Behavior of shrinkage reducing admixtures based on polyether structure in various alkaline solutions

The several types of alkali activated materials (AAM) are in global research interest for number of previous decades. One of them - alkali activated slag mortars/concretes become attractive due to reduction of the worldwide limestone reserves and rapidly growing carbon taxes1, 2, 3. So the development of these materials in large-scale is nowadays substantial. Granulated blast furnace slag is commonly chosen as a suitable source of latent hydraulicity specie, that can be activated by high alkaline solutions (i.e. NaOH or sodium silicate glass). Although these mortars and concretes possess very durable products with quick strength development and good chemical resistance, the high shrinkage phenomena, drying, autogenous (2 – 4 more times higher than when the ordinary Portland cement is applied), is typically observed4, 5. Various type of polymer admixtures are applied to suppress this phenomenon. One of the possible explanation is attributed to capillary stresses resulting from fine pore size of formed hydration products6. The usage of admixtures, which can lower the surface tension and influenced the pore structure of formed CASH gels, is offered. The addition of shrinkage reducing admixture (SRA) based on polyether type is intensively studied and showed the interesting results in the shrinkage development suppression. The main research is done on the interaction between the SRA and blast furnace slag particles. The behavior, interactions and stability in alkaline solutions are still not clear. This work is related to the study of polyethylene glycol and polypropylene glycol based SRA´ behavior in alkaline environment. The polymers (and corresponding monomers) were mixed with different solutions according to pH and ion composition (H2O, NaOH, sodium silicate glass and synthetic pore solution, respectively) with the mass ratio 1:1. The time dependence study was performed on the samples incubated at 25°C in sealed vials. The part of treated samples was separated after 1, 7, 14 and 28 days after mixing and dried for analyses. The Raman and FTIR spectroscopy was used to assess the stability of the chemical structure. The treated samples were also studied in terms of surface tension characterization. Finally, the time dependence reaction has also affected the rheology of solutions, what can extremely influence the workability and casting of final AAS mortars or concretes. So the rheological behavior was examined. The spectra obtained from Raman and FTIR spectroscopy analyses showed the time influence and pointed to ongoing reactions in the high alkaline system. Especially, the rheology behavior was strongly changed within the time and SRA molecular weight from liquid (in case of low weight) to almost solid state (in case of higher ones). The experimental results showed the essential need to study the polyether compound behavior in alkaline environment. References: 1 van Deventer, J.S.J., Provis, J.L, Duxson, P. (2012) Technical and commercial progress in the adoption of geopolymer cement. Miner Eng 29:89–104 2. Provis, J.L., Geopolymers and other alkali activated materials: why, how, and what? 3 Provis, J.L., Palomo,A., Shi, C. (2015) Advances in understanding alkali-activated materials, Cem Concr Res, Vol. 78, Part A: 110-125, 4 Ye, H., Cartwright, C., Rajabipour, F. Radlińska, A. (2017), Understanding the drying shrinkage performance of alkali-activated slag mortars, Cem. Concr. Compos., 76 pp. 13-24 5 Ye, H., Radlińska, A. (2016) Shrinkage mechanisms of alkali-activated slag, Cem. Concr. Res., 88 pp. 126-135 6 Duran Atiş, C., Bilim, C., Çelik, Ö., Karahan, O. (2009) Influence of activator on the strength and drying shrinkage of alkali-activated slag mortar, Constr. Build. Mater., 23 pp. 548-55

Effect of chemical structure on the efficiency of shrinkage reducing admixtures in alkali activated systems

Alkali activated binders, especially those based on alkali activated blast furnace slag (AAS), have the potential to become an alternative construction material to ordinary Portland cement binders. Nevertheless, AAS has some disadvantages which prevent its broader practical applications. An extensive shrinkage is one of the main limiting factors. Therefore, the study of chemical admixtures mitigating especially the drying shrinkage is necessary to be performed. The efficiency of suitable shrinkage reducing admixtures depends on the chemical structure of used surfactants. The study is consequently focused on the molecular architecture of amino alcohol surfactants which are closely associated with their ability to effectively reduce shrinkage. The molecular structure of used chemical compounds is shown in Figure 1. The influence of different substituents bounded to the secondary amine group was studied in terms of their effect on alkali activation, mechanical properties, microstructure arrangement and in particular on the enhancement of drying shrinkage reduction. It was determined that the addition of any tested admixture delayed the CASH gel formation which negatively influenced the flexural as well as compressive strengths in the early stages of hydration process (1 – 7 days). However, only slight decrease in strengths compared to reference sample was measured after 28 days of curing. The deeper insight into the microstructure (Figure 2) confirms previous results. It is obvious that in the case of reference sample the consistent matrix of binding phase is created after 24 hours. On the other hand, only thin layer of hydration products is formed in samples containing the admixture, which increases the porosity of material and tends to the deterioration of mechanical properties. Finally, the study confirms that the reduction of surface tension in pore solution occurs primarily with admixtures containing branched substituents, which further decreases the capillary tension responsible for the shrinkage according to Young-Laplace equation. The presented study highlights the essential role of molecular structure of shrinkage reducing admixtures contributing to the development of a new range of additives designed especially for alkali activated materials. Please click Additional Files below to see the full abstract

Persistent Wnt/β-catenin signaling determines dorsalization of the postnatal subventricular zone and neural Stem cell specification into oligodendrocytes and glutamatergic neurons

In the postnatal and adult central nervous system (CNS), the subventricular zone (SVZ) of the forebrain is the main source of neural stem cells (NSCs) that generate olfactory neurons and oligodendrocytes (OLs), the myelinating cells of the CNS. Here, we provide evidence of a primary role for canonical Wnt/β-catenin signaling in regulating NSC fate along neuronal and oligodendroglial lineages in the postnatal SVZ. Our findings demonstrate that glutamatergic neuronal precursors (NPs) and oligodendrocyte precursors (OPs) are derived strictly from the dorsal SVZ (dSVZ) microdomain under the control of Wnt/β-catenin, whereas GABAergic NPs are derived mainly from the lateral SVZ (lSVZ) microdomain independent of Wnt/β-catenin. Transcript analysis of microdissected SVZ microdomains revealed that canonical Wnt/β-catenin signaling was more pronounced in the dSVZ microdomain. This was confirmed using the β-catenin-activated Wnt-reporter mouse and by pharmacological stimulation of Wnt/β-catenin by infusion of the specific glycogen synthase kinase 3β inhibitor, AR-A014418, which profoundly increased the generation of cycling cells. In vivo genetic/pharmacological stimulation or inhibition of Wnt/β-catenin, respectively, increased and decreased the differentiation of dSVZ-NSCs into glutamatergic NPs, and had a converse effect on GABAergic NPs. Activation of Wnt/β-catenin dramatically stimulated the generation of OPs, but its inhibition had no effect, indicating other factors act in concert with Wnt/β-catenin to fine tune oligodendrogliogenesis in the postnatal dSVZ. These results demonstrate a role for Wnt/β-catenin signaling within the dorsal microdomain of the postnatal SVZ, in regulating the genesis of glutamatergic neurons and OLs

Towards Reflective AI:Needs, Challenges and Directions for Future Research

Harnessing benefits and preventing harms of AI cannot be solved alone through technological fixes and regulation. It depends on a complex interplay between technology, societal governance, individual behaviour, organizational and societal dynamics. Enabling people to understand AI and the consequences of its use and design is a crucial element for ensuring responsible use of AI.In this report we suggest a new framework for the development and use of AI technologies in a way that harnesses the benefits and prevents the harmful effects of AI. We name it Reflective AI. The notion of Reflective AI that we propose calls for adopting a holistic approach in the research and development of AI to investigate both what people need to learn about AI systems to develop better mental models i.e. an experiential knowledge of AI, to be able to use it safely and responsibly, as well as how this can be done and supported

High-Performance, Lightweight, and Flexible Thermoplastic Polyurethane Nanocomposites with Zn2+-Substituted CoFe2O4 Nanoparticles and Reduced Graphene Oxide as Shielding Materials against Electromagnetic Pollution

The development of flexible, lightweight, and thin high-performance electromagnetic interference shielding materials is urgently needed for the protection of humans, the environment, and electronic devices against electromagnetic radiation. To achieve this, the spinel ferrite nanoparticles CoFe2O4 (CZ1), Co0.67Zn0.33Fe2O4 (CZ2), and Co0.33Zn0.67Fe2O4 (CZ3) were prepared by the sonochemical synthesis method. Further, these prepared spinel ferrite nanoparticles and reduced graphene oxide (rGO) were embedded in a thermoplastic polyurethane (TPU) matrix. The maximum electromagnetic interference (EMI) total shielding effectiveness (SET) values in the frequency range 8.2-12.4 GHz of these nanocomposites with a thickness of only 0.8 mm were 48.3, 61.8, and 67.8 dB for CZ1-rGO-TPU, CZ2-rGO-TPU, and CZ3-rGO-TPU, respectively. The high-performance electromagnetic interference shielding characteristics of the CZ3-rGO-TPU nanocomposite stem from dipole and interfacial polarization, conduction loss, multiple scattering, eddy current effect, natural resonance, high attenuation constant, and impedance matching. The optimized CZ3-rGO-TPU nanocomposite can be a potential candidate as a lightweight, flexible, thin, and high-performance electromagnetic interference shielding material

European Language Grid: A Joint Platform for the European Language Technology Community

Europe is a multilingual society, in which dozens of languages are spoken. The only option to enable and to benefit from multilingualism is through Language Technologies (LT), i.e., Natural Language Processing and Speech Technologies. We describe the European Language Grid (ELG), which is targeted to evolve into the primary platform and marketplace for LT in Europe by providing one umbrella platform for the European LT landscape, including research and industry, enabling all stakeholders to upload, share and distribute their services, products and resources. At the end of our EU project, which will establish a legal entity in 2022, the ELG will provide access to approx. 1300 services for all European languages as well as thousands of data sets

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Study of water-extractable fractions from South Moravian lignite

International audienceLignite can be applied directly in natural form on agricultural fields as a soil conditioner. However, there is little information on leaching of risky compounds by its interaction with water. South Moravian lignite was therefore extracted with water at 25 A degrees C and 2.3 % of water-soluble fractions were obtained from lignite corresponding to 0.3 % of total organic carbon. All ten fractions form aromatic and aliphatic structures with oxygen-containing functional groups such as carboxyl groups, alcohols, ethers, esters, can be characterized as fulvic-like and humic-like substances. According to the XPS spectra, the fractions contain two nitrogen forms, one of which is ascribed to pyrroles and the second is related to protonated amines or quaternary nitrogen. Analysis at molecular level showed that the fractions contain compounds such as benzene carboxylic acids and their derivatives, small aliphatic diacids, fatty acids and polyols. Most of the identified molecules reflect clearly the presence of microbial remains in the lignite structure since microbial activity during coalification is well known. The differences between the individual fractions are negligible, especially after 21 days of extraction. From environmental point of view, it seems that the identified compounds do not represent a toxic risk