Diurnal cycles of gaseous mercury within the snowpack at Kuujjuarapik/Whapmagoostui,Québec,Canada

Mercury is a globally dispersed and toxic pollutant that can be transported far from its emission sources. In polar and subpolar regions, recent research activities have demonstrated its ability to be converted and deposited rapidly onto snow surfaces during the so-known Mercury Depletion Events (MDEs). The fate of mercury once deposited onto snow surfaces is still unclear: a part could be re-emitted to the atmosphere, the other part could contaminate water systems at the snowmelt. Its capacity to transform to more toxic form and to bioaccumulate in the food chain has consequently made mercury a threat for Arctic ecosystems. The snowpack is a medium that greatly interacts with a variety of atmospheric gases. Its role in the understanding of the fate of deposited mercury is crucial though it is poorly understood. In April 2002, we studied an environmental component of mercury, which is interstitial gaseous mercury (IGM) present in the air of the snowpack at Kuujjuarapik/Whapmagoostui (55 degrees N, 77 degrees W), Canada on the east shore of the Hudson Bay. We report here for the first time continuous IGM measurements at various depths inside a seasonal snowpack. IGM concentrations exhibit a well-marked diurnal cycle with uninterrupted events of Hg0 depletion and production within the snowpack. A possible explanation of Hg0 depletion within the snowpack may be Hg0 oxidation processes. Additionally, we assume that the notable production of Hg0 during the daytime may be the results of photoreduction and photoinitiated reduction of Hg(II) complexes. These new observations show that the snowpack plays undoubtedly a role in the global mercury cycle.     

Pesticides measured in air and precipitation in the Yamaska Basin (Québec): occurrence and concentrations in 2004

Air and precipitation samples were collected and analyzed for 91 pesticides or metabolites from May to September 2004 at St. Damase, an agricultural site located in Yamaska basin in Québec, Canada. A broad range of pesticides was detected during this experiment where 40 different compounds were measured. Most of the samples showed more than 10 simultaneous pesticide detections and sometimes reaching 19 simultaneous detections. The most detected pesticides in air were trifluralin, metolachlor and captan, which were found in all the samples during the 5 months of measurements. For the detected compounds, the average concentrations ranged from 4 pg/m3 to 8 ng/m3. Some of the pesticides detected in air were found in precipitation samples as well showing that wet deposition can occur and have an impact on aquatic ecosystems. The most important pesticides detected were related to corn and soya cultivations, the two main cultures in this region highlighting that the major sources come from local applications. On the other hand, the detection of some pesticides in precipitation which were undetectable in air implies that some compounds may have a long range transport origin.     

Epidemiological studies of leukaemia in children and young adults around nuclear facilities: a critical review

The existence of an increased risk of childhood leukaemia near nuclear installations is a recurrent issue. A review of the related epidemiological literature is presented here. Results for 198 nuclear sites throughout 10 countries were included in the review. In addition to local studies, 25 multi-site studies have been published for eight countries. A large variability was noticed in the quality of the data as well as in the definition of the study population and in the methods of analysis. Many studies present important limits that make the results difficult to interpret. The review confirms that some clusters of childhood leukaemia cases exist locally. However, results based on multi-site studies around nuclear installations do not indicate an increased risk globally. Many studies were launched to investigate possible origins of the observed clusters around specific sites, but up to now, none of the proposed hypotheses have explained them.     

Scavenging of gaseous mercury by acidic snow at Kuujjuarapik, Northern Québec

One fate of gaseous elemental mercury (GEM) in the Arctic has been identified as gas phase oxidation by halogen-containing radicals, leading to abrupt atmospheric mercury depletion concurrent with ozone depletion. Rapid deposition of oxidized mercury leads to snow enrichment in mercury. In this report, we describe experiments that demonstrate the ability of snow to directly scavenge atmospheric mercury. The study was conducted at Kuujjuarapik, Québec, Canada (latitude 55 degrees 17'N). A mercury depletion event (MDE) caused the mercury concentration in the surface snow of the coastal snowpack to double, from (9.4+/-2.0) to (19.2+/-1.7) ng/L. Independent of the MDE, mercury concentrations increased five-fold, from (10.0+/-0.1) to (51.4+/-6.0) ng/L, upon spiking the snow with 500 microM hydrogen peroxide under solar irradiation. Total organic carbon in the spiked irradiated snow samples also decreased, consistent with the formation of strongly oxidizing species. The role of the snowpack in releasing GEM to the atmosphere has been reported; these findings suggest that snow may also play a role in enhancing deposition of mercury.     

Core flood evaluation of hydrocarbon solvent foams

The possibility of using foams to reduce solvent mobility in hydrocarbon miscible flooding is investigated. The performance of nitrogen foams in oil-free Berea Sandstone cores is compared to the performance of foams generated with four light hydrocarbons (methane, ethane, propane and n-butane), using two surfactants of different sensitivity to oil. Both surfactants were effective in reducing the mobility of nitrogen as well as the four light hydrocarbon solvents, regardless of whether the solvents were gases, liquids or supercritical fluids, implying that foam sensitivity to oil does not translate directly into foam sensitivity to light hydrocarbon solvent. Some dependence of foam performance on solvent type and system pressure was observed. With gaseous and supercritical solvents, the mobility reduction factor decreased with decreasing system pressure, and increased, decreased or remained the same with solvent carbon number. With liquid solvents, mobility reduction was evident, but no obvious trends were observed. With hydrocarbons in the liquid phase at 23 °C, one of the surfactants caused core permeability to be reduced to near-zero by a mechanism that is not fully understood, possibly by hydrate formation.     

Le premier vocabulaire de sciences cognitives en langue fran?aise.

Reviews the book, Vocabulaire de sciences cognitives by O. Houdé, D. Kayser, O. Koenig, J. Proust, and F. Rastier (1998). The Vocabulaire de sciences cognitives contains 130 alphabetically ordered entries, each entry corresponding to a different word or expression used in cognitive science. The entries are treated from the point of view of each of the five main disciplines contributing to cognitive science: artificial intelligence, neuroscience, linguistics, philosophy, and psychology. The texts concerning a given entry form distinct sections labeled with the name of the discipline concerned. Numerous cross-references to related entries are given. Overall, the Vocabulaire contains about 200 different texts, a third of which have been authored by the members of the editorial board, each of whom is specialized in one of the disciplines mentioned; the remaining texts were written by 54 other authors from these various fields. Of the 130 entries, only 2 very pivotal terms in cognitive science (FUNCTION and REPRESENTATION) receive complete multidisciplinary treatment; 15 entries referring mostly to major cognitive functions (e.g., LANGUAGE, LEARNING, MEMORY, PERCEPTION, REASONING) are covered by three or four disciplines, and 31 others receive a bidisciplinary treatment. Analysis of the 144 pairs of disciplines found in these 48 entries shows the neighborhood among disciplines to be fairly evenly distributed except in the case of psychology and neuroscience, whose greater conceptual proximity is explained by the fact that most neuroscience texts have been written by neuropsychologists. The contributions of the various disciplines were reviewed by one specialist and by at least one nonspecialist. Although predictably more critical, the specialists did not identify many serious problems or errors. However, the reviewers expressed some reservations concerning the choice of the terms deemed worth of an entry, the limited number of disciplines contributing to some entries, the variable length and nature of the texts, as well as the exaggerated place sometimes given to secondary research. If the Vocabulaire de sciences cognitives does not constitute a monumental achievement, it is nonetheless an impressive piece of work, especially considering the breadth and state of the domain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Indexing music by mood: design and integration of an automatic content-based annotator

In the context of content analysis for indexing and retrieval, a method for creating automatic music mood annotation is presented. The method is based on results from psychological studies and framed into a supervised learning approach using musical features automatically extracted from the raw audio signal. We present here some of the most relevant audio features to solve this problem. A ground truth, used for training, is created using both social network information systems (wisdom of crowds) and individual experts (wisdom of the few). At the experimental level, we evaluate our approach on a database of 1,000 songs. Tests of different classification methods, configurations and optimizations have been conducted, showing that Support Vector Machines perform best for the task at hand. Moreover, we evaluate the algorithm robustness against different audio compression schemes. This fact, often neglected, is fundamental to build a system that is usable in real conditions. In addition, the integration of a fast and scalable version of this technique with the European Project PHAROS is discussed. This real world application demonstrates the usability of this tool to annotate large-scale databases. We also report on a user evaluation in the context of the PHAROS search engine, asking people about the utility, interest and innovation of this technology in real world use cases.     

Some pesticides occurrence in air and precipitation in Québec, Canada

Air and precipitation samples were collected in three stations located in Quebec between January 1993 and March 1996 to determine spatial and seasonal variations of several organochlorine pesticides and metabolites (alpha-HCH, gamma-HCH, HCB, gamma-chlordane, DDT, DDE, Mirex). alpha-HCH, gamma-HCH, and HCB were more or less measured in large amounts at all sites, whereas gamma-chlordane, DDT, and DDE concentrations were lower and Mirex was undetectable. Higher concentrations levels were observed in air during hot spring/summer periods except for HCB, indicating a probable temperature dependence. Ln concentrations vs reciprocal temperature plots and Henry's law determinations helped to highlight the contribution of soil and/or water volatilization of those compounds. Itwas observed that alpha-HCH came mainly from Atlantic Ocean volatilization at Mingan, whereas sources of gamma-chlordane and DDE were mostly due to volatilization from soils in southern Quebec. DDT may be present in the atmosphere by the way of transport from remote regions. Lindane sources were multiple: it may be found in the atmosphere bythe processes of transport and volatilization coming from soil or water. Finally, a negative correlation between HCB and air temperature implies that processes other than volatilization are involved in transport of this compound.     

Geographic distribution of leukemia mortality in young people aged 0-24 years in France

Patients with significant stenosis at the carotid bifurcation are traditionally subjected to four vessel aortic arch angiography prior to consideration for carotid endarterectomy. The advent of the non-invasive vascular laboratory has necessitated a reappraisal of this approach. AIMS: 1. Determine the yield from aortic arch angiography and its influence on surgical management. 2. Evaluate the accuracy of clinical examination and the non-invasive vascular laboratory in the detection of aortic arch branch lesions. METHODS: One hundred and twenty-nine consecutive patients undergoing evaluation for carotid endarterectomy were prospectively enrolled into the study. The protocol entailed: 1. Clinical recording of upper limb pulses, blood pressure and supraclavicular bruits. 2. Duplex scan examination to evaluate proximal inflow into the carotid arteries. 3. Four vessel aortic arch angiography to detect aortic branch lesions. Data from the non-invasive tests were compared to angiography. Patients with aortic arch branch lesions were further evaluated to determine the proportion requiring additional surgery. RESULTS: Nineteen patients had angiographic evidence of aortic branch disease (14.7%); six involved the common carotid artery, three the innominate artery and 10 the subclavian artery. All of these lesions were detected by the combination of unequal blood pressure, pulse deficit, bruit or duplex scan. Seven patients underwent additional surgery (5.4%) which included carotid-subclavian bypass (five), aortoinnominate bypass (one) and innominate endarterectomy (one). CONCLUSION: In patients with significant stenosis at the carotid bifurcation undergoing evaluation for carotid endarterectomy, aortic arch angiography is unnecessary except in a small percentage of patients with abnormal clinical and non-invasive findings.