Results are reported from the HERMES experiment at HERA on a measurement of the neutron spin structure function ~(x, Q2) in deep inelastic scattering using 27.5 GeV longitudinally polarized positrons incident on a polarized 3He internal gas target. The data cover the kinematic range 0.023 < x < 0.6 and 1 (GeV/c) 2 < Q2 < 15 (GeV/c) 2. The integral fo~i0623 ~(x) dx evaluated at a fixed Qz of 2.5 (GeV/c) 2 is-0.0344-0.013(stat.)+0.005(syst.). Assuming Regge behavior at low x, the first moment F'~ = fl ~(x)dx is-0.037 ± 0.013(stat.)±0.005(syst.)±0.006(extrapol.

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Spin asymmetries of semi-inclusive cross sections for the production of positively and negatively charged hadrons have been measured in deep-inelastic scattering of polarized positrons on polarized hydrogen and He-3 targets, in the kinematic range 0.023 < x < 0.6 and 1 GeV2 < Q(2) < 10 GeV2. Polarized quark distributions are extracted as a function of x for up (u + (u) over bar) and down (d + (d) over bar) flavors. The up quark polarization is positive and the down quark polarization is negative in the measured range. The polarization of the sea is compatible with zero. The first moments of the polarized quark distributions are presented. The isospin non-singlet combination dq, is consistent with the prediction based on the Bjorken sum rule. The moments of the polarized quark distributions are compared to predictions based on SU(3)(f) flavor symmetry and to a prediction from lattice QCD. (C) 1999 Published by Elsevier Science B.V. All rights reserved

The problem of the ideal fluid flow around a spheroidal obstacle inside a coaxial cylinder is solved by a slight variation of the method described earlier [W. R. Smythe, Phys. Fluids 4, 756, (1961)]. Errors in the terminal digits of Table I of that paper have been corrected and the table extended. The flow is confined to the space between spheroid and cylinder by thin vortex sheets of variable strength on the spheroid and cylinder surfaces. The vector potential of the flow is expressed in terms of the circulation density on the spheroid surfaces of which tables are given for the disk, oblate spheroid with axial ratio 2 to 1, sphere and prolate spheroid with axial ratio 1 to 2 for equatorial radii 0.1, 0.2, … , 0.95 of the cylinder radius. A table shows the increase in flow resistance due to the insertion of the spheroid in terms of the equivalent additional tube length.

Two formulas are derived for the capacitance of a flat circular annulus. The first has an accuracy of 1 part in 1000 or better when the ratio of the external to the internal radius lies between 1.1 and ∞ and is exact at ∞. The second, C=34.96R/ln(32R/c) μμf, has an accuracy of 1 part in 1000 when the ratio lies between 1.000 and 1.1 and is exact at 1.000. In this formula c is the difference of the radii and R their mean value in meters. An approximate expression for the charge density is given in the first case.