Particle associations

Table 4. Properties of Stable Particles Associated With Radioactive Decay...

Actually, then, by our symbol jjU we are representing not an atom, but a nucleus. Our equation is written in terms of nuclei and particles associated with them. This nuclear equation tells us nothing about what compound ol uranium was bombarded with neutrons or what compound of barium is formed. We are summarizing only the nuclear changes. During the nuclear change there is much disruption of other atoms because of the tremendous amounts of energy liberated. We do not know in detail what happens but eventually we return to electrically neutral substances (chemical compounds) and the neutrons are consumed by other nuclei. 

A study using resuspended river sediment (Marchesi et al. 1991) illustrated the important interdependence of substrate attachment to particulate matter and its biodegradability. Addition of sodium dodecyl sulfate that is degradable resulted in a relative increase in the number of particle-associated bacteria, whereas this was not observed with the nondegrad-able analogs such as sodium tetradecyl sulfate or sodium dodecane sulfonate. 

Methods to determine the a.i., and/or relevant metabolites in air during or shortly after the application must be submitted unless it can be justified that exposure of operators, workers, or bystanders does not occur. In SANCO/825/00 it is stated that spray drift and particle-associated as well as gaseous substances have to be taken into consideration because both can cause relevant exposure of operators, workers, or bystanders. Therefore, an analytical method must also be submitted for relevant substances with a low vapor pressure (< 10-5 Pa). 

Resolving some of the issues surrounding the use of " Th as a tracer for POC flux, as well as collecting simultaneous °Po and °Pb data, will enable a better characterization of other components of the particulate flux, such as biogenic silica (Buesseler et al. 2001 Friedrich and Rutgers van der Loeff 2002) and particle-associated... 

Aller RC, Benninger LJ, Cochran JK (1980) Tracking particle associated processes in nearshore environments by use of disequilibrium. Earth Planet Sci Lett 47 161-175... 

This model does not explicitly consider that a fraction of the measured Pb-214 actually deposits in the impactor as particle-associated Po-218. The Pb-214 daughters produced under this condition would either not recoil off the plate or, if they did, they might end up associated with a smaller size fraction on a lower stage. In terms of both the model and the measurements, this fraction of the total Po-218 is not operationally different from the fraction which decays before attachment (1-A) or is not lost following recoil both represent Po-218 which does not undergo recoil redistribution. 

Four processes are considered diffusion (absorption), dissolution in rain of gaseous chemical, and wet and dry deposition of particle-associated chemical. 

The bioavailability of selenium to a benthic deposit-feeding bivalve, Macoma balthica from particulate and dissolved phases was determined from AE data. The selenium concentration in the animals collected from San Francisco Bay was very close to that predicted by a model based on the laboratory AE studies of radiolabelled selenium from both particulate and solute sources. Uptake was found to be largely derived from particulate material [93]. The selenium occurs as selenite in the dissolved phase, and is taken up linearly with concentration. However, the particle-associated selenium as organoselenium and even elemental selenium is accumulated at much higher levels. The efficiency of uptake from the sediment of particulate radiolabelled selenium was 22%. This contrasts with an absorption efficiency of ca. 86% of organoselenium when this was fed as diatoms - the major food source of the clam. The experiments demonstrated the importance of particles in the uptake of pollutants and their transfer through the food web to molluscs, but the mode of assimilation was not discussed. 

Radical trapping studies, 14 277 Radicidation, 8 655 Radioactive decay, 21 287—288 particles associated with, 21 291 Radioactive decay properties of uranium isotopes, 25 393 Radioactive emission, interaction with tracer molecules, 21 276 Radioactive iodine, protection from,... 

A thin film of oil-like material was visible after 28 d on the exterior surfaces of the SPMD membrane. Analysis of this film indicated that the triolein impurities, oleic acid and methyl oleate, were the major constituents. This external lipid film (Petty et al., 1993) appeared to contain imbibed particulates. Although the film was removed from the SPMDs by solvent rinsing and analyzed separately, some lipid-mediated desorption of particle-associated PCBs and subsequent diffusion into the SPMD may have occurred prior to solvent-removal of the film. This observation suggests the potential for SPMD concentrations to reflect both vapor phase concentrations and to a lesser extent, lipid-extracted particulate-associated residues (see Section 3.9.2.). Unfortunately, concentrations of more chlorinated congeners in particulates collected on GFFs from the NIOSH method were often below quantitation limits, because only a small volume of air was sampled (1 m ) using this active method. 

Although Rs values of high Ks compounds derived from Eq. 3.68 may have been partly influenced by particle sampling, it is unlikely that the equation can accurately predict the summed vapor plus particulate phase concentrations, because transport rates through the boundary layer and through the membrane are different for the vapor-phase fraction and the particle-bound fraction, due to differences in effective diffusion coefficients between molecules and small particles. In addition, it will be difficult to define universally applicable calibration curves for the sampling rate of total (particle -I- vapor) atmospheric contaminants. At this stage of development, results obtained with SPMDs for particle-associated compounds provides valuable information on source identification and temporal... 

Fig. 3. Fluorescence profiles of 2, 7 -dichlorofluorescin-loaded cells assayed in whole blood. (A) Compares the fluorescence histograms of unstimulated, control cells (shaded curve) with granulocytes exposed to opsonized S. aureus (open curve). (B) illustrates the two-color analysis profde of the granulocytes that were exposed to Texas Red-labeled S. aureus. Red fluorescence is the result of particle association with each granulocyte, whereas green fluorescence is the result of the oxidation of 2, 7 -dichlorofluorescin to 2, 7 -dichlorofluorescein (DCF). The red and green fluorescence analyses were performed with log-scale detection amplification for each fluorochrome.

Compared to the original particles, the new particles associated with c, cj have been dressed by the dynamic correlations in U. Consequently, we can represent the exact wavefunction as a simpler function of the new particles. 

Quantum mechanics tells us that the forces of nature can manifest themselves as particles. Photons of light, for example, are the particles associated with the electromagnetic force. Such particles are not constituents of matter they have an entirely different character. The photons that are responsible for electromagnetic forces are never observed. They are emitted by one matter particle and absorbed by another before they can be detected. However, there is little doubt that these phenomena take place because there is ample indirect evidence that they do. 

The form of nickel in particles from different industries varies. The mineralogical composition, chemical content, and form of dusts from nine industries in Cracow, Poland, were examined (Rybicka 1989). The chemical form of a particle-associated heavy metal that was assessed by a five-step extraction scheme classified the metal as exchangeable, easily reducible (manganese oxides, partly amorphous iron oxyhydrates and carbonates), moderately reducible (amorphous and poorly crystallized iron oxyhydrates), organically bound or sulfidic, and residual. Dusts from power plants had a silicate characteristic with quartz and mullite predominant. Approximately 90% of the nickel from these... 

Rogge, W. F., L. M. Hildemann, M. A. Mazurek, G. R. Cass, and B. R. T. Simoneit, Mathematical Modeling of Atmospheric Fine Particle-Associated Primary Organic Compound Concentrations, J. Geophys. Res., 101, 19379-19394 (1996). 

The physical and chemical complexity of primary combustion-generated POM is illustrated in Fig. 10.1 (Johnson et al., 1994), a schematic diagram of a diesel exhaust particle and associated copollutants. The gas-phase regime contains volatile (2-ring) PAHs and a fraction of the semivolatile (3- and 4-ring) PAHs. The particle-phase contains the remainder of the semivolatile PAHs ( particle-associated ) along with the 5- and 6-ring heavy PAHs adsorbed/absorbed to the surface of the elemental carbon spheres that constitute the backbone of the overall diesel soot particle. Also present is sulfate formed from oxidation of sulfur present in the diesel fuel and gas- and particle-phase PACs. 

Whether or not a given PAH exists virtually entirely in the gas phase or in the particle phase, or is partitioned between them, is a critical factor in determining its physical and chemical fates in ambient air and in subsequent intra- and intermedia transport through our air/water/soil environments. This is true not only for physical processes such as wet and dry deposition but also for their chemical reactivity, lifetimes, and fates in VOC-NOx systems characteristic of polluted airsheds. For example, the homogeneous gas-phase reactions of pyrene and fluoranthene differ dramatically from the rates, mechanisms, and products of their particle-associated heterogeneous reactions (Sections E and F). 

A. NOMENCLATURE AND SELECTED PHYSICAL AND SPECTROSCOPIC PROPERTIES OF PAHs AND PACs 457 TABLE 10.8 Sum of the Particle-Associated (Filter) and Gas-Phase (Solid Adsorbent, PUF Plugs or Tenax Cartridges8) Concentrations of EPA Priority PAH Pollutants and the Percentage of Each PAH in the Particle Phase ... 

As examples, the term blow off refers to a phenomenon in which the pressure drops across a filter can cause particle-associated SOCs (e.g., 3- and 4-ring... 

Dibenzo[a,/]pyrene, a potent mutagen in the MCL-5 assay, was not detected in this analysis of SRM 1649. However, this 6-ring PAH XXIX was identified (but not quantified) by comparison to an authentic standard by Allen and co-workers (1998) in their analysis of size-segregated aerosols in urban Boston ambient air. Furthermore, in their August 1994 study of biologically active, particle-associated PAHs in ambient Riverside, California, Atkinson and Arey (1997) measured concentrations of 18, 20, and 15 pg m-3 of this compound for one daytime and two nighttime sampling events, respectively. These concentrations were 40-50% of the BaP concentrations in the same aerosol samples. 

E. ATMOSPHERIC FATES OF PARTICLE-ASSOCIATED PAHs HETEROGENEOUS REACTIONS... 

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