Filament Transport Control for Enhancing Mechanical Properties of Parts Realised by Fused Filament Fabrication

The fused filament fabrication (FFF) process is widely used for producing prototypes and functional parts for diverse applications. While FFF is particularly attractive due to its cost-effectiveness, on the other hand, the fabricated parts have limitations in terms of large manufacturing time and reduced mechanical properties. The latter is strongly influenced by the fabrication process parameters, which affect the interlayer bonding and the adhesion between consecutive layers. Several works presented in the literature analysed the correlation between mechanical properties and process parameters. It was demonstrated that an increase in the fabrication feed rate causes slippage between filament and the feeding system, which leads to a decrease in the extruded material flow, and thus in part density. This work aims to investigate how the limitation of the slippage phenomenon affects the mechanical properties of parts fabricated using the FFF process. A prototype machine, equipped with a closed-loop control system on filament transport, was used to fabricate samples for tensile tests and dynamical mechanical analysis. Samples fabricated enabling the filament transport control showed an increase both in ultimate tensile strength and elongation at break for those fabricated with disabled control, whilst a decrease in stiffness was observed. In addition, the results showed that the use of a filament transport control system on a FFF machine increases the possibility of fabricating high value-added parts.     

Systematic Evidence Map for Over One Hundred and Fifty Per- and Polyfluoroalkyl Substances (PFAS)

Background: Per- and polyfluoroalkyl substances (PFAS) are a large class of synthetic (man-made) chemicals widely used in consumer products and industrial processes. Thousands of distinct PFAS exist in commerce. The 2019 U.S. Environmental Protection Agency (U.S. EPA) Per- and Polyfluoroalkyl Substances (PFAS) Action Plan outlines a multiprogram national research plan to address the challenge of PFAS. One component of this strategy involves the use of systematic evidence map (SEM) approaches to characterize the evidence base for hundreds of PFAS.Objective: SEM methods were used to summarize available epidemiological and animal bioassay evidence for a set of ∼150 PFAS that were prioritized in 2019 by the U.S. EPA’s Center for Computational Toxicology and Exposure (CCTE) for in vitro toxicity and toxicokinetic assay testing.Methods: Systematic review methods were used to identify and screen literature using manual review and machine-learning software. The Populations, Exposures, Comparators, and Outcomes (PECO) criteria were kept broad to identify mammalian animal bioassay and epidemiological studies that could inform human hazard identification. A variety of supplemental content was also tracked, including information on in vitro model systems; exposure measurement–only studies in humans; and absorption, distribution, metabolism, and excretion (ADME). Animal bioassay and epidemiology studies meeting PECO criteria were summarized with respect to study design, and health system(s) were assessed. Because animal bioassay studies with ≥21-d exposure duration (or reproductive/developmental study design) were most useful to CCTE analyses, these studies underwent study evaluation and detailed data extraction. All data extraction is publicly available online as interactive visuals with downloadable metadata.Results: More than 40,000 studies were identified from scientific databases. Screening processes identified 44 animal and 148 epidemiology studies from the peer-reviewed literature and 95 animal and 50 epidemiology studies from gray literature that met PECO criteria. Epidemiological evidence (available for 15 PFAS) mostly assessed the reproductive, endocrine, developmental, metabolic, cardiovascular, and immune systems. Animal evidence (available for 40 PFAS) commonly assessed effects in the reproductive, developmental, urinary, immunological, and hepatic systems. Overall, 45 PFAS had evidence across animal and epidemiology data streams.Discussion: Many of the ∼150 PFAS were data poor. Epidemiological and animal evidence were lacking for most of the PFAS included in our search. By disseminating this information, we hope to facilitate additional assessment work by providing the initial scoping literature survey and identifying key research needs. Future research on data-poor PFAS will help support a more complete understanding of the potential health effects from PFAS exposures. https://doi.org/10.1289/EHP10343     

Thermostructural Numerical Analysis of the Thrust Chamber of a Liquid Propellant Rocket Engine

The numerical simulation of rocket engine thrust chambers is very challenging as several damaging phenomena, such as plasticity, low-cycle-fatigue (LCF) and creep occur during its service life. The possibility of simulating the thermostructural behavior of the engine, by means of non-linear finite element analyses, allows the engineers to guarantee the structural safety of the structure. This document reports the numerical simulations developed with the aim of predicting the thermostructural behaviour and the service life of the thrust chamber of a liquid-propellant rocket engine. The work represents a step ahead of previous researches by the authors, with particular reference to the addition of the Smith-Watson-Topper (SWT) fatigue criterion, and to the implementation of a sub-modelling technique, for a more accurate assessment of the most critical section of the component. It was found that the equivalent plastic strains in the most critical nodes obtained through the sub-modelling technique were about 20% lower than those calculated without sub-modelling. Consistently with experimental tests from literature conducted on similar geometries, the most critical areas resulted to be on the internal surface of the chamber. The analyses demonstrated that the LCF damaging contribution was significant, with a life prediction for the thrust chamber of about 3400 cycles.     

Liquid Biopsy at Home: Delivering Precision Medicine for Patients with Cancer During the COVID-19 Pandemic

CoronaVirus disease-2019 has changed the delivery of health care worldwide and the pandemic has challenged oncologists to reorganize cancer care. Recently, progress has been made in the field of precision medicine to provide to patients with cancer the best therapeutic choice for their individual needs. In this context, the Foundation Medicine (FMI)-Liquid@Home project has emerged as a key weapon to deal with the new pandemic situation. FoundationOne Liquid Assay (F1L) is a next-generation sequences-based liquid biopsy service, able to detect 324 molecular alterations and genomic signatures, from May 2020 available at patients’ home (FMI-Liquid@Home). We analyzed time and costs saving for patients with cancer, their caregivers and National Healthcare System (NHS) with FMI-Liquid@Home versus F1L performed at our Department. Different variables have been evaluated. Between May 2020 and August 2021, 218 FMI-Liquid@Home were performed for patients with cancer in Italy. Among these, our Department performed 153 FMI-Liquid@Home with the success rate of 98% (vs. 95% for F1L in the hospital). Time saving for patients and their caregivers was 494.86 and 427.36 hours, respectively, and costs saving was 13 548.70€. Moreover, for working people these savings were 1084.71 hours and 31 239.65€, respectively. In addition, the total gain for the hospital was 163.5 hours and 6785€, whereas for NHS was 1084.71 hours and 51 573.60€, respectively. FMI-Liquid@Home service appears to be useful and convenient allowing time and costs saving for patients, caregivers, and NHS. Born during the COVID-19 pandemic, it could be integrated in oncological daily routine in the future. Therefore, additional studies are needed to better understand the overall gain and how to integrate this service in different countries.     

Pregnancy in uremic patients: an eventful journey

Renal damage, which can be caused by gestational anomalies such as pre-eclampsia, carries a risk of gestational complications; the greatest risk being in women who become pregnant while on hemodialysis or peritoneal dialysis. If this rare event occurs, there is a marked increase in the risk of pre-eclampsia, early uterine contractions and hydramnios, hypertensive crisis, preterm delivery and intrauterine growth retard. Furthermore, newborns are almost always of low birthweight. Patients who undergo renal transplantation are another high-risk category. In such cases, the pregnancy itself can compromise the success of the transplant and the immunosuppressive therapy correlated to it can become a threat to the course of the pregnancy and normal fetal growth. Therefore, in view of the lack of appropriate guidelines for the best possible approach to the treatment of women on dialysis or of those with a renal transplantation, it is best to advise these patients against becoming pregnant and/or to provide a valid counselling service illustrating the extreme difficulties and dangers involved in becoming pregnant.