938 research outputs found
Spatial variation in quartz cement type and concentration: An example from the Heidelberg formation (Teufelsmauer outcrops), Upper Cretaceous Subhercynian Basin, Germany
No full textSpatial heterogeneity of cement abundance in sandstones is an important factor for reservoir compartmentalization. Here we present results on the variety of diagenetic products and spatial distribution of intense and focused silica cementation within otherwise friable sandstone without silica cements. The Cretaceous quartz arenite of the Teufelsmauer outcrops near Quedlinburg (Upper Cretaceous Heidelberg formation, Subhercynian Basin, Germany) is cemented by various types of diagenetic silica. The highly cemented sandstone sections contain both syntaxial quartz cement (concentrations: 11-31 vol.%) and microcrystalline pore-filling quartz cement (10-34 vol.%). Microcrystalline cement generations form the latest SiO2 precipitations and overgrow moderate to intense syntaxial rims. At outcrop and sedimentary basin scales, the occurrence of highly cemented sandstone is limited to an area of several hundreds of meters in lateral extension, but does not exceed a layer thickness of about 5 m. The highly cemented sandstone shows internal heterogeneity in cementation with preferred orientation of their length axis, suggesting mainly stationary fluid flow pathways during cementation of several silica generations. Most likely, the source of all diagenetic silica is owing to enhanced dissolution at cataclastic deformation bands, which are found within the same sandstone strata. As a mechanism for locally focused precipitation, we suggest a combination of (1) local enhancement of silica dissolution due to deformation and cataclasis and (2) enhanced fluid flow and expulsion during deformation related to the synchronous thrusting of the Harz block onto the Cretaceous Subhercynian Basin. We interpret that the expelled silica-enriched formation water experienced fluid mixing with ascending water from an overpressured, deeper regime, implying that the observed silica generations trace this unique zone of fluid expulsion, ascension, and mixing. Our investigations show that silica precipitation may result in a pattern of spatially-oriented highly-cemented sections within poorly-cemented sandstone. The type of silica cement does, however, not influence size, frequency, and shape of highly cemented bodies. Implications range from specific conclusions about silica export from cataclastic deformation bands and adjacent precipitation to general conclusions about partitioning in cemented sandstone reservoirs, including information about the spatial scales of fluid movement, silica redistribution (dissolution-precipitation), and heterogeneity and sequence of cement types (syntaxial quartz and microquartz). (C) 2013 Elsevier B.V. All rights reserved
Detecting Flood‐Rich and Flood‐Poor Periods in Annual Peak Discharges Across Europe
Get PDFThis paper proposes a method from Scan statistics for identifying flood-rich and flood-poor periods (i.e., anomalies) in flood discharge records. Exceedances of quantiles with 2-, 5-, and 10-year return periods are used to identify periods with unusually many (or few) threshold exceedances with respect to the reference condition of independent and identically distributed random variables. For the case of flood-rich periods, multiple window lengths are used in the identification process. The method is applied to 2,201 annual flood peak series in Europe between 1960 and 2010. Results indicate evidence for the existence of flood-rich and flood-poor periods, as about 2 to 3 times more anomalies are detected than what would be expected by chance. The frequency of the anomalies tends to decrease with an increasing threshold return period which is consistent with previous studies, but this may be partly related to the method and the record length of about 50 years. In the northwest of Europe, the frequency of stations with flood-rich periods tends to increase over time and the frequency of stations with flood-poor periods tends to decrease. In the east and south of Europe, the opposite is the case. There appears to exist a turning point around 1970 when the frequencies of anomalies start to change most clearly. This turning point occurs at the same time as a turning point of the North Atlantic Oscillation index. The method is also suitable for peak-over-threshold series and can be generalized to higher dimensions, such as space and space-time
Significance testing of rank cross-correlations between autocorrelated time series with short-range dependence
Get PDFStatistical dependency measures such as Kendall’s Tau or Spearman’s Rho are frequently used to analyse the coherence between time series in environmental data analyses. Autocorrelation of the data can, however, result in spurious cross correlations if not accounted for. Here, we present the asymptotic distribution of the estimators of Spearman’s Rho and Kendall’s Tau, which can be used for statistical hypothesis testing of cross-correlations between autocorrelated observations. The results are derived using U-statistics under the assumption of absolutely regular (or β-mixing) processes. These comprise many short-range dependent processes, such as ARMA-, GARCH- and some copula-based models relevant in the environmental sciences. We show that while the assumption of absolute regularity is required, the specific type of model does not have to be specified for the hypothesis test. Simulations show the improved performance of the modified hypothesis test for some common stochastic models and small to moderate sample sizes under autocorrelation. The methodology is applied to observed climatological time series of flood discharges and temperatures in Europe. While the standard test results in spurious correlations between floods and temperatures, this is not the case for the proposed test, which is more consistent with the literature on flood regime changes in Europe
Innovationsmanagement für Kooperationen: Eine instrumentenorientierte Betrachtung
Get PDFInnovationen sind ein kritischer und zentraler Faktor für die nachhaltige Überlebensfähigkeit von Unternehmen und auch Volkswirtschaften. Der stetige Anstieg von Komplexität und Technologieintensität bei Produkten sowie herausfordernde Marktbedingungen erfordern verstärkt Unternehmensgrenzen überschreitende Innovationsaktivitäten. Auch wenn kooperativ gestaltete Innovationsaktivitäten kein vollkommen neues Phänomen darstellen, so ist doch zu eruieren, wie diese Aktivitäten effizient und effektiv durchgeführt werden können. Die vorliegende Publikation gestaltet das Management für kooperative Innovationsaktivitäten. Die Autorin identifiziert einzelne Managementaufgaben und entwirft konkrete unterstützende Instrumente und Methoden. Im Ergebnis entstehen Routinen und Strukturen, die in der Kooperation ein koordiniertes Arbeiten ermöglichen. Das zu gestaltende System von Managementaktivitäten kann als Informationssystem verstanden werden, welches den Partnern der Innovationskooperation entscheidungsrelevante Informationen bereitstellt. Das Buch richtet sich an Dozenten und Studenten der Betriebswirtschaftslehre mit den Schwerpunkten Innovations- sowie Kooperationsmanagement. Praktiker erhalten einen grundlegenden Einblick in aktuelle Managementkonzepte.This publication deals with the management of cooperative innovation activities. The author identifies individual management tasks and designs concrete supporting instruments and methods. The system to be designed by management activities can be understood as an information system which provides the partners of innovation cooperation actionable information. The book is aimed at teachers and students of business administration with a focus on innovation and collaboration management. Practitioners receive a basic insight into the latest management concepts
Supplemental_Figure – Supplemental material for Degenerative aortic valve disease and diabetes: Implications for a link between proteoglycans and diabetic disorders in the aortic valve
No full textSupplemental material, Supplemental_Figure for Degenerative aortic valve disease and diabetes: Implications for a link between proteoglycans and diabetic disorders in the aortic valve by Mareike Barth, Jessica I Selig, Svenja Klose, Antje Schomakers, Lena S Kiene, Silja Raschke, Udo Boeken, Payam Akhyari, Jens W Fischer and Artur Lichtenberg in Diabetes & Vascular Disease Research</p
Analysis of Resistance of Ebola Virus Glycoprotein-Driven Entry Against MDL28170, An Inhibitor of Cysteine Cathepsins
No full textEbola virus (EBOV) infection can cause severe and frequently fatal disease in human patients. The EBOV glycoprotein (GP) mediates viral entry into host cells. For this, GP depends on priming by the pH-dependent endolysosomal cysteine proteases cathepsin B (CatB) and, to a lesser degree, cathepsin L (CatL), at least in most cell culture systems. However, there is limited information on whether and how EBOV-GP can acquire resistance to CatB/L inhibitors. Here, we addressed this question using replication-competent vesicular stomatitis virus bearing EBOV-GP. Five passages of this virus in the presence of the CatB/CatL inhibitor MDL28170 were sufficient to select resistant viral variants and sequencing revealed that all GP sequences contained a V37A mutation, which, in the context of native GP, is located in the base of the GP surface unit. In addition, some GP sequences harbored mutation S195R in the receptor-binding domain. Finally, mutational analysis demonstrated that V37A but not S195R conferred resistance against MDL28170 and other CatB/CatL inhibitors. Collectively, a single amino acid substitution in GP is sufficient to confer resistance against CatB/CatL inhibitors, suggesting that usage of CatB/CatL inhibitors for antiviral therapy may rapidly select for resistant viral variants
An Empirical Analysis of the Amount of Publication Fees
No full textAmong the financing strategies available for Open Access (OA), the author-pays business model has received increasing attention. The consequences of this approach, however, for the system of scholarly communication and for publishing houses as participants In value added, have remained largely unclear. The paper presented here, therefore, analyzes the probable realistic magnitude of publishing fees in different subjects, based on empirical data. The paper shows that the most favorable conditions are met in the Natural Sciences and in Mathematics. However, the analysis also shows that publishing houses would have to raise publishing fees well beyond the level that scientists are willing to pay. Furthermore, the analysis leads to the conclusion that the amount of money currently available in the system of scholarly communication is probably not sufficient for the sustainable financing of publishing fees. Serials Review 2008; 34:257-266. (C) 2008 Elsevier Inc. All rights reserved
Hydrological design in the HELPING decade – inspiring the community to innovate the hydrological design concept
No full textHIV-associated cerebral toxoplasmosis - review and retrospective analysis of 36 patients
No full textHighly active antiretroviral therapy (HAART) has resulted in a reduction of morbidity and mortality in HIV-associated cerebral opportunistic infection. Before HAART, up to 50% of all HIV-infected patients in Europe developed cerebral toxoplasmosis, an encephalitis caused by reactivation of Toxoplasma gondii infection. Although potent therapeutical options exist the prognosis is still poor. We describe the course of 36 AIDS patients with cerebral toxoplasmosis and present a review of clinical signs, diagnosis, therapy, and survival times. The main criteria for differential diagnosis from other secondary neuromanifestations such as primary CNS lymphoma, progressive multifocal leukencephalopathy, abscesses, and ischemic infarctions are described. Indications and problems of stereotactic biopsy are discussed
Studentized U-quantile processes under dependence with applications to change-point analysis
Get PDFAcknowledgement The research was supported by the DFG Sonderforschungsbereich 823 (Collaborative Research Center) Statistik nichtlinearer dynamischer Prozesse. The authors thank Svenja Fischer and Wei Biao Wu for providing the river Elbe discharge data set and the Argentina rainfall data set, respectively. We are very grateful to the anonymous referee for the comments, which have helped to improve and clarify this manuscript.Peer reviewe
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