bluuebunny/crossref_metadata_2025 huggingface dataset:
Ein Beitrag zu Rhenium(II)‐, Osmium(II)‐ und Technetium(II)‐Thionitrosylkomplexen vom Typ [M(NS)Cl4py]—: Darstellung, Strukturen und EPR‐Spektren
Authors: Reinel Martina , Höcher Thomas , Abram Ulrich , Kirmse Reinhard
Published: May 2003

Die Umsetzung von [ReVINCl4]— und [OsVINCl4]— mit S2Cl2 führt über die nicht als reine Substanzen isolierbaren Thionitrosylkomplexe [MII(NS)Cl4]— (M = Re, Os) nach Zugabe von Pyridin zu den stabilen Verbindungen trans‐(Ph4P)[OsII(NS)Cl4py], trans‐(Hpy)[OsII(NS)Cl4py], trans‐(Ph4P)[ReII(NS)Cl4py] und cis‐(Ph4P)[ReII(NS)Cl4py].

Die Kristallstrukturanalysen ergeben für trans‐(Ph4P)[OsII(NS)Cl4py] (monoklin, P21/n, a = 12, 430(3)Å, b = 18, 320(4)Å, c = 15, 000(3)Å, β = 114, 20(3)°, Z = 4), trans‐(Hpy)[OsII(NS)Cl4py] (monoklin, P21/n, a = 7, 689(1)Å, b = 10, 202(2)Å, c = 20, 485(5)Å, β = 92, 878(4)°, Z = 4), trans‐(Ph4P)[ReII(NS)Cl4py] (triklin, P1¯, a = 9, 331(5)Å, b = 12, 068(5)Å, c = 15, 411(5)Å, α = 105, 25(1)°, β = 90, 23(1)°, γ = 91, 62(1)°, Z = 2) und cis‐(Ph4P)[ReII(NS)Cl4py] (monoklin, P21/c, a = 10, 361(1)Å, b = 16, 091(2)Å, c = 17, 835(2)Å, β = 90, 524(2)°, Z = 4) Bindungswinkel (M‐N‐S) zwischen 168‐175° und damit nahezu lineare NS‐ Koordination. Das Metallatom ist jeweils oktaedrisch koordiniert.

Die ReII‐Thionitrosylkomplexe (5d5‐„low‐spin”︁‐Konfiguration, S = 1/2) wurden im X‐Band EPR‐spektroskopisch im Temperaturbereich 295 > T > 130 K untersucht. Neben dem Nachweis der bei der Reaktion von [ReVINCl4]— mit S2Cl2 gebildeten Komplexe wurden EPR‐Untersuchungen an diamagnetisch verdünnten Pulvern und Einkristallen des Systems trans‐(Ph4P)[ReII/OsII(NS)Cl4py] durchgeführt. Die erhaltenen Parameter wurden zur Bestimmung der Spindichteverteilung in den untersuchten Komplexen verwendet.

[TcVINCl4]— reagiert mit S2Cl2 unter Bildung von [TcII(NS)Cl4]—, das aber unter Eliminierung von S8 wieder zum Ausgangskomplex zerfällt. Die Reaktion wurde EPR‐spektroskopisch verfolgt.
Synthesis of Nitrido(phthalocyaninato)metal(V) Complexes RnPcMN (M = Re, Mo, W) and New Compounds with Nitrido‐Bridges between Rhenium and Elements of the Third Main Group
Authors: Verma Sanjiv , Hanack Michael
Published: May 2003

New tetra‐ and octasubstituted nitrido(phthalocyaninato)metal(V) complexes RnPcMN (M = Re, Mo, W) were synthesized to obtain soluble nitrido‐bridged phthalocyanines. Phthalocyanines with nitrido bridges between rhenium and boron, aluminium, gallium and indium, respectively, were synthesized from nitrido(tetra‐tert.‐butylphthalocyaninato)rhenium(V) complex, tBu4PcReN and suitable electrophilic reagents like BCl3, B(C6F5)3, BPh3, BEt3, AlCl3, GaCl3, GaBr3, InCl3, etc. The nitrido‐bridged compounds prepared show different stabilities depending on the substituents at the boron atom. Additionally, the possibility to increase the nucleophilicity of (C5H11)8PcWN by reducing this complex with C8K was studied. The reaction of the reduced complex with electrophiles, e.g. with tBuMeSiCl, Ph3SiCl and Me3GeCl indicates the formation of nitrogen‐bridged complexes.
Centering Pregnancy: A Model for Pregnant Adolescents
Authors: Klima Carrie S.
Published: May 2003

Recent exploration of the experiences of pregnant and parenting adolescents has uncovered the need to address the unique developmental, social, and cultural aspects of adolescent pregnancy. Many adolescents, especially those from urban areas, live in communities with limited opportunities, poverty, violence, and a lack of support. Programs that help young women discover their inner strength, create environments for empowerment, and build community may help adolescents to achieve goals and parent successfully. Centering Pregnancy is a model of group prenatal care that provides for the assessment, education, and support of pregnant women and may be particularly useful in adolescent populations. The model is described and the ways adolescents may benefit from Centering Pregnancy's unique design is discussed.
Minor's Rights Versus Parental Rights: Review of Legal Issues in Adolescent Health Care
Authors: Maradiegue Ann
Published: May 2003

The right of adolescents to access confidential health care is sensitive and controversial. Recent challenges in the court system to adolescents' right to access abortion and contraception are eroding current law, including the Roe v Wade decision. The prospect of more than a million pregnancies in individuals under the age of 20 years in the United States with increasingly fewer alternatives to pregnancy is concerning. New regulations under the Health Insurance Portability and Accountability Act are adding yet another layer of complexity to the care of adolescents. Understanding legal issues surrounding adolescent rights to care can help the health care provider make appropriate care available to this age group. Keywords previously identified in CINAHL and MEDLINE were used to perform the literature search. LexisNexis was the search engine used to identify the laws and statutes.
Wissensaustausch mittels Datenbanken als Öffentliches-Gut-Dilemma
Authors: Creß Ulrike , Barquero Beatriz , Buder Jürgen , Schwan Stephan , Hesse Friedrich Wilhelm
Published: May 2003

Zusammenfassung. Die Eingabe von Information in eine geteilte Datenbank stellt eine spezifische Form des Öffentlichen-Gut-Dilemmas dar. Vorgestellt wird ein computerbasiertes Szenario, das diese Merkmale abbildet und eine experimentelle Untersuchung des Datenbank-Dilemmas ermöglicht. Darin wird untersucht, inwiefern ein Feedback über die Anzahl der Datenbankabrufe und ein Bonussystem, das die Datenbankeingabe entsprechend der Anzahl der Datenbankabrufe belohnt, die Kooperation fördern kann. Es zeigt sich, dass sich ein Bonussystem nicht generell positiv auf die Datenbankeingabe auswirkt, wohl aber die wahrgenommene Instrumentalität der Datenbank erhöht und die Selektion der beizutragenden Information nach ihrer Qualität verstärkt.
Gemeinsame Wissenskonstruktion in computervermittelter Kommunikation:
Authors: Weinberger Armin , Fischer Frank , Mandl Heinz
Published: May 2003

Zusammenfassung. Ziele dieser Studie sind die Analyse und die Förderung des Erwerbs anwendungsorientierten Wissens in kooperativen, computervermittelten Lernumgebungen. Dazu wurden zwei Kooperationsskripts zur Vorstrukturierung der Interaktion untersucht. Ein inhaltsbezogenes Kooperationsskript strukturiert Aktivitäten in einer bestimmten Sequenz hinsichtlich inhaltlicher Aspekte der Lernaufgabe. Ein interaktionsbezogenes Kooperationsskript schreibt den Gruppenmitgliedern bestimmte Rollen sowie rollenspezifische Interaktionen vor. Beide Kooperationsskripts wurden daraufhin untersucht, welchen Einfluss sie auf Prozesse und Ergebnisse gemeinsamer Wissenskonstruktion in einer computervermittelten Lernumgebung haben. Die Faktoren “inhaltsbezogenes Kooperationsskript“ und “interaktionsbezogenes Kooperationsskript“ wurden in einem 2×2-faktoriellen Design unabhängig voneinander variiert. 96 Studierende der Pädagogik nahmen an dem Experiment teil. Die Ergebnisse zeigen, dass interaktionsbezogene Kooperationsskripts die Partizipation und den Erwerb anwendungsorientierten Wissens fördern, während inhaltsbezogene Kooperationsskripts die fokussierte Wissensanwendung im Prozess der gemeinsamen Wissenskonstruktion unterstützen, den individuellen Wissenserwerb aber beeinträchtigen.
Einsatz einer psychologischen Testbatterie bei Arbeitnehmern zur Prävention neurotoxischer Erkrankungen
Authors: Ihrig Andreas , Dietz Michael C.
Published: May 2003

Zusammenfassung. Psychologische Testbatterien werden in der arbeitsmedizinischen Feldforschung zur frühzeitigen Erkennung von neurotoxischen Effekten seit längerem eingesetzt. Ziel der Arbeit ist die Bewertung und der Vergleich von psychologischen Untersuchungsbefunden des Arbeitsmedizinisch-Neurotoxischen Evaluierungs-Systems (ANES) im Rahmen von drei Feldstudien bei Stichproben mit unterschiedlicher beruflicher neurotoxischer Belastung (Lösungsmittel, Mangan, Quecksilber). Bei Lösungsmittelexponierten konnten signifikante Zusammenhänge zwischen der Expositionshöhe und den Ergebnissen in Testverfahren zu kognitiven Fähigkeiten und gesundheitlichen Beschwerdenangaben gefunden werden. Bei Manganexponierten finden sich Expositions-Effekt-Beziehungen mit den psychomotorischen Variablen. Bei den Quecksilberexponierten liegen dahingegen keine signifikanten Zusammenhänge vor. Das ANES ist für die betriebliche Vorsorge bei der Exposition gegenüber neurotoxischen Substanzen hinsichtlich Praktikabilität und Sensitivität geeignet.
FORMOD und PROMOD
Authors: Lecher Silke , Witte Erich H.
Published: May 2003

Zusammenfassung. Innerhalb von Organisationen und Betrieben wird durch den Einsatz von Arbeits- und Projektgruppen ein “Gruppenvorteil“ in Form besserer Ergebnisse, schnellerer Entscheidungsfindung und breiterer Zustimmung erwartet. Häufig bedarf es jedoch eines derart hohen Aufwandes an Koordinations- und Integrationsleistungen, um den vielfältigen Argumenten, Einstellungen und Informationen gerecht zu werden, dass diese Erwartungen sich nicht erfüllen. Der Einsatz von Moderationstechniken soll diese Koordinations- und Integrationsleistungen erleichtern und gleichzeitig sozio-emotionale Prozesse steuern. Moderationstechniken, die theoriegeleitet die wesentlichen kognitions- und sozialpsychologischen Leistungskriterien berücksichtigen, liegen in Form der am Arbeitsbereich Sozialpsychologie der Universität Hamburg entwickelten Formalen Moderation (FORMOD) und Prozeduralen Moderation (PROMOD) vor. Experimentell konnte im Rahmen eines DFG-Projektes gezeigt werden, dass die wissensbasierte Technik PROMOD der ebenfalls untersuchten FORMOD hinsichtlich der Leistung beim komplexen Problemlösen signifikant mit mittlerer Effektstärke überlegen ist und dass sich der Einsatz beider Moderationstechniken als leistungssteigernd im Vergleich zu nicht-moderierten Gruppen erweist. Neben Leistungsparametern wurden die individuellen Problemlösestrategien und die Konformitätsprozesse als abhängige Variablen zur Vergleichsmessung herangezogen. Die experimentell erzielten Ergebnisse bezüglich der Gruppenleistung und die Darstellung der in FORMOD und PROMOD integrierten Leistungsparameter untermauern die Forderung nach einer theoriegeleiteten Entwicklung integrativer und komplexitätsangemessener Methoden zur Leistungsverbesserung in Arbeitsgruppen. Erste Praxistransfers der Methoden in die betriebliche Realität werden dargestellt und diskutiert.
Unterschiede in der Durchführung zwischen internen und externen Assessment Centern - Eine empirische Analyse
Authors: Krause Diana E. , Gebert Diether
Published: May 2003

Zusammenfassung. Dieser Beitrag dokumentiert Unterschiede in der Durchführung zwischen internen und externen Assessment Centern (AC) an einer Stichprobe von N = 281 deutschen, schweizerischen und österreichischen Organisationen. Der Vergleich der Maßnahmen interner und externer AC zeigt, dass interne AC mit einem höheren Aufwand betrieben werden als externe AC (z. B. Mehraufwand bei der Entwicklung und Aktualisierung des AC, höhere Übungs- und Beobachteranzahl). Da diese Maßnahmen zur Verbesserung unterschiedlicher Testgütekriterien beitragen, sind Unternehmen offenbar speziell im Falle interner AC an einer Qualitätssicherung interessiert. Dies wiederum hängt nach unserer Interpretation mit der unterschiedlichen Ausgangslage (u. a. bereits getätigte Investitionen in Humankapital, geringere Reversibilität der Personalentscheidungen bei internen AC) interner und externer AC zusammen.
A Comparison of Authoritarianism in the United States, England, and Hungary with Selected Nonrandom Samples
Authors: Pentony Joseph F. , Petersen Karen S.E. , Philips Olivia , Leong Clare , Harper Paula , Bakowski Alicia , Steward Sarah , Gonzales Rhonda
Published: May 2003

It has been suggested that there is no such thing as a left-wing authoritarian, and that authoritarian attitudes do not correlate with authoritarian behaviors. Studies were done in the United States, England, and Hungary in order to obtain cross-cultural empirical data on these questions. An additional goal of the research was to use common measures across samples, which had not occurred in previous studies where comparisons were drawn. Left-wing authoritarians were not found in the United States or England, but were found in Hungary. An authoritarian attitude did not correlate positively with authoritarian behavior in any of the countries.
The Representation(s) of a New Superordinate Category
Authors: Chryssochoou Xenia
Published: May 2003

The present paper is concerned with the organizing principles of the representation people form about a superordinate category to which they belong. It is argued here that the social relations in the structural societal level play a crucial role in organizing people's representation of the superordinate category. These relations are reflected in their stereotypes. The representation of Europe in the context of the European integration is investigated through the study of the national and European stereotypes of an opportunistic sample of 64 French and 74 Greeks. The Multistage Investigator of Social Identity ( Zavalloni & Louis-Guerrin, 1984 ) was used to elicit these stereotypes. The analysis indicated that different representations emerge that tend to express the relations between subgroups and to refer to their perceived position within the superordinate group.
Derivation of Response Scales for WHOQOL TR
Authors: Eser Erhan , Fidaner Hüray , Eser Sultan Yalçin , Fidaner Caner , Elbi Hayriye
Published: May 2003

This study has two objectives: One is to demonstrate the Likert-type response scale generation for the Turkish version of the WHOQOL. The other is to show the effect of level of education of the subjects to translate their perception into a rating on a Visual Analog Scale (VAS). WHOQOL questions have four types of response scales: frequency, evaluation, capacity, and intensity. The WHOQOL cross-cultural response scale methodology is based on the VAS. Fifty-one low-level educated subjects from the initial study population (n = 228) were excluded by applying two special exclusion criteria, because of the reliability problems. Those subjects with 8 years and less education were more likely than those with 11 years' (OR = 0.25%; 95 CI 0.11-0.56) and 15 years' and more education (OR = 0.11; 95% CI 0.04-0.29) to be excluded from the study. After translating anchor points into Turkish, the VAS were prepared for each of the response scales (intensity, capacity, frequency, and evaluation). A list of descriptors—16 for frequency, 15 for capacity and intensity, 16 and 14 for evaluation scales—were compiled from dictionaries and the relevant literature. Each descriptor was placed on a 10 cm fresh line in a random order in every scale. The study subjects were asked to place a mark on a 10 cm line for each descriptor, according to where they think the descriptor lies in relation to the anchor points. In order to select the intermediate descriptors for each scale, mean distances for each descriptor were calculated and target intermediate descriptors were found for each scale by applying WHOQOL response scale methodology. The intra-class correlation coefficients (ICC), which indicate the interrater reliability in the current setting, were calculated in the included study population (n = 177) for each education category separately. ICCs were found as 0.39 for 5 years', 0.46 for 8 years', 0.66 for 11 years', and 0.79 for 15 years' and more education categories. Categories of at least 11 years' education were found to show sufficient interrater reliability. The mean and the variabilities of the target descriptors produced similar results with the initial 15 WHOQOL centers. On the other hand, the obtained results indicate that visual analog scale methodology should be used with caution on subjects educated less than 9 years in the Turkish context.
Language Emergence in Infants
Authors: Ushakova Tatyana N.
Published: May 2003

The early stage of child development (0-12 months) was investigated in this study. The kernel of language ability was traced within the frame of the system of psychophysiological development. It was shown that in the process of general development several mechanisms are successively put into operation and function in the different spheres of the infant's psychophysiological activity: body movement, contact with adults (an early form of communication), and vocalization (which is regarded as the preverbal form of the future language). On these grounds, and based on the existence of a special mechanism of inborn vocal activity normally presented by the moment of child birth, a framework of communicative operations with ambient people has been developed. The proposed model explains the advantage of using sound communicative forms, namely the infant's first words.
The Antiaggressive Action of Combined Haloperidol-Propranolol Treatment in Schizophrenia
Authors: Maoz Gadi , Stein Daniel , Meged Sorin , Kurzman Larisa , Levine Joseph , Valevski Avi , Aviv Alex , Sirota Pinhas , Kraus Ruth , Weizman Avi , Berger Barry D.
Published: May 2003

Psychopharmacological interventions for managing aggression in schizophrenia have thus far yielded inconsistent results. This study evaluates the antiaggressive efficacy of combined haloperidol-propranolol treatment. Thirty-four newly admitted schizophrenic patients were studied in a controlled double-blind trial. Following a 3-day drug-free period and 7 days of haloperidol treatment, patients were randomly assigned to receive either haloperidol-propranolol or haloperidol-placebo for eight consecutive weeks. Doses of medications were adjusted as necessary; biperiden was administered if required. Rating scales were applied to assess aggression, anger, psychosis, depression, anxiety and extrapyramidal symptoms. The mean daily dose of haloperidol was 21 mg (SD = 6.4) in the research group and 29 mg (SD = 6.9) in the controls. Mean and maximal daily doses of propranolol were 159 mg (SD = 61) and 192 mg (SD = 83), and of placebo, 145 mg (SD = 50) and 180 mg (SD = 70), respectively. Compared with the controls, the scores for the research patients decreased significantly from baseline, particularly after 4 weeks of treatment, for some dimensions of anger, psychosis, anxiety, and neuroleptic-induced parkinsonism. A tendency for reduced aggression was shown in the combined haloperidol-propranolol group for some dimensions but not others. These patients also required significantly less biperiden. The tendency toward elevated antiaggressive effect of combined haloperidol-propranolol treatment compared to haloperidol alone may be explained by a simultaneous decrease in aggression, psychotic symptomatology, and anxiety.
Carbon distribution, fluxes, and budgets in the subtropical North Atlantic Ocean (24.5°N)
Authors: Rosón G. , Ríos A. F. , Pérez F. F. , Lavín A. , Bryden H. L.
Published: May 2003

Hydrographic CO2 system data obtained from World Ocean Circulation Experiment (WOCE) transatlantic zonal section A5 across 24.5°N and Florida Straits are described. By combining CO2 measurements with hydrographic velocity calculations, the zonal and vertical variability of meridional fluxes of total alkalinity (TA), total dissolved inorganic carbon (TIC), and anthropogenic CO2 (δC) are estimated. The resulting CO2 fluxes are examined in four geostrophic mid‐ocean zones as well as in the Gulf Stream flow through Florida Straits and in the surface ageostrophic Ekman flow. This method allows an estimate of the net budgets of these chemical species in the system considering together the Arctic and Atlantic Oceans north of 24.5°N. Taking into account the net flux contribution through Bering Strait, total meridional transports of chemical properties across 24.5°N latitude are also estimated. The slightly divergent net TA budget (−460 ± 200 kmol s−1) suggests that the North Atlantic is a small alkalinity source. The divergent TIC budget (−2430 ± 200 kmol s−1 or −0.92 ± 0.08 GtC yr−1) suggests that the North Atlantic is a source of TIC and therefore a net sink for atmospheric CO2. This value is twice as large as a previous estimation made from a poorly sampled section. Surprisingly, the North Atlantic Ocean appears to act as a net sink of anthropogenic CO2 (+630 ± 200 kmol s−1 or +0.24 ± 0.08 GtC yr−1) and therefore a weak source of anthropogenic CO2 to the atmosphere. Its main contributor is the intense northward flux in the Florida Current (+1280 ± 100 kmol s−1). The calculations imply a divergent inorganic carbon budget of −3060 ± 200 kmol s−1 or −1.16 ± 0.08 GtC yr−1 in preindustrial times (TIC278, when the molar fraction of CO2 in the atmosphere was 278.2 ppm). This means that the North Atlantic would have had a 25% stronger divergence of TIC prior to the beginning of anthropogenic CO2 penetration.
Decadal changes in the North Pacific oceanic frontal zones as revealed in ship and satellite observations
Authors: Nakamura Hisashi , Kazmin Alexander S.
Published: May 2003

Influence of decadal climate changes upon the North Pacific subarctic and subtropical oceanic frontal zones (NP‐SAFZ and NP‐STFZ, respectively) is documented. Both satellite‐ and ship‐measured sea surface temperature (SST) data reveal the strong confinement of wintertime decadal SST anomalies to those frontal zones. The satellite data indicate that the wintertime NP‐SAFZ tended to be narrow and shift northward under the weakened surface westerlies during a warm event in the early 1990s. The opposite was the case under the enhanced westerlies during a cool event in the mid‐1980s. Decadal‐scale modulations in the frontal intensity are also evident in the satellite data. A diagnosis based on a simple linearized mixed layer model suggests that the observed anomalous frontal intensity was contributed by the sign reversal of anomalous wind stress curl through the Ekman processes and by an anomaly dipole of the net heat flux around the SAFZ. These decadal‐scale modulations in the NP‐SAFZ and their relationships with decadal fluctuations in the local surface westerlies are confirmed in the ship‐measured data over the 4 recent decades. It is found that the SAFZ happens to be a region where the decadal variability in the surface westerlies are unlikely to be masked by the higher‐frequency fluctuations, as it almost coincides with the ridge/trough line of the remote atmospheric response to the El Niño/Southern Oscillation.
Variability in oxygen and nutrients in South Pacific Antarctic Intermediate Water
Authors: Russell J. L. , Dickson A. G.
Published: May 2003

Calculation of the initial oxygen based on both phosphate and nitrate data collected along three WOCE transects indicates that the common assumption that new Antarctic Intermediate Water (AAIW) is initially saturated with respect to oxygen is incorrect. The initial oxygen concentration of AAIW is shown to be undersaturated, and the degree of undersaturation varies from year to year. Chlorofluorocarbon data is used to determined the age of AAIW at various latitudes and a frequency analysis of the variability in the initial oxygen concentrations is presented. Possible implications of this variability to the global carbon cycle are suggested.
Three‐dimensional crustal structure of Long Valley caldera, California, and evidence for the migration of CO2under Mammoth Mountain
Authors: Foulger G. R. , Julian B. R. , Pitt A. M. , Hill D. P. , Malin P. E. , Shalev E.
Published: May 2003

A temporary network of 69 three‐component seismic stations captured a major seismic sequence in Long Valley caldera in 1997. We performed a tomographic inversion for crustal structure beneath a 28 km × 16 km area encompassing part of the resurgent dome, the south moat, and Mammoth Mountain. Resolution of crustal structure beneath the center of the study volume was good down to ∼3 km below sea level (∼5 km below the surface). Relatively high wave speeds are associated with the Bishop Tuff and lower wave speeds characterize debris in the surrounding moat. A low‐Vp/Vsanomaly extending from near the surface to ∼1 km below sea level beneath Mammoth Mountain may represent a CO2reservoir that is supplying CO2‐rich springs, venting at the surface, and killing trees. We investigated temporal variations in structure beneath Mammoth Mountain by differencing our results with tomographic images obtained using data from 1989/1990. Significant changes in bothVpandVswere consistent with the migration of CO2into the upper 2 km or so beneath Mammoth Mountain and its depletion in peripheral volumes that correlate with surface venting areas. Repeat tomography is capable of detecting the migration of gas beneath active silicic volcanoes and may thus provide a useful volcano monitoring tool.
Plate‐like regime of a numerically modeled thermal convection in a fluid with temperature‐, pressure‐, and stress‐history‐dependent viscosity
Authors: Ogawa Masaki
Published: May 2003

A series of numerical models are presented for two‐dimensional thermal convection in a fluid with viscosity that nonlinearly depends on “degree of damage” ω as well as temperature and pressure; ω increases and viscosity decreases with time when the convection induces strong viscous dissipation. The convecting fluid recovers from the damage with a characteristic time that depends on temperature. The ω dependence of viscosity induces a stress‐viscosity relationship that consists of two branches, the “intact branch” at low stress and the “damaged branch” at high stress, with a hysteresis between the two branches; ω is small (large) and viscosity is high (low) on the intact (damaged) branch. The hysteresis lets the viscosity depend on stress history. The dependence of viscosity on stress history due to the hysteresis induces a regime where the numerically modeled lithosphere along the surface boundary is fragmented into smaller pieces that are on the intact branch and rigidly move. The pieces of lithosphere are separated by narrow mechanically weak zones that are on the damaged branch. Each piece of lithosphere is further fragmented and mechanically weak zones are newly formed only when the piece is tapped by particularly strong hot uprising plumes. This “plate‐like” regime is the only regime, among the convective regimes searched here, where each piece of lithosphere rigidly moves and still is not ruptured by the forces that drive the piece. The Earth's mantle is suggested to be on the plate‐like regime.
Partial melting experiments on a MORB‐like pyroxenite between 2 and 3 GPa: Constraints on the presence of pyroxenite in basalt source regions from solidus location and melting rate
Authors: Pertermann Maik , Hirschmann Marc M.
Published: May 2003

We present partial melting experiments at 2–3 GPa on a basaltic pyroxenite (G2) similar in composition to typical oceanic crust. The 3.0 GPa solidus is located at 1310 ± 12°C and the liquidus is 1500–1525°C. Clinopyroxene, garnet, quartz, and rutile are subsolidus phases. Garnet, quartz, and rutile are absent above 1475°C, 1365°C, and 1335°C, respectively. At the solidus, the garnet mode is low (18 wt.%) because clinopyroxene is unusually aluminous (13.8–15.5 wt.% Al2O3). In adiabatically upwelling mantle near 2–3 GPa, G2‐like pyroxenite begins melting 35–50 km deeper than peridotite. The calculated near‐solidus adiabatic productivity for G2 is ∼13%/GPa and averages ∼59%/GPa through the melting interval, suggesting substantial partial melting deep in basalt source regions: G2 is ∼60% molten at the 3 GPa peridotite solidus. Small percentages of pyroxenite in the source significantly affect oceanic crust production and composition, as the proportion of pyroxenite‐derived melt contributed to oceanic crust formation is 5 to >10 times the pyroxenite proportion in the source. Given the overall depleted isotopic character of mid‐ocean ridge basalt (MORB), oversampling of fertile G2‐like pyroxenite limits the abundance of such lithologies to ∼<2% of the MORB source. Owing to high extents of partial melting, the effect of modest amounts of pyroxenite on Sm/Yb ratios of aggregated basalts is limited and depends largely on the average bulk composition of the pyroxenite source. Low near‐solidus adiabatic productivities could allow small (∼1–2%) proportions of basaltic pyroxenite to enhance (230Th)/(238U) in oceanic basalts without requiring marked shifts in other indicators of heterogeneity, such as Sr or Pb isotopes.
Interfacial mixing in a highly stratified estuary 1. Characteristics of mixing
Authors: Kay David J. , Jay David A.
Published: May 2003

This article is Part I of a set of papers addressing mixing in a highly stratified estuary. Measurements of interfacial turbulence were made in Columbia River estuary under conditions of moderate river flow and neap tides. A flux correlation method was used to determine buoyancy fluxes, and fits to theoretical velocity and temperature variance spectra were used to measure turbulent kinetic and potential energy dissipation rates. At the measurement site in the interior of the estuary, mixing along the top of the salt wedge is found to occur only on ebb, during periods when the internal Froude number is supercritical. The wedge cannot, therefore, be in a quasiequilibrium state, and vertical mixing plays a dominant role in its ebb retreat. The turbulent Froude number FrT, which represents the ratio of effects of shear and stratification on the mixing, was found to be close to FrT ≈ 1 during mixing episodes. This suggests an interplay between shear and buoyancy effects that corresponds to a condition of maximum mixing efficiency Γ. Γ is measured using both direct calculations of the buoyancy and dissipation terms in the turbulent kinetic energy (TKE) balance (this estimate of Γ is referred to as Γ0), and by estimating the buoyancy term B by its relationship to χT, the dissipation of temperature variance (this estimate of Γ is referred to as Γd). Averages over several mixing events give Γ0 ≈ 0.22 and Γd ≈ 0.36. Sources of bias in these measurements result from (1) approximations to the full TKE and available potential energy (APE) balances, (2) empirical constants used in fits of measured spectra in inertial subranges, (3) frame motion, and (4) high‐pass filtering. The sign of the biases suggest that 0.22 < Γ < 0.36. Flood‐ebb asymmetry in mixing also results in a time dependent force balance (discussed further by Kay and Jay [2003]). This asymmetry is analyzed using a new method to determine profiles of the momentum balance during ebb mixing events.
Interfacial mixing in a highly stratified estuary 2. A “method of constrained differences” approach for the determination of the momentum and mass balances and the energy of mixing
Authors: Kay David J. , Jay David A.
Published: May 2003

This article is part 2 of a set of papers addressing mixing in a highly stratified estuary. In Part 2, turbulence and mean flow measurements are together used to understand the role of mixing in the overall dynamics of the system. Estimates of the partition of energy dissipation between bed‐generated and internal mixing suggest that internal mixing accounts for about two thirds of the total turbulent kinetic energy (TKE) produced in the salt‐wedge reach of the Columbia River estuary during the neap‐tide, moderate river‐flow observation period. This suggests that internal mixing plays a larger role in the energetics of such systems than has previously been recognized. The lack of near‐bed mixing on the neap is also likely a major factor in the accumulation of sediment in the estuary on neap tides. Profiles of estimated turbulent kinetic energy (TKE) dissipation were obtained using a new approach, which we call the “method of constrained differences,” that allows the calculation of all major terms in the momentum and density balances during ebb mixing events from data obtained by a single vessel. The method of constrained differences uses a local equilibrium turbulence closure and measured velocity and density profiles to determine the density flux divergence necessary for internal consistency in the momentum and mass equations. The calculated mixing rates from the iterative procedure compare favorably with measured dissipation rates, tending to validate both the measurements and the procedure. Although this method involves a constraint of the form of a known or inferred stress at some point in the water column, it has the potential for wide application, especially if point measurements of TKE dissipation rates are available.
Multidecadal warming of subsurface temperature in the Indian sector of the Southern Ocean
Authors: Aoki Shigeru , Yoritaka Miwako , Masuyama Akihiro
Published: May 2003

Long‐term variations of subsurface layer temperature were examined for 32 years (1966–1998) of continuous observations in the Indian sector of the Southern Ocean. The data analyzed consist of observations from Japanese Antarctic Research Expeditions and also from other countries. Significant warming trends of about 0.004°C × yr−1 were observed at all depths from 200 to 900 m to the north of the southern Antarctic Circumpolar Current (ACC) front [Orsi et al., 1995]. The rates of warming increase with increasing depth from 0.003°C × yr−1 at 200 m to 0.012°C × yr−1 (statistically significant) at 900 m in the region close to the front. These warming trends were also found after applying a technique to correct for differences in the data sampling locations. The warming tendency in the frontal region is consistent with the assumption of a southward shift of the front and may have a relationship with the observed retreat of sea ice edge.
Local and remote forcing of currents and temperature in the central Southern California Bight
Authors: Hickey B. M. , Dobbins E. L. , Allen S. E.
Published: May 2003

A comprehensive study of the central Southern California Bight shows that subtidal currents are dominated by relatively long time scales (10–25 days), large alongshore scales, and significant offshore and upward phase propagation. A one‐dimensional model shows that observed fluctuating, poleward propagating (speeds 140–260 cm s−1) alongshore pressure gradient disturbances account for a much larger fraction of the alongshore velocity variance than local wind stress (at least 40% in both seasons) and have the longer periods of the dominant currents. With the addition of local wind stress, about half the velocity variance can be accounted for, and overall, about 5% more variance in spring than in summer. Results are consistent with generation of disturbances by remote wind stress several hundred kilometers equatorward of the bight and alongcoast propagation as low‐mode coastally trapped waves. The large‐scale remote forcing is also responsible for much of the velocity variance on the adjacent shelf, the semienclosed Santa Monica Bay. A nonlinear, three‐dimensional model shows that water is pushed into the bay initially as part of a throughflow, later becoming an eddy that gradually fills the bay, producing counterflow on its shoreward side. On the shelf, local alongshore wind stress accounts for only 25% of the velocity variance in spring and none in summer. The large‐scale disturbances also produce significant temperature fluctuations throughout the region, via lateral advection of the mean alongshore temperature gradient. Local wind‐driven coastal upwelling is responsible for temperature fluctuations on the inner shelf during several 2–4 day events in spring, but only very near the coastal wall.
Organic‐rich sediments in ventilated deep‐sea environments: Relationship to climate, sea level, and trophic changes
Authors: Bertrand P. , Pedersen T. F. , Schneider R. , Shimmield G. , Lallier‐Verges E. , Disnar J. R. , Massias D. , Villanueva J. , Tribovillard N. , Huc A. Y. , Giraud X. , Pierre C. , Vénec‐Peyré M.‐T.
Published: May 2003

Sediments on the Namibian Margin in the SE Atlantic between water depths of ∼1000 and ∼3600 m are highly enriched in hydrocarbon‐prone organic matter. Such sedimentation has occurred for more than 2 million years and is geographically distributed over hundreds of kilometers along the margin, so that the sediments of this region contain a huge concentrated stock of organic carbon. It is shown here that most of the variability in organic content is due to relative dilution by buried carbonates. This reflects both export productivity and diagenetic dissolution, not differences in either water column or bottom water anoxia and related enhanced preservation of organic matter. These observations offer a new mechanism for the formation of potential source rocks in a well‐ventilated open ocean, in this case the South Atlantic. The organic richness is discussed in terms of a suite of probable controls including local wind‐driven productivity (upwelling), trophic conditions, transfer efficiency, diagenetic processes, and climate‐related sea level and deep circulation. The probability of past occurrences of such organic‐rich facies in equivalent oceanographic settings at the edge of large oceanic basins should be carefully considered in deep offshore exploration.
Temporal variability of fluxes of eolian‐transported freshwater diatoms, phytoliths, and pollen grains off Cape Blanc as reflection of land‐atmosphere‐ocean interactions in northwest Africa
Authors: Romero Oscar E. , Dupont Lydie , Wyputta Ulrike , Jahns Susanne , Wefer Gerold
Published: May 2003

Fluxes of airborne freshwater diatoms (FD), phytoliths (PH), and pollen grains (PO) collected with sediment traps off Cape Blanc, northwest Africa, from 1988 till 1991 are presented. Both continental rainfall variations and wind mean strength and direction play a key role in the temporal fluctuations of the fluxes of eolian traces in the pelagic realm. Drier conditions in Northern Africa in 1987 could have preceded the high lithogenic input and moderate FD flux in 1988. The PH peak in summer 1988 was probably caused by increased wind velocity. Wetter rainy seasons of 1988/89 might have promoted a significant pollen production in summer 1989, and FD in late 1989 and early 1990, as well as contributed to the reduction of the lithogenic flux in 1989/90. Decreased fluxes of FD, PH and PO, and higher contribution of the 6–11 μm lithogenic fraction in 1991 would mainly reflect minor intensity and decreased amount of continental trade winds. Air‐mass backward trajectories confirm that the Saharan Air Layer is predominantly involved in the spring/summer transport. Trade winds play a decisive role in the fall/winter months, but also contribute to the transport during late spring/summer. Origin of wind trajectories does not support a direct relationship between transporting wind‐layers and material source areas in Northern Africa. High winter fluxes of eolian tracers and high amount of trade winds with continental origin in summer warn against a simplistic interpretation of the seasonal eolian signal preserved in the sediments off Cape Blanc, and the wind layer involved in its transport.
Interannual and interdecadal variability of atmospheric synoptic‐scale activity in the Southern Hemisphere
Authors: Vera Carolina
Published: May 2003

A rotated empirical orthogonal function analysis was applied to anomalies of July atmospheric short time scale variability (or storm tracks) over the Southern Hemisphere (SH) using NCEP reanalyses. The study reveals the existence of two leading modes of storm‐track variations, the first one describing storm‐track changes along the subtropical Pacific and the second one associated with variations over southeast Pacific Ocean. The principal components of both modes exhibit significant variability on interannual (2–7 years) and interdecadal (longer than 7 years) time scales. The interannual variation of the first mode is closely linked to ENSO variability. The corresponding signal on SST anomalies shows a conspicuous maximum over central equatorial Pacific, while the signature on geopotential‐height anomalies shows the typical Pacific South America pattern characterized by a Rossby wave train propagating poleward from the tropics. On interdecadal time scales, the first mode is related to SST anomalies over the subtropical portions of the Pacific, Atlantic, and Indian Oceans and to a Rossby wave train with strongest signals over the southeast Pacific and the Antarctic Peninsula. The second mode that represents storm‐track changes west of the Antarctic Peninsula is related on interannual time scales to SST anomalies over western Pacific between 40°S and 20°S, while on interdecadal time scales, it does not seem to be significantly related to SST changes in any of the basins. In particular, the spatial signature of the REOF2 interdecadal variability on the SH circulation corresponds to the well‐known high latitude mode characterized by a monopole over the Antarctica and a three‐wave pattern at middle latitudes.
Surface characteristics and atmospheric footprint of springtime Arctic leads at SHEBA
Authors: Pinto James O. , Alam A. , Maslanik J. A. , Curry J. A. , Stone R. S.
Published: May 2003

Observations of several freezing leads that occurred in spring near the Surface Heat Budget of the Arctic Ocean (SHEBA) ice station were made. The leads that formed during this study were between 3 and 400 m wide. Ice production in the leads less than 20 m wide was predominantly through congelation growth, while both frazil ice production and congelation ice growth was observed in the wider leads. The production of frazil ice and its advection downwind allowed open water to persist in the wider leads for between 5 and 24 hours, depending on the crossing angle of the wind. The surface energy budget of a wide freezing lead was estimated from observations and with a model that resolves the coupling between surface turbulent fluxes and ice growth across the lead. Both estimates of the net heat flux agreed with the increases in ice thickness observed throughout the 24‐hour period, though the modeled net heat flux deficit was 50% larger. The larger net heat flux deficit obtained with the model can be attributed to the simulation of larger turbulent heat fluxes. It was found that the surface roughness length for nilas given by Guest and Davidson [1991] was too large resulting in excessive surface cooling at night. Using a smaller roughness length improved the nighttime bias but resulted in a warm bias during the day. The daytime warm bias was due, in part, to neglecting the impact of frost flowers on the surface albedo. Additional uncertainty in the treatment of solar absorption by nilas also likely contributed. The modeled ice thickness and skin temperature were also affected by the treatment of the oceanic heat flux, which acted to warm the surface. The length of time that a lead affects the atmosphere is determined by lead surface conditions, atmospheric stability, wind speed, fetch, and upwind temperature. Under lead‐perpendicular winds the atmospheric influence of a 400 m wide lead extended more than 2.5 km downwind. Sensible heat fluxes observed 70 m downwind of the lead were a function of across lead fetch, upwind stability, and open water fraction. The sensible heat fluxes measured at this site were elevated above background values for nearly two days despite 11.5 cm of ice growth in the lead.
Modes of atmospheric variability over the Southern Ocean
Authors: Simmonds Ian
Published: May 2003

The atmosphere over the Southern Ocean (SO) has been historically very poorly observed. Until fairly recently, the climate means of important parameters were known only imperfectly. In the modern era, new sources of data, particularly a wide range of products to come from remote sensing, have alleviated this problem. In addition to these developments, the advent of “data assimilation” and the conduct of “reanalyses” now means that available data may be used in “optimal” ways to obtain meteorological analyses of a quality not available heretofore. This solid base means that we are now for the first time able to confidently document and understand the rich variety of modes of variability over the region. In this paper, we examine aspects of SO atmospheric variability and focus particularly on those associated with the mean sea level pressure (MSLP) in the 40‐year National Centers for Environmental Prediction (NCEP) reanalysis. Discussion is devoted to many aspects of the behavior of cyclonic systems over the Ocean and the variabilities and trends shown in these. Of the variabilities also explored here are those associated with the high‐latitude mode, the semiannual oscillation (SAO), and the Antarctic circumpolar wave (ACW). A wide range of physical processes drives these features and their variability and we investigate some of these here.
Distribution of surface carbon dioxide and air‐sea exchange in the English Channel and adjacent areas
Authors: Borges Alberto Vieira , Frankignoulle Michel
Published: May 2003

In the present paper we report the distribution of the partial pressure of CO2 (pCO2) in surface waters along 13 transects in the English Channel, covering the four seasons. The spatial and temporal variability of pCO2 is controlled by a complex combination of primary production (from May to June), degradation of organic matter, temperature change, and freshwater inputs. Preliminary air‐sea CO2 exchange computations suggest that the Channel is not a major sink of atmospheric CO2 and is probably neutral from the point of view of atmospheric coupling. This is mainly related to a relatively low export and/or burial of organic carbon and intense benthic calcification.
Laboratory observations of gravity‐capillary waves under transient wind forcing
Authors: Uz B. Mete , Hara Tetsu , Bock Erik J. , Donelan Mark A.
Published: May 2003

Laboratory experiments were conducted to investigate the response of short wind waves (wave numbers between 50 and 800 rad m−1) under transient wind forcing. Three‐dimensional wave number frequency spectra of gravity‐capillary waves were measured using a scanning laser slope gauge (SLSG). When wind is started rapidly, gravity‐capillary waves of a particular wave number (initial wavelets) first appear, and they are immediately followed by waves over a wider wave number range (both in magnitude and in direction). These waves all appear to grow exponentially, with each wave number growing at its own growth rate. The observed energy input rates from wind to waves are always maximum for along‐wind waves and are smaller for waves in directions oblique to the wind. When wind speed is modulated periodically in time, the modulation of the wind stress lags behind that of the wind speed, and the short wind wave spectra lag further behind the wind stress. Assuming that waves are modulated according to existing relaxation theory and that the relaxation rate is identical to the wave growth rate, very short wind waves appear to respond to the instantaneous wind speed while longer wind waves appear to respond to the instantaneous wind stress.