Scale Effects on the Ballistic Penetration of Graphene Sheets

AbstractCarbon nanostructures are promising ballistic protection materials, due to their low density and excellent mechanical properties. Recent experimental and computational investigations on the behavior of graphene under impact conditions revealed exceptional energy absorption properties as well. However, the reported numerical and experimental values differ by an order of magnitude. In this work, we combined numerical and analytical modeling to address this issue. In the numerical part, we employed reactive molecular dynamics to carry out ballistic tests on single, double, and triple-layered graphene sheets. We used velocity values within the range tested in experiments. Our numerical and the experimental results were used to determine parameters for a scaling law. We find that the specific penetration energy decreases as the number of layers (N) increases, from ∼15 MJ/kg for N = 1 to ∼0.9 MJ/kg for N = 350, for an impact velocity of 900 m/s. These values are in good agreement with simulations and experiments, within the entire range of N values for which data is presently available. Scale effects explain the apparent discrepancy between simulations and experiments.</jats:p

Aprendizajes de Estudiantes de Enfermería Involucrados en Proyectos de Investigación: Revisión Integrativa de la Literatura

To identify the learning outcomes and skills obtained of undergraduate nursing students involved in research projects. Methods: This was an integrative literature review, based on a research protocol in the CINAHL Complete databases; Cochrane Central Register of Controlled Trials; Cochrane Database of Systematic Reviews; Cochrane Methodology Register; MedicLatina; MEDLINE, Scopus and JBI, including primary and secondary studies, published between 2015 and 2020. Results: A total of five heterogeneous articles were included, which were categorized using Kirkpatrick’s (adapted) model. Seventeen learning outcomes acquired through participation in research projects were identified, from the learning of new knowledge and skills to the development of new attitudes and behaviors. Final considerations: The involvement of nursing students in research projects is important to their professional development. Future investment in research on this topic can help cement the potential of this type of student involvement.info:eu-repo/semantics/publishedVersio

Elastic properties of graphyne-based nanotubes

Graphyne nanotubes (GNTs) are nanostructures obtained from rolled up graphyne sheets, in the same way carbon nanotubes (CNTs) are obtained from graphene ones. Graphynes are 2D carbon-allotropes composed of atoms in sp and sp2 hybridized states. Similarly to conventional CNTs, GNTs can present different chiralities and electronic properties. Because of the acetylenic groups (triple bonds), GNTs exhibit large sidewall pores that influence their mechanical properties. In this work, we studied the mechanical response of GNTs under tensile stress using fully atomistic molecular dynamics simulations and density functional theory (DFT) calculations. Our results show that GNTs mechanical failure (fracture) occurs at larger strain values in comparison to corresponding CNTs, but paradoxically with smaller ultimate strength and Young's modulus values. This is a consequence of the combined effects of the existence of triple bonds and increased porosity/flexibility due to the presence of acetylenic groups

Fecal occult blood and fecal calprotectin as point-of-care markers of intestinal morbidity in Ugandan children with Schistosoma mansoni infection.

BACKGROUND: Calprotectin is a calcium-binding cytoplasmic protein found in neutrophils and increasingly used as a marker of bowel inflammation. Fecal occult blood (FOB) is also a dependable indicator of bowel morbidity. The objective of our study was to determine the applicability of these tests as surrogate markers of Schistosoma mansoni intestinal morbidity before and after treatment with praziquantel (PZQ). METHODS: 216 children (ages 3-9 years old) from Buliisa District in Lake Albert, Uganda were examined and treated with PZQ at baseline in October 2012 with 211 of them re-examined 24 days later for S. mansoni and other soil transmitted helminths (STH). POC calprotectin and FOB assays were performed at both time points on a subset of children. Associations between the test results and infection were analysed by logistic regression. RESULTS: Fecal calprotectin concentrations of 150-300 µg/g were associated with S. mansoni egg patent infection both at baseline and follow up (OR: 12.5 P = 0.05; OR: 6.8 P = 0.02). FOB had a very strong association with baseline anemia (OR: 9.2 P = 0.03) and medium and high egg intensity schistosomiasis at follow up (OR: 6.6 P = 0.03; OR: 51.3 P = 0.003). Both tests were strongly associated with heavy intensity S. mansoni infections. There was a significant decrease in FOB and calprotectin test positivity after PZQ treatment in those children who had egg patent schistosomiasis at baseline. CONCLUSIONS: Both FOB and calprotectin rapid assays were found to correlate positively and strongly with egg patent S. mansoni infection with a positive ameloriation response after PZQ treatment indicative of short term reversion of morbidity. Both tests were appropriate for use in the field with excellent operational performance and reliability. Due to its lower-cost which makes its scale-up of use affordable, FOB could be immediately adopted as a monitoring tool for PC campaigns for efficacy evaluation before and after treatment

Single point incremental forming: An assessment of the progress and technology trends from 2005 to 2015

The last decade has seen considerable interest in flexible forming processes. Among the upcoming flexible forming techniques, one that has captured a lot of interest is single point incremental forming (SPIF), where a flat sheet is incrementally deformed into a desired shape by the action of a tool that follows a defined toolpath conforming to the final part geometry. Research on SPIF in the last ten years has focused on defining the limits of this process, understanding the deformation mechanics and material behaviour and extending the process limits using various strategies. This paper captures the developments that have taken place over the last decade in academia and industry to highlight the current state of the art in this field. The use of different hardware platforms, forming mechanics, failure mechanism, estimation of forces, use of toolpath and tooling strategies, development of process planning tools, simulation of the process, aspects of sustainable manufacture and current and future applications are individually tracked to outline the current state of this process and provide a roadmap for future work on this process

Classification of processed and natural coconut water using HCA, PCA and metallic ion levels obtained by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES).

Inductively Coupled Plasma Optical Emission Spectrometry was used to determine Ca, Mg, Mn, Fe, Zn and Cu in samples of processed and natural coconut water. The sample preparation consisted in a filtration step followed by a dilution. The analysis was made employing optimized instrumental parameters and the results were evaluated using methods of Pattern Recognition. The data showed common concentration values for the analytes present in processed and natural samples. Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) indicated that the samples of different kinds were statistically different when the concentrations of all the analytes were considered simultaneously.29465465

Peripherally Inserted Central Catheter Placement in a Cardiology Ward: A Focus Group Study of Nurses’ Perspectives

info:eu-repo/semantics/publishedVersio

In vitro and in vivo performance of methacrylated gellan gum hydrogel formulations for cartilage repair

Methacrylated gellan gum (GGMA) formulation is proposed as a second‐generation hydrogel for controlled delivery of cartilage‐forming cells into focal chondral lesions, allowing immediate in situ retention of cells and 3D filling of lesion volume, such approach deemed compatible with an arthroscopic procedure. Formulation optimization was carried out in vitro using chondrocytes and adipose mesenchymal stromal/stem cells (ASCs). A proof‐of‐concept in vivo study was conducted using a rabbit model with induced chondral lesions. Outcomes were compared with microfracture or non‐treated control. Three grading scores were used to evaluate tissue repair after 8 weeks by macroscopic, histological and immunohistochemical analysis. Intense collagen type II and low collagen type I gene and protein expression were achieved in vitro by the ASC + GGMA formulation, in light with development of healthy chondral tissue. In vivo, this formulation promoted significantly superior de novo cartilage formation compared with the non‐treated group. Maintenance of chondral height and integration with native tissue was further accomplished. The physicochemical properties of the proposed GGMA hydrogel exhibited highly favorable characteristics and biological performance both in vitro and in vivo, positioning itself as an attractive xeno‐free biomaterial to be used with chondrogenic cells for a cost‐effective treatment of focal chondral lesions