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See detailMechanical properties of highly porous PDLLA/Bioglass (R) composite foams as scaffolds for bone tissue engineering
Blaker, Jonny J.; Maquet, Véronique; Jérôme, Robert ULg et al

in Acta Biomaterialia (2005), 1(6), 643-652

This study developed highly porous degradable composites as potential scaffolds for bone tissue engineering. These scaffolds consisted of poly-d,l-lactic acid filled with 2 and 15 vol.% of 45S5 Bioglass® ... [more ▼]

This study developed highly porous degradable composites as potential scaffolds for bone tissue engineering. These scaffolds consisted of poly-d,l-lactic acid filled with 2 and 15 vol.% of 45S5 Bioglass® particles and were produced via thermally induced solid–liquid phase separation and subsequent solvent sublimation. The scaffolds had a bimodal and anisotropic pore structure, with tubular macro-pores of 100 μm in diameter, and with interconnected micro-pores of 10–50 μm in diameter. Quasi-static and thermal dynamic mechanical analysis carried out in compression along with thermogravimetric analysis was used to investigate the effect of Bioglass® on the properties of the foams. Quasi-static compression testing demonstrated mechanical anisotropy concomitant with the direction of the macro-pores. An analytical modelling approach was applied, which demonstrated that the presence of Bioglass® did not significantly alter the porous architecture of these foams and reflected the mechanical anisotropy which was congruent with the scanning electron microscopy investigation. This study found that the Ishai–Cohen and Gibson–Ashby models can be combined to predict the compressive modulus of the composite foams. The modulus and density of these complex foams are related by a power-law function with an exponent between 2 and 3. [less ▲]

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See detailMechanical properties of spread films from Acacia gums.
Blecker, Christophe ULg

Poster (2000, June)

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See detailMechanical Properties of the Isolated Equine Trachea
Art, Tatiana ULg; Lekeux, Pierre ULg

in Research in Veterinary Science (1991), 51(1), 55-60

In order to study the in vitro mechanical properties of the equine trachea submitted to the compressive pressures observed in vivo, the pressure-volume relationship was determined in intra- and extra ... [more ▼]

In order to study the in vitro mechanical properties of the equine trachea submitted to the compressive pressures observed in vivo, the pressure-volume relationship was determined in intra- and extra-thoracic tracheal segments taken post mortem from 29 healthy horses (one to 15 years old; 352 to 651 kg). At the same time, the cross-sectional lumen area (X-SA) at the mid-point of the segment was measured using a slit-lamp transillumination and photographic measurement by endoscopy. The tracheal specific compliance (Cs) as well as the relative changes in X-SA and in the sagittal and transverse diameters, for intraluminal pressures from 5 to - 5 kPa, were calculated. The extrathoracic tracheal Cs was 0.060 +/- 0.002 kPa-1 and, at an intraluminal pressure of - 5 kPa, X-SA was reduced to about 73 per cent of its resting value. The intrathoracic segments were more compliant and, at similar compressive pressure, their X-SA was more reduced. These data show that the equine tracheal compliance is high and suggest that the increase in pulmonary resistance observed during strenuous exercise may be partly explained by a partial tracheal collapse. [less ▲]

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See detailMechanical properties of weakly segregated block copolymers. 3. Influence of strain rate and temperature on tensile properties of poly(styrene-b-butyl methacrylate) diblock copolymers with different morphologies
Weidisch, Roland; Stamm, Manfred; Michler, G. H. et al

in Macromolecules (1999), 32(3), 742-750

Poly(styrene-b-butyl methacrylate) diblock copolymers, PS-b-PBMA, with different morphologies are investigated with respect to the influence of strain rate and temperature on tensile properties. In the ... [more ▼]

Poly(styrene-b-butyl methacrylate) diblock copolymers, PS-b-PBMA, with different morphologies are investigated with respect to the influence of strain rate and temperature on tensile properties. In the first part the mechanical properties of bicontinuous and perforated lamellar structure are compared with other morphologies. Diblock copolymers with bicontinuous structures (39% PS) show a much higher tensile strength as well as a higher strain at break than diblock copolymers with lamellar structures (50% PS). In the second part the dependence of tensile properties on strain rate and temperature are discussed for different morphologies. A diblock copolymer with a polystyrene content of 76% PS reveals hexagonally packed PBMA−cylinder, and the tensile strength, strain at break, and Young's modulus exceed the values of pure polystyrene at all measured strain rates. The interesting properties of PS-b-PBMA diblock copolymers are discussed with respect to the phase behavior, interface formation, and chain conformation. [less ▲]

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See detailMechanical properties, residual stresses and structural behavior of thin-walled stainless steel profiles
Rossi, Barbara ULg

Doctoral thesis (2008)

Although it offers a wide variety of interesting properties such as fire resistance or durability, stainless steel has been used in limited amount in structures. It is a known fact that the design rules ... [more ▼]

Although it offers a wide variety of interesting properties such as fire resistance or durability, stainless steel has been used in limited amount in structures. It is a known fact that the design rules don't properly account for the additional benefits of stainless steel properties and are largely based on the specifications for carbon steel. Indeed, a number of similarities exist between stainless steel and ordinary carbon steel but there is sufficient differences to afford a specific treatment in design standards. And since stainless steel is an expensive material, it is important to accurately predict the resistance of structural members. The present research work is dedicated to the study of cold-formed stainless steel profiles. It actually follows the life of a stainless steel construction element and falls on three fundamental topics: the material behavior, the through-thickness residual stress distribution and mechanical enhancement due to the cold-forming process and, last, the strength of concentrically compressed thin-walled columns. Firstly, several constitutive models are characterized such as Teodosiu-Hu's micro-structural based hardening model, capable of predicting the behavior of the studied stainless steel grade submitted to biaxial loading causing plastic strain. This model accounts for the nonlinear hardening behavior, the anisotropy, the Bauschinger effect and more complex behavior such as the observed work-hardening stagnation under reversed deformation at large strains. For this purpose, a collection of tests is carried out including multiaxial tests such as tensile-shear tests and successive simple shear tests and plane-strain tests. Secondly, the effects of the forming process on the mechanical properties are studied. To begin with, on the basis of the constitutive models developed previously, an analytical method that calculates the biaxial residual stress distribution in the walls and in the corners of cold-formed profiles is established. Based on the conclusions drawn from this theoretical analysis, a new formula for the evaluation of the actual mechanical properties is established. This formula is not restricted to a single alloy or type of cross-section. Current design standards are then used to calculate the strength of lipped-channel section columns failing by combined distortional and overall flexural-torsional buckling and the results are compared to tests. Indeed, full-scale tests on cold-formed stainless steel lipped channel section columns were achieved in the Structures Laboratory of the University of Liège. And, once verified against the test results, finite element models were used to generate additional results when necessary. The author then presents a new Direct Strength Method taking into account this phenomenon. Finally, a wide amount of reference results are gathered from the literature, without limiting oneself to any kind of cross-section or stainless steel grade. This database is used to propose an improved formulation for the design of stainless steel thin-walled section columns failing by distortion, local or combination of local and overall buckling in the low slenderness range. [less ▲]

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See detailMechanical quantification of porous structures by the combined use of micro-CT and in-situ loading
Kerckhofs, Greet ULg; Schrooten, Jan; Elicegui, Laida et al

in Proceedings book WCNDT 2008 (2008)

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See detailMechanical response and conformational changes of alpha-actinin domains during unfolding: a molecular dynamics study
Soncini, Monica; Vesentini, Simone; Ruffoni, Davide ULg et al

in BIOMECHANICS AND MODELING IN MECHANOBIOLOGY (2007), 6(6), 399-407

Alpha-actinin is a cytoskeleton-binding protein involved in the assembly and regulation of the actin filaments. In this work molecular dynamics method was applied to investigate the mechanical behaviour ... [more ▼]

Alpha-actinin is a cytoskeleton-binding protein involved in the assembly and regulation of the actin filaments. In this work molecular dynamics method was applied to investigate the mechanical behaviour of the human skeletal muscle a-actinin. Five configurations were unfolded at an elongation speed of 0.1 nm/ps in order to investigate the conformational changes occurring during the extension process. Moreover, a sensitivity analysis at different velocities was performed for one of the R2-R3 spectrin-like repeat configuration extracted in order to evaluate the effect of the pulling speed on the mechanical behaviour of the molecule. Two different behaviours were recognized with respect to the pulling speed. In particular, at speed higher than 0.025nm/ps a continuous rearrangement without evident force peaks was obtained, on the contrary at lower speed evident peaks in the range 500-750 pN were detected. R3 repeat resulted more stable than R2 during mechanical unfolding, due to the lower hydrophobic surface available to the solvent. The characterization of the R2-R3 units can be useful for the development of cytoskeleton network models based on stiffness values obtained by analyses performed at the molecular level. [less ▲]

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See detailMECHANICAL STRAIN MODULATES MONOCYTE CHEMOTACTIC PROTEIN-1 AND IL-1BETA EXPRESSION BY CULTURED HUMAN AORTIC SMOOTH MUSCLE CELLS
Defawe, Olivier; Colige, Alain ULg; Deroanne, Christophe ULg et al

in Cardiovascular Pathology (2004), 13(3 suppl), 189

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See detailMechanical stress strongly induces interleukin-6 production by osteoblasts: a new in vitro 3D compression model
Sanchez, Christelle ULg; Gabay, Odile; Salvat, Colette et al

Poster (2007)

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See detailMechanical stress strongly induces interleukin-6 production by osteoblasts: a new in vitro 3D compression model
Sanchez, Christelle ULg; Gabay, Odile; Salvat, Colette et al

in Osteoarthritis and Cartilage (2007), 15(Suppl C), 84-85

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See detailMechanical testing of a modified stabilisation method for tibial tuberosity advancement
Etchepareborde, Sébastien; Barthelemy, Nicolas; Mills, J. et al

in Veterinary and Comparative Orthopaedics and Traumatology (2010)

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See detailMechanical testing of electrospun PCL fibers
Croisier, Florence ULg; Duwez, Anne-Sophie ULg; Jérôme, Christine ULg et al

in Acta Biomaterialia (2012), 8(1), 218-224

Poly(ε-caprolactone) (PCL) fibers ranging from 250 to 700 nm in diameter were produced by electrospinning a polymer tetrahydrofuran/N,N-dimethylformamide solution. The mechanical properties of the fibrous ... [more ▼]

Poly(ε-caprolactone) (PCL) fibers ranging from 250 to 700 nm in diameter were produced by electrospinning a polymer tetrahydrofuran/N,N-dimethylformamide solution. The mechanical properties of the fibrous scaffolds and individual fibers were measured by different methods. The Young’s moduli of the scaffolds were determined using macro-tensile testing equipment, whereas single fibers were mechanically tested using a nanoscale three-point bending method, based on atomic force microscopy and force spectroscopy analyses. The modulus obtained by tensile-testing eight different fiber scaffolds was 3.8 ± 0.8 MPa. Assuming that PCL fibers can be described by the bending model of isotropic materials, a Young’s modulus of 3.7 ± 0.7 GPa was determined for single fibers. The difference of three orders of magnitude observed in the moduli of fiber scaffolds vs. single fibers can be explained by the lacunar and random structure of the scaffolds. [less ▲]

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See detailMechanical work of breathing during treadmill exercise in ponies
Art, Tatiana ULg; Lekeux, Pierre ULg

in Archives Internationales de Physiologie et de Biochimie (1988), 96(5), 42

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See detailMechanics and characteristics of transition to turbulence in elasto-inertial turbulence
Terrapon, Vincent ULg; Dubief, Yves; Soria, Julio

Conference (2012, November 20)

Numerical experiments of transition in elasto-inertial turbulent channel flows are used to highlight the mechanisms of transition and characterize the MDR regime. Specifically, the pressure kernel from ... [more ▼]

Numerical experiments of transition in elasto-inertial turbulent channel flows are used to highlight the mechanisms of transition and characterize the MDR regime. Specifically, the pressure kernel from the generalized pressure Poisson equation is used to demonstrate the role of elastic instabilities in inducing and sustaining a turbulent-like flow. Additionally, dynamic mode decomposition is applied to statistically steady viscoelastic flows at different Reynolds number to identify the relative contributions of elastic and inertial instabilities. It is shown that elastic instabilities can be triggered through long-range interactions from disturbances in the free-stream, similarly to by-pass transition, and are then sufficient to self-sustain. When the Reynolds number is increased, the relative contribution of inertial instabilities becomes more important, and the flow demonstrates features that are characteristic to Newtonian turbulent flows (e.g., streaks, quasi-streamwise vortices), although at lower intensity. [less ▲]

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See detailMechanics of breathing and gas exchanges in healthy cattle: effect of somatic growth
Lekeux, Pierre ULg

in Archives Internationales de Physiologie et de Biochimie (1987, November), 95(2), 5

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See detailMechanics of breathing and ventilatory drive in double-muscled calves during acute hypoxia
Rollin, Frédéric ULg; Amory, Hélène ULg; Desmecht, Daniel ULg et al

in Proceedings of the 8th Comparative Respiratory Society Meeting (1989)

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See detailMechanics of breathing during strenuous exercise in Thoroughbred horses
Art, Tatiana ULg; Anderson, L.; Woakes, A. J. et al

in Respiration Physiology (1990), 82(3), 279-294

The changes induced by exercise on the mechanics of breathing, as well as the simultaneous changes occurring in arterial blood gas tensions and in respiratory gas exchange were investigated in 6 healthy ... [more ▼]

The changes induced by exercise on the mechanics of breathing, as well as the simultaneous changes occurring in arterial blood gas tensions and in respiratory gas exchange were investigated in 6 healthy thoroughbred horses, performing a treadmill exercise of increasing intensity. Respiratory airflow and tidal volume (VT) were measured with ultrasonic flowmeters. Pleural pressure changes were measured by an oesophageal balloon catheter. Gas concentration of the expired air was analysed with a mass spectrometer; the oxygen consumption (VO2) and the carbon dioxide output (VCO2) were computed breath-by-breath. Arterial blood gas values were obtained by sampling from the carotid artery. Between rest and fast gallop VT, respiratory frequency, expired minute ventilation (VE), VO2, VCO2, total pulmonary resistance (RL), mechanical work of breathing (Wrm) and PaCO2 increased significantly while PaO2 decreased significantly. The Wrm.VO2(-1) ratio in galloping horses increased exponentially with VE. This, together with the relationship between the changes in PaO2 and in PaCO2 and the increase in the ventilatory mechanics parameters, suggests that the mechanics of breathing may be one of the factors constraining further increase in ventilation in exercising healthy horses. [less ▲]

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See detailMechanics of Breathing in Goats
Bakima, M.; Gustin, Pascal ULg; Lekeux, Pierre ULg et al

in Research in Veterinary Science (1988), 45(3), 332-336

Common pulmonary function tests used in man and domestic mammals were adapted to the goat. Requirements for intrathoracic pressure record and pulmonary function investigation were determined. The ... [more ▼]

Common pulmonary function tests used in man and domestic mammals were adapted to the goat. Requirements for intrathoracic pressure record and pulmonary function investigation were determined. The elastance of the mid-thoracic portion of the oesophagus was measured in 17 healthy goats. The calculated percentage error in identifying the endoesophageal intrathoracic pressure decreased with somatic growth, and was found to be smaller than 2 per cent for adult goats. The location of the oesophageal balloon catheter used to measure the intrathoracic pressure was standardised. The following regression equation calculated between the length of catheter (Lcat) and the thoracic circumference (TC) was found: Lcat (cm) = 6.19 +/- 0.7163 X TC (cm) (R2 = 0.96). The influence of the dead space of a face mask on respiration pattern and arterial blood gas were studied. There were no significant changes in arterial partial pressure of oxygen (PaO2) and carbon dioxide (PaCO2), pHa, breathing frequency and intrathoracic pressures. The influence of head and neck position was investigated. Upper airway resistance (Ruaw), measured with the head in a normal position did not significantly differ from values obtained with the head in a horizontal position. Ruaw measured with the head in a vertical position was considerably increased. Arterial blood gas tension and pulmonary mechanics were measured to assess the reproducibility of pulmonary function measurements. Variability in blood gas tension, tidal volume and minute volume is small. The variability of peak to peak intrathoracic pressure change (max delta Plp), dynamic lung compliance (Cdyn), total pulmonary resistance (RL) and Rt were relatively large. [less ▲]

Detailed reference viewed: 18 (2 ULg)