3,336 research outputs found
Human supervision and microprocessor control of an optical tracking system
Gunners using small calibre anti-aircraft systems have not been able to track high-speed air targets effectively. Substantial improvement in the accuracy of surface fire against attacking aircraft has been realized through the design of a director-type weapon control system. This system concept frees the gunner to exercise a supervisory/monitoring role while the computer takes over continuous target tracking. This change capitalizes on a key consideration of human factors engineering while increasing system accuracy. The advanced system design, which uses distributed microprocessor control, is discussed at the block diagram level and is contrasted with the previous implementation
A model of the local region of the galaxy
A two-component model of the local interstellar medium was developed, based on the Radio Astronomy Explorer (RAE-1) satellite observations of the low frequency (0.2 - 10 MHz) galactic radio background spectrum. The model shows evidence for a thick spiral arm and a thick electron disk of 600 and 1200 pc slab thicknesses, respectively. The temperature difference between the north galactic pole and anticenter directions supports the concept of a local positive thermal gradient away from the galactic plane. A preliminary discussion of the influence of the Razin effect on the model is also presented
The Bifurcated Age-Metallicity Relation of Milky Way Globular Clusters and its Implications For the Accretion History of the Galaxy
We use recently derived ages for 61 Milky Way (MW) globular clusters (GCs) to
show that their age-metallicity relation (AMR) can be divided into two
distinct, parallel sequences at [Fe/H] \ga -1.8. Approximately one-third of
the clusters form an offset sequence that spans the full range in age (--13 Gyr), but is more metal rich at a given age by dex in
[Fe/H]. All but one of the clusters in the offset sequence show orbital
properties that are consistent with membership in the MW disk. They are not
simply the most metal-rich GCs, which have long been known to have disk-like
kinematics, but they are the most metal-rich clusters at all ages. The slope of
the mass-metallicity relation (MMR) for galaxies implies that the offset in
metallicity of the two branches of the AMR corresponds to a mass decrement of 2
dex, suggesting host galaxy masses of M_{*} \sim 10^{7-8} \msol for GCs that
belong to the more metal-poor AMR. We suggest that the metal-rich branch of the
AMR consists of clusters that formed in-situ in the disk, while the metal-poor
GCs were formed in relatively low-mass (dwarf) galaxies and later accreted by
the MW. The observed AMR of MW disk stars, and of the LMC, SMC and WLM dwarf
galaxies are shown to be consistent with this interpretation, and the relative
distribution of implied progenitor masses for the halo GC clusters is in
excellent agreement with the MW subhalo mass function predicted by simulations.
A notable implication of the bifurcated AMR, is that the identical mean ages
and spread in ages, for the metal rich and metal poor GCs are difficult to
reconcile with an in-situ formation for the latter population.Comment: 16 pages, 9 figures, accepted for publication in MNRA
School Climate Measurement and Analysis
This action research project examined the concept of school climate and measured and analyzed school climate data in a mixed methods study at an independent school in British Columbia. In this study, 341 students participated in a survey which included demographic questions and items from the School Climate Measure (SCM). The quantitative data from the survey measured the school climate in 10 different domains at the school and was used to compare and analyze different subgroups within the student population. Six students were also interviewed to collect qualitative data and analyze the school climate more comprehensively. The data and subsequent analysis were used by the researcher to make recommendations for improvement in the school climate at the school
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Neutralizing the EGF receptor in glioblastoma cells stimulates cell migration by activating uPAR-initiated cell signaling.
In glioblastoma (GBM), the EGF receptor (EGFR) and Src family kinases (SFKs) contribute to an aggressive phenotype. EGFR may be targeted therapeutically; however, resistance to EGFR-targeting drugs such as Erlotinib and Gefitinib develops quickly. In many GBMs, a truncated form of the EGFR (EGFRvIII) is expressed. Although EGFRvIII is constitutively active and promotes cancer progression, its activity is attenuated compared with EGF-ligated wild-type EGFR, suggesting that EGFRvIII may function together with other signaling receptors in cancer cells to induce an aggressive phenotype. In this study, we demonstrate that in EGFRvIII-expressing GBM cells, the urokinase receptor (uPAR) functions as a major activator of SFKs, controlling phosphorylation of downstream targets, such as p130Cas and Tyr-845 in the EGFR in vitro and in vivo. When EGFRvIII expression in GBM cells was neutralized, either genetically or by treating the cells with Gefitinib, paradoxically, the cells demonstrated increased cell migration. The increase in cell migration was explained by a compensatory increase in expression of urokinase-type plasminogen activator, which activates uPAR-dependent cell signaling. GBM cells that were selected for their ability to grow in vivo in the absence of EGFRvIII also demonstrated increased cell migration, due to activation of the uPAR signaling system. The increase in GBM cell migration, induced by genetic or pharmacologic targeting of the EGFR, was blocked by Dasatinib, highlighting the central role of SFKs in uPAR-promoted cell migration. These results suggest that compensatory activation of uPAR-dependent cell signaling, in GBM cells treated with targeted therapeutics, may adversely affect the course of the disease by promoting cell migration, which may be associated with tumor progression
Overexpression of Mcl-1 exacerbates lymphocyte accumulation and autoimmune kidney disease in lpr mice
Cell death by apoptosis has a critical role during embryonic development and in maintaining tissue homeostasis. In mammals,
there are two converging apoptosis pathways: the ‘extrinsic’ pathway, which is triggered by engagement of cell surface ‘death
receptors’ such as Fas/APO-1; and the ‘intrinsic’ pathway, which is triggered by diverse cellular stresses, and is regulated by prosurvival
and pro-apoptotic members of the Bcl-2 family of proteins. Pro-survival Mcl-1, which can block activation of the proapoptotic
proteins, Bax and Bak, appears critical for the survival and maintenance of multiple haemopoietic cell types. To
investigate the impact on haemopoiesis of simultaneously inhibiting both apoptosis pathways, we introduced the vavP-Mcl-1
transgene, which causes overexpression of Mcl-1 protein in all haemopoietic lineages, into Faslpr/lpr mice, which lack functional
Fas and are prone to autoimmunity. The combined mutations had a modest impact on myelopoiesis, primarily an increase in the
macrophage/monocyte population in Mcl-1tg/lpr mice compared with lpr or Mcl-1tg mice. The impact on lymphopoiesis was
striking, with a marked elevation in all major lymphoid subsets, including the non-conventional double-negative (DN) T cells
(TCRβ+
CD4–
CD8–
B220+
) characteristic of Faslpr/lpr mice. Of note, the onset of autoimmunity was markedly accelerated in Mcl-1tg/lpr
mice compared with lpr mice, and this was preceded by an increase in immunoglobulin (Ig)-producing cells and circulating
autoantibodies. This degree of impact was surprising, given the relatively mild phenotype conferred by the vavP-Mcl-1 transgene
by itself: a two- to threefold elevation of peripheral B and T cells, no significant increase in the non-conventional DN T-cell
population and no autoimmune disease. Comparison of the phenotype with that of other susceptible mice suggests that the
development of autoimmune disease in Mcl-1tg/lpr mice may be influenced not only by Ig-producing cells but also other
haemopoietic cell types
Review of Lady Beetles in the \u3ci\u3eCycloneda germainii \u3c/i\u3eSpecies Complex (Coleoptera; Coccinellidae: Coccinellinae: Coccinellini) with Descriptions of New and Unusual Species from Chile and Surrounding Countries
A complex of lady beetle species including Cycloneda germainii (Crotch) is reviewed and seven valid species recognized, including C. germainii, C. eryngii (Mulsant), C. sicardi (Brèthes), C. boliviana (Mulsant), and three new species, C. lacrimosa González & Vandenberg, n. sp., C. disconsolata Vandenberg & González, n. sp., and C. patagonica González & Vandenberg, n. sp. Cycloneda duplaris (Berg) and Arrowella albilacus Brèthes, previously synonymized with C. areata Mulsant, are placed as new synonyms of C. germainii; C. boliviana is removed from synonymy with C. areata and reinstated as a full species; C. sicardi (Brèthes) is recognized as the valid replacement name for C. areata Mulsant. All seven species in the C. germainii species complex are diagnosed, described, and illustrated. Geographical distributions, prey associations (when known), and a key to species are provided. The occurrence of Coccinellini species with reduced (10 or 9) or variable numbers of antennomeres is noted for the first time, as well as loss of gender-specific color pattern polymorphism in some of the species studied
Gamma Group-The Pale Horse: A proposal in response to a commercial air transportation study ort study
A conventional remotely piloted vehicle (RPV) was designed to operate in a fictional 'Aeroworld' as a 30 passenger aircraft. The topics addressed include: economic/cost analysis, aerodynamics, weight and structures, propulsion, stability and control, and performance
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