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Search Results: 1 - 10 of 223984 matches for " R. Neubert "
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Bending Angle and Temperature Climatologies from Global Positioning System Radio Occultations
R. Biondi,T. Neubert
Dataset Papers in Science , 2013, DOI: 10.7167/2013/795749
Abstract: The Global Positioning System (GPS) Radio Occultation (OR) technique provides estimates of atmospheric density, temperature, and water vapour content with high vertical resolution, global coverage, and high accuracy. We have used data acquired using this technique in the period 1995–2009 to create a reference climatology of radio occultation bending angle and atmospheric temperature which are used for meteorological studies. The bending angle is interesting because it is a direct measurement and independent of models. It is given with one-degree spatial resolution and 50-meter vertical sampling. In addition, we give the temperature climatology with one-degree spatial resolution and 100-meter vertical sampling. This dataset can be used for several applications including weather forecast, physics of atmosphere, and climate changes. Since the GPS signal is not affected by clouds and the acquisitions are evenly distributed in the globe, the dataset is well suited for studying extreme events (such as convective systems and tropical cyclones) and remote areas. 1. Introduction The Global Positioning System (GPS) Radio Occultation (RO) technique [1] enables measurements of the global atmospheric density structure under any meteorological condition [2]. As illustrated in Figure 1, the RO technique involves a GPS satellite transmitting the signal and a Low Earth Orbit (LEO) satellite carrying a receiver. The signal transmitted by the GPS satellite is refracted in the atmosphere, and the associated propagation delay, refractive index, and bending angle are measured on the LEO satellite. From the measurements, it is possible to estimate profiles of atmospheric parameters such as temperature, water vapour, and pressure [3]. These parameters are secondary products, derived from the refractivity together with the European Centre for Medium-Range Weather Forecasts (ECMWF) model, and are given with high vertical resolution. The highest accuracy on the refractivity is achieved between 5 and 25?km altitude with average errors estimated in the range 0.3%–0.5% [4]. The RO technique has improved the weather forecast in regions of the globe that is poorly covered by standard measurements, such as the southern hemisphere which is dominated by oceans [5]. For instance, forecasting the track of tropical cyclones (energized over the oceans) has greatly improved [6]. Also the upper atmosphere is better forecasted as in the case of the ECMWF Upper Troposphere Lower Stratosphere (UTLS) model [7]. Figure 1: The GPS RO technique scheme (the proportions are not respected) [ 1]. Dashed
Low temperature phase diagram and critical behaviour of the four-state chiral clock model
M. Pleimling,B. Neubert,R. Siems
Physics , 1998, DOI: 10.1088/0305-4470/31/21/006
Abstract: The low temperature behaviour of the four-state chiral clock ($CC_4$) model is reexamined using a systematic low temperature series expansion of the free energy. Previously obtained results for the low temperature phases are corrected and the low temperature phase diagram is derived. In addition, the phase transition from the modulated region to the high temperature paraphase is shown to belong to the universality class of the 3d-XY model.
Preoperative information for ICU patients to reduce anxiety during and after the ICU-stay: protocol of a randomized controlled trial [NCT00151554]
Almuth Berg, Steffen Fleischer, Michael Koller, Thomas R Neubert
BMC Nursing , 2006, DOI: 10.1186/1472-6955-5-4
Abstract: The trial is designed as a prospective randomized controlled trial including an intervention and a control group. The control group receives the standard preparation currently conducted by surgeons and anesthetists. The intervention group additionally receives a standardized information program with specific procedural, sensory and coping information about the ICU.A measurable clinical relevant difference regarding anxiety will be expected after discharge from ICU. Power calculation (α = 0.05; β = 0.20; Δ = 8.50 score points) resulted in a required sample size of N = 120 cardiac surgical patients (n = 60 vs. n = 60). Furthermore, N = 20 abdominal or thoracic surgical patients will be recruited (n = 10 vs. n = 10) to gain insight to a possible generalization to other patient groups.Additionally the moderating effect of specific patient attributes (need for cognition, high trait anxiety) will be investigated to identify certain patient groups which benefit most.The proposed study promises to strengthen evidence on effects of a specific, concise information program that addresses the information needs of patients scheduled for ICU stay.Technological advances during the last decades in intensive care medicine made it possible to treat an increasing number of high risk surgical patients. Nevertheless, many patients awaiting elective surgery experience diffuse anxiety and a lack of subjective predictability regarding their stay on the intensive care unit. The psychological elements that become salient in the perioperative situation can be characterized as loss of control, irritation and uncertainty. These psychological elements are also known for contributing to postoperative complications such as delayed wound healing and an increased intake of sedatives and analgesics [1]. In addition, the strange and unfamiliar situation on the ICU in combination with sleep deprivation and ICU-noises is closely related with the incidence of a postoperative delirium also called ICU-Synd
Radio occultation bending angle anomalies during tropical cyclones
R. Biondi, T. Neubert, S. Syndergaard,J. K. Nielsen
Atmospheric Measurement Techniques (AMT) & Discussions (AMTD) , 2011,
Abstract: The tropical deep convection affects the radiation balance of the atmosphere changing the water vapor mixing ratio and the temperature of the upper troposphere lower stratosphere. The aim of this work is to better understand these processes and to investigate if severe storms leave a significant signature in radio occultation profiles in the tropical tropopause layer. Using tropical cyclone best track database and data from different GPS radio occultation missions (COSMIC, GRACE, CHAMP, SACC and GPSMET), we selected 1194 profiles in a time window of 3 h and a space window of 300 km from the eye of the cyclone. We show that the bending angle anomaly of a GPS radio occultation signal is typically larger than the climatology in the upper troposphere and lower stratosphere and that a double tropopause during deep convection can easily be detected using this technique. Comparisons with co-located radiosondes, climatology of tropopause altitudes and GOES analyses are also shown to support the hypothesis that the bending angle anomaly can be used as an indicator of convective towers. The results are discussed in connection to the GPS radio occultation receiver which will be part of the Atomic Clock Ensemble in Space (ACES) payload on the International Space Station.
Damage estimation of subterranean building constructions due to groundwater inundation – the GIS-based model approach GRUWAD
R. Schinke,M. Neubert,J. Hennersdorf,U. Stodolny
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2012, DOI: 10.5194/nhess-12-2865-2012
Abstract: The analysis and management of flood risk commonly focuses on surface water floods, because these types are often associated with high economic losses due to damage to buildings and settlements. The rising groundwater as a secondary effect of these floods induces additional damage, particularly in the basements of buildings. Mostly, these losses remain underestimated, because they are difficult to assess, especially for the entire building stock of flood-prone urban areas. For this purpose an appropriate methodology has been developed and lead to a groundwater damage simulation model named GRUWAD. The overall methodology combines various engineering and geoinformatic methods to calculate major damage processes by high groundwater levels. It considers a classification of buildings by building types, synthetic depth-damage functions for groundwater inundation as well as the results of a groundwater-flow model. The modular structure of this procedure can be adapted in the level of detail. Hence, the model allows damage calculations from the local to the regional scale. Among others it can be used to prepare risk maps, for ex-ante analysis of future risks, and to simulate the effects of mitigation measures. Therefore, the model is a multifarious tool for determining urban resilience with respect to high groundwater levels.
Radio occultation bending angle anomalies during tropical cyclones
R. Biondi,T. Neubert,S. Syndergaard,J. Nielsen
Atmospheric Measurement Techniques Discussions , 2011, DOI: 10.5194/amtd-4-1371-2011
Abstract: The tropical deep convection affects the radiation balance of the atmosphere changing the water vapor mixing ratio and the temperature of the upper troposphere lower stratosphere. The aim of this work is to better understand these processes and to investigate if severe storms leave a significant signature in radio occultation profiles in the tropical tropopause layer. Using tropical cyclone best track database and data from different GPS radio occultation missions (COSMIC, GRACE, CHAMP, SACC and GPSMET), we selected 1194 profiles in a time window of 3 h and a space window of 300 km from the eye of the cyclone. We show that the bending angle anomaly of a GPS radio occultation signal is typically larger than the climatology in the upper troposphere and lower stratosphere and that a double tropopause during deep convection can easily be detected using this technique. Comparisons with co-located radiosondes, climatology of tropopause altitudes and GOES analyses are also shown to support the hypothesis that the bending angle anomaly can be used as an indicator of convective towers. The results are discussed in connection to the GPS radio occultation receiver which will be part of the Atomic Clock Ensemble in Space (ACES) payload on the International Space Station.
Factorization analysis for the fragmentation functions of hadrons containing a heavy quark
Neubert, Matthias
High Energy Physics - Phenomenology , 2007,
Abstract: Using methods of effective field theory, a systematic analysis of the fragmentation functions D_{a/H}(x,m_Q) of a hadron H containing a heavy quark Q is performed (with a=Q,Q_bar,q,q_bar,g). By integrating out pair production of virtual and real heavy quarks, the fragmentation functions are matched onto a single nonperturbative function describing the fragmentation of the heavy quark Q into the hadron H in "partially quenched" QCD. All calculable, short-distance dependence on x is extracted in this step. For x->1, the remaining fragmentation function can be matched further onto a universal function defined in heavy-quark effective theory in order to factor off its residual dependence on the heavy-quark mass. By solving the evolution equation in the effective theory analytically, large logarithms of the ratio mu/m_Q are resummed to all orders in perturbation theory. Connections with existing approaches to heavy-quark fragmentation are discussed. In particular, it is shown that previous attempts to extract log^n(1-x) terms from the fragmentation function D_{Q/H}(x,m_Q) are incompatible with a proper separation of short- and long-distance effects.
Unparticle Physics with Jets
Neubert, Matthias
High Energy Physics - Phenomenology , 2007, DOI: 10.1016/j.physletb.2008.01.034
Abstract: Using methods of effective field theory, we show that after resummation of Sudakov logarithms the spectral densities of interacting quark and gluon fields in ordinary quantum field theories such as QCD are virtually indistinguishable from those of "unparticles" of a hypothetical conformal sector coupled to the Standard Model, recently studied by Georgi. Unparticles are therefore less exotic that originally thought. Models in which a hidden sector weakly coupled to the Standard Model contains a QCD-like theory, which confines at some scale much below the characteristic energy of a given process, can give rise to signatures closely resembling those from unparticles.
Documenting, analysing and managing the animal biodiversity in the Middle East – a challenge for the future
Eike Neubert
ZooKeys , 2009, DOI: 10.3897/zookeys.31.370
Abstract:
QCD-Based Interpretation of the Lepton Spectrum in Inclusive $\bar B\to X_u\,\ell\,\barν$ Decays
Matthias Neubert
Physics , 1993, DOI: 10.1103/PhysRevD.49.3392
Abstract: We present a QCD-based approach to the endpoint region of the lepton spectrum in $\bar B\to X_u\,\ell\,\bar\nu$ decays. We introduce a genuinely nonperturbative form factor, the shape function, which describes the fall-off of the spectrum close to the endpoint. The moments of this function are related to forward scattering matrix elements of local, higher-dimension operators. We find that nonperturbative effects are dominant over a finite region in the lepton energy spectrum, the width of which is related to the kinetic energy of the $b$-quark inside the $B$ meson. Applications of our method to the extraction of fundamental standard model parameters, among them $V_{ub}$, are discussed in detail.
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