Unitarity constraints on the ratio of shear viscosity to entropy density in higher derivative gravity
- Authors: Brustein, R , Medved, A J M
- Date: 2011
- Language: English
- Type: text , Article
- Identifier: vital:6815 , http://hdl.handle.net/10962/d1004325
- Description: We discuss corrections to the ratio of shear viscosity to entropy density η/s in higher-derivative gravity theories. Generically, these theories contain ghost modes with Planck-scale masses. Motivated by general considerations about unitarity, we propose new boundary conditions for the equations of motion of the graviton perturbations that force the amplitude of the ghosts modes to vanish. We analyze explicitly four-derivative perturbative corrections to Einstein gravity which generically lead to four-derivative equations of motion, compare our choice of boundary conditions to previous proposals and show that, with our new prescription, the ratio η/s remains at the Einstein-gravity value of 1/4π to leading order in the corrections. It is argued that, when the new boundary conditions are imposed on six and higher-derivative equations of motion, η/s can only increase from the Einstein-gravity value. We also recall some general arguments that support the validity of our results to all orders in the strength of the corrections to Einstein gravity. We then discuss the particular case of Gauss-Bonnet gravity, for which the equations of motion are only of two-derivative order and the value of η/s can decrease below 1/4π when treated in a nonperturbative way. Our findings provide further evidence for the validity of the KSS bound for theories that can be viewed as perturbative corrections to Einstein gravity.
- Full Text:
- Date Issued: 2011
- Authors: Brustein, R , Medved, A J M
- Date: 2011
- Language: English
- Type: text , Article
- Identifier: vital:6815 , http://hdl.handle.net/10962/d1004325
- Description: We discuss corrections to the ratio of shear viscosity to entropy density η/s in higher-derivative gravity theories. Generically, these theories contain ghost modes with Planck-scale masses. Motivated by general considerations about unitarity, we propose new boundary conditions for the equations of motion of the graviton perturbations that force the amplitude of the ghosts modes to vanish. We analyze explicitly four-derivative perturbative corrections to Einstein gravity which generically lead to four-derivative equations of motion, compare our choice of boundary conditions to previous proposals and show that, with our new prescription, the ratio η/s remains at the Einstein-gravity value of 1/4π to leading order in the corrections. It is argued that, when the new boundary conditions are imposed on six and higher-derivative equations of motion, η/s can only increase from the Einstein-gravity value. We also recall some general arguments that support the validity of our results to all orders in the strength of the corrections to Einstein gravity. We then discuss the particular case of Gauss-Bonnet gravity, for which the equations of motion are only of two-derivative order and the value of η/s can decrease below 1/4π when treated in a nonperturbative way. Our findings provide further evidence for the validity of the KSS bound for theories that can be viewed as perturbative corrections to Einstein gravity.
- Full Text:
- Date Issued: 2011
Evaluating the Wald entropy from two-derivative terms in quadratic actions
- Brustein, R, Gorbonos, D, Hadad, M, Medved, A J M
- Authors: Brustein, R , Gorbonos, D , Hadad, M , Medved, A J M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6816 , http://hdl.handle.net/10962/d1004326
- Description: We evaluate the Wald Noether charge entropy for a black hole in generalized theories of gravity. Expanding the Lagrangian to second order in gravitational perturbations, we show that contributions to the entropy density originate only from the coefficients of two-derivative terms. The same considerations are extended to include matter fields and to show that arbitrary powers of matter fields and their symmetrized covariant derivatives cannot contribute to the entropy density. We also explain how to use the linearized gravitational field equation rather than quadratic actions to obtain the same results. Several explicit examples are presented that allow us to clarify subtle points in the derivation and application of our method.
- Full Text:
- Date Issued: 2011
- Authors: Brustein, R , Gorbonos, D , Hadad, M , Medved, A J M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6816 , http://hdl.handle.net/10962/d1004326
- Description: We evaluate the Wald Noether charge entropy for a black hole in generalized theories of gravity. Expanding the Lagrangian to second order in gravitational perturbations, we show that contributions to the entropy density originate only from the coefficients of two-derivative terms. The same considerations are extended to include matter fields and to show that arbitrary powers of matter fields and their symmetrized covariant derivatives cannot contribute to the entropy density. We also explain how to use the linearized gravitational field equation rather than quadratic actions to obtain the same results. Several explicit examples are presented that allow us to clarify subtle points in the derivation and application of our method.
- Full Text:
- Date Issued: 2011
Non-perturbative unitarity constraints on the ratio of shear viscosity to entropy density in ultraviolet-complete theories with a gravity dual
- Authors: Brustein, R , Medved, A J M
- Date: 2011
- Language: English
- Type: text , Article
- Identifier: vital:6817 , http://hdl.handle.net/10962/d1004327
- Description: We reconsider, from a novel perspective, how unitarity constrains the corrections to the ratio of shear viscosity η to entropy density s. We start with higher-derivative extensions of Einstein gravity in asymptotically anti-de Sitter spacetimes. It is assumed that these theories are derived from string theory and thus have a unitary UV completion that is dual to a unitary, UV-complete boundary gauge theory. We then propose that the gravitational perturbations about a solution of the UV-complete theory are described by an effective theory whose linearized equations of motion have at most two time derivatives. Our proposal leads to a concrete prescription for the calculation of η/s for theories of gravity with arbitrary higher-derivative corrections. The resulting ratio can take on values above or below 1/4π and is consistent with all the previous calculations, even though our reasoning is substantially different. For the purpose of calculating η/s, our proposal also leads to only two possible candidates for the effective two-derivative theory: Einstein and Gauss-Bonnet gravity. The distinction between the two is that Einstein gravity satisfies the equivalence principle, and so its graviton correlation functions are polarization-independent, whereas the Gauss-Bonnet theory has polarization-dependent correlation functions. We discuss the graviton three-point functions in this context and explain how these can provide additional information on the value of η/s.
- Full Text:
- Date Issued: 2011
- Authors: Brustein, R , Medved, A J M
- Date: 2011
- Language: English
- Type: text , Article
- Identifier: vital:6817 , http://hdl.handle.net/10962/d1004327
- Description: We reconsider, from a novel perspective, how unitarity constrains the corrections to the ratio of shear viscosity η to entropy density s. We start with higher-derivative extensions of Einstein gravity in asymptotically anti-de Sitter spacetimes. It is assumed that these theories are derived from string theory and thus have a unitary UV completion that is dual to a unitary, UV-complete boundary gauge theory. We then propose that the gravitational perturbations about a solution of the UV-complete theory are described by an effective theory whose linearized equations of motion have at most two time derivatives. Our proposal leads to a concrete prescription for the calculation of η/s for theories of gravity with arbitrary higher-derivative corrections. The resulting ratio can take on values above or below 1/4π and is consistent with all the previous calculations, even though our reasoning is substantially different. For the purpose of calculating η/s, our proposal also leads to only two possible candidates for the effective two-derivative theory: Einstein and Gauss-Bonnet gravity. The distinction between the two is that Einstein gravity satisfies the equivalence principle, and so its graviton correlation functions are polarization-independent, whereas the Gauss-Bonnet theory has polarization-dependent correlation functions. We discuss the graviton three-point functions in this context and explain how these can provide additional information on the value of η/s.
- Full Text:
- Date Issued: 2011
Does the growth of structure affect our dynamical models of the Universe? The averaging, backreaction, and fitting problems in cosmology
- Clarkson, C, Ellis, G, Larena, Julien, Umeh, O
- Authors: Clarkson, C , Ellis, G , Larena, Julien , Umeh, O
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6791 , http://hdl.handle.net/10962/d1006944
- Description: Structure occurs over a vast range of scales in the Universe. Our large-scale cosmological models are coarse-grained representations of what exists, which have much less structure than there really is. An important problem for cosmology is determining the influence the small-scale structure in the Universe has on its large-scale dynamics and observations. Is there a significant, general relativistic, backreaction effect from averaging over structure? One issue is whether the process of smoothing over structure can contribute to an acceleration term and so alter the apparent value of the cosmological constant. If this is not the case, are there other aspects of concordance cosmology that are affected by backreaction effects? Despite much progress, this 'averaging problem' is still unanswered, but it cannot be ignored in an era of precision cosmology, for instance it may affect aspects of baryon acoustic oscillation observations.
- Full Text:
- Date Issued: 2011
- Authors: Clarkson, C , Ellis, G , Larena, Julien , Umeh, O
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6791 , http://hdl.handle.net/10962/d1006944
- Description: Structure occurs over a vast range of scales in the Universe. Our large-scale cosmological models are coarse-grained representations of what exists, which have much less structure than there really is. An important problem for cosmology is determining the influence the small-scale structure in the Universe has on its large-scale dynamics and observations. Is there a significant, general relativistic, backreaction effect from averaging over structure? One issue is whether the process of smoothing over structure can contribute to an acceleration term and so alter the apparent value of the cosmological constant. If this is not the case, are there other aspects of concordance cosmology that are affected by backreaction effects? Despite much progress, this 'averaging problem' is still unanswered, but it cannot be ignored in an era of precision cosmology, for instance it may affect aspects of baryon acoustic oscillation observations.
- Full Text:
- Date Issued: 2011
3000 miles from home: a new Gastrosericus baobabicus Pulawski, 1995 (Hymenoptera, Larridae) distribution record highlights that the Sahel has a distinct entomofaunal signature
- Clitheroe, C-L, Villet, Martin H
- Authors: Clitheroe, C-L , Villet, Martin H
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6846 , http://hdl.handle.net/10962/d1011099
- Description: [from introduction] On October 30, 1953, an unidentified female wasp (Fig. 1) was collected from ‘Belet Uen, Somaliland’ (= Beledweyne, 4°44’N 45°12’E), situated in the valley of the Shebelle River, HiraanProvince,Somalia. It was deposited in the aculeate Hymenoptera collection of the Albany Museum, Grahamstown by D. Greathead prior to 1968. Apart from the words ‘Somaliland’ and ‘Desert Locust Survey’ the label is handwritten and the collector’snameis not recorded. Greathead’s sister, S. Gess (Albany Museum), deciphered the label and stated that he had worked for the Desert Locust Survey, investigating the natural enemies of locusts and had been in Somalia (then Somaliland) at that time (Murphy & Cock 2007). The specimen was sent in 2004 by F. Gess to W. Pulawski, who determined it as Gastrosericus baobabicus Pulawski, 1995. Gastrosericus species prey on spiders and a variety of small insects (Pulawski 1995), including Orthoptera (Krombein & Pulawski 1986), so it is likely that Greathead collected the specimen in connection with his interest in the insect enemies of Acridoidea (Orthoptera) (Greathead 1962).
- Full Text:
- Date Issued: 2011
- Authors: Clitheroe, C-L , Villet, Martin H
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6846 , http://hdl.handle.net/10962/d1011099
- Description: [from introduction] On October 30, 1953, an unidentified female wasp (Fig. 1) was collected from ‘Belet Uen, Somaliland’ (= Beledweyne, 4°44’N 45°12’E), situated in the valley of the Shebelle River, HiraanProvince,Somalia. It was deposited in the aculeate Hymenoptera collection of the Albany Museum, Grahamstown by D. Greathead prior to 1968. Apart from the words ‘Somaliland’ and ‘Desert Locust Survey’ the label is handwritten and the collector’snameis not recorded. Greathead’s sister, S. Gess (Albany Museum), deciphered the label and stated that he had worked for the Desert Locust Survey, investigating the natural enemies of locusts and had been in Somalia (then Somaliland) at that time (Murphy & Cock 2007). The specimen was sent in 2004 by F. Gess to W. Pulawski, who determined it as Gastrosericus baobabicus Pulawski, 1995. Gastrosericus species prey on spiders and a variety of small insects (Pulawski 1995), including Orthoptera (Krombein & Pulawski 1986), so it is likely that Greathead collected the specimen in connection with his interest in the insect enemies of Acridoidea (Orthoptera) (Greathead 1962).
- Full Text:
- Date Issued: 2011
Energy versus angular momentum in black hole binaries
- Damour, T, Nagar, A, Pollney, D, Reisswig, C
- Authors: Damour, T , Nagar, A , Pollney, D , Reisswig, C
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6792 , http://hdl.handle.net/10962/d1006946
- Description: Using accurate numerical-relativity simulations of (nonspinning) black-hole binaries with mass ratios 1∶1, 2∶1, and 3∶1, we compute the gauge-invariant relation between the (reduced) binding energy E and the (reduced) angular momentum j of the system. We show that the relation E(j) is an accurate diagnostic of the dynamics of a black-hole binary in a highly relativistic regime. By comparing the numerical-relativity ENR(j) curve with the predictions of several analytic approximation schemes, we find that, while the canonically defined, nonresummed post-Newtonian–expanded EPN(j) relation exhibits large and growing deviations from ENR(j), the prediction of the effective one body formalism, based purely on known analytical results (without any calibration to numerical relativity), agrees strikingly well with the numerical-relativity results.
- Full Text:
- Date Issued: 2011
- Authors: Damour, T , Nagar, A , Pollney, D , Reisswig, C
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6792 , http://hdl.handle.net/10962/d1006946
- Description: Using accurate numerical-relativity simulations of (nonspinning) black-hole binaries with mass ratios 1∶1, 2∶1, and 3∶1, we compute the gauge-invariant relation between the (reduced) binding energy E and the (reduced) angular momentum j of the system. We show that the relation E(j) is an accurate diagnostic of the dynamics of a black-hole binary in a highly relativistic regime. By comparing the numerical-relativity ENR(j) curve with the predictions of several analytic approximation schemes, we find that, while the canonically defined, nonresummed post-Newtonian–expanded EPN(j) relation exhibits large and growing deviations from ENR(j), the prediction of the effective one body formalism, based purely on known analytical results (without any calibration to numerical relativity), agrees strikingly well with the numerical-relativity results.
- Full Text:
- Date Issued: 2011
The potential for voluntary instruments to achieve conservation planning goals : the case of conservancies in South Africa
- Downsborough, Linda, Shackleton, Charlie M, Knight, Andrew T
- Authors: Downsborough, Linda , Shackleton, Charlie M , Knight, Andrew T
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6629 , http://hdl.handle.net/10962/d1006821
- Description: Spatial prioritizations and gap analyses are increasingly undertaken to allocate conservation resources. Most spatial prioritizations are conducted without specifying the conservation instruments to be implemented and gap analyses typically assess formally protected areas but increasingly include private land conservation instruments. We examine conservancies to see if these voluntary instruments contribute towards achieving goals of South African conservation planning initiatives. We conducted a nationwide survey and interviews with conservancy members in Gauteng and the Eastern Cape. Conservancies have potential for assisting South Africa to achieve conservation planning goals at national and local scales but their inclusion in spatial prioritizations and gap analyses predicates improved protection for nature, operational refinement and increased support. We sound a warning to conservation planning initiatives that incorporate voluntary instruments on private land, and present recommendations for strengthening such instruments to make them more effective. Our findings may assist conservation planners elsewhere to design more effective conservation planning initiatives focused on private land.
- Full Text:
- Date Issued: 2011
- Authors: Downsborough, Linda , Shackleton, Charlie M , Knight, Andrew T
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6629 , http://hdl.handle.net/10962/d1006821
- Description: Spatial prioritizations and gap analyses are increasingly undertaken to allocate conservation resources. Most spatial prioritizations are conducted without specifying the conservation instruments to be implemented and gap analyses typically assess formally protected areas but increasingly include private land conservation instruments. We examine conservancies to see if these voluntary instruments contribute towards achieving goals of South African conservation planning initiatives. We conducted a nationwide survey and interviews with conservancy members in Gauteng and the Eastern Cape. Conservancies have potential for assisting South Africa to achieve conservation planning goals at national and local scales but their inclusion in spatial prioritizations and gap analyses predicates improved protection for nature, operational refinement and increased support. We sound a warning to conservation planning initiatives that incorporate voluntary instruments on private land, and present recommendations for strengthening such instruments to make them more effective. Our findings may assist conservation planners elsewhere to design more effective conservation planning initiatives focused on private land.
- Full Text:
- Date Issued: 2011
Good Chemistry
- Authors: Grange, Helen
- Date: 2011
- Subjects: Nyokong, Tebello , Africa-Arab State 2009 Unesco-L'Oreal Award for Women in Science
- Language: English
- Type: Article , text
- Identifier: vital:7185 , http://hdl.handle.net/10962/d1006276 , Nyokong, Tebello , Africa-Arab State 2009 Unesco-L'Oreal Award for Women in Science
- Description: Helen Grange profiles four women who've fearlessly taken on the complex predominantly male-dominated field of science.
- Full Text:
- Date Issued: 2011
- Authors: Grange, Helen
- Date: 2011
- Subjects: Nyokong, Tebello , Africa-Arab State 2009 Unesco-L'Oreal Award for Women in Science
- Language: English
- Type: Article , text
- Identifier: vital:7185 , http://hdl.handle.net/10962/d1006276 , Nyokong, Tebello , Africa-Arab State 2009 Unesco-L'Oreal Award for Women in Science
- Description: Helen Grange profiles four women who've fearlessly taken on the complex predominantly male-dominated field of science.
- Full Text:
- Date Issued: 2011
Publicising chemistry in a multicultural society through chemistry outreach
- Harrison, T G, Shallcross, D E, Norman, N C, Sewry, Joyce D, Davies-Coleman, Michael T
- Authors: Harrison, T G , Shallcross, D E , Norman, N C , Sewry, Joyce D , Davies-Coleman, Michael T
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6573 , http://hdl.handle.net/10962/d1004136
- Description: Given the emphasis in Higher Education on community engagement in South Africa and the importance of international collaboration, we discuss a joint approach to chemistry outreach in two countries on two continents with widely differing target school audiences. We describe the history of the partnership between the chemistry departments at Rhodes University and the University of Bristol and provide an outline of the chemistry content of their outreach initiatives, the modes of delivery, the advantages to both departments and their students for involvement in various levels of outreach, the challenges they still face and additional opportunities that such work facilitated. The lecture demonstration 'A Pollutant's Tale' was presented to thousands of learners all over the world, including learners at resource-deprived schools in South Africa. Challenges to extend outreach activities in South Africa include long travelling distances, as well as a lack of facilities (such as school halls and electricity) at schools. Outreach activities not only impacted on the target audience of young learners, they also impacted upon the postgraduate and other chemistry students taking part in these initiatives. This collaboration strengthened both institutions and their outreach work and may also lead to chemistry research collaborations between the academics involved.
- Full Text:
- Date Issued: 2011
- Authors: Harrison, T G , Shallcross, D E , Norman, N C , Sewry, Joyce D , Davies-Coleman, Michael T
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6573 , http://hdl.handle.net/10962/d1004136
- Description: Given the emphasis in Higher Education on community engagement in South Africa and the importance of international collaboration, we discuss a joint approach to chemistry outreach in two countries on two continents with widely differing target school audiences. We describe the history of the partnership between the chemistry departments at Rhodes University and the University of Bristol and provide an outline of the chemistry content of their outreach initiatives, the modes of delivery, the advantages to both departments and their students for involvement in various levels of outreach, the challenges they still face and additional opportunities that such work facilitated. The lecture demonstration 'A Pollutant's Tale' was presented to thousands of learners all over the world, including learners at resource-deprived schools in South Africa. Challenges to extend outreach activities in South Africa include long travelling distances, as well as a lack of facilities (such as school halls and electricity) at schools. Outreach activities not only impacted on the target audience of young learners, they also impacted upon the postgraduate and other chemistry students taking part in these initiatives. This collaboration strengthened both institutions and their outreach work and may also lead to chemistry research collaborations between the academics involved.
- Full Text:
- Date Issued: 2011
Elucidation of the complex Baylis-Hillman reaction of 3-methoxy-2-nitrobenzaldehyde with methyl vinyl ketone
- Idahosa, Kenudi C, Molefe, Duduzile M, Pakade, Vusumzi E, Brown, Michael E
- Authors: Idahosa, Kenudi C , Molefe, Duduzile M , Pakade, Vusumzi E , Brown, Michael E
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6574 , http://hdl.handle.net/10962/d1004137
- Description: DABCO-catalyzed reaction of 3-methoxy-2-nitrobenzaldehyde with methyl vinyl ketone (MVK) affords a mixture of products, comprising the ‘normal’ Baylis-Hillman adduct, theMVKdimer and a pair of diastereomeric bis-(MVK)Baylis-Hillman adducts. 1HNMRspectroscopy-based kinetic studies have provided clear insights into the competing pathways and product distribution in this complex reaction.
- Full Text:
- Date Issued: 2011
- Authors: Idahosa, Kenudi C , Molefe, Duduzile M , Pakade, Vusumzi E , Brown, Michael E
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6574 , http://hdl.handle.net/10962/d1004137
- Description: DABCO-catalyzed reaction of 3-methoxy-2-nitrobenzaldehyde with methyl vinyl ketone (MVK) affords a mixture of products, comprising the ‘normal’ Baylis-Hillman adduct, theMVKdimer and a pair of diastereomeric bis-(MVK)Baylis-Hillman adducts. 1HNMRspectroscopy-based kinetic studies have provided clear insights into the competing pathways and product distribution in this complex reaction.
- Full Text:
- Date Issued: 2011
Diverse pollination systems of the twin-spurred orchid genus Satyrium in African grasslands
- Johnson, S.D, Peter, C.I, Ellis, A.G, Boberg, E, Botes, C, Van der Niet, T
- Authors: Johnson, S.D , Peter, C.I , Ellis, A.G , Boberg, E , Botes, C , Van der Niet, T
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6558 , http://hdl.handle.net/10962/d1006025 , http://dx.doi.org/10.1007/s00606-010-0411-1
- Description: The large terrestrial orchid genus Satyrium underwent evolutionary radiations in the Cape floral region and the grasslands of southern and eastern Africa. These radiations were accompanied by tremendous diversification of the unusual twin-spurred flowers that characterize the genus, but pollination data required to interpret these patterns of floral evolution have been lacking for grassland species in the genus. Here we document pollinators, nectar properties, and levels of pollination success for 11 grassland Satyrium species in southern and south-central Africa. Pollinators of these species include bees, beetles, butterflies, hawkmoths, noctuid moths, long-proboscid flies, and sunbirds. Most species appear to be specialized for pollination by one functional pollinator group. Long-proboscid fly pollination systems are reported for the first time in Satyrium (in S. macrophyllum and a high-altitude form of S. neglectum). Floral morphology, especially spur length and rostellum structure, differs markedly among plants with different pollinators, while nectar volume, concentration, and sugar composition are fairly uniform across species. Most taxa exhibited high levels of pollination success (>50% of flowers pollinated), a trend that can be attributed to the presence of nectar in the twin spurs.
- Full Text:
- Date Issued: 2011
- Authors: Johnson, S.D , Peter, C.I , Ellis, A.G , Boberg, E , Botes, C , Van der Niet, T
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6558 , http://hdl.handle.net/10962/d1006025 , http://dx.doi.org/10.1007/s00606-010-0411-1
- Description: The large terrestrial orchid genus Satyrium underwent evolutionary radiations in the Cape floral region and the grasslands of southern and eastern Africa. These radiations were accompanied by tremendous diversification of the unusual twin-spurred flowers that characterize the genus, but pollination data required to interpret these patterns of floral evolution have been lacking for grassland species in the genus. Here we document pollinators, nectar properties, and levels of pollination success for 11 grassland Satyrium species in southern and south-central Africa. Pollinators of these species include bees, beetles, butterflies, hawkmoths, noctuid moths, long-proboscid flies, and sunbirds. Most species appear to be specialized for pollination by one functional pollinator group. Long-proboscid fly pollination systems are reported for the first time in Satyrium (in S. macrophyllum and a high-altitude form of S. neglectum). Floral morphology, especially spur length and rostellum structure, differs markedly among plants with different pollinators, while nectar volume, concentration, and sugar composition are fairly uniform across species. Most taxa exhibited high levels of pollination success (>50% of flowers pollinated), a trend that can be attributed to the presence of nectar in the twin spurs.
- Full Text:
- Date Issued: 2011
Designer ligands : the search for metal ion selectivity
- Authors: Kaye, P T
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6576 , http://hdl.handle.net/10962/d1004139
- Description: The paper reviews research conducted at Rhodes University towards the development of metal-selective ligands. The research has focused on the rational design, synthesis and evaluation of novel ligands for use in the formation of copper complexes as biomimetic models of the metalloenzyme, tyrosinase, and for the selective extraction of silver, nickel and platinum group metal ions in the presence of contaminating metal ions. Attention has also been given to the development of efficient, metal-selective molecular imprinted polymers.
- Full Text:
- Date Issued: 2011
- Authors: Kaye, P T
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6576 , http://hdl.handle.net/10962/d1004139
- Description: The paper reviews research conducted at Rhodes University towards the development of metal-selective ligands. The research has focused on the rational design, synthesis and evaluation of novel ligands for use in the formation of copper complexes as biomimetic models of the metalloenzyme, tyrosinase, and for the selective extraction of silver, nickel and platinum group metal ions in the presence of contaminating metal ions. Attention has also been given to the development of efficient, metal-selective molecular imprinted polymers.
- Full Text:
- Date Issued: 2011
Molecular systematics of the African snake family Lamprophiidae Fitzinger, 1843 (Serpentes: Elapoidea), with particular focus on the genera Lamprophis Fitzinger 1843 and Mehelya Csiki 1903
- Kelly, Christopher M R, Branch, William R, Broadley, Donald G, Barker, Nigel P, Villet, Martin H
- Authors: Kelly, Christopher M R , Branch, William R , Broadley, Donald G , Barker, Nigel P , Villet, Martin H
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6861 , http://hdl.handle.net/10962/d1011151
- Description: The snake family Lamprophiidae Fitzinger (Serpentes: Elapoidea) is a putatively Late Eocene radiation of nocturnal snakes endemic to the African continent. It incorporates many of the most characteristic and prolific of Africa's non-venomous snake species, including the widespread type genus Lamprophis Fitzinger, 1843 (house snakes). We used approximately 2500 bases of mitochondrial and nuclear DNA sequence data from 28 (41%) of the approximately 68 recognised lamprophiid species in nine of the eleven genera to investigate phylogenetic structure in the family and to inform taxonomy at the generic level. Cytochrome b, ND4 and tRNA gene sequences (mitochondrial) and c-mos sequences (nuclear) were analysed using Maximum Likelihood, Bayesian Inference and Maximum Parsimony methods. The genus Mehelya Csiki, 1903 was paraphyletic with respect to Gonionotophis Boulenger, 1893. To address this, the concept of Gonionotophis is expanded to include all current Mehelya species. The genus Lamprophis emerged polyphyletic: the enigmatic Lamprophis swazicus was sister to Hormonotus modestus from West Africa, and not closely related to its nominal congeners. It is moved to a new monotypic genus (Inyoka gen. nov.). The remaining Lamprophis species occur in three early-diverging lineages. (1) Lamprophis virgatus and the widely distributed Lamprophis fuliginosus species complex (which also includes Lamprophis lineatus and Lamprophis olivaceus) formed a clade for which the generic name Boaedon Duméril, Bibron & Duméril, 1854 is resurrected. (2) The water snakes (Lycodonomorphus) were nested within Lamprophis (sensu lato), sister to Lamprophis inornatus. We transfer this species to the genus Lycodonomorphus Fitzinger, 1843. (3) We restrict Lamprophis (sensu strictissimo) to a small clade of four species endemic to southern Africa: the type species of Lamprophis Fitzinger, 1843 (Lamprophis aurora) plus Lamprophis fiskii, Lamprophis fuscus and Lamprophis guttatus.
- Full Text:
- Date Issued: 2011
- Authors: Kelly, Christopher M R , Branch, William R , Broadley, Donald G , Barker, Nigel P , Villet, Martin H
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6861 , http://hdl.handle.net/10962/d1011151
- Description: The snake family Lamprophiidae Fitzinger (Serpentes: Elapoidea) is a putatively Late Eocene radiation of nocturnal snakes endemic to the African continent. It incorporates many of the most characteristic and prolific of Africa's non-venomous snake species, including the widespread type genus Lamprophis Fitzinger, 1843 (house snakes). We used approximately 2500 bases of mitochondrial and nuclear DNA sequence data from 28 (41%) of the approximately 68 recognised lamprophiid species in nine of the eleven genera to investigate phylogenetic structure in the family and to inform taxonomy at the generic level. Cytochrome b, ND4 and tRNA gene sequences (mitochondrial) and c-mos sequences (nuclear) were analysed using Maximum Likelihood, Bayesian Inference and Maximum Parsimony methods. The genus Mehelya Csiki, 1903 was paraphyletic with respect to Gonionotophis Boulenger, 1893. To address this, the concept of Gonionotophis is expanded to include all current Mehelya species. The genus Lamprophis emerged polyphyletic: the enigmatic Lamprophis swazicus was sister to Hormonotus modestus from West Africa, and not closely related to its nominal congeners. It is moved to a new monotypic genus (Inyoka gen. nov.). The remaining Lamprophis species occur in three early-diverging lineages. (1) Lamprophis virgatus and the widely distributed Lamprophis fuliginosus species complex (which also includes Lamprophis lineatus and Lamprophis olivaceus) formed a clade for which the generic name Boaedon Duméril, Bibron & Duméril, 1854 is resurrected. (2) The water snakes (Lycodonomorphus) were nested within Lamprophis (sensu lato), sister to Lamprophis inornatus. We transfer this species to the genus Lycodonomorphus Fitzinger, 1843. (3) We restrict Lamprophis (sensu strictissimo) to a small clade of four species endemic to southern Africa: the type species of Lamprophis Fitzinger, 1843 (Lamprophis aurora) plus Lamprophis fiskii, Lamprophis fuscus and Lamprophis guttatus.
- Full Text:
- Date Issued: 2011
A South African response to ethics in legal education
- Authors: Kruuse, Helen
- Date: 2011
- Language: English
- Type: Article , text
- Identifier: http://hdl.handle.net/10962/54174 , vital:26399 , https://www.routledge.com/The-Ethics-Project-in-Legal-Education/Robertson-Corbin-Tranter-Bartlett/p/book/9780415546515
- Description: The contributions in this volume suggest that "the ethics project in legal education" is increasingly an international one. Even though the strength of commitment by both the profession and the legal academy to "ethics learning" within law schools varies, two fundamental questions confront all who work in this area. First, what is it that we want our students to learn (or, perhaps, in what manner do we want our students to develop) from the teaching of "legal ethics"? Second, how can we create a learning environment that will encourage the nature and quality of learning we think is important?.
- Full Text: false
- Date Issued: 2011
- Authors: Kruuse, Helen
- Date: 2011
- Language: English
- Type: Article , text
- Identifier: http://hdl.handle.net/10962/54174 , vital:26399 , https://www.routledge.com/The-Ethics-Project-in-Legal-Education/Robertson-Corbin-Tranter-Bartlett/p/book/9780415546515
- Description: The contributions in this volume suggest that "the ethics project in legal education" is increasingly an international one. Even though the strength of commitment by both the profession and the legal academy to "ethics learning" within law schools varies, two fundamental questions confront all who work in this area. First, what is it that we want our students to learn (or, perhaps, in what manner do we want our students to develop) from the teaching of "legal ethics"? Second, how can we create a learning environment that will encourage the nature and quality of learning we think is important?.
- Full Text: false
- Date Issued: 2011
The distribution, abundance and composition of street trees in selected towns of the Eastern Cape, South Africa
- Kuruneri-Chitepo, C, Shackleton, Charlie M
- Authors: Kuruneri-Chitepo, C , Shackleton, Charlie M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6639 , http://hdl.handle.net/10962/d1006865
- Description: Street trees are an important component of the urban forest as they provide critical ecosystem services which contribute to human health and environmental quality. However, little is known about the distribution, diversity and density of street trees, particularly in the developing world where urbanisation is most rapid. Thus, the aim of this paper was to assess the distribution, composition and abundance of street trees across three towns along an environmental gradient in the Eastern Cape of South Africa, and identify the key challenges faced by local officials concerned with the provision of street trees. In each town, streets were randomly sampled in the commercial, affluent residential, township settlement and low cost housing areas under the Reconstruction and Development Program (RDP). Attributes recorded per tree were species, circumference, height and health, while semi-structured interviews were conducted with the municipal officials involved in the establishment and maintenance of street trees. A total of 1,485 trees were encountered, comprising 61 species. The majority (56%) of trees were alien species. Noticeable differences in tree density and species richness were evident across suburbs, being highest in the more affluent suburbs and poorly represented in the low income township and RDP areas. There was a decreasing mean tree height and health score along the environmental gradient from the coastal town to the inland town. Although awareness of the benefits of street trees was high, as was the need to reduce the proportion of alien species, the primary constraint to establishment and maintenance of street trees in the three towns was limited budget and human resources.
- Full Text:
- Date Issued: 2011
- Authors: Kuruneri-Chitepo, C , Shackleton, Charlie M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6639 , http://hdl.handle.net/10962/d1006865
- Description: Street trees are an important component of the urban forest as they provide critical ecosystem services which contribute to human health and environmental quality. However, little is known about the distribution, diversity and density of street trees, particularly in the developing world where urbanisation is most rapid. Thus, the aim of this paper was to assess the distribution, composition and abundance of street trees across three towns along an environmental gradient in the Eastern Cape of South Africa, and identify the key challenges faced by local officials concerned with the provision of street trees. In each town, streets were randomly sampled in the commercial, affluent residential, township settlement and low cost housing areas under the Reconstruction and Development Program (RDP). Attributes recorded per tree were species, circumference, height and health, while semi-structured interviews were conducted with the municipal officials involved in the establishment and maintenance of street trees. A total of 1,485 trees were encountered, comprising 61 species. The majority (56%) of trees were alien species. Noticeable differences in tree density and species richness were evident across suburbs, being highest in the more affluent suburbs and poorly represented in the low income township and RDP areas. There was a decreasing mean tree height and health score along the environmental gradient from the coastal town to the inland town. Although awareness of the benefits of street trees was high, as was the need to reduce the proportion of alien species, the primary constraint to establishment and maintenance of street trees in the three towns was limited budget and human resources.
- Full Text:
- Date Issued: 2011
Late Quaternary environmental phases in the Eastern Cape and adjacent Plettenberg Bay-Knysna region and Little Karoo, South Africa
- Authors: Lewis, Colin A
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6712 , http://hdl.handle.net/10962/d1006749
- Description: Four major climato-environmental phases have been identified in the Eastern Cape, Plettenberg Bay-Knysna region and Little Karoo between somewhat before ~ 40 000 cal. a BP and the present: the Birnam Interstadial from before 40 000 cal. a BP until ~ 24 000 cal. a BP; the Bottelnek Stadial (apparently equating with the Last Glacial Maximum) from ~24 000 cal. a BP until before ~ 18 350 cal. a BP; the Aliwal North (apparently equating with the Late Glacial) from before ~ 18 350 cal. a BP until ~ 11 000 cal. a BP; the Dinorben (apparently equating with the Holocene) from ~ 11 000 cal. a BP until the present. The evidence for, and the characteristics of, these phases is briefly described.
- Full Text:
- Date Issued: 2011
- Authors: Lewis, Colin A
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6712 , http://hdl.handle.net/10962/d1006749
- Description: Four major climato-environmental phases have been identified in the Eastern Cape, Plettenberg Bay-Knysna region and Little Karoo between somewhat before ~ 40 000 cal. a BP and the present: the Birnam Interstadial from before 40 000 cal. a BP until ~ 24 000 cal. a BP; the Bottelnek Stadial (apparently equating with the Last Glacial Maximum) from ~24 000 cal. a BP until before ~ 18 350 cal. a BP; the Aliwal North (apparently equating with the Late Glacial) from before ~ 18 350 cal. a BP until ~ 11 000 cal. a BP; the Dinorben (apparently equating with the Holocene) from ~ 11 000 cal. a BP until the present. The evidence for, and the characteristics of, these phases is briefly described.
- Full Text:
- Date Issued: 2011
Culture as a discursive resource opposing legal abortion
- Macleod, Catriona I, Sigcau, Nomakhosi, Luwaca, Pumeza
- Authors: Macleod, Catriona I , Sigcau, Nomakhosi , Luwaca, Pumeza
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6293 , http://hdl.handle.net/10962/d1014721 , http://dx.doi.org/10.1080/09581596.2010.492211
- Description: The notion of ‘culture’ features in the abortion literature to explicate, first, contestation of the meaning of abortion (as in the ‘culture wars’ about abortion), second, the normalisation of abortion in certain countries (as in ‘abortion culture’), third, the response of women to abortion within a particular social milieu and fourth, cross-cultural variability in attitudes towards and experiences of abortion. What is missing is an exploration of how ‘culture’ may be deployed as a discursive resource to oppose legal abortion. In this article, we report on a study conducted in a rural area of South Africa. We conducted focus group discussions utilising hypothetical vignettes to stimulate talk. Although, inconsistencies were evident in participants’ talk, in the context of cultural discussions, abortion was constructed as killing and inevitably destructive of cultural values and traditions. Abortion was equated with colonialist interventions and as something that should be opposed in the preservation of culture. Furthermore, cultural opposition to abortion was rooted in fears around the breakdown of gendered and generational power relations. Examples of how culture may be used in everyday interactions to induce shame and negative experiences are also discussed.
- Full Text:
- Date Issued: 2011
- Authors: Macleod, Catriona I , Sigcau, Nomakhosi , Luwaca, Pumeza
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6293 , http://hdl.handle.net/10962/d1014721 , http://dx.doi.org/10.1080/09581596.2010.492211
- Description: The notion of ‘culture’ features in the abortion literature to explicate, first, contestation of the meaning of abortion (as in the ‘culture wars’ about abortion), second, the normalisation of abortion in certain countries (as in ‘abortion culture’), third, the response of women to abortion within a particular social milieu and fourth, cross-cultural variability in attitudes towards and experiences of abortion. What is missing is an exploration of how ‘culture’ may be deployed as a discursive resource to oppose legal abortion. In this article, we report on a study conducted in a rural area of South Africa. We conducted focus group discussions utilising hypothetical vignettes to stimulate talk. Although, inconsistencies were evident in participants’ talk, in the context of cultural discussions, abortion was constructed as killing and inevitably destructive of cultural values and traditions. Abortion was equated with colonialist interventions and as something that should be opposed in the preservation of culture. Furthermore, cultural opposition to abortion was rooted in fears around the breakdown of gendered and generational power relations. Examples of how culture may be used in everyday interactions to induce shame and negative experiences are also discussed.
- Full Text:
- Date Issued: 2011
Has deregulation of non-timber forest product controls and marketing in Orissa state (India) affected local patterns of use and marketing
- Mahapatra, A K, Shackleton, Charlie M
- Authors: Mahapatra, A K , Shackleton, Charlie M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6643 , http://hdl.handle.net/10962/d1006872
- Description: State control of marketing agricultural or forestry products may lead to a trade monopoly and restricted competition, resulting in inequitable returns to producers. Consequently, market deregulation for agriculture and other natural products has been advocated to improve market efficiencies, participation and returns for the producers and local traders. The study examines the impact of deregulation of state marketing controls on collection, sale and returns to extractors and traders from non-timber forest products. It assessed whether deregulation policy resulted in greater benefits to primary extractors and a win–win situation for both producers and traders? Mixed effects were found, with no significant changes in terms of trade, demand, or quantum of consumption; but there was an overall increase in the procurement price for several products following deregulation. The collection and farm gate price of tree based oilseeds and honey increased due to lower transaction costs, and ease of trading with a continued demand for these products. The impact on less valuable products was insignificant. Abolition of monopolistic trading increased competition and had a pull effect on the local market prices of several NTFPs. Although traders paid a higher price to procure products, overall they also benefited being able to sell the purchased products to merchants and manufacturers at a better margin than previously.
- Full Text:
- Date Issued: 2011
- Authors: Mahapatra, A K , Shackleton, Charlie M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6643 , http://hdl.handle.net/10962/d1006872
- Description: State control of marketing agricultural or forestry products may lead to a trade monopoly and restricted competition, resulting in inequitable returns to producers. Consequently, market deregulation for agriculture and other natural products has been advocated to improve market efficiencies, participation and returns for the producers and local traders. The study examines the impact of deregulation of state marketing controls on collection, sale and returns to extractors and traders from non-timber forest products. It assessed whether deregulation policy resulted in greater benefits to primary extractors and a win–win situation for both producers and traders? Mixed effects were found, with no significant changes in terms of trade, demand, or quantum of consumption; but there was an overall increase in the procurement price for several products following deregulation. The collection and farm gate price of tree based oilseeds and honey increased due to lower transaction costs, and ease of trading with a continued demand for these products. The impact on less valuable products was insignificant. Abolition of monopolistic trading increased competition and had a pull effect on the local market prices of several NTFPs. Although traders paid a higher price to procure products, overall they also benefited being able to sell the purchased products to merchants and manufacturers at a better margin than previously.
- Full Text:
- Date Issued: 2011
Pet stores, aquarists and the internet trade as modes of introduction and spread of invasive macrophytes in South Africa
- Martin, Grant D, Coetzee, Julie A
- Authors: Martin, Grant D , Coetzee, Julie A
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6843 , http://hdl.handle.net/10962/d1011045
- Description: Submerged aquatic invasive plant species are increasingly being recognised as a major threat to South African water ways. Pet stores, aquarists and the internet-mediated trade were investigated as pathways for submerged invasive macrophyte introductions into South Africa. Online and manually distributed surveys were used to determine the extent of movement of invasive as well as indigenous submerged plant species in South Africa. Sixty-four stores and twenty-three aquarists were surveyed. Four areas of risk were identified in this study. Firstly, and most importantly, a variety of invasive and/or prohibited plants are sold by pet stores. Secondly, there is a lack of knowledge regarding identification as well as regulation of submerged species, which may then result in the unintentional trade of potentially invasive species. It seems that, in many cases, the pet stores are ignorant or misinformed of the potential dangers, rather than intentionally attempting to breach the legislation. Thirdly, aquarists own, trade and move plants in and around the country, which makes it very difficult to monitor which species are being moved around South Africa and to what extent. Finally, the internet is a pathway of potential concern, but it is difficult to quantify its contribution to the trade of invasive species in South Africa.
- Full Text:
- Date Issued: 2011
- Authors: Martin, Grant D , Coetzee, Julie A
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6843 , http://hdl.handle.net/10962/d1011045
- Description: Submerged aquatic invasive plant species are increasingly being recognised as a major threat to South African water ways. Pet stores, aquarists and the internet-mediated trade were investigated as pathways for submerged invasive macrophyte introductions into South Africa. Online and manually distributed surveys were used to determine the extent of movement of invasive as well as indigenous submerged plant species in South Africa. Sixty-four stores and twenty-three aquarists were surveyed. Four areas of risk were identified in this study. Firstly, and most importantly, a variety of invasive and/or prohibited plants are sold by pet stores. Secondly, there is a lack of knowledge regarding identification as well as regulation of submerged species, which may then result in the unintentional trade of potentially invasive species. It seems that, in many cases, the pet stores are ignorant or misinformed of the potential dangers, rather than intentionally attempting to breach the legislation. Thirdly, aquarists own, trade and move plants in and around the country, which makes it very difficult to monitor which species are being moved around South Africa and to what extent. Finally, the internet is a pathway of potential concern, but it is difficult to quantify its contribution to the trade of invasive species in South Africa.
- Full Text:
- Date Issued: 2011
The identity of Albuca caudata Jacq. (Hyacinthaceae) and a description of a new related species : A. bakeri
- Martinez-Azorin, Mario, Cresbo, Manuel B, Dold, Anthony P, Barker, Nigel P
- Authors: Martinez-Azorin, Mario , Cresbo, Manuel B , Dold, Anthony P , Barker, Nigel P
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6528 , http://hdl.handle.net/10962/d1005969
- Description: The name Albuca caudata Jacq. has been widely misunderstood or even ignored since its description in 1791. After studying herbarium specimens and living populations in South Africa, plants fitting Jacquin´s concept of that species are found to be widely distributed in the Eastern Cape, mainly in the Albany centre of Endemism. Furthermore, some divergent specimens matching Baker´s concept of Albuca caudata are described as a new related species: Albuca bakeri. Data on typification, morphology, ecology, and distribution are reported for both taxa. Affinities and divergences with other close allies are also discussed.
- Full Text:
- Date Issued: 2011
- Authors: Martinez-Azorin, Mario , Cresbo, Manuel B , Dold, Anthony P , Barker, Nigel P
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6528 , http://hdl.handle.net/10962/d1005969
- Description: The name Albuca caudata Jacq. has been widely misunderstood or even ignored since its description in 1791. After studying herbarium specimens and living populations in South Africa, plants fitting Jacquin´s concept of that species are found to be widely distributed in the Eastern Cape, mainly in the Albany centre of Endemism. Furthermore, some divergent specimens matching Baker´s concept of Albuca caudata are described as a new related species: Albuca bakeri. Data on typification, morphology, ecology, and distribution are reported for both taxa. Affinities and divergences with other close allies are also discussed.
- Full Text:
- Date Issued: 2011