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61.
Arctostylopids are common in Late Palaeocene and Early Eocene mammal faunas of Asia, but they are rare in North America. From the time of their first discovery, arctostylopids were grouped with the strictly endemic South American Notoungulata based on their strikingly similar dental morphology. This relationship was challenged based on dental morphology of more recently discovered arctostylopids and on supposed tarsal morphology (based on unassociated material) of the Asian arctostylopid Palaeostylops. Therefore, Arctostylopidae were placed in a separate order, Arctostylopida, of enigmatic affinities. Many authors, however, continue to unite Arctostylopidae and Notoungulata based on dental similarities. In the Late Palaeocene Subeng site in Inner Mongolia, we identified the Palaeostylops tarsals based on their size and abundance. This identification is supported by comparison to unpublished Arctostylops tarsals from the North American Clarkforkian, derived from a semi-articulated skeleton also including dental material. Tarsal morphology shows moderate similarity to the gliriform Pseudictops, and strong resemblance to the tarsally conservative gliroid Rhombomylus. Hence, Arctostylopidae may best be grouped with Asian non-gliroid Gliriformes, which we interpret as having dispersed into North America in the Late Palaeocene.Pieter Missiaen is an aspirant of the Research Foundation-Flanders (RF-Flanders)  相似文献   
62.
The chemical and physical processes involved in the retention of 10(-2)M Zn, Pb and Cd in a calcareous medium were studied under saturated dynamic (column) and static (batch) conditions. Retention in columns decreased in order: Pb>Cd approximately Zn. In the batch experiments, the same order was observed for a contact time of less than 40h and over, Pb>Cd>Zn. Stronger Pb retention is in accordance with the lower solubility of Pb carbonates. However, the equality of retained Zn and Cd does not fit the solubility constants of carbonated solids. SEM analysis revealed that heavy metals and calcareous particles are associated. Pb precipitated as individualized Zn-Cd-Ca- free carbonated crystallites. All the heavy metals were also found to be associated with calcareous particles, without any change in their porosity, pointing to a surface/lattice diffusion-controlled substitution process. Zn and Cd were always found in concomitancy, though Pb fixed separately at the particle circumferences. The Phreeqc 2.12 interactive code was used to model experimental data on the following basis: flow fractionation in the columns, precipitation of Pb as cerrusite linked to kinetically controlled calcite dissolution, and heavy metal sorption onto proton exchanging sites (presumably surface complexation onto a calcite surface). This model simulates exchanges of metals with surface protons, pH buffering and the prevention of early Zn and Cd precipitation. Both modeling and SEM analysis show a probable significant decrease of calcite dissolution along with its contamination with metals.  相似文献   
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64.
Noroviruses (NoVs), currently recognised as the most common human food-borne pathogens, are ubiquitous in the environment and can be transmitted to humans through multiple foodstuffs. In this study, we evaluated the prevalence of human NoV genogroups I (GI) and II (GII) in 493 food samples including soft red fruits (n = 200), salad vegetables (n = 210) and bivalve mollusc shellfish (n = 83), using the Bovine Enterovirus type 1 as process extraction control for the first time. Viral extractions were performed by elution concentration and genome detection by TaqMan Real-Time RT-PCR (RT-qPCR). Experimental contamination using hepatitis A virus (HAV) was used to determine the limit of detection (LOD) of the extraction methods. Positive detections were obtained from 2 g of digestive tissues of oysters or mussels kept for 16 h in seawater containing 2.0–2.7 log10 plaque-forming units (PFU)/L of HAV. For lettuces and raspberries, the LOD was, respectively, estimated at 2.2 and 2.9 log10 PFU per 25 g. Of the molluscs tested, 8.4 and 14.4 % were, respectively, positive for the presence of GI NoV and GII NoV RNA. Prevalence in GI NoVs varied from 11.9 % for the salad vegetables samples to 15.5 % for the red soft fruits. Only 0.5 % of the salad and red soft fruits samples were positive for GII NoVs. These results highlight the high occurrence of human NoVs in foodstuffs that can be eaten raw or after a moderate technological processing or treatment. The determination of the risk of infection associated with an RT-qPCR positive sample remains an important challenge for the future.  相似文献   
65.
The virucidal efficacy of a pulsed light treatment applied to viral suspensions, glass beads and herb powders was studied for the F-RNA bacteriophage MS2. The experimental results obtained demonstrated the high potential of this technology to efficiently decontaminate simple matrices but underlined the complexity of application to complex food matrices.  相似文献   
66.
The article describes a riverscape approach based on landscape ecology concepts, which aims at studying the multiscale relationships between the spatial pattern of stream fish habitat patches and processes depending on fish movements. A review of the literature shows that few operational methods are available to study this relationship due to multiple methodological and practical challenges inherent to underwater environments. We illustrated the approach with literature data on a cyprinid species (Barbus barbus) and an actual riverscape of the Seine River, France. We represented the underwater environment of fishes for different discharges using two-dimensional geographic information system-based maps of the resource habitat patches, defined according to activities (feeding, resting, and spawning). To quantify spatial patterns at nested levels (resource habitat patch, daily activities area, subpopulation area), we calculated their composition, configuration, complementation, and connectivity with multiple spatial analysis methods: patch metrics, moving-window analysis, and least cost modeling. The proximity index allowed us to evaluate habitat patches of relatively great value, depending on their spatial context, which contributes to the setting of preservation policies. The methods presented to delimit potential daily activities areas and subpopulation areas showed the potential gaps in the biological connectivity of the reach. These methods provided some space for action in restoration schemes.  相似文献   
67.
Cysts located on the tongue are rare and usually diagnosed in childhood. Here we report on the prenatal diagnosis of an unusual cystic malformation of the tongue with heterotopic intestinal tissue explored by prenatal ultrasound, magnetic resonance imaging and on its surgical treatment and histological examination. The prenatal differential diagnoses as well as perinatal management of cystic lesions of the tongue are reviewed. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
68.
Atmospheric concentration of nitrous oxide (N2O), a greenhouse gas (GHG), is rising largely due to agriculture. At the plot scale, N2O emissions from crops are known to be controlled by local agricultural practices such as fertilisation, tillage and residue management. However, knowledge of greenhouse gas emissions at the scale of the cropping system is scarce, notably because N2O monitoring is time consuming. Strategies to reduce impact of farming on climate should therefore be sought at the cropping system level. Agro-ecosystem models are simple alternative means to estimate N2O emissions. Here, we combined ecosystem modelling and field measurements to assess the effect of agronomic management on N2O emissions. The model was tested with series of daily to monthly N2O emission data. It was then used to evaluate the N2O abatement potential of a low-emission system designed to halve greenhouse gas emissions in comparison with a system with high productivity and environmental performance. We found a 29 % N2O abatement potential for the low-emission system compared with the high-productivity system. Among N2O abatement options, reduction in mineral fertiliser inputs was the most effective.  相似文献   
69.
Knowledge of habitat use by top marine predators in response to environmental conditions is crucial in the current context of global changes occurring in the Southern Ocean. We examined the at-sea locations of male Adélie penguins (Pygoscelis adeliae) breeding at Dumont d’Urville during their first, long incubation trip. Compared with the chick-rearing period, penguins performed longer trips, going to oceanic waters as far as 320 km from the colony. We observed 3 strategies: (1) five individuals covered large distances to the north, targeting open-ocean areas and following the currents of two persistent eddies; (2) five individuals foraged to the north-west, close to the Antarctic shelf slope at the limit of the pack ice; and (3) three individuals covered much shorter distances (northwards or eastwards). The foraging range also seemed to be limited by the body condition of the penguins before their departure to sea.  相似文献   
70.
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