Finite Sample Accuracy of Integrated Volatility Estimators

We consider the properties of three estimation methods for integrated volatility, i.e. realized volatility, the Fourier estimator, and the wavelet estimator, when a typical sample of high-frequency data is observed. We employ several different generating mechanisms for the instantaneous volatility process, e.g. Ornstein-Uhlenbeck, long memory, and jump processes. The possibility of market microstructure contamination is also entertained using a model with bid-ask bounce in which case alternative estimators with theoretical justification under market microstructure noise are also examined. The estimation methods are compared in a simulation study which reveals a general robustness towards persistence or jumps in the latent stochastic volatility process. However, bid-ask bounce effects render realized volatility and especially the wavelet estimator less useful in practice, whereas the Fourier method remains useful and is superior to the other two estimators in that case. More strikingly, even compared to bias correction methods for microstructure noise, the Fourier method is superior with respect to RMSE while having only slightly higher bias.Bid-ask bounce, finite sample bias, integrated volatility, long memory, market microstructure, Monte Carlo simulation, realized volatility, wavelet

Functional Characterization of Green Sorption Media and Scaling of Pilot Studies for Copper Removal in Stormwater Runoff

Green adsorption media with the inclusion of renewable and recycled materials can be applied as a stormwater best management practice for copper removal. A green adsorption media mixture composed of recycled tire chunk, expanded clay aggregate, and coconut coir was physicochemically evaluated for its potential use in an upflow media filter. The results found that the use of the green adsorption media mixture in isolation or the coconut coir with an expanded clay filtration chamber could be an effective and reliable stormwater best management practice for copper removal. A suite of tests were conducted on the media mixture and the individual media components including studies of isotherm, reaction kinetics, column adsorption and reaction kinetics. Batch adsorption tests revealed that the media and media mixture follow both the Freundlich and Langmuir isotherm models and that the coconut coir had the highest affinity for copper. A screening of desorbing agents revealed that hydrochloric acid has good potential for copper desorption, while batch tests for desorption with hydrochloric acid as the desorbing agent showed the data fit the Freundlich isotherm model. Reaction kinetics revealed that the adsorption reaction took less than 1 hour to reach equilibrium and that it followed pseudo-second order kinetics for the mixture and coconut. Desorption kinetic data had high correlation with the pseudo-second order model and revealed a rapid desorption reaction. Batch equilibrium data over 3 adsorption/desorption cycles found that the coconut coir and media mixture were the most resilient and demonstrated that they could be used through 3 or more adsorption/desorption cycles. The coconut coir also performed the best under dynamic conditions, having an equilibrium uptake of 1.63 mg?g-1, compared to 0.021 mg?g-1 at an influent concentration of 1.0 mg?L-1 and a hydraulic retention time of 30 minutes. A physical evaluation of the media found the macro-scale properties, such as particle size distribution and mass-volume relationships, and observed the micro-scale properties such as surface and pore microstructures, crystalline structures, and elemental composition. FE-SEM imaging found a strong correlation between the porosity of the micro pore structure and the adsorptive capacity. The equilibrium and dynamic adsorption testing results were confirmed by elemental analysis, which showed measureable quantities of copper in the coconut coir and media mixture after adsorption followed by partial desorption. A new scaling-up theory was developed through a joint consideration of the Damköhler and Péclet numbers for a constant media particle size such that a balance between transport-controlled and reaction-controlled kinetics can be harmonized. A series of column breakthrough tests at varying hydraulic residence times revealed a clear peak adsorptive capacity for the media mixture at a Damköhler number of 2.7. The Péclet numbers for the column breakthrough tests indicated that mechanical dispersion is an important effect that requires further consideration in the scaling-up process. However, perfect similitude of the Damköhler number cannot be maintained for a constant media particle size, and relaxation of hydrodynamic similitude through variation of the Péclet number must occur

Dr. Cooper Holtzclaw: Healing Through Change

In America, the field of healthcare underwent extraordinary changes in the years from 1870-1920. A huge expansion in the number of patients spurred growth in the number of hospitals and physicians. The field became more professionalized and standardized. Dr. Cooper Holtzclaw, an eminent physician in Chattanooga, Tennessee, experienced these changes firsthand during his years of practice, and maintained his respected status among the citizens of Chattanooga

Musiklärares handlingsutrymme - möjligheter och begränsningar

ABSTRACT Titel: Music teachers’ discretionary power – possibilities and limitations. According to previous research in music education, during recent decades the working conditions for professional music teachers in schools have changed radically. The aim of this thesis is to investigate the working conditions of music teachers by focusing on their experiences of and ideas about discretionary power in their professional lives. This is accomplished by addressing the research questions: What does discretionary power mean to the music teachers? How and where is the discretionary power of music teachers created? What enabling and constraining processes in the creation of discretionary power can be identified? The theoretical framework rests on phenomenology and the assumption of the life-world as the complex, everyday world in which we live. In this study, the life-world is perceived as an intentional, lived and social world, and research is understood as the study of lived experience. The methodology is qualitative and the data collection was conducted as in-depth interviews. Student constructed three-dimensional models of what it means to be a music teacher were used as a ”key” to the life world in the interviews. The meaning of discretionary power is shaped in the interplay between knowledge, action and motivation. The creation of discretionary power develops when the inner reality of a music teacher corresponds to the shape and nature of external reality. In relationships with pupils and colleagues different proportions of power, control, demand, social support and trust can be identified. These illuminate the social processes through which discretionary power is created, and they are also enabling and constraining in various ways. The results are discussed as three themes; the meaning of discretionary power in the relationships between (i) music teachers and their institutional settings, (ii) music teachers and their tasks and (iii) music teachers and others. The findings point out the tension between enabling and constraining processes in these three themes. Meaning is formed together with pupils and colleagues. In conclusion, the knowledge base of discretionary power and the creation of discretionary power consist of three dimensions: knowledge about discretionary power, knowledge through discretionary power and knowledge in discretionary power

Temperature-dependent spin gap and singlet ground state in BaCuSi2O6

Bulk magnetic measurements and inelastic neutron scattering were used to investigate the spin-singlet ground state and magnetic gap excitations in BaCuSi2O6, a quasi-2-dimensional antiferromagnet with a bilayer structure. The results are well described by a model based on weakly interacting antiferromagnetic dimers. A strongly temperature-dependent dispersion in the gap modes was found. We suggest that the observed excitations are analogous to magneto-excitons in light rare-earth compounds, but are an intrinsic property of a simple Heisenberg Hamiltonian for the S=1/2 magnetic bilayer.Comment: 10 pages, 4 figures, REVTeX and PS for text, PS for figures direct download: http://papillon.phy.bnl.gov/preprints/bacusio.htm