8,299 research outputs found
An inequality of Kostka numbers and Galois groups of Schubert problems
We show that the Galois group of any Schubert problem involving lines in
projective space contains the alternating group. Using a criterion of Vakil and
a special position argument due to Schubert, this follows from a particular
inequality among Kostka numbers of two-rowed tableaux. In most cases, an easy
combinatorial injection proves the inequality. For the remaining cases, we use
that these Kostka numbers appear in tensor product decompositions of
sl_2(C)-modules. Interpreting the tensor product as the action of certain
commuting Toeplitz matrices and using a spectral analysis and Fourier series
rewrites the inequality as the positivity of an integral. We establish the
inequality by estimating this integral.Comment: Extended abstract for FPSAC 201
International and domestic regulator issues facing the Canadian MSAT system
International and domestic regulatory issues which affect the implementation of a mobile satellite system (MSAT) over North America are addressed. WARC-MOB-87, MSAT frequency co-ordination, frequency sharing and key Canadian domestic issues are discussed
New multivariable capabilities of the INCA program
The INteractive Controls Analysis (INCA) program was developed at NASA's Goddard Space Flight Center to provide a user friendly, efficient environment for the design and analysis of control systems, specifically spacecraft control systems. Since its inception, INCA has found extensive use in the design, development, and analysis of control systems for spacecraft, instruments, robotics, and pointing systems. The (INCA) program was initially developed as a comprehensive classical design analysis tool for small and large order control systems. The latest version of INCA, expected to be released in February of 1990, was expanded to include the capability to perform multivariable controls analysis and design
Do Individual Differences And Aging Effects In The Estimation Of Geographical Slant Reflect Cognitive Or Perceptual Effects?
Several individual differences including age have been suggested to affect the perception of slant. A cross-sectional study of outdoor hill estimation (N = 106) was analyzed using individual difference measures of age, experiential knowledge, fitness, personality traits, and sex. Of particular note, it was found that for participants who reported any experiential knowledge about slant, estimates decreased (i.e., became more accurate) as conscientiousness increased, suggesting that more conscientious individuals were more deliberate about taking their experiential knowledge (rather than perception) into account. Effects of fitness were limited to those without experiential knowledge, suggesting that they, too, may be cognitive rather than perceptual. The observed effects of age, which tended to produce lower, more accurate estimates of hill slant, provide more evidence that older adults do not see hills as steeper. The main effect of age was to lower slant estimates; such effects may be due to implicit experiential knowledge acquired over a lifetime. The results indicate the impact of cognitive, rather than perceptual factors on individual differences in slant estimation
A Molecular Einstein Ring at z=4.12: Imaging the Dynamics of a Quasar Host Galaxy Through a Cosmic Lens
We present high-resolution (0.3") Very Large Array (VLA) imaging of the
molecular gas in the host galaxy of the high redshift quasar PSS J2322+1944
(z=4.12). These observations confirm that the molecular gas (CO) in the host
galaxy of this quasar is lensed into a full Einstein ring, and reveal the
internal dynamics of the molecular gas in this system. The ring has a diameter
of ~1.5", and thus is sampled over ~20 resolution elements by our observations.
Through a model-based lens inversion, we recover the velocity gradient of the
molecular reservoir in the quasar host galaxy of PSS J2322+1944. The Einstein
ring lens configuration enables us to zoom in on the emission and to resolve
scales down to ~1 kpc. From the model-reconstructed source, we find that the
molecular gas is distributed on a scale of 5 kpc, and has a total mass of
M(H2)=1.7 x 10^10 M_sun. A basic estimate of the dynamical mass gives M_dyn =
4.4 x 10^10 (sin i)^-2 M_sun, that is, only ~2.5 times the molecular gas mass,
and ~30 times the black hole mass (assuming that the dynamical structure is
highly inclined). The lens configuration also allows us to tie the optical
emission to the molecular gas emission, which suggests that the active galactic
nucleus (AGN) does reside within, but not close to the center of the molecular
reservoir. Together with the (at least partially) disturbed structure of the
CO, this suggests that the system is interacting. Such an interaction, possibly
caused by a major `wet' merger, may be responsible for both feeding the quasar
and fueling the massive starburst of 680 M_sun/yr in this system, in agreement
with recently suggested scenarios of quasar activity and galaxy assembly in the
early universe.Comment: 9 pages, 7 figures, to appear in ApJ (accepted June 27, 2008
Deaths from Cysticercosis, United States
Most deaths occur among Latino immigrants; US-born persons are affected to a lesser extent
The Secant Conjecture in the real Schubert calculus
We formulate the Secant Conjecture, which is a generalization of the Shapiro
Conjecture for Grassmannians. It asserts that an intersection of Schubert
varieties in a Grassmannian is transverse with all points real, if the flags
defining the Schubert varieties are secant along disjoint intervals of a
rational normal curve. We present theoretical evidence for it as well as
computational evidence obtained in over one terahertz-year of computing, and we
discuss some phenomena we observed in our data.Comment: 19 page
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The Internal Circadian Clock Increases Hunger and Appetite in the Evening Independent of Food Intake and Other Behaviors
Objective: Despite the extended overnight fast, paradoxically, people are typically not ravenous in the morning and breakfast is typically the smallest meal of the day. Here we assessed whether this paradox could be explained by an endogenous circadian influence on appetite with a morning trough, while controlling for sleep/wake and fasting/feeding effects. Design and Methods We studied 12 healthy non-obese adults (6 male; age, 20–42 year) throughout a 13-day laboratory protocol that balanced all behaviors, including eucaloric meals and sleep periods, evenly across the endogenous circadian cycle. Participants rated their appetite and food preferences by visual analog scales. Results: There was a large endogenous circadian rhythm in hunger, with the trough in the biological morning (8 AM) and peak in the biological evening (8 PM; peak-to-trough amplitude=17%; P=0.004). Similarly phased significant endogenous circadian rhythms were present in appetite for sweets, salty and starchy foods, fruits, meats/poultry, food overall, and for estimates of how much food participants could eat (amplitudes 14–25%; all P < 0.05). Conclusions: In people who sleep at night, the intrinsic circadian evening peak in appetite may promote larger meals before the fasting period necessitated by sleep. Furthermore, the circadian decline in hunger across the night would theoretically counteract the fasting-induced hunger increase that could otherwise disrupt sleep
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