Quasi-steady deformation of a two-dimensional bubble placed within a potential viscous flow

The shape evolution of a two-dimensional bubble, bounded by a simple closed curve, which is initially placed within a potential viscous flow, is analysed. It is assumed that the influence of gravity and inertia forces is negligible, so the quasi-steady approximation can be applied. Reformulating the problem for Stokes equations with relevant boundary conditions at the free surface in terms of the bianalytic stress-stream function, and using the time-dependent conformal mappingz(,t) of a unit disk onto an unbounded flow domain sought, an infinite system of ordinary differential equations for the Laurent coefficients ofz(,t) is derived. A class of exact solutions is found for the case when the principal part of the complex velocity of the dominant flow at infinity is a polynomial, and the problem of formation of a pointed bubble is discussed.

---

Sommario E analizzata l'evoluzione di una bolla bi-dimensionale, limitata da una curva chiusa semplice, inizialmente posta in un flusso potenziale viscoso. Si assume che l'influenza della gravità e delle forze inerziali sia trascurabile, cosicchè si può applicare l'approssimazione quasi-stazionaria. Riformulando il problema per le equazioni di Stokes con le opportune condizionial contorno sulla superficie libera in termini della funzione stress-stream bianalitica, e usando la tecnica delle trasformazioni conformi dipendenti dal tempoz(,t) di un disco unitario su un dominio di flusso non limitato incognito, viene derivato un sistema infinito di equazioni differenziali ordinarie per i coefficienti di Laurent diz(,t). Viene trovata una classe di soluzioni esatte per il caso in cui la parte principale della velocità complessa del flusso dominante all'infinito è una polinomiale, ed è discusso il problema della formazione di una bolla lenticolare.

     

Indirect ultrasonication for protein quantification and peptide mass mapping through mass spectrometry-based techniques

We report in this work a fast protocol for protein quantification and for peptide mass mapping that rely on ¹⁸O isotopic labeling through the decoupling procedure. It is demonstrated that the purity and source of trypsin do not compromise the labeling degree and efficiency of the decoupled labeling reaction, and that the pH of the labeling reaction is a critical factor to obtain a significant ¹⁸O double labeling. We also show that the same calibration curve can be used for MALDI protein quantification during several days maintaining a reasonable accuracy, thus simplifying the handling of the quantification process. In addition we demonstrate that ¹⁸O isotopic labeling through the decoupling procedure can be successfully used to elaborate peptide mass maps. BSA was successfully quantified using the same calibration curve in different days and plasma from a freshwater fish, Cyprinus carpio, was used to elaborate the peptide mass maps.     

Rapid Multiphase Flow Dynamics Mapped by Single‐Shot MRI Velocimetry

A new, fast magnetic resonance imaging (MRI) method is described and applied to map flow fields in systems with internal velocities rapidly varying along the streamlines. While conventional MRI techniques encode the velocity information in a preparatory period prior to the imaging acquisition module, our technique repeatedly refreshes the velocity encoding during a single‐shot imaging sequence. In this way, the maximum acceleration responsible for velocity variation of the molecules is increased by up to two orders of magnitude compared to standard procedures. Besides being compatible with high acceleration, this pulse sequence is suited to acquiring in a single scan the multiple velocity images required to construct a full velocity vector map. The power of this new methodology is demonstrated by following the internal dynamics of toluene droplets levitating in a counterflow of water during mass transfer of acetone from the water phase into the drop in the presence of surface‐active impurities. The dramatic reduction in measurement time allows visualization for the first time of the important impact of even small concentrations of acetone on accumulation of surfactants at the drop’s surface.     

The carbon versus mass diagram to visualize and exploit FTICR‐MS data of natural organic matter

A two‐dimensional diagram is proposed, in which the carbon number of each formula is plotted against its nominal mass, to visualize large sets of molecular formula data that can be derived from data generated by ultrahigh‐resolution Fourier transform ion cyclotron resonance‐MS. In such a carbon versus mass (CvM) diagram, each formula (C_cH_hO_o) is unambiguously described by c, its (nominal) mass and the parameter i = c + o. Calculations of chemically allowable formulas illustrate that organic molecules occupy only certain spaces in such a diagram. The extension of these spaces increases with molecular mass in x‐direction (hydrogenation) and y‐direction (oxygenation). The data sets of molecules determined in natural organic matter(NOM) occupy only a certain range of the allowable space. The intensity of the mass spectrometric signals can be included as the third dimension into a CvM diagram. Separate CvM diagrams can be plotted for NOM molecules that include different heteroatoms. The benefits of the CvM diagram are illustrated by application onto data sets of fulvic acids from riverine and marine origin, of secondary organic aerosol, including organosulfates and organonitrates, as well as of ozonation of fulvic acids. The CvM diagram is a useful tool to visualize the elemental regularities in NOM isolates as well as the differences between isolates. It may also be applicable to large sets of molecular formula data generated in other disciplines such as petroleum biogeochemistry or metabolomics. Copyright © 2010 John Wiley & Sons, Ltd.     

Efficient on-column conversion of IgG1 trisulfide linkages to native disulfides in tandem with Protein A affinity chromatography

Protein trisulfide linkages are generated by the post-translational insertion of a sulfur atom into a disulfide bond. Molecular heterogeneity was detected in a recombinant IgG₁ monoclonal antibody (mAb) and attributed to the presence of a protein trisulfide moiety. The predominant site of trisulfide modification was the bond between the heavy and light chains. The trisulfide was eliminated during purification of the IgG₁ mAb via a cysteine wash step incorporated into Protein A affinity column chromatography. Analysis of the cysteine-treated mAb by electrophoresis and peptide mapping indicated that the trisulfide linkages were efficiently converted to intact disulfide bonds (13% trisulfide decreased consistently to 1% or less) without disulfide scrambling or an increase in free sulfhydryls. The on-column trisulfide conversion caused no change in protein folding detectable by hydrogen/deuterium exchange or differential scanning calorimetry. Consistent with this, binding of the mAb to its antigen in vitro was insensitive to the presence of the trisulfide modification and to its removal by the on-column cysteine treatment. Similar, high efficiency trisulfide conversion was achieved for a second IgG₁ mAb using the column wash strategy (at least 7% trisulfide decreased to 1% or less). Therefore, trisulfide/disulfide heterogeneity can be eliminated from IgG₁ molecules via a convenient and inexpensive procedure compatible with routine Protein A affinity capture.     

分担处于一般位置超平面的亚纯映射唯一性定理

本文研究从Cn到复射影空间PN(C)上亚纯映射唯一性问题.根据杨乐处理重值的方法和Dethloff、Quang、Tan等人的技巧,我们分别得到了两个广泛的唯一性定理,改进和推广了一些分担处于一般位置超平面的亚纯映射唯一性结果.     

Noise map validation by continuous noise monitoring

This paper presents a comparison of two noise assessments in the Gdansk agglomeration in Poland. One is based on the noise map produced by computational method for the city in 2007, the second one is based on real data from continuous measurements acquired by a noise monitoring network operating in the city since 2008. Differences are shown and analyzed. Additionally, seasonal and weekday influence on noise indicators (L_DEN, L_D, L_E and L_N) is analyzed and discussed in this paper.     

Probe-type time-of-flight momentum and energy mapping system

A new time-of-flight (TOF) momentum and energy mapping system is proposed. The system consists of two sub-regions with different axial uniform decelerating field. Two position-sensitive detectors (PSDs) on opposite side of the tube are used for the detection of electrons with different axial motion length due to their initial energy ? and emission angle θ. A non-monotonic dependence of energy-resolving performance on electron initial energy can be achieved by choosing appropriate electric field deceleration for these two sub-regions, which forms an “energy resolution probe” possessing a higher level of energy resolution than that of lower energy part. And the local resolution in the probe region could be specifically enhanced while the other parts of all the detection range do not change so much. It is verified by the illustrating example with relative energy resolution Δ?/? smaller than 0.5% for electron energy in probe range from 36 eV to 45 eV.     

Fast fat-suppressed reduced field-of-view temperature mapping using 2DRF excitation pulses

The purpose of this study is to develop a fast and accurate temperature mapping method capable of both fat suppression and reduced field-of-view (rFOV) imaging, using a two-dimensional spatially-selective RF (2DRF) pulse. Temperature measurement errors caused by fat signals were assessed, through simulations. An 11×1140μs echo-planar 2DRF pulse was developed and incorporated into a gradient-echo sequence. Temperature measurements were obtained during focused ultrasound (FUS) heating of a fat-water phantom. Experiments both with and without the use of a 2DRF pulse were performed at 3T, and the accuracy of the resulting temperature measurements were compared over a range of TE values. Significant inconsistencies in terms of measured temperature values were observed when using a regular slice-selective RF excitation pulse. In contrast, the proposed 2DRF excitation pulse suppressed fat signals by more than 90%, allowing good temperature consistency regardless of TE settings. Temporal resolution was also improved, from 12 frames per minute (fpm) with the regular pulse to 28 frames per minute with the rFOV excitation. This technique appears promising toward the MR monitoring of temperature in moving adipose organs, during thermal therapies.     

扰动mKdV耦合系统的孤子解

采用了一个简单而有效的技巧,研究了一类扰动mKdV耦合系统.首先利用同伦映射方法求解一个相应的复值函数微分方程孤子的近似解.然后得到了原扰动mKdV耦合系统孤子的近似解. 关键词： 孤子 扰动mKdV方程 同伦映射