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- Experimentally driven atomistic model of 1,2 polybutadienePublication . Gkourmpis, Thomas; Mitchell, Geoffrey R.We present an efficient method of combining wide angle neutron scattering data with detailed atomistic models, allowing us to perform a quantitative and qualitative mapping of the organisation of the chain conformation in both glass and liquid phases. The structural refinement method presented in this work is based on the exploitation of the intrachain features of the diffraction pattern and its intimate linkage with atomistic models by the use of internal coordinates for bond lengths, valence angles, and torsion rotations. Atomic connectivity is defined through these coordinates that are in turn assigned by pre-defined probability distributions, thus allowing for the models in question to be built stochastically. Incremental variation of these coordinates allows for the construction of models that minimise the differences between the observed and calculated structure factors. We present a series of neutron scattering data of 1,2 polybutadiene at the region 120–400 K. Analysis of the experimental data yields bond lengths for CC and C C of 1.54 Å and 1.35 Å, respectively. Valence angles of the backbone were found to be at 112° and the torsion distributions are characterised by five rotational states, a three-fold trans-skew± for the backbone and gauche± for the vinyl group. Rotational states of the vinyl group were found to be equally populated, indicating a largely atactic chan. The two backbone torsion angles exhibit different behaviour with respect to temperature of their trans population, with one of them adopting an almost all trans sequence. Consequently, the resulting configuration leads to a rather persistent chain, something indicated by the value of the characteristic ratio extrapolated from the model. We compare our results with theoretical predictions, computer simulations, RIS models and previously reported experimental results.
- Influence of commensal bacteria on the proteolytic and antigenic profiles of INFOGEST-like digested wheat gliadinPublication . Pereira-Costa, Flávio; Domingues, Vanessa S.; Roque, Ana; Almeida, Zaida L.; Cruz, Pedro F.; Cordeiro, Rachel; Trindade, Daniela; Moura, Carla; Melo, Joana B.; Pereira, Sónia G.; Vaz, Daniela C.Introduction: Celiac disease (CeD) is a chronic autoimmune enteropathy developed by genetically predisposed individuals when exposed to gluten. Gluten gliadins, along with gut microbiota, may influence CeD onset and progression through mechanisms that remain unclear. Methods: Gliadin-degrading bacterial isolates obtained from CeD patients, and their 1st-degree relatives’ stool and blood were identified (Bacillus tropicus, Enterococcus faecalis, Micrococcus sp., Cronobacter sakazakii, Pseudomonas aeruginosa, and Serratia marcescens) and used in an INFOGEST-like protocol to simulate gliadin digestion after 4 h (digested gliadin, d-gliadin). The d-gliadin digesta were analyzed by fast protein liquid chromatography (FPLC), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), fluorescence spectroscopy, and polyclonal and monoclonal (R5 and G12) enzyme-linked immunosorbent assays (ELISA). Results and discussion: In the absence of the bacterial isolates, gliadin is poorly digested and self-assembles within 1 day into intermediate and large protein oligomers/aggregates, enriched in β-sheet structure (FTIR amide I band between 1,600 and 1,700 cm−1) and able to bind thioflavin T and Congo red. Conversely, in the presence of the bacterial isolates, gliadin is further digested, leading to an increase in protein fragments. After 4 h, the P. aeruginosa, C. sakazakii, and B. tropicus d-gliadin digesta presented a mixture of d-gliadin peptides and aggregates that showed higher antigenicity (associated with the exposure of the 5-amino acid QQPFP and 6-amino acid QPQLPY epitopes, present in the 25-mer and 33-mer, respectively) than control digestions (without bacteria), while E. faecalis led to lower antigenicity. In turn, within 24 h of incubation, all bacterial isolates led to the formation of undigested material with lower antigenicity, either due to fewer 33-mers and 25-mers in solution, or to fragment aggregation into amorphous material, not exposing antigenic sequences. Hence, intestinal flora may enhance or diminish the antigenicity of gliadin, thereby modulating the immunogenic response to gliadin/gluten.
- Fabrication and characterisation of PCL and PCL/PLA scaffolds for tissue engineeringPublication . Patrício, T.; Domingos, M.; Gloria, A.; D'Amora, U.; Coelho, J. F.; Bartolo, P.J.Purpose – The main purpose of this research work is to study the effect of poly lactic acid (PLA) addition into poly (e-caprolactone) (PCL) matrices, as well the influence of the mixing process on the morphological, thermal, chemical, mechanical and biological performance of the 3D constructs produced with a novel biomanufacturing device (BioCell Printing). Design/methodology/approach – Two mixing processes are used to prepare PCL/PLA blends, namely melt blending and solvent casting. PCL and PCL/PLA scaffolds are produced via BioCell Printing using a 300-mm nozzle, 0/908 lay down pattern and 350-mm pore size. Several techniques such as scanning electron microscopy (SEM), simultaneous thermal analyzer (STA), nuclear magnetic resonance (NMR), static compression analysis and Alamar BlueTM are used to evaluate scaffold’s morphological, thermal, chemical, mechanical and biological properties. Findings – Results show that the addition of PLA to PCL scaffolds strongly improves the biomechanical performance of the constructs. Additionally, polymer blends obtained by solvent casting present better mechanical and biological properties, compared to blends prepared by melt blending. Originality/value – This paper undertakes a detailed study on the effect of the mixing process on the biomechanical properties of PCL/PLA scaffolds. Results will enable to prepare customized PCL/PLA scaffolds for tissue engineering applications with improved biological and mechanical properties, compared to PCL scaffolds alone. Additionally, the accuracy and reproducibility of by the BioCell Printing enables to modulate the micro/macro architecture of the scaffolds enhancing tissue regeneration.
- MSCs Conditioned Media and Umbilical Cord Blood Plasma Metabolomics and CompositionPublication . Pereira, Tiago; Ivanova, Galya; Caseiro, Ana Rita; Barbosa, Paula; Bártolo, Paulo Jorge; Santos, José Domingos; Luís, Ana Lúcia; Maurício, Ana Colette; Ivanovic, ZoranHuman mesenchymal stem cells (hMSCs) from umbilical cord (UC) blood (UCB) and matrix are tested clinically for a variety of pathologies but in vitro expansion using culture media containing fetal bovine serum (FBS) is essential to achieve appropriate cell numbers for clinical use. Human UCB plasma (hUCBP) can be used as a supplement for hMSCs culture, since UCB is rich in soluble growth factors and due to worldwide increased number of cryopreserved UCB units in public and private banks, without the disadvantages listed for FBS. On the other hand, the culture media enriched in growth factors produced by these hMSCs in expansion (Conditioned medium - CM) can be an alternative to hMSCs application. The CM of the hMSCs from the UC might be a better therapeutic option compared to cell transplantation, as it can benefit from the local tissue response to the secreted molecules without the difficulties and complications associated to the engraftment of the allo- or xeno-transplanted cells. These facts drove us to know the detailed composition of the hUCBP and CM, by 1H-NMR and Multiplexing LASER Bead Technology. hUCBP is an adequate alternative for the FBS and the CM and hUCBP are important sources of growth factors, which can be used in MSCs-based therapies. Some of the major proliferative, chemotactic and immunomodulatory soluble factors (TGF-β, G-CSF, GM-CSF, MCP-1, IL-6, IL-8) were detected in high concentrations in CM and even higher in hUCBP. The results from 1H-NMR spectroscopic analysis of CM endorsed a better understanding of hMSCs metabolism during in vitro culture, and the relative composition of several metabolites present in CM and hUCBP was obtained. The data reinforces the potential use of hUCBP and CM in tissue regeneration and focus the possible use of hUCBP as a substitute for the FBS used in hMSCs in vitro culture.
- Semidirect Products and Split Short Five Lemma in Normal CategoriesPublication . Martins-Ferreira, Nelson; Montoli, Andrea; Sobral, ManuelaIn this paper we study a generalization of the notion of categorical semidirect product, as defined in [6], to a non-protomodular context of categories where internal actions are induced by points, like in any pointed variety. There we define semidirect products only for regular points, in the sense we explain below, provided the Split Short Five Lemma between such points holds, and we show that this is the case if the category is normal, as defined in [12]. Finally, we give an example of a category that is neither protomodular nor Mal’tsev where such generalized semidirect products exist.
- A Decomposition Formula for the Weighted CommutatorPublication . Martins-Ferreira, Nelson; Van der Linden, TimWe decompose the weighted subobject commutator of M. Gran, G. Janelidze and A. Ursini as a join of a binary and a ternary commutator.
- Computer modelling and simulation of a bioreactor for tissue engineeringPublication . Pereira, Rúben F.; Freitas, Dino; Tojeira, Ana; Almeida, Henrique A.; Alves, Nuno; Bartolo, Paulo J.A conventional approach to tissue engineering involves the implantation of porous, biodegradable and biocompatible scaffolds seeded with cells into the defect site. In some strategies, tissue engineering requires the in vitro culture of tissueengineering constructs for implantation later. In this case, bioreactors are used to grow 3D tissues under controlled and monitored conditions. However, the quality of the resulting 3D tissue is highly dependent on the design and dimensions of the bioreactor, as well on the operating conditions. In this work, a computational fluid dynamic software package was used to investigate the influence of cylindrical bioreactor dimensions (length and diameter) on the fluid flow and scaffold shear stress. Computer simulations were performed using three different rotational movements (horizontal, vertical and biaxial rotation) and appropriate boundary conditions. Results show that the effect of the bioreactor length on the scaffold shear stress is more important than the diameter, while high length is associated to low scaffold shear stress. On the other hand, the fluid flows within the bioreactor and scaffold shear stresses are dependent on the rotational movement, being more uniform in the biaxial rotation due to the combination of rotational movements.
- Collagen surface modified poly(ε-caprolactone) scaffolds with improved hydrophilicity and cell adhesion propertiesPublication . Sousa, Inês; Mendes, Ausenda; Pereira, Rúben F.; Bártolo, Paulo J.Poly(ε-caprolactone) (PCL)/collagen scaffolds were produced using a four-step procedure comprising (i) the fabrication of PCL scaffolds through an additive bioextrusion system, (ii) the PCL surface modification using a plasma treatment, (iii) the acrylic acid (AAc) grafting by ultraviolet (UV) polymerization, and (iv) the immobilization of collagen into the scaffold surface through the carbodiimide chemistry. This procedure allowed the quick fabrication of highly porous scaffolds with interconnected pores, well-defined internal architecture and improved cell adhesion properties. The immobilization of collagen into the PCL surface led to a significant enhancement in the hydrophilicity, while the biological tests showed a further improvement in the adhesion of fibroblast cells. These results indicate that the collagen surface modification is an effective strategy to render the hydrophobic nature of PCL and overcome the limited cell interaction of 3D PCL scaffolds.
- Interlaminar fracture in woven carbon/epoxy laminatesPublication . Reis, Paulo N. B. ; Ferreira, José A. M. ; Costa, José D. M. ; Pereira, António M.This paper describes an experimental study developed to characterize the mode I and mode II fracture toughness of carbon/epoxy woven composites, using DCB and ENF tests, respectively. The laminates were manufactured using an epoxy resin and twelve woven balanced bi-directional layers of carbon fibres, all of them with the same orientation (0/90º). Significant instantaneous delaminations were observed particularly for the DCB specimen, which were responsible for an oscillatory behaviour of GI versus crack length. The maximum values obtained for GIC and GIIC were 281 and 1800 J/m2, respectively.
- Tethered Swimming Can Be Used to Evaluate Force Contribution for Short-Distance Swimming PerformancePublication . Morouço, Pedro G.; Marinho, Daniel A.; Keskinen, Kari L.; Badillo, Juan J.; Marques, Mário C.Morouço, PG, Marinho, DA, Keskinen, KL, Badillo, JJ, and Marques, MC. Tethered swimming can be used to evaluate force contribution for short-distance swimming performance. J Strength Cond Res 28(11): 3093-3099, 2014-The purpose of this study was two-fold: (a) to compare stroke and the physiological responses between maximal tethered and free front crawl swimming and (b) to evaluate the contribution of force exertion for swimming performance over short distances. A total of 34 male swimmers, representing various levels of competitive performance, participated in this study. Each participant was tested in both a 30-second maximal tethered swimming test and a 50-m free swimming test. The tethered force parameters, the swimming speed, stroke (stroke rate [SR]), and the physiological responses (increase in blood lactate concentration [ΔBLa], heart rate, and rate of perceived exertion) were recorded and calculated. The results showed no differences in stroke and the physiological responses between tethered and free swimming, with a high level of agreement for the SR and DBLa. A strong correlation was obtained between the maximum impulse of force per stroke and the speed (r = 0.91; p < 0.001). Multiple regression analysis revealed that the maximum impulse and SR in the tethered condition explained 84% of the free swimming performance. The relationship between the swimming speed and maximum force tended to be nonlinear, whereas linear relationships were observed with the maximum impulse. This study demonstrates that tethered swimming does not significantly alter stroke and the physiological responses compared with free swimming, and that the maximum impulse per stroke should be used to evaluate the balance between force and the ability to effectively apply force during sprint swimming. Consequently, coaches can rely on tethered forces to identify strength deficits and improve swimming performance over short distances.