[en] This paper discusses how a new policy governing disposal of certain low-level radioactive wastes could affect the hazardous waste industry dramatically. A policy statement issued by the Nuclear Regulatory Commission (NRC) formalizes guidelines that would allow it to declare radioactive materials and waste streams generated by certain practices below regulatory concern (BRC), or exempt from regulatory oversight. Once a petition is approved, the exemption will apply to similarly generated wastes at nuclear facilities nationwide. According to an NRC statement issued with the policy, the exemptions would affect materials with levels of radioactivity so low that they do not warrant the same regulatory controls to ensure proper protection of the public and the environment as do higher levels of radioactive materials

[en] This report details the activities in synchrotron radiation and related areas at Daresbury Laboratory during 1989/90. The number and scope of the scientific reports submitted by external users and in-house staff is a reflection of the large amount of scheduled beamtime and high operating efficiency achieved at the Synchrotron Radiation Source (SRS) during the past year. Over 4000 hours of user beam were available, equivalent to about 80% of the total scheduled time. Many of the reports collected here illustrate the increasing technical complexity of the experiments now being carried out at Daresbury. Provision of the appropriate technical and scientific infrastructure and support is a continuing challenge. The development of the Materials Science Laboratory together with the existing Biological Support Laboratory will extend the range of experiments which can be carried out on the SRS. This will particularly facilitate work in which the sample must be prepared or characterised immediately before or during an experiment. The year 1989/90 has also seen a substantial upgrade of several stations, especially in the area of x-ray optics. Many of the advantages of the High Brightness Lattice can only be exploited effectively with the use of focusing optics. As the performance of these stations improves, the range of experiments which are feasible on the SRS will be extended significantly. (author)

[en] The paper on Synchrotron Radiation contains the appendix to the Daresbury Annual Report 1987/88. The appendix is mainly devoted to the scientific progress reports on the work at the Synchrotron Radiation Source in 1987/8. The parameters of the Experimental Stations and the index to the Scientific Reports are also included in the appendix. (U.K.)

[en] The Synchrotron Radiation Source research programme reported from the Daresbury Laboratory has employed the experimental techniques of small angle scattering, protein crystallography, surface diffraction, powder diffraction and x-ray absorption spectroscopy. These have been applied to such problems as corrosion in steels, kinetics in cell biology, the structure of viruses, sulphur disruption of metal surfaces, metal-semiconductor interfaces and the electronic and vibrational structure of molecules. (UK)

[en] Although MR imaging typically shows the meniscus of the temporomandibular joint (TMJ) as a biconcave region of low signal within the joint space, there is a great deal of variability in the MR images of healthy and diseased joints. The authors examined surgically extirpated menisci (n=55), cadaver TMJs (n=16), normal volunteers (n=5), and symptomatic patients (n=25) to identify the important parameters affecting the MR image. The authors found the meniscus has a short T2 (<50 msec), which is shortened further with degenerative changes; short repetition time/echo time (TR/TE) spin-echo images depict morphology well while long TR/TE images provide more information concerning adaptive remodeling of the disc; joint space, disk and condyle relationships are most usefully demonstrated via direct sagittal images; for any given pulse sequence the histopathologic state of the joint is a key determinant of the MR image obtained

[en] Twenty fresh cadaver temporomandibular joints were imaged intact and after removal. Imaging was undertaken to determine those areas of signal which represented discrete regions of anatomic tissue; anterior, posterior, and intermediate zones of the disk; and the joint spaces. Signal/anatomc correlations were generally in agreement with those postulated to date in the literature, with the exception of the posterior band, which is represented by a larger area of signal than previously supposed. The experiments demonstrated that the signals from the joint space include distinct bands representing the articular cartilages. T2 values for the anatomic parts of the normal disk differ significantly, defining a characteristic anteroposterior T2 profile

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No abstract available

[en] The structure of the Ni(111)(³√x³√)R30 degree sign -Pb surface phase formed by a nominal (1/3) monolayer of Pb has been investigated by medium-energy ion scattering using 100 keV H⁺ ions in three different incidence directions. The results show clearly that the Pb atoms occupy fcc hollow sites at the surface, but also favor a structure in which these are surrounded by Ni atoms to form a surface alloy phase. A surface alloy with a surface stacking fault, as has been found for the (³√x³√) surface alloy phases formed by Sb adsorption on Cu(111) and Ag(111), can be clearly excluded. The preference for a surface alloy structure is consistent with the results of an earlier low-energy ion scattering study, but we find significant differences in the quantitative structural parameters. This structural model also implies a considerable reduction of the effective radius of the Pb atoms relative to their size in bulk Pb, and this is discussed in the context of other quantitative structural studies of substitutional surface alloy phases

[en] The search for axions has gained ground in recent years, with laboratory searches for cold dark matter (CDM) axions, relativistic solar axions, and ultra-light axions as the subject of extensive literature. In particular, the interest in axions as CDM candidates has been motivated by their potential to account for all of the inferred values of ${\mathrm{\Omega <!--\; ??\; -->}}_{\mathrm{D}\mathrm{M}}\sim <!--\; ???\; -->0.26$ in the standard $\mathrm{\Lambda <!--\; ??\; -->}\mathrm{C}\mathrm{D}\mathrm{M}$ model. Indeed, the value of ${\mathrm{\Omega <!--\; ??\; -->}}_{\mathrm{D}\mathrm{M}}\sim <!--\; ???\; -->0.26$ could be provided by a light axion. We investigate the possibility of complementing existing axion search experiments with radio telescope observations in an attempt to detect axion conversion in astrophysical magnetic fields. Searching for a CDM axion signal from a large-scale astrophysical environment provides new challenges, with the magnetic field structure playing a crucial role in both the rate of interaction and the properties of the observed photon. However, with a predicted frequency in the radio band (200 MHz–200 GHz) and a distinguishable spectral profile, next-generation radio telescopes may offer new opportunities for detection. The SKA-mid telescope has a planned frequency range of 0.4–13.8 GHz with optimal sensitivity in the range of ∼2–7 GHz. Considering observations at ∼500 MHz, the limiting sensitivity is expected to be ∼0.04 mK based on a 24 hr integration time. This compares with a predicted CDM axion all-sky signal temperature of ∼0.04 mK using SKA Phase 1 telescopes and up to ∼1.17 mK using a collecting area of (1 km)² as planned for Phase 2.