Border collision bifurcations at the change of state-space dimension

We present the theory of border collision bifurcation for the special case where the state space is piecewise smooth, but two-dimensional in one side of the borderline, and one dimensional in the other side. This situation occurs in a class of switching circuits widely used in power electronic industry. We analyze this particular class of bifurcations in terms of the normal form, where the determinant of the Jacobian matrix at one side of the borderline is greater than unity in magnitude, and in the other side it is zero. (c) 2002 American Institute of Physics.     

Structural, dielectric and electromechanical study of Hf-substituted BaTiO3 thin films fabricated by CSD

Hafnium-substituted barium titanate thin films were deposited on platinized silicon substrates. Two different concentrations of solutions (0.1 M and 0.3 M) were used to deposit films of various compositions Ba(Ti_1-x,Hf_x)O₃ (x=0.03, 0.05, 0.07, 0.1, 0.2, 0.3 and 0.4). The microstructure of the films depended on the concentration of the solution. Lower concentration (0.1 M) solutions led to columnar films, but with higher hafnium percent compositions the columnar structure was lost. The films which were derived from the 0.1 M concentration solutions had better dielectric and electrical properties compared to the films derived from a higher concentration (0.3 M). All the films were found to be polycrystalline in nature. The dielectric constant of the films was found to decrease with higher amounts of hafnium substitution. From the I–V characteristics it is noticed that the leakage decreases by almost four orders of magnitude with a hafnium substitution of 40%. The d₃₃ values of the films were between 23 and 5.6 pm/V for the different films. PACS 68.55.-a; 81.20.Fw; 77.84.Dy; 77.55.+f     

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A More General Treatment of Abrasion-Chipping Processes applicable to FAG/SAG Milling

Equations are derived for the rate of loss of mass from a screen interval when the size reduction process is an abrasion-chipping process which follows a wear law of the Bond form or the Davis form, giving cores and fragments. The treatment is extended to steady-state continuous grinding in a fully-mixed reactor, and to the case where first-order disintegrative fracture processes also occur.     

Trapping guests within a nanoporous metal-organic framework through pressure-induced amorphization

The release of guest species from within a nanoporous metal-organic framework (MOF) has been inhibited by amorphization of the guest-loaded framework structure under applied pressure. Thermogravimetric analyses have shown that by amorphizing ZIF-8 following sorption of molecular I(2), a hazardous radiological byproduct of nuclear energy production, the pore apertures in the framework are sufficiently distorted to kinetically trap I(2) and improve I(2) retention. Pair distribution function (PDF) analysis indicates that the local structure of the captive I(2) remains essentially unchanged upon amorphization of the framework, with the amorphization occurring under the same conditions for the vacant and guest-loaded framework. The low, accessible pressure range needed to effect this change in desorption is much lower than in tradition sorbents such as zeolites, opening the possibility for new molecular capture, interim storage, or controlled release applications.     

Formation of organorhodium complexes via C-H bond activation of 1,3-di(phenylazo)benzene

Reaction of a potential NCN-pincer ligand, viz. 1,3-di(phenylazo)benzene (L), with [Rh(PPh(3))(3)Cl] affords, via a C-H bond activation, an interesting dinuclear Rh(II) complex (1), and with RhCl(3)·3H(2)O affords a mononuclear Rh(III) complex (2) containing a catalytically useful Rh-OH(2) fragment.     

Rearrangement of the tris(2-pyridylthio)methanido ligand in an iron(II) complex containing an Fe-C bond

Iron(II) tris(2-pyridylthio)methanido (1) containing an Fe-C bond, obtained from the reaction of tris(2-pyridylthio)methane (HL(1)) and iron(II) triflate, reacts with protic acid to generate iron(II) bis(2-pyridylthio)carbene (1a). The carbene complex is converted to an iron(II) complex (2) of the 1-[bis(2-pyridylthio)methyl]pyridine-2-thione ligand (L(3)) upon treatment with a base. Complex 2 reversibly transforms to 1a in the presence of an acid. During the transformation of 1 to 2, a novel rearrangement of L(1) to L(3) takes place. The iron(II) complexes are reactive toward dioxygen to form the corresponding iron(III) complexes.     

Nickel–Schiff base complex catalyzed C–S cross-coupling of thiols with organic chlorides

We report an efficient, mild and convenient synthetic protocol for the C–S cross-coupling reaction of various aryl, benzyl, allyl chlorides and thiols using 5 mol % Nickel–Schiff base catalyst with NaOH as the base, in DMF at 70 °C. Using this protocol, we have shown that a variety of aryl sulfides can be synthesized in excellent yields from readily available organic chlorides and thiols.