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Richard L. Reynolds Joseph G. Rosenbaum Josh Rapp Michael W. Kerwin J. Platt Bradbury Steven Colman David Adam 《Journal of Paleolimnology》2004,31(2):217-233
Petrological and textural properties of lacustrine sediments from Upper Klamath Lake, Oregon, reflect changing input volumes of glacial flour and thus reveal a detailed glacial history for the southern Cascade Range between about 37 and 15 ka. Magnetic properties vary as a result of mixing different amounts of the highly magnetic, glacially generated detritus with less magnetic, more weathered detritus derived from unglaciated parts of the large catchment. Evidence that the magnetic properties record glacial flour input is based mainly on the strong correlation between bulk sediment particle size and parameters that measure the magnetite content and magnetic mineral freshness. High magnetization corresponds to relatively fine particle size and lower magnetization to coarser particle size. This relation is not found in the Buck Lake core in a nearby, unglaciated catchment. Angular silt-sized volcanic rock fragments containing unaltered magnetite dominate the magnetic fraction in the late Pleistocene sediments but are absent in younger, low magnetization sediments. The finer grained, highly magnetic sediments contain high proportions of planktic diatoms indicative of cold, oligotrophic limnic conditions. Sediment with lower magnetite content contains populations of diatoms indicative of warmer, eutrophic limnic conditions. During the latter part of oxygen isotope stage 3 (about 37–25 ka), the magnetic properties record millennial-scale variations in glacial-flour content. The input of glacial flour was uniformly high during the Last Glacial Maximum, between about 21 and 16 ka. At about 16 ka, magnetite input, both absolute and relative to hematite, decreased abruptly, reflecting a rapid decline in glacially derived detritus. The decrease in magnetite transport into the lake preceded declines in pollen from both grass and sagebrush. A more gradual decrease in heavy mineral content over this interval records sediment starvation with the growth of marshes at the margins of the lake and dilution of detrital material by biogenic silica and other organic matter. 相似文献
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阴离子交换色谱-电感耦合等离子体质谱联用技术用于面粉中溴形态分析 总被引：1，自引：0，他引：1
建立的阴离子交换色谱-电感耦合等离子体质谱联用技术用于测量面粉中的痕量 BrO3-及Br-。使用DIONEX CarBoPac PA-100(4 mm×250 mm,i．d．)色谱柱,在流速1 mL／min 及5 mmol／L NH4NO3淋洗液下分离BrO3-和Br-。该方法在100μL进样量下BrO3-的检出限为 0．0027 μmoL／L(0．22μg／L),Br-为0．0067 μmoL／L(0．54μg／L)。对市场上部分面粉类样品的分析结果表明,所选面粉只有一种检出有BrO3-,其他样品中的BrO3-均低于检出限。方法的回收率可达到98％-109％。 相似文献
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样品用硝酸-高氯酸混合酸消解，考察了氢化物发生-原子荧光光谱法测定面粉中微量砷的实验条件，包括混合酸和还原剂硼氢化钾的用量。方法测定砷的线性范围为0．0—30．0μg／L，仪器的检出限为0．26μg／L，加标回收率为94．0％-104．0％，方法的精密度（RSD，n=11）为1．16％。方法操作简便、快速、灵敏度高。 相似文献
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【目的】研究添加芒果粉对真空油炸面包虾裹浆特性及其品质的影响。【方法】以小麦粉和大豆分离蛋白的裹浆作为对照,研究芒果粉替代部分小麦粉和大豆分离蛋白的裹浆流变学特性;以裹涂率、油脂含量、水分含量、色泽及质构特性为考察指标,研究芒果粉替代部分小麦粉和大豆分离蛋白的裹浆对真空油炸面包虾品质的影响;以最佳芒果粉添加量的真空油炸面包虾为研究对象,测定外裹层黄酮物质含量,并采用羟自由基和DPPH自由基体系对产品外裹层黄酮物质的抗氧化性进行分析。【结果】所有配方的裹浆均表现为触变性,呈现剪切稀化特性,具有假塑性流体特征,并符合幂率流体,芒果粉可显著提升裹浆的黏度;芒果粉可显著增大面包虾裹涂率,改善产品质构和色泽特性,降低产品油脂含量并提升其水分含量(P <0.05)。当芒果粉添加量从10%增加到30%时,面包虾产品油脂质量分数从24.84%降低到20.58%,产品的脆性和色泽中的亮度值(L*)、黄度值(b*)均得到了显著提升(P <0.05)。当小麦粉质量分数66%、大豆分离蛋白质量分数4%、芒果粉质量分数30%时,真空油炸面包虾产品的各项品质最佳;真空油炸面包虾产品外裹层黄酮物质质量分数为(46.75±2.87)mg/100g,其对羟自由基和DPPH自由基的清除效果方面都均强于维生素C。【结论】芒果粉可提升裹浆黏度,改善真空油炸面包虾产品品质,其外裹层较强的抗氧化性对于真空油炸裹涂制品延长货架期具有一定积极作用。 相似文献
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Tidal observations on the West Coast,South Island,New Zealand 总被引：1，自引：1，他引：0
R. A. Heath 《新西兰海洋与淡水研究杂志》2013,47(2):251-261
Harmonic tidal constants, calculated from sea surface elevation observations at Jackson Bay on the West Coast of the South Island, are consistent with available semi‐diurnal and diurnal tidal phase distributions. Current observations taken over a 111 day period at mid‐depth in 1505 m of water on the southern flank of the Challenger Plateau and over a 240 day period in 1430 m of water on the South Island western coast continental slope, are subject to tidal analysis. At both sites there is a component of energy flux directed across the isobaths and only at the northern site for the M2 tide is the phase consistent with a dominant progressive barotropic tide. The successive 30 day harmonic constants at the southern continental slope site exhibit a trend in the M2 tidal ellipse speed and ellipticity suggesting the presence of a regular internal tide. Superposition of ‘internal tidal’ and barotropic tidal flows, as prescribed from progressive‐ and standing‐wave elevations, to fit the observations indicates that the ‘internal tide’ is probably associated with the first baroclinic mode. At the current‐meter depths the speeds of the ‘internal tide’ for the M2 tide are about the same as the barotropic speeds, whereas, the S2 ‘internal tide’ speeds are larger than those of the barotropic tide. The consistency of the trend in ellipse parameters lends support to the theoretical progressive trapped barotropic tidal flows being a good approximation to the actual barotropic tide. Some support for the hypothesis that the S2 tide on the West Coast of New Zealand has a substantial standing wave contribution is given by the northern observations, where the ratio of the S2: M2 internal tidal ellipse current amplitudes are substantially larger than the ratio of the elevations, the internal tide being generated by across‐isobath flows. 相似文献
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正20140958 Mei Huicheng(No.915GeologicalBrigade,Jiangxi Bureau of Geology and Mineral Resources,Nanchang 330002,China);Li Zhongshe Geological Features and Causes of the Huihuang Geotherm in Xiushui,Jiangxi Province(Journal of Geological Hazards and 相似文献
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During the late Wisconsin, glacial flour from alpine glaciers along the east side of the Cascade Range in southern Oregon was deposited in Upper Klamath Lake. Quantitative interpretation of magnetic properties and grain-size data of cored sediments from Caledonia Marsh on the west side of the lake provides a continuous record of the flux of glacial flour spanning the last 37 000 calendar years. For modeling purposes, the lake sediments from the 13-m core were divided into three sedimentary components defined from magnetic, geochemical, petrographic, and grain-size data. The components are (1) strongly magnetic, glacial flour made up of extremely fine-grained, fresh volcanic rock particles, (2) less magnetic lithic material made up of coarser, weathered volcanic detritus, and (3) non-magnetic biogenic material (largely biogenic silica). Quantitative interpretation is possible because there has been no significant postdepositional destruction or formation of magnetic minerals, nor alteration affecting grain-size distributions. Major steps involved in the interpretation include: (1) computation of biogenic and lithic components; (2) determination of magnetic properties and grain-size distributions of the non-glacial and glacial flour end-members; (3) computation of the contents of weathered and glacial flour components for each sample; (4) development of an age model based on the mass accumulation of the non-glacial lithic component; and (5) use of the age model and glacial flour contents to compute the flux of glacial flour. Comparison of the glacial flour record from Upper Klamath Lake to mapped glacial features suggests a nearly linear relation between flux of glacial flour and the extent of nearby glaciers. At 22 ka, following an extended period during which glaciers of limited size waxed and waned, late Wisconsin (Waban) glaciers began to grow, reaching their maximum extent at 19 ka. Glaciers remained near their maximum extent for 1000 years. During this period, lake sediments were made up of 80% glacial flour. The content of glacial flour decreased as the glaciers receded, and reached undetectable levels by 14 ka. 相似文献
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采场底板突水相似材料模拟研究 总被引：15，自引：0，他引：15
利用相似材料模拟试验，模拟了采场底板突水机理。实验表明，在无断层构造条件下，底板在承压水作用下呈Ｏ－Ｘ型破坏，并且在Ｏ与Ｘ的交点处最容易产生突水通道；在有断层构造条件下，断层突水的实质是在承压水作用下断层两盘的关键层向上产生相对移差。当断层越易产生最大位移差时，越容易突水；在突水的同时还伴随着断层带充填的冲刷。 相似文献
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电感耦合等离子体质谱法测定生物样品中超痕量稀土时氧化物干扰的研究 总被引：21，自引：10，他引：11
试验了１００～７００ｕｇ／ＬＢａ的氧化物对Ｅｕ产生的干扰,干扰程度与Ｂａ量呈线性,其相关系数ｒ在０．９９８６～０．９９９５。用模拟样品溶液对不同含量的Ｂa对Ｅu的干扰采取了简单的数学方法校正,校正后的结果在误差允许范围之内。．对小麦和人发标准物质中Ｂa氧化物对Ｅu的干扰及校正效果进行了比较。结果表明,在所使用的仪器条件下,这两个标准物质中的Ｂa对Ｅu的干扰必须校正。研究了ｕｇ／Ｌ水平的轻稀土氧化物对重稀 相似文献
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在 1991年观察到魔芋粉和κ-卡拉胶有很强的协合作用 ,前者能显著增强后者的凝胶强度和弹性 ,并减少泌水性。在 1994年研究确定了其最强协合作用时的配比为 m卡拉胶∶m魔芋粉 =3∶ 2 ,这一性质在食品工业上有很好的实用价值。 相似文献
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