Possible mechanism responsible for observed impurity outward flow under radio frequency heating

The effect of poloidal asymmetry of impurities on impurity transport driven by electrostatic turbulence in tokamak plasmas is analyzed. It is found that in the presence of in-out asymmetric impurity populations the zero-flux impurity density gradient (the so-called peaking factor) is significantly reduced. A sign change in the impurity flux may occur if the asymmetry is sufficiently large. This may be a contributing reason for the observed outward convection of impurities in the presence of radio frequency heating. The effect of in-out asymmetry is most significant in regions with low temperature gradients. In the trapped electron mode dominated case also an up-down asymmetry can lead to a sign change in the peaking factor from positive to negative. The effect of ion parallel compressibility on the peaking factor is significant, and leads to positive peaking factors in regions with high temperature gradients, even in the presence of in-out asymmetry.Comment: 19 pages, 14 figure

Non-neoclassical up/down asymmetry of impurity emission on Alcator C-Mod

We demonstrate that existing theories are insufficient to explain up/down asymmetries of argon x-ray emission in Alcator C-Mod ohmic plasmas. Instead of the poloidal variation, ñ[subscript z]/〈n[subscript z]〉, being of order the inverse aspect ratio, ϵ, and scaling linearly with B[subscript t][superscript _ over n][subscript e]/I[2 over p], it is observed over 0.8 < r/a < 1.0 to be of order unity and exhibits a threshold behaviour between 3.5 <B[subscript t][superscript _ over n][subscript e]/I[subscript p] < 4.0 (T10[superscript 20] m[superscript −3] MA[superscript −1]). The transition from a poloidally symmetric to asymmetric impurity distribution is shown to occur at densities just below those that trigger a reversal of the core toroidal rotation direction, thought to be linked to the transition between the linear and saturated ohmic confinement regimes. A possible drive is discussed by which anomalous radial transport might sustain the impurity density asymmetry as the ratio of the perpendicular to parallel equilibration times, τ[subscript ⊥,z]/τ[subscript ∥,z], approaches unity. This explanation requires a strong up/down asymmetry in radial flux which, while not observable on C-Mod, has been measured in TEXT and Tore Supra ohmic plasmas.United States. Dept. of Energy (Contract DE-FC02-99ER54512)United States. Dept. of Energy (Fusion Research Postdoctoral Research Program

Recent results from the electron cyclotron heated plasmas in Tokamak à Configuration Variable (TCV)

In noninductively driven discharges, 0.9 MW second harmonic (X2) off-axis co-electron cyclotron current drive deposition is combined with 0.45 MW X2 central heating to create an electron internal transport barrier (eITB) in steady plasma conditions resulting in a 1.6-fold increase of the confinement time (tau(Ee)) over ITER-98L-mode scaling. The eITB is associated with a reversed shear current profile enhanced by a large bootstrap current fraction (up to 80%) and is sustained for up to 10 current redistribution times. A linear dependence of the confinement improvement on the product of the global shear reversal factor (q(0)/q(min)) and the reversed shear volume (rho(q-min)(2)) is shown. In other discharges heated with X2 the sawteeth are destabilized (respectively stabilized) when heating just inside (respectively outside) the q=1 surface. Control of the sawteeth may allow the avoidance of neoclassical tearing modes that can be seeded by the sawtooth instability. Results on H-mode and highly elongated plasmas using the newly completed third harmonic (X3) system and achieving up to 100% absorption are also discussed, along with comparison of experimental results with the TORAY-GA ray tracing code [K. Matsuda, IEEE Trans. Plasma Sci. PS-17, 6 (1989); R. H. Cohen, Phys. Fluids 30, 2442 (1987)]. (C) 2003 American Institute of Physics

Characterization of impurities in L- and H-modes created by divertor biasing and plasma triangularity in TdeV

A characterization of the H-mode in Tokamak de Varennes (TdeV) is presented, combining results obtained from spectroscopic measurements with observations of global plasma parameters. Controlled L- and H-modes are obtained by applying an external bias on the divertor plate and/or by varying the plasma triangularity using similar steady-state discharges with electron cyclotron resonance heating (ECRH). A qualitative study of the impurity emission asymmetries is presented and discussed by proposing a simple model which considers that the emissivity has radial and poloidal components. The poloidal velocities are small with no significant variations with respect to the plate biasing, EC power and plasma triangularity. Toroidal. rotation velocities show more consistent trends and have larger values in the H-modes with respect to the L-modes. No significant shear in the radial electric field is observed between the H- and L-modes. Differences in the electric field and in the E x B shear are observed for several discharges, but they are not consistent overall. A study on the impurity transport shows low diffusivity values in the plasma centre and high values in the edge during the H-mode. The energy confinement time decreases with the severity of the edge localized modes and, consequently, with the neutral fluxes. The presence of a toroidal torque which affects the particle transport inside the plasma plays an important role in the TdeV H-modes

Local fibrinolysis in spontaneous supratentorial hematomas: comparison with surgical and medical treatment

Institute of Neurology and Neurosurgery, Department of Neurology and Neurosurgery, Institute of Emergency Medicine, and Department of Radiology and Medical Imaging, Nicolae Testemitsanu State University of Medicine and Pharmacy, Chisinau, Republic of Moldov

Occult Breast Lesion Localization and Concomitant Sentinel Lymph Node Biopsy in Early Breast Cancer (SNOLL). Chirurgia

Rezumat Localizarea leziunilor mamare infraclinice aei biopsia concomitentã a ganglionului santinelã în cancerul glandei mamare (SNOLL) Introducere: Leziunile mamare infraclinice descoperite imagistic ridicã probleme privind atitudinea diagnosticã şi terapeuticã adecvatã. Aceste leziuni pot reprezenta un cancer mamar puåin avansat şi cu cât depistarea bolii se face într-un stadiu mai puåin avansat cu atât tratamentul este mai eficient, mai puåin mutilant. Scopul acestui studiu prospectiv a constat în evaluarea tehnicii de localizare preoperatorie a neoplasmului mamar infraclinic folosind injectarea sub control imagistic a unui trasor radioactiv şi biopsia concomitentã de ganglion santinelã, tehnicã ce poartã denumirea de SNOLL (Sentinel lymph Node biopsy and Occult Lesion Localization). Material şi metodã: Am identificat imagistic un numãr de 107 de paciente cu leziuni mamare infraclinice cu caractere de malignitate la care am injectat peritumoral, preoperator, sub control imagistic, nanoalbuminã marcatã radioactiv cu Techneåiu 99. Excizia chirurgicalã, atât a tumorii primare cât şi identificarea şi biopsia ganglionului santinelã, au fost ghidate intraoperator de sonda gamma. Rezultate: Intraoperator au fost identificate şi biopsiate toate leziunile mamare infraclinice, 98 de tumori fiind confirmate malign prin examen histopatologic intraoperator. 7 leziuni au avut un rezultat microscopic intraoperator neconcludent iar 2 leziuni au fost microscopic benigne. Din cele 7 leziuni incerte intraoperator 6 s-au dovedit a fi maligne la examenul la parafinã, iar 1 leziune a fost benignã. Piesele de rezecåie au avut margini negative cu excepåia unui singur caz. Greutatea pieselor operatorii a fost în medie de 40 grame. Ganglionul santinelã a fost identificat la 95 dintre cele 98 de paciente cu rezultat malign intraoperator al tumorii, iar în 14 de cazuri a fost necesarã limfadenectomia axilarã completã. Concluzii: Localizarea preoperatorie orienteazã actul chirurgical, asigurã cã leziunea evidenåiatã imagistic va fi extirpatã şi evitã rezecåii mamare largi, inutile. Folosirea trasorului a facilitat localizarea şi excizia leziunii mamare iar în cazurile în care aceasta a fost malignã, a permis identificarea şi biopsia ganglionului santinelã. Astfel, s-a realizat în acelaşi timp operator intervenåia curativã necesarã în funcåie de rezultatul histopatologic intraoperator al tumorii primare şi al ganglionului santinelã. Cuvinte cheie: cancer mamar, tumori mamare nepalpabile, ganglion santinelã, SNOLL Abstract Aims: Mammographic screening and the increasing resolution output of mammography have raised the identification number of small-size mammary lesions without clinical expression. The aim of this study was to evaluate in a prospective study the localization techique and concomitent sentinel lymph node biopsy for breast cancer (SNOLL -Sentinel lymph Node biopsy and Occult Lesion Localization). Results: All primary lesions were identified and were clear of invasive margins needing excision. 98 tumors proved to be malignant on frozen sections. 7 lesions could not be clearly examined through frozen section and 2 proved to be benign. 6 out of 7 suspicious lesions confirmed to be malignant on parrafin embedded sections. Sentinel lymph node was identified in a number of 95 out of 98 patients. In 14 cases complete axillary lymphadenectomy was performed. The average specimen weight was 40grams. Occult Breast Lesion Localization and Concomitant Sentinel Lymph Node Biopsy in Early Breast Cancer (SNOLL) C Conclusions: Using this technique, we removed the lesions identified prior to surgery in all cases, achieving a complete pathologic diagnostic, the necessary surgical treatment and also prognostic data by axillary lymph node assessment