The Effects of Model Scaling on Sediment Transport in Brownout

The phenomenon of “brownout” is characterized by a large cloud of sediment or dust that is formed around a rotorcraft when it takes off or lands in arid or dusty environments. To further understand the physics of brownout, a laboratory-scale rotor hovering in water was tested over a ground plane covered with a mobile sediment bed. The sensitivity of the dual-phase flow environment to changes in the values of the similarity parameters that potentially govern the fluid dynamics of the rotor flow and the transport of sediment was explored. First, dye flow visualization was performed to study the general evolution of the rotor flow and its interaction with the ground plane. Then, dual-phase flow visualization was used to expose the details of the processes that mobilize and uplift loose particles from the sediment bed. It was shown using the flow visualization that the trailed vortices from the rotor blades were a primary contributor to the mobilization and suspension of sediment. Particle image velocimetry (PIV) was also used to obtain quantitative measurements of the flow velocities found in the rotor wake and near the ground plane. It is then discussed as to why the steady flow assumptions used in the usual definitions of the classical similarity parameters governing sediment transport are not as applicable to the dual-phase flows produced by a rotor operating over a mobile sediment bed. A Buckingham-π analysis was performed to determine a set of new similarity parameters that potentially better reflect the dual-phase flow characteristics relevant to sediment mobilization and suspension by a rotor wake, including the characteristics of the tip vortices. Sixteen new similarity parameters were initially determined, five of which selected as having particular relevance. Specifically, these new similarity parameters were: 1. The mobile inertia ratio; 2. The stationary inertia ratio, 3. The terminal-swirl velocity ratio; 4. The threshold-swirl velocity ratio; 5. The terminal/threshold-swirl velocity ratio. The values of these similarity parameters were determined using the PIV measurements, and were all found to correlate to the quantity of sediment mobilized and uplifted by the rotor. The terminal/threshold-swirl velocity ratio is proposed as the potentially most important similarity parameter for further characterizing the brownout phenomenon

Bereavement and marriage are associated with antibody response to influenza vaccination in the elderly

Stressful life events exposure including bereavement, an event commonly experienced by elderly people, social support, marital status and satisfaction were examined in relation to antibody response to the annual trivalent influenza vaccination in an elderly community sample (N = 184). Antibody response was assessed at baseline, and at one and 12 months following vaccination. Taking into account baseline antibody titer, overall life events exposure and social support were not associated with response to any of the influenza strains. However, bereavement in the year prior to vaccination was negatively associated with the one-month response to the A/Panama and B/Shangdong strains. Being married and having higher marital satisfaction was also associated with higher peak responses to the A/Panama influenza strain at one month. The positive association between marital satisfaction and A/Panama response was particularly evident in the younger half of the married sample. These associations largely withstood adjustment for potential confounders. Thus, in the elderly, peak antibody response was associated with bereavement and marriage, and not the more general factors, life events and social support, related to antibody response in student samples. This suggests the importance of taking a life course approach to examining relationships between psychosocial factors and immunity, and that interventions to modify the impact of these factors should address those most salient for each age group

South Africa's regional political economy: A critical analysis of reform strategy in the 1980s.

African Studies Seminar series. Paper presented October, 1985Since the late 1970s the apartheid state has faced a sustained and deepening crisis of legitimation.(1) This crisis has been exacerbated by the attempt, and failure, to implement the post- Soweto 'Total Strategy' reforms - reforms which, in the case of the black people of South Africa, left the territorial and political basis of grand apartheid intact. Since the end of the short-lived boom of 1979-82, the crisis of political legitimacy has been amplified by the slide into economic depression, and the scope for concessionary economic reforms has been drastically curtailed. For some time, the state has been caught up with the immediate threat of escalating opposition in the townships, the symptoms of the deepening economic crisis and spreading international hostility to apartheid. But while this has been happening, elements within the ruling groups, both inside and outside the state, have for some time been attempting to map out a longer-term strategic offensive aimed at defusing political conflict and re-structuring the economy. Faced with a shrinking material basis for concessionary economic reform and growing mobilisation behind the demand for the extension of political rights, the country's ruling groups have begun the search for political solutions to the crisis. The schemes now being formulated take as their starting point the ultimate inevitability of political incorporation of black people into a single national state in South Africa. They aim to meet this in ways that ensure that real power remains in the hands of the ruling classes. The move towards political reforms for black people has gone beyond the stage of discussion and planning in certain areas of policy. Already an important pillar of the emerging strategy has gained expression in local government measures passed in 1985. (2) However much of what is planned has so far only appeared in general policy statements. It is also evident that important facets of the strategy are still in the stage of formulation or are deliberately being held back for the moment. The fluidity of political conditions in South Africa is such that state strategy is the subject matter of open debate and contestation, and is unusually susceptible to official reconsideration and reformulation. Nevertheless we believe it is possible to identify the major contours of an emerging strategy which has been pursued with increasing determination by reformers within the commanding heights of the state since late in 1984. This offensive is significant in that it goes well beyond the policy package associated with the Wiehahn and Riekert Commission reports, the Koornhof Bills, the new constitution, and the confederation of ethnic states - it goes beyond the 'Total Strategy' formulated by PW Botha in the late 1970s. (3) In contrast to these policies, it is based on an abandonment of the political and territorial premises of apartheid, though not necessarily of race or ethnicity, and envisages the eventual reincorporation of the bantustans into a single national South African state. The manner in which this will occur is by no means clear or decided. However, this process of political re-integration of the bantustans is intended ultimately to result in the reorganisation of the territorial basis of South Africa's economic and political system. Central to the reform strategy is the conception that the present provinces and bantustans will be superceded by metropolitan and regionally-based administrative structures through a process of merging, absorption and crosscutting of present geographical boundaries. It is this geographic outcome of the intended reform strategy that has led us to describe the complex of evolving measures as the state's regional strategy. The aim of this article is to describe, anticipate and critically analyse the outlines of the emerging regional strategy. Its three major components are new controls on labour movement and settlement, regional development policies (notably industrial decentralisation), and local and second tier government reforms and corresponding constitutional changes. We examine each of these three components and their interconnections. A central issue taken up in the paper is the debate over the possible construction of a federal system in South Africa. We examine major alternative conceptions of the basis of federalism - geographic and ethnic - and show how they correspond to or contradict other plans to divide South Africa into metropolitan and wider planning and administrative regions. The paper ends with an assessment and critical analysis of the regional strategy

U.S. Fresh Fruit and Vegetable Marketing: Emerging Trade Practices, Trends, and Issues

In the past year, trade practices between fresh produce shippers and food retailers gained national attention. Shippers are concerned that recent retail consolidation has led to market power and the growing incidence of fees and services. Retailers argue that these new trade practices reflect their costs of doing business and the demands of consumers. Trade practices include fees such as volume discounts and slotting fees, as well as services like automatic inventory replenishment, special packaging, and requirements for third-party food safety certification. Trade practices also refer to the overall structure of a transaction-for example, long-term relationships or contracts versus daily sales with no continuing commitment. This study compares trade practices in 1999 with those prevalent in 1994, placing them in the broader context of the evolving shipper/retailer relationship. Most shippers and retailers reported that the incidence and magnitude of fees and services associated with transactions has increased over the last 5 years. Fees paid to retailers are usually around 1-2 percent of sales for most of the commodities we examined, but 1-8 percent for bagged salads. Information on the incidence and magnitude of these new practices is scarce. To augment information that is publicly available, we interviewed a limited number of shippers, retailers, and wholesalers about their firms and trade practices. We received a high level of voluntary cooperation from the interviewed firms.produce, fresh fruit and vegetables, fresh-cut produce, trade practices, fees and services, slotting fees, retail consolidation, produce shipper consolidation, Crop Production/Industries, Marketing,

Tumor site immune markers associated with risk for subsequent basal cell carcinomas.

BackgroundBasal cell carcinoma (BCC) tumors are the most common skin cancer and are highly immunogenic.ObjectiveThe goal of this study was to assess how immune-cell related gene expression in an initial BCC tumor biopsy was related to the appearance of subsequent BCC tumors.Materials and methodsLevels of mRNA for CD3ε (a T-cell receptor marker), CD25 (the alpha chain of the interleukin (IL)-2 receptor expressed on activated T-cells and B-cells), CD68 (a marker for monocytes/macrophages), the cell surface glycoprotein intercellular adhesion molecule-1 (ICAM-1), the cytokine interferon-γ (IFN-γ) and the anti-inflammatory cytokine IL-10 were measured in BCC tumor biopsies from 138 patients using real-time PCR.ResultsThe median follow-up was 26.6 months, and 61% of subjects were free of new BCCs two years post-initial biopsy. Patients with low CD3ε CD25, CD68, and ICAM-1 mRNA levels had significantly shorter times before new tumors were detected (p = 0.03, p = 0.02, p = 0.003, and p = 0.08, respectively). Furthermore, older age diminished the association of mRNA levels with the appearance of subsequent tumors.ConclusionsOur results show that levels of CD3ε, CD25, CD68, and ICAM-1 mRNA in BCC biopsies may predict risk for new BCC tumors

Design to Delivery of Additively Manufactured Propulsion Systems for the SWARM-EX Mission

Recent progress in miniaturized spacecraft propulsion technology has allowed for the development of complex, multi-vehicle missions which enable the cost-effective realization of science goals that would previously have been prohibitively expensive. The upcoming NSF-funded Space Weather Atmospheric Reconfigurable Multiscale EXperiment (SWARM-EX) mission leverages these swarm techniques to demonstrate novel autonomous formation flying capabilities while characterizing the spatial and temporal variability of ion-neutral interactions in the Equatorial Ionization Anomaly and Equatorial Thermospheric Anomaly. SWARM-EX will fly a trio of 3U CubeSats in a variety of relative orbits with along-track separations ranging from 3 km to 1300 km. To achieve the required orbital variability, the mission uses a novel hybrid approach of differential drag and an onboard cold gas propulsion system. Mission requirements necessitate a propulsion system that provides each spacecraft with 15 m/s of ∆V and a maximum thrust greater than 5 mN in a volume of roughly 0.7U (7 cm x 10 cm x 10 cm). Unlike many other CubeSat-scale cold gas propulsion systems which are used to provide attitude control and perform reaction wheel desaturation burns, the primary objective of the SWARM-EX propulsion system (SEPS) is to provide ∆V during maneuvers. The Georgia Institute of Technology Space Systems Design Laboratory (SSDL) is conducting the design, assembly, and testing of three identical SEPS. By leveraging additive manufacturing technology, the propellant tanks, nozzle, and tubing are combined into a single structure that efficiently utilizes the allocated volume. The propulsion system uses two-phase R-236fa refrigerant as a propellant, which allows for the storage of the majority of propellant mass as a liquid to maximize volumetric efficiency. The final design allows for 17 m/s of total ∆V per spacecraft and a measured maximum thrust of approximately 35 mN for short pulse lengths at room temperature. Each individual propulsion system has a volume under 0.5U (489 cm3), making them among the smallest formation-flying CubeSat-scale propulsion systems developed thus far. Owing to their two-phase propellant storage and single nozzle, the SEPS have a high impulse density (total impulse provided per unit of system volume) of 176 N-s/L. Additionally, process improvements to mitigate known failure modes such as propellant leaks and foreign object debris are implemented. This paper describes the entire design-to-delivery life cycle of the SWARM-EX propulsion units, including pertinent mission requirements, propulsion system design methodologies, assembly, and testing. Major lessons learned for future small satellite propulsive endeavors are also detailed

Site-specific recombinatorics : in situ cellular barcoding with the Cre Lox system

Background: Cellular barcoding is a recently developed biotechnology tool that enables the familial identification of progeny of individual cells in vivo. In immunology, it has been used to track the burst-sizes of multiple distinct responding T cells over several adaptive immune responses. In the study of hematopoiesis, it revealed fate heterogeneity amongst phenotypically identical multipotent cells. Most existing approaches rely on ex vivo viral transduction of cells with barcodes followed by adoptive transfer into an animal, which works well for some systems, but precludes barcoding cells in their native environment such as those inside solid tissues. Results: With a view to overcoming this limitation, we propose a new design for a genetic barcoding construct based on the Cre Lox system that induces randomly created stable barcodes in cells in situ by exploiting inherent sequence distance constraints during site-specific recombination. We identify the cassette whose provably maximal code diversity is several orders of magnitude higher than what is attainable with previously considered Cre Lox barcoding approaches, exceeding the number of lymphocytes or hematopoietic progenitor cells in mice. Conclusions: Its high diversity and in situ applicability, make the proposed Cre Lox based tagging system suitable for whole tissue or even whole animal barcoding. Moreover, it can be built using established technology