Anti-biofilm activity of ultrashort cinnamic acid peptide derivatives against medical device-related pathogens

The threat of antimicrobial resistance has placed increasing emphasis on the development of innovative approaches to eradicate multidrug-resistant pathogens. Biofilm-forming microorganisms, for example, Staphylococcus epidermidis and Staphylococcus aureus, are responsible for increased incidence of biomaterial infection, extended hospital stays and patient morbidity and mortality. This paper highlights the potential of ultrashort tetra-peptide conjugated to hydrophobic cinnamic acid derivatives. These peptidomimetic molecules demonstrate selective and highly potent activity against resistant biofilm forms of Gram-positive medical device-related pathogens. 3-(4-Hydroxyphenyl)propionic)-Orn-Orn-Trp-Trp-NH2 displays particular promise with minimum biofilm eradication concentration (MBEC) values of 125 µg/ml against methicillin sensitive (ATCC 29213) and resistant (ATCC 43300) S. aureus and activity shown against biofilm forms of Escherichia coli (MBEC: 1000 µg/ml). Kill kinetics confirms complete eradication of established 24-h biofilms at MBEC with 6-h exposure. Reduced cell cytotoxicity, relative to Gram-positive pathogens, was proven via tissue culture (HaCaT) and haemolysis assays (equine erythrocytes).

Existing in nature as part of the immune response, antimicrobial peptides display great promise for exploitation by the pharmaceutical industry in order to increase the library of available therapeutic molecules. Ultrashort variants are particularly promising for translation as clinical therapeutics as they are more cost-effective, easier to synthesise and can be tailored to specific functional requirements based on the primary sequence allowing factors such as spectrum of activity to be varied.

Preparation of La2NiO4+δ powders as a cathode material for SOFC via a PVP-assisted hydrothermal route

Uniform submicron La₂NiO_4+δ (sm-LNO) powders have been synthesized by a facile polyvinylpyrrolidone (PVP)-assisted hydrothermal route. In the presence of PVP, sm-LNO of pure phase has been obtained by calcination at the relatively low temperature of 900 °C for 8 h. Compared micron-sized LNO (m-LNO) particles obtained at 1,000 °C by hydrothermal synthesis route without PVP assisted, the sm-LNO-PVP displays regularly shaped and well-distributed particles in the range of 0.3–0.5 μm. The scanning electron microscopy (SEM) results showed that the sm-LNO sample is submicronic and that the m-LNO sample shows agglomerates with a broad size distribution. The electrochemical performance of m-LNO and sm-LNO-PVP has been investigated by electrochemical impedance spectroscopy. The polarization resistance of the sm-LNO-PVP cathode reaches a value of 0.40 Ω cm² at 750 °C, which is lower than that of m-LNO (0.62 Ω cm²). This result indicates that a fine electrode microstructure with submicron particles can help to increase the active sites, accelerate oxygen diffusion, and reduce polarization resistance. An anode-supported single cell with sm-LNO cathode has been fabricated and tested over a temperature range from 650 to 800 °C. The maximum power density of the cell has achieved 834 mW cm⁻² at 750 °C. These results therefore show that this PVP-assisted hydrothermal method is an effective approach to construct submicron-structured cathode and enhance the performance of intermediate temperature solid oxide fuel cell.

The mitochondrial and autosomal mutation landscapes of prostate cancer

BACKGROUND: Prostate cancer (PCa) is the most common cancer in men. PCa is strongly age associated; low death rates in surveillance cohorts call into question the widespread use of surgery, which leads to overtreatment and a reduction in quality of life. There is a great need to increase the understanding of tumor characteristics in the context of disease progression.

OBJECTIVE: To perform the first multigenome investigation of PCa through analysis of both autosomal and mitochondrial DNA, and to integrate exome sequencing data, and RNA sequencing and copy-number alteration (CNA) data to investigate how various different tumor characteristics, commonly analyzed separately, are interconnected.

DESIGN, SETTING, AND PARTICIPANTS: Exome sequencing was applied to 64 tumor samples from 55 PCa patients with varying stage and grade. Integrated analysis was performed on a core set of 50 tumors from which exome sequencing, CNA, and RNA sequencing data were available.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Genes, mutated at a significantly higher rate relative to a genomic background, were identified. In addition, mitochondrial and autosomal mutation rates were correlated to CNAs and proliferation, assessed as a cell cycle gene expression signature.

RESULTS AND LIMITATIONS: Genes not previously reported to be significantly mutated in PCa, such as cell division cycle 27 homolog (Saccharomyces cerevisiae) (CDC27), myeloid/lymphoid or mixed-lineage leukemia 3 (MLL3), lysine (K)-specific demethylase 6A (KDM6A), and kinesin family member 5A (KIF5A) were identified. The mutation rate in the mitochondrial genome was 55 times higher than that of the autosomes. Multilevel analysis demonstrated a tight correlation between high reactive-oxygen exposure, chromosomal damage, high proliferation, and in parallel, a transition from multiclonal indolent primary PCa to monoclonal aggressive disease. As we only performed targeted sequence analysis; copy-number neutral rearrangements recently described for PCa were not accounted for.

CONCLUSIONS: The mitochondrial genome displays an elevated mutation rate compared to the autosomal chromosomes. By integrated analysis, we demonstrated that different tumor characteristics are interconnected, providing an increased understanding of PCa etiology.

On the triple peaks of SNHunt248 in NGC 5806

We present our findings on a supernova (SN) impostor, SNHunt248, based on optical and near-IR data spanning ~15 yr before discovery, to ~1 yr post-discovery. The light curve displays three distinct peaks, the brightest of which is at MR ~ −15.0 mag. The post-discovery evolution is consistent with the ejecta from the outburst interacting with two distinct regions of circumstellar material. The 0.5–2.2 μm spectral energy distribution at −740 d is well-matched by a single 6700 K blackbody with log (L/L⊙) ~ 6.1. This temperature and luminosity support previous suggestions of a yellow hypergiant progenitor; however, we find it to be brighter than the brightest and most massive Galactic late-F to early-G spectral type hypergiants. Overall the historical light curve displays variability of up to ~ ± 1 mag. At current epochs (~1 yr post-outburst), the absolute magnitude (MR ~ − 9 mag) is just below the faintest observed historical absolute magnitude ~10 yr before discovery.

Tyrosine phosphorylation and dephosphorylation in Burkholderia cenocepacia affect biofilm formation, growth under nutritional deprivation, and pathogenicity

Burkholderia cenocepacia, a member of the B. cepacia complex (Bcc), is an opportunistic pathogen causing serious chronic infections in patients with cystic fibrosis. Tyrosine phosphorylation has emerged as an important post-translational modification modulating the physiology and pathogenicity of Bcc bacteria. Here, we investigated the predicted bacterial tyrosine kinases BCAM1331 and BceF, and the low molecular weight protein tyrosine phosphatases BCAM0208, BceD and BCAL2200 of B. cenocepacia K56-2. We show that BCAM1331, BceF, BCAM0208 and BceD contributed to biofilm formation, while BCAL2200 was required for growth in nutrient-limited conditions. Multiple deletions of either tyrosine kinase or low molecular weight protein tyrosine phosphatases genes resulted in attenuation of B. cenocepacia intramacrophage survival and reduced pathogenicity in the Galleria mellonella larvae infection model. Experimental evidence indicates that BCAM1331 displays a reduced
tyrosine autophosphorylation activity compared to BceF. Using the artificial substrate p-nitrophenyl phosphate, the phosphatase activity of the three low molecular weight protein tyrosine phosphatases demonstrated similar kinetic parameters. However, only BCAM0208 and BceD could dephosphorylate BceF. Further, BCAL2200 becomes tyrosine phosphorylated in vivo and catalyzes its auto-dephosphorylation. Together, our data suggest that despite having similar biochemical activities low molecular weight protein tyrosine phosphatases and tyrosine kinases have both overlapping and specific roles in the physiology of B. cenocepacia.

Escaping the Holocaust: human and health capital of refugees to the United States, 1940-42

The large-scale persecution of Jews during World War II generated massive refugee movements. Using data from 20,441 predominantly Jewish passengers from 19 countries traveling from Lisbon to New York between 1940 and 1942, we analyze the last wave of refugees escaping the Holocaust and verify the validity of height as a proxy for human and health capital. We further show this episode of European migration displays well-known features of migrant self-selection: early migrants were taller than late migrants; a large migrant stock reduces migrant selectivity; and economic barriers to migration
apply. Our findings show that Europe experienced substantial losses in human and health capital while the US benefitted from the immigration of European refugees.

Parades, Flags, Carnivals and Riots: Public Space, Contestation and Transformation in Northern Ireland

This paper explores one of the defining aspects of politics and identity in Northern Ireland: the control and utilization of public space, particularly urban public space. Ethnopolitical conflict consistently reveals itself through contestation over public space. The role of ritual events is important in the development of political identity and group cohesion. The symbolic landscape will be constructed through displays of identity by dominant groups and their ability to control that landscape by inhibiting displays by other groups. This will reveal itself through frequent contests over rituals and symbols. This paper looks at the role of ritual events in civic spaces in Belfast but particularly asks what role they might play in conflict transformation. The 1998 agreement offered political structures that provided for shared power after 30 years of violent conflict. At the same time, there was an increase in contestation over public space as political groups within the previously marginalized Catholic community demanded recognition within the public sphere and a rebalancing of the public space through changes to the previously dominant Protestant and Unionist expression of identity. The paper concludes by suggesting that in “shared space” a new civic identity that spans the political and ethnic divisions has started to develop in Belfast and that this might evolve despite an increased residential division throughout the urban area.

Indications for an influence of hot Jupiters on the rotation and activity of their host stars

Context. The magnetic activity of planet-hosting stars is an importantfactor for estimating the atmospheric stability of close-in exoplanetsand the age of their host stars. It has long been speculated thatclose-in exoplanets can influence the stellar activity level. However,testing for tidal or magnetic interaction effects in samples ofplanet-hosting stars is difficult because stellar activity hindersexoplanet detection, so that stellar samples with detected exoplanetsshow a bias toward low activity for small exoplanets.

Aims: Weaim to test whether exoplanets in close orbits influence the stellarrotation and magnetic activity of their host stars.

Methods: Wedeveloped a novel approach to test for systematic activity-enhancementsin planet-hosting stars. We use wide (several 100 AU) binary systems inwhich one of the stellar components is known to have an exoplanet, whilethe second stellar component does not have a detected planet andtherefore acts as a negative control. We use the stellar coronal X-rayemission as an observational proxy for magnetic activity and analyzeobservations performed with Chandra and XMM-Newton.

Results: Wefind that in two systems for which strong tidal interaction can beexpected the planet-hosting primary displays a much higher magneticactivity level than the planet-free secondary. In three systems forwhich weaker tidal interaction can be expected the activity levels ofthe two stellar components agree with each other.

Conclusions:Our observations indicate that the presence of Hot Jupiters may inhibitthe spin-down of host stars with thick outer convective layers. Possiblecauses for this effect include a transfer of angular momentum from theplanetary orbit to the stellar rotation through tidal interaction, ordifferences during the early evolution of the system, where the hoststar may decouple from the protoplanetary disk early because of a gapopened by the forming Hot Jupiter.

Host Defence Peptide LL-37; Effects of truncation on antimicrobial activity

Background: The oral cavity is an ideal environment for colonisation by micro-organisms. A first line of defence against microbial infection is the secretion of broad spectrum host defence peptides (HDPs). In the current climate of antibiotic resistance, exploiting naturally occurring HDPs or synthetic derivatives (mimetics) to combat infection is particularly appealing. The human cathelicidin, LL-37 is one such HDP expressed ubiquitously by epithelial cells and neutrophils. LL-37 exhibits the ability to bind lipopolysaccharide (LPS) and displays broad spectrum activity against a wide range of bacteria. The current study focuses on truncation of LL-37 and defining the antimicrobial and LPS binding activity of the resultant mimetics. Objectives: To assess the antimicrobial and LPS binding activity of LL-37 and three truncated mimetics (KE-18, EF-14 and KR-12). Methods: Peptides were synthesised in-house by Fmoc solid phase peptide synthesis or obtained commercially. Antimicrobial activity was determined using a radial diffusion assay and ability to bind LPS was determined by indirect ELISA. Results: LL-37 and mimetics displayed antimicrobial activity against Streptococcus mutans and Enterococcus Faecalis. KE-18 and KR-12 were shown to possess antimicrobial activity against both pathogens whereas EF-14 was the least antimicrobial. In terms of LPS binding, KE-18 and KR-12 were both effective whereas EF-14 showed the least activity of the three mimetics. Conclusion: Truncation of LL-37 can yield peptides which retain antimicrobial activities and have the ability to bind LPS. Interestingly in some cases the truncation of LL-37 produced mimetics with greater potency than the parent molecule in terms of antimicrobial activity and LPS binding. This work was funded by DEL and the Diabetes Wellness Foundation.

Holidays in the Danger Zone: Entanglements of War and Tourism

A timely, and uniquely historical, look at how war turns soldiers, and all of us, into tourists. Holidays in the Danger Zone exposes the mundane and everyday entanglements between two seemingly opposed worlds—warfare and tourism. Debbie Lisle shows how a tourist sensibility shapes the behavior of soldiers in warespecially the experiences of Western military forces in “exotic” settings. This includes not only R&R but also how battlefields themselves become landscapes of leisure and tourism. It further explores how a military sensibility shapes the development of tourism in the postwar context, from “Dark Tourism” (engaging with displays of conflict and atrocity) to exhibitions of conflict in museums and at memorial sites, as well as in advertising, film, journals, guidebooks, blogs, and photography. Focused on how war and tourism reinforce prevailing modes of domination, Holidays in the Danger Zone critically examines the long historical arc of the war-tourism nexus from nineteenth-century imperialism to World War I and World War II, from the Cold War to globalization and the War on Terror.

Thermal environments and comfort in dementia friendly dwellings

This study follows on from a research project that developed guidelines for the Universal Design (UD) of Dementia Friendly Dwellings for People with Dementia, their Families and Carers. Research findings point to the need for thermal environments that support people with dementia and do not provoke stress, agitation or anxiety. Using semi-structured interviews and qualitative analysis of people with dementia this paper aims to provide insight into the questions of appropriate thermal environments. The qualitative analysis is supported by example simulated indoor environment studies that investigate comfort in common thermal environment provision scenarios in the homes of people with dementia. This paper focuses on the thermal environment, its impact on people with dementia, its therapeutic value, and its role in encouraging engagement in every day activity.
Findings from the interviews emphasize that control over their own internal environment is a priority for people with dementia. A strong preference for naturally or passively conditioned environments over mechanical conditioning is evident. Preferences are expressed for naturally ventilated environments enabling occupant instigated air movement. Repeated emphasis is placed on familiar elements including the fire and hot water bottle. Little desire is expressed for information feedback or technological displays.

Challenging the cancer molecular stratification dogma: Intratumoral heterogeneity undermines consensus molecular subtypes and potential diagnostic value in colorectal cancer

Purpose:
A number of independent gene expression profiling studies have identified transcriptional subtypes in colorectal cancer (CRC) with potential diagnostic utility, culminating in publication of a CRC Consensus Molecular Subtype classification. The worst prognostic subtype has been defined by genes associated with stem-like biology. Recently, it has been shown that the majority of genes associated with this poor prognostic group are stromal-derived. We investigated the potential for tumor misclassification into multiple diagnostic subgroups based on tumoral region sampled.

Experimental Design:
We performed multi-region tissue RNA extraction/transcriptomic analysis using Colorectal Specific Arrays on invasive front, central tumor and lymph node regions selected from tissue samples from 25 CRC patients.

Results:
We identified a consensus 30 gene list which represents the intratumoral heterogeneity within a cohort of primary CRC tumors. Using a series of online datasets, we showed that this gene list displays prognostic potential (HR=2.914 (CI 0.9286-9.162) in stage II/III CRC patients, but in addition we demonstrated that these genes are stromal derived, challenging the assumption that poor prognosis tumors with stem-like biology have undergone a widespread Epithelial Mesenchymal Transition (EMT). Most importantly, we showed that patients can be simultaneously classified into multiple diagnostically relevant subgroups based purely on the tumoral region analysed.

Conclusions:
Gene expression profiles derived from the non-malignant stromal region can influence assignment of CRC transcriptional subtypes, questioning the current molecular classification dogma and highlighting the need to consider pathology sampling region and degree of stromal infiltration when employing transcription-based classifiers to underpin clinical decision-making in CRC.

Novel furan polymer materials based on the reversible Diels-Alder reaction

A futura e inevitável escassez dos recursos fósseis, juntamente com o aumento imprevisível dos seus preços, levou, nas últimas décadas, a um aumento impressionante de iniciativas dedicadas não só à procura de fontes alternativas de fornecedores de energia, mas também de produtos químicos e polímeros a partir de fontes renováveis, em particular da biomassa vegetal. Entre estes, os polímeros derivados de monómeros furânicos constituem uma classe única de materiais cujas estruturas podem, em princípio, simular virtualmente os seus homólogos actualmente derivados de recursos fósseis. O anel furânico é uma estrutura heterocíclica com um carácter diénico pronunciado, o que torna-o um dieno particularmente apropriado para a reacção de Diels-Alder (DA) com dienófilos como a maleimida. Um dos aspectos mais relevantes da reacção de DA é a sua reversibilidade em função da temperatura, a qual permite que os aductos sejam facilmente revertidos nos seus precursores por aumento da temperatura (reacção de retro-DA). No caso específico da combinação furano-maleimida, a formação do aducto predomina até cerca de 60ºC, enquanto a reacção inversa é dominante acima de 100ºC. A combinação desta característica da reacção de DA com a química de compostos furânicos pode abrir um novo caminho para a preparação de materiais macromoleculares funcionais com base em fontes renováveis e com aplicações promissoras como auto-reparação e reciclabilidade. O principal objectivo desta Tese, é a síntese e caracterização de novos materiais poliméricos termo-reversíveis, aplicando a reacção de DA a monómeros complementares com estruturas dos tipos furânico (o dieno, designado por A) e de maleimida (o dienófilo, designado por B). A primeira etapa neste trabalho envolveu a síntese, purificação e caracterização de novos monómeros furânicos e de maleimida do tipo AA, A3, BB, B3, AB, AB2, cada um com diferentes grupos separadores das funções reactivas. Posteriormente, estes monómeros foram polimerizados e despolimerizados por ciclos de DA/retro-DA utilizando diferentes combinações. A formação e dissociação de todos os aductos de DA foram seguidas por ambas espectroscopias de UV e RMN de 1H. O primeiro sistema de DA estudado foi uma combinação modelo entre reagentes mono-funcionais (-A+-B), nomeadamente o acetato furfurílico (FA) e a N-metilmaleimida (MM), ambos comercialmente disponíveis. O objectivo desta abordagem foi estudar a cinética e o equilíbrio da formação/dissociação dos aductos de DA e obter indicações sobre as condições mais adequadas a serem usadas na preparação dos correspondentes novos materiais macromoleculares. Além disso, pretendia-se verificar a presença ou ausência de reacções secundárias que poderiam intervir em ambas as vias directa e inversa das reacções, mesmo após vários ciclos. A espectroscopia de UV forneceu informação quantitativa sobre a cinética de formação do aducto através da diminuição progressiva da absorvência máxima a 293 nm correspondente ao grupo maleimida, a diferentes temperaturas (35, 50, 65 ºC) Reciprocamente, a correspondente reacção de retro-DA foi seguida a 90 ºC através do aumento do mesmo pico. A reversibilidade destes sistemas foi verificada com sucesso após uma sequência de ciclos de DA/retro-DA. Adicionalmente, verificou-se que os espectros originaram um ponto isosbéstico, provando que estes sistemas não envolvem quaisquer reacções secundárias. Uma vez que foi usado um excesso de FA, as reacções de DA modelo apresentaram um comportamento cinético de pseudo-primeira ordem, com a constante de velocidade k mais alta (2.1x10-5 dm3mol-1s-1) para T=65 ºC. A correspondente energia de activação foi de 39.0 kJ.mol-1. A reacção de retro-DA seguiu um comportamento de primeira ordem, com constante de velocidade de 1.6x10-6 s-1. A evolução deste sistema por RMN de 1H a 65ºC deu-nos informações mais detalhadas sobre a sua evolução estrutural, ou seja, à medida que a intensidade dos picos atribuídos à formação do aducto aumentaram progressivamente ao longo do tempo, os pertencentes aos reagentes iniciais diminuiram proporcionalmente. O “rendimento final”, calculado após 20 dias à temperatura ambiente, foi de aproximadamente 70%. A reacção de retro-DA foi depois seguida a 90ºC, observando-se tal como na espectroscopia de UV, o deslocamento da reacção no sentido da regeneração dos reagentes de partida. A viabilidade de múltiplos ciclos de DA/retro-DA estabelecidos pela espectroscopia de UV foi igualmente confirmada por RMN de 1H. O passo seguinte envolveu o estudo de um sistema de policondensação linear baseado no crescimento gradual por reacção de DA entre um monómero bisfurânico A-A e um do tipo bismaleimida B-B, seguindo a mesma abordagem que no sistema modelo. O poliaducto linear foi obtido a partir de soluções equimolares dos monómeros, por reacção de DA a 65ºC. O progresso desta polimerização foi seguido por espectroscopia de UV e RMN de 1H e, mais qualitativamente, pelo aumento da viscosidade do meio. A reacção seguiu um comportamento de segunda ordem, com uma constante de velocidade de 9.4x10-6 dm3mol-1s-1, e observou-se novamente um ponto isosbéstico nos dados de UV. Os espectros de RMN apresentaram o padrão esperado, nomeadamente o aumento progressivo dos sinais associados ao aducto e a correspondente diminuição dos grupos furano e maleimida livres. A despolimerização do poliaducto através da reacção de retro-DA foi seguida a 110ºC usando as mesmas técnicas. Os dados de UV mostraram o retorno progressivo da absorção dos grupos de maleimida, seguindo um comportamento cinético de primeira ordem, com constante de velocidade de 2.5x10-6 s-1, até à completa regeneração de ambos os monómeros. Os espectros de RMN providenciaram mais uma vez informação estrutural sobre o progresso da despolimerização, a qual foi acompanhada por uma diminuição progressiva da viscosidade. Adicionalmente, para seguir a retro- DA, adicionou-se um excesso de composto furânico monofuncional, nomeadamente o 2,5-dimetilfurano (DMFu), ao sistema de modo a bloquear as funções maleimida complementares, evitando assim a repolimerização após arrefecimento. Os productos isolados foram então o monómero bisfurânico AA, DMFu que não reagiu e o bisaducto não-polimerizável de BB com DMFu. Este resultado indicou claramente que o polímero foi de facto revertido nos seus monómeros durante a reacção de retro-DA. O terceiro sistema estudado foi outra polimerização linear, seguindo as mesmas condições experimentais que os anteriores, mas com uma estratégia diferente de modo a contornar o problema clássico de assegurar a estequiometria exacta dos monómeros. As estruturas dos monómeros utilizados incorporam ambos os grupos reactivos, i.e, moléculas do tipo A-B. A polimerização prematura destes monómeros intrinsecamente reactivos foi evitada com a protecção do grupo maleimida na forma de um aducto de DA com furano, até a incorporação do substituinte furânico na outra extremidade. Portanto, a policondensação destes monómeros foi iniciada após a desprotecção in situ deste composto mediante aquecimento, seguido de arrefecimento até à temperatura adequada para polimerizar. Os resultados obtidos por UV e RMN sugerem que de facto o uso de monómeros do tipo A-B oferece um melhor sistema linear. Em seguida, foram estudados sistemas de policondensação não-linear por reacção de DA, entre monómeros (um ou ambos) com funcionalidade superior a dois, nomeadamente sistemas do tipo A3+B-B ou A-A+B3, seguindo mais uma vez as mesmas condições experimentais. Uma vez que utilizam monómeros complementares contendo, em média, mais de duas funcionalidades, estes sistemas conduzem a materiais reticulados. Nestes estudos, foram usadas três razões molares de [maleimida]/[furano], nomeadamente 1.0, 0.75 e 0.5, de modo a estudar ambas as situações de não-gelificação e reticulação. Ambos sistemas apresentaram um comportamento regular e boa reciclabilidade quer para gerar situações que possam conduzir à formação de redes a diferentes graus de conversão, ou que possam parar antes da sua obtenção, conforme previsto pela equação de Flory-Stockmayer. Como esperado, a utilização de grupos complementares em quantidades estequiométricas produziu o espessamento mais rápido e a reticulação quase completa; à medida que a quantidade relativa de monómero trifuncional decresceu, as reacções pararam antes da reticulação, ou seja, originaram meios altamente viscosos contendo polímeros solúveis altamente ramificados. As reacções de retro-DA a 110 ºC conduziram à gradual dissolução das partículas de gel (quando presentes), tendo sido comprovado pelos espectros de UV e de RMN de 1H, evidenciado a regeneração dos monómeros. Tal como no sistema do tipo A-A+B-B, a reacção de retro-DA foi seguida adicionando um excesso de DMFu ao sistema reaccional. Como esperado, os produtos finais foram os monómeros furânicos, o DMFu em excesso e o trisaducto ou o bisaducto maleimida-DMFu, o que confirma a eficiência da despolimerização com regeneração dos monómeros iniciais. O último sistema de policondensação por reacção de DA envolveu um monómero assimetricamente substituído do tipo AB2, capaz de originar estruturas macromoleculares hiper-ramificadas que não reticulam. Este estudo preliminar deste sistema foi seguido nas mesmas condições experimentais que os anteriores, apresentando um comportamento com as características esperadas.

U-TRACER® - the use of communication technology in higher education - an information visualization tool for the context of Portuguese public higher education

Information Visualization is gradually emerging to assist the representation and comprehension of large datasets about Higher Education Institutions, making the data more easily understood. The importance of gaining insights and knowledge regarding higher education institutions is little disputed. Within this knowledge, the emerging and urging area in need of a systematic understanding is the use of communication technologies, area that is having a transformative impact on educational practices worldwide. This study focused on the need to visually represent a dataset about how Portuguese Public Higher Education Institutions are using Communication Technologies as a support to teaching and learning processes. Project TRACER identified this need, regarding the Portuguese public higher education context, and carried out a national data collection. This study was developed within project TRACER, and worked with the dataset collected in order to conceptualize an information visualization tool U-TRACER®. The main goals of this study related to: conceptualization of the information visualization tool U-TRACER®, to represent the data collected by project TRACER; understand higher education decision makers perception of usefulness regarding the tool. The goals allowed us to contextualize the phenomenon of information visualization tools regarding higher education data, realizing the existing trends. The research undertaken was of qualitative nature, and followed the method of case study with four moments of data collection.The first moment regarded the conceptualization of the U-TRACER®, with two focus group sessions with Higher Education professionals, with the aim of defining the interaction features the U-TRACER® should offer. The second data collection moment involved the proposal of the graphical displays that would represent the dataset, which reading effectiveness was tested by end-users. The third moment involved the development of a usability test to the UTRACER ® performed by higher education professionals and which resulted in the proposal of improvements to the final prototype of the tool. The fourth moment of data collection involved conducting exploratory, semi-structured interviews, to the institutional decision makers regarding their perceived usefulness of the U-TRACER®. We consider that the results of this study contribute towards two moments of reflection. The challenges of involving end-users in the conceptualization of an information visualization tool; the relevance of effective visual displays for an effective communication of the data and information. The second relates to the reflection about how the higher education decision makers, stakeholders of the U-TRACER® tool, perceive usefulness of the tool, both for communicating their institutions data and for benchmarking exercises, as well as a support for decision processes. Also to reflect on the main concerns about opening up data about higher education institutions in a global market.

Electromechanical properties of engineered lead free potassium sodium niobate based materials

K0.5Na0.5NbO3 (KNN), is the most promising lead free material for substituting lead zirconate titanate (PZT) which is still the market leader used for sensors and actuators. To make KNN a real competitor, it is necessary to understand and to improve its properties. This goal is pursued in the present work via different approaches aiming to study KNN intrinsic properties and then to identify appropriate strategies like doping and texturing for designing better KNN materials for an intended application. Hence, polycrystalline KNN ceramics (undoped, non-stoichiometric; NST and doped), high-quality KNN single crystals and textured KNN based ceramics were successfully synthesized and characterized in this work. Polycrystalline undoped, non-stoichiometric (NST) and Mn doped KNN ceramics were prepared by conventional ceramic processing. Structure, microstructure and electrical properties were measured. It was observed that the window for mono-phasic compositions was very narrow for both NST ceramics and Mn doped ceramics. For NST ceramics the variation of A/B ratio influenced the polarization (P-E) hysteresis loop and better piezoelectric and dielectric responses could be found for small stoichiometry deviations (A/B = 0.97). Regarding Mn doping, as compared to undoped KNN which showed leaky polarization (P-E) hysteresis loops, B-site Mn doped ceramics showed a well saturated, less-leaky hysteresis loop and a significant properties improvement. Impedance spectroscopy was used to assess the role of Mn and a relation between charge transport – defects and ferroelectric response in K0.5Na0.5NbO3 (KNN) and Mn doped KNN ceramics could be established. At room temperature the conduction in KNN which is associated with holes transport is suppressed by Mn doping. Hence Mn addition increases the resistivity of the ceramic, which proved to be very helpful for improving the saturation of the P-E loop. At high temperatures the conduction is dominated by the motion of ionized oxygen vacancies whose concentration increases with Mn doping. Single crystals of potassium sodium niobate (KNN) were grown by a modified high temperature flux method. A boron-modified flux was used to obtain the crystals at a relatively low temperature. XRD, EDS and ICP analysis proved the chemical and crystallographic quality of the crystals. The grown KNN crystals exhibit higher dielectric permittivity (29,100) at the tetragonal-to-cubic phase transition temperature, higher remnant polarization (19.4 μC/cm2) and piezoelectric coefficient (160 pC/N) when compared with the standard KNN ceramics. KNN single crystals domain structure was characterized for the first time by piezoforce response microscopy. It could be observed that <001> - oriented potassium sodium niobate (KNN) single crystals reveal a long range ordered domain pattern of parallel 180° domains with zig-zag 90° domains. From the comparison of KNN Single crystals to ceramics, It is argued that the presence in KNN single crystal (and absence in KNN ceramics) of such a long range order specific domain pattern that is its fingerprint accounts for the improved properties of single crystals. These results have broad implications for the expanded use of KNN materials, by establishing a relation between the domain patterns and the dielectric and ferroelectric response of single crystals and ceramics and by indicating ways of achieving maximised properties in KNN materials. Polarized Raman analysis of ferroelectric potassium sodium niobate (K0.5Na0.5)NbO3 (KNN) single crystals was performed. For the first time, an evidence is provided that supports the assignment of KNN single crystals structure to the monoclinic symmetry at room temperature. Intensities of A′, A″ and mixed A′+A″ phonons have been theoretically calculated and compared with the experimental data in dependence of crystal rotation, which allowed the precise determination of the Raman tensor coefficients for (non-leaking) modes in monoclinic KNN. In relation to the previous literature, this study clarifies that assigning monoclinic phase is more suitable than the orthorhombic one. In addition, this study is the basis for non-destructive assessments of domain distribution by Raman spectroscopy in KNN-based lead-free ferroelectrics with complex structures. Searching a deeper understanding of the electrical behaviour of both KNN single crystal and polycrystalline materials for the sake of designing optimized KNN materials, a comparative study at the level of charge transport and point defects was carried out by impedance spectroscopy. KNN single crystals showed lower conductivity than polycrystals from room temperature up to 200 ºC, but above this temperature polycrystalline KNN displays lower conductivity. The low temperature (T < 200 ºC) behaviour reflects the different processing conditions of both ceramics and single crystals, which account for less defects prone to charge transport in the case of single crystals. As temperature increases (T > 200 ºC) single crystals become more conductive than polycrystalline samples, in which grain boundaries act as barriers to charge transport. For even higher temperatures the conductivity difference between both is increased due to the contribution of ionic conduction in single crystals. Indeed the values of activation energy calculated to the high temperature range (T > 300 ºC) were 1.60 and 0.97 eV, confirming the charge transport due to ionic conduction and ionized oxygen vacancies in single crystals and polycrystalline KNN, respectively. It is suggested that single crystals with low defects content and improved electromechanical properties could be a better choice for room temperature applications, though at high temperatures less conductive ceramics may be the choice, depending on the targeted use. Aiming at engineering the properties of KNN polycrystals towards the performance of single crystals, the preparation and properties study of (001) – oriented (K0.5Na0.5)0.98Li0.02NbO3 (KNNL) ceramics obtained by templated grain growth (TGG) using KNN single crystals as templates was undertaken. The choice of KNN single crystals templates is related with their better properties and to their unique domain structure which were envisaged as a tool for templating better properties in KNN ceramics too. X-ray diffraction analysis revealed for the templated ceramics a monoclinic structure at room temperature and a Lotgering factor (f) of 40% which confirmed texture development. These textured ceramics exhibit a long range ordered domain pattern consisting of 90º and 180º domains, similar to the one observed in the single crystals. Enhanced dielectric (13017 at TC), ferroelectric (2Pr = 42.8 μC/cm2) and piezoelectric (d33 = 280 pC/N) properties are observed for textured KNNL ceramics as compared to the randomly oriented ones. This behaviour is suggested to be due to the long range ordered domain patterns observed in the textured ceramics. The obtained results as compared with the data previously reported on texture KNN based ceramics confirm that superior properties were found due to ordered repeated domain pattern. This study provides an useful approach towards properties improvement of KNN-based piezoelectric ceramics. Overall, the present results bring a significant contribution to the pool of knowledge on the properties of sodium potassium niobate materials: a relation between the domain patterns and di-, ferro-, and piezo-electric response of single crystals and ceramics was demonstrated and ways of engineering maximised properties in KNN materials, for example by texturing were established. This contribution is envisaged to have broad implications for the expanded use of KNN over the alternative lead-based materials.