The brightness temperature problem in extreme IDV quasars: a model for PKS 0405-385

I re-examine the brightness temperature problem in PKS 0405-385 which is an extreme intra-day variable radio quasar with an inferred brightness temperature of $\sim 5 \times 10^{14}$ K at 5 GHz, well above the Compton catastrophe limit of $\sim 10^{11}$ K reached when the synchrotron photon energy density exceeds the energy density of the magnetic field. If one takes into account the uncertainty in the distance to the ionized clouds responsible for interstellar scintillation causing rapid intra-day variability in PKS 0405-385 it is possible that the brightness temperature could be as low as $\sim 10^{13}$ K at 5 GHz, or even lower. The radio spectrum can be fitted by optically thin emission from mono-energetic electrons, or an electron spectrum with a low-energy cut-off such that the critical frequency of the lowest energy electrons is above the radio frequencies of interest. If one observes optically thin emission along a long narrow emission region, the average energy density in the emission region can be many orders of magnitude lower than calculated from the observed intensity if one assumed a spherical emission region. I discuss the physical conditions in the emission region and find that the Compton catastrophe can then be avoided using a reasonable Doppler factor. I also show that MeV to 100 GeV gamma-ray emission at observable flux levels should be expected from extreme intra-day variable sources such as PKS 0405-385.Comment: 10 pages, 6 figures. Accepted for publication in MNRA

Integration of digital video sequences and supportive interactive animations into the Level 1 module Introductory Microbiology, to enhance the delivery and effectiveness of experimental microbiology.

Report of a CELT project on supporting students through innovation and researchFrom a previous innovations project during 2002/2003, the feasibility of producing and editing digital video of experimental microbiological procedures was established. The digital video was produced for eventual use on the Level 1 Introductory Microbiology within the University of Wolverhampton virtual learning environment (WOLF), to improve an understanding of the principles and practice of experimental procedures encountered on the module. In addition to the video sequences, supportive animations of the practical exercises were produced, to be viewed eventually by students in association with the video also via WOLF. The end of the previous project had produced several video and animation sequences, although these had not, at that time, been added to the WOLF topic. To provide an effective package of video and animation sequences to fully support the practical component of the module, more sequences were required, together with refinement of existing material. In addition, following integration into the WOLF topic, an analysis of the effectiveness of the sequences, in supporting an understanding of the theory and practice of the experimental exercises, was considered to be of value

Energy spectrum of extragalactic gamma-ray sources

The result of Monte Carlo electron photon cascade calculations for propagation of gamma rays through regions of extragalactic space containing no magnetic field are given. These calculations then provide upper limits to the expected flux from extragalactic sources. Since gamma rays in the 10 to the 14th power eV to 10 to the 17th power eV energy range are of interest, interactions of electrons and photons with the 3 K microwave background radiation are considered. To obtain an upper limit to the expected gamma ray flux from sources, the intergalactic field is assumed to be so low that it can be ignored. Interactions with photons of the near-infrared background radiation are not considered here although these will have important implications for gamma rays below 10 to the 14th power eV if the near infrared background radiation is universal. Interaction lengths of electrons and photons in the microwave background radiation at a temperature of 2.96 K were calculated and are given

Value, Kaizen and Knowledge Management: Developing a Knowledge Management Strategy for Southampton Solent University

The process of development of the strategic plan for Southampton Solent University offered a vehicle for the development of kaizen and knowledge management (KM) activities within the institution. The essential overlap between the methods offers clear benefits in the HE environment. In consideration of the aspects of KM and kaizen, various potential opportunities were identified as targets for improvement, and clarified by knowledge audit as to value and viability. The derived outcomes are listed along with some of the principal factors and perceived barriers in the practical implementation of the outcomes. Knowledge audit applied here focused on the identification of where value arises within the business. Resource constraints and the practicalities of a people-centred system limit the permissible rate of innovation, so precise focus on the areas of business activity of most significance to the mission and client base is crucial. The fundamental question of whether such a strategy should be developed as a separate strand or embedded into existing strategies is discussed. In practice, Solent has chosen to embed, principally for reasons of maintenance of ownership and commitment. Confidence in the process has been built through prior success with trialled activities around retention, where an activity-based pedagogic framework was adopted to address issues with an access course. Other areas of early intervention include the development and reengineering of recruitment and admissions processes, and the development of activities and pedagogy based on the virtual learning environment as exemplars of the importance of cyclical feedback in continuous improvement. The inherent complexity of processes running across the university as an organisation offers opportunities for benefits from the through-process approach implicit in kaizen. The business value of the institution is in the skills of its employees and its deployed intellectual property, and thus the importance of the enhancement of both tangible assets and intangible processes is critical to future success

Neutrino Emission from HBLs and LBLs

The Synchrotron Proton Blazar model is a promising model to explain high energy emission from gamma-ray loud BL Lac objects like Mkn 421. In contrast to leptonic models, the hadronic explanation of gamma-ray emission predicts ultrahigh energy neutrinos. The predicted neutrino spectra from a typical High-energy cutoff BL Lac Object (HBL) and a Low-energy cutoff BL Lac Object (LBL) are presented. We find that cooling due to muon synchrotron radiation causes a cutoff of the neutrino spectrum at $\sim 10^{18}$ eV, with the exception of $\nu_\mu$ from kaon decay which may extend to higher energies if meson production takes place in the secondary resonance region of the cross section. The impact of the neutrino output from both source populations to the diffuse neutrino background is discussed.Comment: 4 pages, 3 figures, to appear in: Proc. 27th Int. Cosmic Ray Conf., Hamburg/German

Cut-offs and pile-ups in shock acceleration spectra

We have examined cutoffs and pile-ups due to various processes in the spectra of particles produced by shock acceleration, and found that, even in the absence of energy losses, the shape of the spectrum of accelerated particles at energies well below the nominal maximum energy depends strongly on the energy dependence of the diffusion coefficient. This has implications in many areas, for example, in fitting the observed cosmic ray spectrum with models based on power-law source spectra and rigidity dependent diffusive escape from the galaxy. With continuous energy losses, prominent pile-ups may arise, and these should be included when modelling synchrotron X-ray and inverse Compton gamma-ray spectra from a shock-accelerated electron population. We have developed a Monte Carlo/numerical technique to model the shape of the spectrum for the case of non-continuous energy losses such as inverse Compton scattering in the Klein-Nishina regime. We find that the shapes of the resulting cut-offs differ substantially from those arising from continuous processes, and we suggest that such differences could be observable through their effect on the spectrum of radiation emitted by a population of recently accelerated electrons as, for example, may exist in young supernova remnants.Comment: 23 pages, 8 figures, submitted to Astroparticle Physic

The physical parameters of Markarian 501 during flaring activity

We determine the physical parameters (magnetic field and Doppler factor) of the homogeneous synchrotron self-Compton model allowed by the observed X-ray to gamma-ray spectra and variability of Markarian~501 during the 15-16 April 1997 flaring activity. We find that magnetic fields between 0.07 G and 0.6 G and Doppler factors between 12 and 36 could fit (depending on observed variability time scale) these observations. We take account of photon-photon pair production interactions of gamma-ray photons occurring both inside the emission region and during propagation to Earth and find these to be extremely important in correctly determining the allowed model parameters. Previous estimates of the allowed parameter space have neglected this effect. Future multi-wavelength campaigns during strong flaring activity, including observations from optical to TeV gamma-rays, should enable the physical parameters to be further constrained.Comment: 18 pages, 5 figures, minor changes, additional reference, accepted for publication in MNRA