457 research outputs found
Relativistic Calculations for the Exclusive Photoproduction of Eta Mesons from Complex Nuclei
A relativistic model for the quasifree photoproduction of eta meson from
complex nuclei is developed. The interactions between fields are introduced
through effective Lagrangians. Contributions from several nucleon resonances as
well as nucleon Born terms and vector meson exchange diagrams are included.
Nucleon and eta wavefunctions are solutions of Dirac and Klein-Gordon
equations, respectively. Final state interactions of the outgoing particles are
included via optical potentials. The effects of these interactions on the cross
sections and photon asymmetries are studied and are found to be large.
Calculations indicate that at energies near threshold the exclusive reaction
takes place mainly through formation of the S_{11}(1535) resonance. Comparisons
with the non-relativistic calculations show differences between the two
approaches both for the cross sections and photon asymmetries. We give some
detailed predictions for the reaction observables for exclusive photoproduction
on ^{12}C, ^{16}O and ^{40}Ca.Comment: Latex, 27 pages, 13 uuencoded postscript figures. Accepted for
publication in Phys. Rev.
Association between TNF-α promoter G-308A and G-238A polymorphisms and obesity
Tumor necrosis factor-α (TNF-α), an adipokine, is produced in adipocytes, and the elevation of its levels has been linked to obesity and insulin resistance in some population. In this study the relationship between TNF-α promoter gene polymorphism and obesity in an Iranian population has been studied. Subjects were randomly selected from Tehran Cohort Lipid and Glucose Study. Adult participants placed in three groups according to their body mass index (BMI): BMI < 25, 25 ≤ BMI < 30, BMI ≥ 30 and under-18 subjects placed in two groups, under 85th percentile BMI and above 85th percentile. Finally, 244 persons were selected for G-308A and G-238A polymorphisms analysis. The FBS, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglyceride, cholesterol levels and blood pressure and HOMA of all subjects were measured. The polymorphism −308 and −238 were revealed by restriction fragment length polymorphism (RFLP; NCOI and MSPI) after the promoter site was amplified by PCR. The allele frequency of TNF-α polymorphism was in the Hardy–Weinberg equilibrium. There was no relation between BMI and the frequency of this allele. The fact that there is no association between G-308A and G-238A TNF-α promoter polymorphisms and obesity probably shows that it is not an important risk factor for obesity and consequently for cardiovascular disease
Prevalence of goiter among schoolchildren from Gorgan, Iran, a decade after national iodine supplementation: Association with age, gender, and thyroperoxidase antibodies
Background: One decade after universal salt iodization in Iran, goiter prevalence, urinary iodine concentration (UIC) and thyroperoxidase antibody (TPOAb) values were assessed among schoolchildren in Gorgan, Iran. Methods: From 2003-2004, 500 girls and 900 boys aged 7-11 yr were evaluated for goiter by palpation. UIC was measured in 183 randomly-selected goitrous children. Serum TSH, T 4, and TPOAb were measured in 53 goitrous and 30 non-goitrous children with adequate UIC. Results: Goiter was detected in 370 (26.4%) children. Goiter was present in 31 % of girls and 17% of boys age 9 (p<0.012); 37% of girls and 20% of boys age 10 (p<0.003); and 52% of girls and 19% of boys age 11 (p<0.0001). Median (range) UIC for all goitrous children sampled was 190 (20-600) μg/l; 220 (30-590) in boys and 170 (20-600) in girls (p=0.001). Eight point seven percent of goitrous children and 22% of goitrous girls aged 10-11 had UIC<100 μg/l, while 47% of the goitrous children had UIC≥200 μg/l. TPOAb was present in 52.8% of goitrous children and 10% of non-goitrous children (p=0.0001 ). TPOAb was present in 53.9% of 10-11 and 22.7% of 7-9 yr old goitrous and non-goitrous children (p=0.003) with adequate UIC. Median (range) TSH was 2.9 (0.3-10.9) mlU/l in TPO-positive and 1.8 (0.5-4.1) in TPO-negative children (p=0.001 ). Conclusions: Gorgan, Iran, is an iodine-sufficient area and almost half of schoolchildren have more than adequate UIC. TPOAb is associated with endemic goiter. Despite sufficient UIC overall, some school-aged girls remain at risk of iodine deficiency. ©2005, Editrice Kurtis
Non-locality and Medium Effects in the Exclusive Photoproduction of Eta Mesons on Nuclei
A relativistic model for the quasifree exclusive photoproduction of
mesons on nuclei is extended to include both non-local and medium effects. The
reaction is assumed to proceed via the dominant contribution of the
S(1535) resonance. The complicated integrals resulting from the
non-locality are simplified using a modified version of a method given by
Cooper and Maxwell. The non-locality effects are found to affect the magnitude
of the cross section. Some possibilities reflecting the effects of the medium
on the propagation and properties of the intermediate S resonance are
studied. The effects of allowing the S to interact with the medium via
mean field scalar and vector potentials are considered. Both broadening of
width and reduction in mass of the resonance lead to a suppression of the
calculated cross sections.Comment: 19 pages, 7 figure
Stagnation Point Flow of a Nanofluid toward an Exponentially Stretching Sheet with Nonuniform Heat Generation/Absorption
Role of polymeric coating on metallic foams to control the aeroacoustic noise reduction of airfoils with permeable trailing edges
Studies on porous trailing edges, manufactured with open-cell Ni-Cr-Al foams with sub-millimeter pore sizes, have shown encouraging results for the mitigation of turbulent boundary-layer trailing-edge noise. However, the achieved noise mitigation is typically dependent upon the pore geometry, which is fixed after manufacturing. In this study, a step to control the aeroacoustics effect of such porous trailing edges is taken, by applying a polymeric coating onto the internal foam structure. Using this method, the internal topology of the foam is maintained, but its permeability is significantly affected. This study opens a new possibility of aeroacoustic control, since the polymeric coatings are temperature responsive, and their thickness can be controlled inside the foam. Porous metallic foams with pore sizes of 580, 800, and 1200 μm are (internally) spray-coated with an elastomeric coating. The uncoated and coated foams are characterized in terms of reduced porosity, average coating thickness and air-flow resistance. Subsequently, the coated and uncoated foams are employed to construct tapered inserts installed at the trailing edge of an NACA 0018 airfoil. The noise mitigation performances of the coated metal foams are compared to those of uncoated metal foams with either similar pore size or permeability value, and both are compared to the solid trailing edge reference case. Results show that that the permeability of the foam can be easily altered by the application of an internal coating on the metallic foams. The noise reduction characteristics of the coated foams are similar to equivalent ones with metallic materials, provided that the coating material is rigid enough not to plastically deform under flow conditions
Orthogonality Effects in Relativistic Models of Nucleon Knockout Reactions
We study the effect of wave function orthogonality in the relativistic
treatment of the nucleon removal reactions (gamma, p) and (e, e' p). The
continuum wave function describing the outgoing nucleon is made orthogonal to
the relevant bound states using the Gram-Schmidt procedure. This procedure has
the advantage of preserving the asymptotic character of the continuum wave
function and hence the elastic observables are unaffected. The orthogonality
effects are found to be negligible for (e, e' p) reactions for missing momenta
up to 700 MeV/c. This holds true for both parallel and perpendicular
kinematics. By contrast the orthogonalization of the wave functions appears to
have a more pronounced effect in the case of (gamma, p) reactions. We find that
the orthogonality effect can be significant in this case particularly for large
angles. Polarization of the outgoing protons and photon asymmetry show more
sensitivity than the cross sections. If the orthogonality condition is imposed
solely on this one hole state the effects are usually smaller.Comment: LaTeX, 7 postscript figure
Inclusive electron scattering in a relativistic Green function approach
A relativistic Green function approach to the inclusive quasielastic (e,e')
scattering is presented. The single particle Green function is expanded in
terms of the eigenfunctions of the nonhermitian optical potential. This allows
one to treat final state interactions consistently in the inclusive and in the
exclusive reactions. Numerical results for the response functions and the cross
sections for different target nuclei and in a wide range of kinematics are
presented and discussed in comparison with experimental data.Comment: 12 pages, 7 figures, REVTeX
TCT-545 Contemporary Safety and Effectiveness of Peripheral Endovascular Interventions and Lower Extremity Bypass Surgery in the Treatment of Symptomatic Peripheral Arterial Disease
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