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A Vailati

Publications and source records attributed to A Vailati.

At least 19 recordsLinked to original sources
PubMed2004

Transient oscillations in Soret-driven convection in a colloidal suspension.

We present measurements of the transient stage of Soret-driven convective instability. The sample is a diluted colloidal suspension of silica spheres in water with an unusually large negative Soret coefficient S(T). A large temperature gradient (heating from above) is rapidly applied over the sample, while a shadowgraph imaging technique provides images of the convective flow. From the processing of the variance of the intensity of the images we are able to recover the time evolution of the overall intensity of the convective flow. A typical evolution of such signal exhibits, after a latency time, a peak followed by some damped oscillations leading to a steady-state value. Both the onset time tau(p) (the temporal position of the first peak), and the oscillation period tau(osc) show a power law dependence as a function of the solutal Rayleigh number R(s). The exponents found are compared with predictions from existing models.

Journal Article↗
PubMed2000

Diffusive mass transfer by nonequilibrium fluctuations: Fick's law revisited.

Recent experimental and theoretical works have shown that giant fluctuations are present during diffusion in liquid systems. We use linearized fluctuating hydrodynamics to calculate the net mass transfer due to these nonequilibrium fluctuations. Remarkably, the mass flow turns out to coincide with the usual Fick's one. The renormalization of the hydrodynamic equations allows us to quantify the gravitational modifications of the diffusion coefficient induced by the gravitational stabilization of long wavelength fluctuations.

Journal Article↗
PubMed2000

Space intensity correlations in the near field of the scattered light: A direct measurement of the density correlation function g(r)

We show that the two point intensity correlation in the near field of the scattered light is directly related to the two point density correlation g(r). Preliminary measurements on two sets of calibrated random pinholes of 140 and 300 &mgr;m diameters, and on aqueous solutions of latex spheres of 5, 10, and 40 &mgr;m are reported. A discussion on the desirability of the technique as a simple and powerful alternative to low angle scattering will be presented.

Journal Article↗
PubMed2000

Universal behavior of nonequilibrium fluctuations in free diffusion processes

We show that giant nonequilibrium fluctuations are present during the free diffusive remixing occurring in ordinary liquid mixtures and in macromolecular solutions. The static structure factor of the fluctuations is measured by using a quantitative shadowgraph technique. We show that structure factors at different times and from different samples can be rescaled onto a single master curve without any adjustable parameter, thus giving strong evidence that nonequilibrium fluctuations are a universal feature of free diffusion processes.

Journal Article↗
PubMed2000

Equilibrium and nonequilibrium fluctuations at the interface between two fluid phases

We have performed small-angle light-scattering measurements of the static structure factor of a critical binary mixture undergoing diffusive partial remixing. An uncommon scattering geometry integrates the structure factor over the sample thickness, allowing different regions of the concentration profile to be probed simultaneously. Our experiment shows the existence of interface capillary waves throughout the macroscopic evolution to an equilibrium interface, and allows us to derive the time evolution of surface tension. Interfacial properties are shown to attain their equilibrium values quickly compared to the system's macroscopic equilibration time.

Journal Article↗
PubMed1993

Hashimoto's thyroiditis in association with Tolosa Hunt syndrome: a case report.

Tolosa Hunt syndrome (THS) is a painful ophthalmoplegia due to a nonspecific inflammatory process in the cavernous sinus or to parasellar neoplasms. Although the cause of the disease is unknown, previous observations support the hypothesis that THS may be only one manifestation of a generalized vasculitis. The diagnosis is based on findings of painful ophthalmoplegia, excellent response to corticosteroids, and exclusion of other causes including aneurysm, diabetes mellitus, paranasal mucocele, and carotid cavernous fistula. We report the case of a 24-year-old woman with THS who had undergone thyroidectomy 4 years before admission for goiter with histologic diagnosis of Hashimoto's thyroiditis. This case shows the unusual association between Hashimoto's thyroiditis and THS and supports the autoimmune origin of both diseases.

Adult↗
PubMed1990

[Survey on goiter in elementary school children in the Bisagno and Trebbia valleys (Liguro-Emilian Apennines)].

The authors have made an inquiry about school-children of two villages of Northern Appennines: Bargagli and Ottone, formerly seats of endemic goiter. The disappearance of endemic goiter in the younger generations of these villages, is in accordance with previous observations by one of the writers suggesting that sheep represent an important ecologic factor in endemic areas.

Child↗
PubMed1983

Changes of biological rhythms in primary headache syndromes.

The circadian periodicity of some endocrine (PRL, cortisol, GH) and vegetative (oral temperature, blood pressure) functions has been studied in cluster headache, common migraine, atypical facial pain, and "mixed" headache. Changes in several biological rhythms have been found not only in cluster headache (CH) but also in other kinds of headache. Although a great individual variability of rhythometric changes has been observed, particularly in CH, the dysrhythmic condition seems to be more evident in chronic than in episodic CH. The clinical and chronobiological effects of lithium administration and of a short-term sleep deprivation have been studied in CH.

Adult↗
PubMed1979

Circadian periodicity of plasma prolactin in some neurological diseases.

The circadian rhythmicity of plasma PRL has been studied in some neurological diseases in which hypothalamic involvement or abnormalities of brain neurotransmitters has been postulated. 11 patients with Steinert's myotonic dystrophy, 7 with cluster headache and 10 with Huntington's chorea have been studied. By the mean cosinor procedure, a significant circadian rhythm of plasma PRL has been observed both in Steinert's disease and in cluster headache, whereas a circadian periodicity is not detectable in Huntington's chorea, a degenerative disorder affecting the basal ganglia, the hypothalamus and many other areas of the CNS.

Adult↗
PubMedDate not supplied

Is gravity on our way? The case of polyacrylamide gel polymerization.

Potential gravity-induced deformations of polyacrylamide matrices during gelling were investigated in two different initiator systems based on (i) photopolymerization with 100 microM methylene blue, 1 mM sodium toluene sulfinate (reducer) and 50 microM diphenyliodonium chloride (oxidizer) (photopolymerization) and (ii) chemical polymerization, utilizing the standard persulfate N,N,N',N'-tetramethylethylenediamine. In both systems, it is seen that convective flows are imprinted in the final gel structure above a critical gelling layer thickness, set at ca. 3 mm. In both systems, progressive increments of the solution density, from normodense (density = 1.0) up to isodense with the growing polymer chains (density = 1.3) do not inhibit the appearance of strong convective flows. However, gel inhomogeneities are completely abolished even in 10 mm gelling layers if polymerization is performed in presence of density gradients, notably of sucrose, from 0 to 20%, 0 to 40% and 0 to 60%. Even the shallower gradient (0-20% sucrose) is able to completely abolish convective flows in persulfate-driven polymerization. It is hypothesized that such disturbances are not created by sedimentation of the growing polymer chains in the gravitational field, but are produced by the reaction exothermality, which produces strong buoyancy-driven flows. It is additionally demonstrated that persulfate polymerization is sensitive to oxygen absorbed from the top liquid layers, which should be carefully protected by an overlay of organic solvent. Methylene blue-induced polymerization appears to offer a series of unique advantages over chemical initiation with persulfate.

Acrylic Resins↗
PubMedDate not supplied

Epithelial ovarian cancer in female pseudohermaphroditism. A diagnosis by computed tomography and review of the literature.

We describe the case of a patient proven to be a female pseudohermaphrodite with a complete virilization syndrome who developed an epithelial tumor of the ovary of borderline malignancy. The tumor appeared as an abdominal mass with cystic features on ultrasonography. The diagnosis of the intersexual condition and adnexal cancer was made by computed tomography (CT).

Disorders of Sex Development↗