• The apparent (gravitational) horizon in cosmology

  Melia, Fulvio; Univ Arizona, Dept Phys, Appl Math Program; Univ Arizona, Dept Astron (AMER ASSOC PHYSICS TEACHERS, 2018-08)

  In general relativity, a gravitational horizon (more commonly known as the "apparent horizon") an imaginary surface beyond which all null geodesics recede from the observer. The Universe has an apparent (gravitational) horizon, but unlike its counterpart in the Schwarzschild and Kerr metrics, it is not static. It may eventually turn into an event horizon-an asymptotically defined membrane that forever separates causally connected events from those that are not-depending on the equation of state of the cosmic fluid. In this paper, we examine how and why an apparent (gravitational) horizon is manifested in the Friedmann-Robertson-Walker metric, and why it is becoming so pivotal to our correct interpretation of the cosmological data. We discuss its observational signature and demonstrate how it alone defines the proper size of our visible Universe. In so doing, we affirm its physical reality and its impact on cosmological models. (C) 2018 American Association of Physics Teachers.
• Clinical learning experiences of nursing students using an innovative clinical partnership model: A non-randomized controlled trial

  Chan, Aileen W.K.; Tang, Fiona W.K.; Choi, Kai Chow; Liu, Ting; Taylor-Piliae, Ruth E.; Univ Arizona, Coll Nursing (CHURCHILL LIVINGSTONE, 2018-09)

  Background: Clinical practicum is a major learning component for pre-registration nursing students. Various clinical practicum models have been used to facilitate students' clinical learning experiences, employing both university-based and hospital-based clinical teachers. Considering the strengths and limitations of these clinical practicum models, along with nursing workforce shortages, we developed and tested an innovative clinical partnership model (CPM) in Hong Kong. Objective: To evaluate an innovative CPM among nursing students actual and preferred clinical learning environment, compared with a conventional facilitation model (CFM). Design: A non-randomized controlled trial examining students' clinical experiences, comparing the CPM (supervised by hospital clinical teacher) with the CFM (supervised by university clinical teacher). Setting One university in Hong Kong. Participants: Pre-registration nursing students (N = 331), including bachelor of nursing (n = 246 year three-BN) and masters-entry nursing (n = 85 year one-MNSP). Methods: Students were assigned to either the CPM (n = 48 BN plus n = 85 MNSP students) or the CFM (n = 198 BN students) for their clinical practice experiences in an acute medical-surgical ward. Clinical teachers supervised between 6 and 8 students at a time, during these clinical practicums (duration = 4-6 weeks). At the end of the clinical practicum, students were invited to complete the Clinical Learning Environment Inventory (CLEI). Analysis of covariance was used to compare groups; adjusted for age, gender and prior work experience. Results: A total of 259 students (mean age = 22 years, 76% female, 81% prior work experience) completed the CLEI (78% response rate). Students had higher scores on preferred versus actual experiences, in all domains of the CLEI. CPM student experiences indicated a higher preferred task orientation (p = 0.004), while CFM student experiences indicated a higher actual (p < 0.001) and preferred individualization (p = 0.005). No significant differences were noted in the other domains. Conclusions: The CPM draws on the strengths of existing clinical learning models and provides complementary methods to facilitate clinical learning for pre-registration nursing students. Additional studies examining this CPM with longer duration of clinical practicum are recommended.
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  Dendrochronological dating in Egypt: Work accomplished and future prospects

  Kuniholm, P.I.; Newton, M.; Sherbiny, H.; Bassir, H. (Tree-Ring Society, 2014)

  We assess the state of and potential for expansion of dendroarchaeological research in Egypt. We also report previously unpublished findings, which we hope will assist with the new effort in constructing tree-ring chronologies in Egypt. In doing so, we explain briefly some of the problems and potential of the future enterprise.
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  Tree Rings and the chronology of ancient Egypt

  Creasman, P.P. (Tree-Ring Society, 2014)

  A fundamental aspect of ancient Egyptian history remains unresolved: chronology. Egyptologists (and researchers in related fields that synchronize their studies with Egypt) currently rely on a variety of insufficiently precise methodologies (king lists, radiocarbon dating, etc.) from which to derive seemingly “absolute” dates. The need for genuine precision has been recognized for a century, as has the potential solution: dendrochronology. This manuscript presents a case for further progress toward the construction of a tree-ring chronology for ancient Egypt.
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  A tree-ring based late summer temperature reconstruction (AD 1675–1980) for the northeastern Mediterranean

  Trouet, V. (Tree-Ring Society, 2014)

  This article presents a late summer temperature reconstruction (AD 1675–1980) for the northeastern Mediterranean (NEMED) that is based on a compilation of maximum latewood density tree-ring data from 21 high-elevation sites. This study applied a novel approach by combining individual series from all sites into one NEMED master chronology. This approach retains only the series with a strong and temporally robust common signal and it improves reconstruction length. It further improved the regional character of the reconstruction by using as a target averaged gridded instrumental temperature data from a broad NEMED region (38–45°N, 15–25°E). Cold (e.g. 1740) and warm (e.g. 1945) extreme years and decades in the reconstruction correspond to regional instrumental and reconstructed temperature records. Some extreme periods (e.g. cold 1810s) reflect European-wide or global-scale climate conditions and can be explained by volcanic and solar forcing. Other extremes are strictly regional in scope. For example, 1976 was the coldest NEMED summer over the last 350 years, but was anomalously dry and hot in northwestern Europe and is a strong manifestation of the summer North Atlantic Oscillation (sNAO). The regional NEMED summer reconstruction thus contributes to an improved understanding of regional (e.g. sNAO) vs. global-scale (i.e. external) drivers of past climate variability.

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