Search results for "Stiffness"

Structures of stiff macromolecules of finite chain length near the coil-globule transition: A Monte Carlo simulation

2000

Using a coarse-grained model of a semiflexible macromolecule, the equilibrium shapes of the chain have been studied varying both the temperature and the chain stiffness. We have applied Monte Carlo techniques using the bond fluctuation model for a chain length of N = 80 effective monomers, and two different types of interactions: a potential depending on the angle between successive bonds along the chain to control the chain stiffness, and an attractive interaction between non-bonded effective monomers to model variable solvent quality. In a diagram of states where chain stiffness and inverse temperature and used as variables, we find regions where the chain exists as coil, as spherical glo…

ASSOCIATION OF RENAL RESISTIVE INDEX WITH CAROTID INTIMA-MEDIA THICKNESS IN HYPERTENSIVE PATIENTS

2014

Stretch-shortening cycle: a powerful model to study normal and fatigued muscle.

2000

Stretch-shortening cycle (SSC) in human skeletal muscle gives unique possibilities to study normal and fatigued muscle function. The in vivo force measurement systems, buckle transducer technique and optic fiber technique, have revealed that, as compared to a pure concentric action, a non-fatiguing SSC exercise demonstrates considerable performance enhancement with increased force at a given shortening velocity. Characteristic to this phenomenon is very low EMG-activity in the concentric phase of the cycle, but a very pronounced contribution of the short-latency stretch-reflex component. This reflex contributes significantly to force generation during the transition (stretch-shortening) pha…

Parameters affecting the fundamental period of infilled RC frame structures

2015

Despite the fact that the fundamental period appears to be one of the most critical parameters for the seismic design of structures according to the modal superposition method, the so far available in the literature proposals for its estimation are often conflicting with each other making their use uncertain. Furthermore, the majority of these proposals do not take into account the presence of infills walls into the structure despite the fact that infill walls increase the stiffness and mass of structure leading to significant changes in the fundamental period numerical value. Toward this end, this paper presents a detailed and in-depth analytical investigation on the parameters that affect…

ASSOCIATION OF SERUM URIC ACID WITH AORTIC STIFFNESS IN UNTREATED HYPERTENSIVE SUBJECTS.

2013

INTRODUCTION: Recent studies have reported an association between serum uric acid (SUA) and reduced arterial elasticity. However, in these studies arterial elastic properties have been assessed chiefly by measuring brachial-ankle pulse wave velocity (PWV) or peripheral PWV and only sometimes by using aortic PWV, that is considered the gold standard for measuring arterial stiffness. Moreover, the studies exploring the influence of SUA on aortic distensibility in subjects with arterial hypertension yielded conflicting results. AIM: The purpose of our study was to evaluate the relationships between SUA and aortic stiffness in a group of essential hypertensive patients. METHODS: We enrolled 222…

FATTORI ASSOCIATI ALLA DISCORDANZA TRA ALTERAZIONI DELLA PULSE WAVE VELOCITY AORTICA E AUMENTO DELLO SPESSORE MIO-INTIMALE CAROTIDEO IN SOGGETTI IPER…

2014

Numerosi studi hanno dimostrato come lo spessore mio-intimale carotideo (IMTc), valutato mediante eco-color-Doppler, sia un importante marcatore di danno d’organo subclinico nonché espressione di alterazione vascolare sistemica. Recenti dati, d’altro canto, hanno evidenziato come anche la pulse wave velocity aortica (PWVa), nota misura di stiffness arteriosa, sia indice di precoce danno vasale. Pur dipendendo parzialmente da comuni fattori patogenetici, IMTc e PWVa non hanno un significato clinico del tutto sovrapponibile e risultano non raramente discordanti tra loro. Appare pertanto interessante identificare quali siano i fattori associati al divergente comportamento di tali parametri. So…

Layer thickness optimisation in a laminated composite

1997

Abstract The paper describes a method to optimise the thickness balance within a composite laminate with layers oriented according to a limited set of angles. The laminate must be symmetric, balanced and loaded in-plane. The optimisation process is particularly suited to be used in conjunction with a finite element program. It provides the designer with the optimal overall engineering characteristics anda list of all the possible orientation combinations ranked with respect to their safety factor. The optimisation method is based on the first order gradient optimum search method and operates iteratively in the engineering elastic characteristics field. The cost function implemented up to no…

Microstructural manipulation of electrospun scaffolds for specific bending stiffness for heart valve tissue engineering

2012

Biodegradable thermoplastic elastomers are attractive for application in cardiovascular tissue construct development due to their amenability to a wide range of physical property tuning. For heart valve leaflets, while low flexural stiffness is a key design feature, control of this parameter has been largely neglected in the scaffold literature where electrospinning is being utilized. This study evaluated the effect of processing variables and secondary fiber populations on the microstructure, tensile and bending mechanics of electrospun biodegradable polyurethane scaffolds for heart valve tissue engineering. Scaffolds were fabricated from poly(ester urethane) urea (PEUU) and the deposition…

Experimental Survey on Dry Asphalt Rubber Concrete for Sub-ballast Layers

2012

The railway traffic through a town or near built-up areas causes heavy effects such as noise and vibration on surroundings. In order to minimize the level of these impacts the railway companies with researchers and practitioners seek suitable solutions especially in the field of the rail-track because the main source of the ground borne vibrations and noise is the bad wheel-track contact. In particular, a big effort is addressed to new materials with high mechanical and environmental performance that can be utilized within the sub-ballast layer. This paper presents the results of an experimental survey on the potential application of Dry Asphalt Rubber Concrete (DARC) in sub-ballast layers …

DAMPING AND MECHANICAL PROPERTIES OF DRY ASPHALT RUBBER FOR SUB-BALLAST LAYERS

2011

The passage of railway lines through a town or near built-up areas poses serious environmental problems such as noise and vibration. Consequently railway companies have shown an increasing interest in developing new materials with high mechanical and environmental performance. This paper presents the results of an experimental research on the potential application of Dry Asphalt Rubber (DAR) in sub-ballast layers by measuring its damping and mechanical properties. An experimental survey based on four point bending and Marshall tests was carried to measure the stiffness modulus and damping ratio both of a standard bituminous mixture and of dry asphalt rubber mixture with a rubber content equ…