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121.
122.
123.
T. Ruskov I. Spirov T. Tomov O. Nikolov S. Asenov L. Dimitrov A. Kirov V. E. Hadji 《Hyperfine Interactions》1986,29(1-4):1587-1590
Conclusions The piezoceramic vibrators have the advantages of simplicity and stability of operation over those with quartz plates. However,
the former show mechanical hysteresis causing distortions of the motion. This effect can be reduced by an appropriate choice
of the ceramic cylinder, but it is not completely avoidable. That is why these distortions should be taken into account or
quartz vibrators should be used in precision measurements.
The displacement piezoceramic sensor described here gives new methodological opportunities in assembling and preliminary testing
of the vibrators to find the optimum of construction and operating conditions as well as for continuous motion control during
spectrum accumulation and eventual corrections of the motion distortions. 相似文献
124.
Kocherginsky NM Lvovich VF 《Langmuir : the ACS journal of surfaces and colloids》2010,26(23):18209-18218
Earlier we have shown that many important properties of ionic aqueous channels in biological membranes can be imitated using simple biomimetic membranes. These membranes are composed of mixed cellulose ester-based filters, impregnated with isopropyl myristate or other esters of fatty acids, and can be used for high-throughput drug screening. If the membrane separates two aqueous solutions, combination of relatively hydrophilic polymer support with immobilized carboxylic groups results in the formation of thin aqueous layers covering inner surface of the pores, while the pore volume is filled by lipid-like substances. Because of these aqueous layers biomimetic membranes even without proteins have a cation/anion ion selectivity and specific (per unit of thickness) electrical properties, which are similar to typical properties of biological membranes. Here we describe frequency-dependent impedance of the isopropyl myristate-impregnated biomimetic membranes in the 4-electrode arrangement and present the results as Bode and Nyquist diagrams. When the membranes are placed in deionized water, it is possible to observe three different dispersion processes in the frequency range 0.1 Hz to 30 kHz. Only one dispersion is observed in 5 mM KH(2)PO(4) solution. It is suggested that these three dispersion features are determined by (a) conductivity in aqueous structures/channels, formed near the internal walls of the filter pores at high frequencies, (b) dielectric properties of the whole membrane at medium frequencies, determined by polymer support, aqueous layers and impregnating oil, and, finally, (c) by the processes in hydrated liquid crystal structures formed in pores by impregnating oil in contact with water at low frequencies. 相似文献
125.
Andrew C. Benniston Dr. Graeme Copley Dr. Helge Lemmetyinen Dr. Nikolai V. Tkachenko Dr. 《Chemphyschem》2010,11(8):1685-1692
Two series of geometrically‐related dyads are discussed based on the difluoroborondipyrromethene (Bodipy) unit, and incorporating covalently attached hydroquinone/quinone groups. These units are anchored directly, or via a phenylene spacer, to the Bodipy core at the meso position in one series ( BD‐MHQ , BD‐MQ , BD‐MPHQ , BD‐MPQ ), but for the second series the attachment site is the 2‐position ( BD‐SHQ , BD‐SQ , BD‐SPHQ , BD‐SPQ ). The compounds show various levels of fluorescence depending on the oxidation state of the appended group and the substitution pattern. In non‐polar solvents such as toluene, diethyl ether and dichlorobenzene, the S1 state deactivation of the Bodipy unit in BD‐SPQ and BD‐MPQ is dominated by 1, 3exciplex formation, which has not been reported for Bodipy derivatives so far. In the latter molecule, the decay of the exciplex is divided between population of the Bodipy triplet state (13 %–21 %) and ground state reformation. This partitioning is not seen for the side‐on substituted derivative, BD‐SPQ , and only ground state reformation is observed following decay of the exciplex. This difference in behavior is explained by the radical‐pair inter‐system‐crossing mechanism, which more effectively operates in BD‐MPQ because of the orthogonality of the donor‐acceptor units. In the more polar solvent CH3CN all the quinone derivatives show fast formation of the charge‐separated state (kCS) followed by slower charge recombination (kCR). The ratio kCS/kCR≤80. 相似文献
126.
Clifford MN Wu W Kirkpatrick J Jaiswal R Kuhnert N 《Rapid communications in mass spectrometry : RCM》2010,24(21):3109-3120
The chlorogenic acids of Gardeniae Fructus used traditionally as a Chinese herbal medicine (zhizi) have been investigated qualitatively by liquid chromatography/multi-stage mass spectrometry (LC/MS(4)). Twenty-nine chlorogenic acids were detected and twenty-five characterised to regioisomer level on the basis of their fragmentation, twenty-four for the first time from this source. Assignment to the level of individual regioisomers was possible for three caffeoylquinic acids, three dicaffeoylquinic acids, three sinapoylquinic acids, four caffeoyl-sinapoylquinic acids, two feruloyl-sinapoylquinic acids, one p-coumaroyl-sinapoylquinic acid, three (3-hydroxy, 3-methyl)glutaroylquinic acids, two (3-hydroxy, 3-methyl)glutaroyl-feruloylquinic acids, one (3-hydroxy, 3-methyl)glutaroyl-dicaffeoylquinic acid, and one (3-hydroxy, 3-methyl)glutaroyl-caffeoyl-feruloylquinic acid. Six (3-hydroxy, 3-methyl)glutaroyl-caffeoylquinic acids were detected and two were tentatively assigned as 3-caffeoyl-4-(3-hydroxy, 3-methyl)glutaroylquinic acid and 3-caffeoyl-5-(3-hydroxy, 3-methyl)glutaroylquinic acid. The (3-hydroxy, 3-methyl)glutaroyl residue modifies the mass spectral fragmentation behavior and elution sequence compared with the chlorogenic acids that contain only a cinnamic acid residue(s). Fourteen of these twenty-nine chlorogenic acids have not previously been reported from any source. 相似文献
127.
Parthey CG Matveev A Alnis J Bernhardt B Beyer A Holzwarth R Maistrou A Pohl R Predehl K Udem T Wilken T Kolachevsky N Abgrall M Rovera D Salomon C Laurent P Hänsch TW 《Physical review letters》2011,107(20):203001
We have measured the 1S-2S transition frequency in atomic hydrogen via two-photon spectroscopy on a 5.8 K atomic beam. We obtain f(1S-2S) = 2,466,061,413,187,035 (10) Hz for the hyperfine centroid, in agreement with, but 3.3 times better than the previous result [M. Fischer et al., Phys. Rev. Lett. 92, 230802 (2004)]. The improvement to a fractional frequency uncertainty of 4.2 × 10(-15) arises mainly from an improved stability of the spectroscopy laser, and a better determination of the main systematic uncertainties, namely, the second order Doppler and ac and dc Stark shifts. The probe laser frequency was phase coherently linked to the mobile cesium fountain clock FOM via a frequency comb. 相似文献
128.
Alexey Pak Matthias Steinhauser Nikolai Zerf 《The European Physical Journal C - Particles and Fields》2011,71(3):1602
We consider the Higgs boson production in the gluon-fusion channel to next-to-next-to-leading order within the Minimal Supersymmetric
Standard Model. In particular, we present analytical results for the matching coefficient of the effective theory and study
its influence on the total production cross section in the limit where the masses of all MSSM particles coincide. For supersymmetric
masses below 500 GeV it is possible to find parameters leading to a significant enhancement of the Standard Model cross section,
the K-factors, however, change only marginally. 相似文献
129.
Nikolai A. Kudryashov Dmitry I. SinelshchikovMaria V. Demina 《Physics letters. A》2011,375(7):1074-1079
The generalized Bretherton equation is studied. The Bäcklund transformations between traveling wave solutions of the generalized Bretherton equation and solutions of polynomial ordinary differential equation are constructed. The classification problem for meromorphic solutions of the latter equation is discussed. Several new families of exact solutions for the generalized Brethenton equation are given. 相似文献
130.
Nikolai Nikolov 《Annali di Matematica Pura ed Applicata》2014,193(6):1595-1605
Estimates for invariant distances of convexifiable, \(\mathbb{C }\) -convexifiable and planar domains are given. 相似文献