On the Nature of the Binary Components of RX J0806.3+1527

We present imaging circular polarimetry and near-infrared photometry of the suspected ultra-short period white-dwarf binary RX J0806.3+1527 obtained with the ESO VLT and discuss the implications for a possible magnetic nature of the white dwarf accretor and the constraints derived for the nature of the donor star. Our V-filter data show marginally significant circular polarization with a modulation amplitude of ~0.5% typical for cyclotron emission from an accretion column in a magnetic field of order 10 MG and not compatible with a direct-impact accretor model. The optical to near-infrared flux distribution is well described by a single blackbody with temperature kT_bb = 35000 K and excludes a main-sequence stellar donor unless the binary is located several scale heights above the galactic disk population.Comment: 2 pages including 2 figures. To appear in RevMexAA(SC) Conference Series, Proc. of IAU Colloquium 194 `Compact Binaries in the Galaxy and Beyond', La Paz (Mexico), eds. G. Tovmassian & E. Sio

Integrated Clinical Pathways: A Model-based Holistic Method

Against the background of increasing multidisciplinarity as well as the focus on quality, transparency and economic efficiency of medical services, clinical pathways (CPs) have been established as a promising tool at the organizational level in recent years. They are primarily intended to ensure an adequate description of the care processes and to manage the balance between best treatment practice and economic viability. CPs standardize the internal care services by explicating the institution-specific knowledge with regard to recommendations for action, service portfolio, organizational structures, infrastructure, etc. of a specific service provider. The development of hospital information systems (HIS) has so far been characterized by an evolutionary development of modules in the field of laboratory, radiology, nursing and picture archiving systems as well as in the area of administrative systems. As one result of this development, the HIS usually comprises a heterogeneous network of software systems of different types and manufacturers. However, the actual control of patients by means of evidence-based processes and integration of CPs into HIS was not addressed until the recent years, when HIS manufacturers started developing modules for CP modeling and workflow support. The objective of this thesis is to provide a holistic methodical support for the description of clinical pathways and their integration into a hospital information system to finally improve the compliance of daily care to standard process definitions. Therefore, conceptual models provide an adequate mean to describe and communicate complex matters in a comprehensible form as well as to configure IT systems due to their semi-formal nature. Hence, a first research thread investigates the question, how clinical pathways can be described adequately using conceptual models. This results in an iterative design of adequate modeling languages for clinical pathways. A second research thread further investigates the question, how conceptual models of clinical pathways can be used to configure process-oriented application systems in health care. This thread therefore describes the design of a model-based method, that enables a consecutive transformation of CPs into technical (workflow) specifications, based on the principles of the Model-Driven Architecture.:A. Synopsis of the Doctoral Dissertation B. Agility in Medical Treatment Processes C. Domain Specific Modeling Language - CPmod D. BPMN4CP - Version 1.0 E. BPMN4CP - Version 2.0 F. BPMN4CP - Version 2.1 G. MDA in Health Care IS Development H. Transforming Clinical Pathways into Care Workflows I. CDA Templates - Utilizing the MediCUB

Two problems in computational geometry

En aquesta tesi s'estudien dos problemes del camp de la geometria computacional. El primer problema és: donat un set S de n punts en el pla en posició general, com de prop són quatre punts de S de ser cocirculars. Definim tres mesures per estudiar aquesta qüestió, la mesura de Tales, la mesura de Voronoi, i la mesura del Determinant. Presentem cotes per la mesura de Tales, i algoritmes per computar aquestes mesures de cocircularitat. També reduïm el problema de computar la cocircularitat emprant la mesura del Determinant al problema de 4SUM. El segon problema és: donat dos sets R i B de punts rojos i blaus respectivament, com computar la discrepància bicromàtica amb caixes i cercles. La discrepància bicromàtica és definida com la diferència entre el nombre de punts vermells i blaus que són a l'interior de la figura examinada. Presentem una comparativa entre algoritmes ja existents per les dues figures. També comparem la discrepància bicromàtica de caixes orientades en els eixos vs. d'orientació general. A més a més, també presentem un nou algoritme per la discrepància en esferes/discs per a altes dimensions, basat en literatura ja existent. També relacionem altres problemes en el tema de separabilitat amb algoritmes sensitius a l'output per la discrepància amb caixes.En esta tesis se estudian dos problemas del campo de la geometría computacional. El primer problema es: dado un set S de n puntos en el plan en posición general, como de cerca son cuatro puntos de S de ser cocirculares. Definimos tres medidas para estudiar esta cuestión, la medida de Tales, la medida de Voronoi, y la medida del Determinante. Presentamos cotas por la medida de Tales, y algoritmos para computar estas medidas de cocircularidad. También reducimos el problema de computar la cocircularidad usando la medida del Determinante al problema de 4SUM. El segundo problema es: dado dos sets R y B de puntos rojos y azules respectivamente, como computar la discrepancia bicromática con cajas y círculos. La discrepancia bicromática es definida como la diferencia entre el número de puntos rojos y azules que están en el interior de la figura examinada. Presentamos una comparativa entre algoritmos ya existentes por las dos figuras. También comparamos la discrepancia bicromática de cajas orientadas en los ejes vs. de orientación general. Además, también presentamos un nuevo algoritmo por la discrepancia en esferas/discos para altas dimensiones, basado en literatura ya existente. También relacionamos otros problemas en el tema de separabilidad con algoritmos sensitivos al output por la discrepancia con cajas.Two different problems belonging to computational geometry are studied in this thesis. The first problem studies: given a set S of n points in the plane in general position, how close are four points of S to being cocircular. We define three measures to study this question, the Thales, Voronoi and Determinant measures. We present bounds on the Thales almost-cocircularity measure over a point set. Algorithms for computing these measures of cocircularity are presented as well. We give a reduction from computing cocircularity using the Determinant measure to the 4SUM problem. The second problem studies: given two sets R and B of red and blue points respectively, how to compute the bichromatic discrepancy using boxes and circles. The bichromatic discrepancy is defined as the difference between the number of red points and blue points inside the shape. We present a comparison of algorithms in the existing literature for the two shapes. Bichromatic discrepancy in axis-parallel boxes .vs non-axis-parallel boxes is also compared. Furthermore, we also present a new algorithm for disk discrepancy in higher dimensions, based on existing literature. We also relate existing problems in separability with existing output sensitive algorithms for bichromatic discrepancy using boxes

Chandra LETGS spectroscopy of the Quasar MR2251-178 and its warm absorber

We present an analysis of our Chandra Low Energy Transmission Grating Spectrometer (LETGS) observation of the quasar MR2251-178. The warm absorber of MR2251-178 is well described by a hydrogen column density, N_H~2x10^21 cm^-2, and an ionization parameter log(xi)~0.6. We find in the spectrum weak evidence for narrow absorption lines from Carbon and Nitrogen which indicate that the ionized material is in outflow. We note changes (in time) of the absorption structure in the band (0.6-1) keV (around the UTAs plus the OVII and OVIII K-edges) at different periods of the observation. We measure a (0.1-2) keV flux of 2.58x10^-11 ergs cm^-2 s^-1. This flux implies that the nuclear source of MR2251-178 is in a relatively low state. No significant variability is seen in the light curve. We do not find evidence for an extra cold material in the line of sight, and set an upper limit of N_H~1.2x10^20 cm^-2. The X-ray spectrum does not appear to show evidence for dusty material, though an upper limit in the neutral carbon and oxygen column densities can only be set to N_CI~2x10^19 cm^-2 and N_OI~9x10^19 cm^-2, respectively.Comment: 42 pages, 12 figures, Accepted in Apj. Typo in abstract (ver2): "We do not find evidence for an extra...

The high-field polar RX J1007.5-2017

We report optical and X-ray observations of the high-field polar RXJ1007.5-2017 performed between 1990 and 2012. It has an orbital period of 208.60 min determined from the ellipsoidal modulation of the secondary star in an extended low state. The spectral flux of the dM3- secondary star yields a distance of 790+-105 pc. At low accretion levels, \RX{} exhibits pronounced cyclotron emission lines. The second and third harmonic fall in the optical regime and yield a field strength in the accretion spot of 94 MG. The source is highly variable on a year-to-year basis and was encountered at visual magnitudes between V \sim 20 and V \sim 16. In the intermediate state of 1992 and 2000, the soft X-ray luminosity exceeds the sum of the luminosities of the cyclotron source, the hard X-ray source, and the accretion stream by an order of magnitude. An X-ray high state, corresponding to the brightest optical level, has apparently not been observed so far.Comment: To be published in A&

Some open problems on geometric separability

En aquest projecte hem considerat dos problemes oberts de separació de punts vermells i blaus en el pla, contextualitzats en el camp de la geometria computacional. Partint de resultats ja coneguts, hem estès i millorat els algoritmes, concretament per la separabilitat emprant 4 rectes paral·leles en tires monocromàtiques. I hem analitzat condicions suficients per a aquests criteris de separabilitat.In this project, we have tackled two open questions regarding the separability of red and blue points in the plane, from the framework of computational geometry. Building on existing results, we have extended and improved algorithms, specifically for the separability using 4 parallel lines that define monochromatic strips. Also, sufficient conditions to meet these separability criteria have been studied