排序方式: 共有49条查询结果,搜索用时 15 毫秒
31.
I. Hiltunen J. Lehtonen R. Mikkonen A. Stenvall 《Physica C: Superconductivity and its Applications》2009,469(22):1987-1990
Superconducting wire characterization can fail owing to many reasons. For example, unintentional sample heating may distort voltage–current-data, i.e. decrease the critical current and increase the n-value. This occurs rarely if a sample is immersed into liquid cryogen, but in conduction cooled measurements, constant sample temperature is difficult to achieve. Ohmic losses are generated at current contacts as well as inside the sample even at subcritical currents. Most of these losses can be extracted using a well designed sample holder, but in any case, significant amount of heat is generated rapidly when critical current is approached and overstepped, especially if n-value is low. Then, heat has no time to conduct away, and thus, the sample will warm up distorting the measurement. In this paper, we present a computational post-processing method to reduce the effect of heating on measured voltage–current characteristics. Simulations are performed for a Bi-2223/Ag tape, but the model can be applied to any other superconductor as well. 相似文献
32.
Svedström U Vuorela H Kostiainen R Laakso I Hiltunen R 《Journal of chromatography. A》2006,1112(1-2):103-111
Polymeric procyanidins, phenolic carboxylic acids and flavonoids of hawthorn (Crataegus laevigata) were fractionated prior to HPLC analysis using column chromatography and solid-phase extraction (SPE). The flavonoid fraction also contained (-)-epicatechin. The three groups of phenolics, each with clearly different UV spectra, were examined by means of high-performance liquid chromatography-diode array detection (HPLC-DAD) analysis. The average repeatability of the method (RSD) was in the range of 8-13% for chlorogenic acid, (-)-epicatechin and hyperoside. The polymeric procyanidins of hawthorn flowers consisted mainly of (-)-epicatechin subunits, and their mean degree of polymerization (DP) was 22.2. The HPLC methods developed can be used for the qualitative and quantitative analysis of different phenolic compounds in hawthorn plant material and their extracts. 相似文献
33.
Identification of bupropion urinary metabolites by liquid chromatography/mass spectrometry 总被引:1,自引:0,他引:1
Petsalo A Turpeinen M Tolonen A 《Rapid communications in mass spectrometry : RCM》2007,21(16):2547-2554
Human urinary metabolism of the antidepressant bupropion was studied using liquid chromatography/time-of-flight mass spectrometry (LC/TOFMS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). A total of 20 metabolites were detected and identified. The phase I metabolism included formation of morpholinohydroxybupropion, threo- and erythrohydrobupropion, aromatic hydroxylation, butyl group hydroxylation with ketone hydrogenation and dihydroxylation. These metabolites were detected either as the free form or as glucuronide and/or sulphate conjugates. In addition also m-chlorohippuric acid was detected. Of the phase I metabolites, a dihydroxylation to the aromatic ring and to the methyl group in the middle of the substrate molecule was reported here for the first time, as well as eight of the glucuronide conjugates (to hydroxy, dihydroxy, hydroxy and hydrogenation metabolites) and three of the sulphate conjugates (to aromatic hydroxy and hydroxy and hydrogenation metabolites). 相似文献
34.
Tolonen A Petsalo A Turpeinen M Uusitalo J Pelkonen O 《Journal of mass spectrometry : JMS》2007,42(7):960-966
A sensitive and rugged LC/MSMS method was developed for a comprehensive in vitro metabolic interaction screening assay with N-in-1 approach reported earlier. A cocktail consisting of ten cytochrome P450 (CYP)-selective probe substrates with known kinetic, metabolic and interaction properties in vivo was incubated in a pool of human liver microsomes, and metabolites of melatonin (CYP1A2), coumarin (CYP2A6), bupropion (CYP2B6), amodiaquine (CYP2C8) tolbutamide (CYP2C9), omeprazole (CYP2C19 and CYP3A4), dextromethorphan (CYP2D6), chlorzoxazone (CYP2E1), midazolam (CYP3A4) and testosterone (CYP3A4) were simultaneously analysed with a single LC/MSMS run. Altogether, 13 metabolites and internal standard phenacetin were analysed in multiple reaction mode. Polarity switching mode was utilized to acquire negative ion mode electrospray data for hydroxychlorzoxazone and positive ionization data for the rest of the analytes. Fast gradient elution was applied, giving total injection cycle of 8 min. The method was modified for two different LC/MSMS systems, and was validated for linear range, detection limit, accuracy and precision for each metabolite. In addition, cocktail inhibition system was further tested using monoclonal anti-CYP antibodies as inhibitors for each probe reaction. 相似文献
35.
Cross‐Linked Proteins with Gold Nanoclusters: A Dual‐Purpose pH‐Responsive Material for Controllable Cell Imaging and Antibiotic Delivery
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Pengchang Liu Hui Wang J. Kalervo Hiltunen Zhijun Chen Jiacong Shen 《Particle & Particle Systems Characterization》2015,32(7):749-755
This report describes the development of a facile method for the synthesis of cross‐linked proteins with gold nanoclusters (CP‐GNC). The synthesis reaction is completed within 15 min at 97 °C. The synthesized CP‐GNC are characterized by using UV–vis absorption, fluorescence, X‐ray photoelectron spectroscopy, and transmission electron microscopy. CP‐GNC are approximately 100 nm in diameter and 700 nm in length, whereas AuNCs within the nanorods are approximately 6 nm in size. These materials are highly fluorescent with quantum yield of 7.2% and can be absorbed onto and release from bacterial cells in a pH‐dependent and reversible manner. The recent data show that CP‐GNC can be a useful, new tool with potential applications in fluorescent cell imaging and antibiotic targeting. 相似文献
36.
Phosphorylation as a posttranslational protein modification is a common subject of proteomic studies, but phosphorylation in mitochondria is still poorly investigated. The study presented here applied 2‐DE to characterize phosphorylation in the yeast mitochondrial proteome and identified 59 spots corresponding to 34 phosphorylated mitochondrial or mitochondria‐associated proteins. Most of these proteins presented putative substrates of mitogen‐activated protein and target of rapamycin kinases, cAMP‐dependent protein kinase, cyclin‐dependent kinases and Snf1p suggesting them as key players in the phosphorylation of mitochondrial or mitochondria‐associated proteins. The dynamic behaviour of the phosphoproteome under a major metabolic change, the shift from fermentation to respiration (diauxic shift), was further studied. Eight proteins (Ald4p, Eft1p/2p, Eno1p, Eno2p, Om14p, Pda1p, Qcr2p, Sdh1p) had growth dependent changes in their phosphorylation, indicating a role of phosphorylation‐dependent regulation of translation, metabolic pathways (e.g. glucose fermentation, tricarboxylic acid cycle, pyruvate dehydrogenase and its bypass) and respiratory chain. 相似文献
37.
38.
B. Ponsard J. Hiltunen P. Penttilla H. Vera Ruiz A. L. Beets S. Mirzadeh F. F. Knapp Jr. 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(1):169-174
The rapidly increasing therapeutic applications of 188Re in nuclear medicine, oncology and interventional cardiology require routine production of large, multi-Curie levels of the 188W parent. The capability and effective coordination of back-up production sites is important to insure that high level 188W/188Re generators are continually available. We have coordinated 188W production at the High Flux Isotope Reactor (HFIR - Oak Ridge, US) with production at the BR2 Reactor (Mol, Belgium) characterized by peak thermal neutron fluxes of 2.51·015 (HFIR) and 1·1015 (BR2) neutrons/cm2·sec, respectively. The long 69-day physical half-life permits receipt of 188W from BR2 within 0.25 T
1/2's, even after the 12-day post irradiation cooling required for 187W decay (T
1/2 = 24 hours). Since 188W production by double neutron capture of enriched 186W is a function of the square of the thermal neutron flux, HFIR production (4-5 Ci 188W/g 186W/cycle) is higher than at the BR2 (1.0-1.1 Ci/g 186W/cycle). However, the specific activity (SA) of BR2-produced 188W is still about 0.8-0.9 Ci/g after processing at ORNL following shipment from Belgium. This SA is sufficiently high to permit fabrication of 1 Ci generators suitable for clinical use, since simple post elution concentration of the saline bolus (30-50 ml) obtained from the generator can provide samples with high specific volume (1 ml volume). The time periods from reactor push in Mol and completion of processing, fabrication and shipment of generators from Oak Ridge have been 19-21 days. Six campaigns have been successfully completed since 1998, with processed levels of 188W in Oak Ridge from 8-26 Curies/campaign. 188W has been provided to MAP Medical technologies Oy (Tikkakoski, Finland) for fabrication and distribution of generators for use at IAEA-supported research projects in developing countries. We have thus established and demonstrated an effective collaboration between the Studiecentrum voor Kernenergie-Centre d'Etude de l'Energie Nucléaire (SCK·CEN) and ORNL for back-up production of 188W. This collaboration continues to be especially helpful during periods when interruption of HFIR operation is necessary for maintenance and upgrades. 相似文献
39.
Pia Vuorela Eeva-Liisa Rahko Raimo Hiltunen Heikki Vuorela 《Journal of chromatography. A》1994,670(1-2):191-198
The retention behaviour of fifteen closely related coumarins in normal-phase overpressured layer chromatography (OPLC) was studied with the aim of comparing the retentions with those in normal-phase thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) when optimization of the mobile phase was carried out according to the PRISMA system. The mobile phase optimization was carried out on TLC plates in unsaturated chambers. The resulting mobile phases were transposed to off-line, non-equilibrated OPLC and further to HPLC. The retention in TLC was measured at 37 selectivity points and in OPLC and HPLC at 13 points. Capacity factors (k′) and separation factors () were calculated in order to study the retention behaviour in the different systems. Two- and three-dimensional evaluations of k′ against selectivity points showed similar retention behaviours for the coumarins in TLC, OPLC and HPLC. The values for TLC, OPLC and HPLC showed similar patterns in the three-dimensional evaluations. The retention behaviour at different solvent strengths was also examined. According to quadratic regression, k′ showed a dependence on the change in solvent strength. OPLC, which can be considered as a “planar column” technique, and TLC are closely related methods, whereas HPLC shows a different behaviour in the elution process with regard to solvent strength. 相似文献
40.
Dr. Maning Liu Hannu Pasanen Dr. Harri Ali-Löytty Dr. Arto Hiltunen Dr. Kimmo Lahtonen Syeda Qudsia Dr. Jan-Henrik Smått Prof. Mika Valden Prof. Nikolai V. Tkachenko Assoc. Prof. Paola Vivo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22301-22309
Colloidal lead-free perovskite nanocrystals have recently received extensive attention because of their facile synthesis, the outstanding size-tunable optoelectronic properties, and less or no toxicity in their commercial applications. Tin (Sn) has so far led to the most efficient lead-free solar cells, yet showing highly unstable characteristics in ambient conditions. Here, we propose the synthesis of all-inorganic mixture Sn-Ge perovskite nanocrystals, demonstrating the role of Ge2+ in stabilizing Sn2+ cation while enhancing the optical and photophysical properties. The partial replacement of Sn atoms by Ge atoms in the nanostructures effectively fills the high density of Sn vacancies, reducing the surface traps and leading to a longer excitonic lifetime and increased photoluminescence quantum yield. The resultant Sn-Ge nanocrystals-based devices show the highest efficiency of 4.9 %, enhanced by nearly 60 % compared to that of pure Sn nanocrystals-based devices. 相似文献