1,291 research outputs found
Dense Molecular Filaments Feeding a Starburst: ALMA Maps of CO(3-2) in Henize 2-10
We present ALMA CO(3-2) observations at 0.3 arcsec resolution of He2-10, a
starburst dwarf galaxy and possible high-z galaxy analogue. The warm dense gas
traced by CO(3--2) is found in clumpy filaments that are kinematically and
spatially distinct. The filaments have no preferred orientation or direction;
this may indicate that the galaxy is not evolving into a disk galaxy. Filaments
appear to be feeding the active starburst; the velocity field in one filament
suggests acceleration onto an embedded star cluster. The relative strengths of
CO(3-2) and radio continuum vary strongly on decaparsec scales in the
starburst. There is no CO(3--2) clump coincident with the non-thermal radio
source that has been suggested to be an AGN, nor unusual kinematics.
The kinematics of the molecular gas show significant activity apparently
unrelated to the current starburst. The longest filament, east of the
starburst, has a pronounced shear of FWHM ~\kms\ across its 50~pc
width over its entire kpc length. The cause of the shear is not
clear. This filament is close in projection to a `dynamically distinct' CO
feature previously seen in CO(1--0). The most complex region and the most
highly disturbed gas velocities are in a region 200~pc south of the starburst.
The CO(3--2) emission there reveals a molecular outflow, of linewidth FWZI
120-140 \kms, requiring an energy . There is
at present {\it no} candidate for the driving source of this outflow.Comment: This was revised 31 October to correct some typos and to replace
Figure
Introduction of interactive learning into French university physics classrooms
We report on a project to introduce interactive learning strategies (ILS) to
physics classes at the Universit\'e Pierre et Marie Curie (UPMC), one of the
leading science universities in France. In Spring 2012, instructors in two
large introductory classes, first-year, second-semester mechanics, and
second-year introductory E&M, enrolling approximately 500 and 250 students
respectively, introduced ILS into some sections of each class. The specific ILS
utilized were Think-Pair-Share questions and Peer Instruction in the main
lecture classrooms, and UW Tutorials for Introductory Physics in recitation
sections. Pre- and post-instruction assessments (FCI and CSEM respectively)
were given, along with a series of demographics questions. We were able to
compare the results of the FCI and CSEM between interactive and non-interactive
classes taught simultaneously with the same curriculum. We also analyzed final
exam results, as well as the results of student and instructor attitude surveys
between classes. In our analysis, we argue that Multiple Linear Regression
modeling is superior to other common analysis tools, including normalized gain.
Our results show that ILS are effective at improving student learning by all
measures used: research-validated concept inventories and final exam scores, on
both conceptual and traditional problem-solving questions. Multiple Linear
Regression analysis reveals that interactivity in the classroom is a
significant predictor of student learning, showing a similar or stronger
relationship with student learning than such ascribed characteristics as
parents' education, and achieved characteristics such as GPA and hours studied
per week. Analysis of student and instructors attitudes shows that both groups
believe that ILS improve student learning in the physics classroom, and
increases student engagement and motivation
Ionized Gas Motions and the Structure of Feedback Near a Forming Globular Cluster in NGC 5253
We observed Brackett 4.05m emission towards the supernebula in
NGC 5253 with NIRSPEC on Keck II in adaptive optics mode, NIRSPAO, to probe
feedback from its exciting embedded super star cluster (SSC). NIRSPEC's
Slit-Viewing Camera was simultaneously used to image the K-band continuum at
resolution. We register the IR continuum with HST imaging, and
find that the visible clusters are offset from the K-band peak, which coincides
with the Br peak of the supernebula and its associated molecular
cloud. The spectra of the supernebula exhibit Br emission with a
strong, narrow core. The linewidths are 65-76 km s, FWHM, comparable to
those around individual ultra-compact HII regions within our Galaxy. A weak,
broad (FWHM150-175 km s) component is detected on the base of
the line, which could trace a population of sources with high-velocity winds.
The core velocity of Br emission shifts by +13 km s from NE to
SW across the supernebula, possibly indicating a bipolar outflow from an
embedded object, or linked to a foreground redshifted gas filament. The results
can be explained if the supernebula comprises thousands of ionized wind regions
around individual massive stars, stalled in their expansion due to critical
radiative cooling and unable to merge to drive a coherent cluster wind. Based
on the absence of an outflow with large mass loss, we conclude that feedback is
currently ineffective at dispersing gas, and the SSC retains enriched material
out of which it may continue to form stars.Comment: 24 pages, 9 figure
ALMA CO(3-2) Observations of Star-Forming Filaments in a Gas-Poor Dwarf Spheroidal Galaxy
We report ALMA observations of CO(3-2) and CO(3-2) in the
gas-poor dwarf galaxy NGC 5253. These 0.3"(5.5 pc) resolution images reveal
small, dense molecular gas clouds that are located in kinematically distinct,
extended filaments. Some of the filaments appear to be falling into the galaxy
and may be fueling its current star formation. The most intense CO(3-2)
emission comes from the central 100 pc region centered on the luminous
radio-infrared HII region known as the supernebula. The CO(3-2) clumps within
the starburst region are anti-correlated with H on 5 pc scales,
but are well-correlated with radio free-free emission. Cloud D1, which
enshrouds the supernebula, has a high CO/CO ratio, as does
another cloud within the central 100 pc starburst region, possibly because the
clouds are hot. CO(3-2) emission alone does not allow determination of cloud
masses as molecular gas temperature and column density are degenerate at the
observed brightness, unless combined with other lines such as CO.Comment: 7 pages, 5 figures, Accepted to Ap
Monte Carlo Analysis of Airport Throughput and Traffic Delays Using Self Separation Procedures
This paper presents the results of three simulation studies of throughput and delay times of arrival and departure operations performed at non-towered, non-radar airports using self-separation procedures. The studies were conducted as part of the validation process of the Small Aircraft Transportation Systems Higher Volume Operations (SATS HVO) concept and include an analysis of the predicted airport capacity using with different traffic conditions and system constraints under increasing levels of demand. Results show that SATS HVO procedures can dramatically increase capacity at non-towered, non-radar airports and that the concept offers the potential for increasing capacity of the overall air transportation system
Highlights of meiotic genes in Arabidopsis thaliana
Meiosis is a fascinating and complex phenomenon and, despite its central role in sexual plant reproduction, little is known on the molecular mechanisms involved in this process. We review the progress made in recent years using Arabidopsis thaliana mutants for isolating meiotic genes. In particular, emphasis is given on the description of mutants affecting either the regular commitment to meiosis, or the mechanisms of synapsis, recombination, and cytokinesis. We believe that the isolation of genes affecting some crucial meiotic events may represent the first step towards the practical use of meiotic genes in plant breeding. The introduction of deviations in the meiotic pathway into sexual crops will have important implications for the exploitation of apomixis and sexual polyploidization.
Key words: Arabidopsis, meiosis, mutants, fertility.
African Journal of Biotechnology Vol. 2 (12), pp.516-520, December 200
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