Influence of the hip joint modeling approaches on the kinematics of human gait

The influence of the hip joint formulation on the kinematic response of the model of human gait is investigated throughout this work. To accomplish this goal, the fundamental issues of the modeling process of a planar hip joint under the framework of multibody systems are revisited. In particular, the formulations for the ideal, dry, and lubricated revolute joints are described and utilized for the interaction of femur head inside acetabulum or the hip bone. In this process, the main kinematic and dynamic aspects of hip joints are analyzed. In a simple manner, the forces that are generated during human gait, for both dry and lubricated hip joint models, are computed in terms of the system’s state variables and subsequently introduced into the dynamics equations of motion of the multibody system as external generalized forces. Moreover, a human multibody model is considered, which incorporates the different approaches for the hip articulation, namely ideal joint, dry, and lubricated models. Finally, several computational simulations based on different approaches are performed, and the main results presented and compared to identify differences among the methodologies and procedures adopted in this work. The input conditions to the models correspond to the experimental data capture from an adult male during normal gait. In general, the obtained results in terms of positions do not differ significantly when the different hip joint models are considered. In sharp contrast, the velocity and acceleration plotted vary significantly. The effect of the hip joint modeling approach is clearly measurable and visible in terms of peaks and oscillations of the velocities and accelerations. In general, with the dry hip model, intra-joint force peaks can be observed, which can be associated with the multiple impacts between the femur head and the cup. In turn, when the lubricant is present, the system’s response tends to be smoother due to the damping effects of the synovial fluid.

Biomaterials for cartilage tissue engineering under mechanical stimulus

Tese de Doutoramento em Ciências (Especialidade de Física)

Nanocomposites: the contribution of multiscale modelling to improve the dispersion levels

Tese de Doutoramento em Ciência e Engenharia de Polímeros e Compósitos

Parameter identification of the fermentative production of fructo-oligosaccharides by Aureobasidium pullulans

In this study, a mathematical model for the production of Fructo-oligosaccharides (FOS) by Aureobasidium pullulans is developed. This model contains a relatively large set of unknown parameters, and the identification problem is analyzed using simulation data, as well as experimental data. Batch experiments were not sufficiently informative to uniquely estimate all the unknown parameters, thus, additional experiments have to be achieved in fed-batch mode to supplement the missing information. © 2015 IEEE.

Development and characterization of lipid-based nanosystems for controlled release of bioactive compounds

Tese de Doutoramento em Engenharia Química e Biológica.

Estudo numérico do escoamento e transporte de sedimentos em torno de pilares de pontes

Dissertação de mestrado integrado em Engenharia Civil

Encapsulation and controlled release of bioactive compounds in lactoferrin-glycomacropeptide nanohydrogels : curcumin and caffeine as model compounds

Curcumin and caffeine (used as lipophilic and hydrophilic model compounds, respectively) were successfully encapsulated in lactoferrin-glycomacropeptide (Lf-GMP) nanohydrogels by thermal gelation showing high encapsulation efficiencies (>90 %). FTIR spectroscopy confirmed the encapsulation of bioactive compounds in Lf-GMP nanohydrogels and revealed that according to the encapsulated compound different interactions occur with the nanohydrogel matrix. The successful encapsulation of bioactive compounds in Lf-GMP nanohydrogels was also confirmed by fluorescence measurements and confocal laser scanning microscopy. TEM images showed that loaded nanohydrogels maintain their spherical shape with sizes of 112 and 126 nm for curcumin and caffeine encapsulated in Lf-GMP nanohydrogels, respectively; in both cases a polydispersity of 0.2 was obtained. The release mechanisms of bioactive compounds through Lf-GMP nanohydrogels were evaluated at pH 2 and pH 7, by fitting the Linear Superimposition Model to the experimental data. The bioactive compounds release was found to be pH-dependent: at pH 2, relaxation is the governing phenomenon for curcumin and caffeine compounds and at pH 7 Ficks diffusion is the main mechanism of caffeine release while curcumin was not released through Lf-GMP nanohydrogels.

Influence of chitosan coating on protein-based nanohydrogels properties and in vitro gastric digestibility

Chitosan coating was applied in Lactoferrin (Lf)-Glycomacropeptide (GMP) nanohydrogels by layer-by-layer coating process. A volume ratio of 0.1 of Lf-GMP nanohydrogels (0.2 mg.mL-1, at pH 5.0) to chitosan (1 mg.mL-1, at pH 3) demonstrated to be the optimal condition to obtain stable nanohydrogels with size of 230 ± 12 nm, a PdI of 0.22 ± 0.02 and a -potential of 30.0 ± 0.15 mV. Transmission electron microscopy (TEM) images showed that the application of chitosan coating in Lf-GMP did not affect the spherical shape of nanohydrogels and confirmed the low aggregation of nanohydrogels in solution. The analysis of chemical interactions between chitosan and Lf-GMP nanohydrogels were performed by Fourier transform infrared spectroscopy (FTIR) and by circular dichroism (CD) that revealed that a specific chemical interaction occurring between functional groups of protein-based nanohydrogels and active groups of the chitosan was established. The effect of chitosan coating on release mechanisms of Lf-GMP nanohydrogels at acid conditions (pH 2, 37 ºC) was evaluated by the encapsulation of a model compound (caffeine) in these systems. Linear Superposition Model was used to fit the experimental data and revealed that Fick and relaxation mechanisms are involved in caffeine release. It was also observed that the Fick contribution increase with the application of chitosan coating. In vitro gastric digestion was performed with Lf-GMP nanohydrogels and Lf-GMP nanohydrogels with chitosan coating and it was observed that the presence of chitosan improve the stability of Lf and GMP (proteins were hydrolysed at a slower rate and were present in solution by longer time). Native electrophoreses revealed that the nanohydrogels without coating remained intact in solution until 15 min and with chitosan coating remained intact until 60 min, during gastric digestion.

Development of nanohydrogels as a vehicle for the release of bioactive compounds in food matrices

PhD in Chemical and Biological Engineering

A multi–physics approach applied to masonry structures with non–hydraulic lime mortars

Tese de Doutoramento em Engenharia Civil (área de especialização em Engenharia de Estruturas).

The application of the equivalent annulus width concept in thermal diffusion separations

The equivalent annulus width concept is used to characterize a small commercial thermogravitational hermal diffusion column and its validity checked experimentally by separating batchwise in the column mixtures of n-heptanebenzene with different initial concentrations. The equation of Ruppell and Coull was used to analyse the data in the short separation times range and determine the equivalent annulus width. Good agreement was obtained between the experimental and predicted time-separation curves when using the equivalent annulus width value and on averaged value of the thermal diffusion constant. A new method is presented for the simultaneous determination of the equivalent annulus width and the thermal diffusion constant of a binary mixture from a single set of experimental data.

Single molecule simulation of diffusion and enzyme kinetics

This work presents a molecular-scale agent-based model for the simulation of enzymatic reactions at experimentally measured concentrations. The model incorporates stochasticity and spatial dependence, using diffusing and reacting particles with physical dimensions. We developed strategies to adjust and validate the enzymatic rates and diffusion coefficients to the information required by the computational agents, i.e., collision efficiency, interaction logic between agents, the time scale associated with interactions (e.g., kinetics), and agent velocity. Also, we tested the impact of molecular location (a source of biological noise) in the speed at which the reactions take place. Simulations were conducted for experimental data on the 2-hydroxymuconate tautomerase (EC 5.3.2.6, UniProt ID Q01468) and the Steroid Delta-isomerase (EC 5.3.3.1, UniProt ID P07445). Obtained results demonstrate that our approach is in accordance to existing experimental data and long-term biophysical and biochemical assumptions.

Insights on the mechanical behavior of keratin fibrils

Supplementary data associated with this article can be found,in the online version, at http://dx.doi.org/10.1016/j.ijbiomac.2016.05.018.

Hereditariedade da homeose

A preliminary account on the normal development of the imaginai discs in holometabolic Insects is made to serve as an introduction to the study of the hereditary homoeosis. Several facts and experimental data furnished specially by the students of Drosophila are brought here in searching for a more adequate explanation of this highly interesting phenomenon. The results obtained from the investigations of different homoeotic mutants are analysed in order to test Goldschmidt's theory of homoeosis. Critical examination of the basis on which this theory was elaborated are equally made. As a result from an extensive theoretical consideration of the matter and a long discussion of the most recent papers on this subject the present writer concludes that the Goldschmidt explanation of the homoeotic phenomena based on the action of diffusing substances produced by the genes, the "evocators", and on the alteration of the normal speed of maturation of the imaginai discs equally due to the activity of the genes, could not be proved and therefore should be abandoned. In the same situation is any other explanation like that of Waddington or Villee considered as fundamentally identical to that of Goldschmidt. In order to clear the problem of homoeosis in terms which seem to put the phenomenon in complete agreement with the known facts the present writer elaborated a theory first published a few years ago (1941) based entirely on the assumption that the imaginai discs are specifically determined by some kind of substances, probably of chemical nature, contained in the cytoplam of the cells entering in the consti- tution of each individual disc. These substances already present in the blastem of the egg in which they are distributed in a definite order, pass to different cells at the time the blastem is transformed into blastoderm. These substances according to their organogenic potentiality may be called antenal-substance, legsubstance, wing-substance, eye-substance, etc. The hipoderm of the embryo resulting from the multiplication of the blastoderm cells would be constituted by a series of cellular areas differing from each other in their particular organoformative capacity. Thus the hypoderm giving rise to the imaginai discs, it follows that each disc must have the same organogenic power of the hypodermal area it came from. Therefore the discs i*re determinated since their origin by substances enclosed in the cytoplasm of their cells and consequently can no longer alter their potentiality. When an antennal disc develops into a leg one can conclude that this disc in spite of its position in the body of the larva is not, properly speaking, an antennal disc but a true leg disc whose cells instead of having in their cytoplasm the antennal substance derived from the egg blastem have in its place the leg-substance. Now, if a disc produces a tarsus or an antenna or even a compound appendage partly tarsus-like, partly antenna-like, it follows tha,t both tarsal and antennal substances are present in it. The ultimate aspect of the compound structure depends upon the reaction of each kind of substance to the different causes influencing development. For instance, temperature may orient the direction of development either lowards arista or tarsus, stimulating, or opposing to the one or the other of these substances. Confering to the genes the faculty of altering the constitution of the substances containing in the cytoplasm forming the egg blastem or causing transposition of these substances from one area to another or promoting the substitution of a given substance by a different one, the hereditary homoeocis may be easily explained. However, in the opinion of the present writer cytoplasm takes the initiative in all developmental process, provoking the chromosomes to react specifically and proportionally. Accordingly, the mutations causing homoeotic phenomena may arise independently at different rime in the cytoplasm and in the chromosomes. To the part taken by the chromosomes in the manifestation of the homoeotic characters is due the mendalian ratio observed in homoeotic X normal crosses. Expression, in itself, is mainly due to the proportion of the different substances in the cells of the affected discs. Homoeotic phenomena not presenting mendelian ratio may appear as consequence of cytoplasmic mutation not accompanied by chromosomal mutation. The great variability in the morphology of the homoeotic characteres, some individual being changed towards an extreme expression of the mutant phenotype while others in spite of their homozigous constitution cannot be distinguished from the normal ones, strongly supports the interpretation based on the relative proportion of the determining substances in the discs. To the same interpretation point also asymetry and other particularities observed in the exteriorization of the phenomenon. In conformity with this new conception homoeosis should not prove homology of Insect appendages (Villee 1942) since a more replacement of substances may cause legs to develop in substitution of the wings, as it was already observed (requiring confirmation in the opinion of Bateson 1894, p. 184) and no one would conclude for the homology of these organs in the usual meaning of the term.

Sôbre uma fórmula para o cálculo da dose mais econômica de adubo

The authors discuss a formula for the determination of the most profitable level of fertilization (x*). This formula, presented by CAREY and ROBINSON (1953), can be written as: x*= (1/c) log cx u L10 + (1/c) log wu _______ ___ 1-10 x u t being c the growth factor in Mitscherlich's equation, x u a standard dressing of the nutrient, L 10 the Naeperian logarithm of 10, u the response to the standard dressing, w the unit price of the crop product, and i the unit price of the nutrient. This formula is a modification of one of the formulas of PIMENTEL GOMES (1953). One of its advantages is that is does not depend on A, the theoretical maximum harvest, which is not directly given by experimental data. But another advantage, proved in this. paper, is that the first term on the right hand side K= 1(/c) log cx u L 10 ____________ 1 - 10-cx u is practically independent of c, and approximately equivalent to (1/2) x u. So, we have approximately x* = (1/2) x u + (1/c) log wu . ____ x u t With experimental data we compute z = wu ____ x u t then using tables 1, 2 and 3, we may obtain Y - (1/c) log z and finally x* = (1/2) x u + Y. This is an easy way to determine the most profitable level of fertilization when experimental data on the response u to a dressing x u are available. Tables for the calculation of Y are included, for nitrogen, phosphorus, potash, and manure.