Finite Element Model study of the Effect of Corner Rounding on Detectability of Corner Cracks using Bolt-Hole Eddy Current

Recent work has shown that the detectability of corner cracks in bolt-holes is compromised when rounding of corners arises, as might occur during bolt-hole removal. Probability of Detection (POD) studies normally require a large number of samples of both fatigue cracks and electric discharge machined notches. In the particular instance of rounding of bolt-hole corners, the generation of such a large set of samples representing the full spectrum of potential rounding would be prohibitive. In this paper, the application of Finite Element Method (FEM) modeling is used to supplement the study of detection of cracks forming at the rounded corners of bolt-holes. FEM models show that rounding of the corner of the bolt-hole reduces the size of the response to a corner crack to a greater extent than can be accounted for by loss of crack area. This reduced sensitivity can be ascribed to a lower concentration of eddy currents at the rounded corner surface and greater lift-off of pick-up coils relative to that of a straight-edge corner. A rounding with a radius of 0.4 mm (.016 inch) showed a 20% reduction in the strength of the crack signal. Assuming linearity of the crack signal with crack size, this would suggest an increase in the minimum detectable size by 25%. Modeling results are consistent with measurements performed on cracks grown on bolt-hole samples extracted from service

Evaluation of Machine Learning Tools for Inspection of Steam Generator Tube Structures using Pulsed Eddy Current

Inspection of multi-component systems, such as nuclear steam generator (SG) tube support structures, is complicated by multiple overlapping degradation modes. The simultaneous and precise measurement of more than two interdependent parameters is challenging when standard statistical regression analysis tools are used. Artificial neural networks (ANNs) have recently been applied to pulsed eddy current (PEC) data for inspection of Alloy 800 SG tube fretting, in the presence of tube off-set within a corroded ferromagnetic support structure. Signals were analyzed using modified principal component analysis (MPCA) followed by an ANN analysis, which simultaneously targeted four parameters associated with the support structure. These were hole diameter, tube off-centering in two mutually orthogonal directions and fret depth. In this work, the ANN analysis is compared with that performed by a Support Vector Machine (SVM) analysis of the same data. Comparable results are achieved for some parameters with both machine learning analysis tools. However, parameters with changing signal variance, such as those associated with support structure diameter, are not as easily compensated for using standard SVM analysis. Both techniques also rely on the availability of a representative training data set that may be difficult to come by for general inspection conditions

Impact of flipper-banding on breeding success of African penguins Spheniscus demersus at Robben Island: comparisons among silicone rubber bands, stainless-steel bands and no bands

From 2001 to 2006, two new designs of flipper bands made from silicone rubbers were tested on African penguins Spheniscus demersus at 365 nests on Robben Island, South Africa. We compared, over six years, the breeding success, from hatching to fledging, of three different groups of penguins: those with rubber bands (117 nests), with conventional stainless-steel bands (103 nests) and without bands (145 nests). There were no significant differences in breeding success between the three groups, suggesting that neither the currently used steel bands, nor either of the new rubber-band designs, were harmful during the seasons investigated. The rubber bands caused less wear of feathers and less drag on a model penguin than the steel bands. In captivity, the behaviours of African penguins fitted with rubber bands were not noticeably different to those of unbanded birds

Estimating Be Star Disk Radii using H-alpha Emission Equivalent Widths

We present numerical models of the circumstellar disks of Be stars, and we describe the resulting synthetic H-alpha emission lines and maps of the wavelength-integrated emission flux projected onto the sky. We demonstrate that there are monotonic relationships between the emission line equivalent width and the ratio of the angular half-width at half maximum of the projected disk major axis to the radius of the star. These relationships depend mainly upon the temperatures of the disk and star, the inclination of the disk normal to the line of sight, and the adopted outer boundary for the disk radius. We show that the predicted H-alpha disk radii are consistent with those observed directly through long baseline interferometry of nearby Be stars (especially once allowance is made for disk truncation in binaries and for dilution of the observed H-alpha equivalent width by continuum disk flux in the V-band).Comment: 12 pages, 2 figures, ApJL in pres

Determining the Physical Properties of the B Stars I. Methodology and First Results

We describe a new approach to fitting the UV-to-optical spectra of B stars to model atmospheres and present initial results. Using a sample of lightly reddened stars, we demonstrate that the Kurucz model atmospheres can produce excellent fits to either combined low dispersion IUE and optical photometry or HST FOS spectrophotometry, as long as the following conditions are fulfilled: 1) an extended grid of Kurucz models is employed, 2) the IUE NEWSIPS data are placed on the FOS absolute flux system using the Massa & Fitzpatrick (1999) transformation, and 3) all of the model parameters and the effects of interstellar extinction are solved for simultaneously. When these steps are taken, the temperatures, gravities, abundances and microturbulence velocities of lightly reddened B0-A0 V stars are determined to high precision. We also demonstrate that the same procedure can be used to fit the energy distributions of stars which are reddened by any UV extinction curve which can be expressed by the Fitzpatrick & Massa (1990) parameterization scheme. We present an initial set of results and verify our approach through comparisons with angular diameter measurements and the parameters derived for an eclipsing B star binary. We demonstrate that the metallicity derived from the ATLAS 9 fits to main sequence B stars is essentially the Fe abundance. We find that a near zero microturbulence velocity provides the best-fit to all but the hottest or most luminous stars (where it may become a surrogate for atmospheric expansion), and that the use of white dwarfs to calibrate UV spectrophotometry is valid.Comment: 17 pages, including 2 pages of Tables and 6 pages of Figures. Astrophysical Jounral, in pres

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Diagnosis and Management in Young People: A Primer

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex disease that affects children and adolescents as well as adults. The etiology has not been established. While many pediatricians and other health-care providers are aware of ME/CFS, they often lack essential knowledge that is necessary for diagnosis and treatment. Many young patients experience symptoms for years before receiving a diagnosis. This primer, written by the International Writing Group for Pediatric ME/CFS, provides information necessary to understand, diagnose, and manage the symptoms of ME/CFS in children and adolescents. ME/CFS is characterized by overwhelming fatigue with a substantial loss of physical and mental stamina. Cardinal features are malaise and a worsening of symptoms following minimal physical or mental exertion. These post-exertional symptoms can persist for hours, days, or weeks and are not relieved by rest or sleep. Other symptoms include cognitive problems, unrefreshing or disturbed sleep, generalized or localized pain, lightheadedness, and additional symptoms in multiple organ systems. While some young patients can attend school, on a full or part-time basis, many others are wheelchair dependent, housebound, or bedbound. Prevalence estimates for pediatric ME/CFS vary from 0.1 to 0.5%. Because there is no diagnostic test for ME/CFS, diagnosis is purely clinical, based on the history and the exclusion of other fatiguing illnesses by physical examination and medical testing. Co-existing medical conditions including orthostatic intolerance (OI) are common. Successful management is based on determining the optimum balance of rest and activity to help prevent post-exertional symptom worsening. Medications are helpful to treat pain, insomnia, OI and other symptoms. The published literature on ME/CFS and specifically that describing the diagnosis and management of pediatric ME/CFS is very limited. Where published studies are lacking, recommendations are based on the clinical observations and practices of the authors

COUNTS OF SURFACE-NESTING SEABIRDS BREEDING AT PRINCE EDWARD ISLAND, SUMMER 2001/02

The first midsummer survey of surface-nesting seabirds at Prince Edward Island was conducted during December 2001. It was also the first census for most species since the early 1980s. Despite concerns about the impacts of longline fishing mortality on various albatrosses and giant petrels, there was no evidence that populations of these species had decreased. Indeed, the estimate of wandering albatrosses Diomedea exulans (Vulnerable) has increased significantly, making Prince Edward Island equal with Marion Island as supporting the largest single-island populations of this species. Species that underwent significant decreases were macaroni penguins Eudyptes chrysolophus (Vulnerable), Crozet shags Phalacrocorax [atriceps] melanogenis and Kerguelen terns Sterna virgata (Near-Threatened). The reasons for these decreases are unclear, but for macaroni penguins may be partly a consequence of competition for space with the burgeoning population of fur seals Arctocephalus spp. The 2001 survey increased the population estimates for Subantarctic skuas Catharacta antarctica, lightmantled sooty albatrosses Phoebetria palpebrata (Vulnerable) and southern giant petrels Macronectes giganteus (Vulnerable), mostly as a result of greater coverage than for previous counts. The 2001 survey confirms that Prince Edward Island remains a globally important breeding site for seabirds.Afr. J. mar. Sci. 25: 441–45

Cygnus X-3 with ISO: investigating the wind

We observed the energetic binary Cygnus X-3 in both quiescent and flaring states between 4 and 16 microns using the ISO satellite. We find that the quiescent source shows the thermal free-free spectrum typical of a hot, fast stellar wind, such as from a massive helium star. The quiescent mass-loss rate due to a spherically symmetric, non-accelerating wind is found to be in the range 0.4-2.9 x 10E-4 solar masses per year, consistent with other infrared and radio observations, but considerably larger than the 10E-5 solar masses per year deduced from both the orbital change and the X-ray column density. There is rapid, large amplitude flaring at 4.5 and 11.5 microns at the same time as enhanced radio and X-ray activity, with the infrared spectrum apparently becoming flatter in the flaring state. We believe non-thermal processes are operating, perhaps along with enhanced thermal emission.Comment: Accepted for publication in MNRAS, 11 pages, 6 figure

Ancient Migratory Events in the Middle East: New Clues from the Y-Chromosome Variation of Modern Iranians

Knowledge of high resolution Y-chromosome haplogroup diversification within Iran provides important geographic context regarding the spread and compartmentalization of male lineages in the Middle East and southwestern Asia. At present, the Iranian population is characterized by an extraordinary mix of different ethnic groups speaking a variety of Indo-Iranian, Semitic and Turkic languages. Despite these features, only few studies have investigated the multiethnic components of the Iranian gene pool. In this survey 938 Iranian male DNAs belonging to 15 ethnic groups from 14 Iranian provinces were analyzed for 84 Y-chromosome biallelic markers and 10 STRs. The results show an autochthonous but non-homogeneous ancient background mainly composed by J2a sub-clades with different external contributions. The phylogeography of the main haplogroups allowed identifying post-glacial and Neolithic expansions toward western Eurasia but also recent movements towards the Iranian region from western Eurasia (R1b-L23), Central Asia (Q-M25), Asia Minor (J2a-M92) and southern Mesopotamia (J1-Page08). In spite of the presence of important geographic barriers (Zagros and Alborz mountain ranges, and the Dasht-e Kavir and Dash-e Lut deserts) which may have limited gene flow, AMOVA analysis revealed that language, in addition to geography, has played an important role in shaping the nowadays Iranian gene pool. Overall, this study provides a portrait of the Y-chromosomal variation in Iran, useful for depicting a more comprehensive history of the peoples of this area as well as for reconstructing ancient migration routes. In addition, our results evidence the important role of the Iranian plateau as source and recipient of gene flow between culturally and genetically distinct population

Parenting in a warming world: thermoregulatory responses to heat stress in an endangered seabird

This is the final version. Available on open access from Oxford University Press via the DOI in this recordThe frequency of extreme weather events, including heat waves, is increasing with climate change. The thermoregulatory demands resulting from hotter weather can have catastrophic impacts on animals, leading to mass mortalities. Although less dramatic, animals also experience physiological costs below, but approaching, critical temperature thresholds. These costs may be particularly constraining during reproduction, when parents must balance thermoregulation against breeding activities. Such challenges should be acute among seabirds, which often nest in locations exposed to high solar radiation and predation risk. The globally endangered bank cormorant Phalacrocorax neglectus breeds in southern Africa in the winter, giving little scope for poleward or phenological shifts in the face of increasing temperatures. Physiological studies of endangered species sensitive to human disturbance, like the bank cormorant, are challenging, because individuals cannot be captured for experimental research. Using a novel, non-invasive, videographic approach, we investigated the thermoregulatory responses of this seabird across a range of environmental temperatures at three nesting colonies. The time birds spent gular fluttering, a behaviour enhancing evaporative heat loss, increased with temperature. Crouching or standing birds spent considerably less time gular fluttering than birds sitting on nests (ca 30% less at 22°C), showing that postural adjustments mediate exposure to heat stress and enhance water conservation. Crouching or standing, however, increases the vulnerability of eggs and chicks to suboptimal temperatures and/or expose nest contents to predation, suggesting that parents may trade-off thermoregulatory demands against offspring survival. We modelled thermoregulatory responses under future climate scenarios and found that nest-bound bank cormorants will gular flutter almost continuously for several hours a day by 2100. The associated increase in water loss may lead to dehydration, forcing birds to prioritize survival over breeding, a trade-off that would ultimately deteriorate the conservation status of this species.National Research FoundationDST-NRF Centre of Excellence fund at the FitzPatrick Institute of African OrnithologyLeiden Conservation Foundatio