bluuebunny/crossref_metadata_2025 huggingface dataset:
Checking the Assumptions of Rasch's Model for Speed Tests
Authors: Jansen M. G. H. , Glas C. A. W.
Published: December 2005

Two new tests for a model for the response times on pure speed tests by Rasch (1960) are proposed. The model is based on the assumption that the test response times are approximately gamma distributed, with known index parameters and unknown rate parameters. The rate parameters are decomposed in a subject ability parameter and a test difficulty parameter. By treating the ability as a gamma distributed random variable, maximum marginal likelihood (MML) estimators for the test difficulty parameters and the parameters of the ability distribution are easily derived. Also the model tests proposed here pertain to the framework of MML. Two tests or modification indices are proposed. The first one is focused on the assumption of local stochastic independence, the second one on the assumption of the test characteristic functions. The tests are based on Lagrange multiplier statistics, and can therefore be computed using the parameter estimates under the null model. Therefore, model violations for all items and pairs of items can be assessed as a by-product of one single estimation run. Power studies and applications to real data are included as numerical examples.
Examining Interindividual Differences in Cyclicity of Pleasant and Unpleasant Affects Using Spectral Analysis and Item Response Modeling
Authors: Ram Nilam , Chow Sy-Miin , Bowles Ryan P. , Wang Lijuan , Grimm Kevin , Fujita Frank , Nesselroade John R.
Published: December 2005

Weekly cycles in emotion were examined by combining item response modeling and spectral analysis approaches in an analysis of 179 college students' reports of daily emotions experienced over 7 weeks. We addressed the measurement of emotion using an item response model. Spectral analysis and multilevel sinusoidal models were used to identify interindividual differences in intraindividual cyclic change. Simulations and incomplete data designs were used to examine how well this combination of analysis techniques might work when applied to other practical data problems. Empirically, we found systematic individual differences in the extent to which individuals' emotions follow a weekly cycle, and in how such cycles are exhibited. Weekly cycles accounted for very little variance in day to day emotions at the individual level. Analytically, we illustrate how measurement, change, and interindividual difference models from different traditions may be combined in a practical manner to describe some of the complexities of human behavior.
Fitting Psychometric Models with Methods Based on Automatic Differentiation
Authors: Cudeck Robert
Published: December 2005

Quantitative psychology is concerned with the development and application of mathematical models in the behavioral sciences. Over time, models have become more complex, a consequence of the increasing complexity of research designs and experimental data, which is also a consequence of the utility of mathematical models in the science. As models have become more elaborate, the problems of estimating them have become increasingly challenging. This paper gives an introduction to a computing tool called automatic differentiation that is useful in calculating derivatives needed to estimate a model. As its name implies, automatic differentiation works in a routine way to produce derivatives accurately and quickly. Because so many features of model development require derivatives, the method has considerable potential in psychometric work. This paper reviews several examples to demonstrate how the methodology can be applied.
The relation between identity status and romantic attachment style in middle and late adolescence
Authors: Berman Steven L. , Weems Carl F. , Rodriguez Eileen T. , Zamora Irving J.
Published: December 2005

This study examined the linkages between identity formation and romantic attachment in an ethnically diverse sample of high school () and college students (). Individuals in the foreclosed identity status group had significantly lower relationship avoidance scores than the diffused identity status group, and the foreclosed group had significantly lower relationship anxiety scores than both the achieved identity and moratorium groups. Identity status and romantic attachment style were significantly related among the college sample, but not among the high school sample. Some ethnic differences in attachment style were noted. Developmental implications are discussed.
On the putative co‐transport of drugs by multidrug resistance proteins
Authors: Borst P. , Zelcer N. , van de Wetering K. , Poolman B.
Published: December 2005

Experiments with multidrug resistance‐associated protein 1 (MRP1) showed 10‐years ago that transport of vincristine (VCR) by MRP1 could be stimulated by GSH, and transport of GSH by VCR. Since then many examples of stimulated transport have been reported for MRP1, 2, 3, 4 and 8. We discuss here three models to explain stimulated transport. We favour a model in which a large promiscuous binding site can bind more than one ligand, allowing cooperative/competitive interactions between ligands within the binding site. We conclude that there is no unambiguous proof for co‐transport of two different ligands by MRPs, but that cross‐stimulated transport can explain the published data.
Inverted repeat domains in membrane proteins
Authors: Pornillos Owen , Chang Geoffrey
Published: December 2005

With the upsurge in known membrane protein structures, common structural themes have started to emerge. One of these is the inverted repeat, a tandem of α‐helical domains that have similar tertiary folds but opposite membrane orientations. In all previously known examples, both repeat units were encoded in a single continuous polypeptide. Recent structures of a bacterial multidrug transporter, EmrE, revealed an inverted repeat membrane protein wherein the two repeat units are assembled from two polypeptides with the same primary sequence. Here, we speculate on some of the implications of the EmrE structure with regards to our understanding of membrane protein evolution and topogenesis.
Inhibition of the ATPase activity of Escherichia coli ATP synthase by magnesium fluoride
Authors: Ahmad Zulfiqar , Senior Alan E.
Published: December 2005

Inhibition of ATPase activity of Escherichia coli ATP synthase by magnesium fluoride (MgFx) was studied. Wild‐type F1‐ATPase was inhibited potently, albeit slowly, when incubated with MgCl2, NaF, and NaADP. The combination of all three components was required. Reactivation of ATPase activity, after removal of unbound ligands, occurred with half‐time of ∼14 h at 22 °C and was quasi‐irreversible at 4 °C. Mutant F1‐ATPases, in which catalytic site residues involved in transition state formation were modified, were found to be resistant to inhibition by MgFx. The data demonstrate that MgFx in combination with MgADP behaves as a tight‐binding transition state analog in E. coli ATP synthase.
Plant polyphenols mobilize endogenous copper in human peripheral lymphocytes leading to oxidative DNA breakage: A putative mechanism for anticancer properties
Authors: Azmi Asfar Sohail , Bhat Showket Hussain , Hanif Sarmad , Hadi S.M.
Published: December 2005

Plant polyphenols are important components of human diet and a number of them are considered to possess chemopreventive and therapeutic properties against cancer. They are recognized as naturally occurring antioxidants but also act as prooxidants catalyzing DNA degradation in the presence of transition metal ions such as copper. Using human peripheral lymphocytes and Comet assay we have previously confirmed that resveratrol–Cu(II) is indeed capable of causing DNA degradation in cells. In this paper we show that the polyphenols alone (in the absence of added copper) are also capable of causing DNA breakage in cells. Incubation of lymphocytes with neocuproine inhibited the DNA degradation confirming that Cu(I) is an intermediate in the DNA cleavage reaction. Further, we have also shown that polyphenols generate oxidative stress in lymphocytes which is inhibited by scavengers of reactive oxygen species and neocuproine. These results are in further support of our hypothesis that anticancer mechanism of plant polyphenols involves mobilization of endogenous copper, possibly chromatin bound copper, and the consequent prooxidant action.
Transcription factor cycling on the insulin promoter
Authors: Barrow John , Hay Colin W. , Ferguson Laura A. , Docherty Hilary M. , Docherty Kevin
Published: December 2005

Using MIN6 β‐cells and chromatin immunoprecipitation (ChIP) assays, the chronological sequence of binding of MafA, E47/β2 and PDX‐1 to the insulin promoter in living β‐cells were investigated. All four factors were shown to bind to the mouse insulin 2 promoter in a cyclical manner with a periodicity of approximately 10–15 min. The cyclical binding of MafA, E47 and β2 was largely unaffected by the glucose or insulin concentration in the media. However, the binding and cycling of PDX‐1 was markedly abolished in low glucose (1 mM), and this was reversed in the presence of low concentrations of insulin.
Methylobacterium extorquens AM1 produces a novel type of acyl‐homoserine lactone with a double unsaturated side chain under methylotrophic growth conditions
Authors: Nieto Penalver Carlos G. , Morin Danièle , Cantet Franck , Saurel Olivier , Milon Alain , Vorholt Julia A.
Published: December 2005

Acyl‐homoserine lactones (acyl‐HSLs) have emerged as important regulatory molecules for many gram‐negative bacteria. We have found that Methylobacterium extorquens AM1, a member of the pink‐pigmented facultative methylotrophs commonly present on plant surfaces, produces several acyl‐HSLs depending upon the carbon source. A novel HSL was discovered with a double unsaturated carbon chain (N‐(tetradecenoyl)) (C14:2) and characterized by MS and proton NMR. This long‐chain acyl‐HSL is synthesized by MlaI that also directs synthesis of C14:1‐HSL. The Alphaproteobacterium also produces N‐hexanoyl‐HSL (C6‐HSL) and N‐octanoyl‐HSL (C8‐HSL) via MsaI.
Interactions of the Escherichia coli hydrogenase biosynthetic proteins: HybG complex formation
Authors: Butland Gareth , Zhang Jie Wei , Yang Wenhong , Sheung Anthony , Wong Peter , Greenblatt Jack F. , Emili Andrew , Zamble Deborah B.
Published: December 2005

Assembly of the active site of the [NiFe]‐hydrogenase enzymes involves a multi‐step pathway and the coordinated activity of many accessory proteins. To analyze complex formation between these factors in Escherichia coli, they were genomically tagged and native multi‐protein complexes were isolated. This method validated multiple interactions reported in separate studies from several organisms and defined a new complex containing the putative chaperone HybG and the large subunit of hydrogenase 1 or 2. The complex also includes HypE and HypD, which interact with each other before joining the larger complex.
Fully oxidized scrambled isomers are essential and predominant folding intermediates of cardiotoxin‐III
Authors: Chang Jui-Yoa , Lu Bao-Yuan , Lin Curtis C.-J. , Yu Chin
Published: December 2005

Scrambled isomers (X‐isomers) are fully oxidized, non‐native isomers of disulfide proteins. They have been shown to represent important intermediates along the pathway of oxidative folding of numerous disulfide proteins. A simple method to assess whether X‐isomers present as folding intermediate is to conduct oxidative folding of fully reduced protein in the alkaline buffer alone without any supplementing thiol catalyst or redox agent. Cardiotoxin‐III (CTX‐III) contains 60 amino acids and four disulfide bonds. The mechanism of oxidative folding of CTX‐III has been systematically characterized here by analysis of the acid trapped folding intermediates. Folding of CTX‐III was shown to proceed sequentially through 1‐disulfide, 2‐disulfide, 3‐disulfide and 4‐disulfide (scrambled) isomers as folding intermediates to reach the native structure. When folding of CTX‐III was performed in the buffer alone, more than 97% of the protein was trapped as 4‐disulfide X‐isomers, unable to convert to the native structure due to the absence of thiol catalyst. In the presence of thiol catalyst (GSH) or redox agents (GSH/GSSG), the recovery of native CTX‐III was 80–85%. These results demonstrate that X‐isomers play an essential and predominant role in the oxidative folding of CTX‐III.
Differentially expressed cortical genes contribute to perivascular deposition in transgenic mice with inducible neuron‐specific expression of TGF‐β1
Authors: Ueberham Uwe , Zobiak Bernd , Ueberham Elke , Brückner Martina K. , Boriss Hinnerk , Arendt Thomas
Published: December 2005

In the brain the expression of transforming growth factor β1 (TGF‐β1) is involved both in neuroprotective and neurodegenerative processes. Recently, we have established a transgenic mouse model with inducible neuron‐specific expression of TGF‐β1 based on the tetracycline‐regulated gene expression system. A long‐term expression of TGF‐β1 results in persisting perivascular thioflavin‐positive depositions, which did not disappear even though the transgene synthesis was repressed completely by administration of doxycycline. Formation and composition of these depositions are hardly elucidated. The aim of this study was to identify TGF‐β1 responding genes potentially participating in forming these depositions. To address this problem we have compared the cortical mRNA expression pattern of TGF‐β1 expressing mice with mice impeded to express the transgenic protein using oligonucleotide microarray analysis. Differential gene expression was further characterized by quantitative real‐time reverse transcription‐polymerase chain reaction including animals, where the long‐lasting TGF‐β1 expression was repressed. While no change of amyloid precursor protein RNA expression level was detected, various genes strongly involved in calcium homeostasis, tissue mineralization or vascular calcification were identified differentially expressed. It is suggested, that these genes might contribute to the perivascular depositions in the TGF‐β1 expressing mice.
Thioflavins released from nanoparticles target fibrillar amyloid β in the hippocampus of APP/PS1 transgenic mice
Authors: Siegemund T. , Paulke B.‐R. , Schmiedel H. , Bordag N. , Hoffmann A. , Harkany T. , Tanila H. , Kacza J. , Härtig W.
Published: December 2005

For the delivery of drugs into the brain, the use of nanoparticles as carriers has been described as a promising approach. Here, we prepared nanoparticles as carriers for the model drugs thioflavin T and thioflavin S that bind fibrillar amyloid β peptides (Aβ). These polymer colloids are composed of a polystyrene core and a degradable PBCA [poly(butyl‐2‐cyanoacrylate)] shell with a diameter of 90–100 nm as shown by dynamic light scattering. Fluorescence spectrophotometric analysis revealed that encapsulated thioflavin T exhibited significantly stronger fluorescence than the free fluorophore. The enzymatic degradation of core‐shell nanoparticles, as required in vivo, was shown after their treatment with porcine liver esterase, a non‐specific esterase, in vitro. Shells of nanoparticles were dose‐dependently degraded while their polystyrene cores remained intact. In the cortices of 7–14 months old APP/PS1 mice with age‐dependent β‐amyloidosis, thioflavins selectively targeted fibrillar Aβ after biodegradation‐induced release from their nanoparticulate carriers upon intracerebral injection. Collectively, our data suggest that core‐shell nanoparticles with controlled degradation in vivo can become versatile tools to trace and clear Aβ in the brain.
Relevance of Baldrige constructs in an international context: A study of national culture
Authors: Flynn Barbara B. , Saladin Brooke
Published: December 2005

Because of the wide acclaim received by the Malcolm Baldrige Award, it has served as a model for national quality awards by many countries throughout the world. Some countries have adopted both the MBNQA criteria and weights, while others have adapted the criteria categories or weights somewhat. The relevance of this conceptual framework across national cultures has yet to be established, despite its use as the foundation for numerous national quality awards. This study uses Hofstede's dimensions of national culture to examine whether the theoretical constructs underlying the Baldrige criteria are relevant across national cultures. Correlation analysis, stepwise regression and analysis of variance are used to analyze hypotheses in manufacturing plants in the U.S., Japan, Germany, Italy and England. There were many interactions between dimensions of national culture and the Baldrige constructs advanced in this study. The findings indicate that national culture plays a strong role in the effectiveness of the Baldrige constructs, with the exception of customer and market focus. The findings are interpreted in light of the need for countries to develop awards and quality initiatives tailored to their national cultures.
Revisiting the theory of production competence: Extensions and cross‐validations
Authors: Schmenner Roger W. , Vastag Gyula
Published: December 2005

This paper examines a widely cited work in operations management, the theory of production competence, advanced initially by Cleveland, Schroeder, and Anderson (CSA). This intuitively appealing proposition asserts that production competence leads to improved business performance. However, CSA's empirical work has been criticized by Vickery and her collaborators and by Safizadeh, Ritzman, and Mallick (SRM). Moreover, SRM's own empirical work suggested that the CSA proposition only holds for batch processes. Using data from two large studies, we avoid the problems that plagued CSA's analysis, improve on their result, and call into question the SRM finding that restricts that result to batch operations.
Conceptions of Political Representation in Canada: An Explanation of Public Opinion
Authors: Anderson Cameron D. , Goodyear-Grant Elizabeth
Published: December 2005

Abstract.Despite widespread attention paid to issues of representation, how Canadians think and feel about different facets of representation are inadequately documented and understood. Using data from the 2000 Canadian Election Study (CES), the article addresses this dearth of systematic research through an examination of popularly held attitudes toward three dimensions of political representation: direct versus representative democracy, the role of the elected representative and territorial versus non-territorial bases of substantive representation. Particular attention is paid to the impact of political knowledge and the individualist/collectivist value cleavage on representational preferences. Results are discussed in light of current debates regarding institutional and representational change in Canada.

Résumé.En dépit de l'attention portée aux enjeux de la représentation, les sentiments et les idées des Canadiens par rapport aux différents aspects de la représentation sont mal documentés et compris. Cet article emploie les données de l'Étude électorale canadienne (ÉÉC) et cherche à combler cette lacune en examinant les attitudes populaires par rapport à trois dimensions de la représentation politique : la démocratie directe versus représentative, le rôle du représentant élu, et les bases de représentation territoriales versus non-territoriales. Nous accordons une attention particulière aux répercussions du niveau de connaissances politiques et des valeurs individualistes ou collectivistes sur les préférences en matière de représentation. Les résultats sont examinés à la lumière des débats récents sur le renouveau institutionnel et les modifications de la représentation au Canada.
Up the Creek: Fishing for a New Constitutional Order
Authors: Ladner Kiera L.
Published: December 2005

Abstract.Everyone familiar with the study of Canadian politics knows the joke about how a French national, an Englishman and a Canadian were asked to write an essay about an elephant: the French national wrote about the culinary uses of the elephant, the Englishman wrote about the elephant and imperialism, and the Canadian wrote a paper entitled, “Elephant: Federal or Provincial Responsibility?” Though simple, the joke conveys the essence of Canadian politics: always defined by jurisdictional disputes. The joke misses the boat, however, by ignoring the fact that indigenous people are now (as they always have been) engaging in jurisdictional debates in an attempt to challenge the Canadian constitutional order and to reaffirm their own constitutional order and autonomy. This paper examines one such dispute—the Mi'kmaw claim of rights and responsibilities for the salmon fishery—and presents it as a case of contested sovereignties and a resulting jurisdictional dispute. In so doing, I pose the question: Is salmon a federal, provincial or Mi'kmaq responsibility? In seeking an answer, this paper proceeds in an exploratory manner to map both constitutional orders, and the interrelation between these orders that results in the debate over responsibility for the salmon.

Résumé.Dans le milieu de la science politique au Canada, tout le monde connaît la blague du Français, du Britannique et du Canadien qui doivent écrire une thèse sur l'éléphant. Le Français disserte sur les usages culinaires de l'éléphant, le Britannique traite de l'éléphant et de l'impérialisme et le Canadien écrit une thèse intitulée : “L'éléphant : responsabilité fédérale ou provinciale?” Cette blague, dans sa simplicité, évoque l'essence même de la politique au Canada, car la politique canadienne a toujours été définie par des conflits juridictionnels. Mais, si elle illustre bien la nature de la politique au Canada, elle n'est cependant pas satisfaisante parce qu'elle ignore qu'aujourd'hui (comme autrefois d'ailleurs) les peuples autochtones s'engagent dans les débats juridictionnels pour contester l'ordre constitutionnel du Canada et pour réaffirmer leur propre ordre constitutionnel et leur autonomie. Cet article examine l'un de ces conflits : la revendication par les Mi'kmaq de leurs droits et responsabilités concernant les pêcheries de saumon – et le présente comme un cas de souverainetés contestées, et, par conséquent, un exemple de conflit juridictionnel. Je pose donc la question : “Saumon : responsabilité fédérale, provinciale ou Mi'kmaq?” En répondant à cette question, l'article explore les caractéristiques des deux ordres constitutionnels et leur connexions, ce qui mène à un débat sur l'attribution des compétences dans le domaine du saumon.
Gender vs. Diversity Mainstreaming: A Preliminary Examination of the Role and Transformative Potential of Feminist Theory
Authors: Hankivsky Olena
Published: December 2005

Abstract.This paper considers why gender mainstreaming (GM), a strategy that many have claimed holds promise for transforming public policy and working towards social justice, is inherently limited and flawed. The paper begins with a brief overview of GM, specifically focusing on the Canadian context, and highlights current discussions in the literature regarding issues of implementation and best practices. It then moves on to reveal that a critical but overlooked dimension of GM is its theoretical foundation. In contextualizing GM within a contemporary feminist theory framework, the paper seeks to illuminate the problematic relationship that currently exists between GM and feminist theory and, moreover, demonstrates why the theoretical premises of GM need significant reworking. The argument put forward is that if insights of recent feminist theorizing are taken seriously, it becomes clear that GM should be replaced by an alternative and broader strategy of diversity mainstreaming. Through the use of practical examples, the paper illustrates how diversity mainstreaming is able to better capture, articulate and make visible the relationship between simultaneously interlocking forms of oppressions that include but are not limited to gender.

Résumé.Cet article étudie pourquoi l'intégration d'une perspective de genre (IPG), une stratégie dans laquelle beaucoup ont vu la promesse d'une transformation de la politique publique et d'un progrès vers la justice sociale, est en soi limitée et défectueuse. L'article débute par un bref exposé sur l'IPG, s'intéressant principalement au contexte canadien, et il met en évidence les discussions actuelles dans la littérature au sujet de problèmes de mise en oeuvre et de pratiques exemplaires. Il révèle ensuite qu'une dimension critique mais négligée de l'IPG est son fondement théorique. En contextualisant l'IPG dans un cadre de théorie féministe contemporaine, l'article cherche à éclairer la relation problématique qui existe actuellement entre l'IPG et la théorie féministe et, de surcroît, démontre pourquoi les prémisses théoriques de l'IPG nécessitent une révision significative. L'argument avancé est que, si l'on prend au sérieux les conclusions des théories féministes récentes, il semble évident que l'IPG devrait être remplacée par une stratégie plus vaste d'intégration d'une perspective de diversité. S'appuyant sur des exemples pratiques, l'article montre que l'intégration d'une perspective de diversité réussit à mieux capturer, mettre en rapport et rendre visible la relation entre des formes d'oppression qui s'entrecroisent simultanément et qui incluent mais ne se limitent pas au genre.
Therapeutisches Drug-Monitoring in der Kinder- und Jugendpsychiatrie - Grundlagen und praktische Empfehlungen
Authors: Gerlach Manfred , Rothenhöfer Silke , Mehler-Wex Claudia , Fegert Joerg M. , Schulz Eberhard , Wewetzer Christoph , Warnke Andreas
Published: December 2005

Zusammenfassung: Gegenüber der Psychopharmakotherapie bei Erwachsenen ergeben sich im Kindes- und Jugendalter einige Besonderheiten: Zum einen gibt es abhängig vom Entwicklungsstadium Unterschiede in der Pharmakokinetik und Pharmakodynamik, wodurch Dosisempfehlungen aus dem Erwachsenenbereich nicht ohne weiteres auf diese Patienten übertragen werden dürfen. Zum anderen liegt in den meisten Fällen keine Zulassung der Arzneimittel für diese Altergruppe vor, wodurch in der Psychopharmakotherapie im Kindes- und Jugendalter die sonst durch das Arzneimittelgesetz garantierten Sicherheits- und Wirksamkeitskriterien nicht gegeben sind. Deshalb wird «Therapeutisches Drug-Monitoring» (TDM) als eine generelle Indikation in der Kinder- und Jugendpsychiatrie angesehen. Das TDM bietet die Chance einer größeren Sicherheit in der Behandlung mit Psychopharmaka im Kindes- und Jugendalter sowie die Möglichkeit, die individuelle Therapie effektiver zu gestalten und somit die Krankheitsdauer zu verkürzen. Zur Ermittlung der notwendigen Referenzwerte für TDM im Kindes- und Jugendalter sind jedoch standardisierte Untersuchungen notwendig, die weitere Aspekte zum Verständnis des Stoffwechsels und der pharmakologischen Effekte bei Kindern und Jugendlichen beitragen können. In diesem Beitrag wird zunächst kurz auf die Strategie des TDM in der Psychiatrie eingegangen. Danach werden die Besonderheiten der Psychopharmakotherapie im Kindes- und Jugendalter erörtert und Gründe für die generelle Indikation von TDM in der Kinder- und Jugendpsychiatrie diskutiert. Schließlich werden praktische Empfehlungen zur Durchführung des TDM gegeben.
Reliability of N flux rates estimated from 15N enrichment and dilution experiments in aquatic systems
Authors: Elskens Marc , Baeyens Willy , Brion Natacha , De Galan Sandra , Goeyens Leo , de Brauwere Anouk
Published: December 2005

This paper investigates the estimation behavior of six increasingly complex 15N models, for estimating flux rates between phytoplankton and dissolved N pools in aquatic ecosystems. The development of these models over the last 40 years reflects increasing realism in the pools and fluxes that constitute the N cycle. The purpose of this paper is to assess how the model results are influenced by the underlying assumptions. For example, with respect to uptake of 15N by phytoplankton, is anything gained by assuming that regenerated N become isotopically enriched after the introduction of the 15N label, or is it just as accurate to assume that no source other than the initial 15N label contributes to the enrichment signal in phytoplankton? To conduct an objective assessment of the models, we compared them to (1) a set of reference values generated numerically by a process oriented model, and (2) real experimental data. The results show that for a number of 15N models, properties such as accuracy and precision cannot both be optimized under the same conditions, and a compromise must be struck. Oversimplified models risk bias when their underlying assumptions are violated, but overly complex models can misinterpret part of the random noise as relevant processes. Therefore none of the 15N model solutions can a priori be rejected, but each should carefully be assessed with hypothesis testing. A backward regression strategy based on a statistical interpretation of the cost function (sum of the weighted least squares residuals) was used to select optimal solution subsets corresponding to a given data set.
Atmospheric global dust cycle and iron inputs to the ocean
Authors: Mahowald Natalie M. , Baker Alex R. , Bergametti Gilles , Brooks Nick , Duce Robert A. , Jickells Timothy D. , Kubilay Nilgün , Prospero Joseph M. , Tegen Ina
Published: December 2005

Since iron is an important micronutrient, deposition of iron in mineral aerosols can impact the carbon cycle and atmospheric CO2. This paper reviews our current understanding of the global dust cycle and identifies future research needs. The global distribution of desert dust is estimated from a combination of observations of dust from in situ concentration, optical depth, and deposition data; observations from satellite; and global atmospheric models. The anthropogenically influenced portion of atmospheric desert dust flux is thought to be smaller than the natural portion, but is difficult to quantify due to the poorly understood response of desert dust to changes in climate, land use, and water use. The iron content of aerosols is thought to vary by a factor of 2, while the uncertainty in dust deposition is at least a factor of 10 in some regions due to the high spatial and temporal variability and limited observations. Importantly, we have a limited understanding of the processes by which relatively insoluble soil iron (typically ∼0.5% is soluble) becomes more soluble (1–80%) during atmospheric transport, but these processes could be impacted by anthropogenic emissions of sulfur or organic acids. In order to understand how humans will impact future iron deposition to the oceans, we need to improve our understanding of: iron deposition to remote oceans, iron chemistry in aerosols, how desert dust sources will respond to climate change, and how humans will impact the transport of bioavailable fraction of iron to the oceans.
Forecasting impulse waves generated by subaerial landslides
Authors: Panizzo A. , De Girolamo P. , Petaccia A.
Published: December 2005

Subaerial landslides falling into reservoirs or open seas generate impulsive water waves, that are usually referred to as a class of tsunami waves. It is important to study landslide‐generated waves occurring both in closed water basins, where the waves interact with the shorelines and eventually the dam, and in open seas, where the generated waves can travel and deliver devastating damages hundreds of kilometers away. In order to gain insight on subaerial landslide generated waves, the Italian National Dam Office recently funded an experimental and numerical research program geared to better understand and forecast tsunamis waves. This paper introduces the experimental work which has been carried out in order to define empirical formulations able to forecast the principal features of the generated waves in a three‐dimensional water body, as a function of the landslide movement. Wave types observed during the experiments are here characterized using a wavelet analysis approach; new forecasting formulations (named RID formulas) are defined on the basis of the experimental study and tested using an artificial neural network model. Results are finally compared to those presented in past experimental studies.
A factorial analysis of the marine carbon cycle and ocean circulation controls on atmospheric CO2
Authors: Cameron David R. , Lenton Timothy M. , Ridgwell Andy J. , Shepherd John G. , Marsh Robert , Yool Andrew
Published: December 2005

A factorial experiment with a new Earth system model of intermediate complexity is used to assess the sensitivity of atmospheric CO2 to organic, carbonate and solubility pumps, ocean circulation state, and climate feedback. An analysis of variance of the results reveals that the organic, carbonate, and solubility pumps act multiplicatively and account for 94% of the variance of atmospheric CO2. The organic pump explains 63% (89 ppm), the solubility pump 24% (55 ppm), the carbonate pump 6% (28 ppm), and ocean circulation 0.3% (12 ppm) of the variance. Removing all pumps increases atmospheric CO2 from 278 to 525 ppm. Including interactions with all the pumps increases the effects of ocean circulation from 12 to 56 ppm. However, the ocean circulation states used are unlikely to span the full range of possible states. Changes in Pacific circulation have more effect on atmospheric CO2 than Atlantic circulation.
Acquisition of the neodymium isotopic composition of the North Atlantic Deep Water
Authors: Lacan Francois , Jeandel Catherine
Published: December 2005

The North Atlantic Deep Water (NADW) neodymium isotopic composition (Nd IC) is increasingly used in oceanography and paleoceanography to trace large‐scale circulation and weathering processes, notably to investigate past variations of the global thermohaline circulation. Although the present‐day NADW Nd IC is well characterized at ɛNd = −13.5, the acquisition of this isotopic signature (in other words, the causes of this value) has so far been very sparsely documented. Such an understanding is, however, fundamental to the interpretation of paleo records. Nd IC and rare earth element concentrations were measured at 9 stations within the North Atlantic Subpolar Gyre (SIGNATURE cruise, summer 1999). The comparison of this data set with our understanding of water mass circulation provides a description of how the three layers constituting the NADW, the Labrador Sea Water (LSW, ɛNd = −13.9 ± 0.4), North East Atlantic Deep Water (NEADW, ɛNd −13.2 ± 0.4), and North West Atlantic Bottom Water (NWABW, ɛNd −14.5 ± 0.4), acquire their Nd IC through distinct water mass mixings and lithogenic inputs. These different mechanisms, acting upon water masses from very diverse sources, seem to bring the Nd IC of the three NADW layers to values close together and similar to that of the NADW. It is suggested that sediment/seawater interactions significantly lower the NEADW and NWABW Nd IC along the South East Greenland margin. Since these interactions do not significantly modify the Nd content of these water masses, sediment remobilizations leading to the Nd IC variations are probably associated with Nd removal fluxes from the water mass toward the sediment, a process called boundary exchange. On the other hand, LSW seems to acquire its Nd IC from the Subpolar Mode Waters from which it is formed by deep convection, and no other mechanism needs to be invoked. Its unradiogenic signature could ultimately be linked to fresh water runoff from the Canadian Shield. These conclusions should allow more precise interpretations of paleoceanographic Nd IC records, taking into account the distinct histories of the three NADW layers, including distinct water mass mixings and distinct lithogenic inputs.
Nitrogen content and isotopic composition of oceanic crust at a superfast spreading ridge: A profile in altered basalts from ODP Site 1256, Leg 206
Authors: Busigny Vincent , Laverne Christine , Bonifacie Magali
Published: December 2005

The present paper provides the first measurements of both nitrogen content and isotopic composition of altered oceanic basalts. Samples were collected from Ocean Drilling Program Site 1256 located at the eastern flank of the East Pacific Rise. Twenty‐five samples affected by low temperature alteration were analyzed. They include moderately altered basalts together with veins and related alteration halos and host rocks, as well as unique local intensely altered basalts showing green (celadonite‐rich) and red (iron oxyhydroxide‐rich) facies. Nitrogen contents of moderately altered basalts range from 1.4 to 4.3 ppm and are higher than in fresh MORB. Their δ15N values vary in a large range from +1.6 to +5.8‰. Veins, halos, and host rocks are all enriched in N relative to moderately altered basalts. Notably, veins show particularly high N contents (354 and 491 ppm) associated with slightly low δ15N values (+0.4 and −2.1‰). The intensely altered red and green facies samples display high N contents of 8.6 and 9.7 ppm, respectively, associated with negative δ15N values of −3.8 and −2.7‰. Detailed petrological examination coupled with N content suggests that N of altered basalts occurs as ammonium ion (NH4+) fixed in various secondary minerals (celadonite, K‐ and Na‐feldspars, smectite). A body of evidence indicates that N is enriched during alteration of oceanic basalts from ODP Site 1256, contrasting with previous results obtained on basalts from DSDP/ODP Hole 504B (Erzinger and Bach, 1996). Nitrogen isotope data support the interpretation that N in metasomatizing fluid occurred as N2, derived from deep seawater and likely mixed with magmatic N2 contained in basalt vesicles.
Diffusion theory improves chamber‐based measurements of trace gas emissions
Authors: Livingston Gerald P. , Hutchinson Gordon L. , Spartalian Kevork
Published: December 2005

Chambers temporarily sealed to the soil surface are an important and for many purposes the only means of measuring trace gas emissions to the atmosphere. However, past interpretations of chamber data systematically underestimated actual emission rates in most applications because they ignored or poorly modeled the effect of the chamber on the gas exchange process. To address this issue, we introduce a time‐dependent diffusion model applicable to non‐steady‐state chamber observations and evaluate its performance, as well as that of previously published models, using concentration data simulated by an independent, 3‐dimensional numeric diffusion model. The results demonstrate that commonly cited past measurement practices underestimate emission rates 15% to 25% under most circumstances and that the error varies with chamber height, soil air‐filled porosity and flux model used to interpret the concentration data. In contrast, our model proved accurate and readily applicable over the entire range of soil and chamber dimensions evaluated.
Space Weather Modeling Framework: A new tool for the space science community
Authors: Tóth Gábor , Sokolov Igor V. , Gombosi Tamas I. , Chesney David R. , Clauer C. Robert , De Zeeuw Darren L. , Hansen Kenneth C. , Kane Kevin J. , Manchester Ward B. , Oehmke Robert C. , Powell Kenneth G. , Ridley Aaron J. , Roussev Ilia I. , Stout Quentin F. , Volberg Ovsei , Wolf Richard A. , Sazykin Stanislav , Chan Anthony , Yu Bin , Kóta József
Published: December 2005

The Space Weather Modeling Framework (SWMF) provides a high‐performance flexible framework for physics‐based space weather simulations, as well as for various space physics applications. The SWMF integrates numerical models of the Solar Corona, Eruptive Event Generator, Inner Heliosphere, Solar Energetic Particles, Global Magnetosphere, Inner Magnetosphere, Radiation Belt, Ionosphere Electrodynamics, and Upper Atmosphere into a high‐performance coupled model. The components can be represented with alternative physics models, and any physically meaningful subset of the components can be used. The components are coupled to the control module via standardized interfaces, and an efficient parallel coupling toolkit is used for the pairwise coupling of the components. The execution and parallel layout of the components is controlled by the SWMF. Both sequential and concurrent execution models are supported. The SWMF enables simulations that were not possible with the individual physics models. Using reasonably high spatial and temporal resolutions in all of the coupled components, the SWMF runs significantly faster than real time on massively parallel supercomputers. This paper presents the design and implementation of the SWMF and some demonstrative tests. Future papers will describe validation (comparison of model results with measurements) and applications to challenging space weather events. The SWMF is publicly available to the scientific community for doing geophysical research. We also intend to expand the SWMF in collaboration with other model developers.
Effect of the latitudinal distribution of temperature at the coronal base on the interplanetary magnetic field configuration and the solar wind flow
Authors: Li Bo , Habbal Shadia Rifai , Li Xing , Mountford Chris
Published: December 2005

Using a two‐dimensional MHD model of the corona and solar wind, we investigate the role of the temperature distribution with latitude at the coronal base on the global magnetic field configuration and solar wind properties at 1 AU. The latitudinal distribution of temperature is aimed at modeling the transition in electron temperature at the Sun from a polar coronal hole to the quiet Sun to active regions. The results of the model calculations illustrate how the variation of temperature with latitude impacts the coronal magnetic field configuration and the distribution of wave energy flux in the solar wind and consequently its thermodynamic properties. The sharp temperature changes at the coronal base lead to the formation of current sheets in the corona. They also modify the location of the streamer cusp and the neutral line originating there. Two different approaches in treating electron heat flux are also compared, one assumes a Spitzer expression throughout the computational domain and the other assumes a collisionless expression beyond some radial distance. Model results thus derived differ little in terms of proton flux and terminal speed.
The “exceptional” earthquake of 3 January 1117 in the Verona area (northern Italy): A critical time review and detection of two lost earthquakes (lower Germany and Tuscany)
Authors: Guidoboni Emanuela , Comastri Alberto , Boschi Enzo
Published: December 2005

In the seismological literature the 3 January 1117 earthquake represents an interesting case study, both for the sheer size of the area in which that event is recorded by the monastic sources of the 12th century, and for the amount of damage mentioned. The 1117 event has been added to the earthquake catalogues of up to five European countries (Italy, France, Belgium, Switzerland, the Iberian peninsula), and it is the largest historical earthquake for northern Italy. We have analyzed the monastic time system in the 12th century and, by means of a comparative analysis of the sources, have correlated the two shocks mentioned (in the night and in the afternoon of 3 January) to territorial effects, seeking to make the overall picture reported for Europe more consistent. The connection between the linguistic indications and the localization of the effects has allowed us to shed light, with a reasonable degree of approximation, upon two previously little known earthquakes, probably generated by a sequence of events. A first earthquake in lower Germany (I0 (epicentral intensity) VII–VIII MCS (Mercalli, Cancani, Sieberg), M 6.4) preceded the far more violent one in northern Italy (Verona area) by about 12–13 hours. The second event is the one reported in the literature. We have put forward new parameters for this Veronese earthquake (I0 IX MCS, M 7.0). A third earthquake is independently recorded in the northwestern area of Tuscany (Imax VII‐VIII MCS), but for the latter event the epicenter and magnitude cannot be evaluated.
Postseismic deformation following the June 2000 earthquake sequence in the south Iceland seismic zone
Authors: Árnadóttir Thóra , Jónsson Sigurjón , Pollitz Fred F. , Jiang Weiping , Feigl Kurt L.
Published: December 2005

We observe postseismic deformation on two spatiotemporal scales following Mw = 6.5 earthquakes in the south Iceland seismic zone on 17 and 21 June 2000. We see a rapidly decaying deformation transient lasting no more than 2 months and extending about 5 km away from the two main shock ruptures. This local, month‐scale transient is captured by several radar interferograms and is also observed at a few campaign GPS sites located near the faults. A slower transient with a characteristic timescale of about a year is detected only by GPS measurements. The month‐scale deformation pattern has been explained by poroelastic rebound due to postearthquake pore pressure changes. In contrast, the year‐scale deformation can be explained by either afterslip at 8–14 km depth or viscoelastic relaxation of the lower crust and upper mantle in response to the coseismic stress changes. The optimal viscoelastic models have lower crustal viscosities of 0.5–1 × 1019 Pa s and upper mantle viscosity of ∼3 × 1018 Pa s. Because of the limitations of our GPS campaign data, we consider both afterslip and viscoelastic relaxation as plausible mechanisms explaining the deformation field. Both types of postseismic deformation models suggest that the areas of large coseismic stress increase east of the 17 June and west of the 21 June ruptures continue to be loaded by the postseismic deformation.
Modeling entrainment of sedimentary particles by wind and water: A generalized approach
Authors: Lu Hua , Raupach Michael R. , Richards Keith S.
Published: December 2005

For long‐standing theoretical reasons, it is often asserted that the threshold shear stress for entrainment of sedimentary particles (τ*t = ρfu*t2, made dimensionless as A = ρfu*t2/((ρp − ρf)gd)) has a universal relationship with the particle Reynolds number (Re*t = u*td/ν), where u*t is the threshold friction velocity, ρf is the fluid density, ρp is the density of the particles, d is the particle diameter, g is the gravitational acceleration and ν is the kinematic viscosity of the fluid. However, experimental plots of A(Re*t) for sediment entrainment in air and water show two major differences: (1) For large Re*t, the values of A in water are, in general, a few times larger than those in air, and (2) when Re*t <1, A increases more rapidly in air than in water as Re*t decreases. This paper derives a new, general theory for A, which incorporates the effects of fluid turbulence, particle cohesion and probabilistic aspects of grain entrainment. It is found that difference (1) is explained by differences in the probability distribution of streamwise velocity fluctuations for typical situations in air and water, which follow from basic scaling laws for velocity variances in turbulent flow. Difference (2) is explained by the different behaviors of interparticle cohesion forces in air and water. The resulting expression is shown to compare well with experimental data.