bluuebunny/crossref_metadata_2025 huggingface dataset:
The social capital of older people
Authors: GRAY ANNE
Published: December 2008

How can the ‘social capital’ inherent in social networks provide contacts through which older people access practical and emotional support? What is the relative importance of kin and non-kin, and of participation in organisations and informal ties such as contacts with neighbours? Following a brief contextualisation that draws on previous literature, this paper addresses these questions through analysis ofBritish Household Panel Survey(BHPS) data. It examines the extent to which people feel they can count on emotional and practical support from friends and relatives. A dependent variable was created that measures the outcome of the ‘social capital’ residing in a respondent's social network. Relatively poor support was found amongst elders who were childless or had been continuously without a partner; relatively rich support was found amongst those who had frequent contact with other people, who interacted frequently with neighbours, and who regarded their neighbourhood as a positive social environment. Being active in organisations had less effect on social support than informal social contacts. Amongst many different forms of organisational activity, the only ones that had a positive association with social support were being in contact with others through religious activities, and engaging in sports clubs. The social support of working-class elders, even those ‘well networked’ in formal or informal ways, was strengthened less by their social capital than was that of the professional and managerial occupational groups.
Angular distribution and conversion of multi-keV L-shell X-ray sources produced from nanosecond laser irradiated thick-foil targets
Authors: Hu G.-Y. , Zhang J.-Y. , Zheng J. , Shen B.-F. , Liu S.-Y. , Yang J.-M. , Ding Y.-K. , Hu X. , Huang Y.-X. , Du H.-B. , Yi R.-Q. , Lei A.-L. , Xu Z.-Z.
Published: December 2008

An experimental study on the angular distribution and conversion of multi-keV X-ray sources produced from 2 ns-duration 527nm laser irradiated thick-foil targets on Shenguang II laser facility (SG-II) is reported. The angular distributions measured in front of the targets can be fitted with the function of f(θ) = α+ (1−α)cosβθ (θ is the viewing angle relative to the target normal), where α = 0.41 ± 0.014, β = 0.77 ± 0.04 for Ti K-shell X-ray sources (~4.75 keV for Ti K-shell), and α = 0.085 ± 0.06, β = 0.59 ± 0.07 for Ag/Pd/Mo L-shell X-ray sources (2–2.8 keV for Mo L-shell, 2.8–3.5 keV for Pd L-shell, and 3–3.8 keV for Ag L-shell). The isotropy of the angular distribution of L-shell emission is worse than that of the K-shell emission at larger viewing angle (>70°), due to its larger optical depth (stronger self-absorption) in the cold plasma side lobe surrounding the central emission region, and in the central hot plasma region (emission region). There is no observable difference in the angular distributions of the L-shell X-ray emission among Ag, Pd, and Mo. The conversion efficiency of Ag/Pd/Mo L-shell X-ray sources is higher than that of the Ti K-shell X-ray sources, but the gain relative to the K-shell emission is not as high as that by using short pulse lasers. The conversion efficiency of the L-shell X-ray sources decreases with increasing atomic numbers (or X-ray photon energy), similar to the behavior of the K-shell X-ray source.
Underrating Human Rights: Gallagher v Church of Jesus Christ of Latter-day Saints
Authors: Sandberg Russell
Published: December 2008

The Human Rights Act 1998 has led to an increase in domestic litigation concerning Article 9 of the European Convention on Human Rights (ECHR). Most such cases have been unsuccessful, particularly at higher level. Moreover, such claims have increasingly failed due to lack of interference under Article 9(1) rather than on grounds of justification under Article 9(2). This has meant that litigants in religious dress cases are now arguing anything but Article 9: the most recent case, concerning the wearing of the Sikh Kara in Aberdare, was successful because, while the school saw the issue as one concerning Article 9, the claimant's legal team relied instead on race and religious discrimination laws. It is not surprising, therefore, that the House of Lords rejected the most recent argument made on grounds of Articles 9 and 14. It is the merits of that argument and the haste displayed in its rejection that are the focus of this brief comment.
Governing Body of the Church in Wales
Authors: Morris Philip
Published: December 2008

In April, a Bill was considered to enable women to be consecrated as bishops. The most crucial amendment for consideration was that ‘the Bench of Bishops will provide pastoral care and support for those who in conscience cannot accept the ordination of women as priests and bishops through the ministry of an Assistant Bishop or Bishops’. The Archbishop resisted the amendment on the grounds that, if it were passed, the Church

would be appointing a male bishop who had doubts about the validity of the orders of a woman bishop. Such a bishop and his followers would have real doubts as to whether the sacraments presided over by her were real sacraments, and real doubts about whether anyone ordained by her, male or female, was actually ordained.
Synod of the Scottish Episcopal Church
Authors: Guild Ivor
Published: December 2008

Synod discussed the question of whether, by way of Covenant, some degree of regulatory certainty could be given to the Lambeth Conference as one of the Instruments of Communion in the Anglican Communion. The Synod was being asked to give commitment to the process ‘in principle’ but not to the details, and an indication of the synodical process by which the Covenant might be adopted. It was therefore remitted to the Faith and Order Board to decide how this could be done. The Bishop of St Andrews considered that the process was a means of broadening discussion; others were concerned that, if the Church committed itself to the process, it committed itself to the outcome; yet others described the whole concept of a Covenant as very un-Anglican.
General Synod of the Anglican Church of Australia
Authors: Blake Garth
Published: December 2008

The 14th General Synod of the Anglican Church of Australia was held in Canberra, against a backdrop of a number of important circumstances. Within the Anglican Church, the Appellate Tribunal had determined by a 4 to 3 majority that there was nothing in the Constitution to prevent a woman becoming a diocesan bishop. Within Australia, there were issues of drought and climate. Within the Anglican Communion, there was the ongoing international turmoil over human sexuality.
Religion in Criminal Law
Authors: Rynkowski Michał
Published: December 2008

The twentieth Annual Congress of the European Consortium for Church and State Research was held in Järvenpää in Finland, on the subject of Religion in Criminal Law. It was held at the Training College of the Evangelical-Lutheran Church, hosted by and ceremonially opened by Matti Repo, Bishop of the Evangelical-Lutheran Church of Finland, Joni Hiitola from the Ministry of Education and Professor Sophie van Bijsterveld, President of the European Consortium.
Identifying Patterns of Resilience Using Classification Trees
Authors: Hobcraft John , Sigle-Rushton Wendy
Published: December 2008

This paper introduces and illustrates the value of a classification trees approach in the study of resilience. The inherently interactive nature of the resilience construct makes this approach useful. Classification trees are a person-centred approach to data analysis, which successively split the sample into pairs of increasingly homogeneous groups of individuals. We outline the approach and then illustrate using adult educational outcomes for children in the British Cohort Study of 1970 who had experienced foster care. The insights gained from the classification tree approach are contrasted with those obtained from standard regression approaches.
Adversity in Childhood and Mental Health in Adulthood: The Role of Social Capital
Authors: Borgonovi Francesca , Huerta M. Carmen
Published: December 2008

The study examines whether social capital fosters resilience among individuals who are at a high risk of developing mental distress in adulthood. Results suggest that social capital is not associated with a reduction in the probability that high-risk individuals will experience mental distress, while one form of social capital, membership in groups and associations, appears to play a protective role among low-risk individuals. Overall, our research suggests that policies aimed at increasing social capital would not be able to reduce the gap in mental health between disadvantaged individuals and the rest of the population.
Farmers and nature conservation: What is known about attitudes, context factors and actions affecting conservation?
Authors: Ahnström Johan , Höckert Jenny , Bergeå Hanna L. , Francis Charles A. , Skelton Peter , Hallgren Lars
Published: December 2008

Farmers' attitudes towards viability of specific conservation practices or actions strongly impact their decisions on adoption and change. This review of ‘attitude’ information reveals a wide range of perceptions about what conservation means and what the impacts of adoption will mean in economic and environmental terms. Farmers operate in a tight financial situation, and in parts of the world they are highly dependent on government subsidies, and cannot afford to risk losing that support. Use of conservation practices is most effective when these are understood in the context of the individual farm, and decisions are rooted in land and resource stewardship and long-term concerns about health of the farm and the soil. The attitudes of farmers entering agri-environmental schemes decide the quality of the result. A model is developed to show how attitudes of the farmer, the farming context and agri-environmental schemes interact and thus influence how the farming community affects nature and biodiversity. As new agri-environmental schemes are planned, agricultural development specialists need to recognize the complexity of farmer attitudes, the importance of location and individual farmer circumstances, and the multiple factors that influence decisions. We provide these insights and the model to conservation biologists conducting research in farming areas, decision makers who develop future agri-environmental schemes, educators training tomorrow's extension officers and nature conservationists, and researchers dealing with nature conservation issues through a combination of scientific disciplines.
Protostar formation in the early universe
Authors: Yoshida Naoki
Published: December 2008

We study the formation of primordial proto-stars in a ΛCDM universe using ultra high-resolution cosmological simulations. Our approach includes all the relevant atomic and molecular physics to follow the thermal evolution of a prestellar gas cloud to “stellar” densities. We describe the numerical implementation of the physics. We also show the result of a simulation of the formation of primordial stars in a reionized gas.
Population III.1 stars: formation, feedback and evolution of the IMF
Authors: Tan Jonathan C.
Published: December 2008

I discuss current theoretical expectations of how primordial, Pop III.1 stars form. Lack of direct observational constraints makes this a challenging task. In particular predicting the mass of these stars requires solving a series of problems, which all affect, perhaps drastically, the final outcome. While there is general agreement on the initial conditions, H2-cooled gas at the center of dark matter minihalos, the subsequent evolution is more uncertain. In particular, I describe the potential effects of dark matter annihilation heating, fragmentation within the minihalo, magnetic field amplification, and protostellar ionizing feedback. After these considerations, one expects that the first stars are massive ≳100M⊙, with dark matter annihilation heating having the potential to raise this scale by large factors. Higher accretion rates in later-forming minihalos may cause the Pop III.1 initial mass function to evolve to higher masses.
Low-metallicity Star Formation: the characteristic mass and upper mass limit
Authors: Omukai Kazuyuki
Published: December 2008

We consider the fragmentation mass scale of low-metallicity clouds based on their thermal evolution. Then we present the protostellar evolution in the main accretion phase, and discuss the upper limit on the stellar mass by the stellar feedback.
Effects of dark matter annihilation on the first stars
Authors: Iocco F. , Bressan A. , Ripamonti E. , Schneider R. , Ferrara A. , Marigo P.
Published: December 2008

We study the evolution of the first stars in the universe (Population III) from the early pre–Main Sequence (MS) until the end of helium burning in the presence of WIMP dark matter annihilation inside the stellar structure. The two different mechanisms that can provide this energy source are the contemporary contraction of baryons and dark matter, and the capture of WIMPs by scattering off the gas with subsequent accumulation inside the star. We find that the first mechanism can generate an equilibrium phase, previously known as a dark star, which is transient and present in the very early stages of pre–MS evolution. The mechanism of scattering and capture acts later, and can support the star virtually forever, depending on environmental characteristics of the dark matter halo and on the specific WIMP model.
The search for Population III stars
Authors: di Serego Alighieri Sperello , Kurk Jaron , Ciardi Benedetta , Cimatti Andrea , Daddi Emanuele , Ferrara Andrea
Published: December 2008

Population III stars, the first generation of stars formed from primordial Big Bang material with a top–heavy IMF, should contribute substantially to the Universe reionization and they are crucial for understanding the early metal enrichment of galaxies. Therefore it is very important that these objects, foreseen by theories, are detected by observations. However PopIII stars, searched through the HeII 1640Å line signature, have remained elusive. We report about the search for the HeII line in a galaxy at z = 6.5, which is a very promising candidate. Unfortunately we are not yet able to show the results of this search. However we call attention to the possible detection of PopIII stars in a lensed HII dwarf galaxy at z = 3.4, which appeared in the literature some years ago, but has been overlooked.
Insights into the Origin of the Galaxy Mass-Metallicity Relation
Authors: Lee Henry , Bell Eric F. , Somerville Rachel S.
Published: December 2008

We examine mass–metallicity relations for nearby (D < 2 Mpc) gas-rich and gas-poor dwarf galaxies. We derived stellar and baryonic masses using photometric data and used average stellar iron abundances as the metallicity indicator. With the inclusion of available data for massive galaxies, we find a continuous mass–metallicity relation for galaxies spanning nine orders of magnitude in mass, and that the mass–metallicity relations are the same for both gas-rich and gas-poor dwarf galaxies. We derive stellar effective yields from the stellar abundances, finding that gas-poor dwarf galaxies form a single sequence with mass, whereas gas-rich dwarf galaxies have higher yields at comparable mass. Simple chemical evolution models show that a mass-dependent star-formation efficiency can simultaneously account for the correlations between metallicity, gas fraction, and stellar effective yield with mass. In agreement with recent and independent results, we conclude that a key driver of the mass-metallicity relation is the variation of star-formation efficiency with galaxy mass, modulated by galaxy mass-dependent outflows and/or stellar IMF variations, and coupled with environmental gas-removal processes.
Three Modes of Metal-Enriched Star Formation at High Redshift
Authors: Smith Britton D. , Turk Matthew J. , Sigurdsson Steinn , O'Shea Brian W. , Norman Michael L.
Published: December 2008

It is generally accepted that the very first stars in the universe were significantly more massive and formed much more in isolation than stars observed today. This suggests that there was a transition in star formation modes that was most likely related to the metallicity of the star-forming environment. We study how the addition of heavy elements alters the dynamics of collapsing gas by performing a series of numerical simulations of primordial star formation with various levels of pre-enrichment, using the adaptive mesh refinement, hydrodynamic + N-body code, Enzo. At high redshifts, the process of star formation is heavily influenced by the cosmic microwave background (CMB), which creates a temperature floor for the gas. Our results show that cloud-collapse can follow three distinct paths, depending on the metallicity. For very low metallicities (log10(Z/Z⊙) < −3.5), star formation proceeds in the primordial mode, producing only massive, singular objects. For high metallicities (log10(Z/Z⊙) > −3), efficient cooling from the metals cools the gas to the CMB temperature when the core density is still very low. When the gas temperature reaches the CMB temperature, the core becomes very thermally stable, and further fragmentation is heavily suppressed. In our simulations with log10(Z/Z⊙) > −3, only a single object forms with a mass-scale of a few hundred M⊙. We refer to this as the CMB-regulated star formation mode. For metallicities between these two limits (−3.5 < log10(Z/Z⊙) < −3), the gas cools efficiently, but never reaches the CMB temperature. In this mode, termed the metallicity-regulated star formation mode, the minimum gas temperature is reached at much higher densities, allowing the core to fragment and form multiple objects with mass-scales of only a few M⊙. Our results imply that the stellar initial mass function was top-heavy at very high redshift due to stars forming in the CMB-regulated mode. As the CMB temperature lowers with time, the metallicity-regulated star formation mode (producing multiple low-mass stars) operates at higher metallicities and eventually becomes the sole mode of star formation.
About the Chemical Evolution of dSphs (and the peculiar Globular Cluster ω Cen)
Authors: Marcolini Andrea , D'Ercole Annibale
Published: December 2008

We present three dimensional hydrodynamical simulations aimed at studying the dynamical and chemical evolution of the interstellar medium (ISM) in isolated dwarf spheroidal galaxies (dSphs). This evolution is driven by the explosion of Type II and Type Ia supernovae, whose different contribution on both the dynamics and chemical enrichment is taken into account. Radiative losses are effective in radiating away the huge amount of energy released by SNe explosions, and the dSph is able to retain most of the gas allowing a long period (≥ 2 − 3 Gyr) of star formation, as usually observed in this kind of galaxies. We are able to reproduce the stellar metallicity distribution function (MDF) as well as the peculiar chemical properties of strongly O-depleted stars observed in several dSphs. The model also naturally predicts two different stellar populations, with an anti-correlation between [Fe/H] and velocity dispersion, similarly to what observed in the Sculptor and Fornax dSphs. These results derive from the inhomogeneous pollution of the SNe Ia, a distinctive characteristic of our model. We also applied the model to the peculiar globular cluster (GC) ω Cen in the hypothesis that it is the remnant of a formerly larger stellar system, possibly a dSph.
Modeling the ISM Properties of Metal-Poor Galaxies and Gamma-Ray Burst Hosts
Authors: Levesque Emily M. , Kewley Lisa J. , Larson Kirsten , Snijders Leonie
Published: December 2008

Recent research has suggested that long-duration gamma-ray bursts (LGRBs) occur preferentially in low-metallicity environments, but the exact nature of this correlation is currently a matter of intense debate. We use the newest generation of the Starburst99/Mappings code to generate an extensive suite of cutting-edge stellar population synthesis models, covering a wide range of physical parameters specifically tailored for modeling the ISM environments of metal-poor galaxies and LGRB host galaxies. With our models, we generate optical emission line diagnostics, which will allow us to examine the ISM properties and stellar populations of a variety of galaxy populations in unprecedented detail. While accurately modeling low-metallicity galaxies still poses a challenge to these models, future improvements to these grids will have profound consequences for our understanding of metal-poor galaxies, their ISM environments, and the nature of their role as the hosts of LGRBs.
Supernova Nucleosynthesis in the early universe
Authors: Tominaga Nozomu , Umeda Hideyuki , Maeda Keiichi , Nomoto Ken'ichi , Iwamoto Nobuyuki
Published: December 2008

The first metal enrichment in the universe was made by supernova (SN) explosions of population (Pop) III stars. The history of chemical evolution is recorded in abundance patterns of extremely metal-poor (EMP) stars. We investigate the properties of nucleosynthesis in Pop III SNe by comparing their yields with the abundance patterns of the EMP stars. We focus on (1) jet-induced SNe with various properties of the jets, especially energy deposition rates [Ėdep = (0.3 − 1500) × 1051 ergs s−1], and (2) SNe of stars with various main-sequence masses (Mms = 13 − 50M⊙) and explosion energies [E = (1 − 40) × 1051ergs]. The varieties of Pop III SNe can explain the observations of the EMP stars: (1) higher [C/Fe] for lower [Fe/H] and (2) trends of abundance ratios [X/Fe] against [Fe/H].
Interstellar Chemistry: Radiation, Dust and Metals
Authors: Spaans Marco
Published: December 2008

An overview is given of the chemical processes that occur in primordial systems under the influence of radiation, metal abundances and dust surface reactions. It is found that radiative feedback effects differ for UV and X-ray photons at any metallicity, with molecules surviving quite well under irradiation by X-rays. Starburst and AGN will therefore enjoy quite different cooling abilities for their dense molecular gas. The presence of a cool molecular phase is strongly dependent on metallicity. Strong irradiation by cosmic rays (>200× the Milky Way value) forces a large fraction of the CO gas into neutral carbon. Dust is important for H2 and HD formation, already at metallicities of 10−4 − 10−3 solar, for electron abundances below 10−3.
Dust Evolution from Nearby Galaxies: Bridging the Gap Between Local Universe and Primordial Systems
Authors: Galliano Frédéric
Published: December 2008

This paper presents the results of a study aimed at understanding the evolution of the dust properties, as a function of both the environmental conditions and the metal enrichment of the system. I first review the peculiar dust properties of dwarf galaxies, and discuss attempts to understand their origin. Then, I discuss the evolution of the PAH and dust abundances, constrained by the UV-to-radio SED of nearby galaxies, comparing the properties of low-metallicity environments and more evolved systems. I discuss the long term evolution of dust in galaxies, comparing the grain production by various stellar progenitors to their destruction by SN blast waves and in H ii regions. Finally, I will show how these models explain the paucity of PAHs in low-metallicity environments.
Evolution of newly formed dust in Population III supernova remnants and its impact on the elemental composition of Population II.5 stars
Authors: Nozawa Takaya , Kozasa Takashi , Habe Asao , Dwek Eli , Umeda Hideyuki , Tominaga Nozomu , Maeda Keiichi , Nomoto Ken'ichi
Published: December 2008

We investigate the evolution of dust formed in Population III supernovae (SNe) by considering its transport and processing by sputtering within the SN remnants (SNRs). We find that the fate of dust grains within SNRs heavily depends on their initial radii aini. For Type II SNRs expanding into the ambient medium with density of nH,0 = 1 cm−3, grains of aini < 0.05 μm are detained in the shocked hot gas and are completely destroyed, while grains of aini > 0.2 μm are injected into the surrounding medium without being significantly destroyed. Grains with aini = 0.05–0.2 μm are finally trapped in the dense shell behind the forward shock. We show that the grains piled up in the dense shell enrich the gas up to 10−6–10−4Z⊙, high enough to form low-mass stars with 0.1–1 M⊙. In addition, [Fe/H] in the dense shell ranges from −6 to −4.5, which is in good agreement with the ultra-metal-poor stars with [Fe/H] < −4. We suggest that newly formed dust in a Population III SN can have great impact on the stellar mass and elemental composition of Population II.5 stars formed in the shell of the SNR.
The Resolved Properties of Extragalactic Giant Molecular Clouds
Authors: Bolatto Alberto D. , Leroy Adam K. , Rosolowsky Erik , Walter Fabian , Blitz Leo
Published: December 2008

Giant molecular clouds (GMCs) are the major reservoirs of molecular gas in galaxies, and the starting point for star formation. As such, their properties play a key role in setting the initial conditions for the formation of stars. We present a comprehensive combined inteferometric/single-dish study of the resolved GMC properties in a number of extragalactic systems, including both normal and dwarf galaxies. We find that the extragalactic GMC properties measured across a wide range of environments, characterized by the Larson relations, are to first order remarkably compatible with those in the Milky Way. Using these data to investigate trends due to galaxy metallicity, we find that: 1) these measurements are not in accord with simple expectations from photoionization-regulated star formation theory; 2) there is no trend in the virial CO-to-H2conversion factor on the spatial scales studied; and 3) there are measurable departures from the Galactic Larson relations in the Small Magellanic Cloud — the object with the lowest metallicity in the sample — where GMCs have velocity dispersions that are too small for their sizes. We will discuss the stability of these clouds in the light of our recent far-infrared analysis of this galaxy, and will contrast the results of the virial and far-infrared studies on the issue of the CO-to-H2conversion factor and what they tell us about the structure of molecular clouds in primitive galaxies.
Is there any pristine gas in nearby starburst galaxies?
Authors: Lebouteiller Vianney , Kunth Daniel
Published: December 2008

We derive the chemical composition of the neutral gas in the blue compact dwarf (BCD) Pox 36 observed with FUSE. Metals (N, O, Ar, and Fe) are underabundant as compared to the ionized gas associated with H ii regions by a factor ~7. The neutral gas, although it is not pristine, is thus probably less chemically evolved than the ionized gas. This could be due to different dispersal and mixing timescales. Results are compared to those of other BCDs observed with FUSE. The metallicity of the neutral gas in BCDs seems to reach a lower threshold of ~1/50 Z⊙ for extremely-metal poor galaxies.
Revision of Star-Formation Measures
Authors: Leitherer Claus
Published: December 2008

Rotation plays a major role in the evolution of massive stars. A revised grid of stellar evolutionary tracks accounting for rotation has recently been released by the Geneva group and implemented into the Starburst99 evolutionary synthesis code. Massive stars are predicted to be hotter and more luminous than previously thought, and the spectral energy distributions of young populations mirror this trend. The hydrogen ionizing continuum in particular increases by a factor of up to 3 in the presence of rotating massive stars. The effects of rotation generally increase towards shorter wavelengths and with decreasing metallicity. Revised relations between star-formation rates and monochromatic luminosities for the new stellar models are presented.
Truncated star formation in dwarf spheroidal galaxies and photometric scaling relations
Authors: De Rijcke Sven , Valcke Sander , Conselice Christopher J. , Penny Samantha
Published: December 2008

We investigate the global photometric scaling relations traced by early-type galaxies in different environments, ranging from dwarf spheroidals, over dwarf elliptical galaxies, up to giant ellipticals (−8 mag ≳ MV ≳ −24 mag). These results are based in part on our new HST/ACS F555W and F814W imagery of dwarf spheroidal galaxies in the Perseus Cluster. We show that at MV ~ −14 mag, the slopes of the photometric scaling relations involving the Sérsic parameters change significantly. We argue that these changes in slope reflect the different physical processes that dominate the evolution of early-type galaxies in different mass regimes. We present N-body/SPH simulations of the formation and evolution of dwarf spheroidals that reproduce these slope changes and discuss the underlying physics. As such, these scaling relations contain a wealth of information that can be used to test models for the formation of early-type galaxies.
Relics of Primordial Star Formation: The Milky Way and Local Dwarfs
Authors: Beers Timothy C. , Lee Young Sun , Carollo Daniela
Published: December 2008

Massive spectroscopic surveys of stars in the thick disk and halo populations of the Galaxy hold the potential to provide strong constraints on the processes involved in (and the timing of) the assembly history of the primary structural components of the Galaxy. In this talk, we explore what has been learned from one of the first such dedicated surveys, SDSS/SEGUE. Over the course of the past three years, SEGUE has obtained spectra for over 200,000 stars, while another hundred thousand stars been added from the calibration star observations of the (primarily extragalactic) SDSS, and other directed programs. A total of well over 10,000 stars with [Fe/H] < −2.0 have been discovered, including several hundred with [Fe/H] < −3.0. Their kinematics have revealed a inner/outer halo structure of the Galaxy.

New determinations of the alpha element ratios for tens of thousands of these stars are reported. Correlations of the alpha-element ratios with kinematics and orbital parameters can be used to test models of the likely formation of the thick-disk and halo components. These new data will (eventually) be considered in connection with possible associations with the present dwarf satellite galaxies of the Milky Way.
Galactic archeology with extremely metal-poor stars
Authors: Komiya Yutaka , Suda Takuma , Habe Asao , Fujimoto Masayuki
Published: December 2008

Extremely metal-poor (EMP) stars are thought to be formed in the low-mass protogalaxies as building blocks of the Milky Way and can be probes to investigate the early stage of galaxy formation and star formation in the early universe. We study the formation history of EMP stars in the Milky Way halo using a new model of chemical evolution based on the hierarchical theory of the galaxy formation. We construct the merging history of the Milky Way halo based on the extended Press-Schechter formalism, and follow the star formation and chemical evolution along the merger tree. The abundance trends and number of low-mass stars predicted in our model are compared with those of observed EMP stars. Additionally, in order to clarify the origin of hyper metal poor stars, we investigate the change of the surface metal abundances of stars by accretion of interstellar matter. We also investigate the pre-enrichment of intergalactic matter by the first supernovae.
Dwarf spheroidal evolution: global view
Authors: Salvadori Stefania , Ferrara Andrea , Schneider Raffaella
Published: December 2008

We propose a cosmological approach to investigate the formation and evolution of dwarf spheroidal galaxies, satellites of the Milky Way, which allows us to follow self-consistently the dSphs and MW formation, matching simultaneously most of their observed properties.
Blue Compact Dwarf Galaxies: Laboratories for probing the Primordial Universe
Authors: Thuan Trinh X.
Published: December 2008

Blue Compact Dwarf (BCD) galaxies are the most metal-deficient star-forming galaxies known in the universe, with metallicities ranging from 1/40 to 1/3 that of the Sun. I review how they constitute excellent nearby laboratories for studying big bang nucleosynthesis and star formation and galaxy evolution processes in a nearly primordial environment.
Broad line emission in dwarf galaxies: the first detection of low-metallicity AGN
Authors: Izotov Yuri I.
Published: December 2008

Observations of AGN show that they generally possess a high metallicity, varying from solar to supersolar metallicities. This is the case since AGN are usually found in massive, bulge-dominated galaxies that have converted most of their gas into stars by the present epoch. Since AGN metallicity is strongly correlated with stellar mass, low-metallicity AGN are expected to be in low-mass dwarf galaxies. However, until now, searches in low-mass galaxies have only turned up AGN with metallicities around half that of typical AGN, i.e. with solar or slightly subsolar values. We report the discovery of four low-metallicity dwarf galaxies in the Data Release 6 of the Sloan Digital Sky survey, with 12 + log O/H in the range 7.4–8.0, and that appear to harbor an AGN. In the course of a long-range program to search for extremely metal-deficient emission-line dwarf galaxies, we have come across four galaxies with very unusual spectra: the strong permitted emission lines, mainly the Hα line, show very prominent broad components, with full widths at zero intensity corresponding to velocities varying between 2200 and 3500 km s−1, and extraordinarily large broad Hα luminosities, varying from 3×1041 to 2×1042 erg s−1. The Balmer lines show a very steep decrement, suggesting collisional excitation and that the broad emission comes from very dense gas (Ne ≫ 104 cm−3). Only the presence of an accretion disk around an intermediate-mass black hole in the dwarf galaxies appears to account for these properties.
The ACS LCID project: accurate measurements of the full star formation history in low metallicity, isolated, Local Group dwarf galaxies
Authors: Monelli Matteo ,   the LCID team
Published: December 2008

We present here the latest results of the LCID project (Local Cosmology from Isolated Dwarfs), aimed at recovering the full star formation history (SFH) of six isolated dwarf galaxies of the Local Group (LG). Our method of analysis is based on the IAC-pop code, which derives the SFH of a resolved stellar system by comparing the observed and a model color-magnitude diagram (CMD). We summarize here basic technical issues and the main results concerning our sample of galaxies. We show that LeoA is the only object showing a clear delay in the onset of the major SF event, while all the other galaxies present a dominant component older than 10 Gyrs.
A global search for stress shadows
Authors: Mallman Ellen P. , Parsons Tom
Published: December 2008

Debate continues regarding the relative proportion of earthquakes triggered by passing seismic waves versus static stress changes from a main shock. Static stress changes are expected to have long‐term effects on earthquake probabilities, whereas dynamic stress changes due to the passing of seismic waves should not. Both mechanisms are expected to raise seismicity rates in some areas, but only static stress change calculations predict rate decrease shadows. Thus, identification of post‐main‐shock earthquake suppression is diagnostic of a static stress change process. We note that in principle, static stress change theory predicts suppression of particular earthquake mechanisms in a shadow zone rather than an overall rate reduction. A stress shadow can therefore be characterized by a change in the average earthquake focal mechanism before and after a main shock that results from suppression of a given mechanism type. We examined average mechanisms from ±2° radii and 5‐year periods before and after 119 Ms ≥ 7 main shock earthquakes drawn from the Harvard Centroid Moment Tensor (CMT) catalog. Significant average mechanism changes caused by earthquake suppression were found in only two cases. However, by stacking the data, we were able to resolve statistically significant suppression of particular post‐main‐shock focal mechanisms. This indicates that, while static stress shadows are subtle, they are indeed present in the global catalog.
Distribution and character of water in a surge‐type glacier revealed by multifrequency and multipolarization ground‐penetrating radar
Authors: Barrett B. E. , Murray T. , Clark R. , Matsuoka K.
Published: December 2008

We have investigated the distribution and character of radar scatterers in the glacier Bakaninbreen, Svalbard, using ground‐penetrating radar (GPR). The GPR profiles showed scattering regions with an undulating upper boundary in both along‐ and across‐glacier orientations. The simplest interpretation of such scattering regions would be a layer of randomly distributed scatterers with an undulating upper boundary, underlying a layer without scatterers. We propose an alternative model of scatterer distribution, in which the scatterers are confined to obliquely dipping planes. This model is shown to be able to reproduce the shape of the scattering regions observed in the field data and is consistent with previous observations of dipping thrust features in Bakaninbreen from radar data and in outcrop. Multifrequency profiles (50, 100, and 200 MHz) contained scatterers with similar measured power, indicating that the scatterers have decimeter‐scale dimensions. Multipolarized antenna configurations were used to detect a preferred polarization direction for scattered radiation, which was approximately across glacier, suggesting that the scatterers are nonspherical and aligned across glacier. The scatterers are thought to be large water bodies confined to dipping planar features and elongated in the strike orientation of the planes.
Watershed flow paths and stream water nitrogen‐to‐phosphorus ratios under simulated precipitation regimes
Authors: Green Mark B. , Wang Dong
Published: December 2008

Stream water nitrogen‐to‐phosphorus (N:P) ratios influence algal community composition and nutrient limitation in lotic ecosystems. N:P ratios trend across climates, with low stream water N:P ratios more common in arid climates, yet little is known about mechanisms that cause this spatial and temporal variation. This study evaluates the relationship between precipitation regime (mean annual precipitation and its frequency), watershed flow pathways, and stream water total N‐to‐total P (TN:TP) ratios, using a model based on a central Minnesota watershed. The purpose of the study was to examine hydrologic mechanisms that control stream water TN:TP ratios. We constructed a model that accounted for hydrological and biogeochemical processes, followed by 161 simulations under a wide range of precipitation frequency and intensity scenarios. Precipitation regime controlled total runoff and subsurface hydrologic connectivity, which had implications for TN and TP concentrations and TN:TP ratios. Results supported the hypothesis that watershed hydrology is an important control on stream water TN:TP ratios and suggested that variation of flow pathways can lead to fundamental changes of N:P ratios.
Natural gas hydrate investigations by synchrotron radiation X‐ray cryo‐tomographic microscopy (SRXCTM)
Authors: Murshed M. Mangir , Klapp Stephan A. , Enzmann Frieder , Szeder Thore , Huthwelker Thomas , Stampanoni Marco , Marone Federica , Hintermüller Christoph , Bohrmann Gerhard , Kuhs Werner F. , Kersten Michael
Published: December 2008

We report the 3D microstructure analyses of natural gas hydrates sampled from Gulf of Mexico. The samples were characterized by synchrotron radiation X‐ray cryo‐tomographic microscopy (SRXCTM) using the ‘TOMCAT’ beam line at the Swiss Light Source (SLS). The SRXCTM demonstrates its applicability to unlock some microscopic features of the marine hydrates, in particular of crystallite size and grain boundary network. The gas hydrate domains are surrounded by a network of pores of typically a few micrometers, which are largely due to decomposition. Out of the SRXCTM data, the porosity, total volume of the voids, the void surface area and number of the total gas‐filled voids have been calculated. The results reveal the capability of SRXCTM to access the 3D microstructure which is of fundamental importance to model the petrophysical properties of natural gas hydrates.
Observational and modelling evidence of tropical deep convective clouds as a source of mid‐tropospheric accumulation mode aerosols
Authors: Engström Anders , Ekman Annica M. L. , Krejci Radovan , Ström Johan , de Reus Marian , Wang Chien
Published: December 2008

High concentrations (up to 550 cm−3 STP) of aerosols in the accumulation mode (>0.12 μm) were observed by aircraft above 7.5 km altitude in the dynamically active regions of several deep convective clouds during the INDOEX campaign. Using a coupled 3‐D aerosol‐cloud‐resolving model, we find that significant evaporation of hydrometeors due to strong updrafts and exchange with ambient air occurs at the boundaries and within the cloud tower. Assuming that each evaporated hydrometeor release an aerosol, an increase in the aerosol concentration by up to 600 cm−3 STP is found in the model at altitudes between 6 and 10 km. The evaporation and release of aerosols occur as the cloud develops, suggesting that deep convective clouds are important sources of mid‐tropospheric aerosols during their active lifetime. This source may significantly impact the vertical distribution as well as long‐range transport of aerosols in the free troposphere.
What is causing the variability in global mean land temperature?
Authors: Hoerling Martin , Kumar Arun , Eischeid Jon , Jha Bhaskar
Published: December 2008

Diagnosis of climate models reveals that most of the observed variability of global mean land temperature during 1880–2007 is caused by variations in global sea surface temperatures (SSTs). Further, most of the variability in global SSTs have themselves resulted from external radiative forcing due to greenhouse gas, aerosol, solar and volcanic variations, especially on multidecadal time scales. Our results indicate that natural variations internal to the Earth's climate system have had a relatively small impact on the low frequency variations in global mean land temperature. It is therefore extremely unlikely that the recent trajectory of terrestrial warming can be overwhelmed (and become colder than normal) as a consequence of natural variability.
Seismicity changes prior to the Ms8.0 Wenchuan earthquake in Sichuan, China
Authors: Huang Qinghua
Published: December 2008

The Region‐Time‐Length (RTL) method was adopted in analyzing the characteristics of the seismicity changes prior to the Ms8.0 Wenchuan earthquake occurred on May 12, 2008. After the pre‐analyses (completeness analysis and aftershock declustering) of the earthquake catalog in China, the RTL parameters in the investigated region were calculated. The temporal variations of the RTL parameters at the epicenter of the Ms8.0 Wenchuan earthquake showed that a seismic quiescence anomaly appeared during 2006–2007. The close investigation indicated that the above quiescence anomaly is unlikely an artifact due to the selections of the model parameters. The investigation of the spatial distribution of seismic quiescence also showed that the quiescence anomaly appeared around the epicenter of the mainshock during 2006–2007, consistent with the results obtained from the temporal variations of the RTL parameters. The above characteristics of the seismicity changes may give better understanding of the seismogenic process of the Wenchuan earthquake.
Interplanetary small‐ and intermediate‐sized magnetic flux ropes during 1995–2005
Authors: Feng H. Q. , Wu D. J. , Lin C. C. , Chao J. K. , Lee L. C. , Lyu L. H.
Published: December 2008

We present a comprehensive survey of 125 small‐ and intermediate‐sized interplanetary magnetic flux ropes during solar cycle 23 (1995–2005) using Wind in situ observations near 1 AU. As a result, we found the following: (1) The annual number of small‐ and intermediate‐sized interplanetary magnetic flux ropes is not very sensitive to the solar cycle, but its trend is very similar to that of magnetic clouds (MCs). (2) Average speeds of the individual small‐ and intermediate‐sized interplanetary magnetic flux ropes varied from 289 to 790 km/s with a mean value of 420 ± 86 km/s. Most small‐ and intermediate‐sized interplanetary magnetic flux ropes were found to have a propagation speed similar to typical slow speed solar wind speed, and only a few small‐ and intermediate‐sized interplanetary magnetic flux ropes had speeds comparable to the typically high speed solar wind. (3) Average magnetic field strength for small‐ and intermediate‐sized interplanetary magnetic flux ropes is less than the average magnetic field strengths of MCs, while it is larger than that of background solar wind. (4) The distributions of the axial orientations for small‐ and intermediate‐sized interplanetary magnetic flux ropes are also similar to that of MCs. The results show that small‐ and intermediate‐sized interplanetary magnetic flux ropes and MCs have many similar (or relative) characters. So we suggest that both MCs and small‐ and intermediate‐sized interplanetary magnetic flux ropes originate from solar eruptions.
Characteristics of magnetohydrodynamic waves in Harris‐type current sheet with guide magnetic field By
Authors: Lee K.‐W. , Hau L.‐N.
Published: December 2008

An overview is presented of the characteristics of hydromagnetic waves propagating in Harris‐type current sheet with magnetic field of Bx(z) and an embedded guide By component based on the ideal magnetohydrodynamic (MHD) model. The wave equations are expressed in the (k∥, k⊥, z) coordinates, and singularities are identified for general cases of ky ≠ 0 and By ≠ 0, where k∥ and k⊥ are the components of the wave vector parallel and perpendicular to the local magnetic field, respectively, and the inhomogeneity is in the z direction. The presence of By may lead to the rotation of the magnetic field relative to the wave vector so that a singular layer with k⊥ = 0 surrounded by a neighboring region of k⊥ ≠ 0 may exist. This result is in contrast with the case of By = 0 for which Alfvén or field‐line resonance associated with the mathematical singularity tends to occur for k⊥ ≠ 0 and ω = k∥CA, where CA is the Alfvén speed. The possibility for MHD waves with frequency of ω = k∥CA to propagate through the inhomogeneous layer with By ≠ 0 is analyzed, and numerical solutions for discrete eigenmodes with various free parameter values are presented.
An empirical model of the Earth's horizontal wind fields: HWM07
Authors: Drob D. P. , Emmert J. T. , Crowley G. , Picone J. M. , Shepherd G. G. , Skinner W. , Hays P. , Niciejewski R. J. , Larsen M. , She C. Y. , Meriwether J. W. , Hernandez G. , Jarvis M. J. , Sipler D. P. , Tepley C. A. , O'Brien M. S. , Bowman J. R. , Wu Q. , Murayama Y. , Kawamura S. , Reid I. M. , Vincent R. A.
Published: December 2008

The new Horizontal Wind Model (HWM07) provides a statistical representation of the horizontal wind fields of the Earth's atmosphere from the ground to the exosphere (0–500 km). It represents over 50 years of satellite, rocket, and ground‐based wind measurements via a compact Fortran 90 subroutine. The computer model is a function of geographic location, altitude, day of the year, solar local time, and geomagnetic activity. It includes representations of the zonal mean circulation, stationary planetary waves, migrating tides, and the seasonal modulation thereof. HWM07 is composed of two components, a quiet time component for the background state described in this paper and a geomagnetic storm time component (DWM07) described in a companion paper.