Universal reconnection of non-Abelian cosmic strings

We show that local and semilocal strings in Abelian and non-Abelian gauge theories with critical couplings always reconnect classically in collision, by using moduli space approximation. The moduli matrix formalism explicitly identifies a well-defined set of the vortex moduli parameters. Our analysis of generic geodesic motion in terms of those shows right-angle scattering in head-on collision of two vortices, which is known to give the reconnection of the strings.     

Dynamics of Multi-Body Rotors: Numerical and Experimental FEM Analysis of the Scientific Earth Experiment Galileo Galilei Ground

Some small scientific satellites can be regarded as free, multi-body, supercritical and statorless rotors. Classical rotordynamics does not cover the dynamic behaviour and the stability analysis of such rotating systems, being focused on fixed rotors. Attitude dynamics usually deals with single rigid spacecrafts, sometimes equipped with flexible appendices like solar arrays or antennas. The case of the Galileo Galilei Ground (GGG) test facility is herewith analyzed through a numerical and experimental investigation on the dynamic behaviour of a fixed multi-body fast-spinning rotor in order to validate the design approach proposed for Galileo Galilei (GG) spacecraft.     

Determination of phospholipids in milk samples by means of hydrophilic interaction liquid chromatography coupled to evaporative light scattering and mass spectrometry detection

The combined use of the state-of-the-art hybrid mass spectrometers together with high efficient liquid chromatography could surely be a useful tool for such a challenging task, as phospholipids (PLs) analysis. In this research, we used hydrophilic interaction liquid chromatography (150 mm×2.1 mm I.D., 2.7 μm d.p. partially porous column) to achieve the separation of major PLs classes in cow's and donkey's milk samples. Solid-phase extraction (SPE) was performed in order to pre-concentrate minor PLs from non polar lipids (triacylglycerols) and the recovery for the extraction method was assayed on a milk sample, fortified with 5 μg/mL of SM pure standard, and analyzed in triplicate. A value of 89.99% was calculated, with a coefficient of variation (CV%) of 1.93. A 70-min long stepwise gradient of water/acetonitrile afforded baseline separation of PLs classes, at 50 μL/min flow rate. Accurate detection by an ion trap-time of flight (IT-TOF) mass spectrometer (in both positive and negative ionization mode) allowed to fully characterize the distinctive phospholipid profile and fatty acid composition of cow's and donkey's milk, the latter being analyzed for the first time. Evaporative light scattering detection was further employed to attain the quantitative evaluation of major PLs classes identified, by the external calibration method using reference material solutions in the 5-200 μg/mL concentration range. Major difference between the two analyzed samples consisted in the total PLs amount, which in cow's milk was determined as over 20-fold higher than the donkey's.     

A molecular clip throws new light on the complexes formed by a family of cyclam-cored dendrimers with Zn(II) ions. Efficient energy transfer in the heteroleptic complexes

Complexation of Zn(II) ions by cyclam cored dendrimers appended with four (G0), eight (G1) and 16 naphthyl chromophores (G2) at the periphery have been investigated in CH?CN-CH?Cl? 1?:?1 (v/v) solution by absorption and emission, ESI-mass and 1H NMR spectroscopy. The results obtained can be interpreted by the formation of complexes of 2?:?1 dendrimer to metal stoichiometry, at low metal ion concentration, and 1?:?1 complexes upon further addition of Zn(II) ions, for all the dendrimer generations. Upon addition of a molecular clip C2? consisting of two anthracene sidewalls bridged by a benzene group with two sulfate substituents in the para positions, heteroleptic complexes of general formula [GnZnC] are formed. Interestingly, in these complexes, a very efficient quenching (practically 100%) of the dendrimer naphthyl luminescence and sensitization (ca. 90%) of the clip anthracene emission take place. The complex [G2ZnC] exhibits a very high molar absorption coefficient in the UV spectral region owing to the 16 naphthyl chromophores of the dendrimer and the two anthracene units of the clip (ε = 1.7 × 10? M?1 cm?1 at 263 nm). Furthermore, the excitation energy absorbed by the naphthyl chromophores is efficiently funneled to the two anthracene units of the clip, which emits in the blue spectral region.     

Surface-enhanced fluorescence and surface-enhanced Raman scattering of push–pull molecules: sulfur-functionalized 4-amino-7-nitrobenzofurazan adsorbed on Ag and Au nanostructured substrates

We investigated the chemisorption of self-assembled monolayers of sulfur-functionalized 4-amino-7-nitrobenzofurazan on gold and silver nanoisland films (NIFs) by means of surface-enhanced fluorescence (SEF) and surface-enhanced Raman scattering (SERS). The ligand is a push–pull molecule, where an intramolecular charge transfer occurs between an electron-donor and an electron-acceptor group, thus exhibiting nonlinear optical properties that are related to both SERS and SEF effects. The presence of different heteroatoms in the molecule ensures the possibility of chemical interaction with both silver and gold substrates. The SERS spectra suggest that furazan is bound to silver via lone pairs of the nitrogen atoms, whereas the ligand is linked to gold via a sulfur atom. Silver NIFs provide more efficient enhancement of both fluorescence and Raman scattering in comparison with gold NIFs. The present SEF and SERS investigation could provide useful information for foreseeing changes in the nonlinear responses of this push–pull molecule.     

Deciding the existence of uniform interpolants over transitive models

We consider the problem of the existence of uniform interpolants in the modal logic K4. We first prove that all ${\square}$ -free formulas have uniform interpolants in this logic. In the general case, we shall prove that given a modal formula ${\phi}$ and a sublanguage L of the language of the formula, we can decide whether ${\phi}$ has a uniform interpolant with respect to L in K4. The ${\square}$ -free case is proved using a reduction to the G?del L?b Logic GL, while in the general case we prove that the question of whether a modal formula has uniform interpolants over transitive frames can be reduced to a decidable expressivity problem on the???-calculus.     

On a positive set theory with inequality

We introduce a quite natural Frege‐style set theory, which we call Strong‐Frege‐2 $(\mathsf {SF}_2)$, a sort of simplification of the theory considered in 13 (under the name Strong‐Frege‐3) and 1 (under the name F2). We give a model of a weaker variant of $\mathsf {SF}_2$, called $\mathsf {SF}_2\mathsf {AC}$, where atoms and coatoms are allowed. To construct the model we use an enumeration “almost without repetitions” of the Π¹₁ sets of natural numbers; such an enumeration can be obtained via a classical priority argument much in the style of 5 and 15 . © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Optical properties of a polyethylene dispersion with a luminescent silica prepared by surface grafting of a perylene derivative

A micrometric silica modified with perylene derivative (SiO₂–TES) has been prepared by hydrolysis–condensation reactions between silica and N,N’-bis-(3-triethoxysilylpropyl)-perylene-tetracarboxyldiimide (P-TES) and utilized as filler in LLDPE films together with a compatibilizer. Spectroscopic analyses on SiO₂–TES confirmed the grafting of P-TES on silica, while its amount was determined by thermogravimetric analysis. Solid state NMR provided information about the structure of silicon atoms involved in the condensation of SiO₂ and P-TES that resulted mainly in silicon atoms grafted with bi-dentate anchorages.UV–Vis and fluorescence analyses carried out on P-TES showed the ability of the dye to generate J-type aggregates in apolar solvents. The same analyses on SiO₂–TES revealed the presence of both isolated and aggregated dye molecules grafted on silica surface, while on polymeric dispersions of SiO₂–TES, they have shown only the presence of P-TES aggregates grafted to silica.Thanks to the direct correlation between optical properties (obtained both by UV–Vis and by fluorescence analyses) and the chemical environment of composites, the luminescent silica SiO₂–TES could be used to estimate the filler dispersion extent in different microcomposite polymer materials.     

Headspace-solid phase microextraction coupled to gas chromatography-combustion-isotope ratio mass spectrometer and to enantioselective gas chromatography for strawberry flavoured food quality control

Authenticity assessment of flavoured strawberry foods was performed using headspace-solid phase microextraction (HS-SPME) coupled to gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). An authenticity range was achieved, investigating on the carbon isotope ratio of numerous selected aroma active volatile components (methyl butanoate, ethyl butanoate, hex-(2E)-enal, methyl hexanoate, buthyl butanoate, ethyl hexanoate, hexyl acetate, linalool, hexyl butanoate, octyl isovalerate, γ-decalactone and octyl hexanoate) of organic Italian fresh strawberries. To the author's knowledge, this is the first time that all these components were investigated simultaneously by GC-C-IRMS on the same sample. The results were compared, when applicable, with those obtained by analyzing the HS-SPME extracts of commercial flavoured food matrices. In addition, one Kenyan pineapple and one fresh Italian peach were analyzed to determine the δ(13)C(VPDB) of the volatile components common to strawberry. The δ(13)C(VPDB) values are allowed to differentiate between different biogenetic pathways (C(3) and CAM plants) and more interestingly between plants of the same CO(2) fixation group (C(3) plants). Additional analyses were performed on all the samples by means of Enantioselective Gas Chromatography (Es-GC), measuring the enantiomeric distribution of linalool and γ-decalactone. It was found that GC-C-IRMS and Es-GC measurements were in agreement to detect the presence of non-natural strawberry aromas in the food matrices studied.     

Absorption and emission spectra of fluorescent silica nanoparticles from TD-DFT/MM/PCM calculations

A multi-scale computational protocol, which combines Quantum Mechanics and Molecular Mechanics (QM/MM) calculations with the polarisable continuum model (PCM), has been used to study the tetramethylrhodamine isothiocyanate (TRITC) fluorophore, embedded in three different environments, namely in water, on an amorphous silica surface and covalently encapsulated in a silica nanoparticle (C dot). Absorption and emission spectra have been simulated by using TD-B3LYP/PCM calculations, performed on the TRITC ground and excited state geometries, optimized at the QM/MM level. The results are in good agreement with experimental data confirming the caging effect played by the silica shell on the mobility of the TRITC molecule when covalently encapsulated in silica nanoparticles. This could result in a decrease of the nonradiative decay rate and thus an increase of the quantum yield of the molecule.