Unusual Two-Step Assembly of a Minimalistic Dipeptide-Based Functional Hypergelator

Self-assembled peptide hydrogels represent the realization of peptide nanotechnology into biomedical products. There is a continuous quest to identify the simplest building blocks and optimize their critical gelation concentration (CGC). Herein, a minimalistic, de novo dipeptide, Fmoc-Lys(Fmoc)-Asp, as an hydrogelator with the lowest CGC ever reported, almost fourfold lower as compared to that of a large hexadecapeptide previously described, is reported. The dipeptide self-assembles through an unusual and unprecedented two-step process as elucidated by solid-state NMR and molecular dynamics simulation. The hydrogel is cytocompatible and supports 2D/3D cell growth. Conductive composite gels composed of Fmoc-Lys(Fmoc)-Asp and a conductive polymer exhibit excellent DNA binding. Fmoc-Lys(Fmoc)-Asp exhibits the lowest CGC and highest mechanical properties when compared to a library of dipeptide analogues, thus validating the uniqueness of the molecular design which confers useful properties for various potential applications.     

Phosphoric Acid-assisted Pretreatment Strategy for the Rational Synthesis of Lignin-derived Hierarchical Porous Carbon Toward High-performance Supercapacitors

In this article, a facile two-step activation method, coupled with phosphoric acid (H₃PO₄)-assisted pretreatment and followed KOH activation, was reported for constructing hierarchical porous carbon (HPC) materials derived from lignin. The introduction of H₃PO₄, cross-linked with lignin sources generated phosphate (and/or polyphosphate) ester groups throughout the lignin structure, which endowed the pre-activated intermediate char (IC) with a hierarchical porous structure. Such phosphate esters contributed to the multi-scale pore structure within the pre-activated IC, which was beneficial for the uniform distribution and impregnation of subsequent KOH activators, thus leading to the formation of HPC materials. The as-prepared HPC exhibited a large specific surface area (SSA) of 1345.1 m²/g, which ensures the accessibility of the ion diffusion pathways. The supercapacitors integrated with HPC delivered a high specific capacitance of 241 F/g (in a three-electrode system) and outstanding rate capability with an 80.9% capacitance retention from 0.5 A/g to an ultra-high current density of 50 A/g.     

Microstructure and mechanical properties of Al2O3/ZrO2 composites by two-step sintering

Composites of Al₂O₃/ZrO₂ (containing 25, 50, and 75 vol% ZrO₂) were prepared by mixing Al₂O₃ and ZrO₂ suspensions. The microstructural control via two-step sintering (TSS) was the main objective of this work. For this purpose, different sintering curves were constructed, aiming to achieve the best temperature combination for the sintering steps that provides higher density and finer microstructure. The results were compared with single-step sintering (SSS). Furthermore, microhardness and fracture toughness were measured for the best TSS specimens under each composition. The results showed that the high densities were obtained, and the reduction of grain size was greater than 40% for two-step sintered specimens, compared to SSS ones. Consequently, microhardness values increased. However, fracture toughness values remained unchanged.     

Mechanisms of synthesis gas production via thermochemical cycles over La0·3Sr0·7Co0·7Fe0·3O3

La_0·3Sr_0·7Co_0·7Fe_0·3O₃ (LSCF3773) was chosen as an oxygen carrier material for synthesis gas production and synthesized using ethylene-diamine-tetra-acetic acid (EDTA) citrate-complexing method. LSCF exhibited a pure cubic structure where 110 and 100 plane diffractions were active for CO₂ splitting, while 111 was more favored by H₂O splitting. Overall oxygen storage capacity (OSC) of LSCF was 4072 μmol/g_cat. During the reduction process, regular cations (Co⁴⁺, Fe⁴⁺), polaron cations (Co³⁺, Fe³⁺) and localized cations (Co²⁺, Fe²⁺) were achieved when the LSCF was reduced at 500, 700 and 900 °C, respectively. The strength of the active sites depended on reduction temperatures. An increase in oxidation temperature enhanced H₂ production at temperature ranging from 500 °C to 700 °C while effected CO production at 900 °C. H₂O and CO₂ was competitively split during the oxidation step, especially at 700 °C. The activation energy of each reaction was ordered as; CO₂ splitting > H₂O splitting > CO₂ adsorption, supporting the above evidence where H₂ and CO production were found to increase when the operating temperature was increased.     

Some concerns regarding the CAT16 chromatic adaptation transform

In recent literature, a new chromatic adaptation transform, CAT16, has been published to improve upon the widely used CAT02 model. The CAT16 model is based on the form of the CAT02 transform adopted in CIECAM02, but uses a slightly different sensor space to fix some gamut problems plaguing CIECAM02 and adopts a two-step CAT to ensure symmetry and transitivity. CAT16 is included in CAM16 but is also being promoted as a stand-alone CAT, one that can be used outside of the CAM16 model. However, the use of CAT16 as a stand-alone model can cause inconsistencies in the calculated corresponding colors due to the presence of the relative luminance of the adapting white (Y_w) in the von Kries-Ives gain control factors. Such inconsistencies are not present for the stand-alone version of the CAT02 model, which, unlike the version adopted in CIECAM02, does not include the Y_w factors. CAT16 should therefore be modified by omitting the Y_w factors. In this article, we will briefly discuss these issues in more detail and provide a consistent two-step CAT adopting the CAT16 sensor space.     

Aflatoxin contamination and exposure in processed cereal-based complementary foods for infants and young children in greater Accra,Ghana

In the study, aflatoxin levels were assessed in thirty five (35) cereal-based food products intended for infants and young children. Additionally, the results showed that 71% of the processed foods intended for infants contained AFB₁ (0.18 ± 0.01 to 36.10 ± 0.32 μgkg⁻¹) levels higher than the European Union permissible limits of 0.1 μg kg⁻¹. Aflatoxin intake was estimated using aflatoxin levels in the food products and the estimated individual consumption rates. The study also revealed mixed cereals as having the highest intake of aflatoxin B₁ contaminants (0.005–0.852 μgkg⁻¹bw d⁻¹; 0.004–0.657 μgkg⁻¹bwd⁻¹) with mean estimated daily intake (EDI) of 0.23 ± 0.16 μgkg⁻¹bwd⁻¹ and 0.153 ± 0.13 μgkg⁻¹bwd⁻¹ for infants and young children respectively. The estimated AFT intake recorded for infants and young children for all the cereal-based food ranged from 0.005 to 1.054 μgkg⁻¹bwd⁻¹ and 0.004–0.838 μgkg⁻¹bwd⁻¹ respectively.     

基于区域特征和质心关系的两步法阀板检测

针对冲压阀板中毛刺、冲压孔堵塞等缺陷的检测问题,提出了一种基于面积特征的通孔数目检测和基于质心关系的快速模板匹配检测的两步视觉检测方案。首先采用通孔数检测初步判定零件是否存在冲压孔堵塞缺陷,之后采用模板匹配精确检测边缘毛刺缺陷。利用区域面积特征实现通孔数检测;提出了一种限定条件的最小二乘法圆拟合方法和一种基于圆心特征的快速模板匹配方法,实现边缘毛刺等缺陷的精确检测。实验结果表明,这种两步检测方案检测速度快精准度高,能够满足阀板生产线的检测要求。     

二阶二段掏槽技术在岩巷掘进中的应用研究

为了解决阳煤一矿岩巷掘进中出现的炮孔利用率低、大块率高、抛渣距离远的问题，在岩巷掘进爆破施工中应用二阶二段掏槽技术。在分析了二阶二段掏槽破岩机理的基础上，依据炸药爆炸在岩石中形成粉碎区和裂隙区半径的计算式确定了一阶及二阶掏槽孔口距、孔底距等二阶二段掏槽技术关键参数，并在现场进行应用。现场试验结果表明：与原方案相比，采用二阶二段掏槽技术后，炮孔利用率由81%提高到90%，大块率降低了72%，抛渣距离减小了29%，月进尺由60m提高到90m，提高50%。应用效果表明二阶二段掏槽技术具有良好的适应性，并具有较高的技术经济效果，可为同类型巷道快速掘进提供借鉴。     

Synthesis and two-step sintering behavior of solution derived corundum abrasives with plate-like grains

Corundum abrasives with plate-like grains were fabricated by a two-step sintering technique using the solution-based process with the addition of the ternary compound additive Na₃AlF₆-CaO-SiO₂. The two-step sintering method showed obvious advantages over conventional sintering methods in promoting sample densification, suppressing grain growth, and homogenizing the microstructure of the corundum abrasives. The sample doped with 2.5?wt% Na₃AlF₆ and 4?wt% CaO + SiO₂ in the molar ratio of 1:1 possessed a relative density of 99.3%, average grain size of 0.54?µm, and single-particle compressive strength of 49?N. The introduction of seeds reduced the temperature of θ- to α-Al₂O₃ phase transformation. The relationship between the microstructure and the mechanical properties of the abrasives was also discussed.     

基于神经网络技术的复杂框架结构节点损伤的两步诊断法

大量研究表明,对于发生损伤的大型复杂结构,采用常规的一步方法进行损伤诊断将是十分困难,甚至是不可能的。因此,本文对多层及高层复杂框架结构节点损伤,提出了基于神经网络技术的两步诊断方法,此方法先将结构划分为n个子区域,将损伤引起的结构前n阶模态频率变化比与损伤区域的关系输入概率神经网络,建立系统,进行损伤子区域判定;然后将结构损伤子区域内第二阶杆端应变模态变化量与节点损伤位置和损伤程度的关系输入径向基神经网络,建立系统,进行损伤位置和损伤程度具体诊断。数值仿真分析结果表明,此方法可对多层及高层框架结构的地震节点损伤做出成功诊断,且具有较好的抗干扰能力。