COTTON EXPORTS: ANALYSIS OF THE RELATIONSHIPS BETWEEN SALES AND SHIPMENTS

Relationships between cotton export sales and export shipments are examined, and a quarter-specific lag structure is estimated. Two econometric systems are estimated, one employing export shipments and the other using export sales. Results indicate that sales are more sensitive to changes in economic variables than shipments and that stocks net of outstanding export sales are more responsive to price and interest rate changes than gross stocks. Sales and shipments are different variables and cannot substitute for one another in econometric modelling. Use of export sales data should be considered in estimation of export demand and stock demand parameters.International Relations/Trade,

The World Bank's role in shaping Third World population policy

Since the World Bank became involved in population work in 1969, it has sought to influence Third World population policy by undertaking several types of activity: lending, policy dialogue, economic and sector work, analysis and research, and collaboration with other international agencies. The Bank's comparative advantage lies in policy development. It uses three main strategies: policy dialogue, sector work, and policy-oriented research. Policy dialogue occurs with government officials and program managers, mainly through discussions, Bank-sponsored seminars, and project development. Population sector work, which analyzes the population sector in a particular country, provides a base for operational activities and for initiating policy dialogue with program managers. Population research in recent years has focused on alternative policy and program strategies. The Bank's work in policy development has contributed greatly to shifts in government population policy in many countries, and its operational strategies have helped shape population programs in others. Its work program in the coming years will continue to stress policy work.Demographics,Agricultural Research,Country Population Profiles,Health Indicators,Health Information&Communications Technologies

A statistical framework for testing functional categories in microarray data

Ready access to emerging databases of gene annotation and functional pathways has shifted assessments of differential expression in DNA microarray studies from single genes to groups of genes with shared biological function. This paper takes a critical look at existing methods for assessing the differential expression of a group of genes (functional category), and provides some suggestions for improved performance. We begin by presenting a general framework, in which the set of genes in a functional category is compared to the complementary set of genes on the array. The framework includes tests for overrepresentation of a category within a list of significant genes, and methods that consider continuous measures of differential expression. Existing tests are divided into two classes. Class 1 tests assume gene-specific measures of differential expression are independent, despite overwhelming evidence of positive correlation. Analytic and simulated results are presented that demonstrate Class 1 tests are strongly anti-conservative in practice. Class 2 tests account for gene correlation, typically through array permutation that by construction has proper Type I error control for the induced null. However, both Class 1 and Class 2 tests use a null hypothesis that all genes have the same degree of differential expression. We introduce a more sensible and general (Class 3) null under which the profile of differential expression is the same within the category and complement. Under this broader null, Class 2 tests are shown to be conservative. We propose standard bootstrap methods for testing against the Class 3 null and demonstrate they provide valid Type I error control and more power than array permutation in simulated datasets and real microarray experiments.Comment: Published in at http://dx.doi.org/10.1214/07-AOAS146 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

COSTS, YIELDS, AND NET RETURNS, COMMERCIAL NO-TILL COTTON PRODUCTION, MISSISSIPPI, 1999

An analysis of a 1999 sample of ten no-till producers indicates that over a reasonable range of cotton lint prices, no-till cotton production may result in larger net returns per acre than conventional tillage. However, the authors caution that additional analysis based on a larger sample of commercial no-till growers on better cotton soils is needed.no-till, spindle harvest, cost of production, yield, Production Economics,

Comparison of analysis and experiment for gearbox noise

Low contact ratio spur gears were tested in the NASA gear-noise rig to study the noise radiated from the top of the gearbox. Experimental results were compared with a NASA acoustics code to validate the code for predicting transmission noise. The analytical code is based on the boundary element method (BEM) which models the gearbox top as a plate in an infinite baffle. Narrow band vibration spectra measured at 63 nodes on the gearbox top were used to produce input data for the BEM model. The BEM code predicted the total sound power based on the measured vibration. The measured sound power was obtained from an acoustic intensity scan taken near the surface of the gearbox at the same 63 nodes used for vibration measurement. Analytical and experimental results were compared at four different speeds for sound power at each of the narrow band frequencies over the range of 400 to 3200 Hz. Results are also compared for the sound power level at meshing frequency plus three sideband pairs and at selected gearbox resonant frequencies. The difference between predicted and measure sound power is typically less than 3 dB with the predicted value generally less than the measured value

Non-stationarity of isomorphism between AF algebras defined by stationary Bratteli diagrams

We first study situations where the stable AF-algebras defined by two square primitive nonsingular incidence matrices with nonnegative integer matrix elements are isomorphic even though no powers of the associated automorphisms of the corresponding dimension groups are isomorphic. More generally we consider neccessary and sufficient conditions for two such matrices to determine isomorphic dimension groups. We give several examples.Comment: 16 page