Estimando evapotranspiración en Puerto Rico

The United Nations Food and Agriculture Organization (FAO) has recommended the Penman-Monteith method as the single method for estimating reference evapotranspiration throughout the world. A disadvantage of the method, however, is its relatively high data requirement. Measurements of wind speed, humidity (or dew point temperature) and radiation tend to be the least available of the required parameters; therefore, the FAO has presented estimation procedures for these parameters. The purpose of this study was to evaluate estimation procedures for climate data to be used in the Penman-Monteith method for estimating long-term daily reference evapotranspiration, and to verify the accuracy of the procedures at four locations in Puerto Rico. Comparison of reference evapotranspiration determined by using the estimated and measured climate data shows reasonably good agreement. The methods presented in this paper are potentially valuable for calculating the long-term average daily reference evapotranspiration at any location in Puerto Rico. An example is provided to illustrate the use of the proposed estimation procedures for climate parameters. This study presents a comparison of reference evapotranspiration calculated by the Penman-Monteith method, with estimates previously made by using the Hargreaves-Samani method, for thirty-four locations in Puerto Rico. In addition, estimated peak evapotranspiration from the Soil Conservation Service (SCS) (now Natural Resources Conservation Service) Irrigation Guide for the Caribbean Area, the SCS Blaney-Criddle method and the Penman-Monteith method were compared for six vegetable crops at three locations in Puerto Rico. The results suggest that some irrigation systems may have been under-designed in terms of flow capacity in Puerto Rico.La Organización de Alimentos y Agricultura de las Naciones Unidas (FAO, por sus siglas en inglés) ha recomendado el método de Penman-Monteith como el único método de calculación que se debería usar para estimar evapotranspiración de referencia a través del mundo. Sin embargo, una desventaja del método es que requiere un número alto de datos. Las medidas de la velocidad del viento, la humedad (o la temperatura de punto de rocío) y la radiación tienden a ser los parámetros requeridos más difíciles de obtener; por ello, la FAO ofrece procedimientos alternos de estimación para estos parámetros. El propósito de este estudio fue evaluar los procedimientos de estimación de los datos del clima requeridos por el método de Penman-Monteith para estimar (a evapotranspiración de referencia promedio diaria a largo plazo y verificar la exactitud de los procedimientos en cuatro zonas de Puerto Rico. Se encontró una alta correlación entre la evapotranspiración de referencia calculada con los datos estimados (FAO) y la calculada con los datos observados del clima. Los métodos presentados son potenciatmente valiosos para calcular la evapotranspiración de referencia promedio diaria en cualquier zona de Puerto Rico. Se provee un ejemplo para ilustrar el uso del procedimiento propuesto para estimar parámetros del clima. Se presenta una comparación de la evapotranspiración de referencia calculada por el método de Penman-Monteith y resultados estimados previamente por el método de Hargreaves-Samani para 34 zonas en Puerto Rico. Además, el estimado máximo de evapotranspiración de la Guía de Riego del Servicio de Conservación de Suelos (SCS) (ahora Servicio de Conservación de Recursos Naturales) para el Área def Caribe, el método de Blaney-Criddfe (SCS) y él método de Penman-Monteith se compararon para seis vegetales en tres localidades en Puerto Rico. Los resultados indican que algunos sistemas de riego no tienen suficiente capacidad para suplir agua en Puerto Rico

Experimental Test of Higher-Order Electron-Capture Processes in Collisions of Fast Protons with Atomic Hydrogen

We present measurements of the angular distribution of fast hydrogen atoms formed by electron capture of 2.8- and 5.0-MeV protons in atomic hydrogen. In the angular region of the Thomas peak (0.47 mrad) the experimental results obtained with this pure three-body collision system are in reasonable agreement with a strong-potential Born calculation and the impulse approximation, but not with other higher-order theories

Multiphoton radiative recombination of electron assisted by laser field

In the presence of an intensive laser field the radiative recombination of the continuum electron into an atomic bound state generally is accompanied by absorption or emission of several laser quanta. The spectrum of emitted photons represents an equidistant pattern with the spacing equal to the laser frequency. The distribution of intensities in this spectrum is studied employing the Keldysh-type approximation, i.e. neglecting interaction of the impact electron with the atomic core in the initial continuum state. Within the adiabatic approximation the scale of emitted photon frequencies is subdivided into classically allowed and classically forbidden domains. The highest intensities correspond to emission frequencies close to the edges of classically allowed domain. The total cross section of electron recombination summed over all emitted photon channels exhibits negligible dependence on the laser field intensity.Comment: 14 pages, 5 figures (Figs.2-5 have "a" and "b" parts), Phys.Rev.A accepted for publication. Fig.2b is presented correctl

Low resolution structures of the retinoid X receptor DNA-binding and ligand-binding domains revealed by synchrotron x-ray solution scattering

Nuclear receptors are ligand-inducible transcription factors that share structurally related DNA-binding (DBD) and ligand-binding (LBD) domains. Biochemical and structural studies have revealed the modular nature of DBD and LBD. Nevertheless, the domains function in concert in vivo. While high-resolution crystal structures of nuclear receptor DBDs and LBDs are available, there are no x-ray structural studies of nuclear receptor proteins containing multiple domains. We report the solution structures of the human retinoid X receptor DBD-LBD (hRXR AB) region. We obtained ab initio shapes of hRXR AB dimer and tetramer to 3.3 and 1.7 nm resolutions, respectively, and established the position and orientation of the DBD and LBD by fitting atomic coordinates of hRXR DBD and LBD. The dimer is U-shaped with DBDs spaced at 2 nm in a head to head orientation forming an angle of about 10° with respect to each other and with an extensive interface area provided by the LBD. The tetramer is a more elongated X-shaped molecule formed by two dimers in head to head arrangement in which the DBDs are extended from the structure and spaced at about 6 nm. The close proximity of DBDs in dimers may facilitate homodimer formation on DNA; however, for the homodimer to bind to a DNA element containing two directly repeated halfsites, one of the DBDs would need to rotate with respect to the other element. By contrast, the separation of DBDs in the tetramers may account for their decreased ability to recognize DNA

Efficient Genetic Method for Establishing Drosophila Cell Lines Unlocks the Potential to Create Lines of Specific Genotypes

Analysis of cells in culture has made substantial contributions to biological research. The versatility and scale of in vitro manipulation and new applications such as high-throughput gene silencing screens ensure the continued importance of cell-culture studies. In comparison to mammalian systems, Drosophila cell culture is underdeveloped, primarily because there is no general genetic method for deriving new cell lines. Here we found expression of the conserved oncogene RasV12 (a constitutively activated form of Ras) profoundly influences the development of primary cultures derived from embryos. The cultures become confluent in about three weeks and can be passaged with great success. The lines have undergone more than 90 population doublings and therefore constitute continuous cell lines. Most lines are composed of spindle-shaped cells of mesodermal type. We tested the use of the method for deriving Drosophila cell lines of a specific genotype by establishing cultures from embryos in which the warts (wts) tumor suppressor gene was targeted. We successfully created several cell lines and found that these differ from controls because they are primarily polyploid. This phenotype likely reflects the known role for the mammalian wts counterparts in the tetraploidy checkpoint. We conclude that expression of RasV12 is a powerful genetic mechanism to promote proliferation in Drosophila primary culture cells and serves as an efficient means to generate continuous cell lines of a given genotype