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排序方式: 共有297条查询结果,搜索用时 15 毫秒
1.
2.
Fabrication of biodegradable poly(ester-amide)s based on tyrosine natural amino acid 总被引:2,自引:0,他引:2
N,N′-Bis[2-(methyl-3-(4-hydroxyphenyl)propanoate)]isophthaldiamide (5), a novel diol monomer containing chiral group, was prepared by the reaction of S-tyrosine methyl ester (3) with isophthaloyl dichloride (4a). A new family of optically active and potentially biodegradable poly(ester-amide)s (PEAs) based on tyrosine amino acid were
prepared by the polycondensation reaction of diol monomer 5 with several aromatic diacid chlorides. The resulting new polymers were obtained in good yields with inherent viscosities
ranging between 0.25 and 0.42 dL/g and are soluble in polar aprotic solvents. They showed good thermal stability and high
optical purity. The synthetic compounds were characterized and studied by FT-IR, 1H-NMR, specific rotation, elemental and thermogravimetric analysis (TGA) techniques and typical ones by 13C-NMR, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM)
analysis. Soil burial test of the diphenolic monomer 5, and obtained PEA6a, and soil enzymatic assay showed that the synthesized diol and its polymer are biologically active and probably biodegradable
in soil environment. 相似文献
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Jason A. Moretz Emília P. Martins Barrie D. Robison 《Environmental Biology of Fishes》2007,80(1):91-101
Because early social experience can have a profound effect on later mate and social choices, the availability of options and
decisions made early in development can have major effects on adult behavior. Herein, we use strain differences among zebrafish,
Danio rerio, as an experimental tool to test the effects of social experience on behavior. By manipulating the strain composition of
groups in which the subject fish are housed at different ages, we tested (1) whether mixing with dissimilar individuals influenced
subsequent behavior, (2) whether prolonged mixing during the juvenile stage had a more pronounced effect than a shorter period
of mixing during adulthood and (3) whether mixing had a lasting effect after animals were resorted into groups of same strain
animals. We found that social experience had a profound impact on social behavior. Both Nadia and TM1 individuals engaged
in more frequent biting after having been in mixed strain groups compared to pure strain groups. This was true of groups mixed
as juveniles, as well as adults, indicating that this response was not dependent on exposure during a critical developmental
period. Also, TM1 fish (but not Nadia) having recently been housed in mixed-strain groups were more willing to leave the immediate
vicinity of a shoal than were TM1 fish raised in pure strain groups. This change was more pronounced in groups mixed as juveniles
than as adults. In addition, the observed changes persisted after mixed groups were separated into pure strain groups for
a month. Other behavioral measures including Activity Level, Predator Response and Stress Recovery were unaffected by previous
social experience. 相似文献
5.
Mikulášová Mária Košíková Božena Alexy Pavol Kačík František Urgelová Emília 《World journal of microbiology & biotechnology》2001,17(6):601-607
The ability of the lignin-degrading microorganism Phanerochaete chrysosporium to attack polyethylene and polypropylene was investigated using a series of polymer blends containing 10, 20 and 30% lignin obtained from the waste product of pulp and paper industry. In the cultivation medium, lignin peroxidase and Mn(II)peroxidase activities were detected. Degradation was verified by quantitative u.v. spectrophotometric analysis of the cultivation medium and by liberation of CO2 from the blends. Measurement of the tensile strength after 30-days cultivation showed that the mechanical properties of the polymer blends were decreased during the biodegradation process. The isolation of oligomer fractions by tetrahydrofuran (THF) extraction of biodegraded polymers and their characterization by gel permeation chromatography (GPC), u.v. and Fourier transmission infrared (FTIR) spectroscopy indicates that biotransformation of the lignin component during the cultivation process initiates partial biodegradation of the synthetic polymer matrix. 相似文献
6.
Minimal criteria for defining multipotent mesenchymal stromal cells. The International Society for Cellular Therapy position statement 总被引:40,自引:0,他引:40
Dominici M Le Blanc K Mueller I Slaper-Cortenbach I Marini F Krause D Deans R Keating A Prockop Dj Horwitz E 《Cytotherapy》2006,8(4):315-317
The considerable therapeutic potential of human multipotent mesenchymal stromal cells (MSC) has generated markedly increasing interest in a wide variety of biomedical disciplines. However, investigators report studies of MSC using different methods of isolation and expansion, and different approaches to characterizing the cells. Thus it is increasingly difficult to compare and contrast study outcomes, which hinders progress in the field. To begin to address this issue, the Mesenchymal and Tissue Stem Cell Committee of the International Society for Cellular Therapy proposes minimal criteria to define human MSC. First, MSC must be plastic-adherent when maintained in standard culture conditions. Second, MSC must express CD105, CD73 and CD90, and lack expression of CD45, CD34, CD14 or CD11b, CD79alpha or CD19 and HLA-DR surface molecules. Third, MSC must differentiate to osteoblasts, adipocytes and chondroblasts in vitro. While these criteria will probably require modification as new knowledge unfolds, we believe this minimal set of standard criteria will foster a more uniform characterization of MSC and facilitate the exchange of data among investigators. 相似文献
7.
8.
Soeth Marcelo Fávaro Luis Fernando Spach Henry Louis Daros Felippe Alexandre Woltrich Ana Emília Correia Alberto Teodorico 《Ichthyological Research》2019,66(1):140-154
Ichthyological Research - This is the first study to investigate the age, growth and reproductive biology of the Atlantic spadefish Chaetodipterus faber in southern Brazil. A total of 625... 相似文献
9.
Carotenoid-producing yeast species such as Rhodotorula glutinis and Sporobolomyces roseus efficiently accumulated selenium from the growth medium. It was observed that incorporation of selenium into yeast cells during the growth inhibited production of beta-carotenoid and other carotenoid precursors (torularhodin and torulene). The yeasts with high content of the carotenoid pigments and selenium may be used for the preparation of a new type of antioxidant formula that could be directly applied for various human and animal diets. We have demonstrated that such a formula can only be produced by separate processes of the cultivation of red yeasts and a subsequent sorption of selenium into the cells. 相似文献
10.
Effects of Passage Through Tamarin Guts on the Germination Potential of Dispersed Seeds 总被引:1,自引:0,他引:1
Knogge Christoph Herrera Emérita R. Tirado Heymann Eckhard W. 《International journal of primatology》2003,24(5):1121-1128
Passage through tamarin guts may have an effect on seed germination potential. To examine these effects, and the variation between 2 sympatric tamarin species, we studied Saguinus mystax and S. fuscicollis in northeastern Peruvian Amazonia. For most of 39 plant species, neither germination success nor latency was modified by gut passage. Neutral effects on seed germination potential suggest that tamarins may fulfill criteria for effective seed dispersal. 相似文献