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.
Attention-control processes transfer relevant information to visual working memory (WM) and prevent irrelevant information from consuming WM resources. Although event-related potentials (ERPs) have ...revealed attention-control processes associated with enhancement of relevant stimuli (targets) and suppression of irrelevant stimuli (distractors), only the suppressive processes have been found to predict WM capacity. We hypothesised a link between target-enhancement processes and WM capacity would be revealed in a task that requires more control than the conventional visual search paradigms used to study target selection. Here, participants searched for a pop-out target on Go trials and withheld responses on an equal number of randomly intermixed No-Go trials, depending on the colour of the stimulus array. Magnitudes of ERP indices associated with target enhancement (the singleton detection positivity, SDP, and N2pc) were positively correlated with individual differences in WM capacity. These relationships vanished when participants searched for the pop-out target on every trial, regardless of stimulus-array colour. Inhibitory processes associated with suppressing distractors (PD) and withholding responses (no-go P3) on No-Go trials did not predict WM capacity. These findings indicate that target-enhancement mechanisms control access to WM in search tasks that require dynamic control and disconfirm the view that the gateway to WM is entirely inhibitory by nature.
► CD polymer grafted magnetic nanoparticles are used for selective heavy metals removal. ► CD polymer grafted on MNP enhances the metal uptake due to its complexation ability. ► The adsorption ...affinity is in the order of Pb2+>Cd2+>Ni2+ in single-metal system. ► CDpoly-MNPs can preferentially adsorb Pb2+ ions in multi-metal system. ► Adsorption mechanism, desorption and reusability of CDpoly-MNPs has been explored.
In this work, carboxymethyl-β-cyclodextrin (CM-β-CD) polymer modified Fe3O4 nanoparticles (CDpoly-MNPs) was synthesized for selective removal of Pb2+, Cd2+, Ni2+ ions from water. This magnetic adsorbent was characterized by TEM, FTIR, XPS and VSM. The adsorption of all studied metal ions onto CDpoly-MNPs was found to be dependent on pH, ionic strength, and temperature. Batch adsorption equilibrium was reached in 45min and maximum uptakes for Pb2+, Cd2+ and Ni2+ in non-competitive adsorption mode were 64.5, 27.7 and 13.2mgg−1, respectively at 25°C. Adsorption data were fitted well to Langmuir isotherm and pseudo-second-order models for kinetic study. The polymer grafted on MNPs enhanced the adsorption capacity because of the complexing abilities of the multiple hydroxyl and carboxyl groups in polymer backbone with metal ions. In competitive adsorption experiments, CDpoly-MNPs could preferentially adsorb Pb2+ ions with an affinity order of Pb2+≫Cd2+>Ni2+ which can be explained by hard and soft acids and bases (HASB) theory. Furthermore, we explored the recyclability of CDpoly-MNPs.
An advancing technology that combines the concrete extrusion with a motion control to create structures with complex geometrical shapes without the need for formwork is known as 3D concrete printing. ...Since this technique prints layer by layer, the time taken to reach the same position in the subsequent layer is important as it will create an anisotropic property that has a weaker tensile strength at the bond interface of the two printed filaments. Through rheological measurement, which reveals the material deformation and flow behaviour, it is possible to examine the material structural build-up due to time-gap effect by measuring at different time delay. This paper focuses on investigating the time-gap effect on the printed filament with rheological and observation at macroscopic-scale to understand the material behaviour of the initial and subsequent printed layer during its fresh phase. Rheological experiment findings reveal that the tensile strength of the printed specimen is correlated to the material modulus at the initial layer.
The disposal of post-consumer glass has been a major issue due to its inert properties that may cause environmental effects, while recycling of these glasses is only feasible if the waste glass ...recovered is sorted into its different colour to prevent chemical incompatibility in the manufacturing process. 3D printing in building and construction has gain increasing attention in the past decade and provides a potential to sustainably utilize the recycled unsorted glasses. This paper examines the use of recycled glass as the fine aggregates for 3D concrete printing applications. Despite the several studies done on the use of recycled glass in concrete, there is a lack of focus on the rheology of the material which is essential to the performance of the material in 3D concrete printing. Although results have shown that the mechanical strength for the recycled glass concrete is lower than the sand aggregates concrete, yet the flow properties of the former is better than the latter. Nonetheless, a balance between the mechanical strength and flowability of the mix design should be studied. The future work revolves around the optimization of the mix design using a combination of sand and recycled glass, adjusting the gradation of recycled glass particles and addition of accelerators to improve its buildability and mechanical strengths.
A facile, efficient, and highly diastereo‐ and enantioselective bromoetherification of diolefinic diols has been developed using an amino‐thiocarbamate catalyst. Further manipulations of the ...bromoether products enabled entry into a new class of spirocycles which are distinctively lacking in the literature.
Seeing double: A facile, efficient, and highly diastereo‐ and enantioselective bromoetherification of diolefinic diols has been developed using an amino‐thio‐carbamate catalyst. Further manipulations of the bromoether products enabled entry into a new class of spirocycles, having three stereogenic quaternary carbon centers, which are distinctively lacking in the literature.
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3D concrete printing can be used to build many complex structures. However, due to its material properties in the fresh state, it is difficult to construct overhanging structures ...without supports. In order to unleash the true capability of 3D concrete printing, a support structure is required to support any overhanging fresh material, which is usually removed during post-processing. This study demonstrates the feasibility of adjusting the printing parameters to print the main structure and support structure using a single type of building material. It was found that the solidity ratio, which is defined as the ratio between actual and expected filament sizes, was significantly affected by the nozzle travel speed and material volume flow rate. Furthermore, a gap distance characterisation test was carried out to find the maximum distance that the filament can cross over without a significant slump. The results were combined to determine the different printable regions for different operations. An overhang structure was printed to verify the results obtained for the different printing operations. This technique allows complex structure to be built without the need for human intervention throughout the printing process.
Scalability is a problem common to most existing 3D printing processes, where the size of the design is strictly constrained by the chamber volume of the 3D printer. This issue is more pronounced in ...the building and construction industry, where it is impractical to have printers that are larger than actual buildings. One workaround consists in printing smaller pieces, which can then be assembled on-site. This workaround generates however additional design and process complexities, as well as creates potential weaknesses at the assembly interfaces. In this paper, we propose a 3D printing system that employs multiple mobile robots printing concurrently a large, single-piece, structure. We present our system in detail, and report simulation and experimental results. To our knowledge, this is the first physical demonstration of large-scale, concurrent, 3D printing of a concrete structure by multiple mobile robots.
•Use multiple mobile robot printers in multi-agent settings for collaborative printing•System incorporates localisation, collision avoidance and optimal robot placement•Improve scalability and time efficiency, and demonstrate on-site printing capability•Large structure printed with proposed system in a safe, efficient and scalable manner•First multi-robot simultaneous printing on single concrete structure
Effectors of Type III Secretion System (T3SS) play a pivotal role in establishing and maintaining pathogenicity in the host and therefore the identification of these effectors is important in ...understanding virulence. However, the effectors display high level of sequence diversity, therefore making the identification a difficult process. There is a need to collate and annotate existing effector sequences in public databases to enable systematic analyses of these sequences for development of models for screening and selection of putative novel effectors from bacterial genomes that can be validated by a smaller number of key experiments.
Herein, we present T3SEdb http://effectors.bic.nus.edu.sg/T3SEdb, a specialized database of annotated T3SS effector (T3SE) sequences containing 1089 records from 46 bacterial species compiled from the literature and public protein databases. Procedures have been defined for i) comprehensive annotation of experimental status of effectors, ii) submission and curation review of records by users of the database, and iii) the regular update of T3SEdb existing and new records. Keyword fielded and sequence searches (BLAST, regular expression) are supported for both experimentally verified and hypothetical T3SEs. More than 171 clusters of T3SEs were detected based on sequence identity comparisons (intra-cluster difference up to ~60%). Owing to this high level of sequence diversity of T3SEs, the T3SEdb provides a large number of experimentally known effector sequences with wide species representation for creation of effector predictors. We created a reliable effector prediction tool, integrated into the database, to demonstrate the application of the database for such endeavours.
T3SEdb is the first specialised database reported for T3SS effectors, enriched with manual annotations that facilitated systematic construction of a reliable prediction model for identification of novel effectors. The T3SEdb represents a platform for inclusion of additional annotations of metadata for future developments of sophisticated effector prediction models for screening and selection of putative novel effectors from bacterial genomes/proteomes that can be validated by a small number of key experiments.
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