Water vapour adsorption on DNA

DNA adsorbed very low amount of water at low relative humidities, amount of adsorption increased to 140% at 98% relative humidity at 25°C. Heat of adsorption was 109 kJ mol^-1 H₂O for the increase of moisture content from 0 to 1.96%. At higher moisture contents the heat released approached heat of condensation of water vapour on free liquid surface, 40 kJ mol^-1 H₂O.     

Characterization of poly(vinyl chloride) powder produced by emulsion polymerization

The effect of emulsion process formulation ingredients on the morphology, structure, and properties of polyvinyl chloride (PVC) powder has been considered in this study. PVC powder was extracted with ethanol and films were obtained by solvent casting from tetrahydrofurane. Characterization of powders, films, and ethanol extract was performed through FTIR spectroscopy, DSC, AFM, SEM, EDX analysis, methylene blue, and nitrogen adsorption. PVC powder was composed of spheres of a large particle size range from 10 nm to 20 μm as shown by SEM. The specific surface area of the PVC powder was determined as 16 and 12 m² g⁻¹ from methylene blue adsorption at 25 °C and from N₂ adsorption at −196 °C, respectively. AFM indicated the surface roughness of the films obtained by pressing the particles was 25.9 nm. Density of PVC powder was determined by helium pycnometry as 1.39 g cm⁻³. FTIR spectroscopy indicated that it contained carbonyl and carboxylate groups belonging to additives such as surface active agents, plasticizers, and antioxidants used in production of PVC. These additives were 1.6% in mass of PVC as determined by ethanol extraction. EDX analysis showed PVC particles surfaces were coated with carbon-rich materials. The coatings had plasticizer effect since, glass transition temperature was lower than 25 °C for PVC powder and it was 80 °C for ethanol extracted powders as found by using differential scanning calorimetry. These additives from polymerization process made PVC powder more thermally stable as understood from Metrom PVC thermomat tests as well.     

Scanning near field thermal microscopy on a micromachined thin membrane

A resistive probe based scanning thermal microscope (SThM) has been used to perform complementary near field thermal measurements on the surface of a thin semiconductor membrane. This thin structure is part of a micromachined thermal rf power sensor and includes an integrated resistive heater used as an absorbing element for the input power. The resulting 2D surface temperature distribution and the 2D thermal wave propagation characteristic were determined. Considering the thermal wave behaviour at near field conditions, the local thermal conductivity of the thin membrane and the surrounding bulk material was investigated by usage of the 3ω-method.     

Pipe-diffusion ripening of Si precipitates in Al-0.5%Cu-1%Si thin films

Al-0.5%Cu-1%Si thin films deposited onto oxidized Si substrates were subjected to both wafer curvature and in situ transmission electron microscopy thermal cycling experiments between room temperature and 450°C. The evolution of precipitates was monitored during cycling. Chemical analysis revealed that the precipitates are pure Si. Their average size increased from 80?nm in the as-deposited state to 300?nm after thermal cycling. The Si precipitates serve as anchoring points for dislocations and grain boundaries. Direct evidence for pipe-diffusion ripening was found in the vicinity of a dissolving precipitate. Real-time measurement of the radius of the precipitate allowed us to estimate the coefficient of pipe diffusion of Si in Al at this temperature. As expected, this coefficient is several orders of magnitude larger than the volume diffusion coefficient. The impact of precipitate ripening on the mechanical behavior of these alloyed Al films will also be discussed.     

Diffusion of Butylated Hydroxy Toluol (BHT) in PVC Films

Abstract

The diffusion coefficient of butylated hydroxy toluol (BHT) in solvent casted PVC films from tetrahydrofurane (THF) was studied by UV spectroscopy. Diffusion coefficient of BHT in PVC at 140, 160 and 180°C were determined as 1.0 × 10^?12 3.0 × 10^?12 and 6.0 × 10^?12 m²/s. The activation energy of diffusion (E_a) was 66 kj/mol.

IR spectroscopic work showed that the complete removal of THF was possible by heating films 15 minutes at 140 °C, but that caused formation of C=0 groups in PVC. No dehydrochlorination of films was observed even for heating them at 180 °C for 60 minutes.

Antioxidant BHT is volatile at high temperatures, so it is not advisable to use it for high temperature applications.     

Measurements of nanoscale domain wall flexing in a ferromagnetic thin film

We use the high spatial sensitivity of the anomalous Hall effect in the ferromagnetic semiconductor Ga(1-x)Mn(x)As, combined with the magneto-optical Kerr effect, to probe the nanoscale elastic flexing behavior of a single magnetic domain wall in a ferromagnetic thin film. Our technique allows position sensitive characterization of the pinning site density, which we estimate to be ～10(14) cm(-3). Analysis of single site depinning events and their temperature dependence yields estimates of pinning site forces (10 pN range) as well as the thermal deactivation energy. Our data provide evidence for a much higher intrinsic domain wall mobility for flexing than previously observed in optically probed μm scale measurements.     

Inclusive semileptonic decays of polarized Λb Baryons into polarized τ-leptons

We employ OPE techniques within HQET to calculate the inclusive semileptonic decays of polarized Λ_b baryons. Lepton mass effects are included which enables us to also discuss rates into polarized τ-leptons. We present explicit results for the longitudinal polarization of the τ in the Λ_b rest frame as well as in the (τ^?, v_τ) c.m. frame. In both the Λ_b rest frame and in the (τ^?, v_τ) c.m. frame we make use of novel calculational techniques which considerably simplify the calculations. The transverse polarization components of the τ are calculated in the (τ^?, v_τ) c.m. frame. We delineate how to measure the full set of 14 polarized and unpolarized structure functions of the decay process by angular correlation measurements. A set of observables are identified that allow one to isolate the contributions of the twoO(1/m _t ²) nonperturbative matrix elementsK _b and ε_b.     

The enigma of the triangular pyramid

This is a story about an old problem of the outstanding French geometer J.D.Gergonne. It is about the answer to this problem which was widely accepted as correct (and rigorously proved) for many decades, and cited as such in highly respected encyclopedias, but is in reality absolutely erroneous — the right answer is just the opposite. It is a story about two other problems closely related to that of Gergonne, about the possibility of finding highly plausible answers to them via computer experimentation.     

Random fluorene copolymers with on‐chain quinoxaline acceptor units

Two series of novel random polyfluorene copolymers containing quinoxaline units were prepared by stressing the coupling according to Yamamoto. The first series contains 2,3‐bis‐(4′‐tert‐butyl‐biphenyl‐4‐yl)benzo[g]quinoxaline and the second series 2,3‐bis‐(4′‐tert‐butyl‐biphenyl‐4‐yl)quinoxaline as energy accepting unit. The copolymers were identified by gel permeation chromatography, infrared spectroscopy, and nuclear magnetic resonance spectroscopy. Thermal properties were analyzed by thermal gravimetric analysis and differential scanning calorimetry revealing amorphous copolymers that are stable up to 430 °C. The morphology was investigated using atomic force microscopy. The optical properties in solutions and thin films were analyzed. Furthermore, the thin film electro‐optical properties were determined in monolayer polymer light‐emitting devices. Single layer devices were built with efficiencies ranging from 0.15 to 2.0 cd/A. For the random copolymers with 5 mol % benzo[g]quinoxazoline in the polyfluorene backbone some threefold efficiency enhancement from 1.1 to 3.0 cd/A was achieved by utilizing an ultra thin interlayer of poly(9,9‐di‐n‐octylfluorene‐2,7‐diyl)‐alt‐[1,4‐phenylene‐(4‐sec‐butylphenylimino)‐1,4‐phenylene] between PEDOT:PSS and the emissive random copolymer layer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4773–4785, 2007