bluuebunny/crossref_metadata_2025_split huggingface dataset:
Onset of the Ordovician cephalopod radiation – evidence from the Rochdale Formation (middle Early Ordovician, Stairsian) in eastern New York
Authors: KRÖGER BJÖRN , LANDING ED 
Published: May 2008

AbstractThe Rochdale Formation of eastern New York (= Fort Ann and lower Bascom formations, designations abandoned) is now recognized to record the earliest stages of the Great Ordovician Radiation of cephalopods. The earliest Bassleroceratidae, Tarphyceratidae and endoceridans on the east Laurentian shallow carbonate platform occur in the upper, thrombolite-bearing member of the Rochdale. This fauna demonstrates that the earliest radiation of Ordovician nautiloids took place in the late Tremadocian and is best recorded in tropical platform facies. Revision of this cephalopod fauna based on approximately 190 specimens collected along a 200 km, N–S belt in easternmost New York has provided new information on inter- and intraspecific variation of earlier described species. The ellesmeroceridVassarocerasand the endoceridsMcqueenocerasandParaendocerasare emended. New taxa includeBassleroceras champlainensesp. nov. andB. triangulumsp. nov.,Mccluskiceras comstockensegen. et sp. nov.,Exoclitendoceras rochdalensegen. et sp. nov. andParaendoceras depressumsp. nov. A rank abundance plot of 146 specimens from a locality in the Lake Champlain lowlands provides information on the community structure of a nautiloid fauna in which the longiconic cyrtoconicBasslerocerasis shown to dominate strongly. The nautiloid community structure of the Rochdale Formation is similar to that of the underlying Tribes Hill Formation (late early Tremadocian) with respect to the depositional setting, diversity and evenness but displays a remarkably increased taxonomic distinctness.
THE LEGISLATIVE ROLE OF THE SECURITY COUNCIL IN ITS FIGHT AGAINST TERRORISM: LEGAL, POLITICAL AND PRACTICAL LIMITS
Authors: Hinojosa Martínez Luis Miguel 
Published: May 2008

AbstractThis article studies the normative activity developed by the Security Council (SC) in recent years, particularly in the fight against terrorism. This legislative activity has aroused a great deal of controversy both among scholars and the States. Is the SC acting ultra vires? Has it revealed a new form of creating of international norms, which overrides definitively States' consent as the only material source of international law? This contribution tries to answer these questions by investigating the scope of the SC powers in the Charter, their historical background and the reaction of UN Member States towards its Resolutions. After this analysis, it is submitted that the SC does have a legislative capacity, but with important legal, political and practical limits.
One-year functional magnetic resonance imaging follow-up study of neural activation during the recall of unresolved negative life events in borderline personality disorder
Authors: Driessen M. , Wingenfeld K. , Rullkoetter N. , Mensebach C. , Woermann F. G. , Mertens M. , Beblo T. 
Published: May 2008

BackgroundRecall of adverse life events under brain imaging conditions has been shown to coincide with activation of limbic and prefrontal brain areas in borderline personality disorder (BPD). We investigate changes of functional magnetic resonance imaging (fMRI) activation patterns during the recall of unresolved adverse life events (ULE) over 1 year.MethodThirteen female BPD patients participated in the study. During fMRI measurement subjects recalled ULE and negative but resolved life events (RLE) after individual cue words to stimulate autobiographical memory retrieval. Subjective intensity of emotional and sensoric experiences during recall was assessed as well as standardized measures of psychopathology.ResultsA 2×2 factorial analysis of fMRI data (Δt1/t2×ΔULE/RLE) revealed major right more than left differences of activation (i.e. t1>t2) of the posterior more than anterior cingulate, superior temporal lobes, insula, and right middle and superior frontal lobes (second-level analysis,t=3.0,puncorrected=0.003). The opposite contrast (Δt2/t1×ΔULE/RLE) did not reveal any differences. We did not find changes of emotional or sensoric qualities during recall (ULEversusRLE) or of psychopathology measures over the 1-year period.ConclusionsAlthough subjective and clinical data did not change within 1 year, we observed a substantial decrease of temporo-frontal activation during the recall of ULE from t1 to t2. If future research confirms these findings, the question arises whether the decrease of neural activation precedes clinical improvement in BPD.
Effects of stressor controllability on psychophysiological, cognitive and behavioural responses in patients with major depression and dysthymia
Authors: Diener C. , Kuehner C. , Brusniak W. , Struve M. , Flor H. 
Published: May 2008

BackgroundThe experience of uncontrollability and helplessness in the face of stressful life events is regarded as an important determinant in the development and maintenance of depression. The inability to successfully deal with stressors might be linked to dysfunctional prefrontal functioning. We assessed cognitive, behavioural and physiological effects of stressor uncontrollability in depressed and healthy individuals. In addition, relationships between altered cortical processing and cognitive vulnerability traits of depression were analysed.MethodA total of 26 unmedicated depressed patients and 24 matched healthy controls were tested in an expanded forewarned reaction (S1–S2) paradigm. In a factorial design, stressor controllability varied across three consecutive conditions: (a) control, (b) loss of control and (c) restitution of control. Throughout the experiment, error rates, ratings of controllability, arousal, emotional valence and helplessness were assessed together with the post-imperative negative variation (PINV) of the electroencephalogram.ResultsDepressed participants showed an enhanced frontal PINV as an electrophysiological index of altered information processing during both loss of control and restitution of control. They also felt more helpless than controls. Furthermore, frontal PINV magnitudes were associated with habitual rumination in the depressed subsample.ConclusionsThese findings indicate that depressed patients are more susceptible to stressor uncontrollability than healthy subjects. Moreover, the experience of uncontrollability seems to bias subsequent information processing in a situation where control is objectively re-established. Alterations in prefrontal functioning appear to contribute to this vulnerability and are also linked to trait markers of depression.
WHAT ARE YOU READING?
Authors: Diamond Elin 
Published: May 2008

“This overheated and distasteful little book—for me the wrong book in many ways—addresses matters about which there is, precisely, nothing left to say.” The Rutgers University library believed this antihype and never purchased Paul Mann's The Theory-Death of the Avant-Garde (1991), a book so amusingly dour, so relentlessly dialectical, as to be, for me, irresistible. A member of Mike Sell's Vectors of the Avant-Garde seminar at last month's ASTR, I decided really to read instead of skim my Alibris-purchased copy of Mann's distasteful little book. In it the main figures of futurism, dada, and surrealism become a failed or self-recuperating aggregate whose discourse of inflammatory “anti-” stances served only to undermine their revolutionary intentions: “[T]he avant-garde's assaults on tradition, cultural establishments, and the formal structure of the work of art tended to place it in the service of, not . . . the revolution, but of its deferral, its displacement. . . . The avant-garde's historical agony is grounded in the brutal paradox of an opposition that sustains what it opposes precisely by opposing it” (11).
Gene flow hampered by low seed size of hybrids between oilseed rape and five wild relatives
Authors: Wei Wei , Darmency Henri 
Published: May 2008

AbstractRecent concern about gene flow from transgenic plants to weedy species has attracted much research on the fitness of their hybrids. However, no studies have been reported on the very early effects of the seed size of hybrids compared with parental plants for germination, seedling establishment and plant growth. We produced hybrids between male sterile Brassica napus L. (oilseed rape) and five weedy relatives, including Brassica juncea (L.) Czern, B. nigra (L.) Koch, B. rapa L., Hirschfeldia incana (L.) Lagrèze-Fossat and Raphanus raphanistrum L. The hybrid seeds formed between B. napus and B. rapa varied in size, while all the hybrid seeds formed with the other species were small. In a direct-seeded field experiment, small seeds of both parents and hybrids had a lower frequency of emergence and a lower seedling survival rate than large seeds, and resulted in later flowering with less biomass. However, no difference was recorded in a transplant experiment, indicating that growth in the juvenile period was sensitive to the small seed class in field conditions only. The optimum environmental conditions in the greenhouse probably homogenized the developmental differences observed at the early stage, and thus reduced the variation during subsequent growth in the field. This point has not been, but should be, considered in risk assessment of transgenic plants. The lower seedling establishment of small-seeded hybrids could hamper further gene flow.
Expression and activity of a Kip-related protein, Zeama;KRP1, during maize germination
Authors: de Jesús Juárez Natividad , Mancilla Alfredo , García Elpidio , Vázquez-Ramos Jorge M. 
Published: May 2008

AbstractPlant KRP proteins are cyclin/cyclin-dependent kinase subunit (Cdk) inhibitors that share a limited homology with mammalian p27Kip1proteins. Several KRPs have been reported in maize (Zea maysL.), of which Zeama;KRP1 was studied during maize germination. Expression of theZeama;KRP1gene did not vary during the 24 h germination period. A homologous antibody raised against the 13 kDa carboxy end of the Zeama;KRP1 polypeptide, a sequence containing the cyclin/Cdk inhibitory domain, indicated the existence of a 22 kDa protein in maize embryonic axes, the amount of which also remained unchanged during germination. Neither abscisic acid nor cytokinins modified the amount of protein. The purified Zeama;KRP1 polypeptide inhibited the kinase activity associated with Zeama;PCNA and Zeama;CycD2;1, and also the kinase activity in p13Suc1-pulled-down complexes. However, there were differences in the inhibition pattern during germination. Whereas kinase activity in proliferating cell nuclear antigen (PCNA) or CycD2;1 immunoprecipitates was strongly inhibited mainly during early germination, that in p13Suc1-pulled-down complexes was mainly inhibited at late times, suggesting that each protein complex is composed of different cyclins and/or Cdks.
The formation, disruption and properties of pressure-supported stellar systems and implications for the astrophysics of galaxies
Authors: Kroupa Pavel 
Published: May 2008

AbstractMost stars form in dense star clusters deeply embedded in residual gas. These objects must therefore be seen as the fundamental building blocks of galaxies. With this contribution some physical processes that act in the very early and also later dynamical evolution of dense stellar systems in terms of shaping their later appearance and properties, and the impact they have on their host galaxies, are highlighted. Considering dense systems with increasing mass, it turns out that near 106M⊙ their properties change fundamentally: stellar populations become complex, a galaxial mass–radius relation emerges and the median two-body relaxation time becomes longer than a Hubble time. Intriguingly, only systems with a two-body relaxation time longer than a Hubble time show weak evidence for dark matter, whereby dSph galaxies form total outliers.
Dynamical Masses of Young Star Clusters: Constraints on the Stellar IMF and Star-Formation Efficiency
Authors: Bastian N. 
Published: May 2008

AbstractThrough the use of detailed light profiles and dynamical measurements of young clusters we investigate claims that the stellar initial mass function within clusters varies greatly. We find a strong age dependence in the clusters which have been claimed to have non-standard stellar IMFs, and suggest that the lack of equilibrium of these clusters is responsible for their ‘strange’ light-to-mass ratios and not IMF variations. The most likely culprit is the rapid removal of residual gas left over from the star-formation process which leaves the clusters severely out of dynamical equilibrium. By comparing the observations to N-body simulations we quantify to what degree a cluster is out of equilibrium and consequently its survival chances. We find that >60% of young clusters will be disrupted, due gas removal, within the first 20–50 Myr of their lives.
The Fraction of Runaway OB Stars in the SMC Field
Authors: Lamb J. B. , Oey M. S. 
Published: May 2008

AbstractThe fraction of field OB stars that originate from clusters can help probe the dynamical evolution of clusters. Field stars represent a significant fraction (20-30%) of the OB population in galaxies, and estimates for the fraction of field OB stars that are runaways range from the classical value of <10% (Blaauw 1961) to contemporary results suggesting >90% (de Wit et al. 2005). We obtained Magellan IMACS observations on the kinematics of field OB stars in the SMC to examine the line-of-sight velocities of this population. Using these observations, we will estimate the fraction of runaways to serve as a probe of cluster evolution.
The Relation Between Field Massive Stars and Clusters
Authors: Oey M. S. , King N. L. , Parker J. Wm. , Lamb J. B. 
Published: May 2008

AbstractMassive “field” stars are those that appear in apparent isolation, in contrast to those in clusters. Whereas cluster stars are formed together in large aggregates, simultaneously, field stars have multiple origins. Some massive field stars may be the “tip of the iceberg” on small groups of physically associated stars, while others appear to be “runaway” stars that are dynamically ejected from clusters. What is the intrinsic relation between clusters and field stars, and what is the faction of runaway stars? Since massive stars are the most luminous stellar population, their demographics are accessible in the nearest external galaxies. We present our current efforts to understand these issues for the Small Magellanic Cloud.
On the Origin of the Orion Trapezium System
Authors: Zinnecker Hans 
Published: May 2008

AbstractNumerical SPH simulations of supersonic gravo-turbulent fragmentation of a protocluster cloud (1000 M⊙) suggest that the cloud develops a few subclusters (star+gas systems) which subsequently merge into a single cluster entity. Each subcluster carries one most massive star (likely multiple), thus the merging of subclusters results in a central Trapezium-type system, as observed in the core of the Orion Nebula cluster.
Observational Evidence of Multiple Stellar Populations in Globular Clusters
Authors: Piotto Giampaolo 
Published: May 2008

AbstractAn increasing number of photometric observations of multiple stellar populations in Galactic globular clusters is seriously challenging the paradigm of GCs hosting single, simple stellar populations. These multiple populations manifest themselves in a split of different evolutionary sequences as observed in the cluster color-magnitude diagrams. In this paper we will summarize the observational scenario.
Multiple Stellar Populations in Globular Clusters: Collection of Information from the Horizontal Branch
Authors: D'Antona Francesca , Caloi Vittoria 
Published: May 2008

AbstractThe majority of the inhomogeneities in the chemical composition of Globular Cluster (GC) stars appear due to primordial enrichment by hot-CNO cycled material processed in stars belonging to a first stellar generation. Either massive AGB envelopes subject to hot bottom burning, or the envelopes of massive fastly rotating stars could be the progenitors. In both cases, the stars showing chemical anomalies must have also enhanced helium abundance, and we have proposed that this higher helium could be at the basis of the many different morphologies of GC horizontal branches (HB) for similar ages and metallicities. The helium variations have been beautifully confirmed by the splitting of the main sequence in the clusters ω Cen and NGC 2808, but this effect can show up only for somewhat extreme helium abundances. Therefore it is important to go on using the HB morphology to infer the number ratio of the first to the second generation in as many clusters as possible. We exemplify how it is possible to infer the presence of a He – rich stellar component in different clusters thanks to different HB features (gaps, RR Lyr periods and period distribution, ratio of blue to red stars, blue tails). In many clusters at least 50% of the stars belong to the second stellar generation, and in some cases we suspect that the stars might all belong to the second generation. We shortly examine the problem of the initial mass function required to achieve the observed number ratios and conclude that: 1) the initial cluster must have been much more massive than today's cluster, and 2) formation of the second stellar generation mainly in the central regions of the cluster may help in obtaining the desired values.
Mass-Loss Timescale of Star Cluster in External Tidal Field
Authors: Fukushige T. , Tanikawa A. 
Published: May 2008

AbstractWe investigate evolution of star clusters in steady external tidal field by means of N-body simulations. We followed several sets of cluster models whose strength and Coriolis's contribution of the external tidal field are different. We found that the mass loss timescale due to the escape of stars, t_mloss, and its dependence on the two-body relaxation timescale, trh,i, are determined by the strength of the tidal field. The logarithmic slope [≡ dln(tmloss)/dln(trh,i)] approaches unity for the cluster models in weaker tidal fields. We also found that stronger Coriolis force against others, produced by parent galaxy whose density profile is shallower, makes the mass loss timescale longer. This is due to the fact that a fraction of stars whose orbit are nearly regular increases as the Coriolis force becomes stronger.
Integrated Properties of Mass Segregated Star Clusters
Authors: Gaburov E. , Gieles M. 
Published: May 2008

AbstractIn this contribution we study integrated properties of dynamically segregated star clusters. The observed core radii of segregated clusters can be 50% smaller than the “true” core radius. In addition, the measured radius in the red filters is smaller than those measured in blue filters. However, these difference are small (≲10%), making it observationally challenging to detect mass segregation in extra-galactic clusters based on such a comparison. Our results follow naturally from the fact that in nearly all filters most of the light comes from the most massive stars. Therefore, the observed surface brightness profile is dominated by stars of similar mass, which are centrally concentrated and have a similar spatial distribution.
Resonance, Chaos and Stability in the General Three-Body Problem
Authors: Mardling R. A. 
Published: May 2008

AbstractThree-body stability is fundamental to astrophysical processes on all length and mass scales from planetary systems to clusters of galaxies, so it is vital we have a deep and thorough understanding of this centuries-old problem. Here we summarize an analytical method for determining the stability of arbitrary three-body hierarchies which makes use of the chaos theory concept of resonance overlap. For the first time the dependence on all orbital elements and masses can be given explicitly via simple analytical expressions which contain no empirical parameters. For clarity and brevity, analysis in this paper is restricted to coplanar systems including a description of a practical algorithm for use in N-body and other applications. A Fortran routine for arbitrarily inclined systems is available from the author, and animations of stable and unstable systems are available at www.maths.monash.edu.au/~ro/Capri.
On the Calculation of Average Lifetimes for the 3-body Problem
Authors: Urminsky David 
Published: May 2008

AbstractNumerical solutions for the 3-body problem can be extremely sensitive to small errors. We consider how small errors in calculations can affect the lifetime of these systems. In particular, we show that numerical errors can shorten the average lifetime of a 3-body system. This is illustrated using the Sitnikov Problem as an example. To give a theoretical explanation, we construct an approximate Poincaré map for this problem and delineate the structure of the escape regions. We show that numerical errors can destroy escape regions and can cause orbits to migrate to a region in which escape is faster.
The Influence of Binary Stars on Post-Collapse Evolution
Authors: Apple Rosemary 
Published: May 2008

AbstractThe results in the N-body simulations in Giersz & Heggie (1996) show that although the masses segregate as expected during core collapse, after core collapse there is self-similar evolution with very little further evidence of mass segregation even though the system has not reached equipartition. Binary stars halt core collapse and it is possible that they also halt the tendency toward equipartition. To investigate this problem, we construct two models. One model is a two-component model which assumes that binary stars form in the region dominated by heavy stars. The other model is a single mass model which assumes that binary stars form only in the region of the core. In both models, when the binary heating term is included, we find the post-collapse evolution to be self-similar. The aim of our work is to combine these two models to form a two-component model which assumes that binary formation only occurs in the core.
The Formation of Contact and Very Close Binaries
Authors: Eggleton Peter P. , Kisseleva-Eggleton Ludmila 
Published: May 2008

AbstractWe explore the possibility that all close binaries, i.e. those with periods < 3 days, including contact binaries, are produced from initially wider binaries by the action of a triple companion through the medium of Kozai Cycles with Tidal Friction (KCTF).
Neutron Stars in Globular Clusters
Authors: Ivanova N. , Heinke C. O. , Rasio F. 
Published: May 2008

AbstractDynamical interactions that occur between objects in dense stellar systems are particularly important for the question of formation of X-ray binaries. We present results of numerical simulations of 70 globular clusters with different dynamical properties and a total stellar mass of 2×107M⊙. We find that in order to retain enough neutron stars to match observations we must assume that NSs can be formed via electron-capture supernovae. Our simulations explain the observed dependence of the number of LMXBs on “collision number” as well as the large scatter observed between different globular clusters. For millisecond pulsars, we obtain good agreement between our models and the numbers and characteristics of observed pulsars in the clusters Terzan 5 and 47 Tuc.