11,999 research outputs found
The Orion constellation as an installation - An innovative three dimensional teaching and learning environment
Visualising the three dimensional distribution of stars within a
constellation is highly challenging for both students and educators, but when
carried out in an interactive collaborative way it can create an ideal
environment to explore common misconceptions about size and scale within
astronomy. We present how the common table top activities based upon the Orion
constellation miss out on this opportunity. Transformed into a walk-through
Orion installation that includes the position of our Solar system, it allows
the students to fully immerse themselves within the model and experience
parallax. It enables participants to explore within the installation many other
aspects of astronomy relating to sky culture, stellar evolution, and stellar
timescales establishing an innovative learning and teaching environment.Comment: 2 pages, submitted to The Physics Teacher - Colum
Collins functions for pions from SIDIS and new e+e- data: a first glance at their transverse momentum dependence
New data from Belle and BaBar Collaborations on azimuthal asymmetries,
measured in e+e- annihilations into pion pairs at Q^2=112 GeV^2, allow to take
the first, direct glance at the transverse momentum dependence of the Collins
functions, in addition to their z dependence. These data, together with
available Semi-Inclusive Deep Inelastic Scattering (SIDIS) data on the Collins
asymmetry, are simultaneously analysed in the framework of the generalised
parton model assuming two alternative Q^2 evolution schemes and exploiting two
different parameterisations for the Collins functions. The corresponding
results for the transversity distributions are presented. Analogous data, newly
released by the BESIII Collaboration, on e+e- annihilations into pion pairs at
the lower Q^2 of 13 GeV^2, offer the possibility to explore the sensitivity of
these azimuthal correlations on transverse momentum dependent evolution
effects.Comment: 20 pages, 15 figures, 4 table
Assessing signals of TMD physics in SIDIS azimuthal asymmetries and in the extraction of the Sivers function
New data on the Sivers azimuthal asymmetry measured in semi-inclusive
deep-inelastic scattering processes have recently been released by the COMPASS
Collaboration at CERN. Their increased precision and their particular binning,
in terms of as well as , motivates a new extraction of the Sivers
function, within the framework of a simple and transparent parametrization.
Signals of TMD effects visible in the Sivers asymmetries are critically
assessed. A thorough study of the uncertainties affecting the extracted Sivers
function is presented, including the low- and large- regions.Comment: 20 pages, 13 figure
Reweighting the Sivers function with jet data from STAR
The reweighting procedure that using Bayesian statistics incorporates the information contained in a new data set, without the need of re-fitting, is applied to the quark Sivers function extracted from Semi-Inclusive Deep Inelastic Scattering (SIDIS) data. We exploit the recently published single spin asymmetry data for the inclusive jet production in polarized pp collisions from the STAR Collaboration at RHIC, which cover a much wider x region compared to SIDIS measurements. The reweighting method is extended to the case of asymmetric errors and the results show a remarkable improvement of the knowledge of the quark Sivers function
Bio-nanohybrids of quantum dots and photoproteins facilitating strong nonradiative energy transfer
Cataloged from PDF version of article.Utilization of light is crucial for the life cycle of many organisms. Also, many organisms can create light by utilizing chemical energy emerged from biochemical reactions. Being the most important structural units of the organisms, proteins play a vital role in the formation of light in the form of bioluminescence. Such photoproteins have been isolated and identified for a long time; the exact mechanism of their bioluminescence is well established. Here we show a biomimetic approach to build a photoprotein based excitonic nanoassembly model system using colloidal quantum dots (QDs) for a new bioluminescent couple to be utilized in biotechnological and photonic applications. We concentrated on the formation mechanism of nanohybrids using a kinetic and thermodynamic approach. Finally we propose a biosensing scheme with an ON/OFF switch using the QD-GFP hybrid. The QD-GFP hybrid system promises strong exciton-exciton coupling between the protein and the quantum dot at a high efficiency level, possessing enhanced capabilities of light harvesting, which may bring new technological opportunities to mimic biophotonic events
On the galactic rotation curves problem within an axisymmetric approach
In U. Nucamendi et al. Phys. Rev. D63 (2001) 125016 and K. Lake, Phys. Rev.
Lett. 92 (2004) 051101 it has been shown that galactic potentials can be
kinematically linked to the observed red/blue shifts of the corresponding
galactic rotation curves under a minimal set of assumptions: the emitted
photons come from stable timelike circular geodesic orbits of stars in a static
spherically symmetric gravitational field, and propagate to us along null
geodesics. It is remarkable that this relation can be established without
appealing at all to a concrete theory of gravitational interaction. Here we
generalize this kinematical spherically symmetric approach to the galactic
rotation curves problem to the stationary axisymmetric realm since this is
precisely the symmetry that spiral galaxies possess. Thus, by making use of the
most general stationary axisymmetric metric, we also consider stable circular
orbits of stars that emit signals which travel to a distant observer along null
geodesics and express the galactic red/blue shifts in terms of three arbitrary
metric functions, clarifying the contribution of the rotation as well as the
dragging of the gravitational field. This stationary axisymmetric approach
distinguishes between red and blue shifts emitted by circularly orbiting
receding and approaching stars, respectively, even when they are considered
with respect to the center of a spiral galaxy, indicating the need of precise
measurements in order to confront predictions with observations. We also point
out the difficulties one encounters in the attempt of determining the metric
functions from observations and list some possible strategies to overcome them.Comment: 7 pages in latex (MNRAS format), no figures, discussion and
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