bluuebunny/crossref_metadata_2025 huggingface dataset:
Rotational excitation of sulfur monoxide by collisions with helium at low temperature
Authors: Lique F. , Spielfiedel A. , Dubernet M.-L. , Feautrier N.
Published: September 2005

We present two new two-dimensional potential-energy surfaces for the SO–He system calculated at SO r distance frozen at its experimental minimum-energy distance. Both are obtained at the RCCSD(T) level using two different basis sets (AVTZ and AVQZ) for the three atoms. Bond functions are placed at mid-distance between the SO center of mass and He for a better description of the van der Waals well. Close-coupling calculations of the collisional excitation cross sections of the fine-structure levels of SO by He are calculated at low energies. The exact level splitting is taken into account. It is found that the results obtained from the two surfaces are very similar, except for some small differences observed in the region of resonances at low energies. The propensity rules between fine-structure levels are studied, it is shown that F-conserving cross sections are much larger for high-N rotational levels than cross sections between F-changing levels, as expected from theoretical considerations. The use of infinite order sudden recoupling techniques from spin-free cross sections is investigated. Excitation rate coefficients among fine-structure levels are calculated at low temperatures.
Transition pathways in complex systems: Application of the finite-temperature string method to the alanine dipeptide
Authors: Ren Weiqing , Vanden-Eijnden Eric , Maragakis Paul , E Weinan
Published: September 2005

The finite-temperature string method proposed by E, et al. [W. E, W. Ren, and E. Vanden-Eijnden, Phys. Rev. B 66, 052301 (2002)] is a very effective way of identifying transition mechanisms and transition rates between metastable states in systems with complex energy landscapes. In this paper, we discuss the theoretical background and algorithmic details of the finite-temperature string method, as well as the application to the study of isomerization reaction of the alanine dipeptide, both in vacuum and in explicit solvent. We demonstrate that the method allows us to identify directly the isocommittor surfaces, which are approximated by hyperplanes, in the region of configuration space where the most probable transition trajectories are concentrated. These results are verified subsequently by computing directly the committor distribution on the hyperplanes that define the transition state region.
Calculation of the birefringences of nematic liquid crystals at optical and infrared wavelengths
Authors: Simpson S. H. , Richardson R. M. , Hanna S.
Published: September 2005

In this paper we critically examine computational methods for predicting the birefringences of nematic liquid crystals, with a view to screening molecules for potential use in infrared applications. Using the liquid-crystal 5CB as a test molecule, we calculate molecular electronic polarizabilities using ab initio quantum-mechanical techniques and a wide range of basis sets. We show that the polarizabilities tend to a limiting value as the quality of the basis set is improved. However, the biggest hurdle remains the determination of the refractive index from the polarizability data. We examine several methods for performing this conversion and conclude that the simplest equation, due to Vuks, is adequate for predicting the birefringence, given the uncertainties involved in other parameters. The agreement between calculation and experiment is best described as “semiquantitative.” We perform similar calculations for a wide range of nematic liquid crystals at both 589 and 1550nm, taking into account the likely impact of molecular vibrations at the longer wavelength. We demonstrate that there is a simple scale factor, for conventional nematics, between the birefringence at visible wavelengths and in the infrared. Thus knowledge of the birefringence at optical wavelengths, as widely available in the literature, is a good guide to the usefulness of conventional nematic liquid crystals as active elements for optical switching in the telecommunications industry.
Infrared spectroscopic study of polytypic effects on the crystal-growth mechanism of n-hexatriacontane (n-C36H74)
Authors: Kubota Hideki , Kaneko Fumitoshi , Kawaguchi Tatsuya , Kawasaki Masatsugu
Published: September 2005

The solution-crystallization mechanism was investigated for two polytypes in the M011 modification of n-hexatriacontane (n-C36H74), single-layered structure Mon, and double-layered one Orth II. The crystal growth under controlled supersaturation was followed with a micro- Fourier-transform-infrared spectrometer equipped with an optical system for oblique transmission measurements. Supersaturation dependence of growth behavior was significantly different between Mon and Orth II. Although the Mon crystal continued growing at a supersaturation of 0.27, the overgrowth of Orth II on the (001) face of the Mon crystal was confirmed at supersaturations below 0.21. Such a polytypic transformation was not observed for the Orth II crystal at any supersaturation below 0.30. The growth rate of Mon showed a quadratic dependence on supersaturation, while that of Orth II was approximately linear, suggesting spiral growth and two-dimensional-nucleation mechanisms for Mon and Orth II, respectively.
The lifetime of the ÃΣu+2 state of the N3 radical
Authors: Brazier Christopher R.
Published: September 2005

The lifetime of the ÃΣu+2 state of N3 has been determined from line broadening in the rotationally resolved laser-induced fluorescence (LIF) spectrum of the ÃΣu+2–X̃Πg2 transition. N3 radicals, produced by fluorine atom abstraction from HN3, were probed with an intracavity doubled ring laser operating near 272nm. Careful examination of the LIF spectrum indicates a significant Lorentzian component to the line shape due to a rapid predissociation in the ÃΣu+2 state. The predissociation lifetime is found to be 132±21ps for the 000 vibrational level and 64±10ps for the 010 level. The short lifetime is consistent with the low intensity of the LIF signal especially for the 010-010 hot band.
An accurate non-Born–Oppenheimer calculation of the first purely vibrational transition in LiH molecule
Authors: Bubin Sergiy , Adamowicz Ludwik , Molski Marcin
Published: September 2005

In this work we study the ground and the first vibrationally excited states of LiH molecule. We performed an extensive nonrelativistic variational calculations of the two states without using the Born–Oppenheimer approximation. The results are analyzed and compared with the data extracted from recent experiments. The 0←1 transition energy obtained in the calculations converged to a value which is less than a wave number above the transition energy estimated from the available experimental data concerning the LiH rovibrational transitions. We discuss the remaining discrepancy and the procedure used to determine the “experimental” transition frequencies.
A driven two-dimensional granular gas with Coulomb friction
Authors: Herbst Olaf , Cafiero Raffaele , Zippelius Annette , Herrmann Hans Jürgen , Luding Stefan
Published: September 2005

We study a homogeneously driven granular gas of inelastic hard particles with rough surfaces subject to Coulomb friction. The stationary state as well as the full dynamic evolution of the translational and rotational granular temperatures are investigated as a function of the three parameters of the friction model. Four levels of approximation to the (velocity-dependent) tangential restitution are introduced and used to calculate translational and rotational temperatures in a mean field theory. When comparing these theoretical results to numerical simulations of a randomly driven monolayer of particles subject to Coulomb friction, we find that already the simplest model leads to qualitative agreement, but only the full Coulomb friction model is able to reproduce/predict the simulation results quantitatively for all magnitudes of friction. In addition, the theory predicts two relaxation times for the decay to the stationary state. One of them corresponds to the equilibration between the translational and rotational degrees of freedom. The other one, which is slower in most cases, is the inverse of the common relaxation rate of translational and rotational temperatures.
An impedance spectroscopic study of n-type phosphorus-doped diamond
Authors: Curat Stephane , Ye Haitao , Gaudin Olivier , Jackman Richard B. , Koizumi Satoshi
Published: September 2005

An important development in the field of diamond electronics has been the production of n-type electrical characteristics following homoepitaxial diamond growth on (111) diamond in the presence of phosphorus-containing gases. Several studies have reported that a phosphorus donor level forms with an activation energy in the range of 0.43–0.6eV; the ground state for the donor level is considered to be at 0.6eV. Little is currently known about other electrically active defects that may be produced alongside the donor state when phosphorus is introduced. In this paper we report upon the use of impedance spectroscopy, which can isolate the differing components that contribute to the overall conductivity of the film. In Cole-Cole plots, two semicircular responses are observed for all temperatures above 75°C; a single semicircle being seen at temperatures below this. The results suggest the presence of two conduction paths with activation energies of 0.53 and 0.197eV. The former can be attributed to the phosphorus donor level, being lower than 0.6eV due to reduced mobility within the film at elevated temperatures. The latter is discussed in terms of defects in the P+-doped region under the Ohmic contacts being used.
Hydrogen plasma effects on ultralow-k porous SiCOH dielectrics
Authors: Grill A. , Sternhagen V. , Neumayer D. , Patel V.
Published: September 2005

This study investigated the interactions of hydrogen plasmas with ultralow-k porous SiCOH (pSiCOH) films and their dependency on the values of the original dielectric constant, porogen used for the preparation of films, and substrate temperature during the plasma treatment. pSiCOH films of similar dielectric constants have been prepared by plasma-enhanced chemical-vapor deposition using an identical SiCOH skeleton precursor, but with two different organic porogens. The films exposed to the hydrogen plasmas have been characterized by optical techniques, shrinkage characterization, and electrical measurements. It was found that the hydrogen plasma modifies the structure of pSiCOH’s oxide skeleton and reduces the concentration of the Si–(CH3)1 bonds, resulting in an increase of the dielectric constant. The degree of modification, for films prepared from the same precursors, is larger for films with lower dielectric constants (k) and is affected by the porogen used to prepare films with similar k values.
High mobility undoped amorphous indium zinc oxide transparent thin films
Authors: Kumar Bhupendra , Gong Hao , Akkipeddi Ramam
Published: September 2005

We investigated the amorphous region of the In2O3-ZnO material system. The composition dependence of the amorphous region was explored and the films exhibited an n-type semiconductor behavior with low resistivities in the range of 4×10−4–6.33×10−4Ωcm. These amorphous films have a very wide transmittance window range of 300–2500nm, and the transmittance is higher than 85% in the fiber-optics telecommunication window of 1.30–1.55μm. The band gap of amorphous films can be engineered from 2.66to3.05eV, by varying the zinc∕(zinc+indium) atomic ratio. A monotonous decrease in mobility from 71.6to59.4cm2∕Vs was observed with an increase in zinc∕(zinc+indium) atomic ratio from 0.19 to 0.43 in the amorphous region. This trend was explained on the basis of percolation theory and overlap integral calculations. The effective mass of these amorphous films was calculated using the Drude model in the free-carrier absorption region and correlated with composition as well as the carrier concentration of the films.
Model reconstructions for the Si(337) orientation
Authors: Chuang Feng-Chuan , Ciobanu Cristian V. , Wang Cai-Zhuang , Ho Kai-Ming
Published: September 2005

Although unstable, the Si(337) orientation has been known to appear in diverse experimental situations such as the nanoscale faceting of Si(112), or in the case of miscutting a Si(113) surface. Various models for Si(337) have been proposed over time, which motivates a comprehensive study of the structure of this orientation. Such a study is undertaken in this article, where we report the results of a genetic algorithm optimization of the Si(337)-(2×1) surface. The algorithm is coupled with a highly optimized empirical potential for silicon, which is used as an efficient way to build a set of possible Si(337) models; these structures are subsequently relaxed at the level of ab initio density-functional methods. Using this procedure, we retrieve the (337) reconstructions proposed in previous works, as well as a number of different ones.
Proposed precision laser spectrometer for trapped, highly charged ions
Authors: Vogel M. , Winters D. F. A. , Segal D. M. , Thompson R. C.
Published: September 2005

We propose a type of precision laser spectrometer for trapped, highly charged ions nearly at rest. It consists of a cylindrical, open-endcap Penning trap in which an externally produced bunch of highly charged ions can be confined and investigated by means of laser spectroscopy. The combination of confinement, cooling, and compression of a dense ion cloud will allow the ground-state hyperfine splitting in highly charged ions to be measured with an accuracy three orders of magnitude better than in any previous experiment. A systematic study of different charge states and different isotopes of the same element allows for highly sensitive tests of bound-state quantum electrodynamics and for a precision determination of nuclear properties. Apart from stable isotopes, radioactive species with half-lives longer than about 1 hour also can be investigated.
Magnesium/nitrogen and beryllium/nitrogen coimplantation into GaN
Authors: Liu K. T. , Su Y. K. , Chang S. J. , Horikoshi Y.
Published: September 2005

The nitrogen coimplantation characteristics in the Mg- and Be-implanted GaN with different dopant concentration ratios have been systematically investigated. The Hall-effect measurements show that the p-type characteristics are produced in the Mg- and Be-implanted GaN by the coimplantation of N atoms and subsequent annealing, which is essentially related to the column II/V dopant concentration ratio and annealing condition. This behavior may be attributed to the reduction of self-compensation induced by N vacancies and the enhanced acceptor substitution, which is in reasonable agreement with the surface stoichiometric switching determined by x-ray photoelectron spectroscopy measurements. From photoluminescence data, the activation energy of the Be acceptor level is evaluated to be about 145meV, which is shallower than that of the Mg acceptor. These experimental results indicate that the selective-area N coimplantation with Mg and Be atoms into GaN is an effective method to enhance the p-type conductivity and to improve the p-type Ohmic contact resistance.
Electrode effects in solid electrolyte capacitors
Authors: Martin Bjoern , Kliem Herbert
Published: September 2005

Thin films of ion-conducting polyethylene oxide (PEO) are prepared as a model system for solid polymer electrolytes. Plane-parallel capacitance structures of the type Al-PEO-Al (Metal-Insulator-Metal, MIM) with blocking electrodes are produced. In the short time range t⩽1s after the application of an external field, an ionic space-charge polarization with an exponential time dependence prevails. In the long time range the samples exhibit a Kohlrausch behavior of the polarization current, i.e., j∝t−α. This time dependence can be explained by image charges in the electrodes which attract the mobile ions. This attraction of ions is responsible for the static and the dynamic behavior of the system. The remanent polarization appearing in hysteresis measurements is an affirmation of the presence of these image charges. Computer simulations of a three-dimensional hopping model yield qualitatively the same results. Here the attraction of ions at the electrodes due to the image charges can be observed, as well as the experimentally determined t−α currents and the hysteresis of the polarization. This behavior cannot be simulated with a standard continuum model.
Surface laser emission from solid polymer dye in a guided mode resonant grating filter structure
Authors: Kobayashi Takashi , Kanamori Yoshiaki , Hane Kazuhiro
Published: September 2005

This letter describes the design, fabrication, and experimental results of a micro solid polymer dye laser designed on the basis of a guided mode resonant grating (GMRG). The resonant condition of GMRG includes the second-order resonance of the distributed feedback cavity. A surface laser emission was obtained in a patterned region by the pulsed-laser pumping. The grating was fabricated by the electron beam lithography and the fast atom beam etching. Dye (rhodamine 6G)-doped poly(methylmethacrylate) was spin-coated on the grating. The laser oscillation occurred in the direction vertical to the grating plane with a sharp peak (Q-value ∼1271) in a single mode designed by the GMRG analysis.
Ex situ ellipsometric investigation of nanocolumns inclination angle of obliquely evaporated silicon thin films
Authors: Beydaghyan Gisia , Buzea Cristina , Cui Yan , Elliott Chelsea , Robbie Kevin
Published: September 2005

We propose an application of spectroscopic ellipsometry pertinent to the characterization of nanostructure inclination of oblique thin films. This technique is employed ex situ in the measurement of silicon thin films fabricated at oblique incidence and modeled as aggregate microstructures formed from amorphous silicon, silicon oxide, and void in the effective medium model. The technique may also be utilized in situ as a powerful probe for the characterization of oblique thin films during their fabrication and processing.
Photoreflectance investigations of a donor-related transition in AlGaN∕GaN transistor structures
Authors: Kudrawiec R. , Syperek M. , Misiewicz J. , Rudziński M. , Grezegorczyk A. P. , Hageman P. R. , Larsen P. K.
Published: September 2005

Below-bandgap photoreflectance (PR) features observed for GaN layers and undoped AlGaN∕GaN transistor structures have been analyzed in this letter. In addition to PR signal associated with the interference oscillations a strong PR feature at ∼3.37eV has been resolved for some AlGaN∕GaN structures. This feature has been attributed to an electron transition between the valence band and a donorlike state located ∼50meV below the conduction band. An absorptiontype experiment, such as PR spectroscopy, makes it possible to observe such a transition because this donorlike state is ionized by the strong internal electric field existing in the GaN layer at the AlGaN∕GaN interface. The existence of this electric field with a magnitude of ∼210kV∕cm has been confirmed by the observation of GaN-related Franz-Keldysh oscillations in the PR spectra. Obtained results show that donorlike states located ∼50meV below the conduction band are one of the sources of high concentration of the two dimensional electron gas in undoped AlGaN∕GaN transistor structures.
Mechanical creep as a life-limiting factor of radio frequency microswitches
Authors: Gregori G. , Clarke D. R.
Published: September 2005

One of the characteristic failure mechanisms of microelectromechanical switches is stiction. Measurements, made using an instrumented nanoindentor, indicate that the adhesion force between hemispherical and flat gold contacts increases logarithmically with the number of actuation cycles. Concurrently, the electrical conductance increases with actuation time and the contact area increases. These time-dependent behaviors are a result of creep of the gold contacts under load, which sets a design limit for the maximum life of a contact switch before stiction failure occurs.
Holographic scattering in photopolymer-dispersed liquid crystals
Authors: Ellabban M. A. , Fally M. , Uršič H. , Drevenšek-Olenik I.
Published: September 2005

Strong polarization-conserving holographic scattering was observed in a photopolymer-dispersed liquid crystal film fabricated from the UV curable mixture of commercially available constituents. During the photopolymerization process a bright corona of diffracted light evolves around the pump beam. The intensity of the rotationally symmetric light distribution increases upon exposure. By rotating the sample, two characteristic diffraction rings appear which can be explained by the Ewald sphere construction. Our results demonstrate that the associated parasitic holograms are very pronounced. Hence, their presence must be accounted for whenever preparing and utilizing holographic polymer-dispersed liquid crystals in any application.
Electrochemical capacitance from manganese oxide nanowire structure synthesized by cyclic voltammetric electrodeposition
Authors: Wu Mao-Sung
Published: September 2005

Manganese oxide electrodes of nanowire structure are electrochemically synthesized by cyclic voltammetric electrodeposition at room temperature without surfactant, catalyst, or template. Electrode morphology depends on the deposition potential, which greatly influences the electrochemical performances of the capacitor. When the deposition potential is the range of 0.1–0.6 V versus saturated calomel electrode, electrode morphology changes from nanorod (15–35 nm in diameter) to nanowire structure (8–16 nm in diameter). Specific capacitance of the electrode reaches 350Fg−1 and the electrode shows a good high-rate charge/discharge capability in aqueous Na2SO4 solution. Manganese oxide electrode of nanowire structure is therefore a suitable candidate for electrochemical capacitor use.
Repeatable nanostructures in dielectrics by femtosecond laser pulse trains
Authors: Jiang Lan , Tsai Hai-Lung
Published: September 2005

Using the plasma model recent developed by the authors, this study predicts the existence of a constant ablation-depth zone with respect to fluence in femtosecond laser ablation of dielectrics, which has also been observed experimentally. It is found that the value of the constant ablation depth is significantly decreased by the pulse train technology. Repeatable nanostructures can be achieved with the parameters in the constant ablation-depth zone of a femtosecond pulse train, even when the laser system is subject to fluctuations in fluences.
Capacity Limitation in Short-Term Visual Memory for Contour Curvature
Authors: Sakai Koji
Published: September 2005

I measured the difference threshold for contour curvature in short-term visual memory (STVM) using a two-interval forced-choice partial discrimination task. In experiments 1 and 2, the study stimulus consisting of 1 to 4 curved contours was briefly presented. It was followed by a single contour stimulus after a retention interval. The subjects judged if the test stimulus had a higher or lower curvature than the corresponding study contour. The results of experiment 1 showed that the Weber fraction increased monotonically with increasing set size. The results of experiment 2 clarified that the set-size effect was not due to a temporal limitation in encoding resulting from the short exposure time. In experiment 3, the study stimuli always consisted of 4 items, but the numbers of memorised items were different in each condition. Nevertheless, the results showed the set-size effect, which indicated that its occurrence depended largely on the capacity limitation in short-term visual memory (STVM) storage. Otherwise, the Weber fraction was not hugely higher for set size 4 compared with set size 1. It was concluded that only 1 object could be retained in STVM with high fidelity, but that at least 4 objects could be retained in STVM with some degree of fidelity.
Interaction of Vision and Movement via a Mirror
Authors: Altschuler Eric Lewin
Published: September 2005

I have noticed a striking effect that vision can have on movement: when a person makes circular motions with both hands, clockwise with the left hand, counterclockwise with the right hand, while watching the reflection of one hand in a parasagitally placed mirror, if one arm makes a vertical excursion, the other arm tends to make the same vertical excursion, but not typically if the excursing arm is viewed in plain vision. This observation may help in understanding how visual feedback via a mirror may be beneficial for rehabilitation of some patients with movement deficits secondary to certain neurologic conditions, and illustrates that the traditional division of neural processes into sensory input and motor output is somewhat arbitrary.
When Feature Information Comes First! Early Processing of Inverted Faces
Authors: Carbon Claus-Christian , Leder Helmut
Published: September 2005

We investigated the early stages of face recognition and the role of featural and holistic face information. We exploited the fact that, on inversion, the alienating disorientation of the eyes and mouth in thatcherised faces is hardly detectable. This effect allows featural and holistic information to be dissociated and was used to test specific face-processing hypotheses. In inverted thatcherised faces, the cardinal features are already correctly oriented, whereas in undistorted faces, the whole Gestalt is coherent but all information is disoriented. Experiment 1 and experiment 3 revealed that, for inverted faces, featural information processing precedes holistic information. Moreover, the processing of contextual information is necessary to process local featural information within a short presentation time (26 ms). Furthermore, for upright faces, holistic information seems to be available faster than for inverted faces (experiment 2). These differences in processing inverted and upright faces presumably cause the differential importance of featural and holistic information for inverted and upright faces.
Perceived Dynamics of Static Images Enables Emotional Attribution
Authors: Pavlova Marina , Sokolov Arseny A , Sokolov Alexander
Published: September 2005

Perception of intentions and dispositions of others is an essential ingredient of adaptive daily-life social behaviour. Dynamics of moving images leads to veridical perception of social attributes. Anecdotal observations in art, science, and popular culture indicate that dynamic imbalance can be revealed in static images. Here, we ask whether perceived dynamics of abstract figures is related to emotional attribution. Participants first estimated instability of geometric shapes rotated in 15° steps in the image plane, and then rated the intensity of basic emotions that can be ascribed to the figures. We found no substantial link between the deviation of the figures from the vertical orientation and perceived instability. Irrespective of shape, a strong positive correlation was found between negative emotions and perceived instability. By contrast, positive emotions were inversely linked with deviation of the figure from vertical orientation. The work demonstrates for the first time that dynamics conveyed by static images enables specific emotional attributions, and agrees well with the assumption that neural networks for production of movements and understanding the dispositions of others are intimately linked. The findings are also of importance for exploring the ability to reveal social properties through dynamics in normal and abnormal development, for example in patients with early brain injury or autistic spectrum disorders.
Central Visual Persistences: I. Visual and Kinesthetic Interactions
Authors: Ingle David
Published: September 2005

Phenomena associated with ‘central visual persistences’ (CPs) are new to both medical and psychological literature. Five subjects have reported similar CPs: positive afterimages following brief fixation of high-contrast objects or drawings and eye closure. CPs duplicate shapes and colors of single objects, lasting for about 15 s. Unlike retinal afterimages, CPs do not move with the eyes but are stable in extrapersonal space during head or body rotations. CPs may reflect sustained neural activity in neurons of association cortex, which mediate object perception.

A remarkable finding is that CPs can be moved in any direction by the (unseen) hand holding the original seen object. Moreover, a CP once formed will ‘jump’ into an extended hand and ‘stick’ in that hand as it moves about. The apparent size of a CP of a single object is determined by the size of the gap between finger and thumb, even when no object is touched. These CPs can be either magnified or minified via the grip of the extended hand. The felt orientation of the hand-held object will also determine the orientation of the CP seen in that hand. Thus, kinesthetic signals from hand and arm movements can determine perceived location, size, and orientation of CPs. A neural model based on physiological studies of premotor, temporal, parietal, and prefrontal cortices is proposed to account for these novel phenomena.
Visually Perceived Eye Level and Horizontal Midline of the Body Trunk Influenced by Optic Flow
Authors: Wu Jun , He Zijiang J , Ooi Teng Leng
Published: September 2005

The eye level and the horizontal midline of the body trunk can serve, respectively as references for judging the vertical and horizontal egocentric directions. We investigated whether the optic-flow pattern, which is the dynamic motion information generated when one moves in the visual world, can be used by the visual system to determine and calibrate these two references. Using a virtual-reality setup to generate the optic-flow pattern, we showed that judged elevation of the eye level and the azimuth of the horizontal midline of the body trunk are biased toward the positional placement of the focus of expansion (FOE) of the optic-flow pattern. Furthermore, for the vertical reference, prolonged viewing of an optic-flow pattern with lowered FOE not only causes a lowered judged eye level after removal of the optic-flow pattern, but also an overestimation of distance in the dark. This is equivalent to a reduction in the judged angular declination of the object after adaptation, indicating that the optic-flow information also plays a role in calibrating the extraretinal signals used to establish the vertical reference.
A revision of the Australian taxa previously attributed to Assiminea buccinoides (Quoy & Gaimard) and Assiminea tasmanica Tenison-Woods (Mollusca:Gastropoda:Caenogastropoda:Assimineidae)
Authors: Fukuda Hiroshi , Ponder Winston F.
Published: September 2005

A new genus, Cryptassiminea, is introduced for the taxon previously known as Assiminea buccinoides (Quoy & Gaimard). These small gastropods are abundant in mangrove and salt marsh habitats in south-eastern and subtropical eastern Australia. Seven species (five new) are recognised using morphological characters in the complex previously treated as a single species. Five taxa have rather narrow ranges while the other two are widespread and often sympatric. Two groups of species are recognised. One contains Cryptassiminea buccinoides, widespread in south-east and east Australia, and two closely related allopatric taxa from South Australia and south-eastern Tasmania (C. adelaidensis, sp. nov. and C. kershawi, sp. nov.). A second group of species is typified by Cryptassiminea tasmanica (Tenison-Woods), also widespread in east and south-east Australia and often sympatric with C. buccinoides. Allied to C. tasmanica, are two closely related taxa from western Victoria: C. glenelgensis, sp. nov. from the Glenelg River estuary and C. surryensis, sp. nov. from the Surry River estuary and Western Port, in the vicinity of Geelong. A distinctive species, Cryptassiminea insolata, sp. nov. from the east coast of Queensland, also has similarities with C. tasmanica. A cladistic analysis using morphological characters of the Cryptassiminea taxa and three other genera of Assimininae, with an omphalotropidine as the outgroup, resulted in a single tree. The new genus has rather poor support, possibly because many of its characters appear to be plesiomorphic within Assimineinae. Cryptassiminea is defined by a unique combination of characters but lacks any obvious synapomorphy. Two clades within Cryptassiminea are well supported, each containing the species-groups referred to above.
Platynini (Coleoptera:Carabidae) of Vanuatu: Miocene diversification on the Melanesian Arc
Authors: Liebherr James K.
Published: September 2005

Vanuatu supports 11 resident species of the carabid beetle tribe Platynini: five indigenous species shared with other Pacific islands and Australia and six newly described precinctive species. Notagonum delaruei, sp. nov. represents a single descendant species of one colonisation event. Helluocolpodes, gen. nov. (type species Colpodes helluo Darlington of New Guinea) is proposed to accommodate a monophylum comprising the type species plus Helluocolpodes discicollis, sp. nov., H. mucronis, sp. nov., H. multipunctatus, sp. nov., H. sinister, sp. nov. and H. vanemdeni, sp. nov., all from Vanuatu. Generic assignments are informed by cladistic analysis of anatomical characters for a variety of Pacific platynine taxa. Metacolpodes Jeannel is redefined cladistically to include seven Pacific and Asian species. Biogeographic relationships among island areas housing platynine taxa on the Australian and Pacific Plates are investigated using a chrono–area cladogram, i.e. a taxon–area cladogram for which terminals are dated based on geological evidence and internal nodes based on non-reversible temporal optimisation. Conclusions reached by constraining the ages of areas within the context of phylogenetic relationships of their resident taxa include: (1) Vanuatu has supported resident platynine taxa since the Middle to Late Miocene; (2) the Hawaiian Blackburnia first colonised that archipelago in the Miocene, long before the present oldest high island, Kauai, came into existence; (3) the New Zealand Ctenognathus most likely arose from Miocene colonisation of New Zealand via Fiji; and (4) the low diversity of the Tahitian platynine fauna is due to relatively recent, Pliocene or later, colonisation of the Society Island chain by this group, also from a Fijian source.
VirA and VirG activate the Ti plasmid
repABC
operon, elevating plasmid copy number in response to wound-released chemical signals
Authors: Cho Hongbaek , Winans Stephen C.
Published: September 2005

The
vir
genes of
Agrobacterium tumefaciens
tumor-inducing (Ti) plasmids direct the transfer of oncogenic portion of the Ti (tumor-inducing) plasmid that is transferred to plant cells (T-DNA) into plant cells and are coordinately induced by plant-released phenolic chemical signals. We have used DNA microarrays, representing all genes of the octopine- and nopaline-type Ti plasmids, to identify all Ti-plasmid-encoded genes in the
vir
regulons of both plasmids. Acetosyringone (AS) induced the expression of all known members of the
vir
regulons, as well as a small number of additional genes. Unexpectedly, AS also caused a modest induction of virtually every Ti plasmid gene. This suggested that the copy number of the Ti plasmid might increase in response to AS, a hypothesis confirmed by DNA dot blotting. VirA and VirG were the only Vir proteins required for this copy number increase. Promoter resections and primer extension analysis of the
repABC
promoter region showed that expression of the promoter closest to
repA
(promoter P4) was induced by AS. We also identified a sequence resembling a consensus VirG-binding motif ≈70 nucleotides upstream from the P4 transcription start site. Mutating this sequence blocked the AS-induced copy number increase of a RepABC-dependent miniplasmid, indicating that phospho-VirG increases copy number solely by enhancing
repABC
expression.
Interfacial metal and antibody recognition
Authors: Zhou Tongqing , Hamer Dean H. , Hendrickson Wayne A. , Sattentau Quentin J. , Kwong Peter D.
Published: September 2005

The unique ligation properties of metal ions are widely exploited by proteins, with approximately one-third of all proteins estimated to be metalloproteins. Although antibodies use various mechanisms for recognition, to our knowledge, none has ever been characterized that uses an interfacial metal. We previously described a family of CD4-reactive antibodies, the archetype being Q425. CD4:Q425 engagement does not interfere with CD4:HIV-1 gp120 envelope glycoprotein binding, but it blocks subsequent steps required for viral entry. Here, we use surface-plasmon resonance to show that Q425 requires calcium for recognition of CD4. Specifically, Q425 binding of calcium resulted in a 55,000-fold enhancement in affinity for CD4. X-ray crystallographic analyses of Q425 in the presence of Ca
2+
, Ba
2+
, or EDTA revealed an exposed metal-binding site, partially coordinated by five atoms contributed from four antibody complementarity-determining regions. The results suggest that Q425 recognition of CD4 involves direct ligation of antigen by the Q425-held calcium, with calcium binding each ligating atom of CD4 with ≈1.5 kcal/mol of binding energy. This energetic contribution, which is greater than that from a typical protein atom, demonstrates how interfacial metal ligation can play a unique role in antigen recognition.
Hairless triggers reactivation of hair growth by promoting Wnt signaling
Authors: Beaudoin Gerard M. J. , Sisk Jeanne M. , Coulombe Pierre A. , Thompson Catherine C.
Published: September 2005

The mammalian hair cycle involves periodic regeneration of a tiny organ, the hair follicle, through a stem-cell-mediated process. The Hairless (Hr) gene encodes a nuclear receptor corepressor (HR) that is essential for hair follicle regeneration, but its role in this process is unknown. Here, we demonstrate that transgenic expression of HR in progenitor keratinocytes rescues follicle regeneration inHr-/-mice. We show that expression of Wise, a modulator of Wnt signaling, is repressed by HR in these cells, coincident with the timing of follicle regeneration. This work links HR and Wnt function, providing a model in which HR regulates the precise timing of Wnt signaling required for hair follicle regeneration.
On a sharp lower bound on the blow-up rate for the 𝐿² critical nonlinear Schrödinger equation
Authors: Merle Frank , Raphael Pierre
Published: September 2005

We consider the

L
2

L^2

critical nonlinear Schrödinger equation

i

u
t

=
−
Δ
u
−

|

u

|

4
N

u

iu_t=-\Delta u-|u|^{\frac {4}{N}}u

with initial condition in the energy space

u
(
0
,
x
)
=

u
0

∈

H
1

u(0,x)=u_0\in H^1

and study the dynamics of finite time blow-up solutions. In an earlier sequence of papers, the authors established for a certain class of initial data on the basis of dispersive properties in

L

l
o
c

2

L^2_{loc}

a sharp and stable upper bound on the blow-up rate:
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartAbsoluteValue nabla u left-parenthesis t right-parenthesis EndAbsoluteValue Subscript upper L squared Baseline less-than-or-equal-to upper C left-parenthesis StartFraction log StartAbsoluteValue log left-parenthesis upper T minus t right-parenthesis EndAbsoluteValue Over upper T minus t EndFraction right-parenthesis Superscript one half">

|

∇
u
(
t
)

|

L
2

≤
C

(

log
⁡

|

log
⁡
(
T
−
t
)

|

T
−
t

)

1
2

|\nabla u(t)|_{L^2}\leq C\left (\frac {\log |\log (T-t)|}{T-t}\right )^{\frac {1}{2}}

. In an earlier paper, the authors then addressed the question of a lower bound on the blow-up rate and proved for this class of initial data the nonexistence of self-similar solutions, that is,

lim

t
→
T

T
−
t

|

∇
u
(
t
)

|

L
2

=
+
∞
.

\lim _{t\to T}\sqrt {T-t}|\nabla u(t)|_{L^2}=+\infty .

In this paper, we prove the sharp lower bound
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartAbsoluteValue nabla u left-parenthesis t right-parenthesis EndAbsoluteValue Subscript upper L squared Baseline greater-than-or-equal-to upper C left-parenthesis StartFraction log StartAbsoluteValue log left-parenthesis upper T minus t right-parenthesis EndAbsoluteValue Over upper T minus t EndFraction right-parenthesis Superscript one half">

|

∇
u
(
t
)

|

L
2

≥
C

(

log
⁡

|

log
⁡
(
T
−
t
)

|

T
−
t

)

1
2

|\nabla u(t)|_{L^2}\geq C \left (\frac {\log |\log (T-t)|}{T-t}\right )^{\frac {1}{2}}

\]
by exhibiting the dispersive structure in the scaling invariant space

L
2

L^2

for this log-log regime. In addition, we will extend to the pure energy space

H
1

H^1

a dynamical characterization of the solitons among the zero energy solutions.
Long arithmetic progressions in sumsets: Thresholds and bounds
Authors: Szemerédi E. , Vu V.
Published: September 2005

For a set

A
A

of integers, the sumset

l
A
=
A
+
⋯
+
A

lA =A+\dots +A

consists of those numbers which can be represented as a sum of

l
l

elements of

A
A

:
\[

l
A
=
{

a
1

+
⋯
+

a
l

|

a
i

∈

A
i

}
.

lA =\{a_1+\dots + a_l| a_i \in A_i \}.

\]
Closely related and equally interesting notion is that of

l

∗

A

l^{\ast }A

, which is the collection of numbers which can be represented as a sum of

l
l

different elements of

A
A

:
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="l Superscript asterisk Baseline upper A equals left-brace a 1 plus midline-horizontal-ellipsis plus a Subscript l Baseline vertical-bar a Subscript i Baseline element-of upper A Subscript i Baseline comma a Subscript i Baseline not-equals a Subscript j Baseline right-brace period">

l

∗

A
=
{

a
1

+
⋯
+

a
l

|

a
i

∈

A
i

,

a
i

≠

a
j

}
.

l^{\ast }A =\{a_1+\dots + a_l| a_i \in A_i, a_i \neq a_j \}.

\]
The goal of this paper is to investigate the structure of

l
A

lA

and

l

∗

A

l^{\ast }A

, where

A
A

is a subset of

{
1
,
2
,
…
,
n
}

\{1,2, \dots , n\}

. As application, we solve two conjectures by Erdös and Folkman, posed in 1960s.
Low-lying zeros of families of elliptic curves
Authors: Young Matthew
Published: September 2005

There is a growing body of work giving strong evidence that zeros of families of

L
L

-functions follow distribution laws of eigenvalues of random matrices. This philosophy is known as the random matrix model or the Katz-Sarnak philosophy. The random matrix model makes predictions for the average distribution of zeros near the central point for families of

L
L

-functions. We study these low-lying zeros for families of elliptic curve

L
L

-functions. For these

L
L

-functions there is special arithmetic interest in any zeros at the central point (by the conjecture of Birch and Swinnerton-Dyer and the impressive partial results towards resolving the conjecture). We calculate the density of the low-lying zeros for various families of elliptic curves. Our main foci are the family of all elliptic curves and a large family with positive rank. An important challenge has been to obtain results with test functions that are concentrated close to the origin since the central point is a location of great arithmetical interest. An application of our results is an improvement on the upper bound of the average rank of the family of all elliptic curves (conditional on the Generalized Riemann Hypothesis (GRH)). The upper bound obtained is less than

2
2

, which shows that a positive proportion of curves in the family have algebraic rank equal to analytic rank and finite Tate-Shafarevich group. We show that there is an extra contribution to the density of the low-lying zeros from the family with positive rank (presumably from the “extra" zero at the central point).
Sharp transition between extinction and propagation of reaction
Authors: Zlatoš Andrej
Published: September 2005

We consider the reaction-diffusion equation
\[

T
t

=

T

x
x

+
f
(
T
)

T_t = T_{xx} + f(T)

\]
on

R

{\mathbb {R}}

with

T
0

(
x
)
≡

χ

[
−
L
,
L
]

(
x
)

T_0(x) \equiv \chi _{[-L,L]} (x)

and

f
(
0
)
=
f
(
1
)
=
0

f(0)=f(1)=0

. In 1964 Kanel

′

^{\prime }

proved that if

f
f

is an ignition non-linearity, then

T
→
0

T\to 0

as

t
→
∞

t\to \infty

when

L
>

L
0

L>L_0

, and

T
→
1

T\to 1

when

L
>

L
1

L>L_1

. We answer the open question of the relation of

L
0

L_0

and

L
1

L_1

by showing that

L
0

=

L
1

L_0=L_1

. We also determine the large time limit of

T
T

in the critical case

L
=

L
0

L=L_0

, thus providing the phase portrait for the above PDE with respect to a 1-parameter family of initial data. Analogous results for combustion and bistable non-linearities are proved as well.
Defects in Structural Integrity of Ergosterol and the Cdc50p-Drs2p Putative Phospholipid Translocase Cause Accumulation of Endocytic Membranes, onto Which Actin Patches Are Assembled in Yeast
Authors: Kishimoto Takuma , Yamamoto Takaharu , Tanaka Kazuma
Published: September 2005

Specific changes in membrane lipid composition are implicated in actin cytoskeletal organization, vesicle formation, and control of cell polarity. Cdc50p, a membrane protein in the endosomal/trans-Golgi network compartments, is a noncatalytic subunit of Drs2p, which is implicated in translocation of phospholipids across lipid bilayers. We found that the cdc50Δ mutation is synthetically lethal with mutations affecting the late steps of ergosterol synthesis (erg2 to erg6). Defects in cell polarity and actin organization were observed in the cdc50Δ erg3Δ mutant. In particular, actin patches, which are normally found at cortical sites, were assembled intracellularly along with their assembly factors, including Las17p, Abp1p, and Sla2p. The exocytic SNARE Snc1p, which is recycled by an endocytic route, was also intracellularly accumulated, and inhibition of endocytic internalization suppressed the cytoplasmic accumulation of both Las17p and Snc1p. Simultaneous loss of both phospholipid asymmetry and sterol structural integrity could lead to accumulation of endocytic intermediates capable of initiating assembly of actin patches in the cytoplasm.
Sequence and Comparative Genomic Analysis of Actin-related Proteins
Authors: Muller Jean , Oma Yukako , Vallar Laurent , Friederich Evelyne , Poch Olivier , Winsor Barbara
Published: September 2005

Actin-related proteins (ARPs) are key players in cytoskeleton activities and nuclear functions. Two complexes, ARP2/3 and ARP1/11, also known as dynactin, are implicated in actin dynamics and in microtubule-based trafficking, respectively. ARP4 to ARP9 are components of many chromatin-modulating complexes. Conventional actins and ARPs codefine a large family of homologous proteins, the actin superfamily, with a tertiary structure known as the actin fold. Because ARPs and actin share high sequence conservation, clear family definition requires distinct features to easily and systematically identify each subfamily. In this study we performed an in depth sequence and comparative genomic analysis of ARP subfamilies. A high-quality multiple alignment of ∼700 complete protein sequences homologous to actin, including 148 ARP sequences, allowed us to extend the ARP classification to new organisms. Sequence alignments revealed conserved residues, motifs, and inserted sequence signatures to define each ARP subfamily. These discriminative characteristics allowed us to develop ARPAnno ( http://bips.u-strasbg.fr/ARPAnno ), a new web server dedicated to the annotation of ARP sequences. Analyses of sequence conservation among actins and ARPs highlight part of the actin fold and suggest interactions between ARPs and actin-binding proteins. Finally, analysis of ARP distribution across eukaryotic phyla emphasizes the central importance of nuclear ARPs, particularly the multifunctional ARP4.