Ottimizzazione di Traiettorie verso Asteroidi con Metodologia PSO

Nel presente lavoro di tesi si è applicato un risolutore basato su metodologie PSO alla soluzione di problemi di ottimizzazione nell’ambito della meccanica del volo spaziale. In particolare, sono stati analizzati trasferimenti a bassa spinta di veicoli spaziali verso alcuni asteroidi. Nella prima parte dell’elaborato viene descritto l’approccio basato su metodi diretti per la risoluzione di un problema di ottimizzazione vincolata. Inoltre, si descrivono le caratteristiche ed il principio di funzionamento del risolutore utilizzato per effettuare le simulazioni. Nella seconda parte, sono presentati le due principali classi di problemi di natura tridimensionale su cui il risolutore è stato provato. Il primo riguarda il problema di ottimizzazione che è stato proposto in occasione della Third Global Optimization Competition: si tratta di effettuare un rendez-vous multiplo con tre asteroidi della classe NEAs. Nel secondo problema ci si è concentrati sull’asteroide 99942 Apophis, cercando le traiettorie ottime sia per l’inserimento orbitale che per il rendez-vous di un veicolo spaziale lanciato dalla Terra dotato di caratteristiche ispirate alle sonde NASA Dawn e Deep Space 1. Inoltre è stato studiato sia l'inserimento orbitale che il rendez-vous con Apophis di un veicolo dotato di sistema propulsivo convenzionale, per mezzo di un trasfrimento a 3 impulsi

Failures of homogeneous and isotropic cosmologies in extended quasidilaton massive gravity

We analyze the extended quasidilaton massive gravity model around a Friedmann-Lemaître-Robertson- Walker cosmological background. We present a careful stability analysis of asymptotic fixed points. We find that the traditional fixed point cannot be approached dynamically, except from a perfectly fine-tuned initial condition involving both the quasidilaton and the Hubble parameter. A less-well examined fixed- point solution, where the time derivative of the zeroth Stückelberg field vanishes φ_ 0 1⁄4 0, encounters no such difficulty, and the fixed point is an attractor in some finite region of initial conditions. We examine the question of the presence of a Boulware-Deser ghost in the theory. We show that the additional constraint that generically allows for the elimination of the Boulware-Deser mode is only present under special initial conditions. We find that the only possibility corresponds to the traditional fixed point and the initial conditions are the same fine-tuned conditions that allow the fixed point to be approached dynamically.Fil: Anselmi, Stefano. Université Paris Diderot - Paris 7; Francia. Institut d’Astrophysique de Paris; Francia. Case Western Reserve University; Estados UnidosFil: Kumar, Saurabh. Case Western Reserve University; Estados UnidosFil: Lopez Nacir, Diana Laura. Cern - European Organization For Nuclear Research; Suiza. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Starkman, Glenn D.. Case Western Reserve University; Estados Unido

The efficiency of the local health systems: investigating the roles of health administrations and health care providers

The analysis of efficiency in health care has largely focused either on individual health care providers, or on sub-national health systems conceived as a unique decision-making unit. However, in hierarchically organized national health services, two separate entities are responsible for turning financial resources into services at the local level: health administrations and health care providers. Their separate roles and the one of health administrations in particular have not been explicitly considered in efficiency analysis. We applied stochastic frontier analysis to district-level panel data from Mozambique (2008-2011) to assess district efficiency in delivering outpatient care. We first assessed the efficiency of the whole district considered as an individual decision-making unit, and then we assessed separately the efficiency of health administrations and health care providers within the same district. We found that on average only 73% of the outpatient consultations deliverable using available inputs were realized, with large differences in performance across districts. Individual districts performed differently in administrative or health care delivery functions. On average, a reduction of administrative inefficiency by 10 percentage points, for a given expenditure would increase by 0.2% the volume of services delivered per thousand population per year. Identifying and targeting the specific drivers of administrative inefficiencies can contribute to increase service

Health service availability and health seeking behaviour in resource poor settings: evidence from Mozambique.

Low-income countries are plagued by a high burden of preventable and curable disease as well as unmet need for healthcare, but detailed microeconomic evidence on the relationship between supply-side factors and service use is limited. Causality has rarely been assessed due to the challenges posed by the endogeneity of health service supply.In this study, using data from Mozambique, we investigate the effect of healthcare service availability, measured as the type of health facilities and their level of staffing and equipment, on the individual decision to seek care. We apply an instrumental variable approach to test for causality in the effect of staff and equipment availability on the decision to seek care and we explore heterogeneous effects based on the distance of households to the closest health facility.We find that living in the proximity of a health facility increases the probability of seeking care. A greater availability of referral health services in the locality has no significant effect on decision to seek care, while greater availability of staff and equipment increases the probability of seeking care when ill. Demand side barriers to health care use exist, but have a smaller impact when health care services are available within one hour walking distance

Understanding causal pathways within health systems policy evaluation through mediation analysis:An application to payment for performance (P4P) in Tanzania

BACKGROUND: The evaluation of payment for performance (P4P) programmes has focused mainly on understanding contributions to health service coverage, without unpacking causal mechanisms. The overall aim of the paper is to test the causal pathways through which P4P schemes may (or may not) influence maternal care outcomes. METHODS: We used data from an evaluation of a P4P programme in Tanzania. Data were collected from a sample of 3000 women who delivered in the 12 months prior to interview and 200 health workers at 150 health facilities from seven intervention and four comparison districts in Tanzania in January 2012 and in February 2013. We applied causal mediation analysis using a linear structural equation model to identify direct and indirect effects of P4P on institutional delivery rates and on the uptake of two doses of an antimalarial drug during pregnancy. We first ran a series of linear difference-in-difference regression models to test the effect of P4P on potential mediators, which we then included in a linear difference-in-difference model evaluating the impact of P4P on the outcome. We tested the robustness of our results to unmeasured confounding using semi-parametric methods. RESULTS: P4P reduced the probability of women paying for delivery care (-4.5 percentage points) which mediates the total effect of P4P on institutional deliveries (by 48%) and on deliveries in a public health facility (by 78%). P4P reduced the stock-out rate for some essential drugs, specifically oxytocin (-36 percentage points), which mediated the total effect of P4P on institutional deliveries (by 22%) and deliveries in a public health facility (by 30%). P4P increased kindness at delivery (5 percentage points), which mediated the effect of P4P on institutional deliveries (by 48%) and on deliveries in a public health facility (by 49%). P4P increased the likelihood of supervision visits taking place within the last 90 days (18 percentage points), which mediated 15% of the total P4P effect on the uptake of two antimalarial doses during antenatal care (IPT2). Kindness during deliveries and the probability of paying out of pocket for delivery care were the mediators most robust to unmeasured confounding. CONCLUSIONS: The effect of P4P on institutional deliveries is mediated by financing and human resources factors, while uptake of antimalarials in pregnancy is mediated by governance factors. Further research is required to explore additional and more complex causal pathways

Creativity and Design Tools as an Emotional Approach to Learning

This paper presents an experience conducted by the IDEActivity research team of the Politecnico di Milano, Department of Design during the CREA International Conference on Creativity and Innovation – a training and resource-sharing event focused on creativity. The CREA event was crafted as a learning activity that allowed participants to delve deeply into the most significant stages of the design process in a very experiential way. The activity was designed as an experience and emotional path intended to introduce non-designers to the main phases and peculiarities of the design process in a very short time. In the event, we employed the IDEActivity method: a dynamic path that includes a series of iterative phases and micro-phases characterised by alternate moments of divergence and convergence allowing for continuous circles of reflection and tuning of the project throughout the design process. The case study presented in this paper shows the potentialities of the emotional involvement of participants, the dynamic use of space, Visual Thinking and a playful approach during a training activity. During the activity, typical and renowned design tools were used along with specialised tools crafted by the IDEActivity Center for the event

The effect of cash transfers on mental health – New evidence from South Africa

Background Mental health and poverty are strongly interlinked. There is a gap in the literature on the effects of poverty alleviation programmes on mental health. We aim to fill this gap by studying the effect of an exogenous income shock generated by the Child Support Grant, South Africa’s largest Unconditional Cash Transfer (UCT) programme, on mental health. Methods We use biennial data on 10,925 individuals from the National Income Dynamics Study between 2008 and 2014. We exploit the programme’s eligibility criteria to estimate instrumental variable Fixed Effects models. Results We find that receiving the Child Support Grant improves adult mental health by 0.822 points (on a 0–30 scale), 4.1% of the sample mean. Conclusion Our findings show that UCT programmes have strong mental health benefits for the poor adult population

Effects of Payment for Performance on accountability mechanisms: Evidence from Pwani, Tanzania.

Payment for Performance (P4P) aims to improve provider motivation to perform better, but little is known about the effects of P4P on accountability mechanisms. We examined the effect of P4P in Tanzania on internal and external accountability mechanisms. We carried out 93 individual in-depth interviews, 9 group interviews and 19 Focus Group Discussions in five intervention districts in three rounds of data collection between 2011 and 2013. We carried out surveys in 150 health facilities across Pwani region and four control districts, and interviewed 200 health workers, before the scheme was introduced and 13 months later. We examined the effects of P4P on internal accountability mechanisms including management changes, supervision, and priority setting, and external accountability mechanisms including provider responsiveness to patients, and engagement with Health Facility Governing Committees. P4P had some positive effects on internal accountability, with increased timeliness of supervision and the provision of feedback during supervision, but a lack of effect on supervision intensity. P4P reduced the interruption of service delivery due to broken equipment as well as drug stock-outs due to increased financial autonomy and responsiveness from managers. Management practices became less hierarchical, with less emphasis on bureaucratic procedures. Effects on external accountability were mixed, health workers treated pregnant women more kindly, but outreach activities did not increase. Facilities were more likely to have committees but their role was largely limited. P4P resulted in improvements in internal accountability measures through improved relations and communication between stakeholders that were incentivised at different levels of the system and enhanced provider autonomy over funds. P4P had more limited effects on external accountability, though attitudes towards patients appeared to improve, community engagement through health facility governing committees remained limited. Implementers should examine the lines of accountability when setting incentives and deciding who to incentivise in P4P schemes

Development of solvent-casting particulate leaching (SCPL) polymer scaffolds as improved three-dimensional supports to mimic the bone marrow niche

The need for new approaches to investigate ex vivo the causes and effects of tumor and to achieve improved cancer treatments and medical therapies is particularly urgent for malignant pathologies such as lymphomas and leukemias, whose tissue initiator cells interact with the stroma creating a three-dimensional (3D) protective environment that conventional mono- and bi-dimensional (2D) models are not able to simulate realistically. The solvent-casting particulate leaching (SCPL) technique, that is already a standard method to produce polymer-based scaffolds for bone tissue repair, is proposed here to fabricate innovative 3D porous structures to mimic the bone marrow niche in vitro. Two different polymers, namely a rigid polymethyl methacrylate (PMMA) and a flexible polyurethane (PU), were evaluated to the purpose, whereas NaCl, in the form of common salt table, resulted to be an efficient porogen. The adoption of an appropriate polymer-to-salt ratio, experimentally defined as 1:4 for both PMMA and PU, gave place to a rich and interconnected porosity, ranging between 82.1 vol% and 91.3 vol%, and the choice of admixing fine-grained or coarse-grained salt powders allowed to control the final pore size. The mechanical properties under compression load were affected both by the polymer matrix and by the scaffold's architecture, with values of the elastic modulus indicatively varying between 29 kPa and 1283 kPa. Preliminary tests performed with human stromal HS-5 cells co-cultured with leukemic cells allowed us to conclude that stromal cells grown associated to the supports keep their well-known protective and pro-survival effect on cancer cells, indicating that these devices can be very useful to mimic the bone marrow microenvironment and therefore to assess the efficacy of novel therapies in pre-clinical studies

KRAS Codons 12 and 13 Mutation Analysis: A Comparative Study between Direct Sequencing and a New Sensitive Real-Time PCR Assay

KRAS somatic mutations are found in 30–40% of colorectal cancer (CRC). Seven mutations in codons 12 and 13 of KRAS (95% of the observed human mutations) preclude the efficacy of anti-EGFR therapy for the treatment of CRC. Assessment of KRAS mutational status has become a standard procedure in the management of patients with CRC. Technically, KRAS mutation testing can be performed with different methods, characterized by distinct sensitivities and specificities. The present study analyzed KRAS in 182 CRC histological samples by using direct sequencing and a new kit based on a Real-Time Sequence-Specific Primers-PCR technology. The kit allowed to recover as positive 17 samples that were negative or unclear by sequencing, with a recovery rate equal to 13.82%. This study proposes a fast, sensitive, and high-throughput system to identify such seven described mutations of KRAS gene in CRC samples