On the Time-Dependent Delta-Shock Model Governed by the Generalized PóLya Process

One of the widely discussed in the literature and relevant in practice shock models is the delta-shock model that is described by the constant time of a system’s recovery after a shock. However, in practice, as time progresses and due to deterioration of a system, this recovery time is gradually increasing. This important phenomenon was not discussed in the literature so far. Therefore, in this paper, we are considering a time-dependent delta-shock model, i.e., the recovery time becomes an increasing function of time. Moreover, we assume that shocks occur according to the generalized Pólya process that contains the homogeneous Poisson process, the non-homogeneous Poisson process and the Pólya process as particular cases. For the defined survival model, we derive the corresponding survival function and the mean lifetime and study the related optimal replacement policy along with some relevant stochastic properties.

     

Concise syntheses of (+)- and (−)-methylenolactocins and phaseolinic acids

(+)- and (−)-Methylenolactocins and phaseolinic acids are synthesized in four steps via asymmetric syn- and anti-aldol reactions of chiral N-succinyl-2-oxazolidinones using the same set of reagents.     

Chemo- and regioselective cyclohydrocarbonylation of alpha-keto alkynes catalyzed by a zwitterionic rhodium complex and triphenyl phosphite

alpha-Keto alkynes react with CO and H(2) in the presence of catalytic quantities of the zwitterionic rhodium complex (eta(6)-C(6)H(5)BPh(3))(-)Rh(+)(1,5-COD) and triphenyl phosphite affording either the 2-, 2(3H)-, or 2(5H)-furanones in 61-93% yields. The cyclohydrocarbonylation is readily accomplished using substrates containing alkyl, aryl, vinyl, and alkoxy groups at the acetylenic terminal, as well as a variety of primary, secondary, and tertiary alkyl, aryl, and heteroaryl groups connected to the ketone functionality. Structural and electronic properties present in the starting materials mediate the chemo- and regioselectivity of the reaction.     

Total synthesis of ring-c aromatic 18-nor steroid1

The total synthesis of (±)-11-methoxy-18-nor-5χ and 5β-androsta-8(9),11,13(14)-triene-3,17-dione is reported.     

One‐shot pseudo‐time method for aerodynamic shape optimization using the Navier–Stokes equations

This paper presents a numerical method for aerodynamic shape optimization problems in compressible viscous flow. It is based on simultaneous pseudo‐time stepping in which stationary states are obtained by solving the pseudo‐stationary system of equations representing the state, costate and design equations. The main advantages of this method are that it blends in nicely with previously existing pseudo‐time‐stepping methods for the state and the costate equations, that it requires no additional globalization in the design space, and that a preconditioner can be used for convergence acceleration which stems from the reduced SQP methods. For design examples of 2D problems, the overall cost of computation can be reduced to less than 2 times the forward simulation runs. Copyright © 2011 John Wiley & Sons, Ltd.     

Chemoenzymatic asymmetric synthesis of fluoxetine,atomoxetine, nisoxetine,and duloxetine

The asymmetric synthesis of two well-known anti-depressant drugs, fluoxetine and duloxetine has been accomplished in a chemoenzymatic manner. The main highlight of the synthesis is the enantioselective cyanohydrin formation by a plant (R)-HNL (hydroxynitrile lyase). The enantiopure cyanohydrins are then synthetically manipulated into the above two drug molecules and two of their structural analogues, atomoxetine and nisoxetine.     

Preparation of NiFe2O4 nanopowder via EDTA precursor and study of its properties

An ethylene diamine tetra acetic acid (EDTA) precursor-based chemical method is reported for preparing single-phase nickel ferrite (NiFe₂O₄) nanopowder. The synthesized powder was characterized by thermogravimetric analysis, differential scanning calorimetric analysis, X-ray diffraction, particle size analysis and scanning electron microscopy. DC electrical resistivity and magnetic property of the synthesized NiFe₂O₄ were measured by using a two-probe method and a vibrating sample magnetometer respectively. The DC resistivity behaviour of the NiFe₂O₄ nanopowder was correlated with the change of microstructure, during sintering. This EDTA precursor-based method is capable of producing nanostructured single-phase NiFe₂O₄ powder at a comparatively low calcination temperature and offers the potential of a simple and cost-effective route, including the preparation of other ferrite nanoparticles.     

Green synthesis of water-dispersible silver nanoparticles at room temperature using green carambola (star fruit) extract

Journal of Sol-Gel Science and Technology - Silver nanoparticles (AgNPs) dispersible in water were synthesized at room temperature in the presence of carambola fruit extract at different pH. The...