Potassium Bromate-Thiourea Redox Initiated Grafting of Methyl Methacrylate onto Polyethylene Terephthalate

Some kinetic features of the grafting of methyl methacrylate onto polyethylene terephthalate initiated by the potassium bromate-thiourea redox system have been investigated in aqueous solution. The effects of potassium bromate, thiourea, monomer, acid, and temperature upon percentage grafting have been determined. The activation energy of the reaction has been computed from an Arrhenius plot. Grafting experiments have been carried out in the presence of such conventional chain-transfer agents as CC1₄ and CHC1₃. The effect of CuSO₄ upon grafting is also studied. The reaction mechanism involved during grafting is pictured.     

Electrodeposition of manganese dioxide: effect of quaternary amines

The effect of quaternary ammonium salts (tetraethyl ammonium bromide, tetrapropyl ammonium bromide, and tetrabutyl ammonium bromide) on the structural, morphological, and electrochemical characteristics of electrolytic manganese dioxide (EMD) obtained from acidic aqueous sulfate solution has been investigated. Physical characterization of the EMD was achieved by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential thermal analysis, and Fourier transform infrared spectroscopy. The charge–discharge profile of the materials was determined to evaluate their potential for alkaline battery applications. The presence of these quaternary ammonium salts as organic additives in the solution increased the current efficiency while decreasing energy consumption during electrochemical deposition of manganese dioxide (MnO₂). All the additives influenced the discharge characteristics of the EMD samples significantly, producing a cathode material with increased cumulative discharge capacity relative to EMD prepared in the absence of additives. This is attributed to the ability of the additives to affect the particle size and morphology, and therefore electrochemical activity, of electrodeposited materials; the effects in the case of the additives investigated in this work were positive, producing a material with potential application to battery technology.     

Measurement of glycerol concentration in B–H–G solution using 3D photonic crystal structure

A novel technique is used to measure the concentration of glycerol in blood-hemoglobin-glycerol (B–H–G) solution using 3D photonic crystal structure is presented in this paper. Glycerol concentration is estimated accurately by measuring the intensities of transmitted light. Here, reflection as well as absorption losses is considered to measure the transmitted intensity of light having wavelength 540 nm. The principle of measurement is based on the linear variation of photonic band gap with respect to glycerol concentration. Simulations for photonic band gap are made using plane wave expansion (PWE) method. An experimental set up is theoretically designed to measure the concentration of glycerol at different hemoglobin concentration.     

Analysis of nonlinear PCF for birefringence application using FDTD method

The effect of ellipticity on birefringence in a hexagonal photonic crystal fiber having elliptical air holes with Kerr nonlinearity is investigated, with and without defect using finite difference time domain (FDTD) simulations. It is found that the birefringence increases with the increase of ellipticity. Further this analysis is extended to a double defect structure, where two adjacent air holes are omitted horizontally from the hexagonal structure. This double defect structure is found to have more birefringence than the structure without defect. It is raveled that birefringence due to no defect is more for lower value of ellipticity; however at higher value of ellipticity, birefringence due to double defect is more than the one that could be due to no defect.     

Mixed Type Duality in Multiobjective Fractional Programming Under Generalized ρ-univex Function

In this paper, three approaches given by Dinklebaeh (Manag Sci 13(7):492–498, 1967) and Jagannathan (Z Oper Res 17:618–630, 1968) for both primal and mixed type dual of a non differentiable multiobjective fractional programming problem in which the numerator of objective function contains square root of positive semi definite quadratic form are introduced. Also, the necessary and sufficient conditions of efficient solution for fractional programming are established and a parameterizations technique is used to established duality results under generalized ρ-univexity assumption.     

Efforts towards the synthesis of microsporin B: ready access to both the enantiomers of the key amino acid fragment

Both the isomers methyl-(2S,8R)-2-((tert-butoxycarbonyl)amino)-8-hydroxydecanoate and methyl-(2S,8S)-2-((tert-butoxycarbonyl)amino)-8-hydroxydecanoate of an unusual amino acid residue and the key fragment of microsporin B are prepared. The key steps include cross metathesis and enzymatic kinetic resolution. In addition, a linear tetrapeptide with desired components towards total synthesis is also reported.     

Photophysics of Soret-excited tetrapyrroles in solution. I. Metalloporphyrins: MgTPP, ZnTPP, and CdTPP

The photophysical behavior of three Soret-excited diamagnetic meso-substituted tetraphenylmetalloporphyrins, MgTPP, ZnTPP, and CdTPP, have been examined in a wide variety of solvents using both steady-state and femtosecond fluorescence upconversion methods. The S 2 population of MgTPP decays to S 1 on the time scale of a few picoseconds with unit S 2-S 1 internal conversion efficiency, and the decay rates conform to the weak coupling case of radiationless transition theory. The energy gap law parameters characterizing the coupling of the S 2 and S 1 states of MgTPP have been obtained. The most important accepting vibrational modes in the S 1 state are multiple in-plane C-C and C-N stretches in the 1200-1500 cm (-1) range. Net S 2-S 1 decay is the dominant decay path for ZnTPP and CdTPP as well, but the process occurs at rates that exceed (in the case of CdTPP, they vastly exceed) those predicted by weak interstate coupling. Alternate mechanisms for the radiationless decay of the S 2 states of ZnTPP and CdTPP have been explored. Large spin-orbit coupling constants and the presence of multiple, near-equiergic triplet states suggest that S 2-T n intersystem crossing might occur at rates competitive with internal conversion. However, the measured efficiencies of S 2-S 1 internal conversion show that, at most, only a few percent of the S 2 population of ZnTPP and no more than about 30% of the S 2 population of CdTPP can decay by a "dark" path such as intersystem crossing.     

Photophysics of soret-excited tetrapyrroles in solution. II. Effects of perdeuteration, substituent nature and position, and macrocycle structure and conformation in zinc(II) porphyrins

The steady-state absorption, fluorescence, and excitation spectra and upper excited-state temporal fluorescence decay profiles of 11 tetrapyrroles in several fluid solvents are presented and analyzed to ascertain the factors that control their S2 population decay times. The S2 lifetimes, which vary by more than 2 orders of magnitude, are controlled exclusively by their rates of radiationless decay. The only important electronic relaxation path is S2-S1 internal conversion, the efficiency of which is near 1.0 in all compounds studied (except CdTPP where it is 0.69). The rate of S1 population rise equals the rate of S2 population decay in all cases. Among the compounds studied, only MgTPP exhibits S2-S1 decay behavior that corresponds to the weak coupling limit of radiationless transition theory; all zinc metalloporphyrins exhibit intermediate to strong coupling. Perdeuteration of ZnTPP produces no significant change in the rate of S2 decay or in the quantum yield of S2-S0 fluorescence, indicating that in-plane C-C and C-N vibrations are the accepting modes in S1 with the largest Franck-Condon factors. The initial vibrational energy content of the S2 states (0 < E(vib) < 3500 cm(-1) over the range of compounds) plays no significant role in determining their overall population decay rates in solution. The S2 population decay rates of these tetrapyrroles are controlled by two factors: the Franck-Condon factor, which is inversely proportional to the exponent of the S2-S1 electronic energy spacing and the S2-S1 coupling energy. The S2-S1 electronic energy spacing is determined in solution by the difference in the polarizabilities of the S2 and S1 states and can be controlled by varying the polarizability of the solvent. The S2-S1 coupling energy is influenced by the nature, location, and effect of the substituents, with beta-alkyl substitution and reduction of symmetry in the tetrapyrrole--for example by loss of planarity--increasing the interstate coupling energy.     

Critical Review on Metal-Based Cosmetic Products

Most people utilize cosmetics to enhance or improve their physical appearance, regardless of their gender, race, or age. Heavy metals (HMs) are impurities or ingredients in many cosmetic products. According to recent studies, these metals can result in a variety of skin and health issues. Numerous studies demonstrate that the mismanaged formulation of such products without sufficient standardization of toxic metals throughout the production process is the primary reason for the high level of HM contamination in the samples. In order to prevent human exposure to such dangerous HMs, it is vital to monitor and manage the fate of HMs in cosmetic items, especially unbranded ones. Due to the wasteful interest of producers in making extra profit, the standards are not being imposed. Moreover, consumers are also ready to compromise with the product due to their unawareness of its hazardous impact on their skin and bodies. Short-term results on their looks may cause fatal effects on their health. Another significant issue that requires attention is the lack of safety regulations in the country for evaluating HMs in cosmetic products. Additionally, there is an urgent need to establish acceptable limits for potential impurities in cosmetic products that must be enforced at local levels. This review provides a comprehensive insight into the content of HMs in cosmetics and their effects on several organs and the site of application.     

How Much Can We Coarse‐Grain while Retaining the Chemical Specificity? A Study of Sulfonated Poly(ether ether ketone)

For mesoscale structural studies of polymers, obtaining maximum level of coarse‐graining that maintains the chemical specificity is highly desirable. Here we present a systematic coarse‐graining study of sulfonated poly(ether ether ketone), sPEEK, and show that a 71:3 coarse‐grained (CG) mapping is the maximum possible map within a CG bead‐spring model. We perform single chain atomistic simulation on the system to collect various structural distributions, against which the CG potentials are optimized using iterative Boltzmann inversion technique. The potentials thus extracted are shown to reproduce the target distributions for larger single chains as well as for multiple chains. The structure at the atomistic level is shown to be preserved when we back‐map the CG system to re‐introduce the atomistic details. By using the same CG mapping for another repeat unit sequence of sPEEK, we show that the nature of the effective interaction at the CG level depends strongly on the polymer sequence and cannot be assumed based on the nature of the corresponding atomistic unit. These CG potentials will be the key to future mesoscopic simulations to study the structure of sPEEK based polymer electrolyte membranes.