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191.
The Banach spaces with the bounded compact approximation property are characterized by the completeness of measures of noncompactness. Applications to the theory of semi-Fredholm operators and to the algebraic properties of their canonical images in the Calkin algebra are discussed. 相似文献
192.
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194.
Anne-Maria Laukkanen Pivi Lindholm Erkki Vilkman Kari Haataja Paavo Alku 《Journal of voice》1996,10(1):67-77
The voiced bilabial fricative /β:/ has been used as a vocal exercise. The present study investigated the effects of the exercise on voice production and voice source. This study compared vowel phonation on the syllable /a:p/ with the production of the exercise and vowel phonation before and immediately after the exercise. The methods were (a) dual-channel electroglottography, from which the vertical laryngeal position was derived, (b) electromyography using surface electrodes, and (c) inverse filtering of the acoustic signal to obtain an estimate of the voice source. In the production of /β:/ as compared with vowel phonation in most of the cases, the vertical laryngeal position seemed to be higher, the muscular activity of the larynx lower, and the slope of the voice source spectrum steeper. In vowel phonation after the exercise, the muscular activity seemed to be lower in most cases, although the voice source remained unchanged. This seems to indicate improved vocal economy. 相似文献
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197.
The increase in the UV exposure of the Finnish population associated with the combined effects of ozone depletion and snow reflection was studied with the aid of theoretical calculations based on Green's clear sky UV model. A simple formula was utilized to transform horizontal irradiances to vertical irradiances averaged over 360 azimuth angle. The model was verified with spectral and broadband measurements. The difference between the theoretical and measured UV radiation falling to horizontal surfaces was in most cases less than ±10%, and the additional error to theoretical vertical irradiances was less than ± 10%. The calculations show that the annual horizontal doses in Helsinki (60.2°N, 25°E) are about 35% higher than in Saariselkä (68.4°N, 27.5°E), but the difference is only 16% for vertical doses owing to the stronger contribution to vertical (facial) surfaces of the reflection of UV from snow. At Saariselkä, the maximum vertical irradiance at the end of April approaches the midsummer values. The ozone depletions up to 40% in February and March 1992 had no significant effect on the annual doses because the total ozone returned to normal before the UV increased to biologically significant levels. 相似文献
198.
Area distortion of quasiconformal mappings 总被引:14,自引:0,他引:14
Kari Astala 《Acta Mathematica》1994,173(1):37-60
199.
Cametti M Nissinen M Dalla Cort A Mandolini L Rissanen K 《Journal of the American Chemical Society》2005,127(11):3831-3837
Hard anions have long been known to bind strongly to the uranium of uranyl-salophen complexes. Upon functionalization of the salophen framework with one or two benzyloxy substituents, efficient ditopic receptors for alkali metal ions are obtained. The solid-state structures of complexes formed by the two-armed receptor 1 with CsF and with the chlorides of K+, Rb+, and Cs+ reported here reveal the existence of dimeric supramolecular assemblies in which two receptor units assemble into capsules fully enclosing (MX)2 ion quartets. In addition to the strong coordinative binding of the anion to the uranyl center and to electrostatic cation-anion interactions, stabilizing interactions arise from coordination of each cation to six oxygens, three from each receptor, and most importantly, to two aromatic sidearms belonging to different receptors. There are marked differences in organization at the supramolecular level in the CsCl complex of the one-armed receptor 3, in that four uranyl-salophen units instead of two are assembled in a capsule-like arrangement housing a (CsCl)2 ion quartet. However, both receptors achieve the common goal of having each metal cation in close contact with carbon atoms of two aromatic rings. 1H NMR data provide strong evidence that cation-pi(arene) interactions with the sidearms participate in binding also in solution. 相似文献
200.
Ngong K. Beyeh Domonkos Fehér Minna Luostarinen Christoph A. Schalley Kari Rissanen 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(3-4):381-394
The syntheses and characterization of new chiral tetrabenzoxazine and tetrakis-(dialkylaminomethyl) resorcinarenes can be
achieved through the reaction of resorcinarene with chiral amines and formaldehyde. In order to examine their host–guest chemistry,
chiral quaternary ammonium guests were synthesized by methylation of different amines and amino acid methyl esters through
a reductive methylation followed by addition of methyl iodide. Subsequent anion exchange of the iodide against tetraphenylborate
helps to improve solubility of the salts in organic solvents. After characterization in solution, mass spectrometry is used
to examine the resorcinarenes’ chemistry in the gas phase. Interesting implications of the fragmentation behavior for their
solution phase chemistry arise, for which a first example is presented. Ammonium ion binding is indicated by mass spectrometry.
Nevertheless, chiral recognition between the chiral hosts and pseudoracemic 1:1 mixtures of appropriately deuterium-labeled
chiral guest cations is however not observed. 相似文献