1,048 research outputs found
Effects of constraint curvature on structural instability: tensile buckling and multiple bifurcations
Bifurcation of an elastic structure crucially depends on the curvature of the
constraints against which the ends of the structure are prescribed to move, an
effect which deserves more attention than it has received so far. In fact, we
show theoretically and we provide definitive experimental verification that an
appropriate curvature of the constraint over which the end of a structure has
to slide strongly affects buckling loads and can induce: (i.) tensile buckling;
(ii.) decreasing- (softening), increasing- (hardening), or constant-load (null
stiffness) postcritical behaviour; (iii.) multiple bifurcations, determining
for instance two bifurcation loads (one tensile and one compressive) in a
single-degree-of-freedom elastic system. We show how to design a constraint
profile to obtain a desired postcritical behaviour and we provide the solution
for the elastica constrained to slide along a circle on one end, representing
the first example of an inflexional elastica developed from a buckling in
tension. These results have important practical implications in the design of
compliant mechanisms and may find applications in devices operating in
quasi-static or dynamic conditions
Tomography on f-oscillators
Symplectic tomographies of classical and quantum states are shortly reviewed.
The concept of nonlinear f-oscillators and their properties are recalled. The
tomographic probability representations of oscillator coherent states and the
problem of entanglement are then discussed. The entanglement of even and odd
f-coherent states is evaluated by the linear entropy
Resistant arterial hypertension in a patient with adrenal incidentaloma multiple steno-obstructive vascular lesions and antiphospholipid syndrome
Resistant hypertension is defined as above of blood pressure (≤ 140/90 mmHg) despite therapy with three or more antihypertensive drugs of different classes at maximum tolerable doses with one bling a diuretic. An important consideration in defining a patient with resistant hypertension is the mislabeling of secondary hypertension as resistant hypertension. Here, we report a patients with resistant hypertension caused by multiple stenoocclusive arteries due to antiphospholipid syndrome and coexisting with subclinical Cushing’s syndrome
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