945 research outputs found
Dynamical Renormalization Group Study for a Class of Non-local Interface Equations
We provide a detailed Dynamic Renormalization Group study for a class of
stochastic equations that describe non-conserved interface growth mediated by
non-local interactions. We consider explicitly both the morphologically stable
case, and the less studied case in which pattern formation occurs, for which
flat surfaces are linearly unstable to periodic perturbations. We show that the
latter leads to non-trivial scaling behavior in an appropriate parameter range
when combined with the Kardar-Parisi-Zhang (KPZ) non-linearity, that
nevertheless does not correspond to the KPZ universality class. This novel
asymptotic behavior is characterized by two scaling laws that fix the critical
exponents to dimension-independent values, that agree with previous reports
from numerical simulations and experimental systems. We show that the precise
form of the linear stabilizing terms does not modify the hydrodynamic behavior
of these equations. One of the scaling laws, usually associated with Galilean
invariance, is shown to derive from a vertex cancellation that occurs (at least
to one loop order) for any choice of linear terms in the equation of motion and
is independent on the morphological stability of the surface, hence
generalizing this well-known property of the KPZ equation. Moreover, the
argument carries over to other systems like the Lai-Das Sarma-Villain equation,
in which vertex cancellation is known {\em not to} imply an associated symmetry
of the equation.Comment: 34 pages, 9 figures. Journal of Statistical Mechanics: Theory and
Experiments (in press
Refractive elastic scattering of carbon and oxygen nuclei: The mean field analysis and Airy structures
The experimental data on the OC and OC elastic
scatterings and their optical model analysis are presented. Detailed and
complete elastic angular distributions have been measured at the Strasbourg
Vivitron accelerator at several energies covering the energy range between 5
and 10 MeV per nucleon. The elastic scattering angular distributions show the
usual diffraction pattern and also, at larger angles, refractive effects in the
form of nuclear rainbow and associated Airy structures. The optical model
analysis unambiguously shows the evolution of the refractive scattering
pattern. The observed structure, namely the Airy minima, can be consistently
described by a nucleus-nucleus potential with a deep real part and a weakly
absorptive imaginary part. The difference in absorption in the two systems is
explained by an increased imaginary (mostly surface) part of the potential in
the OC system. The relation between the obtained potentials and
those reported for the symmetrical OO and CC
systems is drawn.Comment: 10 pages, 9 figures, Phys. rev. C in pres
Modeling the effect of the oxidation status of the ingredient oil on stability and shelf life of low-moisture bakery products: The case study of crackers
In packed low-moisture foods such as crackers, oxidation is generally the main cause of quality depletion during storage. It is commonly believed, but scarcely investigated, that product shelf life depends on the oxidative status of the lipid ingredients. In this study, the influence of oxidation degree of the ingredient sunflower oil on cracker oxidative stability and hence shelf life was investigated. To this aim, oil with increasing peroxide values (PVs) (5, 11, and 25 mEqO2/kgoil) was used to prepare crackers. Just after production, crackers presented similar peroxide and rancid odor intensity, probably due to the interactive pathways of oxidative and Maillard reactions. Crackers were packed and analyzed for PV and rancid odor during storage at 20, 40, and 60 \u25e6C. Rancid odor well discriminated cracker oxidative status. Relevant oxidation rates were used to develop a shelf life predictive model based on the peroxide value of the ingredient oil. It was estimated that an oil PV from 5 to 15 mEqO2/kgoil shortens cracker Shelf Life (SL) by 50%, independently of storage temperature. These results demonstrate the critical impact of ingredient quality on product performance on the market
Impact of high pressure homogenization on physical properties, extraction yield and biopolymer structure of soybean okara
The effect of high pressure homogenization (HPH) on soy okara
was studied. To this purpose, okara dispersions (10 g/100 g) were
subjected to 1 pass at 50, 100 and 150 MPa and to 5 passes at 150 MPa.
Samples were analyzed for stability, particle size, microstructure, and
viscosity. Results highlighted that the increase of HPH intensity was
associated with the structural disruption of okara particles, leading to
physically stable homogenates having increasing viscosity. This was
mainly attributed to an increase in okara solubility, due to fibre and
protein release. The latter resulted almost complete, reaching values up
to 90% of the protein originally entrapped in okara matrix. Absorbance at
280 nm, SH groups and dimension of proteins revealed that HPH treatments
favoured the extraction of the main protein fractions even if, at the
higher intensity level, extracted proteins probably underwent
conformational changes and reassembling phenomena
Exogenous ghrelin attenuates endotoxin fever in rats
AbstractGhrelin is a gut-derived peptide that plays a role in energy homeostasis. Recent studies have implicated ghrelin in systemic inflammation, showing increased plasma ghrelin levels after endotoxin (lipopolysaccharide, LPS) administration. The aims of this study were (1) to test the hypothesis that ghrelin administration affects LPS-induced fever; and (2) to assess the putative effects of ghrelin on plasma corticosterone secretion and preoptic region prostaglandin (PG) E2 levels in euthermic and febrile rats. Rats were implanted with a temperature datalogger capsule in the peritoneal cavity to record body core temperature. One week later, they were challenged with LPS (50ÎĽg/kg, intraperitoneal, i.p.) alone or combined with ghrelin (0.1mg/kg, i.p.). In another group of rats, plasma corticosterone and preoptic region PGE2 levels were measured 2h after injections. In euthermic animals, systemic administration of ghrelin failed to elicit any thermoregulatory effect, and caused no significant changes in basal plasma corticosterone and preoptic region PGE2 levels. LPS caused a typical febrile response, accompanied by increased plasma corticosterone and preoptic PGE2 levels. When LPS administration was combined with ghrelin fever was attenuated, corticosterone secretion further increased, and the elevated preoptic PGE2 levels were relatively reduced, but a correlation between these two variables (corticosterone and PGE2) failed to exist. The present data add ghrelin to the neurochemical milieu controlling the immune/thermoregulatory system acting as an antipyretic molecule. Moreover, our findings also support the notion that ghrelin attenuates fever by means of a direct effect of the peptide reducing PGE2 production in the preoptic region
Universality of cauliflower-like fronts: from nanoscale thin films to macroscopic plants
Chemical vapor deposition (CVD) is a widely used technique to
grow solid materials with accurate control of layer thickness and composition.
Under mass-transport-limited conditions, the surface of thin films thus produced
grows in an unstable fashion, developing a typical motif that resembles the
familiar surface of a cauliflower plant. Through experiments on CVD production
of amorphous hydrogenated carbon films leading to cauliflower-like fronts,
we provide a quantitative assessment of a continuum description of CVD
interface growth. As a result, we identify non-locality, non-conservation and
randomness as the main general mechanisms controlling the formation of these
ubiquitous shapes.We also show that the surfaces of actual cauliflower plants and
combustion fronts obey the same scaling laws, proving the validity of the theory over seven orders of magnitude in length scales. Thus, a theoretical justification
is provided, which had remained elusive so far, for the remarkable similarity
between the textures of surfaces found for systems that differ widely in physical
nature and typical scales.Publicad
IncidĂŞncia de fungos e desempenho de sementes de mamona.
bitstream/item/34753/1/boletim-125.pd
Solitary pulmonary nodules: Morphological and metabolic characterisation by FDG-PET-MDCT [Nodulo polmonare solitario: Caratterizzazione morfologico-metabolica mediante imaging integrato TCms/FDG-PET]
Purpose. This study was done to analyse the additional morphological and functional information provided by the integration of [18F]-2-fluoro- 2-deoxy-D-glucose positron emission tomography ([18F]-FDG-PET) with contrast-enhanced multidetector computed tomography (MDCT) in the characterisation of indeterminate solitary pulmonary nodules (SPNs). Materials and methods. Fifty-six SPNs, previously classified as indeterminate, were evaluated using a Discovery ST16 PET/CT system (GE Medical Systems) with nonionic iodinated contrast material and [18F]-FDG as a positron emitter. Images were evaluated on a dedicated workstation. Semiquantitative parameters of [18F]-FDG uptake and morphological, volumetric and densitometric parameters before and after contrast administration were analysed. Results were correlated with the histological and follow-up findings. Results. Twenty-six SPNs were malignant and 30 were benign. Malignant lesions at both PET/CT and histology had a mean diameter of 1.8±1.2 cm, a volume doubling time (DT) of 222 days, a mean standardized uptake value (SUV) of 4.7 versus 1.08 in benign lesions and a mean postcontrast enhancement of 44.8 HU as opposed to 4.8 HU in benign nodules. Malignant lesions had a significantly shorter doubling time and significantly greater postcontrast enhancement compared with benign nodules. Based on the SUV and using a cut-off value of >2.5, PET/CT had a sensitivity of 76.9%, specificity of 100%, diagnostic accuracy of 89.2%, positive predictive value (PPV) of 100% and negative predictive value (NPV) of 83.3%. Based on doubling time (cut off <400 days), it had a sensitivity of 76.9%, specificity of 93.3%, accuracy of 85.7%, PPV of 90.9% and NPV of 82.3%. Based on postcontrast enhancement (cut off >15 HU), it had a sensitivity of 92.3%, specificity of 100%, accuracy of 96.4%, PPV of 100% and NPV of 93.7%. Conclusion. PET/CT allows accurate analysis of anatomical/morphological and metabolic/functional correlations of SPN, providing useful data for identifying and locating the disease, for differentiating between malignant and benign nodules and for establishing the aggressiveness and degree of vascularity of pulmonary lesions. Therefore, partly in view of the considerable reduction in time and cost of the single examinations, we believe that PET/CT will gain an increasingly dominant role in the diagnostic and therapeutic approach to lung cancer, especially in the preclinical phase. © 2007 Springer-Verlag
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