The structure of demersal assemblages off Namibia in relation to abiotic factors

Groundfish surveys carried out between October 1992 and October 1996 were used to describe the demersal assemblages of the northern Benguela along the Namibian coast. Multivariate analyses indicated a clear separation between shelf and slope habitats, which were divided into three and two assemblages respectively. These divisions were distinct, with clear distributional boundaries separating them. Species determining the structure of these divisions and subdivisions and their relative abundances were identified. Depth, bottom temperature, bottom salinity and dissolved oxygen were all significantly correlated with the spatial distribution of the assemblages. Minor changes or shifts in the distribution of assemblages were observed over the study period, although patterns of species associations remained relatively constant.Keywords: community, demersal, environment, fishery, Namibia, trawlingAfrican Journal of Marine Science 2001, 23: 397–41

The Influence of Large Animal Diversity in Grazed Ecosystems

Field observations in the Serengeti National Park, Tanzania have revealed several modes of grazing system, including migration, sustained-yield grazing and grazing succession which contribute on the one hand to ecological separation of herbivores by habitat choice, but on the other hand to positive association of species on wet season pastures known as hot spots. Drawing from results of experimental field studies, we consider what is known about resource competition and facilitation, the two key ecological processes underlying these grazing systems, and specify the shape of the relationship between species richness and pasture height that is predicted depending on which process is dominating in the grazing system. We test between these alternatives by analysing for the first time data on herbivore distributions and vegetation condition from a series of 33 survey flights over the entire Serengeti ecosystem. Our preliminary results strongly support the importance of facilitation as a process structuring the herbivore community of the Serengeti Plains in the wet season. Resource competition may limit use of the shortest swards

Flux penetration in slab shaped Type-I superconductors

We study the problem of flux penetration into type--I superconductors with high demagnetization factor (slab geometry).Assuming that the interface between the normal and superconducting regions is sharp, that flux diffuses rapidly in the normal regions, and that thermal effects are negligible, we analyze the process by which flux invades the sample as the applied field is increased slowly from zero.We find that flux does not penetrate gradually.Rather there is an instability in the process and the flux penetrates from the boundary in a series of bursts, accompanied by the formation of isolated droplets of the normal phase, leading to a multiply connected flux domain structure similar to that seen in experiments.Comment: 4 pages, 2 figures, Fig 2.(b) available upon request from the authors, email - [email protected]

Predictors of short-term readmission after beyond total mesorectal excision for primary locally advanced and recurrent rectal cancer

Unplanned readmissions heavily affect the cost of health care and are used as an indicator of performance. No clear data are available regarding beyond-total mesorectal excision (bTME) procedure. Aim of the study is to identify patient-related and surgery-related factors influencing the 30-day readmissions after bTME. Retrospective data were collected from 220 patients who underwent bTME procedures at single centre between 2006 and 2016. Patient-related and operative factors were assessed, including body mass index (BMI), age, gender, American Society of Anaesthesiologists’ (ASA) score, preoperative stage, neo-adjuvant therapy, primary tumour vs recurrence, the extent of surgery. The readmission rate was 8.18%. No statistically significant association was found with BMI, ASA score, length of stay and stay in the intensive care unit, primary vs recurrent tumour or blood transfusions. Not quite statistically significant was the association with pelvic side wall dissection (OR 3.32, p = 0.054). Statistically significant factors included preoperative stage > IIIb (OR: 4.77, p = 0.002), neo-adjuvant therapy (OR: 0.13, p = 0.0006), age over 65 years (OR: 5.96, p = 0.0005), any re-intervention during the first admission (OR: 7.4, p = 0.0001), and any post-operative complication (OR: 9.01, p = 0.004). The readmission rate after beyond-TME procedure is influenced by patient-related factors as well as post-operative morbidity

Proposal for the determination of nuclear masses by high-precision spectroscopy of Rydberg states

The theoretical treatment of Rydberg states in one-electron ions is facilitated by the virtual absence of the nuclear-size correction, and fundamental constants like the Rydberg constant may be in the reach of planned high-precision spectroscopic experiments. The dominant nuclear effect that shifts transition energies among Rydberg states therefore is due to the nuclear mass. As a consequence, spectroscopic measurements of Rydberg transitions can be used in order to precisely deduce nuclear masses. A possible application of this approach to the hydrogen and deuterium, and hydrogen-like lithium and carbon is explored in detail. In order to complete the analysis, numerical and analytic calculations of the quantum electrodynamic (QED) self-energy remainder function for states with principal quantum number n=5,...,8 and with angular momentum L=n-1 and L=n-2 are described (j = L +/- 1/2).Comment: 21 pages; LaTe