Some aspects of elliptic variational inequalities

In this paper we study an existence and the approximation of the solution of the elliptic variational inequality from an abstract axiomatic point of view. We discuss convergence results and give an error estimate for the difference of the two solutions in an appropriate norm. Also, we present some computational results by using fixed point method.     

Lifetimes and magnetic moments of two states in62Cu

The lifetimes and the magnetic moments of the two excited⁶²Cu states at 40.84 and 390.19 keV are investigated by time differential perturbed angular distribution measurements of the delayedγ-rays following the nuclear reactions⁶¹Ni(d, n) and⁶²Ni(p, n). The results are:τ=6.7±0.5 nsec,μ=1.32±0.03 n. m. for the 2⁺ state at 40.84 keV, andτ=16.0±0.3 nsec,μ=2.00±0.01 n. m. for the 3⁺ state at 390.19 keV.     

Some aromatic polyimides based on diamines containing hydrazo group and ether linkages

Three new hydrazo-bridged diamines, 4,4′-bis [4-(4-aminophenyloxy) phenylhydrazyl] biphenyl (BPD-2), 4,4′-bis [4-(4-aminophenyloxy) phenylhydrazyl] biphenyl ether (SPD-2) and 4,4-bis [4-(4-aminophenyloxy) phenyl] hydrazine (APD-2), were synthesized by the reduction of three azo-diols, 4,4′-bis (4-azo-1-hydroxyphenyl) biphenyl (BPD), 4,4′-bis (4-azo-1-hydroxyphenyl) biphenyl ether (SPD) and azo-4-hydroxybenzene (APD), and polymerized with pyromellitic dianhydride (PM), 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BP) and 3,4,9,10-perylenetetracarboxylic acid dianhydride (PR) either by one-step solution polymerization or by two-step procedure which includes ring-opening polyaddition to give poly(amic acid) followed by cyclic dehydration to polyimide. The monomers and polyimides were characterized by their elemental analyses, FTIR and ¹H NMR spectroscopy. Glass transition temperatures of the polymers are quite high (175-310 °C), characteristic of polyimides. The decomposition temperatures for 10% weight loss fall in the range of 280-575 °C in nitrogen. Activation energies of pyrolysis for each of the polymers calculated from Horowitz and Metzger's method are also high (52.54-95.28 kJ mol⁻¹). The inherent viscosities of the polyimides at a concentration of 0.5 g/dl in DMF range from 0.94 to 1.93 dl/g.     

Self-assembly, molecular dynamics, and kinetics of structure formation in dipole-functionalized discotic liquid crystals

The self-assembly, the molecular dynamics, and the kinetics of structure formation are studied in dipole-functionalized hexabenzocoronene (HBC) derivatives. Dipole substitution destabilizes the columnar crystalline phase except for the dimethoxy- and monoethynyl-substituted HBCs that undergo a reversible transformation to the crystalline phase. The disk dynamics are studied by dielectric spectroscopy and site-specific NMR techniques that provide both the time-scale and geometry of motion. Application of pressure results in the thermodynamic phase diagram that shows increasing stability of the crystalline phase at elevated pressures. Long-lived metastability was found during the transformation between the two phases. These results suggest new thermodynamic and kinetic pathways that favor the phase with the highest charge carrier mobility.     

Adsorption of monoclonal antibody variants on analytical cation-exchange resin

Monoclonal antibody (MAb) variants differing by one or two C-terminal lysine residues can be separated by cation-exchange chromatography due to the difference in their charge distribution. The adsorption of the three MAb variants on a weak cation-exchange resin was characterized using directly the raw mixture in spite of the presence of some impurities. The effects of both, pH and eluent salt concentration, on the adsorption isotherm were investigated. Under certain experimental conditions distorted peak shapes and even peak doubling for single variant injections were obtained, in addition to unexpectedly long retention times. These observations were explained based on equilibrium theory. The separation of the MAb variants was designed for an isocratic and a linear salt gradient operation. The corresponding optimal values of pH and salt concentration were determined. The use of salt gradients not only allows reducing the process time and increasing enrichment of the variants, but also leads to some loss in purity. A baseline separation could be obtained under isocratic and strongly adsorbing conditions at pH 6.3. A lumped kinetic model and a procedure for estimating the corresponding parameters were developed and validated by comparison with experimental elution chromatograms in a wide range of operating conditions.     

Preparation and characterization of wool fiber reinforced nonwoven alginate hydrogel for wound dressing

Wound healing is a complex process which requires an appropriate environment for quick healing. Recently, biodegradable hydrogel-based wound dressings have been seen to have high potential owing to their biodegradability and hydrated molecular structure. In this work, a novel biodegradable composite of sodium alginate hydrogel with wool needle-punched nonwoven fabric was produced for wound dressing by sol–gel technique. The wool nonwoven was dipped in the sodium alginate-water solution and then soaked in calcium chloride solution which resulted in hydrogel formation. FTIR analysis and SEM images confirm the presence of alginate hydrogel inside the needle-punched wool nonwoven fabric. The wound exudate absorbing capacity of hydrogel based wool nonwoven was increased 30 times as compared to pure wool nonwoven. Moreover, the tensile strength and moisture management properties of hydrogel based nonwoven were also enhanced. The unique combination of alginate hydrogel with biocompatible wool nonwoven fabric provides moist environment and can help in cell proliferation during wound healing process.

     

Upconverting‐Nanoparticle‐Assisted Photochemistry Induced by Low‐Intensity Near‐Infrared Light: How Low Can We Go?

Upconverting nanoparticles (UCNPs) convert near‐infrared (NIR) light into UV or visible light that can trigger photoreactions of photosensitive compounds. In this paper, we demonstrate how to reduce the intensity of NIR light for UCNP‐assisted photochemistry. We synthesized two types of UCNPs with different emission bands and five photosensitive compounds with different absorption bands. A λ=974 nm laser was used to induce photoreactions in all of the investigated photosensitive compounds in the presence of the UCNPs. The excitation thresholds of the photoreactions induced by λ=974 nm light were measured. The lowest threshold was 0.5 W cm^?2, which is lower than the maximum permissible exposure of skin (0.726 W cm^?2). We demonstrate that low‐intensity NIR light can induce photoreactions after passing through a piece of tissue without damaging the tissue. Our results indicate that the threshold for UCNP‐ assisted photochemistry can be reduced by using highly photosensitive compounds that absorb upconverted visible light. Low excitation intensity in UCNP‐assisted photochemistry is important for biomedical applications because it minimizes the overheating problems of NIR light and causes less photodamage to biomaterials.     

Wetting on the microscale: shape of a liquid drop on a microstructured surface at different length scales

Describing wetting of a liquid on a rough or structured surface is a challenge because of the wide range of involved length scales. Nano- and micrometer-sized textures cause pinning of the contact line, reflected in a hysteresis of the contact angle. To investigate contact angles at different length scales, we imaged water drops on arrays of 5 μm high poly(dimethylsiloxane) micropillars. The drops were imaged by laser scanning confocal microscopy (LSCM), which allowed us to quantitatively analyze the local and large-scale drop profile simultaneously. Deviations of the shape of drops from a sphere decay at two different length scales. Close to the pillars, the amplitude of deviations decays exponentially within 1-2 μm. The drop profile approached a sphere at a length scale 1 order of magnitude larger than the pillars' height. The height and position dependence of the contact angles can be understood from the interplay of pinning of the contact line, the principal curvatures set by the topography of the substrate, and the minimization of the air-water interfaces.