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Sulfotransferase (ST) is the first enzyme discovered in association with paralytic shellfish poisoning (PSP) toxin biosynthesis in toxic dinoflagellates. This study investigates the ST activity in crude enzyme extraction of a toxic dinoflagellate species, Alexandrium tamarense CI01. The results show that crude enzyme can transfer a sulfate group from 3’-phosphoadenosine 5’-phosphosulfate (PAPS) to N-21 in the carbamoyl group of gonyautoxin 2/3 (GTX2/3) to produce C1/C2, but is inactive toward STX to produce GTX5. The crude enzyme is optimally active at pH 6.0 and 15°C. The activity is enhanced by Co2 , Mg2 , Mn2 and Ca2 individually, but is inhibited by Cu2 . Moreover, the activity shows no difference when various sulfur compounds are used as sulfate donors. These results demonstrate that the ST specific to GTX2/3 is present in the cells of A. tamarense CI01 and is involved in PSP toxin biosynthesis. In addition, the ST from different dinoflagellates is species-specific, which explains well the various biosynthesis pathways of the PSP toxins in toxic dinoflagellates. 相似文献
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太阳辐射能是海冰融化的最主要能源,基于在2008年8月21~27日北极加拿大海盆中部为期8天的冰站考察中海冰光学观测数据,研究了北冰洋中央密集冰区海冰吸收的太阳辐射能。通过现场直接观测,确定了海冰透射率、反照率、吸收率及其随冰厚的变化,得出海冰对太阳短波辐射的吸收率大约为到达冰面太阳辐射的16%,大部分被冰雪表面反射。为期3天的对太阳辐射的观测表明,虽然到达北冰洋中央密集冰区的太阳辐射能并不少,但由于云和雾覆盖的时间所占的比例很大,有将近57%被大气削弱,其余的又有77%左右被冰雪表面反射回太空,海冰吸收的热量只有10.2 W/m2,相当于每天融化2.6 mm的冰,1 m厚海冰全部融化需要380天,不足以为海冰融化提供足够的热量。因此北冰洋中央密集冰区终年被海冰覆盖,即使在北冰洋海冰面积骤减的现状下,那里的海冰密集度仍然接近100%。然而,文章的结果指出：大气中云和雾大幅度减少、积雪层融化、海冰厚度减小、融池的比例增加等因素都会大幅度增加海冰吸收的热量,未来这些过程的发生有可能导致北冰洋密集冰区的海冰快速融化。 相似文献
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北冰洋中央密集冰区海冰对太阳短波辐射能吸收的观测研究 总被引：8，自引：2，他引：6
太阳辐射能是海冰融化的最主要能源,基于在2008年8月21～27日北极加拿大海盆中部为期8天的冰站考察中海冰光学观测数据,研究了北冰洋中央密集冰区海冰吸收的太阳辐射能.通过现场直接观测,确定了海冰透射率、反照率、吸收率及其随冰厚的变化,得出海冰对太阳短波辐射的吸收率大约为到达冰面太阳辐射的16%,大部分被冰雪表面反射.为期3天的对太阳辐射的观测表明,虽然到达北冰洋中央密集冰区的太阳辐射能并不少,但由于云和雾覆盖的时间所占的比例很大,有将近57%被大气削弱,其余的又有77%左右被冰雪表面反射回太空,海冰吸收的热量只有10.2W/m2,相当于每天融化2.6mm的冰,1m厚海冰全部融化需要380天,不足以为海冰融化提供足够的热量.因此北冰洋中央密集冰区终年被海冰覆盖,即使在北冰洋海冰面积骤减的现状下,那里的海冰密集度仍然接近100%.然而,文章的结果指出:大气中云和雾大幅度减少、积雪层融化、海冰厚度减小、融池的比例增加等因素都会大幅度增加海冰吸收的热量,未来这些过程的发生有可能导致北冰洋密集冰区的海冰快速融化. 相似文献
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研究发现,AMSR-E的垂直极化的18.7 GHz(V18.7)和36.5 GHz(V36.5)的亮温比值在一年冰覆盖区域主要是相应频段的海冰微波发射率之比,而在多年冰覆盖区域受海冰微波发射率和海冰温度共同影响,并且海冰年龄越大亮温比值也越大。应用强度比参数可以比较好地确定冬季一年冰与多年冰之间的阈值,其中,在该阈值处,强度比梯度达到最大。该阈值呈现明显的季节性变化规律,在冬季阈值比较稳定,而在夏季受海水的影响变化范围比较大。应用强度比方法确定的多年冰范围,与NASA Team2(NT2)方法相比在大西洋扇区差异非常小;而在太平洋扇区出现比较大的差异。对比发现强度比法确定的多年冰范围一般大于NT2法。 相似文献
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<正>浅层地温能是一种清洁、价廉、丰富且可再生的新型环保能源,也是一种特殊的矿产资源,利用前景广阔。开发利用浅层地温能对保定市构建资源节约型和环境友好型社会、保障能源安全、改善现有能源结构、促进节能减排战略目标的实现具有非常重要的现实意义。 相似文献
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应用微波辐射亮温确定北极海冰边缘的算法 总被引：1，自引：0，他引：1
张树刚 《中国海洋大学学报(自然科学版)》2012,(11):1-7
海冰边缘区(MIZ)的边缘位置是微波遥感图像的1个基本特征,本文利用AMSR-E微波辐射亮温的强度比,提出1个确定MIZ边缘位置的方法。强度比最初用来确定数字影像中海冰和海水的阈值。研究发现,强度比也可以反应海冰与海水的微波辐射的差异。在无冰水域,垂直极化的18.7(V18.7)和36.5(V36.5)GHz的高级微波扫描辐射计(AM-SR-E)的亮温之比主要在0.86～0.89之间变化,此时它们在散点图中聚集成1条经过原点的直线;而在MIZ,它们的比值发生了显著改变。强度比比较好的体现了V18.7和V36.5的亮温比值在MIZ边缘处的变化特征:强度比快速增大,并且它的梯度出现极大值。全年中MIZ边缘处的亮温比值在0.89～0.90之间变化,此时对应的海冰密集度为0.08。 相似文献
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The dual-polarized ratio algorithm(DPR)for the retrieval of Arctic sea ice concentration from Advanced Microwave Scanning Radiometer-EOS(AMSR-E)data was improved using a contrast ratio(CR)parameter.In contrast to three other algorithms(Artist Sea Ice algorithm,ASI;NASA-Team 2 algorithm,NT2;and AMSR-E Bootstrap algorithm,ABA),this algorithm does not use a series of tie-points or a priori values of brightness temperature of sea-ice constituents,such as open water and 100% sea ice.Instead,it is based on a ratio(a)of horizontally and vertically polarized sea ice emissivity at 36.5 GHz,which can be automatically determined by the CR.aexhibited a clear seasonal cycle:changing slowly during winter,rapidly at other times,and reaching a minimum during summer.The DPR was improved using a seasonala.The systematic diff erences in the Arctic sea ice area over the complete AMSR-E period(2002–2011)were-0.8% ±2.0% between the improved DPR and ASI;-1.3%±1.7% between the improved DPR and ABA;and-0.7% ±1.9% between the improved DPR and NT2.The improved DPR and ASI(or ABA)had small seasonal diff erences.The seasonal diff erences between the improved DPR and NT2 decreased,except in summer.The improved DPR identified extremely low ice concentration regions in the Pacific sector of the central Arctic(north of 83°N)around August 12,2010,which was confirmed by the Chinese National Arctic Research Expedition.A series of high-resolution MODIS images(250 m×250 m)of the Beaufort Sea during summer were used to assess the four algorithms.According to mean bias and standard deviations,the improved DPR algorithm performed equally well with the other three sea ice concentration algorithms.The improved DPR can provide reasonable sea ice concentration data,especially during summer. 相似文献