Hyperbolic Structures and Root Systems

We discuss the construction of a one parameter family of complex hyperbolic structures on the complement of a toric mirror arrangement associated with a simply laced root system. Subsequently we find conditions for which parameter values this leads to ball quotients

An evaluation of the environmental care orientation of deciduous fruit producers in the Western Cape

A classification system developed to evaluate the environmental care orientation of companies and, more specifically, their strategies to deal with the environmental care requirements prescribed by the market was applied to the deciduous fruit sector in the Western Cape. A survey was done to determine the attitude towards and status of, environmental care activities amongst deciduous fruit producers who have already obtained Eurepgap certification or who are busy preparing for the certification audit. A questionnaire was used and the responses were judged in terms of the guidelines of the classification system. The nature of the typical South African - European deciduous fruit export supply chain is that South African producers desire to supply the retail market at higher prices than that of the wholesale market. The producers are then confronted with the stringent environmental care requirements of the retail chains, who use the environmental care product image aggressively as a selling point in the retail market, acting like typical Class III market oriented institutions. The classification shows that the majority of producers try to comply with these requirements with minimum effort (Class I). The more progressive producers accept them as good agricultural practices to increase their production efficiency. (Class II). Some farmers participate in a comprehensive Integrated Crop Management (ICM) system to establish a culture of environmental care at farm level in a more efficient way. ICM implementation also helps to prepare proactively for possible changes in the environmental care requirements of individual retail chains. This seems to be the more effective strategy for the primary producer.Crop Production/Industries, Environmental Economics and Policy,

Cooperating if one’s Goals are Collective-Based: Social Identification Effects in Social Dilemmas as a Function of Goal-Transformation

Prior studies of the effect of group identification on cooperation in social dilemmas have advanced two competing accounts of this effect, the goal-transformation hypothesis, which holds that identification implies a sense of collective self, which makes personal and collective goals interchangeable, and the goal-amplification hypothesis, which states that identification induces positive expectations about others’ cooperative behavior. These prior studies have, however, neglected to assess the process measures necessary to pit the one account against the other. Following prior research, the present study showed that the effect of identification was moderated by participants’ social value orientation (i.e., individual differences in evaluating the importance of outcomes for self and other) in such a way that identification influenced proselfs’ cooperation more than prosocials’ cooperation. This suggests that the consequence of group identification is that collective goals become personal goals. Extending earlier recent research, mediational analyses showed that the effect of our identification manipulation was mediated by participants’ sense of collective self and not by their expectations. Taken together, these results provide strong support in favor of the goal-transformation hypothesis.Goal-amplification hypothesis;Goal-transformation hypothesis

How do neural networks see depth in single images?

Deep neural networks have lead to a breakthrough in depth estimation from single images. Recent work often focuses on the accuracy of the depth map, where an evaluation on a publicly available test set such as the KITTI vision benchmark is often the main result of the article. While such an evaluation shows how well neural networks can estimate depth, it does not show how they do this. To the best of our knowledge, no work currently exists that analyzes what these networks have learned. In this work we take the MonoDepth network by Godard et al. and investigate what visual cues it exploits for depth estimation. We find that the network ignores the apparent size of known obstacles in favor of their vertical position in the image. Using the vertical position requires the camera pose to be known; however we find that MonoDepth only partially corrects for changes in camera pitch and roll and that these influence the estimated depth towards obstacles. We further show that MonoDepth's use of the vertical image position allows it to estimate the distance towards arbitrary obstacles, even those not appearing in the training set, but that it requires a strong edge at the ground contact point of the object to do so. In future work we will investigate whether these observations also apply to other neural networks for monocular depth estimation.Comment: Submitte

Trackways in the Stormberg

Main articleVertebrate trackways in the lower groups of the Karoo Supergroup are mainly pre- Beaufort fish trails, although some tetrapod trackways are known (Griffiths, 1963, p. 292; plate I; specimens in the South African Museum). Recently fish trails have been discovered in the Beaufort, for instance at Kilburn and Wagondrift, but the Beaufort, despite its rich amphibian, reptilian and synapsid fauna, is remarkable for the paucity of its vertebrate trackways. Of the Stormberg (of Lesotho) it was early noted "Fossils are comparatively rare, but reptile tracks are fairly abundant"Non

Insect faunas of South Africa from the upper permian and the Permian/Triassic boundary

Main articleThose sites in South Africa where more than one insect fossil specimen has been found have been interpreted as younger than Middle Triassic or as Late Permian. One site which has yielded a number of specimens and is apparently near the Permian/Triassic boundary is a quarry in the town of Bulwer KwaZulu-Natai. There are six sites with more than one insect specimen which are stratigraphically lower than Bulwer, namely Escourt (a new site), Far End, Mooi River (National Road), Mount West, Balgowan and Lidgetton. According to the 1984 1: 1 000 000 Geological Map of South em Africa Bulwer is situated in the Tarkastad Subgroup of the Beaufort Group near its lower boundary; the Tarkastad has been considered as Triassic. The remaining sites, except Balgowan and Lidgetton, fall in the Estcourt Formation of the Beaufort Group, as do all the sites with single Late Permian specimens except for one similarly aged specimen from the more easterly Emakwezeni Formation. The stratigraphically lowest sites are Lidgetton and slightly younger Balgowan; both are mapped as VoIksrust Formation of the Ecca Group. An analysis is made of vertical distribution of taxa, with those of Lidgetton and Balgowan grouped together as a lower unit, of Bulwer as upper unit, and of the Estcourt Formation sites and Emakwezini site as a middle unit. No obvious break between the three units has been noted.Non

African fossil Lissamphibia

Main articleThe Anura (Frogs and Toads) are represented in Africa and associated regions by fossils of every epoch from the Cretaceous to the Holocene. Pipid frogs of African affinity are known from the Early Cretaceous of Israel and Later Cretaceous of South America and Africa; those of Israel and South America have been well-studied, but only one from Africa has been: Eoxenopoides reuningi from Namaqualand. Two well-studied Palaeocene frogs of South America, Shelania pascuali and Xenopus romeri, have affinities with the African pipids. Apart from a Miocene assemblage from North Africa (including pipids, which are now exclusively sub-Saharan) and one species from Namibia, Xenopus stromeri, the fossil African anurans remain largely unstudied. Deposits in which the African anuran fossils occur represent crater lakes, other lacustrine deposits, including lacustrine tuffs, river terraces, deltas, estuarine/lagoon zones, karst landscapes and archaeological sites; data are not available for several of the recorded fossils. No fossils in Africa appear to have been definitely ascribed to the Urodela or Caecilia.Non

The social cognition of medical knowledge, with special reference to childhood epilepsy

This paper arose out of an engagement in medical communication courses at a Gulf university. It deploys a theoretical framework derived from a (critical) sociocognitive approach to discourse analysis in order to investigate three aspects of medical discourse relating to childhood epilepsy: the cognitive processes that are entailed in relating different types of medical knowledge to their communicative context; the types of medical knowledge that are constituted in the three different text types analysed; and the relationship between these different types of medical knowledge and the discursive features of each text type. The paper argues that there is a cognitive dimension to the human experience of understanding and talking about one specialized from of medical knowledge. It recommends that texts be studied in medical communication courses not just in terms of their discrete formal features but also critically, in terms of the knowledge which they produce, transmit and reproduce