bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of Membrane‐Bound Nitrate Reductase A from Escherichia Coli with Analogues of Physiological Electron Donors
Authors: Giordani Roger , Buc Jean , Cornish‐Bowden Athel , Cárdenas Maria Luz 
Published: September 2004

We have compared the steady‐state kinetics of wild‐type nitrate reductase A and two mutant forms with altered β subunits. To mimic conditions in vivo as closely as possible, we used analogues of the physiological quinols as electron donors and membranes with overexpressed nitrate reductase A in preference to a purified αβγ complex. With the wild‐type enzyme both menadiol and duroquinol supply their electrons for the reduction of nitrate at rates that depend on the square of the quinol concentration, menadiol having the higher catalytic constant. The results as a whole are consistent with a substituted‐enzyme mechanism for the reduction of nitrate by the quinols.Kinetic experiments suggest that duroquinol and menadiol deliver their electrons at different sites on nitrate reductase, with cross‐inhibition. Menadiol inhibits the duroquinol reaction strongly, suggesting that menaquinol may be the preferred substrate in vivo. To examine whether electron transfer from menadiol and duroquinol for nitrate reduction requires the presence of all of the Fe‐S centres, we have studied the steady‐state kinetics of mutants with β subunits that lack an Fe‐S centre. The loss of the highest‐potential Fe‐S centre results in an enzyme without menadiol activity, but retaining duroquinol activity; the kinetic parameters are within a factor of two of those of the wild‐type enzyme, indicating that this centre is not required for the duroquinol activity. The loss of a low‐potential Fe‐S centre affects the activity with both quinols: the enzyme is still active but the catalytic constants for both quinols are decreased by about 75%, indicating that this centre is important but not essential for the activity.The existence of a specific site of reaction on nitrate reductase for each quinol, together with the differences in the effects on the two quinols produced by the loss of the Fe‐S centre of +80 mV, suggests that the pathways for transfer of electrons from duroquinol and menadiol are not identical.
Residual strength of unidirectional fibre‐metal laminates based on JC toughness of C(T) and SE(B) specimens: comparison with M(T) test results
Authors: CASTRODEZA E. M. , BASTIAN F. L. , IPIÑA J. E. PEREZ 
Published: September 2004

ABSTRACTFibre‐metal laminates (FMLs) are structural composites designed with the aim of producing very low fatigue crack‐propagation rate, damage‐tolerant and high‐strength materials, if compared to aeronautical Al alloys. Their application in aeronautical structures demands a deep knowledge of a wide set of mechanical properties and technological values, including both fracture toughness and residual strength. The residual strength of FMLs have been traditionally determined by using wide centre‐cracked tension panels M(T). The use of this geometry requires large quantities of material and heavy laboratory facilities. In this work, fracture toughness ( JC) of some unidirectional FMLs laminates was measured using a recently proposed methodology for critical fracture toughness evaluation on compact tension C(T) and single‐edge bend SE(B) specimens. Additionally, residual strength values of wider M(T) specimens with different widths (W from 150 to 200 mm) and several crack to width ratios (2a/W) were experimentally obtained. Some experimental residual strength values of M(T) specimens (W from 150 to 400 mm and different 2a/W ratios) of Arall were also obtained from the bibliography. Based on JC results from C(T) and SE(B) specimens, and either using or not using crack‐tip plasticity corrections, the residual strengths of the M(T) specimens were predicted and compared to the experimental ones. The results showed good agreement, especially when crack‐tip plasticity corrections were applied.
Fatigue of beta titanium alloy at 20, 482 and 648 °C
Authors: SOLIMINE P. A. , LISSENDEN C. J. 
Published: September 2004

ABSTRACTFatigue life of fibrous metal matrix composites is limited by the distribution of fibre strengths, the fibre‐matrix interfacial strength, and the fatigue resistance of the matrix. The aim of this work is to provide fatigue results for a beta titanium alloy over a range of temperatures and stresses that can be used as input for predicting fatigue life of a titanium matrix composite. Stress controlled tests having fatigue ratios between −1 and −0.2 were conducted on a limited number of samples machined from unreinforced laminated Ti‐15Mo‐3Al‐2.7Nb‐0.2Si (TIMETAL®21S) sheets to represent as closely as possible the in situ matrix material. Stress control was used to enable quantification of strain ratcheting for tensile mean stresses and a fast loading rate was used to minimize time‐dependent (creep) deformation. Stress amplitude‐life data at 20, 482 and 648 °C for fully reversed loading are well fit by a power law. Normalizing the stress amplitude with respect to the power law coefficient appears to account for the temperature dependence of the S–N curves. As the tests had large strains and lives were in the low‐cycle fatigue range, strain range at the half‐life was also correlated to life. For tensile mean stress cycling at 482 and 648 °C, the rate of strain ratcheting per cycle increased to failure; shakedown was not observed.
Quantifying 3H‐thymidine incorporation rates by a phylogenetically defined group of marine planktonic bacteria (Bacteriodetes phylum)
Authors: Van Mooy Benjamin A. S. , Devol Allan H. , Keil Richard G. 
Published: September 2004

SummaryThe rate of [3H‐methyl] thymidine (3H‐TdR) incorporation into DNA has been applied extensively to measure cell production by bacterial communities in aquatic environments. Here we describe a method to quantify 3H‐TdR incorporation by specific, phylogenetically defined members of the bacterial community. The method involves selectively capturing DNA from targeted groups of bacteria and then quantifying its 3H radioactivity. The method was applied to measure 3H‐TdR incorporation by the members of the phylum Bacteriodetes whose members, which include the Cytophaga‐Flavobacter cluster, are ubiquitous in coastal waters. 3H‐labelled DNA from Bacteriodetes was selectively biotinylated in PCR‐like reactions that contained a Bacteriodetes‐specific 16S rRNA gene primer, thermostable DNA polymerase and biotinylated dUTP. The biotinylated DNA was then captured on streptavidin‐coated beads and its 3H radioactivity determined by scintillation counting. We have termed this method ‘selective nucleic acid polymerase‐biotinylation and capture’ or ‘SNAP‐BAC’. Internal 33P‐labelled DNA standards were used to quantify the recovery of 3H‐labelled DNA from the SNAP‐BAC reactions. The method was verified by successfully targeting Bacteriodetes in simple laboratory mixtures of 3H‐labelled DNA extracted from pure cultures of Bacteriodetes and γ‐proteobacteria. Field application of this method in Puget Sound and off the Washington coast determined that Bacteriodetes were responsible for 56 ± 17% and 32 ± 5% of community 3H‐TdR incorporation (1.3 ± 0.3 and 9.9 ± 1.7 pmol l−1 h−1) at these two locations.
Molecular evidence that plastids in the toxin‐producing dinoflagellate genus Dinophysis originate from the free‐living cryptophyte Teleaulax amphioxeia
Authors: Janson Sven 
Published: September 2004

SummarySome species of the dinoflagellate genus Dinophysis form red tides and are toxin producers with a great environmental impact. The dinoflagellates as a group display high plastid diversity. Several cases indicate that plastids have been replaced. In the case of the genus Dinophysis, the plastids show characteristics of a plastid originating from a cryptophyte. Recent molecular evidence showed that the plastid indeed originates from a cryptophyte, but the source could not be identified to species or genus level. The data presented here show that both a 799 bp region of the psbA gene and 1221 bp region of the 16S rRNA gene from Dinophysis spp. are identical to the same loci in Teleaulax amphioxeia SCCAP K434. This strongly indicates that the plastid was acquired recently in Dinophysis and may be a so‐called kleptoplastid, specifically originating from a species of Teleaulax.
Low archaeal diversity linked to subseafloor geochemical processes at the Lost City Hydrothermal Field, Mid‐Atlantic Ridge
Authors: Schrenk Matthew O. , Kelley Deborah S. , Bolton Sheryl A. , Baross John A. 
Published: September 2004

SummaryThe recently discovered Lost City Hydrothermal Field (LCHF) represents a new type of submarine hydrothermal system driven primarily by exothermic serpentinization reactions in ultramafic oceanic crust. Highly reducing, alkaline hydrothermal environments at the LCHF produce considerable quantities of hydrogen, methane and organic molecules through chemo‐ and biosynthetic reactions. Here, we report the first analyses of microbial communities inhabiting carbonate chimneys awash in warm, high pH fluids at the LCHF and the predominance of a single group of methane‐metabolizing Archaea. The predominant phylotype, related to the Methanosarcinales, formed tens of micrometre‐thick biofilms in regions adjacent to hydrothermal flow. Exterior portions of active structures harboured a diverse microbial community composed primarily of filamentous Eubacteria that resembled sulphide‐oxidizing species. Inactive samples, away from regions of hydrothermal flow, contained phylotypes related to pelagic microorganisms. The abundance of organisms linked to the volatile chemistry at the LCHF hints that similar metabolic processes may operate in the subseafloor. These results expand the range of known geological settings that support biological activity to include submarine hydrothermal systems that are not dependent upon magmatic heat sources.
Predictable Investment Horizons and Wealth Transfers among Mutual Fund Shareholders
Authors: JOHNSON WOODROW T. 
Published: September 2004

ABSTRACTThis study analyzes the distribution of investment horizons in a large, proprietary panel of all shareholders in one no‐load mutual fund family. A proportional hazards model shows that there are observable shareholder characteristics that enable the fund to predict reliably on the day each account is opened whether the account will be short term or long term. Simulations show that the liquidity costs imposed on the fund by the expected short‐term shareholders are significantly greater than those imposed by the expected long‐term shareholders. Combining these results, the analysis argues that mutual funds do not provide equitable liquidity‐risk insurance.
Investment–Cash Flow Sensitivities: Constrained versus Unconstrained Firms
Authors: MOYEN NATHALIE 
Published: September 2004

ABSTRACTFrom the existing literature, it is not clear what effect financing constraints have on the sensitivities of firms' investment to their cash flow. I propose an explanation that reconciles the conflicting empirical evidence. I present two models: the unconstrained model, in which firms can raise external funds, and the constrained model, in which firms cannot do so. Using low dividends to identify financing constraints in my generated panel of data produces results consistent with those of Fazzari, Hubbard, and Petersen; using the constrained model produces results consistent with those of Kaplan and Zingales.
Correlated Trading and Location
Authors: FENG LEI , SEASHOLES MARK S. 
Published: September 2004

ABSTRACTThis paper analyzes the trading behavior of stock market investors. Purchases and sales are highly correlated when we divide investors geographically. Investors who live near a firm's headquarters react in a similar manner to releases of public information. We are able to make this identification by exploiting a unique feature of individual brokerage accounts in the People's Republic of China. The data allow us to pinpoint an investor's location at the time he or she places a trade. Our results are consistent with a simple, rational expectations model of heterogeneously informed investors.
Characteristics, Contracts, and Actions: Evidence from Venture Capitalist Analyses
Authors: KAPLAN STEVEN N. , STRÖMBERG PER 
Published: September 2004

ABSTRACTWe study the investment analyses of 67 portfolio investments by 11 venture capital (VC) firms. VCs describe the strengths and risks of the investments as well as expected postinvestment actions. We classify the risks into three categories and relate them to the allocation of cash flow rights, contingencies, control rights, and liquidation rights between VCs and entrepreneurs. The risk results suggest that agency and hold‐up problems are important to contract design and monitoring, but that risk sharing is not. Greater VC control is associated with increased management intervention, while greater VC equity incentives are associated with increased value‐added support.
Monitoring as a Motivation for IPO Underpricing
Authors: ARUǦASLAN ONUR , COOK DOUGLAS O. , KIESCHNICK ROBERT 
Published: September 2004

ABSTRACTBrennan and Franks (1997) and Stoughton and Zechner (1998) provide contrasting arguments for why monitoring considerations create incentives for managers to underprice their firms' IPOs (initial public offerings). Like Smart and Zutter (2003), we examine these arguments using a sample of U.S. IPOs. However, we find evidence that the determinants of initial returns, institutional shareholdings, and post‐IPO likelihood of acquisition are not consistent with these arguments. Thus, we conclude that monitoring considerations are not important determinants of IPO underpricing.
The KwaZulu‐Natal Health Promotion Model
Authors: Uys Leana R. , Majumdar Basanti , Gwele Nomthandaso S. 
Published: September 2004

Purpose

: To describe a health promotion model aimed at assisting primary health care nurses to incorporate health promotion into their practice.
Organizing Structure

: The model is based on empowering people through a systematic, planned, needs‐driven curriculum with comprehensive content, using interactive teaching in small groups, and linking the groups with external resources. The process involves identifying and engaging partners, planning the project, implementing it, and then disengaging.
Methods

: The implementation of this model in a province of South Africa, KwaZulu‐Natal, in a collaborative project involving two universities and the state health services, changed the practice of the primary health care nurses involved. They worked with women's groups over 3 years and changed both their own perspectives and the lives of the women.
Conclusions

: Unless nurses have an implementation model available to them, they frequently focus only on illness needs of people and do not participate in health promotion.
Symptom Clusters in Oncology Patients and Implications for Symptom Research in People with Primary Brain Tumors
Authors: Armstrong Terri S. , Cohen Marlene Z. , Eriksen Lillian R. , Hickey Joanne V. 
Published: September 2004

Purpose

: To provide a critical analysis of the state of the science of research on symptom clusters in the general oncology population, compared to symptom research in the primary brain tumor population.
Organizing Construct

: Symptoms are a multidimensional experience that include perceptions of the frequency, intensity, distress, and meaning as symptoms occur and are expressed. A symptom can influence the occurrence and meaning of other symptoms.
Methods

: Literature pertaining to symptom presentation in people with primary brain tumors and the occurrence of multiple symptoms and symptom clusters in patients with cancer was reviewed and analyzed.
Findings

: Symptoms occur in clusters in general oncology patients, and these clusters have been shown to influence functional status. The potential effect of tumor biology on symptom clusters is shown by the cluster of symptoms theorized to be associated with proinflammatory cytokine production. In patients with primary brain tumors, few researchers have examined the occurrence of symptoms at the time of diagnosis. Studies to date are retrospective and descriptive and were conducted before the use of modern imaging techniques. Studies of symptom clusters have not been reported for patients with primary brain tumors.
Conclusions

: Symptom clusters have recently been identified in the general oncology population and might provide a new strategy for assessment and intervention. Neurologic symptoms in patients with primary brain tumors are those related to increased intracranial pressure and those that are location‐dependent within the brain. Therefore, application of the symptom cluster paradigm to guide research is warranted.
Content Validity and Nursing Sensitivity of Community‐Level Outcomes From the Nursing Outcomes Classification (NOC)
Authors: Head Barbara J. , Aquilino Mary Lober , Johnson Marion , Reed David , Maas Meridean , Moorhead Sue 
Published: September 2004

Purpose

: To evaluate the content validity and nursing sensitivity of six community‐level outcomes from the Nursing Outcomes Classification (NOC; Johnson, Maas, & Moorhead, 2000).
Design and Methods

: A survey research design was used. Questionnaires were mailed to 300 public health nursing experts; 102 nurses responded. Experts evaluated between 11 and 30 indicators for each of the six outcomes for: (a) importance of the indicators for measuring the outcome, and (b) influence of nursing on the indicators. Content validity and nursing sensitivity of the outcomes were estimated with a modified Fehring technique.
Findings

: All outcomes were deemed important; only Community Competence had an outcome content validity score <.80. The outcome sensitivity score for Community Health: Immunity was .80; other outcome scores ranged from .62‐.70. Indicator ratios for all 102 indicators met the study criterion for importance, with 87% designated as critical and 13% as supplemental. Sensitivity ratios reflected judgments that 45% of the indicators were sensitive to nursing intervention.
Conclusions

: The study provided evidence of outcome content validity and nursing sensitivity of the study outcomes; further validation research is recommended, followed by testing of the study outcomes in clinical practice. Community‐level nursing‐sensitive outcomes will potentially enable study of the efficacy and effectiveness of public health interventions focused on improving health of populations and communities.
Development and Psychometric Evaluation of the Professional Practice Environment (PPE) Scale
Authors: Erickson Jeanette Ives , Duffy Mary E. , Gibbons M. Patricia , Fitzmaurice Joan , Ditomassi Marianne , Jones Dorothy 
Published: September 2004

Purpose

: To describe the Professional Practice Environment (PPE) scale, its conceptual development and psychometric evaluation, and its uses in measuring eight characteristics of the professional practice environment in an acute care setting.
Design and Methods

: The 38‐item PPE Scale was validated on a sample of 849 professional practice staff at the Massachusetts General Hospital in Boston. Psychometric analysis included: item analysis, principal components analysis (PCA) with varimax rotation and Kaiser normalization, and internal consistency reliability using Cronbach's alpha coefficient.
Findings

: Eight components were shown, confirming the original conceptually derived model's structure and accounting for 61% of explained variance. Cronbach's alpha coefficients for the eight PPE subscales ranged from .78 to .88.
Conclusions

: Findings showed the 38‐item PPE Scale was reliable and valid for use in health outcomes research to examine the professional practice environment of staff working in acute care settings.
Towards ‘One‐Stop’ Cardiac MR Image Analysis
Authors: Lelieveldt B. P. F. , van der Geest R. J. , Reiber J. H. C. 
Published: September 2004

AbstractCardiac magnetic resonance imaging (CMRI) has evolved towards a powerful diagnostic imaging modality, enabling a detailed and quantitative assessment of the presence, extent and development of cardiovascular disease. Because of its versatility, CMRI can be regarded as a collection of ‘MR modalities’, each dedicated to different aspects of cardiac function: global function, regional function, valvular function, perfusion and coronary function; therefore, CMRI is increasingly referred to as the ‘one‐stop shop in cardiac imaging’. The increased need for quantification in clinical research and practice, combined with the high data volume of CMRI has generated a great demand for software tools that facilitate and further automate the accurate quantitative analysis of cardiovascular MR patient examinations. This paper highlights a few recent advances in automated post‐processing and quantification in the context of ‘one‐stop’ CMR patient examinations, and discusses them for the most common acquisition types.
Comparison of Diversities and Compositions of Bacterial Populations Inhabiting Natural Forest Soils
Authors: Hackl Evelyn , Zechmeister-Boltenstern Sophie , Bodrossy Levente , Sessitsch Angela 
Published: September 2004

ABSTRACT

The diversity and composition of soil bacterial communities were compared among six Austrian natural forests, including oak-hornbeam, spruce-fir-beech, and Austrian pine forests, using terminal restriction fragment length polymorphism (T-RFLP, or TRF) analysis and sequence analysis of 16S rRNA genes. The forests studied differ greatly in soil chemical characteristics, microbial biomass, and nutrient turnover rates. The aim of this study was to relate these differences to the composition of the bacterial communities inhabiting the individual forest soils. Both TRF profiling and clone sequence analysis revealed that the bacterial communities in soils under Austrian pine forests, representing azonal forest types, were distinct from those in soils under zonal oak-hornbeam and spruce-fir-beech forests, which were more similar in community composition. Clones derived from an Austrian pine forest soil were mostly affiliated with high-G+C gram-positive bacteria (49%), followed by members of the α
-Proteobacteria
(20%) and the
Holophaga/Acidobacterium
group (12%). Clones in libraries from oak-hornbeam and spruce-fir-beech forest soils were mainly related to the
Holophaga/Acidobacterium
group (28 and 35%), followed by members of the
Verrucomicrobia
(24%) and the α
-Proteobacteria
(27%), respectively. The soil bacterial communities in forests with distinct vegetational and soil chemical properties appeared to be well differentiated based on 16S rRNA gene phylogeny. In particular, the outstanding position of the Austrian pine forests, which are determined by specific soil conditions, was reflected in the bacterial community composition.