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Aspects of the reproductive biology of monkfish Lophius vomerinus off Namibia

- Maartens, Lima, Booth, Anthony J

Authors: Maartens, Lima , Booth, Anthony J
Date: 2010
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/123831 , vital:35504 , https://doi.10.2989/18142320509504090
Description: Aspects of the reproductive biology of monkfish Lophius vomerinus are described from material collected during hake Merluccius spp. biomass surveys and from commercial monkfish and sole Austroglossus microlepis vessels between January 1996 and June 2000 off Namibia at depths between 97m and 686m. Length-at-50% sexual maturity for males and females were estimated at 39.9cm and 58.2cm respectively, males maturing faster than females. The adult sex ratio of fish >50cm total length was strongly biased towards females. There was reproductive activity throughout the year, peaking slightly between autumn and spring.
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Date Issued: 2010

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Control and integrability on SO (3)

- Remsing, C C

Authors: Remsing, C C
Date: 2010
Language: English
Type: Article
Identifier: vital:6787 , http://hdl.handle.net/10962/d1006938
Description: This paper considers control ane left- invariant systems evolving on matrix Lie groups. Such systems have signicant applications in a variety of elds. Any left-invariant optimal control problem (with quadratic cost) can be lifted, via the celebrated Maximum Principle, to a Hamiltonian system on the dual of the Lie algebra of the underlying state space G. The (minus) Lie-Poisson structure on the dual space g is used to describe the (normal) extremal curves. An interesting, and rather typical, single-input con- trol system on the rotation group SO (3) is investi- gated in some detail. The reduced Hamilton equa- tions associated with an extremal curve are derived in a simple and elegant manner. Finally, these equations are explicitly integrated by Jacobi elliptic functions.
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Date Issued: 2010

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Extending Java’s communication mechanisms for multicore processors

- Wells, George C

Authors: Wells, George C
Date: 2010
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/430526 , vital:72697 , https://citeseerx.ist.psu.edu/document?repid=rep1type=pdfdoi=4068ed60c317e81dc70288cf36ff586dc057233f
Description: With the current trend towards the increased use of multicore proces-sors, there is a growing need for simple, efficient parallel programming mechanisms. While Java has good support for multithreaded and dis-tributed application development, our research into tuple-space systems for multicore processors highlighted a gap in the concurrency facilities available in Java. This arises in the context of independent applications (running in separate virtual machines) that need to synchronise their ac-tivities or communicate with each other. There are several possible solu-tions to this problem, ranging from extensions to the language and/or runtime environment through to the use of distributed programming methods. Using the latter introduces considerable performance over-heads, and so we explored the use of the Java Native Interface in order to take advantage of the interprocess communication (IPC) facilities pro-vided by the underlying operating system. The analysis and comparison of the performance of the standard approaches and our prototype library suggest that there are real benefits to be gained by alternative ap-proaches to the provision of IPC mechanisms for independent Java programs executing on multicore systems. We hope that these findings will spur further investigation of this problem and other possible solu-tions.
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Date Issued: 2010

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Male aggression and mating opportunity in a poeciliid fish

- Magellan, Kit, Kaiser, Horst

Authors: Magellan, Kit , Kaiser, Horst
Date: 2010
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/447556 , vital:74656 , https://doi.org/10.1080/15627020.2010.11657250
Description: One function of aggression in animals is to gain access to mates. Aggression may therefore be favoured by sexual selection, the strength of which can be assessed using repeatability of aggressive behaviour. Here, we tested the hypotheses that male swordtails, Xiphophorus sp., are consistent in the aggressive and mating behaviours exhibited and in the time spent at a close distance to females (female attendance), and that aggressive males gain increased opportunity to attempt copulation compared to their less aggressive conspecifics (sneak frequency). As predicted, aggression between males, and male display and sneak frequency were repeatable. However, male aggression was not significantly correlated with sneak frequency. The function of aggression in this species is not clear-cut and may have an indirect female access function through formation of dominance hierarchies or defence of resources. A surprising finding highlighted by this study was the contradictory results for consistency in female contact, with high repeatability scores indicating consistency in behaviour but the within-subjects component of repeated measures ANOVA showing differences in female contact between trials. The possible reasons for this discrepancy are discussed.
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Date Issued: 2010

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Regional patterns in moult and sexual dimorphism of adult Southern Red Bishops Euplectes orix in southern Africa

- Craig, Adrian J F K, Bonnevie, Bo T, Oschadleus, Hans-Dieter

Authors: Craig, Adrian J F K , Bonnevie, Bo T , Oschadleus, Hans-Dieter
Date: 2010
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/449503 , vital:74826 , https://doi.org/10.2989/00306525.2010.488357
Description: Using the SAFRING database and the Underhill-Zucchini model of primary moult, we analysed the timing of wing moult in Southern Red Bishops Euplectes orix in relation to sex and geographical region. Birds from the winter rainfall region in the south-western sector of the Western Cape start the annual moult more than two months before any other population, but there were no significant differences in starting date within the summer rainfall region. There were striking differences in the estimates of moult duration (62–114 d), which did not follow a consistent pattern in relation to sex or geography; annual variation within a region may be an additional factor. Throughout southern Africa, both sexes showed a trend for longer-winged birds to take more time to complete their moult. We suggest that sex, geographical area and possible annual environmental variations may all influence the timing of moult in local populations. In this sexually dimorphic species, males are consistently longer-winged and heavier than females.
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Date Issued: 2010

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The effects of economic incentives in controlling pollution in the South African leather industry: die uitwerking van ekonomiese insentiewe op die beheer van besoedeling in die Suid-Afrikaanse leerbedryf

- Mowat, Shaun P, Antrobus, Geoffrey G, Fraser, Gavin C G

Authors: Mowat, Shaun P , Antrobus, Geoffrey G , Fraser, Gavin C G
Date: 2010
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/143057 , vital:38197 , DOI: 10.1080/03031853.1997.9523487
Description: Pollution of the environment is becoming an increasingly serious problem. A large contributor to this is industry which generates effluent as a by-product of its production process. Two methods of controlling the pollution generated by industry are the so-called “command and control” techniques and economic incentives. In theory, economic incentives promise a more economically efficient and equitable means of pollution control. This paper sets out to ascertain whether this would hold in practice by applying environmental economic theory to the practical problem of controlling the effluent generated by one particular industry, viz the South African leather industry.
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Date Issued: 2010

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Thermoregulation under seminatural conditions in two species of African barbets (Piciformes Lybiidae)

- McKechnie, Andrew E, Smit, Ben

Authors: McKechnie, Andrew E , Smit, Ben
Date: 2010
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/448413 , vital:74728 , https://doi.org/10.2989/00306525.2010.488384
Description: Torpor has been documented in a number of avian orders, but our understanding of the phylogenetic distribution of this phenomenon is far from complete, and several groups have yet to be investigated. We examined patterns of rest- and active-phase thermoregulation in Acacia Pied Barbets Lybius leucomelas and Crested Barbets Trachyphonus vaillantii held in outdoor aviaries, using surgically-implanted miniature data loggers to record body temperature (Tb). Both species exhibited large circadian rhythms of Tb, with maximum active-phase and minimum rest-phase Tb (ρTbmin) values of 42.3 ± 0.1 °C and 37.7 ± 0.6 °C, respectively, in Acacia Pied Barbets (n = 3) and 42.5 ± 0.4 °C and 37.0 ± 0.6 °C, respectively, in Crested Barbets (n = 5).
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Date Issued: 2010

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Timing of primary wing moult in sexually dimorphic passerines from the Western Cape, South Africa

- Bonnevie, Bo T, Oschadleus, Hans-Dieter

Authors: Bonnevie, Bo T , Oschadleus, Hans-Dieter
Date: 2010
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/448355 , vital:74724 , https://doi.org/10.2989/00306525.2010.455821
Description: SAFRING ringing data was used to investigate the differences in the timing and duration of primary wing moult between males and females of sexually dimorphic passerines from the Western Cape, South Africa. In the sunbirds, weavers and canaries that were considered, the males generally started moult before the females, whereas this was not so for other species. In the species where males started moult before the females, the standard deviation of the start of moult was generally smaller in the males and the males generally took longer to moult. These differences in the patterns of moult are discussed in the context of differences in parental care between males and females of each species and within their taxonomic groups.
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Date Issued: 2010

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Towards IPTV service discovery and selection in an IMS environment

- Tsietsi, Mosiuoa, Musvibe, Ray, Terzoli, Alfredo, Wells, George C

Authors: Tsietsi, Mosiuoa , Musvibe, Ray , Terzoli, Alfredo , Wells, George C
Date: 2010
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/430795 , vital:72716 , 10.1109/ICUMT.2010.5676637
Description: The IP Multimedia Subsystem (IMS) is a telecommunication middleware architecture that behaves as a docking station for a wide range of mul-timedia services. Several so-called killer applications have been envi-sioned for this platform such as multimedia group communications and location based services (LBS), but one of the most common business cases for IMS remains IPTV (Internet Protocol TV). Several IMS stand-ards development bodies and non-IMS players have contributed knowledge to the topic of IPTV, and the mechanisms needed to support various IPTV services are well understood. In addition, there are exam-ples of researchers who have implemented IPTV services in their net-work testbeds. However, many of them do not make use of the full power of the specifications which describe the mechanisms of service discovery and service selection. These processes define support for customer device configuration, service personalisation and service se-lection in a multi-service provider ecosystem. This position paper pro-poses solutions to some of the open questions in this area and pro-vides an architecture for a testbed that properly supports service dis-covery and selection. An initial implementation addressing the topic of auto-configuration of IMS terminals for service discovery is also pre-sented.
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Date Issued: 2010

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Using an RTSP Proxy to implement the IPTV Media Function via a streaming server

- Shibeshi, Zelalem S, Terzoli, Alfredo, Bradshaw, Karen L

Authors: Shibeshi, Zelalem S , Terzoli, Alfredo , Bradshaw, Karen L
Date: 2010
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/429120 , vital:72561 , https://ieeexplore.ieee.org/abstract/document/5676629
Description: Multimedia in IMS, including IPTV, is handled by a separate unit, the Media Function (MF), which is made up of Media Control and Media Delivery Functions (MCF and MDF). According to the different specifications of an IMS based IPTV architecture, the User Equipment (UE) is expected to use the RTSP protocol as a media control protocol to interact with the MCF, and gets delivery of media from the MDF using the RTP protocol. This generally means that the streaming session is initiated from the media controller on behalf of the user but the delivery of media is sent to the UE from the media deliverer (media server). Due to lack of free and open source Media Servers and on the contrary, the availability of free and open source Streaming Servers, the ideal choice for the delivery of media in multimedia services, including IPTV, by the research community are Streaming Servers. Nevertheless, because of denial of service attack and other issues, most streaming servers do not allow different locations for the session setup request and the delivery of media of the streaming session. This makes it difficult to have a separate media control unit for IPTV service in IMS, if one wants to use a streaming server as an MDF unit. For this purpose we propose another component (an RTSP proxy and relay unit) to be part of the IPTV Media Function (MF). The unit will be used to mediate between the MFC and MDF and will properly relay media control (RTSP) commands from the UE and MFC to the MDF and RTP packets from the MDF to the UE. This, we believe, will facilitate the development of an IPTV service using readily available open source streaming servers. In this paper we show how this RTSP proxy and relay unit can be integrated into the Media Function of the IPTV architecture to ease the media delivery process of IMS based IPTV service.
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Date Issued: 2010

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Using JAIN SLEE as an interaction and policy manager for enabler-based services in next generation networks

- Tsietsi, Mosiuoa, Terzoli, Alfredo, Wells, George C

Authors: Tsietsi, Mosiuoa , Terzoli, Alfredo , Wells, George C
Date: 2010
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/431382 , vital:72770 , https://journals.pan.pl/dlibra/publication/100205/edition/86373/content
Description: The IP Multimedia Subsystem is a telecommunications framework with a standard architecture for the provision of services. While the services themselves have not been standardised, standards do exist for basic technologies that can be re-used and aggregated in order to construct more complex services. These elements are called service capabilities by the 3GPP and service enablers by the OMA, both of which are repu-table standards bodies in this area. In order to provide re-usability, there is a need to manage access to the service capabilities. Also, in order to build complex services, there is a further need to be able to manage and coordinate the interactions that occur between service capabilities. The 3GPP and the OMA have separately defined network entities that are responsible for handling aspects of these requirements, and are known as a service capability interaction manager (SCIM) and a policy enforcer respectively. However, the internal structure of the SCIM and the policy enforcer have not been standardised by the relevant bodies. In addition, as the SCIM and the policy enforcer have been defined through complementary yet separate processes, there is an opportunity to unify efforts from both bodies. This paper builds on work and stand-ards defined by the bodies, and proposes the design of an interaction manager with features borrowed from both the SCIM and the policy en-forcer. To help validate the design, we have identified a platform known as JAIN SLEE which we believe conforms to the model proposed, and we discuss how JAIN SLEE can be used to implement our ideas.
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Date Issued: 2010

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Validation of growth zone deposition in otoliths of two large endemic cyprinids in Lake Gariep, South Africa

- Winker, A Henning, Ellender, Bruce R, Weyl, Olaf L F, Booth, Anthony J

Authors: Winker, A Henning , Ellender, Bruce R , Weyl, Olaf L F , Booth, Anthony J
Date: 2010
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/446812 , vital:74562 , https://doi.org/10.1080/15627020.2010.11657263
Description: We tested the hypothesis that growth zones in the astericus otoliths of smallmouth yellowfish (Labeobarbus aeneus) and Orange River mudfish (Labeo capensis) were deposited annually. Two methods, fluorochrome marking and edge analysis of otoliths were used. For fluorochrome marking, specimens of both species were injected with 60 mg/kg fish mass oxytetracycline hydrochloride (OTC) and released into large earthen ponds under ambient conditions adjacent to Lake Gariep. Twenty-three L. aeneus and one L. capensis were recaptured 10–14 months later. Edge analysis was based on the optical interpretation of L. aeneus (n = 342) and L. capensis (n = 512) otolith margins collected between November 2006 and May 2008 from Lake Gariep. The frequency distribution of opaque margins over time was fitted using a binomial periodic regression. The estimated cycle length was not significantly different from a hypothesized 12 months for both species. The number of growth zones distal to the OTC mark was consistent with findings from the edge analysis, providing evidence that growth zones in astericus otoliths of both species can be interpreted as annuli.
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Date Issued: 2010

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