5,499 research outputs found
Word mastery in oral reading: telling versus sounding of unknown words, in grade three.
Thesis (Ed.M.)--Boston University
N.B.: Page 71 is misnumbered. No content is missing
The dependence of HII region properties on global and local surface brightness within galaxy discs
Using B, R, and H-alpha images of roughly equal-sized samples of low surface
brightness (LSB) and high surface brightness (HSB) galaxies (~40 galaxies
apiece), we have explored the dependence of HII region properties on local and
global disc surface brightness. We have done this by constructing co-added HII
region luminosity functions (LFs) according to local and central disc surface
brightness and fitting Schechter functions to these LFs. The results show that
the shape of the HII region LF within LSB galaxies does not change noticeably
as different limiting (i.e., mu>mu_lim) local surface brightness values are
used. However, the LFs for HSB galaxies have larger values of L_* and are less
steep at the faint-end than those of LSB galaxies for limiting B-band local
surface brightness values as faint as mu_B,lim~23-24. Both the LFs and the data
for individual HII regions show that luminous (log L>39 ergs/s) HII regions are
much more common within HSB discs than within LSB discs, implying that the
newly formed star clusters are also larger. Taking this into account along with
the results of Monte Carlo simulations, the shapes of the LFs imply that the
regions within LSB discs and those within the LSB areas of HSB discs are
relatively old (~5 Myr) while the regions within HSB discs for mu_B<24 are
significantly younger (<1 Myr). Since the majority of the LSB galaxies do not
have noticeable spiral arms and the majority of the HSB galaxies do, this may
indicate a transition within HSB discs from spiral arm-driven star formation to
a more locally driven, possibly sporadic form of star formation at mu_B~24, a
transition that does not appear to occur within LSB discs.Comment: Accepted to MNRA
Degenerate mixing of plasma waves on cold, magnetized single-species plasmas
In the cold-fluid dispersion relation ω = ω_p/[1+(k_⊥/k_z)^(2]1/2) for Trivelpiece-Gould waves on an infinitely long magnetized plasma cylinder, the transverse and axial wavenumbers appear only in the combination k_⊥/k_z. As a result, for any frequency ω<ω_p, there are infinitely many degenerate waves, all having the same value of k_⊥/k_z. On a cold finite-length plasma column, these degenerate waves reflect into one another at the ends; thus, each standing-wave normal mode of the bounded plasma is a mixture of many degenerate waves, not a single standing wave as is often assumed. A striking feature of the many-wave modes is that the short-wavelength waves often add constructively along resonance cones given by dz/dr = ±(ω_p^2/ω^2-1)^(1/2). Also, the presence of short wavelengths in the admixture for a predominantly long-wavelength mode enhances the viscous damping beyond what the single-wave approximation would predict. Here, numerical solutions are obtained for modes of a cylindrical plasma column with rounded ends. Exploiting the fact that the modes of a spheroidal plasma are known analytically (the Dubin modes), a perturbation analysis is used to investigate the mixing of low-order, nearly degenerate Dubin modes caused by small deformations of a plasma spheroid
Do the Poor Pay More for Healthy Food? An Empirical Economic Analysis
Food Consumption/Nutrition/Food Safety,
Toward the total synthesis of spirastrellolide A. Part 3: Intelligence gathering and preparation of a ring-expanded analogue
Different methods for the formation of the C.25–C.26 bond of spirastrellolide A (1) are evaluated that might qualify for the end game of the projected total synthesis, with emphasis on metathetic ways to forge the macrocyclic frame
Murine cytomegalovirus genomic material in marrow cells; relation to altered leukocyte counts during sublethal infection of mice
Consumer-Preferred Attributes of a Fresh Ground Beef and Turkey Product: A Conjoint Analysis
A random sample of 3,400 Louisiana households was surveyed by mail to determine their ratings for a number of product profiles involving a combined fresh ground beef and turkey product. The attributes and levels of the new product included form (fresh, frozen), identity of the packager (retailer, processor), percentage of beef in product (50,70,90), and price of the combined product as a percentage of ground beef (80,90,100). Based on 2,781 observations, the order of importance of the attributes were, in order of declining importance, content, form, price, and packager. Consumer utility was highly sensitive to the content of beef, with a higher content being preferred.Consumer/Household Economics,
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