PubMed Health⌕ Search

Biomedical subjects

L Vaccaro

Publications and source records attributed to L Vaccaro.

At least 19 recordsLinked to original sources
PubMed2006

Selective coupling of HE11 and TM01 modes into microfabricated fully metal-coated quartz probes.

We report computational and experimental investigations on injection and transmission of light in microfabricated fully Aluminum-coated quartz probes. In particular, we show that a selective coupling of either the HE(11) or the TM(01) mode can be carried out by injecting focused linearly or radially polarized beams into the probe. Optical fields, emitted by the probe after a controlled injection, are characterized in intensity and phase with the help of an interferometric technique. With the help of near-field measurement, we finally demonstrate that a longitudinally polarized spot localized at the tip apex is actually produced when the TM(01) mode is coupled into the probe.

Journal Article↗
PubMed2005

Observation of amplitude and phase in ridge and photonic crystal waveguides operating at 1.55 microm by use of heterodyne scanning near-field optical microscopy.

We apply heterodyne scanning near-field optical microscopy (SNOM) to observe with subwavelength resolution the amplitude and phase of optical fields propagating in several microfabricated waveguide devices operating around the 1.55 microm wavelength. Good agreement between the SNOM measurements and predicted optical mode propagation characteristics in standard ridge waveguides demonstrates the validity of the method. In situ observation of the subwavelength-scale distribution and propagation of optical fields in straight and 90 degrees bend photonic crystal waveguides facilitates a more detailed understanding of the optical performance characteristics of these devices and illustrates the usefulness of the technique for investigating nanostructured photonic devices.

Crystallization↗
PubMed2001

Efficient O-trimethylsilylation of alcohols and phenols with trimethylsilyl azide catalyzed by tetrabutylammonium bromide under neat conditions.

A very efficient procedure for the trimethylsilylation of a wide variety of alcohols, including primary, allylic, benzylic, secondary, hindered secondary, tertiary, and phenols is reported. The reactions were carried out under neat conditions with trimethylsilyl azide (TMSN(3)) and, when necessary, in the presence of a catalytic amount (20 mol %) of tetrabutylammonium bromide (TBABr) at 30 or 70 degrees C. Under catalytic conditions, the yields of the corresponding trimethylsilyl ethers were greater than 91%. This procedure also allows the selective protection of primary and secondary alcohols in the presence of tertiary ones.

Journal Article↗
PubMed2001

Lewis-acid catalyzed organic reactions in water. The case of AlCl(3), TiCl(4), and SnCl(4) believed to be unusable in aqueous medium.

Classical Lewis acids such as AlCl(3), TiCl(4), and SnCl(4), believed to be unusable as catalysts in aqueous medium, efficiently catalyzed regio- and stereoselective azidolysis and iodolysis of alpha,beta-epoxycarboxylic acids in water at pH 4.0 and 1.5, respectively. The concept of water-tolerant metal-salt is reexamined in direct relationship to the aqua ion hydrolysis constant.

Journal Article↗
PubMed2001

Bromolysis and iodolysis of alpha,beta-epoxycarboxylic acids in water catalyzed by indium halides.

The ring opening of alpha,beta-epoxycarboxylic acids by bromide and iodide ions has been efficiently carried out in water in high regio- and stereoselective fashion. The iodolysis of trans-beta-monoalkylated epoxycarboxylic acids at pH 4.0 was completely alpha-regioselective and anti diastereoselective. The InCl(3)-catalyzed iodolysis of a variety of alpha,beta-epoxycarboxylic acids at pH 1.5 gave the corresponding anti beta-iodohydrins in 88-95% yields. The one-pot synthesis of the alpha- and beta-hydroxyhexanoic acids, starting from the corresponding alpha,beta-epoxycarboxylic acid 1a by iodolysis followed by reduction of the resulting iodohydrins 4a and 4b by NaBH(4)-InCl(3) in water, has been performed.

Journal Article↗
PubMed2001

Azidolysis of alpha,beta-epoxycarboxylic acids. A water-promoted process efficiently catalyzed by indium trichloride at pH 4.0.

The catalytic efficiency of InCl(3), Yb(OTf)(3), and Sc(OTf)(3) in the azidolysis of alpha,beta-epoxycarboxylic acids has been studied in water and in organic solvents, for comparison using NaN(3) and Me(3)SiN(3) as the source of the azido group. In water, the catalytic effectiveness of these metal salts strongly depends on the pH of the aqueous medium and on the type of Lewis acid catalyst. In water their catalytic activity is mostly due to the corresponding aqua ion species, the concentration of which becomes significant when the pH of the aqueous medium is below the corresponding pK(1,1) hydrolysis constant. The process is more efficient in water than in organic solvents. At pH 4.0, InCl(3) is a far better catalyst than Yb(OTf)(3) or Sc(OTf)(3) and allows the highly regio- and diasteroselective preparation of beta-azido-alpha-hydroxycarboxylic acids, which can be isolated in pure form in very high yields.

Journal Article↗
PubMed2001

Control of the vibration damping through surface functionalization of a shear force probe.

Shear force mapping on thiolipid Langmuir-Blodgett monolayers probed with Al-coated tips leads to a contrast highly dependent on the monolayer molecular organization, which does not correspond to the topographical relief of the sample. The use of functionalized surface probes offers the possibility to better control the probe-to-sample interaction. In addition, hydrophilic surface probes are totally insensitive to alkyl chain arrangements in the monolayer. Hydrophobic probes, instead, can be chosen to map shear force on soft samples in liquid environment, since their mechanical properties are not influenced by the surrounding liquid.

Microscopy, Fluorescence↗
PubMed1999

Is computed tomography of nonvisualized C7-T1 cost-effective?

The authors determined the cost-effectiveness of computed tomography (CT) of the inadequately visualized C7-T1 level on conventional radiography in a retrospective cohort study. Routine cervical spine radiography was performed in 360 trauma patients in whom the C7-T1 level was not adequately visualized, but there was no evidence of lower cervical spine injury. In these patients, CT of C7-T1 was performed and reviewed for the presence, location, and pattern of fracture. An orthopaedic surgeon was consulted regarding his proposed treatment and the presumed natural history without treatment of each C7-T1 injury identified. Based on Medicare reimbursement data, cost-effectiveness was then calculated for 1) each fracture identified, 2) each fracture that required surgical fixation secondary to risk of further neurologic sequelae (definitely unstable), and 3) each fracture that required either surgical fixation or halo immobilization secondary to the risk of development of cervical instability and arthritis (potentially or definitely unstable). Eleven of 360 fractures of C7-T1 were identified. The cost-effectiveness of CT for averting potential sequelae was $9,192 for each fracture identified, $16,852 identified for each potentially or definitely unstable fracture identified, and $50,557 for each definitely unstable fracture identified. Computed tomography of the inadequately visualized C7-T1 level on plain radiography is cost-effective, especially given the relatively young age of the trauma population and therefore the high associated morbidity of the sequelae of these injuries over time.

Adolescent↗
PubMed1994

Evaluation of the efficacy of pidotimod in the exacerbations in patients affected with chronic bronchitis.

The efficacy and safety of pidotimod ((R)-3-[(S)-(5-oxo-2-pyrrolidinyl)carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6), a new oral synthetic immunostimulating agent, were investigated in a multicentre study, performed in 10 university and hospital centres of pneumophthisiology and respiratory physiopathology, according to a double-blind vs. placebo experimental design. Primary objective of the investigation was to verify the efficacy of pidotimod against infectious exacerbations in patients affected with chronic bronchitis. 181 inpatients or outpatients (117 male, 64 female; mean age: 62.5 years), affected with chronic bronchitis, were enrolled in the study. Pidotimod 800 mg/die or placebo sachets were administered by oral route for 60 consecutive days, followed by a 60-day follow-up period. Clinical observations were performed at baseline (D 0), after 30 (D 30) and 60 (D 60) days of treatment, as well as at the end of the follow-up (D 120). Time and frequency of infectious relapses were considered as the target variable for the evaluation of the efficacy of the drug. Clinical picture, expectoration characteristics, spirometric parameters and laboratory tests were monitored to evaluate patients' conditions. The results indicate that pidotimod is significantly more effective than placebo against infectious relapses in patients suffering from chronic bronchitis. During the first month, 9% of patients treated with pidotimod were affected with an infectious relapse vs. 39.5% of patients treated with placebo (chi 2, p < 0.001). In the second month, infectious episodes were reported by 1.2% of patients treated with the drug vs. 46.1% of patients treated with placebo (chi 2, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1976

[Homologous and heterologous antibody response induced in man by anti-influenza vaccine containing A/England/42/72 and b/Massachusetts/71].

In november 1973, 43 subjects living in a home for aged were given one dose of influenza vaccine, containing A/England/42/72 and B/Massachusetts/71. After 4 and 20 weeks, sera were tested for antibody contentto the homologous and to A/port Chalmers/1/73 viruses by haemoagglutination inhibition technique. Control group included 23 untreated subjects. The satisfactory increase in the anti-A/England/42/72 antibodies induced by vaccine indicated a good antigenic potency of the A component. The satisfactory cross-reacting response suggests that the "drift" in antigenic content between A England/42/72 and A/Port Chalmers/1/73 was moderate. On the contrary the increase in anti-B/Massachusetts/71 antibodies after vaccination was observed only in a limited number of cases. Twelve subjects (9 treated and 3 controls) experienced upper respiratory tract infections which appeared to be not related to infuenza viruses.

Aged↗