Particle size selection in capillary instability of locally heated co-axial fiber

Harnessing fluidic instabilities to produce structures with robust and regular properties has recently emerged as a new fabrication paradigm. This is exemplified in the work of Gumennik et al. [Nat. Comm. 4:2216, DOI: 10.1038/ncomms3216, (2013)], in which the authors fabricate silicon spheres by feeding a silicon-in-silica co-axial fiber into a flame. Following the localized melting of the silicon, a capillary instability of the silicon-silica interface induces the formation of uniform silicon spheres. Here, we try to unravel the physical mechanisms at play in selecting the size of these particles, which was notably observed by Gumennik et al. to vary monotonically with the speed at which the fiber is fed into the flame. Using a simplified model derived from standard long-wavelength approximations, we show that linear stability analysis strikingly fails at predicting the selected particle size. Nonetheless, nonlinear simulations of the simplified model do recover the particle size observed in experiments, without any adjustable parameters. This shows that the formation of the silicon spheres in this system is an intrinsically nonlinear process that has little in common with the loss of stability of the underlying base flow solution.Comment: 23 pages, 15 figure

Energy Efficient IoT-Sensors Network for Smart Farming

The experience of smart farming can be improved using IoT-based applications. Still, the performance of IoT networks may be degraded due to different factors, i.e., the coverage area of the farm/location (surface or underwater)/environmental conditions etc. Network operations over heterogeneous environments may cause excessive resource consumption and thus may reduce the IoT sensor’s lifespan. To optimise energy consumption, in this paper, an energy-efficient method will be introduced for smart farming, and its performance will be analysed using different parameters (i.e., Throughput/energy consumption/residual energy etc.) using two different IoT standards (Long Range Low powered technology (LoRa)/SigFox)

Patients Operated By Female Surgeons Have Lower Risk-Adjusted Adverse Postoperative Outcomes

        Surgery is the modality of treatment whereby injury, deformity or disease is managed by removal, repair or readjustment of the tissue or organs. One may have to incise and cut open the body cavity to remove or repair the diseased organ. Surgical branches attract the doctors right from their student life. It requires deep knowledge, surgical skill, decision power, and determined mind to handle the complications. In modern era it has been observed that gender ratio in the medical college admissions is shifting more towards female candidates compared to male. Few decades back gynaecology was the preferred branch of medicine for female doctors to pursue their further post graduate studies. In modern times with changing social scenario, we see female doctors in other surgical branches like ENT, ophthalmology, general surgery and even orthopaedics! As our institute is a teaching hospital to affiliated a medical college in outskirt of Baroda city draining vast surrounding peripheral areas and serves to provide free of cost maternal and child health services under various govt maternal and child health schemes, labour rate in our hospital whorls around 300 per month on an average. Unregistered and complicated emergency patients referred from peripheral referral units constitute a sizeable bulk of patients . On average 8 to 10 major and 10 to 12 minor surgeries are performed in our hospital. Post graduate admissions fetch good number of female doctors to the hospital for training.  In view of good no of operable patients and a decent ratio of male and female doctors we were inspired to carry out this study.         In view of the changing trends a study was carried out at Dhiraj hospital to determine the surgeon’s gender based post operative outcome of surgery in patients operated by male and female surgeons. It was observed that the patients operated by female surgeons had lower risk adjusted adverse post operative outcomes considering mortality, readmissions and complications.&nbsp

Achieving Surgical, Obstetric, Trauma, and Anesthesia (SOTA) care for all in South Asia

South Asia is a demographically crucial, economically aspiring, and socio-culturally diverse region in the world. The region contributes to a large burden of surgically-treatable disease conditions. A large number of people in South Asia cannot access safe and affordable surgical, obstetric, trauma, and anesthesia (SOTA) care when in need. Yet, attention to the region in Global Surgery and Global Health is limited. Here, we assess the status of SOTA care in South Asia. We summarize the evidence on SOTA care indicators and planning. Region-wide, as well as country-specific challenges are highlighted. We also discuss potential directions-initiatives and innovations-toward addressing these challenges. Local partnerships, sustained research and advocacy efforts, and politics can be aligned with evidence-based policymaking and health planning to achieve equitable SOTA care access in the South Asian region under the South Asian Association for Regional Cooperation (SAARC)

Achieving Surgical, Obstetric, Trauma, and Anesthesia (SOTA) care for all in South Asia

South Asia is a demographically crucial, economically aspiring, and socio-culturally diverse region in the world. The region contributes to a large burden of surgically-treatable disease conditions. A large number of people in South Asia cannot access safe and affordable surgical, obstetric, trauma, and anesthesia (SOTA) care when in need. Yet, attention to the region in Global Surgery and Global Health is limited. Here, we assess the status of SOTA care in South Asia. We summarize the evidence on SOTA care indicators and planning. Region-wide, as well as country-specific challenges are highlighted. We also discuss potential directions—initiatives and innovations—toward addressing these challenges. Local partnerships, sustained research and advocacy efforts, and politics can be aligned with evidence-based policymaking and health planning to achieve equitable SOTA care access in the South Asian region under the South Asian Association for Regional Cooperation (SAARC)

Response of noise-amplifier flows: From linear control to nonlinear jet breakup

Among hydrodynamically unstable flows, the amplifier-flows are characterized by their large amplification potential in presence of external noise. Since amplifiers do not have an intrinsic dynamics, a chosen forcing can be applied to eventually control the downstream evolution of such flows. With this aim, we intend to analyse the flow control in amplifier-flows, common examples being the flow in a backward facing step and the free surface capillary jet. We begin by analysing the flow control applied over a three-dimensional spanwise-modulating backward facing step. With the objective of reducing the lower recirculation length, we look for small amplitude optimal controls either by blowing/suction or by applying a wall deformation. A similar approach is then applied for the free surface axisymmetric capillary jet. The analysis is simplified by using the one-dimensional equations of Eggers & Dupont (J. Fluid Mech., vol. 262, 1994, 205-221) which describe the flow using only the radius of the jet and its velocity as functions of the jet axial coordinate and time. We concentrate on two jet variations, one has a parallel base flow and the other has a spatially varying base flow due to the stretching effect of gravity. A local stability analysis is sufficient for analysing parallel base flows, whereas the spatially varying jets are analysed in the global framework. Further, we perform numerical simulations with the target of finding the optimal forcing which minimizes the intact jet length, also referred to as the breakup length. Unlike the parallel jets, the optimal forcing frequency for the spatially varying jet is dependent on the forcing amplitude. Similar results are then captured through the global resolvent analysis by introducing the forcing amplitude in the linear resolvent framework. Using a similar linear stability approach we then analyse the special case of silicone-in-silica jets inspired by the experimental results of Gumennik et al. (Nat. Commun., vol. 4, 2013, 2216). Based on the reformulated one-dimensional equations, we predict numerically the drop size as a function given fibre feed speed, which is found to be in close accordance with the experimental results. Finally, we explore experimentally the physical dynamics of drops rising in an external medium in a Hele-Shaw cell due to buoyancy. We specifically analyse the relation between the drop velocity and the mean film thickness magnitude around the drop. We present complete film thickness maps for these drops which highlight the 'catamaran' like shape often observed for similar drops in pressure driven flows inside the Hele-Shaw cell

Solution Electrochemical Approach to Synthesis of Low Stage Graphite Bisulphate

Since their discovery in 1841, Graphite Intercalation Compounds (GICs) have found tremendous applications in various industrial and research fields such as supercapacitors, superconductors, heterogeneous catalysts, anode materials, hydrogen and lithium-ion storage and notably in graphene synthesis. GICs are a type of graphitic compounds formed by the insertion of a different atomic, ionic or molecular species, known as intercalants between the layers of graphite host. Intercalation occurs in stages, and the phenomenon of staging is characterised by stage index n, which is the number of carbon layers present between two successive intercalate layers. The concentration of intercalant in graphite increases as the stage index decreases. Oxyacids readily intercalate in graphite. Researchers have studied intercalation of graphite in a wide variety of such acids such as H2SO4, HNO3, H2SeO4, HClO4 and H3PO4, and concluded that sulphuric acid is the best intercalant for graphite owing to higher efficiency and lesser reaction times. Intercalation in sulphuric acid gives Graphite Bisulphate (GB). Conventional GB chemical synthesis methods, pose an environmental and safety hazard due to the usage of hazardous and explosive oxidants. Moreover, chemical methods such as Hummers’ are primarily oxidation routes for the synthesis of Graphene Oxide (GO) wherein GB is believed to be the process intermediate, which is difficult to isolate. Electrochemical synthesis of GB is inexpensive, scalable and provides an easy defect-free transfer to the application substrate due to its ability to deliver the product in a suspension. Furthermore, the electrochemical approach provides an environment- friendly solution to the synthesis of GB because it replaces harsh chemical oxidants with an external polarisation potential. The quantity of electricity passed can also be controlled by changing the applied potential to obtain desired stages of GB. However, the synthesis of low stage GB by the electrochemical process in aqueous sulphuric acid solutions is an arduous task as a result of the excess water present in the system. Water molecules react with surface C atoms to form bulky surface groups which hinder the process of intercalation. Furthermore, undissociated water molecules may also co-intercalate with the bisulphate ions from aqueous sulphuric acid. Electrochemical oxidation of this intercalated water causes reduction of bisulphate ions and ultimately results in the vigorous evolution of oxygen and sulphur dioxide, which exfoliates graphite. Thus, GB formed before exfoliation is disintegrated and lost. On the other hand, water also facilitates intercalation by opening up graphitic grain boundaries for intercalation by carrying out a nucleophilic attack on the edge sites. Thus an optimal concentration of water in aqueous sulphuric acid along with an optimal positive polarisation potential is required for the synthesis and stability of GB. The present study aims at the electrochemical synthesis and characterisation of low stage GB and determination of optimal reaction conditions for the process. A pure stage GB synthesised and isolated this way can be particularly useful for the synthesis of layer-specific graphene flakes. Intercalation reduces the force of attraction between layers of graphite and hence makes selective cleaving possible by sonication. The stage index is strongly correlated with the number of graphene layers produced upon electrochemical exfoliation and is thus a key parameter to tune the electrochemical exfoliation of graphite. </jats:p

Frequency selection in a gravitationally stretched capillary jet in the jetting regime

A capillary jet falling under the effect of gravity continuously stretches while thinning downstream. We report here the effect of external periodic forcing on such a spatially varying jet in the jetting regime. Surprisingly, the optimal forcing frequency producing the most unstable jet is found to be highly dependent on the forcing amplitude. Taking benefit of the one-dimensional Eggers & Dupont (J. Fluid Mech., vol. 262, 1994, pp. 205-221) equations, we investigate the case through nonlinear simulations and linear stability analysis. In the local framework, the WKBJ (Wentzel-Kramers-Brillouin-Jeffreys) formalism, established for weakly non-parallel flows, fails to capture the nonlinear simulation results quantitatively. However, in the global framework, the resolvent analysis, supplemented by a simple approximation of the required response norm inducing breakup, is shown to correctly predict the optimal forcing frequency at a given forcing amplitude and the resulting jet breakup length. The results of the resolvent analysis are found to be in good agreement with those of the nonlinear simulations