13 research outputs found
Compatibility between electrical energy transmission lines and new railway infrastructures
No full textThe paper deals with the possibility of installing a 1000 MW power link inside a railway tunnel infrastructure. In particular, the power link should be installed in a train running tunnel, which induces specific constraints like limited available space, limited time access for operation and maintenance of the transmission line due to the railway traffic. The possibility of using a separate emergency tunnel or a pilot one [1, 2] was not in the scope of the project. The actual challenge was to include the cable system whereas the tunnel was originally designed for railway operation only.
The paper envisages several technical choices namely AC and DC technologies and demonstrates that the HVDC solution is the only possibility owing to space requirements inside the proper railway tunnel: two poles and a metallic return have been considered for HVDC. The paper highlights only some of the numerous technical issues that have been addressed, in particular:
the electro-magnetic field (EMF) impact considering the possibility of installing both poles in the same tunnel or one pole per tunnel;
the electro-magnetic compatibility between the high-speed railway supply and the DC link considering the possibility of harmonic contents in the DC-side and the screening effect provided by the metallic pole cable sheath;
the safety in case of a pole short-circuit inside the tunnel: theoretical approach and short circuit experimental tests on 300 kV and 450 kV specimens;
the transmission line fire behaviour inside the railway tunnel from a theoretical standpoint.
This study has been financially supported by the European Community in the framework of TEN-ENERGY Programme:
Decisions C(2006)2928&C(2007)3521 – 2005 – E204/05 – TREN/05/TEN-E-S07.59331
Single-nephron filtration rate and proximal reabsorption in aging rats
No full text Age-related changes in the function of individual nephrons were investigated by micropuncture experiments measuring single-nephron filtration rates (SNGFR) and proximal reabsorptions in 10-, 20-, and 30-mo-old rats. The animals were female WAG/Rij rats with low incidence of chronic progressive nephropathy, no loss of nephrons, and renal hypertrophy of both kidneys in the oldest animals. Mean SNGFR values per gram kidney weight were 41.4 +/- 1.1, 37.1 +/- 1.5, and 32.2 +/- 1.1 nl.min-1.g kidney wt-1 (n = 41) in the 10-, 20-, and 30-mo-old animals, respectively. This age-related decrease in filtration was no longer apparent when SNGFR values were expressed per nephron (means 24.3 +/- 0.7, 23.7 +/- 0.9, and 24.4 +/- 0.9 nl/min. Individual filtered loads of sodium, potassium, calcium, and magnesium and their absolute reabsorption by the proximal tubule were not different in the three age groups; however, absolute and fractional reabsorptions of phosphate decreased significantly in the 30-mo-old rats. These results indicate that, with the exception of phosphate, individual filtrations and proximal reabsorptions are well maintained in aging rats free of disease. This may be related to the observed renal hypertrophy. </jats:p
Local field in LiD polarized target material
No full textKisselev Y, Ball J, Baum G, et al. Local field in LiD polarized target material. In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. Nucl.Instrum.Meth. A. Vol 526. Elsevier Science BV; 2004: 105-109.We have experimentally studied the first and the second moments of D, Li-6 and Li-7 (I > 1/2) NMR lines in a granulated LiD-target material as a function of nuclear polarizations and the data has been compared with a theory elaborated by Abragam, Roinel and Bouffard for monocrystalline samples. The experiments were carried out in the large COMPASS twin-target at CERN. The static local magnetic field of the polarized nuclei was measured by frequency shift between the NMR-signals in the two oppositely polarized cells and lead to the first moment, whereas the investigation of the second moment was done through Gaussian approximation. The average field magnitude in granulated material was estimated 20% larger than the value given by the calculations for monocrystalline samples of cylindrical shape. The second moment shows a qualitative agreement with the theory but it is slightly larger at the negative than at the positive polarization. In a polarized mode, the moments depend on the saturated microwave field. (C) 2004 Elsevier B.V. All rights reserved
Correlations between the Respective Fractional Reabsorptions of Water and Different Solutes along the Proximal Tubule and Henle�s Loop of the Rat Kidney
No full textCorrelations between the Respective Fractional Reabsorptions of Water and Different Solutes along the Proximal Tubule and Henle�s Loop of the Rat Kidney
No full textCalcitonin stimulates H+ secretion in rat kidney intercalated cells
No full text Calcitonin (CT) modulates rat intercalated cell (IC) functions of the rat cortical collecting duct (CCD) [E. Siga, B. Mandon, N. Roinel, and C. de Rouffignac. Am.J. Physiol. 264 (Renal Fluid Electrolyte Physiol. 33): F221-F227, 1993]. To characterize the specific function regulated by CT, rat CCDs were perfused in vitro. Total CO2 net fluxes (JtCO2, pmol.mm-1.min-1) and transepithelial voltage (Vt) were measured. Bath CT induced a significant tCO2 reabsorption. This effect was higher on CCDs harvested from acid-loaded than from control rats. When HCO3- secretion was blocked, CT also raised JtCO2 and Vt. When H+ secretion was blocked, CT was ineffective on JtCO2 and Vt. When HCO3- secretion was increased and H+ secretion was inhibited, CT did not change JtCO2, whereas isoproterenol (ISO) increased tCO2 secretion from -13.5 +/- 2.0 (control) to -19.0 +/- 2.4 (ISO). In rat CCD studied under these same preceding conditions plus luminal amiloride to block the Na(+)-dependent Vt, CT did not alter Vt, whereas ISO increased it by 4.5 +/- 0.7 mV. We conclude from these data that, in the rat CCD, calcitonin stimulates H+ secretion, likely by so-called alpha-intercalated (alpha-IC) cells, whereas ISO stimulates HCO3- secretion, likely by so-called beta-IC cells. </jats:p
Phase diagrams of ordered nuclear spins in LiH : a new phase at positive temperature ?
No full textAn antiferromagnetic order of the nuclear spins of 7Li and 1H is produced by Dynamic Polarization followed by Adiabatic Demagnetization in the Rotating Frame. The magnetic field is parallel to a [001] direction, and both positive and negative spin temperatures are investigated. The ordering is studied by means of Nuclear Magnetic Resonance and neutron diffraction. The sublattice proton polarization in zero effective field is measured as a function of temperature. The entropy/effective field and temperature/effective field phase diagram are established. At positive temperature, the results suggest the onset of a new phase, not predicted by the Weiss-field approximation.Un ordre antiferromagnétique des spins nucléaires 7Li et 1H est produit par une polarisation dynamique suivie d'une désaimantation adiabatique dans le référentiel tournant. Le champ magnétique est parallèle à la direction [001]. L'ordre a été étudié, pour des températures de spin positive et négative, à la fois par des mesures de R.M.N. et par diffraction de neutrons. La polarisation de sous-réseau en champ effectif nul a été mesurée en fonction de la température. Les diagrammes de phases entropie/champ effectif et température/champ effectif ont été établis. A température positive, les résultats suggèrent l'existence d'une nouvelle phase, non prévue par l'approximation de Weiss
Relaxation and phonon bottleneck of 169Tm nuclear spins in TmPO 4 : evidence for the direct process ?
No full textThe spin-lattice relaxation time T1 of 169Tm nuclear spins in TmPO4 has been measured at temperatures T between 50 mK and 2.2 K, in a magnetic field H perpendicular to the c-axis, ranging from 15 mtesla to 5.5 tesla. The results above 0.5 tesla are interpreted in terms of a direct process, strongly slowed down by phonon bottleneck. In very low fields ( H < 0.1 tesla), T1 varies like H 2/ T. We discuss the feasibility of producing a nuclear ordered state of the 169Tm spins by « brute force ».Le temps de relaxation T1 des spins nucléaires de 169Tm dans TmPO4 a été mesuré à des températures T comprises entre 50 mK et 2,2 K, dans un champ magnétique H perpendiculaire à l'axe c, dans l'intervalle 15 mtesla à 5,5 tesla. Les résultats au-dessus de 0,5 tesla sont interprétés en termes d'un processus direct, fortement ralenti par l'engorgement de phonons. Dans les champs très bas (H < 0,1 tesla), T1 varie comme H2/T. Nous discutons la possibilité de produire un état nucléaire ordonné des spins de 169Tm par la méthode de « brute force »
Renal phosphate transport: Inhomogeneity of local proximal transport rates and sodium dependence
No full textThe standing droplet method has been used in combination with the peritubular perfusion of blood capillaries to determine the build up of transtubular concentration differences of phosphate Pi in the renal proximal convoluted tubule of parathyroidectomized rats. Electron probe analysis was used to estimate Pi . At zero time both the intraluminal and the contraluminal Pi concentration was 2 mM. The time dependent decrease of the intraluminal Pi concentration was approximately 4 times faster in the early than in the late proximal convoluted tubule. After 45 sec an intraluminal steady state concentration of 0.20 mM Pi was achieved in the early part. In the late part the intraluminal Pi concentration approached a steady state value of 0.54 mM at 120 sec. When sodium free solutions were used the intraluminal Pi concentration increased to 2.22 mM in the earlier and to 2.76 mM in the late part. The data indicate that in the proximal convoluted tubule 1. The rate of phosphate reabsorption is greater in the early part than in the later part, and 2. phosphate reabsorption might occur as co-transport with Na+ ions
