Super High Strength Metabentonite Based Geopolymer

AbstractThe paper presents the results of the study on the effects of the combination of the low liquid/solid (l/s) ratio and pressure compaction of the fresh pastes on the properties of the hardened based geopolymer paste. It is very well known that the mentioned combination gives the possibility to prepare cement composites with the excellent engineering properties. The object of the study was the metabentonite based geopolymer. The results obtained shown the metabentonite based geopolymer prepared under the combination of the low l/s ratio value and pressure compaction as a super strength material. This strength effect was evidently a consequence of the found high dense nano- or near-nano pore structure of the geopolymer

Estudio de caso. Transformation of Multilingual Practices: Contradictions Between Thought and Action. A Case Study

This article presents a formative intervention, grounded in sociocultural theory, that seeks to transform educational practice in multilingual and intercultural contextsby focusing on teacher training and ways of reconceptualizing teaching practice. The training process was carried out with ten teachers from different levels of education. The data was obtained through dialogic and conceptual mediation processes using language life stories, semi-structured interviews, discussion groups, self-confrontation, and specialized literature. The analysis shows that when teachers become aware of and contrast their own representations and actions, tensions and contradictions emerge between what they think and what they do. The originality of this approach lies in a change in knowledge, know-how, and conduct in a complex social context, pointing toa need to move toward transformative practices

Phase Composition of Silica Fume-Portland Cement Systems Formed under Hydrothermal Curing Evaluated by FTIR, XRD, and TGA

Two substitution levels of Portland cement by silica fume (SF; 30 and 50 mass%) and three hydrothermal treatment regimes (0.5, 1.2, and 2 MPa and 165, 195, and 220 degrees C for 7 days, respectively) were selected for the investigation of high-temperature phase formation. A combination of thermogravimetric, X-ray diffraction, and Fourier transform infrared analyses in the mid-IR region was used to overcome the shortcomings of individual techniques for the identification of these complex systems. Changes in molecular water amounts, the polymerization degree of silicate chains, or their decomposition due to transformations and crystallization of phases at hydrothermal conditions were observed and discussed concerning composition. Contrary to the calciochondrite, hydrogrossular phases, alpha-C2SH, and jaffeite detected in the systems without SF, a decrease in CaO/SiO2 ratio resulted in the formation of stable tobermorite in the case of 30 mass% SF, whilst calcium hydrogen silicate, gyrolite, and cowlesite were identified as more thermally stable phases in the samples with 50 mass% SF

STUDY OF HYDRATION PRODUCTS IN THE MODEL SYSTEMS METAKAOLIN-LIME AND METAKAOLIN-LIME-GYPSUM

Possible preferential formation of ettringite instead of required calcium silicate hydrate (CSH) and calcium aluminosilicate hydrate (CASH) phases when aluminosilicates were added to the blended cements was investigated on the model systems comprising of metakaolin, lime and gypsum. Compressive strength, microstructure and phase composition of the samples were evaluated after 7 days of curing at 50oC, using thermal analysis, X-ray diffraction techniques and scanning electronic microscopy. Samples prepared from equal amounts of metakaolin, lime and with more than 8 wt. % of gypsum, displayed the highest compressive strength values. Development of compressive strength was correlated with the formation of ettringite. Further rising of gypsum content resulted in the decrease of compressive strength, which is notable in the samples with a different metakaolin/lime ratio. Lower content of gypsum led to the preferential formation of portlandite, CSH and CASH. Calcite was detected in all the samples and its content declined with increasing amount of ettringite. In addition to calcite, carboaluminates were detected in complementary binary metakaolin - lime system. Tendency to carbonation declined with increasing content of metakaolin and eventuated in the highest compressive strength value for the samples with equal initial content of metakaolin and lime

Optimization of cementitious composite for heavyweight concrete preparation using conduction calorimetry

The present work investigates the hydration heat of different cement composites by means of conduction calorimetry to optimize the composition of binder in the design of heavyweight concrete as biological shielding. For this purpose, Portland cement CEM I 42.5 R was replaced by a different portion of supplementary cementitious materials (blast furnace slag, metakaolin, silica fume/limestone) at 75%, 65%, 60%, 55%, and 50% levels to obtain low hydration heat lower than 250 j g(-1). All ingredients were analyzed by energy dispersive X-ray fluorescence (EDXRF) and nuclear activation analysis (NAA) to assess the content of major elements and isotopes. A mixture of two high-density aggregates (barite and magnetite) was used to prepare three heavyweights concretes with compressive strength exceeding 45 MPa and bulk density ranging between 3400 and 3500 kg m(-3). After a short period of volume expansion (up to 4 h), a slight shrinkage (max. 0.3 degrees/degrees degrees) has been observed. Also, thermophysical properties (thermal conductivity, volumetric specific heat, thermal diffusivity) and other properties were determined. The results showed that aggregate content and not binder is the main factor influencing the engineering properties of heavyweight concretes

Patient Experience in Pancreas-Kidney Transplantation-A Methodological Approach Towards Innovation in an Established Program

Simultaneous pancreas-kidney transplantation (SPKT) leads to increased survival and quality of life, and is an alternative treatment for insulin-dependent diabetes mellitus and end-stage kidney disease. Due to the particularities of this population (often with multiple comorbidities) and of the surgery (only performed in a few centers), a comprehensive analysis of patients' experience along the SPKT process is crucial to improve patient care and add value to this procedure. Therefore, we applied a systematic and iterative methodology with the participation of both patients and professional teams working together to explore and identify unmet needs and value-adding steps along the transplant patient journey at an established pancreas transplant program. Four main steps (to comprehend, to explore, to experiment and to assess) led to several interventions around three major areas: Administration and logistics, information and communication, and perceived quality of assistance. As a result, both displacements to the hospital for diagnostic purposes and the time delay involved in joining the patient waiting list for transplantation were reduced in parallel to the administrative procedures. In conclusion, the methodological implementation of key organizational changes has great impact on overall patient experience. Further quantitative analysis from the patient's perspective will consolidate our program and may add new prototype service design components

A methodology to quantify the differences between alternative methods of heart rate variability measurement

This work proposes a systematic procedure to report the differences between heart rate variability time series obtained from alternative measurements reporting the spread and mean of the differences as well as the agreement between measuring procedures and quantifying how stationary, random and normal the differences between alternative measurements are. A description of the complete automatic procedure to obtain a differences time series (DTS) from two alternative methods, a proposal of a battery of statistical tests, and a set of statistical indicators to better describe the differences in RR interval estimation are also provided. Results show that the spread and agreement depend on the choice of alternative measurements and that the DTS cannot be considered generally as a white or as a normally distributed process. Nevertheless, in controlled measurements the DTS can be considered as a stationary process.Peer ReviewedPostprint (published version

COVID-19 vaccine effectiveness against hospitalization due to SARS-CoV-2: A test-negative design study based on Severe Acute Respiratory Infection (SARI) sentinel surveillance in Spain

Background: With the emergence of SARS-CoV-2, influenza surveillance systems in Spain were transformed into a new syndromic sentinel surveillance system. The Acute Respiratory Infection Surveillance System (SiVIRA in Spanish) is based on a sentinel network for acute respiratory infection (ARI) surveillance in primary care and a network of sentinel hospitals for severe ARI (SARI) surveillance in hospitals. Methods: Using a test-negative design and data from SARI admissions notified to SiVIRA between January 1 and October 3, 2021, we estimated COVID-19 vaccine effectiveness (VE) against hospitalization, by age group, vaccine type, time since vaccination, and SARS-CoV-2 variant. Results: VE was 89% (95% CI: 83-93) against COVID-19 hospitalization overall in persons aged 20 years and older. VE was higher for mRNA vaccines, and lower for those aged 80 years and older, with a decrease in protection beyond 3 months of completing vaccination, and a further decrease after 5 months. We found no differences between periods with circulation of Alpha or Delta SARS-CoV-2 variants, although variant-specific VE was slightly higher against Alpha. Conclusions: The SiVIRA sentinel hospital surveillance network in Spain was able to describe clinical and epidemiological characteristics of SARI hospitalizations and provide estimates of COVID-19 VE in the population under surveillance. Our estimates add to evidence of high effectiveness of mRNA vaccines against severe COVID-19 and waning of protection with time since vaccination in those aged 80 or older. No substantial differences were observed between SARS-CoV-2 variants (Alpha vs. Delta).The data of the study was originally collectedas part of the following projects run by the European Centre for Disease Prevention and Control:“Establishing Severe Acute Respiratory Infections (SARI) surveillance and performing hospital-based COVID-19 transmission studies”, “Developing an infrastructure and performing vaccine effectiveness studies for COVID-19 vaccines in the EU/EEA”, and the “Vaccine Effectiveness, Burden and Impact Studies(VEBIS) of COVID-19 and Influenza".S