10,172 research outputs found

    Optical Detection of Acoustic Emission Signals

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    Piezoelectric transducers, long used in the generation and detection of ultrasonic waves, have more recently been the detector of choice for acoustic emission signals. Optical probing methods, however, have several important advantages for acoustic emission studies: (1) they have an inherent broad frequency response, free from mechanical resonances, (2) they do not interfere with the acoustic waves. (3) since the focused optical beam diameters are typically only a few hundredths of a millimeter, optical methods can probe very close to a crack or a twin, (4) they can probe internally in transparent media, and (5) they can be used over a very wide temperature range. In this paper we compare the response of an optical probe with that of a commercial acoustic emission transducer. Since the optical probe permits absolute calibration, we can not only measure acoustic emission amplitudes, but also determine the quantitative response of the piezoelectric transducer to known acoustic disturbances of various kinds over a range of frequencies. We include measurements of real acoustic emission from twinning in two metals and stress corrosion cracking in steel

    Research Notes: A spontaneous mutant at the st2 locus

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    In 1971, Detroy Green, Department of Agronomy, Iowa State University, found sterile plants in an F4 single-plant progeny row from a cross of Hark X Harosoy Dt2Dt2. This family segregated 66 fertile to 21 sterile plants. Microspore mother cells of the sterile plants were examined, and a low level of chromosome pairing was observed, indicating that the sterile was either an asynaptic or desynaptic mutant

    Baroclinic energy flux at the continental shelf edgemodified by wind-mixing

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    Temperature and current measurements from two moorings onshore of the Celtic Sea shelf break, a well-known hot spot for tidal energy conversion, show the impact of passing summer storms on the baroclinic wavefield. Wind-driven vertical mixing changed stratification to permit an increased on-shelf energy transport, and baroclinic energy in the semidiurnal band appeared at the moorings 1�4 days after the storm mixed the upper 50 m of the water column. The timing of the maximum in the baroclinic energy flux is consistent with the propagation of the semidiurnal internal tide from generation sites at the shelf break to the moorings 40 km away. Also, the �3 day duration of the peak in M2 baroclinic energy flux at the moorings corresponds to the restratification time scale following the first storm

    To see or not to see: a qualitative interview study of patients' views on their own diagnostic images

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    Objectives To ascertain what meaning individuals attach to perceiving images of their own interior body and how the images and their meanings affect the clinical consultation. Design Face-to-face semistructured interviews. Participants 25 adult patients in southern England who, within the preceding 12 months, had been referred for diagnostic imaging. Setting Community. Results For patients, being shown their own X-rays, MRIs or CT images creates a variety of effects: (1) a sense of better understanding of the diagnosis; (2) validation of their sensory and emotional response to the illness or injury and (3) an alteration to the tenor and nature of the clinical encounter between patient and physician. In addition to meanings attached to these images, patients also impute meaning to the physician's decision not to share an image with them. The desire to see their image was greater in those patients with a skeletal injury; patients are less keen on viewing abdominal or other soft tissue images. Conclusions Viewing images of one's interior, invisible body is powerful and resonant in a number of ways. The experience of not seeing, whether through the patient's or the physician's choice, is also fraught with meaning

    Taijiquan the 'Taiji World' way: Towards a cosmopolitan vision of ecology.

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    In this article, we present a case study analysis of data gathered on the practice of the art of Taijiquan (Tai Chi Chuan) in one UK context. Our interest in looking at this physical culture was in exploring if/how physical cultures of shared embodied experience and practice may help “sow the seeds of environmental awareness”. In so doing, we illustrate certain affinities between this interpretation of the art and Beck’s idea of a “cosmopolitan vision of ecology”. We present an analysis of documentary and interview data of one English Taijiquan organisation and how it currently promotes the idea of interconnectedness, wellbeing and an alternative meta-narrative for living through the practice of Taijiquan. We conclude that, while further research is needed, there is evidence that a cosmopolitan vision for ecology is emerging in physical cultures such as Taijiquan

    Turbulence and mixing by internal waves in the Celtic Sea determined from ocean glider microstructure measurements

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    We present a new series of data from a 9-day deployment of an ocean microstructure glider (OMG) in the Celtic Sea during the summer of 2012. The OMG has been specially adapted to measure shear microstructure and coincident density structure from which we derive the dissipation rate of turbulent kinetic energy (ε) and diapycnal diffusion rates (K). The methods employed to provide trustworthy turbulent parameters are described and data from 766 profiles of ε, temperature, salinity and density structure are presented. Surface and bottom boundary layers are intuitively controlled by wind and tidal forcing. Interior dynamics is dominated by a highly variable internal wave-field with peak vertical displacements in excess of 50 m, equivalent to over a third of the water depth. Following a relatively quiescent period internal wave energy, represented by the available potential energy (APE), increases dramatically close to the spring tide flow. Rather than follow the assumed spring-neap cycle however, APE is divided into two distinct peak periods lasting only one or two days. Pycnocline ε also increases close to the spring tide period and similar to APE, is distinguishable as two distinct energetic periods, however the timing of these periods is not consistent with APE. Pycnocline mixing associated with the observed ε is shown to be responsible for the majority of the observed reduction in bottom boundary layer density suggesting that diapycnal exchange is a key mechanism in controlling or limiting exchange between the continental shelf and the deep ocean. Results confirm pycnocline turbulence to be highly variable and difficult to predict however a log-normal distribution does suggest that natural variability could be reproduced if the mean state can be accurately simulated

    Reflecting on 115 years: the chiropractic profession's philosophical path

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    The chiropractic profession struggled with survival and identity in its first decades. In addition to internal struggles between chiropractic leaders and colleges, much of our profession's formative years were stamped with reactions to persecution from external forces. The argument that chiropractic should be recognized as a distinct profession, and the rhetoric that this medicolegal strategy included, helped to develop chiropractic identity during this period of persecution in the early 20th century. This article questions if the chiropractic profession is mature and wise enough to be comfortable in being proud of its past but still capable of continued philosophical growth
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