Modeling and prediction of surgical procedure times

Accurate prediction of medical operation times is of crucial importance for cost efficient operation room planning in hospitals. This paper investigates the possible dependence of procedure times on surgeon factors like age, experience, gender, and team composition. The effect of these factors is estimated for over 30 different types of medical operations in two hospitals, by means of ANOVA models for logarithmic case durations. The estimation data set contains about 30,000 observations from 2005 till 2008. The relevance of surgeon factors depends on the type of operation. The factors found most often to be significant are team composition, experience, and daytime. Contrary to widespread opinions among surgeons, gender has nearly never a significant effect. By incorporating surgeon factors, the accuracy of out-of-sample prediction of case durations of about 1,250 surgical operations in 2009 is improved by up to more than 15 percent as compared to current planning procedures.planning;ANOVA model;European hospital;current procedure terminology (CPT);health care management;lognormal distribution;operation room;surgeon factors

Fusarium species and mycotoxin profiles on commercial maize hybrids in Germany

Abstract High year-to-year variability in the incidence of Fusarium spp. and mycotoxin contamination was observed in a two-year survey investigating the impact of maize ear rot in 84 field samples from Germany. Fusarium verticillioides, F. graminearum, and F. proliferatum were the predominant species infecting maize kernels in 2006, whereas in 2007 the most frequently isolated species were F. graminearum, F. cerealis and F. subglutinans. Fourteen Fusariumrelated mycotoxins were detected as contaminants of maize kernels analyzed by a multi-mycotoxin determination method. In 2006, a growth season characterized by high temperature and low rainfall during anthesis and early grain filling, 75% of the maize samples were contaminated with deoxynivalenol, 34% with fumonisins and 27% with zearalenone. In 2007, characterized by moderate temperatures and frequent rainfall during the entire growth season, none of the 40 maize samples had quantifiable levels of fumonisins while deoxynivalenol and zearalenone were detected in 90% and 93% of the fields, respectively. In addition, 3-acetyldeoxynivalenol, 15-acetyldeoxnivalenol, moniliformin, beauvericin, nivalenol and enniatin B were detected as common contaminants produced in both growing seasons. The results demonstrate a significant mycotoxin contamination associated with maize ear rots in Germany and indicate, with regard to anticipated climate change, that fumonisins-producing species already present in German maize production may become more important. Keywords Deoxynivalenol . Ear rot . F. verticillioides . F. graminearum . Fumonisin . Zearalenon

Quantum integrability of quadratic Killing tensors

Quantum integrability of classical integrable systems given by quadratic Killing tensors on curved configuration spaces is investigated. It is proven that, using a "minimal" quantization scheme, quantum integrability is insured for a large class of classic examples.Comment: LaTeX 2e, no figure, 35 p., references added, minor modifications. To appear in the J. Math. Phy

A new limit on the Ultra-High-Energy Cosmic-Ray flux with the Westerbork Synthesis Radio Telescope

A particle cascade (shower) in a dielectric, for example as initiated by an ultra-high energy cosmic ray, will have an excess of electrons which will emit coherent \v{C}erenkov radiation, known as the Askaryan effect. In this work we study the case in which such a particle shower occurs in a medium just below its surface. We show, for the first time, that the radiation transmitted through the surface is independent of the depth of the shower below the surface when observed from far away, apart from trivial absorption effects. As a direct application we use the recent results of the NuMoon project, where a limit on the neutrino flux for energies above $10^{22}$\,eV was set using the Westerbork Synthesis Radio Telescope by measuring pulsed radio emission from the Moon, to set a limit on the flux of ultra-high-energy cosmic rays.Comment: Accepted for publication in Phys. Rev.

Dust absorption and scattering in the silicon K-edge

The composition and properties of interstellar silicate dust are not well understood. In X-rays, interstellar dust can be studied in detail by making use of the fine structure features in the Si K-edge. The features in the Si K-edge offer a range of possibilities to study silicon-bearing dust, such as investigating the crystallinity, abundance, and the chemical composition along a given line of sight. We present newly acquired laboratory measurements of the silicon K-edge of several silicate-compounds that complement our measurements from our earlier pilot study. The resulting dust extinction profiles serve as templates for the interstellar extinction that we observe. The extinction profiles were used to model the interstellar dust in the dense environments of the Galaxy. The laboratory measurements, taken at the Soleil synchrotron facility in Paris, were adapted for astrophysical data analysis and implemented in the SPEX spectral fitting program. The models were used to fit the spectra of nine low-mass X-ray binaries located in the Galactic center neighborhood in order to determine the dust properties along those lines of sight. Most lines of sight can be fit well by amorphous olivine. We also established upper limits on the amount of crystalline material that the modeling allows. We obtained values of the total silicon abundance, silicon dust abundance, and depletion along each of the sightlines. We find a possible gradient of $0.06\pm0.02$ dex/kpc for the total silicon abundance versus the Galactocentric distance. We do not find a relation between the depletion and the extinction along the line of sight.Comment: 18 pages, 16 figures. Accepted for publication in Astronomy and Astrophysic

Molecular Line Profile Fitting with Analytic Radiative Transfer Models

We present a study of analytic models of starless cores whose line profiles have ``infall asymmetry,'' or blue-skewed shapes indicative of contracting motions. We compare the ability of two types of analytical radiative transfer models to reproduce the line profiles and infall speeds of centrally condensed starless cores whose infall speeds are spatially constant and range between 0 and 0.2 km s-1. The model line profiles of HCO+ (J=1-0) and HCO+ (J=3-2) are produced by a self-consistent Monte Carlo radiative transfer code. The analytic models assume that the excitation temperature in the front of the cloud is either constant (``two-layer'' model) or increases inward as a linear function of optical depth (``hill'' model). Each analytic model is matched to the line profile by rapid least-squares fitting. The blue-asymmetric line profiles with two peaks, or with a blue shifted peak and a red shifted shoulder, can be well fit by the ``HILL5'' model (a five parameter version of the hill model), with an RMS error of 0.02 km s-1. A peak signal to noise ratio of at least 30 in the molecular line observations is required for performing these analytic radiative transfer fits to the line profiles.Comment: 48 pages, 20 figures, accepted for publication in Ap

GPS radio sources: new optical observations and an updated master list

* Aims. Identify optical counterparts, address uncertain identifications and measure previously unknown redshifts of the host galaxies of candidate GPS radio sources, and study their stellar populations. * Methods. Long slit spectroscopy and deep optical imaging in the B, V and R bands, obtained with the Very Large Telescope. * Results. We obtain new redshifts for B0316+161, B0407-658, B0904+039, B1433-040, and identify the optical counterparts of B0008-421 and B0742+103. We confirm the previous identification for B0316+161, B0407-658, B0554-026, and B0904+039, and find that the previous identification for B0914+114 is incorrect. Using updated published radio spectral information we classify as non GPS the following sources: B0407-658, B0437-454, B1648+015. The optical colors of typical GPS sources are consistent with single instantaneous burst stellar population models but do not yield useful information on age or metallicity. A new master list of GPS sources is presented.Comment: 10 pages + GPS master list. Accepeted for publication by A&