Simulation of Cold Flow in a Truncated Ideal Nozzle with Film Cooling

Flow transients during rocket start-up and shut-down can lead to significant side loads on rocket nozzles. The capability to estimate these side loads computationally can streamline the nozzle design process. Towards this goal, the flow in a truncated ideal contour (TIC) nozzle has been simulated using RANS and URANS for a range of nozzle pressure ratios (NPRs) aimed to match a series of cold flow experiments performed at the NASA MSFC Nozzle Test Facility. These simulations were performed with varying turbulence model choices and for four approximations of the supersonic film injection geometry, each of which was created with a different simplification of the test article geometry. The results show that although a reasonable match to experiment can be obtained with varying levels of geometric fidelity, the modeling choices made do not fully represent the physics of flow separation in a TIC nozzle with film cooling

An Official American Thoracic Society Workshop Report: Evaluation and Management of Asthma in the Elderly

Asthma in the elderly (>65 yr old) is common and associated with higher morbidity and mortality than asthma in younger patients. The poor outcomes in this group are due, in part, to underdiagnosis and undertreatment. There are a variety of factors related to aging itself that affect the presentation of asthma in the elderly and influence diagnosis and management. Structural changes in the aging lung superimposed on structural changes due to asthma itself can worsen the disease and physiologic function. Changes in the aging immune system influence the cellular composition and function in asthmatic airways. These processes and differences from younger individuals with asthma are not well understood. Phenotypes of asthma in the elderly have not been clearly delineated, but it is likely that age of onset and overlap with chronic obstructive pulmonary disease impact disease characteristics. Physiologic tests and biomarkers used to diagnose and follow asthma in the elderly are generally similar to testing in younger individuals; however, whether they should be modified in aging has not been established. Confounding influences, such as comorbidities (increasing the risk of polypharmacy), impaired cognition and motor skills, psychosocial effects of aging, and age-related adverse effects of medications, impact both diagnosis and treatment of asthma in the elderly. Future efforts to understand asthma in the elderly must include geriatric-specific methodology to diagnose, characterize, monitor, and treat their disease

Mycobacterium tuberculosis ClpP Proteases Are Co-transcribed but Exhibit Different Substrate Specificities

PMCID: PMC3613350This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Form, content, and the formulaic essay: a case study in student writing and teaching methods at California State University San Marcos and local North County high schools

Digitized as part of the "Retrospective Thesis and Dissertation Digitization Project." No abstract is available

Methods in the measurement of biomechanical response to modifications in footwear design

Orthopaedic problems can be caused or accentuated by both normal and abnormal gait characteristics. Traditionally, footwear modifications and orthotic interventions have been limited to internal and external wedges and other assorted orthotics. This thesis will discuss various methods to measure biomechanical responses of human subjects in response to changes in footwear design. Chapter 1 provides an overview of what is currently known regarding interventions in relation to providing medial compartment knee osteoarthritis relief as well as limiting excessive rear-foot motion. Chapter 2 discusses a method for measuring the center of pressure in multiple steps using an insole pressure measurement system and evaluating the effect that varying midsole stiffness has on the center of pressure. Chapter 3 presents a dynamic segmental model for knee adduction moment measurements and how a full lateral stiffened shoe and five other prototype shoes with varying midsole stiffness change that moment in healthy subjects. Chapter 4 presents a method for measuring rear-foot motion and evaluates a new footwear technology designed to reduce excessive rear-foot motion. Chapter 5 is a summation of the thesis and recommendations for future studies. The information in this thesis could be helpful in providing strategies for changing location and stiffness values of footwear midsoles to elicit positive biomechanical responses in human subjects during gait.Thesis (M.S.)--Michigan State University. Engineering Mechanics, 2010Includes bibliographical reference

High export of dissolved silica from the Greenland Ice Sheet

Silica is an essential element for marine life and plays a key role in the biogeochemistry of the ocean. Glacial activity stimulates rock weathering, generating dissolved silica that is exported to coastal areas along with meltwater. The magnitude of the dissolved silica export from large glacial areas such as the Greenland Ice Sheet is presently poorly quantified and not accounted for in global budgets. Here we present data from two fjord systems adjacent to the Greenland Ice Sheet which reveal a large export of dissolved silica by glacial meltwater relative to other macronutrients. Upscaled to the entire Greenland Ice Sheet, the export of dissolved silica equals 22 ± 10 Gmol Si yr−1. When the silicate-rich meltwater mixes with upwelled deep water, either inside or outside Greenland's fjords, primary production takes place at increased silicate to nitrate ratios. This likely stimulates the growth of diatoms relative to other phytoplankton groups

Restricting digital sites of dissent: commercial social media and free expression

The widespread use of commercial social media platforms by protesters and activists has enhanced protest mobilisation and reporting but it has placed social media providers in the intermediary role as facilitators of dissent and has thereby created new challenges. Companies like Google and Facebook are increasingly restricting content that is published on or distributed through their platforms; they have been subject to obstruction by governments; and their services have been at the core of large-scale data collection and surveillance. This article analyses and categorises forms of infrastructure-based restrictions on free expression and dissent. It shows how private intermediaries have been incorporated into state-led content policies; how they set their own standards for legitimate online communication and intervene accordingly; and how state-based actions and commercial self-regulation intersect in the specific area of online surveillance. Based on a broad review of cases, it situates the role of social media in the wider trend of the privatisation of communications policy and the complex interplay between state-based regulation and commercial rule-making

Trefoil factor 2 rapidly induces interleukin 33 to promote type 2 immunity during allergic asthma and hookworm infection

The molecular mechanisms that drive mucosal T helper type 2 (T[subscript H]2) responses against parasitic helminths and allergens remain unclear. In this study, we demonstrate in mice that TFF2 (trefoil factor 2), an epithelial cell–derived repair molecule, is needed for the control of lung injury caused by the hookworm parasite Nippostrongylus brasiliensis and for type 2 immunity after infection. TFF2 is also necessary for the rapid production of IL-33, a T[subscript H]2-promoting cytokine, by lung epithelia, alveolar macrophages, and inflammatory dendritic cells in infected mice. TFF2 also increases the severity of allergic lung disease caused by house dust mite antigens or IL-13. Moreover, TFF2 messenger RNA expression is significantly increased in nasal mucosal brushings during asthma exacerbations in children. These experiments extend the biological functions of TFF2 from tissue repair to the initiation and maintenance of mucosal T[subscript H]2 responses

Commuting in crosswinds and foraging in fast winds: the foraging ecology of a flying fish specialist

Understanding how the behaviour of volant species is influenced by winds is important at a time when global airflow patterns and intensities are shifting. We investigated how wind speeds and directions influenced the flight and feeding events of a flap-gliding seabird during central place trips searching for aerial prey like Exocoetidae flying fish. We deployed GPS accelerometers on red-footed boobies (Sula sula rubripes) in the Chagos Archipelago (Indian Ocean) for 45 foraging trips. By comparing foraging commutes to simulated alternative routes, we demonstrate that birds preferentially selected tailwinds and crosswinds, with stronger selection during the outbound compared with the inbound leg. By selecting favourable winds, birds reached higher ground speeds without having to increase flapping flight. Selecting favourable wind conditions may be an adaptation to tropical pelagic habitats and ephemeral prey. Hidden Markov models, used to characterize behavioural states, revealed that birds were more likely to forage during windier conditions, perhaps aided by increased accessibility of flying fish—which a small sub-sample of bird-borne video cameras revealed were largely caught on the wing. We therefore show how wind has divergent consequences for foraging journeys and feeding events, with implications for understanding the ecological effects of climate change-driven wind alterations