Combined geophysical and geotechnical approach to ground investigations and hazard zonation of a quick clay area,mid Norway

Mapping of quick clay is important for hazard zonation, planning and protection purposes. The present study focuses on an area prone to quick clay landslides in mid Norway, which is investigated through a combination of geophysical and geotechnical methods. The following classes are suggested for a first-order interpretation of resistivity profiles in areas with few or no previous investigations: Unleached clay deposits: 1–10 Ωm; Leached clay deposits, possibly quick: 10–100 Ωm; Dry crust clay deposits and coarse sediments: >100 Ωm. In the study area, 14–80 Ωm was found as the main resistivity interval for quick clay. The resistivity values from the present study are compared to previously published values. Classification of material from resistivity values is influenced by local conditions, and there is an overlap between the classes. Resistivity profiles can give valuable information for hazard zonation and may assist in maximising subsequent intrusive investigations.     

Academic achievement and self-concept: An analysis of causal predominance in a developmental perspective.

Causal relationships among academic achievement, self-concept of ability, and general self-esteem were examined for two cohorts of Norwegian school children. Measures of the three variables were collected when the students in the two cohorts were attending third and sixth grade and 18 months later. Four hypotheses were tested by a methodology developed in the frame of structural covariance models with latent variables by means of the {lisrel vii} program. Support for the assumptions of discriminability and factorial invariance of the concepts across time was obtained independently from estimating structural parameters. The results supported different causal relationships in the two cohorts, suggesting a recursive model at Grades 3 and 4 and a reciprocal model at Grades 6 and 7. The findings strengthened a further need for longitudinal studies examining relationships between academic achievement and self-concept in a developmental perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Legendre spectral element method for the Stefan problem

In this paper we present a Legendre spectral element method for solution of multi-dimensional unsteady change-of-phase Stefan problems. The spectral element method is a high-order (p-type) finite element technique, in which the computational domain is broken up into general (curved) quadrilateral macroelements, and the solution, data and geometry are expanded within each element in terms of tensor-product Lagrangian interpolants. The discrete equations are generated by a Galerkin formulation followed by Gauss–Lobatto Legendre quadrature, for which it is shown that exponential convergence to smooth solutions is obtained as the polynomial order of fixed elements is increased. The spectral element equations are inverted by conjugate gradient iteration, in which the matrix-vector products are calculated efficiently using tensor-product sum-factorization. To solve the Stefan problem numerically, the heat equations in the liquid and solid phases are transformed to fixed domains applying an interface-local time-dependent immobilization transformation technique. The modified heat equations are discretized using finite differences in time, resulting at each time step in a Helmholtz equation in space that is solved using Legendre spectral element elliptic discretizations. The new interface position is then computed using a variationally consistent flux treatment along the phase boundary, and the solution is projected upon the corresponding updated mesh. The rapid convergence rate and stability of the method are discussed, and numerical results are presented for a one-dimensional Stefan problem using both a semi-implicit and a fully implicit time-stepping scheme. Finally, a two-dimensional Stefan problem with a complex phase boundary is solved using the semi-implicit scheme.     

Laser Synthesis of Low-Agglomerated Submicrometer Silicon Nitride Powders from Chlorinated Silanes

The laser chemical vapor precipitation of Si₃N₄ powder from mixtures of SiH₂Cl₂ and NH₃ has been studied. The reactant gases were mixed at different heights with respect to the laser beam, thus preventing low-temperature reactions and agglomeration of the produced particles. The morphology and the size of the particles formed are dependent on the injection height of NH₃ into the silicon reactant gas stream. Particle diameters are typically between 15 and 110 nm.     

Production of antimicrobial metabolites by strains of Lactobacillus or Lactococcus co-cultured with Bacillus cereus in milk

During co-culture of Lactobacillus (five strains) or Lactococcus (two strains) with Bacillus cereus, organic acids and other potentially antimicrobial metabolites are produced. Lactic acid was produced at very different rates by the lactic acid bacteria (LAB) and the final concentrations varied much, however, the crucial point of rapid pH reduction during the initial hours of fermentation coincides with lactic acid production. Moderate amounts of acetic acid were produced during fermentation and the final concentrations were much smaller compared to lactic acid. According to these experiments, production of diacetyl, carbon dioxide and ethanol was considered too small to contribute to inhibition of B. cereus. The inhibitory substance produced by the LAB strains was not sensitive to proteinase K, trypsin or pepsin, so it was not likely that the LAB strains produced bacteriocins antagonistic against B. cereus. The strains that produced lactic acid fastest inhibited B. cereus best. Increased concentrations of lactic and acetic acid and carbon dioxide were also observed after co-culture with B. cereus compared to growth of the LAB strains alone, which indicates that B. cereus stimulates the biosynthetic capacities of the LAB strains.     

Is formative measurement really measurement? Reply to Bollen (2007) and Bagozzi (2007).

R. D. Howell, E. Breivik, and J. B. Wilcox (2007; see record 2007-07830-006) examined the use of formative measurement models in theory testing in the social sciences. K. A. Bollen (2007; see record 2007-07830-007) and R. P. Bagozzi (2007; see record 2007-07830-008) have provided comments on this work. In this article, the authors reply to the commentators and suggest that the conclusions reached in the original article and the basis for those conclusions remain sound. They address the issue of misspecification raised by Bollen (2007) and the alternative to their realist philosophy of measurement offered by Bagozzi (2007). They conclude that misspecification as construed by Bollen (2007) will typically be undetectable in practice and cannot be distinguished from interpretational confounding. This can result in substantively different constructs retaining the same name from study to study, hindering the accumulation of knowledge. They further conclude that traditional reflective measurement is a better option for researchers in theory testing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spectral element multigrid. I. Formulation and numerical results

A variational spectral element multigrid algorithm is proposed, and results are presented for a one-dimensional Poisson equation on a finite interval. The key features of the proposed algorithm are as follows: the nested spaces and associated hierarchical bases are intra-element, resulting in simple data structures and rapid tensor-product sum-factorization evaluations; smoothing is effected by readily constructed and efficiently inverted (diagonal) Jacobi preconditioners; the technique is readily parallelized within the context of a medium-grained paradigm; and the (work-deflated) multigrid convergence rate is bounded from above well below unity, and is only a weak function of the number of spectral elementsK, the (large) order of the polynomial approximation,N, and the number of multigrid levels,J. Preliminary tests indicate that these convergence properties persist in higher space dimensions.     

Change profiles of a reused class framework vs. two of its applications

Software reuse is expected to improve software productivity and quality. Although many empirical studies have investigated the benefits and challenges of software reuse from development viewpoints, few studies have explored reuse from the perspective of maintenance. This paper reports on a case study that compares software changes during the maintenance and evolution phases of a reused Java class framework with two applications that are reusing the framework. The results reveal that: (1) The reused framework is more stable, in terms of change density, than the two applications that are reusing it. (2) The reused framework has profiles for change types that are similar to those of the applications, where perfective changes dominate. (3) The maintenance and evolution lifecycle of both the reused framework and its applications is the same: initial development, followed by a stage with extending capabilities and functionality to meet user needs, then a stage in which only minor defect repairs are made, and finally, phase-out. However, the reused framework goes faster from the stage of extending capabilities to the stage in which only minor defect repairs are made than its applications. (4) We have validated that several factors, such as are functionalities, development practice, complexity, size, and age, have affected the change densities and change profiles of the framework and applications. Thus, all these factors must be considered to predict change profiles in the maintenance and evolution phase of software.     

Analytical sensitivities for statistically extrapolated extreme load constraints in structural optimization

For some applications in structural optimization, it is required to have constraints on the extreme loads that represent long term loading conditions. This usually involves a statistical extrapolation procedure that fits maxima from simulated load time series to short term extreme value distributions and then extrapolates to an n-year return value. Often such situations are highly simplified because of the apparent complexity involved in evaluating the sensitivity of such constraints. However, such simplification is not necessary. In this study, we present a method to evaluate the sensitivities of such extrapolated extreme load constraints in a semi-analytical way. The method uses the implicit function theorem to obtain local derivatives at the points defined by the solution of the maximum likelihood estimate that is used to calculate the parameters of the short term extreme value distributions. Comparing with high accuracy finite difference estimates, the method is shown to give reasonably accurate values. We also demonstrate how the method can be used to estimate the uncertainty of the estimated n-year return value caused by uncertainty in both the maximum likelihood estimate and inherent uncertainties in the data. The method then is applied to a simple optimization example and shown to perform very well compared with using finite difference estimates for the sensitivities. Finally, we note that the method is in principle fairly general and could be applied to similar problems that do not specifically involve statistical extrapolation.