21 research outputs found
Nano-scale hydrogen-bond network improves the durability of greener cements
More than ever before, the world's increasing need for new infrastructure demands the construction of efficient, sustainable and durable buildings, requiring minimal climate-changing gas-generation in their production. Maintenance-free âgreenerâ building materials made from blended cements have advantages over ordinary Portland cements, as they are cheaper, generate less carbon dioxide and are more durable. The key for the improved performance of blends (which substitute fine amorphous silicates for cement) is related to their resistance to water penetration. The mechanism of this water resistance is of great environmental and economical impact but is not yet understood due to the complexity of the cement's hydration reactions. Using neutron spectroscopy, we studied a blend where cement was replaced by ash from sugar cane residuals originating from agricultural waste. Our findings demonstrate that the development of a distinctive hydrogen bond network at the nano-scale is the key to the performance of these greener materials
An exploratory randomised controlled trial of a premises-level intervention to reduce alcohol-related harm including violence in the United Kingdom
<b>Background</b><p></p>
To assess the feasibility of a randomised controlled trial of a licensed premises intervention to reduce severe intoxication and disorder; to establish effect sizes and identify appropriate approaches to the development and maintenance of a rigorous research design and intervention implementation.<p></p>
<b>Methods</b><p></p>
An exploratory two-armed parallel randomised controlled trial with a nested process evaluation. An audit of risk factors and a tailored action plan for high risk premises, with three month follow up audit and feedback. Thirty-two premises that had experienced at least one assault in the year prior to the intervention were recruited, match paired and randomly allocated to control or intervention group. Police violence data and data from a street survey of study premisesâ customers, including measures of breath alcohol concentration and surveyor rated customer intoxication, were used to assess effect sizes for a future definitive trial. A nested process evaluation explored implementation barriers and the fidelity of the intervention with key stakeholders and senior staff in intervention premises using semi-structured interviews.<p></p>
<b>Results</b><p></p>
The process evaluation indicated implementation barriers and low fidelity, with a reluctance to implement the intervention and to submit to a formal risk audit. Power calculations suggest the intervention effect on violence and subjective intoxication would be raised to significance with a study size of 517 premises.<p></p>
<b>Conclusions</b><p></p>
It is methodologically feasible to conduct randomised controlled trials where licensed premises are the unit of allocation. However, lack of enthusiasm in senior premises staff indicates the need for intervention enforcement, rather than voluntary agreements, and on-going strategies to promote sustainability
Mathematical Modelling of Cell-Fate Decision in Response to Death Receptor Engagement
Cytokines such as TNF and FASL can trigger death or survival depending on cell lines and cellular conditions. The mechanistic details of how a cell chooses among these cell fates are still unclear. The understanding of these processes is important since they are altered in many diseases, including cancer and AIDS. Using a discrete modelling formalism, we present a mathematical model of cell fate decision recapitulating and integrating the most consistent facts extracted from the literature. This model provides a generic high-level view of the interplays between NFÎșB pro-survival pathway, RIP1-dependent necrosis, and the apoptosis pathway in response to death receptor-mediated signals. Wild type simulations demonstrate robust segregation of cellular responses to receptor engagement. Model simulations recapitulate documented phenotypes of protein knockdowns and enable the prediction of the effects of novel knockdowns. In silico experiments simulate the outcomes following ligand removal at different stages, and suggest experimental approaches to further validate and specialise the model for particular cell types. We also propose a reduced conceptual model implementing the logic of the decision process. This analysis gives specific predictions regarding cross-talks between the three pathways, as well as the transient role of RIP1 protein in necrosis, and confirms the phenotypes of novel perturbations. Our wild type and mutant simulations provide novel insights to restore apoptosis in defective cells. The model analysis expands our understanding of how cell fate decision is made. Moreover, our current model can be used to assess contradictory or controversial data from the literature. Ultimately, it constitutes a valuable reasoning tool to delineate novel experiments
The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy
Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations.
Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (>â90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves.
Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45â85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations >â90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SEâ=â0.013, pââ90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score.
Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care
Neutron Time-of-Flight Quantification of Water Desorption Isotherms of Montmorillonite
The multiple energy states of water held by surfaces of a clay mineral can be effectively probed with time-of-flight and fixed elastic window neutron scattering. We used these techniques to quantitatively differentiate water types, including rotational and translational diffusions, in Ca- and Na-montmorillonite (SAz-1) and charge-reduced preparations equilibrated at RH = 33% and 55%, whose gravimetric water contents are in proportion with their layer charge. Quasi-elastic neutron scattering results revealed significant differences within interlayer water populations and between interlayer and interparticle waters. Interlayer cationic and H-bonded waters have residence times ranging from a few nanoseconds to tenths of picoseconds, while interparticle water, obtained for the RH = 55% equilibrated samples, showed an average diffusivity faster than interlayer water, yet slower than bulk water. Our results enabled us to differentiate at least two water motions during dehydration of Ca- and Na-SAz-1 (initially equilibrated at RH = 55%) by using a "controlled water loss" time-of-flight procedure. This work confirms that (a) interlayer and cationic water in dioctahedral smectites are characterized by slower motions than interparticle water, (b) interlayer cations influenced the dynamics of water loss, probably through its affect on clay fabric, and (c) interparticle water behaves more like bulk water. At 55% RH the Ca montmorillonite held more interparticle water, but on dehydration under controlled conditions, it retained interlayer and cationic water more strongly than Na montmorillonite. © 2012 American Chemical Society.Will P. Gates, Heloisa N. Bordallo, Laurence P. Aldridge, Tilo Seydel Henrik Jacobsen, Virginie Marry, and G. Jock Churchma
Two Forms of Ice Identified in Mars-like Clay Using Neutron Spectroscopy
The capacity of clay minerals to store large amounts
of water is
utilized in a number of industrial and environmental applications
on Earth, for example, as components in geosynthetic clay liners in
landfills or ingredients in water-based drilling fluids, and could
prove important on Mars to identify future human landing sites where
water could be harvested. The subzero behavior of water interacting
within the interlayer space of clay minerals is of particular interest
in most applications but remains poorly understood. To better understand
the hydrothermal mechanism by which water ice bonds and separates
from clay interlayers, we have utilized neutron spectroscopy, spectral
analysis, and phonon band assignment. The inelastic neutron scattering
from sodium montmorillonite, hydrated at 24, 73, and 166% water content,
as well as an oven-dried sample, were measured to assess the vibrational
density of states. The water contents studied provide a range of pore
dimensions within clay gels that have varying degrees of confinement.
The type of ice formed from water held in larger intra- and interparticle
pores differs substantially from that confined within the interlayer
(pseudo-two-layer hydrate), and the differences vary with hydration
level. Spectral subtraction over an energy transfer range 50 E â1 (8 E < 70 meV) produces clearly two different forms of ice: hexagonal
and cubic in the two wetter samples. A form of interfacial ice, presumably
of a lower density, is observed in the vibrational density of states
spectrum of the sample hydrated to a pseudo-two-layer hydrate (ie
24% gravimetric water content (GWC), 10 H2O/Na+). No hexagonal or cubic ice is observed in this sample. The four
vibrational modes within the translation band of hexagonal ice are
apparent within the sample hydrated to 166% gravimetric water content,
in which pores greater than 20 nm are largely water-filled. By considering
hydrogen bonding of the water to the clay surface, our data indicate
an increase in the strength of the H-bond due to a shorter distance
to the hydroxyl. We attribute this decrease to the pores in the clay
generating a localized negative pressure or âsuctionâ
effect, thus attracting the water