495 research outputs found
Biotransformation of 3-hydroxydibenzo-\u3b1-pyrone into 3,8 dihydroxydibenzo-\u3b1-pyrone and aminoacyl conjugates by Aspergillus niger isolated from native "shilajit"
"Shilajit" is a panacea in Ayurveda, the Indian traditional system of
medicine. The major bioactives of "shilajit" have been identified as
dibenzo-\u3b1-pyrones (DBPs), its oligomers and aminoacyl conjugated
derivatives. These bioactive compounds play a crucial role in energy
metabolism in all animal cells including those of man.
3-hydroxydibenzo-\u3b1-pyrone (3-OH-DBP), a key DBP component of
"shilajit" is converted, among other products, to another active DBP
derivative, viz. 3,8-hydroxydibenzo-\u3b1-pyrone, 3,8(OH)2-DBP, in
vivo, when its precursor is ingested. 3,8(OH)2-DBP is then involved in
energy synthesis in the mitochondria in the reduction and stabilization
of coenzyme Q10 in the electron transport chain. As the chemical
synthesis of 3,8(OH)2-DBP is a complex, multi-step process and
economically not readily viable, we envisioned the development of a
process using microorganisms for bioconversion of 3-OH-DBP to
3,8(OH)2-DBP. In this study, the biotransformation of 3-OH-DBP is
achieved using Aspergillus niger, which was involved in the
humification process on sedimentary rocks leading to "shilajit"
formation. A 60% bioconversion of 3-OH-DBP to 3,8(OH)2-DBP and to its
aminoacyl derivatives was achieved. The products were characterized and
estimated by high performance liquid chromatography (HPLC), high
performance flash chromatography (HPFC) and gas chromatography-mass
spectrometry (GC-MS) analyses. Among the Aspergillus species isolated
and identified from native "shilajit", A. niger was found to be the
most efficient for this bioconversion
Thermodynamics of apparent horizon and modified Friedman equations
Starting from the first law of thermodynamics, , at apparent
horizon of a FRW universe, and assuming that the associated entropy with
apparent horizon has a quantum corrected relation, , we derive modified Friedmann equations
describing the dynamics of the universe with any spatial curvature. We also
examine the time evolution of the total entropy including the quantum corrected
entropy associated with the apparent horizon together with the matter field
entropy inside the apparent horizon. Our study shows that, with the local
equilibrium assumption, the generalized second law of thermodynamics is
fulfilled in a region enclosed by the apparent horizon.Comment: 11 page
Measurement of the W+W-gamma Cross Section and Direct Limits on Anomalous Quartic Gauge Boson Couplings at LEP
The process e+e- -> W+W-gamma is analysed using the data collected with the
L3 detector at LEP at a centre-of-mass energy of 188.6GeV, corresponding to an
integrated luminosity of 176.8pb^-1. Based on a sample of 42 selected W+W-
candidates containing an isolated hard photon, the W+W-gamma cross section,
defined within phase-space cuts, is measured to be: sigma_WWgamma = 290 +/- 80
+/- 16 fb, consistent with the Standard Model expectation. Including the
process e+e- -> nu nu gamma gamma, limits are derived on anomalous
contributions to the Standard Model quartic vertices W+W- gamma gamma and W+W-Z
gamma at 95% CL: -0.043 GeV^-2 < a_0/Lambda^2 < 0.043 GeV^-2 0.08 GeV^-2 <
a_c/Lambda^2 < 0.13 GeV^-2 0.41 GeV^-2 < a_n/Lambda^2 < 0.37 GeV^-2
Production of Single W Bosons at \sqrt{s}=189 GeV and Measurement of WWgamma Gauge Couplings
Single W boson production in electron-positron collisions is studied with the
L3 detector at LEP. The data sample collected at a centre-of-mass energy of
\sqrt{s} = 188.7GeV corresponds to an integrated luminosity of 176.4pb^-1.
Events with a single energetic lepton or two acoplanar hadronic jets are
selected. Within phase-space cuts, the total cross-section is measured to be
0.53 +/- 0.12 +/- 0.03 pb, consistent with the Standard Model expectation.
Including our single W boson results obtained at lower \sqrt{s}, the WWgamma
gauge couplings kappa_gamma and lambda_gamma are determined to be kappa_gamma =
0.93 +/- 0.16 +/- 0.09 and lambda_gamma = -0.31 +0.68 -0.19 +/- 0.13
Search for an invisibly decaying Higgs boson in e^+e^- collisions at \sqrt{s} = 183 - 189 GeV
A search for a Higgs boson decaying into invisible particles is performed
using the data collected at LEP by the L3 experiment at centre-of-mass energies
of 183 GeV and 189 GeV. The integrated luminosities are respectively 55.3 pb^-1
and 176.4 pb^-1. The observed candidates are consistent with the expectations
from Standard Model processes. In the hypothesis that the production cross
section of this Higgs boson equals the Standard Model one and the branching
ratio into invisible particles is 100%, a lower mass limit of 89.2 GeV is set
at 95% confidence level
Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at \sqrt{s} = 189 GeV
A search for the lightest neutral scalar and neutral pseudoscalar Higgs
bosons in the Minimal Supersymmetric Standard Model is performed using 176.4
pb^-1 of integrated luminosity collected by L3 at a center-of-mass energy of
189 GeV. No signal is observed, and the data are consistent with the expected
Standard Model background. Lower limits on the masses of the lightest neutral
scalar and pseudoscalar Higgs bosons are given as a function of tan(beta).
Lower mass limits for tan(beta)>1 are set at the 95% confidence level to be m_h
> 77.1 GeV and m_A > 77.1 GeV
Measurement of Bose-Einstein Correlations in e+e- -> W+W- at root(s)=189GeV
We investigate Bose-Einstein correlations (BEC) in W-pair production at
root(s)=189GeV using the L3 detector at LEP. We observe BEC between particles
from a single W decay in good agreement with those from a light-quark Z decay
sample. We investigate their possible existence between particles coming from
different W's. No evidence for such inter-W BEC is found
Measurement of the Lifetime of the Tau Lepton
The tau lepton lifetime is measured with the L3 detector at LEP using the
complete data taken at centre-of-mass energies around the Z pole resulting in
tau_tau = 293.2 +/- 2.0 (stat) +/- 1.5 (syst) fs. The comparison of this result
with the muon lifetime supports lepton universality of the weak charged current
at the level of six per mille. Assuming lepton universality, the value of the
strong coupling constant, alpha_s is found to be alpha_s(m_tau^2) = 0.319 +/-
0.015(exp.) +/- 0.014 (theory)
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