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931.
Previously, we had characterized several structurally interesting brominated phenols from the marine red alga Symphyocladia latiuscula collected from various sites. However, Phytochemical investigations on this species collected from the Weihai coastline of Shandong Province remains blank. Therefore, we characterized the chemical constituents of individuals of this species collected from the region. Eight bromophenols were isolated and identified. Using detailed spectroscopic techniques and comparisons with published data, these compounds were identified as 2,3-dibromo-4,5-dihydroxybenzyl methyl ether (1), 3,5-dibromo-4-hydroxybenzoic acid (2), 2,3,6-tribromo-4,5-dihydroxymethylbenzene (3), 2,3,6-tribromo-4,5-dihydroxybenzaldehyde (4), 2,3,6-tribromo-4,5-dihydroxybenzyl methyl ether (5), bis(2,3,6-tribromo-4,5-dihydroxyphenyl)methane (6), 1,2-bis(2,3,6-tribromo-4,5-dihydroxyphenyl)-ethane (7), and 1-(2,3,6-tribromo-4,5-dihydroxybenzyl)-pyrrolidin-2-one (8). Among these compounds, 1 and 2 were isolated for the first time from S. latiuscula. Each compound was evaluated on the ability to inhibit protein tyrosine phosphatase 1B (PTP1B), which is a potential therapeutic target in the treatment of type 2 diabetes. Bromophenols 5, 6, and 7 showed strong activities with IC50 values of 3.9, 4.3, and 3.5 μmol/L, respectively. This study provides further evidence that bromophenols are predominant among the chemical constituents of Symphyocladia, and that some of these compounds may be candidates for the development of anti-diabetes drugs. 相似文献
932.
Mark A ROSS 《中国地理科学(英文版)》2011,21(2):249-256
Air entrapment is an important consideration in environments with shallow water tables and sandy soil, like the condition of highly conductive sandy soils and flat topography in Florida, USA. It causes water table rises in soils, which are significantly faster and higher than those in soils without air entrapment. Two numerical models, Integrated Hydrologic Model (IHM) and HYDRUS-1D (a single-phase, one-dimensional Richards′ equation model) were tested at an area of west central Florida to help further understanding the shallow water table behavior during a long term air entrapment. This investigation employed field data with two modeling approaches to quantify the variation of air pressurization values. It was found that the air pressurization effect was responsible at time up to 40 cm of water table rise being recorded by the observation well for these two models. The values of air pressurization calculated from IHM and HYDRUS-1D match the previously published values. Results also indicated that the two numerical models did not consider air entrapment effect (as the predictive parameters remain uncertain) and thus results of depth to water table from these models did not compare to the observations for these selected periods. Incorporating air entrapment in prediction models is critical to reproduce shallow water table observations. 相似文献
933.
3-bromo-4,5-bis(2,3-dibromo-4,5-dihydroxybenzyl)-1,2-benzenediol (1) is a natural bromophenol isolated from the red algae Rhodomela confervoides that exhibits significant inhibition against protein tyrosine phosphatase 1B (PTP1B). Based on its activity, we synthesized two new synthetic bromophenols and their methoxy derivatives from vanillin using the structure of natural bromophenol 1 as a scaffold. The structures of these bromophenols were elucidated from 1H NMR, 13C NMR, and high resolution electron ionization mass spectrometry as 2,3-dibromo-1-(2p-bromo-6p-(3q,4q-dimethoxybenzyl)- 3p,4p-dimethoxybenzyl)-4,5-dimethoxybenzene(2),2,3-dibromo-1-(2p-bromo-6p-(2q-bromo-4q,5q-dimethoxy-benzyl)-3p,4p-dimethoxybenzyl)-4,5-dimethoxybenzene(3),3,4-dibromo-5-(2p-bromo-6p-(2q-bromo-4q,5q-dihydroxybenzyl)-3p,4p-dihydroxybenzyl)pyrocatechol(4)and 3,4-dibromo-5-(2p-bromo-6p-(3q,4q-dihydroxybenzyl)-3p,4p-dihydroxybenzyl)pyrocatechol (5).PTP1B inhibition activities of these compounds were evaluated using a colorimetric assay,and compounds 3 and 4 demonstrated interesting activity against PTP1B. 相似文献
934.
本文利用MODIS数据反演大气透射率,利用HJ-1B/CCD进行分类,并反演地表比辐射率.在此基础上,借鉴单窗算法,利用HJ-1B/IRS数据反演得到地表温度,并利用MODIS温度产品对反演结果进行了初步验证.最后利用热场变异指数进一步分析重庆的热岛空间分布特征,并对NDVI与NDBI对热岛效应的影响进行了分析.其结论... 相似文献
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939.
福建沿海地区第四系较为发育,是研究晚更新世以来相对海平面变化的理想区域。本文以福建宁德NDQK5岩芯中产出的高分辨率介形类化石为研究对象,结合加速器质谱法(accelerator mass spectrometry, AMS)14C和光释光测年技术建立岩芯年代框架,重建了中全新世期间福建沿海地区的相对海平面变化。结果显示,NDQK5岩芯中的介形类化石记录主要分布于4~17. 1 m段,对应年代约为8. 2~6. 9 ka BP。岩芯内共计识别出海相介形类23属26种,根据优势种以及特征种的相对丰度变化特征可将岩芯内的介形类动物群划分为3个组合:① 介形类组合A以Bicornucythere bisanensis和Sinocytheridea impressa为主,代表潮下带环境;② 介形类组合B以Sinocytheridea impressa和Neomonoceratina delicata为优势种,指示近岸内陆架的沉积环境;③ 介形类组合C以Sinocytheridea impressa和Loxoconcha ocellifera为主,代表潮间带的沉积环境。基于介形类组合的分布特征,本文推断福建沿海地区海平面约在8. 2~7. 4 ka BP期间持续上升,并在约7. 9~7. 4 ka BP区间达到最高;7. 4~7. 0 ka BP期间海平面下降,随后再次上升。因此,介形类化石记录指示福建沿海地区在全新世高海平面背景下依然存在相对海平面的次一级波动。同时,结合已有福建沿海地区海平面变化驱动机制的研究结果,本研究推断8. 2~7 ka BP期间福建沿海地区的海平面变化可能主要受控于冰盖融水;7 ka BP后该地区的海平面波动可能受控于“冰川- 水均衡调整”作用。 相似文献
940.
湘东锡田A型花岗岩的年代学、Hf同位素、地球化学特征及其地质意义 总被引:5,自引:1,他引:4
对湘东锡田岩体进行的LA-ICP-MS定年结果表明,2个第一期中(细)粒斑状黑云母二长花岗岩样品的年龄分别为(220.9±0.6) Ma及(220.7±0.7)Ma;第二期中细粒二云母二长花岗岩的年龄为(154.4±0.7)Ma.两期花岗岩均为高钾、富碱、弱过铝质岩石.稀土元素总量较高,富集U、Th,亏损Ti、P等高场强元素和Ba、Sr等大离子亲石元素,具高的104 Ga/Al,显示A型花岗岩特征.印支期花岗岩略富集轻稀土元素,Eu异常较弱;燕山期花岗岩轻、重稀土元素分异不明显,Eu异常显著.Hf同位素研究显示,两期次花岗岩均具有较低的εHf(t)(-4.91~-11.04),亏损地幔二阶段模式年龄集中在1.6~1.8 Ga,与华夏地块古老的变质基底年龄一致.因此,锡田岩体是华夏地块古元古代地壳物质在伸展的构造背景下部分熔融的产物.锡田A型花岗岩复式岩体的确定,对于研究湖南东部在中生代印支、燕山两期构造事件中所处的构造背景具有重要意义,同时也为华南地区存在印支期A型花岗岩钨锡成矿作用增加了证据. 相似文献