12,836 research outputs found
Mejoramiento genético y taza de autofecundación del camu camu arbustivo en la Amazonía Peruana.
El camu camu (Myrciaria dubia (H.B.K.) MC VAUGH) es una frutera silvestre conocida mundialmente como un excepcional productor de vitamina C. Su mejoramiento se encuentra en fase inicial. Este trabajo tuvo por objetivos estudiar el sistema reproductivo (taza de autofecundación), el efecto del origen del polen (autofecundación o polinización abierta) en la producción de ácido ascórbico y porcentaje de germinación, la repetibilidad de caracteres productivos y sus implicaciones en el programa de mejoramiento. El sistema reproductivo del camu camu es mixto con variables tazas de autofecundación. No fue confirmada la existencia de efecto del origen del polen para el carácter de producción de ácido ascórbico. La repetibilidad individual de la producción fue de moderada magnitud (0.41); la repetibilidad del promedio de 5 cosechas de fruta fue de 0.77, propiciando exactitud selectiva de 0.88. Genotipos superiores pueden ser seleccionados con precisión y, por lo tanto, cinco a seis cosechas por planta es un número adecuado. La selección y clonación de los diez mejores individuos deberá propiciar una ganancia genética del 237.5 %, elevando la productividad media anual de frutas por planta de 7.75 para 26.17 kg/año
Orbital magnetism in axially deformed sodium clusters: From scissors mode to dia-para magnetic anisotropy
Low-energy orbital magnetic dipole excitations, known as scissors mode (SM),
are studied in alkali metal clusters. Subsequent dynamic and static effects are
explored. The treatment is based on a self-consistent microscopic approach
using the jellium approximation for the ionic background and the Kohn-Sham mean
field for the electrons. The microscopic origin of SM and its main features
(structure of the mode in light and medium clusters, separation into low- and
high-energy plasmons, coupling high-energy M1 scissors and E2 quadrupole
plasmons, contributions of shape isomers, etc) are discussed. The scissors M1
strength acquires large values with increasing cluster size. The mode is
responsible for the van Vleck paramagnetism of spin-saturated clusters. Quantum
shell effects induce a fragile interplay between Langevin diamagnetism and van
Vleck paramagnetism and lead to a remarkable dia-para anisotropy in magnetic
susceptibility of particular light clusters. Finally, several routes for
observing the SM experimentally are discussed.Comment: 21 pages, 7 figure
Orbital Magnetic Dipole Mode in Deformed Clusters: A Fully Microscopic Analysis
The orbital M1 collective mode predicted for deformed clusters in a schematic
model is studied in a self-consistent random-phase-approximation approach which
fully exploits the shell structure of the clusters. The microscopic mechanism
of the excitation is clarified and the close correlation with E2 mode
established. The study shows that the M1 strength of the mode is fragmented
over a large energy interval. In spite of that, the fraction remaining at low
energy, well below the overwhelming dipole plasmon resonance, is comparable to
the strength predicted in the schematic model. The importance of this result in
view of future experiments is stressed.Comment: 10 pages, 3 Postscript figures, uses revte
Distance Functions and Normalization Under Stream Scenarios
Data normalization is an essential task when modeling a classification
system. When dealing with data streams, data normalization becomes especially
challenging since we may not know in advance the properties of the features,
such as their minimum/maximum values, and these properties may change over
time. We compare the accuracies generated by eight well-known distance
functions in data streams without normalization, normalized considering the
statistics of the first batch of data received, and considering the previous
batch received. We argue that experimental protocols for streams that consider
the full stream as normalized are unrealistic and can lead to biased and poor
results. Our results indicate that using the original data stream without
applying normalization, and the Canberra distance, can be a good combination
when no information about the data stream is known beforehand.Comment: Paper accepted to the 2023 International Joint Conference on Neural
Network
Nonconventional short-time dc magnetometer for superconducting films
Includes bibliographical references.A nonconventional technique for the measurement of magnetic relaxation in superconducting films at short times (~ 10-5 s) is described. This technique combines the application of a pulsed magnetic field and a synchronized high-energy pulsed laser. Remanent magnetic relaxation in (Y;Gd)Ba2Cu3O7-δ thin films is reported over five decades time at reduced temperatures above 0.8.This work was partially supported by Fundació Sauberán, EX018-UBA and EX285-UBA grants
- …