Experimental investigation on tensile and shear bond behaviour of Basalt-FRCM composites for strengthening calcarenite masonry elements

The use of Fabric Reinforced Cementitious Matrix (FRCM) composites for structural retrofit has seen an increased interest among the scientific community, during the last decade. Various studies have revealed their effectiveness as external retrofitting technique of masonry elements, offering numerous advantages respect to the well know Fibre Reinforced Polymer (FRP) in terms of compatibility with masonry support, reversibility of intervention and sustainability. Despite the growing use, the characterization of FRCM mechanical behaviour is still an open issue, due to numerous uncertainties involved in test set-up adopted and fibre-mortar combination. The proposed experimental study aims to investigate the tensile and shear bond behaviour of Basalt-FRCM for strengthening calcarenite masonry elements. Calcarenite is a natural stone with sedimentary origin and it is widely present in existing buildings of the Mediterranean areas. Direct tensile tests are performed on two types of Basalt-FRCM coupons, with cement-based and lime-based mortar, adopting two different test-set-up based on clamping and clevis grip methods. Moreover, double shear bond tests are carried out to evaluate the adhesion properties of the two types of Basalt-FRCM with calcarenite support. Experimental outcomes are compared in terms of stress-strain curves, evaluating the influence of mortar grade and test set-up on the mechanical performances of Basalt-FRCM composites. The comparisons provide information about the mechanical stress transfer phenomena that occur at the fibre-to-matrix and FRCM-to-substrate interface level and the failure modes

Numerical Modelling of the Constitutive Behaviour of FRCM Composites through the Use of Truss Elements

The modeling of the mechanical behavior of Fabric Reinforced Cementitious Matrix (FRCM) composites is a difficult task due to the complex mechanisms established at the fibre-matrix and composite-support interface level. Recently, several modeling approaches have been proposed to simulate the mechanical response of FRCM strengthening systems, however a simple and reliable procedure is still missing. In this paper, two simplified numerical models are proposed to simulate the tensile and shear bond behavior of FRCM composites. Both models take advantage of truss and non-linear spring elements to simulate the material components and the interface. The proposed approach enables us to deduce the global mechanical response in terms of stress-strain or stress-slip relations. The accuracy of the proposed models is validated against the experimental benchmarks available in the literature

The role of ecotypic variation and the environment on biomass and nitrogen in a dominant prairie grass

Citation: Mendola, M. L., Baer, S. G., Johnson, L. C., & Maricle, B. R. (2015). The role of ecotypic variation and the environment on biomass and nitrogen in a dominant prairie grass. Ecology, 96(9), 2433-2445. doi:10.1890/14-1492.1Knowledge of the relative strength of evolution and the environment on a phenotype is required to predict species responses to environmental change and decide where to source plant material for ecological restoration. This information is critically needed for dominant species that largely determine the productivity of the central U.S. grassland. We established a reciprocal common garden experiment across a longitudinal gradient to test whether ecotypic variation interacts with the environment to affect growth and nitrogen (N) storage in a dominant grass. We predicted plant growth would increase from west to east, corresponding with increasing precipitation, but differentially among ecotypes due to local adaptation in all ecotypes and a greater range of growth response in ecotypes originating from west to east. We quantified aboveground biomass, root biomass, belowground net primary production (BNPP), root C:N ratio, and N storage in roots of three ecotypes of Andropogon gerardii collected from and reciprocally planted in central Kansas, eastern Kansas, and southern Illinois. Only the ecotype from the most mesic region (southern Illinois) exhibited more growth from west to east. There was evidence for local adaptation in the southern Illinois ecotype by means of the local vs. foreign contrast within a site and the home vs. away contrast when growth in southern Illinois was compared to the most distant site in central Kansas. Root biomass of the eastern Kansas ecotype was higher at home than at either away site. The ecotype from the driest region, central Kansas, exhibited the least response across the environmental gradient, resulting in a positive relationship between the range of biomass response and precipitation in ecotype region of origin. Across all sites, ecotypes varied in root C: N ratio (highest in the driest-origin ecotype) and N storage in roots (highest in the most mesic-origin ecotype). The low and limited range of biomass, higher C: N ratio of roots, and lower N storage in the central Kansas ecotype relative to the southern Illinois ecotype suggests that introducing ecotypes of A. gerardii from much drier regions into highly mesic prairie would reduce productivity and alter belowground ecosystem processes under a wide range of conditions

Experimental Investigation on Innovative Stress Sensors for Existing Masonry Structures Monitoring

Historical masonry structures often suffer gradual deterioration that in many cases can compromise the safety levels and the operating conditions of the buildings. In this context, Structural Health Monitoring (SHM) is an effective tool for the prediction of the structural behaviour and the state of conservation of buildings. Although many monitoring systems have recently been proposed, there is a lack of practical application of low-cost systems. This paper presents an experimental study based on the use of two innovative stress sensors—capacitive stress sensor and ceramic stress sensor—for the monitoring of existing masonry elements. In order to reproduce the actual conditions of onsite masonry, sensors are post-installed in the mortar joints of two series of pre-stressed specimens made of calcarenite stone masonry and clay brick masonry. The best practice of post-installation of the two sensors is investigated. The reliability of the proposed sensors is evaluated through comparison with data recorded from classical measurement devices

Acute bleeding obstruction pancreatitis after Roux-en-Y anastomosis in total gastrectomy: a single center experience

Anastomotic intraluminal bleeding is a well-known complication after total gastrectomy. Nevertheless, few data are published on acute bleeding obstruction pancreatitis (BOP) due to a bleeding from the jejunojejunostomy (JJ). In this paper we describe our experience. A total of 140 gastrectomies for EGJ cancer were performed in our Institute from January 2012 to January 2017. All reconstructions were performed with a Roux-en-Y anastomosis: a mechanical end-to-side esophago-jejunostomy and a mechanical end-to-side JJ. Three patients suffered from a bleeding at the JJ with a consequent BOP. We analyzed the time of diagnosis, the treatment and the outcomes. The three patients presented anemia at the laboratory findings on postoperative day (POD) 1. In patient I laboratory findings of acute pancreatitis were found in POD 2. CT scan was performed and showed signs of BOP. Endoscopic treatment was tried without success. Therefore, patient underwent surgery: JJ take down, bleeding control and anastomosis rebuild were performed. In spite of this the patient died of MOF in POD 4. Patient II had a persistent anemia treated with blood transfusions until POD 3, when laboratory tests showed increased lipase and bilirubin levels. Patient was successfully treated with endoscopy but several blood transfusions and a prolonged recovery were necessary. Patient III had laboratory findings of acute pancreatitis on POD 1. Immediate surgery was performed and patient was discharged on POD 9 without sequelae. BOP is a rare but deadly complication after Roux-en-Y anastomosis. An early diagnosis and an aggressive treatment seem to improve the outcome

Probing the Residual Structure in Avian Prion Hexarepeats by CD, NMR and MD Techniques

Many proteins perform essential biological functions by means of regions that lacking specific organized structure exist as an ensemble of interconverting transient conformers. The characterization of such regions, including the description of their structural propensities, number of conformations and relative populations can provide useful insights. Prion diseases result from the conversion of a normal glycoprotein into a misfolded pathogenic isoform. The structures of mammal and chicken prion proteins show a similar fold with a globular domain and a flexible N-terminal portion that contains different repeated regions: octarepeats (PHGGGWGQ) in mammals and hexarepeats (PHNPGY) in chickens. The higher number of prolines in the hexarepeat region suggests that this region may retain a significant amount of residual secondary structure. Here, we report the CD, NMR and MD characterization of a peptide (2-HexaPY) composed of two hexarepeats. We combine experimental NMR data and MD to investigate at atomic level its ensemble-averaged structural properties, demonstrating how each residue of both repeats has a different quantified PPII propensity that shows a periodicity along the sequence. This feature explains the absence of cooperativity to stabilize a PPII conformation. Nonetheless, such residual structure can play a role in nucleating local structural transitions as well as modulating intra-molecular or inter-molecular interactions

Graphene Oxide Nanosheets Tailored With Aromatic Dipeptide Nanoassemblies for a Tuneable Interaction With Cell Membranes

Engineered graphene-based derivatives are attractive and promising candidates for nanomedicine applications because of their versatility as 2D nanomaterials. However, the safe application of these materials needs to solve the still unanswered issue of graphene nanotoxicity. In this work, we investigated the self-assembly of dityrosine peptides driven by graphene oxide (GO) and/or copper ions in the comparison with the more hydrophobic diphenylalanine dipeptide. To scrutinize the peptide aggregation process, in the absence or presence of GO and/or Cu2+, we used atomic force microscopy, circular dichroism, UV–visible, fluorescence and electron paramagnetic resonance spectroscopies. The perturbative effect by the hybrid nanomaterials made of peptide-decorated GO nanosheets on model cell membranes of supported lipid bilayers was investigated. In particular, quartz crystal microbalance with dissipation monitoring and fluorescence recovery after photobleaching techniques were used to track the changes in the viscoelastic properties and fluidity of the cell membrane, respectively. Also, cellular experiments with two model tumour cell lines at a short time of incubation, evidenced the high potential of this approach to set up versatile nanoplatforms for nanomedicine and theranostic applications

A tunable nanoplatform of nanogold functionalised with Angiogenin peptides for anti-angiogenic therapy of brain tumours

Angiogenin (ANG), an endogenous protein that plays a key role in cell growth and survival, has been scrutinised here as promising nanomedicine tool for the modulation of pro-/anti-angiogenic processes in brain cancer therapy. Specifically, peptide fragments from the putative cell membrane binding domain (residues 60-68) of the protein were used in this study to obtain peptide-functionalised spherical gold nanoparticles (AuNPs) of about 10 nm and 30 nm in optical and hydrodynamic size, respectively. Different hybrid biointerfaces were fabricated by peptide physical adsorption (Ang60-68) or chemisorption (the cysteine analogous Ang60-68Cys) at the metal nanoparticle surface, and cellular assays were performed in the comparison with ANG-functionalised AuNPs. Cellular treatments were performed both in basal and in copper-supplemented cell culture medium, to scrutinise the synergic effect of the metal, which is another known angiogenic factor. Two brain cell lines were investigated in parallel, namely tumour glioblastoma (A172) and neuron-like differentiated neuroblastoma (d-SH-SY5Y). Results on cell viability/proliferation, cytoskeleton actin, angiogenin translocation and vascular endothelial growth factor (VEGF) release pointed to the promising potentialities of the developed systems as anti-angiogenic tunable nanoplaftforms in cancer cells treatment

Hyaluronan-carnosine conjugates inhibit Aβ aggregation and toxicity

Alzheimer’s disease is the most common neurodegenerative disorder. Finding a pharmacological approach that cures and/or prevents the onset of this devastating disease represents an important challenge for researchers. According to the amyloid cascade hypothesis, increases in extracellular amyloid-β (Aβ) levels give rise to different aggregated species, such as protofibrils, fibrils and oligomers, with oligomers being the more toxic species for cells. Many efforts have recently been focused on multi-target ligands to address the multiple events that occur concurrently with toxic aggregation at the onset of the disease. Moreover, investigating the effect of endogenous compounds or a combination thereof is a promising approach to prevent the side effects of entirely synthetic drugs. In this work, we report the synthesis, structural characterization and Aβ antiaggregant ability of new derivatives of hyaluronic acid (Hy, 200 and 700 kDa) functionalized with carnosine (Car), a multi-functional natural dipeptide. The bioactive substances (HyCar) inhibit the formation of amyloid-type aggregates of Aβ42 more than the parent compounds; this effect is proportional to Car loading. Furthermore, the HyCar derivatives are able to dissolve the amyloid fibrils and to reduce Aβ-induced toxicity in vitro. The enzymatic degradation of Aβ is also affected by the interaction with HyCar