8,798 research outputs found
Lyman Alpha and MgII as Probes of Galaxies and their Environments
Ly{\alpha} emission, Ly{\alpha} absorption and MgII absorption are powerful
tracers of neutral hydrogen. Hydrogen is the most abundant element in the
universe and plays a central role in galaxy formation via gas accretion and
outflows, as well as being the precursor to molecular clouds, the sites of star
formation. Since 21cm emission from neutral hydrogen can only be directly
observed in the local universe, we rely on Ly{\alpha} emission, and Ly{\alpha}
and MgII absorption to probe the physics that drives galaxy evolution at higher
redshifts. Furthermore, these tracers are sensitive to a range of hydrogen
densities that cover the interstellar medium, the circumgalactic medium and the
intergalactic medium, providing an invaluable means of studying gas physics in
regimes where it is poorly understood. At high redshift, Ly{\alpha} emission
line searches have discovered thousands of star-forming galaxies out to z = 7.
The large Ly{\alpha} scattering cross-section makes observations of this line
sensitive to even very diffuse gas outside of galaxies. Several thousand more
high-redshift galaxies are known from damped Ly{\alpha} absorption lines and
absorption by the MgII doublet in quasar and GRB spectra. MgII, in particular,
probes metal-enriched neutral gas inside galaxy haloes in a wide range of
environments and redshifts (0.1 < z < 6.3), including the so-called redshift
desert. Here we review what observations and theoretical models of Ly{\alpha}
emission, Ly{\alpha} and MgII absorption have told us about the interstellar,
circumgalactic and intergalactic medium in the context of galaxy formation and
evolution.Comment: 59 Pages, 19 Figures, 1 Table. Accepted for publication in
Publications of the Astronomical Society of the Pacifi
The teaching of handwriting
Submitted in partial fulfillment of the requirements for the degree of Master of Arts.Text from page 1: The problem of this investigation is to study the uses of diagnosis and corrective measures in the teaching of handwriting.Includes bibliographic references
Integrable families of hard-core particles with unequal masses in a one-dimensional harmonic trap
We show that the dynamics of particles in a one-dimensional harmonic trap
with hard-core interactions can be solvable for certain arrangements of unequal
masses. For any number of particles, there exist two families of unequal mass
particles that have integrable dynamics, and there are additional exceptional
cases for three, four and five particles. The integrable mass families are
classified by Coxeter reflection groups and the corresponding solutions are
Bethe ansatz-like superpositions of hyperspherical harmonics in the relative
hyperangular coordinates that are then restricted to sectors of fixed particle
order. We also provide evidence for superintegrability of these Coxeter mass
families and conjecture maximal superintegrability.Comment: 9.5+4.5 pages, 5 figures, 2 tables; v3: a few corrections and
addition
Recommended from our members
Long Term Potentiation (LTP) and Long Term Depression (LTD) Cause Differential Spatial Redistribution of the Synaptic Vesicle Protein Synaptophysin in the Middle Molecular Layer of the Dentate Gyrus in Rat Hippocampus
The presynaptic modifications that accompany long-term changes in synaptic plasticity are still not fully understood. Synaptophysin is a major synaptic vesicle protein involved in neurotransmitter release. We have used quantitative electron microscopy to study synaptophysin (Syn) immunolabelling in the hippocampus of adult rats 24h after induction in vivo of long term potentiation (LTP), and long term depression (LTD). Electrodes were implanted chronically in hippocampus with stimulation at either the medial (MPP) or lateral perforant path (LPP). 24h following induction of LTP or LTD rats were rapidly perfusion fixed and hippocampal tissue processed to electron microscopy via freeze substitution method. Anti-synaptophysin post-embedding immunolabelling was performed and tissue was imaged in the middle molecular layer (MML) of the dentate gyrus. There was a significant decrease in number of Syn labelled vesicles per unit area of bouton after LTP, but not LTD. An analysis of the spatial distribution of Syn labelled synaptic vesicles showed an increase in nearest neighbour distances, more so in the LTP than the LTD group, which is consistent with the overall decrease of Syn after LTP. These data are in agreement with the suggestion that Syn is involved in clathrin-dependent and “kiss and run” endocytosis which occurs perisynaptically. Thus, an increase in release of neurotransmitter and in consequence endocytosis would be consistent with an increased active zone distance for vesicles containing Syn
Anomalous Scaling and Solitary Waves in Systems with Non-Linear Diffusion
We study a non-linear convective-diffusive equation, local in space and time,
which has its background in the dynamics of the thickness of a wetting film.
The presence of a non-linear diffusion predicts the existence of fronts as well
as shock fronts. Despite the absence of memory effects, solutions in the case
of pure non-linear diffusion exhibit an anomalous sub-diffusive scaling. Due to
a balance between non-linear diffusion and convection we, in particular, show
that solitary waves appear. For large times they merge into a single solitary
wave exhibiting a topological stability. Even though our results concern a
specific equation, numerical simulations supports the view that anomalous
diffusion and the solitary waves disclosed will be general features in such
non-linear convective-diffusive dynamics.Comment: Corrected typos, added 3 references and 2 figure
Investigation of high-angle-of attack performance of a 14 degree ramp-type inlet in various circumferential body locations : Mach number range 1.5 to 2.0
Analisis Kesesuaian Perairan Untuk Budidaya Ikan Kerapu Macan (Epinephelus Fuscoguttatu) Di Perairan Pulau Tegal Kecamatan Teluk Pandan Kabupaten Pesawaran
Tiger grouper is a marine aquaculture commodities that has good prospects to be developed. One of the areas that could potentially be used as a place of tiger grouper fish farming is the Tegal Island, Pesawaran. The purpose of this research was to analyze the level of water quality for fish farming tiger grouper (Epinephelus fuscoguttatus). This research was carried out in March-May 2017 descriptive analytic nature by doing the observations on the quality of waters which include physical and chemical parameters. The data that used in this research sourced from primary data about the suitability waters of the island while the secondary data is form in research location maps. There were 4 sampling stations which determined with global positioning system (GPS). The results showed that the water quality which is owned by the island's waters on station 1, 2, 3 and 4 were in the quite appropriate category for the cultivation of tiger grouper
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