Development of a simultaneous extraction and cleanup method for pyrethroid pesticides from indoor house dust samples

An efficient and reliable analytical method was developed for the sensitive and selective quantification of pyrethroid pesticides (PYRs) in house dust samples. The method is based on selective pressurized liquid extraction (SPLE) of the dust-bound PYRs into dichloromethane (DCM) with analysis by gas chromatography/mass spectrometry. Various adsorbents and combinations of extraction solvents and temperatures were evaluated to achieve a high-throughput sample preparation that eliminates the post-extraction cleanup step. The final method used sulfuric acid-impregnated silica (acid silica) and neutral silica together in the extraction cell with the dust sample to provide both extraction and cleanup simultaneously. The optimal ratio of dust/acid silica/silica was 1:0.8:8. The extraction was performed at 2000 psi, at 100 °C with DCM for 5 min in three cycles. Method precision and accuracy were evaluated by the analysis of triplicate aliquots of the dust samples and the samples fortified with the target PYRs. The accuracy measured as the recoveries of the PYRs in the fortified samples ranged from 85% to 120%. The precision measured as the relative standard deviation of replicate samples was within ±25%. The SPLE method was applied to 20 house dust samples collected from households that participated in two field studies regarding exposures to pesticides and other pollutants. Similar concentrations of target PYRs were obtained for the SPLE and a stepwise extraction/cleanup procedure. The SPLE procedure reduces organic solvent consumption and increases the sample throughput when compared with a traditional stepwise extraction and cleanup procedure. This study demonstrates that the SPLE procedure can be applied to complex dust matrices for analysis of PYRs for large scale exposure or environmental monitoring studies.     

MOCVD法制备Pd@ZIF-8催化剂及其催化Suzuki反应性能(英文)

以金属有机骨架化合物ZIF-8为载体,Pd(C3H5)(C5H5)为金属有机前体,采用金属有机气相沉积方法在室温下制备了Pd@ZIF-8催化剂.Pd纳米粒子在ZIF-8载体上均匀分布,粒子尺寸约为1.5–3.5 nm.Pd@ZIF-8在温和条件下对多种卤代芳烃和苯硼酸的偶联反应均具有良好的活性.ZIF-8优异的化学稳定性不仅保证了其在制备过程中结构的完整,而且赋予了催化剂优异的循环使用性能.反应后Pd@ZIF-8材料的晶体结构、孔结构以及粒子分布均未发生明显的变化.     

基于二乙烯三胺配体的锌配合物的合成、晶体结构及均相催化性能

以二乙烯三胺(DETA)为配体合成了1个五配位的锌配合物[Zn(OAc)2(DETA)]·H2O,通过元素分析、红外光谱和X射线单晶衍射对其结构进行了表征,并研究了其催化Henry反应的性能和机理.结果表明,配合物属于单斜晶系,P21/c空间群,中心锌原子与配体的3个氮原子及2个羧基氧原子配位,形成扭曲的三角双锥构型;通过分子内和分子间的氢键作用,配合物分子进一步形成三维晶体结构;在优化条件下,配合物对Henry反应有良好的催化性能,不同醛反应底物在Henry反应方面具有一定普适性.     

Type II Intramolecular [5+2] Cycloaddition: Facile Synthesis of Highly Functionalized Bridged Ring Systems

A type II intramolecular oxidopyrylium‐mediated [5+2] cycloaddition reaction allows the efficient and diastereoselective formation of various highly functionalized and synthetically challenging bridged seven‐membered ring systems (such as bicyclo[4.4.1]undecane, bicyclo[4.3.1]decane, bicyclo[5.4.1]dodecane, and bicyclo[6.4.1]]tridecane). This simple, thermal, direct transformation has a broad substrate scope and is high yielding, with high functional‐group tolerance and unique endo selectivity. The highly strained tricyclic cores of ingenol mebutate (picato) and cyclocitrinol are synthesized efficiently and diastereoselectively using this methodology.     

Rapid Formation of a Supramolecular Polypeptide–DNA Hydrogel for In Situ Three‐Dimensional Multilayer Bioprinting

A rapidly formed supramolecular polypeptide–DNA hydrogel was prepared and used for in situ multilayer three‐dimensional bioprinting for the first time. By alternative deposition of two complementary bio‐inks, designed structures can be printed. Based on their healing properties and high mechanical strengths, the printed structures are geometrically uniform without boundaries and can keep their shapes up to the millimeter scale without collapse. 3D cell printing was demonstrated to fabricate live‐cell‐containing structures with normal cellular functions. Together with the unique properties of biocompatibility, permeability, and biodegradability, the hydrogel becomes an ideal biomaterial for 3D bioprinting to produce designable 3D constructs for applications in tissue engineering.     

DYNAMIC MECHANICAL BEHAVIOR AND PENETRATION PERFORMANCE OF WFeNiMo HIGH-ENTROPY ALLOY 1)

为了探究不同应变速率下WFeNiMo高熵合金的变形行为和侵彻性能, 采用万能材料试验机、分离式霍普金森压杆开展了高熵合金的静动态力学性能试验, 讨论了其在不同应变速率下变形特征微观机制. 基于弹道枪试验平台开展了高熵合金与典型钨合金(93W-4.9Ni-2.1Fe,wt%)破片对有限厚钢靶侵彻作用性能试验研究, 分析了两种合金破片侵彻作用过程与靶板破坏特征、侵彻穿孔能量消耗与撞击速度间的关系. 结果表明: 高熵合金、钨合金材料屈服强度与应变率呈正相关, 且在相同的应变率下高熵合金具有更高的屈服强度; 随着应变率的提高, 高熵合金由脆性断裂、韧脆混合的准解理断裂发展至具有黏着特性的破碎变形模式; 高熵合金具有较强的局部绝热变形能力, 在侵彻薄钢靶时体现出较高的剪切敏感性; 相同撞击速度下, 高熵合金破片穿靶消耗的能量低于钨合金破片, 对于薄钢靶具有更强的侵彻穿透能力. 高熵合金具有优异的力学性能和侵彻能力, 在高速撞击薄靶板时除了传统的剪切冲塞作用还具有一定的能量释放特性, 在预制破片上有较好的应用前景.     

Synthesis of 2-(phenoxymethyl)oxirane derivatives through unexpected rearrangement of oxiran-2-ylmethyl benzenesulfonates

The synthesis of 2-(phenoxymethyl)oxirane derivatives from oxiran-2-ylmethyl benzenesulfonates was developed through a base promoted rearrangement. A new C-O bond was formed along with the unexpected cleavage of C-S bond via this process. This unusual reaction was characterized with mild reaction conditions, high efficiency, and excellent functional group tolerance. A plausible reaction mechanism was proposed on the basis of experimental results and control experiments.     

Synthetic study of solanoeclepin A: Cyclobutane cyclization via SmI2-additive-mediated reaction and D ring functionalization

The construction of tricyclo[5.2.1.0^1,6]decene skeleton was achieved by cyclobutane ring formation via improved radical reaction using SmI₂-H₂O-HFIP and SmI₂-LiCl conditions in good yields. Those additives were studied to increase the reactivity of SmI₂. Two interesting reactions via neighboring group participations are described for introducing the C4 oxygen functionality by the assistance of C6 substituent in a regioselective manner.     

Cu/ZnO@H-β-P催化剂在合成气制备液化石油气反应中的性能研究

采用共沉淀法制备Cu/ZnO催化剂、水热合成法制备H-β分子筛、通过物理包膜法制备了具有核壳结构的Cu/ZnO@H-β-P催化剂,并用于合成气制备液化石油气(LPG)反应。通过XRD、NH3-TPD、BET和SEM-EDS等手段对催化剂进行了表征,利用固定床连续反应装置对催化剂进行了活性评价。结果表明,Cu/ZnO@H-β-P催化剂是具有中孔的核壳结构材料,其协同作用打破了原有的热力学平衡,促进了甲醇→DME→LPG串联反应的连续进行。与物理混合的Mix-Cu/ZnO-H-β催化剂相比,Cu/ZnO@H-β-P催化剂的CO转化率和LPG选择性更高,空速和反应温度对催化剂活性影响明显,最佳空速和反应温度分别为2 400 h~(-1)和350℃。使用Cu/ZnO@H-β-P催化剂在最佳条件下进行合成气制备LPG反应,CO转化率达到了57.22%,LPG选择性达到了60.52%。     

Threshold dynamics of a stochastic Keizer’s model with stochastic incidence

In this paper, we incorporate stochastic incidence of a chemical reaction into the standard Keizer’s open chemical reaction. We prove that a positive stationary distribution (PSD) for the associated chemical master equation exists and is globally asymptotically stable. We present threshold dynamics of the stochastic Keizer’s model in term of the profile of the PSD for both finite and infinite volume size V. This establishes a sharp link between deterministic Keizer’s model and the stochastic model. In this way, we resolve Keizer’s paradox from a new perspective. This simple model reveals that such stochastic incidence incorporated, though negligible when V goes to infinity, may play an indispensable role in the stochastic formulation for irreversible biochemical reactions.