DEVELOPMENT OF LASER MICRO-FABRICATED SURFACES TO ACCELERATE & ENHANCE ENDOTHELIAL CELL ADHESION AND PROLIFERATION

The aim of this thesis was to develop novel indirect laser micro-textured polymer substrates to accelerate and enhance bovine aorta endothelium (BAE-1) cell adhesion and proliferation. The response of BAE-1 and human coronary smooth muscle cells (HCASMCs) were studied, including cell adhesion, proliferation, β-actin expression, migration velocity, and migration directionality. The laser used in these experiments was a SPI infrared solid state fibre laser. By using beam overlapping scanning strategies surfaces having two types of distinct surface features were produced: (i) microfringes and (ii) microripples. Through a series of laser parameter optimisation experiments control of the melt expulsion mechanism and the formation of an intact recast ring could be generated. Overlapping of the focused beam resulted in an overlapping of the recast rings, thus resulting in surfaces having microripple and microfringe features. Experimental results found that polyurethane 1A, which has a projecting topography of ~4μm width microfringes, significantly increased BAE-1 cell adhesion, proliferation, and β-actin expression, compared to the non-textured surface. However, strong adhesion to this surface decreased mean cell migration velocity. Furthermore, focal adhesions were confined to the microfringe structure leading to the formation of parallel actin stress fibres and as a result changed the cell migration directionality. On the other hand, Polyurethane 3D, which has a projecting topography of ~6μm width microripples, was also found to significantly enhance BAE-1 cell proliferation (only at 72 hours post cell seeding), β-actin expression and migration velocity, when compared to the non-textured polyurethane. Differences were also found between BAE-1 and HCASMCs cells. HCASMCs were less sensitive to the polymer substrates and were not found to be influenced by the microfringe and microripple structures. However, the microridges with >700nm height on polyurethane 1A, 3A and 3D were found to promote HCASMC alignment parallel to the microridges. In addition, the Z1A1 polyurethane used for pattern transfer through polymer casting has shown delayed HCASMCs adhesion. Further investigation is required to study the effect of Z1A1 polyurethane’s chemical properties on HCASMACs behaviour. Overall, the data obtained from this work, suggests that the width dimension of the microfringes and microripples between ~4-6μm are important regulators for BAE-1 behaviour and microridge heights >700nm are important regulators for HCASMCs alignment. The preliminary data provided from this work can be used for stent technology development in the future

Learning activation functions from data using cubic spline interpolation

Neural networks require a careful design in order to perform properly on a given task. In particular, selecting a good activation function (possibly in a data-dependent fashion) is a crucial step, which remains an open problem in the research community. Despite a large amount of investigations, most current implementations simply select one fixed function from a small set of candidates, which is not adapted during training, and is shared among all neurons throughout the different layers. However, neither two of these assumptions can be supposed optimal in practice. In this paper, we present a principled way to have data-dependent adaptation of the activation functions, which is performed independently for each neuron. This is achieved by leveraging over past and present advances on cubic spline interpolation, allowing for local adaptation of the functions around their regions of use. The resulting algorithm is relatively cheap to implement, and overfitting is counterbalanced by the inclusion of a novel damping criterion, which penalizes unwanted oscillations from a predefined shape. Experimental results validate the proposal over two well-known benchmarks.Comment: Submitted to the 27th Italian Workshop on Neural Networks (WIRN 2017

Carbon dioxide fluxes across the Sierra de Guadarrama, Spain

Understanding the spatial and temporal variation in soil respiration within small geographic areas is essential to accurately assess the carbon budget on a global scale. In this study, we investigated the factors controlling soil respiration in an altitudinal gradient in a southern Mediterranean mixed pine–oak forest ecosystem in the north face of the Sierra de Guadarrama in Spain. Soil respiration was measured in five Pinus sylvestris L. plots over a period of 1 year by means of a closed dynamic system (LI-COR 6400). Soil temperature and water content were measured at the same time as soil respiration. Other soil physico-chemical and microbiological properties were measured during the study. Measured soil respiration ranged from 6.8 to 1.4 lmol m-2 s-1, showing the highest values at plots situated at higher elevation. Q10 values ranged between 1.30 and 2.04, while R10 values ranged between 2.0 and 3.6. The results indicate that the seasonal variation of soil respiration was mainly controlled by soil temperature and moisture. Among sites, soil carbon and nitrogen stocks regulate soil respiration in addition to soil temperature and moisture. Our results suggest that application of standard models to estimate soil respiration for small geographic areas may not be adequate unless other factors are considered in addition to soil temperature

Obesity as Assessed by Body Adiposity Index and Multivariable Cardiovascular Disease Risk

To assess the role of body adiposity index (BAI) in predicting cardiovascular disease (CVD) and coronary heart disease (CHD) mortality, in comparison with body mass index (BMI), waist circumference (WC), and the waist circumference to hip circumference ratio (WHR). This study was a prospective 15 year mortality follow-up of 4175 Australian males, free of heart disease, diabetes and stroke. The Framingham Risk Scores (FRS) for CHD and CVD death were calculated at baseline for all subjects. Multivariable logistic regression was used to assess the effects of the measures of obesity on CVD and CHD mortality, before adjustment and after adjustment for FRS. The predictive ability of BAI, though present in the unadjusted analyses, was generally not significant after adjustment for age and FRS for both CVD and CHD mortality. BMI behaved similarly to BAI in that its predictive ability was generally not significant after adjustments. Both WC and WHR were significant predictors of CVD and CHD mortality and remained significant after adjustment for covariates. BAI appeared to be of potential interest as a measure of % body fat and of obesity, but was ineffective in predicting CVD and CHD

A global view of drug-therapy interactions

Network science is already making an impact on the study of complex systems and offers a promising variety of tools to understand their formation and evolution (1-4) in many disparate fields from large communication networks (5,6), transportation infrastructures (7) and social communities (8,9) to biological systems (1,10,11). Even though new highthroughput technologies have rapidly been generating large amounts of genomic data, drug design has not followed the same development, and it is still complicated and expensive to develop new single-target drugs. Nevertheless, recent approaches suggest that multi-target drug design combined with a network-dependent approach and large-scale systems-oriented strategies (12-14) create a promising framework to combat complex multigenetic disorders like cancer or diabetes. Here, we investigate the human network corresponding to the interactions between all US approved drugs and human therapies, defined by known drug-therapy relationships. Our results show that the key paths in this network are shorter than three steps, indicating that distant therapies are separated by a surprisingly low number of chemical compounds. We also identify a sub-network composed by drugs with high centrality measures (15), which represent the structural back-bone of the drug-therapy system and act as hubs routing information between distant parts of the network. These findings provide for the first time a global map of the largescale organization of all known drugs and associated therapies, bringing new insights on possible strategies for future drug development. Special attention should be given to drugs which combine the two properties of (a) having a high centrality value and (b) acting on multiple targets.Comment: 16 pages, 4 figures. It was submitted to peer review on August 15, 200

Burstiness and tie activation strategies in time-varying social networks

The recent developments in the field of social networks shifted the focus from static to dynamical representations, calling for new methods for their analysis and modelling. Observations in real social systems identified two main mechanisms that play a primary role in networks' evolution and influence ongoing spreading processes: the strategies individuals adopt when selecting between new or old social ties, and the bursty nature of the social activity setting the pace of these choices. We introduce a time-varying network model accounting both for ties selection and burstiness and we analytically study its phase diagram. The interplay of the two effects is non trivial and, interestingly, the effects of burstiness might be suppressed in regimes where individuals exhibit a strong preference towards previously activated ties. The results are tested against numerical simulations and compared with two empirical datasets with very good agreement. Consequently, the framework provides a principled method to classify the temporal features of real networks, and thus yields new insights to elucidate the effects of social dynamics on spreading processes

Targeting vaccinations for the licensed dengue vaccine: considerations for serosurvey design

Background The CYD-TDV vaccine was unusual in that the recommended target population for vaccination was originally defined not only by age, but also by transmission setting as defined by seroprevalence. WHO originally recommended countries consider vaccination against dengue with CYD-TDV vaccine in geographic settings only where prior infection with any dengue serotype, as measured by seroprevalence, was >170% in the target age group. Vaccine was not recommended in settings where seroprevalence was <50%. Test-and-vaccinate strategies suggested following new analysis by Sanofi will still require age-stratified seroprevalence surveys to optimise age-group targeting. Here we address considerations for serosurvey design in the context of vaccination program planning. Methods To explore how the design of seroprevalence surveys affects estimates of transmission intensity, 100 age-specific seroprevalence surveys were simulated using a beta-binomial distribution and a simple catalytic model for different combinations of age-range, survey size, transmission setting, and test sensitivity/specificity. We then used a Metropolis-Hastings Markov Chain Monte-Carlo algorithm to estimate the force of infection from each simulated dataset. Results Sampling from a wide age-range led to more accurate estimates than merely increasing sample size in a narrow age-range. This finding was consistent across all transmission settings. The optimum test sensitivity and specificity given an imperfect test differed by setting with high sensitivity being important in high transmission settings and high specificity important in low transmission settings. Conclusions When assessing vaccination suitability by seroprevalence surveys, countries should ensure an appropriate age-range is sampled, considering epidemiological evidence about the local burden of disease

Search for anomalous t t-bar production in the highly-boosted all-hadronic final state

A search is presented for a massive particle, generically referred to as a Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are sufficiently massive to produce highly Lorentz-boosted top quarks, which yield collimated decay products that are partially or fully merged into single jets. The analysis uses new methods to analyze jet substructure, providing suppression of the non-top multijet backgrounds. The analysis is based on a data sample of proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits in the range of 1 pb are set on the product of the production cross section and branching fraction for a topcolor Z' modeled for several widths, as well as for a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any enhancement in t t-bar production beyond expectations of the standard model for t t-bar invariant masses larger than 1 TeV.Comment: Submitted to the Journal of High Energy Physics; this version includes a minor typo correction that will be submitted as an erratu

Novel metallic implantation technique for osteochondral defects of the medial talar dome: A cadaver study

BACKGROUND AND PURPOSE: A metallic inlay implant (HemiCAP) with 15 offset sizes has been developed for the treatment of localized osteochondral defects of the medial talar dome. The aim of this study was to test the following hypotheses: (1) a matching offset size is available for each talus, (2) the prosthetic device can be reproducibly implanted slightly recessed in relation to the talar cartilage level, and (3) with this implantation level, excessive contact pressures on the opposite tibial cartilage are avoided. METHODS: The prosthetic device was implanted in 11 intact fresh-frozen human cadaver ankles, aiming its surface 0.5 mm below cartilage level. The implantation level was measured at 4 margins of each implant. Intraarticular contact pressures were measured before and after implantation, with compressive forces of 1,000-2,000 N and the ankle joint in plantigrade position, 10 dorsiflexion, and 14 plantar flexion. RESULTS: There was a matching offset size available for each specimen. The mean implantation level was 0.45 (SD 0.18) mm below the cartilage surface. The defect area accounted for a median of 3% (0.02-18) of the total ankle contact pressure before implantation. This was reduced to 0.1% (0.02-13) after prosthetic implantation. INTERPRETATION: These results suggest that the implant can be applied clinically in a safe way, with appropriate offset sizes for various talar domes and without excessive pressure on the opposite cartilag

Vital function of PRELI and essential requirement of its LEA motif

Proteins containing the late embryogenesis abundant (LEA) motif comprise a conserved family, postulated to act as cell protectors. However, their function and mechanisms of action remain unclear. Here we show that PRELI, a mammalian LEA-containing homolog of yeast Ups1p, can associate with dynamin-like GTPase Optic Atrophy-1 (OPA1) and contribute to the maintenance of mitochondrial morphology. Accordingly, PRELI can uphold mitochondrial membrane potential (ΔΨm) and enhance respiratory chain (RC) function, shown by its capacity to induce complex-I/NADH dehydrogenase and ATP synthase expression, increase oxygen consumption and reduce reactive oxygen species (ROS) production. PRELI can also inhibit cell death induced by STS, TNF-α or UV irradiation. Moreover, in vitro and in vivo dominant-negative overexpression of mutant PRELI/LEA− (lacking the LEA motif) and transient in vitro PRELI-specific knockdown can render lymphocytes vulnerable to apoptosis, cause mouse embryo lethality and revert the resistance of lymphoma cells to induced death. Collectively, these data support the long-presumed notion of LEA protein-dependent mechanisms of cytoprotection and suggest that PRELI interacts with OPA1 to maintain mitochondria structures intact, sustain balanced ion−/proton+ gradients, promote oxidative phosphorylation reactions, regulate pro- and antiapoptotic protein traffic and enable cell responses to induced death. These findings may help to understand how bioenergetics is mechanistically connected with cell survival cues