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101.
Y Masuo H Wang D Pélaprat Z Q Chi W Rostène 《Chemical & pharmaceutical bulletin》1992,40(9):2520-2524
We have recently demonstrated that [3H]ohmefentanyl, a non-peptidergic opioid ligand which was suggested to cross the blood brain barrier in contrast to other peptidergic opioid ligands, bound not only to mu opioid receptor sites but also to sigma sites. In order to examine whether [3H]ohmefentanyl can be used as a marker for mu sites, we investigated the effects of brain lesions on [3H]ohmefentanyl binding site densities, as compared with [3H][D-Ala2, MePhe4, Gly-ol5]enkephalin ([3H]DAGO), a selective mu ligand. These binding site densities were measured by quantitative autoradiography in the rat striatum and substantia nigra, two brain structures known to contain a high density of mu receptors, following lesions of the nigro-striatal dopaminergic pathway and striatal intrinsic neurons. Following unilateral nigral lesion with 6-hydroxydopamine, [3H]ohmefentanyl binding site densities were decreased in the patches (-35%) and matrix (-20%) of the ipsilateral striatum and in the lesioned substantia nigra pars compacta (-49%). Unilateral striatal lesion with quinolinic acid induced 72%, 61% and 50% decreases in [3H]ohmefentanyl binding in the patches and matrix of the lesioned striatum and in the ipsilateral substantia nigra pars reticulata, respectively. Similar results were obtained in the binding of [3H]DAGO. Indeed, a significant linear correlation was observed between [3H]ohmefentanyl and [3H]DAGO binding site densities. Therefore, mu opioid receptors may be mainly located on intrinsic neurons in the striatum, dopaminergic cell bodies in the substantia nigra pars compacta and nerve terminals of striatal efferents in the substantia nigra pars reticulata.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
102.
Measurements of dipole strengths of chlorophylls in solution are reviewed and correlated. The refractive index dependence is found to be expressible in a simple empirical fashion that does not rely on the concept of vacuum dipole strength. The index dependence in some respects contradicts the dependence expected on the basis of effective field theories. 相似文献
103.
The deposition of PbO2 on platinum and glassy carbon electrodes was investigated experimentally. The comparison of the different behaviour on the two types of electrodes is presented. The effects of variation of temperature, potential, nucleation order and induction time-lags on the electrocrystallisation process are discussed.The present investigations have confirmed that electrocrystallisation of PbO2 occurs through 3-D nucleation and growth on glassy carbon and most probably also on platinum. The data on platinum contains considerable noise from simultaneous chemical processes and is not amenable for analysis in a simple way. The steady state behaviour is unusual because it has generally been assumed that charge transfer is rate determining under most conditions. However, as shown here, if lattice incorporation is slow even at the steady state, it provides a method for separating the activation energies associated with the nucleation and growth rate constants. Finally, the dissolution of PbO2 into the platinum substrate and its implication on transient rates merits more attention. In this context the Pt-PbO2 system is probably not a good choice because of the large contribution of substrate oxidation to the measured transient rates. 相似文献
104.
105.
This paper presents the results of an experimental study of natural convection heat transfer between a horizontal cylindrical envelope and an internal concentric heated square cylinder with two slots. The internal cylinder was a hollow one with horizontal slots on its top and bottom surfaces. The ratio of slot widthS to the side heightH was 0.0612 and 0.3878. The ratio of the envelope inner diameterD
o
to the side heightH was 2.653. Air was used as the working fluid. The range of Ray-leigh number was 1.77×1028.72×106 forS/H=0.0612 and 1.32×1026.25×106 forS/H=0.3878. The results show that there are three different heat transfer regimes in different Ray-leigh number regions, i.e. pure conduction regime, transition regime and convection regime. The average heat transfer results were correlated into two empirical equations. Comparison was made with the non-slotted case. It is found that slots of the internal cylinder can significantly enhance the heat transfer.
Nomenclature C p specific heat at constant pressure, J/(kg·K) - D i diameter of the related circular cylinder whose circumferential area is equal to that of the unslotted square cylinder, m - D o internal diameter of the outer circular envelope, m - F i surface area of the inner two slot cylinder, m - g gravitational acceleration, m/s2 - H distance between the opposite sides of the square cylinder with two slots, m - K eq dimensionless equivalent thermal conductivity - L axial length of the test section, m - m ratio of the area of the unslotted square cylinder surface to that of the slotted square cylinder - P pressure in the enclosure, Pa - Q total power input to the enclosure, W - Q cond radial heat conduction, W - Q conv convective heat transfer, W - Q r radiation heat transfer, W - Q los end heat dissipation, W - R air gas constant, J/(kg·K) - Ra Rayleigh number - S slot width, m - T i wall temperature of the inner cylinder, K - T o wall temperature of the outer envelope, K - T m mean temperature, K - T temperature difference=T i –T o , K - W maximum gap width of the test annuli=(D o –H)/2 for the square case, m Greek symbols 0 black body radiation constant, W/(m2·K4) - s equation system emissivity - air thermal conductivity, W/(m·K) - eq equivalent thermal conductivity, W/(m·K) - air dynamic viscosity, kg/(m·s) This work was supported by the National Natural Science Foundation of China. 相似文献
Experimentelle Untersuchung des Wärmeübergangs bei natürlicher Konvektion zwischen einer horizontalen zylindrischen Außenhülle und einem konzentrischen, beheizten, quadratischen Prisma mit zwei Schlitzen
Zusammenfassung In der Arbeit werden die Ergebnisse einer experimentellen Untersuchung des Wärmeübergangs bei natürlicher Konvektion zwischen einer horizontalen zylindrischen Außenhülle und einem beheizten quadratischen Prisma mit zwei Schlitzen vorgestellt. Das Prisma selbst ist hohl und weist in der oberen und unteren Begrenzungsfläche je einen horizontalen Längsschlitz auf. Das Verhältnis von SchlitzweiteS zu SeitenhöheH beträgt 0,0612 und 0,3878, das des HülleninnendurchmessersD o zur SeitenhöheH beträgt 2,653. Als Arbeitsmedium diente Luft. Die Rayleigh-Zahlen variierten zwischen 1,7·102 und 8,72·106 fürS/H=0,0612 und zwischen 1,32·102 und 6,25·106 fürS/H=0,3878. Die Ergebnisse belegen die Existenz dreier unterschiedlicher Wärmeübergangsregime in den verschiedenen Rayleigh-Zahl-Bereichen, und zwar reiner Leitungsbereich, Übergangsgebiet und Konvektionsbereich. Die Ergebnisse für den Wärmeübergang werden im Vergleich mit jenen für ein Prisma ohne Schlitze durch zwei Korrelationbeziehungen dargestellt. Es zeigt sich, daß durch Anbringung von Schlitzen am Innenprisma der Wärmeübergang wesentlich verstärkt werden kann.
Nomenclature C p specific heat at constant pressure, J/(kg·K) - D i diameter of the related circular cylinder whose circumferential area is equal to that of the unslotted square cylinder, m - D o internal diameter of the outer circular envelope, m - F i surface area of the inner two slot cylinder, m - g gravitational acceleration, m/s2 - H distance between the opposite sides of the square cylinder with two slots, m - K eq dimensionless equivalent thermal conductivity - L axial length of the test section, m - m ratio of the area of the unslotted square cylinder surface to that of the slotted square cylinder - P pressure in the enclosure, Pa - Q total power input to the enclosure, W - Q cond radial heat conduction, W - Q conv convective heat transfer, W - Q r radiation heat transfer, W - Q los end heat dissipation, W - R air gas constant, J/(kg·K) - Ra Rayleigh number - S slot width, m - T i wall temperature of the inner cylinder, K - T o wall temperature of the outer envelope, K - T m mean temperature, K - T temperature difference=T i –T o , K - W maximum gap width of the test annuli=(D o –H)/2 for the square case, m Greek symbols 0 black body radiation constant, W/(m2·K4) - s equation system emissivity - air thermal conductivity, W/(m·K) - eq equivalent thermal conductivity, W/(m·K) - air dynamic viscosity, kg/(m·s) This work was supported by the National Natural Science Foundation of China. 相似文献
106.
K. W. Cheah L. C. Ho J. B. Xia J. Li W. H. Zheng W. R. Zhuang Q. M. Wang 《Applied Physics A: Materials Science & Processing》1995,60(6):601-606
Photoluminescence studies on porous silicon show that there are luminescence centers present in the surface states. By taking photoluminescence spectra of porous silicon with respect to temperature, a distinct peak can be observed in the temperature range 100–150 K. Both linear and nonlinear relationships were observed between excitation laser power and the photoluminescence intensity within this temperature range. In addition, there was a tendency for the photoluminescence peak to red shift at low temperature as well as at low excitation power. This is interpreted as indicating that the lower energy transition becomes dominant at low temperature and excitation power. The presence of these luminescence centers can be explained in terms of porous silicon as a mixture of silicon clusters and wires in which quantum confinement along with surface passivation would cause a mixing of andX band structure between the surface states and the bulk. This mixing would allow the formation of luminescence centers. 相似文献
107.
The limit of detection for the 4,6 dinitro-orthocresol (DNOC) pesticide, including small latex particles as light scattering samples in water as suspending medium, has been determined for the transversal photothermal deflection technique. The results where compared to conventional spectrophotometry. In the photothermal deflection experiments performed with a continuous Ar+-excitation beam (=363.8 nm) a LOD of 0.8 g/l is achieved for the DNOC in water.Awarded poster prize 相似文献
108.
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
109.
X. H. Yan J. R. Yan J. Q. You Y. P. Mei 《Zeitschrift für Physik B Condensed Matter》1994,94(4):439-446
Electronic properties of a general class of one-dimensional two-tile systems are calculated exactly. The systems containing periodic crystals, generalized Fibonacci quasicrystals, generalized Thue-Morse aperiodic lattices and even other two-tile aperiodic lattices, can be divided into two different families which are constructed by the inflation rules: {A, B}{A
m11
B
m12,A
m21
B
m22} and {A, B}{A
n11
B
n12,B
n21
A
n22}, respectively. As typical examples, global spectra of bands and density of states in some two-tile aperiodic systems are numerically calculated. Some interesting properties are obtained. 相似文献
110.
P. J. M. Peters M. Trentelman Q. C. Mei W. J. Witteman 《Applied physics. B, Lasers and optics》1994,59(5):533-535
The discharge characteristics of the XeF* (BX) laser are investigated. The NF3 and Xe partial pressure of the laser gas mixture and the total gas pressure have been varied. A highest specific output energy of 4.7 J/l with an efficiency of 0.5% was obtained from a X-ray preionized Ne/Xe/NF3 gas mixture at 6 bar with single-pulse excitation through a multichannel spark gap. 相似文献