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Biomedical subjects

S Coda

Publications and source records attributed to S Coda.

At least 19 recordsLinked to original sources
PubMed2005

Inductive current density perturbations to probe electron internal transport barriers in tokamaks.

Improved electron energy confinement in tokamak plasmas, related to internal transport barriers, has been linked to nonmonotonic current density profiles. This is difficult to prove experimentally since usually the current profiles evolve continuously and current injection generally requires significant input power. New experiments are presented, in which the inductive current is used to generate positive and negative current density perturbations in the plasma center, with negligible input power. These results demonstrate unambiguously for the first time that the electron confinement can be modified significantly solely by perturbing the current density profile.

Journal Article↗
PubMed2004

Rapid and localized electron internal-transport-barrier formation during shear inversion in fully noninductive TCV discharges.

Clear evidence is reported for the first time of a rapid localized reduction of core electron energy diffusivity during the formation of an electron internal-transport barrier. The transition occurs rapidly (approximately = 3 ms), during a slow (approximately = 200 ms) self-inductive evolution of the magnetic shear. This crucial observation, and the correlation of the transition with the time and location of the magnetic shear reversal, lend support to models attributing the reduced transport to the local properties of a zero-shear region, in contrast to models predicting a gradual reduction due to a weak or negative shear.

Journal Article↗
PubMed2004

Destabilization of fast-ion-induced long sawteeth by localized current drive in the JET tokamak.

In a tokamak fusion reactor the energetic alpha particles will transiently stabilize the magnetohydrodynamic activity causing sawtooth oscillations. The crash events terminating long sawtooth free periods can provide seed islands for neoclassical tearing modes [Phys. Rev. Lett. 88, 105001 (2002)]]. To shorten the sawtooth periods localized current drive near the q=1 surface is a possibility. This Letter provides the first experimental evidence for the effectiveness of this method in the different physics regime associated with fast-ion-induced long sawteeth on the JET tokamak.

Journal Article↗
PubMed2001

Signature of turbulent zonal flows observed in the DIII-D tokamak.

The spectrum of turbulent density fluctuations at long poloidal wavelengths in the edge plasma of the DIII-D tokamak peaks at nonzero radial wave number. The associated electric-potential fluctuations cause sheared E x B flows primarily in the poloidal direction. These zonal flows have been predicted by theory and are believed to regulate the overall level of turbulence and anomalous transport. This study provides the first indirect experimental identification of zonal flows.

Journal Article↗
PubMed2001

Long-pulse improved central electron confinement in the TCV tokamak with electron cyclotron heating and current drive.

Current profile tailoring by electron cyclotron heating (ECH) and current drive (ECCD) is used to improve central electron energy confinement in the TCV tokamak. Counter-ECCD on axis alone achieves this goal in a transient manner only. A stable scenario is obtained by a two-step sequence of off-axis ECH, which stabilizes magnetohydrodynamics modes, and on-axis counter-ECCD, which generates a flat or inverted current profile. This high-confinement regime, with central temperatures up to 9 keV (at a normalized beta(N) approximately 0.6), has been sustained for the entire duration of the heating pulse, or over 200 electron energy confinement times and 5 current redistribution times.

Journal Article↗
PubMed2001

Circadian rhythm of hunger sensation in obese patients: effects of a short-term, moderately hypocaloric diet with a substitutive meal.

This investigation deals with the circadian rhythm (CR) of hunger sensation (HS) in obese patients before and after a four-week, moderately hypocaloric diet with a substitutive meal. The study was performed on 25 non-diabetic obese patients (5 males and 20 females, mean age: 39.7 +/- 7, mean BMI: 27.9 1.4 Kg/m2), whose obesity was not associated with impaired glucose tolerance (IGT), binge eating, nor endocrine diseases. Their daily HS profile (orexigram) was analysed chronobiometrically. The moderately hypocaloric diet with a substitutive meal reduced the daily HS by about 10% by the fourth week. This reduction was apparently due to a tonic and amplitude modulation of the HS CR and was not accompanied by its disruption. No conclusions, however, could be drawn with regard to its orectic and clinical effects beyond four weeks.

Adult↗
PubMed2000

Steady-state fully noninductive current driven by electron cyclotron waves in a magnetically confined plasma

A steady-state, fully noninductive plasma current has been sustained for the first time in a tokamak using electron cyclotron current drive only. In this discharge, 123 kA of current have been sustained for the entire gyrotron pulse duration of 2 s. Careful distribution across the plasma minor radius of the power deposited from three 0. 5-MW gyrotrons was essential for reaching steady-state conditions. With central current drive, up to 153 kA of current have been fully replaced transiently for 100 ms. The noninductive scenario is confirmed by the ability to recharge the Ohmic transformer. The dependence of the current drive efficiency on the minor radius is also demonstrated.

Journal Article↗
PubMed1999

Daily hunger sensation and body compartments: II. Their relationships in obese patients.

Hunger sensation (HS) is a signal whose levels change during the 24-h day. The daily mean level of HS was correlated with the human body compartments, as investigated by bioelectrical impedance analysis, to detect the relationship between the orectic perception and both the free fat mass (FFM) and the fat body mass (FBM) in 22 clinically healthy subjects (CHS) (2 M, 20 W, BMI: 18.5-24.0 kg/m2) and 48 obese patients (OP) (4 M, 44 W, BMI: 25.2-54.7 kg/m2). In CHS, the daily mean level of HS correlated positively with the FFM and negatively with the FBM. These correlations were not present in OP. This lack of relationships between HS and the body compartments where energy is maximally consumed (i.e., the FFM) and maximally stored (i.e., the FBM) indicates that the orectic response to energy expenditure and the orectic inhibition to fat accumulation are feedback mechanisms which are impaired in obesity.

Adipose Tissue↗
PubMed1999

Anxiety, depression, hunger and body composition: III. Their relationships in obese patients.

The present paper explores the relationships between anxiety, depression, hunger sensation and body composition in obese patients (OP). The aim is to detect whether or not there are abnormalities in these relationships in OP as compared to clinically healthy subjects (CHS). The study was performed on 22 CHS (2 M, 20 W; mean age = 24 +/- 2 years; mean body mass index = 21 +/- 2 kg/m2) and 48 OP (4 M, 44 W; mean age = 40 +/- 17 years; mean body mass index = 32 +/- 7 kg/m2). Anxiety and depression were found to be correlated, negatively, with the relative lean body mass, and, positively, with the fat body mass in OP but not in CHS. These findings corroborate the idea that anxiety and depression can reach an abnormal expression when obesity shows its worst loss in lean body mass and its highest expansion in adipocyte mass. As hunger sensation was found not to correlate with either anxiety or depression in OP, the opinion is expressed that the impairment of anxio-depressive integrity is a corollary of obesity rather than a primary affective disorder leading to obesity via an enhanced food intake.

Adult↗
PubMed1998

Daily hunger sensation and body composition: I. Their relationships in clinically healthy subjects.

The human hunger sensation (HS) is a perceptive signal characterized by day-night variability (DNV). This pattern was investigated with respect to its relations with the body compartments in 22 clinically healthy subjects (CHS, 11 males and 11 females, mean age: 24 +/- 2.5 years, mean BMI: 21 +/- 1.7). The DNV was investigated by means of conventional descriptive statistics and the single cosinor method (SCM). Both procedures were applied to the orexigram, i.e., the 24-h profile of the orectic stimulus (OS) provided by each subject, who self-rated his/her HS (from 1 to 10 hunger units) every half hour. Body composition was investigated by Bioelectrical Impedance Analysis (BIA) on the day when the orexigrams were compiled. It was found that the daily HS level correlates positively with the Free Fat Body Mass (FFBM) and negatively with the Fat Body Mass (FBM). These opposite relations indicate that HS is stimulated by the needs of the FFBM, and inhibited by expansion of the FBM, and provide further evidence of the existence of an "adipostat" anorectic mechanism.

Adult↗
PubMed1979

Radioisotopic and synthetic studies related to caroxazone metabolism in man.

Labelled 2-oxo-2H-1,3-benzoxazine-3(4H)-acetamide (caroxazone), has been synthesized by condensing N-(2-hydroxylbenzyl/glycinamide with 14C phosgene. Metabolic studies were performed administering the labelled drug to man and recovering metabolites from the urines. Beside the unchanged drug, five metabolites were identified and confirmed by synthesis, namely (3,4-dihydro-3-carboxamidomethyl-2-oxo-2H-1,3-benzoxazin-4-yl)urea (IX), N-carboxamidomethyl o-hydroxymethylphenyl carbamate (V), 4-methoxy-2-oxo-2H-1,3-benzoxazine-3(4H)acetamide (VIIIa), 2-oxo-2H-1,3-benzoxazine-3(4H)acetic acid (III) and 4-hydroxy-2-oxo-2H-1,3-benzoxazine-3(4H)acetamide (IV).

Amides↗
PubMedDate not supplied

[Individualization of the "presumptive risk" of hypertensive crisis using fractals interpolation of the 24-hour arterial pressure. Study of patients with essential hypertension].

PURPOSE: The present study applies the "fractal interpolation" (FI) to blood pressure that was nonivasively and ambulatorily monitored over a day-night period in essential hypertensives. The purpose is the identification of cases who are at a "presumptive risk" (PR) for hypertensive crisis. MATERIALS AND METHODS: The investigation was performed on 380 ascertained cases of essential hypertension, who underwent a non-invasive ambulatory monitoring of 24-h blood pressure. The FI was applied to the ambulatory mean arterial pressure. RESULTS: The FI showed that the PR of hypertensive crisis can be found in 14% of the investigated essential hypertensive patients. Such a risk is not significantly higher in dippers as compared to non-dippers, and in those who showed a significant blood pressure circadian rhythm as compared to those who showed the blood pressure circadian rhythm to be abolished. Furthermore, no significant difference was found between the cases "at risk" and "not at risk" as far as the spectrum of harmonic formants of the 24-h blood pressure pattern is concerned. CONCLUSIONS: The PR of hypertensive crisis is not correlated to the dipping/nondipping condition, circadian rhythmicity and complex harmonic structure of 24-h blood pressure pattern. Its occurrence depends essentially from the disorder that is detectable in 24-h blood pressure pattern. Therefore, such a PR in essential hypertensives may be attributed to the mechanisms, likely neurovegetative, which confer a non-linear chaotic variability to 24-h blood pressure values.

Adult↗