Synthesis of thio- and furan-fused heterocycles: furopyranone,furopyrrolone, and thienopyrrolone derivatives

We report herein the synthesis of a novel class of compounds, ethyl 4-oxo-4H-furo[3,2-c]pyran-6-yl carbonate, (7E)-7-[(dimethylamino)methylene]-4H-furo[3,2-c]pyran-4,6(7H)-dione, 5-oxo-N-phenyl-2,5-dihydro-4H-furo[3,2-b]pyrrole-4-carboxamide, and 5-oxo-N-phenyl-5,6-dihydro-4H-thieno[3,2-b]pyrrole-4-carboxamide starting from the corresponding acid derivatives. Intramolecular cyclization in the presence of thionyl chloride formed the target fused ring systems. Additional transformation was seen in the cyclization of furan-fused heterocycle. A mechanism was proposed based on experimental and computational findings.     

Synthesis and characterization of sulfone containing main chain oligobenzoxazine precursors

The preparation of soluble and processable polybenzoxazine precursors capable of forming high performance networks is an important field of research with a broad spectrum of application. This study demonstrates an approach that utilizes aromatic sulfonediamine, bisphenol‐A, and formaldehyde in Mannich‐type polycondesation to prepare polybenzoxazine precursor. The structure of the oligomeric precursor (M_n = 2600) was confirmed by FTIR and ¹H NMR spectral analysis. The precursor contained both sulfone and benzoxazine ring structures in the backbone. It was shown that small amount of ring‐opened phenolic groups were also present. Thermally activated self‐curing behavior of precursor in the absence of catalyst was studied by differential scanning calorimetry. Thermal properties of the cured polymers were also investigated by thermo gravimetric analysis. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Finite element and boundary element contact stress analysis with remeshing technique

The fundamental part of the contact stress problem solution using a finite element method is to locate possible contact areas reliably and efficiently. In this research, a remeshing technique is introduced to determine the contact region in a given accuracy. In the proposed iterative method, the meshes near the contact surface are modified so that the edge of the contact region is also an element’s edge. This approach overcomes the problem of surface representation at the transition point from contact to non-contact region. The remeshing technique is efficiently employed to adapt the mesh for more precise representation of the contact region. The method is applied to both finite element and boundary element methods. Overlapping of the meshes in the contact region is prevented by the inclusion of displacement and force constraints using the Lagrange multipliers technique. Since the method modifies the mesh only on the contacting and neighbouring region, the solution to the matrix system is very close to the previous one in each iteration. Both direct and iterative solver performances on BEM and FEM analyses are also investigated for the proposed incremental technique. The biconjugate gradient method and LU with Cholesky decomposition are used for solving the equation systems. Two numerical examples whose analytical solutions exist are used to illustrate the advantages of the proposed method. They show a significant improvement in accuracy compared to the solutions with fixed meshes.     

Design and Synthesis of Aviram–Ratner‐Type Dyads and Rectification Studies in Langmuir–Blodgett (LB) Films

The design and synthesis of Aviram–Ratner‐type molecular rectifiers, featuring an anilino‐substituted extended tetracyanoquinodimethane (exTCNQ) acceptor, covalently linked by the σ‐spacer bicyclo[2.2.2]octane (BCO) to a tetrathiafulvalene (TTF) donor moiety, are described. The rigid BCO spacer keeps the TTF donor and exTCNQ acceptor moieties apart, as demonstrated by X‐ray analysis. The photophysical properties of the TTF‐BCO‐exTCNQ dyads were investigated by UV/Vis and EPR spectroscopy, electrochemical studies, and theoretical calculations. Langmuir–Blodgett films were prepared and used in the fabrication and electrical studies of junction devices. One dyad showed the asymmetric current–voltage (I–V) curve characteristic for rectification, unlike control compounds containing the TTF unit but not the exTCNQ moiety or comprising the exTCNQ acceptor moiety but lacking the donor TTF part, which both gave symmetric I–V curves. The direction of the observed rectification indicated that the preferred electron current flows from the exTCNQ acceptor to the TTF donor.     

Chloroacetonylation of CC double bonds promoted by manganese(III) acetate

The addition of acetylacetone to alkenes was performed using Mn(OAc)₃·2H₂O in the presence of HCl. The intermediate formed was trapped by chloride. Removal of one of the acetyl groups with ammonia under very mild conditions provided compounds derived from chloroacetonylation of the double bonds.     

Development of measurement system for adsorption of long-lived radon decay products on the leaf surface of tobacco plants

Our previous studies indicated the suitability of tobacco plants for biomonitoring remediated depositories, due to their ²¹⁰Po and ²¹⁰Pb accumulation ability. The methods and requirements of testing ²¹⁰Pb uptake by leaf-surface adsorption was investigated and implemented in the construction of a controlled environment. Uranium ore (theoretical Rn concentration 638 Bqm^?3) was the main source of radon and progeny. Rn concentrations were measured by RAD7, AlphaGUARD, EQF 3220, RTM 2100 and CR-39 SSNTDs (411–516 Bqm^?3). Activity concentrations of the attached and unattached fractions were determined by EQF 3220. The results are indicative of good measurement setup for tracking ²¹⁰Po(Pb) uptake pathways.     

DNA molecule manipulation by motor proteins for analysis at the single-molecule level

Massively parallel and individual DNA manipulation for analysis has been demonstrated by designing a fully self-assembled molecular system using motor proteins. DNA molecules were immobilized by trapping in a polyacrylamide gel replica, and were digested by a restriction enzyme, XhoI, for DNA analysis. One end of the λDNA was modified with biotin and the other end was modified with digoxin molecules by fragment labeling and ligation methods. The digoxin-functionalized end was immobilized on a glass surface coated with anti-digoxigenin antibody. The biotinylated end was freely suspended and experienced Brownian motion in a buffer solution. The free end was attached to a biotinylated microtubule via avidin–biotin biding and the DNA was stretched by a kinesin-based gliding assay. A stretched DNA molecule was fixed between the gel and coverslip to observe the cleavage of the DNA by the enzyme, which was supplied through the gel network structure. This simple process flow from DNA manipulation to analysis offers a new method of performing molecular surgery at the single-molecule scale. Figure DNA molecule manipulation by motor proteins for analysis at the single-molecule level     

Evaluation of high hydrostatic pressure effects on bovine red blood cells and platelets

The objective of this study was to investigate the effects of high hydrostatic pressure (HHP) on the stability of red blood cells (RBCs) and platelets. Bovine blood cells (n=5) were treated with the pressure of 55, 110, 154 and 220 MPa at 25 °C for 5 min. Light microscopy, atomic force microscopy and flow cytometry studies revealed that RBCs were morphologically stable up until the 220 MPa pressure treatments, at which surface modifications were observed. The platelets were found to be less stable than RBCs. HHP application did not cause any significant change in the signal intensity, band area and frequency values of the infrared bands with the exception that a significant variation was observed in the area of the cholesterol band. No statistically significant variations were observed in the secondary structure elements due to HHP treatment according to the artificial neural network study based on the FTIR data.     

Synthesis of new bio‐based hydrogels derived from bile acids by free‐radical photo‐polymerization

In this article, the study on the swelling and thermal behaviors of a new series of bile acid‐based polymeric hydrogels is reported. For this purpose, in the first step, the reduction of carboxyl acid groups of some common bile acids including cholic acid (CA), chenodeoxy cholic acid (CDCA), and lithocholic acid (LCA) to the corresponding alcohols by lithium aluminum hydride (LiAlH₄) in THF solution is performed. Then, hydroxyl functionalities of the obtained products are reacted with the acryloyl chloride in the presence of triethylamine (TEA). Finally, the cross‐linking reactions between acryloyl functionalized bile acids and methoxy poly(ethylene glycol) monomethacrylate (MPEGMA) are conducted by free‐radical photo‐polymerization technique at λ = 350 nm in the presence of 2,2‐Dimethoxy‐2‐phenylacetophenone (DMPA) as an initiator to achieve the desired bile acid‐based polymeric hydrogels. The resulting hydrogels and their intermediates are characterized by Fourier transform infrared (FT‐IR) and Proton nuclear magnetic resonance (¹H‐NMR) spectroscopies. The swelling and thermal behavior of the obtained hydrogels indicates that the hydrogel starting from cholic acid is more swellable and has enhanced thermostability compared to others. Thus, the results of this study offer beneficial insights to researchers working in particularly bio‐medical industry.