Bacteria have transient influences on marine corrosion of steel

The contribution of bacteria to the corrosion mass loss and to pitting of mild steel was observed over 2.5 years using parallel streams of unpolluted natural (biotic) and nominally sterilized (abiotic) Pacific Ocean coastal seawater. As also observed by others, in artificial laboratory exposures, corrosion mass loss within the first few days of exposure was much greater in the biotic stream. However, after only about 10 days the difference in mass losses were gradually reduced and were very similar up to about one year of exposure. Thereafter, the corrosion loss in the biotic stream again became more severe. Pitting corrosion in the biotic stream was more severe from the very first exposure throughout the 2.5 years. Corrosion in both seawater streams exhibited three distinct but transient time-dependent phases. Of these only the first and third obviously involve bacteria. Similar longer-term observations in real seawaters have not been described previously but are generally consistent with some long-term field data. The results show that longer-term corrosion behavior and possible microbial influences cannot be predicted from short-term laboratory observations, even if natural seawater is used

Von der Stammzelle zum Lymphozyten

Zusammenfassung: Zwei Typen von pluripotenten Stammzellen sind die Ursprünge der Zellen des angeborenen und des adaptiven Immunsystems wie auch von essenziellen Elementen kooperierender Umgebungen dieses Systems. Pluripotente hämatopoietische Stammzellen und die ihnen untergeordneten, subspezialisierten Progenitorzellen bilden - ein Leben lang - die roten Blutkörperchen, Blutplättchen, myeloiden und lymphoiden Zellen dieses kontinuierlich sich erneuernden Zellsystems. Pluripotente mesenchymale Stammzellen generieren, neben anderen Typen von differenzierten Zellen, Chondrozyten, epitheliale Zellen, Adipozyten und Osteoblasten. Dieses Osteoblasten produzieren nicht nur Knochen, die primären Orte für die hämatopoietische Zellentwicklung, sondern sie interagieren auch direkt mit den hämatopoietischen Stammzellen und Progenitorzellen - wie auch mit dem reifen, antigenerfahrenen "Gedächtnis"-Typ von Lymphozyten, die nach erfolgreichen Kämpfen mit Antigenen an die Stelle ihres Ursprungs zurückkehren. Diese Interaktionen geschehen durch Zell-Zell-Kontakte wie auch durch Zytokin-Zytokinrezeptor-Erkennungen in sogenannten "Nischen" und induzieren und leiten die Entwicklungen der hämatopoietischen Zellen. Diese frühen Phasen der hämatopoietischen Entwicklung sind antigenunabhängig, weil die Zellen des adaptiven Immunsystems, die Lymphozyten, noch keine antigenspezifischen Rezeptoren entwickelt haben. Sobald diese Zellen aber T-Zell- und B-Zell-Rezeptoren für Antigen exprimieren, werden sie dem Druck von negativer und positiver Selektion ausgesetzt, erst von Autoantigenen in den primären lymphoiden Organen, dann, nach Reifung und Wanderung in die sekundären lymphoiden Organe, auch von externen, fremden Antigenen. Die Repertoire dieser Lymphozyten, die TcR und BcR exprimieren, adaptieren also an die Umgebung von Antigenen des eigenen Körpers, und an die der externen, fremden Einflüsse. Während Zell-Zell-Kontakte mit kooperierenden nichthämatopoietischen wie auch hämatopoietischen Zellen, und Zytokin-Zytokinrezeptor-Interaktionen weiterhin die zellulären Reaktionen induzieren, die zu Proliferation, Differenzierung und/oder programmiertem Zelltod (Apoptose) der reifen hämatopoietischen Zellen führen können, sind diese Reaktionen jetzt aber durch die spezifischen Kontakte von Antigen mit den antigenspezifischen Rezeptoren, TcR's und BcR's, dominier

Predominant utilization of V beta 8+ T cell receptor genes in the H-2Ld- restricted cytotoxic T cell response against the immediate-early protein pp89 of the murine cytomegalovirus

Cytotoxic T cell responses to the murine Cytomegalovirus (MCMV) were elicited in BALB/c mice (H-2d) by infectious virus. Eight days after infection, MCMV-primed local lymph node T cells were either depleted for T cells expressing a V beta 8+ TCR or separated into V beta 8+ and V beta 8- subpopulations by a cell sorter using the mAb F23.1. T cells were then expanded in vitro under limiting dilution conditions in the presence of IL-2 and in the absence of viral Ag to avoid selection by Ag in vitro. Frequencies of CTL precursors specific for the Immediate- Early-Ag 1 of MCMV and restricted to H-2Ld were determined. L cells of the endogenous haplotype H-2k cotransfected with the genes for MCMV-IE 1 and H-2Ld were used as target cells. Detection of a CTL response required previous priming of the animals by infection in vivo (less than 1/10(6) for nonimmunized animals). In primed animals CTL precursors of this specificity and restriction were three to fivefold more frequent in the V beta 8+ population (1/9.900 to 1/22.300) than in the V beta 8- population (1/57.000 to 1/87.200). Control experiments showed that frequencies were not influenced by the treatment with the anti-V beta 8-antibody and the fluorescein-labeled anti-Ig itself. V beta 8+ and V beta 8- T cells did not reveal any frequency differences when several other responses were determined (TNP-specific self- restricted CTL precursor; Th cells specific for keyhole limpet hemocyanin or Listeria monocytogenes)

Field experience and the long-term durability of reinforced concrete structures

For reinforced concrete structures the conventional wisdom is that after some years of exposure to marine conditions reinforcement corrosion is inevitable. Much attention is paid in the literature to the rate of ingress of chlorides through the concrete cover to the reinforcing bars and to ensuring highly impermeable cover and/or deeper cover, to try top prevent chloride-induced or carbonation-induced corrosion initiation. Actual field experience shows that there are many reinforced concrete structures that have survived remarkably well for many decades despite having very high chloride concentrations next to the reinforcing bars. Even with very modest concrete cover by modern standards, exhumation often finds bars free from corrosion. Detailed investigations of a number of such cases showed no corrosion if the concrete pH levels are above about 9. On the other hand, very severe reinforcement corrosion was observed in the few cases where the concrete had cracked right through the cover to the bars. Often there was no external evidence or signs of interior corrosion, including longitudinal cracking. The implications of these findings for practice are discussed

Analytical assessment of mine water rebound. Case study Ruhr coal basin

This study aims to assess key factors that influence mine water rebound on the example of a large amount of hard coal mines flooded or being flooded in Europe. Three German mines have been selected for a detailed study. A mathematical model based on analytical formulae of seepage theory has been employed to calculate time-dependent radial inflow to the shaft simulated as a big well in vertically heterogeneous rocks. The results of modelling showed good conformity with measurements for all studied mines. Besides, we evaluated the sensitivity of the model output to parameter variations for mine water level and initial inflow to the mine

First Passage Time of Filtered Poisson Process with Exponential Shape Function

Solving some integro-differential equation we find the Laplace transformation of the first passage time for Filtered Poisson Process generated by pulses with uniform or exponential distributions. Also, the martingale technique is applied for approximations of expectations accuracy is veryfying with the help of Monte-Carlo simulations.first passage times; laplace transformation; martingales; integro-differential equations; filtered poisson process; ornstein-uhlenbeck process