International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / While the transition to IP internetworking in space-based applications has a tremendous upside, there are significant challenges of communications efficiency and compatibility to overcome. This paper describes a very high efficiency, low-risk, incremental architecture for migrating to IP internetworking based on the use of proxies. In addition to impressive gains in communications bandwidth, the architecture provides encapsulation of potentially volatile decisions such as particular vendors and network technologies. The specific benchmarking architecture is a NetAcquire Corporation COTS telemetry system that includes built-in TCP-Tranquility (also known as SCPS-TP) and Reed-Solomon Forward Error Correction capabilities as well as a specialized proxy-capable network stack. Depending on network conditions, we will show that the effective bandwidth for satellite transmissions can be increased as much as a factor of one hundred with no external changes to existing internetworking equipment.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The CCSDS SCPS FP file transfer performance is compared with that of TCP/IP FTP in a simulated satellite channel environment. The comparison is made as a function of channel bit error rate and forward/return data rates. From these simulations, we see that both protocols work well when the channel error rate is low (below 10^-6) and the SCPS FP generally performs better when the error rate is higher. We also noticed a strong effect on the SCPS FP throughput as a function of forward transmission rate when running unbalanced channel tests.

abstract: The cyanobacterium Synechocystis sp. PCC 6803 performs oxygenic photosynthesis. Light energy conversion in photosynthesis takes place in photosystem I (PSI) and photosystem II (PSII) that contain chlorophyll, which absorbs light energy that is utilized as a driving force for photosynthesis. However, excess light energy may lead to formation of reactive oxygen species that cause damage to photosynthetic complexes, which subsequently need repair or replacement. To gain insight in the degradation/biogenesis dynamics of the photosystems, the lifetimes of photosynthetic proteins and chlorophyll were determined by a combined stable-isotope (15N) and mass spectrometry method. The lifetimes of PSII and PSI proteins ranged from 1-33 and 30-75 hours, respectively. Interestingly, chlorophyll had longer lifetimes than the chlorophyll-binding proteins in these photosystems. Therefore, photosynthetic proteins turn over and are replaced independently from each other, and chlorophyll is recycled from the damaged chlorophyll-binding proteins. In Synechocystis, there are five small Cab-like proteins (SCPs: ScpA-E) that share chlorophyll a/b-binding motifs with LHC proteins in plants. SCPs appear to transiently bind chlorophyll and to regulate chlorophyll biosynthesis. In this study, the association of ScpB, ScpC, and ScpD with damaged and repaired PSII was demonstrated. Moreover, in a mutant lacking SCPs, most PSII protein lifetimes were unaffected but the lifetime of chlorophyll was decreased, and one of the nascent PSII complexes was missing. SCPs appear to bind PSII chlorophyll while PSII is repaired, and SCPs stabilize nascent PSII complexes. Furthermore, aminolevulinic acid biosynthesis, an early step of chlorophyll biosynthesis, was impaired in the absence of SCPs, so that the amount of chlorophyll in the cells was reduced. Finally, a deletion mutation was introduced into the sll1906 gene, encoding a member of the putative bacteriochlorophyll delivery (BCD) protein family. The Sll1906 sequence contains possible chlorophyll-binding sites, and its homolog in purple bacteria functions in proper assembly of light-harvesting complexes. However, the sll1906 deletion did not affect chlorophyll degradation/biosynthesis and photosystem assembly. Other (parallel) pathways may exist that may fully compensate for the lack of Sll1906. This study has highlighted the dynamics of photosynthetic complexes in their biogenesis and turnover and the coordination between synthesis of chlorophyll and photosynthetic proteins. / Dissertation/Thesis / Ph.D. Plant Biology 2011

The spider mite predator Phytoseiulus persimilis Athias-Henriot and the thrips predator Amblyseius cucumeris (Oudemans) are both commercially mass-reared for use as biological control agents for greenhouse pests. The ability to stockpile these mites in cold storage would greatly facilitate economical mass-production and distribution. In addition, these two species provide an opportunity for comparative studies of cold hardiness because P. persimilis originated in subtropical Mediterranean type climates and is thought to be incapable of entering diapause whereas A. cucumeris is widespread in temperate zones where adult females enter a reproductive diapause for overwintering. Temperature/mortality curves confirmed that both species are freezing intolerant in the traditional sense that supercooling points (SCPs), at which freezing of body fluids occurs, represent absolute lower lethal temperatures. Both species were capable of moderate supercooling, into the range of-20°C to -30°C, and both showed a trend of increasing SCP temperatures during development from egg to adult that suggested an inverse relationship between supercooling capacity and body size within species. The only exception to this trend was adult female A. cucumeris, which may be significant because this is the only life stage that is capable of diapause or survival of temperate winters. On the other hand, diapause induction and low temperature acclimation had little or no effect on supercooling capacity, and survival of nonacclimated mites at subzero temperatures above their SCPs was limited to very short periods of exposure, suggesting that the SCP represents a physical property of the mites rather than an adaptation for survival of exposure to subzero temperatures. Cold-storage survival of both species was optimum at 7.5°C, was greatly enhanced when a source of moisture was provided, and was enhanced even further when food was provided even though the mites were held at temperatures below their theoretical temperature threshold for development. Under these conditions, survival of P. persimilis was 80% after six weeks whereas that of A. cucumeris was only 35% after the same period of time. Furthermore, longevity and fecundity of P. persimilis after eight weeks of cold storage were comparable to mites taken directly from rearing cultures whereas oviposition by A. cucumeris after six weeks of cold storage was low and irregular compared to previously reported values. Temperature data from areas where P. persimilis survives outdoors indicate that this species is capable of surviving prolonged exposure to temperatures below 10°C and occasional exposure to subzero temperatures, and apparently does so without diapausing. On the other hand, A. cucumeris may be capable of surviving prolonged exposures to subzero temperatures, but only as diapausing adult females. The results of the current studies are consistent with these ideas and further suggest that nondiapausing A. cucumeris are less cold hardy than P. persimilis. / Graduate

The Small Cab-like Proteins (SCPs) in the cyanobacterium Synechocystis sp. PCC 6803 accumulate in cells grown under different stress conditions. Genes coding for SCPs have been found in all sequenced organisms performing oxygenic photosynthesis and even in the genomes of cyanophages. Deletion of multiple scp genes in Synechocystis resulted in mutants with severely impaired growth and altered pigment content. These findings indicate the importance of SCPs in photosynthesis; however, their specific function is not well understood. SCPs share a chlorophyll-binding motif with the plant light harvesting complex, suggesting that they bind chlorophyll. Here I describe my findings, which unambiguously show that SCPs are able to bind chlorophyll in vitro. Although they affect both the stoichiometric ratio of Photosystem I to II and chlorophyll stability, they do not seem to be directly involved in non-photochemical quenching. I was able to reveal the location of the SCPs within the cyanobacterial cell: in stressed cells they attach to Photosystem II in the thylakoid membrane. Furthermore, I revealed the presence of another light-harvesting like (Lil)/SCP protein in Synechocystis sp. PCC 6803. The gene, slr1544, codifying for this newly characterised LilA protein, co-transcribes together with scpD and also appears to bind to Photosystem II during stress.