260 research outputs found
Circulação de cromo entre os compartimentos biótico e abiótico com indícios de bioindicação em uma turfeira não alterada no município de Guaíba, RS, Brasil
Amostras de sedimento, água e tecido vegetal (Mimosa bimucronata e Paspalum notatum)foram analisadas com respeito a seu conteúdo em cromo. Estas amostras foram coletadas de umaturfeira numa baixada entre elevações graníticas na Fazenda São Maximiniano, município de Guaíba,RS, Brasil. Os resultados indicam que em um meio sem contaminação antrópica do metal propostoas concentrações do metal pesado estão totalmente dependentes da fonte para este, ou seja, arocha granítica. O presente trabalho permitiu estabelecer os níveis naturais de cromo (background)em um ambiente geologicamente conhecido e não alterado antropicamente, assim como o comportamentogeoquímico deste metal entre os compartimentos abióticos e biótico. Foi possívelestabelecer, também, o comportamento de absorção do metal por duas espécies vegetais tidascomo bioindicadoras.Samples of sediment, water and vegetational tissue (Mimosa bimucronata and Paspalumnotatum) were analised with respect of its chromium content. These samples were collected from apeatland located in a basin among granitic elevations in the São Maximiniano Farm, Guaíba municipality,Rio Grande do Sul, Brazil. The results indicate that in a non antropic contaminated environment by theproposed heavy metal, the concentration are totally source dependent for it, the granitic rocks. Thiswork led us to establish the natural levels of chromium (background) in a geologically well known andnon antropically changed environment, as well as geochemical behavior of this metal among theabiotics and biotic compartments. It was also possible to establish the biosorption behavior of the twovegetal species, known as bioindicators
Untersuchungen über die Wirkung von Cadmium auf das Blutbild, die Leitfähigkeit und das Skelettsystem von Forellen
Accuracy of the LEP Spectrometer Beam Orbit Monitors
At the LEP e+/e- collider, a spectrometer is used to determine the beam energy with a target accuracy of 10-4. The spectrometer measures the lattice dipole bending angle of the beam using six beam position monitors (BPMs). The required calibration error imposes a BPM accuracy of a 10-6 m corresponding to a relative electrical signal variation of 2. 10-5. The operating parameters have been compared with beam simulator results and non-linearBPM response simulations. The relative beam current variations between 0.02 and 0.03 and position changes of 0.1 mm during the fills of last year lead to uncertainties in the orbit measurements of well below 10-6 m. For accuracy tests absolute beam currents were varied by a factor of three. The environment magnetical field is introduced to correct orbit readings. The BPM linearity and calibration was checked using moveable supports and wire position sensors. The BPM triplet quantity is used to determine the orbit position monitors accuracy. The BPM triplet changed during the fills between 1 and 2 10-6 m RMS, which indicates a single BPM orbit determination accuracy between 1 and 1.5 10-6 m
Phosphorus placement for annual crops in the tropics.
This article discusses principles for optimizing the placement of P in soils of the tropics?looking towards better agronomic, economic, environmental, and social outcomes. General guidelines are offered for short and long-term sustainability
Performance of BPM Electronics for the LEP Spectrometer
At the LEP e+/e- collider at CERN, Geneva, a Spectrometer is used to determine the beam energy with a relative accuracy of 10-4. The Spectrometer measures the change in bending angle in a well-characterised dipole magnet as LEP is ramped. The beam trajectory is obtained using three beam position monitors (BPMs) on each side of the magnet. The error on each BPM measurement should not exceed 1 micron if the desired accuracy on the bending angle is to be reached. The BPMs used consist of an aluminium block with an elliptical aperture and four capacitive button pickup electrodes. The button signals are fed to customised electronics supplied by Bergoz. The electronics use time multiplexing of individual button signals through a single processing chain to optimise for long-term stability. We report on our experience of the performance of these electronics, describing measurements made with test signals and with beam. We have implemented a beam-based calibration procedure and have monitored the reproducibility of the measurements obtained over time. Measurements show that a relative accuracy better than 300 nm is achievable over a period of 1 hr
Calibration of centre-of-mass energies at LEP 2 for a precise measurement of the W boson mass
The determination of the centre-of-mass energies for all LEP 2 running is
presented. Accurate knowledge of these energies is of primary importance to set
the absolute energy scale for the measurement of the W boson mass. The beam
energy between 80 and 104 GeV is derived from continuous measurements of the
magnetic bending field by 16 NMR probes situated in a number of the LEP
dipoles. The relationship between the fields measured by the probes and the
beam energy is defined in the NMR model, which is calibrated against precise
measurements of the average beam energy between 41 and 61 GeV made using the
resonant depolarisation technique. The validity of the NMR model is verified by
three independent methods: the flux-loop, which is sensitive to the bending
field of all the dipoles of LEP; the spectrometer, which determines the energy
through measurements of the deflection of the beam in a magnet of known
integrated field; and an analysis of the variation of the synchrotron tune with
the total RF voltage. To obtain the centre-of-mass energies, corrections are
then applied to account for sources of bending field external to the dipoles,
and variations in the local beam energy at each interaction point. The relative
error on the centre-of-mass energy determination for the majority of LEP 2
running is 1.2 x 10^{-4}, which is sufficiently precise so as not to introduce
a dominant uncertainty on the W mass measurement.Comment: 79 pages, 45 figures, submitted to EPJ
Determination of the Accuracy of Wire Position Sensors
An energy spectrometer has been installed in the LEP accelerator to determine the beam energy with a relative accuracy of 10-4. A precisely calibrated bending magnet is flanked by 6 beam position monitors (BPM). The beam energy is determined by measuring the deflection angle of the LEP beams and the integrated bending field. An accuracy of less than 10-6 m on the beam position is necessary to reach the desired accuracy on the LEP beam energy. Capacitive wire positioning sensors are used to determine the relative mounting stability of each BPM and to calibrate the beam position monitors. Two-dimensional sensors are attached to each side of every BPM support and provide a position measurement with respect to two stretched wires mounted on either side of the LEP beam pipe. The fixing points of each wire are monitored by additional reference sensors. The position information is digitised via a multiplexed high accuracy digital voltmeter and read out continuously during LEP operations. Wire position sensor accuracy was tested in the laboratory with a laser interferometer, while relative accuracy tests are performed in the LEP environment. Systematic effects of synchrotron radiation on the wire position sensor performance were studied
Effectiveness of phosphate fertilizers of diffrent water solubilities in relation to soil phophorus adsorption
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