Modeling the Accumulation of Degradable Polymer Drug Carriers in the Brain

The blood–brain barrier (BBB) limits the access of drugs to the brain. Intensive research is being conducted on the development of nanoparticulate drug carriers that mediate transfer across the BBB. A question that has been neglected so far is the potential accumulation of the carrier in the brain upon long‐term exposure. Here, we address this question by implementing a kinetic model to relate drug loading, required concentration of drug in the brain, and drug clearance to the degradation half‐life of the carrier. As a test case with clinical relevance we chose poly‐lactic‐co‐glycolic‐acid (PLGA) as a carrier material and a chemotherapeutic for which the required parameters could be recovered from the literature. For methotrexate with a drug load of 8.5 %, a required concentration of free drug of 1 μm , a release from PLGA of 6 hours, a drug clearance from the brain of 3 hours and a half‐life of polymer degradation of 28 days, a steady‐state accumulation of 1.3 g polymer would be reached in the brain (1.5 L) after seven months. While this number is surprisingly small, further physiological research is warranted to assess to which degree this will be in a tolerable range.     

Network representation with clustering tree features

This paper studies the relationship between a case-based decision theory (CBDT) and an ideal point model (IPM). We show that a case-based decision model (CBDM) can be transformed into an IPM under some assumptions. This transformation can allow us to visualize the relationship among data and simplify the calculations of distance between one current datum and the ideal point, rather than the distances between data. Our results will assist researchers with their product design analysis and positioning of goods through CBDT, by revealing past dependences or providing a reference point. Furthermore, to check whether the similarity function, presented in the theoretical part, is valid for empirical analysis, we use data on the viewing behavior of audiences of TV dramas in Japan and compare the estimation results under the CBDM that corresponds to a standard decision model with similarities and other various similarity functions and without a similarity function. Our empirical analysis shows that the CBDM with a similarity function, presented in this study, best fits the data.     

Ionic nanocomposite networks in poly(styrene‐co‐methacrylic acid) copolymers with calcium carbonate

To create reversible supramolecular ionic networks, ionic cross‐links were formed from acid pendant functions in poly(styrene‐co‐methacrylic acid) copolymers by the addition of calcium carbonate. The random dispersion of acid functions in the polystyrene chain is ensured by NMR analysis. The partial reaction of the calcium carbonate with the carboxylic acids is highlighted by a limewater test. The influence of methacrylic acid and calcium‐carbonate contents on the formation of an ionic network has been studied through solubility tests. Two main effects were obtained: the exfoliation of the unreacted calcium carbonate characterized by TEM is due to ionic interactions at the surface of nanometric particles that form the first level of organization of the calcium carbonate. Another part of the calcium carbonate reacts with carboxylic acid and is detached from particles to form clusters as shown by x‐ray analysis. Finally, by analyzing the dynamic rheological spectrum, the conclusion that the strength of the ionic bonds arises with the calcium content is made. The interest of such an approach with a wide range of observed phenomena in the material is a one‐batch process to make thermoreversible nanocomposite networks. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Current knowledge in species-related bioavailability of selenium in food

Selenium is an essential trace element that has raised interest because of its antioxidant and anticancer properties. The beneficial or toxic effect of Se is not only dose-dependent, but also relates to the chemical form of the element and its bioavailability. In this review, recently published data is summarised concerning both Se speciation and Se relative bioavailability in various foodstuffs. In addition, Se bioavailability is discussed in relation to the species-dependent metabolism in humans. In this way, the understanding of the potential health impact of Se species in commonly consumed food is aimed to be improved. It is strongly suggested on the basis of a higher retention and a lower toxicity, that organic Se (especially SeMet, the major species in food) is more recommendable than inorganic Se in the frame of a balanced diet. Further research is however desirable concerning the characterisation of unidentified Se species and determination of their health effects.     

A pattern analysis based underwater video segmentation system for target object detection

Multidimensional Systems and Signal Processing - Detecting and classifying the target objects in the underwater videos is the primary and essential operation in this modern era. The present works...     

Eye tracking as a debriefing tool in upset prevention and recovery training (UPRT) for general aviation pilots

Abstract

Upset prevention and recovery training (UPRT) is intended to improve the ability of pilots to recognize and avoid situations that can lead to airplane upsets and to improve their ability to recover control of an airplane that has exceeded the normal flight envelope. To this end, a set of different training contents – from theoretical knowledge of aerodynamics and human factors to practice-based flight training – is necessary. In order to support the debriefing with an objective feedback, and because visual scanning is a core competence, two studies on subjective evaluation of aviation pilots – one conducted in a flight simulator and the other one in-flight – focussed on the practical application of eye tracking as a debriefing tool in UPRT. From a practitioner’s perspective, eye tracking appeared to be a useful method in terms of visualising instrument scanning techniques, supporting the instructor with objective debriefing material and fostering self-awareness in human processes. The discussion recommends adjusted UPRT instructor training and further improvements to eye tracking hardware and software.

Practitioner Summary: The article focuses on pilot evaluations of eye tracking as a debriefing tool in UPRT and the identification of critical elements in its use. Eye tracking is a promising debriefing tool for UPRT. The discussion points to desirable improvements of eye tracking hardware and software as well as adjustments to instructor training that are pertinent.     

Nanoscale Microstructural and Chemical Analysis of SiO2–Zn1−xAlxO Nanocomposites: Towards a Better Understanding of Si and Al Substitution in ZnO

In this study, we report on the microstructure of SiO₂‐coated Al‐doped ZnO nanoparticles densified by spark plasma sintering(SPS), using a multiscale approach. Our observations show that it is possible to successfully prepare dense pellets while keeping the nanostructure with well‐defined Si‐rich grain boundaries. Although a very limited partial solubility of Si in the ZnO matrix has been observed, Si is mostly concentrated at the grain boundaries. More surprisingly, we evidenced some areas with nanoscale inhomogeneity of the Al concentration, which can locally strongly exceed the average composition of the matrix. It could explain the apparent discrepancy observed in the literature between the simultaneous presence of ZnAl₂O₄ in Al‐doped ZnO, which should be the signature of the doping level exceeding the solubility limit, and the concentration of carriers that still depends on the nominal Al concentration in ZnO even in the presence of ZnAl₂O₄.     

Key Resources and Internationalization Modes of Creative Knowledge‐Intensive Business Services: The Case of Design Consultancies

In the ‘knowledge economy’, knowledge‐intensive business services (KIBS) are a key driver for innovation and competitiveness. The internationalization of these businesses raises challenges given their specificities such as knowledge intensity, the importance of customer interaction and intimacy in service delivery. This paper focuses on design consultancies as a specific type of creative KIBS for which these characteristics are emphasized. The objective of this research is to analyse the resources leveraged by the firms to compete internationally. It is based on 11 case studies of design consultancies located in five different countries (France, Italy, Portugal, Spain and the UK) that were selected for their capacity to perform at the international level for several years. The paper advances three internationalization modes depending on contingent variables and focusing on specific resources that enable international competitiveness: star‐based, process‐based and glocality‐based. In star‐based creative KIBS, the individual designer has developed a reputation that attracts customers internationally, operating as a brand. In process‐based creative KIBS, the reputation of a collective creative process attracts clients from other countries. In glocality‐based creative KIBS, the geographical proximity obtained by opening international offices helps to develop a close understanding of the client through frequent interactions, and also to know the client's market well and to better understand local codes and signs. These modes complement those presented in the existing internationalization literature which takes the peculiarities of creative KIBS into consideration.