Compressor seal rub energetics study

The rub mechanics of compressor abradable blade tip seals at simulated engine conditions were investigated. Twelve statistically planned, instrumented rub tests were conducted with titanium blades and Feltmetal fibermetal rubstrips. The tests were conducted with single stationary blades rubbing against seal material bonded to rotating test disks. The instantaneous rub torque, speed, incursion rate and blade temperatures were continuously measured and recorded. Basic rub parameters (incursion rate, rub depth, abradable density, blade thickness and rub velocity) were varied to determine the effects on rub energy and heat split between the blade, rubstrip surface and rub debris. The test data was reduced, energies were determined and statistical analyses were completed to determine the primary and interactive effects. Wear surface morphology, profile measurements and metallographic analysis were used to determine wear, glazing, melting and material transfer. The rub energies for these tests were most significantly affected by the incursion rate while rub velocity and blade thickness were of secondary importance. The ratios of blade wear to seal wear were representative of those experienced in engine operation of these seal system materials

Film boiling of saturated liquid flowing upward through a heated tube : high vapor quality range

Film boiling of saturated liquid flowing upward through a uniformly heated tube has been studied for the case in which pure saturated liquid enters the tube and nearly saturated vapor is discharged. Since a previous study at the M.I.T. Heat Transfer Laboratory covered the case in which only a small percentage of the total mass flow is vaporized, this investigation has been concentrated on film boiling in the region where the vapor quality is greater than 10 percent. Visual studies of film boiling of liquid nitrogen flowing through an electrically conducting pyrex tube have been made to determine the characteristics of the two-phase flow regimes which occur as a result of the film boiling process. It was found that the annular flow regime with liquid in the core and vapor between the liquid and the tube wall, which exists at very low qualities, is broken up at higher qualities to form a dispersed flow of droplets and filaments of liquid carried along in a vapor matrix. A stainless steel test section having a .319 inch ID and heated electrically, has been used to obtain experimental data of wall temperature distributions along the tube and local heat transfer coefficients for different heat fluxes and flow rates with liquid nitrogen as the teit fluid. Heat flux has been varied from 3500 2 to 30000 BTU/hr-ft and mass velocity from 70000 to 210000 lbm/hr-ft2. From these tests, values of wall superheat, (Tw -Ts ), from 200 to w S 975[degree]F and heat transfer coefficients from 11.1 to 65.5 BTU/hr-ft2-[degree] F have been obtained. A theoretical derivation using the Dittus-Boelter equation as an i,7mptote for the heat transfer to pure vapor has demonstrated that a significant amount of vapor superheat is present throughout the film boiling process. The mechanism of the heat transfer process in the dispersed flow region has been described by a two step theory in which 1) all ofthe heat from the wall is transferred to the vapor and 2) heat iSponsored by the National Science Foundatio

Functional responses can unify invasion ecology.

We contend that invasion ecology requires a universal, measurable trait of species and their interactions with resources that predicts key elements of invasibility and ecological impact; here, we advocate that functional responses can help achieve this across taxonomic and trophic groups, among habitats and contexts, and can hence help unify disparate research interests in invasion ecology

Eureka and beyond: mining's impact on African urbanisation

This collection brings separate literatures on mining and urbanisation together at a time when both artisanal and large-scale mining are expanding in many African economies. While much has been written about contestation over land and mineral rights, the impact of mining on settlement, notably its catalytic and fluctuating effects on migration and urban growth, has been largely ignored. African nation-states’ urbanisation trends have shown considerable variation over the past half century. The current surge in ‘new’ mining countries and the slow-down in ‘old’ mining countries are generating some remarkable settlement patterns and welfare outcomes. Presently, the African continent is a laboratory of national mining experiences. This special issue on African mining and urbanisation encompasses a wide cross-section of country case studies: beginning with the historical experiences of mining in Southern Africa (South Africa, Zambia, Zimbabwe), followed by more recent mineralizing trends in comparatively new mineral-producing countries (Tanzania) and an established West African gold producer (Ghana), before turning to the influence of conflict minerals (Angola, the Democratic Republic of Congo and Sierra Leone)

Sex‐skewed trophic impacts in ephemeral wetlands

Predation can have marked impacts on ecosystem structure, function, and stability. However, quantifications of biotic interactions frequently overlook demographic variabilities within populations, which can modulate interaction strengths, such as sex and reproductive status. Compositional population ratios between males and females, alongside reproductive status, are highly variable temporally in ephemeral aquatic systems, and may profoundly mediate levels of ecological impact and thus stability of trophic groups. In the present study, we apply functional responses (resource intake as a function of resource density) to quantify predatory impacts of adult males, non‐gravid females, and gravid females of the calanoid copepod Lovenula raynerae (Diaptomidae), an abundant ephemeral pond specialist, on larvae of the Culex pipiens (Culicidae) mosquito complex. We then develop a novel metric to forecast population‐level impacts across different population sex ratio scenarios. Lovenula raynerae demonstrated prey population destabilising Type II functional responses irrespective of sex and reproductive status, yet variable functional response magnitudes were found. While male and non‐gravid female copepods exhibited similar functional response maximum feeding rates, gravid female feeding rates were substantially higher, implying higher resource demands for progeny development. Ecological impacts of L. raynerae on lower trophic groups increased markedly where their abundances increased but, crucially, also as population sex ratios became more biased towards gravid female copepods. We demonstrate that population‐level impacts do not only correlate tightly with abundance but may be further modulated by reproductive status variations. Thus, the development of sex‐skewed ratios in favour of gravid females during the hydroperiod probably heightens ecological impacts on lower trophic groups. The implications of these results for prey population stability are discussed in the context of freshwater ecosystems

Consistency of impact assessment protocols for non-native species

Standardized tools are needed to identify and prioritize the most harmful non-native species (NNS). A plethora of assessment protocols have been developed to evaluate the current and potential impacts of non-native species, but consistency among them has received limited attention. To estimate the consistency across impact assessment protocols, 89 specialists in biological invasions used 11 protocols to screen 57 NNS (2614 assessments). We tested if the consistency in the impact scoring across assessors, quantified as the coefficient of variation (CV), was dependent on the characteristics of the protocol, the taxonomic group and the expertise of the assessor. Mean CV across assessors was 40%, with a maximum of 223%. CV was lower for protocols with a low number of score levels, which demanded high levels of expertise, and when the assessors had greater expertise on the assessed species. The similarity among protocols with respect to the final scores was higher when the protocols considered the same impact types. We conclude that all protocols led to considerable inconsistency among assessors. In order to improve consistency, we highlight the importance of selecting assessors with high expertise, providing clear guidelines and adequate training but also deriving final decisions collaboratively by consensus

Long non-coding RNAs and cancer: a new frontier of translational research?

Author manuscriptTiling array and novel sequencing technologies have made available the transcription profile of the entire human genome. However, the extent of transcription and the function of genetic elements that occur outside of protein-coding genes, particularly those involved in disease, are still a matter of debate. In this review, we focus on long non-coding RNAs (lncRNAs) that are involved in cancer. We define lncRNAs and present a cancer-oriented list of lncRNAs, list some tools (for example, public databases) that classify lncRNAs or that scan genome spans of interest to find whether known lncRNAs reside there, and describe some of the functions of lncRNAs and the possible genetic mechanisms that underlie lncRNA expression changes in cancer, as well as current and potential future applications of lncRNA research in the treatment of cancer.RS is supported as a fellow of the TALENTS Programme (7th R&D Framework Programme, Specific Programme: PEOPLE—Marie Curie Actions—COFUND). MIA is supported as a PhD fellow of the FCT (Fundação para a Ciência e Tecnologia), Portugal. GAC is supported as a fellow by The University of Texas MD Anderson Cancer Center Research Trust, as a research scholar by The University of Texas System Regents, and by the Chronic Lymphocytic Leukemia Global Research Foundation. Work in GAC’s laboratory is supported in part by the NIH/ NCI (CA135444); a Department of Defense Breast Cancer Idea Award; Developmental Research Awards from the Breast Cancer, Ovarian Cancer, Brain Cancer, Multiple Myeloma and Leukemia Specialized Programs of Research Excellence (SPORE) grants from the National Institutes of Health; a 2009 Seena Magowitz–Pancreatic Cancer Action Network AACR Pilot Grant; the Laura and John Arnold Foundation and the RGK Foundation