Nano-scaled carbon fillers and their functional polymer composites

The manufacturing of low density conductive plastics, that could replace metals in many applications, is a challenging target that has been pursued by several technological segments. The incorporation of carbon nanofillers, namely carbon nanotubes and graphene, into a polymer matrix is a recent and promising approach. The achievement of highly conductive nanocomposites, with low electrical percolation threshold, depends mostly on the intrinsic properties of the fillers and their state of dispersion throughout the matrix. In this system the macroscopic properties of the composite are undoubtedly governed by the nature and extension of the interactions between filler particles, as well as between filler and polymer matrix. This doctoral dissertation therefore examines the macroscopic electrical behavior of carbon fillers, at initial stage, still as a powder, and subsequently when inserted into polymer matrix to form conductive nanocomposites. The latex technology has proven to be efficient on promoting a homogenous incorporation of exfoliated CNTs into any kind of viscous polymer which can be artificially brought into latex form, or which can be synthetized via emulsion polymerization. One objective of this dissertation is henceforth to study the scope and limitations of multifunctional graphene-based nanocomposites, using the superior DPI-owned water-based latex concept developed for CNTs, for dispersing the two-dimensional graphene nanofiller in polymer matrices (PS, PP, PS/PPO). For comparison, zero-dimensional (statistically spherical) carbon black nanoparticles, one-dimensional MWCNTs, and three-dimensional graphite are also evaluated. We strive to understand differences observed for the different carbon allotropes, each with a high surface-to-volume ratio Special attention is given to graphene as nanofiller, whose properties may be highly variable depending on the preparation method. In order to assess a collective understanding of the main routes utilized in this work for preparation of graphene, Chapter 2 introduces a systematic literature review on the particularities of each preparation method. Techniques used for characterization of single sheet properties and its organization inside polymer composites are presented, with focus on atomic force microscopy and Raman spectroscopy. The conductive performance of a composite is directly related to the formation of a conducting network through the polymer matrix and its understanding depends critically on the knowledge of the electrical behavior of the agglomerated nanoparticles, e.g. in the form of a bulk powder or a paper film. In literature there is still a lack of information concerning these macroscopic bulk properties of carbon powders. Chapter 3 studies the electrical conductivity of the nanofillers MWCNTs, graphene, carbon black and graphite, using compacts produced by a paper preparation process and by powder compression. Powder pressing assays show that the bulk conductivity depends not only on the intrinsic material properties but is also strongly affected by the number of particle contacts and the packing density. Conductivities at high pressure (5 MPa) for the graphene, nanotube and carbon black show lower values (~102 S/m) as compared to graphite (~103 S/m). For nanotube, graphene and graphite particles, the conductive behavior during compaction is governed by mechanical particle arrangement/deformation mechanisms while for carbon black this behavior is mainly governed by the increasing particle contact area. The materials resulting from the paper preparation process for carbon black and graphite showed similar conductivity values as for the compacts, indicating a limited effect of the surfactant on the conductivity. The paper preparation process for the large surface area nanotube and graphene particles induces a highly preferred in-plane orientation, thereby yielding largely the single particle intrinsic conductivity for the in-plane direction, with values in the order of 103 S/m. In Chapter 4, the percolation thresholds and final conductivities of polypropylene (PP) composites, prepared with the fillers studied in Chapter 3, are evaluated and compared with powder and paper results. The latex technology concept is used for the incorporation of the carbon fillers in the polymer. The fillers are first dispersed in water (assisted by surfactants) using ultra-sonication, subsequently mixed with PP latex, then freeze-dried and, finally, hot-pressed into composite tablets. PP composites produced in this work showed well-dispersed fillers inside the polymer, with percolation thresholds as low as 0.3 wt.%. The maximum conductivity obtained for the composites is approximately ~1 S/m, not reaching the high value of ~103 S/m, which are obtained for graphene and nanotube-based paper films or graphite compacts. Chapter 5 focuses on the characterization of graphene layers via micro-Raman spectroscopy, tip-enhanced Raman spectroscopy (TERS) and tip-enhanced Raman spectroscopy mapping (TERM). In particular TERM allows for the investigation of individual graphene sheets with high Raman signal enhancement factors and allows imaging of local defects with nanometer resolution. Enhancement up to 560% of the graphene Raman bands intensity was obtained using TERS. TERM (with resolution better than 100 nm) showed an increase in the number of structural defects (D band) on the edges of both graphene and graphite regions. Continuing the investigation of graphene structures, Chapter 6 compares graphene sheets produced from graphite powder using the three best known water-based conversion approaches. The first two are based on chemical oxidation methods, only differing in the reduction process, either by the use of hydrazine or by thermal expansion, respectively. The third one is based on long-term ultrasonic exfoliation. Water/surfactant solutions were prepared with these three nanofillers and latex technology was applied for the preparation of conductive graphene/polystyrene composites with well-dispersed graphene platelets. The samples were characterized with respect to filler properties and morphology, and their influences on electrical conductive properties of the composites were compared. Microscopic studies showed that both reduction processes lead to agglomeration/wrinkling of the nanoplatelets, even though they yield composites with high conductivity and low percolation threshold. Although mechanical ultrasound exfoliation of graphite produces less defective multi-layer graphene, these platelets have a smaller lateral size and their composites exhibit a higher percolation threshold. As a final attempt, in Chapter 7, the concept of liquid-phase dispersion, inspired on the latex technology, was applied for the preparation of well-dispersed suspensions of multi-wall carbon nanotubes and graphene in chloroform, using long-time ultra-sonication, without the use of surfactants. The dispersions with pre-defined filler concentration (0.5 mg/ml) were monitored via UV-Vis until the achievement of optimum exfoliation (6 h). The mixture of the filler suspensions with a PS/PPO solution, both using chloroform as solvent, subsequent drying and hot pressing, yielded for most of the samples a visually homogeneous and shiny black composite tablet. The well-dispersed organization of the fillers inside the polymer matrix, visualized with scanning electron microscopy, resulted in ultimate conductivities and percolation thresholds of 57 S/m and 0.2 wt.% for nanotubes composites, and 0.9 S/m and ~1 wt.% for graphene composites, respectively. Dynamic mechanical analysis showed that an increase in the storage moduli of the PS/PPO matrix could be gradually obtained by the insertion of fillers, e.g. reaching ~30% of enhancement by the addition of 3 wt.% of graphene filler. The same trend in improvement, at lower augmentation, was observed for the corresponding nanotubes-based composites

Empowering girls, delaying marriage: Exploring the role of marital age and education on domestic violence in India

Domestic violence represents the most important component of violence against women. Whilst some literature report female empowerment as a protective factor against domestic violence, some literature find the opposite because the husband may attempt to compensate for the enhanced status of his wife. This paper aims to investigate the effects of female empowerment in the form of marital age and education on domestic violence in India, where intimate partner violence is amongst the highest in Asia. The analysis is based on the sample of eligible women aged 15-49 with valid response on domestic violence in the 2015- 2016 National Family Health Survey (NFHS-4) (n=9722). Upon estimating a series of instrumental variable (IV) regressions using age at menarche as an exogenous and strong instrument, we establish a causal relationship between empowerment and domestic violence taking into account the endogeneity of marital age and education. We further disentangle the relationships between domestic violence and age at marriage and education, separately. In addition, we investigate how maritage age and education influence domestic violence through labour market participation and spouse quality channels. We find that: i) empowered women do experience less domestic violence; ii) marital age and education are partially complementary; iii) labour market participation and spousal quality are relevant mediators of these relationships. Policies aiming at reducing domestic violence in India hence should be holistic, focussing on investing in education both for women and men and improving the conditions of the women’ labour market

Percolation in suspensions of polydisperse hard rods : quasi-universality and finite-size effects

We present a study of connectivity percolation in suspensions of hard spherocylinders by means of Monte Carlo simulation and connectedness percolation theory. We focus attention on polydispersity in the length, the diameter and the connectedness criterion, and invoke bimodal, Gaussian and Weibull distributions for these. The main finding from our simulations is that the percolation threshold shows quasi universal behaviour, i.e., to a good approximation it depends only on certain cumulants of the full size and connectivity distribution. Our connectedness percolation theory hinges on a Lee-Parsons type of closure recently put forward that improves upon the often-used second virial approximation [ArXiv e-prints, May 2015, 1505.07660]. The theory predicts exact universality. Theory and simulation agree quantitatively for aspect ratios in excess of 20, if we include the connectivity range in our definition of the aspect ratio of the particles. We further discuss the mechanism of cluster growth that, remarkably, differs between systems that are polydisperse in length and in width, and exhibits non-universal aspects.Comment: 7 figure

News from the front: Estimation of excess mortality and life expectancy in the major epicenters of the COVID-19 pandemic in Italy

Existing studies commonly rely on national official reports to estimate the impact of COVID-19 on human life. This is problematic because classification, estimation and reporting of COVID-19 mortality are not consistent across countries. To overcome these problems, this study exploits all cause daily death registrations data provided by the Italian Statistical Office (ISTAT) from January 1 to April 15, 2020. This allows us to: 1) calculate excess mortality in 2020 compared to the average of the years 2015 to 2019; and 2) estimate life expectancy on a seasonal and annual basis. Focusing on the five most severely hit provinces in Italy (Bergamo, Brescia, Cremona, Lodi and Piacenza) and Lombardy region, this analysis captures the impact of COVID-19 on mortality and life expectancy, which are likely to be underestimated when only national level data are considered. We find that seasonal life expectancy in 2020 in the five provinces reduced by 5.1 to 7.8 and 3.2 to 5.8 years for men and women, respectively. For annual life expectancy for the year 2020, in a scenario with no harvesting effect i.e. mortality rates resume to an average level of the years 2015-2019 after the end of the first epidemic wave, the years of life lost is equivalent to 2 to 3.5 years for men and 1.1. to 2.5 years for women in the five provinces. This represents the largest decline in life expectancy after the 1918 influenza pandemic and the Second World War

A experiência de aprendizagem baseada em projetos interdisciplinares em um novo campus de engenharia sob a perspectiva dos discentes

This work aims to describe the experience of Project Based Learning (PBL) in the course of Mechanical Engineering (Engineering Campus - UACSA) of the Federal Rural University of Pernambuco (UFRPE), Brazil. To this end, it were considered both the perceptions of the students and also the data analysis, collected from 20 students, about the experience. The questionnaire answered by the students was organized around six topics: theme of the project, developed competences and learning skills, teamwork, role of teachers, the project assessment and project as a teaching-learning methodology. Also they wrote on the positive and less positive aspects and pointed suggestions for the implementation of PBL. Concisely, the survey results revealed that teamwork, the need for interpersonal relationships and the development of soft skills (autonomy, initiative and creativity in creating the prototype, research capacity, decision, organization, problem solving, time management) are prominent positive aspects, added to the fact that PBL brings the chance for the students to put into practice the theoretical knowledge acquired during the course. Problems for the project's implementation were identified as: lack of instruments and conditions given to students for the development of the prototype, the dense load of disciplines of the semester, the non-suitability of some disciplines involved in the project, plus the bad interaction between them. Besides the fact that there was the need for greater dialogue between the disciplines of the semester and/or a more substantial adjustment of the Pedagogical Course Project (PPC), the PBL as a teaching-learning methodology in the course of Mechanical Engineering met the main expectations, and also collaborated for integration, socialization and learning of students. Therefore it is defended its permanence and expansion (over all semesters of the course) at UACSA/ UFRPE.O presente artigo aborda a primeira experiência da Unidade Acadêmica do Cabo de Santo Agostinho campus das engenharias da UFRPE com o trabalho interdisciplinar através da metodologia de Aprendizagem Baseada em Projetos Interdisciplinares -PBL. Para tal, foi utilizado ao final do semestre letivo um questionário voltado aos discentes, com o objetivo de avaliar a experiência em suas várias dimensões. Os resultados da pesquisa presente neste artigo baseiam-se, sobretudo, nas percepções dos estudantes sobre o processo de implementação e avaliação desta experiência. O questionário respondido pelos estudantes foi organizado em torno de seis tópicos: tema do projeto, aprendizagens e competências desenvolvidas, trabalho em equipe, papel dos docentes, avaliação no projeto e projeto como metodologia de ensino-aprendizagem. Também responderam de forma dissertativa sobre os aspetos positivos e negativos e apontaram sugestões para a implementação do PBL. A investigação realizada através do questionário revela que o trabalho em equipe, o exercício do relacionamento interpessoal e o desenvolvimento de competências transversais são aspectos positivos de destaque, somados ao fato do PBL trazer possibilidade para que os discentes coloquem em prática os conhecimentos teóricos adquiridos durante o curso, promovendo o interesse dos discentes pelo próprio aprendizado ao terem contato com a aplicabilidade dos conceitos aprendidos no curso, além de desenvolver nos mesmos um senso crítico. Somando-se a isto, também foram apontadas algumas dificuldades, principalmente no que diz respeito à articulação entre as disciplinas e a carência de instrumentos para o desenvolvimento dos protótipos. No entanto, embora esses aspectos tenham sido verificados, percebe-se que o uso do PBL como metodologia de ensino cumpre o seu papel de atender aos objetivos propostos para uma aprendizagem ativa e o desenvolvimento de sujeitos críticos e reflexivos(undefined)info:eu-repo/semantics/publishedVersio

Per una cultura di qualità: valutazione partecipata e apertura di contenuti generati dagli utenti nella didattica online

Questo articolo propone un concetto di qualità dell’eLearning (e in generaledell’istruzione universitaria) basato sulla critica alla cultura dominantedi valutazione della qualità legata alla produzione industriale, alla conformitàa standard predefiniti, alla produttività del sistema e dove gli utenti(particolarmente gli studenti) hanno un ruolo passivo, da consumatori; e unripensamento radicale della partecipazione degli studenti nella costruzionedi culture di qualità formativa (Ehlers, Schneckenberg, 2010, Ghislandi,Raffaghelli, 2012a). Il lavoro presenta un’esperienza di ricerca basata suprogetto o design based research (DBR, Pellerey, 2005) relativa ad un insegnamento universitario. Le autrici intendono dimostrare che un processo divalutazione partecipata della qualità dell’apprendimento può innescare unprocesso riflessivo e collaborativo tra docenti e studenti che ha incidenzasulla cultura di qualità. Tale processo si basa sulla generazione da partedegli studenti di alcuni contenuti (Learners’ generated content), per una  apertura della didattica; e tramite un approccio partecipato e costruttivista della verifica dell’apprendimento. Le conclusioni portano ad una migliore comprensione di due elementi portanti nella ricerca: in primo luogo, come la qualità della didattica va costruita in un impegno collaborativo e complesso. In secondo luogo, indica come gli studenti possono partecipare in tale processo collaborativo

Формування теоретичної моделі геополітичного дискурсу у вітчизняній політичній думці кінця ХХ – початку ХХІ століття

У статті висвітлюються питання щодо започаткування новітньої дослідницької традиції геополітичного дискурсу у проблематиці вітчизняної політичної думки ХХ – початку ХХІ століття. Зазначено позиції провідних вітчизняних вчених щодо формування емпіричного та ідейно-теоретичного підґрунтя для утвердження цієї традиції політичного дослідження.The article considers the questions of the becoming of a new research tradition of geopolitical discourse in the topic of native political thought of the 20-th – the beginning of the 21-st century. The views of leading home scientists about the development of empirical, ideological and theoretical basis for the maintenance of this tradition of political research are pointed out

Human costs of the first wave of the COVID-19 pandemic in the major epicentres in Italy

Deaths from COVID-19 can be miscounted due to under-reporting and inaccurate death registration. Mortality is often reported at the national level, which can result in the underestimation of the true scale of the impact of the pandemic since outbreaks tend to be localised. This study exploits all-cause daily death registration data provided by the Italian Statistical Office (ISTAT) from 1 January to 31 October to estimate the excess mortality and the corresponding changes in life expectancy during the first wave of the COVID-19 pandemic. Focusing on the five most severely hit provinces in Italy (Bergamo, Brescia, Cremona, Lodi and Piacenza), we calculate the excess mortality in 2020 compared to the average mortality of the years 2015 to 2019. Moreover, we estimate the excess mortality in the first quadrimester of 2020, and the annual life expectancy at birth. The estimated excess deaths show that during this period, mortality was significantly higher than the official mortality statistics for COVID-19. According to our estimates for the first quadrimester, life expectancy in the five provinces declined by 5.4 to 8.1 for men and by 4.1 to 5.8 years for women. In addition, we find that annual life expectancy decreased by 2.4 to 4.1 years for men and by 1.9 to 2.8 years for women compared to the 2015–2019 average. Thus, we conclude that the first wave of the COVID-19 pandemic had a substantial impact on population health in the hardest hit areas in Italy

Deep-underground search for the decay of 180m-Ta with an ultra-low-background HPGe detector

$^{180m}$Ta is the longest-lived metastable state presently known. Its decay has not been observed yet. In this work, we report a new result on the decay of $^{180m}$Ta obtained with a $2015.12$-g tantalum sample measured for $527.7$ d with an ultra-low background HPGe detector in the STELLA laboratory of the Laboratori Nazionali del Gran Sasso, in Italy. Before the measurement, the sample has been stored deep-underground for ten years, resulting in subdominant background contributions from cosmogenically activated $^{182}$Ta. We observe no signal in the regions of interest and set half-life limits on the process for the two channels EC and $\beta^-$: $T_{1/2,~\mathrm{EC}} > 1.6 \times 10^{18}$ yr and $T_{1/2,~\beta^-} > 1.1\times 10^{18}$ yr ($90$% C. I.), respectively. We also set the limit on the $\gamma$ de-excitation / IC channel: $T_{1/2,~\mathrm{IC}} > 4.1 \times 10^{15}$ yr ($90$% C. I.). These are, as of now, the most stringent bounds on the decay of $^{180m}$Ta worldwide.Comment: 8 pages, 7 figures, 4 table

Response to COVID-19: was Italy (un)prepared?

On 31st January 2020, the Italian cabinet declared a 6-month national emergency after the detection of the first two COVID-19 positive cases in Rome, two Chinese tourists travelling from Wuhan. Between then and the total lockdown introduced on 22nd March 2020 Italy was hit by an unprecedented crisis. In addition to being the first European country to be heavily swept by the COVID-19 pandemic, Italy was the first to introduce stringent lockdown measures. The SARS-CoV-2 outbreak and related COVID-19 pandemic have been the worst public health challenge endured in recent history by Italy. Two months since the beginning of the first wave, the estimated excess deaths in Lombardy, the hardest hit region in the country, reached a peak of more than 23,000 deaths. The extraordinary pressures exerted on the Italian Servizio Sanitario Nazionale (SSN) inevitably leads to questions about its preparedness and the appropriateness and effectiveness of responses implemented at both national and regional levels. The aim of the paper is to critically review the Italian response to the COVID-19 crisis spanning from the first early acute phases of the emergency (March-May 2020) to the relative stability of the epidemiological situation just before the second outbreak in October 2020