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D Pini

Publications and source records attributed to D Pini.

18 recordsLinked to original sources
PubMed2007

Model colloidal fluid with competing interactions: bulk and interfacial properties.

Using a simple mean field density functional theory (DFT), the authors investigate the structure and phase behavior of a model colloidal fluid composed of particles interacting via a pair potential which has a hard core of diameter sigma, is attractive Yukawa at intermediate separations, and is repulsive Yukawa at large separations. The authors analyze the form of the asymptotic decay of the bulk fluid correlation functions, comparing results from DFT with those from the self-consistent Ornstein-Zernike approximation (SCOZA). In both theories the authors find rich crossover behavior, whereby the ultimate decay of correlation functions changes from monotonic to long wavelength damped oscillatory decay on crossing certain lines in the phase diagram or sometimes from oscillatory to oscillatory with a longer wavelength. For some choices of potential parameters the authors find, within the DFT, a lambda line at which the fluid becomes unstable with respect to periodic density fluctuations. SCOZA fails to yield solutions for state points near such a lambda line. The propensity towards clustering of particles, which is reflected by the presence of a long wavelength (>>sigma) slowly decaying oscillatory pair correlation function, and a structure factor that exhibits a very sharp maximum at small but nonzero wave numbers, is enhanced in states near the lambda line. The authors present density profiles for the planar liquid-gas interface and for fluids adsorbed at a planar hard wall. The presence of a nearby lambda transition gives rise to pronounced long wavelength oscillations in the one-body density profiles at both types of interface.

Journal Article↗
PubMed2006

Critical behavior in colloid-polymer mixtures: theory and simulation.

We extensively investigated the critical behavior of mixtures of colloids and polymers via the two-component Asakura-Oosawa model and its reduction to a one-component colloidal fluid using accurate theoretical and simulation techniques. In particular the theoretical approach, hierarchical reference theory [A. Parola and L. Reatto, Adv. Phys. 44, 211 (1995)], incorporates realistically the effects of long-range fluctuations on phase separation giving exponents which differ strongly from their mean-field values, and are in good agreement with those of the three-dimensional Ising model. Computer simulations combined with finite-size scaling analysis confirm the Ising universality and the accuracy of the theory, although some discrepancy in the location of the critical point between one-component and full-mixture description remains. To assess the limit of the pair-interaction description, we compare one-component and two-component results.

Journal Article↗
PubMed2003

Phase diagram of symmetric binary mixtures at equimolar and nonequimolar concentrations: a systematic investigation.

We consider symmetric binary mixtures consisting of spherical particles with equal diameters interacting via a hard-core plus attractive tail potential with strengths epsilon(ij), i,j=1,2, such that epsilon(11)=epsilon(22)>epsilon(12). The phase diagram of the system at all densities and concentrations is investigated as a function of the unlike-to-like interaction ratio delta=epsilon(12)/epsilon(11) by means of the hierarchical reference theory. The results are related to those of previous investigations performed at equimolar concentration, as well as to the topology of the mean-field critical lines. As delta is increased in the interval 0<delta<1, we find first a regime where the phase diagram at equal species concentration displays a tricritical point, then one where both a tricritical and a liquid-vapor critical point are present. We did not find any clear evidence of the critical end point topology predicted by mean-field theory as delta approaches 1, at least up to delta=0.8, which is the largest value of delta investigated here. Particular attention was paid to the description of the critical-plus-tricritical point regime in the whole density-concentration plane. In this situation, the phase diagram shows, in a certain temperature interval, a coexistence region that encloses an island of homogeneous, one-phase fluid.

Journal Article↗
PubMed2001

Determination of absolute configuration of acyclic 1,2-diols with Mo2(OAc)4. 1. Snatzke's method revisited.

The method employing dimolybdenum tetraacetate for the assignment of the absolute configuration of optically active 1,2-diols is thoroughly revisited and applied to several compounds, some of which were synthesized by asymmetric cis-dihydroxylation. No exceptions were found to the empirical rule relating the sign of the induced CD spectrum and the configuration of the substrate, whatever its structure and sterical requirements. To broaden the scope of the method, its applicability to critical situations commonly encountered with synthetic products is tested. It is demonstrated that the method can be applied on samples with low chemical and optical purity, and that it may lend itself as a means to estimate the ee. The roles of the water content of the sample and of the diol-to-dimolybdenum ratio are investigated.

Circular Dichroism↗
PubMed2000

What do young people think about the dangers of sunbathing, skin cancer and sunbeds? A questionnaire survey among Italians.

Previous experience in Australia and Sweden showed that public education programs produced substantial changes in people's opinions, attitudes and perceptions about melanoma, non-melanoma skin cancer, sunlight, sunbeds and suntanning. In order to organize effective prevention campaigns, more must be known about the sunbathing habits of children and adolescents. The aim of our study was to assess the knowledge that young people in a southern European country have about sun exposure. A total of 764 young people ranging from 16 to 22 years old (mean age: 19.3+/-1.2 years) responded to a questionnaire. Our study indicates that young people are very aware of the risks associated with sunbathing but that they continue to expose themselves without taking precautions. This suggests that: a) the majority of young Italians are reasonably well-informed but they do not take preventative measures; b) one effective measure could be promotion of the idea that an untanned body is more esthetically pleasing than a tanned one; c) a crucial point in the programming of future safety measures in suntan centers involves rigorous and regular controls.

Adolescent↗
PubMed1999

Catalytic asymmetric dihydroxylation of alkenes induced by polymeric chiral ligands

Chiral monomers, bearing different quinidine derivatives, were copolymerized with achiral monomers, producing insoluble copolymers which were used for the dihydroxylation of styrene as standard substrate. The structure of the polymeric insoluble support was found to be of great importance in determining the handling, efficiency, and enantioselectivity of the catalyst. The comparison with a soluble model compound showed that the insoluble polymer-bound ligand approach is very promising for both small- and large-scale synthesis of optically active vicinal diols. Copyright 1999 Wiley-Liss, Inc.

Journal Article↗
PubMed1999

Thermodynamically self-consistent theories of fluids interacting through short-range forces.

The self-consistent Ornstein-Zernike approximation (SCOZA), the generalized mean spherical approximation (GMSA), the modified hypernetted chain (MHNC) approximation, and the hierarchical reference theory (HRT) are applied to the determination of thermodynamic and structural properties, and the phase diagram of the hard-core Yukawa fluid (HCYF). We investigate different Yukawa-tail screening lengths lambda, ranging from lambda=1.8 (a value appropriate to approximate the shape of the Lennard-Jones potential) to lambda=9 (suitable for a simple one-body modelization of complex fluids like colloidal suspensions and globular protein solutions). The comparison of the results obtained with computer simulation data shows that at relatively low lambda's all the theories are fairly accurate in the prediction of thermodynamic and structural properties; as far as the phase diagram is concerned, the SCOZA and HRT are able to predict the binodal line and the critical parameters in a quantitative manner. At lambda=4 some discrepancies begin to emerge in the performances of the different theoretical approaches: the MHNC remains, on the whole, reasonably accurate in predicting the energy and the contact value of the radial distribution function; the SCOZA predicts well the equation of state up to the highest lambda values investigated. The GMSA and the MHNC underestimate and overestimate, respectively, the liquid coexisting density, while the SCOZA and HRT yield liquid branches that fall between the two former theoretical predictions, although both appear to overestimate the critical temperature somewhat. At higher lambda's the GMSA and MHNC binodals further worsen, while the SCOZA appears to remain usefully predictive. In general, the predictions of all the theories tend to slightly worsen at low temperatures and high density. The determination of the freezing line, performed by means of a one-phase "freezing criterion" (due to other authors) is not particularly satisfactory within either the SCOZA or the MHNC; the GMSA prediction for the freezing line at lambda=7 and 9 is instead able to follow in a qualitative manner the pattern of the solid-vapor coexistence line as determined through computer simulation studies. The necessity of further assessments of the freezing predictions is also discussed. Finally, versions of the GMSA, SCOZA, and HRT that can be expected to be more accurate for interactions with extremely short-ranged attractions are identified.

Journal Article↗
PubMed1997

Severe herpetic whitlow in an HIV-1 and HIV-2 infected patient.

Our paper describes an unusual case of herpetic whitlow due to HSV-2 in an HIV-1 and HIV-2 infected patient. This patient was a 33-year-old cook, HIV-1Ab and HIV-2Ab positive for 4 years. The CD4+ cell count was below 50 cells/microL and no previous AIDS-defining illness happened. After having had a jagged tearing wound by a carving-knife on index finger of his right hand, he showed a rapid advancing erosion, which completely encircled his forefinger, due to HSV-2. Twenty days later he also showed two small adjacent lesions on penile shaft which rapidly extended with multiple subpreputial lesions. These lesions were caused by HSV-2 infection too. Both, finger and penile lesions, completely healed after a 3-week treatment with intravenous and oral acyclovir.

Journal Article↗
PubMed1996

Plasma nitrate plus nitrite changes during continuous intravenous infusion interleukin 2.

Nitric oxide (NO), a biologically active mediator generated in many cell types by the enzyme NO synthase, may play an important role in cardiovascular toxicity that is frequently observed in cancer patients during intravenous (i.v.) interleukin 2 (IL-2) therapy. The induction of NO synthase and the production of NO seem to be involved in the pathogenesis of the vascular leakage syndrome, as well as in the regulation of myocardial contractility. In the present study, we evaluated the pattern of plasmatic NO changes during multiple cycles of continuous i.v. infusion (CIVI) of IL-2 in ten advanced cancer patients (five males, five females, median age 59 years, range 33-67 years; eight affected by renal cell cancer and two affected by malignant melanoma). The patients received IL-2 at 18 MIU m-2 day-1 (14 cycles) or 9 MIU m-2 day-1 (seven cycles) for 96 h, repeated every 3 weeks. Interferon alpha (IFN alpha) was also administered subcutaneously (s.c) during the 3 week interval between IL-2 cycles. For each cycle, plasma samples were collected before treatment (t0), 24 h (t1), 48 h (t2), 72 h (t3) and 96 h (t4) after the start of IL-2 infusion, and 24 h after the end of the cycle. NO concentration was determined spectrophotometrically by measuring the accumulation of both nitrite and nitrate (after reduction to nitrite). The following observations may be drawn from data analysis: (1) plasma nitrate + nitrite significantly raised during treatment (P = 0.0226 for t0 vs t3), but statistical significance was retained only when cycles administered with IL-2 18 MIU m-2 day-1 are considered (P = 0.0329 for t0 vs t3; P = 0.0354 for t0 vs t2 vs t4) (dose-dependent pattern); (2) during subsequent cycles a significant trend toward a progressive increase of plasma nitrate + nitrite levels, with increasing cumulative dose of IL-2, was observed (linear regression coefficient r = 0.62, P = 0.0141 for t0; r = 0.80, P = 0.0003 for t1; r = 0.62, P = 0.013 for t2; r = 0.69, P = 0.045 for t3); (3) plasma nitrate + nitrite levels peaked earlier in subsequent cycles than in the first cycle; (4) all patients experienced hypotension. The mean of the systolic blood pressure values was significantly lower at the time of plasma nitrate + nitrite peak than at t0 (P = 0.0004); (5) the two cases of grade III hypotension occurred in patients with the higher mean and peak plasma nitrate + nitrite values. We conclude that determination of plasma nitrate + nitrite levels during CIVI IL-2 can usefully estimate, in a dose-dependent pattern, the degree of peripheral vascular relaxation and capillary leakage associated with cytokine action, clinically manifested as hypotension. However, isolated cardiac toxicity that continues to represent a relevant problem during IL-2 therapy, does not appear to correlate with plasma nitrate + nitrite levels; therefore, further studies are required to understand adequately the mechanisms underlying IL-2-induced cardiac toxicity.

Adult↗
PubMedDate not supplied

Synthesis and toxicity to mammalian cells of the carrot dihydroisocoumarins.

The dihydroisocoumarins (+-)-6-methoxy-8-hydroxy-3-methyl-3,4- dihydroisocoumarin (1), (+-)-6,8-dihydroxy-3-methyl-3,4-dihydroisocoumarin (2), and (+-)-6,8-dimethoxy-3-methyl-3,4-dihydroisocoumarin (3) were synthesized with high yields via metalation of o-methylbenzamides. The toxicity of these compounds and that of (-)-1 extracted from carrot cells were tested, in vitro, on Chinese hamster cells. The toxicity was determined according to the presence or absence of a hydroxyl group in the peri position of the lactonic carbonyl group and according to the stereochemistry of the dihydroisocoumarin.

Animals↗