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1.
Minna GünesÛ Jussi Valkonen 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(9):i119-i120
Caesium tetrasilver dizinc nonathiocyanate, Cs[Ag4Zn2(SCN)9], forms a continuous structure, where the Ag atoms and the S atoms of the thiocyanate groups form chains which run along [101]. These chains are bonded together through the Cs and Zn atoms. It is not possible to distinguish between space groups P1 and P, but, if the latter space group is correct, the structure contains a thiocyanate group disordered across a centre of inversion. The structure is described in space group P, in which the Cs atom also lies on a centre of inversion. 相似文献
2.
The self-organizing map (a neural network) was applied to the spectral pattern recognition of voice quality in 34 subjects: 15 patients operated on because of insufficient glottal closure and 19 subjects not treated for voice disorders. The voice samples, segments of sustained /a/, were perceptually rated by six experts. A self-organized acoustic feature map was first computed from tokens of /a/ and then used for the analysis of the samples. The locations of the samples on the map were determined and the distances from a normal reference were compared with the perceptual ratings. The map locations corresponded to the degree of audible disorder: the samples judged as normal were overlapping or close to the normal reference, whereas the samples judged as dysphonie were located further away from it. The comparison of pre- and postoperative samples of the patients showed that the perceived improvement of voice quality was also detected by the map. 相似文献
3.
4.
The investigation of europium(III) sulphate hydrate and samarium(III) sulphate hydrate was performed by thermal analysis (TG-DTG) and simultaneous infrared evolved gas analysis-Fourier transformed infrared (EGA-FTIR) spectroscopy. The TG, DTG and DTA curves were recorded at the 25–1400 °C in the dynamic air atmosphere by TG/DTA analyser. The infrared evolved gas analysis was obtained on the FTIR spectrometer. Eu2(SO4)3·nH2O (n = 3.97) and Sm2(SO4)3·nH2O (n = 8.11) were analysed, the dehydration and decomposition steps were investigated and the water content was calculated. The formation of different oxysulphates was studied.
The trace rare earth elements in Eu and Sm sulphates were determined by ICP-MS. The concentration of trace Eu, Sm, La, Gd, Y and Ce ranged from 3.9 × 10−6 to 1.5 × 10−4% (m/m). 相似文献
5.
The importance of natural antioxidants principally relates to their health-promoting properties. The discovery of new sources of established compounds or more potent compounds is a costly exercise and any technique capable of aiding this procedure would be highly significant. An approach combining chromatographic separation, component analysis and post-column identification of free radical scavenging has been reported. However, its effectiveness is dependent upon various factors and the number of samples analyzed without operator intervention is restricted. A more applicable technique using a 10% to 100% methanol with 2% acetic acid mobile phase and a citric acid-sodium citrate buffered methanolic 1,1-diphenyl-2-picrylhydrazyl free radical reagent is presented, whereby free radical scavengers can be detected within crude extracts of variable polarity without special considerations. As an illustration, acetone, 70% (aq.) methanol and acetonitrile-soluble extracts were prepared from sage (Salvia officinalis L.) for extraction of polar and non-polar radical scavengers and analyzed. Radical scavenging components were identified as carnosic, caffeic and rosmarinic acids and luteolin-7-O-glycoside. Others radical scavengers were tentatively identified as benzoic and hydroxycinnamic acid derivatives, flavonoids and diterpenoids. Through the application of this technique, carnosic acid and rosmarinic acid were identified as the principal free radical scavengers. 相似文献
6.
A monolithic C18-bonded silica rod column (Merck Chromolith) was compared to particle-based C18 and amide C16 sorbents in the HPLC separation of eight microcystins and nodularin-R. Two gradient mobile phases of aqueous trifluoroacetic acid modified with acetonitrile or methanol, different flow-rates and different gradient lengths were tested. The performance of the Chromolith column measured as the resolution of some microcystin pairs, the selectivity, efficiency (peak width) and peak asymmetry equalled, or exceeded, the performance of traditional particle-based columns. The Chromolith column allowed a shortening of the total analysis time to 4.3 min with a flow-rate 4 ml min(-1). 相似文献
7.
Near infrared reflectance spectroscopy for the fast identification of PVC-based films 总被引:2,自引:0,他引:2
Laasonen M Rantanen J Harmia-Pulkkinen T Michiels E Hiltunen R Räsänen M Vuorela H 《The Analyst》2001,126(7):1122-1128
Near infrared (NIR) reflectance spectroscopy was used to develop a non-destructive and rapid qualitative method for the analysis of plastic films used by the pharmaceutical industry for blistering. Three types of films were investigated: 250 microm PVC [poly(vinyl chloride)] films, 250 microm PVC films coated with 40 g m(-2) of PVDC [poly(vinylidene dichloride)] and 250 microm PVC films coated with 5 g m(-2) of TE (Thermoelast) and 90 g m(-2) of PVDC. Three analyses were carried out using different pre-treatment options and a PLS (partial least squares) algorithm. Each analysis was aimed at identifying one type of film and rejecting all types of false sample (different thickness, colour or layer). True and false samples from four plastics manufacturers were included in the calibration sets in order to obtain robust methods that were suitable regardless of the supplier. Specificity was demonstrated by testing validation sets against the methods. The tests showed 0% of type I (false negative identification) and 1% of type II errors (false positive identification) for the PVC method, 13 and 3%, respectively, for the PVC-PVDC method and no error for the PVC-TE-PVDC method. Type II errors, mostly due to the slight sensitivity of the methods to film thickness, are easily corrected by simple thickness measurements. This study demonstrates that NIR spectroscopy is an excellent tool for the identification of PVC-based films. The three methods can be used by the pharmaceutical industry or plastics manufacturers for the quality control of films used in blister packaging. 相似文献
8.
Sara Busi Jarmo Ropponen Jussi Valkonen Kari Rissanen 《Journal of solid state chemistry》2004,177(10):3757-3767
Series of new aromatic R2R′2N+Br− (R=benzyl, 4-methylbenzyl, 2-phenylethyl, 3-phenylpropyl; R′=ethyl, methyl, isopropyl) or RR′2NH+Br−-type (R=benzyl, R′=isopropyl) quaternary ammonium bromides were prepared by using novel synthetic route in which a formamide (N,N-diethylformamide, N,N-dimethylformamide, N,N-diisopropylformamide) is treated with aralkyl halide in presence of a weak base. The compounds were characterized by 1H-NMR and 13C-NMR spectroscopy and mass spectrometry. Structures of the crystalline compounds were determined by X-ray single crystal diffraction, and in addition the powder diffraction method was used to study the structural similarities between the single crystal and microcrystalline bulk material. Three of the compounds crystallized in monoclinic, two in orthorhombic and one in triclinic crystal system, showing ion pairs, which are interconnected by weak hydrogen bonds and weak π-π interactions between the phenyl rings. Three of the compounds appeared as viscous oil or waxes. Finally, TG/DTA and DSC methods were used to analyze thermal properties of the prepared compounds. The lowest melting points were obtained for diethyldi-(2-phenylethyl)ammonium bromide (122.2 °C) and for diethyldi-(3-phenylpropyl)-ammonium bromide (109.1 °C). In general, decomposition of the compounds started at 170-190 °C without identifiable cleavages, thus liquid ranges of 30-70 °C were observed for some of the compounds. 相似文献
9.
If there arek
++ eventually functions fromk
+ intok or if there arek
++ eventually different functions fromk
+ then uniform ultrafilters onk
+ are (k, k
+)-regular.
The research of the first author was supported in part by NSF grant.
The second author is a Miller’s Fellow at the University of California in Berkeley. 相似文献
10.
Jussi Laitila Pekka J. Nieminen Eero Saksman Hans-Olav Tylli 《Complex Analysis and Operator Theory》2013,7(1):163-181
Any analytic map φ of the unit disc ${\mathbb{D}}$ into itself induces a composition operator C φ on BMOA, mapping ${f \mapsto f \circ \varphi}$ , where BMOA is the Banach space of analytic functions ${f\colon \mathbb{D} \to \mathbb{C}}$ whose boundary values have bounded mean oscillation on the unit circle. We show that C φ is weakly compact on BMOA precisely when it is compact on BMOA, thus solving a question initially posed by Tjani and by Bourdon, Cima and Matheson in the special case of VMOA. As a crucial step of our argument we simplify the compactness criterion due to Smith for C φ on BMOA and show that his condition on the Nevanlinna counting function alone characterizes compactness. Additional equivalent compactness criteria are established. Furthermore, we prove the unexpected result that compactness of C φ on VMOA implies compactness even from the Bloch space into VMOA. 相似文献