Simple pressure gauge for uranium hexafluoride

A sensitive detector and pressure gauge for uranium hexafluoride in high‐vacuum systems is described. Negative surface ionization of UF_6 occurs on ribbon filaments operated at temperatures too low for electron emission to be significant. The ion current measured on a cylindrical collector surrounding the filament assembly varies regularly with UF_6 pressure below 10^(−3) Torr. Different filament materials are considered, including rhenium, thoriated tungsten, and platinum. Rhenium is found to be the most satisfactory material for operation of diode emitters as a pressure gauge. Gauge constants (in A Torr^(−1)) are derived from comparing negative surface ionization currents with the response of a capacitance manometer and are shown to be independent of temperature within a reasonable operating range. The effects of exposing the rhenium filament to various gases is considered, and it is shown that brief exposure to acetylene substantially improves the operating characteristics of the gauge

Temperature‐dependent transmission extended electron energy‐loss fine structure of aluminum

Inelastic electron scattering experiments in a transmission electron microscope provide a probe of core electron excitations that have binding energies below 2 keV, and that are localized within submicron diameter sample volumes. Extended electron energy‐loss fine‐structure measurements which show the variation with temperature of the mean squared relative displacement of aluminum yield a localized measurement of the Debye temperature which is in excellent agreement with macroscopic measurements

Applications of flight control system methods to an advanced combat rotorcraft

Advanced flight control system design, analysis, and testing methodologies developed at the Ames Research Center are applied in an analytical and flight test evaluation of the Advanced Digital Optical Control System (ADOCS) demonstrator. The primary objectives are to describe the knowledge gained about the implications of digital flight control system design for rotorcraft, and to illustrate the analysis of the resulting handling-qualities in the context of the proposed new handling-qualities specification for rotorcraft. Topics covered in-depth are digital flight control design and analysis methods, flight testing techniques, ADOCS handling-qualities evaluation results, and correlation of flight test results with analytical models and the proposed handling-qualities specification. The evaluation of the ADOCS demonstrator indicates desirable response characteristics based on equivalent damping and frequency, but undersirably large effective time-delays (exceeding 240 m sec in all axes). Piloted handling-qualities are found to be desirable or adequate for all low, medium, and high pilot gain tasks; but handling-qualities are inadequate for ultra-high gain tasks such as slope and running landings

A general framework for integrating environmental time series into stock assessment models: model description, simulation testing, and example

We present a method to integrate environmental time series into stock assessment models and to test the significance of correlations between population processes and the environmental time series. Parameters that relate the environmental time series to population processes are included in the stock assessment model, and likelihood ratio tests are used to determine if the parameters improve the fit to the data significantly. Two approaches are considered to integrate the environmental relationship. In the environmental model, the population dynamics process (e.g. recruitment) is proportional to the environmental variable, whereas in the environmental model with process error it is proportional to the environmental variable, but the model allows an additional temporal variation (process error) constrained by a log-normal distribution. The methods are tested by using simulation analysis and compared to the traditional method of correlating model estimates with environmental variables outside the estimation procedure. In the traditional method, the estimates of recruitment were provided by a model that allowed the recruitment only to have a temporal variation constrained by a log-normal distribution. We illustrate the methods by applying them to test the statistical significance of the correlation between sea-surface temperature (SST) and recruitment to the snapper (Pagrus auratus) stock in the Hauraki Gulf–Bay of Plenty, New Zealand. Simulation analyses indicated that the integrated approach with additional process error is superior to the traditional method of correlating model estimates with environmental variables outside the estimation procedure. The results suggest that, for the snapper stock, recruitment is positively correlated with SST at the time of spawning

Assets Endowment: The Determinant Factor for Stakeholder Mobilization and Retention for Community Driven Development Projects

Resource and Stakeholder Mobilization are significant in Community Driven Development (CDD). Stakeholder identification, engagement and management are recognized as key project management skills and categorized as resource based as 'soft skills’ requiring both intuition and a strong capacity for analysis. While many studies have focused on the two independently, the relationship between assets and stakeholder participation still remain uncovered with the question being, "to what extent does assets influence Mobilization and vice versa?" This study sought to investigate the relationship between Asset endowment and stakeholder mobilization for CDD initiatives by focusing on the question; “Is there a significant correlation between the asset endowment and individual and community mobilization and willingness to participate in CDD?” A research model comprising three construct variables representing the building blocks of Assets endowment namely; Community Assets building blocks, Individual Mobilization and Community Mobilization was proposed on the basis of the theoretical linkages of prior studies. This was developed into research instruments namely; Community Assets Survey (CAS), Individual Mobilization Survey (IMS), and Community Mobilization Survey (CMS) and correlated as follows; CAS vs CMS, CAS vs IMS, CAS vs ICMS. Where CAS represented components of the larger construct variable – Community assets and its building blocks, while IMS and CMS components of community mobilization. Using the model tool (Jakes et al 2002), the concept was empirically tested by administering questionnaires to 146 gatekeepers randomly sampled from communities in Kisumu West District. A response rate of 72% was achieved well above the 70% rate considered sufficient. The variables were used for stratification of the respondents to determine if they are factors in the correlation between the major constructs. Reliability and validity of measures were tested using the factor analysis and results analyzed to determine relationships. Spearman's rho was employed to determine the relationship between asset endowment and stakeholder mobilization. The results indicate that asset endowment has a direct impact on stakeholder mobilization for CDD. Major determinants assets of community mobilization were revealed to be human capital, motivation, self-efficacy, social assets, physical assets, economic assets and perceived local support. These findings are significant to community development experts, project planners and managers in enabling prediction of participatory trends and advance the development of a theory regarding the CDD. Keywords: Key Words: Community Driven Development; Assets Endowment; Stakeholder Mobilizatio

Genome analysis of a highly virulent serotype 1 strain of streptococcus pneumoniae from West Africa

Streptococcus pneumoniae is a leading cause of pneumonia, meningitis, and bacteremia, estimated to cause 2 million deaths annually. The majority of pneumococcal mortality occurs in developing countries, with serotype 1 a leading cause in these areas. To begin to better understand the larger impact that serotype 1 strains have in developing countries, we characterized virulence and genetic content of PNI0373, a serotype 1 strain from a diseased patient in The Gambia. PNI0373 and another African serotype 1 strain showed high virulence in a mouse intraperitoneal challenge model, with 20% survival at a dose of 1 cfu. The PNI0373 genome sequence was similar in structure to other pneumococci, with the exception of a 100 kb inversion. PNI0373 showed only15 lineage specific CDS when compared to the pan-genome of pneumococcus. However analysis of non-core orthologs of pneumococcal genomes, showed serotype 1 strains to be closely related. Three regions were found to be serotype 1 associated and likely products of horizontal gene transfer. A detailed inventory of known virulence factors showed that some functions associated with colonization were absent, consistent with the observation that carriage of this highly virulent serotype is unusual. The African serotype 1 strains thus appear to be closely related to each other and different from other pneumococci despite similar genetic content