Reconstructing the trade history: provenance study of Han bronze mirrors in and out of Han China

A rapidly increasing number of bronze mirrors dated to the Chinese Han dynasty (202 BC – AD 220), known for their unique decorative patterns and highly developed alloying techniques, have been widely discovered in both China and beyond, providing fresh materials and scientific data to revisit their geological provenance, production and circulation network along the ancient Silk Road. In this paper, 47 bronze mirrors unearthed in the southeastern provinces of China, including Zhejiang, Anhui and Fujian provinces, have been characterized by typo-chronology, lead isotopic analysis, compositional analysis and metallography. A much wider comparative study is also carried out through a combination of data from China, Japan, Central Asia, and Southeast Asia, leading to a more updated lead isotopic database of the Han mirrors spreading out of China in various directions. Compared with the traditional ‘optimal’ model based on the Han mirrors recovered in Japan, the current study contributes several key changes in the bronze mirror production of the Han dynasty. The systematic analysis of the alloy composition, trace elements and typological studies shows that the bronze mirror industry shifted towards a more standardized production in the middle to late Western Han Dynasty. In contrast to the substantial change of non-mirror bronze productions, the similar distribution of lead isotope data in early and middle to late Western Han mirrors suggests that the ‘official monopoly of salt and iron’ policy was less effective for the management of lead involved in mirror production. Bronze mirrors dated to middle to late Western Han discovered outside Han-China, such as Japan, Thailand, Afghanistan, Xiongnu and the ancient Dian Kingdom, appear to be subjected to a more specific type of lead as a result of the state-centralized policy of the Western Han court

Dynamic effect of last glacial maximum ice sheet topography on the east asian summer monsoon

The effect of ice sheet topography on the East Asian summer monsoon (EASM) during the Last Glacial Maximum is studied using CCSM3 in a hierarchy of model configurations. It is found that receding ice sheets result in a weakened EASM, with the reduced ice sheet thickness playing a major role. The lower ice sheet topography weakens the EASM through shifting the position of the midlatitude jet, and through altering Northern Hemisphere stationary waves. In the jet shifting mechanism, the lowering of ice sheets shifts the westerly jet northward and decreases the westerly jet over the subtropics in summer, which reduces the advection of dry enthalpy and in turn precipitation over the EASM region. In the stationary wave mechanism, the lowering of ice sheets induces an anomalous stationary wave train along the westerly waveguide that propagates into the EASM region, generating an equivalent-barotropic low response; this leads to reduced lower-tropospheric southerlies, which in turn reduces the dry enthalpy advection into East Asia, and hence the EASM precipitation

Slow-Relaxation Behavior of a Mononuclear Co(II) Complex Featuring Long Axial Co-O Bond

Co(II) mononuclear complex with different coordination geometry would display various of field-induced single-ion magnet (SIM) behaviors. Here, we identify a field-induced single-ion magnet in a mononuclear complex Co(H2DPA)2·H2O (H2DPA = 2,6-pyridine-dicarboxylic acid) by the hydrothermal method. The long axial Co-O coordination bond (Co1‧‧‧O3) can be formed by Co1 and O3. Therefore, Co(II) ion is six-coordinated in a distorted elongated octahedron. AC magnetization susceptibilities show that the effective energy barrier is up to 43.28 K. This is much larger than most mononuclear Co(II). The distorted elongated octahedron caused by the axial Co-O coordination bond is responsible for the high effective energy barrier. The distribution of electron density in Co1 and O3 atoms in the long axial bond would influence the magnetic relaxation process in turn. Our work deepens the relationship between the effective energy barrier and the weak change of ligand field by long axial bonds, which would facilitate constructing SIM with high energy temperature

Optimization Design Method of a New Stabilized Platform Based on Missile-borne Semi-Strap-down Inertial Navigation System

At present, existing wide range Micro-Electro-Mechanical-Systems (MEMS) inertial sensors have relatively lower precision and direct measurement of the missile’s high-rotation motion inevitably uses a large-range sensor. To achieve high-precision navigation, this paper proposes a novel Semi-strap-down Stabilized Platform (SSP) based on the Missile-borne Semi-Strap-down Inertial Navigation System, which is used to mount sensors and lowers sensor range requirements through isolating the high-rotational motion of missile. First, the author innovatively puts forward a dynamic model under missile-borne environment, then analyses the influence of SSP quality on the range of gyro according to the dynamic model of the SSP. Finally, when the angle of attack of the missile is 2°, the best quality of the SSP with minimum roll angular rate amplitude was calculated through the Runge-Kutta method and the mass gradient control method. Experiments have been carried out by using a high-precision, tri-axial flight simulation turntable to validate the viability of the method. Experiments show that under the same conditions, the angular velocity of the new optimized SSP with the best quality design is reduced to 1/3 of the unoptimized SSP, and the measured roll angle error is reduced to 60% of the unoptimized measurement. The results indicate that the novel SSP has better performance segregating the high-speed rotational motion, and provides theoretical guidance for the high-precision small-range sensor instead of the low-precision wide-range sensor. In addition, the first proposed SSP quality selection method creates a new idea for the improvement of the positioning accuracy in the missile-borne environment

Efficient Synthesis of Rare Disaccharides by Engineered β-Glucosidase Based on Hydropathy Index

Oligosaccharides have important therapeutic applications. A useful route for oligosaccharides synthesis, especially rare disaccharides, is reverse hydrolysis by β-glucosidase. However, the low conversion efficiency of disaccharides from monosaccharides limits its large-scale production because the equilibrium is biased in the direction of hydrolysis. Based on the analysis of the docking results, we hypothesized that the hydropathy index of key amino acid residues in the catalytic site is closely related with disaccharide synthesis and more hydrophilic residues located in the catalytic site would enhance reverse hydrolysis activity. In this study, positive variants TrCel1bI177S, TrCel1bI177S/I174S, and TrCel1bI177S/I174S/W173H, and one negative variant TrCel1bN240I were designed according to the Hydropathy Index For Enzyme Activity (HIFEA) strategy. The reverse hydrolysis with TrCel1bI177S/I174S/W173H was accelerated and then the maximum total production (195.8 mg/ml/mg enzyme) of the synthesized disaccharides was increased 3.5-fold compared to that of wildtype. On the contrary, TrCel1bN240I lost reverse hydrolysis activity. The results demonstrate that the average hydropathy index of the key amino acid residues in the catalytic site of TrCel1b is an important factor for the synthesis of laminaribiose, sophorose, and cellobiose. The HIFEA strategy provides a new perspective for the rational design of β-glucosidases used for the synthesis of oligosaccharides.</p

Manipulating of P2/O3 Composite Sodium Layered Oxide Cathode through Ti Substitution and Synthesis Temperature

P2/O3 composite sodium layered oxide has emerged as a promising cathode for high-performance Na-ion batteries. However, it has been challenging to regulate accurately the phase ratio of P2/O3 composite due to their high compositional diversity, which brings about some difficulty in manipulating the electrochemical performance of P2/O3 composite. Here, we explore the effect of Ti substitution and the synthesis temperature on the crystal structure and Na storage performance of Na0.8Ni0.4Mn0.6O2. The investigation indicates Ti-substitution and altering synthesis temperature can rationally manipulate the phase ratio of P2/O3 composite, thereby purposefully regulating the cycling and rate performance of P2/O3 composite. Typically, O3-rich Na0.8Ni0.4Mn0.4Ti0.2O2-950 shows excellent cycling stability with a capacity retention of 84% (3C, 700 cycles). By elevating the proportion of P2 phase, Na0.8Ni0.4Mn0.4Ti0.2O2-850 displays concurrently improved rate capability (65% capacity retention at 5 C) and comparable cycling stability. These findings will help guide the rational design of high-performance P2/O3 composite cathodes for sodium-ion batteries

Enhancing Photoluminescence of CsPb(ClxBr1&minus;x)3 Perovskite Nanocrystals by Fe2+ Doping

The doping of impurity ions into perovskite lattices has been scrupulously developed as a promising method to stabilize the crystallographic structure and modulate the optoelectronic properties. However, the photoluminescence (PL) of Fe2+-doped mixed halide perovskite NCs is still relatively unexplored. In this work, the Fe2+-doped CsPb(ClxBr1&minus;x)3 nanocrystals (NCs) are prepared by a hot injection method. In addition, their optical absorption, photoluminescence (PL), PL lifetimes, and photostabilities are compared with those of undoped CsPb(Br1&minus;xClx)3 NCs. We find the Fe2+ doping results in the redshift of the absorption edge and PL. Moreover, the full width at half maximums (FWHMs) are decreased, PL quantum yields (QYs) are improved, and PL lifetimes are extended, suggesting the defect density is reduced by the Fe2+ doping. Moreover, the photostability is significantly improved after the Fe2+ doping. Therefore, this work reveals that Fe2+ doping is a very promising approach to modulate the optical properties of mixed halide perovskite NCs