Palladium-catalyzed oxidative heterocyclodehydration-alkoxycarbonylation of 3-yne-1,2-diols: a novel and expedient approach to furan-3-carboxylic esters

A novel and convenient approach to furan-3-carboxylic esters 2 is presented, based on palladium-catalyzed direct oxidative carbonylation of readily available 3-yne-1,2-diols 1. The process, corresponding to a sequential combination between a 5-endo-dig heterocyclodehydration step and an oxidative alkoxycarbonylation stage, is catalyzed by PdI₂ in conjunction with an excess of KI under relatively mild conditions (100 °C in ROH under 40 atm of a 4:1 mixture of CO-air).     

Finite-Volume Excitations of the¶111 Interface in the Quantum XXZ Model

We show that the ground states of the three-dimensional XXZ Heisenberg ferromagnet with a 111 interface have excitations localized in a subvolume of linear size R with energies bounded by O(1/R²). As part of the proof we show the equivalence of ensembles for the 111 interface states in the following sense: In the thermodynamic limit the states with fixed magnetization yield the same expectation values for gauge invariant local observables as a suitable grand canonical state with fluctuating magnetization. Here, gauge invariant means commuting with the total third component of the spin, which is a conserved quantity of the Hamiltonian. As a corollary of equivalence of ensembles we also prove the convergence of the thermodynamic limit of sequences of canonical states (i.e., with fixed magnetization).     

The efficient solution of electromagnetic scattering for inhomogeneous media

We consider an electromagnetic scattering problem for inhomogeneous media. In particular, we focus on the numerical computation of the electromagnetic scattered wave generated by the interaction of an electromagnetic plane wave and an inhomogeneity in the corresponding propagation medium. This problem is studied in the VV polarization case, where some special symmetry requirements for the incident wave and for the inhomogeneity are assumed. This problem is reformulated as a Fredholm integral equation of second kind, which is discretized by a linear system having a special form. This allows to compute efficiently an approximate solution of the scattering problem by using iterative techniques for linear systems. Some numerical examples are reported.     

A mathematical study of the plasticity effects in muscle contraction

Hill's three-element model of contracting muscle is expanded by replacing the series and the parallel elastic elements with elastoplastic elements. The contractile element is structurally described making use of the sliding filament theory. The resulting mathematical model is formulated in terms of an evolution variational inequality for a nonlinear and nonlocal transport-type operator. The existence and uniqueness of the solution are described along with a numerical approach.This work was supported by M.P.I. (fondi per la ricerca scientifica) and by I.A.N. of C.N.R. Pavia.     

Forecasting the integration of immigrants

In this research, we develop and introduce a theoretical and mathematical forecasting framework of immigrant integration using immigrant density as a single driver. First, we introduce the integration concepts we aim at forecasting. Thereafter, we introduce a theoretical and mathematical model of the relationship between integration and immigrant density. Based on this model, we develop a methodological forecasting framework. We test the framework using immigrant integration data from Spain. We produce the forecasts, and conduct the proper evaluation of them. Finally, we conclude with a brief discussion of the wider implications of our results.     

Study of non-covalent interactions of luotonin A derivatives and the DNA minor groove as a first step in the study of their analytical potential as DNA probes

The interaction between DNA and several newly synthesized derivatives of the natural anticancer compound luotonin A has been studied. The results from our work reveal an effective and selective alkaloid/double-stranded DNA (ds-DNA) interaction. In the presence of increasing amounts of ds-DNA, a noticeable fluorescence quenching of the luotonin A derivatives under study was observed. However, this effect did not take place when single-stranded DNA (ss-DNA) was employed. The association constant alkaloids/ds-DNA was calculated by quantitation of such a quenching effect. The influence of other quenchers, namely Co²⁺ and Br⁻ on the native fluorescence of luotonin A and derivatives was also studied, and a remarkable quenching effect was observed for both ions. We have also investigated how by binding DNA the alkaloids could get protected from the external Co²⁺ and Br⁻ quenchers. The Stern–Volmer constants (K _SV) for Co²⁺ and Br⁻ quenching effect on the studied alkaloids were considerably reduced (10–50%) after incubation of the compounds in the presence of DNA with regard to the K _SV values in absence of DNA. An increase in the fluorescence anisotropy values of luotonins was also produced only in the presence of ds-DNA but not in the case of ss-DNA. To better characterize the nature of that interaction, viscosimetry assays and ethidium bromide displacement studies were conducted. With regard to DNA reference solutions, the viscosity of solutions containing DNA and luotonin A derivatives was reduced or not significantly increased. It was also observed that the studied compounds were unable to displace the intercalating agent ethidium bromide. All of these results, together with the obtained association constants values (K _ass = 2.2 × 10² – 1.3 × 10³), support that neither covalent nor intercalating interactions luotonin A derivatives/ds-DNA are produced, leading to the conclusion that these alkaloids bind ds-DNA through the minor groove. The specific changes in the fluorescence behavior of luotonin A and derivatives distinguishing between ss-DNA and ds-DNA binding, lead us to propose these compounds as attractive turn-off probes to detect DNA hybridization.     

A novel approach to improve operation and performance in flow field-flow fractionation

A new system design and setup are proposed for the combined use of asymmetrical flow field-flow fractionation (AF4) and hollow-fiber flow field-flow fractionation (HF5) within the same instrumentation. To this purpose, three innovations are presented: (a) a new flow control scheme where focusing flow rates are measured in real time allowing to adjust the flow rate ratio as desired; (b) a new HF5 channel design consisting of two sets of ferrule, gasket and cap nut used to mount the fiber inside a tube. This design provides a mechanism for effective and straightforward sealing of the fiber; (c) a new AF4 channel design with only two fluid connections on the upper plate. Only one pump is needed to deliver the necessary flow rates. In the focusing/relaxation step the two parts of the focusing flow and a bypass flow flushing the detectors are created with two splits of the flow from the pump. In the elution mode the cross-flow is measured and controlled with a flow controller device. This leads to reduced pressure pulsations in the channel and improves signal to noise ratio in the detectors. Experimental results of the separation of bovine serum albumin (BSA) and of a mix of four proteins demonstrate a significant improvement in the HF5 separation performance, in terms of efficiency, resolution, and run-to-run reproducibility compared to what has been reported in the literature. Separation performance in HF5 mode is shown to be comparable to the performance in AF4 mode using a channel with two connections in the upper plate.     

Tandem hollow-fiber flow field-flow fractionation

Reinjection of one ore more collected fractions of eluted samples is recognized as a useful procedure in analytical separation techniques, among which field-flow fractionation (FFF), to improve the actual separation of complex samples. Hollow-fiber flow FFF (HF5) is a micro-channel subset of flow FFF (F4), which has recently reached a performance comparable to that of standard, flat-channel F4. To further improve HF5 of complex protein samples, we present a new device and method for in-line, reinjection HF5 that we call tandem HF5 (HF5/HF5). HF5 is ideally suited for tandem operation because (1) small channel volume and low operation flow rates allow reducing dilution and volume of the collected fractions, and (2) the relaxation/focusing step that takes place between the 1st and 2nd run (refocusing) allows reestablishing the volume and concentration of the sample plug before the 2nd elution. HF5/HF5 proves particularly effective in the case of oligomeric proteins since it allows collecting and reinjecting the bands that correspond to each separated oligomeric form. This provides information on the dynamic equilibria between the different oligomers. For HF5/HF5 operations, a modified, prototype HF5 instrumentation is presented which includes a "trap" constituted of a four-port, two-way valve positioned downstream the UV detector and a collection loop. The effect of refocusing conditions on HF5/HF5 performance is investigated by varying refocusing time. With a complex protein samples such as blood serum, HF5/HF5 can improve detectability of the low abundance components since overloading effects due to high-abundance components are reduced. This is shown for serum lipoproteins: while after the 1st run high density lipoproteins (HDLs) are not separated from high-abundance serum proteins, after the 2nd run it is shown possible to separate the HDL subclasses.     

Chemical composition and in vitro activity of plant extracts from Ferula communis and Dittrichia viscosa against postharvest fungi

F. communis and D. viscosa are perennial Mediterranean weeds that have been used for different therapeutic purposes in traditional pharmacopeia. Plant extracts were obtained from air dried D. viscosa young shoots (DvA) and F. communis aerial part (FcA) and roots (FcR) with n-hexane. The chemical compositions of the extracts were analyzed by HPLC-DAD, LC-MS (ESI) and LC-Q-TOF techniques. Two sesquiterpene lactones (inuviscolide, tomentosin) and three sesquiterpene acids (costic acid, hydroxycostic acid, ilicic acid) were identified from the D. viscosa extract, while in F. communis extracts three daucane sesquiterpenes (acetoxyferutinin, oxojaeskeanadioyl anisate, fertidin) and one coumarin (ferulenol) derivates were found. Biological activities of plant extracts were studied in in vitro experiments on the colonies and conidia of Botryotinia fuckeliana, Penicillium digitatum, P. expansum, Monilinia laxa, M. fructigena and Aspergillus spp. Extracts showed varying degree of antifungal activities on colony growth and conidia germination. The extract from FcA showed the least effect, while DvA extract had the strongest fungitoxic effects. FcR extract presented a fungitoxic effect on the colony growth, but it was not able to inhibit the conidia germination. These distinctions can be attributed to the differences in chemical composition of plant extracts.