bluuebunny/crossref_metadata_2025 huggingface dataset:
Leadership and Adolescent Girls: A Qualitative Study of Leadership Development
Authors: Hoyt Michael A. , Kennedy Cara L.
Published: October 2008

This research investigated youth leadership experiences of adolescent girls who participated in a comprehensive feminist‐based leadership program. This qualitative study utilized a grounded theory approach to understand changes that occurred in 10 female adolescent participants. The words of the participants revealed that initially they viewed leadership in traditional terms and were hesitant to identify themselves as leaders or to see themselves included within their concepts of leadership. Following the program their view of leadership expanded and diversified in a manner that allowed for inclusion of themselves within it. They spoke with greater strength and confidence and felt better positioned and inspired to act as leaders. Participants identified having examples of women leaders, adopting multiple concepts of leadership, and participating in an environment of mutual respect and trust as factors that contributed to their expanded conceptualization.
Recovery from peripartum cardiomyopathy after treatment with bromocriptine
Authors: Habedank Dirk , Kühnle York , Elgeti Thomas , Dudenhausen Joachim W. , Haverkamp Wilhelm , Dietz Rainer
Published: October 2008

Peripartum cardiomyopathy (PPCM) is a potentially devastating cause of heart failure that affects women late in pregnancy or in early puerperium. Recent findings showed that a 16 kDa fragment of prolactin may induce myocardial damage, and this offered a new option of treating PPCM by blocking prolactin with bromocriptine. We report on a 35‐year‐old woman with a twin gravidity who gave birth to two healthy boys at day 36/6 and developed a potentially fatal PPCM. Within 3 days since delivery she suffered from severe symptoms of heart failure (orthopnoea, pleural and pericardial effusion, reduced systolic function LVEF 15%). Bromocriptine 2.5 mg bid was added to standard heart failure therapy at day 6 after delivery, and within a week the patient recovered to NYHA functional class II. 2 months later she presented in a good state, NYHA class I, and MRI confirmed an LVEF of 60%. Balancing the potential side effects of bromocriptine against the very poor prognosis in severe PPCM our case supports the use of bromocriptine as a specific novel therapy.
Body mass index (BMI) of drug-naïve psychotic adolescents based on a population of adolescent psychiatric inpatients
Authors: Juutinen Jaana , Hakko Helinä , Meyer-Rochow V. Benno , Räsänen Pirkko , Timonen Markku ,   The STUDY-70 research group
Published: October 2008

Objective

To investigate the connection between overweight and first-episode schizophrenia spectrum as well as non-schizophrenia spectrum psychiatric disorders in adolescent male and female drug-naïve psychiatric inpatients, whose illness was early onset.

Method

Three hundred twenty-three adolescents with no past or present psychiatric medication, 12–17 years of age, admitted to the psychiatric inpatient care (Oulu University Hospital, Northern Finland) between April 2001 and March 2006. DSM-IV diagnoses were based on the “Schedule for Affective Disorder and Schizophrenia for School-Age Children Present and Lifetime” (K-SADS-PL). An adolescent was defined as overweight if his or her BMI was greater than or equal to the 85th percentile.

Results

Overweight values were highest in drug-naïve adolescent boys with first-episode schizophrenia spectrum (RR: 2.5, 95%CI: 1.08–4.29) and non-schizophrenia spectrum (RR: 2.80, 95%CI: 2.20–3.45) disorders. The RR in girls with non-schizophrenia spectrum disorders was 1.73 (95%CI: 1.31–2.23), but in those with first-episode schizophrenia spectrum disorders RR did not differ from general population.

Conclusions

In our study sample of first-episode schizophrenia spectrum drug-naïve adolescents, overweight was shown to be prevalent in all diagnostic groups other than first-episode schizophrenia spectrum psychotic girls. To the best of our knowledge, this is the first study in which overweight was analyzed and verified among drug-naïve adolescent boys, suffering from first-episode schizophrenia spectrum disorder. To what extent our results are applicable to other regions and study groups, remains to be seen.
Early detection of psychosis – Establishing a service for persons at risk
Authors: Schultze-Lutter Frauke , Ruhrmann Stephan , Klosterkötter Joachim
Published: October 2008

Purpose

The establishment phase of an early detection centre for prodromal psychosis is introduced and characterised, along with its detaining and promoting factors within a universal multi-payer health care system.

Method

Across the first six years (1998–2003), users' characteristics are compared between different diagnostic groups and to the local population statistics; and, for an exemplary 12-months period (3-1-2002 to 2-28-2003), the characteristics of telephone contacts with the service are studied.

Results

Rising steadily in number across the first three years, 872 persons, predominately of German citizenship and higher education, consulted the service until 2003, 326 with first-episode psychosis and 144 not fulfilling criteria for a current or beginning psychosis. Of the 402 putatively prodromal patients, 94% reported predictive basic symptoms, 68.9% attenuated and 20.6% transient psychotic symptoms. Most contacts by persons meeting any prodromal criterion were initiated by mental health professionals (psychiatrists or psychologists) and counselling services.

Conclusion

Supported by public awareness campaigns, an early detection service is well received by its users and private practitioners as reflected by the large proportion of referrals from the latter. However, persons of non-German background as well as of lower education were underrepresented indicating that these sub-groups should be approached by tailored programmes.
Infracoccygeal sacropexy for uterovaginal prolapse
Authors: Deffieux Xavier , Desseaux Krystel , de Tayrac Renaud , Faivre Erika , Frydman René , Fernandez Hervé
Published: October 2008

Objective

To report on the efficacy and safety of infracoccygeal sacropexy for the treatment of uterovaginal prolapse.

Method

A retrospective analysis of 87 women who underwent an infracoccygeal sacropexy procedure, 53 receiving a multifilament and 34 receiving a monofilament tape.

Results

The mean follow‐up was 27 months. Postoperative perineal pain was reported by 7 women (10%), and dyschesia and dyspareunia were observed de novo in 4 (5%) and 5 women (6%), respectively. There were 5 cases (9%) of vaginal extrusion and 9 cases (18%) of prolapse recurrence in the multifilament tape group, and in the monofilament tape group there were no cases of vaginal extrusion and 4 cases (14%) of prolapse recurrence (P = 0.79 for prolapse recurrence). The recurrence‐free survival curves of the 2 groups were similar. Univariate analysis revealed no independent factors of recurrence.

Conclusion

Although infracoccygeal sacropexy was found to be associated with few prolapse recurrences, complications were not rare.
The effect of short-term hyperammonaemia on milk synthesis in dairy cows
Authors: Purdie Norm G , Trout Donald R , Cieslar Scott R L , Madsen Torben G , Poppi Dennis P , Cant John P
Published: October 2008

To test the hypothesis that ammonia detoxification in ruminants consumes amino acids to the detriment of milk protein production, we infused four lactating dairy cows with ammonium acetate or sodium acetate in switchback experiments. Plasma ammonia concentrations increased to 411 μm within 1 h of the start of infusion of ammonium acetate at 567 mmol/h. The rate constant for ammonia clearance from plasma was 0·054/min and the half-life was 12·9 min. Infusion at 567 mmol/h for 1 h followed by 1 h without infusion, repeated four times between am- and pm-milking, caused a decrease in feed intake. Compared with sodium acetate, continuous infusion of ammonium acetate at 360 mmol/h throughout an entire 10-h milking interval increased plasma ammonia concentrations to 193 μm and caused a 20% decrease in milk, protein and lactose production with no effect on percentage composition of milk or the yield of milk fat. Arterial concentrations of glucose and non-esterified fatty acids tended to increase; there was no effect on arterial acetate, β-hydroxybutyrate or triacylglcerol, and branched-chain amino acids, Lys and Thr decreased. Mammary plasma flow, estimated by assuming 100% uptake/output of Phe+Tyr, was significantly correlated with milk yield. Mammary uptakes of acetate tended to be reduced by hyperammonaemia, but uptakes of other energy metabolites and amino acids were not affected. Thus, while an increase in amino acid consumption during hyperammonaemia was apparent from the drop in circulating concentrations of Leu, Ile, Val, Lys and Thr, there was no evidence to support the hypothesis that milk yield is affected by the lower concentrations. An ammonia-induced depression in feed intake may have caused the decrease in milk synthesis.
Strongly nonlinear Langmuir circulation and Rayleigh–Bénard convection
Authors: CHINI G. P.
Published: October 2008

Most rational asymptotic studies of non-rotating Rayleigh–Bénard convection and its cousins have been restricted to the linear or weakly nonlinear regime. An important exception occurs for large Rayleigh-number thermal convection at effectively infinite Prandtl number, i.e. fast but very viscous convection. In this scenario, the temperature field exhibits a layer-like structure surrounding an isothermal core and, crucially, the momentum equation linearizes. These features have been exploited by several authors to obtain semi-analytical nonlinear solutions. AtO(1) Prandtl number, the fluid dynamics in the vortex core is dominated by nonlinear inertial rather than linear viscous effects, substantially altering the vortex structure. Here, it is shown that a combination of matched asymptotic analysis and global conservation constraints can be used to obtain a semi-analytic yet strongly nonlinear description of two related flows: (i) Rayleigh–Bénard convection between constant heat-flux boundaries at unit Prandtl number, and (ii) Langmuir circulation (LC), a wind and wave-driven convective flow commonly observed in natural water bodies. A simple analytical prediction is given for the roll-vortex amplitude, which is shown to be independent of the horizontal wavenumber of the convection pattern. In marked contrast to weakly nonlinear convection cells, the fully nonlinear asymptotic solutions exhibit flow features relevant to turbulent convection including the complete vertical redistribution of the basic-state temperature (or, for LC, downwind velocity) field. Comparisons with well-resolved pseudospectral numerical simulations of the full two-dimensional governing equations confirm the accuracy of the asymptotic results.
Fluid flow and optical flow
Authors: LIU TIANSHU , SHEN LIXIN
Published: October 2008

The connection between fluid flow and optical flow is explored in typical flow visualizations to provide a rational foundation for application of the optical flow method to image-based fluid velocity measurements. The projected-motion equations are derived, and the physics-based optical flow equation is given. In general, the optical flow is proportional to the path-averaged velocity of fluid or particles weighted with a relevant field quantity. The variational formulation and the corresponding Euler–Lagrange equation are given for optical flow computation. An error analysis for optical flow computation is provided, which is quantitatively examined by simulations on synthetic grid images. Direct comparisons between the optical flow method and the correlation-based method are made in simulations on synthetic particle images and experiments in a strongly excited turbulent jet.
Two-dimensional global low-frequency oscillations in a separating boundary-layer flow
Authors: EHRENSTEIN UWE , GALLAIRE FRANÇOIS
Published: October 2008

A separated boundary-layer flow at the rear of a bump is considered. Two-dimensional equilibrium stationary states of the Navier–Stokes equations are determined using a nonlinear continuation procedure varying the bump height as well as the Reynolds number. A global instability analysis of the steady states is performed by computing two-dimensional temporal modes. The onset of instability is shown to be characterized by a family of modes with localized structures around the reattachment point becoming almost simultaneously unstable. The optimal perturbation analysis, by projecting the initial disturbance on the set of temporal eigenmodes, reveals that the non-normal modes are able to describe localized initial perturbations associated with the large transient energy growth. At larger time a global low-frequency oscillation is found, accompanied by a periodic regeneration of the flow perturbation inside the bubble, as the consequence of non-normal cancellation of modes. The initial condition provided by the optimal perturbation analysis is applied to Navier–Stokes time integration and is shown to trigger the nonlinear ‘flapping’ typical of separation bubbles. It is possible to follow the stationary equilibrium state on increasing the Reynolds number far beyond instability, ruling out for the present flow case the hypothesis of some authors that topological flow changes are responsible for the ‘flapping’.
Optimal flexibility of a flapping appendage in an inviscid fluid
Authors: ALBEN SILAS
Published: October 2008

We present a new formulation of the motion of a flexible body with a vortex-sheet wake and use it to study propulsive forces generated by a flexible body pitched periodically at the leading edge in the small-amplitude regime. We find that the thrust power generated by the body has a series of resonant peaks with respect to rigidity, the highest of which corresponds to a body flexed upwards at the trailing edge in an approximately one-quarter-wavelength mode of deflection. The optimal efficiency approaches 1 as rigidity becomes small and decreases to 30–50% (depending on pitch frequency) as rigidity becomes large. The optimal rigidity for thrust power increases from approximately 60 for large pitching frequency to ∞ for pitching frequency 0.27. Subsequent peaks in response have power-law scalings with respect to rigidity and correspond to higher-wavenumber modes of the body. We derive the power-law scalings by analysing the fin as a damped resonant system. In the limit of small driving frequency, solutions are self-similar at the leading edge. In the limit of large driving frequency, we find that the distribution of resonant rigidities ~k−5, corresponding to fin shapes with wavenumberk. The input power and output power are proportional to rigidity (for small-to-moderate rigidity) and to pitching frequency (for moderate-to-large frequency). We compare these results with the range of rigidity and flapping frequency for the hawkmoth forewing and the bluegill sunfish pectoral fin.
Discontinuous solutions of the boundary-layer equations
Authors: RUBAN A. I. , VONATSOS K. N.
Published: October 2008

Since 1904, when Prandtl formulated the boundary-layer equations, it has been presumed that due to the viscous nature of the boundary layers the solution of the Prandtl equations should be sought in the class of continuous functions. However, there are clear mathematical reasons for discontinuous solutions to exist. Moreover, under certain conditions they represent the only possible solutions of the boundary-layer equations.

In this paper we consider, as an example, an unsteady analogue of the laminar jet problem first studied by Schlichting in 1933. In Schlichting's formulation the jet emerges from a narrow slit in a flat barrier and penetrates into a semi-infinite region filled with fluid which would remain at rest if the slit were closed. Assuming the flow steady, Schlichting was able to demonstrate that the corresponding solution to the Prandtl equations may be written in an explicit analytic form. Here our concern will be with unsteady flow that is initiated when the slit is opened and the jet starts penetrating into the stagnant fluid. To study this process we begin with the numerical solution of the unsteady boundary-layer equations. Since discontinuities were expected, the equations were written in conservative form before finite differencing. The solution shows that the jet has a well-established front representing a discontinuity in the velocity field, similar to the shock waves that form in supersonic gas flows.

Then, in order to reveal the ‘internal structure’ of the shock we turn to the analysis of the flow in a small region surrounding the discontinuity. WithRedenoting the Reynolds number, the size of the inner region is estimated as an orderRe−1/2quantity in both longitudinal and lateral directions. We found that the fluid motion in this region is predominantly inviscid and may be treated as quasi-steady if considered in the coordinate frame moving with the jet front. These simplifications allow a simple formula for the front speed to be deduced, which proved to be in close agreement with experimental observation of Turner (J. Fluid Mech.vol. 13 (1962), p. 356).
On the entrainment coefficient in negatively buoyant jets
Authors: PAPANICOLAOU PANOS N. , PAPAKONSTANTIS ILIAS G. , CHRISTODOULOU GEORGE C.
Published: October 2008

Integral models proposed to simulate positively buoyant jets are used to model jets with negative or reversing buoyancy issuing into a calm, homogeneous or density-stratified environment. On the basis of the self-similarity assumption, ‘top hat’ and Gaussian cross-sectional distributions are employed for concentration and velocity. The entrainment coefficient is considered to vary with the local Richardson number, between the asymptotic values for simple jets and plumes, estimated from earlier experiments in positively buoyant jets. Top-hat and Gaussian distribution models are employed in a wide range of experimental data on negatively buoyant jets, issuing vertically or at an angle into a calm homogeneous ambient, and on jets with reversing buoyancy, discharging into a calm, density-stratified fluid. It is found that geometrical characteristics such as the terminal (steady state) height of rise, the spreading elevation in stratified ambient and the distance to the point of impingement are considerably underestimated, resulting in lower dilution rates at the point of impingement, especially when the Gaussian formulation is applied. Reduction of the entrainment coefficient in the jet-like flow regime improves model predictions, indicating that the negative buoyancy reduces the entrainment in momentum-driven, negatively buoyant jets.
Apex jets from impacting drops
Authors: MARSTON J. O. , THORODDSEN S. T.
Published: October 2008

We present experiments showing vertical jetting from the apex of a viscous drop which impacts onto a pool of lower viscosity liquid. This jet is produced by the ejecta sheet which emerges from the free surface of the pool, and moves up and wraps around the surface of the drop. When this sheet of liquid converges and collides at the top apex of the drop it produces a thin upward jet at velocities of more than 10 times the drop impact velocity. This jetting occurs for a limited range of impact conditions, where the ejecta speed is sufficient for the sheet to travel around the entire drop periphery, but not so fast that it separates from the drop surface. The lower bound for the jetting region is thereby set by a minimal Reynolds number, but the upper bounds are subject to a maximum-Weber-number criterion. The strongest observed jets appear for viscous drops impacting onto liquid pools with the lowest viscosity as well as lowest surface tension, such as acetone and methanol. Jetting has also been observed for drops which are immiscible with the pool liquid, under a different range of impact conditions. However, jetting is never observed for pools of water, as the surface tension is then significantly larger than that of the drop. We believe that Marangoni stresses act in this case to promote separation of the sheet to prevent the jetting. A movie is available with the online version of the paper.
Evidence of seasonal changes in community structure for a coastal ecosystem in the central coast of Brazil, south-west Atlantic
Authors: Pinheiro H.T. , Martins A.S. , Araújo J.N. , Pinto A.S.S.
Published: October 2008

This study reports on the seasonal variations of the community structure of a coastal ecosystem, off the central coast of Brazil. Samples were collected on a monthly basis on board a bottom otter trawl vessel from October 2003 to September 2004. A total of 57 species belonging to 26 families and 10 orders were collected. Resident species, which presented a high proportion of juveniles throughout the year, were the most abundant. Among these, benthonic fish of the Sciaenidae family were the dominant species, followed by Tetraodontiformes, nektonic Sciaenidae and Clupeiformes. Benthonic fish were more abundant during the spring/summer months (October to February) and pelagic species dominated the autumn/winter months (May to September). However, these differences were not statistically significant. The spring/summer months were also characterized by reproduction activity, while the autumn/winter months saw high proportions of juveniles. Indicator species analyses showed that 5 species presented significant differences in their occurrence and abundance throughout the seasons of the year. This study shows that the coastal area is an important place for reproduction and a nursing ground of many species. It also shows evidence of community-level reproductive patterns for a tropical ecosystem. Future studies are necessary to identify the likely ecosystem forcings underlying these patterns.
Cytomorphological peculiarities of Polypodium hydriforme (Cnidaria)
Authors: Raikova E.V.
Published: October 2008

Cytomorphological characters of Polypodium hydriforme—a unique cnidarian, adapted to intracellular parasitism inside oocytes of Acipenseriform fish—are reviewed and analysed. Polypodium's unique characters, those shared with the Myxozoa, and the characters shared with bilateral triploblastic animals are listed. The set of unique features has allowed us to allocate Polypodium to a separate cnidarian class Polypodiozoa Raikova, 1988. The combination of characters displayed by P. hydriforme suggests that this animal is not an aberrant cnidarian, as it was formerly believed, but a relic of a major cnidarian group (class Polypodiozoa) that has undergone reduction due to adaptation to parasitism.
Widening the Colonial Encounter: Asian Connections Inside French Indochina During the Interwar Period
Authors: GOSCHA CHRISTOPHER E.
Published: October 2008

Relying on three inter-Asian colonial debates from French Indochina, this paper attempts to widen our analytical approach to the study of colonialism in Indochina beyond the ‘colonizer’–‘colonized’ opposition by factoring in the relationships among the diverse Asian colonized living within the colonial state without downplaying the important role Western colonialism played in transforming those very relationships or being affected by them. The French Indochinese case is helpful, for it suggests that inter-Asian connections did anything vanish, but rather intensified because of the colonial experience. Numerous Lao, Khmer, Vietnamese and Chinese subject elites continued to engage each otherandthe French in fascinating and sometimes heated debates about the political, legal, cultural and economic place each group held in French Indochina – or did not want to hold. This directly affected how they came to interact with one another in new ways, essential to understanding the complexity of the colonial encounter at the time and can provide new insights into post-colonial and international history. Lastly, this wider approach to studying the colonial encounter allows us to view the French side of the colonial equation from a new vantage point.
Reduction, Unity and the Nature of Science: Kant's Legacy?
Authors: Morrison Margaret
Published: October 2008

One of the hallmarks of Kantian philosophy, especially in connection with its characterization of scientific knowledge, is the importance of unity, a theme that is also the driving force behind a good deal of contemporary high energy physics. There are a variety of ways that unity figures in modern science—there is unity of method where the same kinds of mathematical techniques are used in different sciences, like physics and biology; the search for unified theories like the unification of electromagnetism and optics by Maxwell; and, more recently, the project of grand unification or the quest for a theory of everything which involves a reduction of the four fundamental forces (gravity, electromagnetism, weak and strong) under the umbrella of a single theory. In this latter case it is thought that when energies are high enough, the forces (interactions), while very different in strength, range and the types of particles on which they act, become one and the same force. The fact that these interactions are known to have many underlying mathematical features in common suggests that they can all be described by a unified field theory. Such a theory describes elementary particles in terms of force fields which further unifies all the interactions by treating particles and interactions in a technically and conceptually similar way. It is this theoretical framework that allows for the prediction that measurements made at a certain energy level will supposedly indicate that there is only one type of force. In other words, not only is there an ontological reduction of the forces themselves but the mathematical framework used to describe the fields associated with these forces facilitates their description in a unified theory. Specific types of symmetries serve an important function in establishing these kinds of unity, not only in the construction of quantum field theories but also in the classification of particles; classifications that can lead to new predictions and new ways of understanding properties like quantum numbers. Hence, in order to address issues about unification and reduction in contemporary physics we must also address the way that symmetries facilitate these processes.
The English comparative – language structure and language use
Authors: HILPERT MARTIN
Published: October 2008

Many English adjectives form the comparative in two ways, so that, for instance,prouderoccurs alongsidemore proud. The availability of several forms raises the general questions of when and why speakers choose one variant over the other. The aim of this article is to identify factors of language structure and language use that underlie the comparative alternation and to determine their relative strengths on the basis of data from the BNC through a logistic regression analysis. The results suggest that the alternation is primarily governed by phonological factors, but that syntax and frequency of usage are of importance as well.
Fricated realisations of /t/ in Dublin and Middlesbrough English: an acoustic analysis of plosive frication and surface fricative contrasts
Authors: JONES MARK J. , LLAMAS CARMEN
Published: October 2008

The frication of the voiceless plosives /p,t,k/ in word-final intervocalic position in Dublin and Middlesbrough English is examined in controlled data, and the acoustic characteristics of fricated realisations of /t/ are compared with other fricatives. The findings are that /t/ is not the only plosive to be fricated in the data sample, but does appear to differ from other plosives in terms of the regularity of frication and its nongradient character for some subjects. The realisation of fricated /t/ at both localities differs from that of other fricatives, and is probably perceptually distinct from other fricative contrasts at each locality, but is not identical across the two localities. On the basis of data presented here, it appears unlikely that fricated /t/ in Middlesbrough English is a direct transfer effect from the language of Irish immigrants to Middlesbrough.
Deictification: the development of secondary deictic meanings by adjectives in the English NP
Authors: DAVIDSE KRISTIN , BREBAN TINE , VAN LINDEN AN
Published: October 2008

In this article we make a case for recognizing deictification as a type of grammaticalization and semantic shift in the NP analogous to auxiliarization in the VP. The specific analogy we point out is between lexical verbs that grammaticalize into secondary auxiliaries bound by the finite, as inis going to,has to+ verb, and lexically full adjectives that grammaticalize into postdeterminers bound by the primary determiner, as ina different,the same+ noun. We present five case studies of the development of postdeterminer meanings, based on the analysis of diachronic and synchronic data. The adjectives studied areopposite,complete,old,regularandnecessary, whose postdeterminer uses relate to the basic deictic systems of space, quantity, time and modality. Our analysis of the data shows that the mechanism of secondary deictification can be given a unified characterization as the semantic shift by which a general relation expressed by the adjective is given a subjective reference point in or relative to the speech event.
Radiation-hydrodynamics simulations of surface convection in low-mass stars: connections to stellar structure and asteroseismology
Authors: Ludwig Hans-G. , Caffau Elisabetta , Kučinskas A.
Published: October 2008

Radiation-hydrodynamical simulations of surface convection in low-mass stars can be exploited to derive estimates of i) the efficiency of the convective energy transport in the stellar surface layers; ii) the convection-related photometric micro-variability. We comment on the universality of the mixing-length parameter, and point out potential pitfalls in the process of its calibration which may be in part responsible for the contradictory findings about its variability across the Hertzsprung-Russell digramme. We further comment on the modelling of the photometric micro-variability in HD 49933 – one of the first mainCOROTtargets.
Large-scale numerical simulations: Convection in an annular channel rotating about a vertical axis with side-walls
Authors: Chang Yingli , Liu Yu
Published: October 2008

For the purpose of understanding the dynamics of planetary atmospheres, we use the annular convection model to simulate the dynamics of atmospheres of Jupiter and Saturn. The model (annular channel) rotates about a vertical axis with side-walls, and it is heated from below.

We use the software NaSt3DGP (a parallel software package to solve the 3D incompressible fluid dynamic problems in Cartesian coordinates by using Finite Difference Method) for the computation. It's reliability is tested by our application to simulate fully three-dimensional nonlinear convection in a box with lateral stress-free side-walls, uniformly heated from below. We found that, at moderately large Rayleigh numbers, the complex formation of multiple-jet flows can be maintained by the traveling convective eddies; we also found that the type of the sidewall velocity condition does not play an essential role in determining the primary properties of strongly nonlinear convection.
A large sample of low surface brightness disk galaxies from SDSS
Authors: Zhong G. H. , Liang Y. C. , Deng L. C. , Zhang B.
Published: October 2008

We present the properties of a large sample (12,282) of nearly face-on low surface brightness disk galaxies selected from the main galaxy sample of SDSS-DR4. Those properties includes B-band central surface brightness μ0(B), scale lengths h, distances D, integrated magnitudes, colors and some resulted relations. This sample has μ0(B) from 22 to 24.5 mag arcsec−2 with a median value of 22.44 mag arcsec−2. They are quite bright with MB taking values from −18 to −23 mag with a median value of −20.08 mag. The disk scale lengths h are from 2 kpc to 19 kpc. There exist clear correlations between log h and MB, log h and log D. Both the optical-optical and optical-NIR color-color relations show most of them have a mix of young and old stellar populations.
Progress report on solar age calibration
Authors: Houdek G. , Gough D. O.
Published: October 2008

We report on an ongoing investigation into a seismic calibration of solar models designed for estimating the main-sequence age and a measure of the chemical abundances of the Sun. Only modes of low degree are employed, so that with appropriate modification the procedure could be applied to other stars. We have found that, as has been anticipated, a separation of the contributions to the seismic frequencies arising from the relatively smooth, glitch-free, background structure of the star and from glitches produced by helium ionization and the abrupt gradient change at the base of the convection zone renders the procedure more robust than earlier calibrations that fitted only raw frequencies to glitch-free asymptotics. As in the past, we use asymptotic analysis to design seismic signatures that are, to the best of our ability, contaminated as little as possible by those uncertain properties of the star that are not directly associated with age and chemical composition. The calibration itself, however, employs only numerically computed eigenfrequencies. It is based on a linear perturbation from a reference model. Two reference models have been used, one somewhat younger, the other somewhat older than the Sun. The two calibrations, which use BiSON data, are more-or-less consistent, and yield a main-sequence aget⊙= 4.68 ± 0.02 Gy, coupled with a formal initial heavy-element abundanceZ= 0.0169 ± 0.0005. The error analysis has not yet been completed, so the estimated precision must be taken with a pinch of salt.
Stellar Evolution from AGB to Planetary Nebulae
Authors: Kwok Sun
Published: October 2008

Planetary nebulae are formed by an interacting winds process where the remnant of the AGB wind is compressed and accelerated by a later-developed fast wind from the central star. One-dimensional dynamical models have successfully explained the multi-shell (bubble, shell, crown, haloes) structures and the kinematics of planetary nebulae. However, the origin of the diverse asymmetric morphology of planetary nebulae is still not understood. Recent observations in the visible, infrared, and the submillimeter have suggested that the AGB mass loss becomes aspherical in the very late stages, forming an expanding torus around the star. A fast, highly collimated wind then emerges in the polar directions and carves out a cavity in the AGB envelope to form a bipolar nebula. Newly discovered structures such as concentric arcs, 2-D rings, multiple lobes, and point-symmetric structures suggest that both the slow and fast winds may have temporal and directional variations, and precession can play a role in the shaping of planetary nebulae. In this paper, we review the latest observations of planetary nebulae and proto-planetary nebulae and discuss the various physical mechanisms (rotation, binary, magnetic field, etc) that could lead to the observed morphologies.
AGB star models. Results from 1D stellar evolution and multi-dimensional hydrodynamics simulations
Authors: Herwig Falk
Published: October 2008

In this review I am discussing the current state of simulating the internal evolution of AGB stars. Recent work on AGB stars include the effect of rotation, magnetic fields and internal gravity waves, as well as thermohaline mixing induced by the3He +3He pp-chain reaction. Hydrodynamic simulations of the interior convection of AGB stars are now becoming available, giving insights to convective boundary mixing, for example for He-shell flash convection. At very low metallicity convective-reactive events are encountered in AGB stars (as well as in massive stars), and the necessity of hydrodynamic simulations to address this difficult phase of stellar evolution is emphasized.
The Structure and Kinematics of Envelope around Red Supergiant AH Sco Traced by SiO Masers
Authors: Chen X. , Shen Z.-Q.
Published: October 2008

Observations of 43 GHz v = 1, J = 1−0 SiO masers in the circumstellar envelope of the M-type semi-regular variable star AH Sco were performed with the Very Long Baseline Array (VLBA) at 2 epochs in March 2004. These high-resolution VLBA images reveal that the distribution of SiO masers is roughly on a persistent elliptical ring with the lengths of the major and minor axes of about 18.5 and 15.8 mas, respectively, along a position angle of 150°. The 3-dimensional kinematics model-fitting for proper motions and spatial distributions of maser features clearly indicates that the SiO maser shell around AH Sco was undergoing an overall contraction to the star at a velocity of 15 km s−1 at a distance of 2.26 kpc to AH Sco due to the gravitation of the central star.
Dust Size Effect On IR Colors Of AGB Stars
Authors: Wang Huan , Jiang B. W. , Szczerba R.
Published: October 2008

With the Mie theory and the radiative transfer model, we studied the effect of dust size on the infrared color indexes concerning special filters used in the space infrared missions and typical filters in the near-infrared, of AGB stars with typical oxygen-rich and carbon-rich dust shells. It is found the most affected bands are the near-infrared bands JHK and the Spitzer IRAC bands, meanwhile the wavebands with reference wavelength longer than 10 μm is little affected. The effect increases fast with the mass loss rate. We also discussed the potential to distinguish the O-rich and C-rich dusts, and the difference in IR colors between the AGB stars and other IR sources like YSOs and galaxies.
60Fe and Massive Stars
Authors: Wang Wei
Published: October 2008

Gamma-ray line emission from radioactive decay of60Fe provides constraints on nucleosynthesis in massive stars and supernovae. We detect the γ-ray lines from60Fe decay at 1173 and 1333 keV using three years of data from the spectrometer SPI on boardINTEGRAL. The average flux per line is (4.4 ± 0.9) × 10−5ph cm−2s−1rad−1for the inner Galaxy region. Deriving the Galactic26Al gamma-ray line flux with using the same set of observations and analysis method, we determine the flux ratio of60Fe/26Al gamma-rays as 0.15 ± 0.05. We discuss the implications of these results for the widely-held hypothesis that60Fe is synthesized in core-collapse supernovae, and also for the closely-related question of the precise origin of26Al in massive stars.
Exploring the nucleosynthesis region of metal-poor Stars
Authors: Geng Yuan-Yuan , Cui Dong-Nuan , Zhang Jiang , Zhang Bo
Published: October 2008

The chemical abundances of the very metal poor double-enhanced stars are excellent information to set new constraints on models of neutron-capture processes at low metallicity. There have been many theoretical studies of s-process nucleosynthesis in low-mass AGB stars. Using the parametric approach based on the radiative s-process nucleosynthesis model, we calculate the following five parameters for a series of metal-poor stars. They are: the mass fraction of 13C pocket q, the overlap factor r, the neutron exposure per interpulse Δτ, and the component coefficients that correspond to relative contribution from the s-process and the r-process. We find that the mass fraction of 13C pocket q deduced for the Pb stars is comparable to the overlap factor r, which is about 10 times larger than normal AGB model; q ~ 0.05; and the neutron exposure per interpulse Δτ for all Pb stars are about 10 times smaller than the ST case (Δτ ~ 7.0mb−1). Although the two fundamental parameters Δτ and q obtained for the Pb stars are very different from the AGB stellar model, the results of the larger value of q and the smaller value of Δτ can also explain the abundance distribution of the Pb stars. This suggest that the q change to larger than that of normal AGB model. Then, this factor will result in the descent of the density of 13C in the nuclear synthesis region directly. So, the neutron exposure Δτ will also decrease to the same extent. Although the neutron number density in the larger initial mass AGB stars (m > 3M⊙) is high, the neutron irradiation time is shorter, obviously the neutron exposure per interpulse in the AGB stars should be smaller. It is noteworthy that the total amount of 13C in metal poor condition is close to the ST case, which is consistent with the primary nature of the neutron source.
Study on the spectrum of the injected relativistic protons
Authors: Wang Y. P. , Lu Y. , Chen L.
Published: October 2008

About 10 TeV γ-ray emission within 10 pc region from the Galactic Center had been reported by 4 independent groups. Considering that this TeV γ-ray emission is produced via a hadronic model, and the relativistic protons came from the tidal disruption of stars by massive black holes, we investigate the spectral nature of the injected relativistic protons required by the hadronic model. The calculation was carried on the tidal disruption of the different types of stars and the different propagation mechanisms of protons in the interstellar medium. Compared with the observation data from HESS, we find for the best fitting that the power-law index of the spectrum of the injected protons is about −1.9, when a red giant star is tidally disrupted, and the effective confinement of protons diffusion mechanism is adopted.
Rotational mixing in close binaries
Authors: de Mink S. E. , Cantiello M. , Langer N. , Yoon S.-Ch. , Brott I. , Glebbeek E. , Verkoulen M. , Pols O. R.
Published: October 2008

Rotational mixing a very important but uncertain process in the evolution of massive stars. We propose to use close binaries to test its efficiency. Based on rotating single stellar models we predict nitrogen surface enhancements for tidally locked binaries. Furthermore we demonstrate the possibility of a new evolutionary scenario for very massive (M > 40M⊙) close (P < 3 days) binaries: Case M, in which mixing is so efficient that the stars evolve quasi-chemically homogeneously, stay compact and avoid any Roche-lobe overflow, leading to very close (double) WR binaries.
The duration properties of Swift Gamma-Ray Bursts
Authors: Zhang Z.-B. , Choi C.-S.
Published: October 2008

We report the systematic analysis of the durations for Swift gamma-ray bursts (GRBs) and compare the results with those of pre-Swift data. We show that the durations of Swift bursts also have two log-normal distributions that are clearly divided at T90 = 2 s. Their intrinsic durations also show a bimodal distribution but shift systematically toward the smaller value compared with the observed one. This study confirms the spectra of short GRBs are in general harder than the long GRBs and shows that this trend becomes weak in the source frame.
The energy transfer in W UMa binary stars
Authors: Jiang Dengkai , Wang Jiangcheng , Han Zhanwen , Jiang Tianyu , Li Lifang
Published: October 2008

The properties of W UMa binary stars are studied based on the well-determined physical parameters of 132 W UMa systems. It is found that the energy transfer rate has a maximum value at q ~ 0.58. The relation between the energy transfer rate and the temperature deviation is also investigated, and the temperature of the secondary component is related to the energy transfer rate.
Unveiling de Soto's mystery: property rights, capital formation, and development
Authors: KEREKES CARRIE B. , WILLIAMSON CLAUDIA R.
Published: October 2008

Hernando de Soto attributes the poor economic performance of developing countries to insecure property rights. When property rights are not well-defined individuals do not have the incentives to invest in capital, and assets cannot be used as collateral, hindering capital formation and economic growth. This paper tests de Soto's hypothesis empirically by examining how the security of property rights impacts wealth, collateral, and capital formation across nations. Using several different measures and model specifications, we find support for de Soto's conjecture. Our results suggest that better defined property rights would result in substantial improvements in capital formation and economic growth in developing countries.
Not by rules or choice alone: a pragmatist critique of institution theories in economics and sociology
Authors: GRONOW ANTTI
Published: October 2008

The article discusses institutional theories in economics and sociology. The discussion adopts W. Richard Scott's classification into regulative, normative, and discursive theories. A fourth alternative, habitual institutionalism, is also presented because of the problems encountered with the other theories. Pragmatically inclined habitual institutionalism presents a consistent theory of action wherein conscious action is derived from habitual action, which is also the basis of institutionalization. In addition, habitual institutionalism portrays human rationality more extensively than economists and sociologists have traditionally done. For these reasons, the difficulties associated with other institutional theories can be avoided.
Three-Year-Olds’ Retrospective Revaluation in the Blicket Detector Task
Authors: Beckers Tom , Vandorpe Stefaan , Debeys Ine , De Houwer Jan
Published: October 2008

We presented 3-year-olds with backward blocking and recovery from overshadowing contingencies in the blicket detector task, a causal induction task that uses binary, deterministic outcomes. Results revealed recovery from overshadowing but no backward blocking. These results are consistent with recent inferential and computational models of causal learning and induction. Our findings extend and clarify recent reports of retrospective revaluation in 3- and 4-year-olds (Sobel, D. M., Tenenbaum, J. B., & Gopnik, A. (2004). Children’s causal inferences from indirect evidence: Backwards blocking and Bayesian reasoning in preschoolers. Cognitive Science, 28, 303–333), and underscore the sophistication of causal induction processes in young children.
Detection of Symmetry and Repetition in One and Two Objects
Authors: Koning Arno , Wagemans Johan
Published: October 2008

Symmetry is usually easier to detect within a single object than in two objects (one-object advantage), while the reverse is true for repetition (two-objects advantage). This interaction between regularity and number of objects could reflect an intrinsic property of encoding spatial relations within and across objects or it could reflect a matching strategy. To test this, regularities between two contours (belonging to a single object or two objects) had to be detected in two experiments. Projected three-dimensional (3-D) objects rotated in depth were used to disambiguate figure-ground segmentation and to make matching based on simple translations of the two-dimensional (2-D) contours unlikely. Experiment 1 showed the expected interaction between regularity and number of objects. Experiment 2 used two-objects displays only and prevented a matching strategy by also switching the positions of the two objects. Nevertheless, symmetry was never detected more easily than repetition in these two-objects displays. We conclude that structural coding, not matching strategies, underlies the one-object advantage for symmetry and the two-objects advantage for repetition.