Intra-Community Variability in Total Particle Number Concentrations in the San Pedro Harbor Area (Los Angeles,California)

Recent evidence links elevated ultrafine particle (UFP) concentrations with adverse health effects, but exposure assessments based upon PM _2.5 mass concentrations may be misleading. In order to better understand and quantify intra-community variability in UFP concentrations, a dense network of 14 monitoring sites was set-up in Los Angeles in two clusters—San Pedro/Wilmington and West Long Beach—in communities surrounding the Ports of Los Angeles and Long Beach. The network measured total particle number concentrations greater than 7 nm in diameter. In this range, UFP comprise approximately 90% of the total. Port-related activities—particularly goods movement associated with high volumes of heavy-duty diesel vehicle (HDDV) traffic—represent significant UFP sources. The field study was conducted from mid-February through mid-December 2007 to assess diurnal, seasonal, and spatial patterns and intra-community variability in total particle number concentrations. For sites within a few km of each other, simultaneous particle number concentrations can vary up to a factor of 10 (< 10,000 cm^?3 up to 90,000 cm^?3 for hourly averages calculated by month). The median hourly correlation coefficient (r) across all sites was modest and varied from 0.3 to 0.56. Specific site locations, particularly proximity to roadways used for goods movement, strongly affect observations. Clear diurnal and seasonal patterns are evident in the data. A diurnal pattern associated with high HDDV volumes and goods movement was identified. Coefficients of Divergence calculated for the site pairs suggest moderate heterogeneity overall (median study COD ≈ 0.35). The intra-urban variability observed in this study is comparable to and exceeds the inter-urban variability observed in a previous study in Los Angeles. UFP concentrations can vary considerably on short spatial scales in source-rich environments strongly influencing the accuracy of exposure assessments.     

Soil Erosion Assessment in a Hilly Catchment of North Eastern India Using USLE, GIS and Remote Sensing

In the present study, soil erosion assessment of Dikrong river basin of Arunachal Pradesh (India) was carried out. The river basin was divided into 200 × 200 m grid cells. The Arc Info 7.2 GIS software and RS (ERDAS IMAGINE 8.4 image processing software) provided spatial input data and the USLE was used to predict the spatial distribution of the average annual soil loss on grid basis. The average rainfall erositivity factor (R) for Dikrong river basin was found to be 1,894.6 MJ mm ha⁻¹ h⁻¹ year⁻¹. The soil erodibility factor (K) with a magnitude of 0.055 t ha h ha⁻¹ MJ⁻¹ mm⁻¹ is the highest, with 0.039 t ha h ha⁻¹ MJ⁻¹ mm⁻¹ is the least for the watershed. The highest and lowest value of slope length factor (LS) is 53.5 and 5.39 respectively for the watershed. The highest and lowest values of crop management factor (C) were found out to be 0.004 and 1.0 respectively for the watershed. The highest and lowest value of conservation factor (P) were found to be 1 and 0.28 respectively for the watershed. The average annual soil loss of the Dikrong river basin is 51 t ha⁻¹ year⁻¹. About 25.61% of the watershed area is found out to be under slight erosion class. Areas covered by moderate, high, very high, severe and very severe erosion potential zones are 26.51%, 17.87%, 13.74%, 2.39% and 13.88% respectively. Therefore, these areas need immediate attention from soil conservation point of view.     

Predictive model for vehicle air exchange rates based on a large, representative sample

The in-vehicle microenvironment is an important route of exposure to traffic-related pollutants, particularly ultrafine particles. However, significant particle losses can occur under conditions of low air exchange rate (AER) when windows are closed and air is recirculating. AERs are lower for newer vehicles and at lower speeds. Despite the importance of AER in affecting in-vehicle particle exposures, few studies have characterized AER and all have tested only a small number of cars. One reason for this is the difficulty in measuring AER with tracer gases such as SF(6), the most common method. We developed a simplified yet accurate method for determining AER using the occupants' own production of CO(2), a convenient compound to measure. By measuring initial CO(2) build-up rates and equilibrium values of CO(2) at fixed speeds, AER was calculated for 59 vehicles representative of California's fleet. AER measurements correlated and agreed well with the largest other study conducted (R(2) = 0.83). Multivariable models captured 70% of the variability in observed AER using only age, mileage, manufacturer, and speed. These results will be useful to exposure and epidemiological studies since all model variable values are easily obtainable through questionnaire.     

Hepatitis B Virus Infection,MicroRNAs and Liver Disease

Hepatitis B virus (HBV) attacks the liver and can cause both acute as well as chronic liver diseases which might lead to liver cirrhosis and hepatocellular carcinoma. Regardless of the availability of a vaccine and numerous treatment options, HBV is a major cause of morbidity and mortality across the world. Recently, microRNAs (miRNAs) have emerged as important modulators of gene function. Studies on the role of miRNA in the regulation of hepatitis B virus gene expression have been the focus of modern antiviral research. miRNAs can regulate viral replication and pathogenesis in a number of different ways, which includefacilitation, direct or indirect inhibition, activation of immune response, epigenetic modulation, etc. Nevertheless, these mechanisms can appropriately be used with a diagnosticand/or therapeutic approach. The present review is an attempt to classify specific miRNAs that are reported to be associated with various aspects of hepatitis B biology, in order to precisely present the participation of individual miRNAs in multiple aspects relating to HBV.     

A novel bipolar charger for submicron aerosol particles using carbon fiber ionizers

A simple and novel bipolar charging device using carbon fiber ionizers was developed to neutralize submicron aerosol particles without the generation of ozone. The ion currents of the positive and negative ions generated by carbon fiber ionizers were so chosen as to optimize particle neutralization. The particle penetration, charging probability and charge distribution resulting from the charger were investigated and compared to those from a Kr-85 radioactive neutralizer for the particles in the size range of 20–120 nm. Size distributions for various laboratory-generated aerosols (sodium chloride, ammonium nitrate, ammonium sulfate and glutaric acid) neutralized by the charger were also investigated and compared to those obtained without neutralization. Particle penetration in the charger was over 90% for particles larger than 20 nm. Charging probability and charge distribution for the charger were in good agreement with those from Kr-85 neutralizer and with theoretical estimations. Size distributions observed for the charger and Kr-85 neutralizer were also in good agreement for particles of different concentrations and various chemical compositions. The newly developed bipolar carbon fiber charger can neutralize submicron particles, at least as effectively as currently available radioactive neutralizers and with negligible ozone generation which is its major advantage.     

Simulation studies on the origin of the limiting conversion phenomenon in hybrid miniemulsion polymerization

Hybrid systems of acrylic monomers are studied as they undergo miniemulsion free radical polymerization in the presence of unsaturated alkyd resins. The goal of such polymerizations is to induce grafting between the acrylic and alkyd components, which would retard microdomain phase separation, and produce materials with the crosslinking capability of alkyd coatings (normally applied from a solvent system) with the environmental and cost benefits of an aqueous system. In this paper, the observed limiting monomer conversion phenomenon will be explored via simulation studies.Two mathematical models describing the kinetics of bulk hybrid polymerization of an alkyd-acrylate system were developed. The first was a homogenous model in which the kinetics of retardive chain transfer was used to attempt to simulate the observed phenomenon of limiting conversion. The second model was a core-shell model in which polymerization takes place in an acrylic-rich shell, while the alkyd-rich core serves as a reservoir for acrylic monomer and alkyd. Based on the results from these models, the cause of limiting conversion was attributed to the combined role of the glass effect and the partitioning effect of the monomer into a core-shell system and its subsequent entrapment. Retardive chain transfer was not capable of producing the observed limiting conversion.     

Vehicle and driving characteristics that influence in-cabin particle number concentrations

In-transit microenvironments experience elevated levels of vehicle-related pollutants such as ultrafine particles. However, in-vehicle particle number concentrations are frequently lower than on-road concentrations due to particle losses inside vehicles. Particle concentration reduction occurs due to a complicated interplay between a vehicle's air-exchange rate (AER), which determines particle influx rate, and particle losses due to surfaces and the in-cabin air filter. Accurate determination of inside-to-outside particle concentration ratios is best made under realistic aerodynamic and AER conditions because these ratios and AER are determined by vehicle speed and ventilation preference, in addition to vehicle characteristics such as age. In this study, 6 vehicles were tested at 76 combinations of driving speeds, ventilation conditions (i.e., outside air or recirculation), and fan settings. Under recirculation conditions, particle number attenuation (number reduction for 10-1000 nm particles) averaged 0.83 ± 0.13 and was strongly negatively correlated with increasing AER, which in turn depended on speed and the age of the vehicle. Under outside air conditions, attenuation averaged 0.33 ± 0.10 and primarily decreased at higher fan settings that increased AER. In general, in-cabin particle number reductions did not vary strongly with particle size, and cabin filters exhibited low removal efficiencies.