Search results for "grain"
showing 10 items of 752 documents
Effect of temperature on the growth of alfa-PbO2 nanostructures
2010
Abstract Ordered arrays of α-PbO 2 nanostructures were grown by galvanostatic anodic deposition into the channels of alumina templates. Electrodepositions were performed in an aqueous solution containing lead acetate and sodium acetate at pH 5.4. Bath temperature and electrodeposition time were varied to check their effect on the growth of nanostructures. It has been found that filling of alumina pores is independent of the time and electrodeposition temperature, whilst height and growth kinetics of nanostructures vary with both parameters. Temperature greatly influences morphology: wires grown at room temperature consisted of clusters of particles, leading to poorly compact structures, whi…
Assessing use and suitability of scanning electron microscopy in the analysis of micro remains in dental calculus
2014
AbstractDental calculus is increasingly recognized as a major reservoir of dietary information. Palaeodietary studies using plant and animal micro remains (e.g. phytoliths, pollen, sponge spicules, and starch grains) trapped in calculus have the potential to revise our knowledge of the dietary role of plants in past populations. The conventional methods used to isolate and identify these micro remains rely on removing them from their microenvironment in the calculus, thus the microenvironment that traps and preserves micro remains is not understood. By using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM–EDX) on modern chimpanzee calculus from the Taï Forest, Côt…
A Wind Tunnel and Theoretical Study of the Melting Behavior of Atmospheric Ice Particles. IV: Experiment and Theory for Snow Flakes
1990
Abstract An experiment in the Mainz vertical Cloud Tunnel is described in which natural and laboratory-made aggregates of snow crystals (snow flakes) were melted under free fall conditions in the vertical air stream of the tunnel, which was allowed to warm up at the rates experienced by falling snow flakes in the atmosphere. The variation of the fall mode, the fall velocity, and the percentage of ice melted, as a function of percentage of distance travelled for 99% melting was recorded by cinematography. The laboratory results were confirmed by the results of a theoretical heat transfer model which we developed for the melting of a snow flake. In this model a snow flake was idealized by an …
The onset of the rainy season and farmers’ sowing strategy for pearl millet cultivation in Southwest Niger
2011
A multi-year (2004-2009) field survey of on-farm sowing practices in 10 villages located in south-west Niger close to Niamey, is analysed to investigate the relationships (i) between rainfall and the sowing date of pearl millet and the risk of sowing failure, (ii) between sowing and meteorological/agro-climatic onset dates, (iii) between sowing/onset dates, and simulated and observed yield/biomass at the end of the season. Even if some villages sow without any synchronous or anterior rainfall, most parcels (73% out of the 1551 available cases) are sown during and just after a 2-day wet spell receiving at least 10 mm. In fact, there is a strong correlation (r = 0.82-0.95 depending on onset d…
Initial chemical transport of reducing elements and chemical reactions in oxide cathode base metal
2002
Abstract In the present work, the formation of compounds associated to the diffusion of reducing elements (Mg and Al) to the nickel surface of a one-piece oxide cathode has been studied. Those compounds have been evidenced after the annealing steps at high temperature performed on cathode base metal prior to the emitting coating deposition. Therefore, they form the “initial” interface between the nickel and the coating, in other words, the interface existing at the beginning of cathode life. Extensive analysis to characterize the nickel base prior to coating deposition has been performed by means of scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), …
Impaired Glutamatergic Neurotransmission in Migraine With Aura? Evidence by an Input-Output Curves Transcranial Magnetic Stimulation Study
2011
(Headache 2011;51:726-733) Objective.— An imbalance between activity of inhibitory and facilitatory intracortical circuits could play a central role in migraine etiology. We used input–output curves to achieve further information about intracortical excitability of motor cortex in migraine with aura. Methods.— Input–output curves were measured in the right abductor pollicis brevis muscle at rest in 12 patients suffering from migraine with aura and 8 healthy subjects. Stimuli were delivered at intensity ranging from 100% to 160% of resting motor threshold with 10-second inter-stimulus intervals. Seven patients were studied before and during treatment with levetiracetam. Results.— Results sho…
Understanding sigma-phase precipitation in a stabilized austenitic stainless steel (316Nb) through complementary CALPHAD-based and experimental inves…
2014
Abstract Sigma-phase precipitation in a 316Nb “stabilized” austenitic stainless steel was studied through complementary CALPHAD-based and dedicated experimental investigations. Thermokinetic calculations performed using Thermo-Calc (with the DICTRA module) and MatCalc software showed that the sigma phase (σ) precipitated directly at γ-austenite grain boundaries (GB) via a common solid-state reaction when carbon and nitrogen contents fell below a critical threshold. Residual δ ferrite was found to be more susceptible to σ-phase precipitation; this type of precipitation occurred via two mechanisms that depended on the concentration profiles of δ-ferrite stabilizing elements induced by previou…
Data from: Ancient symbiosis confers desiccation resistance to stored grain pest beetles
2017
Microbial symbionts of insects provide a range of ecological traits to their hosts that are beneficial in the context of biotic interactions. However, little is known about insect symbiont-mediated adaptation to the abiotic environment, e.g. temperature and humidity. Here we report on an ancient clade of intracellular, bacteriome-located Bacteroidetes symbionts that are associated with grain and wood pest beetles of the phylogenetically distant families Silvanidae and Bostrichidae. In the saw-toothed grain beetle Oryzaephilus surinamensis, we demonstrate that the symbionts affect cuticle thickness, melanization and hydrocarbon profile, enhancing desiccation resistance and thereby strongly i…
Learning to Navigate in the Gaussian Mixture Surface
2021
In the last years, deep learning models have achieved remarkable generalization capability on computer vision tasks, obtaining excellent results in fine-grained classification problems. Sophisticated approaches based-on discriminative feature learning via patches have been proposed in the literature, boosting the model performances and achieving the state-of-the-art over well-known datasets. Cross-Entropy (CE) loss function is commonly used to enhance the discriminative power of the deep learned features, encouraging the separability between the classes. However, observing the activation map generated by these models in the hidden layer, we realize that many image regions with low discrimin…
Monte Carlo Simulations of Surfaces and Interfaces in Materials
1996
Many applications of materials are controlled by their surface and interface properties. In particular, metallic alloys (but also mixed dielectric materials and amorphous polymer blends) are not homogeneously mixed on a microscopic length scale, although they are macroscopically homogeneous. Depending on the preparation of the sample, there exists a heterophase microstructure, with typical domain sizes, e.g. in the 1 to 102 µm range, separated by interfaces between them. The physical properties of such intrinsic interfaces (grain boundaries between small crystallites, antiphase domain boundaries in ordered alloys, Bloch walls in magnetic materials, etc.) are not only an important controllin…