bluuebunny/crossref_metadata_2025 huggingface dataset:
H I Imaging Surveys: Gas and Galaxy Evolution in Different Environments
Authors: van Gorkom Jacqueline
Published: December 2011

Our understanding of the formation and evolution of galaxies and the large scale structure has advanced enormously over the last decade, thanks to an impressive synergy between theoretical and observational efforts. While the growth of the dark matter component seems well understood, the physics of the gas, during its accretion, removal and/or depletion is less well understood. Increasingly large scale optical surveys are tracing out the cosmic web of filaments and voids and mathematical tools have been developed to describe these structures and identify galaxies in specific environments. H I imaging surveys begin to answer the question: how do galaxies get and lose their gas. The best evidence for ongoing gas accretion is found in the lowest density environments, while removal of gas in the highest density environments stops star formation and reddens the galaxies. Although current H I emission surveys are limited to redshifts less than 0.2, this is where the LSS is best defined and much can be learned in the local universe.
NRO Legacy Project: M33 all Disk Survey of Giant Molecular Clouds with NRO 45-m and ASTE 10-m telescopes
Authors: Kuno N. , Tosaki T. , Onodera S. , Miura R. , Muraoka K. , Komugi S. , Sawada T. , Nakanishi K. , Kohno K. , Kaneko H. , Hirota A. , Arimoto N. , Nakanishi H. , Kawabe R.
Published: December 2011

We have conducted all disk imaging of M33 in 12CO(1-0) using the 45-m telescope at Nobeyama Radio Observatory. We present preliminary results of this project. The spatial resolution of ~ 80 pc is comparable to the size of GMCs. The identified GMCs show wide variety in star forming activity. The variety can be regarded as the difference of their evolutionary stage. We found that Kennicutt-Schmidt law breaks in GMC scale (~ 80 pc), although it is still valid in 1 kpc scale. The correlation between molecular gas fraction, fmol = Σ(H2)/Σ(HI+H2) and gas surface density shows two distinct sequences and shows that fmol tends to be higher near the center. We also made partial mapping 12CO(3-2) with ASTE telescope. These data show that the variation of physical properties of molecular gas are correlated with the GMC evolution and mass. That is, GMCs with more active star formation and more mass tend to have higher fraction of dense gas.
3D Spectroscopic Surveys of Late-Type Nearby Galaxies in the Optical
Authors: Amram Philippe
Published: December 2011

Two classes of spectro-imagers are available, the first one, usually based on grisms, allows to cover intermediate fields of view and wide spectral ranges (decreasing when the spectral resolution increases) while the second one, usually based on tunable filters (like Fabry-Perot), is generally able to cover larger fields of view but on narrow spectral ranges (also depending on the spectral resolution). Both families of instrument have access to low or high spectral resolution and are used in seeing limited conditions for observing nearby galaxies. Spectro-imagers provide data cubes consisting of a spectrum for each spatial sample on the sky. From these spectra, using both emission and absorption lines, combined with the continuum emission, the history of the stars and the interstellar medium in nearby galaxies, encoded in different physical quantities, such as chemical abundances, kinematics properties, is deciphered. Only a few surveys of galaxies using spectro-imagers have been led up to now and mainly using 4-m class or smaller telescopes. This includes the case of nearby late-type galaxies surveyed in the optical. Two large surveys of some 600 galaxies each have just been launched, one on the Magellan 6m telescope (CGS) and the other one on the William Herschel 4.2m telescope (CALIFA). Surveys containing a smaller number of galaxies have been conducted elsewhere, for instance on the WIYN and Calar Alto 3.5m telescopes (the DiskMass survey, 146 galaxies); on the ESO and CFHT 3.6m telescopes (CIGALE, 269 galaxies); on the OHP 1.92m telescope (GHASP, 203 galaxies); on the mont Mégantic 1.6m telescope (107 galaxies) and on the San Pedro Mártir 2.1m telescope (79 galaxies). Other programs surveying less then 50 galaxies have been also led, like VENGA, SAURON, PINGS or GHaFaS. The scientific drivers of these surveys are broad, they span from the study of the structural properties, star formation histories, AGN content, to mass profiles and uncertainties in rotation-curve decompositions, nature and formation of bulges and disks components.
The Study of Barred Spiral Galaxies with Integral-Field Units
Authors: Robert Carmelle , Cantin Simon , Brière Élaine , Rousseau-Nepton Laurie , Drissen Laurent
Published: December 2011

Integral-Field Units have been used to describe the morphology in numerous continuum and line wavebands of a sample of barred spirals galaxies (some of which known as starbursts and LINERs) and to characterize their gas and stellar populations. The central region of eight galaxies was studied with OASIS and an iterative technique developed to separate superposed stellar populations. Young populations, responsible for nebular emission lines, are found in nuclear structures. Older stellar components are mostly uniformly distributed. The mass distribution of the different populations indicates a long sequence of burst events over the whole galaxy history. An activity of the type composite/transition region is often seen over the whole central region. SpIOMM was also used to map the emission lines over the entire disk of one of these galaxies. Among other results, it confirms the peculiar line ratio.
SpIOMM and SITELLE: Wide-field Imaging FTS for the Study of Galaxy Evolution
Authors: Drissen Laurent , Bernier Anne-Pier , Robert Carmelle ,   the SpIOMM & SITELLE team
Published: December 2011

SpIOMM, a wide-field Imaging Fourier Transform Spectrometer attached to the Mont Mégantic 1.6-m telescope, is capable of obtaining the visible spectrum of every source of light in a 12 arcminute field of view, with a spectral resolution ranging from R = 1 (wide-band image) to R = 25 000, resulting in 1.7 million spectra with a spatial resolution of one arcsecond. SITELLE will be a similar instrument attached to the Canada-France-Hawaii telescope, and will be in operation in early 2013. We present a short description of these instruments and illustrate their capabilities to study nearby galaxies with the results of a data cube of M51.
HII Regions of NGC 628 and M101 as seen with SpIOMM
Authors: Rousseau-Nepton Laurie , Robert Carmelle , Drissen Laurent
Published: December 2011

With SpIOMM, we obtained numerous spectra in the visible range covering simultaneously several emission lines of bright Hii regions in the spiral galaxies NGC 628 and M101. We measured the size and luminosity of the Hii regions as well as the gas metallicity, temperature, and density. We estimated the age and star forming rate of the young stellar populations associated with the Hii regions. We looked for gradients along the galaxy radius and search for relations with the galactic arm positions. This is a first step in a project, based on a detailed study of stellar populations, to rebuild the history of spiral galaxies and to identify the mechanisms responsible for their evolution.
The Evolution of the Baryonic Tully-Fisher Relation over the past 6 Gyr
Authors: Puech M. , Hammer F. , Flores H. , Delgado-Serrano R. , Rodrigues M. , Yang Y.
Published: December 2011

Scaling relations are salient ingredients of galaxy evolution and formation models. I summarize results from the IMAGES survey, which combines spatially-resolved kinematics from FLAMES/GIRAFFE with imaging from HST/ACS and other facilities. Specifically, I will focus on the evolution of the stellar mass and baryonic Tully-Fisher Relations (TFR) from z = 0.6 down to z = 0. We found a significant evolution in zero point and scatter of the stellar mass TFR compared to the local Universe. Combined with gas fractions derived by inverting the Schmidt-Kennicutt relation, we derived for the first time a baryonic TFR at high redshift. Conversely to the stellar mass TFR, the baryonic relation does not appear to evolve in zero point, which suggests that most of the reservoir of gas converted into stars over the past 6 Gyr was already gravitationally bound to galaxies at z = 0.6.
Seeking Completeness for high-z ULIRGs: from SCUBA to Herschel
Authors: Casey Caitlin M.
Published: December 2011

Selection effects in the submillimeter/far-infrared inhibit detailed analysis of extreme starbursts in the early Universe. Submillimeter Galaxy (SMG) detection and characterization biases against warm temperature SEDs Tdust ~50 K, against the highest redshift ULIRGs z > 3, and has so far been limited to a small sample of ~100 sources that have reliably identified optical or radio counterparts and spectroscopic redshifts. Recent observations by Herschel ⋅ ⋅ ⋅ ⋅ and ⋅ ⋅ ⋅⋅ ⋅ in the ~70–500 μm wavelength range provide a more complete census of high-z ULIRG activity than previous SMG surveys. However, source confusion and lack of spectroscopic identification of reliable counterparts limit the analysis of extreme ULIRGs to the most basic calculations, frought with a priori assumptions (e.g. Tdust/(1+z) degeneracy, far-IR/radio relation, confusion boosting factors, etc). Herein I address the biases on conclusions of SMG work and I demonstrate the need for thorough, spectroscopic follow-up of high-z ULIRGs in order to infer their physical conditions.
Lyman Break Analogs: Constraints on the Formation of Extreme Starbursts at Low and High Redshift
Authors: Gonçalves Thiago S. , Overzier Roderik , Basu-Zych Antara , Martin D. Christopher
Published: December 2011

Lyman Break Analogs (LBAs), characterized by high far-UV luminosities and surface brightnesses as detected by GALEX, are intensely star-forming galaxies in the low-redshift universe (z ~ 0.2), with star formation rates reaching up to 50 times that of the Milky Way. These objects present metallicities, morphologies and other physical properties similar to higher redshift Lyman Break Galaxies (LBGs), motivating the detailed study of LBAs as local laboratories of this high-redshift galaxy population. We present results from our recent integral-field spectroscopy survey of LBAs with Keck/OSIRIS, which shows that these galaxies have the same nebular gas kinematic properties as high-redshift LBGs. We argue that such kinematic studies are not an appropriate diagnostic to rule out merger events as the trigger for the observed starburst. Comparison between the kinematic analysis and morphological indices from HST imaging illustrates the difficulties of properly identifying (minor or major) merger events, with no clear correlation between the results using either of the two methods. Artificial redshifting of our data indicates that this problem becomes even worse at high redshift due to surface brightness dimming and resolution loss. Whether mergers could generate the observed kinematic properties is strongly dependent on gas fractions in these galaxies. We present preliminary results of a CARMA survey for LBAs and discuss the implications of the inferred molecular gas masses for formation models.
Ages of Globular Cluster Systems and the Relation to Galaxy Morphology
Authors: Chies-Santos A. L. , Larsen S. S. , Kuntschner H. , Anders P. , Wehner E. M. , Strader J. , Brodie J. P. , Santos J. F. C.
Published: December 2011

We investigate the age distributions of GC systems in 14 E/S0 galaxies by carrying out a differential comparison of the (g–z) vs. (g–K) two-colour diagrams for different GC systems. No significant distinction is detected in the mean ages of GCs among elliptical galaxies. S0 galaxies on the other hand, show evidence for younger GCs. Surprisingly, this appears to be driven by the more metal-poor clusters. This is suggestive of E type galaxies having assembled most of their GCs in a shorter and earlier period than lenticular galaxies. The latter galaxy type, seems to have a more extended period of GC formation/assembly.
Highly-luminous Cool Core Clusters of Galaxies: Mechanically-driven or Radiatively-driven AGN?
Authors: Hlavacek-Larrondo Julie , Fabian Andy
Published: December 2011

Cool core clusters of galaxies require strong feedback from their central AGN to offset cooling. We present a study of strong cool core, highly-luminous (most with Lx ≥ 1045 erg s−1), clusters of galaxies in which the mean central AGN jet power must be very high yet no central point X-ray source is detected. Using the unique spatial resolution of Chandra, a sample of 13 clusters is analysed, including A1835, A2204, and one of the most massive cool core clusters, RXCJ1504.1-0248. All of the central galaxies host a radio source, indicating an active nucleus, and no obvious X-ray point source. For all clusters in the sample, the nucleus has an X-ray bolometric luminosity below 2 per cent of that of the entire cluster. We investigate how these clusters can have such strong X-ray luminosities, short radiative cooling-times of the inner intracluster gas requiring strong energy feedback to counterbalance that cooling, and yet have such radiatively-inefficient cores with, on average, Lkin/Lnuc exceeding 200. Explanations of this puzzle carry significant implications for the origin and operation of jets, as well as on establishing the importance of kinetic feedback for the evolution of galaxies and their surrounding medium.
Comparison of multiple linear and nonlinear regression, autoregressive integrated moving average, artificial neural network, and wavelet artificial neural network methods for urban water demand forecasting in Montreal, Canada
Authors: Adamowski Jan , Fung Chan Hiu , Prasher Shiv O. , Ozga‐Zielinski Bogdan , Sliusarieva Anna
Published: December 2011

Daily water demand forecasts are an important component of cost‐effective and sustainable management and optimization of urban water supply systems. In this study, a method based on coupling discrete wavelet transforms (WA) and artificial neural networks (ANNs) for urban water demand forecasting applications is proposed and tested. Multiple linear regression (MLR), multiple nonlinear regression (MNLR), autoregressive integrated moving average (ARIMA), ANN and WA‐ANN models for urban water demand forecasting at lead times of one day for the summer months (May to August) were developed, and their relative performance was compared using the coefficient of determination, root mean square error, relative root mean square error, and efficiency index. The key variables used to develop and validate the models were daily total precipitation, daily maximum temperature, and daily water demand data from 2001 to 2009 in the city of Montreal, Canada. The WA‐ANN models were found to provide more accurate urban water demand forecasts than the MLR, MNLR, ARIMA, and ANN models. The results of this study indicate that coupled wavelet‐neural network models are a potentially promising new method of urban water demand forecasting that merit further study.
Clarifying ambiguity in intraseasonal Southern Hemisphere climate modes during austral winter
Authors: Matthewman N. Joss , Magnusdottir Gudrun
Published: December 2011

The relative importance of annular and nonannular characteristics in the wintertime Southern Hemisphere circulation is investigated using reanalysis data between 1978 and 2010. Weekly averaged data are chosen to capture the typically short time scale of intraseasonal atmospheric variability. In existing studies, the southern annular mode (SAM) has been shown to exhibit significant nonannular behavior in the western Southern Hemisphere during austral winter. Variability in this region is also characterized by wave‐like disturbances, and this “overlap” in nonannular behavior between different climate modes has led to a lack of consensus when defining and measuring impact from these wave‐like disturbances. A number of approaches are adopted, including empirical orthogonal function analysis, teleconnection correlation analysis, and the application of a vector autoregression model to isolate directions of causality and wave propagation. Austral winter variability is shown to be dominated by nonannular wave‐like disturbances, rather than a seesaw pattern between high and middle latitudes. The wave‐like disturbances have the largest amplitude in the western Southern Hemisphere, are quasi‐stationary, and exhibit eastward propagation of information. This suggests that the dominant pattern of western Southern Hemisphere intraseasonal variability during austral winter, which is commonly associated with the SAM, is, in fact, a wave‐like mode of variability.
Critical reflectance derived from MODIS: Application for the retrieval of aerosol absorption over desert regions
Authors: Wells Kelley C. , Martins J. Vanderlei , Remer Lorraine A. , Kreidenweis Sonia M. , Stephens Graeme L.
Published: December 2011

The determination of aerosol direct radiative forcing over desert regions requires accurate information about the aerosol single‐scattering albedo (SSA); however, the brightness of desert surfaces in the visible and near‐IR range complicates the retrieval of aerosol optical properties using passive space‐based measurements. Here we use the critical reflectance method to retrieve spectral aerosol absorption from space over North Africa, a desert region that is predominantly impacted by absorbing dust and biomass burning aerosol. We examine the sensitivity of the critical reflectance parameter to aerosol physical and optical properties that are representative of the region, and we find that the critical reflectance has low sensitivity to assumptions of aerosol size and refractive index for dust‐like particles, except at scattering angles near 180°, which should be avoided with this method. We use our findings to retrieve spectral SSA from critical reflectance derived from Moderate Resolution Imaging Spectroradiometer (MODIS) reflectances in the vicinity of two Aerosol Robotic Network (AERONET) stations: Tamanrasset, in the Algerian Sahara, and Banizoumbou, in the Sahel. We retrieve lower aerosol SSAs at Banizoumbou, which is often impacted by dust‐smoke mixtures, and higher SSAs at Tamanrasset, where pure desert dust is the dominant aerosol. Our results generally fall within the AERONET uncertainty envelopes, although at Banizoumbou we retrieve a spectral dependence different from that of AERONET. On the basis of our analysis, we expect to be able to retrieve SSA from critical reflectance for pure dust with an uncertainty of 0.02 and to provide spatial and spectral SSA information that will help reduce current uncertainties in the aerosol radiative forcing over desert regions.
Progressive development of block‐in‐matrix fabric in a shale‐dominated shear zone: Insights from the Bobbio Tectonic Window (Northern Apennines, Italy)
Authors: Ogata Kei , Pini Gian Andrea , Carè Davide , Zélic Mario , Dellisanti Francesco
Published: December 2011

Block‐in‐matrix is a common fabric characterizing highly deformed to apparently chaotic rocks originated by sedimentary, tectonic and mud‐diapiric processes, in many exposed orogenic belts. A true mélange originates when this fabric is associated with mixing of rocks of different ages and provenance, as that characterizing the main décollement shear zone developed between the highly allochthonous Ligurian nappe and its substratum of foredeep deposits at the margins of the Bobbio Tectonic Window (Trebbia Valley, Northern Apennines). Mixing of rocks by both mass transport processes and synsedimentary thrusting occurs at the front and tectonic erosion at the base of the nappe during its emplacement. Evidence of polyphased deformations, spanning from liquefaction‐related and hydroplastic structures, to pseudo‐hydrofracturing features and mineralized veining, have been recognized within the marginal portions and along the sheared contacts of blocks encased within a scaly matrix. Crosscutting relationships testify a progressive deformation involving a transition from mesoscopic ductile to brittle conditions with the significant contribution of fluid overpressure. A novel evolutionary scheme for block‐in‐matrix fabric development is here proposed, involving the progressive dismembering of already highly deformed units, originally developed in non‐ to poorly lithified conditions, through a generalized simple shearing achieved during the evolution of the shear zone, coupled with strain hardening due to tectonic compaction, synkinematic diagenesis and fluid expulsion.
Canopy radiation transmission for an energy balance snowmelt model
Authors: Mahat Vinod , Tarboton David G.
Published: December 2011

To better estimate the radiation energy within and beneath the forest canopy for energy balance snowmelt models, a two stream radiation transfer model that explicitly accounts for canopy scattering, absorption and reflection was developed. Upward and downward radiation streams represented by two differential equations using a single path assumption were solved analytically to approximate the radiation transmitted through or reflected by the canopy with multiple scattering. This approximation results in an exponential decrease of radiation intensity with canopy depth, similar to Beer's law for a deep canopy. The solution for a finite canopy is obtained by applying recursive superposition of this two stream single path deep canopy solution. This solution enhances capability for modeling energy balance processes of the snowpack in forested environments, which is important when quantifying the sensitivity of hydrologic response to input changes using physically based modeling. The radiation model was included in a distributed energy balance snowmelt model and results compared with observations made in three different vegetation classes (open, coniferous forest, deciduous forest) at a forest study area in the Rocky Mountains in Utah, USA. The model was able to capture the sensitivity of beneath canopy net radiation and snowmelt to vegetation class consistent with observations and achieve satisfactory predictions of snowmelt from forested areas from parsimonious practically available information. The model is simple enough to be applied in a spatially distributed way, but still relatively rigorously and explicitly represent variability in canopy properties in the simulation of snowmelt over a watershed.
Fracture alteration by precipitation resulting from thermal gradients: Upscaled mean aperture‐effective transmissivity relationship
Authors: Chaudhuri A. , Rajaram H. , Viswanathan H.
Published: December 2011

Precipitation and dissolution reactions in fractures alter apertures, which in turn affects their flow and transport properties. We consider aperture alteration by precipitation in a “gradient‐reaction” regime where fluids are close to chemical equilibrium with a mineral everywhere, but precipitation is driven by solubility gradients. Monte Carlo simulations on computer‐generated aperture fields suggest that the most important feature of fracture alteration by precipitation is the formation of elongated precipitate bodies perpendicular to the mean flow direction. The simulation results provide a basis for a proposed upscaling relationship between mean aperture and the effective transmissivity tensor, incorporating a critical aperture at which the transmissivity decreases steeply.
Allosteric antibody inhibition of human hepsin protease
Authors: Koschubs Tobias , Dengl Stefan , Dürr Harald , Kaluza Klaus , Georges Guy , Hartl Christiane , Jennewein Stefan , Lanzendörfer Martin , Auer Johannes , Stern Alvin , Huang Kuo-Sen , Packman Kathryn , Gubler Ueli , Kostrewa Dirk , Ries Stefan , Hansen Silke , Kohnert Ulrich , Cramer Patrick , Mundigl Olaf
Published: December 2011

Hepsin is a type II transmembrane serine protease that is expressed in several human tissues. Overexpression of hepsin has been found to correlate with tumour progression and metastasis, which is so far best studied for prostate cancer, where more than 90% of such tumours show this characteristic. To enable improved future patient treatment, we have developed a monoclonal humanized antibody that selectively inhibits human hepsin and does not inhibit other related proteases. We found that our antibody, hH35, potently inhibits hepsin enzymatic activity at nanomolar concentrations. Kinetic characterization revealed non-linear, slow, tight-binding inhibition. This correlates with the crystal structure we obtained for the human hepsin–hH35 antibody Fab fragment complex, which showed that the antibody binds hepsin around α3-helix, located far from the active centre. The unique allosteric mode of inhibition of hH35 is distinct from the recently described HGFA (hepatocyte growth factor activator) allosteric antibody inhibition. We further explain how a small change in the antibody design induces dramatic structural rearrangements in the hepsin antigen upon binding, leading to complete enzyme inactivation.
Modulating material interfaces through biologically-inspired intermediates
Authors: Hazar Melis , Steward Robert L. , Chang Chia-Jung , Orndoff Cynthia J. , Zeng Yukai , Ho Mon-Shu , LeDuc Philip R. , Cheng Chao-Min
Published: December 2011

This letter describes the control of molecular filament organization through biologically inspired intermediates, enabling us to obtain large-area regular nanopatterns. We first studied cultured single filamentous actins on an unmodified glass surface (hydrophilic surface) and introduced myosin-II to modify the control. We then utilized an inorganic salt crystallization approach on the response of these two proteins, actin filament and myosin-II, to analyze the resultant spatially localized patterns. Through the utilization of myosin-II and the salt crystallization approach, we were able to induce the filament orientation of 63°; while without myosin-II, we induced an orientation of 90°.
Phase transitions in ferroelectric-paraelectric superlattices
Authors: Levanyuk A. P. , Misirlioglu I. B.
Published: December 2011

Within the phenomenological Landau–Ginzburg–Devonshire theory, we discuss the paraelectric-ferrolectric transition in superstructures consisting of ferroelectric and paraelectric layers of equal thickness. The polar axis of the ferroelectric is perpendicular to the layer plane as expected in fully strained BaTiO3/SrTiO3 superstructures on SrTiO3 substrates with pseudomorphic electrodes. We concentrate on the electrostatic effects and do not take into account the boundary conditions other than the electrostatic ones. We find that when the ferroelectric phase transition in the superstructures is into a multidomain state, both its temperature and its character, i. e., the profile of the polarization appearing at the phase transition is strongly influenced by the nature of the near-electrode region. This is also the case for the layer thickness separating the single-and multidomain regimes of the transition. Such a finding makes us question the idea that these superstructures can be thought of as infinite systems, i.e., periodic superstructures similar to a crystal. The irrelevance of this idea in certain conditions is demonstrated by comparing the phase transitions in two different superstructures consisting of ferroelectric and paraelectric layers of the same thickness. In one of them, the ferroelectric layer is in immediate contact with an ideal metallic electrode, whereas at the other boundary, it is the paraelectric layer that is in contact with the electrode. In another superstructure, one paraelectric layer is split in two equal parts which are placed as the first and last layer between the electrodes and the ferroelectric layers which are closest to the electrodes. We show (with some formal reservations) that the phase transition temperature in the first superstructure can be over 100 °C more than in the second one if the material parameters of BaTiO3/SrTiO3 are used for the estimations. Moreover, the profile of the polarization arising at the phase transition is inhomogeneous along the superstructure and has the maximum amplitude in the ferroelectric layer contacting the electrode. We argue that this situation is general and results in smearing of the phase transition anomalies for the layer thicknesses corresponding to multidomain transitions. The work is mainly analyical but numerical methods have been used to support some statements that have been put forward as hypotheses.
Heavy atom nitroxyl radicals. V. An experimental and ab initio study of the previously unknown H2PS free radical
Authors: Grimminger Robert A. , Clouthier Dennis J. , Tarroni Riccardo
Published: December 2011

The $\tilde B^2 A^{\prime} - \tilde X^2 A^{\prime} $B̃2A′−X̃2A′ transition of the prototypical thiophosphoryl radical, H2PS, was observed for the first time using laser-induced fluorescence and single vibronic level emission spectroscopy. H2PS and its deuterated isotopologues, D2PS and HDPS, were produced in a pulsed supersonic discharge jet from a precursor mixture of Cl3PS and H2 or D2 or an H2/D2 mixture in high-pressure argon. High level ab initio calculations of the lowest three doublet electronic states helped in the definitive assignment of the $\tilde B - \tilde X$B̃−X̃ transition, which involves electron promotion from the π to the π* orbital. Vibrational frequencies were determined for several modes of each isotopologue in the $\tilde X$X̃ and $\tilde B$B̃ states and found to be in accord with theoretical predictions. Although a line-by-line rotational analysis was not possible, the observed band contours are consistent with the geometries obtained from our ab initio calculations. Theory indicates that PS bond length increases upon electronic excitation, while the pyramidalization of the radical does not change significantly.
Local contact potential difference of molecular self-assemblies investigated by Kelvin probe force microscopy
Authors: Spadafora Evan J. , Linares Mathieu , Nisa Yahya Wan Zaireen , Lincker Frédéric , Demadrille Renaud , Grevin Benjamin
Published: December 2011

Self-assembled pi-conjugated oligomer nanowires have been investigated by frequency modulation atomic force microscopy and amplitude modulation Kelvin probe force microscopy under ultra high vacuum. The distance dependence of the contact potential difference (CPD) has been analyzed by combining high resolution imaging with distance-spectroscopy measurements. It is shown that the apparition of a damping contrast characterizes the onset of short range electrostatic (SRE) forces, which are responsible for the occurrence of local CPD (LCPD) modulations correlated with the molecular lattice. By working at the onset of the damping contrast, the tip-surface separation can be adjusted to minimize the contribution of SRE forces to the measured CPD.
Equation of motion with radiation reaction in ultrarelativistic laser-electron interactions
Authors: Seto Keita , Nagatomo Hideo , Koga James , Mima Kunioki
Published: December 2011

The intensity of the ultra-short pulse lasers has reached 1022 W/cm2 owing to the advancements of laser technology. When the motion of an electron becomes relativistic, bremsstrahlung accompanies it. The energy from this bremsstrahlung corresponds to the energy loss of the electron; therefore, the motion of the electron deviates from the case without radiation. The radiation behaves something like resistance. This effect called “radiation reaction” or “radiation damping” and the force converted from the radiation is named the “radiation reaction force” or the “damping force”. The equation of motion with the reaction force is known as the Lorentz-Abraham-Dirac (LAD) equation, but the solution of this equation is not physical due to the fact that it has a “run-away” solution. As one solution of this problem, we have derived a new equation which takes the place of the Lorentz-Abraham-Dirac equation. We will show the validity of this equation with a simple theoretical analysis.
Influence of higher-order dispersion coefficients on near-threshold bound and continuum states: Application to ${}^{88}\text{Sr}_2$Sr288
Authors: Kaiser Alexander , Müller Tim-Oliver , Friedrich Harald
Published: December 2011

We give a simple description of quantum states near the dissociation threshold of deep interatomic potentials. The influence of the potential tail is separated from effects due to the interaction at short distances. We present a general formalism which is valid for weakly bound and low-energy continuum states, both for vanishing and non-vanishing angular momentum. Its applicability is demonstrated for the example of the electronic ground state of the strontium dimer ${}^{88}\text{Sr}_2$Sr288. With an appropriate choice of the potential tail that includes higher-order dispersion coefficients, all short-range effects are incorporated via the threshold quantum number $v_{\text{D}}$vD and one further parameter accounting for residual short-range effects.
Fabrication of large scale nanostructures based on a modified atomic force microscope nanomechanical machining system
Authors: Hu Z. J. , Yan Y. D. , Zhao X. S. , Gao D. W. , Wei Y. Y. , Wang J. H.
Published: December 2011

The atomic force microscope (AFM) tip-based nanomechanical machining has been demonstrated to be a powerful tool for fabricating complex 2D/3D nanostructures. But the machining scale is very small, which holds back this technique severely. How to enlarge the machining scale is always a major concern for the researches. In the present study, a modified AFM tip-based nanomechanical machining system is established through combination of a high precision X-Y stage with the moving range of 100 mm × 100 mm and a commercial AFM in order to enlarge the machining scale. It is found that the tracing property of the AFM system is feasible for large scale machining by controlling the constant normal load. Effects of the machining parameters including the machining direction and the tip geometry on the uniform machined depth with a large scale are evaluated. Consequently, a new tip trace and an increasing load scheme are presented to achieve a uniform machined depth. Finally, a polymer nanoline array with the dimensions of 1 mm × 0.7 mm, the line density of 1000 lines/mm and the average machined depth of 150 nm, and a 20 × 20 polymer square holes array with the scale of 380 μm × 380 μm and the average machined depth of 250 nm are machined successfully. The uniform of the machined depths for all the nanostructures is acceptable. Therefore, it is verified that the AFM tip-based nanomechanical machining method can be used to machine millimeter scale nanostructures.
Impact of adsorbed organic monolayers on vacuum electron tunneling contributions to electrical resistance at an asperity contact
Authors: Berman D. , Walker M. J. , Nordquist C. D. , Krim J.
Published: December 2011

Electrical contact resistance measurements are reported for RF micro-electromechanical switches situated within an ultrahigh vacuum system equipped with in situ oxygen plasma cleaning capabilities. Measurements were performed on fused (permanently adhered) switches with Au/Au contacts and functioning switches with Au/RuO2 contacts in both the presence and absence of adsorbed monolayers of pentane and dodecane. For switches adhered in the closed position, adsorption occurs only in regions external to direct contact. For functioning switches, however, it can occur either within or exterior to the contact. The data are analyzed within the framework of two distinct geometries, to explore how the presence of adsorbed molecules in regions close to the contact may impact vacuum tunneling contributions to the experimentally measured resistance: (1) The resistance associated with direct contact in parallel with a vacuum tunneling path, which upon uptake of the monolayer is replaced by the molecular resistance and (2) a series connection of the direct contact resistance with the molecular layer after adsorption occurs, with the vacuum tunneling path assumed to be negligible. In all cases, the experimental results quantitatively favor scenario (1), whereby uptake of the molecular layer effectively shuts down the vacuum tunneling path, in this case approximately 30 Ω in the absence of an adsorbed film. The methods described herein thus constitute a new and original approach to documenting vacuum tunneling levels in regions of close proximity.
Structural, electronic, and dielectric properties of amorphous hafnium silicates
Authors: Chen Tsung-Ju , Kuo Chin-Lung
Published: December 2011

Using first-principles calculations, we have investigated the evolution of the structural, electronic, and dielectric properties of amorphous Hf1-xSixO2 over the entire range of composition. Our results show that the Si-rich Hf-silicates possess distinct structural characteristics from the Hf-rich ones. The electronic band gaps calculated using hybrid density functional agree well with the experiments, exhibiting nonlinear variation with the Si content. Different from the previous theoretical studies, our results support a nonlinear dependence of the dielectric constants on the composition of silicates, which is mainly attributed to the rapid reduction of the low-frequency vibrational motions of Hf atoms with increasing the Si content.
Dissociative electron attachment to triflates
Authors: Ptasińska Sylwia , Gschliesser David , Bartl Peter , Janik Ireneusz , Scheier Paul , Denifl Stephan
Published: December 2011

Gas phase studies of dissociative electron attachment to simple alkyl (CF3SO3CH3) and aryl (C6H5SO3CF3 and CF3SO3C6H4CH3) triflates, model molecules of nonionic photoacid generators for modern lithographic applications, were performed. The fragmentation pathways under electron impact below 10 eV were identified by means of crossed electron-molecular beam mass spectrometry. Major dissociation channels involved C–O, S–O, or C–S bond scissions in the triflate moiety leading to the formation of triflate (OTf−), triflyl (Tf−), or sulfonate (RSO3−) anions, respectively. A resonance leading to C–O bond breakage and OTf− formation in alkyl triflates occurred at electron energies about 0.5 eV lower than the corresponding resonance in aryl triflates. A resonance leading to S–O bond breakage and Tf− formation in aryl triflates occurred surprisingly at the same electron energies as C–O bond breakage. In case of alkyl triflates S–O bond breakage required 1.4 eV higher electron energies to occur and proceeded with substantially lower yields than in aryl triflates. C–S bond scission occurred for all presently studied triflates at energies close to 3 eV.
A new unstable mode in the wake of a circular cylinder
Authors: Verma Abhishek , Mittal Sanjay
Published: December 2011

The flow past a circular cylinder looses stability at Re ∼ 47, via the primary wake (PW) mode. Linear stability analysis of the steady base flow, in two dimensions, is conducted using a stabilized finite element formulation. A new mode, referred to as the secondary wake (SW) mode, is discovered which is found to be unstable for Re ≥ 110.8. The relative roles of the PW and SW mode in the development of Karman vortex shedding are also investigated.
Analysis of effective mobility and hall effect mobility in high-k based In0.75Ga0.25As metal-oxide-semiconductor high-electron-mobility transistors
Authors: Negara M. A. , Veksler D. , Huang J. , Ghibaudo G. , Hurley P. K. , Bersuker G. , Goel N. , Kirsch P.
Published: December 2011

We report an In0.75Ga0.25As metal-oxide-semiconductor high-electron-mobility transistor with a peak Hall mobility of 8300 cm2/Vs at a carrier density of 2 × 1012 cm−2. Comparison of split capacitance-voltage (CV) and Hall Effect measurements for the extracted electron mobility have shown that the split-CV can lead to an overestimation of the channel carrier concentration and a corresponding underestimation of electron mobility. An analysis of the electron density dependence versus gate voltage allows quantifying the inaccuracy of the split-CV technique. Finally, the analysis supported by multi-channel conduction simulations indicates presence of carriers spill over into the top InP barrier layer at high gate voltages.
Diffusion and incorporation of Cd in solar-grade Cu(In,Ga)Se2 layers
Authors: Hiepko K. , Bastek J. , Schlesiger R. , Schmitz G. , Wuerz R. , Stolwijk N. A.
Published: December 2011

We examined Cd diffusion in Cu(In,Ga)Se2 layers by means of the radiotracer technique. Depth profiles of 109Cd were determined by ion-beam sputter-sectioning upon isothermal diffusion in the range from 197 to 425 °C. The Cd diffusivity can be described by the Arrhenius equation DCd = 4.8 × 10−4 exp (−1.04 eV/kBT )cm2s−1. Atom-probe tomography on a sample saturated with natural Cd at 450 °C revealed its homogeneous incorporation over the crystal volume.
Piezoresponse force microscopy of domains and walls in multiferroic HoMnO3
Authors: Lochocki Edward B. , Park S. , Lee Nara , Cheong S.-W. , Wu Weida
Published: December 2011

We report ambient piezoresponse force microscopy (PFM) studies of the multiferroic hexagonal manganite HoMnO3 performed on the cleaved (110) surface of a single-crystal specimen. By changing the sample orientation with respect to the cantilever, we observed an unexpected out-of-plane PFM signal at domain walls, which depends on domain wall orientation, in addition to the expected in-plane PFM signal in domains. Further studies confirmed that the domain wall PFM signal results from an out-of-plane displacement, which can be explained by a simple model of local elastic response with the conservation of unit cell volume at head-on domain walls.
Optical anisotropy of GaSb type-II nanorods on vicinal (111)B GaAs
Authors: Kawazu Takuya , Akiyama Yoshihiro , Noda Takeshi , Mano Takaaki , Sakuma Yoshiki , Sakaki Hiroyuki
Published: December 2011

We form self-assembled GaSb type-II nanorods on a vicinal (111)B GaAs substrate by molecular beam epitaxy and study their optical anisotropy. The GaSb nanorods are elongated and aligned along the [−1 0 1] direction, where the average length, width, and height are about 84, 30, and 2.5 nm. In polarized photoluminescence (PL) measurements, the peak of the GaSb nanorods is observed at about 1.1 eV, where the PL intensity is largest for the [−1 0 1] polarization and smallest for the polarization perpendicular to it. The degree of polarization is more than 20% and depends on the recombination energy. By comparing with a theoretical model based on 4 × 4 Luttinger-Kohn Hamiltonian, we find that the experimental results are explained by considering the Sb/As inter-diffusion and the nanorod height distribution.
Nanometer optomechanical transistor based on nanometer cavity optomechanics with a single quantum dot
Authors: Li Jin-Jin , Zhu Ka-Di
Published: December 2011

A mechanical oscillator coupled to the optical fields of a cavity has emerged as an important new frontier in modern quantum optics and quantum information processing. In the present article, we report on the smallest optomechanical system with a single quantum dot (QD), where the role of the optical cavity is played by an excitonic resonance of the QD, while the role of the mechanical element is played by the lattice vibrations. The coupling between an exciton and phonons via deformation potential serves as the coupling of a mechanical oscillator to the cavity field via radiation pressure. This single quantum dot system provides a realization of the smallest optomechanical system which can act as a quantum optomechanical transistor and is achievable immediately in current experiments.
Magnetic properties and short-range structure analysis of granular cobalt silicon nitride multilayers
Authors: Jiménez-Villacorta F. , Espinosa A. , Céspedes E. , Prieto C.
Published: December 2011

The magnetic properties and local order of cobalt/silicon nitride metal-insulator multilayered system have been studied. Magnetization characterization reveals an evolution of the magnetic features by varying the metal layer thickness. Results show that multilayers with larger metal thickness (t) present a pure ferromagnetic character, whereas samples with t < 2 nm exhibit a granular superparamagnetic behavior, as it corresponds to discontinuous metal-insulator materials. An important decrease in the magnetization values for the clustered samples has also been observed. X-ray absorption near edge spectroscopy (XANES) and extended x-ray absorption fine structure (EXAFS) at the Co K-edge have been used to determine the local order and electronic configuration around cobalt. Results reveal the formation of an intermediate CoN phase likely located at the Co/Si3N4 interface. Further insight in the electronic structure of cobalt atoms has been investigated through ab-initio XANES calculations based on Green function’s multiple scattering formalism. Local-projected density of states (l-DOS) obtained by simultaneous computations has unveiled the effects of the nitrogen coordination in the electronic structure of the metal atom around the Fermi energy.
Optically switchable molecular device using microsphere based junctions
Authors: Faramarzi V. , Raimondo C. , Reinders F. , Mayor M. , Samorì P. , Doudin B.
Published: December 2011

Metallic planar electrodes are bridged using microspheres coated with chemisorbed azobenzene self-assembled monolayers. The circuit exhibits light-induced switching, with reproducibility over 90%, as statistically determined and compared to junctions incorporating photo-insensitive alkanethiol layers. Microsphere interconnects provide direct access to molecular transport properties, with reliability and stability, making multifunctional molecular electronics devices possible.
Extraction of the contact resistance from the saturation region of rubrene single-crystal transistors
Authors: Imakawa Masaki , Sawabe Kosuke , Yomogida Yohei , Iwasa Yoshihiro , Takenobu Taishi
Published: December 2011

A modified transmission-line method (TLM) is proposed to extract the contact resistance from the transistor saturation region. The conventional TLM requires a linear current–voltage characteristic, and this requirement strongly limits its application. In this study, we focused on the pinch-off point of the output characteristics and analyzed the contact resistance using nonlinear output curves. We applied the modified TLM to both p- and n-type rubrene single-crystal transistors and compared the mobility differences in terms of both the intrinsic bandwidth and the extrinsic carrier trap density.
Transforming from paramagnetism to room temperature ferromagnetism in CuO by ball milling
Authors: Gao Daqiang , Yang Zhaolong , Zhang Jing , Yang Guijin , Zhu Zhonghua , Qi Jing , Si Mingsu , Xue Desheng
Published: December 2011

In this work, we experimentally demonstrate that it is possible to induce ferromagnetism in CuO by ball milling without any ferromagnetic dopant. The magnetic measurements indicate that paramagnetic CuO is driven to the ferromagnetic state at room temperature by ball milling gradually. The saturation magnetization of the milled powders is found to increase with expanding the milling time and then decrease by annealing under atmosphere. The fitted X-ray photoelectron spectroscopy results indicate that the observed induction and weaken of the ferromagnetism shows close relationship with the valence charged oxygen vacancies (Cu1+-VO) in CuO.