73 research outputs found
Un anello ebraico in bronzo da Porto Torres (sec. IV-V e.v.), e l'epigrafe di Anabatia rinvenuta a Gerace (sec. XIV), con una nota su una lucerna funeraria ebraica da Licata (secc. IV-V e.v.)
No full textThe study presents a number of new archaeological discoveries of Jewish artifacts and proposes a new reading of an already known inscription. Perani, author of Part I, describes a recently discovered Jewish bronze ring from Porto Torres, Sardinia, dating to late antiquity (4th-5th centuries e.v.), relating to similar Jewish rings, discovered in Sicily and Sardinia in the past. Colafemmina, author of Part II, presents his reading of the inscription of Anabatyya found in 1990 in Gerace, province of Reggio Calabria. Finally, M.S. Rizzo and A. Toscano Raffa describe a recently discovered Jewish funerary lamp with menorah from late Roman period (4th-5th centuries), just found in Licata (Sicily)
Resolving complex mixtures by means of pulsed field gradient NMR experiments
No full textWe present a method to analyse pulsed gradient spin-echo (PGSE) NMR data from a mixture of compounds sharing the same NMR resonance (e.g. polymer solutions or mixtures of aliphatic compounds). If all the spin-bearing species undergo Brownian motion, their contribution to the experimental echo decay is exponential (i.e. e(-sD), with s a function of the parameters of the PGSE-NMR experiment and D the self-diffusion coefficient). For the case of more than one diffusing species at a given chemical shift, the (normalized) echo attenuation is the Laplace transform of the distribution function of the self-diffusion coefficients. The Laplace transform can be reduced to a Fredholm integral equation of the first kind in the variable z proportional to e(-sD) (in the interval [0,1]). Applying the algorithm previously developed by us (L. Ambrosone, A Ceglie, G. Colafemmina and G. Palazzo, J. Chem. Phys. 1999, 110, 797) we solve the integral equation, obtaining the distribution function of the diffusion coefficients. The method is tailored for small data sets (10-30 points) typical of PGSE-NMR measurements. Moreover, the relevant variable (z) being an exponential function of the self-diffusion coefficient, it allows insight on the ne structure of the diffusion spectrum. The method was successfully tested on a three-component solution and on an aqueous solution of seven PEG oligomers. In the latter case an estimate of the molecular mass distribution function was obtained. The reported results indicate that such an approach permits determination of self-diffusion coefficients differing by 15% with a high accuracy (6-3%)
The impact of alkanes on the structure of Triton X100 micelles
No full textHere we investigate the structural evolution of TX100 micelles upon loading with several linear and cyclic alkanes by DLS, PGSE-NMR, 2D NOESY NMR, viscosity measurements, and molecular dynamic simulations. Our results confirm that TX100 alone forms spherical, onion-like micelles made of several partially interpenetrating surfactant layers where the polyethylene glycol chains are in contact with the tetramethyl-butyl-phenyl moieties. Loading with non-penetrating oils larger than decane induces a decrease in micellar size and hydration because the alkane molecules compete with both water and tetramethyl-butyl-phenyl groups for the polyethylene glycol chains. This results in the partial peeling of the "onion" and in the dehydration of polyethylene glycol chains so that the micelles increase in number and decrease in size upon alkane loading. In contrast, small and penetrable oils (mainly cyclo-alkanes) first swell the onion-like micelles (inducing an increase in size) and only above a critical oil/surfactant ratio does the oil induce the weakening of the multilayer structure and the dehydration of polyethylene glycol chains found in long linear alkanes
Size distribution in emulsions
No full textEmulsions are generally opaque and scatter light widely. This characteristic is a considerable obstacle to the use of optical techniques such as dynamic light scattering and optical microscopy.
However, the optical appearance of a sample is totally irrelevant for nuclear magnetic resonance (NMR) measurements. In this paper we use general methods to calculate the size distribution of a collection of droplets in dilute emulsion systems using NMR pulse gradient spin-echo measurements. We show that such methods are also successful in describing a bimodal distribution of droplets
Multi-wavelength imaging of tissue phantoms by optical feedback interferometry
No full textOptical Feedback Imaging is the most recent advancement of the traditional Laser Self-Mixing. It is a coherent
scanning imaging technique with the unique feature of having the light source acting also as the signal detector.
Optical Feedback Imaging is being increasingly applied to both inorganic and organic samples, especially in the
infrared and Terahertz spectral region. The technique relies on the analysis of the back-scattered (or reflected)
radiation, thus it is contactless, detectorless and suited to be applied also in-vivo. As a coherent technique in reflection,
it is sensitive to both phase (index) contrast and amplitude (absorption) contrast. We demonstrate selective contrast
imaging of different organic pigments at three different visible wavelengths allowing for unambiguous identification
of absorption features in back-scattering geometry. However, a wealth of information about the chemical
composition of tissues is more readily available at mid-infrared wavelengths, where molecular bonds have their
spectral signatures. We also present Optical Feedback images collected in organic (agar-agar) tissue phantoms at mid
infrared wavelengths. 1% sensitivity to potato starch concentration included in the agar-agar matrix was detected at
6.26 μm, in resonance to the amide-I band
Stabilization of charge separation and cardiolipin confinement in antenna-reaction center complexes purified from Rhodobacter sphaeroides
No full textThe reaction center-light harvesting complex 1 (RC–LH1) purified from the photosynthetic bacterium Rhodobacter sphaeroides has been
studied with respect to the kinetics of charge recombination and to the phospholipid and ubiquinone (UQ) complements tightly associated with it.
In the antenna-RC complexes, at 6.5bpHb9.0, P+QB − recombines with a pH independent average rate constant bkN more than three times smaller
than that measured in LH1-deprived RCs. At increasing pH values, for which bkN increases, the deceleration observed in RC–LH1 complexes is
reduced, vanishing at pH N11.0. In both systems kinetics are described by a continuous rate distribution, which broadens at pH N9.5, revealing a
strong kinetic heterogeneity, more pronounced in the RC–LH1 complex. In the presence of the antenna the QAQB − state is stabilized by about
40 meV at 6.5bpHb9.0, while it is destabilized at pH N11. The phospholipid/RC and UQ/RC ratios have been compared in chromatophore
membranes, in RC–LH1 complexes and in the isolated peripheral antenna (LH2). The UQ concentration in the lipid phase of the RC–LH1
complexes is about one order of magnitude larger than the average concentration in chromatophores and in LH2 complexes. Following detergent
washing RC–LH1 complexes retain 80–90 phospholipid and 10–15 ubiquinone molecules per monomer. The fractional composition of the lipid
domain tightly bound to the RC–LH1 (determined by TLC and 31P-NMR) differs markedly from that of chromatophores and of the peripheral
antenna. The content of cardiolipin, close to 10% weight in chromatophores and LH2 complexes, becomes dominant in the RC–LH1 complexes.
We propose that the quinone and cardiolipin confinement observed in core complexes reflects the in vivo heterogeneous distributions of these
components. Stabilization of the charge separated state in the RC–LH1 complexes is tentatively ascribed to local electrostatic perturbations due to
cardiolipin
The role of the cosurfactant in the CTAB/water/n-pentanol/n-hexane system: Pentanol effect on the phase equilibria and mesophases structure
No full textWe report on the effect of 1-pentanol loading on the phase behaviour of mixtures of CTAB/water/n-hexane at fixed mole ratios 1:80:47. The cosurfactant induces changes in the interfacial film curvature. By increasing the pentanol/CTAB mole ratio, the system evolves from oil-in-water to water-in-oil structures. For very large 1-pentanol loading some water is expelled from the reverse micelles resulting in a L(2) plus water equilibrium (emulsification failure). In the range of compositions investigated most of the phase equilibria reveals the coexistence of liquid crystals and hexane/pentanol solutions. In these cases, we estimate the interface composition by assuming a constant 1-pentanol concentration in all the oil domains, and by tacking into account the alcohol solubility in water. In the case of single-phase sample the interfacial composition was determined by means of turbidimetric titration. The adsorption of cosurfactant at the interface of direct micelles, planar lamellae, bicontinuous microemulsions, and spherical reverse micelles follows the same adsorption isotherm (independently from the curvature of the interface). Moreover, the results obtained unambiguously show that the interface composition dictates the spontaneous curvature of interfacial film. Actually positive, null, and negative curvatures correspond to different compositions of the interfacial film. Once the influence of cosurfactant on the spontaneous curvature of the interface is understood, the appearance of the emulsification failure upon pentanol loading can be rationalised within the framework of the flexible surface model
Role of the cosurfactant in the CTAB/water/n-pentanol/n-hexane water-in-oil microemulsion. 1. Pentanol effect on the microstructure
No full textThe microstructure of the quaternary water-in-oil microemulsion CTAB/water/n-pentanol/n-hexane has been
investigated by means of the pulsed gradient spin-echo NMR technique over a wide range of composition.
The composition of the continuous organic phase and of the interfacial phase has been determined through
the analysis of the n-pentanol self-diffusion coefficient. The size of the reverse aggregates has been evaluated
from the CTAB self-diffusion coefficient. The correlation of the reverse micellar size with interfacial
composition has therefore been possible. Results coming from both water dilution lines and interface dilution
lines have been analyzed according to suitable models. A “master plot”, i.e., a graphical representation that
allows us to display the data collected at all the possible compositions of the four components system, is also
proposed
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