The Crystallization,Melting Behaviors and Thermal Stability of Cross-linked Poly(3-hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-3-hydroxyvalerate) by Octavinyloctasilasesquioxane

A series of cross-linked poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/octavinyloctasilasesquioxane (PHBV/OVS) composites were obtained by a simple melt reactive processing technique. Dicumyl peroxide (DCP) and OVS were employed as a free radical initiator and a cross-linking agent, respectively. The chemical structure of these produced composites were identified by ¹H/¹³C/²⁹Si-nuclear magnetic resonance spectroscopy (¹H/¹³C/²⁹Si-NMR) and Fourier transform infrared spectroscopy (FTIR). The melting behavior, non-isothermal crystallization, spherulite morphology and thermal stability property of PHBV/OVS composites were also investigated. The nucleation behaviors and crystallization rate of PHBV/OVS were significantly enhanced with the formation of cross-linked networks with different side-chains and cross-linking points. The red shift of crystalline peak temperature with addition of a small amount of OVS content evidenced the higher crystalline ability compared with the neat PHBV. However there was a threshold content, beyond which the crystallization rate weakened again. Additionally, the cross-linked structure of PHBV/OVS composites could be adjusted by changing the amount of OVS.     

Nano titania-supported sulfonic acid (n-TSA) as an efficient,inexpensive, and reusable catalyst for one-pot synthesis of 1, 8-dioxo-octahydroxanthene and tetrahydrobenzo[<Emphasis Type="Italic">b</Emphasis>]pyran derivatives

This paper explains how with the help of nano titania-supported sulfonic acid (n-TSA), new 1,8-dioxo-octahydroxanthene and tetrahydrobenzo[b]pyran derivatives can be produced. To do this, at first n-TSA, which is relatively cheap, easy separable and reusable was made. Next, using this nano catalyst,1,8-dioxo-octahydroxanthene and tetrahydrobenzo[b]pyran derivatives were synthesized from di-ketones and various aromatic aldehydes/or malononitrile without using solvent. Appropriate one-pot operation using different aromatic aldehydes with both electron donating and withdrawing groups have resulted in the best yields. Reusability of the nano catalyst, environmental friendliness, reduced reaction time, non-toxic reaction medium and catalyst high activity are substantial advantages of this work. Nowadays, it is really important that the catalyst can be recovered easily and reused five times while maintaining catalytic activity.     

Tuning the ferromagnetic resonance by doping strontium hexa-ferrite nanopowders

Mg–Ti substituted strontium hexa-ferrites nanopowders (SrFe_12?x(MgTi)_x/2O₁₉, x?=?0–3) were prepared by the sol–gel method. The morphology, structure and composition of the nanostructures were examined by field emission scanning electron microscopy (FESEM) and X-ray diffraction. The effect of Mg–Ti doping on the magnetic properties of the powders was investigated by vibrating sample magnetometry (VSM) and ferromagnetic resonance (FMR) at ambient temperature. Experimental results showed that the materials exhibit hexagonal structures with tunable magnetic properties. The saturation magnetization and the coercive field (H_c) decreased through the Mg and Ti substitution. FMR proved that by incorporation of Mg and Ti in strontium ferrite lattice, crystalline anisotropy, and microwave absorption can be tuned. SrFe_12?x(MgTi)_x/2O₁₉ ferrites are good candidate for applications at X-band microwave frequencies. A low field absorption signal was observed with the same phase as the FMR absorption in all doped ferrites.

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Preparation of magnetic molecularly imprinted polymer for dispersive solid‐phase extraction of valsartan and its determination by high‐performance liquid chromatography: Box‐Behnken design

In this work, core/shell magnetic molecularly imprinted polymer nanoparticles were synthesized for extraction and pre‐concentration of valsartan from different samples and then it was measured with high‐performance liquid chromatography. For preparation of molecularly imprinted polymer nanoparticles, Fe₃O₄ nanoparticles were coated with tetraethyl orthosilicate and then functionalized with 3‐(trimethoxysilyl) propyl methacrylate. In the next step, molecularly imprinted polymer nanoparticles were synthesized under reflux and distillation conditions via polymerization of methacrylic acid, valsartan (as a template), azobisisobutyronitrile and ethylene glycol dimethacrylate as cross linking. The properties of molecularly imprinted polymer nanoparticle were investigated by FTIR spectroscopy, field emission scanning electron microscopy, and X‐ray diffraction. Box‐Behnken design with the aid of desirability function was used for optimizing the effect of variables such as the amounts of molecularly imprinted polymer nanoparticles, time of sonication, pH, and volume of methanol on the extraction percentage of valsartan. According to the obtained results, the affecting variables extraction condition were set as 10 mg of adsorbent, 16 min for sonication, pH = 5.5 and 0.6 mL methanol. The obtained linear response (r² > 0.995) was in the range of 0.005–10 µg/mL with detection limit 0.0012 µg/mLand extraction recovery was in the range of 92–95% with standard deviation less than 6% (n = 3).     

Strongly amenable involutive representations of involutive Banach algebras

Let \(\mathfrak{A }\) be a Banach \(*\) -algebra and let \(\varphi \) be a nonzero self-adjoint character on \(\mathfrak{A }\) . For a   \(*\) -representation \(\pi \) of \(\mathfrak{A }\) on a Hilbert space \(\mathcal{H }\) , we introduce and study strong \(\varphi \) -amenability of \(\pi \) in terms of certain states on the von Neumann algebra of bounded operators on \(\mathcal{H }\) . We then give some characterizations of this notion in terms of certain positive functionals on \(\mathfrak{A }\) . We finally investigate some hereditary properties of strong \(\varphi \) -amenability of Banach algebras.     

Spectroscopic and Molecular Modeling Based Approaches to Study on the Binding Behavior of DNA with a Copper (II) Complex

Blocking the division of tumor cells by small-molecules is currently of great interest for the design of new antitumor drugs. The interaction of a new metal complex with DNA was investigated through several techniques. Absorption spectroscopy and gel electrophoresis studies on the interaction of the Cu-complex of (2a-4mpyH)₂ [Cu(pyzdc)₂ (H₂O)₂].6 H₂O with DNA have shown that this complex can bind to CT-DNA with binding constant 3.99?×?10⁵ M^?1. The cyclic voltammetry (CV) responses of the metal complex in the presence of CT-DNA have shown that the metal complex can bind to CT-DNA through partial intercalation mode and this is consistent with molecular docking analysis, quenching process and thermal denaturation experiments. The cytotoxicity of this complex has been evaluated by MTT assay. The results of cell viability assay on DU145 cell line revealed that the metal complex had cytotoxic effects.     

Dimension of quantum channel of radiation in pure Lovelock black holes

The effects of a running gravitational coupling and the entropic force on future singularities are considered. Although it is expected that the quantum corrections remove the future singularities or change the singularity type, treating the running gravitational coupling as a function of energy density is found to cause no change in the type of singularity but causes a delay in the time that a singularity occurs. The entropic force is found to replaces the singularity type $II\, \hbox {by} \overline{III} (a=\hbox {const.}, H=\hbox {const.}, \dot{H} \rightarrow \infty , p \rightarrow \infty , \rho \rightarrow \infty )$ which differs from previously known type $III$ and to remove the $w$ -singularity. We also consider an effective cosmological model and show that the types $I$ and $II$ are replaced by the singularity type $III$ .     

Ti(IV) ion-imprinted polymer as a new selective sorbent for extraction and pre-concentration of trace amounts of titanium ions in different samples

ABSTRACT

In this paper, a novel, simple, selective and effective solid phase extraction method based on ion-imprinted polymer (IIP) technology and flame atomic absorption spectrometry (FAAS) for separation and pre-concentration of trace amounts of titanium (IV) ions was reportd?. It was obtained by precipitation polymerisation by using 2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one titanium (IV) complex abbrivated as Ti(IV)-(morin), as the template molecule. After polymerisation, leaching the polymer in HNO₃ (50% (v/v) solution caused formation cavities in the polymer. Characterisation studies of the ?Ti(IV)-imprinted polymer (Ti-IP) was performed by FT-IR, UV-Vis and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) techniques and then, the effective factors on extraction were optimised. A sensitive response to Ti(IV) within a concentration range between 0.01 and 4.0 μg mL^?1 was achieved under the optimum conditions. A total of 10.0 ng mL^?1 and 80.0 mg g^?1 were obtained as limit of detection (LOD, 3Sb/m) and maximum adsorption capacity, respectively. The relative standard deviation (RSD) for eight replicates detections of 0.2 μg mL^?1 of Ti(IV)? was found to be 2.8%. By this method, pre-concentration factor (PF) of 100 was obtained. Successfully applying this method in the water and standard samples, reasonable results were obtained for the extraction and pre-concentration of the titanium ions.     

The Catalytic Performance of Preyssler's Anion, [NaP5W30O110]14−, in the Oxidation of Benzyl Alcohols

Under mild conditions, monosubstituted benzyl alcohols were oxidized to benzaldehydes and benzoic acids in the presence of sodium 30-tungstopentaphosphate (Preyssler's anion), [NaP₅W₃₀O₁₂₀]^14? , and hydrogen peroxide as an oxidant. This polyanion with high hydrolytic stability (pH = 0–12), high thermal stability, and high acidic strength shows good activities. The effects of various parameters on the yield of the products, including a catalyst type, a nature of the substitutents, and temperature, were studied. Comparison between Keggin's heteropolyacids, H₃[PW₁₂O₄₀], H₃[PMo₁₂O₄₀], H₄[SiW₁₂O₄₀], and H₄[SiMo₁₂O₄₀], and Preyssler's anion shows that this polyanion reacts similar to Keggin's acids whitout any degradation of the structure.     

Triphenylphosphine-Catalyzed Preparation of Sterically Congested,Electron-Poor N-Vinylimidazole Derivatives from Acetylenic Esters and Imidazole-Containing NH-Acids

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and alkyl acetylenecarboxylates (or ethyl 3-phenyl-2-propynoate), by azathioprine or imidazole leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce phosphorus ylides. Dipotassium hydrogen phosphate, potassium dihydrogen phosphate, and potassium iodide were found to catalyze the conversion of the phosphorus ylides to electron-poor N-vinyl imidazoles in solvent-free conditions under thermal (90°C, 1 h) conditions. The structural analysis of the products indicated that the reaction is regio- and stereoselective.