371 research outputs found

    On the Corrosion Resistance of Porous Electroplated Zinc Coatings in Different Corrosive Media

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    The corrosion resistance of an electroplated (EP) Zn coating whose surface was chemically etched to produce surface defects (pores) is investigated in this work. Impedance and DC polarisation measururements were employed to study the behaviour of such coating in various corrosive media (NaCl, NaOH and rain water). Four different faradaic relaxation processes were clearly revealed in different NaCl concentrations (from 0.1M to 1M). In the most concentrated solutions at least three relaxation processes at low frequencies (LF) appeared and were related to zinc deposition and dissolution. At lower concentrations and depending on the pH, only one process was observed. The charge transfer resistance (Rct) and the corrosion current (Icorr) were practically stable in the pH range 5 to 10. In deaerated NaCl 0.1M, the EIS diagrams showed two time-constants at very close frequencies. From the EIS diagrams the porous nature of the coating was highlighted and showed that the dissolution mechanisms occurred at the base of the pores

    Use of an Electrochemical Split Cell Technique to Evaluate the Influence of Shewanella oneidensis Activities on Corrosion of Carbon Steel

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    Microbially induced corrosion (MIC) is a complex problem that affects various industries. Several techniques have been developed to monitor corrosion and elucidate corrosion mechanisms, including microbiological processes that induce metal deterioration. We used zero resistance ammetry (ZRA) in a split chamber configuration to evaluate the effects of the facultatively anaerobic Fe(III) reducing bacterium Shewanella oneidensis MR-1 on the corrosion of UNS G10180 carbon steel. We show that activities of S. oneidensis inhibit corrosion of steel with which that organism has direct contact. However, when a carbon steel coupon in contact with S. oneidensis was electrically connected to a second coupon that was free of biofilm (in separate chambers of the split chamber assembly), ZRA-based measurements indicated that current moved from the S. oneidensis-containing chamber to the cell-free chamber. This electron transfer enhanced the O2 reduction reaction on the coupon deployed in the cell free chamber, and consequently, enhanced oxidation and corrosion of that electrode. Our results illustrate a novel mechanism for MIC in cases where metal surfaces are heterogeneously covered by biofilms

    ALADIN is Required for the Production of Fertile Mouse Oocytes

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    Asymmetric cell divisions depend on the precise placement of the spindle apparatus. In mammalian oocytes, spindles assemble close to the cell's center, but chromosome segregation takes place at the cell periphery where half of the chromosomes are expelled into small, nondeveloping polar bodies at anaphase. By dividing so asymmetrically, most of the cytoplasmic content within the oocyte is preserved, which is critical for successful fertilization and early development. Recently we determined that the nucleoporin ALADIN participates in spindle assembly in somatic cells, and we have also shown that female mice homozygously null for ALADIN are sterile. In this study we show that this protein is involved in specific meiotic stages, including meiotic resumption, spindle assembly, and spindle positioning. In the absence of ALADIN, polar body extrusion is compromised due to problems in spindle orientation and anchoring at the first meiotic anaphase. ALADIN null oocytes that mature far enough to be fertilized in vitro are unable to support embryonic development beyond the two-cell stage. Overall, we find that ALADIN is critical for oocyte maturation and appears to be far more essential for this process than for somatic cell divisions

    Identification of SERPINA1 as single marker for papillary thyroid carcinoma through microarray meta analysis and quantification of its discriminatory power in independent validation

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    <p>Abstract</p> <p>Background</p> <p>Several DNA microarray based expression signatures for the different clinically relevant thyroid tumor entities have been described over the past few years. However, reproducibility of these signatures is generally low, mainly due to study biases, small sample sizes and the highly multivariate nature of microarrays. While there are new technologies available for a more accurate high throughput expression analysis, we show that there is still a lot of information to be gained from data deposited in public microarray databases. In this study we were aiming (1) to identify potential markers for papillary thyroid carcinomas through meta analysis of public microarray data and (2) to confirm these markers in an independent dataset using an independent technology.</p> <p>Methods</p> <p>We adopted a meta analysis approach for four publicly available microarray datasets on papillary thyroid carcinoma (PTC) nodules versus nodular goitre (NG) from N2-frozen tissue. The methodology included merging of datasets, bias removal using distance weighted discrimination (DWD), feature selection/inference statistics, classification/crossvalidation and gene set enrichment analysis (GSEA). External Validation was performed on an independent dataset using an independent technology, quantitative RT-PCR (RT-qPCR) in our laboratory.</p> <p>Results</p> <p>From meta analysis we identified one gene (SERPINA1) which identifies papillary thyroid carcinoma against benign nodules with 99% accuracy (n = 99, sensitivity = 0.98, specificity = 1, PPV = 1, NPV = 0.98). In the independent validation data, which included not only PTC and NG, but all major histological thyroid entities plus a few variants, SERPINA1 was again markedly up regulated (36-fold, p = 1:3*10<sup>-10</sup>) in PTC and identification of papillary carcinoma was possible with 93% accuracy (n = 82, sensitivity = 1, specificity = 0.90, PPV = 0.76, NPV = 1). We also show that the extracellular matrix pathway is strongly activated in the meta analysis data, suggesting an important role of tumor-stroma interaction in the carcinogenesis of papillary thyroid carcinoma.</p> <p>Conclusions</p> <p>We show that valuable new information can be gained from meta analysis of existing microarray data deposited in public repositories. While single microarray studies rarely exhibit a sample number which allows robust feature selection, this can be achieved by combining published data using DWD. This approach is not only efficient, but also very cost-effective. Independent validation shows the validity of the results from this meta analysis and confirms SERPINA1 as a potent mRNA marker for PTC in a total (meta analysis plus validation) of 181 samples.</p

    Indigenous peoples, the city and inclusive urban development policies in Latin America: Lessons from Bolivia and Ecuador

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    The historical construction of indigeneity as essentially rural policy category represents a key cause for the ongoing exclusion of urban indigenous peoples and blocks progress in delivering Agenda 2030 in Latin American cities. Even in Bolivia and Ecuador where urban indigeneity is recognised through constitutional reforms there are obstacles to the delivery of policies shaped to urban indigenous interests. By reviewing experiences from these countries, this article highlights that policy delivery problems are a result of multiple factors, including (1) rural constructions of indigeneity, (2) conflicting development priorities, and (3) difficulties in promoting universal rights while simultaneously guaranteeing indigenous rights. The article concludes with policy recommendations for more inclusive urban development approaches which leave no indigenous person behind

    Rice Phospholipase A Superfamily: Organization, Phylogenetic and Expression Analysis during Abiotic Stresses and Development

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    Background: Phospholipase A (PLA) is an important group of enzymes responsible for phospholipid hydrolysis in lipid signaling. PLAs have been implicated in abiotic stress signaling and developmental events in various plants species. Genome-wide analysis of PLA superfamily has been carried out in dicot plant Arabidopsis. A comprehensive genome-wide analysis of PLAs has not been presented yet in crop plant rice. Methodology/Principal Findings: A comprehensive bioinformatics analysis identified a total of 31 PLA encoding genes in the rice genome, which are divided into three classes; phospholipase A 1 (PLA 1), patatin like phospholipases (pPLA) and low molecular weight secretory phospholipase A2 (sPLA2) based on their sequences and phylogeny. A subset of 10 rice PLAs exhibited chromosomal duplication, emphasizing the role of duplication in the expansion of this gene family in rice. Microarray expression profiling revealed a number of PLA members expressing differentially and significantly under abiotic stresses and reproductive development. Comparative expression analysis with Arabidopsis PLAs revealed a high degree of functional conservation between the orthologs in two plant species, which also indicated the vital role of PLAs in stress signaling and plant development across different plant species. Moreover, sub-cellular localization of a few candidates suggests their differential localization and functional role in the lipid signaling. Conclusion/Significance: The comprehensive analysis and expression profiling would provide a critical platform for th

    TRIP13 and APC15 drive mitotic exit by turnover of interphase- and unattached kinetochore-produced MCC

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    The mitotic checkpoint ensures accurate chromosome segregation through assembly of the mitotic checkpoint complex (MCC), a soluble inhibitor of the anaphase-promoting complex/cyclosome (APC/C) produced by unattached kinetochores. MCC is also assembled during interphase by Mad1/Mad2 bound at nuclear pores, thereby preventing premature mitotic exit prior to kinetochore maturation and checkpoint activation. Using degron tagging to rapidly deplete the AAA+ ATPase TRIP13, we show that its catalytic activity is required to maintain a pool of open-state Mad2 for MCC assembly, thereby supporting mitotic checkpoint activation, but is also required for timely mitotic exit through catalytic disassembly of MCC. Strikingly, combining TRIP13 depletion with elimination of APC15-dependent Cdc20 ubiquitination/degradation results in a complete inability to exit mitosis, even when MCC assembly at unattached kinetochores is prevented. Thus, mitotic exit requires MCC produced either in interphase or mitosis to be disassembled by TRIP13-catalyzed removal of Mad2 or APC15-driven ubiquitination/degradation of its Cdc20 subunit
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