Perturbed Ion Temperature and Toroidal Flow Profile Measurements in Rotating Neoclassical Tearing Mode Magnetic Islands.

The perturbed ion temperature and toroidal flow were measured in rotating neoclassical tearing modes (NTM) in a tokamak for the first time. These toroidally and radially resolved profiles were obtained by impurity ion spectroscopy in a 2,1 NTM in DIII-D. In agreement with drift-kinetic simulations, the electron temperature profile is flat, while the ion temperature gradient is restored across the magnetic island O point in the presence of fast ions; the perturbed flow has minima in the O points and maxima at the X points. These measurements provide the first confirmation of the theoretically expected ion temperature and flow response to a magnetic island needed to predict the NTM onset threshold scaling for ITER and other future tokamaks.

Septoplasty: early (first year) and late (fourth year) post-operative results in 604 patients.

OBJECTIVE: As prospective outcomes of septoplasty with or without turbinoplasty beyond the first year are few and have diverging results, this study evaluated later septoplasty results three to four years post-operatively. METHODS: Patients undergoing septoplasty completed the Nasal Surgical Questionnaire pre-operatively, and at 6-12 months (early post-operative assessment) and 36-48 months (late post-operative assessment) after surgery. Primary outcome was visual analogue scale ratings for nasal obstruction (with a scale ranging from 0 to 100). RESULTS: In 604 patients with high response rates, the largest improvements in nasal obstruction were from pre-operative to early post-operative assessments (daytime score reduction = 33.9, night-time reduction 40.5). Nasal obstruction ratings worsened slightly between early and late post-operative assessments (daytime score increase = 5.3, night-time score increase = 9.7). Improvements were better in patients aged over 35 years and in those with pre-operative nasal obstruction scores of more than 62. There were no differences based on surgery type, septal deviation, allergy or smoking. CONCLUSION: Septoplasty improves nasal obstruction in both the first and the fourth year after surgery. Post-operative improvements decline slightly over time but remain significant.

Assessment of non-response in quality control of nasal septal surgery.

OBJECTIVE: This study evaluated the effect of mail non-response on the validity of the results of nasal septal surgery. METHOD: Six months post-operatively, questionnaires with both prospective and retrospective ratings were mailed to patients. Patients who did not respond (non-responders) were contacted by telephone. This study compared two cohorts of patients using different interviewers (a nurse and a surgeon). Cohort one consisted of 182 patients (with 67 per cent mail response), and cohort two consisted of 454 patients (with 64.8 per cent mail response). RESULTS: In both cohorts, the improvement in obstruction scores was significantly better among mail responders than among non-responders (telephone interviewees) using prospective ratings, but worse using retrospective ratings. CONCLUSION: Mail responders had better improvement in nasal obstruction after septoplasty than non-responders. Therefore, low response rates may cause an overestimation of the results. The retrospective ratings obtained through telephone interviews are less reliable because they are influenced by memory and the patients' tendency to give socially acceptable answers.

Good correlation between visual analogue scale and numerical rating scale in the assessment of nasal obstruction.

OBJECTIVE: Results from telephone interviews may be needed to supplement those from mailed questionnaires when response rates are inadequate. This study assessed the correlation between visual analogue scale ratings used in mailed questionnaires and numerical rating scale scores used in telephone interviews. METHODS: Patients scheduled for nasal septal surgery routinely respond to a visual analogue scale of obstruction during the day and at night. In this study, they were also asked to verbally rate their sense of obstruction using whole numbers. RESULTS: There was no significant difference between visual analogue scale and numerical rating scale obstruction scores. CONCLUSION: Ratings of nasal obstruction obtained with a numerical rating scale in telephone interviews are comparable to visual analogue scale scores in mailed questionnaires.

Evaluation of non-response in quality control of nasal septal surgery.

OBJECTIVE: Questionnaires are often used to assess the results of nasal septoplasty, but response rates vary widely. The possible bias caused by non-responders was evaluated to determine the validity of questionnaire results. METHODS: Post-operative questionnaires employing visual analogue scales for nasal obstruction were mailed to 182 patients. The 62 non-responders (34.1 per cent) were contacted by telephone, 58 (93.5 per cent) of whom were contactable and responded orally to the questionnaire. RESULTS: Non-responders were younger, but no different from responders with regard to gender, smoking habits or allergies. Post-operative visual analogue scale obstruction scores were slightly, but not statistically, higher in non-responders. However, because non-responders' pre-operative scores were lower, obstruction scores improved less than in responders. The main reason for not responding was forgetfulness. Some would have preferred an electronic version of the questionnaire. CONCLUSION: Although post-operative obstruction scores did not differ between the groups, nasal obstruction scores improved more among responders than non-responders. Thus, low response rates may cause bias.

Avoiding Tokamak Disruptions by Applying Static Magnetic Fields That Align Locked Modes with Stabilizing Wave-Driven Currents.

Nonrotating ("locked") magnetic islands often lead to complete losses of confinement in tokamak plasmas, called major disruptions. Here locked islands were suppressed for the first time, by a combination of applied three-dimensional magnetic fields and injected millimeter waves. The applied fields were used to control the phase of locking and so align the island O point with the region where the injected waves generated noninductive currents. This resulted in stabilization of the locked island, disruption avoidance, recovery of high confinement, and high pressure, in accordance with the expected dependencies upon wave power and relative phase between the O point and driven current.

Evaluation of a nasal surgical questionnaire designed for monitoring surgical outcomes and comparing different techniques.

OBJECTIVE: This study evaluated a nasal surgical questionnaire designed for monitoring surgical outcomes and comparing different techniques. METHODS: Eighty-three healthy volunteers answered the same questionnaire twice with a minimum interval of five weeks. Three visual analogue scale items were used to assess nasal obstruction during the day, at night and during exercise. Respondents rated nasal obstruction severity by marking on a 10 cm line, with scores ranging from 0 to 100 (measured in millimetres). Other nasal symptoms, considered secondary outcomes, were graded using four-point Likert scales. RESULTS: Mean visual analogue scale scores for nasal obstruction severity experienced during the day, at night and during exercise at initial assessment were 9.99, 12.95 and 11.67, respectively. Thirty-eight per cent of scores indicated no obstruction (scores of 0), 47 per cent indicated mild obstruction (scores 1-30), 13 per cent indicated moderate obstruction (scores 31-70) and 2 per cent indicated severe obstruction (scores 71-100). Males had higher scores than females. The scores for the first and second assessment did not differ, except at night for obstruction in allergic individuals which was considered clinically unimportant. CONCLUSION: The questionnaire reliably assesses nasal symptoms and may be useful for prospective studies of nasal surgery.

IgG4-Related Nasal Pseudotumor.

IgG4-related disease is recognized as one form of autoimmune pancreatitis. During the last ten years, it has also been described in several other organs. We present two patients with lesions showing a histological picture of fibrosis and lymphoplasmacytic infiltrations with abundant IgG4 positive plasma cells at hitherto unreported symmetrical nasal locations. The symmetrical complex consisted of one central lesion in the anterior nasal septum and the two others in each of the lateral nasal walls. The lesions extended from the anterior part of the inferior concha into the vestibulum and caused severe nasal obstruction.

An upgrade of the magnetic diagnostic system of the DIII-D tokamak for non-axisymmetric measurements.

The DIII-D tokamak magnetic diagnostic system [E. J. Strait, Rev. Sci. Instrum. 77, 023502 (2006)] has been upgraded to significantly expand the measurement of the plasma response to intrinsic and applied non-axisymmetric "3D" fields. The placement and design of 101 additional sensors allow resolution of toroidal mode numbers 1 ≤ n ≤ 3, and poloidal wavelengths smaller than MARS-F, IPEC, and VMEC magnetohydrodynamic model predictions. Small 3D perturbations, relative to the equilibrium field (10(-5) < δB/B0 < 10(-4)), require sub-millimeter fabrication and installation tolerances. This high precision is achieved using electrical discharge machined components, and alignment techniques employing rotary laser levels and a coordinate measurement machine. A 16-bit data acquisition system is used in conjunction with analog signal-processing to recover non-axisymmetric perturbations. Co-located radial and poloidal field measurements allow up to 14.2 cm spatial resolution of poloidal structures (plasma poloidal circumference is ~500 cm). The function of the new system is verified by comparing the rotating tearing mode structure, measured by 14 BP fluctuation sensors, with that measured by the upgraded B(R) saddle loop sensors after the mode locks to the vessel wall. The result is a nearly identical 2/1 helical eigenstructure in both cases.

Tokamak operation with safety factor q95 < 2 via control of MHD stability.

Magnetic feedback control of the resistive-wall mode has enabled the DIII-D tokamak to access stable operation at safety factor q(95) = 1.9 in divertor plasmas for 150 instability growth times. Magnetohydrodynamic stability sets a hard, disruptive limit on the minimum edge safety factor achievable in a tokamak, or on the maximum plasma current at a given toroidal magnetic field. In tokamaks with a divertor, the limit occurs at q(95) = 2, as confirmed in DIII-D. Since the energy confinement time scales linearly with current, this also bounds the performance of a fusion reactor. DIII-D has overcome this limit, opening a whole new high-current regime not accessible before. This result brings significant possible benefits in terms of fusion performance, but it also extends resistive-wall mode physics and its control to conditions never explored before. In present experiments, the q(95) < 2 operation is eventually halted by voltage limits reached in the feedback power supplies, not by intrinsic physics issues. Improvements to power supplies and to control algorithms have the potential to further extend this regime.

Endonasal surgery after cocaine abuse: safe at any interval?

Objective. We report a case of poor healing after endonasal surgery for nasal septal perforation ten years after cocaine abuse was ended. Method. The clinical findings are presented. Results. A 35-year-old man presented with a small nasal septal perforation caused by cocaine abuse. He had stopped using it ten years previously so surgery was considered safe. The perforation was surgically closed using an endonasal approach. The perforation, however, recurred, the incision healing delayed, and a saddle deformity developed. Conclusion. The effects of cocaine abuse seem to persist causing poor healing after nasal surgery. Prosthetic treatment should be the primary choice. Caution should be employed when considering surgery even in small perforations due to cocaine abuse even many years after the abuse was terminated.

Surgical closure of nasal septal perforation. Early and long term observations.

BACKGROUND: Results of surgical treatment of nasal septal perforation are usually evaluated using closure of the perforation as criterion of success. Patients, however, may still have symptoms. AIM: To assess the long-term results of surgical treatment of nasal septal perforation with bilateral, posterior based mucoperichondrial septal flaps using a four-point symptom score to ultimately improve treatment and selection criteria. METHODOLOGY: Patients were seen 6 months postoperatively. Questionnaires were sent to 116 surviving patients in 2008-2009. The response was 104. Patients reporting moderate or severe symptoms were seen as outpatients. RESULTS: Between 1987 and 2004, 126 patients were surgically treated using posterior based bilateral mucoperichondrial septal flaps. Sixteen patients had a reperforation during the first 3 months, and another 3 several years later. There was no correlation between early outcome and diagnosis, preoperative size of the perforation, gender or severity of preoperative crusting. There was an increased rate of reperforation with increasing age. Complications seen at the 6 months` follow-up of patients with closed perforations were lachrymal duct stenosis, partial vestibular stenosis, hypoesthesia, crusting and septal deviation, most of which were treatable. Long-term observation mean 10 years) of the same patients showed the following moderate or severe symptoms: crusting, obstruction and bleeding, mainly in men. Obstruction was often due to various forms of perennial rhinitis, sometimes to crusting and more rarely to septal deviation. Crusting was the only independent symptom. There was no correlation between crusting and diagnosis, preoperative size of the perforation, age or severity of preoperative crusting. CONCLUSIONS: Results of the surgical technique using posterior based bilateral mucoperichondrial septal flaps for treatment of nasal septal perforations were good, but depend on surgical expertise and age of the patient. Long-term results from other studies will be a guide to choose the proper surgical procedure to minimize the number of late symptoms. Prosthetic treatment cans be an alternative. Patients with return of symptoms should seek further advice.

Fibro-hyaline extensions from the bony nasal aperture, causing nasal obstruction.

OBJECTIVE: We report a rare case of fibro-hyaline anterior extensions of the bony nasal pyramid. METHOD: The clinical, radiological, intra-operative and histological findings are presented. RESULTS: A 34-year-old man presented with bilateral nasal obstruction due to enlarged lateral walls of the nasal vestibule. Radiology showed normal bony structures. Surgery revealed three histologically identical, non-malignant, fibrous masses, one in the nasal septum and one in each of the vestibular walls. The latter were attached to the bony pyramid, protruding anteriorly and converging medially. CONCLUSION: The location and symmetry of the fibro-hyaline projections indicated that they constituted a malformation mimicking congenital bony nasal pyriform aperture stenosis. Histological analysis showed that the masses were not neoplastic.

Magnetohydrodynamic interference with the edge pedestal motional Stark effect diagnostic on DIII-D.

Accurate measurement of internal magnetic field direction using motional Stark effect (MSE) polarimetry in the edge pedestal is desired for nearly all tokamak scenario work. A newly installed 500 kHz 32-channel digitizer on the MSE diagnostic of DIII-D allows full spectral information of the polarimeter signal to be recovered for the first time. Fourier analysis of this data has revealed magnetohydrodynamic (MHD) fluctuations in the plasma edge pedestal at ρ ≥ 0.92. By correlating edge localized mode fluctuations seen on lock-in amplifier outputs with MSE spectrograms, it has been shown that edge pedestal tearing mode fluctuations cause interference with MSE second harmonic instrument frequencies. This interference results in unrecoverable errors in the real-time polarization angle measurement that are more than an order of magnitude larger than typical polarimeter uncertainties. These errors can cause as much as a 38% difference in local q. By using a redundant measure of the linear polarization found at the fourth harmonic photo-elastic modulator (PEM) frequency, MHD interference can be avoided. However, because of poorer signal-to-noise the fourth harmonic signal computed polarization angle shows no improvement over the MHD polluted second harmonics. MHD interference could be avoided in future edge pedestal tokamak polarimeters by utilizing PEMs with higher fundamental frequencies and a greater separation between their frequencies.

Magnetic-flux pumping in high-performance, stationary plasmas with tearing modes.

Analysis of the change in the magnetic field pitch angles during edge localized mode events in high performance, stationary plasmas on the DIII-D tokamak shows rapid (<1 ms) broadening of the current density profile, but only when a m/n=3/2 tearing mode is present. This observation of poloidal magnetic-flux pumping explains an important feature of this scenario, which is the anomalous broadening of the current density profile that beneficially maintains the safety factor above unity and forestalls the sawtooth instability.

Reduced critical rotation for resistive-wall mode stabilization in a near-axisymmetric configuration.

Recent DIII-D experiments with reduced neutral beam torque and minimum nonaxisymmetric perturbations of the magnetic field show a significant reduction of the toroidal plasma rotation required for the stabilization of the resistive-wall mode (RWM) below the threshold values observed in experiments that apply nonaxisymmetric magnetic fields to slow the plasma rotation. A toroidal rotation frequency of less than 10 krad/s at the q=2 surface (measured with charge exchange recombination spectroscopy using C VI) corresponding to 0.3% of the inverse of the toroidal Alfvén time is sufficient to sustain the plasma pressure above the ideal MHD no-wall stability limit. The low-rotation threshold is found to be consistent with predictions by a kinetic model of RWM damping.

Multitude of core-localized shear Alfvén waves in a high-temperature fusion plasma.

Evidence is presented for a multitude of discrete frequency Alfvén waves in the core of magnetically confined high-temperature fusion plasmas. Multiple diagnostic instruments confirm wave excitation over a wide spatial range from the device size at the longest wavelengths down to the thermal ion Larmor radius. At the shortest scales, the poloidal wavelengths are comparable to the scale length of electrostatic drift wave turbulence. Theoretical analysis confirms a dominant interaction of the modes with particles in the thermal ion distribution traveling well below the Alfvén velocity.

Measurement of the resistive-wall-mode stability in a rotating plasma using active MHD spectroscopy.

The stability of the resistive-wall mode (RWM) in DIII-D plasmas above the conventional pressure limit, where toroidal plasma rotation in the order of a few percent of the Alfve n velocity is sufficient to stabilize the n=1 RWM, has been probed using the technique of active MHD spectroscopy at frequencies of a few Hertz. The measured frequency spectrum of the plasma response to externally applied rotating resonant magnetic fields is well described by a single-mode approach and provides an absolute measurement of the damping rate and the natural mode rotation frequency of the stable RWM.

Suppression of large edge-localized modes in high-confinement DIII-D plasmas with a stochastic magnetic boundary.

A stochastic magnetic boundary, produced by an applied edge resonant magnetic perturbation, is used to suppress most large edge-localized modes (ELMs) in high confinement (H-mode) plasmas. The resulting H mode displays rapid, small oscillations with a bursty character modulated by a coherent 130 Hz envelope. The H mode transport barrier and core confinement are unaffected by the stochastic boundary, despite a threefold drop in the toroidal rotation. These results demonstrate that stochastic boundaries are compatible with H modes and may be attractive for ELM control in next-step fusion tokamaks.