bluuebunny/crossref_metadata_2025 huggingface dataset:
Bathymetric distribution of the meiofaunal polychaetes in the nearshore zone of Martel Inlet, King George Island, Antarctica
Authors: Varella Petti Mônica A. , Nonato Edmundo Ferraz , Skowronski Rodrigo S.P. , Corbisier Thaïs Navajas
Published: June 2006

Polychaetes, the dominant macrofaunal taxa of the Antarctic soft sediments, provided more than 40% of the animals found in Martel Inlet. However, little information is available on the composition of meiofaunal communities in polar areas. This study identified the meiofaunal polychaete species and described their bathymetric distribution in the nearshore zone. Sediment cores were taken by divers from 6–25 m depth in the summer of 1991 and 1994 in front of the Brazilian Antarctic Station (Martel Inlet, Admiralty Bay). Additional sampling was done at the 18 m depth in 1994 in order to study the influence of ice scouring. A total of 1895 specimens in 17 families were found. Three species (Apistobranchus glacierae, Leitoscoloplos kerguelensis and Ophryotrocha notialis), all of them belonging to the temporary meiofauna, provided more than 70% of the total polychaete fraction. This meiofaunal component showed similar distributional patterns to those of the macrofaunal polychaetes in this area.
Distinguishing cryptic species in Antarctic Asellota (Crustacea: Isopoda) - a preliminary study of mitochondrial DNA in Acanthaspidia drygalskii
Authors: Raupach Michael J. , Wägele Johann-Wolfgang
Published: June 2006

Acanthaspid isopods are well known from the deep sea regions of all oceans. Many species have been found also on the continental shelf around Antarctica. Phylogenetic relationships within the Acanthaspidiidae and the genetic differentiation of populations are poorly understood. In this study we analysed 16S rRNA gene sequences of 36 specimens of Acanthaspidiidae, including 17 specimens of Acanthaspidia drygalskii Vanhöffen, 1914. This species is known from several locations along the Antarctic shelf, supporting the idea of a circum-Antarctic distribution of this taxon. Our molecular data support the monophyly of all six species analysed, but there is only limited evidence for the interspecific relationships between the species. However, we were able to identify three distinct groups of haplotypes within Acanthaspidia drygaskii. Our results indicate the evidence of cryptic, reproductively isolated species. Further data are needed to understand mechanisms underlying speciation in deep sea isopods.
Population census of blue petrels Halobaena caerulea at Mayes Island, Iles Kerguelen
Authors: Barbraud Christophe , Delord Karine
Published: June 2006

The blue petrel (Halobaena caerulea) is a small pelagic seabird breeding on just a few Southern Ocean islands. Although it is known that oceanographic and climatic variability affect mortality rates, individual body condition and reproductive success, very few data are available on the global population status. We assessed the status of blue petrels at Mayes Island, Iles Kerguelen, in 2002 by estimating burrow densities and burrow occupancy using acoustic playbacks and response probability. The mean and highest burrow densities recorded were respectively 0.136 ± 0.026 and 2.3 entrances per m2. Burrow occupancy increased with burrow density but stabilized at c. 0.6 occupied burrows per m2. Taking into account the response probability to playback (0.819) the mean burrow occupancy density was 0.037 ± 0.094 per m2, giving an estimated 142 000 (95% CI around 106 000–179 000) or 148 000 breeding pairs (95% CI around 55 000–241 000) on Mayes Island, respectively with and without taking into account spatial autocorrelation in burrow densities. This suggests that the entire breeding population of blue petrels at Kerguelen is much higher than current estimates, and that Kerguelen and Diego Ramírez archipelagos are key breeding sites for this species.
Southern elephant seals north of the Antarctic Polar Front
Authors: Lewis M. , Campagna C. , Marin M.R. , Fernandez T.
Published: June 2006

This paper reports on sightings and dispersion of individual southern elephant seals (Mirounga leonina) along the Atlantic and Pacific coasts of South America based on reports of tagged/marked seals from Patagonia and of animals of unknown origin. From 154 sightings, encompassing at least 354 individuals, we found that individuals dispersed to subequatorial latitudes on both sides of the continent, and to more temperate sites, in the Magellanic region of Tierra del Fuego. Nineteen sites were visited by tagged seals from the established colony of Península Valdés (PV, Argentina). PV and the smaller seal population of the Falklands/Malvinas were regularly connected by adults of both sexes. There were more sightings of males than females. No incipient new breeding colonies were found along the Atlantic coast of South America. Some observations coincided with places where elephant seals had been recorded or exploited in the seventeenth and eighteenth centuries. A shortage of suitable habitat for expansion and proximity to predictable food could act as a stabilizing process preventing colonization of new areas from PV. Dispersion data, coherent with population genetics, support a Patagonian elephant seal stock.
Ice core melt features in relation to Antarctic coastal climate
Authors: Kaczmarska Marzena , Isaksson Elisabeth , Karlöf Lars , Brandt Ola , Winther Jan-Gunnar , van de Wal Roderik S.W. , van den Broeke Michiel , Johnsen Sigfus J.
Published: June 2006

Measurement of light intensity transmission was carried out on an ice core S100 from coastal Dronning Maud Land (DML). Ice lenses were observed in digital pictures of the core and recorded as peaks in the light transmittance record. The frequency of ice layer occurrence was compared with climate proxy data (e.g. oxygen isotopes), annual accumulation rate derived from the same ice core, and available meteorological data from coastal stations in DML. The mean annual frequency of melting events remains constant for the last ∼150 years. However, fewer melting features are visible at depths corresponding to approximately 1890–1930 AD and the number of ice lenses increases again after 1930 AD. Most years during this period have negative summer temperature anomalies and positive annual accumulation anomalies. The increase in melting frequency around ∼1930 AD corresponds to the beginning of a decreasing trend in accumulation and an increasing trend in oxygen isotope record. On annual time scales, a relatively good match exists between ice layer frequencies and mean summer temperatures recorded at nearby meteorological stations (Novolazarevskaya, Sanae, Syowa and Halley) only for some years. There is a poor agreement between melt feature frequencies and oxygen isotope records on longer time scales. Melt layer frequency proved difficult to explain with standard climate data and ice core derived proxies. These results suggest a local character for the melt events and a strong influence of surface topography.
Multidisciplinary radiographer-led review clinics – an example of implementation
Authors: Ellis T. , Ashmore L. , Bray D.
Published: June 2006

In recent years there has been a push to move away from traditional clinician led on treatment review of radiotherapy patients. Despite this impetus there has been little published work relating to how the new system can be implemented. This article describes how one department implemented a change in direction from the conventional and moved forward with radiographer-led review clinics. The Plan–Do–Check–Act cycle is used as a basis for evaluation with results of a small-scale patient audit and a comparison with other departments in the UK being presented. This method of implementation and evaluation proved successful and may serve as an early model for radiotherapy departments elsewhere.
Salvage radiotherapy for patients with increasing prostate-specific antigen levels after radical prostatectomy: evaluation of the role of retrograde urethrography
Authors: Buskirk S. J. , Kraft K. J. , Witt N. J. , Scheuer A. K. , Gianforti B. L. , DeGuzman M. L. , Hunter C. A. , Guida M. , Serago C. F. , Schild S. E. , Collie A. C.
Published: June 2006

Purpose: To evaluate the role of retrograde urethrography in treatment planning for salvage external beam radiotherapy in patients with increasing prostate-specific antigen levels after radical prostatectomy.

Methods and Materials: From July 1988 to December 2002, 173 consecutive patients received external beam radiotherapy for increasing prostate-specific antigen levels after radical prostatectomy. All 173 simulation films were reviewed, and retrograde urethrography was performed in 148 patients (86%). The distance between the line connecting the lower poles of the ischial tuberosities and site of abrupt narrowing of contrast material was measured in all 148 patients. This distance was compared with that measured in 148 consecutive patients with intact prostates who had retrograde urethrography while undergoing treatment planning for definitive radiotherapy.

Results: The mean (median) distance from the line connecting the lower poles of the ischial tuberosities to the abrupt narrowing seen in the urethrogram in patients with increasing prostate-specific antigen levels was 1.54cm (1.50cm) compared with 1.73cm (1.80cm) in those with intact prostates (p = 0.0145).

Conclusion: Retrograde urethrography is important in treatment planning for salvage radiotherapy of the prostate bed after radical prostatectomy to adequately treat the apex of the prostate bed.
Improved peripheral dose calculation accuracy for a small MLC field brought by the latest commercial treatment planning system
Authors: Chow J. C. L. , Grigorov G. N. , Jiang R.
Published: June 2006

A recently released Pinnacle treatment planning system software, v7.4f includes some new physics features such as modeling of the rounded multi-leaf collimator (MLC) leaf ends and the tongue-and-groove structure between leaves. In this study, the above physics modeling improvements were verified by comparing the peripheral dose profiles for the small MLC fields calculated by the new Pinnacle v7.4f and the old Pinnacle v6.2b with those obtained from measurements experimentally. Three test MLC fields with different jaw sizes were prepared, and specific dose profiles (along cross-line, in-line and diagonal axis) at different depths were measured using a Varian 21 EX linear accelerator with 120-leaf Millennium MLC, big scanning water tank and photon diode. Estimated dose profiles for the test fields were calculated using Pinnacle v6.2b and v7.4f. By comparing the measured and calculated results, it was found that both v6.2b and v7.4f performed well in calculating the cross-line (along the gap between the longitudinal lengths of two leaves) and diagonal axis dose profiles at different depths. However, v7.4f gave calculated dose values closer to the measured field for in-line (gap between junctions of two rounded leaf ends) axis dose profiles at different depths. For the shape of the profile along the in-line axis, v7.4f calculated a flat “platform” dose profile of about 34.3% (inter-bank leakage) at depth dmax> beyond the MLC field edge using a clinical dose grid size of 0.4×0.4×0.4cm3, compared to the “zigzag” dose profile varying between 35.4% and 42.1% measured using the water tank and diode. However, both Pinnacle v6.2b and v7.4f calculated the percentage depth dose for the test fields well compared to the measurements.
Properties of Input-Consuming Derivations
Authors: BOSSI ANNALISA , ROSSI SABINA , ETALLE SANDRO
Published: June 2006

We study the properties of input-consuming derivations of moded logic programs. Input-consuming
derivations can be used to model the behavior of logic programs using dynamic
scheduling and employing constructs such as delay declarations. We consider the class of
nicely-moded programs and queries. We show that for these programs a weak version of the
well-known switching lemma holds also for input-consuming derivations. Furthermore, we
show that, under suitable conditions, there exists an algebraic characterization of termination
of input-consuming derivations.
Soundness, idempotence and commutativity of set-sharing
Authors: HILL PATRICIA M. , BAGNARA ROBERTO , ZAFFANELLA ENEA
Published: June 2006

It is important that practical data-flow analyzers are backed by reliably proven theoretical
results. Abstract interpretation provides a sound mathematical framework and necessary
generic properties for an abstract domain to be well-defined and sound with respect to the
concrete semantics. In logic programming, the abstract domain Sharing is a standard choice
for sharing analysis for both practical work and further theoretical study. In spite of this,
we found that there were no satisfactory proofs for the key properties of commutativity and
idempotence that are essential for Sharing to be well-defined and that published statements
of the soundness of Sharing assume the occurs-check. This paper provides a generalization of
the abstraction function for Sharing that can be applied to any language, with or without the
occurs-check. Results for soundness, idempotence and commutativity for abstract unification
using this abstraction function are proven.
Pursuing cost containment in a pluralistic payer environment: from the aftermath of Clinton's failure at health care reform to the Balanced Budget Act of 1997
Authors: Mayes Rick , Hurley Robert E.
Published: June 2006

Following a decade in which Medicare operated as the leading ‘change agent’ within the US health care system, the private sector rose to the fore in the mid 1990s. The failure of President Clinton's attempt at comprehensive, public sector-led reform left managed care as the solution for cost control. And for a period it worked, largely because managed care organizations were able to both squeeze payments to selective networks of medical providers and significantly reduce inpatient hospital stays. There was a lot of ‘fat’ in the nation's convoluted health care system that could be (and was) eliminated through competitive negotiations between medical providers and insurers, employers, or managed care organizations. One of our primary arguments in this article is that managed care operated partly as a systematic suppression of price discrimination or differential pricing (often referred to as ‘cost shifting’), as managed care organizations qua purchasing agents prevented hospitals and physicians from summarily raising prices to private payers to meet their financial requirements. Over time, however, managed care fell victim to inflated expectations, its own initial success, and larger fiscal forces. During this same period, Republicans and Democrats struggled to reach a consensus over the future direction of Medicare. Their disagreements contributed to the impasse over budget policy in 1995 and the infamous partial federal government shutdown. After President Clinton's reelection in 1996, partisan disagreements over Medicare dissipated. And, in 1997, Congress and the president passed the Balanced Budget Act of 1997, which emerged as a massive piece of patchwork legislation that sought to balance the federal budget, rein in Medicare spending, and increase the number of the programme's beneficiaries in private health plans.
Zubereitungen zur Anwendung am Auge unter Berücksichtigung der Therapie des Sicca-Syndroms
Authors: Sauer  , Hoppe-Tichy
Published: June 2006

Da das Auge ein empfindliches Körperorgan ist, stellt die Behandlung von Augenerkrankungen hohe Ansprüche an die applizierten Zubereitungen. So darf die Zubereitung weder chemisch noch physikalisch reizen und muss zu jeder Zeit steril sein. Zudem sollte sie den physiologischen Gegebenheiten des Auges wenn möglich angepasst werden, um Reizungen zu vermeiden. Mit der Wahl der Applikationsform können z.B. Wirkintensität und Wirkdauer bestimmt werden. Vom so genannten Sicca-Syndrom ist ein Großteil der Bevölkerung betroffen. Die Therapie umfasst sowohl nichtmedikamentöse als auch medikamentöse Maßnahmen. Dabei kommen unter anderem künstliche Tränen zum Einsatz. Die Auswahl eines geeigneten Präparates richtet sich nach dem Schweregrad der Erkrankung und auch nach der Viskosität der Zubereitung. In schwerwiegenderen Fällen werden Substanzen wie Hyaluronsäure oder Formulierungen, die Lipide enthalten, hinzugezogen.
Arzneiformen in der Herz-Kreislauftherapie
Authors: Bultmann  , Schweiger
Published: June 2006

Die bei der Behandlung von Herz-Kreislauferkrankungen eingesetzten Arzneiformen werden vorgestellt wobei auch eher seltene Arzneiformen Berücksichtigung finden. Zu jeder Arzneiform werden stichwortartig wichtige Punkte gelistet, die bei der Anwendung zu beachten sind. Die Begründung für diese Einnahmehinweise ergibt sich aus den speziellen Eigenschaften der einzelnen Arzneiformen, die am Ende des Artikels ausführlicher beschrieben werden. Weiterhin werden allgemeine Einnahmehinweise gegeben und auf die Austauschbarkeit und das Teilen bzw. Zerkleinern von Tabletten eingegangen.
Inhalative Applikationsformen bei Asthma bronchiale und COPD
Authors: Schwald  , Schneider  , Meyer
Published: June 2006

Für eine wirksame Therapie von obstruktiven Atemwegserkrankungen sind nicht nur Wirkstoffart und -stärke von entscheidender Bedeutung, sondern auch die optimale Applikation des Wirkstoffs. Nur durch eine gute Inhalationstechnik ist sichergestellt, dass der Wirkstoff auch dort ankommt, wo er wirken soll, nämlich in den Bronchien. Tatsächlich ist dies nicht so einfach, wie es auf den ersten Blick erscheinen mag. Eine effektive Inhalation scheitert häufig an einer mangelnden Koordination von Auslösung des Sprühstoßes und der Inspiration. Die pharmazeutische Industrie hat mit zahlreichen Systemen versucht, hier Abhilfe zu schaffen. Die hierdurch entstehende Vielfalt von Applikationssystemen führt jedoch auch zur Unübersichtlichkeit. Sowohl Patienten als auch Ärzten fällt es schwer zu durchschauen, welches Inhalationssystem für welchen Patienten geeignet ist und wie diese optimal eingesetzt werden können. Um die Auswahl zu erleichtern, wird nachfolgend ein Überblick über die derzeit gängigen Systeme gegeben.
Arzneimittelanwendung bei Kindern und Jugendlichen
Authors: Wagner  , Frey
Published: June 2006

Die Hersteller von Arzneimitteln verzichten häufig auf die aufwändige Zulassung bei Kindern. Dadurch stehen in vielen Fällen keine kindgerechten Arzneiformen und Dosierungen zur Verfügung, und selbst bei für Kinder zugelassenen Arzneimitteln fehlen teilweise die notwendigen Informationen und Hilfsmittel zur korrekten Anwendung. Die Auswahl eines geeigneten Arzneimittels bei individueller Dosierung, die Berücksichtigung der physiologischen Besonderheiten, die Bereitstellung geeigneter Hilfsmittel und die umfassende Information der Eltern oder Pflegekräfte trägt daher entscheidend zum Erfolg der Arzneimitteltherapie von Kindern bei.
Arzneimittelformen und Arzneimittelverabreichung in der Geriatrie
Authors: Heppner  , Sieber  , Esslinger  , Trögner
Published: June 2006

Die Entwicklungen des Alterns stellen veränderte Herausforderungen an die medizinische Versorgung und das Management von geriatrischen Patienten. Der betagte Patient mit seinen altersbedingten Funktionseinschränkungen und der Multimorbidität ist durch alternsphysiologische Veränderungen sowie durch unreflektierte Pharmakotherapie gefährdet und auf die hausärztliche Hilfestellung angewiesen. Beim geriatrischen Patienten ist die Verordnung der geeigneten Arzneiform und der praktikablen Applikationsform der Schlüssel zum Therapieerfolg. Altersgerechte Einnahmeverordnungen, wiederholte Aufklärung und Einnahmeschulung sind unersetzliche Versorgungsleistungen in der hausärztlichen Praxis und dem klinischen Alltag, die zunehmend an Bedeutung gewinnen.
Applikationshilfen aus der Apotheke
Authors: Hersberger  , Indermitte  , Bruppacher
Published: June 2006

Eine sachgerechte Anwendung von Arzneimitteln kann oft nur mit Applikationshilfen erreicht werden. Bei vielen Präparaten sind diese integriert: beschriftete Blisterpackungen, Messbecher, Dosierlöffel, Dosiersprays, Applikatoren für die topische Anwendung oder Fertigspritzen. Spezielle Bedürfnisse können durch zusätzliche Applikationshilfen wie Dosierspritzen für pädiatrische Dosierungen, Vorschaltkammern zu Bronchialsprays, Tablettenteiler und Tablettenmörser abgedeckt werden. Ein Nutzen ist aber nur möglich, wenn durch eine kompetente Beratung die korrekte Anwendung erklärt wird. Schließlich kann die Medikation auch in für den Patienten besser geeignete Behälter oder in Wochendispenser umgefüllt werden. Applikationshilfen leisten einen wichtigen Beitrag zur Gewährleistung der korrekten Dosierung (Sicherheit) sowie zur korrekten Durchführung des Therapieplanes (Compliance) und damit zum Therapieerfolg. Erforderlich sind evidenzbasierte Kriterien für die Wahl geeigneter Applikationshilfen und für die zugehörigen Beratungsinhalte, die leider weitgehend noch fehlen.
Tabletten teilen
Authors: Quinzler  , Haefeli
Published: June 2006

Knapp ein Drittel der ambulanten Patienten teilen ihre Tabletten vor der Einnahme. Diese gängige Praxis birgt, neben etlichen Vorteilen, allerdings auch einige Risiken für die Arzneimitteltherapie. Vor allem ältere Patienten sind häufig nicht in der Lage Tabletten exakt zu teilen und die unsachgemäße Teilung z.B. von Retardpräparaten kann zu einer Überdosierung führen. Ob eine Tablette geteilt werden darf, hängt im Wesentlichen von den Wirkstoffeigenschaften, der Galenik, der Form der Tablette und der Beschaffenheit der Bruchkerbe ab. Darüber hinaus muss gesichert sein, dass der Patient über die erforderliche Bereitschaft und Fingergeschicklichkeit verfügt, seine Tabletten zu teilen, um die Compliance nicht zu beeinträchtigen. Nicht zuletzt muss der Patient über die richtige Teilungstechnik informiert sein, damit beim Teilen zwei gleichgroße Bruchstücke entstehen und die Wirksamkeit der Therapie nicht gefährdet wird.
Significance of atmospheric inputs of calcium over the southwestern Mediterranean region: High mountain lakes as tools for detection
Authors: Pulido‐Villena Elvira , Reche Isabel , Morales‐Baquero Rafael
Published: June 2006

We quantified dry and wet atmospheric deposition of calcium over the southwest Mediterranean region and we assessed its impact on calcium dynamics of two high mountain lakes differing in morphometry and catchment characteristics. Atmospheric deposition of Ca averaged 40 mmol m−2 yr−1, and it showed a seasonal pattern similar to that reported for Saharan dust export to the Mediterranean region, with maxima during spring and summer. Ca enrichment from nonmarine sources was significantly related to the TOMS (Total Ozone Mapping Spectrometer) aerosol index. Atmospheric inputs significantly affected Ca concentration of the selected lakes, which do not presumably receive significant Ca inputs from weathering. The intensity of the effect depended on their corresponding sensitivities to evaporation. Total atmospheric inputs of Ca to each study lake catchment (11300 and 3100 moles) were enough to explain the lake Ca content (5400 and 111 moles, respectively). The results obtained in this study reveal that atmospheric inputs, particularly Saharan dust deposition, may be a significant source of calcium to remote mountain lakes.
ICESat over Arctic sea ice: Interpretation of altimetric and reflectivity profiles
Authors: Kwok R. , Cunningham G. F. , Zwally H. J. , Yi D.
Published: June 2006

We provide an assessment of the ICESat altimeter for studying the Arctic Ocean and examine the magnitude of the large‐ and small‐scale expressions of geophysical processes embedded in the elevation profiles. This analysis includes data from six surveys. At the large scale the response of the ice‐covered ocean to atmospheric loading is near ideal (i.e., approximately −1 cm/hPa). After removal of the inverted barometer effects and best available geoid the elevation signal is still dominated by unresolved geoid residuals (∼0.4 m) that can be seen in the similarity of the remaining spatial patterns. Seasonal differences in elevations over multiyear ice are consistent with snow depth climatology; the broad differential spatial patterns are indicative of interannual differences in multiyear ice coverage associated with advection. Patterns in the derived surface roughness fields correspond to the seasonal and perennial ice zones seen in QuikSCAT data. At the small scale, near‐coincident RADARSAT imagery provides a spatial context for understanding the signature of the observed elevations, waveforms, and reflectivity, in particular, those associated with thin ice, open water, multiyear ice, and ridges. The precision of the elevation estimates measured over relatively flat sea ice, identified in synthetic aperture radar (SAR) imagery, is ∼2 cm. The unambiguous identification of ridged areas in coupled ICESat/RADARSAT analysis could be used to enhance the utility of SAR imagery for examining ridge distributions. Over a 20 day period we monitored the evolution of the reflectivity of a newly opened lead. The steep increase in reflectivity due to snow coverage suggests that dips in ICESat reflectivity are likely areas of thin ice and could serve as a basis for selection of tie points for use as sea level reference. Identification of these tie points is crucial for accurate estimation of sea ice freeboard.
A novel scheme for identifying principal modes in geophysical variability with application to global precipitation
Authors: Chen Ge
Published: June 2006

Any assessment of future climate changes requires knowledge of the full range of variability in the El Niño−Southern Oscillation (ENSO) phenomenon. The recent availability of 1–2 decades of satellite‐based high‐resolution measurements allows, in theory, the principal modes of many geophysical quantities to be fully resolved and well recovered at seasonal to decadal timescales. In this paper, a three‐dimensional (x, y, T, where T is period) harmonic extraction scheme aimed at revealing spatially/temporally independent variability modes is proposed. This scheme is applied to a 308‐month Global Precipitation Climatology Project (GPCP) data set spanning January 1979 through August 2004, allowing 11 principal precipitation modes to be clearly identified. In addition to the well‐known annual, semiannual, and seasonal cycles, seven interannual modes (six in the equatorial Pacific and one in the equatorial Indian Ocean) with intrinsic periods ranging from 1.5 to 7.7 years are identified, and the geophysical background of their generation is discussed in the context of a joint influence by the western Pacific warm pool and the eastern Pacific cold tongue. Also, a well‐defined decadal mode of 13.9 years is found in the central equatorial Pacific. The spatial/temporal structures of these principal modes are provided in detail. An important characteristic of the identified precipitation modes is that they are separated in space and incoherent in time. Identification of interannual precipitation variability as a single ENSO mode in some previous studies appears to be oversimplified and potentially misleading. Our results serve as a significant contribution to the understanding and prediction of the ENSO‐induced precipitation anomaly as well as its related global and regional climate change.
Reassessment of the Antarctic surface mass balance using calibrated output of a regional atmospheric climate model
Authors: van de Berg W. J. , van den Broeke M. R. , Reijmer C. H. , van Meijgaard E.
Published: June 2006

A detailed comparison of model‐simulated and observed Antarctic surface mass balance (SMB) is presented, using output of a regional atmospheric climate model (RACMO2/ANT) for the period 1980 to 2004. All available SMB observations from Antarctica (N = 1900) are used for the comparison, except clearly erroneous observations and data which are in areas where dominant SMB patterns occur on scales smaller than the model resolution. A high correlation is found (r = 0.82), while the regression slope (1.2) indicates that the model slightly overemphasizes SMB gradients. Comparing the model SMB with the latest SMB compilation, a similarly high correlation is found (r = 0.79), but the regression slope is much too steep because model‐simulated SMB agrees less with the compilation in data‐sparse regions. Model‐simulated SMB resembles the observed SMB as a function of elevation very well. This is used to calibrate model‐simulated SMB to reassess the contemporary Antarctic SMB. Compared to the latest SMB compilation, calibrated model‐simulated SMB is up to 1 m yr−1 higher in the coastal zones of East and West Antarctica, which are without exception in areas with few observations. As a result, the SMB integrated over the grounded ice sheet (171 ± 3 mm yr−1) exceeds previous estimates by as much as 15%. Support or falsification of this model result can only be found in new SMB observations from high accumulation regions.
Validation of Polar Ozone and Aerosol Measurement (POAM) III version 4 stratospheric water vapor
Authors: Lumpe J. , Bevilacqua R. , Randall C. , Nedoluha G. , Hoppel K. , Russell J. , Harvey V. L. , Schiller C. , Sen B. , Taha G. , Toon G. , Vömel H.
Published: June 2006

The Polar Ozone and Aerosol Measurement (POAM) III solar occultation instrument has been measuring water vapor at high latitudes since April 1998. Retrievals extend from 5 to 50 km, with 5–7% precision throughout the stratosphere and a vertical resolution of 1 (3) km in the lower (upper) stratosphere. Estimated systematic errors in the stratosphere are 10–15%. In this paper, we validate the POAM III version 4 stratospheric water vapor using correlative measurements from satellite, airborne, and balloon‐borne platforms. The resulting comparisons show that POAM water vapor is high compared to correlative measurements in the middle to lower stratosphere. The satellite (Halogen Occultation Experiment (HALOE) and Stratospheric Aerosol and Gas Experiment (SAGE) II) comparisons also indicate a sunrise/sunset bias in the POAM data, with sunset (Southern Hemisphere) retrievals larger than sunrise (Northern Hemisphere) retrievals by 5–10%. In the Northern Hemisphere, POAM is approximately 5–10% high compared to all validation data sets between 12 and 35 km. At higher altitudes this difference decreases, such that POAM agrees with HALOE at 40 km and is lower by 10% at 50 km. In the Southern Hemisphere, POAM is 15–25% higher than HALOE below 35 km, with differences decreasing to 10% by 50 km. Similar differences are seen with SAGE II. Despite these systematic differences the POAM water vapor data are self‐consistent and show no long‐term trends in accuracy or precision. Statistical comparisons of the water vapor variability measured by POAM, HALOE, and SAGE II show very good agreement. The POAM data are therefore valid for scientific studies, and the science community is encouraged to use this unique data set.
Modeling the equilibrium of tide‐dominated ebb‐tidal deltas
Authors: van der Vegt M. , Schuttelaars H. M. , de Swart H. E.
Published: June 2006

This study focuses on identifying physical mechanisms that lead to symmetric, tide‐dominated ebb‐tidal deltas. An idealized morphodynamic model is developed and analyzed to demonstrate that these deltas can be modeled as morphodynamic equilibria (no evolving bathymetry). It is assumed that the large‐scale alongshore tidal currents are small compared to the cross‐shore tidal currents, that waves have shore‐normal incidence, that the tidal velocity profile over the inlet is symmetric with respect to the midaxis, and that the Coriolis force can be ignored. The modeled tidal hydrodynamics are characterized by an ebb jet during the ebb phase of the tide and a radial inflow pattern during flood. Two residual eddies are formed. The mechanism behind these current patterns is explained with vorticity concepts. The modeled bottom patterns are similar to those of observed symmetric tide‐dominated ebb‐tidal deltas. In the center of the tidal inlet an ebb‐dominated channel is observed that branches further offshore into two flood‐dominated channels. At the end of the ebb‐dominated channel a shoal is present. Varying the tidal prism, the width of the tidal inlet, the wave height, and the bed slope coefficient in the sediment transport formulation within the range of observed values leaves these patterns qualitatively unchanged. However, the exact extent and shape of the modeled deltas are affected by these parameters. Compared to observations, the modeled ebb‐tidal delta is smaller and the ebb‐dominated channel is shorter. The observed exponent in the power law relation between sand volume of the delta and the tidal prism is recovered and explained with the model.
Connecting organic carbon in stream water and soils in a peatland catchment
Authors: Billett Michael F. , Deacon Claire M. , Palmer Sheila M. , Dawson Julian J. C. , Hope Diane
Published: June 2006

We investigated the spatial and temporal connectivity between concentrations of organic carbon in stream water and the soil carbon pool in a small (1.3 km2) upland catchment in NE Scotland by comparing downstream changes in dissolved organic carbon (DOC) with spatial changes in the soil carbon pool. Stream water DOC concentrations increased downstream to reach a maximum in the center of the catchment and then decreased in the lower part of the catchment, a pattern that was linked to spatial changes in the soil carbon pool. Subcatchment analysis of the soil carbon pool and DOC export showed that the strong relationship between percent of peat coverage and stream water DOC in the upper part of the catchment did not hold farther downstream, where freely draining mineral soils become spatially more important. Temporal variations in stream water and soil water DOC concentrations in the central part of the catchment were studied using samples collected from two depths (0.20–0.45 m and 0.65–0.95 m) in the two most important soil types there (histosols and fluvisols). Stream water DOC concentrations were only related to soil water DOC in shallow peat. DOC concentration in shallow peat and stream water were both positively correlated with temperature. Multivariate regression analysis showed that 55% of the variation in stream water DOC concentrations could be explained by a model including stream temperature, discharge, and soil solution DOC concentrations in the shallow histosols. We conclude that the linkage between stream water DOC concentrations and the soil C pool in the upper 1.5 km of the stream reach are likely to be driven by temperature‐related DOC production in near‐surface histosols. Farther downstream, this relationship between organic carbon in the soil and stream becomes weaker as other processes (e.g., lower inputs from minerals soils and allochthonous within‐stream processing of DOC) become more important.
Barium in sediments off northwest Africa: A tracer for paleoproductivity or meltwater events?
Authors: Plewa K. , Meggers H. , Kasten S.
Published: June 2006

High‐resolution down‐core analyses of the solid phase content of total barium (Batot) and total organic carbon (TOC) back to 25 kyr B.P. were performed on a gravity core from the upper continental slope off Cape Yubi (Morocco). The observed discrepancy between the two potential paleoproductivity proxies, Batot and TOC, initiated supplementary examinations of the pore water, the geochemistry of the clay fraction, X‐ray diffraction analyses, and the application of a sequential Ba extraction method of selected samples. Additionally, we analyzed down‐core samples of the planktonic foraminifera Turborotalita quinqueloba and Globorotalia inflata for their Ba/Ca ratios. These analyses, which were performed for the first time on these species, were used to reconstruct past oceanic Ba concentrations. We suggest that in the study area, which is characterized by high accumulation rates, the preserved TOC content is a valuable proxy for past primary productivity, whereas the solid phase Batot contents appear to be affected by other mechanisms and factors. Peaks of total barium content in the clay fraction and of Ba/Ca ratios in the planktonic foraminifera shells found during the Younger Dryas and the Heinrich 1 event are likely to result from increased meltwater influx into the northern North Atlantic. We suggest that Ba‐enriched meltwater was transmitted by the eastern boundary current system from higher latitudes to the region of the Canary Islands. Total barium contents of the clay fraction (Batot,clay) and Ba/Ca in planktonic foraminifera shells seem to be reliable proxies for this discharge of meltwater.
Longitudinal correlation of equatorial ionospheric scintillation
Authors: Caton Ron , Groves Keith
Published: June 2006

Studies at the Air Force Research Laboratory are investigating methods for the incorporation of expected data sets from the Communication/Navigation Outage Forecast System (C/NOFS) satellite into existing scintillation specification models for an improved knowledge of the regional scintillation environment. Results from this research will form the basis for ground‐based empirical scintillation forecast algorithms. One such study involves a determination of the extent to which correlations can be made for scintillation over a range of longitudes providing valid upstream (westward) forecasts of scintillation activity based on near real‐time observations. Using archived data collected on Scintillation Network Decision Aid (SCINDA) receivers, a comprehensive study was conducted to numerically evaluate the correlation of scintillation on link pairings separated by varying degrees of longitude representing up to 3 hours in local time.
Impacts of the tropical Indian and Atlantic Oceans on ENSO
Authors: Dommenget Dietmar , Semenov Vladimir , Latif Mojib
Published: June 2006

The impacts of the tropical Indian and Atlantic Oceans on ENSO are studied using a series of 500 years long GCM simulations, in which the tropical Indian and/or Atlantic Ocean SSTs are fixed. The results indicate that the tropical Indian and/or Atlantic Oceans SST anomalies substantially influence the coupling over the equatorial Pacific. In the absence of SST variability in the tropical Indian and/or Atlantic Ocean, the main ENSO period is shifted by almost one year. The total SST variance in the equatorial Pacific region is reduced if either Indian or Atlantic Ocean variability is present. At the same time the atmospheric ENSO teleconnections are damped more strongly than the SST. The results can be understood in the context of the recharge oscillator model. However, it is difficult to verify the feedback of the Indian and/or Atlantic Oceans onto ENSO only with statistical analyses of the coupled model control integration or observations.
Experimental determination of drag coefficient for volcanic materials: Calibration and application of a model to Popocatépetl volcano (Mexico) ballistic projectiles
Authors: Alatorre‐Ibargüengoitia Miguel A. , Delgado‐Granados Hugo
Published: June 2006

This study shows the results of experiments performed in a subsonic wind tunnel to measure drag coefficients (Cd) for volcanic particles emitted by Popocatépetl volcano (Mexico). The results indicate that volcanic projectiles move in a range of Reynolds number (Re) values where Cd is independent of Re. Drag coefficients of volcanic fragments were found between the values of spheres and cubes with low values. In this study, initial conditions of the ballistic equations were calibrated with the “launching” kinetic energy from ballistics expelled by Popocatépetl volcano during the eruptive event of December 17, 1998. The maximum range of the projectiles calculated with the experimentally measured drag coefficient is in better agreement with the field and observational data reported here than using the values of geometrical bodies as in previous studies. Our study can be useful for definition of safety zones around volcanoes to protect people and infrastructure adequately.
Electronic spectroscopy of the 3d Rydberg states of NO–Rg (Rg=Ne,Ar,Kr,Xe) van der Waals complexes
Authors: Bergeron Denis E. , Musgrave Adam , Gammon Robert T. , Ayles Victoria L. , Silber James A. E. , Wright Timothy G. , Wen Bo , Meyer Henning
Published: June 2006

We have employed (2+1) resonance-enhanced multiphoton ionization spectroscopy to record electronic absorption spectra of NO–Rg (Rg=Ne,Ar,Kr) van der Waals complexes. The nitric oxide molecule is the chromophore, and the excitation corresponds to an electron being promoted from the 2pπ* orbital to 3dσ, 3dπ, and 3dδ Rydberg states. We review the ordering of the 3dλ states of NO and use this as a basis for discussing the 3d components in the NO–Rg complexes, in terms of the interactions between the Rydberg electron, the core, and the Rg atom. Predissociation of the H̃′Π2 state occurs through the F̃Δ2 state for NO–Ar and NO–Kr, and this will be considered. We shall also outline problems encountered when trying to record similar spectra for NO–Xe, related to the presence of atomic Xe resonances.
Collective Langevin dynamics of conformational motions in proteins
Authors: Lange Oliver F. , Grubmüller Helmut
Published: June 2006

Functionally relevant slow conformational motions of proteins are, at present, in most cases inaccessible to molecular dynamics (MD) simulations. The main reason is that the major part of the computational effort is spend for the accurate description of a huge number of high frequency motions of the protein and the surrounding solvent. The accumulated influence of these fluctuations is crucial for a correct treatment of the conformational dynamics; however, their details can be considered irrelevant for most purposes. To accurately describe long time protein dynamics we here propose a reduced dimension approach, collective Langevin dynamics (CLD), which evolves the dynamics of the system within a small subspace of relevant collective degrees of freedom. The dynamics within the low-dimensional conformational subspace is evolved via a generalized Langevin equation which accounts for memory effects via memory kernels also extracted from short explicit MD simulations. To determine the memory kernel with differing levels of regularization, we propose and evaluate two methods. As a first test, CLD is applied to describe the conformational motion of the peptide neurotensin. A drastic dimension reduction is achieved by considering one single curved conformational coordinate. CLD yielded accurate thermodynamical and dynamical behaviors. In particular, the rate of transitions between two conformational states agreed well with a rate obtained from a 150ns reference molecular dynamics simulation, despite the fact that the time scale of the transition (∼50ns) was much longer than the 1ns molecular dynamics simulation from which the memory kernel was extracted.
Parameter estimation of an asymmetric vocal-fold system from glottal area time series using chaos synchronization
Authors: Zhang Yu , Tao Chao , Jiang Jack J.
Published: June 2006

In this paper, we apply an iterative parameter adaption scheme based on chaos synchronization to estimate system parameters of the asymmetric vocal folds from glottal area time series. The original asymmetric vocal-fold system associated with recurrent laryngeal paralysis shows chaotic vibrations with positive Lyapunov exponents. Aperiodic glottal area time series from the original system will be applied as the feedback variable coupling the simulative and the original vocal-fold systems. The parameter adaption technique based on chaos synchronization is employed to manipulate the simulative system parameters. The chaotic vibrations, system parameters, and the bifurcation diagram of the original vocal-fold system can be exactly reproduced in the simulative system, and the two chaotic systems can be synchronized. Furthermore, the effects of noise, sampling rate, and equation difference due to nonlinear spring terms on vocal-fold parameter estimations are investigated. Despite large noise perturbations, large equation differences, and low sampling rate, the parameter adaption scheme can effectively estimate the original vocal-fold system parameters. This study provides a theoretical base to apply chaos synchronization to estimate the vocal-fold system parameters from the glottal area data and show its potential application in laryngeal physiology.
Time minimal trajectories for a spin 1∕2 particle in a magnetic field
Authors: Boscain Ugo , Mason Paolo
Published: June 2006

In this paper we consider the minimum time population transfer problem for the z component of the spin of a (spin 1/2) particle, driven by a magnetic field, that is constant along the z axis and controlled along the x axis, with bounded amplitude. On the Bloch sphere (i.e., after a suitable Hopf projection), this problem can be attacked with techniques of optimal syntheses on two-dimensional (2-D) manifolds. Let (−E,E) be the two energy levels, and ∣Ω(t)∣≤M the bound on the field amplitude. For each couple of values E and M, we determine the time optimal synthesis starting from the level −E, and we provide the explicit expression of the time optimal trajectories, steering the state one to the state two, in terms of a parameter that can be computed solving numerically a suitable equation. For M∕E≪1, every time optimal trajectory is bang-bang and, in particular, the corresponding control is periodic with frequency of the order of the resonance frequency ωR=2E. On the other side, for M∕E>1, the time optimal trajectory steering the state one to the state two is bang-bang with exactly one switching. For fixed E, we also prove that for M→∞ the time needed to reach the state two tends to zero. In the case M∕E>1 there are time optimal trajectories containing a singular arc. Finally, we compare these results with some known results of Khaneja, Brockett, and Glaser and with those obtained by controlling the magnetic field both on the x and y directions (or with one external field, but in the rotating wave approximation). As a byproduct we prove that the qualitative shape of the time optimal synthesis presents different patterns that cyclically alternate as M∕E→0, giving a partial proof of a conjecture formulated in a previous paper.
Irreversibility time scale
Authors: Gallavotti G.
Published: June 2006

Entropy creation rate is introduced for a system interacting with thermostats (i.e., for a system subject to internal conservative forces interacting with “external” thermostats via conservative forces) and a fluctuation theorem for it is proved. As an application, a time scale is introduced, to be interpreted as the time over which irreversibility becomes manifest in a process leading from an initial to a final stationary state of a mechanical system in a general nonequilibrium context. The time scale is evaluated in a few examples, including the classical Joule-Thompson process (gas expansion in a vacuum).
Urban Sustainability: Learning from Best Practice?
Authors: Bulkeley Harriet
Published: June 2006

In the quest for sustainable development, numerous examples of ‘best practice’ have been created and circulated in national and international arenas. Yet despite the vast array of examples, demonstration projects, case studies, and the like, little is known about the ways in which best practices are produced and used, and their role in processes of policymaking. Focusing on best practice for urban sustainability, the author argues that, rather than conceptualising its role and impact in terms of policy transfer or lesson drawing, the creation, dissemination, and use of best practice can be better understood as a discursive process, in which not only is new knowledge created about a policy problem, but the nature and interpretation of the policy problem itself are challenged and reframed. Drawing on insights from concepts of governmentality, the author argues that best practices are at once a political rationality and a governmental technology through which the policy problem of urban sustainability is framed and defined. Illustrations of the practice of best practice show how contradictions emerge between claims for general applicability and the need for policy actors to understand the contingencies of the process of urban sustainability, in order to enrol it for their own struggles over sustainability. The local stickiness of best practices points to the very real struggles that the rationalities of urban sustainability have in competing with other governmentalities which seek to shape urban futures.