Partial Shifts Research Articles

Mössbauer spectra of some low-spin iron(II) complexes with ditertiary phosphines

The Mössbauer spectral data for a range of low-spin iron(II) complexes [FeX(Y)(diphosphine)2]n+(n= 0 or 1), where X and/or Y = Cl, Br, MeNC, MeCN, H, N2, CO, etc., are reported. The isomer shifts and quadrupole splittings have been analysed in terms of ligand partial values assuming that additivity holds, and the partial values are discussed in terms of the bonding properties of the ligands. It is concluded that the partial isomer shifts are of limited use because of the small range of values. Partial quadrupole splittings (p.q.s.) are more informative, and are best computed with reference to p.q.s. (H)= 0.00.

Intrathymic Changes in Murine CD3, CD5 and CD8 Expression after in vivo Administration of anti-CD4

Intrathymic development of murine cortical and medullary thymocyte subpopulations was examined after in vivo administration of anti-CD4 mAb. Four days after mice received 1 mg anti-CD4, expression of CD4 was reduced to about 25 % the level of controls. On cortical CD8 +/PNA high thymocytes, CD5 and CD8 expression both decreased, but not in parallel, whereas CD3 expression increased almost 2-fold. Partial shifts in CD3 expression were seen 3 and 6 h after injection, but modulation of CD4 preceded the increase in CD3 expression. On medullary CD8 -/PNA low thymocytes, both CD3 and CD5 were down regulated. On nontargeted CD8 -/PNA low medullary thymocytes, expression of these molecules was decreased less than 20 %, but the decrease in CD8 expression was primarily due to the appearance of a CD8 -/PNA low subpopulation. The results indicate that anti-CD4 mAb differentially affects the intrathymic development of T cell populations.

Partial Paradigm Shifts in the Social Sciences: Twenty Years of Research in Rural Sociology3

Abstract Falk and Zhao (1989) have recently suggested that increased theoretical diversity characterizes the last decade of published research in Rural Sociology. We suggest that this claim is premature, given paradigmatic trends in the larger discipline of sociology. From a reanalysis of data sources and the use of an analytical framework based on the partial paradigm concept, we conclude that rural sociology is attempting to further integrate theory, methodology, and image of the subject matter within a positivistic partial paradigm framework. We further suggest that rural sociologists continue their pursuit of a reflexive understanding of the practice of social science as an integral part of their research agenda.

The complete spectrum of image line

A derivation is presented of the complete orthonormalized spectrum, under LSA/LSM (longitudinal-section electric/magnetic) assumptions, for image line waveguiding structures by using a so-called method of partial wave phase shifts. The analysis is developed for the even LSM (TM/sup y/) polarization, having H/sub y/=0 and E/sub y/ as the main electric field component: the LSE analysis proceeds along dual lines. An arbitrary radiation field is described as a superposition of the LSM and LSE continua.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Core-level binding-energy shifts during metal adsorption and compound formation: Yb/Ni(100).

A model for core-level shifts in metallic overlayers is introduced. The model is based on a decomposition of the shift into partial shifts which are related to specific structural aspects of the interface system. The model is applied to the Yb/Ni(100) overlayer system which has been studied by He ii and Al K\ensuremath{\alpha} excited photoelectron spectroscopy. The deposition of Yb is investigated at two substrate temperatures, room temperature and 670 K. At 670 K ordered low-energy electron diffraction structures are seen, and at higher Yb depositions intermixing with the substrate occurs. At room temperature no ordered structures are seen. The low mobility of the atoms furthermore prevents strong intermixing with the substrate. It is shown that an analysis of the divalent and trivalent Yb shifts provides detailed structural information about the Yb/Ni(100) overlayer system.

Electron correlation in momentum space: Z-dependent variations throughout a series of Li-like ions

Momentum space is used to analyse electron correlation effects for the individual intra- and intershell electron pairs in the ground and first excited states of a series of Li-like ions when 3<or=Z<or=8. Coulomb shifts Delta f(p12) and partial Coulomb shifts Delta g(p12;p1), where p12= mod p1-p2 mod and p1= mod p1 mod , are reported for the pair descriptions K alpha K beta , K alpha L alpha and K beta L alpha in each state. Total Coulomb shifts are also examined. Radial and angular correlations are found to have opposing influences on the interparticle momentum distributions for each electron pair in the ground states and also for the intrashell electron pairs in the first excited states. Such a feature permits the identification of the major component of correlation in different regions of momentum space. Comparisons are made with a previous Z-dependent analysis of these systems in position space.

Topological short-range disorder in Au1-xNix solid solutions: An extended x-ray-absorption fine-structure spectroscopy and computer-simulation study.

The present extended x-ray-absorption fine-structure (EXAFS) investigation aims at determining the atom-pair displacements on a local scale in the ${\mathrm{Au}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ni}}_{\mathrm{x}}$ system, for the three types of pairs Au-Au, Au-Ni, and Ni-Ni. X-ray-absorption spectra have been obtained above both edges (Au ${L}_{3}$ and Ni K), over the whole composition range. For the purpose of the separation of the Au and Ni scattering contributions, a detailed analysis of EXAFS over a wide photoelectron wave-vector range beginning close to the edge has been performed. The amplitude and phase functions for unlike-neighbor pairs have been obtained in two ways: first by using empirically refined theoretical partial phase shifts, which enabled us to calculate the total phase functions, and secondly by making use of fluorescence recorded spectra of dilute alloys from which appropriate amplitude functions have been extracted. Many low-k amplitude effects such as the photoelectron wave curvature, the experimental energy resolution, the limited core-hole lifetime, and the many-electron excitation factors have been analyzed, and taken into account, as well as the difference between p- and d-symmetry photoelectron scattering.Although the alloys are crystalline, a large positional disorder was found, resulting in a distribution of the three pair distances. An appropriate model for the EXAFS function was selected by use of several constraints relating the structural parameters determined by EXAFS to the ones of the regular fcc lattice, deduced from x-ray diffraction measurements. The three nearest-neighbor partial radial distribution functions are thus described in terms of mean distance and second and third momenta. They are broad and display a marked asymmetry, especially in concentrated alloys, these features increasing in the order Au-Au, Au-Ni, and Ni-Ni. Indeed, the Ni-Ni radial distribution function is very wide, at the extent that it is comparable to those encountered in amorphous metal-metal alloys. The three partial mean distances are distinct from each other by as much as 0.1 A\r{}, and exhibit different dependence on composition. In dilute alloys, the relaxation around the impurity atoms was found to be appreciable. The most striking feature of the local structure, irrespective of the composition, is that the larger Au atoms are more confined (statically and dynamically) on the nodes of the regular lattice than the Ni ones. The positive bowing of the lattice parameter variations with composition is discussed in the light of the present results. The experimental work was completed by a computer simulation of the topological structure of these alloys, based on a minimization of the total elastic energy. The experimental results were quantitatively well reproduced, by use of a Morse interaction pair potential. Qualitative features were found to have small dependence on the particular pair potential chosen to model the interactions. In addition, as a further proof of the adequacy of the function chosen for EXAFS fitting, model EXAFS spectra calculated from the computed radial distribution functions were fitted in the same manner as the experimental ones, yielding an estimate of the results' accuracy.

Education to Prevent AIDS: Prospects and Obstacles

A number of obstacles thwart effective education to prevent AIDS in the United States. These include the biological basis and social complexity of the behaviors that must be changed, disagreement about the propriety of educational messages to prevent AIDS, uncertainty about the degree of risk to the majority of Americans, and dual messages of reassurance and alarm from responsible officials. Long-term protection of an individual from infection requires extreme changes in risk-taking behavior. Partial shifts toward safer practices may be epidemiologically important in retarding the rate and extent of spread of infection. Though some striking changes in behavior have occurred, especially in homosexual populations in areas with high prevalence of AIDS, educational efforts to date have succeeded more in raising awareness and knowledge about AIDS than in producing sufficient changes in behavior. The United States has yet to mount a nationwide comprehensive, intensive, and targeted education program to prevent AIDS.

Electron correlation in momentum space: the ground state of Li(2S)

Electron correlation is examined in momentum space for the individual intra- and inter-shell electron pairs in the ground state of Li(2S). It is established that the radial and angular components of the correlation have opposing influences on the inter-particle momentum distributions f(p12) and g(p12;p1), where p12= mod p1-p2 mod and p1= mod p1 mod . By examining the Coulomb shifts Delta f(p12) and, in particular, the partial Coulomb shifts Delta g(p12;P1) for each electron pair, such a feature enables one to identify the major component of correlation in different regions of momentum space. This represents a distinct advantage over the more traditional position space approach. For K alpha K beta , not only was it found that intra-shell correlation effects were influenced by the occupation of the 2s orbital but, more interestingly, the nature of the influence was seen to change markedly throughout different regions of space. For the K alpha L alpha and K beta L alpha inter-shells, the importance of angular correlation was highlighted and, for K alpha L alpha , the consequence of the Fermi effect was observed. Comparisons were made with a previous, and complementary, position-based study of Li(2S) and with the correlation effects found in momentum space for closed shell Li+(1S) and Be(1S).

Momentum space correlation effects in the 23S, 21P and 23P states of He

A Dirac-Fourier transformation of correlated and Hartree-Fock wavefunctions for some (1s, nl) states of He allowed the authors to analyse electron correlation effects in momentum space for excited states of differing symmetry and spin multiplicity. For the 2 3S, 2 1P and 2 3P states, Coulomb shifts and partial Coulomb shifts were determined, as well as certain radial and angular distribution functions. For 2 3S and 2 1P it was established that, like the ground state of He, angular and radial correlation have opposing effects on the momentum distributions. In contrast to this, for 2 3P these two components of correlation work in unison, as occurs in position space. A rationalisation of this behaviour is given, along with an interpretation of the complex nature of the corresponding partial Coulomb shifts. The latter revealed significant changes in the relative importance of angular and radial correlation as the momentum of a test electron was increased. The success of this analysis rested essentially on a detailed knowledge of the inter-vectorial angular shifts. For these excited states, the use of angular expectation values alone proved to be too insensitive to explain the quite marked differences in the correlation characteristics.

Delay time experienced by a particle undergoing resonant scattering: The case of the 3D square well

A formalism to calculate the time delay experienced by a particle undergoing scattering is presented. The formalism is a natural extension of Wigner’s delay time to wave packets which do not exhibit a well defined angular momentum. The delay depends only on the partial wave phase shifts characterizing the scattering event. The formalism is tested by applying it to the 3D square well. The results are shown to agree with the known properties of resonant scattering as deduced from a study of the poles of the scattering matrix in the complex energy plane.

Pion-helium potential by inverse scattering method.

The inverse scattering formalism is applied to the case of the pion-helium system to obtain the real and imaginary parts of a local phenomenological potential from ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$${\mathrm{\ensuremath{-}}}^{4}$He partial wave phase shifts at a fixed energy. The phase shifts and inelasticities for all partial waves up to angular momentum l=9 are extracted from the differential cross-section data by parametrizing the nuclear amplitude. The method has been tried for a number of incident pion energies between 51 and 110 MeV. The real and imaginary parts of the potential are seen to compare well with the commonly used pion-nucleus Laplacian potential.

Semi-classical expansion for the scattering by a complex potential

For the scattering by a complex potential the partial wave phase shifts are calculated to order ħ 2 without using the method of complex trajectories. This shows how the imaginary part of the potential contributes to the deflection angle for different partial waves.

Pauli-corrected Breit-Wigner formulae for compound resonances in two- and three-cluster systems

Breit-Wigner formulae for compound resonances in two- and three-cluster systems are derived. Analytic corrections due to the Pauli principle with regard to corresponding formulae for partial resonance widths and resonance pole shifts are given. In the case of a system of three composite particles a model is formulated in which sudden decay into three clusters is determined by the knowledge of the microscopical compound state of the metastable decaying nucleus. The derivation of the Breit-Wigner formulae in the case of a three-cluster system is based on the study of the asymptotic behavior of the full three-body Green's function. In the case of the two-body channel situation the formalism presented here is a modification of the Wildermuth-Benöhr reaction theory.

On a unitary description of low-energy pion-nucleus elastic scattering

Within the framework of the method of coupling-constant evolution an approach is developed for description of elastic pion-nucleus scattering. An iteration procedure for calculation of partial phase shifts of pion-nucleus scattering is constructed. In the low-energy limit the scattering amplitude satisfies the condition of two-body unitarity. In the lowest approximation of the theory the pion-nucleus phase shifts can be expressed in terms of the elementary phase shifts of ..pi..N scattering and nuclear form factors. A satisfactory description of pion elastic scattering by light nuclei (/sup 4/He, /sup 12/C) is obtained in the pion-energy region below 70--80 MeV.

Scattering Cross Sections in Argon from Electron Transport Parameters

Previously determined experimental drift velocities Vdr and ratios of lateral diffusion coefficient to mobility DT/µ have been refitted directly with a three parameter modified effective range theory (MER T) representation of the S wave phase shift, a one parameter fit to the P wave phase shift and fixed higher partial wave phase shifts. The MERT representation now extends to 1·0 eV, a threefold extension of the energy range of the MERT fit reported by Milloy et al. (1977). The total cross section derived from the phase shifts is also reported, together with the differential cross section at 1·0 eV which is compared with a previous experimental determination.

Additive character of shift of W4f line in X-ray photoelectronic spectra of phosphine complexes of tungsten

The position of the W4f7/2 line in the XP spectra of the phosphine complexes of tungsten can be described by the additive scheme of partial shifts, caused by the ligands that enter into the complex.

Ionized Impurity Scattering in n‐Type ZnSe from Partial Wave Phase Shifts

Ionized Impurity Scattering in n‐Type ZnSe from Partial Wave Phase Shifts

On the shifts of self-reversed maxima of the sodium resonance radiation

Relationships between partial pressures and shifts of blue wing and red wing maxima of the self-reversed D lines in a high-pressure sodium-mercury discharge have been calculated. A van der Waals model is used in the calculation of the interaction between sodium and mercury atoms. A useful and convenient formula has been derived for estimating mercury pressure in a sodium-mercury discharge from easily measured parameters (the shift of red wing maximum and the shift of blue wing maximum).

A KKRZ calculation on indium. II. The Fermi surface as determined from radio-frequency size effect measurements

For pt.I see ibid., vol.7, no.19, p.206 (1977). New high-precision radio-frequency size effect measurements on indium are presented. Four measured caliper dimensions of the Fermi surface have been used in a KKRZ calculation to determine parameters eta l (l=0,1 and 2) which are directly related to the respective partial wave phase shifts, delta l. The most significant parameters ( eta 0 and eta 1) differ by 1 and 8% respectively from those obtained from the ab initio calculation reported in the first paper. Using the fitted parameters the full Fermi surface of indium has been calculated, which turns out to be in excellent agreement with the experimental results.