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29 pages, 9761 KiB

Open AccessArticle

High-Resolution Spatiotemporal Forecasting with Missing Observations Including an Application to Daily Particulate Matter 2.5 Concentrations in Jakarta Province, Indonesia

by I Gede Nyoman Mindra Jaya and Henk Folmer

Mathematics 2024, 12(18), 2899; https://doi.org/10.3390/math12182899 (registering DOI) - 17 Sep 2024

Abstract

Accurate forecasting of high-resolution particulate matter 2.5 (PM_2.5) levels is essential for the development of public health policy. However, datasets used for this purpose often contain missing observations. This study presents a two-stage approach to handle this problem. The first stage [...] Read more.

Accurate forecasting of high-resolution particulate matter 2.5 (PM_2.5) levels is essential for the development of public health policy. However, datasets used for this purpose often contain missing observations. This study presents a two-stage approach to handle this problem. The first stage is a multivariate spatial time series (MSTS) model, used to generate forecasts for the sampled spatial units and to impute missing observations. The MSTS model utilizes the similarities between the temporal patterns of the time series of the spatial units to impute the missing data across space. The second stage is the high-resolution prediction model, which generates predictions that cover the entire study domain. The second stage faces the big N problem giving rise to complex memory and computational problems. As a solution to the big N problem, we propose a Gaussian Markov random field (GMRF) for innovations with the Matérn covariance matrix obtained from the corresponding Gaussian field (GF) matrix by means of the stochastic partial differential equation (SPDE) method and the finite element method (FEM). For inference, we propose Bayesian statistics and integrated nested Laplace approximation (INLA) in the R-INLA package. The above approach is demonstrated using daily data collected from 13 PM_2.5 monitoring stations in Jakarta Province, Indonesia, for 1 January–31 December 2022. The first stage of the model generates PM_2.5 forecasts for the 13 monitoring stations for the period 1–31 January 2023, imputing missing data by means of the MSTS model. To capture temporal trends in the PM_2.5 concentrations, the model applies a first-order autoregressive process and a seasonal process. The second stage involves creating a high-resolution map for the period 1–31 January 2023, for sampled and non-sampled spatiotemporal units. It uses the MSTS-generated PM_2.5 predictions for the sampled spatiotemporal units and observations of the covariate’s altitude, population density, and rainfall for sampled and non-samples spatiotemporal units. For the spatially correlated random effects, we apply a first-order random walk process. The validation of out-of-sample forecasts indicates a strong model fit with low mean squared error (0.001), mean absolute error (0.037), and mean absolute percentage error (0.041), and a high R² value (0.855). The analysis reveals that altitude and precipitation negatively impact PM_2.5 concentrations, while population density has a positive effect. Specifically, a one-meter increase in altitude is linked to a 7.8% decrease in PM_2.5, while a one-person increase in population density leads to a 7.0% rise in PM_2.5. Additionally, a one-millimeter increase in rainfall corresponds to a 3.9% decrease in PM_2.5. The paper makes a valuable contribution to the field of forecasting high-resolution PM_2.5 levels, which is essential for providing detailed, accurate information for public health policy. The approach presents a new and innovative method for addressing the problem of missing data and high-resolution forecasting. Full article

(This article belongs to the Special Issue Advanced Statistical Application for Realistic Problems)

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20 pages, 1924 KiB

Open AccessArticle

A Numerical Simulation Study of the Dynamic Instability of Gas Swirling Flows in Cyclones

by Liqiang Sun, Jiangfei Li, Ming Xie, Maoli Man, Jianqiang Zhao and Jianfei Song

Processes 2024, 12(9), 2002; https://doi.org/10.3390/pr12092002 (registering DOI) - 17 Sep 2024

Abstract

The gas–phase flow field within a cyclone plays a critical role in the particle separation process. While previous research has primarily focused on the steady–state, time–averaged characteristics of this flow field, there has been limited investigation into its dynamic instability. This study seeks [...] Read more.

The gas–phase flow field within a cyclone plays a critical role in the particle separation process. While previous research has primarily focused on the steady–state, time–averaged characteristics of this flow field, there has been limited investigation into its dynamic instability. This study seeks to address this gap by examining the dynamic instability of gas swirling flows in cyclones, offering new insights into their spatial and temporal dimensions. Numerical simulations were performed via large eddy simulation (LES) for the gas swirling flow in a reverse cyclone and tangential velocity was measured with a hot–wire anemometer (HWA). The model’s accuracy was validated against experimental data. The results demonstrate that the distributions of instantaneous tangential velocity and pressure exhibit spatial asymmetry and temporal instability across different sections of the cyclone. The dynamic instability of the gas swirling flow in the cyclone is the superposition of the spatial asymmetry and the temporal instability. These instabilities are more pronounced in the internal regions than the outer regions. Dynamic instability arises from the combined effects of rotational dynamics and wall curvature, leading to an eccentric rotation of the swirling center, particularly evident in the lower sections of the cyclone cone. This instability increases fluctuations in the instantaneous parameters, enhancing turbulence intensity and fine particle diffusion, and ultimately impairing both separation efficiency and particle size efficiency. Full article

(This article belongs to the Section Separation Processes)

19 pages, 5101 KiB

Open AccessArticle

The Effect of Dense and Hollow Aggregates on the Properties of Lightweight Self-Compacting Concrete

by Aleksandr Sergeevich Inozemtcev and Sergey Dmitrievich Epikhin

Materials 2024, 17(18), 4569; https://doi.org/10.3390/ma17184569 (registering DOI) - 17 Sep 2024

Abstract

The development of self-compacting lightweight concretes is associated with solving two conflicting tasks: achieving a structure with both high flowability and homogeneity. This study aimed to identify the technological and rheological characteristics of the flow of concrete mixtures D1400…D1600 based on hollow microspheres [...] Read more.

The development of self-compacting lightweight concretes is associated with solving two conflicting tasks: achieving a structure with both high flowability and homogeneity. This study aimed to identify the technological and rheological characteristics of the flow of concrete mixtures D1400…D1600 based on hollow microspheres in comparison with heavy fine-grained D2200 concrete and to establish their structural and physico-mechanical characteristics. The study of the concrete mixtures was carried out using the slump flow test and the rotational viscometry method. The physical and mechanical properties were studied using standard methods for determining average density and flexural and compressive strength. According to the results of the research conducted, differences in the flow behaviors of concrete mixtures on dense and hollow aggregates were found. Lightweight concretes on hollow microspheres exhibited better mobility than heavy concretes. It was shown that the self-compacting coefficients of the lightweight D1400...D1600 concrete mixtures were comparable with that of the heavy D2200 concrete. The rheological curves described by the Ostwald–de Waele equation showed a dilatant flow behavior of the D1400 concrete mixtures, regardless of the ratio of quartz powder to fractionated sand. For D1500 and D1600, the dilatant flow behavior changed to pseudoplastic, with a ratio of quartz powder to fractional sand of 25/75. The studied compositions of lightweight concrete can be described as homogeneous at any ratio of quartz powder to fractional sand. It was shown that concrete mixtures with a pronounced dilatant flow character had higher resistance to segregation. The value of the ratio of quartz powder to fractional sand had a statistically insignificant effect on the average density of the studied concretes. However, the flexural and compressive strengths varied significantly more in heavy concretes (up to 38%) than in lightweight concretes (up to 18%) when this factor was varied. The specific strength of lightweight and heavy concrete compositions with a ratio of quartz powder to fractional sand of 0/100 had close values in the range of 20.4...22.9 MPa, and increasing the share of quartz powder increased the difference between compositions of different densities. Full article

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21 pages, 7546 KiB

Open AccessArticle

Unifying Building Instance Extraction and Recognition in UAV Images

by Xiaofei Hu, Yang Zhou, Chaozhen Lan, Wenjian Gan, Qunshan Shi and Hanqiang Zhou

Remote Sens. 2024, 16(18), 3449; https://doi.org/10.3390/rs16183449 (registering DOI) - 17 Sep 2024

Abstract

Building instance extraction and recognition (BEAR) extracts and further recognizes building instances in unmanned aerial vehicle (UAV) images, holds with paramount importance in urban understanding applications. To address this challenge, we propose a unified network, BEAR-Former. Given the difficulty of building instance recognition [...] Read more.

Building instance extraction and recognition (BEAR) extracts and further recognizes building instances in unmanned aerial vehicle (UAV) images, holds with paramount importance in urban understanding applications. To address this challenge, we propose a unified network, BEAR-Former. Given the difficulty of building instance recognition due to the small area and multiple instances in UAV images, we developed a novel multi-view learning method, Cross-Mixer. This method constructs a cross-regional branch and an intra-regional branch to, respectively, extract the global context dependencies and local spatial structural details of buildings. In the cross-regional branch, we cleverly employed cross-attention and polar coordinate relative position encoding to learn more discriminative features. To solve the BEAR problem end to end, we designed a channel group and fusion module (CGFM) as a shared encoder. The CGFM includes a channel group encoder layer to independently extract features and a channel fusion module to dig out the complementary information for multiple tasks. Additionally, an RoI enhancement strategy was designed to improve model performance. Finally, we introduced a new metric, Recall@(K, iou), to evaluate the performance of the BEAR task. Experimental results demonstrate the effectiveness of our method. Full article

(This article belongs to the Special Issue Intelligent Processing and Application of UAV Remote Sensing Image Data)

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17 pages, 728 KiB

Open AccessReview

Prospective Molecular Targets for Natural Killer Cell Immunotherapy against Glioblastoma Multiforme

by Luke C. Cooksey, Derek C. Friesen, Enrique D. Mangan and Porunelloor A. Mathew

Cells 2024, 13(18), 1567; https://doi.org/10.3390/cells13181567 (registering DOI) - 17 Sep 2024

Abstract

Glioblastoma multiforme (GBM) is the most common type of primary malignant brain tumor and has a dismal overall survival rate. To date, no GBM therapy has yielded successful results in survival for patients beyond baseline surgical resection, radiation, and chemotherapy. Immunotherapy has taken [...] Read more.

Glioblastoma multiforme (GBM) is the most common type of primary malignant brain tumor and has a dismal overall survival rate. To date, no GBM therapy has yielded successful results in survival for patients beyond baseline surgical resection, radiation, and chemotherapy. Immunotherapy has taken the oncology world by storm in recent years and there has been movement from researchers to implement the immunotherapy revolution into GBM treatment. Natural killer (NK) cell-based immunotherapies are a rising candidate to treat GBM from multiple therapeutic vantage points: monoclonal antibody therapy targeting tumor-associated antigens (TAAs), immune checkpoint inhibitors, CAR-NK cell therapy, Bi-specific killer cell engagers (BiKEs), and more. NK therapies often focus on tumor antigens for targeting. Here, we reviewed some common targets analyzed in the fight for GBM immunotherapy relevant to NK cells: EGFR, HER2, CD155, and IL-13Rα2. We further propose investigating the Lectin-like Transcript 1 (LLT1) and cell surface proliferating cell nuclear antigen (csPCNA) as targets for NK cell-based immunotherapy. Full article

(This article belongs to the Collection Novel Advances in Cancer Immunology: From Molecular Mechanisms to Therapeutic Applications)

19 pages, 1262 KiB

Open AccessArticle

Between Meteorite, Glacier and Rivers—Towards Geotourism Development in Diverse Landscape

by Dawid Abramowicz and Remigiusz Tritt

Sustainability 2024, 16(18), 8119; https://doi.org/10.3390/su16188119 (registering DOI) - 17 Sep 2024

Abstract

The morphogenetic diversity of an area often determines its high geodiversity, which is subsequently used for geotourism. Areas where geotourism is being intentionally developed note the funded impacts resulting from increased interest in the area by tourists. This paper presents a morphogenetically diverse [...] Read more.

The morphogenetic diversity of an area often determines its high geodiversity, which is subsequently used for geotourism. Areas where geotourism is being intentionally developed note the funded impacts resulting from increased interest in the area by tourists. This paper presents a morphogenetically diverse area that has been formed by glacial activity, cosmic factors—meteorite impacts, fluvial factors and anthropogenic factors—especially those related to industrial activities and settlement processes. In this manuscript, we identified and assessed geosites in the diverse landscape of the Poznań region (Poland), as well as analyzed strengths, weaknesses, opportunities and threats in relation to possible activities aimed at the development of geotourism. The multi-criteria assessment of existing and proposed geosites and SWOT analysis was used by us to assess geotourism development potential in this genetically highly diverse landscape. The work presented here demonstrates that not all formally created geosites by geological institutions are potentially attractive from the point of view of geotourism. The main factors that reduce the attractiveness of geosites are the lack of recreational infrastructure, poor accessibility and low educational values. The spectacularity of geosites is most often determined by their aesthetic value, representativeness, rareness and paleogeographical interest. The Poznań region has a high potential for the development of geotourism due to its valuable sites (Morasko Meteorite Reserve, Dziewicza Hill, post-mining area Szachty, Genius Loci and Ostrów Tumski); however, there is a need to develop a geotourism development strategy in the area. Given the morphogenetic diversity of the study area, there is a need to create a unique landscape geointerpretation center in this part of Europe, with a role in integrating tourism and especially geotourism activities. Full article

(This article belongs to the Section Sustainability, Biodiversity and Conservation)

24 pages, 2140 KiB

Open AccessArticle

A Study on Linguistic Z-Graph and Its Application in Social Networks

by Rupkumar Mahapatra, Sovan Samanta, Madhumangal Pal, Tofigh Allahviranloo and Antonios Kalampakas

Mathematics 2024, 12(18), 2898; https://doi.org/10.3390/math12182898 (registering DOI) - 17 Sep 2024

Abstract

This paper presents a comprehensive study of the linguistic Z-graph, which is a novel framework designed to analyze linguistic structures within social networks. By integrating concepts from graph theory and linguistics, the linguistic Z-graph provides a detailed understanding of language dynamics in online [...] Read more.

This paper presents a comprehensive study of the linguistic Z-graph, which is a novel framework designed to analyze linguistic structures within social networks. By integrating concepts from graph theory and linguistics, the linguistic Z-graph provides a detailed understanding of language dynamics in online communities. This study highlights the practical applications of linguistic Z-graphs in identifying central nodes within social networks, which are crucial for online businesses in market capture and information dissemination. Traditional methods for identifying central nodes rely on direct connections, but social network connections often exhibit uncertainty. This paper focuses on using fuzzy theory, particularly linguistic Z-graphs, to address this uncertainty, offering more detailed insights compared to fuzzy graphs. Our study introduces a new centrality measure using linguistic Z-graphs, enhancing our understanding of social network structures. Full article

(This article belongs to the Section Fuzzy Sets, Systems and Decision Making)

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17 pages, 586 KiB

Open AccessArticle

The Economic Impact of Treatment Sequencing in Chronic Lymphocytic Leukemia in Canada Using Venetoclax plus Obinutuzumab

by Kimberly Guinan, Karine Mathurin, Jean Lachaine, Nancy Paul Roc, Sarah-Jane Bull, Dipti Tankala, Stephane Barakat, Beenish S. Manzoor, Christopher Hillis and Versha Banerji

Cancers 2024, 16(18), 3182; https://doi.org/10.3390/cancers16183182 (registering DOI) - 17 Sep 2024

Abstract

Background: Bruton tyrosine kinase inhibitors (BTKis) represent an advancement in chronic lymphocytic leukemia; however, these agents are administered continuously until disease progression or unacceptable toxicity, raising concerns about their affordability. Venetoclax in combination with obinutuzumab (VO) is a fixed-duration (12-month) treatment, approved in [...] Read more.

Background: Bruton tyrosine kinase inhibitors (BTKis) represent an advancement in chronic lymphocytic leukemia; however, these agents are administered continuously until disease progression or unacceptable toxicity, raising concerns about their affordability. Venetoclax in combination with obinutuzumab (VO) is a fixed-duration (12-month) treatment, approved in Canada in 2020. This study estimated the total cumulative cost of different treatment sequences and evaluated the economic impact of introducing treatment sequences with/without VO, from a Canadian health care system perspective. Methods: A 10-year partitioned survival model was developed, considering key clinical parameters and direct medical costs. Results were stratified by TP53 aberration. Results: Treatment sequences starting with first-line (1L) VO resulted in lower 10-year cumulative costs compared to sequences starting with BTKis administered until disease progression, across both TP53 aberration subgroups. With a maximum of three lines of treatment over a 10-year period, cumulative costs were largely determined by the first two lines of treatment. When comparing sequences with the same 1L treatment, sequences with BTKis in second-line incurred greater costs compared to fixed-duration regimens. Conclusions: Overall, the economic impact of treating all patients with VO led to 10-year cumulative savings of CAD 169,341 and CAD 293,731 per patient, without and with TP53 aberration, respectively. These savings are mainly due to reductions in treatment costs associated with fixed treatment duration. Full article

(This article belongs to the Special Issue Updates in Chronic Lymphocytic Leukemia: 10 Years of Paradigm Change and Outlook for the Future)

13 pages, 2933 KiB

Open AccessArticle

Enhancing Therapeutic Response and Overcoming Resistance to Checkpoint Inhibitors in Ovarian Cancer through Cell Cycle Regulation

by Shiqi Wang, Chenggui Luo, Jiaqing Guo, Rui Hu, Binglin Shen, Fangrui Lin, Chenshuang Zhang, Changrui Liao, Jun He, Yiping Wang, Junle Qu and Liwei Liu

Int. J. Mol. Sci. 2024, 25(18), 10018; https://doi.org/10.3390/ijms251810018 (registering DOI) - 17 Sep 2024

Abstract

Tumor cells invade normal surrounding tissues through continuous division. In this study, we hypothesized that cell cycle regulation changes the immune efficacy of ovarian cancer. To investigate this hypothesis, a Förster resonance energy transfer (FRET) sensor was constructed to characterize the cell activity [...] Read more.

Tumor cells invade normal surrounding tissues through continuous division. In this study, we hypothesized that cell cycle regulation changes the immune efficacy of ovarian cancer. To investigate this hypothesis, a Förster resonance energy transfer (FRET) sensor was constructed to characterize the cell activity in real time. Cell shrinkage caused by apoptosis induces the aggregation of proteins on the cell membrane, leading to variations in the fluorescence lifetime of FRET sensors. Moreover, we tracked cell activity across various cycles following co-culture with an immune checkpoint inhibitor. Consequently, we assessed how cell cycle regulation influences immunotherapy in a tumor mouse model. This approach, which involves inhibiting typical cell cycle processes, markedly enhances the effectiveness of immunotherapy. Our findings suggest that modulating the cycle progression of cancer cells may represent a promising approach to enhance the immune response of ovarian cancer cells and the efficacy of immunotherapy based on immune checkpoint inhibitors. Full article

(This article belongs to the Section Molecular Pathology, Diagnostics, and Therapeutics)

13 pages, 1602 KiB

Open AccessArticle

Wildfire Burnt Area and Associated Greenhouse Gas Emissions under Future Climate Change Scenarios in the Mediterranean: Developing a Robust Estimation Approach

by Tim van der Schriek, Konstantinos V. Varotsos, Anna Karali and Christos Giannakopoulos

Fire 2024, 7(9), 324; https://doi.org/10.3390/fire7090324 (registering DOI) - 17 Sep 2024

Abstract

Wildfires burn annually over 400,000 ha in Mediterranean countries. By the end of the 21st century, wildfire Burnt Area (BA) and associated Green House Gas (GHG) emissions may double to triple due to climate change. Regional projections of future BA are urgently required [...] Read more.

Wildfires burn annually over 400,000 ha in Mediterranean countries. By the end of the 21st century, wildfire Burnt Area (BA) and associated Green House Gas (GHG) emissions may double to triple due to climate change. Regional projections of future BA are urgently required to update wildfire policies. We present a robust methodology for estimating regional wildfire BA and GHG emissions under future climate change scenarios in the Mediterranean. The Fire Weather Index, selected drought indices, and meteorological variables were correlated against BA/GHG emissions data to create area-specific statistical projection models. State-of-the-art regional climate models (horizontal resolution: 12 km), developed within the EURO-CORDEX initiative, simulated data under three climate change scenarios (RCP2.6, RCP4.5, and RCP8.5) up to 2070. These data drove the statistical models to estimate future wildfire BA and GHG emissions in three pilot areas in Greece, Montenegro, and France. Wildfire BA is projected to increase by 20% to 130% up to 2070, depending on the study area and climate scenario. The future expansion of fire-prone areas into the north Mediterranean and mountain environments is particularly alarming, given the large biomass present here. Fire-smart landscape management may, however, greatly reduce the projected future wildfire BA and GHG increases. Full article

(This article belongs to the Special Issue Effects of Climate Change on Fire Danger)

31 pages, 1538 KiB

Open AccessReview

Recent Advances in the Development of 1,4-Cyclohexanedimethanol (CHDM) and Cyclic-Monomer-Based Advanced Amorphous and Semi-Crystalline Polyesters for Smart Film Applications

by Farida Irshad, Nayab Khan, Haidar Howari, Mahvish Fatima, Assad Farooq, Muhammad Awais, Muhammad Ayyoob, Muhammad Qamar Tusief, Razia Virk and Fiaz Hussain

Materials 2024, 17(18), 4568; https://doi.org/10.3390/ma17184568 (registering DOI) - 17 Sep 2024

Abstract

Polyester-based advanced thin films have versatile industrial applications, especially in the fields of textiles, packaging, and electronics. Recent advances in polymer science and engineering have resulted in the development of advanced amorphous and semi-crystalline polyesters with exceptional performance compared to those of conventional [...] Read more.

Polyester-based advanced thin films have versatile industrial applications, especially in the fields of textiles, packaging, and electronics. Recent advances in polymer science and engineering have resulted in the development of advanced amorphous and semi-crystalline polyesters with exceptional performance compared to those of conventional polymeric films. Among these, 1,4-cyclohexanedimethanol (CHDM) and cyclic-monomer-based polyesters have gained considerable attention for their exceptional characteristics and potential applications in smart films. This review article provides a comprehensive overview of the recent advances in the synthesis, characterization, and applications of CHDM and cyclic-monomer-based advanced polymers for smart film applications. It discusses the structure–property relationships of these innovative polyesters and highlights their unique characteristics, including thermal, mechanical, and barrier characteristics. Furthermore, this article also emphasizes the solution, melt, and solid-state polymerizations of the polymers. Special emphasis is placed on the influence of the addition of a second diol or second diacid on the performance characteristics of synthesized polyesters/copolyesters to explore their versatile industrial applications. Additionally, the impact of the stereochemistry of the monomers is explored to optimize the characterization of polyesters suitable for industrial applications. Furthermore, this article explores the potential of these advanced polyesters to be considered as materials for smart film applications, especially in the field of flexible electronics. Finally, this article examines the challenges and future recommendations for the development of CHDM and cyclic-monomer-based polyesters for smart film applications. It discusses potential avenues for further research, including in-depth studies for the synthesis and characterization of polyesters, the development of sustainable and biodegradable alternatives to cyclic monomers, alternative green approaches for the synthesis of polymers, etc. This review article provides valuable insight for researchers in academia and industry who are working in the fields of polymer science and materials engineering. Full article

10 pages, 224 KiB

Open AccessArticle

Methotrexate and Tumor Necrosis Factor Inhibitors Independently Decrease Neutralizing Antibodies after SARS-CoV-2 Vaccination: Updated Results from the SUCCEED Study

by Carol A Hitchon, Dawn M. E. Bowdish, Gilles Boire, Paul R. Fortin, Louis Flamand, Vinod Chandran, Roya M. Dayam, Anne-Claude Gingras, Catherine M. Card, Inés Colmegna, Maggie J. Larché, Gilaad G. Kaplan, Luck Lukusa, Jennifer L.F. Lee, Sasha Bernatsky and on behalf of the SUCCEED Investigative Team

Vaccines 2024, 12(9), 1061; https://doi.org/10.3390/vaccines12091061 (registering DOI) - 17 Sep 2024

Abstract

Objective: SARS-CoV-2 remains the third most common cause of death in North America. We studied the effects of methotrexate and tumor necrosis factor inhibitor (TNFi) on neutralization responses after COVID-19 vaccination in immune-mediated inflammatory disease (IMID). Methods: Prospective data and sera of adults [...] Read more.

Objective: SARS-CoV-2 remains the third most common cause of death in North America. We studied the effects of methotrexate and tumor necrosis factor inhibitor (TNFi) on neutralization responses after COVID-19 vaccination in immune-mediated inflammatory disease (IMID). Methods: Prospective data and sera of adults with inflammatory bowel disease (IBD), rheumatoid arthritis (RA), spondyloarthritis (SpA), psoriatic arthritis (PsA), and systemic lupus (SLE) were collected at six academic centers in Alberta, Manitoba, Ontario, and Quebec between 2022 and 2023. Sera from two time points were evaluated for each subject. Neutralization studies were divided between five laboratories, and each lab’s results were analyzed separately using multivariate generalized logit models (ordinal outcomes: absent, low, medium, and high neutralization). Odds ratios (ORs) for the effects of methotrexate and TNFi were adjusted for demographics, IMID, other biologics and immunosuppressives, prednisone, COVID-19 vaccinations (number/type), and infections in the 6 months prior to sampling. The adjusted ORs for methotrexate and TNFi were then pooled in random-effects meta-analyses (separately for the ancestral strains and the Omicron BA1 and BA5 strains). Results: Of 479 individuals (958 samples), 292 (61%) were IBD, 141 (29.4%) were RA, and the remainder were PsA, SpA, and SLE. The mean age was 57 (62.2% female). For both the individual labs and the meta-analyses, the adjusted ORs suggested independent negative effects of TNFi and methotrexate on neutralization. The meta-analysis adjusted ORs for TNFi were 0.56 (95% confidence interval (CI) 0.39, 0.81) for the ancestral strain and 0.56 (95% CI 0.39, 0.81) for BA5. The meta-analysis adjusted OR for methotrexate was 0.39 (95% CI 0.19, 0.76) for BA1. Conclusions: SARS-CoV-2 neutralization in vaccinated IMID was diminished independently by TNFi and methotrexate. As SARS-CoV-2 circulation continues, ongoing vigilance regarding optimized vaccination is required. Full article

(This article belongs to the Section Vaccine Efficacy and Safety)

16 pages, 15466 KiB

Open AccessArticle

Research on Pre-Compensation and Shape-Control Optimization of Hemming Structures with Dissimilar Materials Based on Forming Process Chain

by Jianjun Li, Qin Sun, Jia Jia and Wenfeng Zhu

Metals 2024, 14(9), 1063; https://doi.org/10.3390/met14091063 (registering DOI) - 17 Sep 2024

Abstract

The steel–aluminum hybrid body closure panels can achieve a more balanced and lightweight performance. However, the differences in the physical properties of metal sheets and the complex changes in the properties of the adhesive material result in cumulative deviations in the composite-forming process. [...] Read more.

The steel–aluminum hybrid body closure panels can achieve a more balanced and lightweight performance. However, the differences in the physical properties of metal sheets and the complex changes in the properties of the adhesive material result in cumulative deviations in the composite-forming process. This paper proposes a deformation pre-compensation modeling method for the autobody closure panels hemming system oriented towards the process chain, in response to the problem that single-process optimization cannot obtain global optimal results. Taking the car door scaled model as an example, based on surface reconstruction and node compensation, the curing deformation amount is fed back in advance to the gluing and hemming processes. The deformation deviation is corrected through geometric parameter pre-compensation to achieve overall process shape control and optimization. Research shows that this method can significantly reduce the surface differences and gaps of hemming structures with dissimilar materials, and a single iteration can reduce the assembly surface difference by more than 90%. This provides a reference for improving the manufacturing quality of steel–aluminum hybrid body closure panels. Full article

(This article belongs to the Section Welding and Joining)

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13 pages, 1989 KiB

Open AccessReview

A Promising Therapeutic Strategy of Combining Acoustically Stimulated Nanobubbles and Existing Cancer Treatments

by Deepa Sharma, Tera N. Petchiny and Gregory J. Czarnota

Cancers 2024, 16(18), 3181; https://doi.org/10.3390/cancers16183181 (registering DOI) - 17 Sep 2024

Abstract

In recent years, ultrasound-stimulated microbubbles (USMBs) have gained great attention because of their wide theranostic applications. However, due to their micro-size, reaching the targeted site remains a challenge. At present, ultrasound-stimulated nanobubbles (USNBs) have attracted particular interest, and their small size allows them [...] Read more.

In recent years, ultrasound-stimulated microbubbles (USMBs) have gained great attention because of their wide theranostic applications. However, due to their micro-size, reaching the targeted site remains a challenge. At present, ultrasound-stimulated nanobubbles (USNBs) have attracted particular interest, and their small size allows them to extravasate easily in the blood vessels penetrating deeper into the tumor vasculature. Incorporating USNBs with existing cancer therapies such as chemotherapy, immunotherapy, and/or radiation therapy in several preclinical models has been demonstrated to have a profound effect on solid tumors. In this review, we provide an understanding of the composition and formation of nanobubbles (NBs), followed by the recent progress of the therapeutic combinatory effect of USNBs and other cancer therapies in cancer treatment. Full article

(This article belongs to the Special Issue Advances in Oncological Imaging)

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14 pages, 3468 KiB

Open AccessArticle

Understanding the High-Temperature Deformation Behaviors in Additively Manufactured Al6061+TiC Composites via In Situ Neutron Diffraction

by Minglei Qu, Dunji Yu, Lianyi Chen, Ke An and Yan Chen

Metals 2024, 14(9), 1064; https://doi.org/10.3390/met14091064 (registering DOI) - 17 Sep 2024

Abstract

Aluminum matrix composites (AMCs) are designed to enhance the performance of conventional aluminum alloys for engineering applications at both room and elevated temperatures. However, the dynamic phase-specific deformation behavior and load-sharing mechanisms of AMCs at elevated temperatures have not been extensively studied and [...] Read more.

Aluminum matrix composites (AMCs) are designed to enhance the performance of conventional aluminum alloys for engineering applications at both room and elevated temperatures. However, the dynamic phase-specific deformation behavior and load-sharing mechanisms of AMCs at elevated temperatures have not been extensively studied and remain unclear. Here, in situ neutron diffraction experiments are employed to reveal the phase-specific structure evolution of additively manufactured Al6061+TiC composites under compressive loading at 250 °C. It is found that the addition of a small amount of nano-size TiC significantly alters the deformation behavior and increases the strength at 250 °C in comparison to the as-printed Al6061. Unlike the two-stage behavior observed in Al6061, the Al6061+TiC composites exhibit three stages during compression triggered by changes in the interphase stress states. Further analysis of Bragg peak intensity and broadening reveals that the presence of TiC alters the dislocation activity during deformation at 250 °C by influencing dislocation slip planes and promoting dislocation accumulation. These findings provide direct experimental observations of the phase-specific dynamic process in AMCs under deformation at an elevated temperature. The revealed mechanisms provide insights for the future design and optimization of high-performance AMCs. Full article

(This article belongs to the Special Issue Advances in Preparation Methods and Numerical Simulation of Composites: Formation and Properties)

37 pages, 3581 KiB

Open AccessReview

Relationship of Signaling Pathways between Rkip Expression and the Inhibition of EMT-Inducing Transcription Factors SNAIL1/2, TWIST1/2 and ZEB1/2

by Andrew Bustamante, Stavroula Baritaki, Apostolos Zaravinos and Benjamin Bonavida

Cancers 2024, 16(18), 3180; https://doi.org/10.3390/cancers16183180 (registering DOI) - 17 Sep 2024

Abstract

Untreated primary carcinomas often lead to progression, invasion and metastasis, a process that involves the epithelial-to-mesenchymal transition (EMT). Several transcription factors (TFs) mediate the development of EMT, including SNAIL1/SNAIL2, TWIST1/TWIST2 and ZEB1/ZEB2, which are overexpressed in various carcinomas along with the under expression [...] Read more.

Untreated primary carcinomas often lead to progression, invasion and metastasis, a process that involves the epithelial-to-mesenchymal transition (EMT). Several transcription factors (TFs) mediate the development of EMT, including SNAIL1/SNAIL2, TWIST1/TWIST2 and ZEB1/ZEB2, which are overexpressed in various carcinomas along with the under expression of the metastasis suppressor Raf Kinase Inhibitor Protein (RKIP). Overexpression of RKIP inhibits EMT and the above associated TFs. We, therefore, hypothesized that there are inhibitory cross-talk signaling pathways between RKIP and these TFs. Accordingly, we analyzed the various properties and biomarkers associated with the epithelial and mesenchymal tissues and the various molecular signaling pathways that trigger the EMT phenotype such as the TGF-β, the RTK and the Wnt pathways. We also presented the various functions and the transcriptional, post-transcriptional and epigenetic regulations for the expression of each of the EMT TFs. Likewise, we describe the transcriptional, post-transcriptional and epigenetic regulations of RKIP expression. Various signaling pathways mediated by RKIP, including the Raf/MEK/ERK pathway, inhibit the TFs associated with EMT and the stabilization of epithelial E-Cadherin expression. The inverse relationship between RKIP and the TF expressions and the cross-talks were further analyzed by bioinformatic analysis. High mRNA levels of RKIP correlated negatively with those of SNAIL1, SNAIL2, TWIST1, TWIST2, ZEB1, and ZEB2 in several but not all carcinomas. However, in these carcinomas, high levels of RKIP were associated with good prognosis, whereas high levels of the above transcription factors were associated with poor prognosis. Based on the inverse relationship between RKIP and EMT TFs, it is postulated that the expression level of RKIP in various carcinomas is clinically relevant as both a prognostic and diagnostic biomarker. In addition, targeting RKIP induction by agonists, gene therapy and immunotherapy will result not only in the inhibition of EMT and metastases in carcinomas, but also in the inhibition of tumor growth and reversal of resistance to various therapeutic strategies. However, such targeting strategies must be better investigated as a result of tumor heterogeneities and inherent resistance and should be better adapted as personalized medicine. Full article

(This article belongs to the Special Issue Revolutionizing Cancer Therapy: Unleashing the Power of MET Inhibitors)

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25 pages, 1711 KiB

Open AccessReview

A Review of Wear in Additive Manufacturing: Wear Mechanism, Materials, and Process

by Xiangjun Jiang, Juntao Lu, Na Zhao, Zhen Chen and Zhiming Zhao

Lubricants 2024, 12(9), 321; https://doi.org/10.3390/lubricants12090321 (registering DOI) - 17 Sep 2024

Abstract

In fields such as industrial engineering and healthcare, additive manufacturing technology is a focal point for researchers. Wear represents a significant challenge for additive manufacturing technology, increasingly emerging as a research hotspot in recent years. This review categorizes and summarizes wear issues in [...] Read more.

In fields such as industrial engineering and healthcare, additive manufacturing technology is a focal point for researchers. Wear represents a significant challenge for additive manufacturing technology, increasingly emerging as a research hotspot in recent years. This review categorizes and summarizes wear issues in additive manufacturing technology, providing a comprehensive overview of wear mechanisms, materials, and the effects of additive manufacturing processes on wear. Research indicates that different wear mechanisms result in varying wear characteristics. The inherent properties of the materials significantly influence wear during the manufacturing process. Modifying material compositions and optimizing microstructures can enhance the wear properties of additive manufacturing products. Additionally, the study of additive manufacturing technology in repair and maintenance is a current and anticipated research hotspot for the coming decades. In the research of additive manufacturing processes, the effective regulation of process parameters and their post-processing play a positive role in enhancing the wear characteristics of products produced via additive manufacturing. Lastly, the challenges and recent advancements concerning wear issues in the field of additive manufacturing technology research are summarized. Full article

(This article belongs to the Special Issue Wear in Additive Manufacturing)

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27 pages, 3971 KiB

Open AccessArticle

The Delayed Turnover of Proteasome Processing of Myocilin upon Dexamethasone Stimulation Introduces the Profiling of Trabecular Meshwork Cells’ Ubiquitylome

by Grazia Raffaella Tundo, Dario Cavaterra, Irene Pandino, Gabriele Antonio Zingale, Sara Giammaria, Alessandra Boccaccini, Manuele Michelessi, Gloria Roberti, Lucia Tanga, Carmela Carnevale, Michele Figus, Giuseppe Grasso, Massimo Coletta, Alessio Bocedi, Francesco Oddone and Diego Sbardella

Int. J. Mol. Sci. 2024, 25(18), 10017; https://doi.org/10.3390/ijms251810017 (registering DOI) - 17 Sep 2024

Abstract

Glaucoma is chronic optic neuropathy whose pathogenesis has been associated with the altered metabolism of Trabecular Meshwork Cells, which is a cell type involved in the synthesis and remodeling of the trabecular meshwork, the main drainage pathway of the aqueous humor. Starting from [...] Read more.

Glaucoma is chronic optic neuropathy whose pathogenesis has been associated with the altered metabolism of Trabecular Meshwork Cells, which is a cell type involved in the synthesis and remodeling of the trabecular meshwork, the main drainage pathway of the aqueous humor. Starting from previous findings supporting altered ubiquitin signaling, in this study, we investigated the ubiquitin-mediated turnover of myocilin (MYOC/TIGR gene), which is a glycoprotein with a recognized role in glaucoma pathogenesis, in a human Trabecular Meshwork strain cultivated in vitro in the presence of dexamethasone. This is a validated experimental model of steroid-induced glaucoma, and myocilin upregulation by glucocorticoids is a phenotypic marker of Trabecular Meshwork strains. Western blotting and native-gel electrophoresis first uncovered that, in the presence of dexamethasone, myocilin turnover by proteasome particles was slower than in the absence of the drug. Thereafter, co-immunoprecipitation, RT-PCR and gene-silencing studies identified STUB1/CHIP as a candidate E3-ligase of myocilin. In this regard, dexamethasone treatment was found to downregulate STUB1/CHIP levels by likely promoting its proteasome-mediated turnover. Hence, to strengthen the working hypothesis about global alterations of ubiquitin-signaling, the first profiling of TMCs ubiquitylome, in the presence and absence of dexamethasone, was here undertaken by diGLY proteomics. Application of this workflow effectively highlighted a robust dysregulation of key pathways (e.g., phospholipid signaling, β-catenin, cell cycle regulation) in dexamethasone-treated Trabecular Meshwork Cells, providing an ubiquitin-centered perspective around the effect of glucocorticoids on metabolism and glaucoma pathogenesis. Full article

(This article belongs to the Special Issue Structure, Function and Dynamics in Proteins: 2nd Edition)

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26 pages, 1384 KiB

Open AccessReview

Exploring Demographic Representation and Reporting in Lung Cancer Clinical Trials with Canadian Sites from 2013 to 2023

by Sierra A. Land, Rajvi J. Wani, Naila Inam, Hilary J. G. Hewitt, Paulo Eduardo Muniz Covizzi and Tarah Sheculski Rivard

Curr. Oncol. 2024, 31(9), 5573-5598; https://doi.org/10.3390/curroncol31090413 (registering DOI) - 17 Sep 2024

Abstract

This review evaluates the reporting of demographic characteristics and the diversity of participants of phase III lung cancer clinical trials with Canadian research sites. A literature search was conducted using the ClinicalTrials.gov registry to identify clinical trials conducted between 1 January 2013, and [...] Read more.

This review evaluates the reporting of demographic characteristics and the diversity of participants of phase III lung cancer clinical trials with Canadian research sites. A literature search was conducted using the ClinicalTrials.gov registry to identify clinical trials conducted between 1 January 2013, and 31 December 2023. The demographic reporting practices and the representation of sex/gender, racial, and ethnic groups were assessed. The location of Canadian research sites was also examined for trends in reporting and representation. Associated publications were reviewed for demographic data collection methods. Of the 25 clinical trials, 24 reported race and 18 also reported ethnicity. All clinical trials reported sex/gender, and the city and province of the participating Canadian sites. Most participants were White (66.1%), identified as not Hispanic or Latino (81.4%), and were male (57.8%). The provinces with the most clinical trial sites were Ontario (43.6%) and Quebec (34.2%). Lung cancer clinical trials lack adequate demographic reporting and representation of females, diverse patient groups, and geographical locations in Canada with high lung cancer incidence rates. Specifically, the Indigenous Peoples of Canada and Nunavut require better representation in lung cancer clinical trials conducted in Canada. These findings highlight the need to improve diversity and demographic representation in clinical research. Full article

8 pages, 533 KiB

Open AccessCommunication

Replication of the Venezuelan Equine Encephalitis Vaccine from a Synthetic PCR Fragment

by Christine Mathew, Colin Tucker, Irina Tretyakova and Peter Pushko

Pharmaceutics 2024, 16(9), 1217; https://doi.org/10.3390/pharmaceutics16091217 (registering DOI) - 17 Sep 2024

Abstract

Background/Objectives: There is no approved human vaccine for Venezuelan equine encephalitis (VEE), a life-threatening disease caused by the VEE virus (VEEV). In previous studies, plasmid DNA encoding the full-length RNA genome of the VEE V4020 vaccine was used for the preparation of experimental [...] Read more.

Background/Objectives: There is no approved human vaccine for Venezuelan equine encephalitis (VEE), a life-threatening disease caused by the VEE virus (VEEV). In previous studies, plasmid DNA encoding the full-length RNA genome of the VEE V4020 vaccine was used for the preparation of experimental live virus VEE vaccines in the plasmid-transfected cell culture. Methods: Here, we used the high-fidelity polymerase chain reaction (PCR) to prepare synthetic, transcriptionally active PCR (TAP) fragments encoding the V4020 genome. Results: TAP fragment initiated the replication of the V4020 live virus vaccine in TAP fragment-transfected cells. A transfection of less than 1 ug of TAP fragment resulted in the replication of the V4020 vaccine virus in CHO cells. Conclusion: We conclude that not only plasmid DNA but also synthetic PCR-generated DNA fragments can be used for the manufacturing of live vaccines for VEEV and, potentially, other viruses. Full article

(This article belongs to the Special Issue Plasmid DNA for Gene Therapy and DNA Vaccine Applications, 2nd Edition)

12 pages, 456 KiB

Open AccessArticle

Preserflo MicroShunt versus Trabeculectomy: Efficacy and Surgical Success within a Heterogenous Patient Cohort

by Lynn Anna Barbara Zweifel, Jens Julian Storp, Friederike Elisabeth Vietmeier, Moritz Fabian Danzer, Ralph-Laurent Merté, Nicole Eter and Viktoria Constanze Brücher

Life 2024, 14(9), 1171; https://doi.org/10.3390/life14091171 (registering DOI) - 17 Sep 2024

Abstract

To compare success rates of trabeculectomy (TE) and Preserflo MicroShunt (PMS) in heterogenous glaucoma cohorts with regards to different pre- and postoperative therapeutic regimens. Data of 187 glaucoma patients who either received TE (73 eyes) or PMS implantation (114 eyes) between January 2018 [...] Read more.

To compare success rates of trabeculectomy (TE) and Preserflo MicroShunt (PMS) in heterogenous glaucoma cohorts with regards to different pre- and postoperative therapeutic regimens. Data of 187 glaucoma patients who either received TE (73 eyes) or PMS implantation (114 eyes) between January 2018 and December 2022 were retrospectively evaluated. Surgical success and failure rates were analyzed within six months of follow-up. Intraocular pressure (IOP) development over the course of follow-up was compared between both groups. Tertiary outcome measures were best-corrected visual acuity (BCVA), number and type of medications, frequency of postoperative complications and revision surgeries. Outcome measures underwent additional assessment based on subgroup categorizations, and failure time hazard ratios were computed. The success rates were comparable between both procedures (TE: 54.1%, PMS: 60.0%; p = 0.17). Both procedures showed significant IOP reduction (p < 0.01); however, overall IOP reduction was greater in the TE group than in the PMS group (TE: Reduction by 12 mmHg (188.9%), PMS: Reduction by 7 mmHg (51.3%); p = 0.01). The number of topical medications decreased significantly in both groups over the course of follow-up (TE: 4 to 0, PMS: 3 to 0; p < 0.01). While the number of complications and revision surgeries were similar in both groups, the time interval until the first revision surgery within the TE group was significantly shorter (TE: 13.5 d, PMS: 163 d; p = 0.01) than within the PMS group. No difference could be detected between TE and PMS with regard to the follow-up regimen. In particular, there was no significant difference in the need for 5-floururacil injections postoperatively (p = 0.29). Less invasive glaucoma surgery with the PMS appeared comparable to the TE within a heterogenous glaucoma cohort with regards to IOP development and freedom from medication. Full article

(This article belongs to the Collection New Diagnostic and Therapeutic Developments in Eye Diseases)

27 pages, 1193 KiB

Open AccessArticle

The Combined Effects of the Thermal Environment and Air Quality at Recreation Places on the Physiology and Psychology of People in Urban Parks

by Yuxiang Lan, Jingjing Wang, Yaling Huang, Yuanyang Tang, Zhanhua Liu, Jiahui Zheng, Xiong Yao, Zhipeng Zhu, Jianwen Dong and Ye Chen

Forests 2024, 15(9), 1640; https://doi.org/10.3390/f15091640 (registering DOI) - 17 Sep 2024

Abstract

Urban forests, crucial to urban ecosystems, are increasingly threatened by the challenges of urbanization, such as deteriorating thermal environments and declining air quality. Despite their recognized benefits to city dwellers’ quality of life, a systematic understanding of the impact of these environmental factors [...] Read more.

Urban forests, crucial to urban ecosystems, are increasingly threatened by the challenges of urbanization, such as deteriorating thermal environments and declining air quality. Despite their recognized benefits to city dwellers’ quality of life, a systematic understanding of the impact of these environmental factors on public psychophysiological well-being in recreational sites is a notable gap in the literature. The objective of this research was to bridge this gap by examining the effects of the thermal environment and air quality in urban forests on the public’s perception, offering scientific evidence to inform environmental optimization and health management strategies for urban parks, essential for sustainable urban development and public health. Three urban parks in Fuzhou, Fujian Province, namely Fuzhou National Forest Park, Xihu Park, and Jinniushan Sports Park, were selected as research sites. Environmental monitoring and questionnaire surveys were conducted at 24 recreation places from October to December 2020, collecting temperature, humidity, and wind speed; the atmospheric composition includes PM2.5, PM10, negative oxygen ion, and psychophysiological data from the public. Multivariate statistical methods were employed to assess the environmental characteristics of different recreation places types and their impact on public health. The findings reveal that environmental factors explained 1.9% to 11.8% of the variation in physiological and psychological responses, mainly influenced by temperature, wind speed, and negative oxygen ions. Forests and waterfront recreation places significantly outperform canopy and open recreation places in promoting mental invigoration, stress relief, emotional tranquility, and attention restoration. Environmental monitoring results indicate that favorable meteorological conditions and good air quality are crucial for enhancing the service functions of recreation places. Notably, the positive correlation between a negative air ion concentration and psychological well-being provides a novel perspective on understanding the health benefits of urban forests. The thermal environment and air quality of urban recreation places exert a significant influence on the psychophysiological status of the public. Increasing green coverage, improving water body environments, and rationally planning recreation places layout are of great theoretical and practical significance for enhancing the environmental quality and service functions of urban forests. Full article

(This article belongs to the Topic Biophilic Cities and Communities: Human-Environment Interaction and Sustainable Governance)

15 pages, 1315 KiB

Open AccessArticle

Quantitative Study of Vitamin K in Plants by Pressurized Liquid Extraction and LC-MS/MS

by Iryna Bryshten, Łukasz Paprotny, Małgorzata Olszowy-Tomczyk and Dorota Wianowska

Molecules 2024, 29(18), 4420; https://doi.org/10.3390/molecules29184420 (registering DOI) - 17 Sep 2024

Abstract

The health-promoting properties of vitamin K stimulate the growing interest in this compound, which translates into the development of new analytical methodologies for its determination. New, more efficient methods of its isolation are sought, paying increasingly more attention to the methods within currently [...] Read more.

The health-promoting properties of vitamin K stimulate the growing interest in this compound, which translates into the development of new analytical methodologies for its determination. New, more efficient methods of its isolation are sought, paying increasingly more attention to the methods within currently available extraction techniques that, owing to the optimization of the process, not only increase the extraction efficiency but are also economical and environmentally friendly. This article proposes a procedure for the extraction and analysis of one of the vitamin K vitamers, i.e., vitamin K1, using PLE and LC-MS/MS. It has been shown that the PLE technique can be optimized with a mathematical model—accelerating and reducing the costs of the extraction process—which, together with process automation, bodes well for industrial applications. The optimized process was used to extract vitamin K1 from various vegetables, showing very different contents of the test compound ranging from 1.22 to 114.30 µg/g dry weight for avocado and spinach, respectively. In addition, by showing the effect of water within the material subjected to extraction on the variable yield of vitamin K1, attention was drawn to the need to standardize the analytical methods used in assessing the quality of food products. Full article

(This article belongs to the Special Issue Phytochemicals from Diet and Medicinal Plants: Chemical Diversity, Delivery Systems and Bioactivity)

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15 pages, 4109 KiB

Open AccessArticle

The Effects of Metakaolin on the Properties of Magnesium Sulphoaluminate Cement

by Lili Jiang, Zhuhui Li, Zhenguo Li and Dongye Wang

Materials 2024, 17(18), 4567; https://doi.org/10.3390/ma17184567 (registering DOI) - 17 Sep 2024

Abstract

Magnesium sulphoaluminate (MSA) cement has good bonding properties and is suitable as an inorganic adhesive for repairing materials in civil engineering. However, there are still some problems with its use, such as its insufficient 1 day (d) strength and poor volumetric stability. This [...] Read more.

Magnesium sulphoaluminate (MSA) cement has good bonding properties and is suitable as an inorganic adhesive for repairing materials in civil engineering. However, there are still some problems with its use, such as its insufficient 1 day (d) strength and poor volumetric stability. This paper aims to investigate the influences of metakaolin (MK) on the physical and mechanical properties of magnesium sulphoaluminate (MSA) cement. The hydration products and microstructures of typical MSA cement samples were also analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results showed that the addition of metakaolin reduces the fluidity and shortens the setting time of the MSA cement. The initial setting time and final setting time shortened maximally by 15–27 min and 25–48 min, respectively, with the addition of 10–30% metakaolin. Moreover, the compressive strength and flexural strength of the MSA cement improved significantly with the addition of 10–30% metakaolin at a curing age of 1 d. Compared with the compressive and flexural strengths of the control sample at 1 d, the compressive strengths of the modified samples showed obvious increases of 98%, 101%, and 109%, and the flexural strengths increased by 39%, 31%, and 26%, respectively, although they decreased slightly when the curing ages were 7 d, 14 d, and 28 d. The addition of 10% metakaolin improved the water resistance of the MSA cement immersed in water for 7 d and resulted in even higher water resistance at 28 d. The addition of 10–30% metakaolin improved the volumetric stability of the MSA cement with increasing dosages before 28 d of ageing. XRD and SEM-EDS analyses showed that the metakaolin accelerated the early hydration reaction and optimised the phase composition of the MSA cement. The results indicate that the addition of 10–20% metakaolin improved the strength after 1 d of ageing, water resistance, and volumetric stability of the MSA cement, providing theoretical support for the application of MAS cement as an inorganic bonding agent for repairing materials. Full article

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