3,269 research outputs found
Knee function through finite element analysis and the role of Miocene hominoids in our understanding of the origin of antipronograde behaviours: the Pierolapithecus catalaunicus patella as a case study
Although extensive research has been carried out in recent years on the origin and evolution of human bipedalism, a full understanding of this question is far from settled. Miocene hominoids are key to a better understanding of the locomotor types observed in living apes and humans. Pierolapithecus catalaunicus, an extinct stem great ape from the middle Miocene (c. 12.0 Ma) of the Vallès-Penedès Basin (north-eastern Iberian Peninsula), is the first undoubted hominoid with an orthograde (erect) body plan. Its locomotor repertoire included above-branch quadrupedalism and other antipronograde behaviours. Elucidating the adaptive features present in the Pierolapithecus skeleton and its associated biomechanics helps us to better understand the origin of hominoid orthogrady. This work represents a new biomechanical perspective on Pierolapithecus locomotion, by studying its patella and comparing it with those drawn from a large sample of extant anthropoids. This is the first time that the biomechanical patellar performance in living non-human anthropoids and a stem hominid has been studied using finite element analysis (FEA). Differences in stress distribution are found depending on body plan and the presence/absence of a distal apex, probably due to dissimilar biomechanical performances. Pierolapithecus’ biomechanical response mainly resembles that of great apes, suggesting a similar knee joint use in mechanical terms. These results underpin previous studies on Pierolapithecus, favouring the idea that a relevant degree of some antipronograde behaviour may have made up part of its locomotor repertoire. Moreover, our results corroborate the presence of modern great ape-like knee biomechanical performances back in the Miocene
Photocatalytic and oxidative synthetic pathways for highly efficient PANI-TIO2 nanocomposites as organic and inorganic pollutant sorbents
Polyaniline (PANI)-materials have recently been proposed for environmental remediation applications thanks to PANI stability and sorption properties. As an alternative to conventional PANI oxidative syntheses, which involve toxic carcinogenic compounds, an eco-friendly procedure was here adopted starting from benign reactants (aniline-dimer and H2O2) and initiated by ultraviolet (UV)-irradiated TiO2. To unlock the full potential of this procedure, we investigated the roles of TiO2 and H2O2 in the nanocomposites synthesis, with the aim of tailoring the properties of the final material to the desired application. The nanocomposites prepared by varying the TiO2:H2O2:aniline-dimer molar ratios were characterized for their thermal, optical, morphological, structural and surface properties. The reaction mechanism was investigated via mass analyses and X-ray photoelectron spectroscopy. The nanocomposites were tested on both methyl orange and hexavalent chromium removal. A fast dye-sorption was achieved also in the presence of interferents and the recovery of the dye was obtained upon eco-friendly conditions. An efficient Cr(VI) abatement was obtained also after consecutive tests and without any regeneration treatment. The fine understanding of the reaction mechanism allowed us to interpret the pollutant-removal performances of the different materials, leading to tailored nanocomposites in terms of maximum sorption and reduction capability upon consecutive tests even in simulated drinking water
Triply green polyaniline: UV irradiation-induced synthesis of highly porous PANI/TiO2 composite and its application in dye removal
An environmentally benign procedure for the preparation of polyaniline/TiO2 composites is presented. The UV irradiation-induced synthesis leads to materials with good crystallinity and tailored morphology, showing promising sorption and recycle properties in dye removal tests. A reaction mechanism is proposed on the basis of LC-MS and FT-IR investigations
Polyaniline/TiO2 composites: green photocatalysic synthesis and application in wastewater remediation
In recent years, polyaniline (PANI) composites and nanocomposites with metal and metal-oxide materials have received growing attention for electrochemical and photoelectrochemical applications (Gu 2013). Among them, PANI/TiO2 composites are probably the most interesting systems due to synergistic effects between the conductive polymer and the oxide photocatalyst in terms of photogenerated charge separation and photocatalytic efficiency (Bae 2011). Moreover, polyaniline has been reported to possess favourable sorption properties, which can be exploited for pollutant remediation (Alcaraz-Espinoza 2015, Janaki 2012). PANI/TiO2 composites are thus promising candidates for wastewater treatment combining different pollutant remediation approaches. Polyaniline is classically synthesised via oxidative polymerization (Tran 2011), which involves noxious reagents (aniline and peroxydisulfates) and leads to toxic and carcinogenic byproducts (such as benzidine and trans-azobenzidine). In recent years, greener alternatives have been reported, such as a synthetic process starting from aniline dimer ((4-aminophenil)aniline) and using Fe3+ as catalyst and H2O2 as oxidant (Della Pina 2018). Unfortunately, this alternative procedure does not offer any control over the polymer morphology, leading to compact materials with low surface area and, as a consequence, poor dye-sorption capability. Very recently, we proposed a new photocatalytically induced green synthesis leading to stable polyaniline/TiO2 composites with porous morphology, wide surface area, high crystallinity and, most important, excellent dye removal performance and reusability (Cionti 2018). The reaction is carried out in two steps: at first, the aniline dimer is dissolved in a HCl aqueous solution and TiO2 is added while starting UV irradiation. In the second step, H2O2 is added in the dark, leading to the final product. In this work, we shed light on the photocatalytic nature of the synthetic mechanism, highlighting the different roles of TiO2 and of H2O2 on the composite structural and morphological features as well as on the composite performance for pollutant abatement. The reaction mechanism was investigated by a combination of spectrometric techniques, radical scavenger tests, and surface characterizations (Fig.1). By sampling the reaction mixture at different irradiation times, we demonstrated that under UV irradiation the growth of the oligomers occurs at the TiO2 particle surfaces. The same experiment carried out without UV irradiation showed the intrinsic photocatalytic nature of the process: in the dark, only short oligomers without appropriate chain conjugation were produced. However, even after prolonged UV irradiation, the final green product could be obtained only upon addition of H2O2, showing that, while oligomer formation is initiated by radicals produced by TiO2 photocatalysis, small amounts of an oxidant (H2O2) are still needed for the polymer chain growth. The role of the H2O2 amount proved to be especially crucial with respect to the composite properties. Increasing the H2O2 amount together with that of TiO2 led to composites with low surface area and reduced dye removal capability (Fig.2 a) due to a faster polymerization step. On the other hand, when only the photocatalyst amount was increased, neither the product morphology, nor its dye-removal ability were affected. This enables to increase the TiO2 content within the composite with the aim of enhancing its photocatalytic performance. In this respect, the composite stability was tested in water under prolonged UV irradiation, showing that the material optical, structural and morphological properties remained unchanged. The composite was tested towards the removal of anionic azo dyes in aqueous solution, evaluating the effect of the matrix composition and the composite reusability (Fig.2 b), showing promising results
Thyroid Function in Patients with Trisomy 21 in a Central Pediatric Hospital
Em crianças e adolescentes com síndrome de trissomia 21 observa-se uma prevalência aumentada de alterações da função tiroideia. A mais frequentemente encontrada é o hipotiroidismo subclínico, seguida do hipotiroidismo clínico e, mais raramente, doença de Graves. O diagnóstico de hipotiroidismo é, por vezes, tardio pois os sintomas são confundidos com as
manifestações características da trissomia 21, sendo portanto fundamental rastrear sistematicamente a função tiroideia
nestas crianças. A velocidade de crescimento é um elemento clínico que pode contribuir quer para a valorização do diagnóstico
quer da terapêutica apesar de esta não ser totalmente consensual. Descreve-se a casuística de um Hospital Central
Pediátrico em foram seguidas quarenta e cinco crianças e adolescentes com trissomia 21, entre Janeiro de 2000 e Maio de 2008. Neste grupo de crianças, foram detectadas alterações da função tiroideia em dezanove; a alteração mais frequente foi o hipotiroidismo subclínico (treze) seguida do hipotiroidismo clínico (cinco); houve apenas um caso de hipertiroidismo. As alterações da função tiroideia aumentaram com a idade dos
doentes, foram mais frequentes no sexo feminino e tiveram uma clínica inespecífica
On the triplet state of poly(N-vinylcarbazole)
Triplet state properties including transient triplet absorption spectrum, intersystem crossing yields in solution at room temperature and phosphorescence spectra, quantum yields and lifetimes at low temperature as well as singlet oxygen yields were obtained for poly(N-vinylcarbazole) (PVK) in 2-methyl-tetrahydrofuran (2-MeTHF), cyclohexane or benzene. The results allow the determination of the energy value for the lowest lying triplet state and also show that triplet formation and deactivation is a minor route for relaxation of the lowest excited singlet state of PVK. In addition, they show the triplet state is at higher energy than reported heavy metal dopants used for electrophosphorescent devices, such that if this is used as a host it will not quench their luminescence.http://www.sciencedirect.com/science/article/B6TFN-4DTTJJC-7/1/b605edb9859b607f1a9b1c1348af029
Automatic coverage based neighbour estimation system: a cloud-based implementation
Over the years, mobile networks have grown exponentially due to rising demand. These networks mix different types of cells, which makes manual configuration difficult, costly and tedious. Furthermore, inefficiencies stemming from these problems can cause problems in Handover performance, since a mobile device may not always connect to the optimal cell upon switching from one to the other, potentially harming service quality and increasing Operational Costs (OPEX). Existing solutions, like Automatic Neighbour Relations (ANR), while they are valuable in estimating the best neighbouring cells through the rate of successful Handovers, fail to take into account topological coverage factors and fictional cells, therefore inefficiencies lie hidden and it isn't suited to calculate relations between planned cells and active cells. In this article, a proposal of a cloud-based, on-demand automatic coverage based neighbour estimation system is proposed, which utilises topological signal coverage data from each cell provided by the network's operations support system, in order to mitigate the aforementioned issues and provide a reliable and convenient coverage analysis paradigm.info:eu-repo/semantics/publishedVersio
Dinâmica do potencial redox em condições de alagamento em amostras de latossolo amarelo, textura média do nordeste paraense.
Resumo: Os Latossolos Amarelos textura média é a classe de solo predominante no nordeste paraense aonde a atividade do cultivo da palma de óleo (dendezeiro) que é uma atividade tradicional e em expansão. Um dos desafios para a expansão da palmicultura é a elucidação da etiologia do agente causal da anomalia conhecida como amarelecimento fatal. Entre as hipóteses que estão sendo testada é estsão os distúrbios provocados na solução do solo devido a alteração do potencial redox em condições de alagamento e consequentemente redução do oxigênio no solo. O presente experimento teve como objetivo estudar a variação do potencial oxirredução em amostras de um Latossolo Amarelo, textura média, distrófico submetido a condições de alagamento por um período de 60 dias. Adicionalmente se testou o efeito da homogeneização da amostras na avaliação do potencial redox. As amostras de solo foram coletadas numa área de cultivo de palma de óleo no município de Moju - PA, com incidência de amarelecimento fatal. Estas amostras posteriormente foram alagadas por um período de 60 dias. Durante este período, o potencial redox foi medido semanalmente . Os resultados mostraram que o potencial redox se reduz com o tempo de alagamento, sendo limitado por deficiência de carbono. Não houve diferenças significativas nas leituras do potencial redox com e sem homogeneização das amostras.A adição de uma fonte adicional de carbono (glucose) levou o potencial a valores de – 350 mV, nestas condições e com baixo valor de pH típico destes solos predominam as formas reduzidas de Fe, Mn e N que podem causar distúrbios fisiológicos a palma de óleo e outros cultivos
A novel way to automatically plan cellular networks supported by linear programming and cloud computing
With the increasing number of mobile subscribers worldwide, there is a need for fast and reliable algorithms for planning/optimization of mobile networks, especially because, in order to maintain a network’s quality of service, an operator might need to deploy more equipment. This paper presents a quick and reliable way to automatically plan a set of frequencies in a cellular network, using both cloud technologies and linear programming. We evaluate our pattern in a realistic scenario of a Global System for Mobile communications protocol (GSM) network and compare the results to another already implemented commercial tool. Results show that even though network quality was similar, our algorithm was twelve times faster and used four times less memory. It was also able to frequency plan seventy cells simultaneously in less than three minutes. This mechanism was successfully integrated in the professional tool Metric, and is currently being used for cellular planning. Its extension for application to 3/4/5G networks is under study.info:eu-repo/semantics/publishedVersio
The effect of substitution and isomeric imperfection on the photophysical behaviour of p-phenylenevinylene trimers
Spectroscopic and photophysical properties of two p-phenylenevinylene (PV) trimers, 2,5-substituted diheptyl-(p-phenylenevinylene) and di-[(2-ethylhexyl)oxy]-(p-phenylenevinylene), were studied using absorption spectroscopy, fluorescence and laser flash photolysis. The change from alkyl to alkyloxy groups red-shifts the absorption and fluorescence bands. The rate of internal conversion is independent of the substitution, whereas alkyloxy substitution increases the S1 [rightwards wave arrow] T1 intersystem crossing rate by an order of magnitude. The relevance for the behaviour of conjugated PPV polymers is discussed. For diheptyl-PV, a sample having ca. 3% of the cis-configuration was also studied. Comparison between the all-trans and the cis-contaminated samples revealed no significant differences in their photophysical properties.http://www.sciencedirect.com/science/article/B6TFN-4C0TKVG-4/1/bb1be7e4a272bb7910483cae927d04a
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