Residual Impact Performance of ECC Subjected to Sub-High Temperatures

Despite the fact that the mechanical properties of Engineered Cementitious Composites (ECC) after high-temperature exposure are well investigated in the literature, the repeated impact response of ECC is not yet explored. Aiming to evaluate the residual impact response of ECC subjected to sub-high temperatures under repeated drop weight blows, the ACI 544-2R repeated impact test was utilized in this study. Disk impact specimens (150 mm diameter and 64 mm thickness) were prepared from the M45 ECC mixture but using polypropylene fibers, while similar 100 mm cube specimens and 100 × 100 × 400 mm prism specimens were used to evaluate the compressive and flexural strengths. The specimens were all cast, cured, heated, cooled, and tested under the same conditions and at the same age. The specimens were subjected to three temperatures of 100, 200 and 300 °C, while a group of specimens was tested without heating as a reference group. The test results showed that heating to 100 and 200 °C did not affect the impact resistance noticeably, where the retained cracking and failure impact numbers and ductility were higher or slightly lower than those of unheated specimens. On the other hand, exposure to 300 °C led to a serious deterioration in the impact resistance and ductility. The retained failure impact numbers after exposure to 100, 200, and 300 °C were 313, 257, and 45, respectively, while that of the reference specimens was 259. The results also revealed that the impact resistance at this range of temperature showed a degree of dependency on the compressive strength behavior with temperature.

Experimental Study of Single-Lap, Hybrid Joints, Made of 3D Printed Polymer and Aluminium Adherends

This paper presents the results of an experimental study into single-lap joints. One part of the joint was made as a 3D printed polymer and had cylindrical tenons, while the other part was made of an aluminium flat bar having mortises whose diameter and distribution corresponded to the polymer tenons. In addition to the mechanical joint, a layer of double-sided VHB (Very High Bond) adhesive tape was also placed in the lap, thus creating a hybrid joint. In total, 80 specimens were made, which were divided into four groups: A—specimens with one tenon of different diameters, B—specimens with different number of tenons of the same diameter, C—specimens characterised by multi-stage operation and R—reference specimens, connected only by double-sided adhesive tape. The joints were subjected to uniaxial tensile tests. The force–displacement characteristics obtained and the energy required, up to the point of the failure of the joints, have been analysed in this paper. The four and six-stage joints designed can significantly increase the safety of the structures in which they will be used.

Fire Performance of Fly Ash-Based Geopolymer Concrete: Effect of Burning Temperature

Geopolymer concrete (GEO) is a cementless concrete produced from the reaction of an aluminosilica-rich material, in particular, fly ash, with an alkaline solution, which can either be sodium or potassium-based. In light of the potential of fly ash-based GPC as an alternative to Ordinary Portland Cement (OPC)-based concrete as a green building material, an investigation on the fire performance of GEO, in comparison to OPC-based concrete, is essential. The results of an experimental study on the fire performance of fly ash-based GEO that was subjected to a flame test using a methane burner torch, after 28 days of curing, to simulate a real fire event, are presented. Concrete specimens were exposed to a fire flame at 500 °C and 1200 °C for two hours and subsequently cooled to the ambient temperature, prior to testing. Visual inspection was performed on the specimens to observe for any cracking, spalling and change in colour. Losses of mass and residual compressive strength were measured. The results were compared with those of OPC-based reference specimens. The findings revealed that, in contrast to OPC-based concrete, the strength of GPC increased when exposed to fire at 500 °C. GEO also suffered a smaller loss of mass as compared to OPC-based concrete due to the smaller amount of loss in moisture from burning. It was also observed that no spalling had occurred on the GEO, with less cracking on the exposed surface in relation to OPC-based concrete, hence indicating that the structural integrity of GEO was successfully maintained.

Influence of Microfibrillated Cellulose Additive on Strength, Elastic Modulus, Heat Release, and Shrinkage of Mortar and Concrete

This work aimed to study the effect of a microfibrillated cellulose additive on strength, elastic modulus, heat release, and shrinkage of mortar and concrete. The dosage of the additive varies from 0.4 to 4.5% by weight of the cement. The change in strength with an increase in the dosage of the additive occurred in a wave-like manner. The uneven character of the change in the results also took place in the determination of heat release and shrinkage. In general, heat release and shrinkage decreased at increasing additive dosage. The additive showed the greatest decrease in the heat release of concrete at a content of 2%. The heat release of concrete practically differed little from the exotherm of the standard at an additive content of 1 and 1.5%. The addition of microfibrillated cellulose additive in small (0.5%) and large (1.5%) amounts reduced shrinkage compared to the reference, and at an intermediate content (1%), the shrinkage was higher than in the reference specimens. In this case, the water evaporation rate from concrete increased with an increase in the additive. With an increase in the additive dosage, the modulus of elasticity decreases. Thus, the microfibrillated cellulose additive provides concrete with lower values of the modulus of elasticity, heat release, and shrinkage, and the additive is recommended for use in concretes with increased crack resistance during the hardening period. The recommended additive content is 0.5% by weight of cement. At the specified dosage, it is possible to provide the class of concrete in terms of compressive strength C35/45.

Rapid reconstruction of neural circuits using tissue expansion and lattice light sheet microscopy

Electron microscopy (EM) allows for the reconstruction of dense neuronal connectomes but suffers from low throughput, limiting its application to small numbers of reference specimens. We developed a protocol and analysis pipeline using tissue expansion and lattice light-sheet microscopy (ExLLSM) to rapidly reconstruct selected circuits across many samples with single synapse resolution and molecular contrast. We validate this approach in Drosophila, demonstrating that it yields synaptic counts similar to those obtained by EM, can be used to compare counts across sex and experience, and to correlate structural connectivity with functional connectivity. This approach fills a critical methodological gap in studying variability in the structure and function of neural circuits across individuals within and between species.

Application of X-Shaped CFRP Ropes for Structural Upgrading of Reinforced Concrete Beam–Column Joints under Cyclic Loading–Experimental Study

The effectiveness of externally applied fiber-reinforced polymer (FRP) ropes made of carbon fibers in X-shape formation and in both sides of the joint area of reinforced concrete (RC) beam–column connections is experimentally investigated. Six full-scale exterior RC beam–column joint specimens are tested under reverse cyclic deformation. Three of them have been strengthened using carbon FRP (CFRP) ropes that have been placed diagonally in the joint as additional, near surface-mounted reinforcements against shear. Full hysteretic curves, maximum applied load capacity, damage modes, stiffness and energy dissipation values per each loading step are presented and compared. Test results indicated that joint sub assemblages with X-shaped CFRP ropes exhibited improved hysteretic behavior and ameliorated performance with respect to the reference specimens. The effectiveness and the easy-to-apply character of the presented strengthening technique is also discussed.

Using MALDI-TOF mass spectrometry to identify ticks collected on domestic and wild animals from the Democratic Republic of the Congo

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) has recently emerged as an alternative to morphological and molecular tools to identify tick species. In this study, we set out to evaluate and confirm the ability of MALDI-TOF MS to identify different species of ticks collected in the Democratic Republic of the Congo and preserved in 70% ethanol. A total of 575 ticks, of which 530 were collected from domestic pigs and 45 from wild animals, were subjected to MALDI-TOF MS analysis to evaluate the intraspecies reproducibility and interspecies specificity of MS profiles obtained from the different species. Morphologically, the ticks belonged to seven different species, namely Rhipicephalus complanatus, Rhipicephalus congolensis, Haemaphysalis muhsamae, Ixodes cumulatimpunctatus, Amblyomma exornatum, Amblyomma compressum and an unidentified Rhipicephalus sp. A total of 535/575 (93%) of the spectra obtained were of good enough quality to be used for our analyses. Our home-made MALDI-TOF MS arthropod database was upgraded with spectra obtained from between one and five randomly selected specimens per species. For these reference specimens, molecular identification of the ticks was also made using 16S, 12S rDNA genes and the Cox1 mtDNA gene sequencing. The remaining good quality spectra were then queried against the upgraded MALDI-TOF MS database, showing that 100% were in agreement with the morphological identification, with logarithmic score values (LSVs) between 1.813 and 2.51. The consistency between our morphological, molecular and MALDI-TOF MS identification confirms the capability and precision of MALDI-TOF MS for tick identification.

A DNA microarray for the authentication of giant tiger prawn (Penaeus monodon) and whiteleg shrimp (Penaeus (Litopenaeus) vannamei): a proof-of-principle

This proof-of-principle study describes the development of a rapid and easy-to-use DNA microarray assay for the authentication of giant tiger prawns and whiteleg shrimp. Following DNA extraction and conventional end-point PCR of a 16S rDNA segment, the PCR products are hybridised to species-specific oligonucleotide probes on DNA microarrays located at the bottom of centrifuge tubes (ArrayTubes) and the resulting signal patterns are compared to those of reference specimens. A total of 21 species-specific probes were designed and signal patterns were recorded for 47 crustacean specimens belonging to 16 species of seven families. A hierarchical clustering of the signal patterns demonstrated the specificity of the DNA microarray for the two target species. The DNA microarray can easily be expanded to other important crustaceans. As the complete assay can be performed within half a day and does not require taxonomic expertise, it represents a rapid and simple alternative to tedious DNA barcoding and could be used by crustacean trading companies as well as food control authorities for authentication of crustacean commodities. Graphical abstract

A synopsis of the African genus Whitfieldia (Acanthaceae: Whitfieldieae) and a key to the species

SummaryWe present a synopsis and an identification key for the 13 species and one subspecies of the African genus Whitfieldia Hook. (Acanthaceae: Acanthoideae: Whitfieldieae). This work is based on the observation and analysis of morphological data from herbarium specimens and photographs of Whitfieldia species, and the study of all the relevant literature on the genus. Whitfieldia latiflos C.B.Clarke ex Stapf from Liberia is reinstated as an accepted species and a full description and illustration are provided. A new subspecies, W. colorata C.B.Clarke ex Stapf subsp. tigrina A.Grall & I.Darbysh., also from Liberia, is described. In addition, W. arnoldiana De Wild. & T.Durand and W. letestui Benoist are treated as synonyms of W. laurentii (Lindau) C.B.Clarke and W. preussii (Lindau) C.B.Clarke respectively for the first time. Eleven names in Whitfieldia are lectotypified. Reference specimens, relevant literature, habitat notes, distribution maps, taxonomic notes and a preliminary assessment of the conservation status and extinction risk are provided for each taxon. Four species are considered to be threatened of which two (W. latiflos and W. rutilans Heine) are assessed as Endangered (EN) while two others (W. purpurata (Benoist) Heine and W. thollonii (Baill.) Benoist) are placed in the Vulnerable (VU) category. In addition, two taxa are assessed as Near Threatened (NT) and one is currently considered to be Data Deficient (DD).