Turbulence and Mixing in the Intracluster Medium

The intracluster medium (ICM) is stably stratified in the hydrodynamic sense with the entropy $s$ increasing outwards. However, thermal conduction along magnetic field lines fundamentally changes the stability of the ICM, leading to the "heat-flux buoyancy instability" when $dT/dr>0$ and the "magnetothermal instability" when $dT/dr<0$. The ICM is thus buoyantly unstable regardless of the signs of $dT/dr$ and $ds/dr$. On the other hand, these temperature-gradient-driven instabilities saturate by reorienting the magnetic field (perpendicular to $\hat{\bf r}$ when $dT/dr>0$ and parallel to $\hat{\bf r}$ when $dT/dr<0$), without generating sustained convection. We show that after an anisotropically conducting plasma reaches this nonlinearly stable magnetic configuration, it experiences a buoyant restoring force that resists further distortions of the magnetic field. This restoring force is analogous to the buoyant restoring force experienced by a stably stratified adiabatic plasma. We argue that in order for a driving mechanism (e.g, galaxy motions or cosmic-ray buoyancy) to overcome this restoring force and generate turbulence in the ICM, the strength of the driving must exceed a threshold, corresponding to turbulent velocities $\gtrsim 10 -100 {km/s}$. For weaker driving, the ICM remains in its nonlinearly stable magnetic configuration, and turbulent mixing is effectively absent. We discuss the implications of these findings for the turbulent diffusion of metals and heat in the ICM.Comment: 8 pages, 2 figs., submitted to the conference proceedings of "The Monster's Fiery Breath;" a follow up of arXiv:0901.4786 focusing on the general mixing properties of the IC

Peak Effect in Superconductors: Absence of Phase Transition and Possibility of Jamming in Vortex Matter

The magnetic field $B$ dependence of the critical current $I_c$ for the vortex phase of a disordered superconductor is studied numerically at zero temperature. The $I_{c}(B)$ increases rapidly near the upper critical field $B_{c2}$ similar to the peak effect (PE) phenomenon observed in many superconductors. The real space configuration across the PE changes continuously from a partially ordered domain (polycrystalline) state into an amorphous state. The topological defect density $n_{d}(B)\sim e^{\alpha B^{k}}$ with $k>1$ for $B\geq 0.4B_{c2}$. There is no evidence of a phase transition in the vicinity of the PE suggesting that an order-disorder transition is not essential for the occurrence of the PE phenomenon. An alternative view is presented wherein the vortex system with high dislocation density undergoes jamming at the onset of the PE.Comment: 8 pages and 5 figure

THE CONTROL OF BACTERIAL BLIGHT OF POMEGRANATE USING THE METHANOLIC EXTRACTS OF INDIAN BAEL AND LEUCAS ASPERA

Objectives: Blight disease occurring due to Xanthomonas axonopodis (pv. Punicae) has been creating a problem in pomegranate cultivation whose symptoms appear on leaves as well as on fruits and stem and thereby causing a detrimental effect on yield by reducing it to nearly 70–75%. In recent years, the disease has been controlled by nanoparticles (silver and copper). We are looking forward to an organic and more economic method for the control of blight disease of pomegranate which is farmer and consumer friendly. Methods: In the present work, the causative agent of disease was isolated from the infected pomegranate fruit which was collected from Bellary, Karnataka on nutrient agar media using streak plating method. Secondary metabolites were extracted from Leucas aspera and Indian bael using methanol as solvent from maceration and soxhlet extraction techniques for about six hours. These methods are considered as the traditional methods for extracting phenolic compounds along with the ultrasound assisted solvent extraction (UASE) method. Since UASE degrades the phenols and certain metabolites which act as nutrients we did not go for this technique. The Phytochemical screening of extracts was conducted to check the presence of secondary metabolites having antimicrobial activity. The methanolic extracts were characterised using thin layer chromatography (TLC) and Fourier transform infra-red (FTIR) spectroscopy. The antimicrobial activity for extracts of L. aspera and Indian bael were tested by agar disc diffusion method. Results: Clear Zone of Inhibition (ZOI) were observed for methanolic extracts of L. aspera (40 mg/ml and 100mg/ml) and Indian bael (160 mg/ml) which shows that the blight disease could be controlled. Conclusion: Indian bael methanolic extract (160 mg/ml) shows better control against growth of Xanthomonas species with higher ZOI values than L. aspera extracts (100 mg/ml and 40 mg/ml)

Radio-wave propagation through a medium containing electron-density fluctuations described by an anisotropic Goldreich-Sridhar spectrum

We study the propagation of radio waves through a medium possessing density fluctuations that are elongated along the ambient magnetic field and described by an anisotropic Goldreich-Sridhar power spectrum. We derive general formulas for the wave phase structure function, visibility, angular broadening, diffraction-pattern length scales, and scintillation time scale for arbitrary distributions of turbulence along the line of sight, and specialize these formulas to idealized cases.Comment: 25 pages, 3 figures, submitted to Ap

The effect of antenatal corticosteroids on maternal glycemic control, in a tertiary care centre in North Kerala - India

Background: Antenatal glucocorticoid therapy (ACT) can be life-saving in preterm babies and risk of PTL is increasing in. The prevalence of GDM also increasing. Virtually, all women will experience deterioration in their glycaemic control following ACT. The NICE guideline recommends additional insulin and the national Indian guidelines recommend a 20% increase. Objective of this study was to evaluate the changes in maternal serum glucose following corticosteroids in antenatal women.Methods: Prospective controlled trial of 206 patients, divided into 2 groups. Group 1:105 patients with no GDM and Group 2: 101 patients with GDM. Ethical committee approved. FBS and PPBS measured for following 5 days of D1. BMI and starting dose of insulin and dose of insulin hike were recorded. FBS >90 mg/dL and PPBS >120 mg/dL were taken as abnormal. Data were analyzed using SPSSV22.Results: There were a total of 206 of which 105 were in group 1(51%) and 101(49%) were in Group 2. FBS >90 mg/dL in over 65% of all women on D2 10 new cases on D3 and PPBS >120 mg/dL in over 66% of all women on D2 and 13 new cases on D3. Insulin was started in a total of 66 patients of 105 (62.9%) in Group 1 and 33 out of 40 (82.5%) in GDM on MNT. Of the 66 patients who started on insulin in Group 1, 17 (16.2%) patients had to continue insulin and out of 33. In MNT subgroup 10 (25%) had to continue. BMI was high in the patients, who was given and continued insulin.Conclusions: The findings support the concept of increasing the dose of insulin even before the hyperglycemia documented. In the Group 1 66 of 105 patients were started on insulin due to hyperglycemia and 17 had to continue insulin 25.7%), and 33 of 40 patients in GDM on MNT were started on insulin and 10 (30.33%) had to continue. We suggest testing all patients for hyperglycemia and to start  insulin especially in the those with high BMI (>25 as per the Asian Indian)