Absorption and fluorescence spectroscopic study on complexation of Oxazine 1 Dye by calix[8]arenesulfonate

It has been established by combined absorption and fluorescence measurements that the cationic dye Oxazine 1 (OX) and the polyvalent anionic host calix[8]arenesulfonate (SCA8) form two complexes in simultaneous reactions: OX + SCA8 <--> OX.SCA8 (1), and OX.SCA8 + OX <--> OX(2).SCA8 (2). The equilibrium constants for the two reactions, as functions of the ionic strength (I), and the absorption and fluorescence spectra of the two complex species have been determined by a least-squares fitting method from the experimental data. The variations of the binding constants with the ionic strength could be described on the basis of Debye-Huckel theory. The equilibrium constants are large; their values extrapolated to I = 0 are K(1) = 5.5 x 10(6) M(-1) and K(2) = 4.4 x 10(5) M(-1). The fluorescence of OX undergoes a strong static quenching upon complexation. These results indicate that the complexes are held together by strong electrostatic forces. The addition of non-fluorescent tetramethylammonium chloride to OX-SCA8 mixtures results in a dramatic fluorescent enhancement, which demonstrates the potential applicability of this supramolecular system in fluorescence assays.     

Derepression of genes on the human inactive X chromosome: evidence for differences in locus-specific rates of derepression and rates of transfer of active and inactive genes after DNA-mediated transformation

Mouse-human hybrid cells that contained an inactive human X chromosome were treated with agents known to alter gene expression and to perturb DNA methylation. 5-Azacytidine greatly increased the rate of derepression of HPRT on the inactive X, while butyrate and dimethyl sulfoxide had smaller effects. Ethionine did not change the rate of derepression. Derepression of two other X-chromosomal loci, PGK and GPD, was also detected. The rate of derepression of PGK was 20-fold higher than the rate for HPRT. Derepression events at the two loci appeared to be independent. Hybrids expressing derepressed X-chromosomal genes had more variable levels of human enzyme activities when compared to control hybrids. HPRT+ clones did not appear after transfer of purified DNA from a cell hybrid containing an inactive human X into HPRT- recipients, but such clones did appear after transfer of DNA from derivative cells in which HPRT had been derepressed.     

The theory of transient photoconductive processes in II–VI compounds with three deep trapping levels

The transient photoconductive rise and decay processes were studied quantitatively in a typical II–VI compound by solving the rate equations on a digital computer. The calculations were based on a model with three deep trapping levels, as proposed by Rose and by Bube. A study was made of the effect of changing the concentration, position, and capture asymmetry fo these levels. We have also considered the way in which the defect centers change their role from trapping to recombination (or vice versa) as a result of free carrier concentration changes. Our work confirms previous explanations of the relation between sensitizing level properties and the steady-state superlinear behavior exhibited by II–VI photoconductors. On the other hand, a different approach appears to be necessary to account for transient phenomena. We do not believe that the position or asymmetry of the trapping levels is crucial in determining photoconductive sensitivity and response times. Instead, we find that these material properties can be predicted from a knowledge of the equilibrium and the steady-state charge concentrations. In addition, we show that the dynamic changes in the function of the deep levels from trapping to recombination, or vice versa, are the consequence—rather than the cause—of the specific way in which the photoconductive rise and decay processes occur.     

The professional option: An alternative to graduate work in psychology.

Discusses the organization of a 4-yr preprofessional curriculum for psychology majors, to offer undergraduate training and help students obtain full-time employment after graduation. Curriculum planning was based on 2 surveys of local business and social service organizations. Results indicate that a BA in psychology was of little help in obtaining work unless field experience supplemented classroom instruction. Specific skills and theoretical knowledge were considered less desirable in prospective employees than facility in personal relations. These findings were of central importance in making recommendations for restructuring the undergraduate curriculum. Suggestions for APA action in this area are outlined. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluating the reduced flight deck crew concept using cognitive work analysis and social network analysis: comparing normal and data-link outage scenarios

Cognition, Technology & Work - The aim of the present paper is to demonstrate how a subset of methods from Cognitive Work Analysis (CWA) in combination with Social Network Analysis (SNA) can be...     

From Facebook to the Neighbourhood: Infrastructuring of Hybrid Community Engagement

In recent years, social media have increased the resources that individuals and organizations are able to mobilize for the development of socially innovative practices. In this article, we engage with a naturally occurring development in a Trentinian neighbourhood to examine the cooperative interactions amongst members of a local community. The first author and local residents of the neighbourhood participated in online discussions, decision making, and physical activities that led to material changes in the area. The interventions are motivated by and based on the concept of Social Street that combines online interactions in a closed Facebook group with face-to-face meetings seeking to practically engage the collective in accomplishing certain immediate or ongoing needs. Over the course of two years, we studied this local instantiation of Social Street in Trento, Italy by way of an action-oriented (digital) ethnography. Through this work, we demonstrate how urban neighbourhoods might benefit from hybrid forms of community engagement that are enacted through a constant back and forth between online and face-to-face interactions. We further argue that the infrastructuring of local urban collectives should follow strategies that pay attention to the multiple issues in urban neighbourhoods and people’s attachments to them. Overall, the paper reflects upon the challenges and configurations of participation that this form of community-work entails.     

Global Approach of Tribomechanical Development of Hybrid Aluminium Matrix Syntactic Foams

Hybrid syntactic foams with AlSi12 aluminium matrix were produced by pressure infiltration. The volume ratio of iron to ceramic hollow sphere reinforcement (in the same size range) was varied, and hybrid syntactic foams were also produced with bimodal size ceramic reinforcement. Previously, a very detailed analysis of the mechanical properties of the composites was made with quasi-static compression tests, and their tribological properties were investigated by pin-on-disc method in dry and lubricated conditions. The present article establishes and clarifies the correlations between mechanical and tribological properties. The coefficient of friction, height loss of the specimens and specific wear showed good correlation with different mechanical parameters, e.g. density, structural stiffness and yield strength. The established trends and correlations between mechanical and tribological behaviour enable a better understanding of materials design and selection for further applications of mechanically loaded sliding machine parts.     

Ausbildung und Beruf

Ausbildung und Beruf

Ausbildung und Beruf     

Detection of ricin contamination in liquid egg by electrochemiluminescence immunosorbent assay

A monoclonal antibody-based electrochemical luminescence method was developed for detecting and quantifying ricin in liquid egg, with a limit of detection of 0.2 ng/mL. Because this highly toxic protein, present in the seeds of Ricinus communis (castor), has been used for intentional poisoning in the past, it is important to have sensitive and reliable analytical methodology to detect ricin in food matrices such as liquid egg. The detection of this quantity of pure or crude ricin spiked into commercial samples of liquid egg provides approximately 50000-fold greater sensitivity than required to detect a toxic dose of ricin (>1 mg) in a 100 g sample. PRACTICAL APPLICATION: Because ricin has been used for intentional poisoning, there is a need for analytical methodology to detect ricin in food matrices to assure a safe food supply. Using monoclonal antibodies to ricin developed in our laboratory, we explored an assay readout system known as electrochemiluminescence. This technique afforded sensitive and specific analysis of ricin intentionally added to liquid egg and could potentially be used to monitor egg-based vaccine production.