University of Patras

About: University of Patras is a education organization based out in Pátrai, Greece. It is known for research contribution in the topics: Population & Catalysis. The organization has 13372 authors who have published 31263 publications receiving 677159 citations. The organization is also known as: Panepistímio Patrón.

Riemannian flag manifolds with homogeneous geodesics

Abstract: A geodesic in a Riemannian homogeneous manifold (M = G/K, g) is called a homogeneous geodesic if it is an orbit of a one-parameter subgroup of the Lie group G. We investigate G-invariant metrics with homogeneous geodesics (i.e., such that all geodesics are homogeneous) when M = G/K is a flag manifold, that is, an adjoint orbit of a compact semisimple Lie group G. We use an important invariant of a flag manifold M = G/K, its T-root system, to give a simple necessary condition that M admits a non-standard G-invariant metric with homogeneous geodesics. Hence, the problem reduces substantially to the study of a short list of prospective flag manifolds. A common feature of these spaces is that their isotropy representation has two irreducible components. We prove that among all flag manifolds M = G/K of a simple Lie group G, only the manifold Com(R 2l+2 ) = SO(2l +1)/U(l) of complex structures in R 2l+2 , and the complex projective space CP 2l-1 = Sp(l)/U(1) " Sp(l- 1) admit a non-naturally reductive invariant metric with homogeneous geodesics. In all other cases the only G-invariant metric with homogeneous geodesics is the metric which is homothetic to the standard metric (i.e., the metric associated to the negative of the Killing form of the Lie algebra g of G). According to F. Podesta and G.Thorbergsson (2003), these manifolds are the only non-Hermitian symmetric flag manifolds with coisotropic action of the stabilizer.

Exploring the adsorption mechanisms of cationic and anionic dyes onto agricultural waste peels of banana, cucumber and potato: adsorption kinetics and equilibrium isotherms as a tool.

Abstract: Banana (BP), cucumber (CP) and potato peels (PP) were used as biosorbents for the removal of both cationic (Methylene blue) and anionic (Orange G) dyes from wastewater. The biosorbents were characterized by ATR-FTIR, N2 Sorption, SEM, and XRD attempting to shed light on the adsorption mechanisms. The ATR-FTIR spectroscopy played a key-role for the chemical characterization of the different biosorbents in order to investigate their composition and in parallel for clarifying the nature of the adsorbent/dye interactions. The effect of pH, biosorbent dose, contact time and dye concentration were investigated. The ranking of adsorption capacity for CMB = 10–80 mg/L was BP > PP > CP whereas for CMB = 80–300 mg/L was BP > CP > PP. Regarding OG, the ranking was CP > PP > BP over the whole concentration range (10–300 mg/L). The biosorption of MB on BP and PP followed the Langmuir isotherm whereas biosorption on CP followed the Freundlich isotherm for low MB concentration values and the Langmuir isotherm for high MB concentrations. The biosorption of OG on BP, PP and CP was better described by the Langmuir isotherm. The maximum monolayer adsorption capacities for MB were found to be 211.9, 107.2 and 179.9 mg/g for BP, PP and CP (pH = 6) respectively, whereas the corresponding ones for OG were found to be 20.9, 23.6 and 40.5 mg/g (pH = 2). Adsorption kinetic models revealed that chemisorption was the dominant biosorption mechanism.

Green governors: A framework for Continuously Adaptive DVFS

Abstract: We present Continuously Adaptive Dynamic Voltage/Frequency scaling in Linux systems running on Intel i7 and AMD Phenom II processors. By exploiting slack, inherent in memory-bound programs, our approach aims to improve power efficiency even when the processor does not sit idle. Our underlying methodology is based on a simple first-order processor performance model in which frequency scaling is expressed as a change (in cycles) of the main memory latency. Utilizing available monitoring hardware we show that our model is powerful enough to i) predict with reasonable accuracy the effect of frequency scaling (in terms of performance loss) and ii) predict the core energy under different V/f combinations. To validate our approach we perform highly accurate, fine-grained power measurements directly on the off-chip voltage regulators. We use our model to implement various DVFS policies as Linux “green” governors to continuously optimize for various power-efficiency metrics such as EDP or ED2P, or achieve energy savings with a user-specified limit on performance loss. Our evaluation shows that, for SPEC2006 workloads, our governors achieve dynamically the same optimal EDP or ED2P (within 2% on avg.) as an exhaustive search of all possible frequencies. Energy savings can reach up to 56% in memory-bound workloads with corresponding improvements of about 55% for EDP or ED2P.

Angiopoietins in angiogenesis and beyond

Abstract: The angiopoietin (Ang) family of growth factors includes four members, all of which bind to the endothelial receptor tyrosine kinase Tie2. Two of the Angs, Ang-1 and Ang-4, activate the Tie2 receptor, whereas Ang-2 and Ang-3 inhibit Ang-1-induced Tie2 phosphorylation. While genetic models have underscored the importance of Angs in the developing cardiovascular system, other studies have demonstrated that Ang-1 promotes endothelial cell survival, sprouting and tube formation. More recently, a new aspect of the biology of this class of growth factors has emerged, namely the ability of Ang-1 to reduce inflammation. This review presents an outline of Angs and their receptors, examining their structure, expression, signalling, regulation and biological significance and comments on the role and potential usefulness of Angs in medicine.