3,914 research outputs found
Dynamic load management and optimum sizing of stand-alone hybrid PV/Wind system.
Simulation algorithms for the sizing of stand-alone hybrid PV/Wind systems are a powerful tool in evaluating the optimum configuration that would cover the energy demand with a predefined reliability level at the lowest cost. Several parameters such as the interval of the simulation (day, day-night, hourly) and the consumption profile may significantly affect the optimum configuration. This paper examines the effect of these parameters within an optimum sizing simulation algorithm developed. The effect of these parameters was particularly evident at low battery capacities, which involve optimum configurations resulting in minimum cost. Furthermore, shift-able loads in the hourly-based weekly profile assumed in this study were identified, and a dynamic load management functionality was developed. In this approach, loads that could be shifted through time were dynamically allocated during periods of excess energy production by the hybrid PV/Wind system. The results showed an increase in system reliability from 95% to 97% when load shifting was introduced. Finally, sizing the system for only the static (non-shift-able loads) proved to withstand the addition of the extra shift-able loads while retaining the 95% reliability level when the load management functionality was introduced. Thus, a smaller installation with lower cost is achieved
Rescuing Quartic and Natural Inflation in the Palatini Formalism
When considered in the Palatini formalism, the Starobinsky model does not
provide us with a mechanism for inflation due to the absence of a propagating
scalar degree of freedom. By (non)--minimally coupling scalar fields to the
Starobinsky model in the Palatini formalism we can in principle describe the
inflationary epoch. In this article, we focus on the minimally coupled quartic
and natural inflation models. Both theories are excluded in their simplest
realization since they predict values for the inflationary observables that are
outside the limits set by the Planck data. However, with the addition of the
term and the use of the Palatini formalism, we show that these models can
be rendered viable.Comment: JCAP accepted version, 16 pages, 7 figure
Delayed systolic blood pressure recovery following exercise as a mechanism of masked uncontrolled hypertension in chronic kidney disease
Background
Among people treated for hypertension, the presence of elevated blood pressure (BP) out of the clinic but normal BP in the clinic is called masked uncontrolled hypertension (MUCH). What causes MUCH remains unknown. The purpose of this study was to answer the question of whether patients with MUCH have an increased hemodynamic reactivity to exercise and delayed hemodynamic recovery following exercise.
Methods
Four groups were compared: controlled hypertension (CH, n = 58), MUCH (n = 34) and uncontrolled hypertension (UCH, n = 12), all of which had chronic kidney disease (CKD), and a group of healthy normal volunteers who did not have hypertension or CKD (n = 16). All participants underwent assessment of 24-h ambulatory BP monitoring, BP measurement during a graded symptom-limited exercise using a cycle ergometer and BP recovery over 7 min following exercise.
Results
Exercise-induced increase in systolic BP was similar among the four groups. When compared with healthy controls, recovery of systolic BP following termination of exercise was blunted among the CKD groups in unadjusted (P < 0.0001) and adjusted (P < 0.001) models. During recovery, the healthy control group had 5.9% decline in systolic BP per minute. In contrast, MUCH had only 3.3% per minute reduction and the UCH group had 0.3% reduction per minute. A test of linear trend was significant (P = 0.002, adjusted model).
Conclusion
Because there was no impairment in the heart rate recovery among groups, we speculate that the parasympathetic pathway appears intact among treated hypertensives with CKD. However, the failure to withdraw sympathetic tone upon termination of exercise causes ongoing vasoconstriction and delayed systolic BP recovery providing a biological basis for MUCH. Delayed recovery from exercise-induced hypertension in those with poorly controlled BP provides potentially a new target to assure round-the-clock BP control
Advanced X-ray Absorption Spectroscopy Analysis to Determine Structure-Activity Relationships for Cu-Zeolites in the Direct Conversion of Methane to Methanol
A randomized trial of intravenous and oral iron in chronic kidney disease
Although iron is commonly used to correct iron deficiency anemia (IDA) in chronic kidney disease (CKD), its effect on kidney function is unclear. To assess this, we randomly assigned patients with stage 3 and 4 CKD and IDA to either open-label oral ferrous sulfate (69 patients to 325 mg three times daily for 8 weeks) or intravenous iron sucrose (67 patients to 200 mg every 2 weeks, total 1 g). The primary outcome was the between-group difference in slope of measured glomerular filtration rate (mGFR) change over two years. The trial was terminated early on the recommendation of an independent data and safety monitoring board based on little chance of finding differences in mGFR slopes, but a higher risk of serious adverse events in the intravenous iron treatment group. mGFR declined similarly over two years in both treatment groups (oral -3.6 ml/min per 1.73 m(2), intravenous -4.0 ml/min per 1.73 m(2), between-group difference -0.35 ml/min per 1.73 m(2); 95% confidence interval -2.9 to 2.3). There were 36 serious cardiovascular events among 19 participants assigned to the oral iron treatment group and 55 events among 17 participants of the intravenous iron group (adjusted incidence rate ratio 2.51 (1.56-4.04)). Infections resulting in hospitalizations had a significant adjusted incidence rate ratio of 2.12 (1.24-3.64). Thus, among non-dialyzed patients with CKD and IDA, intravenous iron therapy is associated with an increased risk of serious adverse events, including those from cardiovascular causes and infectious diseases
Electric-field noise from carbon-adatom diffusion on a Au(110) surface: first-principles calculations and experiments
The decoherence of trapped-ion quantum gates due to heating of their motional
modes is a fundamental science and engineering problem. This heating is
attributed to electric-field noise arising from the trap-electrode surfaces. In
this work, we investigate the source of this noise by focusing on the diffusion
of carbon-containing adsorbates on the surface of Au(110). We show by density
functional theory, based on detailed scanning probe microscopy, how the carbon
adatom diffusion on the gold surface changes the energy landscape, and how the
adatom dipole moment varies with the diffusive motion. A simple model for the
diffusion noise, which varies quadratically with the variation of the dipole
moment, qualitatively reproduces the measured noise spectrum, and the estimate
of the noise spectral density is in accord with measured values.Comment: 8 pages, 6 figure
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