Mid Infrared Photometry of Mass-Losing AGB Stars

We present ground-based mid-infrared imaging for 27 M-, S- and C-type Asymptotic Giant Branch (AGB) stars. The data are compared with those of the database available thanks to the IRAS, ISO, MSX and 2MASS catalogues. Our goal is to establish relations between the IR colors, the effective temperature $T_{eff}$, the luminosity $L$ and the mass loss rate $\dot M$, for improving the effectiveness of AGB modelling. Bolometric (absolute) magnitudes are obtained through distance compilations, and by applying previously-derived bolometric corrections; the variability is also studied, using data accumulated since the IRAS epoch. The main results are: i) Values of $L$ and $\dot M$ for C stars fit relations previously established by us, with Miras being on average more evolved and mass losing than Semiregulars. ii) Moderate IR excesses (as compared to evolutionary tracks) are found for S and M stars in our sample: they are confirmed to originate from the dusty circumstellar environment. iii) A larger reddening characterizes C-rich Miras and post-AGBs. In this case, part of the excess is due to AGB models overestimating $T_{eff}$ for C-stars, as a consequence of the lack of suitable molecular opacities. This has a large effect on the colors of C-rich sources and sometimes disentangling the photospheric and circumstellar contributions is difficult; better model atmospheres should be used in stellar evolutionary codes for C stars. iv) The presence of a long-term variability at mid-IR wavelengths seems to be limited to sources with maximum emission in the 8 -- 20 $\mu$m region, usually Mira variables (1/3 of our sample). Most Semiregular and post-AGB stars studied here remained remarkably constant in mid-IR over the last twenty years.Comment: Accepted for publication in the Astronomical Journal - 35 pages (in preprint), 9 figures, 5 table

The challenge of perioperative pain management in opioid-tolerant patients

The increasing number of opioid users among chronic pain patients, and opioid abusers among the general population, makes perioperative pain management challenging for health care professionals. Anesthesiologists, surgeons, and nurses should be familiar with some pharmacological phenomena which are typical of opioid users and abusers, such as tolerance, physical dependence, hyperalgesia, and addiction. Inadequate pain management is very common in these patients, due to common prejudices and fears. The target of preoperative evaluation is to identify comorbidities and risk factors and recognize signs and symptoms of opioid abuse and opioid withdrawal. Clinicians are encouraged to plan perioperative pain medications and to refer these patients to psychiatrists and addiction specialists for their evaluation. The aim of this review was to give practical suggestions for perioperative management of surgical opioid-tolerant patients, together with schemes of opioid conversion for chronic pain patients assuming oral or transdermal opioids, and patients under maintenance programs with methadone, buprenorphine, or naltrexone

Production and characterization of polyethylene terephthalate nanoparticles

Microplastic (MP) pollution represents one of the biggest environmental problems that is further exacerbated by the continuous degradation in the marine environment of MPs to nanoplastics (NPs). The most diffuse plastics in oceans are commodity polymers, mainly thermoplastics widely used for packaging, such as polyethylene terephthalate (PET). However, the huge interest in the chemical vector role of micro/nanoplastics, their fate and negative effects on the environment and human health is still under discussion and the research is still sparse due also to the difficulties of sampling MPs and NPs from the environment or producing NPs in laboratory. Moreover, the research on MPs and NPs pollution relies on the availability of engineered nanoparticles similar to those present in the marine environment for toxicological, transport and adsorption studies in biological tissues as well as for wastewater remediation studies. This work aims to develop an easy, fast and scalable procedure for the production of representative model nanoplastics from PET pellets. The proposed method, based on a simple and economic milling process, has been optimized considering the peculiarities of the polymer. The results demonstrated the reliability of the method for preparing particle suspensions for aquatic microplastic research, with evident advantages compared to the present literature procedures, such as low cost, the absence of liquid nitrogen, the short production time, the high yield of the process, stability, reproducibility and polydisperse size distribution of the produced water dispersed nanometric PET

On the optimal indoor air conditions for sars-cov-2 inactivation. An enthalpy-based approach

In the CoViD-19 pandemic, the precautionary approach suggests that all possible measures should be established and implemented to avoid contagion, including through aerosols. For indoor spaces, the virulence of SARS-CoV-2 could be mitigated not only via air changes, but also by heating, ventilation, and air conditioning (HVAC) systems maintaining thermodynamic conditions possibly adverse to the virus. However, data available in literature on virus survival were never treated aiming to this. In fact, based on comparisons in terms of specific enthalpy, a domain of indoor comfort conditions between 50 and 60 kJ/kg is found to comply with this objective, and an easy-to-use relationship for setting viable pairs of humidity and temperature using a proper HVAC plant is proposed. If confirmed via further investigations on this research path, these findings could open interesting scenarios on the use of indoor spaces during the pandemic

Design and optimization of a large turboprop aircraft

This paper proposes a feasibility study concerning a large turboprop aircraft to be used as a lower environmental impact solution to current regional jets operated on short/medium hauls. An overview of this market scenario highlights that this segment is evenly shared between regional turboprop and jet aircraft. Although regional jets ensure a large operative flexibility, they are usually not optimized for short missions with a negative effect on block fuel and environmental impact. Conversely, turboprops represent a greener solution but with reduced passenger capacity and speed. Those aspects highlight a slot for a new turboprop platform coupling higher seat capacity, cruise speed and design range with a reduced fuel consumption. This platform should operate on those ranges where neither jet aircraft nor existing turboprops are optimized. This work compares three different solutions: a high‐wing layout with under‐wing engines installation and both two-and three‐lifting‐surface configurations with low‐wing and tail tips‐mounted engines. For each concept, a multi‐disciplinary optimization was performed targeting the minimum block fuel on a 1600 NM mission. Optimum solutions were compared with both a regional jet such as the Airbus A220‐300 operated on 1600 NM and with a jet aircraft specifically designed for this range

Dimensionless Correlations for Natural Convection Heat Transfer from a Pair of Vertical Staggered Plates Suspended in Free Air

Buoyancy-induced convection from a pair of staggered heated vertical plates suspended in free air is studied numerically with the main scope to investigate the basic heat and momentum transfer features and to determine in what measure any independent variable affects the thermal performance of each plate and both plates. A computational code based on the SIMPLE-C algorithm for pressure-velocity coupling is used to solve the system of the governing conservation equations of mass, momentum and energy. Numerical simulations are carried out for different values of the Rayleigh number based on the plate length, as well as of the horizontal separation distance between the plates and their vertical alignment, which are both normalized by the plate length. It is observed that an optimal separation distance between the plates for the maximum heat transfer rate related to the Rayleigh number and the vertical alignment of the plates does exist. Based on the results obtained, suitable dimensionless heat transfer correlations are developed for each plate and for the entire system