Robustness of the Thirty Meter Telescope Primary Mirror Control System

The primary mirror control system for the Thirty Meter Telescope (TMT) maintains the alignment of the 492 segments in the presence of both quasi-static (gravity and thermal) and dynamic disturbances due to unsteady wind loads. The latter results in a desired control bandwidth of 1Hz at high spatial frequencies. The achievable bandwidth is limited by robustness to (i) uncertain telescope structural dynamics (control-structure interaction) and (ii) small perturbations in the ill-conditioned influence matrix that relates segment edge sensor response to actuator commands. Both of these effects are considered herein using models of TMT. The former is explored through multivariable sensitivity analysis on a reduced-order Zernike-basis representation of the structural dynamics. The interaction matrix ("A-matrix") uncertainty has been analyzed theoretically elsewhere, and is examined here for realistic amplitude perturbations due to segment and sensor installation errors, and gravity and thermal induced segment motion. The primary influence of A-matrix uncertainty is on the control of "focusmode"; this is the least observable mode, measurable only through the edge-sensor (gap-dependent) sensitivity to the dihedral angle between segments. Accurately estimating focus-mode will require updating the A-matrix as a function of the measured gap. A-matrix uncertainty also results in a higher gain-margin requirement for focus-mode, and hence the A-matrix and CSI robustness need to be understood simultaneously. Based on the robustness analysis, the desired 1 Hz bandwidth is achievable in the presence of uncertainty for all except the lowest spatial-frequency response patterns of the primary mirror

Alginate hydrogel has a negative impact on in vitro collagen 1 deposition by fibroblasts

Hydrogels have been widely investigated as 3D culture substrates because of their reported structural similarity to the extracellular matrix (ECM). Limited ECM deposition, however, occurs within these materials, so the resulting “tissues” bear little resemblance to those found in the body. Here matrix deposition by fibroblasts encapsulated within a calcium alginate (Ca-alg) hydrogel was investigated. Although the cells transcribed mRNA for coll Iα over a period of 3 weeks, very little collagen protein deposition was observed within the gel by histology or immunohistochemistry (IHC). Although molecular diffusion demonstrated charge dependency, this did not prevent the flux of both positively and negative charged amino acids through the gel, suggesting that the absence of ECM could not be attributed to substrate limitation. The flux of protein, however, was charge-dependent as proteins with a net negative charge passed quickly through the Ca-alg into the medium. The minimal collagen deposition within the Ca-alg was attributed to a combination of rapid movement of negatively charged procollagen through the gel and steric hindrance of fibril formation

Ecology of Thysanoptera within Cabbage Fields

The occurrence and species composition of thrips within cabbage fields were studied during 1981 and 1982. Temporal differences in abundance and species composition depended on the spatial relationship of cabbage fields to cereal and forage crops. Sticky traps within cabbage fields recorded peak flights of thrips during maturation and senescence of adjacent wheat or oat fields and cutting of adjacent alfalfa and red clover fields. These data indicate several important findings regarding the ecology of thrips in general and the possible management of Thrips tabaci Lindeman in particular. First, although there are large numbers of thrips in cabbage fields during certain time periods (e.g., maturation or harvesting of crops), most will not be T. tabaci and need not be of concern to cabbage growers. Second, there are significant differences in thrips phenology and species composition in cabbage fields, and these differences appear to be dependent on phenology and management of adjacent field and forage crops. Third, although many other species are present, T. tabaci appears to be present in adequate numbers to infest cabbage at the critical period of head formation. This critical period occurs at different times depending on area, planting date, variety, and weathe

Superconductivity in a spin liquid - a one dimensional example

We study a one-dimensional model of interacting conduction electrons with a two-fold degenerate band away from half filling. The interaction includes an on-site Coulomb repulsion and Hund's rule coupling. We show that such one-dimensional system has a divergent Cooper pair susceptibility at T = 0, provided the Coulomb interaction $U$ between electrons on the same orbital and the modulus of the Hund's exchange integral $|J|$ are larger than the interorbital Coulomb interaction. It is remarkable that the superconductivity can be achieved for {\it any} sign of $J$. The opening of spectral gaps makes this state stable with respect to direct electron hopping between the orbitals. The scaling dimension of the superconducting order parameter is found to be between 1/4 (small $U$) and 1/2 (large $U$).Comment: 11 pages, Latex, no figure

Overwintering of the Onion Thrips, Thrips tabaci (Thysanoptera: Thripidae), in New York

A survey of overwintering thrips and the potential for Thrips tabaci Lindeman to overwinter in upstate New York were investigated during the winters of 1982-83 and 1983-84. Six species—T. tabaci, Anaphothrips obscurus (Müller), Chirothrips manicatus Haliday, Limothrips denticornis (Haliday), Frankltniella tenuicornis (Uzel), and Aptinothrips rufus (Gmelin)—were able to survive as adults in the vegetation sampled, but only Anaphothripini survived as larvae. T. tabaci adults overwinter within winter wheat, alfalfa, and weedy vegetation, and these overwintering females are capable of ovipositing on these plants during the spring. Winter wheat, oats, and alfalfa were the best oviposition and reproduction hosts we examine

Species Composition and Phenology of Thysanoptera within Field Crops Adjacent to Cabbage Fields

Studies were conducted in 1981 and 1982 to determine the general temporal occurrence of thrips in wheat, alfalfa, oat, and red clover fields adjacent to cabbage fields in upstate New York. Shifts in species composition of thrips on these crops were observed through time, and fluctuations in abundance were attributed to changes in habitat structure (e.g., maturation and senescence in wheat and oats, and cropping practices in alfalfa and red clover). All of these crops serve as a reservoir for Thrips tabaci Lindeman, which may move to and infest nearby cabbage plantings. By sampling the thrips populations within the foliage and utilizing sticky traps to monitor aerial populations, we may be able to predict the population buildup within these crops and the subsequent movement of thrips to adjacent crop

Integrating Students into Interdisciplinary Health and Health Disparities Research Teams

Major initiatives by the U.S. Department of Health and Human Services as well as the World Health Organization have produced a large and compelling body of evidence on how to reduce health disparities, which entails having a clear understanding of how social factors shape health and healthcare outcomes. Specifically, there is a need for healthcare professionals to understand social determinants of health (e.g., low socioeconomic status, lack of health insurance, and poor education) and how these lead to disparities in health for people of minority racial and ethnic groups. Little is known about how students are developed as health disparities researchers or how their research experiences impact their views about addressing social determinants of health as a career goal. The purpose of this paper is to describe how health and human sciences students were integrated into three minority HIV prevention and testing projects using the lifelong learning for health professionals (LLHP) principles and activities framework, which entails a focus on: (a) education, (b) community, and (c) organization in the planning, development, implementation, and evaluation of interdisciplinary research

AS-777-14 Resolution on Proposal to Establish the Strawberry Sustainability Research and Education Center

That the Academic Senate endorses the establishment of the Strawberry Sustainability Research Education Center

Surprisingly Little O VI Emission Arises in the Local Bubble

This paper reports the first study of the O VI resonance line emission (1032, 1038 Angstroms) originating in the Local Bubble (or Local Hot Bubble) surrounding the solar neighborhood. In spite of the fact that O VI absorption within the Local Bubble has been observed, no resonance line emission was detected during our 230 ksec Far Ultraviolet Spectroscopic Explorer observation toward a ``shadowing'' filament in the southern Galactic hemisphere. As a result, tight 2 sigma upper limits are set on the intensities in the 1032 and 1038 Angstrom emission lines: 500 and 530 photons cm^{-2} s^{-1} sr^{-1}, respectively. These values place strict constraints on models and simulations. They suggest that the O VI-bearing plasma and the X-ray emissive plasma reside in distinct regions of the Local Bubble and are not mixed in a single plasma, whether in equilibrium with T ~ 10^6 K or highly overionized with T ~ 4 to 6 x 10^4 K. If the line of sight intersects multiple cool clouds within the Local Bubble, then the results also suggest that hot/cool transition zones differ from those in current simulations. With these intensity upper limits, we establish limits on the electron density, thermal pressure, pathlength, and cooling timescale of the O VI-bearing plasma in the Local Bubble. Furthermore, the intensity of O VI resonance line doublet photons originating in the Galactic thick disk and halo is determined (3500 to 4300 photons cm^{-2} s^{-1} sr^{-1}), and the electron density, thermal pressure, pathlength, and cooling timescale of its O VI-bearing plasma are calculated. The pressure in the Galactic halo's O VI-bearing plasma (3100 to 3800 K cm^{-3}) agrees with model predictions for the total pressure in the thick disk/lower halo. We also report the results of searches for other emission lines.Comment: accepted by ApJ, scheduled for May 2003, replacement astro-ph submission corrects typos and grammatical errors in original versio

The Tropical Grassland Society of Australia Incorporated

The Tropical Grassland Society of Australia was formed in 1962 and became incorporated in 1987 and has the following aims: To publicise information of interest to primary producers and scientists To improve the relevance of research and adoption of technology through the flow of ideas between scientists and producers To publicise the findings of Australian pasture research and development to overseas workers, and to draw on their experience for application in Australi