PhD

dissertationClinically-oriented computer assisted instruction (CAI) has been receiving greater emphasis in the last few years. Similarly progress has been made in the development of (a) generative CAI techniques and (b) the refinement of a formalized medical decision-making criterion. These developments have led to the implementation of a nonauthored CAI system for training clinicians in medical decision-making using actual patient data. The nonauthored CAI system is composed of several subsystems. The principal components include (a) a statistical analysis system providing many options including the generation of histograms, (b) an automated medical decision-making system, and (c) a system for finding patients with desired characteristics and generating populations interactively. The functions and interrelationships of each component are described in detail. The nonauthored CAI system's primary advantages include: (a) it provides the capability of studying medical decision-making procedures in a formal setting; (b) it is a subject-independent system and therefore is relevant to a broad spectrum of clinicians (it is limited by the extent of the clinical data available); (c) because of its generative qualities no courseware authoring"" is required; and (d) because the system requires little training to use, investigations may be conducted in either a formalized group setting or in an independent study mode. Due to the system's relevance to clinical medicine, several persons affiliated with academic medicine have seen the system demonstrated. In addition to these observers, a demonstration of the system in a more structured setting v;as explored. A broad spectrum of clinicians repeatedly used the CAI system to investigate subjects of interest during these structured sessions. Details of their investigations and comments are included. Finally, a few future possibilities and enhancements for the system are explored."

Bayesian Forecasting of Federal Funds Target Rate Decisions

This paper examines which macroeconomic and financial variables are most informative for the federal funds target rate decisions made by the Federal Open Market Committee (FOMC) from a forecasting perspective. The analysis is conducted for the FOMC decision during the period January 1990 - June 2008, using dynamic ordered probit models with a Bayesian endogenous variable selection methodology and real-time data for a set of 33 candidate predictor variables. We find that indicators of economic activity and forward-looking term structure variables as well as survey measures have most predictive ability. For the full sample period, in-sample probability forecasts achieve a hitrate of 90 percent. Based on out-of-sample forecasts for the period January 2001 - June 2008, 82 percent of the FOMC decisions are predicted correctly

An Alternative Bayesian Approach to Structural Breaks in Time Series Models

We propose a new approach to deal with structural breaks in time series models. The key contribution is an alternative dynamic stochastic specification for the model parameters which describes potential breaks. After a break new parameter values are generated from a so-called baseline prior distribution. Modeling boils down to the choice of a parametric likelihood specification and a baseline prior with the proper support for the parameters. The approach accounts in a natural way for potential out-of-sample breaks where the number of breaks is stochastic. Posterior inference involves simple computations that are less demanding than existing methods. The approach is illustrated on nonlinear discrete time series models and models with restrictions on the parameter space

Data report: High-resolution stable isotope stratigraphy of the late Middle Eocene at Site 1051, Blake Nose

The primary aim of the this investigation was to examine the stability of subtropical sea-surface temperatures and reconstruct the surfaceto- benthos thermal gradient. High-resolution stable isotopic analyses (δ18O and δ13C) were conducted on late middle Eocene planktonic and benthic foraminifers recovered from Hole 1051B, Blake Nose, western North Atlantic. The sequence comprises a siliceous nannofossil and foraminifer ooze, with well-preserved calcareous microfossils. Isotopic examination was conducted on the mixed-layer dweller Morozovella spinulosa and the benthic foraminifer Nuttalides truempyi at this subtropical site

Soil Quality in Relation to Forest Conversion to Perennial or Annual Cropping in Southern Brazil

Many forested areas have been converted to intensive agricultural use to satisfy food, fiber, and forage production for a growing world population. There is great interest in evaluating forest conversion to cultivated land because this conversion adversely affects several soil properties. We examined soil microbial, physical, and chemical properties in an Oxisol (Latossolo Vermelho distrófico) of southern Brazil 24 years after forest conversion to a perennial crop with coffee or annual grain crops (maize and soybeans) in conventional tillage or no-tillage. One goal was to determine which soil quality parameters seemed most sensitive to change. A second goal was to test the hypothesis that no-tillage optimized preservation of soil quality indicators in annual cropping systems on converted land. Land use significantly affected microbial biomass and its activity, C and N mineralization, and aggregate stability by depth. Cultivated sites had lower microbial biomass and mineralizable C and N than a forest used as control. The forest and no-tillage sites had higher microbial biomass and mineralizable C and N than the conventional tillage site, and the metabolic quotient was 65 and 43 % lower, respectively. Multivariate analysis of soil microbial properties showed a clear separation among treatments, displaying a gradient from conventional tillage to forest. Although the soil at the coffee site was less disturbed and had a high organic C content, the microbial activity was low, probably due to greater soil acidity and Al toxicity. Under annual cropping, microbial activity in no-tillage was double that of the conventional tillage management. The greater microbial activity in forest and no-tillage sites may be attributed, at least partially, to lower soil disturbance. Reducing soil disturbance is important for soil C sequestration and microbial activity, although control of soil pH and Al toxicity are also essential to maintain the soil microbial activity high

Current status and opportunities for therapeutic drug monitoring in the treatment of tuberculosis

Contains fulltext : 172247.pdf (Publisher’s version ) (Open Access

Suction cup sampler bias in leaching characterization of an undisturbed field soil

An accurate assessment of leaching losses in the vadose zone requires measurement of both solute and water flux to compute flux concentrations (C[subscript F]). Leachate collected at a depth of 1.2 m in 32 passive capillary samplers (PCAPS), which sample soil-pore water continuously at tensions of 0–50 cm H₂O was compared to that collected in 32 suction cup samplers operated under a falling head vacuum of 530-cm H₂O over a 2-year period. There was evidence that PCAPS collected CF and suction cup samplers collected resident concentrations (C[subscript R]) as shown by the earlier breakthrough of a bromide tracer in the PCAPS as compared to the suction cup samplers. C[subscript R] was up to 100% lower than C[subscript F] during the rising branch of Br tracer breakthrough and up to 78% greater during the declining branch of breakthrough. Br content and water flux into PCAPS were correlated with correlation coefficients changing from positive to negative values with the advancement of the tracer breakthrough peak through the profile indicating the declining importance of preferential flow on Br transport. C[subscript R] and C[subscript F] differed significantly (P < 0.05) for 35% of the sampling events for NO₃, but seasonal means were mostly insignificantly different for this regularly applied and therefore more uniformly distributed anion. The early breakthrough of Rhodamine WT and Brilliant Blue FCF, which was applied with the Br, was very low with 0.15% and 0.08% of the initial concentration C₀, respectively, with C[subscript R] differing from C[subscript F] by up to −100%. For all tracers, mass leached using C[subscript R] is therefore prone to bias for short-term (<0.6 pore volumes) monitoring.Keywords: Hydrology: Unsaturated zone, Hydrology: Groundwater quality, Hydrology: Groundwater hydrology, Hydrology: Instruments and technique