Oligomeric products and formation mechanisms from acid-catalyzed reactions of methyl vinyl ketone on acidic sulfate particles

Methyl vinyl ketone (MVK) is a key first-generation product from atmospheric isoprene photo-oxidation, especially under high-NO_x conditions. In this work, acid-catalyzed reactions of gas-phase MVK with ammonium sulfate (AS), ammonium bisulfate (ABS), and sulfuric acid (SA) particles were investigated in a flow reaction system at relative humidity (RH) of 40 % and 80 %. Ultra-performance liquid chromatography with electrospray ionization time-of-flight mass spectrometry (UPLC/ESI-TOFMS) and gas chromatography-mass spectrometry (GC-MS) are utilized to identify particle-phase products for developing the reaction mechanisms. High-order oligomers such as dimers and tetramers were detected when ABS and SA particles were used, while no oligomeric products were found when AS particles were used. Particle-phase oligomeric products were formed via i) acid-catalyzed aldol reaction with or without dehydration and/or ii) acid-catalyzed hydration followed by oligomerization. Reactions on SA particles yield more abundant and higher-order oligomers up to hexamers than on ABS particles. Moreover, aldol reaction occurred only on SA particles, but hydration followed by oligomerization occurred in both ABS and SA particles. The high RH condition with the same type of acidic particles was found to favor hydration and facilitate the subsequent oligomerization, while the low RH condition with the same type of acidic particles was found to favor aldol reaction with dehydration (aldol condensation). Overall, the findings suggest acidic particles can facilitate the formation of high-order oligomers in the particle phase, with particle acidity and RH as key factors.     

边境城镇的产业演化及其机制研究

边境地区是我国的安全屏障和对外交流的门户,其产业演化深受地缘政治、国家和区域政策、当地发展条件等多元要素影响,嵌套于多尺度的社会经济发展框架中。在“一带一路”建设的背景下,边境地区的产业演化研究有着重要意义。本文将“一带一路”的重要节点边境城镇——云南省勐腊县作为案例区域,在进行实地调研和深入访谈的基础上,利用演化图谱、相关分析等方法,剖析了勐腊县的典型产业演化过程及多尺度要素作用下的产业结构演化机制。研究表明：勐腊县的橡胶、制糖和旅游三大典型产业均经历了萌芽、快速发展到成熟的过程;勐腊县作为边境县,产业发展大致可以分为起步、集聚和整合三个阶段;产业的演化受到了全球化进程、国家间关系、地缘政治博弈、国家开发政策、区域发展政策等多尺度因素的影响。随着“一带一路”中国—中南半岛经济走廊建设进一步提速,勐腊县获得了边境合作区、国家重点开发开放试验区等众多跨境合作发展新动能,迸发出新的活力。     

联合星载高光谱影像和堆栈集成学习回归算法的红树林冠层叶绿素含量遥感反演

红树林是世界上生产力最高、价值最高的湿地生态系统之一。冠层叶绿素含量CCC（Canopy Chlorophyll Content）作为红树林重要的生物物理参量,是估算其生产力和评价其健康状况的重要指标。本文利用珠海一号高光谱卫星（OHS）影像与Sentinel-2A多光谱数据计算传统植被指数与组合植被指数并构建了高维数据集,综合利用正态分布检验、最大相关系数法与变量重要性评价进行数据降维和变量优选;分别基于单一线性回归算法、机器学习回归算法和堆栈集成学习回归算法构建了红树林CCC遥感反演模型,探明北部湾红树林CCC的最佳遥感反演模型,验证OHS高光谱影像与Sentinel-2A数据反演红树林CCC的精度差异,评估SNAP-SL2P算法反演红树林CCC的适用性。研究结果表明：（1）通过数据降维和变量选择处理,从高维度OHS数据集选取了8个特征变量,其中RSI_（12,17）、DSI_（12,18）和NDSI_（6,12）组合植被指数对红树林CCC反演精度的贡献率较高;（2）联合OHS数据和最优堆栈GBRT集成学习回归模型（Score=0.999,RMSE=0.963 μg/cm²）的训练精度优于最优RF机器学习回归模型（RMSE降低了7.531 μg/cm²）,明显优于最优Lasso线性回归模型（RMSE降低了19.383 μg/cm²）;（3）在最优堆栈集成学习回归模型下,OHS数据反演红树林CCC的精度（R²=0.761,RMSE=16.738 μg/cm²）高于Sentinel-2A影像（R²=0.615,RMSE=20.701 μg/cm²）;（4）联合OHS和Sentinel-2A数据的最优堆栈集成学习回归模型反演红树林CCC的精度都明显优于SNAP-SL2P算法（R²=0.356,RMSE=49.419 μg/cm²）。研究结果论证了正态分布检验、最大相关系数法和基于XGBoost的特征选择方法有效降低了高维数据集的维度,并得到了最优特征变量;OHS数据的最优堆栈GBRT集成学习回归模型训练精度最高,是估算红树林CCC的最优反演模型;OHS和Sentinel-2A数据都能有效反演红树林CCC（R²均大于0.61）,而OHS数据的估算精度更高（R²大于0.75）;SNAP-SL2P算法不能有效反演红树林CCC（R²小于0.4）,且对红树林CCC数值存在系统性低估。     

贵州六盘水炭质泥岩工程特性研究

六盘水的炭质泥岩跟普通泥岩相比具有特殊的工程特性,通过对该地区炭质泥岩物理力学特性的详细研究探讨,室内进行落锥法测定液限和塑限、击实试验、抗剪强度及压缩试验.研究试验结果表明：①炭质泥岩的可塑性强,遇水易软化崩解,强度变低;②炭质泥岩的压实性能受含水率的影响明显,干密度在含水率12.5％～15％时变化很大;③炭质泥岩的粘聚力在含水率小于11％时,随着含水率的增加而迅速减小,在11％～15％时变化小;④炭质泥岩的压缩沉降量在加荷载后较短时间内发生,在加压后能够很快压缩密实,达到较稳定的状态.     

电子探针化学测年在攀枝花大田晶质铀矿中的应用及其意义

晶质铀矿和沥青铀矿是热液铀矿床的主要工业铀矿物,在研究热液铀矿床成因及成矿规律方面具有重要的意义。攀枝花大田地区是我国混合岩型热液铀矿分布区,已发现粗粒特富铀矿滚石(铀含量10%)及较富基岩矿石(铀含量为0.1%~2%),主要铀矿物为晶质铀矿,对两种晶质铀矿成分及形成时代的研究对该区混合岩型热液铀矿成矿规律研究具有重要的价值。本文通过对大田地区滚石中的晶质铀矿和基岩矿石中的晶质铀矿进行矿物学及电子探针分析,研究了晶质铀矿的成分及形成时代。结果表明:(1)大田地区滚石和基岩矿石中的晶质铀矿除铅之外化学成分较为相似,两类矿石晶质铀矿中UO_2含量为77.36%~84.04%,ThO_2含量为0.98%~5.59%,PbO含量为1.79%~8.8%,其中滚石晶质铀矿中的铅含量低于基岩晶质铀矿,钍含量高于基岩晶质铀矿;(2)电子探针化学定年结果表明,基岩矿石晶质铀矿的形成时代为774.9~785.5 Ma,滚石晶质铀矿的形成时代为783.7 Ma,与传统同位素测年结果(775~777.6 Ma)非常一致,一方面说明滚石晶质铀矿和基岩晶质铀矿为同一时代的产物,另一方面说明电子探针原位测年方法是可靠的;(3)在后期的热液蚀变中,晶质铀矿先后发生了硅化、碳酸盐化及赤铁矿化,蚀变发生的时间分别为730.6Ma、699.8 Ma和664.0 Ma。此结论对研究攀枝花大田地区热液铀矿成矿时代及成矿作用过程提供了依据。     

岛弧火山岩成因和地球化学特征

岛弧火山岩主要为俯冲带的俯冲板片脱水形成的富大离子亲石元素流体交代地幔楔,并使其发生部分熔融,产生岛弧岩浆作用而形成的,岩石组合通常为玄武岩—安山岩—英安岩—流纹岩及相应侵入岩组合。它以Al2O3、K2O高,低Ti O2,且K2ONa2O为特征,相对富集LILE,亏损HFSE,特别是Ti、Nb、Ta等。本文主要从岛弧岩浆作用的起因着手,分析流体和熔体对地幔楔的交代作用,以及岛弧岩浆作用过程,进而分析岛弧火山岩的地球化学特征。     

Tension and Drag Forces of Flexible Risers Undergoing Vortex-Induced Vibration

This paper presents the results of an experimental investigation on the variation in the tension and the distribution of drag force coefficients along flexible risers under vortex-induced vibration (VIV) in a uniform flow for Reynolds numbers (Re) up to 2.2×10⁵. The results show that the mean tension is proportional to the square of the incoming current speed, and the tension coefficient of a flexible riser undergoing VIV can be up to 12. The mean drag force is uniformly and symmetrically distributed along the axes of the risers undergoing VIV. The corresponding drag coefficient can vary between 1.6 and 2.4 but is not a constant value of 1.2, as it is for a fixed cylinder in the absence of VIV. These experimental results are used to develop a new empirical prediction model to estimate the drag force coefficient for flexible risers undergoing VIV for Reynolds number on the order of 10⁵, which accounts for the effects of the incoming current speed, the VIV dominant modal number and the frequency.     

Biomonitoring of trace metals using transplanted mussels, <Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis>, in coastal areas around Ulsan and Onsan Bays,Korea

Mediterranean (blue) mussels (Mytilus galloprovincialis) collected from a reference site were transplanted to 15 stations in coastal areas around Ulsan and Onsan Bays, an extensively metal polluted area in Korean coastal waters, to assess metal contamination in the coastal oceans of Korea. During the biomonitoring periods (June 30 to July 20, 2003; 21 days), transplanted mussels, seawater, and particulate materials were collected for analysis of 15 metals (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Se, Sn, and Zn). Transplanted mussels showed metal enrichment compared to initial concentrations and spatial gradients consistent with dissolved and/or particulate metal concentrations in seawaters. Based on Q mode factor analysis, stations were clustered into three groups. The first group, located on Onsan Bay, showed high Ag, Cd, Cu, Hg, Pb, Sb and Zn enrichment, presumably arising from non-ferrous metal refineries and chemical industries in this area. The second group was located near the mouth of the Oehwang River and was enriched in Co from petrochemical industries. The third group comprised a site intermediate between Group 1 and Group 2, an isolated station with independent metal sources located in Jangsaengpo harbor, where a number of ship repairing and building companies operate, and a less contaminated station near a small fishing village. Metal accumulation rates (%·day^-1) in mussels were estimated to be between 8% (Cr) and 281% (Pb), based on accumulated metal concentrations over 21 days. The active biomonitoring technique using M. galloprovincialis demonstrated here is a useful monitoring method because it reflects the present status of seawaters; furthermore, physiological factors can be standardized, and bioavailable and time-integrated metal concentrations can be obtained. Furthermore, this method can be applied even in coastal seawaters so heavily contaminated that living organisms would not normally survive.     

篮状菌DYM25胞外产物的初步鉴定及其生物学活性

本研究以西太平洋雅浦海沟分离得到的篮状菌(Talaromyces sp.)DYM25为实验菌株,通过水饱和正丁醇萃取菌株DYM25的胞外产物,利用生物碱沉淀显色法初步考察胞外产物的种类,进而研究了胞外产物的抗菌、抗氧化和抗肿瘤活性。结果表明,1 L菌株DYM25的发酵液通过水饱和正丁醇萃取旋蒸后可得到约2 g的产物;生物碱显色反应预示着胞外产物中生物碱盐类物质的存在;篮状菌DYM25胞外产物对枯萎病致病菌木贼镰刀菌(Fusarium equiseti)的生长具有显著的抑制作用,是篮状菌作为F.equiseti拮抗菌的首次报道。同时,此胞外产物还具有一定的抗氧化活性和抗肿瘤活性,其抗氧化能力随产物浓度的升高而增强,对人胰腺癌细胞PANC-1的抑制能力也呈现出一定的浓度依赖性。篮状菌DYM25多样的生物活性凸显了其良好的研究价值和应用前景。