Controlling Sideslip Angle to Reduce the Radar Exposure of a Tactical, Rotary Winged UAV

This work investigates another way of contributing to the radar minimization solution for air vehicles in a threat environment. While much research has been conducted on structural solutions to radar exposure minimization, not much work has been done in the area of using control to continuously assess and present the smallest radar cross section of an air vehicle to oncoming threat radar systems by changing the aircraft\u27s orientation. This work looks at the application of sideslip/beta angle feedback control of an unmanned helicopter to minimize radar cross section exposure in a hostile radar environment. A new way of controlling aircraft trajectory is introduced that incorporates both path and orientation optimization feedback; the aircraft\u27s heading is controlled to orient the vehicle in a way that reduces its radar cross section, while sideslip angle is used to control the aircraft\u27s path. A representative hostile environment is created and results show that a substantial reduction in radar cross section exposure can be achieved with beta feedback control. A linear state space model is derived for the OH-6A helicopter with the JANRAD software program. Eigenstructure assignment is used to shape the response of the helicopter into desired response modes. A Matlab based flight control system is developed around the derived helicopter model with altitude, heading, and beta angle command signals that drive four conventional helicopter control inputs

Mechanisms of HsSAS-6 assembly promoting centriole formation in human cells

SAS-6 proteins are thought to impart the ninefold symmetry of centrioles, but the mechanisms by which their assembly occurs within cells remain elusive. In this paper, we provide evidence that the N-terminal, coiled-coil, and C-terminal domains of HsSAS-6 are each required for procentriole formation in human cells. Moreover, the coiled coil is necessary and sufficient to mediate HsSAS-6 centrosomal targeting. High-resolution imaging reveals that GFP-tagged HsSAS-6 variants localize in a torus around the base of the parental centriole before S phase, perhaps indicative of an initial loading platform. Moreover, fluorescence recovery after photobleaching analysis demonstrates that HsSAS-6 is immobilized progressively at centrosomes during cell cycle progression. Using fluorescence correlation spectroscopy and three-dimensional stochastic optical reconstruction microscopy, we uncover that HsSAS-6 is present in the cytoplasm primarily as a homodimer and that its oligomerization into a ninefold symmetrical ring occurs at centrioles. Together, our findings lead us to propose a mechanism whereby HsSAS-6 homodimers are targeted to centrosomes where the local environment and high concentration of HsSAS-6 promote oligomerization, thus initiating procentriole formation

Not All Nitrogen Is Created Equal: Differential Effects of Nitrate and Ammonium Enrichment in Coastal Wetlands

Excess reactive nitrogen (N) flows from agricultural, suburban, and urban systems to coasts, where it causes eutrophication. Coastal wetlands take up some of this N, thereby ameliorating the impacts on nearshore waters. Although the consequences of N on coastal wetlands have been extensively studied, the effect of the specific form of N is not often considered. Both oxidized N forms (nitrate, NO3−) and reduced forms (ammonium, NH4+) can relieve nutrient limitation and increase primary production. However, unlike NH4+, NO3− can also be used as an electron acceptor for microbial respiration. We present results demonstrating that, in salt marshes, microbes use NO3− to support organic matter decomposition and primary production is less stimulated than when enriched with reduced N. Understanding how different forms of N mediate the balance between primary production and decomposition is essential for managing coastal wetlands as N enrichment and sea level rise continue to assail our coasts

Introducing the Mangrove Microbiome Initiative: Identifying Microbial Research Priorities and Approaches To Better Understand, Protect, and Rehabilitate Mangrove Ecosystems

Mangrove ecosystems provide important ecological benefits and ecosystem services, including carbon storage and coastline stabilization, but they also suffer great anthropogenic pressures. Microorganisms associated with mangrove sediments and the rhizosphere play key roles in this ecosystem and make essential contributions to its productivity and carbon budget. Understanding this nexus and moving from descriptive studies of microbial taxonomy to hypothesis-driven field and lab studies will facilitate a mechanistic understanding of mangrove ecosystem interaction webs and open opportunities for microorganism-mediated approaches to mangrove protection and rehabilitation. Such an effort calls for a multidisciplinary and collaborative approach, involving chemists, ecologists, evolutionary biologists, microbiologists, oceanographers, plant scientists, conservation biologists, and stakeholders, and it requires standardized methods to support reproducible experiments. Here, we outline the Mangrove Microbiome Initiative, which is focused around three urgent priorities and three approaches for advancing mangrove microbiome research

The Effects of Acute High pCO2 Exposure on Growth and Survival of Crassostrea gigas Larvae

Keywords: pCO2; oyster larvae; aquaculture; hatchery; Crassostrea gigas; Pacific oyster; ocean acidification; upwelling; larval development; physiolog

The Violence of the White Man's Burden: the case of the Philippines and the United States

The aim of this work is to present the reader with a description of the history of misrepresentation of Filipinos in war political cartoons and photographs at the time of the Philippine-American War: how these worked together towards the reinforcement of the White Man’s Burden, a mission that justified the conquest and the violence used in the Philippines, and how those misrepresentations can help in making, in particular, both Americans and Filipinos aware of a forgotten and gruesome chapter of their history and in making people reflect on the cultural pluralism of the United States and its values

Steroids regulate α2,6-sialic acid-containing glycoconjugates in murine uterine epithelium at the time of implantation

Sialic acids are involved in many cellular interactions. They can serve as an adhesion ligand or act as an inhibitor to cellular adhesion by charge repulsion or by masking potential ligands. Although sialic acids are implicated in the process of blastocyst implantation, their expression and regulation in uterine epithelium of mice have not been studied. The lectin, Sambucus nigra (SNA) specifically recognizes α2,6-linked sialic acids, which are involved in cell recognition phenomena. It was used to probe frozen uterine sections from mice during days one through six of pregnancy. SNA staining was most intense at the apical surface of uterine epithelial cells on day one of pregnancy, decreased gradually through day four, and was undetectable by day five. The role of the steroid hormones, estrogen and progesterone, in regulating the expression of α2,6-linked sialic acids was studied in uterine sections from mice during the estrous cycle and in ovariectomized mice given hormone replacement using SNA. SNA staining of these sections during the estrous cycle showed that the expression of α2,6-linked sialic acids was stage dependent. Staining was most intense in uterine sections from mice in estrus, and was not detected in sections from mice in diestrus. In ovariectomized mice, staining was most intense in mice injected with estradiol alone, and no staining was evident in mice injected with progesterone alone. These results suggest that the expression of α2,6-linked sialic acids decreases during the time of implantation and that estrogen stimulates and progesterone inhibits its expression. β-Galactoside α2,6-Sialyltransferase (α2,6-ST) is the enzyme that links sialic acids to Galβ1-4GlcNAc termini of N-linked oligosaccharides. In order to investigate the mechanism behind the hormonal regulation of α2,6-linked sialic acids, the expression of α2,6-ST was followed in uterine sections from mice during early pregnancy, during the estrous cycle, and in ovariectomized mice given hormone replacement. In-situ hybridization was performed using digoxigenin labeled RNA probes to characterize α2,6-ST mRNA levels in uterine sections. Expression of α2,6-ST protein was also measured in uterine sections with a polyclonal antibody against α2,6-ST. The expression of α2,6-ST mRNA and protein correlated well with the timing of the appearance of α2,6-linked sialic acids. These results show that the expression of α2,6-linked sialic acids on the surface of mouse uterine epithelium decreases at the time of implantation and furthermore, that this decrease is due to the regulation of α2,6-ST by the steroid hormones. α2,6-linked sialic acids may serve to inhibit cellular adhesion by creating a charge repulsion, or by masking potential binding sites. Removal of this inhibition may permit blastocyst implantation