Nonlocal effects in high energy charged particle beams

Within the framework of the thermal wave model, an investigation is made of the longitudinal dynamics of high energy charged particle beams. The model includes the self-consistent interaction between the beam and its surroundings in terms of a nonlinear coupling impedance, and when resistive as well as reactive parts are included, the evolution equation becomes a generalised nonlinear Schroedinger equation including a nonlocal nonlinear term. The consequences of the resistive part on the propagation of particle bunches are examined using analytical as well as numerical methods.Comment: 6 pages, 6 figures, uses RevTeX

Re-inventing artisanal knowledge and practice: a critical review of innovation in a craft-based industry

This paper presents a critical review of the ways in which the specialised knowledge and working practices of craft-based industries have been transformed in the context of broader processes of industrialisation and global competition. The opening section makes the case for artisanal knowledge as a ‘Cinderella’ subject that remains important yet largely uncharted territory for innovation researchers. It is followed by a critical review of existing empirical and theoretical studies that have examined the reproduction and reinvention of artisanal knowledge. The review concludes that valuable insights remain obscured due to the way in which this literature is distributed across discrete disciplines with little evidence of cross-fertilisation or integration. Several common themes emerge, which provide the basis for an outline theoretical framework. The central arguments are illustrated with reference to a case-based analysis of the technological and social innovations that have taken place in English farmhouse cheesemaking over an extended period, from the pre-industrial era to the beginning of the present century. The concluding section considers how more nuanced understandings of artisanal knowledge and practice might enhance innovation theory and contribute to the continued flourishing of craft-based industries

Comprehensive expression analysis of prostanoid enzymes and receptors in the human endometrium across the menstrual cycle

Prostanoids are well-described primary mediators of inflammatory processes and are essential for the normal physiological function of the female reproductive system. The aim of this study was to determine the temporal expression of the prostanoid biosynthetic enzymes (PTGS1, PTGS2, PTGES, PTGES2, PTGES3, AKR1B1, AKR1C3, CBR1, HPGDS, PTGDS, PTGIS, TBXAS1 and HPGD) and the prostanoid receptors (PTGER1, PTGER2, PTGER3, PTGER4, PTGFR, PTGDR, GPR44, PTGIR and TBXA2R) in the human endometrium throughout the menstrual cycle. The analysis identified PTGFR to have a distinct expression profile compared with other components of the prostanoid system, as expression is maximal during the proliferative phase. Immunohistochemical analysis for PTGER1 suggests a dual function for this receptor depending on its temporal (proliferative versus secretory) and spatial (nuclear versus cell membrane) expression. The expression profiles of the PGF2α synthases identified AKR1B1 and CBR1 as the likely regulators of PGF2α production during the menstrual phase. Immunohistochemical analysis for AKR1B1, CBR1 and AKR1C3 suggest expression to be in the glandular epithelium and vasculature. This study represents the first comprehensive analysis of the components of prostanoid biosynthetic and signalling pathway in the human endometrium. The expression profiles described have the potential to identify specific prostanoid components that may be dysregulated in inflammatory-associated disorders of the endometrium

Understanding how immigrant entrepreneurs view business opportunity formation through ethnicity

Given that international research is now consistently showing higher rates of entrepreneurial activity from immigrants above native people, research regarding our understanding of how immigrant entrepreneurs view business opportunity formation remains underdeveloped. Based upon a review of the literature, this chapter examines how ethnicity relates to business opportunity formation through constant interactions. It also introduces the Visual Mixed Embeddedness Framework as an empirical lens for understanding the differences in the business opportunity formation process models between immigrant and native entrepreneurs. By explaining how factors and traits from both home and host countries impact upon the immigrant entrepreneurial business activity process, the framework clearly identifies how the concept of ethnicity influences immigrant entrepreneurial opportunity formation activities in different ways. The framework contributes to existing knowledge by offering a novel method for examining the influence on business opportunity formation of ethnicity, the role of home and host countries and variations between immigrant and native entrepreneurs

Male pygmy hippopotamus influence offspring sex ratio

Pre-determining fetal sex is against the random and equal opportunity that both conceptus sexes have by nature. Yet, under a wide variety of circumstances, populations shift their birth sex ratio from the expected unity. Here we show, using fluorescence in situ hybridization, that in a population of pygmy hippopotamus (Choeropsis liberiensis) with 42.5% male offspring, males bias the ratio of X- and Y-chromosome-bearing spermatozoa in their ejaculates, resulting in a 0.4337±0.0094 (mean±s.d.) proportion of Y-chromosome-bearing spermatozoa. Three alternative hypotheses for the shifted population sex ratio were compared: female counteract male, female indifferent, or male and female in agreement. We conclude that there appears little or no antagonistic sexual conflict, unexpected by prevailing theories. Our results indicate that males possess a mechanism to adjust the ratio of X- and Y-chromosome-bearing spermatozoa in the ejaculate, thereby substantially expanding currently known male options in sexual conflict

Increased sinusoidal flow is not the primary stimulus to liver regeneration

Background: Hemodynamic changes in the liver remnant following partial hepatectomy (PHx) have been suggested to be a primary stimulus in triggering liver regeneration. We hypothesized that it is the increased sinusoidal flow per se and hence the shear-stress stimulus on the endothelial surface within the liver remnant which is the main stimulus to regeneration. In order to test this hypothesis we wanted to increase the sinusoidal flow without performing a concomitant liver resection. Accordingly, we constructed an aorto-portal shunt to the left portal vein branch creating a standardized four-fold increase in flow to segments II, III and IV. The impact of this manipulation was studied in both an acute model (6 animals, 9 hours) using a global porcine cDNA microarray chip and in a chronic model observing weight and histological changes (7 animals, 3 weeks). Results: Gene expression profiling from the shunted segments does not suggest that increased sinusoidal flow per se results in activation of genes promoting mitosis. Hyperperfusion over three weeks results in the whole liver gaining a supranormal weight of 3.9% of the total body weight (versus the normal 2.5%). Contrary to our hypothesis, the weight gain was observed on the non-shunted side without an increase in sinusoidal flow. Conclusions: An isolated increase in sinusoidal flow does not have the same genetic, microscopic or macroscopic impact on the liver as that seen in the liver remnant after partial hepatectomy, indicating that increased sinusoidal flow may not be a sufficient stimulus in itself for the initiation of liver regeneration

Foliar δ15N values characterize soil N cycling and reflect nitrate or ammonium preference of plants along a temperate grassland gradient

The natural abundance of stable 15N isotopes in soils and plants is potentially a simple tool to assess ecosystem N dynamics. Several open questions remain, however, in particular regarding the mechanisms driving the variability of foliar δ15N values of non-N2 fixing plants within and across ecosystems. The goal of the work presented here was therefore to: (1) characterize the relationship between soil net mineralization and variability of foliar Δδ15N (δ15Nleaf − δ15Nsoil) values from 20 different plant species within and across 18 grassland sites; (2) to determine in situ if a plant’s preference for NO3− or NH4+ uptake explains variability in foliar Δδ15N among different plant species within an ecosystem; and (3) test if variability in foliar Δδ15N among species or functional group is consistent across 18 grassland sites. Δδ15N values of the 20 different plant species were positively related to soil net mineralization rates across the 18 sites. We found that within a site, foliar Δδ15N values increased with the species’ NO3− to NH4+ uptake ratios. Interestingly, the slope of this relationship differed in direction from previously published studies. Finally, the variability in foliar Δδ15N values among species was not consistent across 18 grassland sites but was significantly influenced by N mineralization rates and the abundance of a particular species in a site. Our findings improve the mechanistic understanding of the commonly observed variability in foliar Δδ15N among different plant species. In particular we were able to show that within a site, foliar δ15N values nicely reflect a plant’s N source but that the direction of the relationship between NO3− to NH4+ uptake and foliar Δδ15N values is not universal. Using a large set of data, our study highlights that foliar Δδ15N values are valuable tools to assess plant N uptake patterns and to characterize the soil N cycle across different ecosystems