Obtainment of hierarchical ZSM-5 zeolites by alkaline treatment for the polyethylene catalytic cracking

Great efforts have been applied in order to achieve the synthesis of hierarchical zeolites through post-synthesis alkaline treatment. In this case, the use of hierarchical ZSM-5 zeolites as acid catalysts in the catalytic cracking of polyolefins overcomes some diffusional limitations and expands the selectivity of products. Thus, the purpose of work was to promote a secondary porosity in ZSM-5 zeolite by NaOH treatment (using conventional electric and microwave heating methods), applying cetyltrimethylammonium bromide as pore-directing agent. Both heating methods generated additional secondary porosity, with microwave heating promoting a narrow pore size distribution, when compared to conventional. All hierarchical ZSM-5 have been showed low-density polyethylene conversions superior to the purely microporous ZSM-5, however the hierarchical zeolite processed by conventional electric heating reached the higher temperature reduction (42.6 K). It was evidenced through measurements of morphological and textural properties, ion exchange capacity and catalytic activity in the LDPE cracking that the CTAB cations exerts a protective effect at alkaline treatment avoiding the desilication process. The additional secondary porosity promoting the generation of compounds of lower molecular mass in LDPE catalytic cracking, by thermogravimetric analysis, proving that the alkaline treatment increases the accessibility to the active acidic sites of zeolitic catalysts for bulky molecules.     

Category-specific deficits for grammatical classes of words: evidence for possible anatomical correlates

The sialic acid content and the cell-surface hydrophobicity index of 40 group B streptococci (GBS) strains were assessed. GBS isolated from invasive infections (virulent strains) presented an increased level of sialic acid content (1.4%) when compared with GBS isolated from asymptomatic patients (0.53%). Treatment of GBS strain 85634 with neuraminidase resulted in a decrease (about 25%) in the net negative surface charge as assessed by cell electrophoresis. This finding suggests that sialic acid residues are important anionogenic groups exposed on GBS cell surface. N-acetylneuraminic acid was the only sialic acid derivative characterized in the strain 85634 as evaluated by gas-liquid chromatography. GBS from different serotypes presented a hydrophobic index mean value of 0.9. Even though the sialic acid contributed effectively to the negative charge on GBS cell surface, no difference was observed in the hydrophobic index when virulent and avirulent strains were compared.     

Bone marrow stroma in humans: anti-nerve growth factor receptor antibodies selectively stain reticular cells in vivo and in vitro

Two anti-nerve growth factor receptor (LNGFR or p75NGFR) antibodies, Me20.4 and Me8211, label stromal cells with dendritic features in fresh smears and in formalin-fixed, paraffin-embedded human bone marrow (BM). The LNGFR+ cells have an oval nucleus, a scanty cytoplasm with long dendrites that intermingle with the hematopoietic cells, line the abluminal side of sinus endothelial cells, and provide the scaffold for the hematopoietic marrow. At the electron microscopy level, the immunogold tag labels the body and the long branching dendrites of fibroblast-like cells with scanty cytoplasm containing mitochondria, endoplasmic reticulum, and dense bodies. The LNGFR+ cells are positive for alkaline phosphatase, reticulin, collagen III, vimentin, TE-7, and CD13 but negative for endothelial (vWF, CD34, Pal-E), neural (CD56, neurofilament) and leukocyte markers (CD45, CD68). The LNGFR+ stromal cells appear in the fetal BM before the hematopoietic activity begins, originate from the vessel adventitia, and radiate in the Bm cavity. Long-term BM culture (LTBMC) in vitro contain LNGFR+ stromal cells. We document the presence of RNA message for the low- (LNGFR) and the high-affinity NGF receptor (NTRK1) by using RT-PCR on fresh BM aspirate and on LTBMC. BM biopsies from patients with hematologic fibrogenic diseases and in cytokine-treated cancer patients are evaluated for LNGFR+ cells: the amount of stained cells is correlated with the traditional reticulin stain in cases of myelofibrosis, therapy-related myelodysplasia, leukemia, and detected an increase of stromal cells in cytokine-treated patients. The anti-LNGFR antibodies represent a specific membrane marker for the adventitial reticular cells (ARC) of the human marrow and allow precise evaluation and quantitation of this important BM microenvironment component in vivo and in vitro.     

Thermal evolution of a silicone resin/polyurethane blend from preceramic to ceramic foam

Ceramic foams, prepared by the pyrolysis of a foamed blend of a methylsilicone preceramic polymer and a polyurethane, exhibit excellent mechanical properties. The thermal evolution of process to produce from the foamed blend (weight ratio of 1 to 1) to ceramic foam was investigated from room temperature to 1400°C. Firstly, the methylsilicone preceramic polymer was characterized with various techniques. Secondly, the weight decrease and the degradation gas from the unpyrolyzed foamed blend, the phase morphology change, the compositional change, and the dimensional change were investigated. The main variation of characteristics of the foamed blend was observed in the temperature range 400 to 600°C, where the largest weight loss occurred in TGA, for most of the measurements. At these temperatures, the decomposition of the polyurethane phase is mostly completed, and the polymer-to-ceramic conversion of the silicone resin is under way. The phase-morphological analysis surprisingly showed that the polyurethane was dispersed as particles in a methylsilicone preceramic polymer matrix, although originally polyurethane was intended to be used as a sacrificial template matrix. The polyurethane domain particles gradually aggregated and tended to disappear as the temperature increased, and the ceramic foam walls and struts appeared to be dense (for pyrolysis temperature <1400°C). These features can be explained assuming that the preceramic polymer matrix deformed during the decomposition of the polyurethane and the polymer-to-ceramic conversion.     

Project, Design, and Use of a Pilot Plant for Nanocapsule Production

The aim of this study was to find the scale-up parameters necessary for the preparation of nanocapsules (NCs) for pharmaceutical purposes. Starting from the laboratory scale (0.06 L), we designed and assembled a pilot plant (2 L) to produce NCs with the so-called emulsification-diffusion technique. We wanted to check if classical tools adequate for the pharmaceutical industry and for industrial scale-up purposes according to well-known chemical engineering technique could be used to perform the NC preparation. Experiments were carried out by varying some operative parameters, such as the impeller speed, the agitation duration for the emulsion preparation, and the reagent concentrations. As expected, good accordance between the NC produced at the laboratory scale and at the pilot plant scale was obtained. We conclude that the pilot plant can be used to perform a scale-up study of the industrial production of NC.     

Easy Cases of Probabilistic Satisfiability

The Probabilistic Satisfiability problem (PSAT) can be considered as a probabilistic counterpart of the classical SAT problem. In a PSAT instance, each clause in a CNF formula is assigned a probability of being true; the problem consists in checking the consistency of the assigned probabilities. Actually, PSAT turns out to be computationally much harder than SAT, e.g., it remains difficult for some classes of formulas where SAT can be solved in polynomial time. A column generation approach has been proposed in the literature, where the pricing sub-problem reduces to a Weighted Max-SAT problem on the original formula. Here we consider some easy cases of PSAT, where it is possible to give a compact representation of the set of consistent probability assignments. We follow two different approaches, based on two different representations of CNF formulas. First we consider a representation based on directed hypergraphs. By extending a well-known integer programming formulation of SAT and Max-SAT, we solve the case in which the hypergraph does not contain cycles; a linear time algorithm is provided for this case. Then we consider the co-occurrence graph associated with a formula. We provide a solution method for the case in which the co-occurrence graph is a partial 2-tree, and we show how to extend this result to partial k-trees with k>2.     

Closed-form solution for a line source at the edge of anisorefractive wedge

A closed-form solution is given for the radiation of an electric or magnetic line source located at the edge of an isorefractive wedge. The solution is valid for any wedge angle if the line source is isotropic. For certain nonisotropic line sources, the solution is valid only if the wedge angle is commensurable to π radians     

A method for tracking individual planetary waves in remotely sensed data

We describe a methodology for tracking individual planetary waves in longitude-time plots of satellite data, based on fitting an elementary wave shape model to subsets of the data by maximum likelihood, then reconstructing the trajectory and evolution of every single wave (where for "single wave" we mean an individual positive or negative westward propagating anomaly) by joining the elementary waves according to their similarity. We then illustrate the potential of the methodology with an example at 34/spl deg/N in the Atlantic Ocean and its adaptability to different cases with a second example on eastward-propagating Kelvin waves in the equatorial Pacific. Although the examples given use sea surface height anomaly data, the technique lends itself to be applied to any space-time plot of any dataset displaying propagation and, in particular, to sea surface temperature data.     

Quantifying fractured rock hydraulic heterogeneity and groundwater inflow prediction in underground excavations: the heterogeneity index

This paper presents an approach to quantify the degree of heterogeneity of a fracture network starting from the information that is collected for a geomechanical classification of rock masses. Six synthetic experiments have been used to prove the existence of a correspondence between the variability in fracture properties and in the direction and magnitude of flow. Statistical analyses conducted using fracture data collected at a tunnel crossing the north-western Italian Alps have also shown that variability in fracture characteristics is indeed related to the magnitude of inflows. These findings have proved that it is reasonable to estimate the degree of heterogeneity of a fracture network by combining the variance of those fracture characteristics that regulate both flow and the geomechanical behavior of a rock mass. An index comprising a combination of variances of fracture parameters at different scales is presented. Its dependence on scale showed that the heterogeneity of fractured rock increases with scale up to a certain scale and then gradually decreases at large scales.