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排序方式: 共有533条查询结果,搜索用时 15 毫秒
21.
22.
Chaudhury Dipesh; Manella Laura; Arellanos Adolfo; Escanilla Olga; Cleland Thomas A.; Linster Christiane 《Canadian Metallurgical Quarterly》2010,124(4):490
Habituation is a simple form of memory, yet its neurobiological mechanisms are only beginning to be understood in mammals. In the olfactory system, the neural correlates of habituation at a fast experimental timescale involving very short intertrial intervals (tens of seconds) have been shown to depend on synaptic adaptation in olfactory cortex. In contrast, behavioral habituation to odorants on a longer timescale with intertrial intervals of several minutes depends on processes in the olfactory bulb, as demonstrated by pharmacological studies. We here show that behavioral habituation to odorants on this longer timescale has a neuronal activity correlate in the olfactory bulb. Spiking responses of mitral cells in the rat olfactory bulb adapt to, and recover from, repeated odorant stimulation with 5-min intertrial intervals with a time course similar to that of behavioral habituation. Moreover, both the behavioral and neuronal effects of odor habituation require functioning N-methyl-d-aspartic acid receptors in the olfactory bulb. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
23.
Michel Keddam Christiane Rakotomavo Hisasi Takenouti 《Journal of Applied Electrochemistry》1984,14(4):437-448
When the impedance is measured on a battery, an inductive impedance is often observed in a high frequency range. This inductance is frequently related to the cell geometry and electrical leads. However, certain authors claimed that this inductance is due to the concentration distribution of reacting species through the pores of battery electrodes. Their argument is based on a paper in which a fundamental error was committed. Hence, the impedance is re-calculated on the basis of the same principle. The model shows that though the diffusion process plays an outstanding role, the overall reaction rate is never completely limited by this process. The faradaic impedance due to the concentration distribution is capacitive. Therefore, the inductive impedance observed on battery systems cannot be, by any means, attributed to the concentration distribution inside the pores. Little frequency distribution is found and the impedance is close to a semi-circle. Therefore depressed impedance diagrams in porous electrodes without forced convection cannot be ascribed to either a Warburg nor a Warburg-de Levie behaviour.Nomenclature
A
D¦C¦ (mole cm s–1)
-
B
j+K¦C¦ (mole cm s–1)
-
b
Tafel coefficient (V–1)
-
C(x)
Concentration ofS in a pore at depthx (mole cm–3)
-
C
0
Concentration ofS in the solution bulk (mole cm–3)
- C C(x)
change under a voltage perturbation (mole cm–3)
- ¦C¦
Amplitude of C (mole cm–3)
-
D
Diffusion coefficient (cm2 s–1)
-
E
Electrode potential (V)
- E
Small perturbation inE namely a sine-wave signal (V)
- ¦E¦
Amplitude of E(V)
-
F
Faraday constant (96500 A s mol–1)
-
F(x)
Space separate variable forC
-
f
Frequency in Hz (s–1)
-
g(x)
KC(x)¦E¦(mole cm s–1)
-
I
Apparent current density (A cm–2)
-
I
st
Steady-state current per unit surface of pore aperture (A cm–2)
- j
Imaginary unit [(–1)1/2]
-
K
Pseudo-homogeneous rate constant (s–1)
-
K
Potential derivative ofK, dK/dE (s–1 V–1)
-
K
*
Heterogeneous reaction rate constant (cm s–1)
-
L
Pore depth (cm)
-
n
Reaction order
- P
Reaction product
-
p
Parameter forF(x), see Equation 13
-
q
Parameter forF(x), see Equation 13
-
R
e
Electrolyte resistance (ohm cm)
-
R
p
Polarization resistance per unit surface of pore aperture (ohm cm2)
-
R
t
Charge transfer resistance per unit surface of pore aperture (ohm cm2)
- S
Reacting species
-
S
a
Total surface of pore apertures (cm2)
-
S
0
Geometrical surface area
-
S
p
Developed surface area of porous electrode per unit volume (cm2 cm–3)
-
s
Concentration gradient (mole cm–3 cm–1)
-
t
Time
-
U
Ohmic drop
-
x
Distance from pore aperture (cm)
-
Z
Faradaic impedance per unit surface of pore aperture (ohm cm2)
-
Z
x
Local impedance per unit pore length (ohm cm3)
-
z
Charge transfer number
-
Porosity
-
Thickness of Nernst diffusion layer
-
Penetration depth of reacting species (cm)
-
Penetration depth of a.c. signal determined by the potential distribution (cm)
-
Electrolyte (solution) resistivity (ohm cm)
-
0
Flow of S at the pore aperture (mole cm2 s–1)
-
Angular freqeuncy of a.c. signal, 2f(s–1)
-
Integration constant 相似文献
24.
Gallet C Ibanez S Zinger L Taravel FR Trierweiler M Jeacomine I Despres L 《Journal of chemical ecology》2007,33(11):2078-2089
Plant-seed parasite pollination mutualisms involve a specific pollinator whose larvae develop by consuming a fraction of the
host plant seeds. These mutualisms are stable only if the plant can control seed destruction by the larvae. Here, we studied
the chemical response of the European globeflower Trollius europaeus to infestation by an increasing number of Chiastocheta fly larvae. We used liquid chromatographic analysis to compare the content of phenolic compounds in unparasitized and parasitized
fruits collected in two natural populations of the French Alps, and mass spectrometry and nuclear magnetic resonance to elucidate
the structure of adonivernith, a C-glycosyl-flavone. This compound is present in many of the organs of T. europaeus, but not found in other Trollius species. Furthermore, it is overproduced in the carpel walls of parasitized fruits, and this induced response to infestation
by fly larvae is density-dependent (increases with larval number), and site-dependent (more pronounced in the high-altitude
site). Mechanical damage did not induce adonivernith production. This tissue-specific and density-dependent response of T. europaeus to infestation by Chiastocheta larvae might be an efficient regulation mechanism of seed-predator mutualist population growth if it decreases survival or
growth of the larvae. 相似文献
25.
Marcus Weyd Christian Pflieger Andy Vogel Hannes Richter Volker Prehn Christiane Günther Frank Splittgerber Alessa Gäbler Daniel Kaulbars Patrick Bräutigam Marcus Franke Samira Lambertz Julian Schlechtweg Ingolf Voigt 《化学,工程师,技术》2021,93(9):1432-1439
Reducing micropollutant pollution of water bodies is an important objective of water management and an integral part of environmental policy. Ceramic nanofiltration membranes were developed as multichannel membranes of increased membrane area and rotating disk filters. The membranes developed show retention of over 80 % for PEG 400. The membranes are currently being tested for the separation of micropollutants from wastewater contaminated with pharmaceuticals. With the help of a downstream oxidative process, the trace substances remaining in the permeate are degraded. 相似文献
26.
Christiane L. Ojaimi Julieta A. Ferreira Adilson L. Chinelatto Raphael E. P. Salem Adriana S. A. Chinelatto Eliria M. J. A. Pallone 《International Journal of Applied Ceramic Technology》2020,17(4):1619-1628
Composites of Al2O3/ZrO2 (containing 25, 50, and 75 vol% ZrO2) were prepared by mixing Al2O3 and ZrO2 suspensions. The microstructural control via two-step sintering (TSS) was the main objective of this work. For this purpose, different sintering curves were constructed, aiming to achieve the best temperature combination for the sintering steps that provides higher density and finer microstructure. The results were compared with single-step sintering (SSS). Furthermore, microhardness and fracture toughness were measured for the best TSS specimens under each composition. The results showed that the high densities were obtained, and the reduction of grain size was greater than 40% for two-step sintered specimens, compared to SSS ones. Consequently, microhardness values increased. However, fracture toughness values remained unchanged. 相似文献
27.
Carrasco C Rosu F Gabelica V Houssier C De Pauw E Garbay-Jaureguiberry C Roques B Wilson WD Chaires JB Waring MJ Bailly C 《Chembiochem : a European journal of chemical biology》2002,3(12):1235-1241
The structural selectivity of the DNA-binding antitumor drug ditercalinium was investigated by competition dialysis with a series of nineteen different DNA substrates. The 7H-pyridocarbazole dimer was found to bind to double-stranded DNA with a preference for GC-rich species but can in addition form stable complexes with triplex and quadruplex structures. The preferential interaction of the drug with four-stranded DNA structures was independently confirmed by electrospray mass spectrometry and a detailed analysis of the binding reaction was performed by surface plasmon resonance (SPR) spectroscopy. The BIAcore SPR study showed that the kinetic parameters for the interaction of ditercalinium with the human telomeric quadruplex sequence are comparable to those measured with a duplex sequence. Slow association and dissociation were observed with both the quadruplex and duplex structures. The newly discovered preferential binding of ditercalinium to the antiparallel quadruplex sequence d(AG(3)[T(2)AG(3)](3)) provides new perspectives for the design of drugs that can bind to human telomeres. 相似文献
28.
Christiane Reis Fonseca José Luiz Paiva Eva Maria Rodriguez Fernando Juan Beltrán Antonio Carlos Silva Costa Teixeira 《臭氧:科学与工程》2017,39(4):255-263
The sugar industry is concerned with color formation due to the oxidation of phenolic compounds in the presence of carbohydrates. In this study, we investigated the ozonation of a mixture of five phenolic compounds in water and aqueous sucrose solution: p-coumaric (p-COU), caffeic (CAF), syringic (SYR), and chlorogenic (CHO) acids, as well as the flavonoid quercetin (QUE). The experiments were carried out in a 3-L glass reactor with magnetic stirring and a diffuser plate at the bottom to feed the ozone-oxygen gas mixture. Initial solution concentrations of 5 mg L?1 of each acid, 15 mg L?1 of quercetin, and 40 g L?1 of sucrose were used. The degradation of phenolic compounds followed apparent first-order kinetics, with rate constants and percent removals decreasing in the presence of sucrose. In water, average consumed ozone dosages of 10.4 and 18.7 mg L?1 were necessary for 50% and 90% removals, respectively, for CHO, CAF, and p-COU; for QUE they were slightly higher (13.9 and 20.5 mg L?1, respectively). At a consumed dosage of 20.8 mg O3 L?1, more than 99% removal was obtained for CHO, CAF, and p-COU, while 96.2% was achieved for SYR. In contrast, QUE revealed to be more recalcitrant during ozonation in the absence of sucrose, with only 70% removal at the highest consumed O3 dosage. The consumed ozone dosages for 50% and 90% removals were higher for CHO, CAF, and p-COU in aqueous sucrose solution, which may impact ozone consumption during real sugarcane juice treatment. Sucrose and t-butanol were the main influential parameters that significantly affected the total amount of phenolic compounds degraded. 相似文献
29.
Characterization of C–S–H and C–A–S–H phases by electron microscopy imaging,diffraction, and energy dispersive X‐ray spectroscopy 下载免费PDF全文
Christiane Rößler Frank Steiniger Horst‐Michael Ludwig 《Journal of the American Ceramic Society》2017,100(4):1733-1742
Improving concrete sustainability by increasing durability requires a detailed knowledge about microstructural properties. Due to the nanoscale nature of hydrate phases that determine concrete properties, microstructural characterization remains a challenge. Analytical electron microscopy offers promising techniques to characterize cement hydrates. In this study, electron microscopy imaging, diffraction, and energy dispersive X‐ray spectroscopic information are combined in order to compare the structural properties of calcium silicate hydrate (C–S–H) and calcium aluminum silicate hydrate (C–A–S–H) phases. Results are shown for 28 days hydrated C–(A)–S–H of portland cement and cement containing ground granulated blast‐furnace slag (GGFBS). Electron diffraction patterns of single fibrous C–S–H and foil‐like C–A–S–H phases reveal a nanocrystalline structure. Also, it is shown by electron diffraction pattern that the crystal structures of C–S–H and C–A–S–H phases are similar. It is confirmed that the crystal structure of 14 Å tobermorite serves as good base for the structure of C–S–H. The electron diffraction patterns of fibrous C–S–H show streaks which indicate stacking faults, proofing that polymerization of silicate chains in C–S–H is limited. Here, we demonstrate for the first time that the dreierketten silicate chains contained in the C–S–H structure are oriented in parallel to the long axis of C–S–H fibers. This finding should be implemented in modeling of crystal growth of C–S–H. 相似文献
30.
Mario Cano-Muoz Julie Lucas Li-Yun Lin Samuele Cesaro Christiane Moog Francisco Conejero-Lara 《International journal of molecular sciences》2022,23(5)
Inhibition of the HIV-1 fusion process constitutes a promising strategy to neutralize the virus at an early stage before it enters the cell. In this process, the envelope glycoprotein (Env) plays a central role by promoting membrane fusion. We previously identified a vulnerability at the flexible C-terminal end of the gp41 C-terminal heptad repeat (CHR) region to inhibition by a single-chain miniprotein (named covNHR-N) that mimics the first half of the gp41 N-terminal heptad repeat (NHR). The miniprotein exhibited low stability, moderate binding to its complementary CHR region, both as an isolated peptide and in native trimeric Envs, and low inhibitory activity against a panel of pseudoviruses. The addition of a disulfide bond stabilizing the miniprotein increased its inhibitory activity, without altering the binding affinity. Here, to further study the effect of conformational stability on binding and inhibitory potency, we additionally stabilized these miniproteins by engineering a second disulfide bond stapling their N-terminal end, The new disulfide-bond strongly stabilizes the protein, increases binding affinity for the CHR target and strongly improves inhibitory activity against several HIV-1 strains. Moreover, high inhibitory activity could be achieved without targeting the preserved hydrophobic pocket motif of gp41. These results may have implications in the discovery of new strategies to inhibit HIV targeting the gp41 CHR region. 相似文献