Time filter

Source Type

Kalampounias A.G.,University of Patras | Kalampounias A.G.,Institute of Chemical Engineering And High Temperature Chemical Processes
Journal of Physics and Chemistry of Solids

In this paper we present the picosecond vibrational dynamics of a series of binary metaphosphate glasses, namely Na2OP2O5, MOP2O5 (M=Ba, Sr, Ca, Mg) and Al2O 33P2O5 by means of Raman spectroscopy. We studied the vibrational dephasing and vibrational frequency modulation by calculating time correlation functions of vibrational relaxation by fits in the frequency domain. The fitting method used enables one to model the real line profiles intermediate between Lorentzian and Gaussian by an analytical function, which has an analytical counterpart in the time domain. The symmetric stretching modes νs(PO2 -) and νs(POP) of the PO2 - entity of PØ2O2 - units and of POP bridges in metaphosphate arrangements have been investigated by Raman spectroscopy and we used them as probes of the dynamics of these glasses. The vibrational time correlation functions of both modes studied are rather adequately interpreted within the assumption of exponential modulation function in the context of KuboRothschield theory and indicate that the system experiences an intermediate dynamical regime that gets only slower with an increase in the ionic radius of the cation-modifier. We found that the vibrational correlation functions of all glasses studied comply with the Rothschild approach assuming that the environmental modulation is described by a stretched exponential decay. The evolution of the dispersion parameter α with increasing ionic radius of the cation indicates the deviation from the model simple liquid indicating the reduction of the coherence decay in the perturbation potential as a result of local short lived aggregates. The results are discussed in the framework of the current phenomenological status of the field. © 2011 Elsevier Ltd. All rights reserved. Source

Tsakiroglou C.D.,Institute of Chemical Engineering And High Temperature Chemical Processes
AIChE Journal

A method is suggested to compute the capillary pressure and relative permeability curves of heterogeneous porous media. The broad pore radius distribution (PRD) and throat radius distribution (TRD) are decomposed into relatively narrow component distribution functions which are used for the computer-aided construction of pore-and-throat networks. The quasi-static motion of menisci in pores and throats is tracked by accounting for capillary forces. The presence of fractal roughness along pore walls ensures the coexistence of both phases in pores. The calculation of the hydraulic conductance of each phase is based on the concept of constricted unit cell. Simulations in component pore networks constructed from narrow PRD and TRD produce a set of capillary pressure and relative permeability functions, the arithmetic averaging of which yields the corresponding functions for a heterogeneous synthetic pore network. This information is used by a dynamic simulator of drainage in permeability networks to predict experimental results of soil columns. © 2010 American Institute of Chemical Engineers (AIChE). Source

Gialeli C.,University of Patras | Theocharis A.D.,University of Patras | Karamanos N.K.,University of Patras | Karamanos N.K.,Institute of Chemical Engineering And High Temperature Chemical Processes
FEBS Journal

Matrix metalloproteinases (MMPs) consist of a multigene family of zinc-dependent extracellular matrix (ECM) remodeling endopeptidases implicated in pathological processes, such as carcinogenesis. In this regard, their activity plays a pivotal role in tumor growth and the multistep processes of invasion and metastasis, including proteolytic degradation of ECM, alteration of the cell-cell and cell-ECM interactions, migration and angiogenesis. The underlying premise of the current minireview is that MMPs are able to proteolytically process substrates in the extracellular milieu and, in so doing, promote tumor progression. However, certain members of the MMP family exert contradicting roles at different stages during cancer progression, depending among other factors on the tumor stage, tumor site, enzyme localization and substrate profile. MMPs are therefore amenable to therapeutic intervention by synthetic and natural inhibitors, providing perspectives for future studies. Multiple therapeutic agents, called matrix metalloproteinase inhibitors (MMPIs) have been developed to target MMPs, attempting to control their enzymatic activity. Even though clinical trials with these compounds do not show the expected results in most cases, the field of MMPIs is ongoing. This minireview critically evaluates the role of MMPs in relation to cancer progression, and highlights the challenges, as well as future prospects, for the design, development and efficacy of MMPIs. © 2010 The Authors Journal compilation. Source

Iatridi Z.,University of Patras | Tsitsilianis C.,University of Patras | Tsitsilianis C.,Institute of Chemical Engineering And High Temperature Chemical Processes
Chemical Communications

We report on the association capability of a novel multisegmented, multiarm star terpolymer to form a diversity of pH-responsive amphoteric micellar nanostructured self-assemblies. © 2011 The Royal Society of Chemistry. Source

Tsakiroglou C.D.,Institute of Chemical Engineering And High Temperature Chemical Processes
Transport in Porous Media

The immiscible displacement of a wetting fluid by a non-wetting one in heterogeneous porous media is modeled using a multi-scale network-type analysis: (1) The pressure-controlled immiscible displacement of water by oil in pore-and-throat networks (1st length scale ~ 1 mm) is simulated as a capillary-driven process. (2) The pressure-controlled immiscible displacement in uncorrelated cubic lattices (2nd length scale ~ 1 cm) is simulated as a site percolation process governed by capillary and gravity forces. At this scale, each node represents a network of the previous scale. (3) The rate-controlled immiscible displacement of water by oil in cubic networks (3rd length scale ~ 10 cm), where each node represents a lattice of the previous scale, is simulated by accounting for capillary, gravity, and viscous forces. The multi-scale approach along with the information concerning the pore structure properties of the porous medium can be employed to determine the transient responses of the pressure drop and axial distribution of water saturation, and estimate the effective (up-scaled) relative permeability functions. The method is demonstrated with application to data of highly heterogeneous soils. © 2011 Springer Science+Business Media B.V. Source

Discover hidden collaborations