Laser ultrasound for the study of thin sheets

Laser ultrasound is now an accepted and mature technology. However it is still seeking its first fully commercial industrial application although there are several potential uses in prototype form. The major advantage of laser ultrasound is that it is a non contact technique and can therefore be used on hot or moving components. The pulsed laser source generates simultaneously longitudinal and shear bulk waves and Rayleigh surface waves. When the material is in the form of a thin sheet the latter propagate as Lamb or plate waves providing the ultrasonic wavelength is greater than the sheet thickness

A Description of an Improved Homodyne Laser Interferometer

First appearing on the commercial market in the mid 1980’s, diode-pumped, continuous-wave (cw) Nd:YAG lasers have more recently been used to obtain visible output, by the incorporation of frequency doubling optics in the laser cavity.The laser diode pumping of a Nd:YAG laser rod is selective and highly efficient, resulting in compact, high power, spatial mode lasers. Frequency-doubling processes are non-linear and lead to doubling TEM00 only of the high energy fundamental temporal mode, resulting in operation of the 532 nm laser in a single spatial and single longitudinal mode. The technology is rapidly advancing, and green lasers with energies of up to 1W could soon be available. The beam properties of the lasers described above are highly desirable in the field of interferometry, where such lasers are now in direct competition with the much larger Argon lasers, which have already been employed in high power interferometric systems. We describe here the performance of a modified Michelson interferometer [1–4], built to incorporate a 90 mW ADLAS 300 diode-pumped Nd:YAG laser. In previous versions of the Michelson interferometer, we have used HeNe lasers with a few milliwatts output, requiring mirror-quality surfaces on our samples. A 90 mW laser power enables us to make displacement measurements on metal surfaces with little or no preparation. The laser could also, of course, be used in other, more elaborate interferometer types, such as the confocal Fabry-Perot, which are better suited to industrial environments

Rapid analytical methods for the microalgal and cyanobacterial biorefinery: application on strains of industrial importance.

To realise the potential of microalgae in the biorefinery context, exploitation of multiple products is necessary for profitability and for bioproduct valorisation. Appropriate analytical tools are required for growth optimisation, culture monitoring and quality control purposes, with safe, low-tech and low-cost solutions favourable. Rapid, high-throughput and user-friendly methodologies were devised for a) determination phycobiliproteins, chlorophylls, carotenoids, proteins, carbohydrates and lipids and b) qualitative and quantitative carotenoid profiling using UPLC-PDA-MSE. The complimentary methods were applied on 11 commercially important microalgal strains including Prasinophytes, Haptophytes and cyanobacteria, highlighting the suitability of some strains for coproduct exploitation and the methods utility for research and industrial biotechnology applications. The UPLC method allowed separation of 41 different carotenoid compounds in < 15 minutes. Simple techniques are described for further quantification and comparison of pigment profiles, allowing for easy strain selection and optimisation for pigment production, with suitability for biotechnological or biomedical applications

A proteomic approach to identify endosomal cargoes controlling cancer invasiveness

We have previously shown that Rab17 - a small GTPase associated with epithelial polarity - is specifically suppressed by ERK2 signalling to promote an invasive phenotype. However, the mechanisms through which Rab17 loss permits invasiveness, and the endosomal cargoes that are responsible for mediating this are not known. Using quantitative mass spectrometry-based proteomics, we have found that knockdown of Rab17 leads to highly selective reduction in the cellular levels of a v-SNARE (Vamp8). Moreover, proteomics and immunofluorescence indicate that Vamp-8 is associated with Rab17 at late endosomes. Reduced levels of Vamp8 promote transition between ductal carcinoma in situ (DCIS) and a more invasive phenotype. We developed an unbiased proteomic approach to elucidate the complement of receptors that redistributes between endosomes and the plasma membrane, and have pin-pointed neuropilin-2 (NRP2) as a key pro-invasive cargo of Rab17/Vamp8-regulated trafficking. Indeed, reduced Rab17 or Vamp8 levels lead to increased mobilisation of NRP2-containing late endosomes and upregulated cell surface expression of NRP2. Finally, we show that NRP2 is required for the basement membrane disruption which accompanies transition between DCIS and a more invasive phenotype

Multi-coil focused EMAT for characterisation of surface-breaking defects of arbitrary orientation

Electromagnetic Acoustic Transducers (EMATs) are a useful ultrasonic tool for non-destructive evaluation in harsh environments due to their non-contact capabilities, and their ability to operate through certain coatings. This work presents a new Rayleigh wave EMAT transducer design, employing geometric focusing to improve the signal strength and detection precision of surface breaking defects. The design is robust and versatile, and can be used at frequencies centered around 1 MHz. Two coils are used in transmission mode, which allows the usage of frequency-based measurement of the defect depth. Using a 2 MHz driving signal, a focused beam spot with a width of 1.3±0.25 mm and a focal depth of 3.7±0.25 mm is measured, allowing for defect length measurements with an accuracy of±0.4 mm and detection of defects as small as 0.5 mm depth and 1 mm length. A set of four coils held under one magnet is used to find defects at orientations offset from normal to the ultrasound beam propagation direction. This EMAT has a range which allows detection of defects which propagate at angles from 16° to 170° relative to the propagation direction over the range of 0–180°, and the setup has the potential to be able to detect defects propagating at all angles relative to the wave propagation direction if two coils are alternately employed as generation coils

Local state space geometry and thermal metastability in complex landscapes: the spin-glass case

A simple geometrical characterization of configuration space neighborhoods of local energy minima in spin glass landscapes is found by exhaustive search. Combined with previous Monte Carlo investigations of thermal domain growth, it allows a discussion of the connection between real and configuration space descriptions of low temperature relaxational dynamics. We argue that the part of state-space corresponding to a single growing domain is adequately modeled by a hierarchically organized set of states and that thermal (meta)stability in spin glasses is related to the nearly exponential local density of states present within each trap.Comment: 16 pages, 8 figures, RevTeX, to appear in Physica A The figures have been improved and the text somewhat shortened. New references have been adde

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

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

A Remote Laser System for Material Characterization at High Temperatures

For many years, new techniques have been developed to overcome the problems involved with the generation and detection of ultrasound in materials at high temperature [1,2]. A non-contacting technique is described using lasers to generate and detect ultrasound and which can be used to study the variation in acoustic velocity as a function of temperature. Results are presented for the change in longitudinal velocity (vℓ) with increasing temperature in five polycrystalline materials, namely Dural, aluminum, AISI-310 stainless steel, iron and graphite