543 research outputs found
Macro expectations, aggregate uncertainty, and expected term premia
Based on individual expectations from the Survey of Professional Forecasters, we construct a real-time proxy for expected term premium changes on long-term bonds. We empirically investigate the relation of these bond term premium expectations with expectations about key macroeconomic variables as well as aggregate macroeconomic uncertainty at the level of individual forecasters. We find that expected term premia are (i) time-varying and reasonably persistent, (ii) strongly related to expectations about future output growth, and (iii) positively affected by uncertainty about future output growth and inflation rates. Expectations about real macroeconomic variables seem to matter more than expectations about nominal factors. Additional findings on term structure factors suggest that the level and slope factor capture information related to uncertainty about real and nominal macroeconomic prospects, and that curvature is related to subjective term premium expectations themselves. Finally, an aggregate measure of forecasters' term premium expectations has predictive power for bond excess returns over horizons of up to one year
Variables affecting the probability of complete fusion of the medial clavicular epiphysis
In this study, we have combined data on clavicle fusion from different studies and applied a binomial logistic regression analysis. As such, we aimed to assess whether or not variables such as sex, socioeconomic status, and ethnicity influence the probability of having mature, i.e., completely fused clavicles at a given age. We further explored whether the method of clavicle examination, i.e., diagnosis from either a dry bone specimen, an examination of X-rays, or an examination of computed tomography scans, affects the probability of being diagnosed with mature clavicles. It appeared that only ethnicity did not significantly affect this probability. Finally, we illustrated how the logit model may be used to predict the probability of being diagnosed with mature clavicles
Cellulose Acetate Replica Cleaning Study of Genesis Non-Flight Sample 3CZ00327
The Genesis mission collected solar wind and brought it back to Earth in order to provide precise knowledge of solar isotopic and elemental compositions. The ions in the solar wind were stopped in the collectors at depths on the order of 10 to a few hundred nanometers. This shallow implantation layer is critical for scientific analysis of the composition of the solar wind and must be preserved throughout sample handling, cleaning, processing, distribution, preparation and analysis. We are working interactively with the community of scientists analyzing Genesis samples, using our unique laboratory facilities -- and, where needed, our unique cleaning techniques -- to significantly enhance the science return from the Genesis mission. This work is motivated by the need to understand the submicron contamination on the collectors in the Genesis payload as recovered from the crash site in the Utah desert, and -- perhaps more importantly -- how to remove it. That is, we are evaluating the effectiveness of the wet-chemical "cleaning" steps used by various investigators, to enable them to design improved methods of stripping terrestrial contamination from surfaces while still leaving the solar-wind signal intact
Application of CO2 Snow Jet Cleaning in Conjunction with Laboratory Based Total Reflection X-Ray Fluorescence
The Genesis mission was the first mission returning solar material to Earth since the Apollo program [1,2]. Unfortunately the return of the space craft on September 8, 2004 resulted in a crash landing, which shattered the samples into small fragments and exposed them to desert soil and other debris. Thus only small fragments of the original collectors are available, each having different degrees of surface contamination. Thorough surface cleaning is required to allow for subsequent analysis of solar wind material embedded within. An initial cleaning procedure was developed in coordination with Johnson Space Center which focused on removing larger sized particulates and a thin film organic contamination acquired during collection in space [3]. However, many of the samples have additional residues and more rigorous and/or innovative cleaning steps might be necessary. These cleaning steps must affect only the surface to avoid leaching and re-distribution of solar wind material from the bulk of the collectors. To aid in development and identification of the most appropriate cleaning procedures each sample has to be thoroughly inspected before and after each cleaning step. Laboratory based total reflection X-ray fluorescence (TXRF) spectrometry lends itself to this task as it is a non-destructive and surface sensitive analytical method permitting analysis of elements from aluminum onward present at and near the surface of a flat substrate [4]. The suitability of TXRF has been demonstrated for several Genesis solar wind samples before and after various cleaning methods including acid treatment, gas cluster ion beam, and CO2 snow jet [5 - 7]. The latter one is non-invasive and did show some promise on one sample [5]. To investigate the feasibility of CO2 snow jet cleaning further, several flown Genesis samples were selected to be characterized before and after CO2 snow application with sample 61052 being discussed below
Small Particulate Contamination Survey Of Genesis Flight Sample 61423
The Genesis mission collected solar wind and brought it back to Earth in order to provide precise knowledge of solar isotopic and elemental compositions. The ions in the solar wind stop in the collectors at depths on the order of 10 to a few hundred nanometers. This shallow implantation layer is critical for scientific analysis of the composition of the solar wind and must be preserved throughout sample handling, cleaning, processing, distribution, preparation and analysis. We continue to work with the community of scientists analyzing Genesis samples using our unique laboratory facilities -- and, where needed, our unique cleaning techniques -- to significantly enhance the science return from the Genesis mission. This work is motivated by the need to understand the submicron contamination on the collectors in the Genesis payload as recovered from the crash site in the Utah desert, and -- perhaps more importantly -- how to remove it. We continue to evaluate the effectiveness of the wet-chemical "cleaning" steps used by various investigators, to enable them to design improved methods of stripping spacecraft and terrestrial contamination from surfaces while still leaving the solar-wind signal intact
Applicability of T1-weighted MRI in the assessment of forensic age based on the epiphyseal closure of the humeral head
This work investigates the value of magnetic resonance imaging analysis of proximal epiphyseal fusion in research examining the growth and development of the humerus and its potential utility in establishing forensic age estimation. In this study, 428 proximal humeral epiphyses (patient age, 12-30years) were evaluated with T1-weighted turbo spin echo (T1 TSE) sequences in coronal oblique orientation on shoulder MRI images. A scoring system was created following a combination of the Schmeling and Kellinghaus methods. Spearman's rank correlation analysis revealed a significant positive relationship between age and ossification stage of the proximal humeral epiphysis (all subjects: rho=0.664, p<0.001; males: 0.631, p<0.001; females: rho=0.651, p<0.001). The intra- and inter-observer reliability assessed using Cohen's kappa statistic was =0.898 and =0.828, respectively. The earliest age of epiphysis closure was 17years for females and 18years for males. MRI of the proximal humeral epiphysis can be considered advantageous for forensic age estimation of living individuals in a variety of situations, ranging from monitoring public health to estimating the age of illegal immigrants/asylum seekers, minors engaged in criminal activities, and illegal participants in competitive sports, without the danger of radiation exposure
A comparison of numerical surface topography calculations in geodynamic modelling: an evaluation of the ‘sticky air' method
Calculating surface topography in geodynamic models is a common numerical problem. Besides other approaches, the so-called ‘sticky air' approach has gained interest as a free-surface proxy at the top boundary. The often used free slip condition is thereby vertically extended by introducing a low density, low viscosity fluid layer. This allows the air/crust interface to behave in a similar manner to a true free surface. We present here a theoretical analysis that provides the physical conditions under which the sticky air approach is a valid approximation of a true free surface. Two cases are evaluated that characterize the evolution of topography on different timescales: (1) isostatic relaxation of a cosine perturbation and (2) topography changes above a rising plume. We quantitatively compare topographies calculated by six different numerical codes (using finite difference and finite element techniques) using three different topography calculation methods: (i) direct calculation of topography from normal stress, (ii) body-fitting methods allowing for meshing the topography and (iii) Lagrangian tracking of the topography on an Eulerian grid. It is found that the sticky air approach works well as long as the term (ηst/ηch)/(hst/L)3 is sufficiently small, where ηst and hst are the viscosity and thickness of the sticky air layer, and ηch and L are the characteristic viscosity and length scale of the model, respectively. Spurious lateral fluctuations of topography, as observed in some marker-based sticky air approaches, may effectively be damped by an anisotropic distribution of markers with a higher number of markers per element in the vertical than in the horizontal directio
Forensic age diagnostics by magnetic resonance imaging of the proximal humeral epiphysis
The most commonly used radiological method for age estimation of living individuals is X-ray. Computed tomography is not commonly used due to high radiation exposure, which raises ethical concerns. This problem can be solved with the use of magnetic resonance imaging (MRI), which avoids the use of ionizing radiation. The purpose of the present study was to evaluate the utility of MRI analysis of the proximal humeral epiphyses for forensic age estimations of living individuals. In this study, 395 left proximal humeral epiphyses (patient age 12-30years) were evaluated with fast-spin-echo proton density-weighted image (FSE PD) sequences in a coronal oblique orientation on shoulder MRI images. A five-stage scoring system was used following the method of Dedouit et al. The intra- and interobserver reliabilities assessed using Cohen's kappa statistic were =0.818 and =0.798, respectively. According to this study, stage five first appeared at 20 and 21years of age in males and females, respectively. These results are not directly comparable to any other published study due to the lack of MRI data on proximal humeral head development. These findings may provide valuable information for legally important age thresholds using shoulder MRI. The current study demonstrates that MRI of the proximal humerus can support forensic age estimation. Further research is needed to establish a standardized protocol that can be applied worldwide
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