1,120 research outputs found
Origin of G Magnetic Fields in the Central Engine of Gamma Ray Bursts
Various authors have suggested that the gamma-ray burst (GRB) central engine
is a rapidly rotating, strongly magnetized, G) compact
object. The strong magnetic field can accelerate and collimate the relativistic
flow and the rotation of the compact object can be the energy source of the
GRB. The major problem in this scenario is the difficulty of finding an
astrophysical mechanism for obtaining such intense fields. Whereas, in
principle, a neutron star could maintain such strong fields, it is difficult to
justify a scenario for their creation. If the compact object is a black hole,
the problem is more difficult since, according to general relativity it has "no
hair" (i.e., no magnetic field). Schuster, Blackett, Pauli, and others have
suggested that a rotating neutral body can create a magnetic field by
non-minimal gravitational-electromagnetic coupling (NMGEC). The
Schuster-Blackett form of NMGEC was obtained from the Mikhail and Wanas's
tetrad theory of gravitation (MW). We call the general theory NMGEC-MW.
We investigate here the possible origin of the intense magnetic fields G in GRBs by NMGEC-MW. Whereas these fields are difficult to
explain astrophysically, we find that they are easily explained by NMGEC-MW. It
not only explains the origin of the G fields when the
compact object is a neutron star, but also when it is a black hole.Comment: 9 pages, accepted for publication in JCA
Structural study of CuSe alloys produced by mechanical alloying
The crystalline structures of superionic high temperature copper selenides
CuSe () produced by Mechanical Alloying were
investigated using X-ray diffraction (XRD) technique. The measured XRD patterns
showed the presence of the peaks corresponding to the crystalline superionic
high temperature -CuSe phase in the as-milled sample, and its
structural data were determined by means of a Rietveld refinement procedure.
After a heat treatment in argon at 200C for 90 h, this phase transforms
to the superionic high temperature -CuSe phase, whose
structural data where also determined through the Rietveld refinement. In this
phase, a very low occupation of the trigonal 32(f) sites (%) by Cu ions
is found. In order to explain the evolution of the phases in the samples, two
possible mechanisms are suggested: the high mobility of Cu ions in superionic
phases and the intense diffusive processes in the interfacial component of
samples produced by Mechanical Alloying.Comment: 2 figures, submitted to Acta Crystallographic
Structural and optical studies of FeSb2 under high pressure
Nanostructured orthorhombic FeSb2 and an amorphous phase were formed by
mechanical alloying starting from a mixture of high purity elemental Fe and Sb
powders. The effects of high pressures on structural and optical properties
were studied using X-ray diffraction (XRD) and Raman spectroscopy (RS). XRD
patterns showed the presence of the orthorhombic FeSb2 phase up to the maximum
pressure applied (28.2 GPa). The XRD patterns showed also an increase in the
amount of the amorphous phase with increasing pressure up to 23.3 GPa. At 14.3
GPa, together with the former phases, a new phase was observed and indexed to a
tetragonal FeSb2 phase, but its volume fraction is small at least up to 23.3
GPa. For the orthorhombic FeSb2 phase, the pressure dependence of the volume
fitted to a Birch-Murnaghan equation of state gave a bulk modulus = 74.2 +- 3.0
GPa and its pressure derivative = 7.5 +- 0.6. RS measurements were performed
from atmospheric pressure up to 45.2 GPa. For the orthorhombic FeSb2 phase, the
Raman active mode was observed up to the maximum pressure applied, while the
mode disappeared at 16.6 GPa. For pressures higher than 21 GPa, the Raman
active mode of a tetragonal FeSb2 phase was observed, confirming ab initio
calculations reported in the literature.Comment: 31 pages, 11 figures and 2 tables. Already submitted for publicatio
Experimental and numerical simulation of single-phase flow in a micro heat spreader applied to the cold start of internal combustion engines fueled with ethanol
Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.This work presents the results of numerical simulations and
experimental evaluation of a micro heat spreader applied to the
cold start of internal combustion engines fuelled with ethanol.
At low temperatures (below 11 °C), using only ethanol as fuel,
engines are unable to start. So, it was adopted as solution in
Brazil the use of gasoline to assist the first start. The gasoline is
contained in an additional small reservoir implying on safety
concerns. Additionally, the use of gasoline causes an increase
of emissions compared with the use of only ethanol. Therefore,
in the present study a micro heat spreader containing an
electrical heater was developed in order to heat up the ethanol
and permit the engine start under ambient temperatures down to
-10 °C. Based on this, numerical simulations were performed
using Computational Fluid Dynamics (CFD) software to predict
the thermal behaviour of the device. Then, based on these
simulations, a micro heat spreader was fabricated and
experimentally evaluated. Good agreement between
experimental and simulated results was obtained. Based on the
initial results, the heat spreader seems to attend the
requirements of its application.dc201
Nongenotoxic Effects And A Reduction Of The Dxr-induced Genotoxic Effects Of Helianthus Annuus Linné (sunflower) Seeds Revealed By Micronucleus Assays In Mouse Bone Marrow
Background: This research evaluated the genotoxicity of oil and tincture of H. annuus L. seeds using the micronucleus assay in bone marrow of mice. The interaction between these preparations and the genotoxic effects of doxorubicin (DXR) was also analysed (antigenotoxicity test) .Methods: Experimental groups were evaluated at 24-48 h post treatment with N-Nitroso-N-ethylurea (positive control - NEU), DXR (chemotherapeutic), NaCl (negative control), a sunflower tincture (THALS) and two sources of sunflower oils (POHALS and FOHALS). Antigenotoxic assays were carried out using the sunflower tincture and oils separately and in combination with NUE or DXR. Results: For THALS, analysis of the MNPCEs showed no significant differences between treatment doses (250-2,000 mg.Kg-1) and NaCl. A significant reduction in MNPCE was observed when THALS (2,000 mg.Kg-1) was administered in combination with DXR (5 mg.Kg-1). For POHALS or FOHALS, analysis of the MNPCEs also showed no significant differences between treatment doses (250-2,000 mg.Kg-1) and NaCl. However, the combination DXR + POHALS (2,000 mg.Kg-1) or DXR + FOHALS (2,000 mg.Kg-1) not contributed to the MNPCEs reduction. Conclusions: This research suggests absence of genotoxicity of THALS, dose-, time- and sex-independent, and its combination with DXR can reduce the genotoxic effects of DXR. POHALS and FOHALS also showed absence of genotoxicity, but their association with DXR showed no antigenotoxic effects. © 2014 Boriollo et al.; licensee BioMed Central Ltd.14Sunflowers: Helianthus (Compositae-Heliantheae) (1976) Evolution of Crop Plants, pp. 36-38. , London: Longmans Green, Simmonds NW, Heiser CBEarle, F.R., Vanetten, C.H., Clark, T.F., Wolff, I.A., Compositional data on sunflower seed (1968) J Am Oil Chem Soc, 45, pp. 876-879Salunkhe, D.K., Chavan, J.K., Adsule, R.N., Kadam, S.S., World Oilseeds: Chemistry, Technology and Utilization (1992) Sunflower, , New York: Van Nostrand ReinholdGonzáles-Pérez, S., Vereijken, J.M., Sunflower proteins: Overview of their physicochemical, structural and functional properties (2007) J Sci Food Agric, 87, pp. 2173-2191Warner, K.A., Mounts, T.L., List, G.V.R., Effects of added tocopherols on the flavor stability of purified vegetable oils (1990) Inform, 1, p. 326Ito, T., Tamura, T., Matsumoto, T., Sterol Composition of 19 vegetable oils (1973) J Am Oil Chem Soc, 50, pp. 122-125. , 10.1007/BF02633564, 4707293Trost, V.W., Characterization of corn oil, soybean oil and sunflower oil nonpolar material (1989) J Am Oil Chem Soc, 66, pp. 325-333Dupont, H.L., Sullivan, P., Evans, D.G., Vollet, J.J., Ericsson, C.D., Ackerman, P.B., Tjoa, W.S., Prevention of traveler's diarrhea (emporiatric enteritis). 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Generic Pareto local search metaheuristic for optimization of targeted offers in a bi-objective direct marketing campaign
Cross-selling campaigns seek to offer the right products to the set of customers with the goal of maximizing expected profit, while, at the same time, respecting the purchasing constraints set by investors. In this context, a bi-objective version of this NP-Hard problem is approached in this paper, aiming at maximizing both the promotion campaign total profit and the risk-adjusted return, which is estimated with the reward-to-variability ratio known as Sharpe ratio. Given the combinatorial nature of the problem and the large volume of data, heuristic methods are the most common used techniques. A Greedy Randomized Neighborhood Structure is also designed, including the characteristics of a neighborhood exploration strategy together with a Greedy Randomized Constructive technique, which is embedded in a multi-objective local search metaheuristic. The latter combines the power of neighborhood exploration by using a Pareto Local Search with Variable Neighborhood Search. Sets of non-dominated solutions obtained by the proposed method are described and analyzed for a number of problem instances
Biochemical, genetic and zoosporicidal properties of cyclic lipopeptide surfactants produced by Pseudomonas fluorescens
Zoospores play an important role in the infection of plant and animal hosts by oomycetes and other zoosporic fungi. In this study, six fluorescent Pseudomonas isolates with zoosporicidal activities were obtained from the wheat rhizosphere. Zoospores of multiple oomycetes, including Pythium species, Albugo candida, and Phytophthora infestans, were rendered immotile within 30 s of exposure to cell suspensions or cell culture supernatants of the six isolates, and subsequent lysis occurred within 60 s. The representative strain SS101, identified as Pseudomonas fluorescens biovar II, reduced the surface tension of water from 73 to 30 mN m-1. The application of cell suspensions of strain SS101 to soil or hyacinth bulbs provided significant protection against root rot caused by Pythium intermedium. Five Tn5 mutants of strain SS101lacked the abilities to reduce the surface tension of water and to cause lysis of zoospores. Genetic characterization of two surfactant-deficient mutants showed that the transposons had integrated into condensation domains of peptide synthetases. A partially purified extract from strain SS101 reduced the surface tension of water to 30 mN m-1 and reached the critical micelle concentration at 25 micrograms ml-1. Reverse-phase high-performance liquid chromatography yielded eight different fractions, five of which had surface activity and caused lysis of zoospores. Mass spectrometry and nuclear magnetic resonance analyses allowed the identification of the main constituent as a cyclic lipopeptide (1,139 Da) containing nine amino acids and a 10-carbon hydroxy fatty acid. The other four zoosporicidal fractions were closely related to the main constituent, with molecular massesranging from 1,111 to 1,169 Da
Acute Effect of Caffeine Intake on Hemodynamics after Resistance Exercise in Young Non-hypertensive Subjects
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