Anisotropic Ionic Mobility of Lithium Salts in Lamellar Liquid Crystalline Polymer Networks

New mesogens presenting smectic A (SmA) phases and capable of hosting lithium salts are designed. The mesogens comprise a vinyl‐functionalized spacer to allow further reaction to the polymer backbone, an aromatic core and ethylene oxide chains, able to coordinate lithium ions. Copolymerizing these monomers with a suitable crosslinker yields the first lithium containing liquid crystalline elastomers (LCEs). The SmA structure where the ethylene oxide chains are microphase separated in layers is fixed by the crosslinking and permanent macroscopic orientation is obtained. Diffusion and conductivity measurements of the monomer sample show a large anisotropy of the ion mobility (100 for the cation and 400 for the anion). In the elastomer the anisotropy of the lithium mobility is comparable to that in the monomers.     

Identification of isomeric 5‐hydroxytryptophan‐ and oxindolylalanine‐containing peptides by mass spectrometry

Cells continuously produce reactive oxidative species that can modify all cellular components. In proteins, for example, cysteine, methionine, tryptophan (Trp), and tyrosine residues are particularly prone to oxidation. Here, we report two new approaches to distinguish two isomeric oxidation products of Trp residues, i.e. 5‐hydroxytryptophan (5‐HTP) and oxindolylalanine (Oia) residues, in peptides. First, 2‐nitrobenzenesulfenyl chloride, known to derivatize Trp residues in position 2 of the indole ring, was used to label 5‐HTP residues. The mass shift of 152.98 m/z units allowed identifying 5‐HTP‐ besides Trp‐containing peptides by mass spectrometry, whereas Oia residues were not labeled. Second, fragmentation of the Oia‐ and 5‐HTP‐derived immonium ions at m/z 175.08 produced ions characteristic for each residue that allowed their identification even in the presence of y₁ ions at m/z 175.12 derived from peptides with C‐terminal arginine residues. The pseudo MS³ spectra acquired on a quadrupole time‐of‐flight hybrid mass spectrometer displayed two signals at m/z 130.05 and m/z 132.05 characteristic for Oia‐containing peptides and a group of six signals (m/z 103.04, 120.04, 130.04, 133.03, 146.04, and 148.04) for 5‐HTP‐cointaining peptides. In both cases, the relative signal intensities appeared to be independent of the sequence providing a specific fingerprint of each oxidative modification. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparison of CID,ETD and metastable atom‐activated dissociation (MAD) of doubly and triply charged phosphorylated tau peptides

The fragmentation behavior of the 2+ and 3+ charge states of eleven different phosphorylated tau peptides was studied using collision‐induced dissociation (CID), electron transfer dissociation (ETD) and metastable atom‐activated dissociation (MAD). The synthetic peptides studied contain up to two known phosphorylation sites on serine or threonine residues, at least two basic residues, and between four and eight potential sites of phosphorylation. CID produced mainly b‐/y‐type ions with abundant neutral losses of the phosphorylation modification. ETD produced c‐/z‐type ions in highest abundance but also showed numerous y‐type ions at a frequency about 50% that of the z‐type ions. The major peaks observed in the ETD spectra correspond to the charge‐reduced product ions and small neutral losses from the charge‐reduced peaks. ETD of the 2+ charge state of each peptide generally produced fewer backbone cleavages than the 3+ charge state, consistent with previous reports. Regardless of charge state, MAD achieved more extensive backbone cleavage than CID or ETD, while retaining the modification(s) in most cases. In all but one case, unambiguous modification site determination was achieved with MAD. MAD produced 15–20% better sequence coverage than CID and ETD for both the 2+ and 3+ charge states and very different fragmentation products indicating that the mechanism of fragmentation in MAD is unique and complementary to CID and ETD. Copyright © 2012 John Wiley & Sons, Ltd.     

An Almost Accurate Location of the Maximum Stirling Number(s) of the Second Kind

The Stirling number of the second kind S(n, k) is the number of ways of partitioning a set of n elements into k nonempty subsets. It is well known that the numbers S(n, k) are unimodal in k, and there are at most two consecutive values K _n such that (for fixed n) S(n, K _n ) is maximal. We determine asymptotic bounds for K _n , which are unexpectedly good and improve earlier results. The method used here shows a possible strategy for obtaining numerical bounds such that in almost all cases K _n can be uniquely determined.     

Monotonicity Properties of the Riemann Zeta Function

Let $$F_{a}(s) = \left(1 - 1\frac{1}{\zeta(s)}\right)^{1/(s-a)}(a \leq 1; s > 1),$$ where ?? denotes the Riemann zeta function. We prove: F _a is strictly decreasing on (1, ??) if and only if a ?? 0, whereas F _a is strictly increasing on (1, ??) if and only if a =?1. In particular, this settles a conjecture of Batir, who claimed that F ₀ is strictly monotonic for s >?1. Moreover, we apply the monotonicity theorem to obtain some inequalities involving F _a .     

Three-dimensional simulation of a dust lifting process with varying parameters

This article presents modelling considerations and simulation results for a dust lifting process in a three-dimensional domain. The Eulerian–Lagrangian modelling technique is used. Multiple simulations with different values for the number of particles were performed. The results of the simulations are shown as snapshots of particle position at certain points in time after the passage of a shock wave. Statistical data for the particle positions and collisions are presented. These are: the average height of the particles, the mean square displacement of the particles and the cumulative number of recorded collisions plotted as functions of time. The particle averaged kinetic energy and the mechanical energy lost by particles during collisions are recorded as functions of time in order to study the motion of particles. The results show that simulations of an increasing number of particles render a less intense lifting effect and, more importantly, that the inter-particle and particle–wall collisions represent essential phenomena and need to be included in this type of model. Also, a comparison between two-dimensional and three-dimensional simulations was performed. It was found that, although 2D simulations are still useful, they overestimate the lifting process and therefore a 3D model is preferable. The influence of the magnitude of the restitution and friction coefficients on the process was also studied.     

The transition from direct to delayed ionisation of C 60

The timescale for the coupling of electronic and vibrational excitation in isolated fullerenes is determined by recording positive ion time-of-flight mass spectra on excitation with ultrashort laser pulses at 790 nm of the same fluence but different pulse durations. The coupling leads to the onset of a delayed ionisation “tail” on the parent fullerene ion peak. This occurs for a pulse duration of 500-1000 fs, depending on laser fluence. Received 20 October 2000     

Partonic scattering cross sections in the QCD medium

A medium modified gluon propagator is used to evaluate the scattering cross section for the process gg→gg in the QCD medium by performing an explicit sum over the polarizations of the gluons. We incorporate a magnetic screening mass from a non-perturbative study. It is shown that the medium modified cross section is finite, divergence free, and is independent of any ad-hoc momentum transfer cut-off parameters. The medium modified finite cross sections are necessary for a realistic investigation of the production and equilibration of the minijet plasma expected at RHIC and LHC.     

Free Factorizations

Given any morphism, we construct extensions of the original category in which this morphism admits certain factorizations, in particular a (retraction, section)-factorization. To this end, we solve the word problem for a certain type of systems of generators and relations for categories. This also enables us to prove preservation properties for the said extensions, e.g. preservation of a pair of diagonalizing classes of epimorphisms and monomorphisms.Iterating such extension processes, we obtain factorizable extensions of categories; in particular, we construct a free proper factorization structure on a given category, which leads to a characterization of preimages of proper factorization structures under full embeddings. As a further application, we characterize an absoluteness property regarding factorizations of functorial images of a morphism.     

激光光束传输因子M~2的一些问题

本文讨论与 M2 因子有关的一些问题 ,指出在近轴近似条件下由光束的二阶强度矩定义的 M2 因子满足 M2 ≥ 1 ,其中只有对基模高斯光束等式才成立 .由光束的功率通量值定义的 M2 因子 ( M2pc)有可能小于 1 ,M2pc的大小取决于所定义的光斑半径内包含的光功率的百分数 .通过计算光场的二阶矩 ,我们获得了轴向相干叠加的高斯光束的 M2 因子的解析解