ICP-AES法快速测定不锈钢食具容器中重金属的迁移量

采用ICP–AES法快速测定不锈钢食具容器中的重金属铅、铬、镍、镉和砷的迁移量。样品用4%乙酸溶液浸泡,ICP–AES法测定浸泡液中铅、铬、镍、镉、砷的含量。铅、铬、镍、镉、砷的质量浓度分别在0.03~0.30,1.0~5.0,0.3~2.0,0.015~0.20,0.020~0.30 mg/L范围内与其光谱强度线性相关,相关系数均大于0.999 6。铅、铬、镍、镉、砷的检出限分别为0.009,0.000 5,0.002,0.000 5,0.007 mg/L,加标回收率分别为100.0%~122.5%,100.0%~115.0%,99.0%~117.5%,108.0%~115.0%,60.0%~68.8%,测定结果的相对标准偏差为0.2%~5.0%(n=6)。结果表明,该方法能够满足对不锈钢食具容器中重金属迁移量的快速测定要求,可应用于食品相关产品的监管工作。     

In situ patterning and controlling living cells by utilizing femtosecond laser

Photo-induced processes have high potential in in situ patterning and controlling living cells, whose developments are introduced and recent progresses by utilizing femtosecond laser are described. Photochemical and photothermal surface modification performed by conventional light and nanosecond laser irradiation is summarized and their applicability is considered. Femtosecond laser ablation has superior features due to its photomechanical mechanism, which is confirmed by ultrafast spectroscopy and imaging of a model film under laser ablation. Femtosecond laser ablation of physiological solutions generates shockwave and cavitation bubbles, which is employed for patterning and manipulating living cells. Femtosecond laser ablation fabricating cytophobic and cytophilic domains enable us to form living cell patterns and to study cell migration and cell–cell interaction. Finally summary and perspective are presented.     

Ruthenium‐Catalyzed O‐ to S‐Alkyl Migration: A Pseudoreversible Barton–McCombie Pathway

A practical ruthenium‐catalyzed O‐ to S‐alkyl migration affords structurally diverse thiooxazolidinones in excellent yields. Our studies suggest this catalytic transformation proceeds through a pseudoreversible radical pathway drawing mechanistic parallels to the classic Barton–McCombie reaction.     

Lymphocyte migration in the micro-channel of splenic sheathed capillaries in Chinese soft-shelled turtles,Pelodiscus sinensis

The structural characteristics of the splenic sheathed capillary were investigated using light microscopy and transmission electron microscopy (TEM). This study mainly focused on lymphocyte migration to the splenic white pulp via micro-channels in Chinese soft-shelled turtles, Pelodiscus sinensis. The results showed that the sheathed capillaries in the turtle spleen were high endothelial venule (HEV)-like vessels. These capillaries consist of micro-channels that facilitate lymphocyte migration to the splenic white pulp. The micro-channel is a dynamic structure comprising processes of endothelial cells, supporting cells, and ellipsoid-associated cells (EACs), which provides a microenvironment for lymphocyte migration. The pattern of lymphocyte migration in the micro-channel of the turtle spleen includes the following steps: (i) lymphocyte first adheres to the endothelium of the sheathed capillary, passes through the endothelial cells, and traverses through the basement membrane of the sheathed capillary; (ii) it then enters into the ellipsoid combined with supporting cells and EACs; and (iii) lymphocyte migrates from the ellipsoid to the periellipsoidal lymphatic sheath (PELS) via the micro-channel. This study provides morphological evidence for lymphocyte migration in the micro-channels of turtle spleens and also an insight into the mechanism of lymphocyte homing to the splenic white pulp of reptiles.     

Synthesis and catalytic performance of ferrocene‐based compounds as burning rate catalysts

To overcome migration problems of ferrocene‐based burning rate catalysts and to enhance burning rate of ammonium perchlorate (AP)‐based propellants, eleven ferrocene‐based compounds ( 1 – 11 ) were synthesized by the condensation reaction of ferrocenecarbonyl chloride with corresponding amines and alcohols. The synthesis of 1 – 11 was confirmed using ¹H NMR, Fourier transform infrared and UV–visible spectroscopy. Their electrochemical properties were analyzed using cyclic voltammetry. The compounds showed redox behavior due to the presence of ferrocene. Their catalytic behavior in the thermal decomposition of AP was investigated using thermogravimetry (TG) and differential TG (DTG). In the presence of 5 wt% 1 – 11 , the thermal decomposition temperature of AP was significantly decreased. TG and DTG analyses showed that 1 – 11 had a good catalytic effect in the thermal decomposition of AP. Anti‐migration studies showed that migration of 1 – 11 was slower than that of 2,2‐bis(ethylferrocenyl)propane (catocene) and ferrocene. The effect of the presence of polar elements like oxygen and nitrogen on anti‐migration behavior of small ferrocene‐based compounds was also investigated. Oxygen‐containing compounds showed better anti‐migration behavior than nitrogen‐containing compounds.     

Breakdown of Born‐Oppenheimer Approximation as a Physical Mechanism for Ultrafast Hydrogen Migrations in Strong Laser Driven Molecules

We propose a physical mechanism based on breakdown of the Born‐Oppenheimer approximation to rationalize the ultrafast hydrogen migration in strong laser driven isomerization reactions. A three nuclei (proton, donor, and acceptor) model is employed to develop a three step solution scheme. The proton‐donor Coulomb repulsion is shown to be responsible for the high proton mobility. We identify a proton tunneling process and use the Keldysh‐Faisal‐Reiss theory to calculate the tunneling probability. The effect of laser parameters (intensity, frequency, polarization, and pulse duration) has been studied and found to be consistent with recent experiments.     

膨胀颗粒与甲叉基聚丙烯酰胺复合堵剂堵水研究

应用砂岩微观孔隙模型实验方法，对ＴＰ－９２０膨胀固体颗粒与甲叉基聚丙烯酰胺复合堵剂在双重孔隙介质油层中的封堵机理进行了实验观察研究。通过实验现象观察结合油田现场化学堵水效果分析得出，该类化学堵剂的封堵机理和堵水效果主要表现为：携带液的吸附水膜机理和固体颗粒膨胀后对储层微裂缝及大孔道的物理堵塞机理，由此而产生的驱替—封堵效果对双重孔隙介质油层的化学堵水具有更加理想的控水增油作用。     

Novel ethylene/norbornene copolymers as nonreleasing antioxidants for food‐contact polyolefinic materials

An efficient procedure for the copolymerization of ethylene (E) with a novel norbornenic comonomer (N_ArOH) bearing a stabilizing moiety analogous to commercial antioxidant 2,6‐di‐tert‐butyl‐4‐methylphenol (BHT) is successfully developed. This study is aimed at: i) tuning the concentration of the stabilizing function along the polymer chain, and ii) preparing “nonreleasing” polymeric additives specifically destined to protect commercial low‐density polyethylene (LDPE). Films obtained from blends of the novel E/N_ArOH copolymers with an antioxidant‐free LDPE matrix are characterized by superior thermal, thermo‐oxidative, and photostability when compared not only with neat LDPE films but also with films stabilized by the commercial BHT additive. Specific migration tests conducted in order to investigate the nonreleasing character of the novel macromolecular additives confirm the reduced risk of migration, from the films into food simulants, of unreacted comonomer or degradation products bearing the antioxidant moiety. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 , 51, 1007–1016     

The Deficiency of Internal Migration Research

Most papers discuss migration theories and internal migration without analyzing it on a micro and macro level, without mentioning the effect of globalization. This essay tries to bridge the gap and provide enough researches for government administration.