Four-Dimensional String/String Duality

We present supersymmetric soliton solutions of the four-dimensional heterotic string corresponding to monopoles, strings and domain walls. These solutions admit the $D=10$ interpretation of a fivebrane wrapped around $5$, $4$ or $3$ of the $6$ toroidally compactified dimensions and are arguably exact to all orders in $\alpha'$. The solitonic string solution exhibits an $SL(2,Z)$ {\it strong/weak coupling} duality which however corresponds to an $SL(2,Z)$ {\it target space} duality of the fundamental string.Comment: 14 page

An Efficient Representation of Euclidean Gravity I

We explore how the topology of spacetime fabric is encoded into the local structure of Riemannian metrics using the gauge theory formulation of Euclidean gravity. In part I, we provide a rigorous mathematical foundation to prove that a general Einstein manifold arises as the sum of SU(2)_L Yang-Mills instantons and SU(2)_R anti-instantons where SU(2)_L and SU(2)_R are normal subgroups of the four-dimensional Lorentz group Spin(4) = SU(2)_L x SU(2)_R. Our proof relies only on the general properties in four dimensions: The Lorentz group Spin(4) is isomorphic to SU(2)_L x SU(2)_R and the six-dimensional vector space of two-forms splits canonically into the sum of three-dimensional vector spaces of self-dual and anti-self-dual two-forms. Consolidating these two, it turns out that the splitting of Spin(4) is deeply correlated with the decomposition of two-forms on four-manifold which occupies a central position in the theory of four-manifolds.Comment: 31 pages, 1 figur

Chronic kidney disease care delivered by US family medicine and internal medicine trainees: results from an online survey

BACKGROUND: Complications of chronic kidney disease (CKD) contribute to morbidity and mortality. Consequently, treatment guidelines have been developed to facilitate early detection and treatment. However, given the high prevalence of CKD, many patients with early CKD are seen by non-nephrologists, who need to be aware of CKD complications, screening methods and treatment goals in order to initiate timely therapy and referral. METHODS: We performed a web-based survey to assess perceptions and practice patterns in CKD care among 376 family medicine and internal medicine trainees in the United States. Questions were focused on the identification of CKD risk factors, screening for CKD and associated co-morbidities, as well as management of anemia and secondary hyperparathyroidism in patients with CKD. RESULTS: Our data show that CKD risk factors are not universally recognized, screening for CKD complications is not generally taken into consideration, and that the management of anemia and secondary hyperparathyroidism poses major diagnostic and therapeutic difficulties for trainees. CONCLUSION: Educational efforts are needed to raise awareness of clinical practice guidelines and recommendations for patients with CKD among future practitioners

Gauging the spacetime metric -- looking back and forth a century later

H. Weyl's proposal of 1918 for generalizing Riemannian geometry by local scale gauge (later called {\em Weyl geometry}) was motivated by mathematical, philosophical and physical considerations. It was the starting point of his unified field theory of electromagnetism and gravity. After getting disillusioned with this research program and after the rise of a convincing alternative for the gauge idea by translating it to the phase of wave functions and spinor fields in quantum mechanics, Weyl no longer considered the original scale gauge as physically relevant. About the middle of the last century the question of conformal and/or local scale gauge transformation were reconsidered by different authors in high energy physics (Bopp, Wess, et al.) and, independently, in gravitation theory (Jordan, Fierz, Brans, Dicke). In this context Weyl geometry attracted new interest among different groups of physicists (Omote/Utiyama/Kugo, Dirac/Canuto/Maeder, Ehlers/Pirani/Schild and others), often by hypothesizing a new scalar field linked to gravity and/or high energy physics. Although not crowned by immediate success, this ``retake'' of Weyl geometrical methods lives on and has been extended a century after Weyl's first proposal of his basic geometrical structure. It finds new interest in present day studies of elementary particle physics, cosmology, and philosophy of physics.Comment: 56 pages, contribution to Workshop Hundred Years of Gauge Theory Bad Honnef, July 30 - August 3, 201

Clinical Oversight: Conceptualizing the Relationship Between Supervision and Safety

BACKGROUND: Concern about the link between clinical supervision and safe, quality health care has led to widespread increases in the supervision of medical trainees. The effects of increased supervision on patient care and trainee education are not known, primarily because the current multifacted and poorly operationalized concept of clinical supervision limits the potential for evaluation. OBJECTIVE: To develop a conceptual model of clinical supervision to inform and guide policy and research. DESIGN, SETTING, AND PARTICIPANTS: Observational fieldwork and interviews were conducted in the Emergency Department and General Internal Medicine in-patient teaching wards of two academic health sciences centers associated with an urban Canadian medical school. Members of 12 Internal Medicine and Emergency Medicine teaching teams (n = 88) were observed during regular clinical activities (216 hours). Sixty-five participants (12 physicians, 28 residents, 17 medical students, 8 nurses) also completed interviews about supervision. Field notes and interview transcripts were analyzed for emergent themes using grounded theory methodology. RESULTS: The term clinical oversight was developed to describe patient care activities performed by supervisors to ensure quality of care. Routine oversight (preplanned monitoring of trainees\u27 clinical work) can expose supervisors to concerns that trigger responsive oversight (a double-check or elaboration of trainees\u27 clinical work). Supervisors sometimes engage in backstage oversight (oversight of which the trainee is not directly aware). When supervisors encounter a situation that exceeds a trainee\u27s competence, they move beyond clinical oversight to direct patient care . CONCLUSIONS: This study elaborates a typology of clinical oversight activities including routine, responsive, and backstage oversight. This new typology provides a framework for clinical supervision policy and for research to evaluate the relationship between supervision and safety