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901.
The effects of media properties including buffers, acidity, solvents and surfactant on horseradish peroxidase-catalyzed fluorogenic reaction were investigated. The results showed that the so-called non-fluorescent hydrogen donors were in fact fluorescent. There existed an acid—base equilibrium in the fluorescent dimer product. For p -hydroxyphenylpropionic acid, a pKa value of 8.0 for the product was obtained from its titration curve. The product fluorescence increased with higher pH, however, a longer time was needed to reach the reaction equilibrium due to the pH mismatch problem. Cationic micelles cetyltrimethylammonium bromide and cetyltrimethylammonium chloride could reduce the pH mismatch and offered a way to further increase the determination sensitivity. Finally, a micelle-enhanced flow-injection analysis of horseradish peroxidase is suggested. 相似文献
902.
For the Kantorovich polynomial approximationK n (f, t), 1<p≤∞, we prove that, for somem, This equivalence includes a strong converse inequality of type B. 相似文献
903.
The work of the Brussels-Austin groups on irreversibility over the last years has shown that Quantum Large Poincaré systems with diagonal singularity lead to an extension of the conventional formulation of dynamics at the level of mixtures which is manifestly time asymmetric. States with diagonal singularity acquire meaning as linear fractionals over the involutive Banach algebra of operators with diagonal singularity. We show in this paper that the logic of quantum systems with diagonal singularity is not the conventional logic of Hilbert space, because only finite combinations of prepositions are allowed. 相似文献
904.
57Fe Mössbauer study of amorphous and nanocrystalline Fe73.5Nb3Cu1Si13.5B9 after neutron irradiation
57Fe Mössbauer spectroscopy is used to study neutron irradiation induced changes in the short-range order of Fe73.5Nb3Cu1Si13.5B9 alloy. The samples are investigated in both amorphous and nanocrystalline states. Neutron irradiation leads to an increase of the standard deviation of a hyperfine field distribution (HFD), implying rearrangement of the atoms towards disordering. Simultaneously, changes in the average value of the hyperfine field and a net magnetic moment position occur as a consequence of a spin reorientation, atom mixing and microscopic stress centres which are introduced by neutron irradiation. 相似文献
905.
A. Bernasconi M. Mombelli Z. Fisk H. R. Ott 《Zeitschrift für Physik B Condensed Matter》1994,94(4):423-429
The electrical resistivity (T) and the thermal conductivity (T) have been measured for UCu5 in the temperature range between 0.02 and 20 K. Two distinct anomalies in (T) are due to previously established phase transitions at approximately 15 and 1 K, respectively. They indicate considerable changes in the electronic structure of this compound, implying sizeable truncations of the Fermi surface with decreasing temperature at both transitions. In almost the entire covered temperature range the thermal conductivity is dominated by phonon contributions. Its temperature dependence is fairly well reproduced by a calculation considering phonon scattering by electrons and by point defects. At very low temperatures, asT approaches 0 K, the Wiedemann-Franz law
e
L
0
T, where
e
is the electronic part of (T) andL
0 is the Lorenz number, is almost perfectly fulfilled. 相似文献
906.
Investigations of the superradiating cascade of sodium vapour 4P-4S-3P
1 = 2.21 µm and
2=1.14 µm) arising on the leading edge of the exciting laser pulse were carried out. The dependences of the actual delay time
D
of the
1 pulse on the population rise time of the laser-excited 4P state were measured and compared with those calculated following the existing theoretical model. The dependence of the actual delay time
D
on the inverse density of excited atoms 1/N* is also presented. Analysis of this dependence revealed the influence of the Doppler dephasing and of the second,
2, transition on the formation of the
1 superradiance. 相似文献
907.
Mn2(CO)10 was photolysed in the gas phase by the XeCl-excimer laser with fluence in the range 25–300 mJ/cm2 and a dye laser. The UV/VIS emission of the products was probed on a nanosecond time scale. The emission from excited states of metal atoms was detected only. The Mn atoms are predominantly formed in their ground statea
6
S
2 1/2. The absorption of one photon and the subsequent relaxation process leads to the formation ofz
6
P
J
0
(J = 11/2, 21/2, 31/2) states and emission of photons at a wavelength of 403 nm. The formation of the excited statese
8
D
5 1/2,z
6
F
4 1/2
0
ande
6
D
4 1/2 and the subsequent emission observed at wavelengths of 357, 383 and 446 nm requires the absorption of two photons by the ground-state Mn atoms. In addition, transition from thea
6
D
j (J = 11/2, 21/2) lower states were observed in the wavelength-resolved Laser-Induced Fluorescence (LIF) spectra. 相似文献
908.
Thermal and mechanical coupling between successive pulses in KrF-excimer-laser ablation of polyimide
Z. Ball T. Feurer D. L. Callahan R. Sauerbrey 《Applied Physics A: Materials Science & Processing》1996,62(3):203-211
Multiple-shot effects in laser processing and ablation of polyimide are examined and are found to be the dominant phenomena for processes involving several hundreds or thousands of pulses. For fluences less than 260 mJ/cm2, it was found that it is impossible to cut through 75 m polyimide foils for an arbitrarily large number of excimer pulses even though this fluence is more than ten times the single-shot ablation threshold. The halt in etching is due to the formation, over a number of shots, of a robust carbon matrix with a deep surface roughness which is also responsible for laser-induced electrical conductivity. The effect of thermal coupling between successive shots is shown to be a dominant factor in determining the electrical properties of the carbon layer. Differences in electrical conductivity of up to 12 orders of magnitude were found for only small differences in repetition rate. Transmission electron microscopy revealed the changes in microstructure responsible for the dramatic differences in electrical properties. 相似文献
909.
LetW be a Wiener process of dimensiond3, starting from 0, and letX(t) be the total time spent byW in the ball centered at 0 with radiust. We give an affirmative answer to a conjecture of Taylor and Tricot(16) on the tail distribution ofX(t). Lévy's lower functions ofX(t) are characterized by an integral test. 相似文献
910.
Z. Shi 《Journal of Theoretical Probability》1996,9(4):915-929
LetR be the radial part of ad-dimensional Wiener process, starting from 0. In this paper, small ball probabilities are evaluated for sup0<11(t
–p
R(t)) and sup
t
0(e
–1
R(t)), withp[0, 1/2]. Chung's law of the iterated logarithm is established for the supremum of the local times of a two-dimensional Bessel process. 相似文献