Electrical properties of CdTe near the melting point

A new experimental setup for the investigation of electrical conductivity (σ) in liquid and solid CdTe was built for a better understanding of the properties near the melting point (MP). The temperature dependence of σ was studied, within the interval 1,050-1,130°C, at defined Cd-partial pressures 1.3-1.6 atm, with special attention to the liquid-solid phase transition. We found that the degree of supercooling decreases with increasing Cd overpressure and reaches the lowest value at 1.6 atm without change of the melting temperature during heating

Laser-induced transient currents in CdZnTe quasi-hemispherical radiation detector

Laser-induced transient currents were measured after applying pulsed or direct-current bias to a CdZnTe quasi-hemispherical radiation detector with gold contacts. The temporal evolution of current transients was analyzed to evaluate the dynamics of the space charge formation and its spatial distribution. The observed effects were explained by a model involving hole injection from positively biased contacts. Experimental results were complemented by numerical simulations, which supported the model. This paper discusses how the detected phenomena affect the detector performance and proposes an improved detector design

High temperature mobility of CdTe

The Hall mobility of electrons μH is measured in CdTe in the temperature interval 450-1050°C and defined Cd overpressure in near-intrinsic conditions. The strong decrease of μH above 600°C is reported. The effect is explained within a model of multivalley conduction where both electrons in �1c minimum and in L1c minima participate. The theoretical description is based on the solution of the Boltzmann transport equation within the relaxation time approximation including the polar and acoustic phonon intravalley and intervalley scatterings. The �1c to L1c separation �E=0.29 - 10-4T (eV) for the effective mass in the L valley mL=0.35m0 is found to best fit the experimental data. Such �E is about four times smaller than it is predicted by first-principle calculations. © 2001 American Institute of Physics

Theory of periodic swarming of bacteria: application to Proteus mirabilis

The periodic swarming of bacteria is one of the simplest examples for pattern formation produced by the self-organized collective behavior of a large number of organisms. In the spectacular colonies of Proteus mirabilis (the most common species exhibiting this type of growth) a series of concentric rings are developed as the bacteria multiply and swarm following a scenario periodically repeating itself. We have developed a theoretical description for this process in order to get a deeper insight into some of the typical processes governing the phenomena in systems of many interacting living units. All of our theoretical results are in excellent quantitative agreement with the complete set of available observations.Comment: 11 pages, 8 figure

On tacit knowledge for philosophy of education

This article offers a detailed reading Gascoigne and Thornton’s book Tacit Knowledge (2013), which aims to account for the tacitness of tacit knowledge (TK) while preserving its status as knowledge proper. I take issue with their characterization and rejection of the existential-phenomenological Background—which they presuppose even as they dismiss—and their claim that TK can be articulated “from within”—which betrays a residual Cartesianism, the result of their elision of conceptuality and propositionality. Knowledgeable acts instantiate capacities which we might know we have and of which we can be aware, but which are not propositionally structured at their “core”. Nevertheless, propositionality is necessary to what Robert Brandom calls, in Making It Explicit (1994) and Articulating Reasons (2000), “explicitation”, which notion also presupposes a tacit dimension, which is, simply, the embodied person (the knower), without which no conception of knowledge can get any purchase. On my view, there is no knowledgeable act that can be understood as such separately from the notion of skilled corporeal performance. The account I offer cannot make sense of so-called “knowledge-based” education, as opposed to systems and styles which supposedly privilege “contentless” skills over and above “knowledge”, because on the phenomenological and inferentialist lines I endorse, neither the concepts “knowledge” nor “skill” has any purchase or meaning without the other

Education, knowledge, and symbolic form

This article aims to introduce Ernst Cassirer, and his philosophy of symbolic form, to education studies, and, in doing so, to challenge the widespread but deeply flawed views of knowledge and so-called knowledge-based education that have shaped recent education policy in England. After sketching the current educational landscape, and then some of the main lines of flight in Cassirer’s work, time is given to a comparison with Heidegger—a more familiar figure by far in Anglophone philosophy than Cassirer, and who contributed to the displacement of Cassirer—in order to illustrate more clearly Cassirer’s original contribution, in particular to the relationship between knowledge and time. Cassirer’s view of knowledge stands in marked and critical contrast to that which has shaped recent educational reform in England, as he sees knowledge as a productive and expressive matter, and repudiates what I call the ‘building-blocks’ picture of knowledge and the hierarchisation of subject areas

Influence of quorum sensing signal molecules on biofilm formation in Proteus mirabilis O18

The influence of basis of quorum sensing molecules on Proteus strains is much less known as compared to Pseudomonas or Escherichia. We have previously shown that a series of acylated homoserine lactones (acyl-HSL) does not influence the ureolytic, proteolytic, or hemolytic abilities, and that the swarming motility of Proteus mirabilis rods is strain specific. The aim of the presented study was to find out if the presence of a series of acyl-HSL influences biofilm formation of P. mirabilis laboratory strain belonging to O18 serogroup. This serogroup is characterized by the presence of a unique non-carbohydrate component, namely phosphocholine. Escherichia coli and P. mirabilis O18 strains used in this work contains cloned plasmids encoding fluorescent protein genes with constitutive gene expression. In mixed biofilms in stationary and continuous flow conditions, P. mirabilis O18 overgrow whole culture. P. mirabilis O18 strain has genetically proved a presence of AI–2 quorum sensing system. Differences in biofilm structure were observed depending on the biofilm type and culture methods. From tested acylated homoserine lactones (BHL, HHL, OHL, DHL, dDHL, tDHL), a significant influence had BHL on thickness, structure, and the amount of exopolysaccharides produced by biofilms formed by P. mirabilis O18 pDsRed2