Modelling temporal and spatial features of collaboration network

The collaboration network is an example of a social network which has both non-trivial temporal and spatial dependence. Based on the observations of collaborations in Physical Review Letters, a model of collaboration network is proposed which correctly reproduces the time evolution of the link length distributions, clustering coefficients, degree distributions and assortative property of real data to a large extent.Comment: 8 pages, 10 figures; follow up work on arXiv.org/physics/0511181; accepted for publication in IJMP

Spreading of Non-Newtonian and Newtonian Fluids on a Solid Substrate under Pressure

Strongly non-Newtonian fluids namely, aqueous gels of starch, are shown to exhibit visco-elastic behavior, when subjected to a load. We study arrowroot and potato starch gels. When a droplet of the fluid is sandwiched between two glass plates and compressed, the area of contact between the fluid and plates increases in an oscillatory manner. This is unlike Newtonian fluids, where the area increases monotonically in a similar situation. The periphery moreover, develops an instability, which looks similar to Saffman Taylor fingers. This is not normally seen under compression. The loading history is also found to affect the manner of spreading. We attempt to describe the non-Newtonian nature of the fluid through a visco-elastic model incorporating generalized calculus. This is shown to reproduce qualitatively the oscillatory variation in the surface strain.Comment: 11 page

District level estimates and mapping of prevalence of diarrhoea among under-five children in Bangladesh by combining survey and census data

The demand for district level statistics has increased tremendously in Bangladesh due to existence of decentralised approach to governance and service provision. The Bangladesh Demographic Health Surveys (BDHS) provide a wide range of invaluable data at the national and divisional level but they cannot be used directly to produce reliable district-level estimates due to insufficient sample sizes. The small area estimation (SAE) technique overcomes the sample size challenges and can produce reliable estimates at the district level. This paper uses SAE approach to generate model-based district-level estimates of diarrhoea prevalence among under-5 children in Bangladesh by linking data from the 2014 BDHS and the 2011 Population Census. The diagnostics measures show that the model-based estimates are precise and representative when compared to the direct survey estimates. Spatial distribution of the precise estimates of diarrhoea prevalence reveals significant inequality at district-level (ranged 1.1–13.4%) with particular emphasis in the coastal and north-eastern districts. Findings of the study might be useful for designing effective policies, interventions and strengthening local-level governance

Utility of telemedicine in COVID-19 pandemic: our experience at a tertiary cancer center in North East India

Background: Telemedicine is a very useful tool of communication between the doctor and the patient. The aim of this study was to find out the utility of telemedicine during the lockdown period of COVID-19 pandemic in North East India.Methods: It is a cross sectional study among the cancer patients at our center on follow up or ongoing treatment and analysis of all the data acquired from telephonic conversation with our patients from 30th March, 2020 to 3rd May, 2020. Have contacted 4181 patients during this period over phone. All phone calls were done by respective department doctors.Results: From the demographic data, we get that 35.4% of patients were at good physical condition, 3.5% with poor general condition, 11.6% patients having ongoing treatment in our institute, 21.1% patients expired, 0.9% patients have nonmalignant diagnosis, 1.4% patients left the institute due to various reasons. Analyzed this data with brain storming sessions amongst the COVID-19 task force doctors and tried to find out solutions of each problem.Conclusions: Telemedicine cannot replace conventional method of in person treatment, but it proved to be a useful tool during the COVID-19 pandemic for patient follow up and treatment of cancer patients

Bacteriological examination of drinking water in Burdwan, India with reference to coliforms

Most probable number (MPN) test was done to detect the coliform in water samples collected from mobile vendors, sweet shops and tap water supplied from Burdwan municipality. The study revealed that the number of coliforms was very high (1600) in water samples collected from mobile vendors. The bacteria were identified as Escherichia coli. Bacteriological examination of water samples collected from different sources showed that the water of mobile vendors and sweet shops of Burdwan marketarea was not potable while the municipal tap water was found to be safe for drinking

Simulations of a weakly conducting droplet under the influence of an alternating electric field

We investigate the electrohydrodynamics of an initially spherical droplet under the influence of an external alternating electric field by conducting axisymmetric numerical simulations using a charge-conservative volume-of-fluid based finite volume flow solver. The mean amplitude of shape oscillations of a droplet subjected to an alternating electric field for leaky dielectric fluids is the same as the steady-state deformation under an equivalent root mean squared direct electric field for all possible electrical conductivity ratio $(K_r)$ and permittivity ratio $(S)$ of the droplet to the surrounding fluid. In contrast, our simulations for weakly conducting media show that this equivalence between alternating and direct electric fields does not hold for $K_r \ne S$. Moreover, for a range of parameters, the deformation obtained using the alternating and direct electric fields is qualitatively different, i.e. for low $K_r$ and high $S$, the droplet becomes prolate under alternating electric field but deforms to an oblate shape in the case of the equivalent direct electric field. A parametric study is conducted by varying the time period of the applied alternating electric field, the permittivity and the electrical conductivity ratios. It is observed that while increasing $K_r$ has a negligible effect on the deformation dynamics of the droplet for $K_r<S$, it enhances the deformation of the droplet when $K_r>S$ for both alternating and direct electric fields. We believe that our results may be of immense consequence in explaining the morphological evolution of droplets in a plethora of scenarios ranging from nature to biology.Comment: 10 pages, 8 figure

First mesospheric turbulence study using coordinated rocket and MST radar measurements over Indian low latitude region

A campaign to study turbulence in the mesosphere, over low latitudes in India, using rocket-borne measurements and Indian MST radar, was conducted during July 2004. A rocket-borne Langmuir probe detected a spectrum of electron density irregularities, with scale sizes in the range of about 1m to 1 km, in 67.5-78.0 km and 84-89 km altitude regions over a low latitude station Sriharikota (13.6°N, 80.2°E). A rocket-borne chaff experiment measured zonal and meridional winds about 30 min after the Langmuir probe flight. The MST radar located at Gadanki (13.5°N, 79.2°E), which is about 100 km west of Sriharikota, also detected the presence of a strong scattering layer in 73.5-77.5 km region from which radar echoes corresponding to 3m irregularities were received. Based on the region of occurrence of irregularities, which was highly collisional, presence of significant shears in zonal and meridional components of wind measured by the chaff experiment, 10 min periodicity in zonal and meridional winds obtained by the MST radar and the nature of wave number spectra of the irregularities, it is suggested that the observed irregularities were produced through the neutral turbulence mechanism. The percentage amplitude of fluctuations across the entire scale size range showed that the strength of turbulence was stronger in the lower altitude regions and decreased with increasing altitude. It was also found that the amplitude of fluctuations was large in regions of steeper electron density gradients. MST radar observations showed that at smaller scales of turbulence such as 3 m, (a) the thickness of the turbulent layer was between 2 and 3 km and (b) and fine structures, with layer thicknesses of about a km or less were also embedded in these layers. Rocket also detected 3-m fluctuations, which were very strong (a few percent) in lower altitudes (67.5 to 71.0 km) and small but clearly well above the noise floor at higher altitudes. Rocket and radar results also point to the possibility of existence of thin layers of turbulence (&lt;450 m). The turbulence parameters estimated from rocket-borne measurements of electron density fluctuations are consistent with those determined from MST radar observed Doppler spectra and the earlier works

Deconfinement Transition in Large N Lattice Gauge Theory

We study analytically the phase diagram of the pure $SU(N)$ lattice gauge theory at finite temperature, and we attempt to estimate the critical deconfinement temperature. We apply large $N$ techniques to the Wilson and to the Heat Kernel action, and we study the resulting models both in the strong coupling and in the weak coupling limits. Using the Heat Kernel action, we establish an interesting connection between the Douglas-Kazakov phase transition of two-dimensional QCD and the deconfining transition in $d$ dimensions. The analytic results obtained for the critical temperature compare well with Montecarlo simulations of the full theory in $(2+1)$ and in $(3+1)$ dimensions.Comment: 39 pages (Latex) + 4 ps-figures (using EPSF), DFTT 30/9

Generation of dark pulses in a bismuth tellurite based mode-locked erbium-doped fiber laser

We report on the formation of dark pulses in a highly nonlinear fiber laser passively mode-locked by a Bistmuth Tellurite (Bi2Te3) based SA. The SA was fabricated by embedding Bi2Te3 powder into polyvinyl alcohol (PVA) film by a solution casting technique. By inserting the SA into an EDFL cavity, stable mode-locked operation was achieved at 1592.68 nm with the maximum pulse energy up to 2.38 nJ by adjusting polarization controller. The laser operated at pulse repetition frequency of 1.0 MHz with a pulse width of 215 ns. These results suggested that Bi2Te3 could be developed as an effective SA for mode-locked dark pulses generation in a highly nonlinear cavity