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131.
Angelika Otto Bernd R. T. Simoneit Volker Wilde Lutz Kunzmann Wilhelm Püttmann 《Review of Palaeobotany and Palynology》2002,120(3-4):203-215
The terpenoid composition of three fossil resins from macrofossils of Cretaceous and Tertiary conifers has been analyzed by gas chromatography–mass spectrometry (GC–MS). The mono-, sesqui- and diterpenoids which have been identified in the resin extracts are derived from precursors produced by the respective source plants and may be used as chemosystematic markers when compared with terpenoids in extant conifers. Sesquiterpenoids (cedrene, cuparene, cadinanes) and phenolic diterpenoids (ferruginol and derivatives) are the major components in Cupressospermum saxonicum Mai (Miocene). The terpenoid characteristics strongly support a relationship to the Cupressaceae s. str. The resin of Doliostrobus taxiformis (Sternberg) Kva
ek (Eocene) consists of abietane and pimarane type resin acids accompanied by minor amounts of phenolic diterpenoids (ferruginol, hinokiol). According to morphological and anatomical characteristics, D. taxiformis was previously compared to both, extant Araucariaceae and Cupressaceae s.l., but the terpenoid pattern of the resin now supports a relationship to the Cupressaceae s.l. rather than to Araucariaceae. Degraded diterpenoids of the abietane type are the major compounds in the extract of Tritaenia linkii (Roemer) Mägdefrau et Rudolf (Lower Cretaceous) indicating considerable oxidative alteration of the resin. Since the terpenoids in the resin of T. linkii are highly degraded or belong to the common abietane class, the leaves cannot be assigned or compared to any modern family based on their terpenoid composition. The presence of ferruginol probably excludes pinaceous affinities. Terpenoids proved to be valuable chemosystematic markers for fossil conifers once they are adequately preserved. The analysis of resin extracts by GC–MS is a suitable tool for the investigation of soluble compounds in fossil plants. 相似文献
132.
Twenty-nine flavonoid aglycones have been identified from two populations each of Heterotheca grandiflora and H. psammophila. Considerable qualitative variation was found between populations of the same species. Overall, H. grandiflora is more complex in its flavonoid profile, accumulating a total of 24 compounds based on eight skeletal types, compared with 13 compounds based on four skeletal types in H. psammophila. 相似文献
133.
Genotypic response to sodium chloride salinity of four major olive cultivars (Olea europea L.) 总被引:8,自引:0,他引:8
Anin situ resin bag technique was used to measure the relative availabilities of N and P along a chronosequence of soils in southern
New Mexico, and was compared to two more common indices of nutrient availability. Accumulations of N and P during 10-week
intervals over an 18 month period were separable into wet season (September–January) and dry season (February–August) groups,
with wet season values significantly greater than dry season values. Only accumulations during the wet season showed significant
differences among sites, thus stressing the role of field water regime in interpreting resin accumulation results. Total mineral
N (NO3+NH4) sorbed by resins was significantly correlated to laboratory N mineralization rates. Although accumulation patterns of N
and P were similar to patterns of %N and %P in shrub species growing along the chronosequence, these similarities were not
statistically significant. A laboratory experiment demonstrated that bicarbonate-form anion resins are preferable to hydroxyl-form
resins, as long as standards are made from solutions extracted by resins to account for variable ion recovery efficiencies. 相似文献
134.
In situ evaluation of surface roughness and micromorphology of temporary soft denture liner materials at different time intervals
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Objective
To perform an in situ evaluation of surface roughness and micromorphology of two soft liner materials for dentures at different time intervals.Background
The surface roughness of materials may influence the adhesion of micro‐organisms and inflammation of the mucosal tissues. The in situ evaluation of surface roughness and the micromorphology of soft liner materials over the course of time may present results different from those of in vitro studies, considering the constant presence of saliva and food, the changes in temperature and the pH level in the oral cavity.Materials and methods
Forty‐eight rectangular specimens of each of the two soft liner materials were fabricated: a silicone‐based material (Mucopren Soft) and an acrylic resin‐based material (Trusoft). The specimens were placed in the dentures of 12 participants (n = 12), and the materials were evaluated for surface roughness and micromorphology at different time intervals: 0, 7, 30 and 60 days. Roughness (Ra) was evaluated by means of a roughness tester. Surface micromorphology was evaluated by scanning electron microscopy.Results
Analysis of variance for randomised block design and Tukey's test showed that surface roughness values were lower in the groups using the silicone‐based material at all the time intervals (P < .0001). The average surface roughness was higher at time interval 0 than at the other intervals, for both materials (P < .0001). The surface micromorphology showed that the silicone material presented a more regular and smoother surface than the acrylic resin‐based material.Conclusion
The surface roughness of acrylic resin‐based and silicone‐based denture soft liner materials decreased after 7 days of evaluation, leading to a smoother surface over time. The silicone‐based material showed lower roughness values and a smoother surface than the acrylic resin‐based material, thereby making it preferred when selecting more appropriate material, due its tendency to promote less biofilm build‐up. 相似文献135.
云南血竭的化学成分及抗真菌活性 总被引:53,自引:0,他引:53
云南血竭为剑叶龙血树(Dracaena cochinchinensis(Lour.)S.c.Chen)树脂,从中分离到5个芳香族化合物:对羟基苯甲酸乙酰(1),7,4^′-二羟基黄烷(2),7-羟基-4^′-甲氧基黄烷(3),7,4^′-二羟基黄酮(4)和loureirin A(5)以及1个甾体皂甙(6),并对其中3个酚性成分进行了抗真菌活性检测。另外,用薄层层析法对云南血竭、广西血竭、海南血竭及 相似文献
136.
137.
固体碱催化合成假性紫罗兰酮 总被引:3,自引:0,他引:3
系统地研究了各种固体碱催化剂催化柠檬醛与丙酮缩合制备假性紫罗兰酮的反应活性及选择性,用氢氧化钡或大孔强碱性阴离子交换树脂催化,产品收率高达95%。 相似文献
138.
Dimitrios Gatos Stella Patrianakou Olga Hatzi Kleomenis Barlos 《Letters in Peptide Science》1997,4(3):177-184
Tyr0-Atriopeptin II was synthesized on a 2-chlorotrityl resin by both the stepwise and the convergent approach. For both methods an Fmoc/tBu(Trt)-based protection scheme was used. The convergent methodology utilizes the sequential condensation of four protected peptide fragments. These were chosen so that after every condensation reaction, the amino-terminal region of the newly formed resin-bound peptide did not contain a -turn. This designed convergent synthesis gave the target peptide in much higher yield and purity than the conventional step-by-step synthesis. 相似文献
139.
Labdane diterpene acids were found to be the major resin acid components in Pinus nigra needles of various seed sources. The major constituents have been identified as 4-epiimbricataloic acid, manoyl oxide 19-oic acid, 4-epicommunic acid, and 15-monomethyl pinifolate. A GC method was developed to analytically differentiate pinifolic acid from its monomethyl ester in an admixture of both compounds. A minor resin acid was identified as 18-acetoxy-8(17)-labden-15-oic acid. 10-Nonacosanol and isoabienol were identified as major constituents of the needle and cortex extractives, respectively. 相似文献
140.
Structural and functional characteristics of virgin and fouled Protein A MabSelect resin cycled in a monoclonal antibody purification process
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