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

Epidemiology and treatment for thyroid cancer

The thyroid gland produces thyroid hormones which are important in the normal regulation of the metabolism of the body. Thyroid cancer is the most common malignancy of the endocrine system consisting of several subtypes like papillary carcinoma, and follicular carcinoma, medullary carcinoma, and anaplastic carcinoma. Treatment depends on a number of factors, including the type of thyroid cancer, the size of the nodule, the patient's age, and whether the cancer has spread. Most cases of thyroid cancer can be cured with treatment like Radiation therapy chemotherapy and radioactive iodine. Recommended thyroid treatment approaches depend on the type of thyroid disease, and in some cases, the severity of the condition. © 2011 Srilatha B, et al

From rods to helices: evidence of a screw-like nematic phase

Evidence of a special chiral nematic phase is provided using numerical simulation and Onsager theory for systems of hard helical particles. This phase appears at the high density end of the nematic phase, when helices are well aligned, and is characterized by the C$_2$ symmetry axes of the helices spiraling around the nematic director with periodicity equal to the particle pitch. This coupling between translational and rotational degrees of freedom allows a more efficient packing and hence an increase of translational entropy. Suitable order parameters and correlation functions are introduced to identify this screw-like phase, whose main features are then studied as a function of radius and pitch of the helical particles. Our study highlights the physical mechanism underlying a similar ordering observed in colloidal helical flagella [E. Barry et al. \textit{Phys. Rev. Lett.} \textbf{96}, 018305 (2006)] and raises the question of whether it could be observed in other helical particle systems, such as DNA, at sufficiently high densities.Comment: List of authors correcte

Studi Kebijakan Ergonomi Makro terhadap Output Produksi Menggunakan Pendekatan Sistem Dinamik (Studi Kasus: PT. Sumber Mas Indah Plywood, Gresik)

PT. Sumber Mas Indah Plywood merupakan salah satu Perusahaan manufaktur yang bergerak di bidang pembuatan plywood. Namun, Perusahaan ini juga menghasilkan produk sampingan berupa moulding, polyester, dan lumber core. Penelitian ini bertujuan untuk menganalisis pengaruh kebijakan ergonomi makro terhadap output produksi menggunakan sistem dinamik. Dengan menggunakan perangkat lunak simulasi vensim PLE, dapat diketahui bahwa kebijakan ergonomi makro memberikan pengaruh positif terhadap output produksi, namun pengaruh ini tidak ditunjukkan secara langsung melainkan bertahap sesuai interaksi yang ditunjukkan pada model. Pada pengembangan model sistem dinamik, terdapat 5 skenario untuk mencapai tujuan Perusahaan, yaitu meningkatkan output produksi. Skenario pertama adalah dengan meningkatkan pembiayaan investasi ergonomi dari 1 Milyar menjadi 3 Milyar. Skenario kedua adalah mengurangi jumlah investasi ergonomic dari 1 Milyar menjadi 500juta. Skenario ketiga adalah dengan meningkatkan prosentase investasi Perusahaan. Skenario keempat adalah meningkatkan harga pokok penjualan sebesar 10%. Sedangkan skenario kelima adalah menurunkan biaya operasional. Berdasarkan alternatif skenario, ternyata pada skenario 3 mengasilkan rata-rata output produksi terbesar. Sedangkan dari sisi nilai keuntungan Perusahaan, skenario 5 adalah yang terbaik. Pemilihan skenario tersebut berdasarkan analisis net present value (NPV) dengan menggunakan tingkat bunga sebesar 10%. Pada analisis NPV, diketahui bahwa pada skenario 5 menghasilkan NPV sebesar Rp 7.396.523,07 juta. Dalam kasus seperti ini, Perusahaan memiliki tujuan untuk meningkatkan output produksi sehingga skenario yang berkaitan dengan keuntungan Perusahaan hanya dijadikan pertimbangan. Oleh karena itu, Perusahaan sebaiknya memilih skenario 3 dikarenakan pada alternatif tersebut mengahasilkan rata-rata output produksi yang paling tinggi