2,042 research outputs found
MAX1and MAX2 control shoot lateral branching in Arabidopsis
Plant shoots elaborate their adult form by selective control over the growth of both their primary shoot apical meristem and their axillary shoot meristems. We describe recessive mutations at two loci in Arabidopsis, MAX1 and MAX2, that affect the selective repression of axillary shoots. All the first order (but not higher order) axillary shoots initiated by mutant plants remain active, resulting in bushier shoots than those of wild type. In vegetative plants where axillary shoots develop in a basal to apical sequence, the mutations do not clearly alter node distance, from the shoot apex, at which axillary shoot meristems initiate but shorten the distance at which the first axillary leaf primordium is produced by the axillary shoot meristem. A small number of mutant axillary shoot meristems is enlarged and, later in development, a low proportion of mutant lateral shoots is fasciated. Together, this suggests that MAX1 and MAX2 do not control the timing of axillary meristem initiation but repress primordia formation by the axillary meristem. In addition to shoot branching, mutations at both loci affect leaf shape. The mutations at MAX2 cause increased hypocotyl and petiole elongation in light-grown seedlings. Positional cloning identifies MAX2 as a member of the F-box leucine-rich repeat family of proteins. MAX2 is identical to ORE9, a proposed regulator of leaf senescence (Woo, H. R., Chung, K. M., Park, J.-H., Oh, S. A., Ahn, T., Hong, S. H., Jang, S. K. and Nam, H. G. (2001) Plant Cell 13, 1779-1790). Our results suggest that selective repression of axillary shoots involves ubiquitinmediated degradation of as yet unidentified proteins that activate axillary growth
Impact of nonlocal interactions in dissipative systems: towards minimal-sized localized structures
In order to investigate the size limit on spatial localized structures in a
nonlinear system, we explore the impact of linear nonlocality on their domains
of existence and stability. Our system of choice is an optical microresonator
containing an additional metamaterial layer in the cavity, allowing the
nonlocal response of the material to become the dominating spatial process. In
that case, our bifurcation analysis shows that this nonlocality imposes a new
limit on the width of localized structures going beyond the traditional
diffraction limit.Comment: 4 pages, 4 figure
The connection between mass, environment and slow rotation in simulated galaxies
Recent observations from integral field spectroscopy (IFS) indicate that the
fraction of galaxies that are slow rotators, , depends primarily on
stellar mass, with no significant dependence on environment. We investigate
these trends and the formation paths of slow rotators (SRs) using the EAGLE and
Hydrangea hydro-dynamical simulations. EAGLE consists of several cosmological
boxes of volumes up to , while Hydrangea consists of
cosmological simulations of galaxy clusters and their environment. Together
they provide a statistically significant sample in the stellar mass range
, of galaxies. We
construct IFS-like cubes and measure stellar spin parameters, , and ellipticities, allowing us to classify galaxies into slow/fast
rotators as in observations. The simulations display a primary dependence of
on stellar mass, with a weak dependence on environment. At fixed
stellar mass, satellite galaxies are more likely to be SRs than centrals.
shows a dependence on halo mass at fixed stellar mass for central
galaxies, while no such trend is seen for satellites. We find that % of SRs at have experienced at least one merger with mass ratio , with dry mergers being at least twice more common than wet mergers.
Individual dry mergers tend to decrease , while wet mergers
mostly increase it. However, % of SRs at have not experienced
mergers, and those inhabit halos with median spins twice smaller than the halos
hosting the rest of the SRs. Thus, although the formation paths of SRs can be
varied, dry mergers and/or halos with small spins dominate.Comment: Accepted for publications in MNRAS (20 pages, 17 main body, 1.5
appendix). Changes include analysis of the orbital angular momentum effect on
lambdaR and slightly different ellipticity calculatio
The level and duration of RSV-specific maternal IgG in infants in Kilifi Kenya
Background
Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infection in infants. The rate of decay of RSV-specific maternal antibodies (RSV-matAb), the factors affecting cord blood levels, and the relationship between these levels and protection from infection are poorly defined.
Methods
A birth cohort (n = 635) in rural Kenya, was studied intensively to monitor infections and describe age-related serological characteristics. RSV specific IgG antibody (Ab) in serum was measured by the enzyme linked immunosorbent assay (ELISA) in cord blood, consecutive samples taken 3 monthly, and in paired acute and convalescent samples. A linear regression model was used to calculate the rate of RSV-matAb decline. The effect of risk factors on cord blood titres was investigated.
Results
The half-life of matAb in the Kenyan cohort was calculated to be 79 days (95% confidence limits (CL): 76–81 days). Ninety seven percent of infants were born with RSV-matAb. Infants who subsequently experienced an infection in early life had significantly lower cord titres of anti-RSV Ab in comparison to infants who did not have any incident infection in the first 6 months (P = 0.011). RSV infections were shown to have no effect on the rate of decay of RSV-matAb.
Conclusion
Maternal-specific RSV Ab decline rapidly following birth. However, we provide evidence of protection against severe disease by RSV-matAb during the first 6–7 months. This suggests that boosting maternal-specific Ab by RSV vaccination may be a useful strategy to consider
Coexistence of Paramagnetic-Charge-Ordered and Ferromagnetic-Metallic Phases in La0.5Ca0.5MnO3 evidenced by ESR
Throughout a complete Electron Spin Resonance (ESR) and magnetization study
of La0.5Ca0.5MnO3, we discuss about the nature of the complex phase-segregated
state established in this compound below T~210 K. Between TN<T<TC, the ESR
spectra shows two lines characteristic of two different magnetic phases. From
the resonance field (Hr) derived for each line we argue that the
incommensurate-charge-ordering phase (ICO) which coexists with
ferromagnetic-metallic (FMM) clusters in this temperature interval, is mainly
paramagnetic and not antiferromagnetic. The FMM/ICO ratio can be tuned with a
relatively small field, which suggests that the internal energy associated with
those phases is very similar. Below TN, there is an appreciable FM contribution
to the magnetization and the ESR spectra indicates the presence of FM clusters
in an antiferromagnetic matrix (canted). Our results show that ESR could be a
very useful tool to investigate the nature of the phase-separated state now
believed to play a fundamental role in the physics of mixed valent manganites.Comment: 6 pages, 6 figure
Fast human activity recognition in lifelogging
This paper addresses the problem of fast Human Activity Recognition (HAR) in visual lifelogging. We identify the importance of visual features related to HAR and we specifically evaluate the HAR discrimination potential of Colour Histograms and Histogram of Oriented Gradients. In our evaluation we show that colour can be a low-cost and effective means of low-cost HAR when performing single-user classification. It is also noted that, while much more efficient, global image descriptors perform as well or better than local descriptors in our HAR experiments. We believe that both of these findings are due to the fact that a user’s lifelog is rich in reoccurring scenes and environments
Personalización de la política, storytelling y valores transmitidos
En esta investigación descriptivo-interpretativa sincrónica se analiza el discurso de los candidatos gallegos a las elecciones municipales empleado en 400 vídeos de YouTube con el objetivo de establecer una taxonomía en cuanto a los valores que en ellos transmiten estos políticos. De este modo, en un contexto teórico definido por dos grandes ejes (la personalización de la política y el storytelling como técnica narrativa que contribuye a “ficcionalizar” (Maarek, 2014) la vida de los políticos), se aborda la construcción de la imagen de dichos candidatos, incidiendo en los elementos del discurso que incluyen. Así, a partir de este estudio en el que se han empleado la revisión bibliográfica y el análisis de contenido, se ha podido comprobar que entre los relatos personales de estos candidatos los valores sobre los que mayoritariamente se insiste están asociados a cualidades como la humildad, la cotidianeidad, la preparación intelectual/laboral, la generosidad y la cercanía. Por tanto, se detecta una estrategia discursiva que busca de modo subrepticio y velado trasladar y proyectar cualidades personales a la acción política, en un afán por conciliar el tradicional objetivo de procurar una construcción simbólica de autoridad con la necesidad quizá ahora más acuciante de emplear nuevos framings del candidato que lo muestren como un semejante con el que es posible identificarse
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