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

Analysis of a One-Dimensional Continuous Delay-Tolerant Network Model

The packet speed and transmission cost are examined, for a single packet traveling along a simple one-dimensional, continuous-time network, using a combination of wireless transmissions and physical transports. We assume that the network consists of two nodes moving at constant speed on a circle, and changing their direction of travel after independent exponential times. The packet wishes to travel in the clockwise direction as fast and as far as possible. It travels either by being physically transported on a node’s buffer, or by being wirelessly transmitted to the other node when the two are in the same location. We derive exact, explicit expressions for the long-term average packet speed (in the clockwise direction), and also for the average wireless transmission cost. These results can be viewed as initial steps towards the development of analogous exact expressions for the speed and cost, in more realistic, two-dimensional wireless delay-tolerant network models

A simple network of nodes moving on the circle

Two simple Markov processes are examined, one in discrete and one in continuous time, arising from idealized versions of a transmission protocol for mobile, delay-tolerant networks. We consider two independent walkers moving with constant speed on either the discrete or continuous circle, and changing directions at independent geometric (respectively, exponential) times. One of the walkers carries a message that wishes to travel as far and as fast as possible in the clockwise direction. The message stays with its current carrier unless the two walkers meet, the carrier is moving counter-clockwise, and the other walker is moving clockwise. In that case, the message jumps to the other walker. The long-term average clockwise speed of the message is computed. An explicit expression is derived via the solution of an associated boundary value problem in terms of the generator of the underlying Markov process. The average transmission cost is also similarly computed, measured as the long-term number of jumps the message makes per unit time. The tradeoff between speed and cost is examined, as a function of the underlying problem parameters

VR binoculars: An immersive visualization framework for IoT data streams

Every day we find ourselves moving through a blend of material spaces and immaterial networks. This invisible layer created from the millions of the data streams and network connections that take place around us tends to get denser with the recent development and deployment of the IoT devices in the urban space. In our work we aim to explore how the available technology of Mixed Reality spectrum can be applied to provide us an immerse view of the information that exist within the invisible layer of the “cyberspace” [1]. To this extend, we propose “VR Binoculars”, a digital visualization framework that operates in real time.The available Virtual (VR), Augmented (AR), and Mixed Reality (MR) technology is used as a medium to unveil the information that exist in our surrounding space. Specifically, we situate the user within an environment where the digital data visualizations and the physical space are matched together, providing to the user the ability to interact, orient themselves and navigate naturally.For us the proposed framework it is able to promote a better understanding of the IoT ecosystem, it can justify the use of sensors in the public space, and it can raise awareness about privacy and data sharing. Using different urban environments as test cases (indoor, outdoor) we present our methodology and our first results

Project AUTONOMAD : The design of an unmanned coast guard vessel integrating the use of drones for emission regulation enforcement and territorial water protection in the Mediterranean

Project AUTONOMAD examines the design of an unmanned trimaran vessel for unmanned application, integrating the deployment, recovery and storage of various Unmanned Aerial Vehicles (UAVs) and Unmanned Surface Vehicles (USVs). It is tailor made for the needs of EU Coastguards in order to provide a platform for emission regulation enforcement, maritime monitoring and surveillance in the Mediterranean. This project includes the design of the unmanned vessel, the selection of its payload and the integration of the unmanned technologies in order to create a robust and reliable engineering system. The feasibility of such a vessel is then assessed in terms of reliability and overall benefit

Unseen roots and unfolding flowers? Prison learning, equality and the education of socially excluded groups

The objective of this theoretical article is to critique the notion that adult education, in its current marketised formations, might serve the purpose of rehabilitating learners. To date there has been no detailed interrogation by educationalists of the desirability of rehabilitation as an overarching aim for prison education, or to consider the existing educational philosophies that notions of rehabilitation might cohere with. This article begins to address this gap by engaging with the idea of rehabilitation from a critical adult education perspective. The conceptual framework informing the analysis is critical adult education theory, drawing tangentially on the work of Raymond Williams. The overarching assumption is that education might be understood as the practice of equality, which I employ alongside conceptualisations of empowering adult literacies learning as drawn from writings in the field of New Literacies Studies (NLS). These approaches enable the critique of criminological theory associated with prison learning, alongside the critique of assumptions traceable to NLS. The analysis focuses more specifically on Scotland’s prison system, where the criminological theory of ‘desistance’ currently holds some sway. I observe that whilst perspectives of criminologists and educationists draw upon similar sociological assumptions and underpinnings, different conclusions are inferred about the purpose and practice of adult learning. Here criminologists' conceptualisations tend to neglect power contexts, instead inferring educational practices associated typically with early years education. I also demonstrate the importance of equality in the context of adult education, if educators are to take responsibility for the judgements they make in relation to the education of socially excluded groups

Single-dose administration and the influence of the timing of the booster dose on immunogenicity and efficacy of ChAdOx1 nCoV-19 (AZD1222) vaccine: a pooled analysis of four randomised trials.

BACKGROUND: The ChAdOx1 nCoV-19 (AZD1222) vaccine has been approved for emergency use by the UK regulatory authority, Medicines and Healthcare products Regulatory Agency, with a regimen of two standard doses given with an interval of 4-12 weeks. The planned roll-out in the UK will involve vaccinating people in high-risk categories with their first dose immediately, and delivering the second dose 12 weeks later. Here, we provide both a further prespecified pooled analysis of trials of ChAdOx1 nCoV-19 and exploratory analyses of the impact on immunogenicity and efficacy of extending the interval between priming and booster doses. In addition, we show the immunogenicity and protection afforded by the first dose, before a booster dose has been offered. METHODS: We present data from three single-blind randomised controlled trials-one phase 1/2 study in the UK (COV001), one phase 2/3 study in the UK (COV002), and a phase 3 study in Brazil (COV003)-and one double-blind phase 1/2 study in South Africa (COV005). As previously described, individuals 18 years and older were randomly assigned 1:1 to receive two standard doses of ChAdOx1 nCoV-19 (5 × 1010 viral particles) or a control vaccine or saline placebo. In the UK trial, a subset of participants received a lower dose (2·2 × 1010 viral particles) of the ChAdOx1 nCoV-19 for the first dose. The primary outcome was virologically confirmed symptomatic COVID-19 disease, defined as a nucleic acid amplification test (NAAT)-positive swab combined with at least one qualifying symptom (fever ≥37·8°C, cough, shortness of breath, or anosmia or ageusia) more than 14 days after the second dose. Secondary efficacy analyses included cases occuring at least 22 days after the first dose. Antibody responses measured by immunoassay and by pseudovirus neutralisation were exploratory outcomes. All cases of COVID-19 with a NAAT-positive swab were adjudicated for inclusion in the analysis by a masked independent endpoint review committee. The primary analysis included all participants who were SARS-CoV-2 N protein seronegative at baseline, had had at least 14 days of follow-up after the second dose, and had no evidence of previous SARS-CoV-2 infection from NAAT swabs. Safety was assessed in all participants who received at least one dose. The four trials are registered at ISRCTN89951424 (COV003) and ClinicalTrials.gov, NCT04324606 (COV001), NCT04400838 (COV002), and NCT04444674 (COV005). FINDINGS: Between April 23 and Dec 6, 2020, 24 422 participants were recruited and vaccinated across the four studies, of whom 17 178 were included in the primary analysis (8597 receiving ChAdOx1 nCoV-19 and 8581 receiving control vaccine). The data cutoff for these analyses was Dec 7, 2020. 332 NAAT-positive infections met the primary endpoint of symptomatic infection more than 14 days after the second dose. Overall vaccine efficacy more than 14 days after the second dose was 66·7% (95% CI 57·4-74·0), with 84 (1·0%) cases in the 8597 participants in the ChAdOx1 nCoV-19 group and 248 (2·9%) in the 8581 participants in the control group. There were no hospital admissions for COVID-19 in the ChAdOx1 nCoV-19 group after the initial 21-day exclusion period, and 15 in the control group. 108 (0·9%) of 12 282 participants in the ChAdOx1 nCoV-19 group and 127 (1·1%) of 11 962 participants in the control group had serious adverse events. There were seven deaths considered unrelated to vaccination (two in the ChAdOx1 nCov-19 group and five in the control group), including one COVID-19-related death in one participant in the control group. Exploratory analyses showed that vaccine efficacy after a single standard dose of vaccine from day 22 to day 90 after vaccination was 76·0% (59·3-85·9). Our modelling analysis indicated that protection did not wane during this initial 3-month period. Similarly, antibody levels were maintained during this period with minimal waning by day 90 (geometric mean ratio [GMR] 0·66 [95% CI 0·59-0·74]). In the participants who received two standard doses, after the second dose, efficacy was higher in those with a longer prime-boost interval (vaccine efficacy 81·3% [95% CI 60·3-91·2] at ≥12 weeks) than in those with a short interval (vaccine efficacy 55·1% [33·0-69·9] at <6 weeks). These observations are supported by immunogenicity data that showed binding antibody responses more than two-fold higher after an interval of 12 or more weeks compared with an interval of less than 6 weeks in those who were aged 18-55 years (GMR 2·32 [2·01-2·68]). INTERPRETATION: The results of this primary analysis of two doses of ChAdOx1 nCoV-19 were consistent with those seen in the interim analysis of the trials and confirm that the vaccine is efficacious, with results varying by dose interval in exploratory analyses. A 3-month dose interval might have advantages over a programme with a short dose interval for roll-out of a pandemic vaccine to protect the largest number of individuals in the population as early as possible when supplies are scarce, while also improving protection after receiving a second dose. FUNDING: UK Research and Innovation, National Institutes of Health Research (NIHR), The Coalition for Epidemic Preparedness Innovations, the Bill & Melinda Gates Foundation, the Lemann Foundation, Rede D'Or, the Brava and Telles Foundation, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midland's NIHR Clinical Research Network, and AstraZeneca

Fluid inclusion thermometric and stable isotope (δ18O-δD) evidence for “cryptic boiling” in the Profitis Ilias epithermal gold deposit, Milos : a potential exploration tool for epithermal gold

“Cryptic boiling” has been disclosed throughout the vertical extent of the Profitis Ilias epithermal system (~450 m) by assessing systematic variations in fluid inclusion and stable isotope (δ18O-δD) data in relation to elevation. Highest gold grades (Au: 2-57.9 g/t) are preferentially concentrated in the upper 200-250 m of the system in a “steam-dominated zone” that is separated from a lower “liquid-dominated zone” (Au < 2 g/t). This distribution of gold may be due to colloidal transport in a boiling epithermal system. The identification of the base of the “steam-dominated zone” using fluid inclusion and stable isotope data may potentially guide exploration drilling to depths with high-grade gold ore in productive epithermal systems

The Profitis Ilias deposit, Milos island, Greece : a case study of boiling in an epithermal system recorded by stable isotope and fluid inclusion data

Stable isotope (δD and δ18O) and microthermometric data are presented for the Profitis Ilias adularia-sericite-type epithermal gold deposit on Milos Island, Greece. The deposit was discovered by Midas Enterprise SA, and estimated reserves are 5 million tonnes grading at 4.4 g/t Au and 43 ppm Ag. Microther-mometric data show that the system boiled. Stable isotope ratios were determined on inclusion-fluids (δD and δ18O) and vein quartz (δ18O). The inclusion-fluid data show fractionation trends consistent with single–stage steam separation and are broadly comparable to the currently active Milos geothermal system. The trends and comparisons in the fluid-mineral data are more difficult to interpret. This suggests that data derived by ana-lysing both δD and δ18O on inclusion-fluids can provide a better framework for interpreting fluid processes in epithermal systems than current methodologies based on calculating δ18O from fluid-quartz equilibria

Exact speed and transmission cost in a simple one-dimensional wireless delay-tolerant network

We study a simple one-dimensional, discrete-time network model that consists of two nodes moving on a discrete circle, changing their direction of movement randomly, and a single packet travelling in the clockwise direction, using combinations of transmissions between the two nodes (when they are co-located) and physical transports on their buffers. In this setting, we provide exact, explicit expressions for the long-term averages of the packet speed and the wireless transmission cost. Our work is a first step towards providing simple and exact results for more realistic wireless delay-tolerant network models