低杂波电流驱动的密度极限分析

用低杂波的可的性条件，参量不稳定条件和功率耦合谱分析了低杂波电流驱动。由于波的可近性条件限制耦合谱中平行相速度较大的波进入等离子体中心，参量不稳定性使平行相速度较低的波与离子相互作用，随着等离子体密度的增中，这些作用越来越明显，最终导致低杂波不能在中心与电子相互作用，驱动电流消失，这就是所谓密度极限。在本文建立的模型基础上的计算结果与实验结果符合较好。     

Accessibility and size of <Emphasis Type="Italic">Valonia</Emphasis> cellulose microfibril studied by combined deuteration/rehydrogenation and FTIR technique

We report an FTIR method to measure the accessibility and the size of cellulose microfibrils from the cell wall of Valonia ventricosa. This method is similar to the conventional deuteration technique for measuring the accessibility of cellulosic materials; however, the difference in our method is that the hydroxyl groups O2H, O3H, and O6H in the crystalline region were initially completely deuterated. The sample was then rehydrogenated by soaking in water at 25 °C, so that the OD groups on the surface were rehydrogenated. The ratio of OH to OD absorbance was used to calculate the number of surface vs. core cellulose chains in a microfibril. The obtained experimental ratio of 0.934 was consistent with the value calculated for a previously published 33 × 38 chain Valonia model (Sugiyama et al. 1984). The rehydrogenation process was further investigated by immersing the sample in water at elevated temperatures. At temperatures above 120 °C, rehydrogenation was more efficient, and the efficiency plots vs. rehydrogenation temperature showed two inflection. These points may correspond to the temperature where the cleavage of inter-chain hydrogen bonds and/or crystalline-phase transition would have been occurred.     

Upscaling of Stochastic Micro Model for Suspension Transport in Porous Media

Micro scale population balance equations of suspension transport in porous media with several particle capture mechanisms are derived, taking into account the particle capture by accessible pores, that were cut off the flux due to pore plugging. The main purpose of the article is to prove that the micro scale equations allow for exact upscaling (averaging) in case of filtration of mono dispersed suspensions. The averaged upper scale equations generalise the classical deep bed filtration model and its latter modifications.     

Improving Accessibility and Reactivity of Celluloses of Annual Plants for the Synthesis of Methylcellulose

Pretreatments (water-soaking, pre-mercerization, mercerization under a pressure of 15 bars and steam explosion) were used to improve the accessibilities and reactivities of celluloses of bleached flax, hemp, sisal, abaca and jute pulps for the synthesis of methylcellulose. Degrees of crystallinity were determined by X-ray Diffraction (XRD) spectra. The iodine adsorption accessibilities of pulps were low and accessible fractions ranged from 1.3 to 5.2%. Accessible fractions in amorphous cellulose were calculated in the 5–18% range. The accessibilities of these pulps were hemp pulp > flax pulp > sisal pulp > jute pulp > abaca pulp. Fourier Transform Infrared (FTIR) spectra showed that mean hydrogen bond strengths were weakened and relative crystallinity indexes were decreased by pretreatments. The accessibility and reactivity of the abaca pulp were improved by water soaking, mercerization under 15 bars pressure, steam explosion and preliminary mercerization, of which steam explosion and pre-mercerization were the best treatments. Species was the main factor for the accessibility and reactivity.     

Controlling multiparticle system on the line. II. Periodic case

As in [A. Sarychev, Controlling multiparticle system on the line. I, J. Differential Equations 246 (12) (2009) 4772-4790] we consider classical system of interacting particles P₁,…,Pn on the line with only neighboring particles involved in interaction. On the contrast to [A. Sarychev, Controlling multiparticle system on the line. I, J. Differential Equations 246 (12) (2009) 4772-4790] now periodic boundary conditions are imposed onto the system, i.e. P₁ and Pn are considered neighboring. Periodic Toda lattice would be a typical example. We study possibility to control periodic multiparticle systems by means of forces applied to just few of its particles; mainly we study system controlled by single force. The free dynamics of multiparticle systems in periodic and nonperiodic case differ substantially. We see that also the controlled periodic multiparticle system does not mimic its nonperiodic counterpart.Main result established is global controllability by means of single controlling force of the multiparticle system with a generic potential of interaction. We study the nongeneric potentials for which controllability and accessibility properties may lack. Results are formulated and proven in Sections 2, 3.     

Accessibility of partially hyperbolic endomorphisms with 1D center-bundles

We prove that partially hyperbolic endomorphisms with one dimensional center-bundles and non-trivial unstable bundles are stably accessible. And there is residual subset $\Res$ of partially hyperbolic volume preserving endomorphisms with one dimensional center-bundles such that every $f \in \Res$ is stably accessible. In the end, we prove the accessibility of Gan''s example.     

The molecular electrostatic potential and steric accessibility of C-DNA

The molecular electrostatic potentials and steric accessibilities associated with reactive sites of C-DNA are calculated for the sequences poly(dG · dC) and poly(dA · dT). The distribution of potential on the surface envelopes of the double helices are also presented. The results are compared with those obtained for B-DNA.     

The role of the particle size reduction and morphological changes of solid substrate in the ultrasound-aided enzymatic hydrolysis of cellulose

The contribution of ultrasound-aided particle size reduction to the efficiency of the subsequent enzymatic hydrolysis and the accompanying morphological changes of bleached cotton and linen powders were investigated. The aqueous suspensions of cellulosic powders were pretreated either with an ultrasonic bath (US-B) or with a horn-type reactor (US-H). Results revealed that the impact of US-H was more pronounced than that of the US-B. Clearly, the linen particles were more sensitive to ultrasonication than cotton. The US-H modified the particle size distribution differently for the cotton and linen powders and reduced the mean size of particles from 49 to 40 µm and from 123 to 63 µm, respectively. A significant increase in the water retention and water sorption capacity was also measured. The smaller particles with increased accessibility were preferably digested in the enzyme treatment, resulting in a considerably higher concentration of reducing sugars and an enrichment of the residual particles with a larger average size (cotton: 47 µm; linen: 66 µm).     

超声波活化处理对微晶纤维素结构和氧化反应性能的影响

采用无污染的超声波技术预处理微晶纤维素, 研究了微晶纤维素在活化前后的超分子结构、形态结构和可及度的变化, 超声波活化对微晶纤维素选择性氧化性能的影响.     

Oxycarbonylation of methanol over modified CuY: Enhanced activity by improving accessibility of active sites

To improve the accessibility of Cu⁺ species located in the small cages, Y zeolite was post-treated with NH₄F solution etching. The small cages were opened effectively, which allowed the reactants to interact with more Cu⁺ sites. As a result, an enhanced activity was obtained over modified CuY catalyst in oxidative carbonylation of methanol.