bluuebunny/crossref_metadata_2025 huggingface dataset:
Co-production and Sure Start Children's Centres: Reflecting upon Users', Perspectives and Implications for Service Delivery, Planning and Evaluation
Authors: Pemberton Simon , Mason Jennifer
Published: December 2008

In the UK, there has been a re-awakening of interest in the ‘co-production’ approach to involve service users in modernised public services. Within this context, Sure Start Children's Centres are being created to address child poverty and social exclusion, with an emphasis on participatory approaches. This paper considers the engagement of users in service delivery, service planning and in monitoring and evaluation activities for Children's Centres in Greater Merseyside. Research findings indicate that a lack of time to implement (and develop trust within) the new arrangements, a lack of awareness by users to participate and a broader thematic (employment and education) and geographical remit for Children's Centres is impacting upon the greater involvement of users in all aspects of co-production. Without such participation it is concluded that there is a real risk that the current needs of those most disadvantaged will not be adequately addressed.
Small Acts of Care: Exploring the Potential Impact of the Mental Capacity Act 2005 on Day-to-Day Support
Authors: Stanley Nicky , Manthorpe Jill
Published: December 2008

Exploring the five principles of the newly enacted Mental Capacity Act 2005, this article sets these in the context of day-to-day decisions over care and treatment. These areas figure strongly in the lives of people who have problems making decisions, but there is little consideration of them in contrast to major decisions about financial planning, deprivation of liberty, and healthcare and treatment. Social policy has often found it difficult to encroach upon areas covering intimate and family-based care relationships or the private domain of care at home. This legislation touches on this controversial area.
Review Article: Resilience and Social Exclusion
Authors: Mohaupt Sarah
Published: December 2008

The emphasis of this literature review is on conceptual issues rather than a review of empirical studies. The paper starts by addressing the question why the concept of resilience is particular and what value is added if such a perspective is adopted. Next, the historical context and evolvement of the research on resilience are briefly reviewed with a short overview of the range of research topics in the area. The third section discusses the definition of resilience and its main elements. Section four addresses the main criticisms of the resilience concept. Section five identifies areas for further research.
Open questions in the study of population III star formation
Authors: Glover S. C. O. , Clark P. C. , Greif T. H. , Johnson J. L. , Bromm V. , Klessen R. S. , Stacy A.
Published: December 2008

The first stars were key drivers of early cosmic evolution. We review the main physical elements of the current consensus view, positing that the first stars were predominantly very massive. We continue with a discussion of important open questions that confront the standard model. Among them are uncertainties in the atomic and molecular physics of the hydrogen and helium gas, the multiplicity of stars that form in minihalos, and the possible existence of two separate modes of metal-free star formation.
The formation of the first galaxies and the transition to low-mass star formation
Authors: Greif T. H. , Schleicher D. R. G. , Johnson J. L. , Jappsen A.-K. , Klessen R. S. , Clark P. C. , Glover S. C. O. , Stacy A. , Bromm V.
Published: December 2008

The formation of the first galaxies at redshifts z ~ 10−15 signaled the transition from the simple initial state of the universe to one of ever increasing complexity. We here review recent progress in understanding their assembly process with numerical simulations, starting with cosmological initial conditions and modelling the detailed physics of star formation. In this context we emphasize the importance and influence of selecting appropriate initial conditions for the star formation process. We revisit the notion of a critical metallicity resulting in the transition from primordial to present-day initial mass functions and highlight its dependence on additional cooling mechanisms and the exact initial conditions. We also review recent work on the ability of dust cooling to provide the transition to present-day low-mass star formation. In particular, we highlight the extreme conditions under which this transition mechanism occurs, with violent fragmentation in dense gas resulting in tightly packed clusters.
Dark Stars: Dark matter in the first stars leads to a new phase of stellar evolution
Authors: Freese Katherine , Spolyar Douglas , Aguirre Anthony , Bodenheimer Peter , Gondolo Paolo , Sellwood J. A. , Yoshida Naoki
Published: December 2008

The first phase of stellar evolution in the history of the universe may be Dark Stars, powered by dark matter heating rather than by fusion. Weakly interacting massive particles, which are their own antiparticles, can annihilate and provide an important heat source for the first stars in the the universe. This talk presents the story of these Dark Stars. We make predictions that the first stars are very massive (~800M⊙), cool (6000 K), bright (~106L⊙), long-lived (~106years), and probable precursors to (otherwise unexplained) supermassive black holes. Later, once the initial DM fuel runs out and fusion sets in, DM annihilation can predominate again if the scattering cross section is strong enough, so that a Dark Star is born again.
Searching for Pop III stars and galaxies at high redshift
Authors: Schaerer Daniel
Published: December 2008

We review the expected properties of Pop III and very metal-poor starbursts and the behaviour the Lyα and Heiiλ1640 emission lines, which are most likely the best/easiest signatures to single out such objects. Existing claims of Pop III signatures in distant galaxies are critically examined, and the searches for Heiiλ1640 emission at high redshift are summarised. Finally, we briefly summarise ongoing and future deep observations atz> 6 aiming in particular at detecting the sources of cosmic reionisation as well as primeval/Pop III galaxies.
Observational Search for Population III Stars in High-Redshift Galaxies
Authors: Nagao Tohru
Published: December 2008

In this contribution we present our new photometric search for high-z galaxies hosting Population III (PopIII) stars based on deep intermediate-band imaging observations, by using Supreme-Cam on the Subaru Telescope. By combining our new data with the existing broad-band and narrow-band data in the target field, we searched for galaxies which emit strongly both in Lyα and in Heiiλ1640 (“dual emitters”) that are promising candidates for PopIII-hosting galaxies, at 4 ≲ z ≲ 5. Although we found 10 “dual emitters”, most of them turn out to be [Oii]-[Oiii] dual emitters or Hβ-Hα dual emitters at z < 1, as inferred from their broad-band colors and from the ratio of the equivalent widths. No convincing candidate of Lyα-Heii dual emitter with SFRPopIII ≳ 2M⊙ yr−1 was found. This result disfavors low feedback models for PopIII star clusters, and implies an upper limit of the PopIII SFR density of SFRDPopIII < 5 × 10−6M⊙ yr−1 Mpc−3. This new selection method to search for PopIII-hosting galaxies should be useful in future surveys for the first observational detection of PopIII-hosting galaxies at high redshift.
Cosmic metal enrichment
Authors: Ferrara Andrea
Published: December 2008

I review the present understanding of the process by which the universe has been enriched in the course of its history with heavy elements produced by stars and transported into the surrounding intergalactic medium. This process goes under the name of “cosmic metal enrichment” and presents some of the most challenging puzzles in present day physical cosmology. These are reviewed along with some proposed explanations that all together form a coherent working scenario.
Primordial Supernovae and the Assembly of the First Galaxies
Authors: Whalen Daniel , Van Veelen Bob , O'Shea Brian W. , Norman Michael L.
Published: December 2008

Current numerical studies suggest that the first protogalaxies formed a few stars at a time and were enriched only gradually by the first heavy elements. However, these models do not resolve primordial supernova (SN) explosions or the mixing of their heavy elements with ambient gas, which could result in intervening, prompt generations of low-mass stars. We present multiscale 1D models of Population III supernovae in cosmological minihalos that evolve the blast from its earliest stages as a free expansion. We find that if the star ionizes the halo, the ejecta strongly interacts with the dense shell swept up by the H II region, potentially cooling and fragmenting it into clumps that are gravitationally unstable to collapse. If the star fails to ionize the halo, the explosion propagates metals out to 20 - 40 pc and then collapses, heavily enriching tens of thousands of solar masses of primordial gas, in contrast to previous models that suggest that such explosions ‘fizzle’. Rapid formation of low-mass stars trapped in the gravitational potential well of the halo is unavoidable in these circumstances. Consequently, it is possible that far more stars were swept up into the first galaxies, at earlier times and with distinct chemical signatures, than in present models. Upcoming measurements by the James Webb Space Telescope (JWST) and Atacama Large Millimeter Array (ALMA) may discriminate between these two paradigms.
Damped Lyα systems as probes of chemical evolution over cosmological timescales
Authors: Dessauges-Zavadsky Miroslava
Published: December 2008

We review the current state of knowledge of damped Lyα systems (DLAs) selected in absorption on quasar sightlines. These objects are extremely useful to study the interstellar medium of high-redshift galaxies and the nucleosynthesis in the early Universe. The characteristics of this galaxy population has been investigated for years and slowly we are getting information on their puzzling nature. Imaging atz<1 shows that DLAs are associated with a mixing bag of galaxies with no especially large contribution from dwarf galaxies. Evidence for a mild evolution of the cosmic mean metallicity with time is observed. The star formation histories of these high-redshift galaxies begin to be accessible and indicate that DLAs tend to be young, gas-dominated galaxies with low star formation rates per unit area. Finally, indirect estimation of the DLA stellar masses from the mass-metallicity relations observed for emission-selected star-forming galaxies atz= 2−3 points to intermediate-mass galaxies withM*< 109M⊙.
Effects of reionization on dwarf galaxy formation
Authors: Ricotti Massimo
Published: December 2008

In this talk I revisit the problem of gas accretion onto minihalos after reionization. I show that primordial minihalos with vcir < 20 km s−1 stop accreting gas after reionization, as is usually assumed, but in virtue of their increasing concentration and the decreasing temperature of the intergalactic medium as redshift decreases, they have a late phase (at redshift z<2) of gas accretion and possibly star formation. As a result we expect that pre-reionization fossils have a more complex star formation history than previously envisioned. A signature of this model is a bimodal star formation history. The dwarf spheroidal galaxy Leo T, that inspired the present work, fits with this scenario. Another prediction of the model is the existence of a population of gas rich minihalos that never formed stars. A subset of compact high-velocity clouds may be identified as such objects but the bulk of them may still be undiscovered.
Young Star Clusters in the Small Magellanic Cloud: Impact of Local and Global Conditions on Star Formation
Authors: Sabbi Elena , Smith Linda J. , Carlson Lynn R. , Nota Antonella , Tosi Monca , Cignoni Michele , Gallagher Jay S. , Sirianni Marco , Meixner Margaret
Published: December 2008

We compared deep images acquired with the Advanced Camera for Surveys on board of the Hubble Space Telescope with mid-IR Spitzer Space Telescope images and University College London Echelle Spectrograph spectra of NGC 346 and NGC 602, two of the youngest star clusters in the Small Magellanic Cloud. Our multi-wavelength approach allowed us to infer very different origins for the clusters: while NGC 346 is likely the result of the hierarchical collapse of a giant molecular cloud, NGC 602 is probably the result of the collision and consequent interaction of two H I shells of gas.
Dwarf galaxies and the Magnetisation of the IGM
Authors: Klein Uli
Published: December 2008

With the operation of LOFAR, a great opportunity exists to shed light on a problem of some cosmological significance. Diffuse radio synchrotron emission not associated to any obvious discrete sources as well as Faraday rotation in clusters of galaxies both indicate that the intergalactic or intracluster medium (IGM, ICM) is pervaded by a weak magnetic field, along with a population of relativistic particles. Both, particles and fields must have been injected into the IGM either by Active Galactic Nuclei (AGN) or by normal star-forming galaxies. Excellent candidates for the latter are starburst dwarf galaxies, which in the framework of hierarchical structure formation must have been around in large numbers. If this is true, one should be able to detect extended synchrotron halos of formerly highly relativistic particles around local starburst or post-starburst dwarf galaxies. With LOFAR, one should easily find these out to the Coma Cluster and beyond.
First Stars – Type Ib Supernovae Connection
Authors: Nomoto Ken'ichi , Tanaka Masaomi , Kamiya Yasuomi , Tominaga Nozomu , Maeda Keiichi
Published: December 2008

The very peculiar abundance patterns observed in extremely metal-poor (EMP) stars can not be explained by conventional normal supernova nucleosynthesis but can be well-reproduced by nucleosynthesis in hyper-energetic and hyper-aspherical explosions, i.e., Hypernovae (HNe). Previously, such HNe have been observed only as Type Ic supernovae. Here, we examine the properties of recent Type Ib supernovae (SNe Ib). In particular, SN Ib 2008D associated with the luminous X-ray transient 080109 is found to be a more energetic explosion than normal core-collapse supernovae. We estimate that the progenitor's main sequence mass isMMS= 20 − 25M⊙with an explosion of kinetic energy ofEK~ 6.0 × 1051erg. These properties are intermediate between those of normal SNe and hypernovae associated with gamma-ray bursts. Therefore, such energetic SNe Ib could also make an important contribution to the chemical enrichment in the early Universe.
Powerful explosions atZ= 0?
Authors: Ekström Sylvia , Meynet Georges , Hirschi Raphael , Maeder André
Published: December 2008

Metal-free stars are assumed to evolve at constant mass because of the very low stellar winds. This leads to large CO-core mass at the end of the evolution, so primordial stars with an initial mass between 25 and 85M⊙are expected to end as direct black holes, the explosion energy being too weak to remove the full envelope.

We show that when rotation enters into play, some mass is lost because the stars are prone to reach the critical velocity during the main sequence evolution. Contrary to what happens in the case of very low- but non zero-metallicity stars, the enrichment of the envelope by rotational mixing is very small and the total mass lost remains modest. The compactness of the primordial stars lead to a very inefficient transport of the angular momentum inside the star, so the profile of Ω(r) is close to Ωr2= const. As the core contracts, the rotation rate increases, and the star ends its life with a fast spinning core. Such a configuration has been shown to modify substantially the dynamics of the explosion. Where one expected a weak explosion or none at all, rotation might boost the explosion energy and drive a robust supernova. This will have important consequences in the way primordial stars enriched the early Universe.
Wind anisotropy and stellar evolution
Authors: Georgy Cyril , Meynet Georges , Maeder André
Published: December 2008

Mass loss is a determinant factor which strongly affects the evolution and the fate of massive stars. At low metallicity, stars are supposed to rotate faster than at the solar one. This favors the existence of stars near the critical velocity. In this rotation regime, the deformation of the stellar surface becomes important, and wind anisotropy develops. Polar winds are expected to be dominant for fast rotating hot stars.

These polar winds allow the star to lose large quantities of mass and still retain a high angular momentum, and they modify the evolution of the surface velocity and the final angular momentum retained in the star's core. We show here how these winds affect the final stages of massive stars, according to our knowledge about Gamma Ray Bursts. Computation of theoretical Gamma Ray Bursts rate indicates that our models have too fast rotating cores, and that we need to include an additional effect to spin them down. Magnetic fields in stars act in this direction, and we show how they modify the evolution of massive star up to the final stages.
Low-Mass and Metal-Poor Gamma-Ray Burst Host Galaxies
Authors: Savaglio Sandra
Published: December 2008

Gamma-ray bursts (GRBs) are cosmologically distributed, very energetic and very transient sources detected in the γ-ray domain. The identification of their x-ray and optical afterglows allowed so far the redshift measurement of 150 events, from z = 0.01 to z = 6.29. For about half of them, we have some knowledge of the properties of the parent galaxy. At high redshift (z > 2), absorption lines in the afterglow spectra give information on the cold interstellar medium in the host. At low redshift (z < 1.0) multi-band optical-NIR photometry and integrated spectroscopy reveal the GRB host general properties. A redshift evolution of metallicity is not noticeable in the whole sample. The typical value is a few times lower than solar. The mean host stellar mass is similar to that of the Large Magellanic Cloud, but the mean star formation rate is five times higher. GRBs are discovered with γ-ray, not optical or NIR, instruments. Their hosts do not suffer from the same selection biases of typical galaxy surveys. Therefore, they might represent a fair sample of the most common galaxies that existed in the past history of the universe, and can be used to better understand galaxy formation and evolution.
The Luminosity Function of Long Gamma-Ray Burst and their rate at z ≥ 6
Authors: Salvaterra R. , Campana S. , Chincarini G. , Choudhury T. R. , Covino S. , Ferrara A. , Gallerani S. , Guidorzi C. , Tagliaferri G.
Published: December 2008

We compute the luminosity function (LF) and the formation rate of long gamma ray bursts (GRBs) in three different scenarios: i) GRBs follow the cosmic star formation and their LF is constant in time; ii) GRBs follow the cosmic star formation but the LF varies with redshift; iii) GRBs form preferentially in low–metallicity environments. We then test model predictions against the Swift 3-year data, showing that scenario i) is robustly ruled out. Moreover, we show that the number of bright GRBs detected by Swift suggests that GRBs should have experienced some sort of luminosity evolution with redshift, being more luminous in the past. Finally we propose to use the observations of the afterglow spectrum of GRBs at z ≥ 5.5 to constrain the reionization history, and then applied our method to the case of GRB 050904.
Dust and Gas as Seeds for Metal-Poor Star Formation
Authors: Hunter Deidre A.
Published: December 2008

I address the issue of dust and gas as seeds for metal-poor star formation by reviewing what we know about star formation in nearby dwarf galaxies and its relationship to the gas and dust. I (try to) speculate on the extent to which processes in nearby galaxies mimic star formation in the early universe.
Dust properties and distribution in dwarf galaxies
Authors: Lisenfeld Ute , Relaño Monica , Vílchez José , Battaner Eduardo , Hermelo Israel
Published: December 2008

We present a study of the extinction, traced by the Balmer decrement, in HII regions in the dwarf galaxies NGC 1569 and NGC 4214. We find that the large-scale extinction around the most prominent HII regions in both galaxies forms a shell in which locally the intrinsic extinction can adopt relatively high values (AV= 0.8 − 0.9 mag) despite the low metallicity and thus the low overall dust content. The small-scale extinction (spatial resolution ~0.3″) shows fluctuations that are most likely due to variations in the dust distribution. We compare the distribution of the extinction to that of the dust emission, traced bySpitzeremission at 8 and 24μm, and to the emission of cold dust at 850μm. We find in general a good agreement between all tracers, except for the 850μm emission in NGC 4214 which is more extended than the extinction and the other emissions. Whereas in NGC 1569 the dust emission at all wavelengths is very similar, NGC 4214 shows spatial variations in the 24-to-850μm ratio.

We furthermore compared the 24μm and the extinction-corrected Hα emission from HII regions in a sample of galaxies with a wide range of metallicities and found a good correlation, independent of metallicity. We suggest that this lack of dependence on metallicity might be due to the formation of dust shells with a relatively constant opacity, like the ones observed here, around ionizing stars.
Stars at Low Metallicity in Dwarf Galaxies
Authors: Tolstoy Eline , Battaglia Giuseppina , Cole Andrew
Published: December 2008

Dwarf galaxies offer an opportunity to understand the properties of low metallicity star formation both today and at the earliest times at the epoch of the formation of the first stars. Here we concentrate on two galaxies in the Local Group: the dwarf irregular galaxy Leo A, which has been the recent target of deep HST/ACS imaging (Cole et al. 2007) and the Sculptor dwarf spheroidal, which has been the target of significant wide field spectroscopy with VLT/FLAMES (Battaglia 2007).
The size-density relation of H ii regions in blue compact dwarf galaxies
Authors: Hirashita Hiroyuki , Hunt Leslie K.
Published: December 2008

We investigate the size-density relation of H ii regions in blue compact dwarf galaxies (BCDs) by compiling observational data of their size (Di) and electron density (ne). We find that the size-density relation follows a relation with constant column density (ne ∝ Di−1) rather than with constant luminosity (ne ∝ Di−1.5). Such behavior resembles that of Galactic H ii regions, and may imply an underlying “scale-free” connection. Because this size-density relation cannot be explained by static models, we model and examine the evolution of the size-density relation of H ii regions by considering the star formation history and pressure-driven expansion of H ii regions. We find that the size-density relation of the entire BCD sample does not result from an evolutionary sequence of H ii regions but rather reflects a sequence with different initial gas densities (or “hierarchy” of density). We also find that the dust extinction of ionizing photons is significant for the BCD sample, despite their blue optical colors. This means that as long as the emission from H ii regions is used to trace massive star formation, we would miss the star formation activity in dense environments even in low-metallicity galaxies such as BCDs.
Ionized gas in dwarf galaxies: Abundance indicators
Authors: Stasińska Grażyna
Published: December 2008

We discuss the four basic methods to derive HII region abundances in metal-poor galaxies by presenting a few recent results obtained with these methods. We end up by commenting on the yet unsolved problem of temperature fluctuations in HII regions, which may plague abundance determinations, as well as the discrepancy between abundances derived from recombination lines and collisionally excited lines, to which inhomogeneous chemical composition might be the explanation.
SMC in space and time: a project to study the evolution of the prototype interacting late-type dwarf galaxy
Authors: Tosi M. , Gallagher J. , Sabbi E. , Glatt K. , Grebel E. K. , Christian C. , Cignoni M. , Clementini G. , Cole A. , Da Costa G. , Harbeck D. , Marconi M. , Meixner M. , Nota A. , Sirianni M. , Smecker-Hane T.
Published: December 2008

We introduce the SMC in space and time, a large coordinated space and ground-based program to study star formation processes and history, as well as variable stars, structure, kinematics and chemical evolution of the whole SMC. Here, we present the Colour-Magnitude Diagrams (CMDs) resulting from HST/ACS photometry, aimed at deriving the star formation history (SFH) in six fields of the SMC. The fields are located in the central regions, in the stellar halo, and in the wing toward the LMC. The CMDs are very deep, well beyond the oldest Main Sequence Turn-Off, and will allow us to derive the SFH over the entire Hubble time.
A New Age and Distance for I Zw 18, the Most Metal-Poor Galaxy in the Nearby Universe
Authors: Aloisi A. , Clementini G. , Tosi M. , Annibali F. , Contreras R. , Fiorentino G. , Mack J. , Marconi M. , Musella I. , Saha A. , Sirianni M. , van der Marel R. P.
Published: December 2008

The blue compact dwarf galaxy I Zw 18 holds the record of the lowest metallicity ever observed in the local universe. As such, it represents the closest analog to primordial galaxies in the early universe. More interestingly, it has recurrently been regarded as a genuinely young galaxy caught in the process of forming in the nearby universe. However, stars of increasingly older ages are found within I Zw 18 every time deeper high-resolution photometric observations are performed with the Hubble Space Telescope (HST): from the original few tens of Myrs to, possibly, several Gyrs. Here we summarize the history of I Zw 18 age and present an ongoing HST/ACS project which allowed us to precisely derive the galaxy distance by studying its Cepheid variables, and to firmly establish the age of its faintest resolved populations.
Mozambique earthquake sequence of 2006: High‐angle normal faulting in southern Africa
Authors: Yang Zhaohui , Chen Wang‐Ping
Published: December 2008

We report source mechanisms for the six largest shocks of the Mozambique earthquake sequence of 22 February 2006. The main shock of this sequence is one of the largest (Mw ∼ 7.0) to occur in Africa over the past 100 years and its P waveforms alone are sufficient to show that north‐south trending normal faulting near the surface continues to depths of more than 15 km along an exceptionally steep dip of 76° ± 4°. This new result shows that globally seismogenic normal faulting spans a wide range of dips, from about 30° to 75°. S waveforms, when combined with a minor component of left‐lateral slip observed in the field, indicate the rake to be between −80° and −89° which, in turn, places a new constraint on relative plate motions: Complications from a nonspecific Rovuma microplate notwithstanding, our results favor the Euler pole between the Somalia and Nubia plates to lie southward of the epicenters.
Significance of carbonate buffers in natural waters reacting with supercritical CO2: Implications for monitoring, measuring and verification (MMV) of geologic carbon sequestration
Authors: Newell Dennis L. , Kaszuba John P. , Viswanathan Hari S. , Pawar Rajesh J. , Carpenter Thomas
Published: December 2008

Successful geologic sequestration of carbon in deep saline aquifers requires accurate predictive models of rock‐brine‐CO2 interaction. Often overlooked in siliciclastic‐hosted saline reservoirs is the carbonate buffering of the groundwater. Carbonate minerals are ubiquitous, even in siliciclastic host rocks, resulting in some carbonate buffering. Geochemical modeling of rock‐brine‐CO2 systems often do not accurately predict the geochemical evolution of the system leading to significant doubts in predicting the performance of carbon repositories. New data from a simple NaCl brine‐plagioclase hydrothermal experiment tests carbon sequestration in dawsonite and sensitivity to carbonate buffering. This is contrasted to a NaCl brine ‐ siliciclastic rock system containing some initial bicarbonate buffering, analogous to most saline‐aquifer sequestration targets, and show that critical errors are caused by incomplete or inaccurate characterization of the in situ geochemistry. We provide a methodology that accurately predicts the in situ condition using samples collected from brine‐rock‐CO2 experiments or well‐heads in a carbon sequestration monitoring scenario.
DMS air/sea flux and gas transfer coefficients from the North Atlantic summertime coccolithophore bloom
Authors: Marandino C. A. , De Bruyn W. J. , Miller S. D. , Saltzman E. S.
Published: December 2008

Dimethylsulfide (DMS) atmospheric and oceanic concentrations and eddy covariance air/sea fluxes were measured over the N. Atlantic Ocean during July 2007 from Iceland to Woods Hole, MA, USA. Seawater DMS levels north of 55°N ranged from 3 to 17 nM, with variability related to the satellite‐derived distributions of coccoliths and to a lesser extent, chlorophyll. For the most intense bloom region southwest of Iceland, DMS air/sea fluxes were as high as 300 μmol m−2 d−1, larger than current model estimates. The observations imply that gas exchange coefficients in this region are significantly greater than those estimated using most gas transfer parameterizations. South of 55°N, DMS levels were lower and the gas transfer coefficients were similar to those observed in other regions of the ocean. The data suggest that DMS emissions from the bloom region may be significantly larger than current estimates. The anomalous gas exchange coefficients likely reflect strong near‐surface, water column DMS gradients influenced by physical and biological processes.
A multi‐instrument technique for localization of scintillation‐causing regions in the equatorial ionosphere
Authors: Miller E. S. , Makela J. J.
Published: December 2008

Scintillation of transionospheric radio signals is a phenomenon of great practical consequence for users of satellite communication and navigation systems, often rendering these systems inaccurate or simply useless for periods of time. In order to understand the occurrence and underlying physics of the plasma instabilities that generate scintillation‐causing irregularities, it is necessary to study the scale and velocity of these irregularities as well as their distribution in altitude. Scintillation is a diffraction effect; hence the observed diffraction pattern at the Earth's surface contains information on these three parameters. Often, the range is taken at an assumed altitude, allowing the velocity and scale to be estimated. However, the accuracy of these estimates depends on the quality of the assumed altitude. In this paper, we introduce the combination of field‐aligned airglow images and satellite‐to‐satellite occultation links as a method to independently estimate the altitude of scattering regions at low latitudes. During the September–October equinox period of 2006, observations in the American sector show most irregularities in the 200–375 km altitude range.
Behavior of the F2 peak ionosphere over the South Pacific at dusk during quiet summer conditions from COSMIC data
Authors: Burns A. G. , Zeng Z. , Wang W. , Lei J. , Solomon S. C. , Richmond A. D. , Killeen T. L. , Kuo Y.‐H.
Published: December 2008

The six‐satellite Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) mission makes routine ionospheric measurements over the entire globe using occultation techniques. These observations have been used in this study to develop global‐scale climate maps of NmF2 and hmf2 during the southern (northern) summer (winter). Enhanced electron densities that appear to be associated with the southern, equatorial (Appleton) anomaly are displaced far southward at dusk and, within about an hour, form the Weddell Sea anomaly. Coincidentally, the height of the F2 peak increases on the northern boundary of this anomaly. This height increase is also displaced southward as the enhanced electron densities are displaced southward, suggesting that the electron density increases are associated with the F2 peak rising. As well as being an interesting phenomenon in its own right, this behavior may shed new light on the formation of the Weddell Sea anomaly. No unambiguous explanation for this behavior can be determined from the data presently available, but an examination of some possibilities suggests that an evening downward flux of plasma from the plasmasphere may be at least partly responsible for the phenomenon.
Estimating total heliospheric magnetic flux from single‐point in situ measurements
Authors: Owens M. J. , Arge C. N. , Crooker N. U. , Schwadron N. A. , Horbury T. S.
Published: December 2008

A fraction of the total photospheric magnetic flux opens to the heliosphere to form the interplanetary magnetic field carried by the solar wind. While this open flux is critical to our understanding of the generation and evolution of the solar magnetic field, direct measurements are generally limited to single‐point measurements taken in situ by heliospheric spacecraft. An observed latitude invariance in the radial component of the magnetic field suggests that extrapolation from such single‐point measurements to total heliospheric magnetic flux is possible. In this study we test this assumption using estimates of total heliospheric flux from well‐separated heliospheric spacecraft and conclude that single‐point measurements are indeed adequate proxies for the total heliospheric magnetic flux, though care must be taken when comparing flux estimates from data collected at different heliocentric distances.
Influence of contiguity on seismic velocities of partially molten aggregates
Authors: Hier‐Majumder Saswata
Published: December 2008

The microstructure of partially molten rocks plays a key role in determining their physical properties. The area fraction of intergranular contact, contiguity, governs the establishment of a skeletal framework of solid grains and controls the effective elastic moduli of the aggregate. This work presents a theoretical calculation of steady state grain shape, contiguity, effective elastic moduli, andSandPwave velocities for a partially molten aggregate containing an approximate melt volume fraction of 0.09. The steady state microstructure is controlled by surface tension gradients arising from interaction among adjacent grains in a close‐packed aggregate. The ratio of viscosity between the grains and the melt, as well as the capillary number, strongly influence the contiguity. For an aggregate with a high viscosity ratio, surface tension‐driven faceting is suppressed due to the large viscous resistance of the grains, leading to a small contiguity. BothVSandVPdecrease in a nonlinear fashion with an increasing viscosity ratio for all capillary numbers. When extrapolated to the conditions similar to the core‐mantle boundary, a 3:1 ratio of shear toPwave velocity reduction can be explained by a melt volume fraction of 0.15.
A refraction seismic transect from the Faroe Islands to the Hatton‐Rockall Basin
Authors: Funck Thomas , Andersen Morten S. , Keser Neish Judith , Dahl‐Jensen Trine
Published: December 2008

The crustal structure of the Faroe‐Rockall Plateau was studied by a 790‐km‐long refraction seismic transect consisting of two intersecting lines. The air gun shot spacing was 200 m, and the signals were recorded by 77 ocean bottom seismometers. A P wave velocity model was developed from forward and inverse modeling of the wide‐angle seismic data and incorporation of coincident multichannel reflection seismic data. Continental crust with velocities ranging from 5.6 to 6.8 km/s can be traced from the Faroe Islands, across the banks to the SW of the Faroes and into the Hatton‐Rockall Basin. The thickness of the subvolcanic crust is up to 25 km on the banks but is as little as 8 km in the channels between the banks. The thinning in the channels may be related to NW‐trending shear zones extending from major lineaments in NE Rockall Trough. Basalt layers are found along the entire transect with a total thickness of up to 4 km. Two layers with velocities of 4.9–5.2 and 5.3–5.6 km/s are thought to represent Paleogene flood basalts that can be correlated from the Faroe Islands to George Bligh Bank. Close to George Bligh Bank, an 80‐km‐wide and up to 9‐km‐thick body with velocities of 6.5 km/s is interpreted as intrusion. A 5‐km‐thick, high‐velocity lower crustal layer (7.3 km/s) extends from the area of the intrusion into the northern Hatton‐Rockall Basin. At the northern flank of Lousy Bank the transition zone to oceanic crust was encountered.
Origin of a crustal splay fault and its relation to the seismogenic zone and underplating at the erosional north Ecuador–south Colombia oceanic margin
Authors: Collot J.‐Y. , Agudelo W. , Ribodetti A. , Marcaillou B.
Published: December 2008

Splay faults within accretionary complexes are commonly associated with the updip limit of the seismogenic zone. Prestack depth migration of a multichannel seismic line across the north Ecuador–south Colombia oceanic margin images a crustal splay fault that correlates with the seaward limit of the rupture zone of the 1958 (Mw 7.7) tsunamogenic subduction earthquake. The splay fault separates 5–6.6 km/s velocity, inner wedge basement rocks, which belong to the accreted Gorgona oceanic terrane, from 4 to 5 km/s velocity outer wedge rocks. The outer wedge is dominated by basal tectonic erosion. Despite a 3‐km‐thick trench fill, subduction of 2‐km‐high seamount prevented tectonic accretion and promotes basal tectonic erosion. The low‐velocity and poorly reflective subduction channel that underlies the outer wedge is associated with the aseismic, décollement thrust. Subduction channel fluids are expected to migrate upward along splay faults and alter outer wedge rocks. Conversely, duplexes are interpreted to form from and above subducting sediment, at ∼14‐ to 15‐km depths between the overlapping seismogenic part of the splay fault and the underlying aseismic décollement. Coeval basal erosion of the outer wedge and underplating beneath the apex of inner wedge control the margin mass budget, which comes out negative. Intraoceanic basement fossil listric normal faults and a rift zone inverted in a flower structure reflect the evolution of the Gorgona terrane from Cretaceous extension to likely Eocene oblique compression. The splay faults could have resulted from tectonic inversion of listric normal faults, thus showing how inherited structures may promote fluid flow across margin basement and control seismogenesis.
Secondary waves generated by breaking of convective gravity waves in the mesosphere and their influence in the wave momentum flux
Authors: Chun Hye‐Yeong , Kim Young‐Ha
Published: December 2008

Gravity waves generated by convective clouds are numerically simulated using a two‐dimensional mesoscale model that extends to the upper mesosphere (physical model top of 105 km), and characteristics of the waves are investigated before and after wave breaking occurred in the mesosphere. Gravity waves generated by convective clouds have wide spectrum corresponding to their sources, but large portions of the waves with short horizontal and vertical wavelengths are reflected, trapped, and filtered out before they reach to the upper mesosphere. After wave breaking occurs in the mesosphere (z = 65–85 km), secondary waves are generated by momentum forcing due to breaking of the primary waves. The mesospheric forcing has a wide spectrum with strong power not only for components at which the primary waves have strong power but also for components with short zonal wavelengths and periods. Interaction between upward‐propagating primary waves (UPW) and downward‐propagating secondary waves (DSW) are investigated below the mesospheric forcing region by comparing the result from an additional simulation with a lower model top (z = 60 km) that excludes wave breaking in the mesosphere. It was found that DSWs increase spectral powers for both short and long horizontal and vertical wavelengths and for westward‐propagating components that are mostly filtered in the UPWs. For a given easterly basic‐state wind in the middle atmosphere, DSWs produce negative momentum flux at wide phase speeds, and this cancels a large portion of the positive momentum flux by the UPWs. Consequently, the magnitude of the positive momentum flux decreases and the negative momentum flux increases, which is caused by DSWs. This change reduces the gravity wave drag significantly below the mesospheric forcing region. This result implies that current gravity wave parameterizations without considering DSWs may overestimate the momentum flux and resultant drag and suggests the need to include the effects of secondary waves in the parameterizations of gravity waves.
Characterization of mesoscale gravity waves in the upper and lower clouds of Venus from VEX‐VIRTIS images
Authors: Peralta J. , Hueso R. , Sánchez‐Lavega A. , Piccioni G. , Lanciano O. , Drossart P.
Published: December 2008

Images obtained from the Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS)‐M instrument onboard Venus Express present visible trains of alternating bands of cloud brightness in two different layers: at the upper cloud tops (∼66 km altitude) observed in the dayside hemisphere using reflected ultraviolet light (380 nm) and in the lower cloud (∼47 km altitude) observed in the nightside hemisphere using thermal radiation (1.74 μm). The waves are nearly zonal (with the bands perpendicular to latitude circles), have wavelengths of 60–150 km, propagate westward with low phase velocities relative to the zonal flow, and are confined in wave packets of 400 to 1800 km in length. The waves in the lower cloud observed in the infrared are widely distributed around the planet, and their appearance varies widely throughout the VIRTIS data set. The locations of both types of waves seem not correlated with latitude, local times, surface topography, or the structure of the wind. In both cases the characteristics of the waves correspond to gravity waves propagating in confined stable layers of the atmosphere. We examine the properties of these waves in terms of a linear model and perform a simple analysis to discuss the vertical stability of the atmosphere within Venus clouds.
Inhibition of the Inflammasome Complex Reduces the Inflammatory Response after Thromboembolic Stroke in Mice
Authors: Abulafia Denise P , de Rivero Vaccari Juan Pablo , Lozano J Diego , Lotocki George , Keane Robert W , Dietrich W Dalton
Published: December 2008

Inflammation is a major contributor to the pathogenesis of cerebral ischemia and stroke. In the peripheral immune response, caspase-1 activation involves the formation of a macromolecular complex termed the inflammasome. We determined whether nucleotide-binding, leucine-rich repeat, pyrin domain containing 1 (NLRP1), molecular platform consisting of capase-1, apoptosis-associated speck-like protein containing a caspase-activating recruitment domain (ASC), and NLRP1, is expressed in the normal and postischemic brain. Mice underwent thromboembolic stroke to investigate the formation of the inflammasome and subsequent activation of downstream inflammatory responses. Western blot analysis showed expression and activation of interleukin (IL) IL-1β and IL-18 at 24 h after stroke. Size-exclusion chromatography and coimmunoprecipitation analysis showed protein association between NLRP1, ASC, caspase-1, and the X-linked inhibitor of apoptosis protein (XIAP). After ischemia, immunohistochemical analysis revealed inflammasome proteins in neurons, astrocytes, and microglia/macrophages. The potential of the inflammasome as an antiinflammatory target was showed by interference of inflammasome activation resulting in reduced cytokine levels in mice treated after ischemia with a neutralizing antibody against NLRP1. These findings show that the inflammasome complex forms after focal brain ischemia and may be a novel therapeutic target for reducing the detrimental consequences of postischemic inflammation.
Cell Fusion Contributes to Pericyte Formation after Stroke
Authors: Piquer-Gil Marina , García-Verdugo José M , Zipancic Ivan , Sánchez María J , Álvarez-Dolado Manuel
Published: December 2008

Recent reports have shown that bone marrow-derived cells (BMDCs) contribute to the formation of vasculature after stroke. However, the mechanism by which mural cells are formed from BMDC remains elusive. Here, we provide direct evidence that the cell fusion process contributes to the formation of pericytes after stroke. We generated mouse bone marrow chimeras using a cre/lox system that allows the detection of fusion events by X-gal staining. In these mice, we detected X-gal-positive cells that expressed vimentin and desmin, specific markers of mature murine pericytes. Electron microscopy confirmed that fused cells possessed basal lamina and characteristics of pericytes. Furthermore, induction of stroke increased significantly the presence of fused cells in the ischemic area. These cells expressed markers of developing pericytes such as NG2. We conclude that cell fusion participates actively in the generation of vascular tissue through pericyte formation under normal as well as pathologic conditions.
Psychiatric and Behavioral Genetics: A Useful Distinction?
Authors: Hallmayer Joachim
Published: December 2008

Dr. Hallmayer began with a discussion of the Nuffield Council on Bioethics' work on genetics, mental disorders and human behavior. He further explored psychiatric genetics and urged against the oversimplification of dynamic interactions. To watch Dr. Hallmayer’s presentation, please see the "Google Video posting.":http://video.google.com/videoplay?docid=-5387564337084407366&hl=enTo watch the deliberative discussion concluding the first Symposium panel, please see the "Google Video posting.":http://video.google.com/videoplay?docid=3871777823134971240&hl=en
Psychiatric Genetics: Methods, Findings and Ethical Issues
Authors: Kendler Kenneth
Published: December 2008

This talk has 4 major sections. First, I review the basic definition of a complex trait, especially as it applies to psychiatric disorders. Second, I outline the 4 basic paradigms of psychiatric genetics: simple genetic epidemiology, advanced genetic epidemiology, gene-finding methods and molecular genetics. Third, I review a few basic facts about psychiatric genetics - the level of heritabilities found for most common disorders and the difficulties the field has had in obtaining replicated evidence for single gene effects. Finally, I briefly review three conceptual/philosophical issues that relate to psychiatric genetics: i) why do people become much more concerned in learning about possible genetic influences on personality or risk for depression than genes that influence risk for cancer, atherosclerosis or asthma? ii) how have the results of research in behavioral/Psychiatric Genetics impacted on the sense of Parental Responsibility for psychiatric illness in their offspring.To watch Dr. Kendler’s presentation, please see the "Google Video posting.":http://video.google.com/videoplay?docid=-3261606556062804269&hl=en