A characterization of shortest geodesics on surfaces

Any finite configuration of curves with minimal intersections on a surface is a configuration of shortest geodesics for some Riemannian metric on the surface. The metric can be chosen to make the lengths of these geodesics equal to the number of intersections along them.Comment: Published by Algebraic and Geometric Topology at http://www.maths.warwick.ac.uk/agt/AGTVol1/agt-1-17.abs.htm

The relative price of non-traded goods under imperfect competition

We consider the role of imperfect competition in explaining the relative price of non-traded to traded goods within the Balassa-Samuelson framework. Under imperfect competition in these two sectors, relative prices depend on both productivity and mark-up differentials. We test this hypothesis using a panel of sectors for 12 OECD countries. The empirical evidence suggests that relative price movements are well explained by productivity and mark-up differentials.This study is partly funded by the Galician government under grants INCITE09201042PR and MTM2008-03010

Constraints on the properties of the turbulent magnetic field around Geminga using HAWC measurements

We place constraints on the properties of the interstellar turbulence that surrounds Geminga pulsar, using the recent measurements from the HAWC Observatory in this region. We propagate very-high-energy electrons in realizations of 3D isotropic Kolmogorov or Kraichnan turbulence, calculate their gamma-ray emission, and compare with HAWC measurements. We show that the measurements can be well fitted for both models of the turbulence and for reasonable values of its strength, $B_{\rm rms}$, and coherence length, $L_{\rm c}$. Our best fits are obtained for $B_{\rm rms} \simeq 3 \mu$G and $L_{\rm c} \simeq 1$ pc. Furthermore, the absence of strong asymmetries in the observed emission favours $L_{\rm c} \leq 5$ pc.Comment: 6 pages, 3 figures. Submitted to Journal of Physics: Conference Series. Talk presented at the 26th Extended European Cosmic Ray Symposium, Barnaul, July 201

An Exploratory Study of Patient Falls

Debate continues between the contribution of education level and clinical expertise in the nursing practice environment. Research suggests a link between Baccalaureate of Science in Nursing (BSN) nurses and positive patient outcomes such as lower mortality, decreased falls, and fewer medication errors. Purpose: To examine if there a negative correlation between patient falls and the level of nurse education at an urban hospital located in Midwest Illinois during the years 2010-2014? Methods: A retrospective crosssectional cohort analysis was conducted using data from the National Database of Nursing Quality Indicators (NDNQI) from the years 2010-2014. Sample: Inpatients aged ≥ 18 years who experienced a unintentional sudden descent, with or without injury that resulted in the patient striking the floor or object and occurred on inpatient nursing units. Results: The regression model was constructed with annual patient falls as the dependent variable and formal education and a log transformed variable for percentage of certified nurses as the independent variables. The model overall is a good fit, F (2,22) = 9.014, p = .001, adj. R2 = .40. Conclusion: Annual patient falls will decrease by increasing the number of nurses with baccalaureate degrees and/or certifications from a professional nursing board-governing body

Investment cost channel and monetary transmission

Copyright @ 2011 Central Bank Review. This article is available open access through the publisher’s website at the link below.We show that a standard DSGE model with investment cost channels has important model stability and policy implications. Our analysis suggests that in economies characterized by supply side well as demand side channels of monetary transmission, policymakers may have to resort to a much more aggressive stand against inflation to obtain locally unique equilibrium. In such an environment targeting output gap may cause model instability. We also show that it is difficult to distinguish between the New Keynesian model and labor cost channel only case, while with investment cost channel differences are more significant. This result is important as it suggests that if one does not take into account the investment cost channel, one is underestimating the importance of supply side effects

The relative price of non-traded goods under imperfect competition

This article is available open access through the publisher’s website. Copyright @ 2012 The Department of Economics, University of Oxford.We consider the role of imperfect competition in explaining the relative price of non-traded to traded goods within the Balassa–Samuelson framework. Under imperfect competition in these two sectors, relative prices depend on both productivity and mark-up differentials. We test this hypothesis using a panel of sectors for 12 OECD countries. The empirical evidence suggests that relative price movements are well explained by productivity and mark-up differentials.The Galician governmen

Constraining the properties of the magnetic turbulence in the Geminga region using HAWC γ\gamma-ray data

Observations of extended gamma-ray emission around Galactic cosmic-ray (CR) sources can be used as novel probes of interstellar magnetic fields. Using very-high-energy gamma-ray data from the HAWC Observatory, we place constraints on the properties of the magnetic turbulence within $\approx 25$ pc from Geminga. We inject and propagate individual CR electrons in 3D realizations of turbulent magnetic fields, calculate the resulting gamma-ray emission, and compare with HAWC measurements of this region. We find that HAWC data is compatible with expectations for Kolmogorov or Kraichnan turbulence, and can be well fitted for reasonable coherence lengths and strengths of the turbulence, despite implying a CR diffusion coefficient significantly smaller than those suggested by Galactic CR propagation codes. The best fit is found for a coherence length $L_{\rm c} \approx 1$ pc and a magnetic field strength $B_{\rm rms} \approx 3 \mu$G, and the preferred value for $L_{\rm c}$ increases with $B_{\rm rms}$. Moreover, the apparent lack of strong asymmetries in the observed emission allows us to constrain the coherence length to $L_{\rm c} \lesssim 5$ pc in this region.Comment: submitted to MNRA

The Relative Price of Non-traded Goods in an Imperfectly Competitive Economy: Empirical Evidence for G7 Countries

In this paper, we consider the role of imperfect competition in explaining the relative price of non-traded to traded goods within the Balassa-Samuelson framework. Under imperfect competition in the two sectors, relative prices depend on both productivity differentials and mark-up differentials. We test this implication using a panel of sectors for the seven major OECD countries. The empirical evidence suggests that relative price movements are well explained by productivity and mark-up differentials. Unlike the original Balassa-Samuelson model, aggregate demand could affect the real exchange rate by changing the mark ups. The empirical results show that aggregate demand fluctuations lead to changes on the mark-ups