Site-Specific Colloidal Crystal Nucleation by Template-enhanced Particle Transport

The monomer surface mobility is the single most important parameter that decides the nucleation density and morphology of islands during thin film growth. During template-assisted surface growth in particular, low surface mobilities can prevent monomers from reaching target sites and this results in a partial to complete loss of nucleation control. While in atomic systems a broad range of surface mobilities can be readily accessed, for colloids, owing to their large size, this window is substantially narrow and therefore imposes severe restrictions in extending template-assisted growth techniques to steer their self-assembly. Here, we circumvented this fundamental limitation by designing templates with spatially varying feature sizes, in this case moire patterns, which in the presence of short-range depletion attraction presented surface energy gradients for the diffusing colloids. The templates serve a dual purpose, first, directing the particles to target sites by enhancing their surface mean free paths and second, dictating the size and symmetry of the growing crystallites. Using optical microscopy, we directly followed the nucleation and growth kinetics of colloidal islands on these surfaces at the single-particle level. We demonstrate nucleation control, with high fidelity, in a regime that has remained unaccessed in theoretical, numerical and experimental studies on atoms and molecules as well. Our findings pave the way for fabricating non-trivial surface architectures composed of complex colloids and nanoparticles.Comment: 12 pages, 3 figure

Dynamical facilitation governs glassy dynamics in suspensions of colloidal ellipsoids

One of the greatest challenges in contemporary condensed matter physics is to ascertain whether the formation of glasses from liquids is fundamentally thermodynamic or dynamic in origin. While the thermodynamic paradigm has dominated theoretical research for decades, the purely kinetic perspective of the dynamical facilitation (DF) theory has attained prominence in recent times. In particular, recent experiments and simulations have highlighted the importance of facilitation using simple model systems composed of spherical particles. However, an overwhelming majority of liquids possess anisotropy in particle shape and interactions and it is therefore imperative to examine facilitation in complex glass-formers. Here, we apply the DF theory to systems with orientational degrees of freedom as well as anisotropic attractive interactions. By analyzing data from experiments on colloidal ellipsoids, we show that facilitation plays a pivotal role in translational as well as orientational relaxation. Further, we demonstrate that the introduction of attractive interactions leads to spatial decoupling of translational and rotational facilitation, which subsequently results in the decoupling of dynamical heterogeneities. Most strikingly, the DF theory can predict the existence of reentrant glass transitions based on the statistics of localized dynamical events, called excitations, whose duration is substantially smaller than the structural relaxation time. Our findings pave the way for systematically testing the DF approach in complex glass-formers and also establish the significance of facilitation in governing structural relaxation in supercooled liquids.Comment: 22 pages, 3 main figues, 3 supplementary figures. Submitted to Proceedings of the National Academy of Sciences, USA, on the 15th of July, 201

Complex Hydrodynamic Interactions and Stokes-Einstein Relation in Quasi-Two-Dimensional Colloidal Fluids

Long-ranged hydrodynamic interactions are intrinsic to diverse physical systems \cite{malvania2021generalized, cao2011universal, kovtun2005viscosity, bricard2013emergence, cui2004anomalous, riedel2005self, shani2014long} and, in fact, are the most prominent ones for low Reynold number systems, such as flows involving micro-organisms and particle-laden suspensions \cite{son2013bacteria, lauga2016bacterial, riedel2005self, shani2014long}, and protein diffusion across membranes \cite{vereb2003dynamic, ramadurai2009lateral}. While hydrodynamics is well-understood in the \textit{far-field} (asymptotic limit) \cite{cui2004anomalous, molaei2021interfacial, shani2014long}, it has been less explored in the \textit{near-field} \cite{zhang2021effective}. We experimentally elucidate the hydrodynamic correlations in quasi-two-dimensional colloidal fluids in the near-field, uncovering a new filling-the-void mode formed by the combination of well-known drag and anti-drag hydrodynamic dipolar modes. These modes superpose, creating a rugged potential landscape for the diffusing colloids that leads to the violation of the Stokes-Einstein relation (SER), whose validity is believed to be a hallmark feature of liquids \cite{einstein1956investigations}. We find pair-wise colloid interactions unravel complex emergent dynamics due to hydrodynamics, which in contrast to dynamics emanating from single particles are observed to be anisotropic. Remarkably, insights gleaned enabled us to pick out the directions unique to each pair, in which hydrodynamic correlations are the weakest, thereby recovering the validity of SER along these. Our experiments revealing the effects of distinct modes of hydrodynamic interactions on SER will have significant ramifications for fluids' underlying dynamic structure and transport properties in two dimensions.Comment: 4 figure

Discrete Electronic Warfare Signal Processing using Compressed Sensing Based on Random Modulator Pre-Integrator

Electronic warfare receiver works in the wide electromagnetic spectrum in dense radar signal environment. Current trends in radar systems are ultra wideband and low probability of intercept radar technology. Detection of signals from various radar stations is a concern. Performance and probability of intercept are mainly dependent on high speed ADC technology. The sampling and reconstruction functions have to be optimized to capture incoming signals at the receiver to extract characteristics of the radar signal. The compressive sampling of the input signal with orthonormal base vectors, projecting the basis in the union of subspaces and recovery through convex optimisation techniques is the current traditional approach. Modern trends in signal processing suggest the random modulator pre-integrator (RMPI), which sample the input signal at information rate non-adaptively and recovery by the processing of discrete and finite vectors. Analysis of RMPI theory, application to EW receiver, simulation and recovery of EW receiver signals are discussed

A comparative study between plating versus titanium elastic nail system in mid-shaft clavicle fracture management

Background: Clavicle fracture is one of most common bony injuries. Despite of high frequency, choice of proper treatment is still a challenge. So a comparative randomized study was planned to compare Plating verses TENS for clavicle fractures management.Methods: Study was conducted in Department of Orthopedics, M.K.C.G Medical College, Berhampur from November 2015 to October 2017.Patients aged from 20-55 years with closed displaced were included in study. Patients were randomized in two groups- One group (25 pateints) treated with TENS and second group (25) with plate. Outcome assessed by pain VAS score, Constant & Murley score, DASH score, cosmetic result, radiological fracture healing time.Results: Mean fracture union time in TENS group was 11.4±2.12 weeks and in plate group 13.4±3.46 weeks (difference was significant p=0.016). Mean pain VAS score in TENS group was 2.56±0.91 and in plating group 3.12±0.8 (p=0.023). Tens group were cosmetically more satisfied (mean score 4.48±0.7) than plate group (mean score 3.8±1.0, p=0.009). Mean DASH and Constant Shoulder Score in TENS group were 1.87±3.4, 9.36±7.04 and plate group 4.8±9.0 and 15.08±9.4 respectively. Both were significant (p=0.039, p=0.000).Conclusions: Our study found that patients treated with TENS showed excellent outcome in 84% cases while 60% in plating group for displaces mid-shaft clavicle fracture. Patients in TENS group better in terms of Constant & Murley score and DASH score than treated with plate

LCL filter based UPQC configuration for power quality improvement

This paper proposes a unified power quality conditioner (UPQC) configuration employing an LCL filter at front of shunt voltage source inverter (VSI). As compared to conventional UPQC with L filter at the front of the shunt VSI, the proposed UPQC provides improved compensation while using much smaller value of filter inductance. With the smaller filter inductance, voltage requirement of common dc link also gets reduced. It results in reduced switching losses in the series and shunt VSIs. Therefore, proposed UPQC achieves reduction in weight, cost, size, and losses while providing improved current compensation capability. Simulation results are presented to verify all the features

Correlations between short- and long-time relaxation in colloidal supercooled liquids and glasses

Spatiotemporal dynamics of short- and long-time structural relaxation are measured experimentally as a function of packing fraction, φ, in quasi-two-dimensional colloidal supercooled liquids and glasses. The relaxation times associated with long-time dynamic heterogeneity and short-time intracage motion are found to be strongly correlated and to grow by orders of magnitude with increasing φ toward dynamic arrest. We find that clusters of fast particles on the two timescales often overlap, and, interestingly, the distribution of minimum-spatial-separation between closest nonoverlapping clusters across the two timescales is revealed to be exponential with a decay length that increases with φ. In total, the experimental observations suggest short-time relaxation events are very often precursors to heterogeneous relaxation at longer timescales in glassy materials