Challenge Test Improvement: Analytical Costs and Time Optimization

The study’s aim was to develop a quantitative risk assessment model of Listeria monocytogenes in liver chicken paté. The model was performed using the Integrated Challenge Test (Italian Journal of Food Safety, Vol. 1 N. 6 2012) with the objective to reduce the analytical cost and time. The challenge test was carried out on 3 different batches stored at 12°C and inoculated with a mix of Listeria monocytogenes strains. Lactobacillus spp. and Listeria monocytogenes plate counts were performed daily on each sample until the stationary phase was reached by both populations. The challenge test results at 12°C were input in the Combase DMfit software to determine the growth parameters of Listeria monocytogenes and lactic flora which showed mutual interaction. Then, using the Combase Predictor for Listeria monocytogenes and the FSSP (Food Spoilage and Safety Predictor) software for lactic flora, the growth parameters were extrapolated at 4°C and 8°C. The growth parameters of both populations at 4°C, 8°C and 12°C were then used to apply the model in order to predict the maximum daily concentration of Listeria monocytogenes. Model results were assessed against the results of an additional challenge test conducted with the same strain mix inoculum in 3 different batches stored for 4 days at 4°C, 4 days at 8°C and then 4 days at 12°C. The proposed model represents a reliable quantitative risk evaluation which provides realistic results with limited cost

Narrative and Cultural History in the Hippocratic Treatise On Ancient Medicine

This paper focuses on the ‘history of medicine’ outlined by the author of the Hippocratic treatise On Ancient Medicine, in order to reflect on the relationship between medicine and narrative in Classical Greece. At the outset of the work, the author provides an account of the beginnings of his discipline, conceiving of medicine’s history as a continuum of research and findings that unravel the nature of the human body and the cause of diseases. As this paper shows, the physician-narrator assigns to his craft a crucial role in fostering the birth and progress of human civilization. The rhetorical goals of the historical account are, as I argue, attained through a subtle narrative strategy. In fact, the narrator locates the origins of medicine within a teleological framework, marked by strong emphasis on the heuristic method that characterizes the past, the present, and the future of medical knowledge at once

The local impact of closing undersized schools

The availability of public education services can influence residential choices. Hence, policies aiming to ‘rationalise’ service provision by reducing the number of undersized nodes in the public school network can lead to population decline. This paper examines the demographic and income effects of primary school closures by exploiting an Italian education reform that resulted in a significant contraction of the school network. We assess whether school closures impact households’ residential choices, on top and beyond preexisting negative population trends that motivate school closures. To address endogeneity, we combine a Two-Way Fixed Effects model with an instrumental variable approach, constructing the IVs based on institutional thresholds for school sizing adopted by some Italian regions. Our findings suggest that municipalities affected by school closures experience significant reductions in population and income. The effect is driven by peripheral municipalities located far from economic centres and distant from the next available primary school. This evidence indicates that school ‘rationalisation policies’, by fostering depopulation of peripheral areas, have an influence on the spatial distribution of households and income, thus affecting territorial disparities

On the X-ray feature associated with the Guitar Nebula

Context: A mysterious X-ray nebula, showing a remarkably linear geometry, was recently discovered close to the Guitar Nebula, the bow-shock nebula associated with B2224+65, which is the fastest pulsar known. The nature of this X-ray feature is unknown, and even its association with pulsar B2224+65 is unclear. Aims: We attempt to develop a self-consistent scenario to explain the complex phenomenology of this object. Methods: We assume that the highest energy electrons accelerated at the termination shock escape from the bow shock and diffuse into the ambient medium, where they emit synchrotron X-rays. The linear geometry should reflect the plane-parallel geometry of its ambient field. Results: We estimate the Lorentz factor of the X-ray emitting electrons and the strength of the magnetic field. The former (~10^8) is close to its maximum possible value, while the latter, at ~45 uG, is higher than typical interstellar values and must have been amplified in some way. The magnetic field must also be turbulent to some degree to trap the electrons sufficiently for synchrotron X-ray emission to occur effectively. We propose a self-consistent scenario in which, by some streaming instability, the electrons themselves generate a turbulent field in which they then diffuse. Some numerical coincidences are explained, and tests are proposed to verify our scenario. Conclusions: Electron leaking may be common in the majority of pulsar bow-shock nebulae, even though the X-ray nebulosity in general is too diffuse to be detectable.Comment: 4 pages. Accepted for publication in A&A, Letters to the Edito

Knowledge economy, internal migration, and the effect on local labour markets

Knowledge-intensive activities may generate significant multiplicative effects at the local level. In particular, inflows of workers in knowledge-related sectors may contribute to make local labour markets more attractive for other kind of workers as well. This paper assesses how the employment growth and inflow of workers in knowledge-intensive sectors affect wage, employment, and probability of outmigration of local workers in other sectors. We focus on Italy during the 2005-2019 period, taking advantage of matched employer-employee social-security data, which allows to track workers’ histories across jobs and locations. To address the identification concerns of sorting and idiosyncratic shocks, we implement a two-step procedure combined with a shift-share IV strategy. We separately identify the contribution of sorting and spillovers to labour market outcomes. Our results suggest that the employment growth and inflow of workers in knowledge-intensive sectors have multiplicative effects on employment, increasing the number of days worked by local workers, and they also seem to reduce the probability of outmigration. Nominal wages of localworkers seem unaffected, while house prices increase producing a negative effect on local real wages

Fast and Reliable Modeling of Piezoelectric Transducers for Energy Harvesting Applications

The paper presents a fast and reliable model identification technique for piezoelectric transducers based on an equivalent electromechanical circuit easily implementable on SPICE-like simulation tools. Model parameter extraction is simple and requires just standard and inexpensive laboratory equipment. Indeed, the equivalent circuit representation permits the evaluation of the response of a real energy harvesting system, where the electronic load is a synchronized switching converter which usually causes a significant feedback on the mechanical part of the system during energy extraction. Both simulation and measurements show that the damping effect is particularly important near resonance, where the adopted model is able to fit the experimental data and provides a more realistic description of the behavior of the system

A 32 mV/69 mV input voltage booster based on a piezoelectric transformer for energy harvesting applications

This paper presents a novel method for battery-less circuit start-up from ultra-low voltage energy harvesting sources. The approach proposes for the first time the use of a Piezoelectric Transformer (PT) as the key component of a step-up oscillator. The proposed oscillator circuit is first modelled from a theoretical point of view and then validated experimentally with a commercial PT. The minimum achieved start-up voltage is about 69 mV, with no need for any external magnetic component. Hence, the presented system is compatible with the typical output voltages of thermoelectric generators (TEGs). Oscillation is achieved through a positive feedback coupling the PT with an inverter stage made up of JFETs. All the used components are in perspective compatible with microelectronic and MEMS technologies. In addition, in case the use of a ∼40 μH inductor is acceptable, the minimum start-up voltage becomes as low as about 32 mV