A uniform isotopic and chemical signature of dust exported from Patagonia: Rock sources and occurrence in southern environments

Patagonia is considered to be the most important source of dust from South America that is deposited in surrounding areas, and we present here a systematic Sr and Nd isotopic study of sediment currently being exported. Eolian and suspended riverine sediments from Patagonia have a homogeneous chemical and isotopic composition that results from the mixing of by-products from explosive Andean volcanism, derived from the extensive Jurassic silicic Province of Chon Aike and pyroclastic materials from the basic to intermediate southern Andean Quaternary arc, which are easily denudated and dispersed. The main Andean uplift and the glaciations that began in the Late Tertiary account for the extensive distribution of these sediments in the extra-Andean region. The present geochemical signature of Patagonian sediments was produced during the Pleistocene, along with the onset of the southern Andean explosive arc volcanism. Previously published compositions of sediments from other southern South American source regions, assumed to be representative of Patagonia, are distinct from our data. Considering the alleged importance of Patagonia as a dust source for different depositional environments in southern latitudes, it is surprising to verify that the chemical and isotopic signatures of Patagonian-sourced sediments are different from those of sediments from the Southern Ocean, the Pampean Region or the Antarctic ice. Sediments from these areas have a crustal-like geochemical signature reflecting a mixed origin with sediment from other southern South American sources, whereas Patagonian sediments likely represent the basic to intermediate end-member composition

Climat organisationnel, satisfaction au travail et perception du syndicalisme

Les auteurs tentent de vérifier empiriquement la relation entre le climat organisationnel et la perception de l'instrumentation des syndicats tout en considérant l'effet de la satisfaction au travail sur la relation entre ces deux variables.During the past decade, researchers in the field of Industrial RelationsPsychology have attempted to find a scientific explanation for the unionization of workers through the identification of psychological variables related to behaviour patterns during certification. Workers appeared to favour entry of a union into their organization, and to demonstrate their support for it, insofar as they understood the Personal advantage of unionization in its role of reducing work-related problems. Unionization can thus be seen in an instrumental perspective. Work environment constitutes an important determinant in the behaviour of the employee according to Lewin's formula (1951), which stipulates that human behaviour is based on the personality of an individual as well as on his environment. Work environment, or organizational climate, can play a role in the desire for unionism of workers who experience it, because of the structure it imposes on work and the possibility of participation it provides for employees. This is particularly so with regard to its influence on the perception of employees concerning unions as instruments for realizing demands in defense of their interests. The purpose of this article is to present the results of a research project based on the empirical verification of the relationship between organizational climate and perception of the usefulness of unions. As a result, we formulated the hypothesis that organizational climate is linked negatively to perception of the usefulness of unions. In addition, the effect of job satisfaction on the relations between these two variables is also examined. The subjects of this study are lower management personnel employed by a firm specialized in telecommunications. The sample includes 625 people. Of them, 92,5% are drawn from this specifie managerial group, 64,6% are male, 73,8% have less than 15 years' experience in the firm, and 54,9% are less than 30 years of age. The questionnaires used include the Job Description Index (J.D.I.), the Likert organizational Profile (L.O.P., abridged version), and the Lorrain questionnaire (1979) on the perception of unions among management personnel. Results indicate that organizational climate correlated with perception of the usefulness of the union among management personnel in this firm. Thus, the more management personnel in this case consider the work climate as cold, rigid and bureaucratie, the more they will have a tendency to see unionism as an attractive means of voicing demands to solve the problems facing them. It is also clear that, if lower management have the impression that their superiors have little confidence in them and are not concerned with their opinions or ideas, they will tend to view very favourably the role of a union in improving their working conditions. The study also reveals that the concept of work satisfaction does not play an important role in the perception of a union as an instrument for managers in this organization, as well as that there is no significant relationship between job satisfaction and organizational climate. Finally, the present research demonstrates the pertinence of studying the influence of the characteristics of the organization on phenomena linked to the unionization

A Flow Time Model for Melt-Cast Insensitive Explosive Process

International audienceDiphasic flows of concentrated suspensions of melt-cast insensitive explosives exhibit specific rheological properties. In order to limit the handling of pyrotechnical products presenting a risk with respect to the mechanical and thermal shocks, a lot of work has been undertaken for many years in the civil engineering sector. The objective of this study is to propose a predictive model of the flow time of a concentrated suspension through a nozzle located at the bottom of a tank. Similar to our industrial process, the suspension is made out of insensitive energetic materials and flows under gravity. Experimental results are compared to three models (Quemada, Krieger-Dougherty, and Mooney) predicting the viscosity μ of a suspension as a function of the solid volume fraction ϕ, the maximum packing density ϕm and the viscosity μ0 of the interstitial liquid. De Larrard's model is used to calculate ϕm. The value of viscosity measured for the pure liquid is close to the one predicted by the Bernoulli theorem, where liquids are considered as incompressible and inviscid. Finally, it was found that the Quemada's model gives a fair agreement between predictions and experiments

d13C tracing of dissolved inorganic carbon sources in Patagonian rivers (Argentina)

The main Patagonian rivers (Colorado, Negro, Chubut, Deseado, Coyle, Chico, Santa Cruz and Gallegos) were sampled between September 1995 and November 1998 to determine their chemical and isotopic compositions, the origins of the suspended and dissolved river loads and their inputs to the South Atlantic Ocean. This paper focuses on the dissolved inorganic carbon (DIC) transport and its υ13C isotopic signature. The υ13CDIC values vary between 12Ð8 and 1Ð8‰ and allow one to distinguish two river groups: (i) the Colorado, Negro, Chubut and Santa Cruz, which display the highest values and the lowest seasonal variations; (ii) the Deseado, Coyle, Chico and Gallegos, which show the lowest values and the highest seasonal variations. For the first group, υ13CDIC is mainly controlled by important exchanges between the river waters and atmospheric CO2, due to the presence of lakes and dams. For the second group, υ13CDIC also appears to be controlled by the oxidation of organic carbon, showing a negative relationship between υ13CDIC and the dissolved organic carbon. These biogeochemical processes interfere with the contribution of carbonate and silicate weathering to the riverine DIC and do not allow use of υ13CDIC alone to distinguish these contributions. The annual DIC flux exported by Patagonian Rivers to the South Atlantic Ocean averages 621 ð 109 g. of C, i.e. a specific yield of 2Ð7 g m2 year1. The mean υ13CDIC can be estimated to 4Ð9‰, which is high compared with other rivers of the world

Terrestrial and fluvial carbon fluxes in a tropical watershed: Nyong basin, Cameroon

The Nyong watershed, with an area of 27 800 km2 and a mean annual discharge of 390 m3 s−1, is the second largest river in Cameroon. The Nyong watershed serves as an outstanding study area for the examination of carbon fluxes in humid tropical environments because of its limited anthropogenic impact and homogeneous silicate bedrock. Between April 2005 and April 2007, we sampled water at seven stations, from the small watershed of the Mengong (0.6 km2) to the Nyong at Edea (24 500 km2), and monitored temperature, pH, dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) contents, as well as the isotopic composition of DIC (δ13CDIC)andDOC(δ13CDOC).We estimated terrestrial net ecosystemproductivity in theNyong River watershed and measured fluvial fluxes of carbon to the ocean and the atmosphere. The Nyong River basin sequesters significant amounts of carbon on an annual basis: ~7 920 000t C year−1 (300 g C m−2 year−1). The combined dissolved organic, dissolved inorganic and atmospheric fluxes of carbon from the Nyong River only export 3% of this flux fromthe basin on an annual basis. This includes a minimumCO2 outgassing of 1487 g Cm−2 year−1, comparable to 115% of the annual flux of DOC and four times greater than the flux of DIC

Development of a new mixing rheometer for studying rheological behaviour of concentrated energetic suspensions

International audienceThe overall objective is to present a procedure based on a Couette analogy to quantitatively analyse torque/rotor speed data and extract viscosity/shear-rate curves using a non-conventional geometry. Diphasic flows of energetic concentrated suspensions of melt-cast insensitive explosives exhibit particular rheological properties. The characterization of these complex fluids may be a challenging task when conventional rheometers are used. Placing these tense suspensions in a classic cylindrical geometry may lead to a partial destruction of the internal fluid structure. To prevent that, a "RheoXF" a mixer-type rheometer has been developed : it consists of a mixing device with quite a complex geometry rotating in a cylindrical tank

Effects of Some Insecticides on the Viability and the ATP Synthesis of Honeybee Drone’s Spermatozoid in vitro Exposed

Honeybee (Apis mellifera) reproduction is polyandrous: the queen obtains millions of spermatozoid by mating with several drones outside the colony. Fertility problems of honeybee queens are reported where failure of the production and quality of sperm drones are suspected. Several factors can affect sperm quality drones include pesticides. The aim of this study is to determinate the in vitro effect of fipronil, ethiprole, imidacloprid, thiamethoxam, cypermethrin, and coumaphos at different concentrations from 0.1 to 100 µM on the viability and the energetic state, through ATP content, of spermatozoids of honeybee drones. Exposure during 24 h showed that all the active ingredients used in this test increase the ATP levels. Four of them i.e. fipronil, ethiprole, imidacloprid, and thiamethoxam reduced significantly the viability of spermatozoids. Hence, pesticides could affect the drone’s spermatozoids which may have negative impact on semen quality and further queen fecundity

Effect of aneurysm size on procedure-related rupture in patients with subarachnoid hemorrhage treated with coil occlusion

Objective: Procedure-related rupture is one of the most feared complications in treating patients with cerebral aneurysm. The primary aim of this study was to estimate the effect of aneurysm size on procedure-related rupture. We also estimated its effect on peri-procedural thromboembolic events. Methods: This observational study was conducted using routinely-collected health data on patients admitted for subarachnoid hemorrhage and treated with aneurysm coil occlusion in the CHU de Québec — Enfant-Jésus hospital from January 1st, 2000 until sample size was reached. Patients were identified from the Discharge Abstract Database using the Canadian Classification of Health codes. Assessment of complications was blind to aneurysm size. Logistic regression models were performed to test associations between aneurysm size and procedure-related rupture or peri-procedural thromboembolic events, and between both procedure-related rupture and thromboembolic events and patients' outcomes. Results: This study included 532 aneurysms treated with coil occlusion in 505 patients. Procedure-related rupture occurred in 34 patients (6.7%) and thromboembolic events in 53 (10.5%) patients. Aneurysms of 2 to 3 mm inclusively were not more significantly associated with procedure-related rupture or thromboembolic events than those larger than 3 mm (OR 1.02, 95% CI: 0.9–1.16, p = 0.78 and OR 1.06, 95% CI: 0.96–1.17, p = 0.3, respectively). However, procedure-related rupture had a significant effect on patient mortality (OR 3.86, 95% CI: 1.42–10.53, p < 0.01). Conclusions: Very small aneurysm size should not preclude aneurysm coil occlusion. Every measure should be taken to prevent procedure-related rupture as it is strongly associated with higher mortality