Time dependent spectral modeling of Markarian 421 during a violent outburst in 2010

We present the results of extensive modeling of the spectral energy distributions (SEDs) of the closest blazar (z=0.031) Markarian 421 (Mrk 421) during a giant outburst in February 2010. The source underwent rapid flux variations in both X-rays and very high energy (VHE) gamma-rays as it evolved from a low-flux state on 2010 February 13-15 to a high-flux state on 2010 February 17. During this period, the source exhibited significant spectral hardening from X-rays to VHE gamma-rays while exhibiting a "harder when brighter" behavior in these energy bands. We reproduce the broadband SED using a time-dependent multi-zone leptonic jet model with radiation feedback. We find that an injection of the leptonic particle population with a single power-law energy distribution at shock fronts followed by energy losses in an inhomogeneous emission region is suitable for explaining the evolution of Mrk 421 from low- to high-flux state in February 2010. The spectral states are successfully reproduced by a combination of a few key physical parameters, such as the maximum $\&$ minimum cutoffs and power-law slope of the electron injection energies, magnetic field strength, and bulk Lorentz factor of the emission region. The simulated light curves and spectral evolution of Mrk 421 during this period imply an almost linear correlation between X-ray flux at 1-10 keV energies and VHE gamma-ray flux above 200 GeV, as has been previously exhibited by this source. Through this study, a general trend that has emerged for the role of physical parameters is that, as the flare evolves from a low- to a high-flux state, higher bulk kinetic energy is injected into the system with a harder particle population and a lower magnetic field strength.Comment: 13 pages, 5 figures, accepted for publication in MNRA

High titers of transmissible spongiform encephalopathy infectivity associated with extremely low levels of PrP in vivo

Rona Barron - ORCID: 0000-0003-4512-9177 https://orcid.org/0000-0003-4512-9177Diagnosis of transmissible spongiform encephalopathy (TSE) disease in humans and ruminants relies on the detection in post-mortem brain tissue of the protease-resistant form of the host glycoprotein PrP. The presence of this abnormal isoform (PrPSc) in tissues is taken as indicative of the presence of TSE infectivity. Here we demonstrate conclusively that high titers of TSE infectivity can be present in brain tissue of animals that show clinical and vacuolar signs of TSE disease but contain low or undetectable levels of PrPSc. This work questions the correlation between PrPSc level and the titer of infectivity and shows that tissues containing little or no proteinase K-resistant PrP can be infectious and harbor high titers of TSE infectivity. Reliance on protease-resistant PrPSc as a sole measure of infectivity may therefore in some instances significantly underestimate biological properties of diagnostic samples, thereby undermining efforts to contain and eradicate TSEs.https://doi.org/10.1074/jbc.M704329200282pubpub4

Reentrant phase behaviour for systems with competition between phase separation and self-assembly

In patchy particle systems where there is competition between the self-assembly of finite clusters and liquid-vapour phase separation, reentrant phase behaviour is observed, with the system passing from a monomeric vapour phase to a region of liquid-vapour phase coexistence and then to a vapour phase of clusters as the temperature is decreased at constant density. Here, we present a classical statistical mechanical approach to the determination of the complete phase diagram of such a system. We model the system as a van der Waals fluid, but one where the monomers can assemble into monodisperse clusters that have no attractive interactions with any of the other species. The resulting phase diagrams show a clear region of reentrance. However, for the most physically reasonable parameter values of the model, this behaviour is restricted to a certain range of density, with phase separation still persisting at high densities.Comment: 13 pages, 10 figure

Anomalous Radio-Wave Scattering from Interstellar Plasma Structures

This paper considers scattering screens that have arbitrary spatial variations of scattering strength transverse to the line of sight, including screens that are spatially well confined, such as disks and filaments. We calculate the scattered image of a point source and the observed pulse shape of a scattered impulse. The consequences of screen confinement include: (1) Source image shapes that are determined by the physical extent of the screen rather than by the shapes of much-smaller diffracting microirregularities. These include image elongations and orientations that are frequency dependent. (2) Variation with frequency of angular broadening that is much weaker than the trademark \nu^{-2} scaling law (for a cold, unmagnetized plasma), including frequency-independent cases; and (3) Similar departure of the pulse broadening time from the usually expected \nu^{-4} scaling law. We briefly discuss applications that include scattering of pulses from the Crab pulsar by filaments in the Crab Nebula; image asymmetries from Galactic scattering of the sources Cyg X-3, Sgr A*, and NGC 6334B; and scattering of background active galactic nuclei by intervening galaxies. We also address the consequences for inferences about the shape of the wavenumber spectrum of electron density irregularities, which depend on scaling laws for the image size and the pulse broadening. Future low-frequency (< 100 MHz) array observations will also be strongly affected by the Galactic structure of scattering material. Our formalism is derived in the context of radio scattering by plasma density fluctuations. It is also applicable to optical, UV and X-ray scattering by grains in the interstellar medium.Comment: 21 pages, LaTeX2e with AASTeX-4.0, 6 PostScript figures, accepted by ApJ, revised version has minor changes to respond to referee comments and suggestion

Perceived vocal morbidity in a problem asthma clinic

&lt;p&gt;Aims: Asthma treatment has the potential to affect patients' voices. We undertook detailed characterisation of voice morbidity in patients attending a problem asthma clinic, and we determined how patients' perceptions related to objective assessment by an experienced observer.&lt;/p&gt; &lt;p&gt;Methods: Forty-three patients took part in the study. Subjects completed the self-administered voice symptom score (VoiSS) questionnaire and underwent digital voice recording. These voice recordings were scored using the grade–roughness–breathiness–asthenicity–strain system (GRBAS). Laryngoscopy was also performed.&lt;/p&gt; &lt;p&gt;Results: The median VoiSS was 26 (range three to 83). VoiSS were significantly lower in the 17 patients with normal laryngeal structure and function (range four to 46; median 22), compared with the 26 patients with functional or structural laryngeal abnormality (range three to 83; median 33) (95 per cent confidence intervals for difference 0.0–21.0; p = 0.044). The overall grade score for the GRBAS scale did not differ between these two groups, and only 13 patients had a GRBAS score of one or more, recognised as indicating a voice problem. There were positive correlations between related GRBAS score and voice symptom score subscales. Although voice symptom scores were significantly more abnormal in patients with structural and functional abnormalities, this score performed only moderately well as a predictive tool (sensitivity 54 per cent; specificity 71 per cent). Nevertheless, the voice symptom score performed as well as the more labour-intensive GRBAS score (sensitivity 57 per cent; specificity 60 per cent). Patients' inhaled corticosteroid dose (median dose 1000 µg beclomethasone dipropionate or equivalent) had a statistically significant relationship with their overall grade score for the GRBAS scale (r = 0.56; p &#60; 0.001), but not with their VoiSS. Only one patient had evidence of laryngeal candidiasis, and only two had any evidence of abnormality suggesting steroid-induced myopathy.&lt;/p&gt; &lt;p&gt;Conclusions: Vocal morbidity is common in patients with asthma, and should not be immediately attributed to steroid-related candidiasis. The VoiSS merits further, prospective validation as a screening tool for ENT and/or speech and language therapy referral in patients with asthma.&lt;/p&gt

Spectroscopic applications and frequency locking of THz photomixing with distributed-Bragg-reflector diode lasers in low-temperature-grown GaAs

A compact, narrow-linewidth, tunable source of THz radiation has been developed for spectroscopy and other high-resolution applications. Distributed-Bragg-reflector (DBR) diode lasers at 850 nm are used to pump a low-temperature-grown GaAs photomixer. Resonant optical feedback is employed to stabilize the center frequencies and narrow the linewidths of the DBR lasers. The heterodyne linewidth full-width at half-maximum of two optically locked DBR lasers is 50 kHz on the 20 ms time scale and 2 MHz over 10 s; free-running DBR lasers have linewidths of 40 and 90 MHz on such time scales. This instrument has been used to obtain rotational spectra of acetonitrile (CH3CN) at 313 GHz. Detection limits of 1 × 10^–4 Hz^1/2 (noise/total power) have been achieved, with the noise floor dominated by the detector's noise equivalent power

Generational Equity, Generational Interdependence, and the Framing of the Debate Over Social Security Reform

This article analyzes the differences between the generational equity and generational interdependence conceptual packages used to frame arguments in the debate over policies such as Social Security reform. It begins with a history of the generational equity debate. This is followed by an analysis of the assumptions, values, and beliefs that inform each of these two ideological frames. It presents an analysis of why the generational equity frame has dominated the debate and highlights some of the limitations of this perspective

Estimating Small Area Income Deprivation: An Iterative Proportional Fitting Approach

Small area estimation and in particular the estimation of small area income deprivation has potential value in the development of new or alternative components of multiple deprivation indices. These new approaches enable the development of income distribution threshold based as opposed to benefit count based measures of income deprivation and so enable the alignment of regional and national measures such as the Households Below Average Income with small area measures. This paper briefly reviews a number of approaches to small area estimation before describing in some detail an iterative proportional fitting based spatial microsimulation approach. This approach is then applied to the estimation of small area HBAI rates at the small area level in Wales in 2003-5. The paper discusses the results of this approach, contrasts them with contemporary ‘official’ income deprivation measures for the same areas and describes a range of ways to assess the robustness of the results

What's the point of knowing how?

Why is it useful to talk and think about knowledge-how? Using Edward Craig’s discussion of the function of the concepts of knowledge and knowledge-how as a jumping off point, this paper argues that considering this question can offer us new angles on the debate about knowledge-how. We consider two candidate functions for the concept of knowledge-how: pooling capacities, and mutual reliance. Craig makes the case for pooling capacities, which connects knowledge-how to our need to pool practical capacities. I argue that the evidence is much more equivocal. My suggested diagnosis is that the concept of knowledge-how plays both functions, meaning that the concept of knowledge-how is inconsistent, and that the debate about knowledge-how is at least partly a metalinguistic negotiation. In closing, I suggest a way to revise the philosophical concept of knowledge how