bluuebunny/crossref_metadata_2025 huggingface dataset:
Simple model of bulk and surface excitation effects to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes
Authors: Kyriakou Ioanna , Emfietzoglou Dimitris , Garcia-Molina Rafael , Abril Isabel , Kostarelos Kostas
Published: September 2011

The effect of bulk and surface excitations to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes (MWNTs) is studied using the dielectric formalism. Calculations are based on a semiempirical dielectric response function for MWCNTs determined by means of a many-pole plasmon model with parameters adjusted to available experimental spectroscopic data under theoretical sum-rule constrains. Finite-size effects are considered in the context of electron gas theory via a boundary correction term in the plasmon dispersion relations, thus, allowing a more realistic extrapolation of the electronic excitation spectrum over the whole energy-momentum plane. Energy-loss differential and total inelastic scattering cross sections as a function of electron energy and distance from the surface, valid over the energy range ∼50–30,000 eV, are calculated with the individual contribution of bulk and surface excitations separated and analyzed for the case of normally incident and escaping electrons. The sensitivity of the results to the various approximations for the spatial dispersion of the electronic excitations is quantified. Surface excitations are shown to have a strong influence upon the shape and intensity of the energy-loss differential cross section in the near surface region whereas the general notion of a spatially invariant inelastic mean free path inside the material is found to be of good approximation.
Non-destructive detection of killer defects of diamond Schottky barrier diodes
Authors: Ohmagari Shinya , Teraji Tokuyuki , Koide Yasuo
Published: September 2011

Reverse characteristics of vertical-type Au/p-diamond (100) Schottky barrier diodes were investigated and characterized with cathodoluminescence, which showed a correlation with crystalline defects. Electrical measurements revealed that most diodes had low reverse current below 0.1 pA in the bias voltage range up to 50 V, although reverse current increases rapidly in some diodes and reaches 0.1 mA at 10 V. A four-fold symmetrical luminescence pattern that aligned crystallographically to the substrate was observed from the Schottky diodes, showing large reverse current. Removal of these defects is a key issue to increase the diode area of diamond-based rectifiers.
Characterization of the electrical contact between a conductive atomic force microscope cantilever and a carbon nanotube
Authors: Ghanem Tarek K. , Williams Ellen D. , Fuhrer Michael S.
Published: September 2011

A full characterization of the electrical contact between conductive atomic force microscope (AFM) cantilevers and carbon nanotubes (CNTs) is presented. The dependence of current through the contact on loading force, geometric parameters, bias conditions, and time is studied in a two-terminal configuration, where a gold coated AFM cantilever serves as a movable electrode. We find that for an optimized placement of the cantilever relative to the CNT, the current through the contact becomes independent of the loading force beyond a certain limit, and this behavior is also independent of bias conditions. In that load-independent regime, the contact is stable in time to within the current fluctuations imposed by 1/f and telegraph noise in the CNT channel. Under certain conditions of tip placement, the current through the contact exhibits a non-monotonic behavior with loading, which is well explained by the parasitic planar motion of the cantilever.
Generation of laser-induced plasma in supercritical water and vibrational spectroscopic study of accompanying stimulated Raman scattering
Authors: Yui Hiroharu , Tomai Takaaki , Sawada Masayoshi , Terashima Kazuo
Published: September 2011

We have formed a laser-induced plasma (LIP) in supercritical water (SCW) and studied associated molecular vibrations using spectroscopic methods. The accompanying forward and backward stimulated Raman scattering (SRS) of water molecules showed anisotropic behavior at supercritical conditions (>647 K and >22.1 MPa). The Raman shift of the backward SRS indicated that attractive interactions between water molecules and excess electrons generated by the LIP were dominant in the SCW. The backward SRS spectrum provided a microscopic view of the hydration environment around an excess electron, which is useful for controlling electron-driven chemical reactions and materials processing in SCW.
Carrier capture into semiconductor quantum dots via quantum wire barriers: Localization and thermionic emission effects
Authors: Szeszko J. , Zhu Q. , Gallo P. , Rudra A. , Kapon E.
Published: September 2011

Carrier transport and capture paths via barriers of different dimensionality in AlGaAs/GaAs quantum wire (QWR)/quantum dot (QD) heterostructures, grown in inverted pyramids, are studied by photoluminescence (PL) spectroscopy. Evidence for thermally activated diffusion related to potential disorder in the QWR barriers and thermionic emission of carriers from the QD into the QWR barrier is observed in temperature dependent PL spectra. Similar activation energies for the thermionic emission are derived from the continuous-wave and time-resolved PL spectroscopy.
Donor bound excitons involving a hole from the B valence band in ZnO: Time resolved and magneto-photoluminescence studies
Authors: Chen S. L. , Chen W. M. , Buyanova I. A.
Published: September 2011

Time-resolved and magneto-photoluminescence (PL) studies are performed for the so-called I6B and I7B excitonic transitions, previously attributed to neutral donor bound excitons involving a hole from the B valence band (VB), D0XB. It is shown that PL decays of these emissions at 2 K are faster than that of their I6 and I7 counterparts involving an A VB hole, which is interpreted as being due to energy relaxation of the hole assisted by acoustic phonons. From the magneto-PL measurements, values of effective Landé g factors for conduction electrons and B VB holes are determined as ge = 1.91, gh//=1.79, and gh⊥=0, respectively.
Predicted thermochemistry and unimolecular kinetics of nitrous sulfide
Authors: Marshall Paul , Gao Yide , Glarborg Peter
Published: September 2011

The geometry of N2S was obtained at the CCSD(T)/aug-cc-pV(T + d)Z level of theory and energies with coupled-cluster single double triple (CCSD(T)) and basis sets up to aug-cc-pV(6 + d)Z. After correction for anharmonic zero-point energy, core-valence correlation, correlation up to CCSDT(Q) and relativistic effects, D0 for the N–S bond is estimated as 71.9 kJ mol−1, and the corresponding thermochemistry for N2S is ${\rm \Delta }_{\rm f} {\rm H}_0^ \circ = 205.4\,{\rm kJ}\,{\rm mol}^{ - 1}$ΔfH0∘=205.4 kJ mol −1 and ${\rm \Delta }_{\rm f} {\rm H}_{298}^ \circ = 202.6\,{\rm kJ}\,{\rm mol}^{ - 1}$ΔfH298∘=202.6 kJ mol −1 with an uncertainty of ±2.5 kJ mol−1. Using CCSD(T)/aug-cc-pV(T + d) theory the minimum energy crossing point between singlet and triplet potential energy curves is found at r(N–N) ≈ 1.105 Å and r(N–S) ≈ 2.232 Å, with an energy 72 kJ mol−1 above N2 + S(3P). Application of Troe's unimolecular formalism yields the low-pressure-limiting rate constant for dissociation of N2S k0 = 7.6 × 10−10 exp(−126 kJ mol−1/RT) cm3 molecule−1 s−1 over 700–2000 K. The estimated uncertainty is a factor of 4 arising from unknown parameters for energy transfer between N2S and Ar or N2 bath gas. The thermochemistry and kinetics were included in a mechanism for CO/H2/H2S oxidation and the conclusion is that little NO is produced via subsequent chemistry of NNS.
Comparative study of cluster Ag17Cu2 by instantaneous normal mode analysis and by isothermal Brownian-type molecular dynamics simulation
Authors: Tang Ping-Han , Wu Ten-Ming , Yen Tsung-Wen , Lai S. K. , Hsu P. J.
Published: September 2011

We perform isothermal Brownian-type molecular dynamics simulations to obtain the velocity autocorrelation function and its time Fourier-transformed power spectral density for the metallic cluster Ag17Cu2. The temperature dependences of these dynamical quantities from T = 0 to 1500 K were examined and across this temperature range the cluster melting temperature Tm, which we define to be the principal maximum position of the specific heat is determined. The instantaneous normal mode analysis is then used to dissect the cluster dynamics by calculating the vibrational instantaneous normal mode density of states and hence its frequency integrated value Ij which is an ensemble average of all vibrational projection operators for the jth atom in the cluster. In addition to comparing the results with simulation data, we look more closely at the entities Ij of all atoms using the point group symmetry and diagnose their temperature variations. We find that Ij exhibit features that may be used to deduce Tm, which turns out to agree very well with those inferred from the power spectral density and specific heat.
Quantum Monte Carlo calculations of the dimerization energy of borane
Authors: Fracchia Francesco , Bressanini Dario , Morosi Gabriele
Published: September 2011

Accurate thermodynamic data are required to improve the performance of chemical hydrides that are potential hydrogen storage materials. Boron compounds are among the most interesting candidates. However, different experimental measurements of the borane dimerization energy resulted in a rather wide range (−34.3 to −39.1) ± 2 kcal/mol. Diffusion Monte Carlo (DMC) simulations usually recover more than 95% of the correlation energy, so energy differences rely less on error cancellation than other methods. DMC energies of BH3, B2H6, BH3CO, CO, and BH2+ allowed us to predict the borane dimerization energy, both via the direct process and indirect processes such as the dissociation of BH3CO. Our De = −43.12(8) kcal/mol, corrected for the zero point energy evaluated by considering the anharmonic contributions, results in a borane dimerization energy of −36.59(8) kcal/mol. The process via the dissociation of BH3CO gives −34.5(2) kcal/mol. Overall, our values suggest a slightly less De than the most recent W4 estimate De = −44.47 kcal/mol [A. Karton and J. M. L. Martin, J. Phys. Chem. A 111, 5936 (2007)]. Our results show that reliable thermochemical data for boranes can be predicted by fixed node (FN)-DMC calculations.
Dynamical phase of driven colloidal systems with short-range attraction and long-range repulsion
Authors: Chen Jiang-Xing , Mao Jun-Wen , Thakur Snigdha , Xu Jiang-Rong , Liu Fu-yang
Published: September 2011

We study the nonequilibrium dynamics of colloidal system with short-range depletion attraction and screened electrostatic repulsion on a disordered substrate. We find a growth-melting process of the clusters as the temperature is increased. By strengthening the screened electrostatic repulsion, a depinning transition from moving cluster to plastic flow is observed, which is characterized by a peak in threshold depinning force. The corresponding phase diagram is then mapped out. Due to the influences of disorder from substrate, the clusters are polarized by the strong external force, accompanied by the appearance of interesting orientational order parallel to the force and translational order perpendicular to the force. Under the condition of strong external force, the influences of density of pins and temperature are also studied.
A study on the spectral response of back-illuminated p-i-n AlGaN heterojunction ultraviolet photodetector
Authors: Zhao D. G. , Zhang S. , Jiang D. S. , Zhu J. J. , Liu Z. S. , Wang H. , Zhang S. M. , Zhang B. S. , Yang H.
Published: September 2011

The spectral responses of back-illuminated p-i-n AlGaN ultraviolet photodetector under different bias voltage are investigated. The device structure is composed of p-GaN/p-Al0.3Ga0.7N/i-Al0.3Ga0.7N/n-Al0.6Ga0.4N and Ohmic contacts, where the p-GaN layer is very thin. There are two peaks in the spectral response of photocurrent located at 350 and 290 nm, respectively. It is found that in some devices the relative intensity and phase of these two peaks may change strongly with applied forward bias. A detailed analysis suggests that the possible Schottky-type-like behavior of metal and p-GaN contact and an unsatisfactory doping of p-GaN and p-AlGaN are responsible for the abnormal phenomenon.
Thermoelectric properties for single crystal bismuth nanowires using a mean free path limitation model
Authors: Nakamura Daiki , Murata Masayuki , Yamamoto Hiroya , Hasegawa Yasuhiro , Komine Takashi
Published: September 2011

We present a mean free path limitation model to describe the temperature dependence of both resistivity and Seebeck coefficient for bismuth nanowire. Since the mobility of carriers for bismuth nanowire was limited due to dominant collision at wire boundary, the effective mobility for each carrier was estimated using cyclotron mass, appropriate band structure, and temperature dependence of Fermi energy from 4 to 300 K. Then, the resistivity and the Seebeck coefficient were calculated by using carrier density reported for bulk single crystal. In addition, an individual single-crystal bismuth nanowire sample (725 nm diameter and 2.37 mm length) grown into a quartz template was prepared to estimate the model, and the measurements were also performed. The temperature dependences of not only resistivity, but also Seebeck coefficient were quantitatively and qualitatively in very good agreement in the whole temperature region by using its crystal orientation measured from Laue measurement. We conclude that the mean free path limitation model proposed made us understand the temperature dependences of single-crystal bismuth nanowire without a finite size effect.
Rovibrational bound states of neon trimer: Quantum dynamical calculation of all eigenstate energy levels and wavefunctions
Authors: Yang Benhui , Chen Wenwu , Poirier Bill
Published: September 2011

Exact quantum dynamics calculations of the eigenstate energy levels and wavefunctions for all bound rovibrational states of the Ne3 trimer (J = 0–18) have been performed using the ScalIT suite of parallel codes. These codes employ a combination of highly efficient methods, including phase-space optimized discrete variable representation, optimal separable basis, and preconditioned inexact spectral transform methods, together with an effective massive parallelization scheme. The Ne3 energy levels and wavefunctions were computed using a pair-wise Lennard-Jones potential. Jacobi coordinates were used for the calculations, but to identify just those states belonging to the totally symmetric irreducible representation of the G12 complete nuclear permutation-inversion group, wavefunctions were plotted in hyperspherical coordinates. “Horseshoe” states were observed above the isomerization barrier, but the horseshoe localization effect is weaker than in Ar3. The rigid rotor model is found to be applicable for only the ground and first excited vibrational states at low J; fitted rotational constant values are presented.
Note: Updates to an ultra-low noise laser current driver
Authors: Troxel Daylin L. , Erickson Christopher J. , Durfee Dallin S.
Published: September 2011

We describe updates to our current driver design allowing for higher output currents, both positive and negative currents, and updated digital interfacing to the microcontroller. We also discuss measurement of the noise spectral density of the driver with a better technique, showing that the driver's actual current noise density is about an order of magnitude lower than the upper limit we previously determined.
Picosecond kinetic confirmation of overlapping Ca cluster and MNa absorption bands in UV grade CaF2
Authors: Zeuner T. , Paa W. , Triebel W. , Mühlig C. , Stafast H.
Published: September 2011

The ArF laser induced absorption feature between 450 and 700 nm observed in the bulk of mono crystalline calcium fluoride (CaF2) upon prolonged 193 nm irradiation is shown to have two origins: The first band at 530 nm is revealed by a transient femtosecond (fs) laser transparency spectrum and attributed to Ca clusters (colloid). The second band at 600 nm originates from MNa centers as identified by their laser induced fluorescence excitation spectrum, emission wavelength, and fluorescence lifetime. The analysis of the absorption feature by fs pump-probe techniques benefits from the different lifetimes of the transient transparency (excited states of the Ca clusters) and the fluorescing MNa centers of about 5 ps and 22 ns, respectively.
Shock resistance of metal-organic framework Cu-1,3,5-benzenetricarboxylate with and without ferrocene inclusion
Authors: Wei Q. , Xu H. W. , Yu X. H. , Shimada T. , Rearick M. S. , Hickmott D. D. , Zhao Y. S. , Luo S. N.
Published: September 2011

A first-of-its-kind study on the shock response of a metal-organic framework (MOF) material to planar impact is reported. MOF Cu-1,3,5-benzenetricarboxylate (Cu-BTC) without and with ferrocene inclusion show anisotropic structural collapse under shock loading. The shock resistance of the Cu-BTC framework is enhanced drastically (by a factor of six) via molecular-level inclusion of ferrocene into the pore structures.
A method for the determination of speed-dependent semi-classical vector correlations from sliced image anisotropies
Authors: Grubb Michael P. , Warter Michelle L. , Freeman C. Daniel , West Niclas A. , Usakoski Kelly M. , Johnson Kurt M. , Bartz Jeffrey A. , North Simon W.
Published: September 2011

We present analytical expressions relating the bipolar moment $\beta _Q^K (k_1 k_2)$βQK(k1k2) parameters of Dixon to the measured anisotropy parameters of different pump/probe geometry sliced ion images. In the semi-classical limit, when there is no significant coherent contribution from multiple excited states to fragment angular momentum polarization, the anisotropy of the images alone is sufficient to extract the $\beta _Q^K (k_1 k_2)$βQK(k1k2) parameters with no need to reference relative image intensities. The analysis of sliced images is advantageous since the anisotropy can be directly obtained from the image at any radius without the need for 3D-deconvolution, which is not applicable for most pump/probe geometries. This method is therefore ideally suited for systems which result in a broad distribution of fragment velocities. The bipolar moment parameters are obtained for NO2 dissociation at 355 nm using these equations, and are compared to the bipolar moment parameters obtained from a proven iterative fitting technique for crushed ion images. Additionally, the utility of these equations in extracting speed-dependent bipolar moments is demonstrated on the recently investigated NO3 system.
Hole mobility increase in ultra-narrow Si channels under strong (110) surface confinement
Authors: Neophytou Neophytos , Kosina Hans
Published: September 2011

We report on the hole mobility of ultra-narrow [110] Si channels as a function of the confinement length scale. We employed atomistic bandstructure calculations and linearized Boltzmann transport approach. The phonon-limited mobility of holes in thin [110] channels can be improved by more than 3 × as the thickness of the (110) confining surface is reduced down to 3 nm. This behavior originates from confinement induced bandstructure changes that decrease the hole effective mass and the scattering rates. Our results provide explanations for recent mobility measurements in nanobelts of similar dimensions.
Large digital-characterized electrostrain in Mn-doped (Pb,Sr)TiO3 electro-shape-memory ceramics
Authors: Liu Wenfeng , Zhang Lixue , Chen Wei , Li Shengtao , Ren Xiaobing
Published: September 2011

In the present letter, we report that through a reversible domain switching mechanism, a large electro-shape-memory effect (up to 0.23% under the electric field of 5 kV/mm) is achieved in the aged Mn-doped (Pb,Sr) TiO3 ceramics. We also provide the microscopic understanding on the relationship between the strain (ɛ) and field (E) curve with aging phenomenon. Different from the common analogue response (linear converse piezoelectric effect), such electrostrain exhibits a digital characteristic and consequently enables a promising “on-off” application. Owing to the domain switching nature, the key parameters (e.g., maximum strain, coercive field and working temperature range) of the present electrostrain can be customized by changing the ratio of Pb/Sr and thus the ratio of c/a to facilitate the possible practical applications.
Experimental research on a modular miniaturization nanoindentation device
Authors: Huang Hu , Zhao Hongwei , Mi Jie , Yang Jie , Wan Shunguang , Yang Zhaojun , Yan Jiwang , Ma Zhichao , Geng Chunyang
Published: September 2011

Nanoindentation technology is developing toward the in situ test which requires miniaturization of indentation instruments. This paper presents a miniaturization nanoindentation device based on the modular idea. It mainly consists of macro-adjusting mechanism, x-y precise positioning platform, z axis precise driving unit, and the load-depth measuring unit. The device can be assembled with different forms and has minimum dimensions of 200 mm × 135 mm × 200 mm. The load resolution is about 0.1 mN and the displacement resolution is about 10 nm. A new calibration method named the reference-mapping method is proposed to calibrate the developed device. Output performance tests and indentation experiments indicate the feasibility of the developed device and calibration method. This paper gives an example that combining piezoelectric actuators with flexure hinge to realize nanoindentation tests. Integrating a smaller displacement sensor, a more compact nanoindentation device can be designed in the future.
N-channel metal-oxide-semiconductor characterization with static and dynamic backside laser reflectance modulation techniques
Authors: Teo J. K. J. , Chua C. M. , Koh L. S. , Phang J. C. H.
Published: September 2011

An n-channel metal-oxide-semiconductor (NMOS) transistor has been characterized using backside laser reflectance modulation based on static and dynamic techniques. The static techniques do not have the required sensitivity. With the dynamic technique, the reflectance modulations of the channel at different operating points of the NMOS transistor are distinct, with the pinch-off clearly visible.
Precessional dynamics and damping in Co/Cu/Py spin valves
Authors: Salikhov R. , Abrudan R. , Brüssing F. , Buschhorn St. , Ewerlin M. , Mishra D. , Radu F. , Garifullin I. A. , Zabel H.
Published: September 2011

We have studied the precessional dynamics of Co/Cu/Py (where Py = Ni81Fe19) trilayers by time-resolved x-ray resonant magnetic scattering at the synchrotron radiation facility BESSY II. We have found that the magnetic precessional decay time of Fe magnetic moments in Py layers decreases when changing the mutual orientation of the magnetization direction of Py and Co layers from parallel to antiparallel. The observed changes of the decay time can be associated with the spin pumping induced damping effect.
Extraction of voltage-dependent series resistance from I-V characteristics of Schottky diodes
Authors: Durmuş Haziret , Atav Ülfet
Published: September 2011

A method for extracting the bias dependent behaviour of the series resistance of a Schottky barrier diode from experimental I-V data is presented. It was assumed that the behaviour of the Schottky barrier is well defined by thermionic emission theory. Relative merit of the method was determined by applying the method on some artificial sets of I-V data corresponding to known values of series resistances and comparing the results with existing methods.
Room temperature, continuous-wave coupled-cavity InAsP/InP photonic crystal laser with enhanced far-field emission directionality
Authors: Huang Jingqing , Kim Se-Heon , Gardner Jonathan , Regreny Philippe , Seassal Christian , Aitor Postigo Pablo , Scherer Axel
Published: September 2011

We demonstrate room temperature, continuous-wave lasing with enhanced far field emission directionality in coupled-cavity photonic crystal lasers, made with InAsP/InP quantum well material. These surface-emitting lasers can have a very low effective threshold power of 14.6 μW, with a linewidth of 60 pm, and 40% of the surface emitted power concentrated within a small divergence angle of ±30°.
Classical limit of the d-bar operators on quantum domains
Authors: Klimek Slawomir , McBride Matt
Published: September 2011

We study one parameter families Dt, \documentclass[12pt]{minimal}\begin{document}$0<t<1$\end{document}0<t<1 of non-commutative analogs of the d-bar operator \documentclass[12pt]{minimal}\begin{document}$D_0 = \frac{\partial }{\partial \overline{z}}$\end{document}D0=∂∂z¯ on disks and annuli in complex plane and show that, under suitable conditions, they converge in the classical limit to their commutative counterpart. More precisely, we endow the corresponding families of Hilbert spaces with the structures of continuous fields over the interval [0, 1) and we show that the inverses of the operators Dt subject to APS boundary conditions form morphisms of those continuous fields of Hilbert spaces.
All-optical four-state magnetization reversal in (Ga,Mn)As ferromagnetic semiconductors
Authors: Kapetanakis M. D. , Lingos P. C. , Piermarocchi C. , Wang J. , Perakis I. E.
Published: September 2011

Using density matrix equations of motion and a tight-binding band calculation, we predict all-optical switching between four metastable magnetic states of (III,Mn)As ferromagnets. This switching is initiated non-thermally within 100 fs, during nonlinear coherent photoexcitation. For a single optical pulse, magnetization reversal is completed after ∼100 ps and controlled by the coherent femtosecond photoexcitation. Our predicted switching comes from magnetic nonlinearities triggered by a femtosecond magnetization tilt that is sensitive to un-adiabatic light-induced spin interactions.
Twin boundary energy of hierarchically twinned magnetic shape memory alloys
Authors: Diestel Anett , Backen Anja , Rößler Ulrich K. , Schultz Ludwig , Fähler Sebastian
Published: September 2011

Magnetic shape memory alloys exhibit a hierarchy of “twins within twins” microstructures, covering all length scale from nanometer to millimeter. Modulated structures as nano-twinned adaptive martensite are the first generation of twinning. Using epitaxial Ni-Mn-Ga films as model system, we observe a regular twinning of 14M modulated variants, which represent the second generation of twinning hierarchy. We analyzed a thickness series from 30 nm to 2 μm and found a square-root dependency of the twinning period on film thickness. From the Landau-Lifshitz-Kittel scaling law, the twin boundary energy between mesoscopic 14M modulated variants is estimated the value of 0.7 eV/Å2.
Harvesting low grade heat to generate electricity with thermosyphon effect of room temperature liquid metal
Authors: Li Peipei , Liu Jing
Published: September 2011

Based on thermosyphon effect of room temperature liquid metal, a technical strategy of harvesting low grade heat to generate electricity was proposed. A conceptual system was constructed and an open circuit voltage of 2.62 V with an electrical output power of 110 mW was yielded when the heating power was 45.6 W. This method resolves the difficulty of installing an electric generator in confined space and significantly enlarges the area for converting heat to electricity. Due to its simplicity, avoidance of moving parts, wide working temperature range, and self powering feature, this electric generation system is extremely reliable, completely silent, and flexible.
Communication: Probable scenario of the liquid–liquid phase transition of SnI4
Authors: Fuchizaki Kazuhiro , Hamaya Nozomu , Hase Takaki , Katayama Yoshinori
Published: September 2011

We have shown from in situ synchrotron x-ray diffraction measurements that there are two thermodynamically stable liquid forms of SnI4, depending on the pressure. Based on the liquid–liquid critical point scenario, our recent measurements suggest that the second critical point, if it exists, may be located in a region close to the point at which the melting curve of the crystalline phase abruptly breaks. This region is, unlike that of water, experimentally accessible with relative ease.
Origin of photocurrent generation and collection losses in large area organic solar cells
Authors: Pandey Ajay K. , Nunzi Jean-Michel
Published: September 2011

Loss of performance in large area devices is a major concern for organic solar cells. We present studies highlighting up-scaling loss mechanisms caused by interfacial resistance at organic-metal interface in pentacene/C60 heterojunction solar cells. Devices with different active areas and electrodes are investigated, revealing the origin of higher series resistance in large area devices. We also simulate influence of spatial non-uniformity and anisotropic charge collection in active layer through selective coverage using customized electrode geometries and identify grain boundaries as the dominating link behind loss in photocurrent generation and collection.
Carbon dioxide adsorption in graphene sheets
Authors: Mishra Ashish Kumar , Ramaprabhu Sundara
Published: September 2011

Control over the CO2 emission via automobiles and industrial exhaust in atmosphere, is one of the major concerns to render environmental friendly milieu. Adsorption can be considered to be one of the more promising methods, offering potential energy savings compared to absorbent systems. Different carbon nanostructures (activated carbon and carbon nanotubes) have attracted attention as CO2 adsorbents due to their unique surface morphology. In the present work, we have demonstrated the CO2 adsorption capacity of graphene, prepared via hydrogen induced exfoliation of graphitic oxide at moderate temperatures. The CO2 adsorption study was performed using high pressure Sieverts apparatus and capacity was calculated by gas equation using van der Waals corrections. Physical adsorption of CO2 molecules in graphene was confirmed by FTIR study. Synthesis of graphene sheets via hydrogen exfoliation is possible at large scale and lower cost and higher adsorption capacity of as prepared graphene compared to other carbon nanostructures suggests its possible use as CO2 adsorbent for industrial application. Maximum adsorption capacity of 21.6 mmole/g was observed at 11 bar pressure and room temperature (25 ºC).
Brazil aims for its science to have greater impact
Authors: Feder Toni
Published: September 2011

After a period of expansion, Brazilian science is shifting emphasis from quantity to quality, with an eye toward reaping benefits for society.
Neural language networks at birth
Authors: Perani Daniela , Saccuman Maria C. , Scifo Paola , Anwander Alfred , Spada Danilo , Baldoli Cristina , Poloniato Antonella , Lohmann Gabriele , Friederici Angela D.
Published: September 2011

The ability to learn language is a human trait. In adults and children, brain imaging studies have shown that auditory language activates a bilateral frontotemporal network with a left hemispheric dominance. It is an open question whether these activations represent the complete neural basis for language present at birth. Here we demonstrate that in 2-d-old infants, the language-related neural substrate is fully active in both hemispheres with a preponderance in the right auditory cortex. Functional and structural connectivities within this neural network, however, are immature, with strong connectivities only between the two hemispheres, contrasting with the adult pattern of prevalent intrahemispheric connectivities. Thus, although the brain responds to spoken language already at birth, thereby providing a strong biological basis to acquire language, progressive maturation of intrahemispheric functional connectivity is yet to be established with language exposure as the brain develops.
Structure-based discovery of prescription drugs that interact with the norepinephrine transporter, NET
Authors: Schlessinger Avner , Geier Ethan , Fan Hao , Irwin John J. , Shoichet Brian K. , Giacomini Kathleen M. , Sali Andrej
Published: September 2011

The norepinephrine transporter (NET) transports norepinephrine from the synapse into presynaptic neurons, where norepinephrine regulates signaling pathways associated with cardiovascular effects and behavioral traits via binding to various receptors (e.g., β2-adrenergic receptor). NET is a known target for a variety of prescription drugs, including antidepressants and psychostimulants, and may mediate off-target effects of other prescription drugs. Here, we identify prescription drugs that bind NET, using virtual ligand screening followed by experimental validation of predicted ligands. We began by constructing a comparative structural model of NET based on its alignment to the atomic structure of a prokaryotic NET homolog, the leucine transporter LeuT. The modeled binding site was validated by confirming that known NET ligands can be docked favorably compared to nonbinding molecules. We then computationally screened 6,436 drugs from the Kyoto Encyclopedia of Genes and Genomes (KEGG DRUG) against the NET model. Ten of the 18 high-scoring drugs tested experimentally were found to be NET inhibitors; five of these were chemically novel ligands of NET. These results may rationalize the efficacy of several sympathetic (tuaminoheptane) and antidepressant (tranylcypromine) drugs, as well as side effects of diabetes (phenformin) and Alzheimer’s (talsaclidine) drugs. The observations highlight the utility of virtual screening against a comparative model, even when the target shares less than 30% sequence identity with its template structure and no known ligands in the primary binding site.
Ticks: the vectors of Lyme disease.
Authors: Smith R. P.
Published: September 2011

This book chapter reviews the existing evidence of the evolution of ticks, their means of dispersal and the reasons for range expansion, the mechanisms they use to transmit disease, and the effectiveness of interventions to bring about their control.
Laboratory diagnostic testing for Borrelia burgdorferi infection.
Authors: Johnson B. J. B.
Published: September 2011

This chapter describes the different serological tests and direct assays used for the laboratory diagnosis of Borrelia burgdorferi infection. The appropriate use of diagnostic tests is discussed.
Lyme borreliosis in the UK and Ireland.
Authors: O'Connell S.
Published: September 2011

This book chapter reviews the epidemiology, clinical aspects, diagnosis, treatment, prognosis and prevention of Lyme borreliosis in the UK and Ireland. Controversies associated with the definition, diagnosis and management of chronic Lyme disease are also discussed.
Lyme borreliosis: the European perspective.
Authors: Stanek G. , Strle F.
Published: September 2011

This book chapter reviews the clinical manifestations (neuroborreliosis, carditis, joint involvement, eye involvement) of Lyme disease, laboratory diagnosis, treatment (antibiotic therapy) and prophylaxis, and epidemiology in Europe.
Cardiac involvement.
Authors: Harburger J. M. , Halperin J. L.
Published: September 2011

This book chapter reviews epidemiology, pathogenesis, clinical manifestations, diagnosis, treatment (antibiotic therapy, antiinflammatory medication) and prognosis of Lyme carditis.
Rheumatological involvement.
Authors: Sigal L. H.
Published: September 2011

This book chapter discusses musculoskeletal consequences of Lyme borreliosis, hypothesized pathogenesis of the clinical manifestations, proposed treatments for the clinical consequences (hyperbaric therapy, cholestyramine, antibiotic therapy, diet therapy).
The psychology of 'post-Lyme disease syndrome' and 'not Lyme'.
Authors: Hassett A. L. , Sigal L. H.
Published: September 2011

This chapter addresses the psychological aspects of symptom persistence in patients who attribute such symptoms to 'chronic Lyme disease.' The 3 categories of patients with persistent complaints thought to be related to Lyme disease are described: (1) patients with current Lyme disease who may or may not have been treated previously with antibiotics; (2) patients who once had Lyme disease but no longer have active infection with Borrelia burgdorferi (post-Lyme disease syndrome, PLDS); and (3) patients who have never had Lyme disease but believes that Lyme disease is the cause of their ongoing complaints ('not Lyme'). The commitment to the diagnosis of 'chronic Lyme disease,' the role of psychiatric comorbidity and other psychological factors in PLDS and 'not Lyme,' and the role of physicians in the management of these patients are discussed.
Lyme disease: the great controversy.
Authors: Halperin J. J. , Baker P. , Wormser G. P.
Published: September 2011

This chapter addresses some of the key myths associated with the laboratory and clinical diagnosis, symptomatology, lethality, antibiotic treatment and symptom persistence of Lyme disease.
The Art of Smoking in Iran and Other Uses of Tobacco
Authors: Floor Willem
Published: September 2011

Tobacco was ‘discovered’ by Christopher Columbus when he reached the Caribbean islands. The Carib Indians used tobacco, both for its medicinal and pleasurable properties and for ceremonial purposes. The result was tobacco's conquest of the world, which began with its introduction to Europe (France in 1556; Portugal, 1558; Spain, 1559, and England, 1565). The Portuguese soon also introduced it in India, probably around 1580. Tobacco is said to have been introduced to the Ottoman Empire (Istanbul) about 1601, but this probably happened much earlier. Its introduction into Iran, via India and/or Turkey, most likely occurred in the late 1590s. One source states that tobacco came to Iran in or around 1605. However, tobacco was certainly known before that time in both the Ottoman and Safavid Empires, since Anthony Sherley used tobacco when he arrived at the Orontes River (al-ᶜAsi) in Syria (part of the Ottoman Empire) on his first journey to Iran in 1598 and, as a tobacco addict, he certainly would have taken it with him to the latter country.
Modelling withdrawal and persistence for initial teacher training: Revising Tinto's Longitudinal Model of Departure
Authors: Roberts Deborah
Published: September 2011

This paper proposes a theoretical model to explain trainee withdrawal and persistence within higher education (HE) based initial teacher training (ITT). Within ITT, attrition and persistence are under‐researched and under‐theorised, thus providing the rationale for this study. Within HE more broadly, a number of models have been proposed, most notably the seminal work of Tinto. However Tinto's Longitudinal Model of Departure was postulated for undergraduate academic courses, and has weaknesses in the study of trainees on professional courses, such as ITT. The proposed theoretical model is informed by interview and questionnaire evidence from a new case study of withdrawal and persistence in primary HE‐based ITT. In this study, withdrawal and persistence were affected by factors across a range of domains: intra‐personal, inter‐personal, academic, professional, institutional and external. Tinto's model is evaluated against the empirical findings of the case study, allowing the proposal of a revised model which more effectively explains persistence and attrition in ITT.
Assessing Protective Factors in Forensic Psychiatric Practice: Introducing the SAPROF
Authors: de Vogel Vivienne , de Vries Robbé Michiel , de Ruiter Corine , Bouman YvonneH.A.
Published: September 2011

In this article, the Structured Assessment of PROtective Factors for violence risk (SAPROF), a structured professional guideline for protective factors, is introduced and the incremental value of this instrument for treatment planning and risk management in forensic settings is discussed. The most important goal of the standardized assessment of protective factors is to complement violence risk assessment resulting in a more balanced and possibly more accurate risk assessment. Furthermore, the positive, strengths-focused approach of the SAPROF may be motivating for both staff and patients, leading to more elaborate and patient-adjusted risk management strategies and improved risk communication.
Does oligomenorrhoea/amenorrhoea and underweight imply athlete triad syndrome in young female dancers?
Authors: To William , Wong Margaret
Published: September 2011

The aim of this study was to compare the bone mineral density (BMD) of young dancers suspected of suffering from the female athlete triad syndrome and eumenorrhoeic/normal weight dancers with eumenorrhoeic non‐exercising controls. Full‐time dance students from a collegiate academy of performing arts were recruited. The female athlete triad syndrome was suspected when oligo/amenorrhoea was present together with underweight (body mass index below 18.5 kg · m−2). The non‐exercising group consisted of eumenorrhoeic age‐matched patients presenting to an adolescent gynaecology clinic. All participants had a full hormonal profile, pelvic ultrasound, bio‐impedance estimation of body fat, together with dual energy X‐ray absorptiometry (DXA) and quantitative peripheral computed tomography scans (pQCT) to determine bone mineral density. A total of 47 dancers aged 17–20 years were recruited, of whom 14 (29.7%) fell within the criteria for suspected female athlete triad syndrome. Comparing the dancers with suspected female athlete triad with 36 non‐exercising controls showed no significant differences in BMD at most sites between the two groups. Comparing the normal dancers (n=33) with the same control group showed the dancers had significantly higher BMD at the hip sites (P<0.005), as well as higher core tibial volumetric BMD (P=0.04) than the controls. Young dancers with oligo/amenorrhoea and apparent under‐nutrition that fitted the clinical diagnosis of female athlete triad syndrome did not have lower BMD than non‐exercising eumenorrhoeic controls, while eumenorrhoeic dancers actually had higher BMD. In addition, no significant differences were seen between eumenorrhoeic dancers and those with suspected female athlete triad. The risk of osteoporosis was apparently offset by the benefits of regular intensive weight‐bearing exercises in those participants with suspected female athlete triad.
Gaussian interaction profile kernels for predicting drug–target interaction
Authors: van Laarhoven Twan , Nabuurs Sander B. , Marchiori Elena
Published: September 2011

Motivation: The in silico prediction of potential interactions between drugs and target proteins is of core importance for the identification of new drugs or novel targets for existing drugs. However, only a tiny portion of all drug–target pairs in current datasets are experimentally validated interactions. This motivates the need for developing computational methods that predict true interaction pairs with high accuracy.

Results: We show that a simple machine learning method that uses the drug–target network as the only source of information is capable of predicting true interaction pairs with high accuracy. Specifically, we introduce interaction profiles of drugs (and of targets) in a network, which are binary vectors specifying the presence or absence of interaction with every target (drug) in that network. We define a kernel on these profiles, called the Gaussian Interaction Profile (GIP) kernel, and use a simple classifier, (kernel) Regularized Least Squares (RLS), for prediction drug–target interactions. We test comparatively the effectiveness of RLS with the GIP kernel on four drug–target interaction networks used in previous studies. The proposed algorithm achieves area under the precision–recall curve (AUPR) up to 92.7, significantly improving over results of state-of-the-art methods. Moreover, we show that using also kernels based on chemical and genomic information further increases accuracy, with a neat improvement on small datasets. These results substantiate the relevance of the network topology (in the form of interaction profiles) as source of information for predicting drug–target interactions.

Availability: Software and Supplementary Material are available at http://cs.ru.nl/~tvanlaarhoven/drugtarget2011/.

Contact:  tvanlaarhoven@cs.ru.nl; elenam@cs.ru.nl

Supplementary Information:  Supplementary data are available at Bioinformatics online.
Role of sialidase in glycoprotein utilization by Tannerella forsythia
Authors: Roy Sumita , Honma Kiyonobu , Douglas C. W. Ian , Sharma Ashu , Stafford Graham P.
Published: September 2011

The major bacterial pathogens associated with periodontitis includeTannerella forsythia. We previously discovered that sialic acid stimulates biofilm growth ofT. forsythia, and that sialidase activity is key to utilization of sialoconjugate sugars and is involved in host–pathogen interactionsin vitro. The aim of this work was to assess the influence of the NanH sialidase on initial biofilm adhesion and growth in experiments where the only source of sialic acid was sialoglycoproteins or human oral secretions. After showing thatT. forsythiacan utilize sialoglycoproteins for biofilm growth, we showed that growth and initial adhesion with sialylated mucin and fetuin were inhibited two- to threefold by the sialidase inhibitor oseltamivir. A similar reduction (three- to fourfold) was observed with ananHmutant compared with the wild-type. Importantly, these data were replicated using clinically relevant serum and saliva samples as substrates. In addition, the ability of thenanHmutant to form biofilms on glycoprotein-coated surfaces could be restored by the addition of purified NanH, which we show is able to cleave sialic acid from the model glycoprotein fetuin and, much less efficiently, 9-O-acetylated bovine submaxillary mucin. These data show for the first time that glycoprotein-associated sialic acid is likely to be a keyin vivonutrient source forT. forsythiawhen growing in a biofilm, and suggest that sialidase inhibitors might be useful adjuncts in periodontal therapy.
Epithelial barrier biology: good fences make good neighbours
Authors: Moens Emmanuelle , Veldhoen Marc
Published: September 2011

The external surfaces of the body, such as the skin and the gastrointestinal mucosal membrane, are an important line of defence preventing the invasion of microorganisms and their products. Mucosal immune cells, especially intraepithelial lymphocytes, are involved in maintaining the integrity of these epithelial barriers. They contribute towards the tolerance to commensal organisms, which occupy these same sites, and to the immune responses against harmful organisms and their products. The composition of the microbiota is influenced by immune cells as well as external environmental factors, especially the use of antibiotics and diet. There is an increasing appreciation that the microbiota affects systemic immune responses in addition to local immunity. Failure to control the occupancy by microorganisms may result in the disruption of the delicate homeostasis between beneficial and harmful microorganisms and contribute to inflammatory pathologies. This review will discuss some of our current understanding of the impact of immune cells and diet on the microbiota.