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1.
CV Tomy D Pal SS Banerjee S Ramakrishnan AK Grover S Bhattacharya MJ Higgins G Balakrishnan McK Paul 《Pramana》2002,58(5-6):925-935
The weakly pinned single crystals of the hexagonal 2H-NbSe2 compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder
transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of
the peak effect phenomenon in three crystals of 2H-NbSe2, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of
a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability
effects and pinning. 相似文献
2.
Øystein Stakkestad Anja CV Larsen Anne-Katrine Kvissel Sissel Eikvar Sigurd Ørstavik Bjørn S Skålhegg 《BMC biochemistry》2011,12(1):7
Background
Protein kinase A type I (PKAI) and PKAII are expressed in most of the eukaryotic cells examined. PKA is a major receptor for cAMP and specificity is achieved partly through tissue-dependent expression and subcellular localization of subunits with different biochemical properties. In addition posttranslational modifications help fine tune PKA activity, distribution and interaction in the cell. In spite of this the functional significance of two forms of PKA in one cell has not been fully determined. Here we have tested the ability of PKAI and PKAII formed by expression of the regulatory (R) subunits RIα or RIIα in conjunction with Cα1 or Cβ2 to activate a co-transfected luciferace reporter gene, controlled by the cyclic AMP responsive element-binding protein (CREB) in vivo. 相似文献3.
An optical transition of 3489 A has been shown to arise from Li using beam foil spectroscopic technique. The mean life of the state emitting this radiation has been measured to be 2.23 ä 0.08 n sec. 相似文献
4.
A study of the hyperfine interaction in the ESR of Cu-Cu pairs in single crystals of copper diethyldithiocarbamate as a function
of temperature has shown distinct differences in the hyperfine structure in the two fine structure transitions at 20 K, the
spectrum not having the same hyperfine intensity pattern in the low field fine structure transition in contrast to that of
the high field transition. The details of the structure of both the fine structure transitions in the 20 K spectrum have now
been explained by recognizing the fact that the mixing of the nuclear spin states caused by the anisotropic hyperfine interaction
affects the electron spin states | + 1 > and | −> differently. This has incidentally led to a determination of the sign ofD confirming the earlier model. The anomalous hyperfine structure is found to become symmetric at 77 K and 300 K. It is proposed
that the reason for this lies in the dynamics of spin-lattice interaction which limits the lifetime of the spin states in
each of the electronic levels | − 1 >, | 0 > and | + 1 > The estimate of spin-lattice relaxation time agrees with those indicated
from other studies. The model proposed here for the hyperfine interaction of pairs in the electronic triplet state is of general
validity. 相似文献
5.
The mere mixing of N-alkylphenothiazines with three channel-type acid zeolites with various structures (ferrierite, H-MFI, and mordenite) induces the spontaneous ionization of the heterocyclic molecule in high yield upon adsorption. The diffuse reflectance UV-visible absorption and Raman scattering spectra show that the accessibility of the highly polarizing acid sites is not indispensable to induce the spontaneous ionization process. Due to their particularly low ionization potential values (6.7 eV), the adsorption of the molecules on the external surface or in the inner volume is the key parameter to generate the radical cation. However, the ionization yield and charge stabilization are intimately correlated to the possibility of the zeolites accommodating molecules inside their channels. Moreover, the higher electrostatic field gradient induced by high confinement is required to favor the second ionization and dication formation. The alkyl chain length plays a decisive role by either slowing down the diffusion process or blocking the molecule at the pore entry. Therefore, the efficiency of the ionization process that depends on the number of adsorbed molecules decreases significantly from phenothiazine to the N-alkylphenothiazines. The spectral data demonstrate that deformation of the alkyl group is necessary to allow the diffusion of the molecules into the channels. 相似文献
6.
Z. Tahri F. Luchez I. Yordanov O. Poizat A. Moissette V. Valtchev S. Mintova M. Mostafavi V. De Waele 《Research on Chemical Intermediates》2009,35(4):379-388
The process of formation and the subsequent aggregation of silver atoms (Ag0) in nanosized zeolite beta (BEA) are studied by transient absorption spectroscopy. The zeolite nanocrystals are stabilized
in aqueous colloidal suspensions with a narrow particle size distribution in the range 30–60 nm. The reduction of silver cations
is initiated either by pulse radiolysis of the aqueous suspension or by photoinduced electron transfer using an organic electron
donor adsorbed in the zeolite framework. The silver atom in BEA nanosized crystals is found to be stable on the microsecond
timescale. 相似文献
7.
8.
A simple method to generate an effective electron-ion interaction pseudopotential from the energy wave number characteristic
obtained by first principles calculations has been suggested. This effective potential has been used, in third order perturbation,
to study the effect of three-body forces on the lattice dynamics of noble metals. It is found that three-body forces, in these
metals, do play an important role. The inclusion of such three-body forces appreciably improves the agreement between the
experimental and theoretical phonon dispersion curves. 相似文献
9.
A comparative study of the thermomagnetic memory effects of J
c in two weakly pinned low T
c superconductors, Ca3Rh4Sn13 (CaRhSn) and Yb3Rh4Sn13 (YbRhSn), is presented. In both the systems, the peak effect (PE) phenomenon appears as an order-disorder transformation
through stepwise amorphization of the flux line lattice (FLL). However, in CaRhSn. we can witness another disorder-driven
transition (Bragg glass (BG) to a vortex glass (VG) in a distinct manner as in a single crystal of high T
c YBa2Cu3O7-δ for H‖c. 相似文献
10.
Fernandes JP Carvalho BS Luchez CV Politi MJ Brandt CA 《Ultrasonics sonochemistry》2011,18(2):489-493
Allyl 1-naphthyl ethers are useful compounds for different purposes, but reported methods to synthesize them require long reaction times. In this work, we have obtained allyl 1-naphthyl ether in good yield using ultrasonic-assisted methodology in a 1-h reaction. A central composite design was used to obtain a statistical model and a response surface (p<0.05; R(2)=0.970; R(2)(adj)=0.949; R(2)(pred)=0.818) that can predict the optimal conditions to maximize the yield, validated experimentally. 相似文献