393 research outputs found
Dynamics of H atoms surface recombination in low-temperature plasma
The dynamics of H atom recombination on materials of interest for a EUV
lithographer was studied under a longterm low-pressure H2 plasma exposure. The
similarity of the experimental plasma with the typical EUV-induced plasma over
the multi-layer mirrors (MLMs) surface of the EUV lithographic machine is
demonstrated by means of 2D PIC MC simulation. The measurement of the temporal
dynamics of the H atom surface loss probability is chosen for testing the
surface modification during the treatment. Time-resolved actinometry of H atoms
with Kr as the actinometer gas was used to detect the dynamics of the H-atom
loss probability on the surface of Al, Ru, RVS and SiO2. It is demonstrated
that significant changes of the materials surface occur only at the very
beginning of the treatment and ist due to the surface heating and cleaning
effects. After that no changes of the H recombination rate are found,
indicating that the surface stays absolutely stable. A special test of the
sensitivity of the used method to the state of surface was carried out.
Dynamics of the H recombination rate changes with the small O2 addition clearly
demonstrated modification of the Al surface due to oxidation with the next
removal of the oxygen by the H2 plasma treatment. The rate of oxide removal is
shown to be determined by plasma parameters such as the ion energy and flux to
the surface
Histamine as a marker for hydroxyl radicals
During inflammation an influx of neutrophils and release of mediators from mast cells (such as histamine) take place. The stimulated neutrophils can produce reactive oxygen species (ROS). One of these ROS is the highly reactive hydroxyl radical (OH.). It would be interesting to be able to quantify the extent of ROS formation. We investigated if histamine which is present at the inflammation site can serve as an endogenous marker for the formation of OH.. We found that histamine after incubation with OH. gave two distinct products in our HPLC system. One of the products gave the same characteristics as the synthesized 2-imidazolone derivative of histamine. This suggests that this derivative will be formed when histamine is incubated with OH.
Thyroid status and mortality in nonagenarians from long-lived families and the general population
Pathophysiology, epidemiology and therapy of agein
Interrelationships Between Pituitary Hormones as Assessed From 24-hour Serum Concentrations in Healthy Older Subjects
Context: Hormones of the hypothalamic-pituitary-target gland axes are mostly investigated separately, whereas the interplay between hormones might be as important as each separate hormonal axis.Objective: Our aim is to determine the interrelationships between GH, TSH, ACTH, and cortisol in healthy older individuals.Design: We made use of 24-hour hormone serum concentrations assessed with intervals of 10 minutes from 38 healthy older individuals with a mean age (SD) of 65.1 (5.1) years from the Leiden Longevity Study. Cross-correlation analyses were performed to assess the relative strength between 2 24-hour hormone serum concentration series for all possible time shifts. Cross-approximate entropy was used to assess pattern synchronicity between 2 24-hour hormone serum concentration series.Results: Within an interlinked hormonal axis, ACTH and cortisol were positively correlated with a mean (95% confidence interval) correlation coefficient of 0.78 (0.74-0.81) with cortisol following ACTH concentrations with a delay of 10 minutes. Between different hormonal axes, we observed a negative correlation coefficient between cortisol and TSH of -0.30 (-0.36 to -0.25) with TSH following cortisol concentrations with a delay of 170 minutes. Furthermore, a positive mean (95% confidence interval) correlation coefficient of 0.29 (0.22-0.37) was found between TSH and GH concentrations without any delay. Moreover, cross-approximate entropy analyses showed that GH and cortisol exhibit synchronous serum concentration patterns.Conclusions: This study demonstrates that interrelations between hormones from interlinked as well as different hypothalamic-pituitary-target gland axes are observed in healthy older individuals. More research is needed to determine the biological meaning and clinical consequences of these observations.Pathophysiology, epidemiology and therapy of agein
Effect of erythropoietin levels on mortality in old age: the Leiden 85-plus Study
BACKGROUND: The production of erythropoietin is triggered by impaired oxygen delivery to the kidney, either because of anemia or hypoxemia. High erythropoietin levels have been shown to predict the risk of death among patients with chronic heart failure. We investigated the prognostic value of elevated erythropoietin levels on mortality among very elderly people in the general population. METHODS: The Leiden 85-plus Study is a population-based prospective follow-up study involving 599 people aged 85 years in Leiden, the Netherlands, enrolled between September 1997 and September 1999. Erythropoietin levels were determined at age 86. For this analysis, we included 428 participants with a creatinine clearance of at least 30 mL/min. Mortality data, recorded until Feb. 1, 2008, were obtained from the municipal registry. RESULTS: During follow-up, 324 (75.7%) participants died. Compared with participants whose erythropoietin levels were in the lowest tertile (reference group), those whose levels were in the middle tertile had a 25% increased risk of death (hazard ratio [HR] 1.25, 95% confidence interval [CI] 0.95–1.64), and those whose levels were in the highest tertile had a 73% increased risk (HR 1.73, 95% CI 1.32–2.26) (p value for trend < 0.01). The association between erythropoietin levels and mortality remained largely unchanged after we adjusted for sex, creatinine clearance, hemoglobin level, comorbidity, smoking status and C-reactive protein level, and was similar for deaths from cardiovascular and noncardiovascular causes. INTERPRETATION: Among people aged 85 years and older, elevated erythropoietin levels were associated with an increased risk of death, independent of hemoglobin levels
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