Motion processing deficits in migraine are related to contrast sensitivity

Background: There are conflicting reports concerning the ability of people with migraine to detect and discriminate visual motion. Previous studies used different displays and none adequately assessed other parameters that could affect performance, such as those that could indicate precortical dysfunction. Methods: Motion-direction detection, discrimination and relative motion thresholds were compared from participants with and without migraine. Potentially relevant visual covariates were included (contrast sensitivity; acuity; stereopsis; visual discomfort, stress, triggers; dyslexia). Results: For each task, migraine participants were less accurate than a control group and had impaired contrast sensitivity, greater visual discomfort, visual stress and visual triggers. Only contrast sensitivity correlated with performance on each motion task; it also mediated performance. Conclusions: Impaired performance on certain motion tasks can be attributed to impaired contrast sensitivity early in the visual system rather than a deficit in cortical motion processing per se. There were, however, additional differences for global and relative motion thresholds embedded in noise, suggesting changes in extrastriate cortex in migraine. Tasks to study the effects of noise on performance at different levels of the visual system and across modalities are recommended. A battery of standard visual tests should be included in any future work on the visual system and migraine

Teaching UbiComp with Sense

Modern computer science education has to take account of the recent changes towards smart ubiquitous computing devices. In addition, existing programming languages are needlessly difficult for novice programmers to learn concepts. We have developed Sense, an extension to the graphical programming language Scratch, and an associated sensor/actuator board. Together, these will allow novice undergraduate students to quickly develop their own smart devices while learning the fundamentals of programming. Students will first study with Sense in 2011 but developmental feedback has been positive

Do fluid inclusions preserve δ18O values of hydrothermal fluids in epithermal systems over geological time? : evidence from paleo- and modern geothermal systems, Milos island, Aegean Sea

Stable isotope compositions of quartz (δ18Oquartz) and fluid inclusion waters (δ18OFI and δDFI) were analysed from Profitis Ilias, a low-sulphidation epithermal gold mineralisation deposit on Milos island Greece, to establish if δ18OFI preserve a record of paleo-geothermal processes. Previous studies show that mineralisation at Profitis Ilias resulted from extreme boiling and vaporisation and a zone located at approximately 430 m asl represents the transition between a liquid- and vapour-dominated system [Mineral. Dep. 36 (2001) 43]. The deposit is also closely associated with an active geothermal system, whose waters have a well-characterised stable isotope geochemistry [Pagel and Leroy (1991) Source, transport and deposition of metals. Balkema, Rotterdam, 107–112]. The samples were collected over an elevation interval of 440 m (210 to 650 m asl) to give information on the liquid- and vapour-segments of the paleo-system. The data show systematic variations with sample elevation. Samples from the highest elevations (c. 650 m asl) have the lightest δ18OFI (–7.3 ‰) and δDFI (–68.0 ‰) whilst the deepest (c. 210 m asl) are isotopically heavier (δ18OFI –3.7 ‰; δDFI –19.0 ‰). Relative changes in δ18OFI closely parallel those in δDFI. δ18Oquartz shows an opposite trend, from the lightest values (+13.9 ‰) at the lowest elevations to the heaviest (+15.1 ‰) at the highest. δ18OFI show correlations with other parameters. For example, variable fluid inclusion homogenisation temperatures in the vapour-dominated part of the system, correlate with a rapid shift in δDFI (–33.3 to –50.5 ‰) and δ18OFI (–4.1 to –6.2 ‰) and gold contents also increase in the same zone (up to 50 ppm). Comparable correlations in δ18Oquartz or δ18Ocalculated (estimated geothermal fluid from fluid inclusion homogenisation data) are absent. δ18Ocalculated are always 5 to 10 ‰ heavier than δ18OFI. Comparison with the modern geothermal system shows that δDFI–δ18OFI are similar. Isotope data for the modern system and fluid inclusion waters fall on linear trends sub-paralleling the meteoric water line and project towards seawater values. Numerical modelling favours kinetically controlled fractionation to explain differences in δ18Ocalculated and δ18Ofluid rather than diffusive post-trapping equilibration. The evidence suggests, that in low-temperature epithermal systems, δ18OFI may represent a better record of fluid process and the isotopic composition of the geothermal fluid than temperature-corrected quartz data

Two-dimensional photonic band-gap structures as quasi-metals

By considering waves that propagate out of the transverse plane, we show that common high index materials (eg GaAs) with a 2D array of air holes can act in some ways like a 3D photonic band-gap structure. In particular, we describe a dielectric "quasi-metal" that reflects all propagating light incident from free space

Complications of pregnancy and delivery in relation to psychosis in adult life: data from the British perinatal mortality survey sample

Original article can be found at: http://www.pubmedcentral.nih.gov/tocrender.fcgi?iid=137629 Copyright BMJ PublishingTo evaluate whether events occurring at or around the time of birth contribute to the onset of psychotic illness in adult life.Peer reviewe

Fluids and mineralisation in the Scottish Dalradian

Fluid inclusion studies of orogenic vein-type gold deposits show a strong genetic association with high-temperature, low-salinity, and volatile-rich fluids. Although fluid models for this type of mineralisation are well established, they commonly ignore several important facts that indicate a role for low temperature fluids. Visible gold is invariably fracture-controlled and is hence related to fluid processes represented by later (secondary) fluid inclusions. In the limited number of cases where these have been studied, a multiple fluid history involving low-temperature brines (<250ºC) is commonly observed. Gold is often associated with a suite of minerals characterised by sulphosalts, tellurides, sulpho-tellurides and rare gold alloys. Some of these are only stable below 275ºC, indicating an association with low-temperature processes. This study collates fluid inclusion and mineralogical data representing the major styles of mineralisation (e.g. Cononish and Calliachar Burn [Au–quartz]; Lagalochan [porphyry–Cu±Au]; Tomnadashan [igneous related Cu]; Tyndrum, Castleton and Inverneil [Pb–Zn]; Stronchullin and Corrie Buie [Pb–Zn±Au]) and regional fluids (e.g. Loch Lomond) in the Scottish Dalradian. Six fluid types are identified: 1. High-salinity (halite-bearing: NaCl>35 wt %) and high-temperature (>300ºC) fluid inclusions. These are typical of porphyry copper deposits world-wide and were recorded from samples at Lagalochan, Tomnadashan and Comrie. 2. High-temperature (250–400ºC), volatile-rich (major CO2+CH4+N2: 15–25 wt % NaCl eq) and moderate salinity (7–10 wt % NaCl eq) fluids inclusions. In the Dalradian, this fluid is ubiquitous. It occurs in veins and breccias, associated with igneous intrusions. It is also one of the major fluid-types in regional metamorphic quartz-veins and is recorded at nearly all mineralised localities. Elsewhere, this fluid-type is associated with orogenic gold mineralisation. However, in the Scottish Dalradian, its presence is not indicative of gold mineralisation. 3. Moderate to high-temperature (200–350ºC) and moderate salinity (7–10 wt % NaCl eq) fluids containing volatiles (minor CO2+CH4+N2: 10–15 wt %% NaCl eq). These have the same distribution and associations as Fluid 2. 4. Low to moderate-temperature (150–250ºC) low-salinity brines (<10 wt % NaCl eq) with little or no volatile component. This is analogous to fluids associated with epithermal gold mineralisation. It occurs in both igneous and metasedimentary rock-hosted mineralisation, and is present in a number of metamorphic quartz veins. Its presence as primary fluid inclusions in sphalerite, at Stronchullin, shows it plays a significant role in mineralisation. 5. Low-temperature (<150ºC) high-salinity (c. 20 wt % NaCl eq) brines. This fluid is typical of Mississippi Valley Type Pb–Zn deposits world-wide. It is present in most gold mineralised localities, but inclusions are low in abundance. Its role in Au metallogenesis is unclear, but a similar type of fluid is associated with gold-free base metal mineralisation (e.g. Tyndrum Pb–Zn). 6. A low temperature (monophase) aqueous fluid. This could be a low temperature equivalent of either Fluid 4 or Fluid 5. This fluid is sparsely distributed over a wide area. Types 1 and 2 and possibly 3 represent prograde fluids, which have a deep crustal (magmatic and metamorphic) origin, and are probably responsible for introduction of metals into the system. Then initiation of extensional tectonics permitted a major ingress of meteoric–basinal fluids (Types 4, 5 and 6). Fluid 4 and/or 5 remobilises earlier Fe–Cu–(Mo)–As–Au–S mineralisation and results in a base metal–gold overprint at many of the localities. Late-stage (Devonian-Carboniferous?) basin development is a possible source for the high-salinity low-temperature brines (Type 5 fluid). Fluid 6 could be responsible for the localised dickite–kaolinite mineralisation in the Highland Boundary Fault Zone and supergene alteration seen in mineralised localities (e.g. Calliachar Burn). Although the volatile-rich fluids play a major role in metallogenesis in the Scottish Dalradian, it is clear that low-temperature brines played a significant role in gold mineralisation. In terms of understanding the deposit-scale distribution of gold, it is of prime importance to know how these late-stage fluids interacted with pre-existing mineralised structures. Also, for exploration, there is a need to develop new technologies to predict where and how these fluids have acted, as they are probably responsible for the erratic distribution of gold-grades that characterise many orogenic gold deposits

Stereo-SCIDAR: optical turbulence profiling with high sensitivity using a modified SCIDAR instrument

The next generation of adaptive optics systems will require tomographic reconstruction techniques to map the optical refractive index fluctuations, generated by the atmospheric turbulence, along the line of sight to the astronomical target. These systems can be enhanced with data from an external atmospheric profiler. This is important for Extremely Large Telescope scale tomography. Here we propose a new instrument which utilizes the generalized Scintillation Detection And Ranging (SCIDAR) technique to allow high sensitivity vertical profiles of the atmospheric optical turbulence and wind velocity profile above astronomical observatories. The new approach, which we refer to as ‘stereo-SCIDAR’, uses a stereoscopic system with the scintillation pattern from each star of a double-star target incident on a separate detector. Separating the pupil images for each star has several advantages including increased magnitude difference tolerance for the target stars; negating the need for re-calibration due to the normalization errors usually associated with SCIDAR; an increase of at least a factor of 2 in the signal-to-noise ratio of the cross-covariance function and hence the profile for equal magnitude target stars and up to a factor of 16 improvement for targets of 3 mag difference and easier real-time reconstruction of the wind-velocity profile. Theoretical response functions are calculated for the instrument, and the performance is investigated using a Monte Carlo simulation. The technique is demonstrated using data recorded at the 2.5-m Nordic Optical Telescope and the 1.0-m Jacobus Kapteyn Telescope, both on La Palma

Application of mineralogical, petrological and geochemical tools for evaluating the palaeohdrogeological evolution of the PADAMOT study sites

The role of Work Package (WP) 2 of the PADAMOT project – ‘Palaeohydrogeological Data Measurements’ - has been to study late-stage fracture mineral and water samples from groundwater systems in Spain, Sweden, United Kingdom and the Czech Republic, with the aim of understanding the recent palaeohydrogeological evolution of these groundwater systems. In particular, the project sought to develop and evaluate methods for obtaining information about past groundwater evolution during the Quaternary (about the last 2 million years) by examining how the late-stage mineralization might record mineralogical, petrographical and geochemical evidence of how the groundwater system may have responded to past geological and climatological changes. Fracture-flow groundwater systems at six European sites were studied: • Melechov Hill, in the Bohemian Massif of the Czech Republic: a shallow (0-100 m) dilute groundwater flow system within the near-surface weathering zone in fractured granitic rocks; • Cloud Hill, in the English Midlands: a (~100 m) shallow dilute groundwater flow system in fractured and dolomitized Carboniferous limestone; • Los Ratones, in southwest Spain: an intermediate depth (0-500 m) dilute groundwater flow system in fractured granitic rocks; • Laxemar, in southeast Sweden: a deep (0-1000 m) groundwater flow system in fractured granitic rocks. This is a complex groundwater system with potential recharge and flushing by glacial, marine, lacustrine and freshwater during the Quaternary; • Sellafield, northwest England: a deep (0-2000 m) groundwater flow system in fractured Ordovician low-grade metamorphosed volcaniclastic rocks and discontinuous Carboniferous Limestone, overlain by a Permo-Triassic sedimentary sequence with fracture and matrix porosity. This is a complex coastal groundwater system with deep hypersaline sedimentary basinal brines, and deep saline groundwaters in crystalline basement rocks, overlain by a shallow freshwater aquifer system. The site was glaciated several times during the Quaternary and may have been affected by recharge from glacial meltwater; • Dounreay, northeast Scotland: a deep (0-1400 m) groundwater flow system in fractured Precambrian crystalline basement overlain by fractured Devonian sedimentary rocks. This is within the coastal discharge area of a complex groundwater system, comprising deep saline groundwater hosted in crystalline basement, overlain by a fracture-controlled freshwater sedimentary aquifer system. Like Sellafield, this area experienced glaciation and may potentially record the impact of glacial meltwater recharge. In addition, a study has been made of two Quaternary sedimentary sequences in Andalusia in southeastern Spain to provide a basis of estimating the palaeoclimatic history of the region that could be used in any reconstruction of the palaeoclimatic history at the Los Ratones site: • The Cúllar-Baza lacustrine sequence records information about precipitation and palaeotemperature regimes, derived largely from the analysis of the stable isotope (δ18O and δ13C) signatures from biogenic calcite (ostracod shells). • The Padul Peat Bog sequence provided information on past vegetation cover and palaeogroundwater inputs based on the study of fossil pollen and biomarkers as proxies for past climate change. Following on from the earlier EC 4th Framework EQUIP project, the focus of the PADAMOT studies has been on calcite mineralization. Calcite has been identified as a late stage mineral, closely associated with hydraulically-conductive fractures in the present-day groundwater systems at the Äspö-Laxemar, Sellafield, Dounreay and Cloud Hill sites. At Los Ratones and Melechov sites late-stage mineralization is either absent or extremely scarce, and both the quantity and fine crystal size of any late-stage fracture mineralization relevant to Quaternary palaeohydrogeological investigations is difficult to work with. The results from the material investigated during the PADAMOT studies indicate that the fracture fillings at these sites are related to hydrothermal activity, and so do not have direct relevance as Quaternary indicators. Neoformed calcite has not been found at these two sites at the present depth of the investigations. Furthermore, the HCO3 - concentration in all the Los Ratones groundwaters is mainly controlled by complex carbonate dissolution. The carbonate mineral saturation indices do not indicate precipitation conditions, and this is consistent with the fact that neoformed calcite, ankerite or dolomite have not been observed petrographically

Gold in the Dalradian terrane : a review of previous work

The Dalradian Supergroup comprises a Late Precambrian sequence of marine clastic sedimentary rocks and minor basic volcanic rocks which was folded and metamorphosed during the early Palaeozoic Caledonian Orogeny. Intrusive igneous rocks are widespread throughout the Dalradian terrane. The most important in terms of gold metallogenesis are the post-tectonic granites which comprise a diverse suite of calc-alkaline intrusions emplaced between 420 and 395 Ma. Numerous occurrences of gold in bedrock and alluvium are documented in the Dalradian terrane of Scotland. Mesothermal vein occurrences are the most important and include the Cononish deposit, near Tyndrum in Perthshire, where planning permission for mining has been granted. Gold mineralisation of several other styles, including intrusion-related, epithermal, stratiform and occurrences associated with mafic-ultramafic intrusions, is also present. This report has been compiled for the BGS Core Programme project ‘Sedimentary Basin Resources: Gold in orogenic extensional basins – the Dalradian’. This project, carried out between 1997–2000, was designed to investigate the factors controlling the distribution of gold in the Dalradian and to develop a predictive metallogenic model for gold mineralisation in this terrane. This report provides a` review of known gold occurrences and the results of past mineral exploration activity in the Dalradian terrane. The latter has been compiled from records held in BGS archives and the available data are summarised in a series of appendices. Exploration for metalliferous mineralisation has been carried out widely in the Dalradian terrane by commercial mining companies and by BGS. In the 1970s most work focused on Cu, Pb, Zn, Ni and Mo, while more recently, from 1981 onwards, precious metals (Au and PGE) were the prime target. Between 1972 and 1984 the DTI sought to encourage private-sector mineral exploration by the provision of grants under the Mineral Exploration and Investment Grants Act (MEIGA). About 150 reports derived from these projects are available on open-file at BGS. Exploration by BGS was carried out mainly through the DTI-funded Mineral Reconnaissance Programme (MRP), which ran between 1972 and 1997. Nearly 150 reports and associated data releases were produced by the MRP. Together the MEIGA and MRP reports have been the major sources of information used in this report. The combination of improved genetic models for gold deposits, the increased availability of multidisciplinary digital geoscience data and the information on previous exploration summarised in this report provides a sound basis for research on gold mineralisation in the Dalradian terrane. Potential exists in a range of settings that may host economic gold deposits