种子贮藏特性研究的实验影响因素

简述了确定种子贮藏类型和适宜贮藏环境条件的基本实验设计思路。确定种子贮藏特性的实验研究通常采用两步程序法:首先测定种子的脱水耐性,然后测定种子在不同环境中贮存后的生活力变化。种子采集、运输、加工、脱水、含水量测定、生活力测定的方法都会影响实验结果的准确性。     

An improved methodology for the quantification of uronic acid units in xylans and other polysaccharides

Uronic acids can be quantified either by a colorimetric determination after treatment with concentrated sulfuric acid and carbazole or by gas chromatography after methanolysis and subsequent acetylation. Both methods suffer from incomplete hydrolysis, an unavoidable degradation of the products to be analysed, and an inability to separate and quantify different types of uronic acids. In the present work, the fundamental chemistry involved in the two methods has been evaluated, and some modifications to increase their accuracy are suggested. By combining the two methods, a complete quantification of all individual types of uronic acids present in a sample can be achieved.     

Reevaluation of colorimetric iron determination methods commonly used in geomicrobiology

The ferrozine and phenanthroline colorimetric assays are commonly applied for the determination of ferrous and total iron concentrations in geomicrobiological studies. However, accuracy of both methods depends on slight changes in their protocols, on the investigated iron species, and on geochemical variations in sample conditions. Therefore, we tested the performance of both methods using Fe(II)((aq)), Fe(III)((aq)), mixed valence solutions, synthetic goethite, ferrihydrite, and pyrite, as well as microbially-formed magnetite and a mixture of goethite and magnetite. The results were compared to concentrations determined with aqua regia dissolution and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Iron dissolution prior to the photometric assays included dissolution in 1M or 6M HCl, at 21 or 60°C, and oxic or anoxic conditions. Results indicated a good reproducibility of quantitative total iron determinations by the ferrozine and phenanthroline assays for easily soluble iron forms such as Fe(II)((aq)), Fe(III)((aq)), mixed valence solutions, and ferrihydrite. The ferrozine test underestimated total iron contents of some of these samples after dissolution in 1M HCl by 10 to 13%, whereas phenanthroline matched the results determined by ICP-AES with a deviation of 5%. Total iron concentrations after dissolution in 1M HCl of highly crystalline oxides such as magnetite, a mixture of goethite and magnetite, and goethite were underestimated by up to 95% with both methods. When dissolving these minerals in 6M HCl at 60°C, the ferrozine method was more reliable for total iron content with an accuracy of ±5%, related to values determined with ICP-AES. Phenanthroline was more reliable for the determination of total pyritic iron as well as ferrous iron after incubation in 1M HCl at 21°C in the Fe(II)((aq)) sample with a recovery of 98%. Low ferrous iron concentrations of less than 0.5mM were overestimated in a Fe(III) background by up to 150% by both methods. Heating of mineral samples in 6M HCl increased their solubility and susceptibility for both photometric assays which is a need for total iron determination of highly crystalline minerals. However, heating also rendered a subsequent reliable determination of ferrous iron impossible due to fast abiotic oxidation. Due to the low solubility of highly crystalline samples, the determination of total iron is solely possible after dissolution in 6M HCl at 60°C which on the other hand makes determination of ferrous iron impossible. The recommended procedure for ferrous iron determination is therefore incubation at 21°C in 6M HCl, centrifugation, and subsequent measurement of ferrous iron in the supernatant. The different procedures were tested during growth of G. sulfurreducens on synthetic ferrihydrite. Here, the phenanthroline test was more accurate compared to the ferrozine test. However, the latter provided easy handling and seemed preferable for larger amounts of samples.     

Determination of the antenna heterogeneity of Photosystem II by direct simultaneous fitting of several fluorescence rise curves measured with DCMU at different light intensities

Several methods for determination of the antenna heterogeneity of Photosystem II from fluorescence rise curves measured with DCMU have been developed so far. Using these methods, two, three or four types of Photosystem II with respect to the antenna heterogeneity were determined. However, the accuracy of some of these methods is under debate. Here, we present a new method for the determination of the antenna heterogeneity of Photosystem II. The method is based on direct simultaneous fitting of several fluorescence rise curves measured with DCMU at different intensities of light excitation. As several curves measured under different light conditions are fitted simultaneously by the same model, reliability and accuracy in determination of model parameters increase. Our method was applied to two plant materials with different structure of the thylakoid membrane: wheat leaves and cells of green alga Chlamydomonas reinhardtii. This revised version was published online in June 2006 with corrections to the Cover Date.     

Detection of the hip center in computer-assisted surgery: An in vitro assessment study

The HKA i.e. the angle between the hip, knee and ankle centers is a clinical parameter widely used in orthopedic surgery. It can be intraoperatively assessed with computer-assisted surgery navigation systems by computing the 3D location of these joint centers. The hip center is computed using functional methods but is defined by the experts as the anatomical center of the femoral head. The aim of this in vitro study is therefore to assess, first, the accuracy of these functional methods for the determination of the HKA and, second, their reproducibility. We have analyzed on six cadaveric lower limbs the accuracy and the reproducibility of functional methods and their impact on the HKA values. The anatomical hip center has been used as the reference value. The reproducibility is 5.2 mm for the determination of the functional hip centers. The average impact on the HKA is 1.2° (4° max). Despite a lack of reproducibility of the functional methods, the impact on the HKA is limited. The accuracy of the functional methods on the HKA can therefore be enough for some clinical applications.     

A new method for the determination of N-sulfate in heparin and its analogs.

A new method for the determination of N-sulfate in heparin and its analogs is described. The method is based on the determination of inorganic sulfate liberated by deamination with nitrous acid. The accuracy, simplicity, and validity of this method are evaluated by comparing it with previous methods.     

The development and validation of liquid chromatography method for the simultaneous determination of metformin and glipizide, gliclazide, glibenclamide or glimperide in plasma

This article describes the development of SPE and HPLC methods for the simultaneous determination of metformin and glipizide, gliclazide, glibenclamide or glimperide in plasma. Several extraction and HPLC methods have been described previously for the determination of each of these analytes in plasma separately. The simultaneous determination of these analytes is important for the routine monitoring of diabetic patients who take combination medications and for studying the pharmacokinetics of the combined dosage forms. In addition this developed method can serve as a standard method for the plasma determination of these analytes therefore saving time, effort and money. The recoveries of the developed methods were found to be between 76.3% and 101.9%. The limits of quantification were between 5 and 22.5 ng/ml. The intraday and interday precision (measured by coefficient of variation, CV%) was always less than 9%. The accuracy (measured by relative error %) was always less than 12%. Stability analysis showed that all analytes are stable for at least 3 months when stored at -70 degrees C.     

Evaluation of flow cytometric methods for determining population potential doubling times using cultured cells

Various methods have been proposed for determining the potential doubling times (Tpot) of mammalian cell populations by using flow cytometric techniques after labeling the cells with bromodeoxyuridine (BrdUrd). We show here that, in a well-defined in vitro system where multiple time measurements are possible, all the methods give similar results that are close to the true population doubling time. Of ultimate interest, however, is the accuracy of determination of Tpot from a single time point. In this paper we compare the accuracy and precision of the methods in making such determinations at different times after labeling. The relative movement (RM) of BrdUrd-labeled cells that have not divided at the time of assay allows for computation of the length of S phase (Ts). The precision of estimation of Ts was enhanced when a quantity, v (a function of the fraction of BrdUrd-labeled divided and the fraction of BrdUrd-labeled undivided cells), was used to estimate the initial intercept of RM. Furthermore, calculation of Tpot from the formula, Tpot = ln(2) Ts/v, gave values closest to the observed population doubling time. It is suggested that the use of RM with v be the analytical method of choice for the calculation of Tpot from single time-point observations, preferably made at times between the length of the G2 and M phases (TG2M) and Ts.     

Pregnancy diagnosis in swine by palpation and by amplitude-depth ultrasound scanning

The relative accuracy of two pregnancy testing methods for swine were compared in a field study. The procedures used were manual palpation and amplitude-depth ultrasonic scanning. A total of 369 sows were examined by both methods. Seven additional gilts were examined by ultrasound only and 46 sows by palpation per rectum only. The number of correct positive and negative diagnoses made by both methods were calculated, and determination of accuracy as well as comparison between the tests were made on this basis. The relative accuracy was 97.6% for the manual method and 96.8% for the ultrasound method. Both tests had a high sensitivity, 99.2 and 98.9%, respectively. The ability of the tests to detect the non-pregnant animals was not as high, which is reflected by a lower specificity. No significant differences were noted between the two methods. A lower specificity and a lower negative predictive value were provided by ultrasound scanning as compared with those acquired by manual palpation. Both procedures were considered to be quick and convenient to perform. It was concluded that in spite of the new pregnancy testing methods introduced in the swine industry, manual palpation remains the most practical in terms of its accuracy, ease, and the minimal requirement for equipment. In gilts, palpation is unsuitable and ultrasonography currently remains the best choice for the diagnosis of pregnancy.     

Applications of surface-surface matching algorithms for determination of orthodontic tooth movements

Orthodontic tooth movements are described as the differences between initial and final tooth positions. A computer based method for determination of tooth movements for different treatment methods was developed. A total of 20 casts of the upper jaw of patients treated with tooth positioners or fixed appliances were used as a basis for this study. Tooth movement was analysed on casts before (Ci) and after treatment (Cf). The casts were digitized either with a COMT or 3D laser scanning systems. After digitization, the models were superimposed in the palate by using a surface-surface matching algorithm. Tooth surfaces of the orthodontically moved teeth were segmented and determination of tooth movement was accomplished by matching the moved teeth from Ci to Cf. The resulting transformations delivered three dimensional information on translations and rotations. An accuracy of 0.2 mm in translations and 1 degree in rotations could be demonstrated, showing the different efficiency of treatment schemes.     

Ultramicro determination of plasma testosterone by electron-capture detection of testosterone diheptafluorobutyrate

1. A new highly sensitive and accurate ultramicro method for the estimation of testosterone in human peripheral plasma is described. The method uses paper-and thin-layer-chromatographic separation of plasma testosterone, which is determined as testosterone diheptafluorobutyrate by electron-capture detection after gas-liquid chromatography. 2. The average difference between duplicates is +/-2% (range 1-5%) with as little as 2.5ml. of human male peripheral plasma. With 10ml. of plasma the method is sensitive enough for the accurate determination of testosterone in human female plasma. The high order of accuracy is achieved by the use of a radioactive label and an internal standard for gas chromatography, and by obtaining several gas chromatograms from the same plasma sample. 3. As little as 40mumug. of peripheral plasma testosterone can be detected. The method is 20 times as sensitive as electron-capture techniques with the monochloroacetate derivative. 4. The method is simpler and quicker than double-isotope-derivative methods, and slightly more sensitive. The advantages of the method, which is specific for testosterone, are its high sensitivity and accuracy, which are achieved with relative convenience.     

Automated quantitative gas—liquid chromatography of intact lipids : II. Accuracy,precision and reproducibility of results

The effect of various factors on the precision and accuracy of the gas chromatographic determination of neutral lipids was studied in the concentration range where the correction factors are dependent on the amount analyzed. The mutual effect of individual components of the neutral lipid spectrum on the recovery was examined. A method is described which provides the stable recovery of the components present at low concentrations, using the addition of high-molecular-weight triglyceride (triarachidin) which does not interfere in the determination of the usual triglycerides. The validity of the correction factors measured with pure compounds was verified by hydrogenation of biological samples of various compositions. Hydrogenation of the sample also solves the problem of the determination of the triglyceride fraction of carbon number 46, which interferes under normal conditions with the determination of the cholesteryl ester fraction of carbon number 47. A method for the standardization of the gas chromatographic determination of neutral lipids is given, using pure compounds instead of lyophilized biological samples.Long-term quality control was carried out using synthetic control samples. The results show sufficiently low values of the variation coefficients over the whole period. The values of the variation coefficients measured over an interval of 25 weeks are about 4% for the main components of the neutral lipid spectrum and 6.3% for the components present at concentrations up to 5%. The within-day variation for the most neutral lipid fractions and for lipid classes attains a value of 40–75% of the day-to-day variation. The most satisfactory values are obtained for the variation within a single series which amounts to less than 2% for all substances except for triglyceride fractions 48 and 54. The correlation of the determination of total cholesterol and triglycerides by gas chromatography and by enzymatic methods shows a very good agreement between the results obtained by the two methods. Using quality control, it is possible to follow the accuracy of the calibration and to demonstrate objectively the necessity for system recalibration.     

Changes in HDL-cholesterol, subfractions HDL2 and HDL3 and apo-A, apo-A1 and apo-B lipoproteins in patients with chronic renal failure subjected to maintenance hemodialysis

Hyperlipoproteinemia was found in 200 patients affected by chronic renal failure on maintenance hemodialysis, due to increase in Total Cholesterol, VLDL-TG, LDL, TG, LDL and VLDL. In 30 of these patients, the analysis was extended to the dosing of decreased Total Serum HDL-Cholesterol, HDL2, HDL3, Apoprotein A and Apoprotein A1 values, and of increased Apoprotein B values. These findings further contribute to proving accelerated atherogenesis in the patients examined.     

Accuracy, precision and quality control in age determination, including a review of the use and abuse of age validation methods

Many calcified structures produce periodic growth increments useful for age determination at the annual or daily scale. However, age determination is invariably accompanied by various sources of error, some of which can have a serious effect on age-structured calculations. This review highlights the best available methods for insuring ageing accuracy and quantifying ageing precision, whether in support of large-scale production ageing or a small-scale research project. Included in this review is a critical overview of methods used to initiate and pursue an accurate and controlled ageing program, including (but not limited to) validation of an ageing method. The distinction between validation of absolute age and increment periodicity is emphasized, as is the importance of determining the age of first increment formation. Based on an analysis of 372 papers reporting age validation since 1983, considerable progress has been made in age validation efforts in recent years. Nevertheless, several of the age validation methods which have been used routinely are of dubious value, particularly marginal increment analysis. The two major measures of precision, average percent error and coefficient of variation, are shown to be functionally equivalent, and a conversion factor relating the two is presented. Through use of quality control monitoring, ageing errors are readily detected and quantified; reference collections are the key to both quality control and reduction of costs. Although some level of random ageing error is unavoidable, such error can often be corrected after the fact using statistical ('digital sharpening)' methods.     

New spectrofluorimetric and spectrophotometric methods for the determination of the analgesic drug,nalbuphine in pharmaceutical and biological fluids

We describe the first studies of a simple and sensitive spectrofluorimetric and spectrophotometric methods for the analysis of nalbuphine (NLB) in dosage form and biological fluids. The spectrofluorimetric method was based on the oxidation of NLB with Ce(IV) to produce Ce(III) and its fluorescence was monitored at 352 nm after excitation at 250 nm. The spectrophotometric method involves addition of a known excess of Ce(IV) to NLB in acid medium, followed by determination of residual Ce(IV) by reacting with a fixed amount of methyl orange and measuring absorbance at 510 nm. In both methods, the amount of Ce(IV) reacted corresponds to the amount of NLB and measured fluorescence or absorbance were found to increase linearly with the concentration of NLB, which are corroborated by correlation coefficients of 0.9997 and 0.9999 for spectrofluorimetric and spectrophotometric methods, respectively. Different variables affecting the reaction conditions such as concentrations of Ce(IV), type and concentration of acid medium, reaction time, temperature, and diluting solvents were carefully studied and optimized. The accuracy and precision of the methods were evaluated on intra‐day and inter‐day basis. The proposed methods were successfully applied for the determination of NLB in pharmaceutical formulation and biological samples with good recoveries. Copyright © 2012 John Wiley & Sons, Ltd.     

High-performance liquid chromatographic determination of the conjugate metabolites of moxisylyte in human plasma and urine

Sensitive and specific high-performance liquid chromatographic methods with fluorescence detection are described for the determination of the metabolites of mox sylyte (4-(2-dimethylaminoethoxy)-5-isopropyl-2-methylphenyl acetate) in human plasma and urine. Deacetylmoxisylyte glucuroconjugate (DAM-G) was hydrolysed enzymatically using β-glucuronidase and quantified as the difference between the DAM concentrations determined after and before hydrolysis. The two sulphate derivatives (deacetylmoxisy;yte sulphoconjugate, DAM-S and monomethyldeacetylmoxisylyte sulphoconjugate, MDAM-S), were analysed without prior hydrolysis. Their extraction from plasma and urine, as well as that of DAM from plasma, involved the use of C₁₈ cartridges adapted on a Benchmate workstation. DAM in urine was quantified after liquid-liquid extraction. The two methods were validated for specificity, linearity, intra- and inter-day precision and accuracy. Precision was generally ≤15% and accuracy ≤12%. In plasma, the limits of quantification were 2.5 ng/ml for DAM and 2.8 ng/ml for the two sulphates; in urine, they were 40 ng/ml for DAM and 200 ng/ml for the sulphates. These methods were used for pharmacokinetic studies in healthy subjects.     

Sex determination using the scapula in medieval skeletons from East Anatolia

Sex determination from skeletal human remains by discriminant function analysis is one of the methods utilized in the forensic and osteoarcheological sciences. The purpose of the present study is to establish metric standards for sex determination for medieval Anatolian populations using scapular measurements. The database for this research consisted of 93 adult skeletal remains (47 males and 46 females) from the Dilkaya medieval collection. Four measurements were taken: maximum scapular height, maximum scapular breadth, glenoid cavity height, glenoid cavity breadth, and subjected to discriminant function analysis. All measurements demonstrated some degree of sexual dimorphism, with the highest accuracy of sex determination (94.8%) obtained using maximum scapular breadth. Overall accuracies of the functions ranged from 82.9% to 95.0%, with a higher accuracy rate obtained for female skeletons than for males. Population specific discriminant formulas were developed using combinations of measurements, which can be used in ancient Anatolian populations.     

利用直接法和间接法测定针阔混交林叶面积指数的季节动态

利用光学仪器法能够快速、高效地测定森林生态系统的叶面积指数(leaf area index, LAI)。然而, 评估该方法测定针阔混交林LAI季节动态准确性的研究较少。该研究基于凋落物法测定了小兴安岭地区阔叶红松(Pinus koraiensis)林LAI的季节动态, 其结果可代表真实的LAI。参考真实的LAI, 对半球摄影法(digital hemispherical photography, DHP)和LAI-2000植物冠层分析仪测定的有效叶面积指数(effective LAI, L_e)进行了评估。首先对DHP测定LAI过程中采用的不合理曝光模式(自动曝光)进行了系统校正。同时, 测定了光学仪器法估测LAI的主要影响因素(包括木质比例(woody-to-total area ratio, α)、集聚指数(clumping index, Ω_E)和针簇比(needle-to-shoot area ratio, γ_E))的季节变化。结果表明: 3种不同方法测定的LAI均表现为单峰型的季节变化, 8月初达到峰值。从5月至11月, DHP测定的L_e比真实的LAI低估50%-59%, 平均低估55%; 而LAI-2000植物冠层分析仪测定的L_e比真实的LAI低估19%-35%, 平均低估27%。DHP测定的L_e 经过自动曝光, α、Ω_E和γ_E校正后, 精度明显提高, 但仍比真实的LAI低估6%-15%, 平均低估9%; 相对而言, LAI-2000植物冠层分析仪测定的L_e经过α、Ω_E和γ_E校正后, 精度明显提高, 各时期与真实的LAI的差异均小于9%。研究结果表明, 考虑木质部和集聚效应对光学仪器法的影响后, DHP和LAI-2000植物冠层分析仪均能相对准确地测定针阔混交林LAI的季节动态, 其中, DHP的测定精度高于85%, 而LAI-2000植物冠层分析仪的测定精度高于91%。     

Measuring seasonal dynamics of leaf area index in a mixed conifer-broadleaved forest with direct and indirect methods

利用光学仪器法能够快速、高效地测定森林生态系统的叶面积指数(leaf area index, LAI)。然而, 评估该方法测定针阔混交林LAI季节动态准确性的研究较少。该研究基于凋落物法测定了小兴安岭地区阔叶红松(Pinus koraiensis)林LAI的季节动态, 其结果可代表真实的LAI。参考真实的LAI, 对半球摄影法(digital hemispherical photography, DHP)和LAI-2000植物冠层分析仪测定的有效叶面积指数(effective LAI, L_e)进行了评估。首先对DHP测定LAI过程中采用的不合理曝光模式(自动曝光)进行了系统校正。同时, 测定了光学仪器法估测LAI的主要影响因素(包括木质比例(woody-to-total area ratio, α)、集聚指数(clumping index, Ω_E)和针簇比(needle-to-shoot area ratio, γ_E))的季节变化。结果表明: 3种不同方法测定的LAI均表现为单峰型的季节变化, 8月初达到峰值。从5月至11月, DHP测定的L_e比真实的LAI低估50%-59%, 平均低估55%; 而LAI-2000植物冠层分析仪测定的L_e比真实的LAI低估19%-35%, 平均低估27%。DHP测定的L_e 经过自动曝光, α、Ω_E和γ_E校正后, 精度明显提高, 但仍比真实的LAI低估6%-15%, 平均低估9%; 相对而言, LAI-2000植物冠层分析仪测定的L_e经过α、Ω_E和γ_E校正后, 精度明显提高, 各时期与真实的LAI的差异均小于9%。研究结果表明, 考虑木质部和集聚效应对光学仪器法的影响后, DHP和LAI-2000植物冠层分析仪均能相对准确地测定针阔混交林LAI的季节动态, 其中, DHP的测定精度高于85%, 而LAI-2000植物冠层分析仪的测定精度高于91%。     

Neutron activation analysis: A powerful tool for assay of rare-earth elements in terrestrial materials

Neutron activation analysis methods for determination of rare-earth elements in different matrices have been developed at the University of Pavia using the 250 Kw TRIGA Mark II reactor. A critical review of both instrumental and destructive methods is presented, as well as the indication of the best working conditions for irradiation, counting and radiochemical separations. The optimized procedures were utilized in the determination of rare-earth elements in standard reference materials of both mineral and biological origin. The adopted radiochemical procedure is based on the separation of the rare-earth element group by fluoride precipitation.Results, given as the average of six independent determinations and relative standard deviations, are reported and discussed. Precision of the methods can be deduced from the reproducibility of data, whereas accuracy is evaluated by comparison with existing values in the literature. Sensitivity limits under the described operational conditions are also reported, as are trends and correlations among data.