Effect of process conditions on phase mixtures of sol–gel-synthesized nanoscale orthorhombic, tetragonal, and monoclinic zirconia

Zirconia particles synthesized under ambient conditions are frequently amorphous, requiring heat to produce a crystalline phase. Synthesized nanoparticles are generally found in the tetragonal phase. In this article, a room temperature sol–gel synthesis of crystalline sub-10-nm zirconia particles is described. By adjusting the acid concentration of the reaction, it is found that the particles’ crystalline phase can be modified. Under acidic conditions with moisture present, the tetragonal phase is produced, whereas under acidic conditions with low water content, 2–5-nm particles suggestive of the metastable orthorhombic phase are produced. Subsequent heat treatment of all powders produced with this technique resulted in their transformation first to the tetragonal phase, and ultimately to the monoclinic phase. The extent of the transformation to the monoclinic phase depends upon the atmosphere, however, suggesting that oxygen vacancies play a significant role in the stabilization and determination of the resulting phase.     

Multitemporal thermal analysis to detect moisture on a building façade

It is well known that the content of water does affect materials behaviour and may cause important damages to buildings, including structural deterioration. Thermography is a non-intrusive imaging technique that allows the inspection of different materials based on their surface temperatures. Within an appropriate thermal analysis, moisture and other structural damages can be detected. The present research work deals with multitemporal thermal analysis to detect moisture on buildings, as well as other alterations. Two different approaches are tested to determine the effectiveness on the moisture surveys, one simple based on image differences, and another more sophisticated based on principal components analysis (PCA). The results are tested at the front door of the Arenberg Castle (Leuven, Belgium). Some moisture maps are derived and used to determine the reliability of either the computation of image differences or the PCA to carry out semi-automatically moisture surveys on architectural façades. The latter method is proven to be superior when using thermal imagery acquired at different times.     

Road extraction from aerial images using a region competition algorithm.

In this paper, we present a user-guided method based on the region competition algorithm to extract roads, and therefore we also provide some clues concerning the placement of the points required by the algorithm. The initial points are analyzed in order to find out whether it is necessary to add more initial points, and this process will be based on image information. Not only is the algorithm able to obtain the road centerline, but it also recovers the road sides. An initial simple model is deformed by using region growing techniques to obtain a rough road approximation. This model will be refined by region competition. The result of this approach is that it delivers the simplest output vector information, fully recovering the road details as they are on the image, without performing any kind of symbolization. Therefore, we tried to refine a general road model by using a reliable method to detect transitions between regions. This method is proposed in order to obtain information for feeding large-scale Geographic Information System.     

Vocal dialogues in the neonatal period.

63 mothers and their 3-day-old infants were observed during breast feeding. The analysis of dyadic vocal interaction suggested that during the neonatal period, the infant's vocalization is already responsive to both presence and absence of maternal vocalization. Maternal vocalization was shown to be responsive to antecedent vocal behavior of the newborn. No sex differences were found in the patterns of sequential vocal exchanges at this period. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial and temporal sequence of events in cell adhesion: from molecular recognition to focal adhesion assembly

A new concept that attributes a pivotal role to the pericellular coat in the regulation of the early stages of cell adhesion is presented. Quick, adaptable, and transient adhesion through multiple cooperative weak interactions provides the cell with an additional level of modulation in the decision-making process that precedes the commitment to adhesion at a particular site. Hyaluronan emerges as a modulator of cell adhesion in certain cells, mediating binding or repulsion through its polyelectrolyte character, in addition to its chirality and molecular-recognition properties. The biophysical properties of hyaluronan as well as its ultrastructural organization are analyzed in relation to this proposed function.     

Polyplexes of polyethylenimine and per-N-methylated polyethylenimine-cytotoxicity and transfection efficiency

For non-viral gene delivery, the carriers for DNA transfer into cells must be vastly improved. The branched cationic polymer polyethylenimine has been described as an efficient gene carrier. However, polyethylenimine was demonstrated to mediate substantial cytotoxicity. Therefore, this study is aimed at investigating per-N-methylated polyethylenimine, which is thought to have a much lower cytotoxicity due to its lower charge density. Results from a gel retardation assay and laser light scattering indicated that per-N-methylated polyethylenimine condenses DNA into small and compact nanoparticles with a mean diameter <150 nm. Furthermore, polyplexes of polyethylenimine and per-N-methylated polyethylenimine with DNA had a positive zeta potential and the polymers protected DNA from nuclease-mediated digestion. The transfection efficiency of polyethylenimine and per-N-methylated polyethylenimine was tested in CHO-K1 cells. Using green fluorescent protein as reporter gene and flow cytometry analysis, we demonstrated that per-N-methylated polyethylenimine has a lower cytotoxicity, but also a significantly lower transfection efficiency. Using propidium iodide staining, we could additionally distinguish between viable and dead cells. At NP > or = 12, per-N-methylated polyethylenimine showed a much higher cell viability and the ratio of viable and transfected cells to dead and transfected cells was about 1.5 to 1.7 fold higher than for polyethylenimine. The results of cell viability from flow cytometry analysis were confirmed by the MTS assay. Using luciferase reporter gene for transfection experiments, the gene expression of per-N-methylated polyethylenimine was lower at NP 6, 12 and 18 as compared to polyethylenimine, but at NP 24 it yielded similar levels.     

Semivolatile organic compounds in window films from lower Manhattan after the September 11th World Trade Center attacks

The September 11th World Trade Center (WTC) terrorist attacks resulted in the large-scale release of contaminants that were deposited on the environment of New York City (NYC). Six weeks after the attacks, samples of an organic film on window surfaces were collected and analyzed for polybrominated diphenyl ethers (PBDE), polychlorinated biphenyls (PCB), polychlorinated naphthalenes (PCN), polycyclic aromatic hydrocarbons (PAH), and organochlorine pesticides (OCPs). Concentrations dropped by an order of magnitude within 1 km of the WTC and reached background concentrations by 3.5 km. Concentrations within 1 km of the WTC averaged 3280 ng/m2 for sigmaPBDE, 900 ng/m2 for sigmaPCB, 33 ng/m2 for sigmaPCN, and 77100 ng/m2 for sigmaPAH. Congener profiles of the sites nearest the WTC suggested a combination of combustion and evaporative sources of all compounds, whereas the background sites exhibited profiles consistent with evaporative sources. PBDE profiles showed enrichment in lower molecular weight congeners near the WTC, suggesting that these congeners were formed as a result of the combustion conditions. Homologue fractions of PCN combustion markers were approximately 2-9 times greater at near WTC sites compared to background NYC. Gas-phase air concentrations were back-calculated from measured film concentrations using the film-air partition coefficient (KFA), and calculated air concentrations followed spatial trends observed in films.