Vestibular heading discrimination and sensitivity to linear acceleration in head and world coordinates

Effective navigation and locomotion depend critically on an observer\u27s ability to judge direction of linear self-motion, i.e., heading. The vestibular cue to heading is the direction of inertial acceleration that accompanies transient linear movements. This cue is transduced by the otolith organs. The otoliths also respond to gravitational acceleration, so vestibular heading discrimination could depend on (1) the direction of movement in head coordinates (i.e., relative to the otoliths), (2) the direction of movement in world coordinates (i.e., relative to gravity), or (3) body orientation (i.e., the direction of gravity relative to the otoliths). To quantify these effects, we measured vestibular and visual discrimination of heading along azimuth and elevation dimensions with observers oriented both upright and side-down relative to gravity. We compared vestibular heading thresholds with corresponding measurements of sensitivity to linear motion along lateral and vertical axes of the head (coarse direction discrimination and amplitude discrimination). Neither heading nor coarse direction thresholds depended on movement direction in world coordinates, demonstrating that the nervous system compensates for gravity. Instead, they depended similarly on movement direction in head coordinates (better performance in the horizontal plane) and on body orientation (better performance in the upright orientation). Heading thresholds were correlated with, but significantly larger than, predictions based on sensitivity in the coarse discrimination task. Simulations of a neuron/anti-neuron pair with idealized cosine-tuning properties show that heading thresholds larger than those predicted from coarse direction discrimination could be accounted for by an amplitude-response nonlinearity in the neural representation of inertial motion

IMPACT OF MEAT IMPORTS ON LEAST-COST UNITED STATES BEEF PRODUCTION

International Relations/Trade,

Finite Element Modeling of Thermal Cycling Induced Microcracking in Carbon/Epoxy Triaxial Braided Composites

The microcrack distribution and mass change in PR520/T700s and 3502/T700s carbon/epoxy braided composites exposed to thermal cycling was evaluated experimentally. Acoustic emission was utilized to record the crack initiation and propagation under cyclic thermal loading between -55 C and 120 C. Transverse microcrack morphology was investigated using X-ray Computed Tomography. Different performance of two kinds of composites was discovered and analyzed. Based on the observations of microcrack formation, a meso-mechanical finite element model was developed to obtain the resultant mechanical properties. The simulation results exhibited a decrease in strength and stiffness with increasing crack density. Strength and stiffness reduction versus crack densities in different orientations were compared. The changes of global mechanical behavior in both axial and transverse loading conditions were studied. Keywords: Thermal cycles; Microcrack; Finite Element Model; Braided Composit

Measurements of pernitric acid at the South Pole during ISCAT 2000

The first measurements of pernitric acid at the South Pole were performed during the second Investigation of Sulfur Chemistry in the Antarctic Troposphere (ISCAT 2000). Observed HO2NO2 concentrations averaged 25 pptv. Simple steady-state calculations constrained by measurements show that the lifetime of pernitric acid was largely controlled by dry deposition, with thermal decomposition becoming increasingly important at warmer temperatures. We determined that the pernitric acid equilibrium constant is less uncertain than indicated in the literature. One consequence of pernitric acid deposition to the snow surface is that it is an important sink for both NOx and HOx. Another is that the photochemistry of HO2NO2 in the Antarctic snowpack may be a NOx source in addition to nitrate photolysis. This might be one of the important differences in snow photochemistry between the South Pole and warmer polar sites

Section 409A Deferred Compensation Issues for Domestic and International Businesses

Internal Revenue Code (the “Code”) §409A creates special rules for nonqualified deferred compensation plans, including discounted stock options, severance arrangement, and even some expense reimbursement arrangements.  The primary themes of Section 409A are restrictions that it places upon operation of the deferred compensation plan.  In general, it places restrictions on the elections necessary to defer compensation, restrictions on the funding of the plan, and restrictions on the distributions from the plan.   If the requirements of Code §409A and its regulations are not met, all amounts that had been excluded from gross income under the deferred compensation plan are currently included in gross income.  Additionally. there is interest due from the original deferral that is one percentage point higher than the regular rate of interest for underpayments, plus a crushing additional 20 percent penalty.[1] Accordingly it is of paramount importance to understand how these rules apply, and how to avoid the severe penalties. [1] Code §409A(a)

Pattern and Potential Causes of White-faced Ibis, Plegadis chihi, Establishment in the Northern Prairie and Parkland Region of North America

The Northern Prairie and Parkland Waterbird Conservation Plan calls for renewed attention to determining the current status of waterbird populations, their distributions, and conservation needs. It highlights the need for baseline information on the White-faced Ibis (Plegadis chihi). In response, we examined the historical and current distribution of the ibis in North Dakota and summarized first sightings and nest records for the provinces and other states composing the northern prairie and parkland region. The establishment of breeding colonies of White-faced Ibis here may be due to climate and precipitation patterns, invasion and spread of Narrowleaf Cattail (Typha angustifolia), changes in agricultural practices, habitat loss and range expansion in the southern and western portions of the species’ range, and increases in ibis populations in the Intermountain West. We placed special emphasis on North Dakota, a state for which there is scant published information concerning the current status of this species. In recent decades, the ibis has become a regular breeding-season resident in North Dakota and in other areas of the northern prairie and parkland region. From 1882 to 2002, there were 145 reports of one or more Whitefaced Ibis in North Dakota, including 93 reports during the breeding season (15 May to 31 August), 49 during the nonbreeding season (1 September to 14 May), and three for which the season of occurrence was not reported. Prior to the 1960s, there were only three records of the species in North Dakota. Observations of White-faced Ibises in North Dakota increased dramatically between the 1960s and the early 21st century, and the species has been observed nearly annually since 1971. The first White-faced Ibis nesting activity in the state was recorded in 1978, and to date, there have been 21 known records of nesting activity in the state. The species nested in large (>300 ha) semipermanent or permanent wetlands within mixed-species colonies ranging in areal extent from small (0.1 ha) to fairly large (27 ha), and colonies were located in patches of emergent vegetation dominated by cattails (Typha) and bulrushes (Scirpus). We classify the White-faced Ibis as a fairly common migrant and a locally uncommon breeder east of the Missouri River and a casual migrant west of the Missouri River

Surface Gravities for 228 M, L, and T Dwarfs in the NIRSPEC Brown Dwarf Spectroscopic Survey

We combine 131 new medium-resolution (R~2000) J-band spectra of M, L, and T dwarfs from the Keck NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS) with 97 previously published BDSS spectra to study surface-gravity-sensitive indices for 228 low-mass stars and brown dwarfs spanning spectral types M5-T9. Specifically, we use an established set of spectral indices to determine surface gravity classifications for all M6-L7 objects in our sample by measuring equivalent widths (EW) of the K I lines at 1.1692, 1.1778, 1.2529 um, and the 1.2 um FeHJ absorption index. Our results are consistent with previous surface gravity measurements, showing a distinct double peak - at ~L5 and T5 - in K I EW as a function of spectral type. We analyze K I EWs of 73 objects of known ages and find a linear trend between log(Age) and EW. From this relationship, we assign age ranges to the very low gravity, intermediate gravity, and field gravity designations for spectral types M6-L0. Interestingly, the ages probed by these designations remain broad, change with spectral type, and depend on the gravity sensitive index used. Gravity designations are useful indicators of the possibility of youth, but current datasets cannot be used to provide a precise age estimate.Comment: 33 pages, 13 figures, ApJ in pres