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Biomedical subjects

G Cipparrone

Publications and source records attributed to G Cipparrone.

16 recordsLinked to original sources
PubMed2004

Photorefractive effect due to a photoinduced surface-charge modulation in undoped liquid crystals.

We demonstrate that some peculiarities of the surface-induced photorefractive effect (SIPRE) in undoped nematic planar cells can be simply explained considering the electric field induced by a modulated surface-charge distribution. Polarization-dependent forced light scattering and two-beam coupling experiments indicate that the observed anisotropy of the diffraction efficiency and the energy transfer between the pump beams strongly depend on the experimental geometry. The investigation suggests that the unusual dichotomy between local and nonlocal behavior can be ascribed to a modulated longitudinal electric field component, in phase with the interference pattern, which is not accountable by the conventional photorefractivity. In a simple and general approach we demonstrate that the conceived charge distribution model for the SIPRE produces a space-charge field having two orthogonal modulated components, in-phase and pi/2 out of phase, respectively. The electric field configuration within the nematic sample gives reason for the main experimental features.

Journal Article↗
PubMed2004

Influence of the ions on the dynamical response of a nematic cell submitted to a dc voltage.

The influence of the ions present in a liquid crystal on the dynamical response of a nematic slab submitted to a dc voltage is studied. The evolution of the system toward the equilibrium state is investigated by solving the continuity equation for the electric charge, taking into account the current of drift and of diffusion. Our analysis shows that the formation of the double layers close to the electrodes strongly modifies the distribution of the electric field across the sample. We evaluate the surface polarization due to the ions movements and the contribution to the anisotropic part of the surface energy having a dielectric origin. We show also that, even if the optical response of the liquid crystal is a slow phenomenon, the distribution of the ionic charge is rather fast. Consequently, the presence of the ions cannot be neglected in the determination of the flexoelectric coefficients when the nematic sample is submitted to a square wave having a period of the order of 1 s.

Journal Article↗
PubMed2001

Homoclinic gluing bifurcations during the light induced reorientation in nematic-liquid-crystal films.

An s-polarized laser beam that impinges at small incidence angle on a homeotropically aligned nematic liquid crystal produces very interesting nonlinear phenomena. In this paper, we show that, due to the symmetry of the system, a cascade of successive homoclinic gluing bifurcations is responsible for the transition towards a stochastic regime in the experiment. We compare the experimental results with a model describing a sequence of gluing bifurcations.

Journal Article↗
PubMed2000

Nonlinear dynamics optically induced in nematic liquid crystals

We report the analysis of the dynamical regimes induced in a homeotropically aligned nematic liquid-crystal layer when an s-polarized laser beam impinges at a small incident angle. These regimes are studied by analyzing the time series of the variation of the polarization state of a light probe beam, recorded at different light intensities. A detailed description of the dynamical regimes, based on the analysis of the wavelet transforms performed on the observed time series, is presented. We recognize a first Hopf bifurcation followed by a gluing bifurcation, and a further transition toward an irregular regime. Similarities between our experimental results and a scenario of transition to chaos via a sequence of gluing bifurcations have been discussed.

Journal Article↗
PubMed1990

Colposcopic survey of Papanicolaou test-negative cases with hyperkeratosis or parakeratosis.

A colposcopic survey was performed in 269 consecutive women with negative cytology showing hyperkeratosis or parakeratosis. A colposcopy-guided biopsy specimen of cervical abnormalities was taken in 88 cases, and human papillomavirus infection (HPV) was detected histologically in 25 cases. No cervical intraepithelial neoplasia (CIN) was detected. The detection rate of HPV was not significantly different from that observed in a consecutive series of 1073 Papanicolaou test-negative subjects self-referred for colposcopy. Colposcopic screening of subjects showing hyperkeratosis or parakeratosis with otherwise negative smears is not recommended because it does not allow detection of cytologically false-negative CIN.

Adult↗
PubMed1988

Famotidine in the short-term treatment of duodenal ulcer and of concomitant peptic lesions: comparison with cimetidine.

Twenty patients affected with endoscopically demonstrated duodenal ulcer were studied. They were randomly divided into two groups of ten individuals each. The first group was treated with famotidine 40 mg/die/os, the second one with cimetidine 800 mg/die/os; both drugs were administered in one medication at bedtime. In each group, eight patients completed the treatment: six out of eight famotidine treated and five out of eight cimetidine treated patients showed ulcer healing on upper digestive endoscopy after four weeks of treatment; after eight weeks of therapy, all patients of both groups displayed ulcer healing. Nevertheless, an overall quantitative evaluation of all peptic lesions (performed according to an endoscopic arbitrary score) indicated a higher effectiveness of famotidine. Famotidine did not affect humoral parameters of renal, hepatic and myelopoietic function and did not significantly change fasting serum gastrin levels.

Cimetidine↗
PubMedDate not supplied

Contribution of cytology, colposcopy, target biopsy and conization to the early diagnosis of precancerous and cancerous lesions of the cervix uteri.

The study is based on 334 cytologic suspect or positive women observed in the area of Florence. Cytologic diagnoses of dysplasia, carcinoma in situ (CIS), and invasive carcinoma are related to the histologic reports. To the same histologic reports are related the colposcopic aspects. Lastly, diagnoses made by target biopsy are compared with the final diagnoses made by cone biopsy. The 3 diagnostic methods and their diagnostic accuracy are then compared. As regards dysplasia, the diagnostic precision of cytology is 40.2% and for target biopsy in 76.9%. In the diagnosis of CIS, cytology shows a diagnostic accuracy (77.7%) that is a little lower than that of target biopsy (81.7%). In invasive carcinoma, cytology has a good diagnostic precision (88.2%), which becomes 100% if the diagnosis is made by target biopsy. The correlation between colposcopic aspects and histologic reports is not very reliable. We conclude that cytology is a valid test in an extensive mass screening, that colposcopy is essential to execute target biopsy, and that the latter is useful in defining dysplasia and invasive carcinoma diagnoses. On the contrary, in the case of CIS, target biopsy does not greatly increase cytology diagnostic precision.

Biopsy↗
PubMedDate not supplied

Analysis of false-negative and underreported smears in the Florence district screening program for cervical carcinoma.

AIMS AND BACKGROUND: To review false-negative or underreported (reactive changes, squamous or glandular atypia) smears performed in women developing histologically proven CIN2 or more severe lesions within 24 months and evaluate error causes. The study setting was the Florence District cervical cancer population-based screening: about 60,000 women age 25-60 years screened per year. METHODS: 118 false-negative or underreported cases were identified at screening files-cancer Registry matching, and the original smears were reviewed by six independent readers to judge smear adequacy and error type. RESULTS: Sampling errors (reported as inadequate, negative or less severe than CIN1 at review) accounted for 74% and screening/interpretation errors (reported as CIN1 or more severe at review) accounted for 26% of studied cases. Screening/interpretation errors were more likely ascribed to misinterpretation and underreporting than to misperception of cellular abnormalities. CONCLUSIONS: Quality control should above all address the problem of sampling adequacy. Due to the rarity of misperceived abnormalities (true screening errors), manual or automated rescreening of negative smears would not be an effective procedure for quality control.

Adult↗
PubMedDate not supplied

Double pylorus: report of two cases and review of the literature.

Double pylorus is a rare condition consisting of a double communication between gastric antrum and duodenal bulb; in most cases it is a complication of penetrating ulcer, sometimes it is a congenital abnormality. The prevalence of this rare anomaly ranges from 0.02% to 0.13%; the male:female ratio is about 2:1. Two cases of acquired double pylorus are reported with a review of the literature. The first case represented an occasional report; in the other one the development of double pylorus from confluent prepiloric and bulbar ulcers was documented through serial endoscopies. Both patients were affected with chronic renal failure and referred previous treatment with diclofenac; however, their relationship with double pylorus onset remains unproven.

Duodenal Diseases↗
PubMedDate not supplied

Routine colposcopic survey of patients with squamous atypia. A method for identifying cases with false-negative smears.

Routine colposcopy was performed on 376 women with cervical squamous atypia (originally reported as "inflammatory atypia"). Colposcopy showed no abnormalities in 240 cases and a lesion in 136 cases; the latter were sampled by colposcopy-guided biopsy. The biopsy samples showed evidence of human papillomavirus (HPV) infection and/or grade I cervical intraepithelial neoplasia (CIN I) in 42 cases (11.1%), CIN II in 4 cases (1.1%) and CIN III in 5 cases (1.3%); the other 85 biopsied cases were histologically negative. Most cases of HPV/CIN I (35 of 42) and all of the cases of CIN II-III occurred in women under the age of 40. The detection rates were 4.4% for CIN II-III in women under the age of 40, 4.0% for HPV/CIN I in women 40 and older and 17.2% for HPV/CIN I in women under the age of 40 (P less than .001). It thus appears that women under the age of 40 who show cytologic evidence of squamous atypia would benefit from colposcopic examination.

Adult↗
PubMedDate not supplied

"Nonclassic" cytologic signs of cervical condyloma. A case-control study.

The association between "nonclassic" cytologic signs of condyloma and human papillomavirus (HPV) infection in women with negative Papanicolaou smears was analyzed via a case-control study. The cytologic signs considered were mild koilocytosis, mild dyskeratosis, binucleation or multinucleation, cleared cytoplasm and nuclear hyperchromatism. The Papanicolaou smears of 166 cases that showed colposcopic and histologic evidence of HPV infection (but whose smears lacked the classic cytologic signs of condyloma) and 166 controls that were negative colposcopically were randomly admixed and blindly reviewed by a panel of cytologists. A significant association to HPV infection was observed for all of the nonclassic signs studied, but multivariate analysis showed a weakly independent association only for mild koilocytosis. The sensitivity (0.46) and the specificity (0.87) of these nonclassic signs were not satisfactory. The utility of selecting women with negative Papanicolaou smears for colposcopy on the basis of these signs is discussed.

Adult↗