4,474 research outputs found
Note sur l'amélioration du maïs dans l'ouest Cameroun : compte-rendu de mission du 16 au 23 juillet 1969
Enquête sur les sorghos et mils du Tchad. Compte-rendu de mission du 2 au 8 novembre 1965
E-β-Ocimene, a Volatile Brood Pheromone Involved in Social Regulation in the Honey Bee Colony (Apis mellifera)
Background: In honey bee colony, the brood is able to manipulate and chemically control the workers in order to sustain their own development. A brood ester pheromone produced primarily by old larvae (4 and 5 days old larvae) was first identified as acting as a contact pheromone with specific effects on nurses in the colony. More recently a new volatile brood pheromone has been identified: E-β-ocimene, which partially inhibits ovary development in workers. [br/]
Methodology and Principal Finding: Our analysis of E-β-ocimene production revealed that young brood (newly hatched to 3 days old) produce the highest quantity of E-b-ocimene relative to their body weight. By testing the potential action of this molecule as a non-specific larval signal, due to its high volatility in the colony, we demonstrated that in the presence of E-β-ocimene nest workers start to forage earlier in life, as seen in the presence of real brood. [br/]
Conclusions/Significance: In this way, young larvae are able to assign precedence to the task of foraging by workers in order to increase food stores for their own development. Thus, in the complexity of honey bee chemical communication, E-β- ocimene, a pheromone of young larvae, provides the brood with the means to express their nutritional needs to the workers
Intrabeam scattering analysis of measurements at KEK's ATF damping ring
We derive a simple relation for estimating the relative emittance growth in x
and y due to intrabeam scattering (IBS) in electron storage rings. We show that
IBS calculations for the ATF damping ring, when using the formalism of
Bjorken-Mtingwa, a modified formalism of Piwinski (where eta squared divided by
beta has been replaced by the dispersion invariant), or a simple high-energy
approximate formula all give results that agree well. Comparing theory,
including the effect of potential well bunch lengthening, with a complete set
of ATF steady-state beam size vs. current measurements we find reasonably good
agreement for energy spread and horizontal emittance. The measured vertical
emittance, however, is larger than theory in both offset (zero current
emittance) and slope (emittance change with current). The slope error indicates
measurement error and/or additional current-dependent physics at the ATF; the
offset error, that the assumed Coulomb log is correct to within a factor of
1.75.Comment: 17 pages, 6 figures, .bbl fil
KP line solitons and Tamari lattices
The KP-II equation possesses a class of line soliton solutions which can be
qualitatively described via a tropical approximation as a chain of rooted
binary trees, except at "critical" events where a transition to a different
rooted binary tree takes place. We prove that these correspond to maximal
chains in Tamari lattices (which are poset structures on associahedra). We
further derive results that allow to compute details of the evolution,
including the critical events. Moreover, we present some insights into the
structure of the more general line soliton solutions. All this yields a
characterization of possible evolutions of line soliton patterns on a shallow
fluid surface (provided that the KP-II approximation applies).Comment: 49 pages, 36 figures, second version: section 4 expande
A JWST investigation into the bar fraction at redshifts 1 < z < 3
The presence of a stellar bar in a disc galaxy indicates that the galaxy
hosts a dynamically settled disc and that bar-driven processes are taking place
in shaping the evolution of the galaxy. Studying the cosmic evolution of the
bar fraction in disc galaxies is therefore essential to understand galaxy
evolution in general. Previous studies have found, using the Hubble Space
Telescope (HST), that the bar fraction significantly declines from the local
Universe to redshifts near one. Using the first four pointings from the James
Webb Space Telescope (JWST) Cosmic Evolution Early Release Science Survey
(CEERS) and the initial public observations for the Public Release Imaging for
Extragalactic Research (PRIMER), we extend the studies on the bar fraction in
disc galaxies to redshifts , i.e., for the first time beyond
redshift two. We only use galaxies that are also present in the Cosmic Assembly
Near-IR Deep Extragalactic Legacy Survey (CANDELS) on the Extended Groth Strip
(EGS) and Ultra Deep Survey (UDS) HST observations. An optimised sample of 768
close-to-face-on galaxies is visually classified to find the fraction of bars
in disc galaxies in two redshift bins: and .
The bar fraction decreases from per cent to per cent (from the lower to the higher redshift bin), but
is times greater than the bar fraction found in previous studies
using bluer HST filters. Our results show that bar-driven evolution commences
at early cosmic times and that dynamically settled discs are already present at
a lookback time of Gyrs.Comment: Submitted to MNRAS. 15 pages, 10 figures. Figure 6 and 7 summarises
the main result
A JWST investigation into the bar fraction at redshifts 1 ≤ z ≤ 3
The presence of a stellar bar in a disc galaxy indicates that the galaxy hosts in its main part a dynamically settled disc and that bar-driven processes are taking place in shaping its evolution. Studying the cosmic evolution of the bar fraction in disc galaxies is therefore essential to understand galaxy evolution in general. Previous studies have found, using the Hubble Space Telescope (HST), that the bar fraction significantly declines from the local Universe to redshifts near one. Using the first four pointings from the JWST Cosmic Evolution Early Release Science Survey and the initial public observations for the Public Release Imaging for Extragalactic Research, we extend the studies of the bar fraction in disc galaxies to redshifts 1 ≤ z ≤ 3, that is, for the first time beyond redshift two. We only use galaxies that are also present in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey on the Extended Groth Strip and Ultra Deep Survey HST observations. An optimized sample of 368 close-to-face-on galaxies is visually classified to find the fraction of bars in disc galaxies in two redshift bins: 1 ≤ z ≤ 2 and 2 < z ≤ 3. The barfraction decreases from ≈ 17.8+5.1 −4.8 per cent to ≈ 13.8+6.5−5.8 per cent (from the lower to the higher redshift bin), but is about twicethe bar fraction found using bluer HST filters. Our results show that bar-driven evolution might commence at early cosmic times and that dynamically settled discs are already present at a lookback time of ∼11 Gyr
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