Dominance and population structure of freshwater crabs (Potamonautes perlatus Milne Edwards)

Although freshwater crabs, Potamonautes spp, are abundant (up to 23 crabs m-2) in southern African freshwater systems and form a major part of the diet of many vertebrates, little is known about their biology. Understanding crab population dynamics and behaviour, for example, is important to understanding their role in the ecosystem more clearly. In this paper we report on dominance in Potamonautes perlatus and test the prediction that larger crabs are dominant to smaller ones, i.e. a linear hierarchy exists and it is size dependent. To understand how this would affect wild populations we also investigated the population structure (sex ratio, size distribution, density and population growth) of a wild population. Using Landau's index of linearity (h) we found three captive groups of P. perlatus to show moderate linearity, i.e. h = 0.9; 0.81 and 0.83. In all three groups the largest individual was the most dominant. There was a significant Spearman rank correlation between dominance rank and size of largest chelae in two of the groups, and a significant Spearman rank correlation between dominance rank and carapace width in only one of the three groups. Densities of crabs in the Eerste River, Western Cape Province, ranged from a mean of 2.89 ±2.11 to 15.57 ± 7.21 crabs m-2. Unexpectedly the size class distribution of the crabs remained unchanged during the year. The lack of a significant increase in the mean size of the crabs can probably be ascribed to a year-round consistency in the availability of refugia for specific/different size classes. Intraspecific aggression, predation and refuge availability are probable strong selection pressures in determining population structures of wild populations of P. perlatus.Keywords: Dominance. linear hierarchy, population structure, refuge availability, rivers, South Afric

Enhancement of plastic surgery training by including simulation in education and training programmes

Background. This research investigated the possibility of integrating simulation in plastic surgery residency training. The problem addressed was the lack of knowledge about using simulation as a teaching method to enhance the training of plastic surgeons. There was a lack of empirical evidence regarding learning outcomes that could be mastered by simulation-based education and training and their specific cognitive levels.Objectives. To identify and describe: (i) learning outcomes for plastic surgery education and training for which simulation might be an important (essential and useful) training method; and (ii) simulation modalities, linked to specific cognitive levels, to establish the influence of simulation on plastic surgery education and training. The objectives entail determining the importance of simulation in plastic surgery training and identifying simulation modalities most suited to attain specific outcomes.Methods. Data were collected by means of a Delphi survey to obtain consensus from an expert panel comprising 9 plastic surgeons, supplemented by semi-structured interviews conducted with 8 national and international role players in simulation and postgraduate education.Results. Learning outcomes, levels of training, possible simulation modalities, cognitive levels and descriptive verbs and phrases were described, as these pertain to learning. Participants agreed that simulation in medical education can be used to enhance postgraduate plastic surgery training, with special reference to specific outcomes and cognitive levels. Participants made recommendations for the planning and support of the implementation, aimed at ensuring the quality of training.Conclusion. The objectives set were achieved and the results of the study serve as encouragement and guidance in the striving for the enhancement of postgraduate plastic surgery education and training, and in other medical disciplines

Rock mass loss on a nunatak in Western Dronning Maud Land, Antarctica

This paper presents the first rock mass loss data for uncut clasts from continental Antarctica. A rock mass loss experiment using doleritic rock samples was conducted over a seven-year period, between 2008 and 2014, at the Vesleskarvet nunataks, Western Dronning Maud Land. The data show that approximately 10% of clasts suffered a mass loss that is an order of magnitude greater than the remaining 90% of clasts. Thus, the observed rock mass loss is suggested to occur in a series of events that are impossible to predict in terms of frequency and/or magnitude. However, extrapolating from the data obtained during the seven-year period indicates that rates of mass loss are slow and of the order of 1% per 100 years. Direct erosion by wind (including abrasion) as well as mechanical and chemical weathering are suggested to be responsible for rock mass loss. Rock properties, the weathering environment, and a lack of available moisture may be contributing factors to the slow rate of rock decay. This paper suggests that in this area of Antarctica, the slow rate of rock mass loss increases the longevity of existing periglacial landforms such as patterned ground and blockfields, but inhibits development of new patterned ground through the slow production of fines.The Department of Environmental Affairs and the National Research Foundation are gratefully acknowledged for logistical and financial support. This work is published under the NRF/SANAP project : Landscape and climate interactions in a changing sub-Antarctic environment (Grant no 93075).http://instaar.colorado.edu/AAAR/index.phphb2016Geography, Geoinformatics and Meteorolog

The BEST study - a prospective study to compare business class versus economy class air travel as a cause of thrombosis

Background. As many as 10% of airline passengers travelling without prophylaxis for long distances may develop a venous thrombosis. There is, however, no evidence that economy class travellers are at increased risk of thrombosis.Objectives. A suitably powered prospective study, based on the incidence of deep-vein thrombosis (DVT) reported in previous studies on long-haul flights, was designed to determine the incidence of positive venous duplex scans and D-dimer elevations in low and intermediate-risk passengers, comparing passengers travelling in business and economy class.Patients/methods. Eight hundred and ninety-nine passengers were recruited (180 travelling business class and 719 travelling economy). D-dimers were measured before and after the flight. A value greater than 500 ng/ml was accepted as abnormal. A thrombophilia screen was conducted which included the factor V Leiden mutation, the prothombin 20210A mutation, protein C and S levels, antithrombin levels, and anticardiolipin antibodies immunoglobulin G (IgG) and immunoglobulin M (IgM). On arrival, lower limb compression ultrasonography of the deep veins was performed. Logistical regression analysis was used to determine the risk factors related to abnormally high D-dimer levels.Results. Only 434 subjects had a full venous duplex scan performed. None had ultrasonic evidence of venous thrombosis. Nine passengers tested at departure had elevated D-dimer levels and these volunteers were excluded from further study. Seventy-four of the 899 passengers had raised D-dimers on arrival. Twenty-two of 180 business class passengers (12%) developed elevated D-dimers compared with 52 of 719 economy class passengers (7%). There was no significant association between elevation of D-dimers and the class flown (odds ratio (OR) 0.61, p = 0.109). The factor V Leiden mutation, factor VIII levels and the use of aspirin were, however, associated with raised D-dimers (OR 3.36, p = 0.024; OR 1.01, p = 0.014; and OR 2.04, p = 0.038, respectively). Five hundred and five passengers were contacted within 6 months and none reported any symptoms of a clinical thrombosis or pulmonary embolus.Conclusion. The incidence of ultrasonically proven DVT is much lower than previously reported. However, more than 10% of all passengers developed raised D-dimers, which were unrelated to the class flown. A rise in D-dimers is associated with an inherent risk of thrombosis and/ or thrombophilia, demonstrates activation of both the coagulation and fibrinolytic systems during long-haul flights, and may indicate the development of small thrombi

Defects in swift heavy ion irradiated n-4H-SiC

Please read abstract in the article.http://www.elsevier.com/locate/nimb2020-12-01hj2020Physic

Terrestrial and submarine evidence for the extent and timing of the Last Glacial Maximum and the onset of deglaciation on the maritime-Antarctic and sub-Antarctic islands

This paper is the maritime and sub–Antarctic contribution to the Scientific Committee for Antarctic Research (SCAR) Past Antarctic Ice Sheet Dynamics (PAIS) community Antarctic Ice Sheet reconstruction. The overarching aim for all sectors of Antarctica was to reconstruct the Last Glacial Maximum (LGM) ice sheet extent and thickness, and map the subsequent deglaciation in a series of 5000 year time slices. However, our review of the literature found surprisingly few high quality chronological constraints on changing glacier extents on these timescales in the maritime and sub–Antarctic sector. Therefore, in this paper we focus on an assessment of the terrestrial and offshore evidence for the LGM ice extent, establishing minimum ages for the onset of deglaciation, and separating evidence of deglaciation from LGM limits from those associated with later Holocene glacier fluctuations. Evidence included geomorphological descriptions of glacial landscapes, radiocarbon dated basal peat and lake sediment deposits, cosmogenic isotope ages of glacial features and molecular biological data. We propose a classification of the glacial history of the maritime and sub–Antarctic islands based on this assembled evidence. These include: (Type I) islands which accumulated little or no LGM ice; (Type II) islands with a limited LGM ice extent but evidence of extensive earlier continental shelf glaciations; (Type III) seamounts and volcanoes unlikely to have accumulated significant LGM ice cover; (Type IV) islands on shallow shelves with both terrestrial and submarine evidence of LGM (and/or earlier) ice expansion; (Type V) Islands north of the Antarctic Polar Front with terrestrial evidence of LGM ice expansion; and (Type VI) islands with no data. Finally, we review the climatological and geomorphological settings that separate the glaciological history of the islands within this classification scheme

A function-based typology for Earth’s ecosystems

As the United Nations develops a post-2020 global biodiversity framework for the Convention on Biological Diversity, attention is focusing on how new goals and targets for ecosystem conservation might serve its vision of ‘living in harmony with nature’1,2. Advancing dual imperatives to conserve biodiversity and sustain ecosystem services requires reliable and resilient generalizations and predictions about ecosystem responses to environmental change and management3. Ecosystems vary in their biota4, service provision5 and relative exposure to risks6, yet there is no globally consistent classification of ecosystems that reflects functional responses to change and management. This hampers progress on developing conservation targets and sustainability goals. Here we present the International Union for Conservation of Nature (IUCN) Global Ecosystem Typology, a conceptually robust, scalable, spatially explicit approach for generalizations and predictions about functions, biota, risks and management remedies across the entire biosphere. The outcome of a major cross-disciplinary collaboration, this novel framework places all of Earth’s ecosystems into a unifying theoretical context to guide the transformation of ecosystem policy and management from global to local scales. This new information infrastructure will support knowledge transfer for ecosystem-specific management and restoration, globally standardized ecosystem risk assessments, natural capital accounting and progress on the post-2020 global biodiversity framework

A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum

A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20 ka, 15 ka, 10 ka and 5 ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse 1a. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorities for future work. The synthesis is intended to be a resource for the modelling and glacial geological community

Aonyx capensis African clawless otter

University of Pretoria, CI

Diet in relation to prey of Cape clawless otters in two rivers in the Western Cape Province, South Africa

The annual and seasonal diet of Cape clawless otters (Aonyx capensis (Schinz, 1821)) in the Olifants and Eerste rivers, Western Cape Province, South Africa, is described. Seasonal diet is discussed in relation to the availability of river crabs (Potamonautes perlatus) and fish. Crabs were found to be the main prey and fish the second most common prey of Cape clawless otters in the rivers during all seasons. Plant material ranked third in the diet of the otters from the Olifants River but only seventh in the Eerste River. Other prey included frogs, insects, birds and mammals. In terms of the number of prey, crabs again dominated the diet in both rivers. There was no significant difference between the relative numbers of crabs in spraints (faeces) from the two rivers. The percentage occurence of prey of Cape clawless otters in both rivers shows an increase in the amount of crab in summer and a corresponding decrease in the number of fish eaten. There was a significant seasonal difference in size of crabs eaten by the otters in the Olifants and Eerste rivers. The seasonal fluctuation in crab and fish corresponded to the expected frequencies as determined by trapping.Articl