Expert opinion: uncertainties in hydraulic roughness

Water level predictions in rivers are used for a variety of purposes in water management. For example, designing flood defence measures and evaluating natural rehabilitation in flood plains, cannot be done without water level predictions. However, these water level predictions are uncertain and a major part of this uncertainty is caused by the uncertainty in the roughness coefficient (Van der Klis, 2003; Van Vuren, 2005). Hydraulic roughness in rivers results from (among others): grain roughness, form roughness and vegetation roughness. The roughness coefficient is uncertain because different elements creating the hydraulic roughness are uncertain (e.g. grain size, dune height). To quantify the influence of the uncertain roughness coefficient on water level predictions, we first need a quantification of the uncertainty in the roughness coefficient

Variations in roughness predictions (flume experiments)

Data of flume experiments with bed forms are used to analyze and compare different roughness predictors. In this study, the hydraulic roughness consists of grain roughness and form roughness. We predict the grain roughness by means of the size of the sediment. The form roughness is predicted by three approaches: Van Rijn (1984), Vanoni & Hwang (1967) and Engelund (1966). The total roughness values (friction factors) are compared with the roughness values according to the DarcyWeisbach equation. Results show that the different methods predict different friction factors. In future research uncertainties in the hydraulic roughness will be taken into account to determine their influence on the computed water levels

Radio-frequency driven dipole-dipole interactions in spatially separated volumes

Radio-frequency (rf) fields in the MHz range are used to induce resonant energy transfer between cold Rydberg atoms in spatially separated volumes. After laser preparation of the Rydberg atoms, dipole-dipole coupling excites the 49s atoms in one cylinder to the 49p state while the 41d atoms in the second cylinder are transferred down to the 42p state. The energy exchanged between the atoms in this process is 33 GHz. An external rf-field brings this energy transfer into resonance. The strength of the interaction has been investigated as a function of amplitude (0-1 V/cm) and frequency (1-30 MHz) of the rf-field and as a function of a static field offset. Multi-photon transitions up to fifth order as well as selection rules prohibiting the process at certain fields have been observed. The width of the resonances has been reduced compared to earlier results by switching off external magnetic fields of the magneto-optical trap, making sub-MHz spectroscopy possible. All features are well reproduced by theoretical calculations taking the strong ac-Stark shift due to the rf-field into account

Antioxidant Supplementation in Oxidative Stress-Related Diseases: What Have We Learned from Studies on Alpha-Tocopherol?

Oxidative stress has been proposed as a key contributor to lifestyle- and age-related diseases. Because free radicals play an important role in various processes such as immune responses and cellular signaling, the body possesses an arsenal of different enzymatic and non-enzymatic antioxidant defense mechanisms. Oxidative stress is, among others, the result of an imbalance between the production of various reactive oxygen species (ROS) and antioxidant defense mechanisms including vitamin E (α-tocopherol) as a non-enzymatic antioxidant. Dietary vitamins, such as vitamin C and E, can also be taken in as supplements. It has been postulated that increasing antioxidant levels through supplementation may delay and/or ameliorate outcomes of lifestyle- and age-related diseases that have been linked to oxidative stress. Although supported by many animal experiments and observational studies, randomized clinical trials in humans have failed to demonstrate any clinical benefit from antioxidant supplementation. Nevertheless, possible explanations for this discrepancy remain underreported. This review aims to provide an overview of recent developments and novel research techniques used to clarify the existing controversy on the benefits of antioxidant supplementation in health and disease, focusing on α-tocopherol as antioxidant. Based on the currently available literature, we propose that examining the difference between antioxidant activity and capacity, by considering the catabolism of antioxidants, will provide crucial knowledge on the preventative and therapeutical use of antioxidant supplementation in oxidative stress-related diseases

Numerical study of two-body correlation in a 1D lattice with perfect blockade

We compute the dynamics of excitation and two-body correlation for two-level "pseudoatoms" in a 1D lattice. We adopt a simplified model where pair excitation within a finite range is perfectly blocked. Each superatom is initially in the ground state, and then subjected to an external driving laser with Rabi frequency satisfying a Poissonian distribution, mimicking the scenario as in Rydberg gases. We find that two-body quantum correlation drops very fast with the distance between pseudoatoms. However, the total correlation decays slowly even at large distance. Our results may be useful to the understanding of Rydberg gases in the strong blockade regime

Subtraction of Bright Point Sources from Synthesis Images of the Epoch of Reionization

Bright point sources associated with extragalactic AGN and radio galaxies are an important foreground for low frequency radio experiments aimed at detecting the redshifted 21cm emission from neutral hydrogen during the epoch of reionization. The frequency dependence of the synthesized beam implies that the sidelobes of these sources will move across the field of view as a function of observing frequency, hence frustrating line-of-sight foreground subtraction techniques. We describe a method for subtracting these point sources from dirty maps produced by an instrument such as the MWA. This technique combines matched filters with an iterative centroiding scheme to locate and characterize point sources in the presence of a diffuse background. Simulations show that this technique can improve the dynamic range of EOR maps by 2-3 orders of magnitude.Comment: 11 pages, 8 figures, 1 table, submitted to PAS

Both low circulating insulin-like growth factor-1 and high-density lipoprotein cholesterol are associated with hair loss in middle-aged women.

YesBackground: Multiple biomarkers have been associated with hair loss in women, but studies showed inconsistent results. Objective: We investigated the association between markers of cardiovascular disease risk (e.g., serum lipid levels and hypertension) and aging (e.g., 25-hydroxyvitamin D and insulin-like growth factor) with hair loss in a population of middle-aged women. Methods: In a random subgroup of 323 middle-aged women (mean age: 61.5 years) from the Leiden Longevity Study, hair loss was graded by three assessors using the Sinclair scale; women with a mean score higher than 1.5 were classified as cases with hair loss. Results: Every standard deviation increase in HDL cholesterol was associated with a 0.65 times lower risk (95% confidence interval [CI]: 0.46–0.91) of hair loss; for IGF-1 the risk was 0.68 times lower (95% CI: 0.48–0.97) per standard deviation increase, independent of the other studied variables. Women with both IGF-1 and HDL cholesterol levels below the median of the study population had a 3.47 times higher risk (95% CI: 1.30–9.25) of having hair loss. Limitations: The observational setting limits causal inference of the findings. Conclusion: Low HDL cholesterol and IGF-1 were associated with a higher risk of hair loss in women.This study was funded by the Innovation Oriented Research Program on Genomics (SenterNovem; IGE01014 and IGE5007), the Centre for Medical Systems Biology (CMSB), the Netherlands Genomics Initiative/Netherlands Organization for Scientific Research (05040202 and 050-060-810, NCHA), Unilever PLC and the European Union-funded Network of Excellence Lifespan (FP6 036894)

Разработка технологического процесса изготовления корпуса КС-4372.205.152.001

В аналитической части приводится описание служебного назначения детали, а также рассмотрен базовый технологический процесс с отработкой его на технологичность. В технологической части производится выбор заготовки и методов ее получения, составление маршрута механической обработки в условиях серийного производства. В конструкторской части спроектировано специальное приспособление. В разделе "Финансовый менеджмент, ресурсоэффективность и ресурсосбережение" произведен расчет себестоимости изготовления детали. В части "Социальная ответственность" рассмотрены опасные и вредные производственные факторы, возникающие при изготовлении детали, и мероприятия по улучшению условий труда.The analytical part is a description of a service appointment details, and also consider the basic process of working off it at the techno-logical. In the process of selection is blank, and methods of obtaining, compiling mechanical processing route in a series of production. In the design of the designed special devic. In the section “Financial Management, Resource Efficiency and Resource Saving”, the cost of manufacturing the part is calculated. As part of the " Social Responsibility " considered dangerous and harmful factors arising in the manufacture of parts and activities to improve working conditions