Quality assurance in immunogenetics and histocompatibility: experience with EFI Accreditation

 The European Federation for Immunogenetics (EFI) has its own standards for histocompatibility testing. Compared with EN 45001 and ISO Standards, EFI Standards are more detailed, actually stating "what to do" in the laboratory. The decision of Eurotransplant that all its organ transplantation programmes must be EFI-accredited by the year 2000, illustrates the importance of the these standards. It took us 11 months to prepare the EFI questionnaire, describing the main features of our laboratory and how they complied with EFI Standards. After approval of this file, inspection was performed by a team of two peers who routinely worked in an EFI-accredited tissue typing laboratory. The pre-analytical, analytical and post-analytical phases were inspected during a one day visit. Furthermore, a checklist was reviewed against the laboratory's documentation system. Within 1 month of reception of the inspection report, we were expected to send a reply listing the corrective actions taken. Upon acknowledgement of the latter, EFI Accreditation was granted, for 1 year. We feel that detailed standards, specifically designed for a certain type of laboratory, offer many advantages. Received: 15 April 2000 · Accepted: 15 April 2000     

Theory of angular momentum waves in solid ortho-hydrogen

The Theory of angular momentum waves in pure ortho-hydrogen is presented in the Bloch spin wave approximation. Since there is a large energy gap between the ground state and the excitation this approximation can be justified. Quadrupole-quadrupole interaction of nearest neighbours is used. We have derived some dispersion curves and the spectrum.     

Random phase approximation of angular momentum waves in solid Ortho-hydrogen

A short derivation of the Random Phase Approximation of angular momentum waves in solid Ortho-H₂ is presented. Methods and results of papers on the same topic are compared.     

Soliton ratchets out of point-like inhomogeneities

We introduce and study a novel design for a ratchet potential for soliton excitations. The potential is implemented by means of an array of point-like (delta) inhomogeneities in an otherwise homogeneous potential. We use collective coordinates which predict that the effective potential acting on the soliton is periodic but asymmetric and gives rise to the ratchet effect. Numerical simulations fully confirm this prediction; quantitative agreement is reached by an improved version of the theory. Although we specifically show that it is most interesting for building Josephson junction ratchets capable to rectify time-symmetric ac forces, the proposed mechanism is very general and can appear in many contexts, including biological systems.Received: 25 November 2003, Published online: 19 February 2004PACS: 05.45.Yv Solitons - 05.60.-k Transport processes - 63.20.Pw Localized modes     

Light nuclei as distinct probes for transient magnetic fields

Salient features of transient magnetic fields are brought out from nuclear spin precession measurements on light ions penetrating polarized Fe-, Ni- and Gd-hosts. At low velocities ion fractions with singleK-shell vacancies, at high velocities H-like charge state fractions, can account for the observed precessions. The data suggest a sharp reduction of theK-shell field at a velocityv _ion?0.5v ₀. Large degrees ofK-shell polarization have been derived for C- and O-ions. Measurements in different ferromagnets show that the transient fields scale with the polarized electron density of the host.     

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Densities and velocity distributions of atomic hydrogen and carbon,measured by laser-induced fluorescence with frequency tripling into the vacuum UV

By focussing a commercial dye laser pumped with a XeCl excimer laser into phase matched Xe-A or Kr-A gas mixtures, radiation at the third-harmonic frequency has been generated in the wavelength regions: 1142–1165, 1178–1186, 1203–1224, and 1268–1290 Å. VUV powers up to about 200 W have been detected by a calibrated Au-photodiode. The vacuum uv radiation has been used for the fluorescence excitation of H and C atoms produced by thermal dissociation or by a gas discharge. Absolute densities have been derived by a comparison of fluorescence intensities with intensities from Rayleigh scattering in argon. As a further application, velocity distributions of C atoms sputtered from a graphite target by 1.5 keV argon ions have been measured. These data are in good agreement with a Thompson distribution corresponding to a surface energy of 8.2 eV.