bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular signaling cascades involved in nonmelanoma skin carcinogenesis
Authors: Feehan Robert P. , Shantz Lisa M.
Published: September 2016

Nonmelanoma skin cancer (NMSC) is the most common cancer worldwide and the incidence continues to rise, in part due to increasing numbers in high-risk groups such as organ transplant recipients and those taking photosensitizing medications. The most significant risk factor for NMSC is ultraviolet radiation (UVR) from sunlight, specifically UVB, which is the leading cause of DNA damage, photoaging, and malignant transformation in the skin. Activation of apoptosis following UVR exposure allows the elimination of irreversibly damaged cells that may harbor oncogenic mutations. However, UVR also activates signaling cascades that promote the survival of these potentially cancerous cells, resulting in tumor initiation. Thus, the UVR-induced stress response in the skin is multifaceted and requires coordinated activation of numerous pathways controlling DNA damage repair, inflammation, and kinase-mediated signal transduction that lead to either cell survival or cell death. This review focuses on the central signaling mechanisms that respond to UVR and the subsequent cellular changes. Given the prevalence of NMSC and the resulting health care burden, many of these pathways provide promising targets for continued study aimed at both chemoprevention and chemotherapy.
Sphingolipid biosynthesis upregulation by TOR complex 2–Ypk1 signaling during yeast adaptive response to acetic acid stress
Authors: Guerreiro Joana F. , Muir Alexander , Ramachandran Subramaniam , Thorner Jeremy , Sá-Correia Isabel
Published: September 2016

Acetic acid-induced inhibition of yeast growth and metabolism limits the productivity of industrial fermentation processes, especially when lignocellulosic hydrolysates are used as feedstock in industrial biotechnology. Tolerance to acetic acid of food spoilage yeasts is also a problem in the preservation of acidic foods and beverages. Thus understanding the molecular mechanisms underlying adaptation and tolerance to acetic acid stress is increasingly important in industrial biotechnology and the food industry. Prior genetic screens for Saccharomyces cerevisiae mutants with increased sensitivity to acetic acid identified loss-of-function mutations in the YPK1 gene, which encodes a protein kinase activated by the target of rapamycin (TOR) complex 2 (TORC2). We show in the present study by several independent criteria that TORC2–Ypk1 signaling is stimulated in response to acetic acid stress. Moreover, we demonstrate that TORC2-mediated Ypk1 phosphorylation and activation is necessary for acetic acid tolerance, and occurs independently of Hrk1, a protein kinase previously implicated in the cellular response to acetic acid. In addition, we show that TORC2–Ypk1-mediated activation of l-serine:palmitoyl-CoA acyltransferase, the enzyme complex that catalyzes the first committed step of sphingolipid biosynthesis, is required for acetic acid tolerance. Furthermore, analysis of the sphingolipid pathway using inhibitors and mutants indicates that it is production of certain complex sphingolipids that contributes to conferring acetic acid tolerance. Consistent with that conclusion, promoting sphingolipid synthesis by adding exogenous long-chain base precursor phytosphingosine to the growth medium enhanced acetic acid tolerance. Thus appropriate modulation of the TORC2–Ypk1–sphingolipid axis in industrial yeast strains may have utility in improving fermentations of acetic acid-containing feedstocks.
Reappraisal of putative glyoxalase 1-deficient mouse and dicarbonyl stress on embryonic stem cellsin vitro
Authors: Shafie Alaa , Xue Mingzhan , Barker Guy , Zehnder Daniel , Thornalley Paul J. , Rabbani Naila
Published: September 2016

Glyoxalase 1 (Glo1) is a cytoplasmic enzyme with a cytoprotective function linked to metabolism of the cytotoxic side product of glycolysis, methylglyoxal (MG). It prevents dicarbonyl stress — the abnormal accumulation of reactive dicarbonyl metabolites, increasing protein and DNA damage. Increased Glo1 expression delays ageing and suppresses carcinogenesis, insulin resistance, cardiovascular disease and vascular complications of diabetes and renal failure. Surprisingly, gene trapping by the International Mouse Knockout Consortium (IMKC) to generate putative Glo1 knockout mice produced a mouse line with the phenotype characterised as normal and healthy. Here, we show that gene trapping mutation was successful, but the presence of Glo1 gene duplication, probably in the embryonic stem cells (ESCs) before gene trapping, maintained wild-type levels of Glo1 expression and activity and sustained the healthy phenotype. In further investigation of the consequences of dicarbonyl stress in ESCs, we found that prolonged exposure of mouse ESCs in culture to high concentrations of MG and/or hypoxia led to low-level increase in Glo1 copy number. In clinical translation, we found a high prevalence of low-level GLO1 copy number increase in renal failure where there is severe dicarbonyl stress. In conclusion, the IMKC Glo1 mutant mouse is not deficient in Glo1 expression through duplication of the Glo1 wild-type allele. Dicarbonyl stress and/or hypoxia induces low-level copy number alternation in ESCs. Similar processes may drive rare GLO1 duplication in health and disease.
Effects of loss on the determination of antenna energy and Q
Authors: Thal Herbert L.
Published: September 2016

Expressions for the stored energy and Q factor of an antenna in terms of its radiated spherical modes and reflection coefficient have been extended to include the effects of loss. Three variations are given for excitation by matched, voltage, or current generators, and the importance of the proper phase reference for the radiated fields is emphasised. Two low‐Q, self‐resonant spherical antennas are used to illustrate the application of the energy formulae with and without loss. The results for these examples are validated by direct integration of the electric energy and by self‐consistency of the radiation and dissipation terms. Approximation equations appropriate for processing experimental data are derived, and their predictions are compared with the actual Q’s for the examples. Estimates of the lossless Q’s are determined from the lossy data.
Dual‐band, dual‐polarised metallic slot transmitarray antenna
Authors: Bagheri Mohammad Omid , Hassani Hamid Reza , Rahmati Bahman
Published: September 2016

A metallic, dual‐band, dual polarised slot‐based transmitarray antenna is presented. The antenna consists of three thin metallic layers do not use any dielectric substrates, with air gaps in between the layers. The unit cell uses interleaved orthogonal slots, as well as crossed‐dipole slot and uniplanar compact photonic bandgap slot elements to provide the lower and upper frequency band resonators, respectively. The frequency separation between the two resonances can be adjusted from closely spaced to far from each other. The antenna provides dual linear polarisation and circular polarisation with the use of the appropriate feed. The fabricated transmitarray antenna provides two independent frequency bands with a band ratio of 1.13 and low mutual coupling. The measurement of a 14 × 14 element transmitarray antenna at 11 GHz shows a maximum gain of 23.74 dB with −1 dB gain bandwidth of 6.8% and aperture efficiency of 38%; at 12.5 GHz, a maximum gain of 24.45 dB is obtained with −1 dB gain bandwidth of 5.4% and aperture efficiency of 34.6%. The antenna is simulated by using the CST software; the ADS package is used for equivalent circuit simulation.
Compact transmit receive hybrid electromagnetic isolation in antenna array transceiver system for full duplex applications
Authors: Abdalla Mahmoud A. , Abdelraheem Ahmed M.
Published: September 2016

This study presents a hybrid electromagnetic isolation mechanism in a transceiver array antenna operating at 5.8 GHz. Maximum isolation between transmitting and receiving array antennas, at a very close spacing (3 mm = 0.058λ0), and minimum mutual coupling between each array elements is achieved without antenna radiation pattern degradation. The achieved separation is equivalent to 44% size reduction compared with conventional half wavelength spacing criterion. Each of the transmitting and receiving array antennas is a four‐element linear microstrip patch array antenna. The employed hybrid isolation technique is composed of defected ground structure, to minimise coupling between array elements, and uniplanar electromagnetic bandgap, to minimise the coupling between the transmitting and receiving antennas. The resulting transceiver array antenna system fulfils −35 dB mutual coupling between array elements, and 60 dB isolation between opponent transmitting and receiving array antennas. The proposed design procedures are discussed and analysed using electromagnetic full wave simulations. Results were verified through experimental measurements for reflection coefficient, mutual coupling and radiation characteristics in which a good agreement with simulated results is granted.
Débits écologiques : la place des modèles d’habitat hydraulique dans une démarche intégrée
Authors: Lamouroux N. , Augeard B. , Baran P. , Capra H. , Le Coarer Y. , Girard V. , Gouraud V. , Navarro L. , Prost O. , Sagnes P. , Sauquet E. , Tissot L.
Published: September 2016

Deux types d’approches techniques complémentaires sont utilisées pour guider l’établissement des débits écologiques, à l’échelle des tronçons de cours d’eau (ex. : débits réservés) comme à l’échelle de bassins versants (ex. : débits objectifs d’étiage). Les approches « hydrologiques » visent à quantifier les altérations de multiples caractéristiques du régime hydrologique et reposent sur l’identification (délicate) de relations empiriques entre altérations hydrologiques et biologiques. Les approches « habitat hydraulique », ciblées sur les débits bas à moyens, couplent des modèles hydrauliques et des modèles biologiques pour traduire certaines modifications hydrologiques en modification de qualité de l’habitat hydraulique pour les organismes. Elles ont parfois apporté des prédictions convaincantes des effets biologiques des modifications de débits d’étiage. Ces deux approches techniques ne fournissent pas directement de valeurs de débits écologiques. Nous formalisons ici une démarche technique de définition des débits écologiques, basée sur la comparaison de scénarios de gestion et une meilleure combinaison des deux approches. La démarche comprend quatre étapes : (1) la description du contexte hydrologique naturalisé et actuel, des usages actuels et des scénarios de gestion envisagés (2) la description du contexte écologique au sens large, (3) l’identification des métriques pertinentes (hydrologiques et/ou habitats et/ou autres) pour décrire les effets des scénarios (modifications des usages, effets sur le milieu) et (4) la comparaison des scénarios. Cette démarche ne se passe pas d’expertise et doit s’accompagner d’une définition des objectifs partagée par les acteurs ainsi que de retours d’expérience, aspects non détaillés ici.
Papillendiagnostik mithilfe der optischen Kohärenztomografie
Authors: Unterlauft J. , Tegetmeyer H.
Published: September 2016

Hintergrund: Die Untersuchung des Sehnervenkopfs mit der optischen Kohärenztomografie (OCT) ist beim kooperativen Patienten schnell und einfach durchzuführen und erleichtert die Erkennung und Verlaufskontrolle verschiedener pathologischer Veränderungen der Papille deutlich.

Material und Methoden: Anhand von Beispielen sollen Möglichkeiten und typische Befunde der OCT-Untersuchung der Papille dargestellt werden, um die Erkennung auch seltener Erkrankungen des Sehnervs zu vereinfachen und korrekte Therapieentscheidungen fundiert treffen zu können.

Ergebnisse: Pathologische Veränderungen an der Papille und typische Papillen-OCT-Befunde bei Glaukom, bei verschiedenen Papillenanomalien, bei nicht glaukomatös bedingten Optikusatrophien und bei Papillenschwellungen unterschiedlicher Genese werden beschrieben. Darüber hinaus werden diejenigen OCT-Parameter und Untersuchungsmodalitäten dargestellt, mithilfe derer sich die jeweiligen Krankheitsbilder am einfachsten durch den Untersucher erkennen lassen.

Schlussfolgerung: Die Untersuchung der Papille mittels OCT ermöglicht eine schnelle Diagnostik auch seltener und ophthalmoskopisch schwierig zu erkennender Pathologien des Sehnervenkopfs und genaueste Verlaufsuntersuchungen chronisch-progredienter Erkrankungen. Mithilfe der OCT-Untersuchung der Papille können bei richtiger Anwendung und Auswertung die richtigen Diagnosen korrekt gestellt werden und wichtige Therapieentscheidungen deutlich vereinfacht werden.
Erratum: A deterministic model of a research organization’s evolution and dynamics of performance
Authors: Goswami Prashant , Nishad Shiv Narayan , Selvaratnam Dhanya
Published: September 2016

Correction to: Palgrave Communications (2016) 1, Article number: 15012. doi: 10.1057/palcomms.2015.12; Published 9 Jun 2015; Updated 27 September 2016 The correct affiliation for Prashant Goswami has been added to the manuscript: National Institute of Science, Technology and Development Studies (NISTADS), New Delhi, India
A femtosecond Raman generator for long wavelength two-photon and third harmonic generation imaging
Authors: Trägårdh J. , Schniete J. , Parsons M. , McConnell G.
Published: September 2016

We demonstrate a femtosecond single pass Raman generator based on an YVO4 crystal pumped by a high energy fiber laser at a wavelength of 1064 nm and a repetition rate of 1 MHz. The Raman generator shifts the pump wavelength to 1175 nm, in a broadband spectrum, making it suitable for multi-photon microscopy. We use the Raman generator for third harmonic generation imaging of live plant specimens as well as for two-photon fluorescence imaging of red fluorescent protein expressing HeLa cells. We demonstrate that the photo-damage to a live specimen is low.
Analysis of vibrational resonance in bi-harmonically driven plasma
Authors: Roy-Layinde T. O. , Laoye J. A. , Popoola O. O. , Vincent U. E.
Published: September 2016

The phenomenon of vibrational resonance (VR) is examined and analyzed in a bi-harmonically driven two-fluid plasma model with nonlinear dissipation. An equation for the slow oscillations of the system is analytically derived in terms of the parameters of the fast signal using the method of direct separation of motion. The presence of a high frequency externally applied electric field is found to significantly modify the system's dynamics, and consequently, induce VR. The origin of the VR in the plasma model has been identified, not only from the effective plasma potential but also from the contributions of the effective nonlinear dissipation. Beside several dynamical changes, including multiple symmetry-breaking bifurcations, attractor escapes, and reversed period-doubling bifurcations, numerical simulations also revealed the occurrence of single and double resonances induced by symmetry breaking bifurcations.
Detection of atmospheric infrasound with a ring laser interferometer
Authors: Dunn Robert W. , Meredith John A. , Lamb Angela B. , Kessler Elijah G.
Published: September 2016

In this paper, the results from using a large active ring laser interferometer as an infrasound detector are presented. On April 27, 2014, an EF4 tornado struck Central Arkansas and passed within 21 km of the ring laser interferometer. The tornado resulted in 16 fatalities and millions of dollars in damage. Using the ring laser to study the tornado infrasound produced results that qualitatively agree with several findings from a long-term study of weather generated infrasound by the National Oceanic and Atmospheric Administration. A Fast Fourier Transform of the ring laser output revealed a coherent frequency of approximately 0.94 Hz that lasted during the life of the storm. The 0.94 Hz frequency was initially observed 30 min before the funnel was reported on the ground. Infrasound signatures from four separate tornadoes are presented. In each case, coherent infrasound was detected at least 30 min before the tornado was reported on the ground. Examples of the detection of distant coherent acoustic-gravity waves from volcanoes and typhoons are also presented. In addition, buoyancy waves were recorded.
Invited Article: Generation of one-million-mode continuous-variable cluster state by unlimited time-domain multiplexing
Authors: Yoshikawa Jun-ichi , Yokoyama Shota , Kaji Toshiyuki , Sornphiphatphong Chanond , Shiozawa Yu , Makino Kenzo , Furusawa Akira
Published: September 2016

In recent quantum optical continuous-variable experiments, the number of fully inseparable light modes has drastically increased by introducing a multiplexing scheme either in the time domain or in the frequency domain. Here, modifying the time-domain multiplexing experiment reported in the work of Yokoyama et al. [Nat. Photonics 7, 982 (2013)], we demonstrate the successive generation of fully inseparable light modes for more than one million modes. The resulting multi-mode state is useful as a dual-rail continuous variable cluster state. We circumvent the previous problem of optical phase drifts, which has limited the number of fully inseparable light modes to around ten thousands, by continuous feedback control of the optical system.
A novel instrument to measure differential ablation of meteorite samples and proxies: The Meteoric Ablation Simulator (MASI)
Authors: Bones D. L. , Gómez Martín J. C. , Empson C. J. , Carrillo Sánchez J. D. , James A. D. , Conroy T. P. , Plane J. M. C.
Published: September 2016

On entering the Earth’s atmosphere, micrometeoroids partially or completely ablate, leaving behind layers of metallic atoms and ions. The relative concentration of the various metal layers is not well explained by current models of ablation. Furthermore, estimates of the total flux of cosmic dust and meteoroids entering the Earth’s atmosphere vary over two orders of magnitude. To better constrain these estimates and to better model the metal layers in the mesosphere, an experimental Meteoric Ablation Simulator (MASI) has been developed. Interplanetary Dust Particle (IDP) analogs are subjected to temperature profiles simulating realistic entry heating, to ascertain the differential ablation of relevant metal species. MASI is the first ablation experiment capable of simulating detailed mass, velocity, and entry angle-specific temperature profiles whilst simultaneously tracking the resulting gas-phase ablation products in a time resolved manner. This enables the determination of elemental atmospheric entry yields which consider the mass and size distribution of IDPs. The instrument has also enabled the first direct measurements of differential ablation in a laboratory setting.
Non-perturbative Anderson localization in heavy-tailed potentials via large deviations moment analysis
Authors: Chulaevsky Victor
Published: September 2016

We study a class of Anderson Hamiltonians with heavy-tailed independent and identically distributed random potential on graphs with sub-exponential growth of the balls and of the number of self-avoiding paths connecting pairs of points. We show that for a class of marginal distributions, Anderson localization occurs non-perturbatively, i.e., for any nonzero amplitude of the potential, like in one-dimensional systems. The proof is based on the moment analysis of the Green functions via large deviations estimates.
Theory on bright and dark soliton formation in strongly magnetized plasmas
Authors: Feng W. , Li J. Q. , Kishimoto Y.
Published: September 2016

The existence and properties of bright and dark solitons in strongly magnetized warm plasmas are investigated analytically. These solitons are solutions to a four-dimensional Hamiltonian system with zero and non-zero boundary conditions. Based on the dynamical systems theory, the parametric domains of magnetic field and soliton frequency for the existence of bright and dark solitons in both cold and warm plasmas are identified. It is found that the temperature effects play an important role in determining the parametric domains and properties of the solitons. Specifically, the temperature effects make it possible for the existence of multi-hump dark solitons and remove the constraint on magnetic field and soliton frequency caused by the non-negative condition of the density profile. The numerical integration of the soliton equations shows that the bright soliton amplitude increases with magnetic field while the dark soliton amplitude decreases with it. For both bright and dark solitons, the temperature effects suppress the soliton amplitude.
Development of low temperature atomic force microscopy with an optical beam deflection system capable of simultaneously detecting the lateral and vertical forces
Authors: Arima Eiji , Wen Huanfei , Naitoh Yoshitaka , Li Yan Jun , Sugawara Yasuhiro
Published: September 2016

The atomic force microscopy (AFM) is a very important tool for imaging and investigating the complex force interactions on sample surfaces with high spatial resolution. In the AFM, two types of detection systems of the tip-sample interaction forces have been used: an optical detection system and an electrical detection system. In optical detection systems, such as optical beam deflection system or optical fiber interferometer system, both the lateral and the vertical tip-sample forces can be measured simultaneously. In electrical detection systems, such as qPlus or Kolibri sensors, either the lateral or vertical forces can be measured. Simultaneous measurement of the lateral and vertical interaction forces effectively allows investigation of force interactions because the force is a vector with magnitude and direction. In this study, we developed a low-temperature, frequency-modulation AFM using an optical beam deflection system to simultaneously measure the vertical and lateral forces. In this system, the heat sources, such as a laser diode and a current-to-voltage converter, for measuring the photocurrent of the four-segmented photodiode are located outside the observation chamber to avoid a temperature increase of the AFM unit. The focused optical beam is three-dimensionally adjustable on the back side of the cantilever. We demonstrate low-noise displacement measurement of the cantilever and successful atomic resolution imaging using the vertical and lateral forces at low temperatures.
Using VISAR to assess the M-band isotropy in hohlraums
Authors: Lanier N. E. , Kline J. L. , Morton J.
Published: September 2016

In laser based radiation flow experiments, drive variability can often overwhelm the physics sensitivity that one seeks to quantify. Hohlraums can help by providing a more symmetrized, Planckian-like source. However, at higher temperatures, the hohlraum’s actual emission can deviate significantly from a truly blackbody, Lambertian source. At the National Ignition Facility (NIF), Dante provides the best quantification of hohlraum output. Unfortunately, limited diagnostic access coupled with NIF’s natural symmetry does not allow for Dante measurements at more than two angles. As part of the CEPHEUS campaign on NIF, proof-of-principle experiments to better quantify the gold M-band isotropy were conducted. These experiments positioned beryllium/aluminum mirrors at differing angles, offset from the hohlraum. Filtering removes the thermal emission of the hohlraum and the remaining M-band radiation is preferentially absorbed in the aluminum layer. The subsequent hydrodynamic motion is measured via VISAR. Although indirect, this M-band measurement can be made at any angle.
Feasibility of line-ratio spectroscopy on helium and neon as edge diagnostic tool for Wendelstein 7-X
Authors: Barbui T. , Krychowiak M. , König R. , Schmitz O. , Muñoz Burgos J. M. , Schweer B. , Terra A. ,   W7-X Team
Published: September 2016

A beam emission spectroscopy system on thermal helium (He) and neon (Ne) has been set up at Wendelstein 7-X to measure edge electron temperature and density profiles utilizing the line-ratio technique or its extension by the analysis of absolutely calibrated line emissions. The setup for a first systematic test of these techniques of quantitative atomic spectroscopy in the limiter startup phase (OP1.1) is reported together with first measured profiles. This setup and the first results are an important test for developing the technique for the upcoming high density, low temperature island divertor regime.
Simulation of a non-equilibrium helium plasma bullet emerging into oxygen at high pressure (250–760 Torr) and interacting with a substrate
Authors: Yan Wen , Economou Demetre J.
Published: September 2016

A two-dimensional computational study of a plasma bullet emanating from a helium gas jet in oxygen ambient at high pressure (250–760 Torr) was performed, with emphasis on the bullet interaction with a substrate. Power was applied in the form of a trapezoidal +5 kV pulse lasting 150 ns. A neutral gas transport model was employed to predict the concentration distributions of helium and oxygen in the system. These were then used in a plasma dynamics model to investigate the characteristics of the plasma bullet during its propagation and interaction with a substrate. Upon ignition, the discharge first propagated as a surface wave along the inner wall of the containing tube, and then exited the tube with a well-defined ionization front (streamer or plasma bullet). The plasma bullet evolved from a hollow (donut-shaped) feature to one where the maximum of ionization was on axis. The bullet propagated in the gap between the tube exit and the substrate with an average speed of ∼2 × 105 m/s. Upon encountering a metal substrate, the bullet formed a conductive channel to the substrate. Upon encountering a dielectric substrate, the bullet turned into an ionization wave propagating radially along the substrate surface. For a conductive substrate, the radial species fluxes to the surface peaked on the symmetry axis. For a dielectric substrate, a ring-shaped flux distribution was observed. The “footprint” of plasma-surface interaction increased either by decreasing the gap between tube exit and substrate, decreasing the relative permittivity of an insulating substrate, or decreasing pressure. As the system pressure was lowered from 760 to 250 Torr, the discharge was initiated earlier, and the plasma bullet propagation speed increased. A reverse electric field developed during the late stages of the ramp-down of the pulse, which accelerated electrons forming a brief backward discharge.
Comment on “The physics origin of the hierarchy of bodies in space” [J. Appl. Phys. 119, 094901 (2016)]
Authors: Swartz C. H.
Published: September 2016

A recent paper [A. Bejan and R. W. Wagstaff, J. Appl. Phys. 119, 094901 (2016)] concludes that bodies of the same size suspended uniformly in space are in a state of high internal tension. The tension is then relieved by rearrangement of the bodies into a non-uniform distribution of mass. In this Comment, it is shown that the conclusions are based upon calculations which are in error, and that the amount of tension is not in fact decreased by such a rearrangement.
Exploiting total internal reflection geometry for efficient optical modulation of terahertz light
Authors: Liu Xudong , Parrott Edward P. J. , Ung Benjamin S.-Y. , Pickwell-MacPherson Emma
Published: September 2016

Efficient methods to modulate terahertz (THz) light are essential for realizing rapid THz imaging and communication applications. Here we report a novel THz modulator which utilizes the evanescent wave in a total internal reflection setup coupled with a conductive interface to enhance the attenuation efficiency of THz light. This approach makes it possible to achieve close to 100% modulation with a small interface conductivity of 12 mS. The frequency dependence of this technique is linked to the optical properties of the materials: a material with close to frequency independent conductivity that is also controllable will result in an achromatic modulation response, and the device performance can be optimized further by tuning the internal reflection angle. In this work, we focus on applying the technique in the terahertz frequency range. Using an LED array with a pump intensity of 475 mW/cm2 to produce carriers in a silicon wafer, we have achieved a modulation depth of up to 99.9% in a broad frequency range of 0.1 THz–0.8 THz. The required pumping power for the generation of the required free carriers is low because the sheet conductivity needed is far less than required for traditional transmission techniques. Consequently, the device can be modulated by an LED making it a very practical, low cost, and scalable solution for THz modulation.
sl(2)-modules by sl(2)-coherent states
Authors: Fakhri H. , Sayyah-Fard M.
Published: September 2016

Irreducible sp(4)-module with highest weight, labeled by the azimuthal and magnetic quantum numbers l and m, is split into the direct sums of the irreducible su(2)- and su(1, 1)-submodules in four different ways: finite integer unitary irreducible subspaces corresponding to the orbital angular momentum algebra su(2), infinite positive discrete series of su(1, 1) with an arbitrary half-integer Bargmann index, and the positive and negative discrete series of su(1, 1) with both the Bargmann indices 1/4 and 3/4. Even and odd coherent states for the positive su(1, 1)-submodules with the Bargmann indices 1/4 and 3/4 are constructed and it is shown that they enjoy the property of completeness by two appropriate positive definite measures. We show that the even and odd coherent states themselves form the positive discrete series of su(1, 1) with the Bargmann indices 1/4 and 3/4, respectively. For these even and odd coherent states, we consider the uncertainty relations for the x- and y-components of the angular momentum as well as the generators of the negative discrete series of su(1, 1) with the Bargmann indices 1/4 and 3/4.
Integrated four-channel all-fiber up-conversion single-photon-detector with adjustable efficiency and dark count
Authors: Zheng Ming-Yang , Shentu Guo-Liang , Ma Fei , Zhou Fei , Zhang Hai-Ting , Dai Yun-Qi , Xie Xiuping , Zhang Qiang , Pan Jian-Wei
Published: September 2016

Up-conversion single photon detector (UCSPD) has been widely used in many research fields including quantum key distribution, lidar, optical time domain reflectrometry, and deep space communication. For the first time in laboratory, we have developed an integrated four-channel all-fiber UCSPD which can work in both free-running and gate modes. This compact module can satisfy different experimental demands with adjustable detection efficiency and dark count. We have characterized the key parameters of the UCSPD system.
Accelerating potential of mean force calculations for lipid membrane permeation: System size, reaction coordinate, solute-solute distance, and cutoffs
Authors: Nitschke Naomi , Atkovska Kalina , Hub Jochen S.
Published: September 2016

Molecular dynamics simulations are capable of predicting the permeability of lipid membranes for drug-like solutes, but the calculations have remained prohibitively expensive for high-throughput studies. Here, we analyze simple measures for accelerating potential of mean force (PMF) calculations of membrane permeation, namely, (i) using smaller simulation systems, (ii) simulating multiple solutes per system, and (iii) using shorter cutoffs for the Lennard-Jones interactions. We find that PMFs for membrane permeation are remarkably robust against alterations of such parameters, suggesting that accurate PMF calculations are possible at strongly reduced computational cost. In addition, we evaluated the influence of the definition of the membrane center of mass (COM), used to define the transmembrane reaction coordinate. Membrane-COM definitions based on all lipid atoms lead to artifacts due to undulations and, consequently, to PMFs dependent on membrane size. In contrast, COM definitions based on a cylinder around the solute lead to size-independent PMFs, down to systems of only 16 lipids per monolayer. In summary, compared to popular setups that simulate a single solute in a membrane of 128 lipids with a Lennard-Jones cutoff of 1.2 nm, the measures applied here yield a speedup in sampling by factor of ∼40, without reducing the accuracy of the calculated PMF.
Ponderomotive forces in electrodynamics of moving media: The Minkowski and Abraham approaches
Authors: Nesterenko V. V. , Nesterenko A. V.
Published: September 2016

In the general setting of the problem, the explicit compact formulae are derived for the ponderomotive forces in the macroscopic electrodynamics of moving media in the Minkowski and Abraham approaches. Taking account of the Minkowski constitutive relations and making use of a special representation for the Abraham energy-momentum tensor enable one to obtain a compact expression for the Abraham force in the case of arbitrary dependence of the medium velocity on spatial coordinates and the time and for nonstationary external electromagnetic field. We term the difference between the ponderomotive forces in the Abraham and Minkowski approaches as the Abraham force not only under consideration of media at rest but also in the case of moving media. The Lorentz force is found which is exerted by external electromagnetic field on the conduction current in a medium, the covariant Ohm law, and the constitutive Minkowski relations being taken into account. The physical argumentation is traced for the definition of the 4-vector of the ponderomotive force as the 4-divergence of the energy-momentum tensor of electromagnetic field in a medium.
Attenuation of strong external blast by foam barriers
Authors: Sembian S. , Liverts M. , Apazidis N.
Published: September 2016

The mitigation of externally generated strong blast waves by an aqueous foam barrier of varying configurations within fixed distance between the explosion origin and the object to be protected is investigated and quantified both experimentally and numerically. The blast waves of shock Mach number 4.8 at 190 mm from the explosion plane are generated using exploding wire technique. The initially cylindrical blast waves are transformed into a plane blast wave in a specially constructed test unit in which the experiments are performed. The shock waves emanating from the foam barrier are captured using shadowgraph technique. A simple numerical model treating the foam by a pseudo-gas approach is used in interpreting and re-constructing the experimental results. The additional contribution of the impedance mismatch factor is analysed with the aid of numerical simulation and exploited for achieving greater blast wave pressure reduction.
Low frequency limit of X-mode in non-uniform space and bounded laboratory plasmas
Authors: Saleem Hamid , Saeed Usman
Published: September 2016

It is pointed out that the high frequency extraordinary wave in a non-uniform density plasma contains a low frequency drift type mode which may couple with lower hybrid oscillations in the low-Z material plasmas. In the limit ω2≪ωpe2,Ωe2,c2k2 (where ωpe is the electron plasma frequency, Ωe is electron gyrofrequency, and c is the speed of light), the X-mode becomes a hybrid frequency wave Ωi < ω < Ωe (where Ωi is the ion gyrofrequency) in a pure electron plasma. This partially longitudinal/partially transverse wave is important in the plasmas of heavier atoms/molecules. In hydrogen plasmas, this wave couples with the lower hybrid frequency ωLH = (ΩeΩi)1/2. Several waves in the range of lower hybrid frequency are analyzed. Since heavier ion plasmas have been produced in cylindrical devices initially, therefore the dynamics of these modes in a cylindrically bounded plasma are also discussed.
Operating modes of field emission assisted microplasmas in the microwave regime
Authors: Alamatsaz Arghavan , Venkattraman Ayyaswamy
Published: September 2016

The operating modes of microwave microplasma devices integrated with field emitting cathodes are studied using one-dimensional particle-in-cell with Monte Carlo collision (PIC-MCC) simulations. The PIC-MCC simulations predict operation in two modes—an α-mode characterized by a positive differential resistance with negligible influence of boundary processes and a γ-mode with significant field-induced electron emission. PIC-MCC results are presented for two representative 0.5 GHz argon microplasmas operating in the α and γ modes. The field emission-induced transition to γ-mode modifies the electron number density profiles in the sheath apart from leading to a higher contribution of conduction current in the sheath. The interpretation of electrical characteristics using time history of voltage and current demonstrates that the microplasma device impedance decreases as a result of the thinner sheath. It is also shown that the presence of field emitting cathodes leads to lower power requirements (about 64% of the case presented without field emission) to achieve a given plasma density.
High precision Hugoniot measurements on statically pre-compressed fluid helium
Authors: Seagle Christopher T. , Reinhart William D. , Lopez Andrew J. , Hickman Randy J. , Thornhill Tom F.
Published: September 2016

The capability for statically pre-compressing fluid targets for Hugoniot measurements utilizing gas gun driven flyer plates has been developed. Pre-compression expands the capability for initial condition control, allowing access to thermodynamic states off the principal Hugoniot. Absolute Hugoniot measurements with an uncertainty less than 3% on density and pressure were obtained on statically pre-compressed fluid helium utilizing a two stage light gas gun. Helium is highly compressible; the locus of shock states resulting from dynamic loading of an initially compressed sample at room temperature is significantly denser than the cryogenic fluid Hugoniot even for relatively modest (0.27–0.38 GPa) initial pressures. The dynamic response of pre-compressed helium in the initial density range of 0.21–0.25 g/cm3 at ambient temperature may be described by a linear shock velocity (us) and particle velocity (up) relationship: us = C0 + sup, with C0 = 1.44 ± 0.14 km/s and s = 1.344 ± 0.025.
Effect of self assembled quantum dots on carrier mobility, with application to modeling the dark current in quantum dot infrared photodetectors
Authors: Youssef Sarah , El-Batawy Yasser M. , Abouelsaood Ahmed A.
Published: September 2016

A theoretical method for calculating the electron mobility in quantum dot infrared photodetectors is developed. The mobility calculation is based on a time-dependent, finite-difference solution of the Boltzmann transport equation in a bulk semiconductor material with randomly positioned conical quantum dots. The quantum dots act as scatterers of current carriers (conduction-band electrons in our case), resulting in limiting their mobility. In fact, carrier scattering by quantum dots is typically the dominant factor in determining the mobility in the active region of the quantum dot device. The calculated values of the mobility are used in a recently developed generalized drift-diffusion model for the dark current of the device [Ameen et al., J. Appl. Phys. 115, 063703 (2014)] in order to fix the overall current scale. The results of the model are verified by comparing the predicted dark current characteristics to those experimentally measured and reported for actual InAs/GaAs quantum dot infrared photodetectors. Finally, the effect of the several relevant device parameters, including the operating temperature and the quantum dot average density, is studied.
Air sensitivity of MoS2, MoSe2, MoTe2, HfS2, and HfSe2
Authors: Mirabelli Gioele , McGeough Conor , Schmidt Michael , McCarthy Eoin K. , Monaghan Scott , Povey Ian M. , McCarthy Melissa , Gity Farzan , Nagle Roger , Hughes Greg , Cafolla Attilio , Hurley Paul K. , Duffy Ray
Published: September 2016

A surface sensitivity study was performed on different transition-metal dichalcogenides (TMDs) under ambient conditions in order to understand which material is the most suitable for future device applications. Initially, Atomic Force Microscopy and Scanning Electron Microscopy studies were carried out over a period of 27 days on mechanically exfoliated flakes of 5 different TMDs, namely, MoS2, MoSe2, MoTe2, HfS2, and HfSe2. The most reactive were MoTe2 and HfSe2. HfSe2, in particular, showed surface protrusions after ambient exposure, reaching a height and width of approximately 60 nm after a single day. This study was later supplemented by Transmission Electron Microscopy (TEM) cross-sectional analysis, which showed hemispherical-shaped surface blisters that are amorphous in nature, approximately 180–240 nm tall and 420–540 nm wide, after 5 months of air exposure, as well as surface deformation in regions between these structures, related to surface oxidation. An X-ray photoelectron spectroscopy study of atmosphere exposed HfSe2 was conducted over various time scales, which indicated that the Hf undergoes a preferential reaction with oxygen as compared to the Se. Energy-Dispersive X-Ray Spectroscopy showed that the blisters are Se-rich; thus, it is theorised that HfO2 forms when the HfSe2 reacts in ambient, which in turn causes the Se atoms to be aggregated at the surface in the form of blisters. Overall, it is evident that air contact drastically affects the structural properties of TMD materials. This issue poses one of the biggest challenges for future TMD-based devices and technologies.
A new system for continuous and remote monitoring of patients receiving home mechanical ventilation
Authors: Battista L.
Published: September 2016

Home mechanical ventilation is the treatment of patients with respiratory failure or insufficiency by means of a mechanical ventilator at a patient’s home. In order to allow remote patient monitoring, several tele-monitoring systems have been introduced in the last few years. However, most of them usually do not allow real-time services, as they have their own proprietary communication protocol implemented and some ventilation parameters are not always measured. Moreover, they monitor only some breaths during the whole day, despite the fact that a patient’s respiratory state may change continuously during the day. In order to reduce the above drawbacks, this work reports the development of a novel remote monitoring system for long-term, home-based ventilation therapy; the proposed system allows for continuous monitoring of the main physical quantities involved during home-care ventilation (e.g., differential pressure, volume, and air flow rate) and is developed in order to allow observations of different remote therapy units located in different places of a city, region, or country. The developed remote patient monitoring system is able to detect various clinical events (e.g., events of tube disconnection and sleep apnea events) and has been successfully tested by means of experimental tests carried out with pulmonary ventilators typically used to support sick patients.
Evolution of dislocation loops in He ion irradiated nickel under different temperature
Authors: Chen H. C. , Lui R. D. , Ren C. L. , Huang H. F. , Li J. J. , Lei G. H. , Xue W. D. , Wang W. X. , Huang Q. , Li D. H. , Yan L. , Zhou X. T.
Published: September 2016

The effect of temperature on the evolution of loops in nickel was investigated under 30 keV He+ irradiation. The size, Burgers vector, and nature of loops were analyzed by a transmission electron microscope (TEM). In addition, the Weibull statistical analysis was introduced to analyze the size distributions of the loops. The TEM results indicate that the sizes of loops increase with increasing irradiation temperature, where they are mainly in the range of 10–30, 20–50, and 30–80 nm at 300, 400, and 500 °C, respectively. In the irradiation temperature range of 300–500 °C, the size distributions of loops fit Weibull distribution very well, which suggests that the loops tend to grow larger and/or be merged. In addition, almost all the loops formed under He+ irradiation are the interstitial loops with Burgers vectors b =  a2⟨110⟩, which is ascribed to the assistance of the He atom on the formation process of loops.
Thin film thermistor with positive temperature coefficient of resistance based on phase separated blends of ferroelectric and semiconducting polymers
Authors: Lenz Thomas , Sharifi Dehsari Hamed , Asadi Kamal , Blom Paul W. M. , Groen Wilhelm A. , de Leeuw Dago M.
Published: September 2016

We demonstrate that ferroelectric memory diodes can be utilized as switching type positive temperature coefficient (PTC) thermistors. The diode consists of a phase separated blend of a ferroelectric and a semiconducting polymer stacked between two electrodes. The current through the semiconducting polymer depends on the ferroelectric polarization. At the Curie temperature the ferroelectric polymer depolarizes and consequently the current density through the semiconductor decreases by orders of magnitude. The diode therefore acts as switching type PTC thermistor. Unlike their inorganic counterparts, the PTC thermistors presented here are thin film devices. The switching temperature can be tuned by varying the Curie temperature of the ferroelectric polymer.
Micromagnetic modeling of the shielding properties of nanoscale ferromagnetic layers
Authors: Iskandarova I. M. , Knizhnik A. A. , Popkov A. F. , Potapkin B. V. , Stainer Q. , Lombard L. , Mackay K.
Published: September 2016

Ferromagnetic shields are widely used to concentrate magnetic fields in a target region of space. Such shields are also used in spintronic nanodevices such as magnetic random access memory and magnetic logic devices. However, the shielding properties of nanostructured shields can differ considerably from those of macroscopic samples. In this work, we investigate the shielding properties of nanostructured NiFe layers around a current line using a finite element micromagnetic model. We find that thin ferromagnetic layers demonstrate saturation of magnetization under an external magnetic field, which reduces the shielding efficiency. Moreover, we show that the shielding properties of nanoscale ferromagnetic layers strongly depend on the uniformity of the layer thickness. Magnetic anisotropy in ultrathin ferromagnetic layers can also influence their shielding efficiency. In addition, we show that domain walls in nanoscale ferromagnetic shields can induce large increases and decreases in the generated magnetic field. Therefore, ferromagnetic shields for spintronic nanodevices require careful design and precise fabrication.
Gap-mode enhancement on MoS2 probed by functionalized tip-enhanced Raman spectroscopy
Authors: Alajlan Abdulrahman M. , Voronine Dmitri V. , Sinyukov Alexander M. , Zhang Zhenrong , Sokolov Alexei V. , Scully Marlan O.
Published: September 2016

Surface enhancement of molecular spectroscopic signals has been widely used for sensing and nanoscale imaging. Because of the weak electromagnetic enhancement of Raman signals on semiconductors, it is motivating but challenging to study the electromagnetic effect separately from the chemical effects. We report tip-enhanced Raman scattering measurements on Au and bulk MoS2 substrates using a metallic tip functionalized with copper phthalocyanine molecules and demonstrate similar gap-mode enhancement on both substrates. We compare the experimental results with theoretical calculations to confirm the gap-mode enhancement on MoS2 using a well-established electrostatic model. The functionalized tip approach allows for suppressing the background and is ideal for separating electromagnetic and chemical enhancement mechanisms on various substrates. Our results may find a wide range of applications in MoS2-based devices, sensors, and metal-free nanoscale bio-imaging.