Protein adsorption on titanium dioxide: Effects on double layer and semiconductor space charge region studied by EIS

The semiconductor properties of an n-type TiO₂ oxide surface and its modification by protein adsorption using electrochemical impedance spectroscopy (EIS) were studied. Impedance spectra under steady state conditions were obtained as a function of electrode potential and human serum albumin (HSA) concentration in solution. The effect of the adsorption potential on the EIS response was also analyzed (E_ads −0.70, −0.50 and −0.080 V vs. saturated calomel electrode). The impedance spectra were modeled using different equivalent circuits, and data analysis were performed by data fitting in the whole frequency range, as well as in the low and high frequency ranges. The electric representation that better fit experimental data consisted of two equivalent subcircuits composed by a combination of constant phase elements (cpe₁ and cpe₂) and resistances (R_s and R₁). The cpe₁ element represented the distributed capacity in the semiconductor oxide. The cpe₂ element was associated with diffusional processes. We have analyzed EIS data based on a theoretical calculation of interface apparent capacitance (C_app) from the cpe₁ parameters (Q₁ and ?₁) and resistance elements. The changes in capacitance, produced by the presence of HSA, were associated to changes in the space charge layer capacitance of the semiconductor, as a result of the energy band bending near the surface. The values obtained for the R₁ element from the theoretical fitting procedures (in the high and whole frequency range) were correlated to the electric resistance inherent to the semiconductor properties having a value of 6.10³ Ω cm².     

Thermal and Fluid Dynamic Simulation of Automotive Fin-and-Tube Heat Exchangers,Part 2: Experimental Comparison

A detailed model for the simulation of automotive fin-and-tube heat exchangers previously developed by the authors (Part 1) has been experimentally validated for a wide range of geometries and boundary conditions. Some of this experimental information was collected in an academic testing unit, while a second group of experiments was conducted in the experimental set-up of an industrial partner. The data cover a wide range of operational conditions and analyze the effect of most influential geometric parameters. The paper presents the experimental units and shows the comparison between numerical predictions and experimental values. The numerical calculations have been carried out using the most suitable available air-side heat transfer and friction correlations. Although the comparison is reasonably accurate, the deviations appearing among the predictions using different correlations indicate that further research work is still necessary to describe in a more accurate way the fundamental behavior of the louver fin geometry.     

Annealing properties of high quality Nb/Al-AlOx/Nbtunnel junctions

High quality, low current density Josephson tunnel junctions are obtained from Nb/Al-AlO_x/Nb trilayers, using a SNAP process to define the junction area. A large number of junctions has been annealed in air for several hours at temperatures as high as 300°C. The most relevant effects observed were: a) a marked decrease of the junction current density and a related increase of the normal-state resistance; b) under suitable conditions, a barrier quality improvement measured in terms of the subgap current and of the quality factor V_m; the most remarkable result is a V_m as large as 2.5 V at T=1.2 K for our best sample. We believe that oxygen diffusion through the Nb grain boundaries is the main mechanism responsible for the normal-state resistance increase and that device quality variation is closely related to the modification of the barrier interfaces     

Classification of scene photographs from local orientations features

Natural image understanding is a very active and promising research domain both in psychology for visual perception modelling and in computer science for image retrieval. In this study, we investigate the efficiency of orientation distributions over the whole image in the scale space. The global distribution of the local dominant orientations (LDO) appears to be a powerful feature for discriminating between four semantic categories of real world scenes (indoor scenes, urban scenes, open landscapes, closed landscapes). The selected optimal scale is compatible with psychological experiments and classification performances show that a global representation of dominant orientations is a simple, efficient and compact method for scene recognition.     

Statistics of natural image categories

In this paper we study the statistical properties of natural images belonging to different categories and their relevance for scene and object categorization tasks. We discuss how second-order statistics are correlated with image categories, scene scale and objects. We propose how scene categorization could be computed in a feedforward manner in order to provide top-down and contextual information very early in the visual processing chain. Results show how visual categorization based directly on low-level features, without grouping or segmentation stages, can benefit object localization and identification. We show how simple image statistics can be used to predict the presence and absence of objects in the scene before exploring the image.     

An overview of IEEE 802.21: media-independent handover services

In recent years multitechnology-enabled terminals have become available. Such multimode terminals pose new challenges to mobility management. In order to address some of these challenges, the IEEE is currently working on a new specification on media-independent handover services (IEEE 802.21 MIH). The main aim of this specification is to improve user experience of mobile terminals by enabling handovers between heterogeneous technologies while optimizing session continuity. In this article we provide an overview of the current status of the IEEE 802.21 specification.     

Comparison of shelf-life estimates for a human insulin pharmaceutical preparation using the matrix and full-testing approaches

The design of a stability study is intended to establish a shelf-life based on testing a limited number of batches of a drug product, which is applicable to all future batches of the drug product manufactured under similar circumstances. In the FDA guidelines for stability testing of new drug products, the matrix design is suggested as the alternative statistical design to the full testing approach. In the last few years, the matrix design has received increasing attention from pharmaceutical companies in order to reduce the cost of stability studies. For this, the full and matrix stability test plans were used on three batches of human insulin pharmaceutical preparation stored under a kinetic mean temperature of 22.7 degrees C for 3 years. The statistical method was suggested by Ruberg and Stegeman (Biometrics, 1991, 47, 1059-1069) and Llabrés et al. (Int. J. Pharm. 2000, 204, 61-68), and was used for comparing batches, and the maximum allowable difference in slopes between batches was used as criteria for estimating a common shelf-life. The results obtained show the conservative nature of the matrix approach, although the difference between the matrix and full shelf-life was less than 1 month. The effect of the matrix method on shelf-life was also studied. The results showed that the model for estimating the shelf-life varied as a function of the permutation used, after testing for both slope and intercept poolability at alpha = 0.25. The batches should be pooled for both full testing and matrix design since the critical significance level required to obtain a power of 0.80 was achieved when the maximum allowable difference in slopes between batches was 1%/month, according to Ruberg and Stegeman. In contrast, when the proposed method by Llabrés et al. was used, the results varied in function of the maximum allowable difference in slopes.     

Clinical and histological outcome after hepatitis B e antigen to antibody seroconversion in children with chronic hepatitis B

Data regarding the outcome of children with chronic hepatitis B after seroconversion are scarce. We describe the long-term evolution of these patients. One hundred and three children with antibody against hepatitis B e antigen and normal alanine aminotransferase (ALT) levels were followed for 0.6 to 12.5 years (mean, 6.3 years). Paired liver biopsies (before and after seroconversion) were available in 83 cases. Final biopsies were obtained 0.5 to 12.5 years (mean, 4.5 years) after seroconversion. ALT levels remained normal in most of the children (79%) throughout the follow-up. All children, except five who lost hepatitis B surface antigen, had serum viral DNA detected by polymerase chain reaction. When comparing baseline and final liver biopsies, a significant improvement (P <.001) was found in the histological activity index and in the necrosis, cytolysis, inflammation, and fibrosis scores. The histological diagnosis improvement in the final biopsy was significantly related (P <.001) to the time from seroconversion to the biopsy performance. All children had viral DNA on their final liver biopsy. In summary, seroconversion and ALT normalization are quite stable findings in children, and no differences in the long-term outcome between treated and untreated children were found. In light of the histological outcome, it seems unnecessary to perform a follow-up liver biopsy in these cases.