An improved analog equation method for non-linear dynamic analysis of time-fractional beams with discontinuities

Meccanica - In this paper, an improved version of the analog equation method (AEM) is proposed, ideally suitable for non-linear dynamic analysis of time-fractional beams with discontinuities....     

Zinc(II) complexes of ubiquitin: speciation, affinity and binding features

Intraneuronal inclusions consisting of hypermetallated, (poly-)ubiquitinated proteins are a hallmark of neurodegeneration. To highlight the possible role played by metal ions in the dysfunction of the ubiquitin-proteasome system, here we report on zinc(II)/ubiquitin binding in terms of affinity constants, speciation, preferential binding sites and effects on protein stability and self-assembly. Potentiometric titrations allowed us to establish that at neutral pH only two species, ZnUb and Zn(2)Ub, are present in solution, in line with ESI-MS data. A change in the diffusion coefficient of ubiquitin was observed by NMR DOSY experiments after addition of Zn(II) ions, and thus indicates metal-promoted formation of protein assemblies. Analysis of (1)H, (15)N, (13)Cα and (13)CO chemical-shift perturbation after equimolar addition of Zn(II) ions to ubiquitin outlined two different metal-binding modes. The first involves a dynamic equilibrium in which zinc(II) is shared between a region including Met1, Gln2, Ile3, Phe4, Thr12, Leu15, Glu16, Val17, Glu18, Ile61 and Gln62 residues, which represent a site already described for copper binding, and a domain comprising Ile23, Glu24, Lys27, Ala28, Gln49, Glu51, Asp52, Arg54 and Thr55 residues. A second looser binding mode is centred on His68. Differential scanning calorimetry evidenced that addition of increasing amounts of Zn(II) ions does not affect protein thermal stability; rather it influences the shape of thermograms because of the increased propensity of ubiquitin to self-associate. The results presented here indicate that Zn(II) ions may interact with specific regions of ubiquitin and promote protein-protein contacts.     

Photosensitive heterojunctions of silicon coated with sol–gel derived TiO2 dispersed in poly(3,4-ethylendi oxythiophene)/poly(styrenesulfonate)

Sol–gel derived aggregates of titania nanocrystals, synthesized starting from alcohol–water solutions of titanium isopropoxide, were characterized by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) measurements. The TiO₂ powder was dispersed in aqueous solutions of poly(3,4-ethylendioxythiophene)/poly(styrenesulfonate) (PEDOT-PSS), and the blends were coated on n-doped silicon substrates to achieve simple design heterojunctions. Current versus voltage measurements performed both in the dark and under broad band light irradiation show that the nSi/PEDOT-PSS/TiO₂ heterojunctions have remarkable photosensitive behaviour, promising in view of applications as hybrid photovoltaic cells.     

Forward and backward electron emission cross-sections for 23 MeVu<Superscript>-1</Superscript> C,Ni and Au projectiles traversing C,Al , Ni,Ag , Au and Bi foils

A rather complete experimental study of forward and backward electron velocity spectra from thin foils bombarded with ions at constant velocity of 30 atomic units (23MeV u^-1) was performed. Three different beams ( ¹²C³⁺ , ⁵⁸Ni¹⁴⁺ and ¹⁹⁷Au³⁶⁺ and six different targets ( ¹²C , ²⁷Al , ^natNi , ^natAg , ¹⁹⁷Au and ²⁰⁹Bi of approximately 90μg cm^-2 thickness were used. This procedure allowed to study the evolution of electron emission (velocity and angular distributions) for the [projectile; target] matrix [ C , Ni , Au ; C , Al , Ni , Ag , Au , Bi ] in a wide angular range. The projectile and target dependence of absolute cross-sections for binary encounter-, Auger- and backward-emitted electrons are analyzed.     

Influence of the substrate electronic structure on metallic quantum well state dispersions in ultrathin metal films

We have studied ultrathin Cu films grown on three related ferromagnetic (FM) layers to clarify the role of the substrate in determining the two-dimensional dispersion of metallic quantum well (MQW) states in the overlayer. The dispersions with parallel momentum of Cu MQW states above the Fermi level E_F were measured in the Cu/fccFe/Cu(1 0 0) and Cu/fccCo/Cu(1 0 0) systems using inverse photoemission, and below E_F in the Cu/fccNi/Cu(1 0 0) system using angle resolved photoemission spectroscopy. This study focussed on the direction of the two-dimensional Brillouin zone. For states away from the projected band gaps of the FM layer, the identity of the FM layer (i.e., Fe or Co) has little influence on Cu MQW states and their dispersions closely resemble those of a free standing Cu film. In contrast, all three systems exhibit nondispersing MQW states when the Cu bands overlap the minority spin projected band gaps of the FM metal. A phase accumulation approach gives a very simple explanation of this behavior, showing that the flat dispersion occurs because the phase shift upon reflection from the FM layer has a strong energy dependence in the projected gap.     

Evaluation of matrix effect in one‐dimensional and comprehensive two‐dimensional liquid chromatography for the determination of the phenolic fraction in extra virgin olive oils

Olea europaea, meaning “European olive,” is a small tree belonging to the family Oleaceae, occurring in the Mediterranean Basin. Olive oil is an essential component of a balanced diet because of its nutritional value. Among micronutrients, phenolic compounds did show important beneficial effects for human health. The majority of the research studies on the phenol content are carried out by liquid chromatography combined to photodiode array and/or mass spectrometry detection; however, because of matrix complexity, one‐dimensional liquid chromatography cannot be sometimes sufficient to obtain rewarding separations, requiring more advanced analytical techniques. In this work, comprehensive two‐dimensional liquid chromatography, incorporating RP‐Amide and C18 stationary phases, in the first and second dimension, respectively, both under reversed phase conditions, was investigated for the determination of the phenolic fraction in extra virgin olive oil samples. As far as detection is concerned, triple quadrupole mass spectrometry was employed under multi reaction monitoring mode offering superior selectivity and sensitivity. The reduction of matrix effects, when using comprehensive two‐dimensional liquid chromatography with respect to conventional one‐dimensional liquid chromatography, was assessed by comparing the slopes of calibration curves built from standard solutions and spiked olive oil samples.     

The European Food Legislation and its impact on honey sector

The paper discusses the role of EC Directive 2001/110 on honey trading. Authors have demonstrated that, being the amount of developed hydroxymenthylfurfural (HMF) also correlated to honey chemical composition, the limit of 15mg\Lg, in low enzume honeys, is unjustifiable and become a barrier to trade for some unifloral honeys (citrus) Electronic Supplementary Material Supplementary material is available for this article at Presented at AOAC Europe/Eurachem Symposium, March 2005, Brussels, Belgium     

Finite difference solution of Euler equations arising in variational image segmentation

This paper deals with finite-difference approximations of Euler equations arising in the variational formulation of image segmentation problems. We illustrate how they can be defined by the following steps: (a) definition of the minimization problem for the Mumford–Shah functional (MSf), (b) definition of a sequence of functionals Γ-convergent to the MSf, and (c) definition and numerical solution of the Euler equations associated to the kth functional of the sequence. We define finite difference approximations of the Euler equations, the related solution algorithms, and we present applications to segmentation problems by using synthetic images. We discuss application results, and we mainly analyze computed discontinuity contours and convergence histories of method executions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Analysis of the phosphorescence of thianthren crystals

Summary The room temperature phosphorescence of crystalline thianthren in the 1.6–3.3 eV energy region has been measured using time delays going from 0.03 to 9.5 ms. The time dependence of the emission spectra which show the presence of three resolved bands, was analysed by means of a numerical best-fitting procedure, and the results obtained have been compared with those predicted by means ofab initio and semiempirical molecular orbital calculations.