1,453 research outputs found
Effect of Electron Beam Irradiation on Survival of Brucella spp. in Traditional Ice Cream
Irradiation is a new technology which can be used for foods especially for the ones which common methods such as thermal method cannot be applied. Traditional ice cream samples were purchased from a local market. After applying a 15 kGy dose for sterilization, Brucella abortus and Brucella melitensis were inoculated to samples and then treated with four doses of 1, 2, 3 and 5 kGy electron beam irradiation at −18C storage temperature. Microbial examinations were performed in 3, 7, 14 and 21 days after treatment with electron beam irradiation. Results showed that no bacteria were observed in the initial test after use of 5 kGy dose. Applying 2 and 3 kGy reduced significantly (P < 0.05) the microbial population but could not eliminate it completely. This study confirmed that electron beam irradiation is a reliable way to reduce microbial population of Brucella spp. in traditional ice cream and therefore improve food safety. Practical Applications: To maintain palatability of traditional ice cream, milk must not be too heated or else pasteurization is not achieved. So, electron beam irradiation could ensure the safety of ice cream, instead of heat treatment. © 2015 Wiley Periodicals, Inc
Viral self-assembly as a thermodynamic process
The protein shells, or capsids, of all sphere-like viruses adopt icosahedral
symmetry. In the present paper we propose a statistical thermodynamic model for
viral self-assembly. We find that icosahedral symmetry is not expected for
viral capsids constructed from structurally identical protein subunits and that
this symmetry requires (at least) two internal "switching" configurations of
the protein. Our results indicate that icosahedral symmetry is not a generic
consequence of free energy minimization but requires optimization of internal
structural parameters of the capsid proteins.Comment: pdf file, 13 pages, three figure
Universality versus material dependence of fluctuation forces between metallic wires
We calculate the Casimir interaction between two parallel wires and between a
wire and a metall plate. The dielectric properties of the objects are described
by the plasma, Drude and perfect metal models. We find that at asymptotically
large separation interactions involving plasma wires and/or plates are
independent of the material properties, but depend on the dc conductivity
for Drude wires. Counterintuitively, at intermediate separations the
interaction involving Drude wires can become independent of . At
smaller separations, we compute the interaction numerically and observe an
approach to the proximity approximation
The effect of quercetin on fertility of frozen-thawed ram epididymal spermatozoa
The aim of the present study was to evaluate the effects of quercetin as an antioxidant supplement on frozen-thawed ram epididymal sperm quality. Quercetin is a type of flavonoid antioxidant that is found in plants, with the ability to scavenge free radicals. Twenty testicles from mature rams were collected from a nearby slaughterhouse immediately after slaughter. Epididymal spermatozoa were recovered from the caudal of epididymides by injecting Bracket and Oliphant's (BO) medium retrogradely through the ductus deferens and extended with a tris egg-yolk-based extender and supplemented with 0, 5, 10, 15, 20, and 50 μg/mL quercetin. Following equilibration, the straws were frozen, and then plunged into liquid nitrogen. After thawing, optimized concentrations of quercetin were defined based on their viabilities and used to assess fertilization and developmental potential. The results showed that the viability of frozen-thawed spermatozoa significantly increased by using 5 and 10 μg/mL quercetin in the freezing extender. However, total and progressive motility of frozen-thawed spermatozoa were not affected by 5 and 10 μg/mL quercetin in comparison with control (0 μg/mL). The mean number of zygote, morula, and blastocyst stage embryos increased significantly by using 5 and 10 μg/mL quercetin compared with other frozen-thawed treatments(P <0.05). However, the blastocyst rate of fresh sperm was significantly higher (P <0.05). In conclusion, to improve the quality of frozen-thawed ram epididymal spermatozoa, 5 and 10 μg/mL quercetin appears to be an attractive option. Further studies are suggested to understand the synergistic effect of quercetin with other antioxidants to improve the ram freezing–thawing process.Keywords: antioxidant, cryopreservation, fertility, freezing extende
What drives the translocation of stiff chains?
We study the dynamics of the passage of a stiff chain through a pore into a
cell containing particles that bind reversibly to it. Using Brownian Molecular
Dynamics simulations we investigate the mean-first-passage time as a function
of the length of the chain inside, for different concentrations of binding
particles. As a consequence of the interactions with these particles, the chain
experiences a net force along its length whose calculated value from the
simulations accounts for the velocity at which it enters the cell. This force
can in turn be obtained from the solution of a generalized diffusion equation
incorporating an effective Langmuir adsorption free energy for the chain plus
binding particles. These results suggest a role of binding particles in the
translocation process which is in general quite different from that of a
Brownian ratchet. Furthermore, non-equilibrium effects contribute significantly
to the dynamics, \emph{e.g.}, the chain often enters the cell faster than
particle binding can be saturated, resulting in a force several times smaller
than the equilibrium value.Comment: 7 pages, 4 figure
Collective charge fluctuations and Casimir interactions for quasi one-dimensional metals
We investigate the Casimir interaction between two parallel metallic
cylinders and between a metallic cylinder and plate. The material properties of
the metallic objects are implemented by the plasma, Drude and perfect metal
model dielectric functions. We calculate the Casimir interaction numerically at
all separation distances and analytically at large separations. The
large-distance asymptotic interaction between one plasma cylinder parallel to
another plasma cylinder or plate does not depend on the material properties,
but for a Drude cylinder it depends on the dc conductivity . At
intermediate separations, for plasma cylinders the asymptotic interaction
depends on the plasma wave length while for Drude cylinders
the Casimir interaction can become independent of the material properties. We
confirm the analytical results by the numerics and show that at short
separations, the numerical results approach the proximity force approximation
A Morphometric Survey among Three Iranian Horse Breeds with Multivariate Analysis
Three Iranian horse breeds, Turkoman, Caspian, and Kurdish, are the most important Iranian horse breeds which are well known in all around of the world because of their beauty, versatility, great stamina, and intelligence. Phenotypic characterization was used to identify and document the diversity within and between distinct breeds, based on their observable attributes. Phenotypic characterization and body biometric in 23 traits were measured in 191 purebred horses belonging to three breeds, i.e. Turkoman (70 horses), Kurdish (77 horses), and Caspian (44 horses). Caspian breed was sampled from the Provinces of Alborz and Gilan. Kurdish breed was sampled from the Provinces of Kurdistan, Kermanshah, and Hamadan. Turkoman breed was sampled from the Provinces of Golestan, Markazi, and Isfahan. Multivariate analysis of variance (MANOVA) was implemented. In addition, Canonical Discriminate Analysis (CDA), Principal Component Analysis (PCA), and Custer analysis were executed for assessing the relationship among the breeds. All statistical analysis was executed by SAS statistical program. The results of our investigation represented the breeds classification into 3 different classes (Caspian, Turkoman, and Kurdish) based on different morphometrical traits. Caspian breed with smaller size in most variables was detached clearly from the others with more distance than Kurdish and Turkoman breeds. The result showed that the most variably trait for classification was Hind Hoof Length. Adaptation with different environments causes difference in morphology and difference among breeds. We can identify and classify domestic population using PCA, CDA, and cluster analysis
Quantum and thermal Casimir interaction between a sphere and a plate: Comparison of Drude and plasma models
We calculate the Casimir interaction between a sphere and a plate, both
described by the plasma model, the Drude model, or generalizations of the two
models. We compare the results at both zero and finite temperatures. At
asymptotically large separations we obtain analytical results for the
interaction that reveal a non-universal, i.e., material dependent interaction
for the plasma model. The latter result contains the asymptotic interaction for
Drude metals and perfect reflectors as different but universal limiting cases.
This observation is related to the screening of a static magnetic field by a
London superconductor. For small separations we find corrections to the
proximity force approximation (PFA) that support correlations between geometry
and material properties that are not captured by the Lifshitz theory. Our
results at finite temperatures reveal for Drude metals a non-monotonic
temperature dependence of the Casimir free energy and a negative entropy over a
sizeable range of separations.Comment: 11 pages, 5 figure
Laser detection utilizing coherence
Lasers are an unnatural occurrence, rendered almost impossible in nature due to the laws of thermodynamics. Thus, the presence of laser radiation is always accompanied by an intent for that laser such as sensing, targeting, range finding etc. Detection of laser radiation is therefore important as it may be a precursor to impending action. Laser warning receivers have been around for decades and have been aligned with the type of laser threat. In the last few years new threats have appeared in the form of low-cost diode lasers with dangerously high power levels (several Watts for a few hundred US dollars) and an ever expanding range of wavelengths. Protecting against such threats requires its detection, analysis and classification. In this paper we will discuss the types of technologies that have been used to detect lasers and the properties they can discern. We then focus on the developments in the detection of coherence properties and its ability to detect weak continuous wave (CW) laser sources
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