The role of constraints in expert memory

A great deal of research has been devoted to developing process models of expert memory. However, K. J. Vicente and J. H. Wang (1998) proposed (a) that process theories do not provide an adequate account of expert recall in domains in which memory recall is a contrived task and (b) that a product theory, the constraint attunement hypothesis (CAH), has received a significant amount of empirical support. We compared 1 process theory (the template theory; TT; F. Gobet & H. A. Simon, 1996c) with the CAH in chess. Chess players (N = 36) differing widely in skill levels were required to recall briefly presented chess positions that were randomized in various ways. Consistent with TT, but inconsistent with the CAH, there was a significant skill effect in a condition in which both the location and distribution of the pieces were randomized. These and other results suggest that process models such as TT can provide a viable account of expert memory in chess

Comment on "Geometric phases for mixed states during cyclic evolutions"

It is shown that a recently suggested concept of mixed state geometric phase in cyclic evolutions [2004 {\it J. Phys. A} {\bf 37} 3699] is gauge dependent.Comment: Comment to the paper L.-B. Fu and J.-L. Chen, J. Phys. A 37, 3699 (2004); small changes; journal reference adde

Improvising in music:A learning biography study to reveal skill acquisition

Wopereis, I. G. J. H., Van Merriënboer, J. J. G., & Kirschner, P. A. (2010). Improvising in music: A learning biography study to reveal skill acquisition. In K. Gomez, L. Lyons, & J. Radinsky (Eds.), Proceedings of the 9th International Conference of the Learning Sciences: Vol. 2 (pp. 419-420). Chicago, IL: International Society of the Learning Sciences.This poster addresses a learning biography study which aims at analyzing learning histories of both expert and non-expert improvisers (five recognized expert improvisers and five renowned musicians lacking improvisational expertise). It was hypothesized that by choosing both experts and non-experts it is possible to distinguish successful and unsuccessful learning strategies and instructional methods. Results of within-case analyses and cross-case analyses are presented. Further, consequences for two subsequent experimental studies will be discussed

Mutually Unbiased Bases and The Complementarity Polytope

A complete set of N+1 mutually unbiased bases (MUBs) forms a convex polytope in the N^2-1 dimensional space of NxN Hermitian matrices of unit trace. As a geometrical object such a polytope exists for all values of N, while it is unknown whether it can be made to lie within the body of density matrices unless N=p^k, where p is prime. We investigate the polytope in order to see if some values of N are geometrically singled out. One such feature is found: It is possible to select N^2 facets in such a way that their centers form a regular simplex if and only if there exists an affine plane of order N. Affine planes of order N are known to exist if N=p^k; perhaps they do not exist otherwise. However, the link to the existence of MUBs--if any--remains to be found.Comment: 18 pages, 3 figure

Effect of Dy substitution in the giant magnetocaloric properties of HoB2_{2}

Recently, a massive magnetocaloric effect near the liquefaction temperature of hydrogen has been reported in the ferromagnetic material HoB$_{2}$. Here we investigate the effects of Dy substitution in the magnetocaloric properties of Ho$_{1-x}$Dy$_{x}$B$_{2}$ alloys ($\textit{x}$ = 0, 0.3, 0.5, 0.7, 1.0). We find that the Curie temperature ($\textit{T}$$_{C}$) gradually increases upon Dy substitution, while the magnitude of the magnetic entropy change |$\Delta \textit{S}_{M}$| at $\textit{T}$ = $\textit{T}_{C}$ decreases from 0.35 to 0.15 J cm$^{-3}$ K$^{-1}$ for a field change of 5 T. Due to the presence of two magnetic transitions in these alloys, despite the change in the peak magnitude of |$\Delta \textit{S}_{M}$|, the refrigerant capacity ($\textit{RC}$) and refrigerant cooling power ($\textit{RCP}$) remains almost constant in all doping range, which as large as 5.5 J cm$^{-3}$ and 7.0 J cm$^{-3}$ for a field change of 5 T. These results imply that this series of alloys could be an exciting candidate for magnetic refrigeration in the temperature range between 10-50 K.Comment: 19 pages, 5 figures, 2 table

Organic fertilizers in organic greenhouse production systems – a review

From a sustainability point of view, there are strong arguments of nutrient recycling within the society, which means more use of organic nutrient sources within agriculture and horticulture. At the same time, there is an increasing consumer demand for certified organic products, and incentives from governments to increase the conversion of production areas to organic production. This also applies to greenhouse horticulture. Many different raw materials for organic fertilizers are used as of today, such as animal manures, slaughterhouse byproducts, vegetable byproducts, green manure, algae, composts, anaerobic digestates etc. In common for all these fertilizer types is that they are limited in availability, not always consistent with respect to nutrient content, and that they require microbial degradation in order to mineralize its content of nutrients, and are thereby more or less to be characterized as slow release fertilizers. Greenhouse horticulture is different from open field agriculture in several ways with respect to nutrient supply. Firstly, the use of fallow crops and crop rotation is not practical due to the high investment costs bound in the greenhouse structure. Secondly, growth per unit area is significantly higher than in outdoor production, with subsequently higher nutrient demand, often concentrated to a relatively short period of time. On the other hand, climatic factors such as soil temperature and moisture can be controlled which is beneficial for the control of nutrient release. Traditionally, animal by-products such as manure and slaughterhouse wastes have been widely used as organic fertilizers. However, limited availability and ethical concerns is currently driving forces in the search for alternative nutrient sources. The use of solid and liquid anaerobic digestates as fertilizers is a promising practice for greenhouse horticulture. Energy is a “by product” from the production and the nutrient content of the digestates can be modified by feeding the anaerobic reactor with different stock. Furthermore, it is suggested that techniques for fine-tuning the nutrient supply in organic greenhouse horticulture is further developed and adopted, such as the use of microbial biofertilizers and foliar sprays

Comment on "Theoretical design of molecular nanomagnets for magnetic refrigeration" [Appl. Phys. Lett. 103, 202410 (2013)]

Garlatti et al. [Appl. Phys. Lett. 103, 202410 (2013)] report theoretical simulations aimed at showing that the best molecular nanomagnets for magnetic refrigeration between T = 10 K and sub-Kelvin region are those made of strongly ferromagnetically-coupled magnetic ions. This Comment revises such conclusion based on results that, apparently, contrast with the established belief in this research field.Comment: 3 pages, 2 figure

An approach to optimization of low-power Stirling cryocoolers

A method for optimizing the design (shape of the displacer) of low power Stirling cryocoolers relative to the power required to operate the systems is described. A variational calculation which includes static conduction, shuttle and radiation losses, as well as regenerator inefficiency, was completed for coolers operating in the 300 K to 10 K range. While the calculations apply to tapered displacer machines, comparison of the results with stepped displacer cryocoolers indicates reasonable agreement

Some shortcomings of long-term working memory

Within the framework of their long-term working memory theory, Ericsson and Kintsch (1995) propose that experts rapidly store information in long-term memory through two mechanisms: elaboration of long-term memory patterns and schemas and use of retrieval structures. They use chess players’ memory as one of their most compelling sources of empirical evidence. In this paper, I show that evidence from chess memory, far from supporting their theory, limits its generality. Evidence from other domains reviewed by Ericsson and Kintsch, such as medical expertise, is not as strong as claimed, and sometimes contradicts the theory outright. I argue that Ericsson and Kintsch’s concept of retrieval structure conflates three different types of memory structures that possess quite different properties. One of these types of structures—generic, general-purpose retrieval structures—has a narrower use than proposed by Ericsson and Kintsch: it applies only in domains where there is a conscious, deliberate intent by individuals to improve their memory. Other mechanisms, including specific retrieval structures, exist that permit a rapid encoding into long-term memory under other circumstances