Wagging the Contact Line: Transverse and Longitudinal Waves

Kinetics of wetting has been explored where the contact line not only sees a steady spreading but also has longitudinal or transverse oscillations imposed on it. The latter case is realized when spreading takes place over a rough surface. The effects of the imposed motion are small, which seem to be due to low spreading rates and small dynamic contact angles used in this study. However, a singularity is seen in viscous dissipation during the movement on the model rough surface, which is interpreted here as an instability that is similar to Haines\u27 jumps and stick-slip phenomena, with possible entrainment of the displaced fluid. This is the first time that all of these have been associated with each other

Wetting Kinetics of a Thin Film Evaporating in Air

The conservation equation and the equations of motion are solved for a case where a thin liquid film moves out of a slot onto a horizontal surface. The liquid is allowed to evaporate into air. The evaporation process is taken to be isothermal. Lubrication theory approximation is used where only the tangential velocity and its dependence only in the normal direction are considered. The dynamics of thin films includes the use of disjoining pressure for a pure liquid and where there is a dissolved polymer. The results show that evaporation is quicker than film thinning such that a spreading regime dominated by the effects of disjoining pressure is never achieved. However, unlike the cases of pinning studied so far, there is no singularity in the evaporative flux near the contact line because of the use of disjoining pressure on evaporation. It is also observed that a balance between the rate of viscous dissipation and surface work is able to quantify the steady state contact angle. Consequently, a more macroscopic (and quantitative) description of contact line can be found that avoids the singularities discussed earlier and also the detailed calculations shown here. However, the detailed calculations are necessary to make the above point

Room temperature multiferroicity in orthorhombic LuFeO3_3

From the measurement of dielectric, ferroelectric, and magnetic properties we observe simultaneous ferroelectric and magnetic transitions around $\sim$600 K in orthorhombic LuFeO$_3$. We also observe suppression of the remanent polarization by $\sim$95\% under a magnetic field of $\sim$15 kOe at room temperature. The extent of suppression of the polarization under magnetic field increases monotonically with the field. These results show that even the orthorhombic LuFeO$_3$ is a room temperature multiferroic of type-II variety exhibiting quite a strong coupling between magnetization and polarization.Comment: 5 pages with 5 figures; published in Appl. Phys. Let

Wetting Kinetics of Films Containing Non-Adsorbing Polymers

Kinetics of wetting by a polymer solution have been studied theoretically for a film pinned to a slot. The fluid mechanical equations have been solved using a numerical scheme. The role of polymers appears in the disjoining pressure in the model. The spreading kinetics are observed to follow a power law: a power of (1/4) is observed at short times due to the Laplace pressure, and (1/2) at large times under the Hamaker part of the disjoining pressure at very large times and with no equilibration. It is argued and demonstrated that techniques which have low resolutions such as microscopy will measure quite different kinetics: at short times a power of (1/4) as for wetting liquids and then a sudden equilibration as reported in these experiments. It is also argued on the basis of steric exclusion, and quantified in the disjoining pressure, that the behavior returns to that of wetting liquids when the polymer molecular weight becomes very high, as also observed in the experiments. Examples of how these features can find practical applications, and hence, the importance of use of polymers as additives are given

Self-assembled deoxyguanosine based molecular electronic device on GaN substrates

Nanoscale hybrid molecular organic photodetectors based on self-assembled guanosine molecules conjugated to wide-bandgap GaNsemiconductors has been realized in the ultraviolet wavelength regime. Metal-semiconductor-metal based photodetector is fabricated using ordering of modified guanosine based semiconductor nanowires which exhibit I-Vcharacteristics with high current response and higher rectification ratio compared to Si based hybrid photodetectors. Photocurrent response of a two-terminal device shows the typical characteristics of a semiconductorphotodiode with a cutoff wavelength at ∼325nm. The I-Vcharacteristics have been elucidated using the induced polarization properties of self-assembled guanosine semiconductor

On the Parameterized Complexity of Deletion to ?-Free Strong Components

Directed Feedback Vertex Set (DFVS) is a fundamental computational problem that has received extensive attention in parameterized complexity. In this paper, we initiate the study of a wide generalization, the H-SCC Deletion problem. Here, one is given a digraph D, an integer k and the objective is to decide whether there is a vertex set of size at most k whose deletion leaves a digraph where every strong component excludes graphs in the fixed finite family H as (not necessarily induced) subgraphs. When H comprises only the digraph with a single arc, then this problem is precisely DFVS. Our main result is a proof that this problem is fixed-parameter tractable parameterized by the size of the deletion set if H only contains rooted graphs or if H contains at least one directed path. Along with generalizing the fixed-parameter tractability result for DFVS, our result also generalizes the recent results of Göke et al. [CIAC 2019] for the 1-Out-Regular Vertex Deletion and Bounded Size Strong Component Vertex Deletion problems. Moreover, we design algorithms for the two above mentioned problems, whose running times are better and match with the best bounds for DFVS, without using the heavy machinery of shadow removal as is done by Göke et al. [CIAC 2019].publishedVersio

Sundarban mangroves: diversity, ecosystem services and climate change impacts

The Bengal delta coast harboring the famous Sundarban mangroves is extremely vulnerable to climate change. Already, salinity intrusion, increasing cyclones and anomalies in rainfall, and temperature, are causing many social and livelihood problems. However, our knowledge on the diversified climate change impacts on Sundarban ecosystems services, providing immense benefits, including foods, shelters, livelihood, and health amenities, is very limited. Therefore, this article has systematically reviewed the major functional aspects, and highlights on biodiversity, ecosystem dynamics, and services of the Sunderban mangroves, with respect to variations in climatic factors. The mangrove ecosystems are highly productive in terms of forest biomass, and nutrient contribution, especially through detritus-based food webs, to support rich biodiversity in the wetlands and adjacent estuaries. Sundarban mangroves also play vital role in atmospheric CO2 sequestration, sediment trapping and nutrient recycling. Sea level rise will engulf a huge portion of the mangroves, while the associated salinity increase is posing immense threats to biodiversity and economic losses. Climate-mediated changes in riverine discharge, tides, temperature, rainfall and evaporation will determine the wetland nutrient variations, influencing the physiological and ecological processes, thus biodiversity and productivity of Sundarban mangroves. Hydrological changes in wetland ecosystems through increased salinity and cyclones will lower the food security, and also induce human vulnerabilities to waterborne diseases. Scientific investigations producing high resolution data to identify Sundarban‟s multidimensional vulnerabilities to various climatic regimes are essential. Sustainable plans and actions are required integrating conservation and climate change adaptation strategies, including promotion of alternative livelihoods. Thus, interdisciplinary approaches are required to address the future climatic disasters, and better protection of invaluable ecosystem services of the Sunderban mangroves.Fil: Neogi, Sucharit Basu. Coastal Development Partnership; Bangladesh. Osaka Prefecture University; Japón. Leibniz Center for Tropical Marine Ecology GmbH; AlemaniaFil: Dey, Mouri. University of Chittagong; BangladeshFil: Lutful Kabir, S. M.. Bangladesh Agricultural University; BangladeshFil: Masum, Syed Jahangir H.. Coastal Development Partnership; BangladeshFil: Kopprio, Germán Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Leibniz Center for Tropical Marine Ecology GmbH; AlemaniaFil: Yamasaki, Shinji. Osaka Prefecture University; JapónFil: Lara, Ruben Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentin