On the existence of non-geometric sections of arithmetic fundamental groups

We show the existence of group-theoretic sections of the “étale-by-geometrically abelian” quotient of the arithmetic fundamental group of hyperbolic curves over $p$ -adic local fields relative to a proper and flat model which are non-geometric, i.e., which do not arise from rational points.     

The Cut-off Phenomenon for Brownian Motions on Compact Symmetric Spaces

In this paper, we prove the cut-off phenomenon in total variation distance for the Brownian motions traced on the classical symmetric spaces of compact type, that is to say:

1. the classical simple compact Lie groups: special orthogonal groups SO(n), special unitary groups SU(n) and compact symplectic groups USp(n);
2. the real, complex and quaternionic Grassmannian varieties (including the real spheres, and the complex or quaternionic projective spaces when q?=?1): SO(p?+?q)/(SO(p)×SO(q)), SU(p?+?q)/S(U(p)×U(q)) and USp(p?+?q)/(USp(p)×USp(q));
3. the spaces of real, complex and quaternionic structures: SU(n)/SO(n), SO(2n)/ U(n), SU(2n)/USp(n) and USp(n)/UU(n).

Denoting μ _t the law of the Brownian motion at time t, we give explicit lower bounds for d _TV(μ _t ,Haar) if $t < t_{\text{cut-of\/f}}=\alpha \log n$ , and explicit upper bounds if $t > t_{\text{cut-of\/f}}$ . This provides in particular an answer to some questions raised in recent papers by Chen and Saloff-Coste. Our proofs are inspired by those given by Rosenthal and Porod for products of random rotations in SO(n), and by Diaconis and Shahshahani for products of random transpositions in $\mathfrak{S}_{n}$ .     

Calculation and analysis of thermal impedance of microelectronic structures from analytical models

This article deals with thermal impedances of microelectronic components that are useful in Simulation Programs with Integrated Circuit Emphasis (SPICE). In devices like heterojunction bipolar transistors, the active regions thicknesses are often much smaller than the substrates thicknesses. The devices can then be thermally assimilated to heat densities located on top of solid media. In addition to that, when the other dimensions of the heat sources are also much smaller than the substrates dimensions, it is reasonable to consider that the substrate is semi-infinite. First, the expression of the thermal impedance Z of a circular shape heat source centered on top of a half space is presented. For this purpose, the integral transform technique has been used to solve the tri-dimensional heat conduction equation in the frequency domain. The original expression is explicit, exact and allows obtaining results very quickly. After that, the case of a circular heat source on top of a cylinder is treated. A complete analysis of the substrate dimensions influence on the thermal impedance is done. It is based on the impedance decomposition into the one-dimensional impedance and the spreading impedance. By comparing these impedances with that obtained for the heat source on top of the semi-infinite medium, the threshold pulsation at which the thermal impedance of the finite medium differs from the thermal impedance of the half space is extracted. Moreover the geometrical criteria resulting in an error of less than 2% between the spreading impedance of the finite medium and the semi-infinite one are extracted. When these criteria are observed the impedance can be calculated using two perfectly known impedances: the spreading impedance of the semi-infinite medium and the one-dimensional impedance. The results are plotted on the Nyquist diagram, providing a compact representation. Finally the assumption of a circular shape heat source to approximate the thermal impedance of a square shape heat source is validated by evaluating the associated error. The calculation times have been compared to confirm the interest of using this hypothesis.     

Comments on two Notes by L. Ma and X. Xu

In this Note I discuss some assertions made by L. Ma and X. Xu (2009) [6] and L. Ma (2010) [5], which need to be corrected and supplemented with additional references.     

Separation and Thermal Racemization of the Enantiomers of Spiro[cyclohexadiene-dihydroacridines]

 The enantiomers of substituted spiro[cyclohexadiene-dihydroacridines] were separated by enantioselective liquid chromatography with the sorbent/solvent systems triacetylcellulose/methanol, tris-(3,5-dimethylphenylcarbamoyl)-cellulose/silica gel (Chiralcel OD^TM)/n-heptane/2-propanol, and (+)-poly-(trityl methacrylate)/silica gel/n-heptane/2-propanol. Interconversion barriers of the enantiomers were determined for a series of derivatives by thermal racemization. Electrocyclic ring opening/ring closure in terms of the Woodward-Hoffmann rules is discussed for the enantiomerization mechanism; the interconversion of the enantiomers by enolization is ruled out by deuterium exchange experiments.     

Hydrophilic magnetic polymer latexes. 2. Encapsulation of adsorbed iron oxide nanoparticles

The encapsulation of seed polymer particles coated by anionic iron oxide nanoparticles has been investigated using N-isopropylacrylamide as a main monomer, N,N-methylene bisacrylamide as a crosslinking agent, itaconic acid as a functional monomer and potassium persulfate as an anionic initiator. The magnetic latexes obtained have been characterized with regard to particle size, iron oxide content and electrophoretic mobility. All these properties have been examined by varying several polymerization parameters: reaction medium, monomer(s) and crosslinking agent concentrations, nature of seed latexes and type of polymerization (batch versus shot process). The magnetic content in the polymer microspheres strongly depends on the polymerization procedure (i.e., encapsulation process) and varies between 6 and 23 wt%, and monodisperse magnetic polymer particles were obtained. Received: 28 December 1999 Accepted in revised form: 15 June 1999     

Interaction of the general volatile anesthetic Enflurane with bacteriorhodopsin-DPPC proteoliposomes

Thermal decomposition of dried crystalline powder obtained from titanium(IV) bis(acetylacetonate) diisopropoxide (75% solution in 2-propanol) (1) was monitored by simultaneous TG/DTA, EGA-FTIR and EGA-MS measurements and the results were compared with those of amorphous powder obtained by gelling of acetylacetonate-modified titanium(IV) tetra-isopropoxide at molar ratio of 1:2 in boiling 2-methoxyethanol (2). Thermal degradation of 1 in the temperature range of 25–700°C consists of 5 steps with a total mass loss of 62.5%. EGA by FTIR and MS revealed the release of H₂O below 120°C; followed by an intensive evolution of acetylacetone around 245°C. The release of acetone and acetic acid occurs up to 270°C and that of CO and CO₂ up to 530°C.     

Polymerization kinetics of phosphonic acids and esters using an iodonium initiator

Phosphonic acids are known to be useful monomers in dental restorative materials because of their good potential to provide enhanced adhesion to hydroxyapatite and their high hydrolytic stability. In this study, the photopolymerization of phosphonic acid‐based monomer via the camphorquinone (CQ)/ethyl‐4‐(dimethylaminobenzoate) (EDAB) photoredox system is compared with a ternary system composed of iodonium hexafluorophosphate and CQ/EDAB. Photocalorimetry shows that the ternary system does not provide a significant acceleration of the polymerization with either acrylamide or methacrylate phosphonic acids. The complexation of the iodonium by the phosphonic moiety of the acidic monomers leads to a lowered iodonium reactivity and reduced polarizability of the medium and as a consequence limits the rate enhancement effect normally observed by phosphonic acids on the polymerization rate. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5046–5055     

Classification des Représentations Tempérées d’un Groupe p-Adique non Connexe

Let G be the group of points defined over a p-adic field of a non-connected reductive group. In this note, we prove that every tempered irreducible representation of G is irreducibly induced from an essential one of a cuspidal Levi subgroup of G.