Impact and Compression-After-Impact Performance of a Thin Z-Pinned Composite Laminate

Impact and compression-after-impact (CAI) tests were carried out on [02/ ± 45]s carbon/epoxy samples to characterize the effect of z-pinning on the delamination resistance and damage tolerance properties of the laminate. Unpinned and z-pinned samples were subjected to impacts between 2 and 36 J to produce damage conditions that extend from barely visible impact damage (BVID) to complete penetration. The damage induced by impact and the damage modes leading to ultimate CAI failure were examined by Xradiography and by direct observations of the sample faces during CAI loading. The analyses indicate that the role of z-pins on the impact and CAI response of the laminate is dependent on the size and features of the damage. Z-pins do not modify the structural response to impact of the laminate, but they are effective in reducing the extent of damage for impact energies above a threshold value. Z-pinning is also effective in improving the CAI strength of the laminate for impact energies above this threshold value, even though it degrades the residual compressive strength for lower impact energies. Reductions in impact delamination size of up to 50% and improvements in CAI strength of about 20% were achieved by z-pinning for highenergy impacts. The mechanisms by which the z-pins affect the CAI response of the samples are illustrated and examined in detail for different impact damage severities

Synthesis and antibacterial effects of cobalt–cellulose magnetic nanocomposites

© The Royal Society of Chemistry. Green synthesis is employed to prepare cobalt/cellulose nanocomposites with cubic (α-cobalt) cobalt as a main component with antibacterial and magnetic properties. An in situ reduction of aqueous solutions of cobalt ions on a model cellulose substrate surface using hydrogen gas affords spherical, cellulose-stabilised cobalt nanoclusters with magnetic properties and an average diameter of 7 nm that are distributed evenly over the surface of the cellulose fibres. These cobalt/cellulose nanocomposites exhibit good antibacterial action against opportunistic pathogens both Gram-positive (S. aureus) and Gram-negative (E. coli, A. baumannii and P. aeruginosa), with zones of inhibition up to 15 mm, thereby encouraging the deployment of these advanced materials for the treatment of wastewater or within medical dressings. This method of preparation is compared with the analogous in situ reduction of cobalt ions on a cellulose surface using sodium borohydride as reducing agent

HIV-1 Tat alters neuronal intrinsic excitability

Objective: In HIV+ individuals, the virus enters the central nervous system and invades innate immune cells, producing important changes that result in neurological deficits. We aimed to determine whether HIV plays a direct role in neuronal excitability. Of the HIV peptides, Tat is secreted and acts in other cells. In order to examine whether the HIV Tat can modify neuronal excitability, we exposed primary murine hippocampal neurons to that peptide, and tested its effects on the intrinsic membrane properties, 4 and 24 h after exposure. Results: The exposure of hippocampal pyramidal neurons to Tat for 4 h did not alter intrinsic membrane properties. However, we found a strong increase in intrinsic excitability, characterized by increase of the slope (Gain) of the input-output function, in cells treated with Tat for 24 h. Nevertheless, Tat treatment for 24 h did not alter the resting membrane potential, input resistance, rheobase and action potential threshold. Thus, neuronal adaptability to Tat exposure for 24 h is not applicable to basic neuronal properties. A restricted but significant effect on coupling the inputs to the outputs may have implications to our knowledge of Tat biophysical firing capability, and its involvement in neuronal hyperexcitability in neuroHIV

A Simple Biomimetic Receptor Selectively Recognizing the GlcNAc2 Disaccharide in Water

AbstractGlcNAc2 is the core disaccharide fragment present in N‐glycans exposed on the surface of enveloped viruses of high health concern, such as coronaviruses. Because N‐glycans are directly involved in the docking of viruses to host cells, recognition of GlcNAc2 by a biomimetic receptor may be a convenient alternative to the use of lectins to interfere with viral entry and infection. Herein, we describe a simple biomimetic receptor recognizing the methyl‐β‐glycoside of GlcNAc2 in water with an unprecedented affinity of 160 μM, exceeding that of more structurally complex receptors reported in the literature. The tweezers‐shaped acyclic structure exhibits marked selectivity among structurally related disaccharides, and complete discrimination between mono‐ and disaccharides. Molecular modelling calculations supported by NOE data provided a three‐dimensional description of the binding mode, shedding light on the origin of the affinities and selectivities exhibited by the receptor

Effect of parent concrete on the performance of recycled aggregate concrete

Recycling concrete construction waste is a promising way towards sustainable construction. Indeed, replacing natural aggregates with recycled aggregates obtained from concrete waste lowers the environmental impact of concrete constructions and improves natural resource conservation. This paper reports on an experimental study on mechanical and durability properties of concretes casted with recycled aggregates obtained from two different parent concretes, belonging to two structural elements of the old Cagliari stadium. The effects of parent concretes on coarse recycled aggregates and on new structural concretes produced with different replacement percentages of these recycled aggregates are investigated. Mechanical properties (compressive strength, modulus of elasticity, and splitting tensile strength) and durability properties (water absorption, freeze thaw, and chloride penetration resistance) are experimentally evaluated and analyzed as fundamental features to assess structural concrete behavior. The results show that the mechanical performance of recycled concrete is not related to the parent concrete characteristics. Furthermore, the resistance to pressured water penetration is not reduced by the presence of recycled aggregates, and instead, it happens for the chloride penetration resistance. The resistance to frost–thawing seems not related to the recycled aggregates replacement percentage, while an influence of the parent concrete has been assessed

Changes in food access by mestizo communities associated with deforestation and agrobiodiversity loss in Ucayali, Peruvian Amazon

Few longitudinal studies link agricultural biodiversity, land use and food access in rural landscapes. In this paper, we test the hypothesis that, in a context of economic change, cash crop expansion is associated with deforestation, reduced agrobiodiversity and changes in food access. For this purpose, we analysed data collected from the same 53 upland and floodplain mestizo households in Ucayali, Peru, in 2000 and 2015. We found an emerging transition towards less diversified food access coupled with loss of forest cover and reduced agricultural biodiversity. In 2015, diets appeared to rely on fewer food groups, fewer food items, and on products increasingly purchased in the market compared to 2000. Wild fruits and plants were mentioned, but rarely consumed. Agricultural production systems became more specialised with a shift towards commercial crops. Peak deforestation years in the 15-year period appeared linked with incentives for agricultural expansion. Our results suggest an overall trend from diversified productive and “extractive” systems and more diverse food access, towards specialized productive systems, with less diverse food access and stronger market orientation (both in production and consumption). The assumption in the food and agricultural sciences that increased income and market-orientation is linked to improved food security, is challenged by our integrated analyses of food access, agrobiodiversity, land use and forest cover. Our results highlight the importance of longitudinal, multidimensional, systemic analyses, with major implications for land use, food and health policies. The potential risks of parallel homogenisation of diets and agricultural production systems require interdisciplinary research and policies that promote integrated landscape approaches for sustainable and inclusive food systems

The management of atrophies classified as V class according to Cawood & Howell by piezo-electric surgery

Introducción: Los casos analizados presentaban atrofias severas (V clase según Cawood y Howell) (1), que se caracterizan por presentar una densidad de la cresta transversal inferior a 4 mm y vertical inferior a 6 mm; ello hace pensar en la posibilidad de una rehabilitación implanto-soportada. Objetivo: Evaluación de la rehabilitación de pacientes afectados por severa atrofia del maxilar superior clase V según Cawood y Howell) (1) rehabilitados con elevación del seno maxilar e injerto de hueso autólogo. Materiales y métodos: Estudio longitudinal a partir de una muestra de 32 pacientes, con atrofia maxilar severa y edentulismo parcial o total. En todos los pacientes se ha colocado un injerto con técnica de reconstrucción onlay mono o bicortical y se ha adoptado la cirugía piezoeléctrica para realizar el elevación del seno, el cual podía ser mono o bilateral, de hueso autólogo procedente de la cresta ilíaca anterior. Seguimiento realizado durante 2 años. Resultados: A los dos años del control final, el 94,05% de todos los implantes colocados tras la intervención de elevación se presentan osteointegrados y cargados protésicamente. La cresta ilíaca anterior resulta ser la zona idónea para la extracción medular, necesaria para la elevación del seno. Las posibilidades de supervivencia del implante son realmente elevadas si se espera el tiempo clínico necesario para la recuperación y la integración del injerto. El éxito de todas las intervenciones de elevación del seno maxilar se debe a la adopción de la cirugía piezoeléctrica, que permite efectuar la incisión de entrada y realizar el desprendimiento de los tejidos con un traumatismo mínimo para la membrana de Schneider. La integridad de la membrana y la utilización de bone-chips de origen autólogo no ha hecho necesario recurrir a la utilización de membranas reabsorbibles, simplificando así el procedimiento quirúrgico. La utilización de la cresta ilíaca anterior como zona donante, permite disponer de abundante tejido óseo cortical, necesario para colocar los onlay y para reconstruir el defecto óseo. Introduction: Valutation of rehabilitated patients by sinus lift in upper jaw and by autologous bone graft from iliac crest. Materials and methods: Rehabilitation of 32 patients with severe atrophies of upper jaw and partial or total edentulism by positioning of mono- or bicortical onlay with piezosurgery to obtain a sinus lift mono- or bilateral by autologous bone grafts from anterior iliac crest. Results: 94.05% of successes after a two years follow-up. Conclusions: Respecting of timing surgery, a correct use of the piezosurgery technique and of the autologous bone graft from anterior iliac crest let a successful implantological rehabilitation. Moreover the iliac crest is a very good donor site of bone tissue for the management of severe atrophies in the upper jaw. An accidental laceration of Schneider's membrane was observed in filling phase in the 5.26% of cases

Surgical treatment of symptomatic degenerative lumbar spondylolisthesis by decompression and instrumented fusion

Degenerative spondylolisthesis is characterized by the slippage of one vertebral body over the one below, with association of intervertebral disc degeneration and degenerative arthritis of the facet joints, which cause spinal stenosis. The aim of this study was to evaluate the clinical and radiographic results of 22 patients with symptomatic degenerative spondylolisthesis, operated on by decompressive laminectomy and instrumented posterolateral fusion associated with interbody fusion (PLIF). Mean age at surgery was 64 years (range, 57\u201372). Clinical results were evaluated on a questionnaire at the last follow-up visit concerning postoperative low back and leg pain, restriction of daily life activities, and resumption of sports activity. Lumbar spine radiographs were used to evaluate the status of fixation devices, the reduction of the spondylolisthesis, the lumbar sagittal balance and the presence of spinal fusion. No intraoperative or postoperative complications were encountered. There were no superficial or deep infections, fixation device loosening, or hardware removal. Mean follow-up time was 4 years (range, 3\u20136 years). Clinical outcome was excellent or good in 19 patients and fair in 3 patients. Preoperatively, mean forward vertebral slipping on neutral lateral radiographs was 5 mm, while postoperatively it decreased to 3 mm. Preoperatively, mean sagittal motion was 3 mm and angular motion was 8\ub0, while postoperatively these values decreased to 1 mm and 1\ub0, respectively. This study demonstrated that spinal decompression followed by transpedicular instrumentation associated with PLIF technique is a valid surgical option for the treatment of degenerative spondylolisthesis with symptomatic spinal stenosis. Clinical outcome, intended as relief of pain and resumption of activity, was improved significantly and fusion rate was high