Positron acceleration to ultrarelativistic energies by an oblique magnetosonic shock wave in an electron-positron-ion plasma

Positron acceleration in a shock wave in a plasma consisting of electrons, positrons, and ions is studied with theory and simulations. From the relativistic equation of motion, it is found that an oblique shock wave can accelerate some positrons with the energy increase rate proportional to E?B. They move nearly parallel to the external magnetic field, staying in the shock transition region for long periods of time. Then, this acceleration is demonstrated with one-dimensional, relativistic,electromagnetic particle simulations with full particle dynamics. Some positrons have been accelerated to ultrarelativistic energies sg,1000d with this mechanism. Parametric study of this acceleration is also made

Persistent acceleration of positrons in a nonstationary shock wave

Long-time evolution of positrons accelerated in an oblique shock wave in an electron-positron-ion plasma is studied with relativistic, electromagnetic, particle simulations. In the early stage, some positrons move nearly parallel to the external magnetic field in the shock transition region and gain energy from the parallel electric field. The acceleration can become stagnant owing to the deformation of the wave profile. After the recovery of the shock profile, however, the acceleration can start again. By the end of simulation runs, omega_pet=5000, positron Lorentz factors reached values ~2000. In this second stage, three different types of acceleration are found. In the first type, the acceleration process is the same as that in the early stage. In the second type, positrons make gyromotions in the wave frame and gain energy mainly from the perpendicular electric field. In the third type, particle orbits are similar to curtate cycloids. Theoretical estimate for this energy increase is given

Influence of lumbar kyphosis and back muscle strength on the symptoms of gastroesophageal reflux disease in middle-aged and elderly people

OBJECTIVE: The objectives of this study was to clarify the relationship between kyphosis and Gastroesophageal reflux disease (GERD) by evaluation of spinal alignment, obesity, osteoporosis, back muscle strength, intake of oral drugs, and smoking and alcohol history in screening of a community population to determine the factors related to GERD symptoms. SUMMARY OF BACKGROUND DATA: GERD increases with age and is estimated to occur in about 30% of people. Risk factors for GERD include aging, male gender, obesity, oral medicines, smoking, and alcohol intake. It has also been suggested that kyphosis may influence the frequency of GERD, but the relationship between kyphosis and GERD is unclear. SUBJECTS AND METHODS: We examined 245 subjects (100 males and 145 females; average age 66.7 years old) in a health checkup that included evaluation of sagittal balance and spinal mobility with SpinalMouse(®), GERD symptoms using the Frequency Scale for Symptoms of GERD (FSSG) questionnaire, body mass index, osteoporosis, back muscle strength, number of oral drugs taken per day, intake of nonsteroidal anti-inflammatory drugs (NSAIDs), intake of bisphosphonates, and smoking and alcohol intake. RESULTS: Multivariate logistic regression analysis including all the variables showed that lumbar lordosis angle, sagittal balance, number of oral drugs taken per day, and back muscle strength had significant effects on the presence of GERD (OR, 1.10, 1.11, 1.09 and 1.03; 95%CI, 1.03–1.17, 1.02–1.20, 1.01–1.18 and 1.01–1.04; p = 0.003, 0.015, 0.031 and 0.038, respectively). The other factors showed no association with GERD. CONCLUSION: This study is the first to show that lumbar kyphosis, poor sagittal balance; increased number of oral drugs taken per day, and decreased back muscle strength are important risk factors for the development of GERD symptoms. Thus, orthopedic surgeons and physicians should pay attention to GERD in elderly patients with spinal deformity

Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ): a patient-based evaluation tool for hip-joint disease. The Subcommittee on Hip Disease Evaluation of the Clinical Outcome Committee of the Japanese Orthopaedic Association

AbstractBackgroundThe Japanese Orthopaedic Association Hip Score is widely used in Japan, but this tool is designed to reflect the viewpoint of health-care providers rather than that of patients. In gauging the effect of medical therapies in addition to clinical results, it is necessary to assess quality of life (QOL) from the viewpoint of patients. However, there is no tool evaluating QOL for Japanese patients with hip-joint disease.MethodsWith the aim of more accurately classifying QOL for Japanese patients with hip-joint disease, we prepared a questionnaire with 58 items for the survey derived from 464 opinions obtained from approximately 100 Japanese patients with hip-joint disease and previously devised evaluation criteria. In the survey, we collected information on 501 cases, and 402 were subjected to factor analysis. From this, we formulated three categories—movement, mental, and pain—each comprising 7 items, for a total of 21 items to be used as evaluation criteria for hip-joint function.ResultsThe Cronbach’s α coefficients for the three categories were 0.93, 0.93, and 0.95, respectively, indicating the high reliability of the evaluation criteria. The 21 items included some related to the Asian lifestyle, such as use of a Japanese-style toilet and rising from the floor, which are not included in other evaluation tools.ConclusionsThis self-administered questionnaire may become a useful tool in the evaluation of not only Japanese patients, but also of members of other ethnic groups who engage in deep flexion of the hip joint during daily activities

Surgical Skills Training for Primary Total Hip Arthroplasty

A total of 483 hips treated by primary total hip arthroplasty (THA) were investigated to evaluate the surgical skill of the performing surgeon. Surgical trainees operated on 259 hips and instructors on 224 hips. The average age of the patients at the time of THA in the trainee and instructor group was 61.9 and 60.8 years old, respectively. The average follow-up duration was 5.1 years. The operative time in the trainee group and instructor group was 87.0 and 73.1 min, respectively (p=0.031). Complications were noted in 11 hips (3.5%) in the trainee group; acetabular fracture, 3 hips; dislocation, 3 hips; femoral artery lacerations that needed repair surgery, 2 hips; sciatic nerve palsy, 2 hips; and skin necrosis, 1 hip. Complication were noted in three hips (1.3%) in the instructor group; femoral fracture, 1 hip; acetabular fracture, 1 hip; dislocation, 1 hip. Complication rate in the trainee group was higher than in the instructor group. The monitored quality of the surgeries performed by trainees and instructors was not significantly different. Poor quality was identified in 14 hips in the trainee group and 6 hips in instructor group. No significant difference was found in the hip score between the trainees and instructors before and after surgery. Revision arthroplasty was defined as the end-point for primary THA. Kaplan-Meier survivorship at 5 years after primary THA was 97.2% in trainee group and 97.3% in the instructor group. Short-term clinical and radiographic results of primary THA in the trainee and instructor groups were considered safe and satisfactory