Similarities between the structure functions of thermal convection and hydrodynamic turbulence

In this paper, we analyze the scaling of velocity structure functions of turbulent thermal convection. Using high-resolution numerical simulations, we show that the structure functions scale similar to those of hydrodynamic turbulence, with the scaling exponents in agreement with She and Leveque's predictions [Phys. Rev. Lett. 72, 336-339 (1994)]. The probability distribution functions of velocity increments are non-Gaussian with wide tails in the dissipative scales and become close to Gaussian in the inertial range. The tails of the probability distribution follow a stretched exponential. We also show that in thermal convection, the energy flux in the inertial range is less than the viscous dissipation rate. This is unlike in hydrodynamic turbulence where the energy flux and the dissipation rate are equal.Comment: 21 pages, 9 figure

Drug utilization study in Cardiology outpatient department at a tertiary care hospital

Background: Cardiovascular diseases are the most frequent cause of morbidity and mortality throughout the world particularly in South Asian population. With advent of newer, highly efficacious heterogeneous drugs and changing treatment guidelines, there’s a need to identify the cardiologist preference and prescribing patterns for rational utilization.Methods: It was an open label, prospective, cross-sectional, descriptive type of study conducted in Cardiology Outpatients at a Tertiary care hospital, Navi Mumbai. The study included 100 patients suffering from cardiovascular diseases attending cardiology outpatient department from October 2016 to March 2017. Informed consent was obtained and the currently prescribed drug details were recorded from prescription. The data was analysed for WHO core prescribing indicators and different types of drugs prescribed.Results: The average number of drug products prescribed was 3.4. Most commonly prescribed drugs were Antiplatelets (23%) followed by Statins (19.71%), β blockers (16%), Nitrates (11.70%), Angiotensin converting enzyme inhibitors (8.03%), Calcium channel blockers (5.50%), Angiotensin receptor blockers (4.70%), Diuretics (2.55%), Anticoagulant (1.83%), α+β blocker (1.46%), Cardiac glycosides ((1.09%), Potassium sparing diuretic and central sympatholytics. Majority of drugs were prescribed as single drugs (79.88%) while 20.11% as fixed dose combination (FDC). The combination of Telmisartan + Hydrochlorthiazide was the commonest prescribed FDC. Majority drugs were prescribed from NEDL 2015, but documented low generic prescribing.Conclusions: Antiplatelet and Statins dominated the prescribing pattern with high prescribing trend from national essential drug list, but showed scope for improvement in encouraging the cardiologist to prescribe by generic name

Drug utilization study in ophthalmology in OPD patients at a tertiary care teaching hospital

Background: Drug therapy is a major component of patient care management in health care settings. Irrational and inappropriate use of drugs in health care system observed globally is being a major concern. In the field of ophthalmology, there have been many drug developments and different classes of drugs with combinational products are available in ophthalmology for the treatment of ophthalmic diseases. Periodic prescription analysis in the form of drug utilization study can improve the quality of prescription and curb the menace of irrational prescribing. Aim and objectives were to study the prescribing pattern and drug utilization trends in Ophthalmology outpatient department at a tertiary care hospital in Navi Mumbai.Methods: A cross-sectional, observational study was conducted over a period of six months in Ophthalmology department of a tertiary care teaching hospital, Navi-Mumbai. A total of 103 adult patients visiting Ophthalmology OPD for curative symptoms were included and their prescriptions were analyzed with WHO prescribing indicators and additional indices.Results: Analysis showed that the average number of drugs per prescription was 1.9. Percentage of drugs prescribed by brand was 100 % versus generic 0 %. Percentage of drugs prescribed from National Essential drug list (NEDL) was 53%. The percentage of encounters with antibiotics was 30.6%. The commonest prescribed drugs were ocular lubricants followed by antibiotics. Eye drops were the commonest prescribed dosage form.Conclusions: Ocular lubricants and antibiotics dominated the prescribing pattern in this study with restraint on polypharmacy, but showed ample scope for improvement in encouraging the ophthalmologist to prescribe generic and selection of essential drugs

Complexity of viscous dissipation in turbulent thermal convection

Using direct numerical simulations of turbulent thermal convection for Rayleigh number ($\mathrm{Ra}$) between $10^6$ and $10^8$ and unit Prandtl number, we derive scaling relations for viscous dissipation in the bulk and in the boundary layers. We show that contrary to the general belief, the total viscous dissipation in the bulk is larger, albeit marginally, than that in the boundary layers. The bulk dissipation rate is similar to that in hydrodynamic turbulence with log-normal distribution, but it differs from $(U^3/d)$ by a factor of $\mathrm{Ra}^{-0.18}$. Viscous dissipation in the boundary layers are rarer but more intense with a stretched-exponential distribution.Comment: 5 pages, 4 figures, 1 supplemental materia

The NANOGrav 15-year Data Set: Evidence for a Gravitational-Wave Background

We report multiple lines of evidence for a stochastic signal that is correlated among 67 pulsars from the 15-year pulsar-timing data set collected by the North American Nanohertz Observatory for Gravitational Waves. The correlations follow the Hellings-Downs pattern expected for a stochastic gravitational-wave background. The presence of such a gravitational-wave background with a power-law-spectrum is favored over a model with only independent pulsar noises with a Bayes factor in excess of $10^{14}$, and this same model is favored over an uncorrelated common power-law-spectrum model with Bayes factors of 200-1000, depending on spectral modeling choices. We have built a statistical background distribution for these latter Bayes factors using a method that removes inter-pulsar correlations from our data set, finding $p = 10^{-3}$ (approx. $3\sigma$) for the observed Bayes factors in the null no-correlation scenario. A frequentist test statistic built directly as a weighted sum of inter-pulsar correlations yields $p = 5 \times 10^{-5} - 1.9 \times 10^{-4}$ (approx. $3.5 - 4\sigma$). Assuming a fiducial $f^{-2/3}$ characteristic-strain spectrum, as appropriate for an ensemble of binary supermassive black-hole inspirals, the strain amplitude is $2.4^{+0.7}_{-0.6} \times 10^{-15}$ (median + 90% credible interval) at a reference frequency of 1/(1 yr). The inferred gravitational-wave background amplitude and spectrum are consistent with astrophysical expectations for a signal from a population of supermassive black-hole binaries, although more exotic cosmological and astrophysical sources cannot be excluded. The observation of Hellings-Downs correlations points to the gravitational-wave origin of this signal.Comment: 30 pages, 18 figures. Published in Astrophysical Journal Letters as part of Focus on NANOGrav's 15-year Data Set and the Gravitational Wave Background. For questions or comments, please email [email protected]

Analysing the Performance and Stability of LED-to-Camera Links

Recently, Visible light communication systems have been gaining the interest of the research community due to their great potential for creating high-speed data links and providing an alternative to the crowded radio spectrum. As smartphones have become an integral part of life, it would be great if visible light communication could provide additional benefits like line-of-sight data transfer, via the smartphone. Recent studies have demonstrated the feasibility of using the light-to-camera communication to take advantage of the current VLC infrastructure. The current systems present different approaches to establish the light-to-camera communication link. The performance of these links depends on many variables like the camera frame-rate, operational frequency, exposure time, etc., thus, their direct comparison is not possible. There is no common ground on which these state-of-the-art schemes can be evaluated. This thesis presents a model where these schemes are compared on a common platform.The current systems are also very inflexible in terms of adjusting their performance based on the distance between the transmitter and the receiver. Creating a flexible light-to-camera communication system requires some form of synchronisation between the transmitter and the receiver.In this thesis, we also present a Mathematical model to optimise the reliability of the communication link with varying distances between the transmitter and the receiver. This model can also be used for calculating the performance of the communication link based on the aforementioned variables (i.e. camera frame-rate, operational frequency, read=out duration)Electrical Engineer | Embedded System

Drug utilization study in ophthalmology in OPD patients at a tertiary care teaching hospital

Background: Drug therapy is a major component of patient care management in health care settings. Irrational and inappropriate use of drugs in health care system observed globally is being a major concern. In the field of ophthalmology, there have been many drug developments and different classes of drugs with combinational products are available in ophthalmology for the treatment of ophthalmic diseases. Periodic prescription analysis in the form of drug utilization study can improve the quality of prescription and curb the menace of irrational prescribing. Aim and objectives were to study the prescribing pattern and drug utilization trends in Ophthalmology outpatient department at a tertiary care hospital in Navi Mumbai.Methods: A cross-sectional, observational study was conducted over a period of six months in Ophthalmology department of a tertiary care teaching hospital, Navi-Mumbai. A total of 103 adult patients visiting Ophthalmology OPD for curative symptoms were included and their prescriptions were analyzed with WHO prescribing indicators and additional indices.Results: Analysis showed that the average number of drugs per prescription was 1.9. Percentage of drugs prescribed by brand was 100 % versus generic 0 %. Percentage of drugs prescribed from National Essential drug list (NEDL) was 53%. The percentage of encounters with antibiotics was 30.6%. The commonest prescribed drugs were ocular lubricants followed by antibiotics. Eye drops were the commonest prescribed dosage form.Conclusions: Ocular lubricants and antibiotics dominated the prescribing pattern in this study with restraint on polypharmacy, but showed ample scope for improvement in encouraging the ophthalmologist to prescribe generic and selection of essential drugs