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Search Results: 1 - 10 of 8294 matches for " Teresa Selistrovski "
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Importance of grain boundary Josephson junctions in the electron-doped infinite-layer cuprate superconductor Sr$_{1-x}$La$_x$CuO$_2$
Jochen Tomaschko,Victor Leca,Teresa Selistrovski,Reinhold Kleiner,Dieter Koelle
Physics , 2011, DOI: 10.1103/PhysRevB.84.214507
Abstract: Grain boundary bicrystal Josephson junctions of the electron-doped infinite-layer superconductor Sr$_{1-x}$La$_x$CuO$_2$ ($x = 0.15$) were grown by pulsed laser deposition. BaTiO$_3$-buffered $24\,^\circ$ [001]-tilt symmetric SrTiO$_3$ bicrystals were used as substrates. We examined both Cooper pair (CP) and quasiparticle (QP) tunneling by electric transport measurements at temperatures down to 4.2\,K. CP tunneling revealed an extraordinary high critical current density for electron-doped cuprates of $j_c > 10^3\,$A/cm$^2$ at 4.2\,K. Thermally activated phase slippage was observed as dissipative mechanism close to the transition temperature. Out-of-plane magnetic fields $H$ revealed a remarkably regular Fraunhofer-like $j_c(H)$ pattern as well as Fiske and flux flow resonances, both yielding a Swihart velocity of $3.1\cdot10^6\,$m/s. Furthermore, we examined the superconducting gap by means of QP tunneling spectroscopy. The gap was found to be V-shaped with an extrapolated zero temperature energy gap $\Delta_0 \approx 2.4\,$meV. No zero bias conductance peak was observed.
Properties of the electron-doped infinite-layer superconductor Sr$_{1-x}$La$_{x}$CuO$_{2}$ epitaxially grown by pulsed laser deposition
Jochen Tomaschko,Victor Leca,Teresa Selistrovski,Sebastian Diebold,Josef Jochum,Reinhold Kleiner,Dieter Koelle
Physics , 2011, DOI: 10.1103/PhysRevB.85.024519
Abstract: Thin films of the electron-doped infinite-layer cuprate superconductor Sr$_{1-x}$La$_x$CuO$_2$ (SLCO) with doping $x \approx 0.15$ were grown by means of pulsed laser deposition. (001)-oriented KTaO$_3$ and SrTiO$_3$ single crystals were used as substrates. In case of SrTiO$_3$, a BaTiO$_3$ thin film was deposited prior to SLCO, acting as buffer layer providing tensile strain to the SLCO film. To induce superconductivity, the as-grown films were annealed under reducing conditions, which will be described in detail. The films were characterized by reflection high-energy electron diffraction, atomic force microscopy, x-ray diffraction, Rutherford backscattering spectroscopy, and electric transport measurements at temperatures down to $T = 4.2\,$K. We discuss in detail the influence of different process parameters on the final film properties.
Phase-sensitive evidence for dx2-y2-pairing symmetry in the parent-structure high-Tc cuprate superconductor Sr1-xLaxCuO2
J. Tomaschko,S. Scharinger,V. Leca,J. Nagel,M. Kemmler,T. Selistrovski,D. Koelle,R. Kleiner
Physics , 2012, DOI: 10.1103/PhysRevB.86.094509
Abstract: Even after 25 years of research the pairing mechanism and - at least for electron doped compounds - also the order parameter symmetry of the high transition temperature (high-Tc) cuprate superconductors is still under debate. One of the reasons is the complex crystal structure of most of these materials. An exception are the infinite layer (IL) compounds consisting essentially of CuO2 planes. Unfortunately, these materials are difficult to grow and, thus, there are only few experimental investigations. Recently, we succeeded in depositing high quality films of the electron doped IL compound Sr1-xLaxCuO2 (SLCO), with x approximately 0.15, and on the fabrication of well-defined grain boundary Josephson junctions (GBJs) based on such SLCO films. Here we report on a phase sensitive study of the superconducting order parameter based on GBJ SQUIDs from a SLCO film grown on a tetracrystal substrate. Our results show that also the parent structure of the high-Tc cuprates has dx2-y2-wave symmetry, which thus seems to be inherent to cuprate superconductivity.
Greedy Friensdhip Decompositions of Graphs  [PDF]
Teresa Sousa
Open Journal of Discrete Mathematics (OJDM) , 2011, DOI: 10.4236/ojdm.2011.11004
Abstract: A graph that consists of t cliques sharing a vertex v is said to be a t-friendship graph with center v. A friendship graph is a graph that is t-friendship for some . We solve the problem of finding the best upper bound for the size of a greedy 2-friendship decomposition and a greedy friendship decomposition of graphs of order n.
The H-Decomposition Problem for Graphs  [PDF]
Teresa Sousa
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.311237
Abstract: The concept of H-decompositions of graphs was first introduced by Erd?s, Goodman and Pósa in 1966, who were motivated by the problem of representing graphs by set intersections. Given graphs G and H, an H-decomposition of G is a partition of the edge set of G such that each part is either a single edge or forms a graph isomorphic to H. Let Ф(n,H) be the smallest number Ф, such that, any graph of order n admits an H-decomposition with at most Ф parts. The exact computation of Ф(n,H) for an arbitrary H is still an open problem. Recently, a few papers have been published about this problem. In this survey we will bring together all the results about H-decompositions. We will also introduce two new related problems, namely Weighted H-Decompositions of graphs and Monochromatic H-Decom- positions of graphs.
4-Cycle Decompositions of Graphs  [PDF]
Teresa Sousa
Open Journal of Discrete Mathematics (OJDM) , 2012, DOI: 10.4236/ojdm.2012.24024
Abstract: In this paper we consider the problem of finding the smallest number such that any graph G of order n admits a decomposition into edge disjoint copies of C4 and single edges with at most elements. We solve this problem for n sufficiently large.
Friendship Decompositions of Graphs: The general problem  [PDF]
Teresa Sousa
Open Journal of Applied Sciences (OJAppS) , 2012, DOI: 10.4236/ojapps.2012.24B008
Abstract: A friendship graph is a graph consisting of cliques sharing a common vertex. In this paper we investigate the maximum number of elements in an optimal friendship decomposition of graphs of order n. We obtain upper and lower bounds for this number. These bounds relate this problem with the classical Ramsey numbers.
Justification of public investment initiatives on water transfer systems as an instrument for water balances in Spain: the case of the Júcar–Vinalopó water transfer system  [PDF]
Martin Sevilla, Teresa Torregrosa
Agricultural Sciences (AS) , 2011, DOI: 10.4236/as.2011.24067
Abstract: One of the most controversial issues in recent years in water management has been finding a balance between available resources and water needs related to certain territories. The changes brought about by a new awareness over the need to preserve the environment, the social perception of the ownership of the river channels, the need for adjust financial costs arising from the waterworks and the compliance with European standards urgently require redesign of water supply policies in force at this time. The Júcar-Vinalopó water transfer, considered as an historic aspiration for many years in the region, has been regarded as a key element for solving the depletion of groundwater in a large area located in the southeast of the Iberian Peninsula, mainly for irrigation purposes. In this paper we present an approach to the economic aspects related to the implementation of the project, its investment and financing arrangements and the question of the subsequent management with the impact of the well-known “recovery cost principle", highlighting the current difficulties in carrying out projects of this size, due to severe limitations, as social and economic conditions of the transfer.
Phosphoinositide and phospholipid phosphorylation and hydrolysis pathways
—Organophosphate and organochlorine pesticides effects
 [PDF]

Teresa Fonovich, Gladis Magnarelli
Advances in Biological Chemistry (ABC) , 2013, DOI: 10.4236/abc.2013.33A004
Abstract:

Phospholipid and phosphoinositide phosphorylation pathways have been shown to be of crucial importance on producing lipid mediators. The earlier findings reported on lipid molecules playing roles in different metabolic pathways used to assign them the exclusive role of second messenger generators. Several researchers have recently described how direct interaction of phospholipids and phosphoinositides with molecules or organelles, without the need for producing second messenger molecules, is responsible for their mechanism of action. Organophosphate and organochlorine pesticide toxicity mechanisms have been extensively studied in relation to their well known effects on cholinesterase activities and on the alterations of electric activity in the nervous system of different organisms respectively. There is little but consistent evidence that some compounds, including in both groups of pesticides, are also able to interact with phospholipid and phosphoinositide phosphorylation pathways in several organisms and tissues. The present review consists of an actualization of basic research on phospholipid and phosphoinositide phosphorylation and hydrolysis pathways, as well as a description of some reported evidences for the effects of the above mentioned pesticides on them.

Protein phosphorylation pathways disruption by pesticides  [PDF]
Gladis Magnarelli, Teresa Fonovich
Advances in Biological Chemistry (ABC) , 2013, DOI: 10.4236/abc.2013.35050
Abstract: Phosphosites in the human proteome represent an excellent source of potential biomarkers of pesticide toxicity. In fact, experimental animal models as well as in vitro studies have revealed phosphorylation disruption associated to metabolic regulation, hormone signaling, neuronal function and differentiation, cell survival and death. Due to their estrogen-mimicking ability, pesticides are considered as prime etiological suspects of increasing tumor incidence. Evidences of alterations in the signal transduction pathways involved in the tumor progression stage of pesticides were also provided. Despite progress in understanding the effect of pesticides on the human phosphorproteome and their health outcomes, it remains a complex issue to be studied. By now, the potential impact of pesticides in epigenetic phosphorylation pathways remains poorly explored. In addition, studies involving pesticides mixtures effects are needed. This review updates and provides a comprehensive discussion on the molecular and biochemical events underlying protein phosphorylation pathway disruption caused by pesticides most frequently detected in human tissues and fluids, such as organochlorine pesticides and organophosphates. The link between epidemiological studies and experimental approaches is also considered. Future challenges, such as micro-array phosphoproteome studies to complement gene expression arrays to understand the mechanisms involved in pesticide toxicology are briefly discussed.
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