Exploiting the secondary codes to improve signal acquisition performance in Galileo receivers.

In GNSS, longer integrations are required to obtain better signal-to-noise ratio during the signal synchronization process. However the presence of secondary codes on the top of primary codes puts a constraint on the coherent integration duration for pilot channels in a similar way to the effect of data bits in data-carrying channels. In this paper we explore the problem of coherent integration over periods longer than one primary code length and the acquisition of secondary code chip position. We propose an acquisition engine architecture which can handle both these problems together

Testing metabolic ecology theory for allometric scaling of tree size, growth and mortality in tropical forests

The theory of metabolic ecology predicts specific relationships among tree stem diameter, biomass, height, growth and mortality. As demographic rates are important to estimates of carbon fluxes in forests, this theory might offer important insights into the global carbon budget, and deserves careful assessment. We assembled data from 10 old-growth tropical forests encompassing censuses of 367 ha and > 1.7 million trees to test the theory's predictions. We also developed a set of alternative predictions that retained some assumptions of metabolic ecology while also considering how availability of a key limiting resource, light, changes with tree size. Our results show that there are no universal scaling relationships of growth or mortality with size among trees in tropical forests. Observed patterns were consistent with our alternative model in the one site where we had the data necessary to evaluate it, and were inconsistent with the predictions of metabolic ecology in all forests

Phenotypic and genetic variation in the response of chickens to Eimeria tenella induced coccidiosis

Background: Coccidiosis is a major contributor to losses in poultry production. With emerging constraints on the use of in-feed prophylactic anticoccidial drugs and the relatively high costs of effective vaccines, there are commercial incentives to breed chickens with greater resistance to this important production disease. To identify phenotypic biomarkers that are associated with the production impacts of coccidiosis, and to assess their covariance and heritability, 942 Cobb500 commercial broilers were subjected to a defined challenge with Eimeria tenella (Houghton). Three traits were measured: weight gain (WG) during the period of infection, caecal lesion score (CLS) post mortem, and the level of a serum biomarker of intestinal inflammation, i.e. circulating interleukin 10 (IL-10), measured at the height of the infection.Results: Phenotypic analysis of the challenged chicken cohort revealed a significant positive correlation between CLS and IL-10, with significant negative correlations of both these traits with WG. Eigenanalysis of phenotypic covariances between measured traits revealed three distinct eigenvectors. Trait weightings of the first eigenvector, (EV1, eigenvalue = 59%), were biologically interpreted as representing a response of birds that were susceptible to infection, with low WG, high CLS and high IL-10. Similarly, the second eigenvector represented infection resilience/resistance (EV2, 22%; high WG, low CLS and high IL-10), and the third eigenvector tolerance (EV3, 19%; high WG, high CLS and low IL-10), respectively. Genome-wide association studies (GWAS) identified two SNPs that were associated with WG at the suggestive level.Conclusions: Eigenanalysis separated the phenotypic impact of a defined challenge with E. tenella on WG, caecal inflammation/pathology, and production of IL-10 into three major eigenvectors, indicating that the susceptibility-resistance axis is not a single continuous quantitative trait. The SNPs identified by the GWAS for body weight were located in close proximity to two genes that are involved in innate immunity (FAM96B and RRAD)

Proceedings of the 2011 International Technical Meeting of The Institute of Navigation January 24 - 26, 2011

This paper proposes a new modulation for a Global NavigationSatellite System (GNSS) to efficiently utilize a givenbandwidth. This modulation, referred to as Time-MultiplexedMulti-Carrier (TMMC), divides the available bandwidth intoN sub-bands such that each sub-band resembles a QuadraturePhase Shift Keying (QPSK) modulation and at the same timeallows the receiver to exploit the benefits of a widebandsignal. The generation of the new signal and its propertiesare described and the performance of TMMC is compared tothe other existing modulation schemes. The benefits of usingTMMC modulation for wideband signals in terms of overcomingthe errors due to propagation channel impairments,continuous wave (CW) interference mitigation and receiverdesign complexity is discussed

Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008)

In GNSS, longer integrations are required to obtain better signal-to-noise ratio during the signal synchronization process. However the presence of secondary codes on the top of primary codes puts a constraint on the coherent integration duration for pilot channels in a similar way to the effect of data bits in data-carrying channels. In this paper we explore the problem of coherent integration over periods longer than one primary code length and the acquisition of secondary code chip position. We propose an acquisition engine architecture which can handle both these problems together