Equivalence of Hadamard matrices

Supposem is a square-free odd integer, andA andB are any two Hadamard matrices of order 4m. We will show thatA andB are equivalent over the integers (that is,B can be obtained fromA using elementary row and column operations which involve only integers).     

The measurement of fetal liver T(*)(2) in utero before and after maternal oxygen breathing: progress towards a non-invasive measurement of fetal oxygenation and placental function

Utero-placental insufficiency is thought to be a major cause of growth retardation in utero and an important risk factor in the perinatal period. The purpose of this study was to investigate whether MRI could detect changes of fetal oxygenation, based on the blood oxygenation level dependence (BOLD) of the MRI tissue signal. Nine third trimester women (34-38 weeks) with normal pregnancies underwent abdominal MRI examinations. Following localization of the fetal liver using T(2)-weighted single-shot HASTE scans, up to 7 breath-held transaxial single-slice gradient-echo image sets were obtained through the fetal liver. The mother then commenced oxygen breathing with the imaging procedure repeated after 20 minutes of O(2) breathing. For each image set, T(*)(2) values are calculated using linear regression of log (signal) versus TE for a region of interest within the fetal liver selected by the attending radiologist. Fetal liver T(*)(2) values were calculated before and after O(2) breathing for each multi-echo image acquisition set. A signed rank test was used to test for a significant change in fetal liver T(*)(2) between the pre-O(2) and post-O(2) image sets. A significant increase in T*(2) (alpha < 0.05) was seen in 5 of the 9 fetal livers, a smaller increase (of borderline statistical significance, alpha = 0.057) in 2 livers, and no significant change (alpha > 0.05) in 2 livers. Our study indicates that T(*)(2) measurement of the fetal liver may detect alteration in fetal oxygen level following maternal oxygenation using the BOLD effect. This technique may potentially be applied to the identification and understanding of placental dysfunction in intra-uterine growth retardation.     

Laser-Generated Plasmas as X-Ray Sources in the keV-Range

This report will give an introduction to the X-line emission processes in laser-generated plasmas according to a plasma physical point of view. After a short discussion of the experimental results using laser pulses in the range of ? 10 J and irreadiances of 1 to 100 MW/cm² and of first conclusions about the temperature scaling and the dependence of the emission concerning the atomic number of the target material some models of laser-generated plasmas are analysed. The simple hot-spot model neglects any hydrodynamics and only solves for the rate equations. We discuss the underlying collisional-radiative model and evaluate the numerical results of a more complete model for the spatial and temporal plasma evolution including the hydrodynamics. The applications of such plasmas as small, strong, short sources of X-rays in the keV range is discussed with regard to the lithographic replication of sub-μm structures and to the EXAFS spectroscopy. Laser-generated plasmas are compared with conventional X-ray tubes (with rotating anode) and with synchrotrons. The question of amplified spontaneous emission in the XUV range (superradicant X-ray sources) is only shortly touched upon. In conclusion some comments are given to the recoil momentum effects of the ablating plasma on the target are given (rocket model).     

Theory of surface force-constant changes in body-centered cubic lattices

A calculation has been made of force-constant changes at the (100) and (110) surfaces of body-centered cubic crystals. A model consisting of first, second and third-neighbor Lennard-Jones interactions together with harmonic angle-bending interactions is employed. The parameters characterizing the interactions are chosen to fit the equilibrium lattice spacing, the elastic constants, and certain phonon frequencies at high symmetry points in the Brillouin zone. The procedure consists of first calculating the static displacements produced by the creation of the surface and then calculating the change in force constants produced by the cubic and quartic anharmonic terms in the potential energy. Specific results have been obtained for chromium, iron, tungsten, and molybdenum.     

Theory of surface polaritons in n-type silicon in the presence of a dc current,including the electron thermal pressure gradient

A theoretical investigation has been made of the effect of a drift current, including the electron thermal pressure gradient, on surface polaritons in n-type Si. The polariton propagation and drift current directions are taken to be either parallel or antiparallel. Retardation is included, but damping is neglected. The specular reflection approach of Kliewer and Fuchs is used to obtain the polariton dispersion relation. The results show that the drift current and surface polaritons interact, leading to evanescent waves for certain frequencies. However, no wave amplification is obtained.     

Countercurrent gas-liquid flow in parallel vertical tubes

The subject of this paper is the flow between an upper reservoir, containing a liquid, and a lower reservoir, containing a gas, interconnected by parallel vertical tubes. The characteristics of the combined system are predicted from a knowledge of the behavior of flow in individual tubes. Numerous modes of possible operation are described analytically and demonstrated experimentally. The effects of system geometry, changes in gas supply characteristics, operating procedure and two-phase flow regimes on the transitions between modes and system stability are presented. Predictions are made for the limiting case of a large number of identical parallel channels.     

Compressibility effects on waves in stratified two-phase flow

Ardron (1980) presented both one-dimensional and two-dimensional analyses of wave propagation in horizontal stratified two-phase flow. He compared the two approaches and concluded that the comparison helped to improve confidence in the use of one-dimensional approximations for the analysis of complex systems such as nuclear reactors.There are several assumptions in Ardron's developments. When alternative assumptions are made the results change. By examining the consequences of several possible assumptions we have learned from this example that considerable care may be necessary in the reduction of a multi-dimensional two-phase flow problem to a simpler form.This paper presents a more complete two-dimensional solution of this problem and discusses the limitations of the approximate solutions.     

Cluster chemistry. partial hydrogenation of coordinated isocyanide on a ruthenium cluster carbonyl.

Addition of dihydrogen to Ru₃(CO)₁₁(CNBu^t) affords HRu₃(CO)₉(HC:NB as the major product; this complex and four other minor products were identified from their IR, NMR and mass spectra.