bluuebunny/crossref_metadata_2025 huggingface dataset:
State-averaged Monte Carlo configuration interaction applied to electronically excited states
Authors: Coe J. P. , Paterson M. J.
Published: October 2013

We introduce state-averaging into the method of Monte Carlo configuration interaction (SA-MCCI) to allow the stable and efficient calculation of excited states. We show that excited potential curves for H3, including a crossing with the ground state, can be accurately reproduced using a small fraction of the full configuration interaction (FCI) space. A recently introduced error measure for potential curves [J. P. Coe and M. J. Paterson, J. Chem. Phys. 137, 204108 (2012)] is also shown to be a fair approach when considering potential curves for multiple states. We demonstrate that potential curves for LiF using SA-MCCI agree well with the FCI results and the avoided crossing occurs correctly. The seam of conical intersections for CH2 found by Yarkony [J. Chem. Phys. 104, 2932 (1996)] is used as a test for SA-MCCI and we compare potential curves from SA-MCCI with FCI results for this system for the first three triplet states. We then demonstrate the improvement from using SA-MCCI on the dipole of the 2 1A1 state of carbon monoxide. We then look at vertical excitations for small organic molecules up to the size of butadiene where the SA-MCCI energies and oscillator strengths are compared with CASPT2 values [M. Schreiber, M. R. Silva-Junior, S. P. A. Sauer, and W. Thiel, J. Chem. Phys. 128, 134110 (2008)]. We finally see if the SA-MCCI results for these excitation energies can be improved by using MCCIPT2 with approximate natural orbitals when the PT2 space is not onerously large.
Corresponding states principle and van der Waals potentials of Zn2, Cd2, and Hg2
Authors: Wei L. M. , Li P. , Qiao L. W. , Tang K. T.
Published: October 2013

Based on the assumptions that the corresponding states principle is valid for the group 12 dimers and that the interaction potentials of these dimers can be described by the Tang-Toennies potential model, a set of correlation relations between the spectroscopic constants of these dimers are derived. Some recently measured spectroscopic constants satisfy these relations quite well, but older experimental data do not. These recent spectroscopic constants and the newly available dispersion coefficients are used to construct the entire van der Waals potentials of Zn2, Cd2, and Hg2. There are indications that the ground state Hg2 potential predicted by the present study is possibly the most accurate to date. No unequivocal conclusion can be made for Zn2 and Cd2 potentials. Compared with the recent experiments, the present Zn2 bond length is eight percent too small, and the present Cd2 bond length is eight percent too large. However, both Zn2 and Cd2 bond lengths predicted by the present study are in good agreement with the quantum Monte Carlo results.
Faceted growth of primary Al2Cu crystals during directional solidification in high magnetic field
Authors: Li Chuanjun , Ren Zhongming , Shen Yu , Wang Qiuliang , Dai Yinming , Wang Hui
Published: October 2013

The high magnetic field is widely used to modify the crystal morphology. In this work, the effect of the magnetic field on growing behavior of faceted crystals in the Al-40 wt. %Cu alloy was investigated using directional solidification technique. It was found that the faceted growth of primary Al2Cu phase was degraded and the primary spacing was reduced upon applying the magnetic field. Additionally, the length of the mushy zone first decreased and then increased with increase of the magnetic field intensity. The quantitative analysis reveals that the shear stress induced by the fluid motion is insufficient to break the atom bonds at the solid-liquid interface. However, both of the thermoelectric magnetic convection (TEMC) and the thermoelectric magnetic force (TEMF) cause dendrites to fracture and reduce the primary spacing. The two effects also weaken the faceting growth. Moreover, the instability of the solid-liquid interface is generated by the TEMF, which further leads to degrade the faceted growth. The length of mushy zone was changed by the TEMC and reached the minimum in the magnetic field of 0.5 T, which is in good agreement with the predicted value (0.83 T).
Surface electronic inhomogeneity of the (001)-SrTiO3:Nb crystal with a terrace-structured morphology
Authors: Li Y. , Sun J. R. , Zhao J. L. , Shen B. G.
Published: October 2013

Local surface conduction of the (001)-orientated SrTiO3:Nb crystal with a terrace-structured morphology has been studied by means of conductive atomic force microscope analysis. We found that the surface conductance is inhomogeneous on the atomic scale; it is high near step edges and low on terrace plateaus. The surface conductance fluctuation is susceptible to post annealing, first enhancing and then weakening while repeatedly annealed at 700 °C in vacuum. Considering the fact that the oxygen content is most sensitive to vacuum annealing for the temperatures adopted here, the inhomogeneous conductance implies the difference of oxygen vacancy content at step edges and terrace plateaus. The present work clearly demonstrated the influence of surface microstructure on physical properties, and could be helpful for the understanding of the atomic scale non-uniformity of the ultrathin films fabricated on step-featured SrTiO3 surface.
Reaction of positronium with doped ions in silica-based glasses in the size determination of subnanometer structural open spaces
Authors: Inoue K. , Kataoka H. , Nagai Y. , Hasegawa M. , Kobayashi Y.
Published: October 2013

Positron annihilation spectroscopy is employed to estimate the size of subnanometer-scale open spaces in insulating materials. In most cases, the size is estimated from the lifetime of long-lived ortho-positronium (o-Ps) by pickoff annihilation using a simplified model. However, reactions of Ps with surrounding electrons other than the pickoff reaction, such as spin conversion or chemical reaction, could give a substantially underestimated size using the simplified model. In the present paper, we report that the size of the open spaces can be evaluated correctly by the angular correlation of positron annihilation radiation (ACAR) with a magnetic field using the spin-polarization effect on Ps formation, even if such reactions of Ps occur in the material. This method is applied to the subnanometer-scale structural open spaces of silica-based glass doped with Fe. We demonstrate the influence of the Ps reaction on size-estimation of the open spaces from the o-Ps lifetime. Furthermore, the type of reaction, whether spin conversion or chemical, is distinguished from the magnetic field dependence of the Ps self-annihilation component intensity in the ACAR spectra. The Ps reaction in silica-based glass doped with Fe is a chemical reaction (most likely oxidation) rather than spin conversion, with Fe ions. The chemical quenching rate with Fe ions is determined from the dependence of the o-Ps lifetime on the Fe content.
Note: Characterization of a high-photon-energy X-ray imager
Authors: Storm M. , Eichman B. , Zhong Z. , Theobald W. , Schiebel P. , Mileham C. , Stoeckl C. , Begishev I. A. , Fiksel G. , Stephens R. B. , Freeman R. R. , Akli K. U.
Published: October 2013

The Bragg angle, rocking curve, and reflection efficiency of a quartz crystal x-ray imager (Miller indices 234) were measured at photon energy of 15.6909 keV, corresponding to the Kα2 line of Zr, using the X15A beamline at the National Synchrotron Light Source at Brookhaven National Laboratory. One flat and three spherically curved samples were tested. The peak reflectivity of the best-performing crystal was determined to be (3.6 ± 0.7) × 10−4 with a rocking-curve full width at half maximum of 0.09°. The Zr Kα2 emission was imaged from a hot Zr plasma generated by a 10-J multiterawatt laser.
Fractal dynamics of light scattering intensity fluctuation in disordered dusty plasmas
Authors: Safaai S. S. , Muniandy S. V. , Chew W. X. , Asgari H. , Yap S. L. , Wong C. S.
Published: October 2013

Dynamic light scattering (DLS) technique is a simple and yet powerful technique for characterizing particle properties and dynamics in complex liquids and gases, including dusty plasmas. Intensity fluctuation in DLS experiments often studied using correlation analysis with assumption that the fluctuation is statistically stationary. In this study, the temporal variation of the nonstationary intensity fluctuation is analyzed directly to show the existence of fractal characteristics by employing wavelet scalogram approach. Wavelet based scale decomposition approach is used to separate non-scaling background noise (without dust) from scaling intensity fluctuation from dusty plasma. The Hurst exponents for light intensity fluctuation in dusty plasma at different neutral gas pressures are determined. At low pressures, weaker damping of dust motions via collisions with neutral gases results in stronger persistent behavior in the fluctuation of DLS time series. The fractal scaling Hurst exponent is demonstrated to be useful for characterizing structural phases in complex disordered dusty plasma, especially when particle configuration or sizes are highly inhomogeneous which makes the standard pair-correlation function difficult to interpret. The results from fractal analysis are compared with alternative interpretation of disorder based on approximate entropy and particle transport using mean square displacement.
Kelvin-Helmholtz instability for flow in porous media under the influence of oblique magnetic fields: A viscous potential flow analysis
Authors: Moatimid Galal M. , Obied Allah M. H. , Hassan Mohamed A.
Published: October 2013

In this paper, the Kelvin-Helmholtz instability of viscous incompressible magnetic fluid fully saturated porous media is achieved through the viscous potential theory. The flow is considered to be through semi-permeable boundaries above and below the fluids through which the fluid may either be blown in or sucked out, in a direction normal to the main streaming direction of the fluid flow. An oblique magnetic field, mass, heat transfer, and surface tension are present across the interface. Through the linear stability analysis, a general dispersion relation is derived and the natural curves are plotted. Therefore, the linear stability condition is discussed in some depth. In view of the multiple time scale technique, the Ginzburg–Landau equation, which describes the behavior of the system in the nonlinear approach, is obtained. The effects of the orientation of the magnetic fields on the stability configuration in linear, as well as nonlinear approaches, are discussed. It is found that the Darcy's coefficient for the porous layers plays a stabilizing role. The injection of the fluids at both boundaries has a stabilizing effect, in contrast with the suction at both boundaries.
Millimeter and terahertz wave absorption in a lossy conducting layer
Authors: Shen M. K. , Chiang W. Y. , Wu K. L. , Chu K. R.
Published: October 2013

Relativistic electronics research in recent years has produced powerful millimeter waves on the MW level, while also extending the frequency range into the terahertz (THz) region and beyond. These developments have opened up new horizons in applications. The current study is motivated by the associated need for high-power absorbers not readily available at such frequencies. Our focus is on effective absorber schemes which can handle high power while also possessing a structural simplicity for easy implementation. In and above the THz region, the electrical conductivity can no longer be treated as a real constant. We begin with a derivation of the field penetration depth applicable to all frequencies. Requirements to meet the intended criteria are then determined from the wave penetration and reflection properties. Design examples in the 1–1000 GHz range are illustrated, which consist of a thin lossy conducting layer on the surface of a pyramidal shaped metal base. It is shown in theory that such structures can function effectively in the millimeter and THz regions.
Phase-stepping interferometry of GaAs nanowires: Determining nano-wire radius
Authors: Little D. J. , Kuruwita R. L. , Joyce A. , Gao Q. , Burgess T. , Jagadish C. , Kane D. M.
Published: October 2013

Phase stepping interferometry is used to measure the size of near-cylindrical nanowires. Nanowires with nominal radii of 25 nm and 50 nm were used to test this by comparing specific measured optical phase profile values with theoretical values calculated using a wave-optic model of the Phase stepping interferometry (PSI) system. Agreement within 10% was found, which enabled nanowire radii to be predicted within 4% of the nominal value. This demonstration highlights the potential capability for phase stepping interferometry to characterize single nanoparticles of known geometry in the optical far-field.
Development of in situ energetic ion injector for magnetically confined plasmas using hydrogen storage electrode
Authors: Okamoto A. , Oku T. , Koike S. , Sato Y. , Ishii K. , Kitajima S.
Published: October 2013

To develop a compact ion injector made of hydrogen storage material, we investigate a plasma response for a positively biased hydrogen storage electrode in a small standard heliac device. When the bias voltage of the electrode increases, a positive potential between the electrode and the space potential on the magnetic surface emerges. The emission of hydrogen atom line also increases. To clarify the origin of the increase in emission, we designed an imaging system with sufficient temporal resolution.
Non-thermal plasma jet without electrical shock for biomedical applications
Authors: Baik Ku Youn , Kang Han Lim , Kim Junseong , Park Shin Young , Bang Ji Yun , Uhm Han S. , Choi Eun Ha , Cho Guangsup
Published: October 2013

A plasma jet without an electrical shock was generated through a Y-shaped tube in which voltages with opposite phases were applied to a pair of tubes. The plasma plume generated at the intersection had a plasma potential of a 60–90 V and high concentrations of reactive species sufficient to induce a high level of lethality on gram-negative bacteria on a tissue mimic. The selective lethality of bacteria on an epithelial-cell-containing tissue mimic could be modulated using oxidant and antioxidant chemicals, thereby leading to the possibility of a shock-reduced plasma jet for biomedical applications.
Effect of confined acoustic phonons on the electron mobility of rectangular nanowires
Authors: Tienda-Luna I. M. , Ruiz F. G. , Godoy A. , Donetti L. , Martínez-Blanque C. , Gámiz F.
Published: October 2013

In this paper, we assess the impact of the confined acoustic phonon boundary conditions on the electron mobility of semiconductor nanowires. Specifically, we present an approach to compute the phonon dispersion relationship considering clamped boundary conditions when the nanowires are considered as an anisotropic continuum. Phonon spectra for free-standing and clamped boundary conditions are compared, and scattering rates are calculated. Electron states in the nanowire are computed by self-consistently solving the Poisson and Schrödinger equations, and electron mobility is obtained by the Kubo formula. We show how the use of different boundary conditions affects the mobility depending on the device size.
Charge carrier dynamics and recombination in graded band gap CuIn1−xGaxSe2 polycrystalline thin-film photovoltaic solar cell absorbers
Authors: Kuciauskas Darius , Li Jian V. , Contreras Miguel A. , Pankow Joel , Dippo Patricia , Young Matthew , Mansfield Lorelle M. , Noufi Rommel , Levi Dean
Published: October 2013

We report the results of spectroscopic time-resolved photoluminescence (TRPL) analysis for polycrystalline CuIn1−xGaxSe2 (CIGS) films. On the <5 ns time scale, we investigated minority carrier spatial redistribution from the initial absorption profile near the surface of the films to the conduction band minimum. Based on these data, the estimated minority carrier mobility is 75–230 cm2 V−1 s−1. Full TRPL decays were analyzed using models for donor-acceptor pair (DAP) recombination. We estimated that the concentration of DAP recombination centers was 5 × 1015–1017 cm−3. Data also show that Shockley-Reed-Hall and surface recombination are not significant for polycrystalline CIGS absorbers used in high-efficiency photovoltaic solar cells.
Position and mode dependent coupling of terahertz quantum cascade laser fields to an integrated diode
Authors: Dyer Gregory C. , Nordquist Christopher D. , Cich Michael J. , Ribaudo Troy , Grine Albert D. , Fuller Charles T. , Reno John L. , Wanke Michael C.
Published: October 2013

A Schottky diode integrated into a terahertz quantum cascade laser waveguide couples directly to the internal laser fields. In a multimode laser, the diode response is correlated with both the instantaneous power and the coupling strength to the diode of each lasing mode. Measurements of the rectified response of diodes integrated in two quantum cascade laser cavities at different locations indicate that the relative diode position strongly influences the laser-diode coupling.
Thermoelectric properties of β-FeSi2
Authors: Pandey Tribhuwan , Singh David J. , Parker David , Singh Abhishek K.
Published: October 2013

We investigate the thermoelectric properties of β-FeSi2 using first principles electronic structure and Boltzmann transport calculations. We report a high thermopower for both p- and n-type β-FeSi2 over a wide range of carrier concentration and in addition find the performance for n-type to be higher than for the p-type. Our results indicate that, depending upon temperature, a doping level of 3 × 1020 to 2 × 1021 cm−3 may optimize the thermoelectric performance.
Effects of laser polarization in the expansion of plasma waveguides
Authors: Lemos N. , Grismayer T. , Cardoso L. , Geada J. , Figueira G. , Dias J. M.
Published: October 2013

We experimentally demonstrate that a column of hydrogen plasma generated by an ultra-short (sub-picosecond), moderate intensity (∼1015–16 W.cm–2) laser, radially expands at a higher velocity when using a circularly polarized laser beam instead of a linearly polarized beam. Interferometry shows that after 1 ns there is a clear shock structure formed, that can be approximated to a cylindrical blast wave. The shock velocity was measured for plasmas created with linearly and circularly polarized laser beams, indicating an approximately 20% higher velocity for plasmas generated with a circularly polarized laser beam, thus implying a higher plasma electron temperature. The heating mechanism was determined to be the Above Threshold Ionization effect. The calculated electrum energy spectrum for a circularly polarized laser beam was broader when compared to the one generated by a linearly polarized laser beam, leading to a higher plasma temperature.
Study on the effect of target on plasma parameters of magnetron sputtering discharge plasma
Authors: Saikia P. , Kakati B. , Saikia B. K.
Published: October 2013

In this study, the effect of magnetron target on different plasma parameters of Argon/Hydrogen (Ar - H2) direct current (DC) magnetron discharge is examined. Here, Copper (Cu) and Chromium (Cr) are used as magnetron targets. The value of plasma parameters such as electron temperature (kTe), electron density (Ne), ion density (Ni), degree of ionization of Ar, and degree of dissociation of H2 for both the target are studied as a function of input power and hydrogen content in the discharge. The plasma parameters are determined by using Langmuir probe and Optical emission spectroscopy. On the basis of the different reactions in the gas phase, the variation of plasma parameters and sputtering rate are explained. The obtained results show that electron and ion density decline with gradual addition of Hydrogen in the discharge and increase with rising input power. It brings significant changes on the degree of ionization of Ar and dissociation of H2. The enhanced value of electron density (Ne), ion density (Ni), degree of Ionization of Ar, and degree of dissociation of H2 for Cr compared to Cu target is explained on the basis of it's higher Ion Induced Secondary Electron Emission Coefficient (ISEE) value.
Magnetic topology and current channels in plasmas with toroidal current density inversions
Authors: Ciro D. , Caldas I. L.
Published: October 2013

The equilibrium magnetic field inside axisymmetric plasmas with inversions on the toroidal current density is considered. Previous works have shown that internal regions with negative current density lead to non-nested magnetic surfaces inside the plasma. Following these results, we derive a general expression relating the positive and negative currents inside the non-nested surfaces. This is done in terms of an anisotropy parameter that is model-independent and is based in very general properties of the magnetic field. We demonstrate that the positive currents in axisymmetric islands screen the negative one in the plasma center by reaching about twice its magnitude. Further, we illustrate these results by developing a family of analytical local solutions for the poloidal magnetic field in a region of interest that contains the inverted current. These local solutions exhibit non-nested magnetic surfaces with a combined current of at least twice the magnitude of the negative one, as prescribed from the topological arguments, and allow to study topological transitions driven by geometrical changes in the current profile. To conclude, we discuss the signatures of internal current density inversions in a confinement device and show that magnetic pitch measurements may be inappropriate to differentiate current reversals and small current holes in plasmas.
Influence of plasma-based in-situ surface cleaning procedures on HfO2/In0.53Ga0.47As gate stack properties
Authors: Chobpattana Varistha , Mates Thomas E. , Mitchell William J. , Zhang Jack Y. , Stemmer Susanne
Published: October 2013

We report on the influence of variations in the process parameters of an in-situ surface cleaning procedure, consisting of alternating cycles of nitrogen plasma and trimethylaluminum dosing, on the interface trap density of highly scaled HfO2 gate dielectrics deposited on n-In0.53Ga0.47As by atomic layer deposition. We discuss the interface chemistry of stacks resulting from the pre-deposition exposure to nitrogen plasma/trimethylaluminum cycles. Measurements of interface trap densities, interface chemistry, and surface morphology show that variations in the cleaning process have a large effect on nucleation and surface coverage, which in turn are crucial for achieving low interface state densities.
Electricity generated from ambient heat across a silicon surface
Authors: Tai Guoan , Xu Zihan , Liu Jinsong
Published: October 2013

We report generation of electricity from the limitless thermal motion of ions across a two-dimensional (2D) silicon (Si) surface at room temperature. A typical Si device with Au-Ag electrodes could generate an open-circuit voltage of up to 0.40 V in a 5M CuCl2 solution and an output current of more than 11 μA when a 25 kΩ resistor was loaded into the circuit. A possible momentum transfer process was proposed to explain the electronic excitation, and modified thermionic emission theory was used to explain the experimental results. This finding provides a self-charging technology for energy harvesting from ambient heat.
Effects of core/shell structure on magnetic induction heating promotion in Fe3O4/γ-Fe2O3 magnetic nanoparticles for hyperthermia
Authors: Lee Shih-Chi , Fu Chao-Ming , Chang Fu-Hsiung
Published: October 2013

Fe3O4/γ-Fe2O3 core-shell magnetic nanoparticles have demonstrated superior heating efficiency by applying the alternating magnetic field. The magnetic induction heating properties of core-shell magnetic nanoparticles were analyzed by the rate-dependent hysteresis model, taken into account the magnetic anisotropies and actual size distribution of particles. The analyzed results have disclosed the significance of magnetic anisotropies and shell-thickness to the promotion of magnetic induction heating performance. Further experiments about the cancer cells with uptake of these core-shell magnetic nanoparticles conjugated biocompatible cationic liposomes have achieved in vitro intracellular magnetically induced hyperthermia under a weak alternating magnetic field.
Wirelessly powering miniature implants for optogenetic stimulation
Authors: Yeh Alexander J. , Ho John S. , Tanabe Yuji , Neofytou Evgenios , Beygui Ramin E. , Poon Ada S. Y.
Published: October 2013

Conventional methods for in vivo optogenetic stimulation require optical fibers or mounted prosthesis. We present an approach for wirelessly powering implantable stimulators using electromagnetic midfield. By exploiting the properties of the midfield, we demonstrate the ability to generate high intensity light pulses in a freely moving animal.
Micro/nanofabrication of poly(L-lactic acid) using focused ion beam direct etching
Authors: Oyama Tomoko Gowa , Hinata Toru , Nagasawa Naotsugu , Oshima Akihiro , Washio Masakazu , Tagawa Seiichi , Taguchi Mitsumasa
Published: October 2013

Micro/nanofabrication of biocompatible and biodegradable poly(L-lactic acid) (PLLA) using focused Ga ion beam direct etching was evaluated for future bio-device applications. The fabrication performance was determined with different ion fluences and fluxes (beam currents), and it was found that the etching speed and fabrication accuracy were affected by irradiation-induced heat. Focused ion beam (FIB)-irradiated surfaces were analyzed using micro-area X-ray photoelectron spectroscopy. Owing to reactions such as the physical sputtering of atoms and radiation-induced decomposition, PLLA was gradually carbonized with increasing C=C bonds. Controlled micro/nanostructures of PLLA were fabricated with C=C bond-rich surfaces expected to have good cell attachment properties.
Two-photon excitation microscopy using the second singlet state of fluorescent agents within the “tissue optical window”
Authors: Pu Yang , Shi Lingyan , Pratavieira Sebastião , Alfano R. R.
Published: October 2013

Two-photon (2P) excitation of the second singlet (S2) state of a group of fluorescent agents with near infrared emission was used to extend the optical excitation and imaging regime of 2P microscope into “tissue optical window” (650–1100 nm). As the first step to achieve deeper optical imaging, Chlorophyll a and Indocyanine green are investigated and demonstrated as imaging agents using 2P S2 excitation at 800 nm for microscope imaging at 685 nm. The salient feature is to drive both the 2P excitation and emission wavelengths of the imaging agents to fall into the “tissue optical window.”
Temperature-dependent Raman scattering and multiple phase coexistence in relaxor ferroelectric Pb(In1∕2Nb1∕2)O3-Pb(Mg1∕3Nb2∕3)O3-PbTiO3 single crystals
Authors: Zhu J. J. , Jiang K. , Xu G. S. , Hu Z. G. , Li Y. W. , Zhu Z. Q. , Chu J. H.
Published: October 2013

We report direct observation for the structural transformations of relaxor ferroelectric Pb(In1∕2Nb1∕2)O3-Pb(Mg1∕3Nb2∕3)O3-PbTiO3 single crystals with the aid of temperature-dependent polarized Raman scattering and X-ray diffraction. The cubic to tetragonal phase transition is observed at 460 K and tetragonal to rhombohedral structural transformation takes place at 390 K, which are consistent with the results determined by dielectric spectroscopy. In addition to two well-known phase transitions above room temperature, anomalous structure deformations involving octahedral rotations and tilting angle of polarization can be found around 200 K. A comparison of experimental results with the Devonshire expansion of the free energy by Vanderbilt et al. [Phys. Rev. B 63, 094108 (2001)] allows us to elucidate the peculiar characteristic as the variation of volume fractions among coexistence of three phases, including a first-order phase transition between the orthorhombic and rhombohedral phases and a second-order phase transition between the monoclinic and orthorhombic ones at low temperature.
Dependence of electromigration damage on Sn grain orientation in Sn–Ag–Cu solder joints
Authors: Chen Jian-Qiang , Guo Jing-Dong , Liu Kai-Lang , Shang Jian-Ku
Published: October 2013

The relationship between the “polarity effect” of electromigration on interfacial intermetallic growth and the Sn grain orientation was investigated in Sn-Ag-Cu solder joints. The growth of the interfacial intermetallic compound was found to depend strongly on the Sn grain orientation. When the c-axes of the Sn grains were closely aligned to the current flow direction, a severe polarity effect was observed in which the anode interface was covered with a thick layer of Cu-Sn intermetallic while the intermetallic layer at the cathode interface was almost depleted. If the c-axes of the Sn grains were rotated away from the current direction, the polarity effect became less pronounced. When the c-axis was perpendicular to the current direction, the polarity effect essentially disappeared. The difference in the intermetallic layer thickness between the anode and the cathode, Δd, followed a parabolic function of the cosine of the angle, α, between the c-axis and the current direction. A kinetic model based on the highly anisotropic diffusion behavior of Cu in Sn was presented to explain the relationship between the electromigration polarity effect and Sn-grain orientation. The model showed good agreement with the experimental data.
Modification of the formation of high-Mach number electrostatic shock-like structures by the ion acoustic instability
Authors: Dieckmann M. E. , Sarri G. , Doria D. , Pohl M. , Borghesi M.
Published: October 2013

The formation of unmagnetized electrostatic shock-like structures with a high Mach number is examined with one- and two-dimensional particle-in-cell (PIC) simulations. The structures are generated through the collision of two identical plasma clouds, which consist of equally hot electrons and ions with a mass ratio of 250. The Mach number of the collision speed with respect to the initial ion acoustic speed of the plasma is set to 4.6. This high Mach number delays the formation of such structures by tens of inverse ion plasma frequencies. A pair of stable shock-like structures is observed after this time in the 1D simulation, which gradually evolves into electrostatic shocks. The ion acoustic instability, which can develop in the 2D simulation but not in the 1D one, competes with the nonlinear process that gives rise to these structures. The oblique ion acoustic waves fragment their electric field. The transition layer, across which the bulk of the ions change their speed, widens and their speed change is reduced. Double layer-shock hybrid structures develop.
Self-recovery of mechanoluminescence in ZnS:Cu and ZnS:Mn phosphors by trapping of drifting charge carriers
Authors: Chandra V. K. , Chandra B. P. , Jha Piyush
Published: October 2013

The long time dream of mechanoluminescence (ML) research to fabricate mechanoluminescence white light sources and mechanoluminescence displays seems to be turning into reality after the recent demonstration of highly bright and durable mechanoluminescent flexible composite films with a brightness of ≈120 cd/m2 and durability over ≈100 000 repeated mechanical stresses by using a combination of copper-doped zinc sulfide (ZnS:Cu) particles and polydimethylsiloxane. The present paper explores that self-recovery of mechanoluminescence of deforming piezoelectric semiconductors takes place by trapping of drifting charge carriers in the presence of piezoelectric field. This may be useful in enhancing the intensity and durability of ML devices.
Inhomogeneity of donor doping in SrTiO3 substrates studied by fluorescence-lifetime imaging microscopy
Authors: Rodenbücher C. , Gensch T. , Speier W. , Breuer U. , Pilch M. , Hardtdegen H. , Mikulics M. , Zych E. , Waser R. , Szot K.
Published: October 2013

Fluorescence-lifetime imaging microscopy (FLIM) was applied to investigate the donor distribution in SrTiO3 single crystals. On the surfaces of Nb- and La-doped SrTiO3, structures with different fluorescence intensities and lifetimes were found that could be related to different concentrations of Ti3+. Furthermore, the inhomogeneous distribution of donors caused a non-uniform conductivity of the surface, which complicates the production of potential electronic devices by the deposition of oxide thin films on top of doped single crystals. Hence, we propose FLIM as a convenient technique (length scale: 1 μm) for characterizing the quality of doped oxide surfaces, which could help to identify appropriate substrate materials.
Enhanced Raman scattering from sub-wavelength silicon gratings
Authors: Khorasaninejad M. , Walia J. , Saini S. S.
Published: October 2013

A one-dimensional sub-wavelength silicon grating with enhanced Raman response is demonstrated. Furthermore, the polarization response of the Raman is investigated. This study shows that, contrary to intuitive expectation, the Raman intensity can be similar for both input polarizations: parallel and perpendicular to the ruling direction. This similarity is achieved due to inter-ridge coupling and polarization dependent characteristics of the grating. Through optimization of the ridge width and spacing, enhanced Raman intensity is realized in both polarizations, simultaneously. The results are further understood using a finite difference time domain model based on the light interaction with the grating for each polarization.
Microwave permittivity and permeability experiments in high-loss dielectrics: Caution with implicit Fabry-Pérot resonance for negative imaginary permeability
Authors: Hou Zhi-Ling , Zhang Min , Kong Ling-Bao , Fang Hui-Min , Li Zhong-Jun , Zhou Hai-Feng , Jin Hai-Bo , Cao Mao-Sheng
Published: October 2013

Various materials have been examined to obtain permittivity and permeability values required for detailed investigations on functional materials like microwave-absorbing and high-permittivity dielectrics. We call for caution when samples exhibit negative imaginary permeability, whether containing a resonance peak or not. In the retrieval procedure, the Fabry-Pérot resonance (FPR) can produce a negative imaginary permeability, which should be classified as an extrinsic rather than an intrinsic physical attribute. In particular, for high-loss materials, the implicit FPR would bring a plausible negative imaginary permeability. Here we have listed a dielectric dispersion of FPR behavior for BiFeO3 samples.
Communication: The ionization spectroscopy of mixed carboxylic acid dimers
Authors: Yang Zhijun , Gu Quanli , Trindle Carl O. , Knee J. L.
Published: October 2013

We report mass analyzed threshold ionization spectroscopy of supersonically cooled gas phase carboxylic complexes with 9-hydroxy-9-fluorenecarboxylic acid (9HFCA), an analog of glycolic acid. The vibrationally resolved cation spectrum for the 9HFCA complex with formic acid allows accurate determination of its ionization potential (IP), 64 374 ± 8 cm−1. This is 545 cm−1 smaller than the IP of 9HFCA monomer. The IPs of 9HFCA complexes with acetic acid and benzoic acid shift by −1133 cm−1 and −1438 cm−1, respectively. Density functional calculations confirm that Cs symmetry is maintained upon ionization of the 9HFCA monomer and its acid complexes, in contrast to the drastic geometric rearrangement attending ionization in complexes of 9-fluorene carboxylic acid. We suggest that the marginal geometry changes and small IP shifts are primarily due to the collective interactions among one intramolecular and two intermolecular hydrogen bonds in the dimer.
Single molecule magnets with protective ligand shells on gold and titanium dioxide surfaces: In situ electrospray deposition and x-ray absorption spectroscopy
Authors: Handrup Karsten , Richards Victoria J. , Weston Matthew , Champness Neil R. , O’Shea James N.
Published: October 2013

Two single molecule magnets based on the dodecamanganese (III, IV) cluster with either benzoate or terphenyl-4-carboxylate ligands, have been studied on the Au(111) and rutile TiO2(110) surfaces. We have used in situ electrospray deposition to produce a series of surface coverages from a fraction of a monolayer to multilayer films in both cases. X-ray absorption spectroscopy measured at the Mn L-edge (Mn 2p) has been used to study the effect of adsorption on the oxidation states of the manganese atoms in the core. In the case of the benzoate-functionalised complex reduction of the manganese metal centres is observed due to the interaction of the manganese core with the underlying surface. In the case of terphenyl-4-carboxylate, the presence of this much larger ligand prevents the magnetic core from interacting with either the gold or the titanium dioxide surfaces and the characteristic Mn3+ and Mn4+ oxidation states necessary for magnetic behaviour are preserved.
Multiplatform single-sample estimates of transcriptional activation
Authors: Piccolo Stephen R. , Withers Michelle R. , Francis Owen E. , Bild Andrea H. , Johnson W. Evan
Published: October 2013

Significance

We present our Universal exPression Code (UPC) approach for deriving “barcodes,” which estimate the active/inactive state of genes in a sample. UPCs normalize for technological variance and standardize data so they can be combined across microarray and RNA-sequencing experiments with high concordance. Because our method is applied to one sample at a time and thus bypasses the need to standardize samples together, it is distinctively suitable for situations in which samples arrive serially rather than in batches. We demonstrate our method’s utility in various biomedical research applications and compare against technology-specific approaches.
Comparing a simple theoretical model for protein folding with all-atom molecular dynamics simulations
Authors: Henry Eric R. , Best Robert B. , Eaton William A.
Published: October 2013

Significance

Although protein folding has been studied extensively by both theory and simulations, there have been very few attempts to test theoretical models by comparison with properties actually measured in equilibrium and kinetic experiments or with folding mechanisms observed in fully atomistic simulations. Here we compare the folding mechanisms of an Ising-like model that quantitatively explains a wide range of experimental data with fully atomistic simulations from the Shaw group. Not only are the simplifying assumptions of the theoretical model consistent with the simulations, but the folding mechanisms are remarkably similar. One of the key assumptions, that the 3D structure of the folded protein determines folding mechanisms, is strongly supported by the analysis in the accompanying paper by Best et al. (16).
Drug resistance confounding prion therapeutics
Authors: Berry David B. , Lu Duo , Geva Michal , Watts Joel C. , Bhardwaj Sumita , Oehler Abby , Renslo Adam R. , DeArmond Stephen J. , Prusiner Stanley B. , Giles Kurt
Published: October 2013

Significance

As people live longer, the prevalence and economic impact of neurodegenerative diseases rise. No cures or effective treatments exist for any of these fatal disorders, so identifying potential therapeutics that extend survival in animal models is vital. Many neurodegenerative illnesses have been shown to be caused by the accumulation of self-propagating misfolded proteins—the hallmark of prion diseases. We report the efficacy of 2-aminothiazoles, which were identified in cell-based screens as antiprion compounds, in extending the lives of prion-infected animals. Efficacy was limited by the development of drug-resistant prions, which is likely to have important implications for creating therapeutics in many different neurodegenerative diseases.
Risk Factors for Homelessness Among Recently Released Offenders
Authors: Parhar Karen , Wormith Stephen
Published: October 2013

The current study examined characteristics related to homelessness among released offenders to improve housing services for this group. Forty-one incarcerated Canadian prisoners were interviewed approximately 3 months prior to release about their former and anticipated accommodations. Homelessness prior to incarceration was positively related to violent institutional behavior, violence risk level, and criminogenic needs but not recidivism. Stable housing prior to incarceration was positively related to greater community support. Recommendations include creating more community and institutional housing programs for offenders more likely to experience housing difficulties in the community.
Violent Death Among Recently Released Prison Inmates: Stories Behind the Numbers
Authors: Scheyett Anna , Morgan Candice , Lize Steven E. , Proescholdbell Scott , Norwood Tammy , Edwards David
Published: October 2013

Research on rates of violent deaths in prison releasees exists, however little work has gone into examining their associated contexts and circumstances. Using North Carolina Department of Corrections and North Carolina Violent Death Reporting System data, the authors sought to understand the contexts surrounding the deaths of recently released inmates. Findings revealed that homicides (64% of deaths) were associated with violence as a result of argument and with criminal activity. Suicides (30%) were in response to risk of reincarceration, relationship problems, depression, and situational difficulties. Six percent of deaths were the result of legal intervention. Implications for social work practice and research are examined.
Letter from the Editors (5)
Authors: Vaughan-Eden Viola , Butters Rob
Published: October 2013

no abstract
Kin selection, genomics and caste-antagonistic pleiotropy
Authors: Hall David W. , Yi Soojin V. , Goodisman Michael A. D.
Published: October 2013

Kin selection is a fundamentally important process that affects the evolution of social behaviours. The genomics revolution now provides the opportunity to test kin selection theory using genomic data. In this commentary, we discuss previous studies that explored the link between kin selection and patterns of variation within the genome. We then present a new theory aimed at understanding the evolution of genes involved in the development of social insects. Specifically, we investigate caste-antagonistic pleiotropy, which occurs when the phenotypes of distinct castes are optimized by different genotypes at a single locus. We find that caste-antagonistic pleiotropy leads to narrow regions where polymorphism can be maintained. Furthermore, multiple mating by queens reduces the region in which worker-favoured alleles fix, which suggests that multiple mating impedes worker caste evolution. We conclude by discussing ways to test these and other facets of kin selection using newly emerging genomic data.
Towards greater realism in inclusive fitness models: the case of worker reproduction in insect societies
Authors: Wenseleers Tom , Helanterä Heikki , Alves Denise A. , Dueñez-Guzmán Edgar , Pamilo Pekka
Published: October 2013

The conflicts over sex allocation and male production in insect societies have long served as an important test bed for Hamilton's theory of inclusive fitness, but have for the most part been considered separately. Here, we develop new coevolutionary models to examine the interaction between these two conflicts and demonstrate that sex ratio and colony productivity costs of worker reproduction can lead to vastly different outcomes even in species that show no variation in their relatedness structure. Empirical data on worker-produced males in eight species ofMeliponabees support the predictions from a model that takes into account the demographic details of colony growth and reproduction. Overall, these models contribute significantly to explaining behavioural variation that previous theories could not account for.
Nice to kin and nasty to non-kin: revisiting Hamilton's early insights on eusociality
Authors: Boomsma Jacobus J. , d'Ettorre Patrizia
Published: October 2013

When helping behaviour is costly, Hamiltonian logic implies that animals need to direct helpful acts towards kin, so that indirect fitness benefits justify the costs. We revisit inferences about nepotism and aggression in Hamilton's 1964 paper to argue that he overestimated the general significance of nepotism, but that other issues that he raised continue to suggest novel research agendas today. We now know that nepotism in eusocial insects is rare, because variation in genetic recognition cues is insufficient. A lower proportion of individuals breeding and larger clutch sizes selecting for a more uniform colony odour may explain this. Irreversible worker sterility can induce both the fiercest possible aggression and the highest likelihood of helping random distant kin, but these Hamiltonian contentions still await large-scale testing in social animals.
Embryonic growth and antioxidant provision in avian eggs
Authors: Deeming D. Charles , Pike Thomas W.
Published: October 2013

Avian embryos undergo extremely rapid development over a relatively short period of time, and so are likely to suffer high levels of oxidative damage unless this is mitigated by sufficient maternal allocation of appropriate antioxidants. At a species level, it is therefore predicted that antioxidants should be allocated to eggs according to the rate of embryonic growth, such that eggs containing embryos that grow faster are furnished with higher antioxidant levels, independent of egg size. We tested this prediction for three potentially important classes of dietary-derived yolk antioxidants: carotenoids, vitamin E and vitamin A. Across species, we found positive relationships between embryonic growth rate and total yolk levels of each of the three antioxidant classes. Moreover, there were consistent differences in antioxidant provision between pairs of species that share a common initial egg mass yet have differing rates of embryonic growth, such that the eggs of the faster-developing species have higher levels of carotenoids and vitamin E. These results may explain the marked interspecific variation in antioxidant provision and provide evidence for the role that these antioxidants play during embryonic development.