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Tev And Multi-Wavelength Observations Of Mrk 421 In 2006-2008
Get PDFWe report on TeV γ-ray observations of the blazar Mrk 421 (redshift of 0.031) with the VERITAS observatory and the Whipple 10 m Cherenkov telescope. The excellent sensitivity of VERITAS allowed us to sample the TeV γ-ray fluxes and energy spectra with unprecedented accuracy where Mrk 421 was detected in each of the pointings. A total of 47.3 hr of VERITAS and 96 hr of Whipple 10 m data were acquired between 2006 January and 2008 June. We present the results of a study of the TeV γ-ray energy spectra as a function of time and for different flux levels. On 2008 May 2 and 3, bright TeV γ-ray flares were detected with fluxes reaching the level of 10 Crab. The TeV γ-ray data were complemented with radio, optical, and X-ray observations, with flux variability found in all bands except for the radio wave band. The combination of the Rossi X-ray Timing Explorer and Swift X-ray data reveal spectral hardening with increasing flux levels, often correlated with an increase of the source activity in TeV γ-rays. Contemporaneous spectral energy distributions were generated for 18 nights, each of which are reasonably described by a one-zone synchrotron self-Compton model
Multi-Wavelength Observations Of The Flaring Gamma-Ray Blazar 3c 66a In 2008 October
Get PDFThe BL Lacertae object 3C 66A was detected in a flaring state by the Fermi Large Area Telescope (LAT) and VERITAS in 2008 October. In addition to these gamma-ray observations, F-GAMMA, GASP-WEBT, PAIRITEL, MDM, ATOM, Swift, and Chandra provided radio to X-ray coverage. The available light curves show variability and, in particular, correlated flares are observed in the optical and Fermi-LAT gamma-ray band. The resulting spectral energy distribution can be well fitted using standard leptonic models with and without an external radiation field for inverse Compton scattering. It is found, however, that only the model with an external radiation field can accommodate the intra-night variability observed at optical wavelengths
Veritas observations of the unusual extragalactic transient swift j164449.3+573451
Get PDFWe report on very high energy (\u3e100 GeV) gamma-ray observations of Swift J164449.3+573451, an unusual transient object first detected by the Swift Observatory and later detected by multiple radio, optical, and X-ray observatories. A total exposure of 28 hr was obtained on Swift J164449.3+573451 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) during 2011 March 28-April 15. We do not detect the source and place a differential upper limit on the emission at 500 GeV during these observations of 1.4 × 10–12 erg cm–2 s–1 (99% confidence level). We also present time-resolved upper limits and use a flux limit averaged over the X-ray flaring period to constrain various emission scenarios that can accommodate both the radio-through-X-ray emission detected from the source and the lack of detection by VERITAS
A Modified Surface on Titanium Deposited by a Blasting Process
Get PDFAbstract
: Hydroxyapatite (HA) coating of hard tissue implants is widely employed for its biocompatible and osteoconductive properties as well as its improved mechanical properties. Plasma technology is the principal deposition process for coating HA on bioactive metals for this application. However, thermal decomposition of HA can occur during the plasma deposition process, resulting in coating variability in terms of purity, uniformity and crystallinity, which can lead to implant failure caused by aseptic loosening. In this study, CoBlast™, a novel blasting process has been used to successfully modify a titanium (V) substrate with a HA treatment using a dopant/abrasive regime. The impact of a series of apatitic abrasives under the trade name MCD, was investigated to determine the effect of abrasive particle size on the surface properties of both microblast (abrasive only) and CoBlast (HA/abrasive) treatments. The resultant HA treated substrates were compared to substrates treated with abrasive only (microblasted) and an untreated Ti. The HA powder, apatitic abrasives and the treated substrates were characterized for chemical composition, coating coverage, crystallinity and topography including surface roughness. The results show that the surface roughness of the HA blasted modification was affected by the particle size of the apatitic abrasives used. The CoBlast process did not alter the chemistry of the crystalline HA during deposition. Cell proliferation on the HA surface was also assessed, which demonstrated enhanced osteo-viability compared to the microblast and blank Ti. This study demonstrates the ability of the CoBlast process to deposit HA coatings with a range of surface properties onto Ti substrates. The ability of the CoBlast technology to offer diversity in modifying surface topography offers exciting new prospects in tailoring the properties of medical devices for applications ranging from dental to orthopedic settings
Beverage consumption and BMI of British schoolchildren aged 9-13 years
Get PDFObjective Adequate fluid intake has been well documented as important for health but whether it has adverse effects on overall energy and sugar intakes remains under debate. Many dietary studies continue to refrain from reporting on beverage consumption, which the present study aimed to address. Design A cross-sectional survey investigated self-reported measures of dietary intake and anthropometric measurements. Setting Primary and secondary schools in south-west London, UK. Subjects Boys and girls (n 248) aged 9-13 years. Results Boys consumed 10 % and girls consumed 9 % of their daily energy intake from beverages and most children had total sugar intakes greater than recommended. Beverages contributed between a quarter and a third of all sugars consumed, with boys aged 11-13 years consuming 32 % of their total sugar from beverages. There was a strong relationship between consumption of beverages and energy intake; however, there was no relationship between beverage type and either BMI or BMI Z-score. Fruit juices and smoothies were consumed most frequently by all girls and 9-10-year-old boys; boys aged 11-13 years preferred soft drinks and consumed more of their daily energy from soft drinks. Milk and plain water as beverages were less popular. Conclusions Although current health promotion campaigns in schools merit the attention being given to improving hydration and reducing soft drinks consumption, it may be also important to educate children on the energy and sugar contents of all beverages. These include soft drinks, as well as fruit juices and smoothies, which are both popular and consumed regularly. © 2011 The Authors
Veritas Observations Of Gamma-Ray Bursts Detected By Swift
Get PDFWe present the results of 16 Swift-triggered Gamma-ray burst (GRB) follow-up observations taken with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) telescope array from 2007 January to 2009 June. The median energy threshold and response time of these observations were 260 GeV and 320 s, respectively. Observations had an average duration of 90 minutes. Each burst is analyzed independently in two modes: over the whole duration of the observations and again over a shorter timescale determined by the maximum VERITAS sensitivity to a burst with a t –1.5 time profile. This temporal model is characteristic of GRB afterglows with high-energy, long-lived emission that have been detected by the Large Area Telescope on board the Fermi satellite. No significant very high energy (VHE) gamma-ray emission was detected and upper limits above the VERITAS threshold energy are calculated. The VERITAS upper limits are corrected for gamma-ray extinction by the extragalactic background light and interpreted in the context of the keV emission detected by Swift. For some bursts the VHE emission must have less power than the keV emission, placing constraints on inverse Compton models of VHE emission
Relationships in Fast Moving Consumer Goods Markets: The Consumers’ Perspective
Get PDFPurpose: This study explores relationship marketing and the existence of relationships in mass consumer markets from the consumers’ perspective, with the focus on the Fast Moving Consumer Good (FMCG) sector.
Methodology Approach: A total of 10 focus groups were conducted with consumers from a broad range of demographic and socio-economic backgrounds to enable in-depth exploration of the research issue.
Findings: The study highlights the dominant negative attitudes that exist among consumers to relationship marketing as it is operationalised in FMCG markets. It is found that from the consumers’ perspective relationships do not and cannot exist in these markets and that the nature of exchange in such markets is not relationship based. Consequently, the research concludes that there is a necessity to move away from relationship rhetoric in FMCG markets, and to explore the true nature of exchange in the quest for effective marketing strategies. The research also suggests that further research on relationship marketing should focus on situations where relationships do and can exist and consequently the boundaries of relationship marketing should be limited to only these situations.
Originality/Value: By offering the consumer perspective on relationships and relationship marketing this study broadens understanding of the phenomenon and makes an important contribution to the relationship marketing debate
Spectral Energy Distribution Of Markarian 501: Quiescent State Versus Extreme Outburst
Get PDFThe very high energy (VHE; E \u3e 100 GeV) blazar Markarian 501 (Mrk 501) has a well-studied history of extreme spectral variability and is an excellent laboratory for studying the physical processes within the jets of active galactic nuclei. However, there are few detailed multiwavelength studies of Mrk 501 during its quiescent state, due to its low luminosity. A short-term multiwavelength study of Mrk 501 was coordinated in 2009 March, focusing around a multi-day observation with the Suzaku X-ray satellite and including γ-ray data from VERITAS, MAGIC, and the Fermi Gamma-ray Space Telescope with the goal of providing a well-sampled multiwavelength baseline measurement of Mrk 501 in the quiescent state. The results of these quiescent-state observations are compared to the historically extreme outburst of 1997 April 16, with the goal of examining variability of the spectral energy distribution (SED) between the two states. The derived broadband SED shows the characteristic double-peaked profile. We find that the X-ray peak shifts by over two orders of magnitude in photon energy between the two flux states while the VHE peak varies little. The limited shift in the VHE peak can be explained by the transition to the Klein-Nishina (KN) regime. Synchrotron self-Compton models are matched to the data and the implied KN effects are explored
Veritas Observations Of The Tev Binary Ls I+61 Degrees 303 During 2008-2010
Get PDFWe present the results of observations of the TeV binary LS I +61° 303 with the VERITAS telescope array between 2008 and 2010, at energies above 300 GeV. In the past, both ground-based gamma-ray telescopes VERITAS and MAGIC have reported detections of TeV emission near the apastron phases of the binary orbit. The observations presented here show no strong evidence for TeV emission during these orbital phases; however, during observations taken in late 2010, significant emission was detected from the source close to the phase of superior conjunction (much closer to periastron passage) at a 5.6 standard deviation (5.6σ) post-trials significance. In total, between 2008 October and 2010 December a total exposure of 64.5 hr was accumulated with VERITAS on LS I +61° 303, resulting in an excess at the 3.3σ significance level for constant emission over the entire integrated data set. The flux upper limits derived for emission during the previously reliably active TeV phases (i.e., close to apastron) are less than 5% of the Crab Nebula flux in the same energy range. This result stands in apparent contrast to previous observations by both MAGIC and VERITAS which detected the source during these phases at 10% of the Crab Nebula flux. During the two year span of observations, a large amount of X-ray data were also accrued on LS I +61° 303 by the Swift X-ray Telescope and the Rossi X-ray Timing Explorer Proportional Counter Array. We find no evidence for a correlation between emission in the X-ray and TeV regimes during 20 directly overlapping observations. We also comment on data obtained contemporaneously by the Fermi Large Area Telescope
Collaborative Learning and Developing the Capacity as a Reflective Practitioner
Get PDFThe BA in Community Development has no final written exams and instead depends on a number of other approaches to assess the students learning. In year 1, semester 1 students take a module called ‘Portfolio Methods for RPL’ which explores the process of RPL, and what a learning portfolio is. More importantly, it requires the students to focus on their prior learning and not experience per se. In the following semester the method is used to report on work placement and to capture the authentic and individual learning of each student. This paper explores the collective approach to documenting work based learning through the use of learning portfolios and the process of reflection to enhance and enrich the learning experience. The emphasis is on the student taking ownership for their own learning, away from the input approach and towards individual ownership. It also looks at students as co-creators of knowledge in the community sector which strengthens the engagement with higher education and the community at large. A key aspect is for the student to identify their learning and develop the capacity to enhance this learning through reflective practice. Beyond this engagement it is transferable means of incorporating the prior learning of adults in meeting the standards of higher education institutions