Growing Dynamical Facilitation on Approaching the Random Pinning Colloidal Glass Transition

Despite decades of research, it remains to be established whether the transformation of a liquid into a glass is fundamentally thermodynamic or dynamic in origin. While observations of growing length scales are consistent with thermodynamic perspectives like the Random First-Order Transition theory (RFOT), the purely dynamic approach of the Dynamical Facilitation (DF) theory lacks experimental validation. Further, for glass transitions induced by randomly freezing a subset of particles in the liquid phase, simulations support the predictions of RFOT, whereas the DF theory remains unexplored. Here, using video microscopy and holographic optical tweezers, we show that dynamical facilitation in a colloidal glass-forming liquid unambiguously grows with density as well as the fraction of pinned particles. In addition, we show that heterogeneous dynamics in the form of string-like cooperative motion, which is believed to be consistent with RFOT, emerges naturally within the framework of facilitation. Most importantly, our findings demonstrate that a purely dynamic origin of the glass transition cannot be ruled out.Comment: 13 pages, 3 figures. Submitted to Nature Communications on the 17th of March, 201

Direct measurements of growing amorphous order and non-monotonic dynamic correlations in a colloidal glass-former

While the transformation of flowing liquids into rigid glasses is omnipresent, a complete understanding of vitrification remains elusive. Of the numerous approaches aimed at solving the glass transition problem, the Random First-Order Theory (RFOT) is the most prominent. However, the existence of the underlying thermodynamic phase transition envisioned by RFOT remains debatable, since its key microscopic predictions concerning the growth of amorphous order and the nature of dynamic correlations lack experimental verification. Here, by using holographic optical tweezers, we freeze a wall of particles in an equilibrium configuration of a 2D colloidal glass-forming liquid and provide direct evidence for growing amorphous order in the form of a static point-to-set length. Most remarkably, we uncover the non-monotonic dependence of dynamic correlations on area fraction and show that this non-monotonicity follows directly from the change in morphology of cooperatively rearranging regions, as predicted by RFOT. Our findings suggest that the glass transition has a thermodynamic origin

Influence of an amorphous wall on the distribution of localized excitations in a colloidal glass-forming liquid

Elucidating the nature of the glass transition has been the holy grail of condensed matter physics and statistical mechanics for several decades. A phenomenological aspect that makes glass formation a conceptually formidable problem is that structural and dynamic correlations in glass-forming liquids are too subtle to be captured at the level of conventional two-point functions. As a consequence, a host of theoretical techniques, such as quenched amorphous configurations of particles, have been devised and employed in simulations and colloid experiments to gain insights into the mechanisms responsible for these elusive correlations. Very often, though, the analysis of spatio-temporal correlations is performed in the context of a single theoretical framework, and critical comparisons of microscopic predictions of competing theories are thereby lacking. Here, we address this issue by analysing the distribution of localized excitations, which are building blocks of relaxation as per the Dynamical Facilitation (DF) theory, in the presence of an amorphous wall, a construct motivated by the Random First-Order Transition theory (RFOT). We observe that spatial profiles of the concentration of excitations exhibit complex features such as non-monotonicity and oscillations. Moreover, the smoothly varying part of the concentration profile yields a length scale $\xi_c$, which we compare with a previously computed length scale $\xi_{dyn}$. Our results suggest a method to assess the role of dynamical facilitation in governing structural relaxation in glass-forming liquids.Comment: 19 pages, 7 figure

Growing Surface Tension of Amorphous-Amorphous Interfaces on Approaching the Colloidal Glass Transition

There is mounting evidence indicating that relaxation dynamics in liquids approaching their glass transition not only becomes increasingly cooperative (1,2) but the relaxing regions also become more compact in shape(3-7). While the surface tension of the interface separating neighboring relaxing regions is thought to play a crucial role in deciding both their size and morphology(8-10), owing to the amorphous nature of these regions, even identifying these interfaces has not been possible in bulk liquids. Here, by devising a scheme to identify self-induced disorder sites in bulk colloidal liquids, we directly quantified the dynamics of interfaces delineating regions of high and low configurational overlap. This procedure also helped unveil a non-monotonicity in dynamical correlations that has never been observed in bulk supercooled liquids. Using the capillary fluctuation method (11,12), we measured the surface tension of amorphous-amorphous interfaces with supercooling and find that it increases rapidly across the mode-coupling area fraction. Remarkably, a similar growth in the surface tension is also seen in the presence of a pinned amorphous wall. Our observations help prune theories of glass formation and opens up new research avenues aimed at tuning the properties of amorphous-amorphous interfaces, and hence the glass itself, in a manner analogous to grain boundary engineering in polycrystals (13)

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

Harnessing Medicinal Plant Phytochemicals: Unveiling Pharmacological Potential and Novel Drug Delivery Strategies

The significant progress in the field of anticancer research has spurred a growing interest in bioactive compounds with potential pharmacological properties. One well-established challenge in utilizing these natural bioactives is their inherent low solubility, leading to limited bioavailability and difficulties in formulating effective drug delivery strategies to specific target sites. In response to this challenge, this review provides a comprehensive overview of the latest advancements in the development of innovative drug delivery systems. Our analysis focuses on published data related to key plant secondary metabolites known for their potent anticancer potential, specifically the flavone, isoflavone, and stilbene groups, which have been successfully formulated using novel drug delivery systems. While the precise mechanisms of action for these selected natural compounds remain a subject of ongoing investigation, their anticancer effects are undeniable. Consequently, current research efforts are primarily dedicated to identifying these bioactive compounds' most effective delivery systems. Recent studies aim to elucidate the exact mechanisms of action and therapeutic benefits of these compounds and address the crucial issue of designing suitable natural compound delivery systems capable of efficiently transporting therapeutic doses to the intended target sites. This multifaceted approach underscores the ongoing commitment to advancing the field of anticancer research and improving the delivery of bioactive compounds with promising anticancer potential

Study of gastrointestinal toxicity of selective COX-2 inhibitors in comparison with conventional NSAIDs

Background: Adverse gastrointestinal events are the commonest unwanted effects of the NSAIDs, and are believed to result mainly from the inhibition of gastric COX-1, which is responsible for the synthesis of prostaglandins that normally inhibit acid secretion and protect the mucosa. Previous studies report, that selective COX-2 inhibitors are safer when compared to non-selective cyclooxygenase inhibitors, regarding their adverse effects on gastrointestinal system. But, recent studies reveal, that gastrointestinal safety of these selective COX-2 inhibitors is not much better than that of conventional NSAIDs. In view of the wider usage of selective COX-2 inhibitors, the study has been taken up to report, whether selective COX-2 inhibitors have got any advantages over conventional NSAIDs or not, in regard to their gastrointestinal side effects.Methods: Patients were divided into eight groups, fifteen patients of each. Each group was given one of the NSAIDs from the eight drugs those were selected for the study, for 15 days. In the selected group, along with the symptomatic assessment of gastric toxicity, both pre and post-treatment values of Hb% are estimated, tabulated & subjected to statistical analysis.Results: Both the drugs, diclofenac & meloxicam have shown significant changes in the Hb% values (‘p’ value 0.02 each), whereas selective COX-2 inhibitors like nimesulide & celecoxib were no less in gastric toxicity, in comparison with diclofenac, on symptomatic assessment.Conclusions: In our short-term study, selective COX-2 inhibitors did not show any advantage over non-selective NSAIDs regarding their gastrointestinal toxicity

Effect of pregnancy induced hypertension on pregnancy outcome: a hospital based cross sectional study at a tertiary care hospital

Background: I Pregnancy induced hypertension causes intra uterine growth retardation, pre-mature delivery, intra uterine death of fetus, abruption placentae. It also causes increased morbidity and mortality among women. The objective of the present study is to observe the effect of pregnancy induced hypertension on pregnancy outcome.Methods: A hospital based cross sectional study was carried out to study the effect of pregnancy induced hypertension on pregnancy outcome for a period of two years from April 2004 to March 2006 at Gandhi Medical College, Hyderabad. Results: The mean maternal age in group I was 22.9 years comparable to group II. The incidence of PIH was 10.7% among primipara compared to 9.1% among multi parous women. Mean gestational age at entry to the present study was comparable among both the groups. Mean gestational age at delivery was higher in normotensive women compared to women with PIH. The incidence of low birth weight was 70% among PIH group compared to only 16.7% in normotensive group and this difference was found to be statistically significant. The incidence of intra-uterine growth retardation (IUGR) was 70% among PIH group compared to only 16.7% in normotensive group and this difference was found to be statistically significant. The incidence of pre-term delivery was 70% among PIH group compared to only 16.7% in normotensive group and this difference was found to be statistically significant.Conclusions: T Pregnancy induced hypertension was positively associated with adverse outcome. Early diagnosis and proper management can help to overcome and tackle most of the adverse outcomes. 

Simulation of High Step-Up Resonant Parallel LC Converter for Grid Connected Renewable Energy Sources

With the rapid improvement of large-scale renewable energy sources and HVDC grid, it is a capable alternative to connect the renewable energy sources to the HVDC grid with a pure dc system, in which high-power high-voltage step-up dc–dc converters are the key equipment to transmit the electrical energy. This paper presents a High step up LC converter it can achieve high voltage gain using an LC parallel resonant tank.Also provided zero voltage switching (ZVS) technology under switch turn-On condition also at turn-Off conditions at main power switches by rectifying diodes to reduce the conduction losses. The operation principle of the converter and its resonant parameter selection is presented in this paper. The operation principle of the converter has been successfully verified with the help of MATLAB/SIMULINK