Synthesis and spectroscopic studies of new Schiff bases

Five novel Schiff bases have been prepared from o-formylphenoxyacetic acid and a series of aminothiazoles to form a number of potentially biologically active compounds. The structures of these Schiff bases have been characterized using IR and (1)H-and (13)C-NMR spectroscopy.     

A simple linear cavity dual-wavelength fiber laser using AWG as wavelength selective mechanism

In this paper, a simple design of linear cavity dual-wavelength fiber laser (DWFL) is proposed. Operating in the C-band region stretching from 1538.3 nm to 1548.6 nm, an arrayed waveguide grating (AWG) is used to generate the dual-wavelengths output together with a broadband fiber Bragg grating as a back reflector and an optical circulator with a 10% output coupling ratio which acts as a front mirror. The measured average output power of the DWFL is about −5.66 dBm and with a side mode suppression ratio (SMSR) of 53.1 dB. The spacing between the two output wavelengths can be varied from 0.8 nm to 10.3 nm with a stable output and minimum power fluctuations.     

Cycloaddition Reaction of 1,4‐Dihydronaphthalene 1,4‐Epoxide with Cyclooctatetraene: Cope Rearrangement in an Adduct

The reaction of 1,4‐dihydro‐1,4‐epoxynaphthalene with cyclooctatetraene at 130±5° for 14 days gave the four products 2a,3,3a,4,9,9a,10,10a‐octahydro‐4,9‐epoxy‐3,10‐ethenocyclobuta[b]anthracene ( 13 ), 25‐oxanonacyclo[10.10.2.2^5,9.1^14,21.0^2,11.0^3,10.0^4,6.0^13,22.0^15,20]heptacosa‐7,15,17,19,23,26‐hexaene ( 14 ), 5,5a,6,6a,6b,6c,12a,12b,12c,13,13a,14‐dodecahydro‐5,14‐epoxy‐6,13‐ethenocycloocta[3′,4′]cyclobuta[1′,2′:3,4]cyclobuta[1,2‐b]anthracene ( 15 ) and bis‐adduct 16 . The structures of the products were determined by spectroscopic methods. It was observed that adduct 14 undergoes a Cope rearrangement. The Cope rearrangement of this adduct was investigated in the temperature range of ?85° to 100° by NMR spectroscopy.     

Functional Mutations in and Characterization of VHH Against Helicobacter pylori Urease

Manipulation of clinically significant antibodies can effectively improve the processes of diagnosis and treatment. Affinity maturation process has a significant role in improvement of antibodies efficiency. Error-prone PCR technique is one of the proposed methods for improvement of the affinity of antibodies. In the present research, a method was applied to camel heavy-chain antibody (VHH, nanobody) raised against UreC subunit of urease enzyme from Helicobacter pylori. This VHH was used as a starting molecule to construct a highly diversified phage displayed VHH library. The constructed library of nanobody mutants was subjected to several rounds of panning against UreC antigen. High-affinity mutant was selected. Our VHH (HMR23) showed 1.5-fold higher binding activity than the parental VHH. In addition, the mutant VHH presented a better performance in inhibition of urease activity at low concentrations retaining its specificity and thermal stability.     

Effect of Heat Exposure on Activity Degradation of Enzymes in Mango Varieties Sindri,SB Chaunsa,and Tommy Atkins during Drying

Mango has been described as a valuable source of nutrients and enzymes that are beneficial to human health. Drying at different temperatures not only affects the nutritional properties but can also contribute to the degradation of valuable enzymes in dried fruit. The novelty of this paper is to investigate the quality of hot air dried mango in terms of activity retention of the heat-sensitive enzymes (HSE). For this, HSE was first screened in fresh mango flesh of the variety Samar Bahisht (SB) Chaunsa. Later, the combined effect of different drying temperatures (40 °C, 50 °C, 60 °C, 70 °C, and 80 °C) and air velocities (1.0 ms⁻¹ and 1.4 ms⁻¹) on the activity retention of HSE in dried mango slices of the varieties Sindri, SB Chaunsa, and Tommy Atkins were investigated. The results showed that the drying temperature had a significant impact on the degradation of HSE, while at the same time some influence of the air velocity was also observed. Drying at 40 °C and an air velocity of 1.4 ms⁻¹ retained more HSE compared to those samples dried at higher temperatures. The least retention of HSE was found in samples dried at 80 °C.     

Facile One Pot Microwave Assisted Solvent‐Free Synthesis of Novel Spiro‐Fused Pyran Derivatives via the Three‐Component Condensation of Ninhydrin with Malononitrile and Active Methylene Compounds

Three‐component condensation of ninhydrin, malononitrile, and some nucleophilic reagents in the presence of piperidine under microwave irradiation without solvent afforded the corresponding spiro‐fused pyran derivatives. The structures of the products were proved by elemental analyses, IR, ¹H NMR and MS spectroscopy.     

Two new electronic transitions of Bi2

The absorption spectra of Bi₂ molecule has been obtained in the region 3166–3380 Å in the second order of a 3.4 m Ebert Spectrograph with a reciprocal dispersion of 2.6 Å/mm. The bands obtained are found to belong to two new systems named G-X and J-X. Vibrational analysis is performed and computer methods have been used to determine the molecular constants.     

Facile one‐pot syntheses of new polyfunctional pyrazolyl substituted and pyrazolofused pyridines

Ethyl 2‐cyano‐3‐(5‐chloro‐1,3‐diphenylpyrazol‐4‐yl)acrylate ( 1 ) undergoes both conjugate addition of a number of methylene‐active ethanenitriles and direct addition of other active methylene donors to the cyano carbon atom. These additions are the starting events of cascades of subsequent reactions eventually forming (i) novel polyfunctional pyrazolyl‐substituted monocyclic pyridines ( 4a , b and 6 ), (ii) 1,3‐benzothiazole and benzimidazole‐fused pyridines ( 11, 13 ) and (iii) pyrazolo[5,4‐b]pyridines ( 19b, 20 ) in one‐pot reactions in ethanolic solution containing catalytic amounts of piperidine.     

Effect of annealing on the structure and morphology of nylon 6 fibers

Changes in the structure of nylon 6 fibers annealed in dry and wet atmospheres were studied by small-and wide-angle x-ray diffraction. In the presence of water or saturated steam, fibers can be annealed to the same strucutral state at temperatures 70°C lower than in dry atmosphere. This is due to the enhanced mobility of the molecular segments in the amorphous region, a mechanism which is also known to lower the T_g by the same amount. Upon annealing under unconstrained conditions, lamellar spacing, crystallite size in the equatorial plane, crystalline as well as fiber density, and the chain-axis repeat increase with annealing-temperature; whereas crystalline orientation and the Van der Waals separation of the hydrogen-bonded sheets decrease. The monoclinic angle 8 remains constant at 66.7° (σ = 0.3°) and might depend on the starting fiber rather than on the treatment of the fiber. Most of these changes occur above a critical temperature of 170°C if dry, or 100°C if wet; rate of crystallization is also the highest under these conditions in nylon. The effect of these changes on such fiber properties as dyeing and the role of micro voids in dye diffusion and in dye uptake are discussed. Surface premelting and the accompanying changes in the surface structure of the lamellae, selective melting, and more importantly, the longitudinal motion of the nylon 6 chains and the resulting folding of interfibrillar extended amorphous chains are invoked to explain the shrinkage of the fiber, disorientation of the crystallites, increase in crystalline perfection, and the increase in lamellar spacing.     

Minimization of the auxiliary reagent loading for direct arylation polymerization (DArP) of 2‐bromo‐3‐hexylthiophene

In this work, we present a powerful set of synthetic strategies aimed at minimization of auxiliary reagent loading for direct arylation polymerization (DArP) of 2‐bromo‐3‐hexylthiophene. As such, we report efficient lowering of Pd(OAc)₂ catalyst loading as well as loading of other auxiliary reagents, such as neodecanoic acid and N,N‐dimethylacetamide. Unprecedented low loadings of catalyst down to 0.0313% (313 ppm) were achieved, while producing polymer in high yield (91% after Soxhlet extraction), with a high molecular weight (24.2 kDa) and carefully controlled chemical structure thus making the optimized DArP protocol significantly more cost‐effective, convenient, sustainable, and environmentally friendly. The resulting polymer samples were thoroughly investigated in terms of their chemical structure as well as optical, thermal, chain ordering and electronic properties using GPC analysis, ¹H NMR, MALDI, UV–vis, GIXRD spectroscopy, DSC, and SCLC hole mobility measurements. The results demonstrate that the reagent lowering strategies increase the polymer regioregularity from 94.6 to 96.5% as evidenced by ¹H NMR spectra and corroborated by GIXRD, DSC, and UV–vis measurements. Additionally, polymer samples obtained at low reagent loading are more uniformly proton‐terminated as evidenced by ¹H NMR and MALDI end‐group analysis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1492–1499