bluuebunny/crossref_metadata_2025 huggingface dataset:
An open source digital servo for atomic, molecular, and optical physics experiments
Authors: Leibrandt D. R. , Heidecker J.
Published: December 2015

We describe a general purpose digital servo optimized for feedback control of lasers in atomic, molecular, and optical physics experiments. The servo is capable of feedback bandwidths up to roughly 1 MHz (limited by the 320 ns total latency); loop filter shapes up to fifth order; multiple-input, multiple-output control; and automatic lock acquisition. The configuration of the servo is controlled via a graphical user interface, which also provides a rudimentary software oscilloscope and tools for measurement of system transfer functions. We illustrate the functionality of the digital servo by describing its use in two example scenarios: frequency control of the laser used to probe the narrow clock transition of 27Al+ in an optical atomic clock, and length control of a cavity used for resonant frequency doubling of a laser.
Microfluidic platform for separation and extraction of plasma from whole blood using dielectrophoresis
Authors: Szydzik Crispin , Khoshmanesh Khashayar , Mitchell Arnan , Karnutsch Christian
Published: December 2015

Microfluidic based blood plasma extraction is a fundamental necessity that will facilitate many future lab-on-a-chip based point-of-care diagnostic systems. However, current approaches for providing this analyte are hampered by the requirement to provide external pumping or dilution of blood, which result in low effective yield, lower concentration of target constituents, and complicated functionality. This paper presents a capillary-driven, dielectrophoresis-enabled microfluidic system capable of separating and extracting cell-free plasma from small amounts of whole human blood. This process takes place directly on-chip, and without the requirement of dilution, thus eliminating the prerequisite of pre-processed blood samples and external liquid handling systems. The microfluidic chip takes advantage of a capillary pump for driving whole blood through the main channel and a cross flow filtration system for extracting plasma from whole blood. This filter is actively unblocked through negative dielectrophoresis forces, dramatically enhancing the volume of extracted plasma. Experiments using whole human blood yield volumes of around 180 nl of cell-free, undiluted plasma. We believe that implementation of various integrated biosensing techniques into this plasma extraction system could enable multiplexed detection of various biomarkers.
Effective bichromatic potential for ultra-high Q-factor photonic crystal slab cavities
Authors: Alpeggiani Filippo , Andreani Lucio Claudio , Gerace Dario
Published: December 2015

We introduce a confinement mechanism in photonic crystal slab cavities, which relies on the superposition of two incommensurate one-dimensional lattices in a line-defect waveguide. It is shown that the resulting photonic profile realizes an effective quasi-periodic bichromatic potential for the electromagnetic field confinement yielding extremely high quality (Q) factor nanocavities, while simultaneously keeping the mode volume close to the diffraction limit. We apply these concepts to pillar- and hole-based photonic crystal slab cavities, respectively, and a Q-factor improvement by over an order of magnitude is shown over existing designs, especially in pillar-based structures. Thanks to the generality and easy adaptation of such confinement mechanism to a broad class of cavity designs and photonic lattices, this work opens interesting routes for applications where enhanced light–matter interaction in photonic crystal structures is required.
A strategic policy framework for promoting the marine energy sector in Spain
Authors: Vazquez A. , Astariz S. , Iglesias G.
Published: December 2015

Marine renewable energy (MRE), which includes wave, tidal, and offshore wind energy, has the potential to make significant contributions towards a sustainable energy future in a number of countries worldwide. One such country is Spain, where MREs are among the largest renewable resources; yet they are not playing their full part in the national energy mix. Among other constraints, the lack of a specific policy framework promoting this emerging sector is often pointed to as the main barrier for MRE grid penetration. This paper assesses the Spanish MRE sector, in terms of resource availability, government plans, policy regulations, and projects undertaken, with a view to establish a comparison with the situation in other European countries. In particular, the United Kingdom is used as a case study to analyze ongoing research activities, pilot projects, and lessons learned. As a result, it is found that public funding needs to be increased; the economic crisis should be seen as an opportunity for job creation and industrial development rather than a barrier; administrative procedures must be simplified and cross-national cooperation should be increased. Policies focused on these aspects may contribute to boost the MRE sector in Spain.
Recasting a model atomistic glassformer as a system of icosahedra
Authors: Pinney Rhiannon , Liverpool Tanniemola B. , Royall C. Patrick
Published: December 2015

We consider a binary Lennard-Jones glassformer whose super-Arrhenius dynamics are correlated with the formation of icosahedral structures. Upon cooling, these icosahedra organize into mesoclusters. We recast this glassformer as an effective system of icosahedra which we describe with a population dynamics model. This model we parameterize with data from the temperature regime accessible to molecular dynamics simulations. We then use the model to determine the population of icosahedra in mesoclusters at arbitrary temperature. Using simulation data to incorporate dynamics into the model, we predict relaxation behavior at temperatures inaccessible to conventional approaches. Our model predicts super-Arrhenius dynamics whose relaxation time remains finite for non-zero temperature.
Low-energy positron scattering by pyrimidine
Authors: Barbosa Alessandra Souza , Pastega Diego F. , Bettega Márcio H. F.
Published: December 2015

This work reports elastic integral and differential cross sections for positron collisions with pyrimidine, for energies up to 20 eV. The cross sections were computed with the Schwinger multichannel method in the static plus polarization approximation. We also employed the Born closure procedure to account for the long range potential due to the permanent dipole moment of the molecule. Our results are compared with the experimental total cross section of Zecca et al. [J. Phys. B 43, 215204 (2010)], the experimental grand-total, quasi-elastic integral and differential cross section of Palihawadana et al. [Phys. Rev. A 88, 12717 (2013)]. We also compare our results with theoretical integral and differential cross sections obtained by Sanz et al. [Phys. Rev. A 88, 62704 (2013)] with the R-matrix and the independent atom model with screening-corrected additivity rule methods, and with the results computed by Franz and Gianturco [Phys. Rev. A 88, 042711 (2013)] using model correlation-polarization potentials. The agreement between the theory and the experiment is encouraging.
The production of monodisperse explosive particles with piezo-electric inkjet printing technology
Authors: Staymates M. E. , Fletcher R. , Verkouteren M. , Staymates J. L. , Gillen G.
Published: December 2015

We have developed a method to produce discrete microparticles from compounds dissolved in nonpolar or polar solvents using drop-on-demand inkjet printer technology. A piezoelectric inkjet printhead located atop a drying tube produces precise droplets containing defined quantities of analyte. Droplets solidify into microparticles with known composition and size as they traverse down the drying tube. Because this is a drop-on-demand printing process, a known number of droplets are produced providing quantitative particle delivery to a variety of substrates. Particular emphasis is placed on the development and characterization of the drying tube in this work. The drying tube was modeled using computational fluid dynamics and experimentally evaluated using laser-based flow visualization techniques. A notable design feature of the drying tube is the ability to push heated air through the tube rather than the need to pull air from the exit. This provides the ability to place a known number of well-defined particles onto almost any substrate of interest, rather than having to collect particles onto a filter first and then transfer them to another surface. Several types of particles have been produced by this system, examples of which are pure particles of cyclotrimethylenetrinitramine ranging from 10 μm to 30 μm in diameter, and ammonium nitrate particles of 40 μm diameter. The final particle size is directly related to the solute concentration of the printing solution and the size of the initial jetted droplet.
Investigation on plasma generated during hypervelocity impact at different impact velocities and angles
Authors: Song Weidong , Lv Yangtao , Wang Cheng , Li Jianqiao
Published: December 2015

A 3D Smoothed Particle Hydrodynamics code was developed to investigate plasma generation by considering a chemical reaction process in hypervelocity impacts of an aluminum projectile on an aluminum target. The chemical reaction process was described by the reaction rate based on the Arrhenius equation and used to calculate the plasma generation during the impact simulation. The predicted result was verified by empirical formulas and a new empirical formula was proposed based on the comparisons and analyses. The influence of the impact angle was discussed for different impact velocities. Then, the application of both the new and original empirical formulas for protection design from plasma generated by hypervelocity impact was discussed, which demonstrated that the code and model were useful in the prediction of hypervelocity impacts on spacecraft.
Electronic transport in VO2—Experimentally calibrated Boltzmann transport modeling
Authors: Kinaci Alper , Kado Motohisa , Rosenmann Daniel , Ling Chen , Zhu Gaohua , Banerjee Debasish , Chan Maria K. Y.
Published: December 2015

Materials that undergo metal-insulator transitions (MITs) are under intense study, because the transition is scientifically fascinating and technologically promising for various applications. Among these materials, VO2 has served as a prototype due to its favorable transition temperature. While the physical underpinnings of the transition have been heavily investigated experimentally and computationally, quantitative modeling of electronic transport in the two phases has yet to be undertaken. In this work, we establish a density-functional-theory (DFT)-based approach with Hubbard U correction (DFT + U) to model electronic transport properties in VO2 in the semiconducting and metallic regimes, focusing on band transport using the Boltzmann transport equations. We synthesized high quality VO2 films and measured the transport quantities across the transition, in order to calibrate the free parameters in the model. We find that the experimental calibration of the Hubbard correction term can efficiently and adequately model the metallic and semiconducting phases, allowing for further computational design of MIT materials for desirable transport properties.
Molecular hydrogen solvated in water – A computational study
Authors: Śmiechowski Maciej
Published: December 2015

The aqueous hydrogen molecule is studied with molecular dynamics simulations at ambient temperature and pressure conditions, using a newly developed flexible and polarizable H2 molecule model. The design and implementation of this model, compatible with an existing flexible and polarizable force field for water, is presented in detail. The structure of the hydration layer suggests that first-shell water molecules accommodate the H2 molecule without major structural distortions and two-dimensional, radial-angular distribution functions indicate that as opposed to strictly tangential, the orientation of these water molecules is such that the solute is solvated with one of the free electron pairs of H2O. The calculated self-diffusion coefficient of H2(aq) agrees very well with experimental results and the time dependence of mean square displacement suggests the presence of caging on a time scale corresponding to hydrogen bond network vibrations in liquid water. Orientational correlation function of H2 experiences an extremely short-scale decay, making the H2–H2O interaction potential essentially isotropic by virtue of rotational averaging. The inclusion of explicit polarizability in the model allows for the calculation of Raman spectra that agree very well with available experimental data on H2(aq) under differing pressure conditions, including accurate reproduction of the experimentally noted trends with solute pressure or concentration.
Electric field-modulated amplified spontaneous emission in organo-lead halide perovskite CH3NH3PbI3
Authors: Yuan Fang , Wu Zhaoxin , Dong Hua , Xia Bin , Xi Jun , Ning Shuya , Ma Lin , Hou Xun
Published: December 2015

The electric field-modulation of the spontaneous emission (SE) and amplified spontaneous emission (ASE) in organo-lead halide perovskite CH3NH3PbI3 (aliased as MAPbI3) layer has been investigated. With the increase of the external applied electric field, the electric field-induced quenching of the SE and ASE intensity was observed, accompanying with a blue-shift of the ASE emission peaks, which can be attributed to field-induced ionization of photogenerated excitons in the MAPbI3 layer. Based on the analysis of quenching factor and the dielectric constant, we estimated an exciton binding energy ∼36 meV at room temperature, which will provide useful insights into the optical-electrical characteristics of MAPbI3 and pave the way for the future optoelectronic applications.
In situ controlled heteroepitaxy of single-domain GaP on As-modified Si(100)
Authors: Supplie Oliver , May Matthias M. , Kleinschmidt Peter , Nägelein Andreas , Paszuk Agnieszka , Brückner Sebastian , Hannappel Thomas
Published: December 2015

Metalorganic vapor phase epitaxy of III-V compounds commonly involves arsenic. We study the formation of atomically well-ordered, As-modified Si(100) surfaces and subsequent growth of GaP/Si(100) quasisubstrates in situ with reflection anisotropy spectroscopy. Surface symmetry and chemical composition are measured by low energy electron diffraction and X-ray photoelectron spectroscopy, respectively. A two-step annealing procedure of initially monohydride-terminated, (1 × 2) reconstructed Si(100) in As leads to a predominantly (1 × 2) reconstructed surface. GaP nucleation succeeds analogously to As-free systems and epilayers free of antiphase disorder may be grown subsequently. The GaP sublattice orientation, however, is inverted with respect to GaP growth on monohydride-terminated Si(100).
Comment on “Exploring the potential energy landscape of the Thomson problem via Newton homotopies” [J. Chem. Phys. 142, 194113 (2015)]
Authors: Bofill Josep Maria
Published: December 2015

We show that the Newton homotopy used in the paper [D. Mehta et al., J. Chem. Phys. 142, 194113 (2015)] is related to the Newton trajectory method. With the theory of the Newton trajectories at hand, we can sharpen some findings of the paper.
Laser-induced particle size tuning and structural transformations in germanium nanoparticles prepared by stain etching and colloidal synthesis route
Authors: Karatutlu Ali , Little William , Ersoy Osman , Zhang Yuanpeng , Seker Isa , Sapelkin Andrei
Published: December 2015

In this study, with the aid of Raman measurements, we have observed transformations in small (∼3 nm and ∼10 nm) free-standing Ge nanoparticles under laser light exposure. The nanoparticles were obtained by the chemical stain etching of a monocrystalline Ge wafer and of Ge powder and by colloidal synthesis route. We found that the transformation path depends on laser power and exposure time. At relatively low values of the laser power (2 mW) over a period of 100 min, the Raman signal indicates transformation of the sample from a nanocrystaline to bulk-like state, followed by partial oxidation and finally a conversion of the entire sample into alpha-quartz type GeO2. However, when the laser power is set at 60 mW, we observed a heat release during an explosive crystallization of the nanocrystalline material into bulk Ge without noticeable signs of oxidation. Together with the transmission electron microscopy measurements, these results suggest that the chemical stain etching method for the preparation of porous Ge may not be a top-down process as has been widely considered, but a bottom up one. Systematic studies of the laser exposure on Ge nanoparticles prepared by colloidal synthesis results in the fact that the explosive crystallisation is common for H-terminated and partially disordered Ge nanoparticles regardless of its particle size. We suggest possible bio-medical applications for the observed phenomena.
Radiation response of multi-quantum well solar cells: Electron-beam-induced current analysis
Authors: Maximenko S. I. , Lumb M. P. , Hoheisel R. , Gonzalez M. , Scheiman D. A. , Messenger S. R. , Tibbits T. N. D. , Imaizumi M. , Ohshima T. , Sato S. I. , Jenkins P. P. , Walters R. J.
Published: December 2015

Solar cells utilizing multi-quantum well (MQW) structures are considered promising candidate materials for space applications. An open question is how well these structures can resist the impact of particle irradiation. The aim of this work is to provide feedback about the radiation response of In0.01Ga0.99As solar cells grown on Ge with MQWs incorporated within the i-region of the device. In particular, the local electronic transport properties of the MQW i-regions of solar cells subjected to electron and proton irradiation were evaluated experimentally using the electron beam induced current (EBIC) technique. The change in carrier collection distribution across the MQW i-region was analyzed using a 2D EBIC diffusion model in conjunction with numerical modeling of the electrical field distribution. Both experimental and simulated findings show carrier removal and type conversion from n- to p-type in MQW i-region at a displacement damage dose as low as ∼6.06–9.88 × 109 MeV/g. This leads to a redistribution of the electric field and significant degradation in charge carrier collection.
Communication: Dimensionality of the ionic conduction pathways in glass and the mixed-alkali effect
Authors: Novy Melissa , Avila-Paredes Hugo , Kim Sangtae , Sen Sabyasachi
Published: December 2015

A revised empirical relationship between the power law exponent of ac conductivity dispersion and the dimensionality of the ionic conduction pathway is established on the basis of electrical impedance spectroscopic (EIS) measurements on crystalline ionic conductors. These results imply that the “universal” ac conductivity dispersion observed in glassy solids is associated with ionic transport along fractal pathways. EIS measurements on single-alkali glasses indicate that the dimensionality of this pathway D is ∼2.5, while in mixed-alkali glasses, D is lower and goes through a minimum value of ∼2.2 when the concentrations of the two alkalis become equal. D and σ display similar variation with alkali composition, thus suggesting a topological origin of the mixed-alkali effect.
Electronic ground states of Fe2+ and Co2+ as determined by x-ray absorption and x-ray magnetic circular dichroism spectroscopy
Authors: Zamudio-Bayer V. , Hirsch K. , Langenberg A. , Ławicki A. , Terasaki A. , v. Issendorff B. , Lau J. T.
Published: December 2015

The 6Π electronic ground state of the Co2+ diatomic molecular cation has been assigned experimentally by x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap. Three candidates, 6Φ, 8Φ, and 8Γ, for the electronic ground state of Fe2+ have been identified. These states carry sizable orbital angular momenta that disagree with theoretical predictions from multireference configuration interaction and density functional theory. Our results show that the ground states of neutral and cationic diatomic molecules of 3d transition elements cannot generally be assumed to be connected by a one-electron process.
VUV action spectroscopy of protonated leucine-enkephalin peptide in the 6-14 eV range
Authors: Ranković M. Lj. , Canon F. , Nahon L. , Giuliani A. , Milosavljević A. R.
Published: December 2015

We have studied the Vacuum Ultraviolet (VUV) photodissociation of gas-phase protonated leucine-enkephalin peptide ion in the 5.7 to 14 eV photon energy range by coupling a linear quadrupole ion trap with a synchrotron radiation source. We report VUV activation tandem mass spectra at 6.7, 8.4, and 12.8 eV photon energies and photodissociation yields for a number of selected fragments. The obtained results provide insight into both near VUV radiation damage and electronic properties of a model peptide. We could distinguish several absorption bands and assign them to particular electronic transitions, according to previous theoretical studies. The photodissociation yields appear to be very different for the various observed fragmentation channels, depending on both the types of fragments and their position along the peptide backbone. The present results are discussed in light of recent gas-phase spectroscopic data on peptides.
Entropic transport without external force in confined channel with oscillatory boundary
Authors: Ding Huai , Jiang Huijun , Hou Zhonghuai
Published: December 2015

The dynamics of point-like Brownian particles in a periodic confined channel with oscillating boundaries has been studied. Directional transport (DT) behavior, characterized by net displacement along the horizontal direction, is observed even without external force which is necessary for the conventional DT where the boundaries are static. For typical parameter values, the average velocity Vt of DT reaches a maximum with the variation of the noise intensity D, being alike to the phenomenon of stochastic resonance. Interestingly, we find that Vt shows nontrivial dependences on the particle gravity G depending on the noise level. When the noise is large, Vt increases monotonically with G indicating that heavier particle moves faster, while for small noise, Vt shows a bell-shape dependence on G, suggesting that a particle with an intermediate weight may move the fastest. Such results were not observed for DT in a channel with static boundaries. To understand these findings, we have adopted an effective one-dimensional coarsening description, which facilitates us to introduce an effective entropic force along the horizontal direction. The average force is apparently nonzero due to the oscillatory boundary, hence leading to the net transport, and it shows similar dependences as Vt on the noise intensity D and particle gravity G. The dependences of the DT behavior on other parameters describing the oscillatory channel have also been investigated, showing that DT is more pronounced for larger oscillation amplitude and frequency, and asymmetric geometry within a channel period and phase difference between neighboring periods are both necessary for the occurrence of DT.
Theoretical investigation of second hyperpolarizability of trans-polyacetylene: Comparison between experimental and theoretical results for small oligomers
Authors: Andrade Ageo Meier de , Inacio Patrícia Loren , Camilo Alexandre
Published: December 2015

The development of new conductive polymers nowadays is one of the most important technological areas in materials design. Computational investigation of desired properties in conductive polymers could save financial resources and time, but it is important to choose the methodology that produces good results comparing to experimental results. To verify the prediction of second hyperpolarizability (γ) in oligomers of Trans-Polyacetylene (TPA) by theoretical calculations, a series of semi-empirical, Hartree-Fock (HF), and Density Functional Theory (DFT) calculations were performed and analysed through linear fitting statistical analysis to investigate the accuracy of such theoretical predictions in comparison to the experimental ones. The results showed that HF and DFT methodologies do not describe γ with good accuracy, but the use of diffuse and polarizability functions in HF methodology provided better results than 3-21G and 6-31G functions. It was concluded that RM1 methodology better agrees with γ experimental results for TPA oligomers, and linear fitting statistical analysis is a useful tool to compare experimental and theoretical results.
Status and decomposition analysis on building energy consumption of China in the last decade
Authors: Zhou Li , Chen Wen ying
Published: December 2015

As the need for international climate change negotiation and national sustainable development increases, China has announced its energy conservation and emission reduction target, in which building energy consumption is an important part. The energy consumption and total energy consumption of classified buildings in China during 2004–2013 are calculated, taking into consideration the characteristics of China's building sector. The LMDI (Logarithmic Mean Divisia Index) method is adopted to carry out the factor decomposition research and discussion of the four factors influencing the energy consumption (comprising different building types of GFA (gross floor area) per capita, the energy consumption per unit GFA, the urban population proportion, and the total population) of China's building sector. The results show that the continuous increase of GFA per capita is the primary factor influencing the increase in China's building energy consumption and the increase of urbanization ratio is the secondary factor. Meanwhile, controlling building energy consumption per unit GFA is the effective way to decrease the total energy consumption. The core method of controlling the energy consumption demands of China's building sector in the future is to reasonably control the future GFA per capita and to simultaneously take corresponding measures to reduce the building energy consumption per unit GFA.
(11-22) semipolar InGaN emitters from green to amber on overgrown GaN on micro-rod templates
Authors: Bai J. , Xu B. , Guzman F. G. , Xing K. , Gong Y. , Hou Y. , Wang T.
Published: December 2015

We demonstrate semipolar InGaN single-quantum-well light emitting diodes (LEDs) in the green, yellow-green, yellow and amber spectral region. The LEDs are grown on our overgrown semipolar (11-22) GaN on micro-rod array templates, which are fabricated on (11-22) GaN grown on m-plane sapphire. Electroluminescence measurements on the (11-22) green LED show a reduced blue-shift in the emission wavelength with increasing driving current, compared to a reference commercial c-plane LED. The blue-shifts for the yellow-green and yellow LEDs are also significantly reduced. All these suggest an effective suppression in quantum confined Stark effect in our (11-22) LEDs. On-wafer measurements yield a linear increase in the light output with the current, and external quantum efficiency demonstrates a significant improvement in the efficiency-droop compared to a commercial c-plane LED. Electro-luminescence polarization measurements show a polarization ratio of about 25% in our semipolar LEDs.
Ge2Sb2Te5/Sb superlattice-like thin film for high speed phase change memory application
Authors: Hu Yifeng , Zou Hua , Zhang Jianhao , Xue Jianzhong , Sui Yongxing , Wu Weihua , Yuan Li , Zhu Xiaoqin , Song Sannian , Song Zhitang
Published: December 2015

In order to improve the operation speed of phase change memory (PCM), superlattice-like Ge2Sb2Te5/Sb (SLL GST/Sb) thin films were prepared in a sputtering method to explore the suitability as an active material for PCM application. Compared with GST, SLL GST/Sb thin film has a lower crystallization temperature, crystallization activation energy, thermal conductivity, and smaller crystalline grain size. A faster SET/RESET switching speed (10 ns) and a lower operation power consumption (the energy for RESET operation 9.1 × 10−13 J) are obtained. In addition, GST/Sb shows a good endurance of 8.3 × 104 cycles.
Mechanism of Ti/Al/Ti/W Au-free ohmic contacts to AlGaN/GaN heterostructures via pre-ohmic recess etching and low temperature annealing
Authors: Zhang Jinhan , Huang Sen , Bao Qilong , Wang Xinhua , Wei Ke , Zheng Yingkui , Li Yankui , Zhao Chao , Liu Xinyu , Zhou Qi , Chen Wanjun , Zhang Bo
Published: December 2015

The physical mechanism of low-thermal-budget Au-free ohmic contacts to AlGaN/GaN heterostructures is systematically investigated with current-voltage, high-resolution transmission electron microscopy, and temperature-dependent contact resistivity characterizations. With a low annealing temperature of 600 °C, pre-ohmic recess etching of the AlGaN barrier down to several nanometers is demonstrated to be an effective method to reduce the contact resistance between Ti/Al/Ti/W ohmic metals and AlGaN/GaN heterostructures. However, further over recess of the AlGaN barrier leads to only sidewall contact to 2D electron gas channel and thus degraded contact performance. It is verified by temperature-dependent contact resistivity measurements that field emission (tunneling) dominates the current transport mechanism in Au-free ohmic contacts with AlGaN barrier partially and over recessed, while both field emission and thermionic emission contribute to traditional Ti/Al/Ni/Au ohmic contacts to AlGaN/GaN heterostructures that annealed at high temperature (850 °C).
A detailed analysis of the energy levels configuration existing in the band gap of supersaturated silicon with titanium for photovoltaic applications
Authors: Pérez E. , Dueñas S. , Castán H. , García H. , Bailón L. , Montero D. , García-Hernansanz R. , García-Hemme E. , Olea J. , González-Díaz G.
Published: December 2015

The energy levels created in supersaturated n-type silicon substrates with titanium implantation in the attempt to create an intermediate band in their band-gap are studied in detail. Two titanium ion implantation doses (1013 cm-2 and 1014 cm-2) are studied in this work by conductance transient technique and admittance spectroscopy. Conductance transients have been measured at temperatures of around 100 K. The particular shape of these transients is due to the formation of energy barriers in the conduction band, as a consequence of the band-gap narrowing induced by the high titanium concentration. Moreover, stationary admittance spectroscopy results suggest the existence of different energy level configuration, depending on the local titanium concentration. A continuum energy level band is formed when titanium concentration is over the Mott limit. On the other hand, when titanium concentration is lower than the Mott limit, but much higher than the donor impurity density, a quasi-continuum energy level distribution appears. Finally, a single deep center appears for low titanium concentration. At the n-type substrate, the experimental results obtained by means of thermal admittance spectroscopy at high reverse bias reveal the presence of single levels located at around Ec-425 and Ec-275 meV for implantation doses of 1013 cm−2 and 1014 cm−2, respectively. At low reverse bias voltage, quasi-continuously distributed energy levels between the minimum of the conduction bands, Ec and Ec-450 meV, are obtained for both doses. Conductance transients detected at low temperatures reveal that the high impurity concentration induces a band gap narrowing which leads to the formation of a barrier in the conduction band. Besides, the relationship between the activation energy and the capture cross section values of all the energy levels fits very well to the Meyer-Neldel rule. As it is known, the Meyer-Neldel rule typically appears in processes involving multiple excitations, like carrier capture and emission in deep levels, and it is generally observed in disordered systems. The obtained Meyer-Neldel energy value, 15.19 meV, is very close to the value obtained in multicrystalline silicon samples contaminated with iron (13.65 meV), meaning that this energy value could be associated to the phonons energy in this kind of substrates.
Continuous sheath-free separation of particles by shape in viscoelastic fluids
Authors: Lu Xinyu , Zhu Lin , Hua Ri-mao , Xuan Xiangchun
Published: December 2015

Shape is an important indicator of cell type, cycle, and state, etc., and can thus serve as a specific marker for label-free bioparticle separation. We demonstrate in this work a shape-based separation of equal-volumed spherical and peanut particles in viscoelastic fluids through straight rectangular microchannels. This continuous sheath-free separation arises from the shape-dependent equilibrium particle position(s) as a result of the flow-induced elasto-inertial lift and shear thinning effects. A continuous transition from single to dual and to triple equilibrium positions is observed for both types of particles with the increase in flow rate. However, the flow rate at which the transition takes place differs with the particle shape. This phenomenon occurs only in microchannels with a large aspect ratio (width/height) and has not been reported before. It is speculated to correlate with the dissimilar dependences of elastic and inertial lift forces on particle size and flow rate as well as the rotational effects of non-spherical particles.
Bioengineered yeast-derived vacuoles with enhanced tissue-penetrating ability for targeted cancer therapy
Authors: Gujrati Vipul , Lee Miriam , Ko Young-Joon , Lee Sangeun , Kim Daejin , Kim Hyungjun , Kang Sukmo , Lee Soyoung , Kim Jinjoo , Jeon Hyungsu , Kim Sun Chang , Jun Youngsoo , Jon Sangyong
Published: December 2015

Significance

Tumor tissues have formidable physiological barriers, such as a high interstitial pressure and a densely entangled ECM. Most synthetic nanomaterials used for drug delivery fail to penetrate tumor tissues deeply and localize only in perivascular areas, thereby limiting their therapeutic efficacy. This report describes bioengineered yeast-derived natural nanocarriers for cancer-specific targeting and drug delivery. Budding yeast was genetically engineered to produce large numbers of nanosized compartments—vacuoles that display cancer—targeting ligands on their surface. The nanosized vacuoles significantly enhanced drug penetration in tumor xenografts, and consequently prevented tumor growth without eliciting immune responses. This result shows that the biological nanocarriers overcome the limitations associated with synthetic cancer-targeting nanomaterials, and thus can be used to treat various cancers.
Size-dependent control of colloid transport via solute gradients in dead-end channels
Authors: Shin Sangwoo , Um Eujin , Sabass Benedikt , Ault Jesse T. , Rahimi Mohammad , Warren Patrick B. , Stone Howard A.
Published: December 2015

Significance

Dead-end geometries are commonly found in many porous systems. Particle transport into such dead-end pores is often important, but is difficult to achieve owing to the confinement. It is natural to expect that Brownian motion is the sole mechanism to deliver the particles into the pores, but that mechanism is, unfortunately, slow and inefficient. Here, we introduce solute gradient to control the transport of particles in dead-end channels. We demonstrate a size effect such that larger particles tend to focus more and reside deeper in the channels. Our findings suggest a potential pathway to many useful applications that are difficult to achieve in dead-end geometries such as particle sorting and sample preconcentration, which are important in pharmaceuticals and healthcare industries.
Trace incorporation of heavy water reveals slow and heterogeneous pathogen growth rates in cystic fibrosis sputum
Authors: Kopf Sebastian H. , Sessions Alex L. , Cowley Elise S. , Reyes Carmen , Van Sambeek Lindsey , Hu Yang , Orphan Victoria J. , Kato Roberta , Newman Dianne K.
Published: December 2015

Significance

A major challenge in treating chronic infections is the lack of insight into microbial survival mechanisms in vivo. Many drugs require cells to be doubling rapidly to have their greatest effect, yet the in vivo pathogen growth rate is largely unknown. By labeling freshly expectorated mucus from cystic fibrosis patients with heavy water, we found that the effective growth rates of
Staphylococcus aureus
are at least two orders of magnitude slower, on average, than typically studied in the laboratory, and are extremely heterogeneous at the single-cell level. These findings underscore the need to study slow growth physiology to gain insight into pathogen survival mechanisms, motivated by the hope that such insight will ultimately help improve drug design and clinical outcomes.
Evolutionary transformation of rod photoreceptors in the all-cone retina of a diurnal garter snake
Authors: Schott Ryan K. , Müller Johannes , Yang Clement G. Y. , Bhattacharyya Nihar , Chan Natalie , Xu Mengshu , Morrow James M. , Ghenu Ana-Hermina , Loew Ellis R. , Tropepe Vincent , Chang Belinda S. W.
Published: December 2015

Significance

This study provides compelling evidence that the previously reported all-cone retina of a diurnal garter snake in fact contains a population of rod photoreceptors with the appearance, and presumably function, of cones. Our results suggest that the evolution of all-cone retinas occurred not through loss of rods but rather via the evolutionary transmutation of ancestral rods into more “cone-like” photoreceptors, to regain functionality that was lost during the early, possibly fossorial, origin of snakes. This study provides a better understanding of the process by which complex molecular/cellular structures and tissue types can evolve, and how, particularly for sensory systems, physiological constraints can be shaped by selective forces to produce evolutionary novelty.
An inhibitor of HIV-1 protease modulates constitutive eIF2α dephosphorylation to trigger a specific integrated stress response
Authors: De Gassart Aude , Bujisic Bojan , Zaffalon Léa , Decosterd Laurent A. , Di Micco Antonia , Frera Gianluca , Tallant Rémy , Martinon Fabio
Published: December 2015

Significance

The integrated stress response (ISR) is an adaptation pathway that integrates multiple stress signals to decrease translation rates and promote specific transcriptional programs. Modulation of this pathway is emerging as a possible therapeutic strategy in pathologies associated with defects in protein homeostasis. In this paper, the antiviral drug Nelfinavir is found to be a strong and unconventional inducer of the ISR both in vitro and in vivo. This study uncovers an atypical mechanism that can initiate this pathway and provides insights on possible mechanisms underlying the metabolic deregulations observed in Nelfinavir-treated patients. Nelfinavir has been used for years to treat HIV; its repositioning in diseases that would benefit from decreased translation speed could therefore be of interest.
Zinc-dependent mechanical properties of
Staphylococcus aureus
biofilm-forming surface protein SasG
Authors: Formosa-Dague Cécile , Speziale Pietro , Foster Timothy J. , Geoghegan Joan A. , Dufrêne Yves F.
Published: December 2015

Significance

Hospital-acquired infections often involve surface-associated microbial communities called biofilms that show increased resistance to antibiotics. A molecular understanding of the fundamental interactions driving adhesion and biofilm formation by microbial pathogens is a key step toward the development of novel antimicrobial therapies. Here we demonstrate that the SasG surface protein from
Staphylococcus aureus
displays remarkable zinc-dependent mechanical properties that are critical for its adhesive function during biofilm formation. We find that zinc activates SasG-mediated adhesion through a mechanism whereby adsorption of zinc ions to the bacterial cell surface increases cell wall cohesion and favors zinc-dependent homophilic bonds between SasG proteins protruding from opposing cell surfaces. The zinc-dependent adhesive function of SasG represents a promising target for the design of antibacterial compounds.
Redox potential of the terminal quinone electron acceptor QBin photosystem II reveals the mechanism of electron transfer regulation
Authors: Kato Yuki , Nagao Ryo , Noguchi Takumi
Published: December 2015

Significance

In photosynthesis, photosystem II (PSII) has a function of abstracting electrons from water using light energy and transferring them to a quinone molecule. In addition to the forward electron transfer in PSII, which is essential in energy conversion, backward electron transfer is important in photoprotection of PSII proteins. Forward and backward electron transfers in PSII are regulated by the redox potential (Em) gap of quinone electron acceptors, QAand QB. However, the regulation mechanism is still unclear becauseEmof QBhas not been determined. We directly measuredEmof QBusing an electrochemical method in combination with Fourier transform infrared spectroscopy. Our results clearly explain the mechanism of electron transfer regulation in PSII relevant to photoprotection.
CAMSAP3 orients the apical-to-basal polarity of microtubule arrays in epithelial cells
Authors: Toya Mika , Kobayashi Saeko , Kawasaki Miwa , Shioi Go , Kaneko Mari , Ishiuchi Takashi , Misaki Kazuyo , Meng Wenxiang , Takeichi Masatoshi
Published: December 2015

Significance

Polarization is essential for epithelial cells to exert a variety of functions. Epithelial polarization includes characteristic microtubule array formation. The microtubules are oriented along the apicobasal axis with their minus ends facing apically. The molecules that regulate such epithelial-specific microtubule assembly remain unknown, however. Our study demonstrates that in intestinal epithelial cells, the microtubule minus-end binding protein CAMSAP3 (calmodulin-regulated–spectrin-associated protein 3) tethers noncentrosomal microtubules to the apical cortex, leading to their longitudinal orientation. This mechanism is essential for maintaining epithelial intracellular organization, such as positioning of organelles. Our findings facilitate our understanding of how epithelial cells acquire polarized structures, which are crucial for their physiological functions.
Critical role of RAGE and HMGB1 in inflammatory heart disease
Authors: Bangert Anna , Andrassy Martin , Müller Anna-Maria , Bockstahler Mariella , Fischer Andrea , Volz Christian H. , Leib Christoph , Göser Stefan , Korkmaz-Icöz Sevil , Zittrich Stefan , Jungmann Andreas , Lasitschka Felix , Pfitzer Gabriele , Müller Oliver J. , Katus Hugo A. , Kaya Ziya
Published: December 2015

Significance

Myocardial inflammation leads in many cases to cardiomyopathy and contributes to progressive heart failure. The exact pathological mechanism of disease induction and progression in the setting of heart failure is unknown. High-mobility group box 1 (HMGB1), an evolutionarily abundant and highly conserved protein, promotes cardiac inflammation, and in turn immunity, as a damage-associated molecular pattern. HMGB1 stimulates immunity, at least in part, through interaction with its principal binding partner RAGE (receptor for advanced glycation end products). Here we show that HMGB1 and RAGE appear to be important components in cardiac troponin I-induced experimental autoimmune myocarditis as well as in patients with myocarditis. Both molecules represent potential drug targets and show significant potential in heart failure treatment.
Chromosome position determines the success of double-strand break repair
Authors: Lee Cheng-Sheng , Wang Ruoxi W. , Chang Hsiao-Han , Capurso Daniel , Segal Mark R. , Haber James E.
Published: December 2015

Significance

Based on published chromosome conformation capture data, we investigated the effect of 3D nuclear architecture in budding yeast on repair of a broken chromosome by homologous recombination. When a nuclease-induced double-strand break (DSB) is created at one locus, efficiency of repair depends on the contact frequency of the donor locus with the DSB site. When the location of the DSB is shifted to another location, the recombination rate of a donor can change by almost 20-fold. The rate of repair of a given locus is strongly influenced by four key factors: the size of donor homology, the rate of 5′ to 3′ resection of DSB ends, and the abundance of single-strand DNA binding protein complex, replication protein factor A (RPA), as well as a
cis
-acting recombination enhancer.
Nonequivalent release sites govern synaptic depression
Authors: Wen Hua , McGinley Matthew J. , Mandel Gail , Brehm Paul
Published: December 2015

Significance

Activity-dependent depression is a common aspect of synaptic plasticity resulting from an inability to recover full-release competency during bouts of high-frequency stimulation. At the zebrafish neuromuscular synapse, frequencies between 1 and 10 Hz lead to 50% depression, but paradoxically, this synapse can still follow frequencies approaching the refractory period of the action potential without failure. Capitalizing on the advantages offered by this synapse, we report a new mechanism causal to nonlinear dependence of steady-state depression on frequency involving two types of release sites differing in vesicle reloading rates. The slow sites cannot sustain vesicle release at high frequencies, and therefore, it is the number of fast reloading sites that determines the steady-state level of transmission associated with depression.
Morphotactic variation, prosodic domains and the changing structure of the Murrinhpatha verb
Authors: Mansfield John
Published: December 2015

Bound morphology is usually realized on lexical stems following fixed rules of sequencing, but in some highly agglutinative languages this is not the case. Morphotactic variation has previously been described in detail for Chintang and Tagalog, and more briefly noted for various other languages including Udi, Totonac and Athapaskan languages (Bickel et al., 2007; Harris, 2002; McFarland, 2009; Rice, 2000; Ryan, 2010). I here report another case of variable ordering, in Murrinhpatha, spoken in northern Australia. I argue that in this case the variable ordering of verb suffixes reflects change in progress in the morphological structure of the verb, and the dynamic nature of prosodic domains in this language. I also note that in Chintang, Udi and Murrinhpatha, morphotactic variation is associated with word-like prosodic domains occurring inside the syntactic verbal word.
Directive-giving and grammatical forms
Authors: Chan Angela , Zhang Wei , Zayts Olga , Yin Tang Mary Hoi , Tam Wai Keung
Published: December 2015

This paper investigates the use of grammatical forms in directive sequences by drawing on daily interactions between colleagues in a medical laboratory in Hong Kong. From a conversation analytic perspective, we focus on how directives in Cantonese are commonly formulated and how the force of a directive is mitigated. Our analysis shows that (1) the imperative seems to be the most frequently used syntactic form for giving directives and there is no apparent hierarchical (‘power’) differentiation, (2) the imperative-formulated directives are frequently mitigated by the use of a range of linguistic forms as well as interactional resources.
Corpus-based Chinese studies
Authors: Xu Jiajin
Published: December 2015

This article reviews corpus-based Chinese studies, both applied and theoretical, from the 1920s to the present. It will be shown that, while corpus-based Chinese studies have been gaining momentum for only the last couple of decades, the roots of Chinese corpus linguistics go all the way back to the beginning of the 20th century. Today the bulk of corpus-based Chinese studies is oriented toward applied linguistics, with the compilation of frequency character/word lists and interlanguage Chinese studies being the most popular types of research. In addition to applied linguistic studies, this overview also highlights some innovative corpus studies on lexical and grammatical aspects of both classical and modern Chinese, as well as studies of sociolinguistic variation and discourse pragmatics. Overall, important groundwork in Chinese corpus linguistics is acknowledged and future directions are discussed.