bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurements of 3He in Galactic HII regions and planetary nebulae
Authors: Bania T. M. , Rood R. T. , Balser D. S.
Published: April 2010

The cosmic abundance of the 3He isotope has important implications for many fields of astrophysics. We are using the 8.665 GHz hyperfine transition of 3He+ to determine the 3He/H abundance in Milky Way H ii regions and planetary nebulae. Here we review the 30 year history of our 3He program, report on its current status, and describe our future plans.
4He abundances: Optical versus radio recombination line measurements
Authors: Balser Dana S. , Rood Robert T. , Bania T. M.
Published: April 2010

Accurate measurements of the 4He/H abundance ratio are important in constraining Big Bang nucleosynthesis, models of stellar and Galactic evolution, and H ii region physics. We discuss observations of radio recombination lines using the Green Bank Telescope toward a small sample of H ii regions and planetary nebulae. We report 4He/H abundance ratio differences as high as 15–20% between optical and ratio data that are difficult to reconcile. Using the H ii regions S206 and M17 we determine 4He production in the Galaxy to be dY/dZ = 1.71 ± 0.86.
The primordial abundance of 4He from a large sample of low-metallicity H ii regions
Authors: Izotov Yuri I.
Published: April 2010

We determine the primordial helium mass fraction Yp using 1700 spectra of low-metallicity extragalactic H ii regions. This sample is selected from the Data Release 7 of the Sloan Digital Sky Survey, from European Southern Observatory archival data and from our own observations. We have considered known systematic effects which may affect the 4He abundance determination. They include collisional and fluorescent enhancements of He i recombination lines, underlying He i and hydrogen stellar absorption lines, collisional excitation of hydrogen lines, temperature and ionization structure of the H ii region. Monte Carlo methods are used to solve simultaneously the above systematic effects. We find a primordial helium mass fraction Yp = 0.2512 ± 0.0006(stat.) ± 0.0020 (syst.). This value is higher than the value given by Standard Big Bang Nucleosynthesis (SBBN) theory. If confirmed, it would imply slight deviations from SBBN.
Uncertainties in nebular helium abundances
Authors: Skillman Evan D.
Published: April 2010

Efforts to determine the primordial helium abundance via observations of metal poor HII regions have been limited by significant uncertainties. Because of a degeneracy between the solutions for density and temperature, the precision of the helium abundance determinations is limited. Spectra from the literature are used to show the effects of new atomic data and to demonstrate the challenges of determining precise He abundances. Several suggestions are made for meeting these challenges.
Revisiting the helium abundance in globular clusters with multiple main sequences
Authors: Casagrande Luca , Portinari Laura , Flynn Chris
Published: April 2010

For nearby K dwarfs, the broadening of the observed Main Sequence at low metallicities is much narrower than expected from isochrones with the standard helium–to–metal enrichment ratio ΔY/ΔZ~2. A much higher value, of order 10, is formally needed to reproduce the observed broadening, but it returns helium abundances in awkward contrast with Big Bang Nucleosynthesis. This steep enrichment ratio resembles, on a milder scale, the very high ΔY/ΔZ estimated from the multiple Main Sequences observed in some metal-poor Globular Clusters. We argue that a revision of low Main Sequence stellar models, suggested from nearby stars, could help to reduce the overwhelmingly high ΔY/ΔZ deduced so far for those clusters. Under the most favourable assumptions, the estimated helium content for the enriched populations may decrease from Y ≃ 0.4 to as low as Y ≃ 0.3, with intermediate values being plausible.
Helium-rich stars in globular clusters: constraints for self-enrichment by massive stars
Authors: Decressin Thibaut , Meynet G. , Charbonnel C.
Published: April 2010

Globular clusters exhibit peculiar chemical patterns where Fe and heavy elements are constant inside a given cluster while light elements (Li to Al) show strong star-to-star variations. This pattern can be explained by self-pollution of the intracluster gas by the slow winds of fast rotating massive stars. Besides, several main sequences have been observed in several globular clusters which can be understood only with different stellar populations with distinct He content. Here we explore how these He abundances can constrain the self-enrichment in globular clusters.
Primordial helium abundance of the SMC: a view from intermediate mass stars
Authors: Costa Roberto D. D. , Maciel Walter J. , Idiart Thais E. P.
Published: April 2010

Helium abundances were derived for a sample of planetary nebulae of the Small Magellanic Cloud. These abundances were corrected from the chemical evolution of the galaxy as well as from stellar nucleosynthesis, and the primordial helium abundance then was estimated for the sample. Results indicate that the resulting average value for the sample is consistent with the expected values for primordial helium from SBBN and other values derived from HII regions in different stellar systems, even varying the enrichment ratio within its uncertainty range.
Lithium and proton-capture elements in globular clusters: the case of 47 Tucanae
Authors: D'Orazi Valentina , Lucatello Sara , Gratton Raffaele , Bragaglia Angela , Carretta Eugenio
Published: April 2010

The determination of lithium (Li) abundances in Globular Clusters (GCs), along with proton-capture elements (Na, O, Mg, Al), offer a key tool to address the pollution scenario and its mechanisms, the dilution process acting within each star and the first phases in the lifetime of GCs. We present our results on Na, O and Li abundance determination in a large sample of dwarf stars in the GC 47 Tucanae (NGC 104). While we found a clear Na-O anti-correlation, in perfect agreement with giant members by Carretta et al. (2009a, b), Li abundance appears neither positively correlated with oxygen, nor anti-correlated with sodium. Our finding unveils an intrinsic scatter in Li content, independent of intra-cluster pollution by a first generation of more massive, faster evolving stars.
Chemical composition of stellar populations in ω Centauri
Authors: Marino A. F. , Piotto G. , Gratton R. , Milone A. P. , Zoccali M. , Bedin L. R. , Villanova S. , Bellini A.
Published: April 2010

We derive abundances of Fe, Na, O, α and s-elements from GIRAFFE@VLT spectra for more than 200 red giant stars in the Milky Way satellite ω Centauri. Our preliminary results are that: (i) we confirm that ω Centauri exhibits large star-to-star metallicity variation (~1.4 dex); (ii) the metallicity distribution reveals the presence of at least five stellar populations with different [Fe/H]; (iii) a distinct Na-O anticorrelation is clearly observed for the metal-poor and metal-intermediate stellar populations while apparently the anticorrelation disappears for the most metal rich populations. Interestingly the Na level grows with iron.
The light elements in the light of 3D and non-LTE effects
Authors: Asplund Martin , Lind Karin
Published: April 2010

In this review we discuss possible systematic errors inherent in classical 1D LTE abundance analyses of late-type stars for the light elements (here: H, He, Li, Be and B). The advent of realistic 3D hydrodynamical model atmospheres and the availability of non-LTE line formation codes place the stellar analyses on a much firmer footing and indeed drastically modify the astrophysical interpretations in many cases, especially at low metallicities. For the Teff-sensitive hydrogen lines both stellar granulation and non-LTE are likely important but the combination of the two has not yet been fully explored. A fortuitous near-cancellation of significant but opposite 3D and non-LTE effects leaves the derived 7Li abundances largely unaffected but new atomic collisional data should be taken into account. We also discuss the impact on 3D non-LTE line formation on the estimated lithium isotopic abundances in halo stars in light of recent claims that convective line asymmetries can mimic the presence of 6Li. While Be only have relatively minor non-LTE abundance corrections, B is sensitive even if the latest calculations imply smaller non-LTE effects than previously thought.
Li isotopes in metal-poor halo dwarfs: a more and more complicated story
Authors: Spite Monique , Spite François
Published: April 2010

The nuclei of the lithium isotopes are fragile, easily destroyed, so that, at variance with most of the other elements, they cannot be formed in stars through steady hydrostatic nucleosynthesis.

The7Li isotope is synthesized during primordial nucleosynthesis in the first minutes after the Big Bang and later by cosmic rays, by novae and in pulsations of AGB stars (possibly also by the ν process).6Li is mainly formed by cosmic rays. The oldest (most metal-deficient) warm galactic stars should retain the signature of these processes if, (as it had been often expected) lithium is not depleted in these stars. The existence of a “plateau” of the abundance of7Li (and of its slope) in the warm metal-poor stars is discussed. At very low metallicity ([Fe/H] < −2.7dex) the star to star scatter increases significantly towards low Li abundances. The highest value of the lithium abundance in the early stellar matter of the Galaxy (logϵ(Li) = A(7Li) = 2.2 dex) is much lower than the the value (logϵ(Li) = 2.72) predicted by the standard Big Bang nucleosynthesis, according to the specifications found by the satellite WMAP. After gathering a homogeneous stellar sample, and analysing its behaviour, possible explanations of the disagreement between Big Bang and stellar abundances are discussed (including early astration and diffusion). On the other hand, possibilities of lower productions of7Li in the standard and/or non-standard Big Bang nucleosyntheses are briefly evoked.

A surprisingly high value (A(6Li)=0.8 dex) of the abundance of the6Li isotope has been found in a few warm metal-poor stars. Such a high abundance of6Li independent of the mean metallicity in the early Galaxy cannot be easily explained. But are we really observing6Li?
Observational signatures for depletion in the Spite plateau: solving the cosmological Li discrepancy?
Authors: Meléndez Jorge , Casagrande Luca , Ramírez Iván , Asplund Martin , Schuster William J.
Published: April 2010

We present Li abundances for 73 stars in the metallicity range −3.5 < [Fe/H] < −1.0 using improved IRFM temperatures (Casagrande et al. 2010) with precise E(B-V) values obtained mostly from interstellar NaI D lines, and high-quality equivalent widths (σEW ~ 3%). At all metallicities we uncover a fine-structure in the Li abundances of Spite plateau stars, which we trace to Li depletion that depends on both metallicity and mass. Models including atomic diffusion and turbulent mixing seem to reproduce the observed Li depletion assuming a primordial Li abundance ALi = 2.64 dex (MARCS models) or 2.72 (Kurucz overshooting models), in good agreement with current predictions (ALi = 2.72) from standard BBN. We are currently expanding our sample to have a better coverage of different evolutionary stages at the high and low metallicity ends, in order to verify our findings.
Convection and 6Li in the atmospheres of metal-poor halo stars
Authors: Steffen Matthias , Cayrel R. , Bonifacio P. , Ludwig H.-G. , Caffau E.
Published: April 2010

Based on 3D hydrodynamical model atmospheres computed with the CO5BOLD code and 3D non-LTE (NLTE) line formation calculations, we study the effect of the convection-induced line asymmetry on the derived 6Li abundance for a range in effective temperature, gravity, and metallicity covering the stars of the Asplund et al. (2006) sample. When the asymmetry effect is taken into account for this sample of stars, the resulting 6Li/7Li ratios are reduced by about 1.5% on average with respect to the isotopic ratios determined by Asplund et al. (2006). This purely theoretical correction diminishes the number of significant 6Li detections from 9 to 4 (2σ criterion), or from 5 to 2 (3σ criterion). In view of this result the existence of a 6Li plateau appears questionable. A careful reanalysis of individual objects by fitting the observed lithium 6707 Å doublet both with 3D NLTE and 1D LTE synthetic line profiles confirms that the inferred 6Li abundance is systematically lower when using 3D NLTE instead of 1D LTE line fitting. Nevertheless, halo stars with unquestionable 6Li detection do exist even if analyzed in 3D-NLTE, the most prominent example being HD 84937.
Boron abundances in diffuse interstellar clouds
Authors: Ritchey Adam M. , Federman S. R. , Sheffer Y. , Lambert D. L.
Published: April 2010

We present a comprehensive survey of B abundances in diffuse interstellar clouds from HST/STIS observations along 56 Galactic sight lines. Our sample is the result of a complete search of archival STIS data for the B II λ1362 resonance line, with each detection confirmed by the presence of absorption from other dominant ions at the same velocity. The data probe a range of astrophysical environments including both high-density regions of massive star formation as well as low-density paths through the Galactic halo, allowing us to clearly define the trend of B depletion onto interstellar grains as a function of gas density. Many extended sight lines exhibit complex absorption profiles that trace both local gas and gas associated with either the Sagittarius-Carina or Perseus spiral arm. Our analysis indicates a higher B/O ratio in the inner Sagittarius-Carina spiral arm than in the vicinity of the Sun, which may suggest that B production in the current epoch is dominated by a secondary process. The average gas-phase B abundance in the warm diffuse ISM [log ϵ(B) = 2.38±0.10] is consistent with the abundances determined for a variety of Galactic disk stars, but is depleted by 60% relative to the solar system value. Our survey also reveals sight lines with enhanced B abundances that potentially trace recent production of 11B either by cosmic-ray or neutrino-induced spallation. Such sight lines will be key to discerning the relative importance of the two production routes for 11B synthesis.
Lithium in globular clusters
Authors: Korn Andreas J.
Published: April 2010

I review recent progress in mapping out and understanding the behaviour of stellar surface abundances of lithium as evidenced by spectroscopic studies of nearby globular clusters (GCs). It will become clear that these observations necessitate revisions to the canonical picture of stellar and globular-cluster evolution: stars evolve with additional non-convective mixing processes and GCs are not simple stellar populations. In spite of these complications, GCs are excellent test beds for chemical-abundance studies. Spectroscopic observations of GC stars of different evolutionary stages reveal systematic trends of surface abundances likely caused by atomic diffusion and mixing. Correcting for their combined effect on surface lithium, a stellar solution to the cosmological lithium discrepancy is likely, if not probable. However, a definitive answer can only be given once we know the effective temperatures of warm subdwarfs and subgiants to high accuracy and understand the processes which give rise to the mixing needed to moderate atomic diffusion.
Observational signatures of lithium depletion in the metal-poor globular cluster NGC6397
Authors: Lind Karin , Primas Francesca , Charbonnel Corinne , Grundahl Frank , Asplund Martin
Published: April 2010

The “stellar” solution to the cosmological lithium problem proposes that surface depletion of lithium in low-mass, metal-poor stars can reconcile the lower abundances found for Galactic halo stars with the primordial prediction. Globular clusters are ideal environments for studies of the surface evolution of lithium, with large number statistics possible to obtain for main sequence stars as well as giants. We discuss the Li abundances measured for >450 stars in the globular cluster NGC 6397, focusing on the evidence for lithium depletion and especially highlighting how the inferred abundances and interpretations are affected by early cluster self-enrichment and systematic uncertainties in the effective temperature determination.
Lithium in a metal-poor external galaxy: ω Centauri
Authors: Bonifacio P. , Monaco L. , Sbordone L. , Villanova S. , Pancino E.
Published: April 2010

ω Centauri is a massive stellar system which is currently going through the Galactic Halo. Its compact aspect and spheroidal shape have for a long time led to it being classified as a Globular Cluster. However the fact that its stars cover a wide metallicity range (−0.6 < [Fe/H] < −2.1), points to this object as an external galaxy, satellite of the Milky Way. Lithium among warm metal-poor stars shows a roughly constant abundance, the “Spite Plateau”. This has been interpreted as evidence for a primordial origin of the lithium nucleus, at the time of nucleosynthesis. After the physical conditions under which nucleosynthesis occurred, have been constrained by the observations of the fluctuations of the Cosmic Microwave Background, we are facing a “cosmological lithium problem”, namely the primordial lithium was a factor of three to four higher than what observed in the Spite plateau. Several avenues may be taken to solve this conundrum, either relying on fundamental physics or on stellar physics, however the realm of possibilities may be considerably narrowed by observing stellar populations in different galaxies, which have experienced different evolutionary histories. Some of the proposed “solutions” may be clearly ruled out, depending on the observation of lithium in the metal-poor populations of external galaxies. ω Centauri is the only external galaxy amenable to such an investigation in the era of 8m telescopes. We have pushed to its limits FLAMES at the ESO 8.2m telescope to obtain high resolution spectra of the Li i doublet in 91 Turn-Off and Sub-Giant stars at V ~ 18 in ω Centauri. We present our preliminary results on this data which suggest that the Li content in ω Centauri warm stars is comparable to that observed in Galactic Halo field stars of similar metallicities and temperatures. This may effectively rule out a whole class of models which invoke a severe Li depletion through processing of material in an early generation of massive stars.
Observations of Lithium in red giant stars
Authors: Smith Verne V.
Published: April 2010

Connections between observations of the lithium abundance in various types of red giants and stellar evolution are discussed here. The emphasis is on three main topics; 1) the depletion of Li as stars ascend the red giant branch for the first time, 2) the synthesis of 7Li in luminous and massive asymptotic giant branch stars via the mechanism of hot-bottom burning, and 3) the possible multiple sources of excess Li abundances found in a tiny fraction of various types of G and K giants.
Mass loss and luminosities of S and C AGB stars with and without Li
Authors: Guandalini Roald , Palmerini Sara , Busso Maurizio , Maiorca Enrico , Uttenthaler Stefan
Published: April 2010

We present the preliminary results of an analysis performed on two samples of thermally pulsing Asymptotic Giant Branch stars from our Galaxy, the first made of carbon-rich sources and the second of S-type stars. We have estimated their absolute luminosities and updated rates of the stellar winds through methods based on their infrared spectrophotometry and on updated estimates of their variability and distance.

We then focus on those sources in our database showing Li in their spectra looking for correlations between the Li abundance and the other physical parameters, in the aim of establishing observational criteria for understanding the conditions for the occurrence of the deep mixing phenomena to which the production of Li is currently attributed.
Observations of light elements in massive stars
Authors: Kaufer A.
Published: April 2010

Observations of light elements in hot massive stars are limited to few transitions of boron in the satellite-ultraviolet; lithium and beryllium are not observable at all. But because of its high sensitivity to the effects of rotational mixing, boron abundance determinations in massive stars have excelled as the definite test for evolutionary models with rotation. In this paper the observational evidence for rotational mixing in massive stars is reviewed and alternative interpretations are discussed.
Survey for Li-rich K giants
Authors: Kumar Y. Bharat , Reddy Bacham E.
Published: April 2010

We present results from an ongoing survey of searching Li-rich K giants among low mass giants along the Red Giant Branch (RGB). A sample of 2500 stars with accurate astrometry have been selected from Hipparcos catalogue covering both the RGB luminosity bump and the red clump regions on the HR diagram. Lithium abundances have been determined for half of the sample from low resolution spectra using line depth ratio method. Results confirm the rarity of Li-rich K giants, just under 1%, in the solar neighbourhood. This study increased the total number of known Li-rich K giants by a factor of two. The analysis of high resolution spectra of candidate Li-rich K giants showed that the K giant HD 77361 is highly enriched in lithium (log ϵ(Li) = 3.82) and at the same time has anomalously low carbon isotopic ratio (12C/13C = 4.3). The results put important constraints on the theoretical modelling of the stellar structure and the mixing process, particularly, of the K giants.
Ultra-lithium-deficient halo stars
Authors: Elliott Lisa M. , Ryan Sean G.
Published: April 2010

While most warm halo dwarfs show lithium abundances at the level of the Spite Plateau, a small number (~5%) have undetectable lithium lines. The existence of these stars has long raised questions when interpreting the plateau abundances: are they an extreme example of a depletion mechanism that has affected the plateau stars, or do they have an entirely different history? We provide an overview of what is currently known about the lithium-poor halo stars and discuss a possible origin for the lithium deficiency in this unique group of stars.
Interstellar Lithium as a probe of the primordial abundance
Authors: Howk J. Christopher
Published: April 2010

The cosmic abundance of lithium continues to represent a conundrum, as predictions from BBN theory are inconsistent with measurements in the atmospheres of the lowest-metallicity stars. While there are worries that modifications of the stellar Li abundances may play a role in this discrepancy, no satisfactory solution has yet been found. We suggest an alternate approach to studying the cosmic abundance of Li: measurements of interstellar gas-phase Li in low-metallicity environments.
Lithium abundances in the α Persei Cluster
Authors: Mallik Sushma V. , Balachandran Suchitra C. , Lambert David L.
Published: April 2010

As a sequel to the Li observations by Balachandran, Lambert & Stauffer (1988, 1996) in 35 stars of the 50 Myr old cluster α Persei, we have obtained and analyzed high resolution spectra of another 51 stars. Following a reconsideration of the cluster membership of the stars (Prosser 1992, Makarov 2006, Mermilliod et al. 2008, and Patience et al. 2002), we discuss the Li abundances for 70 stars. With our larger sample, we reexamine the question of whether the scatter in Li abundance at a given Teff seen in young clusters at cool temperatures is real or not.
Lithium in other Suns: no connection between stars and planets
Authors: Meléndez Jorge , Ramírez Iván , Asplund Martin , Baumann Patrick
Published: April 2010

An unbiased sample of solar twins shows that the Sun has a normal Li abundance for its age and that a low Li abundance does not imply the presence of planets. We find a tight correlation between Li and age, which holds for all stars analyzed in our sample: solar twins, stars with and without detected giant planets, and stars that may host terrestrial planets.
HD 232 862 : a magnetic and lithium-rich giant star
Authors: Palacios A. , Lèbre A. , do Nascimento J. D. , Konstantinova-Antova R. , Kolev D. , Aurière M. , de Laverny P. , de Medeiros J. R.
Published: April 2010

Using spectropolarimetric data acquired with the ESPaDOnS and NARVAL instruments at CFHT and at TBL, we present a detailed spectral synthesis analysis of HD 232 862, a field giant classified as a G8II star hosting a magnetic field. This star is the first lithium-rich field giant hosting a magnetic field. Stellar evolution models suggest that HD 232 862 should be a 1.5 to 2.0 M⊙ star at the bottom of the red giant branch. Its unsually high lithium content (A(Li) = 2.45 ± 0.25 dex) is even more puzzling and challenges our understanding of the evolution of this star.
The metal–poor end of the Spite plateau: gravity sensitivity of the Hα wings fitting.
Authors: Sbordone L. , Bonifacio P. , Caffau E. , Ludwig H.-G. , Behara N. , Gonzalez-Hernandez J. I. , Steffen M. , Cayrel R. , Freytag B. , Van't Veer C. , Molaro P. , Plez B. , Sivarani T. , Spite M. , Spite F. , Beers T. C. , Christlieb N. , François P. , Hill V.
Published: April 2010

We recently presented (Sbordone et al., 2009a) the largest sample to date of lithium abundances in extremely metal-poor (EMP) Halo dwarf and Turn-Off (TO) stars. One of the most crucial aspects in estimating Li abundances is the Teff determination, since the Li I 670.8 nm doublet is highly temperature sensitive. In this short contribution we concentrate on the Teff determination based on Hα wings fitting, and on its sensitivity to the chosen stellar gravity.
Light elements as diagnostics on the structure and evolution of low-mass stars
Authors: Talon Suzanne , Charbonnel Corinne
Published: April 2010

Low-mass stars exhibit, at all stages of their evolution, the signatures of complex physical processes that require challenging modelling beyond standard stellar theory. In this review, we focus on lithium depletion in low-mass stars. After disecting the Li dip, we discuss how large scale mixing due to rotation and internal gravity waves may interact to explain this feature. We also briefly discuss the impact that is expected on Population II stars.
Effects of rotation and magnetic fields on the structure and surface abundances of solar-type stars
Authors: Eggenberger P. , Maeder A. , Meynet G.
Published: April 2010

The effects of shellular rotation on the modelling of solar-type stars (in particular internal structure, evolutionary tracks in the HR diagram, lifetimes and surface abundances) are first examined. Then the effects of a dynamo possibly occuring in the internal stellar radiative zone by imposing nearly solid body rotation are studied. These results are finally discussed in the context of the rotational history of exoplanet host stars and the link between lithium depletion and the presence of exoplanets.
The light elements in a helio- and asteroseismic perspective
Authors: Vauclair Sylvie
Published: April 2010

Asteroseismology is a powerful tool to derive stellar parameters, including the helium content and internal helium gradients, and the macroscopic motions which can lead to lithium, beryllium, and boron abundance variations. Precise determinations of these parameters need deep analyses for each individual stars. After a general introduction on helio and asteroseismology, I first discuss the solar case, the results which have been obtained in the past two decades, and the crisis induced by the new determination of the abundances of heavy elements. Then I discuss asteroseismology in relation with light element abundances, especially for the case of main sequence stars.
Lithium destruction induced by planetary accretion in solar-type stars
Authors: Théado Sylvie , Bohuon Elise , Vauclair Sylvie
Published: April 2010

Accretion of planetary (metal-rich) material onto a star in its early phases can produce episodes of thermohaline convection below the outer convective zone. These extra-mixing phases lead to rapid lithium destruction. The observed dispersion of lithium abundances in solar-type stars can be related to such events.
Thermohaline mixing in stars : solving the long-standing 3He problem
Authors: Charbonnel Corinne , Lagarde Nadège
Published: April 2010

Thermohaline mixing has been recently identified as the dominating process that governs the photospheric composition of low-mass bright giant stars (Charbonnel & Zahn 2007a). Here we present the predictions of stellar models computed with the code STAREVOL that takes into account this mechanism together with rotational mixing and atomic diffusion. We compare our theorical predictions with recent observations and discuss how the corresponding yields for 3He are compatible with the observed behaviour of this light element in our Galaxy.
Galactic evolution of 7Li
Authors: Matteucci Francesca
Published: April 2010

Lithium represents a key element in cosmology, as it is one of the few nuclei synthesized during the Big Bang. The primordial abundance of 7Li allows us to impose constraints on the primordial nucleosynthesis and on the baryon density of the universe. However, 7Li is not only produced during the Big Bang but also during galactic evolution: measures of stellar Li in our Galaxy suggest an almost constant Li abundance (the so-called Spite plateau) at low metallicities and a subsequent increase in the disk stars, leading to a Li abundance in Population I stars higher by a factor of ten than in Population II stars. This means that there must exist several possible stellar sources of 7Li: asymptotic giant branch stars, supernovae, novae, red giant stars. 7Li is also partly produced in spallation processes while 6Li is entirely produced by such processes. All of these sources have been included in galactic chemical evolution models and constraints have been derived on the primordial 7Li and its evolution, as well on stellar models. I will review these models and their results and what we have learned about 7Li evolution. Some still open problems, such as the disagreement between the primordial 7Li abundance as derived by WMAP and as measured in Population II stars, and the uncertainties about the main sources of stellar 7Li will be discussed.
The search for the origin of the light nuclei Li, Be, B
Authors: Reeves Hubert
Published: April 2010

My aim is to show how the abundance ratios of the light elements (6 to 11) are related to the properties of the strong nuclear interaction and, in particular, to the major influence of closed shells of neutrons and protons, (the magic numbers : 2, 8, etc) on the binding energies of the nuclei.
Origin of cosmic rays and evolution of spallogenic nuclides Li, Be and B
Authors: Prantzos Nikos
Published: April 2010

A short overview is presented of current issues concerning the production and evolution of Li, Be and B in the Milky Way. In particular, the observed “primary-like” evolution of Be is re-assessed in the light of a novel idea: it is argued that Galactic Cosmic Rays are accelerated from the wind material of rotating massive stars, hit by the forward shock of the subsequent supernova explosions. The pre-galactic levels of both Li isotopes remain controversial at present, making it difficult to predict their Galactic evolution. A quantitative estimate is provided of the contributions of various candidate sources to the solar abundance of Li.
Discussion D: Observational problems with Li, Be and B
Authors: Nissen Poul Erik
Published: April 2010

In Discussion D the following problems were addressed: Has6Li really been detected in the atmospheres of metal-poor halo stars? Is there a downward trend or increased scatter of Li abundances in stars on the ‘Li-plateau’ at metallicities [Fe/H] ≲ −2.5? Are there significant differences of Li abundances in main-sequence, turn-off, and sub-giant stars in globular clusters? Is the Li abundance in solar-type stars related to the presence of planets? How does the Be abundance in dwarf stars increase with the heavy-element abundance, and is there a cosmic scatter in Be at a given [Fe/H]? The discussion of these problems is summarized and some suggestions for future observational and theoretical studies are mentioned.
The Relationship Between Texture Responses on the Rorschach and Adult Attachment
Authors: Iwasa Kazunori , Ogawa Toshiki
Published: April 2010

We examined the relationship between texture responses (T) on the Rorschach and adult attachment in the Japanese population. 47 Japanese undergraduate and graduate students (mean age = 20.16, SD = 1.87) completed a self-report adult attachment scale as well as the Rorschach. An ANOVA revealed that T = 1 participants were attached more securely than were other groups. T > 1 participants were more preoccupied with attachment and scored higher on an attachment anxiety scale than the T = 1 group. Although these results were consistent with the interpretation of the texture response according to the Comprehensive System (CS), the results obtained for T = 0 participants were inconsistent with hypotheses derived from the CS. T = 0 participants were high on preoccupied and attachment anxiety scores, although they were theoretically expected to be high on dismissing or attachment avoidance. These results indicated that – at least in Japan – T should be regarded as a sensitive measure of attachment anxiety.
On Being a Child of an Ill Parent
Authors: Flahault Cecile , Sultan Serge
Published: April 2010

Cancer in a parent has a devastating effect on the psychological well-being of the children. In this comparative study, we examined the hypothesis that children who have a parent suffering from cancer experience greater difficulty in terms of psychological adaptation than children with a parent suffering from another chronic pathology. A group of 52 children of parents with cancer was compared with a group of 50 children whose parents were suffering from another chronic disease (respiratory insufficiency, diabetes) (mean age = 12.3 ± 2.8 years, 46 boys, 56 girls). All the children took part in a Rorschach Comprehensive System examination. Results showed that the children who had a parent suffering from cancer exhibited a higher number of signs of anxiety and depressive affects as well as reduced self-esteem. These difficulties were more pronounced in the case of girls and when it was the mother who was suffering from cancer. These results confirm the data reported in the literature in a large sample and using an indirect performance-based evaluation method. They emphasize the need to develop specific interventions which take account of the gender of the child and the ill parent.
No Measure Is Perfect, but Some Measures Can be Quite Useful
Authors: Greenwald Anthony G. , Sriram N.
Published: April 2010

The comment articles in this issue by Friese and Fiedler (F&F) and by Rothermund and Wentura (R&W) offer perspectives on the validity of the Brief Implicit Association Test (BIAT) ( Sriram & Greenwald, 2009 ; S&G). F&F concluded that construct validity of the BIAT can be established only by conducting studies that experimentally manipulate association strengths. We suggest that this conclusion overvalues experimental strategies and undervalues correlational validation strategies. R&W’s critique was predicated on their use of a semantic-network theoretical understanding of the concept of association. In contrast, S&G offered the BIAT as a technique for measuring association strengths in the context of a broader concept of association that has roots in antiquity – and remains widely used in psychology. With this broader understanding of association, some of the phenomena that R&W treated as threats to the BIAT’s validity are viewed, instead, as contributors to its validity.
An analysis of HF radar measured surface currents to determine tidal, wind‐forced, and seasonal circulation in the Gulf of the Farallones, California, United States
Authors: Gough Matt K. , Garfield Newell , McPhee‐Shaw Erika
Published: April 2010

A complete year of hourly 3 km resolution high‐frequency radar measured surface currents covering the Gulf of the Farallones were analyzed with the following three primary objectives: (1) describe the seasonal surface circulation, (2) identify tidal currents, and (3) determine the influence of wind forcing. Three predominant seasonal circulation regimes were identified: relaxation, storm, and upwelling. The relaxation period exhibited mean poleward flow over the slope, variable equatorward flow over the shelf, and cyclonic and anticyclonic eddies south of Pt. Reyes. The storm period mean flow was variable and exhibited evidence of coastally trapped buoyancy flow from the mouth of the San Francisco Bay. The upwelling period exhibited equatorward flow throughout the gulf with regions of intensified flow at the northern and southern regions over the slope. The tidal variance ranged from 4 to 60%, was highest around the mouth of the Bay, decreased past the shelf, and its spatial pattern reflected the combined influence of the K1 and M2 tidal current amplitudes. K1 ellipses typically rotated clockwise throughout the gulf and decreased in amplitude past the shelf. M2 ellipses were comparably more variable in orientation and magnitude. Harmonic “tidal” analyses of buoy wind data over 4 month time periods showed significant K1 amplitudes which did not appear when the analysis was done for the entire year. This indicates that harmonic tidal analyses on surface currents are probably more effective at disassociating diurnal sea breeze driven currents when performed over long periods of time such as a year.
Micrometeorological and morphological observations of surface hoar dynamics on a mountain snow cover
Authors: Stössel F. , Guala M. , Fierz C. , Manes C. , Lehning M.
Published: April 2010

The formation, growth, and destruction of surface hoar crystals is an important feature of mountain snow covers as buried surface hoar layers are a frequent weak layer leading to unstable snowpacks. The energy and mass exchange associated with surface hoar dynamics is further an important part of land‐atmosphere interaction over snow. A quantitative prediction of surface hoar evolution based on local environmental conditions is, however, difficult. We carried out measurements of crystal hoar size and total surface mass changes in the period between January and March 2007 on the Weissfluhjoch study plot of the WSL Institute for Snow and Avalanche Research SLF, located above Davos, Switzerland, at 2540 m above sea level. For the first time, a direct comparison between eddy correlation measurements of latent heat flux and lysimeter‐like measurements of surface mass change has been made. Results show that the growth of surface hoar crystals is very well correlated with deposition of water vapor during clear‐sky nights as measured by two eddy correlation systems placed close to the ground. By analyzing local meteorological data, we confirm that low to moderate wind speed, humid air, and clear‐sky nights are the necessary ingredients for the occurrence of significant vapor fluxes toward the surface and thus for the growth of surface hoar. We also confirm that surface hoar crystals tend to preserve during daytime, when strong sublimation occurs, although their size significantly reduces. Despite the complexities associated with mountain terrain and snow surfaces, such as nonequilibrium boundary layers and stratification effects, the hoar formation could be predicted by the snow cover model SNOWPACK, which uses a bulk Monin‐Obukhov (MO) parameterization for the turbulent heat fluxes. On the basis of the comparison between direct observations and model predictions, we suggest that neutral stability conditions in the MO formulation provide the most stable and least flawed prediction for surface hoar formation.
Climatic and ecological controls of equilibrium drainage density, relief, and channel concavity in dry lands
Authors: Collins D. B. G. , Bras R. L.
Published: April 2010

Drainage density has long been observed to vary among climates, a relationship often attributable to differences in the erosivity of runoff and resistivity of vegetation. There is also evidence, though much less, that relief and channel concavity also vary with climate. The biophysical chain of events that connect climate to these topographic expressions, however, deserves greater attention. Using a numerical landscape evolution model, we examine how a gradient of mean annual precipitation is expressed in the topography of low‐ to medium‐relief, sediment‐mantled, water‐limited ecosystems. We find equilibrium landscapes have the lowest drainage density, greatest relief, and lowest concavity at intermediate levels of rainfall. This climatic threshold represents the transition from vegetation‐dominated sediment flux in drier climates to runoff‐dominated flux with more precipitation. In drier climates, marginal increases in precipitation manifest themselves primarily as increases in vegetation while runoff is relatively constant; this acts to suppress sediment transport and decreases the drainage density. In wetter environments, marginal increases in precipitation lead to increases primarily in runoff while vegetation cover remains relatively constant; this results in increased sediment transport and increases the drainage density. The location of the transition depends at least in part on plant community structure and composition. The modeling study illustrates the complexities inherent in biogeomorphic systems but also that a simplified conceptual model of landscape evolution may indeed be sufficient to understand the large‐scale patterns. The study also illustrates the opportunities offered by approaching questions of landform development from an ecohydrological perspective.
Proposed NOAA Budget Includes Hefty Increase for Satellites
Authors: Showstack Randy
Published: April 2010

The Obama administration's proposed fiscal year (FY) 2011 budget for the U.S. National Oceanic and Atmospheric Administration (NOAA) would provide the agency with $5.55 billion, which represents a total increase of $806.1 million, or 17% above the FY 2010 budget enacted by Congress. At a February briefing about the budget, NOAA administrator Jane Lubchenco said the budget is a very good package for the agency and that it reflects the administration's commitment to the environment, science, public safety, and job creation.

Noting that the agency's budget remained essentially fl at between FY 2005 and FY 2008 during the George W. Bush administration, Lubchenco said, “the increasing demand for NOAA's services, coupled with a static budget, created a major challenge for NOAA in delivering on expectations.” She said the funding picture for the agency improved with the FY 2009 and FY 2010 enacted budgets. Lubchenco noted that the proposed budget would include $949 million for research and development, an $82 million increase, adding, “Our 2011 request for each line office [within NOAA] is higher than it was in 2010, and we are better aligned with congressional funding levels than in previous budgets.”
Characterizing Water, Sediment, Nutrients, and Contaminant Fluxes in Coastal Egypt: Marine Constituent Dynamics in Coastal Egypt; Alexandria, Egypt, 20 November 2009
Authors: Peterson Richard N. , El‐Gamal Ayman
Published: April 2010

The Egyptian coastal area is a highly dynamic region in which materials (water, sediment, nutrients, and contaminants) are transported from various sources to the Mediterranean and Red seas. At a workshop in Egypt, U.S. and Egyptian scientists discussed these largely unquantified processes and how they interact to drive coastal ecology. A major goal of the workshop was to identify the most pressing research priorities for the region for both scientific and management purposes. The workshop concluded by recommending that international multidisciplinary efforts be undertaken to characterize water, nutrient, sediment, and contaminant delivery fluxes and mechanisms to coastal regions of the Nile Delta.

The Nile River is thought to be the most significant source of sediments to coastal Egypt, but as workshop participants discussed, the Aswan High Dam and water diversion practices have essentially shut off the sediment supply to the delta. This change has initiated massive erosion that is now threatening arable land and infrastructure. A workshop conclusion recommends that future studies focus on understanding sediment transport and mobility throughout the delta and also on predicting sea level rise rates for the region to better forecast the extent of future land loss.
Climate and Geomorphic Risks in High‐Mountain Environments: Glacier Hazards, Permafrost Hazards, and Glacier Lake Outburst Floods in Mountain Areas: Processes, Assessment, Prevention, Mitigation; Vienna, Austria, 10–13 November 2009
Authors: Huggel Christian , Kääb Andreas , Schneider Jean
Published: April 2010

Recent atmospheric warming is profoundly affecting high‐mountain environments around the world. Glaciers are thinning and retreating, new and often unstable lakes are forming at glacier margins, other lakes are suddenly draining, and permafrost is degrading. These changes pose serious hazards to people and property in mountain valleys. Several tens of thousands of people were killed by landslides, floods, and debris flows from high‐mountain regions during the twentieth century, and there is concern that such events will increase as temperatures warm through the 21st century.
Flood impact map
Authors: Showstack Randy
Published: April 2010

The U.S. Federal Emergency Management Agency (FEMA) and the National Oceanic and Atmospheric Administration (NOAA) have created an interactive “flood impact map.”
Australian and Chinese Scientists Discuss Coastal Zone Management: Integrated Coastal Zone Management Workshop; Canberra, Australian Capital Territory, Australia, 11–14 November 2009
Authors: Wang Xiao Hua , Xu Xiangmin
Published: April 2010

A 3‐day workshop was held in Australia to discuss problems and issues facing coastal zones, including degradation of coastal ecosystems and the impacts of climate change such as sea level rise and changed weather patterns, and to formulate a collaborative research strategy to improve the coastal zone management (CZM) system to tackle these problems. The workshop, which brought together experts from University of New South Wales (UNSW) and Ocean University of China (OUC), highlighted the similarities in topics important to Australia and China. This workshop focused on science, policy, and the legal framework required to manage sustainable development of these coastal zones.

Many parallels exist between the difficult issues facing CZM in both countries. Significant research into changes in coastal areas and their causes has been undertaken, but this research effort has not been fully reflected in coastal zone planning and management activities. Workshop participants reviewed current progress in understanding scientific, engineering, and socioeconomic processes in the coastal zones, brainstormed challenges in developing a multidisciplinary research framework capable of integrating science into coastal zone management, and identified a cross‐institutional approach to addressing these issues.
South Pacific hotspot swells dynamically supported by mantle flows
Authors: Adam Claudia , Yoshida Masaki , Isse Takehi , Suetsugu Daisuke , Fukao Yoshio , Barruol Guilhem
Published: April 2010

The dynamics of mantle plumes and the origin of their associated swells remain some of the most controversial topics in geodynamics. Here we construct a numerical model of the mantle flow beneath the French Polynesia region. Our study is based on a new regional seismic tomography model, which high resolution allows obtaining information at the scale of plumes. We find excellent correlations between the observed and the modeled dynamic swells, between the modeled flow pattern and the active volcanism and between the buoyancy fluxes obtained from our numerical model and the ones deduced from the swells morphology. These outstanding fits reveal for the first time that a direct link exists between the surface observations and mantle flows.