1,437 research outputs found
A Single Acquisition Channel Receiver for GPS L1CA and L2C Signals Based on Orthogonal Signal Processing
The GPS L1CA and L2C signals are transmitted from the same GPS Satellite Vehicles constellation. It is desirable, especially in commercial GNSS receivers, to have both of these signals acquired by a single receiver so to assure better signal acquisition and improved reliability at wider operating areas. To achieve this in an efficient process, we propose to integrate the GPS L1CA and L2CM signals orthogonally and acquire them in a single processing channel. After removing the Doppler frequency, our receiver first adds the quadrature components of the L2CM signal and the L1CA signal. This new signal is then shifted by 90o. This is then added to the remaining components of these two signals; thus resulting in an orthogonal form of the combined signals. Secondly, the FFT of this orthogonal signal is then mixed with the complex conjugate of the FFT of a locally generated replica of the CA code combined with a 90o-shifted replica of the CM code. Finally, the output signal is then converted back to the time domain to acquire the signal’s peak. The complexity of our dual-signal receiver implementation is half of that used in dual acquisition methods. Furthermore, MATLAB Simulation results show that our acquisition method compares favorably with other approaches in terms of detection of low sensitivity signals and false alarm probability
Galileo Signals Acquisition Using Enhanced Subcarrier Elimination Conversion and Faster Processing
To solve multipath and to enhance the localisation accuracy in a harsh environment, BOC modulation has been adopted in modern GNSS transmission, such as GPS-M-code and Galileo-OS-code signals. The designers of the BOC technique have pointed out that the correlation function becomes ambiguous when the received signal is correlated with the reference BOC signal at code phase resolutions of 0.5 Chip. This has motivated many contributions to resolving this ambiguity, for example, by processing each side of the BOC lobes as a BPSK signal. Our literature survey concluded that solutions claiming to have mitigated this ambiguity actually have resulted in a more complex receiver implementation. The Enhanced Subcarrier Elimination (ESCE) method detailed in this paper proposes combining the two side lobes into a single lobe centered at the main frequency, thus gaining 2dB more signal power as well as reducing the correlation requirements (signal’s mixing and transforming operations) to the half; i.e. accelerating the acquisition process. HaLo-430 platform generated signals used for testing the MATLAB model of ESCE proves that we outperform three of the most used unambiguous methods
Evolutionary history of Leishmania killicki (synonymous Leishmania tropica) and taxonomic implications
Background: Leishmania (L.) killicki is responsible for the chronic cutaneous leishmaniasis. The
taxonomic status of this parasite is still not well defined. It was suggested on one hand to include
this taxon within L. tropica complex but also on the other hand to consider it as a distinct
phylogenetic complex. The present work represents the more detailed study on the evolutionary
history of L. killicki relative to L. tropica and the taxonomic implications.
Methods: Thirty five L. killicki and 25 L. tropica strains isolated from humans and from several
countries were characterized using the MultiLocus Enzyme Electrophoresis (MLEE) and the
MultiLocus Sequence Typing (MLST) approaches.
Results: The genetic and phylogenetic analyses strongly support that L. killicki belongs to L.
tropica complex. The study suggests the emergence of L. killicki by a funder effect followed by an
independent evolution from L. tropica, but does not validate the species status of this taxon. In this
context, we suggest to call this taxon L. killicki (synonymous L. tropica) until further
epidemiological and phylogenetic studies justify the L. killicki denomination.
Conclusions: These findings provided taxonomic and phylogenetic informations on L. killicki and
helped to better know the evolutionary history of this taxon
Geographical distribution and epidemiological features of Old World Leishmania infantum and Leishmania donovani foci, based on the isoenzyme analysis of 2277 strains
A series of 2277 Leishmania strains from Old World visceral leishmaniasis foci, isolated between 1973 and 2008, were studied by isoenzyme analysis. The strains were obtained from humans, domestic and wild carnivores, rodents and phlebotomine sandflies, and came from 36 countries. In all, 60 different zymodemes were identified and clustered by a phenetic analysis into 3 different groups corresponding to the typically visceralizing species L. donovani (20 zymodemes, 169 strains), L. archibaldi (3 zymodemes, 46 strains) and L. infantum (37 zymodemes, 2,062 strains). The taxonomic position of these isoenzymatic groups is discussed in view of contradictory results obtained from recent molecular studie
The Leishmania donovani species complex: A new insight into taxonomy.
Among the 20 or so Leishmania spp. described as pathogenic for humans, those of the Leishmania donovani complex are the exclusive causative agents of systemic and fatal visceral leishmaniasis. Although well studied, the complex is taxonomically controversial, which hampers clinical and epidemiological research. In this work, we analysed 56 Leishmania strains previously identified as L. donovani, Leishmania archibaldi or Leishmania infantum, isolated from humans, dogs and sandfly vectors throughout their distribution area. The strains were submitted to biochemical and genetic analyses and the resulting data were compared for congruence. Our results show: i) a partial concordance between biochemical and genetic-based data, ii) very limited genetic variability within the L. donovani complex, iii) footprints of frequent genetic exchange along an east-west gradient, marked by a widespread diffusion of alleles across the geographical range, and iv) a large-scale geographical spreading of a few genotypes. From a taxonomic point of view, considering the absence of relevant terminology in existing classes, the L. donovani complex could be treated as a single entit
Search for a Technicolor omega_T Particle in Events with a Photon and a b-quark Jet at CDF
If the Technicolor omega_T particle exists, a likely decay mode is omega_T ->
gamma pi_T, followed by pi_T -> bb-bar, yielding the signature gamma bb-bar. We
have searched 85 pb^-1 of data collected by the CDF experiment at the Fermilab
Tevatron for events with a photon and two jets, where one of the jets must
contain a secondary vertex implying the presence of a b quark. We find no
excess of events above standard model expectations. We express the result of an
exclusion region in the M_omega_T - M_pi_T mass plane.Comment: 14 pages, 2 figures. Available from the CDF server (PS with figs):
http://www-cdf.fnal.gov/physics/pub98/cdf4674_omega_t_prl_4.ps
FERMILAB-PUB-98/321-
Observation of Hadronic W Decays in t-tbar Events with the Collider Detector at Fermilab
We observe hadronic W decays in t-tbar -> W (-> l nu) + >= 4 jet events using
a 109 pb-1 data sample of p-pbar collisions at sqrt{s} = 1.8 TeV collected with
the Collider Detector at Fermilab (CDF). A peak in the dijet invariant mass
distribution is obtained that is consistent with W decay and inconsistent with
the background prediction by 3.3 standard deviations. From this peak we measure
the W mass to be 77.2 +- 4.6 (stat+syst) GeV/c^2. This result demonstrates the
presence of two W bosons in t-tbar candidates in the W (-> l nu) + >= 4 jet
channel.Comment: 20 pages, 4 figures, submitted to PR
Measurement of the B0 anti-B0 oscillation frequency using l- D*+ pairs and lepton flavor tags
The oscillation frequency Delta-md of B0 anti-B0 mixing is measured using the
partially reconstructed semileptonic decay anti-B0 -> l- nubar D*+ X. The data
sample was collected with the CDF detector at the Fermilab Tevatron collider
during 1992 - 1995 by triggering on the existence of two lepton candidates in
an event, and corresponds to about 110 pb-1 of pbar p collisions at sqrt(s) =
1.8 TeV. We estimate the proper decay time of the anti-B0 meson from the
measured decay length and reconstructed momentum of the l- D*+ system. The
charge of the lepton in the final state identifies the flavor of the anti-B0
meson at its decay. The second lepton in the event is used to infer the flavor
of the anti-B0 meson at production. We measure the oscillation frequency to be
Delta-md = 0.516 +/- 0.099 +0.029 -0.035 ps-1, where the first uncertainty is
statistical and the second is systematic.Comment: 30 pages, 7 figures. Submitted to Physical Review
Inclusive Search for Anomalous Production of High-pT Like-Sign Lepton Pairs in Proton-Antiproton Collisions at sqrt{s}=1.8 TeV
We report on a search for anomalous production of events with at least two
charged, isolated, like-sign leptons with pT > 11 GeV/c using a 107 pb^-1
sample of 1.8 TeV ppbar collisions collected by the CDF detector. We define a
signal region containing low background from Standard Model processes. To avoid
bias, we fix the final cuts before examining the event yield in the signal
region using control regions to test the Monte Carlo predictions. We observe no
events in the signal region, consistent with an expectation of
0.63^(+0.84)_(-0.07) events. We present 95% confidence level limits on new
physics processes in both a signature-based context as well as within a
representative minimal supergravity (tanbeta = 3) model.Comment: 15 pages, 4 figures. Minor textual changes, cosmetic improvements to
figures and updated and expanded reference
Measurement of the lepton charge asymmetry in W-boson decays produced in p-pbar collisions
We describe a measurement of the charge asymmetry of leptons from W boson
decays in the rapidity range 0 enu, munu events from
110+/-7 pb^{-1}of data collected by the CDF detector during 1992-95. The
asymmetry data constrain the ratio of d and u quark momentum distributions in
the proton over the x range of 0.006 to 0.34 at Q2 \approx M_W^2. The asymmetry
predictions that use parton distribution functions obtained from previously
published CDF data in the central rapidity region (0.0<|y_l|<1.1) do not agree
with the new data in the large rapidity region (|y_l|>1.1).Comment: 13 pages, 3 tables, 1 figur
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