Expressions for the precession quantities and their partial derivatives

Precession quantities and numerical partial derivatives as power series in time from arbitrary epoc

Study of extravehicular protection and operations

Extravehicular protection and operation

Newtonian Planetary Ephemerides 1800-2000 - Development Ephemeris Number 28

Computer-calculated Newtonian ephemerides, 1800-2000, for nine principal planets - Development ephemeris number 2

Climate Change Adaptation Challenges Facing New Brunswick Coastal Communities: A Review of the Problems and a Synthesis of Solutions Suggested by Regional Adaptation Research

Through a detailed examination of research conducted in Sackville, New Brunswick, this study synthesizes the findings of a series of focus groups and one-on-one interviews with the aim of achieving the following objectives: to identify and elucidate the important challenges related to climate change that New Brunswick coastal communities are currently facing; and to highlight solutions to these challenges. A number of key impediments are identified (e.g., low levels of community consensus) and the following solutions are proposed: to use flood risk visualization and software to aid adaptation planning; to ensure that high quality data are routinely gathered and shared; to build on ongoing community collaboration and communication; and to strengthen political and community leadership.Grâce à un examen détaillé d’une recherche menée à Sackville, au Nouveau-Brunswick, cette étude résume les trouvailles d’une série de groupes de discussion et d’entretiens de face à face en vue de réaliser les objectifs suivants : déterminer et élucider les défis importants en matière de changement climatique auxquels sont actuellement aux prises les populations côtières du Nouveau-Brunswick et mettre en évidence des solutions aux problèmes en question. On a cerné un certain nombre de principaux obstacles (p. ex. peu de consensus au sein des membres de la collectivité), et les solutions suivantes ont été proposées : utiliser la visualisation des zones exposées aux inondations et des logiciels afin de faciliter le programme d’adaptation, veiller à ce que des données de grande qualité soient recueillies régulièrement et partagées, miser sur la collaboration et la communication continues au sein de la collectivité, renforcer le leadership politique et communautaire

Understanding, justifying, and optimizing radiation exposure for CT imaging in nephrourology

An estimated 4-5 million CT scans are performed in the USA every year to investigate nephrourological diseases such as urinary stones and renal masses. Despite the clinical benefits of CT imaging, concerns remain regarding the potential risks associated with exposure to ionizing radiation. To assess the potential risk of harmful biological effects from exposure to ionizing radiation, understanding the mechanisms by which radiation damage and repair occur is essential. Although radiation level and cancer risk follow a linear association at high doses, no strong relationship is apparent below 100 mSv, the doses used in diagnostic imaging. Furthermore, the small theoretical increase in risk of cancer incidence must be considered in the context of the clinical benefit derived from a medically indicated CT and the likelihood of cancer occurrence in the general population. Elimination of unnecessary imaging is the most important method to reduce imaging-related radiation; however, technical aspects of medically justified imaging should also be optimized, such that the required diagnostic information is retained while minimizing the dose of radiation. Despite intensive study, evidence to prove an increased cancer risk associated with radiation doses below ~100 mSv is lacking; however, concerns about ionizing radiation in medical imaging remain and can affect patient care. Overall, the principles of justification and optimization must remain the basis of clinical decision-making regarding the use of ionizing radiation in medicine

Reconsidering the galactic coordinate system

Initially defined by the IAU in 1958, the galactic coordinate system was thereafter in 1984 transformed from the B1950.0 FK4-based system to the J2000.0 FK5-based system. In 1994, the IAU recommended that the dynamical reference system FK5 be replaced by the ICRS, which is a kinematical non-rotating system defined by a set of remote radio sources. However the definition of the galactic coordinate system was not updated. We consider that the present galactic coordinates may be problematic due to the unrigorous transformation method from the FK4 to the FK5, and due to the non-inertiality of the FK5 system with respect to the ICRS. This has led to some confusions in applications of the galactic coordinates. We tried to find the transformation matrix in the framework of the ICRS after carefully investigating the definition of the galactic coordinate system and transformation procedures, however we could not find a satisfactory galactic coordinate system that is connected steadily to the ICRS. To avoid unnecessary misunderstandings, we suggest to re-consider the definition of the galactic coordinate system which should be directly connected with the ICRS for high precise observation at micro-arcsecond level.Comment: 10 pages, 3 figures, accepted for publication in A&

The theory of canonical perturbations applied to attitude dynamics and to the Earth rotation. Osculating and nonosculating Andoyer variables

The Hamiltonian theory of Earth rotation, known as the Kinoshita-Souchay theory, operates with nonosculating Andoyer elements. This situation parallels a similar phenomenon that often happens (but seldom gets noticed) in orbital dynamics, when the standard Lagrange-type or Delaunay-type planetary equations unexpectedly render nonosculating orbital elements. In orbital mechanics, osculation loss happens when a velocity-dependent perturbation is plugged into the standard planetary equations. In attitude mechanics, osculation is lost when an angular-velocity-dependent disturbance is plugged in the standard dynamical equations for the Andoyer elements. We encounter exactly this situation in the theory of Earth rotation, because this theory contains an angular-velocity-dependent perturbation (the switch from an inertial frame to that associated with the precessing ecliptic of date). While the osculation loss does not influence the predictions for the figure axis of the planet, it considerably alters the predictions for the instantaneous spin-axis' orientation. We explore this issue in great detail