Disaggregated estimates of output supply and input demand elasticities

Designed for consistency with competitive theory, nonrejected simplifying assumptions and multi stage choice, aggregate dual models are specified of Texas agricultural production. Disaggregated own and cross price elasticities are derived for 25 commodity supplies and six input demands. Estimated supplies and demands are largely inelastic. Outputs are mainly economic substitutes and inputs are economic complements.

MULTIPLE-OUTPUT PRODUCTION MODELED WITH THREE FUNCTIONAL FORMS

Aggregate dual models are specified to examine multiple-output production relationships in each of four major, geographically dispersed, agricultural states (California, Iowa, Texas, and Florida). Three locally-flexible functional forms (translog, generalized Leontief, and normalized quadratic) are employed to conduct analytic simplification tests, estimate systems of output supply and input demand equations consistent with nonrejected hypotheses, derive elasticities, and determine to what extent analytic simplification tests and policy-relevant results are sensitive to functional form and state. Important differences in empirical implications were found due both to functional form and geographic unit, but differences were greater for the latter.Production Economics,

The reaction between silylene and ammonia: some gas-phase kinetic and quantum chemical studies

Time-resolved kinetic studies of the reaction of silylene, SiH2, generated by 193 nm laser flash photolysis of silacyclopent-3-ene, have been carried out in the presence of ammonia, NH3. Second order kinetics were observed. The reaction was studied in the gas phase at 10 Torr total pressure in SF6 bath gas at each of the three temperatures, 299, 340 and 400 K. The second order rate constants (laser pulse energy of 60 mJ/pulse) fitted the Arrhenius equation: log(k/cm3 molecule-1 s-1) = (-10.37 ± 0.17) + (0.36 ± 1.12 kJ mol-1)/RTln10 Experiments at other pressures showed that these rate constants were unaffected by pressure in the range 10-100 Torr, but showed small decreases in value at 3 and 1 Torr. There was also a weak intensity dependence, with rate constants decreasing at laser pulse energies of 30 mJ/pulse. Ab initio calculations at the G3 level of theory, show that SiH2 + NH3 should form an initial adduct (donor-acceptor complex), but that energy barriers are too great for further reaction of the adduct. This implies that SiH2 + NH3 should be a pressure dependent association reaction. The experimental data are inconsistent with this and we conclude that SiH2 decays are better explained by reaction of SiH2 with the amino radical, NH2, formed by photodissociation of NH3 at 193 nm. The mechanism of this previously unstudied reaction is discussed

Design issues and experimental characterization of a continuously-tuned adaptive CMOS LNA

This paper presents the design implementation and experimental characterization of an adaptive Low Noise Amplifier (LNA) intended for multi-standard Radio Frequency (RF) wireless transceivers. The circuit —fabricated in a 90-nm CMOS technology— is a two-stage inductively degenerated common-source topology that combines PMOS varactors with programmable load to make the operation of the circuit continuously tunable. Practical design issues are analyzed, considering the effect of circuit parasitics associated to the chip package and integrated inductors, capacitors and varactors. Experimental measurements show a continuous tuning of NF and Sparameters within the 1.75-2.23GHz band, featuring NF19.6dB and IIP3> −9.8dBm, with a power dissipation < 23mW from a 1-V supply voltage.Ministerio de Ciencia e Innovación (FEDER) TEC2007-67247-C02-01/MICJunta de Andalucía, Consejo Regional de Innovación, ciencia y empresa TIC-253

Anomalous phase of MnP at very low field

Manganese phosphide MnP has been investigated for decades because of its rich magnetic phase diagram. It is well known that the MnP exhibits the ferromagnetic phase transition at \Tc=292 K and the helical magnetic phase below \TN=47 K at zero field. Recently, a novel magnetic phase transition was observed at $T^* = 282$ K when the magnetic field is lower than 5 Oe. However, the nature of the new phase has not been illuminated yet. In order to reveal it, we performed the AC and the DC magnetization measurements for a single crystal MnP at very low field. A divergent behavior of the real and the imaginary part of the AC susceptibility and a sharp increase of the DC magnetization was observed at $T^*$, indicating the magnetic phase transition at $T^*$. Furthermore a peculiar temperature hysteresis was observed: namely, the magnetization depends on whether cooling sample to the temperature lower than \TN or not before the measurements. This hysteresis phenomenon suggests the complicated nature of the new phase and a strong relation between the magnetic state of the new phase and the helical structure.Comment: 4 pages, 2 figure

Genes implicados en el desarrollo de la semilla de Arabidopsis thaliana (L.) : caracterización de los genes AtAnkTm /

Consultable des del TDXA la portada: Consorcio CSIC/IRTA, Laboratorio de Genética Molecular Vegetal, Instituto de Biología Molecular de Barcelona, Departamento de Genética MolecularTítol obtingut de la portada digitalitzadaLa embriogénesis es uno de los procesos más cruciales en el desarrollo vegetal. La secuenciación de ESTs (Expressed Sequences Tags) de la genoteca ATISLA, de semillas de 2 a 6 DDA (Días Después de Antesis), permitió identificar categorías funcionales típicas de desarrollo temprano de semilla como ciclo de división celular, reserva de nutrientes y traducción. A través del análisis in silico, considerando las ESTs de semilla inmadura depositadas en las bases de datos en una primera etapa y aquellos genes cuya expresión era elevada en semilla utilizando el programa Meta analyzer de Genevestigator en una segunda, se lograron identificar 49 genes cuya expresión es específica de semilla inmadura, resultados que fueron confirmados por RT-PCR e hibridación in situ. Al comparar estos 49 genes con el genoma completo de Arabidopsis, se encontraron diferencias estadísticas significativas para las categorías funcionales de reserva de reserva de nutrientes, metabolismo de carbohidratos, respuesta a estrés abiótico y tráfico subcelular y transporte. Las repeticiones anquirina son motivos de 33 aminoácidos repetidos en tándem cuya principal función descrita en animales es de interacción proteína-proteína. Participan en diversas funciones tanto en animales como en vegetales. Mediante análisis in silico fue posible identificar 509 repeticiones anquirina, que son codificadas por 105 genes. Se obtuvo una secuencia consenso de repetición anquirina de Arabidopsis que es similar a la de animales, por lo que es posible que las repeticiones anquirina en plantas cumplan la misma función que en animales. Los 105 genes codifican proteínas que se dividieron en 16 clases diferentes en función de los dominios o motivos que acompañaban a las repeticiones anquirina. El grupo más numeroso corresponde a las proteínas con dominios de repeticiones anquirina y transmembrana (37, proteínas ATANKTM). Mediante análisis neighbor joining de la región de dominios de repeticiones anquirina, estas proteínas se clasificaron en 6 familias distintas. Los genes AtAnkTm se encuentran repartidos en los cinco cromosomas de Arabidopsis y existen eventos de duplicación tanto a nivel inter- como intracromosómico, además de la presencia de genes duplicados en tándem (con 1 grupo de hasta 7 miembros). Mediante RT-PCR en diferentes órganos y bajo diferentes condiciones de estrés, fue posible observar que los genes AtAnkTm poseen patrones de expresión muy diferentes incluso dentro de una misma familia, por lo tanto, es posible que cumplan funciones muy variadas. Estos resultados fueron contrastados con análisis de bases de datos de ESTs y micromatrices utilizando el programa de visualización de expresión de genes de AtGenExpress. Se identificó un gen (AtAnkTm28) cuya expresión es en silicua inmadura y específicamente de semilla, mediante RT-PCR. Por hibridación in situ, se detectó expresión en embrión, suspensor y endospermo nuclear libre. La fusión de la región transmembrana de la proteína ATANKTM28 a GFP se localiza en algunos puntos específicos de la membrana citoplasmática. La mutación en los genes AtAnkTm2 y AtAnkTm9 produce una reducción en la viabilidad de los granos de polen. La mutación de AtAnktm2 también produce cambios en la estructura de la exina.Embryogenesis is one of the most important steps in plant development. We have built a cDNA library (ATISLA) from isolated Arabidopsis seeds 2-6 DAA (Days After Anthesis) and used it for sequencing ESTs (Expressed Sequences Tags). The most abundant functional categories of the genes sequenced corresponded to cell division, nutrient reservoir and translation. We have used a two-step in silico subtraction analysis in order to identify genes specifically expressed in immature seeds. The first subtraction step was based on ESTs abundance in databases. The second subtraction step was based on microarray hybridization data obtained from the database Genevestigator. We identified 49 genes with specific expression in immature seed and we used RT-PCR and in situ hybridization analysis in order to verify the goodness of our selection method. Comparison of the functional categories of the 49 selected genes with the genes in the whole genome we identified statistically differences in some functional categories as for example nutrient reservoir, carbohydrate metabolism, abiotic stress response and sub cellular traffic and transport. Ankyrin repeats are 33-amino-acid domains that occur in tandemly arrayed sets of two or more, and are believed to function as protein-protein interaction domains. Several proteins having ankyrin repeats have been reported in animals and plants and they appear to be involved in many processes. We used in silico analysis to identify all Arabidopsis genes coding for proteins with ankyrin repeats. A total of 509 ankyrin repeats codified by 105 genes were identified. An ankyrin-repeat consensus sequence for Arabidopsis was determined, being very similar to the animal consensus, suggesting that ankyrin-repeats in plants play a similar role as in animals in protein-protein interactions. Arabidopsis ankyrin coding genes were classified in 16 groups according to the protein structures. The most abundant group contains 37 genes coding for proteins with ankyrin repeats and transmembrane domains (ATANKTM proteins). According to sequence similarity, they were classified in 6 families. The AtAnkTm genes are distributed through the five Arabidopsis chromosomes, including duplicated genes (intra- and inter- chromosomally) and groups of tandemly arrays genes. We used semi quantitative RT-PCR in order to determine the patterns of expression of these genes and we found that they were very variable, even inside a single family. These results were compared with ESTs databases and microarrays analysis using the tool Gene Expression Visualization of AtGeneExpress. One of the genes (AtAnkTm28) is expressed specifically in seeds at very early stages of development. In situ hybridization determined that this gene is expressed in the embryo proper, suspensor and free nuclear endosperm. Fusions of the transmembrane region of ATANKTM28 with GFP seem to localize at few specifics points of the plasma membrane. Mutations of two other AtAnkTm genes (AtAnkTm2 and AtAnkTm9) produce a reduction in pollen viability. Mutation in AtAnkTm2 also generates changes in the structure of the pollen surface (exin)