1,084 research outputs found
The kinetics of fluoride uptake by synthetic hydroxyapatite
The kinetics of fluoride uptake by synthetic hydroxyapatite from aqueous solution has been studied. Experiments involved
exposing 0.1 g of synthetic hydroxyapatite to 5 cm3 of sodium fluoride solution in the concentration range 100-1000 ppm fluoride and determining fluoride concentration at regular time intervals with a fluoride ion-selective electrode. In all cases, uptake was found to follow pseudo-second order kinetics with correlation coefficients of at least 0.998; all systems equilibrated by 24 hours with equilibrium uptake values that varied with the initial fluoride concentration. The kinetic results
differ from those previously reported for much lower concentrations of fluoride, but in the present case, the concentrations were of clinical relevance, as they are those used in fluoride-containing dental products. Further work is necessary to determine how well these findings model uptake by natural hydroxyapatite and hence the extent to which they might apply in vivo
Do environmental factors influence the movement of estuarine fish? A case study using acoustic telemetry
Telemetry methods were used to investigate the influence of selected environmental variables on the position and movement of an estuarine-dependent haemulid, the spotted grunter Pomadasys commersonnii (Lacepède 1801), in the Great Fish Estuary, South Africa. Forty individuals (263–698 mm TL) were surgically implanted with acoustic coded transmitters and manually tracked during two periods (7 February to 24 March 2003; n = 20 and 29 September to 15 November 2003; n = 20). Real-time data revealed that spotted grunter are euryhaline (0–37) and are able to tolerate large variations in turbidity (4–356 FTU) and temperature (16–30 °C). However, the fish altered their position in response to large fluctuations in salinity, temperature and turbidity, which are characteristic of tidal estuarine environments. Furthermore, tidal phase had a strong influence on the position of spotted grunter in the estuary
Automated electronic medical record sepsis detection in the emergency department
Background. While often first treated in the emergency department (ED), identification of sepsis is difficult. Electronic medical record (EMR) clinical decision tools offer a novel strategy for identifying patients with sepsis. The objective of this study was to test the accuracy of an EMR-based, automated sepsis identification system.Methods. We tested an EMR-based sepsis identification tool at a major academic, urban ED with 64,000 annual visits. The EMR system collected vital sign and laboratory test information on all ED patients, triggering a “sepsis alert” for those with ≥2 SIRS (systemic inflammatory response syndrome) criteria (fever, tachycardia, tachypnea, leukocytosis) plus ≥1 major organ dysfunction (SBP ≤ 90 mm Hg, lactic acid ≥2.0 mg/dL). We confirmed the presence of sepsis through manual review of physician, nursing, and laboratory records. We also reviewed a random selection of ED cases that did not trigger a sepsis alert. We evaluated the diagnostic accuracy of the sepsis identification tool.Results. From January 1 through March 31, 2012, there were 795 automated sepsis alerts. We randomly selected 300 cases without a sepsis alert from the same period. The true prevalence of sepsis was 355/795 (44.7%) among alerts and 0/300 (0%) among non-alerts. The positive predictive value of the sepsis alert was 44.7% (95% CI [41.2–48.2%]). Pneumonia and respiratory infections (38%) and urinary tract infection (32.7%) were the most common infections among the 355 patients with true sepsis (true positives). Among false-positive sepsis alerts, the most common medical conditions were gastrointestinal (26.1%), traumatic (25.7%), and cardiovascular (20.0%) conditions. Rates of hospital admission were: true-positive sepsis alert 91.0%, false-positive alert 83.0%, no sepsis alert 5.7%.Conclusions. This ED EMR-based automated sepsis identification system was able to detect cases with sepsis. Automated EMR-based detection may provide a viable strategy for identifying sepsis in the ED
Spatial description of hake-directed fishing activity off the west coast of South Africa
Historically, the two species of Cape hakes Merluccius capensis and M. paradoxus off South Africa were commercially exploited exclusively by demersal trawling. In 1994, hake-directed demersal longline was introduced on an experimental basis, and in 1998 was initiated as a commercial fishing sector. The effect of a combined fleet composed of both trawlers and longliners on the Cape hake resource is not fully understood. Analysis of fishing intensity and catch-rate data revealed that the highest catch rates were found around the 400m and 500m isobaths for the trawl and longline fisheries respectively. Catch rates from both fishing sectors were also noted to be higher over sediments with a sand component. Differences between areas of the highest fishing intensity and highest catch rates were noted. In addition to other factors, it is suggested that a ‘friction of distance’ effect applies — vessels will trade-off higher catch rates with the increased costs associated with fishing in deeper waters
Renewable energy resource assessment
© The Author(s) 2019. Literature overview of published global and regional renewable energy potential estimates. This section provides definitions for different types of RE potentials and introduces a new category, the economic renewable energy potential in space constrained environments. The potential for utility scale solar and onshore wind in square kilometre and maximum possible installed capacity (in GW) are provided for 75 different regions. The results set the upper limits for the deployment of solar- and wind technologies for the development of the 2.0 °C and 1.5 °C energy pathways
Implementing an electronic sideband offset lock for precision spectroscopy in radium
We demonstrate laser frequency stabilization with at least 6 GHz of offset
tunability using an in-phase/quadrature (IQ) modulator to generate electronic
sidebands (ESB) on a titanium sapphire laser at 714 nm and we apply this
technique to the precision spectroscopy of Ra, and Ra. By
locking the laser to a single resonance of a high finesse optical cavity and
adjusting the lock offset, we determine the frequency difference between the
magneto-optical trap (MOT) transitions in the two isotopes to be
MHz, a factor of 29 more precise than the previously available data. Using the
known value of the hyperfine splitting of the level, we calculate
the isotope shift for the to transition to be
MHz, which is a factor of 8 more precise than the best available
value. Our technique could be applied to countless other atomic systems to
provide unprecedented precision in isotope shift spectroscopy and other
relative frequency comparisons
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Refractory Hypertension: Determination of Prevalence, Risk Factors and Comorbidities in a Large, Population-Based Cohort
Refractory hypertension is an extreme phenotype of antihypertensive treatment failure. Participants in the REasons for Geographic And Racial Differences in Stroke (REGARDS) Study, a large (n=30 239), population-based cohort were evaluated to determine the prevalence of refractory hypertension and associated cardiovascular risk factors and comorbidities. Refractory hypertension was defined as uncontrolled blood pressure (systolic/diastolic, ≥140/90 mm Hg) on ≥5 antihypertensive drug classes. Participants with resistant hypertension (systolic/diastolic, ≥140/90 mm Hg on ≥3 or <140/90 mm Hg on ≥4 antihypertensive classes) and all participants treated for hypertension served as comparator groups. Of 14 809 REGARDS participants receiving antihypertensive treatment, 78 (0.5%) had refractory hypertension. The prevalence of refractory hypertension was 3.6% among participants with resistant hypertension (n=2144) and 41.7% among participants on ≥5 antihypertensive drug classes. Among all participants with hypertension, black race, male sex, living in the stroke belt or buckle, higher body mass index, lower heart rate, reduced estimated glomerular filtration rate, albuminuria, diabetes mellitus, and history of stroke and coronary heart disease were associated with refractory hypertension. Compared with resistant hypertension, prevalence ratios for refractory hypertension were increased for blacks (3.00; 95% confidence interval, 1.68–5.37) and those with albuminuria (2.22; 95% confidence interval, 1.40–3.52) and diabetes mellitus (2.09; 95% confidence interval, 1.32–3.31). The median 10-year Framingham risk for coronary heart disease and stroke was higher among participants with refractory hypertension when compared with those with either comparator group. These data indicate that although resistant hypertension is relatively common among treated patients with hypertension, true antihypertensive treatment failure is rare
Apparent treatment-resistant hypertension and risk for stroke, coronary heart disease, and all-cause mortality
Apparent treatment-resistant hypertension (aTRH) is defined as uncontrolled hypertension despite the use of three or more antihypertensive medication classes or controlled hypertension while treated with four or more antihypertensive medication classes. We evaluated the association of aTRH with incident stroke, coronary heart disease (CHD), and all-cause mortality. Participants from the population-based REasons for Geographic And Racial Differences in Stroke (REGARDS) Study treated for hypertension with aTRH (n = 2043) and without aTRH (n = 12,479) were included. aTRH was further categorized as controlled aTRH (≥4 medication classes and controlled hypertension) and uncontrolled aTRH (≥3 medication classes and uncontrolled hypertension). Over a median of 5.9, 4.4, and 6.0 years of follow-up, the multivariable adjusted hazard ratio for stroke, CHD, and all-cause mortality associated with aTRH versus no aTRH was 1.25 (0.94–1.65), 1.69 (1.27–2.24), and 1.29 (1.14–1.46), respectively. Compared with controlled aTRH, uncontrolled aTRH was associated with CHD (hazard ratio, 2.33; 95% confidence interval, 1.21–4.48), but not stroke or mortality. Comparing controlled aTRH with no aTRH, risk of stroke, CHD, and all-cause mortality was not elevated. aTRH was associated with an increased risk for coronary heart disease and all-cause mortality
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The contributions of unhealthy lifestyle factors to apparent resistant hypertension: findings from the Reasons for Geographic And Racial Differences in Stroke (REGARDS) study
Objectives: Unhealthy lifestyle factors may contribute to apparent treatment resistant hypertension (aTRH). We examined associations of unhealthy lifestyle factors with aTRH in individuals taking antihypertensive medications from three or more classes.
Methods: Participants (n = 2602) taking three or more antihypertensive medication classes were identified from the population-based REasons for Geographic And Racial Differences in Stroke (REGARDS) study. aTRH was defined as having SBP/DBP at least 140/90 mmHg despite the use of three or more antihypertensive medication classes or the use of four or more classes to achieve blood pressure control. Lifestyle factors included obesity, physical inactivity, current smoking, heavy alcohol consumption, a low Dietary Approaches to Stop Hypertension (DASH) diet score and high sodium-to-potassium (Na/K) intake.
Results: Among participants taking three or more antihypertensive medication classes, 1293 (49.7%) participants had aTRH. The prevalence of unhealthy lifestyle factors in participants with and without aTRH was 55.2 and 51.7%, respectively, for obesity, 42.2 and 40.5% for physical inactivity, 11.3 and 11.5% for current smoking, 3.1 and 4.0% for heavy alcohol consumption, 23.1 and 21.5% for low-DASH diet score, and 25.4 and 24.4% for high Na/K intake. After adjustment for age, sex, race, and geographic region of residence, none of the unhealthy lifestyle factors were associated with aTRH. The associations between each unhealthy lifestyle factor and aTRH remained nonsignificant after additional adjustment for education, income, depressive symptoms, total calorie intake, and comorbidities.
Conclusions: Unhealthy lifestyle factors did not have independent associations with aTRH among individuals taking three or more antihypertensive medication classes
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