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101.
102.
Jaakko Laakia Alexey Adamov Matti Jussila Christian S. Pedersen Alexey A. Sysoev Tapio Kotiaho 《Journal of the American Society for Mass Spectrometry》2010,21(9):1565-1572
This study demonstrates how positive ion atmospheric pressure photoionization-ion mobility spectrometry-mass spectrometry
(APPI-IMS-MS) can be used to produce different ionic forms of an analy te and how these can be separated. When hexane:toluene
(9:1) is used as a solvent, 2,6-di-tert-butylpyridine (2,6-DtBPyr) and 2,6-di-tert-4-methylpyridine (2,6-DtB-4-MPyr) efficiently produce radical cations [M]+ and protonated [M + H]+ molecules, whereas, when the sample solvent is hexane, protonated molecules are mainly formed. Interestingly, radical cations
drift slower in the drift tube than the protonated molecules. It was observed that an oxygen adduct ion, [M + O2]+, which was clearly seen in the mass spectra for hexane:toluene (9:1) solutions, shares the same mobility with radical cations,
[M]+. Therefore, the observed mobility order is most likely explained by oxygen adduct formation, i.e., the radical cation forrning
a heavier adduct. For pyridine and 2-tert-butylpyridine, only protonated molecules could be efficiently formed in the conditions used. For 1- and 2-naphthol it was
observed that in hexane the protonated molecule typically had a higher intensity than the radical cation, whereas in hexane:toluene
(9:1) the radical cation [M]+ typically had a higher intensity than the protonated molecule [M + H]+. Interestingly, the latter drifts slower than the radical cation [M]+, which is the opposite of the drift pattern seen for 2,6-DtBPyr and 2,6-DtB-4-MPyr. 相似文献
103.
Isabel Díez Dr. Matti Pusa Sakari Kulmala Prof. Hua Jiang Dr. Andreas Walther Anja S. Goldmann Axel H. E. Müller Prof. Olli Ikkala Prof. Robin H. A. Ras Dr. 《Angewandte Chemie (International ed. in English)》2009,48(12):2122-2125
Colorful clusters : Silver nanoclusters consisting of only a few atoms exhibit large chemical‐environment‐responsive shifts of their optical absorption and emission bands, that is, large solvatochromism (see picture). The photophysical characteristics and electrochemiluminescence of the Ag clusters give them remarkable advantages over larger nanoparticles in applications such as molecular sensing.
104.
Matti Jutila 《Journal of Number Theory》2009,129(11):2853-2878
An analogue of Atkinson's formula is proved for the integral function of Hardy's function Z(t). As an application of this formula, we analyze the behavior of the function F(T) showing that it can be approximated by a simple step-function. It follows that F(T)=O(T1/4) and F(T)=Ω±(T1/4); these results were recently obtained by M.A. Korolev using an alternative method. 相似文献
105.
Alku P Airas M Björkner E Sundberg J 《The Journal of the Acoustical Society of America》2006,120(2):1052-1062
This study presents an approach to visualizing intensity regulation in speech. The method expresses a voice sample in a two-dimensional space using amplitude-domain values extracted from the glottal flow estimated by inverse filtering. The two-dimensional presentation is obtained by expressing a time-domain measure of the glottal pulse, the amplitude quotient (AQ), as a function of the negative peak amplitude of the flow derivative (d(peak)). The regulation of vocal intensity was analyzed with the proposed method from voices varying from extremely soft to very loud with a SPL range of approximately 55 dB. When vocal intensity was increased, the speech samples first showed a rapidly decreasing trend as expressed on the proposed AQ-d(peak) graph. When intensity was further raised, the location of the samples converged toward a horizontal line, the asymptote of a hypothetical hyperbola. This behavior of the AQ-d(peak) graph indicates that the intensity regulation strategy changes from laryngeal to respiratory mechanisms and the method chosen makes it possible to quantify how control mechanisms underlying the regulation of vocal intensity change gradually between the two means. The proposed presentation constitutes an easy-to-implement method to visualize the function of voice production in intensity regulation because the only information needed is the glottal flow wave form estimated by inverse filtering the acoustic speech pressure signal. 相似文献
106.
A novel reaction between 3- and 3,5-substituted pyrazoles with selenium dioxide proceeds with formation of bis(3R,5R′-1H-pyrazol-4-yl)selenides in high yield. On this basis, an efficient one-pot synthetic procedure has been developed. In the case of the unsubstituted pyrazole a selenonium compound has been obtained. The identity and structure of the isolated selenium derivatives have been confirmed by spectral methods and their molecular structures investigated by X-ray analysis. 相似文献
107.
Possible ways for manipulating carbon nanotubes (CNTs) with cyclic supermolecules are studied using density functional theory. Electronic structure calculations with structure optimizations have been performed for the (4,4) and (8,0) single-walled carbon nanotubes (SWNTs) complexed with crown ethers as well as for the (4,0) SWNT with beta-cyclodextrin. A slight polarization of charge in both the nanotube and the supermolecule is observed upon rotaxane complexation, but the interaction is mainly repulsive, and the systems stay 2.8-3.5 A apart. The supermolecule does not affect the electronic band structure of the nanotube significantly within such a configuration. The situation differs noticeably for chemically cross-linked SWNTs and crown ethers, where a peak arises at the Fermi energy in the density of states. As a result, the band gap of semiconducting CNT(8,0) (0.5 eV) vanishes, and a new conduction channel opens for the metallic CNT(4,4). 相似文献
108.
Vadim I. Ponomarenko Dmitrii V. Krupenya Elena V. Grachova Vladimir A. Gindin Stanislav I. Selivanov Igor O. Koshevoy Sergey P. Tunik Prof. Dr. Matti Haukka Jouni Pursiainen Päivi Pirilä 《无机化学与普通化学杂志》2009,635(15):2515-2526
A novel chiral phosphane (S)‐2‐(4‐isopropyl‐2‐oxazoline‐2‐yl)phenyl‐di‐N‐pyrrolylphosphane (S‐PyrPOx) based on asymmetric oxazoline ring has been prepared and characterised. Reaction of this ligand and its phenyl‐substituted analogue (S‐PhPOx) with H4Ru4(CO)12 and H3RhOs3(CO)12 gave substituted derivatives H4Ru4(CO)10(1,1‐PhPOx) ( 2 ), H4Ru4(CO)10(1,1‐PyrPOx) ( 3 ), and H3RhOs3(CO)10(1,1‐PyrPOx) ( 4 ), which were structurally characterised by X‐ray crystallography in solid state and by a variety of multinuclear NMR spectroscopic measurements in solution. In all studied clusters the coordinated ligands form five‐membered chelate rings through phosphorus and nitrogen atoms of oxazoline moiety to afford a novel chiral center associated with the substituted metal atom. The substitution reactions demonstrate extremely high stereoselectivity, which results in formation of only one diastereomer in all three cases to give S,S isomer in 2 and S,R isomer in 3 and 4 . 相似文献
109.
In this paper, two identities involving a function defined by the complete elliptic integrals of the first and second kinds are proved. Some functional inequalities and elementary estimates for this function are also derived from the properties of monotonicity and convexity of this function. As applications, some functional inequalities and the growth of the exterior modulus of a rectangle are studied. 相似文献
110.
Suomi J Sirén H Jussila M Wiedmer SK Riekkola ML 《Analytical and bioanalytical chemistry》2003,376(6):884-889
The iridoid glycosides, methyl catalpol, asperuloside, verbenalin, cinnamoyl catalpol, catalpol and aucubin, were studied from both larvae and adults of butterfly Melitaea cinxia. Special emphasis in the study was put on finding a correlation between the iridoid glycoside content in butterflies and plants. An optimised partial filling micellar electrokinetic capillary chromatographic–electrospray ionisation mass spectrometric (PF-MECC-ESI-MS) method was employed for the separation and identification of the six iridoid glycosides. In this work, the isolation and determination of catalpol and aucubin from extracts of both larvae and adults of Melitaea cinxia butterflies is demonstrated. The PF-MECC-ESI-MS method, using the [M+Na]+, [M+Li]+ and/or [M+NH4]+ adducts in ESI-MS, was used for quantification of aucubin and catalpol in the insects. In addition, the identification of all analytes was attempted by direct infusion MS/MS analysis. LOQ values for the iridoid glycosides varied between 10 mg/l (for verbenalin) to 50 mg/l (for catalpol and aucubin) corresponding to 0.1% of the sample´s dry mass. A correlation was noticed between the concentrations of iridoid glycosides in plants and the concentrations in larvae feeding on them. 相似文献