Exotic polarizations of D2 branes and oblique vacua of (S)YM2+1_{2+1}

We investigate the oblique vacua in the perturbed 2+1 dimensional gauge theory living on D2 branes. The string theory dual of these vacua is expected to correspond to polarizations of the D2 branes into NS5 branes with D4 brane charge. We perturb the gauge theory by adding fermions masses. In the nonsupersymmetric case, we also consider the effect of slight variations of the masses of the scalars. For certain ranges of scalar masses we find oblique vacua. We show that D4 charge is an essential ingredient in understanding D2 -> NS5 polarizations. We find that some of the polarization states which appear as metastable vacua when D4 charge is not considered are in fact unstable. They decay by acquiring D4 charge, tilting and shrinking to zero size.Comment: 15 pages, 3 figures, LaTe

The sign of charge carriers in luminescent transitions

A thorough treatment of the luminescent mechanisms in high resistivity semiconductors (up to 10 12 ohm cm), has as yet not been satisfactorily established. This is due to the lack of data as is provided by the Hall effect. An AC-AC Hall apparatus has been assembled to determine the sign of charge carriers, and their densities when involved in luminescent transitions. Results of preliminary measurements on CdS will be presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42575/1/10582_2005_Article_BF01699279.pd

A Biometric Model for Mineralization of Type-I Collagen Fibrils

The bone and dentin mainly consist of type-I collagen fibrils mineralized by hydroxyapatite (HAP) nanocrystals. In vitro biomimetic models based on self-assembled collagen fibrils have been widely used in studying the mineralization mechanism of type-I collagen. In this chapter, the protocol we used to build a biomimetic model for the mechanistic study of type-I collagen mineralization is described. Type-I collagen extracted from rat tail tendon or horse tendon is self-assembled into fibrils and mineralized by HAP in vitro. The mineralization process is monitored by cryoTEM in combination with two-dimensional (2D) and three-dimensional (3D) stochastic optical reconstruction microscopy (STORM), which enables in situ and high-resolution visualization of the process

Sustitución nucleofílica aromática con complejos metal(II)-aminas bifuncionales en tolueno: Determinaciones cinéticas y cálculos químico cuánticos

Se realizaron estudios cinéticos de Sustitución Nucleofílica Aromática (SNAr) empleando complejos Metal(II)-amina entolueno y cálculos químicos cuánticos para determinar la geometría y energía deformación de los complejos. Los estudios previamente informados del mecanismo SNAr se centran principalmente en la naturaleza del sustrato, la basicidad delnucleófilo y la polaridad del disolvente, aunque el estudio con complejos de coordinación es escaso. Los complejos metal-amina exhiben una reactividad diferencial con respecto a las aminas no complejadas dependiendo, principalmente, del metal y la estructura del ligando. El presente trabajo describe estudios cinéticos realizados en tolueno con 1-cloro-2,4-dinitrobenceno y complejos de Cu(II) y Fe(II) con aminas bifuncionales, y se compararon con estudios previos utilizando las aminas no complejadas. Considerando la diferente reactividad de los complejos metal-amina, los resultados sugieren una diferente labilidad de los complejos atribuidos al efecto quelato y efectos estereoelectrónicos, para formar aminas no complejadas que luego reaccionarían con el sustrato, ya que los resultados cinéticos no proporcionan evidencia que los complejos metal-amina reaccionan como entidad nucleofílica. Por el contrario, se disocian antes de reaccionar y los resultados obtenidos son consistentes con elmecanismo del "Nucleófilo Dímero". Mediante cálculos teóricos basados en la Teoría Funcional Densidad determinamos la estructura de equilibrio y energíade complejación de dichos complejos. Los cálculos teóricos indican que los complejos más estables son aquellos con tres moléculas de amina como ligando, y que los complejos de Cu(II) son más estables que los de Fe(II), resultados que se correlacionan con el orden de reactividad obtenido experimentalmente.Kinetic studies of Aromatic Nucleophilic Substitutions (ANS) of Metal(II)-amine complexes in toluene and quantum chemical calculations were carried out. Reported studies of ANS mechanism are mainly centered on the nature of substrates, nucleophile basicity and solvent polarity, while the study with coordination complexes are scarce. Amine complexes exhibit a differential reactivity with respect to uncomplexed amines depending on, among other factors, the metal center and the ligand structure. The present work describes kinetic studies carried out in toluene with 1-chloro-2,4-dinitrobenzene (DNClB) and Cu(II) and Fe(II) complexes with bifunctional amines. They were chosen considering their characteristics of bi-dentate ligands, the possible size of the metalo-cycle formed and their ability to form intra- or intermolecular hydrogen-bonds. Taking into account the dissimilar reactivity of amine-complexes, the results suggest a different stability of the complexes attributed to stereo-electronic and chelate effects, to form uncomplexed amines that would then react with the substrate, since the observed results do not provide evidence that metal-amine complexes react as a nucleophilic entity. On the contrary, they seem to dissociate prior to react rendering results consistent with a “dimer nucleophile” mechanism. To interpret kinetic results, we performed Density Functional Theory calculations to determine the equilibrium structure and the binding energy for Cu(II) and Fe(II) amine complexes. Quantum chemical calculations indicate that the most stable complexes are those with three amines molecules as ligands, and that Cu(II) complexes are more stable than those with Fe(II), results that correlate with the order of reactivity experimentally obtained.Fil: Alvaro, Cecilia Elisabeth Silvana. Universidad Nacional del Comahue. Facultad de Ingeniería. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; ArgentinaFil: Bergero, Federico Daniel. Universidad Nacional del Comahue. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Bolcic, Federico Martin. Universidad Nacional del Comahue. Facultad de Medicina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ramos, Susana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; Argentina. Universidad Nacional del Comahue. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Nudelman Norma S.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Orgánica; Argentin

Modeling of Small DC Magnetic Field Response in Trilayer Magnetoelectric Laminate Composites

We consider a magnetoelectric laminate which comprises two magnetostrictive (Ni) layers and an in-between piezoelectric layer (PZT). Using the finite-element method-based software COMSOL, we numerically calculate the induced voltage between the two faces of the PZT piezoelectric layer, by an external homogeneous small-signal magnetic field threading the three-layer Ni/PZT/Ni laminate structure. A bias magnetic field is simulated as being produced by two permanent magnets, as it is done in real experimental setups. For approaching the real materials’ properties, a measured magnetization curve of the Ni plate is used in the computations. The reported results take into account the finite-size effects of the structure, such as the fringing electric field effect and the demagnetization, as well as the effect of the finite conductivity of the Ni layers on the output voltage. The results of the simulations are compared with the experimental data and with a widely known analytical result for the induced magnetoelectric voltage

Discovery-driven ontology evolution

In this paper, we present a methodology for ontology evolution, by focusing on the specific case of multimedia ontology volution. In particular, we discuss the situation where the ontology needs to be enriched because it does not contain any concept that could be used to explain a new multimedia resource. The paper shows how ontology matching techniques can be used to enforce the discovery of new relevant concepts by probing external knowledge sources using both the information available in the multimedia resource and the knowledge contained in the current version of the ontology

Disordered Filaments Mediate the Fibrillogenesis of Type I Collagen in Solution

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Readthrough of nonsense mutations in Rett syndrome: evaluation of novel aminoglycosides and generation of a new mouse model

Thirty-five percent of patients with Rett syndrome carry nonsense mutations in the MECP2 gene. We have recently shown in transfected HeLa cells that readthrough of nonsense mutations in the MECP2 gene can be achieved by treatment with gentamicin and geneticin. This study was performed to test if readthrough can also be achieved in cells endogenously expressing mutant MeCP2 and to evaluate potentially more effective readthrough compounds. A mouse model was generated carrying the R168X mutation in the MECP2 gene. Transfected HeLa cells expressing mutated MeCP2 fusion proteins and mouse ear fibroblasts isolated from the new mouse model were treated with gentamicin and the novel aminoglycosides NB30, NB54, and NB84. The localization of the readthrough product was tested by immunofluorescence. Readthrough of the R168X mutation in mouse ear fibroblasts using gentamicin was detected but at lower level than in HeLa cells. As expected, the readthrough product, full-length Mecp2 protein, was located in the nucleus. NB54 and NB84 induced readthrough more effectively than gentamicin, while NB30 was less effective. Readthrough of nonsense mutations can be achieved not only in transfected HeLa cells but also in fibroblasts of the newly generated Mecp2R168X mouse model. NB54 and NB84 were more effective than gentamicin and are therefore promising candidates for readthrough therapy in Rett syndrome patients

Warping and vacua of (S)YM3+1(S)YM_{3+1}

We use dielectric branes to find non singular string theory duals of a perturbed 2+1 dimensional gauge theory living on D2 branes. By adding fermion masses we obtain theories with reduced supersymmetry. The Higgs vacua of the perturbed theory correspond to polarization of the D2 branes into D4 branes. The confining vacua correspond to polarization of the D2 branes into NS5 branes. We consider different mass perturbations. Adding three equal masses preserves N=2 supersymmetry. In this case there are no confining vacua. By adding a fourth fermion mass we break all the supersymmetry, and find confining vacua. We also obtain duals for domain walls, condensates, baryon vertices, glueballs and flux tubes. We comment on the Kahler potentials for the Higgs and confining phases. In the course of the calculations we also find a nontrivial consistency check of the NS5 brane action in a D2 brane background.Comment: 33 pages, 2 figures, LaTeX. A factor in the last term of (67) and some typos are corrected, references adde

Anticancer prodrugs of butyric acid and formaldehyde protect against doxorubicin-induced cardiotoxicity

Formaldehyde has been previously shown to play a dominant role in promoting synergy between doxorubicin (Dox) and formaldehyde-releasing butyric acid (BA) prodrugs in killing cancer cells. In this work, we report that these prodrugs also protect neonatal rat cardiomyocytes and adult mice against toxicity elicited by Dox. In cardiomyocytes treated with Dox, the formaldehyde releasing prodrugs butyroyloxymethyl diethylphosphate (AN-7) and butyroyloxymethyl butyrate (AN-1), but not the corresponding acetaldehyde-releasing butyroyloxydiethyl phosphate (AN-88) or butyroyloxyethyl butyrate (AN-11), reduced lactate dehydrogenase leakage, prevented loss of mitochondrial membrane potential (ΔΨm) and attenuated upregulation of the proapoptotic gene Bax. In Dox-treated mice, AN-7 but not AN-88 attenuated weight-loss and mortality, and increase in serum lactate dehydrogenase. These findings show that BA prodrugs that release formaldehyde and augment Dox anticancer activity also protect against Dox cardiotoxicity. Based on these observations, clinical applications of these prodrugs for patients treated with Dox warrant further investigation