A biofilm model for flowing systems in the food industry

When bacteria attach to the walls of pipelines, they can form biofilms, which can cause the recontamination of food products. In order to quantify such recontamination, a one-dimensional biofilm model was developed taking into account adsorption, desorption, and the growth of cells. The model consisted of two mass balances describing increases in biofilm formation at the wall and the accumulation of cells in the liquid phase. The necessary parameters for the model were obtained in laboratory biofilm experiments. These experiments involved a flowing system and the use of Staphylococcus aureus as a model pathogen and silicon tubing as a testing material. S. aureus was inoculated into the system for 2 h, and then the system was changed to a sterile medium. Both biofilm formation and the release of cells into the flowing liquid were measured until steady-state conditions were reached (for up to 9 days). The experiments were performed in duplicate for different flow conditions (i.e., for Reynolds numbers of 3.2, 32, and 170). It was shown that at higher Reynolds numbers, the biofilm developed faster, probably owing to an increase in the transfer of nutrients to the surface. The proposed biofilm model was capable of describing the data obtained for the three different flow conditions with the use of the specific growth rate in the biofilm and the desorption coefficient as fit parameters. The specific growth rates were 0.16, 0.27, and 0.49 h(-1) for Reynolds numbers of 3.2, 32, and 170, respectively, and the desorption coefficients were about 1% of these values.     

Regional economic dynamics and convergence in the European Union

This paper uses an alternative approach to convergence analysis, which, in our opinion, is richer than those traditionally proposed. We believe that the evolution of the whole regional distribution is what matters, not that of an average or representative economy, implicit in the or convergence concepts. Moreover, when analyzing inequality among regional economies, geographic space acquires a preeminent role. We therefore apply spatial association tests recently developed in the spatial econometrics literature and relate them to convergence analysis. Specifically, we apply this methodology to the analysis of regional dynamics and convergence in the European Union (EU). In this context, the progress made in the integration process has highlighted the question of economic disparities at regional level. The process of convergence came to an end in the late seventies, coinciding with major changes in economic activity. This paper shows how these factors appear to have provoked a regionally differentiated response which, though significant, did not, in all likelihood, exacerbate the decrease in regional inequalities.     

Palladium‐nanoparticle intercalated vermiculite for selective hydrogenation of α,β‐unsaturated aldehydes

Palladium nanoparticles were generated in the interlamellar region of swelling 2:1 type vermiculite clay using an adsorption excess isotherm. An adsorption excess isotherm was constructed for vermiculite after exchanging the exchangeable Na⁺ ions in the interlamellar region using a binary liquid mixture (ethanol:toluene). Based on adsorption excess isotherm, 1% w/w palladium was intercalated into the interlamellar space of vermiculite. The Pd‐intercalated vermiculite was characterized by X‐ray diffraction, transmission electron microscopy and atomic absorption spectroscopy. The 1% w/w Pd‐intercalated vermiculite was tested for its catalytic activity towards selective hydrogenation reactions involving some α,β‐unsaturated carbonyl compounds using a pulse reactor and its catalytic activity was compared with commercial 1% Pd/C. The intercalated catalyst was found to be very selective towards the desired product of unsaturated alcohols. Copyright © 2007 Society of Chemical Industry     

Shear resistance in stainless steel plate girders with transverse and longitudinal stiffening

This paper summarizes and presents main results of the investigation conducted in the Department of Construction Engineering of the UPC dealing with shear behaviour of stainless steel plate girders. Initial shear buckling stress together with ultimate shear capacity of these structural elements have been evaluated with special attention paid to the effect of including stiffeners, both transverse and longitudinal. The studies conducted, both numerical and experimental tests, have permitted the development of new and simple design expressions to determine more accurately the initial shear buckling stress in stainless steel web panels and the ultimate capacity of plate girders considering the presence of a rigid or non-rigid end post.     

Energy transfer and compatibility analysis of PVK/MEH-PPV blends processed via electrospraying and electrospinning

Solution polymer blends of a high molecular weight and a low molecular weight poly(9-vinyl carbazole) PVK with poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), at a fixed blend ratio of 95.5:0.5, were processed via electrospraying and electrospinning. SEM studies revealed that electrosprayed particles were produced when low molecular weight PVK was used, while electrospun fibers were successfully obtained from solutions containing high molecular weight PVK, over a concentration range of 4–10% (w/v). From the absorption spectra of the neat polymers it was determined that Urbach energy E_u increase and optical band gap E_g decreases due to the physical defects along the main chain introduced by these electrostatic processing methods. Photoluminescence spectroscopy revealed a particular applied voltage, which depends on concentration and molecular weight, where aggregation of PVK levels off. Luminescence quenching of MEH-PPV is also observed to increase with applied voltage consistent with possible energy transfer from shorter conjugation length segments to nearby longer conjugated segments. The ratio of the intensity of the excitation spectra of the PVK (donor, both PVK_L or PVK_H) and the MEH-PPV (acceptor), I_D/I_A, exhibited minima at this particular voltage and then levels off, indicating not only maximum interpenetration and thus compatibility of both polymers but also maximum energy transfer. Hence, we demonstrate that compatibility and energy transfer can be optimized varying concentration and applied voltage during both electrospraying and electrospinning processes.     

STUDY OF GLAZE PENETRATION AND ITS EFFECT ON GLAZE FIT: I-III*

A method for determining glaze penetration was developed and the effect of glaze penetration on glaze fit studied. The effects of twenty-four fluxes on penetration of a base glaze into semivitreous, hotel china, terra cotta, cordierite, pyrophyllite, wall tile, and steatite bodies were determined. The result shows that glaze penetration affects glaze fit and that penetration varies greatly, depending on glaze composition and the character of the body.     

Alteration in the Synaptic and Extrasynaptic Organization of AMPA Receptors in the Hippocampus of P301S Tau Transgenic Mice

Tau pathology is a hallmark of Alzheimer’s disease (AD) and other tauopathies, but how pathological tau accumulation alters the glutamate receptor dynamics driving synaptic dysfunction is unclear. Here, we determined the impact of tau pathology on AMPAR expression, density, and subcellular distribution in the hippocampus of P301S mice using immunoblot, histoblot, and quantitative SDS-digested freeze-fracture replica labeling (SDS-FRL). Histoblot and immunoblot showed differential regulation of GluA1 and GluA2 in the hippocampus of P301S mice. The GluA2 subunit was downregulated in the hippocampus at 3 months while both GluA1 and GluA2 subunits were downregulated at 10 months. However, the total amount of GluA1-4 was similar in P301S mice and in age-matched wild-type mice. Using quantitative SDS-FRL, we unraveled the molecular organization of GluA1-4 in various synaptic connections at a high spatial resolution on pyramidal cell spines and interneuron dendrites in the CA1 field of the hippocampus in 10-month-old P301S mice. The labeling density for GluA1-4 in the excitatory synapses established on spines was significantly reduced in P301S mice, compared to age-matched wild-type mice, in the strata radiatum and lacunosum-moleculare but unaltered in the stratum oriens. The density of synaptic GluA1-4 established on interneuron dendrites was significantly reduced in P301S mice in the three strata. The labeling density for GluA1-4 at extrasynaptic sites was significantly reduced in several postsynaptic compartments of CA1 pyramidal cells and interneurons in the three dendritic layers in P301S mice. Our data demonstrate that the progressive accumulation of phospho-tau is associated with alteration of AMPARs on the surface of different neuron types, including synaptic and extrasynaptic membranes, leading to a decline in the trafficking and synaptic transmission, thereby likely contributing to the pathological events taking place in AD.     

Note on a simple algorithm for a computer-produced reading ease score.

Describes 3 relatively simple computer algorithms for estimating the average number of syllables/word in text from letter counts. The syllable counts were used to determine Flesch Reading Ease Scores for text by computer. Vowel counts worked well. (PsycINFO Database Record (c) 2010 APA, all rights reserved)