Novel technique for measuring dispersion and detuning of a UV written silica-on-silicon waveguide

We shall present a new method of measuring the dispersive properties of UV written waveguides in the silica-on-silicon platform used to fabricate planar Bragg gratings. The technique involves direct measurement of the modal refractive index of a waveguide produced in the material. The data obtained also provides additional information about the spectral range of Bragg grating inscription. This direct writing technique reported previously differs from fibre Bragg grating fabrication by the small spot size of the writing beam and permits detuning of the Bragg wavelength from 1250nm to 1625nm. The fabrication technique provides the exact period of the grating and thus interrogation of the gratings produces information on the effective index of the mode. A series of integrated gratings were fabricated in a direct UV written waveguide via the direct grating writing technique in order to measure the wavelength dependence of the refractive index of the material. The Sellmeier curve obtained is shown

Halite and stable chlorine isotopes in the Zag H3-6 breccia

Zag is an H3-6 chondrite regolith breccia within which we have studied 14 halite grains ?3mm. The purity of the associated NaCl-H2O brine is implied by freezing characteristics of fluid inclusions in the halite and EPMA analyses together with a lack of other evaporite-like phases in the Zag H3-6 component. This is inconsistent with multistage evolution of the fluid involving scavenging of cations in the Zag region of the parent body. We suggest that the halite grains are clastic and did not crystallise in situ. Halite and water-soluble extracts from Zag have light Cl isotopic compositions, ?37-Cl = -1.4 to '2.8 �. Previously reported bulk carbonaceous chondrite values are approximately ?37-Cl = +3 to +4 �. This difference is too great to be the result of fractionation during evaporation and instead we suggest that Cl isotopes in chondrites are fractionated between a light reservoir associated with fluids and a heavier reservoir associated with higher temperature phases such as phosphates and silicates. Extraterrestrial carbon released at 600 degrees Celsius from the H3-4 matrix has ?13-C = -20 �, consistent with poorly graphitised material being introduced into the matrix rather than indigenous carbonate derived from a brine. We have also examined 28 other H-chondrite falls in order to ascertain how widespread halite or evaporite-like mineral assemblages are in ordinary chondrites. We did not find any more to add to Zag (H3-6) and Monahans (H5), which suggests that such highly soluble phases were not usually preserved on the parent bodies

Affective issues in learning technologies: emotional responses to technology and technology's role in supporting socio-emotional skills

This paper focuses on some of the author's research studies over the past thirty years and places these in a wider context to reflect on research into affective issues in learning technologies over this period, and to consider whether and how the issues uncovered by research have changed as technologies have developed over time. Three issues are given particular attention: firstly the reasons for learners' use or lack of use of technologies for their learning; secondly adult learners' attitudes towards using technology for learning and thirdly how technology might support socio-emotional development and expression in children. The discussion of these issues is framed by two of the author's research projects. For the first two issues this is an early study of students' perceptions and attitudes towards using computers for tutorial learning in 1980. The factors that influenced the students' use of the computer tutorials are discussed (including access, assessment and anxiety about using computers) and also the extent to which some of these factors persist for many learners using (or not using) technologies today. The discussion of the third issue draws on a series of studies conducted in the 1990s to investigate whether educational technology could support children and young people's emotional expression and communication and development of socio-emotional skills. Finally the paper considers how these kinds of issues have been taken forward and how they are represented in contemporary research and suggests that trust is an important factor in using learning technologies

Monitoring the deflection of a membrane using direct UV written planar Bragg gratings

A thin (~100 µm thick) silica-on-silicon square membrane (10 mm x 10 mm) has been fabricated and its deflection monitored through a 100 Bragg grating array defined within the membrane

An integrated Bragg grating oxygen sensor using a hydrophobic sol-gel layer doped with an organic dye

Oxygen sensing is required for the understanding of many chemical processes across a diverse set of fields including medicine, environmental science and chemical synthesis. Oxygen sensing can be achieved through the use of electronic sensors. However, there are limitations associated with electronic sensors including susceptibility to electromagnetic interference and presenting a spark risk in flammable environments. Optical fiber and integrated optical chemical sensors overcome these limitations of electrical based sensing methods

Optofluidic integrated Bragg grating chemical sensor: Utilising a sodium-elective receptor surface to enhance detection

Planar waveguides can be written with a UV-laser into photosensitised silica to produce a wide range of optical devices. Careful modulation of two interfering beams allows Bragg gratings to be directly written into the channel. These Bragg gratings are inherently sensitive to temperature and strain, however etching away the surface exposes the mode within the grating to its surroundings. The corresponding observed shift in Bragg wavelength can be used to detect changes in this environment [1]. It has been previously reported [2] that the sensitivity of such a refractometer can be enhanced by over an order of magnitude through use of a high-index overlayer of tantalum pentoxide. This enhanced sensor has shown the potential to detect a single molecular monolayer upon the sensor surface [2]. This sensitivity was confirmed through the successful attachment and detection of a single molecular monolayer of a fluorescein-based organic dye to the sensor surface [3

Infection of Gammarus duebeni populations by two vertically transmitted microsporidia; parasite detection and discrimination by PCR–RFLP

We screened a population of the brackish water crustacean Gammarus duebeni from the Isle of Cumbrae for the presence of vertically transmitted microsporidia. We compared 2 screening techniques; light microscopy and PCR-based detection using generic 16S rDNA microsporidian primers. Fifty percent of females from this population tested positive for vertically transmitted microsporidia. The PCR screen was 100% efficient in comparison with existing LM based screening. In addition, the PCR screen produced bands of 2 sizes suggesting that more than 1 species of microsporidian was present. Sequencing revealed 2 distinct species of vertically transmitted microsporidia; 33% of females were infected with the feminizer Nosema granulosis and 17% were infected with a new species which we provisionally designate Microsporidium sp. On the basis of sequence information, we developed a discriminatory PCR–RFLP test based on MspI and HaeIII digests. This screen allows rapid detection and discrimination of vertically transmitted microsporidia in natural field populations. We applied the PCR–RFLP screen to a second G. duebeni population from the Isle of Man. This population also hosted these 2 parasite species. In total 45% of females harboured N. granulosis and 10% harboured Microsporidium sp. No dual-infected individuals were found in either population. The occurrence of 2 vertically transmitted parasites within a population has implications for our understanding of parasite–host relationships in the field and we discuss factors affecting the dynamics of parasite–parasite competition and coexistence

Real Interest Rates, Saving and Investment.

This paper investigates the determinants of real interest rates at world and country level. The starting point is the idea that the real interest rates reflect the interaction of desired saving and planned investment, using the framework developed by Barro and Sala-i- Martin (1990) and Barro (1992).INTEREST RATE;SAVINGS;INVESTMENTS;ECONOMIC MODELS

An integrated reconfigurable Bragg grating utilising a photoresponsive co-polymer

Reconfigurable Bragg grating devices are of significant interest for telecomm applications. Such devices can be fabricated by combining a UV-written silica Bragg grating with an azobenzene-based polymer - a photoresponsive material that undergoes reversible refractive index change on exposure to ultraviolet light. The preliminary 17 GHz tuning response suggests future applicability