Polyesters with Aromatic Groups in the Backbone from Reactions of 3- and 4-Bromomethylbenzoic Acids with Triethylamine

Abstract

Aromatic polyesters were obtained in relatively good yields (～ 70%) from reactions of 3- and 4-bromomethylbenzoic acids with tri-ethylamine in chlorobenzene. A copolymer was prepared in 58% yield by reaction of a 1:1 mixture of the two acids under similar conditions. The polyesters were characterized by IR, ¹H- and ¹³3C-NMR spectra, x-ray powder diffraction, DSC behavior, solution viscosity, and hydrolysis to the corresponding hydroxymethylbenzoic acids. Molecular weights were determined by ¹H-NMR endgroup analysis. Possible mechanisms for the reactions are discussed.     

Synthesis of Phosphonopeptide Derivatives

In 1959, Horiguchi and Kandatsu¹ first isolated 2-aminomethylphos-phonic acid from ciliate protozoa. Since then the compound has been found in numerous other organisms² and recently it has been found in human brain³, liver, heart and skeletal muscles⁴, and in red blood cell membrane. These findings establish the biological importance of the carbon-phosphorus bond in nature. Quin² suggested that the naturally occurring aminophosphonic acids are bound to proteins and peptides.     

Wavelet method to film-pore diffusion model for methylene blue adsorption onto plant leaf powders

In this paper, we have developed an accurate and efficient Haar wavelet method to solve film-pore diffusion model. Film-pore diffusion model is widely used to determine study the kinetics of adsorption systems. To the best of our knowledge, until now rigorous wavelet solution has been not reported for solving film-pore diffusion model. The use of Haar wavelets is found to be accurate, simple, fast, flexible, convenient, and computationally attractive. The power of the manageable method is confirmed. It is shown that film-pore diffusion model satisfactorily describes the kinetics of methylene blue adsorption onto three low-cost adsorbents, Gauva, teak and gulmohar plant leaf powders, used in this study.     

Off-on Fluorescent Sensor from On-off Sensor: Exploiting Silver Nanoparticles Influence on the Organic Fluorophore Fluorescence

Turn-off fluorescence of organic fluorophore, 2-{[4-(2H-Naphtho[1,2-d][1,2,3]triazol-2-yl)-phenyl]carboxylic acid (NTPC), with metal ions (Fe³⁺, Cu²⁺, Pb²⁺) was converted into turn-on fluorescent sensor for biologically important Zn²⁺, Cu²⁺ and Fe³⁺ metal ions in aqueous solution at ppb level by exploiting strong fluorescence quenching phenomena of metal nanoparticles when organic fluorophores assembled in the vicinity of metallic surface. Amino acid attached phenolic ligands (L) were used as reducing as well as functional capping agents in the synthesis of silver nanoparticles (AgNPs). The hydrogen bonding functionality of L facilitated the assembling of NTPC in the vicinity of metallic surfaces that leads to complete quenching of NTPC fluorescence. The strong and selective coordination of L with metal ions (Zn²⁺, Cu²⁺ and Fe³⁺) separates the NTPC from the AgNPs surface that turn-on the NTPC fluorescence. HR-TEM and absorption studies confirm the metal coordination with L and separation of NTPC from the AgNPs surface. Mn²⁺ showed selective red shifting of NTPC fluorescence after 12 h with all sample. Effects of different amino acid attached phenolic ligands were explored in the metal ion sensitivity and selectivity. This approach demonstrates the multifunctional utility of metal NPs in the development of turn-on fluorescence sensor for paramagnetic heavy metal ions in aqueous solution.

Geometric complexity theory III: on deciding nonvanishing of a Littlewood–Richardson coefficient

We point out that the positivity of a Littlewood?CRichardson coefficient $c^{\gamma}_{\alpha, \beta}$ for sl _n can be decided in strongly polynomial time. This means that the number of arithmetic operations is polynomial in n and independent of the bit lengths of the specifications of the partitions ??,??, and ??, and each operation involves numbers whose bitlength is polynomial in n and the bit lengths ??,??, and ??. Secondly, we observe that nonvanishing of a generalized Littlewood?CRichardson coefficient of any type can be decided in strongly polynomial time assuming an analogue of the saturation conjecture for these types, and that for weights ??,??,??, the positivity of $c^{ 2\gamma}_{2\alpha, 2\beta}$ can (unconditionally) be decided in strongly polynomial time.     

Influence of stack geometry and resonator length on the performance of thermoacoustic engine

Thermoacoustic engines convert heat energy into high amplitude sound waves, which is used to drive thermoacoustic refrigerator or pulse tube cryocoolers by replacing the mechanical pistons such as compressors. The increasing interest in thermoacoustic technology is of its potentiality of no exotic materials, low cost and high reliability compared to vapor compression refrigeration systems. The experimental setup has been built based on the linear thermoacoustic model and some simple design parameters. The engines produce acoustic energy at the temperature difference of 325–450 K imposed along the stack of the system. This work illustrates the influence of stack parameters such as plate thickness (PT) and plate spacing (PS) with resonator length on the performance of thermoacoustic engine, which are measured in terms of onset temperature difference, resonance frequency and pressure amplitude using air as a working fluid. The results obtained from the experiments are in good agreement with the theoretical results from DeltaEc.     

Modified pinhole spatial filter producing a clean flat-topped beam

The expanded beam from a laser has a sharply peaked intensity profile. As a result, in many applications where uniform illumination of an extended field is required, it is only possible to use the central part of the beam. We show that if the pinhole normally used to spatially filter the beam is replaced by an annular phase mask, it should be possible to obtain a clean beam providing very nearly uniform illumination over an extended area, with a minimal loss of light.     

Thermal and FTIR spectral studies of various proportions of zinc magnesium ammonium sulfate

Mixed crystals of various proportions of zinc magnesium ammonium sulfate were grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized through thermal (TG–DTA) and FTIR spectral analyses. A fitting decomposition pattern for the compound was formulated on the TG curve which shows two stage mass losses between 133 and 478.75 °C. DTA curve shows exothermic peaks in this temperature range supporting the formulated decomposition pattern. The FTIR spectra show the vibration frequencies due to the formation of zinc magnesium ammonium sulfate mixed crystals. Detailed structural analysis of the compound is under progress.     

The wavelet methods to linear and nonlinear reaction–diffusion model arising in mathematical chemistry

In this paper, we have applied an accurate and efficient wavelet scheme (due to Legendre polynomial) to find the numerical solutions for a set of coupled reaction–diffusion equations. This technique provides the solutions in rapid convergence series with computable terms for the problems with high degree of non linear terms appearing in the governing differential equations. The highest derivative in the differential equation is expanded into wavelet series, this approximation is then integrated while the boundary conditions are applied by using integration constants. With the help of operational matrices, the nonlinear reaction–diffusion equations are converted into a system of algebraic equations. Finally, some numerical examples to demonstrate the validity and applicability of the method have been furnished. The use of Legendre wavelets is found to be accurate, efficient, simple, and computationally attractive. This wavelet method can be used for obtaining quick solution in many chemical Engineering problems.