Cold gas in cluster cores: Global stability analysis and non-linear simulations of thermal instability

We perform global linear stability analysis and idealized numerical simulations in global thermal balance to understand the condensation of cold gas from hot/virial atmospheres (coronae), in particular the intracluster medium (ICM). We pay particular attention to geometry (e.g., spherical versus plane-parallel) and the nature of the gravitational potential. Global linear analysis gives a similar value for the fastest growing thermal instability modes in spherical and Cartesian geometries. Simulations and observations suggest that cooling in halos critically depends on the ratio of the cooling time to the free-fall time ($t_{cool}/t_{ff}$). Extended cold gas condenses out of the ICM only if this ratio is smaller than a threshold value close to 10. Previous works highlighted the difference between the nature of cold gas condensation in spherical and plane-parallel atmospheres; namely, cold gas condensation appeared easier in spherical atmospheres. This apparent difference due to geometry arises because the previous plane-parallel simulations focussed on {\em in situ} condensation of multiphase gas but spherical simulations studied condensation {\em anywhere} in the box. Unlike previous claims, our nonlinear simulations show that there are only minor differences in cold gas condensation, either in situ or anywhere, for different geometries. The amount of cold gas condensing depends on the shape of the gravitational potential well; gas has more time to condense if gravitational acceleration decreases toward the center. In our idealized simulations with heating balancing cooling in each layer, there can be significant mass/energy/momentum transfer across layers that can trigger condensation and drive $t_{cool}/t_{ff}$ far beyond the critical value close to 10. Triggered condensation is very prominent in plane-parallel simulations, in which a large amount of cold gas condenses out.Comment: 17 pages, 16 figures, 2 tables, version accepted in MNRAS. Links to python codes for global stability analysis: https://drive.google.com/folderview?id=0B2HaDXI2USsZWUdESVVsN2RGeVU&usp=sharin

Use of Unmanned Aerial System (UAS) for High Throughput Evaluation of Forage Yield in Oat Breeding Nurseries

Current strategies for phenotyping (for traits like biomass) numerous breeding lines under field conditions demand significant investment in both time and labor. Unmanned aerial systems (UAS) can be used to collect vegetation indexes (VI) with high throughput and could provide an efficient way to predict forage yield in breeding nurseries with accuracy. The main objective of the study was to evaluate the use of VIs derived from UAV collected images for estimating crop biomass. For this study, forage trials consisting of 35 oat genotypes were carried out at three locations in 2018 and four locations in 2019. Unmanned aerial vehicles (UAV) equipped with multispectral and visible sensors were flown over experimental plots in Volga, South Shore, and Beresford, several times throughout the 2018 and 2019 growing seasons. Images were also collected in Pierre in 2019 just prior forage harvest. Fresh and dry biomass were collected on each plot at each location. Several VIs derived from the UAV collected pictures were significantly positively correlated with fresh and dry biomass for the locations Volga and Beresford (r=0.2-0.65). However, none of the VIs were significantly correlated with crop biomass in South Shore. Multiple linear regression models (MLR) were developed for each location to predict fresh and dry biomass using VIs, plant height, crown rust severity and chlorophyll content as explanatory variables. The best predictive models for dry biomass prediction had a R-square value of 0.52 for Volga, 0.67 for Beresford and 0.25 for South Shore. For fresh biomass prediction, selected models had a R-square values of 0.83 for Volga, 0.9 for Beresford, and 0.44 for South Shore. Results from Beresford and Volga suggests that VIs derived from UAV collected could be useful for biomass prediction. Yet, multiple years of trial data would be necessary to further validate the potential use of UAV for estimating oat biomass

Multiphase gas in the circumgalactic medium: relative role of tcool/tfft_{\rm cool}/t_{\rm ff} and density fluctuations

We perform a suite of simulations with realistic gravity and thermal balance in shells to quantify the role of the ratio of cooling time to the free-fall time ($t_{\rm cool}/t_{\rm ff}$) and the amplitude of density perturbations ($\delta \rho/\rho$) in the production of multiphase gas in the circumgalactic medium (CGM). Previous idealized simulations, focussing on small amplitude perturbations in the intracluster medium (ICM), found that cold gas can condense out of the hot ICM in global thermal balance when the background $t_{\rm cool}/t_{\rm ff} \lesssim 10$. Recent observations suggest the presence of cold gas even when the background profiles have somewhat large values of ${t_{\rm cool}/t_{\rm ff}}$. This partly motivates a better understanding of additional factors such as large density perturbations that can enhance the propensity for cooling and condensation even when the background ${t_{\rm cool}/t_{\rm ff}}$ is high. Such large density contrasts can be seeded by galaxy wakes or dense cosmological filaments. From our simulations, we introduce a condensation curve in the $(\delta \rho/\rho)$ - min$(t_{\rm cool}/t_{\rm ff})$ space, that defines the threshold for condensation of multiphase gas in the CGM. We show that this condensation curve corresponds to ${(t_{\rm cool}/t_{\rm ff})}_{\rm blob} \lesssim 10$ applied to the overdense blob instead of the background for which $t_{\rm cool}/t_{\rm ff}$ can be higher. We also study the modification in the condensation curve by varying entropy stratification. Steeper (positive) entropy gradients shift the condensation curve to higher amplitudes of perturbations (i.e., make condensation difficult). A constant entropy core, applicable to the CGM in smaller halos, shows condensation over a larger range of radii as compared to the steeper entropy profiles in the ICM.Comment: 17 pages, 14 figures, 2 tables, the version accepted in MNRA

A 1-dimensional hydrodynamic model for accretion, cooling and heating of gas in dark matter halos from z=6z=6 to z=0z=0

We study an idealized 1D model for the evolution of hot gas in dark matter halos for redshifts $z=[0,6]$. We introduce a numerical setup incorporating cosmological accretion of gas, along with the growth of the halo, based on the Van den Bosch model for the average growth of halos as a function of cosmic time. We evolve one-dimensional Lagrangian shells with radiative cooling of the gas and heating due to feedback from the gas cooling and moving in toward the center. A simple Bondi accretion model on to a central black hole is used to include feedback heating. The setup captures some of the key characteristics of spherically symmetric accretion onto the halos: formation of virial shocks slightly outside $r_{200}$ and long-term thermal balance in the form of cooling and heating cycles. The gas density outside our initial halos at $z=6$ is constrained by requiring that the baryon fraction within the virial radius for non-radiative evolution be equal to the universal value at almost all times. The total mass in the cold phase (taken to be $\sim 10^4$ K) within $40$ kpc is tracked as a function of the halo mass and redshift. We compare the evolution of the cold gas mass to the observed stellar-mass versus halo mass relations, following which, we can constrain the feedback energy required for different halo masses and redshifts. We also compare and match the hot gas density and temperature profiles for our most massive halo to those of clusters observed upto redshift $2$. Our model is thus an improvement over the semi-analytic models in which isothermal condition and $\rho \propto r^{-2}$ are assumed.Comment: 17 pages, 13 figures, 3 tables. Accepted in MNRAS. Comments are welcom

Life cycle and eco-friendly management of Chinese fruit fly (Bactrocera minax) in sweet orange (Citrus sinesis Osbeck) in Nepal

Sweet orange (Citrus sinensis Osbeck) is a highly profitable fruit crop of Nepal. However, for the past five years, farmers experienced poor productivity partly attributed to the severe infestation of exotic Chinese fruit fly (Bactorcera minax), particularly in Sindhuli and Ramechhap district of Nepal. In this context, we attempted to review on identification, life cycle, and eco-friendly management of Chinese fruit fly. The review is documented based on a field visit and relevant works of literature from Journal articles, books, pamphlets, etc. The Chinese fruit fly has tremendous ability to take a long-range flight, thus,  migrated from China to Bhutan and crossing the Indo-Nepal eastern border, finally reached to eastern mid-hills of Nepal.  Moderate temperature and low humidity of mid-hills of Nepal are favorable for the exponential growth of the pest. Being sweet orange most preferable commodity, the host range of the fly includes almost all the citrus fruits. The fly has damaged 20-50% of the fruit every year and resulted in a loss of millions of rupees.  Therefore various pest management practices can be deployed for sustainable eco-friendly management of the pest. The Chinese fruit fly can be successfully managed by hydrolase protein baits, regular pruning, augmentation of bio-control agents, and using soft systemic insecticides. Various other options for the management of Chinese fruit fly are also discussed with their biological efficacy for the sustainable and eco-friendly management of pests

ASSESSMENT OF KNOWLEDGE AND AWARENESS ABOUT LEPROSY AMONG MEDICAL COLLEGE STUDENTS IN MEWAT REGION OF HARYANA

Introduction -Leprosy is a chronic infectious disease which still remains a serious public health problem due to its ability to cause disability. The prevention of leprosy ultimately lies in the early diagnosis and treatment of the individuals having leprosy. Changing leprosy scenario has led to requirement of leprosy education. However the knowledge of medical college students on leprosy remains unknown. Aim: To assess the post-sensitization knowledge and awareness of medical students after state leprosy sensitization program. Materials and methods: A questionnaire based, cross sectional study was conducted among 107 medical students of different years starting from 2nd year and onwards in the month of July 2017 after state leprosy sensitization program. Results: Among the medical students 70 (75%) were male students and 37(25%) were female students coming from different years of their admission in medical college .Regarding the basic knowledge of leprosy 100 % of 3nd year and final year students were having knowledge about the cause of leprosy and 100% of final year and 3rd year medical students know about other name of Leprosy (Hansen,s disease) respectively.100% of final year, 3rd year and 2nd year medical students had knowledge about multidrug therapy (MDT) in in-depth knowledge of leprosy respectively. Regarding the virulence of bacilli 87%, 60% and 63% of final, 3rd and 2nd year medical students had apt knowledge respectively. Conclusion-These observations suggest that the basic and in-depth knowledge of medical students about cause, types, prevention and treatment etc. of leprosy shows increasing trend owing to the part of their curriculum. However there is still a need to organize sensitization programs at regular intervals to impart basic and in-depth knowledge to new medical students, as well as to update the knowledge of those who already had such sensitization programs.Keywords: Awareness; Knowledge; Leprosy; Sensitization

ASSESSMENT OF KNOWLEDGE AND AWARENESS ABOUT LEPROSY AMONG MEDICAL COLLEGE STUDENTS IN MEWAT REGION OF HARYANA

Introduction -Leprosy is a chronic infectious disease which still remains a serious public health problem due to its ability to cause disability. The prevention of leprosy ultimately lies in the early diagnosis and treatment of the individuals having leprosy. Changing leprosy scenario has led to requirement of leprosy education. However the knowledge of medical college students on leprosy remains unknown. Aim: To assess the post-sensitization knowledge and awareness of medical students after state leprosy sensitization program. Materials and methods: A questionnaire based, cross sectional study was conducted among 107 medical students of different years starting from 2nd year and onwards in the month of July 2017 after state leprosy sensitization program. Results: Among the medical students 70 (75%) were male students and 37(25%) were female students coming from different years of their admission in medical college .Regarding the basic knowledge of leprosy 100 % of 3nd year and final year students were having knowledge about the cause of leprosy and 100% of final year and 3rd year medical students know about other name of Leprosy (Hansen,s disease) respectively.100% of final year, 3rd year and 2nd year medical students had knowledge about multidrug therapy (MDT) in in-depth knowledge of leprosy respectively. Regarding the virulence of bacilli 87%, 60% and 63% of final, 3rd and 2nd year medical students had apt knowledge respectively. Conclusion-These observations suggest that the basic and in-depth knowledge of medical students about cause, types, prevention and treatment etc. of leprosy shows increasing trend owing to the part of their curriculum. However there is still a need to organize sensitization programs at regular intervals to impart basic and in-depth knowledge to new medical students, as well as to update the knowledge of those who already had such sensitization programs.Keywords: Awareness; Knowledge; Leprosy; Sensitization