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Search Results: 1 - 10 of 5472 matches for " Giuseppe Caputo "
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Supercritical Fluid Adsorption of Domperidone on Silica Aerogel  [PDF]
Giuseppe Caputo
Advances in Chemical Engineering and Science (ACES) , 2013, DOI: 10.4236/aces.2013.33024
Abstract:

Silica aerogel (SA) was loaded with domperidone to demonstrate the potentiality of adsorption processes based on the usage of supercritical carbon dioxide to treat poorly water-soluble drugs, forming new kinds of drug delivery systems. The effects of pressure, temperature and solution concentration on loaded SA were studied. Adsorption isotherms were measured at 35and 45 and fitted with Langmuir model. Release kinetics of the adsorbed drug were also evaluated by in vitro dissolution tests. Results showed that domperidone can be uniformly dispersed into the aerogel and that the release rate of domperidone from the composite, constituted by drug and silica aerogel, is much faster than that of the crystalline drug. The proposed adsorption method is suitable for the production of domperidone fast release tablets.

Fixed Bed Adsorption of Drugs on Silica Aerogel from Supercritical Carbon Dioxide Solutions
Giuseppe Caputo
International Journal of Chemical Engineering , 2013, DOI: 10.1155/2013/752719
Abstract: Supercritical adsorption coupled with the high adsorption capacity of silica aerogel allows the preparation of a new kind of delivery systems of poor water soluble drugs. In order to overcome drawbacks of conventional techniques where the use of liquid solvents can cause the fracture of aerogel porous structure, in this work a new adsorption process of drugs from a supercritical mixture is proposed. Adsorption takes place from a fluid solution of the drug in supercritical CO2 and ethanol as cosolvent. A fixed bed adsorption plant has been developed to allow fast mixing of fluid phase and effective contact in the adsorption column. The use of ethanol as cosolvent allows to overcome the limitation of supercritical adsorption due to low solubility of many drugs in supercritical CO2. Adsorption isotherms were measured for one-model substance, nimesulide, at 40°C, and breakthrough curve was experimentally obtained. The drug loading of the drug into silica aerogel was up to 9?wt%. The drug composite was characterized using scanning electron microscopy, and release kinetics of the adsorbed drug were also evaluated by in vitro dissolution tests. The dissolution of nimesulide from loaded aerogel is much faster than dissolution of crystalline nimesulide. Around 80% of nimesulide dissolves from the aerogel within 6 minutes, whereas dissolving 80% of the crystalline drug takes about 90?min. 1. Introduction The poor water solubility of some drugs limited their bioavailability. A fast dissolving system can be defined as a dosage form for oral administration, which, when placed in mouth, rapidly dispersed or dissolved increasing compliance and efficacy of the therapy. Fast dissolving and fast dispersing drug delivery system may offer a solution to these problems. A possible approach for ensuring maximum bioavailability is the increase of drug dissolution rate and/or solubility. To improve the dissolution rate of drugs, different techniques have been developed [1]. The most common approach is based on particle size reduction that can be achieved by processes based on micronization or nanosuspension. In the field of supercritical fluids, various promising techniques of micronization of drugs and excipients with supercritical carbon dioxide (SC-CO2) have been developed [2, 3], and also the use of water solvent and the less-expensive supercritical nitrogen is being explored [4–6]. An alternative way to improve the availability of a drug is its dispersion on a biocompatible substrate [7]. Silica-based materials used as substrate are widely employed as additives, free flow
Abnormal Femoral Origin of the Anterior Cruciate Ligament Associated with Osteochondritis Dissecans of the Medial Femoral Condyle  [PDF]
Massimiliano Salvi, Francesco Caputo, Giuseppe Piu, Marco Sanna, Cristina Sanna
Surgical Science (SS) , 2013, DOI: 10.4236/ss.2013.410093
Abstract:

We report a case of abnormal meniscal-like anterior cruciate ligament (ACL), inserting at the 9 o’clock position just beside the cartilage of the lateral femoral condyle, in a stable knee associated with osteochondritis dissecans (OCD) of the medial femoral condyle.

On the Theoretical Period-Radius Relation of Classical Cepheids
Bono Giuseppe,Caputo Filippina,Marconi Marcella
Physics , 1998,
Abstract: We present the results of a comprehensive theoretical investigation on the Period-Radius (PR) relation of classical Cepheids based on new sequences of full amplitude, nonlinear convective models constructed by adopting a wide range of both stellar masses and chemical compositions. For log P in the range 0.9 - 1.8 a very good agreement is found between theoretical predictions and current available data whereas outside this range, both at shorter and at longer periods, nonlinear radii attain intermediate values between empirical relations based on different Baade-Wesselink (BW) methods and photometric bandpasses.
Metal Rich RR Lyrae Variables: I. The Evolutionary Scenario
Giuseppe Bono,Filippina Caputo,Santi Cassisi,Vittorio Castellani,Marcella Marconi
Physics , 1996, DOI: 10.1086/303872
Abstract: This paper presents evolutionary computations which investigate the theoretical predictions concerning metal rich RR Lyrae pulsators found both in the Galactic field and in the Galactic bulge. The main aim of this investigation is to provide a homogeneous evolutionary context for further analyses concerning the pulsational properties of these evolving structures. In this connection a suitable set of stellar models characterized by two different metal contents, namely Z=0.01 and Z=0.02 were followed through both H and He burning phases. This evolutionary scenario covers the theoretical expectations for pulsating He burning structures with ages ranging from 20 to less than 1 Gyr. For each given assumption about the star metallicity we find that "old" He burning pulsators with ages larger than 2 Gyr have a common behavior, with Z=0.01 pulsators slightly more luminous and more massive than Z=0.02 pulsators. However, as soon as the metallicity increases above the solar value, the luminosity of Horizontal Branch (HB) stars increases again. This effect is a direct consequence of the expected simultaneous increase of both original He and metals. The occurrence of "young" RR Lyrae pulsators is discussed. Hydrogen burning isochrones for the quoted metallicity values are also presented and discussed. Finally, the occurrence of a new "gravonuclear instability" in some HB models during the ignition of He shell burning is discussed.
Double-mode RR Lyrae Variables: Pulsational Masses Revisited
Giuseppe Bono,Filippina Caputo,Vittorio Castellani,Marcella Marconi
Physics , 1996, DOI: 10.1086/310320
Abstract: Double-mode RR Lyrae variables (i.e. radial variables which are simultaneously pulsating in both fundamental and first overtone modes) appear a fundamental tool for investigating the mass of old Population II Horizontal Branch (HB) stars. The most widespread method adopted for evaluating the masses of these objects is based on the Petersen (1973) approach, which relies only on pulsational periods and therefore is independent of any preliminary evaluation of the reddening and/or of the distance modulus of the stellar cluster. In this paper we supply an overview of the mass estimates and underline the role played by opacities as well as by full amplitude nonlinear models for removing the discrepancy between pulsational and evolutionary masses. On the basis of the comparison between the theoretical scenario and double- mode RR Lyrae stars belonging to selected Galactic globular clusters (IC4499, M3, M15, M68, NGC2419, NGC6426) we show that the Petersen diagram can provide valuable constraints also on the luminosity of these variables.
Metal Rich RR Lyrae Variables: II. The Pulsational Scenario
Giuseppe Bono,Filippina Caputo,Santi Cassisi,Roberta Incerpi,Marcella Marconi
Physics , 1997, DOI: 10.1086/304284
Abstract: We present a theoretical investigation on the pulsational behavior of metal-rich RR Lyrae variables over the range of evolutionary parameters suitable for stars with metallicities Z= 0.006, 0.01 and 0.02. With the addition of similar results for metal-poor pulsators we discuss the theoretical pulsational scenario covering the metallicity range from Z=0.0001 to 0.02. We find that the distribution of field ab-type RR Lyrae stars in the period-metallicity plane can be easily understood within the framework of the present theoretical scenario, suggesting that the Oosterhoff dichotomy also affects field variables. Theoretical predictions concerning the amplitude-period diagram are discussed and compared with observational data. We find a general agreement for metal-poor ([Fe/H]<-1.4) RR Lyrae stars, whereas more metal-rich variables show amplitudes smaller than those predicted for pulsators originated from old, low-mass evolving stars. Alternatively, the agreement between theory and observations would require that a substantial fraction of metal-rich RR Lyrae variables in the Galactic field were younger than approximately 2 Gyr. The comparison between the pulsational behavior of RR Lyrae either in the Galactic field or in the Galactic bulge discloses the evidence that, at least as far as RR Lyrae variables are concerned, the metal-rich components of the bulge and of the field population appear quite similar.
Evolutionary and Pulsational Constraints for Super-metal-rich Stars with Z=0.04
Bono Giuseppe,Caputo Filippina,Cassisi Santi,Castellani Vittorio,Marconi Marcella
Physics , 1997,
Abstract: We investigate the evolutionary behavior of stellar structures with metallicity Z=0.04 in order to disclose theoretical expectations for both evolutionary and pulsational behaviors of Super-Metal-Rich (SMR) objects, which are found in the solar neighborhood, in the Galactic bulge and in elliptical galaxies. We find that at the exhaustion of central helium SMR stars definitely undergo the gravonuclear instabilities previously found in some He burning structures with solar metallicity (Bono et al. 1997b). On the basis of the evolutionary scenario, we investigate the expected pulsational behavior of He burning SMR stars for suitable assumptions on the pulsators evolutionary parameters. Nonlinear, nonlocal, and time-dependent convective models are discussed, the modal stability is investigated for the first two modes, and the theoretical predictions about the period distribution inside the instability strip and the shape of both light and velocity curves are presented. Full amplitude, nonlinear envelope models show that the range of effective temperatures where SMR RR Lyrae variables present a stable limit cycle is smaller in comparison with pulsators characterized by lower metal abundances. We show that both periods and light curves of different groups of type II Cepheids with periods shorter than six days, presented by Diethelm (1983,1990), can be all reproduced by suitable variations in the effective temperature or in the luminosity level of our SMR post-HB models, supporting evidence of a substantial homogeneity of these variable.
Second Overtone Pulsators Among Delta Scuti Stars
Giuseppe Bono,Filippina Caputo,Santi Cassisi,Vittorio Castellani,Marcella Marconi,Robert F. Stellingwerf
Physics , 1996, DOI: 10.1086/303710
Abstract: We investigate the modal stability of stellar models at masses and luminosity levels corresponding to post main sequence luminous delta scuti pulsators. The envelope models have been computed at fixed mass value, luminosity level and chemical composition (Y=0.28, Z=0.02). According to a nonlinear approach to radial oscillations the present investigation predicts the occurrence of stable second overtone pulsators for the first time. The shape of both light and velocity curves are presented and discussed, providing a useful tool for the identification of second overtone pulsators among the known groups of radially pulsating stars. The period ratios of mixed mode pulsators obtained by perturbing the first and the second overtone radial eigenfunctions are in agreement with observative values. Finally, the physical structure and the dynamical properties of second overtone pulsators are discussed in detail. The role played by the nodal lines in the destabilization of second overtone pulsators is also pointed out.
On the period distribution of cluster RR Lyrae stars to constrain their helium content: the case of omega Centauri
Marcella Marconi,Giuseppe Bono,Filippina Caputo,Anna M. Piersimoni,Adriano Pietrinferni,Robert F. Stellingwerf
Physics , 2011, DOI: 10.1088/0004-637X/738/1/111
Abstract: We present new sets of nonlinear, time-dependent convective hydrodynamical models of RR Lyrae stars assuming two metal (Z=0.0005, Z=0.001) and three helium abundances (Y=0.24, 0.30, 0.38). For each chemical composition we constructed a grid of fundamental (FU) and first overtone (FO) models covering a broad range of stellar masses and luminosities. To constrain the impact of the helium content on RR Lyrae properties, we adopted two observables --period distribution, luminosity amplitudes-- that are independent of distance and reddening. The current predictions confirm that the helium content has a marginal effect on the pulsation properties. The key parameter causing the difference between canonical and He-enhanced observables is the luminosity. We compared current predictions with the sample of 189 RR Lyrae stars in omega Cen and we found that the period range of He-enhanced models is systematically longer than observed. These findings apply to metal-poor and metal-intermediate He-enhanced models. To further constrain the impact of He-enhanced structures on the period distribution we also computed a series of synthetic HB models and we found that the predicted period distribution, based on a Gaussian sampling in mass, agrees quite well with observations. This applies not only to the minimum fundamentalized period of RR Lyrae stars (0.39 vs 0.34 day), but also to the fraction of Type II Cepheids (2% vs 3%). We also computed a series of synthetic HB models assuming a mixed HB population in which the 80% is made of canonical HB structures, while the 20% is made of He-enhanced (Y=0.30) HB structures. We found that the fraction of Type II Cepheids predicted by these models is almost a factor of two larger than observed (5% vs 3%). This indicates that the fraction of He-enhanced structures in omega Cen cannot be larger than 20%.
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