Active and passive stabilization of body pitch in insect flight

Flying insects have evolved sophisticated sensory–motor systems, and here we argue that such systems are used to keep upright against intrinsic flight instabilities. We describe a theory that predicts the instability growth rate in body pitch from flapping-wing aerodynamics and reveals two ways of achieving balanced flight: active control with sufficiently rapid reactions and passive stabilization with high body drag. By glueing magnets to fruit flies and perturbing their flight using magnetic impulses, we show that these insects employ active control that is indeed fast relative to the instability. Moreover, we find that fruit flies with their control sensors disabled can keep upright if high-drag fibres are also attached to their bodies, an observation consistent with our prediction for the passive stability condition. Finally, we extend this framework to unify the control strategies used by hovering animals and also furnish criteria for achieving pitch stability in flapping-wing robots.     

Lateral diffusion of thiol ligands on the surface of au nanoparticles: an electron paramagnetic resonance study

The lateral mobility of the thiolate ligands on the surface of Au nanoparticles was probed by EPR spectroscopy. This was achieved by using bisnitroxide ligands, which contained a disulfide group (to ensure attachment to the Au surface) and a cleavable ester bridge connecting the two spin-labeled branches of the molecule. Upon adsorption of these ligands on the surface of Au nanoparticles, the two spin-labeled branches were held next to each other by the ester bridge as evidenced by the spin-spin interactions. Cleavage of the bridge removed the link that kept the branches together. CW and pulsed EPR (DEER) experiments showed that the average distance between the adjacent thiolate branches on the Au nanoparticle surface only marginally increased after cleaving the bridge and thermal treatment. This implies that the lateral diffusion of thiolate ligands on the nanoparticle surface is very slow at room temperature and takes hours even at elevated temperatures (90 degrees C). The changes in the distance distribution observed at high temperature are likely due to ligands hopping between the nanoparticles rather than diffusing on the particle surface.     

Testing tubewell platform color as a rapid screening tool for arsenic and manganese in drinking water wells

A low-cost rapid screening tool for arsenic (As) and manganese (Mn) in groundwater is urgently needed to formulate mitigation policies for sustainable drinking water supply. This study attempts to make statistical comparison between tubewell (TW) platform color and the level of As and Mn concentration in groundwater extracted from the respective TW (n = 423), to validate platform color as a screening tool for As and Mn in groundwater. The result shows that a black colored platform with 73% certainty indicates that well water is safe from As, while with 84% certainty a red colored platform indicates that well water is enriched with As, compared to WHO drinking water guideline of 10 μg/L. With this guideline the efficiency, sensitivity, and specificity of the tool are 79%, 77%, and 81%, respectively. However, the certainty values become 93% and 38%, respectively, for black and red colored platforms at 50 μg/L, the drinking water standards for India and Bangladesh. The respective efficiency, sensitivity, and specificity are 65%, 85%, and 59%. Similarly for Mn, black and red colored platform with 78% and 64% certainty, respectively, indicates that well water is either enriched or free from Mn at the Indian national drinking water standard of 300 μg/L. With this guideline the efficiency, sensitivity, and specificity of the tool are 71%, 67%, and 76%, respectively. Thus, this study demonstrates that TW platform color can be potentially used as an initial screening tool for identifying TWs with elevated dissolved As and Mn, to make further rigorous groundwater testing more intensive and implement mitigation options for safe drinking water supplies.     

基于主观评价的非织造布质量客观评价方法——QualiVlies

非织造布在世界范围内广泛生产.全球标准是非织造布生产的一个竞争因素.目前,非织造布在市场中的优势不仅是价格便宜,而且质量优良.因此,为了保持非织造布的市场,有必要提高非织造布质量.在线检测系统可检测破洞、薄区、厚区等疵点,但影响非织造布质量的不仅仅是疵点,还取决于其光学均匀性.尤其对于面密度较小(如15 g/m2)的非织造布,明显的不规则纤维分布会影响顾客的主观评价.阐述了一种代表主观评价的客观图像分析方法.     

Verification of cardiac tissue electrophysiology simulators using an N-version benchmark

Ongoing developments in cardiac modelling have resulted, in particular, in the development of advanced and increasingly complex computational frameworks for simulating cardiac tissue electrophysiology. The goal of these simulations is often to represent the detailed physiology and pathologies of the heart using codes that exploit the computational potential of high-performance computing architectures. These developments have rapidly progressed the simulation capacity of cardiac virtual physiological human style models; however, they have also made it increasingly challenging to verify that a given code provides a faithful representation of the purported governing equations and corresponding solution techniques. This study provides the first cardiac tissue electrophysiology simulation benchmark to allow these codes to be verified. The benchmark was successfully evaluated on 11 simulation platforms to generate a consensus gold-standard converged solution. The benchmark definition in combination with the gold-standard solution can now be used to verify new simulation codes and numerical methods in the future.     

Chemistry effects on the crack susceptibility of structural steels during continuous casting

This work is a review of research results, which have been determined in recent years in order to reveal the effects of the chemical compositions on the high temperature properties of structural steels. Special emphasis has been laid on the solidification structure, phase reactions and precipitates. For this comparison exemplary different structural steel grades have been chosen. The effect of the chemical composition on the solidification structure is shown by increasing Ni mass contents up to 10 %, the influence on the phase transformation is illustrated on the basis of a steel with a Mn mass content of 1.6 % and varying carbon contents. The influence of precipitates has been investigated both on the basis of the Mn/S‐ratio and by microalloyed structural steels with different Nb, V and Ti additions. For all these steel grades the laboratory testing conditions were the same. The high temperature properties of steels can be investigated by high temperature tensile tests; the range of good ductility is determined by the measurement of the reduction of area, e.g. RoA > 50 % or >70 %. The upper limit of the ductility range is the temperature of zero ductility, T_ZD%. The lower limit of the good ductility range is marked by the transition to the ductility minimum II. The experiments for a series of different structural steels show that the hot ductility properties are affected by the metallurgical phenomena mentioned before.     

Titanium–aluminum–nitride coatings for satellite temperature control

Intense solar irradiation, radiative cooling to outer space, and internal heat generation determine the equilibrium temperature of a spacecraft. The balance between the solar absorption and thermal emittance of the surface is therefore crucial, in particular for autonomous parts directly exposed to the solar radiation and thermally insulated from the main thermal mass of the spacecraft. The material composition but also the coating thickness are found to influence the equilibrium temperature of an object in space. In this paper we report on a systematic search for a suitable composition and thickness of Ti_xAl_yN_z alloy coatings prepared by reactive, unbalanced magnetron sputtering from targets consisting of differently sized titanium and aluminum sectors. The films were deposited on glass, glassy carbon, aluminum sheet metal, and on sputtered aluminum and Ti_xAl_(1−x) films on glass. The stoichiometry and sheet resistance of the films was determined with Rutherford backscattering and four-point probe measurements respectively. Reflectance spectra for the visible and infrared spectral ranges were used to obtain average solar absorptance and thermal emittance values used in model calculations of the equilibrium temperature. Neglecting internal heat contributions, the lowest calculated equilibrium temperature in orbit around the Earth, 32.5°C, was obtained for a 505-nm-thick Ti_0.14Al_0.47N_0.40-film.     

Lead associated caries development in children living in a lead contaminated area, Thailand

In an observational cross-sectional design, a sample of 292 children aged 6-11 years from two primary schools around a shipyard area, known to be an area contaminated with lead (from the industry), were examined to verify the cariogenicity of lead. The number of decayed and filled surfaces on deciduous teeth (dfs), and the number of decayed, missing, and filled surfaces on permanent teeth (DMFS), the salivary flow rate, pH, buffer capacity, oral hygiene, Lactobacillus spp. and mutans streptococci counts were recorded. The mean (range) of DMFS and dfs were respectively 1.3 (range 0-17) and 13.2 (range 0-45); and the geometric mean blood lead level (PbB) and SD were 7.2 and 1.5 microg/dl. The level of dfs, but not DMFS correlated with the blood lead level (R(s)=0.25, p=0.00 / R(s)=0.09, p=0.14). The odds ratio for DMFS>or=1 and dfs>5 for a doubling of PbB after adjusting for other factors were 1.28 (95%CI, 0.81-2.04; p value=0.35) and 2.39 (95%CI, 1.36-4.20; p value=0.004), respectively. The cariogenicity of lead is evident in deciduous teeth but not in permanent teeth for this age group.     

Distribution and mobility of arsenic in the Río Dulce alluvial aquifers in Santiago del Estero Province, Argentina

Factors controlling arsenic (As) mobilization in the aquifers of the Río Dulce alluvial cone were investigated. Groundwater analyses show severe As contamination (average concentration of 743 mug/L) from geogenic sources, but spatial variability of As concentration is considerable. Sequential leaching of sediment samples from unsaturated zone using de-ionised water, bicarbonate, acetate, and oxalate extracted As to different extents. Sediment oxalate extraction showed that Al and Mn oxide and hydroxides are more abundant than Fe oxides and hydroxides, in spite of similar total Fe, Mn, and Al concentrations in the sediment. Speciation calculations performed for saturated zone samples indicated that Fe and Al oxides and hydroxides are stable in groundwater, suggesting that As adsorption processes may be to some extent controlled by the presence of Fe and Al mineral phases. Principal Component Analysis (PCA) showed that As is related to F, V, Mo, B, Si, most likely due to their common origin in volcanic ash. This suggests the volcanic ash as the probable source of groundwater As. Locally, elevated pH values linked to carbonate dissolution, cation exchange, and dissolution of silicates promote release of adsorbed As. Another factor contributing to the release of As locally may be the input of organic matter from excessive irrigation. The conceptual model of As release includes: i) As influx from dissolution of volcanic glass in volcanic ash, ii) adsorption of As on the surface of Fe and Al mineral phases in relatively low pH zones, and iii) high mobility of As in high pH zones. Future work should be focused on the determination of mineralogical forms of As in volcanic ash and on detailed investigation on factors controlling As mobility.