177,343 research outputs found
A model linking organic matter decomposition, chemistry and aggregate dynamics
No full textThe interaction of organic materials with mineral particles is a fundamental process in the surface horizons of most soils. Organo-mineral interactions not only influence the dynamics of soil organic matter (Oades, 1988; Amato and Ladd, 1992; Golchin et al., 1995a; Oades, 1995; Chenu et al., 1996), but also contribute to the formation and stabilization of soil aggregates (Tisdall and Oades, 1982; Oades, 1993). Interactions between small organic molecules and clay surfaces have been described and reviewed at length (Mortland, 1970; Theng, 1974) and interactions of organic polymers with clays are reasonably well understood (Theng, 1979; 1982). Interaction of particulate organic matter (POM) with mineral particles, however, has received less attention and the turnover, composition, and distribution of POM within the soil matrix are not well known. In classical fractionation schemes, SOM has been extracted from soils using alkaline solutions and the unextractable fraction or humin, which includes POM, has not been studied extensively. In this chapter we will focus on the interaction of POM with mineral particles and consider the role of POM in the formation of aggregates of different sizes. We present a conceptual model describing the involvement of POM and microbial metabolites derived from its decomposition in soil aggregation. The importance of biological processes associated with the decomposition of POM and the associated chemical changes will be identified and discussed with respect to their involvement in the proposed model of aggregation. The conceptual model, which is based on our previous works and selected literature results, may be applied generally to soils where organic matter is an important agent responsible for binding soil mineral particles together creating an aggregate hierarchy (Oades and Waters, 1991; Oades, 1993). In the model, we proposed the existence of three levels of aggregation ( 250 µm) in which the mechanisms of stabilization differ
Validity and reliability concerns associated with cardiopulmonary exercise testing young people with cystic fibrosis
No full textThis is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Letter to the Edito
Measurement of V̇O2<sub>max</sub> in clinical groups is feasible and necessary
No full textThis is the author accepted manuscript. The final version is available from American Physiological Society via the DOI in this record
Reproducibility of maximal cardiopulmonary exercise testing for young cystic fibrosis patients
No full textAuthor manuscript version of an article published in the Journal of Cystic Fibrosis. The definitive published version is available via http://dx.doi.org/10.1016/j.jcf.2013.04.012.BACKGROUND: The reproducibility of cardiopulmonary exercise testing (CPET) has not been established in young cystic fibrosis (CF) patients using a valid protocol. METHODS: Thirteen 7-18 year olds completed three CPETs, separated by 48 h and 4-6 weeks. CPET involved a ramp-incremental cycling test with supramaximal verification. RESULTS: Maximal oxygen uptake was repeatedly determined with no learning effect and typical errors expressed as a coefficient of variation (TE(CV%)) of 9.3% (48 h) and 13.3% (4-6 weeks). The reproducibility of additional parameters of aerobic function [gas exchange threshold (TE(CV%): 11.2%, 16.8%); VO2 mean response time (TE(CV%): 37.8%, 89.4%); VO2 gain (TE(CV%): 17.4%, 24.5%)] and clinical utility [e.g. SaO2% (TE(CV%): 2.2%, 3.1%); ventilatory drive (V(E)/VCO2-slope) (TE(CV%): 7.8%, 17.7%)] was also established over the short- and the medium-term, respectively. CONCLUSION: These results establish limits of variability to determine meaningful changes over the short- and the medium-term for CPET outcomes in young CF patients
WS16.2 the reliability of maximal cardiopulmonary exercise testing for young cystic fibrosis patients
No full textBackground: Maximal cardiopulmonary exercise testing (CPET) is the most precise method for evaluating physical function of patients with mild-to-moderate cystic fibrosis (CF). This study sought to establish the between trial variation of CPET parameters across three different time points. Methods: Fourteen 7−18 year olds (10 male) completed an incremental ramp cycle test to exhaustion. Peak oxygen uptake (V˙ O2peak), power output (Wpeak), heart rate (HRpeak ) and end-exercise oxygen saturation (SaO2%) and breathlessness (RPD) were determined. Following 15-min recovery supramaximal exercise to exhaustion was performed at a work rate (WR) equal to 110% ramp Wpeak (T1). Testing was repeated 48 h (T2) and 4−6 weeks later (T3). Intra-class retest correlations, change in the mean score [V˙ O2peak] and the typical error for all measurements assessed reliability. Results: Intra-class correlations ranged from r = 0.57–0.99 and were highest for WR. No significant differences in mean (SD) V˙ O2peak were found between T1-T2; 1.91 (0.80) and 1.93 (0.66) L×min−1, p = 0.79; T2-T3 1.81 (0.48) and 1.68 (0.50) L×min−1, n = 13, p = 0.20 and T1-T3 1.77 (0.63) and 1.68 (0.50) L×min−1, n = 13, p = 0.25, respectively. The highest typical error for HRpeak (T1-T2), WR (T2-T3), RPD (T1-T2), SaO2% (T2-T3), and V˙ O2peak (T1-T2) were 12, 9.3, 1.4, 1.3 and 0.3%, respectively. Conclusion: CPET derived variables especially V˙ O2peak are highly reproducible between 1 and 42 days. Clinicians can have confidence in precisely reproducing the effect of exercise/pharmacological interventions or CF disease on parameters obtained during CPET. Acknowledgments: Supported by the Peninsula NIHR Research Facility
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A protocol to determine valid in young cystic fibrosis patients
No full textClinical TrialJournal ArticleResearch Support, Non-U.S. Gov'tOBJECTIVES: Measuring aerobic fitness (V˙O2max) via a maximal cardiopulmonary exercise test is an important clinical tool in cystic fibrosis. This study sought to establish: (1) the validity of traditional criteria to verify maximal efforts during a ramp cardiopulmonary exercise test; and (2) whether V˙O2 measured during an exhaustive cardiopulmonary exercise test represents a valid V˙O2max in paediatric patients, using a subsequent exhaustive supramaximal (Smax) exercise test. DESIGN: Cross-sectional. METHODS: Fourteen patients (7-18 years; 10 males) completed an exhaustive ramp test to determine V˙O2max. Following 15-min recovery, Smax (110% ramp peak power output) was performed. RESULTS: Ramp test V˙O2peak was significantly higher than V˙O2 documented at traditional endpoint criteria, including a RER of 1.00 (0.99±0.47 L min(-1) vs. 1.83±0.78 L min(-1), p9%) increase in V˙O2peak (range 9.9-38.3%) compared with V˙O2peak from the ramp test in 3 of 14 cases (21.4%). CONCLUSIONS: Traditional criteria significantly underestimate V˙O2max in young cystic fibrosis patients. Conversely, Smax can confirm when 'true' V˙O2max is achieved. The use of Smax following cardiopulmonary exercise test represents an appropriate method to measure V˙O2max in young cystic fibrosis patients.NIHR Exeter Clinical Research FacilityRoyal Devon and Exeter NHS Foundation Trust Hospita
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
168 A protocol to determineVO<sub>2max</sub> in young patients with cystic fibrosis:recommendations for clinical practice
No full textWS08.1 The utility of oxygen uptake efficiency as a marker of aerobic fitness in children with cystic fibrosis
No full textThis is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record
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