Confocal Microscopy using an InGaN violet laser diode at 406nm

We report on the application of a novel all-solid-state violet laser diode source to confocal microscopy. The source has the potential to replace argon ion lasers in a range of fluorescence based imaging systems. Improvements in system performance and image quality through the use of anamorphic prisms to modify the beam profile have been characterised. These modifications have permitted high quality, optically sectioned images to be obtained from laser diodes operating around 406nm. Living mammalian cells stained with a range of biologically significant fluorophores have been imaged. In addition, it has been shown that at this wavelength it is possible to image dyes that normally require excitation with UV argon laser lines

Simultaneous stimulated Raman scattering and second harmonic generation in periodically poled lithium niobate

Simultaneous stimulated Raman scattering (SRS) and second harmonic generation (SHG) are demonstrated in periodically poled lithium niobate (PPLN). Using a simple single-pass geometry, conversion efficiencies of up to 12% and 19% were observed for the SRS and SHG processes respectively. By changing the PPLN period interacting with the photonic crystal fibre based pump source and varying the PPLN temperature, the SHG signal was measured to be tunable from λ =584 nm to λ =679 nm. The SRS output spectrum was measured at λ=1583 nm, with a spectral full-width at half-maximum of λ =85 nm

High-average-power (>20-W) Nd:YVO-4 lasers mode locked by strain-compensated saturable Bragg reflectors

Strain-compensated double InGaAs quantum-well saturable Bragg reflectors (SBR’s) with high damage thresholds have been developed for use as mode-locking elements in high-average-power neodymium lasers. Nd:YVO4 lasers have been developed with these new SBR’s, which produce transform-limited pulses of 21-ps duration at 90 MHz and an average power of 20 W in a diffraction-limited output beam. The peak pulse power at an output power of 20 W was 10.6 kW. A comparison of the operating parameters of strained single and strain-compensated double-well SBR’s indicates that the damage threshold increased by a factor of at least 2–3. Long cavity laser variants were nvestigated to assess the limitations of further power scaling. At a repetition frequency of 36-MHz stable mode-locked pulses with peak pulse powers of 24.4 kW and pulse energies of 0.6 mJ could be generated

Assessing the repeatability of automated seafloor classification algorithms, with application in marine protected area monitoring

The number and areal extent of marine protected areas worldwide is rapidly increasing as a result of numerous national targets that aim to see up to 30% of their waters protected by 2030. Automated seabed classification algorithms are arising as faster and objective methods to generate benthic habitat maps to monitor these areas. However, no study has yet systematically compared their repeatability. Here we aim to address that problem by comparing the repeatability of maps derived from acoustic datasets collected on consecutive days using three automated seafloor classification algorithms: (1) Random Forest (RF), (2) K–Nearest Neighbour (KNN) and (3) K means (KMEANS). The most robust and repeatable approach is then used to evaluate the change in seafloor habitats between 2012 and 2015 within the Greater Haig Fras Marine Conservation Zone, Celtic Sea, UK. Our results demonstrate that only RF and KNN provide statistically repeatable maps, with 60.3% and 47.2% agreement between consecutive days. Additionally, this study suggests that in low-relief areas, bathymetric derivatives are non-essential input parameters, while backscatter textural features, in particular Grey Level Co-occurrence Matrices, are substantially more effective in the detection of different habitats. Habitat persistence in the test area between 2012 and 2015 was 48.8%, with swapping of habitats driving the changes in 38.2% of the area. Overall, this study highlights the importance of investigating the repeatability of automated seafloor classification methods before they can be fully used in the monitoring of benthic habitat

The Paracoccus denitrificans NarK-like nitrate and nitrite transporters—probing nitrate uptake and nitrate/nitrite exchange mechanisms

Nitrate and nitrite transport across biological membranes is often facilitated by protein transporters that are members of the major facilitator superfamily. Paracoccus denitrificans contains an unusual arrangement whereby two of these transporters, NarK1 and NarK2, are fused into a single protein, NarK, which delivers nitrate to the respiratory nitrate reductase and transfers the product, nitrite, to the periplasm. Our complementation studies, using a mutant lacking the nitrate/proton symporter NasA from the assimilatory nitrate reductase pathway, support that NarK1 functions as a nitrate/proton symporter while NarK2 is a nitrate/nitrite antiporter. Through the same experimental system, we find that Escherichia coli NarK and NarU can complement deletions in both narK and nasA in P. denitrificans, suggesting that, while these proteins are most likely nitrate/nitrite antiporters, they can also act in the net uptake of nitrate. Finally, we argue that primary sequence analysis and structural modelling do not readily explain why NasA, NarK1 and NarK2, as well as other transporters from this protein family, have such different functions, ranging from net nitrate uptake to nitrate/nitrite exchange

The Self Model and the Conception of Biological Identity in Immunology

The self/non-self model, first proposed by F.M. Burnet, has dominated immunology for sixty years now. According to this model, any foreign element will trigger an immune reaction in an organism, whereas endogenous elements will not, in normal circumstances, induce an immune reaction. In this paper we show that the self/non-self model is no longer an appropriate explanation of experimental data in immunology, and that this inadequacy may be rooted in an excessively strong metaphysical conception of biological identity. We suggest that another hypothesis, one based on the notion of continuity, gives a better account of immune phenomena. Finally, we underscore the mapping between this metaphysical deflation from self to continuity in immunology and the philosophical debate between substantialism and empiricism about identity

The colour magnitude relation for galaxies in the Coma cluster

We present a new photometric catalogue of the Coma galaxy cluster in the Johnson U- and V- bands. We cover an area of 3360arcmin2 of sky, to a depth of V=20 mag in a 13 arcsec diameter aperture, and produce magnitudes for ~1400 extended objects in metric apertures from 8.8 to 26arcsec diameters. The mean internal RMS scatter in the photometry is 0.014 mag in V, and 0.026 mag in U, for V13 < 17 mag. We place new limits on the levels of scatter in the colour--magnitude relation (CMR) in the Coma cluster, and investigate how the slope and scatter of the CMR depends on galaxy morphology, luminosity and position within the cluster. As expected, the lowest levels of scatter are found in the elliptical galaxies, while the late type galaxies have the highest numbers of galaxies bluewards of the CMR. We investigate whether the slope of the CMR is an artifact of colour gradients within galaxies and, show that it persists when the colours are measured within a diameter that scales with galaxy size. Looking at the environmental dependence of the CMR, we find a trend of systematically bluer galaxy colours with increasing projected cluster-centric radius which we associate with a gradient in the mean galactic ages.Comment: 18 pages, 13 Figures. For associated data file, see ftp://ftp.sr.bham.ac.uk/pub/ale/ComaPhot

Transferrin saturation ratio and risk of total and cardiovascular mortality in the general population.

peer-reviewedThe transferrin saturation (TSAT) ratio is a commonly used indicator of iron deficiency and iron overload in clinical practice but precise relationships with total and cardiovascular mortality are unclear.Purpose: To better understand this relationship, we explored the association of TSAT ratio (serum iron/total iron binding capacity) with mortality in the general population.PUBLISHEDpeer-reviewe

Single-mode neodymium fibre lasers

A laser medium in the form of a single mode optical fibre offers a number of attractive features. For example, using a laser to end pump such a fibre provided with feedback mirrors, allows a very low oscillation threshold to be attained. In the case of Nd doped fibre a GaAs diode laser can be used as the pump, thus providing a very simple and compact laser device. The low threshold performance also suggests that other, weaker transitions may be capable of laser action eg. the 1.3µm 4F3/2 to 4I13/2 transition in Nd or transitions in other dopants which have not previously shown laser action in a glass host. Other possible applications include the use of fibres as amplifiers e.g. as an in-line amplifier in an optical communication system where it could play the role of a repeater. As a power amplifier the fibre device could have advantages over the bulk glass systems by reducing the problems of thermal distortion and thermal fracture. In this paper we report some results obtained with neodymium-doped single mode fibres

CLES, Code Liegeois d'Evolution Stellaire

Cles is an evolution code recently developed to produce stellar models meeting the specific requirements of studies in asteroseismology. It offers the users a lot of choices in the input physics they want in their models and its versatility allows them to tailor the code to their needs and implement easily new features. We describe the features implemented in the current version of the code and the techniques used to solve the equations of stellar structure and evolution. A brief account is given of the use of the program and of a solar calibration realized with it.Comment: Comments: 8 pages, Astrophys. Space Sci. CoRoT-ESTA Volume, in the pres