Rheology of vitreous humour and pharmacological substitutes used in the treatment of vitreoretinal pathologies

Vitreoretinal pathologies are the second leading cause of blindness worldwide. They can be caused by age-related changes in vitreous humour (VH) or as a consequence of some diseases that lead to rheological, biochemical and structural rearrangements. So far, the most effective treatment for these diseases is the injection of a VH substitute in the vitreous cavity. These substances can be used intra- operatively to push a detached retina into its normal position, to restore the volume of the vitreous cavity, and to help surgeons in membrane dissection. The major vitreous substitutes commercially available are silicone oils and perfluorocarbon liquids, but currently there is little information about the rheological properties of these fluids, that are intimately linked to their functionality. The aim of this work is to compare the rheological properties of the VH and five commercial vitreous substitutes currently used in vitreoretinal surgeries. Six fluids were analysed: VH extracted from New Zealand white rabbit specimen, three silicone oils (RS-Oil1000 and RS-Oil5000, Alchimia and Siluron 2000, Fluoron), two perfluorocarbon liquids (HPF8 and HPF10, Alchimia) and a mixture of silicone oil with perfluorocarbon (Densiron68, Fluoron). Extensional measurements were performed with a capillary break-up extensional rheometer (Haake CaBER1, ThermoElectron) and an in-house extensional rheometer. The steady shear and small amplitude oscillatory shear measurements (SAOS) were performed with a hybrid rheometer (DHR-2, TA Instruments). Our results show that VH substitutes used for same purpose exhibit significantly different rheological properties between them and when compared with the VH. Vitreous humour shows viscoelastic behaviour and all the pharmacological fluids tested display a Newtonian-like behaviour in steady shear flow with viscosities varying from 0.49 mPa s to 4.57 Pa s, at 37°C

Efeito de um programa de Halliwick na competência aquática, postura, equilíbrio estático e dinâmico de pessoas diagnosticadas com deficiência.

O objetivo deste estudo foi verificar qual o Efeito de um programa de Halliwick na competência aquática, postura, equilíbrio estático e dinâmico de pessoas diagnosticadas com deficiência. Dez sujeitos (33±12,3 anos) diagnosticados com paralisia cerebral (n=3), incapacidade mental (n=4) e trissomia 21 (n=3) participaram num programa de 10 pontos de Halliwick. O programa decorreu ao longo de 15 semanas com uma sessão por semana de 1 hora de duração. Todas as sessões foram planeadas e implementadas por um terapeuta especializado. No início (pré) e no final (pós) do programa foram avaliados a competência aquática, postura, equilíbrio estático e dinâmico. A competência aquática foi medida com recurso à Water Orientation Test Align 2 (WOTA) circunscrita a uma pontuação máxima de 81 pontos. A postura estática foi avaliada com recurso a fotogrametria de modo a obter os desvios do centro de massa (CoM) nos planos sagital e frontal. O equilíbrio estático foi avaliado através do teste de apoio unipodal, alcance funcional e teste de Romberg nas suas variantes. O teste Time Up & Go foi selecionado como medida de equilíbrio dinâmico. A competência aquática demonstrou melhorias significativas (WOTApré = 36±15 pontos vs WOTApós = 52±21 pontos, p <0,01). Não se registram alterações nos indicadores do CoM em termos estáticos. Verificou-se uma alteração nos registos do apoio unipodal (Unipodalpré = 14,20±12,22 s vs Unipodalpós = 16,30±12,03 s, p = 0,03) e alcance funcional (Alcancepré = 18,5±0,09 cm vs Alcancepós = 22,5±0,11 cm, p < 0,01). Existiu uma redução dos 70% para os 30% nas oscilações do teste de Romberg com os pés paralelos. Verificou-se ainda uma melhoria no equilíbrio dinâmico (Up&Gopré = 9,49±2,72 vs Up&Gopós = 8,08±2,81 s, p < 0,01) após o programa. No final verificou-se uma associação significativa entre a competência aquática e o Unipodal (Rs = 0,81, p < 0,01) e o Up&Go (Rs = -0,78, p < 0,01). Pode-se concluir que 15 semanas de experiência aquática com base no método de Halliwick são suficientes para induzir melhorias na competência aquática de indivíduos diagnosticados com deficiência. Parece ainda existir uma transferência positiva de capacidades adquiridas em meio aquático para a postura e equilíbrio em meio terrestre

Rheological behaviour of vitreous humour

The vitreous humour (VH) is a complex biofluid that occupies a large portion of the eyeball between the lens and the retina, and exhibits non-Newtonian rheological properties that are key for its function in the eye. It is often possible to distinguish two different phases in VH, known as liquid and gel phases (Sebag, 1987). In this work, we present a detailed rheological characterisation of the two phases of the VH under shear and extensional flow conditions. Healthy New Zealand rabbit eyes were used to measure the surface tension and the shear and extensional rheological properties of VH in different phase conformations and at different times after dissection. The results show that VH liquid phase exhibits a surface tension of 47.8 mN/m, a shear thinning behaviour reaching a viscosity plateau around 10-3 Pa.s for shear rates above 1000 s-1, and an average relaxation time of 9.7 ms in extensional flow. Interestingly, both VH phases present higher storage modulus than loss modulus and the measurements performed with VH gel phase 4±1 hours after dissection exhibit the highest moduli values. The compliance measurements for the gel phase show a viscoelastic gel behaviour and that compliance values decrease substantially with time after dissection. Our results show that the two VH phases exhibit viscoelastic behaviour, but with distinct rheological characteristics, consistent with a gel phase mostly composed of collagen entangled by hyaluronan and a second phase mainly composed of hyaluronan in aqueous solution

Development of an easy and effective attachment system for lower limb prosthesis

This study aimed to introduce a new suspension system that is capable of increasing the amputee’s satisfaction in terms of locking the residual limb inside the prosthetic socket. This paper describes the design and development phases carried out to optimize the final solution. The design system was based on the amputee’s needs and the requirements of prosthetic suspension systems. The final solution is a combination of a guiding and fixation system, to overcome some of the reported problems with the current systems, presenting a new simple suspension method that improves the donning and doffing of prosthesis. The new suspension system is a good alternative system to improve the life quality of amputees with lower activity level on the daily basis and, consequently, ease their rehabilitation.info:eu-repo/semantics/publishedVersio

Olefin oligomerisation over nanocrystalline MFI-based micro/mesoporous zeotypes synthesised via bottom-up approaches

The oligomerisation of 1-butene was studied under high-pressure continuous-flow conditions (200–250 °C, 30–40 bar), in the presence of micro/mesoporous zeotypes based on the MFI topology, which were prepared via different non-destructive bottom-up strategies: crystallization of silanized protozeolitic units; co-templating with a dual function (polymeric) template; and using a sole structure directing agent (non-surfactant and non-polymeric) to generate mesoporosity. The synthesis method influenced the material properties and consequently the catalytic performance. In targeting hydrocarbons with boiling point ranges characteristics of diesel, the zeotypes benefited from regular morphology, reduced crystallite size, mesoporosity and enhanced molar ratio of Lewis (L) to Brønsted (B) acid sites (L/B). In general, the zeotypes outperformed commercial zeolite ZSM-5. The best-performing zeotype was prepared according to the Serrano strategy based on the crystallization of silanized zeolitic seeds, and led to 97% conversion and an average space-time yield of liquid products of 1077 mg gcat−1 h−1, at 250 °C, 40 bar. The zeotypes seemed more stable than the commercial zeolite, based on molecular level characterization studies of the used/regenerated catalysts, with some differences in catalytic activity.publishe

Rheological behaviour and flow dynamics of Vitreous Humour substitutes used in eye surgery during saccadic eye movements

This work discusses the rheology of several vitreous humour (VH) substitutes used in eye surgery (perfluorocarbons and silicone oils) and their flow behaviour when subjected to saccadic eye movements. Shear rheology experiments revealed that all fluids tested exhibit a constant shear viscosity, while extensional rheological experiments showed that Siluron 2000 is the only fluid tested that exhibits a measurable elasticity. To characterise the dynamics during saccadic eye movements, numerical simulations of all the VH substitutes under study were performed with the open source software OpenFOAM and compared with Vitreous Humour flow dynamics to assess their potential mechanical performance. Minor differences were found between the numerical results of a viscoelastic fluid reproducing the rheology of Siluron 2000 and a Newtonian model. Perfluorocarbon (PFLC) shows a distinct flow behaviour relative to Silicone Oils (SiO). None of the pharmacological fluids tested can adequately mimic the rheological and consequently the flow behaviour of VH gel phase (Silva et al., 2020).Comment: 16 figure

Fluoxetine and Nutrients Removal from Aqueous Solutions by Phycoremediation

The tertiary treatment using microalgae offers an attractive alternative to the removal of low but relevant concentrations of pharmaceuticals from domestic wastewaters. The removal of fluoxetine from aqueous solutions by living and non-living (lyophilized) Chlorella vulgaris was assessed. The determination of the pH at the point of zero charge, Fourier transmittance infrared analysis, and scanning electron microscopy were performed to characterize the microalgae biomass. Kinetic and equilibrium experiments were performed. The pseudo-second-order model described the kinetics of fluoxetine. The corresponding kinetic constants indicated that biosorption was faster onto non-living biomass than onto living biomass. The equilibrium results showed that the systems followed the Langmuir isotherm model. The maximum capacity of living microalgae (1.9 ± 0.1 mg·g−1) was slightly higher than the non-living microalgae (1.6 ± 0.2 mg·g−1). Living Chlorella vulgaris, free and immobilized in calcium-alginate, were also used to remove fluoxetine and nutrients (nitrogen and phosphorus) from treated municipal wastewater in a batch system. In both experiments, fluoxetine was completely removed within six days. The total phosphorus (TP) and total nitrogen (TN) removal efficiencies achieved for free and immobilized cells were, null and 65.0 ± 0.1%, and 86.2 ± 0.1% and 81.8 ± 3.1, respectivelyThis research was funded by the Associate Laboratory for Green Chemistry-LAQV, which received financial support from UIDB/50006/2020, UIDP/50006/2020, and LA/P/0008/2020 by the Fundação para a Ciência e a Tecnologia (FCT)/Ministério da Ciência, Tecnologia e En sino Superior (MCTES) through national funds. This research was also funded by the EU and FCT/UEFISCDI/FORMAS, in the frame of the collaborative international consortium REWATER— “Sustainable and safe water management in agriculture: increasing the efficiency of water reuse for crop growth while protecting ecosystems, services and citizens’ welfare” (WaterJPI/0007/2016), which was financed under the ERA-NET Co-fund WaterWorks2015 Call, as an integral part of the 2016 Joint Activities developed by the Water Challenges for a Changing World Joint Program Initiative (Water JPI). The research was funded also by FCT and BiodivRestore Joint Call 2020–2021-European Union’s Horizon 2020 research and innovation program under grant agreement No. 101003777- BiodivRestore-406/DivRestore/0002/2020-BioReset-“Biodiversity restoration and conservation of inland water ecosystems for environmental and human well-being”. A.D.M. Silva would like to thank FCT for her Ph.D. Grant SFRH/BD/138/780/2018. The authors are greatly indebted to all financing sources. The authors are grateful to Materials Centre of the University of Porto (CEMUP), Porto, Portugal, for expert assistance with SEM/EDSinfo:eu-repo/semantics/publishedVersio

Micro/mesoporous LTL derived materials for catalytic transfer hydrogenation and acid reactions of bio-based levulinic acid and furanics

The biomass-derived platform chemicals furfural and 5-(hydroxymethyl)furfural (HMF) may be converted to α-angelica lactone (AnL) and levulinic acid (LA). Presently, LA (synthesized from carbohydrates) has several multinational market players. Attractive biobased oxygenated fuel additives, solvents, etc., may be produced from AnL and LA via acid and reduction chemistry, namely alkyl levulinates and γ-valerolactone (GVL). In this work, hierarchical hafnium-containing multifunctional Linde type L (LTL) related zeotypes were prepared via top-down strategies, for the chemical valorization of LA, AnL and HMF via integrated catalytic transfer hydrogenation (CTH) and acid reactions in alcohol medium. This is the first report of CTH applications (in general) of LTL related materials. The influence of the post-synthesis treatments/conditions (desilication, dealumination, solid-state impregnation of Hf or Zr) on the material properties and catalytic performances was studied. AnL and LA were converted to 2-butyl levulinate (2BL) and GVL in high total yields of up to ca. 100%, at 200°C, and GVL/2BL molar ratios up to 10. HMF conversion gave mainly the furanic ethers 5-(sec-butoxymethyl)furfural and 2,5-bis(sec-butoxymethyl)furan (up to 63% total yield, in 2-butanol at 200°C/24 h). Mechanistic, reaction kinetics and material characterization studies indicated that the catalytic results depend on a complex interplay of different factors (material properties, type of substrate). The recovered-reused solids performed steadily.publishe

Abordagem aos Endoleaks tipo II – Uma Revisão Sistemática dos últimos 5 anos de literatura

INTRODUÇÃO: Os endoleaks tipo II são a complicação e causa de reintervenção mais frequente do EVAR sendo, contudo, tema de debate entre a comunidade científica. Este trabalho tem como objetivo rever as diferentes abordagens aos endoleaks tipo II após reparação endovascular de aneurismas da aorta infrarrenal. MATERIAIS E MÉTODOS: Para a realização deste trabalho os autores selecionaram e analisaram de forma sistemática artigos publicados na plataforma PubMed em língua inglesa entre 2015 e 2020, segundo a metodologia PRISMA. RESULTADOS: Até ao momento não existe evidência clara quanto ao limiar para tratamento e qual a melhor abordagem aos endoleaks tipo II. Entre as técnicas minimamente invasivas reportadas – embolização transarterial e percutânea direta do saco – não parece haver diferença significativa tanto na eficácia como nas complicações. Contudo ambas demonstram taxas de falência e necessidade de reintervenção elevadas. Quanto à embolização profilática – do saco ou de eferentes patentes – parece haver diminuição significativa do risco de desenvolver endoleak tipo II. Porém o impacto na sobrevida destas intervenções permanece por esclarecer. CONCLUSÕES: Serão necessários estudos de maior qualidade com critérios de seleção uniformes para que se possam tirar conclusões de maior validade