Formation of enamides via palladium(II)-catalyzed vinyl transfer from vinyl ethers to nitrogen nucleophiles

Palladium(II) complexes catalyze the formation of enamides via the formal cross-coupling reaction between nitrogen nucleophiles and vinyl ethers. These vinyl transfer reactions proceed in good yields with amide, carbamate, and sulfonamide nucleophiles, and the optimal catalyst is (DPP)Pd(OCOCF(3))(2) (DPP = 4,7-diphenyl-1,10-phenanthroline). [reaction: see text]     

A functional central limit theorem for diffusions on periodic submanifolds of ℝ N

We prove a functional central limit theorem for diffusions on periodic sub- manifolds of ℝ^N. The proof is an adaptation of a method presented in [BenLioPap] and [Bha] for proving functional central limit theorems for diffusions with periodic drift vectorfields. We then apply the central limit theorem in order to obtain a recurrence and a transience criterion for periodic diffusions. Other fields of applications could be heat-kernel estimates, similar to the ones obtained in [Lot].Mathematics Subject Classification (2000): 35B27, 60F05, 58J65The author wants to express his gratitude toward the National Cheng Kung University in Tainan (Taiwan) for its kind hospitality.     

A one-pot synthesis of disiloxy,dihalo and dithiocyanato dioxo complexes bearing a bidentate N-ligand from sodium or potassium molybdate tungstate and perrhenate

Disiloxy, dichloro, dibromo and dithiocyanato molybdenum, tungsten and rhenium-oxo complexes bearing bidendate N-ligands have been synthesized in a one-pot process and fully characterized spectroscopically. The reaction, in acetonitrile, is significantly simpler to run than previously reported methods for the synthesis of analogous compounds and appears to be general in character.     

Synthesis and Crystal Structure of Dimethyl-7-oxabicyclo[2.2.1]hept-5-ene exo,exo-2,3-dicarboxylate

Dimethyl-7-oxabicyclo[2.2.1]hept-5-ene exo,exo-2,3-dicarboxylate (1) was prepared by Fisher esterification of 7-oxabicyclo[2.2.1]-hept-5-ene exo-2,3-dicarboxylic anhydride (2) in methanol. The colorless plates obtained were characterized by FT-IR, ¹H- and ¹³C-NMR, TGA-DSC, and single crystal X-ray diffraction. The material crystallizes in space group P2₁/c, with a = 9.2375(14) Å, b = 12.8757(18) Å, c = 9.4608(15) Å, β = 115.327(3)°, V = 1017.1(3) Å³, and Z = 4. Chains of hydrogen-bonded molecules along the c-axis interact in the b direction to form layers parallel to the bc plane.     

Semi-classical spectral estimates for Schrödinger operators at a critical level. Case of a degenerate maximum of the potential

We study the semi-classical trace formula at a critical energy level for a Schrödinger operator on Rn. We assume here that the potential has a totally degenerate critical point associated to a local maximum. The main result, which establishes the contribution of the associated equilibrium in the trace formula, is valid for all time in a compact subset of R and includes the singularity in t=0. For these new contributions the asymptotic expansion involves the logarithm of the parameter h. Depending on an explicit arithmetic condition on the dimension and the order of the critical point, this logarithmic contribution can appear in the leading term.     

A Semi-Classical Trace Formula at a Totally Degenerate Critical Level

We study the semi-classical trace formula at a critical energy level for an h-pseudo-differential operator on n whose principal symbol has a totally degenerate critical point for that energy. This problem is studied for a large time behavior and under the hypothesis that the principal symbol of the operator has a local extremum at the critical point.This work was supported by the IHP-Network Analysis and Quantum, reference number HPRN-CT-2002-00277. We thank Raymond Brummelhuis for encouragement and for advice concerning this work. We also thank Bernard Helffer for constructive remarks on this work.     

Effect of the addition of D-xylose on xylanase activity and digestibility of fiber in an artificial rumen

The effect of adding D-xylose at two different levels as a continuous infusion to an artificial rumen was determined with respect to pH, methane production, volatile fatty acid production, fiber digestion, and xylanase activity. No changes in pH, methane production, or fiber digestion were observed as consequences of increased D-xylose concentrations. Although the propionic acid production was slightly raised on addition of D-xylose, the acetic acid production was lowered to the same extent. A low-xylose infusion increased the xylanase activity by 25%, whereas a high-xylose infusion lowered the activity by 17%. It was concluded that D-xylanase activity was not a rate-determining step in fiber degradation in the rumen.     

A new method of stirring for LPE growth

This paper describes a method of stirring a liquid during crystal growth in which each point on the growth face moves round a circle of radius b. If the face has a radius a and completes n revolutions per second, then the stirring is roughly equivalent to rotating the disc about a single axis at a rate $\text{2πc}{}^2\text{b}{}^2\text{n}\text{a}{}^2$ where c is a constant (c ∽ 2) but the system behaves as if only the liquid up to a distance $\text{(}\text{2v}\text{n}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ from the face is stirred. Uniform stirring occurs over the whole face except for an annulus of width 2b at the periphery. The necessary design criteria are discussed and a simple dynamically balanced apparatus and the results obtained with it whilst growing iron garnet films are described.     

Change point testing for the drift parameters of a periodic mean reversion process

In this paper we investigate the problem of detecting a change in the drift parameters of a generalized Ornstein–Uhlenbeck process which is defined as the solution of $$\begin{aligned} dX_t=(L(t)-\alpha X_t) dt + \sigma dB_t \end{aligned}$$ and which is observed in continuous time. We derive an explicit representation of the generalized likelihood ratio test statistic assuming that the mean reversion function $L(t)$ is a finite linear combination of known basis functions. In the case of a periodic mean reversion function, we determine the asymptotic distribution of the test statistic under the null hypothesis.