bluuebunny/crossref_metadata_2025 huggingface dataset:
Propofol Induction Reduces the Capacity for Neural Information Integration: Implications for the Mechanism of Consciousness and General Anesthesia
Authors: Lee UnCheol , Kim Seunghwan , Noh Gyu-Jeong , Choi Byung-Moon , Mashour George A.
Published: November 2008

The cognitive unbinding paradigm suggests that the synthesis of cognitive information is attenuated by general anesthesia. Here, we investigated the functional organization of brain activities in the conscious and anesthetized states, based on characteristic functional segregation and integration of electroencephalography (EEG). EEG recordings were obtained from 14 subjects undergoing induction of general anesthesia with propofol. We quantified changes in mean information integration capacity in each band of the EEG. After induction with propofol, mean information integration capacity was reduced most prominently in the gamma band of the EEG (p=0.0001). Furthermore, we demonstrate that loss of consciousness is reflected by the breakdown of the spatiotemporal organization of gamma waves. Induction of general anesthesia with propofol reduces the capacity for information integration in the brain. These data directly support the information integration theory of consciousness and the cognitive unbinding paradigm of general anesthesia.
Oxidative Stress in Severely Obese Persons Is Greater in Those With Insulin Resistance
Authors: Tinahones Francisco J. , Murri‐Pierri Mora , Garrido‐Sánchez Lourdes , García‐Almeida Jose M. , García‐Serrano Sara , García‐Arnés Juan , García‐Fuentes Eduardo
Published: November 2008

The postprandial state seems to have a direct influence on oxidative status and insulin resistance. We determined the effect of an increase in plasma triglycerides after a high‐fat meal on oxidative stress in severely obese patients with differing degrees of insulin resistance. The study was undertaken in 60 severely obese persons who received a 60‐g fat overload with a commercial preparation. Measurements were made of insulin resistance, the plasma activity of various antioxidant enzymes, the total antioxidant capacity (TAC) and the plasma concentration of thiobarbituric acid reactive substances (TBARS). The patients with greater insulin resistance had a lower plasma superoxide dismutase (SOD) activity (P < 0.05) and a greater glutathione peroxidase (GSH‐Px) activity (P < 0.05). The high‐fat meal caused a significant reduction in SOD activity and an increase in the plasma concentration of TBARS in all the patients. Only the patients with lower insulin resistance experienced a significant increase in plasma catalase activity (2.22 ± 1.02 vs. 2.93 ± 1.22 nmol/min/ml, P < 0.01), remaining stable in the patients with greater insulin resistance. These latter patients had a reduction in plasma TAC (6.92 ± 1.93 vs. 6.29 ± 1.80 mmol/l, P < 0.01). In conclusion, our results show a close association between the degree of insulin resistance and markers of oxidative stress, both before and after a high‐fat meal. The postprandial state causes an important increase in oxidative stress, especially in severely obese persons with greater insulin resistance. However, we are unable to determine from this study whether there is first an increase in oxidative stress or in insulin resistance.
Spindle assembly defects leading to the formation of a monopolar mitotic apparatus
Authors: Tillement Vanessa , Remy Marie‐Hélène , Raynaud‐Messina Brigitte , Mazzolini Laurent , Haren Laurence , Merdes Andreas
Published: November 2008

Mitotic spindle formation in animal cells involves microtubule nucleation from two centrosomes that are positioned at opposite sides of the nucleus. Microtubules are captured by the kinetochores and stabilized. In addition, microtubules can be nucleated independently of the centrosome and stabilized by a gradient of Ran—GTP, surrounding the mitotic chromatin. Complex regulation ensures the formation of a bipolar apparatus, involving motor proteins and controlled polymerization and depolymerization of microtubule ends. The bipolar apparatus is, in turn, responsible for faithful chromosome segregation. During recent years, a variety of experiments has indicated that defects in specific motor proteins, centrosome proteins, kinases and other proteins can induce the assembly of aberrant spindles with a monopolar morphology or with poorly separated poles. Induction of monopolar spindles may be a useful strategy for cancer therapy, since ensuing aberrant mitotic exit will usually lead to cell death. In this review, we will discuss the various underlying molecular mechanisms that may be responsible for monopolar spindle formation.
Study of laser excited vibration of silicon cantilever
Authors: Song Yaqin , Cretin Bernard , Todorović D. M. , Vairac Pascal
Published: November 2008

In this paper an interferometric setup called “thermoelastic microscopy” has been used to measure the vibration response of the semiconductor cantilevers under modulated laser thermal source. The small vibration amplitude has been detected well below 10 pm magnitude in accurate adjustment conditions. The results showed that experimental responses have a good agreement with the theoretical ones. Also from the analysis we could conclude that the signal amplitude has a power functional dependence on the modulation frequency and that the phase angle linearly depended on the square root of modulation frequency.
Fabrication of submicron structures in nanoparticle/polymer composite by holographic lithography and reactive ion etching
Authors: Zhang A. Ping , He Sailing , Kim Kyoung Tae , Yoon Yong-Kyu , Burzynski Ryszard , Samoc Marek , Prasad Paras N.
Published: November 2008

We report on the fabrication of nanoparticle/polymer submicron structures by combining holographic lithography and reactive ion etching. Silica nanoparticles are uniformly dispersed in a (SU8) polymer matrix at a high concentration, and in situ polymerization (cross-linking) is used to form a nanoparticle/polymer composite. Another photosensitive SU8 layer cast upon the nanoparticle/SU8 composite layer is structured through holographic lithography, whose pattern is finally transferred to the nanoparticle/SU8 layer by the reactive ion etching process. Honeycomb structures in a submicron scale are experimentally realized in the nanoparticle/SU8 composite.
Glassy properties and viscous slowing down: An analysis of the correlation between nonergodicity factor and fragility
Authors: Niss Kristine , Dalle-Ferrier Cécile , Giordano Valentina M. , Monaco Giulio , Frick Bernhard , Alba-Simionesco Christiane
Published: November 2008

We present an extensive analysis of the proposed relationship [T. Scopigno et al., Science 302, 849 (2003)] between the fragility of glass-forming liquids and the nonergodicity factor as measured by inelastic x-ray scattering. We test the robustness of the correlation through the investigation of the relative change under pressure of the speed of sound, nonergodicity factor, and broadening of the acoustic exitations of a molecular glass former, cumene, and of a polymer, polyisobutylene. For polyisobutylene, we also perform a similar study by varying its molecular weight. Moreover, we have included new results on liquids presenting an exceptionally high fragility index m under ambient conditions. We show that the linear relation, proposed by Scopigno et al. [Science 302, 849 (2003)] between fragility, measured in the liquid state, and the slope α of the inverse nonergodicity factor as a function of T∕Tg, measured in the glassy state, is not verified when increasing the data base. In particular, while there is still a trend in the suggested direction at atmospheric pressure, its consistency is not maintained by introducing pressure as an extra control parameter modifying the fragility: whatever is the variation in the isobaric fragility, the inverse nonergodicity factor increases or remains constant within the error bars, and one observes a systematic increase in the slope α when the temperature is scaled by Tg(P). To avoid any particular aspects that might cause the relation to fail, we have replaced the fragility by other related properties often evoked, e.g., thermodynamic fragility, for the understanding of its concept. Moreover, we find, as previously proposed by two of us [K. Niss and C. Alba-Simionesco, Phys. Rev. B 74, 024205 (2006)], that the nonergodicity factor evaluated at the glass transition qualitatively reflects the effect of density on the relaxation time even though in this case no clear quantitative correlations appear.
A first principles theoretical study of vibrational spectral diffusion and hydrogen bond dynamics in aqueous ionic solutions: D2O in hydration shells of Cl− ions
Authors: Mallik Bhabani S. , Semparithi A. , Chandra Amalendu
Published: November 2008

A theoretical study of vibrational spectral diffusion and hydrogen bond dynamics in aqueous ionic solutions is presented from first principles without employing any empirical potential models. The present calculations are based on ab initio molecular dynamics for trajectory generation and wavelet analysis of the simulated trajectories for time dependent frequency calculations. Results are obtained for two different deuterated aqueous solutions: the first one is a relatively dilute solution of a single Cl− ion and the second one is a concentrated solution of NaCl (∼3M) dissolved in liquid D2O. It is found that the frequencies of OD bonds in the anion hydration shell, i.e., those which are hydrogen bonded to the chloride ion, have a higher stretch frequency than those in the bulk water. Also, on average, the frequencies of hydration shell OD modes are found to increase with increase in the anion-water hydrogen bond distance. On the dynamical side, when the vibrational spectral diffusion is calculated exclusively for the hydration shell water molecules in the first solution, the dynamics reveals three time scales: a short-time relaxation (∼200 fs) corresponding to the dynamics of intact ion-water hydrogen bonds, a slower relaxation (∼3 ps) corresponding to the lifetimes of chloride ion-water hydrogen bonds, and another longer-time constant (∼20 ps) corresponding to the escape dynamics of water from the anion hydration shell. Existence of such three time scales for hydration shell water molecules was also reported earlier for water containing a single iodide ion using classical molecular dynamics [B. Nigro et al., J. Phys. Chem. A 110, 11237 (2006)]. Hence, the present study confirms the basic results of this earlier work using a different methodology. However, when the vibrational spectral diffusion is calculated over all the OD modes, only two time scales of ∼150 fs and ∼2.7 ps are found without the slowest component of ∼20 ps. This is likely because of the very small weight that the hydration shell water molecules carry to the overall spectral diffusion in the solution containing a single ion. For the concentrated solution also, the slowest component of ∼20 ps is not found in the spectral diffusion of all water molecules because a distinct separation between the hydration shell and bulk water in terms of their stretch frequencies does not hold at this high concentration regime. The present first principles results are compared with those of the available experiments and classical simulations.
Magnetoelectric properties of core-shell particulate nanocomposites
Authors: Islam Rashed A. , Bedekar Vishwas , Poudyal Narayan , Liu J. Ping , Priya Shashank
Published: November 2008

In this study, we report results on magnetoelectric (ME) core-shell Pb(Zr,Ti)O3 (PZT)-NiFe2O4 (NF) particulate nanocomposites. NF particles forming the shell had size in range of 20–30 nm. The grain size of sintered nanocomposites was found to be in the range of 500–800 nm. The sintered nanocomposite exhibited piezoelectric coefficient (d33) of 60 pC/N, dielectric constant of 865, and ME coefficient of 195 mV/cm Oe. High ME coefficient was observed for wide range of dc bias magnetic field. This approach of fabricating layered composite has a promise to provide large ME coefficients in particulate sintered structures.
Optical absorption of small silver clusters: Agn, (n=4–22)
Authors: Harb M. , Rabilloud F. , Simon D. , Rydlo A. , Lecoultre S. , Conus F. , Rodrigues V. , Félix C.
Published: November 2008

We present a joint theoretical and experimental investigation of the absorption spectra of silver clusters Agn (4≤n≤22). The experimental spectra of clusters isolated in an Ar matrix are compared with the calculated ones in the framework of the time-dependent density functional theory. The analysis of the molecular transitions indicates that the s-electrons are responsible for the optical response of small clusters (n≤8) while the d-electrons play a crucial role in the optical excitations for larger n values.
Quantum trajectory calculations for bipolar wavepacket dynamics in one dimension
Authors: Park Kisam , Poirier Bill , Parlant Gérard
Published: November 2008

Quantum trajectory methods (QTMs) hold great promise as a potential means of obtaining dynamical insight and computational scaling similar to classical trajectory simulations but in an exact quantum dynamical context. To date, the development of QTMs has been stymied by the “node problem”—highly nonclassical and numerically unstable trajectories that arise when the wavepacket density |ψ|2 exhibits substantial interference oscillations. In a recent paper, however [B. Poirier, J. Chem. Phys. 128, 164115 (2008)], a “bipolar decomposition,” ψ=ψ++ψ−, was introduced for one-dimensional (1D) wavepacket dynamics calculations such that the component densities |ψ±|2 are slowly varying and otherwise interference-free, even when |ψ|2 itself is highly oscillatory. The bipolar approach is thus ideally suited to a QTM implementation, as is demonstrated explicitly in this paper. Two model 1D benchmark systems exhibiting substantial interference are considered—one with more “quantum” system parameters and the other more classical-like. For the latter, more challenging application, synthetic QTM results are obtained and found to be extremely accurate, as compared to a corresponding fixed-grid calculation. Ramifications of the bipolar QTM approach for the classical limit and also for multidimensional applications, are discussed.
Equilibrium fluctuations of the Lennard-Jones cluster surface
Authors: Zhukhovitskii D. I.
Published: November 2008

Spectra of the cluster surface equilibrium fluctuations are treated by decomposition into the bulk and net capillary ones. The bulk fluctuations without capillary ones are simulated by the surface of a cluster truncated by a sphere. The bulk fluctuation spectrum is shown to be generated primarily by the discontinuity in the spatial distribution of cluster internal particles. The net capillary fluctuation slice spectrum is obtained in molecular dynamics simulation by subtraction of the bulk fluctuation spectrum from the total one. This net spectrum is in the best agreement with a theoretical estimation if we assume the intrinsic surface tension to be independent of the wave number. The wave number cutoff is brought in balance with the intrinsic surface tension and excess surface area induced by the capillary fluctuations. It is shown that the ratio of the ordinary surface tension to the intrinsic one can be considered as a universal constant independent of the temperature and cluster size.
Nanomechanical properties of piezoresistive cantilevers: Theory and experiment
Authors: Wilkinson Paul R. , Klug William S. , Van Leer Brandon , Gimzewski James K.
Published: November 2008

Concise analytical expressions for the effective spring constant, resonance frequency, and effective mass are derived using elementary beam theory for cantilevers, which exhibit a basic rectangular cross section modified by a rectangular hole centered at the base, which is a typical case for piezoresistive cantilevers. The results demonstrate that each of these mechanical properties can be represented as the property of the same cantilever in the absence of the hole times a dimensionless function of the hole geometry. The derivations are used to determine the mass sensitivity of the modified levers and to optimize the mass sensitivity of the piezoresistive geometry. The beam theories are shown to be consistent with two dimensional plate theory (finite element analysis) and in good agreement with our experimental results on cantilevers milled using a focused ion beam.
Controlled electron injection into laser wakefields with a perpendicular injection laser pulse
Authors: Wang W.-M. , Sheng Z.-M. , Zhang J.
Published: November 2008

Electron injection into laser wakefields for acceleration by two orthogonally directed laser pulses is investigated theoretically. It is found that efficient injection occurs provided the two pulses are collinearly polarized, even if the injection pulse is much weaker than the pump pulse driving wakefields. Compared with the head-on colliding injection geometry, this scheme allows for a shorter propagation distance less than a Rayleigh length for the injection pulse, before its overlapping with the pump pulse. Moreover, it can generate electron beams stably with comparable low energy spread and emittance, as demonstrated by particle-in-cell simulations. The optimization of laser parameters is also investigated.
High-performance C60 n-channel organic field-effect transistors through optimization of interfaces
Authors: Zhang Xiao-Hong , Kippelen Bernard
Published: November 2008

High-performance C60 organic field-effect transistors (OFETs) have been obtained by engineering the essential electrode/semiconductor and dielectric/semiconductor interfaces. By using calcium (Ca) as the source and drain electrodes, the width-normalized contact resistance (RCW) at the electrode/semiconductor interface for devices with channel lengths ranging from 200 down to 25 μm could be reduced to a constant value of 2 kΩ cm at a gate-source voltage (VGS) of 2.6 V, leading to electrical properties that are dominated by gate-modulated resistance of the channel as in conventional metal-oxide-semiconductor field-effect transistors. Channel length scaling of the source-drain current and transconductance is observed. Average charge mobility values of 2.5 cm2/V s extracted at VGS<5 V are found independent of channel length within the studied range. Besides high mobility, overall high electrical performance and stability at low operating voltages are demonstrated by using a 100-nm-thick high-κ gate dielectric layer of aluminum oxide (Al2O3) fabricated by atomic layer deposition and modified with divinyltetramethyldisiloxane-bis (benzocyclobutene). The combined operating properties of these OFETs, obtained in a N2-filled glovebox, are comparable to the best p-channel OFETs and outperform those of amorphous silicon thin-film transistors.
Diagnosis of x-ray heated Mg/Fe opacity research plasmas
Authors: Bailey J. E. , Rochau G. A. , Mancini R. C. , Iglesias C. A. , MacFarlane J. J. , Golovkin I. E. , Pain J. C. , Gilleron F. , Blancard C. , Cosse Ph. , Faussurier G. , Chandler G. A. , Nash T. J. , Nielsen D. S. , Lake P. W.
Published: November 2008

Understanding stellar interiors, inertial confinement fusion, and Z pinches depends on opacity models for mid-Z plasmas in the 100–300 eV temperature range. These models are complex and experimental validation is crucial. In this paper we describe the diagnosis of the first experiments to measure iron plasma opacity at a temperature high enough to produce the charge states and electron configurations that exist in the solar interior. The dynamic Hohlraum x-ray source at Sandia National Laboratories’ Z facility was used to both heat and backlight Mg/Fe CH tamped foils. The backlighter equivalent brightness temperature was estimated to be Tr∼314 eV±8% using time-resolved x-ray power and imaging diagnostics. This high brightness is significant because it overwhelms the sample self-emission. The sample transmission in the 7–15.5 Å range was measured using two convex potassium acid phthalate crystal spectrometers that view the backlighter through the sample. The average spectral resolution over this range was estimated to be λ/δλ∼700 by comparing theoretical crystal resolution calculations with measurements at 7.126, 8.340, and 12.254 Å. The electron density was determined to be ne=6.9±1.7×1021 cm−3 using the Stark-broadened Mg Heβ, Heγ, and Heδ lines. The temperature inferred from the H-like to He-like Mg line ratios was Te=156±6 eV. Comparisons with three different spectral synthesis models all have normalized χ2 that is close to unity, indicating quantitative consistency in the inferred plasma conditions. This supports the reliability of the results and implies the experiments are suitable for testing iron opacity models.
Patterning polycrystalline thin films by defocused ion beam: The influence of initial morphology on the evolution of self-organized nanostructures
Authors: Toma A. , Batič B. Šetina , Chiappe D. , Boragno C. , Valbusa U. , Godec M. , Jenko M. , Buatier de Mongeot F.
Published: November 2008

We report on self-organized patterning of polycrystalline noble metal films, supported on dielectric substrates, by defocused Ar+ ion beam irradiation. The initial surface morphology affects the formation of nanostructures, forcing the growth of ripples with a lateral periodicity imposed by the pristine polycrystalline grain distribution. At the early stages, the self-organization process is dominated by the shadowing of taller grains, while a crossover to the conventional erosive regime, observed for single crystals, sets in at longer sputtering times. The grain boundaries, although providing an additional bias for diffusion of mobile defects, do not affect the propagation of nanoscale ripples across individual grains.
The role of poly(3,4-ethylenedioxythiophene):poly(styrenesulphonate) as a hole injection layer in a blue-emitting polymer light-emitting diode
Authors: Bange Sebastian , Kuksov Andriy , Neher Dieter , Vollmer Antje , Koch Norbert , Ludemann Aurelie , Heun Susanne
Published: November 2008

The authors study the role of the conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrenesulphonate) (PEDOT:PSS) in determining the transient and steady-state operation of a blue-emitting polymer light-emitting diode. Combining the results from photoemission spectroscopy, time-of-flight photocurrent measurements, and studies on hole-only devices reveals a significant barrier for the injection of holes into the polymer. Simulations with a numerical drift-diffusion model, however, show that the injection currents determined from single-carrier devices cannot account for the rapid transient luminance onset and the efficient steady-state luminance output of the corresponding bipolar light-emitting devices. It is shown that the transient electroluminescence traces measured at different external bias can be well reproduced when assuming the presence of a weak barrier for electron extraction at this interface, which is attributed to electron accumulation at a thin phase-segregated PSS-rich layer at the surface of PEDOT:PSS. In addition, interface conditioning, presumably due to electron trapping near PEDOT:PSS, renders the anode-polymer interface nearly Ohmic. This conditioning, however, occurs on intermediate time scales normally not addressed by either transient or steady-state measurements.
Optical properties of m-plane GaN quantum dots and quantum wires
Authors: Renard Julien , Amstatt Benoit , Bougerol Catherine , Bellet-Amalric Edith , Daudin Bruno , Gayral Bruno
Published: November 2008

We have studied the optical properties of m-plane GaN/AlN quantum dots and quantum wires. The photoluminescence, both on an ensemble of nanostructures and on single nanostructures, shows a strong degree of linear polarization perpendicular to the c-axis. Time-resolved photoluminescence evidences the strong reduction in the quantum confined Stark effect. Temperature dependence measurements suggest a difference in nonradiative processes between quantum dots and quantum wires.
Effect of compensation and of metallic impurities on the electrical properties of Cz-grown solar grade silicon
Authors: Libal Joris , Novaglia Sara , Acciarri Maurizio , Binetti Simona , Petres Roman , Arumughan Jayaprasad , Kopecek Radovan , Prokopenko Aleksander
Published: November 2008

In this work we present a study of a p-type Czochralski-grown Si ingot which was grown using 10% solar grade silicon (SoG-Si). As the SoG-Si contains a relatively high concentration of impurities including phosphorus, the electrical properties of the as-grown wafers from this ingot are affected by both the compensating dopants and other impurities. Measurements of the minority charge carrier lifetime in the as-grown material reveal very low values (4–8μs). The Hall mobilities at room temperature correspond to normal values for Czochralski silicon in the upper part of the ingot (which solidifies first) and decrease significantly toward the bottom of the ingot. Segregation leads to an accumulation of impurities toward the lower parts of the ingot as well as to a stronger increase in phosphorus than of boron, the latter of which results in a high compensation level (i.e., an increasing resistivity). A priori, both effects could be responsible for the degradation of the electrical properties in the lower parts of the ingot, whereas theoretical considerations show that the level of compensation should not cause a strong decrease in Hall mobility at room temperature. Untextured solar cells have been processed from wafers originating from different positions of the ingot. As expected, the phosphorus diffusion leads to a gettering effect: the recombination active impurities are removed out of the wafer volume. This results in relatively high efficiencies (>16%) of the solar cells but does not show a strong correlation between ingot height and cell efficiency. This observation is also confirmed by the high bulk lifetimes (>200μs) measured after the process even for samples originating from the last solidified (lower)part of the ingot. The Hall mobility of samples cut from finished solar cells has been measured and shows the same trend as the as-grown samples, the values for the bottom of the ingot still being very low. With the concentrations of boron and phosphorus studied up to this point, compensation showed no detrimental effect on the cell efficiency of industrial-like solar cells.
Decomposition of methylene blue in water using a dielectric barrier discharge: Optimization of the operating parameters
Authors: Magureanu Monica , Piroi Daniela , Mandache Nicolae Bogdan , Parvulescu Vasile
Published: November 2008

The decomposition of methylene blue (MB) in aqueous solution was investigated using a dielectric barrier discharge in coaxial configuration operated in pulsed regime. The MB solution (volume=300 ml, concentration=50 mg/l) contained in a reservoir was circulated by a pump and made to flow as a film over the surface of the inner electrode of the plasma reactor. The best results were obtained when the discharge was operated in oxygen. The conversion of MB reached 95% after 30 min of plasma treatment and the corresponding yield was 57 g/kW h. Increasing the amplitude of the voltage pulses, and implicitly, the power dissipated in the discharge led to faster decomposition of the dye; however, the yield for MB degradation was lower. Better results were obtained for negative polarity of the applied voltage as compared to positive polarity, but after 30 min treatment the conversion had similar values for both cases. The gas flow rate did not influence the decomposition of MB in the range investigated, 300–900 ml/min. The solution flow rate had an effect on the dye degradation only for short treatment times, where a lower flow rate led to improved results, while for long treatment times the conversion was similar for 30 and 90 ml/min.
Characterization of converging shock waves generated by underwater electrical wire array explosion
Authors: Efimov S. , Fedotov A. , Gleizer S. , Gurovich V. Tz. , Bazalitski G. , Krasik Ya. E.
Published: November 2008

Results of ∼200 kbar pressure generation at 50 μm distance from the implosion axis of the converging shock wave produced by an underwater electrical explosion of a cylindrical wire array are reported. The array was exploded using a submicrosecond high-current generator (stored energy of ∼4.2 kJ, current amplitude of ∼325 kA, rise time of ∼1 μs). Multiframe shadow imaging of the shock wave was used to determine its time of flight. These data were applied for calculating the pressure at the vicinity of the implosion axis using one dimensional hydrodynamic calculations and the Whitham approach. However, it was found that in the case of wire array radius ≤5 mm, multiframe imaging cannot be used at the final stage of the shock wave implosion because of possible changes in the optical properties of the water. Optical and spectroscopic methods based on either the change in the refraction index of the optical fiber or spectroscopy of the plasma formed inside the capillary placed at the implosion axes were used for shock wave characterization. A satisfactory agreement was found between the results obtained by these methods.
Spectroscopic study on rotational and vibrational temperature of N2 and N2+ in dual-frequency capacitively coupled plasma
Authors: Huang Xiao-Jiang , Xin Yu , Yang Lei , Yuan Quan-Hua , Ning Zhao-Yuan
Published: November 2008

By using optical emission spectroscopy, the vibrational and rotational temperatures of N2 and N2+ in capacitively coupled plasma (CCP) discharges driven by dual-frequency 41MHz and 2MHz are investigated. The vibrational and rotational temperatures are measured based on the N2+ first negative system and N2 second positive system overlapped molecular emission optical spectrum, using the method of comparing the measured and calculated spectra with a least-square procedure. The influence of the rotational and vibrational temperatures with input power of the high frequency (HF) and low frequency (LF) as well as the gas pressure is discussed. It is found that the vibrational or rotational temperatures of N2 and N2+ are decoupled in dual-frequency CCP discharge. The influence of the LF power on N2+ rotational and vibrational temperature is much more than that of N2, while the influence of HF power is just opposite to the case of LF power. The reason for this is thought to be the variation of electron temperature when applying HF or LF power. Additionally, the increase of gas pressure makes the difference between the vibrational and rotational temperature decrease.
Liquid surface waves in parabolic tanks
Authors: Núñez-Fernández Y. , Trallero-Giner C. , Buchleitner A.
Published: November 2008

Surface waves in cylindrical tanks with parabolic cross section formed by two confocal parabolas are studied. Exact general solutions for the inviscid gravity-capillary waves as function of the parabolic curvatures are presented, and the symmetry of the eigensolutions for the velocity potential modes is also investigated. For a complete characterization of the velocity potential and of the amplitude of the liquid surface, their analytic expressions in terms of hypergeometric functions are given. It is shown that for the particular case of two confocal parabolas with the same curvature, the velocity potential is described by the cylindrical functions. The evolution of the nodal structure for gravity-capillary waves for variable excitation, and in terms of the parabolic tank curvature, is analyzed.
Influence of Mg doping on the giant dielectric tunability in LuFe2O4
Authors: Liu Yi , Li Chang-Hui , Zhang Xiang-Qun , Cheng Zhao-Hua , Sun Young
Published: November 2008

A giant dielectric tunability effect in LuFe2O4 was recently discovered by our group. Here we report the influence of Mg doping on the dielectric tunability and dielectric loss in LuFe2−xMgxO4 (x≤0.1) samples. It was found that the temperature interval of the giant dielectric tunability is broadened by a slight (5%) Mg doping, while the dielectric loss remains the same order. The maximum value of tunability is reduced by Mg doping, which supports the viewpoint that the giant dielectric tunability is crucially related to charge ordering of Fe2+ and Fe3+ ions. These results suggest that the giant dielectric tunability in LuFe2O4 can be finely tuned by Mg doping.
Structural characterization of GaAs and InAs nanowires by means of Raman spectroscopy
Authors: Begum N. , Piccin M. , Jabeen F. , Bais G. , Rubini S. , Martelli F. , Bhatti A. S.
Published: November 2008

We report Raman studies of GaAs and InAs nanowires (NWs) grown on SiO2 and GaAs surfaces by means of catalyst-assisted molecular beam epitaxy. We have investigated several tens of NWs grown using either Mn or Au as a catalyst. The LO and TO phonon lines of the NWs showed an energy downshift and a broadening as compared to the lines usually observed in the corresponding bulk materials. A doublet is sometimes observed in the LO region due to the observation of a signal attributed to the surface optical (SO) phonon. The energy position of the SO phonon agrees with the values expected considering the section diameter of the NWs. LO and TO downshifts are due to the presence of structural defects within the NWs. The larger the energy downshift, the smaller the dimension of the defect-free regions. The results demonstrate that different catalysts provide wires with comparable crystal quality. The measurements also point out that differences in defect density can be found in wires coming from the same batch indicating that a substantial effort will be needed to obtain high homogeneities of the NW quality.
Electrical characterization of gold island films: A route to control of nanoparticle deposition
Authors: Lassesson A. , Brown S. A. , van Lith J. , Schulze M.
Published: November 2008

The evaporation of gold onto SiN or SiOx leads to the formation of nanoscale islands separated by tunneling barriers. As the deposited thickness of Au increases, there is a linear increase in island size and an exponential decrease in film resistance, resulting from coalescence of neighboring islands. This understanding of film morphology allows the construction of a simple model of film resistivity. The model also accounts for the exponential decrease of resistance observed during deposition of Pd nanoparticles onto Au island films. The results suggest the use of discontinuous Au island films as a sensitive way of controlling nanoparticle deposition.
Self-aligned flexible all-polymer transistor: Ultraviolet printing
Authors: Kang Hyewon , Kim Tae-il , Lee Hong H.
Published: November 2008

Flexible all-polymer transistor has received much attention because it is needed for the unique area of flexible circuits and displays, and the solution processing allowed with polymers would enable low-cost production. In this work, we introduce and utilize ultraviolet (UV) printing technique for the fabrication of flexible all-polymer transistor. The technique allows printing of submicron patterns of polymers without applying heat or pressure, requiring only UV light. The UV printing also allows self-aligned gate formation, which can be accomplished through a simple roll-to-roll printing. The electrical performance of the flexible transistor thus fabricated is better than that of the other flexible all-polymer transistors.
Fabrication of YBa2Cu3O7 thin film on cube-textured Cu tape
Authors: Tokudome Makoto , Doi Toshiya , Tomiyasu Ryota , Sato Shinya , Hakuraku Yoshinori , Kubota Shuichi , Shima Kunihiro , Kashima Naoji , Nagaya Shigeo
Published: November 2008

We achieved a biaxially oriented YBa2Cu3O7 film on a {100} ⟨001⟩ textured Cu tape with Jc of 1.9×106 A cm−2 at 77 K. A Ni overlayer was deposited by electroplating technique on the {100} ⟨001⟩ textured Cu tape to improve oxidation resistance of Cu substrate, and then YBa2Cu3O7 was deposited on the CeO2/YSZ/CeO2 buffered Ni-electroplated Cu tape. We confirmed that the Ni-electroplated Cu tape lost its ferromagnetism after 700 °C at 1 h heat treatment. Our rolling assisted biaxially textured substrate (RABiTS) type coated conductor can be used for ac applications and is thought to be more cost feasible than the standard RABiTS architecture using Ni-alloy tapes.
Electric-field induced modification of electronic properties of few-layer graphene nanoribbons
Authors: Huang Y. C. , Chang C. P. , Lin M. F.
Published: November 2008

In the presence of electric fields, the low-energy electronic properties of AB-stacked few-layer graphene nanoribbons are studied by using the tight-binding model. They are strongly dependent on the geometric structures (the interlayer interactions, the ribbon edges, the ribbon width Ny, and the ribbon number Nz) and the field strength. The interlayer interactions significantly affect density of states (DOS), energy gap (Eg), band structure, and free carriers. DOS exhibits many special structures including plateau, discontinuities, and divergent peaks. The effective electric field modifies the energy dispersions, alters the subband spacing, changes the subband curvature, produces the new edge state, switches the band gap, and causes the metal-semiconductor (or semiconductor-metal) transitions. In gapless zigzag ribbons, electric fields not only lifts the degeneracy of partial flatbands at EF but also induces an energy gap. Eg is dependent on the ribbon width, ribbon edges, and the field strength. The semiconductor-metal transitions occur in both armchair ribbons and zigzag ribbons in the increase in electric fields. Due to electric fields, the above-mentioned effects are completely reflected in the features of DOS, such as the generation of special structures, the shift of peak position, the change in peak height, and the alternation of band gap. The predicted electronic properties could be examined by the experimental measurements on absorption spectra and transport properties.
Vacancy generation during Cu diffusion in GaAs
Authors: Elsayed M. , Bondarenko V. , Petters K. , Gebauer J. , Krause-Rehberg R.
Published: November 2008

Positron lifetime and Doppler broadening spectroscopy were applied for a study of defect properties of semi-insulating GaAs after diffusion of copper. A 30 nm layer of Cu was deposited by evaporation to the undoped GaAs samples. The diffusion of Cu was performed during an annealing step at 1100 °C at different arsenic vapor pressures. The samples were quenched into room temperature water. The initial semi-insulating (SI) undoped GaAs sample shows no positron traps. After annealing, a vacancy-type complex and a shallow positron trap were observed to be efficient positron traps. Due to the Cu contamination during the annealing process, the shallow trap is believed to be the CuGa double acceptor. The nature of the vacancy-type defects could not be determined unambiguously. The concentration of these vacancies shows inverse relationship to the As vapor pressure that refers to the arsenic vacancy as a part of this complex. Moreover, Doppler-coincidence spectroscopy shows clearly that Cu atoms are not bound in the direct vicinity to the observed vacancies.
Influence of a bimodal eutectic structure on the plasticity of a (Ti70.5Fe29.5)91Sn9 ultrafine composite
Authors: Han J. H. , Kim K. B. , Yi S. , Park J. M. , Kim D. H. , Pauly S. , Eckert J.
Published: November 2008

Systematic investigations on the microstructural evolution of a bimodal eutectic (Ti70.5Fe29.5)91Sn9 ultrafine composite containing Ti3Sn dendrites upon compression reveal that local deformation of the dendrites dominates the early stage of deformation with a plastic strain of εp=5.8%. After further deformation (εp=10.2%), a wavy propagation of shear bands indicative of dissipation of the shear stress is caused by a rotation of the coarse eutectic structure along the interfaces of the bimodal eutectic structure.
Charge transport dynamics of polymer solar cells under operating conditions: Influence of trap filling
Authors: McNeill Christopher R. , Greenham Neil C.
Published: November 2008

The authors report time-of-flight measurements on photovoltaic blends of poly(3-hexylthiophene) and poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2′,2″-diyl) (F8TBT). Through the use of an additional illumination source to provide a background current density, the influence of the charge density and trap population on hole and electron dynamics is studied. For holes, little change in the transit time is observed with this background illumination, whereas for electrons, a clear electron transient is observed with background illumination that is not observed without. Under solar illumination the electron trap states are sufficiently populated such that charge transport in all-polymer blends may not be as unbalanced as previously thought.
Bloch-point-mediated magnetic antivortex core reversal triggered by sudden excitation of a suprathreshold spin-polarized current
Authors: Xing X. J. , Yu Y. P. , Wu S. X. , Xu L. M. , Li S. W.
Published: November 2008

We report on spin dynamics of single magnetic antivortices driven by sudden excitation of a spin-polarized direct current. Using micromagnetic simulations, we find that there is a critical current density where spin dynamics transition occurs. Above the critical value, the core is switched on a time scale of ∼200 ps through two Bloch points injection after fully suppressed by a quadruple-vortices array, not through the well-known process involving an antivortex-vortex pair creation and annihilation. As the current density decreases, the time required to switch the core increases. The state after full relaxation depends on the current density (the excitation parameter).
Exponential or Power Distance-Decay for Commuting? An Alternative Specification
Authors: de Vries Jacob J , Nijkamp Peter , Rietveld Piet
Published: November 2008

In this paper we investigate the functional form of distance decay for commuting flows between municipalities in Denmark. Our inference is based on a single equation that includes variables to capture the effect of spatial structure. Special attention is given to a proper estimation method: we estimate the distance-decay parameters by nonlinear weighted least-squares with balancing factors. It appears that neither an exponential nor a power distance-decay function fits the data well. Using a spline regression we find a cost elasticity of – 4 for distances around 20 km and a much smaller value for shorter and longer distances. It appears that the logarithm of distance decay can be described adequately as a (downward) logistic function of log cost.
Spatiotemporal Dimensions of Modal Accessibility Disparity in Boston and San Francisco
Authors: Kawabata Mizuki
Published: November 2008

The disparity of accessibility between cars and public transit provides important information about the degree of auto orientation in urban spatial structure. Using spatial data from 1990 and 2000 and a geographical information system, the present study examined the degrees and spatial variations of accessibility disparity between commuting by car and public transit as well as the temporal changes in this disparity in the metropolitan areas of Boston and San Francisco. In both metropolitan areas there was a considerable disparity in job accessibility in a comparison between users of cars and public transit, which turned out to differ substantially by location. Between 1990 and 2000 regional levels of this accessibility disparity lessened in the two metropolitan areas, but the temporal changes in the accessibility disparity varied considerably among different locations within the metropolitan areas. The accessibility disparity decreased in the majority of central areas and in a number of suburban zones near rail stations, whereas the accessibility disparity increased in a number of suburban zones near major highways. Improving accessibility for public transit, relative to that for cars, should be a key strategy for redressing auto-orientation urban spatial structure, an important objective of sustainable development.
Valuing the Cultural Monuments of Armenia: Bayesian Updating of Prior Beliefs in Contingent Valuation
Authors: Alberini Anna , Longo Alberto
Published: November 2008

The most appropriate way to measure the social benefits of conserving built cultural heritage sites is to ask the beneficiaries of conservation interventions how much they would be willing to pay for them. We use contingent valuation—a survey-based approach that elicits willingness to pay (WTP) directly from individuals—to estimate the benefits of a nationwide conservation of built cultural heritage sites in Armenia. The survey was administered to Armenian nationals living in Armenia, and obtained extensive information about the respondents' perceptions of the current state of conservation of monuments in Armenia, described the current situation, presented a hypothetical conservation program, elicited WTP for it, and queried individuals about what they thought would happen to monument sites in the absence of the government conservation program. We posit that respondents combined the information about the fate of monuments provided by the questionnaire with their prior beliefs, and that WTP for the good, or program, is likely to be affected by these updated beliefs. We propose a Bayesian updating model of prior beliefs, and empirically implement it with the data from our survey. We found that uncertainty about what would happen to monuments in the absence of the program results in lower WTP amounts.
Single-molecule FRET measures bends and kinks in DNA
Authors: Woźniak Anna K. , Schröder Gunnar F. , Grubmüller Helmut , Seidel Claus A. M. , Oesterhelt Filipp
Published: November 2008

We present advances in the use of single-molecule FRET measurements with flexibly linked dyes to derive full 3D structures of DNA constructs based on absolute distances. The resolution obtained by this single-molecule approach harbours the potential to study in detail also protein- or damage-induced DNA bending. If one is to generate a geometric structural model, distances between fixed positions are needed. These are usually not experimentally accessible because of unknown fluorophore-linker mobility effects that lead to a distribution of FRET efficiencies and distances. To solve this problem, we performed studies on DNA double-helices by systematically varying donor acceptor distances from 2 to 10 nm. Analysis of dye–dye quenching and fluorescence anisotropy measurements reveal slow positional and fast orientational fluorophore dynamics, that results in an isotropic average of the FRET efficiency. We use a nonlinear conversion function based on MD simulations that allows us to include this effect in the calculation of absolute FRET distances. To obtain unique structures, we performed a quantitative statistical analysis for the conformational search in full space based on triangulation, which uses the known helical nucleic acid features. Our higher accuracy allowed the detection of sequence-dependent DNA bending by 16°. For DNA with bulged adenosines, we also quantified the kink angles introduced by the insertion of 1, 3 and 5 bases to be 32° ± 6°, 56° ± 4° and 73 ± 2°, respectively. Moreover, the rotation angles and shifts of the helices were calculated to describe the relative orientation of the two arms in detail.