Secondary instability of electromagnetic ion-temperature-gradient modes for zonal flow generation

An analytical model for zonal flow generation by toroidal ion-temperature-gradient (ITG) modes, including finite $\beta$ electromagnetic effects, is derived. The derivation is based on a fluid model for ions and electrons and takes into account both linear and nonlinear $\beta$ effects. The influence of finite plasma $\beta$ on the zonal flow growth rate ($\gamma_{ZF}$) scaling is investigated for typical tokamak plasma parameters. The results show the importance of the zonal flows close to marginal stability where $\gamma_{ZF}/\gamma_{ITG}>>1$ is obtained. In this region the parameter $\gamma_{ZF}/\gamma_{ITG}$ increases with $\beta$, indicating that the ITG turbulence and associated transport would decrease with $\beta$ at a faster rate than expected from a purely linear or quasi-linear analysis.Comment: RevTex 17 pages, 4 figures, submitted to Physics of Plasma

Geodesic acoustic modes in a fluid model of tokamak plasma : the effects of finite beta and collisionality

Starting from the Braginskii equations, relevant for the tokamak edge region, a complete set of nonlinear equations for the geodesic acoustic modes (GAM) has been derived which includes collisionality, plasma beta and external sources of particle, momentum and heat. Local linear analysis shows that the GAM frequency increases with collisionality at low radial wave number $k_{r}$ and decreases at high $k_{r}$. GAM frequency also decreases with plasma beta. Radial profiles of GAM frequency for two Tore Supra shots, which were part of a collisionality scan, are compared with these calculations. Discrepency between experiment and theory is observed, which seems to be explained by a finite $k_{r}$ for the GAM when flux surface averaged density $\langle n \rangle$ and temperature $\langle T \rangle$ are assumed to vanish. It is shown that this agreement is incidental and self-consistent inclusion of $\langle n \rangle$ and $\langle T \rangle$ responses enhances the disagreement more with $k_r$ at high $k_{r}$ . So the discrepancy between the linear GAM calculation, (which persist also for more "complete" linear models such as gyrokinetics) can probably not be resolved by simply adding a finite $k_{r}$

Trends of maternal mortality in a tertiary care hospital: a five year retrospective study

Background: Maternal mortality is a measure of quality of health care in community. Maternal mortality ratio is a very sensitive index that reflect the quality of reproductive care provided to the pregnant women. The aims and objectives were to study the institutional maternal mortality, the causes of maternal death and the impact of COVID-19 on MMR.Methods: A retrospective hospital-based study of 38 maternal death was done over a period of 5 years from June 2016 to May 2021 in obstetrics and gynaecology department, RIMS Imphal. Details of all the mortalities were collected from individual case sheets, facility based maternal death review forms and MDR case summary.Results: A total of 38 deaths were analysed. MMR in the study period was 86 per 1 lakh live births. Maximum maternal deaths were reported in the age group of 30-34 years. Majority of maternal death were reported in multipara (57.9%) as compared to primipara (34.2%). Most of them were un-booked (63.2%) and belonged to rural areas (60.5%). The commonest cause was obstetrics haemorrhage (42.1%) followed by hypertensive disorders (23.6%). Acute respiratory distress syndrome associated with SARS-CoV-2 is one of the most important causes of increasing mortality rate (10.5%).Conclusions: Early identification of high-risk pregnancy, regular antenatal check-up and proper training of health personnel along with timely referral to tertiary care centre can help to reduce the mortality. There is an increase in MMR during the current pandemic 2020-2021