17,557 research outputs found

    60 Years of Rural Reconstruction Movement in the Philippines (PRRM) = 回顧菲律賓鄉村建設運動60年

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    PRRM did not go to the countryside to disperse buffalos though that’s not necessarily a bad thing. PRRM did disperse buffalos and other farm animals but it went to the countryside for nobler reason---the liberation of the peasant from poverty and oppression. It sought to do this through mass education and mass movement. By 2012 PRRM will have spanned a period running in parallel to the postwar development history of the Philippines. It was founded in 1952 during the administration of President Magsaysay, called “Man of the Masses”. PRRM peaked in the 1960s, declined in the late 1970s through to the 1980s, and rebounded after the 1986 EDSA revolution

    On the distribution of proportions and ratios as indicators of ungulate body condition

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    In the wildlife literature various studies have shown that the amount of fat around the kidneys is often a good indicator of body condition and health of ungulate species ([1],[2]). Wildlife biologies often measure the weights of fat around the kidneys and the kidneys themselves (without fat), comparing these two quantities and transforming them into a ratio or a proportion as surrogates of body condition of dead animals. Later, they use these indices as response variables to model the e®ect of covariates or treatments, such as age group and season of the year, on body condition. The more commonly used models are ANOVA-type. Most debate has been concentrated on whether or not to use a simple ANOVA model of ratios or proportions with ¯xed e®ects, or an ANCOVA model using fat weight as response variable, and the kidneys weight as a covariate ([3]). Results have taken by surprise some biologists because using one or another model with both response variables could lead to very di®erent results for what it considered the most important e®ects. In this manuscript we attempt to highlight the main di®erences and the distributional properties of these response variables, ratio and proportion

    Neural-network selection of high-redshift radio quasars, and the luminosity function at z~4

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    We obtain a sample of 87 radio-loud QSOs in the redshift range 3.6<z<4.4 by cross-correlating sources in the FIRST radio survey S{1.4GHz} > 1 mJy with star-like objects having r <20.2 in SDSS Data Release 7. Of these 87 QSOs, 80 are spectroscopically classified in previous work (mainly SDSS), and form the training set for a search for additional such sources. We apply our selection to 2,916 FIRST-DR7 pairs and find 15 likely candidates. Seven of these are confirmed as high-redshift quasars, bringing the total to 87. The candidates were selected using a neural-network, which yields 97% completeness (fraction of actual high-z QSOs selected as such) and an efficiency (fraction of candidates which are high-z QSOs) in the range of 47 to 60%. We use this sample to estimate the binned optical luminosity function of radio-loud QSOs at z4z\sim 4, and also the LF of the total QSO population and its comoving density. Our results suggest that the radio-loud fraction (RLF) at high z is similar to that at low-z and that other authors may be underestimating the fraction at high-z. Finally, we determine the slope of the optical luminosity function and obtain results consistent with previous studies of radio-loud QSOs and of the whole population of QSOs. The evolution of the luminosity function with redshift was for many years interpreted as a flattening of the bright end slope, but has recently been re-interpreted as strong evolution of the break luminosity for high-z QSOs, and our results, for the radio-loud population, are consistent with this.Comment: 20 pages. Accepted for publication in MNRAS on 3 March 201

    Use of neural networks for the identification of new z>=3.6 QSOs from FIRST-SDSS DR5

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    We aim to obtain a complete sample of redshift > 3.6 radio QSOs from FIRST sources having star-like counterparts in the SDSS DR5 photometric survey (r<=20.2). We found that simple supervised neural networks, trained on sources with SDSS spectra, and using optical photometry and radio data, are very effective for identifying high-z QSOs without spectra. The technique yields a completeness of 96 per cent and an efficiency of 62 per cent. Applying the trained networks to 4415 sources without DR5 spectra we found 58 z>=3.6 QSO candidates. We obtained spectra of 27 of them, and 17 are confirmed as high-z QSOs. Spectra of 13 additional candidates from the literature and from SDSS DR6 revealed 7 more z>=3.6 QSOs, giving and overall efficiency of 60 per cent. None of the non-candidates with spectra from NED or DR6 is a z>=3.6 QSO, consistently with a high completeness. The initial sample of z>=3.6 QSOs is increased from 52 to 76, i.e. by a factor 1.46. From the new identifications and candidates we estimate an incompleteness of SDSS for the spectroscopic classification of FIRST 3.6<=z<=4.6 QSOs of 15 percent for r<=20.2.Comment: 16 pages, 9 figures accepted for publication in MNRA

    SPH simulations of the chemical evolution of bulges

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    We have implemented a chemical evolution model on the parallel AP3M+SPH DEVA code which we use to perform high resolution simulations of spiral galaxy formation. It includes feedback by SNII and SNIa using the Qij matrix formalism. We also include a diffusion mechanism that spreads newly introduced metals. The gas cooling rate depends on its specific composition. We study the stellar populations of the resulting bulges finding a potential scenario where they seem to be composed of two populations: an old, metal poor, α\alpha-enriched population, formed in a multiclump scenario at the beginning of the simulation and a younger one, formed by slow accretion of satellites or gas, possibly from the disk due to instabilities.Comment: 2 pages, 3 figures. Proceedings of IAUS 245 "Formation and Evolution of Galaxy Bulges

    The role of magnetoplasmons in Casimir force calculations

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    In this paper we review the role of magneto plasmon polaritons in the Casimir force calculations. By applying an external constant magnetic field a strong optical anisotropy is induced on two parallel slabs reducing the reflectivity and thus the Casimir force. As the external magnetic field increases, the Casimir force decreases. Thus, with an an external magnetic field the Casimir force can be controlled.The calculations are done in the Voigt configuration where the magnetic field is parallel to the slabs. In this configuration the reflection coefficients for TE and TM modes do not show mode conversion.Comment: contribution to QFEXT09, Norman, Oklahoma 200
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