Search

Vacuum UV (VUV) process is an incipient advanced oxidation process, which can be used for water treatment. This process relies on the formation of hydroxyl radicals through the VUV-induced photolysis of water. In particular, the use of ozone-generating mercury vapor lamps, which emit 10% of the radiation at 185 nm and 90% at 254 nm, is showing very promising results for the degradation of micropollutants. The kinetics of VUV process has been studied in batch- and flow-through reactors, but the effect of 254 and 185 nm photons cannot be isolated, mass transfer resistances can take place and the interpretation of the results is complex. In this technical note, a new VUV collimated beam to conduct kinetic tests is presented, which offers several advantages: (1) it allows the irradiation of samples with 185, 254 nm photons, or both, (2) the concentration of reagents is uniform in the reaction volume and (3) it allows to change the fluence rate by changing the distance between the lamp and the photoreactor. Details of the geometry are presented, as well as an analysis of the collimation and uniformity of the radiation of the new VUV-collimated beam setup., (© 2013 The American Society of Photobiology.)

An Ising-like model of proteins is used to investigate the mechanical unfolding of the green fluorescent protein along different directions. When the protein is pulled from its ends, we recover the major and minor unfolding pathways observed in experiments. Upon varying the pulling direction, we find the correct order of magnitude and ranking of the unfolding forces. Exploiting the direction dependence of the unfolding force at equilibrium, we propose a force sensor whose luminescence depends on the applied force.

The study of the photocatalytic activity of TiO(2) inverse opals showed that these structures behave as metamaterials: their properties arise principally from the 3D periodic structure of the material and marginally from porosity, reflectivity and scattering.

We study the mechanical unfolding pathways of the FnIII(10) domain of fibronectin by means of an Ising-like model, using both constant force and constant velocity protocols. At high forces and high velocities our results are consistent with experiments and previous computational studies. Moreover, the simplicity of the model allows us to probe the biologically relevant low force regime, where we predict the existence of two intermediates with very close elongations. The unfolding pathway is characterized by stochastic transitions between these two intermediates.

Mechanical unfolding and refolding of ubiquitin are studied by Monte Carlo simulations of a Gō model with binary variables. The exponential dependence of the time constants on the force is verified, and folding and unfolding lengths are computed, with good agreement with experimental results. Furthermore, the model exhibits intermediate kinetic states, as observed in experiments. Unfolding and refolding pathways and intermediate states, obtained by tracing single secondary structure elements, are consistent with simulations of previous all-atom models and with the experimentally observed step sizes.

The mechanical unfolding of proteins is studied by extending the Wako-Saitô-Muñoz-Eaton model. This model is generalized by including an external force, and its thermodynamics turns out to be exactly solvable. We consider two molecules, the 27th immunoglobulin domain of titin and protein PIN1. We determine equilibrium force-extension curves for the titin and study the mechanical unfolding of this molecule, finding good agreement with experiments. By using an extended form of the Jarzynski equality, we compute the free energy landscape of the PIN1 as a function of the molecule length.

The interaction of water with Si- and C- terminated beta-SiC(001) surfaces was investigated by means of ab initio molecular dynamics simulations. Irrespective of coverage, varied from 1/4 to 1 monolayer, we found that water dissociates on the Si-terminated surface, substantially modifying the clean surface reconstruction, while the C-terminated surface is nonreactive and hydrophobic. Based on our results, we propose that STM images and photoemission experiments may detect specific changes induced by water on both the structural and electronic properties of SiC(001) surfaces., (Copyright 2004 The American Physical Society)

The high lattice mismatched SiC/Si(001) interface was investigated by means of combined classical and ab initio molecular dynamics. Among the several configurations analyzed, a dislocation network pinned at the interface was found to be the most efficient mechanism for strain relief. A detailed description of the dislocation core is given, and the related electronic properties are discussed for the most stable geometry: we found interface states localized in the gap that may be a source of failure of electronic devices.

Three weeks following the splenectomy of young chickens an increased number of the hypertrophic epithelial cells, which presented various signs of secretory activity, could be observed in the thymus. After splenectomy, these cells usually present a single, large-sized intracytoplasmic vesicle or vacuole lined with microvilli. The lumen of such vesicles is always full of granulated and membranous material. The ultrastructural appearance of the hypertrophic epithelial cells strongly suggests an intensive metabolic activity and a possible active protein synthesis. These results lead to the hypothesis that hypertrophic epithelial cells secrete a lymphopoietic hormones which is active in normal chickens and which is secreted at an accelerated rate during certain hyperfunctional circumstances such as the period following splenectomy.

The author's aim was to investigate conservation of rat liver by continuous perfusion of the isolated organ in conditions of normal temperature, as well as in hypothermia. A complex solution was used, lacking hemoglobin. Over a period of 5 hours of conservation the authors evaluated the perfusion rate, the concentration of lactate and pyruvate in the conservation medium, while on histological preparations was investigated the formation of fibrin deposits in the intra-hepatic vessels. The results confirmed the positive effects of hypothermia, that is not due exclusively to a limiting of the metabolic necessities of the organ but also to a reduction of the fibrinogenesis and a slowing down of the formation of intra-hepatic microaggregates.

The dynamics of the fibrinoplastic process were studied in rat isolated liver, perfused in normothermia with a synthetical medium. For the autohistoradiographical study, 125I-labelled fibrinogen was added to the perfusing medium. The historadiograms obtained suggest that the main link in the rise of trans-hepatic vascular resistance is thickening of the fibrin muff of the sinusoids. Consequent reduction of the capillary permeability determines favourable conditions for stasis and massive precipitation of fibrinogen under the form of fibrin thrombi into the intrahepatic vessels. Streptase addition to the perfusion medium prevents the intervention of these mechanisms during the studied period.

One of the factors limiting the duration of rat liver storage is the excessive accumulation of catabolites in the perfusion medium. In view of obtaining of an efficient depuration the authors have introduced a new circuit allowing for the concomittant perfusion of the liver and of the kidneys. The excretion effort of the kidneys is assessed by the estimation of urea nitrogen in the perfusion medium and in the urine collected over the entire duration of the experiment. The results have confirmed the good function of the system which provides possibilities for improved storage conditions of rat liver.

Accumulation of radioactive material in the isolated rat liver was noted when 125I-fibrinogen was added to the perfusing medium. Owing to an enhanced production of fibrinogen and to a diminished fibrinolysis, fibrin deposits were found to occur in the capillaries of fhe isolated liver. This would cause a decrease of hepatic flow and an impairment of the nutrition of this organ which leads to subsequent necrosis. Administration of streptase removed the fibrin deposits and restored the perfusive flow in the isolated liver.