Detecting and quantifying oxygen functional groups on graphite nanofibers by fluorescence labeling of surface species

The ability to quantify functional groups on graphitic carbon nanofiber (GCNF) surfaces and to covalently attach ligands chemoselectively will aid in the development of functionalized GCNFs and potentially other carbon nanomaterials for applications in nanotechnology. Herein, we report the identification and quantification of functional groups on the surface of GCNFs using fluorescence labeling of surface species (FLOSS). Using reactions that are selective for specific functional groups and fluorescent dyes containing the dansyl group, surface aldehyde/ketone, carboxyl, and hydroxyl groups were identified and quantified in their total and relative amounts by FLOSS. Oxygen-containing functionality that was detected by FLOSS on nitric acid-oxidized GCNFs totaled approximately 2.5% of surface carbon, present as 0.9% aldehyde/ketone, 1.2% carboxyl groups on average, and 0.4% hydroxyl groups. The amounts of oxygen-containing functional groups on as-produced and demineralized GCNFs were much lower, amounting to no more than 0.05% of aldehyde/ketone groups on demineralized GCNFs and 0.3% of these groups on as-produced fibers. The FLOSS method has revealed information about the fiber surface that is not accessible by other methods, while also providing insight into the chemical reactivities of functional groups that can be used as sites for the attachment of ligands to give covalently functionalized materials.     

Spectroscopic and computational studies on a new Pd(II)-bis(pyrazol-1-yl)methane aqua-complex

By reacting a stoichiometric amount of BPM or Me₂BPM (BPM = bis(pyrazol-1-yl)methane, Me₂BPM = bis(3,5-dimethylpyrazol-1-yl)methane) with Pd(OAc)₂ (OAc = acetate) in CH₂Cl₂, the new neutral complexes [Pd(OAc)₂(BPM)] (1) and [Pd(OAc)₂(Me₂BPM)] (1^Me) were isolated and characterized by NMR and IR spectroscopy. Acidolysis of one Pd-OAc bond of compound 1 by using aqueous perchloric acid in methanol led to the formation of the stable cationic aqua-complex [Pd(OAc)(H₂O)(BPM)](ClO₄) (2-ClO₄). The [Pd(OAc)(H₂O)(BPM)]⁺ cation was obtained also by reacting 1 with trifluoromethanesulfonic acid. NMR studies on inter- and intra-molecular hydrogen bonding of the aqua-ligand have been carried out and the data obtained have been interpreted on the basis of the results of DFT calculations.     

A comparative study of water gas shift reaction over gold and platinum supported on ZrO2 and CeO2–ZrO2

In this study platinum- and gold-based catalysts supported on ZrO₂ and ceria–zirconia solid solution have been characterized by several techniques (TPR, XRD, BET, HRTEM) and tested in the water gas shift (WGS) reaction under feed conditions typical of an autothermal reformer outlet. Platinum and gold catalysts behave differently especially in the range of 423–513 K, with gold being superior than platinum. The possibility of modifying the redox and structural characteristics of zirconia with the insertion of ceria allowed us to conclude that the bulk redox properties of the support play a secondary role, while the key parameter for an active WGS catalyst is the nature of metal support interface. This, in turn, depends on the metal particle distribution and on the structural and morphological properties of support. It has been found that the synergism between precious metals and support can be designed with an appropriate choice of the parameters of synthesis and the characteristics of support.     

Improving the gravure printed PEDOT:PSS electrode by gravure printing DMSO post-treatment

The poly(3,4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most attractive conducting polymers proposed as electrode for flexible electronics. Promising methods for enhancing its low conductivity, main limit for its use, are based on post-treatment. However, most of them are not suitable for mass production. In this study, the gravure printing technique was tried for the post-treatment of the PEDOT layer using dimethylsulfoxide (DMSO), as practical, safe and cost effective process for improving the printed electrode. An increase of the conductivity of the printed PEDOT:PSS layer was found and attributed to the rearrangement of the polymeric chains that leads to the formation of PEDOT-rich regions improving the conducting pathways. In addition, smoother film surface and improved stability to the humidity were obtained, representing further advantages for its employment in plastic electronics. Therefore, the feasibility and the efficacy of the DMSO post-treatment of the PEDOT:PSS films by gravure printing were demonstrated, showing the way for the low cost all in-line industrial production of large area PEDOT:PSS electrodes.     

A fusion-based approach to digital movie restoration

Many algorithms have been proposed in literature for digital movie restoration; unfortunately, none of them ensures a perfect result whichever is the image sequence to be restored. Here we propose a new digital scratch restoration algorithm which achieves accuracy results higher than that of already existing algorithms and naturally adapts for implementation into high-performance computing environments.The basic idea of the proposed algorithm is to adopt several relatively well-settled algorithms for the problem at hand and combine obtained results through suitable image fusion techniques, with the aim of taking advantage of the adopted algorithms’ capabilities and, at the same time, limiting their deficiencies.Extensive experiments on real image sequences deeply investigate both accuracy results of the presented scratch restoration approach, which is shown to outperform other existing approaches, and performance of its parallel implementation, which allows for real-time restoration.     

Different membrane modifications revealed by atomic force/lateral force microscopy after doping of human pancreatic cells with Cd, Zn, or Pb

The interaction of the cytotoxic metals cadmium, zinc, and lead with pancreatic cells was studied by atomic force/lateral Force microscopy (AFM/LFM), an approach that provides both topographic (with nanometer scale lateral resolution) and chemical information on the membrane. Different morphological modifications of the overall cell shape and roughness took place as consequence of 100 muM metal-dependent treatment. Furthermore, after exposure to Cd(Cl(2)) and Zn(Cl(2)), but not Pb(Cl(2)), the LFM images revealed several areas of the cell's surface showing lateral friction contrasts that have been interpreted as marker of different alterations of the cell physiology induced by the metal loading. Thus, the coupling of LFM detection to topographic AFM characterization allows to distinguish, through a nondestructive and surface characterising approach, between different metal-induced cytotoxic effects on cells. In this framework, the role of the LFM as an important tool to discriminate between different alteration of a biological system has to be highlighted.     

Turnover frequency for NO decomposition over Cu-ZSM-5 catalysts: insight into the reaction mechanism

In this letter we present a simple model useful to understand the relationship between the turnover frequency for NO decomposition over Cu-ZSM-5 catalysts (N _Cu), the number of Al atoms per unit cell of the ZSM-5 zeolite (p),and the copper loading expressed as percent of exchange (E). Our simple model is able to explain the literature data. We show that: (1) on catalysts with the highest activity (Cu exchange levelsE>90%),N _Cu increases withp (i.e. decreasing the Si/A1 ratio) indicating that the most active sites may contain two close copper ions; (2) at low Cu exchange levels (E<80%) the catalysts have lower activity and, moreover,N _Cu decreases withP, according to previous results of Iwamoto et al. (1986). The present results are also in agreement with the evidence that the redox couple Cu^2–/Cu^– play a key role in the reaction mechanism.Some of the ideas discussed in this letter were presented at the 2nd Italian national meeting on Science and Technology of Zeolites held in Modena, Italy, 6–8 October 1993.     

Penalized factor mixture analysis for variable selection in clustered data

A model-based clustering approach which contextually performs dimension reduction and variable selection is presented. Dimension reduction is achieved by assuming that the data have been generated by a linear factor model with latent variables modeled as Gaussian mixtures. Variable selection is performed by shrinking the factor loadings though a penalized likelihood method with an L1 penalty. A maximum likelihood estimation procedure via the EM algorithm is developed and a modified BIC criterion to select the penalization parameter is illustrated. The effectiveness of the proposed model is explored in a Monte Carlo simulation study and in a real example.     

Accurate Analysis of Planar Microstrip Antenna Array

For the microstrip patch resonator, as a planar antenna of a microstrip, a set of equations that represents the electromagnetic fields in the x and z direction as function of the electric field in the y direction are obtained applying the TTL method. This method is very suitable at microwave and antenna applications, and gives accurate complex resonant frequency, which contributes definitively to obtain higher precision antenna parameters. For each type of array is calculated the array factor, considering the excitation, phase and the relative displacement between the elements as well as the dimensions and number of elements.