Five dimensional cosmological traversable wormhole

In this paper, a traversable wormhole in the Friedmann–Lemaître–Robertson–Walker (FLRW) model with one extra spacelike compact dimension is studied. We have chosen dynamical compactification as the evolution of the fifth dimension. In this respect, we study how the existence of the extra dimension affects the behavior of the energy density, the shape function and the scale factor. It is shown that the total matter can be non-exotic and the violation of the weak energy condition can be avoided.     

Characterization of the physical–mechanical properties of dental resin composites reinforced with novel micro-nano hybrid silica particles: An optimization study

Abstract

In the study, dental composites of color A2 using Bis-GMA/UDMA/TEGDMA resins (ratios 70/10/20), and silica filler (70%wt, 75%wt, and 80%wt) which is a hybrid of two silica types in nano and micro dimensions were made using two different photoinitiators namely BAPO and camphorquinone. The optimum photoinitiator was selected based on the mechanical tests results after which the composites were subjected to the following tests: FTIR to evaluate polymerization degree, microhardness test, UTM, and SEM micrographs were taken to analyze the surface fracture of samples. The results of photoinitiator selection (flexural strength test) is 36.54?MPa, 37.62?MPa, and 75.08?MPa for BAPO?+?camphorquinone, camphorquinone, and BAPO respectively. The results show that the BAPO photoinitiator exhibits better results over camphorquinone and also BAPO/camphorquinone initiator systems. Then after choosing the photoinitiator system composites with different filler contents show higher mechanical strength than existing dental composites. The results of the mechanical tests for the composites with different filler contents synthesized after initiator system selection were significantly higher than the values specified in ISO 4049:2009 (102?MPa over 80?MPa). FTIR results indicate that the degree of conversion in these composite is 25.41%, 37.68, and 40.94% for composites with different filler amounts.     

Antioxidant Activity of Substituted Enterolactone Derivatives in the Gas Phase and Water

ABSTRACT The antioxidant activity of ortho and meta substituted Enterolactone derivatives has been investigated in the gas phase and water.The reaction enthalpies of antioxidant activity of the studied derivatives have been calculated and compared with the corresponding values of Enterolactone.Results show that EWG substituents increase the BDE and IP,while the EDG ones rise in the PA.The Enterolactone derivatives with the lowest BDE,IP and PA values were identified as the compounds with high antioxidant activity.Results show that the substituents in the ortho position have high potential for the synthesis of novel Enterolactone derivatives.Results show that Enterolactone derivatives can processes their protective role via HAT and SPLET mechanism in gas phase and solvent,respectively.The calculated reaction enthalpies of the substituted Enterolactones have linear dependence with Hammett constants and EHOMO that can be utilized in the selection of suitable substituents for the synthesis of novel antioxidants based on Enterolactone.     

A higher‐order Boussinesq‐type model with moving bottom boundary: applications to submarine landslide tsunami waves

A two‐dimensional depth‐integrated numerical model is developed using a fourth‐order Boussinesq approximation for an arbitrary time‐variable bottom boundary and is applied for submarine‐landslide‐generated waves. The mathematical formulation of model is an extension of (4,4) Padé approximant for moving bottom boundary. The mathematical formulations are derived based on a higher‐order perturbation analysis using the expanded form of velocity components. A sixth‐order multi‐step finite difference method is applied for spatial discretization and a sixth‐order Runge–Kutta method is applied for temporal discretization of the higher‐order depth‐integrated governing equations and boundary conditions. The present model is validated using available three‐dimensional experimental data and a good agreement is obtained. Moreover, the present higher‐order model is compared with fully potential three‐dimensional models as well as Boussinesq‐type multi‐layer models in several cases and the differences are discussed. The high accuracy of the present numerical model in considering the nonlinearity effects and frequency dispersion of waves is proven particularly for waves generated in intermediate and deeper water area. Copyright © 2006 John Wiley & Sons, Ltd.     

Yb3+sensitized Er3+-doped waveguide amplifiers: a theoretical approach

Silicate and phosphate glass waveguide amplifiers doped with Er³⁺, and co-doped with Er³⁺/Yb³⁺ are theoretically studied. Configurations for core and core–cladding doped waveguide amplifiers are considered. It is shown that gain in the core–cladding doped amplifiers is considerably higher than core doped amplifiers. It is also shown that with input signal power up to 1 and 200mW pump power, a 12.5dB gain can be achieved in a 3cm long waveguide amplifier, with a noise figure of 3dB.     

Zeolite and sulfated zirconia as catalysts for the synthesis of 5-substituted 1H-tetrazoles via [2+3] cycloaddition of nitriles and sodium azide

The [2+3] cycloaddition between various nitriles and sodium azide proceeds smoothly in the presence of zeolite and sulfated zirconia as effective catalysts, in water and DMF/MeOH, to give the corresponding 5-substituted 1H-tetrazoles in good to high yields. The reaction most probably proceeds through the in situ formation of catalyst azide species, followed by a successive [2+3] cycloaddition with the nitriles. This method has the advantages of high yields, simple methodology and easy work-up. The catalyst can be recovered by simple filtration and reused with good yields.     

Effects of α‐cyclopropyl on heterocyclic carbenes stability at DFT

α‐Cyclopropyl stability impacts on singlet and triplet heterocyclic carbenes with acyclic, cyclic, and cyclic‐unsaturated structures are compared and contrasted to di‐t‐butyl as well as t‐butylcyclopropylcarbenes through appropriate isodesmic reactions at B3LYP/AUG‐cc‐pVTZ level. Substitution of one of the t‐butyl groups of di‐t‐butylcarbene with a cyclopropyl alters the ground state multiplicity from triplet to singlet with a singlet–triplet energy separation (ΔE_s–t) of 7.2 kcal/mol. Additional heteroatom substitution increases ΔE_s–t values for the resulting α‐heteroatom cyclopropylcarbenes in the following order: amino > oxy > thio > phophino. α‐Cyclopropyl group stabilizes singlet states of all our carbenes two to three times more than their corresponding triplet states. The ΔE_s–t values of all the carbenes are increased through cyclization, while the introduction of unsaturation in the rings causes small and rather random changes. To probe the kinetic stability of the species, we calculated the transition states for the opening of cyclopropyl through 1,2‐C shift. Interestingly, the 4.1 kcal/mol energy barrier in cyclopropylcarbene is significantly increased in the presence of heteroatoms to 31.2 kcal/mol for aminocyclopropylcarbene. The reactivity of the species is discussed in terms of nucleophilicity and electrophilicity issues showing our carbenes, especially acyclic ones, more nucleophilic than the common N‐heterocyclic carbenes. Copyright © 2010 John Wiley & Sons, Ltd.     

The weakly generalized unicorns in Finsler geometry

We classify the almost regular weakly stretch non-Randers-type(α, β)-metrics with vanishing Scurvature. In the class of regular metrics, they reduce to Berwald ones. Here, we demonstrate that when an almost regular weakly stretch non-Randers-type(α, β)-metric with vanishing S-curvature is not Berwaldian, then it is a weakly generalized unicorn. This yields an extension of Zou-Cheng and Chen-Liu's theorems. Finally, we show that any projective non-Randers β-change of a unicorn is a unicorn.     

4E assessment of power generation systems for a mobile house in emergency condition using solar energy: a case study

Journal of Thermal Analysis and Calorimetry - This contribution experimentally and analytically addresses the dripping and ignition mechanism of vertically discrete polypropylene (PP) and...