A general decay result for a memory-type thermoelasticity with second sound

In this paper, we consider an n-dimensional system of thermoelasticity with second sound in the presence of a viscoelastic term acting in the domain. We prove a general decay result from which the usual exponential and polynomial decay results are only special cases.     

The structure and synthesis of fadyenolide,a new butemolide from piper fadyenii

The isolation, structure and synthesis of 5,6-$\text{Z}$- and $\text{E}$- fadyenolides, the simplest butenolides of the piperolide series, are reported.     

Syntheses, crystal structure and ab initio calculations of two new phosphoric triamides

The reaction of N-benzoylphosphoramidic dichloride with piperidine and 4-methylpiperidine lead to PhC(O)N(H)P(O)R₂ with R=piperidine (1) and R=4-methylpiperidine (2) as N-benzoyl-N′,N″-bis(piperidine) phosphoric triamide and N-benzoyl-N′,N″-bis(4-methylpiperidine) phosphoric triamide, respectively. The products have been characterized by ¹H, ¹³C, ³¹P NMR spectra, and by elemental analysis. The crystalline solid for (1) and (2) consists surprisingly of four and two independent molecules, respectively. There is a disorder in one amine group due to ring inversion in each conformer in compound 1. In the solid state, comparable magnitudes for the stabilization of the stable conformers for the more or less discrete molecules, the polarization effects, hydrogen bonding and the packing effects could be anticipated.

The geometry of compound (1) optimized by density functional calculations at the B3LYP/6-31++G* (d,p) level, is in good agreement with data obtained from X-ray crystallography.     

Carbon-carbon bond formation by ‘double activation’. The synthesis of piperolide and fadyenolide intermediates.

Buenolide anions do not react with orthoesters and butenolides do not react with carbocations derived from acetals and orthoesters. However double activation of the butenolide (as the carbanion) and the alkoxyalkanes (as the stabilised carbocations) leads to high yield carbon-carbon bond formation of some generality.     

Mixed Spin-1/2 and Spin-5/2 Model by Renormalization Group Theory: Recursion Equations and Thermodynamic Study

Using the renormalization group approximation, specifically the Migdal-Kadanoff technique, we investigate the Blume-Capel model with mixed spins S = 1/2 and S = 5/2 on d-dimensional hypercubic lattice. The flow in the parameter space of the Hamiltonian and the thermodynamic functions are determined. The phase diagram of this model is plotted in the (anisotropy, temperature) plane for both cases d = 2 and d = 3 in which the system exhibits the first and second order phase transitions and critical end-points. The associated fixed points are drawn up in a table, and by linearizing the transformation at the vicinity of these points, we determine the critical exponents for d = 2 and d = 3. We have also presented a variation of the free energy derivative at the vicinity of the first and second order transitions. Finally, this work is completed by a discussion and comparison with other approximation.     

Anti-Depressant Properties of Crocin Molecules in Saffron

Saffron is a valued herb, obtained from the stigmas of the C. sativus Linn (Iridaceae), with therapeutic effects. It has been described in pharmacopoeias to be variously acting, including as an anti-depressant, anti-carcinogen, and stimulant agent. The therapeutic effects of saffron are harbored in its bioactive molecules, notably crocins, the subject of this paper. Crocins have been demonstrated to act as a monoamine oxidase type A and B inhibitor. Furthermore, saffron petal extracts have experimentally been shown to impact contractile response in electrical field stimulation. Other research suggests that saffron also inhibits the reuptake of monoamines, exhibits N-methyl-d-aspartate antagonism, and improves brain-derived neurotrophic factor signaling. A host of experimental studies found saffron/crocin to be similarly effective as fluoxetine and imipramine in the treatment of depression disorders. Saffron and crocins propose a natural solution to combat depressive disorders. However, some hurdles, such as stability and delivery, need to be overcome.     

Renormalization Group Study of the Mixed Spin-1 and Spin-3/2 Blume-Emery-Griffiths Model with Attractive Biquadratic Coupling

The mixed spin-1 and spin-3/2 Blume-Emery-Griffiths model with attractive biquadratic coupling is investigated in the framework of the Migdal-Kadanoff Renormalization Group method. By changing the ratio R > 0 of biquadratic and bilinear exchange interactions and according to the different values of crystal field interactions, we have determined six main types of phase diagrams. The full flow in the parameters space of the Hamiltonian was established and the fixed points obtained are drawn up in a table. In addition, we have determined the eigenvalues of the transformation of the group in the vicinity of the critical points. Finally, the introduction of a positive biquadratic interaction was discussed.

     

Impact of γ-rays on constructional,optical and thermal behavior of alkaline and non alkaline low density polyethylene

ABSTRACT

In this study, we investigated the graft copolymerization of methyl methacrylate (MMA) onto low-density polyethylene (LDPE) in the presence of aniline as an inhibitor by gamma radiation. An alkaline treatment was carried out for the prepared graft copolymer. The structural properties of the prepared samples were examined via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD peaks were slightly shifted, indicating an interaction between MMA and the polyethylene matrix. The morphology of the samples confirmed the homogenous grafted phase scattered onto the LDPE surface. Analysis of the absorption spectra indicated an allowed indirect transition mechanism. The Urbach energy (E_U) results showed that the value of the E_U for grafted LDPE was found to be higher than that of pure LDPE—up to 15?kGy irradiation dose, although this value decreases upon grafting. However, the value of the E_U for alkaline-treated grafted films decreases systematically by increasing the degree of grafting. The thermogravimetric analysis (TGA) of the sample indicated that the thermal stability of LDPE samples is significantly changed by grafting MMA onto it. Horowitz and Metzger's models were utilized to measure the activation energy of the thermal decomposition of all samples.     

Effects of Convection and Fracture Boundary Conditions on Heat Transfer Shape Factor in Fractured Geothermal Reservoirs

The yield stress fluids porosimetry method (YSM) was recently presented as a simple and non-toxic potential alternative to the extensively used mercury intrusion porosimetry (MIP). The success of YSM heavily relies on the choice of an appropriate yield stress fluid to be injected through the investigated porous medium. In previous works, xanthan gum aqueous solutions were used due to their ability to exhibit a pseudo-yield stress without substantial levels of unwanted thixotropy or viscoelasticity. Given that YSM is based on the existence of a yield stress, the accuracy of the obtained pore size distribution (PSD) crucially depends on the capacity of the injected fluid to emulate the shear rheology of a yield stress fluid. However, this capacity has still not been fully assessed in the case of xanthan gum solutions. Neither has the robustness of YSM with regard to errors in the determination of the shear-rheology parameters of the injected fluid been analysed. The shear viscosity of polymer solutions is known to be deeply influenced by polymer concentration. For these reasons, a first objective of this work is to evaluate the effect of polymer concentration on the accuracy of PSDs obtained by YSM when using xanthan gum solutions as injected fluids in laboratory experiments. To do so, xanthan gum solutions with different polymer concentrations were injected through analogous samples of a sintered silicate and the obtained PSDs were compared to the results of standard MIP. Moreover, the sensitivity of YSM to errors in the experimental determination of the shear-rheology parameters was also investigated through numerical experiments. The results of the present work permitted to gain further insight into the viability of YSM as an efficient alternative to MIP.