Near-Curie magnetic anomaly at the Ni/C interface observed by electron holography

We analyze with electron holography carried out in a transmission electron microscope the near-Curie behavior of magnetism at the edge of a Nickel thin film coated with Carbon. In-situ experiments with finely controlled variations of the sample temperature reveal an anomaly in the ferromagnetic to paramagnetic phase transition when the film temperature is a few degrees above the nominal Curie point. We interpret the anomaly as a strain-induced spin reorientation transition triggered by the differential thermal expansion of Carbon and Nickel. We present a model that quantitatively reproduces the main features of the observed signal. The model is developed in terms of an anisotropic, temperature dependent exchange coupling between the Nickel moments at the Carbon interface that favors their vertical alignment at low temperatures.     

Lower bounds for the norms of decomposable symmetrized tensors

Lower bounds are given for the difference of two decomposable symmetrized tensors. The first bound uses a norm which makes the component vectors in a decomposable symmetrized tensor part of an orthonormal basis. The second bound holds only for decomposable elements of symmetry classes whose associated characters are linear.     

Discrete velocity models with small data

Summary It is shown that all discrete velocity models conserving mass, momentum and energy and without self-interactions have global, uniformly bounded solutions for small enough initial data with compact support. This is interesting because of a recent example with small data inL ¹ L whose solution is not bounded, and shows the unboundedness is due to mass being fed in from infinity.

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Sommario Si dimostra che tutti i modelli con velocità discretizzate che conservano la massa, la quantità di moto e l'energia e senza autointerazioni hanno soluzioni globali, uniformemente limitate per dati iniziali a supporto compatto e abbastanza piccoli. Questo è interessante a causa di un esempio recente con dati piccoli inL ¹ L la cui soluzione non è limitata e mostra che l'illimitatezza è dovuta ad un flusso di massa dall'infinito.

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Research supported by the Natural Science and Engineering Research Council Canada under Grant No. A8560.     

Interactive classification using data envelopment analysis

In this paper, we illustrate how data envelopment analysis (DEA) can be used to aid interactive classification. We assume that the scoring function for the classification problem is known. We use DEA to identify difficult to classify cases from a database and present them to the decision-maker one at a time. The decision-maker assigns a class to the presented case and based on the decision-maker class assignment, a tradeoff cutting plane is drawn using the scoring function and decision-maker’s input. The procedure continues for finite number of iterations and terminates with the final discriminant function. We also show how a hybrid DEA and mathematical programming approach can be used when user interaction is not desired. For non-interactive case, we compare a hybrid DEA and mathematical programming based approach with several statistical and machine learning approaches, and show that the hybrid approach provides competitive performance when compared to the other machine learning approaches.     

Uragogin and blepharodin, unprecedented hetero-Diels-Alder adducts from Celastraceae species

Uragogin and blepharodin were isolated from Crossopetalum uragoga and Maytenus magellanica, respectively. They represent the first examples of a triterpene-neolignan ester and a heptacyclic arylpropanoid-nor-triterpenephenol, hetero-Diels-Alder adducts built with dioxane bridges. Their proposed biosynthetic route is discussed.     

A Convenient Synthesis of N-Methoxy-N-Methylamides from Carboxylic Acids

Carboxylic acids can be converted to their corresponding N-methoxy-N-methylamides in high yields using 2-chloro-1-methylpyridinium iodide as the coupling agent. The reaction proceeds without racemization when chiral carboxylic acids are used as the starting material.     

Construction of orthonormal bases in higher symmetry classes of tensors

We present a method for constructing an orthonormal basis for a symmetry class of tensors from an orthonormal basis of the underlying vector space. The basis so obtained is not composed of decomposable symmetrized tensors. Indeed, we show that, for symmetry classes of tensors whose associated character has degree higher than one, it is impossible to construct an orthogonal basis of decomposable symmetrized tensors from any basis of the underlying vector space. We end with an open problem on the possibility of a symmetry class having an orthonormal basis of decomposable symmetrized tensors.     

Assessing Elementary Understanding of Multiplication Concepts

This article summarizes the basic concepts of multiplication and provides some evidence that the traditional third‐grade curriculum and instruction emphasizing memorization of multiplication facts produces much less understanding of the basic concepts of multiplication than a standards‐based curriculum and instruction emphasizing construction of number sense and meaning for operations. This study also describes a collection of assessment tasks that provided meaningful evidence of children's understandings of basic multiplication concepts, including understandings of the relationships between multiplication and addition.     

Energetics and structural stability of Cs3C60

Using the ab initio pseudopotential total-energy method and the density-functional theory, we study the energetics of face-centered-cubic Cs₃C₆₀ which is a material of great interest as a possible high transition-temperature superconductor. At the optimized lattice constant the volume per C₆₀ is found to be smaller than the the most-stable hexagon-coordination A15 phase, while the total energy of the fcc phase is about 0.9 eV higher than the A15 phase. These results indicate that a low-temperature and high-pressure synthesis method might be a possible way to produce the fcc Cs₃C₆₀ phase. In addition, it is also found that the A15 Cs₃C₆₀ should show a phase transformation from a hexagon-coordination phase to a pentagon-coordination phase under hydrostatic pressure.