866 research outputs found
Maize Production and Agricultural Policies in Central America and Mexico
This paper reviews trends in maize production and consumption in Central America and Mexico in the context of the political and economic changes taking place in the region since the 1970s. The authors focus on the effects of the structural adjustment programs in the 1980s and 1990s. The analysis begins by reviewing the economic context in which maize production occurs in the region and the main economic policy instruments affecting the maize economy. Next, trends in maize consumption and production are analyzed, along with the main factors influencing maize production, including trends in the public financing of maize research and extension. The authors find that several factors related to structural adjustment have defined--and are still defining--the course of agriculture, including maize production, in the countries of the region. The impact of these factors on maize production, consumption, and import trends has been different in Central America and in Mexico. In particular, the reduction or complete elimination of production incentives, the reduction of trade barriers, the liberalization of input and product prices, the deregulation of the currency exchange rate, the control of inflation, and the restructuring of agricultural research systems between the public and the private sectors have determined how basic grains are produced in the region and how they will be produced in the future. Furthermore, the visible and increasing deterioration of the natural resource base has raised great concern about the need to promote more sustainable, environmentally friendly uses of production systems and natural resources.Agricultural and Food Policy, Crop Production/Industries,
Instabilities and Spatio-temporal Chaos of Long-wave Hexagon Patterns in Rotating Marangoni Convection
We consider surface-tension driven convection in a rotating fluid layer. For
nearly insulating boundary conditions we derive a long-wave equation for the
convection planform. Using a Galerkin method and direct numerical simulations
we study the stability of the steady hexagonal patterns with respect to general
side-band instabilities. In the presence of rotation steady and oscillatory
instabilities are identified. One of them leads to stable, homogeneously
oscillating hexagons. For sufficiently large rotation rates the stability
balloon closes, rendering all steady hexagons unstable and leading to
spatio-temporal chaos.Comment: 26 pages, 9 jpeg figures. Postscript file with all figures included
available at http://www.esam.northwestern.edu/~riecke/lit/lit.html Movies
available at
http://www.esam.northwestern.edu/~riecke/research/Marangoni/marangoni.htm
Clovis Blade Technology at the Topper Site (38AL23): Assessing Lithic Attribute Variation and Regional Patterns of Technological Organization
This monograph, by Douglas A. Sain, is based on his master’s thesis research on the organization of Clovis blade technology. This second monograph of the Occasional Papers series of the Southeastern Paleoamerican Survey closely follows the first in terms of the meticulousness of the study, and the new information it provides about the Topper Site. Detailed studies of Clovis material are eagerly sought by Paleoindian archaeologists, enthusiasts, and particularly by lithic analysts. Sain provides a well-rounded literature review for these groups, and an innovative approach to identifying technological blades. The “mixed assemblage” problem resulting when multiple lithic technologies were used at a single site is one with which lithic analysts continue to struggle. With a quarry site such as Topper and the wide variety of core forms and tools recovered, a nuanced and consistent approach to blade identification is a necessity if one wants to consider broader questions of technological organization. Recognizing variability in the end-product of blade manufacture and the relative importance of some characteristics over others, Sain weights six attributes from three to one and through detailed study of individual detached pieces produces a score. With a maximum value of 12, those with a score of seven or higher are considered a blade. This provides a consistent, replicable procedure for separating blades from blade-like flakes, and using these data in the consideration of Clovis lifeways. The small percentage of blades at Topper with modification, when coupled with a consideration of assemblages in the local and broader region, provide evidence that blades were part of a curated technology and toolkit, a transportable and reliable product that could be maintained as people moved across the landscape. This work provides a specific reconstruction of Clovis technological organization in the Savannah River Valley, and should inspire broader considerations of blade technology elsewhere in the Americas.https://scholarcommons.sc.edu/archanth_occasional_paleoam_papers/1001/thumbnail.jp
Stretching force dependent transitions in single stranded DNA
Mechanical properties of DNA, in particular their stretch dependent extension
and their loop formation characteristics, have been recognized as an effective
probe for understanding the possible biochemical role played by them in a
living cell. Single stranded DNA (ssDNA), which, till recently was presumed to
be an simple flexible polymer continues to spring surprises. Synthetic ssDNA,
like polydA (polydeoxyadenosines) has revealed an intriguing force-extension
(FX) behavior exhibiting two plateaus, absent in polydT (polydeoxythymidines)
for example. Loop closing time in polydA had also been found to scale
exponentially with inverse temperature, unexpected from generic models of
homopolymers. Here we present a new model for polydA which incorporates both a
helix-coil transition and a over-stretching transition, accounting for the two
plateaus. Using transfer matrix calculation and Monte-Carlo simulation we show
that the model reproduces different sets of experimental observations,
quantitatively. It also predicts interesting reentrant behavior in the
temperature-extension characteristics of polydA, which is yet to be verified
experimentally.Comment: 5 pages, 3 figure
Alternatives for jet engine control
The development of models of tensor type for a digital simulation of the quiet, clean safe engine (QCSE) gas turbine engine; the extension, to nonlinear multivariate control system design, of the concepts of total synthesis which trace their roots back to certain early investigations under this grant; the role of series descriptions as they relate to questions of scheduling in the control of gas turbine engines; the development of computer-aided design software for tensor modeling calculations; further enhancement of the softwares for linear total synthesis, mentioned above; and calculation of the first known examples using tensors for nonlinear feedback control are discussed
Medium-throughput processing of whole mount in situ hybridisation experiments into gene expression domains
This is the final version of the article. Available from the publisher via the DOI in this record.Understanding the function and evolution of developmental regulatory networks requires the characterisation and quantification of spatio-temporal gene expression patterns across a range of systems and species. However, most high-throughput methods to measure the dynamics of gene expression do not preserve the detailed spatial information needed in this context. For this reason, quantification methods based on image bioinformatics have become increasingly important over the past few years. Most available approaches in this field either focus on the detailed and accurate quantification of a small set of gene expression patterns, or attempt high-throughput analysis of spatial expression through binary pattern extraction and large-scale analysis of the resulting datasets. Here we present a robust, "medium-throughput" pipeline to process in situ hybridisation patterns from embryos of different species of flies. It bridges the gap between high-resolution, and high-throughput image processing methods, enabling us to quantify graded expression patterns along the antero-posterior axis of the embryo in an efficient and straightforward manner. Our method is based on a robust enzymatic (colorimetric) in situ hybridisation protocol and rapid data acquisition through wide-field microscopy. Data processing consists of image segmentation, profile extraction, and determination of expression domain boundary positions using a spline approximation. It results in sets of measured boundaries sorted by gene and developmental time point, which are analysed in terms of expression variability or spatio-temporal dynamics. Our method yields integrated time series of spatial gene expression, which can be used to reverse-engineer developmental gene regulatory networks across species. It is easily adaptable to other processes and species, enabling the in silico reconstitution of gene regulatory networks in a wide range of developmental contexts.The laboratory of Johannes Jaeger and this study in particular was funded by the MEC-EMBL agreement for the EMBL/CRG Research Unit in Systems
Biology, by grant 153 (MOPDEV) of the ERANet: ComplexityNET program, by SGR grant 406 from the Catalan funding agency AGAUR, by grant BFU2009-10184
from the Spanish Ministry of Science, and by European Commission grant FP7-KBBE-2011-5/289434 (BioPreDyn)
Pengaruh Alat Permainan Edukatif terhadap Aspek Perkembangan pada Anak PRA Sekolah di Wilayah Puskesmas Ondong Kabupaten Kepulauan Siau Tagulandang Biaro
Educated gane tool is a kind of gane which consists of educational value it is functioned to stimuli children\u27s imagination cognitively. The process is to give stimulus so it can increase the development skill and socializing a independency. The purpose of this research is to know the effect of educated game tool to preschool children development. The method of this research is one pre-post test group which the researcher observed before and after treatment. The sample is purposive sampling, total of the sampling is 17 respondent. Data which was gotten then analyzed by using wilcoxon signed ranks. The result of the research shows (p=0,000 < α=0,05), it means that there is effect from educated game tool to pre school childreen. From these result, it is suggested to parents a school to pay more attention to pre school children\u27s development especially speaking, language, socializing a independence ability
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