Condensed Mode Cooling for Ethylene Polymerization: Part IV. The Effect of Temperature in the Presence of Induced Condensing Agents

An experimental investigation of the impact of changes in temperature on the observed rate of polymerization of ethylene in the gas phase using a commercial Ziegler–Natta catalyst in the presence of induced condensing agents (ICAs) reveals some unexpected behavior. In the absence of ICA, the effect of temperature is as expected: raising the temperature of the gas phase from 70 to 90 °C causes the observed rate of polymerization to increase monotonically. It is demonstrated in the past that ICA can increase rate of polymerization of the ethylene in the gas phase due to a cosolubility effect. However, in the current study, it is shown that when ICA is present in the reactor, the same increase in temperature can actually lead to an observable decrease in the reaction rate under certain conditions of temperature and pressure. This is attributed to a lower impact of the ICA on the solubility of ethylene in the amorphous phase of the high‐density polyethylene in the reactor at higher temperatures. An order of magnitude analysis also reveals that the presence of ICA can have an impact on the particle temperature as well.     

Condensed Mode Cooling for Ethylene Polymerization: Part I. The Effect of Different Induced Condensing Agents on Polymerization Rate

The effect of commonly used induced condensing agents (ICAs) on the rate of polymerization of ethylene on a supported Ziegler–Natta catalyst in a gas‐phase process is investigated. It is observed that the instantaneous rate of ethylene polymerization is promoted in presence of all ICAs studied. This is attributed to the effect of the heavy ICAs in enhancing the local concentration of ethylene at the active polymerization sites that are dispersed within the growing polymer particles. It is found that the higher the solubility of ICA in the polymer, the greater the observed effect. It is also observed that the enhancement due to the presence of an ICA is greater during the initial phase of the polymerization.

     

Condensed Mode Cooling for Ethylene Polymerization: Part V—Reduction of the Crystallization Rate of HDPE in the Presence of Induced Condensing Agents

The crystallization of high‐density polyethylene (HDPE) alone, and in the presence of n‐hexane (a common induced condensing agent [ICA]) is studied using differential scanning calorimetry. The presence of a noncrystallizable ICA which is partially soluble in the amorphous phase of HDPE reduces the rate of crystallization. This is reflected by a shifting of the crystallization and melting peaks of HDPE to lower temperatures when the ICA concentration in the medium increases. It is also observed that the rate of crystallization of HDPE can be very slow when the ratio of ICA to HDPE increases from zero. This behavior is useful to better understand the physical effects that can potentially occur at the beginning of the gas phase polymerization of ethylene, and suggests that the crystallization of the nascent polymer, and thus the properties of the polymer in the reactor will be quite different from those of the powder at later stages of the reaction when running in condensed mode.     

Condensed Mode Cooling for Ethylene Polymerization: Part III. The Impact of Induced Condensing Agents on Particle Morphology and Polymer Properties

The presence of different commonly used induced condensing agents (ICAs) in the gas phase polymerization of ethylene on the supported catalyst has a significant impact on the crystallinity and the molecular weight distribution of the resulting high density polyethylene. The crystallinity of the polymer is found to be higher in the presence of vaporized n‐pentane or n‐hexane, than in “dry mode” (i.e., with no ICA). This is primarily attributed to the mechanism of crystallization of polymer chains in presence of the solubilized ICA which might act to promote solvent vapor annealing. In addition, vaporized ICA also provokes a significant increase in the weight average molecular weight, with values being estimated at over one million.

     

Condensed‐Mode Cooling for Ethylene Polymerization: The Influence of Inert Condensing Agent on the Polymerization Rate

Inert condensing agents (ICAs) are used principally to cool down gas‐phase fluidized bed reactors used to polymerize ethylene over supported catalysts. While these ICAs are chemically inert, it appears that they might nevertheless increase the polymerization rate. n‐Hexane is used as an ICA, and an enhancement in the instantaneous rate of ethylene polymerization in the gas phase is observed. This is attributed to a rise in the local ethylene concentration in the amorphous polymer phase surrounding the active sites, due to increases in both the solubility and diffusivity of ethylene in the amorphous polymer. In addition, the polymer particles have a smoother surface with less formation of fiber‐like substructures as the n‐hexane concentration increases.

     

Spherical MgCl2 Supported Iron Catalyst for Ethylene Polymerization: Effect of the Preparation Procedure on Catalyst Activity and the Morphology of Polyethylene Particles

Summary: A new procedure was developed to support [(ArN?C(Me))₂C₅H₃N]FeCl₂ (Ar?2,4,6‐trimethylphenyl) on spherical MgCl₂ for ethylene polymerization. The resultant catalysts showed ten times higher activity of the corresponding catalyst in homogeneous catalysis. The morphologies of polyethylene particles strongly depended on supported catalyst preparation procedure and polymerization conditions. In addition, the GPC measurements showed bimodal polyethylene for the homogeneous polymerization while mono‐modal polyethylene of those supported catalysts.

EDX Line Scan analysis of the catalyst SMSIC‐1 regarding the aluminium and iron distribution in the volume (25 kV accelerating voltage, magnification 1 500).     

Ethylene Polymerization over Homogeneous and Supported Catalysts Based on Bis(imino)pyridine Co(II) Complex: Data on the Number of Active Centers and Propagation Rate Constant

The number of active centers (C_P) and propagation rate constant (k_P) for ethylene polymerization with homogeneous catalyst LCoCl₂ + MAO and supported catalyst LCoCl₂/SiO₂ + Al(i‐Bu)₃, where L is 2,6‐(2,6‐(Me)₂C₆H₃N = CMe)₂C₅H₃N, have been determined using the method of polymerization quenching by radioactive carbon monoxide (¹⁴CO). The unstable rate profile of the reaction was attributed to a decrease in the number of active centers from 0.23 to 0.14 mol · mol^?1(Co) corresponding to an increase in the reaction time from 5 to 15 min, whereas the k_P value remained constant, amounting to 3.5 × 10³ L · mol^?1 · s at 35 °C. A narrow molecular weight distribution of the obtained polyethylene (PE) samples ( = 1.9) testifies that the homogeneous catalyst LCoCl₂ + MAO can be regarded as a single‐site system. The activity of the supported catalyst was stable and noticeably lower than that of the homogeneous catalyst due to the low concentration of the active centers (0.02–0.03 mol · mol^?1(Co)). PE with a broad molecular weight distribution ( = 36) and noticeably higher molecular weight is formed in the presence of the supported catalysts. The activity of the supported catalyst increases sharply at polymerization in the presence of hydrogen. The data obtained on the C_P and k_P values allow suggesting the formation of the “dormant” centers at polymerization without hydrogen and regeneration of the active centers in the presence of hydrogen. The average k_P values for the supported catalyst containing multiple active centers were determined to be 5.9 × 10³ and 10.5 × 10³ L · mol^?1 · s, respectively, at 35 and 50 °C.

     

RAFT Dispersion Polymerization of Styrene in Water/Alcohol: The Solvent Effect on Polymer Particle Growth during Polymer Chain Propagation

The RAFT polymerization of styrene in a solvent consisting of a water/alcohol mixture with different water contents is performed and the solvent effects on polymerization kinetics, polymer chain propagation, and polymer particle growth are evaluated. It is found that the solvent affects the RAFT polymerization kinetics greatly, and the apparent polymerization rate constant (K_p ^app) increases with an increase in the water content of the water/alcohol mixture. In addition, RAFT polymerization in a water/alcohol mixture with a higher water content affords better control of the polydispersity index (PDI) of the synthesized polymers. Furthermore, the solvent also exerts a great influence on the growth of the polymer particles. Hollow particles are formed either at the initial polymerization with low monomer conversion or in the solvent with a low water content, whereas solid polymer particles are produced either at high monomer conversion or in the solvent with a high water content.

     

二甲亚砜和乙二醇对人卵母细胞毒性作用的研究

目的评估在不同温度、时间条件下,二甲亚砜和乙二醇对人GV、MⅠ、未受精MⅡ卵子的毒性。方法收集本中心废弃的GV、MⅠ及未受精MⅡ卵子,并随机分配到A、B及C组。A组：将卵子于不同温度下放入ES中10min或20min。B组：将卵子于不同温度下放入VS中1min或5min;C组为对照组。统计分析卵子的发育潜能。结果A组或B1、B2组中各种卵子的发育潜能没有显著差异（P〉0．05）,而MⅠ卵子的体外成熟率都显著低于C组（P〈0．05）。B3、B4两组中GV卵子的体外成熟率显著低于C组（P〈0．05）。B3组中MⅠ、未受精MⅡ卵子的成活率要显著高于B4组（P〈0．05）。B3、B4两组中MI卵子的体外成熟率、受精率显著低于C组,MⅡ卵子的受精率、囊胚率显著低于C组（P〈0．05）。结论室温或37℃条件下,亚砜和乙二醇混合剂对GV、MⅠ或未受精MⅡ卵子的毒性无明显差异。     

维持治疗期间不同剂量氨磺必利对精神分裂症认知功能及临床疗效的影响

目的:探讨维持治疗期间不同剂量氨磺必利对精神分裂症认知功能及远期疗效的影响。方法:采用2012年3月-2013年3月在我院住院采用氨磺必利治疗并获得临床痊愈的精神分裂症患者,共96例。随机分为全剂量组和半剂量组,急性期治疗3个月后,全剂量组(46例)维持原治疗剂量600~800mg/d;半剂量组(50例)给予原治疗量的一半作维持量300~400mg/d,纳入病例在出院后持续随访1年,采用韦氏成人智力量表(WAIS)、临床记忆量表评价认知功能,采用阳性与阴性症状量表(PANSS)、大体评定量表(GAS)来衡量评价临床疗效。结果:1年随访后两组认知功能比较差异显著,WAIS量表:言语智商、操作智商、总智商(t=6.1276,3.2526,5.1423;P<0.05);记忆量表:联想学习、图像自由回忆、人像特点回忆及记忆商数(t=3.0972,3.3938,3.0565,2.8937;P<0.05)。两组临床疗效比较:PANSS总分(t=3.6915,P<0.05);GAS量表评分(t=9.5153,P<0.05);1年累计缓解率分别为82.2%和60.4%(χ2=5.32,P<0.05);复发率分别为15.22%和34.00%(χ2=4.51,P<0.05)。副作用发生率分别为45.65%和34.00%(χ2=1.36,P>0.05)。结论:采用氨磺必利全治疗剂量维持治疗对认知功能改善明显,远期疗效较好、复发率较少。     

Synthesis and application of new microcarriers for animal cell culture. Part II: Application of polystyrene microcarriers

In this work (Part II) the application of new polystyrene based microcarriers in cell culture technology is demonstrated. Carriers with a variety of surface modifications were tested as a growth support for cell line BHK 21. The growth behavior of the cells and cell to surface attachment were compared to Cytodex 3 (Pharmacia), which was used as a reference carrier. To select carriers with growth supporting surfaces, broad screening in petri dish experiments was carried out. Candidates with the highest growth rates were investigated in spinner flask experiments in further detail. Polystyrene carrier with a surface modification like triethylamine, maltamine or N-methylglucosamine were able to support growth as good or better as the reference carrier Cytodex 3. Economies of ingredients and ease in laboratory handling could make amine-modified polystyrenes a competitive alternative to currently commercially available microcarrier types.     

Ultra-high-resolution scanning electron microscopic studies on the sarcoplasmic reticulum and mitochondria of the rat intrafusal muscle fibers. Part II: The extracapsular region.

The three-dimensional structure of the transverse-axial tubular system, sarcoplasmic reticulum (SR) and mitochondria in the extracapsular region of the intrafusal muscle fibers of the rat lumbrical muscle was observed by ultra-high-resolution scanning electron microscopy after removal of the cytoplasmic matrix by the osmium-DMSO-osmium procedure. Nuclear chain fibers possessed thick to moderately sized column-forming mitochondria with occasional I-band branches. The transverse tubules (T-tubules) running at the level of the A-band side of the A-I junction were sandwiched between two large terminal cisternae for most of their length, forming triads. The sarcotubules arising from the terminal cisternae formed single-layered networks at the A-band level, and well developed, double-layered, three-dimensional networks at the I-band level. Nuclear bag1 fibers possessed slender column-forming mitochondria devoid of I-band branches. The T-tubules were located at the level of the A-I junction. Both the T- and the axial-tubules were occasionally coupled with small terminal cisternae, forming dyads or triads. At the I-band level, the SR was well developed and formed single layered networks, but at the A-band level only a few longitudinally arranged sarcotubules and axial tubules were observed. Nuclear bag2 fibers contained medium to large diameter column-forming mitochondria without I-band branches. The T-tubules ran at the level of the A-band adjacent to the A-I junction, and were coupled at some intervals with terminal cisternae of various lengths. Swollen, large terminal cisternae were frequently seen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Microbead analysis of cell binding to immobilized lectin. Part II: Quantitative kinetic profile assay for possible identification of anti-infectivity and anti-cancer reagents

There has been a re-emergence of the use of lectins in a variety of therapeutic venues. In addition lectins are often responsible for the binding of pathogens to cells and for cancer cell clumping that increases their escape from body defenses. It is important to define precisely the activity of inhibitors of lectin-binding that may be used in anti-infection and anti-cancer therapeutics. Here we describe a kinetic assay that measures the activity of saccharide inhibitors of lectin binding using a model system of yeast (Saccharomyces cerevisiae) and lectin (Concanavalin A, Con A) derivatized agarose microbeads that mimics pathogen-cell binding. We show that old methods (part I of this study) used to identify inhibitor activity using only one sugar concentration at one time point can easily provide wrong information about inhibitor activity. We assess the activity of 4 concentrations of 10 saccharides at 4 different times in 400 trials and statistically evaluate the results. We show that d-melezitose is the best inhibitor of yeast binding to the lectin microbeads. These results, along with physical chemistry studies, provide a solid foundation for the development of drugs that may be useful in anti-infectivity and anti-cancer therapeutics.     

The use of pedometer and actometer in studying daily physical activity in man. Part II: Validity of pedometer and actometer measuring the daily physical activity

Summary The validity of the pedometer and actometer for estimating the daily physical activity was evaluated by means of an observation study. The physical activity in a classroom of 11 pupils of a kindergarten was assessed by means of a pedometer, actometer and by observation. Besides this an activity questionnaire was completed by the infant-quide. On basis of the individual observation it is clear that the infant-guide can give valuable information about the activity of the children at school.The results of the pedometer attached to the waist and the actometers attached to the ankle were significantly correlated with the results of the observation method. The wrist actometer showed a smaller but still significant correlation with the other variables. Implications of this findings are discussed in regard toward the physical activity. The pedometer results point out that when the percentage of intense activity is high the pedometer tends to underestimate the level of activity.The actometer results indicate that such a motion recorder gives a reliable estimation of activity in children. The findings are discussed in terms of the practical applications of the actometer in the research of daily physical activity and the physical rehabilitation treatment of certain diseases.     

The Mechanism of the Inhibitory Effect of Progesterone on Lymphocyte Cytotoxicity: II. Relationship Between Cytotoxicity and the Cyclooxygenase Pathway of Arachidonic Acid Metabolism

ABSTRACT: In the previous paper we have demonstrated that progesterone-treated lymphocytes of healthy pregnant women produce a 34,000 MW protein that inhibits cytotoxic activity and prostaglandin F₂α synthesis. Since recently it has been shown that certain leukotrienes have a stimulatory effect on natural killer activity, in this study an attempt was made to determine whether there is a relationship between cytotoxicity and PGF₂α synthesis or if alterations in the values of these parameters are independent. Arachidonic acid increased cytotoxic activity of healthy pregnant women's peripheral blood mononuclear cells (PBMC) in a concentration-dependent manner. Exogenous arachidonic acid was able to counteract the blocking effect of the above-mentioned protein produced by progesterone-treated lymphocytes. To determine whether the products of the cyclooxygenase or the lipoxygenase pathway of arachidonic acid metabolism are responsible for increased cytotoxicity, both enzyme systems were blocked separately. Both indomethacin and the lipoxygenase inhibitor BW 755C reduced cytotoxicity in a dose-dependent fashion. However, the lipoxygenase inhibitor prevented prostaglandin synthesis to the same extent, or even more than indomethacin, in all concentrations used; so, its blocking effect cannot be considered as supportive evidence for the role of leukotrienes in cytotoxicity. On the other hand, lipopolysaccharide, with a selective stimulatory effect on prostaglandin synthesis, increased cytotoxicity. Lipopolysaccharide had no effect on progesterone-pretreated PBMC. The above data allow the assumption that besides leukotrienes, cyclooxygenase products may also increase cytotoxicity.