Search results for "Reproducibility"
showing 10 items of 1976 documents
Ki-67 assessment of pancreatic neuroendocrine neoplasms: Systematic review and meta-analysis of manual vs. digital pathology scoring
2022
Ki-67 assessment is a key step in the diagnosis of neuroendocrine neoplasms (NENs) from all anatomic locations. Several challenges exist related to quantifying the Ki-67 proliferation index due to lack of method standardization and inter-reader variability. The application of digital pathology coupled with machine learning has been shown to be highly accurate and reproducible for the evaluation of Ki-67 in NENs. We systematically reviewed all published studies on the subject of Ki-67 assessment in pancreatic NENs (PanNENs) employing digital image analysis (DIA). The most common advantages of DIA were improvement in the standardization and reliability of Ki-67 evaluation, as well as its spee…
New Hepatocyte In Vitro Systems for Drug Metabolism: Metabolic Capacity and Recommendations for Application in Basic Research and Drug Development, S…
2003
Primary hepatocytes represent a well-accepted in vitro cell culture system for studies of drug metabolism, enzyme induction, transplantation, viral hepatitis, and hepatocyte regeneration. Recently, a multicentric research program has been initiated to optimize and standardize new in vitro systems with hepatocytes. In this article, we discuss five of these in vitro systems: hepatocytes in suspension, perifusion culture systems, liver slices, co-culture systems of hepatocytes with intestinal bacteria, and 96-well plate bioreactors. From a technical point of view, freshly isolated or cryopreserved hepatocytes in suspension represent a readily available and easy-to-handle in vitro system that c…
Chemical separation and MC-ICPMS analysis of U, Th, Pa and Ra isotope ratios of carbonates
2018
Diagenetic alteration of fossil reef corals may have severe effects on the reliability of 230Th/U-ages. The widely applied criteria introduced to test for the reliability of coral 230Th/U-ages are often not sufficient to identify all altered ages. The combination of 230Th/U- with 231Pa/U-dating has been suggested as a promising method to identify altered ages. Furthermore, 226Ra/230Th ratios can provide information about the diagenetic history during the last 10 000 years. Here we present a method to chemically separate U, Th, Pa and Ra from the same aliquot of a carbonate sample. The isotope ratios of our mixed U–Th–Pa–Ra spike are calibrated using a secular equilibrium material treated in…
Überprüfung der Präzision von Kapnometern
1992
Capnometry, i.e. measurement of CO2 concentration (cCO2, vol%) and calculation of the respective CO2 partial pressure (pCO2, mmHg), is simple to apply, but the user must understand its principles of operation in order to appreciate its power and its limitations. However, sidestream capnometers use to dry the humidified respired gas (37 degrees C, pH2O 47 mmHg) for methodological reasons, thus increasing pCO2 by ca. 6% which, in turn, requires correction. With infrared spectroscopy, overestimation of pCO2 in presence of N2O and underreporting of pCO2 in presence of O2 also require to be corrected. These require either knowledge of the respective gas concentrations (mainstream analyzers) or a…
An effective negative pressure cavitation-microwave assisted extraction for determination of phenolic compounds in P. calliantha H. Andr.
2013
A novel negative pressure and microwave assisted extraction technique (NMAE) was first proposed and applied for extraction of phenolic compounds from pyrola. [C₄MIM]BF₄ aqueous solution was selected as extraction solvent. Optimal extraction conditions were microwave power 700 W, negative pressure -0.07 MPa, temperature 40 °C, liquid-solid ratio 20 : 1, ionic liquid (IL) concentration 0.5 M, extraction time 15 min. The predominance of NMAE was investigated by comparing with microwave-assisted extraction (MAE) and negative pressure cavitation extraction (NPCE) using a first-order kinetics equation. The C∞ values of the target compounds by NMAE were from 0.406 to 5.977 mg g⁻¹ higher than these…
Reflux reactions for chromatography
1976
Reactions under pressure are mainly used to prepare derivatives before chromatographic analysis because of the lack of microequipment. A ml-refluxer has been designed to allow reactions under atmospheric pressure for volumes from 0.2 to 5 cm3. The reaction temperature is determined by the boiling point of the solvent thus derivatives of heat sensitive compounds can be made in the micro scale. With the aid of the ml-refluxer large series of derivatisations can be carried out and hence the reaction parameters can be optimized. This is shown at the example of the alkylation of barbituric acids for gas chromatography, where thus only N,N′-derivatives were obtained. The reliability of the appara…
An automatic system for stepwise treatment of solid samples and application to pollution evaluation by measuring ion lixiviation rates in lichens
1999
An automatic system for the stepwise treatment of solid samples is described. The system is controlled by a PC computer that is connected to a burette equipped with a three-way valve, to a peristaltic pump, and to a robot arm through two serial interfaces. In a cycle, the burette introduces a solvent volume in the sample cell, sonication is applied, and, after a fixed time, the pump carries the solvent to the vial selected by the robot arm. Measurements can be performed both in-line and off-line by analyzing the vial series. The program was written in Visual Basic 3. Lixiviation rates of several cations from the lichen Ramalina farinacea were measured by capillary zone electrophoresis using…
Determination of acetazolamide in human urine samples by reversed-phase high-performance liquid chromatography in the presence of xanthines.
1992
A simple, rapid and selective high-performance liquid chromatographic assay for the determination of acetazolamide in urine samples is described. After extraction with ethyl acetate, the drug is chromatographed on an HP-Hypersil ODS-C18 column with a mobile phase of acetonitrile-phosphate buffer (pH 3) and ultraviolet detection at 275 nm. The efficiency of the extraction, the linearity and the reproducibility of the method permit the evaluation of acetazolamide urinary excretion a long time after its administration.
Rapid analysis of effluents generated by the dairy industry for fat determination by preconcentration in nylon membranes and attenuated total reflect…
2014
Abstract This paper describes a new approach for the determination of fat in the effluents generated by the dairy industry which is based on the retention of fat in nylon membranes and measurement of the absorbances on the membrane surface by ATR-IR spectroscopy. Different options have been evaluated for retaining fat in the membranes using milk samples of different origin and fat content. Based on the results obtained, a method is proposed for the determination of fat in effluents which involves the filtration of 1 mL of the samples through 0.45 µm nylon membranes of 13 mm diameter. The fat content is then determined by measuring the absorbance of band at 1745 cm −1 . The proposed method c…
Critical assessment of particle size analysis of porous silica microbead high-performance liquid chromatographic packings by photosedimentation
1979
Abstract Particle size analysis of commercial spherical silica packings of graduated pore size by means of photosedimentation (PS) is critically examined and compared to results obtained by microscopy. To avoid particle fractionation, the suspension prepared for PS measurements should be subjected to gentle ultrasonic treatment. For computing the particle size distribution, the effective density of solvent-filled porous particles has to be inserted into the Stokes equation. Reproducibility of d p , estimated by PS is found to be largely dependent upon the accuracy of the specific pore volume determination. Satisfactory agreement of data between PS and microscopy is obtained for all products…