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111.
Xinting Wang Xiangjie Li Christian Grimme Andrew Olah Eric Baer Gary E. Wnek 《应用聚合物科学杂志》2019,136(42):48046
We report the fabrication of poly (ethylene-co-methacrylic acid) sodium-neutralized ionomer (Surlyn 8940) fibers via a forced-assembly coextrusion and layer multiplication process with polystyrene (PS) as the matrix material. The PS separating materials were removed by toluene extraction to yield independent Surlyn fibers. The tensile properties of Surlyn fiber strands were studied under different strain rates. Surlyn fibers were oriented to 300% strain at different temperatures to study the effect of orientation on the tensile properties. The oriented Surlyn fibers were annealed after orientation to further enhance the mechanical properties. Further drawing of these oriented fiber mats to a draw ratio of 4 at 60 °C followed by annealing at 60 °C can afford moduli in excess of 350 MPa and tensile strengths in excess of 70 MPa. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48046. 相似文献
112.
D Gautrin C Infante-Rivard TV Dao M Magnan-Larose D Desjardins JL Malo 《Canadian Metallurgical Quarterly》1997,155(6):1841-1847
Atopy, specific IgE sensitization, and bronchial hyperresponsiveness (BHR) were examined in a cohort of 769 apprentices starting career programs in animal health or veterinary medicine (Group 1), pastry making (Group 2), and dental hygiene (Group 3). The hypothesis were that: (1) a proportion of subjects can be "sensitized" although no significant specific occupational exposure has occurred; and (2) there is a relationship between baseline specific sensitization to work-related antigens and host characteristics. Skin tests were administered using 11 common inhalants and specific allergens, including six laboratory animal extracts, three cereal antigens, alpha-amylase, and latex. Methacholine challenge tests were performed. The prevalence of atopy was 54.4% in Group 1, 58.1% in Group 2, and 52.5% in Group 3. Skin reactivity to work-specific proteins was as follows: laboratory animal proteins, 13.8% in Group 1, 14.0% in Group 2, and 15.6% in Group 3. No subject was sensitized to alpha-amylase, whereas 1.2% in Group 1, 5% in Group 2, and 4.1% in Group 3 were sensitized to flour. Five subjects reacted to latex. BHR (PC20 < or = 8 mg/ml) was present in 17.6%, 21.2%, and 14.8% of subjects in Groups 1, 2, and 3, respectively. Specific sensitization was associated with positive skin reactions to common allergens, work-related symptoms, and BHR. These results suggest that students starting career programs with exposure to high-molecular-weight allergens have a low but substantial frequency of specific sensitization to work-related allergens that is related to atopy and BHR. 相似文献
113.
Individual somatotype parameters and peculiarities of constitution in 7-12 years boys were evaluated in the present investigation. The age range studied was shown to be divided on 3 stages. Regular growth processes with the prevalence of "infantal" proportions occur at the age of 7-9. Signs of definite constitutional type are expressed yet insufficiently. The age of 10-11 is transitional which shows in delay of muscle growth. At the age of 11-12 prepubescent sets in, during which features of constitution types and appropriate somatotype parameters are distinctly manifested. 相似文献
114.
MA Gorbunov LI Pavlova IA Titov TA Bektimirov VP Selezneva OIu Shitikova TV Mamontova IN Indikova 《Canadian Metallurgical Quarterly》1997,(6):55-58
The results of field clinical trials of Russian and American yeast vaccines against hepatitis B are presented. The study revealed that both vaccines were faintly reactogenic, safe and exhibited high immunological activity. After the full course of immunization following the schedule 0-1-2 months 92.5% and 97.5% of patients receiving, respectively. Russian vaccine "Combiotech" and American vaccine "H-B-Vax II" were found to have specific antibodies. The maximum effect was registered when the vaccines were introduced according to the schedule 0-1-6 months. Seroconversions were observed in 97.5% and 100% of the vaccinees receiving the Russian and American vaccines respectively, in the latter case the highest antibody level being observed. The use of the vaccines within the prophylactic immunization schedule showed that antibodies to hepatitis B appeared in immunized children in 93-100% of cases. Seroconversion indices and the levels of antibodies to diphtheria, tetanus, poliomyelitis and measles were statistically significant and were the same in children receiving only the vaccines according to the immunization schedule and in children immunized, in addition to these vaccines, against hepatitis B. 相似文献
115.
High oxygen barrier film/foam system had been developed using multilayer coextrusion technology. The film/foams contained alternating ethylene–vinyl alcohol (EVOH) copolymer film layers and low‐density polyethylene (LDPE) foam layers. To ensure good adhesion and layer integrity, the LDPE was preblended with LDPE grafted maleic anhydride. The layered structure of film/foam was characterized by scanning electron microscopy. The film/foams showed adjustable density, oxygen permeability, and mechanical properties by changing the film and foam composition. Film/foam with 10% EVOH film layer was successfully thermoformed at room temperature. The cells in the foam layer were observed to deform during the mechanical forming process. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46425. 相似文献
116.
A novel environmentally friendly co‐extrusion and multiplication technology in combination with a water jet procedure was utilized to produce dual‐component fibrous filters. Polyvinylidene fluoride (PVDF)/high‐density polyethylene (HDPE) systems were selected as the filter materials. The orientation procedure was shown to greatly enhance the mechanical properties of the fibers as well as the filters. These filters were found to have micron‐size pores, high porosity, and high surface areas. Various physical treatments were applied on these filters which decrease the filter pore size. It was found that filter pore size decreased to 0.2 μm and the mechanical properties were enhanced. Water flux tests and microparticle separation tests were performed on these filters to evaluate their microfiltration behavior. PVDF/HDPE filters exhibit high water flux with low pressure requirement, making them good candidates for microfiltration water filters. In addition, the PVDF/HDPE filters exhibit high separation efficiencies 90% on 1 μm particles, 96% on 2 μm particles, and 99% on 5 and 10 μm particles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45557. 相似文献
117.
One of the most reliable methods for characterizing an activated sludge is by measurement of its activity. The measuring principle of the method developed is based upon the determination of glucose activity of the activated sludge. The activated sludge sample is continuously aerated in a reactor and glucose standard solution is given to it. The glucose uptake in the activated sludge system is measured by a glucose selective electrode. The sludge activity is calculated on the basis of the reaction time required for the 50% decomposition of the glucose. Only the change of dissolved oxygen concentration of the sample interferes the measurement. This interference is eliminated by the measurement of dissolved oxygen. The electrical response of glucose electrode is corrected with that of the oxygen electrode. The method is selective, the reproducibility of it is better than 10%. 相似文献
119.
Burova TV; Choiset Y; Tran V; Haertle T 《Protein engineering, design & selection : PEDS》1998,11(11):1065-1073
Mixed disulfide derivatives of bovine beta-lactoglobulin (BLG) were studied
by circular dichroism (CD), gel-permeation HPLC and high- sensitivity
differential scanning calorimetry (HS-DSC). It was shown that modification
of Cys121 with mercaptopropionic acid and mercaptoethanol does not affect
the secondary structure of BLG, but results instead in tertiary and
quaternary structure changes. At neutral pH, the equilibrium
dimer<==>monomer of modified beta- lactoglobulin is shifted towards
monomeric form. In contrast to native BLG, thermal denaturation of modified
beta-lactoglobulin is fully reversible in neutral and acidic pH as
demonstrated by CD and HS-DSC measurements. Modification of Cys121 results
in a significant decrease of transition temperature (-6 degrees C) and
enthalpy (-106 kJ/mol) at pH 2.05 while unfolding heat capacity increment
remains unchanged. Thermal unfolding transitions of native and modified
beta-lactoglobulin at pH 2.05 are well approximated by a two-state model
suggesting that no intermediate states appear after modification. The
difference in Gibbs energy of denaturation between native and modified
beta- lactoglobulin, 8.5 kJ/mol at 37 degrees C and pH 2.05, does not
depend on the nature of the introduced group (charged or neutral). Computer
analysis of possible interactions involving Cys121 in a three- dimensional
structure of beta-lactoglobulin revealed that the thiol group is too far
away from neighboring residues to form side-chain hydrogen bonds. This
suggests that the sulfhydryl group of Cys121 may contribute to the
maintenance of BLG tertiary structure via water mediated H-bonding.
相似文献
120.
Green chemical processes play a crucial role in sustainable development, and efficient recyclable catalysts that can be conveniently applied in various chemical reactions are the key elements for the development of sustainable synthetic processes. Many organic transformations rely on Lewis and Br?nsted acid catalysts, and such molecules have been widely studied in organic synthesis. Over the years, researchers have looked for Lewis acid catalysts that provide high selectivity and high turnover frequency but are also stable in aqueous media and recoverable. Since the first preparation of trifluoromethanesulfonic acid by Hazeldine (triflic acid, HOTf), researchers have synthesized and used numerous metal triflates in a variety of organic reactions. Even though the rare earth metal triflates have played a major role in these studies, the majority of rare earth triflates lack one or more of the primary properties of sustainable catalysts: low cost and easy availability of the metals, easy preparation of triflates, aqueous/thermal stability, recyclability, and catalytic efficiency. In this Account, we describe the synthetic applications of Ga(OTf)(3) and its advantages over similar catalysts. Ga(OTf)(3) can be conveniently prepared from gallium metal or gallium chloride in excess of trifluoromethanesulfonic acid (triflic acid) under reflux. Among many Lewis acid catalysts recently studied, Ga(OTf)(3) is water tolerant and soluble and requires very low catalyst loading to drive various acid-catalyzed reactions including Friedel-Crafts alkylation, hydroxyalkylation, and acylation selectively and efficiently. In many reactions Ga(OTf)(3) demonstrated high chemo- and regioselectivity, high yields, excellent stability, and recyclability. We successfully synthesized many biologically active heterocycles and their fluoroanalogs under mild conditions. Many challenging reactions such as the ketonic Strecker reactions proceed efficiently via Ga(OTf)(3) catalysis. Because it is stable in water, this catalyst provides the opportunity to study substrates and develop new synthetic protocols in aqueous media, significantly reducing the production of hazardous waste from organic solvents and toxic catalyst systems. 相似文献