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It is well documented that per- and polyfluoroalkyl substances (PFAS) are routinely detected in leachate from municipal solid waste (MSW) landfills. PFAS-containing products are ubiquitous in society and in end-of-life discarded materials. While considerable data have been generated in recent years for PFAS concentrations in landfill leachate, little published information exists concerning longer-term trends in leachate concentrations. In this study, we examine a ten-year dataset for three MSW landfills located in the upper Midwestern United States where leachate PFAS testing has been performed on a quarterly basis. The significance of these data are considered in light of phase-out initiatives implemented in the US manufacturing companies for longer-chain PFAS including perfluorooctanoic acid (PFOA), perfluorooctane sulphonate (PFOS) and perfluorononanoic acid (PFNA). Findings from this study indicate that the average concentration of longer-chain PFOA in the three landfills decreased from 2400 to 1900 ng/L and the average PFOS concentrations decreased from 1000 to 370 ng/L. This may be indicative of reduced domestic production and use of these compounds. The phase-out of long-chain PFAS has also led to the introduction of shorter-chain replacement compounds such as perfluorobutanoic acid, perfluorobutane sulphonate and perfluorohexanoic acid, and this paper also examines long-term trends in leachate concentrations of these compounds.

Low on-resistance LDMOS transistors frequently utilize a self-aligned body to minimize resistance and size of the device. This paper discusses the challenges associated with ultra-short channels and proposes contrarian solutions to address them while maintaining key operating characteristics. These include a retrograde body for e-field modulation and an elegant, cost effective process flow incorporating a self-aligned body and hybrid source. The novel architectures are illustrated by simulation and 12V n-LDMOS implementation on a 0.18um SOI platform.

Notas: Documento pegado a una hoja en blanco., Tipo de publicación: Periódico, Título de la publicación: The Miami News, Periodicidad: Diario

This paper introduces the first application of a Schottky source approach for the purpose of expanding the Electrical Safe Operating Area (E-SOA) of a HV Transistor. Replacing the conventional PN source with a Schottky source suppresses the parasitic BJT enabling significant improvement in the E-SOA, particularly for very fast pulses. Under these conditions, improvement in the trigger voltage and current of a 40V n-LDMOS is 5.6% and 117% respectively. The breakdown voltage of 57V is maintained and a competitive on-resistance of 31.5 mOhm.mm2 achieved.

This paper explores the application of a statistical analysis technique known as ‘wavestrapping’ to a railway data analysis problem in train aerodynamics. This simulation technique is used to reproduce/reconstruct signals with the same statistical properties of the initial signal(s) and to estimate an extreme value in train aerodynamics. This technique is compared with the method currently used in practice to estimate the peak value of slipstream air speed, according to the European standard EN 14067.

This chapter considers the effects of high winds on train operation. The various issues that arise from trains in high crosswinds are first outlined and a generic methodology is proposed for the consideration of these issues. Firstly, methods are outlined for determining the aerodynamic force and moment coefficients through the use of full-scale testing, physical model testing and CFD calculations. It is clear that the nature of the crosswind flow around trains at full scale is very complex, and model scale measurements and CFD calculations only provide a limited representation of the full-scale situation. Nonetheless, the force and moment coefficients from such tests are adequate for the overall calculation methodology. Such measurements have been made for a wide variety of trains in many different situations. These are tabulated in Appendix 2 , and this chapter provides a simple method of parameterising the results. A range of methods for simulating the natural wind are then critically presented, and the manner in which these simulations are combined with the force and moment coefficients and models of the vehicle dynamic system are set out to calculate the characteristic wind curve, which is used for train authorisation purposes. A simple methodology for calculating such curves is then described. Methods are then outlined for the calculation of the probability of a wind-induced accident occurring along an entire route. Finally, methods of reducing this accident risk, both through physical interventions and operational strategies, are discussed.

This chapter, building on the description of tunnel pressures and flows in Chapter 6 , discusses a range of practical issues associated with aerodynamic effects in railway tunnels. Firstly, pressure transients in tunnels are considered, and the range of methods used for calculating pressure transients in tunnels is set out, together with their input requirements. Aural pressure comfort is then considered, and the pressure transient limits specified by standards are described, together with an overview of the experiments from which these standards were derived. A probability-based approach to assessing aural comfort is also provided. Methods of reducing these pressure transients are then presented – through modification of tunnel geometry and train operating conditions, through the provision of airshafts or through the sealing of trains. Secondly, the emission of micropressure waves from tunnels is considered. Methods to reduce the inlet pressure gradients (and thus to reduce the magnitudes of these waves) are described – tunnel entrance hoods, elongated train noses, provision of cross shafts and the use of both passive and active aerodynamic damping devices. Finally, the chapter describes a range of other tunnel aerodynamic issues – train drag in tunnels, structural loading in tunnels and on trains and the very specific problems associated with long tunnels.

This chapter considers the aerodynamic behaviour of pantographs and overhead line systems. After an introduction to the geometry of such systems, the mechanical and aerodynamic forces on the overhead wire are set out. The static and dynamic displacement of the wire due to wind effects is described. Wire instabilities caused by galloping are then discussed at length and the circumstances under which these instabilities might occur are derived. The different types of pantograph are then discussed and the types of mechanical and aerodynamic forces experienced by pantographs are outlined. Full-scale measurements, wind tunnel measurements and CFD calculations of pantograph aerodynamic characteristics are considered. The important issue of pantograph aerodynamic optimisation is then discussed at length for both lift forces and drag forces. Finally, methods are described for analysing the dewirement problem and for predicting the risk of such incidents.

This chapter sets out some basic fluid mechanics concepts that are required in the study of train aerodynamics and that will be referred to later in this book. Dimensionless analysis and dimensionless variables are described, and this is followed by a discussion of two different frames of reference – the ground and train frames. Qualitative descriptions are then given of the principles of conservation of mass, momentum and energy, and of the concepts of free flows, boundary layers, turbulence, separated flows and wakes. This leads into a more quantitative discussion of the equations of motion in a variety of different forms, which will all be referred to later in this book. This section attempts to show the interrelated nature of many of the practical problems in train aerodynamics that might otherwise appear quite diverse. The nature of flow turbulence is then discussed in more detail, and this is followed by a description of the natural wind close to the ground, including wind speed probabilities, wind speed and turbulence profiles and turbulence spectra.

This chapter gives an introduction to the flow around trains in the open air and provides the basic description of the flow field on which the discussion of the applications in Part 2 is based. The discussion is built on the results of full-scale experiments, for a wide range of different train types, with data from model-scale experiments and computational fluid dynamics being used where no full-scale data are available. Firstly, the flow around trains on level ground is discussed, and the five basic flow regions are introduced – the nose region, the boundary layer region, the near wake region, the far wake region and the underbody flow region. Each of these regions is then analysed in turn, and data for typical pressure and velocity fields are presented. Information is presented on nose peak-to-peak pressure coefficients: train side, roof and underbody boundary layer parameters and roof and underbody skin friction for different train types. The unsteady vortex flow in the near wake region of high-speed trains is discussed in qualitative terms. The discussion then moves on to consider the flow around trains on level ground in crosswinds, considering both low and high wind speed conditions. The complexity and transient nature of these flow fields is emphasised. Finally, the flow around trains in a range of different environments is presented, and the effects of ballast platform height, embankments, viaducts and different station environments are discussed.

This chapter describes the nature of the flow in railway tunnels and forms the basis for the consideration of a number of practical issues in tunnel aerodynamics in Chapter 12 . The nature of the pressure transients caused by trains passing through tunnels is discussed in detail, and in particular the large changes in pressure as the train enters the tunnel are described. The concept of wave diagrams is presented, and the way it can be used to describe wave interactions is illustrated. The various factors that are associated with tunnel pressure changes are set out and discussed. In addition to the pressure changes, velocity changes in tunnels as trains pass through are also presented. The effects of airshafts on both tunnel pressures and velocities are then considered. Finally, the issue of micropressure waves (or sonic booms) from the exits of tunnels is discussed – both in terms of their generation through the steepening of entry pressure transients and their radiation outside the tunnel.

This chapter considers the aerodynamic loads caused by passing trains on trackside structure, people and other trains. These loads are of two forms – pressure loads and slipstream loads. Pressure loads are considered first and then the ways of quantifying the peak-to-peak pressure transients are described. The use of full-scale measurements, physical model measurements and CFD calculations to calculate these transients are then described, and the role of simple analytical methods are discussed. A range of correlations of pressure load data from standards is then presented, primarily concerned with loads on vertical structures next to the track and horizontal surfaces above the track. Pressure loads in station environments and on passing trains are also considered. The ways in which these pressure loads can be used to calculate structural loading are then described, ranging from simple static methods through to fully dynamic methods. With regard to slipstream loads, full-scale measurements require the measurement of slipstream gust speeds from a large number of train passes and the formation of an ensemble of gust speeds. Both physical model tests and CFD have some limitations in providing similar data. A collation of gust velocities for a wide range of train types is presented. The application of these gust speeds to loading of people and objects is then considered. A number of different approaches can be used and an overall framework that shows the interaction between these approaches is set out and described.

The European Union Seventh Framework Programme research project AeroTRAIN aimed at delivering limit criteria for crosswinds to the ‘Rolling stock – locomotives and passenger rolling stock’ Technical Specification for Interoperability (CR LOC&PAS TSI) and for class 2 trains of the high-speed rolling stock TSI (HS RST TSI). A first objective was the assessment of characteristic wind curve (CWC) for identified class 2 and conventional vehicles with low, but sufficient, crosswind stability (as proven by their safe operational records) on the EN 14067-6: 2010 single track with ballast and rails (STBR) standard configuration. In the same manner, and as a second objective, Reference CWC and limit criteria for class 1 trains of HS RST TSI were planned to be determined. For all these trains, the aerodynamic coefficients were obtained in a unique wind tunnel campaign using the STBR ground configuration. Their crosswind sensitivity was assessed against a calculated CWC obtained from vehicle dynamics simulations. The resulting database will allow the derivation of the relevant limit criteria still needed for vehicle authorization regarding crosswind stability.

Plant roots are reported to enhance the aeration of soil by creating secondary macropores which improve the diffusion of oxygen into soil as well as the supply of methane to bacteria. Therefore, methane oxidation can be improved considerably by the soil structuring processes of vegetation, along with the increase of organic biomass in the soil associated with plant roots. This study consisted of using a numerical model that combines flow of water and heat with gas transport and oxidation in soils, to simulate methane emission and oxidation through simulated vegetated and non-vegetated landfill covers under different climatic conditions. Different simulations were performed using different methane loading flux (5–200 g m−2 d−1) as the bottom boundary. The lowest modeled surface emissions were always obtained with vegetated soil covers for all simulated climates. The largest differences in simulated surface emissions between the vegetated and non-vegetated scenarios occur during the growing season. Higher average yearly percent oxidation was obtained in simulations with vegetated soil covers as compared to non-vegetated scenario. The modeled effects of vegetation on methane surface emissions and percent oxidation were attributed to two separate mechanisms: (1) increase in methane oxidation associated with the change of the physical properties of the upper vegetative layer and (2) increase in organic matter associated with vegetated soil layers. Finally, correlations between percent oxidation and methane loading into simulated vegetated and non-vegetated covers were proposed to allow decision makers to compare vegetated versus non-vegetated soil landfill covers. These results were obtained using a modeling study with several simplifying assumptions that do not capture the complexities of vegetated soils under field conditions.

Solid waste landfills need to have final covers to 1) reduce the infiltration of rainfall into the waste mass and 2) reduce surface greenhouse gas emissions. Most regulations require that such final covers include hydraulic barriers, such as compacted clays with or without geomembrane. Significant research has been undertaken to allow the use of evapotranspiration-based covers (often termed: Evapotranspiration (ET) Cover, Water Balance Covers, or Phyto Covers) as an alternative to the barrier concept covers. ET covers are designed so that they have the capacity to store water by the soil and also have plants or vegetation to remove the stored water. In ET covers, plant roots can enhance the aeration of soil by creating secondary macropores which improve the diffusion of oxygen into soil. Therefore, biological methane oxidation (a natural process in landfill soils) can be improved considerably by the soil structuring processes of vegetation, along with the increase of organic biomass in the soil associated with plant roots. This paper summarizes a study to investigate the capacity of an ET cover to reduce surface greenhouse gas emissions when implemented on a solid waste landfill. This study consisted of using a numerical model to estimate methane emission and oxidation through an ET cover under average climatic conditions in Bennignton, Nebraska, USA. Different simulations were performed using different methane loading flux (5 to 200 gm-2·d-1) as the bottom boundary. For all simulations, surface emissions were the lowest during the growing season and during warmer days of the year. Percent oxidation is the highest during the growing season and during warmer days. The lowest modeled surface emissions were always obtained during the growing season. Finally, correlations between percent oxidation and methane loading into simulated ET covers were proposed to estimate methane emissions and methane oxidation in ET covers.

This is the first part of a two-part paper that describes the results of an experimental investigation to measure the aerodynamic pressure forces on structures in the vicinity of railway tracks. The investigations were carried out in order to obtain a fundamental understanding of the nature of the phenomenon and to obtain data for a variety of railway infrastructure geometries of particular relevance to the UK situation, in order to provide material for a National Annex to the relevant Eurocode. The experiments were carried out on the moving model TRAIN Rig, with models of three different sorts of trains with different nose types, and a variety of infrastructures types: vertical hoardings, overbridges, station canopies and trestle platforms. The transient loads that were measured had a characteristic form: a positive pressure peak followed by a negative pressure peak. In general the magnitudes of the two peaks were different, and varied with infrastructure type and position, as well as with train type. As would be expected, the more streamlined the train, the lower were the magnitudes of the pressure transients. A comparison of the experimental results was made with a variety of existing model- scale and full-scale data and a broad consistency was demonstrated, within the limits that the rather different experimental conditions in the various cases would allow. An analysis of the scaling of these pressure transients was carried out, and it was shown that whilst there was a reasonable coalescence around a theoretical formulation, the complexity of the flows involved meant that a general scaling formulation could not be achieved. Part 2 of this paper will consider the application of the results to the development of revised standards formulations.

As the speeds of both passenger and freight trains increase, there is increasing concern that the unsteady gusts generated in train boundary layers and wakes will become more of for a risk to passengers waiting on platforms and for trackside workers. In addition, the demands of interoperability make this a problem of growing relevance to railway operators across Europe. A number of model scale and full-scale experiments have been carried out in recent years that have provided robust experimental data to quantify these flows. This paper considers all the available datasets for high-speed passenger trains and container freight trains, and in making a comparison between them, arrives at a number of conclusions concerning the characteristics of train slipstreams. It is concluded that the identification of a number of distinct flow regions in earlier work is generally valid and forms a useful framework for the consideration of the problem. The flow characteristics are different in each region, and, depending upon the train type, the measurement distance from the train and height above ground, the observed peak gusts for a train may occur at any time during the train passage or in its wake. It is also concluded that results obtained from measurements around small scale moving models are in good agreement with the full scale measurements and reproduce all the important flow features.

Ottawa sand and a synthetic fiber were tested for filtration of stormwater sediments. Laboratory column tests were performed using water spiked with Bentonite clay as a surrogate for sediment. Filter media column height was varied from 20 cm to 90 cm. 10 to 20 pore volumes of Bentonite spiked water was permeated through each filter medium. Influent turbidity and effluent turbidity were monitored. Ratios of effluent turbidity to influent turbidity and hydraulic conductivity as a function of pore volumes of flow were evaluated for each filter medium as an indicator of hydraulic efficiency. Hydraulic conductivity of Ottawa sand and Synthetic Fiber were 0.08 cm/sec. and 0.20 cm/sec., respectively. Increase in filter column height of Ottawa sand increased the filtration efficiency as quantified by lower turbidity effluent vs. pore volume. However, hydraulic conductivity decreased with increasing filtration efficiency for Ottawa sand due to clogging. Compared to Ottawa sand, filtration efficiency and hydraulic conductivity of synthetic fibers was higher throughout the experiments.

A principal concern regarding the safety of HIV-1-based vectors is replication-competent lentivirus (RCL). We have developed two PCR assays for detecting RCL; the first detects recombination between gag regions in the transfer vector and the packaging construct (sensitivity of detection approximately 10-100 copies of target sequence). The second assay uses real-time PCR to detect vesicular stomatitis virus glycoprotein (VSVG) envelope DNA (sensitivity approximately 5-50 VSVG sequences). In an attempt to amplify any RCL, test vectors were used to transduce C8166 and 293 cells, which were then screened weekly for 3 weeks. Psi-gag recombinants were routinely detected (20 of 21 analyses) in four transductions using the RRL-CMV-GFP vector. In contrast, VSVG sequences were detected only once in 21 analyses. Interestingly, p24 levels (as measured by ELISA) were occasionally detectable after 3 weeks of culture. To determine if a true RCL was present, 21-day cell-free medium was used to transduce naïve cells. No evidence of psi-gag or VSVG transfer was detected, indicating that the recombination events were insufficient to reconstitute a true RCL. These findings have important implications for the design and safety of HIV-1-based vectors intended for clinical applications.

Landfill emissions include volatile organic compounds (VOCs) and, particularly, benzene, toluene, ethyl-benzene and xylene isomers (collectively called BTEX). The latter are the most common VOCs found in landfill biogas. BTEX affect air quality and may be harmful to human health. In conjunction with a study aiming to evaluate the efficiency of passive methane oxidizing biocovers, a complementary project was developed with the specific goal of evaluating the reduction in VOC emissions due to the installation of a biocover. One of the biocovers constructed at the Saint-Nicephore (Quebec, Canada) landfill site was instrumented for this purpose. The total BTEX concentration in the raw biogas ranged from 28.7 to 65.4ppmv, and the measured concentration of BTEX in biogas emitted through the biocover ranged from below the limit of detection (BLD) to 2.1ppmv. The other volatile organic compounds (OVOCs) concentration varied from 18.8 to 40.4ppmv and from 0.8 to 1.2ppmv in the raw biogas and in the emitted biogas, respectively. The results obtained showed that the biocover effectiveness ranged from 67% to 100% and from 96% to 97% for BTEX and OVOC, respectively.

Since the demise of the Soviet Union, and creation of the Russian Federation in 1992, the fishing industries of the Russian Far East (RFE) have undergone dramatic change.1 The Soviet Union was once the world's top fishing nation, and the fleets of the RFE produced some 70% of the total catch, which peaked in 1988 and 1989 at more than ten million metric tons (mmt). Current production is closer to 4.5 mmt, or about three-quarters of the volume of America's Pacific fisheries (including Alaska). Conversion from a command economy, where the Communist Party set production targets,2 to a market economy continues to occur throughout the industry. This conversion is accompanied by large-scale privatization of the capital resources of the country. Because the economic restructuring occurred largely as a result of the Soviet state's worsening financial condition, there has been little government aid available to struggling state enterprises, which previously made up the bulk of the fisheries production capacity, and little financial assistance available to the newlyconstituted private enterprises. This financial pinch initially has had several effects. One was a shortage of fuel, which kept many vessels in port. For example, in Petropavlovsk-Kamchatsky in 1993, dozens of trawlers, crabbers, and processors lay at the dock or anchored in scenic Avacha Bay due to a lack of fuel. Another was an inability to replace obsolete harvesting and processing equipment. At a time when Japanese importers were paying handsome prices for quality frozen sockeye salmon, Russian processors were forced to salt or can their fish for the low-priced domestic market if they could even obtain sufficient cans or salt to do the job. However, Russian entrepreneurs soon devised creative financing schemes, or entered into various kinds of joint ventures with foreigners. Fuel supplies are now adequate (in part because of purchases from Alaska), production is increasing, and revitalization of the industry is underway. In Kamchatka, fish production in 1995 was up 33% from the previous year, contributing to a 15% increase in overall indus