The influence of winter oilseed rape (Brassica napus ssp oleifera var. biennis) cultivar and grass genotype on the competitive balance between crop and grass weeds

Three experiments conducted over two years (2002-04) at the Crops Research Unit, University of Reading, investigated competition between autumn sown oilseed rape cultivars (Brassica napus L. ssp. oleifera var. biennis (DC.) Metzg.) and Lolium multiflorum Lam., L. x boucheanum Kunth and Alopecurus myosuroides Huds., sown as indicative grass weeds. Rape cultivar (cv.) had a substantial effect on grass weed seed return. Over the six cultivars tested, L. multiflorum spikelet production ranged from just under 400 spikelets/m(2) in the presence of cv. Winner to nearly 5800 in competition with cv. Lutin. Cultivar competitiveness was associated with high biomass, large dense floral layers and early stem extension. There was some evidence of differential competitive tolerance between rape cultivars. The results suggested that rape cultivars could be screened for competitiveness by measuring floral layer interception of photosynthetic active radiation. L. x boucheanum cultivars varied in ability to compete with rape. In the absence of inter-specific competition, spikelet density was similar for Aberecho and Polly (circa 31000 spikelets/m(2)) but when grown with rape Polly outyielded Aberecho (i.e. 12 090 and 7990 spikelets/m(2) respectively).

Song development in birds: the role of early experience and its potential effect on rehabilitation success

Environmental conditions during the early life stages of birds can have significant effects on the quality of sexual signals in adulthood, especially song, and these ultimately have consequences for breeding success and fitness. This has wide-ranging implications for the rehabilitation protocols undertaken in wildlife hospitals which aim to return captive-reared animals to their natural habitat. Here we review the current literature on bird song development and learning in order to determine the potential impact that the rearing of juvenile songbirds in captivity can have on rehabilitation success. We quantify the effects of reduced learning on song structure and relate this to the possible effects on an individual's ability to defend a territory or attract a mate. We show the importance of providing a conspecific auditory model for birds to learn from in the early stages post-fledging, either via live- or tape-tutoring and provide suggestions for tutoring regimes. We also highlight the historical focus on learning in a few model species that has left an information gap in our knowledge for most species reared at wildlife hospitals.

Detection and enumeration of sulphate-reducing bacteria in estuarine sediments by competitive PCR

The distribution of sulphate-reducing bacteria (SRB) in the sediments of the Colne River estuary, Essex, UK covering different saline concentrations of sediment porewater was investigated by the use of quantitative competitive PCR. Here, we show that a new PCR primer set and a new quantitative method using PCR are useful tools for the detection and the enumeration of SRB in natural environments. A PCR primer set selective for the dissimilatory sulphite reductase gene (dsr) of SRB was designed. PCR amplification using the single set of dsr-specific primers resulted in PCR products of the expected size from all 27 SRB strains tested, including Gram-negative and positive species. Sixty clones derived from sediment DNA using the primers were sequenced and all were closely related with the predicted dsr of SRB. These results indicate that PCR using the newly designed primer set are useful for the selective detection of SRB from a natural sample. This primer set was used to estimate cell numbers by dsr selective competitive PCR using a competitor, which was about 20% shorter than the targeted region of dsr. This procedure was applied to sediment samples from the River Colne estuary, Essex, UK together with simultaneous measurement of in situ rates of sulphate reduction. High densities of SRB ranging from 0.2 - 5.7 × 108 cells ml-1 wet sediment were estimated by the competitive PCR assuming that all SRB have a single copy of dsr. Using these estimates cell specific sulphate reduction rates of 10-17 to 10-15 mol of SO42- cell-1 day-1 were calculated, which is within the range of, or lower than, those previously reported for pure cultures of SRB. Our results show that the newly developed competitive PCR technique targeted to dsr is a powerful tool for rapid and reproducible estimation of SRB numbers in situ and is superior to the use of culture-dependent techniques.

Efficient and cost-effective experimental determination of kinetic constants and data: the success of a Bayesian systematic approach to drug transport, receptor binding, continuous culture and cell transport kinetics

Details about the parameters of kinetic systems are crucial for progress in both medical and industrial research, including drug development, clinical diagnosis and biotechnology applications. Such details must be collected by a series of kinetic experiments and investigations. The correct design of the experiment is essential to collecting data suitable for analysis, modelling and deriving the correct information. We have developed a systematic and iterative Bayesian method and sets of rules for the design of enzyme kinetic experiments. Our method selects the optimum design to collect data suitable for accurate modelling and analysis and minimises the error in the parameters estimated. The rules select features of the design such as the substrate range and the number of measurements. We show here that this method can be directly applied to the study of other important kinetic systems, including drug transport, receptor binding, microbial culture and cell transport kinetics. It is possible to reduce the errors in the estimated parameters and, most importantly, increase the efficiency and cost-effectiveness by reducing the necessary amount of experiments and data points measured. (C) 2003 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Invertebrate food supply and breeding success of Mallards Anas platyrhynchos at flooded gravel quarries in southern Britain

Reproductive parameters of Mallard Anas platyrhynchos were investigated in relation to vegetative development, physical characteristics and invertebrate food abundance of a complex of flooded gravel quarries in southern Britain. Breeding pair density over the study area was particularly high with 2.2 pairs km(-1) of shoreline. Across all lakes breeding success was limited to an average of 0.9 ducklings fledged pair(-1), yet an associated study showed that very little of the mortality could be attributed to predation. The results of stepwise multiple regressions indicated that the availability of emerging insects was important in determining the breeding density and breeding success of Mallards rather than habitat structure. We suggest that the overall great availability of suitable nest-sites combined with the variable but unmeasured stocking densities of fish may explain the lack of the latter correlations.

Incubation success of released hand-reared pheasants Phasianus colchicus compared with wild ones

We investigated previously observed but unexplained differences in incubation success between wild and hand-reared common pheasants Phasianus colchicus. Hand-reared birds are widely released in late summer in Britain and elsewhere to supplement wild stocks for shooting purposes. We radio-tracked 53 wild and 35 previously released reared female pheasants occupying simultaneously the same areas on a game-keepered estate in eastern England between February and mid July 1999 and 2000. Predation of adult birds was comparatively low for both wild and reared birds, and overall survival did not differ between years or between groups. However, of 52 nests incubated by wild females 49% hatched, whereas of 30 nests incubated by reared pheasants only 22% hatched. Mayfield estimates of daily nest survival probability thus differed significantly between groups. However, predation of eggs was similar for both wild and reared birds. Instead the observed difference in hatch rates was due to nest abandonment, with more reared females (41%) deserting apparently unmolested nest sites than wild females (6%).

Competitive strategy revisited: contested concepts and dynamic capabilities

Strategy is a contested concept. The generic literature is characterized by a diverse range of competing theories and alternative perspectives. Traditional models of the competitive strategy of construction firms have tended to focus on exogenous factors. In contrast, the resource-based view of strategic management emphasizes the importance of endogenous factors. The more recently espoused concept of dynamic capabilities extends consideration beyond static resources to focus on the ability of firms to reconfigure their operating routines to enable responses to changing environments. The relevance of the dynamics capabilities framework to the construction sector is investigated through an exploratory case study of a regional contractor. The focus on how firms continuously adapt to changing environments provides new insights into competitive strategy in the construction sector. Strong support is found for the importance of path dependency in shaping strategic choice. The case study further suggests that strategy is a collective endeavour enacted by a loosely defined group of individual actors. Dynamic capabilities are characterized by an empirical elusiveness and as such are best construed as situated practices embedded within a social and physical context.

The competitive dialogue procedure: Advantages, disadvantages, and its implementation into English and Dutch law

Competitive Dialogue (CD) is a new contract award procedure of the European Community (EC). It is set out in Article 29 of the 'Public Sector Directive' 2004/18/EC. Over the last decades, projects were becoming more and more complex, and the existing EC procedures were no longer suitable to procure those projects. The call for a new procedure resulted in CD. This paper describes how the Directive has been implemented into the laws of two member states: the UK and the Netherlands. In order to implement the Directive, both lawmakers have set up a new and distinct piece of legislation. In each case, large parts of the Directive’s content have been repeated ‘word for word’; only minor parts have been reworded and/or restructured. In the next part of the paper, the CD procedure is examined in different respects. First, an overview is given on the different EC contract award procedures (open, restricted, negotiated, CD) and awarding methods (lowest price and Most Economically Advantageous Tender, MEAT). Second, the applicability of CD is described: Among other limitations, CD can only be applied to public contracts for works, supplies, and services, and this scope of application is further restricted by the exclusion of certain contract types. One such exclusion concerns services concessions. This means that PPP contracts which are set up as services concessions cannot be awarded by CD. The last two parts of the paper pertain to the main features of the CD procedure – from ‘contract notice’ to ‘contract award’ – and the advantages and disadvantages of the procedure. One advantage is that the dialogue allows the complexity of the project to be disentangled and clarified. Other advantages are the stimulation of innovation and creativity. These advantages are set against the procedure’s disadvantages, which include high transaction costs and a perceived hindrance of innovation (due to an ambiguity between transparency and fair competition). It is concluded that all advantages and disadvantages are related to one of three elements: communication, competition, and/or structure of the procedure. Further research is needed to find out how these elements are related.

Recovering potential: factors associated with success in engaging challenging students with alternative pre-16 provision

The study focuses on a group of young people for whom conventional school placements had broken down and were attending vocational courses at an FE college while still of compulsory school age. The students had been excluded by, or had failed to attend, their schools or had achieved at very low levels in the academic curriculum. Over half successfully completed the vocational course at college. Many factors conventionally regarded as predictors for poor educational outcomes were not associated with completion and non-completion. For example, students who had been excluded, who had statements of special educational needs and had been involved with the criminal justice system were as likely to complete their courses as other students. However, students who had very poor attendance records at school also tended to drop out of college. The results suggest that the increased flexibility, guidance and elements of work-related learning promised in current 14 - 19 developments may help meet the needs of this group of students.

Mathematical modelling of competitive LDL/VLDL binding and uptake by hepatocytes

Elevated levels of low-density-lipoprotein cholesterol (LDL-C) in the plasma are a well-established risk factor for the development of coronary heart disease. Plasma LDL-C levels are in part determined by the rate at which LDL particles are removed from the bloodstream by hepatic uptake. The uptake of LDL by mammalian liver cells occurs mainly via receptor-mediated endocytosis, a process which entails the binding of these particles to specific receptors in specialised areas of the cell surface, the subsequent internalization of the receptor-lipoprotein complex, and ultimately the degradation and release of the ingested lipoproteins' constituent parts. We formulate a mathematical model to study the binding and internalization (endocytosis) of LDL and VLDL particles by hepatocytes in culture. The system of ordinary differential equations, which includes a cholesterol-dependent pit production term representing feedback regulation of surface receptors in response to intracellular cholesterol levels, is analysed using numerical simulations and steady-state analysis. Our numerical results show good agreement with in vitro experimental data describing LDL uptake by cultured hepatocytes following delivery of a single bolus of lipoprotein. Our model is adapted in order to reflect the in vivo situation, in which lipoproteins are continuously delivered to the hepatocyte. In this case, our model suggests that the competition between the LDL and VLDL particles for binding to the pits on the cell surface affects the intracellular cholesterol concentration. In particular, we predict that when there is continuous delivery of low levels of lipoproteins to the cell surface, more VLDL than LDL occupies the pit, since VLDL are better competitors for receptor binding. VLDL have a cholesterol content comparable to LDL particles; however, due to the larger size of VLDL, one pit-bound VLDL particle blocks binding of several LDLs, and there is a resultant drop in the intracellular cholesterol level. When there is continuous delivery of lipoprotein at high levels to the hepatocytes, VLDL particles still out-compete LDL particles for receptor binding, and consequently more VLDL than LDL particles occupy the pit. Although the maximum intracellular cholesterol level is similar for high and low levels of lipoprotein delivery, the maximum is reached more rapidly when the lipoprotein delivery rates are high. The implications of these results for the design of in vitro experiments is discussed.

Conversational success in Williams syndrome: communication in the face of cognitive and linguistic limitations

Williams syndrome (WS) is characterized by apparent relative strengths in language, facial processing and social cognition but by profound impairment in spatial cognition, planning and problem solving. Following recent research which suggests that individuals with WS may be less linguistically able than was once thought, in this paper we begin to investigate why and how they may give the impression of linguistic proficiency despite poor standardized test results. This case study of Brendan, a 12-year-old boy with WS, who presents with a considerable lack of linguistic ability, suggests that impressions of linguistic competence may to some extent be the result of conversational strategies which enable him to compensate for various cognitive and linguistic deficits with a considerable degree of success. These conversational strengths are not predicted by his standardized language test results, and provide compelling support for the use of approaches such as Conversation Analysis in the assessment of individuals with communication impairments.