Asymptotically FRW black holes

Special solutions of the LTB family representing collapsing over-dense regions corresponding to asymptotically closed, open, or flat FRW models are found. These solutions may be considered as representing dynamical mass condensations leading to black holes immersed in a FRW universe. We study the dynamics of the collapsing region, and its density profile. The question of the strength of the central singularity and its nakedness, as well as the existence of an apparent horizon and an event horizon is dealt with in detail, shedding light to the notion of cosmological black holes. Differences to the Schwarzschild black hole are addressed.     

Sur les variétés sous-riemanniennes de contact isotropes

In this Note, we show that contrary to the dimension 3 case, isotropic contact sub-Riemannian manifolds of dimension greater than 3 do not exist. To cite this article: A.-R. Mansouri, C. R. Acad. Sci. Paris, Ser. I 339 (2004).     

Walk-off reduction,using an external optical plate and Bessel–Gaussian interaction

To reduce the walk-off angle of the extraordinary third-harmonic ultraviolet wave at 355 nm generated by type ⅡKTiOPO_4 and type I β-BaB_2O_4 optical crystals,and the Gaussian output beam of a Q-switched Nd:YAG laser,a simple theoretical model was developed based on a rotatable BK7 plate of variable thickness.By rotating the plate up to 35°along the beam direction,we reduced the walk-off angle up to ~ 13%.The same phenomenon is predicted by the model,confirming the performance of the model.It is found that,due to the walk-off effect,the intensity profile of the thirdharmonic generation beam is slightly degraded.To compensate for the observed phenomena and further reduce the walkoff,we used a combination of a convex lens and an axicon to transform the beam profile of the interacting fundamental and second-harmonic generation waves to the zero-order Bessel-Gaussian form.As a result,the walk-off is decreased to~ 48.81 mrad,providing ~ 30%relative reduction.By using the same BK7 plate rotated up to 35° along the third-harmonic beam direction,the walk-off angle is further reduced to 38.9 mrad.Moreover,it is observed that the beam profile of the emerged Bessel-Gaussian third-harmonic generation beam remains unchanged with no degradation.     

MicroRNA‐2861 and nanofibrous scaffold synergistically promote human induced pluripotent stem cells osteogenic differentiation

Tissue engineering using new strategies has become a growing and promising method for treating large tissue lesions in the body. On the other hand, microRNAs (miRNAs), which are small non‐coding regulatory RNAs, are a new class of genetic materials that can have effective pharmacological roles. The combination of these two themes has created promising prospects for the treatment of diseases. Herein, human induced pluripotent stem cells (iPSCs) were transduced with miRNA‐2861 and then the osteogenic differentiation potential of transduced iPSCs and non‐transduced iPSCs was investigated while cultured on the electrospun poly lactic‐co‐glycolic acid (PLGA) nanofibrous scaffold and culture plate. MiR‐2861‐transduced iPSCs showed a significantly higher viability, mineralization, alkaline phosphatase (ALP) activity, calcium content, and bone‐related gene expression in comparison with those iPSCs that non‐transduced. The results also indicated that this increase is improved when miR‐2861 transduced iPSCs are cultured on the PLGA nanofibrous scaffold synergistically. This synergy was also confirmed by the results obtained from of Western blot analysis. It can be concluded that, miR‐2861, by negative regulation of those proteins that decrease/inhibit osteogenic differentiation and PLGA nanofibrous scaffold by preparation of a suitable artificial extracellular matrix, have a great positive impact in improving iPSCs osteogenic differentiation potential and this blend can be proposed to use in bone tissue engineering application.     

Experimental study on effect of different parameters on size and shape of triangular silver nanoparticles prepared by a simple and rapid method in aqueous solution

This paper continues our previous work on preparation of truncated triangular silver nanoparticles. The method proceeds with reaction of silver nitrate with hydrazine in the presence of sodium citrate in aqueous solution, in which triangular nanoparticles are formed in a few minutes with some spherical ones. In particular range of reactants, especially high reductant concentration, only spherical nanoparticles are formed. In further investigation we observed that spherical nanoparticles shape could change to triangular by aging. This means that controlled growth of nanoparticles could lead to the formation of triangular ones. Therefore, a method was devised to slow down the rate of reduction by adding Fe³⁺ to the reaction solution. The results show that in this case more triangular nanoparticles are formed compared to the original one. This result also confirms that with the increasing hydrazine concentration, growth becomes less important compared to nucleation and smaller triangles are formed.     

A new approach for modeling of RO membranes using MD-SF-PF model and CFD technique

The modified surface force-pore flow (MD-SF-PF) model is a successful and powerful model for prediction of reverse osmosis (RO) membrane separation. In the MD-SF-PF model, a suitable mass and momentum balances were made through the cylindrical micro porous of the membranes. A one-dimensional potential function in radial direction was used to attain the velocity profile. The obtained nonlinear equations were solved by orthogonal collocation method. In our model, extended MD-SF-PF (Ex-MD-SF-PF) model, the potential function of the MD-SF-PF model was developed as both radial and axial directions. Both Ex-MD-SF-PF and MD-SF-PF models were solved by finite volume and finite difference methods based on a computational fluid dynamics (CFD) technique. The profiles of velocity and concentration were achieved and thereby the values of separation factors and fluxes for both models were obtained and were compared accordingly. This approach affected only at the end of pore, mainly on the concentration profile and slightly on the velocity profile.     

An Arc Search Infeasible Interior-Point Algorithm for Symmetric Optimization Using a New Wide Neighborhood

In this paper, we propose an infeasible interior-point algorithm for symmetric optimization problems using a new wide neighborhood and estimating the central path by an ellipse. In contrast of most interior-point algorithms for symmetric optimization which search an \(\varepsilon\)-optimal solution of the problem in a small neighborhood of the central path, our algorithm searches for optimizers in a new wide neighborhood of the ellipsoidal approximation of central path. The convergence analysis of the algorithm is shown and it is proved that the iteration bound of the algorithm is \(O ( r\log\varepsilon^{-1} ) \) which improves the complexity bound of the recent proposed algorithm by Liu et al. (J. Optim. Theory Appl., 2013,  https://doi.org/10.1007/s10957-013-0303-y) for symmetric optimization by the factor \(r^{\frac{1}{2}}\) and matches the currently best-known iteration bound for infeasible interior-point methods.     

Electronic structure and UV–Vis spectra simulation of square planar Bis(1-(4-methylphenylazo)-2-naphtol)-Transition metal complexes [M(L)2]x (M = Ni,Pd, Pt,Cu, Ag,and x = − 1, 0, + 1): DFT and TD-DFT study

Structural Chemistry - DFT/B3LYP calculations with full geometry optimizations have been carried out on 1-phenylazo-2-naphthol and their metal complexes of formula M(MePhNap)2 (M?=?Ni,...     

Non-abelian isometries and dimensional reduction

Dimensional reduction is carried out for space-times, with or without torsion, which possess non-abelian isometries. The spectra and the equations of motion of the dimensionally reduced theory are obtained directly from the higher dimensional theory. The spectra of the reduced theories are naturally given in terms of scalar fields and antisymmetric tensor field strengths. A method of studying the dependence on the extra dimensions is suggested.