Investigation via morphological analysis of aluminium foams produced by replication casting

Foams and porous materials with cellular structure have many interesting combinations of physical and mechanical properties coupled with low specific weight. By means of replication casting it is possible to manufacture foams from molten metal without direct foaming. A soluble salt is used as space holder, which is removed by leaching in water. This can be done successfully if the content of space holding fillers is so high that all the granules are interconnected. One of the main advantages of using the replication casting is a close control of pore sizes which is given by the distribution of particle sizes of the filler material. This contrasts with the pore size distribution of the materials foamed by other processes where a wider statistical distribution of pores is found. On the other hand, the maximum porosities that can be achieved using space holders are limited to values below 60%, whereas the other methods allow for porosities up to 98%. Temperature of the mould and infiltration pressure are critical process parameters: a typical problem encountered is the premature solidification of the melt, especially due to the high heat capacity of the salt. In this work foam properties such as cell shape, distribution and anisotropy and defect presence are investigated by using digital image processing technique. For this purpose replicated AlSi7Mg0.3 alloy foams are produced by infiltrating preforms of NaCl particles, varying the metal infiltration pressure and the mould preheating temperature. An original procedure based on image analysis has been set up to determine size, morphology and distribution of cells. The paper demonstrates that this methodology, coupled with microstructural analysis, is a useful tool for investigating the effects of process parameters on foam properties

Selective laser melting process of Al–based pyramidal horns for the w-band: fabrication and testing

In the context of exploring the possibility of using Al-powder Selective Laser Meltingto fabricate horn antennas for astronomical applications at millimeter wavelengths,we describe the design, the fabrication, the mechanical characterization, and theelectromagnetic performance of additive manufactured horn antennas for the W-band. Our aim, in particular, is to evaluate the performance impact of two basickinds of surface post-processing (manual grinding and sand-blasting) to deal withthe well-known issue of high surface roughness in 3D printed devices. We performedcomparative tests of co-polar and cross-polar angular response across the whole W-band, assuming a commercially available rectangular horn antenna as a reference.Based on gain and directivity measurements of the manufactured samples, we finddecibel-level detectable deviations from the behavior of the reference horn antenna,and marginal evidence of performance degradation at the top edge of the W-band.We conclude that both kinds of post-processing allow achieving good performancefor the W-band, but the higher reliability and uniformity of the sand-blasting post-process encourage exploring similar techniques for further development of aluminumdevices at these frequencies

How regulating and cultural services of ecosystems have changed over time in Italy

In this experimental study, different components are computed for three different ecosystem services (ES). Specifically, supply, demand and use are estimated for pollination service, flood risk regulation service and nature-based tourism. These are analysed and assessed in 2012 and 2018 for the Italian context, in order to estimate the evolution over this period and to allow a significant comparison of results. The same methodology and models are applied for the selected accounting years and accounting tables and tend to reflect as closely as possible the System of Environmental-Economic Accounting-Ecosystem Accounting (SEEA EA), which is the international standard endorsed by the United Nations to compile Natural Capital Accounting in 2021. Both biophysical and monetary assessments are performed using the ARIES technology, an integrated modelling platform providing automatic and flexible integration of data and models, via its semantic modelling nature. Models have been run adjusting the components of the global modelling approach to the Italian context and, whenever available, prioritising the use of local data to carry out the study. This approach is particularly useful to analyse trends over time, as potentially biased components of models and data are substantially mitigated when the same biases is constant over time. This study finds an increase in benefits over the period analysed for the ES examined. The main contribution of this pioneering work is to support the idea that ES accounting or Natural Capital Accounting can provide a very useful tool to improve economic and environmental information at national and regional level. This can support processes to provide the necessary incentives to steer policy-making towards preventative rather than corrective actions, which are usually much less effective and more costly, both at environmental and economic levels. Nevertheless, particular attention must be paid to the meaning of the estimates and the drivers of these values to derive a direct or indirect relationship between the benefits observable and the actual Italian ecosystems condition. © Capriolo A et al

How fast can vanadium dioxide neuron-mimicking devices oscillate? Physical mechanisms limiting the frequency of vanadium dioxide oscillators

The frequency of vanadium dioxide (VO2) oscillators is a fundamental figure of merit for the realization of neuromorphic circuits called oscillatory neural networks (ONNs) since the high frequency of oscillators ensures low-power consuming, real-time computing ONNs. In this study, we perform electrothermal 3D technology computer-aided design (TCAD) simulations of a VO2 relaxation oscillator. We find that there exists an upper limit to its operating frequency, where such a limit is not predicted from a purely circuital model of the VO2 oscillator. We investigate the intrinsic physical mechanisms that give rise to this upper limit. Our TCAD simulations show that it arises a dependence on the frequency of the points of the curve current versus voltage across the VO2 device corresponding to the insulator-to-metal transition (IMT) and metal-to-insulator transition (MIT) during oscillation, below some threshold values of $C_{\mathrm{ext}}$. This implies that the condition for the self-oscillatory regime may be satisfied by a given load-line in the low-frequency range but no longer at higher frequencies, with consequent suppression of oscillations. We note that this variation of the IMT/MIT points below some threshold values of $C_{\mathrm{ext}}$ is due to a combination of different factors: intermediate resistive states achievable by VO2 channel and the interplay between frequency and heat transfer rate. Although the upper limit on the frequency that we extract is linked to the specific VO2 device we simulate, our findings apply qualitatively to any VO2 oscillator. Overall, our study elucidates the link between electrical and thermal behavior in VO2 devices that sets a constraint on the upper values of the operating frequency of any VO2 oscillator

Donne e Tecnologie Informatiche

Un approfondimento quantitativo e qualitativo del gender gap esistente nelle ICT attraverso dati statistici, analisi del web, rapporti ufficiali, norme e politiche, con particolare attenzione alla realta' del Veneto

Forced expiratory volume in one second: A novel predictor of work disability in subjects with suspected obstructive sleep apnea

Whether the association of work disability with obstructive sleep apnea (OSA) is mainly due to the disease, i.e. the number and frequency of apneas-hypoapneas, or to coexisting factors independent from the disease, is not well-established. In this study, we aim to evaluate work ability in a group of subjects undergoing OSA workup and to identify the major contributors of impaired work ability. In a cross-sectional study, we enrolled 146 consecutive subjects who have been working for the last five years and referred to the sleep disorders outpatients’ clinic of the University-Hospital of Ferrara, Italy, with suspected OSA. After completing an interview in which the Work Ability Index (WAI) and the Epworth Sleepiness Scale (ESS) questionnaires were administered to assess work ability and excessive daytime sleepiness, respectively, subjects underwent overnight polysomnography for OSA diagnosing and spirometry. Of the 146 subjects, 140 (96%) completed the tests and questionnaires and, of these, 66 exhibited work disability (WAI < 37). OSA was diagnosed (apnea-hypopnea index 5) in 45 (68%) of the 66 subjects. After controlling for confounders, a lower level of forced expiratory volume at 1 second (FEV1), [odds ratio 0.97 (95% CI 0.95–1.00)], older age [1.09 (95% CI 1.03–1.15)], excessive daytime sleepiness [3.16 (95% CI 1.20–8.34)] and a worse quality of life [0.96 (95% CI 0.94–1.00)], but not OSA [1.04 (95% CI 0.41–2.62)], were associated with work disability. Patients with a higher number of diseases, in which OSA was not included, and a lower quality of life had an increased probability of absenteeism in the previous 12 months. In subjects with suspected OSA, FEV1 can be an important predictor of work disability

Antifibrotic treatment response and prognostic predictors in patients with idiopathic pulmonary fibrosis and exposed to occupational dust

BACKGROUND: Idiopathic Pulmonary Fibrosis (IPF) is an aggressive interstitial lung disease with an unpredictable course. Occupational dust exposure may contribute to IPF onset, but its impact on antifibrotic treatment and disease prognosis is still unknown. We evaluated clinical characteristics, respiratory function and prognostic predictors at diagnosis and at 12 month treatment of pirfenidone or nintedanib in IPF patients according to occupational dust exposure. METHODS: A total of 115 IPF patients were recruited. At diagnosis, we collected demographic, clinical characteristics, occupational history. Pulmonary function tests were performed and two prognostic indices [Gender, Age, Physiology (GAP) and Composite Physiologic Index (CPI)] calculated, both at diagnosis and after the 12 month treatment. The date of long-term oxygen therapy (LTOT) initiation was recorded during the entire follow-up (mean = 37.85, range 12-60 months). RESULTS: At baseline, patients exposed to occupational dust [≥ 10 years (n = 62)] showed a lower percentage of graduates (19.3% vs 54.7%; p = 0.04) and a higher percentage of asbestos exposure (46.8% vs 18.9%; p 0.002) than patients not exposed [< 10 years (n = 53)]. Both at diagnosis and after 12 months of antifibrotics, no significant differences for respiratory function and prognostic predictors were found. The multivariate analysis confirmed that occupational dust exposure did not affect neither FVC and DLCO after 12 month therapy nor the timing of LTOT initiation. CONCLUSION: Occupational dust exposure lasting 10 years or more does not seem to influence the therapeutic effects of antifibrotics and the prognostic predictors in patients with IPF

Tuning a Schottky barrier in a photoexcited topological insulator with transient Dirac cone electron-hole asymmetry

The advent of Dirac materials has made it possible to realize two dimensional gases of relativistic fermions with unprecedented transport properties in condensed matter. Their photoconductive control with ultrafast light pulses is opening new perspectives for the transmission of current and information. Here we show that the interplay of surface and bulk transient carrier dynamics in a photoexcited topological insulator can control an essential parameter for photoconductivity - the balance between excess electrons and holes in the Dirac cone. This can result in a strongly out of equilibrium gas of hot relativistic fermions, characterized by a surprisingly long lifetime of more than 50 ps, and a simultaneous transient shift of chemical potential by as much as 100 meV. The unique properties of this transient Dirac cone make it possible to tune with ultrafast light pulses a relativistic nanoscale Schottky barrier, in a way that is impossible with conventional optoelectronic materials.Comment: Nature Communications, in press (12 pages, 6 figures

Breathlessness, but not cough, suggests chronic obstructive pulmonary disease in elderly smokers with stable heart failure.

Chronic obstructive pulmonary disease (COPD) is a common comorbidity of heart failure (HF), but remains often undiagnosed, and we aimed to identify symptoms predicting COPD in HF. As part of an observational, prospective study, we investigated stable smokers with a confirmed diagnosis of HF, using the 8-item COPD-Assessment-Test (CAT) questionnaire to assess symptoms. All the items were correlated with the presence of COPD, and logistic regression models were used to identify independent predictors. 96 HF patients were included, aged 74, 33% with COPD. Patients with HF and COPD were more symptomatic, but only breathlessness when walking up a hill was an independent predictor of COPD (odds ratio=1.33, p=0.0484). Interestingly, COPD-specific symptoms such as cough and phlegm were not significant. Thus, in elderly smokers with stable HF, significant breathlessness when walking up a hill is most indicative of associated COPD, and may indicate the need for further lung function evaluation