bluuebunny/crossref_metadata_2025 huggingface dataset:
Shaping the active, autonomous and responsible modern retiree: an analysis of discursive technologies and their links with neo-liberal political rationality
Authors: LALIBERTE RUDMAN DEBBIE
Published: February 2006

Retirement is undergoing structural and discursive transformations that have implications for the individual and social experience and management of later life. Although discourses about retirement do not determine how individuals will prepare for and act as ‘retirees’, they provide morally-laden messages that shape people's possibilities for being and acting. Using Canadian newspaper articles published in 1999 and 2000, and drawing upon the governmentality perspective, this study explores the interconnections between neo-liberal political rationality and discursive constructions of ‘retiree’ subjectivities. The analysis demonstrates the ways in which certain subjectivities, and their associated technologies and practices of the self that are consistent with neo-liberal political rationality, are being shaped as ideal for ‘retirees’. The paper critically examines this process and its implications, and argues that the personal ‘freedom’ promised with the idealised life practices is ultimately illusory, because they oblige older people to resist or defy ageing through relentless projects of self-reflection and improvement, self-marketing, risk management, lifestyle maximisation and body optimisation. The implications of the neo-liberal discourse about old age and ‘retirees’ for future social policies and older people's services are critically examined.
The influence of patient's age on clinical decision-making about coronary heart disease in the USA and the UK
Authors: ADAMS ANN , BUCKINGHAM CHRISTOPHER D. , ARBER SARA , MCKINLAY JOHN B. , MARCEAU LISA , LINK CAROL
Published: February 2006

This paper examines UK and US primary care doctors' decision-making about older (aged 75 years) and midlife (aged 55 years) patients presenting with coronary heart disease (CHD). Using an analytic approach based on conceptualising clinical decision-making as a classification process, it explores the ways in which doctors' cognitive processes contribute to ageism in health-care at three key decision points during consultations. In each country, 56 randomly selected doctors were shown videotaped vignettes of actors portraying patients with CHD. The patients' ages (55 or 75 years), gender, ethnicity and social class were varied systematically. During the interviews, doctors gave free-recall accounts of their decision-making. The results do not establish that there was substantial ageism in the doctors' decisions, but rather suggest that diagnostic processes pay insufficient attention to the significance of older patients' age and its association with the likelihood of co-morbidity and atypical disease presentations. The doctors also demonstrated more limited use of ‘knowledge structures’ when diagnosing older than midlife patients. With respect to interventions, differences in the national health-care systems rather than patients' age accounted for the differences in doctors' decisions. US doctors were significantly more concerned about the potential for adverse outcomes if important diagnoses were untreated, while UK general practitioners cited greater difficulty in accessing diagnostic tests.
Globality, plurality and freedom: the Arendtian perspective
Authors: AXTMANN ROLAND
Published: February 2006

This article reconstructs Hannah Arendt’s theory of political freedom in the context of her analysis of globality. In a first step it is shown that Arendt builds her theory of political freedom around the core concepts of plurality, action, sovereignty and judgment. This theory arises out of Arendt’s experience and understanding of totalitarianism. This experience also underpins Arendt’s analysis of the ‘global condition’. Having argued in her analysis of totalitarianism that the modern state in the form of the nation-state had become compromised as the space of political freedom since its development in the early nineteenth century, Arendt asks in which alternative space, in the post-totalitarian global age, freedom can be located. In her tentative answer, Arendt develops a political and philosophical understanding of federalism. Going back to Thomas Jefferson’s discussion of ‘elementary republics’, Arendt attempts to combine her notion of participatory citizenship with the idea of confederal structures of ward republics. Reflections upon the conditions of the possibility of the interrelationships between such confederations lead Arendt back to Karl Jasper’s notion of ‘limitless communication’. This notion opens her analysis up to contemporary ‘intercultural’ arguments.
The state, international competitiveness and neoliberal globalisation: is there a future beyond ‘the competition state’?
Authors: FOUGNER TORE
Published: February 2006

This article seeks to contribute to opening up a space of possibility for the state to become something other than a competitive entity in and through a critical (re)problematisation of ‘international competitiveness’ as a governmental problem. In more specific terms, it inquires into how international competitiveness was constituted as such a problem in the first place; how both the meaning of international competitiveness and the terms of the ‘competitiveness problem’ have been transformed by globalisation talk and multilateral efforts at neoliberal global governance; and how the discourse of international competitiveness works to (re)produce the state as a competitive entity on a continuous basis.
Triggered codeswitching: A corpus-based evaluation of the original triggering hypothesis and a new alternative
Authors: BROERSMA MIRJAM , DE BOT KEES
Published: February 2006

In this article the triggering hypothesis for codeswitching proposed by Michael Clyne is discussed and tested. According to this hypothesis, cognates can facilitate codeswitching of directly preceding or following words. It is argued that the triggering hypothesis in its original form is incompatible with language production models, as it assumes that language choice takes place at the surface structure of utterances, while in bilingual production models language choice takes place along with lemma selection. An adjusted version of the triggering hypothesis is proposed in which triggering takes place during lemma selection and the scope of triggering is extended to basic units in language production. Data from a Dutch–Moroccan Arabic corpus are used for a statistical test of the original and the adjusted triggering theory. The codeswitching patterns found in the data support part of the original triggering hypothesis, but they are best explained by the adjusted triggering theory.
Cross-linguistic transfer in adjective–noun strings by preschool bilingual children
Authors: NICOLADIS ELENA
Published: February 2006

One hypothesis holds that bilingual children's cross-linguistic transfer occurs in spontaneous production when there is structural overlap between the two languages and ambiguity in at least one language (Döpke, 1998; Hulk and Müller, 2000). This study tested whether overlap/ambiguity of adjective–noun strings in English and French predicted transfer. In English, there is only one order (adjective–noun) while in French both adjective–noun and noun–adjective order are allowed, with the latter as the default. Unidirectional transfer from English to French was predicted. 35 French–English preschool bilingual children (and 35 age-matched English monolinguals and 10 French monolinguals) were asked to name pictures by using an adjective–noun string. In addition to the reversing adjective–noun strings in French as predicted by the overlap/ambiguity hypothesis, the bilingual children reversed more adjective–noun strings in English than monolinguals. It is proposed that cross-linguistic transfer might better be understood as an epiphenomenon of speech production.
English vocabulary development in bilingual kindergarteners: What are the best predictors?
Authors: UCHIKOSHI YUUKO
Published: February 2006

This study examines growth rates in vocabulary over an academic year for 150 Latino English language learners. In October, February, and June of kindergarten, participants completed standardized measures of receptive and expressive vocabulary. Before the second and third assessments, a third of the children watched Arthur three times a week during school hours, while another third viewed Between the Lions. The last third did not view either show during school hours. Data on children's preschool experiences and home literacy activities were collected. Growth modeling analyses show while there were no effects of classroom viewing, children who viewed Arthur and Between the Lions at home had steeper growth trajectories than those who had not. Additional effects of native language home use and preschool attendance were seen. Boys displayed better English vocabulary skills than girls. These findings suggest the importance of English exposure and native language maintenance for English L2 vocabulary development.
Production of coronal stops by simultaneous bilingual adults
Authors: SUNDARA MEGHA , POLKA LINDA , BAUM SHARI
Published: February 2006

This study investigated acoustic-phonetics of coronal stop production by adult simultaneous bilingual and monolingual speakers of Canadian English (CE) and Canadian French (CF). Differences in the phonetics of CF and CE include voicing and place of articulation distinctions. CE has a two-way voicing distinction (in syllable initial position) contrasting short-and long-lag VOT; coronal stops in CE are described as alveolar. CF also has a two-way voicing distinction, but contrasting lead and short-lag VOT; coronal stops in CF are described as dental. Acoustic analyses of stop consonants for both VOT and dental/alveolar place of articulation are reported. Results indicate that simultaneous bilingual as well as monolingual adults produce language-specific differences, albeit not in the same way, across CF and CE for voicing and place. Similarities and differences between simultaneous bilingual and monolingual adults are discussed to address phonological organization in simultaneous bilingual adults.
Accumulation of mineral ballast on organic aggregates
Authors: Passow Uta , De La Rocha Christina L.
Published: February 2006

To address whether the incorporation of suspended minerals drives the sedimentation of particulate organic carbon in the ocean or vice versa, incubations of phytoplankton‐detritus aggregates were set up in rolling tanks containing seawater and suspended clay (illite) or calcium carbonate at concentrations ranging between 10 and 50,000 μg L−1. The suspended minerals were efficiently scavenged by and incorporated into the organic aggregates. The volume and porosity of aggregates decreased with increasing mineral concentrations, and at suspended mineral concentrations higher than 500 μg L−1 the initially medium‐sized aggregates were fragmented into thousands of tiny, dense aggregates. Because radius and density have opposite effects on aggregate sinking rates, the relationship between aggregate particulate organic carbon (POC) to mineral ratio and sinking rate is not a straightforward one that necessarily results in higher sinking rates with increased mineral content. In these experiments the saturating capacity of organic aggregates for mineral particles appeared to be 97 to 98 weight‐percent mineral (i.e., a POC to dry weight ratio of 0.02 to 0.03 μg C μg−1). This parallels the values of 0.05 μg C μg−1 observed for sinking particles in the deep sea and suggests that it is the flux of POC that determines the flux of minerals to the deep and not the other way around.
Manifestations of the Indian Ocean tsunami of 2004 in satellite nadir‐viewing radar backscatter variations
Authors: Troitskaya Yuliya I. , Ermakov Stanislav A.
Published: February 2006

The paper reports on the first experimental evidence for space‐observed manifestation of the open ocean tsunami in the microwave radar backscatter (in C‐ and Ku‐bands; electromagnetic wave lengths 6cm and 2 cm respectively). Significant (a few dB) variations of the radar cross section synchronous with the sea level anomaly were found in the geophysical data record of the altimetry satellite Jason‐1 for the track which crossed the head wave of the catastrophic tsunami of 26 December 2004. The simultaneous analysis of the available complementary data provided by the satellite three‐channel radiometer enabled us to exclude meteorological factors as possible causes of the observed signal modulation. A possible physical mechanism of modulation of short wind waves due to transformation of the thin boundary layer in the air by a tsunami wave is discussed. The results open new possibilities of monitoring tsunamis from space.
Zonal patterns of δ13C, δ15N and 210Po in the tropical and subtropical North Pacific
Authors: Chen Min , Guo Laodong , Ma Qiang , Qiu Yusheng , Zhang Run , Lv E , Huang Yipu
Published: February 2006

Nitrogen fixation process may supply a significant fraction of bioavailable nitrogen to surface waters, increase the oceanic sequestration of atmospheric CO2, and alter the distribution of geochemical parameters. We report a zonal pattern of δ15N and δ13C in particulate organic matter (POM), and ratios of particulate 210Po to dissolved 210Po along a transect through the subtropical and tropical North Pacific. Both 15N and 210Po signals indicated an enhanced N2 fixation in the northwestern subtropical North Pacific. The eastward decrease of N2 fixation along this transect testified the role of aeolian Fe and P in controlling marine N2 fixation. Associated with the zonal variations of 15N and 210Po, the δ13C of suspended POM increased eastward, reflecting the decrease of anthropogenic CO2 concentration in surface seawater from west to east in the study area. Our results highlight the need to examine more closely the mechanisms of possible longitudinal variation in N2 fixation in the ocean and the role of aeolian Fe and P in controlling marine N2 fixation and anthropogenic CO2.
Influence of a variable thermal conductivity on the thermochemical evolution of Mars
Authors: Schumacher Sandra , Breuer Doris
Published: February 2006

The influences of variations in thermal conductivity due to composition, temperature, and pressure in mantle and crust on the thermochemical evolution of Mars have been examined with parameterized convection models. We use a temperature‐ and pressure‐dependent thermal conductivity in the mantle and column‐averaged values between 1.5 and 4 Wm−1K−1 for the crust (with 2 Wm−1K−1 as the representative value for a basaltic crust). The major characteristic of the models is a slower cooling of the upper mantle with a long‐existing global partial melt zone and a stronger crustal production late in the evolution compared to earlier models which assume a constant thermal conductivity of 4 Wm−1K−1. To explain the observed crustal thickness and the early crustal formation on Mars, the formation of an enriched primordial crust is required. Recent volcanism can be explained by lateral temperature variations that are caused by thickness variations of the low conducting crust. These melt zones which occur underneath thicker than average crust may be the source region for the observed longstanding volcanism in Tharsis and Elysium instead of plumes rising from the core‐mantle boundary. The evolution of the elastic lithosphere is characterized by a transition at which the elastic strength is first provided by the crust and later also by the upper mantle. This finding may explain the estimated elastic lithosphere thickness of less than 16 km in the Noachian and more than 100 km in the Hesperian and Amazonian.
A method to reconstruct past accumulation rates in alpine firn regions: A study on Fiescherhorn, Swiss Alps
Authors: Schwerzmann Aurel , Funk Martin , Blatter Heinz , Lüthi Martin , Schwikowski Margit , Palmer Anne
Published: February 2006

Annual snow layers in the accumulation zone of glaciers become thinner by viscous deformation while moving to greater depth. The reconstruction of the accumulation rate history requires the correction of the thickness of annual layers. We apply a novel method to determine the vertical velocity by repeated survey with a caliper probe of grooves scratched into the wall of a borehole. With this information and the assumptions of steady state velocity and density fields, the correction of layer thicknesses can be determined without knowledge of the ice density profile and thus can be applied to boreholes without ice cores. The method is applied to a borehole on Fiescherhorn, Swiss Alps, resulting in a substantially larger correction than with the simpler method of Nye (1963).
Diatom δ18O evidence for the development of the modern halocline system in the subarctic northwest Pacific at the onset of major Northern Hemisphere glaciation
Authors: Swann George E. A. , Maslin Mark A. , Leng Melanie J. , Sloane Hilary J. , Haug Gerald H.
Published: February 2006

Establishing a time frame for the development of the modern halocline and stratified water column in the subarctic North Pacific has significant paleoclimatic implications. Here we present a δ18O(diatom) record consisting of only two species that represents autumn/winter conditions in the region across the onset of major Northern Hemisphere glaciation boundary. At circa 2.73 Ma a decrease in δ18O(diatom) of 4.6‰ occurs, whereas previously published δ18O(foram) results show a 2.6‰ increase. The δ18O(diatom) and U37k sea surface reconstructions indicate both a significant freshening of 2–4 practical salinity units and an increase in surface temperatures in the summer to early winter period from circa 2.73 Ma onward. In contrast, the concomitant increase in δ18O(foram) is likely to be reflective of conditions beneath the mesothermal structure and/or spring conditions when warmer sea surface temperatures are not present in the region. These results are consistent with the development of the modern halocline system at 2.73 Ma with year‐round stratification of the water column and a strengthened seasonal thermocline during the summer to early winter period, resulting in one of the largest summer to winter temperature gradients in the open ocean. The onset of stratification would also have led to a warm pool of surface water from circa 2.73 Ma, which may have provided a potential source of extra moisture needed to supply the growing North American ice sheets at this time.
A framework for assessing uncertainties in climate change impacts: Low‐flow scenarios for the River Thames, UK
Authors: Wilby R. L. , Harris I.
Published: February 2006

A probabilistic framework is presented for combining information from an ensemble of four general circulation models (GCMs), two greenhouse gas emission scenarios, two statistical downscaling techniques, two hydrological model structures, and two sets of hydrological model parameters. GCMs were weighted according to an index of reliability for downscaled effective rainfall, a key determinant of low flows in the River Thames. Hydrological model structures were weighted by performance at reproducing annual low‐flow series. Weights were also assigned to sets of water resource model (CATCHMOD) parameters using the Nash‐Sutcliffe efficiency criterion. Emission scenarios and downscaling methods were unweighted. A Monte Carlo approach was then used to explore components of uncertainty affecting projections for the River Thames by the 2080s. The resulting cumulative distribution functions (CDFs) of low flows were most sensitive to uncertainty in the climate change scenarios and downscaling of different GCMs. Uncertainties due to the hydrological model parameters and emission scenario increase with time but were less important. Abrupt changes in low‐flow CDFs were attributed to uncertainties in statistically downscaled summer rainfall. This was linked to different behavior of atmospheric moisture among the chosen GCMs.
Equivalence of two models for biodegradation during contaminant transport in groundwater
Authors: Cunningham J. A. , Mendoza‐Sanchez I.
Published: February 2006

We compare two models that have been used frequently for describing biodegradation during contaminant transport in groundwater. One is a “simple” model based upon macroscopic properties only, and the other is a “biofilm” model that accounts for contaminant diffusion and reaction in biofilms. Although the simple model has been used frequently, its mathematical formulation appears inadequate to describe the physics of the biodegradation process. Hence it is unclear when the simple model should be considered valid, and analyses predicated upon the simple model are called into question. We resolve this issue by arguing that the simple model should be considered valid when it is mathematically equivalent to the conceptually superior biofilm model. We demonstrate that the two models are exactly equivalent at the macroscopic scale when steady state conditions prevail. Under these conditions the equivalent macroscopic degradation rate coefficient k can be related to microscopic rate parameters that describe mass transfer across a boundary layer, diffusion within the biofilm, and reaction within the biofilm. Under transient (nonsteady state) conditions the two models are not strictly equivalent. However, the error between the two models is negligible in certain cases. In particular, when the rate‐limiting step for biodegradation is either mass transfer across the boundary layer or diffusion within the biofilm, there is no distinguishable difference between the predictions of the two models. Thus this paper can be considered a theoretical foundation for use of the commonly employed simple biodegradation model as well as an elucidation of the conditions for its validity.
Cannabinoids and cancer: pros and cons of an antitumour strategy
Authors: Bifulco Maurizio , Laezza Chiara , Pisanti Simona , Gazzerro Patrizia
Published: February 2006

In the last two decades, research has dramatically increased the knowledge of cannabinoids biology and pharmacology. In mammals, compounds with properties similar to active components ofCannabis sativa, the so called ‘endocannabinoids’, have been shown to modulate key cell‐signalling pathways involved in cancer cell growth, invasion and metastasis. To date, cannabinoids have been licensed for clinical use as palliative treatment of chemotherapy, but increased evidences showed direct antiproliferative actions of cannabinoid agonists on several tumour cellsin vitroand in animal models. In this article, we will review the principal molecular pathways modulated by cannabinoids on cancer and summarizeprosandconsevidence on the possible future use of endocannabinoid‐based drugs in cancer therapy.

British Journal of Pharmacology(2006)148, 123–135. doi:10.1038/sj.bjp.0706632
[3H]GR205171 displays similar NK1 receptor binding profile in gerbil and human brain
Authors: Griffante Cristiana , Carletti Renzo , Andreetta Filippo , Corsi Mauro
Published: February 2006

In this study, [3H]GR205171 (3(S)‐(2‐methoxy‐5‐(5‐trifluoromethyltetrazol‐1‐yl)‐phenylmethylamino)‐2(S)‐phenylpiperidine), a potent and selective NK1 receptor antagonist, was characterised in autoradiographic studies in gerbil brain and in binding experiments on homogenates from gerbil and human brain cortex and striatum.

In autoradiographic studies in gerbil brain, highest levels of [3H]GR205171 binding sites were observed in caudate putamen, nucleus accumbens, medial and cortical nuclei of the amygdala and intermediate levels were detected in the hypothalamus, basolateral amygdala, septum, and cortex.

Saturation experiments in homogenates of brain striatum from gerbil showed that [3H]GR205171 binds to a single receptor population with a pKd value of 10.8±0.2 and a Bmax value of 607±40 fmol mg−1. A lower number of NK1 receptor sites was found in cortex, where a Bmax of 94±6 fmol mg−1 protein was obtained. Saturation experiments performed on homogenates from brain striatum of two human subjects and brain cortex of three human subjects showed that [3H]GR205171 binds with pKd values not different from gerbil and Bmax values ranging from 318±51 to 432±27 fmol mg−1 protein in striatum and from 59±1 to 74±21 fmol mg−1 protein in cortex. The natural ligand [3H]Substance P (SP) bound with sub‐nanomolar affinity to 15 and 6% sites compared to [3H]GR205171 in gerbil and human striatum, respectively.

In competition binding experiments, GR205171 and the NK1 receptor antagonists aprepitant (MK‐869), L‐733,060 and NKP‐608 bound with similar pKi values in gerbil and human striatum, irrespective of the use of [3H]GR205171 or [3H]SP as radioligand. The following rank order was found in terms of pKi values: GR205171>aprepitantL‐733,060>NKP‐608. In homologous displacement experiments in gerbil and human striatum, SP showed nanomolar affinity, whereas in [3H]GR205171 competition experiments SP bound with pIC50 values in the micromolar range and Hill slopes significantly lower than one.

It is concluded that the similarities of [3H]GR205171 binding characteristics and pharmacology between gerbil and human in cortex and striatum support the use of gerbil in preclinical models to study the effects of NK1 receptor antagonists in the central nervous system.

British Journal of Pharmacology (2006) 148, 39–45. doi:10.1038/sj.bjp.0706697
Gene regulatory networks: A coarse-grained, equation-free approach to multiscale computation
Authors: Erban Radek , Kevrekidis Ioannis G. , Adalsteinsson David , Elston Timothy C.
Published: February 2006

We present computer-assisted methods for analyzing stochastic models of gene regulatory networks. The main idea that underlies this equation-free analysis is the design and execution of appropriately initialized short bursts of stochastic simulations; the results of these are processed to estimate coarse-grained quantities of interest, such as mesoscopic transport coefficients. In particular, using a simple model of a genetic toggle switch, we illustrate the computation of an effective free energy Φ and of a state-dependent effective diffusion coefficient D that characterize an unavailable effective Fokker-Planck equation. Additionally we illustrate the linking of equation-free techniques with continuation methods for performing a form of stochastic “bifurcation analysis”; estimation of mean switching times in the case of a bistable switch is also implemented in this equation-free context. The accuracy of our methods is tested by direct comparison with long-time stochastic simulations. This type of equation-free analysis appears to be a promising approach to computing features of the long-time, coarse-grained behavior of certain classes of complex stochastic models of gene regulatory networks, circumventing the need for long Monte Carlo simulations.
Vector coherent state theory of the generic representations of so(5) in an so(3) basis
Authors: Turner P. S. , Rowe D. J. , Repka J.
Published: February 2006

For applications of group theory in quantum mechanics, one generally needs explicit matrix representations of the spectrum generating algebras that arise in bases that reduce the symmetry group of some Hamiltonian of interest. Here we use vector coherent state techniques to develop an algorithm for constructing the matrices for arbitrary finite-dimensional irreps of the SO(5) Lie algebra in an SO(3) basis. The SO(3) subgroup of SO(5) is defined by regarding SO(5) as linear transformations of the five-dimensional space of an SO(3) irrep of angular momentum two. A need for such irreps arises in the nuclear collective model of quadrupole vibrations and rotations. The algorithm has been implemented in MAPLE, and some tables of results are presented.
Large atom number Bose-Einstein condensate machines
Authors: Streed Erik W. , Chikkatur Ananth P. , Gustavson Todd L. , Boyd Micah , Torii Yoshio , Schneble Dominik , Campbell Gretchen K. , Pritchard David E. , Ketterle Wolfgang
Published: February 2006

We describe experimental setups for producing large Bose-Einstein condensates of Na23 and Rb87. In both, a high-flux thermal atomic beam is decelerated by a Zeeman slower and is then captured and cooled in a magneto-optical trap. The atoms are then transferred into a cloverleaf-style Ioffe-Pritchard magnetic trap and cooled to quantum degeneracy with radio-frequency-induced forced evaporation. Typical condensates contain 20×106 atoms. We discuss the similarities and differences between the techniques used for producing large Rb87 and Na23 condensates in the context of nearly identical setups.
High-sensitivity vector magnetometer for measuring magnetic torque at low temperatures
Authors: Benito L. , Arnaudas J. I. , del Moral A.
Published: February 2006

We present a fully automated vector vibrating-sample magnetometer where the sample can be rotated against the applied magnetic field Hap, so that the angular dependence of the longitudinal, Mlong, and transversal, Mtrans, components of M with respect to Hap on the rotation plane are determined. The magnetic field range is ±20kOe and temperature ranges between 4.2 and 340 K. The resolution is better than 2×10−7emu and the sensitivity is 5×10−6emu. Standard hysteresis loop measurements are possible as well. As examples of its capability we display torque curves performed at low temperatures in a [Ho8Lu15]50 superlattice and in a 60-nm-thick Terfenol-D thin film.
Regge trajectories of the Coulomb potential in the space of constant negative curvature S31
Authors: Kurochkin Yu. , Shoukavy Dz.
Published: February 2006

Analytic properties of the scattering amplitude for Coulomb potential on the background of the space of constant negative curvature are studied. Special attention is given to the comparison of the Regge trajectories for curved and flat spaces. We show that there exist considerably differences in the behavior of the Regge trajectories in these spaces.
Upper and lower bounds for an eigenvalue associated with a positive eigenvector
Authors: Mouchet Amaury
Published: February 2006

When an eigenvector of a semibounded operator is positive, we show that a remarkably simple argument allows to obtain upper and lower bounds for its associated eigenvalue. This theorem is a substantial generalization of Barta-type inequalities and can be applied to non-necessarily purely quadratic Hamiltonians. An application for a magnetic Hamiltonian is given and the case of a discrete Schrödinger operator is also discussed. It is shown how this approach leads to some explicit bounds on the ground-state energy of a system made of an arbitrary number of attractive Coulombian particles.
Quantum and Fisher information from the Husimi and related distributions
Authors: Slater Paul B.
Published: February 2006

The two principal/immediate influences—which we seek to interrelate here—upon the undertaking of this study are papers of Życzkowski and Słomczyński [J. Phys. A 34, 6689 (2001)] and of Petz and Sudár [J. Math. Phys. 37, 2262 (1996)]. In the former work, a metric (the Monge one, specifically) over generalized Husimi distributions was employed to define a distance between two arbitrary density matrices. In the Petz-Sudár work (completing a program of Chentsov), the quantum analog of the (classically unique) Fisher information (monotone) metric of a probability simplex was extended to define an uncountable infinitude of Riemannian (also monotone) metrics on the set of positive definite density matrices. We pose here the questions of what is the specific/unique Fisher information metric for the (classically defined) Husimi distributions and how does it relate to the infinitude of (quantum) metrics over the density matrices of Petz and Sudár? We find a highly proximate (small relative entropy) relationship between the probability distribution (the quantum Jeffreys’ prior) that yields quantum universal data compression, and that which (following Clarke and Barron) gives its classical counterpart. We also investigate the Fisher information metrics corresponding to the escort Husimi, positive-P and certain Gaussian probability distributions, as well as, in some sense, the discrete Wigner pseudoprobability. The comparative noninformativity of prior probability distributions—recently studied by Srednicki [Phys. Rev. A 71, 052107 (2005)]—formed by normalizing the volume elements of the various information metrics, is also discussed in our context.
Effects of ion-ion collisions and inhomogeneity in two-dimensional kinetic ion simulations of stimulated Brillouin backscattering
Authors: Cohen B. I. , Divol L. , Langdon A. B. , Williams E. A.
Published: February 2006

Two-dimensional simulations with the BZOHAR [B. I. Cohen, B. F. Lasinski, A. B. Langdon, and E. A. Williams, Phys. Plasmas 4, 956 (1997)] hybrid code (kinetic particle ions and Boltzmann fluid electrons) have been used to investigate the saturation of stimulated Brillouin backscatter (SBBS) instability, including the effects of ion-ion collisions and inhomogeneity. Two types of Langevin-operator, ion-ion collision models were implemented in the simulations. In both models the collisions are functions of the local ion temperature and density, but the collisions have no velocity dependence in the first model. In the second model the collisions are also functions of the energy of the ion that is being scattered so as to represent a more physical Fokker-Planck collision operator. Collisions decorrelate the ions from the acoustic waves in SBS, which disrupts ion trapping in the acoustic wave. Nevertheless, ion trapping leading to a hot ion tail and two-dimensional physics that allows the SBS ion waves to nonlinearly scatter, remain important saturation mechanisms for SBBS in a high-gain limit over a range of ion collisionality. Ion-ion collisions tend to increase ion-wave dissipation, which decreases the gain exponent for stimulated Brillouin backscattering; and the peak Brillouin backscatter reflectivities decrease with increasing collisionality in the simulations for velocity-independent collisions and very weakly decrease for the range of Fokker-Planck collisionality considered. SBS backscatter in the presence of a spatially nonuniform plasma flow is also investigated. Simulations show that, depending on the sign of the spatial gradient of the flow relative to the backscatter, ion trapping effects that produce a nonlinear frequency shift can enhance (autoresonance) reflectivities relative to anti-autoresonant configurations, in agreement with theoretical arguments.
Construction of a Cantilever-Andreev-Tunneling rig and its applications to superconductors
Authors: Park W. K. , Greene L. H.
Published: February 2006

A technique for point-contact spectroscopy, based on an electromechanical mechanism for the contact formation, has been developed. It is designed to be used in both He4 and He3 cryostats. The performance has been demonstrated by conductance measurements on various kinds of superconductors, including the conventional superconductor Nb, the two-band superconductor MgB2, and the heavy-fermion superconductor CeCoIn5. Characteristic conductance spectra obtained prove that this technique is useful for the investigation of the superconducting order parameter. Advantages of this technique such as its simplicity and versatility are described.
BabySQUID: A mobile, high-resolution multichannel magnetoencephalography system for neonatal brain assessment
Authors: Okada Yoshio , Pratt Kevin , Atwood Christopher , Mascarenas Anthony , Reineman Richard , Nurminen Jussi , Paulson Douglas
Published: February 2006

We developed a prototype of a mobile, high-resolution, multichannel magnetoencephalography (MEG) system, called babySQUID, for assessing brain functions in newborns and infants. Unlike electroencephalography, MEG signals are not distorted by the scalp or the fontanels and sutures in the skull. Thus, brain activity can be measured and localized with MEG as if the sensors were above an exposed brain. The babySQUID is housed in a moveable cart small enough to be transported from one room to another. To assess brain functions, one places the baby on the bed of the cart and the head on its headrest with MEG sensors just below. The sensor array consists of 76 first-order axial gradiometers, each with a pickup coil diameter of 6mm and a baseline of 30mm, in a high-density array with a spacing of 12–14mm center-to-center. The pickup coils are 6±1mm below the outer surface of the headrest. The short gap provides unprecedented sensitivity since the scalp and skull are thin (as little as 3–4mm altogether) in babies. In an electromagnetically unshielded room in a hospital, the field sensitivity at 1kHz was ∼17fT∕√Hz. The noise was reduced from ∼400to200fT∕√Hz at 1Hz using a reference cancellation technique and further to ∼40fT∕√Hz using a gradient common mode rejection technique. Although the residual environmental magnetic noise interfered with the operation of the babySQUID, the instrument functioned sufficiently well to detect spontaneous brain signals from babies with a signal to noise ratio (SNR) of as much as 7.6:1. In a magnetically shielded room, the field sensitivity was 17fT∕√Hz at 20Hz and 30fT∕√Hz at 1Hz without implementation of reference or gradient cancellation. The sensitivity was sufficiently high to detect spontaneous brain activity from a 7month old baby with a SNR as much as 40:1 and evoked somatosensory responses with a 50Hz bandwidth after as little as four averages. We expect that both the noise and the sensor gap can be reduced further by approximately half with a gain in SNR of about four. Thus, we conclude from the performance of the prototype that it should be feasible to improve the babySQUID to detect cortical activity in infants in real time with high spatial resolution.
Automation of a McBain-Bakr-type thermogravimetric analyzer using a digital image correlation technique
Authors: Trexler M. D. , Sanders T. H. , Singh P. M.
Published: February 2006

Thermogravimetric analysis was used to obtain corrosion kinetics data for several materials in high-temperature environments. A thermogravimetric analyzer has been developed that uses a McBain-Bakr quartz spring balance in conjunction with a digital image acquisition and analysis package to accurately characterize materials through image correlation. This provides a new method for automatically measuring mass changes continuously with a variable resolution depending on the spring component. The decomposition of calcium oxalate was used to verify the validity of the technique. The results show two reactions, whose reaction temperatures were determined by the intercept method, upon heating to 650 °C. The mass loss at the first reaction temperature, 200 °C, was 20% and a 30% loss was observed at 500 °C. Comparison of the experimentally obtained results with those of other researchers who used commercial instruments suggests that the method of using digital image analysis in conjunction with a spring to monitor mass change is a viable and accurate replacement for automatic electrobalances and cathetometers for thermal analysis of materials. Additional comparison between corrosion tests performed on SA210 steel in H2S using both a commercial thermobalance and the developed technique confirmed that high-temperature corrosion can be monitored accurately with the proposed method.
Simple hybrid current-voltage source for the characterization of organic light-emitting devices
Authors: Beaudoin Normand , Essiambre Sophie , Gauvin Serge
Published: February 2006

Some organic light-emitting devices (OLEDs) behave better and longer when driven with alternating bias. It is believed that the reverse bias helps to remove the trapped charges and prevents permanent drift of ionic dopants or ion migration from electrodes. OLEDs behave much like diodes. When driven with a voltage source, the highly asymmetrical exponential I-V curve of diodes makes the accurate control of the forward current difficult. Using a voltage-controlled current source, the voltage can constantly adjust to maintain the desired current through the device. The reverse resistance of a diode is large. Using a current source to reverse bias can produce a large reverse voltage that would destroy the junction. In this article we present an electronic device used to drive and characterize organic light-emitting devices. It consists of a high voltage (±225V) hybrid source, which alternatively generates direct voltage-controlled current pulses, up to 200 mA, and reverse voltage-controlled voltage pulses. Furthermore, it allows simultaneous measurement of both, direct and reverse, current and voltage. This hybrid source, driven by an arbitrary wave form generator, makes possible the dynamical characterization of OLED when submitted to a wide variety of current and voltage signals.
Mechanical loss of laser-welded fused silica fibers
Authors: Harry Gregory , Corbitt Thomas , Freytsis Marat , Ottaway David , Mavalvala Nergis , Penn Steve
Published: February 2006

The mechanical quality factor of a carbon dioxide laser-welded fiber was measured and compared to flame-welded fibers to determine the suitability of laser welding for attaching suspension fibers to test masses in precision experiments. The loss in the fiber was found to be limited primarily by thermoelastic damping and surface loss, rather than loss from the weld. This technique is attractive for the attachment of fused silica suspensions where low thermal noise and precision location of the weld are considered.
A simple and unified approach to identify integrable nonlinear oscillators and systems
Authors: Chandrasekar V. K. , Pandey S. N. , Senthilvelan M. , Lakshmanan M.
Published: February 2006

In this paper, we consider a generalized second-order nonlinear ordinary differential equation (ODE) of the form ẍ+(k1xq+k2)ẋ+k3x2q+1+k4xq+1+λ1x=0, where ki’s, i=1,2,3,4, λ1, and q are arbitrary parameters, which includes several physically important nonlinear oscillators such as the simple harmonic oscillator, anharmonic oscillator, force-free Helmholtz oscillator, force-free Duffing and Duffing–van der Pol oscillators, modified Emden-type equation and its hierarchy, generalized Duffing–van der Pol oscillator equation hierarchy, and so on, and investigate the integrability properties of this rather general equation. We identify several new integrable cases for arbitrary value of the exponent q,q∊R. The q=1 and q=2 cases are analyzed in detail and the results are generalized to arbitrary q. Our results show that many classical integrable nonlinear oscillators can be derived as subcases of our results and significantly enlarge the list of integrable equations that exists in the contemporary literature. To explore the above underlying results we use the recently introduced generalized extended Prelle-Singer procedure applicable to second-order ODEs. As an added advantage of the method, we not only identify integrable regimes but also construct integrating factors, integrals of motion, and general solutions for the integrable cases, wherever possible, and bring out the mathematical structures associated with each of the integrable cases.
The interaction of patterned solutes in binary solvent mixtures
Authors: Overduin S. D. , Patey G. N.
Published: February 2006

Mean solute-solute forces and solute-induced solvent structure are investigated for pairs of chemically patterned (patched) solutes in binary mixtures near demixing coexistence. The isotropic and anisotropic hypernetted-chain integral equation theories as well as a superposition approximation are solved and compared. The patched solutes consist of one end that favors the majority species in the mixture while the other end favors the minority species. A wide range of patch sizes is considered. The isotropic and anisotropic theories are found to be in good agreement for most orientations, including the most attractive and most repulsive configurations. However, some differences arise for asymmetrical orientations where unlike ends of the solute particles face each other. In contrast, superposition often gives a rather poor approximation to the mean force, even though the results obtained for the solvent densities agree qualitatively with the anisotropic theory. The mean force is sensitive to small differences in the densities particularly near demixing. For patched solutes the influence of demixinglike behavior is evident both in the orientational dependence and in the range of the mean force acting between solutes.
The molecular structure and a Renner-Teller analysis of the ground and first excited electronic states of the jet-cooled CS2+ molecular ion
Authors: He Sheng-Gui , Clouthier Dennis J.
Published: February 2006

The ÃΠu2−X̃Πg2 electronic band system of the jet-cooled CS2+ ion has been studied by laser-induced fluorescence and wavelength-resolved emission techniques. The ions were produced in a pulsed electric discharge jet using a precursor mixture of carbon disulfide vapor in high-pressure argon. Rotational analysis of the high-resolution spectrum of the Π3∕22 component of the 000 band gave linear-molecule molecular structures of r0″=1.5554(10)Å and r0′=1.6172(12)Å. Renner-Teller analyses of the vibronic structure in the spectra showed that the ground-state spin-orbit splitting (A=−447.0cm−1) is much larger than that of the excited state (A=−177.5cm−1), but that the Renner-Teller parameters are of similar magnitude and that a strong ν1−2ν2 Fermi resonance occurs in both states. Previous analyses of the vibronic structure in the ground and excited states of the ion from pulsed field-ionization–photoelectron data are shown to be substantially correct.
Surface-emitting microlaser combining two-dimensional photonic crystal membrane and vertical Bragg mirror
Authors: Ben Bakir B. , Seassal Ch. , Letartre X. , Viktorovitch P. , Zussy M. , Di Cioccio L. , Fedeli J. M.
Published: February 2006

We report on the design and fabrication of heterogeneous and compact surface-emitting microlasers, optically pumped and operating at 1.5μm at room-temperature. A very low threshold, below 15μW, is achieved. The devices consists of a top two-dimensional InP photonic crystal slab, including four InAsP quantum wells, a SiO2 bonding layer, and a bottom high index contrast Si∕SiO2 Bragg mirror deposited on a Si wafer. The graphitelike photonic crystal lattice is tailored for vertical emission. We theoretically and experimentally demonstrate that the Bragg reflector can strongly enhance the quality factor of the photonic crystal resonant mode, leading to a drastic decrease of the lasing threshold.
Blue light-emitting diode-based, enhanced resonant excitation of longitudinal acoustic modes in a closed pipe with application to NO2
Authors: Santiago Guillermo D. , González Martín G. , Peuriot Alejandro L. , González Francisco , Slezak Verónica B.
Published: February 2006

We present a new, very compact resonant photoacoustic system based on a simple closed pipe, transversally illuminated by an array of blue light-emitting diodes uniformly distributed along the tube to produce an acoustic signal from NO2–N2 samples. The illumination is modulated in a particular way as to produce amplification of the acoustic resonance corresponding to the second longitudinal mode. The linearity of the system for NO2 trace detection is studied. This arrangement provides a simple, compact, and cheap setup, useful for both measuring emissions from diesel engines and teaching photoacoustic spectroscopy in gases.
Monodispersed metal clusters in solid matrices: A new experimental setup
Authors: Hillenkamp Matthias , di Domenicantonio Giulia , Félix Christian
Published: February 2006

We describe a new experimental setup for the production of samples of metal clusters embedded in matrices stable at ambient conditions. The cluster ions are generated in the gas phase and codeposited fragmentation-free together with the evaporated matrix. Mean cluster sizes range from a few to many thousands of atoms. For small clusters (n<20) mass selection is possible; larger clusters are deposited in narrow size distributions. Matrix materials include metals (Cu and Ag) and oxides such as quartz. The performance of the apparatus as well as sample characterization procedures are described. We show first results on the magnetic properties of different cobalt cluster size distributions (⟨n⟩=15,600,2300,6500) embedded in copper matrices, demonstrating intercluster as well as cluster-lattice interactions.