Applications of the magneto-optical filter to stellar pulsation measurements

A proposed method of employing the Cacciani magneto-optical filter (MOF) for stellar seismology studies is described. The method relies on the fact that the separation of the filter bandpasses in the MOF can be changed by varying the level of input power to the filter cells. With the use of a simple servosystem the bandpass of a MOF can be tuned to compensate for the changes in the radial velocity of a star introduced by the orbital motion of the Earth. Such a tuned filter can then be used to record intensity fluctuations through the MOF bandpass over an extended period of time for each given star. Also, the use of a two cell version of the MOF makes it possible to alternately chop between the bandpass located in the stellar line wing and a second bandpass located in the stellar continuum. Rapid interchange between the two channels makes it possible for atmospheric-introduced noise to be removed from the time series

The 1984 solar oscillation program of the Mount Wilson 60-foot tower

The instrumentation, data, and preliminary results from the summer, 1984, solar oscillation observing program which was carried out using the 60-foot tower telescope of the Mt. Wilson Observatory are described. This program was carried out with a dedicated solar oscillation observing system and obtained full-disk Dopplergrams every 40 seconds for up to 11 hours per day. Between June and September, 1984, observations were obtained with a Na magneto-optical filter on 90 different days. The data analysis has progressed to the point that spherical harmonic filter functions were employed to generate a few one-dimensional power spectra from a single day's observations

The analysis of solar models: Neutrinos and oscillations

Tests of solar neutrino flux and solar oscillation frequencies were used to assess standard stellar structure theory. Standard and non-standard solar models are enumerated and discussed. The field of solar seismology, wherein the solar interior is studied from the measurement of solar oscillations, is introduced

Hi-C and AIA observations of transverse magnetohydrodynamic waves in active regions

The recent launch of the High resolution Coronal imager (Hi-C) provided a unique opportunity of studying the EUV corona with unprecedented spatial resolution. We utilize these observations to investigate the properties of low-frequency (50−200 s) active region transverse waves, whose omnipresence had been suggested previously. The five-fold improvement in spatial resolution over SDO/AIA reveals coronal loops with widths 150−310 km and that these loops support transverse waves with displacement amplitudes <50 km. However, the results suggest that wave activity in the coronal loops is of low energy, with typical velocity amplitudes <3 km s-1. An extended time-series of SDO data suggests that low-energy wave behaviour is typical of the coronal structures both before and after the Hi-C observations

Anatomical variations of knee ligaments in magnetic resonance imaging: pictorial essay

Evaluation with magnetic resonance imaging (MRI) is currently a gold standard for comprehensive posttraumatic assessment of the knee joint. Increasing availability of MR systems with stronger magnetic fields and new sequences results in higher resolution of images and thus allows imaging smaller and finer anatomical details, including different anatomical variations. This article focuses on anatomical variations of knee ligaments, which can mimics pathological structures. Well-known and less common ligaments that are sporadically observed and may raise the most doubt will be discussed. Familiarity with those variations of ligaments is indispensable for precise MRI reporting to avoid misinterpretation as meniscal tears, loose bodies or mass lesions especially in cases. This paper is addressed to both radiology and orthopaedics specialists. Illustrations show discussed ligaments in standard planes while, for less known ligaments, we add information on how to adjust planes to properly visualise a particular structure, which will hopefully facilitate finding and differentiating those structures in clinical practice

Detection of root canals in historical population from Radom (Poland)

Background: The aim of this study was to analyse the number of root canals in maxillary first premolars, first molars and mandibular first molar teeth from an 18th to 19th century Radom (Poland) population, and then assess whether the diversity of root canals has fluctuated for about two hundred years. Materials and methods: A total of 139 human permanent teeth were analysed by cone beam computed tomography in three projections. The types of root canal systems were classified in each tooth root separately. Results: In one-rooted maxillary premolars, two canals occurred most often (53%). In two-rooted majority buccal (91%) and every palatal roots there is one canal. All three-rooted maxillary premolars have one root canal. In two-rooted first maxillary molars, fused roots have two canals. All mesiobuccal roots presented type 2-1 canal configurations. In three-rooted maxillary first molars in the mesiobuccal roots the most common root canal type is 2-1 (72%). A second mesiobuccal canal occurred in 86%. The distobuccal and palatal roots presented one canal in all cases. First mandibular molars occurred in two-rooted form in 98%. In mesial roots, two root canals predominated (59%). Most distal root (66%) had one canal. In three-rooted teeth one root canal was the most frequent finding. Conclusions: Knowledge about the variation in root canals is important in studies of past populations. This evidence may be important in relation to assessing the variability of human populations. The analysis carried out show the cohesion between the historical population of Radom and other groups from modern Poland

Coronal loop widths and pressure scale heights

The scale heights of stratification and the widths of steady solar coronal loops exhibit properties unexplained by standard theory: observed scale heights are often much greater than static theory predicts, while the nearly-constant widths of loop emission signatures defy theoretical expectations for large flux tubes in stratified media. In this work we relate the cross-sectional profile of a coronal flux tube to its density scale height in steady-state plasma flow regimes. Steady flows may shorten or lengthen the scale height according to how the tube cross-sectional area varies with arclength. In a near-potential corona the flux tubes are expected to be sufficiently expansive in many active regions for scale heights to be increased by steady flows. On the other hand, cases where scale lengths are actually increased to observed sizes form a small part of the solution space, close to regimes where density profiles reverse. Therefore, although steady flows are the only steady process known to be capable of extending scale heights significantly, they are not expected to be not responsible for the majority of extended active region scale heights

Analysis of the solar cycle and core rotation using 15 years of Mark-I observations:1984-1999. I. The solar cycle

High quality observations of the low-degree acoustic modes (p-modes) exist for almost two complete solar cycles using the solar spectrophotometer Mark-I, located at the Observatorio del Teide (Tenerife, Spain) and operating now as part of the Birmingham Solar Oscillations Network (BiSON). We have performed a Fourier analysis of 30 calibrated time-series of one year duration covering a total period of 15 years between 1984 and 1999. Applying different techniques to the resulting power spectra, we study the signature of the solar activity changes on the low-degree p-modes. We show that the variation of the central frequencies and the total velocity power (TVP) changes. A new method of simultaneous fit is developed and a special effort has been made to study the frequency-dependence of the frequency shift. The results confirm a variation of the central frequencies of acoustic modes of about 450 nHz, peak-to-peak, on average for low degree modes between 2.5 and 3.7 mHz. The TVP is anti-correlated with the common activity indices with a decrease of about 20% between the minimum and the maximum of solar cycle 22. The results are compared with those obtained for intermediate degrees, using the LOWL data. The frequency shift is found to increase with the degree with a weak l-dependence similar to that of the inverse mode mass. This verifies earlier suggestions that near surface effects are predominant.Comment: Accepted by A&A October 3 200

Non-axisymmetric oscillations of stratified coronal magnetic loops with elliptical cross-sections

We study non-axisymmetric oscillations of a straight magnetic tube with an elliptic cross-section and density varying along the tube. The governing equations for kink and fluting modes in the thin tube approximation are derived. We found that there are two kink modes, polarised along the large and small axes of the elliptic cross-section. We have shown that the ratio of frequencies of the first overtone and fundamental harmonic is the same for both kink modes and independent of the ratio of the ellipse axes. On the basis of this result we concluded that the estimates of the atmospheric scale height obtained using simultaneous observations of the fundamental harmonic and first overtone of the coronal loop kink oscillations are independent of the ellipticity of the loop cross-section