Gas/particle partitioning of seven volatile polycyclic aromatic hydrocarbons in a heavy traffic urban area

Air samples (vapor- and particle-phase) were taken for 19 sampling events during the period from December 1997 to July 1998 in an urban site in the center of Athens. The urban site is densely populated and characterized by heavy traffic circulation and elevated concentrations of VOCs, NO(x), CO and smoke. Seven volatile polycyclic aromatic hydrocarbons (PAHs) were determined in samples. The temperature dependence of gas-phase atmospheric concentration of PAHs, C(g), was investigated using diagrams of natural logarithm of partial pressures (lnP) vs. reciprocal mid-point temperatures. For the six of seven volatile PAHs, the temperature dependence of lnP was statistically significant (at least at the 90% confidence level) and the temperature accounted for 21-67% of the variability in gas-phase concentrations. The gas-phase concentration C(g) of the very volatile PAHs was affected more significantly by changes in temperature, but the variation of the less-volatile PAHs fluoranthene and pyrene C(g), was better explained by changes in temperature. The temperature dependence of gas/particle partitioning constant K(P) was also examined. Regressions of log(K(P))(-1) vs. T(-1) for fluorene, fluoranthene and pyrene were classified into two different temperature ranges. The gas/particle partitioning of PAHs was studied by correlating the partition constant to the sub-cooled liquid saturation vapor pressure (P(L)(o)). The Junge adsorption model underestimated the particle fraction of volatile PAHs probably due to the presence of non-exchangeable fraction. Slopes (m(r)) of the regressions logK(P) vs. logP(L)(o) were different from the value -1 as Pankow's theory predicts. The short distance between the sampling point and the emission sources is also estimated to be a factor that causes deviations from the theoretical value. Evidence that atmospheric conditions favorable for secondary aerosol formation coincide with higher value of m(r), was provided by limited sampling events. An interrelation was found to exist between the m(r) values, allowing the prediction of the gas/particle partitioning of a series of seven PAHs by the measurement of a single PAH partitioning.     

Transmission and radiation in a slab waveguide coupled to a whispering-gallery resonator: volume-integral-equation analysis

The excitation of a whispering gallery resonator by a surface wave guided in a dielectric slab is analyzed with a rigorous volume-integral-equation approach. The analysis is based on the Green's function concept and the application of the entire-domain Galerkin technique through expansion of the electric field in the resonator in terms of cylindrical wave functions. The algorithm developed yields highly accurate results for the transmission and reflection coefficients in the waveguide. The radiated far field is computed, and the effect of the excitation of a whispering gallery mode on the radiation pattern is studied.     

Effect of vitamin E supplementation on neutrophil function, milk composition and plasmin activity in dairy cows in a commercial herd

Fifty-six Holstein dairy cows from a commercial dairy herd in the Northern part of Greece were used to determine the effect of vitamin E supplementation on immune parameters, milk composition and milk quality. Cows were assigned to one of two experimental groups: control (no vitamin E supplementation) and vitamin E supplementation. Supplementation of vitamin E started 4 weeks prior to and continued up to 12 weeks after parturition. Supplementation included daily oral administration of vitamin E at 3000 i.u./cow prepartum and was reduced to 1000 i.u./cow post partum. Blood samples were collected weekly for 8 weeks starting 4 weeks before parturition, neutrophils were isolated and the following parameters were determined in neutrophils activated by phorbol myristate acetate: total cell-associated and membrane-bound urokinase plasminogen activator (u-PA) activity and superoxide production. Milk samples were collected weekly and fat, protein, lactose, somatic cell count (SCC), plasmin and plasminogen-derived activity were determined. Activated neutrophils isolated from cows that received supplemental vitamin E had higher (P<0.01) total and membrane-bound u-PA activities during the first 3 weeks after parturition and higher (P<0.01) superoxide production during week 1 prepartum and week 1 post partum compared with the corresponding values of activated neutrophils isolated from control cows. Vitamin E supplementation had no effect (P=0.28) on plasminogen-derived activity in milk. Milk obtained from cows that received supplemental vitamin E had SCC lower by 25% (P<0.05) and plasmin lower by 30% (P<0.01) than corresponding values in milk obtained from control cows. The reduction in plasmin as a result of vitamin E supplementation is very beneficial to the dairy industry because plasmin reduces the cheese-yielding capacity of milk, affects the coagulating properties of milk and its overall ability to withstand processing during cheesemaking. In conclusion, vitamin E supplementation had positive effects on the function of bovine neutrophils and milk quality in a commercial dairy herd.     

Sub-glassy relaxation modes in PMMA and PMMA + SiO<Subscript>2</Subscript> hosts of non-polar perylene derivatives

The dielectric response of poly(methyl methacrylate) (PMMA) in solid solutions of perylene derivative laser dyes in PMMA and PMMA + SiO₂ has been studied by means of the thermally stimulated depolarization currents (TSDC) technique, with the aim to isolate molecular and phase interactions in the dye blends. The changes in characteristics of the β-relaxation mode of PMMA are interpreted with respect to the dissimilar local environments of the polar carboxy-methyl pendant groups of PMMA. An important "chemical" effect on the β relaxation mechanism recorded in the organic-inorganic composites, is the formation of hydrogen bonds between the acidic pore surfaces of SiO₂ and the acetate side-groups. Several "physical" effects produced by the chromophores and the geometrical confinement, like the modification of the monomer-to-polymer conversion rates, the polymer's free volume and the extent of the PMMA-SiO₂ interaction, are discussed.     

Incrementally updating a hybrid rule base based on empirical data

Abstract: Neurules are a kind of hybrid rules that combine a symbolic (production rules) and a connectionist (adaline unit) representation. One way that the neurules can be produced is from training examples/patterns, extracted from empirical data. However, in certain application fields not all of the training examples are available a priori. A number of them become available over time. In those cases, updating the neurule base is necessary. In this paper, methods for updating a hybrid rule base, consisting of neurules, to reflect the availability of new training examples are presented. They can be considered as a type of incremental learning method that retains the entire induced hypothesis and all past training examples. The methods are efficient, since they require the least possible retraining effort and the number of neurules produced is kept as small as possible. Experimental results that prove the above argument are presented.     

Coalitional tracking

We propose a novel tracking method that uses a network of independent particle filter trackers whose interactions are modeled using coalitional game theory. Our tracking method is general, it maintains pixel level accuracy, and can negotiate surface deformations and occlusions. We tested our method on a substantial video set featuring non-trivial motion from over 40 objects in both the infrared and visual spectra. The coalitional tracker demonstrated fault tolerant behavior that exceeds by far the performance of single particle filter trackers. Our method represents a shift from the typical tracking paradigms and may find application in demanding imaging problems across the electromagnetic spectrum.     

On labeling in graph visualization

When visualizing graphs, it is essential to communicate the meaning of each graph object via text or graphical labels. Automatic placement of labels in a graph is an NP-Hard problem, for which efficient heuristic solutions have been recently developed. In this paper, we describe a general framework for modeling, drawing, editing, and automatic placement of labels respecting user constraints. In addition, we present the interface and the basic engine of the Graph Editor Toolkit - a family of portable graph visualization libraries designed for integration into graphical user interface application programs. This toolkit produces a high quality automated placement of labels in a graph using our framework. A brief survey of automatic label placement algorithms is also presented. Finally we describe extensions to certain existing automatic label placement algorithms, allowing their integration into this visualization tool.     

Benefits of the use of impairment constraint routing in optical networks

In transparent optical networks, the optical signal accumulates the effects of all physical impairments present along the path it traverses. The conventional selection of signal paths based on e.g. shortest path routing without considering the signal quality and its association with the physical impairments does not always provide the optimum solution in terms of network performance such as blocking and resource utilization. This paper proposes an impairment constraint based routing algorithm to achieve an optimal combination of physical and networking performance taking into account all physical linear impairments including noise, chromatic and polarization mode dispersion, crosstalk and filter concatenation effects in an integrated approach. The performance of a typical metropolitan area network is examined and the improvement achieved when using the proposed approach compared to the conventional shortest path routing is demonstrated.     

Controlled Drug Release and Chemotherapy Response in a Novel Acoustofluidic 3D Tumor Platform

Overcoming transport barriers to delivery of therapeutic agents in tumors remains a major challenge. Focused ultrasound (FUS), in combination with modern nanomedicine drug formulations, offers the ability to maximize drug transport to tumor tissue while minimizing toxicity to normal tissue. This potential remains unfulfilled due to the limitations of current approaches in accurately assessing and quantifying how FUS modulates drug transport in solid tumors. A novel acoustofluidic platform is developed by integrating a physiologically relevant 3D microfluidic device and a FUS system with a closed‐loop controller to study drug transport and assess the response of cancer cells to chemotherapy in real time using live cell microscopy. FUS‐induced heating triggers local release of the chemotherapeutic agent doxorubicin from a liposomal carrier and results in higher cellular drug uptake in the FUS focal region. This differential drug uptake induces locally confined DNA damage and glioblastoma cell death in the 3D environment. The capabilities of acoustofluidics for accurate control of drug release and monitoring of localized cell response are demonstrated in a 3D in vitro tumor mode. This has important implications for developing novel strategies to deliver therapeutic agents directly to the tumor tissue while sparing healthy tissue.