On strong approximation of continuous functions

An embedding theorem concerning strong approximation of continuous functions by their Fourier series is proved.     

Efficient and green microwave-assisted one-pot synthesis of azaindolizines in PEG-400 and water

A facile, convenient, environmentally benign, and one-pot synthesis of imidazo[1,2-a]pyridines from 2-aminopyridines and in-situ generated phenacyl bromides under microwave irradiation in polyethylene glycol (PEG-400) and water (1:2) has been developed. The protocol provides a better alternative to the existing method as it involves utilization of in-situ-generated α-bromoacetophenones, avoids the use of lachrymatric α-haloketones as well as volatile toxic organic solvents, and reduces the reaction time to obtain excellent yield.     

Synthesis and characterization of new soluble thermally stable poly(azomethine‐ether‐imide)s: discerning the possibility for high temperature applications

A new series of polyimides was synthesized by the condensation of monomers (azomethine‐ether diamine, DA‐1 and DA‐2) with pyromelliticdianhydride (PMDA), 3,4,9,10‐perylenetetracarboxylic dianhydride (PD) and 3,3′4,4′‐benzophenonetetracarboxylic dianhydride (BD). The structural explications of monomers and polyimides was conducted by FT‐IR, ¹H NMR and elemental analysis. All polyimides were found soluble in polar aprotic solvents and found to be semicrystalline in nature confirmed by XRD. The inherent viscosities were found in the range of 0.67–0.77 g/dl. %. Average molecular weight (M_W) and number average molecular weight (Mn) of the polyimides were found in the range of 5.72 × 10⁵ g/mol–6.58 × 10⁵ g/mol and 3.79 × 10⁵ g/mol 4.11 × 10⁵ g/mol respectively. The polyimides exhibited excellent thermal properties having a glass transition temperature T_g in the range of 230–290°C and the 10% weight loss temperature was above 450°C. The values of thermodynamic parameters, activation energy, enthalpy and entropy fall in the range of 45.2–53.90 kJ/mol, 43.5–52.30 kJ/mol and 0.217 kJ/mol k to 0.261 kJ/mol k respectively. Copyright © 2015 John Wiley & Sons, Ltd.     

Role of diffusion tensor imaging metrics and in vivo proton magnetic resonance spectroscopy in the differential diagnosis of cystic intracranial mass lesions

The purpose of this study was to determine whether proton magnetic resonance spectroscopy (PMRS) and diffusion tensor imaging (DTI) indices, fractional anisotropy (FA) and mean diffusivity (MD) can be used to distinguish brain abscess from cystic brain tumors, which are difficult to distinguish by conventional magnetic resonance imaging (MRI). Fifty-three patients with intracranial cystic mass lesions and 10 normal controls were studied. Conventional MRI, PMRS and DTI of all the patients were performed on a 1.5-T GE scanner. Forty patients were with brain abscess and 13 with cystic tumors. Cytosolic amino acids (AAs) were present in 32 of 40 brain abscess patients. Out of 13 patients with cystic tumors, lactate and choline were seen in 3 and only lactate was present in 10 patients on PMRS. All 40 cases of abscess had high FA, while all 13 cases of tumor cysts had high MD values. We conclude that FA measurements are more sensitive in predicting the abscess, while PMRS and MD are more specific in differentiating abscess from cystic tumors. We suggest that PMRS should be combined with DTI rather than with diffusion-weighted imaging as FA can be used as an additional parameter for separation of abscess from other cystic intracranial mass lesions.     

Low temperature synthesis of fluorescent ZnO nanoparticles

Fluorescent ZnO nanoparticles have been prepared by mixing aqueous solutions of zinc nitrate and ammonium carbonate in the presence of a non-ionic surfactant, Tween-80. Increased concentrations of the surfactant were found to affect both the morphology and purity of the synthesized ZnO nanoparticles. XRD, SEM, FTIR, TGA and Confocal laser scanning microscopy were employed to characterize the as-prepared samples. ZnO nanoparticles ranging in particle size from 11 to 15 nm were formed at the reaction temperature of 70-80 °C. The results of FTIR and TGA analysis indicate the self assembly of Tween molecules on the surface of ZnO nanoparticles. A bright emission in the visible region from the as-prepared ZnO nanoparticles was recorded using confocal laser scanning microscopy. This property of the as-prepared nanoparticles may find potential application in bio-imaging.     

Synthesis,characterization, and biological studies of tri‐ and diorganotin(IV) complexes with 2′,4′‐difluoro‐4‐hydroxy‐[1,1′]‐biphenyle‐3‐carbolic acid: Crystal structure of [(CH3)3Sn(C13H7O3F2)]

Eight tri‐ and diorganotin(IV) carboxylates with general formulae R₃SnL and R₂SnL₂ (where R = CH₃, n‐C₄H₉, C₆H₅, C₇H₇, and L = 2′,4′‐difluoro‐4‐hydroxy‐[1,1′]‐biphenyl‐3‐carboxylic acid) were synthesized and characterized by UV–vis, IR, conductance, multinuclear (¹H, ¹³C, and ¹¹⁹Sn) NMR spectroscopy, and mass spectrometry. The crystal structure of [(CH₃)₃Sn(C₁₃H₇O₃F₂)] indicates that the tin atom in the asymmetric unit exists in a trigonal bipyramidal geometry having a space group Pbca with an orthorhombic crystal system. These complexes were also screened for their antibacterial and antifungal activities. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:638–649, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10057     

Fluxional behavior in dimeric tetraorganodicarboxylato stannoxanes

The mechanism of the fluxional process occurring in dimeric tetraorganodicarboxylato stannoxanes is presented on the basis of multinuclear NMR studies carried out in noncoordinating solvents. This fluxional process is a consequence of rapid migration of carboxylate groups from one tin atom to the other. It has been proposed that larger carboxylates will also execute this behavior. The effect of cis and trans positions on the fluxional process is discussed. The fluxional process is very fast and could not be stopped even at low temperatures, as measured on the NMR time scale. © 1996 John Wiley & Sons, Inc.