Fetal behavior and heart rate in twin pregnancy: a review

Fetal movements and fetal heart rate (FHR) are well-established markers of fetal well-being and maturation of the fetal central nervous system. The purpose of this paper is to review and discuss the available knowledge on fetal movements and heart rate patterns in twin pregnancies. There is some evidence for an association or similarity in fetal movement incidences or FHR patterns between both members of twin pairs. However, the temporal occurrence of these patterns seems to be for the most part asynchronous, especially when stricter criteria are used to define synchrony. The available data suggest that fetal behavior is largely independent of sex combination, fetal position, and presentation. Conversely, chorionicity appears to have some influence on fetal behavior, mainly before 30 weeks of gestation. There is preliminary evidence for the continuity of inter-individual differences in fetal activity and FHR patterns over pregnancy. Comparisons between studies are limited by large methodological differences and absence of uniform concepts and definitions. Future studies with high methodological quality are needed to provide a more comprehensive knowledge of normal fetal behavior in twin pregnancy.

Acellular Gellan-gum based bilayered structures for the regeneration of osteochondral defects: a preclinical study

 In orthopaedics, the management and treatment of osteochondral (OC) defects remains an ongoing clinical challenge. Autologous osteochondral mosaicplasty has been used as a valid option for OC treatments although donor site morbidity remains a source of concern [1]. Engineering a whole structure capable of mimicking different tissues (cartilage and subchondral bone) in an integrated manner could be a possible approach to regenerate OC defects. In our group we have been proposing the use of bilayered structures to regenerate osteochondral defects [2,3]. The present study aims to investigate the pre-clinical performance of bilayered hydrogels and spongy-like hydrogels in in vivo  models (mice and rabbit, respectively), in both subcutaneous and orthotopic models. The bilayered structures were produced from Low Acyl Gellan Gum (LAGG) from Sigma-Aldrich, USA. Cartilage-like layers were obtained from a 2wt% LAGG solution. The bone-like layers were made of 2wt% LAGG with incorporation of hydroxyapatite at 20% and 30% (w/v). Hydrogels and spongy-like were subcutaneouly implanted in mice to evaluate the inflammatory response. Then, OC defects were induced in rabbit knee to create a critical size defect (4 mm diameter and 5 mm depth), and then hydrogels and sponges implanted. Both structures followed different processing methods. The hydrogels were injected allowing in situ  crosslinking. Unlike, the spongy-like were pre-formed by freeze-drying. The studies concerning subcutaneous implantation and critical size OC defect were performed for 2 and 4 weeks time, respectively. Cellular behavior and inflammatory responses were assessed by means of histology staining and biochemical function and matrix deposition by immunohistochemistry. Additionally, both OC structures stability and new cartilage and bone formation were evaluated by using vivo- computed tomography (Scanco 80). The results showed no acute inflammatory response for both approaches. New tissue formation and integration in the adjacent tissues were also observed, which present different characteristic behaviors when comparing hydrogels and sponges response. As future insights, a novel strategy for regeneration of OC defects can be designed encompassing both, hydrogels and spongy-like structures and cellular approaches. References: 1. Espregueira-Mendes J. et al. Osteochondral transplantation using autografts from the upper tibio-fibular joint for the treatment of knee cartilage lesions. Knee Surgery, Sports Traumatology, Arthroscopy 20,1136, 2012. 2. Oliveira JM. et al, Novel hydroxyapatite/chitosan bilayered scaffold for osteochondral tissue-engineering applications: Scaffold design and its performance when seeded with goat bone marrow stromal cells. Biomaterials 27, 6123, 2006. 3. Pereira D R. et al. Gellan Gum-Based Hydrogel Bilayered Scaffolds for Osteochondral Tissue Engineering. Key Engineering Materials 587, 255, 2013.

A continuous solvent- and oil-free method to prepare injectable PEGylated fibrinogen cell-laden microparticles

Injectable biomaterials with in situ cross-linking reactions have been suggested to minimize the invasiveness associated with most implantation procedures. However, problems related with the rapid liquid-to-gel transition reaction can arise because it is difficult to predict the reliability of the reaction and its end products, as well as to mitigate cytotoxicity to the surrounding tissues. An alternative minimally invasive approach to deliver solid implants in vivo is based on injectable microparticles, which can be processed in vitro with high fidelity and reliability, while showing low cytotoxicity. Their delivery to the defect can be performed by injection through a small diameter syringe needle. We present a new methodology for the continuous, solvent- and oil-free production of photopolymerizable microparticles containing encapsulated human dermal fibroblasts. A precursor solution of cells in photo-reactive PEG-fibrinogen (PF) polymer was transported through a transparent injector exposed to light-irradiation before being atomized in a jet-in-air nozzle. Shear rheometry data provided the cross-linking kinetics of each PF/cell solution, which was then used to determine the amount of irradiation required to partially polymerize the mixture prior to atomization. The partially polymerized drops fell into a gelation bath for further polymerization. The system was capable of producing cell-laden microparticles with high cellular viability, with an average diameter of between 88.1 µm to 347.1 µm and a dispersity of between 1.1 and 2.4, depending on the parameters chosen.

In-line rheo-optical characterization during small-scale polymer processing and compounding

As increasingly more sophisticated materials and products are being developed and times-to-market need to be minimized, it is important to make available fast response characterization tools using small amounts of sample, capable of conveying data on the relationships between rheological response, process-induced material structure and product characteristics. For this purpose, a single / twin-screw mini-extrusion system of modular construction, with well-controlled outputs in the range 30-300 g/h, was coupled to a in- house developed rheo-optical slit die able to measure shear viscosity and normal-stress differences, as well as performing rheo-optical experiments, namely small angle light scattering (SALS) and polarized optical microscopy (POM). In addition, the mini-extruder is equipped with ports that allow sample collection, and the extrudate can be further processed into products to be tested later. Here, we present the concept and experimental set-up [1, 2]. As a typical application, we report on the characterization of the processing of a polymer blend and of the properties of extruded sheets. The morphological evolution of a PS/PMMA industrial blend along the extruder, the flow-induced structures developed and the corresponding rheological characteristics are presented, together with the mechanical and structural characteristics of produced sheets. The application of this experimental tool to other material systems will also be discussed.

Microinjection molding of polyamide 6/carbon nanotube composites

Microinjection molding of polymer composites with carbon nanotubes (CNT) requires previous production of the nanocomposites, often by melt extrusion. Each processing step has a thermo-mechanical effect on the polymer melt, conveying different properties to the final product. In this work, polyamide 6 and its composites with pristine and functionalized CNT (f-CNT) were processed by a mini twin-screw extrusion, followed by microinjection molding. The morphology induced on the polymer by each process was analyzed by differential scanning calorimetry and wide angle X-ray diffraction. Calorimetric analysis showed a secondary crystallization for the microinjected materials, absent for the extruded materials. The characterization of microinjected polyamide 6 by X-ray diffraction revealed a large contribution of the c phase to the total crystallinity, mainly in the skin region, while the nanocomposites and extruded materials were characterized by a larger contribution of the a phase. Functionalization of CNT did not affect significantly the polymer morphology compared to composites with pristine CNT.

La dimensione di diritto fondamentale della maternità nel Diritto dell’Unione: politiche europee di conciliazione della vita famigliare e della vita professionale in tempo di crisi

Dissertação de mestrado em Direito da União Europeia

Understanding the dispersion of fillers in polymer matrices

Understanding the mixing process of complex composite materials is fundamental in several industrial processes. For instance, the dispersion of fillers in polymer melt matrices is commonly employed to manufacture polymer composites, using a twin-screw extruder. The effectiveness of the filler dispersion depends not only on the complex flow patterns generated, but also on the polymer melt rheological behavior. Therefore, the availability of a numerical tool able to predict mixing, taking into account both fluid and particles phases would be very useful to increase the process insight, and thus provide useful guidelines for its optimization. In this work, a new Eulerian-Lagrangian numerical solver is developed OpenFOAM® computational library, and used to better understand the mechanisms determining the dispersion of fillers in polymer matrices. Particular attention will be given to the effect of the rheological model used to represent the fluid behavior, on the level of dispersion obtained. For the Eulerian phase the averaged volume fraction governing equations (conservation of mass and linear momentum) are used to describe the fluid behavior. In the case of the Lagrangian phase, Newton’s second law of motion is used to compute the particles trajectories and velocity. To study the effect of fluid behavior on the filler dispersion, several systems are modeled considering different fluid types (generalized Newtonian or viscoelastic) and particles volume fraction and size. The results obtained are used to correlate the fluid and particle characteristics on the effectiveness of mixing and morphology obtained.

Improvign mixing processes with the help of numerical tools

In several industrial applications, highly complex behaviour materials are used together with intricate mixing processes, which difficult the achievement of the desired properties for the produced materials. This is the case of the well-known dispersion of nano-sized fillers in a melt polymer matrix, used to improve the nanocomposite mechanical and/or electrical properties. This mixing is usually performed in twin-screw extruders, that promote complex flow patterns, and, since an in loco analysis of the material evolution and mixing is difficult to perform, numerical tools can be very useful to predict the evolution and behaviour of the material. This work presents a numerical based study to improve the understanding of mixing processes. Initial numerical studies were performed with generalized Newtonian fluids, but, due to the null relaxation time that characterize this type of fluids, the assumption of viscoelastic behavior was required. Therefore, the polymer melt was rheologically characterized, and, a six mode Phan-Thien-Tanner and Giesekus models were used to fit the rheological data. These viscoelastic rheological models were used to model the process. The conclusions obtained in this work provide additional and useful data to correlate the type and intensity of the deformation history promoted to the polymer nanocomposite and the quality of the mixing obtained.

Synthesis, physical and magnetic properties of BaFe12O19/P(VDF-TrFE) multifunctional composites

Composite films with filler microparticles of Barium ferrite dispersed within P(VDF-TrFE) as polymeric matrix have been prepared by solvent evaporation. The lowest BaFO content of 1% wt acts as a small defect within the polymeric matrix, reducing the values of the dielectric and mechanical properties of the pure P(VDF-TrFE). For filler contents up to a 20%, the BaFO filler reinforces the matrix and measured properties increase their values. This trend is not followed by the electrical conductivity. We extended the study to fibers composed by BaFe12O19 microparticles in a PVDF matrix. Due to the big size of BaFO particles (1 micron in diameter), proper fabrication of the fiber shaped composites has not been achieved. We found that true BaFO content are always lower than nominal ones. Results are discussed in terms of the influence of size and morphology of the BaFO particles on the initial properties of the polymeric matrix.

Electronic transport across linear defects in graphene

We investigate the low-energy electronic transport across grain boundaries in graphene ribbons and infinite flakes. Using the recursive Green’s function method, we calculate the electronic transmission across different types of grain boundaries in graphene ribbons. We show results for the charge density distribution and the current flow along the ribbon. We study linear defects at various angles with the ribbon direction, as well as overlaps of two monolayer ribbon domains forming a bilayer region. For a class of extended defect lines with periodicity 3, an analytic approach is developed to study transport in infinite flakes. This class of extended grain boundaries is particularly interesting, since the K and K0 Dirac points are superposed.

Implementação de um sistema de abastecimento logístico numa empresa de cilindros de aço

Dissertação de mestrado integrado em Engenharia e Gestão Industrial

Pseudomonas aeruginosa diversification during infection development in cystic fibrosis lungs

Dissertação de mestrado integrado em Engenharia Biomédica (área de especialização em Engenharia Clínica)

Scarless laparoscopic repair of epigastric hernia in children

Background Despite the small size of the incision, the scar left by open repair of epigastric hernia in children is unaesthetic. Few laparoscopic approaches to epigastric hernia repair have been previously proposed, but none has gain wide acceptance from pediatric surgeons. In this study, we present our experience with a scarless laparo- scopic approach using a percutaneous suturing technique for epigastric hernia repair in children. Methods Ten consecutive patients presenting with epi- gastric hernia 15 mm or further from the umbilicus were submitted to laparoscopic hernia repair. A 5-mm 308-angle laparoscope is introduced through a umbilical trocar and a 3-mm laparoscopic dissector is introduced through a stab incision in the right flank. After opening and dissecting the parietal peritoneum, the fascial defect is identified and closed using 2–0 polyglactin thread through a percutaneous suturing technique. Intraoperative and postoperative clinical data were collected. Results All patients were successfully submitted to la- paroscopic epigastric hernia repair. Median age at surgery was 79 months old and the median distance from the um- bilicus to the epigastric defect was 4 cm. Operative time ranged from 35 to 75 min. Every hernia was successfully closed without any incidents. Follow-up period ranges from 2 to 12 months. No postoperative complications or recurrence was registered. No scar was visible in these patients. Conclusion This scarless laparoscopic technique for epi- gastric hernia repair is safe and reliable. We believe this technique might become gold standard of care in the near future.

Development of advanced cell/tissue culture systems, based on enhanced polymeric scaffolds and sophisticated bioreactors, for tissue engineering applications

Programa Doutoral em Engenharia Biomédica

Lower NPAS3 expression during the later stages of abnormal lung development in rat congenital diaphragmatic hernia

Purpose Congenital diaphragmatic hernia (CDH) is characterized by a developmental defect in the diaphragm, pulmonary hypoplasia and pulmonary hypertension. NPAS3 is a PAS domain transcription factor regulating Drosophila tracheogenesis. NPAS3 null mice develop pulmonary hypoplasia in utero and die after birth due to respiratory failure. We aimed to evaluate NPAS3 expres- sion during normal and abnormal lung development due to CDH. Methods CDH was induced by administering 100 mg/ml nitrofen to time-pregnant dams on embryonic day (E) 9 of gestation. Lungs were isolated on E15, E18 and E21 and NPAS3 localization was determined by immunohisto- chemistry and quantified using Western blotting. Results We found that only E21 hypoplastic CDH lungs have reduced expression of NPAS3 in the terminal sac- cules. Western blotting confirmed the down-regulation of NPAS3 protein in the nitrofen-induced hypoplastic lungs. Conclusions We demonstrate for the first time that ni- trofen-induced hypoplastic CDH lungs have reduced NPAS3 expression in the terminal saccules during the later stages of abnormal lung development. Our findings suggest that NPAS3 is associated with pulmonary hypoplasia in CDH.