Hybrid Cements with ZnO Additions: Hydration, Compressive Strength and Microstructure.

The effect of ZnO has already been studied for Portland cement, but the study of its impact on hybrid pastes is scarce. Thus, in this investigation, the influence of ZnO addition on hydration, compressive strength, microstructure, and structure of hybrid pastes is presented. The analyses were made by setting time tests, compressive strength tests, X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis with differential scanning calorimetry, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The results indicate that the setting time of the cements was delayed up to 39 min with additions of 3 wt% ZnO. Alternatively, the higher values of compressive strength were observed when 0.5 wt% ZnO was added to the cements for all curing days. In addition, no important differences in the microstructure of samples with different additions of ZnO were observed after 28 days of curing. It is expected that the use of ZnO contributes to the delay of the setting time and the increase of the compressive strength without negatively modifying the microstructure of hybrid pastes.

Sunlight Photocatalytic Performance of ZnO Nanoparticles Synthesized by Green Chemistry Using Different Botanical Extracts and Zinc Acetate as a Precursor.

In this work, the assessment of Azadirachta indica, Tagetes erecta, Chrysanthemum morifolium, and Lentinula edodes extracts as catalysts for the green synthesis of zinc oxide nanoparticles (ZnO NPs) was performed. The photocatalytic properties of ZnO NPs were investigated by the photodegradation of methylene blue (MB) dye under sunlight irradiation. UV-visible (UV-Vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Thermogravimetric (TGA), and Brunauer-Emmett-Teller analysis (BET) were used for the characterization of samples. The XRD results indicate that all synthesized nanoparticles have a hexagonal wurtzite crystalline structure, which was confirmed by TEM. Further, TEM analysis proved the formation of spherical and hemispherical nanoparticles of ZnO with a size in the range of 14-32 nm, which were found in aggregate shape; such a size was well below the size of the particles synthesized with no extract (~43 nm). ZnO NPs produced with Tagetes erecta and Lentinula edodes showed the best photocatalytic activity, matching with the maximum adsorbed MB molecules (45.41 and 58.73%, respectively). MB was completely degraded in 45 min using Tagetes erecta and 120 min using Lentinula edodes when subjected to solar irradiation.

Evaluation of two in-house immunoenzymatic tests to serodiagnose subclinical paratuberculisis in a sheep flock in Mexicali valley, Mexico.

Paratuberculosis (PTB) or Johne's disease is a common ruminant infectious disease caused by Mycobacterium avium subsp. paratuberculosis (MAP). In this study, two MAP antigens were compared for their diagnostic utility to detect subclinical PTB in a sheep flock in Mexicali, Mexico. Sheep (n = 31) without clinical signs but positive on a direct fecal-polymerase chain reaction were tested with two preabsorbed in-house enzyme linked immunosorbent assays (ELISAs) using: (1) an ethanol-extracted surface lipid antigen (EVELISA) and (2) a protoplasmic antigen (ELISA-PPA). Sensitivities of the EVELISA and ELISA-PPA were 84% (95% CI; 66-95%) and 29% (95% CI; 14-48%), respectively. The EVELISA test could be a fast and effective way to identify subclinical ovine PTB for severely affected flocks.

Turbostratic Carbon/Graphene Prepared via the Dry Ice in Flames Method and Its Purification Using Different Routes: A Comparative Study.

Although the dry ice method used to synthesize turbostratic carbon/graphene is little known and used, it has significant advantages over others, such as the following: it is low cost, simple, and a large quantity of material can be obtained using some inorganic and highly available acids (which can be reused). Despite the above advantages, the main reason for its incipient development is the resulting presence of magnesium oxide in the final product. In the present work, three different treatments were tested to remove this remnant using some acid chemical leaching processes, including hydrochloric acid, aqua regia, and piranha solution. Based on the experimental evidence, it was determined that using aqua regia and combining the leaching process with mechanical milling was the most efficient way of removing such a remnant, the residue being only 0.9 wt.%. This value is low compared to that obtained with the other acid leaching solutions and purification processes (2.8-29.6 wt.%). A mandatory high-energy mechanical milling stage was necessary during this treatment to expose and dissolve the highly insoluble oxide without secondary chemical reactions on the turbostratic carbon. High-energy mechanical milling is an effective route to exfoliate graphite, which allows the magnesium oxide to be more susceptible to acid treatment. A yield of turbostratic carbon/graphene of 1 wt.% was obtained from the metallic Mg. The obtained surface area was 504.8 m2g-1; this high value resulting from the intense exfoliation can potentiate the use of this material for a wide variety of applications.

Sustainable Biocomposites for Structural Applications with Environmental Affinity.

In this work, we report a facile preparation of biocomposites using a chitosan matrix that is reinforced with morphed graphene in amounts from 1 to 5 wt % C. The composites are processed by milling and conventional sintering. The morphed graphene additions show clear improvements in mechanical properties, having a direct correlation with temperature in particular for 180 °C. Higher temperatures are detrimental to chitosan and the properties drop because chitosan degrades. Mechanical properties in the composite such as yield strength and compressive strength increase between 40 and 50% with respect to the pure chitosan samples. The Young's modulus presents a drop of approximately 10%, but the fracture toughness increases up to 3.5 fold. The properties of our sustainable composites are comparable to those seen in polymers such as polyethylene, polypropylene, nylon, and poly(methyl methacrylate), among other commodity or single use plastics. The enhancement in the mechanical properties is attributed to the morphed graphene embedded chitosan matrix that generates a network of intergranular "anchors" that hold the chitosan crystals in place, preventing failure. The composites can be molded into near-net-shape products, machined, or shaped using various methods including laser lithography. These studies demonstrate the feasibility of fabricating biocomposites with different architectures and sizes for disposable structural components. Both chitosan and the composites are compostable and biodegradable with the potential to sustain plant growth when discarded. In addition, morphed graphene and chitosan are produced from byproducts or waste, which may result in a negative carbon footprint on the environment.

Detection of Intestinal Parasites in Stray Dogs from a Farming and Cattle Region of Northwestern Mexico.

Stray dogs are one of the main reservoirs of intestinal parasitic infections and some have zoonotic potential. An epidemiological survey was carried out between September 2017 and May 2018 in Mexicali Valley, this area sacrifices around 92,470 head of cattle monthly, which represents 27% of the national slaughter and has 71,307 hectares for crops. In this period the Municipal Animal Control Center during their routine visits to the Mexicali Valley captured 103 dogs. All the dogs were evaluated using copromicroscopic techniques to detect intestinal parasites. The general frequency of parasitic infections was 28.15% (29/103), the most frequent parasite being Dipylidium caninum 16.50% (17/103), followed by Taenia spp. 6.79% (7/103), Taenia hydatigena 2.91% (3/103), Taenia serialis 0.97% (1/103), Taenia pisiformis (0.97%), Toxocara canis 3.88% (4/103), Toxascaris leonina 1.94% (2/103), and Cystoisospora spp. 1.94% (2/103). No significant statistical associations were found between parasitic infections and the studied variables (sex, age, and size) however; there was a significant statistical association with the capture area. Most of the parasites found in this survey have potential to affect the human population and animal production.

Influence of Size on the Microstructure and Mechanical Properties of an AISI 304L Stainless Steel-A Comparison between Bulk and Fibers.

In this work, the mechanical properties and microstructural features of an AISI 304L stainless steel in two presentations, bulk and fibers, were systematically studied in order to establish the relationship among microstructure, mechanical properties, manufacturing process and effect on sample size. The microstructure was analyzed by XRD, SEM and TEM techniques. The strength, Young's modulus and elongation of the samples were determined by tensile tests, while the hardness was measured by Vickers microhardness and nanoindentation tests. The materials have been observed to possess different mechanical and microstructural properties, which are compared and discussed.