10,822 research outputs found
Especiação em solos: aspectos gerais.
ConsideraçÔes sobre a especiação aplicada a solos.bitstream/CNPS/11580/1/doc47_2003_especiacao_solos.pd
Solução do solo: importùncia e extração por centrifugação.
ConsideraçÔes sobre estudos de técnicas de extração da fase aquosa do solo
Brane Structure from a Scalar Field in Warped Spacetime
We deal with scalar field coupled to gravity in five dimensions in warped
geometry. We investigate models described by potentials that drive the system
to support thick brane solutions that engender internal structure. We find
analytical expressions for the brane solutions, and we show that they are all
linearly stable.Comment: 10 pages, 7 eps figures; version to be published in JCA
S wave velocity structure below central Mexico using high-resolution surface wave tomography
Shear wave velocity of the crust below central Mexico is estimated using surface wave dispersion measurements from regional earthquakes recorded on a dense, 500 km long linear seismic network. Vertical components of regional records from 90 well-located earthquakes were used to compute Rayleigh-wave group-velocity dispersion curves. A tomographic inversion, with high resolution in a zone close to the array, obtained for periods between 5 and 50 s reveals significant differences relative to a reference model, especially at larger periods (>30 s). A 2-D S wave velocity model is obtained from the inversion of local dispersion curves that were reconstructed from the tomographic solutions. The results show large differences, especially in the lower crust, among back-arc, volcanic arc, and fore-arc regions; they also show a well-resolved low-velocity zone just below the active part of the Trans Mexican Volcanic Belt (TMVB) suggesting the presence of a mantle wedge. Low densities in the back arc, inferred from the low shear wave velocities, can provide isostatic support for the TMVB
Biomass burning and urban air pollution over the Central Mexican Plateau
Observations during the 2006 dry season of highly elevated concentrations of cyanides in the atmosphere above Mexico City (MC) and the surrounding plains demonstrate that biomass burning (BB) significantly impacted air quality in the region. We find that during the period of our measurements, fires contribute more than half of the organic aerosol mass and submicron aerosol scattering, and one third of the enhancement in benzene, reactive nitrogen, and carbon monoxide in the outflow from the plateau. The combination of biomass burning and anthropogenic emissions will affect ozone chemistry in the MC outflow
Twenty six years of wheat breeding activities at IAPAR.
The description of the IAPAR wheat breeding program in its 26 th years of existence aims at presenting its major achievements giving an idea of the program size, breeding objectives and methodology. A germplasm flow chart will show the steps by which the populations have to follow starting either from crosses or from introductions until an advanced inbred line can be evaluated and elected as a new cultivar. A list of 23 wheat cultivars released by the program along with their pedigrees is presented as a special contribution. From the recent developed cultivars, data on grain yield, agronomic characteristics, technological quality and kernel properties are presented. The pedigree description for IAPAR 53 and the development of IPR 85 are presented in some detail. New biotechnological tools to help wheat breeding become more efficient are discussed
Monitorización de la oxidación del aceite de semillas de sacha inchi (Plukenetia volubilis) suplementado con extractos de vainas de tara (Caesalpinia spinosa) mediante técnicas convencionales y MIR
This work focuses on the characterization of the oxidation of the oil from sacha inchi seeds (Plukenetia volubilis) under accelerated conditions at 60 ÂșC for 15 days. Five samples were monitored: three supplemented with 200 ppm of non-hydrolyzed or partially hydrolyzed (for 4 and 9 hours) extracts from tara (Caesalpinia spinosa) pods, one without antioxidant and one with 200 ppm of BHT. Several conventional techÂniques (induction time, peroxide value, conjugated dienoic acid, p-anisidine value, total unsaturated fatty acids and α-linolenic acid contents) and the MIR spectroscopy coupled with chemometric tools were used and comÂpared. The results revealed that whatever the antioxidant added, the oil from sacha inchi is fairly stable over time. The results also pointed out that extracts from tara pods, mainly those partially hydrolyzed, were more efficient than BHT against oil oxidation for up to 7 days. Finally, this paper shows that MIR spectroscopy presÂents an interesting alternative technique for the monitoring of the oxidation of the oil from sacha inchi.Este trabajo se centra en la caracterizaciĂłn de la oxidaciĂłn de aceites de sacha inchi (Plukenetia volubilis) en condiciones aceleradas a 60 ÂșC durante 15 dĂas. Se monitorean cinco muestras: tres suplementadas con 200 ppm de extractos no hidrolizados o parÂcialmente hidrolizados (durante 4 y 9 horas) de vainas de tara (Caesalpinia spinosa), una sin antioxidante y otra con 200 ppm de BHT. Se utilizan y comparan varias tĂ©cnicas convencionales (tiempo de inducciĂłn, Ăndice de perĂłxido, ĂĄcido dienoico conjugado, Ăndice de p-anisidina, ĂĄcidos grasos insaturados totales y contenido de ĂĄcido α-linolĂ©nico) y la espectroscopĂa MIR junto con herramientas quimiomĂ©tricas. Los resultados revelan que, cualquiera que sea el antioxidante agregado, el aceite de sacha inchi es bastante estable a lo largo del tiempo. Los resultados tambiĂ©n señaÂlan que los extractos de las vainas de tara, principalmente aquellos parcialmente hidrolizados, son mĂĄs eficientes que el BHT contra la oxidaciĂłn del aceite hasta los 7 dĂas. Finalmente, el trabajo muestra que la espectroscopĂa MIR se presenta como una tĂ©cnica alternativa interesante para el monitoreo de la oxidaciĂłn del aceite de sacha inchi
Optical polarimetric monitoring of the type II-plateau SN 2005af
Aims. Core-collapse supernovae may show significant polarization that implies
non-spherically symmetric explosions. We observed the type II-plateau SN 2005af
using optical polarimetry in order to verify whether any asphericity is present
in the supernova temporal evolution. Methods. We used the IAGPOL imaging
polarimeter to obtain optical linear polarization measurements in R (five
epochs) and V (one epoch) broadbands. Interstellar polarization was estimated
from the field stars in the CCD frames. The optical polarimetric monitoring
began around one month after the explosion and lasted ~30 days, between the
plateau and the early nebular phase. Results. The weighted mean observed
polarization in R band was [1.89 +/- 0.03]% at position angle (PA) 54 deg.
After foreground subtraction, the level of the average intrinsic polarization
for SN 2005af was ~0.5% with a slight enhancement during the plateau phase and
a decline at early nebular phase. A rotation in PA on a time scale of days was
also observed. The polarimetric evolution of SN 2005af in the observed epochs
is consistent with an overall asphericity of ~20% and an inclination of ~30
deg. Evidence for a more complex, evolving asphericity, possibly involving
clumps in the SN 2005af envelope, is found.Comment: 6 pages, 5 figures, to be published A&
Determinação da cor do solo a partir de dados radiométricos e sua relação com teores de hematita.
Color is widely recognized as a primary identifying parameter of soil. The physical, mineralogical, and chemical properties can be derived from assessing the subsurface color characteristics. The present research aimed to estimating the hematite content clay fraction, in laboratory, from data related to soil color obtained by using automatic devices. Fifteen subsurface soil samples from SĂŁo Paulo State had their clay fraction hematite contents semiquantitavely determined by the association of chemical and physical methods and their colors evaluated in laboratory through measurements made with a spectro-radiometer. The radiometric data were used to the determination of soil color in L*a*b* and Munsell systems and to the calculation of reddish indexes (RI). The RI values show functional dependence of hematite contents and the best relation is verified with RI values derived from color determined in the L*a*b* system. Exponential models, developed from remote sensors, show themselves adequate in predicting the soil hematite contents
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