bluuebunny/crossref_metadata_2025 huggingface dataset:
Big Bang nucleosynthesis with long-lived strongly interacting relic particles
Authors: Kusakabe Motohiko , Kajino Toshitaka , Yoshida Takashi , Mathews Grant J.
Published: April 2010

We study effects of relic long-lived strongly interacting massive particles (X particles) on big bang nucleosynthesis (BBN). The X particle is assumed to have existed during the BBN epoch, but decayed long before detected. The interaction strength between an X and a nucleon is assumed to be similar to that between nucleons. Rates of nuclear reactions and beta decay of X-nuclei are calculated, and the BBN in the presence of neutral charged X0 particles is calculated taking account of captures of X0 by nuclei. As a result, the X0 particles form bound states with normal nuclei during a relatively early epoch of BBN leading to the production of heavy elements. Constraints on the abundance of X0 are derived from observations of primordial light element abundances. Particle models which predict long-lived colored particles with lifetimes longer than ~200 s are rejected. This scenario prefers the production of 9Be and 10B. There might, therefore, remain a signature of the X particle on primordial abundances of those elements. Possible signatures left on light element abundances expected in four different models are summarized.
The total deuterium abundance in the local Galactic disk: decisions and implications
Authors: Linsky Jeffrey L.
Published: April 2010

Analyses of FUSE spacecraft spectra have provided measurements of D/H in the gas phase of the interstellar medium for many lines of sight extending to several kpc from the Sun. These measurements, together with the earlier Copernicus, HST, and IMAPS data, show a wide range of D/H values that have challenged both observers and chemical evolution modellers. I believe that the best explanation for the diverse D/H measurements is that deuterium can be sequestered on to carbonaceous grains and PAH molecules and thereby removed from the interstellar gas. Grain destruction can raise the gas phase D/H value to approximately the total D/H value. Supernovae and stellar winds, however, can decrease the total D/H value along lines of sight on time scales less than mixing time scales. I will summarize the theoretical and observational arguments for this model and estimate the most likely range for the total D/H in the local Galactic disk. This range in total D/H presents a constraint on realistic Galactic chemical evolution models or the primordial value of D/H or both.
The Galactic deuterium gradient
Authors: Lubowich Donald , Pasachoff Jay M.
Published: April 2010

The Galactic deuterium abundance gradient has been determined from observations of DCN in Galactic molecular clouds. This is the only way to observe D throughout the Galaxy because the molecular clouds are not limited to the 2 kpc region around the Sun observed with FUSE and from DI. We used an astrochemistry model and the DCN/HCN ratios to estimate the underlying D/H ratios in 16 molecular clouds including five in the Galactic Center. The resulting positive Galactic D gradient and reduced Galactic Center D/H ratio imply that there are no significant Galactic sources of D, there is continuous infall of low-metallicity gas into the Galaxy, and that deuterium is cosmological.
Helium abundances in planetary nebulae: Nucleosynthesis and chemical evolution
Authors: Maciel W. J. , Costa R. D. D. , Idiart T. E. P.
Published: April 2010

We have obtained a large sample of PN with accurately determined helium abundances, as well as abundances of several heavy elements. The nebulae are located in the solar neighbourhood, in the galactic bulge, disk and anticentre, and in the Magellanic Clouds. The abundances are analyzed both in terms of the nucleosynthesis of intermediate mass stars and the chemical evolution of the host galaxies. In particular, correlations between the He/H ratio and the abundances of N and O are used as constraints of the nucleosynthetic processes occurring in the progenitor stars.
On the origin of the helium-rich population in the peculiar globular cluster Omega Centauri
Authors: Romano Donatella , Tosi M. , Cignoni M. , Matteucci F. , Pancino E. , Bellazzini M.
Published: April 2010

In this contribution we discuss the origin of the extreme helium-rich stars which inhabit the blue main sequence (bMS) of the Galactic globular cluster Omega Centauri. In a scenario where the cluster is the surviving remnant of a dwarf galaxy ingested by the Milky Way many Gyr ago, the peculiar chemical composition of the bMS stars can be naturally explained by considering the effects of strong differential galactic winds, which develop owing to multiple supernova explosions in a shallow potential well.
Lithium and beryllium in Population I dwarf stars
Authors: Randich Sofia
Published: April 2010

In the last few years a variety of lithium and beryllium surveys have been carried out among Pop. I stars in the field and open clusters, with the goal to trace the dependence of these element abundances on stellar mass, age, metallicity, and to understand the physical processes that lead to their depletion. I summarize here the most recent results, focusing on stars with temperatures similar to the Sun. In particular, I will discuss Li measurements in solar-type members of old open clusters, which definitively show that the low solar lithium is not the standard for a star of that age and mass.
Lithium in stars with exoplanets
Authors: Israelian Garik
Published: April 2010

Our recent study of solar-type stars from the HARPS GTO sample provides highly accurate information with regard to Lithium abundances in stars with and without detected planets (Israelian et al. 2009). When the Li abundances of planet bearing stars are compared with the “single” stars, we find an excess of Li depletion in planet hosts with effective temperatures in the range 5700-5850 K. We also found that small amounts of Li have survived in the atmospheres of some planet-host solar analogs. Enhanced Li depletion in planet host stars puts constraints on mixing processes responsible for this phenomenon. We show that neither age nor metallicity are responsible for this observational fact.
A 3D-NLTE study of the 670 nm solar lithium feature
Authors: Caffau Elisabetta , Ludwig Hans-Günter , Steffen Matthias , Bonifacio Piercarlo
Published: April 2010

We derive the 3D-NLTE lithium abundance in the solar photosphere from the Lii line at 670 nm as measured in several solar atlases. The Li abundance is obtained from line profile fitting with 1D/3D-LTE/3D-NLTE synthetic spectra, considering several possibilities for the atomic parameters of the lines blending the Li feature. The 670 nm spectral region shows considerable differences in the two available disc-centre solar atlases, while the two integrated disc spectra are very similar. We obtain A(Li)3D–NLTE = 1.03. The 1D-LTE abundance is 0.07 dex smaller. The line-lists giving the best fit for the Sun may fail for other stars, while some line-lists fail to reproduce the solar profile satisfactorily. We need a better knowledge of the atomic parameters of the lines blending the Li feature in order to be able to reproduce both the solar spectrum and the spectra of other stars. An improved line-list is also required to derive reliable estimates of the isotopic Li ratio in solar-metallicity stars.
Li-rich giants in the Galactic Bulge. Is Li linked only to evolutionary status?
Authors: Gonzalez Oscar A.
Published: April 2010

In our detailed study of chemical abundances in the Galactic bulge (see Zoccali et al. 2008 for a description of the entire project) we have measured Li abundances by fitting synthetic spectra to the 7Li (6707.18Å) line for ~400 giants in Baade's Window and a field at b=−6 (Gonzalez et al. 2009). We have found 13 stars showing strong 7Li lines in complete contrast to the rest of the sample for which only upper limits could be obtained. Our sample is at least 1.2 mag brighter than the expected RGB bump, therefore we interpreted our results as evidence for stars that might have avoided the observed extra-mixing process or undergoing a Li enrichment process not necessarily linked to the RGB bump.
A very low upper limit for a Be abundance of a carbon-enhanced metal-poor star
Authors: Ito Hiroko , Aoki Wako , Honda Satoshi , Beers Timothy C. , Tominaga Nozomu
Published: April 2010

We performed a 1D LTE chemical abundance analysis of an extremely metal-poor star BD+44°493 ([Fe/H]= −3.7), and set a very low upper limit for its Be abundance: A(Be) < −2.0. It may indicate that the decreasing trend of Be abundances with lower [Fe/H] still holds at [Fe/H] < −3.5, and demonstrate that high C and O abundances do not necessarily imply high Be abundances. However, since the star is a subgiant with Teff ~ 5500K, Be may be depleted.
New results of the spectral observations of CP stars
Authors: Polosukhina N. S. , Shavrina A. V. , Drake N. A. , Kudryavtsev D. O. , Smirnova M. A.
Published: April 2010

The lithium problem in Ap-CP stars has been, for a long time, a subject of debate. Individual characteristics of CP stars, such as high abundance of the rare-earth elements presence of magnetic fields, complicate structure of the surface distribution of chemical elements, rapid oscillations of some CP-stars, make the detection of the lithium lines and the determination of the lithium abundance, a difficult task. During the International Meeting in Slovakia in 1996, the lithium problem in Ap-CP stars was discussed. The results of the Li study carried out in CrAO Polosukhina (1973–1976), the works of Hack & Faraggiana (1963), Wallerstein & Hack (1964), Faraggiana et al. (1992–1996) formed the basis of the International project ‘Lithium in the cool CP-stars with magnetic fields’. The main goal of the project was, using systematical observations of Ap-CP stars with phase rotation in the spectral regions of the resonance doublet Li I 6708 Å and subordinate 6104 Å lithium lines with different telescopes, to create a database, which will permit to explain the physical origin of anomalous Li abundance in the atmospheres of these stars.
Lithium production by thermohaline mixing in low-mass, low-metallicity asymptotic giant branch stars
Authors: Stancliffe Richard J. , Angelou George C. , Lattanzio John C.
Published: April 2010

We examine the effects of thermohaline mixing on the composition of the envelopes of low-metallicity asymptotic giant branch (AGB) stars. We have evolved models of 1, 1.5 and 2M⊙ and of metallicity Z = 10−4 from the pre-main sequence to the end of the thermal pulsing asymptotic giant branch with thermohaline mixing applied throughout the simulations. We find that the small amount of 3He that remains after the first giant branch is enough to drive thermohaline mixing on the AGB and that the mixing is most efficient in the early thermal pulses, with the efficiency dropping from pulse to pulse. We note a surprising increase in the 7Li abundance, with log10ϵ(7Li) reaching values of over 2.5 in the 1.5M⊙ model. It is thus possible to get stars which are both C- and Li-rich at the same time. We compare our models to measurements of carbon and lithium in carbon-enhanced metal-poor stars which have not yet reached the giant branch. These models can simultaneously reproduced the observed C and Li abundances of carbon-enhanced metal-poor turn-off stars that are Li-rich.
Light elements in massive single and binary stars
Authors: Langer N. , Brott I. , Cantiello M. , de Mink S. E. , Izzard R. G. , Yoon S.-C.
Published: April 2010

We highlight the role of the light elements (Li, Be, B) in the evolution of massive single and binary stars, which is largely restricted to a diagnostic value, and foremost so for the element boron. However, we show that the boron surface abundance in massive early type stars contains key information about their foregoing evolution which is not obtainable otherwise. In particular, it allows to constrain internal mixing processes and potential previous mass transfer event for binary stars (even if the companion has disappeared). It may also help solving the mystery of the slowly rotating nitrogen-rich massive main sequence stars.
Boron depletion in 9 to 15 M⊙ stars with rotation
Authors: Frischknecht U. , Hirschi R. , Meynet G. , Ekström S. , Georgy C. , Rauscher T. , Winteler C. , Thielemann F.-K.
Published: April 2010

The treatment of mixing is still one of the major uncertainties in stellar evolution models. One open question is how well the prescriptions for rotational mixing describe the real effects. We tested the mixing prescriptions included in the Geneva stellar evolution code (GENEC) by following the evolution of surface abundances of light isotopes in massive stars, such as boron and nitrogen. We followed 9, 12 and 15 M⊙ models with rotation from the zero age main sequence up to the end of He burning. The calculations show the expected behaviour with faster depletion of boron for faster rotating stars and more massive stars. The mixing at the surface is more efficient than predicted by prescriptions used in other codes and reproduces the majority of observations very well. However two observed stars with strong boron depletion but no nitrogen enrichment still can not be explained and let the question open whether additional mixing processes are acting in these massive stars.
Li survey in giant stars : probing non-standard stellar physics
Authors: Lagarde N. , Charbonnel C. , Jasniewicz G. , North P. , Shetrone M. , Hollek J. , Smith V. V.
Published: April 2010

Lithium has long been known to be a good tracer of non-standard mixing processes occurring in stellar interiors. Here we present the results of a large survey aimed at determining the surface Li abundance in a sample of about 800 giant (RGB and AGB) stars with accurate Hipparcos parallaxes. We compare the observed Li behaviour with that predicted by stellar models including rotation and thermohaline mixing.
Theoretical stellar ΔY/ΔO in the early Universe
Authors: Ekström Sylvia , Meynet Georges , Maeder André , Chiappini Cristina , Georgy Cyril , Hirschi Raphael
Published: April 2010

Population III stars initiated the chemical enrichment of the Universe. Chemical evolution models seem to favour fast rotators among the very low-metallicity population. When a star rotates fast, it ejects significant quantities of He and its nucleosynthesic products are modified compared to the case without rotation. The value of ΔY/ΔO is explored from a theoretical point of view through stellar models of zero- or very low-metallicity.
Lithium, beryllium, and boron production in core-collapse supernovae
Authors: Nakamura Ko , Yoshida Takashi , Shigeyama Toshikazu , Kajino Toshitaka
Published: April 2010

Type Ic supernova (SN Ic) is the gravitational collapse of a massive star without H and He layers. It propels several solar masses of material to the typical velocity of 10,000 km/s, a very small fraction of the ejecta nearly to the speed of light. We investigate SNe Ic as production sites for the light elements Li, Be, and B, via the neutrino-process and spallations. As massive stars collapse, neutrinos are emitted in large numbers from the central remnants. Some of the neutrinos interact with nuclei in the exploding materials and mainly 7Li and 11B are produced. Subsequently, the ejected materials with very high energy impinge on the interstellar/circumstellar matter and spall into light elements. We find that the ν-process in the current SN Ic model produces a significant amount of 11B, consistent with observations if combined with B isotopes from the following spallation production.
Defining Nation and Religious Minorities in Russia and Turkey: A Comparative Analysis
Authors: Tasch Laman
Published: April 2010

Many countries today face the challenges posed by their ethnic and religious diversity. This article comparatively analyzes how defining nation in Russia and Turkey affects what groups constitute religious minorities and what their prospects of integration into the Russian and Turkish societies are. It conceptualizes religious minorities as those religious groups that are excluded from the prevailing and institutionalized definitions of nation. This article studies what role religion, comprising Orthodox Christianity, and Sunni Islam, respectively, has played historically and until nowadays in Russia and Turkey in the definitions of their national identities and what kind of religious minorities each of these definitions created. It argues that a position of religious minorities depends not only on the informal association of national identity of the majority with certain religion, but also on the institutionalized support for the dominant religion by the ruling political forces.
Birth weights smaller or larger than the placenta predict BMI and blood pressure at age 7 years
Authors: Misra D. P. , Salafia C. M. , Charles A. K. , Miller R. K.
Published: April 2010

We hypothesized that the altered placental proportions that influence birth weight affect childhood body proportions, and that these effects would be independent of birth weight. We also hypothesized that altered placental proportions might affect the fetal cardiovascular system, and may be reflected in variation in childhood blood pressure. By using linear regression with birth weight as the dependent variable, placental variables were entered as predictors. The predicted birth weights based on placental factors were then obtained. The ratio of the actual birth weight to that predicted by placental parameters (observed/expected ratio, OER) was used as the independent variable in analyses of age 7 year body mass index (BMI) and diastolic blood pressure (DBP) in the 15,902 singleton liveborns delivered between 34 and 43 weeks. The standardized residual birth weight was also used as a variable to examine the effects of birth weight that is not consistent with placental parameters. For each unit increase in the OER, BMI at 7 years increased 1 kg/m2 (P < 0.0001). The OER also had a significant effect on DBP (β = 4.52, P < 0.001) at 7 years of age but only among African-American children. Results for the standardized residual birth weight variable were consistent with the OER. All results were adjusted for gestational age, sex, socioeconomic status, African-American race and maternal pre-pregnancy BMI. Being larger or smaller than predicted by one’s placenta affects childhood body composition and blood pressure. The placental measurements provide insight into pathophysiological mechanisms of the developmental origins of adult disease.
Persönlichkeitsentwicklung im mittleren Erwachsenenalter
Authors: Lehmann Regula , Allemand Mathias , Zimprich Daniel , Martin Mike
Published: April 2010

Zusammenfassung. Die vorliegende Studie beschäftigt sich mit der Frage, ob sich die Persönlichkeit im mittleren Erwachsenenalter verändert. Mit Daten der Interdisziplinären Längsschnittstudie des Erwachsenenalters (ILSE) wurden die differenzielle Stabilität, Mittelwertsveränderungen und individuelle Veränderungen von Persönlichkeitseigenschaften zu drei Messzeitpunkten über einen Zeitraum von 12 Jahren untersucht. Die Stichprobe bestand aus 323 Erwachsenen mit einer Alterspanne von 42 bis 46 Jahren zu Beginn der Studie. Die Resultate weisen bei Neurotizismus und Extraversion auf kleine Mittelwertsveränderungen hin. Die längsschnittlichen Stabilitätskoeffizienten bewegten sich um den Wert .70, was auf eine hohe differenzielle Stabilität hinweist. Schließlich findet sich bei 67% der Erwachsenen mittleren Alters mindestens eine reliable Veränderung in einer Persönlichkeitsdimension innerhalb eines Messzeitraums. Insgesamt legen die längsschnittlichen Ergebnisse nahe, dass die Persönlichkeitsentwicklung im mittleren Erwachsenenalter sowohl von Stabilität auf der Populationsebene wie auch von Veränderung auf der individuellen Ebene gekennzeichnet ist.
Was muss man tun, um sicher die richtige Lösung zu finden?
Authors: Porsch Torsten , Bromme Rainer , Pollmeier Judith
Published: April 2010

Zusammenfassung. In der vorliegenden Arbeit wird untersucht, welche Wissensquellen GrundschülerInnen für die Lösung von Schulaufgaben in unterschiedlichen Fachkontexten präferieren. Dazu werden in einem experimentellen Design Aufgabenthema („Schwimmen und Sinken”, „Anordnen von Größen” und „Werte bestimmen”) und Fachdisziplin (Mathematik- oder Sachkundeunterricht) als Kontext des Präferenzurteils variiert. Kinder (N = 225) aus der Klassenstufe vier bewerteten für jeweils sechs Schulaufgaben ihre Präferenzen für acht Quellen des Wissens. Die Ergebnisse zeigen in den Präferenzen für Wissensquellen eine systematische Unterscheidung nach Aufgabenthemen und Fachkontexten. Die GrundschülerInnen haben eine klare Vorstellung davon, woher sie am liebsten Informationen bekommen wollen: Grundsätzlich bevorzugen sie für die Informationsgewinnung zur Bearbeitung der schulischen Aufgaben das eigene Handeln (Ausprobieren und Planen des Ausprobierens) und das eigenständige Rechnen im Kontrast zu externen Quellen (z.B. Buch, Lehrer, Internet). Außerdem sind die Präferenzen für externe Quellen im Kontext des Sachkundeunterrichts ausgeprägter als im Mathematikunterricht.
Lernverlaufsdiagnostik: Ein Ansatz zur längerfristigen Lernfortschrittsmessung
Authors: Strathmann Alfons M. , Klauer Karl Josef
Published: April 2010

Zusammenfassung. Am Beispiel des Rechnens in der Grundschule wird eine Weiterentwicklung des amerikanischen „Curriculum – based measurement” demonstriert. Ein ganzes Jahr lang erhalten 190 Kinder aus sieben Grundschulklassen und drei Sonderschulklassen alle zwei Wochen einen Rechentest. Bei den Tests handelt es sich um Zufallsstichproben aus Grundgesamtheiten von Aufgaben, die dem Lehrziel für jedes der Schuljahre entsprechend definiert sind. Für jedes Kind und jeden Termin wird eine eigene neue Zufallsstichprobe generiert, so dass kein Test zweimal gegeben wird, ein jeder aber die geforderte Fertigkeit kontentvalide erfasst. Solche Tests lassen sich als kriteriumsorientierte Binomialtests darstellen. Im vorliegenden Beitrag wird (1) das ursprüngliche Konzept und seine Weiterentwicklung kurz vorgestellt, (2) empirisch getestet, ob das neue Verfahren geeignet ist, von Klassenlehrern vertretbar eingesetzt zu werden, und (3) werden Ausblicke auf dringend erwünschte weiterführende Forschungen geboten. Die vorgelegten Daten erlauben, das Spektrum von Verläufen auf Klassen- wie Individualebene zu dokumentieren, aber auch, die Probleme und vielversprechenden Möglichkeiten des Ansatzes kritisch offen zu legen.
Rorschach Usefulness in Treatment Planning
Authors: Sendín Maria Concepcion
Published: April 2010

To achieve a therapeutic design, we should examine three main information sources: clinical history, Rorschach test, and the subject’s communication style during the diagnostic interviews. We should study people from the perspective of their individuality and always consider groups of data, not isolated elements. Professionals should do this task by examining five basic areas: explicit symptoms, strong and weak points, motivation level, definition of short-term and long-term objectives, and available therapeutic approaches. Clinical vignettes from two different Rorschach protocols, Case 1, a 25-year-old man, and Case 2, a 30-year-old woman, are included in this article.
The Encounter with the Unfamiliar
Authors: Peterson Charles A.
Published: April 2010

Some patients and some Rorschachers pay insufficient attention to the rich and variegated world of the Rorschach stimuli. The Rorschach stimuli have been either ignored or miscast as blank screens or receptive x-ray film, as unstructured or ambiguous, when they are best described as unfamiliar. Examiner unfamiliarity – in fact, ignorance about the stimuli – is unacceptable, since testing is an encounter between the known (what we know about the test stimuli) and the unknown (what we want to know about the patient’s personality). The more that is known about the stimuli, the more that is potentially knowable about the patient. Greater attention to the test stimuli may enrich the interpretive yield of the Comprehensive System, the use of which is the bedrock of reliable and valid Rorschach interpretation. Hoping to encourage more attention to the contribution of the stimulus factors to the response, I explore here various perceptual dimensions of the inkblots, occasionally illustrating them with clinical examples. Finally, I propose various “exercises” to heighten examiner familiarity with the “unfamiliar” Rorschach stimuli.
Increasing anthropogenic nitrogen inputs and riverine DIN exports from the Changjiang River basin under changing human pressures
Authors: Yan Weijin , Mayorga Emilio , Li Xinyan , Seitzinger Sybil P. , Bouwman A. F.
Published: April 2010

In this paper, we estimate the inputs of nitrogen (N) and exports of dissolved inorganic nitrogen (DIN) from the Changjiang River to the estuary for the period 1970–2003, by using the global NEWS‐DIN model. Modeled DIN yields range from 260 kg N km−2 yr−1 in 1970 to 895 kg N km−2 yr−1 in 2003, with an increasing trend. The study demonstrated a varied contribution of different N inputs to river DIN yields during the period 1970–2003. Chemical fertilizer and manure together contributed about half of the river DIN yields, while atmospheric N deposition contributed an average of 21% of DIN yields in the period 1970–2003. Biological N fixation contributed 40% of DIN yields in 1970, but substantially decreased to 13% in 2003. Point sewage N input also showed a decreasing trend in contribution to DIN yields, with an average of 8% over the whole period. We also discuss possible future trajectories of DIN export based on the Global NEWS implementation of the Millennium Ecosystem Assessment scenarios. Our result indicates that anthropogenically enhanced N inputs dominate and will continue to dominate river DIN yields under changing human pressures in the basin. Therefore, nitrogen pollution is and will continue to be a great challenge to China.
Excess volatiles supplied by mingling of mafic magma at an andesite arc volcano
Authors: Edmonds M. , Aiuppa A. , Humphreys M. , Moretti R. , Giudice G. , Martin R. S. , Herd R. A. , Christopher T.
Published: April 2010

We present the results of a study of volcanic gases at Soufrière Hills Volcano, Montserrat, which includes the first spectroscopic measurements of the major gas species CO2 and H2S at this volcano using a Multisensor Gas Analyzer System (MultiGAS) sensor. The fluxes of CO2 and H2S were 640–2750 t/d and 84–266 t/d, respectively, during July 2008, during a prolonged eruptive pause. The flux of CO2 is similar to estimates for the entire arc from previous geochemical studies, while the measured H2S flux significantly alters our interpretation of the sulphur budget for this volcano. The fluxes of both sulphur and carbon show considerable excesses over that which can be supplied by degassing of erupted magma. We demonstrate, using thermodynamic models and published constraints on preeruptive volatile concentrations, that the gas composition and fluxes are best modeled by mixing between (1) gases derived from isobaric quenching of mafic magma against cooler andesite magma at depth and (2) gases derived from shallower rhyolitic interstitial melt within the porpyritic andesite. The escape of deep‐derived gases requires pervasive permeability or vapor advection extending to several kilometers depth in the conduit and magma storage system. These results provide more compelling evidence for both the contribution of unerupted mafic magma to the volatile budget of this andesitic arc volcano and the importance of the intruding mafic magma in sustaining the eruption. From a broader perspective, this study illustrates the importance and role of underplating mafic magmas in arc settings. These magmas play an important role in triggering and sustaining eruptions and contribute in a highly significant way to the volatile budget of arc volcanoes.
How crack porosity and shape control seismic velocities in the upper oceanic crust: Modeling downhole logs from Holes 504B and 1256D
Authors: Carlson R. L.
Published: April 2010

Mounting evidence from Holes 504B and 1256D suggests that porosity is the principal factor affecting velocities in the upper oceanic crust. Spheroidal inclusion and asperity compression models based on reprocessed sonic velocity logs and apparent fractional porosities estimated from deep resistivity logs reveal how both porosity and the geometry of the pore space affect seismic velocities in Layer 2. Models that best match the data indicate the following: First, there are three populations of cracks in Hole 504B; most of the transition zone and the dike section are populated by low concentrations of weak cracks, while the upper part of the transition zone and the extrusive pile contain a higher concentration of stiffer cracks. Similarly, the deepest part of the dike section in Hole 1256D can be modeled by a dilute concentration of thin or weak cracks, while the overlying dikes, the transition zone, and the extrusive pile contain a higher concentration of stiffer cracks. Second, in a striking confirmation that porosity controls velocities throughout Layer 2, 90% or more of the variance of sonic velocities logged at both sites is explained by porosity in these models, while third, the effect of pressure on the variation of sonic velocity is essentially negligible. Fourth, while there is no direct correlation between crack populations and igneous lithostratigraphy, some changes of crack population do correspond to metamorphic transitions, and fifth, velocities typical of Layer 3 are reached when the porosity falls to low values (0.2% in Hole 1256D and 0.6% in Hole 504B).
State of stress in slabs as a function of large‐scale plate kinematics
Authors: Carminati Eugenio , Petricca Patrizio
Published: April 2010

The state of stress of slabs subducting worldwide, as revealed by seismicity, is extremely variable both with depth and between different subduction zones. Although in principle, slab pull should enhance downdip extension in the slab, the reconstructed stress fields for intermediate depths (between 100 and 300 km) range from downdip compression to downdip extension. Using 2‐D viscoelastic plane strain models we investigate the dependency of the stress field of slabs on geometry (dip of the slab) and kinematics (velocity of convergence between upper and lower plates and their absolute velocity with respect to the underlying mantle) of subduction zones. We conclude that although the state of stress in slabs is also controlled by other processes, downdip compression in the subducting slab is enhanced by mantle flow opposing the direction of the dip of the slab, whereas downdip extension is favored by mantle flow in the same direction of the slab dip (i.e., sustaining it). These predictions are in agreement with available geophysical observations, although exceptions to this simple pattern are observed worldwide. In addition, if the slab is decoupled from the upper plate, convergence between upper and lower plates induces a downdip compressional component of stress within the slab, decreasing the magnitude of extension in models characterized by mantle flow sustaining the slab and increasing compression in models with mantle flow opposing subduction. However, these are second‐order variations when compared to the control exerted by absolute plate kinematics and by the magnitude of slab pull. Sensitivity analysis of rheological parameters allows us to conclude that these results are generally consistent, although low values of viscosity of the lithospheric mantle render this prediction less stable.
Strain heterogeneity in deformed Carrara marble using a microscale strain mapping technique
Authors: Xu Lili , Evans Brian
Published: April 2010

Using high‐resolution surface imaging and a split‐cylinder technique, we mapped the strain heterogeneity in Carrara marble samples deformed to bulk strains <25%, under conventional triaxial loading, at 400–700°C, 300 MPa confining pressure, and strain rates of 10−4 to 10−5 s−1. To map strain, we deposited grid markers on the polished surface of a half cylinder, performed mechanical tests on composites of two half cylinders, compared the positions of each marker in undeformed and deformed samples, and computed the spatial distribution of strain. Strains over the scale of a few microns varied by as much as 300%. Localized deformation occurred along twins and grain boundaries but was also present as patches in intragranular regions. The heterogeneity is more pronounced at scales smaller than grains, but the strain averaged over individual grains also varied by 50%. After deformation, the crystallographic orientation of individual grains relative to the compression direction was measured by electron backscattered diffraction. Inverse pole figures of the aggregate lattice‐preferred orientation (LPO) have a maximum near e(018) and are consistent with previous studies. The observed LPO is qualitatively consistent with that produced by simulations using a simple viscoplastic self‐consistent (VPSC) code that did not include mechanisms other than slip or twinning. The qualitative comparison of observed and simulated LPO was not sensitive to the model for the crystallographic resolved shear stresses for slip. However, the VPSC simulation was ineffective in predicting individual grain rotations.
On the influence of gravel bed dynamics on velocity power spectra
Authors: Singh Arvind , Porté‐Agel Fernando , Foufoula‐Georgiou Efi
Published: April 2010

A series of flume experiments were conducted to study the effect of bed form dynamics on the flow over a gravel bed comprising a wide distribution of grain sizes. Instantaneous high‐frequency streamwise flow velocities were sampled using an acoustic Doppler velocimeter at a frequency of 200 Hz, while the simultaneous bed elevations were sampled using sonar transducers at a frequency of 0.2 Hz for a duration of 20 h. Spectral analysis of the measured velocity fluctuations reveals the existence of two distinct power law scaling regimes. At high frequencies, an inertial subrange of turbulence with ∼−5/3 Kolmogorov scaling is observed. At low frequencies, another scaling regime with spectral slope of about −1.1 is found. We interpret this range as the signature of the evolving multiscale bed topography on the near‐bed velocity fluctuations. The two scaling ranges are separated by a spectral gap, i.e., a range of intermediate scales with no additional energy contribution. The high‐frequency limit of the spectral gap corresponds to the integral scale of turbulence. The low‐frequency end of the gap corresponds to the scale of the smallest bed forms identified by the velocity sensor, which depends on the position of the sensor. Our results also show that the temporal scales of the largest bed forms can be potentially identified from spectral analysis of low‐resolution velocity measurements collected near the channel bed.
Unique Baltic Outcrops Reveal Millennia of Ecological Changes
Authors: Buynevich Ilya V. , Bitinas Albertas , Damušytė Aldena , Pupienis Donatas
Published: April 2010

Throughout Earth's history, tectonic forces, often violent and unpredictable, have been responsible for exposing geological formations to scientific scrutiny. But forces of uplift are not restricted to plate boundaries. For example, when looking at forested coastal dunes bordering placid Curonian Lagoon along the Lithuanian coast of the Baltic Sea, one hardly suspects that any powerful forces are at work. Yet this is a site where massive migrating hills of sand have put pressure on the deep strata of the ancient lagoon, forcing its sediments to the surface and offering rare access to fossils of the Holocene, which spans the past 10,000 years.
Promoting China‐U.S. Collaboration on Soil and Water Resources: China‐U.S. Workshop on Sustainable Management of Soil and Water Resources; Shenyang, China, 5–8 January 2010
Authors: Zhang Xu‐Dong , Parker Jack
Published: April 2010

Population growth and rapid urbanization in China have intensified competition for land use, with consequences for agricultural productivity, water use allocation, and soil and water quality. Sustainable management and effective remediation technologies are needed in all regions of China. Similar problems exist in the United States, due, for example, to urban sprawl and pressures to increase biofuel production driven by government subsidy programs. As globally dominant contributors to greenhouse gas emissions, China and the United States also have a mutual interest in understanding their consequences.

To discuss current research on soil and water resource sustainability issues and to promote bilateral collaboration in research and graduate education between U.S. and Chinese institutions, a workshop was hosted by the Chinese Academy of Sciences (CAS) Institute of Applied Ecology.
AGU Journals Among Most Cited Publications in Climate Change Research
Authors: Sears Jon
Published: April 2010

Geophysical Research Letters (GRL) and Journal of Geophysical Research‐Atmospheres (JGR‐D) both ranked among the top 10 of the most highly cited research publications on climate change over the past decade in a recent analysis by sciencewatch.com, an Internet tool published by the Thomson Reuters Web of Science® that tracks trends and performances in basic research. Although Nature and Science—the multidisciplinary heavyweights—led the field, GRL ranked fifth and JGR‐D ranked sixth.

The study was conducted by searching the Web of Science® database for terms such as “global warming,” “climate change,” “human impact,” and other key phrases in journal articles published and cited between 1999 and the spring of 2009. The analysis produced over 28,000 papers, from which sciencewatch.com identified the most cited institutions, authors, and journals.
Independent review slated for climate change panel
Authors: Showstack Randy
Published: April 2010

The InterAcademy Council (IAC) has agreed to conduct an independent review of the processes and procedures followed by the Intergovernmental Panel on Climate Change (IPCC) in preparing its assessment reports. The review was requested by IPCC chair Rajendra Pachauri and United Nations secretary general Ban Ki‐moon following some criticism of IPCC, including the inclusion in IPCC's Fourth Assessment Report (AR4) of non‐peer‐reviewed information about the disappearance of Himalaya glaciers.

At a 10 March briefing, Ban noted that there were “a very small number of errors” in AR4 and that the IPCC process needs to ensure “full transparency, accuracy, and objectivity, and minimize the potential for any errors going forward.” Ban added, “The threat posed by climate change is real. Nothing that has been alleged or revealed in the media recently alters the fundamental scientific consensus on climate change, nor does it diminish the unique importance of the IPCC work.”
A Fool's Errand: How Not to Conduct a Research Solicitation
Authors: Schwartz Stephen E.
Published: April 2010

In early December 2009, I participated in a panel review of proposals submitted to the U.S. Department of Energy's Atmospheric System Research Program in response to a call for proposals from early‐career investigators. Fourteen panel members, each of whom had reviewed four to eight proposals, spent a day discussing and evaluating 28 proposals. Yet all was not what it had seemed.

Early‐career research awards, which fund scientists for 5 years at approximately US$150,000 per year, are highly sought by tenure‐track investigators because they provide support for an extended period of time and serve to move young scientists forward in their careers. The concept of such a program is thus much to be lauded. The particular call for proposals for which I served as a reviewer was undertaken as part of the American Recovery and Reinvestment Act, with the objective of promoting useful governmental activity while stimulating the economy.
Ecohydrologists Ponder the Implications of a Rapidly Changing Planet: AGU Chapman Conference: Examining Ecohydrological Feedbacks of Landscape Change Along Elevation Gradients in Semiarid Regions; Sun Valley, Idaho, 5–8 October 2009
Authors: Wilcox Bradford P. , Seyfried Mark S.
Published: April 2010

Unprecedented and complex changes are occurring in semiarid regions in the United States and across the globe. These changes include massive die‐offs of trees, invasion by non‐native species, altered fire regimes, woody plant encroachment, and desertification. All of these changes affect how water moves and is allocated in these landscapes, which in turn affects ecological interactions. The feedbacks and interactions between the drivers of change and the responses to change are exceedingly complex. An AGU Chapman Conference was held in Idaho to examine the ecohydrological feedbacks of landscape change along elevation and precipitation gradients in semiarid regions. The conference drew more than 100 participants, including many students and early‐career scientists.
Jian Receives 2009 F. L. Scarf Award
Authors: Anonymous
Published: April 2010

Lan Jian has been awarded the AGU F. L. Scarf Award, given annually to recent Ph.D recipients for outstanding dissertation research that contributes directly to solar planetary sciences. Jian's thesis is entitled “Radial evolution of large‐scale solar wind structures.” She was formally presented with the award at the Space Physics and Aeronomy section dinner during the 2009 AGU Fall Meeting, held 14–18 December in San Francisco, Calif.

Lan Jian received her B.S. in geophysics from University of Science and Technology of China in 2003. She received her M.S. and Ph.D. degrees in geophysics and space physics, under the supervision of Christopher T. Russell, at University of California, Los Angeles in 2006 and 2008, respectively.
Vertical heat flux and lateral mass transport in nonlinear internal waves
Authors: Shroyer E. L. , Moum J. N. , Nash J. D.
Published: April 2010

Comprehensive observations of velocity, density, and turbulent dissipation permit quantification of the nonlinear internal wave (NLIW) contribution to vertical heat flux and lateral mass transport over New Jersey's shelf. The effect of NLIWs on the shelf heat budget was significant. On average, heat flux in NLIWs was 10 times larger than background at the pycnocline depth. NLIWs were present at midshelf <10% of the time, yet we estimate that they contributed roughly one−half the heat flux across the pycnocline during the observation period, which was characterized by weak to moderate winds. Lateral transport distances due to the leading 3 waves in NLIW packets were typically (100 m) but ranged several kilometers. The month‐averaged daily onshore transport (per unit alongshelf dimension) by NLIWs is estimated as 0.3 m2s−1. This is comparable to a weak downwelling wind, but sustained over an entire month.
Destabilizing effect of compressibility on Rayleigh–Taylor instability for fluids with fixed density profile
Authors: Xue Chuang , Ye Wenhua
Published: April 2010

Analytical solutions for the growth rate of the Rayleigh–Taylor instability (RTI) for two superimposed fluids of exponentially varying densities are obtained by variational approach, which has been introduced to solve the eigenvalue problems related to RTI for inviscid compressible fluid. In order to distinguish the effect of density profile from compressibility effects, two independent parameters have been introduced to describe the static fluid states, one (Pa) is for the variation of pressure near the interface and the other (Pb) for setting the density profile. Three factors related to the RTI growth for compressible fluids have been discussed in detail. For incompressible fluids, the only factor to affect the RTI growth is the density profile. While for compressible fluids, besides the density profile, the specific heat ratio and the interface pressure also contribute to the growth rate of RTI. Analytic dispersion relations and growth rates have been compared to numerical results. It is found that compressibility alone acts a destabilizing role for fluids with fixed density profile.
High tunability mixed order photonic crystal
Authors: Dorjgotov Enkh-Amgalan , Bhowmik Achintya K. , Bos Philip J.
Published: April 2010

We propose a design for high tunability one-dimensional photonic-crystal which consists of alternating layers of isotropic material and liquid crystal layers. Numerical models confirm the tunability over the visible region ranging from 480 to 560 nm for a mixed order device using a material birefringence of 0.3, and to 620 nm if a birefringence of 0.6 is allowed. Modeled devices having active layers with mλ/4 and passive layers with nλ/4 thickness for the case of m and n odd integers are presented. The advantage of m>n is shown to be greater tunability for a given free spectral range.
Vibrating coil magnetometer for milli-Kelvin temperatures
Authors: Legl S. , Pfleiderer C. , Krämer K.
Published: April 2010

We report the development of a vibrating coil magnetometer (VCM) as combined with a top-loading dilution refrigerator for measurements of the magnetization down to millikelvin temperatures. The VCM offers unique measurement conditions, notably efficient cooling of the sample, data collection in uniform magnetic fields, the possibility to study strong magnetic anisotropies, fast data collection over a very wide range of magnetic fields, and the possibility of fast sample changes. In first measurements of the dipolar Ising magnet LiHoF4 we readily achieved an excellent long-term stability of the vibration drive system of the VCM providing a sensitivity in excess of 10−4 emu.
Code-division SQUID multiplexing
Authors: Niemack M. D. , Beyer J. , Cho H. M. , Doriese W. B. , Hilton G. C. , Irwin K. D. , Reintsema C. D. , Schmidt D. R. , Ullom J. N. , Vale L. R.
Published: April 2010

Multiplexed superconducting quantum interference device (SQUID) readout systems are critical for measuring large arrays of superconducting transition-edge sensors (TES). We demonstrate a code-division SQUID multiplexing (CDM) architecture that is modulated by Walsh codes. Measurements and simulations of a prototype multiplexer show that this modulation scheme is not degraded by SQUID-noise aliasing, suppresses parasitic pickup, and has low levels of crosstalk. These properties enable this architecture to scale to large TES arrays. Furthermore, CDM modulation suppresses the 1/f knee in the noise to below 20 mHz, suggesting the use of this circuit for low-frequency-noise mitigation in more general SQUID applications.
High-pressure phase transitions and compressibility of wolframite-type tungstates
Authors: Ruiz-Fuertes J. , López-Moreno S. , Errandonea D. , Pellicer-Porres J. , Lacomba-Perales R. , Segura A. , Rodríguez-Hernández P. , Muñoz A. , Romero A. H. , González J.
Published: April 2010

This paper reports an investigation on the phase diagram and compressibility of wolframite-type tungstates by means of x-ray powder diffraction and absorption in a diamond-anvil cell and ab initio calculations. X-ray diffraction experiments show that monoclinic wolframite-type MgWO4 suffers at least two phase transitions, the first one being to a triclinic polymorph with a structure similar to that of CuWO4 and FeMoO4-II. The onset of each transition is detected at 17.1 and 31 GPa. In ZnWO4 the onset of the monoclinic-triclinic transition has been also found at 16.7 GPa. This transition does not involve any change in the atomic coordination as confirmed by x-ray absorption measurements. These findings are supported by density-functional theory calculations, which predict the occurrence of additional transitions upon further compression. Calculations have been also performed for wolframite-type MnWO4, which is found to have an antiferromagnetic configuration. In addition, our study reveals details of the local-atomic compression in MgWO4 and ZnWO4. In particular, below the transition pressure the ZnO6 and equivalent polyhedra tend to become more regular, whereas, the WO6 octahedra remain almost unchanged. Fitting the pressure-volume data we obtained the equation of state for the low-pressure phase of MgWO4 and ZnWO4. These and previous results on MnWO4 and CdWO4 are compared with the calculations. The compressibility of wolframite-type tungstates is also systematically discussed. Finally Raman spectroscopy measurements and lattice dynamics calculations are presented for MgWO4.