PARTICULATE CONCENTRATION IN AUTOMOBILE PASSENGER COMPARTMENTS

An experimental study of the dust concentration in automobile passenger compartments was conducted to understand how driving conditions and a vehicle's ventilation system can affect cabin air quality. The results of this study are essential for designing appropriate cabin air filters and developing proper test procedures.

The particle size distribution of atmospheric contaminants entering the vehicle's passenger compartment through air registers and in the occupants' breathing zone was measured using an optical particle counter. The concentration and size distribution of aerosol in the cabin was found to be dependent on traffic conditions, road surface, environmental conditions (e.g., weather) and ventilation mode. In all cases over 90% of the particles were smaller than 1 µm. The vehicle's HVAC system (evaporator core) reduces the concentration of aerosol entering the car interior, especially larger particles. Commercial vehicle ventilation filters decrease particle concentrations in a driver's breathing zone for all particle sizes. However, the reduction in the submicron particle range is not sufficient to substantially improve air quality in the passenger cabin.     

OPTIMIZATION OF NONWOVEN FILTER PERFORMANCE FOR INTERMEDIATE REYNOLDS NUMBERS

The selection of a nonwoven air filter structure that is optimal for specific conditions is not simple and is affected by many factors. Traditionally, the selection process is based on experience and professional instinct. However, this approach to decision-making lacks an objective basis for making comparisons between alternative structures. In order to optimize the effectiveness of the filter performance, the decision-making process must be placed on a rational and objective basis.

In this paper, a general approach to a multicriteria optimization is discussed. Linear and nonlinear models are analyzed as well as compound criteria obtained by various combinations of simple criteria. An essential component of the optimization model is the criterion function, which is a mathematical expression of the optimization criterion deduced from the goals. Each criterion represents a filter characteristic, such as filter efficiency, pressure drop, flow rate, dust-holding capacity and, in some cases, economic indices.

The formulation of the optimization problem involves transforming filter performance into an equivalent mathematical model. A set of equations was developed to describe initial efficiency and pressure drop as well as efficiency and pressure drop for dust loaded nonwoven media at intermediate Reynolds numbers.

Using a simple mathematical method, the optimal structure of a nonwoven filter for a given set of conditions was obtained. A compound criterion can also be used as a quality factor in order to make comparisons between filters of different structures.     

The secondary structure of the insect defensin A depends on its environment. A circular dichroism study

Defensin A is an inducible antibacterial protein isolated from the larvae of Phormia terranovae. The conformation of defensin A has been previously determined by two-dimensional 1H-NMR for concentrations in the range of 4-8 mM in water (Bonmatin JM et al (1992) J Biomol NMR 2, 235-256). CD spectroscopic data of defensin A at lower concentrations (10(-5) to 10(-3) M) are reported herein. The ellipticity in the 200-240 nm wavelength range for various solvents varies as follows: acetonitrile < water < methanol < HFIP. The magnitude of theta 222 is strongly dependent on defensin concentration in a buffer solution, suggesting an aggregation process. The helical content of defensin A is maximum at a pH value range (7.5-8) for which the optimum antibacterial activity was observed (Cociancich S et al (1993) J Biol Chem 268, 19239-19245).     

Immunological signals which control T cell responses

A number of identifiable immunological parameters can influence the elicitation and regulation of antigen-specific inflammatory responses to immunogenic epitopes. Injection of antigen in vivo can lead to the activation of type IV hypersensitivity responses, or to the induction of immunological tolerance to that antigen. We have used the hapten trinitrophenol as a model system for studying the factors which influence the generation and regulation of hypersensitivity responses to immunogenic epitopes in vivo. The generation of hypersensitivity or tolerance to trinitrophenyl depends on a number of immunological factors, including the form of the antigen, the route of immunization, and the presence of immune complexes of antibody and antigen on the surface of the antigen-presenting cell. Immunization with trinitrophenyl resulting in unresponsiveness can be the result of either the inability to prime inflammatory cells in vivo or the induction of suppressor T cells.     

Multitracer-Versuch im kontaminierten Grundwasser des Testfeldes Süd

A natural gradient multitracer-experiment (fluorescein, eosin, naphthionate, bromide) was performed at an experimental site with contaminated groundwater. The break-through curves were evaluated by fitting an analytical solution of the transport equation to the breakthrough curves, different calculation methods based on the tracer arrival times, and with numerical transport simulations. The observed transport direction differed markedly from the expected direction based on equipotential lines. The method of temporal moments proved to be best suited to describe the transport velocity. Transverse dispersivites could not be evaluated satisfactorily, even though numerous observation wells existed. The interactions of the tracers and nonaqueous phase liquids (octanol, tar oil, lubrication oil) were investigated with laboratory experiments. None of the tracers was affected. Fluorescein and eosin could be applied successfully even when nonaqueous phase liquids were present, but the application of naphthionate suffered from high background fluorescence.     

Cell interactions that regulate the T-cell dose-response profile to concanavalin A

We have tested the ability of structures on macrophage (M phi) membranes (M phi-MEM) and on several other types of cells with Fc receptors to affect the DNA synthetic response of concanavalin-A-stimulated T cells. Of the cells tested, only M phi-MEM have the capacity to relieve the suppression produced by supra-optimal doses of the mitogen. The M phi-MEM do not increase Con A responses by altering the stimulatory capacity of the Con A. These observations, analysed together with previous results, which have indicated that live intact M phi are required for the transfer of information between lymphocyte sets and that M phi-MEM preparations can act as competitive antagonists for this function, are interpreted as follows: some supraoptimal doses of Con A activate suppressor cells, which are responsible for limiting the DNA synthetic response to the mitogen; the M phi-MEM abrogate this suppression by absorbing the signal that activates the suppressor cell. Kinetic studies suggest that the M phi-MEM do not affect the activity of already activated suppressor cells. We also found that Con A usually activates two separately responding T-cell populations with different sensitivities to dose and to time of contact with mitogen and that the suppression of both populations can be relieved by M phi-MEM. These results support the notion that the overall immunological circuit is composed of multiple independently regulated mini-circuits, with M phi acting as transmission posts for intra- and perhaps also inter-circuit communication.     

Electrical and thermophysical properties of mechanochemically obtained lanthanide hafnates

This contribution presents the synthesis and thermophysical characterization of seven lanthanide hafnates Ln₂Hf₂O₇ (Ln=Sm³⁺, Eu³⁺, Gd³⁺, Dy³⁺, Y³⁺, Ho³⁺, Yb³⁺); the title samples were prepared at room temperature by mechanically milling stoichiometric mixtures of the corresponding elemental oxides. Irrespective of the lanthanide ion involved, milling promotes the formation of highly disordered fluoritelike materials. Postmilling thermal treatments facilitate the formation of the fluorite ordered derivative, the pyrochlore structure, but only for the larger lanthanides (Sm³⁺, Eu³⁺, Gd³⁺). Impedance spectroscopy measurements revealed that these materials show a moderate‐to‐good oxygen ion conductivity at high temperatures; furthermore, those adopting the pyrochlore structure give higher σ_dc and lower E_dc than their fluorite analogues (σ_dc at 750°C>10^?3 S·cm^?1 vs <5·10^?4 S·cm^?1, respectively). The same trend also holds for the thermal resistivity at high temperatures; the highest thermal resistivity and thus, lowest κ was obtained for Eu₂Hf₂O₇ (κ~1.3·W·m^?1·K^?1 at 800°C). Therefore, Ln₂Hf₂O₇ phases might be attractive component materials for electrochemical devices and thermal insulating coatings.     

Tracerexperimente zur Erkundung hydraulisch-hydrogeochemischer Eigenschaften heterogener Grundwasserleiter

In heterogeneous aquifers, predictions of contaminant transport require detailed knowledge of aquifer parameters and their spatial distribution. In most cases this information cannot easily be obtained at acceptable expenses. In general, subsurface investigation techniques are applied only at borehole locations, and the parameter values measured need to be regionalized in order to obtain continuous parameter fields. In such situations particularly forced gradient tracer tests offer the possibility to quickly and efficiently investigate the aquifer between the wells and to characterize the relevant aquifer properties based on effective parameters values. If, in addition, reactive tracers are used in the experiments, it is possible to investigate both the hydraulic and hydrogeochemical aquifer properties. This paper presents some selected tracer testing methods and gives examples of application at field scale.     

Heterotrophic Bacteria Associated with the Degradation of Zooplankton Fecal Pellets in Lake Michigan

Heterotrophic microbes decompose most of the calanoid copepod fecal pellets produced in Lake Michigan before they reach the sediment. Rod-shaped nonfermenters isolated from copepod and Mysis relicta fecal pellets were identified as Pseudomonas maltophilia and Pseudomonas fluorescens species. No enterobacteriaceae or fungal hyphae were found on or in any pellets. This investigation suggests that Psetfdomonas species are attached to and may degrade Mysis relicta and calanoid copepod fecal pellets in the water column of Lake Michigan.     

Resistance of human cytomegalovirus to benzimidazole ribonucleosides maps to two open reading frames: UL89 and UL56

2,5,6-Trichloro-1-beta-D-ribofuranosyl benzimidazole (TCRB) is a potent and selective inhibitor of human cytomegalovirus (HCMV) replication. TCRB acts via a novel mechanism involving inhibition of viral DNA processing and packaging. Resistance to the 2-bromo analog (BDCRB) has been mapped to the UL89 open reading frame (ORF), and this gene product was proposed as the viral target of the benzimidazole nucleosides. In this study, we report the independent isolation of virus that is 20- to 30-fold resistant to TCRB (isolate C4) and the characterization of the virus. The six ORFs known to be essential for viral DNA cleavage and packaging (UL51, UL52, UL56, UL77, UL89, and UL104) were sequenced from wild-type HCMV, strain Towne, and from isolate C4. Mutations were identified in UL89 (D344E) and in UL56 (Q204R). The mutation in UL89 was identical to that previously reported for virus resistant to BDCRB, but the mutation in UL56 is novel. Marker transfer analysis demonstrated that each of these mutations individually caused approximately 10-fold resistance to the benzimidazoles and that the combination of both mutations caused approximately 30-fold resistance. The rate and extent of replication of the mutants was the same as for wild-type virus, but the viruses were less sensitive to inhibition of DNA cleavage by TCRB. Mapping of resistance to UL56 supports and extends recent work showing that UL56 codes for a packaging motif binding protein which also has specific nuclease activity (E. Bogner et al., J. Virol. 72:2259-2264, 1998). Resistance which maps to two different genes suggests that their putative proteins interact and/or that either or both have a benzimidazole ribonucleoside binding site. The results also suggest that the gene products of UL89 and UL56 may be antiviral drug targets.