Evaluating Satellite Drag Coefficient Modeling Assumptions in Helium-Rich Space Environments

Thousands of satellites and debris reside in the thermosphere. The ability to model atmospheric drag is critical for precise satellite orbit prediction below 1000 km altitudes. The space domain awareness community relies heavily on thermospheric density data to understand long-term thermospheric variability, construct assimilative, empirical, and semi-empirical global atmospheric models, and validate model performance. One of the challenges in resolving accurate thermospheric density datasets from satellite orbital drag measurements is modeling appropriate physical aerodynamic drag force coefficients. The drag coefficient may change throughout the thermosphere due to model dependencies on composition and altitude. As such, existing drag coefficient model errors and corresponding errors in orbit-derived density datasets and models may be altitude and solar cycle dependent, with greater errors at higher altitudes around 500 km near the oxygen-to-helium transition region. Drag coefficient models are based on assumptions about the energy and momentum exchange between the atmospheric gas and the satellite surface, and the associated interaction parameters are the main source of uncertainty. In this work, inter-satellite observed-to-modeled density comparisons at ~500 km are evaluated to constrain drag coefficient modeling assumptions. Observed densities are derived from accelerometer data for the GRACE satellites and Two-Line Element data for a set of compact satellites, while the TIE-GCM and NRLMSISE-00 atmospheric models are used to obtain modeled densities and composition information. Drag coefficient modeling assumptions are evaluated based on density discrepancies between satellites of different shapes. It is shown that observed density discrepancies can be attributed to drag coefficient modeling assumptions through detailed uncertainty analysis of multiple sources of error, like the TLE-derived densities. This uncertainty analysis leads to the development of a density error model for TLE-derived densities. Density discrepancy results suggest that current drag coefficient assumptions may lead to drag-derived mass densities that are underestimated by up to 35% in helium-rich conditions at and above 500 km. While decreasing the level of energy accommodation in the modeled drag coefficient slightly improves low-drag density comparisons, results indicate that the tangential momentum exchange is a key parameter in drag coefficient modeling. Results suggest that decreasing the tangential momentum to achieve quasi-specular scattering will improve density discrepancies in helium-rich conditions. Through expanded and refined orbital density discrepancy analysis, density consistency results indicate that drag coefficient models with incomplete energy and momentum accommodation produce the most consistent densities near 500 km, while the standard diffuse modeling approach may not be appropriate at these altitudes. Models with tangential momentum accommodation between 0.5 - 0.9 and energy accommodation between 0.83 - 0.96 may be the most appropriate at upper thermospheric altitudes. Modeling drag coefficients with diffuse gas-surface interactions for the GRACE satellites could lead to errors in derived density of ~25% and in-track satellite orbit prediction uncertainty during solar maximum conditions on the order of kilometers. Drag coefficients in orbital conditions are further constrained using laboratory surface scattering experiments. Laboratory scattered flux data are well represented by a scattering kernel model that combines cosine and quasi-specular gas-surface interactions. Laboratory experiments indicate that the portion of particles that scatter with a cosine distribution decreases as incident angle increases. Ultimately, the laboratory-derived gas-surface interaction parameters are incorporated into drag coefficient models used to process orbital density data for GRACE and the compact satellites. Results of this work provide robust evidence that the impact of surface material on the drag coefficient is less than 5%. Additionally, results indicate that laboratory data suggests a larger cosine portion at low incident angles than the orbital data. This may be due to differences between the laboratory and GRACE orbital environments. This finding provides evidence suggesting that scattering dynamics change as altitude increases and there is more helium and less atomic oxygen in the thermosphere.</p

Cybersafety: Educating individuals with aphasia or cognitive-communication disorders

The Internet poses risks, also known as cyberthreats. Everyone is vulnerable to cyberthreats, including individuals with aphasia (IwA) or cognitive-communication disorders (IwCCD). When speech-language pathologists introduce Internet into treatment plans for IwA or IwCCD the ASHA Code of Ethics dictates they “shall fully inform the persons they serve of the nature and possible effects of services rendered and products dispensed”. Yet safe-use products and protocols designed to inform or educate IwA and IwCCD about cybersafety are not reported in the literature. In this project we examine cyberthreats and cybersafety as they affect IwA and IwCCD by1) reviewing literature on cyberthreats; 2) reporting anecdotes from IwA and IwCCD who are Internet users; and 3) proposing strategies to support safer Internet use. We examine information and knowledge needed to create adaptations and scaffolds supporting safer Internet-use for people with language/cognitive-communication disabilities, and propose strategies for teaching cybersafety concepts. Issues drawn from the human-computer interaction (HCI) literature will facilitate discussion of privacy, accessibility, and universal design (Hochheister & Lazar, 2007)

Licuala Palms in Brunei Dusun Ethnobotany

Several species of Licuala occur in the Merimbun area of Tutong district, Brunei Darussalam. One kind of Licuala, called benjiru by the local Dusun population, is often collected for sale as a vegetable. While Licuala is not generally considered an important economic plant, overharvesting in the Merimbun area suggests that conservation measures may be needed to protect it from local extinction. Besides benjiru, other kinds of Licuala recognized by the Dusun are called silad and ukang. The three kinds of Licuala do not have one overall name in the Dusun language, but constitute a covert category at the intermediate ethnobotanical rank. They are also associated with different ecological zones. Benjiru is found in the alluvium and low-lying ground, while silad is generally found in hilly forest land, and ukang in hilly belukar (recent secondary growth)

Activation of angiotensin type 2 receptors prevents diabetic complications in female db/db mice by nitric oxide‐mediated mechanisms

Background and Purpose: The AT2 receptor plays a role in metabolism by opposing the actions triggered by the AT1 receptors. Activation of AT2 receptors has been shown to enhance insulin sensitivity in both normal and insulin resistance animal models. In this study, we investigated the mechanism by which AT2 receptors activation improves metabolism in diabetic mice. Experimental Approach: Female diabetic (db/db) and non-diabetic (db/+) mice were treated for 1 month with the selective AT2 agonist, compound 21 (C21, 0.3 mg·kg−1·day−1, s.c.). To evaluate whether the effects of C21 depend on NO production, a subgroup of mice was treated with C21 plus a sub-pressor dose of the NOS inhibitor l-NAME (0.1 mg·ml−1, drinking water). Key Results: C21-treated db/db mice displayed improved glucose and pyruvate tolerance compared with saline-treated db/db mice. Also, C21-treated db/db mice showed reduced liver weight and decreased hepatic lipid accumulation compared with saline-treated db/db mice. Insulin signalling analysis showed increased phosphorylation of the insulin receptor, Akt and FOXO1 in the livers of C21-treated db/db mice compared with saline-treated counterparts. These findings were associated with increased adiponectin levels in plasma and adipose tissue and reduced adipocyte size in inguinal fat. The beneficial effects of AT2 receptors activation were associated with increased eNOS phosphorylation and higher levels of NO metabolites and were abolished by l-NAME. Conclusion and Implications: Chronic C21 infusion exerts beneficial metabolic effects in female diabetic db/db mice, alleviating type 2 diabetes complications, through a mechanism that involves NO production.Fil: Dominici, Fernando Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Veiras, Luciana Cecilia. Cedars Sinai Medical Center; Estados UnidosFil: Shen, Justin Z.Y.. Cedars Sinai Medical Center; Estados UnidosFil: Bernstein, Ellen A.. Cedars Sinai Medical Center; Estados UnidosFil: Quiroga, Diego Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Steckelings, Ulrike M.. University of Southern Denmark; DinamarcaFil: Bernstein, Kenneth E.. Cedars Sinai Medical Center; Estados UnidosFil: Giani, Jorge F.. Cedars Sinai Medical Center; Estados Unido

More Pace, Less Fillers: A Verbal Strategy for High-level Aphasic Patient

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Renal inflammation induces salt sensitivity in male db/db mice through dysregulation of ENaC

Background Hypertension is considered a major risk factor for the progression of diabetic kidney disease. Type 2 diabetes is associated with increased renal sodium reabsorption and salt-sensitive hypertension. Clinical studies show that men have higher risk than premenopausal women for the development of diabetic kidney disease. However, the renal mechanisms that predispose to salt sensitivity during diabetes and whether sexual dimorphism is associated with these mechanisms remains unknown. Methods Female and male db/db mice exposed to a high-salt diet were used to analyze the progression of diabetic kidney disease and the development of hypertension. Results Male, 34-week-old, db/db mice display hypertension when exposed to a 4-week high-salt treatment, whereas equivalently treated female db/db mice remain normotensive. Salt-sensitive hypertension in male mice was associated with no suppression of the epithelial sodium channel (ENaC) in response to a high-salt diet, despite downregulation of several components of the intrarenal renin-angiotensin system. Male db/db mice show higher levels of proinflammatory cytokines and more immune-cell infiltration in the kidney than do female db/db mice. Blocking inflammation, with either mycophenolate mofetil or by reducing IL-6 levels with a neutralizing anti-IL-6 antibody, prevented the development of salt sensitivity in male db/db mice. Conclusions The inflammatory response observed in male, but not in female, db/db mice induces salt-sensitive hypertension by impairing ENaC downregulation in response to high salt. These data provide a mechanistic explanation for the sexual dimorphism associated with the development of diabetic kidney disease and salt sensitivity.Fil: Veiras, Luciana Cecilia. Cedars Sinai Medical Center; Estados UnidosFil: Shen, Justin Z. Y.. Cedars Sinai Medical Center; Estados UnidosFil: Bernstein, Ellen A.. Cedars Sinai Medical Center; Estados UnidosFil: Regis, Giovanna C.. Cedars Sinai Medical Center; Estados UnidosFil: Cao, DuoYao. Cedars Sinai Medical Center; Estados UnidosFil: Okwan Duodu, Derick. Cedars Sinai Medical Center; Estados UnidosFil: Khan, Zakir. Cedars Sinai Medical Center; Estados UnidosFil: Gibb, David R.. Cedars Sinai Medical Center; Estados UnidosFil: Dominici, Fernando Pablo. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Bernstein, Kenneth E.. Cedars Sinai Medical Center; Estados UnidosFil: Giani, Jorge Fernando. Cedars Sinai Medical Center; Estados Unido

Pragmatic and Syntactic Improvement in Fluent and Nonfluent Aphasia

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