bluuebunny/crossref_metadata_2025_split huggingface dataset:
Colonization of Sphagnum on land uplift islands in the Baltic Sea: time, area, distance and life history
Authors: Sundberg S. , Hansson J. , Rydin H. 
Published: June 2006

AbstractAim  To test whether species richness of Sphagnum mosses on islands in a land uplift archipelago is related to island age, area or connectivity, and whether the frequency of different species can be predicted by their life history and autecology.Location  The northern Stockholm archipelago in the Baltic Sea, east‐central Sweden, with a current land uplift rate of 4.4 mm year−1.Methods  We sampled 17 islands differing in area (0.55–55 ha), height (3.6–18 m, representing c. 800–4000 years of age) and distance from mainland (1.6–41 km). For each Sphagnum patch we measured area, height above sea level, horizontal distance from the shore and shading from vascular plants. Factors affecting island species richness, species frequency and habitats on the islands were tested by stepwise regressions. Species frequency was tested on nine life history and autecological variables, including estimated abundance and spore output on the mainland, habitat preference and distribution.Results  We recorded 500 patches of 19 Sphagnum species, distributed in 83 rock pools on 14 islands. Island species richness correlated positively with island area and with degree of shelter by surrounding islands, while distance from the mainland, connectivity, height or age did not add to the model. Species frequency (number of colonized islands and rock pools) was mainly predicted by spore output on the mainland and by habitat preference (swamp forest species were more frequent than others), while spore size, for example, did not add to the model. Species differed in mean height above and horizontal distance from the shore, area of occupied rock pools and in the degree of shading of patches. The mean horizontal distance from the shore and the area of occupied rock pools correlated positively with the normal growth position above the water table among species. Spore capsules were found in only 2% of patches, mostly in the bisexual Sphagnum fimbriatum.Main conclusions  The presence of Sphagnum in the Stockholm archipelago seems to be governed by regional spore production and habitat demands. Sphagnum does not appear to be dispersal limited at distances up to 40 km and time spans of centuries. Species with a high regional spore output have had a higher colonization rate, which, together with the rarity of spore capsules on the islands, indicate the mainland as a source for colonization rather than dispersal among islands. Swamp forest species seem more tolerant to the island conditions (summer droughts and some salt spray) than open mire species. The different distances from the sea occupied by the species indicate a slow, continuous succession and species replacement towards the island interior as islands are being uplifted and thus expand in area. This partly explains why larger islands harbour more species. Our results thus support some of the island biogeographical theories related to the species–area relationship.
The mode of action of the lantibiotic lacticin 3147 – a complex mechanism involving specific interaction of two peptides and the cell wall precursor lipid II
Authors: Wiedemann Imke , Böttiger Tim , Bonelli Raquel R. , Wiese Andre , Hagge Sven O. , Gutsmann Thomas , Seydel Ulrich , Deegan Lucy , Hill Colin , Ross Paul , Sahl Hans‐Georg 
Published: June 2006

SummaryLacticin 3147 is a two‐peptide lantibiotic produced by Lactococcus lactis in which both peptides, LtnA1 and LtnA2, interact synergistically to produce antibiotic activities in the nanomolar concentration range; the individual peptides possess marginal (LtnA1) or no activity (LtnA2). We analysed the molecular basis for the synergism and found the cell wall precursor lipid II to play a crucial role as a target molecule. Tryptophan fluorescence measurements identified LtnA1, which is structurally similar to the lantibiotic mersacidin, as the lipid II binding component. However, LtnA1 on its own was not able to substantially inhibit cell wall biosynthesis in vitro; for full inhibition, LtnA2 was necessary. Both peptides together caused rapid K+ leakage from intact cells; in model membranes supplemented with lipid II, the formation of defined pores with a diameter of 0.6 nm was observed. We propose a mode of action model in which LtnA1 first interacts specifically with lipid II in the outer leaflet of the bacterial cytoplasmic membrane. The resulting lipid II:LtnA1 complex is then able to recruit LtnA2 which leads to a high‐affinity, three‐component complex and subsequently inhibition of cell wall biosynthesis combined with pore formation.
Secretion signal of the filamentous haemagglutinin, a model two‐partner secretion substrate
Authors: Hodak Hélène , Clantin Bernard , Willery Eve , Villeret Vincent , Locht Camille , Jacob‐Dubuisson Françoise 
Published: June 2006

SummaryThe sorting of proteins to their proper subcellular compartment requires specific addressing signals that mediate interactions with ad hoc transport machineries. In Gram‐negative bacteria, the widespread two‐partner secretion (TPS) pathway is dedicated to the secretion of large, mostly virulence‐related proteins. The secreted TpsA proteins carry a characteristic 250‐residue‐long N‐terminal ‘TPS domain’ essential for secretion, while their TpsB transporters are pore‐forming proteins that specifically recognize their respective TpsA partners and mediate their translocation across the outer membrane. However, the nature of the secretion signal has not been elucidated yet. The whooping cough agent Bordetella pertussis secretes its major adhesin filamentous haemagglutinin (FHA) via the TpsB transporter FhaC. In this work, we show specific interactions between an N‐terminal fragment of FHA containing the TPS domain and FhaC by using two different techniques, an overlay assay and a pull‐down of the complex. FhaC recognizes only non‐native conformations of the TPS domain, corroborating the model that in vivo, periplasmic FHA is not yet folded. By generating single amino acid substitutions, we have identified interaction determinants forming the secretion signal. They are found unexpectedly far into the TPS domain and include both conserved and variable residues, which most likely explains the specificity of the TpsA–TpsB interaction. The N‐terminal domain of FhaC is involved in the FHA–FhaC interaction, in agreement with its proposed function and periplasmic localization.
Differential modulation of E. coli mRNA abundance by inhibitory proteins that alter the composition of the degradosome
Authors: Gao Junjun , Lee Kangseok , Zhao Meng , Qiu Ji , Zhan Xiaoming , Saxena Ankur , Moore Christopher J. , Cohen Stanley N. , Georgiou George 
Published: June 2006

SummaryIn Escherichia coli the initial step in the processing or decay of many messenger and structural RNAs is mediated by the endonuclease RNase E, which forms the core of a large RNA‐catalysis machine termed the degradosome. Previous experiments have identified a protein that globally modulates RNA abundance by binding to RNase E and regulating its endonucleolytic activity. Here we report the discovery of RraB, which interacts with a different site on RNase E and interferes with cleavage of a different set of transcripts. We show that expression of RraA or RraB in vivo is accompanied by dramatic, distinct, and inhibitor‐specific changes in degradosome composition – and that these are in turn associated with alterations in RNA decay and global transcript abundance profiles that are dissimilar to the profile observed during simple RNase E deficiency. Our results reveal the existence of endonuclease binding proteins that modulate the remodelling of degradosome composition in bacteria and argue that such degradosome remodelling is a mechanism for the differential regulation of RNA cleavages in E. coli.
Cytokine Responses to CpG DNA in Human Leukocytes
Authors: Ågren J. , Thiemermann C. , Foster S. J. , Wang J. E. , Aasen A. O. 
Published: June 2006

AbstractPrevious studies have implicated a role of bacterial DNA, containing unmethylated cytosine‐phosphate‐guanosine (CpG) motifs, in the initiation of systemic inflammation. This is based on the ability of CpG‐DNA to act in synergy with lipopolysaccharide (LPS) to trigger tumor necrosis factor alpha (TNFα) production in murine monocytes and to enhance LPS toxicity in rodents. In this study we investigated the capacity of CpG‐DNA to trigger and modulate cytokine responses in human leukocytes.A human blood assay, as well as isolated cultures of monocytes and neutrophils, was exposed to the synthetic oligodeoxynucleotides (ODNs) CpG ODN (2006) and GpC ODN (2006‐GC), alone or in combination with peptidoglycan or LPS. Plasma or supernatants were isolated and analyzed for TNFα, interleukin‐1 beta (IL‐1β), IL‐6 and IL‐8 by ELISA.In the blood, 2006 (but not 2006‐GC) induced the release of TNFα (P < 0.05) and possibly IL‐1β and IL‐6. IL‐8 was induced in a CpG‐independent manner. When co‐administered with peptidoglycan, both ODNs enhanced the release of cytokines, but not consistently CpG dependent. When co‐administered with LPS, only IL‐8 values were enhanced, whereas IL‐6 was suppressed at early time points. In monocyte and neutrophil cultures, CpG dependent induction of cytokine release was not observed. However, both ODNs inhibited LPS‐induced IL‐6.In conclusion, the capacity of CpG DNA to trigger the release of TNFα and to enhance LPS‐induced release of this cytokine is confirmed in human whole blood, but not in adherent human monocytes. Most effects of the ODNs on cytokine release in human leukocytes were CpG independent.
Allelic Diversity and Affinity Variants of MICA are Imbalanced in Spanish Patients with Behçet's Disease
Authors: Muñoz‐Saá I. , Cambra A. , Pallarés L. , Espinosa G. , Juan A. , Pujalte F. , Matamoros N. , Milà J. , Julià M. R. 
Published: June 2006

AbstractThe aetiology of Behçet's disease (BD) is still unknown, but genetic and environmental factors are involved. HLA‐B*51 is considered a susceptibility marker and some MICA alleles have also been associated. Cytotoxic T lymphocytes have been suggested as responsible for BD lesions by engaging MICA through NKG2D surface molecules. In the present study, HLA‐B and MICA alleles were typed by polymerase chain reaction using sequence‐specific primers, in 165 healthy Spanish controls and 42 BD patients. In the healthy group, MICA*008 (28.48%), MICA*004 (17.58%), MICA*002 (14.24%) and MICA*009 (9.39%) were the predominant alleles and the most common haplotype was MICA*004‐B*44 (12.12%). MICA*001 (5.15%), MICA*004, MICA*011 (4.54%) and MICA*018 (5.15%) were more frequent, and MICA*010 (1.81%) and MICA*008 were less prevalent than in other Caucasoid populations. Similar results have been reported in North African individuals and this could support the hypothesis of a common ancestral origin of both populations. The frequencies of MICA*009 and MICA*019 were significantly increased in our BD patients in comparison with controls: 22.62% versus 9.39% and 10.71% versus 1.81% respectively. The increase of MICA*019 had not been described in other BD cohorts, and it corroborates the genetic heterogeneity at MICA locus in BD patients. High‐affinity MICA alleles for NKG2D were more frequent in controls than in patients. Moreover, high‐affinity alleles were not found in homozygous BD patients. These results argue against the hypothesis of an autoaggressive response in BD patients through MICA–NKG2D interactions.
A major sulphur isotope event at c. 510 Ma: a possible anoxia–extinction–volcanism connection during the Early–Middle Cambrian transition?
Authors: Hough M.L. , Shields G.A. , Evins L.Z. , Strauss H. , Henderson R.A. , Mackenzie S. 
Published: June 2006

AbstractA new approach to constraining seawater δ34S and sulphate concentration using francolite‐bound sulphate reveals an abrupt increase in δ34S to +50‰ around the Early–Middle Cambrian boundary. Such high δ34S values are best explained by increased rates of pyrite burial due to ocean anoxia coupled with an increased sensitivity of the ocean sulphate reservoir to perturbations due to low sulphate concentrations of 500–700 μgL−1. We argue that the spread of anoxic waters at this time was partly the result of greenhouse warming related to the eruption of the Kalkarindji Large Igneous Province of northern Australia and that it triggered the collapse of early metazoan reef ecosystems during the latest Early Cambrian. Mass extinctions of the last 260 Myr have all coincided with enhanced volcanic activity, while several are also associated with positive shifts in seawater δ34S. Extending this correlation back in time further implicates volcanically induced climate change as a major determining factor in biosphere evolution.Terra Nova, 18, 257–263, 2006
Damage analysis for structural integrity and durability of composite materials
Authors: TALREJA R. 
Published: June 2006

ABSTRACTComposite structures for mechanical and aerospace applications are designed to retain structural integrity and remain durable for the intended service life. Since the early 1970s important advances have been made in characterizing and modelling the underlying mechanical behaviour and developing tools and methodologies for predicting fracture and fatigue of composite materials. This paper presents a review of the concepts and analyses related to this area, and illustrates these by a few examples. The topics discussed are composite material strength in tension, compression and shear, damage and its progression in monotonic and cyclic loading, fatigue life prediction and damage induced changes in visco‐elastic response.
Fatigue behaviour of SiCp‐reinforced aluminium composites in the very high cycle regime using ultrasonic fatigue
Authors: HUANG J. , SPOWART J. E. , JONES J. W. 
Published: June 2006

ABSTRACTThe fatigue behaviour of a 2009/SiC/15p‐T4 DRA composite has been examined in the very high cycle fatigue (VHCF) regime where 107≤Nf≤ 109 cycles. Ultrasonic fatigue was used to achieve the very high cycle counts. Careful processing yielded a composite with a very homogeneous particle distribution with minimal clustering. Fatigue crack initiation was observed almost exclusively at AlCuFe inclusions with no crack initiation observed at SiC particle clusters. Fatigue lives at a given stress level exhibited minimal scatter and subsurface crack initiation was observed in all cases. This behaviour is consistent with the presence of a low number density of critical inclusions that are responsible for crack initiation very early in fatigue life.
Limited weld residual stress measurements in fatigue crack propagation: Part I. Complete field representation through least‐squares finite‐element smoothing
Authors: GE Y. Z. , SUTTON M. A. , DENG X. , REYNOLDS A. P. 
Published: June 2006

ABSTRACTAn equilibrium‐based, weighted least‐squares algorithm is developed to reconstruct the complete residual stress field tensor throughout the specimen volume using a limited set of residual stress measurements and a priori boundary conditions.Using a set of residual stress data acquired by neutron diffraction over a limited region of an AA2024‐T351 friction‐stir‐welded specimen, the method is used to reconstruct the complete residual stress tensor field. Results indicate that (1) the algorithm is robust and effective in quantifying the complete residual stress field throughout the region of interest; (2) appropriate smoothing parameters are readily obtained so that the reconstructed, complete residual stress field accurately reflects the experimental measurements and (3) the resulting residual stress field is in self‐equilibrium.
Limited weld residual stress measurements in fatigue crack propagation: Part II. FEM‐based fatigue crack propagation with complete residual stress fields
Authors: SUTTON M. A. , REYNOLDS A. P. , GE Y. Z. , DENG X. 
Published: June 2006

ABSTRACTUsing a limited set of residual stress measurements acquired by neutron diffraction and an equilibrium‐based, weighted least square algorithm to reconstruct the complete residual stress tensor field from the measured residual stress data, the effect of weld residual stress on fatigue crack propagation is investigated for 2024‐T351 aluminium alloy plate joined by friction stir welding. Through incorporation of the least squares, complete equilibrated residual stress field into a finite element model of the Friction Stir Weld (FSW) region, progressive crack growth along a direction perpendicular to the welding line is simulated as part of the analysis. Both the residual stress redistribution and the stress intensity factor due to the residual stress field, Kres, are calculated during the crack extension process.Results show that (a) incorporation of the complete, self‐equilibrated residual stress field into a finite element (FE) model of the specimen provides a robust, hybrid approach for assessing the importance of residual stress on fatigue crack propagation, (b) the calculated stress‐intensity factor due to the residual stress field, Kres, has the same trend as measured experimentally by the ‘cut‐compliance method’ and (c) the da/dN results are readily explained with reference to the effect of the residual stress field on the applied stress intensity factor.
Thermographic analysis in ultrasonic fatigue tests
Authors: XUE H. , WAGNER D. , RANC N. , BAYRAKTAR E. 
Published: June 2006

ABSTRACTThree kinds of alloys used in the automotive industry for structures and engine components are subjected to very high cycle fatigue damage during working service. In the study, fatigue damage progression of the three kinds of alloys was investigated in the very high cycles fatigue regime by means of thermographic analysis. The specimens have been tested at ambient temperature without cooling air using a piezoelectric fatigue system (20 kHz) with a stress ratio of R=−1 to determine the effects of increased specimen temperature caused by internal damping due to cycling at a very high frequency. The temperature evolution of specimens for different alloys at various load levels have been recorded. Results indicated that the temperature evolution of the fatigue specimen depends on the material, testing frequency and loading level; the temperature increased just at the beginning of the test, which corresponds to the thermal dissipation in the specimen. In the process of small crack propagation, the temperature in a local plastic zone increased sharply, evidently irreversible local plastic deformation can result in a local temperature increase. The basis of microstructural characterization and fracture surface analysis by scanning electron microscopy, it was found that the temperature field in an ultrasonic fatigue specimen corresponds to the fatigue damage process.
A novel test method to measure the fracture toughness of ceramic balls used in bearings
Authors: PIOTROWSKI A. E. , O'Brien M. J. 
Published: June 2006

ABSTRACTA novel mechanical test has been developed to measure the fracture toughness of the silicon‐nitride (Si3N4) balls used in modern hybrid bearings. The ball is compressed diametrally between two hemispherical conforming dies, which causes the ball's equator to bulge, generating a tensile hoop stress. Under applied load, a precrack placed at the equator grows. To calculate the ball's fracture toughness at crack instability, finite‐element calculations of the applied stress field and an analytical solution for the stress intensity factor are used in the ‘two point plus semiellipse’ method. Tests of 16 Si3N4 balls and three soda‐lime glass balls gave fracture toughness measurements in good agreement with accepted published values. The new technique appears to be more accurate than the indentation technique used to measure the toughness of ceramics. As future work, the test can be extended to measure fatigue and stress corrosion properties for Si3N4 balls.
Perceiving the moral dimension of practice: insights from Murdoch, Vetlesen, and Aristotle
Authors: Scott P. Anne 
Published: June 2006

Abstract  This paper situates the moral domain of practice within the context of a particular description of nursing practice – one that sees human interaction at the heart of that practice. Such a description fits not only with professional rhetoric but also with literature from patients and recent empirical work exploring the nature of nursing practice.Martha Levine in her 1977 description of ethics, within the context of nursing practice, indicated that what was important from an ethical perspective was how we interact with each other, with patients and colleagues, on a daily basis. What enables such interaction to display moral sensitivity, insight into patient need, and a focus on the good for the patient? Of relevance when answering this question is the empirical evidence indicating that professional socialization, as a nurse or a doctor, may dull the individual’s moral sense. If this is the case, cognizance needs to be taken of such evidence when identifying theoretical approaches from mainstream ethics that may provide insight and value for nurse education. It is suggested that such insight and value can be gained from a consideration of the work of Aristotle, Murdoch, and Vetlesen.
A pluralist view of nursing ethics
Authors: McCarthy Joan 
Published: June 2006

Abstract  This paper makes the case for a pluralist, contextualist view of nursing ethics. In defending this view, I briefly outline two current perspectives of nursing ethics – the Traditional View and the Theory View. I argue that the Traditional View, which casts nursing ethics as a subcategory of healthcare ethics, is problematic because it (1) fails to sufficiently acknowledge the unique nature of nursing practice; and (2) applies standard ethical frameworks such as principlism to moral problems which tend to alienate or undermine nursing ethical concerns. Alternatively, the Theory View, which aims to build an independent and comprehensive theory of nursing ethics, is also found wanting because it (1) fails to sufficiently acknowledge the heterogeneous nature of nursing practices; (2) overemphasizes the differences and undervalues the similarities between nurses and other health professionals; and (3) assumes that one ethical framework can be meaningfully applied across diverse moral problems and contexts.My alternative, is to argue that nursing ethics inquiry should take a pluralist and critical stance towards available ethical frameworks and the negotiation of the ethical realm. On this view, the search for moral consensus or a unique ethical framework for nursing is replaced by the task of working strategically with multiple frameworks in order to expand the moral agency of nurses and empower them to positively engage with moral uncertainty as an inevitable feature of living a moral life. I conclude by indicating some of the implications that this has for the teaching of nursing ethics.