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151.
W.J. Nuttall S.C. Perry D.R. Bowyer W.G. Stirling G.H. Lander O. Vogt 《Physica B: Condensed Matter》1997,240(4):353-361
A high resolution X-ray diffraction study has been performed on a single crystal of USb0.8Te0.2. At room temperature this material has the cubic FCC (NaCl) structure. On cooling through the Néel point of 205 K USb0.8Te0.2 is known to enter a triple-q antiferromagnetic phase. Below TC 175 K USb0.8Te0.2 is a ferromagnet with net magnetisation along the 1 1 1 body diagonal. Four-circle X-ray scattering data from high-symmetry {h O h} and {h h h} reflections are presented as a function of temperature. We confirm that this magnetisation directly leads to a magneto-elastic distortion of the crystal lattice with a rhombohedral extension along the 1 1 1 body diagonals. At 130 K, this distortion is found to correspond to a rhombohedral bond angle of = 89.856° ± 0.004° consistent with previous results. In this single-crystal study we also present evidence for additional associated effects which we attribute to inter-grain stresses and sample mosaic structure. 相似文献
152.
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154.
Characteristics of fluorogenic substrates designed for detection of enzyme activity in living cells are reviewed. Improved retention of the fluorescent products in the cell of origin can be achieved by structural modifications to the substrate that result in association with membrane lipids or conjugation to intracellular glutathione. Newly-developed substrates that yield fluorescent precipitates provide the additional advantage of allowing subcellular localization of sites of enzymatic activity. Improved detection sensitivity can also be achieved by targeted delivery of substrates for processing by specific organelles. Substrates designed for monitoring oxidative activity and lipid metabolism provide examples of this approach. 相似文献
155.
A.D. Martin R.G. Roberts M.G. Ryskin W.J. Stirling 《The European Physical Journal C - Particles and Fields》1998,2(2):287-300
We present a formulation which allows heavy quark mass effects to be explicitly incorporated in both the coefficient functions and the splitting functions in the parton evolution
equations. We obtain a consistent procedure for evolution through the threshold regions for and production in deep inelastic scattering, which allows the prediction of the charm and bottom quark densities. We use the
new formulation to perform a next-to-leading order global parton analysis of deep inelastic and related hard scattering data.
We find that the optimum fit has . We give predictions for the charm components of the proton structure functions and as functions of and and, in particular, find that is in good agreement with the existing measurements. We examine the range of validity of the photon-gluon fusion model for electroproduction. We emphasize the value of a precision measurement of the charm component at HERA.
Received: 12 May 1997 / Revised version: 12 June 1997 相似文献
156.
A. C. Bawa Maria Krawczyk W. J. Stirling 《Zeitschrift fur Physik C Particles and Fields》1991,50(2):293-304
Deep inelastic Compton scattering at HERA is investigated with the intention of determining the usefulness of this process in pinning down the photon and proton structure functions. We examine the contributions of the various
s
and
s
2
subprocesses that arise from the nonelementary structure of the photon atS
p
=30000 GeV2. An assessment is made of the sensitivity of this process to the various parton and photon structure functions presently available. In particular we study the possibility of directly measuring the gluon content of the proton and the photon as well as the quark fragmentation into a photon with this process. Theep laboratory frame helps to separate out the different contributions and in particular may allow a quantitative study of the box diagram term. 相似文献
157.
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159.
A. Ballestrero V. A. Khoze E. Maina S. Moretti W. J. Stirling 《Zeitschrift fur Physik C Particles and Fields》1996,72(1):71-78
We examine the colour structure and charged particle yield for both the $t\bar t$ signal and the irreducible background processes contributing to $e^ + e^ - \to b\bar bW^ + W^ - $ production close to the $t\bar t$ threshold. The charged particle multiplicity for the various components of the cross section is computed as a function of several kinematic variables. Our study may have important implications for recently proposed studies of interconnection phenomena in $t\bar t$ production at high-energye + e ? colliders. 相似文献
160.