186,842 research outputs found
Characterising physicochemical sediment conditions at selected bacterial decayed wooden pile foundation sites in the Netherlands, Germany, and Italy
No full textWe investigated the relationship between wood degradation caused by erosion bacteria and the physicochemical properties of foundations with wooden piles from sites in the Netherlands, Germany, and Italy. Wooden foundation piles have been widely used to stabilise urban settlements along coastal areas and river sites for several millennia. Recently a number of these buildings have suffered from structural instability because their foundations have suddenly lost supporting strength. This loss of strength has been associated with the activity of erosion bacteria that can colonise and destroy wood under low-oxygen conditions, such as those that exist below the groundwater level. Knowledge of bacterial species involved in this process and their growth requirements is sparse, but it has been documented that the damage to wooden foundation piles caused by these bacteria can occur relatively rapidly. Redox potential (platinum electrodes) measurements, sediment, and sedimental water samples were obtained from nine European sites. Sediments were characterised and analysed for total contents of carbon, nitrogen, sulphur, phosphate, and major cations, whereas sedimental water was analysed for pH, conductivity, total and dissolved carbon and nitrogen, NH4+, NO3-, SO42-, PO43-, Cl-, and major cations. The chemical sediment composition was governed mainly by sediment type (sand, clay), whereas sediment water composition reflected the exposure to sea or freshwater and the redox status of the sampling location. Bacterial wood decay was detected at all sites but with different magnitude orders reflecting the different environments. When the physicochemical properties of sedimental water from foundations in sandy sediments were compared with wood degradation levels, it was observed that decreasing total nitrogen concentration, but not that of phosphate, accompanied increasing bacterial wood decay. (C) 2007 Elsevier Ltd. All rights reserved
Investigating physicochemical sediment conditions at decayed wooden pile foundation sites in Amsterdam
No full textFor thousands of years wooden foundation piles have been widely used along coastal areas and river sites to stabilise urban settlements. Recent investigations, however, indicate that colonising bacteria can destroy the wood even below the groundwater level under low-oxygen conditions and cause severe strength loss over unexpectedly short periods. Existing knowledge of the species involved and the conditions required for growth of the bacteria is insufficient. The aim of this study was to characterise physicochemical site conditions by taking oxygen, redox potential, and chemical measurements at wooden foundation sites in Amsterdam, The Netherlands, that showed different decay intensities but had comparable sediment profiles. Oxygen (optode principle), redox potential (platinum electrodes), and groundwater table measurements were conducted biweekly over a year. Sediment solution was sampled every three months and analysed for pH, conductivity, total and dissolved carbon and nitrogen, NH4+, NO3-, SO42- PO43-, Cl-, and major cations. Oxygen and redox measurements indicated oxygen-free conditions at both sites examined, but the water surrounding piles exhibited significantly higher total nitrogen concentrations at the site showing light decay. As other simultaneous investigations revealed a positive correlation between the nitrogen content in wooden pile samples and the decay intensities, we conclude that nitrogen might be a key factor in the decay process. We hypothesise that concentration gradients between sediment and wood matrix may control the decay intensity. (C) 2007 Elsevier Ltd. All rights reserved
Studying bacterial wood decay under low oxygen conditions - results of microcosm experiments
No full textIn recent years various studies have indicated that bacterial wood attack can cause considerable strength loss of waterlogged pile foundations in unexpectedly short periods of time. In this study we set up microcosm experiments with pine sticks placed in waterlogged sediment to establish, monitor, and manipulate the bacterial wood decay process. Microcosms were equipped with oxygen sensors (optodes) and CO2, CH4, and N2O head space measurement devices. Microcosm head space was aerated with air, air + O-2, N-2, air + water circulation and sediments were supplied with NO3- , NH4+, PO43-, SO42-, and glucose. Wood decay was microscopically detected and classified for low decay intensities, and was found to have occurred in all treatments after 150 days. The fastest rate of decay developed in 120 days and was most intense under air + water circulation treatment. Gas emissions and C-budget calculations did not show any reliable correlation with bacterial decay intensity. Sediment nitrate addition prevented bacterial decay in wood samples but sediment pH was also affected by such additions. We conclude, therefore, that wood surrounded by low sediment nitrogen concentrations is more likely to be affected by bacterial attack than is wood in nitrogen-rich sediments. Glucose SO42- and addition also prevented bacterial attack on other lignocellulosic test materials (kapok fibres) after 28 days, indicating that reducing the redox potential might serve as a protection strategy. (C) 2007 Elsevier Ltd. All rights reserved
Kretschmar Georg, Die Offenbarung des Johannes. Die Geschichte ihrer Auslegung im 1. Jahrtausend (Calwer Theologische Monographien, 9), 1985
No full textPrigent Pierre. Kretschmar Georg, Die Offenbarung des Johannes. Die Geschichte ihrer Auslegung im 1. Jahrtausend (Calwer Theologische Monographien, 9), 1985. In: Revue d'histoire et de philosophie religieuses, 66e année n°2, Avril-juin 1986. p. 241
W. D. Hausschild, G. Kretschmar, C. Nicolaisen (éd.), Die lutherischen Kirchen und die Bekenntnissynode von Barmen, 1984
No full textLienhard Marc. W. D. Hausschild, G. Kretschmar, C. Nicolaisen (éd.), Die lutherischen Kirchen und die Bekenntnissynode von Barmen, 1984. In: Revue d'histoire et de philosophie religieuses, 66e année n°3, Juillet-septembre 1986. p. 376
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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