Spitzer 70-micron Confusion Level

Spitzer 70μm confusion measurements are presented based on ultra-deep MIPS-70μm observations of GOODS Hubble Deep Field North (HDFN). The instrument noise for the MIPS-70μm band integrates down with nearly t^(−0.5) for the low background HDF-N field. The estimated confusion level is σ_c = 0.30 ± 0.15mJy for a limiting flux density of 1.5mJy (q = 5)

Stable scalable control of soliton propagation in broadband nonlinear optical waveguides

We develop a method for achieving scalable transmission stabilization and switching of $N$ colliding soliton sequences in optical waveguides with broadband delayed Raman response and narrowband nonlinear gain-loss. We show that dynamics of soliton amplitudes in $N$-sequence transmission is described by a generalized $N$-dimensional predator-prey model. Stability and bifurcation analysis for the predator-prey model are used to obtain simple conditions on the physical parameters for robust transmission stabilization as well as on-off and off-on switching of $M$ out of $N$ soliton sequences. Numerical simulations for single-waveguide transmission with a system of $N$ coupled nonlinear Schr\"odinger equations with $2 \le N \le 4$ show excellent agreement with the predator-prey model's predictions and stable propagation over significantly larger distances compared with other broadband nonlinear single-waveguide systems. Moreover, stable on-off and off-on switching of multiple soliton sequences and stable multiple transmission switching events are demonstrated by the simulations. We discuss the reasons for the robustness and scalability of transmission stabilization and switching in waveguides with broadband delayed Raman response and narrowband nonlinear gain-loss, and explain their advantages compared with other broadband nonlinear waveguides.Comment: 37 pages, 7 figures, Eur. Phys. J. D (accepted

Independent Orbiter Assessment (IOA): Assessment of the manned maneuvering unit

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the Manned Maneuvering Unit (MMU) hardware, generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contain within the NASA FMEA/CIL documentation. The IOA results were then compared to the proposed Martin Marietta FMEA/CIL Post 51-L updates. A discussion of each discrepancy from the comparison is provided through additional analysis as required. These discrepancies were flagged as issues, and recommendations were made based on the FMEA data available at the time. The results of this comparison for the Orbiter MMU hardware are documented. The IOA product for the MMU analysis consisted of 204 failure mode worksheets that resulted in 95 potential critical items being identified. Comparison was made to the NASA baseline which consisted of 179 FMEAs and 110 CIL items. This comparison produced agreement on all 121 FMEAs which caused differences in 92 CIL items

Partner orbits and action differences on compact factors of the hyperbolic plane. Part I: Sieber-Richter pairs

Physicists have argued that periodic orbit bunching leads to universal spectral fluctuations for chaotic quantum systems. To establish a more detailed mathematical understanding of this fact, it is first necessary to look more closely at the classical side of the problem and determine orbit pairs consisting of orbits which have similar actions. In this paper we specialize to the geodesic flow on compact factors of the hyperbolic plane as a classical chaotic system. We prove the existence of a periodic partner orbit for a given periodic orbit which has a small-angle self-crossing in configuration space which is a `2-encounter'; such configurations are called `Sieber-Richter pairs' in the physics literature. Furthermore, we derive an estimate for the action difference of the partners. In the second part of this paper [13], an inductive argument is provided to deal with higher-order encounters.Comment: to appear on Nonlinearit

Another Record of Foliage Roosting in the Little Brown Bat, Myotis lucifugus, in Canada

Another record of foliage-roosting behaviour in little brown bats (Myotis lucifugus) is reported. This is only the second such observation ever recorded for this species and the first for Atlantic Canada

Improving the tensile strength of carbon nanotube spun yarns using a modified spinning process

A modified process for the dry spinning of carbon nanotube (CNT) yarn is reported. The approach gives an improved structure of CNT bundles in the web drawn from the CNT forest and in the yarn produced from the twisted web leading to improved mechanical properties of the yarn. The process enables many different mechanical and physical treatments to be applied to the individual stages of the pure CNT spinning system, and may allow potential for the development of complex spinning processes such as polymer–CNT-based composite yarns. The tensile strength and yarn/web structure of yarn spun using this approach have been investigated and evaluated using standard tensile testing methods along with scanning electron microscopy. The experimental results show that the tensile properties were significantly improved. The effect of heat treatments and other yarn constructions on the tensile properties are also reported

Developing skilled labour : an analysis of the major factors which enable and hinder employee training in construction companies in Vietnam

This thesis makes a contribution to the literature on training practices and attitudes, within the context of the Vietnamese construction industry. Drawing on the international scholarship in the area of training practices and attitudes, the thesis tests a series of hypotheses about the nature of training in Vietnam. The conceptual framework for the thesis utilised the established methods and insights from a range of studies on the relationship between training provision, company size, company ownership, and attitudes of managers. Within this scholarship, the nature of those relationships is still unclear and under-theorised in particular contexts. Specifically, the international research suggest particular patterns of training provision, namely that larger companies will be more likely to provide training than smaller companies and that larger companies will be more likely to provide off-the-job training. It was unclear, however, whether these findings, and the key theoretical premises that underpin them, had application to the Vietnamese construction industry. This thesis, therefore, makes a valuable contribution to this area of research in attempting to deal with these issues. In the context of the discussions and debates within the literature, the specific contribution of the thesis spans a number of dimensions. First, it has generated, presented, and analysed a new data set about the general characteristics of training practices in the Vietnamese construction industry. Based on a survey of 510 construction companies in Ho Chi Minh City, this is the largest database to analyse training within Vietnam, and the largest database to document the construction industry. Second, it has applied statistical analysis and methods consistent with examinations of training practices evident in the international scholarship, and thereby extended the study of the construction industry in Vietnam beyond anecdotal information and simple descriptive statistics. In this sense, the use of such a large database to focus on one industry is particularly valuable. Third, it has interpreted these results and findings both in the context of the international literature, but also noted the relevant features of the local context in which these results are observed, i.e., an economy that is in transition from high level of central control to one that is developing a market orientation. The specific findings of the thesis are interesting and extend across the range of issues emphasised in the international literature on training. The thesis affirms the role of training in developing skilled labour in the Vietnamese construction industry and indicates that training fulfills this function of developing human capital for different sized companies and companies with different ownership structures. The thesis demonstrates that company size has some correlation with training provision in the industry, although there is some divergence with the international literature in this regard. In the context of a transitioning economy and increased levels of foreign investment, the thesis makes a key contribution in understanding the pattern of training provision by company ownership type and examining in particular the impact of foreign capital in shaping training provision in Vietnam. Indeed, the results demonstrate that ownership type exercises a distinctive effect on training provision with a higher evidence of training in foreign invested companies than in other company types. In considering the attitudes of managers within the construction industry, the results show that managers of construction companies have positive attitudes towards training and the utility of training for a series of strategic purposes. These attitudes were evident despite the absence of a sophisticated training infrastructure. Company size was not a significant differentiating factor in the attitudes of managers. Company ownership was a greater predictor of the strength of positive attitudes by managers with the managers of foreign-invested companies demonstrating more positive attitudes towards training than managers in other company types. The findings of the thesis facilitate a more nuanced understanding of key premises in the research scholarship about training. The fact that some of the patterns commonly observed in the international literature are not entrenched in the Vietnamese construction industry identifies the benefits of industry-based research. However, these findings might also reflect the transition of the Vietnamese economy more generally from a centralised, controlled economy to a market economy, noting that this transition is unlikely to be uniform and that companies will move to adopt human resource development practices at different rates. One final issue identified and discussed by the thesis is that despite the affirmations of training demonstrated by manager attitudes, the Vietnamese construction industry in Ho Chi Minh City confronts persistent skill shortages. This dissonance contributes to the development of recommendations to policy makers, and to the industry leaders more generally, as to the potential to facilitate and support successful training policies and human resource functions for the range of construction companies in Vietnam

An Agent Based Model for the Simulation of Transport Demand and Land Use

Agent based modelling has emerged as a promising tool to provide planners with insights on social behaviour and the interdependencies characterising urban system, particularly with respect to transport and infrastructure planning. This paper presents an agent based model for the simulation of land use and transport demand of an urban area of Sydney, Australia. Each individual in the model has a travel diary which comprises a sequence of trips the person makes in a representative day as well as trip attributes such as travel mode, trip purpose, and departure time. Individuals are associated with each other by their household relationship, which helps define the interdependencies of their travel diary and constrains their mode choice. This allows the model to not only realistically reproduce how the current population uses existing transport infrastructure but more importantly provide comprehensive insight into future transport demands. The router of the traffic micro-simulator TRANSIMS is incorporated in the model to inform the actual travel time of each trip and changes of traffic density on the road network. Simulation results show very good agreement with survey data in terms of the distribution of trips done by transport modes and by trip purposes, as well as the traffic density along the main road in the study area

Space Biosciences Division

In the Space Biosciences Division at NASA's Ames Research Center, we perform the biological research and technology development necessary to tackle the challenges of living in the extreme environments of space and to enable NASA's long-term human exploration mission. This brochure provides a broad overview for our research and development capabilities, several case study examples, and finally real-world applications and collaborative partnerships