1,721,039 research outputs found
THYROTROPIN STIMULATES GLUCOSE-TRANSPORT IN CULTURED RAT-THYROID CELLS
No full textGlucose transport by FRTL-5 cells, a rat thyroid cell line, was found to be TSH dependent. The effect of TSH on the uptake of 2-deoxy-D-glucose, a nonmetabolizable glucose analogue, was prompt, being 200% over basal value after 10 min and maximal after 12 h (600-700% increase). The TSH effect was dose dependent, with half-maximum stimulation at 10 μU TSH/ml, and maximum stimulation at 1 mU TSH/ml. TSH enhanced also the uptake of 3-O-methyl-D-glucose by FRTL-5 cells. The TSH activation of glucose transport had the following characteristics: 1) it was mimicked by (Bu)2-cAMP (1 mM) and by agents that increase cAMP levels in thyroid cells, such as forskolin (10 μM) and cholera toxin (50 μg/ml); 2) it involved the facilitated glucose transport system in that it was inhibited in a dose-related manner by both cytochalasin B and phloretin; 3) it showed a glucose stereochemical sensitivity, being affected by D-glucose and 3-O-methyl-glucose, and not by L-glucose; 4) it was characterized by an increase in the maximum velocity (V(max)) of glucose uptake (from 15.3 to 66.0 fmol/min x μg DNA) without change in the Michaelis-Menten constant (K(m)) (5.3 mM); 5) the effect on the V(max) was due to an increase in the number of surface glucose transporters as indicated by the enhancement of the D-glucose-sensitive fraction of [3H]cytochalasin B binding sites that in thyroid plasma membranes of cells exposed to TSH for 2 and 8 h, increased from 5.0 (basal value) to 10.4 and 23.1 pmol/mg protein, respectively. These data indicate that in FRTL-5 cells TSH stimulates the glucose transport system by an enhancement of the number of functional glucose transporters in the thyroid plasma membrane
Aluminium-steel energy dissipators for passive protection of structures
No full textIn the present paper, the design optimization and the buckling analysis of an aluminium-steel device for the seismic protection of structures are presented. Moreover, it is detailed discussed the dynamical response of a 3D two-storey steel frame, equipped with the proposed device and subjected to 14 natural earthquakes, which are compatible with the response spectra provided by Eurocode 8
The dynamic experimental behavior of a new aluminium passive protection device in a 3d frame
No full textIn this paper the behaviour of a new hysteretic dissipater for seismic passive protection of structures is analysed. The device is made in aluminium and steel and the results of a series of shaking table tests on a 3D two-floor steel frame equipped with these dissipaters are described. The device is subjected to shear forces during a seismic event and it has been designed on the basis of an optimization procedure having the objective of maximizing the energy dissipation. The experimental analysis gives a better characterization of the devices and the real quantity of the dissipated energy. The results show the values of the maximum acceleration and maximum displacements at each floor, together with the maximum interstory drifts measured on the 3D frame subjected to some earthquake records. The same measurements realized on the 3D model without dissipaters
subjected to the same earthquakes give the level of the efficacy of the proposed device in reducing the seismic effects on structures
Non-destructive monitoring of an old masonry clock tower with forced and environmental actions
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Design optimization of aluminium-steel devices for passive protection of structures
No full textThe present paper deals with the design optimization of an aluminium yielding-based device. The design criteria and the response of a 3D steel frame equipped with the proposed device under seismic actions are discussed
Hysteretic dissipators made of aluminium and steel: optimal design and preliminary characterization tests
No full textIn this paper the optimal design of a dissipator made of aluminium and steel and principally subjected to shear forces and the preliminary results of the characterization tests are described. The device has been designed on the basis of an optimization procedure with the objective to maximize the energy dissipated in the device. The response of a 3D frame equipped with the device and subjected to 7 earthquakes compatible with the response spectrum of Eurocode 8 is shown. The optimal response obtained from the characterization tests exhibits a good dissipative behavior of the device, highlighted by a wide enough hysteresis cycle
Optimal design of a new seismic passive protection device made in aluminium and steel
No full textIn recent years many techniques for the seismic control of structures have been developed. Among these, the metallic hysteretic devices are able to dissipate a great amount of the energy entering the building during a seismic event, thanks to a stable behavior under cyclic loads that produces a wide hysteretic loop. Steel shear panels are examples of elasto-plastic elements, which dissipate energy under a shear behavior. Generally such dampers are known to possess large energy-dissipation capacity relative to their size; they are cost-effective and are able to protect non-structural elements too. Moreover, the shear panels may be easily installed and substituted in the structure by mean of diagonals on which may be mounted and then connected to the frame. As disadvantage, this kind of energy dissipating devices can dissipate energy only after they sustain inelastic excursions. As a consequence they are ineffective for vibrations that produce interstory drifts smaller than the yielding drift of the device. To overcome this constraint, Rai and Wallace and Foti and Diaferio proposed shear panels made in aluminium alloys. In fact, these alloys are very ductile with a yielding limit lower than ordinary steel. Numerical and experimental researches have been developed on aluminium shear links. Foti and Nobile performed characterization and shaking-table tests on some aluminium shear panels showing instability phenomena and problems of the connections of the devices to the structure.
The aim of the present note is to find out the optimum geometrical configuration of an aluminium-steel shear panel in order to dissipate a large amount of the seismic energy
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