pH Dependent Thermal Stabilization of DNA by Glcβ(1→3)GlcNAcβ1→STol

A disaccharide, Glcβ(1→3)GlcNAcβ1→STol (GGS, 1 ), was synthesized and demonstrated to stabilize ct‐DNA during the denaturing process. GGS at 50 μM shifted T_m of ct‐DNA by 23 °C and the behavior was pH dependent. Poly(dA‐dT)₂ was found to be the preferable type of DNA for GGS stabilization by circular dichroism spectroscopy study.     

Novel Nucleophilic Substitution Reactions of 5‐Halo‐4‐Sulfur‐Substituted 5,6‐Dihydro‐2‐Pyridones

The title compounds ( 3 , 8 , 9 and 10 ) were efficiently synthesized, and their substitution reactions with various nucleophiles were carried out. The effects of leaving group, sulfur‐substituent, solvent, reaction temperature, and the nature of the nucleophiles on the reactivity and S_N2/S_N2′ regioselectivity were studied and rationalized with semi‐empirical calculations.     

Mild and high-yielding syntheses of diethyl phosphoramidate-stoppered [2]rotaxanes

The mild and efficient reaction between triethyl phosphite and benzylic azides allows us not only to construct rotaxanes in high yield from dibenzo[24]crown-8 (DB24C8) and dibenzylammonium (DBA(+))-derived threads but also to incorporate di(p-toluidine)[24]crown-8, which binds DBA(+) ions much more weakly than does DB24C8, into a corresponding [2]rotaxane.     

Kinetic modeling of promotion and inhibition of temperature on photocatalytic degradation of benzene vapor

This study investigated the effects of temperature, humidity, and benzene concentration on the photocatalytic oxidation of benzene vapor over titanium dioxide. An annular packed-bed photocatalytic reactor was employed to determine the intrinsic oxidation rates for the photocatalysis of benzene. Degussa P-25 TiO₂ was used as the photocatalyst and a 15 W near-UV lamp (350 nm) was used as the light source. The experiments were conducted at influent benzene concentrations of 250–450 ppmv, water vapor concentrations of 13,500–27,500 ppmv, and reaction temperatures ranging from 100 to 200 °C. Benzene oxidation rates increased with temperature below 160–180 °C, but decreased with temperature above 160–180 °C. Raising the reaction temperature increased the chemical reaction rates but reduced the reactant adsorption rate on TiO₂ surfaces. The overall reaction rate increased with temperature, indicating that the reduction of reactant adsorption rate did not affect the overall reaction, and thus the chemical reaction was the rate-limiting step. As the chemical reaction rate gradually exceeds the reactant adsorption rate with temperature, the rate-limiting step was shifted from the chemical reaction to the reactant adsorption. Additionally, the competitive adsorption between benzene and water for the active sites on TiO₂ resulted in the promotion and inhibition of reaction rate by humidity. This study developed a modified bimolecular Langmuir–Hinshelwood kinetic model to simulate the temperature and humidity related promotion and inhibition of the photocatalysis of benzene. The correlation developed here was used as a basis for determining the apparent activation energy of 0.76 kcal/mol and adsorption enthalpies of benzene and water of −20.1 and −13.7 kcal/mol.     

A Long Cycle-Life High-Voltage Spinel Lithium-Ion Battery Electrode Achieved by Site-Selective Doping

Spinel LiNi_0.5Mn_1.5O₄ (LNMO) is a promising cathode candidate for the next-generation high energy-density lithium-ion batteries (LIBs). Unfortunately, the application of LNMO is hindered by its poor cycle stability. Now, site-selectively doped LNMO electrode is prepared with exceptional durability. In this work, Mg is selectively doped onto both tetrahedral (8a) and octahedral (16c) sites in the Fd m structure. This site-selective doping not only suppresses unfavorable two-phase reactions and stabilizes the LNMO structure against structural deformation, but also mitigates the dissolution of Mn during cycling. Mg-doped LNMOs exhibit extraordinarily stable electrochemical performance in both half-cells and prototype full-batteries with novel TiNb₂O₇ counter-electrodes. This work pioneers an atomic-doping engineering strategy for electrode materials that could be extended to other energy materials to create high-performance devices.     

Synthesis and Crystal Structures of Nickel(II) and Copper(II) Complexes of Meso-3,6,6,9-Tetramethyl-4,8-Diazaundecane-2,10-Dione Dioxime

The nickel(II) and copper(II) complexes of meso-3,6,6,9-tetramethyl-4,8-diazaundecane-2,10-dione dioxime (meso-HM-PAO) have an intramolecular hydrogen bond between cis oxime groups. [Cu(meso-HM-PAO-H)(H₂O)](NCS) crystallizes in space group P2₁/n with a = 7.692(1), b = 12.028(2), c=20.235(3) Å, β=93.03(1)°, Z = 4 and Dc=1.46 g/cm³. The final R value for this complex was 0.034 for 2223 observed reflections with I ≥ 2.5σ (I). The Cu(II) coordination is a distorted square pyramid. The Cu(II) ion is five-coorinated with the diazadioxime N atoms equatorial and water O atom axial. The Cu(II) is 0.12 Å from the equatorial plane towards the hydrate. The equatorial Cu-N distances span a narrow range, 1.953(3)-1.999(3) Å. The axial Cu-O distance is 2.314(3) Å. The thiocyanate group is almost linear. The intramolecular O ?O hydrogen bond length is 2.479(4) Å. [Ni(meso-HM-PAO-H)](ClO₄) crystallizes in space group P2₁/c with a = 14.774(3), b = 12.752(3), c = 20.035(4) Å, β = 92.94(3)°, Z = 8 and Dc = 1.51 g/cm³. The final R value for the complex was 0.053 for 4794 observed reflections with F ≥ 4σ (F). The coordination about Ni(II) is a slightly distorted square plane. The Ni(II) ion is 0.0673(7) Å from the best plane of the four donor nitrogen atoms away from the perchlorate ion. The Ni-N distances span a narrow range 1.863(4)-1.927(4) Å. There are two molecules per asymmetrical unit resulting in eight molecules being packed in an unit cell; they are bound together by van der Waals interactions. The O-H ?O bonds of these complexes give characteristic infrared absorptions as well as chemical shift of the ¹H NMR signal (Ni complex).     

Non-vanishing of central L-values of canonical CM elliptic curves with quadratic twists

The aim of this paper is to extend results of Rorlich, Villegas and Yang about the non-vanishing of central L-values of canonical characters of imaginary quadratic fields over the rationals. One of the new ingredients in our paper is the local computations at the place “2”. Therefore, we extend their non-vanishing results to include imaginary quadratic fields of even discriminant. As a consequence, we show that the rank of the Mordell–Weil groups of certain canonical CM elliptic curves are zero.     

Polyamorphism of liquid silica under compression based on five order-parameters and two-state model: a completed and unified description

The polyamorphism of liquid silica (SiO₂) at 3200?K and in a wide pressure range is investigated by molecular dynamics simulation. Results show that the structure of liquid SiO₂ consists of five order-parameters that do not depend on compression. Three order parameters that relate to the short-range order are SiO_x coordination units (x?=?4, 5, 6) and two order parameters that relate to the intermediate-range order are OSi₂ and OSi₃ linkages. The structure of liquid silica under compression can be described by the two-state model: low-density and high-density states. The low-density state is formed by clustering of OSi₂ linkages (in the low-density state, the short-range order (SRO) is mainly characterized by SiO₄ coordination units), conversely, clustering of OSi₃ linkages will form high-density state (in the high-density state, the SRO is mainly characterized by SiO₅ and SiO₆ coordination units). Under compression, in the liquid silica co-exist two phases: low-density and high-density phases. The size of phase regions significantly depends on compression.     

Mesoporous Silica Particles Integrated with All‐Inorganic CsPbBr3 Perovskite Quantum‐Dot Nanocomposites (MP‐PQDs) with High Stability and Wide Color Gamut Used for Backlight Display

All‐inorganic CsPbX₃ (X=I, Br, Cl) perovskite quantum dots (PQDs) have been investigated because of their optical properties, such as tunable wavelength, narrow band, and high quantum efficiency. These features have been used in light emitting diode (LED) devices. LED on‐chip fabrication uses mixed green and red quantum dots with silicone gel. However, the ion‐exchange effect widens the narrow emission spectrum. Quantum dots cannot be mixed because of anion exchange. We address this issue with a mesoporous PQD nanocomposite that can prevent ion exchange and increase stability. We mixed green quantum‐dot‐containing mesoporous silica nanocomposites with red PQDs, which can prevent the anion‐exchange effect and increase thermal and photo stability. We applied the new PQD‐based LEDs for backlight displays. We also used PQDs in an on‐chip LED device. Our white LED device for backlight display passed through a color filter with an NTSC value of 113 % and Rec. 2020 of 85 %.