bluuebunny/crossref_metadata_2025 huggingface dataset:
Systematic misestimation in a vernier task arising from contrast mismatch
Authors: SUN HAO , LEE BARRY B. , BARAAS RIGMOR C.
Published: March 2008

Luminance signals mediated by the magnocellular (MC) pathway play an important role in vernier tasks. MC ganglion cells show a phase advance in their responses to sinusoidal stimuli with increasing contrast due to contrast gain control mechanisms. If the phase information in MC ganglion cell responses were utilized by central mechanisms in vernier tasks, one might expect systematic errors caused by the phase advance. This systematic error may contribute to the contrast paradox phenomenon, where vernier performance deteriorates, rather than improves, when only one of the target pair increases in contrast. Vernier psychometric functions for a pair of gratings of mismatched contrast were measured to seek such misestimation. In associated electrophysiological experiments, MC and parvocellular (PC) ganglion cells' responses to similar stimuli were measured to provide a physiological reference. The psychophysical experiments show that a high-contrast grating is perceived as phase advanced in the drift direction compared to a low-contrast grating, especially at a high drift rate (8 Hz). The size of the phase advance was comparable to that seen in MC cells under similar stimulus conditions. These results are consistent with the MC pathway supporting vernier performance with achromatic gratings. The shifts in vernier psychometric functions were negligible for pairs of chromatic gratings under the conditions tested here, consistent with the lack of phase advance both in responses of PC ganglion cells and in frequency-doubled chromatic responses of MC ganglion cells.
The representation of English articles in second language grammars: Determiners or adjectives?
Authors: TRENKIC DANIJELA
Published: March 2008

An article-choice study involving L1 Mandarin/L2 English bilinguals is reported. It tested two recent accounts on the representation of English articles in L2 grammars (where L1 has no articles). The Fluctuation Hypothesis (Ionin, Ko and Wexler, 2004) predicts that L2 speakers will have full access to UG, but will fluctuate between the settings of the postulated Article Choice Parameter; article choices will be influenced by [±specificity]. The syntactic misanalysis account, on which L2 articles are treated as adjectives (Trenkic, 2007), predicts that article choices will be influenced by the objective identifiability of referents. By discussing the notion of specificity and emphasising problems in its operationalisation, the current study introduces an innovative design to reveal that what was previously observed as the effect of specificity on L2 article choices (full UG access) is better described as an effect of the stated/denied familiarity with the referent (an extra-linguistic factor).
Strong and clitic pronouns in monolingual and bilingual acquisition of French and Italian
Authors: SCHMITZ KATRIN , MÜLLER NATASCHA
Published: March 2008

The present article investigates the acquisition of the pronominal systems by French and Italian monolingual children and by bilingual German–French and German–Italian children, demonstrating a stable asymmetry: object and reflexive clitics are acquired later than nominative clitics and strong subject and object pronouns. We will widen the scope of former investigations to include the acquisition of strong pronouns and argue that the observed asymmetry can be accounted for if we combine the external (categorial status) and internal syntax of pronouns (internal structure). In particular, we argue for the relevance of the absence/presence of a nominal layer (N-layer) in the internal structure of a pronoun. This approach can account for the observation that pronouns containing an N-layer, i.e., strong subject pronouns, subject clitics and strong object pronouns, are acquired simultaneously and earlier than pronouns which lack the N-layer, i.e., object clitics and reflexive clitics.
Bimodal bilingualism
Authors: EMMOREY KAREN , BORINSTEIN HELSA B. , THOMPSON ROBIN , GOLLAN TAMAR H.
Published: March 2008

Speech–sign or “bimodal” bilingualism is exceptional because distinct modalities allow for simultaneous production of two languages. We investigated the ramifications of this phenomenon for models of language production by eliciting language mixing from eleven hearing native users of American Sign Language (ASL) and English. Instead of switching between languages, bilinguals frequently produced code-blends (simultaneously produced English words and ASL signs). Code-blends resembled co-speech gesture with respect to synchronous vocal–manual timing and semantic equivalence. When ASL was the Matrix Language, no single-word code-blends were observed, suggesting stronger inhibition of English than ASL for these proficient bilinguals. We propose a model that accounts for similarities between co-speech gesture and code-blending and assumes interactions between ASL and English Formulators. The findings constrain language production models by demonstrating the possibility of simultaneously selecting two lexical representations (but not two propositions) for linguistic expression and by suggesting that lexical suppression is computationally more costly than lexical selection.
The development of two types of inhibitory control in monolingual and bilingual children
Authors: MARTIN-RHEE MICHELLE M. , BIALYSTOK ELLEN
Published: March 2008

Previous research has shown that bilingual children excel in tasks requiring inhibitory control to ignore a misleading perceptual cue. The present series of studies extends this finding by identifying the degree and type of inhibitory control for which bilingual children demonstrate this advantage. Study 1 replicated the earlier research by showing that bilingual children perform the Simon task more rapidly than monolinguals, but only on conditions in which the demands for inhibitory control were high. The next two studies compared performance on tasks that required inhibition of attention to a specific cue, like the Simon task, and inhibition of a habitual response, like the day–night Stroop task. In both studies, bilingual children maintained their advantage on tasks that require control of attention but showed no advantage on tasks that required inhibition of response. These results confine the bilingual advantage found previously to complex tasks requiring control over attention to competing cues (interference suppression) and not to tasks requiring control over competing responses (response inhibition).
Inter-lingual homograph letter detection in mixed language text: Persistent missing-letter effects and the effect of language switching
Authors: GREENBERG SETH N. , SAINT-AUBIN JEAN
Published: March 2008

Heretofore, we learned that bilinguals better detected letters in inter-lingual homographs when the context language ascribed a content role to the homograph as compared to a function role. In previous work the target homographs appeared in passages that were of a single language. The present work investigated whether this letter detection pattern would hold if both languages were activated by intermixing languages in a passage. Results suggested that despite intermixing of languages that would excite competing function and content meanings, local sentence context was sufficient to engender a content over function word advantage for inter-lingual homographs that was reminiscent of that obtained with homogenous text.
Modeling Collaborative and Individual Work Sequences to Improve Information Integration in Hidden Profile Tasks
Authors: Piontkowski Ursula , Keil Wolfgang , Hartmann Juliane
Published: March 2008

Information exchange and decision making on the group level require complex coordination, which often causes process losses. The present study proposes a sequential model of group task processing that integrates the approaches of Bales, Hollingshead, and McGrath, as well as Dennis and Valacich. It is designed to analyze how hidden profile tasks are processed and to guide information pooling and decision making on the individual and group levels. Further, an experiment was conducted to validate the assumptions of the model. Results show that the use of a group support system that implements a sequential structuring positively affected information exchange, information integration, and prediscussion preferences.
Morphology of Piton de la Fournaise basaltic shield volcano (La Réunion Island): Characterization and implication in the volcano evolution
Authors: Michon Laurent , Saint‐Ange Francky
Published: March 2008

The topography of Piton de la Fournaise volcano (PdF) differs from the classic view of basaltic shield volcanoes as it is characterized by (1) several steep slope zones on its flanks and (2) a large U‐shaped caldera, the Enclos‐Grand Brûlé structure (EGBS). Most of these structures were previously interpreted as the scars of lateral landslides, the deposits of which cover the submarine flanks of PdF. We carried out a detailed analysis of the morphology of PdF, which reveals that the steep slope zones form two independent, circumferential structures that continue into the caldera. The development of circumferential steep slopes on volcano flanks may have several origins: constructive, destructive, and deformation processes. We interpret those processes acting on PdF as caused by the spreading of the volcanic edifice above a weak hydrothermal core, leading to outward displacements and a summit extensive stress field. The continuity of the steep slope on both sides of the EGBS escarpments suggests that this structure was not caused by a 4.5 ka old giant landslide as it is usually proposed but is due to a mainly vertical collapse. The recent debris avalanche deposits east of the island indicate that this event likely destabilized part of the submarine flank. We propose that the collapse of the Grand Brûlé, the lower half of the EGBS, was due to the downward drag related to the dense intrusive complex of the Alizés volcano, which is located 1 km below the Grand Brûlé. The collapse of the Enclos is interpreted as the consequence of the deformation of the hydrothermal system of the pre‐Enclos volcano. Although the continuity of the geological and morphological structures between the Enclos and the Grand Brûlé suggests a narrow link between these two collapse events, their chronology and relationship are still uncertain. Finally, we hypothesize that the persistence of the NE and SE rift zones during the last 150 ka, despite the large changes of the topography related to the recurrent flank destabilizations, is linked to a deep sources, which can be either underlying crustal faults or the continuous downward subsidence of the Alizés intrusive complex.
Seeking sprite‐induced signatures in remotely sensed middle atmosphere NO2
Authors: Arnone E. , Kero A. , Dinelli B. M. , Enell C.‐F. , Arnold N. F. , Papandrea E. , Rodger Craig J. , Carlotti M. , Ridolfi M. , Turunen E.
Published: March 2008

The local chemical impact of sprites is investigated for the first time. This study is motivated by the current understanding of the streamer nature of sprites: streamers are known to produce NOx, thus sprites are expected to lead to a local enhancement of the background abundances, and possibly impact ozone. We adopted the following strategy: middle atmosphere MIPAS/GMTR NO2 satellite measurements were correlated with ground‐based WWLLN detections of large tropospheric thunderstorms as a proxy for sprite activity. We found no evidence of any significant impact at a global scale, but an indication of a possible sprite induced NO2 enhancement of about 10% at 52 km height in correspondence with active thunderstorms. This local enhancement appears to increase with height from a few percent at 47 km to tens of percent at 60 km.
Impact of dense shelf water cascading on the transfer of organic matter to the deep western Mediterranean basin
Authors: Sanchez‐Vidal A. , Pasqual C. , Kerhervé P. , Calafat A. , Heussner S. , Palanques A. , Durrieu de Madron X. , Canals M. , Puig P.
Published: March 2008

During winter 2005–2006, particle fluxes and near‐bottom currents were measured in and around the Lacaze‐Duthiers and Cap de Creus submarine canyons (western Gulf of Lion). Current anomalies show the occurrence of a major dense shelf water cascading event down to the slope, the latest recorded up to date in the area. Concomitant increased total mass fluxes highlight the ability of cascading waters to transport large amounts of coarse sediment and organic matter, which is predominantly of terrestrial origin. In addition, results reveal that the current regime and associated grain size sorting is the responsible for a geochemical gradient of settling organic particles along the slope.
Measurements of organic trace gases including oxygenated volatile organic compounds at the high alpine site Jungfraujoch (Switzerland): Seasonal variation and source allocations
Authors: Legreid Geir , Folini Doris , Staehelin Johannes , Balzani Lööv Jacob , Steinbacher Martin , Reimann Stefan
Published: March 2008

At the high alpine site Jungfraujoch (Switzerland) mixing ratios of 21 oxygenated volatile organic compounds (OVOCs) and selected nonmethane hydrocarbons (NMHCs) have been measured by a newly developed two‐stage double adsorbent system coupled to a gas chromatograph–mass spectrometer (GC–MS). In addition, formaldehyde was measured by the Hantzsch technique. Four measurement campaigns were performed once every season in 2005, providing for the first time a unique data set of OVOCs in the free troposphere of central Europe. The dominating OVOCs measured were acetone, methanol, formaldehyde and acetaldehyde, with mean mixing ratios of 622–867 ppt, 362–790 ppt, 303–505 ppt and 310–392 ppt, respectively. These compounds explained 95% of the measured organic compounds in summer and 83% in fall. Elevated mixing ratios in summer were observed for compounds with strong biogenic sources (e.g., methanol and acetone), whereas mainly anthropogenic compounds (e.g., ethanol and benzene) had higher mixing ratios during winter. Potential European source regions were estimated for the organic trace gases by combining the measured data with a statistical trajectory model. Northern Italy, southern France and southern and eastern Germany were identified as the main European contributors to the measured organic compounds at Jungfraujoch.
Multi‐model decadal potential predictability of precipitation and temperature
Authors: Boer G. J. , Lambert S. J.
Published: March 2008

A first multi‐model estimate of the long timescale potential predictability of precipitation is obtained based on over 8000 years of data from the control simulations of 21 state‐of‐the‐art coupled climate models. The analysis also updates earlier estimates of the potential predictability of temperature to provide a consistent estimate for these basic climate parameters. Long timescale potential predictability is found mainly over the oceans at middle to high latitudes and predominantly where the surface is connected to the deeper ocean. Precipitation's modest potential predictability resembles an attenuated version of that for temperature on these timescales. Over land, predictability is largely absent for precipitation and comparatively weak for temperature where it is found over the northern and western parts of northern hemisphere land masses bordering the oceans. Regions exhibiting potential predictability indicate where we may hope to find predictive skill at long timescales and also points indirectly to the processes involved.
Vibrio cholerae and Aeromonas: do they share a mutual host?
Authors: Senderovich Yigal , Gershtein Yana , Halewa Etti , Halpern Malka
Published: March 2008

Species of the genus Aeromonas are native inhabitants of aquatic environments and have recently been considered as an emergent human pathogen. It is estimated that aeromonads cause up to 13% of reported gastroenteritis cases in the United States. Although the autochthonous existence of Aeromonas in the aquatic environment has been established, its natural reservoir is as yet unknown. Chironomids are closely related to mosquitoes except they do not bite and they are the most widely distributed insects in freshwater. They infest drinking water systems in Israel and all over the world. Vibrio cholerae inhabit chironomids and are able to degrade their egg masses. The degradation of the egg masses is followed by failure of the eggs to hatch. In the current study, egg masses from a waste stabilization pond and a river in northern Israel were collected and cultured during a five-month period. Bacterial colonies were randomly chosen and checked for their egg mass degradation abilities. In addition to V. cholerae, most of the other isolates that had the ability to degrade the egg masses were identified as Aeromonas species, thus, demonstrating that Aeromonas species are natural inhabitants of chironomid egg masses. The following virulence-associated genes were detected in Aeromonas species that were isolated from chironomid egg masses: alt (78%); ahpB (76%); act/aerA/hlyA (65%); fla (59%); pla/lipH3/apl-1/lip (43%); and ast (2%). These findings indicate that the Aeromonas species inhabiting chironomid egg masses pose a potential health risk. Understanding the natural reservoir of Aeromonas will help to develop methods to monitor and control the bacteria in fresh and drinking water reservoirs and to better understand the relationships between chironomids, V. cholerae and Aeromonas populations.
Pricing Strategies of Originator and Generic Medicines following Patent Expiry in Belgium
Authors: Adriaen Michael , De Witte Kristof , Simoens Steven
Published: March 2008

There is little European evidence on how originator and generic medicines set prices in the off-patent market and on the factors that influence pricing strategies. The aim of this study was to examine pricing strategies of originator and generic medicines following patent expiry in Belgium. To this effect, the evolution of the public price of originator and generic medicines was investigated from July 2001 to December 2005. Regression and scenario analyses show that the Belgian off-patent market is a segmented market when it comes to pricing. Pricing strategies are influenced by regulatory aspects, such as successive reductions in reference prices and prescription status of medicines; by market incentives in the form of price competition between generic medicines and competition between originator and generic medicines; by medication class; and by market power of the manufacturer of the originator medicine. Therefore, there is no single pricing strategy that authorities or manufacturers can use to predict the pricing behaviour of originator and generic medicines following patent expiry and to foresee the development of the generic medicines market.
Recommended Liquid-Liquid Equilibrium Data. Part 5. Ether-Water Systems
Authors: Góral Marian , Mączyński Andrzej , Oracz Paweł
Published: March 2008

Recommended liquid-liquid equilibrium (LLE) data for 12 binary ether-water systems have been obtained after the critical evaluation of all data (168 data sets) reported for 17 systems in the open literature up to the end of 2006. An equation for the prediction of the ether solubilities in water was developed. The predicted ether solubilities were used for the calculation of water solubility in the ether-rich phase. The LLE calculations were done with the equation of state appended with a chemical term (EoSC) proposed by Góral [Fluid Phase Equilib. 118, 27 (1996)]. The recommended data are presented in the form of individual tables with references. Using these recommended data, predictive ability has been tested for several UNIFAC and ASOG group-contribution methods.
Tangential magnetic field at the surface of pot core transformers
Authors: Namjoshi K. V. , Lavers J. D. , Sadeghian A.
Published: March 2008

This paper presents an analytical approach using simplified expressions whereby the tangential component of the magnetic field at the surface of pot core transformers can be quickly estimated. Knowledge of the tangential field can be used to estimate the core loss, which is an important consideration in the design of transformers used at high frequency. Influence of parameters such as winding length is considered. Results both for gapped and ungapped pot cores are in agreement with those obtained using an accurate numerical method.
Electronic structure of cluster assembled nanostructured TiO2 by resonant photoemission at the Ti L2,3 edge
Authors: Caruso T. , Lenardi C. , Agostino R. G. , Amati M. , Bongiorno G. , Mazza T. , Policicchio A. , Formoso V. , Maccallini E. , Colavita E. , Chiarello G. , Finetti P. , Šutara F. , Skála T. , Piseri P. , Prince K. C. , Milani P.
Published: March 2008

The electronic structure of cluster assembled nanostructured TiO2 thin films has been investigated by resonant photoemission experiments with photon energies across the Ti L2,3 edge. The samples were produced by supersonic cluster beam deposition with a pulsed microplasma cluster source. The valence band shows resonance enhancements in the binding energy region between 4 and 8eV, populated by O 2p and hybridized Ti 3d states, and in the region about 1eV below the Fermi level associated with defects related Ti 3d states. The data show that in as-deposited films Ti atoms are mainly fully (sixfolds) coordinated to oxygen atoms in octahedral symmetry and only a small fraction is in a broken symmetry environment. Since resonant photoemission is closely linked to the local electronic and structural configurations around the Ti atom, it is possible to correlate the resonant photoemission intensity and lineshape with the presence of defects of the films and with the degree of hybridization between the titanium and oxygen atoms.
X-ray magnetic circular dichroism in d and f ferromagnetic materials: recent theoretical progress. Part II (Review Article)
Authors: Antonov V. N. , Shpak A. P. , Yaresko A. N.
Published: March 2008

The present state of theoretical understanding of the x-ray magnetic circular dichroism (XMCD) of 4f and 5f compounds is reviewed. Energy band theory based upon the local spin-density approximation (LSDA) describes the XMCD spectra of transition metal compounds with high accuracy. However, the LSDA does not suffice for lanthanide compounds which have a correlated 4f shell. A satisfactory description of the XMCD spectra could be obtained by using a generalization of the LSDA, in which explicitly f electron Coulomb correlations are taken into account (LSDA+U approach). As examples of this group we consider the compound GdN. We also consider uranium 5f compounds. In those compounds where the 5f electrons are rather delocalized, the LSDA describes the XMCD spectra reasonably well. As an example of this group we consider UFe2. Particular differences occur for uranium compounds in which the 5f electrons are neither delocalized nor localized, but more or less semilocalized. Typical examples are UXAl (X=Co, Rh, and Pt), and UX (X=S, Se, Te). However, the semilocalized 5f’s are not inert, but their interaction with conduction electrons plays an important role. We also consider the electronic structure and XMCD spectra of the heavy-fermion compounds UPt3, URu2Si2, UPd2Al3, UNi2Al3, and UBe13, where the degree of the 5f localization is increased in comparison with other uranium compounds. The electronic structure and XMCD spectra of UGe2 which possesses simultaneously ferromagnetism and superconductivity also presented. Recently achieved improvements for describing 5f compounds are discussed.
Design considerations of electromagnetic force in a direct drive permanent magnet brushless motor
Authors: Chen H. S. , Tsai M. C.
Published: March 2008

In this paper, a numerical study of electromagnetic force associated with the width of stator teeth, width of rotor back iron, and slot opening for a ten-pole nine-slot direct drive permanent magnet brushless motor is presented. The study calculates the amplitude of the electromagnetic force on the rotating rotor by using the finite-element method. The results show that the amplitude of electromagnetic force, which may cause the noise and vibration of motors, changes with the variation of these above mentioned three factors. The relationship between the considerations of output torque and the minimization of noise and vibration is also established in this paper.
Electron transport across the two-dimensional-electron gas in InSb heterostructure under the influence of a vertical magnetic field and a parabolic potential
Authors: Wan F. , Jalil M. B. A. , Tan S. G. , Fujita T.
Published: March 2008

The electron transport properties are studied in a two-dimensional-electron gas in InSb heterostructure with a transverse parabolic potential well, and under the influence of a uniform external magnetic (B) field. The Schrödinger equation is solved and the resulting Landau-like eigenstates are described by Hermitian functions. The resulting transmission and spin polarization of the device is strongly dependent on the potential well width, the Landau level index, and the strength of applied magnetic field. It is found that the device is capable of achieving almost perfect spin polarization of 100% due to the distinct spin-split in the transmission threshold. For large B fields, the transmission and spin polarization profiles show distinct resonantlike behavior.
Electronic and magnetic properties of Heusler alloy Co2MnSi epitaxial ultrathin films facing a MgO barrier studied by x-ray magnetic circular dichroism
Authors: Saito Toshiaki , Katayama Toshikazu , Emura Ai , Sumida Noa , Matsuoka Nanae , Ishikawa Takayuki , Uemura Tetsuya , Yamamoto Masafumi , Asakura Daisuke , Koide Tsuneharu
Published: March 2008

The electronic and magnetic states of an epitaxially grown full-Heusler alloy Co2MnSi (CMS) 1.1nm (4 ML) thick ultrathin film and a CMS 50-nm-thick film both facing an epitaxial MgO(001) tunnel barrier were element-specifically studied by means of x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD). The observed XAS and XMCD spectra revealed that both the CMS films were not oxidized. The Co and Mn spin magnetic moments for the 4 ML thick CMS film obtained by applying the sum rules were close to those for the 50-nm-thick one and the theoretical values for bulk CMS with the L21 structure. These results indicate that 4 ML thick CMS ultrathin films facing a MgO barrier still retain the electronic and magnetic states for the L21 structure.
Electronic properties of homoepitaxial (111) highly boron-doped diamond films
Authors: Ye Haitao , Tumilty Niall , Bevilacqua Mose , Curat Stephane , Nesladek Milos , Bazin Bertrand , Bergonzo Philippe , Jackman Richard B
Published: March 2008

The use of diamond as a semiconductor for the realization of transistor structures, which can operate at high temperatures (>700 K), is of increasing interest. In terms of bipolar devices, the growth of n-type phosphorus doped diamond is more efficient on the (111) growth plane; p-type boron-doped diamond growth has been most usually grown in the (100) direction and, hence, this study into the electronic properties, at high temperatures, of boron-doped diamond (111) homoepitaxial layers. It is shown that highly doped layers (hole carrier concentrations as high as 2×1020 cm−3) can be produced without promoting the onset of (unwanted) hopping conduction. The persistence of valance-band conduction in these films enables relatively high mobility values to be measured (∼20 cm2/V s) and, intriguingly, these values are not significantly reduced at high temperatures. The layers also display very low compensation levels, a fact that may explain the high mobility values since compensation is required for hopping conduction. The results are discussed in terms of the potential of these types of layers for use with high temperature compatible diamond transistors.
Spatially localized states in natural doubly diffusive convection
Authors: Bergeon A. , Knobloch E.
Published: March 2008

Numerical continuation is used to compute a multiplicity of stable spatially localized steady states in doubly diffusive convection in a vertical slot driven by imposed horizontal temperature and concentration gradients. The calculations focus on the so-called opposing case, in which the imposed horizontal thermal and solutal gradients are in balance. No-slip boundary conditions are used at the sides; periodic boundary conditions with large spatial period are used in the vertical direction. The results demonstrate the presence of homoclinic snaking in this system, and can be interpreted in terms of a pinning region in parameter space. The dynamics outside of this region are studied using direct numerical simulation.
Interpreting viscosity isotherms in materials with significant structural disorder
Authors: Viddal C. A. , Roshko R. M.
Published: March 2008

Numerical simulations of viscosity isotherms are presented for a model system with substantial structural disorder. The system consists of an ensemble of metastable two-level subsystems, characterized individually by an elementary activation moment μ and a double well potential with a dissipation barrier Wd=μHd and a level splitting Ws=2μHs, and collectively by a distribution of equivalent fields p(Hd,Hs)=(2πσd2Hd2)−1∕2exp{−[ln(Hd∕Hdm)]2∕2σd2}×(2πσs2)−1∕2exp(−Hs2∕2σs2). The disorder is modeled with broad dispersions σd=σs∕Hdm=1.0. Under these conditions, a typical experimental observation window 10s⩽t⩽104s reveals only a short quasilogarithmic fragment of the complete relaxation isotherm. In the current investigation, we present a prescription for evaluating the thermal fluctuation field Hf=kT∕μ based on a plot of Tln(tr∕τ0) versus Ha, where tr is the “reversal time” at which an isotherm changes sign (or passes through m=0), and we discuss the merits of this approach with respect to scaling strategies.
Magnetic interaction in nanometer line width elliptical ring arrays
Authors: Chang L. J. , Yu C. , Chiang T. W. , Cheng K. W. , Chiu W. T. , Lee S. F. , Liou Y. , Yao Y. D.
Published: March 2008

Magnetic interactions between permalloy elliptical rings in different arrangements of two-dimensional arrays were investigated. The edge-to-edge distances between units along the long axis were changed from 2μm down to 100nm. Formation of domain walls during magnetization reversals results in magnetostatic coupling between adjacent units. When two neighboring rows were shifted one-half pitch along the short axis to form a shift-type array, large stable field range for vortex states was obtained.
Thermal emittance and response time measurements of negative electron affinity photocathodes
Authors: Bazarov Ivan V. , Dunham Bruce M. , Li Yulin , Liu Xianghong , Ouzounov Dimitre G. , Sinclair Charles K. , Hannon Fay , Miyajima Tsukasa
Published: March 2008

The thermal emittance and temporal response of a photocathode set an upper limit on the maximum achievable electron beam brightness from a photoemission electron source, or photoinjector. We present measurements of these parameters over a broad range of laser wavelength for two different negative electron affinity (NEA) photocathodes. The thermal emittance of NEA GaAs and GaAsP has been measured by two techniques—a measurement of the beam size downstream from a solenoid, whose strength was varied, and a double slit transmission measurement—for different laser spot sizes and shapes. The effect of space charge on the beam spot size allows a good estimation of the photoemission response time from these cathodes. Both cathodes show a subpicosecond response for laser wavelengths shorter than 520 nm.
Femtosecond carrier dynamics in electron-beam-irradiated C60 film
Authors: Toda Y. , Ryuzaki S. , Onoe J.
Published: March 2008

Time-resolved temperature-dependent transmission changes were measured for both pristine C60 and electron-beam-irradiated C60 polymer films using an optical pump-probe technique. Only the signals obtained for the C60 polymer show a temperature-dependent slow decay, which appears in the low temperature region below ∼60K. This slow decay component exhibits a monotonic increase in both relaxation time and amplitude with decreasing temperature, providing evidence of gap formation associated with ordering fluctuations.
Mn–Zn ferrites for magnetic sensor in space applications
Authors: Lebourgeois R. , Coillot C.
Published: March 2008

We describe the optimization of Mn–Zn ferrites having a high permeability between −50 and +150°C. These ferrites are intended to be integrated into a magnetic field sensor for space mission. The chemical composition Mnx2+Zny2+Fe0.052+Ti0.014+Fe23+O4 was investigated by varying the Mn∕Zn ratio. The magnetic characterizations revealed that the initial permeability was increased for high Zn content while the Curie temperature was decreased. A local maximum of the permeability was observed at a specific temperature meaning, the magnetocrystalline anisotropy K1 became zero. The temperature T0 at which K1 was canceled (compensation temperature) depends on the chemical composition just like the Curie temperature TC: the higher the zinc content, the lower T0 and TC. The best compromise was obtained for a ferrite formulation with a Mn∕Zn ratio around 1.8 and with a small titanium oxide addition. Permeability higher than 2400 was obtained between −50 and +150°C and up to 500kHz. The use of ferrite core with the best formulation and shape will allow to measure magnetic field as low as 50fT∕√Hz on a wide frequency range, from 300Hz up to 200kHz.
Origin of the dependence of magnetoresistance on the composition of Co100−xFex electrodes in magnetic tunnel junctions
Authors: Yang J. Joshua , Bengtson A. K. , Ji C.-X. , Morgan D. , Chang Y. A.
Published: March 2008

The tunneling magnetoresistance value of a Co100−xFex (4nm)∕AlOx 1.7nm∕Co100−xFex (4nm) magnetic tunnel junction has been demonstrated to depend on the composition of the Co100−xFex electrodes. The interface roughness, crystal structure, and tunneling spin polarization versus the composition of the Co100−xFex electrode were studied to address the origin of this compositional dependence. Ab initio calculations of s-like electron spin polarization predict a composition dependence similar to that observed experimentally. The combined experimental and computational results show that the trends in Co100−xFex tunneling magnetoresistance are modified slightly by the interface roughness but mainly determined by the s-like electron spin polarization values associated with different compositions and crystal structures.
Evolution of isolated turbulent trailing vortices
Authors: Duraisamy Karthik , Lele Sanjiva K.
Published: March 2008

In this work, the temporal evolution of a low swirl-number turbulent Batchelor vortex is studied using pseudospectral direct numerical simulations. The solution of the governing equations in the vorticity-velocity form allows for accurate application of boundary conditions. The physics of the evolution is investigated with an emphasis on the mechanisms that influence the transport of axial and angular momentum. Excitation of normal mode instabilities gives rise to coherent large scale helical structures inside the vortical core. The radial growth of these helical structures and the action of axial shear and differential rotation results in the creation of a polarized vortex layer. This vortex layer evolves into a series of hairpin-shaped structures that subsequently breakdown into elongated fine scale vortices. Ultimately, the radially outward propagation of these structures results in the relaxation of the flow towards a stable high-swirl configuration. Two conserved quantities, based on the deviation from the laminar solution, are derived and these prove to be useful in characterizing the polarized vortex layer and enhancing the understanding of the transport process. The generation and evolution of the Reynolds stresses is also addressed.
Improving spatial resolution and reducing aspect ratio in multiphoton polymerization nanofabrication
Authors: Dong Xian-Zi , Zhao Zhen-Sheng , Duan Xuan-Ming
Published: March 2008

The authors investigate the phenomena affecting lateral spatial resolution (LSR) and aspect ratio (AR) in multiphoton polymerization (MPP) nanofabrication. A LSR of 50nm and an AR of 1.38 were achieved for photocured polymer lines on the surface of a substrate by continuing scanning mode. Theoretical analysis based on the distribution of light intensity in this setup indicates that the LSR could be improved to better than 20nm. The asymmetric shrinkage of voxel in the axial and lateral directions has a significant impact for obtaining features of low AR, which are a critical requirement for construction of micro/nanodevices by MPP nanofabrication.
High-performance metal oxide nanowire chemical sensors with integrated micromachined hotplates
Authors: Ryu Koungmin , Zhang Daihua , Zhou Chongwu
Published: March 2008

We demonstrate the fast and scalable integration of nanowire chemical sensors with micromachined hotplates built on SiN membranes. These hotplates allowed nanowire chemical sensors to operate at elevated temperatures in order to enhance the sensitivity of chemical sensors to target gases. By applying different currents through the platinum heating filament, we can easily vary the device temperature from room temperature to 350°C. These nanosensors with integrated hot plates have been exploited for the detection of ethanol, CO, and hydrogen down to concentrations of 1, 10, and 50ppm, respectively.
Volume measurement of cryogenic deuterium pellets by Bayesian analysis of single shadowgraphy images
Authors: Szepesi T. , Kálvin S. , Kocsis G. , Lang P. T. , Wittmann C.
Published: March 2008

In situ commissioning of the Blower-gun injector for launching cryogenic deuterium pellets at ASDEX Upgrade tokamak was performed. This injector is designed for high repetitive launch of small pellets for edge localised modes pacing experiments. During the investigation the final injection geometry was simulated with pellets passing to the torus through a 5.5m long guiding tube. For investigation of pellet quality at launch and after tube passage laser flash camera shadowgraphy diagnostic units before and after the tube were installed. As indicator of pellet quality we adopted the pellet mass represented by the volume of the main remaining pellet fragment. Since only two-dimensional (2D) shadow images were obtained, a reconstruction of the full three-dimensional pellet body had to be performed. For this the image was first converted into a 1-bit version prescribing an exact 2D contour. From this contour the expected value of the volume was calculated by Bayesian analysis taking into account the likely cylindrical shape of the pellet. Under appropriate injection conditions sound pellets with more than half of their nominal mass are detected after acceleration; the passage causes in average an additional loss of about 40% to the launched mass. Analyzing pellets arriving at tube exit allowed for deriving the injector’s optimized operational conditions. For these more than 90% of the pellets were arriving with sound quality when operating in the frequency range 5–50Hz.
Accurate miscut angle determination for spherically bent Bragg crystals
Authors: Covita D. S. , Ay M. , Schlesser S. , Gotta D. , Simons L. M. , Le Bigot E.-O. , dos Santos J. M. F.
Published: March 2008

Spherically bent crystals are used as analyzers in high-resolution spectroscopy, in particular, in low count-rate applications such as exotic-atom research. The focal conditions are determined not only by the bending radius and the Bragg angle but also by the crystal cut angle between its surface and the reflecting crystal planes, along with their orientation with respect to the direction of dispersion. We describe a simple but precise method for measuring the cut angle and its orientation for mounted spherically bent crystals, by combining x-ray diffraction and laser optical alignment, which can be easily performed with standard x-ray laboratory equipment.
Routh’s procedure for non-Abelian symmetry groups
Authors: Crampin M. , Mestdag T.
Published: March 2008

We extend Routh’s reduction procedure to an arbitrary Lagrangian system (that is, one whose Lagrangian is not necessarily the difference of kinetic and potential energies) with a symmetry group which is not necessarily Abelian. To do so, we analyze the restriction of the Euler–Lagrange field to a level set of momentum in velocity phase space. We present a new method of analysis based on the use of quasivelocities. We discuss the reconstruction of solutions of the full Euler–Lagrange equations from those of the reduced equations.
Effects of residual impurities in electroplated Cu on the Kirkendall void formation during soldering
Authors: Kim J. Y. , Yu Jin
Published: March 2008

Additions of bis-(sodium sulfopropyl)-disulfide (SPS) to the Cu electroplating bath strongly affected the characteristics of Kirkendall void formation when the Cu film is soldered with Sn–3.5Ag solder and subsequently aged. Voids were predominantly distributed near the Cu3Sn∕Cu interface with SPS, but randomly distributed in the Cu3Sn layer without SPS. In situ Auger electron spectroscopy of voids at the Cu3Sn∕Cu interface revealed surface segregation of S atoms, which came from SPS put into the bath as an additive. The S segregation to Cu3Sn∕Cu interface lowers the interface energy, thereby accelerating the void nucleation. Assisted by the high surface diffusivity of Cu and the presence of excess vacancies arising from the Kirkendall effect, voids tend to localize at the interface, which would result in serious degradation of the joint reliability.
Theoretical investigation on force sensitivity in Q-controlled phase-modulation atomic force microscopy in constant-amplitude mode
Authors: Kobayashi Naritaka , Li Yan Jun , Naitoh Yoshitaka , Kageshima Masami , Sugawara Yasuhiro
Published: March 2008

We theoretically investigate the force sensitivity of phase-modulation atomic force microscopy in the constant amplitude mode with Q-control technique, which enables to increase or decrease the effective Q factor (Qeff) of the cantilever. The relation between the minimum detectable interaction force and the effective Q factor is derived from the equation of motion for the cantilever at low Q environment such as liquid environment. It indicates that the minimum detectable interaction force can be reduced in proportion to Qeff1∕2 under strong Q enhancement, while it does not depend on the effective Q factor under weak Q enhancement.
Optically tuned resonant optical reflectance filter
Authors: Yang Fuchyi , Yen Gary , Rasigade Gilles , Soares Julio A. N. T. , Cunningham Brian T.
Published: March 2008

We describe the design, fabrication, and characterization of a narrow band tunable guided mode resonance (GMR) reflectance filter that is actuated by optically induced trans-cis isomerization of an azobenzene liquid crystal. Constructing a plastic replica-molded containment cell with a rubbed polyimide film to initially direct the liquid crystal molecular orientation parallel to the grating lines of the GMR filter, isomerization caused by exposure to a λ=532nm laser results in a −25nm shift of the resonant reflected wavelength.
Birefringence of β-BaB2O4 crystal in the terahertz region for parametric device design
Authors: Estacio Elmer , Saito Shigeki , Nakazato Tomoharu , Furukawa Yusuke , Sarukura Nobuhiko , Cadatal Marilou , Pham Minh Hong , Ponseca Carlito , Mizuseki Hiroshi , Kawazoe Yoshiyuki
Published: March 2008

β - Ba B 2 O 4 (BBO) was found to have huge birefringence in the 0.1–1.1THz frequency region. Polarized terahertz transmission spectroscopy revealed a Δn∕n value of about 0.12±0.02. This result could be related to a polarization-dependent absorption that was observed at about 0.65THz; in close agreement with first principles-calculations, showing this to be due to low-frequency phonon modes of the [B3O6]3-rings. These findings suggest the utilization of the birefringent properties of BBO for optical parametric devices including amplifiers and oscillators, operating in the terahertz regime.
Large room-temperature inverse magnetoresistance in tunnel junctions with a Fe3O4 electrode
Authors: Kado T.
Published: March 2008

Magnetic tunnel junctions (MTJs) consisting of Fe3O4 and three-dimensional ferromagnetic metal electrodes with MgO or MgO∕Al2O3 as a barrier layer have been fabricated. Fe3O4∕MgO(5nm)∕Al2O3(1nm)∕CoFe MTJs had room-temperature (RT) magnetoresistance (MR) ratios ranging from −26% to 18%, and Fe3O4∕MgO(6nm)∕CoFe MTJs with a mildly heat-treated Fe3O4∕MgO interface had only inverse tunneling MR ratios that were as large as −8% at RT. The sign of the MR ratio changed when the absolute value of the bias voltage V was about 1V, and normal MR was evident when ∣V∣>1V because the nontunneling current was dominant.
Electro-optical response of ion-irradiated 4H-SiC Schottky ultraviolet photodetectors
Authors: Sciuto Antonella , Roccaforte Fabrizio , Raineri Vito
Published: March 2008

Visible blind 4H-SiC UV detectors were investigated with respect to radiation hardness since they can find applications in the aerospace field. Effects of ion irradiation on their response were studied by monitoring the spectral response as a function of irradiation beam energy and dose. The devices irradiated by 1, 4, and 10MeV Si+-ion beam show a change of the response depending on the ion irradiation energy. The unexpected huge optical effect, compared to the negligible influence on reverse bias leakage current, was correlated to the nature of irradiation induced damage and to its location inside the optical active device layer.
Cone kinetics model for two-phase film silicon deposition
Authors: Teplin Charles W. , Jiang C.-S. , Stradins Paul , Branz Howard M.
Published: March 2008

We study quantitatively the morphology of nanocrystalline silicon (nc-Si:H) cones that appear during amorphous silicon (a-Si:H) film growth by chemical vapor deposition from hydrogen-diluted silane. The shapes of the nc-Si:H inclusions are found to be spherical cones, consistent with our “cone kinetics” model for silicon film growth. This model predicts cone development when growth is isotropic and there is sparse nucleation of a second material phase with a higher growth rate. Application of the cone kinetics model provides insights into the deposition of technologically important thin film materials, including protocrystalline silicon, highly P-doped nc-Si:H, silicon heterojunctions, and silicon epitaxy.