bluuebunny/crossref_metadata_2025 huggingface dataset:
Systematics and bird conservation policies: the importance of species limits
Authors: ROJAS-SOTO OCTAVIO R. , NAVARRO-SIGÜENZA ADOLFO G. , ESPINOSA DE LOS MONTEROS ALEJANDRO
Published: December 2009

The taxonomic criteria used as bases for endangered species lists can affect conservation policy decisions. We emphasize that the use of different taxonomic units affects the baselines of such lists. Recent taxonomic reviews for the Mexican avifauna provided the tools for assessing this effect on a highly diverse avifauna which is currently in need of serious conservation actions. Most ornithologists have used a taxonomy based on the biological species concept (BSC) to make decisions on species limits and therefore to set them into endangered species lists. However, the application of the phylogenetic species concept (PSC) as an alternative for delimiting species, results in a different panorama of what should be protected. Our analysis shows that the current official Mexican endangered species list, BSC based, encompasses 371 birds, ranked as 277 species and 94 subspecies. The same list of protected forms changes under the phylogenetic species concept because 47 of them are not recognized as valid species, while another 28 forms merit higher levels of protection. Additionally, under this concept another 11 forms should be candidates for inclusion based on their restricted distribution. We call attention to the fact that the use of one or another species concept affects endangered species lists.
Foreword: special issue in memory of Nadia Busi
Authors: ACETO LUCA , INGOLFSDOTTIR ANNA
Published: December 2009

We still recall very vividly the announcement of Nadia Busi's death. It was Wednesday, 5 September 2007, and we were enjoying the half-day excursion at CONCUR 2007, a conference where just before lunch on that very day some of Nadia's latest work had been presented. The weather was splendid and we were enjoying the gorgeous view from the Arrábida Convent, basking in the glorious sunlight and admiring the blue sea in the distance. Everything was a celebration of life until death struck. Mario Bravetti, one of our colleagues from Bologna, received a phone call and broke the news to us that ‘Nadia has passed away’. After receiving this message, a cloud came over all the CONCUR participants who had known her.
(Tissue) P systems with cell polarity
Authors: BESOZZI DANIELA , BUSI NADIA , CAZZANIGA PAOLO , FERRETTI CLAUDIO , LEPORATI ALBERTO , MAURI GIANCARLO , PESCINI DARIO , ZANDRON CLAUDIO
Published: December 2009

We consider the structure of the intestinal epithelial tissue and of cell–cell junctions as the biological model inspiring a new class of P systems. First we define the concept of cell polarity, a formal property derived from epithelial cells, which present morphologically and functionally distinct regions of the plasma membrane. Then we show two preliminary results for this new model of computation: on the theoretical side, we show that P systems with cell polarity are computationally (Turing) complete; on the modelling side, we show that the transepithelial movement of glucose from the intestinal lumen into the blood can be described by such a formal system. Finally, we define tissue P systems with cell polarity, where each cell has fixed connections to the neighbouring cells and to the environment, according to both the cell polarity and specific cell–cell junctions.
An expressiveness study of priority in process calculi
Authors: VERSARI CRISTIAN , BUSI NADIA , GORRIERI ROBERTO
Published: December 2009

Priority is a frequently used feature of many computational systems. In this paper we study the expressiveness of two process algebras enriched with different priority mechanisms. In particular, we consider a finite (that is, recursion-free) fragment of asynchronous CCS with global priority (FAP, for short) and Phillips' CPG (CCS with local priority), and contrast their expressive power with that of two non-prioritised calculi, namely the π-calculus and its broadcast-based version, called bπ. We prove, by means of leader-election-based separation results, that, under certain conditions, there exists no encoding of FAP in π-Calculus or CPG. Moreover, we single out another problem in distributed computing, which we call thelast man standingproblem (LMS for short), that better reveals the gap between the two prioritised calculi above and the two non-prioritised ones, by proving that there exists no parallel-preserving encoding of the prioritised calculi in the non-prioritised calculi retaining anysincere(complete but partially correct, that is, admitting divergence or premature termination) semantics.
Nadia Busi's publications
Authors: ZAVATTARO GIANLUIGI
Published: December 2009

We conclude this special issue ofMathematical Structures in Computer Sciencewith a list of Nadia Busi's scientific output (excluding the papers in the current volume).
Amygdala activation to masked happy facial expressions
Authors: JURUENA MARIO F. , GIAMPIETRO VINCENT P. , SMITH STEPHEN D. , SURGULADZE SIMON A. , DALTON JEFFREY A. , BENSON PHILIP J. , CLEARE ANTHONY J. , FU CYNTHIA H.Y.
Published: December 2009

The amygdala has a key role in automatic non-conscious processing of emotions. Highly salient emotional stimuli elicit amygdala activity, and happy faces are among the most rapidly perceived facial expressions. In backward masking paradigms, an image is presented briefly and then masked by another stimulus. However, reports of amygdala responses to masked happy faces have been mixed. In the present study, we used functional magnetic resonance imaging (fMRI) to examine amygdala activation to masked happy, sad, and neutral facial expressions. Masked happy faces elicited greater amygdala activation bilaterally as compared to masked sad faces. Our findings indicate that the amygdala is highly responsive to non-consciously perceived happy facial expressions. (JINS, 2010, 16, 383–387.)
Deficits in the automatic activation of religious concepts in patients with Parkinson’s disease
Authors: BUTLER PAUL M. , MCNAMARA PATRICK , DURSO RAYMON
Published: December 2009

Religion is central to the lives of billions of people worldwide. To probe processing dynamics of religious cognition and its potential brain correlates, we used a novel priming procedure to assess the integrity of religious and control semantic networks in patients with Parkinson’s disease (PD) and controls. Priming for control, but not religious, concepts was intact in PD patients. Patients with left-onset (right-forebrain disease) evidenced severe impairment activating religious concepts. We next modeled the priming performance with modified cable equations. These analyses suggested that deficient performance of PD patients on activation of religious concepts was due to a change in the time constants governing gain and rate of decay of activation in these semantic networks. These modeling results are consistent with dopaminergic dysfunction in right-sided striatal-prefrontal networks. We conclude that right striatal-prefrontal dopaminergic networks support activation of complex religious concepts but not equally complex and related control concepts. (JINS, 2010,16, 252–261.)
INDETERMINACY IN CASH-IN-ADVANCE MODELS AND THE ROLE OF FRICTIONS
Authors: Akay Koray
Published: December 2009

A monetary cash-in-advance model is known to be prone to real indeterminacy if the intertemporal elasticity of substitution in consumption is sufficiently low. Moreover, if the model features habit formation in consumption, the scope of indeterminacy increases substantially. This paper shows that many of the nominal frictions and real rigidities commonly used in the New Keynesian paradigm act to decrease the scope of this indeterminacy. These frictions include stickiness in prices and wages, adjustment costs in investment, and variable capacity utilization. When they are all used together in the model, the problem of indeterminacy nearly vanishes, even when habit formation in consumption is allowed.
AN INTEGRAL EQUATION FOR THE DISTRIBUTION OF THE FIRST EXIT TIME OF A REFLECTED BROWNIAN MOTION
Authors: DE-LA-PEÑA VICTOR , HERNÁNDEZ-DEL-VALLE GERARDO , PACHECO-GONZÁLEZ CARLOS G.
Published: December 2009

Reflected Brownian motion is used in areas such as physiology, electrochemistry and nuclear magnetic resonance. We study the first-passage-time problem of this process which is relevant in applications; specifically, we find a Volterra integral equation for the distribution of the first time that a reflected Brownian motion reaches a nondecreasing barrier. Additionally, we note how a numerical procedure can be used to solve the integral equation.
ANALYSIS OF BLOCK-SOR ITERATION FOR THE THREE-DIMENSIONAL LAPLACIAN
Authors: ZHENG WENJUN , ZHAO ZHIQIN
Published: December 2009

The successive over-relaxation (SOR) iteration method for solving linear systems of equations depends upon a relaxation parameter. A well-known theory for determining this parameter was given by Young for consistently ordered matrices. In this paper, for the three-dimensional Laplacian, we introduce several compact difference schemes and analyse the block-SOR method for the resulting linear systems. Their optimum relaxation parameters are given for the first time. Analysis shows that the value of the optimum relaxation parameter of block-SOR iteration is very sensitive for compact stencils when solving the three-dimensional Laplacian. This paper provides a theoretical solution for determining the optimum relaxation parameter in real applications.
REFLECTED BACKWARD STOCHASTIC DIFFERENTIAL EQUATIONS DRIVEN BY A LÉVY PROCESS
Authors: REN YONG , FAN XILIANG
Published: December 2009

In this paper, we deal with a class of reflected backward stochastic differential equations (RBSDEs) corresponding to the subdifferential operator of a lower semi-continuous convex function, driven by Teugels martingales associated with a Lévy process. We show the existence and uniqueness of the solution for RBSDEs by means of the penalization method. As an application, we give a probabilistic interpretation for the solutions of a class of partial differential-integral inclusions.
Geologic evidence for multiple slip weakening mechanisms during seismic slip in crystalline rock
Authors: Kirkpatrick J. D. , Shipton Z. K.
Published: December 2009

We examine exhumed seismogenic faults to investigate the mechanisms that may have achieved dynamic fault weakening during ancient ruptures. Field and microscope observations imply more than one weakening mechanism must have been active during slip events on the faults. Pseudotachylytes that are continuous over the scale of field exposures are indicative of melt lubrication. A fault breccia crosscutting earlier formed cataclasites was mobilized during faulting and possibly represents a pressurized fault rock that resulted from thermal pressurization or elastohydrodynamic lubrication. In some faults, pseudotachylytes are developed in patches several meters long. Cataclasites in which there is no evidence for melting are present immediately along strike from the pseudotachylyte patches. By considering the energy required for melting, we show that the pseudotachylytes must have formed during ruptures larger than the patches, implying that the cataclasites also accommodated seismic slip. The distribution of fault rock types shows that the frictional response to slip during a single event was spatially variable. Reworked pseudotachylytes also indicate that coseismic processes change over time at a point on a fault. These observations emphasize that macroscopic dynamic fault weakening is a function of multiple coeval processes at microscales to mesoscales. Detailed observations of the discontinuous pseudotachylytes show that slip zone thickness is the critical parameter that controls active coseismic processes. The frictional response of a fault to slip is therefore dependent on the internal structure of faults; given the along‐strike heterogeneity of most mapped fault zones, the coexistence of multiple slip weakening mechanisms in a single earthquake will be common.
An assessment of Saharan dust loading and the corresponding cloud‐free longwave direct radiative effect from geostationary satellite observations
Authors: Brindley Helen E. , Russell Jacqueline E.
Published: December 2009

Previously, a method was developed to quantify Saharan dust optical thickness and simultaneously diagnose the cloud‐free longwave dust direct radiative effect (LWDRE) over a single surface site using observations from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) and Geostationary Earth Radiation Budget (GERB) instrument both flying on the Meteosat Second Generation series of satellites. In this paper the overall utility of the approach is investigated using a more comprehensive suite of observations, and the inherent uncertainties associated with the method are assessed. On the basis of these findings, the approach has been updated to account for the effects of varying dust layer altitude. Comparisons with colocated observations from the Aerosol Robotic Network (AERONET) and Multiangle Imaging Spectroradiometer (MISR) using the modified approach indicate that the visible optical thickness at 0.55 μm, τ055, can be obtained with an RMS uncertainty of ∼0.3 over North Africa and Arabia during sunlit hours, while monthly maps of optical depth derived over this region through spring and summer of 2006 show similar variability to that identified in the long‐term climatology provided by the Total Ozone Mapping Spectrometer (TOMS) Aerosol Index. The regional mean instantaneous cloud‐free LWDRE and associated LW radiative efficiency estimated from GERB over the same period are relatively constant with season, ranging from 9 to 11 W m−2 and 16–20 W m−2τ055−1, respectively.
Field Geophysics Class at Volcán Tungurahua, Ecuador
Authors: Johnson Jeffrey , Ruiz Mario
Published: December 2009

Ecuador's erupting Volcán Tungurahua was the recent site of a 3‐week graduate‐level geophysical course on volcanoes, hosted by Ecuador's Instituto Geofisico of the Escuela Politecnica Nacional (IG‐EPN) and the Department of Earth Science at the New Mexico Institute of Mining and Technology (NMT). Sixteen students from 12 universities and four countries participated in the intensive course, which entailed broadband seismometer and infrasound sensor deployment followed by subsequent data processing, analysis, interpretation, and result synthesis. Hardware for the course was provided by the Incorporated Research Institutes for Seismology (IRIS) through the Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL) as well as the IG‐EPN and NMT geophysics programs.
Improving the Resolution of Climate Models to Address Regional Climate Change: Simulating the Spatial‐Temporal Patterns of Anthropogenic Climate Change: A Workshop in the Bridging Disciplines, Bridging Scale Series; Santa Fe, New Mexico, 20–22 July 2009
Authors: Rauscher Sara A. , Ringler Todd D.
Published: December 2009

For decades, general circulation models (GCMs) have been one of the primary tools used to understand anthropogenic climate change. Now GCMs are faced with a substantially more complicated task: to provide information of sufficient spatial and temporal resolution to support policy initiatives that will address regional climate change. Different approaches are being developed and used to provide this information, including dynamic downscaling with limited area models (LAMs); high‐resolution GCMs with quasi‐uniform and variable‐resolution grids; and statistical downscaling of limited area and global simulations. At a workshop in New Mexico, participants discussed each method's strengths and limitations as well as associated uncertainty.
Source complexity of the 6 April 2009 L'Aquila (central Italy) earthquake and its strongest aftershock revealed by elementary seismological analysis
Authors: Pino Nicola Alessandro , Di Luccio Francesca
Published: December 2009

Seismic recordings are immediately available when an earthquake occurs. Their analysis allows the reconstruction of the rupture dynamics by means of sophisticated techniques, which usually need some tests to provide robust results. However, immediate information on the source kinematics is required in order to imagine the fault location and extent and quickly reconstruct the areas of stress release and subsequent accumulation. Very simple analysis may provide useful information, giving insight in source complexity. Right after the 6 April 2009 L'Aquila earthquake (MW = 6.3), we analyzed the seismograms recorded at broadband and strong motion stations and provided firm constraints on rupture kinematics, slip distribution, and static surface deformation, also discriminating the actual fault plane. The fracture occurred in two stages, with initial updip propagation, successively proceeding toward SE, possibly on a different plane. We also analyzed the strongest aftershock (MW = 5.6), showing that useful indications could be retrieved for lower magnitude events.
Temperature enhancements and vertical winds in the lower thermosphere associated with auroral heating during the DELTA campaign
Authors: Kurihara J. , Oyama S. , Nozawa S. , Tsuda T. T. , Fujii R. , Ogawa Y. , Miyaoka H. , Iwagami N. , Abe T. , Oyama K.‐I. , Kosch M. J. , Aruliah A. , Griffin E. , Kauristie K.
Published: December 2009

A coordinated observation of the atmospheric response to auroral energy input in the polar lower thermosphere was conducted during the Dynamics and Energetics of the Lower Thermosphere in Aurora (DELTA) campaign. N2 rotational temperature was measured with a rocket‐borne instrument launched from the Andøya Rocket Range, neutral winds were measured from auroral emissions at 557.7 nm with a Fabry‐Perot Interferometer (FPI) at Skibotn and the KEOPS, and ionospheric parameters were measured with the European Incoherent Scatter (EISCAT) UHF radar at Tromsø. Altitude profiles of the passive energy deposition rate and the particle heating rate were estimated using data taken with the EISCAT radar. The local temperature enhancement derived from the difference between the observed N2 rotational temperature and the MSISE‐90 model neutral temperature were 70–140 K at 110–140 km altitude. The temperature increase rate derived from the estimated heating rates, however, cannot account for the temperature enhancement below 120 km, even considering the contribution of the neutral density to the estimated heating rate. The observed upward winds up to 40 m s−1 seem to respond nearly instantaneously to changes in the heating rates. Although the wind speeds cannot be explained by the estimated heating rate and the thermal expansion hypothesis, the present study suggests that the generation mechanism of the large vertical winds must be responsible for the fast response of the vertical wind to the heating event.
Tracking the influence of a continental margin on growth of a magmatic arc, Fiordland, New Zealand, using thermobarometry, thermochronology, and zircon U‐Pb and Hf isotopes
Authors: Scott J. M. , Cooper A. F. , Palin J. M. , Tulloch A. J. , Kula J. , Jongens R. , Spell T. L. , Pearson N. J.
Published: December 2009

Geothermobarometric, radiogenic isotopic and thermochronologic data are used to track the influence of an ancient continental margin (Western Province) on development of an adjacent Carboniferous‐Cretaceous magmatic arc (Outboard Median Batholith) in Fiordland, New Zealand. The data show a record of complicated Mesozoic Gondwana margin growth. Paragneiss within the Outboard Median Batholith is of Carboniferous to Jurassic age and records burial to middle crustal depths in Late Jurassic–Early Cretaceous during subduction‐related plutonism and arc thickening. In contrast, Western Province metasedimentary rocks in the area of study immediately west of the Outboard Median Batholith are Late Cambrian–Early Ordovician in age, recrystallized at the amphibolite facies in the Late Devonian–Early Carboniferous and exhibit no evidence for Mesozoic textural or isotopic reequilibration. A phase of deformation, between 128 and 116 Ma deformed, exhumed, and cooled the Outboard Median Batholith to greenschist facies temperatures, while large parts of the Western Province underwent ≥9 kbar metamorphic conditions. Zircon grains from Mesozoic inboard plutons are isotopically more evolved (ɛHf(t) = +2.3 to +4.0) than those in the Outboard Median Batholith (ɛHf(t) = +9.4 to +11.1). The contrasting zircon Hf isotope ratios, absence of S‐type plutons or Proterozoic–Early Paleozoic inherited zircon, and the apparent absence of Early Paleozoic metasedimentary rocks indicates that the Outboard Median Batholith is unlikely to be underlain by the Western Province continental lithosphere. The new data are consistent with the Outboard Median Batholith representing an allochthonous (although not necessarily exotic) arc that was juxtaposed onto the Gondwana continental margin along the intervening Grebe Mylonite Zone.
Polarized traffic towards the cell surface: how to find the route
Authors: Carmosino Monica , Valenti Giovanna , Caplan Michael , Svelto Maria
Published: December 2009

Polarity is the structural and functional hallmark of epithelia. The apical plasma membrane, facing the organism's exterior (the lumen of the gut, renal tubule and glandular duct), differs in many important respects from the basolateral plasma membrane that is apposed to the interior of the organism. The generation and maintenance of epithelial polarity require a highly specialized subcellular machinery to bring proteins to their appropriate sites of action. This is a dynamic process involving the interpretation of sorting signals, vectorial delivery mechanisms, membrane‐specific fusion and retention processes. Here, we will provide a review of the field, highlighting recent advances within a historically relevant context.
Effect of misfit strain and surface roughness on the tunable dielectric behavior of Ba0.5Sr0.5TiO3 thin films
Authors: Saravanan K. Venkata , Krishna M. Ghanashyam , Raju K. C. James
Published: December 2009

The effect of substrate temperature on the crystallographic texture and surface morphology of Ba0.5Sr0.5TiO3 deposited by rf magnetron sputtering on (111) oriented Pt (150 nm)/Ti (10 nm)/SiO2 (300 nm)/Si (100) substrates is reported. The onset of crystallinity is observed above 500 °C, beyond which all films are oriented along the (111) plane up to a temperature of 800 °C. Over this temperature range, the misfit strain and root mean square roughness (rmsroughness) peak at 600 °C, decreasing beyond this peak value. The tunability of the dielectric constant at 100 kHz is highest (60% for a field strength of 300 kV/cm) at the lowest values of rmsroughness and misfit strain and decreases as these values increase. It is also shown that the morphology of the Pt underlayers is strongly affected by the processing conditions. This in turn influences the tunable behavior of the BST films as much as the substrate temperature during growth and the consequent microstructural variations.
Thermal properties of the optically transparent pore-free nanostructured yttria-stabilized zirconia
Authors: Ghosh S. , Teweldebrhan D. , Morales J. R. , Garay J. E. , Balandin A. A.
Published: December 2009

The authors report results of investigation of thermal conductivity of nanocrystalline yttria-stabilized zirconia. The optically transparent pore-free bulk samples were prepared via the spark plasma sintering process to ensure homogeneity. Thermal conductivity K was measured by two different techniques. It was found that the pore-free nanostructured bulk zirconia is an excellent thermal insulator with the room-temperature K∼1.7–2.0 W/m K. It was also shown that the “phonon-hopping” model can accurately describe specifics of K dependence on temperature and the grain size. The obtained results are important for optimization of zirconia properties for specific applications in advanced electronics and coatings.
Electrofragmentation modeling of conductive coatings on polymer substrates
Authors: Leterrier Yves , Pinyol Albert , Rougier Luc , Waller Judith H. , Månson Jan-Anders E.
Published: December 2009

Damage occurring under tensile loading and the resulting increase in electrical resistance of tin-doped indium oxide and amorphous graphite coatings on various polymer substrates are investigated, using an electrofragmentation method in situ in an optical microscope. The electrical resistance is modeled as a function of damage state assuming that the resistance of coating cracks is proportional to their opening, and that there exists a conducting path of constant thickness at the coating/substrate interface across the crack. The model reproduces the experimental data with good accuracy apart from the damage initiation and saturation stages where it underestimates the measured coating resistance. This is due to the presence of stable cracks of finite length in the initiation stage and delamination in the saturation stage. Impedance spectroscopy measurements confirm the purely resistive nature of the conducting path, whose resistivity is found to be three to four orders of magnitude higher than that of the uncracked coating.
Photothermal determination of thermal diffusivity and polymerization depth profiles of polymerized dental resins
Authors: Martínez-Torres P. , Mandelis A. , Alvarado-Gil J. J.
Published: December 2009

The degree and depth of curing due to photopolymerization in a commercial dental resin have been studied using photothermal radiometry. The sample consisted of a thick layer of resin on which a thin metallic gold layer was deposited, thus guaranteeing full opacity. Purely thermal-wave inverse problem techniques without the interference of optical profiles were used. Thermal depth profiles were obtained by heating the gold coating with a modulated laser beam and by performing a frequency scan. Prior to each frequency scan, photopolymerization was induced using a high power blue light emitted diode (LED). Due to the highly light dispersive nature of dental resins, the polymerization process depends strongly on optical absorption of the blue light, thereby inducing a depth dependent thermal diffusivity profile in the sample. A robust depth profilometric method for reconstructing the thermal diffusivity depth dependence on degree and depth of polymerization has been developed. The thermal diffusivity depth profile was linked to the polymerization kinetics.
Ring-polymer molecular dynamics rate-theory in the deep-tunneling regime: Connection with semiclassical instanton theory
Authors: Richardson Jeremy O. , Althorpe Stuart C.
Published: December 2009

We demonstrate that the ring-polymer molecular dynamics (RPMD) method is equivalent to an automated and approximate implementation of the “Im F” version of semiclassical instanton theory when used to calculate reaction rates in the deep-tunneling regime. This explains why the RPMD method is often reliable in this regime and also shows how it can be systematically improved. The geometry of the beads at the transition state on the ring-polymer potential surface describes a finite-difference approximation to the “instanton” trajectory (a periodic orbit in imaginary time βℏ on the inverted potential surface). The deep-tunneling RPMD rate is an approximation to the rate obtained by applying classical transition-state theory (TST) in ring-polymer phase-space using the optimal dividing surface; this TST rate is in turn an approximation to a free-energy version of the Im F instanton rate. The optimal dividing surface is in general a function of several modes of the ring polymer, which explains why centroid-based quantum-TSTs break down at low temperatures for asymmetric reaction barriers. Numerical tests on one-dimensional models show that the RPMD rate tends to overestimate deep-tunneling rates for asymmetric barriers and underestimate them for symmetric barriers, and we explain that this is likely to be a general trend. The ability of the RPMD method to give a dividing-surface-independent rate in the deep-tunneling regime is shown to be a consequence of setting the bead-masses equal to the physical mass.
Conformation and dynamics of model polymer in connected chamber-pore system
Authors: Saltzman Erica J. , Muthukumar Murugappan
Published: December 2009

Single polymer chains under spatially heterogeneous confinement are investigated through simulation of a chain in an infinite linear series of chambers and pores. Conformational properties studied include the number of occupied chambers and the radius of gyration along the chamber axis, both of which vary with chain length and chamber size according to simple scaling predictions. The probability distribution of chain spatial extent along the chamber axis is characterized by distinct peaks and troughs corresponding to favored and disfavored chain sizes. The large scale dynamics is characterized by the center-of-mass diffusion constant along the chamber axis, which exhibits an exponential dependence on chamber size with dramatically slower diffusion in larger chambers. Stepping time distributions change as the chamber size increases or chain length decreases from a symmetric form to a Poisson distribution. The evolution of the dynamics is suggestive of a substantial barrier, independent of chain length, that controls the large-scale motion for short-enough chains in large-enough chambers. Other known signatures of anomalous, nondiffusive dynamics are also observed. The onset of barrier-controlled or anomalous dynamics is conjectured to be the result of chains occupying only a small number of chambers simultaneously.
A conformational and vibrational study of CF3COSCH2CH3
Authors: Lestard María Eliana Defonsi , Tuttolomondo María Eugenia , Wann Derek A. , Robertson Heather E. , Rankin David W. H. , Ben Altabef Aida
Published: December 2009

The molecular structure and conformational properties of S-ethyl trifluorothioacetate, CF3COSCH2CH3, were determined in the gas phase by electron diffraction and vibrational spectroscopy (IR and Raman). The experimental investigations were supplemented by ab initio (Møller Plesset of second order) and density functional theory quantum chemical calculations at different levels of theory. Both experimental and theoretical methods reveal two structures with Cs (anti, anti) and C1 (anti, gauche) symmetries, although there are disagreements about which is more stable. The electron diffraction intensities are best interpreted with a mixture of 51(3)% anti, anti and 49(3)% anti, gauche conformers. This conformational preference was studied using the total energy scheme and the natural bond orbital scheme. In addition, the infrared spectra of CF3COSCH2CH3 are reported for the gas, liquid and solid phases as well as the Raman spectrum of the liquid. Using calculated frequencies as a guide, evidence for both Cs and C1 structures is obtained in the IR spectra. Harmonic vibrational frequencies and scaled force fields have been calculated for both conformers.
Yttrium and hydrogen superstructure and correlation of lattice expansion and proton conductivity in the BaZr0.9Y0.1O2.95 proton conductor
Authors: Braun A. , Ovalle A. , Pomjakushin V. , Cervellino A. , Erat S. , Stolte W. C. , Graule T.
Published: December 2009

Bragg reflections in Y-resonant x-ray diffractograms of BaZr0.9Y0.1O2.95 (BZY10) reveal that Y is organized in a superstructure. Comparison with neutron diffraction superstructure reflections in protonated/deuterated BZY10 suggests that both superstructures are linked, and that protons move in the landscape imposed by the Y. The thermal lattice expansion decreases abruptly for protonated BZY10 at T≥648±20 K, coinciding with the onset of lateral proton diffusion and suggesting a correlation of structural changes and proton conductivity. The chemical shift in the Y L1-shell x-ray absorption spectra reveals a reduction from Y3+ toward Y2+ upon protonation.
An ac field probe for the magnetic ordering of magnets with random anisotropy
Authors: Nguyen Ha M. , Hsiao Pai-Yi
Published: December 2009

A Monte Carlo simulation is carried out to investigate the magnetic ordering in magnets with random anisotropy (RA). Our results show peculiar similarities to recent experiments that the real part of ac susceptibility presents two peaks for weak RA and only one for strong RA regardless of glassy critical dynamics manifested for them. We demonstrate that the thermodynamic nature of the low-temperature peak is a ferromagneticlike dynamic phase transition to quasilong range order (QLRO) for the former. Our simulation, therefore, is able to be incorporated with the experiments to help clarify the existence of the QLRO theoretically predicted so far.
Rounded stretched exponential for time relaxation functions
Authors: Powles J. G. , Heyes D. M. , Rickayzen G. , Evans W. A. B.
Published: December 2009

A rounded stretched exponential function is introduced, C(t)=exp{(τ0/τE)β[1−(1+(t/τ0)2)β/2]}, where t is time, and τ0 and τE are two relaxation times. This expression can be used to represent the relaxation function of many real dynamical processes, as at long times, t⪢τ0, the function converges to a stretched exponential with normalizing relaxation time, τE, yet its expansion is even or symmetric in time, which is a statistical mechanical requirement. This expression fits well the shear stress relaxation function for model soft soft-sphere fluids near coexistence, with τE⪡τ0. The function gives the correct limits at low and high frequency in Cole–Cole plots for dielectric and shear stress relaxation (both the modulus and viscosity forms). It is shown that both the dielectric spectra and dynamic shear modulus imaginary parts approach the real axis with a slope equal to 0 at high frequency, whereas the dynamic viscosity has an infinite slope in the same limit. This indicates that inertial effects at high frequency are best discerned in the modulus rather than the viscosity Cole–Cole plot. As a consequence of the even expansion in time of the shear stress relaxation function, the value of the storage modulus derived from it at very high frequency exceeds that in the infinite frequency limit (i.e., G∞).
Structural and electronic properties of protein/thiolate-protected gold nanocluster with “staple” motif: A XAS, L-DOS, and XPS study
Authors: Simms Gordon A. , Padmos J. Daniel , Zhang Peng
Published: December 2009

Following the recent breakthrough of total structural determination of a Au-thiolate nanocluster [P. Jadzinsky et al., Science 318, 430 (2007)], extensive interests have been stimulated to unveil (or revisit) the structure-property relationship of various thiolate-Au nanostructures in light of the new finding of –SR–(Au–SR)x– “staple” motif. Here, we present experimental x-ray absorption spectroscopy (XAS) and x-ray photoelectron spectroscopy (XPS) results on the local structure and electronic properties of thiolate-protected Au nanocluster encapsulated in bovine serum albumin (Au-BSA) together with theoretical calculation of projected local density of states (l-DOS) of Au25(SR)18 model cluster. Analysis of the Au L3-edge extended x-ray absorption fine structure (EXAFS) of Au-BSA suggested that the nanocluster is Au25 with Au-thiolate “staple” motif. X-ray absorption near-edge structure (XANES) and Au 4f XPS were used to probe the electronic behavior of Au-BSA. The Au d-electron density of Au-BSA was found to decrease by 0.047 e− relative to that of the bulk. A self-consistent real space Green’s function approach implemented in ab initio FEFF8 program was used to calculate the l-DOS of Au25(SR)18 and other model clusters from a site-specific perspective. The theoretical results are in good agreement with the experimental d-DOS data of Au-BSA and, importantly, systematically illustrate the effect of Au-thiolate “staple” motif on the electronic behavior of Au25(SR)18. The present work sheds light on the structure-property relationship of thiolate-protected Au25 from both experimental and theoretical perspectives and illustrates the usefulness of XAS/l-DOS method in such studies.
Magnetization of graphane by dehydrogenation
Authors: Şahin H. , Ataca C. , Ciraci S.
Published: December 2009

Using first principles calculations, we show that each hydrogen vacancy created at graphane surface results in a local unpaired spin. For domains of hydrogen vacancies the situation is, however, complex and depends on the size and geometry of domains, as well as whether the domains are single or double sided. In single-sided domains, hydrogen atoms at the other side are relocated to pair the spins of adjacent carbon atoms by forming π-bonds. Owing to the different characters of exchange coupling in different ranges and interplay between unpaired spin and the binding geometry of hydrogen, vacancy domains can attain sizable net magnetic moments.
Magnetic-field-induced transformation in FeMnGa alloys
Authors: Zhu W. , Liu E. K. , Feng L. , Tang X. D. , Chen J. L. , Wu G. H. , Liu H. Y. , Meng F. B. , Luo H. Z.
Published: December 2009

A kind of ferromagnetic shape memory alloy with off-stoichiometric composition of Heusler alloy Fe2MnGa has been synthesized. By optimizing composition, the martensitic transformation has been modified to occur at about 163 K accompanying spontaneous magnetization, which enables a magnetic field-induced structural transition from a paramagnetic parent phase to a ferromagnetic martensite with high magnetization of 93.8 emu/g. The material performs a quite large lattice distortion through the transformation, (c−a)/c=33.5%, causing a shape memory strain upto 3.6%. Such large lattice distortions strongly influence the electron structures, and thus some special physical behavior related to the transport and conductive properties is investigated.
Carbon nanotube/nanodiamond structures: An innovative concept for stable and ready-to-start electron emitters
Authors: Guglielmotti V. , Chieppa S. , Orlanducci S. , Tamburri E. , Toschi F. , Terranova M. L. , Rossi M.
Published: December 2009

Efficient and robust cold cathodes have been assembled using as emitting material mats of single wall carbon nanotubes (SWCNTs) coated with nanodiamonds. The preparation of the hybrid nanotube/nanodiamond structures by chemical vapor deposition is a route suitable to be scaled up and adapted to the electronic industry requirements. Turn-on field of 1.7 V/μm and emission current density J of 6 mA/cm2 at applied field E of 6.2 V/μm were measured. The field emission properties of SWCNT coated with nanodiamond are very attractive in terms of reproducibility, current stability under medium vacuum and lack of arcing. Moreover, the diamond coating acts against the adsorption of chemical species, making it possible to avoid the outgassing procedures usually needed for current stabilization and allowing to reduce the time response for electron sources assembled with these hybrid materials.
Oscillatory behavior of perpendicular magnetic anisotropy in Pt/Co/Al(Ox) films as a function of Al thickness
Authors: Dahmane Y. , Arm C. , Auffret S. , Ebels U. , Rodmacq B. , Dieny B.
Published: December 2009

The evolution of the perpendicular magnetic anisotropy of Pt/Co/AlOx structures has been followed by extraordinary Hall Effect measurements as a function of both Al thickness and annealing treatment. A nonmonotonous evolution of the magnetic anisotropy is observed with increasing aluminum thickness, with a maximum around 1.4 nm attributed to the formation of quantum well states in the remaining metallic Al layer. This maximum gradually disappears after annealing. High resolution electron microscopy images indicate that the vanishing of this maximum is associated with homogenization of oxygen throughout the whole Al layer.
Terahertz emission mechanism of magnesium doped indium nitride
Authors: Ahn H. , Yeh Y.-J. , Hong Y.-L. , Gwo S.
Published: December 2009

We report carrier concentration-dependence of terahertz emission from magnesium doped indium nitride (InN:Mg) films. Near the critical concentration (nc∼1×1018 cm−3), the competition between two emission mechanisms determines the polarity of terahertz emission. InN:Mg with n>nc exhibits enhanced positive polarity terahertz emission compared to the undoped InN, which is due to the reduced screening of the photo-Dember field. For InN:Mg with n<nc, the polarity of terahertz signal changes to negative, indicating the dominant contribution of the surface electric field due to the large downward surface band bending within the surface layer extending over the optical absorption depth.
Surface adsorption and disordering in LiFePO4 based battery cathodes
Authors: Kayyar Archana , Qian Haijun , Luo Jian
Published: December 2009

A recent study [Kang and Ceder, Nature (London) 458, 190 (2009)] suggested that a Li4P2O7-like “fast ion-conducting surface phase” could form on the surfaces of LiFePO4 particles, enabling ultrafast discharging of Li-ion batteries. We demonstrate that these nanoscale surface films exhibit a self-selecting or “equilibrium” thickness, akin to those observed in simpler binary oxides [Luo and Chiang, Annu. Rev. Mater. Res. 38, 227 (2008)]. These observations can be interpreted as a case of coupled prewetting and premelting. Similar nanoscale intergranular films are also observed. These nanoscale interfacial phenomena can be utilized to tailor nanoparticles for battery and many other applications.
Electron spin relaxation by nuclei and holes in single InAs quantum dots
Authors: Dou X. M. , Chang X. Y. , Sun B. Q. , Xiong Y. H. , Niu Z. C. , Ni H. Q. , Jiang D. S.
Published: December 2009

Electron spin relaxation of charged excitons X+ and X2+ are investigated by time-resolved and polarization-resolved photoluminescence spectroscopy. For X+ configuration, the electron spin relaxation shows a typical decay curve induced by hyperfine interaction with nuclei, whereas for X2+ state the electron spin relaxation is affected not only by nuclei but also by electron-hole exchange interaction, leading to a power-law time dependence.
Temperature dependence of competition between interlayer and interfacial exchange couplings in ferromagnetic/antiferromagnetic/ferromagnetic trilayers
Authors: Liu X. H. , Liu W. , Yang F. , Lv X. K. , Cui W. B. , Guo S. , Gong W. J. , Zhang Z. D.
Published: December 2009

The competition between interlayer and interfacial exchange couplings is found to be temperature dependent in Co(3 nm)/AF/Fe(10 nm) trilayers with AF≡antiferromagnetic NiO, Cr2O3 or Cr. The temperature dependence in trilayers with AF insulating NiO or Cr2O3 spacer layer differs from that with AF metallic Cr. In the insulator case, the enhancement in the interlayer exchange coupling and the reduction in interfacial exchange coupling with increasing temperature results in dominating interlayer exchange coupling at high temperature. In the metallic spacer case, both the couplings decrease with increasing temperature, resulting in decoupling at high temperatures.
Frequency-agile terahertz-wave parametric oscillator in a ring-cavity configuration
Authors: Minamide Hiroaki , Ikari Tomofumi , Ito Hiromasa
Published: December 2009

We demonstrate a frequency-agile terahertz wave parametric oscillator (TPO) in a ring-cavity configuration (ring-TPO). The TPO consists of three mirrors and a MgO:LiNbO3 crystal under noncollinear phase-matching conditions. A novel, fast frequency-tuning method was realized by controlling a mirror of the three-mirror ring cavity. The wide tuning range between 0.93 and 2.7 THz was accomplished. For first demonstration using the ring-TPO, terahertz spectroscopy was performed as the verification of the frequency-agile performance, measuring the transmission spectrum of the monosaccharide glucose. The spectrum was obtained within about 8 s in good comparison to those of Fourier transform infrared spectrometer.
Emission of terahertz radiations from fractal antennas
Authors: Miyamaru F. , Saito Y. , Takeda M. W. , Liu L. , Hou B. , Wen W. , Sheng Ping
Published: December 2009

We investigate the emission of terahertz radiation from a photoconductive fractal antenna fabricated on a semi-insulating gallium arsenide substrate. Owing to the self-similarity of fractal structures, our fractal antenna shows a multiband emission of terahertz radiation. The emission intensity at peak frequency is about twice that from a bow-tie antenna. We also investigate the mechanism of the multiband emission by using the finite-difference time-domain calculation.
The interaction of oxygen vacancies with grain boundaries in monoclinic HfO2
Authors: McKenna Keith , Shluger Alexander
Published: December 2009

The diffusion and segregation of oxygen vacancies near a grain boundary in m-HfO2 is investigated by first principles calculations. We find that both neutral and positive vacancies segregate to the grain boundary. Positive vacancies, which are mobile in the bulk with activation energies for diffusion ∼0.7 eV, have enhanced mobility parallel to the boundary plane but once at the boundary face high barriers to climb out.
Direct-current effects on magnetization reversal properties of submicron-size Permalloy patterns for radio-frequency devices
Authors: Zhang Hanqiao , Hoffmann Axel , Divan Ralu , Wang Pingshan
Published: December 2009

Ferromagnetic resonance (FMR) spectroscopy is used to measure direct-current (dc) effects on the magnetization reversal properties of submicron-sized lateral patterned magnetic material. The observed FMR frequency-field relationship shows that for both 240 and 550 nm wide Permalloy (Py) nanowires the coercivity is reduced by ∼33% when a 50 mA dc passes through the transmission line where the nanowires are incorporated. The temperature dependence of the coercivity has a T relationship which suggests the coherent rotation mode tendency in such 100 nm thick Py nanowires.
Reconstitution of bacterial outer membrane TonB-dependent transporters in planar lipid bilayer membranes
Authors: Udho Eshwar , Jakes Karen S. , Buchanan Susan K. , James Karron J. , Jiang Xiaoxu , Klebba Phillip E. , Finkelstein Alan
Published: December 2009

Micronutrients such as siderophore-bound iron and vitamin B
12
cross the outer membrane of Gram-negative bacteria through a group of 22-stranded β-barrel proteins. They share the unusual feature that their N-terminal end inserts from the periplasmic side into the β-barrel and plugs the lumen. Transport results from energy-driven movement of TonB protein, which either pulls the plug out of the barrel or causes it to rearrange within the barrel. Attempts to reconstitute native plugged channels in an ion-conducting state in lipid bilayer membranes have so far been unsuccessful. We, however, have discovered that if the
cis
solution contained 4 M urea, then, with the periplasmic side of the channel facing that solution, macroscopic conductances and single channel events could be observed. These results were obtained with FhuA, Cir, and BtuB; for the former two, the channels were closed by removing the 4 M urea. Channels generated by 4 M urea exposure were not a consequence of general protein denaturation, as their ligand-binding properties were preserved. Thus, with FhuA, addition of ferrichrome (its siderophore) to the
trans
, extracellular-facing side reversibly inhibited 4 M urea-induced channel opening and blocked the channels. With Cir, addition of colicin Ia (the microbial toxin that targets Cir) to the
trans
, extracellular-facing side prevented 4 M urea-induced channel opening. We hypothesize that 4 M urea reversibly unfolds the FhuA and Cir plugs, thereby opening an ion-conducting pathway through these channels, and that this mimics to some extent the in vivo action of TonB on these plugs.