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991.
Barbosa M. S. da F. Costa L. Bernardes E. S. Ramakers G. van Pelt J. 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,37(1):109-115
The European Physical Journal B - The complexity of a neuronal cell shape is known to be related to its function. Specifically, among other indicators, a decreased complexity in the dendritic trees... 相似文献
992.
Rafael Jimnez Elena Bueno Israel Cano Elizabeth Corbacho M. Eugenia Fernndez Lidia Gmez Jesús Graciani María Hernndez M. Teresa Matitos Jos Ortíz Pilar Lpez‐Cornejo Rafael Prado‐Gotor 《国际化学动力学杂志》2004,36(12):627-633
The kinetics of substitution of H2O by Ru(NH3)5pz2+ (pz = pyrazine) in Fe(CN)5H2O3? have been studied in micellar aqueous solutions of sodium dodecylsulfate (SDS). Experimental results are discussed by using an approach based on the transition‐state theory. This approach is better than others based on the pseudophase model, which can also be used, because it is able to give a clear meaning to the parameters of the model. Trends in the observed reactivity are explained by a change in the degree of association of one of the reactants to the micelles (Ru(NH3)5pz2+ in the present work). This association is governed by an equilibrium constant that depends on the electrostatic potential at the surface of the micelles. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 627–633, 2004 相似文献
993.
In this work we present Electric Quadrupole Interaction (EQI) measurements, made by Time Differential Perturbed Angular Correlation
(TDPAC), on111Cd in YBa2Cu3O
x
and some related compounds. These studies were intended to determine the relationship between the EQI and the actual probe
site. The probes were introduced into the materials as a diluted111In-complex or via In(111In)2O3. Our observations indicated that there is no need to suppose the presence of many probe sites in YBa2Cu3O
x
to explain the experimental results. 相似文献
994.
Well-crystallized hematite was suspended in water and treated at room-temperature (RT) with sodium borohydride. The product
of the reaction is a highly magnetic black powder, which is stable at RT. The NaBH4 treatment converts about half of the hematite to an amorphous Fe–B alloy and to a small fraction of sub-micron sized, amorphous
metallic-Fe nodules. Heating at 400°C of this composite has resulted in the crystallization and/or oxidation of more than
half of the amorphous Fe–B phase to α-Fe and Fe3O4 and B2O3, respectively. After treatment at 800°C, the metallic Fe and the amorphous Fe–B have completely vanished, and the resulting
product consists of hematite and FeBO3 embedded in the matrix of α-Fe2O3. 相似文献
995.
Mössbauer absorption of Fe57 in naturally occuring and synthetic crystals of FeS2, marcasite, has been studied in the ideal absorber thickness in the transmission geometry from a Co57/Rh and Co57/LiNbO3 source. The recoilles fraction at room temperature, 298 K, has been obtained to be 0.2 and the mean square displacement < r2 > was found to be 13×10-19 cm2 at room temperature, 298 K. Because of the small size of marcasite crystals it has not been possible to record good spectra of the monocrystals as a function of the orientation of the incident gamma rays from Co57/LiNbO3 source. 相似文献
996.
J.M. Nitschke M. Fowler A. Ghiorso R.E. Leber M.E. Leino M.J. Nurmia L.P. Somerville K.E. Williams E.K. Hulet J.H. Landrum R.W. Lougheed J.F. Wild C.E. Bemis R.J. Silva P. Eskola 《Nuclear Physics A》1981,352(1):138-146
A rotating drum system was used to search for an 80 ms spontaneous fission (sf) activity in the reaction of 15N with 249Bk. No such activity was found beyond a cross section limit of 0.5 nb. A sf activity with a half-life of 23 ± 2 ms and a maximum formation cross section of 19 ± 4 nb at 82 MeV was observed. The identity of this activity has not been determined. 相似文献
997.
S.M.S. da Costa M.H.F. Bettega 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(1):67-71
We report elastic integral, momentum transfer and differential cross sections for electron scattering by N2O for energies up to 50 eV. These results were obtained at the static-exchange approximation with the Schwinger Multichannel
Method with Pseudopotentials [M.H.F. Bettega, L.G. Ferreira and M.A.P. Lima, Phys. Rev. A 47, 1111 (1993)]. In general our results show good agreement with experimental data and with other theoretical results but some
discrepancies are found. We have also found a shape resonance around 4 eV in agreement with previous calculations using the R-matrix Method of Sarpal et al. [J. Phys. B 29, 857 (1996)]. On the other hand, the existence of a resonance at about 13 eV, clearly seen by the Schwinger Variational Iterative Method [Michelin et al., J. Phys. B 29, 2115 (1996)], can not be confirmed by our calculations. At this energy, our cross sections show a broad bump with no clear resonant behavior given by the eigenphase sum.
Received: 13 November 1997 / Revised: 13 March 1998 / Accepted: 9 April 1998 相似文献
998.
A thermodynamic model of magnetic insulator-to-metal transitions is presented. As the parameters are varied it shows with increasing temperatures; (a) antiferromagnetic insulator → paramagnetic insulator; or (b) antiferromagnetic insulator → metal → paramagnetic insulator; or (c) antiferromagnetic insulator → metal; or (d) metal at all temperatures. Behaviors (b) and (c) are separated by a classical critical point. The model reproduces well the behavior encounted in (V1-xCrx)2O3 and can be applied to magnetic semiconductors in general. 相似文献
999.
Summary Bohm's theory on plasma probes has been modified, by taking into account the effect of the applied RF voltage on the ion saturation
current, for explaining the experimentally detected behaviour of the plasma sheath resonance frequency in a low-temperature
and low-density plasma
Riassunto La teoria di Bohm sulle sonde nei plasmi è stata modificata, tenendo conto dell'effetto dovuto alla tensione RF applicata sulla corrente ionica di saturazione. Si spiega cosi l'andamento della frequenza di risonanza plasma-guaina ionica, rilevato sperimentalmente, in un plasma a bassa temperatura e bassa densità.
Резюме Предлагается модификация теории Бома для плазменных зондов, которая учитывает влияние приложенного радиочастотного напряжения на ионный ток насыщения. Предложенная модификация позволяет объяснить экспериментально обнаруженное поведение резонансной частоты плазменной оболочки при низкой температуре и при низкой плотности плазмы.相似文献
1000.
E. M. Gopalakrishna W. H. Watson M. Hoeneisen M. Silva 《Journal of chemical crystallography》1977,7(1):49-57
Ovatifolin, C17H22O5, is a sesquiterpene lactone isolated from the aerial parts ofPodanthus mitiqui Lindl. (Compositae) collected near Pichidangui, Chile. Extracts of the plant exhibit cytotoxic activity against KB cell cultures. The pale yellow crystals belong to the orthorhombic space groupP212121 with cell dimensionsa = 8.159(1),b = 6.640(1), andc = 29.314(4) Å. Data were collected on an automatic diffractometer and the structure was solved by direct methods. The model was refined anisotropically to anR value of 0.047 using all 1742 measured intensities. The 10-memberedtrans-trans-germacradiene ring adopts a chair-chair conformation with C(4) and C(10) methyl groups orientedsyn on the face of the molecule. The conformation leads to a crossed double-bond system in which transannular interactions shift the ultraviolet absorption to 210 nm. The five-membered lactone ring adopts a distorted chair conformation and istrans-fused to the 10-membered ring.FASTBIOS contribution number 36. 相似文献