bluuebunny/crossref_metadata_2025 huggingface dataset:
Spall response of 1100-O aluminum
Authors: Williams C. L. , Ramesh K. T. , Dandekar D. P.
Published: June 2012

Plate impact experiments were conducted to study the effects of peak shock stress and pulse duration on the spall response of fully annealed 1100 aluminum. The spall strength was observed to decrease as the pulse duration was increased from approximately 0.58 μs to 1.17 μs. Also, an increase in tensile unloading strain rate increases the spall strength. However, our results also show an increase in spall strength with increase in peak shock stress up to approximately 8.3 GPa, followed by a decrease in spall strength for higher shock stresses.
Internal magnetic field measurement on C-2 field-reversed configuration plasmas
Authors: Gota H. , Thompson M. C. , Knapp K. , Van Drie A. D. , Deng B. H. , Mendoza R. , Guo H. Y. , Tuszewski M.
Published: June 2012

A long-lived field-reversed configuration (FRC) plasma has been produced in the C-2 device by dynamically colliding and merging two oppositely directed, highly supersonic compact toroids (CTs). The reversed-field structure of the translated CTs and final merged-FRC state have been directly verified by probing the internal magnetic field structure using a multi-channel magnetic probe array near the midplane of the C-2 confinement chamber. Each of the two translated CTs exhibits significant toroidal fields (Bt) with opposite helicity, and a relatively large Bt remains inside the separatrix after merging.
The effects of group-I elements co-doping with Mn in ZnO dilute magnetic semiconductor
Authors: Zhang Liqiang , Zhang Yinzhu , Ye Zhizhen , Lu Jianguo , Lu Bin , He Bo
Published: June 2012

Mn-Li codoped ZnO (Zn(Mn,Li)O), Mn-Na codoped ZnO (Zn(Mn,Na)O), and Mn-K codoped ZnO (Zn(Mn,K)O) thin films were deposited on quartz substrates by pulsed laser deposition. The doping effects of group-I elements (e.g., Li, Na, and K) on the structural, magnetic, and optical properties of the Mn doped ZnO (ZnMnO) films were discussed. X-ray diffraction and K-edge x-ray absorption near-edge structure measurements revealed that all the films showed a hexagonal wurtzite ZnO structure, and no other clusters, precipitates, or second phases were detected. Zn(Mn,Na)O and Zn(Mn,Li)O films showed a weak p-type conductivity, while the Zn(Mn,K)O film appeared a highly resistivity. The saturation magnetization of Zn(Mn,Na)O and Zn(Mn,Li)O films was 1.2 and 0.18 μB/Mn, respectively. The hole-related defects, induced by doping with a low content of Li or Na, contributed to the room temperature ferromagnetism in the ZnMnO system.
Angular magnetoresistance of stretched carbon nanotube sheets
Authors: Cimpoiasu E. , Sandu V. , Levin G. A. , Simpson A. , Lashmore D.
Published: June 2012

We studied the anisotropic properties of mechanically stretched bulk carbon nanotube sheets using magnetoresistance (MR) measurements in magnetic fields applied under different orientations with respect to the stretching direction. The stretching direction was either parallel or perpendicular to the direction of the electric current. The magnetic field was rotated either in-the-plane or out-of-the-plane of the sheets. We found that the angular dependence of the MR is a superposition of two terms, one with twofold symmetry and the other one with fourfold symmetry. We also found that the field-dependence of the MR is composed of two terms, one positive and one negative, whose magnitudes are largest when the field is parallel with the stretching direction. If the sheets are treated with nitric acid, the positive term is removed and the MR is smallest when the field is aligned with the magnetic field. We attribute these anisotropic features to magnetoelastic effects induced by the coupling between the magnetic catalyst nanoparticles, the magnetic field, and the network of nanotubes.
Excitonic energy transfer in light-harvesting complexes in purple bacteria
Authors: Ye Jun , Sun Kewei , Zhao Yang , Yu Yunjin , Kong Lee Chee , Cao Jianshu
Published: June 2012

Two distinct approaches, the Frenkel-Dirac time-dependent variation and the Haken-Strobl model, are adopted to study energy transfer dynamics in single-ring and double-ring light-harvesting (LH) systems in purple bacteria. It is found that the inclusion of long-range dipolar interactions in the two methods results in significant increase in intra- or inter-ring exciton transfer efficiency. The dependence of exciton transfer efficiency on trapping positions on single rings of LH2 (B850) and LH1 is similar to that in toy models with nearest-neighbor coupling only. However, owing to the symmetry breaking caused by the dimerization of BChls and dipolar couplings, such dependence has been largely suppressed. In the studies of coupled-ring systems, both methods reveal an interesting role of dipolar interactions in increasing energy transfer efficiency by introducing multiple intra/inter-ring transfer paths. Importantly, the time scale (4  ps) of inter-ring exciton transfer obtained from polaron dynamics is in good agreement with previous studies. In a double-ring LH2 system, non-nearest neighbor interactions can induce symmetry breaking, which leads to global and local minima of the average trapping time in the presence of a non-zero dephasing rate, suggesting that environment dephasing helps preserve quantum coherent energy transfer when the perfect circular symmetry in the hypothetic system is broken. This study reveals that dipolar coupling between chromophores may play an important role in the high energy transfer efficiency in the LH systems of purple bacteria and many other natural photosynthetic systems.
Does the low hole transport mass in 〈110〉 and 〈111〉 Si nanowires lead to mobility enhancements at high field and stress: A self-consistent tight-binding study
Authors: Kotlyar R. , Linton T. D. , Rios R. , Giles M. D. , Cea S. M. , Kuhn K. J. , Povolotskyi Michael , Kubis Tillmann , Klimeck Gerhard
Published: June 2012

The hole surface roughness and phonon limited mobility in the silicon 〈100〉, 〈110〉, and 〈111〉 square nanowires under the technologically important conditions of applied gate bias and stress are studied with the self-consistent Poisson-sp3d5s*-SO tight-binding bandstructure method. Under an applied gate field, the hole carriers in a wire undergo a volume to surface inversion transition diminishing the positive effects of the high 〈110〉 and 〈111〉 valence band nonparabolicities, which are known to lead to the large gains of the phonon limited mobility at a zero field in narrow wires. Nonetheless, the hole mobility in the unstressed wires down to the 5 nm size remains competitive or shows an enhancement at high gate field over the large wire limit. Down to the studied 3 nm sizes, the hole mobility is degraded by strong surface roughness scattering in 〈100〉 and 〈110〉 wires. The 〈111〉 channels are shown to experience less surface scattering degradation. The physics of the surface roughness scattering dependence on wafer and channel orientations in a wire is discussed. The calculated uniaxial compressive channel stress gains of the hole mobility are found to reduce in the narrow wires and at the high field. This exacerbates the stressed mobility degradation with size. Nonetheless, stress gains of a factor of 2 are obtained for 〈110〉 wires down to 3 nm size at a 5×1012 cm–2 hole inversion density per gate area.
The conduction band absorption spectrum of interdiffused InGaAs/GaAs quantum dot infrared photodetectors
Authors: Jolley G. , McKerracher I. , Fu L. , Tan H. H. , Jagadish C.
Published: June 2012

We report on a theoretical study of the relationship between interdiffusion and the conduction band optical absorption of In(Ga)As/GaAs quantum dots. Quantum dot geometries are progressively interdiffused based on Fick’s model and the quantum dot strain, band structure and optical absorption cross-section are calculated numerically. Quantifying the effects of interdiffusion on quantum dot optical absorption is important for applications that utilize post-growth techniques such as selective area intermixing.
High-frequency asymptote for the velocity auto-correlation function spectrum of argon-like systems
Authors: Bardik V. Yu. , Malomuzh N. P. , Shakun K. S.
Published: June 2012

The work is devoted to the analysis of high-frequency behavior of the velocity auto-correlation function spectrum $\varphi _{\vec V} (\omega)$φV⃗(ω) for argon-like systems. The theoretical predictions are compared with results of computer simulations of $\varphi _{\vec V} (\omega)$φV⃗(ω). It is shown that (1) $\varphi _{\vec V} (\omega)$φV⃗(ω) takes the exponential behavior $\mathop {\varphi _{\vec V} (\omega) \Rightarrow \omega ^{q(n)} }\limits_{\omega \to \infty } \exp({ - ( {\omega \tau _a (n)})^{p(n)} })$φV⃗(ω)⇒ωq(n)ω→∞exp(−(ωτa(n))p(n)), where p(n), q(n), and τa(n) are the definite functions of the steepness exponent n for the power repulsive part of interparticle potential; (2) there is full agreement between theoretical predictions and the values of p(n), q(n), and τa(n) obtained in computer simulations. Weighty arguments about the universal character of the exponential frequency decay exp(−(ωτa(n))p(n)) for spectra of different correlation functions are given. The experimental spectrum of the depolarized light scattering in argon for high frequencies is analyzed. It is shown that the steepness exponent n for the power repulsive potential takes the value: n ≈ 24 that is essentially different from n = 12 characteristic for the Lennard-Jones potential.
Sensitivity of 2H NMR spectroscopy to motional models: Proteins and highly viscous liquids as examples
Authors: Kruk D. , Mielczarek A. , Korpala A. , Kozlowski A. , Earle K. A. , Moscicki J.
Published: June 2012

In order to study to what extent mechanisms of molecular motion can be unambiguously revealed by 2H NMR spectroscopy, 2H spectra for proteins (chicken villin protein headpiece HP36, selectively methyl-deuterated at leucine-69, Cδ D3) and binary systems of high viscosity (benzene-d6 in tricresyl phosphate) have been carefully analyzed as illustrative examples (the spectra are taken from the literature). In the first case, a model of restricted diffusion mediated by jumps between rotameric orientations has been tested against jump- and free diffusion models which describe rotational motion combined with jump dynamics. It has been found that the set of 2H spectra of methyl-deuterated at leucine-69 chicken villin protein headpiece HP36 can be consistently explained by different motional models as well as by a Gaussian distribution of correlation times assuming isotropic rotation (simple Brownian diffusion model). The last finding shows that when the possible distribution of correlation times is not very broad one might not be able to distinguish between heterogeneous and homogenous (but more complex) dynamics by analyzing 2H lineshapes. For benzene-d6 in tricresyl phosphate, the dynamics is heterogeneous and it has been demonstrated that a Gaussian distribution of correlation times reproduces well the experimental lineshapes, while for a Cole-Davidson distribution the agreement is somewhat worse. For inquires into the sensitivity of quadrupolar NMR spectral analysis (by “quadrupolar NMR spectroscopy we understand NMR spectroscopy of nuclei possessing quadrupole moment), the recently presented theoretical approach [Kruk et al., J. Chem. Phys. 135, 224511 (2011)]10.1063/1.3664783 has been used as it allows simulating quadrupolar spectra for arbitrary motional conditions by employing the stochastic Liouville equation.
Binary and ternary recombination of para-${\rm H}_3^+$H3+ and ortho-${\rm H}_3^+$H3+ with electrons: State selective study at 77–200 K
Authors: Dohnal Petr , Hejduk Michal , Varju Jozef , Rubovič Peter , Roučka Štěpán , Kotrík Tomáš , Plašil Radek , Glosík Juraj , Johnsen Rainer
Published: June 2012

Measurements in \documentclass[12pt]{minimal}\begin{document}${\rm H}_3^+$\end{document}H3+ afterglow plasmas with spectroscopically determined relative abundances of \documentclass[12pt]{minimal}\begin{document}${\rm H}_3^+$\end{document}H3+ ions in the para-nuclear and ortho-nuclear spin states provide clear evidence that at low temperatures (77–200 K) para-\documentclass[12pt]{minimal}\begin{document}${\rm H}_3^+$\end{document}H3+ ions recombine significantly faster with electrons than ions in the ortho state, in agreement with a recent theoretical prediction. The cavity ring-down absorption spectroscopy used here provides an in situ determination of the para/ortho abundance ratio and yields additional information on the translational and rotational temperatures of the recombining ions. The results show that \documentclass[12pt]{minimal}\begin{document}${\rm H}_3^+$\end{document}H3+ recombination with electrons occurs by both binary recombination and third-body (helium) assisted recombination, and that both the two-body and three-body rate coefficients depend on the nuclear spin states. Electron-stabilized (collisional-radiative) recombination appears to make only a small contribution.
Micro-Raman spectroscopy of graphene grown on stepped 4H-SiC (0001) surface
Authors: Grodecki K. , Bozek R. , Strupinski W. , Wysmolek A. , Stepniewski R. , Baranowski J. M.
Published: June 2012

Graphene grown by chemical vapor deposition on 4H-SiC (0001) was studied using micro-Raman spectroscopy and atomic force microscopy (AFM). AFM revealed that the graphene structure grown on on-axis substrates has a stepped morphology. This is due to step bunching, which results from etching in hydrogen as well as from the process of graphene formation itself. It was shown by micro-Raman spectroscopy that the properties of graphene present on step edges and on terraces are quite different. Graphene on terraces is uniform with a relatively small thickness and strain fluctuations. On the other hand, graphene on step edges has a large thickness and strain variations occur. A careful analysis of micro-Raman spatial maps led us to the conclusion that the carrier concentration on step edge regions is lowered when compared with terrace regions.
Uniaxial magnetic anisotropy in Pd/Fe bilayers on Al2O3 (0001) induced by oblique deposition
Authors: Chi Chiao-Sung , Wang Bo-Yao , Pong Way-Faung , Ho Tsung-Ying , Tsai Cheng-Jui , Lo Fang-Yuh , Chern Ming-Yau , Lin Wen-Chin
Published: June 2012

This study reports the preparation of self-organized 1-dimensional magnetic structures of Fe on Al2O3 (0001) by oblique deposition. The x-ray diffraction (XRD) results in this study show the preferred (110) texture of the Fe films. XRD and extended x-ray adsorption fine structure measurements indicate larger oblique deposition angle (65°) leads to more disorder in the Fe crystalline structure. After capping with a Pd overlayer, the Pd/Fe/Al2O3 (0001) still exhibits uniaxial magnetic anisotropy induced by the underlying 1-dimensional Fe nanostructure. This uniaxial magnetic anisotropy changes with the variation in Fe thickness and oblique deposition angle. These results clearly indicate the feasibility of manipulating uniaxial magnetic anisotropy and crystalline order through the oblique deposition of magnetic materials.
Valence band tail states in disordered superlattices embedded in wide parabolic AlGaAs well
Authors: dos Santos L. Fernandes , Pusep Yu. A. , Bakarov A. K. , Toropov A. I.
Published: June 2012

Optical properties of intentionally disordered multiple quantum well (QW) system embedded in a wide AlGaAs parabolic well were investigated by photoluminescence (PL) measurements as functions of the laser excitation power and the temperature. The characterization of the carriers localized in the individual wells was allowed due to the artificial disorder that caused spectral separation of the photoluminescence lines emitted by different wells. We observed that the photoluminescence peak intensity from each quantum well shifted to high energy as the excitation power was increased. This blue-shift is associated with the filling of localized states in the valence band tail. We also found that the dependence of the peak intensity on the temperature is very sensitive to the excitation power. The temperature dependence of the photoluminescence peak energy from each QW was well fitted using a model that takes into account the thermal redistribution of the localized carriers. Our results demonstrate that the band tails in the studied structures are caused by alloy potential fluctuations and the band tail states dominate the emission from the peripheral wells.
Use of magnetite as anode for electrolysis of water
Authors: Halley J. W. , Schofield A. , Berntson B.
Published: June 2012

We have studied the oxidation of magnetite to Fe2O3 in an electrolytic cell in which the anode is magnetite and the cathode is platinum. We report cyclic voltammagram data consistent with the hypothesis that magnetite, without oxygen gas production but with hydrogen gas production at the cathode, is occurring. The reaction occurs at a potential at the anode of about 0.3 V vs SCE in 1 M NaOH electrolyte, consistent with colloid experiments which also estimated the equilibrium potential of the hypothesized reaction. Electrode characterization results using BET, XEDS, and macroscopic volume and mass measurements are reported, as well as the measurements of the amount of hydrogen gas generated per unit current. The quantity of gas generated is also consistent with our hypothesis concerning the electrode chemistry. Some samples exhibit evidence of two oxidation reactions occurring at the anode and a possible interpretation of these is also discussed. These results suggest the use of magnetite as an anode in a cell electrolysing water to produce hydrogen gas and Fe2O3. In such an electrolyser, the electrical energy cost of producing hydrogen gas could be significantly lower than the cost in a standard electrolyser. The measured steady state currents, equivalent to about 400 mA/g of magnetite, are too low to make a practical electrolyser. We briefly discuss several ways in which the currents might be increased to the levels required.
Crystalline anisotropic magnetoresistance with two-fold and eight-fold symmetry in (In,Fe)As ferromagnetic semiconductor
Authors: Nam Hai Pham , Sasaki Daisuke , Anh Le Duc , Tanaka Masaaki
Published: June 2012

We have investigated the anisotropic magnetoresistance (AMR) of (In,Fe)As ferromagnetic semiconductor layers grown on semi-insulating GaAs substrates. In a 10 nm-thick (In,Fe)As layer which is insulating at low temperature, we observed crystalline AMR with two-fold and eight-fold symmetries. In a metallic 100 nm-thick (In,Fe)As layer with higher electron concentration, only two-fold symmetric crystalline AMR was observed. Our results demonstrate the macroscopic ferromagnetism in (In,Fe)As with magnetic anisotropy that depends on the electron concentration. Very small (∼10−5) non-crystalline AMR is also observed in the 100 nm-thick layer, suggesting that there is no s-d scattering near the Fermi level of (In,Fe)As.
Low cost alternative of high speed visible light camera for tokamak experiments
Authors: Odstrcil T. , Odstrcil M. , Grover O. , Svoboda V. , Ďuran I. , Mlynář J.
Published: June 2012

We present design, analysis, and performance evaluation of a new, low cost and high speed visible-light camera diagnostic system for tokamak experiments. The system is based on the camera Casio EX-F1, with the overall price of approximately a thousand USD. The achieved temporal resolution is up to 40 kHz. This new diagnostic was successfully implemented and tested at the university tokamak GOLEM (R = 0.4 m, a = 0.085 m, BT < 0.5 T, Ip < 4 kA). One possible application of this new diagnostic at GOLEM is discussed in detail. This application is tomographic reconstruction for estimation of plasma position and emissivity.
Thermo-mechanical analysis of ITER first mirrors and its use for the ITER equatorial visible/infrared wide angle viewing system optical design
Authors: Joanny M. , Salasca S. , Dapena M. , Cantone B. , Travère J. M. , Thellier C. , Fermé J. J. , Marot L. , Buravand O. , Perrollaz G. , Zeile C.
Published: June 2012

ITER first mirrors (FMs), as the first components of most ITER optical diagnostics, will be exposed to high plasma radiation flux and neutron load. To reduce the FMs heating and optical surface deformation induced during ITER operation, the use of relevant materials and cooling system are foreseen. The calculations led on different materials and FMs designs and geometries (100 mm and 200 mm) show that the use of CuCrZr and TZM, and a complex integrated cooling system can limit efficiently the FMs heating and reduce their optical surface deformation under plasma radiation flux and neutron load. These investigations were used to evaluate, for the ITER equatorial port visible/infrared wide angle viewing system, the impact of the FMs properties change during operation on the instrument main optical performances. The results obtained are presented and discussed.
Enhanced electrical and noise properties of nanocomposite vanadium oxide thin films by reactive pulsed-dc magnetron sputtering
Authors: Basantani H. A. , Kozlowski S. , Lee Myung-Yoon , Li J. , Dickey E. C. , Jackson T. N. , Bharadwaja S. S. N. , Horn M.
Published: June 2012

Thin films of VOx (1.3 ≤ x ≤ 2) were deposited by reactive pulsed-dc magnetron sputtering of a vanadium metal target while RF-biasing the substrate. Rutherford back scattering, glancing angle x-ray, and cross-sectional transmission electron microscopy measurements revealed the formation of nanocolumns with nanotwins within VOx samples. The resistivity of nanotwinned VOx films ranged from 4 mΩ·cm to 0.6 Ω·cm and corresponding temperature coefficient of resistance between −0.1% and −2.6% per K, respectively. The 1/f electrical noise was analyzed in these VOx samples using the Hooge-Vandamme relation. These VOx films are comparable or surpass commercial VOx films deposited by ion beam sputtering.
Intense white luminescence in ZnTe embedded porous silicon
Authors: de Melo O. , de Melo C. , Santana G. , Santoyo J. , Zelaya-Angel O. , Mendoza-Álvarez J. G. , Torres-Costa V.
Published: June 2012

Porous silicon layers were embedded with ZnTe using the isothermal close space sublimation technique. The presence of ZnTe was demonstrated using cross-sectional energy dispersive spectroscopy maps. ZnTe embedded samples present intense room temperature photoluminescence along the whole visible range. We ascribe this PL to ZnTe nanocrystals of different sizes grown on the internal pore surface. Such crystals, with different orientations and sizes, were observed in transmission electron microscopy images, while transmission electron diffraction images of the same regions reveal ZnTe characteristic patterns.
Detection of a piezoelectric effect in thin films of thermally grown SiO2 via lock-in ellipsometry
Authors: Lazovski Guy , Wachtel Ellen , Lubomirsky Igor
Published: June 2012

We report the observation of structural piezoelectricity in partially ordered thin films of thermally grown silicon dioxide (SiO2). The piezoelectric coefficient was determined to be 0.14-0.26 pm/V, and the piezoelectricity was found to originate in a layer with thickness at least 3.5 nm. This value is consistent with literature descriptions of SiO2 residual ordering based on structural measurements and modeling. Our observation demonstrates that the residual ordering in thermally grown silicon SiO2 is non-centrosymmetric and provides a rare example of diffusion controlled uniaxial growth producing macroscopic piezoelectricity.
Investigation of electronic trap states in organic photovoltaic materials by current-based deep level transient spectroscopy
Authors: Neugebauer Stefan , Rauh Julia , Deibel Carsten , Dyakonov Vladimir
Published: June 2012

Current-based deep level transient spectroscopy was used to study trap states in poly(3-hexylthiophene-2,5-diyl) (P3HT), [6,6]-phenyl-C61 butyric acid methyl ester (PCBM), and P3HT:PCBM blend. The obtained spectra showed traps of 87 meV activation energy in pure P3HT and 21 meV for PCBM. The blend shows a complex emission rate spectrum consisting of several different emission rate bands in the range of 0.1–30 s−1, yielding activation energies between about 30 meV and 160 meV.
Cylindrical ion-acoustic solitary waves in electronegative plasmas with superthermal electrons
Authors: Eslami Parvin , Mottaghizadeh Marzieh
Published: June 2012

By using the standard reductive perturbation technique, a three-dimensional cylindrical Kadomtsev-Petviashvili equation (CKPE), which governs the dynamics of ion acoustic solitary waves (IASWs), is derived for small but finite amplitude ion-acoustic waves in cylindrical geometry in a collisionless unmagnetized plasma with kappa distributed electrons, thermal positrons, and cold ions. The generalized expansion method is used to solve analytically the CKPE. The existence regions of localized pulses are investigated. It is found that the solution of the CKPE supports only compressive solitary waves. Furthermore, the effects of superthermal electrons, the ratio of the electron temperature to positron temperature, the ratio of the positron density to electron density and direction cosine of the wave propagation on the profiles of the amplitudes, and widths of the solitary structures are examined numerically. It is shown these parameters play a vital role in the formation of ion acoustic solitary waves.
Selective precipitation of high electrical conductivity crystals from vanadate glasses by microwave heating
Authors: Fujieda T. , Aoyagi T. , Naito T.
Published: June 2012

High electrical conductivity crystals were selectively precipitated from vanadate glasses by microwave heating. Both the V2O5 and the CuxV2O5 (x = 0.26-0.55) crystals were precipitated in a conventional electric furnace, but CuxV2O5, which has an electrical conductivity about 106 times higher than V2O5, was precipitated preferentially by microwave heating. The conductivity of the glass crystallized by microwave heating was three times higher than that of the glass crystallized by conventional heating. In addition, the Seebeck coefficient of the microwave crystallization glass was about two times higher than that of the conventional crystallization glass. The power factor was improved about 12 times by microwave crystallization.
Controlling the electrical properties of ZnO films by forming zinc and oxide bridges by a plasma and electron-assisted process
Authors: Shimoi Norihiro , Harada Takamitsu , Tanaka Yasumitsu , Tanaka Shun-ichiro
Published: June 2012

A new method to produce electrically steady ZnO films without any heating process has been developed by using plasma and electron beams to facilitate bonding between the metallic component and the oxygen on coated ZnO films. Both plasma atmosphere and electron beams can function as sources of nonequilibrium bonding energy, forming bridges between the zinc present in the zinc complex and the oxygen in the ZnO particles to construct a zinc-oxide thin film. Our results confirm that it is possible to achieve low conductive characteristics by controlling the acceleration voltage of electrons used to irradiate the ZnO coating. The electrically steady films fabricated have various potential applications, being particularly well-suited to electrical devices on a plastic medium.
Analytical analysis of modulation instability in fiber optics
Authors: Aslam M. Saeed , Hamza M. Yousaf , Sarwar Nadeem
Published: June 2012

In this paper, an improved analysis for modulation instability, which results from interaction between optical wave and noise, is presented. It is shown that Nonlinear Schrodinger equation (NLSE), which governs this process, leads to the coupled wave equations that result to Riccati's differential equations. A completely analytical solution of Riccati's equation is obtained for small fiber length that results in efficient computation of the modulation instability effect.
Band gap of β-PtO2 from first-principles
Authors: Yang Yong , Sugino Osamu , Ohno Takahisa
Published: June 2012

We studied the band gap of β-PtO2 using first-principles calculations based on density functional theory (DFT). The results are obtained within the framework of the generalized gradient approximation (GGA), GGA+U, GW, and the hybrid functional methods. For the different types of calculations, the calculated band gap increases from ∼0.46 eV to 1.80 eV. In particular, the band gap by GW (conventional and self-consistent) calculation shows a tendency of converging to ∼1.25 ± 0.05 eV. The effect of on-site Coulomb interaction on the bonding characteristics is also analyzed.
Commentary: JWST near-infrared detector degradation— finding the problem, fixing the problem, and moving forward
Authors: Rauscher Bernard J. , Stahle Carl , Hill Robert J. , Greenhouse Matthew , Beletic James , Babu Sachidananda , Blake Peter , Cleveland Keith , Cofie Emmanuel , Eegholm Bente , Engelbracht C. W. , Hall Donald N. B. , Hoffman Alan , Jeffers Basil , Jhabvala Christine , Kimble Randy A. , Kohn Stanley , Kopp Robert , Lee Don , Leidecker Henning , Lindler Don , McMurray Robert E. , Misselt Karl , Mott D. Brent , Ohl Raymond , Pipher Judith L. , Piquette Eric , Polis Dan , Pontius Jim , Rieke Marcia , Smith Roger , Tennant W. E. , Wang Liqin , Wen Yiting , Willmer Christopher N. A. , Zandian Majid
Published: June 2012

The James Webb Space Telescope (JWST) is the successor to the Hubble Space Telescope. JWST will be an infrared-optimized telescope, with an approximately 6.5 m diameter primary mirror, that is located at the Sun-Earth L2 Lagrange point. Three of JWST’s four science instruments use Teledyne HgCdTe HAWAII-2RG (H2RG) near infrared detector arrays. During 2010, the JWST Project noticed that a few of its 5 μm cutoff H2RG detectors were degrading during room temperature storage, and NASA chartered a “Detector Degradation Failure Review Board” (DD-FRB) to investigate. The DD-FRB determined that the root cause was a design flaw that allowed indium to interdiffuse with the gold contacts and migrate into the HgCdTe detector layer. Fortunately, Teledyne already had an improved design that eliminated this degradation mechanism. During early 2012, the improved H2RG design was qualified for flight and JWST began making additional H2RGs. In this article, we present the two public DD-FRB “Executive Summaries” that: (1) determined the root cause of the detector degradation and (2) defined tests to determine whether the existing detectors are qualified for flight. We supplement these with a brief introduction to H2RG detector arrays, some recent measurements showing that the performance of the improved design meets JWST requirements, and a discussion of how the JWST Project is using cryogenic storage to retard the degradation rate of the existing flight spare H2RGs.
A New Approach to Argument by Analogy: Extrapolation and Chain Graphs
Authors: Steel Daniel
Published: June 2012

This essay sketches an account of extrapolation in terms of analogical reasoning that generalizes the notion of comparative process tracing. The account offered here relies on something known as chain graphs, which are used to explicate the role of “fingerprints,” or distinctive markers, as a strategy for avoiding an underdetermination problem having to do with spurious analogies. Moreover, I show how the extrapolator's circle, one of the central challenges for extrapolation, is closely tied to distinctive markers and the Markov condition as it applies to chain graphs.
A Mereological Interpretation of the Phase Rule
Authors: Needham Paul
Published: June 2012

Gibbs's phase rule treats mixtures by relating the number of independent variables governing their state to the numbers of phases and independent substances. For the case of a single substance, it provides a criterion of purity. But where more substances are involved, the notion of independent substance is less readily understood. Textbook writers sometimes use algebraic terminology in ways that are suggestive but cannot be taken as literally accurate. I suggest that a mereological interpretation applies to these cases, as it captures more concisely the insights underlying the use of algebraic terminology and illuminates the general notion of substance.
Entropy and Chemical Substance
Authors: Hendry Robin Findlay
Published: June 2012

In this essay I critically examine the role of entropy of mixing in articulating a macroscopic criterion for the sameness and difference of chemical substances. Consider three cases of mixing in which entropy change occurs: isotopic variants, spin isomers, and populations of atoms in different orthogonal quantum states. Using these cases I argue that entropy of mixing tracks differences between physical states, differences that may or may not correspond to a difference of substance. It does not provide a criterion for the sameness and difference of substance that is appropriate to chemistry.
The Ontology of Patterns in Empirical Data
Authors: McAllister James W.
Published: June 2012

This article defends the following claims. First, for patterns exhibited in empirical data, there is no criterion on which to demarcate patterns that are physically significant and patterns that are not physically significant. I call a pattern physically significant if it corresponds to a structure in the world. Second, all patterns must be regarded as physically significant. Third, distinct patterns must be regarded as providing evidence for distinct structures in the world. Fourth, in consequence, the world must be conceived as showing all possible structures.
Species Have (Partly) Intrinsic Essences
Authors: Devitt Michael
Published: June 2012

The paper defends the doctrine that Linnaean taxa, including species, have essences that are, at least partly, underlying intrinsic, mostly genetic, properties. The consensus among philosophers of biology is that such essentialism is deeply wrong, indeed incompatible with Darwinism. I argue that biological generalizations about the morphology, physiology, and behavior of species require structural explanations that must advert to these essential properties. The paper concludes by summarizing my responses to the objection that, according to current “species concepts,” species are relational, and to the objection that essentialism cannot accommodate features of Darwinism associated with variation and change.
Smoothness of the truncated display functor
Authors: Lau Eike
Published: June 2012

We show that to every

p
p

-divisible group over a

p
p

-adic ring one can associate a display by crystalline Dieudonné theory. For an appropriate notion of truncated displays, this induces a functor from truncated Barsotti-Tate groups to truncated displays, which is a smooth morphism of smooth algebraic stacks. As an application we obtain a new proof of the equivalence between infinitesimal

p
p

-divisible groups and nilpotent displays over

p
p

-adic rings, and a new proof of the equivalence due to Berthelot and Gabber between commutative finite flat group schemes of

p
p

-power order and Dieudonné modules over perfect rings.
A journey from reductionist to systemic cell biology aboard the schooner Tara
Authors: Karsenti Eric
Published: June 2012

In this essay I describe my personal journey from reductionist to systems cell biology and describe how this in turn led to a 3-year sea voyage to explore complex ocean communities. In describing this journey, I hope to convey some important principles that I gleaned along the way. I realized that cellular functions emerge from multiple molecular interactions and that new approaches borrowed from statistical physics are required to understand the emergence of such complex systems. Then I wondered how such interaction networks developed during evolution. Because life first evolved in the oceans, it became a natural thing to start looking at the small organisms that compose the plankton in the world's oceans, of which 98% are … individual cells—hence the Tara Oceans voyage, which finished on 31 March 2012 in Lorient, France, after a 60,000-mile around-the-world journey that collected more than 30,000 samples from 153 sampling stations.
Atg16L1, an essential factor for canonical autophagy, participates in hormone secretion from PC12 cells independently of autophagic activity
Authors: Ishibashi Koutaro , Uemura Takefumi , Waguri Satoshi , Fukuda Mitsunori
Published: June 2012

Autophagy is a bulk degradation system in all eukaryotic cells and regulates a variety of biological activities in higher eukaryotes. Recently involvement of autophagy in the regulation of the secretory pathway has also been reported, but the molecular mechanism linking autophagy with the secretory pathway remains largely unknown. Here we show that Atg16L1, an essential protein for canonical autophagy, is localized on hormone-containing dense-core vesicles in neuroendocrine PC12 cells and that knockdown of Atg16L1 causes a dramatic reduction in the level of hormone secretion independently of autophagic activity. We also find that Atg16L1 interacts with the small GTPase Rab33A and that this interaction is required for the dense-core vesicle localization of Atg16L1 in PC12 cells. Our findings indicate that Atg16L1 regulates not only autophagy in all cell types, but also secretion from dense-core vesicles, presumably by acting as a Rab33A effector, in particular cell types.
The TAM-family receptor Mer mediates production of HGF through the RhoA-dependent pathway in response to apoptotic cells
Authors: Park Hyun-Jung , Baen Ji-Yeon , Lee Ye-Ji , Choi Youn-Hee , Kang Jihee Lee
Published: June 2012

The TAM receptor protein tyrosine kinases Tyro3, Axl, and Mer play important roles in macrophage function. We investigated the roles of the TAM receptors in mediating the induction of hepatocyte growth factor (HGF) during the interaction of macrophages with apoptotic cells. Mer-specific neutralizing antibody, small interfering RNA (siRNA), and a recombinant Mer protein (Mer/Fc) inhibited HGF mRNA and protein expression, as well as activation of RhoA, Akt, and specific mitogen-activated protein (MAP) kinases in response to apoptotic cells. Inhibition of Axl or Tyro3 with specific antibodies, siRNA, or Fc-fusion proteins did not prevent apoptotic cell–induced HGF mRNA and protein expression and did not inhibit activation of the postreceptor signaling molecules RhoA and certain MAP kinases, including extracellular signal-regulated protein kinase and c-Jun NH2-terminal kinase. However, Axl- and Tyro3-specific blockers did inhibit the activation of Akt and p38 MAP kinase in response to apoptotic cells. In addition, none of the TAM receptors mediated the effects of apoptotic cells on transforming growth factor-β or epidermal growth factor mRNA expression. However, they were involved in the induction of vascular endothelial growth factor mRNA expression. Our data provide evidence that when macrophages interact with apoptotic cells, only Mer of the TAM-family receptors is responsible for mediating transcriptional HGF production through a RhoA-dependent pathway.
The future of ciliary and flagellar membrane research
Authors: Bloodgood Robert A.
Published: June 2012

There has been a dramatic shift of attention from the ciliary axoneme to the ciliary membrane, much of this driven by the appreciation that cilia play a widespread role in sensory reception and cellular signaling. This Perspective focuses attention on some of the poorly understood aspects of ciliary membranes, including the establishment of ciliary and periciliary membrane domains, the trafficking of membrane components into and out of these membrane domains, the nonuniform distribution of ciliary membrane components, the regulation of membrane morphogenesis, functional collaboration between the axoneme and the membrane, and the evolving field of therapeutics targeted at the ciliary membrane.
NAC functions as a modulator of SRP during the early steps of protein targeting to the endoplasmic reticulum
Authors: Zhang Ying , Berndt Uta , Gölz Hanna , Tais Arlette , Oellerer Stefan , Wölfle Tina , Fitzke Edith , Rospert Sabine
Published: June 2012

Nascent polypeptide-associated complex (NAC) was initially found to bind to any segment of the nascent chain except signal sequences. In this way, NAC is believed to prevent mistargeting due to binding of signal recognition particle (SRP) to signalless ribosome nascent chain complexes (RNCs). Here we revisit the interplay between NAC and SRP. NAC does not affect SRP function with respect to signalless RNCs; however, NAC does affect SRP function with respect to RNCs targeted to the endoplasmic reticulum (ER). First, early recruitment of SRP to RNCs containing a signal sequence within the ribosomal tunnel is NAC dependent. Second, NAC is able to directly and tightly bind to nascent signal sequences. Third, SRP initially displaces NAC from RNCs; however, when the signal sequence emerges further, trimeric NAC·RNC·SRP complexes form. Fourth, upon docking to the ER membrane NAC remains bound to RNCs, allowing NAC to shield cytosolically exposed nascent chain domains not only before but also during cotranslational translocation. The combined data indicate a functional interplay between NAC and SRP on ER-targeted RNCs, which is based on the ability of the two complexes to bind simultaneously to distinct segments of a single nascent chain.
α-Actinin and fimbrin cooperate with myosin II to organize actomyosin bundles during contractile-ring assembly
Authors: Laporte Damien , Ojkic Nikola , Vavylonis Dimitrios , Wu Jian-Qiu
Published: June 2012

The actomyosin contractile ring assembles through the condensation of a broad band of nodes that forms at the cell equator in fission yeast cytokinesis. The condensation process depends on actin filaments that interconnect nodes. By mutating or titrating actin cross-linkers α-actinin Ain1 and fimbrin Fim1 in live cells, we reveal that both proteins are involved in node condensation. Ain1 and Fim1 stabilize the actin cytoskeleton and modulate node movement, which prevents nodes and linear structures from aggregating into clumps and allows normal ring formation. Our computer simulations modeling actin filaments as semiflexible polymers reproduce the experimental observations and provide a model of how actin cross-linkers work with other proteins to regulate actin-filament orientations inside actin bundles and organize the actin network. As predicted by the simulations, doubling myosin II Myo2 level rescues the node condensation defects caused by Ain1 overexpression. Taken together, our work supports a cooperative process of ring self-organization driven by the interaction between actin filaments and myosin II, which is progressively stabilized by the cross-linking proteins.
A stochastic T cell response criterion
Authors: Currie James , Castro Mario , Lythe Grant , Palmer Ed , Molina-París Carmen
Published: June 2012

The adaptive immune system relies on different cell types to provide fast and coordinated responses, characterized by recognition of pathogenic challenge, extensive cellular proliferation and differentiation, as well as death. T cells are a subset of the adaptive immune cellular pool that recognize immunogenic peptides expressed on the surface of antigen-presenting cells by means of specialized receptors on their membrane. T cell receptor binding to ligand determines T cell responses at different times and locations during the life of a T cell. Current experimental evidence provides support to the following: (i) sufficiently long receptor–ligand engagements are required to initiate the T cell signalling cascade that results in productive signal transduction and (ii) counting devices are at work in T cells to allow signal accumulation, decoding and translation into biological responses. In the light of these results, we explore, with mathematical models, the timescales associated with T cell responses. We consider two different criteria: a stochastic one (the mean time it takes to have hadNreceptor–ligand complexes bound for at least a dwell time,τ, each) and one based on equilibrium (the time to reach a threshold numberNof receptor–ligand complexes). We have applied mathematical models to previous experiments in the context of thymic negative selection and to recent two-dimensional experiments. Our results indicate that the stochastic criterion provides support to the thymic affinity threshold hypothesis, whereas the equilibrium one does not, and agrees with the ligand hierarchy experimentally established for thymic negative selection.
Characterization of a porcine intestinal epithelial cell line for influenza virus production
Authors: Sun Zhi , Huber Victor C. , McCormick Kara , Kaushik Radhey S. , Boon Adrianus C. M. , Zhu Longchao , Hause Ben , Webby Richard J. , Fang Ying
Published: June 2012

We have developed a porcine intestine epithelial cell line, designated SD-PJEC for the propagation of influenza viruses. The SD-PJEC cell line is a subclone of the IPEC-J2 cell line, which was originally derived from newborn piglet jejunum. Our results demonstrate that SD-PJEC is a cell line of epithelial origin that preferentially expresses receptors of oligosaccharides with Sia2-6Gal modification. This cell line is permissive to infection with human and swine influenza A viruses and some avian influenza viruses, but poorly support the growth of human-origin influenza B viruses. Propagation of swine-origin influenza viruses in these cells results in a rapid growth rate within the first 24 h post-infection and the titres ranged from 4 to 8 log10TCID50ml−1. The SD-PJEC cell line was further tested as a potential alternative cell line to Madin–Darby canine kidney (MDCK) cells in conjunction with 293T cells for rescue of swine-origin influenza viruses using the reverse genetics system. The recombinant viruses A/swine/North Carolina/18161/02 (H1N1) and A/swine/Texas/4199-2/98 (H3N2) were rescued with virus titres of 7 and 8.25 log10TCID50ml−1, respectively. The availability of this swine-specific cell line represents a more relevant substrate for studies and growth of swine-origin influenza viruses.
Signatures of contemporary selection in the Israeli Holstein dairy cattle
Authors: Glick G. , Shirak A. , Uliel S. , Zeron Y. , Ezra E. , Seroussi E. , Ron M. , Weller J. I.
Published: June 2012

Strong selection in the Israeli Holstein dairy cattle population over the last three decades should have left clear signatures of selection. Two experimental approaches were applied to detect evidence of contemporary selection based on the 54K BeadChip genotypes of ~1000 Israeli Holstein bulls: (i) the long‐range haplotype test, which searches for structural evidence resulting from selective sweep, and (ii) direct analysis of the changes in haplotypes frequencies over time combined with linkage disequilibrium blocks haplotype‐based association analysis. Ten traits were analyzed: the PD07 Israeli selection index, milk, milk fat, % fat, milk protein, % protein, somatic cell score, female fertility, milk production persistency and herd life. The long‐range haplotype test detected ~15% of the 3288 haplotypes that showed significant positive frequency trends (P < 0.05) and was significantly correlated with the substitution effects of the haplotypes and the selection intensities for the different traits. Thirty signatures of recent selection, which correspond to both approaches and affect the Israeli PD07 selection index, were identified on 17 of the 29 autosomes. The second experimental approach also was used to estimate the selection intensity of the different traits. The correlation between the selection intensities for the traits analyzed, derived from changes in haplotype frequencies in the population of bulls, and those derived from trait‐based analysis of the cow population was 0.93 over all traits. Thus, the changes in haplotypes frequencies in the bulls’ population accurately estimate genetic trends in the general cow population and can be used to detect signatures of recent selection.