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A new technique for measuring the spatial and temporal structure of the poloidal field is presented, whereby the magnetic field causes the polarization of light traveling through an optical fiber to rotate via the Faraday effect by an amount proportional to the strength of the field oriented along the fiber. In fiber optic pulsed polarimetry, changes in the polarization of the backscatter light from the fiber are detected, thereby permitting measurement of the field as a function of position along the fiber. In this proof-of-principle experiment, specially prepared single-mode fibers with weak fiber Bragg gratings were installed in the poloidal direction on the outside of the thermal blanket on DIII-D. Light at 532 nm from a mode-locked Nd:YAG laser was injected into the optical fibers. The laser repetition rate was 895 kHz with a pulse length of <10 ps, resulting in ∼1 µs temporal resolution. A photodetector system measured the Stokes polarization components necessary to determine the amount of polarization rotation. For this experiment, bandwidth limitations of the detectors resulted in a spatial resolution of ≈2 cm. The measured temporal and spatial distributions of the poloidal field are consistent with inductive probe measurements and Elastodynamic Finite Integration Technique reconstructions of the spatial distribution. This demonstrates the ability of this technique to provide real-time detection of the temporal and spatial variations of the poloidal field. Besides revealing more detailed information about the plasma, this new diagnostic capability can also help in detecting instabilities in real time, thereby enabling enhanced machine protection.

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We demonstrate that the giant chirp of coherent, nanosecond pulses generated in an 846 m long, all-normal dispersion, nanotube mode-locked fiber laser can be compensated using a chirped fiber Bragg grating compressor. Linear compression to 11 ps is reported, corresponding to an extreme compression factor of ∼100. Experimental results are supported by numerical modeling, which is also used to probe the limits of this technique. Our results unequivocally conclude that ultra-long cavity fiber lasers can support stable dissipative soliton attractors and highlight the design simplicity for pulse-energy scaling through cavity elongation.

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RGS4, a mammalian GTPase-activating protein for G protein alpha subunits, requires its N-terminal 33 amino acids for plasma membrane localization and biological activity (Srinivasa, S. P., Bernstein, L. S., Blumer, K. J., and Linder, M. E. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 5584-5589). In this study, we tested the hypothesis that the N-terminal domain mediates membrane binding by forming an amphipathic alpha-helix. RGS4 bound to liposomes containing anionic phospholipids in a manner dependent on the first 33 amino acids. Circular dichroism spectroscopy of a peptide corresponding to amino acids 1-31 of RGS4 revealed that the peptide adopted an alpha-helical conformation in the presence of anionic phospholipids. Point mutations that either neutralized positive charges on the hydrophilic face or substituted polar residues on the hydrophobic face of the model helix disrupted plasma membrane targeting and biological activity of RGS4 expressed in yeast. Recombinant mutant proteins were active as GTPase-activating proteins in solution but exhibited diminished binding to anionic liposomes. Peptides corresponding to mutants with the most pronounced phenotypes were also defective in forming an alpha-helix as measured by circular dichroism spectroscopy. These results support a model for direct interaction of RGS4 with membranes through hydrophobic and electrostatic interactions of an N-terminal alpha-helix.

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Manganese tetroxide (Mn3O4) is a product from the combustion of methylcyclopentadienyl manganese tricarbonyl. Exposure to high levels of manganese can lead to serious health effects especially to the central nervous and respiratory systems. Very few studies on the effects of long-term low level exposure to Mn3O4 have been reported. The present study was therefore conducted to examine the bioaccumulation and toxicity of manganese in various organs of feral pigeons (Columba livia) when exposed to low levels of Mn3O4 via inhalation and hence to find any possible relationship between these two parameters. A total of 22 pigeons was exposed to 239 micrograms/m3 of manganese for 7 h/day, 5 days/week for 5, 9, and 13 consecutive weeks. Manganese concentrations in various tissues, e.g., brain (mesencephalon), lung, liver, intestine, pancreas, kidney, muscle, bone, and whole blood, were measured by neutron activation analysis. Various biochemical parameters in blood, e.g., hematocrit, total proteins, glucose, uric acid, alanine aminotransferase, total iron, blood urea nitrogen and triglycerides, were also measured. Manganese concentrations in brain, lung, and bone were significantly higher in Mn3O4-exposed pigeons (0.59, 0.58, and 3.02 micrograms wet tissue, respectively) than in the control group (0.46, 0.19, 1.74 micrograms/g wet tissue, respectively). However, except for total proteins such exposure did not produce any changes in various biochemical parameters which were within the normal values. Thus these results have shown that, despite significant bioaccumulation of manganese in some tissues, no significant toxic effects could be seen.

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Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organometallic compound used as an octane improver in unleaded gasoline. The combustion of MMT leads to the formation of manganese (Mn) oxides, mainly Mn3O4. The objective of this study is to assess the variations over time and space of respirable (MnR) and total (MnT) Mn in the urban atmosphere and to evaluate human exposure by inhalation. Two sampling sites were selected on the island of Montreal based on their local traffic density (municipal botanical garden, C- = 10,000-15,000 vehicles d-1; Montreal Waterworks, C+ = 100,000-130,000 vehicles d-1). Air samplings were made during the day at stations located 10 m from the road using portable pumps, some of which were equipped with a cyclone. MnR and MnT and other metals were measured on Teflon filters by neutron activation. Mn exposure doses by inhalation were calculated using Monte-Carlo simulations. MnR and MnT average concentrations were significantly higher at site C+ (MnR = 0.024 microgram m-3; MnT = 0.050 microgram m-3) than at site C- (MnR = 0.015 microgram m-3; MnT = 0.027 microgram m-3). Temporal profiles at sites C+ and site C- were similar, with a coefficient of correlation of 0.24 for MnR and 0.26 for MnT. Trend analyses (ARIMA) also showed that the period of the week (work days vs. off days) was significantly related to MnR and MnT variations at both sites. The average exposure dose by inhalation to MnR and MnT ranged from 0.001 to 0.030 microgram kg-1 day-1 and 0.001 to 0.05 microgram kg-1 day-1. MnR and MnT concentrations reflected a positive relationship with traffic density. However, it remains difficult to attribute these results directly to the combustion of MMT in unleaded gasoline. On average, the MnR and MnT inhalation doses were 2 to 15 times lower than the reference dose (RfC) proposed by the U.S. Environmental Protection Agency (EPA) for the general population.

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The organization and acetylation of nascent histones prior to their stable incorporation into chromatin were examined. Through sedimentation and immunoprecipitation analyses of HeLa cytosolic extracts, two somatic non-nucleosomal histone complexes were detected: one containing nascent H3 and H4, and a second containing H2A (and probably H2B) in association with the nonhistone protein NAP-1. The H3/H4 complex has a sedimentation coefficient of 5-6S, consistent with the presence of one or more escort proteins. H4 in the cytosolic H3/H4 complex is diacetylated, fully in accord with the acetylation state of newly synthesized H4 in chromatin. The diacetylation of nascent human H4 is therefore completed prior to nucleosome assembly. As part of our studies of the nascent H3/H4 complex, the cytoplasmic histone acetyltransferase most likely responsible for acetylating newly synthesized H4 was also investigated. HeLa histone acetyltransferase B (HAT B) acetylates H4 but not H3 in vitro, and maximally diacetylates H4 even in the presence of sodium butyrate. Human HAT B acetylates H4 exclusively on the lysine residues at positions 5 and 12, in complete agreement with the highly conserved acetylation pattern of nascent nucleosomal H4 (Sobel et al., 1995), and has a native molecular weight of approximately 100 kDa. Based on our findings a model is presented for the involvement of histone acetylation and NAP-1 in H2A/H2B deposition and exchange, during nucleosome assembly and chromatin remodeling in vivo.

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This paper presents the results of a risk assessment study made using CalTOX, a multimedia, multiple pathway risk assessment model. The case study is based on the Polycyclic Aromatic Hydrocarbon (PAH) soil contamination resulting from the activities of a natural gas power station over a period of 70 years. It describes model characteristics and input parameters such as physico-chemical properties, landscape description, and human exposure factors. Model simulations and risk estimations corresponding to different remedial scenarios in an industrial zone are also presented. These estimations were based on soil contamination by 16 PAHs in the root-zone and vadose-zone layer. Results show that adult exposure (workers) to contaminated soil will lead to a potential health risk of carcinogenic effects, and to no potential risk of non-carcinogenic effects. On the other hand, the addition of 10 cm of clean soil over the contaminated soil (mitigated scenario) decreases the lifetime cancer risk to an acceptable level. The sensitivity analysis showed that the half-life of benzo[a]pyrene in the root-zone soil is the most sensitive parameter and that it contributes significantly to the variability of the cancer risk estimation. In addition, the cancer risk level of the workers exposed to this substance, as estimated by CalTOX (point estimate) in the mitigated and unmitigated scenario, corresponds approximately to the 95th percentile value obtained by means of Monte-Carlo simulations. Finally, CalTOX has proven to be a valuable tool to predict and elaborate scenarios for the risk management of sites contaminated as a result of industrial activities.

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Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic derivative of manganese (Mn) used as an additive in unleaded gasoline. The combustion of MMT leads to the formation of oxides of manganese. The objective of the present study is to predict the environmental levels of Mn and the human exposure in the St-Lawrence ecozone (fluvial section, Quebec, Canada) using an environmental fate/exposure model: GEOTOX. The results of our MMT research program on abiotic and biotic components of the ecosystem and on the human exposure were used to validate the model estimations. Air and surface soil were selected as source terms with an annual Mn input rate in each compartment of 0.083-0.113 mol km-2 d-1 and 0.44-0.87 mol km-2 d-1 respectively (Mn3O4 equivalent). The predicted air, soil, plant, surface water and sediment concentrations were similar (+/- 50%) to values measured in the Montreal region. As expected, the ingestion pathway was the main absorption route for adults (> 99%), with vegetables and fruits contributing almost 80% of the dietary intake of Mn. The multimedia exposure doses for adult men predicted by the model ranged between 0.04 and 0.08 mg kg-1 d-1 compared to 0.004 and 0.201 mg kg-1 d-1 (average = 0.05) for workers from the MMT study. Considering the landscape configuration and the source vectors (air and soil) included in the model, GEOTOX estimations were in good agreement with measured values.

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This research measured the exposure of two groups of workers to respirable and total manganese (Mn) and characterized the Mn particles emitted from an automobile tailpipe. The exposure of 20 office workers and 9 taxi drivers in Toronto to total airborne Mn and respirable Mn was measured over a 7-day period, 24 hours per day. Subjects were asked to wear two pumps (one included a size-selective cyclone that collected the respirable particles), and two battery chargers were supplied to each person so that the pump batteries could be recharged overnight while sampling continued. All filters were analyzed by neutron activation. In addition, Mn particles emitted from a car were collected directly at the exhaust. Particles were observed using secondary electron images in a scanning electron microscope (SEM), and their elemental composition was determined by energy dispersive x-ray spectrometry. The Mn concentrations obtained for the group of office workers ranged from 0.001 to 0.034 microgram/m3 for respirable Mn and from 0.002 to 0.044 microgram/m3 for total Mn. For the taxi drivers the Mn concentrations ranged from 0.007 to 0.032 microgram/m3 for respirable Mn and from 0.008 to 0.073 microgram/m3 for total Mn. There was a significant difference (p < 0.05) between the two groups for both respirable and total Mn. SEM analysis showed that the particles were mostly heterogeneous agglomerates varying from 1 to 100 microns. Even if the specific exposure to Mn from automobiles has not been directly established, these results suggest that the related increase of exposure may be limited.

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The Mn contamination arising from the combustion of MMT (methylcyclopentadienyl manganese tricarbonyl) in unleaded gasoline was assessed using snow collected at different distances 15, 25, 125 and 150 m from an expressway (Montreal, Canada) in February 1993. The snow samples were analyzed by atomic absorption and by neutron activation for total Mn, Mg, Cu, V, Al, Zn, Fe, Na, and Ca concentrations in the soluble (<0.4 microm) and particulate fractions. ANOVA with ranked values was performed to compare element concentrations and soluble/particulate ratios among receptor sites and depths. Principal component analysis was used to describe the spatiotemporal variations of the deposition rates and the influence of meteorological factors. The average concentration of all trace elements, except Mg, Cu, and V, decreased significantly (p<0.05) from receptor sites near the road (15-25 m) to those farther away (125-150 m). The deposition rates of all metals and ions, except Cu, were highly positively correlated (tau = 0.5-0.9) with each other and inversely correlated with snowfalls. Wind frequency showed no correlation with deposition rate. The spatial trend was similar for all these elements making it difficult to distinguish Mn arising from the combustion of MMT from that due to other sources, such as road dust. Only the soluble/particulate ratio calculated for Mn seemed higher than that for the other metals, which might be explained by the particle size of Mn from MMT (0.2-0.4 microm). The present study only indicates a direct contamination of the snow by road activities and substantial deposition of trace elements near the roadway; no clear link can be established between motor vehicle emissions and the concentration of Mn in snow.

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Inhalation exposure to manganese (Mn) was measured for a group of garage mechanics and a control group of nonautomotive workers. The airborne Mn exposure of 35 garage mechanics suspected of being relatively highly exposed to Mn from MMT was measured at the workplace over one-week period. It also was measured for 30 nonautomotive workers at the University of Montreal. The environmental exposure also was measured for the two groups, as was the exposure to three other metals, aluminum (Al), iron (Fe), and zinc (Zn). At work the mechanics were exposed to Mn concentrations varying from 0.010 to 6.673 micrograms m-3 with a mean of 0.45 microgram m-5, while the control group was exposed to concentrations varying from 0.011 to 1.862 microgram m-3 with a mean of 0.04 microgram m-3. The mean environmental exposure for the two groups was similar to the Mn concentrations gathered in Montreal in 1992. Workplace concentrations of Al, Fe, and Zn also were higher for the garage mechanics. The results suggest that less than 10% of the Mn exposure of the garage mechanics was due to MMT. The levels of the metals measured were below the established limits for industrial and even environmental exposure.

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Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic additive used in Canada since 1976 as an anti-knock agent in unleaded gasoline. Its combustion leads to the emission of Mn oxides, especially Mn3O4. Since no study has assessed the potential risk of chronic exposure to low concentrations resulting from these emissions, the present investigation was undertaken to assess the level of environmental and occupational exposure of the human population. The multimedia exposure of two groups of workers (garage mechanics and blue-collar workers) potentially exposed to different levels of Mn from the combustion of MMT was assessed using personal air samplers, a dietary compilation, water samples at their places of residence, an epidemiological questionnaire and blood and hair samples. Results show that garage mechanics were exposed on average to higher atmospheric Mn at work (0.42 microgram/m3) than the blue-collar workers (0.04 microgram/m3). However, the contribution of atmospheric Mn to the total absorbed dose was less than 1%, and well below the standards established for occupational or environmental exposure; food contributes more than 95% of the multimedia dose. The average whole blood Mn concentrations were similar for the two groups (0.67-0.76 microgram/100 ml) and fall within the normal adult range. The average hair Mn concentrations were significantly higher for the garage mechanics (0.66 microgram/g) than for the blue-collar workers (0.39 microgram/g). The contribution of exogenous Mn versus endogenous Mn is questioned. As judged by the governmental standards or criteria for occupational and non-occupational environments, the current Mn levels in food, water and air may not cause any problems for the workers.

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Methylcyclopentadienyl manganese tricarbonyl (MMT) has been used in Canada since 1976 as an additive in unleaded gasoline. The combustion of MMT leads to the emission of Mn oxides to the environment and may represent a potential risk to public health. It therefore seems important to assess the associated Mn exposure. The present study is part of a broader research program on total human exposure to Mn and aims specifically at assessing the level of exposure to Mn and other metals via drinking water. A comparative study was performed between two groups of workers (garage mechanics and blue collar workers of the University of Montreal) differentiated by their exposure to inhaled Mn. For Pb, Cu and Zn in residential tap water, significant differences were observed between the first sample and the one taken after one minute of flow. A significant difference was also found between the two groups of workers (combined flow time) for Mn, Cu and Ca. The Mn contribution from water is estimated to be 1% of the total dose from ingested food. This low exposure may become important (17%) for persons drinking well water, especially if we consider interactions between metals following multimedia exposure.

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Occupational and environmental exposure to airborne manganese has been measured for two groups of workers in Montreal, taxi drivers and garage mechanics. In Canada methylcyclopentadienyl manganese tricarbonyl (MMT) has replaced lead as an anti-knock agent in gasoline and represents a potentially important source of manganese contamination for the population in general and for the two chosen groups of workers in particular. Twenty workers (10 taxi drivers and 10 garage mechanics) wore a personal air sampler for five consecutive working days and two off-work periods. The amount of total Mn on each filter was determined by neutron activation analysis and then converted to atmospheric Mn concentrations. The values obtained varied from 0.004 microgram m-3 to 2.067 micrograms m-3. At work the garage mechanics were exposed to an average of 0.250 microgram m-3 and the taxi drivers to 0.024 microgram m-3. Off-work, the two groups were exposed respectively to an average of 0.007 microgram m-3 and 0.011 microgram m-3. In the garages there was twice as much Mn in the air on days when the doors were closed compared to days when they were left opened (0.314 micrograms m-3/0.152 microgram m-3). The levels found in this study remain well below the established limits for occupational and environmental airborne exposure. These results will lead to further studies to positively identify the source of Mn as MMT and to explore other pathways leading to the contamination of the general population.

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