Effects of donor age and proliferative aging on the phenotype stability of rat aortic smooth muscle cells

Age-related effects of the vascular wall have been associated with several hemodynamic dysfunctions, including medial vascular calcification. Vascular aging has been traditionally addressed using proliferative senescence of vascu- lar smooth muscle cells (VSMC) in vitro, which induces osteoblastic transition and favors calcification in vitro. In this work, we have analyzed the relation- ship between organismal aging and proliferative senescence by comparing the proliferative aging of VSMC obtained from young, mature, and old rats (2-, 12-, and 24-month cell lines [CL], respectively). VSMC proliferated to more than 100 cumulative population doublings (CPD) without evidence of prolif- erative senescence, most likely as a consequence of telomerase induction. The apoptosis rate increased with CPD in all three CL, but the oxidation status of the cells was not modified. The magnitude of all gene expression changes caused by CPD was higher than the magnitude of the changes caused by donor age: the expressions of VSMC markers a-actin and SM22a decreased, while the expressions of transcription factors Msx2 and Runx2 and of bone morphogenetic protein-2 increased. Treatment of the cells with 2 mmol/L Pi revealed that the intensity of the effect of CPD on calcium deposition was greater than the effect of donor age. In conclusion, the proliferative lifespan of VSMC magnifies the effect of donor age on the osteoblastic transition of VSMC, therefore suggesting that in vivo vascular aging changes can be less dramatic than what is shown by in vitro aging

Electron Bernstein waves emission in the TJ-II Stellarator

Taking advantage of the electron Bernstein waves heating (EBWH) system of the TJ-II stellarator, an electron Bernstein emission (EBE) diagnostic was installed. Its purpose is to investigate the B-X-O radiation properties in the zone where optimum theoretical EBW coupling is predicted. An internal movable mirror shared by both systems allows us to collect the EBE radiation along the same line of sight that is used for EBW heating. The theoretical EBE has been calculated for different orientations of the internal mirror using the TRUBA code as ray tracer. A comparison with experimental data obtained in NBI discharges is carried out. The results provide a valuable information regarding the experimental O-X mode conversion window expected in the EBW heating experiments. Furthermore, the characterization of the radiation polarization shows evidence of the underlying B-X-O conversion process.Comment: 21 pages, 14 figure

Study of the neoclassical radial electric field of the TJ-II flexible heliac

Calculations of the monoenergetic radial diffusion coefficients are presented for several configurations of the TJ-II stellarator usually explored in operation. The neoclassical radial fluxes and the ambipolar electric field for the standard configuration are then studied for three different collisionality regimes, obtaining precise results in all cases

Extension and its characteristics of ECRH plasma in the LHD

One of the main objectives of the LHD is to extend the plasma confinement database for helical systems and to demonstrate such extended plasma confinement properties to be sustained in steady state. Among the various plasma parameter regimes, the study of confinement properties in the collisionless regime is of particular importance. Electron cyclotron resonance heating (ECRH) has been extensively used for these confinement studies of the LHD plasma from the initial operation. The system optimizations including the modification of the transmission and antenna system are performed with the special emphasis on the local heating properties. As the result, central electron temperature of more than 10 keV with the electron density of 0.6 x 10$^{19}$ m$^{-3}$ is achieved near the magnetic axis. The electron temperature profile is characterized by a steep gradient similar to those of an internal transport barrier observed in tokamaks and stellarators. 168 GHz ECRH system demonstrated efficient heating at over the density more than 1.0 x 10$^{20}$ m$^{-3}$. CW ECRH system is successfully operated to sustain 756 s discharge.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

Calculation of the bootstrap current profile for the TJ-II stellarator

Calculations of the bootstrap current for the TJ-II stellarator are presented. DKES and NEO-MC codes are employed; the latter has allowed, for the first time, the precise computation of the bootstrap transport coefficient in the long mean free path regime of this device. The low error bars allow a precise convolution of the monoenergetic coefficients, which is confirmed by error analysis. The radial profile of the bootstrap current is presented for the first time for the 100_44_64 configuration of TJ-II for three different collisionality regimes. The bootstrap coefficient is then compared to that of other configurations of TJ-II regularly operated. The results show qualitative agreement with toroidal current measurements; precise comparison with real discharges is ongoing

Latest physics results of TJ-II flexible heliac

This paper is devoted to the presentation of the most relevant recent Physics results obtained in the TJ-II flexible heliac. Firstly ECRH modulation and plasma breakdown studies are summarised; then the particle control techniques used to obtain reproducible discharges with density under control are presented. Transport studies show internal heat transport barriers that reduce heat conductivity to neoclassical values, and ELM-like transport events, similar to those observed in tokamaks and in other stellarators before and during H mode transition. Evidence of ExB sheared has been observed both in the proximity of rational surfaces. Finally, a high resolution Thomsom Scattering system has shown Te and ne profile structures

Perturbative transport experiments on TJ-II Flexible Heliac

Transport properties of TJ-II are explored performing perturbative experiments and taking advantage of TJ-II flexibility. Rotational transform can be varied in a wide range, which allows one to introduce low order rationals and to study their effect on transport. On the other hand, confinement properties can be studied at very different rotational transform values and for different values of magnetic shear: Experiments on influence of the magnetic shear on confinement are reported. In these cases a Ohmic current has been induced in TJ-II plasma to modify magnetic shear and to evaluate itsd effect on confinement, showing that negative shear improves the confinement. Heat transport is also reduced by locating a low order rational near the power deposition profile. Plasma potential profiles have been recently measured in some configurations up to the plasma core with the Heavy Ion Beam Probe (HIBP) diagnostic and the electric field values measured in low-density plasmas are consistent with neoclassical calculations near the plasma core. Plasma edge turbulent transport has been studied in configurations that are marginally stable due to decreased magnetic well. Results show a dynamical coupling between gradients and turbulent transport. Finally, cold pulse propagation has been studied showing ballistic non diffusive propagation

Effect of the aspect ratio on the stability limits of TJ-II-like stellarators

The four-field-period device TJ-II has a major radius of 1.5 m and an average plasma radius of 0.10--0.25 m, with a typical plasma aspect ratio A{sub P} of 10. In the infinite aspect ratio, helically symmetric limit, the region of the stability to low-n modes has been shown to extend to average betas of at least 40%, for a relatively highly indented plasma. It is possible to approximate the helically symmetric limit from the actual TJ-II parameters increasing the number of toroidal periods N{sub T} and choosing the major radius R{sub O} such as to obtain a constant helical pitch h = N{sub T}/R{sub O}. In this way the aspect ratio per period is fixed. In this work we analyze a shear-less TJ-II configuration with a rotational transform per period of 0.36 and a vacuum magnetic well of 3.5%. By taking for N{sub T} the values N{sub T} = 3, 4, 5, 8, 10, 11, 12, 19 and 100 a sequence of equilibria is generated. These equilibria are calculated with the fixed boundary version of the VMEC code. The Mercier stability properties are then analyzed