The role of hydroxyl groups in interchain interactions in cellulose Iα and Iβ

Complex networks of hydrogen bonds within the cellulose I_α and I_β contribute greatly to cellulose's anisotropic physical properties such as material stiffness. The interchain hydrogen bonding interactions through hydroxyl groups are isolated in each of the three lattice planes of the adjacent chains within the unit cell of two allomorphs of natural cellulose. In our density function theory study with dispersion corrected Perdew–Burke–Ernzerhof (PBE‐D2) functional, these hydroxyl groups participate in strong hydrogen bonding interactions (?24.8 and ?24.8 kcal/mol for cellulose I_α and I_β, respectively) in the side‐to‐side lattice plane. Unexpectedly, the hydroxyl groups also participate significantly in hydrogen bonding interactions (?11.0 and ?12.4 kcal/mol for cellulose I_α and I_β, respectively) in one of the diagonal lattice planes in both cellulose I_α and I_β. Both PM7 and PBE‐D2 method predict that the overall interaction is asymmetric and stronger in the right diagonal lattice plane. While hydrogen bonding interactions are strongest in side‐to‐side lattice plane as expected, the role of hydrogen bonding interactions for keeping the sheet together is more significant than previously thought.     

Torsion in the Cohomology of Torus Orbifolds

The authors study torsion in the integral cohomology of a certain family of 2n-dimensional orbifolds X with actions of the n-dimensional compact torus.Compact simplicial toric varieties are in our family.For a prime number p,the authors find a necessary condition for the integral cohomology of X to have no p-torsion.Then it is proved that the necessary condition is sufficient in some cases.The authors also give an example of X which shows that the necessary condition is not sufficient in general.     

Use of a heterogeneous buffer combination in microchip electrophoresis for high-resolution separation by on-line concentration of DNA samples

We have developed a novel high-resolution separation technique of DNA fragments in a heterogeneous combination of a sample buffer and a separation buffer. The use of a heterogeneous buffer combination is a simple method for on-line concentration of DNA fragments, in which a sample buffer is simply exchanged with one including taurine anions. The mobility of taurine anions, co-ions for DNA, is lower than the that of acetate anions in a separation buffer. The difference in the mobility invokes transient isotachophoresis. The current technique allows DNA fragments to be effectively concentrated and the separation length of microchips to be shorter than that of conventional ones by a factor of three without deterioration in separation resolution and any modification of a chip design. Fragments of 100-bp DNA ladders (100-1000 bp) were separated with high resolution (0.72-10.7) within 60 s with a 10 mm separation length on a polymethyl methacrylate chip. Furthermore, fragments of 10-bp DNA ladders (10-330 bp) were separated with high resolution (0.69-2.00) with a 10 mm separation length within 50 s without band broadening. The current achievements will make it possible to fabricate compact devices for microchip electrophoresis.     

A novel proton-selective sensor based on a sugar with hinge flexibility

A hinge sugar, a 2,4-diamino-2,4-dideoxy-beta-D-xylopyranoside derivative, turns its four equatorial substituents into axial orientations through a (4)C(1)-to-(1)C(4) ring flip in response to chelation to a metal ion. This hinge-like motion enables two components attached at the 1- and 3-positions to switch between far and near states. In this study, we examined the effect of N-alkylation on the bendability of the hinge molecule and synthesized a 2,4-dipyrenylmethyl derivative as a proton-selective sensor. (1)H NMR studies showed that N-alkylations of the hinge sugar facilitated (1)C(4) formation in the presence of an acid, probably because the increased basicity of the amino group promoted the intramolecular hydrogen bond between the 2- and 4-amino substituents, whereas chelation to a metal ion was hampered by the increased bulkiness. In accordance with the above results, N,N'-dipyrenylmethyl hinge sugar 3 emitted excimer fluorescence (445 nm) owing to the pyrene stacking as a result of the (1)C(4) formation at lower concentrations of trifuluoroacetic acid (TFA), while no significant changes in fluorescence spectra were observed when metal ions were added. Increase of the monomer fluorescence (375 nm) at higher TFA concentrations was also observed. These observations indicate that 3 could be used as a proton-selective sensor that covers a wide range of proton concentrations through monitoring of the two fluorescence maxima.     

Dzyaloshinskii–Moriya interaction: How to measure its sign in weak ferromagnets?

Three experimental techniques sensitive to the sign of the Dzyaloshinskii-Moriya interaction are discussed: neutron diffraction, Mössbauer γ-ray diffraction, and resonant x-ray scattering. Classical examples of hematite (α-Fe₂O₃) and MnCO₃ crystals are considered in detail.     

Application of Parallel Hybrid Algorithm in Massively Parallel GPGPU—The Improved Effective and Efficient Method for Calculating Coulombic Interactions in Simulations of Many Ions with SIMION

In our previous study, we introduced a new hybrid approach to effectively approximate the total force on each ion during a trajectory calculation in mass spectrometry device simulations, and the algorithm worked successfully with SIMION. We took one step further and applied the method in massively parallel general-purpose computing with GPU (GPGPU) to test its performance in simulations with thousands to over a million ions. We took extra care to minimize the barrier synchronization and data transfer between the host (CPU) and the device (GPU) memory, and took full advantage of the latency hiding. Parallel codes were written in CUDA C++ and implemented to SIMION via the user-defined Lua program. In this study, we tested the parallel hybrid algorithm with a couple of basic models and analyzed the performance by comparing it to that of the original, fully-explicit method written in serial code. The Coulomb explosion simulation with 128,000 ions was completed in 309?s, over 700 times faster than the 63?h taken by the original explicit method in which we evaluated two-body Coulomb interactions explicitly on one ion with each of all the other ions. The simulation of 1,024,000 ions was completed in 2650?s. In another example, we applied the hybrid method on a simulation of ions in a simple quadrupole ion storage model with 100,000 ions, and it only took less than 10 d. Based on our estimate, the same simulation is expected to take 5-7 y by the explicit method in serial code.     

Modification of gold nanorods using phosphatidylcholine to reduce cytotoxicity

Hexadecyltrimethylammonium bromide (CTAB), which is necessary for the preparation of gold nanorods (NRs), was extracted from a NR solution into a chloroform phase containing phosphatidylcholine (PC). After three extractions, the zeta potential of the NRs remained positive, but its magnitude decreased from +67 +/- 1 to +15 +/- 1 mV. Transmission electron microscopy and energy-dispersive X-ray analysis indicated that the NRs were passivated with PC. The PC layer on the NR surface contributed to the prevention of NR aggregation. The PC-passivated NRs showed low cytotoxicity in comparison with twice-centrifuged NRs. It was shown that a negligible amount of CTAB was dispersed in the NR solution after the extraction. The extraction using a chloroform phase containing PC was found to be a convenient way of replacing the CTAB with alternative capping agents such as PC. This is a key technique for preparing functional NRs that can have practical applications.     

Does decalcification alter the tissue sound speed of rabbit supraspinatus tendon insertion? In vitro measurement using scanning acoustic microscopy

Failure of the tendon or ligament insertions is one of the most common injuries in the Orthopaedic field. To elucidate the pathogenesis of those injuries, the authors had attempted to measure the tissue sound speed that could be correlated to its elasticity using scanning acoustic microscopy (SAM). For the application of SAM to tendon or ligament insertions, it was necessary to determine the role of decalcification in SAM measurements since mineralized tissues including bone or mineralized fibrocartilage were present at the insertion site. To assess whether decalcification alters the tissue sound speed or not, supraspinatus tendon insertion of six Japanese white rabbits were measured with SAM operating in the frequency range of 50-150 MHz. Right supraspinatus tendons attached to the humeral head were cut into two pieces at the center of the tendon. Then, they were fixed with 10% neutralized formalin for 12 h. In each specimen, medial half was not decalcified, while lateral half was decalcified with ethylene-diamine-tetra-acetic acid (EDTA). After embedding in paraffin, 5 microm thick specimens were prepared for the measurement using SAM. The mean sound speed in each histologic zone was evaluated, and subsequently compared to that measured in the undecalcified and the decalcified specimens. Mean sound speed of non-mineralized fibrocartilage was 1544 m/s in the undecalcified specimens, while the value of 1541 m/s was determined in the decalcified ones. On the other hand, it decreased 2-3% after decalcification in the mineralized tissue including mineralized fibrocartilage and bone (mineralized fibrocartilage: undecalcified = 1648 m/s, decalcified = 1604 m/s; bone: undecalcified = 1716 m/s, decalcified = 1677 m/s). However, no significant differences were found between the undecalcified and the decalcified specimens (non-mineralized fibrocartilage: p = 0.84, mineralized fibrocartilage: p = 0.35, bone: p = 0.28). These results indicate that SAM could be applied to determine the properties of the tendon or the ligament insertions after decalcification with EDTA. Although SAM is applicable only for in vitro experimental study, it is expected that these data will contribute to better understanding concerning the biomechanics of tendon or ligament insertions as well as the pathogenesis of their failure at a microscopic level.