bluuebunny/crossref_metadata_2025_split huggingface dataset:
ATLAS 9 and ATLAS 12 under GNU-Linux
Authors: Sbordone Luca , Bonifacio Piercarlo , Castelli Fiorella 
Published: May 2007

AbstractWe successfully ported the suite of codes developed by R. L. Kurucz for stellar atmosphere modelling, abundance determination and synthetic spectra calculation, to run under GNU-Linux. The ported codes include ATLAS 9 and ATLAS 12 for 1-D plane-parallel atmosphere model calculation, DFSYNTHE, which calculates the Opacity Distribution Functions (ODF) to be used with ATLAS 9, WIDTH to derive chemical abundances from measured line Equivalent Widths (EW) and SYNTHE to calculate synthetic spectra. The codes input and output files remain fully compatible with the VMS versions, while the computation speed has been greatly increased due to the high efficiency of modern PC CPUs. As an example, ATLAS 9 model calculations and the computation of large (e.g. 10 nm) synthetic spectra can be executed in a matter of minutes on any mainstream laptop computer. Arbitrary chemical compositions can be used in calculations (by using ATLAS 12 through opacity sampling or by calculating ad-hoc ODFs for ATLAS 9). The large set of scripting languages existing under Linux (shell, perl, python. . .) and the availability of low-cost multiprocessor Linux architectures (such as Beowulf) makes the port highly effective to build model farms to produce large quantities of atmosphere models or synthetic spectra (e.g. for the production of integrated light synthetic spectra). The port is hosted on a dedicated website including a download section for source codes, precompiled binaries, needed data (opacities, line lists and so on), sample launch scripts and documentation.
Helioseismic inferences on subsurface solar convection
Authors: Kosovichev Alexander G. 
Published: May 2007

AbstractHelioseismology has provided robust estimates of global properties of the solar convection zone, its depth, stratification, and revealed rotational shear layers at the boundaries. New methods of local helioseismology provide 3D maps of subsurface convective flows. In the quiet Sun regions, these maps reveal that supergranular-scale convection extends to the depth of 12–15 Mm. Analysis of evolution of the supergranular convection pattern shows evidence for a wave-like behavior which might be related to the interaction between convection and the subsurface rotational sheer layer. Helioseismology also reveals large-scale circulation flows around magnetic regions. These flows affect the evolution of the mean meridional flow during the solar cycle and, probably, the magnetic flux transport from mid-latitudes to the polar regions, a process important for solar dynamo theories. Helioseismic measurements on a smaller scale, below sunspots, give insight on how convection interacts with strong magnetic fields.
Eclipsing binaries as a test for synthetic photometry
Authors: Heiter U. , Smalley B. , Stütz Ch. , Kupka F. , Kochukhov O. 
Published: May 2007

AbstractNarrow band photometry is a useful tool to characterize large numbers of stars, but observed colors and indices must be connected to astrophysical parameters by synthetic photometry. We present synthetic Hβ indices calculated from 1D model atmospheres implementing different convection treatments. The calculated indices are transformed to the standard system using observed medium-resolution spectra. We test the synthetic photometry with observed indices of eclipsing binary systems. The computed indices agree with the observed ones up to an amount expected from the observational errors, the accuracy of the atmospheric parameters, and computational uncertainties.
Convection-driven planetary dynamos
Authors: Christensen Ulrich R. , Aubert Julien , Olson Peter 
Published: May 2007

AbstractNumerical simulations of convection-driven dynamos in rotating spherical shells are employed to better understand the observed strength and geometry of planetary magnetic fields. The model computations cannot be performed for realistic values of several of the control parameters. By varying parameters within the accessible range, it is possible to derive scaling laws for the magnetic field strength and the flow velocity in the dynamo region and for the dipole moment. Our scaling laws suggest that, even though diffusivities are far too large in the models, diffusive processes do not play an important role, just as in planetary cores. Extrapolating the scaling laws to planetary values of the control parameters leads to reasonable predictions for the field strength in the dynamo region and fits the observed dipole moments decently, in particular in the cases of Earth and Jupiter. For Mercury, which does not fit well when applying the scaling laws in a straightforward way, a model is proposed in which the upper part of the fluid core is stably stratified and the dynamo operates only in its deep regions. The time-varying dynamo field must diffuse through the stable region and is attenuated by the skin effect. The model explains why Mercury has a very weak but probably dipole-dominated magnetic field.
Prospects of using simulations to study the photospheres of brown dwarfs
Authors: Ludwig Hans-Günter 
Published: May 2007

AbstractWe discuss prospects of using multi-dimensional time-dependent simulations to study the atmospheres of brown dwarfs and extrasolar giant planets, including the processes of convection, radiation, dust formation, and rotation. We argue that reasonably realistic simulations are feasible, however, separated into two classes of local and global models. Numerical challenges are related to potentially large dynamic ranges, and the treatment of scattering of radiation in multi-D geometries.
Heat transport in 3D anelastic simulations of the internal dynamics of giant planets without cores
Authors: Evonuk Martha , Glatzmaier Gary A. 
Published: May 2007

AbstractDifferential rotation, similar to that seen on our gas giants, is manifested at the surface of three-dimensional (3D) computer simulations of thermal convection in density-stratified rotating planets without solid cores. Below the surface, the flow forms short axially-aligned vortices, generated by fluid expanding as it rises and contracting as it sinks. The convergence of the nonlinear Reynolds stresses resulting from the vorticity generated by fluid flowing through the density stratification maintains the surface banded zonal flow without the classical vortex stretching of Taylor columns. These preliminary simulations demonstrate that large non-convecting cores are not required to obtain multiple zonal jets at the surface, and show greater convective heat flux towards the poles relative to that seen at the equator. This result could help explain the nearly uniform with latitude thermal emission observed at the surface of Jupiter.
Toward three-dimensional simulations of stellar core collapse with magnetic fields
Authors: Liebendörfer M. , Whitehouse S. , Fischer T. 
Published: May 2007

AbstractIn spherical symmetry, very reliable models of stellar core collapse, bounce, and the postbounce phase can be constructed based on general relativistic Boltzmann neutrino transport. However, even if the time-integrated neutrino luminosity in the region between the surface of the protoneutron star and the stalled accretion shock is one or two orders of magnitude larger than the energy of a supernova explosion, it is generally accepted that the net energy transfer is not efficient enough to drive an explosion, unless the fluid instabilities in this regime are taken into account. Complementary to other groups, who are elaborating an extension of the accurate neutrino physics to axisymmetric simulations, we construct efficient parameterizations of the neutrino physics that enable three-dimensional magneto-hydrodynamics simulations that do not constrain the fluid instabilities by artificially imposed symmetries. We evaluate our approximations with respect to spherically symmetric Boltzmann neutrino transport, present preliminary MHD simulations with a resolution of 600 zones cubed, and illustrate the questions that can be addressed by this approach.
Comparing convection in the Sun with Procyon A
Authors: Robinson Frank , Demarque Pierre 
Published: May 2007

AbstractAs well as reproducing observable features like solar granulation, 3D simulations can provide useful information for local or non-local stellar modeling. Examples include testing out the mixing length theory in the surface layers, providing the turbulent correction for stellar models ofp-mode frequencies, testing eddy viscocity prescriptions used in tidal dissipation models and comparing different closures of higher order moments. Having validated the 3D code with the sun we applied it to other stars. For Procyon A the turbulence is about twice as strong as it is in the Sun (estimated by the peak root mean square vertical velocity which is about 6.5 km/s) and the granules are nearly an order of magnitude larger, with plumes regularly extending down 2-3 pressure scale heights below the surface of Procyon A. An interesting feature of the Procyon simulation is that the horizontal layers in the vicinity of the granules appear to radially pulsate in a quasi-periodic manner. This makes the superadiabatic layer move in and out over a distance of about half a pressure scale height in a time of about 20-30 minutes. This motion appears to be tied to the granulation but there may be other phenomena involved such as some kind of local kappa-mechanism confined to the granulation surface layers. We find similar behaviour in a simulation of an 11 Gyr subgiant sun. As the velocities are more like the sun (about 3km/s), the time period of the pulsation in the subgiant is 2-3 times longer than in Procyon A.
Small amplitude variable red giants
Authors: Xiong D. R. , Deng L. 
Published: May 2007

AbstractSmall amplitude variable red giants were discovered long time ago (Eggen 1969, Henry et al. 2000, Jorison et al. 1997). The revolutionary turning point for the study of this type of variable was due to the work of Wood (2000) and Soszyński et al. (2004) based on the very large stellar sample of the Magellanic clouds MACHO project and OGLE photometric data. By using our non-local time-dependent theory of convection (Xiong 1989), we carried out a linear stability survey for red giants with initial mass of M = 1 − 3M⊙. Explanations for the observed variabilities and analysis of mode identifications in red giant stars are presented in this work.
Turbulent compressible convection with rotation
Authors: Brummell Nicholas H. 
Published: May 2007

AbstractWe examine the effect of rotation on turbulent compressible penetrating convection, motivated by the dynamics of the solar interior. We find that rotation can influence large-scale coherent structures in the turbulent flow whilst leaving the small-scales isotropic. The dynamics in this case are very different from more laminar situations where all scales are rotationally-influenced. This may hint as to why full models of the global solar differential rotation are difficult.
Large-scale flows and convection at the base of solar convection zone
Authors: Tikhomolov Evgeniy 
Published: May 2007

AbstractDevelopment of convection in sun's outer shell is caused by reduction of effectiveness of energy transfer by radiation. Traditionally, models of solar convection are considered to be axisymmetric on the scale of solar radius. Such models provide basic understanding of convection under solar conditions. However, interpretation of a number of observable large-scale long-lived solar phenomena requires developing a non-axisymmetric approach. We present such a model in which large-scale non-axisymmetry is caused by large-scale flows such as Rossby waves and vortices. We model flows near the base of the solar convection zone. Anelastic approximation is used, which is valid for flow velocities much smaller than local sound speed. Our three-dimensional numerical simulations show that interaction of convection with large-scale flows leads to the establishment of non-axisymmetric large-scale temperature distribution. The interaction also gives rise to large-scale variations of penetration depth of convective plumes. Generation of the magnetic field by large-scale non-axisymmetric flows can explain such solar phenomena as complexes of activity, active longitudes, drifts of large-scale magnetic fields from equator to the poles, and appearance of distinct rotation periods of magnetic fields at some latitudes. We discuss a possibility of detection of large-scale non-axisymmetric flows and temperature distributions associated with them by the methods of helioseismology.
On the interactions of turbulent convection and rotation in RGB stars
Authors: Palacios Ana , Brun Allan S. 
Published: May 2007

AbstractWe have performed the first three-dimensional non-linear simulation of the turbulent convective envelope of a rotating 0.8 M⊙ RGB star using the ASH code. Adopting a global typical rotation rate of a tenth of the solar rate, we have analyzed the dynamical properties of the convection and the transport of angular momentum within the inner 50% in radius of the convective envelope. The convective patterns consist of a small number of large cell, associated with fast flows (∼3000m/s) and large temperature fluctuations (∼300K) in order to carry outward the large luminosity (L ∼ 400L⊙) of the star. The interactions between convection and rotation give rise to a large radial differential rotation and a meridional circulation possessing one cell per hemisphere, the flow being poleward in both hemisphere. By analysing the redistribution of angular momentum, we find that the meridional circulation transports the angular momentum outward in the radial direction, and poleward in the latitudinal direction, and that the transport by Reynolds stresses acts in the opposite direction. From this 3-D simulation, we have derived an average radial rotation profile, that we will ultimately introduce back into 1-D stellar evolution code.
Simulations of solar magnetic dynamo action in the convection zone and tachocline
Authors: Browning Matthew K. , Miesch Mark S. , Brun Allan Sacha , Toomre Juri 
Published: May 2007

AbstractWe present results from a global 3-D nonlinear simulation of magnetic dynamo action achieved by solar convection in a penetrative geometry. We include within the spherical computational domain both the bulk of the convection zone and a portion of the underlying stable layer. A tachocline of rotational shear is realized below the convection zone, where we have imposed both a hydrodynamic drag term and small thermal perturbations consistent with thermal wind balance. Thus we are capturing many of the dynamical elements thought to be essential in the operation of the global solar dynamo, including differential rotation arising from convection, magnetic pumping, and the stretching and amplification of toroidal fields within the tachocline. In the stable region, the simulation reveals that strong axisymmetric toroidal magnetic fields (about 3000 G in strength) are realized, in contrast to the mostly fluctuating fields that predominate in the convection zone. The toroidal fields in the stable region exhibit a striking antisymmetric parity akin to that observed in sunspots, with fields in the northern hemisphere largely of the opposite sign to those in the southern hemisphere. These deep toroidal fields are accompanied by mostly dipolar mean poloidal fields, whose polarity has retained the same sense over multiple years of simulated evolution.
Comparison of the effects of dietary saturated, mono-unsaturated and polyunsaturated fatty acids on very-low-density lipoprotein secretion when delivered to hepatocytes in chylomicron remnant-like particles
Authors: Lopez-Soldado I. , Avella M. , Botham K.M. 
Published: May 2007

The effect of chylomicron remnant-like particles (CRLPs) enriched in saturated, mono-unsaturated or n−6 polyunsaturated fatty acids (derived from palm, olive or corn oil, respectively) on the secretion of VLDL (very-low-density lipoprotein) by rat hepatocytes in culture was investigated. CRLPs were incubated with cultured hepatocytes for 5 h. The medium was then removed and the secretion of cholesterol and triacylglycerol (TAG) into the whole medium during the following 16 h was determined. After exposure of the cells to olive oil as compared with corn and palm oil CRLPs, secretion of TAG into the medium was decreased. The TAG content of the cells was also lower in experiments with olive oil as compared with corn oil CRLPs. The levels of apoB48 (apolipoprotein B48) found in the medium remained unchanged after the exposure of the cells to the different types of remnants. These findings indicate that the type of fat in the diet directly affects VLDL lipid secretion on delivery to the liver in chylomicron remnants.
Dietary fats induce human monocyte activation in vitro
Authors: Bentley C. , Bejta F. , De Pascale C. , Avella M. , Wheeler-Jones C.P.D. , Botham K.M. , Lawson C. 
Published: May 2007

In early atherosclerosis the frequency of activated monocytes in the peripheral circulation is amplified, and migration of monocytes into the walls of the aorta and large arteries is increased, due partly to de novo expression or activation of monocyte adhesion molecules. Although there is increasing evidence that CMRs (chylomicron remnants) are strongly atherogenic, the outcomes of interactions between blood monocytes and circulating CMRs are not known. Here, we have studied the effects of CRLPs (CMR-like particles) on THP-1 human monocyte oxidative burst. The particles induced a significant increase in reactive oxygen species within 1 h, which persisted for 24 h. We suggest that monocyte–CMR interactions may be important in early atherosclerosis when many activated monocytes are found in susceptible areas of the artery wall.
Hepatoid carcinoma of the ovary and management
Authors: LAZARO JESUS , RUBIO DOLORES , REPOLLES MANUEL , CAPOTE LUIS 
Published: May 2007

AbstractThe designation ‘hepatoid carcinoma’ has been introduced as a unique type of carcinoma that arises outside the liver but resembles, to a considerable extent, hepatocellular carcinoma both histologically and immunohistochemically in its staining for α‐fetoprotein (AFP). The minimum histological criteria of hepatoid carcinomas are the evidence of AFP production and abundant eosinophilic cytoplasm. These tumors have been reported in the ovary, the lung, the stomach, the renal pelvis, and the bladder. We, in this study, present a rare patient with primary hepatoid carcinoma of the ovary (OHC) and review the previous reports.
Place of delivery among women who had antenatal care in a teaching hospital
Authors: EKELE BISSALLAH A. , TUNAU KARIMA A. 
Published: May 2007

AbstractBackground. The utilization of antenatal care services does not necessarily equate to delivery at the health facility. The objectives of this study were to determine the proportion of pregnant women who had antenatal care and delivered in the hospital and the reasons for delivery elsewhere. Materials and methods. Pregnant women of low risk who initiated antenatal care at the University Teaching Hospital were recruited consecutively from January to June 2004 and longitudinally followed up until delivery. A two‐part questionnaire was used to obtain information on biosocial data, place of delivery, accoucher, fetomaternal outcome, and reason(s) for delivery elsewhere. Results. Of the 1,080 women studied, 740 (68.5%) delivered in the hospital while 340 (31.5%) delivered elsewhere. The majority (52) of the deliveries elsewhere were at the woman's home. There were more literate women amongst the hospital delivery group, while there were more women of high parity and with a previous home birth in the home delivery group (p<0.05). Fetomaternal outcomes were similar in both groups. Nurses/midwives conducted most (60%) of the home deliveries and the principal reasons for home births were privacy and lack of transport during labor. Conclusion. 68.5% of women who had uneventful antenatal care delivered in the hospital. Home delivery was the commonest site for delivery elsewhere and the main reasons were privacy and lack of transportation. Skilled attendants conducted most of the home deliveries with good fetomaternal outcome. There might be a need to encourage women during antenatal care to reach out for skilled attendants when home delivery becomes inevitable.
Pregnancy‐related pelvic girdle pain in the Netherlands
Authors: VAN DE POL GEERTE , VAN BRUMMEN H. JORIEN , BRUINSE HEIN W. , HEINTZ A. PETER M. , VAN DER VAART C. HUUB 
Published: May 2007

AbstractObjective. In this longitudinal cohort study, we assessed the prevalence, associated delivery‐related and psychosocial factors and consequences of self‐reported pelvic girdle pain during and after pregnancy in the Netherlands. Methods. A total of 412 women, expecting their first child, answered questionnaires regarding back and pelvic girdle pain, habits, and biomedical, sociodemographic and psychosocial factors, at 12 and 36 weeks gestation, and 3 and 12 months after delivery. In addition, birth records were obtained. Possible associations were studied using non‐parametric tests. Results. The prevalence of self‐reported pelvic girdle pain was at its peak in late pregnancy (7.3%). One out of 7 women suffering from pelvic girdle pain at 36 weeks gestation, and almost half of the women suffering from pelvic girdle pain 3 months after delivery, continued to report symptoms 1 year after delivery. Women reporting pelvic girdle pain are less mobile than women without pain or women with back pain only, and more frequently have to use a wheelchair or crutches. No association was found between obstetric factors and pelvic girdle pain. Women with pelvic girdle pain report more co‐morbidity and depressive symptoms. Recommendations. Normal obstetric procedures can be followed in women reporting pregnancy‐related pelvic girdle pain. Prognosis is generally good, however, women reporting pelvic girdle pain 3 months after delivery need extra consideration. Attention needs to be given to psychosocial factors, in particular depressive symptoms.
Screening for pre‐eclampsia and small for gestational age fetuses at the 11–14 weeks scan by uterine artery Dopplers
Authors: PILALIS ATHANASIOS , SOUKA ATHENA P. , ANTSAKLIS PANAYIOTIS , BASAYIANNIS KONSTANTINOS , BENARDIS PANAYIOTIS , HAIDOPOULOS DIMITRIOS , PAPANTONIOU NIKOLAOS , MESOGITIS SPYROS , ANTSAKLIS ARIS 
Published: May 2007

AbstractObjective. To assess the role of uterine artery Doppler studies at 11‐14 weeks in screening for pre‐eclampsia (PET), small for gestational age (SGA) fetuses, and placental abruption. Methods. Prospective study on 1,123 women presenting for routine ultrasound examination at 11–14 weeks for nuchal translucency measurement. Uterine artery blood flow was studied by transvaginal colour Doppler, the mean pulsatility index (PI) was calculated, and the presence of a diastolic notch was recorded. Results. The mean, median and 95th centile of uterine artery PI were 1.71, 1.64 and 2.54, respectively. Bilateral notches were observed in 63.4%, and a unilateral notch in 18.4% of cases. The sensitivity of mean uterine artery PI ≥95th centile for PET, early onset severe PET necessitating delivery before 34 weeks, SGA ≤5th centile, SGA necessitating delivery before 34 weeks, SGA ≤10th centile and placental abruption were 21.4, 33.3, 17.8, 100, 9.6 and 44.4%, respectively. One in 6 women with increased resistance in the uterine arteries at 11–14 weeks will develop a complication related to utero‐placental insufficiency. Conclusions. Abnormal uterine Dopplers at 11–14 weeks identified one‐third of women with severe early onset pre‐eclampsia, all fetuses with SGA ≤5th centile that were delivered at ≤34 weeks, and 40% of cases with placental abruption. Uterine artery Doppler examination at the 11–14 weeks scan can identify a high risk population in which preventive or therapeutic interventions might be effective.