Performance des lieux d'enfouissement sanitaire de Laterrière et de Ste-Sophie, Québec, Canada

Ce travail décrit les caractéristiques hydrogéologiques et chimiques de deux lieux d'enfouissement de déchets municipaux localisés au Québec. Le site de Laterrière est en opération depuis 1971 dans une ancienne sablière. Sous les dépôts meubles, la topographie du sotte rocheux est marquée par une vallée qui forme une limite imperméable à l'aquifère de sable et impose un écoulement convergent de l'eau souterraine vers la rivière Chicoutimi. Le site de Ste-Sophie, en opération depuis 1976, repose sur une couche de 3,5 mètres de sables fins saturés recouvrant un lit d'argile marine. La surélévation de la nappe dans les déchets favorise un écoulement divergent vers le périmètre de la zone d'enfouissement.Un réseau de piézomètres installé en bordure des deux sites a permis pendant trente mois de prélever des échantillons d'eau et de les analyser. Dans chaque panache de contamination, l'alcalinité, les ions majeurs Na+, K+, Ca2+, Mg2+, Cl¯, le fer, le manganèse, l'azote total et ammoniacal, les DCO et DBO5 montrent des concentrations généralement supérieures à celles de L'eau naturelle ambiante. A proximité des deux Lieux d'enfouissement, les teneurs en cadmium, chrome, nickel et plomb excèdent les normes québécoises de potabiLité de l'eau. Dans chaque cas, ta distribution des contaminants est surtout régie par le réseau d'écoulement. La dispersion hydrodynamique et les réactions géochimiques dans le sous-sol sont des processus importants d'atténuation des contaminants.This paper describes the hydrogeological and geochemical features of two sanitary landfill sites located in the Province of Quebec : Laterriere and Ste-Sophie. The main objective is to evaluate the leachate attenuation performance of each site. For this project, the Quebec Ministry of the Environment chose two sites with contrasting hydrogeological settings.The Laterriere landfill, in operation since 1971, covers an area of about 32 ha. The refuse is deposited in an old sandpit and the landfill boundary is located 400 meters away from the Chicoutimi River, 25 meters above the stream water level. The bedrock topography shows a valley under the landfill which acts an an impervious base for the sand aquifer and induces a convergent groundwater flow towards the river.The Ste-Sophie landfill covers an area of 48 ha and began operating in 1976. The refuse zone is located on flat ground 350 meters away from the Ruisseau-aux-Castors. The refuse is deposited on a 3.5 meter layer of fine sands nearly saturated overlying a marine clay bed. A water table mound is observed beneath the landfill, resulting in diverging low lines outward from the center of the Landfill.For each site, the occurence and migration of contaminants was investigated using networks of piezometers. Sampling was performed monthly over a period of thirty months and thirty parameters were analyzed on each sample. The analytical results were entered in a database and treated by statistical methods.The shape of each contamination plume is controlled mainly by the groundwater flow system. At Laterriere, the plume is restricted to a narrow path between the landfill and the river and inside a bedrock valley. This flow net has been simulated by a two-dimensional finite elements model. At Ste-Sophie, the divergence of flow lines due to groundwater mounding beneath the site causes dispersion of contaminants around the landfill. The use of an analytical solution shows that longitudinal dispersivity is a major process of contaminant migration.For the two landfills, the highest concentrations of contaminants occur directly beneath or close to the boundaries of the landfills. Total alkalinity, Na+, K+, Ca2+, Mg2+, Cl¯, iron, manganèse, total and ammoniacal nitrogen, chemical and biological oxygen demand (COD and BOD) are much above background levels throughout the plume. Sulfate is also a major contaminant at Ste-Sophie with concentration of 1100/mg/l. The concentrations of cadmium, chrome, nickel and lead exceed the drinking water standards near the two landfill sites but they decline rapidly in the direction of flow. At Laterriere, the decline in chloride concentration measured at the discharge point S-23 is about 85 % while the decline of reactive contaminants, such as iron and COD, is respectively 98 and 99.7 %.Finally, we discuss hydrogeological criteria for landfill site selection in Quebec

The Digital Flynn Effect: Complexity of Posts on Social Media Increases over Time

Parents and teachers often express concern about the extensive use of social media by youngsters. Some of them see emoticons, undecipherable initialisms and loose grammar typical for social media as evidence of language degradation. In this paper, we use a simple measure of text complexity to investigate how the complexity of public posts on a popular social networking site changes over time. We analyze a unique dataset that contains texts posted by 942, 336 users from a large European city across nine years. We show that the chosen complexity measure is correlated with the academic performance of users: users from high-performing schools produce more complex texts than users from low-performing schools. We also find that complexity of posts increases with age. Finally, we demonstrate that overall language complexity of posts on the social networking site is constantly increasing. We call this phenomenon the digital Flynn effect. Our results may suggest that the worries about language degradation are not warranted

Resistless electron beam lithography process for the fabrication of sub-50 nm silicide structures

We report on a study of the fabrication of submicron silicide structures with a resistless lithography technique. Several different metals can be used as a basis for producing silicide using this method; in this work, results will be discussed for both platinum and nickel silicide. The feasibility of producing nanostructures using polycrystalline silicon as a base growth layer for metal–oxide– semiconductor, and other device applications have also been demonstrated. Threshold doses for this method for submicron lines (<50 nm) and square areas were obtained in order to establish a framework for the fabrication of more complex devices. Preliminary electrical measurements were carried out which indicate that the resistivity of the silicide is 45 [mu omega] cm, and that the barrier height of the silicide/(high resistivity silicon) interface is 0.56 eV

Torsion–rotation global analysis of the first three torsional states (νt = 0, 1, 2) and terahertz database for methanol

Stimulated by recent THz measurements of the methanol spectrum in one of our laboratories, undertaken in support of NASA programs related to the Herschel Space Observatory (HSO) and the Atacama Large Millimeter Array (ALMA), we have carried out a global analysis of available microwave and high-resolution infrared data for the first three torsional states (νt = 0, 1, 2), and for J values up to 30. This global fit of approximately 5600 frequency measurements and 19 000 Fourier transform far infrared (FTFIR) wavenumber measurements to 119 parameters reaches the estimated experimental measurement accuracy for the FTFIR transitions, and about twice the estimated experimental measurement accuracy for the microwave, submillimeter-wave, and terahertz transitions. The present fit is essentially a continuation of our earlier work, but we have greatly expanded our previous data set and have added a large number of new torsion–rotation interaction terms to the Hamiltonian in our previously used computer program. The results, together with a number of calculated (but unmeasured) transitions, including their line strength, estimated uncertainty, and lower state energy, are made available in the supplementary material as a database formatted to be useful for astronomical searches. Some discussion of several open spectroscopic problems, e.g., (i) an improved notation for the numerous parameters in the torsion–rotation Hamiltonian, (ii) possible causes of the failure to fit frequency measurements to the estimated measurement uncertainty, and (iii) pitfalls to be avoided when intercomparing apparently identical parameters from the internal axis method and the rho axis method are also given

Laboratory Characterization and Astrophysical Detection of Vibrationally Excited States of Vinyl Cyanide in Orion-KL

New laboratory data of CH$_2$CHCN (vinyl cyanide) in its ground and vibrationally excited states at the microwave to THz domain allow searching for these excited state transitions in the Orion-KL line survey. Frequency-modulated spectrometers combined into a single broadband 50-1900 GHz spectrum provided measurements of CH$_2$CHCN covering a spectral range of 18-1893 GHz, whose assignments was confirmed by Stark modulation spectra in the 18-40 GHz region and by ab-initio anharmonic force field calculations. For analyzing the emission lines of CH$_2$CHCN species detected in Orion-KL we used the excitation and radiative transfer code (MADEX) at LTE conditions. The rotational transitions of the ground state of this molecule emerge from four cloud components of hot core nature which trace the physical and chemical conditions of high mass star forming regions in the Orion-KL Nebula. The total column density of CH$_2$CHCN in the ground state is (3.0$\pm$0.9)x10$^{15}$ cm$^{-2}$. We report on the first interstellar detection of transitions in the v10=1/(v11=1,v15=1) dyad in space, and in the v11=2 and v11=3 states in Orion-KL. The lowest energy vibrationally excited states of vinyl cyanide such as v11=1 (at 328.5 K), v15=1 (at 478.6 K), v11=2 (at 657.8 K), the v10=1/(v11=1,v15=1) dyad (at 806.4/809.9 K), and v11=3 (at 987.9 K) are populated under warm and dense conditions, so they probe the hottest parts of the Orion-KL source. Column density and rotational and vibrational temperatures for CH$_2$CHCN in their ground and excited states, as well as for the isotopologues, have been constrained by means of a sample of more than 1000 lines in this survey. Moreover, we present the detection of methyl isocyanide (CH$_3$NC) for the first time in Orion-KL and a tentative detection of vinyl isocyanide (CH$_2$CHNC) and give column density ratios between the cyanide and isocyanide isomers.Comment: 46 pages, 22 figures, 14 tables, 9 online table

Approximate probabilistic verification of hybrid systems

Hybrid systems whose mode dynamics are governed by non-linear ordinary differential equations (ODEs) are often a natural model for biological processes. However such models are difficult to analyze. To address this, we develop a probabilistic analysis method by approximating the mode transitions as stochastic events. We assume that the probability of making a mode transition is proportional to the measure of the set of pairs of time points and value states at which the mode transition is enabled. To ensure a sound mathematical basis, we impose a natural continuity property on the non-linear ODEs. We also assume that the states of the system are observed at discrete time points but that the mode transitions may take place at any time between two successive discrete time points. This leads to a discrete time Markov chain as a probabilistic approximation of the hybrid system. We then show that for BLTL (bounded linear time temporal logic) specifications the hybrid system meets a specification iff its Markov chain approximation meets the same specification with probability $1$. Based on this, we formulate a sequential hypothesis testing procedure for verifying -approximately- that the Markov chain meets a BLTL specification with high probability. Our case studies on cardiac cell dynamics and the circadian rhythm indicate that our scheme can be applied in a number of realistic settings

Influence of the substrate-induced strain and irradiation disorder on the Peierls transition in TTF-TCNQ microdomains

The influence of the combined effects of substrate-induced strain, finite size and electron irradiation-induced defects have been studied on individual micron-sized domains of the organic charge transfer compound tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) by temperature-dependent conductivity and current-voltage measurements. The individual domains have been isolated by focused ion beam etching and electrically contacted by focused ion and electron beam induced deposition of metallic contacts. The temperature-dependent conductivity follows a variable range hopping behavior which shows a crossover of the exponent as the Peierls transition is approached. The low temperature behavior is analyzed within the segmented rod model of Fogler, Teber and Shklowskii, as originally developed for a charge-ordered quasi one-dimensional electron crystal. The results are compared with data obtained on as-grown and electron irradiated epitaxial TTF-TCNQ thin films of the two-domain type

Method for fabricating submicron silicide structures on silicon using a resistless electron beam lithography process

Abstract : A novel resistless lithography process using a conventional electron beam system is presented. Metallic lines with widths of less than 50 nm were produced on silicon substrates. The process is based on localized heating with a focused electron beam of thin platinum layers deposited on silicon. It is demonstrated that silicide formation occurs at the Pt-Si interface. By using a dilute solution of aqua regia, it is possible to obtain a sufficient difference in etch rates between exposed and unexposed regions of the platinum thin film to selectively remove only the unexposed areas