A special anisotropic model of the universe

Applying laws of the kind previously published by the author for isotropic models, we obtain an anisotropic cosmological model with a Bianchi I metric. The interesting features of this model are its simplicity and the easy way we may define overall Hubble and deceleration parameters.     

A Model of the Evolution of a Two-dimensional Defective Structure

A model of the anelastic evolution law of a two-dimensional defective solid crystal body is proposed. Assuming that the material body is made of triclinic crystals and that the evolution process does not alter the basic material symmetry group, we postulate that the evolution is driven by the present state of the density of the distribution of defects. We show that a linear relation between the inhomogeneity velocity gradient and the torsion tensor is rich enough to model such phenomena as relaxation of defects and dislocation pile-up.     

A composite grid approach for the Euler equations

A zonal grid methodology has been developed for the calculation of compressible fluid flows. The domain subdivision is based on patched grid systems composed of zones or blocks within which a distinct curvilinear grid is generated. The flow simulation is then carried out with a modified scheme based on the Euler finite volume solver of Ni. This scheme uses a distribution procedure that provides an easy and accurate way for the transfer of information from one block to another. This method results in a naturally conservative computation at the interfaces. It is analysed and developed for the treatment of embedded grids with a grid point common to more than four blocks.     

Controlled surface temperature laser heat treating

The analysis and experimental procedure of a controlled temperature laser heat treating process are reported.Key features are the ease of predicting working results and the capability of getting on-line process diagnostics for use in a highly automated industrial environment.     

Adaptive-optics correction of a stellar interferometer with a single pyramid wave-front sensor

We investigate the pyramid wave-front sensor's capability to reconstruct in a closed loop, with only one sensor, the wave fronts on both apertures of a stellar interferometer, including the differential piston: The method consists of placing the principal element of this sensor, namely, a refractive-square-based pyramid, in a combined focal plane of the interferometer instead of using two sensors, one for each individual telescope. We show that the sensor signals allow one to measure the wave-front aberrations on both apertures and the differential piston at the same time. The performance of an adaptive-optics loop is computed numerically for the Large Binocular Telescope in terms of differential-piston rejection under several conditions. The results show that atmospheric correction including differential-piston compensation is possible as long as the corrected Strehl ratio at the wave-front sensing wavelength is greater than 20%.     

MRI fast tree log scanning with helical undersampled projection acquisitions

Magnetic Resonance Imaging opens an alternative way to analyze wood structures using a non-destructive technology. It provides high resolution, compound-based contrast manipulation and increased data acquisition flexibility. The technique is particularly useful for tree logs, since they present several characteristics that can be used to reduce the long scan time. This study proposes a method that takes advantage of the log cylindrical symmetry, acquiring transverse 1-D projections with a helical and undersampled pattern. Linear interpolation is used to estimate the skipped data and slice images are reconstructed by filtered backprojection. The sequence is improved using selective multi-pass scanning, without major variations of the scan time. Computer simulations and experimental results show that the proposed technique can increase the scan speed by a factor of 6, while maintaining the ability to identify typical tree log characteristics.     

Antisymmetric exchange in two tricopper(II) complexes containing a [Cu3(micro3-OMe)]5+ core

Reaction of CuX2(X-=Cl- or Br-) with 2 molar equivalents of 3[5]-(2,4,6-trimethylphenyl)pyrazole (HpzMes) in MeOH in the presence of NaOH yields [Cu3X(HpzMes)2(micro-pzMes)3(micro3-OMe)]X (X-=Cl- or Br-). Crystal structures of these compounds show almost identical triangles of Cu(II) ions, centred by a triply bridging methoxide ligand and with three edge-bridging pyrazolide groups. The mesityl substituents on the bridging pyrazolide ligands are arranged in HT, HH, TT fashion. chi(M)T for both compounds decreases steadily with decreasing temperature, reaching 0.40 cm(3) mol(-1) K at 70 K before decreasing further below 40 K. This low temperature behaviour could not be interpreted using conventional superexchange Hamiltonians, but was reproduced by an alternative model that incorporated an additional antisymmetric exchange term. This interpretation was confirmed by the Q-band EPR spectra of the two compounds. NMR experiments show that the structures of these compounds are not retained in solution, in contrast to other closely related tricopper compounds. These are the first examples of triangular Cu(II) compounds bearing a [Cu3micro3-OR)]5+(R is not equal to H) core motif, and the first triangular compounds showing antisymmetric exchange to have been analysed by both susceptibility and EPR measurements.     

A numerical barotropic model of marine currents in the archipelago of La Maddalena

Summary The marine currents inside the archipelago of La Maddalena between Sardinia and Corsica islands have been studied. The results of an implicit numerical barotropic unidimensional model are discussed and compared with experimental data.

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Riassunto Sono state studiate le correnti, marine nell'arcipelago della Maddalena, tra la Sardegna e la Corsica. I risultati di un modello numerico implicito unidimensionale sono discussi e confrontati con i dati sperimentali.

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Резюме Исследуются морские течения внутри архипелага Ла Мадалена между острвами Сардинией и Корсикой. Обсуждаются результаты численной баротропной одномерной модели и проводится сравнение с экспериментальными результатами.

     

Reactions of copper(II) salts with 3[5]-tert-butylpyrazole: double-cubane complexes with bound exogenous anions, and a novel pyrazole coordination mode

Reaction of CuX(2) (X(-)=Cl(-), Br(-), NO(3) (-)), NaOH, and 3[5]-tert-butylpyrazole (Hpz(tBu)) in a 1:1:2 molar ratio in MeOH at 293 K for three days affords [[Cu(3)(Hpz(tBu))(6)(mu(3)-X)(mu(3)-OH)(3)](2)Cu]X(6) (X(-)=Cl(-), 1; X(-)=Br(-), 2; X(-)=NO(3)(-), 3) in moderate yields. These compounds contain a centrosymmetric, vertex-sharing double-cubane [[Cu(3)(Hpz(tBu))(6)(mu(3)-X)(mu(3)-OH)(3)](2)Cu](6+) core, surrounded by a belt of six hydrogen-bonded X(-) ions. For 1 and 2, the ring of guest anions has near C(3) symmetry, that is slightly distorted owing to the axis of Jahn-Teller elongation at the central Cu ion. For 3 only, the NO(3)(-) guest ions are crystallographically disordered, reflecting their poor complimentarity with complex host. A similar reaction employing CuF(2) yields [[Cu(3)(Hpz(tBu))(4)(mu-pz(tBu))(2)(mu-F)(2)(mu(3)-F)](2)]F(2) (4), whose structure contains a cyclic hexacopper core with approximate C(2v) symmetry. Finally, an analogous reaction using Cu(NCS)(2) gives a mixture of trans-[Cu(NCS)(2)(Hpz(tBu))(2)] (5) and [Cu(2)(NCS)(2)(mu-pz(tBu))(2)(mu-Hpz(tBu))(Hpz(tBu))(2)] (6). The latter compound contains a Hpzt(Bu) ligand bridging the two Cu ions in an unusual kappa(1),mu-coordination mode. The variable temperature magnetic properties of 1-3 show antiferromagnetic behavior, leading to a S=1/2 ground state in which the seven copper(II) ions are associated into three mutually independent distinct spin systems. In confirmation of this interpretation, Q-band EPR spectra of solid 1 and 2 at 5 K also demonstrate a S= 1/2 spin system and exhibit hyperfine coupling to three (63,65)Cu nuclei. Unusually, the coupling is manifest as an eight-line splitting of the parallel feature, rather than the usual 10 lines. This has been rationalized by a spin-projection calculation, and results from the relative magnitudes of coupling to the three Cu nuclei. UV/Vis and mass spectrometric data show that 1-4 decompose to lower nuclearity species in solution.