Reliability and surface degradation aspects of synthetic insulator materials for HV application

This study is a theoretical and experimental investigation on the state of the art of synthetic insulators for outdoor high voltage transmission systems. The surface of a polymeric material is known to be degraded by, among other things, environmental stresses such as UV, air pollutants, etc. The reliability of an insulator material is governed by the surface and other characteristics that do not drift much as a function of stresses and time. The surface characteristics of various synthetic materials, when these materials were exposed to UV radiation in the laboratory were studied. The changes in the surface properties of these materials were observed by measuring the electrical noise generated on the surface as a result of applied electric field, the hydrophilicity of the surface (θH2O) and the leakage current developed on application of electric stress before and after UV aging. UV aging decreases θH2O. The amount of change in the wettability of a particular specimen due to UV aging was related to the amount of change in the leakage current of the specimen and the amount of change in the surface noise generated on the specimen. Increase in hydrophilicity increases the surface noise and the leakage current, thereby degrading its effectiveness as an insulator. Experiments were done to investigate the effects of exposing a typical polymer insulator made of R.B.G.F. core covered with silicone elastomer to polluting gases like NO2, SO2, H2S, and CL2, UV, and polluting gases plus UV. From the data obtained on the accelerated life tests, the life of the material in normal usage was extrapolated as a function of the above stresses using a modified Arrhenius equation. Suggestions are given for further research on the studies of insulator surfaces in new as well as degraded conditions

A Spitzer Spectroscopic Survey of Low Ionization Nuclear Emission-line Regions: Characterization of the Central Source

We have conducted a comprehensive mid-IR spectroscopic investigation of 67 Low Ionization Nuclear Emission Line Regions (LINERs) using archival observations from the high resolution modules of the Infrared Spectrograph on board the Spitzer Space Telescope. Using the [NeV] 14 and 24um lines as active galactic nuclei (AGN) diagnostics, we detect active black holes in 39% of the galaxies in our sample, many of which show no signs of activity in either the optical or X-ray bands. In particular, a detailed comparison of multi-wavelength diagnostics shows that optical studies fail to detect AGN in galaxies with large far-IR luminosities. These observations emphasize that the nuclear power source in a large percentage of LINERs is obscured in the optical. Indeed, the majority of LINERs show mid-IR [NeV]14/[NeV]24um flux ratios well below the theoretical low-density limit, suggesting that there is substantial extinction toward even the [NeV]-emitting region . Combining optical, X-ray, and mid-IR diagnostics, we find an AGN detection rate in LINERs of 74%, higher than previously reported statistics of the fraction of LINERs hosting AGN. The [NeV]24um /[OIV]26um mid-IR line flux ratio in "AGN-LINERs" is similar to that of standard AGN, suggesting that the spectral energy distribution (SED) of the intrinsic optical/UV continuum is similar in the two. This result is in contrast to previous suggestions of a UV deficit in the intrinsic broadband continuum emission in AGN-LINERs. Consistent with our finding of extinction to the [NeV]-emitting region, we propose that extinction may also be responsible for the observed optical/UV deficit seen in at least some AGN-LINERs.Comment: Accepted for publication in Ap

Origin of the subscapular artery in the South African Black population

There is great variability in the branching patterns of the axillary artery (AA). Racial differences have been reported to play a role in this variability. The subscapular artery (SA) is the largest and most variable branch of the AA. It usually arises from the third part of the AA at the inferior border of the subscapularis muscle. Approximately 4 cm from its origin, the SA divides into the circumflex scapular and thoracodorsal arteries. Two types of the SA have been described, depending on the site of its origin from the AA in relation to the point where the AA passes between the lateral and medial roots of the median nerve. It is referred to as the superficial SA (SSA), when proximal, and the deep SA (DSA), when distal to this point, respectively. This study aimed to determine the site and distance of origin of the SA from the outer border of the first rib in the South African Black population. The study comprised bilateral gross anatomical dissections of 50 adult Black South African cadavers (n = 100 AAs). The site and distance of origin of each vessel from the outer border of the first rib were recorded. Additional branches and variations were also noted. The SSA and DSA were found in 52.8% and 47.2% of cases, respectively. In 16.8% of cases, the SA gave rise to the posterior circumflex humeral artery and the lateral thoracic artery in 33.7% cases. The SA was absent in 11% of the cases. The prevalence of the SSA reported in this study differs from values ranging between 1.7% and 16% reported in the literature. The high incidence of the SSA in this study may have clinical significance as a superficial course of the arteries make them vulnerable to injury during surgical procedures

Reflective journals: unmasking student perceptions of anatomical education

Background: In medical education, reflection has been considered to be a core skill in professional competence. The anatomy laboratory is an ideal setting for faculty/ student interaction and provides invaluable opportunities for active learning and reflection on anatomical knowledge. Materials and methods: This study was designed to record student attitudes regarding human cadaveric dissection, explore their experiences of anatomy through an analysis of their journal-reflective writings and determine whether this type of creative writing had a beneficial effect on those students who chose to complete them. A total of 75 journals from Medical and Allied Health Science students were collected and analysed. Results: Results were categorised according to the following themes: (i) Dissecting room stressors (27.6%); (ii) Educational value of dissection (26.3%); (iii) Appreciation, Gratitude, Respect and Curiosity for the cadaver (18.9%); (iv) Positive and negative sentiments expressed in the dissecting room (25.8%); (v) Benefit of alternate teaching modalities (4.6%); (vi) Spirituality/Religious Beliefs (3.7%); (vii) Shared humanity and emotional bonds (3.69%); (viii) Acknowledgement of human anatomical variations (3.2%); (ix) Beauty and complexity of the human body (1.8%) and (x) Psychological detachment (0.9%). Students appreciated the opportunity to share their emotions and reflect on the humanistic dimension of anatomy as a subject. Student reflections illustrated clearly their thoughts and some of the difficult issues with which they wrestled. Conclusions: The anatomy laboratory is seen as the budding clinician’s first encounter with a patient, albeit a cadaver. This was the first time that reflective journals were given to students in the discipline. Reflective journals allow students to express themselves in an open-ended and creative fashion. It also assists students to integrate anatomy and clinical medicine and assists in applying their basic anatomical knowledge in an authentic, yet safe environmen