A Combined Magnetoelectric Sensor Array and MRI-Based Human Head Model for Biomagnetic FEM Simulation and Sensor Crosstalk Analysis.

Magnetoelectric (ME) magnetic field sensors are novel sensing devices of great interest in the field of biomagnetic measurements. We investigate the influence of magnetic crosstalk and the linearity of the response of ME sensors in different array and excitation configurations. To achieve this aim, we introduce a combined multiscale 3D finite-element method (FEM) model consisting of an array of 15 ME sensors and an MRI-based human head model with three approximated compartments of biological tissues for skin, skull, and white matter. A linearized material model at the small-signal working point is assumed. We apply homogeneous magnetic fields and perform inhomogeneous magnetic field excitation for the ME sensors by placing an electric point dipole source inside the head. Our findings indicate significant magnetic crosstalk between adjacent sensors leading down to a 15.6% lower magnetic response at a close distance of 5 mm and an increasing sensor response with diminishing crosstalk effects at increasing distances up to 5 cm. The outermost sensors in the array exhibit significantly less crosstalk than the sensors located in the center of the array, and the vertically adjacent sensors exhibit a stronger crosstalk effect than the horizontally adjacent ones. Furthermore, we calculate the ratio between the electric and magnetic sensor responses as the sensitivity value and find near-constant sensitivities for each sensor, confirming a linear relationship despite magnetic crosstalk and the potential to simulate excitation sources and sensor responses independently.

A Web-Based COVID-19 Tool for Testing Residents in Retirement Homes: Development Study.

BACKGROUND: Long-term care facilities have been widely affected by the COVID-19 pandemic. Empirical evidence demonstrated that older people are the most impacted and are at higher risk of mortality after being infected. Regularly testing care facility residents is a practical approach to detecting infections proactively. In many cases, the care staff must perform the tests on the residents while also providing essential care, which in turn causes imbalances in their working time. Once an outbreak occurs, suppressing the spread of the virus in retirement homes (RHs) is challenging because the residents are in contact with each other, and isolation measures cannot be widely enforced. Regular testing strategies, on the other hand, have been shown to effectively prevent outbreaks in RHs. However, high-frequency testing may consume substantial staff working time, which results in a trade-off between the time invested in testing and the time spent providing essential care to residents. OBJECTIVE: We developed a web application (Retirement Home Testing Optimizer) to assist RH managers in identifying effective testing schedules for residents. The outcome of the app, called the "testing strategy," is based on dividing facility residents into groups and then testing no more than 1 group per day. METHODS: We created the web application by incorporating influential factors such as the number of residents and staff, the average rate of contacts, the amount of time spent to test, and constraints on the test interval and size of groups. We developed mixed integer nonlinear programming models for balancing staff workload in long-term care facilities while minimizing the expected detection time of a probable infection inside the facility. Additionally, by leveraging symmetries in the problem, we proposed a fast and efficient local search method to find the optimal solution. RESULTS: Considering the number of residents and staff and other practical constraints of the facilities, the proposed application computes the optimal trade-off testing strategy and suggests the corresponding grouping and testing schedule for residents. The current version of the application is deployed on the server of the Where2Test project and is accessible on their website. The application is open source, and all contents are offered in English and German. We provide comprehensive instructions and guidelines for easy use and understanding of the application's functionalities. The application was launched in July 2022, and it is currently being tested in RHs in Saxony, Germany. CONCLUSIONS: Recommended testing strategies by our application are tailored to each RH and the goals set by the managers. We advise the users of the application that the proposed model and approach focus on the expected scenarios, that is, the expected risk of infection, and they do not guarantee the avoidance of worst-case scenarios.

Materials for High Temperature Liquid Lead Storage for Concentrated Solar Power (CSP) Air Tower Systems.

Today the technical limit for solar towers is represented by the temperature that can be reached with current accumulation and exchange fluids (molten salts are generally adopted and the max temperatures are generally below 600 °C), even if other solutions have been suggested that reach 800 °C. An innovative solution based on liquid lead has been proposed in an ongoing experimental project named Nextower. The Nextower project aims to improve current technologies of the solar sector by transferring experience, originally consolidated in the field of nuclear plants, to accumulate heat at higher temperatures (T = 850-900 °C) through the use of liquid lead heat exchangers. The adoption of molten lead as a heat exchange fluid poses important criticalities of both corrosion and creep resistance, due to the temperatures and structural stresses reached during service. Liquid lead corrosion issues and solutions in addition to creep-resistant material selection are discussed. The experimental activities focused on technical solutions adopted to overcome these problems in terms of the selected materials and technologies. Corrosion laboratory tests have been designed in order to verify if structural 800H steel coated with 6 mm of FeCrAl alloy layers are able to resist the liquid lead attack up to 900 °C and for 1000 h or more. The metallographic results were obtained by mean of scanning electron microscopy with an energy dispersive microprobe confirm that the 800H steel shows no sign of corrosion after the completion of the tests.

Influence of Lipase Immobilization Mode on Ethyl Acetate Hydrolysis in a Continuous Solid-Gas Biocatalytic Membrane Reactor.

Solid-gas biocatalysis was performed in a specially designed continuous biocatalytic membrane reactor (BMR). In this work, lipase from Candida rugosa (LCR) and ethyl acetate in vapor phase were selected as model enzyme and substrate, respectively, to produce acetic acid and ethanol. LCR was immobilized on functionalized PVDF membranes by using two different kinds of chemical bond: electrostatic and covalent. Electrostatic immobilization of LCR was carried out using a membrane functionalized with amino groups, while covalent immobilization was carried out using membrane, with or without surface-immobilized polyacrylamide (PAAm) microgels, functionalized with aldehyde groups. These biocatalytic membranes were tested in a solid-gas BMR and compared in terms of enzyme specific activity, catalytic activity, and volumetric reaction rate. Results indicated that lipase covalently immobilized is more effective only when the immobilization is mediated by microgels, showing catalytic activity doubled with respect to the other system with covalently bound enzyme (4.4 vs 2.2 µmol h-1). Enzyme immobilized by ionic bond, despite a lower catalytic activity (3.5 vs 4.4 µmol h-1), showed the same specific activity (1.5 mmol·h-1·g-1ENZ) of the system using microgels, due to a higher enzyme degree of freedom coupled with an analogously improved enzyme hydration. Using the optimized operating conditions regarding immobilized enzyme amount, ethyl acetate, and molar water flow rate, all three BMRs showed continuous catalytic activity for about 5 months. On the contrary, the free enzyme (in water/ethyl acetate emulsion) at 50 °C was completely inactive and at 30 °C (temperature optimum) has a specific activity 2 orders of magnitude lower (8.4 × 10-2 mmol h-1 g-1) than the solid-gas biocatalytic membrane reactor. To the best of our knowledge, this is the first example of solid-gas biocatalysis, working in the gaseous phase in which a biocatalytic membrane reactor, with the enzyme/substrate system lipase/ethyl acetate, was used.

Electron Beam Welding of IN792 DS: Effects of Pass Speed and PWHT on Microstructure and Hardness.

Electron Beam (EB) welding has been used to realize seams on 2 mm-thick plates of directionally solidified (DS) IN792 superalloy. The first part of this work evidenced the importance of pre-heating the workpiece to avoid the formation of long cracks in the seam. The comparison of different pre-heating temperatures (PHT) and pass speeds (v) allowed the identification of optimal process parameters, namely PHT = 300 °C and v = 2.5 m/min. The microstructural features of the melted zone (MZ); the heat affected zone (HAZ), and base material (BM) were investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), electron back-scattered diffraction (EBSD), X-ray diffraction (XRD), and micro-hardness tests. In the as-welded condition; the structure of directionally oriented grains was completely lost in MZ. The γ' phase in MZ consisted of small (20-40 nm) round shaped particles and its total amount depended on both PHT and welding pass speed, whereas in HAZ, it was the same BM. Even if the amount of γ' phase in MZ was lower than that of the as-received material, the nanometric size of the particles induced an increase in hardness. EDS examinations did not show relevant composition changes in the γ' and γ phases. Post-welding heat treatments (PWHT) at 700 and 750 °C for two hours were performed on the best samples. After PWHTs, the amount of the ordered phase increased, and the effect was more pronounced at 750 °C, while the size of γ' particles in MZ remained almost the same. The hardness profiles measured across the joints showed an upward shift, but peak-valley height was a little lower, indicating more homogeneous features in the different zones.

Self-assembly of tissue spheroids on polymeric membranes.

In this study, multicellular tissue spheroids were fabricated on polymeric membranes in order to accelerate the fusion process and tissue formation. To this purpose, tissue spheroids composed of three different cell types, myoblasts, fibroblasts and neural cells, were formed and cultured on agarose and membranes of polycaprolactone (PCL) and chitosan (CHT). Membranes prepared by a phase-inversion technique display different physicochemical, mechanical and transport properties, which can affect the fusion process. The membranes accelerated the fusion process of a pair of spheroids with respect to the inert substrate. In this process, a critical role is played by the membrane properties, especially by their mechanical characteristics and oxygen and carbon dioxide mass transfer. The rate of fusion was quantified and found to be similar for fibroblast, myoblast and neural tissue spheroids on membranes, which completed the fusion within 3 days. These spheroids underwent faster fusion and maturation on PCL membrane than on agarose, the rate of fusion being proportional to the value of oxygen and carbon dioxide permeances and elastic characteristics. Consequently, tissue spheroids on the membranes expressed high biological activity in terms of oxygen uptake, making them more suitable as building blocks in the fabrication of tissues and organs. Copyright © 2015 John Wiley & Sons, Ltd.

Carcinoma of the pharynx and tonsils in an occupational cohort of asphalt workers.

BACKGROUND: We investigated a possible association between pharyngeal/tonsillar carcinoma and mixed carcinogen exposures in an asphalt roll company in Italy that used asbestos until 1979, when a new factory was built using a different production process. METHODS: We evaluated all workers involved in the entire production history of the company, divided into two subcohorts based on exposure status (workers in the original factory, 1964-1979, and those who worked only in the new factory, 1980-1997). We ascertained the vital status of the study population in February 2001. RESULTS: Among the subset of workers in the earlier subcohort, there were five deaths from pharyngeal/tonsillar carcinoma for a standardized mortality ratio of 21 (95% confidence interval = 8.8-51). No cases were recorded among workers hired after 1979. CONCLUSION: The increased standardized mortality ratio for this relatively rare cancer among workers exposed before 1979 may have been due to carcinogenic exposures at the plant.

A case report of vibration-induced hand comorbidities in a postwoman.

BACKGROUND: Prolonged exposure to hand-transmitted vibration is associated with an increased occurrence of symptoms and signs of disorders in the vascular, neurological and osteoarticular systems of the upper limbs. However, the available epidemiological evidence is derived from studies on high vibration levels caused by vibratory tools, whereas little is known about possible upper limb disorders caused by chronic exposure to low vibration levels emitted by fixed sources. CASE PRESENTATION: We present the case of a postwoman who delivered mail for 15 years using a low-powered motorcycle. The woman was in good health until 2002, when she was diagnosed with bilateral Raynaud's phenomenon. In March 2003 a bilateral carpal tunnel syndrome was electromyographically diagnosed; surgical treatment was ineffective. Further examinations in 2005 highlighted the presence of chronic tendonitis (right middle finger flexor). RISK ASSESSMENT: From 1987, for 15 years, our patient rode her motorcycle for 4 h/day, carrying a load of 20-30 kg. For about a quarter of the time she drove over country roads. Using the information collected about the tasks carried out every day by the postwoman and some measurements performed on both handles of the motorcycle, as well as on both iron parts of the handlebars, we reconstructed the woman's previous exposure to hand-arm vibration. 8-hour energy-equivalent frequency weighted acceleration was about 2.4 m/s². The lifetime dose was 1.5 × 109(m²/s4)hd. CONCLUSIONS: The particular set of comorbidities presented by our patient suggests a common pathophysiological basis for all the diseases. Considering the level of exposure to vibrations and the lack of specific knowledge on the effects of vibration in women, we hypothesize an association between the work exposure and the onset of the diseases.

Inhibition by CO and polarization in Pd-based membranes: a novel permeation reduction coefficient.

In this Article, a novel permeation reduction coefficient (PRC) is defined and used to take into account the presence of both inhibition by CO and concentration polarization in hydrogen permeation through Pd-based membranes. The usefulness of this coefficient consists in the possibility of describing simply, but at the same time powerfully, the behavior of the membrane subject to the combined effect of inhibition and polarization. According to this approach, the effective permeance, which is generally unknown because it depends on these two phenomena, can be directly evaluated by multiplying the "clean" intrinsic membrane Sieverts permeance (measurable by simple pure hydrogen permeation tests) by a PRC function, that is, [effective permeance] = (1-PRC) [clean Sieverts permeance]. The values of PRC are evaluated by means of a complex model that takes into account the several elementary permeation steps, in which the inhibitory effect of CO is also considered as well as the concentration polarization. The membrane behavior is evaluated in terms of some "performance maps", where PRC and other two coefficients (concentration polarization coefficient (CPC) and inhibition coefficient (IC)) are reported as functions of several operating conditions (hydrogen molar fraction, CO partial pressure, and upstream total pressures). Therefore, these maps provide a useful tool to estimate directly the main design parameter (the overall permeance) in situations where complex transport and kinetic phenomena affect the membrane performances, allowing the membrane performance to be estimated much better and the separation equipment to be better designed.

Sieverts law empirical exponent for Pd-based membranes: critical analysis in pure H2 permeation.

In this paper, the physical meaning of the Sieverts-type driving force exponent n is analyzed for hydrogen permeation through Pd-based membranes by considering a complex model involving several elementary permeation steps (adsorption on the membrane surface on the feed side, desorption from the surface on the permeate side, diffusion through the metal lattice, and the two transition phenomena surface-to-bulk and bulk-to-surface). First, the characteristic driving force of each step is evaluated, showing that adsorption and desorption singularly considered and the adsorption and desorption considered at the same time are characterized by driving forces depending on the ratio of feed and permeate hydrogen pressure. On the contrary, the diffusion step is found to present a driving force that is composed of two terms, one which corresponds to the original Sieverts law (with an exponent of 0.5) and the other which is the product of the pressure difference and a temperature-dependent factor. Then, the characteristic n is evaluated by applying the multistep model to two different membranes from the literature in several cases, (a) considering each permeation step as the only limiting one and (b) considering the overall effect of all steps. The results of the analysis show that for a low temperature and thin membrane thickness, the effect of the surface phenomena is, in general, a decrease of the overall exponent n toward values lower than 0.5, even though, under particular operating conditions, the n theoretical value of the surface phenomena is equal to unity. At a higher temperature and thickness (diffusion-controlled permeation), n tends to 0.5, even though the rapidity of this tendency depends strictly on the membrane diffusional parameters. In this frame, the expression developed for the diffusion step provides a theoretical reason why n values higher than 0.5 are found even for thick membranes and high temperature, where diffusion is the only rate-determining step.

Mass transfer and metabolic reactions in hepatocyte spheroids cultured in rotating wall gas-permeable membrane system.

Isolated hepatocytes in spheroid configuration exhibit a high degree of cell-cell contacts, which are important in the maintenance of viability and liver specific functions. In the absence of a vascular network, the cells in a large spheroid size experience mass transfer limitations of metabolites and oxygen in the core of aggregates. In this paper transport phenomena related to the diffusion and reaction of oxygen, glucose and lactate are mathematically described and experimentally verified for hepatocyte spheroids cultured in a rotating-wall polystyrene system (RWPS) not permeable for gases and in a rotating-wall membrane system (RWMS) with oxygen-permeable membrane. The concentration profiles of glucose, oxygen and lactate in the hepatocyte spheroids were estimated for different diameters of aggregates by solving the mass transfer equations for simultaneous diffusion and reaction, by finite element method. Simulation results evidenced that, for aggregates with size lower than 300 microm cultured in both RWPS and RWMS systems, the concentration profiles of glucose and lactate towards the core of spheroids (effective diffusion coefficients in the order of 10(-11)m(2)/s) are not significantly affected by the metabolic rate (c.a 10(-6)microg/mm(3)/s for glucose and about one order of magnitude less for lactate). On the contrary, the transport of oxygen (diffusion coefficient: 3.4 x 10(-10)m(2)/s, reaction rate: 1.5 x 10(-5)microg/mm(3)/s) is critically affected by the size of the multicellular spheroids and significant gradients in oxygen concentration may develop in spheroids. Aggregates with a size greater than 200 microm suffer severe oxygen limitation in the most part of its size attaining the lowest partial pressure in the centre. The improved viability predicted by the model culturing hepatocyte spheroids in the RWMS, characterized by a higher O(2) permeability with respect to RWPS, was experimentally confirmed. The results demonstrated that the mathematical model used in this study represents a useful support to experimental procedures in order to obtain hepatocyte spheroids with optimal size.

Fetuin-A gene expression, synthesis and release in primary human hepatocytes cultured in a galactosylated membrane bioreactor.

This paper reports on human hepatocytes cultured in a galactosylated membrane bioreactor in order to explore the modulation of the effects of a pro-inflammatory cytokine, Interleukin-6 (IL-6) on the liver cells at molecular level. In particular the role of IL-6 on gene expression and production of a glycoprotein, fetuin-A produced by hepatocytes, was investigated by culturing hepatocytes in the membrane bioreactor, both in the absence and presence of IL-6 (300 pg/ml). IL-6 modulated the fetuin-A gene expression, synthesis and release by primary human hepatocytes cultured in the bioreactor. A 75% IL-6-induced reduction of fetuin-A concentration in the medium was associated with a 60% increase of C-reactive protein in the same samples. Real-time-PCR demonstrated an 8-fold IL-6-induced reduction of fetuin-A gene expression. These results demonstrate that the hepatocyte galactosylated membrane bioreactor is a valuable tool to study IL-6 effects and gave evidence, for the first time, that IL-6 down-regulates the gene expression and synthesis of fetuin-A by primary human hepatocytes. The human hepatocyte bioreactor behaves like the in vivo liver, reproducing the same hepatic acute-phase response that occurs during the inflammatory process.

Grand rounds: could occupational exposure to n-hexane and other solvents precipitate visual failure in leber hereditary optic neuropathy?

CONTEXT: Leber hereditary optic neuropathy (LHON) is a maternally inherited loss of central vision related to pathogenic mutations in the mitochondrial genome, which are a necessary but not sufficient condition to develop the disease. Investigation of precipitating environmental/occupational (and additional genetic) factors could be relevant for prevention. CASE PRESENTATION: After a 6-month period of occupational exposure to n-hexane and other organic solvents, a 27-year-old man (a moderate smoker) developed an optic neuropathy. The patient had a full ophthalmologic and neurologic investigation, including standardized cycloergometer test for serum lactic acid levels and a skeletal muscle biopsy. His exposure history was also detailed, and he underwent genetic testing for LHON mitochondrial DNA mutations. The patient suffered a sequential optic neuropathy with the hallmarks of LHON and tested positive for the homoplasmic 11778G--> A/ND4 mutation. Routine laboratory monitoring revealed increased concentrations of urinary 2.5 hexandione (n-hexane metabolite) and hippuric acid (toluene metabolite) in the period immediately preceding the visual loss. DISCUSSION: In a subject carrying an LHON mutation, the strict temporal sequence of prolonged appreciable occupational exposure followed by sudden onset of visual loss must raise a suspicion of causality (with a possible further interaction with tobacco smoke). RELEVANCE: In this article, we add to the candidate occupational/environmental triggers of LHON and highlight the need for appropriate case-control (and laboratory) studies to validate the causal effect of mixed toxic exposures.