Cellulose - Bookkeeper, the most widely used deacidification process based on MgO particles, was systematically evaluated on two sets of nonvaluable historical paper samples. Established analytical... 相似文献
Analysis of inorganic ions in cerebrospinal fluid (CSF) is used mainly in the diagnostics of central nervous system diseases, such as Alzheimer’s disease or multiple sclerosis. A new analytical method for fast determination of inorganic cations (ammonium, calcium, magnesium, sodium and potassium) and anions (chloride, sulfate, nitrite and nitrate) in CSF on an electrophoretic microchip was developed in this context. Zone electrophoresis (ZE) separations were performed on the microchip with coupled channels (CC) and contact conductivity detection. Two different propionate background electrolytes were used for the sequential determination of cations at pH 3.1 and anions at pH 4.3. ZE was used for the determination of cationic constituents while ZE–ZE approach was employed for the determination of chloride in the first separation channel on the CC microchip and other anionic micro-constituents in the second channel. LOD values were in the range of 0.003–0.012 mg L−1 and 0.019–0.047 mg L−1 for cations and anions, respectively. Repeatability of migration time was up to 1.2 % for both cations and anions. Repeatability of peak area ranged from 0.3 to 5.6 % for cations and from 0.6 to 6.0 % for anions. Recovery of both cations and anions was in the range 90–106 %. CSF samples were only diluted appropriately without other sample pretreatment prior to analysis. Developed sequential method is suitable for fast determination of the studied cations and anions in CSF with total analysis time <15 min.
Multiple emulsions with an “onion” topology are useful vehicles for drug delivery, biochemical assays, and templating materials. They can be assembled by ternary liquid phase separation by microfluidics, but the control over their design is limited because the mechanism for their creation is unknown. Herein we show that phase separation occurs through self‐similar cycles of mass transfer, spinodal decomposition or nucleation, and coalescence into multiple layers. Mapping out the phase diagram shows a linear relationship between the diameters of concentric layers, the slope of which depends on the initial ternary composition and the molecular weight of the surfactant. These general rules quantitatively predict the number of droplet layers (multiplicity), which we used to devise self‐assembly routes for polymer capsules and liposomes. Moreover, we extended the technique to the assembly of lipid‐stabilized droplets with ordered internal structures. 相似文献
In the title compound, the coordination geometry of the CoIII atom is only slightly distorted from regular octahedral, and the racemic nature of the material was confirmed by X‐ray structure analysis. 相似文献
In this paper, analysis strategies developed for a sequencing problem concerning the identification of an S100 protein isolated from human granulocytes are discussed. The analysis of a trypsinized lyophilized sample suggested the presence of a number of peptides which are non-tryptic in origin. During purification of proteins from cell lysates nonspecific cleavage can be observed which may reflect biological processes and can become an unavoidable analytical problem. Current mass spectrometric software is evaluated for the analysis of nonspecific digests in this context. Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), high-performance liquid chromatography (HPLC)-MS/MS, and selected ion monitoring (SIM)-MS/MS have been used for peptide analysis and in addition HPLC-MS was carried out for protein analysis leading to the detection of an N-terminal modification of the protein. The success of the study is mainly due to the careful investigation of nonspecific cleavage products. Data obtained from the routine mass spectrometric analysis of an in-gel-digest allowed the identification of this protein as S100 calcium-binding protein A6-calcyclin whose expression in granulocytes has not been described so far. 相似文献
The fluorescence characteristics of the Schiff bases 2-(3-pyridylmethyliminornethyl)phenol (1), 2-(2 pyridyliminomethyl)phenol (2), N.N-bis(salicylidene)-2,3-pyridinediamine (3), N,N'-bis(salicylidene)-2,6-pyridinediamine (4) and 2-(2-amino-4-methoxymethyl-6-methyl-3-pyridylmethyliminomethyl)phenol (5) were studied in various solvents at different pH values. Corresponding quantum efficiencies were determined. Compound 1, which showed a tendency towards tautomeric mterconversion to ketoamine in polar protic solvents, was not fluorescent at pH < 8. The fluorescence of other compounds was very sensitive to solvent polarity and the pH of the medium. Compounds 2-4, preferably present as enolimines in all solvents, were not fluorescent in non-polar and moderately polar solvents, whereas weak emission was observed in polar solvents, like methanol, dimethylformamide and dioxane/water 1/1 (0.001 < Q < 0.072). A significant increase in Stokes shifts and in quantum efficiencies was noted as a result of increasing polarity of dioxane/water mixtures, indicating specific interactions with polar water molecules. The emission was promoted at acidic pH values where a pyridinium cation was formed (0.061 < Q < 0.519, in dioxane/water 1/1 at pH 3.4). Compound 5, which was a tautomeric mixture of enoiimine and cyclic diamine in all solvents, was fluorescent in polar as well as in non-polar media. The quantum efficiency varied dependent on the solvent and pH (0.023 <Q< 0.435). The cyclic diamine, i. e. the more rigid structure was supposed to be responsible for the fluorescence in non-polar and aprotic solvents as well as at neutral, and weakly basic pH values. 相似文献
We classify, up to a local isometry, all non-K?hler almost K?hler 4-manifolds for which the fundamental 2-form is an eigenform
of the Weyl tensor, and whose Ricci tensor is invariant with respect to the almost complex structure. Equivalently, such almost
K?hler 4-manifolds satisfy the third curvature condition of A. Gray. We use our local classification to show that, in the
compact case, the third curvature condition of Gray is equivalent to the integrability of the corresponding almost complex
structure.
Received: 1 October 2001 / Published online: 17 June 2002 相似文献