6,953 research outputs found
Lightside Atmospheric Revitalization System
The system was studied as a replacement to the present baseline LiOH system for extended duration shuttle missions. The system consists of three subsystems: a solid amine water desorbed regenerable carbon dioxide removal system, a water vapor electrolysis oxygen generating system, and a Sabatier reactor carbon dioxide reduction system. The system is designed for use on a solar powered shuttle vehicle. The majority of the system's power requirements are utilized on the Sun side of each orbit, when solar power is available
The Cartan form for constrained Lagrangian systems and the nonholonomic Noether theorem
This paper deals with conservation laws for mechanical systems with
nonholonomic constraints. It uses a Lagrangian formulation of nonholonomic
systems and a Cartan form approach. We present what we believe to be the most
general relations between symmetries and first integrals. We discuss the
so-called nonholonomic Noether theorem in terms of our formalism, and we give
applications to Riemannian submanifolds, to Lagrangians of mechanical type, and
to the determination of quadratic first integrals.Comment: 25 page
The associations of adipokines with selected markers of the renin-angiotensinogen-aldosterone system: the multi-ethnic study of atherosclerosis.
Among obese individuals, increased sympathetic nervous system (SNS) activity results in increased renin and aldosterone production, as well as renal tubular sodium reabsorption. This study determined the associations between adipokines and selected measures of the renin-angiotensinogen-aldosterone system (RAAS). The sample consisted of 1970 men and women from the Multi-Ethnic Study of Atherosclerosis who were free of clinical cardiovascular disease at baseline and had blood assayed for adiponectin, leptin, plasma renin activity (PRA) and aldosterone. The mean age was 64.7 years and 50% were female. The mean (s.d.) PRA and aldosterone were 1.45 (0.56) ng ml(-1) and 150.1 (130.5) pg ml(-1), respectively. After multivariable adjustment, a 1-s.d. increment of leptin was associated with a 0.55 ng ml(-1) higher PRA and 8.4 pg ml(-1) higher aldosterone (P<0.01 for both). Although adiponectin was not significantly associated with PRA levels, the same increment in this adipokine was associated with lower aldosterone levels (-5.5 pg ml(-1), P=0.01). Notably, the associations between aldosterone and both leptin and adiponectin were not materially changed with additional adjustment for PRA. Exclusion of those taking antihypertensive medications modestly attenuated the associations. The associations between leptin and both PRA and aldosterone were not different by gender but were significantly stronger among non-Hispanic Whites and Chinese Americans than African and Hispanic Americans (P<0.01). The findings suggest that both adiponectin and leptin may be relevant to blood pressure regulation via the RAAS, in that the associations appear to be robust to antihypertension medication use and that the associations are likely different by ethnicity
Hemostasis biomarkers and incident cognitive impairment: the REGARDS study
Essentials Cognitive disorders are increasing and vascular risk factors play a role in this. We performed a nested case control study of hemostasis biomarkers and cognitive impairment (CI). Higher baseline fibrinogen, factor VIII and D-dimer were related to incident CI over 3.5 years. Adjusted for other risk factors, 2+ abnormal markers (but not single ones) led to higher risk.
SUMMARY:
Background Vascular risk factors are associated with cognitive impairment, a condition that imposes a substantial public health burden. We hypothesized that hemostasis biomarkers related to vascular disease would be associated with the risk of incident cognitive impairment. Methods We performed a nested case-control study including 1082 participants with 3.5 years of follow-up in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a longitudinal cohort study of 30 239 black and white Americans aged ≥ 45 years. Participants were free of stroke or cognitive impairment at baseline. Baseline D-dimer, fibrinogen, factor VIII and protein C levels were measured in 495 cases who developed cognitive impairment during follow-up (based on abnormal scores on two or more of three cognitive tests) and 587 controls. Results Unadjusted odds ratios (ORs) for incident cognitive impairment were 1.32 (95% confidence interval [CI] 1.02-1.70) for D-dimer > 0.50 μg mL-1 , 1.83 (95% CI 1.24-2.71) for fibrinogen > 90th percentile, 1.63 (95% CI 1.11-2.38) for FVIII > 90th percentile, and 1.10 (95% CI 0.73-1.65) for protein C < 10th percentile. There were no differences in associations by race or region. Adjustment for demographic, vascular and health behavior risk factors attenuated these associations. However, having at least two elevated biomarkers was associated with incident cognitive impairment, with an adjusted OR of 1.73 (95% CI 1.10-2.69). Conclusion Elevated D-dimer, fibrinogen and FVIII levels were not associated with the occurrence of cognitive impairment after multivariable adjustment; however, having at least two abnormal biomarkers was associated with the occurrence of cognitive impairment, suggesting that the burden of these biomarkers is relevant
Suppression of 12-O-tetradecanoylphorbol-13-acetate-induced ornithine decarboxylase activity by resveratrol derivatives
As demonstrated previously, resveratrol (3,4',5-trihydroxy-trans-stilbene) inhibits 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ornithine decarboxylase (ODC), the key rate limiting enzyme in mammalian polyamine synthesis. Using human bladder epithelial carcinoma HTB-24 cells in culture where resveratrol inhibits induction with an IC50 of 8.8 µM, we now report potential metabolites demonstrate greater activity [tetrabutylammonium (E)-4-(3,5-dihydroxystyryl)phenyl sulfate (IC50 1.2 µM), resveratrol tripotassium 3,5,4'-trisulfate (IC50 1.8 µM), resveratrol tripotassium 3,4'-disulfate (IC50 1.8 µM), and resveratrol tripotassium 3,5-disulfate (IC50 2.3 µM)]. Based on RT-PCR studies, ODC inhibition occurs at the transcriptional level, but this was not due to direct inhibition of protein kinase C (e.g., resveratrol IC50, 79 µM; resveratrol tripotassium 3,5-disulfate IC50, 49 µM). Additional work is underway to more fully investigate this potentially important observation. [This work was supported by program project P01 CA48112 awarded by the National Cancer Institute. SL acknowledges Indo-US Science and Technology Forum (IUSSTF), New Delhi for a Research Fellowship]
Adiabatically coupled systems and fractional monodromy
We present a 1-parameter family of systems with fractional monodromy and
adiabatic separation of motion. We relate the presence of monodromy to a
redistribution of states both in the quantum and semi-quantum spectrum. We show
how the fractional monodromy arises from the non diagonal action of the
dynamical symmetry of the system and manifests itself as a generic property of
an important subclass of adiabatically coupled systems
Blood Pressure and Cognitive Decline Over 8 Years in Middle-Aged and Older Black and White Americans
Although the association between high blood pressure (BP), particularly in midlife, and late-life dementia is known, less is known about variations by race and sex. In a prospective national study of 22 164 blacks and whites ≥45 years without baseline cognitive impairment or stroke from the REGARDS cohort study (Reasons for Geographic and Racial Differences in Stroke), enrolled 2003 to 2007 and followed through September 2015, we measured changes in cognition associated with baseline systolic and diastolic BP (SBP and DBP), as well as pulse pressure (PP) and mean arterial pressure, and we tested whether age, race, and sex modified the effects. Outcomes were global cognition (Six-Item Screener; primary outcome), new learning (Word List Learning), verbal memory (Word List Delayed Recall), and executive function (Animal Fluency Test). Median follow-up was 8.1 years. Significantly faster declines in global cognition were associated with higher SBP, lower DBP, and higher PP with increasing age ( P<0.001 for age×SBP×follow-up-time, age×DBP×follow-up-time, and age×PP×follow-up-time interaction). Declines in global cognition were not associated with mean arterial pressure after adjusting for PP. Blacks, compared with whites, had faster declines in global cognition associated with SBP ( P=0.02) and mean arterial pressure ( P=0.04). Men, compared with women, had faster declines in new learning associated with SBP ( P=0.04). BP was not associated with decline of verbal memory and executive function, after controlling for the effect of age on cognitive trajectories. Significantly faster declines in global cognition over 8 years were associated with higher SBP, lower DBP, and higher PP with increasing age. SBP-related cognitive declines were greater in blacks and men
Quantum integrability of quadratic Killing tensors
Quantum integrability of classical integrable systems given by quadratic
Killing tensors on curved configuration spaces is investigated. It is proven
that, using a "minimal" quantization scheme, quantum integrability is insured
for a large class of classic examples.Comment: LaTeX 2e, no figure, 35 p., references added, minor modifications. To
appear in the J. Math. Phy
Finite-channel chromatic derivative filter banks
Two previous contributions discussed the theory of perfect-reconstruction (PR) chromatic derivative filter banks comprising an infinite number of channels. This paper extends the theory to the case of finite channels. A novel time domain procedure is delineated for designing the synthesis filters that achieve PR in this case
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