1,345 research outputs found
Antioxidant and antihemolytic activities of methanol extract of Hyssopus angustifolius
This study was designed to evaluate antioxidant and antihemolytic activities of Hyssopus angustifolius flower, stem and leaf methanol extracts by employing various in vitro assays. The leaf extract showed the best activity in DPPH (63.2 ± 2.3 μg mL-1) and H2O2  (55.6 ± 2.6 μg mL-1) models compared to the other extracts. However, flower extract exhibited the highest Fe2+ chelating activity (131.4 ± 4.4 μg mL-1). The extracts exhibited good antioxidant activity in linoleic acid peroxidation and reducing power assays, but were not comparable to vitamin C. The stem (23.58 ± 0.7 μg mL-1) and leaf (26.21 ± 1 μg mL-1) extracts showed highest level of antihemolytic activity than the flower extract
Cosmic microwave background constraints on cosmological models with large-scale isotropy breaking
Several anomalies appear to be present in the large-angle cosmic microwave
background (CMB) anisotropy maps of WMAP, including the alignment of
large-scale multipoles. Models in which isotropy is spontaneously broken (e.g.,
by a scalar field) have been proposed as explanations for these anomalies, as
have models in which a preferred direction is imposed during inflation. We
examine models inspired by these, in which isotropy is broken by a
multiplicative factor with dipole and/or quadrupole terms. We evaluate the
evidence provided by the multipole alignment using a Bayesian framework,
finding that the evidence in favor of the model is generally weak. We also
compute approximate changes in estimated cosmological parameters in the
broken-isotropy models. Only the overall normalization of the power spectrum is
modified significantly.Comment: Accepted for publication in Phys. Rev.
Effect of pulsed power on particle matter in diesel engine exhaust using a DBD plasma reactor
Nonthermal plasma (NTP) treatment of exhaust gas is a promising technology for both nitrogen oxides (NOX) and particulate matter (PM) reduction by introducing plasma into the exhaust gases. This paper considers the effect of NTP on PM mass reduction, PM size distribution, and PM removal efficiency. The experiments are performed on real exhaust gases from a diesel engine. The NTP is generated by applying high-voltage pulses using a pulsed power supply across a dielectric barrier discharge (DBD) reactor. The effects of the applied high-voltage pulses up to 19.44 kVpp with repetition rate of 10 kHz are investigated. In this paper, it is shown that the PM removal and PM size distribution need to be considered both together, as it is possible to achieve high PM removal efficiency with undesirable increase in the number of small particles. Regarding these two important factors, in this paper, 17 kVpp voltage level is determined to be an optimum point for the given configuration. Moreover, particles deposition on the surface of the DBD reactor is found to be a significant phenomenon, which should be considered in all plasma PM removal tests
Feshbach resonances in ultracold ^{6,7}Li + ^{23}Na atomic mixtures
We report a theoretical study of Feshbach resonances in Li + Na
and Li + Na mixtures at ultracold temperatures using new accurate
interaction potentials in a full quantum coupled-channel calculation. Feshbach
resonances for in the initial collisional open channel LiNa are found to agree with previous
measurements, leading to precise values of the singlet and triplet scattering
lengths for the LiNa pairs. We also predict additional Feshbach
resonances within experimentally attainable magnetic fields for other collision
channels.Comment: 4 pages, 3 figure
Photodissociation of O-2 via the Herzberg continuum: Measurements of O-atom alignment and orientation
Comparison of near-threshold reactivity of ground-state and spin-orbit excited chlorine atoms with methane
Electron mean free path from angle-dependent photoelectron spectroscopy of aerosol particles
We propose angle-resolved photoelectron spectroscopy of aerosol particles as
an alternative way to determine the electron mean free path of low energy
electrons in solid and liquid materials. The mean free path is obtained from
fits of simulated photoemission images to experimental ones over a broad range
of different aerosol particle sizes. The principal advantage of the aerosol
approach is twofold. Firstly, aerosol photoemission studies can be performed
for many different materials, including liquids. Secondly, the size-dependent
anisotropy of the photoelectrons can be exploited in addition to size-dependent
changes in their kinetic energy. These finite size effects depend in different
ways on the mean free path and thus provide more information on the mean free
path than corresponding liquid jet, thin film, or bulk data. The present
contribution is a proof of principle employing a simple model for the
photoemission of electrons and preliminary experimental data for potassium
chloride aerosol particles
Solvent effect on 14N NMR shielding of glycine, serine, leucine, and threonine: comparison between chemical shifts and energy versus dielectric constant
The polarizable continuum model (PCM) is employed to describe the system in the condensed phase. The performance of DFT and PCM in describing high order nonlinear mixed electric and magnetic effects in condensed phase are described. In this paper we consider the effect of 10 solvents with a wide range of dielectric constants on 4 amino acids. NMR shielding values (ppm), isotropic and anisotropic effects, energy interaction between solute and solvent, and the effect of hydrogen bond on shielding are described. Direct and indirect solvent effects on shielding are also calculated. The observed solvent-induced shielding variation is more strongly related to the intensity of the solvent reaction field rather than on the change of molecular geometry induced by the solvent. KEY WORDS: Solvent effect, 14N NMR shielding, Solvent-induced shielding, Polarizable continuum model, Amino acids   Bull. Chem. Soc. Ethiop. 2007, 21(1), 111-116
Strong-field approximation for Coulomb explosion of H_2^+ by short intense laser pulses
We present a simple quantum mechanical model to describe Coulomb explosion of
H by short, intense, infrared laser pulses. The model is based on the
length gauge version of the molecular strong-field approximation and is valid
for pulses shorter than 50 fs where the process of dissociation prior to
ionization is negligible. The results are compared with recent experimental
results for the proton energy spectrum [I. Ben-Itzhak et al., Phys. Rev. Lett.
95, 073002 (2005), B. D. Esry et al., Phys. Rev. Lett. 97, 013003 (2006)]. The
predictions of the model reproduce the profile of the spectrum although the
peak energy is slightly lower than the observations. For comparison, we also
present results obtained by two different tunneling models for this process.Comment: 8 pages, 4 figure
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