Porous silica beads produced by nanofluid emulsion freezing

It is shown that porous spherical particles can be obtained via the freezing of silica nanoparticle aqueous suspensions emulsified in a continuous oil phase. After two freeze-thaw cycles, nanoparticles turn aggregated into flocculated objects with microstructure that depends upon emulsion volume fraction and droplet size. For low volume fractions, regular microspheres are produced while for large ones, irregular beads with several tens of micrometer radius are formed. Electronic microscopy, mercury porosimetry and nitrogen adsorption are used to get insights into these porous particles typical radius, pore size distribution, surface area and pore network structure. All exhibit mesopores that result from inter-nanoparticle spacing after flocculation. An unexpected macroporous domain appears which is not observed when drying non-emulsified suspensions. This macroporosity is interpreted as the signature of dendrite formation during the undercooled period, right before freezing occurs. Beside this additional macroporosity, the protocols presented in this article constitute also promising emulsion-based routes for porous material synthesis with original geometry, chemical composition and porosity.Comment: 20 pages, 8 figure

Microstructure Formation in Freezing Nanosuspension Droplets

The structural evolution of suspensions upon freezing is studied with optical microscopy in a suspended droplet configuration. Droplets have millimeter size and consist in an aqueous mixture of silica particles while the surroundings phase is hexane. Freeze-thaw cycles are applied to this system and a two-step freezing mechanism evidenced. A fast adiabatic growth of dendrites that invade the full droplets is first observed, and occurs within a few milliseconds. Then a slow process lasts for several seconds and corresponds to the release of solidification latent heat into the hexane phase. The striking feature of this work is to evidence that after the first freeze-thaw cycle flocculated microstructures are generated. When a second cycle is performed, microstructures further flocculate and generate, for dense silica suspensions, stable porous spheres of the size of the droplets. A phenomenological description based on repulsion or engulfment of particles by solidifying ice fronts is proposed

Investigation of cement substitution by blends of calcined clays and limestone

This thesis investigates the replacement of Portland cement by addition of high amounts of calcined clays and limestone. Such ternary blends can become more ecological and economical binders to answer the worldwide housing shortage. It could be demonstrated that up to 60% of cement could be replaced by such combined addition of pure metakaolin and limestone with acceptable compressive strengths after 7 and 28 days. With natural clays, with about 50% kaolinite content, cement can still be replaced by 45% with mixtures of calcined clays and limestone without significantly impairing strength development. The good compressive strengths obtained at 7 and 28 days have been explained by the synergetic formation of carboaluminates phases and the porosity refinement. The aluminates from the metakaolin react together with the carbonates from the limestone and calcium hydroxide, from cement hydration and could be confirmed by thermodynamic calculations. The synergetic reaction could be optimized by carefully adjusting the sulfate content and controlling the alkali content of the cement. The durability aspects of these novel blends were studied. The STADIUM ® multiionic transport model has been used and successfully adapted to the specificities of our materials. The ternary blends have very low ionic diffusion coefficients, more than one order of magnitude lower than Portland cement. These explain the good resistance to chloride ingress observed in ponding tests. Carbonation resistance was also investigated. The first results tend to demonstrate that the ternary blends have somewhat lower carbonation resistance than Portland cement, due to the lower Portlandite content. However, in the short term investigated here, performance in natural carbonation condition is still good. Accelerated carbonation leads to the formation of aragonite rather than calcite in the blended system. The different densities of these polymorphs means that the porosity after carbonation will be higher in the accelerated conditions than in natural carbonation. Considering that the rate of carbonation in the long term is determined by the diffusion through the carbonated structure, this indicates that accelerated tests are likely to overestimate long term rates of carbonation

Molecular Dynamics Thermal Conductivity Computation of a Quantum Cascade Laser Diode Super-Lattice

This paper reports work in which molecular dynamics are used to simulate a single cascade of a quantum cascade laser diode with the intent of computing the effective thermal conductivity in the cross-plane direction. The Tersoff potential is used with coefficients found from the literature for inter-atomic forces, and the Green-Kubo relation is used to compute the conductivity from the integral of the system heat flux autocorrelation. The computed conductivity lies in the same range as measurements found in the literature

A multi-domain group-based intervention to promote physical activity, healthy nutrition and psychological wellbeing in older people with losses in intrinsic capacity: AMICOPE development study

The World Health Organization has developed the Integrated Care of Older People (ICOPE) strategy, a program based on the measurement of intrinsic capacity (IC) as 'the composite of all physical and mental attributes on which an individual can draw'. Multicomponent interventions appear to be the most effective approach to enhance IC and to prevent frailty and disability since adapted physical activity is the preventive intervention that has shown the most evidence in the treatment of frailty and risk of falls. Our paper describes the development of a multi-domain group-based intervention addressed to older people living in the community, aimed at improving and/or maintaining intrinsic capacity by means of promoting physical activity, healthy nutrition, and psychological wellbeing in older people. The process of intervention development is described following the Guidance for reporting intervention development studies in health research (GUIDED). The result of this study is the AMICOPE intervention (Aptitude Multi-domain group-based intervention to improve and/or maintain IC in Older PEople) built upon the ICOPE framework and described following the Template for Intervention Description and Replication (TIDieR) guidelines. The intervention consists of 12 face-to-face sessions held weekly for 2.5 h over three months and facilitated by a pair of health and social care professionals. This study represents the first stage of the UK Medical Research Council framework for developing and evaluating a complex intervention. The next step should be carrying out a feasibility study for the AMICOPE intervention and, at a later stage, assessing the effectiveness in a randomized controlled trial.This research was funded by the program POCTEFA (European Union) in the context of the APTITUDE project, reference EFA232/16. Nicolás Martínez-Velilla received funding from La Caixa Foundation (ID 100010434), under agreement LCF/PR/PR15/51100006

Reactivity tests for supplementary cementitious materials: RILEM TC 267-TRM phase 1

A primary aim of RILEM TC 267-TRM: “Tests for Reactivity of Supplementary Cementitious Materials (SCMs)” is to compare and evaluate the performance of conventional and novel SCM reactivity test methods across a wide range of SCMs. To this purpose, a round robin campaign was organized to investigate 10 different tests for reactivity and 11 SCMs covering the main classes of materials in use, such as granulated blast furnace slag, fly ash, natural pozzolan and calcined clays. The methods were evaluated based on the correlation to the 28 days relative compressive strength of standard mortar bars containing 30% of SCM as cement replacement and the interlaboratory reproducibility of the test results. It was found that only a few test methods showed acceptable correlation to the 28 days relative strength over the whole range of SCMs. The methods that showed the best reproducibility and gave good correlations used the R3 model system of the SCM and Ca(OH)2, supplemented with alkali sulfate/carbonate. The use of this simplified model system isolates the reaction of the SCM and the reactivity can be easily quantified from the heat release or bound water content. Later age (90 days) strength results also correlated well with the results of the IS 1727 (Indian standard) reactivity test, an accelerated strength test using an SCM/Ca(OH)2-based model system. The current standardized tests did not show acceptable correlations across all SCMs, although they performed better when latently hydraulic materials (blast furnace slag) were excluded. However, the Frattini test, Chapelle and modified Chapelle test showed poor interlaboratory reproducibility, demonstrating experimental difficulties. The TC 267-TRM will pursue the development of test protocols based on the R3 model systems. Acceleration and improvement of the reproducibility of the IS 1727 test will be attempted as well

Extended Coagulation Profiling in Isolated Traumatic Brain Injury:A CENTER-TBI Analysis

Background: Trauma-induced coagulopathy in traumatic brain injury (TBI) remains associated with high rates of complications, unfavorable outcomes, and mortality. The underlying mechanisms are largely unknown. Embedded in the prospective multinational Collaborative European Neurotrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study, coagulation profiles beyond standard conventional coagulation assays were assessed in patients with isolated TBI within the very early hours of injury. Methods: Results from blood samples (citrate/EDTA) obtained on hospital admission were matched with clinical and routine laboratory data of patients with TBI captured in the CENTER-TBI central database. To minimize confounding factors, patients with strictly isolated TBI (iTBI) (n = 88) were selected and stratified for coagulopathy by routine international normalized ratio (INR): (1) INR &lt; 1.2 and (2) INR ≥ 1.2. An INR &gt; 1.2 has been well adopted over time as a threshold to define trauma-related coagulopathy in general trauma populations. The following parameters were evaluated: quick’s value, activated partial thromboplastin time, fibrinogen, thrombin time, antithrombin, coagulation factor activity of factors V, VIII, IX, and XIII, protein C and S, plasminogen, D-dimer, fibrinolysis-regulating parameters (thrombin activatable fibrinolysis inhibitor, plasminogen activator inhibitor 1, antiplasmin), thrombin generation, and fibrin monomers. Results: Patients with iTBI with INR ≥ 1.2 (n = 16) had a high incidence of progressive intracranial hemorrhage associated with increased mortality and unfavorable outcome compared with patients with INR &lt; 1.2 (n = 72). Activity of coagulation factors V, VIII, IX, and XIII dropped on average by 15–20% between the groups whereas protein C and S levels dropped by 20%. With an elevated INR, thrombin generation decreased, as reflected by lower peak height and endogenous thrombin potential (ETP), whereas the amount of fibrin monomers increased. Plasminogen activity significantly decreased from 89% in patients with INR &lt; 1.2 to 76% in patients with INR ≥ 1.2. Moreover, D-dimer levels significantly increased from a mean of 943 mg/L in patients with INR &lt; 1.2 to 1,301 mg/L in patients with INR ≥ 1.2. Conclusions: This more in-depth analysis beyond routine conventional coagulation assays suggests a counterbalanced regulation of coagulation and fibrinolysis in patients with iTBI with hemostatic abnormalities. We observed distinct patterns involving key pathways of the highly complex and dynamic coagulation system that offer windows of opportunity for further research. Whether the changes observed on factor levels may be relevant and explain the worse outcome or the more severe brain injuries by themselves remains speculative.</p

Rehabilitation and outcomes after complicated vs uncomplicated mild TBI:results from the CENTER-TBI study

Background: Despite existing guidelines for managing mild traumatic brain injury (mTBI), evidence-based treatments are still scarce and large-scale studies on the provision and impact of specific rehabilitation services are needed. This study aimed to describe the provision of rehabilitation to patients after complicated and uncomplicated mTBI and investigate factors associated with functional outcome, symptom burden, and TBI-specific health-related quality of life (HRQOL) up to six months after injury. Methods: Patients (n = 1379) with mTBI from the Collaborative European NeuroTrauma Effectiveness Research in TBI (CENTER-TBI) study who reported whether they received rehabilitation services during the first six months post-injury and who participated in outcome assessments were included. Functional outcome was measured with the Glasgow Outcome Scale – Extended (GOSE), symptom burden with the Rivermead Post Concussion Symptoms Questionnaire (RPQ), and HRQOL with the Quality of Life after Brain Injury – Overall Scale (QOLIBRI-OS). We examined whether transition of care (TOC) pathways, receiving rehabilitation services, sociodemographic (incl. geographic), premorbid, and injury-related factors were associated with outcomes using regression models. For easy comparison, we estimated ordinal regression models for all outcomes where the scores were classified based on quantiles. Results: Overall, 43% of patients with complicated and 20% with uncomplicated mTBI reported receiving rehabilitation services, primarily in physical and cognitive domains. Patients with complicated mTBI had lower functional level, higher symptom burden, and lower HRQOL compared to uncomplicated mTBI. Rehabilitation services at three or six months and a higher number of TOC were associated with unfavorable outcomes in all models, in addition to pre-morbid psychiatric problems. Being male and having more than 13 years of education was associated with more favorable outcomes. Sustaining major trauma was associated with unfavorable GOSE outcome, whereas living in Southern and Eastern European regions was associated with lower HRQOL. Conclusions: Patients with complicated mTBI reported more unfavorable outcomes and received rehabilitation services more frequently. Receiving rehabilitation services and higher number of care transitions were indicators of injury severity and associated with unfavorable outcomes. The findings should be interpreted carefully and validated in future studies as we applied a novel analytic approach. Trial registration: ClinicalTrials.gov NCT02210221.</p

The burden of traumatic brain injury from low-energy falls among patients from 18 countries in the CENTER-TBI Registry: A comparative cohort study.

BACKGROUND: Traumatic brain injury (TBI) is an important global public health burden, where those injured by high-energy transfer (e.g., road traffic collisions) are assumed to have more severe injury and are prioritised by emergency medical service trauma triage tools. However recent studies suggest an increasing TBI disease burden in older people injured through low-energy falls. We aimed to assess the prevalence of low-energy falls among patients presenting to hospital with TBI, and to compare their characteristics, care pathways, and outcomes to TBI caused by high-energy trauma. METHODS AND FINDINGS: We conducted a comparative cohort study utilising the CENTER-TBI (Collaborative European NeuroTrauma Effectiveness Research in TBI) Registry, which recorded patient demographics, injury, care pathway, and acute care outcome data in 56 acute trauma receiving hospitals across 18 countries (17 countries in Europe and Israel). Patients presenting with TBI and indications for computed tomography (CT) brain scan between 2014 to 2018 were purposively sampled. The main study outcomes were (i) the prevalence of low-energy falls causing TBI within the overall cohort and (ii) comparisons of TBI patients injured by low-energy falls to TBI patients injured by high-energy transfer-in terms of demographic and injury characteristics, care pathways, and hospital mortality. In total, 22,782 eligible patients were enrolled, and study outcomes were analysed for 21,681 TBI patients with known injury mechanism; 40% (95% CI 39% to 41%) (8,622/21,681) of patients with TBI were injured by low-energy falls. Compared to 13,059 patients injured by high-energy transfer (HE cohort), the those injured through low-energy falls (LE cohort) were older (LE cohort, median 74 [IQR 56 to 84] years, versus HE cohort, median 42 [IQR 25 to 60] years; p < 0.001), more often female (LE cohort, 50% [95% CI 48% to 51%], versus HE cohort, 32% [95% CI 31% to 34%]; p < 0.001), more frequently taking pre-injury anticoagulants or/and platelet aggregation inhibitors (LE cohort, 44% [95% CI 42% to 45%], versus HE cohort, 13% [95% CI 11% to 14%]; p < 0.001), and less often presenting with moderately or severely impaired conscious level (LE cohort, 7.8% [95% CI 5.6% to 9.8%], versus HE cohort, 10% [95% CI 8.7% to 12%]; p < 0.001), but had similar in-hospital mortality (LE cohort, 6.3% [95% CI 4.2% to 8.3%], versus HE cohort, 7.0% [95% CI 5.3% to 8.6%]; p = 0.83). The CT brain scan traumatic abnormality rate was 3% lower in the LE cohort (LE cohort, 29% [95% CI 27% to 31%], versus HE cohort, 32% [95% CI 31% to 34%]; p < 0.001); individuals in the LE cohort were 50% less likely to receive critical care (LE cohort, 12% [95% CI 9.5% to 13%], versus HE cohort, 24% [95% CI 23% to 26%]; p < 0.001) or emergency interventions (LE cohort, 7.5% [95% CI 5.4% to 9.5%], versus HE cohort, 13% [95% CI 12% to 15%]; p < 0.001) than patients injured by high-energy transfer. The purposive sampling strategy and censorship of patient outcomes beyond hospital discharge are the main study limitations. CONCLUSIONS: We observed that patients sustaining TBI from low-energy falls are an important component of the TBI disease burden and a distinct demographic cohort; further, our findings suggest that energy transfer may not predict intracranial injury or acute care mortality in patients with TBI presenting to hospital. This suggests that factors beyond energy transfer level may be more relevant to prehospital and emergency department TBI triage in older people. A specific focus to improve prevention and care for patients sustaining TBI from low-energy falls is required.CENTER-TBI was supported by the European Union 7th Framework program (EC grant 602150), recipient A.I.R. Maas. Additional funding was obtained from the Hannelore Kohl Stiftung (Germany) - recipient A.I.R. Maas, from OneMind (USA) - recipient A.I.R. Maas and from Integra LifeSciences Corporation (USA) - recipient A.I.R. Maas. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript