Cosmic-Ray Events as Background in Imaging Atmospheric Cherenkov Telescopes

The dominant background for observations of gamma-rays in the energy region above 50 GeV with Imaging Atmospheric Cherenkov telescopes are cosmic-ray events. The images of most of the cosmic ray showers look significantly different from those of gamma-rays and are therefore easily discriminated. However, a small fraction of events seems to be indistinguishable from gamma-rays. This constitutes an irreducible background to the observation of high-energy gamma-ray sources, and limits the sensitivity achievable with a given instrument. Here, a Monte Carlo study of gamma-like cosmic-ray events is presented. The nature of gamma-like cosmic-ray events, the shower particles that are responsible for the gamma-like appearance, and the dependence of these results on the choice of the hadronic interaction model are investigated. Most of the gamma-like cosmic ray events are characterised by the production of high-energy pi0's early in the shower development which dump most of the shower energy into electromagnetic sub-showers. Also Cherenkov light from single muons can mimic gamma-rays in close-by pairs of telescopes. Differences of up to 25% in the collection area for gamma-like proton showers between QGSJet/FLUKA and Sibyll/FLUKA simulations have been found.Comment: Accepted by Journal of Astroparticle Physic

Using the ‘recovery’ and ‘rehabilitation’ paradigms to support desistence of substance-involved offenders: Exploration of dual and multi-focus interventions (Invited Paper)

Purpose The links between substance use and offending are well evidenced in the literature, and increasingly, substance misuse recovery is being seen as a central component of the process of rehabilitation from offending, with substance use identified as a key criminogenic risk factor. In recent years, research has demonstrated the commonalities between recovery and rehabilitation, and the possible merits of providing interventions to substance-involved offenders that address both problematic sets of behaviours. The purpose of this paper is to provide an overview of the links between substance use and offending, and the burgeoning literature around the parallel processes of recovery and rehabilitation. Design/methodology/approach This is provided as a rationale for a new treatment approach for substance-involved offenders, Breaking Free Online (BFO), which has recently been provided as part of the “Gateways” throughcare pathfinder in a number of prisons in North-West England. The BFO programme contains specific behaviour change techniques that are generic enough to be applied to change a wide range of behaviours, and so is able to support substance-involved offenders to address their substance use and offending simultaneously. Findings This dual and multi-target intervention approach has the potential to address multiple, associated areas of need simultaneously, streamlining services and providing more holistic support for individuals, such as substance-involved offenders, who may have multiple and complex needs. Practical implications Given the links between substance use and offending, it may be beneficial to provide multi-focussed interventions that address both these behaviours simultaneously, in addition to other areas of multiple and complex needs. Specifically, digital technologies may provide an opportunity to widen access to such multi-focussed interventions, through computer-assisted therapy delivery modalities. Additionally, using digital technologies to deliver such interventions can provide opportunities for joined-up care by making interventions available across both prison and community settings, following offenders on their journey through the criminal justice system. Originality/value Recommendations are provided to other intervention developers who may wish to further contribute to widening access to such dual- and multi-focus programmes for substance-involved offenders, based on the experiences developing and evidencing the BFO programme

Variability in the high energy gamma ray emission from Cyg X-3 over a two-year period (1983 - 1984) at E 4 x 10(11) eV

Cygnus X-3 is observed to emit gamma rays with energies in excess of 4 x 10 to the 11th power eV during two out of 9 observational categories over an 18 month time span. The emissions are observed at the 0.6 phase of the characteristic 4.8 hr light curve for this binary system. We estimate a peak flux at phase 0.6 of 5 x 10 to the minus 10th power photons cm-2s-1 at a software threshold of 8 x 10 to the 11th power eV for Oct/Nov 1983. A flux for the June 84 effect cannot be reliably calculated at present due to lack of Monte Carlo simulations for the energy range and spectral region. For the other 7 observational categories the observations are consistent with zero source emission. The light curve would appear to be variable on a time scale of a couple of weeks at these categories. Selection of compact images in accordance with Monte Carlo simulations combined with empirical optimization techniques have led to an enriched gamma ray light curve for the Oct/Nov 1983 data. Selection on the basis of shower orientation, however, has not led to any notable enhancement of the gamma ray content. Individual Cherenko images can be reliably sorted on an event by event basis into either proton-induced or photon-induced showers

Human cytomegalovirus: taking the strain

In celebrating the 60th anniversary of the first isolation of human cytomegalovirus (HCMV), we reflect on the merits and limitations of the viral strains currently being used to develop urgently needed treatments. HCMV research has been dependent for decades on the high-passage strains AD169 and Towne, heavily exploiting their capacity to replicate efficiently in fibroblasts. However, the genetic integrity of these strains is so severely compromised that great caution needs to be exercised when considering their past and future use. It is now evident that wild-type HCMV strains are not readily propagated in vitro. HCMV mutants are rapidly selected during isolation in fibroblasts, reproducibly affecting gene RL13, the UL128 locus (which includes genes UL128, UL130 and UL131A) and often the UL/b′ region. As a result, the virus becomes less cell associated, altered in tropism and less pathogenic. This problem is not restricted to high-passage strains, as even low-passage strains can harbour biologically significant mutations. Cloning and manipulation of the HCMV genome as a bacterial artificial chromosome (BAC) offers a means of working with stable, genetically defined strains. To this end, the low-passage strain Merlin genome was cloned as a BAC and sequentially repaired to match the viral sequence in the original clinical sample from which Merlin was derived. Restoration of UL128L to wild type was detrimental to growth in fibroblasts, whereas restoration of RL13 impaired growth in all cell types tested. Stable propagation of phenotypically wild-type virus could be achieved only by placing both regions under conditional expression. In addition to the development of these tools, the Merlin transcriptome and proteome have been characterized in unparalleled detail. Although Merlin may be representative of the clinical agent, high-throughput whole-genome deep sequencing studies have highlighted the remarkable high level of interstrain variation present in circulating virus. There is a need to develop systems capable of addressing the significance of this diversity, free from the confounding effects of genetic changes associated with in vitro adaptation. The generation of a set of BAC clones, each containing the genome of a different HCMV strain repaired to match the sequence in the clinical sample, would provide a pathway to address the biological and clinical effects of natural variation in wild-type HCMV