Task-Specific Experience and Task-Specific Talent: Decomposing the Productivity of High School Teachers

We use administrative panel data to decompose worker performance into components relating to general talent, task-specific talent, general experience, and task-specific experience. We consider the context of high school teachers, in which tasks consist of teaching particular subjects in particular tracks. Using the timing of changes in the subjects and levels to which teachers are assigned to provide identifying variation, we show that much of the productivity gains to teacher experience estimated in the literature are actually subject-specific. By contrast, very little of the variation in the permanent component of productivity among teachers is subject-specific or level-specific. Counterfactual simulations suggest that maximizing the value of task-specific experience could produce nearly costless efficiency gains on the order of .02 test score standard deviations

Studies of phagocytic activity in experimental African trypanosomiasis

Imperial Users onl

A spot check of the status of music education of grades four, five and six in the elementary schools of Massachusetts as of the year 1956-57.

Thesis (Ed.M.)--Boston Universit

Bone and metal - an orthopaedic perspective on osseointegration of metals

The area of implant osseointegration is of major importance, given the predicted significant rise in the number of orthopaedic procedures and an increasingly ageing population. Osseointegration is a complex process involving a number of distinct mechanisms affected by the implant bulk properties and surface characteristics. Our understanding and ability to modify these mechanisms through alterations in implant design is continuously expanding. The following review considers the main aspects of material and surface alterations in metal implants, and the extent of their subsequent influence on osseointegration. Clinically, osseointegration results in asymptomatic stable durable fixation of orthopaedic implants. The complexity of achieving this outcome through incorporation and balance of contributory factors is highlighted through a clinical case report

A Comparison of Daughters of Sires in Artificial Breeding at Different Levels of Management

One of t he largest problems facing the successful dairyman of today is selection of proper sires to mate to his high producing cows. Many breeders and dairymen have the impression that proven sires will give the same increase in production regardless of the dam\u27s production or the level of environment present. Even though sires come from high producing herds, some as high as 600 pounds of butterfat, the average production of all cows in the state of Utah remains at a much lower figure. The average for all cows in Utah is about 250 pounds of butterfat and the average in 1958 of cows on Dairy Herd Improvement test was 403 pounds. This difference in level of production may be attributed to either genetic or environmental factors and possibly an interaction of the two. Most workers agree that the heritability estimates for milk production and fat yield are from .2 to .3. This means t hat about 25 per cent of the variance in milk yield is due to inheritance, and the other 75 per cent is due to management or environment. Therefore, there is a need to study daughters of the same sire at various levels of production to determine the amount of increase or decrease found at these levels. This thesis presents a study of daughters of Holstein sires used in artificial breeding. Sires in artificial breeding were used because they have a larger number of daughters, and their daughters come from a wide range of production and management levels

Capturing Atmospheric Effects on 3-D Millimeter Wave Radar Propagation Patterns

The need to model millimeter wave (MMW) radar propagation is imperative to proper design of aeronautical, civil, and military systems. Traditional radar propagation modeling is done using a path transmittance with little to no input for weather and atmospheric conditions. As radar advances into the MMW regime, atmospheric effects, such as attenuation and refraction, become more pronounced than at traditional radar wavelengths. The DoD High Energy Laser Joint Technology Offices High Energy Laser End-to-End Operational Simulation (HELEEOS), in combination with the Laser Environmental Effects Definition and Reference (LEEDR) code, is a powerful tool for simulating laser propagation and effects tied to atmospheric phenomena such as turbulence and extinction. Although LEEDR is already developed to characterize radiative transfer effects, this research attempts to extend HELEEOS to characterize the far field radar pattern in three dimensions as a signal propagates from an antenna through realistic atmospheres and weather conditions. The latter are derived from NOAA numerical weather prediction models or the Extreme and Percentile Environmental Reference Tables (ExPERT) climatological database. The results from these simulations are compared to those from traditional radar propagation software packages. In summary, this research explored adapting a laser propagation model to extend understanding of MMW propagation through various atmospheric and weather conditions