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Biomedical subjects

F Simonetti

Publications and source records attributed to F Simonetti.

At least 19 recordsLinked to original sources
PubMed2006

Multiple scattering: the key to unravel the subwavelength world from the far-field pattern of a scattered wave.

For more than a century the possibility of imaging the structure of a medium with diffracting wave fields has been limited by the tradeoff between resolution and imaging depth. While long wavelengths can penetrate deep into a medium, the resolution limit precludes the possibility of observing subwavelength structures. Near-field microscopy has recently demonstrated that the resolution limit can be overcome by bringing a probing sensor within one wavelength distance from the surface to be imaged. This paper extends the scope of near-field microscopy to the reconstruction of subwavelength structures from measurements performed in the far-field. It is shown that the distortion undergone by a wave field as it travels through an inhomogeneous medium and the subsequent generation of local evanescent fields encode subwavelength information in the far-field due to multiple scattering within the medium. This argument is proved theoretically and supported by a limited view experiment performed with elastic waves in which an image with a resolution better than a third of the wavelength is achieved.

Journal Article↗
PubMed2006

Transitory, spontaneously recovering, peripheral facial nerve palsy after vinorelbine administration.

Childhood intrinsic brain-stem gliomas have a dismal prognosis. Different treatment strategies have been adopted over the years without changing the final outcome of this ominous disease. Due to this grim prognosis, experimental therapeutic designs are worthwhile. Vinorelbine is a semi-synthetic vinca alkaloid that has demonstrated a broad spectrum of activity both in in vitro and in vivo experimental systems. By adopting vinorelbine during and after focal radiotherapy in the last two years, we have tried to evocate its known synergistic effect in brain-stem tumour control. Vinorelbine was administered intravenously before, during and after radiotherapy on tumour bed for a total duration of 10 months. All the consecutive patients whose clinical and radiological features corresponded to the diagnosis of an intrinsic brain-stem tumour, i.e., diffuse pontine glioma, have been accrued to this treatment protocol since July 2002. A histological assessment was not required. All patients were treated during hospital stay or in the outpatient clinic at the Istituto Nazionale Tumori of Milan (n=12) and at the Pediatric Clinic of Policlinico in Catania (n=1). Two of the thirteen patients so far treated have developed multiple subsequent, and transitory, episodes of monolateral peripheral facial nerve palsy during vinorelbine administration. The palsy always completely and spontaneously resolved at a short interval-around 30 min-after the end of the drug infusion. Obvious tumour progression was excluded by means of MRI; therefore the drug was administered as scheduled until the end of the treatment. We describe possible neurological and oncological implications of this unusual side effect, until now not reported in any other series dealing with vinorelbine as adjuvant treatment.

Bell Palsy↗
PubMed2005

National character does not reflect mean personality trait levels in 49 cultures.

Most people hold beliefs about personality characteristics typical of members of their own and others' cultures. These perceptions of national character may be generalizations from personal experience, stereotypes with a "kernel of truth," or inaccurate stereotypes. We obtained national character ratings of 3989 people from 49 cultures and compared them with the average personality scores of culture members assessed by observer ratings and self-reports. National character ratings were reliable but did not converge with assessed traits. Perceptions of national character thus appear to be unfounded stereotypes that may serve the function of maintaining a national identity.

Adolescent↗
PubMed2005

On the meaning of Lamb mode nonpropagating branches.

The modes of vibration of an elastic plate are usually divided into propagating and nonpropagating kinds. While nonpropagating modes characterize local vibration nearby a perturbation source, which can be either an external force or a geometrical discontinuity, propagating modes carry energy along the waveguide and account for the vibration far away from the perturbation source. In this paper, by considering that the modes of an absorbing plate are always propagating, it is shown that each elastic mode consists of propagating and nonpropagating branches, which turn into a single propagating mode as soon as internal absorption is considered. Moreover, it is shown how introducing a little material damping leads to a rigorous differentiation of elastic modes when they are connected. A similar result can be obtained by loading the plate with a light fluid [Rokhlin et al., J. Acoust. Soc. Am. 85, 1074-1080 (1989)].

Journal Article↗
PubMed2004

Ultrasonic interferometry for the measurement of shear velocity and attenuation in viscoelastic solids.

A method for the measurement of the shear properties of solid viscoelastic materials is presented. The viscoelastic material is cut into a cylindrical sample which is clamped between two rods. The transmission and reflection coefficient spectra of the fundamental torsional mode through the sample are measured by means of two pairs of piezoelectric transducers placed at the free ends of the rod-sample-rod system. Such spectra exhibit maxima and minima which occur approximately at the resonance frequencies of the free viscoelastic cylinder. Therefore, the shear velocity can be obtained by measuring the frequency interval between two consecutive maxima or minima. The shear attenuation is derived by best fitting the analytical expression of the reflection and transmission coefficients to the experimental spectra. The test is very quick to set up as the sample is simply clamped between the two rods.

Journal Article↗
PubMed2003

A guided wave technique for the characterization of highly attenuative viscoelastic materials.

The measurement of the acoustic properties of highly attenuative materials such as bitumen is very difficult. One possibility is to use measurements of the extent to which filling a cylindrical waveguide with the material affects the dispersion relationship of the cylinder. Torsional modes have been excited using piezoelectric transducers placed at one end of the cylinder, while the phase velocity and attenuation spectra have been measured by means of laser scanning. At each frequency, under the hypothesis of linear viscoelasticity, the phase velocity and attenuation of the fundamental torsional mode have been calculated as a function of the bulk shear velocity and the bulk shear attenuation of the inner core at that frequency. The resulting phase velocity and guided wave attenuation contour plots have been employed for deriving the unknown shear properties from the measured velocity and attenuation of the guided wave. The monochromaticity of the approach has not required a particular frequency dependence of the material properties to be assumed. Results for bitumen are given.

Journal Article↗
PubMed2001

Dejerine's syndrome or Spiller's syndrome?

We report the difference existing between two clinical syndromes: Spiller's syndrome is caused by a complete involvement of the medial hemimedulla, while Déjérine's syndrome is determined by lesions restricted to the anterior portion of the medial hemimedulla and is characterized by hypoglossal nerve palsy and contralateral hemiparesis.

Adult↗
PubMed2001

Intravascular lymphomatosis (IL) in a child mimicking a posterior fossa tumor.

Intravascular lymphomatosis (IL) is a rare entity only recently included in lymphoma classification, whose main feature is the exclusive or predominant growth of neoplastic cells within blood vessels. The vast majority of the patients affected by IL belong to the 7th or 8th decade of life and present with skin rash or CNS diffuse necrotic or demyelinating lesions. Case report. SS, a 13-year-old girl, was admitted to a Neurosurgery Unit because of endocranic hypertension, where, after CT and MRI documenting a IV ventricle 3 cm diameter tumor, she was submitted to complete tumor excision: extemporary diagnosis was suggestive of medulloblastoma. When referred to us she had persistent fever with normal blood and spinal fluid cultures. Whole CNS MRI did not give evidence of residual or metastatic disease while CSF cytology showed only pleiocytosis. Treatment was started according to our ongoing protocol for medulloblastoma with pre-radiation chemotherapy. Before delivering radiotherapy (RT), upon review of histologic specimens, the definitive diagnosis of IL B-phenotype was made. The girl was re-admitted and, after a complete re-staging, chemotherapy was intensified according to our schedule for high-grade B-cell lymphoma and CNS was irradiated up to a total dose of 25 Gy. She remained alive in continuous complete remission at 21 months after diagnosis. The case here reported is unique for age, tumor presentation, and, so far, favourable outcome, in spite of the delayed histological diagnosis.

Adolescent↗
PubMed2000

Migraine with aura and white matter abnormalities: Notch3 mutation.

The authors report on an Italian family with eight affected members who show autosomal dominant migraine with prolonged visual, sensory, motor, and aphasic aura. These symptoms are associated with white matter abnormalities on brain MRI. All living affected members carry a Notch3 mutation (Arg153Cys) previously reported in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). White matter abnormalities occur in a variable percentage of the general migraine population; CADASIL should be suspected in migraineurs with prolonged atypical aura and white matter abnormalities.

Brain↗
PubMed2000

A CLN2 gene nonsense mutation is associated with severe caudate atrophy and dystonia in LINCL.

Clinical features and results of the blood DNA analysis are reported of a child affected with a distinct phenotype of the late infantile form of neuronal ceroid-lipofuscinosis (LINCL). He was affected by microcephaly and hypotonia since the fourth month of life; acquisition of motor and language abilities was severely impaired, and a disorder of communication with stereotyped movements followed. By age four, he developed signs and symptoms of progressive myoclonic encephalopathy along with motor and cognitive deterioration. Extrapyramidal signs were associated with neuroradiological findings of marked atrophy of the caudate nucleus. Specific curvilinear bodies were observed in blood lymphocytes and skin biopsy. Homozygous, nonsense mutation in the CLN2 gene was found giving origin to an Arg208stop, which produces an early transcription termination with loss of translation of about 50% of the gene product. Any relationship between the severe clinical features of our patient and the homozygous mutation here reported must be investigated on a larger number of LINCL patients bearing the same mutation.

Atrophy↗
PubMed1996

Disseminated encephalitis following streptococcal infection.

Various neurological disorders have been related to Streptococcus pyogenes infection. Only recently, and for the first time, it has been suggested that acute disseminated encephalitis may also complicate a streptococcal infection. The case reported in this paper seems to confirm this hypothesis.

Adolescent↗
PubMed1995

[Encephalitis lethargica].

We report the case of a 34-year old patient who first complained of fever, confusion and transient ophthalmoplegia and then developed akinetic mutism, frontal lobe, pyramidal tract and extrapyramidal signs. Clinical and electrophysiological data support a diagnosis of encephalitis lethargica. Magnetic resonance imaging showed hyperintensive lesions in various brain regions. The patient responded to corticosteroid treatment. Two years after the onset of the first clinical signs he had recovered completely and today, after 5 years, he shows no sign of disease.

Adult↗