arXiv subjects

Jieh-Wen Tsung

Publications and source records attributed to Jieh-Wen Tsung.

4 recordsLinked to original sources

arXiv2026

Chiral cellulose fibril organization in a plant cell wall as liquid crystal confined in a cylindrical boundary

The order of cellulose microfibrils in xylem cell walls is identified using polarized optical microscopy. The line, helix, ring, crossed helix, and twisted helix organizations in a cylindrical shell are the equilibrium states of balanced elastic deformation and surface anchoring. A computational model of the five organizations is established to simulate their birefringent-colored profiles. These five textures present unique optical textures, which are clearly recognized in the cross sections of Eucalyptus grandis. The libriform fiber cell for support has a twisted helical cell wall. The vessel cell for high-speed water uptake consists of a helical layer covered by a layer of vortex array. The ray cell for radial transportation is crossed helical. The microfibril angles versus the radius of the cell wall were measured utilizing the distribution of birefringence colors. In fiber cell walls, the MFA is significantly correlated with the curvature, bending, and surface anchoring, respectively. In vessel cell walls, the vortex array includes focal conic domains of chiral order and topological defects of nematic order, suggesting that the phase transition of cellulose fibrils leads to pattern formation. Liquid crystal phases and patterns in the cell walls reveal how the cell wall thickens and how cells differentiate. Out of the frustration of long, stiff, twisting fibrils packed in slender tubes, trees generate the helical channel networks, transforming the brittle lamina into an elastic, tear-resistant, self-healing tissue.

cond-mat.soft↗

arXiv2026

Birefringent-colored optical profiling of wood presenting the 3D cellulose microfibril architecture

Wood slices under a polarized optical microscope show a spectrum of interference colors, such as cyan, blue, magenta, yellow, and bluish gray because of the birefringent cellulose in the microfibrils. An optical model is established to simulate the birefringent-colored micrograph of wood. Five typical cell wall architectures, line, helix, ring, crossed helix, and twisted helix, are considered. With a retardation wave plate to distinguish fibrils of different orientations, each structure displays its unique birefringent-colored texture, presenting its underlying 3D structure with the vivid colors. Cross sections of the trunk and twig of Eucalyptus grandis presented birefringent-colored profiles. Three identification methods were compared: visible fibril trends, birefringent-colored optical textures, and the simulated look-up library. The three methods gave consistent results, proving that the birefringent-color tags are efficient and accurate. Electron and atomic force microscopy are unable to resolve cellulose microfibrils embedded in the lignin and hemicellulose matrix. Polarized optical microscopy overcomes this by selectively detecting birefringent cellulose, enabling accurate identification of complex helical structures. This method enables statistical and spatial analysis of complex biomaterial compositions. Capable of profiling dozens of cells simultaneously, this high-throughput optical method provides a potentially fully automated analysis framework for plant science, biomechanics, and bioinspired cellulose materials.

cond-mat.soft↗

arXiv2019

Conservation Laws for Crystal of Topological Defects

Stable array of point defects was generated in nematic liquid crystal. Point defects with topological charge of +1 and -1 (hedgehogs) were generated in vertically aligned liquid crystal cell. The hedgehogs were arranged in square or hexagonal arrays, and the shape of defect, such as radial or circular hedgehogs, were under the control of delicately patterned electrodes. Base on the two-dimensional defect array discovered in experiments, three-dimensional crystals of defects were postulated. The flux of the liquid crystal director field was summarized for each unit cell. The analysis showed that the crystal structure is periodic and stable if the total flux in a unit cell is zero. The surface and bulk topological charges of each unit cells were analyzed. The summation of topological charges of a unit cell obeys the topological rules of a homeotropic droplet. The hidden conservation laws of flux and topological charges in a soft crystal of defects were discovered, which can be implemented in templates for self-assembled micro-structure and tissue design. Most important of all, the conservation laws may answer why natural structures and tissues grow in to a particular shape and form.

cond-mat.soft↗

arXiv2012

Signal and noise of Diamond Pixel Detectors at High Radiation Fluences

CVD diamond is an attractive material option for LHC vertex detectors because of its strong radiation-hardness causal to its large band gap and strong lattice. In particular, pixel detectors operating close to the interaction point profit from tiny leakage currents and small pixel capacitances of diamond resulting in low noise figures when compared to silicon. On the other hand, the charge signal from traversing high energy particles is smaller in diamond than in silicon by a factor of about 2.2. Therefore, a quantitative determination of the signal-to-noise ratio (S/N) of diamond in comparison with silicon at fluences in excess of 10$^{15}$ n$_{eq}$ cm$^{-2}$, which are expected for the LHC upgrade, is important. Based on measurements of irradiated diamond sensors and the FE-I4 pixel readout chip design, we determine the signal and the noise of diamond pixel detectors irradiated with high particle fluences. To characterize the effect of the radiation damage on the materials and the signal decrease, the change of the mean free path $λ_{e/h}$ of the charge carriers is determined as a function of irradiation fluence. We make use of the FE-I4 pixel chip developed for ATLAS upgrades to realistically estimate the expected noise figures: the expected leakage current at a given fluence is taken from calibrated calculations and the pixel capacitance is measured using a purposely developed chip (PixCap). We compare the resulting S/N figures with those for planar silicon pixel detectors using published charge loss measurements and the same extrapolation methods as for diamond. It is shown that the expected S/N of a diamond pixel detector with pixel pitches typical for LHC, exceeds that of planar silicon pixels at fluences beyond 10$^{15}$ particles cm$^{-2}$, the exact value only depending on the maximum operation voltage assumed for irradiated silicon pixel detectors.

physics.ins-det↗