bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vitamin B12 malabsorption following bladder reconstruction or diversion with bowel segments
Authors: Ganesan Thirumalai , Khadra Mohamed H. , Wallis Jonathan , Neal David E. 
Published: March 2003

Background:  Vitamin B12 is absorbed exclusively in the terminal ileum the resection of which may produce malabsorption of B12. The present study aimed to determine whether the length or specific segment of the intestine used in bladder reconstruction affects the overall incidence of B12 malabsorption. It was also aimed at the reasonable way of following these patients.Methods:  Seventy patients who underwent urinary reconstruction between 1988 and 1997 were studied: 28 had undergone orthotopic reconstruction, 14 had ileal conduit diversion, 8 had continent diversion and 20 had undergone enterocystoplasty. The median follow up was 65 months (10−137 months). Indications for operation included carcinoma of the bladder, neurogenic bladder dysfunction, idiopathic detrusor instability and interstitial cystitis. Schilling tests were performed, and serum B12 level and haematological indices were measured.Results:  Patients were classified depending on whether the ileocaecal junction was used. Group 1 included ileal conduit and entero­cystoplasty where 15−20 cm of ileum, 15−20 cm from ileocaecal junction was used. Group 2 consisted of orthotopic reconstruction and continent diversions where the ileocaecal segment was used. Group 3 comprised patients in whom long ileal segments (50−60 cm) had been used for reconstruction. Five patients in group 1 and one in group 2 had low B12 levels, but none had developed neuropathy or megaloblastic anaemia. One patient in group 1, and six patients in group 2 had low Schilling tests indicating intestinal malabsorption of B12. No patient in group 3 had a low B12 or an abnormal Schilling test.Conclusion:  This study showed that use of ileocaecal segments results in intestinal malabsorption of B12. The length of ileum alone does not seem to be the determinant factor in causing B12 deficiency or B12 malabsorption.
Factors affecting surgical outcome in the elderly at Auckland Hospital
Authors: El‐Haddawi Falah , Abu‐Zidan Fikri M. , Jones Wayne 
Published: March 2003

Background:  The aim of the present study was to define the factors which affect the outcome of major abdominal surgery in elderly patients.Method:  Data were collected prospectively using the surgical audit on all patients who were 65‐years‐old or older and had undergone major abdominal surgery at Auckland Hospital between January 1997 and November 2000. Risk factors studied were age, sex, American Society of Anesthesiologists grade, operative duration, timing of surgery (elective, urgent or emergency), surgeon (consultant or registrar) and the presence of the scrubbed consultant in theatre. Surgical outcome (no complications, complications or death) was defined according to the complication stratification and severity score developed by the University of Otago. Direct logistic regression was used to determine the significance of the risk factors.Results:  1141 patients (614 women and 527 men) who underwent 1248 procedures were studied. The factors that affected the mortality were the ASA grade (P = 0.0001) and operative timing (P = 0.0008). The factors that affected the severity of postoperative complications were ASA (P = 0.0001), operative timing (P = 0.0001) and duration (P = 0.0001).Conclusions:  The ASA, timing and duration of surgery were the most significant factors affecting patient outcome. Age had a less important effect. Arranged surgery and short operative duration have a favourable outcome in selected elderly patients. Therefore, the elderly should not be denied indicated major abdominal surgery on basis of age alone.
New methodology for assessment of intimal hyperplasia of vascular prostheses
Authors: Hawthorne Wayne J. , Ao Peng Y. , Vicaretti Mauro , Fletcher John P. 
Published: March 2003

Background:  When investigating the degree of formation of intimal hyperplasia (IH) quantification of the extent of the lesion is crucial to its assessment and analysis. The aim of the present study was to establish a new methodology (IH index) for estimating the degree of IH associated with vascular prosthesis implantation.
Methods:  Ten female Merino sheep underwent a standard gelatin sealed Dacron (GSD) patch grafting procedure in the left common carotid artery. The grafts were harvested 4 weeks following implantation and processed for assessment of IH by two methodologies − mean intimal thickness (MIT) and IH index. The advantages and disadvantages of the two methods for expressing the degree of IH were compared.
Results:  The IH index is less labour intensive but is as accurate as the MIT method in quantifying the IH lesion, statistical analysis showing high correlation and measurement agreement between the two methods.
Conclusion:  The IH index is a labour saving standardized methodology for quantification of IH in the current animal model.
Fractured zygomas
Authors: Tadj Armin , Kimble Frank W. 
Published: March 2003

Background:  The purpose of this paper is to provide a review, based on collected data, on the topic of ‘fractured zygoma’. The review is presented under the headings of epidemiology, fracture patterns, treatment modalities and complications. Throughout the paper comparison is made with published data from around the world.Methods:  A 10‐year retrospective audit was undertaken of all hospitalized patients, at the Royal Hobart Hospital, Tasmania, who had sustained a fractured zygoma. All Le Fort fractures involving the zygoma were excluded.Results:  A total of 263 fractures was sustained, largely due to assault. Alcohol was a significant contributing factor. Tetrapod fractures were the most frequent type of fractures witnessed. Plating was the most frequently employed fixation. Inferior orbital nerve dysfunction and other complications were seen in 24.6% and 20.7% of follow‐up cases, respectively. Open reductions were nearly 4 times more likely to be accompanied by complications if inferior orbital nerve dysfunction was excluded.Conclusions:  Both closed and open reductions are good treatment modalities and were used in near equal numbers of patients. There is a higher incidence of postoperative facial deformity in the closed reduction group, but more complications related to the incisions in the open reduction group. Open reduction and internal fixation is advocated for the unstable, markedly displaced or comminuted fractures. Silastic sheeting is a favoured graft for repair of the associated orbital floor defects and is associated with few complications.
FRACTURE MECHANICS AND FATIGUE: A HISTORICAL PERSPECTIVE
Authors: Paris  
Published: March 2003

It was just 40 years ago that some of us became aware that the methods of Irwin’s ‘Fracture Mechanics’ could be applied to fatigue crack growth. After the first 10 years of establishing that approach, many things were known which impact this Symposium’s theme of prediction of structural life.In the subsequent 30 years to the present, the Fracture Mechanics approach applied to life prediction has often been misused, or has ignored obvious characteristics which effect the precision and relevance of the predictions. This paper will emphasize some of these areas for improvements, which have been too often overlooked in practical applications. Some of the overlooked areas are:(1) the misuse of crack propagation laws in life prediction;(2) the modelling of crack shape effects in life calculations;(3) the neglect of significant statistical effects and considerations for particular applications.In conclusion, it is argued that life prediction methodology should be tailored to the application, rather than vice versa, which has all too often been the case. Keywords—Crack growth; Fatigue; Fracture mechanics; Life prediction; Load interaction; Statistical effects.
Evolution of surface deformation during fatigue of PH 13‐8 Mo stainless steel using atomic force microscopy
Authors: Cretegny L. , Saxena A. 
Published: March 2003

ABSTRACTThe relationship between microstructure and nucleation of fatigue cracks in PH 13‐8 Mo stainless steel was explored with the use of atomic force microscopy (AFM) that allowed an accurate quantitative characterization of the surface features. Fully reversed strain‐ controlled fatigue tests were performed at 0.4 and 0.6% strain amplitudes, and the evolution of the surface deformation was observed at various fractions of life. At 0.4% strain amplitude, fatigue surface damage occurred first in the shape of streaks about 4 nm deep that formed at the interface between martensite laths and at prior austenite grain boundaries, and eventually coalesced to form crack nuclei. The increase in strain amplitude to 0.6% led to the formation of large extrusions, on average between 2 and 5 μm long with heights between 10 and 200 nm, which were the preferred crack nucleation sites.
Effects of microstructure on mixed‐mode, high‐cycle fatigue crack‐growth thresholds in Ti‐6Al‐4V alloy
Authors: Nalla R. K. , Campbell J. P. , Ritchie R. O. 
Published: March 2003

ABSTRACTEffect of microstructure on mixed‐mode (mode I + II), high‐cycle fatigue thresholds in a Ti‐6Al‐4V alloy is reported over a range of crack sizes from tens of micrometers to in excess of several millimeters. Specifically, two microstructural conditions were examined—a fine‐grained equiaxed bimodal structure (grain size ∼20 µm) and a coarser lamellar structure (colony size ∼500 µm). Studies were conducted over a range of mode‐mixities, from pure mode I (ΔKII/ΔKI = 0) to nearly pure mode II (ΔKII/ΔKI ∼ 7.1), at load ratios (minimum load/maximum load) between 0.1 and 0.8, with thresholds characterized in terms of the strain‐energy release rate (ΔG) incorporating both tensile and shear‐loading components. In the presence of through‐thickness cracks—large (> 4 mm) compared to microstructural dimensions—significant effects of mode‐mixity and load ratio were observed for both microstructures, with the lamellar alloy generally displaying the better resistance. However, these effects were substantially reduced if allowance was made for crack‐tip shielding. Additionally, when thresholds were measured in the presence of cracks comparable to microstructural dimensions, specifically short (∼200 µm) through‐thickness cracks and microstructurally small (< 50 µm) surface cracks, where the influence of crack‐tip shielding would be minimal, such effects were similarly markedly reduced. Moreover, small‐crack ΔGTH thresholds were some 50–90 times smaller than corresponding large crack values. Such effects are discussed in terms of the dominant role of mode I behaviour and the effects of microstructure (in relation to crack size) in promoting crack‐tip shielding that arises from significant changes in the crack path in the two structures.
Parameter C lifetime calculation for the high cycle regime
Authors: PÖTING S. , ZENNER H. 
Published: March 2003

ABSTRACTAn analytical fatigue lifetime prediction using the nominal stress concept and the Palmgren‐Miner‐Rule is performed. A comparison of prediction and experiment shows a large uncertainty. Miner‐Rule modifications have been developed to improve the fatigue lifetime prediction. Stress amplitudes below the fatigue limit are assumed to contribute to the damage at different ratings.The modifications have a significant influence on the predicted fatigue lifetime especially in the high cycle regime. When the maximum stress value is just above the fatigue limit, this influence is most significant. Because there are not many test results of variable amplitude loads available for the high cycle regime, a verification is difficult.In the present paper a new modification for the lifetime prediction is applied. The modification was introduced in 1988 by Hück and suggests a variable slope of a reference S–N‐curve for the damage accumulation. A parameter C and the relation between the maximum stress value of the load spectrum distribution and the fatigue limit determine the slope of the reference S–N curve.The aim is to characterize the influence factors of the parameter C using test results for the high cycle regime achieved on a new test facility and from published test data. This would lead to an improvement of the lifetime prediction in the high cycle regime.
A notch stress intensity approach applied to fatigue life predictions of welded joints with different local toe geometry
Authors: LAZZARIN P. , LASSEN T. , LIVIERI P. 
Published: March 2003

ABSTRACTIn the Notch Stress Intensity Factor (N‐SIF) approach the weld toe region is modelled as a sharp V‐shaped corner and local stress distributions in planar problems can be expressed in closed form on the basis of the relevant mode I and mode II N‐SIFs. Initially thought of as parameters suitable for quantifying only the crack initiation life, N‐SIFs were shown able to predict also the total fatigue life, at least when a large part of the life is spent as in the propagation of small cracks in the highly stressed region close to the notch tip. While the assumption of a welded toe radius equal to zero seems to be reasonable in many cases of practical interest, it is well known that some welding procedures are able to assure the presence of a mean value of the weld toe radius substantially different from zero. Under such conditions any N‐SIF‐based prediction is expected to underestimate the fatigue life. In order to investigate the degree of conservatism, a total of 128 fillet welded specimens are re‐analysed in the present work by using an energy‐based N‐SIF approach. The local weld toe geometry, characterised by its angle and radius, has been measured with accuracy for the actual test series. The aim of the work is to determine if the N‐SIF‐based model is capable of taking into account the large variability of the toe angle, and to quantify the inaccuracy in the predictions due to the simplification of setting the toe radius equal to zero.
The relationship between sensitisation and small punch test behaviour in a high‐nitrogen austenitic stainless steel at cryogenic temperatures
Authors: KWON I. H. , LEE S. I. , YU H. S. 
Published: March 2003

ABSTRACTAustenitic stainless components used in nuclear fusion reactors must be capable of maintaining reasonable mechanical properties to thermal ageing caused by welding and in‐service. Recently, high‐nitrogen (High‐N) austenitic stainless steels (SS) are receiving increased attention because of their strength advantages, but they have been found to be susceptible to dichromium nitride (Cr2N) precipitation during thermal exposure at 823–1073 K. The susceptibility to sensitisation at thermal ageing temperature for high‐N austenitic SS is examined using the single‐loop electrochemical potentiokinetic reactivation (EPR) test. High‐N SS were found to be susceptible to sensitisation caused by grain boundary precipitation of Cr2N, with the degree of sensitisation increasing systematically with ageing time and temperature. In particular, it was found that the precipitates, which effected sensitisation, were changed from carbides (M23C6) to nitrides (Cr2N) with increasing ageing time and temperature. The deterioration of mechanical properties associated with thermal ageing in high‐N SS was investigated by a small punch (SP) test using miniature specimens at cryogenic temperatures. Results indicated that the degradation of mechanical properties in this alloy was caused by a decrease of cohesive strength resulting from carbides (Cr23C6) and nitrides (Cr2N) precipitated in grain boundaries.
Nitrogen fixation in seagrass meadows: Regulation, plant–bacteria interactions and significance to primary productivity
Authors: Welsh D.T. 
Published: March 2003

The rhizosphere sediments of seagrasses are generally a site of intense nitrogen fixation activity and this can provide a significant source of “new” nitrogen for the growth of the plants. In this paper, I review the data concerning nitrogen fixation in seagrass ecosystems, the transfer of the fixed nitrogen from the bacteria to the plants and its contribution to the overall productivity of seagrasses in different climatic zones.The relationship between the plants and diazotrophic heterotrophic bacteria in the rhizosphere is discussed, particularly focusing on the potentially important role of nitrogen‐fixing, sulphate‐reducing bacteria. The regulation of nitrogen fixation rates in the rhizosphere by photosynthetically driven oxygen and fixed carbon release by the plant roots and rhizomes, and the availability of ammonium in the porewater, is assessed. Finally, the hypothesis that a mutualistic or symbiotic association exists between the seagrasses and heterotrophic nitrogen fixers in the rhizosphere, based on the mutual exchange of fixed carbon and nitrogen, is discussed.
Rethinking ecological inference: density dependence in reef fishes
Authors: Osenberg Craig W. , St. Mary Colette M. , Schmitt Russell J. , Holbrook Sally J. , Chesson Peter , Byrne Barbara 
Published: March 2003

AbstractWe use a meta‐analysis of density dependence in reef fishes to evaluate how ecologists approach detection, inference, and estimation. We compared two groups of studies: those that detected effects of density on survival and those that did not. Distinctions between these groups have spawned heated debate about the processes that affect fish dynamics. Per capita effects of density were similar between the two groups, although total effects (and hence ambient density) were greater in studies that detected density effects. The majority of the variation in effects of density was not resolved by the classification of studies based on the authors' conclusions. These results suggest (1) that standard inferences based on null hypothesis tests may miss important sources of variation in effects and give rise to unnecessary debate; and (2) that estimation of effect sizes and model parameters (including their uncertainty) is a powerful alternative to detection of ecological processes.
Heteromyopia and the spatial coexistence of similar competitors
Authors: Murrell David J. , Law Richard 
Published: March 2003

AbstractMost spatial models of competing species assume symmetries in the spatial scales of dispersal and interactions. This makes analysis tractable, and has led to the conclusion that segregation of species in space does not promote coexistence. However, these symmetries leave parts of the parameter space uninvestigated. Using a moment‐approximation method, we present a spatial version of the Lotka–Volterra competition equations to investigate effects of removing symmetries in the distances over which individuals disperse and interact. Some spatial segregation of the species always comes about due to competition, and such segregation does not necessarily lead to coexistence. But, if interspecific competition occurs over shorter distances than intraspecific competition (heteromyopia), spatial segregation becomes strong enough to promote coexistence. Such coexistence is most likely when the species have similar dynamics, in contrast to the competition–colonization trade‐off that requires large competitive differences between species.
Monitoring of activity dynamics of an anaerobic digester bacterial community using 16S rRNA polymerase chain reaction–single‐strand conformation polymorphism analysis
Authors: Delbès Céline , Moletta René , Godon Jean‐Jacques 
Published: March 2003

The influence of parameter changes on the bacterial community of a laboratory‐scale anaerobic digester fed with glucose was investigated using a culture‐independent approach based on single‐strand conformation polymorphism (SSCP) analysis of total 16S rDNA and 16S rRNA amplification products. With the digester operating at steady state, the 16S rDNA SSCP patterns of the bacterial community showed eight peaks, whereas the 16S rRNA patterns showed six peaks with a very prominent one corresponding to a Spirochaetes‐related bacterium. An acidic shock at pH 6 caused an increase in the 16S rRNA level of two Clostridium‐related bacteria. After a 1 week starvation period, the major bacteria present reverted to a basal 16S rRNA level proportional to their 16S rDNA level. Starvation revealed the presence of a previously undetected peak whose corresponding sequence was deeply branched into the low G+C Gram‐positive bacteria phylum. Twenty‐four hours after a spiked addition to the starved digester community of starch, glucose, lactate or sulphate, an upsurge in several new 16S rRNA‐derived peaks was observed. Thus, the perturbation approach combined with 16S rRNA analysis revealed bacteria that had not been detected through 16S rDNA analysis.
Deciphering the action of aromatic effectors on the prokaryotic enhancer‐binding protein XylR: a structural model of its N‐terminal domain
Authors: Devos D. , Garmendia J. , Lorenzo V. de , Valencia A 
Published: March 2003

SummaryThe prokaryotic enhancer‐binding protein XylR is the central regulator of the toluene degradation pathway in Pseudomonas species. Copious genetic and biochemical data indicate that the N‐terminal domain of the protein (domain A) interacts directly with m‐xylene, which renders the protein competent as a transcriptional activator. Single‐site and shuffling mutants of XylR or homologues have been reported to change or expand their effector profiles. Here, we follow a fold recognition approach to generate three‐dimensional models of the domain A of XylR and DmpR with the purpose of deciphering the molecular activity of this protein family. The model is based on the crystallographic data of the rat catechol O‐methyltransferase, a typical α/β fold, consisting of eight α‐helices and seven β‐strands. The fold identification is supported by physico‐chemical properties of conserved amino acids, distribution of residues characteristic of the sequence families and confrontation with experimental data. The model not only provides a rationale for understanding published experimental data, but also suggests the molecular mechanism of the activation step and is a potentially useful conceptual tool for designing regulators with predefined inducer specificities.
Substrate‐regulated cyanide hydratase (chy) gene expression in Fusarium solani: the potential of a transcription‐based assay for monitoring the biotransformation of cyanide complexes
Authors: Barclay M. , Day J. C. , Thompson I. P. , Knowles C. J. , Bailey M. J. 
Published: March 2003

SummaryThe fungus Fusarium solani detoxifies cyanide through induction of the cyanide
hydratase gene activity (chy) in the presence of either KCN or the metal‐complexed
cyanides, K2Ni(CN)4 or K4Fe(CN)6, at
pH 7.0 and 4.0 respectively. Sequence analysis of the chy gene identified
primers for reverse transcriptase–polymerase chain reaction (RT–PCR)‐directed
analysis of mRNA transcripts, which demonstrated that activity correlated to the
substrate‐specific induction of gene expression. chy transcription was initiated
30–60 min after exposure of F. solani cultures to cyanide complexes.
Maximum expression was detected within 4.5 h, after which chy mRNA synthesis
declined below the limits of detection within 26 h. A lag period of ≈ 2
h, following initial transcription, was recorded before cyanide complexes were converted
to formamide. mRNA transcripts of chy were not detected in the absence of
cyanide or cyanide complexes. The presence of introns within the gene resulted in
a difference in size of 100 bp for DNA compared with mRNA of the corresponding 5′
region. This size difference facilitated PCR detection of gene and transcript respectively.
Comparisons of the predicted amino acid sequence of the F. solani chy gene
and those of Gloeocerospora sorghi, Fusarium lateritium and Leptosphaeria
maculans demonstrate that cyanide hydratase genes are highly conserved and of
a similar evolutionary origin. These data predict that the functional assay described
here to monitor the induction of chy gene expression and, potentially, cyanide degradation would be applicable to a variety of polluted environments.