Regularisation of classical self interaction in strings

A general method of regularisation of classical self interaction in strings is extended from the electromagnetic case (for which it was originally developed) to the gravitation case, for which the result can also be represented as a renormalisation.Comment: 4 pages, Latex. Contribution to proceedings of 1997 Cargese A.S.I. ``Strings, branes, and dualities'', ed. L. Baulieu, P. Winde

Drosophila heat shock response requires the jnk pathway and phosphorylation of mixed lineage kinase at a conserved serine-proline motif

Defining context specific requirements for proteins and pathways is a major challenge in the study of signal transduction. For example, the stress-activated protein kinase (SAPK) pathways are comprised of families of closely related transducers that are activated in a variety of tissues and contexts during development and organismal homeostasis. Consequently, redundant and pleiotropic effects have hampered a complete understanding of the individual contributions of transducers in distinct contexts. Here, we report on the function of a context-specific regulatory phosphorylation site, PXSP, in the Drosophila mixed lineage kinase protein, Slpr, a mitogen-activated protein kinase kinase kinase (MAP3K) in the Jun Kinase (JNK) pathway. Genetic analysis of the function of non-phosphorylatable (PXAP) and phosphomimetic mutant (PXEP) Slpr transgenes in several distinct contexts revealed minimal effects in JNK-dependent tissue closure processes but differential requirements in heat stress response. In particular, PXAP expression resulted in sensitivity of adults to sustained heat shock, like p38 and JNK pathway mutants. In contrast, PXEP overexpression conferred some resistance. Indeed, phosphorylation of the PXSP motif is enriched under heat shock conditions and requires in part, the p38 kinases for the enrichment. These data suggest that coordination of signaling between p38 and Slpr serves to maintain JNK signaling during heat stress. In sum, we demonstrate a novel role for JNK signaling in the heat shock response in flies and identify a posttranslational modification on Slpr, at a conserved site among MAP3K mixed lineage kinase family members, which bolsters stress resistance with negligible effects on JNK-dependent developmental processes. © 2012 Gonda et al

Growth and optical characterisation of multilayers of InGaN quantum dots

We report on the growth (using metal-organic vapour phase epitaxy) and optical characterization of single and multiple layers of InGaN quantum dots (QDs), which were formed by annealing InGaN epilayers at the growth temperature in nitrogen. The size and density of the nanostructures have been found to be fairly similar for uncapped single and three layer QD samples if the GaN barriers between the dot layers are grown at the same temperature as the InGaN epilayer. The distribution of nanostructure heights of the final QD layer of three is wider and is centred around a larger size if the GaN barriers are grown at two temperatures (first a thin layer at the dot growth temperature, then a thicker layer at a higher temperature). Micro-photoluminescence studies at 4.2 K of capped samples have confirmed the QD nature of the capped nanostructures by the observation of sharp emission peaks with full width at half maximum limited by the resolution of the spectrometer. We have also observed much more QD emission per unit area in a sample with three QD layers, than in a sample with a single QD layer, as expected

Dynamical coupled-channels: the key to understanding resonances

Recent developments on a dynamical coupled-channels model of hadronic and electromagnetic production of nucleon resonances are summarized.Comment: Invited Plenary talk at the 20th European Conference on Few-Body Problems in Physics (EFB20), September 10-14 2007, Pisa, Italy. To appear in the proceedings in Few-Body System

Flow-distributed spikes for Schnakenberg kinetics

This is the post-print version of the final published paper. The final publication is available at link.springer.com by following the link below. Copyright @ 2011 Springer-Verlag.We study a system of reaction–diffusion–convection equations which combine a reaction–diffusion system with Schnakenberg kinetics and the convective flow equations. It serves as a simple model for flow-distributed pattern formation. We show how the choice of boundary conditions and the size of the flow influence the positions of the emerging spiky patterns and give conditions when they are shifted to the right or to the left. Further, we analyze the shape and prove the stability of the spikes. This paper is the first providing a rigorous analysis of spiky patterns for reaction-diffusion systems coupled with convective flow. The importance of these results for biological applications, in particular the formation of left–right asymmetry in the mouse, is indicated.RGC of Hong Kon

Auto-tail dependence coefficients for stationary solutions of linear stochastic recurrence equations and for GARCH(1,1)

We examine the auto-dependence structure of strictly stationary solutions of linear stochastic recurrence equations and of strictly stationary GARCH(1, 1) processes from the point of view of ordinary and generalized tail dependence coefficients. Since such processes can easily be of infinite variance, a substitute for the usual auto-correlation function is needed

How sex-biased dispersal affects conflict over parental investment

This article is a preprint and has not been peer-reviewed. It is availble from bioRxiv via the DOI in this record.Existing models of parental investment have mainly focused on interactions at the level of the family, and have paid much less attention to the impact of population-level processes. Here we extend classical models of parental care to assess the impact of population structure and limited dispersal. We find that sex-differences in dispersal substantially affect the amount of care provided by each parent, with the more philopatric sex providing the majority of the care to young. This effect is most pronounced in highly viscous populations: in such cases, when classical models would predict stable biparental care, inclusion of a modest sex difference in dispersal leads to uniparental care by the philopatric sex. In addition, mating skew also affects sex-differences in parental investment, with the more numerous sex providing most of the care. However, the effect of mating skew only holds when parents care for their own offspring. When individuals breed communally, we recover the previous finding that the more philopatric sex provides most of the care, even when it is the rare sex. Finally, we show that sex-differences in dispersal can mask the existence of sex-specific costs of care, because the philopatric sex may provide most of the care even in the face of far higher mortality costs relative to the dispersing sex. We conclude that sex-biased dispersal is likely to be an important, yet currently overlooked driver of sex-differences in parental care.We would like to thank the other members of the Transgen group, Tom Ezard, Stuart Townley and Jonathan Wells for discussion. The Dutch Academy of Arts and Sciences (KNAW) and the Lorentz Centre at the University of Leiden, the Netherlands, funded a week-long workshop on nongenetic effects that contributed to this paper. The authors acknowledge the use of the UCL Legion High Performance Computing Facility (Legion@UCL), and associated support services, in the completion of this work. This study was funded by an EPSRC sandpit grant on transgenerational effects, grant number EP/H031928/1 awarded to RAJ and an EPSRC-funded 2020 Science fellowship awarded to BK (grant number EP/I017909/1)

Towards the sustainability of road transport through the introduction of AV technology

The paper investigates the potential for Level 2 autonomous vehicle (AV) technology to improve four prevailing sustainability issues specifically on highways: high congestion levels, increasing accident rates, high CO_2 emissions and poor journey time reliability. Co-operative Adaptive Cruise Control (CACC) shows potential to achieve high volume co-operative driving on highways by controlling these parameters and forming vehicle platoons. Accident rates, CO_2 emissions and journey times can be reduced as a result. The risks of platooning are discussed and a minimum safe platoon headway is established to mitigate the risk of vehicle platoon collisions. This headway is applied to a real highway case study demonstrating the potential to increase notional highway design capacity from 3,600 vehicles per hour (vph) to 9,213 vph, with significant sustainability improvements possible. Recommendations are made to complete a number of policy implementation and technology development tasks aimed to create the best chance of achieving the identified sustainability benefits within a 20 year timeframe.This is the author accepted manuscript. The final version is available from ICE Publishing via https://doi.org/10.1680/ensu.14.0005

Diurnal variability of tropical rainfall retrieved from combined GOES and TRMM satellite information

Recent progress in satellite remote-sensing techniques for precipitation estimation, along with more accurate tropical rainfall measurements from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and precipitation radar (PR) instruments, have made it possible to monitor tropical rainfall diurnal patterns and their intensities from satellite information. One year (August 1998-July 1999) of tropical rainfall estimates from the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN) systems were used to produce monthly means of rainfall diurnal cycles at hourly and 1° × 1° scales over a domain (30°S-30°N, 80°E-10°W) from the Americas across the Pacific Ocean to Australia and eastern Asia. The results demonstrate pronounced diurnal variability of tropical rainfall intensity at synoptic and regional scales. Seasonal signals of diurnal rainfall are presented over the large domain of the tropical Pacific Ocean, especially over the ITCZ and South Pacific convergence zone (SPCZ) and neighboring continents. The regional patterns of tropical rainfall diurnal cycles are specified in the Amazon, Mexico, the Caribbean Sea, Calcutta, Bay of Bengal, Malaysia, and northern Australia. Limited validations for the results include comparisons of 1) the PERSIANN-derived diurnal cycle of rainfall at Rondonia, Brazil, with that derived from the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) radar data; 2) the PERSIANN diurnal cycle of rainfall over the western Pacific Ocean with that derived from the data of the optical rain gauges mounted on the TOGA-moored buoys: and 3) the monthly accumulations of rainfall samples from the orbital TMI and PR surface rainfall with the accumulations of concurrent PERSIANN estimates. These comparisons indicate that the PERSIANN-derived diurnal patterns at the selected resolutions produce estimates that are similar in magnitude and phase

How Sex-Biased Dispersal Affects Sexual Conflict over Care

This is the author accepted manuscript. The final version is available from University of Chicago Press via the DOI in this record.Existing models of parental investment have mainly focused on interactions at the level of the family and have paid much less attention to the impact of population-level processes. Here we extend classical models of parental care to assess the impact of population structure and limited dispersal. We find that sex differences in dispersal substantially affect the amount of care provided by each parent, with the more philopatric sex providing the majority of care to young. This effect is most pronounced in highly viscous populations: in such cases, when classical models would predict stable biparental care, inclusion of a modest sex difference in dispersal leads to uniparental care by the philopatric sex. In addition, mating skew also affects sex differences in parental investment, with the more numerous sex providing most of the care. However, the effect of mating skew holds only when parents care for their own offspring. When individuals breed communally, we recover the previous finding that the more philopatric sex provides most of the care even when it is the rarer sex. We conclude that sex-biased dispersal is likely to be an important yet currently overlooked driver of sex differences in parental care.BK has been funded by an EPSRC 2020 Science fellowship (grant number EP/I017909/1) and a Leverhulme Trust Early Career Research Fellowship (ECF 2015-273). RAJ has been funded by a EPSRC grant number EP/H031928/1. This work has made use of the Carson computing cluster at the Environment and Sustainability Institute at the University of Exeter. In addition, the authors acknowledge the use of the UCL Legion High Performance Computing Facility (Legion@UCL) and associated support services in the completion of this work. The Dutch Academy of Arts and Sciences (KNAW) and the Lorentz Centre at the University of Leiden, the Netherlands funded a workshop on nongenetic effects that contributed to this article