Who should be leading in the process of successful supply chain management in construction?

Despite the critical role of a client in enabling supply chain integration, parties on the supply side of the construction supply chain – the lower tiers of the construction supply chain – are believed to be able to develop into more integrated production systems, independently from the demand. Main contractors are acknowledged to have a central position in the management of supply chains, offering great potential in the effective integration of their supply chains. This is deemed to be necessary as construction supply chains are fragmented, complex, highly uncertain and with many stakeholders requiring a leading actor to coordinate the process and relationships – projects are characterised by a high supplier involvement. This study sets out to explore the differences between the organisations involved at the lower tiers of the construction supply chain, focusing specifically on the internal SCM organisation of main contractor and supplier organisations, and their direct inter-relationships. SC Maturity levels are formulated according to relevant SCM concepts and based on Holti et al.’s (2000) seven principles of SCM organisation, and used to examine the relative SC Maturity of eight large main contractor and supplier organisations within the context of the Dutch construction industry. A case study, representing a construction supply chain initiated by a main contractor as a result of ongoing poor financial performance during the economic crisis and the existence of high failure costs, is further investigated to examine the SC Maturity levels based on one of the principles in more detail. This way the paper starts a discussion towards the development of an improvement framework and brings up the need for a more mature supply chain integrator, an organisation leading in the process of SCM implementation

The hawk–dove game in a sexually reproducing species explains a colourful polymorphism of an endangered bird

The hawk-dove game famously introduced strategic game theory thinking into biology and forms the basis of arguments for limited aggression in animal populations. However, aggressive 'hawks' and peaceful 'doves', with strategies inherited in a discrete manner, have never been documented in a real animal population. Thus, the applicability of game-theoretic arguments to real populations might be contested. Here, we show that the head-colour polymorphism of red and black Gouldian finches (Erythrura gouldiae) provides a real-life example. The aggressive red morph is behaviourally dominant and successfully invades black populations, but when red 'hawks' become too common, their fitness is severely compromised (via decreased parental ability). We also investigate the effects of real-life deviations, particularly sexual reproduction, from the simple original game, which assumed asexual reproduction. A protected polymorphism requires mate choice to be sufficiently assortative. Assortative mating is adaptive for individuals because of genetic incompatibilities affecting hybrid offspring fitness, but by allowing red 'hawks' to persist, it also leads to significantly reduced population sizes. Because reductions in male contributions to parental care are generally known to lead to lower population productivity in birds, we expect zero-sum competition to often have wide ranging population consequences.6 page(s

Sexual selection of multiple ornaments in the red-collared widowbird.

Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.Although sexual selection often explains the evolution and maintenance of a single male ornament, it is unclear how the multicomponent nature of most sexual displays evolves. Theoretical models suggest that handicap signalling should converge on a single most informative quality indicator, whereas additional signals are more likely to be arbitrary Fisherian traits, amplifiers, or exploitations of receiver psychology. Despite the predictions that multiple handicap signals are unlikely to be stable, the male nuptial plumage of the highly polygynous (ca. 3, but up to 9 actively nesting females) red-collared widowbird Euplectes ardens comprises two classic quality-indicating avian ornaments (handicaps); a long graduated tail (22 cm) and a red carotenoid throat patch (collar). To investigate the evolution and maintenance of these handicaps in the red-collared widowbird, a population was studied in the Hilton district, KwaZulu-Natal, South Africa, where these small (males ca. 20 g) African weaverbirds (Ploeceidae) inhabit a grassy valley during the breeding season. Multivariate selection analyses, used to investigate net, direct and indirect female selection, demonstrated an unusually strong fitness effect of natural tail length (47%) on male reproductive success (the order and total number of nests acquired). There were no other effects of morphology, ectoparasite load, display rate, territory quality, tail asymmetry or collar measures (hue, brightness and size) on reproductive success, suggesting that females base their mate choice exclusively on only one handicap signal, extreme tail elongation. Although ignored in mate choice, there is strong evidence that the variable carotenoid collar (ranging from yellow to red) functions as a status or agonistic signal in male contest competition for territories. Compared to 'floating' males (that did not establish a territory in the area), resident males had a 60% larger and 23 nm 'redder' (longwave hue) collar. Model presentations also corroborated the status signalling function of the collar as territorial males were less aggressive towards conspecific models with intense collar displays, and males with greater carotenoid investment responded more aggressively to the models. In captive experiments, non-breeding brown males painted with red 'collars' dominated orange painted, control brown, novel blue collared and testosterone-implanted males in dyadic contests over food resources. In addition, experiments in the field demonstrated that males manipulated with larger and redder collars established and maintained territories in the area, whereas most males with small, orange or blackened collars failed to establish or retain territories. Thus the size and particularly redness of the costly carotenoid collar reliably signals male status and fighting ability in male contests. The unique negative phenotypic relationship between the expression of tail length and carotenoid pigmentation, suggests strong overlapping developmental costs (and allocation conflicts) between the two handicap ornaments. This tradeoff is predicted to be strongest between signals with the same or similar costs. Although current theory predicts that multiple handicaps should be evolutionary unstable, the coexistence of multiple costly ornaments in the red-collared widowbird is stable because of selection by different receivers, females and males (i.e., multiple receivers)

Digital Deblurring of CMB Maps II: Asymmetric Point Spread Function

In this second paper in a series dedicated to developing efficient numerical techniques for the deblurring Cosmic Microwave Background (CMB) maps, we consider the case of asymmetric point spread functions (PSF). Although conceptually this problem is not different from the symmetric case, there are important differences from the computational point of view because it is no longer possible to use some of the efficient numerical techniques that work with symmetric PSFs. We present procedures that permit the use of efficient techniques even when this condition is not met. In particular, two methods are considered: a procedure based on a Kronecker approximation technique that can be implemented with the numerical methods used with symmetric PSFs but that has the limitation of requiring only mildly asymmetric PSFs. The second is a variant of the classic Tikhonov technique that works even with very asymmetric PSFs but that requires discarding the edges of the maps. We provide details for efficient implementations of the algorithms. Their performance is tested on simulated CMB maps.Comment: 9 pages, 13 Figure

SCM and extended integration at the lower tiers of the construction supply chain: An explorative study in the Dutch construction industry

Several studies have underlined the potential of Supply Chain Management (SCM) in meeting the formidable challenges associated with fragmentation, adversarial relationships and insufficient customer focus in the delivery of construction projects (e.g. Dainty et al., 2001; Cox and Ireland, 2002; Gadde and Dubois, 2010). However, there remains a paucity of properly documented examples of successfully implemented SCM initiatives, particularly at the lower tiers of the supply chain. This study sets out to explore the enablers and barriers to the implementation of SCM at the lower tiers of the supply chain, particularly the problematic collaboration between main contractors and subcontractors. A SCM Maturity Model is developed based on Holti et al.’s (2000) seven principles of SCM organisation. An explorative study is conducted based on interviews from eight large main contractor and subcontractor organisations in the Dutch construction industry. Discouragingly, across the organisations, more barriers than enablers to supply chain management are identified. Organisations are found to be particularly struggling to compete through superior value, manage costs collaboratively, and develop continuous improvement within their supply chains. The findings also underline the low SCM maturity of main contractors and their inability to play the essential role of supply chain managers. Indeed the principles of integrating project activities and mobilising and developing people are found to be better exercised by subcontractors. The study may highlight the need for a greater degree of contractor leadership and improved internal organisation of both types of firms in order to achieve greater collaboration at the lower tiers of the construction supply chain

Universality of electron-positron distributions in extensive air showers

Using a large set of simulated extensive air showers, we investigate universality features of electron and positron distributions in very-high-energy cosmic-ray air showers. Most particle distributions depend only on the depth of the shower maximum and the number of particles in the cascade at this depth. We provide multi-dimensional parameterizations for the electron-positron distributions in terms of particle energy, vertical and horizontal momentum angle, lateral distance, and time distribution of the shower front. These parameterizations can be used to obtain realistic electron-positron distributions in extensive air showers for data analysis and simulations of Cherenkov radiation, fluorescence signal, and radio emission.Comment: 13 pages, 22 figures, 1 tabl

Using an Electronic Monitoring System to Link Offspring Provisioning and Foraging Behavior of a Wild Passerine

Although the costs of parental care are at the foundations of optimal-parental-investment theory, our understanding of the nature of the underlying costs is limited by the difficulty of measuring variation in foraging effort. We simultaneously measured parental provisioning and foraging behavior in a free-living population of Zebra Finches (Taeniopygia guttata) using an electronic monitoring system. We fitted 145 adults with a passive transponder tag and remotely recorded their visits to nest boxes and feeders continuously over a 2-month period. After validating the accuracy of this monitoring system, we studied how provisioning and foraging activities varied through time (day and breeding cycle) and influenced the benefits (food received by the offspring) and costs (interclutch interval) of parental care. The provisioning rates of wild Zebra Finches were surprisingly low, with an average of only one visit per hour throughout the day. This was significantly lower than those reported for this model species in captivity and for most other passerines in the wild. Nest visitation rate only partially explained the amount of food received by the young, with parental foraging activity, including the minimum distance covered on foraging trips, being better predictors. Parents that sustained higher foraging activity and covered more distance during the first breeding attempt took longer to renest. These results demonstrate that in some species matching foraging activity with offspring provisioning may provide a better estimate of the true investment that individuals commit to a reproductive attempt

Application of a Self-Similar Pressure Profile to Sunyaev-Zel'dovich Effect Data from Galaxy Clusters

We investigate the utility of a new, self-similar pressure profile for fitting Sunyaev-Zel'dovich (SZ) effect observations of galaxy clusters. Current SZ imaging instruments - such as the Sunyaev-Zel'dovich Array (SZA) - are capable of probing clusters over a large range in physical scale. A model is therefore required that can accurately describe a cluster's pressure profile over a broad range of radii, from the core of the cluster out to a significant fraction of the virial radius. In the analysis presented here, we fit a radial pressure profile derived from simulations and detailed X-ray analysis of relaxed clusters to SZA observations of three clusters with exceptionally high quality X-ray data: A1835, A1914, and CL J1226.9+3332. From the joint analysis of the SZ and X-ray data, we derive physical properties such as gas mass, total mass, gas fraction and the intrinsic, integrated Compton y-parameter. We find that parameters derived from the joint fit to the SZ and X-ray data agree well with a detailed, independent X-ray-only analysis of the same clusters. In particular, we find that, when combined with X-ray imaging data, this new pressure profile yields an independent electron radial temperature profile that is in good agreement with spectroscopic X-ray measurements.Comment: 28 pages, 6 figures, accepted by ApJ for publication (probably April 2009