Feasibility experiments on time-resolved fluorosensing applied to oil slicks

The introduction of time resolved observations can provide a very penetrating tool in the practice of laser fluorosensing. The investigations have demonstrated a relevance of multispectral, time resolved analysis for oil fingerprinting. By comparative studies on a variety of crude oils and their most significant fractions, it was found that the process of time decay in a composite oil is characterized by a few steps, which are associated with specific components in the medium light range. The average decay times of these pure fractions are markedly differentiated as to absolute values and spectral spread; as a consequence, the corresponding parameters in the resultant crude are quite sensitive to the particular mixture of these components. Measurements of the time response give then a finer discrimination between oil classes, depending on the relative content of certain fractions. Experiments were pursued with an improved fluorosensor facility, in order to test the application of time resolved fluorosensing to remote samples on water

On-line mixed hemodiafiltration with a feedback for ultrafiltration control: Effect on middle-molecule removal

On-line mixed hemodiafiltration with a feedback for ultrafiltration control: Effect on middle-molecule removal.BackgroundIncreased middle-molecular uremic toxin removal seems to favorably influence survival in dialysis patients. The aim of this study was to verify if, in on-line mixed hemodiafiltration, solute removal by convection may be enhanced by forcing the ultrafiltration rate (QUF) and optimizing the infusion technique in order to achieve the highest possible filtration fraction (FF).MethodsRemoval of β2-microglobulin (β2-m), urea, creatinine, and phosphate were compared in 20 patients randomly submitted to one dialysis session (A), one postdilution hemodiafiltration session (B), and three sessions of mixed hemodiafiltration (C, D, and E) at different infusion rates (QS). In mixed hemodiafiltration, a newly developed feedback system automatically maintained the transmembrane pressure (TMP) within its highest range of safety (250 to 300mm Hg) at constant QUF, while ensuring the maximum FF by splitting infusion between pre- and postdilution.ResultsA mean QS of 134 ± 20mL/min (mean FF = 0.65) was attained in post-HDF, and up to 307 ± 41mL/min (mean FF = 0.69) in mixed hemodiafiltration. The mean dialysate clearances (KDQ) for all tested solutes and urea eKt/V were significantly higher in all hemodiafiltration sessions than in dialysis. Only in the case of urea did the infusion mode have no significant effect. KDQ for β2-m was maximal in session D and significantly higher than in session B (90.2 ± 11mL/min vs. 77.5 ± 11mL/min; P = 0.02). KDQ for β2-m significantly correlated with QS and the plasma water flow rate (QPW). The highest KDQ for β2-m was found at values of QS∼ QPW. Beyond this value KDQ decreased.ConclusionThe mixed infusion mode in hemodiafiltration, controlled by the TMP-ultrafiltration feedback, seems to improve the efficiency of hemodiafiltration by fully exploiting the convective mechanism of solute removal. The feedback automatically adjusted the infusion rate and site to the maximum FF taking into account flow conditions, internal pressures, and hydraulic permeability of the dialyzer and their complex interactions

Location of the Energy Levels of the Rare-Earth Ion in BaF2 and CdF2

The location of the energy levels of rare-earth (RE) elements in the energy band diagram of BaF2 and CdF2 crystals is determined. The role of RE3+ and RE2+ ions in the capture of charge carriers, luminescence, and the formation of radiation defects is evaluated. It is shown that the substantial difference in the luminescence properties of BaF2:RE and CdF2:RE is associated with the location of the excited energy levels in the band diagram of the crystals

VECTOR LATTICES, POLYHEDRAL GEOMETRY, AND VALUATIONS

The present thesis explores the connections between Hadwiger\u2019s Characterization Theorem for valuations, vector lattices, and MV-algebras. The study of valuations can be seen as a precursor to the measure theory of modern probability. For this reason, valuations are one of the most important topics of geometric probability. One of the topics that turns out to be central is the study of measures on polyconvex sets (i.e., finite unions of compact convex sets) in Euclidean spaces of arbitrary finite dimension, that are invariant under the group of Euclidean motions. Hadwiger\u2019s Characterization Theorem states that the linear space of such invariant measures is of dimension n + 1, if the ambient has dimension n. Moreover, its proof shows that the Euler-Poincar\ue9 characteristic is a basic invariant measure. The Euler-Poincar\ue9 characteristic, indeed, is the unique such measure that assigns value one to each compact and convex set. The main topic of the first part of our work is the characterization of the Euler-Poinca\ue9 characteristic as a valuation on finitely presented unital vector lattices. By the Baker-Baynon duality, we represent each finitely presented unital vector lattice as the lattice of continuous and piecewise linear real-valued functions on a suitable polyhedron in the Euclidean space. Then we define vl-Schauder hats, that are special elements of the vector lattice with a \u201cpyramidal shape\u201d, and that can be used to generate the vector lattice, via addition and products by real scalars. On the positive cone of every finitely presented vector lattice V we define a pc-valuation as a valuation (in the usual classical sense) that is insensitive to addition. The (Euler-Poincar\ue9) number \u3c7(f) of any function f in the positive cone of V is next defined as the Euler-Poincar\ue9 characteristic of the support of f. Pc-valuations uniquely extend to a suitable kind of valuations over V, called vl-valuations. We then prove a Hadwiger-like theorem, to the effect that our \u3c7 is the only vl-valuation assigning 1 to each vl-Shauder hat of V. In the second part of the thesis we explore two different ways to associate continuous and piecewise linear functions (and hence elements of vector lattices) to geometric objects. First we use the notion of support function to establish a correspondence between a suitable subset of the free vector lattice on n generators and the set of polytopes of the n-dimensional euclidean space. This special set of algebraic objects generates the whole free vector lattice via finite meets. We call it the set of support elements. Then we consider valuations on the free vector lattice that are also additive on the set of support elements. By the Volland-Groemer Extension Theorem, we prove that such valuations are in a one-to-one correspondence with the valuations on the lattice of polyconvex sets that are additive on the subset of convex objects. Next we proceed in a similar way, using gauge functions. In this case, the first correspondence that we prove is between the positive cone of the vector lattice of continuous and positively homogeneous real-valued functions of the n-dimensional euclidean space and a lattice, equipped with appropriate vector space operations, of a new kind of geometric objects. We call these sets star-shaped objects. Then we define a geometric notion of good sequence (a tool introduced by D.Mundici in the study of MV-algebras), and we prove a representation theorem for star-shaped objects, in terms of good sequences. Imposing a polyhedral condition on our star-shaped objects, we obtain a correspondence between them and the elements of the positive cone of the free vector lattice on n generators. Finally, we specialize the result obtained for good sequences to these polyhedral star-shaped objects

The Role of Chain Length in Cucurbit[8]uril Complexation of Methyl Alkyl Viologens

Viologens are among the most studied guests for cucurbit[8]uril (CB[8]) and their complexation is usually driven by bipyridyl core inclusion inside the cavity to maximize both hydrophobic and cation-dipole interactions. The presence of alkyl substituents on the guest alters this complexation mode, switching to aliphatic chain inclusion in U-folded conformation. Herein, we report a thorough study of the influence of the alkyl chain length on the binding mode of methyl alkyl viologens. The chain length of the studied guests was increased by two methylene groups starting from methyl dodecyl viologen (MVC12) to the octadecyl analogue (MVC18). Complexation in water, investigated by NMR spectroscopy and ITC, revealed a clear switch from 1 : 1 to 2 : 1 host/guest stoichiometry moving from 12 to 16 carbon atoms, as a consequence of the chain folding of the major portion of the longer alkyl chain in one CB[8] cavity and the inclusion of the full viologen unit by another host molecule. The CB[8]2.MVC18 complex crystal structure evidences the unprecedented 2 : 1 stoichiometry and quantified in 12 the number of carbon atoms necessary to fill the CB[8] cavity in U-shaped conformation

Localized versus itinerant magnetic moments in Na0.72CoO2

Based on experimental 59Co-NMR data in the temperature range between 0.1 and 300 K, we address the problem of the character of the Co 3d-electron based magnetism in Na0.7CoO2. Temperature dependent 59Co-NMR spectra reveal different Co environments below 300 K and their differentiation increases with decreasing temperature. We show that the 23Na- and 59Co-NMR data may consistently be interpreted by assuming that below room temperature the Co 3d-electrons are itinerant. Their magnetic interaction appears to favor an antiferromagnetic coupling, and we identify a substantial orbital contribution corb to the d-electron susceptibility. At low temperatures corb seems to acquire some temperature dependence, suggesting an increasing influence of spin-orbit coupling. The temperature dependence of the spin-lattice relaxation rate T1-1(T) confirms significant variations in the dynamics of this electronic subsystem between 200 and 300K, as previously suggested. Below 200 K, Na0.7CoO2 may be viewed as a weak antiferromagnet with TN below 1 K but this scenario still leaves a number of open questions.Comment: 8.7 pages, 6 Figures, submitted to Phys. Rev.

Germano Sartelli

Libro-catalogo della mostra sugli artisti imolesi che hanno partecipato alle Biennali Internazionali d'arte di Venezia. Capitolo dedicato all'opera dello scultore Germano Sartelli, tra i principali esponenti dell'informale italiano

Methyl Hexadecyl Viologen Inclusion in Cucurbit[8]uril: Coexistence of Three Host-Guest Complexes with Different Stoichiometry in a Highly Hydrated Crystal

The host-guest inclusion complexes of cucurbiturils with alkyl viologen have interesting architectures, chemical properties, and potential applications in sensors and nanotechnology. A highly hydrated triclinic crystal of cucurbit[8]uril (CB[8]) complexed by methyl hexadecyl viologen (MVC16) is characterized by the unprecedented coexistence in the crystal of three host-guest complexes with 3:2, 2:2, and 1:1 stoichiometries. In all these complexes, the hook-shaped alkyl chain of the MVC16 is hosted in the CB[8] macrocycles, while the methyl viologen moieties have various environments. In the Z-shaped 3:2 complex, a central CB[8] unit hosts two viologen heads in the cavity, while the 2:2 complex is held together by \u3c0-stacking interactions between two viologen units. In the square 2D tiling crystal packing of CB[8] macrocycles, the same site which favors the dimerization observed in the 2:2 complex is also statistically occupied by a single methyl viologen moiety of the 1:1 complex. The rational interpretation of the crystal structure represented an intriguing challenge, due to the complicated statistical disorder in the alkyl chains hosted in CB[8] units and in the methyl viologen moieties of 2:2 and 1:1 complexes. In contrast with the solution behavior dominated by the 2:1 complex, the coexistence of three host-guest complexes with 3:2, 2:2, and 1:1 ratios highlights the fundamental importance of packing effects in the crystallized supramolecular complexes. Therefore, the crystallization process has permitted us to capture different host-guest systems in a single crystal, revealing a supramolecular landscape in a single photo