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21.
Samuni U Ouellet Y Guertin M Friedman JM Yeh SR 《Journal of the American Chemical Society》2004,126(9):2682-2683
HbN and HbO are two truncated hemoglobins from Mycobacterium tuberculosis. Resonance Raman spectra of the deoxy derivatives of these two homodimeric hemoglobins indicate that there is no proximal strain imposed by intersubunit interactions on the proximal iron-histidine bond as that observed in the tetrameric human hemoglobin. In addition, with nanosecond laser flash photolysis, it was concluded that movement along the Fe-His bond following the dissociation of CO does not trigger a quaternary structural transition in these two hemoglobins. 相似文献
22.
Ralph F. Guertin 《International Journal of Theoretical Physics》1975,14(6):405-416
We second quantize a relativistic Schrödinger equation involving a HamiltonianH that describes free spin-1/2 particles and that depends on a parameterG. We require a positive definite metric and a positive definite energy in the Fock space in which the field ψ(x,t) and its adjoint operate. IfG=±i, one obtains the usual second-quantized Dirac theory, but for real values ofG one has Bose statistics. Whereas the anticommutator [ψ(x,t), ψ * (x′,t′)]+ vanishes for a Dirac field when the interval between (x,t) and (x′,t′) lies outside the light cone, whenG is real the commutator [ψ (x,t), ψ * (x′,t′)? vanishes for such points. 相似文献
23.
24.
S Chanda Sarmishtha Bhattacharyya Tumpa Bhattacharjee SS Ghugre Swapan Kumar Basu S Muralithar RP Singh B Mukherjee RK Bhowmik SN Ray 《Pramana》2001,57(1):175-179
The high spin states in N=80 139Pr have been investigated by in-beam γ-spectroscopic techniques following the reaction 130Te (14N, 5n) reaction at E=75 MeV, using a gamma detector array, consisting of seven 23% compton-suppressed high purity germanium detectors and a multiplicity
ball of fourteen bismuth germanate elements. Based on γ-γ coincidence data, the level scheme of 139Pr has been considerably extended up to 7.2 MeV excitation. Tentative spin-parity assignments are done for the newly proposed
levels on the basis of the DCO ratios corresponding to strong gates and the available information from the earlier light ion
experiments. 相似文献
25.
Measurements of the hydrostatic pressure dependence of the Neél temperatures, TN, are reported for PrSn3, GdSn3, GdSn3 and CeIn3. TN is found to increase with applied pressure for PrSn3 and NdSn3, whereas TN is pressure independent within experimental error for GdSn3 and CeIn3. Slightly Sn-deficient RESn3 (RE=rare earth) compounds are found consistently to be weakly ferromagnetic. The physical properties of the RESn3 compounds exhibit analogies with the corresponding properties of dilute superconducting (RE)Sn3 alloys. The high pressure data for PrSn3 and CeIn3 are qualitatively consistent with a “Kondo necklace” model for magnetically ordered RE compounds with unstable 4f shells. 相似文献
26.
The pressure dependence to 9.4 kbar of the magnetization of the induced ferromagnet, Pr3Se4, is presented. Two ferromagnetic transitions near 15 K are identified. The magnetic component associated with one decreases rapidly with increasing pressure and the high field moment increases. The results are compared to recent work on Pr3Tl. 相似文献
27.
Ralph F Guertin 《Annals of Physics》1974,88(2):504-553
We discuss 2(2J + 1)-component Poincaré-invariant Hamiltonian theories that describe free particles of definite mass and spin and that are subject to the conditions (a) every observable is either Hermitian or pseudo-Hermitian (i.e., O = ?3O+?3) and (b) the theory is invariant under the discrete symmetries. Our treatment is based on the Heisenberg equations of motion and on the Lie algebra of the Poincaré group. Explicit formulas are found for the generators of this algebra, including the Hamiltonian H, and all relations between the operators Γ and H that are both necessary and sufficient for to generate Lorentz boosts are found. To illustrate the utility of our results, we apply them to obtain explicit generalizations of the Dirac equation to any spin, by requiring that Γ = 0, and of the Sakata-Taketani spin-0 and spin-1 equations to any spin, by requiring that . 相似文献
28.
Ralph F Guertin 《Annals of Physics》1975,91(2):386-412
We give the generalized Foldy-Wouthuysen transformation for any 2(2J + 1)-component Poincaré-invariant Hamiltonian theory that describes free massive spin-J particles and that is subject to the conditions: (a) every observable is either Hermitian ( = +) or pseudo-Hermitian ( = ?3+?3) and (b) the theory is invariant under the discrete symmetries. The requirement that the Hamiltonian be defined in the rest frame specifies one and only one boost generator that is also defined at p = 0. 相似文献
29.
J. M. Ferreira M. B. Maple H. Zhou R. R. Hake B. W. Lee C. L. Seaman M. V. Kuric R. P. Guertin 《Applied Physics A: Materials Science & Processing》1988,47(1):105-110
Finely ground powders ofRBa2Cu3O7 – (R=Y, Nd, Sm, Eu, Dy, Ho, Er, Tm, Yb) have been mixed at dilute 3%-by-volume concentrations into epoxy matrices which were then allowed to harden in applied magnetic fieldsH
A=18 kOe. X-ray diffractometry studies and 4.3 K measurements of supercurrent-induced magnetization hysteresisM are interpreted as indicating at least partial alignment of single-crystal-grain c-axes (1) parallel toH
A forR=Y, Nd, Sm, Dy, Ho (as earlier found by Farrell et al. forR=Y), and (2) perpendicular toH
A forR=Eu, Er, Tm, Yb. With a few exceptions (Y, Sm, Eu) the alignment direction correlates with the sign of the second-order Stevens factor
J of the crystalline electric field Hamiltonian in the manner suggested by Livingston et al. For the best aligned specimens (Ho, Dy) critical current densitiesJ
c (4.3 K, 5 kOe) for individual grains are estimated fromM and the Bean model to be of order 107 A/cm2 for the measuring fieldH parallel to the original alignment fieldH
A, and of order 106 A/cm2 forH perpendicular toH
A. 相似文献
30.
Geng Bang Jin Robert P. Guertin Corwin H. Booth 《Journal of solid state chemistry》2007,180(9):2581-2586
Dark red single crystals of PrLnYb2S6 (Ln=Pr/Yb, Tb, Dy) have been synthesized through the reactions of elemental rare earth metals and S using a Sb2S3 flux at 1000 °C. These isotypic compounds adopt the F-Ln2S3 three-dimensional open-channel structure type. Eight-coordinate Pr3+ ions sit in the channels that are constructed from three different edge-shared double chains running down the b-axis that contain Yb(1)S6 octahedra, Yb(2)S6 octahedra, and LnS7 monocapped trigonal prisms. Each double chain connects to four other neighbors by sharing vertices and edges. Considerable disordering in Ln positions was observed in single X-ray diffraction experiments only in the case of Pr/Yb. Least-squares refinements gave rise to the formulas of Pr1.34Yb2.66S6, of PrTbYb2S6, and PrDyYb2S6, which are confirmed by the elemental analysis and magnetic susceptibility measurements. Pr1.34Yb2.66S6, PrTbYb2S6, and PrDyYb2S6 are paramagnetic down to 2 K, without any indications of long-range magnetic ordering. The optical transitions for Pr1.34Yb2.66S6, PrTbYb2S6, and PrDyYb2S6 are at approximately 1.6 eV. Crystallographic data are listed as an example for PrTbYb2S6: monoclinic, space group P21/m, a=10.9496(10) Å, b=3.9429(4) Å, c=11.2206(10) Å, β=108.525(2)°, V=459.33(7) Å3, Z=2. 相似文献