34,162 research outputs found

    Population Control in Japan: An Economic Theory and Its Application

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    Information technology (IT) have for several decades been used in university education. An increasing number of classrooms today are built around a concept which uses IT in collaboration with the room itself. However, little is known about the experience of university teachers when working in such classrooms. This study examines the views and opinions of teachers at a Swedish university regarding using and interacting with these classrooms. Furthermore, we identify possible underlying factors that influence these views. Using data from qualitative interviews we apply Technology acceptance model (TAM) and Activity theory (AT) used in both education and human computer interaction to identify how different factors interact to form these opinions. Our study finds that teachers experience a lack of proper training in the use of classrooms as a concept and tend to stay in established norms of how education is to be conducted. These results leads to questions whether education in the use of these classrooms is adequate for teachers or if education needs to focus more on outcomes of the concept and changing established norms rather than to focus on the use of technology. Our study also shows that teachers do not view the classrooms as a whole where artefacts enable and form each other. Rather they view the physical room, the technology and themselves as separate entities that operate separately from each other

    Optimal Galaxy Distance Estimators

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    The statistical properties of galaxy distance estimators are studied and a rigorous framework is developed for identifying and removing the effects of Malmquist bias due to obsevational selection. The prescription of Schechter (1980) for defining unbiased distance estimators is extended to more general -- and more realistic -- cases. The derivation of `optimal' unbiased distance estimators of minimum dispersion, by utilising information from additional -- suitably correlated -- observables, is discussed and the results applied to a calibrating sample from the Fornax cluster, as used in the Mathewson spiral galaxy redshift survey. The optimal distance estimator derived from I-band magnitude, diameter and 21cm line width has an intrinsic scatter which is 25 \% smaller than that of the Tully-Fisher relation quoted for this calibrating sample. (Figures are available on request).Comment: Plain Latex, 19 pages, Sussex-AST-93/9-

    Structural and mutagenic analysis of the RM controller protein C.Esp1396I

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    Bacterial restriction-modification (RM) systems are comprised of two complementary enzymatic activities that prevent the establishment of foreign DNA in a bacterial cell: DNA methylation and DNA restriction. These two activities are tightly regulated to prevent over-methylation or auto-restriction. Many Type II RM systems employ a controller (C) protein as a transcriptional regulator for the endonuclease gene (and in some cases, the methyltransferase gene also). All high-resolution structures of C-protein/DNA-protein complexes solved to date relate to C.Esp1396I, from which the interactions of specific amino acid residues with DNA bases and/or the phosphate backbone could be observed. Here we present both structural and DNA binding data for a series of mutations to the key DNA binding residues of C.Esp1396I. Our results indicate that mutations to the backbone binding residues (Y37, S52) had a lesser affect on DNA binding affinity than mutations to those residues that bind directly to the bases (T36, R46), and the contributions of each side chain to the binding energies are compared. High-resolution X-ray crystal structures of the mutant and native proteins showed that the fold of the proteins was unaffected by the mutations, but also revealed variation in the flexible loop conformations associated with DNA sequence recognition. Since the tyrosine residue Y37 contributes to DNA bending in the native complex, we have solved the structure of the Y37F mutant protein/DNA complex by X-ray crystallography to allow us to directly compare the structure of the DNA in the mutant and native complexes

    Robust Iterative Solution of a Class of Time-Dependent Optimal Control Problems

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    The fast iterative solution of optimal control problems, and in particular PDE-constrained optimization problems, has become an active area of research in applied mathematics and numerical analysis. In this paper, we consider the solution of a class of time-dependent PDE-constrained optimization problems, specifically the distributed control of the heat equation. We develop a strategy to approximate the (1,1)-block and Schur complement of the saddle point system that results from solving this problem, and therefore derive a block diagonal preconditioner to be used within the MINRES algorithm. We present numerical results to demonstrate that this approach yields a robust solver with respect to step-size and regularization parameter

    Distributions associated with general runs and patterns in hidden Markov models

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    This paper gives a method for computing distributions associated with patterns in the state sequence of a hidden Markov model, conditional on observing all or part of the observation sequence. Probabilities are computed for very general classes of patterns (competing patterns and generalized later patterns), and thus, the theory includes as special cases results for a large class of problems that have wide application. The unobserved state sequence is assumed to be Markovian with a general order of dependence. An auxiliary Markov chain is associated with the state sequence and is used to simplify the computations. Two examples are given to illustrate the use of the methodology. Whereas the first application is more to illustrate the basic steps in applying the theory, the second is a more detailed application to DNA sequences, and shows that the methods can be adapted to include restrictions related to biological knowledge.Comment: Published in at http://dx.doi.org/10.1214/07-AOAS125 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

    The Helper-Therapy Principle Applied to Weight Management Specialists

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    One hundred twenty applicants to a weight management specialist training program were studied over a 33-month period. Following a nine-month training period, Specialists (N = 29; those leading at least one posttraining weight management group) were compared to Contact Controls (N = 31; persons participating in the weight management program, but not in the helper role) and No Contact Controls (N = 60; those not accepted into the training program and whose only contact with the program was for data collection purposes) in a test of the helper-therapy principle. The major question was, What are the long-term physical, psychological, and behavioral effects on overweight and formerly overweight individuals involved in helping other persons manage their weight? Data gathered at 12 and 24 months posttraining revealed few differences between the total group of specialists and persons in the two control groups. However, when the data were analyzed by the amount of commitment to the specialist role, it was found that the Higher Involved Specialists (N = 16; those who led two or more weight management groups in the year posttraining) were significantly more likely to lose additional weight (or maintain earlier weight losses), to be more consistent in their adherence to the eating and activity levels advocated by the program, to feel better about themselves and their bodies, and to maintain their levels of general well-being than control subjects or the Lesser Involved Specialists. These latter individuals (N = 13) were significantly the worse for having gone through specialist training, but not fully carrying out the specialist role

    Impredicative Encodings of (Higher) Inductive Types

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    Postulating an impredicative universe in dependent type theory allows System F style encodings of finitary inductive types, but these fail to satisfy the relevant {\eta}-equalities and consequently do not admit dependent eliminators. To recover {\eta} and dependent elimination, we present a method to construct refinements of these impredicative encodings, using ideas from homotopy type theory. We then extend our method to construct impredicative encodings of some higher inductive types, such as 1-truncation and the unit circle S1
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