bluuebunny/crossref_metadata_2025_split huggingface dataset:
Is the relationship between syndromes of depression and dementia temporal? The MRC-ALPHA and Hefei-China studies
Authors: Chen R. , Hu Z. , Wei L. , Qin X. , Copeland J. R. 
Published: June 2008

BackgroundRecent studies have shown a temporal association between depressive symptoms and cognitive decline. However, the relationship between syndromes of depression and dementia is unknown.MethodA total of 1736 people aged ⩾65 years in China and 5222 older people in the UK were interviewed using the Geriatric Mental State Examination (GMS) and reinterviewed at follow-up. Five levels of syndromes of depression and dementia were diagnosed using the Automated Geriatric Examination for Computer Assisted Taxonomy (AGECAT).ResultsAlthough there were fewer depressive syndromes in Chinese than British participants, both populations showed a similarly high level of syndromes of dementia (organic disorder) (20% for women, 14% for men). There was a significant cross-sectional correlation between syndrome levels of depression and dementia (correlation coefficients: 0.141–0.248 for Chinese, 0.168–0.248 for British). This was maintained for different age, gender and people with and without cardiovascular disease (CVD). The relationship between syndromes of baseline depression and follow-up dementia was less substantial: the correlation coefficient was 0.075 [95% confidence interval (CI) 0.021–0.128] for the Chinese sample at the 1-year follow-up, and 0.093 (95% CI 0.061–0.125) for the British at the 2-year follow-up and 0.093 (95% CI 0.049–0.130) at the 4-year follow-up. This relationship disappeared in participants without baseline organic syndromes. In a multiple adjusted logistic regression analysis, an increased risk of organic syndromes seemed to be associated with baseline, mainly in the highest level of, depressive syndromes.ConclusionsThe relationship between syndromes of depression and dementia might be temporal. The lack of an obvious dose–response relationship between baseline depressive syndromes and follow-up dementia syndromes suggests that the causal relationship between depression and dementia needs further investigation.
A class of pairwise-independent joinings
Authors: JANVRESSE ÉLISE , DE LA RUE THIERRY 
Published: June 2008

AbstractWe introduce a special class of pairwise-independent self-joinings for a stationary process: those for which one coordinate is a continuous function of the two others. We investigate which properties on the process the existence of such a joining entails. In particular, we prove that if the process is aperiodic, then it has positive entropy. Our other results suggest that such pairwise independent, non-independent self-joinings exist only in very specific situations: essentially when the process is a subshift of finite type topologically conjugate to a full-shift. This provides an argument in favor of the conjecture that two-fold mixing implies three-fold-mixing.
Numerical methods based controller design for mobile robots
Authors: Scaglia Gustavo , Montoya Lucía Quintero , Mut Vicente , di Sciascio Fernando 
Published: June 2008

SUMMARYThis paper presents the design of four controllers for a mobile robot such that the system may follow a preestablished trajectory. To reach this aim, the kinematic model of a mobile robot is approximated using numerical methods. Then, from such approximation, the control actions to get a minimal tracking error are calculated. Both simulation and experimental results on a PIONEER 2DX mobile robot are presented, showing a good performance of the four proposed mobile robot controllers. Also, an application of the proposed controllers to a leader robot following problem is shown; in it, the relative position between robots is obtained through a laser.
Smart wheelchair perception using odometry, ultrasound sensors, and camera
Authors: Horn O. , Kreutner M. 
Published: June 2008

SUMMARYThis paper deals with the perception mode of smart wheelchairs. First we evoke the many mobility aid prototypes developed in rehabilitation robotics by considering the point of view of perception. Then we describe the localization mode of the VAHM**. We show how the odometric, ultrasound, and vision sensors are used in a complementary way in order to locate the wheelchair in its known environment. The mode of adjustment of the odometric position by the least-squared method using ultrasonic measurements is detailed. Then the use of vision to perceive the vertical segments of the environment so as to refine the orientation is presented. The results of the tests carried out on the wheelchair are given and commented.
A Neglectful Parenting Style Moderates the Effect of the Verbal Threat Information Pathway on Children's Heart Rate Responses to Novel Animals
Authors: Price-Evans Khanya , Field Andy P. 
Published: June 2008

AbstractParenting styles are associated with anxiety in children. Part of this association can be explained by how parenting interacts with known pathways to anxiety. Although parenting interacts with the verbal threat information pathway to create anxiogenic cognitions in children, it is not known whether parenting styles mediate the physiological component of the anxiety emotion. An experiment is reported in which 6–10-year-old children (N = 54) completed parenting styles, and anxiety beliefs questionnaires. They were then given threat, positive or no verbal information about three novel animals before being asked to place their hands in boxes they believed these animals inhabited. Their average heart rate during the approach was recorded. The results suggest that a neglectful maternal parenting style mediates the effect that verbal threat information has on physiological responses. However, a punitive maternal parenting style, maternal warmth, overprotection, and accurate monitoring were not found to have a significant effect. Paternal parenting styles were not found to have any significant effect. This experiment adds to the existing evidence demonstrating that parenting practices can mediate components of acquired anxiety emotions.
Properties of Wolf-Rayet Stars
Authors: Crowther Paul A. 
Published: June 2008

AbstractA review of recent progress relating to Wolf-Rayet (WR) stars is presented. Topics include improved Milky Way statistics from near-IR surveys, different flavours of hydrogen-rich and hydrogen-poor WN stars, WR masses from binary orbits, plus spectroscopic analysis of WR stars resulting in stellar temperatures, luminosities, ionizing fluxes, plus wind properties accounting for clumping. Chemical abundances of WN and WC stars are presented, including a discussion of neon abundances in WC and WO stars fromSpitzerobservations. Empirical evidence supporting metallicity-dependent winds is also presented, including its effect on subtype distributions in different environments. Finally, difficulties in comparisons between evolutionary models and observations are highlighted, plus outstanding issues with predictions from continuous star formation and instantaneous bursts in the Milky Way,
Pulsation-Initiated Mass Loss in Luminous Blue Variables: A Parameter Study
Authors: Onifer Andrew J. , Guzik Joyce A. 
Published: June 2008

AbstractLuminous blue variables (LBVs) are characterized by semi-periodic episodes of enhanced mass-loss, or outburst. The cause of these outbursts has thus far been a mystery. One explanation is that they are initiated by κ-effect pulsations in the atmosphere caused by a blocking of luminosity at temperatures near the so-called “iron bump” (T ~ 200,000 K), where the Fe opacity suddenly increases and blocks the luminosity. Due to a lag in the onset of convection, the luminosity can build until it exceeds the Eddington limit locally, seeding pulsations and possibly driving some mass from the star. We present preliminary results from a parameter study focusing on the conditions necessary to trigger normal S-Dor type (as opposed to extreme η-Car type) outbursts. We find that as Y increases or Z decreases, the pulsational amplitude decreases and outburst-like behavior, indicated by a large, sudden increase in photospheric velocity, becomes less likely.
Massive Binaries
Authors: Moffat Anthony F. J. 
Published: June 2008

AbstractAs with all binaries, those that contain massive stars reveal various degrees of interaction, depending mainly on orbital separation and age, although things happen much faster in massive binaries. Those massive binaries with initial periods exceeding ~10 years generally only interact via wind-wind collisions, with little or no effect on their subsequent evolution (unless located in dense clusters). Shorter-period systems show even stronger wind-wind collisions as a rule, but also interact more directly via Roche Lobe Overflow or Common Envelope, with dramatic effects on their evolution. If we didn't have binaries among massive stars, we would be missing a whole host of interesting phenomena in the Universe, such as sources of enhanced stellar X-ray or non-thermal radio emission, WR dust-spirals, inverse mass-ratios, very rapid spin, rejuvenation and massive blue-stragglers, enhanced cluster dynamics, many runaways and possibly even SMBHs and GRBs! On the other hand, non(or little)-interacting massive binaries are also useful to provide information on Star-Formation processes and determination of stellar parameters (such as the mass) that would otherwise be difficult or impossible to obtain from single stars. In this review, I highlight some of the developments that have occurred during the past few years since the last IAU Symposium on Massive Stars in 2002.
3-D SPH Simulations of Colliding Winds in η Carinae
Authors: Okazaki Atsuo T. , Owocki Stanley P. , Russell Christopher M. P. , Corcoran Michael F. 
Published: June 2008

AbstractWe study colliding winds in the superluminous binary η Carinae by performing three-dimensional, Smoothed Particle Hydrodynamics (SPH) simulations. For simplicity, we assume both winds to be isothermal. We also assume that wind particles coast without any net external forces. We find that the lower density, faster wind from the secondary carves out a spiral cavity in the higher density, slower wind from the primary. Because of the phase-dependent orbital motion, the cavity is very thin on the periastron side, whereas it occupies a large volume on the apastron side. The model X-ray light curve using the simulated density structure fits very well with the observed light curve for a viewing angle of i = 54° and φ = 36°, where i is the inclination angle and φ is the azimuth from apastron.
The First Determination of the Rotation Rates of Wolf-Rayet Stars
Authors: Chené André-Nicolas , St-Louis Nicole 
Published: June 2008

AbstractThe most recent stellar models have shown that the faster a massive star spins, the more its nuclear yields, mass-loss rate and lifetime are different from the standard model. One thus needs to know the rotation rate of massive stars to trace their evolutionary tracks adequately. In Wolf-Rayet (WR) stars, the direct measurement of the rotational velocity is impossible, since their continuum emission is formed in the dense wind that hides the hydrostatic, stellar surface. Here, we present a technique to derive the rotation rates of WR stars from a periodic wind phenomenon, the corotating interaction regions (CIR). For five WR stars, a first estimate of the rotation rates has been deduced from the CIR periods.
Developments in Physics of Massive Stars
Authors: Meynet Georges , Ekström Sylvia , Maeder André , Hirschi Raphael , Georgy Cyril , Beffa Coralie 
Published: June 2008

AbstractNew constraints on stellar models are provided by large surveys of massive stars, interferometric observations and asteroseismology. After a review of the main results so far obtained, we present new results from rotating models and discuss comparisons with observed features. We conclude that rotation is a key feature of massive star physics.
Rotation and Massive Close Binary Evolution
Authors: Langer Norbert , Cantiello Matteo , Yoon Sung-Chul , Hunter Ian , Brott Ines , Lennon Danny , de Mink Selma , Verheijdt Marcel 
Published: June 2008

AbstractWe review the role of rotation in massive close binary systems. Rotation has been advocated as an essential ingredient in massive single star models. However, rotation clearly is most important in massive binaries where one star accretes matter from a close companion, as the resulting spin-up drives the accretor towards critical rotation. Here, we explore our understanding of this process, and its observable consequences. When accounting for these consequences, the question remains whether rotational effects in massive single stars are still needed to explain the observations.
The Effect of Massive Binaries on Stellar Populations and Supernova Progenitors
Authors: Eldridge John J. , Izzard Robert G. , Tout Christopher A. 
Published: June 2008

AbstractWe have calculated a large set of detailed binary models and used them to test the observed stellar population ratios that compare the relative populations of blue supergiants, red supergiants and Wolf-Rayet stars at different metallicities. We have also used our models to estimate the relative rate of type Ib/c to type II supernovae. We find, with an interacting binary fraction of about two thirds, that we obtain better agreement between our models and observations than with single stars. We discuss the use of models in determining the nature of supernova progenitors and show the surprising result that many type Ib/c supernova progenitors are less luminous and less massive in our models than the observed population of Wolf-Rayet stars.
Thoughts on Core-Collapse Supernova Theory
Authors: Burrows Adam , Dessart Luc , Ott Christian D. , Livne Eli , Murphy Jeremiah 
Published: June 2008

AbstractAn emerging conclusion of theoretical supernova research is that the breaking of spherical symmetry may be the key to the elusive mechanism of explosion. Such explorations require state-of-the-art multi-dimensional numerical tools and significant computational resources. Despite the thousands of man-years and thousands of CPU-years devoted to date to studying the supernova mystery, both require further evolution. There are many computationally-challenging instabilities in the core, before, during, and after the launch of the shock, and a variety of multi-dimensional mechanisms are now being actively explored. These include the neutrino heating mechanism, the MHD jet mechanism, and an acoustic mechanism. The latter is the most controversial, and, as with all the contenders, requires detailed testing and scrutiny. In this paper, we analyze recent attempts to do so, and suggests methods to improve them.
Episodic Mass Loss and Pre-SN Circumstellar Envelopes
Authors: Smith Nathan 
Published: June 2008

AbstractI discuss observational clues concerning episodic mass-loss properties of massive stars in the time before the final supernova explosion. In particular, I will focus on the mounting evidence that LBVs and related stars are candidates for supernova progenitors, even though current paradigms place them at the end of core-H burning. Namely, conditions in the immediate circumstellar environment within a few 102 AU of Type IIn supernovae require very high progenitor mass-loss rates. Those rates are so high that the only known stars that come close are LBVs during rare giant eruptions. I will highlight evidence from observations of some recent extraordinary supernovae suggesting that explosive or episodic mass loss (a.k.a. LBV eruptions like the 19th century eruption of Eta Car) occur in the 5-10 years immediately preceding the SN. Finally, I will discuss some implications for stellar evolution from these SNe, the most important of which is the observational fact that the most massive stars can indeed make it to the ends of their lives with substantial H envelopes intact, even at Solar metallicity.
The Progenitor Stars of Core-Collapse Supernovae
Authors: Smartt Stephen J. , Crockett R. Mark , Eldridge John J. , Maund Justyn R. 
Published: June 2008

AbstractKnowledge of the nature and mass of the progenitor stars of core-collapse supernovae are critical elements to test theoretical models of stellar evolution and stellar explosions. Here we describe the current limits and restrictions that can be placed on the progenitor stars of type II SNe and those of Ib/c. There are detections of some type II-P SN progenitors but the exploding stars that produce type Ib/c have eluded discovery. We discuss implications of these quantitative limits and the conclusions that we can now draw.
Can Very Massive Stars Avoid Pair-Instability Supernovae?
Authors: Ekström Sylvia , Meynet Georges , Maeder André 
Published: June 2008

AbstractVery massive primordial stars (140 M⊙ < M < 260 M⊙) are supposed to end their lives as PISN. Such an event can be traced by a typical chemical signature in low metallicity stars, but at the present time, this signature is lacking in the extremely metal-poor stars we are able to observe. Does it mean that those very massive objects were not formed, contrarily to the primordial star formation scenarios ? Could it be possible that they avoided this tragic fate ?We explore the effects of rotation, anisotropical mass loss and magnetic field on the core size of very massive Population III models. We find that magnetic fields provide the strong coupling that is lacking in standard evolution metal-free models and our 150 M⊙ Population III model avoids indeed the pair-instability explosion.
Evolution of Progenitor Stars of Type Ibc Supernovae and Long Gamma-Ray Bursts
Authors: Yoon Sung-Chul , Langer Norbert , Cantiello Matteo , Woosley Stan E. , Glatzmaier Gary A. 
Published: June 2008

AbstractWe discuss how rotation and binary interactions may be related to the diversity of type Ibc supernovae and long gamma-ray bursts. After presenting recent evolutionary models of massive single and binary stars including rotation, the Tayler-Spruit dynamo and binary interactions, we argue that the nature of SNe Ibc progenitors from binary systems may not significantly differ from that of single star progenitors in terms of rotation, and that most long GRB progenitors may be produced via the quasi-chemically homogeneous evolution at sub-solar metallicity. We also briefly discuss the possible role of magnetic fields generated in the convective core of a massive star for the transport of angular momentum, which is potentially important for future stellar evolution models of supernova and GRB progenitors.
Young Massive Clusters
Authors: Figer Donald F. 
Published: June 2008

AbstractOver the past ten years, there has been a revolution in our understanding of massive young stellar clusters in the Galaxy. Initially, there were no known examples having masses >104, yet we now know that there are at least a half dozen such clusters in the Galaxy. In all but one case, the masses have been determined through infrared observations. Several had been identified as clusters long ago, but their massive natures were only recently determined. Presumably, we are just scratching the surface, and we might look forward to having statistically significant samples of coeval massive stars at all important stages of stellar evolution in the near future. I review the efforts that have led to this dramatic turn of events and the growing sample of young massive clusters in the Galaxy.
Massive Stars in the Galactic Center
Authors: Martins F. , Hillier D. J. , Genzel R. , Eisenhauer F. , Ott T. , Gillessen S. , Trippe S. 
Published: June 2008

AbstractWe present results of two studies aiming at better understanding the properties of massive stars in the Galactic Center. We focus on the youngest and oldest of the three massive clusters harboring this region, namely the Arches and central cluster. We show that the development of powerful observational techniques in the near infrared spectral range (mainly 3D spectroscopy) allows to uncover the entire massive star population in these clusters. Using CMFGEN models, we derive the classical stellar and wind properties of 46 stars, as well as their surface abundances. The latter allow us to investigate in detail their evolutionary status and to identify evolutionary sequences between different types of stars. We thus constrain stellar evolution in the upper part of the HR diagram.
Massive Stars in the Nuclei and Arms of Spirals
Authors: Bresolin Fabio 
Published: June 2008

AbstractMany of the properties of massive stars in external galaxies, such as chemical compositions, mass functions, and ionizing fluxes, can be derived from the study of the associated clouds of ionized gas. Moreover, the signatures of Wolf-Rayet stars are often detected in the spectra of extragalactic H ii regions. This paper reviews some aspects of the recent work on the massive star content of nearby spiral galaxies, as inferred from the analysis of giant H ii regions. Particular attention is given to regions of high metallicity, including nuclear hot spots, and to the chemical abundance comparison between supergiant stars and ionized gas.
Extragalactic Stellar Astronomy with the Brightest Stars in the Universe
Authors: Kudritzki Rolf , Urbaneja Miguel A. , Bresolin Fabio , Przybilla Norbert 
Published: June 2008

AbstractA supergiants are objects in transition from the blue to the red (and vice versa) in the uppermost HRD. They are the intrinsically brightest “normal” stars at visual light with absolute visual magnitudes up to −9. They are ideal to study young stellar populations in galaxies beyond the Local Group to determine chemical composition and evolution, interstellar extinction, reddening laws and distances. We discuss most recent results on the quantitative spectral analysis of such objects in galaxies beyond the Local Group based on medium and low resolution spectra obtained with the ESO VLT and Keck. We describe the analysis method including the determination of metallicity and metallicity gradients. A new method to measure accurate extragalactic distances based on the stellar gravities and effective temperatures is presented, the flux weighted gravity – luminosity relationship (FGLR). The FGLR is a purely spectroscopic method, which overcomes the uncertainties introduced by interstellar extinction and variations of metallicity, which plague all photometric stellar distance determination methods. We discuss the perspectives of future work using the giant ground-based telescopes of the next generation such as the TMT, the GMT and the E-ELT.
LBT Discovery of a Yellow Supergiant Eclipsing Binary in the Dwarf Galaxy Holmberg IX
Authors: Prieto J. L. , Stanek K. Z. , Kochanek C. S. , Weisz D. R. 
Published: June 2008

AbstractIn a variability survey of M81 using the Large Binocular Telescope we have discovered a peculiar eclipsing binary (MV ≃ −7.1) in the field of the dwarf galaxy Holmberg IX. It has a period of 271 days and the light curve is well-fit by an overcontact model in which both stars are overflowing their Roche lobes. It is composed of two yellow supergiants (V − I ≃ 1 mag, Teff = 4800 K), rather than the far more common red or blue supergiants. Such systems must be rare. While we failed to find any similar systems in the literature, we did, however note a second example. The SMC F0 supergiant R47 is a bright (MV ≃ −7.5) periodic variable whose All Sky Automated Survey (ASAS) light curve is well-fit as a contact binary with a 181 day period. We propose that these massive systems are the progenitors of supernovae like SN 2004et and SN 2006ov, which appeared to have yellow progenitors. The binary interactions (mass transfer, mass loss) limit the size of the supergiant to give it a higher surface temperature than an isolated star at the same core evolutionary stage.