Transport properties of copper-doped carbon aerogels

The magnetic susceptibility, conductivity, magnetoresistance (MR) and Hall effect of copper-doped carbon aerogels are measured and compared with corresponding results from the original carbon aerogels. The experimental results indicate that the temperature-dependent magnetic susceptibility of the copper-doped and of the original carbon aerogels is well fit by a Curie function at low temperatures. The copper-doped carbon aerogels show a higher susceptibility and spin concentration than the original carbon aerogel. After doping by copper, the materials exhibit a more linear current-voltage curve than the original carbon aerogel under the same measurement conditions. The electrical resistance of the copper-doped carbon aerogels is strikingly lower than that of the original carbon aerogels, and decreases with increasing copper content in the samples. The temperature-dependent resistivity ρ(T) of all of the copper-doped and original carbon aerogels can be fitted by an exp(T^−1/2) dependence for T<100 K. The copper-doped and pristine carbon aerogels follow a quadratic MR behavior Δρ/ρ=AB² in the magnetic field range B investigated (up to 5 T), except at very low temperatures (T<4 K).     

Variational approach to wetting problems: Calculation of a shape of sessile liquid drop deposited on a solid substrate in external field

Analysis of the shape of sessile drops pinned to a solid substrate and exposed to the external potential is presented. Explicit expressions describing the drops’ shape are obtained with a calculus of variations for 2D and 3D wetting problems. The presented approach is applicable for analysis of electrowetting problems, the study of vibrated and centrifuged drops.     

Introduction of a New Devices for Sampling Organic Pollutants

A new mimic biological sampling devices, which consisted of lipid-containing semipermeable-membrane (SPMD) for sampling organic pollutants has been introduced.     

Evaluating partially observed survival histories: retrospective projection of covariate trajectories

The use of maximum likelihood methods in analysing times to failure in the presence of unobserved randomly changing covariates requires constrained optimization procedures. An alternative approach using a generalized version of the EM-algorithm requires smoothed estimates of covariate values. Similar estimates are needed in evaluating past exposures to hazardous chemicals, radiation or other toxic materials when health effects only become evident long after their use. In this paper, two kinds of equation for smoothing estimates of unobserved covariates in survival problems are derived. The first shows how new information may be used to update past estimates of the covariates' values. The second can be used to project the covariates' trajectory from the present to the past. If the hazard function is quadratic in form, both types of smoothing equation can be derived in a closed analytical form. Examples of both types of equation are presented. Use of these equations in the extended EM-algorithm, and in estimating past exposures to hazardous materials, are discussed. © 1997 by John Wiley & Sons, Ltd.     

Novel mechanism for the formation of long-chain branching in polyethylene

Polyethylene produced by a vanadium-based polymerization catalyst contains long-chain branching as determined by NMR and rheology, even though the polymer has very low levels of vinyl unsaturation. A new mechanism is proposed for the formation of the long-chain branching, which involves C H bond activation of the polyethylene backbone through a σ-bond metathesis reaction, followed by ethylene insertion at the new V C bond. Consistent with the proposed C H bond activation mechanism, the polymerization catalyst was also found to insert ethylene into the C H bonds of alkanes such as heptane. A bridged metallocene catalyst was also found to activate C H bonds of alkanes suggesting this new mechanism may explain the formation of long-chain branching in some metallocene-produced polyethylene. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2889–2898, 1998     

Correlation of Spatial and Temporal Filtering Methods for Turbulence Quantification in Spark-Ignition Direct-Injection (SIDI) Engine Flows

High-speed particle image velocimetry (HSPIV) was applied to an optical spark-ignition direct-injection engine in order to analyse various turbulent properties of the flow-field. The engine was motored at 1200 RPM with an intake pressure of 100 kPa, while HSPIV images were acquired at a sampling frequency of 5 kHz on both a vertical (tumble) plane and a horizontal (swirl) plane. The flow was decomposed in mean and fluctuating components via three different methods — ensemble averaging, spatial filtering, and temporal filtering. It was found that the velocity fluctuations calculated via the ensemble average method were more closely linked to low-frequency rather than high-frequency fluctuations, suggesting that they are more representative of cycle-to-cycle variation rather than true turbulence. Visual inspection of the high-frequency fluctuating flow-fields derived through the two filter based approaches revealed turbulent structures of similar size, shape and distribution. To equate the two filtering methods quantitatively, a spatial filter was designed with a mean flow speed scaled cut-off length, which was tuned in order to match the turbulent kinetic energy (TKE) of a 300 Hz temporal filter. A brief case study was then performed on a fuel-injected operating condition, run at the same 1200 RPM engine speed and 100 kPa intake pressure. A 1:1 split ratio dual-injection strategy was employed, with the first injection at 300°CA bTDC and the second injection at 110°CA bTDC. The relatively late second injection was found to significantly increase both the mean and turbulent velocities present in the flow-field in comparison to the motored condition, with TKE magnitudes being ～5 to 10 fold higher, depending on the choice of cut-off length.     

Micrometrically scaled textured metallic hydrophobic interfaces validate the Cassie-Baxter wetting hypothesis

The possibility of forming a hydrophobic metallic interface is shown when it is micrometrically textured. On such surface obtained by gold coating the polymer honeycomb template, the apparent contact angle of water was observed to be close to or greater than 90 degrees . The metal hydrophobicity is explained by trapping air inside pores of pattern according to the Cassie-Baxter wetting model. The agreement between calculated and observed values of the apparent contact angle justifies the applicability of this model in the present case. Formation of the acute local (Young) angle on the pore surface is provided by its concave form.     

Detection of Cancer Cell Death Mediated by a Synthetic Granzyme B-like Peptide Fluorescent Conjugate and the same Peptide Binding in Bacteria

Granzyme-mediated apoptosis, supported by pore-forming perforin, plays an important role in CD8+ T lymphocytes (CTL)-dependent cellular immunity protection against both cancer and viral infection. Quantitative and qualitative problems with CTL are potential contributing factors to disease progression. The feasibility of developing CTL-independent cellular immunity is desired but must first overcome the barrier of CTL-independent target cell recognition. Granzyme B with its strong pro-apoptotic activity in many different target cells is investigated for use in the CTL-independent cellular immunity approach, and granzyme B or its bioactive peptides without the enzymatic activity are more desirable for use. Native granzyme B with enzymatic activity is usually investigated in cancer cells for its mediation of apoptosis by detection of DNA fragmentation. Detection of cell death mediated by such peptides in cancer cells is needed to demonstrate the potential therapeutic purposes. We show with never-before-seen microscopic images using fluorescence microscopy that a synthetic granzyme B-like peptide fluorescent conjugate (GP1R) can: 1) mediate cell death of different cancer cells via membrane extrusion, 2) bind to constitutively expressed binding targets in different cancer cells and bacteria, and 3) promote bacterial phagocytosis. The putative binding targets may serve as a universal pathologic biomarker detectable by GP1R. Our data taken together demonstrate the potential applications of GP1R for use in CTL-independent target cell recognition and target cell death induction. It may lead to development of rapid targeted detection and new treatment of cancer, viral and bacterial infections. The new treatment may show mutual benefits for two or more diseases.