Numerical simulation of 3D bubbles rising in viscous liquids using a front tracking method

10.1016/j.jcp.2007.12.002Journal of Computational Physics22763358-3382JCTP

Disulfide bond reconstruction: A novel approach for grafting of thiolated chitosan onto wool

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Chitosan, a natural biopolymer, is used as a multifunctional agent for modification of wool either through chemical crosslinking or physical coating. For the first time, wool fabric has been modified with chitosan through disulfide bond breaking and reforming reactions. The chitosan was thiolated and then grafted onto the reduced wool fibers through disulfide bonds. In order to understand the mechanism of the grafting of thiolated chitosan onto wool, glutathione was used as a model compound for wool in the research. The structures of thiolated chitosan reacted with glutathione and wool fabrics grafted with thiolated chitosan were investigated by FTIR, 13CNMR, XPS, XRD, SEM. The dyeability, shrink-resistance and biocompatibility were also tested. The results suggested that glutathione reacted with thiolated chitosan and formed disulfide bond. The thiolated chitosan-grafted wool fabric had good shrink-resistance and dyeability. Hydrophilicity and antibacterial properties were also improved compared with untreated wool fabric. The results provide a novel approach for modification of wool through fiber-intrinsic groups like disulfide bonds

Enzymatic thiol-ene click reaction: an eco-friendly approach for MPEGMA-grafted modification of wool fibers

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The thiol–ene click reaction has been commonly used for the modification of many materials due to its high efficiency, high selectivity, and reliability. To further promote the sustainable technology for the modification of keratin-based materials, enzymatic biotechnology and thiol–ene click chemistry was integrated for the first time for grafting modification of wool fibers with methoxy polyethylene glycol methacrylate (MPEGMA). Wool fibers were reduced to create thiol groups and then grafted with MPEGMA through a horseradish peroxidase (HRP)-mediated thiol–ene click reaction. In order to understand the grafting mechanism of MPEGMA on wool, l-cysteine was used as a model compound for the thiol group of the reduced wool in the current research. The structures of MPEGMA reacted with l-cysteine and grafted on wool fabrics were investigated by FTIR, MALDI-TOF, Raman spectra, and XPS. The surface morphology, wettability, moisture penetrability, and regain of modified wool fibers were also assessed. The results showed that l-cysteine reacted with MPEGMA through the thiol–ene click reaction. The MPEGMA-grafted wool fabric had good surface wettability, and its moisture penetrability and regain were also improved when compared with untreated wool fabric. The HRP-initiated thiol–ene grafting reaction not only encouraged green and sustainable click chemistry but also provide an alternative eco-friendly approach for modification and functionalization of keratin and keratin-containing materials

A new method to determine the tropopause

The tropopause has a complex structure and some interference information may exist in high-resolution global positioning system (GPS)/low earth-orbiting (LEO) radio occultation (RO) data. The position of the tropopause cannot be accurately determined using traditional cold point tropopause (CPT) and lapse rate tropopause (LRT) algorithms. In this paper, an integrative algorithm is developed to determinate tropopause parameters. The algorithm is applied to GPS/COSMIC RO data to obtain a global distribution of the height and temperature of the tropopause. This algorithm improves the utilization rate of GPS/LEO RO data by 30% compared with that from the traditional CPT method. The rationality and reliability of GPS/LEO RO data in probing the Earth’s atmosphere are verified by our study of the tropopause using COSMIC data

How Spin Relaxes and Dephases in Bulk Halide Perovskites

Spintronics in halide perovskites has drawn significant attention in recent years, due to highly tunable spin-orbit fields and intriguing interplay with lattice symmetry. Spin lifetime -- a key parameter that determines the applicability of materials for spintronics and spin-based quantum information applications -- has been extensively measured in halide perovskites, but not yet assessed from first-principles calculations. Here, we leverage our recently-developed \emph{ab initio} density-matrix dynamics framework to compute the spin relaxation time ($T_{1}$) and ensemble spin dephasing time ($T_{2}^{*}$) in a prototype halide perovskite, namely CsPbBr$_{3}$ with self-consistent spin-orbit coupling (SOC) and quantum descriptions of the electron scattering processes. We also implement the Land\'e $g$-factor for solids from first principles and take it into account in our dynamics, which is required to accurately capture spin dephasing at external magnetic fields. We thereby predict intrinsic spin lifetimes as an upper bound for experiments, identify the dominant spin relaxation pathways, and evaluate the dependence on temperature, external fields, carrier density,and impurities. Importantly, we find that the Fr{\"o}hlich interaction that dominates carrier relaxation contributes negligibly to spin relaxation, consistent with the spin-conserving nature of this interaction. We investigated the effect of spin-orbit field with inversion asymmetry on spin lifetime, and we demonstrated from our calculation, persistent spin helix can enhance spin lifetime when the spin-split is large, but it can not be realized by Rashba SOC. Our theoretical approach may lead to new strategies to optimize spin and carrier transport properties in spintronics and quantum information applications.Comment: 10 pages, 6 figure

Centrosome-associated regulators of the G2/M checkpoint as targets for cancer therapy

In eukaryotic cells, control mechanisms have developed that restrain cell-cycle transitions in response to stress. These regulatory pathways are termed cell-cycle checkpoints. The G2/M checkpoint prevents cells from entering mitosis when DNA is damaged in order to afford these cells an opportunity to repair the damaged DNA before propagating genetic defects to the daughter cells. If the damage is irreparable, checkpoint signaling might activate pathways that lead to apoptosis. Since alteration of cell-cycle control is a hallmark of tumorigenesis, cell-cycle regulators represent potential targets for therapy. The centrosome has recently come into focus as a critical cellular organelle that integrates G2/M checkpoint control and repairs signals in response to DNA damage. A growing number of G2/M checkpoint regulators have been found in the centrosome, suggesting that centrosome has an important role in G2/M checkpoint function. In this review, we discuss centrosome-associated regulators of the G2/M checkpoint, the dysregulation of this checkpoint in cancer, and potential candidate targets for cancer therapy

Laccase-catalyzed polymerization of diaminobenzenesulfonic acid for pH-responsive colour-changing and conductive wool fabrics

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.In recent years, there has been an extensive interest in the research of smart fabrics and functional textiles. The present work has successfully developed the enzymatic approach for dyed wool fabrics in possession of special pH-responsive colour-changing and conductive properties, via in-situ polymerization of 2,5-diaminobenzenesulfonic acid (DABSA) by laccase from Trametes versicolor. The enzymatically synthesized product, poly(2,5-diaminobenzenesulfonic acid) (PDABSA), were characterized by FT-IR, UV-Vis spectrophotometry and matrix assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). The redox property and thermal stability of the polymer products were studied by cyclic voltammetry (CV) and TGA analysis, respectively. The results proved that the resulting polymer reached to 2 KDa and showed strong pH-dependence of UV-Vis absorption, electrochemical activity and high thermal stability. Utilizing the doping/dedoping process of PDABSA, the dyed wool fabrics were endowed with a pH-dependent redox potential. Furthermore, the dyed wool fabrics exhibited reversible colour change from dark purple at pH 1.8 to yellowish-brown at pH 10.0, indicating that the PDABSA showed unusual pH-dependent colour-changing properties on dyed wool fabrics

Laccase-catalyzed poly(ethylene glycol)-templated ‘zip’ polymerization of caffeic acid for functionalization of wool fabrics

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link

A multi band study of the optically dark GRB 051028

Observations were made of the optical afterglow of GRB 051028 with the Lulin observatory's 1.0 m telescope and the WIDGET robotic telescope system. R band photometric data points were obtained on 2005 October 28 (UT), or 0.095-0.180 days after the burst. There is a possible plateau in the optical light curve around 0.1 days after the burst; the light curve resembles optically bright afterglows (e.g. GRB 041006, GRB 050319, GRB060605) in shape of the light curve but not in brightness. The brightness of the GRB 051028 afterglow is 3 magnitudes fainter than that of one of the dark events, GRB 020124. Optically dark GRBs have been attributed to dust extinction within the host galaxy or high redshift. However, the spectrum analysis of the X-rays implies that there is no significant absorption by the host galaxy. Furthermore, according to the model theoretical calculation of the Ly$\alpha$ absorption to find the limit of GRB 051028's redshift, the expected $R$ band absorption is not high enough to explain the darkness of the afterglow. While the present results disfavor either the high-redshift hypothesis or the high extinction scenario for optically dark bursts, they are consistent with the possibility that the brightness of the optical afterglow, intrinsically dark.Comment: 5page, 5 figures, 1 table, accepted for publication in PASJ Letter. PASJ styl