Cellulose nanocomposites based on silane reinforced 3-butynoate-substituted zirconium-oxocluster copolymers: Mechanical,thermal and hydrophobic properties

Silica based cellulose nanocomposites obtained from (3-mercaptopropyl)trimethoxysilane or vinyltrimethoxysilane and 3-butynoate-substituted zirconium-oxoclusters were prepared and their surface morphology, wettability, and thermo-mechanical properties were studied. The composites showed a hydrophobic surface, high strength, and resistance to thermal degradation and aging; in comparison to the untreated paper they required a higher temperature to activate combustion and generated less heat during all thermal processes.     

The Influence of Oxygen Volumetric Mass Transfer Rates on Cyclodextrin Glycosyltransferase Production by Alkaliphilic Bacillus circulans in Batch and Fed-Batch Cultivations

In this work, the influence of oxygen mass transfer rates on the production of cyclodextrin glycosyltransferase (CGTase) by the alkaliphilic bacterium Bacillus circulans ATCC 21783 was investigated. Experimental design and response surface methodology were applied to optimize agitation speed and air flow rate in batch cultivations, in order to identify their significant effects and interactions with the synthesis of CGTase. Results were expressed as the volumetric mass transfer rates of oxygen (k_la, [per hour]). The maximal CGTase productivity of 155 U mL⁻¹ h⁻¹ was achieved with k_la of 48 h⁻¹. CGTase production was also studied in fed-batch cultures using the optimized parameters obtained in the batch experiments. The maximal CGTase productivity on fed-batch cultivations was 137 U mL⁻¹ h⁻¹ with feeding rates of starch at 0.17 g L⁻¹ h⁻¹.     

Characterization procedure for ancient mortars' restoration: The plasters of the Cavallerizza courtyard in the Ducal Palace in Mantua (Italy)

The problem of the characterisation of ancient mortars and plasters for restoration purposes is discussed and a methodology is proposed starting from the physical separation of the binder from aggregates. The procedure was applied to the plasters of the Ducal Palace in Mantua [Mantova] (Cavallerizza courtyard, XVI cent.): the results show the suitability of the proposed methodology for the determination of the plasters' nature, microstructure and even original formulation.     

Electrochemical impedance spectroscopy study of a surface confined redox reaction: The reduction of azobenzene on mercury in the absence of diffusion

The kinetics of azobenzene reduction on mercury electrodes in the absence of diffussional mass transport is studied by electrochemical impedance spectroscopy (EIS) in acetic acid/acetate buffered solutions at different pH values. Cyclic voltammetry experiments confirm the absence of diffusion effects and provide the values of the surface equilibrium potential. The analysis of the impedance frequency spectrums at every potential within the faradaic region conforms well the model and provides the global rate constant of the process, k_f. The potential dependence of k_f suggests the existence of an EE mechanism, with two electron transfers controlling the overall rate. The kinetic parameters of every step are obtained and their pH dependences clarify the role played by the protonation steps.     

Mental space travel: Damage to posterior parietal cortex prevents egocentric navigation and reexperiencing of remote spatial memories.

The ability to navigate in a familiar environment depends on both an intact mental representation of allocentric spatial information and the integrity of systems supporting complementary egocentric representations. Although the hippocampus has been implicated in learning new allocentric spatial information, converging evidence suggests that the posterior parietal cortex (PPC) might support egocentric representations. To date, however, few studies have examined long-standing egocentric representations of environments learned long ago. Here we tested 7 patients with focal lesions in PPC and 12 normal controls in remote spatial memory tasks, including 2 tasks reportedly reliant on allocentric representations (distance and proximity judgments) and 2 tasks reportedly reliant on egocentric representations (landmark sequencing and route navigation; see Rosenbaum, Ziegler, Winocur, Grady, & Moscovitch, 2004). Patients were unimpaired in distance and proximity judgments. In contrast, they all failed in route navigation, and left-lesioned patients also showed marginally impaired performance in landmark sequencing. Patients' subjective experience associated with navigation was impoverished and disembodied compared with that of the controls. These results suggest that PPC is crucial for accessing remote spatial memories within an egocentric reference frame that enables both navigation and reexperiencing. Additionally, PPC was found to be necessary to implement specific aspects of allocentric navigation with high demands on spontaneous retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimal strategies in the average consensus problem

Let a set of communicating agents compute the average of their initial positions, where every agent is restricted to communicate to a given small number of other agents (average consensus problem). We prove that the optimal topology of communication is given by a de Bruijn graph. Consensus is then reached in finitely many steps. This solution is valid when the number of agents is an exact power of the out-degree of the communication graph. We introduce an algebraic tool, the shifted Kronecker product, and a more general family of strategies, also based on a de Bruijn communication graph. Those strategies are compared to Cayley strategies in terms of the speed of convergence. We also show that quantized communication between the agents still allows finite convergence, to a consensus, which is not in general the average of the initial positions.     

Materials decay and environmental attack in the Pio Palace at Carpi: A holistic approach for historical architectural surfaces conservation

Since the XIV century the Pio Palace in Carpi (MO, Italy) has been subjected to many additions and rearrangements and, in the last decades, to wide restoration works. Nevertheless the XVII century main portal has not been restored yet, due to its complex and peculiar surface alteration forms in comparison with the other parts of the building, and still suffers a deep decay and degradation by complex chemical-physical processes.     

Blends composed of poly(N‐isopropylacrylamide) and an ethylene/vinyl alcohol copolymer: Thermal and morphological studies

Blends of poly(N‐isopropylacrylamide) (PNIPAM) and an ethylene/vinyl alcohol copolymer (EVAL) were obtained through casting from dimethyl sulfoxide (DMSO) solutions and phase inversion in 50/50 DMSO/H₂O solutions. The miscibility and morphology of the PNIPAM/EVAL blends were investigated with thermal and morphological analysis. Differential scanning calorimetry indicated that the crystallinity of EVAL decreased with increasing PNIPAM content and that the blends cast from DMSO/H₂O solutions were miscible in the melt state. Measurements of the melting point depression allowed the determination of the interaction energy density (B) and Flory–Huggins interaction parameter (χ₁₂) with the Nishi–Wang equation. The negative B and χ₁₂ values obtained were examined in terms of the specific intermolecular interactions between the polymers. Scanning electron micrographs revealed that blends obtained by the casting method led to dense membranes, whereas the phase‐inversion method rendered typical macroporous membranes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 501–505, 2004