Synthesis of CaWO4:Er3+@SiO2 and CaWO4:Tm3+@SiO2 nano-particles via a combustion pathway and study of their optical properties

Use of citric acid as a chelating agent and fuel, ammonium nitrate as fuel, boric acid as flux material and silica as supports, CaWO₄:Ln³⁺@SiO₂ (Ln = Er and Tm) nanoparticles were synthesized via a combustion reaction at 800 °C. Characterization of the samples was performed by X-ray diffractometer (XRD), reflectance UV–Vis spectrophotometer, fluorescence spectrophotometer (PL) and transmission electron microscope (TEM). XRD patterns showed that tetragonal crystalline structure of scheelite and silica supports were formed, and that the formation of a silica support could enhance the luminescence intensity of CaWO₄:Ln³⁺. The reflectance UV–Vis and PL spectra indicated the broad absorption band of WO₄ ^2? groups about 240 nm, the WO₄ ^2? wide excitation band with maximum at 240 nm, a broad emission band of WO₄ ^2? with maximum about 420 nm, and characteristic emissions of Ln³⁺ ions. According to the TEM analysis, CaWO₄:Er³⁺@SiO₂ and CaWO₄:Tm³⁺@SiO₂ nanoparticles have almost the same morphology with average particle sizes about 50 nm.     

Synthesis,in vitro antimicrobial assessment,and computational investigation of pharmacokinetic and bioactivity properties of novel trifluoromethylated compounds using in silico ADME and toxicity prediction tools

1,3-Dipolar cycloaddition reactions of a sugar-based trifluoromethylated nitrone-to-maleimide and allyl bromide afforded a series of cycloadducts in good yield. The same nitrone reacts with propargyl acetate lead, after rearrangement of 4-isoxazoline, to aziridine with good yield. The obtained compounds were evaluated for their in vitro antimicrobial potency. Additionally, we are interested in predicting their physicochemical parameters such as lipophilicity and bioactivity score as well as their pharmacokinetic properties such as absorption, distribution, metabolism, and excretion (ADME) such as plasma protein binding (PPB) penetration of the blood–brain barrier (BBB), human intestinal absorption (HIA), cellular permeability (PCaco-2), cell permeability of Madin–Darby canine kidney (PMDCK), P-glycoprotein (P-gp) efflux, CYP inducers, substrates and inhibitors’ skin and permeability (PS), and their toxicological behavior [mutagenicity, carcinogenicity, acute, environmental, cardiotoxicity (hERG inhibition)] using in silico computational methods. Also, we aimed to validate QSAR models for the elucidation of their antitarget using 32 sets of end-points (IC50, Ki and Kact). The obtained result provides good information about the pharmacotherapy potential and toxicity of the examined molecules with good compliance between in vitro antimicrobial and the predicted properties. Findings indicated and encouraged the use of these compounds and their derivatives for further in vivo evaluations in the design and the elucidation of the intrinsic mechanisms as well as the efficacy of the selected powerful drug.     

Numerical simulation of natural gas/diesel dual-fuel engine for investigation of performance and emission

Journal of Thermal Analysis and Calorimetry - Due to global concerns about the emissions, limited hydrocarbon fuel resources and high fuel prices, a lot of researches have been done to improve the...     

Dynamical Analysis of a New Chaotic Fractional Discrete-Time System and Its Control

This article proposes a new fractional-order discrete-time chaotic system, without equilibria, included two quadratic nonlinearities terms. The dynamics of this system were experimentally investigated via bifurcation diagrams and largest Lyapunov exponent. Besides, some chaotic tests such as the 0–1 test and approximate entropy (ApEn) were included to detect the performance of our numerical results. Furthermore, a valid control method of stabilization is introduced to regulate the proposed system in such a way as to force all its states to adaptively tend toward the equilibrium point at zero. All theoretical findings in this work have been verified numerically using MATLAB software package.     

Image based simulation of one-dimensional compression tests on carbonate sand

Meccanica - High factors of safety and conservative methods are commonly used on foundation design on shelly carbonate soils. A better understanding of the behavior of this material is, thus,...     

Boundary null-controllability of linear diffusion–reaction equations

This Note deals with the boundary null-controllability of linear diffusion–reaction equations in a 2D bounded domain. We transform the determination of the sought HUM boundary control into the minimization of a continuous and strictly convex functional. In the case of a rectangular domain where the diffusion tensor is represented by a diagonal matrix, we establish a procedure based on the inner product method that uses a complete orthonormal family of Sturm–Liouville's eigenfunctions to express explicitly the sought control.     

A mass-conservative switching algorithm for modeling fluid flow in variably saturated porous media

Numerical solutions of flow equation in fluid content-based form or in fluid pressure head-based form are often tradeoffs between speed, accuracy, and convenience. The fluid-content based form can be solved quite rapidly with low CPU time and perfect mass balance. However, it cannot be used in saturated regions (as diffusivity function becomes infinite) and strictly becomes invalid in composite, layered, and real heterogeneous porous materials, due to singularity and discontinuity in fluid content profile. This formulation also gives misleading impression that gradient in fluid content causes the flow of fluid in porous materials, where in reality gravity and fluid pressure potential gradient produce the motion. The pressure head-based form, on the other hand, is more flexible but due to its highly nonlinear nature is much more time-consuming and produces poor global mass balance for dry initial conditions. Very fine spatial and temporal discretizations are needed to maintain mass balance property for these scenarios. The mixed form of the flow equation partially solves these issues as it maintains acceptable mass balance and is applicable to layered, heterogeneous, and composite fractured foundations. However, it is only applicable in unsaturated zones. In this study, a switching algorithm was proposed and implemented in which the mass conservative mixed form and the pressure head-based form were, respectively, used in the unsaturated and saturated zones of an initial-boundary value flow problem involving a variably saturated porous medium. The algorithm showed excellent agreement with a reference solution, obtained on a very fine spatiotemporal mesh. The simulator was then calibrated with several real-world large-scale experimental datasets. In all cases, the proposed algorithm exhibited close agreements with the experimental time–space series. The algorithm poses excellent mass balance property and can easily be used in both saturated and unsaturated regions without special treatment of fluid content discontinuities in heterogeneous and layered porous media. The proposed algorithm can also be extended to simulate multiphase and multidimensional flow problems.     

Rigid tetranitroresorcinarenes

[reaction: see text]. o-alkylation of C2V-symmetrical resorcinarene tetraesters 2 with 2 equiv of 1,3-difluoro-4,6-dinitrobenzene readily affords conformationally rigid octanitro resorcinarene 3, which is a potential scaffold for the design of supramolecular structures.