Showing papers by "University of Stirling published in 1992"

Chimpanzee Material Culture: Implications for Human Evolution

Abstract: The chimpanzee (Pan troglodytes, Pongidae) among all other living species, is our closest relation, with whom we last shared a common ancestor less than five million years ago. These African apes make and use a rich and varied kit of tools. Of the primates, and even of the other Great Apes, they are the only consistent and habitual tool-users. Chimpanzees meet the criteria of working definitions of culture as originally devised for human beings in socio-cultural anthropology. They show sex differences in using tools to obtain and to process a variety of plant and animal foods. The technological gap between chimpanzees and human societies living by foraging (hunter-gatherers) is surprisingly narrow, at least for food-getting. Different communities of chimpanzees have different tool-kits, and not all of this regional and local variation can be explained by the varied physical and biotic environments in which they live. Some differences are likely customs based on non-functionally derived and symbolically encoded traditions. Chimpanzees serve as heuristic, referential models for the reconstruction of cultural evolution in apes and humans from an ancestral hominoid. However, chimpanzees are not humans, and key differences exist between them, though many of these apparent contrasts remain to be explored empirically and theoretically.

The principal components of natural images

Abstract: A neural net was used to analyse samples of natural images and text. For the natural images, components resemble derivatives of Gaussian operators, similar to those found in visual cortex and inferred from psychophysics. While the results from natural images do not depend on scale, those from text images are highly scale dependent. Convolution of one of the text components with an original image shows that it is sensitive to inter-word gaps.

Uncoupling of hypomyelination and glial cell death by a mutation in the proteolipid protein gene

Abstract: PROTEOLIPID protein (PLP; Mr 30,000) is a highly conserved major polytopic membrane protein in myelin but its cellular function remains obscure. Neurological mutant mice can often provide model systems for human genetic disorders. Mutations of the X-chromosome-linked PLP gene are lethal, identified first in the jimpy mouse1,2 and subsequently in patients with PelizaeusMerzbacher disease3,4. The unexplained phenotype of these mutations includes degeneration and premature cell death of oligodendrocytes with associated hypomyelination5. Here we show that a new mouse mutant rumpshaker6 is defined by the amino-acid substitution Ile-to-Thr at residue 186 in a membrane-embedded domain of PLP. Surprisingly, rumpshaker mice, although myelindeficient, have normal longevity and a full complement of morphologically normal oligodendrocytes7. Hypomyelination can thus be genetically separated from the PLP-dependent oligodendrocyte degeneration. We suggest that PLP has a vital function in glial cell development, distinct from its later role in myelin assembly, and that this dichotomy of action may explain the clinical spectrum8 of Pelizaeus–Merzbacher disease.

Primary Lowland Dipterocarp Forest at Danum Valley, Sabah, Malaysia: Structure, Relative Abundance and Family Composition

Abstract: Trees greater than or equal to 10 cm gbh were enumerated, mapped and identified in two 4 hectare (ha) (40 000 m 2 ) plots in 1985-1987. The number of species recorded was 511 (in 164 genera and 59 families) in a total sample of 17 985 individuals. Plots 1 and 2 contain 388 and 387 species respectively, and for trees greater than or equal to 30 cm gbh there are 247 and 242 species. Relative abundance patterns were fitted to a logseries distribution. In each plot, 51% of species are rare ( f f = 1). Common species ( f ≥ 5 ) achieve a minimum area at 2 ha. The plots are close ‘replicates’ in many respects, and 8 ha gives an adequate sample. The mean density of trees greater than or equal to 10 cm gbh and 30 cm gbh is 2248 ha -1 and 470 ha -1 , with corresponding basal areas of 30.7 m 2 ha -1 and 26.6 m 2 ha -1 . The linear relation between In frequency and In gbh, the small (0.5% ) ground area of gaps, and the low contribution by pioneer species show little recent disturbance. Dominance by 2-4 understorey species is pronounced. For trees greater than or equal to 30 cm gbh, the Euphorbiaceae contribute the most to density at 21% , with Dipterocarpaeceae second at 16%: corresponding basal areas are 7% and 49% . For trees greater than or equal to 10 cm gbh, density of the Euphorbiaceae reaches 28% , Dipterocarpaceae 9% , followed by Annonaceae 8% , Lauraceae 7% and Meliaceae 6% . Lauraceae was the most species-rich family (83 species), then Euphorbiaceae (51 species) and Meliaceae (36 species). Compared with the means of nine other sites in this forest type, Danum has 84% of the density and 74% of the basal area for trees greater than or equal to 30 cm gbh; and 60% of the species richness for this size class on a 1-1.6 ha basis. The forest is differentiated by its dominance by Euphorbiaceae, in terms of tree density, and the high contributions made by Lauraceae and Meliaceae. These attributes may reflect special site conditions and/or a late stage in recovery from past disturbance.

Reduced sensitivity of the salmon louse, Lepeophtheirus salmonis, to the organophosphate dichlorvos

Abstract: . Anecdotal reports from the Scottish fish farming industry suggested a reduction in the sensitivity of salmon lice, Lepeophtheirus salmonis, to the organophosphate dichlorvos. In this study, pro-adult and adult lice were collected from marine salmon sites showing a variety of ‘sensitivities’ to dichlorvos and subjected to dichlorvos exposure at a range of doses for a 48-h period in vitro. From the lice mortalities, 24 and 48 h LC50 values were calculated, and using a ‘sensitive’ source of lice as a reference, resistance ratios calculated. The data generated suggests that L. salmonis from different geographic areas shows differences in sensitivity to dichlorvos. The implications for the salmon farming industry are discussed.

Measurements in a Braided River chute and lobe: 1. Flow pattern, sediment transport, and channel change

Abstract: This paper and its companion (Ashworth et al., this issue) discuss measurements of channel change and associated flow and sediment transport processes in a representative chute-and-bar reach within a proglacial gravel-bed river, the Sunwapta River in the Canadian Rockies. During a week in which water discharge through the reach increased then decreased, a sediment wave passed into and partly along the reach. At first the chute aggraded, then sediment was eroded from the chute and deposited in a prograding lobe to one side of the original bar head between two distributaries. Measurements of velocity, shear stress, and gravel transport rate revealed day-to-day changes in the divergent pattern of flow and sediment transport. The off-center location of the lobe reflected an initial asymmetry in the pattern of flow and sediment transport, but as the lobe grew, the flow and transport gradually switched away to the other distributary. Width-averaged bed load transport rates do not agree well with average rates inferred from bar head deposition or from volumes and spatial patterns of scour and fill; the indirect estimates are considered more reliable than those based on direct sampling for necessarily brief durations. By the end of the study the new lobe had almost accreted onto the original bar head, supporting the idea that most braid bars are of compound origin. Temporal and spatial patterns in grain size distributions of the bed, bed load, and deposited sediment are discussed in the companion paper.

Evaluating Social Work Effectiveness

Abstract: Evaluation in social work social work effectiveness review of evaluative strategies methods of data collection the social work process service based outcomes client based outcomes monitoring and effectiveness studying cost-effectiveness disseminating the results of research conclusions.

A comparison of the enzymological and biophysical properties of two distinct classes of dehydroquinase enzymes.

Abstract: This paper compares the biophysical and mechanistic properties of a typical type I dehydroquinase (DHQase), from the biosynthetic shikimate pathway of Escherichia coli, and a typical type II DHQase, from the quinate pathway of Aspergillus nidulans. C.d. shows that the two proteins have different secondary-structure compositions; the type I enzyme contains approx. 50% alpha-helix while the type II enzyme contains approx. 75% alpha-helix. The stability of the two types of DHQase was compared by denaturant-induced unfolding, as monitored by c.d., and by differential scanning calorimetry. The type II enzyme unfolds at concentrations of denaturant 4-fold greater than the type I and through a series of discrete transitions, while the type I enzyme unfolds in a single transition. These differences in conformational stability were also evident from the calorimetric experiments which show that type I DHQase unfolds as a single co-operative dimer at 57 degrees C whereas the type II enzyme unfolds above 82 degrees C and through a series of transitions suggesting higher orders of structure than that seen for the type I enzyme. Sedimentation and Mr analysis of both proteins by analytical ultracentrifugation is consistent with the unfolding data. The type I DHQase exists predominantly as a dimer with Mr = 46,000 +/- 2000 (a weighted average affected by the presence of monomer) and has a sedimentation coefficient s0(20,w) = 4.12 (+/- 0.08) S whereas the type II enzyme is a dodecamer, weight-average Mr = 190,000 +/- 10,000 and has a sedimentation coefficient, s0(20,w) = 9.96 (+/- 0.21) S. Although both enzymes have reactive histidine residues in the active site and can be inactivated by diethyl pyrocarbonate, the possibility that these structurally dissimilar enzymes catalyse the same dehydration reaction by the same catalytic mechanism is deemed unlikely by three criteria: (1) they have very different pH/log kcat. profiles and pH optima; (2) imine intermediates, which are known to play a central role in the mechanism of type I enzymes, could not be detected (by borohydride reduction) in the type II enzyme; (3) unlike Schiff's base-forming type I enzymes, there are no conserved lysine residues in type II amino acid sequences.

Measurements in a Braided River chute and lobe: 2. Sorting of bed load during entrainment, transport, and deposition

Abstract: Grain size distributions of bed material, bed load, and bar head deposition were sampled during the evolution of a chute and lobe in the braided gravel bed Sunwapta River, Alberta. Although bed shear stress and total bed load transport rate varied substantially within the reach and from day to day (Ferguson et al., this issue), the median diameter D50 of bed load was remarkably constant. The bed initially fined from chute to bar head but became more uniform. Sediment deposited on the bar head also had a near constant D50, similar to that of the bed load truncated at the same lower size limit. Both load and deposition were finer on average than the bed, suggesting overall selective transport despite little sign of local sorting. In contrast to median diameters, maximum sizes (Dmax) of sediment in motion and deposited on the bar head varied substantially and showed a weak but significant dependence on shear stress. Inferring selective entrainment from this evidence alone would be dubious because Dmax was also found to increase systematically with the mass of sediment sampled. However, two different methods of analysis of fractional transport rates throughout the size range also showed size-selective entrainment and transport. In the marginal transport conditions of this study, size sorting appears to occur but only weakly and mainly in the coarser fractions.

Genetic algorithms and permutation problems: a comparison of recombination operators for neural net structure specification

Abstract: The specification of neural net architectures by genetic algorithm (GA) is thought to be hampered by difficulties with crossover. This is the 'permutation' or 'competing conventions' problem: similar nets may have the hidden units defined in different orders so that they have very dissimilar genetic strings, preventing successful recombination of building blocks. Previous empirical tests of a number of recombination operators using a simulated net-building task indicated the superiority of one that sorts hidden unit definitions by overlap prior to crossover. However, simple crossover also fared well, suggesting that the permutation problem is not serious in practice. This is supported by an observed reduction in performance when the permutation problem is removed. The GA is shown to be able to resolve the permutations, so that the advantages of an increase in the number of maxima outweigh the difficulties of recombination. >

The histopathology associated with the pre-adult and adult stages of Lepeophtheirus salmonis on the Atlantic salmon, Salmo salar L.

Abstract: Atlantic salmon, Salmo salar L, infected with the pre-adult and adult stages of Lepeophtheirus salmonis were obtained from sea loch cage sites on the west coast of Scotland, and infection experiments were carried out in the laboratory The motile parasites were retained at the point of attachment by prefixation with cooled alcohol They were studied using light and scanning electron microscopy Lepeophtheirus salmonis were found to leave an oval‘imprint’ corresponding to the margin of the parasite cephalothorax on the host skin and/or to wedge under its scales General pathological changes including oedema, hyperplasia, sloughing of cells and cellular inflammation were observed in the host at and around the point of feeding and attachment In gross lesions, serious damage occurred to the host epidermis with scale loss and haemorrhage a common feature The most obvious changes were associated with the louse mouthtube, marginal membrane, second antenna, maxilliped and sternal furca

Accounting for the worth of employees: A new look at an old problem

Abstract: Accounting for the worth of employees has long posed a challenge to the accountancy profession. Despite the attention it has received over the past 30 years, the subject has failed to develop much in the way of practical applications and as a result it is effectively a non-issue today. This is rather disturbing since the 1990s are a time when accounting for the worth of employees is probably more necessary than ever. The present paper seeks to rejuvenate interest in the subject and to see it returned to the research agenda. It proposes a third approach to the subject, one which overcomes the shortcomings of previous efforts and which constitutes a much needed breakthrough in its development. Underlying the paper is the belief that accounting for the worth of employees will benefit from a major paradigm shift away from the narrow economic-accounting perspective of the past, to a broader social scientific perspective, one which is consistent with a more strategic emphasis and the proposal to generate softer accounting numbers rather than those required to put people on the balance sheet.

Are there environmental limits to cost benefit analysis

Abstract: This paper considers the problem areas found in applying cost-benefit analysis (CBA) to projects involving environmental costs or benefits. This is particularly relevant given recent moves by the UK government to include environmental valuations in CBA exercises, and in other related appraisal activities, following the publication of the Pearce Report. The paper argues that a major problem lies in placing monetary values on non-market goods. The paper also addresses the problems of (i) differences between citizen and consumer values; (ii) complexity of ecosystems; (iii) irreversibility and uniqueness; and (iv) intergenerational equity and discounting. The extent to which CBA is an institution open to capture is also discussed.

The costs of infant carrying in captive cotton-top tamarins.

Abstract: Marmosets and tamarins have a communal rearing system in which all group members help to care for the twin infants characteristic of this family of primates. Helpers are likely to incur time and energy costs by contributing to infant care. Predictions that cotton-top tamarin (Saguinus oedipus) helpers would change their behavior when carrying infants because of reduced mobility and/or a need for increased vigilance were tested in a captive colony. Tamarins carrying an infant spent significantly less time feeding, foraging, moving, or engaging in social activities such as grooming than they did when not carrying. Frequencies of scratching, autogrooming, and scent marking were significantly reduced in carriers, suggesting that their mobility was reduced. However, carriers were significantly less likely to be vigilant (measured by direction of gaze) than when not carrying. Further observations showed that carriers spent more time in concealed areas than they did when not carrying and were probably therefore adopting a cryptic strategy to reduce predation risks to themselves and to infants. These results demonstrate that tamarin helpers pay costs by carrying infants. Some possible compensating benefits are indicated.

Interclonal variation in the performance of Daphnia-magna Straus in chronic bioassays

Abstract: As an ecotoxicological test organism, Daphnia magna Straus has a long history and is now used extensively. Despite this, considerable variation in interlaboratory bioassays using the same reference toxicant has been reported. Using a standard quantitative genetics approach, the relative tolerance of different genotypes of Daphnia magna to two toxicants (sodium bromide and 3,4-dichloroaniline) was assessed. As expected, the environmental component of variability dominated the chronic response with a significant component of interaction. Differences between genotypes, although significant, were not large. It was concluded that genotype-environment interactions played a key role in determining chronic responses of Daphnia magna to both compounds. Some suggestions are given to improve the level of repeatability in Daphnia magna bioassays.

Trust in Distributed Artificial Intelligence

Abstract: A discussion of trust is presented which focuses on multiagent systems, from the point of view of one agent in a system. The roles trust plays in various forms of interaction are considered, with the view that trust allows interactions between agents where there may have been no effective interaction possible before trust. Trust allows parties to acknowledge that, whilst there is a risk in relationships with potentially malevolent agents, some form of interaction may produce benefits, where no interaction at all may not. In addition, accepting the risk allows the trusting agent to prepare itself for possibly irresponsible or untrustworthy behaviour, thus minimizing the potential damage caused. A formalism is introduced to clarify these notions, and to permit computer simulations. An important contribution of this work is that the formalism is not allen-compassing: there are some notions of trust that are excluded. What it describes is a specific view of trust.

Xyloglucan structure and post‐germinative metabolism in seeds of Copaifera langsdorfii from savanna and forest populations

Abstract: The cotyledons of Copaifera langsdorfii Desf, have been shown to contain a water-soluble xyloglucan (amyloid), which represents about 40% of the seed's dry weight. On acid hydrolysis its composition (Glc:Xyl:Gal = 4.0:2.8–2.9:1.5–1.7) was similar to that of the well-characterized xyloglucan of Tamarindus indica L. (Glc:Xyl:Gal = 4.0:3.0–3.1:1.4). On hydrolysis with pure Trichoderma viride cellulase, both C. langsdorfii and T. indica xyloglucan gave the same xyloglucan oligosaccharides: but in significantly different proportions A:B1:B2:C = 1:0.4–0.5:2.1–2.2:3.1–3.4 in T. indica, and 1:1.1:1.8:7.4 and 1:1.3:2.6:12 for C. langsdorfii, savanna and forest populations respectively. This demonstrated a difference in fine molecular structure, notably in the distribution of the terminal non-reducing galactose substituents, between the xyloglucans of the two species and indicated differences in the specificities of their biosynthetic mechanisms. The xyloglucans obtained from C. langsdorfii seeds harvested from savanna and forest environments were slightly different, one from the other, in their sugar-residue composition (Glc:Xyl:Gal = 4.0:2.9:1.5 and 4.0:2.8:1.7, respectively), and were significantly different in the relative proportions of the xyloglucan oligosaccharides released on cellulase hydrolysis (above). Using light microscopy and biochemical methods, no difference in the pattern or rate of postgerminative xyloglucan metabolism was detected in seeds of savanna and forest origin. This is the first clear experimental evidence for differences in a storage xyloglucan structure between populations of the same species. It may indicate environmental influences on xyloglucan biosynthesis.

Control of mannose/galactose ratio during galactomannan formation in developing legume seeds.

Abstract: Galactomannan deposition was investigated in developing endosperms of three leguminous species representative of taxonomic groups which have galactomannans with high, medium and low galactose content. These were fenugreek (Trigonella foenum-graecum L.; mannose/galactose (Man/Gal) = 1.1), guar (Cyamopsis tetragonoloba (L.) Taub.; Man/Gal = 1.6) and Senna occidentalis (L.) Link. (Man/Gal = 3.3), respectively. Endosperms were analysed at different stages of seed development for galactomannan content and the levels, in cell-free extracts, of a mannosyltransferase and a galactosyltransferase which have been shown to catalyse galactomannan biosynthesis in vitro (M. Edwards et al., 1989, Planta 178, 41-51). There was a close correlation in each case between the levels of the biosynthetic mannosyl- and galactosyltransferases and the deposition of galactomannan. The relative in vitro activities of the mannosyl- and galactosyltransferases in fenugreek and guar were similar, and almost constant throughout the period of galactomannan deposition. In Senna the ratio mannosyltransferase/galactosyltransferase was always higher than in the other two species, and it increased substantially throughout the period of galactomannan deposition. In fenugreek and guar the galactomannans present in the endosperms of seeds at different stages of development had the Man/Gal ratios characteristic of the mature seeds. By contrast the galactomannan present in Senna endosperms at the earliest stages of deposition had a Man/Gal ratio of about 2.3. During late deposition this ratio increased rapidly, stabilising at about 3.3, the ratio characteristic of the mature seed. The levels of α-galactosidase in the developing endosperms of fenugreek and guar were low and remained fairly constant throughout the deposition of the galactomannan. In Senna, α-galactosidase activity in the endosperm was low during early galactomannan deposition, but increased subsequently, peaking during late galactomannan deposition. The developmental patterns of the α-galactosidase activity and of the increase in Man/Gal ratio of the Senna galactomannan were closely similar, indicating a cause-and-effect relationship. The endosperm α-galactosidase activity in Senna was capable, in vitro, of removing galactose from guar galactomannan without prior depolymerisation of the molecule. In fenugreek and in guar the genetic control of the Man/Gal ratio in galactomannan is not the result of a post-depositional modification, and must reside in the biosynthetic process. In Senna, the Man/Gal ratio of the primary biosynthetic galactomannan product is controlled by the biosynthetic process. Yet the final Man/Gal ratio of the galactomannan in the mature seed is, to an appreciable extent, the result of galactose removal from the primary biosynthetic product by an α-galactosidase activity which is present in the endosperm during late galactomannan deposition.

A Kantian approach to codes of ethics

Abstract: The paper discusses whether codes of ethics are Kantian notions through an analysis of their intention and structure. The article also discusses some of the ideas put forward by William Starr in his article, ‘Codes of Ethics — Towards a Rule-Utilitarian Justification’,Journal of Business Ethics 2(2) (May 1983). The paper refers to recent definitions of codes of ethics and considers reasons for the proliferation of such codes. It examines the moral justification for these codes and analyses the underlying ethical theory particularly in relation to Kantian ethics. There is an account of how Kant's views of the source of morality and moral obligation, the structure and nature of Kantian moral law and the role of the individual and his/her relationship with others, which is relevant to the development of a theoretical base for codes of ethics. There is some discussion of potential problems in the practical application of Kantian ethics to a specific code.