Effect of film thickness, type of buffer layer, and substrate temperature on the morphology of dicyanovinyl-substituted sexithiophene films

The influence of film thickness, type of buffer underlayer, and deposition substrate temperature on the crystal structure, microstructure, and morphology of the films of dicyanovinyl-substituted sexithiophene with four butyl-chains (DCV6T-Bu₄) is investigated by means of X-ray diffraction (XRD) and X-ray reflectivity methods. A neat Si wafer or a Si wafer covered by a 15 nm buffer underlayer of fullerene C₆₀ or 9,9-Bis[4-(N,N-bis-biphenyl-4-yl-amino)phenyl]-9H-fluorene (BPAPF) is used as a substrate. The crystalline nature and ordered molecular arrangement of the films are recorded down to 6 nm film thickness. By using substrates heated up to 90 °C during the film deposition, the size of the DCV6T-Bu₄ crystallites in direction perpendicular to the film surface increases up to value of the film thickness. With increasing deposition substrate temperature or film thickness, the DCV6T-Bu₄ film relaxes, resulting in reducing the interplane distances closer to the bulk values. For the films of the same thickness deposited at the same substrate temperature, the DCV6T-Bu₄ film relaxes for growth on Si to BPAPF to C₆₀. Thicker films grown at heated substrates are characterized by smaller density, higher roughness and crystallinity and better molecular ordering. A thin (up to about 6 nm-thick) intermediate layer with linear density-gradient is formed at the C₆₀/DCV6T-Bu₄ interface for the films with buffer C₆₀ layer. The XRD pattern of the DCV6T-Bu₄ powder is indexed using triclinic unit cell parameters.     

Hydrogenation of Cinnamaldehyde over Pd/Al2O3 Catalysts Modified with Thiol Monolayers

Modification of supported Pt catalysts with thiols has recently been shown to improve the hydrogenation selectivity of α,β-unsaturated aldehydes to unsaturated alcohols. Here, we apply a variety of organic thiol coatings to Pd/Al₂O₃ catalysts that typically have a much lower intrinsic selectivity for desired product formation. Thiol monolayers were found to increase hydrogenation selectivity to cinnamyl alcohol; however, unlike with Pt catalysts, the increase was independent of the identity of the organic tail.     

Synthesis and characterization of polyelectrolyte hydrogels with controlled swelling behaviour

Copolymerization of sulfopropyl methacrylate potassium salt (K‐SPMA) and 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) has been studied in the range 10–90% K‐SPMA in the feedstock. The reactivity ratios have been determined for K‐SPMA/AMPS copolymers. The copolymer compositions, utilized for determining the reactivity ratio, have been determined from nitrogen content. Crosslinked poly(AMPS) and K‐SPMA/AMPS copolymers were prepared in water in the presence of potassium persulfate as initiator and N,N‐methylene bisacrylamide (MBA) as tetrafunctional crosslinker. Irradiation of K‐SPMA and AMPS with an electron‐beam was carried out at 50 wt% aqueous solution with low pH and irradiation dose 40–120 kGy. The swelling behaviour of highly crosslinked K‐SPMA/AMPS copolymer polyelectrolyte gels in aqueous medium was studied in the presence of different types of salts. The crosslink density, the average molecular weight between the crosslinks and the dissociation constant (pK_a) of the crosslinked polymer were determined from stress–strain measurements. © 2001 Society of Chemical Industry     

Stable linker peptides for a cellulose-binding domain-lipase fusion protein expressed in Pichia pastoris

Fusion proteins composed of a cellulose-binding domain fromNeocallimastix patriciarum cellulase A and Candida antarcticalipase B were constructed using different linker peptides. Theaim was to create proteolytically stable linkers that were ableto join the functional modules without disrupting their function.Six fusion variants containing linkers of 4–44 residueswere expressed in Pichia pastoris and analysed. Three variantswere found to be stable throughout 7-day cultivations. The cellulose-bindingcapacities of fusion proteins containing short linkers wereslightly lower compared with those containing long linkers.The lipase-specific activities of all variants, in solutionor immobilized on to cellulose, were equal to that of the wild-typelipase.     

Perinatal lead and mercury exposure in Austria

Objective

The heavy metals lead (Pb) and mercury (Hg) are ubiquitous environmental pollutants with high neurotoxic potential. We aimed to compare perinatal Pb and Hg concentrations and to explore the potential association between Pb and Hg exposure and newborn anthropometry.

Study design

Pregnant women were recruited in 2005 at the General Hospital Vienna for participation in this longitudinal study. Pb and Hg concentrations were measured in maternal blood and hair, placenta, cord blood, meconium, and breast milk of 53 mother-child pairs by CV-AAS, GF-AAS, and HPLC-CV-ICPMS. We conducted bivariate analyses and categorical regression analysis (CATREG) to evaluate the determinants of Pb and Hg exposure, and of infant anthropometry.

Results

Median Pb and total Hg contents were low, i.e., 25 μg/L (maternal blood-Pb), 13 μg/L (cord blood-Pb), 0.7 μg/L (maternal blood-Hg), and 1.1 μg/L (cord blood-Hg). Hg levels in maternal and fetal tissues were frequently correlated (r > 0.3, P < 0.05, respectively). Regarding Pb, only maternal blood and cord blood concentrations correlated (P = 0.043). Cord blood levels indicated higher Hg exposure but lower Pb exposure relative to maternal blood contents. Adjusted CATREG models indicated the significant predictors of birth length (placenta-Pb, gestational length, meconium-Pb), birth weight (placenta-Pb, gestational length, maternal blood-Pb), and head circumference (maternal education, maternal height). Besides one significant correlation between maternal hair Hg and birth length, the mercury levels were not associated with newborn anthropometry.

Conclusions

Our data implicate that different modes of action may exist for placentar transfer of Pb and Hg as well as that low Pb exposure levels can result in lower birth weight. The findings related to newborn anthropometry need to be confirmed by the examination of larger study groups. Further research is needed to clarify the mechanisms of Pb and Hg transfer via the placenta, and to explore how prenatal Pb exposure is related to intrauterine growth.     

Kinetics of internal steam reforming of methane on Ni/YSZ-based anodes for solid oxide fuel cells

The kinetics of steam reforming of methane was determined on a Ni-YSZ anode, which we refer to as anode ‘A’ and on a Ni-YSZ anode modified by the addition of a basic compound, which we refer to as anode ‘B’. A salient feature of our work is that the data were collected on 50 μm thick anodes screen-printed on 110 μm thick YSZ electrolytes and the experiments were carried out in a fuel cell configuration. Orders in methane and steam were both higher on the modified Ni-YSZ anode. Activation energy was also higher on this anode suggesting different nature of sites in the two anodes. In the present study we have attempted to generate kinetic data at steam/carbon ratios which are economically attractive for fuel cell operation.     

THERMAL RESPONSE OF SILICON CRYSTAL TO PICO-FEMTOSECOND HEAT PULSE BY MOLECULAR DYNAMICS

We investigate the thermal response of a silicon crystal irradiated by a pico-femto heat pulse by using molecular dynamics technique and a linear response theory–based statistical analysis. The thermal susceptibility is first defined in terms of computed quantities and then convoluted with time Gaussian temperature pulses. The qualitative difference between the responses to various pulse durations is explained and the results are compared to those of classical Fourier model. Non-Fourier behaviors are emphasized and a mean phonon relaxation time is identified.     

Enhanced predictive corrosion modeling with implicit corrosion products

An advanced mathematical approach to describe the influence of corrosion products on the corrosion rate is presented here. The related model can be used as input equation for numerical predictive corrosion simulations or simply as an empirical model, to extrapolate experimental data of corrosion tests to longer times and to interpret the physical parameters behind. This semiempirical model assumes that a constant share of the dissolved metal precipitates on the surface and hinders the diffusion processes. Hence, the effective corrosion rate decreases exponentially with increasing dissolution. The explicit corrosion progress over time is derived by time integration on a newly developed, time dependent corrosion rate equation. The derived expression can be effortlessly implemented in existing for example finite element method, which is demonstrated for the uniform corrosion of a zinc surface. Furthermore, this approach is qualitatively compared with other empirical models for corrosion products and the validity is demonstrated by fitting of experimental data. A very good agreement between experiment and theory can be achieved for various materials and environments considering no change of the driving corrosion mechanism.     

Mixtures of general linear models for functional neuroimaging

We set out a new general framework for making inferences from neuroimaging data, which includes a standard approach to neuroimaging analysis, statistical parametric mapping (SPM), as a special case. The model offers numerous conceptual and statistical advantages that derive from analyzing data at the "cluster level" rather than the "voxel level" and from explicit modeling of the shape and position of clusters of activation. This provides a natural and principled way to pool data from nearby voxels for parameter and variance-component estimation. The model can also be viewed as performing a spatio-temporal cluster analysis. The parameters of the model are estimated using an expectation maximization (EM) algorithm.