Investigation of the causes of retardation and maladjustment of pupils in public school of the United States and remedial measures.

Thesis (M.A.)--Boston University This item was digitized by the Internet Archive

Economic Comparison of the Undercutter and Traditional Tillage Systems for Winter Wheat-Summer Fallow Farming

Wind erosion and blowing dust are major problems for traditional tillage winter wheat-summer fallow in eastern Washington. Wind erosion reduces soil productivity and dust particulates are a major air quality concern. Conservation tillage summer fallow can reduce wind erosion markedly, but is used by relatively few farmers in the low-precipitation (less than 12 inch/year) region of the Inland Pacific Northwest. Barriers to adoption include the cost of conservation tillage implements and reluctance to change "tried and proven"traditional tillage methods. This bulletin compares economic results for the V-sweep undercutter and traditional fallow tillage systems on a case study farm located near Ritzville, WA. The farm’s eight-year average wheat yield is 46 bu/ac. Grain yields are similar for the two systems. This study shows that the undercutter method of summer fallow farming is more profitable than the traditional system on the case study farm due to slightly lower production costs. The undercutter system is eligible for conservation payments, but the traditional system is not. Receipt of these payments further strengthens the profitability advantage of the undercutter systemcapital, labor, land and management resources, type and size of machinery complement

ECONOMICALLY OPTIMAL NITROGEN FERTILIZATION FOR YIELD AND PROTEIN IN HARD RED SPRING WHEAT

This analysis determines profit maximizing N fertilization levels of hard red spring wheat (HRSW) for various wheat prices, N prices, and protein-based HRSW price premium/discount (P/D) structures for south eastern Washington data. Fertilizer response data consisting of rates of N fertilization (lb/ac), grain yield (bu/ac), and grain protein (%) were used to statistically estimate regression relationships that predicted yield and protein in response to N. All predicted net return maximizing N, protein, and yield levels were within the data range. Increasing P/D incentives for protein increased optimal N, the expected economic result. At the high P/D structures, the P/D structure dominated N and wheat prices in determining optimal N application levels. Overall, net return-maximizing yields varied only modestly with changes in both N and wheat price in this data set. However, in all scenarios, as P/D incentives increased, net return maximizing N levels were beyond the level that resulted in maximum yield. At the two lowest P/D structures, which provided the lowest reward for protein, it was most profitable to fertilize for slightly less than 14% expected protein. These results indicate that it is not always profitable to use 14% protein as an N fertilization goal. Abbreviations: CT, conventional tillage; HRSW, hard red spring wheat; HRWW, hard red winter wheat; N, nitrogen; NO3, nitrate; NT, No Tillage; P/D, premium/discount; SWSW, soft white spring wheat; SWW, soft white wheat.Crop Production/Industries,

Trends in Archaic and Woodland Period Use of the Middle Sabine River Basin Based on Dart Point Proportions

In this article, we use the varying proportions of a large sample of Archaic and Woodland period dart points to explore trends in settlement and occupational intensity from ca. 10,000 to 1200 years B.P. in the Pineywoods and Post Oak Savannah of East Texas. These darts were collected from sites in Gregg, Harrison, Rusk, and Smith counties, Texas, mainly on sites in the middle reaches of the Sabine River basin

RISK PERCEPTIONS AND MANAGEMENT RESPONSES: PRODUCER-GENERATED HYPOTHESES FOR RISK MODELING

Farm level risk analyses have used price and yield variability almost exclusively to represent risk. Results from a survey of 149 agricultural producers in 12 states indicate that producers consider a broader range of sources of variability in their operations. Significant differences exist among categories with respect to the importance of the sources of variability in crop and livestock production. Producers also used a variety of management responses to variability. There were significant difference among categories in the importance given to particular responses and their use of them. These results have implications for research, extension, and policy programs.Risk and Uncertainty,

Mixing by microorganisms in stratified fluids

We examine the vertical mixing induced by the swimming of microorganisms at low Reynolds and Péclet numbers in a stably stratified ocean, and show that the global contribution of oceanic microswimmers to vertical mixing is negligible. We propose two approaches to estimating the mixing efficiency, η, or the ratio of the rate of potential energy creation to the total rate-of-working on the ocean by microswimmers. The first is based on scaling arguments and estimates η in terms of the ratio between the typical organism size, a, and an intrinsic length scale for the stratified flow, l = (νκ/N2)1/4, where ν is the kinematic viscosity, κ the diffusivity, and N the buoyancy frequency. In particular, for small organisms in the relevant oceanic limit, a/l \u3c\u3c 1, we predict the scaling η ∼ (a/l)3. The second estimate of η is formed by solving the full coupled flow-stratification problem by modeling the swimmer as a regularized force dipole, and computing the efficiency numerically. Our computational results, which are examined for all ratios a/l, validate the scaling arguments in the limit a/l \u3c\u3c 1 and further predict η ≈ 1.2(a/l)3 for vertical swimming and η ≈ 0.15 (a/l)3 for horizontal swimming. These results, relevant for any stratified fluid rich in biological activity, imply that the mixing efficiency of swimming microorganisms in the ocean is at very most 8% and is likely smaller by at least two orders of magnitude

The Effects of a Topically Applied Anti-Inflammatory Agent on Root Resorption in the Replanted Teeth of Canines

Root resorption is a constant finding on the roots of replanted teeth. In this study it was suggested that root resorption is perhaps related to inflammation and that teeth incubated in an anti-inflammatory agent such as triamcinolone acetonide, a corticosteroid, before replantation would have less resorption. To investigate this hypothesis nineteen mature teeth in five mongrel dogs were extracted and replanted. Ten of the teeth were incubated for five minutes in the steroid and nine control teeth for the same period in a saline solution. Before euthanizing the animals at one, three, five, and seven weeks, a clinical evaluation of the teeth for attachment and mobility was made. A blind study of the histological sections showed that root resorption occurred on all of the teeth. The use of localized triamcinolone acetonide did not improve the prognosis of replanted teeth in these animals either clinically or histologically

The Orbital Light Curve of Aquila X-1

We obtained R- and I-band CCD photometry of the soft X-ray transient/neutron- star binary Aql X-1 in 1998 June while it was at quiescence. We find that its light curve is dominated by ellipsoidal variations, although the ellipsoidal variations are severely distorted and have unequal maxima. After we correct for the contaminating flux from a field star located only 0.46" away, the peak-to-peak amplitude of the modulation is ~0.25 mag in the R band, which requires the orbital inclination to be greater than 36 degrees. The orbital period we measure is consistent with the 18.95 h period measured by Chevalier & Ilovaisky (1998). During its outbursts the light curve of Aql X-1 becomes single humped. The outburst light curve observed by Garcia et al. (1999) agrees in phase with our quiescent light curve. We show that the single humped variation is caused by a ``reflection effect,'' that is, by heating of the side of the secondary star facing towards the neutron star.Comment: 18 manuscript pages, 7 figures; accepted by A