Cubatic phase for tetrapods

We investigate the phase behavior of tetrapods, hard non-convex bodies formed by 4 rods connected under tetrahedral angles. We predict that, depending on the relative lengths of the rods these particles can form a uniaxial nematic phase, and more surprisingly they can exhibit a cubatic phase, a special case of the biaxial nematic phase. These predictions may be experimentally testable, as experimental realizations of tetrapods have recently become available.Comment: 8 pages ReVTeX 4, including 3 EPS figure

Do cylinders exhibit a cubatic phase?

We investigate the possibility that freely rotating cylinders with an aspect ratio $L/D=0.9$ exhibit a cubatic phase similar to the one found for a system of cut-spheres. We present theoretical arguments why a cubatic phase might occur in this particular system. Monte Carlo simulations do not confirm the existence of a cubatic phase for cylinders. However, they do reveal an unexpected phase behavior between the isotropic and crystalline phase.Comment: 24 pages, 12 figures, RevTex (Submitted to J. Chem. Phys.

Confinement and crowding control the morphology and dynamics of a model bacterial chromosome

Motivated by recent experiments probing shape, size and dynamics of bacterial chromosomes in growing cells, we consider a polymer model consisting of a circular backbone to which side-loops are attached, confined to a cylindrical cell. Such a model chromosome spontaneously adopts a helical shape, which is further compacted by molecular crowders to occupy a nucleoid-like subvolume of the cell. With increasing cell length, the longitudinal size of the chromosome increases in a non-linear fashion to finally saturate, its morphology gradually opening up while displaying a changing number of helical turns. For shorter cells, the chromosome extension varies non-monotonically with cell size, which we show is associated with a radial to longitudinal spatial reordering of the crowders. Confinement and crowders constrain chain dynamics leading to anomalous diffusion. While the scaling exponent for the mean squared displacement of center of mass grows and saturates with cell length, that of individual loci displays broad distribution with a sharp maximum.Comment: 12 pages, 12 figure

BENTUK DAN PERUBAHAN ASYIEK NITI NAIK MAHLIGAI MENJADI TARI NITI NAIK MAHLIGAI MASYARAKAT SIULAK MUKAI, KABUPATEN KERINCI, PROVINSI JAMBI (1995-2020)

Niti Naik Mahligai merupakan upacara yang digunakan sebagai penobatan seorang Raja atau yang dikenal dengan nama Belian Salih dengan melewati berbagai rintangan yang berbahaya seperti meniti di atas bara api, bambu tajam, dan pedang. Seiring perkembangan zaman, upacara Asyiek Niti Naik Mahligai kemudian menjadi Tari Niti Naik Mahligai yang dilakukan masyarakat Siulak Mukai sejak tahun 1995 dengan berbagai ritual magis agar para penari dapat dirasuki oleh roh leluhur atau nenek moyang mereka. Hal inilah yang menjadi alasan dari gerakan penari bebas dan tidak terluka meski melwati berbagai adegan berbahaya selama menarikannya.Penelitian ini dilakukan untuk mengetahui perubahan secara tekstual dan kontekstual dari Asyiek Niti Naik Mahligai menjadi tari Niti Naik Mahligai. Penelitian ini menggunakan metode deskriptif kualitatif yang mana data yang dikumpulkan melalui wawancara, dokumentasi dan observasi di analisis melalui reduksi data dan tringulasi data

Designing colloidal ground state patterns using short-range isotropic interactions

DNA-coated colloids are a popular model system for self-assembly through tunable interactions. The DNA-encoded linkages between particles theoretically allow for very high specificity, but generally no directionality or long-range interactions. We introduce a two-dimensional lattice model for particles of many different types with short-range isotropic interactions that are pairwise specific. For this class of models, we address the fundamental question whether it is possible to reliably design the interactions so that the ground state is unique and corresponds to a given crystal structure. First, we determine lower limits for the interaction range between particles, depending on the complexity of the desired pattern and the underlying lattice. Then, we introduce a `recipe' for determining the pairwise interactions that exactly satisfies this minimum criterion, and we show that it is sufficient to uniquely determine the ground state for a large class of crystal structures. Finally, we verify these results using Monte Carlo simulations.Comment: 19 pages, 7 figure

Microtubule length distributions in the presence of protein-induced severing

Microtubules are highly regulated dynamic elements of the cytoskeleton of eukaryotic cells. One of the regulation mechanisms observed in living cells is the severing by the proteins katanin and spastin. We introduce a model for the dynamics of microtubules in the presence of randomly occurring severing events. Under the biologically motivated assumption that the newly created plus end undergoes a catastrophe, we investigate the steady state length distribution. We show that the presence of severing does not affect the number of microtubules, regardless of the distribution of severing events. In the special case in which the microtubules cannot recover from the depolymerizing state (no rescue events) we derive an analytical expression for the length distribution. In the general case we transform the problem into a single ODE that is solved numerically.Comment: 9 pages, 4 figure