High energy electron diffraction instrument with tunable camera length.

Ultrafast electron diffraction (UED) stands as a powerful technique for real-time observation of structural dynamics at the atomic level. In recent years, the use of MeV electrons from radio frequency guns has been widely adopted to take advantage of the relativistic suppression of the space charge effects that otherwise limit the temporal resolution of the technique. Nevertheless, there is not a clear choice for the optimal energy for a UED instrument. Scaling to beam energies higher than a few MeV does pose significant technical challenges, mainly related to the inherent increase in diffraction camera length associated with the smaller Bragg angles. In this study, we report a solution by using a compact post-sample magnetic optical system to magnify the diffraction pattern from a crystal Au sample illuminated by an 8.2 MeV electron beam. Our method employs, as one of the lenses of the optical system, a triplet of compact, high field gradients (>500 T/m), small-gap (3.5 mm) Halbach permanent magnet quadrupoles. Shifting the relative position of the quadrupoles, we demonstrate tuning the magnification by more than a factor of two, a 6× improvement in camera length, and reciprocal space resolution better than 0.1 Å-1 in agreement with beam transport simulations.

Gleason scoring varies among pathologists and this affects clinical risk in patients with prostate cancer.

AIMS: To investigate whether our practice of specialist review of all diagnostic biopsies was necessary to prevent misgrading of referred prostate cancer patients, and whether this misclassification, if any, would have resulted in misclassification of clinical risk grouping (Seattle Risk Grouping [SRG]) and subsequent treatment strategy and prognosis. MATERIALS AND METHODS: Important prognostic indicators for prostate cancer include the presenting prostate-specific antigen (PSA), clinical stage and Gleason sum of the tumour. These three variables are incorporated into the SRG cohorts to establish treatment strategy. Patients with prostate cancer referred for brachytherapy had their prostate biopsies reviewed by a reference pathologist (PD) with a special interest in prostate cancer. We compared the agreement between the scoring of the referring pathologists with that of PD, and evaluated if any differences changed the SRG and therefore the clinical risk and treatment strategy for the patients. RESULTS: In only 52% (43/83) of cases, was there total agreement between the two sets of pathologists. The inter-rater agreement was statistically 'fair' (unweighted kappa statistic 0.27). In 90% (36/40) of cases with disagreement, PD assigned higher Gleason sums. In 40% (16/40) of cases with disagreement, the change in Gleason sum altered the SRG; in one out of 16 cases, the SRG was downgraded from 'intermediate' to 'low' risk disease; in six out of 16 cases, it was upgraded from 'low' to 'intermediate' risk, and, in nine out of 16, from 'intermediate' to 'high' risk. CONCLUSION: Our findings confirm previous reports of only limited correlation between pathologists in reporting Gleason sums. In this study, 19% (16/83) of cases had their grading changed to a level that altered clinical risk, almost always (94%; 15/16) to one that worsened prognosis. This would have significantly affected treatment strategy for these patients, and thus we recommend that all centres ensure accurate Gleason grading by the use of pathologists with special interests in prostate cancer.

Masked deposition techniques for achieving multilayer period variations required for short-wavelength (68-A) soft-x-ray imaging optics.

Practical issues in the development of multilayer coatings for reflective imaging systems operating at λ ≈ 68 Å are discussed. The 1% bandpass of Ru/B(4) C multilayers at this short wavelength imposes stringent tolerances with which the actual multilayer period variation across the curved surfaces must match the ideal period variation for a 20× demagnifying Schwarzschild objective. New deposition techniques that use masks to correct the period variation across the curved surfaces of each optic have been developed to ensure reflectance over the entire clear aperture. The narrow bandpass together with steep lateralperiod gradients and steeply curved surfaces requires improved metrology for an acceptable period variation to be obtained and the overlap of the reflectance peaks on the two mirrors to be verified.