Higher Order Peak Algebras

Using the theory of noncommutative symmetric functions, we introduce the higher order peak algebras (Sym(N))_N≥1, a sequence of graded Hopf algebras which contain the descent algebra and the usual peak algebra as initial cases (N=1 and N=2). We compute their Hilbert series, introduce and study several combinatorial bases, and establish various algebraic identities related to the multisection of formal power series with noncommutative coefficients. Received November 19, 2004     

RSOS Models and Jantzen–Seitz Representations of Hecke Algebras at Roots of Unity

A special family of partitions occurs in two apparently unrelated contexts: the evaluation of one-dimensional configuration sums of certain RSOS models, and the modular representation theory of symmetric groups or their Hecke algebras H_m. We provide an explanation of this coincidence by showing how the irreducible H_m-modules which remain irreducible under restriction to H_{m_1} (Jantzen–Seitz modules) can be determined from the decomposition of a tensor product of representations sl_n.     

Enthalpy–Entropy Compensation Combined with Cohesive Free‐Energy Densities for Tuning the Melting Temperatures of Cyanobiphenyl Derivatives

This work illustrates how minor structural perturbations produced by methylation of 4′‐(dodecyloxy)‐4‐cyanobiphenyl leads to enthalpy–entropy compensation for their melting processes, a trend which can be analyzed within the frame of a simple intermolecular cohesive model. The transformation of the melting thermodynamic parameters collected at variable temperatures into cohesive free‐energy densities expressed at a common reference temperature results in a novel linear correlation, from which melting temperatures can be simply predicted from molecular volumes.     

Noncommutative symmetric functions with matrix parameters

We define new families of noncommutative symmetric functions and quasi-symmetric functions depending on two matrices of parameters, and more generally on parameters associated with paths in a binary tree. Appropriate specializations of both matrices then give back the two-vector families of Hivert, Lascoux, and Thibon and the noncommutative Macdonald functions of Bergeron and Zabrocki.     

Microwave-assisted conversion of carbohydrates. State of the art and outlook

The valorisation of carbohydrates arising from the hydrolysis of renewable feedstocks (i.e., lignocellulosic biomass) is nowadays an area of utmost interest. In this context, the implementation of fast, expeditious and cost-effective methodologies for the modification of these naturally occurring compounds is becoming a prerequisite. With this aim, the application of microwaves has gained progressive attention in laboratories for making a range of high-added value sugars derivative scaffolds. The advantages of microwaves are numerous, and include enhancement of reaction rates and yields, combined with improved regio-, chemo- and anomeric selectivities.     

Microwave-assisted synthesis of d-glucuronic acid derivatives using cost-effective solid acid catalysts

Monomode microwave-assisted coupling of d-glucuronic acid with alcohols, in the presence of various impregnated acid catalysts, was successfully performed, affording in almost quantitative yields the corresponding monosubstituted β-d-glucofuranosidurono-6,3-lactones in less than 10 min at 85 °C. This study evidences the synergy of microwaves and impregnated acid catalysts as a fast and clean strategy in the field of carbohydrate chemistry.     

First glances at the transversity parton distribution through dihadron fragmentation functions

We present first observations of the transversity parton distribution based on an analysis of pion-pair production in deep-inelastic scattering off transversely polarized targets. The extraction of transversity relies on the knowledge of dihadron fragmentation functions, which we take from electron-positron annihilation measurements. This is the first attempt to determine the transversity distribution in the framework of collinear factorization.     

13CH4分子v3振动带空气和氮气加宽系数温度依赖性研究

采用中红外波段连续可调谐二极管激光器和自行研制的低温吸收池, 测量了温度为296 K, 252 K, 213 K, 173 K时, 3.38 μm附近¹³CH₄分子的四条跃迁谱线的氮气和空气加宽光谱; 首次通过实验获得空气和氮气对¹³CH₄分子的碰撞加宽系数, 以及谱线加宽系数的温度依赖系数. 实验过程中, 利用Voigt线型对所测量的光谱进行拟合. 实验结果表明, 氮气和空气对¹³CH₄分子的碰撞诱导加宽系数随温度的降低而增大; 相同温度下, 氮气对¹³CH₄分子的碰撞加宽系数普遍大于空气加宽系数. 实验数据为地球和外星体大气遥感探测提供了依据.