[Clinical characteristics and risk factors of rheumatoid arthritis with ulcerative keratitis].

OBJECTIVE: To investigate the clinical characteristics, risk factors and prognosis of ulcerative keratitis (UK) in patients with rheumatoid arthritis (RA). METHODS: Sixteen patients with UK (the UK group) were screened among 4 773 RA patients hospitalized at Peking University People's Hospital from January 2003 to May 2021, and 72 patients with RA without UK in the control group were selected by propensity score matching (PSM). The clinical features, laboratory data and medications between the two groups were collected and analyzed. RESULTS: The average age of the patients with RA was 60 years at the time of the complication of UK. UK appeared on average in the 16th year of RA, with the majority of UK occurring in the 7th year of RA and beyond (14 cases), however, a minority of UK was the first symptom of RA (1 case). UK associated with RA manifested as simple marginal UK in 8 cases, marginal UK with perforation in 5 cases, marginal UK with uveitis in 2 cases and central UK with perforation in 1 case. The number of swollen joints was significantly higher in the UK group than in the control group [6.0(2.5, 23.0) vs. 3.0(1.0, 9.8), Z=-2.047, P=0.041], and the proportion of secondary Sjögren syndrome (SS, 37.5% vs. 6.9%, χ2=11.175, P=0.004) and interstitial lung disease (ILD, 37.5% vs. 8.3%, χ2=9.456, P=0.008) were significantly higher in the RA patients with UK than the patients without UK. The uses of sulfasalazine (12.5% vs. 48.6%, χ2=7.006, P=0.008), leflunomide (31.3% vs. 63.9%, χ2=5.723, P=0.017) and gold salt(6.3% vs. 33.8%, χ2=4.841, P=0.032)were significantly lower in the UK group than in the control group. However, there was no statistically significant comparison between the two groups for the 28-joint disease activity score-erythrocyte sedimentation rate (5.3±1.8 vs. 5.1±1.6, t=0.309, P=0.761). Logistic analysis showed the number of swollen joints (OR=1.148), secondary SS (OR=79.118), complicated with ILD (OR=6.596) and the use of sulfasalazine (OR=0.037) were independent relevant factors (P < 0.05) for UK in RA patients. CONCLUSION: The number of swollen joints, secondary SS, complicated with ILD and the use of sulfasalazine are independent relevant factors for UK in patients with RA.

Studies on characteristics of resistive power calculated with discrete Fourier transform in a pulse-modulated radio frequency discharge.

In a pulse-modulated (PM) radio-frequency (RF) capacitively coupled plasma, the DFT (Discrete Fourier Transform)-calculated RF power and the corresponding phase shift between voltage and current measured with calibrated voltage and current probes present oscillations in the pulse rising and falling edges. The oscillating phase shift between voltage and current obtained in the falling edge is outside the expected value for a resistive-capacitive RF discharge. Numerical simulation and analytical analysis are made to interpret these abnormal characteristics and seek an approach to obtaining the reliable resistive (active) RF power. The oscillation is proved to be originated from the oscillating non-zero reactive RF power of the capacitor(s) in the load. At the time instant when the reactive RF power within an integer RF period is not zero, the reactive RF power is mistakenly regarded as the active RF power in the DFT analysis, as a result, the corresponding phase is thus incorrect and even outside the expected value for a resistive-capacitive load. The resistive RF power and the phase can be only correctly calculated at the time instant when the reactive RF power is zero. For a series (or parallel) RC (resistor-capacitor) load and a combined RC load with the dominated series (or parallel) RC impedance, the time instant of the zero reactive RF power is calculated with one of the two proposed empirical formulae. In practice, the DFT-calculated resistive RF power is obtained according to the following procedures: (1) applying DFT to the measured RF voltage and current signals to obtain the power and time instants for minimal phase shifts between voltage and current; (2) selecting the empirical formula to calculate time instants of the zero reactive RF power; (3) getting resistive powers at time instants of the zero reactive RF power. In real PM RF capacitively coupled plasmas, the empirical formula for the series RC load is selected to calculate the resistive RF power. The accuracy of DFT-calculated resistive RF power is proved to be related to two kinds of errors. The first is the error of the time instant of the zero reactive RF power calculated using the empirical formula. This error is relatively lower when the requirement that the dominated parallel or series RC impedance is met and is almost independent of the impedance phase angle of a combined RC load. The second is the error of the DFT-calculated resistive RF power compared with the corresponding time integral RF power at the real zero reactive RF power. This error is independent of the load type or the load impedance but varies with the slope of PM RF voltage amplitude vs. time. The two kinds of errors both increase in the pulse rising and falling edges.

The resonant radio-frequency magnetic probe tuned by coaxial cable.

In this paper, the resonant rf magnetic probe is upgraded by replacing the rotary capacitor in the old version with the series-connected coaxial cable. The numerical calculation and the measurement with the prototype probe show that the rf magnetic probe can achieve resonance at a middle length of the series-connected coaxial cable. The good electrical symmetry of the new rf magnetic probe is ensured by both the identity of series-connected coaxial cables and the new structure of the primary winding. Practical measurements conduced on an rf inductively coupled plasma source demonstrate that performances of the new rf magnetic probe are good.

A tunable radio-frequency magnetic probe.

A tunable center-tapped transformer is proposed to increase the output of a rf magnetic probe and improve the signal-to-noise ratio. The tuning is implemented by a variable capacitor connected parallel with the primary winding of the tunable center-tapped transformer. Undesirable common-to-differential conversion is reduced by installing a compensating capacitor. In addition, a planar Faraday shield is installed between the windings of the transformer to further suppress the electrostatic coupling. It is found that tuning the variable capacitor can result in a resonance in the output voltage of the rf magnetic probe. The largest output voltage, achieved with the tunable magnetic probe under the optimal condition, is higher than that with a conventional one by an order of magnitude. Effects of the compensating capacitance on the common-mode output voltage are studied and discussed. Influences of parameters such as cable length, the coupling coefficient, and the step-up ratio of the transformer on the output voltage are also presented. Analytical derivations and numerical calculations based on the equivalent circuit are performed to elucidate the characteristics of the differential mode.