Showing papers by "Romanian Academy published in 2008"

Dysregulation of apoptotic signaling in cancer: molecular mechanisms and therapeutic opportunities.

Abstract: Apoptosis is a tightly regulated cell suicide program that plays an essential role in the maintenance of tissue homeostasis by eliminating unnecessary or harmful cells. Defects in this native defense mechanism promote malignant transformation and frequently confer chemoresistance to transformed cells. Indeed, the evasion of apoptosis has been recognized as a hallmark of cancer. Given that multiple mechanisms function at many levels to orchestrate the regulation of apoptosis, a multitude of opportunities for apoptotic dysregulation are present within the intricate signaling network of cell. Several of the molecular mechanisms by which cancer cells are protected from apoptosis have been elucidated. These advances have facilitated the development of novel apoptosis-inducing agents that have demonstrated single-agent activity against various types of cancers cells and/or sensitized resistant cancer cells to conventional cytotoxic therapies. Herein, we will highlight several of the central modes of apoptotic dysregulation found in cancer. We will also discuss several therapeutic strategies that aim to reestablish the apoptotic response, and thereby eradicate cancer cells, including those that demonstrate resistance to traditional therapies.

Water–methanol mixtures: topology of hydrogen bonded network

Abstract: Molecular dynamics simulation has been performed to study the structure of water–methanol mixtures. Besides the evaluation of partial radial distribution functions describing the hydrogen-bonded structure of the mixtures with different composition, the statistical analysis of configurations was introduced resulting in a new insight in the clustering properties and topology of hydrogen-bonded network. The results have shown that mixtures of methanol and water exhibit extended structures in solution. At low methanol concentration the water molecules form a percolated network, the methanol molecules are incorporated as monomers or short chains and together form a percolated system. In methanol-rich mixtures short water chains and longer methanol chains build up the hydrogen-bonded clusters in the system. On the basis of the statistical analysis of configurations obtained from molecular dynamics simulation it has been found that more methanol molecules are connected to non-cyclic entities, while more water molecules form rings that might have been predicted on the basis of the stoichiometry of the mixtures. This finding can be explained by the presence of microscopic configurational inhomogeneity in water–methanol mixtures.

Protein tyrosine phosphatases: structure-function relationships

Abstract: Structural analysis of protein tyrosine phosphatases (PTPs) has expanded considerably in the last several years, producing more than 200 structures in this class of enzymes (from 35 different proteins and their complexes with ligands) The small-medium size of the catalytic domain of approximately 280 residues plus a very compact fold makes it amenable to cloning and overexpression in bacterial systems thus facilitating crystallographic analysis The low molecular weight PTPs being even smaller, approximately 150 residues, are also perfect targets for NMR analysis The availability of different structures and complexes of PTPs with substrates and inhibitors has provided a wealth of information with profound effects in the way we understand their biological functions Developments in mammalian expression technology recently led to the first crystal structure of a receptor-like PTP extracellular region Altogether, the PTP structural work significantly advanced our knowledge regarding the architecture, regulation and substrate specificity of these enzymes In this review, we compile the most prominent structural traits that characterize PTPs and their complexes with ligands We discuss how the data can be used to design further functional experiments and as a basis for drug design given that many PTPs are now considered strategic therapeutic targets for human diseases such as diabetes and cancer

Monitoring pollution in River Mureş, Romania, part II: Metal accumulation and histopathology in fish

Abstract: As a part of an exposure and effect monitoring conducted along the river Mures, Western Romania in 2004, the health status of two indigenous fish species, sneep (Chondrostoma nasus) and European chub (Leuciscus cephalus) was investigated upstream and downstream the city of Arad. In fish, histopathology was assessed in liver and gills, and heavy metals (cadmium, copper, lead and zinc) were analyzed in liver samples. In both fish species, histopathological reactions in the gills (epithelial lifting, focal proliferation of epithelial cells of primary and secondary lamellae and resulting fusion of secondary lamellae, hyperplasia and hypertrophy of mucous cells, focal inflammation and necrosis of epithelial cells) were most severe at the two sampling sites upstream Arad city, which were shown to be polluted by copper, cadmium, faecal coliforms and streptococci in a parallel study. At these two sites, also histopathology in the liver of L. cephalus was more prominent than at the two downstream sites. In C. nasus, symptoms in the liver (focal inflammation with lymphocytic infiltrations, macrophage aggregates and single cell necrosis) were also highly pronounced at the sampling site located directly downstream the municipal sewage treatment plant of Arad. With the exception of copper accumulation in L. cephalus caught at the most upstream sampling site, in both fish species cadmium and copper accumulation were exceptionally high and did not differ significantly between the four sampling sites.

On the solitons and nonlinear wave equations

Abstract: The paper is focused on the solitons and nonlinear equations for an uniaxial deformation problem. The aim is to determine a parametrical representation for a class of constitutive laws for nonhomogeneous media for which the motion equations attached to a material system, is associated to a pseudospherical surface (with negative Gaussian curvature K). A subclass of these constitutive laws can be associated to a Tzitzeica surface, for which the ratio K/d4(d is the distance from the origin to the tangent plane at an arbitrary point), is constant. A genetic algorithm is performed to study three inverse problems associated to some experimental results.

Toeplitz Operators on Symplectic Manifolds

Abstract: We study the Berezin-Toeplitz quantization on symplectic manifolds making use of the full off-diagonal asymptotic expansion of the Bergman kernel. We give also a characterization of Toeplitz operators in terms of their asymptotic expansion. The semi-classical limit properties of the Berezin-Toeplitz quantization for non-compact manifolds and orbifolds are also established.

Indenylidene‐Ruthenium Complexes Bearing Saturated N‐Heterocyclic Carbenes: Synthesis and Catalytic Investigation in Olefin Metathesis Reactions

Abstract: The synthesis of complexes of the general formula Cl2Ru(SIMes)(L)(3-phenylinden-1-ylidene) (5, L = PCy3; 6, L = py; and 7, L = PPh3) from Cl2Ru(PR3)2(3-phenylinden-1-ylidene) (2a, R = Ph; 2b, R = Cy) is reported. This family of olefin metathesis catalysts was fully characterized (1H, 13C and 31P NMR spectroscopy and elemental analysis) and provided excellent activity in the ring-opening metathesis polymerization of 1,5-cyclooctadiene and the ring-closing metathesis of diethyl diallylmalonate. Comparison with the corresponding benzylidene-containing catalysts, 1a,c and 8b, established the decisive role of the carbene ligand on the procedure of the reaction and led to the observation of an unusual catalytic phenomenon, here called “self-inhibition”.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Existence and Non-Existence Results for Quasilinear Elliptic Exterior Problems with Nonlinear Boundary Conditions

Abstract: Existence and non-existence results are established for quasilinear elliptic problems with nonlinear boundary conditions and lack of compactness. The proofs combine variational methods with the geometrical feature, due to the competition between the different growths of the nonlinearities.

A Quick Method for Estimating the Propagation Direction of Coronal Mass Ejections Using STEREO-COR1 Images

Abstract: We describe here a method to obtain the position of a coronal moving feature in a three-dimensional coordinate system based on height – time measurements applied to STEREO data. By using the height – time diagrams from the two SECCHI-COR1 coronagraphs onboard STEREO, one can easily determine the direction of propagation of a coronal mass ejection (i.e., if the moving plasma is oriented toward or away from the Earth). This method may prove to be a useful tool for space weather forecasting by easily identifying the direction of propagation as well as the real speed of the coronal mass ejections.

Surfactant double layer stabilized magnetic nanofluids for biomedical application

Abstract: Magnetite nanoparticles were coated with surfactant double layers in order to prepare water based magnetic fluids (MFs). The effects of head group (sulfonate, carboxylate) and alkyl chain length (11-17 C atoms) and the combination of surfactants were studied. Adsorption, dynamic light scattering (DLS) and electrophoretic mobility measurements were performed. The quantity of surfactant varied between 0.3 and 0.5 g, i.e. their specific amount ranges over 1.5-2 mmol g(-1) magnetite in MFs. The adsorption isotherm of Na oleate on magnetite proved the double layer formation with 2 mmol g(-1) saturation value in good harmony with the empirical doses. The effect of diluting MFs, pH and salt concentration was studied. The pH-dependent stability and the salt tolerance of MFs were different owing to the dissociation of the outermost hydrophilic groups and the hydrophobic interactions scaling with the alkyl chain length of surfactant. The hydrophobic interactions are favored only for oleic and myristic acid double layers. In these MFs, aggregation cannot be observed even in fairly dilute systems up to the physiological salt concentration around neutral pH 6-8 favored in biomedical application. The stable oleic and myristic acid double layers can hinder effectively the aggregation of magnetite particles due to the combined steric and electrostatic stabilization.

Overview of the CLEF 2007 Multilingual Question Answering Track

Abstract: The fifth QA campaign at CLEF [1], having its first edition in 2003, offered not only a main task but an Answer Validation Exercise (AVE) [2], which continued last year's pilot, and a new pilot: the Question Answering on Speech Transcripts (QAST) [3, 15]. The main task was characterized by the focus on cross-linguality, while covering as many European languages as possible. As novelty, some QA pairs were grouped in clusters. Every cluster was characterized by a topic (not given to participants). The questions from a cluster possibly contain co-references between one of them and the others. Finally, the need for searching answers in web formats was satisfied by introducing Wikipedia as document corpus. The results and the analyses reported by the participants suggest that the introduction of Wikipedia and the topic related questions led to a drop in systems' performance.

The Lebesgue decomposition of the free additive convolution of two probability distributions

Abstract: We prove that the free additive convolution of two Borel probability measures supported on the real line can have a component that is singular continuous with respect to the Lebesgue measure on $${\mathbb{R}}$$ only if one of the two measures is a point mass. The density of the absolutely continuous part with respect to the Lebesgue measure is shown to be analytic wherever positive and finite. The atoms of the free additive convolution of Borel probability measures on the real line have been described by Bercovici and Voiculescu in a previous paper.

On iterated twisted tensor products of algebras

Abstract: We introduce and study the definition, main properties and applications of iterated twisted tensor products of algebras, motivated by the problem of defining a suitable representative for the product of spaces in noncommutative geometry. We find conditions for constructing an iterated product of three factors and prove that they are enough for building an iterated product of any number of factors. As an example of the geometrical aspects of our construction, we show how to construct differential forms and involutions on iterated products starting from the corresponding structures on the factors and give some examples of algebras that can be described within our theory. We prove a certain result (called "invariance under twisting") for a twisted tensor product of two algebras, stating that the twisted tensor product does not change when we apply certain kind of deformation. Under certain conditions, this invariance can be iterated, containing as particular cases a number of independent and previously unrel...

Continuous spectrum for a class of nonhomogeneous differential operators

Abstract: We study the boundary value problem $$-{\rm div}((| abla u|^{p_1(x)-2}+| abla u|^{p_2(x)-2}) abla u)=\lambda|u|^{q(x)-2}u$$ in Ω, u = 0 on ∂Ω, where Ω is a bounded domain in $$\mathbb{R}^N$$ with smooth boundary, λ is a positive real number, and the continuous functions p 1, p 2, and q satisfy 1 < p 2(x) < q(x) < p 1(x) < N and $$\max_{y\in\overline\Omega}q(y) < \frac{N p_2(x)}{N-p_2(x)}$$ for any $$x\in\overline\Omega$$ . The main result of this paper establishes the existence of two positive constants λ0 and λ1 with λ0 ≤ λ1 such that any $$\lambda\in[\lambda_1,\infty)$$ is an eigenvalue, while any $$\lambda\in(0,\lambda_0)$$ is not an eigenvalue of the above problem.

Hodge genera of algebraic varieties I

Abstract: The aim of this paper is to study the behavior of Hodge-theoretic (intersection homology) genera and their associated characteristic classes under proper morphisms of complex algebraic varieties. We obtain formulae that relate (parametrized families of) global invariants of a complex algebraic variety X to such invariants of singularities of proper algebraic maps defined on X. Such formulae severely constrain, both topologically and analytically, the singularities of complex maps, even between smooth varieties. Similar results were announced by the first and third author in [13, 32]. © 2007 Wiley Periodicals, Inc.

Preparation of core-shell nanospheres of silica-silver : SiO2@Ag

Abstract: We prepared SiO 2 @Ag core–shell nanospheres: silver nanoparticles (∼4 ± 2 nm in diameter) coated silica nanospheres (∼50 ± 10 nm in diameter). The preparation route is a modification of the Stober method, and involves the preparation of homogeneous silica spheres at room temperature, combined with the deposition of silver nanoparticles from Ag + in solution, by using water/ethanol mixtures, tetraethyl-orthosilicate as Si source and silver nitrate as Ag source in a single-pot wet chemical route without an added coupling agent or surface modification, which leads to the formation of core@shell homogeneous nanospheres. We present the preparation and characterization of the SiO 2 @Ag core–shell nanospheres and also of bare silica spheres in the absence of silver, and propose a reaction mechanism for the formation of the core–shell structure.

A method of solving fully fuzzified linear fractional programming problems

Abstract: In this paper, we propose a method of solving the fully fuzzified linear fractional programming problems, where all the parameters and variables are triangular fuzzy numbers. We transform the problem of maximizing a function with triangular fuzzy value into a deterministic multiple objective linear fractional programming problem with quadratic constraints. We apply the extension principle of Zadeh to add fuzzy numbers, an approximate version of the same principle to multiply and divide fuzzy numbers and the Kerre’s method to evaluate a fuzzy constraint. The results obtained by Buckley and Feuring in 2000 applied to fractional programming and disjunctive constraints are taken into consideration here. The method needs to add extra zero-one variables for treating disjunctive constraints. In order to illustrate our method we consider a numerical example.

Interface-Stabilized Phases of Metal-on-Oxide Nanodots

Abstract: The control of the structure of oxide-supported metal nanoparticles is crucial in determining their properties and possible applications. Here, building principles are derived for predicting the epitaxies of metal nanoparticles on square-symmetry oxide surfaces. Unusual phases are found for an appropriate choice of the metal−oxide pair, where nanoparticles with hcp structure are stabilized for fcc metals such as Ni, Pd, and Pt, or for Co in a size range in which Co has typically nonhcp arrangements. These predictions are supported by a comparison with available experimental data on Ni/MgO(100) nanodots, and generalized to a whole class of metal−oxide systems of great potential interest, such as Pd and Pt on CaO, Ni on CoO, and Co on MgO. The atomistic features of the nanoparticles in turn suggest that these materials should possess peculiar properties; in particular, the facets exposed by the nanodots reveal adsorption sites with unusual geometry of possible effect on their catalytic properties, while the...

RACAI's Linguistic Web Services.

Abstract: Nowadays, there are hundreds of Natural Language Processing applications and resources for different languages that are developed and/or used, almost exclusively with a few but notable exceptions, by their creators. Assuming that the right to use a particular application or resource is licensed by the rightful owner, the user is faced with the often not so easy task of interfacing it with his/her own systems. Even if standards are defined that provide a unified way of encoding resources, few are the cases when the resources are actually coded in conformance to the standard (and, at present time, there is no such thing as general NLP application interoperability). Semantic Web came with the promise that the web will be a universal medium for information exchange whatever its content. In this context, the present article outlines a collection of linguistic web services for Romanian and English, developed at the Research Institute for AI for the Romanian Academy (RACAI) which are ready to provide a standardized way of calling particular NLP operations and extract the results without caring about what exactly is going on in the background.

Properties of Polymer Composites with Cellulose Microfibrils

Abstract: Polypropylene-based composites containing 10–30% by weight cellulose microfibrils were studied. Composites with polypropylene and cellulose microfibrils were characterised by MS-coupled simultaneous TGA-DSC and the reinforcing effect of cellulose microfibrils was emphasised by mechanical characterization. Experimental results are discussed in connection with the composite preparation method by mixing and extrusion. The effect of cellulose on the thermal stability and degradation behaviour of the polypropylene matrix is pointed out.

Magnetite Nanoparticles Stabilized Under Physiological Conditions for Biomedical Application

Abstract: The biomedical application of water based magnetic fluids (MFs) is of great practical importance. Their colloidal stability under physiological conditions (blood pH ∼ 7.2–7.4 and salt concentration ∼0.15 M) and more in high magnetic field gradient is crucial. Magnetite or maghemite nanoparticles are used in general. In the present work, magnetite nanoparticles were stabilized with different compounds (citric acid (CA) and phosphate) and sodium oleate (NaO) as the most used surfactant in the stabilization of MFs. The adsorption and overcharging effect were quantified, and the enhancement in salt tolerance of stabilized systems was studied. Adsorption, electrophoretic mobility and dynamic light scattering (DLS) measurements were performed. The electrolyte tolerance was tested in coagulation kinetic measurements. Above the adsorption saturation, the nanoparticles are stabilized in a way of combined steric and electrostatic effects. The aim was to research these two important effects and demonstrate that none of them alone is enough. The phosphate was not able to stabilize the ferrofluid in spite of our expectation, but the other two additives proved to be effective stabilizing agents. The magnetite was well stabilized by the surface complexation of CA above pH ∼ 5, however, the salt tolerance of citrate stabilized MFs remained much below the concentration of physiological salt solution, and more the dissolution of magnetite nanocrystals was enhanced due to Fe-CA complexation in aqueous medium, which may cause problems in vivo. The oleate double layers were able to stabilize magnetite nanoparticles perfectly at pH ∼ 6 preventing particle aggregation effectively even in physiological salt solution.

Solubility of carbon dioxide in two pentaerythritol ester oils between (283 and 333) K

Abstract: In this work, the solubility of carbon dioxide, CO2, in pentaerythritol tetrapentanoate (PEC5) and in pentaerythritol tetra(2-ethylhexanoate) (PEBE8) has been performed from (283 to 333) K and pressures up to 7 MPa in a new high-pressure gas solubility apparatus. The results show that in the present analyzed range CO2 is highly soluble in these oils and that the solubility expressed as CO2 mole fraction is practically not dependent on the branching of the acid chain, whereas it increases slightly with the length of the PE acid chains in the present range of compositions. The gas solubility data were satisfactorily correlated with the Soave−Redlich−Kwong (SRK) equation of state (EOS) using the conventional quadratic mixing rule with two interaction parameters for each temperature.

Free Base Porphyrins as Ionophores for Heavy Metal Sensors.

Abstract: Two functionalized porphyrins: 5,10,15,20-tetrakis(3,4-dimethoxyphenyl) porphyrin (A) and 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (B) obtained and characterized by us were used as ionophores (I) for preparing PVC-based membrane sensors selective to Ag + , Pb 2+ and Cu 2+ . The membranes were prepared using three different plasticizers: (bis(2-ethylhexyl)sebacate (DOS), dioctylphtalate (DOP), o -nitro-phenyl octyl ether (NPOE) and potassium tetrakis(4-chlorophenyl)borate (KTClPB) as additive. The functional parameters (linear concentration range, slope and selectivity) of the sensors with membrane composition: (I:PVC:KTClPB:Plasticizer) in different ratios were investigated. The best results were obtained for the membranes in the ratio I:PVC:KTClPB:Plasticizer 10:165:5:330. The influence of pH on the sensors response was studied. The sensors were used for a period of four months and their utility has been tested on synthetic and real samples. Keywords: Porphyrins, ionophores, sensors, heavy metals, PVC-matrix.