Measuring neuromuscular junction functionality

Neuromuscular junction (NMJ) functionality plays a pivotal role when studying diseases in which the communication between motor neuron and muscle is impaired, such as aging and amyotrophic lateral sclerosis (ALS). Here we describe an experimental protocol that can be used to measure NMJ functionality by combining two types of electrical stimulation: direct muscle membrane stimulation and the stimulation through the nerve. The comparison of the muscle response to these two different stimulations can help to define, at the functional level, potential alterations in the NMJ that lead to functional decline in muscle. Ex vivo preparations are suited to well-controlled studies. Here we describe an intensive protocol to measure several parameters of muscle and NMJ functionality for the soleus-sciatic nerve preparation and for the diaphragm-phrenic nerve preparation. The protocol lasts approximately 60 min and is conducted uninterruptedly by means of a custom-made software that measures the twitch kinetics properties, the force-frequency relationship for both muscle and nerve stimulations, and two parameters specific to NMJ functionality, i.e. neurotransmission failure and intratetanic fatigue. This methodology was used to detect damages in soleus and diaphragm muscle-nerve preparations by using SOD1G93A transgenic mouse, an experimental model of ALS that ubiquitously overexpresses the mutant antioxidant enzyme superoxide dismutase 1 (SOD1)

Flexural check at high temperatures of reinforced concrete bridge decks strengthened with EBR-FRP

In this paper the thermo-mechanical behaviour of RC bridge decks strengthened with externally bonded FRP laminates is investigated by considering environmental conditions responsible of thermal states different from the normal ones. A parametric analysis is performed by varying the slab thickness, the FRP reinforcing percentage, the type of fibre and the thickness of the protection layer. The results are given in terms of ultimate bearing capacity of the slabs, which allows individuating the conditions responsible of premature FRP-to-concrete debonding or temperature levels greater than the glass transition temperature of the adhesive

A DIC based technique to measure the contraction of a skeletal muscle engineered tissue

Tissue engineering is a multidisciplinary science based on the application of engineering approaches to biologic tissue formation. Engineered tissue internal organization represents a key aspect to increase biofunctionality before transplant and, as regarding skeletal muscles, the potential of generating contractile forces is dependent on the internal fiber organization and is reflected by some macroscopic parameters, such as the spontaneous contraction. Here we propose the application of digital image correlation (DIC) as an independent tool for an accurate and noninvasive measurement of engineered muscle tissue spontaneous contraction. To validate the proposed technique we referred to the X-MET, a promising 3-dimensional model of skeletal muscle. The images acquired through a high speed camera were correlated with a custom-made algorithm and the longitudinal strain predictions were employed for measuring the spontaneous contraction. The spontaneous contraction reference values were obtained by studying the force response.The relative error between the spontaneous contraction frequencies computed in both ways was always lower than 0.15%. In conclusion, the use of a DIC based systemallows for an accurate and noninvasive measurement of biological tissues’ spontaneous contraction, in addition to the measurement of tissue strain field on any desired region of interest during electrical stimulation

Design Space Investigation by RSMs Techniques in Aeronautical Metal Cutting Applications

none3A. DEL PRETE; A. DE VITIS; D. MAZZOTTADEL PRETE, Antonio; DE VITIS, ANTONIO ALBERTO; D., Mazzott

A Physically Based Model to Predict Microstructural Modifications in Inconel 718 High Speed Machining

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Al-Si10-Mg Manufactured by Selective Laser Melting: Microstructure Sensitivity to Close Values of the Heat Input

Selective Laser Melting (SLM) is an attractive Additive Manufacturing (AM) technology for the fabrication of metallic components with complex structures and high performances. This process fulfills the goals of sustainable production by reducing material waste, optimizing product topology, and recycling metallic powder. Aluminum alloys exhibit also sustainable performances being lightweight and recyclable. Al-Si10-Mg alloy is suitable for SLM processing due to its good castability, good strength, wear, and corrosion resistance. However, the laser processing of aluminum alloys to date needs to be optimized. In this study, the authors have analyzed the role of close values of heat input on microstructure and defects (Electron and Optical microscope, DRX analysis), porosity (optical microscope and X-ray tomography), melting pool geometries (both in transversal and longitudinal sections of the samples) and mechanical performance (hardness and tensile test) of Al-Si10-Mg samples. The results have shown that even at very close values of energy density, the microstructure and properties of the samples differ from each other

HIGH Tg FRP & CEMENTITIOUS ADHESIVE, Potential benefits in fire for NSM FRP strengthened reinforced concrete beams

Near surface mounted FRP strengthening is potentially less prone to damage due tofire exposure than externally bonded FRP reinforcement (EBR), provided that: (a) an FRP strengthening material with high glass transition and decomposition temperatures (Tg andTd, respectively); and (b) a bonding agent with low thermal conductivity and good thermal stability, are used. This paper presents a project undertaken on a specific high Tg and cementitious adhesive bonded NSM FRP strengthening system. Dynamic Mechanic Analysis (DMA) and Thermogravimetric Analysis (TGA) performed on the novel high Tg commercial CFRP bar yielded a Tg value of 220°C (based on  peak) and Td of about 360°C. Thermal conductivity tests were also performed on the cementitious grout. The results were used to better explain the failure modes of NSM FRP strengthened reinforced concrete beams at elevated temperature. The paper highlights the importance of understandingthe thermo-mechanical properties of the various constituent materials for improving the performance of FRP strengthening systems in fire