The question of whether or not global warming has paused since more than ten years ago, namely ＂warming hia- tus＂, has attracted the attention of climate science community including the IPCC. Some ...authors have attributed the ＂warming hiatus＂ to the internal changes in the climate system, i.e., the recombination of ocean-atmosphere circulations. Therefore, it is necessary to propose higher requirements on reconstructing circulation background of climate change for the past millennium. However, the analyses of changes in atmospheric circulation over the last millennium as well as the conclusions of related re- gional climate patterns are so widely different and contradictory, bringing uncertainties to our understanding of regional even global climate change to a great extent. On the other hand, in the last 10 years the high-precision U/Th-dated stalagmite oxygen isotope ratio （δ^18O） sequences provided an accurate chronological frame for the paleoclimate study of the middle and late Pleistocene, in which all authors from China took the Chinese stalagmite δ^18O as the summer monsoon index without excep- tion. However, this point of view misleads the climate scientists into thinking that the stalagmite δ^18O can be as the proxy of precipitation amount. Nevertheless, it is well known that all of these records have a lot in common in the low frequency trend. However, most sequences cannot be calibrated by instrumental precipitation records, and thus the uncertainty of the climate research framework of China and even of the world has increased. Therefore, it is imperative for climatology to clarify the origin of contradiction and to reduce the uncertainty as early as possible. On the basis of analyzing the significance of stalag- mite ~180 in the monsoon regions of China, the author tries to propose a new circulation proxy in this paper： integrating the Chinese stalagmite oxygen isotope sequence to reconstruct the tropical Pacific sea surface temperature gradient, i.e., the large-scale ENSO-like state over the past millennium. Furthermore, the author speculates that it was warm in the modern times and the Medieval Period, but the circulation recombination was different in both periods. And this inference could be support- ed by the longer record since Last Glacial Maximum. In other words, the attribution analysis of the identical low-frequency trends of Chinese stalagmite t~180 on a large scale shows that the ENSO-like state controls the climate change in the monsoon regions of China at different time scales （from interannual to century or even longer time scales）. Wherein the important connection of circulations is the western Pacific subtropical high （WPSH）, that is to say, besides the interannual and decadal time scales, the WPSH would possess the circulation mode on longer timescales. For example, we may discuss the change of the WPSH in the whole Holocene epoch, i.e., the half precession period. These discussions could make sense to the study of not only the paleoclimate but also the modern climate.
This paper presents the material design and fresh properties of geopolymer mortar developed for 3D concrete printing application. Unlike traditional casting, in 3D printing, extruded materials are ...deposited layer-by-layer to build complex architectural and structural components without the need of any formwork and human intervention. Extrudability, shape retention, buildability and thixotropic open time (TOT) are identified as critical early-age properties to characterize the 3D printable geopolymer material. Five different mix designs of geopolymer are tested in a systematic experimental approach to obtain a best printable mix and later it is used to print a 60-centimeter-tall freeform structure using a concrete gantry printer to validate the formulation.
Noroviruses are the major viral pathogens causing epidemic and endemic acute gastroenteritis with significant morbidity and mortality. While vaccines against norovirus diseases have been shown to be ...of high significance, the development of a broadly effective norovirus vaccine remains difficult, owing to the wide genetic and antigenic diversity of noroviruses with multiple co-circulated variants of various genotypes. In addition, the absence of a robust cell culture system, an efficient animal model, and reliable immune markers of norovirus protection for vaccine evaluation further hinders the developmental process. Among the vaccine candidates that are currently under clinical studies, recombinant VP1-based virus-like particles (VLPs) that mimic major antigenic features of noroviruses are the common ones, with proven safety, immunogenicity, and protective efficacy, supporting a high success likelihood of a useful norovirus vaccine. This short article reviews the recent progress in norovirus vaccine development, focusing on those from recent clinical studies, as well as summarizes the barriers that are being encountered in this developmental process and discusses issues of future perspective.
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•A novel fiber reinforced fly ash based geopolymer was developed for large scale 3D printing application.•Effect of short glass fiber (different fiber lengths and percentages) on ...mechanical properties was investigated.•Mechanical properties are found to be improved on fiber addition up to 1% and mostly dependent of loading directions.
Around the globe, ground breaking projects and case studies are being presented to showcase the potential of digital fabrication with concrete, better known as 3D printing of concrete. With these explorations, underway, the key quest in 3D concrete printing is for structural stability by means of high strength and ductility. This need could be avoided by designing printable fiber reinforcement concrete or concrete with in-process ‘printed’ reinforcement. Therefore, in this paper, an experimental investigation was carried out by reinforcing short glass fiber (GF) of different lengths (3mm, 6mm and 8mm) and percentages (0.25%–1%) in a custom-made sustainable construction material developed for 3D printing application. Thixotropic GF/geopolymer mortar was printed using a 4-Axis gantry system and later loaded in different directions for measuring the mechanical properties. Our experimental results revealed, improved properties of the printed specimens with increase in fiber percentage up to 1% and an obvious directional dependency behaviour, caused by the layer wise deposition.
Rheological studies are important for successful 3D concrete printing. The main challenge for successful 3D concrete printing is the complex characteristic the materials should possess. It should be ...flowable enough to be pumped and extruded through the hose, as well as gaining sufficient strength and stiffness for buildability after the layer by layer deposition. Existing literature has various mixtures proposed for successful 3D concrete printing. Most of these studies used rheometers to measure the dynamic yield stress and plastic viscosity. As the measurement with rheometer is sensitive to the protocols and is controlled by the rheologists, as well as data processing if non-standardized measuring geometries are used, results could vary significantly. This study used standardized field-friendly protocols to measure the slump and slump-flow of the mortars. The pumpability and buildability are evaluated in terms of the pumpability index and maximum height printed before collapsing. These result together with the slump and slump-flow values are used to define the printable region.
The effect of nano-attapulgite clay (NC) addition on the fresh, hardened and microstructural properties of high volume fly ash (HVFA) mixes designed for 3D printing was investigated in this study. ...Experimental results showed that the addition of 0.1–0.5% (i.e. by mass of binder) NC increased the static yield stress of HVFA mortars without significantly affecting the apparent viscosity, due to particle re-flocculation and enhanced thixotropy. When compared to the control mix, the use of 0.5% NC also led to increased viscosity recovery and improved structural build-up at different resting times and shear rates. These advancements were useful for 3D concrete printing, during which the material should be extrudable and buildable layer-by-layer without any deformation. Successful implementation of mixes containing NC was demonstrated via the printing of a 20-layer structure. Further optimization of the NC content and associated HVFA mix design is recommended, depending on the geometrical and mechanical properties required.
Abstract Compared to normal cells, cancer cells strongly upregulate glucose uptake and glycolysis to give rise to increased yield of intermediate glycolytic metabolites and the end product pyruvate. ...Moreover, glycolysis is uncoupled from the mitochondrial tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) in cancer cells. Consequently, the majority of glycolysis-derived pyruvate is diverted to lactate fermentation and kept away from mitochondrial oxidative metabolism. This metabolic phenotype is known as the Warburg effect. While it has become widely accepted that the glycolytic intermediates provide essential anabolic support for cell proliferation and tumor growth, it remains largely elusive whether and how the Warburg metabolic phenotype may play a role in tumor progression. We hereby review the cause and consequence of the restrained oxidative metabolism, in particular in the context of tumor metastasis. Cells change or lose their extracellular matrix during the metastatic process. Inadequate/inappropriate matrix attachment generates reactive oxygen species (ROS) and causes a specific type of cell death, termed anoikis, in normal cells. Although anoikis is a barrier to metastasis, cancer cells have often acquired elevated threshold for anoikis and hence heightened metastatic potential. As ROS are inherent byproducts of oxidative metabolism, forced stimulation of glucose oxidation in cancer cells raises oxidative stress and restores cells’ sensitivity to anoikis. Therefore, by limiting the pyruvate flux into mitochondrial oxidative metabolism, the Warburg effect enables cancer cells to avoid excess ROS generation from mitochondrial respiration and thus gain increased anoikis resistance and survival advantage for metastasis. Consistent with this notion, pro-metastatic transcription factors HIF and Snail attenuate oxidative metabolism, whereas tumor suppressor p53 and metastasis suppressor KISS1 promote mitochondrial oxidation. Collectively, these findings reveal mitochondrial oxidative metabolism as a critical suppressor of metastasis and justify metabolic therapies for potential prevention/intervention of tumor metastasis.
Digital construction is gradually opening unlimited possibilities for building and concrete industry. The key secret for a robust print process lies in our understanding of the processing technology ...and material fresh properties, in addition to developing novel measurement and control techniques. This paper aims to gain a better understanding of early age mechanical properties of 3D printable materials and improve it for the requirement of large scale concrete printing. Experimental investigations were carried out to measure green strength and stiffness of fresh fly ash-cement mortar with applied 3D optical metrology. The compressive green strength was linked with material yield strength evolution and later, modified with nanoclay for higher buildability properties. Nanoclay addition deceased the layer deformation due to significant increase in Young's modulus and to estimate this uncontrolled deformation, a mathematical function was formulated, which subsequently validated by comparison to printing experiments.
This study compared the three-dimensional (3D) accuracy of conventional impressions with digital impression systems (intraoral scanners and dental laboratory scanners) for two different interimplant ...distances in maxillary edentulous arches.
Six impression systems comprising one conventional impression material(Impregum), two intraoral scanners (TRIOS and True Definition), and three dental laboratory scanners (Ceramill Map400, inEos X5, and D900) were evaluated on two completely edentulous maxillary arch master models (A and B) with six and eight implants, respectively. Centroid positions at the implant platform level were derived using either physical or virtual probe hits with a coordinate measuring machine. Comparison of centroid positions between master and test models (n = 5) defined linear distortions (d
, d
, d
), global linear distortions (d
), and 3D reference distance distortions between implants (ΔR). The two-dimensional (2D) angles between the central axis of each implant to the x- or y-axes were compared to derive absolute angular distortions (Absdθ
, Absdθ
).
Model A mean d
ranged from 8.7 ± 8.3 μm to 731.7 ± 62.3 μm. Model B mean d
ranged from 16.3 ± 9 μm to 620.2 ± 63.2 μm. Model A mean Absdθ
ranged from 0.021 ± 0.205 degrees to -2.349 ± 0.166 degrees, and mean Absdθ
ranged from -0.002 ± 0.160 degrees to -0.932 ± 0.290 degrees. Model B mean Absdθ
ranged from -0.007 ± 0.076 degrees to -0.688 ± 0.574 degrees, and mean Absdθ
ranged from -0.018 ± 0.048 degrees to -1.052 ± 0.297 degrees. One-way analysis of variance (ANOVA) by Impression system revealed significant differences among test groups for d
and ΔR in both models, with True Definition exhibiting the poorest accuracy. Independent samples t tests for d
, between homologous implant location pairs in Model A versus B, revealed the presence of two to four significant pairings (out of seven possible) for the intraoral scanner systems, in which instances d
was larger in Model A by 110 to 150 μm.
Reducing interimplant distance may decrease global linear distortions (d
) for intraoral scanner systems, but had no effect on Impregum and the dental laboratory scanner systems. Impregum consistently exhibited the best or second-best accuracy at all implant locations, while True Definition exhibited the poorest accuracy for all linear distortions in both Models A and B. Impression systems could not be consistently ranked for absolute angular distortions.
•Influence of gradations on rheology of cementitious materials has been investigated.•Effect of rheology of 3DP materials on printability and buildability are studied.•Appropriate 3DP materials can ...be designed by applying Fuller Thompson Theory.
Cementitious materials for 3D printing have special requirements for rheological properties, which are significantly affected by many factors, including sand gradation and packing fraction. Fuller Thompson theory and Marson-Percy model are classic approaches for sand gradation and packing fraction optimization, respectively. This paper attempts to apply Fuller Thompson theory and Marson-Percy model in designing cementitious materials for 3D Cementitious Materials Printing (3DCMP). Various gradation methods adopted in this study were Fuller Thompson gradation (mixture A), uniform-gradations (mixture B and C), gap-gradations (mixture D and E). Besides these mixtures with special gradation approaches, one mixture using natural river sand (mixture F) was prepared as well. Rheological properties were characterized by static/dynamic yield stress and plastic viscosity in Bingham Plastic model. Buildability was examined by printing a column with 10 cm inner diameter via a gantry printer. Rheological test results indicate that mixture A designed by continuous gradation possesses the highest static/dynamic yield stress and lowest plastic viscosity. During printing test for buildability, mixture A can easily reach up to 40 layers without notable deformation, while all other mixtures deformed noticeably and fell down before the 35th layer. Finally, a large-scale printing was carried out with mixture A and a structure with the height of 80 cm was printed successfully without notable deformation. Density, compressive strength and flexural strength of printed filaments were also characterized. Mechanical performance test results illustrate mixture A has the highest density and appropriate compressive strength, and a relative high flexural strength at different curing ages. These results indicate that Fuller Thompson theory and Marson-Percy model can serve as a reasonable guide for material rheology design for 3DCMP.
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