Fatigue analysis of ambient-cured geopolymer concrete for high-traffic pavements.

The building sector is growing at a rapid rate, leading to an increased demand for construction materials. Concrete made with Ordinary Portland Cement (OPC) has long been the preferred choice due to its excellent bonding properties and versatility as demanded by construction process. However, the manufacturing of Ordinary Portland Cement (OPC) leads to negative impacts on the environment, with the cement sector responsible for around 5-8% of global CO2 emissions. In addition, the manufacture of OPC necessitates significant amounts of natural raw materials and energy. Contrastingly, using geopolymers promises to save substantial amounts of energy and reduce CO2 emissions. This potential has sparked growing interest in the application of geopolymers within transportation infrastructure. For pavements, the workability requirement is less, and hence, geopolymer concrete (GPC) is a viable option, but fatigue-resistance of GPC is not seen reported in literatures. This article evaluates the properties of geopolymer concrete with low-calcium fly ash partially replaced with ground granular blast furnace slag (GGBS) with 8 M NaOH alkaline solution and cured under ambient atmospheric conditions to evaluate its usage in pavements and develop an environmentally sustainable and durable GPC capable of withstanding heavy traffic. The study involves adjusting the pavement quality concrete (PQC) mix design; evaluating the mechanical characteristics, abrasion resistance, and shrinkage strain of the GPC; and analyzing its microstructure. Additionally, the study compares the fatigue life of GPC to that of PQC using various Weibull distribution approaches. The results showed that GPC4 (70% Fly ash and 30% GGBS) mix achieved best results at 28 days, with a compressive strength of 45.68 MPa, split tensile strength of 3.76 MPa, and flexural strength of 4.62 MPa. Also, shrinkage strains were nearly 31% lesser than PQC at 90 days. In addition, developing GPC needs 27% lesser embodied energy than PQC. Fatigue analysis prove that ambient cured fly ash-GGBS based geopolymer concrete with 8 M NaOH exhibits less stress development than PQC at medium loads, even though it is brittle. Thus, the study proves that it is suitable as a material for pavements to resist medium-loaded traffic-resisting pavements.

A highly selective coumarin-based chemosensor for dual sensing of Cu2+ and Zn2+ ions with logic gate integration and live cell imaging.

In this paper, a coumarin-based Schiff base chemosensor has been synthesized and developed to detect Cu2+ and Zn2+ ions in nanomolar concentrations. The probe selectively distinguishes Cu2+ and Zn2+ from among several metal ions in DMF : H2O (7 : 3, v/v, pH 7.4) HEPES buffer. The structure of the probe and its sensing behavior were investigated by FT-IR, UV-vis, fluorescence, HRMS, and NMR analyses, along with X-ray crystallography and computational studies. CIH detects Zn2+ and Cu2+ using different strategies: CHEF-induced fluorescence enhancement and paramagnetic fluorescence quenching, respectively. Job's plots show a 1 : 1 binding interaction between CIH and Cu2+ or Zn2+ ions. The binding constant values for Cu2+ (1.237 × 105 M-1) and Zn2+ (1.24 × 104 M-1) suggest a better ability for Cu2+ to interact with CIH than Zn2+. An extremely high sensitivity of the probe was highlighted by its very low detection limits (LOD) of 5.36 nM for Cu2+ and 3.49 nM for Zn2+. The regeneration of the probe with the addition of EDTA in its complexes allows the formation of molecular logic gates. CIH has been successfully employed in mitotracking and intracellular detection of Zn2+ and Cu2+ in SiHa cells.

Properties of SCC containing pozzolans, Wollastonite micro fiber, and recycled aggregates.

Self compacting concretes (SCC) containing higher volumes of pozzolanic materials possess compressive strengths up to 30MPa. Fibers like steel, polypropylene, and carbon fibers are added in small volumes ranging from 0.25-2% v/v of concrete to increase the strength (>40MPa) of such concretes as higher volumes of fiber cause balling effect on account of inhomogeneity, thereby reducing the strength and workability. Hence higher volume of cement substitution either with mineral admixtures or fibers, or with both, to increase strength and workability is limited in the case of SCC. The condition worsens further if recycled aggregates replace normal aggregates. Wollastonite micro fiber (WMF) is a promising material that could be used in higher contents but its interaction with recycled aggregates to affect workability and strength has not been studied. Therefore this study tries to obtain a high strength concrete (>M40) by use of WMF along with flyash @ 5%, maximally up to 10% each. Microsilica was added @ 2.5%, maximally up to 10% to improve the interphase strength and make the concrete homogeneous. Results indicated that in order to obtain a high strength mix for such composites, higher amounts of WMF (≥10% by weight of binder) such that WMF:flyash varies from 1:1 to 2:1 is required, along with microsilica contents ≥7.5%. Literature suggests 5% microsilica along with either 20% WMF or 10% flyash, for yielding high strength SCC without recycled aggregates. Hence use of nearly equal amounts of WMF, flyash, and microsilica such that nearly 30% of cement is substituted, is recommended.

Bioinformatic discovery of a toxin family in Chryseobacterium piperi with sequence similarity to botulinum neurotoxins.

Clostridial neurotoxins (CNTs), which include botulinum neurotoxins (BoNTs) and tetanus neurotoxin (TeNT), are the most potent toxins known to science and are the causative agents of botulism and tetanus, respectively. The evolutionary origins of CNTs and their relationships to other proteins remains an intriguing question. Here we present a large-scale bioinformatic screen for putative toxin genes in all currently available genomes. We detect a total of 311 protein sequences displaying at least partial homology to BoNTs, including 161 predicted toxin sequences that have never been characterized. We focus on a novel toxin family from Chryseobacterium piperi with homology to BoNTs. We resequenced the genome of C. piperi to confirm and further analyze the genomic context of these toxins, and also examined their potential toxicity by expression of the protease domain of one C. piperi toxin in human cells. Our analysis suggests that these C. piperi sequences encode a novel family of metalloprotease toxins that are distantly related to BoNTs with similar domain architecture. These toxins target a yet unknown class of substrates, potentially reflecting divergence in substrate specificity between the metalloprotease domains of these toxins and the related metalloprotease domain of clostridial neurotoxins.

Enhancement of the endopeptidase activity of purified botulinum neurotoxins A and E by an isolated component of the native neurotoxin associated proteins.

In botulism disease, neurotransmitter release is blocked by a group of structurally related neurotoxin proteins produced by Clostridium botulinum. Botulinum neurotoxins (BoNT, A-G) enter nerve terminals and irreversibly inhibit exocytosis via their endopeptidase activities against synaptic proteins SNAP-25, VAMP, and Syntaxin. Type A C. botulinum secretes the neurotoxin along with 5 other proteins called neurotoxin associated proteins (NAPs). Here, we report that hemagglutinin-33 (Hn-33), one of the NAP components, enhances the endopeptidase activity of not only BoNT/A but also that of BoNT/E, both under in vitro conditions and in rat synaptosomes. BoNT/A endopeptidase activity in vitro is about twice as high as that of BoNT/E under disulfide-reduced conditions. Addition of Hn-33 separately to nonreduced BoNT/A and BoNT/E (which otherwise have only residual endopeptidase activity) enhanced their in vitro endopeptidase activity by 21- and 25-fold, respectively. Cleavage of rat-brain synaptosome SNAP-25 by BoNTs was used to assay endopeptidase activity under nerve-cell conditions. Reduced BoNT/A and BoNT/E cleaved synaptosomal SNAP-25 by 20% and 15%, respectively. Addition of Hn-33 separately to nonreduced BoNT/A and BoNT/E enhanced their endopeptidase activities by 13-fold for the cleavage of SNAP-25 in synaptosomes, suggesting a possible functional role of Hn-33 in association with BoNTs. We believe that Hn-33 could be used as an activator in the formulation of the neurotoxin for therapeutic use.