bluuebunny/crossref_metadata_2025 huggingface dataset:
Dimensions that shape teacher–scientist collaborations for teacher enhancement
Authors: Drayton Brian , Falk Joni
Published: March 2006

Partnerships of teachers with scientists are thought to be important for many aspects of science education reform, but it is not always clear how to make such partnerships productive. Between 1994 and 1997, high school teachers were partnered with scientists, to design yearlong ecological research projects in which the teachers were learning for their own sake, rather than to create new curriculum. In these partnerships the relationships with the scientists took many forms. We found that negotiations around five dimensions seemed particularly important: (1) Whose question was being investigated? (2) Was the focus primarily on data collection or data analysis? (3) Was the research based on the ecologist's area of expertise, or the teachers' interest? (4) Was the focus primarily on the teachers' learning on their students' classroom learning? (5) Was the research intended for an external audience, or primarily for the teachers' own benefit? Three case studies are presented, showing how these dimensions shaped the negotiations of more successful and less successful collaborations. Implications for inquiry‐based pedagogy, and cultural issues arising in scientist‐teacher collaborations, are discussed. © 2006 Wiley Periodicals, Inc. Sci Ed, 90:734–761, 2006
Shags in Antarctica: their feeding behaviour and ecological role in the marine food web
Authors: Casaux Ricardo , Barrera-Oro Esteban
Published: March 2006

Feeding behaviour, ecological role in the marine food web and population trends of the Antarctic shag Phalacrocorax bransfieldensis and the South Georgia shag P. georgianus in Antarctica are analysed. The diving depths and duration recorded for these shags are the deepest and longest among all flying birds in Antarctica and match deep dives performed by small Antarctic penguins. Individual shags of both sexes partition foraging depths and food resources, which might diminish intra-specific competition. Like other sub-Antarctic shags, P. bransfieldensis and P. georgianus are bottom feeders that prey predominantly on demersal fish. In the southern Scotia Arc and west Antarctic Peninsula, nototheniids, mainly Notothenia coriiceps, constitute their main prey. Shag partners alternate the time at sea and, as the energy requirements at the nest increase, they increase the number but reduce the duration of the feeding trips. A steady declining trend in the number of breeding pairs of both species has been observed in the last decade at several Antarctic localities; this phenomenon at the South Shetland Islands might be at least partially explained by the effect of the commercial fishery on their prey. In inshore shallow waters shags occupy the trophic niche of main predators of demersal fish and play an important ecological role as regulators of populations of particular fish prey that have marked site fidelity. The potential use of shags as biomonitors in Antarctica is discussed.
Cholinesterase activities in the adductor muscle of the Antarctic scallop Adamussium colbecki
Authors: Bonacci Stefano , Corsi Ilaria , Focardi Silvano
Published: March 2006

Antarctica is regarded as one of the most pristine parts of the Earth but even this remote ecosystem is affected by contamination and high levels of certain heavy metals, such as cadmium, which may occur naturally in Antarctic waters. The bivalve scallop Adamussium colbecki is considered a key species of Antarctic benthic ecosystems and a sensitive target for bioaccumulation of xenobiotics and metals. Since cholinesterases (ChEs) in the adductor muscle of A. colbecki presumably play a prominent physiological role through regulation of swimming movements, the main aims of this study was to characterize ChE activities in adductor muscle of A. colbecki and to investigate their sensitivity to organophosphate pesticides and heavy metals. The results suggest that an acetylcholinesterase-like enzyme in the adductor muscle of the scallop has low sensitivity to organophosphates but was significantly inhibited by exposure to cadmium.
Taxonomy and biogeography of Molgolaimus Ditlevsen, 1921 (Nematoda: Chromadoria) with reference to the origins of deep sea nematodes
Authors: Fonseca Gustavo , Vanreusel Ann , Decraemer Wilfrieda
Published: March 2006

Molgolaimus is a genus of free-living marine nematodes which is found in high densities (10–35% of the total community) up to 2000 m depth. Its occurrence is often associated with organically enriched and recently disturbed areas. Currently, only 16 species have been described, mainly from shallow waters. The present study contributes 17 new species mainly from the Weddell Sea but also from the Pacific Ocean, and provides an illustrated polytomous identification key to species level. The 33 Molgolaimus species described can be identified based on just a few morphometric features: spicule length, body length, anal body diameter, tail length and pharynx length. A first insight into the biogeography of this deep sea genus at species level is presented. A comparison of morphometric characteristics between species suggests that the most similar species co-occur in the same geographical region, rather than within the same bathymetric zones or similar ecosystems separated over long distances. These observations suggest that deep sea nematodes may not have a common origin but might have derived “recently” from shallow water taxa. Therefore, global distribution of nematodes could be explained by means of palaeogeographical events.
Modern Archaeomonadaceae from the land-fast ice off Adélie Land, East Antarctica: a preliminary report
Authors: Riaux-Gobin C. , Stumm K.
Published: March 2006

The land-fast ice and the platelet ice layer off Adélie Land are inhabited by a dense and diversified diatom community. Along with Bacillariophyceae, Archaeomonadaceae sensu Deflandre are present and relatively abundant. These modern siliceous nanostructures are similar to the nanofossils described by geologists in marine sediments from upper Cretaceous to Pliocene, Pleistocene and recently in Holocene and modern sediments, and are probably related to chrysophyte cysts. The two most abundant taxa were Achaeomonas cf areolata Deflandre and Litheusphaerella cf spectabilis Deflandre. The other taxa were not common. Despite the taxonomic uncertainty of immature forms, the diversity of archaeomonads was high. Three new species of Archaeomonas are described. The morphology of A. cf areolata is highly variable, showing a possible diversification over geologic time. Litheusphaerella cf spectabilis also shows some differences between fossil and modern specimens. Recent studies confirm that archaeomonads are extant in diverse marine water bodies and recent sediments. There is growing evidence that these siliceous structures represent possible reliable proxies of sea ice extent, even if their presence in geologic time is not always linked exclusively to sea ice. Further studies are needed to elucidate the exact origin of these cysts and their real taxonomic affinities.
A review of the Cenozoic stratigraphy and glacial history of the Lambert Graben—Prydz Bay region, East Antarctica
Authors: Whitehead J.M. , Quilty P.G. , Mckelvey B.C. , O’Brien P.E.
Published: March 2006

The Cenozoic glacial history of East Antarctica is recorded in part by the stratigraphy of the Prydz Bay—Lambert Graben region. The glacigene strata and associated erosion surfaces record at least 10 intervals of glacial advance (with accompanying erosion and sediment compaction), and more than 17 intervals of glacial retreat (enabling open marine deposition in Prydz Bay and the Lambert Graben). The number of glacial advances and retreats is considerably less than would be expected from Milankovitch frequencies due to the incomplete stratigraphic record. Large advances of the Lambert Glacier caused progradation of the continental shelf edge. At times of extreme glacial retreat, marine conditions reached > 450 km inland from the modern ice shelf edge. This review presents a partial reconstruction of Cenozoic glacial extent within Prydz Bay and the Lambert Graben that can be compared to eustatic sea-level records from the southern Australian continental margin.
New model alternatives for improving the representation of the core magnetic field of Antarctica
Authors: Gaya-Piqué Luis R. , Ravat Dhananjay , De Santis Angelo , Torta J. Miquel
Published: March 2006

Use of the International Geomagnetic Reference Field Model (IGRF) to construct magnetic anomaly maps can lead to problems with the accurate determination of magnetic anomalies that are readily apparent at the edges of local or regional magnetic surveys carried out at different epochs. The situation is severe in areas like Antarctica, where ionospheric activity is intense and only a few ground magnetic observatories exist. This makes it difficult to properly separate from ionospheric variations the secular variation of the core magnetic field. We examine two alternatives to the piecewise-continuous IGRF core magnetic field in Antarctica for the last 45 years: the present global Comprehensive Model (CM4) and the new version of the Antarctic Reference Model (ARM). Both these continuous models are better at representing the secular variation in Antarctica than the IGRF. Therefore, their use is recommended for defining the crustal magnetic field of Antarctica (e.g. the next generation of the Antarctic Digital Magnetic Anomaly Map).
Seasonal stable oxygen isotope cycles in an Antarctic bivalve shell (Laternula elliptica): a quantitative archive of ice-melt runoff
Authors: Tada Yohei , Wada Hideki , Miura Hideki
Published: March 2006

Oxygen isotope ratios in the shell of a Recent Antarctic marine bivalve Laternula elliptica are shown and their potential for environmental reconstruction is discussed. The shell δ18O profiles of this species represent the seasonal change in melted ice water inflow. Oscillations in the shell δ18O values reflect seasonal change in seawater δ18O values, caused by an addition of meltwater in summer. Since annual temperature variation is minimal and the inflow of the regional ice-melt is the dominant control on the shell δ18O values, the oxygen isotope record of L. elliptica is a quantitative indicator of the palaeo-ice-melting events in the Antarctic continental margin.
Late Miocene Asterozoans (Echinodermata) in the James Ross Island Volcanic Group
Authors: Williams Mark , Smellie John L. , Johnson Joanne S. , Blake Daniel B.
Published: March 2006

Asterozoans (Echinodermata) of Late Miocene age (6.02 ± 0.12 Ma) are preserved as external moulds in water-lain tuffs of the James Ross Island Volcanic Group (JRIVG), James Ross Island, Antarctic Peninsula. The asterozoans are complete, and appear to represent specimens suffocated after having been pinioned by rapid sedimentation on the distal fringe of an erupting sub-aqueous tuff cone. Although the coarse nature of the host sediments has obliterated the fine morphological detail of the specimens, at least one suggests evidence of entrainment by a turbidity current. A second shows evidence of detachment of the distal tip of one of its arms. In addition to fossil discoveries from glaciomarine sediments, the volcanic tuffs of the JRIVG represent a new source of fossil data that can be used to interpret the ecology and environment of the Antarctic marine shelf biota during the Neogene.
Precipitation trapped in datable rock-forming minerals: estimating Antarctic palaeoelevations - a discussion
Authors: Wendt Anke S. , Vaughan Alan P.M. , Boyce Adrian J.
Published: March 2006

Meteoric water that interacted with minerals during retrogressive metamorphism and hydrothermalism in the late-stage of mountain building processes contains hydrogen and oxygen isotopes that are potential proxies for palaeoelevation reconstruction in Antarctica. The effects of temperature on meteoric isotopic signatures, meteoric crustal infiltration processes, and the mechanisms of capture and preservation of meteoric δD and δ18O values in rock-forming minerals are discussed. Special emphasis is given to Antarctica’s geographical high-latitude position and climatic fluctuations over time and to the highmountain ranges of continental Antarctica, which were tectonically active regions in the past. In this context, a new compilation of recent Antarctic snow and ice δD and δ18O data is presented, by which we demonstrate that net elevations versus isotopic depletions are positively correlated for continental Antarctica - a prime requisite when estimating palaeoelevations.
Tidal currents of the Ross Sea and their time stability
Authors: Johnson Eric S. , Van Woert Michael L.
Published: March 2006

Current measurements obtained from a sparse array of moorings on the Ross Continental Shelf during the 1980 and 90s are analysed for their tidal constituents. Diurnal (K1 and O1) tides are about five times stronger than semi-diurnal tides, and are strongest near the shelf break in agreement with recent model results. At some energetic locations the diurnal tides are significantly weaker at depth, presumably due to bottom friction. Complex demodulation analysis shows that at some locations the tidal response varies significantly in time. This time variability rises markedly above the noise floor expected from the spectral continuum between tidal bands, and does not scale with tidal bandwidth as would be expected of broadband noise. Further its magnitude is generally proportional to the associated tidal constituent, indicating that it is truly a varying tidal response. Space scales of this tidal instability were not resolved but are less than 150 km, while time scales appear mostly seasonal to interannual. The rms magnitude of the unstable response can be 1/3 of a given component’s mean magnitude, placing substantial limits on the ability of prognostic or even data assimilative models to accurately predict these tides for any specific time period.
Solidarity in competitive health insurance markets: analysing the relevant EC legal framework
Authors: Paolucci Francesco , Exter Andre Den , De Ven Wynand Van
Published: March 2006

In this article we perform an economic analysis of different regulatory frameworks that aim at guaranteeing solidarity in competitive health insurance markets. Thereafter, we analyse the legal conformity of these intervention strategies with EC law. We find that risk compensation schemes are the first-best intervention strategy because they guarantee an ‘acceptable level of solidarity’ without hindering free trade and competition and without reducing efficiency. Second-best options are premium and excess-loss compensation schemes, which guarantee solidarity at the expense of some efficiency. Premium rate restrictions and open enrolment should be avoided because they reduce efficiency and are unnecessary, not proportional, and undesirable to the pursuit of the general good. These conclusions are relevant for EU countries that adopt premium rate restrictions and open enrolment in combination with a risk compensation scheme, such as Ireland and the Netherlands. In these countries policy makers should design the health insurance schemes in conformity with EC law, for example by replacing premium rate restrictions and open enrolment with premium and/or excess-loss compensation schemes.
The case for risk-based premiums in public health insurance
Authors: Zweifel Peter , Breuer Michael
Published: March 2006

Uniform, risk-independent insurance premiums are accepted as part of ‘managed competition’ in health care. However, they are not compatible with optimality of health insurance contracts in the presence of both ex ante and ex post moral hazard. They have adverse effects on insurer behaviour even if risk adjustment is taken into account. Risk-based premiums combined with means-tested, tax-financed transfers are advocated as an alternative.
Public involvement policies in health: exploring their conceptual basis
Authors: Wait Suzanne , Nolte Ellen
Published: March 2006

Despite its obvious appeal, the concept of public involvement is poorly defined and its rationale and objectives are rarely specified when applied to current health policy contexts. This paper explores some of the underlying concepts, definitions, and issues underpinning public involvement policies and proposes a set of criteria and questions that need to be addressed to allow for the evaluation of public involvement strategies and their impact on the health policy process. It aims to further our understanding of the role that public involvement may play in contributing to health systems that are responsive to the needs and priorities of the public, and, ultimately, providing better health and health care services to the community at large.
Conceptualizing decentralization in European health systems: a functional perspective
Authors: Saltman Richard B. , Bankauskaite Vaida
Published: March 2006

Although decentralization has been widely implemented in health systems, there is little agreement as to how it should be defined or the outcomes it should produce. This article develops a functional typology based on political, administrative, and fiscal dimensions of decentralization. It utilizes these three categories to identify and highlight key theoretical issues concerning decentralization, emphasizing the likely advantages and disadvantages that decentralization can be expected to generate. It then examines the usefulness of this functional framework in explaining recent policy-making decisions within a number of tax-based health systems in Western Europe. The article concludes by suggesting that this three-part typology can be helpful to both policy makers and academics in evaluating the effectiveness of decentralization as a policy mechanism within health care systems.
Transformation of the US Veterans Health Administration
Authors: Perlin Jonathan B.
Published: March 2006

Ten years ago, it would have been hard to imagine the publication of an issue of
a scholarly journal dedicated to applying lessons from the transformation of the
United States Department of Veterans Affairs Health System to the renewal of
other countries' national health systems. Yet, with the recent publication of a
dedicated edition of the Canadian journal Healthcare Papers (2005), this actually
happened. Veterans Affairs health care also has been similarly lauded this
past year in the lay press, being described as ‘the best care anywhere’ in the
Washington Monthly, and described as ‘top-notch healthcare’ in US News
and World Report's annual health care issue enumerating the ‘Top 100
Hospitals’ in the United States (Longman, 2005; Gearon, 2005).
Der Einfluss des regulatorischen Fokus auf integrative Verhandlungen
Authors: Werth Lioba , Mayer Jennifer , Mussweiler Thomas
Published: March 2006

Zusammenfassung: In vorliegender Studie wurde die Theorie des regulatorischen Fokus ( Higgins, 1997 ; 1998 ) auf den Bereich von Verhandlungen übertragen. Es wird aufgezeigt, dass Kompatibilität zwischen dem regulatorischen Fokus des Verhandelnden und dem Verhandlungsgegenstand die Präferenzen der Verhandlungspartner/innen und in Folge die Ergebnisse integrativer Verhandlungen beeinflusst. So erzielt in Verhandlungsdyaden, in denen Personen mit unterschiedlichem Fokus aufeinander treffen und sowohl prevention- als auch promotion-bezogene Verhandlungsgegenstände zu verhandeln sind, jeder Verhandlungspartner bzw. jede Verhandlungspartnerin in den jeweils fokus-kompatiblen Verhandlungsgegenständen das höhere Ergebnis. Personen im Prevention-Fokus sind stärker an wenig riskanten und verlustsicheren Verhandlungsgegenständen interessiert, während Personen im Promotion-Fokus verstärkt Interesse an Verhandlungsgegenständen bekunden, die sich durch höhere Gewinnchancen bei gleichzeitig höherem Verlustrisiko auszeichnen. Die Bedeutung des regulatorischen Fokus für Verhandlungssituationen sowie praktische Implikationen für den Verhandlungsalltag werden diskutiert.
Moderator- und Mediatoreffekte bei dyadischen Daten
Authors: Ledermann Thomas , Bodenmann Guy
Published: March 2006

Zusammenfassung: Zur Analyse von Moderator- und Mediatoreffekten bei dyadischen Daten werden zwei Erweiterungen des Akteur-Partner-Interdependenz-Modells (z. B. Kenny, 1996 ) vorgestellt. Die Modelle, die als Akteur-Partner-Moderator-Modell und Akteur-Partner-Mediator-Modell bezeichnet werden, dienen im Rahmen von dyadischen Untersuchungen der Überprüfung von Drittvariablen, welche die Zusammenhänge zwischen abhängigen und unabhängigen Variablen moderieren bzw. mediieren. Neben einer Anleitung zur Analyse des Moderatormodells mittels Regressionsanalysen finden sich Hinweise zur Durchführung von Bootstrap-Analysen bei Verwendung von Strukturgleichungsanalysen. Zur Einschätzung der Mediation werden verschiedene Indikatoren erörtert. Beide Modelle werden anhand von Daten zu Alltagsstress, Partnerschaftsqualität, Depressivität und sexuellen Störungen bei 198 Paaren illustriert. Die zum Akteur-Partner-Moderator-Modell durchgeführten Regressions- und Bootstrap-Analysen stützen die Hypothese, dass der Zusammenhang zwischen Alltagsstress und sexuellen Störungen durch die Partnerschaftsqualität moderiert wird. Die auf dem Akteur-Partner-Mediator-Modell basierenden strukturanalytischen Ergebnisse stützen die Annahme, dass der Zusammenhang zwischen Alltagsstress und Partnerschaftsqualität durch die Depressivität mediiert wird. Abschließend werden neben dem Nutzen die Vorzüge und Grenzen dieser Modelle diskutiert.
Analyseebenen und Dateninterdependenz in der Kleingruppenforschung am Beispiel netzbasierter Wissensintegration
Authors: Piontkowski Ursula , Keil Wolfgang , Hartmann Juliane
Published: March 2006

Zusammenfassung: In Experimenten mit Kleingruppen fallen Daten auf Person- und Gruppenebene an, die ebenenspezifische Konstrukte und Indikatoren erfordern. Bei einer Analyse auf Person- oder Gruppenebene muss berücksichtigt werden, dass die anfallenden Daten oft nicht unabhängig sind, wobei zugleich die Interdependenz ein sinnvoller und wichtiger Gegenstand der Analyse von Gruppenprozessen ist. In den letzten Jahren sind vermehrt Vorschläge sowohl zur Konzeptualisierung ebenenspezifischer Indikatoren als auch zur statistischen Analyse von Daten aus Experimenten mit interagierenden Gruppen gemacht worden. Am Beispiel eines Experiments zum computer-mediierten Informationsaustausch und zur Informationsintegration in Gruppen wird gezeigt, wie eine inhaltlich sinnvolle Interdependenz von Individuum und Gruppe modelliert und überprüft werden kann. Darüber hinaus werden die Möglichkeiten von Analyseverfahren mit Datenaggregierung oder mit statistischen Methoden, wie etwa gemischten Modellen, diskutiert.
Reactance Theory - 40 Years Later
Authors: Miron Anca M. , Brehm Jack W.
Published: March 2006

Abstract: In this paper we review the basic assumptions formulated by Jack Brehm in 1966 in his theory of psychological reactance and we sample some interesting directions of research on reactance that have been carried out by social psychologists during the last 40 years. We conclude that although there has been impressive development in the reactance research, more exciting avenues of investigation lie ahead. Throughout the paper we outline some of these future directions.
Evaluation de la qualité de vie après prélèvement de la veine fémorale superficielle lors de reconstructions infra-inguinales
Authors: Probst  , Ducrey  , Depairon  , Saucy  , Hayoz  , Haller  , Corpataux
Published: March 2006

Introduction: La veine fémorale superficielle (VFS) constitue une alternative bien connue en terme de matériel de pontage dans le cadre de reconstructions infra-inguinales. Le développement possible d'une hypertension veineuse aiguë ou chronique secondaire à son prélèvement peut être à l'origine d'une importante morbidité. Cette étude a pour but de valider la VFS en qualité de matériel de pontage et d'analyser les modifications anatomiques et physiologiques du membre prélevé et leurs relations avec l'apparition de complications veineuses. Méthodes: De mai 1999 à novembre 2003, 23 VFS ont été prélevées chez 21 patients ayant une reconstruction infra-inguinale. Les pontages ont été contrôlés régulièrement sur le plan clinique et par examens écho-doppler répétés. La mesure des périmètres jambiers, la pléthysmographie à jauges mercurielles et un questionnaire de qualité de vie, selon VEINES-QoL ont permis d'évaluer la morbidité veineuse. Résultats: Sur un suivi moyen de 10.4 mois (1 à 56 mois), les taux de perméabilité primaire, secondaire et de sauvetage de membre sont de 71.4%, 76.2% et 85.7% respectivement. Dans les suites post-opératoires, aucun patient n'a souffert de claudication veineuse. Neuf patients ont présenté un oedème significatif du membre prélevé. La pléthysmographie à jauges mercurielles a démontré une obstacle au retour veineux dans tous les cas. Le questionnaire VEINES-QoL a révélé une limitation modérée de l'activité sociale et domestique, ainsi qu'une sensation de jambes lourdes peu invalidante malgré la présence de l'oedème. Conclusion: La VFS est un conduit utilisable lors de reconstructions infra-inguinales et son prélèvement n'occasionne qu'une morbidité veineuse modérée en terme d'altérations fonctionnelles et de qualité de vie.
Syndrome de compression de la veine iliaque primitive «May Thurner Syndrome»
Authors: Doenz
Published: March 2006

Le syndrome de compression de la veine iliaque primitive gauche, aussi appelé May-Thurner Syndrome est une compression de la veine iliaque primitive par l'artère iliaque primitive droite. Il en résulte des changements dans la structure de l'intima qui provoquent une thrombose de l'axe iliaque. Le traitement de choix est endovasculaire par thrombolyse et stenting.
La chirurgie des reflux veineux profonds des membres inférieurs
Authors: Perrin
Published: March 2006

La valeur de la chirurgie des reflux veineux profonds (RVP) reste encore discutée. Au plan étiologique c'est le syndrome post-thrombotique qui est le plus fréquent, mais l'insuffisance veineuse profonde primitive est souvent occultée. L'agénésie valvulaire est une étiologie rarissime. L'examen clinique ne permet pas toujours de différencier les insuffisances veineuses superficielles des insuffisances veineuses profondes et les insuffisances primaires des insuffisances secondaires c'est-à-dire post-thrombotiques. Au plan des investigations, l'écho-doppler fournit à la fois des informations anatomiques, étiologiques et hémodynamiques. Les pléthysmographies volumiques permettent de quantifier la sévérité globale de l'insuffisance veineuse, mais ne fournissent pas d'élément sur l'étiologie et ne permettent pas de façon fiable de déterminer la responsabilité respective des différents systèmes veineux pathologiques. Si une chirurgie du RVP est envisagée, il faut compléter ces investigations par une mesure des pressions et des phlébographies ascendante et descendante sachant qu'en présence de contre-indications à la chirurgie, elles ne doivent pas être entreprises. L'objectif de la chirurgie du RVP est de corriger le reflux responsable d'une augmentation permanente de la pression veineuse, mais on doit garder en mémoire que le RVP est le plus souvent associé à un reflux dans le réseau veineux superficiel et/ou dans les perforantes, en conséquence il faut corriger ces trois anomalies. Les techniques chirurgicales qui visent à traiter les RVP peuvent être classées en deux groupes: celles qui nécessitent une phlébotomie et celles sans phlébotomie. Les résultats de la chirurgie du RVP sont difficiles à estimer dans la mesure où elle est le plus souvent associée à la chirurgie de l'insuffisance veineuse superficielle et/ou des perforantes, bien qu'assez souvent celles-ci aiont été réalisées préalablement. Les indications de la chirurgie du RVP reposent sur des éléments cliniques, hémodynamiques et d'imagerie. L'étiologie est également un facteur de décision, sachant que la chirurgie sera plus volontiers proposée dans les reflux primaires. La chirurgie du RVP ne doit être entreprise que par des équipes spécialisées dans ce domaine.
Does the subtropical jet catalyze the midlatitude atmospheric regimes?
Authors: Ruti Paolo M. , Lucarini Valerio , Dell'Aquila Alessandro , Calmanti Sandro , Speranza Antonio
Published: March 2006

Understanding the atmospheric low‐frequency variability is of crucial importance in fields such as climate studies, climate change detection, and extended‐range weather forecast. The Northern Hemisphere climate features the planetary waves as a relevant ingredient of the atmospheric variability. Several observations and theoretical arguments seem to support the idea that winter planetary waves indicator obey a non‐Gaussian statistics and may present a multimodal probability density function, thus characterizing the low‐frequency portion of the climate system. We show that the upper tropospheric jet strength is a critical parameter in determining whether the planetary waves indicator exhibits a uni‐ or bimodal behavior, and we determine the relevant threshold value of the jet. These results are obtained by considering the data of the NCEP‐NCAR and ECMWF reanalyses for the overlapping period. Our results agree with the non‐linear orographic theory, which explains the statistical non‐normality of the low‐frequency variability of the atmosphere and its possible bimodality.
Spatial and temporal variations of Richardson number on Georges Bank
Authors: Pease Christopher , Sundermeyer Miles A.
Published: March 2006

Buoyancy frequency and shear were used to estimate spatial and temporal variations in Richardson number, Ri, on Georges Bank. Calculations were based on CTD and ADCP data from 41 stations occupied repeatedly over 17 cruises during winter and spring, 1995–1999. Stations were grouped into five spatial averaging regions, two depth zones, and two seasons. Average Ri ranged from 0.01 to 1.63 with a general tendency of increasing Ri with total water depth. Significant differences in average Ri between the two seasons and two depth zones were also found. These differences were largely due to variations in buoyancy frequency, and to a lesser degree due to variations in shear. Our results offer an empirical context for examining spatial and temporal variability of vertical mixing on the Bank.
Salinity changes along the upper limb of the Atlantic thermohaline circulation
Authors: Blanke Bruno , Arhan Michel , Speich Sabrina
Published: March 2006

Lagrangian analyses of a global ocean circulation model quantify the salinity changes experienced by the warm limb of the thermohaline circulation during the northward flow to the Atlantic deep convection regions. 6 Sv out of the estimated 10‐Sv transfer from 45°S to 47°N flow through regions of prevailing surface evaporation: the southern and northern formation regions of Salinity Maximum Water and the Gulf of Cadiz/Mediterranean Sea domain. The remaining transport gains salinity through mixing with adjacent waters. As much as 6 Sv flow through the low‐salinity surface mixed layer at the latitudes of the ITCZ whose effect annihilates that of the southern region of Salinity Maximum Water. Most of the salinity increase corresponds to the transformation of South to North Atlantic Central Water, with strong diapycnal transfers for the water that intersects the high and low salinity regions, and nearly isopycnal modifications for the water that avoids these regions.
Second‐order random internal and surface waves in a two‐fluid system
Authors: Liu Chi‐Min
Published: March 2006

Second‐order solutions for internal and surface waves in a two‐fluid system are derived using a perturbation technique. As expected, solutions of the second order are composed of the products of the first‐order components. Super‐ and subharmonic transfer functions describing the relation between the first‐ and second‐order wave amplitudes are introduced. For the self interaction of the first‐order waves with a fixed wavenumber, there exist three combinations of linear waves. The associated superharmonic transfer function and the effects of second‐order waves on wave profiles are examined. Furthermore, taking the density of the upper layer to be zero, present results include most existing theories for second‐order surface waves as special cases.
Effect of the motional electric field on the Venus nightside ionopause
Authors: Kanao M. , Terada N. , Yamazaki A. , Yoshikawa I. , Abe T. , Nakamura M.
Published: March 2006

The purpose of this paper is to clarify how the average structure of the Venus nightside ionopause for solar zenith angles (SZA) greater than 90° depends on (1) the direction and (2) the magnitude of the motional electric field of the solar wind. Plasma density structure in the Venus nightside ionosphere has been investigated by using data sets of the Pioneer Venus Orbiter observations. It is found that the distribution of the nightside ionopause locations is asymmetric with respect to the direction of the solar wind electric field, leaning opposite to the electric field vector. It is also found that the asymmetry is increasingly prominent as the magnitude of the motional electric field increases, while not so prominent for small field magnitude. This result suggests that the asymmetric ionopause location in the nightside is related to the acceleration of pickup ions.
Physics‐based tests to identify the accuracy of solar wind ion measurements: A case study with the Wind Faraday Cups
Authors: Kasper J. C. , Lazarus A. J. , Steinberg J. T. , Ogilvie K. W. , Szabo A.
Published: March 2006

We present techniques for comparing measurements of velocity, temperature, and density with constraints imposed by the plasma physics of magnetized bi‐Maxwellian ions. Deviations from these physics‐based constraints are interpreted as arising from measurement errors. Two million ion spectra from the Solar Wind Experiment Faraday Cup instruments on the Wind spacecraft are used as a case study. The accuracy of velocity measurements is determined by the fact that differential flow between hydrogen and helium should be aligned with the ambient magnetic field. Modeling the breakdown of field alignment suggests velocity uncertainties are less than 0.16% in magnitude and 3° in direction. Temperature uncertainty is found by examining the distribution of observed temperature anisotropies in high‐beta solar wind intervals where the firehose, mirror, and cyclotron microinstabilities should drive the distribution to isotropy. The presence of a finite anisotropy at high beta suggests overall temperature uncertainties of 8%. Hydrogen and helium number densities are compared with the electron density inferred from observations of the local electron plasma frequency as a function of solar wind speed and year. We find that after accounting for the contribution of minor ions, the results are consistent with a systematic offset between the two instruments of 3–4%. The temperature and density methods are sensitive to non‐Maxwellian features such as heat flux and proton beams and as a result are more suited to slow solar wind where these features are rare. These procedures are of general use in identifying the accuracy of observations from any solar wind ion instrument.
Drift and mixing under the ocean surface: A coherent one‐dimensional description with application to unstratified conditions
Authors: Rascle Nicolas , Ardhuin Fabrice , Terray Eugene A.
Published: March 2006

Waves have many effects on near‐surface dynamics: Breaking waves enhance mixing, waves are associated with a Lagrangian mean drift (the Stokes drift), waves act on the mean flow by creating Langmuir circulations and a return flow opposite to the Stokes drift, and, last but not least, waves modify the atmospheric surface roughness. A realistic ocean model is proposed to embrace all these aspects, focusing on near‐surface mixing and surface drift associated with the wind and generated waves. The model is based on the generalized Lagrangian mean that separates the momentum into a wave pseudomomentum and a quasi‐Eulerian momentum. A wave spectrum with a reasonably high frequency range is used to compute the Stokes drift. A turbulent closure scheme based on a single evolution equation for the turbulent kinetic energy includes the mixing due to breaking wave effects and wave‐turbulence interactions. The roughness length of the closure scheme is adjusted using observations of turbulent kinetic energy near the surface. The model is applied to unstratified and horizontally uniform conditions, showing good agreement with observations of strongly mixed quasi‐Eulerian currents near the surface when waves are developed. Model results suggest that a strong surface shear persists in the drift current because of the Stokes drift contribution. In the present model the surface drift only reaches 1.5% of the wind speed. It is argued that stratification and the properties of drifting objects may lead to a supplementary drift as large as 1% of the wind speed.
Cross‐shore variation of wind‐driven flows on the inner shelf in Long Bay, South Carolina, United States
Authors: Gutierrez Benjamin T. , Voulgaris George , Work Paul A.
Published: March 2006

The cross‐shore structure of subtidal flows on the inner shelf (7 to 12 m water depth) of Long Bay, South Carolina, a concave‐shaped bay, is examined through the analysis of nearly 80 days of near‐bed (1.7–2.2 m above bottom) current observations acquired during the spring and fall of 2001. In the spring and under northeastward winds (upwelling favorable) a two‐layered flow was observed at depths greater than 10 m, while closer to the shore the currents were aligned with the wind. The two‐layered flow is attributed to the presence of stratification, which has been observed under similar conditions in the South Atlantic Bight. When the wind stress was southwestward (downwelling favorable) and exceeded 0.1 N/m2, vertical mixing occurred, the two‐layered flow pattern disappeared, and currents were directed alongshore with the wind at all sites and throughout the water column. In the fall, near‐bed flows close to the shore (water depth <7 m) were often reduced compared to or opposed those measured farther offshore under southwestward winds. A simplified analysis of the depth‐averaged, alongshore momentum balance illustrates that the alongshore pressure gradient approached or exceeded the magnitude of the alongshore wind stress at the same time that the nearshore alongshore current opposed the wind stress and alongshore currents farther offshore. In addition, the analysis suggests that the wind stress is reduced closer to shore so that the alongshore pressure gradient is large enough to drive the flow against the wind.
Application of GPS radio occultation method for observation of the internal waves in the atmosphere
Authors: Liou Y. A. , Pavelyev A. G. , Wickert J. , Liu S. F. , Pavelyev A. A. , Schmidt T. , Igarashi K.
Published: March 2006

In this study, we show that the amplitude radio occultation (RO) method, which employs high‐precision global positioning system (GPS) signals, allows one to determine the vertical gradients of refractivity and monitor wave structures in the atmosphere on a global scale at altitudes ranging from 10 to 40 km. We show that the sensitivity of the RO amplitude data to the wave structures in the atmosphere with vertical periods from 0.8 to 4 km exceeds one of the RO phase data by a factor of order 10. As an example of this approach, analytical results of the Challenging Minisatellite Payload's (CHAMP) RO events are presented. Wave clusters were found in the amplitude variations of the RO signals with interior vertical periods from 0.8 to 4 km in the tropopause and lower stratosphere within the heights of 15–24 km (low latitudes) to 10–15 km (moderate latitudes). We demonstrate that the amplitude variations can be considered as a radio‐holographic image of the wave structures in the atmosphere. For internal gravity waves (GW), we show that the GW portrait, which consists of the altitude dependence of the GW phase, amplitude and vertical spatial frequency, can be retrieved from the amplitude variations of the RO signal. The GW dispersion and polarization relationships allow one to estimate the vertical profile of the horizontal wind perturbations, its gradient and the GW intrinsic phase speed. In general, when the origin and type of internal waves are not known, the height dependence of the vertical gradient of refractivity can be applied for monitoring the seasonal and geographical distributions of wave activities at different levels in the atmosphere.
Future change of precipitation extremes in Europe: Intercomparison of scenarios from regional climate models
Authors: Frei Christoph , Schöll Regina , Fukutome Sophie , Schmidli Jürg , Vidale Pier Luigi
Published: March 2006

An analysis of the climate of precipitation extremes as simulated by six European regional climate models (RCMs) is undertaken in order to describe/quantify future changes and to examine/interpret differences between models. Each model has adopted boundary conditions from the same ensemble of global climate model integrations for present (1961–1990) and future (2071–2100) climate under the Intergovernmental Panel on Climate Change A2 emission scenario. The main diagnostics are multiyear return values of daily precipitation totals estimated from extreme value analysis. An evaluation of the RCMs against observations in the Alpine region shows that model biases for extremes are comparable to or even smaller than those for wet day intensity and mean precipitation. In winter, precipitation extremes tend to increase north of about 45°N, while there is an insignificant change or a decrease to the south. In northern Europe the 20‐year return value of future climate corresponds to the 40‐ to 100‐year return value of present climate. There is a good agreement between the RCMs, and the simulated change is similar to a scaling of present‐day extremes by the change in average events. In contrast, there are large model differences in summer when RCM formulation contributes significantly to scenario uncertainty. The model differences are well explained by differences in the precipitation frequency and intensity process, but in all models, extremes increase more or decrease less than would be expected from the scaling of present‐day extremes. There is evidence for a component of the change that affects extremes specifically and is consistent between models despite the large variation in the total response.
Ozone profiles in the high‐latitude stratosphere and lower mesosphere measured by the Improved Limb Atmospheric Spectrometer (ILAS)‐II: Comparison with other satellite sensors and ozonesondes
Authors: Sugita T. , Nakajima H. , Yokota T. , Kanzawa H. , Gernandt H. , Herber A. , von der Gathen P. , König‐Langlo G. , Sato K. , Dorokhov V. , Yushkov V. A. , Murayama Y. , Yamamori M. , Godin‐Beekmann S. , Goutail F. , Roscoe H. K. , Deshler T. , Yela M. , Taalas P. , Kyrö E. , Oltmans S. J. , Johnson B. J. , Allaart M. , Litynska Z. , Klekociuk A. , Andersen S. B. , Braathen G. O. , De Backer H. , Randall C. E. , Bevilacqua R. M. , Taha G. , Thomason L. W. , Irie H. , Ejiri M. K. , Saitoh N. , Tanaka T. , Terao Y. , Kobayashi H. , Sasano Y.
Published: March 2006

A solar occultation sensor, the Improved Limb Atmospheric Spectrometer (ILAS)‐II, measured 5890 vertical profiles of ozone concentrations in the stratosphere and lower mesosphere and of other species from January to October 2003. The measurement latitude coverage was 54–71°N and 64–88°S, which is similar to the coverage of ILAS (November 1996 to June 1997). One purpose of the ILAS‐II measurements was to continue such high‐latitude measurements of ozone and its related chemical species in order to help accurately determine their trends. The present paper assesses the quality of ozone data in the version 1.4 retrieval algorithm, through comparisons with results obtained from comprehensive ozonesonde measurements and four satellite‐borne solar occultation sensors. In the Northern Hemisphere (NH), the ILAS‐II ozone data agree with the other data within ±10% (in terms of the absolute difference divided by its mean value) at altitudes between 11 and 40 km, with the median coincident ILAS‐II profiles being systematically up to 10% higher below 20 km and up to 10% lower between 21 and 40 km after screening possible suspicious retrievals. Above 41 km, the negative bias between the NH ILAS‐II ozone data and the other data increases with increasing altitude and reaches 30% at 61–65 km. In the Southern Hemisphere, the ILAS‐II ozone data agree with the other data within ±10% in the altitude range of 11–60 km, with the median coincident profiles being on average up to 10% higher below 20 km and up to 10% lower above 20 km. Considering the accuracy of the other data used for this comparative study, the version 1.4 ozone data are suitably used for quantitative analyses in the high‐latitude stratosphere in both the Northern and Southern Hemisphere and in the lower mesosphere in the Southern Hemisphere.
Estimation of the impact of land‐surface forcings on temperature trends in eastern United States
Authors: Kalnay Eugenia , Cai Ming , Li Hong , Tobin Jayakar
Published: March 2006

We use the “observation minus reanalysis” difference (OMR) method to estimate the impact of land‐use changes by computing the difference between the trends of the surface temperature observations (which reflect all the sources of climate forcing, including surface effects) and the NCEP‐NCAR reanalysis surface temperatures (only influenced by the assimilated atmospheric temperature trends). This includes not only urbanization effects but also changes in agricultural practices, such as irrigation and deforestation, as well as other near‐surface forcings related to industrialization, such as aerosols. We slightly correct previous results by including the year 1979 within the satellite decades and by excluding stations in the West Coast of the United States. The OMR estimate for surface impact on the mean temperature is similar to that obtained using satellite observations of night light to discriminate between rural and urban stations, with regions of large positive and negative trends, in contrast with the urban corrections based on population density, which are uniformly positive and much smaller. The OMR seasonal cycle results suggest that the impact of the greenhouse gases dominates in the winter, whereas it appears that the impact of surface forcings dominates in the summer. The impact of the USHCN adjustments for nonclimatic trends in the observations does not affect the geographical distribution of the OMR trends. The effect of using a model with constant CO2 in the reanalysis, the use of other reanalyses, and the possible use of the reanalyses to correct for nonclimatic jumps in the observations are also discussed.
Development of zeolite ion source for beam probe measurements of high temperature plasma
Authors: Ohshima Shinsuke , Fujisawa Akihide , Shimizu Akihiro , Nakano Haruhisa
Published: March 2006

A zeolite ion source has been developed for plasma diagnostics. Extracted beam current is increased by a factor of ∼10 after redesigning the ion source structure and improving the method to make emitter material (zeolite). The article introduces an experiment on making desirable ion emitter, and describes the properties of the developed ion source.
Density and velocity of H− in the extraction region of a negative ion source estimated from the change in H− beam current due to a pulse laser injection
Authors: Matsumoto Y. , Nishiura M. , Matsuoka K. , Wada M. , Sasao M. , Yamaoka H.
Published: March 2006

A method to estimate H− density and velocity in the extraction region of a negative ion source plasma without a Langmuir probe is developed. It utilizes the laser photodetachment with a Faraday cup (PD-FC). The H− parameters estimated by PD-FC are compared to the results measured by laser-photodetachment with a Langmuir probe (PD-LP). The result shows that H− velocity estimated by PD-FC is in good agreement with the PD-LP result. Meanwhile, H− density estimated by PD-FC is twice larger than the PD-LP result. Though a more detailed research, including more effects that are ignored in this study, is needed for H− density measurement, PD-FC will be a very useful tool for H− measurements especially near an extraction hole in negative ion sources.