Synthesis and characterization of side-chain oxazoline–methyl methacrylate copolymers bearing azo-dye

We synthesized new polymeric structures by attaching a side-chain azo-moiety on poly(oxazoline) and poly(oxazoline-co-methyl methacrylate)s. For the polymer analogous transformation, we took advantage of the highly effective ring-opening addition of carboxyl group to the oxazoline cycle. The comonomers feed ratio allowed us to control the composition of the products while the kinetic treatment, employing an integral method, revealed a statistical copolymerization tendency of 2-isopropenyl-2-oxazoline with methyl methacrylate in acetonitrile at 70 °C. The elemental analysis and ¹H NMR spectroscopy provided almost identical composition data for both the substrates and the side-chain copolymers. The UV spectroscopy sustained the quantitative addition of 4-(4-hydroxy-3,5-dimethylphenylazo)benzoic acid to the oxazoline rings. Both the unmodified copolymers and the coloured ones exhibited good thermal stabilities, up to 371 °C and 302 °C, respectively. The glass transition temperatures ranged from 141.5 to 177.5 °C and from 153.8 to 200.9 °C for the substrates and for the modified copolymers, respectively. Preliminary investigations showed fluorescence activity for all copolymers bearing azo-moieties.     

Origin of dielectric response and conductivity of some alicyclic polyimides

High‐performance alicyclic‐containing polyimides for advanced applications, derived from 5‐(2,5‐dioxotetrahydrofurfuryl)‐3‐methyl‐3‐cyclohexene‐1,2‐dicarboxylic acid anhydride or bicyclo[2.2.2]oct‐7‐ene‐2,3,5,6‐ tetracarboxylic dianhydride and two flexible aromatic diamines, were synthesized by a classical two‐step polycondensation reaction. The dielectric spectra behavior over wide frequency and temperature ranges of 1 Hz‐1 MHz and –150°C÷+250°C, respectively, was investigated according to chemical and micro‐structural aspects. The dielectric constants have low values and are dependent on dianhydride flexibility and diamine links, in relation with the charge–transfer complex (CTC) and free volume, and, consequently, with packing of the polymer chains and polarizable groups per volume units. All polyimide films develop two relaxation processes, i.e., γ and β relaxation, involving different enthalpy and entropy contributions induced by their chemical structures. Frequency–temperature‐dependent conductivity showed that conductivity increased with frequency and also that energy bandgap representation could be suitable for explaining the temperature influence on AC‐conductivity. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Holmium-Loaded PLLA Nanoparticles for Intratumoral Radiotherapy Via the TMT Technique: Preparation,Characterization, and Stability Evaluation after Neutron Irradiation

This article describes the preparation of biocompatible radioactive holmium-loaded particles with appropriate nanoscale size for radionuclide intratumoral administration by the targeted multitherapy (TMT) technique. For this objective, holmium acetylacetonate has been encapsulated in poly-l-lactide (PLLA)-based nanoparticles (NP) by oil-in-water emulsion–solvent evaporation method. NP sizes ranged between 100 and 1,100 m being suitable for the TMT administration method. Elemental holmium loading was found to be around 18% wt/wt and the holmium acetylacetonate trihydrate (HoAcAc) encapsulation efficacy was about 90%. Different experiments demonstrated an amorphous state of HoAcAc after incorporation in NPs. The NPs were irradiated in a nuclear reactor with a neutron flux of 1.1 × 10¹³ n/cm²/s for 1 h, which yielded a specific activity of about 27.4 GBq/g of NPs being sufficient for our desired application. Microscopic analysis of irradiated NPs showed some alteration after neutron irradiation as some NPs looked partially coagglomerated and a few pores appeared at their surface because of the locally released heat in the irradiation vials. Furthermore, differential scanning calorimetry (DSC) results indicated a clear decrease in PLLA melting point and melting enthalpy reflecting a decrease in polymer crystallinity. This was accompanied by a clear decrease in polymer molecular weights, which can be ascribed to a radiation-induced chain scission mechanism. However, interestingly, other experiments confirmed the chemical identity retention of both HoAcAc and PLLA in irradiated NPs despite this detected decrease in the polymer crystallinity and molecular weight. Although neutron irradiation has induced some NPs damage, these NPs kept out their overall chemical composition, and their size distribution remained suitable for the TMT administration technique. Coupled with the TMT technique, these NPs may represent a novel potential radiopharmaceutical agent for intratumoral radiotherapy.     

Modeling of the electrostatic coupling between nanocrystals of a disordered nanocrystal floating gate memory

This paper presents a realistic model that explicitly takes into account the electrostatic coupling between the nanocrystals of a disordered layer constituting the floating gate of a non-volatile memory. A statistical study of the neighborhood of a given nanocrystal is carried out, leading to the mean number of neighboring nanocrystals as a function of the radius of the central nanocrystal. We show that the empty neighborhood of every nanocrystal can be represented by an equivalent torus ring in the previous model of a single nanocrystal. Then the effects of charged nanocrystals are taken into account by an appropriate rigid shift of the energy levels of the central nanocrystal. The proposed model is validated by statistical comparisons with exact 3D computations, and the influence of the electrostatic coupling is analyzed and discussed.     

Adaptive fractional‐order blood glucose regulator based on high‐order sliding mode observer

Type I diabetes is described by the destruction of the insulin‐producing beta‐cells in the pancreas. Hence, exogenous insulin administration is necessary for Type I diabetes patients. In this study, to estimate the states that are not directly available from the Bergman minimal model a high‐order sliding mode observer is proposed. Then fractional calculus is combined with sliding mode control (SMC) for blood glucose regulation to create more robustness performance and make more degree of freedom and flexibility for the proposed method. Then an adaptive fractional‐order SMC is proposed. The adaptive SMC protect controller against disturbance and uncertainties while the fractional calculus provides robust performance. Numerical simulation verifies that the proposed controllers have better performance in the presence of disturbance and uncertainties without chattering.Inspec keywords: variable structure systems, biochemistry, blood, robust control, medical control systems, observers, sugar, diseases, calculus, adaptive control, cellular biophysicsOther keywords: fractional‐order SMC, adaptive SMC, fractional calculus, robust performance, adaptive fractional‐order blood glucose regulator, insulin‐producing beta‐cells, exogenous insulin administration, diabetes patients, Bergman minimal model, mode control, blood glucose regulation, pancreas, type I diabetes, state estimation, high‐order sliding mode observer, sliding mode control, degree of freedom, numerical simulation     

Copolymerization of the pair maleic anhydride–dicyclopentadiene: I. Copolymerization and post‐copolymerization at high conversion

The present study describes the kinetic investigation of the complex binary copolymerization system maleic anhydride (MA)—dicyclopentadiene (DCPD). All syntheses were carried out in homogeneous solution; high conversions in soluble and linear copolymer are achievable when starting from an equimolecular monomer feed. Excess of DCPD would limit the attainable conversions, while surplus of MA would induce crosslinking of the copolymers. The findings of the thorough kinetic study were sustained by structural assessment from IR and NMR spectra recorded for various copolymers, both soluble and gels. Copyright © 2004 Society of Chemical Industry     

Competitive numerical analysis for stochastic HIV/AIDS epidemic model in a two‐sex population

This study is an attempt to explain a reliable numerical analysis of a stochastic HIV/AIDS model in a two‐sex population considering counselling and antiretroviral therapy (ART). The authors are comparing the solutions of the stochastic and deterministic HIV/AIDS epidemic model. Here, an endeavour has been made to explain the stochastic HIV/AIDS epidemic model is comparatively more pragmatic in contrast with the deterministic HIV/AIDS epidemic model. The effect of threshold number H ^* holds on the stochastic HIV/AIDS epidemic model. If H ^*  < 1 then condition helps us to control disease in a two‐sex human population while H ^*  > 1 explains the persistence of disease in the two‐sex human population. Lamentably, numerical methods such as Euler–Maruyama, stochastic Euler, and stochastic Runge–Kutta do not work for large time step sizes. The recommended structure preserving framework of the stochastic non‐standard finite difference (SNSFD) scheme conserve all vital characteristics such as positivity, boundedness, and dynamical consistency defined by Mickens. The effectiveness of counselling and ART may control HIV/AIDS in a two‐sex population.Inspec keywords: diseases, stochastic processes, epidemics, patient treatment, finite difference methodsOther keywords: two‐sex human population, antiretroviral therapy, competitive numerical analysis, stochastic HIV‐AIDS epidemic model, structure preserving framework, stochastic nonstandard finite difference scheme, SNSFD scheme, deterministic HIV‐AIDS epidemic model     

Isolation and Characterization of the First Microsatellite Markers for the Endangered Relict Mussel Hypanis colorata (Mollusca: Bivalvia: Cardiidae)

Hypanis colorata (Eichwald, 1829) (Cardiidae: Lymnocardiinae) is a bivalve relict species with a Ponto-Caspian distribution and is under strict protection in Romania, according to national regulations. While the species is depressed in the western Black Sea lagoons from Romania and Ukraine, it is also a successful invader in the middle Dniepr and Volga regions. Establishing a conservation strategy for this species or studying its invasion process requires knowledge about the genetic structure of the species populations. We have isolated and characterized nine polymorphic microsatellite markers in H. colorata. The number of alleles per locus ranged from 4 to 28 and the observed heterozygosity ranged from 0.613 to 1.000. The microsatellites developed in the present study are highly polymorphic and they should be useful for the assessment of genetic variation within this species.