A Fast Algorithm for Computing the p-Curvature

We design an algorithm for computing the $p$-curvature of a differential system in positive characteristic $p$. For a system of dimension $r$ with coefficients of degree at most $d$, its complexity is \softO (p d r^\omega) operations in the ground field (where $\omega$ denotes the exponent of matrix multiplication), whereas the size of the output is about $p d r^2$. Our algorithm is then quasi-optimal assuming that matrix multiplication is (\emph{i.e.} $\omega = 2$). The main theoretical input we are using is the existence of a well-suited ring of series with divided powers for which an analogue of the Cauchy--Lipschitz Theorem holds.Comment: ISSAC 2015, Jul 2015, Bath, United Kingdo

Metric, nonmetric, and geometric morphometric methods of sex estimation using the distal humerus

Sex estimation is one of the most important, and arguably the first, parts of the biological profile that is estimated for purposes of human identification. This study will examine the utility of the distal humerus in sex estimation. The goal of this research is to corroborate the usefulness of the distal humerus in sex estimation and the usefulness of geometric morphometrics in sex estimation, as well as validate metric and visual methods for sex estimation using the distal humerus. Multiple methods of sex estimation are necessary because complete skeletons are rarely found, and often only fragments are discovered. Three methods of sex estimation utilizing the distal humerus are used in this study: epicondylar breadth (n=448), nonmetric traits per Rogers (1999) and Vance et al. (2011 (n=444)), and geometric morphometrics via a Microscribe digitizer and MorphoJ software (n=227). The sample was taken from the William M. Bass Donated Skeletal Collection and was primarily composed of White Americans. The male to female ratio was approximately equal. The results of the metric aspect of the study showed a classification accuracy of 88.84% with low intra-observer and inter-observer error rates. The results of the nonmetric aspect of the study showed a classification accuracy of 77% when all traits were combined with low intra-observer and high inter-observer error rates. The results of the geometric morphometric aspect of the study showed a classification accuracy of 55% for all landmarks, 57% for anterior landmarks, and 63% for posterior landmarks. The results show that not only is the epicondylar breadth a reliable and effective method of sex estimation, it is easily repeatable by other observers. The nonmetric method is useful when epicondylar breadth cannot be measured or when an observer is familiar with the method. The geometric morphometric method is not as strong as the other two methods, but with further research and modifications may become a feasible option for sex estimation using the distal humerus. The author concludes that the distal humerus is sexually dimorphic and can be used to estimate sex accurately

Synthesis of carburets of hydrogen

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On the galvanic oxidation of gold

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Wireless Wearable Photoplethysmography Sensors for Continuous Blood Pressure Monitoring

Blood Pressure (BP) is a crucial vital sign taken into consideration for the general assessment of patient’s condition: patients with hypertension or hypotension are advised to record their BP routinely. Particularly, hypertension is emphasized by stress, diabetic neuropathy and coronary heart diseases and could lead to stroke. Therefore, routine and long-term monitoring can enable early detection of symptoms and prevent life-threatening events. The gold standard method for measuring BP is the use of a stethoscope and sphygmomanometer to detect systolic and diastolic pressures. However, only discrete measurements are taken. To enable pervasive and continuous monitoring of BP, recent methods have been proposed: pulse arrival time (PAT) or PAT difference (PATD) between different body parts are based on the combination of electrocardiogram (ECG) and photoplethysmography (PPG) sensors. Nevertheless, this technique could be quite obtrusive as in addition to at least two contacts/electrodes to measure the differential voltage across the left arm/leg/chest and the right arm/leg/chest, ECG measurements are easily corrupted by motion artefacts. Although such devices are small, wearable and relatively convenient to use, most devices are not designed for continuous BP measurements. This paper introduces a novel PPG-based pervasive sensing platform for continuous measurements of BP. Based on the principle of using PAT to estimate BP, two PPG sensors are used to measure the PATD between the earlobe and the wrist to measure BP. The device is compared with a gold standard PPG sensor and validation of the concept is conducted with a preliminary study involving 9 healthy subjects. Results show that the mean BP and PATD are correlated with a 0.3 factor. This preliminary study shows the feasibility of continuous monitoring of BP using a pair of PPG placed on the ear lobe and wrist with PATD measurements is possible

Variability in energy cost of running at the end of a triathlon and a marathon

International audienceThe aim of this study was to investigate the increase in energy cost of running occurring at the end of a triathlon and a marathon event and to link them to the metabolic and hormonal changes, as well as to variations in stride length. Seven subjects took part in 3 experimental situations: a 2 h 15 min triathlon (30 min swimming, 60 min cycling and 45 min running), a 2 h 15 min marathon (MR) were the fast 45 min were run at the same speed as the triathlon run (TR), and a 45 min isolated run (IR) done at triathlon speed. The results show that energy cost during MR was higher than during TR (p < 0.01) (+ 8.9 %). Similar observations were made for pulmonary ventilation (+ 7.9 %) and heart rate (+ 6.3 %). Moreover, the values were significantly greater than the values obtained during the IR. TR and MR lead to greater weight loss (p < 0.01) (2.4±0.3 kg) than IR (1 ± 0.2 kg). The triathlon and the marathon produced a large decrease in plasma volume (respectively 19.6 ± 1.4 % and 12.9 ± 1.1 %) compared to IR (2 ± 0.4 %). Plasma renin activity was higher for the triathlon and the marathon than for the IR (p < 0.01). MR produces a significantly greater increase in plasma free fatty acids (F.F.A.) than TR (p < 0.05) and IR (p < 0.01). In addition, the F.F.A. at the end of TR were significantly higher than IR (p < 0.05). At the end of the trial the mean stride lengths for TR and IR were greater (+ 15 %) (p <0.01) than for MR. This study, carried out with subjects running overground, confirms the decrease in running efficiency previously shown at the end of a laboratory triathlon, and demonstrates that this decrease is lower than that occurring during a marathon

Ice Formation on Kaolinite: Insights from Molecular Dynamics Simulations

The formation of ice affects many aspects of our everyday life as well as technologies such as cryotherapy and cryopreservation. Foreign substances almost always aid water freezing through heterogeneous ice nucleation, but the molecular details of this process remain largely unknown. In fact, insight into the microscopic mechanism of ice formation on different substrates is difficult to obtain even via state-of-the-art experimental techniques. At the same time, atomistic simulations of heterogeneous ice nucleation frequently face extraordinary challenges due to the complexity of the water-substrate interaction and the long timescales that characterize nucleation events. Here, we have investigated several aspects of molecular dynamics simulations of heterogeneous ice nucleation considering as a prototypical ice nucleating material the clay mineral kaolinite, which is of relevance in atmospheric science. We show via seeded molecular dynamics simulations that ice nucleation on the hydroxylated (001) face of kaolinite proceeds exclusively via the formation of the hexagonal ice polytype. The critical nucleus size is two times smaller than that obtained for homogeneous nucleation at the same supercooling. Previous findings suggested that the flexibility of the kaolinite surface can alter the time scale for ice nucleation within molecular dynamics simulations. However, we here demonstrate that equally flexible (or non flexible) kaolinite surfaces can lead to very different outcomes in terms of ice formation, according to whether or not the surface relaxation of the clay is taken into account. We show that very small structural changes upon relaxation dramatically alter the ability of kaolinite to provide a template for the formation of a hexagonal overlayer of water molecules at the water-kaolinite interface, and that this relaxation therefore determines the nucleation ability of this mineral

Mesopelagic N-2 fixation related to organic matter composition in the Solomon and Bismarck Seas (Southwest Pacific)

Dinitrogen (N-2) fixation was investigated together with organic matter composition in the mesopelagic zone of the Bismarck (Transect 1) and Solomon (Transect 2) Seas (Southwest Pacific). Transparent exopolymer particles (TEP) and the presence of compounds sharing molecular formulae with saturated fatty acids and sugars, as well as dissolved organic matter (DOM) compounds containing nitrogen (N) and phosphorus (P) were higher on Transect 1 than on Transect 2, while oxygen concentrations showed an opposite pattern. N-2 fixation rates (up to similar to 1 nmol N L-1 d(-1)) were higher in Transect 1 than in Transect 2, and correlated positively with TEP, suggesting a dependence of diazotroph activity on organic matter. The scores of the multivariate ordination of DOM molecular formulae and their relative abundance correlated negatively with bacterial abundances and positively with N-2 fixation rates, suggesting an active bacterial exploitation of DOM and its use to sustain diazotrophic activity. Sequences of the nifH gene clustered with Alpha-, Beta-, Gamma- and Deltaproteobacteria, and included representatives from Clusters I, III and IV. A third of the clone library included sequences close to the potentially anaerobic Cluster III, suggesting that N-2 fixation was partially supported by presumably particle-attached diazotrophs. Quantitative polymerase chain reaction (qPCR) primer-probe sets were designed for three phylotypes and showed low abundances, with a phylotype within Cluster III at up to 10(3) nifH gene copies L-1. These results provide new insights into the ecology of non-cyanobacterial diazotrophs and suggest that organic matter sustains their activity in the mesopelagic ocean