Nanostructure of CaO-(Na2O)-Al2O3-SiO2-H2O gels revealed by multinuclear solid-state magic angle spinning and multiple quantum magic angle spinning nuclear magnetic resonance spectroscopy

(Calcium,alkali)-aluminosilicate gel frameworks are the basis of modern cements and alkali-activated materials for sustainable infrastructure and radioactive waste immobilization and also find application in glass alteration, mineral weathering, and zeolite synthesis. Here, we resolve the nanostructure of these gels that dictates mass transport, solubility, and mechanical properties. The key structural motifs comprising hydrous (calcium,alkali)-aluminosilicate gels are identified via 17O, 23Na, and 27Al triple-quantum magic angle spinning and 29Si magic angle spinning nuclear magnetic resonance spectroscopy of a novel class of stoichiometrically controlled 17O-enriched multiphase gels. Increased Ca content promotes low-Al, high-Ca chain-structured “C-S-H-type” products exhibiting significant nanostructural ordering, low levels of chain cross-linking, predominant Ca coordination of nonbridging oxygen atoms, and an increase in proton association with CaO layers to form Ca–OH sites. Al substitution is identified in multiple sites in the silicate chains, including cross-linking, bridging, and pairing tetrahedra. Increased Al content increases the proportion of cross-linking sites and gel disorder. The large increase in SiIV–O–AlIV sites increases the relative amounts of Na+ and AlV species charge-balancing AlO4– tetrahedra and results in the formation of an additional disordered low-calcium, framework-structured alkali aluminosilicate (“N-A-S-H-type”) gel, with high Al and Na contents. Changes in bulk composition significantly alter the nanostructures of the C-S-H-type and N-A-S-H-type gels. Mean SiIV–O–AlIV bond angles for each type of AlIV site environment are highly consistent, with compositional changes dictating the relative proportions of individual AlIV species but not altering the local structure of each AlIV site. These findings reveal the molecular interactions governing the (calcium,alkali)-aluminosilicate gel nanostructure, which are crucial in controlling material properties and durability

Furthering the understanding of silicate-substitution in α-tricalcium phosphate : an X-ray diffraction, X-ray fluorescence and solid-state nuclear magnetic resonance study

High-purity (SupT) and reagent-grade (ST), stoichiometric and silicate-containing α-tricalcium phosphate (α-TCP: ST0/SupT0 and Si-TCP x = 0.10: ST10/SupT10) were prepared by solid-state reaction based on the substitution mechanism Ca3(PO4)(2-x)(SiO4)x. Samples were determined to be phase pure by X-ray diffraction (XRD), and Rietveld analysis performed on the XRD data confirmed inclusion of Si in the α-TCP structure as determined by increases in unit cell parameters; particularly marked increases in the b-axis and β-angle were observed. X-ray fluorescence (XRF) confirmed the presence of expected levels of Si in Si-TCP compositions as well as significant levels of impurities (Mg, Al and Fe) present in all ST samples; SupT samples showed both expected levels of Si and a high degree of purity. Phosphorus (31P) magic-angle-spinning solid-state nuclear magnetic resonance (MAS NMR) measurements revealed that the high-purity reagents used in the synthesis of SupT0 can resolve the 12 expected peaks in the 31P spectrum of α-TCP compared to the low-purity ST0 that showed significant spectral line broadening; line broadening was also observed with the inclusion of Si which is indicative of induced structural disorder. Silicon (29Si) MAS NMR was also performed on both Si-TCP samples which revealed Q0 species of Si with additional Si Q1/Q2 species that may indicate a potential charge-balancing mechanism involving the inclusion of disilicate groups; additional Q4 Si species were also observed, but only for ST10. Heating and cooling rates were briefly investigated by 31P MAS NMR which showed no significant line broadening other than that associated with the emergence of β-TCP which was only realised with the reagent-grade sample ST0. This study provides an insight into the structural effects of Si-substitution in α-TCP and could provide a basis for understanding how substitution affects the physicochemical properties of the material

Improved Understanding of Atomic Ordering in Y4SixAl2- xO9- xNxMaterials Using a Combined Solid-State NMR and Computational Approach

Ceramics based around silicon aluminum oxynitrides are of both fundamental structural chemistry and technological interest. Certain oxynitride crystal structures allow very significant compositional variation through extensive Si/N exchange for Al/O, which implies a degree of atomic ordering. In this study, solid-state 29Si MAS NMR and variable field 1D and 2D 27Al MAS NMR measurements are combined with density functional theory calculations of both the structural and NMR interaction parameters for various points across the Y4Si2O7N2-Y4Al2O9 compositional range. This series provides numerous possibilities for significant variation of atomic ordering in the local ditetrahedral (Si,Al)2O7-xNx units. The two slightly structurally inequivalent aluminum sites in Y4Al2O9 are unambiguously assigned to the observed resonances. Computational findings on Y4Si2O7N2 demonstrate that the single observed 29Si NMR resonance covers a range of local inequivalent silicon environments. For the first time, the MAS NMR and neutron diffraction data from the Y4SiAlO8N structure have been directly reconciled, thus establishing aspects of atomic order and disorder that characterize this system. This comparison suggests that, although the diffraction data indicates long-range structural order supporting a highly crystalline character, the short-range information afforded by the solid-state NMR measurements indicates significant atomic disorder throughout the (Si,Al)2O7-xNx units

Cold sintering of bioglass and bioglass/polymer composites

Bioactive glasses are widely utilized to regenerate bone tissue and aid bonding of orthopedic implants. Forming composites of bioglass with bioactive polymers allow the mechanical properties and biological response to be tailored. Although several methods for creating bioglass–polymer composites exist, they require dissolution of the polymer, controlled phase separation, and appear to have an upper limit of ∼30 vol.% bioglass. Cold sintering is a novel technique for the densification of ceramics and glasses which utilizes a liquid phase and pressure to allow the production of components at reduced temperatures. We demonstrate that cold sintering (100°C) of Bioglass 45S5 powder produced via flame spray pyrolysis and the fabrication of Bioglass 45S5–polymer composites. Assessment of the in vitro response revealed that composites were not cytotoxic. Solid-state 31P and 29Si MAS NMR studies of the silicon and phosphorus speciation in the glass powder, as-received, wetted, and sintered samples show similarities to reactions expected when bioglass is implanted in the body which along with Raman spectroscopy data gave insight into the cold sintering densification mechanism

Sex-related differences in oncologic outcomes, operative complications and health-related quality of life after curative-intent oesophageal cancer treatment: multicentre retrospective analysis.

Oesophageal cancer, in particular adenocarcinoma, has a strong male predominance. However, the impact of patient sex on operative and oncologic outcomes and recovery of health-related quality of life is poorly documented, and was the focus of this large multicentre cohort study. All consecutive patients who underwent oncological oesophagectomy from 2009 to 2015 in the 20 European iNvestigation of SUrveillance after Resection for Esophageal cancer study group centres were assessed. Clinicopathologic variables, therapeutic approach, postoperative complications, survival and health-related quality of life data were compared between male and female patients. Multivariable analyses adjusted for age, sex, tumour histology, treatment protocol and major complications. Specific subgroup analyses comparing adenocarcinoma versus squamous cell cancer for all key outcomes were performed. Overall, 3974 patients were analysed, 3083 (77.6%) male and 891 (22.4%) female; adenocarcinoma was predominant in both groups, while squamous cell cancer was observed more commonly in female patients (39.8% versus 15.1%, P < 0.001). Multivariable analysis demonstrated improved outcomes in female patients for overall survival (HRmales 1.24, 95% c.i. 1.07 to 1.44) and disease-free survival (HRmales 1.22, 95% c.i. 1.05 to 1.43), which was caused by the adenocarcinoma subgroup, whereas this difference was not confirmed in squamous cell cancer. Male patients presented higher health-related quality of life functional scores but also a higher risk of financial problems, while female patients had lower overall summary scores and more persistent gastrointestinal symptoms. This study reveals uniquely that female sex is associated with more favourable long-term survival after curative treatment for oesophageal cancer, especially adenocarcinoma, although long-term overall and gastrointestinal health-related quality of life are poorer in women

Characterization of and structural insight into struvite-K, MgKPO4·6H2O, an analogue of struvite

Struvite-K (MgKPO4·6H2O) is a magnesium potassium phosphate mineral with naturally cementitious properties, which is finding increasing usage as an inorganic cement for niche applications including nuclear waste management and rapid road repair. Struvite-K is also of interest in sustainable phosphate recovery from wastewater and, as such, a detailed knowledge of the crystal chemistry and high-temperature behavior is required to support further laboratory investigations and industrial applications. In this study, the local chemical environments of synthetic struvite-K were investigated using high-field solid-state 25Mg and 39K MAS NMR techniques, alongside 31P MAS NMR and thermal analysis. A single resonance was present in each of the 25Mg and 39K MAS NMR spectra, reported here for the first time alongside the experimental and calculated isotropic chemical shifts, which were comparable to the available data for isostructural struvite (MgNH4PO4·6H2O). An in situ high-temperature XRD analysis of struvite-K revealed the presence of a crystalline–amorphous–crystalline transition that occurred between 30 and 350 °C, following the single dehydration step of struvite-K. Between 50 and 300 °C, struvite-K dehydration yielded a transient disordered (amorphous) phase identified here for the first time, denoted δ-MgKPO4. At 350 °C, recrystallization was observed, yielding β-MgKPO4, commensurate with an endothermic DTA event. A subsequent phase transition to γ-MgKPO4 was observed on further heating, which reversed on cooling, resulting in the α-MgKPO4 structure stabilized at room temperature. This behavior was dissimilar from that of struvite exposed to high temperature, where NH4 liberation occurs at temperatures >50 °C, indicating that struvite-K could potentially withstand high temperatures via a transition to MgKPO4

Multimodality treatment for esophageal adenocarcinoma: Multi-center propensity-score matched study

Background: The primary aim of this study was to compare survival from neoadjuvant chemoradiotherapy plus surgery (NCRS) versus neoadjuvant chemotherapy plus surgery (NCS) for the treatment of esophageal or junctional adenocarcinoma. The secondary aims were to compare pathological effects, short-term mortality and morbidity, and to evaluate the effect of lymph node harvest upon survival in both treatment groups. Methods: Data were collected from 10 European centers from 2001 to 2012. Six hundred and eight patients with stage II or III oesophageal or oesophago-gastric junctional adenocarcinoma were included; 301 in the NCRS group and 307 in the NCS group. Propensity score matching and Cox regression analyses were used to compensate for

Gamma-ray Observations Under Bright Moonlight with VERITAS

Imaging atmospheric Cherenkov telescopes (IACTs) are equipped with sensitive photomultiplier tube (PMT) cameras. Exposure to high levels of background illumination degrades the efficiency of and potentially destroys these photo-detectors over time, so IACTs cannot be operated in the same configuration in the presence of bright moonlight as under dark skies. Since September 2012, observations have been carried out with the VERITAS IACTs under bright moonlight (defined as about three times the night-sky-background (NSB) of a dark extragalactic field, typically occurring when Moon illumination > 35%) in two observing modes, firstly by reducing the voltage applied to the PMTs and, secondly, with the addition of ultra-violet (UV) bandpass filters to the cameras. This has allowed observations at up to about 30 times previous NSB levels (around 80% Moon illumination), resulting in 30% more observing time between the two modes over the course of a year. These additional observations have already allowed for the detection of a flare from the 1ES 1727+502 and for an observing program targeting a measurement of the cosmic-ray positron fraction. We provide details of these new observing modes and their performance relative to the standard VERITAS observations

Biomarkers and heart failure events in patients with atrial fibrillation in the ARISTOTLE trial evaluated by a multistate model

Background: Atrial fibrillation (AF) and heart failure (HF) often coexist. We investigated the prognostic impact of biomarkers on the development of HF and death in patients with AF and different left ventricular systolic function considering the influence of competing events. Methods: The study included 11,818 patients with AF from the ARISTOTLE trial who at entry had information on history of HF, an estimate of left ventricular function and plasma samples for determination of biomarkers representing cardiorenal dysfunction (NT-proBNP, troponin T, cystatin C) and inflammation (GDF-15, IL-6, CRP). Patients were categorized into: (I) HF with reduced ejection fraction (HFrEF, n=2,048), (II) HF with preserved ejection fraction (HFpEF, n=2,520), and (III) No HF (n=7,250). Biomarker associations with HF hospitalization and death were analyzed using a multi-state model accounting also for repeated events. Results: Baseline levels of NT-proBNP, troponin T, cystatin C, GDF-15, IL-6, and CRP were highest in HFrEF and lowest in No HF. During median 1.9 years follow-up, 546 patients were hospitalized at least once for HF and 819 died. Higher levels of all investigated biomarkers were associated with both outcomes (all p<0.0001), with highest event rates in HFrEF and lowest in No HF. The associations remained after adjustments and were more pronounced for first than for recurrent events. Conclusions: In anticoagulated patients with AF, biomarkers indicating cardiorenal dysfunction and inflammation improve the identification of patients at risk of developing HF or worsening of already existing HF. These biomarkers might be useful for targeting novel HF therapies in patients with AF

Some aspects of the Liouville equation in mathematical physics and statistical mechanics

This paper presents some mathematical aspects of Classical Liouville theorem and we have noted some mathematical theorems about its initial value problem. Furthermore, we have implied on the formal frame work of Stochastic Liouville equation (SLE)