3,124 research outputs found

    Collectivity and Agency in Remembering and Reconciliation

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    This paper examines how British war veterans fold together war time and post war experiences in practices of remembering and reconciliation. We examine these practices as networks of association between British ex-servicemen (veterans) and the people, places and circumstances associated with their experiences as prisoners in Japan during WW2. We focus on the experience of World War 2 British ex-servicemen (veterans) who were prisoners of war in Far East. During their period of captivity they worked to build Thai-Burma Railway before transfer to a copper mine in Japan. Some 50 years later they participated in a "reconciliation trip" to Japan. We discuss two related issues. First, how and in what ways are the post war lives and war time experiences of these veterans gathered up in the emergent collectivity of such practices? In other words in what ways do these practices emerge and sustain themselves as a process of collection and dispersion of circulating reference in networks of association between people places and things. Second, we examine how accounts of redemption (claims to the consequences of experience as being other than you would expect them to be) create the basis for emergent forms of agency and settlement in expanding networks of remembering and reconciliation

    Empowerment or repression? Opening up questions of identification and surveillance in Brazil through a case of 'identity fraud'

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    A real but typical case of identity fraud is used to open up the complex web of identification systems in Brazil. It is argued that identification has two poles related to the nature of citizenship—repression and inclusion—and that reactions from citizens to new identification schemes can be attributed to how they view the purpose of the cards in these terms. In Brazil, a sense of inclusion and citizenship based on a fear of anonymity and exclusion predominates leading to widespread support amongst even critics of state activities. However, this may be undermined by the lack of state preparation for an information society, particularly the absence of meaningful data protection laws

    Evaluation of Giga-bit Ethernet Instrumentation for SalSA Electronics Readout (GEISER)

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    An instrumentation prototype for acquiring high-speed transient data from an array of high bandwidth antennas is presented. Multi-kilometer cable runs complicate acquisition of such large bandwidth radio signals from an extensive antenna array. Solutions using analog fiber optic links are being explored, though are very expensive. We propose an inexpensive solution that allows for individual operation of each antenna element, operating at potentially high local self-trigger rates. Digitized data packets are transmitted to the surface via commercially available Giga-bit Ethernet hardware. Events are then reconstructed on a computer farm by sorting the received packets using standard networking gear, eliminating the need for custom, very high-speed trigger hardware. Such a system is completely scalable and leverages the hugh capital investment made by the telecommunications industry. Test results from a demonstration prototype are presented.Comment: 8 pages, to be submitted to NIM

    Prototyping Operational Autonomy for Space Traffic Management

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    Current state of the art in Space Traffic Management (STM) relies on a handful of providers for surveillance and collision prediction, and manual coordination between operators. Neither is scalable to support the expected 10x increase in spacecraft population in less than 10 years, nor does it support automated manuever planning. We present a software prototype of an STM architecture based on open Application Programming Interfaces (APIs), drawing on previous work by NASA to develop an architecture for low-altitude Unmanned Aerial System Traffic Management. The STM architecture is designed to provide structure to the interactions between spacecraft operators, various regulatory bodies, and service suppliers, while maintaining flexibility of these interactions and the ability for new market participants to enter easily. Autonomy is an indispensable part of the proposed architecture in enabling efficient data sharing, coordination between STM participants and safe flight operations. Examples of autonomy within STM include syncing multiple non-authoritative catalogs of resident space objects, or determining which spacecraft maneuvers when preventing impending conjunctions between multiple spacecraft. The STM prototype is based on modern micro-service architecture adhering to OpenAPI standards and deployed in industry standard Docker containers, facilitating easy communication between different participants or services. The system architecture is designed to facilitate adding and replacing services with minimal disruption. We have implemented some example participant services (e.g. a space situational awareness provider/SSA, a conjunction assessment supplier/CAS, an automated maneuver advisor/AMA) within the prototype. Different services, with creative algorithms folded into then, can fulfil similar functional roles within the STM architecture by flexibly connecting to it using pre-defined APIs and data models, thereby lowering the barrier to entry of new players in the STM marketplace. We demonstrate the STM prototype on a multiple conjunction scenario with multiple maneuverable spacecraft, where an example CAS and AMA can recommend optimal maneuvers to the spacecraft operators, based on a predefined reward function. Such tools can intelligently search the space of potential collision avoidance maneuvers with varying parameters like lead time and propellant usage, optimize a customized reward function, and be implemented as a scheduling service within the STM architecture. The case study shows an example of autonomous maneuver planning is possible using the API-based framework. As satellite populations and predicted conjunctions increase, an STM architecture can facilitate seamless information exchange related to collision prediction and mitigation among various service applications on different platforms and servers. The availability of such an STM network also opens up new research topics on satellite maneuver planning, scheduling and negotiation across disjoint entities

    Redshift Dependent Lag-Luminosity Relation in 565 BASTE Gamma Ray Bursts

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    We compared redshifts zYz_Y from Yonetoku relation and zlagz_{lag} from the lag-luminosity relation for 565 BASTE GRBs and were surprised to find that the correlation is very low. Assuming that the luminosity is a function of both zYz_Y and the intrinsic spectral lag τlag\tau_{lag}, we found a new redshift dependent lag-luminosity relation as L=7.5×1050erg/s(1+z)2.53τlag0.282L=7.5\times 10^{50}{\rm erg/s}(1+z)^{2.53}\tau_{lag}^{-0.282} with the correlation coefficient of 0.77 and the chance probability of 7.9×10757.9\times 10^{-75}. To check the validity of this method, we examined the other luminosity indicator, Amati relation, using zYz_Y and the observed fluence and found the correlation coefficient of 0.92 and the chance probability of 5.2×101065.2\times 10^{-106}. Although the spectral lag is computed from two channels of BATSE, our new lag-luminosity relation suggests that a possible lag-luminosity relation in the \swift era should also depend on redshift

    A spontaneous tRNA suppressor of a mutation in the Chlamydomonas reinhardtii nuclear MCD1 gene required for stability of the chloroplast petD mRNA

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    Numerous nuclear gene products are required for the correct expression of organellar genes. One such gene in the green alga Chlamydomonas reinhardtii is MCD1, whose product is required for stability of the chloroplast-encoded petD mRNA. In mcd1 mutants, which are non-photosynthetic, petD mRNA is degraded by a 5′–3′ exonuclease activity, resulting in a failure to synthesize its product, subunit IV of the cytochrome b (6)/f complex. Here, we report the sequence of the wild-type MCD1 gene, which encodes a large and novel putative protein. Analysis of three mutant alleles showed that two harbored large deletions, but that one allele, mcd1-2, had a single base change resulting in a nonsense codon near the N-terminus. This same mutant allele can be suppressed by a second-site mutation in the nuclear MCD2 gene, whereas mcd2-1 cannot suppress the deletion in mcd1-1 (Esposito,D. Higgs,D.C. Drager,R.G. Stern, D.B. and Girard-Bascou,J. (2001) Curr. Genet., 39, 40–48). We report the cloning of mcd2-1, and show that the mutation lies in a tRNA(Ser)(CGA), which has been modified to translate the nonsense codon in mcd1-2. We discuss how the existence of a large tRNA(Ser) gene family may permit this suppression without pleiotropic consequences

    Space Traffic Management with a NASA UAS Traffic Management (UTM) Inspired Architecture

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    Space is becoming increasingly congested as the number of on-orbit satellites and debris objects continues to grow. Space traffic management (STM) is critical for ensuring that the expanding orbital population operates safely and efficiently, avoiding collisions and radio-frequency interference while still facilitating widespread space operations. Recent events such as the FCC approval of SpaceXs ~12,000 satellite constellation, the signing of Space Policy Directive 3 (which moves Space Situational Awareness responsibilities away from the Department of Defense and to a civil agency), and the growth in rideshare and small launch vehicles illustrate the rapidly changing nature of this domain. This paper will describe the concept of operations (ConOps) for a civilian STM research initiative, which has been developed from previous NASA work to enable safe operation of small unmanned aircraft systems. The STM ConOps proposes an architecture to enable efficient data sharing and coordination between participants to facilitate safe spaceflight operations. It is designed to utilize and promote the emerging field of commercial STM services, as a complement to existing government-provided STM services. The concept envisions a phased evolution that would gradually integrate additional capabilities, proposing a first phase architecture and tentative plans for a broader system. Work towards developing an STM research and prototyping platform is also discussed

    Development and Testing of a Refractory Millimeter-Wave Absorbent Heat Exchanger

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    Central to the Millimeter-Wave Thermal Launch System (MTLS) is the millimeter-wave absorbent heat exchanger. We have developed metallic and ceramic variants, with the key challenge being the millimeter-wave absorbent coatings for each. The ceramic heat exchanger came to fruition first, demonstrating for the first time 1800 K peak surface temperatures under illumination by a 110 GHz Gaussian beam. Absorption efficiencies of up to 80 are calculated for mullite heat exchanger tubes and up to 50 are calculated for alumina tubes. These are compared with estimates based on stratified layer and finite element analyses. The problem of how to connect the 1800 K end of the ceramic tubes to a graphite outlet manifold and nozzle is solved by press fitting, or by threading the ends of the ceramic tubes and screwing them into place. The problem of how to connect the ceramic tubes to a metallic or nylon inlet pipe is solved by using soft compliant PTFE and PVC tubes that accommodate thermal deformations of the ceramic tubes during startup and operation. We show the resulting heat exchangers in static tests using argon and helium as propellants
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