In vitro
, cellular processing on polymeric surfaces is fundamental to the development of biosensors, scaffolds for tissue engineering and transplantation. However, the effect of surface energy and ...roughness on the cell-surface interaction remains inconclusive, indicating a lack of complete understanding of the phenomenon. Here, we study the effect of surface energy (
E
s
) and roughness ratio (
r
) of a polydimethylsiloxane (PDMS) substrate on cell attachment, growth, and proliferation. We considered two different cell lines, HeLa and MDA MB 231, and rough PDMS surfaces of different surface energy in the range
E
s
= 21-100 mJ m
−2
, corresponding to WCA 161°-1°, and roughness ratio in the range
r
= 1.05-3, corresponding to roughness 5-150 nm. We find that the cell attachment process proceeds through three different stages marked by an increase in the number of attached cells with time (stage I), flattening of cells (stage II), and elongation of cells (III) on the surface. Our study reveals that moderate surface energy (
E
s
70 mJ m
−2
) and intermediate roughness ratio (
r
2) constitute the most favourable conditions for efficient cell adhesion, growth, and proliferation. A theoretical model based on the minimization of the total free energy of the cell-substrate system is presented and is used to predict the spread length of cells that compares well with the corresponding experimental data within 10%. The performance and reusability of the rough PDMS surface of moderate energy and roughness prepared
via
facile surface modification are compared with standard T-25 cell culture plates for cell growth and proliferation, which shows that the proposed surface is an attractive choice for efficient cell culture.
In vitro
, cellular processing on polymeric surfaces is fundamental to the development of biosensors, scaffolds for tissue engineering and transplantation.
We consider a low redshift ( z < 0.7 ) cosmological data set comprising megamasers, cosmic chronometers, type Ia supernovae and baryon acoustic oscillations, which we bin according to their redshift. ...For each bin, we read the value of H0 by fitting directly to the flat Λ CDM model. Doing so, we find that H0 descends with redshift, allowing one to fit a line with a nonzero slope of statistical significance 2.1σ. Our analysis rests on the use of cosmic chronometers to break a degeneracy in baryon acoustic oscillations data and it will be imperative to revisit this feature as data improves. Nevertheless, our results provide the first independent indication of the descending trend reported by the H0LiCOW Collaboration. If substantiated going forward, early Universe solutions to the Hubble tension will struggle explaining this trend.
We report a simple, inexpensive, rapid, and one-step method for the fabrication of a stable and biocompatible superhydrophobic and superhemophobic surface. The proposed surface comprises candle soot ...particles embedded in a mixture of PDMS+n-hexane serving as the base material. The mechanism responsible for the superhydrophobic behavior of the surface is explained, and the surface is characterized based on its morphology and elemental composition, wetting properties, mechanical and chemical stability, and biocompatibility. The effect of %n-hexane in PDMS, the thickness of the PDMS+n-hexane layer (in terms of spin coating speed) and sooting time on the wetting property of the surface is studied. The proposed surface exhibits nanoscale surface asperities (average roughness of 187 nm), chemical compositions of soot particles, very high water and blood repellency along with excellent mechanical and chemical stability and excellent biocompatibility against blood sample and biological cells. The water contact angle and roll-off angle is measured as 160° ± 1° and 2°, respectively, and the blood contact angle is found to be 154° ± 1°, which indicates that the surface is superhydrophobic and superhemophobic. The proposed superhydrophobic and superhemophobic surface offers significantly improved (>40%) cell viability as compared to glass and PDMS surfaces.
An uncertain glory Drèze, Jean; Sen, Amartya
2013, 2013., 20130811, 2013-08-11
eBook, Book
When India became independent in 1947 after two centuries of colonial rule, it immediately adopted a firmly democratic political system, with multiple parties, freedom of speech, and extensive ...political rights. The famines of the British era disappeared, and steady economic growth replaced the economic stagnation of the Raj. The growth of the Indian economy quickened further over the last three decades and became the second fastest among large economies. Despite a recent dip, it is still one of the highest in the world. Maintaining rapid as well as environmentally sustainable growth remains an important and achievable goal for India. In An Uncertain Glory, two of India's leading economists argue that the country's main problems lie in the lack of attention paid to the essential needs of the people, especially of the poor, and often of women. There have been major failures both to foster participatory growth and to make good use of the public resources generated by economic growth to enhance people's living conditions. There is also a continued inadequacy of social services such as schooling and medical care as well as of physical services such as safe water, electricity, drainage, transportation, and sanitation. In the long run, even the feasibility of high economic growth is threatened by the underdevelopment of social and physical infrastructure and the neglect of human capabilities, in contrast with the Asian approach of simultaneous pursuit of economic growth and human development, as pioneered by Japan, South Korea, and China. In a democratic system, which India has great reason to value, addressing these failures requires not only significant policy rethinking by the government, but also a clearer public understanding of the abysmal extent of social and economic deprivations in the country. The deep inequalities in Indian society tend to constrict public discussion, confining it largely to the lives and concerns of the relatively affluent. (Author's abstract, IAB-Doku) ".
Droplets can be used as carrier vehicles for the transportation of biological and chemical reagents. Manipulation of water- and oil-based ferromagnetic droplets in the presence of a magnetic field ...has been well-studied. Here, we elucidate the transport of a sessile aqueous (diamagnetic) droplet placed over spikes of oil-based ferrofluid (FF) in the presence of a nonuniform magnetic field. An oil-based FF droplet, dispensed over a rigid oleophilic surface, interacts with a magnetic field to get transformed into an array of spikes which then act as a carrier for the transportation of the aqueous droplet. Our study reveals that transportation phenomena is governed by the interplay of three different forces: magnetic force F m, frictional force F f, and interfacial tension force F i, which is expressed in terms of the magnetic Laplace number (La m) and magnetic Bond number (Bo m) as La m –1 = (F f1/F m,x ) and Bo m La m –1 = (F f2/F i). Based on the values of the dimensionless numbers, three different regimes, steady droplet transport, spike extraction, and magnet disengagement, are identified. It is found that steady droplet transport is observed for La m –1 ≤ 1 and Bo m La m –1 ≤ 1, whereas extraction of spikes is observed for La m –1 ≤ 1 and Bo m La m –1 > 1 and magnet disengagement is observed for La m –1 > 1. In the steady droplet transport regime, velocity of the aqueous droplet U ds was found to be dependent on the volumes of the aqueous droplet V w and FF droplet V FF following U ds ∼ V w –0.19 V FF 0.36. A simple model is presented that accurately predicts the aqueous droplet velocity U ds within 5% of the corresponding experimental data. In the spike extraction regime, the spike extraction distance L se was found to vary with V w, V FF, and the magnet velocity U ms following L se ∼ V w –1.75 V FF 0.75 U ms –1.56.
A
bstract
Strong cosmic censorship conjecture has been one of the most important leap of faith in the context of general relativity, providing assurance in the deterministic nature of the associated ...field equations. Though it holds well for asymptotically flat spacetimes, a potential failure of the strong cosmic censorship conjecture might arise for spacetimes inheriting Cauchy horizon along with a positive cosmological constant. We have explicitly demonstrated that violation of the censorship conjecture holds true in the presence of a Maxwell field even when higher spacetime dimensions are invoked. In particular, for a higher dimensional Reissner-Nordström-de Sitter black hole the violation of cosmic censorship conjecture is at a larger scale compared to the four dimensional one, for certain choices of the cosmological constant. On the other hand, for a brane world black hole, the effect of extra dimension is to make the violation of cosmic censorship conjecture weaker. For rotating black holes, intriguingly, the cosmic censorship conjecture is always respected even in presence of higher dimensions. A similar scenario is also observed for a rotating black hole on the brane.
Explaining the late-time acceleration is one of the most challenging tasks for theoretical physicists today. Infrared modification of Einstein’s general theory of relativity (GR) is a possible route ...to model late-time acceleration. In this regard, vector-tensor theory, as a part of gravitational interactions on large cosmological scales, has been proposed recently. This involves generalization of a massive Proca Lagrangian in curved spacetime. Black hole solutions in such theories have also been constructed. In this paper, we study different astrophysical signatures of such black holes. We first study the strong lensing and time delay effect of such static spherically symmetric black hole solutions, in particular for the case of gravitational lensing of the star S2 by Sagittarius A ∗ at the centre of Milky Way. We also construct the rotating black hole solution from this static spherically symmetric solution in Proca theories using the Newman-Janis algorithm and subsequently study lensing, time delay and black hole shadow effect in this rotating black hole spacetime. We discuss the possibility of detecting the Proca hair in future observations.
Microwell arrays are amongst the most commonly used platforms for biochemical assays. However, the coalescence of droplets that constitute the dispersed phase of suspensions housed within microwells ...has not received much attention to date. Herein, we study the coalescence of droplets in a two-phase system in a microwell driven by surface acoustic waves (SAWs). The microwell structure, together with symmetric exposure to SAW irradiation, coupled from beneath the microwell via a piezoelectric substrate, gives rise to the formation of a pair of counter-rotating vortices that enable droplet transport, trapping, and coalescence. We elucidate the physics of the coalescence phenomenon using a scaling analysis of the relevant forces, namely, the acoustic streaming-induced drag force, the capillary and viscous forces associated with the drainage of the thin continuous phase film between the droplets and the van der Waals attraction force. We confirm that droplet–droplet interface contact is established through the formation of a liquid bridge, whose neck radius grows linearly in time in the preceding viscous regime and proportionally with the square root of time in the subsequent inertial regime. Further, we investigate the influence of the input SAW power and droplet size on the film drainage time and demarcate the coalescence and non-coalescence regimes to derive a criterion for the onset of coalescence. The distinct deformation patterns observed for a pair of contacting droplets in both the regimes are elucidated and the possibility for driving concurrent coalescence of multiple droplets is demonstrated. We expect the study will find relevance in the demulsification of immiscible phases and the mixing of samples/reagents within microwells for a variety of biochemical applications.
•In this work, we present a unique approach for the manipulation of aqueous droplets on a soot-wax coated PDMS-iron particle composite substrate.•The method used for the preparation of the substrate ...and the surface is simple, less time consuming and economical thus making it suitable for microfluidics applications.•The proposed substrate has embedded microparticles which enable a unique method of creating a local deformation for droplet manipulation.•The superhydrophobic surface offers higher contact angle (∼170°) and lower roll off angle (<7°) to facilitate rapid motion of droplets.
We report controlled motion of aqueous droplets on soot-wax coated superhydrophobic surface of a PDMS-iron particle composite substrate. The surface profile around a droplet is altered due to magnetic force acting on the iron particles embedded in the substrate, which leads to droplet motion. The contact angle and roll off angle depend on the soot deposit time and particle distribution. Endurance test is performed to confirm stability of the surface. The deformation behaviour of the substrate is studied with particle size, surface to magnet gap and the cone angle of the magnet. The proposed surface could find applications in the manipulation of sample drops in biological and chemical assays.
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