystallography. While this new technology is powerful, optimization of the process is still needed to improve data quality and analysis efficiency. One area is sample heterogeneity, where variations in crystal size (among other factors) lead to the requirement of large data sets (and thus 10–100 mg of protein) for determining accurate structure factors. To decrease sample dispersity, we developed a high-throughput microfluidic sorter operating on the principle of dielectrophoresis, whereby polydisperse particles can be transported into various fluid streams for size fractionation. Using this microsorter, we isolated several milliliters of photosystem I nanocrystal fractions ranging from 200 to 600 nm in size as characterized by dynamic light scattering, nanoparticle tracking, and electron microscopy. Sorted nanocrystals were delivered in a liquid jet via the gas dynamic virtual nozzle into the path of the XFEL at the Linac Coherent Light Source. We obtained diffraction to ∼4 Å resolution, indicating that the small crystals were not damaged by the sorting process. We also observed the shape transforms of photosystem I nanocrystals, demonstrating that our device can optimize data collection for the shape transform-based phasing method. Using simulations, we show that narrow crystal size distributions can significantly improve merged data quality in serial crystallography. From this proof-of-concept work, we expect that the automated size-sorting of protein crystals will become an important step for sample production by reducing the amount of protein needed for a high quality final structure and the development of novel phasing methods that exploit inter-Bragg reflection intensities or use variations in beam intensity for radiation damage-induced phasing. This method will also permit an analysis of the dependence of crystal quality on crystal size.
Excited state of protonated benzene and toluene
Authors: Esteves-López Natalia , Dedonder-Lardeux Claude , Jouvet Christophe
Published: August 2015

We present photo-fragmentation electronic spectra of the simplest protonated aromatic molecules, protonated benzene and toluene, recorded under medium resolution conditions and compared with the photo-fragmentation spectrum of protonated pyridine. Despite the resolution and cold temperature achieved in the experiment, the electronic spectra of protonated benzene and toluene are structure-less, thus intrinsically broadened. This is in agreement with the large geometrical changes and the fast dynamic toward internal conversion predicted by ab initio calculations for protonated benzene [Rode et al., J. Phys. Chem. A 113, 5865–5873 (2009)].
Minimum-dissipation models for large-eddy simulation
Authors: Rozema Wybe , Bae Hyun J. , Moin Parviz , Verstappen Roel
Published: August 2015

Minimum-dissipation eddy-viscosity models are a class of sub-filter models for large-eddy simulation that give the minimum eddy dissipation required to dissipate the energy of sub-filter scales. A previously derived minimum-dissipation model is the QR model. This model is based on the invariants of the resolved rate-of-strain tensor and has many desirable properties. It appropriately switches off for laminar and transitional flows, has low computational complexity, and is consistent with the exact sub-filter tensor on isotropic grids. However, the QR model proposed in the literature gives insufficient eddy dissipation. It is demonstrated that this can be corrected by increasing the model constant. The corrected QR model gives good results in simulations of decaying grid turbulence on an isotropic grid. On anisotropic grids the QR model is not consistent with the exact sub-filter tensor and requires an approximation of the filter width. It is demonstrated that the results of the QR model on anisotropic grids are primarily determined by the used filter width approximation, and that no approximation gives satisfactory results in simulations of both a temporal mixing layer and turbulent channel flow. A new minimum-dissipation model for anisotropic grids is proposed. This anisotropic minimum-dissipation (AMD) model generalizes the desirable practical and theoretical properties of the QR model to anisotropic grids and does not require an approximation of the filter width. The AMD model is successfully applied in simulations of decaying grid turbulence on an isotropic grid and in simulations of a temporal mixing layer and turbulent channel flow on anisotropic grids.