Determination of phenylacetic acid in cerebrospinal fluid by gas chromatography-mass spectrometry.

Using gas chromatography-mass spectrometry, we developed a sensitive and reliable technique to measure phenylacetic acid (PAA), an oxidatively deaminated metabolite of beta-phenylethylamine (PEA), in small amounts of cerebrospinal fluid (CSF). In a preliminary analysis, PAA concentrations in depressive patients were significantly lower than those in controls, while there were no differences in PAA levels between schizophrenic patients and controls. This suggests a possible link between the decreased PEA metabolism in the brain and the etiology of depression. However, further studies are needed to clarify the effects of neuroleptics and antidepressants on PAA levels in CSF, since the samples were obtained without regard to medication in the present study. In control subjects, a U-shaped distribution was obtained when the values of PAA were plotted as a function of age. There were no sex differences and no significant concentration gradients in CSF PAA levels.</p

Effects of thyrotropin-releasing hormone in chronic schizophrenic patients

The effects of oral and intravenous thyrotropin-releasing hormone (TRH) were studied in 11 male, chronic schizophrenic inpatients in an open trial and a double-blind, crossover design. The general beneficial effects of TRH as assessed on the Brief Psychiatric Rating Scale were not obtained, although improvement of contact, apathy and emotional rapport was observed in a few patients. Serum prolactin, L-triiodothyronine and thyroxine were assayed throughout the study. Since the effects of TRH on behavior were not related to changes in these endocrine factors, the mechanism of action might be independent of its original functions on the pituitary-thyroid axis.</p

Homovanillic acid in human cerebrospinal fluid.--Its concentration gradient and reduced levels in patients with epilepsy

The homovanillic acid (HVA) concentrations in the lumbar cerebrospinal fluid (CSF) were determined in 38 epileptic and 39 control patients. The mean concentration of HVA was 23.9 ng/ml +/- 2.8 SEM for the epileptic group and 30.2 ng/ml +/- 2.1 SEM for the control group, respectively. Thus, HVA was significandly reduced in the patients with epilepsy compared with the controls. The mean HVA in the female patients was higher than in the male patients in both groups but this failed to reach statistical significance. There was no apparent relationship between the degree of reduced HVA concentration and other clinical indexes of the epilepsy (age, type and frequency of seizures, and anticonvulsant medication). For the determination of concentration gradient of HVA three fractions of the spinal CSF were obtained from 11 patients. A pronounced gradient of HVA concentration was found with a ratio of 1 : 1.46 : 1.97 for the first, second and third fractions. This suggests that a standardized conditions for collecting CSF should be employed to study HVA levels in humans.</p

Effect of long-term storage on monoamine metabolite levels in human cerebrospinal fluid.

Concentrations of homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were measured in human cerebrospinal fluid (CSF) following long-term storage at -20 degrees C for intervals of three to 60 months. No significant changes in HVA levels were detected in CSF stored for up to 60 months. On the other hand, 5-HIAA concentrations remained stable for up to 6 months, but decreased significantly in the specimens stored for longer time intervals. The results indicate that 5-HIAA should be determined within 6 months after CSF collection, while HVA determinations may be delayed.</p

Self-Sustained Divertor Oscillation Driven by Magnetic Island Dynamics in Torus Plasma

A new type of self-sustained divertor oscillation is discovered in the Large Helical Device stellarator, where the peripheral plasma is detached from material diverters by means of externally applied perturbation fields. The divertor oscillation is found to be a self-regulation of an isolated magnetic field structure (the magnetic island) width induced by a drastic change in a poloidal inhomogeneity of the plasma radiation across the detachment-attachment transitions. A predator-prey model between the magnetic island width and a self-generated local plasma current (the bootstrap current) is introduced to describe the divertor oscillation, which successfully reproduces the experimental observation

Experimental study of non-inductive current in Heliotron J

It is important to control non-inductive current for generation and steady-state operation of highperformance plasmas in toroidal fusion devices. Helical devices allow dynamic control of non-inductivecurrent through a wide variety of magnetic configurations. The reversal of non-inductive current consisting of bootstrap current and electron cyclotron driven current in electron cyclotron heating plasmas has been observed in a specific configuration at low density in Heliotron J device. By analyzing thenon-inductive current for normal and reversed magnetic fields, we present experimental evidence for the reversal of bootstrap current. Our experiments and calculations suggest that the reversal is caused bya positive radial electric field of about 10 kV/m. Moreover, we show that the typical electron cyclotron current drive efficiency in Heliotron J plasma is about 1.0 × 1017 AW?1m?2, which is comparable to other helical devices. We have found that the value is about 10 times lower than that of tokamak devices. This might be due to an enhanced Ohkawa effect by trapped particles

Three-dimensional structure of radiative cooling in impurity seeded plasmas in the Large Helical Device

Three-dimensionally localization of radiative cooling due to nitrogen (N2) seeding for divertor detachment was detected experimentally. Since the localization along some magnetic field lines induces toroidal asymmetry of heat load reduction on divertor plates, it should be avoided for fusion reactors. The three-dimensionally localized structure was extracted using Principal Component Analysis (PCA) from two-dimensional radiation images measured with an InfraRed imaging Video Bolometer (IRVB). By applying PCA to 34 images each in N2 seeded plasmas with toroidally-asymmetric heat load reduction and in neon (Ne) seeded plasmas with toroidally-symmetric heat load reduction, a radiation feature in N2 seeded plasmas was found as one of the principal components (PC). The three-dimensional transport code EMC3-EIRENE indicated that the ionization in one of the divertor legs is enhanced in nitrogen seeding compared with Ne seeding due to the difference in the first ionization energy. The magnetic field lines from the divertor leg were along the extracted radiation structure and were terminated by the divertor where the heat load decreased due to the N2 seeding. These results indicate that three-dimensionally localized structure of radiative cooling was detected experimentally

A mechanism of ion temperature peaking by impurity pellet injection in a heliotron plasma

Experiments on the Large Helical Device with the injection of carbon pellets into discharges of low density have demonstrated a significant reduction of the ion heat conduction in the plasma core and an increase in the central ion temperature by a factor of up to 2. These results are interpreted in the framework of a transport model elaborated on the basis of those applied previously to explain the improvement in confinement by impurity seeding into the tokamak devices TEXTOR and JET. The calculations performed reproduce well the strong peaking of the ion temperature profile with increasing carbon density nZ and the consequent drop in the confinement as nZ exceeds a certain critical level. The importance of different elements in the model, such as braking of the main ion rotation by friction with impurity ones and the shape of the density profiles, are investigated. A qualitative assessment of the applicability under fusion reactor conditions, e.g. of much higher plasma density and heating power, is performed

Confinement improvement during detached phase with RMP application in deuterium plasmas of LHD

In order to explore the compatibility of good core plasma performance with divertor heat load mitigation, the interaction between cold edge plasma and core plasma transport, including the edge transport barrier (ETB), has been analysed in the divertor detachment discharges of deuterium plasmas in LHD with resonant magnetic perturbation (RMP) field application. The RMP application introduces a widened edge stochastic layer and sharp boundary in the magnetic field structure between the confinement region and the edge stochastic layer. The widened edge stochastic layer enhances impurity radiation and provides stable detachment operation as compared with the case without RMP. It is found that ETB is formed at the confinement boundary at the onset of detachment transition. However, as the detachment deepens, the resistive pressure gradient-driven MHD mode is excited, which degrades the ETB. At the same time, however, the core transport decreases to keep global plasma stored energy (Wp) unchanged, showing clear core-edge coupling. After a gradual increase of density fluctuation during the MHD activity, a spontaneous increase of Wp and the recovery of ETB are observed while the detachment is maintained. Then, the coherent MHD mode ceases and ELM-like bursts appear. In the improved mode, impurity decontamination occurs, and the divertor heat load increases slightly. Key controlling physical processes in the interplay between core and cold edge plasma are discussed. A comparison between deuterium and hydrogen plasmas shows that hydrogen plasmas exhibit similar features to the deuterium ones in terms of density and magnetic fluctuations, impurity decontamination towards higher confinement, etc. But most of the features are modest in the hydrogen plasmas and thus no clear confinement mode transition with clear ETB formation is defined. Better global confinement is obtained in the deuterium plasmas than the hydrogen ones at a higher radiation level

Three-dimensional impurity transport modeling of neon-seeded and nitrogen-seeded LHD plasmas

Modeling of impurity-seeded plasma in Large Helical Device is presented for the first time by using the three-dimensional transport code EMC3-EIRENE. High and low recycling coefficients for impurity ions are assumed to include low and high absorption rates on wall surfaces due to low and high chemical activity of neon and nitrogen, respectively. Radiation power measured by two bolometer systems and particle flux measured by divertor probes installed in multiple toroidal sections are utilized to determine impurity amount in the plasma. The toroidal uniformity and the non-uniformity of a divertor flux reduction observed experimentally for neon and nitrogen seeding, respectively, are reproduced by the model. Validations by measurements and deviations between the model and the experiment are discussed