Critical evaluation of factors required to terminate the postclosure monitoring period at solid waste landfills

Regulations governing the disposal of solid waste in landfills specify that they must be monitored for 30 years after closure unless this period is extended by the governing regulatory authority. Given the wide range of conditions under which refuse is buried, technical criteria, rather than a specific time period, are preferable for evaluation of when it is acceptable to terminate postclosure monitoring. The objectives of this paper are to identify and evaluate parameters that can be used to define the end of the postclosure monitoring period and to present a conceptual framework for an investigation of whether postclosure monitoring can be terminated at a landfill. Parameters evaluated include leachate composition and leachate and gas production. Estimates of leachate production from closed landfills are used to assess the potential environmental impacts of a hypothetical release to surface water or groundwater. The acceptability of gaseous releases should be evaluated against criteria for odors, the potential for subsurface migration, and greenhouse gas and ozone precursor emissions. The approach presented here must be tested on a site-specific basis to identify additional data requirements and regulatory activity that might be required to prepare regulators for the large number of requests to terminate postclosure monitoring expected over the next 20 years. An approach in which the frequency and extent of postclosure monitoring is reduced as warranted by site-specific data and impact analysis should provide an effective strategy to manage closed landfills.     

Kernel density weighted principal component analysis of combustion processes

Principal component analysis (PCA) has been successfully applied to the analysis of combustion data-sets. However using PCA on a raw direct numerical simulation or an experimental data-set is not straightforward. Indeed, those data-sets usually show non-homogenous data density, hot and cold zones being generally over represented. This can introduce bias in the PCA reconstruction, especially when strong non-linear relationships characterize the data sample. To tackle this problem, a combination of the kernel density method and PCA is introduced here. This new PCA algorithm, called Temperature BAsed KErnel Density weighted PCA (T-BAKED PCA) allows to enhance the PCA accuracy especially in the flame front zone, which is the principal zone of interest. The performance of this new approach is benchmarked against classical PCA. Moreover, a new method called Hybrid T-BAKED PCA or HT-BAKED PCA, combining both classical and T-BAKED PCA, is proposed to provide an optimal representation of all flame regions.     

Redox chemistry of copper-amyloid-beta: the generation of hydroxyl radical in the presence of ascorbate is linked to redox-potentials and aggregation state

Aggregation of the beta-amyloid peptide (Abeta) to amyloid plaques is a key event in Alzheimer's disease. According to the amyloid-cascade hypothesis, Abeta aggregates are toxic to neurons through the production of reactive oxygen species (ROS). Copper ions play an important role, because they are able to bind to Abeta and influence its aggregation properties. Moreover, Cu-Abeta is supposed to be directly involved in ROS production. To get a better understanding of these reactions, we measured the production of HO(.) and the redox potential of Cu-Abeta. The results were compared to other biological copper-peptide complexes in order to get an insight into the biological relevance. Cu-Abeta produced more HO(.) than the complex of copper with Asp-Ala-His-Lys (Cu-DAHK), but less than with Gly-His-Lys (Cu-GHK). Cyclic voltammetry revealed that the order for reduction potential is Cu-GHK>Cu-Abeta>Cu-DAHK, but for the oxidation potential the order is reversed. Thus, easier copper redox cycling correlated to higher HO(.) production. The copper complex of the form Abeta1-42 showed a HO(.) production five-times higher than that of the form Abeta1-40. Time-dependence and aggregation studies suggest that an aggregation intermediate is responsible for this increased HO(.) production.     

The Purinergic P2X7 Receptor-NLRP3 Inflammasome Pathway: A New Target in Alcoholic Liver Disease?

The World Health Organization has estimated that approximately 3 million deaths are attributable to alcohol consumption each year. Alcohol consumption is notably associated with the development and/or progression of many non-communicable inflammatory diseases—particularly in the liver. Although these alcoholic liver diseases were initially thought to be caused by the toxicity of ethanol on hepatocytes, the latest research indicates Kupffer cells (the liver macrophages) are at the heart of this “inflammatory shift”. Purinergic signaling (notably through P2X7 receptors and the NLRP3 inflammasome) by Kupffer cells appears to be a decisive factor in the pathophysiology of alcoholic liver disease. Hence, the modulation of purinergic signaling might represent a new means of treating alcoholic liver disease. Here, we review current knowledge on the pathophysiology of alcoholic liver diseases and therapeutic perspectives for targeting these inflammatory pathways.     

Genetic control of antibody responses induced by recombinant Mycobacterium bovis BCG expressing a foreign antigen

Recombinant Mycobacterium bovis BCG expressing foreign antigens represents a promising candidate for the development of future vaccines and was shown in several experimental models to induce protective immunity against bacterial or parasitic infections. Innate resistance to BCG infection is under genetic control and could modify the immune responses induced against an antigen delivered by such engineered microorganisms. To investigate this question, we analyzed the immune responses of various inbred strains of mice to recombinant BCG expressing beta-galactosidase. These experiments demonstrated that BALB/c mice developed strong antibody responses against BCG expressing beta-galactosidase under the control of two different promoters. In contrast, C57BL/6, C3H, and CBA mice produced high anti-beta-galactosidase antibody titers only when immunized with recombinant BCG expressing beta-galactosidase under the control of the pblaF* promoter, which induced the production of high levels of this antigen. This difference in mouse responsiveness to recombinant BCG was not due to innate resistance to BCG infection, since similar immune responses were induced in Ity(r) and Ity(s) congenic strains of mice. In contrast, the analysis of anti-beta-galactosidase antibody responses of H-2 congenic mice in two different genetic backgrounds demonstrated that H-2 genes are involved in the immune responsiveness to beta-galactosidase delivered by recombinant BCG. Together, these results demonstrate that immune responses to an antigen delivered by recombinant BCG are under complex genetic influences which could play a crucial role in the efficiency of future recombinant BCG vaccines.     

Assembly kinetics of replicating chromatin: isolation and characterization of prenucleosomal and nucleosomal DNA

Replicating chromatin is known to be more sensitive to micrococcal nuclease than bulk chromatin. We have used this property and a fractionation procedure based on the specific release of replicating material under mild micrococcal nuclease digestion, in order to analyse both the kinetics of maturation of newly replicated DNA into nucleosomes and the structure of the replicating material. As other authors, we initially observed that repetitive unit of newly replicated chromatin was shorter than that of bulk chromatin, however this result appears to be due to sliding of nucleosomes along the chromatin fibers close to the replicating fork. Replicative chromatin was fractionated and analysed. A prenucleosomal peak was observed and preliminary characterized.     

Large eddy simulation of mean and oscillating flow in a side-dump ramjet combustor

Ramjet flows are very sensitive to combustion instabilities that are difficult to predict using numerical simulations. This paper describes compressible large eddy simulation on unstructured grids used to investigate nonreacting and reacting flows in a simplified twin-inlet ramjet combustor. The reacting flow is compared to experimental results published by ONERA in terms of mean fields. Simulations show a specific flow topology controlled by the impingement of the two air jets issuing from the twin air inlets and by multiple complex recirculation zones. In a second part, all unsteady modes appearing in the reacting LES are analyzed using spectral maps and POD (proper orthogonal decomposition) tools. A Helmholtz solver also computes the frequencies and structures of all acoustic modes in the ramjet. Pure longitudinal, transverse and combined modes are identified by all three diagnostics. In addition, a mode-by-mode analysis of the Rayleigh criterion is presented thanks to POD. This method shows that the most intense structure (at 3750 Hz) is the first transverse acoustic mode of the combustor chamber and the Rayleigh criterion obtained with POD illustrates how this transverse mode couples with unsteady combustion.     

SID大会展现了业界未来的技术和产品走向

近期在美国西雅图举行的信息显示学会大会(Society for Information Display Confenrence),是迄今为止展出新型显示技术及尚处于开发阶段的显示技术最多的一届盛会。     

Analysis of Film-Boiling Heat Transfer on a High Temperature Sphere Immersed into Liquid Sodium

Film-boiling heat transfer is a key phenomenon governing severe accident sequence in a sodium-cooled fast reactor. Experimental the fuel-coolant interaction process which may occur during a and theoretical work on film-boiling heat transfer in sodium has hardly been carried out in the past. An experiment has been conducted in the early seventies to investigate sodium pool boiling. In this experiment, a hot tantalum sphere was immersed into subcooled liquid sodium. Film boiling was obtained for various sets of parameters： sodium subcooling from 4.1 K to 29. 1 K, initial sphere temperature ranging from 1,802.6 K to 2,633.7 K, sphere diameters of 1.27, 1.91 and 2.54 cm and sodium depths of 7.6 cm and 11.4 cm. In the present work, a simplified analysis based on the boundary layer theory is developed to describe pool film-boiling heat transfer on a hot sphere in liquid sodium. Two extreme cases are considered depending on sodium subcooling. In the case of high subcooling, most of the heat lost by the sphere is used to heat the sodium while for low subcooling, it is used to vaporize the liquid at the liquid-vapor interface. It will be shown that the scaling analysis predicts the heat fluxes within the order of magnitude when compared to the available experimental data. Besides, it allows an estimation of the contribution of these fluxes to the liquid heating and vaporization processes.     

Flame propagation in aeronautical swirled multi-burners: Experimental and numerical investigation

Driven by pollutant emissions stringent regulations, engines manufacturers tend to reduce the number of injectors and rely on lean combustion which impacts the light-around phase of ignition. To improve knowledge of the ignition process occurring in real engines, current research combines fundamental and increasingly complex experiments with high fidelity numerical simulations. This work investigates the flame propagation, using a multi-injector experiment located at CORIA (France) in combination with Large Eddy Simulation (LES) obtained by CERFACS (France). The comparison of numerical fully transient ignition sequences with experimental data shows that LES recovers features found in the experiment. Global events such as the propagation of the flame front to neighboring swirlers are well captured by LES, with the correct propagation mode (spanwise or axial) and the correct overall ignition time delay. The detailed analysis of LES data allows to identify the driving mechanisms leading to each propagation mode.