Model fitting of kink waves in the solar atmosphere: Gaussian damping and time-dependence

{Observations of the solar atmosphere have shown that magnetohydrodynamic waves are ubiquitous throughout. Improvements in instrumentation and the techniques used for measurement of the waves now enables subtleties of competing theoretical models to be compared with the observed waves behaviour. Some studies have already begun to undertake this process. However, the techniques employed for model comparison have generally been unsuitable and can lead to erroneous conclusions about the best model. The aim here is to introduce some robust statistical techniques for model comparison to the solar waves community, drawing on the experiences from other areas of astrophysics. In the process, we also aim to investigate the physics of coronal loop oscillations. } {The methodology exploits least-squares fitting to compare models to observational data. We demonstrate that the residuals between the model and observations contain significant information about the ability for the model to describe the observations, and show how they can be assessed using various statistical tests. In particular we discuss the Kolmogorov-Smirnoff one and two sample tests, as well as the runs test. We also highlight the importance of including any observational trend line in the model-fitting process.} {To demonstrate the methodology, an observation of an oscillating coronal loop undergoing standing kink motion is used. The model comparison techniques provide evidence that a Gaussian damping profile provides a better description of the observed wave attenuation than the often used exponential profile. This supports previous analysis from Pascoe et al. (2016). Further, we use the model comparison to provide evidence of time-dependent wave properties of a kink oscillation, attributing the behaviour to the thermodynamic evolution of the local plasma.}Comment: Accepted in Astronomy & Astrophysics http://dx.doi.org/10.1051/0004-6361/20162861

The Homflypt skein module of a connected sum of 3-manifolds

If M is an oriented 3-manifold, let S(M) denote the Homflypt skein module of M. We show that S(M_1 connect sum M_2) is isomorphic to S(M_1) tensor S(M_2) modulo torsion. In fact, we show that S(M_1 connect sum M_2) is isomorphic to S(M_1) tensot S(M_2) if we are working over a certain localized ring. We show the similar result holds for relative skein modules. If M contains a separating 2-sphere, we give conditions under which certain relative skein modules of M vanish over specified localized rings.Comment: Published by Algebraic and Geometric Topology at http://www.maths.warwick.ac.uk/agt/AGTVol1/agt-1-31.abs.htm

Believing in Others

Suppose some person 'A' sets out to accomplish a difficult, long-term goal such as writing a passable Ph.D. thesis. What should you believe about whether A will succeed? The default answer is that you should believe whatever the total accessible evidence concerning A's abilities, circumstances, capacity for self-discipline, and so forth supports. But could it be that what you should believe depends in part on the relationship you have with A? We argue that it does, in the case where A is yourself. The capacity for "grit" involves a kind of epistemic resilience in the face of evidence suggesting that one might fail, and this makes it rational to respond to the relevant evidence differently when you are the agent in question. We then explore whether similar arguments extend to the case of "believing in" our significant others -- our friends, lovers, family members, colleagues, patients, and students

Occasional Publications on Northern Life, No. 04

The need to exchange information on research in reindeer and caribou diseases became apparent to investigators attending the Second International Reindeer/Caribou Symposium in Roros, Norway, in 1979. Initially, bibliographies were to be exchanged by being submitted to and subsequently distributed by workers at the University of Alaska. When the bibliographies were submitted, it seemed sensible to computerize the lists to facilitate searches for specific information in the future. An apparently simple task became amazingly complex. This is the resultant collection of publications by reindeer/caribou disease researchers. Because researchers in wildlife diseases tend to work on more than one species or topic, out of interest or necessity, a decision was made to include all of a person's references rather than to limit them to strictly reindeer/caribou diseases. The authors hope this will provide a good basis for exchange of information among all those interested in reindeer/caribou diseases

Dynamics of internetwork chromospheric fibrils: Basic properties and MHD kink waves

Using the spectroscopic imaging capabilities of the Swedish Solar Telescope, we aim to provide the first investigation on the nature and dynamics of elongated absorption features (fibrils) observed in H$\alpha$ in the internetwork. We observe and identify a number of internetwork fibrils, which form away from the kilogauss, network magnetic flux, and we provide a synoptic view on their behaviour. The internetwork fibrils are found to support wave-like behaviour, which we interpret as Magnetohydrodynamic (MHD) kink waves. The properties of these waves, that is, amplitude, period, and propagation speed, are measured from time-distance diagrams and we attempt to exploit them via magneto-seismology in order to probe the variation of plasma properties along the wave-guides. We found that the Internetwork (IN) fibrils appear, disappear, and re-appear on timescales of tens of minutes, suggesting that they are subject to repeated heating. No clear photospheric footpoints for the fibrils are found in photospheric magnetograms or H$\alpha$ wing images. However, we suggest that they are magnetised features as the majority of them show evidence of supporting propagating MHD kink waves, with a modal period of $120$~s. Additionally, one IN fibril is seen to support a flow directed along its elongated axis, suggesting a guiding field. The wave motions are found to propagate at speeds significantly greater than estimates for typical chromospheric sound speeds. Through their interpretation as kink waves, the measured speeds provide an estimate for local average Alfv\'en speeds. Furthermore, the amplitudes of the waves are also found to vary as a function of distance along the fibrils, which can be interpreted as evidence of stratification of the plasma in the neighbourhood of the IN fibril.Comment: Accepted Astronomy & Astrophysic

Pittsburgh's Failed Industry Targeting Strategy of the 1960s

In the 1960's and early 1970's, public and private leaders made a substantial effort to promote Pittsburgh's existing transportation industry as a center for the emerging urban transportation market. The selection of the rapid transit industry for targeting in the 1960's purportedly addressed two issues. Despite national acclaim for its Renaissance redevelopment since World War II, the metropolitan region still needed an effective mass transportation system. Moreover, industrial development efforts had not substantially diversified the region's manufacturing base that still specialized in primary metals. Operating in the region's Renaissance tradition of a public and private partnership, corporate executives and public officials pursued a three-pronged strategy: build an innovative rapid transportation system for Allegheny County, use it as a showcase for testing and marketing rapid transit hardware of regional corporations, and promote the city as a center of the rapid transportation industry. They settled on Westinghouse's automated, rubber-tired vehicle running on a separate cement guideway, known locally as "Skybus," for the demonstration project and the region's mass transit solution. The mass transit plan and industry targeting strategy foundered by the early 1970's because leadership weakened in both poles of the partnership. The Westinghouse technology divided the corporate community, while populist political sentiment diminished the ability of the Democratic party's political machine to deliver key public decisions. The Pittsburgh case suggests that a successful industry targeting strategy may depend more on effective leadership and local politics than on the quality of the selection process and vigorous pursuit of traditional economic development programs in support of the targeted industry

Coercivity for One-dimensional Cell Vertex Approximations

Previous error analysis for the cell vertex scheme has been limited to situations where the cell residuals can be set to zero. However, in practical use for compressible flow computations it is necessary to extend the method by the use of distribution matrices and the careful addition of artificial viscosity terms. In this paper we make a start on the error analysis that is required for this more general method. The chosen example is a one-dimensional convection-diffusion problem with an expansion critical or turning point

Urinary felinine excretion in intact male cats is increased by dietary cystine

Felinine is a branched-chain sulfur amino acid present in the urine of certain Felidae, including domestic cats. The objective of the present study was to determine if additional cystine and/or dietary N would increase felinine and N-acetylfelinine excretion by intact male cats fed a low-protein (LP) diet. Feeding five adult intact male cats an LP diet (18·8% of metabolisable energy (ME) as protein) v. a high-protein diet (38·6% of ME as protein) resulted in a trend (P¼0·08) for decreased urinary felinine and no change in N-acetylfelinine excretion. In a 23 d study, when the LP diet was supplemented with L-cystine at 9·3 g/kg DM, urinary felinine:creatinine ratio showed a linear two-fold (121 %) increase (P,0·01) from 0·24 (SEM 0·05) to 0·53 (SEM 0·13) after 10 d. Subsequent feeding of the LP diet resulted in a decrease in felinine excretion to base levels. Plasma gglutamylfelinylglycine concentrations were consistent with the excretion of felinine. Supplementation of the LP diet with L-cystine (9·3 g/kg DM), dispensable amino acids and arginine to a second group (n 5) also resulted in a significant (P,0·01) but smaller (þ72 %) increase in the daily felinine:creatinine ratio (0·25 (SEM 0·04) to 0·43 (SEM 0·05)). The degree of felinine N-acetylation within groups was unaffected by dietary addition and withdrawal of amino acids. The results indicate that felinine synthesis is regulated by cystine availability, and that arginine may be physiologically important in decreasing felinine biosynthesis in intact male cats