The preparation and characterisation of monomeric and linked metal carbonyl clusters containing the closo-Si2Co4 pseudo-octahedral core

PhSiH3 reacts with [Co₄(CO)₁₂] at 50 °C in hydrocarbon solvents to give [(µ₄-SiPh)₂Co₄(CO)₁₁], 2c, shown by an X-ray crystal structure determination to have a pseudo-octahedral Si₂Co₄ core. Substituted aryl-silanes behaved similarly. Mixtures of PhSiH₃, H₃SiC₆H₄SiH₃ and [Co₄(CO)₁₂] in a ca. 2 1 2 ratio gave the dimeric cluster [{Co₄(µ₄-SiPh)(CO)₁₁Si}₂C₆H₄], 3a, which has the two Si₂Co₄ cores linked by a C₆H₄ group to give a rigid molecule which an X-ray structure analysis shows to be over 23 Å long. Related dimers linked by –(CH₂)₈– groups were isolated from mixtures of PhSiH₃, α ,ω-(H₃Si)₂(CH₂)₈ and [Co₄(CO)₁₂]. Electrochemical studies show the two cluster units in 3a do not interact electronically

Dissolved gas separation for engineered anaerobic wastewater systems

Dissolved gases produced within engineered anaerobic processes subsequently create a fugitive emission which can have financial, environmental and health and safety implications. Whilst desorption technology has been used to control dissolved gases in the drinking water sector, there is considerably less understanding of its deployment in wastewater for which there are numerous existing and emerging challenges. This review therefore focuses on existing and proposed technological approaches to gas desorption in engineered anaerobic wastewater processes, with specific emphasis on technology compatibility and downstream gas phase management. Simplified engineered solutions such as diffused aeration and multi-tray aerators appear robust solutions for implementation into wastewater. However, these processes are characterised by a low mass transfer coefficient and require high gas to liquid ratios (G/L) to achieve reasonable separation, which suggests their suitability is limited to small scale applications, in which gas recovery is not a priority. Packed columns and membrane contactors afford process intensification through increasing interfacial area which favours large scale applications; although both will require prefiltration technology to obviate media clogging. Vacuum or steam is the preferred driving force for separation when gas recovery is sought, while sweep-gas is energetically favoured. Sweep-gas has been used for gas recovery by operating at G/L toward the equilibrium value, which somewhat constrains mass transfer. Process selection must therefore be weighted on whole life cost, but will also be dependent upon process scale, financial (e.g. incentivisation) and non-financial (e.g. carbon) instruments, which are strongly influenced by regional policy

Changing epidemiology of methicillin-resistant Staphylococcus aureus colonization in paediatric intensive-care units

Community-associated methicillin-resistant S. aureus (CA-MRSA) accounts for a growing proportion of hospital-onset infections, and colonization is a risk factor. This study aimed to determine changes in the prevalence of CA-MRSA colonization in paediatric intensive-care units (ICUs). A total of 495 paediatric patients colonized with MRSA from neonatal, medical, surgical, and cardiac ICUs between 2001 and 2009 were identified. Isolates were characterized by spa type, staphylococcal cassette chromosome (SCC) mec type and the presence of the genes encoding Panton–Valentine leukocidin (PVL). The proportion of patients colonized with MRSA remained stable (average 3·2%). The proportion of isolates with spa type 1, SCCmec type IV and PVL increased over time to maximums in 2009 of 36·1% (P < 0·001), 54·2% (P = 0·03) and 28·9% (P = 0·003), respectively. Antibiotic susceptibility patterns showed increasing proportions susceptible to clindamycin, gentamicin, tetracycline and trimethoprim-sulfamethoxazole (P values <0·001). In conclusion, the proportion of MRSA-colonized children in ICUs with CA-MRSA increased significantly over time

Aqueous Processes and Microbial Habitability of Gale Crater Sediments from the Blunts Point to the Glenn Torridon Clay Unit

A driving factor for sending the Mars Science Laboratory, Curiosity rover to Gale Crater was the orbital detection of clay minerals in the Glen Torridon (GT) clay unit. Clay mineral detections in GT suggested a past aqueous environment that was habitable, and could contain organic evidence of past microbiology. The mission of the Sample Analysis at Mars (SAM) instrument onboard Curiosity was to detect organic evidence of past microbiology and to detect volatile bearing mineralogy that can inform on whether past geochemical conditions would have supported microbiological activity. The objective of this work was to 1) evaluate the depositional/alteration conditions of Blunts Point (BP) to GT sediments 2) search for evidence of organics, and 3) evaluate microbial habitability in the BP, Vera Rubin Ridge (VRR), and GT sedimentary rock

delta C-13 Analysis of Mars Analog Carbonates Using Evolved Gas Cavity - Ringdown Spectrometry on the 2010 Arctic Mars Analog Svalbard Expedition (AMASE)

The 2010 Arctic Mars Analog Svalbard Expedition (AMASE) investigated two distinct geologic settings on Svalbard, using instrumentation and techniques in development for future Mars missions, such as the Mars Science Laboratory (MSL), ExoMars, and Mars Sample Return (MSR). The Sample Analysis at Mars (SAM) instrument suite, which will fly on MSL, was developed at Goddard Space Flight Center (GSFC), together with several partners. SAM consists of a quadrupole mass spectrometer (QMS), a gas chromatograph CGC), and a tunable laser spectrometer (TLS), which all analyze gases created by evolved gas analysis (EGA). The two sites studied represent "biotic" and "abiotic" analogs; the "biotic" site being the Knorringfjell fossil methane seep, and the "abiotic" site being the basaltic Sigurdfjell vent complex. The data presented here represent experiments to measure the carbon isotopic composition of carbonates from these two analogs using evolved gas analysis coupled with a commercial cavity ringdown CO2 isotopic analyzer (Picarro) as a proxy for the TLS on SAM

Compositional Explanation of Types and Algorithmic Debugging of Type Errors

The type systems of most typed functional programming languages are based on the Hindley-Milner type system. A practical problem with these type systems is that it is often hard to understand why a program is not type correct or a function does not have the intended type. We suggest that at the core of this problem is the difficulty of explaining why a given expression has a certain type. The type system is not defined compositionally. We propose to explain types using a variant of the Hindley-Milner type system that defines a compositional type explanation graph of principal typings. We describe how the programmer understands types by interactive navigation through the explanation graph. Furthermore, the explanation graph can be the foundation for algorithmic debugging of type errors, that is, semi-automatic localisation of the source of a type error without even having to understand the type inference steps. We implemented a prototype of a tool to explore the usefulness of the proposed methods

Randomised controlled trial of an augmented exercise referral scheme using web-based behavioural support for inactive adults with chronic health conditions: the e-coachER trial.

OBJECTIVE: To determine whether adding web-based support (e-coachER) to an exercise referral scheme (ERS) increases objectively assessed physical activity (PA). DESIGN: Multicentre trial with participants randomised to usual ERS alone (control) or usual ERS plus e-coachER (intervention). SETTING: Primary care and ERS in three UK sites from 2015 to 2018. PARTICIPANTS: 450 inactive ERS referees with chronic health conditions. INTERVENTIONS: Participants received a pedometer, PA recording sheets and a user guide for the web-based support. e-coachER interactively encouraged the use of the ERS and other PA options. MAIN OUTCOME MEASURES: Primary and key secondary outcomes were: objective moderate-to-vigorous PA (MVPA) minutes (in ≥10 min bouts and without bouts), respectively, after 12 months. Secondary outcomes were: other accelerometer-derived and self-reported PA measures, ERS attendance, EQ-5D-5L, Hospital Anxiety and Depression Scale and beliefs about PA. All outcomes were collected at baseline, 4 and 12 months. Primary analysis was an intention to treat comparison between intervention and control arms at 12-month follow-up. RESULTS: There was no significant effect of the intervention on weekly MVPA at 12 months between the groups recorded in ≥10 min bouts (mean difference 11.8 min of MVPA, 95% CI: -2.1 to 26.0; p=0.10) or without bouts (mean difference 13.7 min of MVPA, 95% CI: -26.8 to 54.2; p=0.51) for 232 participants with usable data. There was no difference in the primary or secondary PA outcomes at 4 or 12 months. CONCLUSION: Augmenting ERS referrals with web-based behavioural support had only a weak, non-significant effect on MVPA. TRIAL REGISTRATION NUMBER: ISRCTN15644451

Visible, Near-Infrared, and Mid-Infrared Spectral Characterization of Hawaiian Fumarolic Alteration Near Kilauea's December 1974 Flow: Implications for Spectral Discrimination of Alteration Environments on Mars

The December 1974 flow in the SW rift zone at Kilauea Volcano, Hawaii, has been established as a Mars analog due to its physical, chemical, and morphological properties, as well as its interaction with the outgassing plume from the primary Kilauea caldera. We focus on a solfatara site that consists of hydrothermally altered basalt and alteration products deposited in and around a passively degassing volcanic vent situated directly adjacent to the December 1974 flow on its northwest side. Reflectance spectra are acquired in the visible/near-infrared (VNIR) region and emission spectra in the mid-infrared (MIR) range to better understand the spectral properties of hydrothermally altered materials. The VNIR signatures are consistent with silica, Fe-oxides, and sulfates (Ca, Fe). Primarily silica-dominated spectral signatures are observed in the MIR and changes in spectral features between samples appear to be driven by grain size effects in this wavelength range. The nature of the sample coating and the thermal emission signatures exhibit variations that may be correlated with distance from the vent. Chemical analyses indicate that most surfaces are characterized by silica-rich material, Fe-oxides, and sulfates (Ca, Fe). The silica and Fe-oxide-dominated MIR/VNIR spectral signatures exhibited by the hydrothermally altered material in this study are distinct from the sulfate-dominated spectral signatures exhibited by previously studied low-temperature aqueous acid-sulfate weathered basaltic glass. This likely reflects a difference in open vs. closed system weathering, where mobile cations are removed from the altered surfaces in the fumarolic setting. This work provides a unique infrared spectral library that includes martian analog materials that were altered in an active terrestrial solfatara (hydrothermal) setting. Hydrothermal environments are of particular interest as they potentially indicate habitable conditions. Key constraints on the habitability and astrobiological potential of ancient aqueous environments are provided through detection and interpretation of secondary mineral assemblages; thus, spectral detection of fumarolic alteration assemblages observed from this study on Mars would suggest a region that could have hosted a habitable environment