Search Results

You are looking at 1 - 10 of 22 items for :

  • Refine by Access: All Content x
Clear All

Nowadays, GPS is the best positioning system with its constellation, but number of GLONASS satellites increased to the required number, with launched new ones, for positioning. With recent revitalization of GLONASS, a great number of high precision GLONASS and GPS/GLONASS receivers have been produced. In this paper, baselines of two networks have been analyzed in order to assess the usability of GLONASS on global positioning. In both networks, repeatabilities of results were investigated by using GPS, GLONASS and GPS/GLONASS data. Results revealed that repeatabilities of all baselines by using GLONASS observations are not consistent when compared to the GPS and GPS/GLONASS.

Restricted access

D1/D2 region of the 28S rDNA, and the intergenic spacer 1 (IGS1) region are the most frequently used techniques for the identification of species [ 5 , 8 , 9 ]. In addition, IGS1 is also used for the genotyping of T. asahii [ 10 ]. Moreover, a

Restricted access

The effects of three geomagnetic storms on the ionospheric F region and the influence of the G condition on TEC estimates have been analysed by using ionospheric data from INTA El Arenosillo Atmospheric Sounding Station (37.1N, 353.3E) and GPS TEC measurements obtained at the IGS station of San Fernando (36.5N, 353.8E). The results stress the importance of these perturbations and the need of using edited ionograms.

Restricted access
Biologia Futura
Authors:
Arne Thell
,
Mats Hansson
,
Per-Erik Persson
,
Mark R. D. Seaward
,
Maik Veste
, and
Mikael Hedrén

Background and aims

Betony (Betonica officinalis L.) is one of the rarest and most spectacular plants in the Scandinavian flora. A long-term question has been whether it is spontaneous or introduced, or whether it comprises both spontaneous and introduced populations. This study aimed to answer this question by analyzing sequence data from the nuclear external transcribed spacer (ETS) region and three regions of the plastid genome, the trnT–trnL intergenic spacer (IGS) region, tRNA-Leu (trnL) intron, and the trnS–trnG IGS.

Materials and methods

Altogether 41 samples from 11 European countries were analyzed. A unique duplication in the trnT–trnL IGS was detected in material from Skåne (southern Sweden), the “Skåne-duplication.” Populations with this duplication are united on a moderately supported branch in the phylogeny based on plastid sequences. A distinct heath genotype from Yorkshire was discovered in the phylogeny based on plastid sequences and in a comparative cultivation.

Results

Phylogeny based on ETS sequences does not support any Scandinavian group, whereas a principal coordinates analysis ordination based on variable ETS positions indicated a spontaneous origin for all Scandinavian populations, which comprise a genetically well-defined subgroup of the species, most closely related to other spontaneous populations from adjacent parts of continental parts of northern Europe.

Discussion

Seven possible naturally occurring localities remain in Scandinavia, five in central Skåne, southernmost Sweden, and two on the southwestern part of the Danish island of Lolland.

Restricted access

The paper describes a procedure of the ionospheric total electron content (TEC) specification on-line over Europe intended to provide the vertical total electron content in an operational environment. TEC data are derived from the International Global Positioning System (GPS) Service for Geodynamics (IGS) signal phase and amplitude measurements at European ground station network. Specification here refers to the fusion and visualization of available observations into a map representation of the plasmaspheric-ionospheric state over Europe with a maximum delay of up to about 24 hours. It is designed for models of operations that include post-analysis and real-time.

Restricted access

The radio limb sounding or occultation technique is capable of deriving accurate vertical profiles of atmospheric refractivity. This has been shown by very promising results of the first active GPS limb sounding GPS/MET experiment on Microlab 1. In this paper we report early results of ionospheric radio occultation (IRO) measurements carried out onboard the German satellite mission CHAMP (CHAllenging Minisatellite Payload) that contributes also to essential improvements of gravity and magnetic field models of the Earth.  First radio occultation measurements of the ionosphere were carried out by CHAMP on 11 April 2001.  Fortunately, ionospheric radio occultation measurements were switched on during the High Rate GPS/GLONASS  measuring campaign (HIRAC) initiated by the International GPS Service (IGS) and supported by COST 271 activities. So a comprehensive analysis of coordinated measurements will be possible within COST 271 cooperation in the near future.  The achieved accuracy of the retrieved electron density profiles is estimated by comparing them with independent ionosonde data.

Restricted access

Abstract  

A simple, rapid, effective and eco-friendly decomposition method is developed for the determination of uranium (U) by laser induced fluorimetry (LIF). The salts of sodium di-hydrogen phosphate (NaH2PO4) and di-sodium hydrogen phosphate (Na2HPO4) were used in the ratio of 1:1 (phosphate flux) for the decomposition and dissolution of refractory, non silicate minerals like ilmenite, rutile, columbite, tantalite, and xenotime. The effect of associated matrix elements (Ti, Fe, Nb, Ta, Mn and Y present in the sample) on quenching of uranyl fluorescence was studied. The flux used for the sample decomposition has several advantages. In the reported sample decomposition methods, α-hydroxy acids are used as complexing agents to prevent hydrolysis and to get clear and stable solution. This solution can not be directly used for U determination by LIF as α-hydroxy acids quench uranyl fluorescence, hence separation is required. In the present method no such separation is required. The flux itself acts as fluorescence enhancing reagent and buffer (maintaining the optimum pH of 7.1 ± 0.1). The fused melt of the flux mixture, when disintegrated in water, gives clear and stable solution and has high tolerance for most of inorganic quenchers compared to reported phosphate buffers. Also just by dilution (due to high sensitivity of LIF), the concentration of quenchers could be brought down well within the tolerance limit. The accuracy and precision of the method was evaluated by analyzing Certified Reference Materials (IGS-33 and IGS-34 of Institute of Geological Sciences, UK) and Synthetic Minerals. The accuracy of the data is further evaluated by comparing with standard decomposition methods. The results are well within the experimental error. The RSD of the method is ±10% (n = 6) at 10 ppm level for Ilmenite and for other minerals the RSD of the method is ±5% (n = 6) at 50 ppm level. The method is being routinely applied to various refractory samples received from Rare Metal and Rare Earth Investigations for determination of uranium by laser fluorimetry.

Restricted access
Cereal Research Communications
Authors:
Beáta Tóth
,
János Varga
,
Ágnes Szabó-Hevér
,
Szabolcs Lehoczki-Krsjak
, and
Ákos Mesterházy

Fusarium head blight caused mainly by Fusarium graminearum and F. culmorum is the most important disease of wheat in Central Europe. While F. graminearum is homothallic, no sexual cycle has been observed in F. culmorum . Knowledge regarding the species distribution and population structure of these pathogens is important to estimate their significance for breeding. There are two fundamental means by which fungi and other organisms transmit genes to the next generation: through clonal reproduction or by sexual recombination. To clarify the population structures of F. culmorum and F. graminearum in Central Europe, RAPD and IGS-RFLP data sets of the isolates were subjected to both the index of association tests and tree length tests. Our data indicate that the world-wide F. graminearum and F. culmorum populations have recombining structures, while both the Hungarian F. culmorum and F. graminearum populations reproduce clonally. The frequent occurrence of F. graminearum perithecia on corn residues indicates that this species undergoes a sexual cycle. Both mating type genes have been identified in each examined F. graminearum isolate, while the heterothallic distribution of mating type genes in F. culmorum indicates that this species lost its sexual cycle relatively recently.

Restricted access

In the global navigation satellite system (GNSS) carrier phase data processing, cycle slips are limiting factors and affect the quality of the estimators in general. When differencing phase observations, a problem in phase ambiguity parameterization may arise, namely linear relations between some of the parameters. These linear relations must be considered as additional constraints in the system of observation equations. Neglecting these constraints, results in poorer estimators. This becomes significant when ambiguity resolution is in demand. As a clue to detect the problem in GNSS processing, we focused on the equivalence of using undifferenced and differenced observation equations. With differenced observables this equivalence is preserved only if we add certain constraints, which formulate the linear relations between some of the ambiguity parameters, to the differenced observation equations. To show the necessity of the additional constraints, an example is made using real data of a permanent station from the network of the international GNSS service (IGS). The achieved results are notable to the GNSS software developers.

Restricted access

1997 102 5005 5017 Kouba J., Héroux, P. Precise point positioning using IGS orbit and clock products, GPS Solut , Vol

Restricted access