Ru-catalyzed synthesis of substituted phthalides through C–H bond activation and functionalization

Synthesis of substituted phthalides through a ruthenium-catalyzed reaction of phthalic anhydrides with acrylates is described. The reaction proceeds via CH bond activation and leads to the formation of vinylated phthalides through a successive double vinylation accompanied by decarboxylation and annulation reactions.     

Some singular value and unitarily invariant norm inequalities for Hilbert space operators

In this paper, we prove some singular value inequalities for sum and product of operators. Also, we obtain several generalizations of recent inequalities. Moreover, as applications we establish some unitarily invariant norm and trace inequalities for operators which provide refinements of previous results.     

Nuclear model calculation on charge particle induced reaction on Rb and Kr targets and targetry for 82Sr production

The ⁸²Sr/⁸²Rb radionuclide generator is used very commonly in positron emission tomography. ALICE/ASH and TALYS 1.0 codes were used to calculate excitation functions for proton, alpha and ³He induced on various targets that lead to produce ⁸²Sr radioisotope using intermediate energy accelerators. Recommended thickness of the targets according to SRIM code was premeditated. The application of those data, particularly in the calculation of integral yields, is discussed and theoretical integral yields for any reaction were computed. To consider precision of TALYS 1.0 code calculations, ⁸⁵Rb(p,4n)⁸²Sr process was determined as most interesting one due to radionuclide purity. The TALYS 1.0 code predicts a maximum cross-section of about 130 mb at 47 MeV for this reaction. Rubidium chloride deposition on copper substrate was carried out via sedimentation method in order to produce ⁸²Sr. 2.98 g RbCl, 1.043 g ethyl cellulose, 10 mL acetone were used to prepare a layer of enriched rubidium chloride of 11.69 cm² area and 0.34 g/cm² thickness.     

Phytotherapeutic inhibition of supragingival dental plaque

Antimicrobial activities and biofilm-formation preventive properties of Mentha piperita and Cuminum cyminum essential oils and chlorhexidine were assessed against Streptococcus mutans and Streptococcus pyogenes. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analysis led to the identification of 26 and 32 compounds in the essential oils of M. piperita and C. cyminum, respectively. Minimal bactericidal concentrations (MBC) of the oils and chlorhexidine and microbial decimal reduction time (D value) were determined. Antibacterial and in vivo biofilm preventive efficacies of all the concentrations of M. piperita oil were significantly (p<0.001) higher. The biofilm inhibitory properties in planktonic cultures were in M. piperita > chlorhexidine > C. cyminum order. In vivo experiments conducted on male and female volunteers who brushed with essential oil blended toothpastes indicated that lower concentrations of the oils, in particular the M. piperita oil, were significantly higher (p<0.001) and effective during the course of the study as compared to chlorhexidine. In conclusion, there may be a potential role for essential oils in the development of novel anticaries treatments.     

Computational study of plasma-assisted photoacoustic response from gold nanoparticles irradiated by off-resonance ultrafast laser

The gold nanoparticles (AuNPs) are capable of enhancing the incident laser field in the form of scattered near field for even an off-resonance irradiation where the incident laser wavelength is far away from the localized surface plasmon resonance (LSPR). If the intensity of the pulse laser is large enough, this capability can be employed to generate a highly localized free electron (plasma) in the vicinity of the particles. The generated plasma can absorb more energy during the pulse, and this energy deposition can be considered as an energy source for structural mechanics calculations in the surrounding media to generate a photoacoustic (PA) signal. To show this, in this paper, we model plasma-mediated PA pressure wave propagation from a 100-nm AuNPs and the surrounding media irradiated by an ultrashort pulse laser. In this model, the AuNP is immersed in water and the laser pulse width is ranging from 70 fs to 2 ps at the wavelength of 800 nm (off-resonance). Our results qualitatively show the substantial impact of the energy deposition in plasma on the PA signal through boosting the pressure amplitudes up to ～1000 times compared to the conventional approach.     

A numerical approach based on the meshless collocation method in elastodynamics

In this paper, a collocation technique with the modified equilibrium on line method （ELM） for imposition of Neumann （natural） boundary conditions is presented for solving the two-dimensional problems of linear elastic body vibrations. In the modified ELM, equilibrium over the lines on the natural boundary is satisfied as Neumann boundary condition equations. In other words, the natural boundary conditions are satisfied naturally by using the weak formulation. The performance of the modified version of the ELM is studied for collocation methods based on two different ways to construct meshless shape functions： moving least squares approximation and radial basis point interpolation. Numerical examples of two-dimensional free and forced vibration analyses show that by using the modified ELM, more stable and accurate results would be obtained in comparison with the direct collocation method.     

Thermal Degradation Kinetics and Modeling Study of Ultra High Molecular Weight Polyethylene (UHMWP)/Graphene Nanocomposite

The incorporation of nanofillers such as graphene into polymers has shown significant improvements in mechanical characteristics, thermal stability, and conductivity of resulting polymeric nanocomposites. To this aim, the influence of incorporation of graphene nanosheets into ultra-high molecular weight polyethylene (UHMWPE) on the thermal behavior and degradation kinetics of UHMWPE/graphene nanocomposites was investigated. Scanning electron microscopy (SEM) analysis revealed that graphene nanosheets were uniformly spread throughout the UHMWPE’s molecular chains. X-Ray Diffraction (XRD) data posited that the morphology of dispersed graphene sheets in UHMWPE was exfoliated. Non-isothermal differential scanning calorimetry (DSC) studies identified a more pronounced increase in melting temperatures and latent heat of fusions in nanocomposites compared to UHMWPE at lower concentrations of graphene. Thermogravimetric analysis (TGA) and derivative thermogravimetric (DTG) revealed that UHMWPE’s thermal stability has been improved via incorporating graphene nanosheets. Further, degradation kinetics of neat polymer and nanocomposites have been modeled using equations such as Friedman, Ozawa–Flynn–Wall (OFW), Kissinger, and Augis and Bennett’s. The "Model-Fitting Method” showed that the auto-catalytic nth-order mechanism provided a highly consistent and appropriate fit to describe the degradation mechanism of UHMWPE and its graphene nanocomposites. In addition, the calculated activation energy (E_a) of thermal degradation was enhanced by an increase in graphene concentration up to 2.1 wt.%, followed by a decrease in higher graphene content.     

Synthesis of D,L-Lactide–ε-Caprolactone Copolymers and Preparation of Films Based on Them

D,L-Lactide–ε-caprolactone copolymers were synthesized by polymerization in the bulk. Films of these copolymers were prepared, and their strain properties and degradation rate under physiological conditions were studied. Introduction of ε-caprolactone into the copolymer increases the film elasticity and decreases the degradation rate compared to poly(D,L-lactide) homopolymer, and also favors spreading of human keratinocytes. The films obtained can be used for treatment of wounds and burns.