Integration of geometric consistency contributory factors in three-leg junctions collision prediction models of Portuguese two-lane national highways

This paper aims at developing a collision prediction model for three-leg junctions located in national roads (NR) in Northern Portugal. The focus is to identify factors that contribute for collision type crashes in those locations, mainly factors related to road geometric consistency, since literature is scarce on those, and to research the impact of three modeling methods: generalized estimating equations, random-effects negative binomial models and random-parameters negative binomial models, on the factors of those models. The database used included data published between 2008 and 2010 of 177 three-leg junctions. It was split in three groups of contributing factors which were tested sequentially for each of the adopted models: at first only traffic, then, traffic and the geometric characteristics of the junctions within their area of influence; and, lastly, factors which show the difference between the geometric characteristics of the segments boarding the junctionsâ area of influence and the segment included in that area were added. The choice of the best modeling technique was supported by the result of a cross validation made to ascertain the best model for the three sets of researched contributing factors. The models fitted with random-parameters negative binomial models had the best performance in the process. In the best models obtained for every modeling technique, the characteristics of the road environment, including proxy measures for the geometric consistency, along with traffic volume, contribute significantly to the number of collisions. Both the variables concerning junctions and the various national highway segments in their area of influence, as well as variations from those characteristics concerning roadway segments which border the already mentioned area of influence have proven their relevance and, therefore, there is a rightful need to incorporate the effect of geometric consistency in the three-leg junctions safety studies.

Tensile creep of a structural epoxy adhesive: experimental and analytical characterization

Epoxy adhesives are nowadays being extensively used in Civil Engineering applications, mostly in the scope of the rehabilitation of reinforced concrete (RC) structures. In this context, epoxy adhesives are used to provide adequate stress transference from fibre reinforced polymers (FRP) to the surrounding concrete substrate. Most recently, the possibility of using prestressed FRPs bonded with these epoxy adhesives is also being explored in order to maximize the potentialities of this strengthening approach. In this context, the understanding of the long term behaviour of the involved materials becomes essential. Even when non-prestressed FRPs are used a certain amount of stress is permanently applied on the adhesive interface during the serviceability conditions of the strengthened structure, and the creep of the adhesive may cause a continuous variation in the deformational response of the element. In this context, this paper presents a study aiming to experimentally characterize the tensile creep behaviour of an epoxy-based adhesive currently used in the strengthening of concrete structures with carbon FRP (CFRP) systems. To analytically describe the tensile creep behaviour, the modified Burgers model was fitted to the experimental creep curves, and the obtained results revealed that this model is capable of predicting with very good accuracy the long term behaviour of this material up to a sustained stress level of 60% of the adhesive’s tensile strength.

A spectrum-driven damage Identification technique : application and validation through the numerical simulation of the Z24 Bridge

The present paper focuses on a damage identification method based on the use of the second order spectral properties of the nodal response processes. The explicit dependence on the frequency content of the outputs power spectral densities makes them suitable for damage detection and localization. The well-known case study of the Z24 Bridge in Switzerland is chosen to apply and further investigate this technique with the aim of validating its reliability. Numerical simulations of the dynamic response of the structure subjected to different types of excitation are carried out to assess the variability of the spectrum-driven method with respect to both type and position of the excitation sources. The simulated data obtained from random vibrations, impulse, ramp and shaking forces, allowed to build the power spectrum matrix from which the main eigenparameters of reference and damage scenarios are extracted. Afterwards, complex eigenvectors and real eigenvalues are properly weighed and combined and a damage index based on the difference between spectral modes is computed to pinpoint the damage. Finally, a group of vibration-based damage identification methods are selected from the literature to compare the results obtained and to evaluate the performance of the spectral index.

Short-term corneal changes with gas-permeable contact lens wear in keratoconus subjects: a comparison of two fitting approaches

Purpose: To evaluate changes in anterior corneal topography and higher-order aberrations (HOA) after 14-days of rigid gas-permeable (RGP) contact lens (CL) wear in keratoconus subjects comparing two different fitting approaches. Methods: Thirty-one keratoconus subjects (50 eyes) without previous history of CL wear were recruited for the study. Subjects were randomly fitted to either an apical-touch or three-pointtouch fitting approach. The lens’ back optic zone radius (BOZR) was 0.4 mm and 0.1 mm flatter than the first definite apical clearance lens, respectively. Differences between the baseline and post-CL wear for steepest, flattest and average corneal power (ACP) readings, central corneal astigmatism (CCA), maximum tangential curvature (KTag), anterior corneal surface asphericity, anterior corneal surface HOA and thinnest corneal thickness measured with Pentacam were compared. Results: A statistically significant flattening was found over time on the flattest and steepest simulated keratometry and ACP in apical-touch group (all p < 0.01). A statistically significant reduction in KTag was found in both groups after contact lens wear (all p < 0.05). Significant reduction was found over time in CCA (p = 0.001) and anterior corneal asphericity in both groups (p < 0.001). Thickness at the thinnest corneal point increased significantly after CL wear (p < 0.0001). Coma-like and total HOA root mean square (RMS) error were significantly reduced following CL wearing in both fitting approaches (all p < 0.05). Conclusion: Short-term rigid gas-permeable CL wear flattens the anterior cornea, increases the thinnest corneal thickness and reduces anterior surface HOA in keratoconus subjects. Apicaltouch was associated with greater corneal flattening in comparison to three-point-touch lens wear.

Efficacy of a gas permeable contact lens to induce peripheral myopic defocus

Purpose. The purpose of this work was to evaluate the potential of a novel custom-designed rigid gas permeable (RGP) contact lens to modify the relative peripheral refractive error in a sample of myopic patients. Methods. Fifty-two right eyes of 52 myopic patients (mean [TSD] age, 21 [T2] years) with spherical refractive errors ranging from j0.75 to j8.00 diopters (D) and refractive astigmatism of 1.00 D or less were fitted with a novel experimental RGP (ExpRGP) lens designed to create myopic defocus in the peripheral retina. A standard RGP (StdRGP) lens was used as a control in the same eye. The relative peripheral refractive error was measured without the lens and with each of two lenses (StdRGP and ExpRGP) using an open-field autorefractometer from 30 degrees nasal to 30 degrees temporal, in 5-degree steps. The effectiveness of the lens design was evaluated as the amount of relative peripheral refractive error difference induced by the ExpRGP compared with no lens and with StdRGP conditions at 30 degrees in the nasal and temporal (averaged) peripheral visual fields. Results. Experimental RGP lens induced a significant change in relative peripheral refractive error compared with the nolens condition (baseline), beyond the 10 degrees of eccentricity to the nasal and temporal side of the visual field (p G 0.05). The maximum effect was achieved at 30 degrees. Wearing the ExpRGP lens, 60% of the eyes had peripheral myopia exceeding j1.00 D, whereas none of the eyes presented with this feature at baseline. There was no significant correlation (r = 0.04; p = 0.756) between the degree of myopia induced at 30 degrees of eccentricity of the visual field with the ExpRGP lens and the baseline refractive error. Conclusions. Custom-designed RGP contact lenses can generate a significant degree of relative peripheral myopia in myopic patients regardless of their baselin spherical equivalent refractive error.

Peripheral refraction with eye and head rotation with contact lenses

Purpose: To evaluate the impact of eye and head rotation in the measurement of peripheral refraction with an open-field autorefractometer in myopic eyes wearing two different center-distance designs of multifocal contact lenses (MFCLs). Methods: Nineteen right eyes from 19 myopic patients (average central M ± SD = −2.67 ± 1.66 D) aged 20–27 years (mean ± SD = 23.2 ± 3.3 years) were evaluated using a Grand-Seiko autorefractometer. Patients were fitted with one multifocal aspheric center-distance contact lens (Biofinity Multifocal D®) and with one multi-concentric MFCL (Acuvue Oasys for Presbyopia). Axial and peripheral refraction were evaluated by eye rotation and by head rotation under naked eye condition and with each MFCL fitted randomly and in independent sessions. Results: For the naked eye, refractive pattern (M, J0 and J45) across the central 60◦ of the horizontal visual field values did not show significant changes measured by rotating the eye or rotating the head (p > 0.05). Similar results were obtained wearing the Biofinity D, for both testing methods, no obtaining significant differences to M, J0 and J45 values (p > 0.05). For Acuvue Oasys for presbyopia, also no differences were found when comparing measurements obtained by eye and head rotation (p > 0.05). Multivariate analysis did not showed a significant interaction between testing method and lens type neither with measuring locations (MANOVA, p > 0.05). There were significant differences in M and J0 values between naked eyes and each MFCL. Conclusion: Measurements of peripheral refraction by rotating the eye or rotating the head in myopic patients wearing dominant design or multi-concentric multifocal silicone hydrogel contact lens are comparable.

Stabilization in early adult-onset myopia with corneal refractive therapy

Purpose: To describe the stabilization of early adult-onset myopia in three university students after initiating orthokeratology treatment with corneal refractive therapy contact lenses. Methods: Three Caucasian early adult-onset progressing myopic subjects (1 male, 2 females) were fitted with corneal refractive therapy lenses to correct myopia between ?1.50 and ?2.50 D of sphere using Paragon CRT (Paragon Vision Sciences, Mesa, AZ)lenses for overnight orthokeratology. The pre-treatment refractive history from 2005 as well as refraction and axial length after treatment onset are reported over a period of 3 years between December 2009 and January 2013 with an additional year of follow-up after treatment discontinuation (January–December 2013). The peripheral refractive patterns and topographic changes are also reported individually. Results: Treatment was successful in all three subjects achieving uncorrected visual acuity of 20/20 or better monocularly. During a period of 3 years of follow-up the subjects did not experience progression in their refractive error, nor in their axial length (measured during the last 2 years of treatment and 1 year after discontinuation). Furthermore, the subjects recovered to their baseline refraction and did not progressed further over the following year after lens wear discontinuation. Conclusions: We cannot attribute a causative effect to the orthokeratology treatment alone as underlying mechanism for myopia stabilization in this 3 patients. However, the present report points to the possibility of stabilization of early adult-onset myopia progression in young adults using corneal refractive therapy treatment.

Changes in peripheral refractive profile after orthokeratology for different degrees of myopia

Purpose: The purpose of this study was to evaluate the effect of orthokeratology for different degrees of myopia correction in the relative location of tangential (FT) and sagittal (FS) power errors across the central 70 of the visual field in the horizontal meridian. Methods: Thirty-four right eyes of 34 patients with a mean age of 25.2 ± 6.4 years were fitted with Paragon CRT (Mesa, AZ) rigid gas permeable contact lenses to treat myopia (2.15 ± 1.26D, range: 0.88 to 5.25D). Axial and peripheral refraction were measured along the central 70 of the horizontal visual field with the Grand Seiko WAM5500 open-field auto-refractor. Spherical equivalent (M), as well as tangential (FT) and sagittal power errors (FS) were obtained. Analysis was stratified in three groups according to baseline spherical equivalent: Group 1 [MBaseline = 0.88 to 1.50D; n = 11], Group 2 [MBaseline = 1.51 to 2.49D; n = 11], and Group 3 [MBaseline = 2.50 to 5.25D; n = 12]. Results: Spherical equivalent was significantly more myopic after treatment beyond the central 40 of the visual field (p50.001). FT became significantly more myopic for all groups in the nasal and temporal retina with 25 (p 0.017), 30 (p 0.007) and 35 (p 0.004) of eye rotation. Myopic change in FS was less consistent, achieving only statistical significance for all groups at 35 in the nasal and temporal retina (p 0.045). Conclusions: Orthokeratology changes significantly FT in the myopic direction beyond the central 40 of the visual field for all degrees of myopia. Changes induced by orthokeratology in relative peripheral M, FT and FS with 35 of eye rotation were significantly correlated with axial myopia at baseline. Keywords: Field

Removal of Erythrosine B dye from water effluents using crop waste pumpkin seed hulls as adsorbent

Erythrosine B is widely used for coloring in various applications, especially in the food industry, despite its already proved toxicity and carcinogenicity. The agrowaste pumpkin seed hulls were applied as potential adsorbent for the removal of Erythrosine from aqueous solutions. Adsorption mechanism and kinetics were analyzed for design purposes. The seed hulls were characterized by specific techniques before and after dye retention. It was found that the attachment of Erythrosine B molecules on adsorbent surface may be attributed to the interactions between carboxyl and/or carbonyl groups of both dye and agrowaste wall components. A univariate approach followed by a factorial design was applied to study and analyze the experimental results as well as to estimate the combined effects of the process factors on the removal efficiency and dye uptake. Adsorption mechanism may be predominantly due to intraparticle diffusion, dependent on pore size. The four equilibrium models applied fitted the data well; the maximum adsorption capacity for Erythrosine was 16.4 mg/g. The results showed that adsorbent is effective for Erythrosine B removal for a large concentration range in aqueous solutions (5400 mg/L) in batch systems.

Assessing the application of polypropylene multifilament yarns in brain phantoms

The currently available clinical imaging methods do not provide highly detailed information about location and severity of axonal injury or the expected recovery time of patients with traumatic brain injury [1]. High-Definition Fiber Tractography (HDFT) is a novel imaging modality that allows visualizing and quantifying, directly, the degree of axons damage, predicting functional deficits due to traumatic axonal injury and loss of cortical projections. This imaging modality is based on diffusion technology [2]. The inexistence of a phantom able to mimic properly the human brain hinders the possibility of testing, calibrating and validating these medical imaging techniques. Most research done in this area fails in key points, such as the size limit reproduced of the brain fibers and the quick and easy reproducibility of phantoms [3]. For that reason, it is necessary to develop similar structures matching the micron scale of axon tubes. Flexible textiles can play an important role since they allow producing controlled packing densities and crossing structures that match closely the human crossing patterns of the brain. To build a brain phantom, several parameters must be taken into account in what concerns to the materials selection, like hydrophobicity, density and fiber diameter, since these factors influence directly the values of fractional anisotropy. Fiber cross-section shape is other important parameter. Earlier studies showed that synthetic fibrous materials are a good choice for building a brain phantom [4]. The present work is integrated in a broader project that aims to develop a brain phantom made by fibrous materials to validate and calibrate HDFT. Due to the similarity between thousands of hollow multifilaments in a fibrous arrangement, like a yarn, and the axons, low twist polypropylene multifilament yarns were selected for this development. In this sense, extruded hollow filaments were analysed in scanning electron microscope to characterize their main dimensions and shape. In order to approximate the dimensional scale to human axons, five types of polypropylene yarns with different linear density (denier) were used, aiming to understand the effect of linear density on the filament inner and outer areas. Moreover, in order to achieve the required dimensions, the polypropylene filaments cross-section was diminished in a drawing stage of a filament extrusion line. Subsequently, tensile tests were performed to characterize the mechanical behaviour of hollow filaments and to evaluate the differences between stretched and non-stretched filaments. In general, an increase of the linear density causes the increase in the size of the filament cross section. With the increase of structure orientation of filaments, induced by stretching, breaking tenacity increases and elongation at break decreases. The production of hollow fibers, with the required characteristics, is one of the key steps to create a brain phantom that properly mimics the human brain that may be used for the validation and calibration of HDFT, an imaging approach that is expected to contribute significantly to the areas of brain related research.

Importance of contact lens power and thickness in oxygen transmissibility

PURPOSE: The aim of this work was to study the central and peripheral thickness of several contact lenses (CL) with different powers and analyze how thickness variation affects CL oxygen transmissibility. METHODS: Four daily disposable and five monthly or biweekly CL were studied. The powers of each CL were: the maximum negative power of each brand; -6.00 D; -3.00 D; zero power (-0.25 D or -0.50 D), +3.00 D and +6.00 D. Central and peripheral thicknesses were measured with an electronic thickness gauge. Each lens was measured five times (central and 3mm paracentral) and the mean value was considered. Using the values of oxygen permeability given by the manufacturers and the measured thicknesses, the variation of oxygen transmissibility with lens power was determined. RESULTS: For monthly or biweekly lenses, central thickness changed between 0.061 ± 0.002 mm and 0.243 ± 0.002 mm, and peripheral thickness varied between 0.084 ± 0.002 mm and 0.231 ± 0.015 mm. Daily disposable lenses showed central values ranging between 0.056 ± 0.0016 mm and 0.205 ± 0.002 mm and peripheral values between 0.108 ± 0.05 and 0.232 ± 0.011 mm. Oxygen transmissibility (in units) of monthly or biweekly CL ranged between 39.4 ± 0.3 and 246.0 ± 14.4 and for daily disposable lenses the values range between 9.5 ± 0.5 and 178.1 ± 5.1. CONCLUSIONS: The central and peripheral thicknesses change significantly when considering the CL power and this has a significant impact on the oxygen transmissibility. Eyecare practitioners must have this fact in account when high power plus or minus lenses are fitted or when continuous wear is considered.

Estudo e implementação de testes de software em desenvolvimento ágil

Dissertação de mestrado em Engenharia de Sistemas

“PhenoWorld”: a new multidimensional strategy for studying behaviour in rodents

Tese de Doutoramento em Ciências da Saúde

Synthesis of new peptide derivatives that self-assemble into nanostructured hydrogels for biomedical applications

Tese de Doutoramento em Ciências (área de especialização em Química)

Longitudinal analysis of tumor marker CEA of breast cancer patients from Braga's hospital

Allied to an epidemiological study of population of the Senology Unit of Braga’s Hospital that have been diagnosed with malignant breast cancer, we describe the progression in time of repeated measurements of tumor marker Carcinoembryonic antigen (CEA). Our main purpose is to describe the progression of this tumor marker as a function of possible risk factors and, hence, to understand how these risk factors influences that progression. The response variable, values of CEA, was analyzed making use of longitudinal models, testing for different correlation structures. The same covariates used in a previous survival analysis were considered in the longitudinal model. The reference time used was time from diagnose until death from breast cancer. For diagnostic of the models fitted we have used empirical and theoretical variograms. To evaluate the fixed term of the longitudinal model we have tested for a changing point on the effect of time on the tumor marker progression. A longitudinal model was also fitted only to the subset of patients that died from breast cancer, using the reference time as time from date of death until blood test.