bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustical cues and grammatical units in speech to two preverbal infants
Authors: SODERSTROM MELANIE , BLOSSOM MEGAN , FOYGEL RINA , MORGAN JAMES L.
Published: October 2008

The current study examines the syntactic and prosodic characteristics of the maternal speech to two infants between six and ten months. Consistent with previous work, we find infant-directed speech to be characterized by generally short utterances, isolated words and phrases, and large numbers of questions, but longer utterances are also found. Prosodic information provides cues to grammatical units not only at utterance boundaries, but also at utterance-internal clause boundaries. Subject–verb phrase boundaries in questions also show reliable prosodic cues, although those of declaratives do not. Prosodic information may thus play an important role in providing preverbal infants with information about the grammatically relevant word groupings. Furthermore, questions may play an important role in infants' discovery of verb phrases in English.
The psycholinguistics of developing text construction
Authors: BERMAN RUTH A.
Published: October 2008

This paper outlines functionally motivated quantifiable criteria for characterizing different facets of discourse – global-level principles, categories of referential content, clause-linking complex syntax, local linguistic expression and overall discourse stance – in relation to the variables of development, genre and modality. Concern is with later, school-age language development, in the conviction that the long developmental route of language acquisition can profitably be examined in the context of extended discourse. Findings are reviewed from a cross-linguistic project that elicited narrative and expository texts in both speech and writing at four age groups: (9–10 years, 12–13, 16–17 and adults). Clear developmental patterns emerge from middle childhood to adulthood, with significant shifts in adolescence; global-level text organization is mastered earlier in narratives than in expository essays, but the latter promote more advanced use of local-level lexicon and syntax; and spoken texts are more spread out than their denser written counterparts in clause-linkage, referential content and lexical usage. These and other findings are discussed in terms of the growth and reorganization of knowledge about types of discourse and text-embedded language use.
The role of evidentiality in Bulgarian children's reliability judgments
Authors: FITNEVA STANKA A.
Published: October 2008

Evidentials are grammatical source-of-knowledge markers. In Bulgarian they provide information about authorship – whether the speaker has personally acquired the information or not – and modality – whether perceptual or cognitive mechanisms were involved in the information's generation. In two experiments, Bulgarian kindergarteners and third-graders (ages 6 and 9,N=96) had to decide which one of two utterances containing different evidentials to believe. Experiment 1 showed that children draw on modality information in their decisions: Third-graders favored perceptual over cognitive and kindergartners cognitive over perceptual sources. Experiment 2 showed that third-graders can also draw on the authorship information carried by evidentials: they favored first- over second-hand information. The discussion focuses on understanding the development of children's use of evidentials.
Audiovisual speech recalibration in children*
Authors: VAN LINDEN SABINE , VROOMEN JEAN
Published: October 2008

In order to examine whether children adjust their phonetic speech categories, children of two age groups, five-year-olds and eight-year-olds, were exposed to a video of a face saying /aba/ or /ada/ accompanied by an auditory ambiguous speech sound halfway between /b/ and /d/. The effect of exposure to these audiovisual stimuli was measured on subsequently delivered auditory-only speech identification trials. Results were compared to a control condition in which the audiovisual exposure stimuli contained non-ambiguous and congruent sounds /aba/ or /ada/. The older children learned to categorize the initially ambiguous speech sound in accord with the previously seen lip-read information (i.e. recalibration), but this was not the case for the younger age group. Moreover, all children displayed a tendency to report the stimulus that they were exposed to during the exposure phase. Methodological improvements for adjusting such a response bias are discussed.
Theory and applications of subtyping: Introduction
Authors: COMPAGNONI ADRIANA , GOGUEN HEALFDENE
Published: October 2008

This special issue of Mathematical Structures in Computer Science is devoted to recent work in subtyping. When subtyping was first proposed, it presented a new vehicle for understanding programming languages, together with challenging theoretical issues. The papers in this special issue include a new approach to the decidability of subtyping, a metatheoretic investigation of transitivity of coercive subtyping for parametrised dependent types, and applications of subtyping to the classic programming language concerns of flow analysis and typing for distributed systems. We believe that the scope of the papers demonstrates convincingly that the theory and practice of subtyping continue to be extended in novel and interesting ways.
Structural subtyping for inductive types with functorial equality rules
Authors: LUO ZHAOHUI , ADAMS ROBIN
Published: October 2008

In this paper we study subtyping for inductive types in dependent type theories in the framework of coercive subtyping. General structural subtyping rules for parameterised inductive types are formulated based on the notion of inductive schemata. Certain extensional equality rules play an important role in proving some of the crucial properties of the type system with these subtyping rules. In particular, it is shown that the structural subtyping rules are coherent and that transitivity is admissible in the presence of the functorial rules of computational equality.
Type-based flow analysis and context-free language reachability
Authors: FÄHNDRICH MANUEL , REHOF JAKOB
Published: October 2008

We present a novel approach to computing the context-sensitive flow of values through procedures and data structures. Our approach combines and extends techniques from two seemingly disparate areas: polymorphic subtyping and interprocedural dataflow analysis based on context-free language reachability. The resulting technique offers several advantages over previous approaches: it works directly on higher-order programs; provides demand-driven interprocedural queries; and improves the asymptotic complexity of a known algorithm based on polymorphic subtyping fromO(n8) toO(n3) for computing all queries. For intra-procedural flow restricted to equivalence classes, our algorithm yields linear inter-procedural flow queries.
Individual Displacements in Hashing with Coalesced Chains
Authors: JANSON SVANTE
Published: October 2008

We study the asymptotic distribution of the displacements in hashing with coalesced chains, for both late-insertion and early-insertion. Asymptotic formulas for means and variances follow. The method uses Poissonization and some stochastic calculus.
Dobrushin Conditions and Systematic Scan
Authors: DYER MARTIN , GOLDBERG LESLIE ANN , JERRUM MARK
Published: October 2008

We consider Glauber dynamics on finite spin systems. The mixing time of Glauber dynamics can be bounded in terms of the influences of sites on each other. We consider three parameters bounding these influences: α, the total influence on a site, as studied by Dobrushin; α′, the total influence of a site, as studied by Dobrushin and Shlosman; and α″, the total influence of a site in any given context, which is related to the path-coupling method of Bubley and Dyer. It is known that if any of these parameters is less than 1 then random-update Glauber dynamics (in which a randomly chosen site is updated at each step) is rapidly mixing. It is also known that the Dobrushin condition α < 1 implies that systematic-scan Glauber dynamics (in which sites are updated in a deterministic order) is rapidly mixing. This paper studies two related issues, primarily in the context of systematic scan: (1) the relationship between the parameters α, α′ and α″, and (2) the relationship between proofs of rapid mixing using Dobrushin uniqueness (which typically use analysis techniques) and proofs of rapid mixing using path coupling. We use matrix balancing to show that the Dobrushin–Shlosman condition α′ < 1 implies rapid mixing of systematic scan. An interesting question is whether the rapid mixing results for scan can be extended to the α = 1 or α′ = 1 case. We give positive results for the rapid mixing of systematic scan for certain α = 1 cases. As an application, we show rapid mixing of systematic scan (for any scan order) for heat-bath Glauber dynamics for properq-colourings of a degree-Δ graphGwhenq≥ 2Δ.
America's first monetary policy: inflation and seigniorage during the Revolutionary War
Authors: Baack Ben
Published: October 2008

This examination of America's original monetary policy as implemented by the Continental Congress during the Revolutionary War finds that the extreme inflation experienced during the war resulted from a policy designed to circumvent a free-rider problem institutionalised by the Articles of Confederation, and that war news played a critical role in the behaviour of the money base over time. Furthermore, despite the extreme inflation, the inflation tax that accrued to Congress remained on the left side of the Laffer curve.
The secondary market for bank shares in nineteenth-century Britain
Authors: Acheson Graeme G. , Turner John D.
Published: October 2008

Stock transferability and liquidity are viewed as vital characteristics of capital markets. Surprisingly, we know very little about the level of trading activity on, and liquidity of the market for, company stock during the rapid growth of the British capital market in the nineteenth century. This article attempts to shed some light on this important issue by examining the market for bank shares using trading data collected from bank archives. Our evidence suggests that trading activity and liquidity changed imperceptibly over the century. We also find that ownership structure is a major determinant of trading activity and liquidity; whereas shareholder liability regimes don't appear to affect liquidity.
Central banking in nineteenth-century Belgium: was the NBB a lender of last resort?
Authors: Buyst Erik , Maes Ivo
Published: October 2008

The creation of the National Bank of Belgium (NBB) in 1850 marked a fundamental reform of the Belgian financial system. It clearly aimed at rendering the financial system more crisis resistant, especially by restricting the leverage of the banking sector. The NBB, which received the privilege to issue banknotes, was subject to strict rules to grant only short-term credit against collateral. The NBB took up a key role in maintaining monetary stability, especially by safeguarding the convertibility of banknotes. The NBB also took part in certain rescue operations of financial institutions. However, this was mostly on explicit demand from the finance minister and for crises concerning discount banks. It would then be an exaggeration to consider it as a lender of last resort, in the sense of taking responsibility for the stability of the financial system. This should be no surprise, given the limitations imposed by its statutes, especially the limitation to short-term credits and the strict rules on collateral, the role of the profit motive in its commercial activities and the priority for safeguarding the convertibility of banknotes.
Free banking and bank entry in nineteenth-century New York
Authors: Bodenhorn Howard
Published: October 2008

Previous studies of entry under New York's free banking law of 1838 have generated conflicting results. This article shows that different measures of entry lead to different conclusions about the competitive effects of the law. Measured by the entry of new banks, New York's free banking law led to increased rates of entry relative to other states. Free banking did not, however, lead to significant increases in capital accumulation in the industry. This paradoxical outcome resulted from the regulatory features of free banking, especially the bond security feature, which reduced profitability and incentives to invest in banking.
LEOPOLD RANKE'S ARCHIVAL TURN: LOCATION AND EVIDENCE IN MODERN HISTORIOGRAPHY
Authors: ESKILDSEN KASPER RISBJERG
Published: October 2008

From 1827 to 1831 the German historian Leopold von Ranke travelled through Germany, Austria, and Italy, hunting for documents and archives. During this journey Ranke developed a new model for historical research that transformed the archive into the most important site for the production of historical knowledge. Within the archive, Ranke claimed, the trained historian could forget his personal predispositions and political loyalties, and write objective history. This essay critically examines Ranke's model for historical research through a study of the obstacles, frustrations, and joys that he encountered on his journey. It shows how Ranke's archival experiences inspired him to re-evaluate his own identity as a historian and as a human being, and investigates some of the affiliations between his model for historical research and the political realities of Prince Metternich's European order. Finally, the essay compares Ranke's historical discipline to other nineteenth-century disciplines, such as anthropology and archaeology.
THE WILL TO BEHOLD: THORSTEIN VEBLEN'S PRAGMATIC AESTHETICS
Authors: THRONTVEIT TRYGVE
Published: October 2008

No philistine, Thorstein Veblen thought humankind's innate impulse to imbue experience with aesthetic unity advanced all knowledge, and that the most beautiful objects, ideas, and actions met a standard of communal benefit reflecting humanity's naturally selected sociability. Though German idealism was an early influence, it clashed with Veblen's historicist critique of Western institutions, and it was William James's psychology that refined his ideas into a coherent aesthetics with ethical and political applications, by clarifying how instinct, habit, and environment could interact to institutionalize standards of beauty subverting the native altruism of the aesthetic impulse. Over years of association with John Dewey, Veblen concluded that a redeemed and reflective will to behold and create beauty in and through selfless activity could advance a more efficient and egalitarian society, and that humans cooperatively shaping their environments for the common good could approximate the German tradition's ideal of harmonizing personal freedom and external reality.
THE ORWELL CENTURY AND AFTER: RETHINKING RECEPTION AND REPUTATION
Authors: VANINSKAYA ANNA
Published: October 2008

The Orwell centenary of 2003 has come and gone, but the pace of academic publications that usually accompany such biographical milestones has not slackened. The Cambridge Companion to George Orwell was released in summer 2007, John Rodden's Every Intellectual's Big Brother: George Orwell's Literary Siblings was published in 2006, On Nineteen Eighty-Four: Orwell and Our Future, the proceedings of a 1999 conference, came out in 2005. The striking thing about many of these publications, not to mention the ones which emerged out of the commemorative activities of 2003 itself, is that they are more concerned with Orwell's reputation and relevance today than with his oeuvre as such. As many as five chapters of the Cambridge Companion have a “posthumous” focus; the proceedings of the largest centenary conference, George Orwell: Into the Twenty-First Century, raise the issue of Orwell and the war in Iraq more frequently than that of Orwell and World War II.The latter is not entirely surprising for an American conference which featured the “liberal hawk” and former Trotskyist journalist Christopher Hitchens as the keynote speaker, and whose proceedings were edited in accordance with a corresponding political agenda, but it is also indicative of a larger phenomenon, a phenomenon most thoroughly examined by John Rodden in books like George Orwell: The Politics of Literary Reputation and Scenes from an Afterlife: The Legacy of George Orwell. Few imaginative writers have been so compulsively remoulded, coopted, and invoked outside of their proper literary sphere; as Rodden's scrupulous documentation shows, no modern crisis from the Cold War to the war on terror has gone by without an Orwell headline to define it. What, one may ask, are the mechanisms behind this astounding popularity? How are reputations on this vast scale made? Looking at “the writer and his work” will only get one so far; one must also look outward, for the world's perception of Orwell is as interesting and intriguing a subject as Orwell himself. Rodden, the most prolific Orwell critic publishing today, has made this reception history his focus.
MILTON, LOCKE AND THE NEW HISTORY OF TOLERATION
Authors: COFFEY JOHN
Published: October 2008

For three centuries now, John Milton and John Locke have been hailed as heroic advocates of religious freedom. Securely ensconced in the pantheon of liberal icons, they continue to be enlisted in the cause of liberty. In the wake of 9/11, a number of writers have retold the tale of how enlightened progressives rescued the West from the forces of theocratic repression. Milton and Locke loom large in that story. They have starring roles in Perez Zagorin's study ofHow the Idea of Religious Toleration Came to the West(2003), and they feature prominently as “two champions of liberty” in the philosopher A. C. Grayling's bookTowards the Light: The Story of the Struggles for Liberty and Rights that Made the Modern West(2007). Whig history is not dead yet. Indeed, Grayling is refreshingly honest about his old-fashioned liberalism—in the British edition, his book's dust jacket is laid out like the title page of a nineteenth-century pamphlet: “By Mr. A. C. Grayling. London. Printed in the Year 2007”.
EDITING HUME'S TREATISE
Authors: HARRIS JAMES A.
Published: October 2008

In 1975 the Clarendon Press at Oxford published Peter Nidditch's edition of John Locke's An Essay concerning Human Understanding. In his Introduction Nidditch says that his edition “offers a text that is directly derived, without modernization, from the early published versions; it notes the provenance of all its adopted readings (some of which are new, correcting long-established errors); and it aims at recording all relevant differences between these versions”. As Nidditch goes on to acknowledge, the “relevant differences” were many, “requiring several thousand registrations both in the case of material variants (deletions, additions, or changes of wording) and in the case of formal variants (changes of punctuation, parentheses, italics, etc.)”. The textual history of Locke's Essay is extremely complicated. While there is no manuscript of the first edition of the book, there were four editions in Locke's lifetime, each new one containing extensive and significant revisions, as well as a posthumous edition published shortly after the author's death. There was a translation into French made with Locke's cooperation and published in 1700, and a Latin translation came out a year later. Nevertheless, Nidditch managed to record all the material variants in footnotes to the text, in a way that makes it fairly easy to track the changes that Locke made to successive editions of the book, and to locate points at which judgements had to be made as a critical text was established on the basis of the chosen copy text. Sometimes a critical edition succeeds in completely changing the way that a text is read. Peter Laslett's 1960 edition of Locke's Two Treatises of Government is a good example. Nidditch's edition of the Essay did not have that kind of very dramatic effect on Locke scholarship. Rather, it made it possible for those without direct access to all the early editions to engage in careful, historically sensitive studies of Locke's account of human understanding. The result was a slow revolution in Locke studies that continues to shed new light on even the most familiar aspects of the Lockean philosophy.
Modeling the effects of secular variation of geomagnetic field orientation on the ionospheric long term trend over the past century
Authors: Yue Xinan , Liu Libo , Wan Weixing , Wei Yong , Ren Zhipeng
Published: October 2008

A middle‐ and low‐latitude ionospheric theoretical model is used for the first time to assess the effects of the secular variations of geomagnetic field orientation on ionospheric long‐term trends over the past century. It is found that the varied geomagnetic field can produce ionospheric long‐term trends in both foF2 and hmF2. Since the amplitudes of geomagnetic field change depend on location, the modeled trends by secular variations of geomagnetic field orientation differ from place to place. The modeled ionospheric trends have obvious seasonal and diurnal variations. These variations show typical regional features. By comparison with existing results, we suggest that the changes of the global geomagnetic field may partly contribute to the inconsistent seasonal and local time variation patterns in ionospheric trends from different observations. The average trends of foF2 and hmF2 are −0.0047 MHz/a and −0.0107 km/a during 1900–2005, which is near or even comparable with those of other trend origins. In comparison with the trend results from worldwide observations, we conclude that the effects of geomagnetic field orientation on the ionospheric long‐term trend cannot be ruled out, especially in areas with large geomagnetic field variations.
Methane escape from Titan's atmosphere
Authors: Yelle R. V. , Cui J. , Müller‐Wodarg I. C. F.
Published: October 2008

Measurements of the mole fractions of CH4 and 40Ar by the Ion Neutral Mass Spectrometer on the Cassini orbiter are analyzed to determine the rate of vertical mixing in Titan's atmosphere and the escape flux of CH4. Analysis of the 40Ar data indicates an eddy mixing rate of 2–5 × 107 cm2 s−1, an order of magnitude smaller than previously determined from analysis of the CH4 distribution. The eddy profile determined from the 40Ar data implies that CH4 distribution is best explained by postulating that it is escaping the atmosphere at the diffusion limited rate of 2.5–3.0 × 109 cm−2 s−1, referred to the surface. This represents a significant loss of atmospheric CH4, smaller than but comparable to the photochemical destruction rate. The escape rate is much larger than predicted by the Jeans escape formula and vigorous nonthermal mechanisms are not apparent.
Horizontal structures and dynamics of Titan's thermosphere
Authors: Müller‐Wodarg I. C. F. , Yelle R. V. , Cui J. , Waite J. H.
Published: October 2008

The Cassini Ion Neutral Mass Spectrometer (INMS) measures densities of gases including N2 and CH4 in situ in Titan's upper atmosphere. We have used data from 13 targeted flybys of Titan (T5–T32) to construct an empirical model that describes the mean state of the thermosphere in the northern hemisphere, giving the N2 and CH4 densities between 1000 and 1600 km as a function of latitude and height. The principal features in the INMS data are well reproduced by this simple model. We find a pronounced oblateness in the thermosphere, with densities above 1100 km altitude increasing by around 70% from the northern (winter) pole to the equator, resulting in isobaric surfaces being ≃45 km higher over the equator than at the northern pole. Thermospheric temperatures derived from the densities tend to decrease with height from 149 ± 10 K to 140 ± 13 K near 1600 km. Considerable latitude differences are present in the temperatures below 1200 km. Near 1000 km altitude, temperatures reach 164 ± 6 K at 20°N and 131 ± 6 K near 80°N. Using our Thermosphere General Circulation Model with this thermal structure imposed, we derive thermospheric horizontal wind speeds reaching ∼150 m s−1, with primarily poleward flow at equatorial latitudes which, northward of around 60°N, is accompanied by a band of prograde zonal winds of up to 50 m s−1. At high latitudes, converging horizontal winds generate regions of strong subsistence. We find thermospheric dynamics to be sensitive to coupling from below. CH4 abundances are enhanced in the northern polar region, which may result from transport by thermospheric winds.
Spectral signatures of characteristic spatial scales and nonfractal structure in landscapes
Authors: Perron J. Taylor , Kirchner James W. , Dietrich William E.
Published: October 2008

Landscapes are sometimes argued to be scale‐invariant or random surfaces, yet qualitative observations suggest that they contain characteristic spatial scales. We quantitatively investigate the existence of characteristic landscape scales by analyzing two‐dimensional Fourier power spectra derived from high‐resolution topographic maps of two landscapes in California. In both cases, we find that spectral power declines sharply above a frequency that corresponds roughly to hillslope length, implying that the landscape is relatively smooth at finer scales. The spectra also show that both landscapes contain quasiperiodic ridge‐and‐valley structures, and we derive a robust measure of the ridge‐valley wavelength. By comparing the spectra with the statistical properties of spectra derived from randomly generated topography, we show that such uniform valley spacing is unlikely to occur in a random surface. We describe several potential applications of spectral analysis in geomorphology beyond the identification of characteristic spatial scales, including a filtering technique that can be used to measure topographic attributes, such as local relief, at specific scales or in specific orientations.
Evolution of sediment accommodation space in steady state bedrock‐incising valleys subject to episodic aggradation
Authors: Lancaster Stephen T.
Published: October 2008

Steepland valleys subject to debris flows incise bedrock even as episodic deposition typically covers valley bottoms. This paper's hypothesis is that, while continual fluvial processes evacuate deposits, storage of episodic deposition drives valley widening and, thereby, creation of accommodation space for sediment storage on the valley floor. Data from three headwater valleys in the Oregon Coast Range show that valley‐to‐channel width ratios and valley bottom deposit depths are variable, have little systematic variation with respect to contributing area, and are similar on average among sites. A model of valley cross‐section evolution couples soil production, nonlinear diffusion, contrasting rates of channel incision into deposits and bedrock, and stochastic valley bottom deposition. The model reproduces observed flat, deposit‐covered valley bottoms and abrupt transitions to valley sides with oversteepened toe slopes. Simulations address sensitivity of valley morphologies and incision rates to dimensionless numbers, the ratio of instantaneous bedrock and deposit erosion rates (incision number), and the ratio of deposition and evacuation rates (deposition number). For steady state simulations, increasing deposition number by <101 leads to deposit depth and valley bottom width increasing by 101 and 101.5, respectively, and valley bottom incision relative to the instantaneous rate decreasing by 10−3. For incision number increasing by 103, valley capacity (width times toe slope height) relative to mean deposit volume increases by 101.5. Simulations, consistent with field data, imply that steady state valley widths are adjusted to episodic deposition rates and respond more quickly to changes than profile gradients because of contrasting limitations by instantaneous versus long‐term lowering rates.
Global search algorithm for nondispersive flow path extraction
Authors: Paik Kyungrock
Published: October 2008

A new algorithm is developed to extract flow paths from digital elevation data without planar dispersion on the basis of the concept of global search. Widely used nondispersive algorithms, such as deterministic eight‐neighbor flow direction retrieval algorithms, suffer serious uncertainty in their determined flow paths because of the lack of variability, i.e., only eight allowed flow directions. Although uncertainty at the local level is an inherent problem residing in the domain discretization, this study shows that more reasonable flow paths at the global scale can be obtained by maximizing the use of all information stored in the given digital elevation data. By utilizing information stored in cells other than those in the direct vicinity, this alternative approach can reduce the uncertainty residing in the extraction of flow paths. The proposed algorithm makes a significant improvement in flow path variability on both theoretical and real landscapes, while it is still simple.
Comparative study of radiation enhancement due to metamaterials
Authors: Khodja Mohamed R. , Marengo Edwin A.
Published: October 2008

We present a comparative study on radiation enhancement due to metamaterial antenna substrates. The study is performed via electromagnetic inverse source theory and constrained optimization. The aim of the study is to understand the effect of reference antennas on enhancement level estimates. The geometry of the problem is that of a piecewise‐constant, radially symmetric, three‐region system (spherical core‐shell system). Particular attention is given to the case when the core and the shell are made up of lossless materials having oppositely signed constitutive parameters.
Identification of a subduction zone component in the Higganum dike, Central Atlantic Magmatic Province: A LA‐ICPMS study of clinopyroxene with implications for flood basalt petrogenesis
Authors: Dorais Michael J. , Tubrett Michael
Published: October 2008

Determining the primary compositions of continental flood basalts has proven allusive because of the masking effects of crustal contamination. The Higganum dike (Connecticut, USA) that fed the Talcott basalt of the Central Atlantic Magmatic Province hosts strongly zoned clinopyroxenes. The cores are Mg‐ and Cr‐rich, containing up to 1 wt % Cr2O3. The grains show optical and major, minor, and trace element continua between cores and their mantles and rims, indicating that the cores are early crystallizing phenocrysts, not xenocrysts. Laser ablation inductively coupled plasma mass spectrometry analyses of the cores were used to calculate liquid compositions of the most primitive component in the Higganum system and to make inferences about composition of continental flood basalt parental magmas. The Cr‐rich cores yield calculated liquids with Mg numbers of 63. The high‐Cr contents of these calculated liquids indicate the absence of significant clinoproxene or chromite fractionation. Olivine or orthopyroxene fractionation may have lowered the liquid Mg number but would not have significantly influenced the calculated incompatible trace element patterns. Extended rare earth element diagrams for the most Cr‐rich liquids show enrichment in incompatible elements, similar to arc basalts. Prominent negative Nb anomalies are present as are distinct positive Pb anomalies indicative of the influence of subduction zone fluids in the mantle source. Calculated liquid Ba/La values range from 3 to 30, also suggestive of fluid input. These data indicate that the mantle source experienced subduction zone fluid metasomatism. Subsequent crustal contamination is evident in bulk‐rock Nd and Sr isotopic compositions.
Rise and deflection of mantle plume tails
Authors: Kerr Ross C. , Lister John R.
Published: October 2008

Experimental observations by Kerr and Mériaux (2004) of the deflection of thermal plume tails by an imposed background shear are reanalyzed using a corrected velocity profile. The deflected plumes are found to be accurately described by a constant vertical rise velocity (equation (14)) that depends primarily on the plume buoyancy flux and the ambient viscosity. Our results can be used to further improve the predictions of numerical models of the shearing of plume tails in the Earth's mantle.
Halogen and 129I systematics in gas hydrate fields at the northern Cascadia margin (IODP Expedition 311): Insights from numerical modeling
Authors: Lu Zunli , Hensen Christian , Fehn Udo , Wallmann Klaus
Published: October 2008

We measured halogen concentrations and 129I/I ratios in five drilling sites of Integrated Ocean Drilling Program Expedition 311 (offshore Vancouver Island, Canada) in order to identify potential sources of fluids and methane in gas hydrate fields. Iodine is dominated by organic decomposition and transports with fluids in reducing environments and the presence of the cosmogenic radioisotope 129I (T1/2 = 15.7 Ma) allows the age determination of organic sources for iodine. Here we report halogen concentrations in 135 pore water samples, I concentrations in 48 sediment samples, and 129I/I ratios measured in a subset of 20 pore water samples. Most 129I/I ratios fall into a range around 500 × 10−15, corresponding to a minimum age of 25 Ma and the lowest ratio of 188 × 10−15 (Tmin = 47 Ma) was observed at 208 m below sea floor (mbsf) in Site 1326. These ages are considerably older than that of the local sediments in the gas hydrate fields and that of the subducting sediments on the Juan de Fuca plate, indicating that old, accreted sediments in the accretionary wedge contribute a significant amount of iodide and, by association, of methane to the gas hydrate occurrences. A geochemical transport‐reaction model was applied to simulate the advection of deeply sourced fluids and the release of iodide, bromide, and ammonia in the host sediments due to organic matter degradation. The model was first tested with data from two well studied areas, Ocean Drilling Program Site 1230 (Peru margin) and Site 1245 (Hydrate Ridge). The model results for the Expedition 311 sites indicate that the in situ release of young iodine is relatively minor in comparison to the contribution of migrating fluids, carrying large amounts of old iodine from deep sources. The comparison between the sites demonstrates that the total organic content has a strong effect on the rate of in situ iodine release and that lateral flows along fractures can have a significant influence on pore water chemistry, especially at the Cascadia margin. The iodine results indicate that mobilization and transport of methane from sources in the upper plate of active margins is an important process which can also play a substantial role in the formation of gas hydrate fields.
Climatic aspects of extreme temperatures in coastal waters
Authors: Lwiza Kamazima M. M.
Published: October 2008

Daily temperature records from Woods Hole, Massachusetts, USA are used to examine characteristics of temperature extremes from 1945 to 2006. Winter extreme temperatures are increasing at 2.0 degrees C/century compared to the rate of summer extremes of 0.8 degree C/century, which leads to a reduction of the annual temperature range. An even more intriguing result is that while summer peak is not changing, winter minimum and spring are arriving earlier by approximately 22 and 10 days/century, respectively. The results seem to suggest that the unequal seasonal distribution of greenhouse gases could be the cause for faster winter warming trend. The mean values of the scale and shape parameters of the Weibull probability density functions for winter and summer observations are identical. The Weibull distribution parameters derived in this study can be used to estimate the hottest and coldest daily temperatures for any given year provided the mean temperature is known.
Sodium recycling at Europa: what do we learn from the sodium cloud variability?
Authors: Cipriani F. , Leblanc F. , Witasse O. , Johnson R. E.
Published: October 2008

We study the ejection of sodium atoms from Europa's surface by both magnetospheric ion and electron sputtering and desorption stimulated by UV solar photons. The depletion of the surface by ejection and its enrichment by redeposition of sodium atoms are described. The redistribution of sodium atoms at the surface induced by photo‐stimulated desorption from the dayside and by sputtering ejection from the trailing hemisphere cannot explain the observed variation of the Na emission brightness. However, a transient increase of the sputtering rate due to a plasma injection may explain such an increase. The relationship between the sodium surface content and the sodium exosphere are also discussed.
A one‐year experimental Arctic reanalysis and comparisons with ERA‐40 and NCEP/NCAR reanalyses
Authors: Fan Xingang , Walsh John E. , Krieger Jeremy R.
Published: October 2008

A one‐year (1998) experimental Arctic reanalysis was produced using an experimental Arctic reanalysis system (EARS), which was based on the MM5 model and 3DVAR data assimilation, implemented in combination with an intermittent nudging scheme. TOVS retrieval data and conventional surface observations and upper‐air sounding data are assimilated by EARS, which is driven by the ERA‐40 reanalysis. The domain covers a pan‐Arctic region at a horizontal resolution of 30 km. The EARS reanalysis results, as well as ERA‐40 and NCEP/NCAR reanalyses (NNRP), are verified against station observations. Comparisons show that the ERA‐40 analysis is significantly better than NNRP for the metrics of root‐mean‐square error and bias. The EARS performed significantly better than both ERA‐40 and NNRP at lower levels; it produced especially good results for surface wind and upper‐air humidity. For the surface temperature, dew point, relative humidity, sea level pressure, as well as upper‐air variables, the yearly average of the EARS results lie in between those of the ERA‐40 and NNRP, closer to those of ERA‐40.
Polar rain gradients and field‐aligned polar cap potentials
Authors: Fairfield D. H. , Wing S. , Newell P. T. , Ruohoniemi J. M. , Gosling J. T. , Skoug R. M.
Published: October 2008

ACE SWEPAM measurements of solar wind field‐aligned electrons have been compared with simultaneous measurements of polar rain electrons precipitating over the polar cap and detected by DMSP spacecraft. Such comparisons allow investigation of cross‐polar‐cap gradients in the intensity of otherwise‐steady polar rain. The generally good agreement of the distribution functions, f, from the two data sources confirms that direct entry of solar electrons along open field lines is indeed the cause of polar rain. The agreement between the data sets is typically best on the side of the polar cap with most intense polar rain but the DMSP f's in less intense regions can be brought into agreement with ACE measurements by shifting all energies by a fixed amounts that range from tens to several hundred eV. In most cases these shifts are positive which implies that field‐aligned potentials of these amounts exist on polar cap field lines which tend to retard the entry of electrons and produce the observed gradients. These retarding potentials undoubtedly appear in order to prevent the entry of low‐energy electrons and maintain charge quasi‐neutrality that would otherwise be violated since most tailward flowing magnetosheath ions are unable to follow polar rain electrons down to the polar cap. In more limited regions near the boundary of the polar cap there is sometimes evidence for field‐aligned potentials of the opposite sign that accelerate polar rain electrons. A solar electron burst is also studied and it is concluded that electrons from such bursts can enter the magnetotail and precipitate in the same manner as polar rain.
Near‐surface ocean velocity from infrared images: Global Optimal Solution to an inverse model
Authors: Chen Wei , Mied Richard P. , Shen Colin Y.
Published: October 2008

We address the problem of obtaining ocean surface velocities from sequences of thermal (AVHRR) space‐borne images by inverting the heat conservation equation (including sources of surface heat fluxes and vertical entrainment). We demonstrate the utility of the technique by deriving surface velocities from (1) The motion of a synthetic surface tracer in a numerical model and (2) a sequence of five actual AVHRR images from 1 day. Typical formulations of this tracer inversion problem yield too few equations at each pixel, which is often remedied by imposing additional constraints (e.g., horizontal divergence, vorticity, and energy). In contrast, we propose an alternate strategy to convert the underdetermined equation set to an overdetermined one. We divide the image scene into many subarrays and define velocities and sources within each subarray using bilinear expressions in terms of the corner points (called knots). In turn, all velocities and sources on the knots can be determined by seeking an optimum solution to these linear equations over the large scale, which we call the Global Optimal Solution (GOS). We test the accuracy of the GOS by contaminating the model output with up to 10% white noise but find that filtering the data with a Gaussian convolution filter yields velocities nearly indistinguishable from those without the added noise. We compare the GOS velocity fields with those from the numerical model and from the Maximum Cross Correlation (MCC) technique. A histogram of the difference between GOS and numerical model velocities is narrower and more peaked than the similar comparison with MCC, irrespective of the time interval (Δt = 2 or 4 h) between images. The calculation of the root mean square error difference between the GOS (and MCC) results and the model velocities indicates that the GOS/model error is only half that of the MCC/model error irrespective of the time interval (Δt = 2 or 4 h) between images. Finally, the application of the technique to a sequence of five NOAA AVHRR images yields a velocity field, which we compare with that from a Coastal Ocean Dynamics Radar (CODAR) array. We find that the GOS velocities generally agree more closely with those from the CODAR than they do with those from the MCC. Specifically, the root mean square error obtained by differencing GOS and CODAR velocities is smaller than that from the similar calculation with MCC velocities. The magnitude of the complex correlation between GOS and CODAR is larger than that between MCC and CODAR. The phase of the complex correlation indicates that both MCC and GOS on average yield velocity vectors biased in the clockwise direction relative to the CODAR vectors for the period examined.
Venus surface data extraction from VIRTIS/Venus Express measurements: Estimation of a quantitative approach
Authors: Arnold Gabriele , Haus Rainer , Kappel David , Drossart Pierre , Piccioni Giuseppe
Published: October 2008

Nightside emission measurements of the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on the Venus Express spacecraft were used to estimate the potential for surface data extraction. A selection of orbits over the northern hemisphere was performed for footprints that cover different scales of surface elevation variations. A correction method was used to remove stray light from the measured spectra that is due to direct sunlight striking the instrument. A preliminary radiative transfer calculation technique was applied to simulate Venus nightside radiation. The basic features of the measured spectra are well reproduced. Present limitations of the algorithm are discussed. The variability of the emission window radiances with respect to cloud opacity and surface elevation is modeled and discussed in direct comparison with the measurements. It is demonstrated that a multispectral analysis in the surface and deep atmosphere window ranges (1.0–2.3 μm) and the use of radiance ratios are well suited to decloud the data and to extract surface information from the VIRTIS measurements. This method allows a mapping of surface topography and the retrieval of the surface temperature. A preliminary topography retrieval at Beta Regio was performed and compared with Magellan radar data. Differences are possibly due to emissivity variations on the surface.
Origin of oxygen species in Titan's atmosphere
Authors: Hörst S. M. , Vuitton V. , Yelle R. V.
Published: October 2008

The detection of O+ precipitating into Titan's atmosphere by the Cassini Plasma Spectrometer (CAPS) represents the discovery of a previously unknown source of oxygen in Titan's atmosphere. The photochemical model presented here shows that those oxygen ions are incorporated into CO and CO2. We show that the observed abundances of CO, CO2 and H2O can be simultaneously reproduced using an oxygen flux consistent with the CAPS observations and an OH flux consistent with predicted production from micrometeorite ablation. It is therefore unnecessary to assume that the observed CO abundance is the remnant of a larger primordial CO abundance or to invoke outgassing of CO from Titan's interior as a source of CO.
Regional groundwater flow in mountainous terrain: Three‐dimensional simulations of topographic and hydrogeologic controls
Authors: Gleeson Tom , Manning Andrew H.
Published: October 2008

This study uses numerical simulations to define the salient controls on regional groundwater flow in 3‐D mountainous terrain by systematically varying topographic and hydrogeologic variables. Topography for idealized multiple‐basin mountainous terrain is derived from geomatic data and literature values. Water table elevation, controlled by the ratio of recharge to hydraulic conductivity, largely controls the distribution of recharged water into local, regional, and perpendicular flow systems, perpendicular flow being perpendicular to the regional topographic gradient. Both the relative (%) and absolute (m3/d) values of regional flow and perpendicular flow are examined. The relationship between regional flow and water table elevation is highly nonlinear. With lower water table elevations, relative and absolute regional flow dramatically increase and decrease, respectively, as the water table is lowered further. However, for higher water table elevations above the top of the headwater stream, changes in water table elevation have little effect on regional flow. Local flow predominates in high water table configurations, with regional and perpendicular flow <15% and <10%, respectively, of total recharge in the models tested. Both the relative and the maximum absolute regional flow are directly controlled by the degree of incision of the mountain drainage network; the elevation of mountain ridges is considerably less important. The percentage of the headwater stream with perennial streamflow is a potentially powerful indicator of regional flow in all water table configurations and may be a good indicator of the susceptibility of mountain groundwater systems to increased aridity.