Approximation de rayon de Larmor fini pour les plasmas magnétisés collisionnels

This Note concerns the derivation of the finite Larmor radius approximation, when collisions are taken into account. We concentrate on the Boltzmann relaxation operator whose study reduces to the gyroaverage computation of velocity convolutions. We emphasize that the resulting gyroaverage collision kernel is no local in space anymore and that the standard physical properties (i.e., mass balance, entropy inequality) hold true only globally in space and velocity. This is a first step in this direction and it will allow us to handle more realistic collisional mechanisms, like the Fokker–Planck or Fokker–Planck–Landau kernels (Bostan and Caldini-Queiros (submitted for publication) [3]).     

Hierarchical Characterization of Complex Networks

While the majority of approaches to the characterization of complex networks has relied on measurements considering only the immediate neighborhood of each network node, valuable information about the network topological properties can be obtained by considering further neighborhoods. The current work considers the concept of virtual hierarchies established around each node and the respectively defined hierarchical node degree and clustering coefficient (introduced in cond-mat/0408076), complemented by new hierarchical measurements, in order to obtain a powerful set of topological features of complex networks. The interpretation of such measurements is discussed, including an analytical study of the hierarchical node degree for random networks, and the potential of the suggested measurements for the characterization of complex networks is illustrated with respect to simulations of random, scale-free and regular network models as well as real data (airports, proteins and word associations). The enhanced characterization of the connectivity provided by the set of hierarchical measurements also allows the use of agglomerative clustering methods in order to obtain taxonomies of relationships between nodes in a network, a possibility which is also illustrated in the current article.     

Dielectric properties of deuterated ammonium Rochelle salt

The dielectric constant of deuterated ammonium Rochelle salt along the three crystallographic axes as well as the pyroelectric charge density developed on the crystal surface perpendicularly to the b-axis have been measured with a high temperature resolution. The para- to ferroelectric transition at T_c = ?159°C shows a thermal hysteresis of ΔT = 0.15°C. This and the discontinuities in the dielectric constant along all three axes show that the phase transition is of the first-order. No phase intermediate between the para- and the ferroelectric phases could be detected.     

Dynamics of a belt-drive system using a linear complementarity problem for the belt–pulley contact description

The aim of this study was to develop an efficient and realistic numerical model in order to predict the dynamic response of belt drives. The belt was modeled as a planar beam element based on an absolute nodal coordinate formulation. A viscoelastic material was adopted for the belt and the corresponding damping and stiffness matrices were determined. The belt–pulley contact was formulated as a linear complementarity problem together with a penalty method. This made it possible for us to accurately predict the contact forces, including the stick and slip zones between the belt and the pulley. The belt-drive model was verified by comparing it with the available analytical solutions. A good agreement was found. Finally, the applicability of the method was demonstrated by considering non-steady belt-drive operating conditions.     

Ray optics simulations of polarised microscopy textures in chiral nematic droplets

We present a simple method for simulating optical polarised micrographs of director fields in optically birefringent structures. Jones matrix method is applied for simulating polarised micrographs with focusing optics that can sufficiently account for different focusing distances and numerical apertures (NAs) in the polarised microscopy, which are the typical experimental variables. Accuracy of the method is assessed by comparing experimental and numerical micrographs of various structures in cholesteric liquid crystal droplets. The effects of varied focusing distance and scale are tested. The performance of the developed method is further demonstrated by varying viewing direction, position of focusing plane and the size of the observed structure, which prove to be elementary and easily changed parameters of this approach.     

Uninterrupted and accelerated vibrational fatigue testing with simultaneous monitoring of the natural frequency and damping

A mechanical system's modal parameters change when fatigue loading is applied to the system. In order to perform an accelerated vibration-based fatigue test these changes must be taken into account in order to maintain constant-stress loading. This paper presents an improved accelerated fatigue-testing methodology based on the dynamic response of the test specimen to the harmonic excitation in the near-resonant area with simultaneous monitoring of the modal parameters. The measurements of the phase angle and the stress amplitude in the fatigue zone are used for the real-time adjustment of the excitation signal according to the changes in the specimen's modal parameters. The presented methodology ensures a constant load level throughout the fatigue process until the final failure occurs. With the proposed testing methodology it is possible to obtain a S-N point of the Woehler curve relatively quickly and to simultaneously monitor the changes of the specimen's natural frequency and damping loss factor. The presented methodology with real-time control is verified on an aluminum Y-shaped specimen (10⁶ load cycles are achieved in 21 min) and is applicable to a specimen with arbitrary geometry. Besides the faster completion of the fatigue test the methodology can be adopted for the validation of the vibrational fatigue analysis.     

1,3-dipolar cycloaddition of diazomethane to azolopyridazines. The synthesis of isomeric 7-methyl-7h- and 8-methyl-8h-pyrazolo[4,3-d]azolopyridazmes

1,3-Dipolar cycloaddition of diazomethane to 6-chloro substituted azolopyridazines 1-4 produces isomeric pairs of 7-methyl-7H- 9-12 and 8-methyl-8H-pyrazolo[4,3-d]azolopyridazines 13-16 . The nucleophilic substitution of chlorine at position 6 affords the corresponding 6-amino 17, 20, 23, 26, 29,32,35 and 38 , 6-methoxy 18, 21, 24, 27, 30,33, 36 , and 39 and 6-hydrazino derivatives 19, 22, 25, 28, 31, 34, 37 , and 40 of these tricyclic systems.     

Dielectric properties of CsH2PO4 and CsD2PO4

Orthorhombic CsH₂PO₄ undergoes a ferroelectric transition at T_c = ?119.5°C, whereas the ferroelectric transition temperature in isomorphous CsD₂PO₄ is T_c = ?5.55°C. The transitions are of first order in both cases. The rather large isotope effect demonstrates the importance of the OHO bonds in the transition mechanism.     

Transformations of 2,2,6-trimethyl-1,3-dioxen-4-one with heterocyclic amines and other amino compounds

Heterocyclic amines were acetoacetylated with 2,2,6-trimethyl-1,3-dioxen-4-one and the obtained compounds reacted on the reactive methylene group to give C-substituted products. Nitrosation, followed by reduction afforded a pyrazine derivative. Azido- or chloroacetamide were also acetoacetylated, with heterocyclic amines, the corresponding enamines were prepared and reduction of the azido group of 15 afforded compounds 22 and/or amides of substituted 3-oxobutanoic acid 23 . An X-ray structural determination of compound 23a revealed that the orientation about the double bond is Z.     

Is the Polar Relative Monodromy of Finite Order？ An Example

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