Pseudo-rotations of the open annulus

In this paper, we study pseudo-rotations of the open annulus, \emph{i.e.} conservative homeomorphisms of the open annulus whose rotation set is reduced to a single irrational number (the angle of the pseudo-rotation). We prove in particular that, for every pseudo-rotation $h$ of angle $\rho$, the rigid rotation of angle $\rho$ is in the closure of the conjugacy class of $h$. We also prove that pseudo-rotations are not persistent in $C^r$ topology for any $r\geq 0$.Comment: 25 page

Lack of increased availability of root-derived C may explain the low N2O emission from low N-urine patches

Urine deposition on grassland causes significant N2O losses, which in some cases may result from increased denitrification stimulated by labile compounds released from scorched plant roots. Two 12-day experiments were conducted in 13C-labelled grassland monoliths to investigate the link between N2O production and carbon mineralization following application of low rates of urine-N. Measurements of N2O and CO2 emissions from the monoliths as well as δ13C signal of evolved CO2 were done on day -4, -1, 0, 1, 2, 4, 5, 6 and 7 after application of urine corresponding to 3.1 and 5.5 g N m-2 in the first and second experiment, respectively. The δ13C signal was also determined for soil organic matter, dissolved organic C and CO2 evolved by microbial respiration. In addition, denitrifying enzyme activity (DEA) and nitrifying enzyme activity (NEA) were measured on day -1, 2 and 7 after the first urine application event. Urine did not affect DEA, whereas NEA was enhanced 2 days after urine application. In the first experiment, urine had no significant effect on the N2O flux, which was generally low (-8 to 14 μg N2O-N m-2 h-1). After the second application event, the N2O emission increased significantly to 87 μg N2O-N m-2 h-1 and the N2O emission factor for the added urine-N was 0.18 %. However, the associated 13C signal of soil respiration was unaffected by urine. Consequently, the increased N2O emission from the simulated low N-urine patches was not caused by enhanced denitrification stimulated by labile compounds released from scorched plant roots

Some fossil ginkgophytes and a possible vojnovskyalean element from the Glossopteris flora of Vereeniging, Transvaal

Main articleA short historical review is given of previously described sites where plant fossils occur in Lower Karroo beds at Vereeniging in the Southern Transvaal. Reference is made to the importance of these sites because of the outstanding discoveries made here in the past. Some new material from the same sites is described and several unusual elements in the Glossopteris flora of Vereeniging are recorded for the first time. Leaves of a plant not previously recorded from Gondwanaland are provisionally described under the term cf. Nephropsis on account of a strong resemblance to leaves of the Russian Permian genus Nephropsis Zalessky. The remaining specimens in the assemblage are tentatively placed in the genera Ginkgoites Seward and Psygmophyllum Schimper respectively. Owing to the paucity of material, type numbers are assigned in certain cases, instead of specific names. Specific identification is attempted, however, in the case of four of the specimens, which are provisionally assigned to Psygmophyllum kidstoni Seward.Non

On some "northern" elements in the Lower Gondwana flora of Vereeniging, Transvaal

Main articleA small assemblage of plant elements from the Lower Permian of Vereeniging, in the southern Transvaal, is described here. The assemblage is constituted of form-genera normally only found in the palaeo floristic regions of the northern hemisphere. The genera concerned are: Pecopteris (Asterotheca), Cladophlebis, Sphenophyllum and Psygmophyllum. The intermingling of these "Northern" elements with the Glossopteris flora of Vereeniging serves to illustrate the mixed nature of this flora. Reference is made to similar mixed Gondwana floras elsewhere in Africa and also in South America.Non

Connected Choice and the Brouwer Fixed Point Theorem

We study the computational content of the Brouwer Fixed Point Theorem in the Weihrauch lattice. Connected choice is the operation that finds a point in a non-empty connected closed set given by negative information. One of our main results is that for any fixed dimension the Brouwer Fixed Point Theorem of that dimension is computably equivalent to connected choice of the Euclidean unit cube of the same dimension. Another main result is that connected choice is complete for dimension greater than or equal to two in the sense that it is computably equivalent to Weak K\H{o}nig's Lemma. While we can present two independent proofs for dimension three and upwards that are either based on a simple geometric construction or a combinatorial argument, the proof for dimension two is based on a more involved inverse limit construction. The connected choice operation in dimension one is known to be equivalent to the Intermediate Value Theorem; we prove that this problem is not idempotent in contrast to the case of dimension two and upwards. We also prove that Lipschitz continuity with Lipschitz constants strictly larger than one does not simplify finding fixed points. Finally, we prove that finding a connectedness component of a closed subset of the Euclidean unit cube of any dimension greater or equal to one is equivalent to Weak K\H{o}nig's Lemma. In order to describe these results, we introduce a representation of closed subsets of the unit cube by trees of rational complexes.Comment: 36 page

Investigating an Ethical Approach to Genetically Modified Crops in Environmental Educational Processes

Genetically modified (GM) crops gained attention in southern Africa in the context of broader debates about the struggle for food security and poverty alleviation to achieve sustainable development. The prospects of GM crops as a technological innovation have provoked numerous debates and environmental concern groups have challenged their use. Environmental educators’ concern for greater ethical practices regarding environmental issues can be applied to the subject of GM crops. This article focuses on the perceptions of environmental educators regarding the use of GM crops towards sustainable development. Interviews were conducted with a small group of environmental educators to gain some insight into their perceptions. The interviews reflected some contextual relevance of GM crops, understanding of the concepts ‘GM crops’ and ‘sustainable  development’ as well as four unique themes. These emphasise the plurality of the GM crops issue and the importance thereof in working towards an ethical approach in environmental educational processes

Wave identification and separation on seismic data

In order to study the influence of the sea-floor on the oceanic acoustic wave propagation, we try to qualify the energetic contributions of the waves which propagate in the subsurface compared to the water propagating modes . The treated shallow water data have been recorded in the Beaulieu Bay (Mediterranean Sea) . A realistic propagation model is obtained by successive comparisons between field and simulated data. Most of the time delays and amplitudes of the dominant waves can be explained if some velocity gradients are included in the sediments layers models. The presented method consists to define the separation parameters from the propagation model to extract the dominant waves from the field data .Afin d'étudier l'influence du fond marin sur la propagation acoustique océanique ultra basse fréquence UBF (< 100 Hz), on cherche à évaluer les contributions énergétiques des ondes se propageant dans le sous-sol par rapport aux modes de propagation dans l'eau à partir de données sismiques obtenues en eaux peu profondes dans la baie de Beaulieu (mer Méditerranée). Les comparaisons successives entre la section sismique expérimentale et une simulation de la section conduisent à l'élaboration d'un modèle de propagation réaliste du site où les temps d'arrivées et les amplitudes des différentes ondes s'expliquent à condition d'introduire un gradient de vitesse dans la couche de sédiments. La méthode développée consiste à séparer les ondes dominantes de la section expérimentale à partir du modèle de propagatio

Enhancing ICT for Inclusive Human Development in Sub-Saharan Africa

​This study assesses if increasing information and communication technology (ICT) enhances inclusive human development in a sample of 49 countries in Sub-Saharan Africa for the period 2000-2012. The empirical evidence present in this study, is based on instrumental variable Tobit regressions, in order to account for simultaneity and the limited range in the dependent variable. In the interest of increasing room for policy implications and controlling for the unobserved heterogeneity, the analysis is decomposed into the fundamental characteristics that human development based on: income levels, legal origins, religious dominations, political stability, landlockedness and resource-wealth. Our findings show that policies designed to boost ICT (mobile phone, internet, telephone) penetration will increase inclusive development in the post-2015 sustainable development agenda. The degree of positive responsiveness of inclusive development to ICT varies across fundamental characteristics of human development and ICT dynamics. The study has substantial policy relevance because the adoption and/or penetration rate of ICT can be influenced by policy to achieve inclusive development outcomes. Further policy implications are also discussed