bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tensile and compressive damage coupling for fully‐reversed bending fatigue of fibre‐reinforced composites
Authors: Van Paepegem W. , Degrieck J. 
Published: March 2003

ABSTRACT Due to their high specific stiffness and strength, fibre‐reinforced composite materials are winning through in a wide range of applications in automotive, naval and aerospace industry. Their design for fatigue is a complicated problem and a large research effort is being spent on it today. However there is still a need for extensive experimental testing or large safety factors to be adopted, because numerical simulations of the fatigue damage behaviour of fibre‐reinforced composites are often found to be unreliable. This is due to the limited applicability of the theoretical models developed so far, compared to the complex multi‐axial fatigue loadings that composite components often have to sustain in in‐service loading conditions.In this paper a new phenomenological fatigue model is presented. It is basically a residual stiffness model, but through an appropriate choice of the stress measure, the residual strength and thus final failure can be predicted as well. Two coupled growth rate equations for tensile and compressive damage describe the damage growth under tension–compression loading conditions and provide a much more general approach than the use of the stress ratio R. The model has been applied to fully‐reversed bending of plain woven glass/epoxy specimens. Stress redistributions and the three stages of stiffness degradation (sharp initial decline – gradual deterioration – final failure) could be simulated satisfactorily.
Fatigue notch sensitivity of steel blunt‐notched specimens
Authors: CHAPETTI M. D. , TAGAWA T. , MIYATA T. 
Published: March 2003

ABSTRACTThe notch sensitivity of three steels with similar plain fatigue limits was analysed and modelled. The analysis was made by using a model previously derived which estimated the fatigue limit of blunt notched components by means of the parameter ktd defined as the stress concentration introduced by the notch at a distance d from the notch root surface equal to the distance between microstructural barriers. The analyses show how the first two or three microstructural barriers define the fatigue limit and the fatigue notch sensitivity of blunt notched specimens.
Prediction of fatigue crack growth path in mechanical joints using a weight function approach
Authors: HEO S. P. , YANG W. H. 
Published: March 2003

ABSTRACTCracks often initiate from the mechanical joints which are widely used in structural components. It has been reported that cracks in mechanical joints are under mixed‐mode condition and there is a critical angle at which mode I stress intensity factor becomes maximum. The crack propagates in an arbitrary direction and the prediction of fatigue crack growth path is needed to provide against crack propagation and examine safety. In this study, mixed‐mode fatigue crack growth tests are performed for horizontal and critical inclined cracks in mechanical joints. Fatigue crack growth paths are predicted using a weight function approach and maximum tangential stress criterion.
Fracture assessment of a clad steel using various SINTAP defect assessment procedure levels
Authors: MOTARJEMI A. K. , KOÇAK M. 
Published: March 2003

ABSTRACTIn many critical industries such as nuclear, chemical and petrochemical industries, bi‐material components in the form of clad plates are used due to their superior environmental and mechanical properties. During the service life of these bi‐material components, cracks or crack‐like defects may develop in the clad layer and penetrate into the substrate. The assessment of the integrity of such a cracked as well as complex structure would be an important task. Hence, this study is aimed at applying the recently developed European Structural Integrity Assessment Procedure (SINTAP) to a through thickness centre cracked clad steel wide plate to validate the procedure for this type of bi‐material structure. Based on the available input data, various assessment levels as well as two different assessment routes, namely crack driving force (CDF) and failure assessment diagram (FAD), can be used for predicting the failure loads. In principle both routes should provide similar results and this has been verified by having very similar results for both SINTAP routes. Furthermore, the degree of conservatism has been reduced by using higher analysis levels of SINTAP.
Near threshold fatigue crack growth versus long finite life
Authors: PARIS P. C. , TADA H. 
Published: March 2003

ABSTRACT A brief review of the discovery of the fatigue crack growth threshold is provided with a discussion of the main variables, Kmax and ΔK, which control the threshold over the low and high load ratio ranges, respectively. The significant effect on near threshold growth rates as illustrated by Donald are shown, for an example the aluminium alloy, 2324‐T39. Attention is then turned to the ‘partial closure model’ as a means of correlating near threshold fatigue crack growth rates. This seems to be the most promising model with a physical basis. For this reason, the discussion goes on to present a new theoretical analysis of the load displacement record characteristics, which should accompany ‘partial closure’ of fatigue cracks. In addition it is concluded that secondary stress effects should be explored for near threshold fatigue crack growth rates.
Fatigue crack propagation prediction by cyclic plasticity damage accumulation models
Authors: DURÁN J. A. R. , CASTRO J. T. P. , FILHO J. C. P. 
Published: March 2003

ABSTRACTDifferent analytical models of damage accumulation by cyclic plasticity have been developed to predict fatigue crack growth from monotonic, cyclic, fracture toughness and crack propagation threshold properties. The models' development logic is condensed as a flowchart, which emphasizes, in a clear and easily comprehensive way, all the required modeling steps. 1020 and API 5L X60 steels and 7075‐T6 aluminum alloy were used in the experimental verification of the models. Samples were extracted from materials of the same heat, in order to have a reliable comparison. The experimental results are better predicted by the models that use the plastic part of Coffin–Manson's equation to calculate the fatigue life of small volume elements ahead of the crack tip, and expressions of the HRR type to represent the elastic–plastic strain amplitude in the cyclic plastic zone.
Bacteria divert resources from growth for magellanic penguin chicks
Authors: Potti Jaime , Moreno Juan , Yorio Pablo , Briones Víctor , García‐Borboroglu Pablo , Villar Susana , Ballesteros Cristina 
Published: March 2003

AbstractThe influence of bacteria on the growth of their wild avian hosts is unknown. We tested experimentally whether administration of a wide‐spectrum antibiotic (cephalosporine) during early development of magellanic penguin (Spheniscus magellanicus) chicks had any effect on their growth rates in the wild. Chicks that were injected in two occasions with cephalosporine grew faster than control untreated chicks. The positive effect of medication on nestling growth disappeared after the treatment ceased, did not alter haematological indices indicative of health status, had no influence on chick survival until near independence and was related to a changed bacterial composition of the faecal microbiota of treated chicks when compared with that from control chicks. These results were similar to those obtained for poultry with antimicrobials promoting growth and chick nutrient assimilation rates. Gram‐positive bacilli in the diphtheroid genusCorynebacteriumare likely candidates to cause decreased growth rates in magellanic penguin chicks.
Biodiversity hotspots, centres of endemicity, and the conservation of coral reefs
Authors: Hughes Terry P. , Bellwood David R. , Connolly Sean R. 
Published: March 2003

AbstractOn land, biodiversity hotspots typically arise from concentrations of small‐range endemics. For Indo‐Pacific corals and reef fishes, however, centres of high species richness and centres of high endemicity are not concordant. Moreover ranges are not, on average, smaller inside the Central Indo‐Pacific (CI‐P) biodiversity hotspot. The disparity between richness and endemicity arises because corals and reef fishes have strongly skewed range distributions, with many species being very widespread. Consequently, the largest ranges overlap to generate peaks in species richness near the equator and the CI‐P biodiversity hotspot, with only minor contributions from endemics. Furthermore, we find no relationship between the number of coral vs. fish endemics at locations throughout the Indo‐Pacific, even though total richness of the two groups is strongly correlated. The spatial separation of centres of endemicity and biodiversity hotspots in these taxa calls for a two‐pronged management strategy to address conservation needs.
Complete mineralization of dodecyldimethylamine using a two‐membered bacterial culture
Authors: Kroon A. G. M. , Van Ginkel C. G. 
Published: March 2003

Complete degradation of dodecyldimethylamine was achieved using a two‐membered bacterial culture isolated from activated sludge. One member, identified as Burkholderia cepacia, was capable of degrading the alkyl chain of the molecule. The other member, identified as Stenotrophomonas maltophilia, was able to degrade dimethylamine, the product of the former. Batch culture experiments revealed that the two‐membered culture consisting of B. cepacia and S. maltophilia was based on a commensalistic relationship under carbon‐limited conditions. Under nitrogen‐limited conditions, the relationship of this culture was transformed from a commensalistic to a mutualistic one. A two‐membered culture was therefore imperative for growth on dodecyldimethylamine under nitrogen‐limited conditions, whereas a pure culture of B. cepacia was capable of growth on dodecyldimethylamine under carbon‐limited conditions.
The structure of a local population of phytopathogenic Pseudomonas brassicacearum from agricultural soil indicates development under purifying selection pressure
Authors: Sikorski Johannes , Jahr Holger , Wackernagel Wilfried 
Published: March 2003

Among the isolates of a bacterial community from a soil sample taken from an agricultural plot in northern Germany, a population consisting of 119 strains was obtained that was identified by 16S rDNA sequencing and genomic fingerprinting as belonging to the recently described species Pseudomonas brassicacearum. Analysis of the population structure by allozyme electrophoresis (11 loci) and random amplified polymorphic DNA–polymerase chain reaction (RAPD–PCR; four primers) showed higher resolution with the latter method. Both methods indicated the presence of three lineages, one of which dominated strongly. Stochastic tests derived from the neutral theory of evolution (including Slatkin's exact test, Watterson's homozygosity test and the Tajima test) indicated that the population had developed under strong purifying selection pressure. The presence of strains clearly divergent from the majority of the population can be explained by in situ evolution or by influx of strains as a result of migration or both. Phytopathogenicity of a P. brassicacearum strain determined with tomato plants reached the level obtained with the type strain of the known pathogen Pseudomonas corrugata. The results show that a selective sweep was identified in a local population. Previously, a local selective sweep had not been seen in several populations of different bacterial species from a variety of environmental habitats.
Predominant growth of Alcanivorax strains in oil‐contaminated and nutrient‐supplemented sea water
Authors: Kasai Yuki , Kishira Hideo , Sasaki Tetsuya , Syutsubo Kazuaki , Watanabe Kazuya , Harayama Shigeaki 
Published: March 2003

SummaryWe found that bacteria closely related to Alcanivorax became a dominant
bacterial population in petroleum‐contaminated sea water when nitrogen and phosphorus
nutrients were supplied in adequate quantity. The predominance of Alcanivorax
bacteria was demonstrated under three experimental conditions: (i) in batch cultures
of sea water containing heavy oil; (ii) in columns packed with oil‐coated gravel
undergoing a continuous sea water flow; and (iii) in a large‐scale tidal flux reactor
that mimics a beach undergoing tidal cycles with fresh sea water. These results suggest
that bacteria related to Alcanivorax are major players in the bioremediation of oil‐contaminated marine environments.
Pseudomonas aeruginosa O‐antigen chain length is determined before ligation to lipid A core
Authors: Daniels Craig , Griffiths Corrie , Cowles Bryony , Lam Joseph S. 
Published: March 2003

Summary Pseudomonas aeruginosa is a Gram‐negative opportunistic pathogen that infects immunocompromised patients and trauma victims and causes fatal lung infections in people with cystic fibrosis. This microorganism produces a number of virulence factors, one of which is lipopolysaccharide (LPS), which has been shown to mediate many biological effects including resistance to serum killing and phagocytosis. These biological activities have been correlated to the length of the O‐polysaccharide and its distribution on the outer membrane. Wzz is responsible for regulation of the size distribution of the O‐antigen. Wzz has been found to participate solely in the Wzy‐dependent pathway for LPS biosynthesis, which produces heteropolymeric O‐polysaccharide such as the B‐band LPS of P. aeruginosa. Our laboratory has previously reported characterization of a Wzz protein encoded in the B‐band O‐antigen biosynthesis cluster of PAO1. The availability of the genome sequence of P. aeruginosa PAO1 has made it possible to identify a second functional Wzz protein (PA0938, Wzz2). Gene replacement was used to generate an unmarked wzz2Δ knock‐out and a wzz2Δ/wzz1::Gm double knock‐out. As expected, the wzz2Δ strain produced LPS with modal length imparted by Wzz1, and the wzz2Δ/wzz1::Gm strain produced LPS O‐antigen with a non‐modal (random) length. Both wzz1 and wzz2 from P. aeruginosa PAO1 were cloned and expressed with an N‐terminal His6 tag. His6‐Wzz1 and His6‐Wzz2 were purified to near homogeneity by immobilized metal affinity chromatography (IMAC). These preparations were used to develop specific polyclonal antibodies against each of the proteins. In vivo protein cross‐linking followed by Western immunoblotting indicated that Wzz1 forms dimers whereas Wzz2 forms octamers. By generation of a wzz2Δ/rmlC double mutant and analysis of the LPS, we have made the novel observation that polymerization of modal chain length‐distributed O‐antigen occurred before ligation to the lipid A core. We have shown an association between the Wzz proteins and O‐antigen polymer chains using immunoprecipitation with anti‐O5 O‐antigen monoclonal antibody MF15‐4. Both Wzz1 and Wzz2 could be co‐precipitated with O5 polymer.
Discrimination and taxonomy of geographically diverse strains of nitrile‐metabolizing actinomycetes using chemometric and molecular sequencing techniques
Authors: Brandão Pedro F. B. , Clapp Justin P. , Bull Alan T. 
Published: March 2003

SummaryMycolic acid‐containing actinomycetes capable of metabolizing nitriles were recovered from deepsea sediments and terrestrial soils by enrichment culture on acetonitrile, benzonitrile, succinonitrile or bromoxynil. A total of 43 nitrile‐degrading strains were isolated and, together with previously reco‐vered nitrile‐degrading rhodococci, were identified by a polyphasic taxonomic approach, which included mycolic acid profiles, pyrolysis mass spectrometry (PyMS), genomic fingerprinting based on sequence variability of the 16S ribosomal RNA gene using polymerase chain reaction‐restriction fragment length polymorphism‐single‐strand conformational polymorphism, and 16S rRNA gene sequence comparison. Isolates phylogenetically related to Rhodococcus erythropolis
dominated the culturable microorganisms from most marine and terrestrial samples.
These isolates clustered together in a major pyrogroup that showed high congruence
with PRS profiles of the 16S rRNA gene. Such high congruence also was obtained for
other recovered isolates that were assigned to species of Rhodococcus and
Gordonia. Sequencing data validated the results obtained by PRS analysis and enabled phylogenetic relationships to be established. Some of the recovered bacteria probably represent novel microbial species. The fact that nitrile‐metabolizing microorganisms were recovered from a wide range of habitat types suggests that nitrile transforming enzymatic activity is geographically widely distributed in nature.
In vitro demonstration of anaerobic oxidation of methane coupled to sulphate reduction in sediment from a marine gas hydrate area
Authors: Nauhaus Katja , Boetius Antje , Krüger Martin , Widdel Friedrich 
Published: March 2003

SummaryAnaerobic oxidation of methane (AOM) and sulphate reduction were examined in sediment samples from a marine gas hydrate area (Hydrate Ridge, NE Pacific). The sediment contained high numbers of microbial consortia consisting of organisms that affiliate with methanogenic archaea and with sulphate‐reducing bacteria. Sediment samples incubated under strictly anoxic conditions in defined mineral medium (salinity as in seawater) produced sulphide from sulphate if methane was added as the sole organic substrate. No sulphide production occurred in control experiments without methane. Methane‐dependent sulphide production was fastest between 4°C and 16°C, the average rate with 0.1 MPa (approximately 1 atm) methane being 2.5 μmol sulphide day−1 and (g dry mass sediment)−1. An increase of the methane pressure to 1.1 MPa (approximately 11 atm) resulted in a four to fivefold increase of the sulphide production rate. Quantitative measurements using a special anoxic incubation device without gas phase revealed continuous consumption of dissolved methane (from initially 3.2 to 0.7 mM) with simultaneous production of sulphide at a molar ratio of nearly 1:1. To test the response of the indigenous community to possible intermediates of AOM, molecular hydrogen, formate, acetate or methanol were added in the absence of methane; however, sulphide production from sulphate with any of these compounds was much slower than with methane. In the presence of methane, such additions neither stimulated nor inhibited sulphate reduction. Hence, the experiments did not provide evidence for one of these compounds acting as a free extracellular intermediate (intercellular shuttle) during AOM by the presently investigated consortia.
Microbial diseases of corals and global warming
Authors: Rosenberg Eugene , Ben‐Haim Yael 
Published: March 2003

SummaryCoral bleaching and other diseases of corals have increased dramatically during the last few decades. As outbreaks of these diseases are highly correlated with increased sea‐water temperature, one of the consequences of global warming will probably be mass destruction of coral reefs. The causative agent(s) of a few of these diseases have been reported: bleaching of Oculina patagonica by Vibrio shiloi; black band disease by a microbial consortium; sea‐fan disease (aspergillosis) by Aspergillus sydowii; and coral white plague possibly by Sphingomonas sp. In addition, we have recently discovered that Vibrio coralyticus is the aetiological agent for bleaching the coral Pocillopora damicornis in the Red Sea. In the case of coral bleaching by V. shiloi, the major effect of increasing temperature is the expression of virulence genes by the pathogen. At high summer sea‐water temperatures, V. shiloi produces an adhesin that allows it to adhere to a β‐galactoside‐containing receptor in the coral mucus, penetrate into the coral epidermis, multiply intracellularly, differentiate into a viable‐but‐not‐culturable (VBNC) state and produce toxins that inhibit photosynthesis and lyse the symbiotic zooxanthellae. In black band disease, sulphide is produced at the coral–microbial biofilm interface, which is probably responsible for tissue death. Reports of newly emerging coral diseases and the lack of epidemiological and biochemical information on the known diseases indicate that this will become a fertile area of research in the interface between microbial ecology and infectious disease.
Genomic analysis of the aromatic catabolic pathways from Pseudomonas putida KT2440
Authors: Jiménez José Ignacio , Miñambres Baltasar , García José Luis , Díaz Eduardo 
Published: March 2003

SummaryAnalysis of the catabolic potential of Pseudomonas putida KT2440 against a wide range of natural aromatic compounds and sequence comparisons with the entire genome of this microorganism predicted the existence of at least four main pathways for the catabolism of central aromatic intermediates, that is, the protocatechuate (pca genes) and catechol (cat genes) branches of the β‐ketoadipate pathway, the homogentisate pathway (hmg/fah/mai genes) and the phenylacetate pathway (pha genes). Two additional gene clusters that might be involved in the catabolism of N‐heterocyclic aromatic compounds (nic cluster) and in a central meta‐cleavage pathway (pcm genes) were also identified. Furthermore, the genes encoding the peripheral pathways for the catabolism of p‐hydroxybenzoate (pob), benzoate (ben), quinate (qui), phenylpropenoid compounds (fcs, ech, vdh, cal, van, acd and acs), phenylalanine and tyrosine (phh, hpd) and n‐phenylalkanoic acids (fad) were mapped in the chromosome of P. putida KT2440. Although a repetitive extragenic palindromic (REP) element is usually associated with the gene clusters, a supraoperonic clustering of catabolic genes that channel different aromatic compounds into a common central pathway (catabolic island) was not observed in P. putida KT2440. The global view on the mineralization of aromatic compounds by P. putida KT2440 will facilitate the rational manipulation of this strain for improving biodegradation/biotransformation processes, and reveals this bacterium as a useful model system for studying biochemical, genetic, evolutionary and ecological aspects of the catabolism of aromatic compounds.
Testing the limits of biological tolerance to arsenic in a fungus isolated from the River Tinto
Authors: Cánovas David , Durán Consuelo , Rodríguez Nuria , Amils Ricardo , De Lorenzo Víctor 
Published: March 2003

SummaryThe Tinto river in Spain, with its high acidity and heavy metal concentrations (As, Cu, Cr, Zn), is an example of an environment hostile to life. Yet despite these extreme conditions, the site possesses a great diversity of eukaryotic life forms. We report the isolation of a filamentous fungus able to grow at 200 mM arsenic (∼15 000 p.p.m.), i.e. a concentration 20‐fold above that withstood by the reference microorganismsEscherichia coli,Saccharomyces cerevisiaeandAspergillus nidulans, and 200 times greater than that tolerated byAspergillus niger. Based on morphological, physiological and genotypic criteria, the strain belongs to the genusAspergillus. High concentrations of the metalloid induced vacuolation, suggesting that this organelle is someway connected to arsenic tolerance. Concentrations that are lethal to other organisms do not stressAspergillussp. P37. The fungus was capable of removing arsenic from culture media. In addition to arsenic hyper‐resistance, it also displayed a polyresistant phenotype to copper and chromium.