Biomedical subjects

Roberto Caputo

Publications and source records attributed to Roberto Caputo.

6 recordsLinked to original sources

PubMed2006

In situ optical control and stabilization of the curing process of holographic gratings with a nematic film-polymer-slice sequence structure.

We report on the realization of what we believe to be a new holographic setup for the fabrication of polymer liquid-crystal polymer-slice diffraction gratings, which utilizes an optical-feedback-driven nanopositioning technique. We have increased the stability of the interference pattern by means of a simple piezomirror used in a feedback configuration to keep constant the phase of the interferometer. The feedback system is driven by a proportional, integral, derivative control software, and the stability degree is controlled by the reference signal coming from a standard test grating. A preliminary experimental characterization indicates that good control and stabilization of parasitic fluctuations of the interference pattern are obtained.

Journal Article↗

PubMed2005

Observation of two-wave coupling during the formation of POLICRYPS diffraction gratings.

We report on the experimental observation of two-wave mixing that occurs inside a sample between the beams used for the fabrication of polymer-liquid-crystal-polymer slices (POLICRYPS) diffraction gratings. The effect depends on the phase shift between the curing interference pattern and the grating being cured. This shift can be mechanically induced by accidental vibrations of the experimental setup; thus a high setup stability is needed. We devised a mechanism that enables us to control setup vibrations in situ and used it to monitor the experiment. When the mechanically induced shift was significantly small, wave mixing was observed only if the initial intensities of the two curing beams were different from each other.

Journal Article↗

PubMed2005

Color-tunable organic microcavity laser array using distributed feedback.

Distributed feedback microstructures play a fundamental role in confining and manipulating light to obtain lasing in media with gain. Here, we present an innovative array of organic, color-tunable microlasers which are intrinsically phase locked. Dye-doped helixed liquid crystals were embedded within periodic, polymeric microchannels sculptured by light through a single-step process. The helical superstructure was oriented along the microchannels; the lasing was observed along the same direction at the red edge of the stop band. Several physical and technological advantages arise from this engineered heterostructure: a high quality factor of the cavity, ultralow lasing threshold, and thermal and electric control of the lasing wavelength and emission intensity. This level of integration of guest-host systems, embedded in artificially patterned small sized structures, might lead to new photonic chip architectures.

Journal Article↗

PubMed2005

Long eyelashes in a case series of 93 children with vernal keratoconjunctivitis.

OBJECTIVE: Vernal keratoconjunctivitis (VKC) is a chronic conjunctivitis that affects children mainly in temperate areas, with exacerbations in spring and summer. Eyelashes provide natural protection for the eyes from sunshine, wind, and foreign bodies. These factors induce a worsening of signs and symptoms in VKC, whereas mechanical protection of the eyes produces relief. The aim of this study was to evaluate eyelash length in a large series of VKC patients and in age- and gender-matched healthy subjects. METHODS: Upper eyelash length was measured in 93 VKC patients (mean age: 8.7 years; range: 4-18 years) with a digital caliper. History, clinical form, type of presentation, degree of severity, and drug therapy were evaluated. Skin tests and serum-specific immunoglobulin E for common allergens, serum-total immunoglobulin E, peripheral blood eosinophil counts, and serum eosinophil cationic protein were determined. Two age- and gender-matched control subjects for each VKC patient underwent the same eyelash measurement. RESULTS: The upper eyelashes were significantly longer in VKC patients than in control subjects (mean +/- SD: 8.9 +/- 1.17 mm vs 7.9 +/- 1.07 mm). In healthy subjects, a negative correlation was found between eyelash length and age. With multivariate analysis, unlike control subjects, the eyelash length in VKC patients did not correlate with age, was positively correlated with the degree of severity of VKC, and was negatively correlated with the use of topical cyclosporine. CONCLUSIONS: Patients with VKC had longer eyelashes than healthy matched subjects. The ocular inflammation, by unknown chemical mediators, was likely responsible for the excessive eyelash growth. The finding may represent a defensive mechanism against physical agents that might have a crucial role in the etiopathogenesis of this disease.

Adolescent↗

PubMed2004

Development of a new kind of switchable holographic grating made of liquid-crystal films separated by slices of polymeric material.

We present a new kind of UV-cured holographic grating that consists of polymer slices alternated with pure nematic films. By preventing the appearance of the nematic phase during the curing process, it is possible to avoid the formation of liquid-crystal droplets and obtain a sharp and uniform morphology, which reduces scattering losses and increases diffraction efficiency.

Journal Article↗

PubMed2002

Efficacy and safety of cyclosporine eyedrops in vernal keratoconjunctivitis.

BACKGROUND: Corticosteroids have been the only effective topically administered treatment for severe vernal keratoconjunctivitis (VKC), but their prolonged use is often associated with complications. Topical cyclosporine therapy has been used in the past decade, but few controlled trials have been conducted, and conflicting results have been reported. OBJECTIVE: This study sought to evaluate the efficacy and safety of ocular administration of cyclosporine in VKC. METHODS: Twenty-four children with severe VKC were treated with cyclosporine 2% eyedrops. The treatment began in spring and lasted 4 months. One eye was treated with cyclosporine (Cs-eye); the fellow eye received the vehicle as placebo (Pl-Cs-eye) during the first 2 weeks in a double-blind, placebo-controlled trial and thereafter was treated with cyclosporine (open trial). Patients were instructed to protect their eyes against sunlight. Ocular symptoms and signs were scored at entry and at 2 weeks, 4 weeks, and 4 months after the beginning of treatment. All children underwent biochemical and immunologic evaluations. RESULTS: Compared with baseline, scores for ocular signs and symptoms at 2 weeks decreased significantly in the Cs-eyes (P < 0.001), and signs improved in the Pl-Cs-eyes (P = 0.001). A significant difference was noted between Cs-eyes and Pl-Cs-eyes at 2 weeks for both subjective (P < 0.005) and objective (P < 0.001) scores. At 4 weeks, scores for signs (P < 0.001) and symptoms (P = 0.01) were reduced in the Pl-Cs-eyes, with no further improvement in the Cs-eyes. At 4 months, clinical scores had declined further, and serum eosinophil cationic protein levels were significantly lower than at entry (P = 0.009). Most patients reported mild burning sensation and tearing after administration of cyclosporine. Four patients (17%) required an additional brief period of topical corticosteroid therapy. CONCLUSIONS: Cyclosporine eyedrops were effective and safe for treating severe VKC, without causing major side effects. Most of the therapeutic effect was achieved after 2 weeks. The initial therapeutic effect was maintained during the next 3 months, with a further slow decrease in the symptoms.

Anti-Allergic Agents↗