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Sustainable 4D printing of magneto-electroactive shape memory polymer composites
Typical techniques for creating synthetic morphing structures suffer from a compromise between quick shape change and geometric complexity. A novel approach is proposed for encoding numerous shapes and forms by magneto-electroactive shape memory polymer composite (SMPC) structures and integrating sustainability with 4D printing (4DP) technology. Electrically driven, remote controllability, and quick reaction are the features of these sustainable composite structures. Low-cost 4D-printed SMPC structures can be programmed remotely at high temperatures to achieve multi-stable shapes and can snap repeatedly between all programmed temporary and permanent configurations. This allows for multiple designs in a single structure without wasting material. The strategy is based on a knowledge of SMPC mechanics, magnetic response, and the manufacturing idea underlying fused deposition modelling (FDM). Iron-filled magnetic polylactic acid (MPLA) and carbon black-filled conductive PLA (CPLA) composite materials are investigated in terms of microstructure properties, composite interface, and mechanical properties. Characterisation studies are carried out to identify how to control the structure with a low magnetic field. The shape morphing of magneto-electroactive SMPC structures is studied. FDM is used to 4D print MPLA and CPLA adaptive structures with 1D/2D-to-2D/3D shapeshifting by the magnetic field. The benefits of switchable multi-stable structures are reducing material waste and effort/energy and increasing efficiency in sectors such as packaging
Insights into the single-particle composition, size, mixing state, and aspect ratio of freshly emitted mineral dust from field measurements in the Moroccan Sahara using electron microscopy
The chemical and morphological properties of mineral dust aerosols emitted by wind erosion from arid and semi-arid regions influence climate, ocean, and land ecosystems; air quality; and multiple socio-economic sectors. However, there is an incomplete understanding of the emitted dust particle size distribution (PSD) in terms of its constituent minerals that typically result from the fragmentation of soil aggregates during wind erosion. The emitted dust PSD affects the duration of particle transport and thus each mineral's global distribution, along with its specific effect upon climate. This lack of understanding is largely due to the scarcity of relevant in situ measurements in dust sources. To advance our understanding of the physicochemical properties of the emitted dust PSD, we present insights into the elemental composition and morphology of individual dust particles collected during the FRontiers in dust minerAloGical coMposition and its Effects upoN climaTe (FRAGMENT) field campaign in the Moroccan Sahara in September 2019. We analyzed more than 300 000 freshly emitted individual particles by performing offline analysis in the laboratory using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDX). Eight major particle-type classes were identified with clay minerals making up the majority of the analyzed particles both by number and mass, followed by quartz, whereas carbonates and feldspar contributed to a lesser extent. We provide an exhaustive analysis of the PSD and potential mixing state of different particle types, focusing largely on iron-rich (Fe oxide-hydroxides) and feldspar particles, which are key to the effects of dust upon radiation and clouds, respectively. Nearly pure or externally mixed Fe oxide-hydroxides are present mostly in diameters smaller than 2 µm, with the highest fraction below 1 µm at about 3.75 % abundance by mass. Fe oxide-hydroxides tend to be increasingly internally mixed with other minerals, especially clays, as particle size increases; i.e., the volume fraction of Fe oxide-hydroxides in aggregates decreases with particle size. Pure (externally mixed) feldspar represented 3.2 % of all the particles by mass, of which we estimated about a 10th to be K-feldspar. The externally mixed total feldspar and K-feldspar abundances are relatively invariant with particle size, in contrast to the increasing abundance of feldspar-like (internally mixed) aggregates with particle size with mass fractions ranging from 5 % to 18 %. We also found that overall the median aspect ratio is rather constant across particle size and mineral groups, although we obtain slightly higher aspect ratios for internally mixed particles. The detailed information on the composition of freshly emitted individual dust particles and quantitative analysis of their mixing state presented here can be used to constrain climate models including mineral species in their representation of the dust cycle.</p
Anuário científico da Escola Superior de Tecnologia da Saúde de Lisboa - 2021
É com grande prazer que apresentamos a mais recente edição (a 11.ª) do Anuário Científico da Escola Superior de Tecnologia da Saúde de Lisboa. Como instituição de ensino superior, temos o compromisso de promover e incentivar a pesquisa científica em todas as áreas do conhecimento que contemplam a nossa missão. Esta publicação tem como objetivo divulgar toda a produção científica desenvolvida pelos Professores, Investigadores, Estudantes e Pessoal não Docente da ESTeSL durante 2021. Este Anuário é, assim, o reflexo do trabalho árduo e dedicado da nossa comunidade, que se empenhou na produção de conteúdo científico de elevada qualidade e partilhada com a Sociedade na forma de livros, capítulos de livros, artigos publicados em revistas nacionais e internacionais, resumos de comunicações orais e pósteres, bem como resultado dos trabalhos de 1º e 2º ciclo. Com isto, o conteúdo desta publicação abrange uma ampla variedade de tópicos, desde temas mais fundamentais até estudos de aplicação prática em contextos específicos de Saúde, refletindo desta forma a pluralidade e diversidade de áreas que definem, e tornam única, a ESTeSL. Acreditamos que a investigação e pesquisa científica é um eixo fundamental para o desenvolvimento da sociedade e é por isso que incentivamos os nossos estudantes a envolverem-se em atividades de pesquisa e prática baseada na evidência desde o início dos seus estudos na ESTeSL. Esta publicação é um exemplo do sucesso desses esforços, sendo a maior de sempre, o que faz com que estejamos muito orgulhosos em partilhar os resultados e descobertas dos nossos investigadores com a comunidade científica e o público em geral. Esperamos que este Anuário inspire e motive outros estudantes, profissionais de saúde, professores e outros colaboradores a continuarem a explorar novas ideias e contribuir para o avanço da ciência e da tecnologia no corpo de conhecimento próprio das áreas que compõe a ESTeSL. Agradecemos a todos os envolvidos na produção deste anuário e desejamos uma leitura inspiradora e agradável.info:eu-repo/semantics/publishedVersio
Perspectives on high-frequency nanomechanics, nanoacoustics, and nanophononics
Nanomechanics, nanoacoustics, and nanophononics refer to the engineering of
acoustic phonons and elastic waves at the nanoscale and their interactions with
other excitations such as magnons, electrons, and photons. This engineering
enables the manipulation and control of solid-state properties that depend on
the relative positions of atoms in a lattice. The access to advanced
nanofabrication and novel characterization techniques enabled a fast
development of the fields over the last decade. The applications of
nanophononics include thermal management, ultrafast data processing,
simulation, sensing, and the development of quantum technologies. In this
review, we cover some of the milestones and breakthroughs, and identify
promising pathways of these emerging fields.Comment: 19 pages, 3 figure
A direct-laser-written heart-on-a-chip platform for generation and stimulation of engineered heart tissues
In this dissertation, we first develop a versatile microfluidic heart-on-a-chip model to generate 3D-engineered human cardiac microtissues in highly-controlled microenvironments. The platform, which is enabled by direct laser writing (DLW), has tailor-made attachment sites for cardiac microtissues and comes with integrated strain actuators and force sensors. Application of external pressure waves to the platform results in controllable time-dependent forces on the microtissues. Conversely, oscillatory forces generated by the microtissues are transduced into measurable electrical outputs. After characterization of the responsivity of the transducers, we demonstrate the capabilities of this platform by studying the response of cardiac microtissues to prescribed mechanical loading and pacing.
Next, we tune the geometry and mechanical properties of the platform to enable parametric studies on engineered heart tissues. We explore two geometries: a rectangular seeding well with two attachment sites, and a stadium-like seeding well with six attachment sites. The attachment sites are placed symmetrically in the longitudinal direction. The former geometry promotes uniaxial contraction of the tissues; the latter additionally induces diagonal
fiber alignment. We systematically increase the length for both configurations and observe a positive correlation between fiber alignment at the center of the microtissues and tissue length. However, progressive thinning and “necking” is also observed, leading to the failure of longer tissues over time. We use the DLW technique to improve the platform, softening
the mechanical environment and optimizing the attachment sites for generation of stable microtissues at each length and geometry. Furthermore, electrical pacing is incorporated into the platform to evaluate the functional dynamics of stable microtissues over the entire range of physiological heart rates. Here, we typically observe a decrease in active force and contraction duration as a function of frequency.
Lastly, we use a more traditional ?TUG platform to demonstrate the effects of subthreshold electrical pacing on the rhythm of the spontaneously contracting cardiac microtissues. Here, we observe periodic M:N patterns, in which there are ? cycles of stimulation for every ? tissue contractions. Using electric field amplitude, pacing frequency, and homeostatic beating frequencies of the tissues, we provide an empirical map for predicting the emergence of these rhythms
Understanding interactions between Ramularia collo-cygni and barley leaf physiology to target improvements in host resistance and disease control strategy
Ramularia Leaf Spot (RLS) is an increasingly problematic disease of barley.
Control options are limited as the causal fungus, Ramularia collo-cygni, has
developed resistance to several of the major fungicide groups. Developing
new methods for controlling this disease is therefore a priority. R. collo-cygni
can grow systemically in barley plants from infected seed, without inducing
visible symptoms. In the field, visible symptoms normally only appear after
flowering. The relative contribution of the latent and symptomatic stages of
the fungal lifecycle to reduction in barley yield is not currently known with any
certainty. Two possibilities are that the effect of asymptomatic infection on
pre-flowering photosynthetic activity, and the development of grain sink
capacity, plays an important role; or that reduction in photosynthetic activity
during grain filling, resulting from lesion development and loss of green leaf
area, is the predominant factor. This research aimed to increase our
understanding of the impact of different phases of the fungal lifecycle on
barley photosynthesis and yield formation, to better target host resistance
and disease control strategies.
Controlled environment and field experiments were used to determine the
relative effects of asymptomatic and symptom-expressing phases of R. collo-cygni infection on photosynthesis and yield formation in spring barley. In
controlled environment experiments leaf photosynthetic activity was
measured in seedlings inoculated with suspensions of R. collo-cygni mycelia.
Measurements were made before and after visible symptom development
using Infra-Red Gas Analysis (IRGA), chlorophyll fluorescence analysis and
chlorophyll fluorescence imaging. No reduction in photosynthetic activity was
observed in leaves infected with R. collo-cygni, compared to those of non-
infected leaves, during the latent phase of infection. After the appearance of
visible symptoms, photosynthetic activity within lesions reduced as the
lesions developed. However, this did not lead to reductions in photosynthetic
activity when measured across the whole leaf area, suggesting that for there
to be a significant effect of disease on whole leaf photosynthetic activity,
visible symptoms must develop into mature lesions and coalesce to cover
larger areas of the leaf surface.
In field experiments plots were treated with a full fungicide regime, left
untreated, or inoculated with R. collo-cygni and treated with fungicide to
which R. collo-cygni is resistant (the latter as a precaution against lack of
natural RLS disease that year and/or other diseases developing on untreated
plots). RLS was the only disease of significance that developed in untreated
or inoculated plots. Symptoms first appeared after flowering, around Zadoks
Growth Stage 72. Fungicide-treated plots remained free of disease.
Chlorophyll fluorescence analysis of field plants showed no effect of infection
on the maximum quantum efficiency of Photosystem II (Fv/Fm) before visible
symptom development, consistent with results from controlled environment
experiments. Grain yield of untreated and fungicide-treated plots was
predicted from fixed common values of radiation use efficiency (RUE) and
utilisation of soluble sugar reserves, and measured values of post-flowering
healthy (green) leaf area light interception. Grain yields predicted from the
difference in post-flowering light interception between fungicide-treated plants
and untreated or inoculated plants displaying symptoms of RLS were
comparable with the measured yield response to fungicide. This suggests
that yield loss to RLS is primarily associated with a reduction in light capture
during grain filling, resulting from lesion development and loss of green leaf
area.
Results from controlled environment and field experiments suggested that
symptom expression was associated with leaf senescence. Further controlled
environment experiments tested this relationship by using treatments to vary
the onset and rate of leaf senescence. Seedlings that were treated with
cytokinin to delay senescence after inoculation with suspensions of R. collo-cygni mycelia developed fewer lesions than control plants. Fungal growth, as
measured by quantification of R. collo-cygni DNA in leaves, was also
restricted in plants treated with cytokinin.
Collectively these results suggest that prevention of visible symptom
development, rather than prevention of asymptomatic growth, is the most
important target for management of this disease. Control methods targeted at
delaying senescence could be a useful avenue for further investigation
Increased lifetime of Organic Photovoltaics (OPVs) and the impact of degradation, efficiency and costs in the LCOE of Emerging PVs
Emerging photovoltaic (PV) technologies such as organic photovoltaics (OPVs) and perovskites (PVKs) have the potential to disrupt the PV market due to their ease of fabrication (compatible with cheap roll-to-roll processing) and installation, as well as their significant efficiency improvements in recent years. However, rapid degradation is still an issue present in many emerging PVs, which must be addressed to enable their commercialisation. This thesis shows an OPV lifetime enhancing technique by adding the insulating polymer PMMA to the active layer, and a novel model for quantifying the impact of degradation (alongside efficiency and cost) upon levelized cost of energy (LCOE) in real world emerging PV installations.
The effect of PMMA morphology on the success of a ternary strategy was investigated, leading to device design guidelines. It was found that either increasing the weight percent (wt%) or molecular weight (MW) of PMMA resulted in an increase in the volume of PMMA-rich islands, which provided the OPV protection against water and oxygen ingress. It was also found that adding PMMA can be effective in enhancing the lifetime of different active material combinations, although not to the same extent, and that processing additives can have a negative impact in the devices lifetime.
A novel model was developed taking into account realistic degradation profile sourced from a literature review of state-of-the-art OPV and PVK devices. It was found that optimal strategies to improve LCOE depend on the present characteristics of a device, and that panels with a good balance of efficiency and degradation were better than panels with higher efficiency but higher degradation as well. Further, it was found that low-cost locations were more favoured from reductions in the degradation rate and module cost, whilst high-cost locations were more benefited from improvements in initial efficiency, lower discount rates and reductions in install costs
Starch hydrogels as targeted colonic drug delivery vehicles
Targeted colonic drug delivery systems are needed for the treatment of endemic colorectal pathologies, such as Crohn's disease, ulcerative colitis, and colorectal cancer. These drug delivery vehicles are difficult to formulate, as they need to remain structurally intact whilst navigating a wide range of physiological conditions across the upper gastrointestinal tract. In this work we show how starch hydrogel bulk structural and molecular level parameters influence their properties as drug delivery platforms. The in vitro protocols mimic in vivo conditions, accounting for physiological concentrations of gastrointestinal hydrolytic enzymes and salts. The structural changes starch gels undergo along the entire length of the human gastrointestinal tract have been quantified, and related to the materials' drug release kinetics for three different drug molecules, and interactions with the large intestinal microbiota. It has been demonstrated how one can modify their choice of starch in order to fine tune its corresponding hydrogel's pharmacokinetic profile
Towards A Graphene Chip System For Blood Clotting Disease Diagnostics
Point of care diagnostics (POCD) allows the rapid, accurate measurement of analytes near to a patient. This enables faster clinical decision making and can lead to earlier diagnosis and better patient monitoring and treatment. However, despite many prospective POCD devices being developed for a wide range of diseases this promised technology is yet to be translated to a clinical setting due to the lack of a cost-effective biosensing platform.This thesis focuses on the development of a highly sensitive, low cost and scalable biosensor platform that combines graphene with semiconductor fabrication tech-niques to create graphene field-effect transistors biosensor. The key challenges of designing and fabricating a graphene-based biosensor are addressed. This work fo-cuses on a specific platform for blood clotting disease diagnostics, but the platform has the capability of being applied to any disease with a detectable biomarker.Multiple sensor designs were tested during this work that maximised sensor ef-ficiency and costs for different applications. The multiplex design enabled different graphene channels on the same chip to be functionalised with unique chemistry. The Inverted MOSFET design was created, which allows for back gated measurements to be performed whilst keeping the graphene channel open for functionalisation. The Shared Source and Matrix design maximises the total number of sensing channels per chip, resulting in the most cost-effective fabrication approach for a graphene-based sensor (decreasing cost per channel from £9.72 to £4.11).The challenge of integrating graphene into a semiconductor fabrication process is also addressed through the development of a novel vacuum transfer method-ology that allows photoresist free transfer. The two main fabrication processes; graphene supplied on the wafer “Pre-Transfer” and graphene transferred after met-allisation “Post-Transfer” were compared in terms of graphene channel resistance and graphene end quality (defect density and photoresist). The Post-Transfer pro-cess higher quality (less damage, residue and doping, confirmed by Raman spec-troscopy).Following sensor fabrication, the next stages of creating a sensor platform involve the passivation and packaging of the sensor chip. Different approaches using dielec-tric deposition approaches are compared for passivation. Molecular Vapour Deposi-tion (MVD) deposited Al2O3 was shown to produce graphene channels with lower damage than unprocessed graphene, and also improves graphene doping bringing the Dirac point of the graphene close to 0 V. The packaging integration of microfluidics is investigated comparing traditional soft lithography approaches and the new 3D printed microfluidic approach. Specific microfluidic packaging for blood separation towards a blood sampling point of care sensor is examined to identify the laminar approach for lower blood cell count, as a method of pre-processing the blood sample before sensing.To test the sensitivity of the Post-Transfer MVD passivated graphene sensor de-veloped in this work, real-time IV measurements were performed to identify throm-bin protein binding in real-time on the graphene surface. The sensor was function-alised using a thrombin specific aptamer solution and real-time IV measurements were performed on the functionalised graphene sensor with a range of biologically relevant protein concentrations. The resulting sensitivity of the graphene sensor was in the 1-100 pg/ml concentration range, producing a resistance change of 0.2% per pg/ml. Specificity was confirmed using a non-thrombin specific aptamer as the neg-ative control. These results indicate that the graphene sensor platform developed in this thesis has the potential as a highly sensitive POCD. The processes developed here can be used to develop graphene sensors for multiple biomarkers in the future
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