Electrical Network-Based Time-Dependent Model of Electrical Breakdown in Water

A time-dependent, two-dimensional, percolative approach to model dielectric breakdown based on a network of parallel resistor–capacitor elements having random values, has been developed. The breakdown criteria rely on a threshold electric field and on energy dissipation exceeding the heat of vaporization. By carrying out this time-dependent analysis, the development and propagation of streamers and prebreakdown dynamical evolution have been obtained directly. These model simulations also provide the streamer shape, characteristics such as streamer velocity, the prebreakdown delay time, time-dependent current, and relationship between breakdown times, and applied electric fields for a given geometry. The results agree well with experimental data and reports in literature. The time to breakdown (tbr) for a 100 μm water gap has been shown to be strong function of the applied bias, with a 15–185 ns range. It is also shown that the current is fashioned not only by dynamic changes in local resistance, but that capacitive modifications arising from vaporization and streamer development also affect the transient behavior

Apokamps produced by repetitive discharges in air

New experimental and computational data on apokamps produced by repetitive discharges in air, including a detailed description of the research techniques used, are presented. It has been shown that plasma bullets–streamers in apokamps at low frequencies could start not only from the bright offshoot but also directly from the discharge channel. The experimental and computational data demonstrate that the visual color of apokamp changes from blue to red as the intensity ratio of the second to the first positive nitrogen system decreases with the decreasing pressure

Simulation of the discharge propagation in a capillary tube in air at atmospheric pressure

International audienceThis paper presents simulations of an air plasma discharge at atmospheric pressure initiated by a needle anode set inside a dielectric capillary tube. We have studied the influence of the tube inner radius and its relative permittivity ε r on the discharge structure and dynamics. As a reference, we have used a relative permittivity ε r = 1 to study only the influence of the cylindrical constraint of the tube on the discharge. For a tube radius of 100 µm and ε r = 1, we have shown that the discharge fills the tube during its propagation and is rather homogeneous behind the discharge front. When the radius of the tube is in the range 300 to 600 µm, the discharge structure is tubular with peak values of electric field and electron density close to the dielectric surface. When the radius of the tube is larger than 700 µm, the tube has no influence on the discharge which propagates axially. For a tube radius of 100 µm, when ε r increases from 1 to 10, the discharge structure becomes tubular. We have noted that the velocity of propagation of the discharge in the tube increases when the front is more homogeneous and then, the discharge velocity increases with the decrease of the tube radius and ε r. Then, we have compared the relative influence of the value of tube radius and ε r on the discharge characteristics. Our simulations indicate that the geometrical constraint of the cylindrical tube has more influence than the value of ε r on the discharge structure and dynamics. Finally, we have studied the influence of photoemission processes on the discharge structure by varying the photoemission coefficient. As expected, we have shown that photoemission, as it increases the number of secondary electrons close to the dielectric surface, promotes the tubular structure of the discharge

Factors affecting the results of analgesic therapy. Results of the Russian multicentre study of NOTE (NSAID: Open-label Trial of Efficacy)

Non-steroidal anti-inflammatory drugs (NSAIDs) are most popular medications for the treatment of pain in common musculoskeletal diseases such as osteoarthritis (OA) and non-specific low back pain (LBP). However, the factors affecting the effectiveness of these drugs have not been determined fully. Aim: to identify factors affecting the effectiveness of NSAIDs in patients with OA and LBP. Materials and methods. An observational study was conducted to evaluate the effectiveness of a 2-week course of NSAIDs in OA and LBP in real clinical practice. The study group consisted of 3604 patients with OA and LBP (60.6% women and 39.4% men, mean age 55.0±13.4 years). According to the study design, aceclofenac (Airtal) and other NSAIDs used in the ratio 1:1. The main criterion of effectiveness was the frequency of complete pain relief after 2 weeks of therapy. In addition, the decrease of pain and general health were determined on a 10-point numerical rating scale (NRS). We compared the frequency of complete pain relief in patients who had and did not have the studied factors. The value of the studied factors was determined using OR (95% CI). Results and discussion. Most patients received aceclofenac (54.9%), as well as diclofenac (2.0%), ketoprofen (1.9%), lornoxicam (2.2%), meloxicam (13.7%), naproxen (2.1%), nimesulide (5.8%), celecoxib (5.9%), ethicoxib (7.1%) and other NSAIDs (4.4%); 56.2% of patients received muscle relaxants, mainly tolperisone (74.7%), vitamin B (10.4%), and proton pump inhibitors (42.8%). Complete pain relief was achieved in 54.8% of patients. The pain decrease and general health improvement were (for NRS) 63.9±13.4% and 61.7±14.8%, respectively. The efficacy of aceclofenac was slightly higher than in the whole group: complete pain relief was in 59.9% of patients. Adverse events in aceclofenac use were observed in 2.3% of patients, other NSAIDs-from 2.4 to 14.1%. The frequency of complete pain relief was higher in men: OR 1,239 (95% CI 1.08-1.418; p=0.002), who had the first episode of pain - OR 3.341 (95% CI 2.873-3.875; p=0.000), a good" response " to NSAIDs in history - OR 1.656 (95% CI 1.385-1.980; p=0.000) and received NSAIDs in combination with muscle relaxants - OR 1.218 (95% CI 1.067-1.390; p=0.004). The effect of therapy is lower in patients 65 years and older-OR 0,378 (95% CI 0.324-0.442; p=0,000), with body mass index >30 kg/m² - OR 0.619 (95% CI 0.529-0.723; p=0.000), with severe pain (≥7 points NRS) - OR 0.662 (95% CI 0.580-0.756; p=0.002), with pain at rest, - OR 0.515 (95% CI 0.450-0,589; p=0.000), pain at night - OR 0.581 (95% CI 0.501-0.672; p=0.000) and the presence of stiffness - OR 0.501 (95% CI 0.438-0,573; p=0.000). Treatment results are significantly worse in the cases of combination of LBP and joint pain, as well as pain in the trochanter major and pes anserinus area (