1,001 research outputs found
Activation mechanisms of butyrylcholinesterase by 2,4,6-trinitrotoluene, 3,3-dimethylbutyl-N-n-butylcarbamate, and 2-trimethylsilyl-ethyl-N-n-butylcarbamate
The goal of this work was to propose a possible mechanism for the butyrylcholinesterase activation by 2,4,6-trinitrotoluene (TNT), 3,3-dimethylbutyl-N-n-butylcarbamate (1), and 2-trimethylsilyl-ethyl-N-n-butylcarbamate (2). Kinetically, TNT, and compounds 1 and 2 were characterized as the nonessential activators of butyrylcholinesterase. TNT, and compounds 1 and 2 were hydrophobic compounds and were proposed to bind to the hydrophobic activator binding site, which was located outside the active site gorge of the enzyme. The conformational change from a normal active site gorge to a more accessible active site gorge of the enzyme was proposed after binding of TNT, and compounds 1 and 2 to the activator binding site of the enzyme. Therefore, TNT, and compounds 1 and 2 may act as the excess of butyrylcholine in the substrate activator for the butyrylcholinesterase catalyzed reactions
Substitutional doping of Cu in diamond: Mott physics with orbitals
Discovery of superconductivity in the impurity band formed by heavy doping of
boron into diamond (C:B) as well as doping of boron into silicon (Si:B) has
provided a rout for the possibility of new families of superconducting
materials. Motivated by the special role played by copper atoms in high
temperature superconducting materials where essentially Cu orbitals are
responsible for a variety of correlation induced phases, in this paper we
investigate the effect of substitutional doping of Cu into diamond. Our
extensive first principle calculations averaged over various geometries based
on density functional theory, indicates the formation of a mid-gap band, which
mainly arises from the and states of Cu. For impurity
concentrations of more than 2pt_{2g}4p\sim 5%, completely closes the
spectral gap of the host diamond.Comment: 5 figure
Constraints on accelerating universe using ESSENCE and Gold supernovae data combined with other cosmological probes
We use recently observed data: the 192 ESSENCE type Ia supernovae (SNe Ia),
the 182 Gold SNe Ia, the 3-year WMAP, the SDSS baryon acoustic peak, the X-ray
gas mass fraction in clusters and the observational data to constrain
models of the accelerating universe. Combining the 192 ESSENCE data with the
observational data to constrain a parameterized deceleration parameter,
we obtain the best fit values of transition redshift and current deceleration
parameter , .
Furthermore, using CDM model and two model-independent equation of
state of dark energy, we find that the combined constraint from the 192 ESSENCE
data and other four cosmological observations gives smaller values of
and , but a larger value of than the combined
constraint from the 182 Gold data with other four observations. Finally,
according to the Akaike information criterion it is shown that the recently
observed data equally supports three dark energy models: CDM,
and .Comment: 18 pages, 8 figure
Combined constraints on modified Chaplygin gas model from cosmological observed data: Markov Chain Monte Carlo approach
We use the Markov Chain Monte Carlo method to investigate a global
constraints on the modified Chaplygin gas (MCG) model as the unification of
dark matter and dark energy from the latest observational data: the Union2
dataset of type supernovae Ia (SNIa), the observational Hubble data (OHD), the
cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and the
cosmic microwave background (CMB) data. In a flat universe, the constraint
results for MCG model are,
()
,
()
,
()
,
()
, and ()
.Comment: 12 pages, 1figur
Charmless Decays Based on the six-quark Effective Hamiltonian with Strong Phase Effects II
We provide a systematic study of charmless decays (
and denote pseudoscalar and vector mesons, respectively) based on an
approximate six-quark operator effective Hamiltonian from QCD. The calculation
of the relevant hard-scattering kernels is carried out, the resulting
transition form factors are consistent with the results of QCD sum rule
calculations. By taking into account important classes of power corrections
involving "chirally-enhanced" terms and the vertex corrections as well as weak
annihilation contributions with non-trivial strong phase, we present
predictions for the branching ratios and CP asymmetries of decays into
PP, PV and VV final states, and also for the corresponding polarization
observables in VV final states. It is found that the weak annihilation
contributions with non-trivial strong phase have remarkable effects on the
observables in the color-suppressed and penguin-dominated decay modes. In
addition, we discuss the SU(3) flavor symmetry and show that the symmetry
relations are generally respected
Higher order WKB corrections to black hole entropy in brick wall formalism
We calculate the statistical entropy of a quantum field with an arbitrary
spin propagating on the spherical symmetric black hole background by using the
brick wall formalism at higher orders in the WKB approximation. For general
spins, we find that the correction to the standard Bekenstein-Hawking entropy
depends logarithmically on the area of the horizon. Furthermore, we apply this
analysis to the Schwarzschild and Schwarzschild-AdS black holes and discuss our
results.Comment: 21 pages, published versio
Electrical transport and magnetic properties of nanostructured La0.67Ca0.33MnO3
Nanostructured La0.67Ca0.33MnO3 (NS-LCMO) was formed by pulsed-laser
deposition on the surface of porous Al2O3. The resistance peak temperature (Tp)
of the NS-LCMO increases with increasing average thickness of the films, while
their Curie temperatures (Tc) remain unchanged. The coercive field of the
samples increases with decreasing film thickness and its temperature dependence
can be well described by Hc(T) = Hc(0)[1-(T/TB)1/2]. A large magnetoresistance
and strong memory effect were observed for the NS-LCMO. The results are
discussed in terms of the size effect, Coulomb blockade and magnetic tunneling
effect. This work also demonstrates a new way to get nanostructured manganites
Feasibility and dominance rules in the electromagnetism-like algorithm for constrained global optimization
This paper presents the use of a constraint-handling technique, known as feasibility and dominance rules, in a electromagnetismlike
(ELM) mechanism for solving constrained global optimization problems. Since the original ELM algorithm is specifically designed for solving bound constrained problems, only the inequality and equality constraints violation together with the objective function value are used to select
points and to progress towards feasibility and optimality. Numerical experiments are presented, including a comparison with other methods recently reported in the literature
Magnetically recoverable Ni@C composites: The synthesis by carbonization and adsorption for Fe3+
Carbon-encapsulated nickel particles (Ni@C composites) for removing Fe3+ in wastewater have been prepared by the carbonization of phenolic resin mixing with nickel particles. XRD results reveal that the Ni@C composites are consisted of C, Ni, and Ni3S2. The TG-DTG curves of Ni@C composites are almost same as that of phenolic resin. The morphology investigation shows that Ni is distributed randomly on carbon. Based on analysis of N2 adsorption-desorption isotherm, the surface area and pore volume of Ni@C composites are 187.47 m2 gâ1 and 0.06900 cm3 gâ1 nmâ1, respectively. The saturation magnetization values for Ni@C composites are 68.99 emu·gâ1 determined by the Vibrating Sample Magnetometer. Ni@C composites exhibit a high adsorption capacity for Fe3+. The adsorption behavior follows the pseudo-second-order kinetic and Langmuir model between the adsorbents and Fe3+. Furthermore, the adsorption capacity of Ni@C composites derives from the attractive force between the adsorbed anion and the surface positive charge of Ni@C composites, as well as the bond between the adsorbed cation and the COOâ groups. From the above results Ni@C composites can be widely applied in wastewater treatment as a new efficiency and excellent recoverable adsorbent
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