Exemplification of catalyst design for microwave selective heating and its application to efficient in situ catalyst synthesis

The use of dielectric spectroscopy to develop an underpinning understanding of the molecular transformations involved in achieving the successful, rapid in situ synthesis of a catalytic chain transfer polymerisation (CCTP) catalyst using microwave heating is reported. The hypothesis behind the molecular design of this catalyst, such that it was tailored towards the application of microwave heating (MWH), is discussed, reviewed relative to the empirically results and compared to the performance of a benchmark preformed catalyst. The overall number/type of function group present in the catalyst, the degree of flexibility exhibited by its organic ligand system and level of solvation achieved are shown to be key factors affecting the interaction between the catalyst and the applied microwave energy. Use of microwave heating leads to fast, in situ formation of the catalyst (less than 30 second) within the polymerisation mixture, rendering prepreparation steps unnecessary and ensuring it is generated prior to the polymerisation reaction commencing. The data also suggests catalysts’ synthesis is achieved at levels of microwave power as low as 5 Watts, further adding to the efficiency and sustainability of the method and presents a potentially enormous opportunity to intensify current industrial processes

Neurocognitive and Neurophysiological Functions Related to ACL Injury:A Framework for Neurocognitive Approaches in Rehabilitation and Return-to-Sports Tests

Context: Only 55% of the athletes return to competitive sports after an anterior cruciate ligament (ACL) injury. Athletes younger than 25 years who return to sports have a second injury rate of 23%. There may be a mismatch between rehabilitation contents and the demands an athlete faces after returning to sports. Current return-to-sports (RTS) tests utilize closed and predictable motor skills; however, demands on the field are different. Neurocognitive functions are essential to manage dynamic sport situations and may fluctuate after peripheral injuries. Most RTS and rehabilitation paradigms appear to lack this aspect, which might be linked to increased risk of second injury. Objective: This systematic and scoping review aims to map existing evidence about neurocognitive and neurophysiological functions in athletes, which could be linked to ACL injury in an integrated fashion and bring an extensive perspective to assessment and rehabilitation approaches. Data Sources: PubMed and Cochrane databases were searched to identify relevant studies published between 2005 and 2020 using the keywords ACL, brain, cortical, neuroplasticity, cognitive, cognition, neurocognition, and athletes. Study Selection: Studies investigating either neurocognitive or neurophysiological functions in athletes and linking these to ACL injury regardless of their design and technique were included. Study Design: Systematic review. Data Extraction: The demographic, temporal, neurological, and behavioral data revealing possible injury-related aspects were extracted and summarized. Results: A total of 16 studies were included in this review. Deficits in different neurocognitive domains and changes in neurophysiological functions could be a predisposing risk factor for, or a consequence caused by, ACL injuries. Conclusion: Clinicians should view ACL injuries not only as a musculoskeletal but also as a neural lesion with neurocognitive and neurophysiological aspects. Rehabilitation and RTS paradigms should consider these changes for assessment and interventions after injury

Optimised use of dielectric spectroscopy at microwave frequencies for direct online monitoring of polymerisation reactions

This study reports the first use of dielectric spectroscopy over at a wide frequency range to monitor, in real time, the progress of a ring opening polymerisation. An open-ended coaxial line sensor was placed directly into the reaction medium of a polymerisation of ε-caprolactone and used to characterise the dielectric properties of the polymerisation mixture both ‘in-situ’ and with time at microwave frequencies. In addition to measurements obtained by the sensor, samples of the medium were extracted at various time points for off-line analysis, to confirm the level of conversion and polymer molecular weights that had been achieved. The results demonstrated that the dielectric properties values exhibited by the reaction medium with time could be correlated directly to the progress of the reaction. Thus, the experimental data allowed the construction of a calibration curve which could be used to predict the conversion of monomer to polymer at any given point of the reaction. The dielectric data permitted also the identification of key reaction parameters, such as the optimum point of termination for the reaction. Furthermore, the analysis of the dielectric data over a wide frequency spectrum enabled the identification of the most suitable frequencies for the practical operation of the sensor, in terms of linearity and sensitivity. This will enable the development of suitable instrumentation and an improved strategy for the online monitoring and control of a broad range of polymerisation reactions

Electromagnetic shielding effectiveness of carbon fibre reinforced composites

This paper reports results on the shielding effectiveness parameter of laminated epoxy composites with carbon fibre reinforcements. Measurements of shielding effectiveness were carried out with a coaxial transmission line testing chamber according to ASTM 4935 standard and epoxy-matrix composites with continuous carbon-fibres were proven to be an excellent electromagnetic interference shielding material, where a composite slab made of 4 layers of prepregs provided more than 99.9% of electromagnetic attenuation. It was found that the reflection mechanism of the shielding material was mainly influenced by the fibre volume ratio, and that an increase in the number of layers of the composite resulted in higher shielding effectiveness due to a greater absorption mechanism. Calculations of the shielding effectiveness parameter of the material used were made by means of commercial electromagnetic simulation tools, having determined experimentally the overall resistivity of the composite. The findings presented in this work suggest that in presence of a greater number of interfaces at different impedance the separate modelling of matrix and fibres at mesoscopic scale must be taken into account

Refinement of the grain structure of additive manufactured titanium alloys via epitaxial recrystallization enabled by rapid heat treatment

The coarse prior-β grain structure in titanium alloys produced by additive manufacturing is associated to mechanical anisotropy and limited fatigue life. Here we report a novel methodology to refine such structure by rapid heat treatment of Ti-6Al-4V produced by laser powder-bed fusion. The refinement was analysed using high-temperature EBSD that showed, for the first time, how high angle boundary β grains nucleated and grew with quasi-equiaxed morphology by epitaxial recrystallization. These findings show the potential for such heating regime to be applied to control grain size, morphology and distribution in a wider category of structural alloys produced by additive manufacturing

Optimised mode selection in electromagnetic sensors for real time, continuous and in-situ monitoring of water cut in multi-phase flow systems

Measurements of the composition of multiphase flows, especially water-cut in oil-water flow, is a frequently encountered problem in the petroleum industry. New techniques that can offer improvements towards that are continuously sought and the use of microwave sensors is considered very promising. The current paper reports on the performance of a microwave cylindrical resonator, integrated into a multiphase flow experimental facility, used to determine water-cut in an upward flowing oil-water mixture. The performance and suitability of two microwave resonant modes (TM010 and TM110) was studied. The TM110 mode was found to be less dependent on the spatial phase distribution of the oil-water flowing mixture and provided more consistent results across a broader flow regime. The relative errors between the predicted and actual water-cut were from −6.53% to 9.16% and relative errors of 78% of the total data points were inside −5% to 5%. The results suggest that appropriate sensor design and careful selection of the operating frequency/resonant pattern can offer a powerful technique for real time, on-line and non-destructive determination of water-cut in multiphase flow systems

A concise review on microwave-assisted polycondensation reactions and curing of polycondensation polymers with focus on the effect of process conditions

During the past 15 years, increasing application of microwave heating to polycondensation reactions has been witnessed. Experiments have been carried out at laboratory scale using widely different experimental procedures. The use of microwaves has often led to significant benefits compared to conventional heating experiments in terms of multi-fold decrease in reaction times and energy consumption and production of polymers with increased molecular weight and improved mechanical properties. In other cases, microwaves do not appear to produce any significant benefits compared to conventional heating. At present, guidelines to experimentalist as to the process conditions and experimental design that should be applied are missing and experimentation seems to be based on an empirical trial-and-error approach. In view of the very different experimental protocols that have been applied and the contradictory trends that are frequently reported, we aim in this review to shed light on the role of important process parameters, such as the presence and type of solvent, the dielectric properties of the mixture and the individual phases, the use of heterogeneous catalysts, pressure, stirring, reflux conditions, temperature measurement method and microwave absorbing fillers, which all seem to determine the occurrence and magnitude of the benefits enabled by microwaves during polycondensation reactions

An experimental study on the effect of gas injection configuration on flow characteristics in high viscosity oil columns

Gas-viscous liquid bubbly and slug flow are very common in petroleum, chemical, bioengineering, polymer, and food processing. However, there is a major knowledge gap in two-phase flow research in the design of gas injectors/distributers in very high viscosity oil systems. The present study investigates the effect of gas injection methods in columns containing very high viscosity oils (i.e., realistic liquids), and more specifically using 360 Pa · s viscosity oil in a 240-mm diameter column. The effects that the radial positioning, number of gas nozzles, and their distance from each other have on the structure of the flow in viscous liquids are presented in detail. Electrical capacitance tomography (ECT) is used to extract experimental data. Void fraction, bubble velocity, frequency, liquid film thickness, and bubble length were measured and analyzed at different radial gas injection positions. It has been observed that bubble length increases significantly by 0.3 m when the injection nozzle is located next to the wall of the pipe. Bubble velocity and length also increase by 0.217 m/s and 3.6 m, respectively, with increasing gas flowrate when multiple injection points are used. Increasing the distance between the gas injection points increased bubbles' length by 1.2 m. Bubbles' velocity and frequency (at higher gas flow rate) were also increased

Small bubbles formation and contribution to the overall gas holdup in large diameter columns of very high viscosity oil

A limited number of studies are available in literature on the small bubbles which create from gas-very high viscosity oils interaction and its contribution to the gas holdup in the system. The rate of small bubble formation has an important impact on heat and mass transfer in many chemical and industrial processes. The work presented in the current paper provides unique information on the formation of bubbles of millimetre diameter in high viscosity oil. A column of 290 mm diameter and Silicon oil of 330 Pa.s viscosity, were employed besides Electrical Capacitance Tomography and a high-resolution camera to investigate the characteristics of the small bubbles. Mechanism of bubble generation, effect of gas injection time and flowrate were studied. The average void fraction, total gas-liquid height, overall Probability Density Function (PDF) profile, small bubbles volume fractions and diameter were measured. Small bubbles generate from the eruption of large bubbles, at gas injection nozzles, coalescence of large bubbles, and at liquid bridges at transition to churn flow regime. Properties and concentration of the small bubbles are controlled by the location of the bubble generation, gas flowrate, and gas injection time. Small bubbles contribute by 6.6- 30% to the total gas holdup. Bubble diameter increased from 0.68 mm to 0.75 mm and decreased from 1.1 mm to 0.75 mm at the top and the bottom sections of the column respectively after 60 minof gas injection

Effects of doxorubicin cancer therapy on autophagy and the ubiquitin-proteasome system in long-term cultured adult rat cardiomyocytes

The clinical use of anthracyclines in cancer therapy is limited by dose-dependent cardiotoxicity that involves cardiomyocyte injury and death. We have tested the hypothesis that anthracyclines affect protein degradation pathways in adult cardiomyocytes. To this aim, we assessed the effects of doxorubicin (Doxo) on apoptosis, autophagy and the proteasome/ubiquitin system in long-term cultured adult rat cardiomyocytes. Accumulation of poly-ubiquitinated proteins, increase of cathepsin-D-positive lysosomes and myofibrillar degradation were observed in Doxo-treated cardiomyocytes. Chymotrypsin-like activity of the proteasome was initially increased and then inhibited by Doxo over a time-course of 48 h. Proteasome 20S proteins were down-regulated by higher doses of Doxo. The expression of MURF-1, an ubiquitin-ligase specifically targeting myofibrillar proteins, was suppressed by Doxo at all concentrations measured. Microtubule-associated protein1 light chain 3B (LC3)-positive punctae and both LC3-I and -II proteins were induced by Doxo in a dose-dependent manner, as confirmed by using lentiviral expression of green fluorescence protein bound to LC3 and live imaging. The lysosomotropic drug chloroquine led to autophagosome accumulation, which increased with concomitant Doxo treatment indicating enhanced autophagic flux. We conclude that Doxo causes a downregulation of the protein degradation machinery of cardiomyocytes with a resulting accumulation of poly-ubiquitinated proteins and autophagosomes. Although autophagy is initially stimulated as a compensatory response to cytotoxic stress, it is followed by apoptosis and necrosis at higher doses and longer exposure times. This mechanism might contribute to the late cardiotoxicity of anthracyclines by accelerated aging of the postmitotic adult cardiomyocytes and to the susceptibility of the aging heart to anthracycline cancer therap