2,234 research outputs found
Efecto del origen de plantas y silvicultura de establecimiento en la inclinación de plantaciones jóvenes de Pinus radiata D. Don por efecto del viento
Gallegos, J. Forestal Mininco S.A., Los Ángeles, Chile.
Muñoz, F.;Cancino, J. Facultad de Ciencias Forestales, Universidad de Concepción. Casilla 160-C, Concepción, Chile.El fenómeno de pérdida de estabilidad por viento en árboles jóvenes de Pinus radiata D. Don, es una perturbación abiótica que se manifiesta en forma de inclinaciones anormales, derribamiento, formación de cuencas en la base del árbol y descalces. La investigación tiene como objetivo identificar el efecto del origen de la planta, control de malezas y fertilización en el daño por viento en plantaciones jóvenes de pino radiata.
El ensayo fue establecido en el año 2003 en predios ubicados en la Comuna de Cunco, IX Región. Se establecieron cuatro orígenes de plantas (estacas de huerto, estacas de setos juveniles, estacas de setos envejecidos y plantas provenientes de semilla), combinados con tres esquemas de control de malezas y dos de fertilización (total 24 tratamientos). La variable respuesta fue la inclinación expresada en porcentaje, previamente normalizada, la cual fue medida luego de los temporales de viento durante el invierno del año 2005.
Como resultado se determinó que el origen de planta desde estacas de huerto en combinación con control de malezas en tazas en el primer año de establecido y sin fertilización, presenta la mejor resistencia al daño por viento. El tratamiento con peor resistencia al daño de viento, esta formado por estacas de setos juveniles, control de malezas en banda durante los 2 primeros años y sin fertilización. Se determinó que la edad del material fisiológico es determinante en el daño por efecto del viento en plantaciones jóvenes de Pinus radiata D. Don
Coleman-Weinberg mechanism in a three-dimensional supersymmetric Chern-Simons-matter model
Using the superfield formalism, we study the dynamical breaking of gauge
symmetry in the N=1 three-dimensional supersymmetric Chern-Simons model,
coupled to a complex scalar superfield with a quartic self-coupling. This is an
analogue of the conformally invariant Coleman-Weinberg model in four spacetime
dimensions. We show that a mass for the gauge and matter superfields are
dynamically generated after two-loop corrections to the effective
superpotential. We also discuss the N=2 extension of our work, showing that the
Coleman-Weinberg mechanism in such model is not feasible, because it is
incompatible with perturbation theory.Comment: 14 pages, 2 figures. Minor corrections, references added. Journal
versio
Geotechnical Aspects on Seismic Risk Assessment in Cusco, Peru
Results from many efforts to better understand the nature of ground motions and the seismic behavior or structures in Cusco, Peru, give now the possibility to combine several sources of information to produce estimates of seismic hazard and risk. A model is presented which estimates expected damage, based on geotechnical characteristics and intensity-damage relations derived for several types of buildings representative of Cusco’s constructions. The study area was divided into smaller sections covering the whole city. This information, along with the geographic distribution of soil types and construction density, allows computation of expected losses during a given event for sites distributed throughout the city
Dynamical (super)symmetry vacuum properties of the supersymmetric Chern-Simons-matter model
By computing the two-loop effective potential of the D=3 N=1 supersymmetric
Chern-Simons model minimally coupled to a massless self-interacting matter
superfield, it is shown that supersymmetry is preserved, while the internal
U(1) and the scale symmetries are broken at two-loop order, dynamically
generating masses both for the gauge superfield and for the real component of
the matter superfield.Comment: revtex4, 12 pages, 2 figures, journal versio
A New Pleiades Member at the Lithium Substellar Boundary
We present the discovery of an object in the Pleiades open cluster, named
Teide 2, with optical and infrared photometry which place it on the cluster
sequence slightly below the expected substellar mass limit. We have obtained
low- and high-resolution spectra that allow us to determine its spectral type
(M6), radial velocity and rotational broadening; and to detect H in
emission and Li I 670.8 nm in absorption. All the observed properties strongly
support the membership of Teide 2 into the Pleiades. This object has an
important role in defining the reappearance of lithium below the substellar
limit in the Pleiades. The age of the Pleiades very low-mass members based on
their luminosities and absence or presence of lithium is constrained to be in
the range 100--120 Myr.Comment: 17 pages, 3 figure
Spherical Mexican Hat wavelet: an application to detect non-Gaussianity in the COBE-DMR maps
The spherical Mexican Hat wavelet is introduced in this paper, with the aim
of testing the Gaussianity of the Cosmic Microwave Background temperature
fluctuations. Using the information given by the wavelet coefficients at
several scales, we have performed several statistical tests on the COBE-DMR
maps to search for evidence of non-Gaussianity. Skewness, kurtosis, scale-scale
correlations (for two and three scales) and Kolmogorov-Smirnov tests indicate
that the COBE-DMR data are consistent with a Gaussian distribution. We have
extended the analysis to compare temperature values provided by COBE-DMR data
with distributions (obtained from Gaussian simulations) at each pixel and at
each scale. The number of pixels with temperature values outside the 95% and
the 99% is consistent with that obtained from Gaussian simulations, at all
scales. Moreover, the extrema values for COBE-DMR data (maximum and minimum
temperatures in the map) are also consistent with those obtained from Gaussian
simulations.Comment: to be published in MNRA
Possible Patient Early Diagnosis by Ultrasonic Noninvasive Estimation of Thermal Gradients into Tissues Based on Spectral Changes Modeling
To achieve a precise noninvasive temperature estimation, inside patient tissues, would open promising research fields, because its clinic results would provide early-diagnosis tools. In fact, detecting changes of thermal origin in ultrasonic echo spectra could be useful as an early complementary indicator of infections, inflammations, or cancer. But the effective clinic applications to diagnosis of thermometry ultrasonic techniques, proposed previously, require additional research. Before their implementations with ultrasonic probes and real-time electronic and processing systems, rigorous analyses must be still made over transient echotraces acquired from well-controlled biological and computational phantoms, to improve resolutions and evaluate clinic limitations. It must be based on computing improved signal-processing algorithms emulating tissues responses. Some related parameters in echo-traces reflected by semiregular scattering tissues must be carefully quantified to get a precise processing protocols definition. In this paper, approaches for non-invasive spectral ultrasonic detection are analyzed. Extensions of author's innovations for ultrasonic thermometry are shown and applied to computationally modeled echotraces from scattered biological phantoms, attaining high resolution (better than 0.1°C). Computer methods are provided for viability evaluation of thermal estimation from echoes with distinct noise levels, difficult to be interpreted, and its effectiveness is evaluated as possible diagnosis tool in scattered tissues like liver
Self-Assembly of Amphiphilic Dendrimers: The Role of Generation and Alkyl Chain Length in siRNA Interaction
Citation: Marquez-Miranda, V., Araya-Duran, I., Camarada, M. B., Comer, J., Valencia-Gallegos, J. A., & Gonzalez-Nilo, F. D. (2016). Self-Assembly of Amphiphilic Dendrimers: The Role of Generation and Alkyl Chain Length in siRNA Interaction. Scientific Reports, 6, 15. https://doi.org/10.1038/srep29436An ideal nucleic-acid transfection system should combine the physical and chemical characteristics of cationic lipids and linear polymers to decrease cytotoxicity and uptake limitations. Previous research described new types of carriers termed amphiphilic dendrimers (ADs), which are based on polyamidoamine dendrimers (PAMAM). These ADs display the cell membrane affinity advantage of lipids and preserve the high affinity for DNA possessed by cationic dendrimers. These lipid/dendrimer hybrids consist of a low-generation, hydrophilic dendron (G2, G1, or G0) bonded to a hydrophobic tail. The G2-18C AD was reported to be an efficient siRNA vector with significant gene silencing. However, shorter tail ADs (G2-15C and G2-13C) and lower generation (G0 and G1) dendrimers failed as transfection carriers. To date, the self-assembly phenomenon of this class of amphiphilic dendrimers has not been molecularly explored using molecular simulation methods. To gain insight into these systems, the present study used coarse-grained molecular dynamics simulations to describe how ADs are able to self-assemble into an aggregate, and, specifically, how tail length and generation play a key role in this event. Finally, explanations are given for the better efficiency of G2/18-C as gene carrier in terms of binding of siRNA. This knowledge could be relevant for the design of novel, safer ADs with well-optimized affinity for siRNA
Studies of Vibrational Properties in Ga Stabilized d-Pu by Extended X-ray Absorption Fine Structure
Temperature dependent extended x-ray absorption fine structure (EXAFS)
spectra were measured for a 3.3 at% Ga stabilized Pu alloy over the range T= 20
- 300 K at both the Ga K-edge and the Pu L_III-edge. The temperature dependence
of the pair-distance distribution widths, \sigma(T) was accurately modeled
using a correlated-Debye model for the lattice vibrational properties,
suggesting Debye-like behavior in this material. We obtain pair- specific
correlated-Debye temperatures, \Theta_cD, of 110.7 +/- 1.7 K and 202.6 +/- 3.7
K, for the Pu-Pu and Ga-Pu pairs, respectively. These results represent the
first unambiguous determination of Ga-specific vibrational properties in PuGa
alloys, and indicate the Ga-Pu bonds are significantly stronger than the Pu-Pu
bonds. This effect has important implications for lattice stabilization
mechanisms in these alloys.Comment: 7 pages, 4 figures, Phys. Rev. B in pres
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