Nonlinear Breathing-like Localized Modes in C60 Nanocrystals

We study the dynamics of nanocrystals composed of C60 fullerene molecules. We demonstrate that such structures can support long-lived strongly localized nonlinear oscillatory modes, which resemble discrete breathers in simple lattices. We reveal that at room temperatures the lifetime of such nonlinear localized modes may exceed tens of picoseconds; this suggests that C60 nanoclusters should demonstrate anomalously slow thermal relaxation when the temperature gradient decays in accord to a power law, thus violating the Cattaneo-Vernotte law of thermal conductivity.Comment: 6 pages, 6 figure

A linear domain decomposition method for two-phase flow in porous media

This article is a follow up of our submitted paper [11] in which a decomposition of the Richards equation along two soil layers was discussed. A decomposed problem was formulated and a decoupling and linearisation technique was presented to solve the problem in each time step in a fixed point type iteration. This article extends these ideas to the case of two-phase in porous media and the convergence of the proposed domain decomposition method is rigorously shown.Comment: 8 page

LA IMPORTANCIA DEL SET-UP CEFALOMETRICO EN EL DIAGNOSTICO ORTODONCICO

Podemos mentalmente anticipar la cantidad y dirección de movimiento o cambio requerido para acompañar este propósito de tratamiento. Por tal motivo debemos sentir la cantidad de movimiento molar a cuerpo entero o rotación, y la cantidad de retracción incisal y torque. Asímismo, frecuentemente cambiamos los modelos para demostrar los cambios que necesitamos. Sin embargo,como llegamos a ser críticos, debemos desear a ejecutar un set up de yeso. Los dientes que son cortados desde sus bases y reposicionados con cera en una oclusión ideal o normal, mucho como un posicionador es hecho en un set up. Frecuentemente,un sólo lado del arco necesitamos ser el set-up en orden de visualizar la cantidad de cambio necesario para mover los dientes a una posición escogida ideal. Esto facilitará un acercamiento de la necesidad de remodelación y recontomo del proceso alveolar. El set up de yeso, frecuentemente magnifica ciertas limitaciones que están presentes. Esto puede sugerir procedimientos de tratamiento para acomodar estas limitaciones, porque este tipo de análisis es puramente estático. El set-up de yeso producirá información de discrepancia de variaciones en la anatomía dental y forma de arcos. Pero, de nuevo, son estáticos, este procedimiento está limitado y más información es necesaria para el clínico concerniente al hueso subyacente de las estructuras de los maxilares desde los cuales los dientes son soportados. El análisis de los modelos de yeso tienen otro principal defecto, por tratamiento no están incluídos. Finalmente, un análisis de modelos con un set-up es también un tiempo consumido y gastado, y que el clínico conjura up el caso en la imaginación.Podemos mentalmente anticipar la cantidad y dirección de movimiento o cambio requerido para acompañar este propósito de tratamiento. Por tal motivo debemos sentir la cantidad de movimiento molar a cuerpo entero o rotación, y la cantidad de retracción incisal y torque. Asímismo, frecuentemente cambiamos los modelos para demostrar los cambios que necesitamos. Sin embargo,como llegamos a ser críticos, debemos desear a ejecutar un set up de yeso. Los dientes que son cortados desde sus bases y reposicionados con cera en una oclusión ideal o normal, mucho como un posicionador es hecho en un set up. Frecuentemente,un sólo lado del arco necesitamos ser el set-up en orden de visualizar la cantidad de cambio necesario para mover los dientes a una posición escogida ideal. Esto facilitará un acercamiento de la necesidad de remodelación y recontomo del proceso alveolar. El set up de yeso, frecuentemente magnifica ciertas limitaciones que están presentes. Esto puede sugerir procedimientos de tratamiento para acomodar estas limitaciones, porque este tipo de análisis es puramente estático. El set-up de yeso producirá información de discrepancia de variaciones en la anatomía dental y forma de arcos. Pero, de nuevo, son estáticos, este procedimiento está limitado y más información es necesaria para el clínico concerniente al hueso subyacente de las estructuras de los maxilares desde los cuales los dientes son soportados. El análisis de los modelos de yeso tienen otro principal defecto, por tratamiento no están incluídos. Finalmente, un análisis de modelos con un set-up es también un tiempo consumido y gastado, y que el clínico conjura up el caso en la imaginación

Resonant hyper-Raman scattering in spherical quantum dots

A theoretical model of resonant hyper-Raman scattering by an ensemble of spherical semiconductor quantum dots has been developed. The electronic intermediate states are described as Wannier-Mott excitons in the framework of the envelope function approximation. The optical polar vibrational modes of the nanocrystallites (vibrons) and their interaction with the electronic system are analized with the help of a continuum model satisfying both the mechanical and electrostatic matching conditions at the interface. An explicit expression for the hyper-Raman scattering efficiency is derived, which is valid for incident two-photon energy close to the exciton resonances. The dipole selection rules for optical transitions and Fr\"ohlich-like exciton-lattice interaction are derived: It is shown that only exciton states with total angular momentum $L=0,1$ and vibrational modes with angular momentum $l_p=1$ contribute to the hyper-Raman scattering process. The associated exciton energies, wavefunctions, and vibron frequencies have been obtained for spherical CdSe zincblende-type nanocrystals, and the corresponding hyper-Raman scattering spectrum and resonance profile are calculated. Their dependence on the dot radius and the influence of the size distribution on them are also discussed.Comment: 12 pages REVTeX (two columns), 2 tables, 8 figure

Residual Expression of the Reprogramming Factors Prevents Differentiation of iPSC Generated from Human Fibroblasts and Cord Blood CD34+ Progenitors

Human induced pluripotent stem cells (hiPSC) have been generated from different tissues, with the age of the donor, tissue source and specific cell type influencing the reprogramming process. Reprogramming hematopoietic progenitors to hiPSC may provide a very useful cellular system for modelling blood diseases. We report the generation and complete characterization of hiPSCs from human neonatal fibroblasts and cord blood (CB)-derived CD34+ hematopoietic progenitors using a single polycistronic lentiviral vector containing an excisable cassette encoding the four reprogramming factors Oct4, Klf4, Sox2 and c-myc (OKSM). The ectopic expression of OKSM was fully silenced upon reprogramming in some hiPSC clones and was not reactivated upon differentiation, whereas other hiPSC clones failed to silence the transgene expression, independently of the cell type/tissue origin. When hiPSC were induced to differentiate towards hematopoietic and neural lineages those hiPSC which had silenced OKSM ectopic expression displayed good hematopoietic and early neuroectoderm differentiation potential. In contrast, those hiPSC which failed to switch off OKSM expression were unable to differentiate towards either lineage, suggesting that the residual expression of the reprogramming factors functions as a developmental brake impairing hiPSC differentiation. Successful adenovirus-based Cre-mediated excision of the provirus OKSM cassette in CB-derived CD34+ hiPSC with residual transgene expression resulted in transgene-free hiPSC clones with significantly improved differentiation capacity. Overall, our findings confirm that residual expression of reprogramming factors impairs hiPSC differentiation

Comparison of different methodologies for obtaining nickel nanoferrites

Nickel nanoferrites were obtained by means of four different synthetic wet-routes: co-precipitation (CP), sonochemistry (SC), sonoelectrochemistry (SE) and electrochemistry (E). The influence of the synthesis method on the structural and magnetic properties of nickel ferrite nanoparticles is studied. Although similar experimental conditions such as temperature, pH and time of synthesis were used, a strong dependence of composition and microstructure on the synthesis procedure is found, as electron microscopy, X-ray diffraction and Mössbauer spectroscopy studies reveal. Whereas by means of the CP and SC methods particles of a small size around 5–10 nm, respectively, and composed by different phases are obtained, the electrochemical routes (E and SE) allow obtaining monodisperse nanoparticles, with sizes ranging from 30 to 40 nm, and very close to stoichiometry. Magnetic characterization evidences a superparamagnetic behavior for samples obtained by CP and SC methods, whereas the electrochemical route leads to ferromagnetic ferrite nanoparticles

Determination of non-polar and mid-polar monomeric oxidation products of stigmasterol during thermo-oxidation

Oxidation products of stigmasterol were characterised by their polarity and molecular size using solid phase extraction (SPE) and high-performance size exclusion chromatography (HPSEC) methods. Monomeric oxides were studied further by GC–MS and GC–FID. The focus was on identifying and quantifying non-polar and mid-polar monomeric oxides after SPE fractionation. Commercial stigmasterol was subjected to 180 °C up to 3 h. Six oxidation products were identified by GC–MS in the non-polar and mid-polar monomeric fractions; all appeared during the first hour of heating. Quantification by GC–FID showed an increase in the non-polar and mid-polar oxidation products during the heating time, and their amounts reached values of 6.1 and 47.0 g/kg of commercial stigmasterol, respectively. Polar oxidation products commonly measured reached a value of 193 g/kg after 1 h of heating, while after 3 h of heating their concentration was only 164 g/kg. Since as much as 550 g/kg of stigmasterol was decomposed, the monomeric products explained only partly the stigmasterol loss. Dimeric and polymeric products contributed to 165 g/kg of the loss showing the importance of polymerisation reactions at 180 °C

Inducible Deletion of Protein Kinase Map4k4 in Obese Mice Improves Insulin Sensitivity in Liver and Adipose Tissues

Studies in vitro suggest that mitogen-activated protein kinase kinase kinase kinase 4 (Map4k4) attenuates insulin signaling, but confirmation in vivo is lacking since Map4k4 knockout is lethal during embryogenesis. We thus generated mice with floxed Map4k4 alleles and a tamoxifen-inducible Cre/ERT2 recombinase under the control of the ubiquitin C promoter to induce whole-body Map4k4 deletion after these animals reached maturity. Tamoxifen administration to these mice induced Map4k4 deletion in all tissues examined, causing decreased fasting blood glucose concentrations and enhanced insulin signaling to AKT in adipose tissue and liver but not in skeletal muscle. Surprisingly, however, mice generated with a conditional Map4k4 deletion in adiponectin-positive adipocytes or in albumin-positive hepatocytes displayed no detectable metabolic phenotypes. Instead, mice with Map4k4 deleted in Myf5-positive tissues, including all skeletal muscles tested, were protected from obesity-induced glucose intolerance and insulin resistance. Remarkably, these mice also showed increased insulin sensitivity in adipose tissue but not skeletal muscle, similar to the metabolic phenotypes observed in inducible whole-body knockout mice. Taken together, these results indicate that (i) Map4k4 controls a pathway in Myf5-positive cells that suppresses whole-body insulin sensitivity and (ii) Map4k4 is a potential therapeutic target for improving glucose tolerance and insulin sensitivity in type 2 diabetes