Systems engineering analysis of aplanatic Wolter type I x-ray telescopes

It is well known that normal-incidence aplanatic telescope designs perform better at small field angles than ones corrected only for spherical aberration. This is why most large astronomical telescopes fabricated in the past fifty years have been of the Ritchey-Chretien (aplanatic) design rather than of the classical Cassegrain design. For the relatively new field of x-ray astronomy, the Welter type I grazing incidence design has been extensively utilized. It consists of a paraboloidal primary mirror coaxial with a confocal hyperboloidal secondary mirror. Aplanatic versions of the Welter type I grazing incidence x-ray telescope have been discussed in detail in the literature, and are widely touted as being superior designs. However, scattering effects from residual optical fabrication errors and other practical engineering error sources prevent these grazing-incidence telescopes from being near diffraction-limited (even on axis) at the very short operational x-ray wavelengths. A systems engineering analysis of these error sources indicates that they will dominate coma at the small field angles, and of course astigmatism, field curvature, and higher-order aberrations dominate coma at the large field angles. Hence, there is little improvement in performance when going to an aplanatic design. Comparison of performance predictions for the classical versus aplanatic Welter type I x-ray telescope are presented for the special case of the Solar X-Ray Imager (SXI) baseline design. SXI is expected to become a standard subsystem aboard the next generation of NOAA/GOES weather satellites

The Rise of the Social in Entrepreneurial Activities in National and International Contexts: A Clarification of Terms in the Development of a New Conceptual Framework

In examining the ‘social’ in entrepreneurial activities in national and international contexts our focus is on social innovation and business enterprise. Attention is given to what we understand by ‘social’ in entrepreneurial behaviours, innovation and change and the importance of social capital and social networks to understanding the dynamics that drive social innovation within the enterprise. Our social focus takes us on a conceptual journey in examining the meaning and import of social innovation, social capital, social networks and social enterprise. The rise in the import and media attention to social business within the international arena and the growing call for a social-orientation among business practitioners from small to medium enterprises to larger multi-national enterprises has promoted dialogue and debate about social processes that have also brought in its wake a certain amount of confusion and obfuscation. We set out to clarify this growing range of socially-oriented terms and identify the relationships between these concepts with the aim of extending knowledge in this emergent field. A key objective is to build a robust conceptual framework that informs our understanding of these complex relationships and provides a platform for further debate and research

The Rise of the Social in Entrepreneurial Activities in National and International Contexts: A Clarification of Terms in the Development of a New Conceptual Framework

In examining the ‘social’ in entrepreneurial activities in national and international contexts our focus is on social innovation and business enterprise. Attention is given to what we understand by ‘social’ in entrepreneurial behaviours, innovation and change and the importance of social capital and social networks to understanding the dynamics that drive social innovation within the enterprise. Our social focus takes us on a conceptual journey in examining the meaning and import of social innovation, social capital, social networks and social enterprise. The rise in the import and media attention to social business within the international arena and the growing call for a social-orientation among business practitioners from small to medium enterprises to larger multi-national enterprises has promoted dialogue and debate about social processes that have also brought in its wake a certain amount of confusion and obfuscation. We set out to clarify this growing range of socially-oriented terms and identify the relationships between these concepts with the aim of extending knowledge in this emergent field. A key objective is to build a robust conceptual framework that informs our understanding of these complex relationships and provides a platform for further debate and research

The dynamics of innovation and social capital in social enterprises: a relational sense-making perspective

We develop a relational sense-making framework in order to understand the ways in which knowledge and information, when transferred across social networks, enable or inhibit the innovation process and its sustainability within social enterprises. Our model comprises four main elements: (i) Social capital, (ii) the Innovation, (iii) the Process, and (iv) Adoption and ongoing support (SIPA). Collective understanding through sense-making and sense-giving is fundamental to the successful management and sustainability of innovation projects. The social capital which emerges and develops may incorporate formal and/or informal group(s) linked by particular interests, common goals and/or shared agenda(s). Broadly speaking, the innovation may be directed towards either a problem or an opportunity for the collective. The ‘black box’ process through which different views and interests are presented, interpreted and collective sense-making occurs in the further development and uptake of innovation is by its nature: multifaceted, complex and non-linear. The temporal fragility of certain innovations necessitates ongoing support and acceptance in order to achieve longer-term sustainability. The iterative relations between these elements of social capital, innovation, process and adoption occur within a social, political and economic context in which sense-making and sense-giving of individuals and groups often compete. A key objective of our research is, therefore, to tease out the extent to which and the ways in which social relationships and networks, innovation intentions and technology development are influenced by social capital dynamics within organizations, social enterprises in particular

Fine root dynamics and trace gas fluxes in two lowland tropical forest soils

Fine root dynamics have the potential to contribute significantly to ecosystem-scale biogeochemical cycling, including the production and emission of greenhouse gases. This is particularly true in tropical forests which are often characterized as having large fine root biomass and rapid rates of root production and decomposition. We examined patterns in fine root dynamics on two soil types in a lowland moist Amazonian forest, and determined the effect of root decay on rates of C and N trace gas fluxes. Root production averaged 229 ( 35) and 153 ( 27) gm 2 yr 1 for years 1 and 2 of the study, respectively, and did not vary significantly with soil texture. Root decay was sensitive to soil texture with faster rates in the clay soil (k5 0.96 year 1) than in the sandy loam soil (k5 0.61 year 1),leading to greater standing stocks of dead roots in the sandy loam. Rates of nitrous oxide (N2O) emissions were significantly greater in the clay soil (13 1ngNcm 2 h 1) than in the sandy loam (1.4 0.2 ngNcm 2 h 1). Root mortality and decay following trenching doubled rates of N2O emissions in the clay and tripled them in sandy loam over a 1-year period. Trenching also increased nitric oxide fluxes, which were greater in the sandy loam than in the clay. We used trenching (clay only) and a mass balance approach to estimate the root contribution to soil respiration. In clay soil root respiration was 264–380 gCm 2 yr 1, accounting for 24% to 35% of the total soil CO2 efflux. Estimates were similar using both approaches. In sandy loam, root respiration rates were slightly higher and more variable (521 206 gCm2 yr 1) and contributed 35% of the total soil respiration. Our results show that soil heterotrophs strongly dominate soil respiration in this forest, regardless of soil texture. Our results also suggest that fine root mortality and decomposition associated with disturbance and land-use change can contribute significantly to increased rates of nitrogen trace gas emissions

The Charlotte (TM) intra-vehicular robot

NASA has identified telerobotics and telescience as essential technologies to reduce the crew extra-vehicular activity (EVA) and intra-vehicular activity (IVA) workloads. Under this project, we are developing and flight testing a novel IVA robot to relieve the crew of tedious and routine tasks. Through ground telerobotic control of this robot, we will enable ground researchers to routinely interact with experiments in space. Our approach is to develop an IVA robot system incrementally by employing a series of flight tests with increasing complexity. This approach has the advantages of providing an early IVA capability that can assist the crew, demonstrate capabilities that ground researchers can be confident of in planning for future experiments, and allow incremental refinement of system capabilities and insertion of new technology. In parallel with this approach to flight testing, we seek to establish ground test beds, in which the requirements of payload experimenters can be further investigated. In 1993 we reviewed manifested SpaceHab experiments and defined IVA robot requirements to assist in their operation. We also examined previous IVA robot designs and assessed them against flight requirements. We rejected previous design concepts on the basis of threat to crew safety, operability, and maintainability. Based on this insight, we developed an entirely new concept for IVA robotics, the CHARLOTTE robot system. Ground based testing of a prototype version of the system has already proven its ability to perform most common tasks demanded of the crew, including operation of switches, buttons, knobs, dials, and performing video surveys of experiments and switch panels

Characterization of Samples for Optimization of Infrared Stray Light Coatings

NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) is a converted 747SP that houses a 2.5 m telescope that observes the sky through an opening in the side of the aircraft. Because it flies at altitudes up to 45,000 feet, SOFIA gets 99.99% transmission in the infrared. Multiple science instruments mount one at a time on the telescope to interpret infrared and visible light from target sources. Ball Infrared Black (BIRB) currently coats everything that the optics sees inside the telescope assembly (TA) cavity in order to eliminate noise from the glow of background sky, aircraft exhaust, and other sources. A reflectometer and emissometer were used to measure and characterize the coatings in terms of their ability to absorb stray light. These measurements were then compared to the BIRB currently used. Though Aeroglaze Z306 showed lower better (lower) reflectance values than Desothane, neither of these coatings showed better reflectance values than the current BIRB. These characterizations help us to determine an improved recipe for TA cavity coating

System and Method for Null-Lens Wavefront Sensing

A method of measuring aberrations in a null-lens including assembly and alignment aberrations. The null-lens may be used for measuring aberrations in an aspheric optic with the null-lens. Light propagates from the aspheric optic location through the null-lens, while sweeping a detector through the null-lens focal plane. Image data being is collected at locations about said focal plane. Light is simulated propagating to the collection locations for each collected image. Null-lens aberrations may extracted, e.g., applying image-based wavefront-sensing to collected images and simulation results. The null-lens aberrations improve accuracy in measuring aspheric optic aberrations

Use of short-tandem repeat (STR) fingerprinting to validate sample origins in hepatitis C virus molecular epidemiology studies

Sequence analysis is used to define the molecular epidemiology and evolution of the hepatitis C virus. Whilst most studies have shown that individual patients harbour viruses that are derived from a limited number of highly related strains, some recent reports have shown that some patients can be co-infected with very distinct variants whose frequency can fluctuate greatly. Whilst co-infection with highly divergent strains is possible, an alternative explanation is that such data represent contamination or sample mix-up. In this study, we have shown that DNA fingerprinting techniques can accurately assess sample provenance and differentiate between samples that are truly exhibiting mixed infection from those that harbour distinct virus populations due to sample mix-up. We have argued that this approach should be adopted routinely in virus sequence analyses to validate sample provenance

Single nucleotide polymorphisms (SNPs) distinguish Indian-origin and Chinese-origin rhesus macaques (Macaca mulatta)

BACKGROUND: Rhesus macaques serve a critical role in the study of human biomedical research. While both Indian and Chinese rhesus macaques are commonly used, genetic differences between these two subspecies affect aspects of their behavior and physiology, including response to simian immunodeficiency virus (SIV) infection. Single nucleotide polymorphisms (SNPs) can play an important role in both establishing ancestry and in identifying genes involved in complex diseases. We sequenced the 3' end of rhesus macaque genes in an effort to identify gene-based SNPs that could distinguish between Indian and Chinese rhesus macaques and aid in association analysis. RESULTS: We surveyed the 3' end of 94 genes in 20 rhesus macaque animals. The study included 10 animals each of Indian and Chinese ancestry. We identified a total of 661 SNPs, 457 of which appeared exclusively in one or the other population. Seventy-nine additional animals were genotyped at 44 of the population-exclusive SNPs. Of those, 38 SNPs were confirmed as being population-specific. CONCLUSION: This study demonstrates that the 3' end of genes is rich in sequence polymorphisms and is suitable for the efficient discovery of gene-linked SNPs. In addition, the results show that the genomic sequences of Indian and Chinese rhesus macaque are remarkably divergent, and include numerous population-specific SNPs. These ancestral SNPs could be used for the rapid scanning of rhesus macaques, both to establish animal ancestry and to identify gene alleles that may contribute to the phenotypic differences observed in these populations