3,275 research outputs found
Effects of different drying methods on the antioxidant activities of leaves and berries of cayratia trifolia
This study aimed to assess the effects of fresh, thermal drying method (vacuum oven drying), and nonthermal drying method (freeze drying) on the antioxidant activities of leaves and berries of Cayratia trifolia using ferric reducing antioxidant power (FRAP) and 1,1-diphenyl-1-picrylhydrazyl radical scavenging capacity (DPPH) assays. The total phenolic content (TPC) and flavonoid content (TFC) of the leaves and berries of C. trifolia were also measured. Based on the results obtained, the TPC, TFC, and antioxidant activities of the leaves and berries were arranged in the following order: freeze-dried sample with methanol extraction > vacuum-dried sample with methanol extraction > freeze-dried sample with water extraction > vacuum-dried sample with water extraction > fresh sample with methanol extraction > fresh sample with water extraction. The results showed a significant difference (p<0.05) between the fresh and dried samples. In conclusion, freeze drying was found to be a good method for maintaining TPC, TFC, and antioxidant activities by FRAP and DPPH methods in the leaves and berries of C. trifolia
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Methods of genotype imputation for genome-wide association studies
In genetic epidemiological studies, missing data problems arise when genotypes of particular markers are unavailable for reasons of data quality, cost efficiency or technical design. Genotype imputation is a well-established statistical technique for estimating unobserved genotypes in association studies. Imputation methods are implemented by copying haplotype segments from a densely genotyped reference panel into individuals typed at a subset of the reference variants. By this way, genotypes can be estimated and tested for association at variants that were not assayed in a study. This report first summarizes the missing data mechanisms. Then an overview of the different methods that have been proposed for genotype imputation is provided and some thoughts for future directions are given.Statistic
Myosin Drives Retrograde F-Actin Flow in Neuronal Growth Cones
AbstractActin filaments assembled at the leading edge of neuronal growth cones are centripetally transported via retrograde F-actin flow, a process fundamental to growth cone guidance and other forms of directed cell motility. Here we investigated the role of myosins in retrograde flow, using two distinct modes of myosin inhibition: microinjection of NEM inactivated myosin S1 fragments, or treatment with 2,3-butanedione-2-monoxime, an inhibitor of myosin ATPase. Both treatments resulted in dose-dependent attenuation of retrograde F-actin flow and growth of filopodia. Growth was cytochalasin sensitive and directly proportional to the degree of myosin inhibition, suggesting that retrograde flow results from superimposition of two independent processes: actin assembly and myosin-based filament retraction. These results provide the first direct evidence for myosin involvement in neuronal growth cone function
Magnetic and pair correlations of the Hubbard model with next-nearest-neighbor hopping
A combination of analytical approaches and quantum Monte Carlo simulations is
used to study both magnetic and pairing correlations for a version of the
Hubbard model that includes second-neighbor hopping as a
model for high-temperature superconductors. Magnetic properties are analyzed
using the Two-Particle Self-Consistent approach. The maximum in magnetic
susceptibility as a function of doping appears both at finite
and at but for two totally different physical reasons. When
, it is induced by antiferromagnetic correlations while at
it is a band structure effect amplified by interactions.
Finally, pairing fluctuations are compared with -matrix results to
disentangle the effects of van Hove singularity and of nesting on
superconducting correlations. The addition of antiferromagnetic fluctuations
increases slightly the -wave superconducting correlations despite the
presence of a van Hove singularity which tends to decrease them in the
repulsive model. Some aspects of the phase diagram and some subtleties of
finite-size scaling in Monte Carlo simulations, such as inverted finite-size
dependence, are also discussed.Comment: Revtex, 8 pages + 15 uuencoded postcript figure
A remotely-operated facility for evaluation of post-combustion CO2 capture technologies on industrial sites
ACTTROM (Advanced Capture Testing in a Transportable Remotely-Operated Minilab) is a transportable test facility for bench-scale evaluation of postcombustion CO2 capture technologies using real industrial flue gases. It is designed to be remote-operable, requiring visits only once per month for maintenance and sample collection. ACTTROM is the first facility of its kind, owned and operated by academia for collaborative research in an industrial environment, and this has resulted in a number of unique developments to facilitate remote operation at an industrial host site. Specifically, it has been necessary to design the unit to automatically correct or mitigate the effects of fault conditions, and to be remotely-monitored via a user interface at 24 hour intervals
Equilibrium and stability properties of a coupled two-component Bose-Einstein condensate
The equilibrium and stability properties of a coupled two-component BEC is
studied using a variational method and the one-dimensional model of Williams
and collaborators. The variational parameters are the population fraction,
translation and scaling transformation of the condensate densities, assumed to
have a Gaussian shape. We study the equilibrium and stability properties as a
function of the strength of the laser field and the traps displacement. We find
many branches of equilibrium configurations, with a host of critical points. In
all cases, the signature of the onset of criticality is the collapse of a
normal mode which is a linear combination of the out of phase translation and
an in phase breathing oscillation of the condensate densities. Our calculations
also indicate that we have symmetry breaking effects when the traps are not
displacedComment: 13 pages,3 figure
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Induced biochemical interactions in crude oils
In the evolution of oil from sedimentary to reservoir conditions, the hydrogen to carbon ratios decrease while the oxygen, nitrogen, and sulfur to carbon ratios increase. During this process, the oils become heavier and richer in asphaltenes. In terms of chemical composition, the oils become enriched in resins, asphaltenes, and polar compounds containing the heteroatoms and metals. Over the geological periods of time, the chemical and physical changes have been brought about by chemical, biological (biochemical) and physical (temperature and pressure) means as well as by the catalytic effects of the sedimentary matrices, migration, flooding, and other physical processes. Therefore, different types of oils are the end products of a given set of such interactions which were brought about by multiple and simultaneous physicochemical processes involving electron transfer, free radical, and chemical reactions. A biocatalyst introduced into a reaction mixture of the type produced by such reactions will seek available chemical reaction sites and react at the most favorable ones. The rates and the chemical pathways by which the biocatalytic reactions will proceed will depend on the oil type and the biocatalyst(s). Some of the possible reaction pathways that may occur in such complex mixtures are discussed
Chern-Simons Reduction and non-Abelian Fluid Mechanics
We propose a non-Abelian generalization of the Clebsch parameterization for a
vector in three dimensions. The construction is based on a group-theoretical
reduction of the Chern-Simons form on a symmetric space. The formalism is then
used to give a canonical (symplectic) discussion of non-Abelian fluid
mechanics, analogous to the way the Abelian Clebsch parameterization allows a
canonical description of conventional fluid mechanics.Comment: 12 pages, REVTeX; revised for publication in Phys Rev D; email to
[email protected]
Theoretical analysis of the focusing of acoustic waves by two-dimensional sonic crystals
Motivated by a recent experiment on acoustic lenses, we perform numerical
calculations based on a multiple scattering technique to investigate the
focusing of acoustic waves with sonic crystals formed by rigid cylinders in
air. The focusing effects for crystals of various shapes are examined. The
dependance of the focusing length on the filling factor is also studied. It is
observed that both the shape and filling factor play a crucial role in
controlling the focusing. Furthermore, the robustness of the focusing against
disorders is studied. The results show that the sensitivity of the focusing
behavior depends on the strength of positional disorders. The theoretical
results compare favorably with the experimental observations, reported by
Cervera, et al. (Phys. Rev. Lett. 88, 023902 (2002)).Comment: 8 figure
Origin of the shadow Fermi surface in Bi-based cuprates
We used angle-resolved photoemission spectroscopy to study the shadow Fermi
surface in one layer Bi2Sr1.6La0.4CuO6+delta and two layer
(Bi,Pb)2Sr2CaCu2O8+delta. We find the shadow band to have the same peakwidth
and dispersion as the main band. In addition, the shadow band/main band
intensity ratio is found to be binding energy independent. Consequently, it is
concluded that the shadow bands in Bi-based HTSC do not originate from
antiferromagnetic interactions but have a structural origin.Comment: 10 pages, 2 figure
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