Effect of open-path gas analyzer wetness on eddy covariance flux measurements: A proposed solution

Open-path gas analyzers are popular in eddy covariance flux measurements of trace gasses (i.e. CO₂). The quality of the data, however, may be influenced by several factors. Exposure in an outdoor environment invariably causes the instrument to become colder or warmer than the air temperature. Instruments with internal temperature regulation and/or from heat generated by active electrical components can also influence the sensor temperature. In addition, sensors can have condensation problems on their optical windows thus affecting the quality of the measurement. Unreasonable measurements have been widely discussed, especially in moist, high-latitude regions. As this is a very important research problem facing flux studies, we examined how wetness (dew and raindrops) on the surface of the focus lens of the popular LI-COR LI-7500 infrared gas analyzer may affect flux measurements from the open-path eddy-covariance system. Field experiments showed that additional sensor heating may inhibit dew formation yet greatly improve the quality of flux measurements. A detailed energy balance approach was used to model the gas analyzer window temperature under environmental conditions and dew effect through a pair of LI-COR LI-7500, with and without heat treatment, in a grassland ecosystem in the Netherlands. With the proposed model, existing datasets can be filtered for dew events. Data from three different flux measurement sites were then used to assess the magnitude of dew effects on longer time-scales; 2 years from the Netherlands and 3 weeks of data from an arid coastal desert. About 30% of the measurements were affected by dew in the grassland area versus 4% in the arid region during the dry season. Sensor heating suppresses dew formation but might lead to errors in trace gas fluxes evaluated over long periods, thus we analyzed how sensor heating or cooling affects trace gas flux measurements. Additions to a recent (2006) correction and application to a horizontally and vertically oriented LI-COR LI-7500 are presented as they deal with sensor heating problems in eddy-covariance systems. The sensor energy balance model, together with the proposed modified sensor heating corrections, were used to estimate sensor temperature effects on long-term scale CO₂ flux measurements and showed that additional heating does affect the turbulent trace gas CO₂ fluxes but is very minor, especially for a horizontally mounted LI-COR LI-7500 gas analyzer. Further efforts are urgently needed to improve the data quality and quality of flux measurements.     

Comparison of two dry chemistry analyzers and a wet chemistry analyzer using canine serum

Canine serum was used to compare seven chemistry analytes on two tabletop clinical dry chemistry analyzers, Boehringer's Reflotron and Kodak's Ektachem. Results were compared to those obtained on a wet chemistry reference analyzer, Roche Diagnostic's Cobas Mira. Analytes measured were urea nitrogen (BUN), creatinine, glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), cholesterol and bilirubin. Nine to 12 canine sera with values in the low, normal, and high range were evaluated. The correlations were acceptable for all comparisons with correlation coefficients greater than 0.98 for all analytes. Regression analysis resulted in significant differences for both tabletop analyzers when compared to the reference analyzer for cholesterol and bilirubin, and for glucose and AST on the Kodak Ektachem. Differences appeared to result from proportional systematic error occurring at high analyte concentrations.     

Validation of the Sysmex XT‐2000iV hematology system for dogs,cats, and horses. I. Erythrocytes,platelets, and total leukocyte counts

Background: The Sysmex XT‐2000iV is a laser‐based, flow cytometric hematology system that has been introduced for use in large and referral veterinary laboratories. Objective: The purpose of this study was to validate the Sysmex XT‐2000iV for counting erythrocytes, reticulocytes, platelets, and total leukocytes in blood from ill dogs, cats, and horses. Methods: Blood samples from diseased animals (133 dogs, 65 cats, and 73 horses) were analyzed with the Sysmex XT‐2000iV and the CELL‐DYN 3500. Manual reticulocyte counts were done on an additional 98 canine and 14 feline samples and manual platelet counts were done on an additional 73 feline and 55 canine samples, and compared with automated Sysmex results. Results: Hemoglobin concentration, RBC counts, and total WBC counts on the Sysmex were highly correlated with those from the CELL‐DYN (r≥0.98). Systematic differences occurred for MCV and HCT. MCHC was poorly correlated in all species (r=0.33–0.67). The Sysmex impedance platelet count in dogs was highly correlated with both the impedance count from the CELL‐DYN (r=0.99) and the optical platelet count from the Sysmex (r=0.98). The Sysmex optical platelet count included large platelets, such that in samples from cats, the results agreed better with manual platelet counts than with impedance platelet counts on the Sysmex. Canine reticulocyte counts on the Sysmex correlated well (r=0.90) with manual reticulocyte counts. Feline reticulocyte counts on the Sysmex correlated well with aggregate (r=0.86) but not punctate (r=0.50) reticulocyte counts. Conclusion: The Sysmex XT‐2000iV performed as well as the CELL‐DYN on blood samples from dogs, cats, and horses with a variety of hematologic abnormalities. In addition, the Sysmex detected large platelets and provided accurate reticulocyte counts.     

哀牢山4类植物群落叶面积指数比较

采用演替阶段的划分方法,把哀牢山人工灌木林、次生落叶阔叶林、次生常绿落叶阔叶混交林及原始常绿阔叶林4种群落划分为演替较早期、演替早期、演替中期和演替后期4个时期,利用植物冠层仪测定了4种群落的叶面积指数。结果表明:从演替较早期到晚期,物种多样性和树种密度逐渐增加,叶面积指数值也逐渐增大,演替较早期叶面积指数最小(2.27),演替晚期叶面积指数最大(5.60)。各个演替阶段的叶面积指数间差异极显著(P<0.01),各演替阶段内测定的叶面积指数也有较大的标准差(0.35~0.73),说明各群落之间甚至同一种群落内,林冠结构都有较大差异。演替晚期乔木层叶面积指数最大,早期最小;演替中期灌木层叶面积指数最大,早期最小;4个阶段草本层叶面积指数差异不大。     

次郎柿冠层受光特性分析

运用ACCUPAR LP-80冠层分析仪对果园两种密度下次郎柿冠层光学特性进行测定,结果表明,树冠不同高度和方位在一天内的光合有效辐射呈单峰曲线变化,且各个部位和方位的光合有效辐射在一天中的最大值和出现的时间差别很大,而同一密度下柿树的各个部位和方位光合有效辐射在一天4个时间段的显著变化情况也是不一致的。天顶角﹑叶态分布参数在同一地区基本没有变化,对有效辐射值基本没有影响,而果园密度﹑行向对有效辐射值影响比较大。     

AA3型连续流动分析仪与钒钼黄比色法测定玉米植株全磷含量之比较

选择69个玉米秸秆和籽粒样品,经浓H₂SO₄和H₂O₂消煮后,用连续流动分析仪与钒钼黄比色法分别测定消煮液中磷含量,对2种方法检测数据之间进行比较分析,探讨利用连续流动分析仪测定植株样品消煮液中磷含量的可行性。t检验表明:2种方法测定植株全磷含量相比无明显差异。测定结果之间呈显著线性相关系,回归直线方程为Y(连续流动分析仪-P)=0.927X(钒钼黄比色法-P)-0.002,相关系数r=0.985(n=69,P<0.01)。连续流动分析仪测定加标回收率在99.3%~103.8%之间,对4个样品消煮液中磷浓度分别重复测定10次,相对标准偏差小于1.5%。连续流动分析仪分析速度快,消耗试剂少,推荐用于大批量玉米植株样品H₂SO₄-H₂O₂消煮液中磷含量分析。     

米饭食味计评价华南籼稻食味品质

 利用STA1A米饭食味计和感官食味品尝对133份籼稻米样食味进行评价,建立了可见光和近红外光谱值与籼稻米饭食味综合评分的回归方程,发现可见光和近红外光谱值与籼稻米饭食味综合评分的相关性达到显著水平。利用STA1A可方便、准确、快速地测定籼稻的蒸煮食味品质。       

播期和地点对南粳46稻米品质及RVA谱的影响

[目的]研究不同播期、地点对南粳46稻米品质及RVA谱的影响。[方法]大田试验于江苏省5个试点进行,每个试点设置7个播期,成熟后测定 RVA谱各相关指标。[结果]随着播期的推迟,南粳46稻米加工品质呈先升后降的变化趋势,外观品质变优,蒸煮食用品质下降;随着地点的南移,南粳46稻米加工品质、外观品质和蒸煮食用品质总体均呈先降后升的变化趋势。不同性状对地点和播期的反应不同,糙米率、粒宽、粒长、长宽比、精米率和整精米率受影响较小,而垩白率和垩白度受影响较大,糊化温度、蛋白质含量、直链淀粉含量、胶稠度和食味值居两者之间。 RVA谱特征值分析表明,崩解值、消减值和起始糊化温度同时受播期和地域环境的影响。峰值黏度、热浆黏度、最终黏度和峰值黏度时间受地域环境的影响较大。随播期的推迟,峰值黏度、热浆黏度、最终黏度、消减值和起始糊化温度呈先降后升的变化趋势,崩解值先升后降,峰值粘度时间变化规律不明显。随纬度的降低,峰值黏度、热浆黏度、崩解值和最终黏度总体上均呈先降后升的变化趋势,消减值和峰值黏度时间降低,起始糊化温度升高。[结论]该研究为南粳46的“优质、高效”生产提供理论依据。     

Standardization of Automated Vario EL III CHNS Analyzer for Total Carbon and Nitrogen Determination in Plants

Carbon (C) and nitrogen (N) determination with traditional methods is more laborious and time-consuming than automated analyzers. Microprocessor-based technologies led to the development of automated analyzers and have reduced the time of analysis. However, these need to be standardized with respect to weight and mesh size of plant/organic material sample used. For standardization of Vario EL III carbon (C), hydrogen (H), nitrogen (N), and sulfur (S) analyzer for the particle size and amount of sample, laboratory studies were carried out for C and N determination by CHNS analyzer in comparison to the traditional methods for different categories of organics such as green manure (cowpea), crop residues (rice straw), animal residues (farmyard manure), and industrial by-product (press mud). Organic samples of <0.25-mm size resulted in greater amounts of C and N with both CHNS analyzer and traditional methods than with other size groups. The C and N contents were greater with a sample weight of 5 than with 10 mg.     

晋西地区不同树龄富士苹果树群体冠层结构特征研究

【目的】探讨苹果树群体在生长过程中冠层结构的变化特征及其影响。【方法】以山西省吉县东城乡3～20年生富士苹果树为试材,每种树龄群体选择12株样树,使用LAI-2000冠层分析仪,对其叶面积指数(LAI)、冠层开度(DIFN)、平均叶倾角(MTA)、消光系数(K)等冠层参数进行测算,同时测定干周粗、树高、冠幅、枝下高、冠高和郁闭度等果树形态指标,然后对不同树龄富士苹果树群体的冠层参数及其形态指标进行对比分析。【结果】随着树龄的增加,苹果树群体的DIFN不断减小,从0.89下降到0.09;LAI逐渐增加,从0.29增加到3.54;MTA的变化总体呈下降趋势,但是8和12年生的苹果树群体MTA又呈上升趋势,MTA与树冠的5个天顶角关系密切,当两者角度接近时,该天顶角方向上的太阳光线入射较多;K逐渐增加,从0.38增加到0.68。【结论】综合冠层结构参数来看,3～10年生苹果树群体内透光、通风状况良好,其中3～8年生苹果树群体DIFN在0.4以上,LAI小于1.5,MTA在30°以上,K小于0.4;10年生苹果树群体整体长势好,DIFN为0.28,LAI为2.17,MTA为26°,K为0.59,这种冠层结构有利于群体发展;12年以上苹果树群体DIFN在0.2以下,K增加到0.6以上,群体内部光照少,通风差;而20年生苹果树群体DIFN不足0.1,LAI高于3.5,MTA为8°,K接近0.7,此时群体长势差,果树群体外围郁闭,内部光秃。同时,当冠层天顶角与MTA角度相近时,该天顶角方向的冠层开度较大,可根据不同树龄MTA的特征,并结合当地太阳高度角的变化特征,来进行果树修剪,控制树冠张开的角度。