EPS architecture analysis for future highpower missions

The space tug can represent a valid solution to provide transportation capabilities for future space missions. In particular, the tug can be effectively adopted for different applications such as electric orbit raising for commercial satellites and cargo transfer to resupply space infrastructures. The adoption of high-power electric propulsion is a fundamental enabler for these mission scenarios, owing to its advantages in terms of long lifetime, high performance and operational flexibility. However, further investigation should be performed in order to optimize the design of the space tug considering different architecture alternatives. We defined two sets of thruster operative points for a more representative comparison of EPS architecture cases. In particular, we analyzed three aspects: the adoption of a cluster of thrusters vs the monolithic approach; the implementation of a direct drive power supply vs the traditional power processing unit; the selection of krypton propellant vs xenon. The design of the space tug is performed with MAGNETO tool, a software developed in a collaboration between SITAEL and Politecnico di Torino in the framework of an ESA GSTP project. The results are compared by means of the analytical hierarchy process to identify the optimal design solution for the spacecraft design

Breech presentation at term and associated obstetric risks factors-a nationwide population based cohort study

Purpose The aim of this study was to estimate whether breech presentation at term was associated with known individual obstetric risk factors for adverse fetal outcome. Methods This was a retrospective, nationwide Finnish population-based cohort study. Obstetric risks in all breech and vertex singleton deliveries at term were compared between the years 2005 and 2014. A multivariable logistic regression model was used to determine significant risk factors. Results The breech presentation rate at term for singleton pregnancies was 2.4%. The stillbirth rate in term breech presentation was significantly higher compared to cephalic presentation (0.2 vs 0.1%). The odds ratios (95% CIs) for fetal growth restriction, oligohydramnios, gestational diabetes, a history of cesarean section and congenital fetal abnormalities were 1.19 CI (1.07-1.32), 1.42 CI (1.27-1.57), 1.06 CI (1.00-1.13), 2.13 (1.98-2.29) and 2.01 CI (1.92-2.11). Conclusions The study showed that breech presentation at term on its own was significantly associated with antenatal stillbirth and a number of individual obstetric risk factors for adverse perinatal outcomes. The risk factors included oligohydramnios, fetal growth restriction, gestational diabetes, history of caesarean section and congenital anomalies.Peer reviewe

Role of drug transporters and drug accumulation in the temporal acquisition of drug resistance

<p>Abstract</p> <p>Background</p> <p>Anthracyclines and taxanes are commonly used in the treatment of breast cancer. However, tumor resistance to these drugs often develops, possibly due to overexpression of drug transporters. It remains unclear whether drug resistance <it>in vitro </it>occurs at clinically relevant doses of chemotherapy drugs and whether both the onset and magnitude of drug resistance can be temporally and causally correlated with the enhanced expression and activity of specific drug transporters. To address these issues, MCF-7 cells were selected for survival in increasing concentrations of doxorubicin (MCF-7_DOX-2), epirubicin (MCF-7_EPI), paclitaxel (MCF-7_TAX-2), or docetaxel (MCF-7_TXT). During selection cells were assessed for drug sensitivity, drug uptake, and the expression of various drug transporters.</p> <p>Results</p> <p>In all cases, resistance was only achieved when selection reached a specific threshold dose, which was well within the clinical range. A reduction in drug uptake was temporally correlated with the acquisition of drug resistance for all cell lines, but further increases in drug resistance at doses above threshold were unrelated to changes in cellular drug uptake. Elevated expression of one or more drug transporters was seen at or above the threshold dose, but the identity, number, and temporal pattern of drug transporter induction varied with the drug used as selection agent. The pan drug transporter inhibitor cyclosporin A was able to partially or completely restore drug accumulation in the drug-resistant cell lines, but had only partial to no effect on drug sensitivity. The inability of cyclosporin A to restore drug sensitivity suggests the presence of additional mechanisms of drug resistance.</p> <p>Conclusion</p> <p>This study indicates that drug resistance is achieved in breast tumour cells only upon exposure to concentrations of drug at or above a specific selection dose. While changes in drug accumulation and the expression of drug transporters does occur at the threshold dose, the magnitude of resistance cannot be attributed solely to changes in drug accumulation or the activity of drug transporters. The identities of these additional drug-transporter-independent mechanisms are discussed, including their likely clinical relevance.</p

FINITE DIFFERENCES SOLUTION OF THREE PHASES STEFAN PROBLEM WITH HIGH POWER INPUT

The numerical solution of a one dimensional, three-phases Stefan problem with a low Stefan number is presented. Joule heating and thermal radiation are demonstrated to be negligible compared to the high power input. The Front Tracking Method is used along with a second order Lagrangian interpolation of the temperature profile near the moving surface defined by the location of the phase change. Results are compared with analytical, numerical and experimental solutions available in literature

POWER DISSIPATION IN HEAVY METALS RECOVERY FROM INCINERATOR ASHES

Under controlled conditions waste-to-energy plants are very useful systems to dispose solid wastes in combination with energy production. For common urban wastes, hence excluding special wastes, the incineration products are fly and heavy ashes where heavy metals are concentrated due to their impossibility to be vaporized. Those metals are usually lost because up to now the common ashes disposal methods have been cement or clay inertization or simple ashes storage in safe places. In order to recover those otherwise lost valuable and useful heavy metals we present the concept of an electromagnetic device able to separate and collect the different atomic species. The proposed device is essentially composed by an atomization stage followed by a separation one. The former atomizes and ionizes ash components allowing the second stage to perform separation of the desired metals by means of an electromagnetic field. Power dissipation represents one of the major issues of such devices due to the high power required to perform species separation. In this paper the major power sources and losses are also identified

THERMAL MODELLING OF LASER ABLATION SIMULATION BY NUMERICAL SOLUTION OF A THREE PHASE STEPHAN PROBLEM

Laser ablation is an important industrial process to remove material from a solid surface by means of a laser beam that heats and evaporates or sublimates the material. One of the most interesting applications of such technique is the laser machining, technique that allow to drill holes and perform other operations on even very hard material in an extremely precise way. Usually this process is performed not continuously but with a pulsed laser, meaning that an extremely high amount of energy is discharged on an extremely small surface, achieving a strong energy density in a small amount of time such that the surrounding material absorbs a very small amount of energy; consequently it does not heat, preserving its properties. This process can be easily modeled as a three phase Stephan problem to which a finite difference solution with the Front Tracking Method is applied. Such methodology has been already used by authors to model electrodes erosion by the establishing of electric arches, with good agreement with literature data. The same methodology is now applied to laser ablation technique taking into account the additional energy contribution mechanisms that could have been previously negligible for an electric arc shock but that are of high relevance in a laser ablation process