Grazing function g and collimation angular acceptance

The grazing function g is introduced—a synchrobetatron optical quantity that is analogous (and closely connected) to the Twiss and dispersion functions β, α, η, and η′. It parametrizes the rate of change of total angle with respect to synchrotron amplitude for grazing particles, which just touch the surface of an aperture when their synchrotron and betatron oscillations are simultaneously (in time) at their extreme displacements. The grazing function can be important at collimators with limited acceptance angles. For example, it is important in both modes of crystal collimation operation—in channeling and in volume reflection. The grazing function is independent of the collimator type—crystal or amorphous—but can depend strongly on its azimuthal location. The rigorous synchrobetatron condition g=0 is solved, by invoking the close connection between the grazing function and the slope of the normalized dispersion. Propagation of the grazing function is described, through drifts, dipoles, and quadrupoles. Analytic expressions are developed for g in perfectly matched periodic FODO cells, and in the presence of β or η error waves. These analytic approximations are shown to be, in general, in good agreement with realistic numerical examples. The grazing function is shown to scale linearly with FODO cell bend angle, but to be independent of FODO cell length. The ideal value is g=0 at the collimator, but finite nonzero values are acceptable. Practically achievable grazing functions are described and evaluated, for both amorphous and crystal primary collimators, at RHIC, the SPS (UA9), the Tevatron (T-980), and the LHC

American Indian Self-Determination: The Political Economy of a Policy that Works

Since the 1970s, federal American Indian policy in the United States has been aimed at promoting self-determination through self-governance by federally-recognized tribes. This policy has proven to be the only policy that has worked to make significant progress in reversing otherwise distressed social, cultural and economic conditions in Native communities. The policy of self-determination reflects a political equilibrium which has held for four decades and which has withstood various shifts in the party control of Congress and the White House. While Republicans have provided relatively weak support for social spending on Indian issues when compared to Democrats, both parties’ representatives have generally been supportive of self-determination and local self-rule for tribes. Analysis of thousands of sponsorships of federal legislation over 1970-present, however, finds the equilibrium under challenge. In particular, since the late 1990s, Republican congressional support for policies of self-determination has fallen off sharply and has not returned. The recent change in the party control of Congress calls into question the sustainability of self-determination through self-governance as a central principle of federal Indian policy

Status Report of the Inter-Laboratory Task Force on Remote Operation

In February 2000, the International Committee for Future Accelerators initiated a study of a new model for international collaboration on a future large accelerator project, the Global Accelerator Network. The study is based on a model of a facility, which is remote from most of the collaborating institutions. It is designed, built and operated by a collaboration of equal partner institutions distributed around the world. According to this model, the expert-staff from each laboratory remains based at their home institution but continues to participate in the operation of the machine after construction. This report summarizes the conclusions of the Task Force on Remote Operation, which investigated the general and technical implications of far-remote operations.Comment: 32 pages, PDF, report of ICFA sponsored task forc

Donor whole blood DNA methylation is not a strong predictor of acute graft versus host disease in unrelated donor allogeneic haematopoietic cell transplantation

Allogeneic hematopoietic cell transplantation (HCT) is used to treat many blood-based disorders and malignancies. While this is an effective treatment, it can result in serious adverse events, such as the development of acute graft-versus-host disease (aGVHD). This study aimed to develop a donor-specific epigenetic classifier that could be used in donor selection in HCT to reduce the incidence of aGVHD. The discovery cohort of the study consisted of 288 donors from a population receiving HLA-A, -B, -C and -DRB1 matched unrelated donor HCT with T cell replete peripheral blood stem cell grafts for treatment of acute leukaemia or myelodysplastic syndromes after myeloablative conditioning. Donors were selected based on recipient aGVHD outcome; this cohort consisted of 144 cases with aGVHD grades III-IV and 144 controls with no aGVHD that survived at least 100 days post-HCT matched for sex, age, disease and GVHD prophylaxis. Genome-wide DNA methylation was assessed using the Infinium Methylation EPIC BeadChip (Illumina), measuring CpG methylation at >850,000 sites across the genome. Following quality control, pre-processing and exploratory analyses, we applied a machine learning algorithm (Random Forest) to identify CpG sites predictive of aGVHD. Receiver operating characteristic (ROC) curve analysis of these sites resulted in a classifier with an encouraging area under the ROC curve (AUC) of 0.91. To test this classifier, we used an independent validation cohort (n=288) selected using the same criteria as the discovery cohort. Different attempts to validate the classifier using the independent validation cohort failed with the AUC falling to 0.51. These results indicate that donor DNA methylation may not be a suitable predictor of aGVHD in an HCT setting involving unrelated donors, despite the initial promising results in the discovery cohort. Our work highlights the importance of independent validation of machine learning classifiers, particularly when developing classifiers intended for clinical use