Cone Beam Computed Tomography in observing the presence and location of canalis sinuosus.

OBJECTIVE: Cone Beam Computed Tomography (CBCT) was used to observe and describe the distribution of canalis sinuosus (CS) in the Chinese population and the location of CS in the maxillary alveolar bone, so as to help oral surgeons evaluate the intraoperative risk and prognosis before maxillary surgery and reduce the complications caused by the injury of this structure in anterior surgery. PATIENTS AND METHODS: CBCT images of 600 patients admitted from 2021 to 2022 were collected to observe the anatomical structure of CS in the maxillary region. The following parameters were recorded: age, sex, number of CS, left and right distribution of CS, CS diameter, and location. Statistical analysis was performed on all of the collected data. RESULTS: The discovery rate of CS in this study was 59.75%, and it is commonly found in the lateral incisor area (64.82%). No significant difference can be found in the presence and number of CS in different gender and age groups (p>0.05). CONCLUSIONS: The use of high-resolution CBCT before implantation is of irreplaceable significance in the diagnosis and analysis of CS, which is conducive to reducing implantation complications and failure rate. The incidence of CS was independent of age or sex, while the location of CS was statistically significant.

Is chronic obstructive pulmonary disease an independent predictor for adverse outcomes in coronavirus disease 2019 patients?

OBJECTIVE: This study aimed to investigate whether pre-existing chronic obstructive pulmonary disease (COPD) was an independent predictor for adverse outcomes in coronavirus disease 2019 (COVID-19) patients. MATERIALS AND METHODS: We searched electronic databases, including PubMed, Web of Science, EMBASE, and Chinese National Knowledge Infrastructure (CNKI) to screen for eligible articles. A quantitative meta-analysis was performed on the basis of adjusted effect estimates. RESULTS: We observed that COPD was significantly associated with an increased risk of adverse outcomes in COVID-19 patients, which is based on 18 studies with 26,075 cases reporting adjusted effect estimates (pooled effect = 1.53, 95% confidence interval (CI): 1.29-1.8; I2 = 35.4%, random-effects model). CONCLUSIONS: We found that pre-existing COPD was an independent risk factor for predicting the adverse outcomes in COVID-19 patients.

[Evaluation of lower facial esthetics in females with different skeletal patterns].

Objective: To evaluate lower facial profile in females in different skeletal patterns. Methods: Investigation pictures of three females with beautiful lower facial profiles from Department of Orthodontics, Henan Stomatological Hospital were collected. The skeletal patterns of these females were classified as average, low and high angle, respectively.Upper lip process point (UL) was moved backwards horizontally to reach towards the E line and go even further gradually in above pictures. The distance changed according to E line was defined as DE value. If UL was in front of E line,DE value was denoted as positive, or else negative. Collectively, we obtained 30 pictures (10 pictures in each skeletal facial type) with different DE values (-5, -4, -3, -2, -1, 0, 1, 2, 3, 4 mm), which were divided into average, low and high angle group according to the skeletal facial type. The pictures were evaluated by 144 randomly-selected adult orthodontic patients [66 males, 78 females, aged (29.4±7.7) years] who visited Department of Orthodontics, Henan Stomatological Hospital from June to September, 2019 and 138 orthodontists (including qualified orthodontists and postgraduate orthodontic students [60 males, 78 females, aged (32.2±7.1) years] who participated orthodontics conferences in Henan Stomatological Hospital in June, 2019. The acceptance rate was calculated and rate above 60% was deemed as acceptable DE range. Evaluators were also asked to choose the most esthetic profiles for the best DE value in each skeletal facial type.Data discrepancy was analyzed using Kruskal-Wallis analysis and chi-square test. Results: Most accepted DE was -2 mm among total investigators including orthodonticpatients and orthodontists. There was no difference in total acceptance rate between orthodontists and patients (P>0.05). There was statistic difference in total acceptance rate in different skeletal patterns between orthodontic patients and orthodontists (P<0.05). In total investigators, total acceptance rate was 62.1% (1 752/2 820) in average angle group, 55.4%(1 563/2 820) in high angle group and 33.5%(946/2 820) in low angle group, respectively. Acceptable DE range in three facial types was -4~2 mm (average angle), -2~2 mm (high angle) and -2~-1 mm (low angle), respectively. Conclusions: According to the evaluation of both orthodontic patients and orthodontists, the best DE was-2 mm.Total acceptance rate and acceptable DE range ranked first in average angle group, second in high angle group and third in low angle group.

[Comparison of long-term efficacy between watch and wait strategy and total mesorectal excision in locally advanced rectal cancer patients with clinical complete response after neoadjuvant therapy].

Objective: To compare long-term efficacy between watch and wait (W&W) strategy and total mesorectal excision (TME) in patients who were diagnosed with locally advanced rectal cancer (LARC) and attained clinical complete response (cCR) after neoadjuvant chemoradiotherapy (nCRT). Methods: A retrospective cohort study was carried out. A total of 238 patients with stage II-III LARC exhibiting cCR after nCRT in Sun Yat-sen University Cancer Center from September 16, 2010 to January 9, 2018 were enrolled. Patients who were diagnosed with other malignant tumor within 5 years, did not receive regular follow-up in our center for more than 1 year and had no complete examination items after nCRT were excluded. Of 238 patients, 151 were male and 87 were female with a median age of 57 (27-83) years old. According to TNM stage, 61 cases were cII, 177 cases were cIII. Concurrent chemoradiotherapy (CCRT) was performed in 20 patients. CCRT plus induction/consolidated chemotherapy was performed in 218 patients. Intensity-modulated radiotherapy (IMRT) was applied to radiotherapy. The median radiation dose was 50 Gy/25 Fr for both the primary tumor and clinical target volumes, and the total dose was 45.0 to 50.6 Gy for 227 patients. In 27 patients, single-agent fluorouracil or capecitabine was used as concurrent chemotherapy. But in the other 211 patients, a combined regimen of oxaliplatin and fluorouracil or capecitabine was used. After nCRT, 59 and 179 patients received W&W (W&W group) and TME 6-12 weeks later (TME group), respectively. After the ending of treatment, patient was interviewed one time every 3 months and after 3 years, one time every six months. Overall survival (OS) rate, distant-metastasis-free survival (DMFS) rate, and local-recurrence-free survival (LRFS) rate were compared between two groups. The salvage treatment and sphincter preservation rate were analyzed. The survival curve was drawn with Kaplan-Meier method and evaluated by log-rank method. Results: In the cases treated with TME, the median interval from nCRT to surgery was 59 days. The postoperative pCR rate was 63.1%(113/179). The median follow-up time of the whole cohort was 41.8 (12.0-99.0) months. The 3-year and 5-year OS rates were 98.4% and 96.5%; the 3-year and 5-year LRFS rates were 96.5% and 96.5%; the 3- and 5-year DMFS rates were 91.0% and 87.9%, respectively. The 3-year OS rates in the W&W group and the TME group were 100% and 97.9%; the 5-year OS rates in W&W group and the TME group were 90.6% and 97.9% (P=0.339); The 3-year local recurrence rate (LRR) in the W&W group was 12.9% (7 cases recurred within 2 years), which was significanthy higher then that in the TME group (0.6%, P=0.003). Salvage surgery was successful in 5/6 cases. After salvage surgery, LRFS rate was not significantly different between the two groups (P=0.137). The 3-year DMFS rate in the W&W group and the TME group were 88.4% and 81.1%, whose difference was not significant (P=0.593). Recurrence with simultaneous metastasis was seen in 3/7 cases of the W&W group. The sphincter was preserved in 89.8% (53/59) of patients in the W&W group, which was significantly higher than 73.7% (132/179) in the TME group (P<0.001). When distance of tumor from the anal verge was ≤ 5 cm, the sphincter preservation rate (SPR) in the W&W group was 88.0% (44/50), which was significantly higher than the 54.4% (56/103) in the TME group (P<0.001). Conclusions: W&W is safe and feasible for patients with LARC and cCR after nCRT. The results should be verified by further clinical trials.

Effect of GGCX on the differentiation function of osteoporosis bone marrow mesenchymal stem cells through regulating TGFß/smad signaling pathway.

OBJECTIVE: Osteoporosis (OP) has a high incidence and can be found in multiple age groups. The bone marrow mesenchymal stem cells (BMSCs) have the potential for self-renewal and multi-directional differentiation, which are often used for investigating the differentiation function of osteoporosis bone marrow mesenchymal stem cells. γ-glutamyl carboxylase (GGCX) is a carboxylase-related carboxylase and was observed to be abnormally expressed in osteoarthritis. However, the role and related mechanisms of GGCX in OP have not been fully elucidated. This work aimed to evaluate the effect of GGCX on the differentiation function of BMSCs. PATIENTS AND METHODS: Sprague-Dawley rats were randomly divided into the OP group prepared by ovariectomy and sham group. GGCX expression was tested by enzyme-linked immunosorbent assay (ELISA). BMSCs were isolated from OP rats and transfected with pcDNA-GGCX plasmids. BMSC proliferation was detected by tetrazolium salt colorimetry (MTT) assay. The osteogenic and adipogenic differentiation of BMSCs was analyzed by alizarin red staining and oil red O staining. The ALP activity was determined by alkaline phosphatase (ALP) activity colorimetric assay. Real time-PCR was used to test the expressions of osteogenesis-related genes RUNX2 and OPN mRNA. Western blot was adopted to assess the TGFß/smad signaling pathway activity. RESULTS: GGCX expression was significantly decreased in the serum of OP rats compared with the sham group (p < 0.05). The transfection of pcDNA-GGCX plasmid significantly promoted BMSC cell proliferation, increased calcified nodule formation, inhibited adipogenic differentiation, enhanced ALP activity, elevated RUNX2, and OPN mRNA expressions, and upregulated TGFß1, Smad2, and Smad7 expressions (p < 0.05). CONCLUSIONS: GGCX secretion is reduced in osteoporosis. GGCX can regulate osteoporosis via promoting the TGFß/smad signaling pathway, facilitating BMSCs osteogenic differentiation, and inhibiting BMSCs adipogenic differentiation.

[Transition of treatment strategy for locally advanced rectal cancer towards "watch and wait"].

Therapeutic goal for locally advance rectal cancer (LARC) patients includes long-term survival and function preservation of pelvic organs. During the recent two decades, treatment strategy for LARC is gradually shifing to minimally invasive surgery, even avoiding a major surgery. "Watch and wait (W&W)" strategy is effective in dramatically decreasing surgical trauma and significantly improving preservation of defecation, urination and sexual function. Total neoadjuvant therapy (TNT) shifts all or part of adjuvant chemotherapy to the neoadjuvant phase and has showed obvious advantage in tumor shrinkage and complete clinical response (cCR) achievement. This article will summarize the transition of treatment strategy of LARC towards W&W from standard treatment. After more than ten years of development, both NCCN and ESMO guidelines recommend stratified neoadjuvant treatment considerations based on distinct risk classifications and especially suggest TNT for LARC patients with advanced diseases, which affirms the value of TNT in tumor shrinkage. Although accumulating data show that pelvic control and organ preservation using W&W strategy after cCR is equal or non-inferior to standard surgery, impact on long-term survival still needs prospective randomized controlled study; no consensus has been achieved for the detail of the W&W strategy. Thus W&W strategy is suggested to applied in hospitals specialized in the treatment of rectal cancer within the framework of multiple disciplinary treatment. In view of special medical conditions of our country, we still need to accumulate more experience and data of W&W strategy for rectal cancer patients with appeals for sphincter preservation and actively participate in international researches.

Response of broiler chickens to dietary soybean bioactive peptide and coccidia challenge.

Growth performance, nutrient digestibility, jejunal morphology, plasma cytokine, and gene expression responses of broiler chickens (Cobb 500) to graded concentrations of dietary soybean bioactive peptide (SBP) and coccidia challenge (CC) were investigated in 2 experiments. In experiment 1, 384 male broiler chicks were used to investigate the effect of graded dietary concentrations of SBP on growth performance, nutrient digestibility, and intestinal morphology in a randomized complete block design with 8 replicate cages and 6 diets. Corn-soybean meal-based diet was supplemented with 0, 1, 2, 3, 4, and 5 g of SBP/kg of diet. There were linear effects (P < 0.05) of graded concentrations of SBP on BW, BW gain, gain:feed, ileal villus height, and jejunal crypt depth at day 22 post hatching. There were linear effects (P < 0.01) of graded SBP concentrations on Ileal DM and energy digestibility. Experiment 2 was conducted to investigate the immune-protective properties of SBP on broiler chickens during a coccidia challenge. A total of 256 male broiler chicks were randomly assigned to 8 replicate cages in a 2 × 2 factorial arrangement of treatments with 2 SBP levels (0 or 4 g/kg of diet) and with or without CC. On day 14 post hatching, birds in the challenged group received 20×, which is twice the recommended coccidia vaccine dose of 25 doses/kg BW, whereas the non-challenged group received physiological saline. Dietary SBP ameliorated the CC-induced effect (P = 0.01) on gain: feed. Coccidia challenge reduced (P < 0.05) jejunal villi height, whereas dietary SBP supplementation increased (P < 0.05) jejunal villi height. Dietary SBP attenuated the CC-induced effects (P < 0.05) on the expression of plasma IL-1ß, transforming growth factor-ß, claudin-1, and occludin genes. In conclusion, dietary SBP improved growth performance, nutrient digestibility, and jejunal morphology. In addition, dietary SBP reduced the impact of coccidia challenge, and may be beneficial in the feed of broiler chickens for alleviation of health-related effects of coccidia infection.

Propagation Dynamics Associated with Resonant Magnetic Perturbation Fields in High-Confinement Mode Plasmas inside the KSTAR Tokamak.

The propagation dynamics of resonant magnetic perturbation fields in KSTAR H-mode plasmas with injection of small edge perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the perturbation field first excites a plasma response on the q=3 magnetic surface and then propagates inward to the q=2 surface with a radially averaged propagation velocity of resonant magnetic perturbations field equal to 32.5 m/ s. As a result, the perturbation field brakes the toroidal rotation on the q=3 surface first causing a momentum transport perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic perturbations field is larger than the radial propagation velocity of the perturbation in the toroidal rotation.

[Analysis of clinical prognosis and the correlation between bile duct injury after transcatheter arterial chemoembolization and the level of hepatic arterial embolization in patients with hepatocellular carcinoma].

Objective: To evaluate the correlation between bile duct injury after transcatheter arterial chemoembolization and the level of hepatic arterial embolization, and to analyze the clinical prognosis of hepatocellular carcinoma patients. Methods: From January18, 2012 to December18, 2014, 21 patients underwent TACE for HCC were retrospectively reviewed, including patients' clinical and pathological data. The clinical outcome and relevant factors for bile duct injury were analyzed. Results: A total of 21 patients were identified with bile duct injury at our single institution. All patients received 48 TACE treatments, including proper hepatic artery (14), left hepatic artery (3), the right hepatic artery (10), left and right hepatic artery (9) and tumor artery branches (12). Thirty-five bile duct injury occurred in 21 patients: 7 cases was close to the tumor, 2 distant to the tumor, 7 at right liver, 2 left liver, 11 both lobes of liver and 6 hepatic hilar. After medical conservative treatment and biliary tract inside and outside drainage, liver function of 10 cases were improved. In four patients with hepatic bile duct stricture and biloma, the effect of drainage was not obvious, which subsequently caused biliary complications such as infection, gallbladder and common bile duct stones. Three patients with liver cirrhosis at decompensation stage developed complications, and one of them died of hepatic encephalopathy. Four patients experienced tumor recurrence during the follow-up period. Conclusions: The location of bile duct injury after transcatheter arterial chemoembolization is quite consistent with the level of hepatic arterial embolization. There may be some blood vessels mainly involved in blood supply of biliary duct. Complete embolism of these vessels may lead to bile duct injuries. Biliary drainage is ineffective in patients with hilar bile duct stricture, and can lead to complications of biliary tract later on.

[Value of intravoxel incoherent motion diffusion-weighted imaging in differential diagnosis of benign and malignant hepatic lesions and blood perfusion evaluation].

Objective: To investigate the value of intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) in the differential diagnosis and blood perfusion evaluation of benign and malignant hepatic lesions. Methods: A retrospective analysis was performed for 86 patients (96 lesions) with pathologically or clinically confirmed hepatic lesions or hepatic lesions diagnosed based on follow-up results, among whom 48 had malignant lesions (53 lesions) and 38 had benign lesions (43 lesions). The patients underwent conventional magnetic resonance (MR) plain scan, contrast-enhanced scan, and diffusion-weighted imaging (DWI) with different b values (b = 0, 50, 100, 150, 200, 400, 600, 800, 1 000, and 1 200 s/mm2) to determine the parameters of the double exponential model for intravoxel incoherent motion (IVIM): fast diffusion coefficient Dfast, slow diffusion coefficient Dslow, and percentage of fast-diffusion constituent F value. The patients were divided into groups according to the blood supply to lesions on conventional MR plain scan and contrast-enhanced scan, and there were 47 lesions in abundant blood supply group and 49 in poor blood supply group. The data for analysis were Dfast, Dslow, and F values of benign/malignant lesion groups and abundant/poor blood supply groups. The independent samples t-test was used for statistical analysis; the independent samples non-parametric test Mann-Whitney U test was used for the comparison of F value; the receiver operating characteristic (ROC) curve was used to evaluate the value of above parameters in the differentiation of benign and malignant lesions and blood supply evaluation. Results: Compared with the malignant lesion group, the benign lesion group had significantly higher Dslow, and F values (P< 0.001 orP= 0.001) and a higher Dfast value (P= 0.053). Compared with the poor blood supply group, the abundant blood supply group had significantly higher Dfast and F values (P< 0.001 orP= 0.001) and a higher Dslow value (P= 0.185). According to the ROC curve, the cut-off values of Dslow, Dfast, and F values in the diagnosis of benign/malignant hepatic lesions and evaluation of abundant/poor blood supply were 1.18×10-3mm2/s, 27.20×10-3mm2/s, 20.25%, 1.17×10-3mm2/s, 20.30×10-3mm2/s, and 17.80%, respectively, with sensitivities, specificities, accuracy, and areas under the ROC curve of 90.69%/92.45%/91.66%/0.938, 46.51%/73.58%/61.45%/0.589, 74.41%/50.94%/62.50%/0.653, 59.57%/57.14%/58.33%/0.559, 55.32%/63.26%/59.37%/0.618, and 93.61%/89.79%/90.62%/0.961, respectively. Conclusion: The parameter of the double exponential model for IVIM, Dslow value, has a certain value in the differential diagnosis of benign and malignant hepatic lesions, and F value can show blood perfusion in benign and malignant hepatic lesions without the need for contrast-enhanced scan, which provides a reference for the qualitative diagnosis of liver tumor.

Late toxicities after intensity-modulated radiotherapy for nasopharyngeal carcinoma: patient and treatment-related risk factors.

BACKGROUND: The objective of this study is to analyse the factors affecting late toxicity for nasopharyngeal carcinoma (NPC) patients treated with intensity-modulated radiotherapy (IMRT). METHODS: Seven hundred and eighty-nine consecutive NPC patients treated with IMRT at our centre from January 2003 to February 2008 were retrospectively analysed. Radiotherapy-related complications were categorised using the RTOG Late Radiation Morbidity Scoring Criteria and the Common Terminology Criteria for Adverse Events (Version 3.0). Two hundred and thirty-three patients were treated with IMRT alone (group 1) and 556 patients underwent cisplatin-based chemotherapy (group 2). RESULTS: Median follow-up was 65 months (range, 4-106 months). The 5-year major late toxicity rate was significantly greater in group 2 than group 1 (63.2% vs 42.0%, P<0.001). Multivariate analyses showed that N category, T category and chemotherapy were significant factors. The maximal dose (Dmax) to the temporal lobe was a significant factor affecting temporal lobe injury (TLI), with a hazard ratio of 1.26 (95% confidence interval (CI), 1.18-1.35; P<0.001) per 1-Gy increase. The 5-year TLI rate increased from 0.8% for 284 lobes with Dmax <65.77 Gy to 27.1% for 176 lobes with greater doses (P<0.001). Logistic regression showed that the hazard ratio attributed to the parotid gland mean dose was 1.36 (95% CI, 1.21-1.53; P<0.001) per 1-Gy increase. Chemotherapy was not a significant factor (P=0.211). CONCLUSION: With the application of IMRT, the incidence of radiation-related complications has been reduced except for TLI. The significant factors affecting the risk of TLI included T category, chemotherapy and Dmax.

Physics of stimulated L→H transitions.

We report on model studies of stimulated L→H transitions. These studies use a novel reduced mesoscale model. Studies reveal that L→H transitions can be triggered by particle injection into a subcritical state (i.e., P

A novel marine drug, SZ-685C, induces apoptosis of MMQ pituitary tumor cells by downregulating miR-200c.

OBJECTIVE: We found a novel marine drug, SZ-685C, that was isolated from the secondary metabolites of a mangrove endophytic fungus (No. 1403) collected from the South China Sea, which has been reported to inhibit the proliferation of certain tumor cells. However, its anticancer mechanism remains unknown. The aims of this study were to observe the effectiveness of SZ-685C on pituitary adenoma cells and determine the underlying mechanisms of action. METHODS: A rat prolactinoma cell line, MMQ, was used in this study. A dose escalation of SZ-685C was performed on this cell line, and cell viability was assessed using an MTT assay. Hoechst 33342, Annexin V-FITC/PI, TUNEL staining and flow cytometry were used to evaluate the extent of apoptosis at each concentration of SZ-685C. The effect of SZ-685C on prolactin expression was also evaluated using RT-PCR and immunoblotting. Quantitative RT-PCR was used to detect the expression of miR-200c in SZ-685C-stimulated MMQ cells and pituitary adenoma tissues. This miRNA was then overexpressed in MMQ cells via transfection of a miR-200c mimic to identify the mechanism underling the anti-tumor effect of SZ-685C. RESULTS: SZ-685C inhibited MMQ cell growth in a dose-dependent manner but showed little toxicity toward rat pituitary cells (RPCs). The IC50s of SZ-685C in MMQ cells and RPCs were 13.2 ± 1.3 mM and 49.1 ± 11.5 mM, respectively, which was statistically significant. Increasing numbers of apoptotic cells were observed in response to escalating concentrations of SZ-685C, and the expression level of prolactin (PRL) was inhibited. Nevertheless, the level of PRL mRNA was unchanged. Additionally, miR-200c was upregulated in MMQ cells compared with RPCs, and downregulation of miR- 200c was observed in SZ-685C-treated MMQ cells. Furthermore, the overexpression of miR-200c weakened the effect of SZ-685C-induced apoptosis of MMQ cells. CONCLUSIONS: Our results suggest that SZ-685C induces MMQ cell apoptosis in a miR-200c-dependent manner. Therefore, SZ-685C might be a useful alternative treatment for pituitary adenoma.

Time-frequency analysis for microwave reflectometry data processing in the HL-2A tokamak.

The Choi-Williams distribution (CWD) technique is introduced as a time-frequency tool for processing data measured from the new developed homodyne and the fixed frequency reflectometry in the HL-2A tokamak. The comparison between spectrogram and CWD for the simulated signal is presented. It indicates that the CWD can greatly improve the representation of the time-frequency content of the multi-components signal. Its effectiveness is demonstrated through two applications in HL-2A, which are the extraction of beat frequencies from the frequency modulated-continuous wave reflectometry (FM-CW) and the characterizing of the fluctuations. The density profile inversed from the group delay of the FM-CW and the density fluctuations deduced from the fixed-frequency reflectometry would be more reliable and accurate by using the CWD technique.

Observation of turbulence suppression after electron-cyclotron-resonance-heating switch-off on the HL-2A tokamak.

The formation of a transient internal transport barrier (ITB) is observed after the electron-cyclotron-resonance-heating (ECRH) switch-off in the HL-2A plasmas, characterized by transient increase of central electron temperature. The newly developed correlation reflectometer provided direct measurements showing reduction of turbulence in the region of steepened gradients for the period of ITB formation triggered by the ECRH switch-off. Furthermore, the reduction of core turbulence is correlated in time with the appearance of a low-frequency mode with a spectrally broad poloidal structure that peaks near zero frequency in the core region. These structures have low poloidal mode number, high poloidal correlation, and short radial correlation and are strongly coupled with high-frequency ambient turbulence. Observation indicates that these structures play important roles in the reduction of the core turbulence and in improvements of the core transport after the off-axis ECRH is turned off.

Observation of a spontaneous particle-transport barrier in the HL-2A tokamak.

Using the profile analysis, the density perturbation transport analysis, and the Doppler reflectometry measurement, for the first time a spontaneous and steady-state particle-transport barrier has been evidenced in the Ohmic plasmas in the HL-2A tokamak with no externally applied momentum or particle input except the gas puffing. A threshold in density has been found for the observation of the barrier. The particle diffusivity is well-like, and the convection is found to be inward outside the well and outward inside the well. The formation of the barrier coincides with the transition between the trapped electron mode and the ion temperature gradient driven mode.

A method of particle transport study using supersonic molecular beam injection and microwave reflectometry on HL-2A tokamak.

A method of the particle transport study using supersonic molecular beam injection (SMBI) and microwave reflectometry is reported in this paper. Experimental results confirm that pulsed SMBI is a good perturbation source with deeper penetration and better localization than the standard gas puffing. The local density modulation is induced using the pulsed SMBI and the perturbation density is measured by the microwave reflectometry. Using Fourier transform analysis for the local density perturbation, radial profiles of the amplitude and phase of the density modulation can be obtained. The experimental results in HL-2A show that the particle injected by SMBI is located at about r/a=0.65-0.75. The position of the main particle source can be determined through three aspects: the minimum of the phase of the first harmonic of the Fourier transform of the modulated density measured by microwave reflectometry; the H(a) intensity profile and the local density increase ratio. The maximum of the amplitude of the first harmonic shifts often inward relative to the particle source location, which indicates clearly there is an inward particle pinch in this area. Good agreement has been found between the experimental results and the simulation using analytical transport model. The particle diffusivity D and the particle convection velocity V have been obtained by doing this simulation. The sensitivity in the transport coefficients of the amplitude and the phase of the density modulation has been discussed.