1,228 research outputs found
Suppression of beta1,3galactosyltransferase beta3Gal-T5 in cancer cells reduces sialyl-Lewis a and enhances poly-N-acetyllactosamines and sialyl-Lewis x on O-glycans
We investigated the role of beta 3 Gal-T5, a member of the beta 1,3galactosyltransferase (beta 1,3Gal-T) family, in cancer-associated glycosylation, focusing on the expression of sialyl-Lewis a (sLea, the epitope of CA19.9 antigen), poly N-acetyllactosamines, and sialyl-Lewis x (sLex) antigen. A clone permanently expressing an antisense fragment of beta 3Gal-T5 was obtained from the human pancreas adenocarcinoma cell line BxPC3 and characterized. Both beta 1,3Gal-T activity and sLea expression are dramatically impaired in the clone. Analysis of the oligosaccharides synthesized in cells metabolically labelled with tritiated galactose shows that a relevant amount of radioactivity is associated to large O-glycans. Endo-beta-galactosidase mostly releases NeuAc alpha 2-3Gal beta 1-3[Fuc alpha 1-4]GlcNAc beta 1-3Gal and NeuAc alpha 2-3Gal beta 1-3GlcNAc beta 1-3Gal from such O-glycans of BxPC3 membranes, but GlcNAc beta 1-3Gal and type 2 chain oligosaccharides, including NeuAc alpha 2-3Gal beta 1-4[Fuc alpha 1-3]GlcNAc beta 1-3Gal, from those of the antisense clone. Furthermore, BxPC3 cells secrete sLea in the culture media but not sLex, while antisense clone secretes mostly sLex, and accumulation of both antigens is prevented by benzyl-alpha-GalNAc. These data indicate that beta 3Gal-T5 suppression turns synthesis of type 1 chain O-glycans to poly N-acetyllactosamine elongation and termination by sLex. In other cell lines and clones, beta 3Gal-T5 transcript, beta 1,3Gal-T activity, and sLea antigen are also correlated, but quantitatively the relative expression ratios are very different from cell type to cell type. We suggest that beta 3Gal-T5 plays a relevant role in gastrointestinal and pancreatic tissues counteracting the glycosylation pattern associated to malignancy, and is necessary for the synthesis and secretion of CA19.9 antigen, whose expression still depends on multiple interacting factors
Heat transfer and turbulent heat flux budgets in cooling films
Statistics from large-eddy-simulation (LES) of cooling films with different cooling holes are used to evaluate budgets in the transport equation of turbulent heat flux. The capability of LES has been assessed by comparing simulated results with experimental data, while the correctness of the procedure generating turbulent heat flux budgets has been examined on a turbulent boundary layer. The mechanism of heat transfer has been preliminarily studied throughout the three-dimensional flow field at different blowing ratios using a general outer scaling, to recognize specific regions with corresponding heat transfer patterns. A compressible version of budget terms in the transport equation of turbulent heat flux is then explored to show the thermal behavior of flow downstream from the cooling film holes. Characteristics of each budget term are presented in a defect scaling consistent with the scaling suitable for Reynolds stresses and Reynolds stress budgets. Furthermore, these budget terms are compared among an array of different cooling hole shapes combined with different blowing ratios to explore self-similarity. Results show that the dynamic balance of all budget terms is significantly influenced by the cooling hole shape, while each turbulent heat flux budget term may scale with the velocity defect, temperature deficit, and the normalized streamwise distance to the power of an exponent dependent on the hole shape
Opinion formation models based on game theory
A way to simulate the basic interactions between two individuals with
different opinions, in the context of strategic game theory, is proposed.
Various games are considered, which produce different kinds of opinion
formation dynamics. First, by assuming that all individuals (players) are
equals, we obtain the bounded confidence model of continuous opinion dynamics
proposed by Deffuant et al. In such a model a tolerance threshold is defined,
such that individuals with difference in opinion larger than the threshold can
not interact. Then, we consider that the individuals have different
inclinations to change opinion and different abilities in convincing the
others. In this way, we obtain the so-called ``Stubborn individuals and
Orators'' (SO) model, a generalization of the Deffuant et al. model, in which
the threshold tolerance is different for every couple of individuals. We
explore, by numerical simulations, the dynamics of the SO model, and we propose
further generalizations that can be implemented.Comment: 18 pages, 4 figure
Analysis of the commutation error of filtering operators for the double-averaged equations of flows in porous media in a LES formalism
The continuum approach employing porous media models is an attractive
solution method in the area of Computational Fluid Dynamics (CFD) simulation of
fixed-bed reactors due to its robustness and efficiency. This paper applies the
double-averaging methodology to refine the mathematical basis for the continuum
approach, opening a way to alleviate its main limitations: space-invariant
averaging volume and inaccurate treatment of the porous/non-porous interface.
The averaging operator is recast as a general space-time filter and a detailed
analysis of commutation errors is performed, using a classic Large Eddy
Simulation (LES) formalism. An explicit filtering framework has been
implemented in the open-source CFD library OpenFOAM to carry out an
a-posteriori evaluation of the unclosed terms appearing in the Double-Averaged
Navier-Stokes (DANS) equations also considering a space-varying filter width.
Two resolved simulations have been performed. First, the flow around a single,
stationary particle has been considered and used to validate derived equations
and the filtering procedure. Second, an LES of the turbulent flow in a channel
partly occupied with a porous medium has been conducted. The results have been
filtered, and the commutation error at the porous-fluid interface has been
evaluated and compared to the prediction of two models. The significance of the
commutation error terms is also discussed and assessed. Finally, the solver for
DANS equations has been developed and used to simulate both of the studied
geometries. The magnitude of the error associated with neglecting the
commutation errors has been investigated and an LES simulation combined with a
porous drag model was performed. Very encouraging results have been obtained
indicating that the inaccuracy of the drag closure overshadows the error
related to the commutation of operators.Comment: This material has been submitted to Physics of Fluids. It contains 33
pages and 21 Figure
Generating high-efficiency swimming kinematics using hydrodynamic eigenmode decomposition
This paper explores the use of hydrodynamic eigenmode decomposition as a means of generating optimal swimming kinematics of slender three-dimensional bodies. The eigenvectors of the unsteady hydrodynamic system are used as basis functions for the response to external forcing, such as perturbations generated by the deformation of the body. Exploiting the orthogonality of the modes, we show that swimming according to a single appropriately selected hydrodynamic eigenmode results in high-efficiency swimming. To demonstrate this result, we use an inviscid three-dimensional vortex lattice model to investigate the hydrodynamic eigenmodes of a selection of geometries. We find that for all of the body geometries tested, hydrodynamic efficiency far exceeding that of pure heaving or pitching can be achieved. All eigenmodes tested produce high-efficiency motion, as long as the beat frequency is higher than the mode's “cut-in” frequency for thrust generation. The eigenmodes show qualitative similarity to swimming patterns observed in nature and also correspond well to the existing classifications of undulatory and oscillatory swimming. This study demonstrates that the hydrodynamic eigenmode analysis can generate high-efficiency swimming kinematics based only on information about the body and wake geometry, and as such, this method has significant potential for further development and application to autonomous underwater vehicle design
Fast calculation of real fluid properties for steam turbine CFD analysis with the new IAPWS standard on the spline-based table look-Up method (SBTL)
Workshop byl částečně podpořen projektem CZ.1.07/2.3.00/20.0139. Tento projekt je spolufinancován
Evropským sociálním fondem a státním rozpočtem České republiky
Cortical linear lesions in Wernicke's encephalopathy: can diffusion-weighted imaging herald prognostic information?
- …