429 research outputs found
Trace element content and magnetic properties of commercial HOPG samples studied by ion beam microscopy and SQUID magnetometry
In this study, the impurity concentration and magnetic response of nine
highly oriented pyrolytic graphite (HOPG) samples with different grades and
from different providers were determined using ion beam microscopy and SQUID
magnetometry. Apart from sideface contaminations in the as-received state, bulk
contamination of the samples in most cases consists of disk-shaped micron-sized
particles made of Ti and V with an additional Fe contamination around the grain
perimeter. The saturation magnetization typically increases with Fe
concentration, however, there is no simple correlation between Fe content and
magnetic moment. The saturation magnetization of one, respectively six, out of
nine samples clearly exceeds the maximum contribution from pure Fe or Fe3C. For
most samples the temperature dependence of the remanence decreases linearly
with T - a dependence found previously for defect-induced magnetism (DIM) in
HOPG. We conclude that apart from magnetic impurities, additional contribution
to the ferromagnetic magnetization exists in pristine HOPG in agreement with
previous studies. A comparative study between the results of ion beam
microscopy and the commonly used EDX analysis shows clearly that EDX is not a
reliable method for quantitative trace elemental analysis in graphite,
clarifying weaknesses and discrepancies in the element concentrations given in
the recent literature.Comment: submitted to Carbo
Magnetization of BiSrCaCuO micrometer thin ring and its depinning line
We demonstrate a geometrical effect on the depinning line (DL) of the flux
line lattice of the BiSrCaCuO high-T
superconductor (HTSC) micrometer ring. The DL shifts to notably lower
temperatures in comparison to bulk crystals and thin flakes of the same sample.
The shift is attributed to a decrease in the overall pinning potential due to a
double size effect, namely: a) the ring thickness m being smaller
than the pinning correlation length, and b) the increase in the effective
London penetration depth of the vortices (Pearl vortices). The large shift of
the DL to lower temperatures may influence the suitability of this HTSC for
applications in microstrip antennas and THz emitters.Comment: Reviewed, AAM. 13 pages, 10 figure
Monitoramento orbital das queimadas no Brasil.
Este trabalho apresenta dados numéricos e cartográficos, obtidos por um sistema de monitoramento orbital da ocorrência de queimadas no Brasil. Uma descrição sucinta dos métodos desenvolvidos é apresentada, assim como dos resultados e progressos obtidos por esse esforço multi-institucional entre 1991 e 1993. O trabalho contém 46 mapas nacionais, regionais e estaduais de queimadas, uma amostragem dos cerca de 350 mapas gerados anualmente pelo sistema de monitoramento orbital de queimadas.bitstream/item/107935/1/1474.pd
A combined first and second order variational approach for image reconstruction
In this paper we study a variational problem in the space of functions of
bounded Hessian. Our model constitutes a straightforward higher-order extension
of the well known ROF functional (total variation minimisation) to which we add
a non-smooth second order regulariser. It combines convex functions of the
total variation and the total variation of the first derivatives. In what
follows, we prove existence and uniqueness of minimisers of the combined model
and present the numerical solution of the corresponding discretised problem by
employing the split Bregman method. The paper is furnished with applications of
our model to image denoising, deblurring as well as image inpainting. The
obtained numerical results are compared with results obtained from total
generalised variation (TGV), infimal convolution and Euler's elastica, three
other state of the art higher-order models. The numerical discussion confirms
that the proposed higher-order model competes with models of its kind in
avoiding the creation of undesirable artifacts and blocky-like structures in
the reconstructed images -- a known disadvantage of the ROF model -- while
being simple and efficiently numerically solvable.Comment: 34 pages, 89 figure
Turmeric and Its Major Compound Curcumin on Health: Bioactive Effects and Safety Profiles for Food, Pharmaceutical, Biotechnological and Medicinal Applications
Curcumin, a yellow polyphenolic pigment from the Curcuma longa L. (turmeric) rhizome, has been used for centuries for culinary and food coloring purposes, and as an ingredient for various medicinal preparations, widely used in Ayurveda and Chinese medicine. In recent decades, their biological activities have been extensively studied. Thus, this review aims to offer an in-depth discussion of curcumin applications for food and biotechnological industries, and on health promotion and disease prevention, with particular emphasis on its antioxidant, anti-inflammatory, neuroprotective, anticancer, hepatoprotective, and cardioprotective effects. Bioavailability, bioefficacy and safety features, side effects, and quality parameters of curcumin are also addressed. Finally, curcumin’s multidimensional applications, food attractiveness optimization, agro-industrial procedures to offset its instability and low bioavailability, health concerns, and upcoming strategies for clinical application are also covered
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