bluuebunny/crossref_metadata_2025_split huggingface dataset:
Folic acid facilitates in vitro maturation of mouse and Xenopus laevis oocytes
Authors: Huang Xiaoli , Gao Shu , Xia Wei , Hou Shaoying , Wu Kun 
Published: August 2012

The water-soluble B vitamins, folate and folic acid, play an important role in reproductive health, but little is known about the effects of folic acid on infertility. The present study tested the hypothesis that folic acid affects oocyte maturation, a possible cause of female infertility. We have studied the in vitro maturation of mouse and Xenopus oocytes. Hypoxanthine (Hx) was used as an inhibitor of mouse oocyte maturation to mimic in vivo conditions by maintaining high levels of cyclic-AMP. The frequency of first polar body (PB1) formation and germinal vesicle breakdown (GVBD) in mouse oocytes was decreased by Hx. This effect was counteracted by folic acid added to the medium. PB1 extrusion and GVBD percentages rose to 27·7 and 40·0 % from 12·8 and 19·9 %, respectively, by exposure to 500 μm-folic acid. Folic acid also restored the spindle configuration, which had been elongated by Hx, as well as normalising the distribution of cortical granules (CG). In folic acid-treated Xenopus eggs, extracellular signal-regulated kinase 1 was phosphorylated, cyclin B2 and Mos were up-regulated and the frequency of GVBD was accelerated. Taken together, the findings suggest that folic acid facilitates oocyte maturation by altering the expression and phosphorylation of proteins involved in M-phase-promoting factor and mitogen-activated protein kinase pathways, as well as causing changes in spindle configuration and CG migration.
Finite p-solvable groups with three p-regular conjugacy class sizes
Authors: Akhlaghi Zeinab , Beltrán Antonio , Felipe María José , Khatami Maryam 
Published: August 2012

AbstractLet G be a finite p-solvable group. We describe the structure of the p-complements of G when the set of p-regular conjugacy classes has exactly three class sizes. For instance, when the set of p-regular class sizes of G is {1, pa, pam} or {1, m, pam} with (m, p) = 1, then we show that m = qb for some prime q and the structure of the p-complements of G is determined.
The “Bargain” of Collaboration: African Intermediaries, Indirect Recruitment, and Indigenous Institutions in the Ghanaian Gold Mining Industry, 1900–1906
Authors: Mark-Thiesen Cassandra 
Published: August 2012

SummaryThis article argues that during the formative years of the colonial state in Ghana, European employers established new collaborative mechanisms with African intermediaries for the purpose of expanding the modern mining sector. They were forced to do so on account of severe labour-market limitations, resulting primarily from the slow death of slavery and debt bondage. These intermediaries, or “headmen”, were engaged because of their apparent affluence and authority in their home villages, from which they recruited mineworkers. However, allegiances between them and managers in the Tarkwa gold mines considerably slowed the pace towards free labour. Indeed, a system in which managers reinforced economic coercion and repressive relationships of social dependency between Africans, allocating African labour contractors fixed positions of power, resulted from the institutionalization of purportedly traditional processes of labour recruitment into the modern market.
Patterns of a novel association between the scyphomedusaChrysaora plocamiaand the parasitic anemonePeachia chilensis
Authors: Riascos Jose M. , Villegas Viviana , Cáceres Ignacio , Gonzalez Jorge E. , Pacheco Aldo S. 
Published: August 2012

Jellyfish display strong population variability. Competitive interactions between fish and jellyfish have been depicted as a major mechanism controlling this variability. Biological associations involving jellyfish are, however, more diverse than predation–prey interactions and remain poorly understood. Parasitic associations in particular may have relevant effects on jellyfish host populations. We studied basic patterns (temporal patterns of parasite intensity–biomass and the distribution pattern of parasites among hosts) of the association between the parasitic anemonePeachia chilensisand its scyphozoan host,Chrysaora plocamia. The mean number of parasites per host (MI) was high (average = 465) and showed significant differences during the pelagic life phase of the medusa. The mean biomass of parasites per host was also significantly different among months but showed a different temporal pattern to that of MI, which may reflect recruitment pulses of parasitic larvae. The mean biomass ofP. chilensisper host averaged 56.3 mg ash-free dry mass, which represents a trophic flow of energy probably linking pelagic and benthic food webs. The distribution of parasites among hosts was best fitted to the negative binomial distribution model, as typical for host–parasite systems. We concluded that the parasite-induced host mortality and reduction of fecundity, represented by parasitic castration, is restricted to a few hosts and is therefore under the expected levels that characterize the dynamic equilibrium of host–parasite systems.
Self-critical perfectionism and its relationship to fatigue and pain in the daily flow of life in patients with chronic fatigue syndrome
Authors: Kempke S. , Luyten P. , Claes S. , Goossens L. , Bekaert P. , Van Wambeke P. , Van Houdenhove B. 
Published: August 2012

BackgroundResearch suggests that the personality factor of self-critical or maladaptive perfectionism may be implicated in chronic fatigue syndrome (CFS). However, it is not clear whether self-critical perfectionism (SCP) also predicts daily symptoms in CFS.MethodIn the present study we investigated whether SCP predicted fatigue and pain over a 14-day period in a sample of 90 CFS patients using a diary method approach. After completing the Depressive Experiences Questionnaire (DEQ) as a measure of SCP, patients were asked each day for 14 days to complete Visual Analogue Scales (VAS) of fatigue, pain and severity of depression. Data were analysed using multilevel analysis.ResultsThe results from unconditional models revealed considerable fluctuations in fatigue over the 14 days, suggesting strong temporal variability in fatigue. By contrast, pain was relatively stable over time but showed significant inter-individual differences. Congruent with expectations, fixed-effect models showed that SCP was prospectively associated with higher daily fatigue and pain levels over the 14-day period, even after controlling for levels of depression.ConclusionsThis is the first study to show that SCP predicts both fatigue and pain symptoms in CFS in the daily course of life. Hence, therapeutic interventions aimed at targeting SCP should be considered in the treatment of CFS patients with such features.
Longitudinal course of depressive symptoms in adulthood: linear stochastic differential equation modeling
Authors: Rosenström T. , Jokela M. , Hintsanen M. , Pulkki-Råback L. , Hutri-Kähönen N. , Keltikangas-Järvinen L. 
Published: August 2012

BackgroundAlthough many studies have addressed the topic of stabilityversuschange in depressive symptoms, few have further decomposed the change to continuous accumulationversusnon-systematic state fluctuations or measurement errors. This further step requires a longitudinal follow-up and an appropriate stochastic model; it would, for example, evaluate the hypothesis that women accumulate more susceptibility events than men.MethodA linear stochastic differential equation model was estimated for a 16-year longitudinal course of depressive symptoms in the Young Finns community sample of 3596 participants (1832 women, 1764 men). This model enabled us to decompose the variance in depression symptoms into a stable trait, cumulative effects and state/error fluctuations.ResultsWomen showed higher mean levels and higher variance of depressive symptoms than men. In men, the stable trait accounted for the majority [61%, 90% confidence interval (CI) 48.9–69.2] of the total variance, followed by cumulative effects (23%, 90% CI 9.9–41.7) and state/error fluctuations (16%, 90% CI 5.6–23.2). In women, the cumulative sources were more important than among men and accounted for 44% (90% CI 23.6–58.9) of the variance, followed by stable individual differences (32%, 90% CI 18.5–54.2) and state fluctuations (24%, 90% CI 19.1–27.3).ConclusionsThe results are consistent with previous observations that women suffer more depression than men, and have more variance in depressive symptoms. We also found that continuously accumulating effects are a significant contributor to between-individual differences in depression, especially for women. Although the accumulating effects are often confounded with non-systematic state fluctuations, the latter are unlikely to exceed 27% of the total variance of depressive symptoms.
Neurological soft signs in obsessive-compulsive disorder: two empirical studies and meta-analysis
Authors: Jaafari N. , de la Cruz L. Fernández , Grau M. , Knowles E. , Radua J. , Wooderson S. , Segalas C. , Alonso P. , Phillips M. L. , Menchón J. M. , Mataix-Cols D. 
Published: August 2012

BackgroundNeurological soft signs (NSS) have been inconsistently reported in obsessive-compulsive disorder (OCD) but may make an impact on treatment response.MethodThe current study examined the presence of NSS in two independent European samples of OCD patients (combined 85 patients and 88 matched healthy controls) using a standardized instrument and conducted a meta-analysis of all published studies identified in the literature with the aim to provide a more definitive answer to the question of whether OCD patients are characterized by increased NSS.ResultsBoth empirical studies found elevated NSS scores in patients compared with matched controls. The results of the meta-analysis, which included 15 studies (combined 498 patients and 520 controls) showed large effect sizes (Hedges'g=1.27, 95% confidence interval 0.80–1.75), indicating that OCD patients have significantly higher rates of NSS than matched controls on both sides of the body and in multiple domains (motor coordination, sensory integration and primitive reflexes). The results were robust and remained largely unchanged in our reliability analyses, which controlled for possible outliers. Meta-regression was employed to examine the role of potential variables of interest including sociodemographic variables, symptom severity, medication effects and the use of different instruments, but none of these variables was clearly associated with NSS.ConclusionsAs a group, OCD patients are characterized by increased rates of NSS, compared with healthy controls. However, their origins and potential clinical importance remain to be clarified. Future directions for research are discussed.
A characterization of biholomorphic automorphisms of Teichmüller space
Authors: MINEYAMA RYOSUKE , MIYACHI HIDEKI 
Published: August 2012

AbstractIn this paper, we give an alternative approach to Royden–Earle–Kra–Markovic's characterization of biholomorphic automorphisms of Teichmüller space of Riemann surface of analytically finite type.
Historical overview of planetary nebulae research
Authors: Kwok Sun 
Published: August 2012

AbstractPlanetary nebulae (PNs) were first discovered over 200 years ago and our understanding of these objects has undergone significant evolution over the years. Developments in astronomical optical spectroscopy and atomic physics have shown that PNe are gaseous objects photoionized by UV radiation from a hot central star. Studies of the kinematics of the nebulae coupled with progress in theories of stellar evolution have led to the identification that PNe are evolved stars and progenitors of white dwarfs. Development of infrared and millimeter-wave technology in the 1970s made us realize that there is significant amount of neutral matter (molecules and dust) in PNe. The link of PNe to the stellar winds from their progenitor asymptotic giant branch (AGB) stars and subsequent dynamical interactions are now believed to be the underlying causes of the morphological structures of PNe. The role of PNe as prolific molecular factories producing complex molecules and organic solids has significant implications on the chemical enrichment of the Galaxy.In this paper, we discuss the misconceptions and errors that we have encountered in our journey of understanding the nature of PN. The various detours and dead ends that had happened during our quest to pin down the evolutionary status and causes of nebulae ejection will be discussed. As there are still many unsolved problems in PN research, these lessons of history have much to offer for future progress in this field.
Spitzer IRS spectra of compact Galactic planetary nebulae: The link between dust, evolution, and metallicity
Authors: Stanghellini L. , García-Hernández D. A. , García-Lario P. , Davies J. E. , Shaw R. A. , Villaver E. , Manchado A. , Perea-Calderón J. V. 
Published: August 2012

AbstractA sample of ~150 compact Galactic PNe has been observed with the Spitzer/IRS spectrograph to characterize their dust properties. These PNe are likely to be at the onset of the PN evolutionary phase, and are therefore ideal for probing dust evolution. The molecular emission features in these Galactic PN spectra are similar to those found in our Magellanic Cloud sample, except that we found a sizable fraction of PNe with mixed-chemistry dust which are not observed in the Clouds. We also found that the distribution among dust types depends strongly on the metallicity of the parent population, implying that the metallicity of the progenitors affects the evolution of a PN from its early stages.
Observational studies of mass loss from AGB stars
Authors: Matsuura Mikako 
Published: August 2012

AbstractIt is important to properly describe the mass-loss rate of AGB stars, in order to understand their evolution from the AGB to PN phase. The primary goal of this study is to investigate the influence of metallicity on the mass-loss rate, under well determined luminosities. The luminosity of the star is a crucial parameter for the radiative driven stellar wind. Many efforts have been invested to constrain the AGB mass-loss rate, but most of the previous studies use Galactic objects, which have poorly known distances, thus their luminosities. To overcome this problem, we have studied mass loss from AGB stars in the Galaxies of the Local Group. The distance to the stars have been independently measured, thus AGB stars in these galaxies are ideal for understanding the mass-loss rate. Moreover, these galaxies have a lower metallicity than the Milky Way, providing an ideal target to study the influence of metallicity on the mass-loss rate. We report our analysis of mass loss, using the Spitzer Space Telescope and the Herschel Space Observatory. We will discuss the influence of AGB mass-loss on stellar evolution, and explore AGB and PN contribution to the lifecycle of matter in galaxies.
Asymptotic giant branch evolution: Where do we stand?
Authors: Marigo Paola 
Published: August 2012

AbstractI provide a synthetic overview of the present status of stellar models for the asymptotic giant branch phase, one of the most complex and still uncertain stages of stellar evolution. In particular I will focus on two aspects that are most relevant in the context of the planetary nebulæ progeny, namely: the chemical composition of the AGB ejecta, and the mass of the bare CO core left after the ejection of the stellar mantle at the AGB tip. Recent progress, present uncertainties, and future perspectives to constrain AGB models are briefly discussed.
Shaping proto-planetary nebulae by binary systems
Authors: Riera A. , Velázquez P. F. , Steffen W. , Raga A. C. , Cantó J. 
Published: August 2012

AbstractWe present the results of 3D hydrodynamic simulations aimed to explore the binary scenario for shaping bipolar, point- and mirror-symmetric proto-Planetary Nebulae. We consider a jet launched by the secondary star of a binary system, located at the center of the PPN, which propagates within a circumstellar medium swept previously up by the wind of the giant companion. As a result of the presence of the companion star, the accretion disk around the jet source is likely to precess. We have carried out 3D hydrodynamical simulations with the YGUAZÚ-A code including the combination of an orbital motion plus a precession. Our results show that to produce a multipolar nebula, it is necessary to have a precessing jet in a binary system with a time-dependent ejection velocity.
Ongoing surveys for close binary central stars and wider implications
Authors: Miszalski Brent 
Published: August 2012

AbstractBinary central stars have long been invoked to explain the vexing shapes of planetary nebulae (PNe) despite there being scant direct evidence to support this hypothesis. Modern large-scale surveys and improved observing strategies have allowed us to significantly boost the number of known close binary central stars and estimate at least 20% of PNe have close binary nuclei that passed through a common-envelope (CE) phase. The larger sample of post-CE nebulae appears to have a high proportion of bipolar nebulae, low-ionisation structures (especially in SN1987A-like rings) and polar outflows or jets. These trends are guiding our target selection in ongoing multi-epoch spectroscopic and photometric surveys for new binaries. Multiple new discoveries are being uncovered that further strengthen the connection between post-CE trends and close binaries. These ongoing surveys also have wider implications for understanding CE evolution, low-ionisation structure and jet formation, spectral classification of central stars, asymptotic giant branch (AGB) nucleosynthesis and dust obscuration events in PNe.
Reduce, reuse, recycle: Planetary nebulae as green galactic citizens
Authors: Kwitter Karen B. , Henry Richard B. C. 
Published: August 2012

AbstractWe review gas-phase abundances in PNe and describe their dual utility as archives of original progenitor metallicity via the α elements, as well as sources of processed material from nucleosynthesis during the star's evolution, i.e., C, N, and s-process elements. We describe the analysis of PN spectra to derive abundances and discuss the discrepancies that arise from different choices at each step. Abundance results for the Milky Way and Magellanic Clouds from various groups of investigators are presented; the observational results are compared with theoretical predictions of AGB stellar yields. Finally, we suggest areas where more work is needed to improve our abilities to determine abundances in PNe.
Atomic processes in planetary nebulae
Authors: Liu Xiaowei 
Published: August 2012

AbstractProgress in the study of the atomic processes in planetary nebulae (PNe) is reviewed, focusing on the literature published since the last IAU symposium on PNe five years ago. High quality photoionization cross sections and recombination coefficients are now available for the first six ions of the trans-iron elements selenium and krypton, enabling robust modeling of their ionization structure and consequently converting the measured ionic abundances to elemental abundances. Major progress has been achieved in utilizing the recombination spectra of helium and heavy element ions to probe the nebular physical conditions. New ab initio, density-dependent effective recombination coefficients have been calculated for the recombination spectra of O ii and N ii, down to very low temperatures (~ 100–300 K). Plasma diagnostics based entirely on those heavy element recombination lines are developed and applied to the observations. It is shown that these heavy element recombination lines originate predominately from cold plasmas of temperatures ~ 1,000 K, in agreement with the predictions of the bi-abundance model that has been proposed to explain the dichotomy of nebular plasma diagnostics and abundance determinations using collisional excited lines (CELs) on the one hand and optical recombination lines (ORLs) on the other.
Magnetic fields during the evolution towards planetary nebulae
Authors: Vlemmings Wouter 
Published: August 2012

AbstractMagnetic fields appear ubiquitous throughout the envelopes of evolved stars. However, their origin and role in the formation of planetary nebulae is still unclear. As observations of magnetic fields are complicated and time consuming, the observed samples of AGB and post-AGB stars and planetary nebulae are still small. Still, magnetic energy seems to dominate the energy budget out to a distance of several tens of AU from the central star and the field morphology often appears to be well ordered. A short summary is given of the current observations and the potential of new instruments such as ALMA is discussed.
Understanding the immediate progenitors of planetary nebulae
Authors: Sahai R. , Morris M. R. , Contreras C. Sánchez , Claussen M. J. 
Published: August 2012

AbstractPre-Planetary Nebulae (PPNe) are believed to represent a relatively short, intermediate evolutionary phase in the evolution of AGB stars to Planetary Nebulae (PNe). Our unbiased, high-resolution imaging surveys with HST of young PNe and PPNe show very strong morphological similarities between these classes, enabling us to extend our morphological scheme for PPN classification to young PNe, preserving virtually all of the primary and secondary descriptors, and adding a few new ones. These morphological surveys show that the primary shaping of PNe begins during the PPNe and/or late-AGB phase, and the key to understanding the shaping process lies in the study of these PNe progenitors. Here we present results from two recent studies of PNe progenitors: (i) Hα emission with very broad wings and P-Cygni profiles as probes of the region where the fast post-AGB outflows that do the shaping are most likely launched from, and (ii) equatorial waists with large-sized dust grains and large masses.
Central stars of planetary nebulae: The white dwarf connection
Authors: Werner Klaus 
Published: August 2012

AbstractThis paper is focused on the transition phase between central stars and white dwarfs, i.e. objects in the effective temperature range 100 000 – 200 000 K. We confine our review to hydrogen-deficient stars because the common H-rich objects are subject of the paper by Ziegleret al. in these proceedings. We address the claimed iron-deficiency in PG1159 stars and [WC] central stars. The discovery of new Neviiand Neviiilines in PG1159 stars suggests that the identification of Oviiand Oviiilines that are used for spectral classification of [WCE] stars is wrong. We then present evidence for two distinct post-AGB evolutionary sequences for H-deficient stars based on abundance analyses of the He-dominated O(He) stars and the hot DO white dwarf KPD 0005+5106. Finally, we report on evidence for an H-deficient post-super AGB evolution sequence represented by the hottest known, carbon/oxygen-atmosphere white dwarf H 1504+65 and the recently discovered carbon-atmosphere “hot DQ” white dwarfs.
Modeling the diffuse X-ray emission of planetary nebulae with different chemical composition
Authors: Steffen Matthias , Sandin Christer , Jacob Ralf , Schönberner Detlef 
Published: August 2012

AbstractBased on time-dependent radiation-hydrodynamics simulations of the evolution of Planetary Nebulae (PNe), we have carried out a systematic parameter study to address the non-trivial question of how the diffuse X-ray emission of PNe with closed central cavities is expected to depend on the evolutionary state of the nebula, the mass of the central star, and the metallicity of stellar wind and circumstellar matter. We have also investigated how the model predictions depend on the treatment of thermal conduction at the interface between the central ‘hot bubble’ and the ‘cool’ inner nebula, and compare the results with recent X-ray observations. Our study includes models whose properties resemble the extreme case of PNe with Wolf-Rayet type central stars. Indeed, such models are found to produce the highest X-ray luminosities.