bluuebunny/crossref_metadata_2025 huggingface dataset:
The investigation and correction of recall bias for an ordinal response in a case‐control study
Authors: Barry Daniel , Livingstone Victoria
Published: June 2005

Consider a case‐control study designed to investigate the possible association between development of a particular disease and the value of a putative risk factor measured on an ordinal scale. Let E denote a subject's true risk factor value and let E* denote a subject's recorded risk factor value. Misclassification bias occurs if conclusions reached regarding the relationship between disease status and E* do not also apply to the relationship between disease status and E. We propose a model for the conditional probability distribution of E* given E. We show how the model may be used to investigate misclassification bias in a validation study where measurements of E* and E are available for both cases and controls and apply the methods developed to data from a test–retest study of recall bias in the context of screening for hypertension. We also consider a situation where the validation study is carried out on a subset of the subjects within a larger case‐control study. In that case, values for E* are available for all subjects but values for E are available only for those subjects included in the validation study. We show how correct likelihood‐based inference concerning association between disease status and risk factor value may be carried out using all of the available data. A Monte Carlo study shows how the inclusion of a validation study leads to a correction of recall bias problems at the cost of an increased standard error for the estimated association parameter. Copyright © 2005 John Wiley & Sons, Ltd.
Model mis‐specification and overestimation of the intraclass correlation coefficient in cluster randomized trials
Authors: Giraudeau Bruno
Published: June 2005

Intraclass correlation coefficient (ICC) estimates must be provided when reporting the results of a cluster randomized trial. This study demonstrates that estimating this parameter with one‐way ANOVA and an underlying mixed‐effects statistical model leads to biased estimates. The bias depends on the effect size of the studied treatment. Copyright © 2005 John Wiley & Sons, Ltd.
Relationship between nuchal translucency thickness and prevalence of major cardiac defects in fetuses with normal karyotype
Authors: Atzei A. , Gajewska K. , Huggon I. C. , Allan L. , Nicolaides K. H.
Published: June 2005

Objective

To define the prevalence of major cardiac defects according to nuchal translucency (NT) thickness at the 11 to 13 + 6‐week scan in fetuses with normal karyotype.

Methods

Specialist fetal echocardiography was carried in 6921 fetuses with normal or presumed normal karyotype at a median gestation of 20 (range 12–35) weeks. The indications for fetal echocardiography were increased NT thickness (n = 3444), detailed second‐trimester scan either for assessment of risk of chromosomal abnormalities (n = 2980) or previous or family history of fetal defects (n = 497). The cardiac defects were grouped into six functional categories: septal defect, left inflow obstruction, right inflow obstruction, left outflow obstruction, right outflow obstruction and other.

Results

Major cardiac defects were identified in 132 (19.1 per 1000) fetuses and the prevalence increased with fetal NT thickness from 4.9 per 1000 in those with NT below the median, to 8.7 for NT between the median and less than the 95th centile, 18.2 for NT between the 95th and 99th centiles, and exponentially thereafter to 35.2, 64.4 and 126.7 for respective NTs of 3.5–4.4 mm, 4.5–5.4 mm and ≥ 5.5 mm. There was no obvious difference in the distribution of NT in the different types of cardiac defects.

Conclusions

The prevalence of major cardiac defects increases exponentially with fetal NT thickness and in fetuses with NT of 3.5 mm or more it is higher than in pregnancies with a family history of cardiac defects. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Asymptotic expansions and analytic dynamic equations
Authors: Bohner M. , Lutz D.A.
Published: June 2005

Time scales have been introduced in order to unify the theories of differential and difference equations and in order to extend these cases to many other so‐called dynamic equations. In this paper we consider a linear dynamic equation on a time scale together with a perturbed equation. We show that, if certain exponential dichotomy conditions are satisfied, then for any solution of the perturbed equation there exists a solution of the unperturbed equation that asymptotically differs from the solution of the perturbed equation no more than the order of the perturbation term. In order to show this perturbation theorem, we use many properties of the exponential function on time scales and derive several bounds for certain monomials that appear in the dynamic version of Taylor's formula.
Analysis of paper pressing: the saturated one‐dimensional case
Authors: Bežanović D. , van Duijn C.J. , Kaasschieter E.F.
Published: June 2005

We derive a one‐dimensional model that describes pressing of water saturated paper in the press‐section of the paper machine. The model involves two nonlinear diffusion equations which are coupled across an internal boundary. Existence and uniqueness as a number of qualitative properties are demonstrated. Further, computational results for a concrete case are discussed.
Relationships among negative and positive behaviours in adolescence
Authors: Boles Shawn , Biglan Anthony , Smolkowski Keith
Published: June 2005

The authors calculated binary indicators of seven positive and 23 negative behaviours for 22,898 8th and 15,828 11th grade students who participated in the Oregon Healthy Teens Survey across two school years. Relationships among these variables, using both the Jaccard measure of co‐occurrence and the relative risk for each member of each variable pair, given exposure to the other, showed strong inter‐relationships within, but not between, the sets of behaviours. The likelihood of negative behaviours given negative behaviours was much stronger than the likelihood of positive behaviours given positive behaviours. Positive behaviours provided little protection against the likelihood of negative behaviors.
Adhesiveness of β5 integrin variant lacking FNK767–769 is similar to that of the prototype containing FNKFNK764–769
Authors: Kawahara Ei , Saito Ayumi , Kobayashi Jun , Maenaka Shiori , Minamoto Toshinari , Imai Miwa Akasofu , Oda Yoshio
Published: June 2005

Little is known about the functions of two different β5 integrins: repeated‐FNK (FNKFNK764–769) and single‐FNK (FNK764–766) amino acid sequences in the cytoplasmic domain. We examined whether they occurred as germ line mutations or somatic mutations associated with neoplastic transformation, and whether there were functional alterations. Out of six cultured cell lines, only KATO‐III cells had the single‐FNK β5 sequence. The single‐FNK β5 was found in 9 out of 79 patients with colon carcinoma, but no somatic mutations were detected in cancerous tissues. CHO cells were transformed with expression vectors containing single‐FNK or repeated‐FNK β5 cDNA, which were derived from KATO‐III cells. CHO cells transfected with single‐FNK and repeated‐FNK showed similar adhesiveness to, and proliferative activity on, vitronectin substrates.
Identification and expression of the amphioxus Cks1 gene
Authors: Yang Hui , Chen Zhong‐Ke , Zhang Xiao‐Hui , Huang Xiang‐Wei , Zhang Pei‐Jun , Zhang Hong‐Wei
Published: June 2005

A full‐length Cks1 homologue gene, AmphiCks1, was identified in amphioxus, Branchiostoma belcheri tsingtauense. Sequence characteristics, phylogeny and patterns of expression during embryonic and larval development were established. The protein predicted from AmphiCks1 showed high sequence identity with vertebrate and invertebrate homologues. Protein structural studies and phylogenetic analysis suggested that Cks homologues are evolutionarily conserved. The AmphiCks1 transcript was detected in most early developmental stages by northern blotting and whole‐mount in situ hybridization, suggesting a role for the gene in cell division.
Human erythrocyte δ‐aminolevulinate dehydratase inhibition by monosaccharides is not mediated by oxidation of enzyme sulfhydryl groups
Authors: Gabriel D. , Pivetta L. , Folmer V. , Soares J.C.M. , Augusti G.R. , Nogueira C.W. , Zeni G. , Rocha J.B.T.
Published: June 2005

The heme pathway enzyme δ‐aminolevulinate dehydratase is a good marker for oxidative stress and metal intoxication. This sulfhydryl enzyme is inhibited in such oxidative pathologies as lead, mercury and aluminum intoxication, exposure to selenium organic species and diabetes. Oxidative stress is a complicating factor in diabetes, inducing non‐enzymatic glucose‐mediated reactions that change protein structures and impair enzyme functions. We have studied the effects of high glucose, fructose and ribose concentrations on δ‐ALA‐D activity in vitro. These reducing sugars inhibited δ‐ALA‐D with efficacies in the order fructose = ribose > glucose. The possible mechanism of glucose inhibition was investigated using lysine, DTT, and t‐butylamine. Oxidation of the enzyme's critical sulfhydryl groups was not involved because DTT had no effect. We concluded that high concentrations of reducing sugars or their autoxidation products inhibit δ‐ALA‐D by a mechanism not related to thiol oxidation. Also, we are not able to demonstrate that the formation of a Schiff base with the critical lysine residue of the enzyme is involved in the inhibition of δ‐ALA‐D by hexoses.
Treatment of peripheral neuropathic pain: A simulation model
Authors: Vera‐Llonch Montserrat , Dukes Ellen , Delea Thomas E. , Wang Si‐Tien , Oster Gerry ,   The Neuropathic Pain Outcomes Modeling Working Group
Published: June 2005

Objective To describe the use of a generalizable stochastic‐simulation model of the treatment of neuropathic pain associated with peripheral neuropathies.

Methods We developed a model to simulate treatment outcomes in a hypothetical cohort of patients with peripheral neuropathies. Each patient was randomly assigned an average pretreatment daily pain score (on a 0–10 scale), based on an assumed distribution of mean pretreatment pain scores in the cohort. Patients were randomly assigned daily pain scores, based on their pretreatment average and an assumed distribution of daily pain scores around this mean. Treatment outcomes were then simulated using the expected mean change (vs. baseline) in pain scores. Model outcomes include the expected increase in days with no or mild pain (score ≤3), days with ≥30% and ≥50% reductions in pain intensity, and days with 2‐ and 3‐point absolute reductions in pain intensity. To illustrate its use, the model was estimated over a 12‐week period using data from a recent clinical trial of a new antiepileptic (pregabalin).

Results Treatment over 12 weeks (84 days) was projected to result in 26 (−0.4) (mean [−SE]) additional (vs. no treatment) days with no or mild pain, 33 (−0.5) days with a ≥30% reduction in pain intensity, 28 (−0.4) days with ≥50% reduction in pain intensity, and 34 (−0.5) and 30 (−0.5) days with ≥2‐point and ≥3‐point absolute reductions in pain intensity.

Conclusions When combined with data on health‐state utilities and treatment costs, this new analytical tool can provide a foundation for formal cost‐effectiveness evaluations of interventions for painful peripheral neuropathies.
Solution structure of the isolated Pelle death domain
Authors: Moncrieffe Martin C. , Stott Katherine M. , Gay Nicholas J.
Published: June 2005

The interaction between the death domains (DDs) of Tube and the protein kinase Pelle is an important component of the Toll pathway. Published crystallographic data suggests that the Pelle–Tube DD interface is plastic and implies that in addition to the two predominant Pelle–Tube interfaces, a third interaction is possible. We present the NMR solution structure of the isolated death domain of Pelle and a study of the interaction between the DDs of Pelle and Tube. Our data suggests the solution structure of the isolated Pelle DD is similar to that of Pelle DD in complex with Tube. Additionally, they suggest that the plasticity observed in the crystal structure may not be relevant in the functioning death domain complex.
Inducible expression of a degradation‐resistant form of p27Kip1 causes growth arrest and apoptosis in breast cancer cells
Authors: Zhang Qingxiu , Tian Ling , Mansouri Abdel , Korapati Anita L. , Johnson Terry J. , Claret Francois X.
Published: June 2005

The cyclin‐dependent kinase (CDK) inhibitor p27Kip1 (p27) is an important regulator of cell cycle progression controlling the transition from G to S‐phase. Low p27 levels or accelerated p27 degradation correlate with excessive cell proliferation and poor prognosis in several forms of cancer. Phosphorylation of p27 at Thr187 by cyclin E–CDK2 is required to initiate the ubiquitination‐proteasomal degradation of p27. Protecting p27 from ubiquitin‐mediated proteasomal degradation may increase its potential in cancer gene therapy. Here we constructed a non‐phosphorylatable, proteolysis‐resistant p27 mutant containing a Thr187‐to‐Ala substitution (T187A) which is not degraded by ubiquitin‐mediated proteasome pathway, and compared its effects on cell growth, cell‐cycle control, and apoptosis with those of wild‐type p27. In muristerone A‐inducible cell lines overexpressing wild‐type or mutant p27, the p27 mutant was more resistant to proteolysis in vivo and more potent in inducing cell‐cycle arrest and other growth‐inhibitory effects such as apoptosis. Transduction of p27(T187A) in breast cancer cells with a doxycycline‐regulated adenovirus led to greater inhibition of proliferation, more extensive apoptosis, with a markedly reduced protein levels of cyclin E and increased accumulation of cyclin D1, compared with wild‐type p27. These findings support the potential effectiveness of a degradation‐resistant form of p27 in breast cancer gene therapy.
Oxygen and hydrogen peroxide enhance light‐induced carotenoid synthesis in Neurospora crassa
Authors: Iigusa Hideo , Yoshida Yusuke , Hasunuma Kohji
Published: June 2005

Previously, we found that intracellular reactive oxygen species (ROS) affect photomorphogenesis in Neurospora crassa. In this study, we investigated the physiological roles of ROS in the response to light and found that the exposure of mycelia to air was important for the light‐induced carotenogenesis. Mycelia treated with a high concentration of O2 gas and H2O2 to release ROS showed an enhancement of light‐induced carotenoid accumulation and the expression of gene related to light‐inducible carotenogenesis. These results suggested that stimuli caused by the exposure of the mycelia to air containing O2 gas triggered the light‐induced carotenoid synthesis.
Immediate impacts and recovery trajectories of macrofaunal communities following hydraulic clam dredging on Banquereau, eastern Canada
Authors: Gilkinson Kent D. , Gordon Donald C. , MacIsaac Kevin G. , McKeown David L. , Kenchington Ellen L.R. , Bourbonnais Cynthia , Vass W. Peter
Published: June 2005

A hydraulic clam dredging experiment, designed to mimic offshore commercial dredging practices, was carried out at a depth of approximately 70 m on a sandy seabed on Banquereau, on the Scotian Shelf, eastern Canada. The experiment was designed to study the separate and combined effects of dredging through three treatment boxes (Dredging Only, Dredging and Discarding, Discarding Only) and two spatially separated reference boxes. In all, 270 taxa were identified from grab samples. Of these, four bivalves are targeted in the commercial fishery (Arctica islandica, Cyrtodaria siliqua, Mactromeris polynyma, and Serripes groenlandicus) while 266 taxa were non-target species. Sample biomass was dominated by the propellerclam, C. siliqua, and the echinoderm, Echinarachnius parma, while the polychaete, Spiophanes bombyx, was the numerical dominant. The dredges captured 33 invertebrate and two fish taxa, although >80% of the catch biomass comprised propellerclams and echinoderms. Immediately after dredging, most macrofaunal species decreased in abundance, with the greatest declines inside dredge furrows (which covered 53–68% of the area inside the dredged boxes). Large numbers of propellerclams were excavated to the seabed surface, with a large proportion showing massive damage. There were few signs of discards on the sediment surface. Recovery trajectories of target and non-target species were followed for 2 years. Following initial declines in abundance and biomass of most taxa immediately after dredging, there were marked increases in abundance of polychaetes and amphipods after 1 year. Two years after dredging, abundances of opportunistic species were generally elevated by ≫100% relative to pre-dredging levels. Two years after dredging, average taxonomic distinctness had decreased (i.e. taxonomic relatedness between species had increased) due, in part, to increased numbers of species of certain polychaetes and amphipods, while communities had become numerically dominated (50–70%) by S. bombyx. It is concluded that the disturbed community was still in the colonizing phase 2 years after dredging. The mobile brittlestar, Ophiura sarsi, displayed increases in abundance ranging from 200% to 300% in the dredged and reference boxes over the 2-year post-dredging. A similar response of non-target macrofauna in the reference boxes suggests, possibly, a coincident natural recruitment pulse. Dredging resulted in pronounced, sustained reductions in biomass (up to 67%) of the target bivalves with no signs of recovery after 2 years. Recruitment of target bivalves (>1-mm shell length) was very low throughout the experimental area during this interval.
Acoustic backscattering by Atlantic mackerel as being representative of fish that lack a swimbladder. Backscattering by individual fish
Authors: Gorska Natalia , Ona Egil , Korneliussen Rolf
Published: June 2005

Developing acoustic methods for the identification of fish remains a long-term objective of fisheries acoustics. The accuracy of abundance estimation may be increased when the acoustic-scattering characteristics of the fish are known, including their expected variability and uncertainty. The modelling approach is valuable during the process of interpreting multi-frequency echograms. This paper attempts to improve the understanding of sound backscattering of fish without a swimbladder, here represented by Atlantic mackerel (Scomber scombrus). Our approach includes results from modelling as well as comparisons with field data. There will be two papers. The first is a study of the non-averaged backscattering characteristics. This initial analysis is important for the understanding of the averaged backscattering cross-section, which will be considered in the second paper. In that paper the relative importance of bones in acoustic backscattering at higher frequencies will be verified.
Postnatal cerebellar defects in mice deficient in methylenetetrahydrofolate reductase
Authors: Chen Zhoutao , Schwahn Bernd C. , Wu Qing , He Xinying , Rozen Rima
Published: June 2005

Patients with severe deficiency of methylenetetrahydrofolate reductase (MTHFR) suffer from a wide variety of neurological problems, which can begin in the neonatal period. MTHFR is a critical enzyme in folate metabolism; the product of the MTHFR reaction, 5‐methyltetrahydrofolate, is required for homocysteine remethylation to methionine and synthesis of S‐adenosylmethionine (SAM). To understand the mechanisms by which MTHFR deficiency leads to significant neuropathology, we examined early postnatal brain development in mice with a homozygous knockout of the Mthfr gene. These mice displayed a dramatically reduced size of the cerebellum and cerebral cortex, with enlarged lateral ventricles. Mthfr deficiency affected granule cell maturation, but not neurogenesis. Depletion of external granule cells and disorganization of Purkinje cells were mainly confined to the anterior lobules of mutant cerebella. Decreased cellular proliferation and increased cell death contributed to the granule cell loss. Reduced expression of Engrailed‐2 (En2), Reelin (Reln) and inositol 1,4,5‐triphosphate receptor type 1 (Itpr1) genes was observed in the cerebellum. Supplementation of Mthfr+/− dams with an alternate methyl donor, betaine, reduced cerebellar abnormalities in the Mthfr−/− pups. Our findings suggest that MTHFR plays a role in cerebellar patterning, possibly through effects on proliferation or apoptosis.
Ectopic Nail Formation in the Hand
Authors: ABOOD A. , GROBBELAAR A. O.
Published: June 2005

This paper reports an unusual case of ectopic nail formation, reviews the literature and proposes a simple classification of this anomaly.
Rivalry under price and quantity uncertainty
Authors: Paxson Dean , Pinto Helena
Published: June 2005

We present a real option model for a duopoly setting where there are two stochastic factors and where the roles of the players are defined both exogenously and endogenously. The two stochastic factors are the number of units (market volume) and the profit per unit, which may have significantly different drifts and volatilities, and different correlations, depending on market structure and (dis)economies of scale.

The paper shows that the degree of correlation between unit profits and market volume might result in different value functions and triggers, especially for followers and simultaneous investors in non‐pre‐emptive games. Monopoly‐like volume is a critical determinant of the leader's trigger in both pre‐emptive and non‐pre‐emptive games. First‐mover advantages are significant in the definition of the leader's optimal entry moment, if the players are fighting for the leader's position (pre‐emptive game).
Erfassung und Struktur des phonologischen und visuell-räumlichen Arbeitsgedächtnisses bei 4-jährigen Kindern
Authors: Roebers Claudia M. , Zoelch Christof
Published: June 2005

Zusammenfassung. Vor dem Hintergrund der Tatsache, dass Kompetenzen des Arbeitsgedächtnisses eine wesentliche Rolle in vielen Bereichen der kognitiven Entwicklung spielen und insbesondere für schulleistungsrelevante Fähigkeiten (Lesen, Mathematik, Fremdspracherwerb) eine bedeutsame Vorhersagekraft haben, wurden gängige Aufgaben zur Untersuchung des phonologischen und visuell-räumlichen Arbeitsgedächtnisses an die spezifischen Erfordernisse von 4-jährigen Kindern angepasst und evaluiert. Diese Aufgaben sollen schon bei jungen Kindern Arbeitsgedächtniskapazitäten erfassen, um eine möglichst frühe Identifikation von Risikofaktoren für die weitere kognitive Entwicklung zu ermöglichen. Die Ergebnisse zeigen, dass die Messung subsystemspezifischer Arbeitsgedächtniskapazitäten bei 4-Jährigen möglich ist. Darüber hinaus interessierte die Binnenstruktur der theoretisch angenommenen Subkomponenten des Arbeitsgedächtnisses. Die Ergebnisse der korrelativen und konfirmatorischen Analysen legen bereits bei 4-Jährigen eine deutliche Trennung der phonologischen und visuell-räumlichen Subsysteme des Arbeitsgedächtnisses im Sinne des Modells von Baddeley und Hitch (2000) nahe.
Mütter als Entwicklungsdiagnostikerinnen
Authors: Deimann Pia , Kastner-Koller Ursula , Benka Margareta , Kainz Sabine , Schmidt Helene
Published: June 2005

Zusammenfassung. Die Frage, ob Eltern als Diagnostiker über ausreichende Fähigkeiten verfügen, um den Entwicklungsstand ihrer Kinder einschätzen zu können, wird in der angewandten entwicklungspsychologischen Forschung immer wieder aufgeworfen und kontrovers diskutiert. Einerseits werden Eltern als Experten gesehen und ihre Informationen über das Kind als relevanter beurteilt als Testinformationen, die beim Kind selbst erhoben wurden, andererseits zeigen eine Reihe von empirischen Befunden, dass Eltern ihre Kinder in der Regel überschätzen. Ziel der vorliegenden Studie war es zu untersuchen, ob die Einschätzung von Müttern bezüglich der Entwicklung ihres Kindes unterschiedlich ausfällt, wenn Mütter von normal entwickelten Kindern und Mütter von Kindern mit Verhaltensauffälligkeiten befragt werden. Dazu wurde der Entwicklungsstand von Kindergartenkindern (3 bis 6 Jahre) mit sozialen Auffälligkeiten (n = 40) sowie von altersgleichen Kindern mit unauffälligem Sozialverhalten (n = 40) mit dem Wiener Entwicklungstest (WET, Kastner-Koller & Deimann, 2002 ) untersucht. Zugleich wurden die Mütter dieser Kinder gebeten, für jeden Subtest des WET einzuschätzen, was ihr Kind würde lösen können. Eine zweifaktorielle multivariate Varianzanalyse mit Messwiederholung war hochsignifikant: Sozial auffällige und unauffällige Kinder weisen ein signifikant unterschiedliches Entwicklungsprofil auf, das von den Müttern generell überschätzt wird. Die signifikante Wechselwirkung zwischen dem Sozialverhalten und der Messwiederholung (Testergebnis des Kindes/Einschätzung der Mutter) ist darauf zurückzuführen, dass Mütter von sozial auffälligen Kindern das Entwicklungsniveau ihrer Kinder um eine Standardabweichung überschätzen, während dieser Effekt bei Müttern unauffälliger Kinder nur 0,3 beträgt.
Verhaltensbeurteilung durch Gleichaltrige
Authors: Pössel Patrick , von Dellemann Ulrike , Hautzinger Martin
Published: June 2005

Zusammenfassung. Beurteilungen durch Gleichaltrige gelten als valide und reliable Informationsquelle, dennoch gibt es im deutschen Sprachraum kein methodisch bewährtes Erhebungsinstrument zur Beurteilung des Verhaltens von Jugendlichen durch Gleichaltrige. Um diese Lücke zu füllen wurden die “Adjustment Scales for Sociometric Evaluation of Secondary-School Students“ (ASSESS) von Prinz, Swan, Liebert, Weintraub und Neale (1978) übersetzt und evaluiert. Die an 301 Jugendlichen faktorenanalytisch ermittelten fünf Skalen klären 66.77% der Gesamtvarianz auf. Die Internen Konsistenzen (Cronbachs Alpha) der 34 Items umfassenden ASSESS-D liegen zwischen α = .81 und .95 und die Retest-Reliabilität über drei Wochen liegt zwischen r = .84 und .95. Die Korrelationen mit externalisierenden Störungen sind überwiegend erwartungskonform, während sich keine bedeutsamen Zusammenhänge mit Internalisierungsstörungen zeigen. Varianzanalysen zeigten die erwarteten Unterschiede zwischen Geschlecht, Alter und Schultyp. Mit der deutschen Version der ASSESS liegt nach den bisherigen Daten ein ökonomisches und reliables Instrument zur Erfassung von Verhalten Jugendlicher aus der Sicht Gleichaltriger vor.
Der Übergang von der Schule in die berufliche Erstausbildung
Authors: Nagy Gabriel , Köller Olaf , Heckhausen Jutta
Published: June 2005

Zusammenfassung. Der Übergang von der Schule in die Berufsausbildung ist eine Entwicklungsaufgabe, deren Bewältigung zentral für den weiteren beruflichen Lebensweg ist. Welche Rolle Emotionen während der Lehrstellensuche spielen, wurde bis heute kaum untersucht. Auf der Grundlage des Handlungsphasenmodells der Entwicklungsregulation ( Heckhausen, 1999b ) und der Kontroll-Prozess-Theorie ( Carver & Scheier, 1990 ) wurden in der vorliegenden Arbeit Vorhersagen zur Funktion von affektiven Reaktionen bei der Lehrstellensuche abgeleitet. Diese wurden auf Grundlage einer Längsschnittstudie (N = 363) während der 10. Realschulklasse überprüft. Strukturgleichungsmodelle zeigten, dass der Bewerbungsverlauf von Schülerinnen und Schülern mit deren negativem lehrstellenspezifischen Affekt zusammenhängt. Im Gegensatz zu unspezifischen Maßen der Gestimmtheit, erweist sich der zielspezifische negative Affekt als vermittelnde Variable zwischen dem Zeitpunkt des Bewerbungserfolgs und dem nachfolgenden Bewerbungsengagement. Auch nach Kontrolle des Geschlechts, der Mathematiknote und des Sozialschichtbereichs der Schulen erweist sich der negative Affekt als prädiktiv für den Anstieg der Bewerbungsaktivität im 2. Halbjahr des 10. Schuljahres. Implikationen der Befunde werden diskutiert.
Morphologically based model of bed load transport capacity in a headwater stream
Authors: Mueller Erich R. , Pitlick John
Published: June 2005

Field measurements of channel and bed material properties are used to develop a network‐based model of bed load transport capacity in Halfmoon Creek, a high‐gradient stream in the Rocky Mountains of Colorado. The formerly glaciated watershed contains self‐formed reaches that are generally disconnected from hillslopes and major sediment perturbations, strung together by a sequence of bedrock and cascade channels. Measurements of channel geometry, slope, and bed sediment texture (surface and substrate) were taken in 27 reaches with gradients ranging from 0.6 to 6% to examine interactions among key variables affecting bed load transport. The analysis shows that the grain size distribution of the substrate is relatively uniform throughout the basin; however, the distinction between surface and substrate texture varies systematically with channel gradient and shear stress. Reaches with high shear stress are characterized by coarse surface layers, with a high threshold for transport, limiting the mobility of the sediment supplied. In reaches with lower gradient and shear stress the difference between surface and substrate texture is less, increasing both the frequency of transport and the mobility of the bed load. While it might appear that the steeper reaches of Halfmoon Creek have a high capacity for carrying fine‐medium gravel, the relative mobility of these sizes is affected by the presence of very coarse sediment on the bed surface. As a result, modeled estimates of bed load transport rate indicate that average annual bed load sediment yields increase downstream nearly linearly with discharge, suggesting a simple scaling of bed load transport capacity with discharge and drainage area.
Revised deformation history of the central Andes: Inferences from Cenozoic foredeep and intermontane basins of the Eastern Cordillera, Bolivia
Authors: Horton Brian K.
Published: June 2005

Investigation of Cenozoic deformation, sediment accumulation, and provenance in the Eastern Cordillera of Bolivia at 17–21°S indicates major shortening (60–140 km) and foredeep development followed by limited internal shortening and intermontane basin development. Contrasting histories of shortening, deposition, sediment dispersal, and detrital composition distinguish a formerly extensive Paleogene foredeep exposed along an eastern belt of synclines from a zone of principally Neogene intermontane basins in the central Eastern Cordillera. New40Ar/39Ar ages of 25–17 Ma for interbedded tuffs reveal latest Oligocene–early Miocene accumulation in intermontane basins at rates <80 m/Myr, several times lower than Andean foredeeps. Although poorly dated, foredeep evolution probably coincided with middle Eocene–Oligocene deformation and denudation in adjoining regions to the west. A mid‐Cenozoic transition from foredeep to intermontane conditions may be attributable to emplacement of a basement‐involved tectonic wedge beneath the Eastern Cordillera. In this interpretation, wedge emplacement drove flexural foredeep subsidence from roughly 40 to 25 Ma, whereas subsequent accumulation occurred in localized internally drained basins in elevated intermontane areas. Regardless of the regional subsurface structural geometry,40Ar/39Ar ages define a 25–21 Ma onset of intermontane sedimentation that signifies the termination of major upper crustal shortening over large parts of the Eastern Cordillera and possibly the age of initial shortening in the Interandean and Subandean zones to the east. In contrast to several popular models, the revised tectonic history presented here suggests significant pre‐Neogene shortening in the Eastern Cordillera and underscores the large uncertainties in estimates of long‐term shortening rates in the Andes.
Stable organic carbon isotope stratigraphy across Oceanic Anoxic Event 2 of Demerara Rise, western tropical Atlantic
Authors: Erbacher Jochen , Friedrich Oliver , Wilson Paul A. , Birch Heather , Mutterlose Jörg
Published: June 2005

Ocean Drilling Program (ODP) Leg 207 recovered expanded sections of organic‐carbon‐rich laminated shales on Demerara Rise (western tropical Atlantic). High‐resolution organic carbon isotope and total organic carbon (TOC) records are presented, which span the Cenomanian‐Turonian boundary interval (CTBI), including the Oceanic Anoxic Event (OAE) 2, from four sites oriented along a NW striking depth transect. These records represent the first high‐resolution carbon isotope records across OAE 2 from the South American margin of the tropical Atlantic. Due to the scarcity of age significant fossils, the main purpose of this study was to develop a detailed carbon isotope stratigraphy in order to correlate the CTBI across the depth transect and to tie this to biostratigraphically well‐defined sections in the Western Interior Basin (Pueblo, USA), boreal shelf seas (Eastbourne, England), and western Tethys (Oued Mellegue, Tunisia). All four sections studied document a 6‰ increase of δ13Corg values at the base of the CTBI, which is followed by an interval of elevated δ13Corg values and a subsequent decrease. Our results supply an important stratigraphic base for subsequent paleoceanographic studies on Late Cenomanian to Early Turonian sediments from Demerara Rise and elsewhere.
An improved bio‐optical model for the remote sensing of Trichodesmium spp. blooms
Authors: Westberry T. K. , Siegel D. A. , Subramaniam A.
Published: June 2005

The cyanobacterium Trichodesmium spp. can be an important ecological and biogeochemical component for both the coastal and open ocean ecosystems by way of its nitrogen fixation ability. However, information regarding its spatial and temporal distribution remains sparse. Trichodesmium has unique optical properties that should allow for its spectral signature to be detectable in satellite ocean color data sets. Here, a global data set of concurrent measurements of Trichodesmium abundance and radiometric reflectance was compiled and used to develop bio‐optical models for Trichodesmium. The most robust global model related the water‐leaving radiance signal to the identification of an occurrence of a Trichodesmium bloom above a threshold value of 3200 trichomes L−1. Using the in situ data set, this model is trained to successfully predict Trichodesmium blooms (∼92%) while minimizing false positive retrievals (∼16% of nonbloom observations). A validation of the approach applied to Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) ocean color imagery shows that the model correctly predicts 76% of the bloom occurrences of an independent validation data set of in situ Trichodesmium observations. Ultimately, maps of Trichodesmium bloom occurrence will provide a means of addressing the ecology of Trichodesmium and its contribution to new production of the world oceans.
Mapping of ice layer extent and snow accumulation in the percolation zone of the Greenland ice sheet
Authors: Nghiem S. V. , Steffen K. , Neumann G. , Huff R.
Published: June 2005

The Greenland ice sheet underwent record extensive melt in 2002 and prolonged melt in 2003. The severe melting created a significant and extensive ice layer over the Greenland ice sheet. An innovative approach is developed to detect the ice layer formation using data acquired by the SeaWinds scatterometer on the QuikSCAT satellite. QuikSCAT backscatter together with in situ data from automatic weather stations of the Greenland Climate Network are used to map the extent of ice layer formation. The results reveal areas of extensive ice layer formed by the 2002 melt, which is consistent with the maximum melt extent in 2002. Moreover, during freezing seasons, QuikSCAT data show a linear decrease in backscatter (in decibels or dB) that is related to the amount of snow accumulation in the ice layer formation region. This snow accumulation signature is caused by the attenuation of radar waves in the snow layer, accumulating since the last major melt event, whose thickness appears as an exponential function in relation to the backscatter signature. We use the Greenland Climate Network data to calibrate the QuikSCAT accumulation rate in order to estimate and map snow accumulation. QuikSCAT results capture the extreme snowfall in mid‐April 2003, which deposited more than 0.5 m of snow in a day as measured by the automated weather station at the NASA South East site. Large‐scale QuikSCAT results show an anomalous increase of snow accumulation over the southeast region of Greenland during the 2002–2003 freezing season.
Regulation of landslide motion by dilatancy and pore pressure feedback
Authors: Iverson Richard M.
Published: June 2005

A new mathematical model clarifies how diverse styles and rates of landslide motion can result from regulation of Coulomb friction by dilation or contraction of water‐saturated basal shear zones. Normalization of the model equations shows that feedback due to coupling between landslide motion, shear zone volume change, and pore pressure change depends on a single dimensionless parameter α, which, in turn, depends on the dilatancy angle ψ and the intrinsic timescales for pore pressure generation and dissipation. If shear zone soil contracts during slope failure, then α < 0, and positive pore pressure feedback and runaway acceleration are inevitable. If the shear zone dilates, then α > 0, and negative feedback permits slow, steady landslide motion to occur while positive pore pressure is supplied by rain infiltration. Steady state slip velocities v0 obey v0 = −(K/ψ) p*e, where K is the hydraulic conductivity and p*e is the normalized (dimensionless) negative pore pressure generated by dilation. If rain infiltration and attendant pore pressure growth continue unabated, however, their influence ultimately overwhelms the stabilizing influence of negative p*e. Then, unbounded landslide acceleration occurs, accentuated by an instability that develops if ψ diminishes as landslide motion proceeds. Nonetheless, numerical solutions of the model equations show that slow, nearly steady motion of a clay‐rich landslide may persist for many months as a result of negative pore pressure feedback that regulates basal Coulomb friction. Similarly stabilized motion is less likely to occur in sand‐rich landslides that are characterized by weaker negative feedback.
Expected performance of the Superconducting Submillimeter‐Wave Limb Emission Sounder compared with aircraft data
Authors: Buehler S. A. , Verdes C. L. , Tsujimaru S. , Kleinböhl A. , Bremer H. , Sinnhuber M. , Eriksson P.
Published: June 2005

The simulated retrieval performance of a submillimeter wave limb sounder was compared with that of an up‐looking instrument with identical observation frequency bands and comparable noise temperature. The frequency bands were 624.32–626.32 and 649.12–650.32 GHz, and the retrieval simulations focused on the key trace gas species O3, HCl, and ClO. As expected, the limb geometry leads to a better altitude resolution and larger measurement altitude range. The same retrieval setup was applied to measured spectra, taken by the up‐looking Airborne Submillimeter Radiometer (ASUR) instrument on 4 September 2002 at 19.11°E, 71.90°N and on 19 September 2002 at 44.10°E, 4.10°S. The observed structures in the fit residual near the HCl spectral lines at 625.9 GHz lead to the conclusion that the pressure shift parameter of HCl is likely to be higher than the value in the HITRAN spectroscopic database. Depending on the assumed temperature dependence of the shift, the HCl pressure shift value consistent with the ASUR data is 0.090–0.117 MHz/hPa instead of the 0.030 MHz/hPa reported in HITRAN. This result is in good agreement with very recent independent laboratory work which suggests a value of 0.110 MHz/hPa for the shift.
Experimental analysis of microscale rain cells and their dynamic evolution
Authors: Enjamio C. , Vilar E. , Redaño A. , Fontán F. P. , Ndzi D.
Published: June 2005

This paper presents a detailed space‐time analysis of rainfall rate using two dense networks of rain gauges covering two microscale areas of some 100 km2 each and located in two distinct climatic areas in the United Kingdom and Spain. The study has been carried out with the main objective of addressing dynamic fade mitigation techniques and scatter interference problems in terrestrial and satellite communication systems. The two databases, using a total of 49 and 23 rain gauges, respectively, are described, and the continuous interpolated field used for the subsequent analyses is explained in detail. The suitability of the networks in terms of density, correlation distance, and fractal dimension are briefly addressed. A to‐scale comparison grid of the networks is also given. It has been found that when the maximum intensity reached during a rain event surpasses a certain threshold, different for each of the two areas, rainfall rates exhibit a spatial structure in the form of closed contours of thresholds referred to as cells. In statistical terms, the most probable diameter found is about 3.5 km, and distributions are presented. They are similar for the two sites but not so for the maxima reached inside the cells. Using cross‐correlation techniques, displacement and velocities are analyzed in detail. Cells “zigzag” around a dominant trend because of the global cloud movements (driven by winds at heights of about 700 hPa). Local topography strongly affects local behavior. Analytical approximations to the experimental statistical distributions and selected histograms of the results are presented.
Interference mitigation using a focal plane array
Authors: Hansen Chad K. , Warnick Karl F. , Jeffs Brian D. , Fisher J. Richard , Bradley Richard
Published: June 2005

We consider the use of spatial filtering algorithms for radio frequency interference (RFI) mitigation in conjunction with a focal plane feed array of electrically small elements. Numerical simulations are used to study the performance of 7 and 19 element hexagonal dipole arrays with a 25 m reflector at an operating frequency of 1612 MHz. Using the maximum SNR algorithm to generate array weights, an interfering signal was attenuated by 40 dB or more. The effective sensitivity of the system, including interferer power in the system noise temperature, was comparable to the sensitivity attained in the absence of RFI. Moving the interferer through the reflector pattern sidelobes caused fluctuations in the gain and system sensitivity. This effect was exacerbated by a reflector model with random surface distortions. These results indicate that array feeds are a promising approach for RFI mitigation, but achieving stable radiation patterns in the presence of an interferer may require a trade‐off between pattern control and maximum attainable sensitivity.
Radio frequency interference shielding and mitigation techniques for a sensitive search for the 327 MHz line of deuterium
Authors: Rogers Alan E. E. , Pratap Preethi , Carter Joseph C. , Diaz Marcos A.
Published: June 2005

An array of 24 stations, each with 24 crossed dipoles, has been built at the Haystack Observatory in Westford, Massachusetts. This array has been designed to make a sensitive search for the 327 MHz spectral line of deuterium. Since the deuterium line is expected to be about 50 dB weaker than the 1420 MHz hydrogen line, the amelioration of radio frequency interference (RFI) is a major challenge for the performance of the deuterium array. Locally generated RFI from the array and from nearby sites has been reduced by extensive shielding and in some cases by the removal of consumer electronics, like certain digital answering machines that emit strong signals in the 327.3–327.5 MHz band, which is of prime importance for the search. Since almost all the RFI comes from the horizon, the station array has parasitic directors added to the dipoles to reduce the response at the horizon. An RFI monitor with 12 active Yagi antennas pointed every 30° in azimuth provides a way of determining the direction of the RFI and yields information on frequencies and time spans that need to be excised from the array data. We describe the RFI excision techniques and the levels of spectral and continuum RFI measured at the observatory.
A complementary evaporation approach to the scalar roughness length
Authors: Crago Richard , Hervol Nicole , Crowley Raphael
Published: June 2005

A method is developed to estimate the scalar roughness length for water vapor z0v using the complementary evaporation concept. On the basis of the advection‐aridity approach, estimates of z0v and of kB−1 (kB−1 = ln(z0/z0v), where z0 is the momentum roughness length) are available that do not require any estimate of surface temperature or humidity or of stomatal resistance. When applied to grassland data from Cooperative Atmosphere‐Surface Exchange Study‐1997, the resulting values of kB−1 corresponded well with those found from surface temperatures measured with a radiometer having an oblique view of the surface. They also displayed variability with z0+ (z0+ = u*z0/ν, where u* is the friction velocity and ν is the kinematic viscosity), which corresponded well with theoretical and wind tunnel test results from the literature. These results imply that useful estimates of kB−1 are available with this method, and they seem to support the complementary evaporation concept. Strict screening of the data was required to select only those data yielding the smallest uncertainties in the resulting values of kB−1.
Degassing and hydrothermal activity at Mt. Spurr, Alaska during the summer of 2004 inferred from the complex frequencies of long‐period events
Authors: De Angelis S. , McNutt S. R.
Published: June 2005

Results of analyses of unusual long‐period earthquakes, recorded between July and September 2004 at Mt. Spurr, Alaska, are presented. The waveforms of these events are characterized by quasi‐sinusoidal signatures of long duration (up to 40 sec) with slowly decaying amplitudes; bandwidths of 0.5–4.0 Hz are typical; amplitude spectra are marked by strong and sharp peaks, reflecting the quasi‐monochromatic nature of the signal. The temporal variations of the complex frequencies are investigated by use of the Sompi method; the dominant mode is resolved and its Q factor estimated for each available event. Dominant frequencies are found in the band 0.8–2.2 Hz with Q varying between 25 and 100. The variations of the complex frequencies show an overall decline with time. The dynamic response of a shallow fracture filled with bubbly water to the flux of hot gases from depth, is proposed as a possible mechanism for the generation of the observed waveforms.
Energetic ion acceleration in Saturn's magnetotail: Substorms at Saturn?
Authors: Mitchell D. G. , Brandt P. C. , Roelof E. C. , Dandouras J. , Krimigis S. M. , Mauk B. H. , Paranicas C. P. , Krupp N. , Hamilton D. C. , Kurth W. S. , Zarka P. , Dougherty M. K. , Bunce E. J. , Shemansky D. E.
Published: June 2005

The Magnetospheric Imaging Instrument (MIMI) Ion and Neutral Camera (INCA) on the Cassini spacecraft has recorded abrupt increases in energetic neutral atom flux coming from the general direction of Saturn's magnetotail. These bursts of ion activity in the tail are well correlated with enhancements in the Saturn kilometric radiation. Given the similarities between these events and substorm activity on Earth, including their dependence on interplanetary conditions, we conclude that Earth‐like substorms occur within Saturn's magnetosphere.
Fossil methane source dominates Cariaco Basin water column methane geochemistry
Authors: Kessler J. D. , Reeburgh W. S. , Southon J. , Varela R.
Published: June 2005

Natural radiocarbon measurements on methane (14C‐CH4) extracted from the Cariaco Basin water column show that 98% of the methane in Cariaco Basin waters is derived from fossil (radiocarbon‐free) sources. Previous work on Cariaco Basin methane (CH4) considered only a diagenetic sediment source. Similar measurements of sediment 14C‐CH4 indicate that sediment CH4 is produced from modern particulate material; thus the sediment and water column CH4 have distinct sources. Using time‐dependent CH4 geochemical box models which include a fossil seep CH4 source term, we estimate 1) 0.024–0.028 Tg y−1 of seep CH4 are added to the Cariaco Basin water column, 2) the water column CH4 will reach a steady‐state concentration by the year 2065, and 3) the seep CH4 inputs possibly began in 1967, following the July 30 Caracas earthquake. Oxidizing this CH4 to dissolved inorganic carbon does not appear to affect Cariaco Basin 14C chronologies.