441 research outputs found
Testing of newly developed glycophospholipid antigen for the detection of P. falciparum malaria by laser light immunoassay in endemic and non-endemic areas
A glycophospholipid (GPL) antigen isolated from Plasmodium falciparum culture supernatant hasbeen tested for its antigenicity. Detection of malaria positive known blood samples and unknown fieldsamples from endemic and non-endemic areas were compared. In this study laser light scattering immunoassay(LIA) was used for the detection of P. falciparum malaria. Test results of control (malaria negativesamples from Surat) were compared with known positive samples and unknown malaria positivefield samples. A positive correlation has been observed (97%) in falciparum positive samples from laboratoryand unknown samples from endemic area (Haldwani) by LIA method using GPL antigen. Fromthe results of the study it was found that GPL antigen has a better antigenic property and can detectalmost all the cases of Pf malaria by LIA method
Reaction-diffusion systems and nonlinear waves
The authors investigate the solution of a nonlinear reaction-diffusion
equation connected with nonlinear waves. The equation discussed is more general
than the one discussed recently by Manne, Hurd, and Kenkre (2000). The results
are presented in a compact and elegant form in terms of Mittag-Leffler
functions and generalized Mittag-Leffler functions, which are suitable for
numerical computation. The importance of the derived results lies in the fact
that numerous results on fractional reaction, fractional diffusion, anomalous
diffusion problems, and fractional telegraph equations scattered in the
literature can be derived, as special cases, of the results investigated in
this article.Comment: LaTeX, 16 pages, corrected typo
Solution of generalized fractional reaction-diffusion equations
This paper deals with the investigation of a closed form solution of a
generalized fractional reaction-diffusion equation. The solution of the
proposed problem is developed in a compact form in terms of the H-function by
the application of direct and inverse Laplace and Fourier transforms.
Fractional order moments and the asymptotic expansion of the solution are also
obtained.Comment: LaTeX, 18 pages, corrected typo
Fractional reaction-diffusion equations
In a series of papers, Saxena, Mathai, and Haubold (2002, 2004a, 2004b)
derived solutions of a number of fractional kinetic equations in terms of
generalized Mittag-Leffler functions which provide the extension of the work of
Haubold and Mathai (1995, 2000). The subject of the present paper is to
investigate the solution of a fractional reaction-diffusion equation. The
results derived are of general nature and include the results reported earlier
by many authors, notably by Jespersen, Metzler, and Fogedby (1999) for
anomalous diffusion and del-Castillo-Negrete, Carreras, and Lynch (2003) for
reaction-diffusion systems with L\'evy flights. The solution has been developed
in terms of the H-function in a compact form with the help of Laplace and
Fourier transforms. Most of the results obtained are in a form suitable for
numerical computation.Comment: LaTeX, 17 pages, corrected typo
Semiclassical kinetic theory of electron spin relaxation in semiconductors
We develop a semiclassical kinetic theory for electron spin relaxation in
semiconductors. Our approach accounts for elastic as well as inelastic
scattering and treats Elliott-Yafet and motional-narrowing processes, such as
D'yakonov-Perel' and variable g-factor processes, on an equal footing. Focusing
on small spin polarizations and small momentum transfer scattering, we derive,
starting from the full quantum kinetic equations, a Fokker-Planck equation for
the electron spin polarization. We then construct, using a rigorous multiple
time scale approach, a Bloch equation for the macroscopic (-averaged)
spin polarization on the long time scale, where the spin polarization decays.
Spin-conserving energy relaxation and diffusion, which occur on a fast time
scale, after the initial spin polarization has been injected, are incorporated
and shown to give rise to a weight function which defines the energy averages
required for the calculation of the spin relaxation tensor in the Bloch
equation. Our approach provides an intuitive way to conceptualize the dynamics
of the spin polarization in terms of a ``test'' spin polarization which
scatters off ``field'' particles (electrons, impurities, phonons). To
illustrate our approach, we calculate for a quantum well the spin lifetime at
temperatures and densities where electron-electron and electron-impurity
scattering dominate. The spin lifetimes are non-monotonic functions of
temperature and density. Our results show that at electron densities and
temperatures, where the cross-over from the non-degenerate to the degenerate
regime occurs, spin lifetimes are particularly long.Comment: 29 pages, 10 figures, final versio
Short and canonical GRBs
Within the "fireshell" model for the Gamma-Ray Bursts (GRBs) we define a
"canonical GRB" light curve with two sharply different components: the
Proper-GRB (P-GRB), emitted when the optically thick fireshell of
electron-positron plasma originating the phenomenon reaches transparency, and
the afterglow, emitted due to the collision between the remaining optically
thin fireshell and the CircumBurst Medium (CBM). We outline our "canonical GRB"
scenario, with a special emphasis on the discrimination between "genuine" and
"fake" short GRBs.Comment: 4 pages, 3 figures, in the Proceedings of the "Gamma Ray Bursts 2007"
meeting, November 5-9, 2007, Santa Fe, New Mexico, US
Black Rings in Taub-NUT and D0-D6 interactions
We analyze the dynamics of neutral black rings in Taub-NUT spaces and their
relation to systems of D0 and D6 branes in the supergravity approximation. We
employ several recent techniques, both perturbative and exact, to construct
solutions in which thermal excitations of the D0-branes can be turned on or
off, and the D6-brane can have -fluxes turned on or off in its worldvolume.
By explicit calculation of the interaction energy between the D0 and D6 branes,
we can study equilibrium configurations and their stability. We find that
although D0 and D6 branes (in the absence of fields, and at zero
temperature) repeal each other at non-zero separation, as they get together
they go over continuosly to an unstable bound state of an extremal singular
Kaluza-Klein black hole. We also find that, for -fields larger than a
critical value, or sufficiently large thermal excitation, the D0 and D6 branes
form stable bound states. The bound states with thermally excited D0 branes are
black rings in Taub-NUT, and we provide an analysis of their phase diagram.Comment: 50 pages, 8 figures; v3: minor changes and references added; v4:
improved figs. 7 and 8, matches with published versio
Mesoscopic interplay of superconductivity and ferromagnetism in ultra-small metallic grains
We review the effects of electron-electron interactions on the ground-state
spin and the transport properties of ultra-small chaotic metallic grains. Our
studies are based on an effective Hamiltonian that combines a superconducting
BCS-like term and a ferromagnetic Stoner-like term. Such terms originate in
pairing and spin exchange correlations, respectively. This description is valid
in the limit of a large dimensionless Thouless conductance. We present the
ground-state phase diagram in the fluctuation-dominated regime where the
single-particle mean level spacing is comparable to the bulk BCS pairing gap.
This phase diagram contains a regime in which pairing and spin exchange
correlations coexist in the ground-state wave function. We discuss the
calculation of the tunneling conductance for an almost-isolated grain in the
Coulomb-blockade regime, and present measurable signatures of the competition
between superconductivity and ferromagnetism in the mesoscopic fluctuations of
the conductance.Comment: 6 pages, 3 figures, To be published in the proceedings of the NATO
Advance Research Workshop "Recent Advances in Nonlinear Dynamics and Complex
System Physics.
Anaerobic granular sludge as a biocatalyst for 1,3-propanediol production from glycerol in continuous bioreactors
1,3-propanediol (1,3-PDO) was produced from glycerol in three parallel Expanded Granular Sludge Blanket (EGSB) reactors inoculated with granular sludge (control reactor-R1), heat-treated granular sludge (R2) and disrupted granular sludge (R3) at Hydraulic Retention Times (HRT) between 3 and 24 h. Maximum 1,3-PDO yield (0.52 mol mol-1) and productivity (57 g L-1 d-1) were achieved in R1 at HRTs of 12 h and 3 h, respectively. DGGE profiling of PCR-amplified 16S rRNA gene fragments showed that variations in the HRT had a critical impact in the dominant community of microorganisms. However, no appreciable differences in the bacterial population were observed between R2 and R3 at low HRTs. Production of H2 was observed at the beginning of the operation, but no methane production was observed. This study proves the feasibility of 1,3-PDO production in EGSB reactors and represents a novel strategy to valorise glycerol generated in the biodiesel industry.The financial support given to Roberto Gallardo from Fundacao da Ciencia e da Tecnologia (ref SFRH/BD/42900/2008) is gratefully acknowledged. The authors thank the MIT- Portugal Program for the support given to R. Gallardo and C. Faria
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