The orbifold transform and its applications

We discuss the notion of the orbifold transform, and illustrate it on simple examples. The basic properties of the transform are presented, including transitivity and the exponential formula for symmetric products. The connection with the theory of permutation orbifolds is addressed, and the general results illustrated on the example of torus partition functions

Giving calves 'the best start': perceptions of colostrum management on dairy farms in England

Good colostrum management can confer protective immunity to newborn calves, making calves less susceptible to infectious disease, and fundamentally improving both their short- and long-term health, welfare and productivity. Industry recommendations commonly refer to 'The Three 'Q's' of colostrum management: the need for calves to receive sufficient 'Quantity' of high 'Quality' colostrum 'Quickly' after birth; some also include 'sQueaky clean' and 'Quantification of passive transfer'. However, research to date suggests that the failure of passive transfer of colostral antibodies is common on commercial dairy farms, contributing to sub-optimal calf health and mortality. This paper explores why this may be the case by investigating stakeholder perceptions of colostrum management and how these perceptions might affect the practice of ensuring adequate colostrum administration to newborn calves. Calf rearing and youngstock management practices on English dairy farms were investigated using 40 in-depth semi-structured interviews: 26 with dairy farmers and 14 with advisors (including veterinarians, feed and pharmaceutical company representatives). Interviews were audio-recorded, transcribed and thematically coded for analysis. 'The Three 'Q's' were found to act as useful reminders about the goals of colostrum management, and a case can be made for further publicising the inclusion of 'sQueaky clean' and 'Quantification of passive transfer' as there remains a lack of focus on colostrum hygiene and measurement of successful antibody transfer. Knowledge of the 'Q's' did not guarantee implementation, and time and labour constraints alongside farmer misconceptions must be addressed when offering professional advice on improving calf health. Further research to encourage on-farm collection and analysis of monitoring data including rates of passive transfer is particularly needed. Advisors must not overlook the importance of colostrum management when assessing farm practices and ensure that they promote evidence-based recommendations if dairy calf morbidity and mortality is to be reduced

Stakeholder perceptions of disease management for dairy calves: “it’s just little things that make such a big difference”

Calf morbidity and mortality rates are often high in dairy herds, raising animal welfare concerns and negatively affecting farm economic efficiency and future performance. Disease prevention is critical to maintain calves in good health, but interventions are dependent upon the persons conducting them. This paper explores the perceptions of farmers, farm workers, veterinarians, and other advisors on the management of calfhood disease on dairy farms in England. Participants were recruited using purposive and “snowball” sampling, resulting in 40 in-depth, semi-structured interviews—26 with dairy farmers and 14 with advisors. Interviews were recorded, transcribed, and thematically coded. Three major themes were derived on the basis of interview data: disease occurrence and treatments, management of calf environment, and the role of stockmanship and perceived control. Respiratory and gastrointestinal diseases in calves were those reported to be most problematic on dairy farms. Limited time and financial resources caused some farmers and advisors to experience a perceived inability to control calf health without antimicrobial treatments. Overall, the findings emphasise the importance of human influences on calf health and disease in the context of influencing the interactions among the host, pathogens, and the environment. Further research should investigate what “attention to detail” means within different farm contexts and practices, as this was believed to be important in the promotion of better husbandry standards and health. We recommend the use of supportive knowledge exchange processes, including facilitation, to empower farmers to promote continuous improvement in calf health

Youngstock management as “The key for everything”? Perceived value of calves and the role of calf performance monitoring and advice on dairy farms

Replacement heifers are key to the future milking herd and farm economic efficiency but are not always prioritised on dairy farms. Dairy enterprises are comprised of components which compete for limited resources; scarce information about calf performance and the associated losses and (potential) gains on farms can mean calves are prioritised less in management and investment decisions. The research reported in this paper explored the personal and contextual factors that influence calf management decisions on dairy farms. Forty in-depth, semi-structured interviews were conducted with dairy farmers (26 interviews) and farm advisors (14 interviews) who were recruited using purposive and “snowball” sampling. Interviews were recorded, transcribed, and thematically analysed. Six major themes were constructed from the interview data relating to: the perceived importance of youngstock management, the role and influence of calf rearers, calf performance monitoring, farmer engagement with information and advice, the quality of communication and advice, and veterinary involvement in calf rearing. Results indicated that although the wider dairy industry has promoted the importance of youngstock, calves often have not been fully integrated into the whole dairy farm system, nor culturally accepted as an integral part of the productive herd. Calves tended to be marginalised on farms, largely due to limited resources, lack of data monitoring, and their unrecognised potential, as well as social norms and scarcity of support structures impacting upon farm investment and management decisions. Many calf rearers were disappointed by the repetition and impractical nature of information in print media. Most farmers did not routinely consult their veterinarian about their calves, rather following a reactive treatment model even when a preventive herd health strategy was applied to the adult herd. Advisory structures often require a driven individual with calf-centric interest to prevent calves from being overlooked. Furthermore, advisory efforts often failed to motivate farmers to act on advice. These findings indicate the need for greater focus on how to achieve rearing targets by provision of technical and support structures to foster action toward improved calf wellbeing, and for the status of calves to be raised in line with their vital importance for the future dairy herd

Supersymmetric, cold and lukewarm black holes in cosmological Einstein-Maxwell theory

In flat space, the extreme Reissner-Nordstr\o m (RN) black hole is distinguished by its coldness (vanishing Hawking temperature) and its supersymmetry. We examine RN solutions to Einstein-Maxwell theory with a cosmological constant $\Lambda$, classifying the cold black holes and, for positive $\Lambda$, the ``lukewarm" black holes at the same temperature as the de Sitter thermal background. For negative $\Lambda$, we classify the supersymmetric solutions within the context of $N=2$ gauged supergravity. One finds supersymmetric analogues of flat-space extreme RN black holes, which for nonzero $\Lambda$ differ from the cold black holes. In addition, there is an exotic class of supersymmetric solutions which cannot be continued to flat space, since the magnetic charge becomes infinite in that limit.Comment: (18 pp., plain tex

UV and X-Ray Monitoring of AG Draconis During the 1994/1995 Outbursts

The recent 1994-1995 active phase of AG Draconis has given us for the first time the opportunity to follow the full X-ray behaviour of a symbiotic star during two successive outbursts and to compare with its quiescence X-ray emission. With \ros observations we have discovered a remarkable decrease of the X-ray flux during both optical maxima, followed by a gradual recovering to the pre-outburst flux. In the UV the events were characterized by a large increase of the emission line and continuum fluxes, comparable to the behaviour of AG Dra during the 1980-81 active phase. The anticorrelation of X-ray/UV flux and optical brightness evolution is shown to very likely be due to a temperature decrease of the hot component. Such a temperature decrease could be produced by an increased mass transfer to the burning compact object, causing it to slowly expand to about twice its original size.Comment: 12 pages postscript incl. figures, Proc. of Workshop on Supersoft X-Ray Sources, to appear in Lecture Notes in Physics vol. 472 (1996

Molecular spintronics: Coherent spin transfer in coupled quantum dots

Time-resolved Faraday rotation has recently demonstrated coherent transfer of electron spin between quantum dots coupled by conjugated molecules. Using a transfer Hamiltonian ansatz for the coupled quantum dots, we calculate the Faraday rotation signal as a function of the probe frequency in a pump-probe setup using neutral quantum dots. Additionally, we study the signal of one spin-polarized excess electron in the coupled dots. We show that, in both cases, the Faraday rotation angle is determined by the spin transfer probabilities and the Heisenberg spin exchange energy. By comparison of our results with experimental data, we find that the transfer matrix element for electrons in the conduction band is of order 0.08 eV and the spin transfer probabilities are of order 10%.Comment: 13 pages, 6 figures; minor change

Maximal Neutrino Mixing from a Minimal Flavor Symmetry

We study a number of models, based on a non-Abelian discrete group, that successfully reproduce the simple and predictive Yukawa textures usually associated with U(2) theories of flavor. These models allow for solutions to the solar and atmospheric neutrino problems that do not require altering successful predictions for the charged fermions or introducing sterile neutrinos. Although Yukawa matrices are hierarchical in the models we consider, the mixing between second- and third-generation neutrinos is naturally large. We first present a quantitative analysis of a minimal model proposed in earlier work, consisting of a global fit to fermion masses and mixing angles, including the most important renormalization group effects. We then propose two new variant models: The first reproduces all important features of the SU(5)xU(2) unified theory with neither SU(5) nor U(2). The second demonstrates that discrete subgroups of SU(2) can be used in constructing viable supersymmetric theories of flavor without scalar universality even though SU(2) by itself cannot.Comment: 34 pages LaTeX, 1 eps figure, minor revisions and references adde

Explaining ecological shifts: the roles of temperature and primary production in the long-term dynamics of benthic faunal composition

Predicting the ecological consequences of environmental change requires that we can identify the drivers of long‐term ecological variation. Biological assemblages can exhibit abrupt deviations from temporal trends, potentially resulting in irreversible shifts in species composition over short periods of time. Such dynamics are hypothesised to occur as gradual forcing eventually causes biological thresholds to be crossed, but could also be explained by biota simply tracking abrupt changes to their environment. Here, we modelled temporal variation in a North Sea benthic faunal assemblage over a 40‐year period (1972–2012) to test for changes to temporal trends of biota and determine whether they could be explained by underlying patterns in sea temperature and primary production. These extrinsic factors were postulated to influence community dynamics through their roles in determining and sustaining the metabolic demands of organisms, respectively. A subset of mainly large and long‐lived taxa (those loaded on the first principal component of taxa densities) exhibited two significant changes to their temporal trends, which culminated in a shift in assemblage composition. These changes were explained by an increase in pelagic primary production, and hence detrital food input to the seabed, but were unrelated to variation in sea temperature. A second subset of mainly small and short‐lived taxa (those loaded on the second principal component) did not experience any significant changes to their temporal trends, as enhanced pelagic primary production appeared to mitigate the impact of warming on these organisms. Our results suggest that abrupt ecological shifts can occur as biota track underlying variation in extrinsic factors, in this case primary production. Changes to the structure of ecosystems may therefore be predictable based on environmental change projections.</jats:p

U(2)-like Flavor Symmetries and Approximate Bimaximal Neutrino Mixing

Models involving a U(2) flavor symmetry, or any of a number of its non-Abelian discrete subgroups, can explain the observed hierarchy of charged fermion masses and CKM angles. It is known that a large neutrino mixing angle connecting second and third generation fields may arise via the seesaw mechanism in these models, without a fine tuning of parameters. Here we show that it is possible to obtain approximate bimaximal mixing in a class of models with U(2)-like Yukawa textures. We find a minimal form for Dirac and Majorana neutrino mass matrices that leads to two large mixing angles, and show that our result can quantitatively explain atmospheric neutrino oscillations while accommodating the favored, large angle MSW solution to the solar neutrino problem. We demonstrate that these textures can arise in models by presenting a number of explicit examples.Comment: 20 pages RevTex4, 2 figure