bluuebunny/crossref_metadata_2025 huggingface dataset:
Current views on the source of the autophagosome membrane
Authors: Tooze Sharon A.
Published: October 2013

Autophagy was discovered in the late 1950s when scientists using the first electron microscopes saw membrane-bound structures in cells that contained cytoplasmic organelles, including mitochondria. Pursuant to further morphological characterization it was recognized that these vesicles, now called autophagosomes, are found in all eukaryotic cells and undergo changes in morphology from a double-membraned vesicle with recognizable content, i.e. sequestered organelles, to a uniformly dense core autolysosome. Genetic screens in the yeast Saccharomyces cerevisiae in the 1990s provided a molecule framework for the next era of discovery during which the interest in, and research into, autophagy has rapidly expanded into many areas of human biology and disease. A relatively small cohort of approximately 36 proteins, called Atgs (autophagy-related proteins), orchestrate the formation of the autophagosome, and these are now being studied and functionally characterized. Although the function of these proteins is being elucidated, the underlying molecular mechanisms of how autophagosomes form are still not completely understood. Recent advances have, however, provided a significant advance in both our understanding of the molecular control of the Atg proteins and the source of the membranes. A consensus view is emerging from these advances that the endoplasmic reticulum is the nucleation site for the autophagosome, and that contributions from other compartments (Golgi, endosomes and plasma membrane) are required. In the present chapter, I review the data from the pre-molecular decades, and discuss the most recent publications to give an overview of the current view of where, and how, autophagosomes form in mammalian cells.
Two ubiquitin-like conjugation systems that mediate membrane formation during autophagy
Authors: Nakatogawa Hitoshi
Published: October 2013

In autophagy, the autophagosome, a transient organelle specialized for the sequestration and lysosomal or vacuolar transport of cellular constituents, is formed via unique membrane dynamics. This process requires concerted actions of a distinctive set of proteins named Atg (autophagy-related). Atg proteins include two ubiquitin-like proteins, Atg12 and Atg8 [LC3 (light-chain 3) and GABARAP (γ-aminobutyric acid receptor-associated protein) in mammals]. Sequential reactions by the E1 enzyme Atg7 and the E2 enzyme Atg10 conjugate Atg12 to the lysine residue in Atg5, and the resulting Atg12–Atg5 conjugate forms a complex with Atg16. On the other hand, Atg8 is first processed at the C-terminus by Atg4, which is related to ubiquitin-processing/deconjugating enzymes. Atg8 is then activated by Atg7 (shared with Atg12) and, via the E2 enzyme Atg3, finally conjugated to the amino group of the lipid PE (phosphatidylethanolamine). The Atg12–Atg5–Atg16 complex acts as an E3 enzyme for the conjugation reaction of Atg8; it enhances the E2 activity of Atg3 and specifies the site of Atg8–PE production to be autophagy-related membranes. Atg8–PE is suggested to be involved in autophagosome formation at multiple steps, including membrane expansion and closure. Moreover, Atg4 cleaves Atg8–PE to liberate Atg8 from membranes for reuse, and this reaction can also regulate autophagosome formation. Thus these two ubiquitin-like systems are intimately involved in driving the biogenesis of the autophagosomal membrane.
Model-free simulation approach to molecular diffusion tensors
Authors: Chevrot Guillaume , Hinsen Konrad , Kneller Gerald R.
Published: October 2013

In the present work, we propose a simple model-free approach for the computation of molecular diffusion tensors from molecular dynamics trajectories. The method uses a rigid body trajectory of the molecule under consideration, which is constructed a posteriori by an accumulation of quaternion-based superposition fits of consecutive conformations. From the rigid body trajectory, we compute the translational and angular velocities of the molecule and by integration of the latter also the corresponding angular trajectory. All quantities can be referred to the laboratory frame and a molecule-fixed frame. The 6 × 6 diffusion tensor is computed from the asymptotic slope of the tensorial mean square displacement and, for comparison, also from the Kubo integral of the velocity correlation tensor. The method is illustrated for two simple model systems – a water molecule and a lysozyme molecule in bulk water. We give estimations of the statistical accuracy of the calculations.
Microfabricated suspended island platform for the measurement of in-plane thermal conductivity of thin films and nanostructured materials with consideration of contact resistance
Authors: Alaie Seyedhamidreza , Goettler Drew F. , Abbas Khawar , Su Mehmet F. , Reinke Charles M. , El-Kady Ihab , Leseman Zayd C.
Published: October 2013

A technique based on suspended islands is described to measure the in-plane thermal conductivity of thin films and nano-structured materials, and is also employed for measurements of several samples with a single measurement platform. Using systematic steps for measurements, the characterization of the thermal resistances of a sample and its contacts are studied. The calibration of the contacts in this method is independent of the geometry, size, materials, and uniformity of contacts. To verify the technique, two different Si samples with different thicknesses and two samples of the same SiNx wafer are characterized on a single device. One of the Si samples is also characterized by another technique, which verifies the current results. Characterization of the two SiNx samples taken from the same wafer showed less than 1% difference in the measured thermal conductivities, indicating the precision of the method. Additionally, one of the SiNx samples is characterized and then demounted, remounted, and characterized for a second time. The comparison showed the change in the thermal resistance of the contact in multiple measurements could be as small as 0.2 K/μW, if a similar sample is used.
Infinite-dimensional Lie algebras, classical r-matrices, and Lax operators: Two approaches
Authors: Skrypnyk T.
Published: October 2013

For each finite-dimensional simple Lie algebra \documentclass[12pt]{minimal}\begin{document}$\mathfrak {g}$\end{document}g, starting from a general \documentclass[12pt]{minimal}\begin{document}$\mathfrak {g}\otimes \mathfrak {g}$\end{document}g⊗g-valued solutions r(u, v) of the generalized classical Yang-Baxter equation, we construct infinite-dimensional Lie algebras \documentclass[12pt]{minimal}\begin{document}$\widetilde{\mathfrak {g}}^{-}_r$\end{document}g̃r− of \documentclass[12pt]{minimal}\begin{document}$\mathfrak {g}$\end{document}g-valued meromorphic functions. We outline two ways of embedding of the Lie algebra \documentclass[12pt]{minimal}\begin{document}$\widetilde{\mathfrak {g}}^{-}_r$\end{document}g̃r− into a larger Lie algebra with Kostant-Adler-Symmes decomposition. The first of them is an embedding of \documentclass[12pt]{minimal}\begin{document}$\widetilde{\mathfrak {g}}^{-}_r$\end{document}g̃r− into Lie algebra \documentclass[12pt]{minimal}\begin{document}$\widetilde{\mathfrak {g}}(u^{-1},u))$\end{document}g̃(u−1,u)) of formal Laurent power series. The second is an embedding of \documentclass[12pt]{minimal}\begin{document}$\widetilde{\mathfrak {g}}^{-}_r$\end{document}g̃r− as a quasigraded Lie subalgebra into a quasigraded Lie algebra \documentclass[12pt]{minimal}\begin{document}$\widetilde{\mathfrak {g}}_r$\end{document}g̃r: \documentclass[12pt]{minimal}\begin{document}$\widetilde{\mathfrak {g}}_r=\widetilde{\mathfrak {g}}^{-}_r+\widetilde{\mathfrak {g}}^{+}_r$\end{document}g̃r=g̃r−+g̃r+, such that the Kostant-Adler-Symmes decomposition is consistent with a chosen quasigrading. We construct dual spaces \documentclass[12pt]{minimal}\begin{document}$\widetilde{\mathfrak {g}}^*_r$\end{document}g̃r*, \documentclass[12pt]{minimal}\begin{document}$(\widetilde{\mathfrak {g}}^{\pm }_r)^*$\end{document}(g̃r±)* and explicit form of the Lax operators L(u), L±(u) as elements of these spaces. We develop a theory of integrable finite-dimensional hamiltonian systems and soliton hierarchies based on Lie algebras \documentclass[12pt]{minimal}\begin{document}$\widetilde{\mathfrak {g}}_r$\end{document}g̃r, \documentclass[12pt]{minimal}\begin{document}$\widetilde{\mathfrak {g}}^{\pm }_r$\end{document}g̃r±. We consider examples of such systems and soliton equations and obtain the most general form of integrable tops, Kirchhoff-type integrable systems, and integrable Landau-Lifshitz-type equations corresponding to the Lie algebra \documentclass[12pt]{minimal}\begin{document}$\mathfrak {g}$\end{document}g.
Electro-optic polymer/silicon hybrid slow light modulator based on one-dimensional photonic crystal waveguides
Authors: Inoue Shin-ichiro , Otomo Akira
Published: October 2013

An electro-optic (EO) modulator composed of EO polymer/silicon hybrid one-dimensional photonic crystal nanobeam waveguides is proposed and experimentally demonstrated. The optical field of the photonic crystal nanobeam is designed to concentrate at the nanoscale low refractive index EO polymer region. We have demonstrated enhanced EO modulation efficiencies as a result of the slower group velocity in the 100-μm-long photonic crystal nanobeam phase-shifters. The results agree well with the behavior predicted from band dispersion characteristics, indicating that EO polymer/silicon hybrid photonic crystal nanobeam waveguides are an effective platform for realizing extremely small and ultrafast EO modulators with low operational power.
Investigating the source of deep-level photoluminescence in ZnO nanorods using optically detected x-ray absorption spectroscopy
Authors: Hatch Sabina M. , Sapelkin Andrei , Cibin Giannantonio , Taylor Richard , Dent Andrew , Briscoe Joe , Dunn Steve
Published: October 2013

A zinc oxide (ZnO) nanorod array exhibiting an intense deep-level emission (DLE) was probed at the Zn K edge (9659 eV) using extended x-ray absorption fine structure (EXAFS) analysis. X-ray excited optical luminescence was used to obtain site-specific information around the absorbing Zn atom using optically detected EXAFS (ODXAS). The visible-emission corresponds to defects in ZnO crystal lattice introduced during growth. A comparative study between red (660 nm) and green (500 nm) DLE was conducted by collecting specific wavelength emissions of the optically detected x-ray absorption spectra. It was shown that red emission primarily originates from the nanorod surface, and green emission was linked to disorder occurring on Zn sites. We show that ODXAS can distinguish between two emission regions and provides a platform to link defect emission with specific crystal structures.
Reconfigurable microfluidic pump enabled by opto-electrical-thermal transduction
Authors: Takeuchi Masaru , Hagiwara Masaya , Haulot Gauvain , Ho Chih-Ming
Published: October 2013

Flexible integration of a microfluidic system comprising pumps, valves, and microchannels was realized by an optoelectronic reconfigurable microchannels (OERM) technique. Projecting a low light fluidic device pattern—e.g., pumps, valves, and channels—onto an OERM platform generates Joule heating and melts the substrate in the bright area on the platform; thus, the fluidic system can be reconfigured by changing the projected light pattern. Hexadecane was used as the substrate of the microfluidic system. The volume change of hexadecane during the liquid–solid phase transition was utilized to generate pumping pressure. The system can pump nanoliters of water within several seconds.
Photoacoustic correlation signal-to-noise ratio enhancement by coherent averaging and optical waveform optimization
Authors: Telenkov Sergey A. , Alwi Rudolf , Mandelis Andreas
Published: October 2013

Photoacoustic (PA) imaging of biological tissues using laser diodes instead of conventional Q-switched pulsed systems provides an attractive alternative for biomedical applications. However, the relatively low energy of laser diodes operating in the pulsed regime, results in generation of very weak acoustic waves, and low signal-to-noise ratio (SNR) of the detected signals. This problem can be addressed if optical excitation is modulated using custom waveforms and correlation processing is employed to increase SNR through signal compression. This work investigates the effect of the parameters of the modulation waveform on the resulting correlation signal and offers a practical means for optimizing PA signal detection. The advantage of coherent signal averaging is demonstrated using theoretical analysis and a numerical model of PA generation. It was shown that an additional 5–10 dB of SNR can be gained through waveform engineering by adjusting the parameters and profile of optical modulation waveforms.
Perturbation facilitated two-color four-wave-mixing spectroscopy of C3
Authors: Sych Y. , Bornhauser P. , Knopp G. , Liu Y. , Gerber T. , Marquardt R. , Radi P. P.
Published: October 2013

Perturbation-facilitated two-color resonant four-wave-mixing spectroscopy is realized to access the (dark) triplet manifold of the C3 molecule from the singlet \documentclass[12pt]{minimal}\begin{document}$\tilde{X} ^1\Sigma _{\rm g}^+$\end{document}X̃1Σg+ ground state. The inherent nonlinear signal dependence and coherence of the technique result in a favorable detection of the excited triplet states of interest. The observation of a newly found 3Δu electronic state is achieved by a two-step excitation via “gate-way” levels (i.e., singlet-triplet mixed levels). Additionally, by fixing the probe laser on a transition exhibiting mainly triplet-triplet character and scanning the pump laser, we demonstrate an effective spin-filtering in a four-wave mixing measurement where only transitions to the perturber \documentclass[12pt]{minimal}\begin{document}$^3\Sigma _{\rm u}^-$\end{document}Σu−3 state appear exclusively in an otherwise congested spectral range of the Comet band. Ab initio calculations of excited triplet states complement our analysis with the electronic assignment of the observed resonances.
Non-Born–Oppenheimer molecular dynamics of the spin-forbidden reaction O(3P) + CO(X 1Σ+) → CO2($\tilde X{}^1\Sigma _g^ +$X̃Σg+1)
Authors: Jasper Ahren W. , Dawes Richard
Published: October 2013

The lowest-energy singlet (1 1A′) and two lowest-energy triplet (1 3A′ and 1 3A″) electronic states of CO2 are characterized using dynamically weighted multireference configuration interaction (dw-MRCI+Q) electronic structure theory calculations extrapolated to the complete basis set (CBS) limit. Global analytic representations of the dw-MRCI+Q/CBS singlet and triplet surfaces and of their CASSCF/aug-cc-pVQZ spin–orbit coupling surfaces are obtained via the interpolated moving least squares (IMLS) semiautomated surface fitting method. The spin-forbidden kinetics of the title reaction is calculated using the coupled IMLS surfaces and coherent switches with decay of mixing non-Born–Oppenheimer molecular dynamics. The calculated spin-forbidden association rate coefficient (corresponding to the high pressure limit of the rate coefficient) is 7–35 times larger at 1000–5000 K than the rate coefficient used in many detailed chemical models of combustion. A dynamical analysis of the multistate trajectories is presented. The trajectory calculations reveal direct (nonstatistical) and indirect (statistical) spin-forbidden reaction mechanisms and may be used to test the suitability of transition-state-theory-like statistical methods for spin-forbidden kinetics. Specifically, we consider the appropriateness of the “double passage” approximation, of assuming statistical distributions of seam crossings, and of applications of the unified statistical model for spin-forbidden reactions.
Analysis of the breakdown spot spatial distribution in Pt/HfO2/Pt capacitors using nearest neighbor statistics
Authors: Saura X. , Suñé J. , Monaghan S. , Hurley P. K. , Miranda E.
Published: October 2013

The breakdown spot spatial distribution in Pt/HfO2/Pt capacitors is investigated using nearest neighbor statistics in combination with more conventional estimation methods such as the point-event and event-event distance distributions. The spots appear as a random point pattern over the top metal electrode and arise as a consequence of significant localized thermal effects caused by the application of high-voltage ramped stress to the devices. The reported study mainly involves the statistical characterization of the distances between each failure site and the nearest, second nearest, … kth nearest event and the comparison with the corresponding theoretical distributions for a complete spatial randomness (CSR) process. A method for detecting and correcting deviations from CSR based on a precise estimation of the average point intensity and the effective damaged device area is proposed.
Dynamics of interacting solitons in dual core Bragg gratings with dispersive reflectivity
Authors: Baratali B. H. , Atai Javid
Published: October 2013

Interactions of in-phase and out-of-phase quiescent gap solitons in a system of two linearly-coupled Bragg gratings with dispersive reflectivity are studied. By means of systematic numerical simulations, we show that the interaction of the in-phase solitons may lead to merger, repulsion, destruction, or separation of solitons which may be symmetric or asymmetric. A key feature of the interactions is that even in the absence of dispersive reflectivity the interaction of solitons may result in the formation of two moving solitons and one quiescent one. To the best of our knowledge, such outcomes have not been observed in the standard models of gap solitons (i.e., single core Bragg gratings without dispersive reflectivity). Another interesting finding is that in the region where solitons do not have sidelobes, the outcomes of the interactions are weakly dependent on the initial separation of the solitons. On the other hand, the presence of sidelobes, which occur for larger values of dispersive reflectivity, results in more complex interactions. The π-out-of-phase solitons without sidelobes always repel each other. On the other hand, the interaction of solitons with sidelobes is affected by the initial separation. In this case, the interactions may either result in the repulsion of solitons or the formation of a temporary bound state that subsequently splits into two separating solitons.
Proposal for a local heating driven spin current generator
Authors: Hwang Sun-Yong , Soo Lim Jong , López Rosa , Lee Minchul , Sánchez David
Published: October 2013

We propose a two-terminal spin-orbit interferometer with a hot molecule inserted in one of its arms to generate pure spin currents. Local heating is achieved by coupling the vibrational modes of the molecule to a third (phononic) reservoir. We show that this spin caloritronic effect is due to the combined influence of spin-dependent wave interference and inelastic scattering. Remarkably, the device converts heat flow into spin-polarized current even without applying any voltage or temperature difference to the electronic terminals.
Highly efficient, spatially coherent distributed feedback lasers from dense colloidal quantum dot films
Authors: Dang C. , Lee J. , Roh K. , Kim H. , Ahn S. , Jeon H. , Breen C. , Steckel J. S. , Coe-Sullivan S. , Nurmikko A.
Published: October 2013

Colloidal quantum dots (CQD) are now making their entry to full-color displays, endowed by their brightness and single-material base. By contrast, many obstacles have been encountered in their use towards lasers. We demonstrate here optically pumped distributed feedback (DFB) lasers, based on close-packed, solid films self-assembled from type-I CQDs. Notably, the single mode CQD-DFB lasers could reach such a low threshold as to be pumpable with a compact pulsed source in a quasi-continuous wave regime. Our results show the spatially and temporally coherent laser beam outputs with power of 400 μW and a quantum efficiency of 32%.
A pneumatic valve controlled microdevice for bioanalysis
Authors: Zhou Xiaohu , Zhou Xuechang , Zheng Bo
Published: October 2013

This paper describes a pneumatic valve controlled microdevice for performing mixing and reaction. This microdevice combined the degassed polydimethylsiloxane (PDMS) pumping method with a syringe-actuated valve system to control the dispensing and mixing of nanoliter solutions. The syringe was used to manually generate vacuum and to open the valves. Upon the opening of the valve, the microchamber was filled with the solution, which was driven by the external atmosphere through the degassed PDMS microchannel. With this microdevice, the enzymatic kinetics of alkaline phosphatase converting the fluorescein diphosphate was studied, and the Michaelis-Menten kinetics was analyzed. The microdevice has the advantages of simplicity and low cost in fabrication and operation.
Light-induced conical intersections in polyatomic molecules: General theory, strategies of exploitation, and application
Authors: Demekhin Philipp V. , Cederbaum Lorenz S.
Published: October 2013

When the carrier frequency of a laser pulse fits to the energy difference between two electronic states of a molecule, the potential energy surfaces of these states dressed by the field become energetically close and the states can couple strongly to each other. Recently, it has been predicted that for diatomic molecules these surfaces may exhibit a conical intersection induced by the laser light in the space of the nuclear internal and external coordinates. Here, we report a general theory of the light-induced conical intersections emerging in polyatomic molecules where additional internal degrees of freedom are involved in the dynamics. Freely rotating and also fixed-in-space arbitrary polyatomic molecules exposed to differently polarized optical laser pulses of resonant carrier frequency are considered. Detailed analysis of the theory shows how the light-induced conical intersections can be controlled by molecular orientation and by the carrier frequency, polarization, strength, and duration of the laser pulse. This opens the possibility to also control the ensuing non-adiabatic dynamics. Different strategies of exploitation of the light-induced conical intersections are proposed. The present theory is exemplified by utilizing the light-induced conical intersections to control photodissociation of the second electronically excited state S2 of the fixed-in-space cis-methyl nitrite CH3ONO.
Effect of simultaneous excitation of singlet and triplet excitons on the operation of organic solar cells
Authors: Narayan Monishka Rita , Singh Jai
Published: October 2013

Primary steps of exciton formation in organic solar cells are presented here. The rates of absorption of photons to excite singlet and triplet excitons are derived using exciton-photon and exciton-spin-orbit-photon-interaction, respectively, as perturbation operators. In both singlet and triplet absorptions, the rates are found to depend on the absorption energy, excitonic Bohr radius, and the dielectric constant of the donor organic material. Incorporation of heavy metal atoms enhances the exciton-spin-orbit-photon interaction and hence the rate of excitation of triplet excitons because it depends on the square of the heaviest atomic number. The new exciton-spin-orbit-photon interaction operator flips the spin to a singlet form leading to faster dissociation into charge carriers and resulting in higher photon to electron-hole pair conversion efficiency in organic solar cells.
Thin film transistors fabricated by evaporating pentacene under electric field
Authors: Mandal Tapendu , Garg Ashish , Deepak
Published: October 2013

Organizing the pentacene molecules with respect to the substrate is an essential prerequisite for achieving high field effect mobility in organic thin film transistors. Here, we report electrical characteristics of bottom gate, top contact Sin++/SiO2/pentacene/gold thin film transistors using electric field assisted thermal evaporation of pentacene. We find that the field assisted devices exhibit a five-fold enhancement in the field effect mobility, along with improvement in the saturation current as compared with a standard device. Simulation of electric field distribution in the substrate-electrode arrangement due to the application of external voltage during pentacene deposition shows an existence of a non-uniform electric field in the bottom gate top contact configuration and hence another configuration that avoids metal before pentacene deposition is proposed. The observed improvement in the transistor characteristics of field assisted device is explained by ab-initio calculation of anisotropy in the polarizability of isolated pentacene molecule, followed by an estimate of molecules that would align due to the field. Furthermore, the preferential molecular alignment in field deposited pentacene films is confirmed using X-ray diffraction and atomic force microscopy.
Degradation mechanisms in GaN light-emitting diodes undergoing reverse-bias operations in water vapor
Authors: Chen Hsiang , Yun Huang Bo , Cheng Chu Yu
Published: October 2013

Reverse-bias testing light-emitting diodes (LEDs) enables devices to be rapidly screened for weaknesses and pinpoints the origins of failure. In this study, GaN LED reliability was examined by reverse-bias, stressing the device in water vapor. The LED failure origins were investigated using electrical characterizations, optical measurements, and material analyses, namely, focused ion beam deposition, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The results indicated that diffused Au atoms from the surface of the LED can increase leakage current, generate high electric fields, and degrade device performance levels. Moreover, hot-carrier-induced emissions for LEDs undergoing reverse-bias operations confirmed that gold distribution caused by the water vapor generated high electric fields.
Magnetic domain structure and transverse induced magnetic anisotropy in CoFeCuNbSiB alloys
Authors: Kolano-Burian A.
Published: October 2013

The magnetic domain structure is a specific property of ferromagnetic materials. The main magnetic properties and core losses depend on its configuration and dimensions. The aim of this work was to determine a relationship between the domain structure, observed by means of magneto-optic Kerr effect on the surface of the Fe14.7Co58.8Cu1Nb3Si13.5B9 (FeCo58) and Fe13.8Co65Cu0.6Nb2.6Si9B9 (FeCo65) toroidal cores, and the induced transverse magnetic anisotropy Ku and magnetic characteristics B = f(H). The transverse magnetic anisotropy has been induced in the FeCo58 and FeCo65 amorphous cores by annealing at the temperature of 420–500 °C under an external magnetic field of 500 kA/m. It was found that the FeCo58 cores, characterized by three times smaller Ku compared to the FeCo65 cores, had different domain structures than those of the FeCo65 cores. The domain structure of the FeCo65 cores is characterized by almost parallel domains of an average width d varying from 28 to 50 μm after heat treatment at the temperatures ranging from 420 to 500 °C.
Single shot ptychographical iterative engine based on multi-beam illumination
Authors: Pan Xingchen , Liu Cheng , Zhu Jianqiang
Published: October 2013

An optical alignment and a corresponding reconstruction algorithm are proposed to realize a single shot Ptychographical Iterative Engine (PIE). Multiple light beams generated by a cross grating are used to illuminate the specimen, and the resulting diffraction patterns formed on the detector plane by each beam are recorded simultaneously. The modulus and phase images are properly reconstructed with standard PIE algorithm. The proposed single shot method omits the needs for a mechanical x-y scanning of standard PIE algorithm and hence dramatically reduces the data acquisition time.
Micro-pore development phenomenon in hydrogen pre-charged aluminum alloy studied using synchrotron X-ray micro-tomography
Authors: Gupta C. , Toda H. , Fujioka T. , Kobayashi M. , Uesugi K. , Takeuchi A. , Suzuki Y.
Published: October 2013

The paper provides an insight into the development of the micro-pore damage phenomenon during the hydrogen ingress and egress in a high strength aluminum alloy. High resolution micro tomography scans on samples subjected to combinations of cathodic hydrogen charging and de-sorption heat treatment were carried out. The quantitative analysis, spatial mapping, and probabilistic evaluation of the 3D datasets revealed that the development of micro-pore damage during hydrogen ingress–egress had a non-trivial dependence on the particle size distribution. This provides a rationale to mitigate the deleterious effects of hydrogen in aluminum alloys by controlling particle size characteristics.
Dynamics of percolative breakdown mechanism in tantalum oxide resistive switching
Authors: Lohn Andrew J. , Mickel Patrick R. , Marinella Matthew J.
Published: October 2013

Switching dynamics are studied for tantalum oxide resistive random access memory subjected to long-duration constant current pulses for both SET and RESET transitions. The processes draw parallels to the widely studied percolation model for dielectric breakdown. The RESET transition is shown to consist of changes to critical local conduction sites and their effect on performance parameters such as switching speed and energy are discussed. Additionally, the SET transition shows an unexpected minimum stable resistance state. When driven below that state the device is found to increase resistance, returning to the stable state.
Asymmetric electron transport and highest occupied molecular orbital assisted tunneling through Zn-porphyrin molecular junctions
Authors: Saha Swatilekha , Owens Jonathan R. , Meunier Vincent , Lewis K. M.
Published: October 2013

We report electron transport measurements from gold-zinc-porphyrin-gold molecular junctions formed in an electromigrated nanogap. Asymmetric current-voltage (I-V) behaviors about the zero bias voltage were observed at room temperature and 4.2 K. These observations are in contrast to measurements from a nanogap without any molecules, which are dominated by tunneling and display symmetric I-V characteristics. In addition, increasing the gate voltage suppressed the current through the junction at room temperature, indicating electron tunneling proceeded through the highest occupied molecular orbital. Density of states calculations were performed to explain these findings and understand the microscopic origins of the observations.
Thermal conductivity of hybrid graphene/silicon heterostructures
Authors: Jing Yuhang , Hu Ming , Guo Licheng
Published: October 2013

The success of fabricating single layer graphene and silicon nanofilm (could be as thin as single layer so far) has triggered enormous interest in exploring their unique physics and novel applications. An intuitive idea is to investigate what happens if we construct a heterostructure composed of these two sheets. In this paper, we perform nonequilibrium molecular dynamics simulations to systematically investigate the in-plane thermal transport in graphene/silicon/graphene (Gr/Si/Gr) heterostructures. The effects of Si film thickness, interfacial interaction strength, and length on the thermal conductivity of the Gr/Si/Gr heterostructures are explicitly considered. Our simulations identify a unified scaling law for thickness dependence of thermal conductivity of the Gr/Si/Gr heterostructures, despite different interfacial interaction forms are used (weak van der Waals interaction and strong covalent bonding). By quantifying relative contribution from phonon polarizations and defining heat flux onto single atom, we reveal and fully understand the different mechanisms governing the phonon transport in the Gr/Si/Gr heterostructures for the two different interfacial interaction forms. We also found that the thermal conductivity of Gr/Si/Gr heterostructure is nonmonotonically dependent on the van der Waals interaction strength between graphene and Si, but monotonically dependent on the graphene-silicon covalent bonding strength. Moreover, length dependence study shows that phonon transport in Gr/Si/Gr heterostructure becomes diffusive at much shorter length as compared with single layer graphene and bilayer graphene. Comparing to single and double graphene layers, the thermal conductivity of the Gr/Si/Gr heterostructure can be reduced with more than one order of magnitude for very long structures. These results suggest that Gr/Si/Gr heterostructures are promising for nanoscale devices due to their unique thermal transport properties.
Electromechanical properties of relaxor ferroelectric foams
Authors: Singh J. , Venkatesh T. A. , Challagulla K. S.
Published: October 2013

Three-dimensional finite element models are developed to characterize the complete electromechanical properties of relaxor ferroelectric-based foams. It is demonstrated that microstructural features such as porosity volume fraction and connectivity play significant roles in determining the elastic, dielectric, and piezoelectric properties of relaxor foams. Furthermore, piezoelectric figures of merit such as the coupling constant (Kt), the hydrostatic strain coefficient (dh), and the hydrostatic figure of merit (dhgh) of (PMN-PT based) relaxor foams are significantly higher (by 40%, 900%, and 3000%, respectively, for 3-3 type foams with 50% porosity) than those observed in equivalent (PZT-7A based) traditional piezoelectric foams.
Intense terahertz emission from relativistic circularly polarized laser pulses interaction with overdense plasmas
Authors: Chen Zi-Yu , Li Xiao-Ya , Yu Wei
Published: October 2013

During the interaction of a relativistic circularly polarized laser pulse with an overdense plasma target, the longitudinal motion of bunches of electrons under the action of light pressure and electrostatic restore force can emit intense terahertz (THz) pulses. This mechanism allows high pump laser intensity and large electron number participating in the emission. Two-dimensional particle-in-cell simulations are carried out to investigate the THz emission. The results suggest that such a source can produce remarkably intense THz pulses with energy of several mJ/sr and power of tens of gigawatts, which could find applications in nonlinear studies and relativistic laser-plasma interaction diagnostics.
Polarization-resolved second-harmonic generation imaging for liver fibrosis assessment without labeling
Authors: Lin Jian , Pan Shiying , Zheng Wei , Huang Zhiwei
Published: October 2013

We apply the polarization-resolved second-harmonic generation (PR-SHG) microscopy to investigate the changes of collagen typings (type I vs type III) and collagen fibril orientations of liver tissue in bile-duct-ligation (BDL) rat models. The PR-SHG results show that the second-order susceptibility tensor ratios (χ31/χ15 and χ33/χ15) of collagen fibers increase with liver fibrotic progression after BDL surgery, reflecting an increase of the type III collagen component with the severity of liver fibrosis; and the square root of the collagen type III to type I ratio linearly correlates (R2 = 0.98) with histopathological scores. Furthermore, the collagen fibril orientations become more random with liver fibrosis transformation as compared to normal liver tissue. This work demonstrates that PR-SHG microscopy has the potential for label-free diagnosis and characterization of liver fibrosis based on quantitative analysis of collagen typings and fibril orientations.
Electrical properties of amorphous-Al2O3/single-crystal ZnO heterointerfaces
Authors: Liu J. W. , Kobayashi A. , Ohta J. , Fujioka H. , Oshima M.
Published: October 2013

Electrical properties of Al/Al2O3/ZnO (0001¯) and Al/Al2O3/ZnO (0001) metal-insulator-semiconductor (MIS) diodes have been investigated. The capacitance-voltage curves of them suggest that there are lower fixed and trapped charge densities for the Al/Al2O3/ZnO (0001¯) MIS diode than those for the Al/Al2O3/ZnO (0001) one. X-ray photoelectron spectroscopy has revealed that the valence band offset of the high-quality Al2O3/ZnO (0001¯) heterointerface is 1.2 ± 0.2 eV. These findings indicate that the Al2O3/ZnO (0001¯) heterointerface can be regarded as a suitable combination for the fabrication of ZnO-based field effect transistors.
On-chip microfluidic biosensor using superparamagnetic microparticles
Authors: Kokkinis G. , Keplinger F. , Giouroudi I.
Published: October 2013

In this paper, an integrated solution towards an on-chip microfluidic biosensor using the magnetically induced motion of functionalized superparamagnetic microparticles (SMPs) is presented. The concept of the proposed method is that the induced velocity on SMPs in suspension, while imposed to a magnetic field gradient, is inversely proportional to their volume. Specifically, a velocity variation of suspended functionalized SMPs inside a detection microchannel with respect to a reference velocity, specified in a parallel reference microchannel, indicates an increase in their non-magnetic volume. This volumetric increase of the SMPs is caused by the binding of organic compounds (e.g., biomolecules) to their functionalized surface. The new compounds with the increased non-magnetic volume are called loaded SMPs (LSMPs). The magnetic force required for the manipulation of the SMPs and LSMPs is produced by current currying conducting microstructures, driven by a programmable microcontroller. Experiments were carried out as a proof of concept. A promising decrease in the velocity of the LSMPs in comparison to that of the SMPs was measured. Thus, it is the velocity variation which determines the presence of the organic compounds in the sample fluid.
The European Union and equal opportunities policies
Authors: Walby Sylvia
Published: October 2013

The impact of the European Union policy on gender relations is often underestimated, while the significance of gender has often been underestimated in analyses of the EU. Yet the EU has made significant changes to the governance of gender relations. This has been significantly achieved through the legal regulation of equal opportunities in employment. This paper subjects to detailed critique those arguments that equal opportunities policies can do little to enhance the position of women. The impact of EU equal opportunities policies have been underestimated as a result of: the traditional focus of the social dimension on welfare rather than on social regulation; the theorization of gender relations through the lens of the family and welfare rather than employment, and the underestimation of the power of law.
Private and public transfers between generations: linking the family and the state
Authors: Kohli Martin
Published: October 2013

In the conventional story of modernization, the emergence of the nuclear family and of public old age security have been seen as parallel and mutually reinforcing processes. According to this view, the traditional intergenerational transfers in the family have been crowded out and replaced by those in the public sphere. In recent years, a growing body of research has demonstrated that substantial transfers between adult generations in the family beyond the nuclear households still exist. Their direction has been reversed, however. The new evidence shows that there is a net downward flow of private resources from the older generations to their adult offspring, i.e. counter to the public transfers. Two questions then arise: How are private and public transfers linked, i.e. to what extent do the private transfers from the older to the younger generations in the family depend on public transfers through old age pensions? And what are the effects of channelling public resources to younger family generations by way of older pension recipients? The paper addresses these questions by taking Germany as the model case.
Unemployment, employment and poverty1
Authors: Haataja Anita
Published: October 2013

Although unemployment has been pointed out as one of the greatest risk factors of poverty and social exclusion, there are few comparative studies describing the effects of unemployment on the disposable income of households. This article focuses on unemployment as income poverty risk among working age households, with data based on the Luxembourg Income Study (LIS). It investigates differences in relative poverty rates between those working age households affected and those not affected by unemployment since the early 1980s to the mid-1990s. The study consists of eight OECD countries representing four different social policy models: encompassing model (Nordic countries), the corporatistic earned-benefits-principle model (Germany), the means-tested, targeted social security model (Australia) and the so-called liberal basic security model (UK, USA and Canada). The results classified the countries into three groups. In the encompassing model and Canada, no differences were found in the poverty rates of the working age unemployed and employed households; there was also no indication that this situation was changing. Canada, however, had higher poverty rates among all working age households compared with Nordic countries. The situation in Germany can be characterized as stable polarization: unemployment there was a great poverty risk, but the difference between the unemployed and others was not growing. In all the other countries unemployment constituted a great and growing poverty risk, creating a threat of polarization among working age households. The poverty risk of working age households does not seem to be directly connected to the unemployment rate or the share of long-term unemployment. This article asserts the importance of income transfers in poverty prevention. It also suggests that the significance of women’s paid employment as a poverty-reducing factor deserves further empirical study.
Molecular analysis of transplant rejection: marching onward
Authors: Lakkis Fadi G. , Billiar Timothy R.
Published: October 2013

Transcriptional profiling of organ transplants is increasingly defining the biological pathways responsible for graft rejection at the molecular level and identifying gene transcripts that diagnose or predict rejection. These advances hold significant promise for the treatment of organ rejection and for improving clinical outcomes after transplantation, but hurdles remain.
Normothermic Cardiopulmonary Bypass with Beating Heart for Management of Renal Cell Carcinoma with Atrial Tumor Thrombus
Authors: Calcaterra Domenico , Collins Thomas E. , Turek Joseph W. , Parekh Kalpaj R. , Bashir Mohammad , Ueda Kenichi , Hanada Satoshi , Brown James A.
Published: October 2013

Renal cell carcinoma is occasionally complicated by the formation of a neoplastic thrombus invading the inferior vena cava. Rarely, the thrombus extends into the vena cava, reaching the right atrium. In these situations, despite the advanced tumor stage, surgical resection continues to offer the best chance for effective treatment. The operation requires a complex surgical approach with mobilization of the liver and use, in most cases, of extracorporeal circulation, which allows removal of the tumor thrombus from the right atrium. Traditionally, the intervention is performed using deep hypo-thermic circulatory arrest or, less frequently, using moderate hypothermia, aortic cross clamping, and cardioplegic cardiac arrest. These strategies have the downside of causing increased blood loss, coagulopathy, and long operative time and can potentially have a negative impact on survival. We report a different operative approach using normothermic cardiopulmonary bypass, with the expectation of lowering the rate of blood product transfusions, hospital length of stay, and overall incidence of complications.
Starting with a handicap: phenotypic differences between early‐ and late‐born king penguin chicks and their survival correlates
Authors: Stier Antoine , Viblanc Vincent A. , Massemin‐Challet Sylvie , Handrich Yves , Zahn Sandrine , Rojas Emilio R. , Saraux Claire , Le Vaillant Maryline , Prud'homme Onésime , Grosbellet Edith , Robin Jean‐Patrice , Bize Pierre , Criscuolo Francois
Published: October 2013

The exceptionally long (c. 11 months) growth period of king penguin chicks (Aptenodytes patagonicus) is interrupted by the Austral winter. As a consequence, penguin chicks born late in the breeding season have little time to build‐up their energy reserves before the drastic energy bottleneck they experience during winter and face greater risks of mortality than early‐born chicks.

Whereas it is well known that breeding adults alternate between early‐ and late‐breeding attempts, little is known on the phenotype of early‐ and late‐chicks, and on the potential existence of specific adaptive phenotypic responses in late‐born individuals.

We investigated phenotypic differences between early‐ and late‐chicks and tested their survival correlates both before the winter and at fledgling. Chicks were sampled 10 days after hatching to measure body mass, plasma corticosterone levels, oxidative stress parameters and telomere length.

Late‐chicks were heavier than early‐chicks at day 10. Late‐chicks also had higher corticosterone and oxidative stress levels, shorter telomere lengths and suffered from higher mortality rates than early‐chicks. For both early‐ and late‐chicks, high body mass close to hatching was a strong predictor of survival up to, and over, the winter period.

In late but not early‐chicks, high corticosterone levels and long telomeres were significant predictors of survival up to winter and fledging, respectively.

Our study provides evidence that late‐ and early‐king penguin chicks showed marked phenotypic differences 10 days after hatching. We provide an integrative discussion on whether these differences may be adaptive or not, and to what extent they may be driven by active maternal effects, indirectly induced by environmental effects, or stem from individual differences in parental quality.