bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of rare cells at a frequency of one per million by flow cytometry
Authors: Gross Hans‐Joachim , Verwer Ben , Houck David , Recktenwald Diether
Published: August 2005

In a model study we seeded the pre‐B‐cell line REH into 250 million peripheral blood mononuclear cells (PBMC) at frequencies of 10−4, 10−5, and 10−6. By flow cytometry we could detect the REH cells and found a background of about one event per 100 million PBMC. This sensitivity was achieved by removing four sources of false positive events, including nonspecific immunofluorescence, autofluorescence, background particles from previous experiments, and bursts of events during acquisition. To overcome limits to rare event detection imposed by nonspecific staining and autofluorescence, we used positive and negative selection for the REH cells. Another fluorochrome was added to stain the background cells and particles. In order to remove particles and background from previous experiments, a cleaning technique was developed and event bursts were removed from the analysis by developing an algorithm that screens the list‐mode data for events that were not Poisson distributed. © 1993 Wiley‐Liss, Inc.
Determining Tpot in heterogeneous systems: A new approach illustrated with multicell spheroids
Authors: Durand Ralph E.
Published: August 2005

Like many tumors, multicell spheroids from Chinese hamster V79‐171b fibroblasts display karyotypic heterogeneity as they enlarge. This creates significant problems for analysis of univariate DNA content histograms of cells from spheroids, and even for bivariate bromodeoxyuridine (BrdUrd)/DNA flow histograms. While attempting to routinely measure spheroid cell kinetics with the latter approach, a simple alternative that overcomes many of the inherent problems emerged. The exit rate of BrdUrd‐la‐belled cells from the S‐phase compartment(s), determined using standard DNA analysis software, is used to define the duration of S‐phase and ultimately the potential doubling time of the clonogenic cell population. This approach appears to offer several advantages over the conventional “relative movement” technique for heterogeneous samples, particularly since the subjective distinction between labelled/divided tetraploid G1 cells vs. labelled/undivided diploid G2 is no longer required. Further, the technique avoids some potential artifacts that might be expected for heterogeneous tumors where cell subpopulations proliferate with quite different cell kinetics. © 1993 Wiley‐Liss, Inc.
Comparison of pepsin and trypsin digestion on paraffin‐embedded tissue preparation for DNA flow cytometry
Authors: Tagawa Yutaka , Nakazaki Takayuki , Yasutake Toru , Matsuo Satoshi , Tomita Masao
Published: August 2005

Preparation with enzymes plays an important part in obtaining good results in cellular DNA content measurements from paraffin‐embedded tissue using flow cytometry. Therefore, we have compared two groups of DNA histograms obtained with pepsin (Hedley method) and trypsin digestion (Schutte method). Samples of five tumor types were compared: eight lung, seven breast, five thyroid, seven stomach, and six colon cancer cases. All samples were stained with propidium iodide (PI).

The incidence of DNA aneuploidy determined by the Schutte method indicated a higher ratio in four tumor types than that determined by the Hedley method.

Concerning the coefficient of variation (CV) used to estimate the quality of the DNA histogram, the diploid G1 peak determined by the Schutte method produced a smaller CV in five tumor types than did the Hedley method. This Schutte method had especially good results in lung and thyroid cancer. Furthermore, the amount of debris (background) determined by the Schutte method indicated a decrease in four tumor types compared with the Hedley method.

In cell‐cycle analysis of ten DNA diploid cases, DNA histograms by the Hedley method showed an increased S‐phase fraction due to an overlapping of debris and aggregated cells.

These results indicate that preparation by trypsin digestion is a method superior to pepsin digestion when the sample from paraffin‐embedded tissue is stained with PI for the purpose of DNA content measurement. © 1993 Wiley‐Liss, Inc.
Variations in DNA aneuploid cell content during tumor dissociation in human colon and head and neck cancers analyzed by flow cytometry
Authors: Ensley John F. , Maciorowski Zosia , Hassan Mohammad , Pietraszkiewicz Haline , Sakr Wael , Heilbrun Lance K.
Published: August 2005

Experimental research involving human solid tumors often requires single cell suspensions of high yield that are representative of the tissue of origin and in which the cellular property of interest is preserved. This is particularly necessary for the determination of DNA ploidy by flow cytometry. Mechanical dissaggregation and proteolytic enzyme digestion are the most commonly employed dissociation techniques for solid tumors. Comparative testing of techniques is often not performed. Mechanical and proteolytic enzyme dissociation techniques were comparatively tested in 77 human squamous cell cancers of the head and neck (SCCHN) and 25 human colon cancers for cellular yield, dye exclusion viability, quality, and morphology of DNA histograms, and the presence and proportion of DNA aneuploid subpopulations. Significant and consistent DNA aneuploid subpopulation losses were noted in mechanical preparations of SCCHN and enzymatic preparations of colon cancers. The frequency of SCCHN specimens with DNA aneuploid subpopulations was underestimated by 52% in mechanical cell suspensions, and the proportion of DNA aneuploid cells was diminished in an additional 30% of the specimens. Conversely, the frequency of specimens with DNA aneuploid subpopulations was underestimated by 38% in cell suspensions from enzymatically dissociated human colon cancer and their proportion diminished in an additional 50% of the specimens. Incubations of human colon cancers with three commonly employed proteolytic enzymes demonstrated a progressive loss of DNA aneuploid subpopulations as a function of enzyme concentration and incubation time. This is a serious potential source of error in the flow cytometric determination of DNA ploidy in human solid tumors, and may contribute to the diversity of results obtained and occasional contradictory conclusions reached in such studies. © 1993 Wiley‐Liss, Inc.
An improved assay for the detection of Toxoplasma gondii antibodies in human serum by flow cytometry
Authors: Cozon Grégoire , Roure Chantal , Lizard Gérard , Greenland Timothy , Larget‐Piet Dominique , Gandilhon Françoise , Peyron François
Published: August 2005

The diagnosis of toxoplasmosis relies primarily on the demonstration of specific antibodies to Toxoplasma gondii. We describe a flow cytometry method for the determination of antibodies to whole fixed tachyzoites by indirect immunofluorescence. Fixed tachyzoites in suspension have characteristic light scattering properties. The amount of IgM, IgG, and IgA antibodies from patients' sera bound to the tachyzoites can be estimated from the mean fluorescence intensities observed using class‐specific conjugates for different Ig heavy chains. Appropriate serum dilutions for the estimation of specific IgG titres and for the discrimination between sera positive and negative for IgA and IgM antibodies were established using 40 random sera from pregnant women. The method proved to be quantitative and highly sensitive as compared with currently used assays. Coefficients of variation between series ranged from 6.4% to 12.2% and could be controlled by the inclusion of positive and negative standard sera in the test series. The method might represent a major improvement in cost effectiveness as compared with routine immunofluorescence assay by fluorescent microscopy when the volume of testing is sufficient. It can be fully automated, and its large scale application is currently under investigation. © 1993 Wiley‐Liss, Inc.
White blood cell differentiation using a solid state flow cytometer
Authors: Doornbos R. M. P. , Hennink E. J. , Putman C. A. J. , De Grooth B. G. , Greve J.
Published: August 2005

A flow cytometer using a solid state light source and detector was designed and built. For illumination of the sample stream two types of diode lasers (670 nm and 780 nm) were tested in a set‐up designed to differentiate human leukocytes by means of light scattering. The detector is an avalanche photodiode, which was used to detect the weak scattered light in the orthogonal direction. The new flow cytometer set‐up is very small, relatively cheap and yields similar results as a standard flow cytometer set‐up using a helium‐neon laser and photomultipliers. © 1993 Wiley‐Liss, Inc.
Heterochromatin study demonstrating the non‐linearity of fluorometry useful for calculating genomic base composition
Authors: Godelle Bernard , Cartier Delphine , Marie Dominique , Brown Spencer C. , Siljak‐Yakovlev Sonja
Published: August 2005

A novel procedure for calculating basepair frequencies in whole genomes is reported. This has been developed during a study of the role of heterochromatin in microevolution. Closely related species of the Crepis praemorsa complex have similar karyotypes but for their heterochromatin. The changes in relative AT frequency between species have been attributed to heterochromatin sequences by in situ banding of chromosomes with two base‐specific fluorochromes. The absolute genome size of species, measured by cytofluorometry, correlated positively with increased karyotypic heterochromatin, as did the proportion of AT bases in the DNA. However, the determination of base content has called for a curvilinear interpretation of data obtained with two base‐specific fluorochromes (bisbenzimide Hoechst 33342 and mithramycin), in contrast to the commonly assumed but erroneous direct relationship between fluorescence intensity and base content. Essentially, the fluorochromes' requirements for a sequence of certain basepairs lead to the notion of Coefficients or' Overspecificity: the result is a simple for mula for calculating the AT proportion in a genome relative to a reference species from cytometric data, taking account of ligand binding statistics. These statistics and probabilities of oligonucleotide binding are essentially the same. © 1993 Wiley‐Liss, Inc.
Cluster analysis of flow cytometric list mode data on a personal computer
Authors: Schut Tom C. Bakker , De Grooth Bart G. , Greve Jan
Published: August 2005

A cluster analysis algorithm, dedicated to analysis of flow cytometric data is described. The algorithm is written in Pascal and implemented on an MS‐DOS personal computer. It uses k‐means, initialized with a large number of seed points, followed by a modified nearest neighbor technique to reduce the large number of subclusters. Thus we combine the advantage of the k‐means (speed) with that of the nearest neighbor technique (accuracy). In order to achieve a rapid analysis, no complex data transformations such as principal components analysis were used.

Results of the cluster analysis on both real and artificial flow cytometric data are presented and discussed. The results show that it is possible to get very good cluster analysis partitions, which compare favorably with manually gated analysis in both time and in reliability, using a personal computer. © 1993 Wiley‐Liss, Inc.
False aneuploidy in flow cytometric DNA analysis of paraffin embedded tissue: Effects of carnoy's fixation
Authors: Carr Robert F. , Abaza Ann M.
Published: August 2005

False aneuploidy was detected on flow cytometric DNA analysis of paraffin embedded axillary lymph nodes negative for tumor. It was hypothesized that “clearing” of axillary fat in Carnoy's solution to facilitate lymph node dissection might be responsible for false aneuploidy. Various tissues fixed overnight in Carnoy's were compared to formalin fixed paraffin embedded controls. Under these conditions no false aneuploid peaks were detected, but Carnoy's fixation did shift the G0/G1 histogram peak to the left, increase the G0/G1 CV and increase the S phase fraction relative to formalin fixed controls. It was then hypothesized that partial fixation of nodes in Carnoy's followed by formalin fixation might result in false aneuploid peaks. Twenty‐two lymph nodes were partially fixed in Carnoy's for periods ranging from 5 to 60 min followed by complete fixation in formalin. Seven of these nodes did show false aneuploid peaks. By contrast, no aneuploidy was detected in formalin fixed controls. It was concluded that tissues in contact with Carnoy's solution may be a source of false aneuploidy and/or false elevation of S phase fraction. This reinforces the need for matched negative tissue controls for DNA analysis of paraffin embedded specimens whenever possible. © 1993 Wiley‐Liss, Inc.
Improved dna content histograms from formalin‐fixed, paraffin‐embedded liver tissue by proteinase K digestion
Authors: Albro James , Bauer Kenneth D. , Hitchcock Charles L. , Wittwer Carl T.
Published: August 2005

An improved method for the enzymatic digestion of formalin‐fixed, paraffin‐embedded liver tissue for DNA content analysis by flow cytometry is presented. Forty samples of histologically normal liver were alternately digested by the traditional pepsin method or a new method utilizing proteinase K and heat. Sixteen (40%) of the pepsin‐digested samples had apparent DNA aneuploid peaks by flow cytometry. False DNA aneuploid peaks were not present in any of the histograms obtained after proteinase K digestion. Microscopy showed that the pepsin‐digested samples had residual cytoplasmic remnants which contained fluorescent material. Samples digested with proteinase K had few cytoplasmic remnants. The average G0/G1 coefficient of variation after proteinase K treatment was lower (41%) and the fluorescent intensity higher (128%) than the pepsin‐treated samples. The apparent mean S‐phase (a combination of S‐phase cells and underlying debris) after proteinase K digestion was 35% of the pepsin‐treated samples. Primary and secondary tumors of the liver that were DNA aneuploid after pepsin treatment were also DNA aneuploid after proteinase K treatment. A modified digestion protocol utilizing proteinase K and heat can provide superior results for DNA content analysis of formalin‐fixed, paraffin‐embedded liver tissue. © 1993 Wiley‐Liss, Inc.
CD4 T‐lymphocyte determinations on whole blood specimens using a single‐tube three‐color assay
Authors: Nicholson Janet K. A. , Jones Bonnie M. , Hubbard Marjorie
Published: August 2005

We evaluated a flow cytometrïc method for determining the proportion of CD4‐positive T lymphocytes in whole blood using a single three‐color tube containing fluorochrome‐labeled CD45, CD3, and CD4. Various ways of gating this sample were evaluated and results were compared with data obtained in our standard six‐tube, two‐color assay gated on light scatter parameters. Excellent correlation was found between the three‐color analysis using a CD45/side scatter gate and the standard two‐color analysis with a light scatter gate. This single‐tube three‐color test is a promising assay for monitoring CD4+ T‐lymphocytes. © 1993 Wiley‐Liss, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Determination of the percentage of thiazole orange (TO)‐positive, “reticulated” platelets using autologous erythrocyte TO fluorescence as an internal standard
Authors: Bonan Jayne L. , Rinder Henry M. , Smith Brian R.
Published: August 2005

Determination of the percentage of thiazole orange (TO)‐positive or “reticulated” platelets by flow cytometry has been advocated as an aid in the diagnosis of thrombocytopenic disorders. However, a reproducible method for determining control fluorescence and setting threshold values on a routine clinical basis has not been described. We used erythrocyte TO fluorescence in whole blood as an internal standard to set threshold markers for TO fluorescence of autologous, purified platelets. Since platelets have approximately a threefold higher TO fluorescence than erythrocytes, multiplying the erythrocyte threshold marker by 3 allowed a determination of the percentage of “reticulated” platelets in 29 normal controls. This value was 3.64% ± 2.10% (S.D.) in men and 5.79% ± 2.22% (S.D.) in women; there was a significant (P < 0.05) difference between normal men and women for this measurement. Applying this method to our earlier studies of normals and patients with immune thrombocytopenic purpura confirmed its ability to discriminate between these populations with similar sensitivity and specificity as previously reported. This method controls for fluctuations in TO labeling and fluorescence and does not require daily determination of a new normal control value. © 1993 Wiley‐Liss, Inc.
Three‐deimensional visualization of multi‐channel volume data: The amSFP algorithm
Authors: Messerli J. M. , van der Voort H. T. M. , Rungger‐Brändle E. , Perriard J. ‐C.
Published: August 2005

In this paper we present a three‐dimensional visualization technique for multi‐channel volume data. The technique simulates the physical process of fluorescence, hence its name: achromatic multi‐channel simulated fluorescent process (amSFP). The data set is simulated as 3D distribution of different fluorescent dyes, where each channel is represented by a particular type of dye. Apart from the spatial density map, no additional characteristics about the data set have to be defined; no image segmentation is needed prior to visualization. The degree of interaction among the channels in the fluorescence process can be adapted to optimally render specific structures in the image. 3D multi‐channel data can be obtained by a three‐dimensional imaging device that is able to measure a number of physical quantities at a given location within a specimen. The fluorescence principle, the algorithm, and its implementation are presented. We have used the technique to investigate the relative spatial arrangement of blood vessels and astrocytes in the cat retina. The two components have been stained with different fluorescence dyes and recorded in a confocal light microscope to form a two‐channel 3D data set. © 1993 Wiley‐Liss, Inc.
Preparation of cell nuclei from fresh tissues for high‐quality DNA flow cytometry
Authors: Castro Juan , Heiden Thomas , Wang Naining , Tribukait Bernhard
Published: August 2005

An easy method for preparation of bare cell nuclei from fresh solid tissues for DNA flow cytometry is described. Pieces of up to 2 × 2 × 2 mm3 size from fresh tissues were fixed in formalin. After removal of formalin by washing with ethanol and rehydration with tap water, the tissue pieces were incubated with subtilisin Carlsberg (pronase, Sigma protease XXIV) and then stained directly with DAPI. Staining with ethidium bromide gave unsatisfactory results. Neither mechanical disaggregation nor centrifugation were used. The resulting cell nucleus suspensions had extremely low frequencies of debris particles and of clumped cell nuclei. A good yield, a minimized loss, and a good stainability of cell nuclei were obtained.

The applicability of the method was exemplified by the analysis of biopsies from the colon‐rectum in patients with ulcerative colitis and of biopsies from the bladder in patients with bladder cancer and compared to the standard method of this laboratory, which uses mechanical disaggregation, ethanol fixation, pepsin treatment, and staining with ethidium bromide. The formalin‐nubtilisin Carlsberg technique resulted in good agreement of ploidy measurements compared to the standard method, a higher number of evaluable histograms, an improved detectability of aneuploid cell populations, and an improved accuracy of the S‐ and G2‐phase analysis, particularly in samples with low proliferation. The method also makes it possible to use long‐term storage and to transport samples by post. © 1993 Wiley‐Liss, Inc.
Automatic lineage assignment of acute leukemias by flow cytometry
Authors: Verwer Ben J. H. , Terstappen Leon W. M. M.
Published: August 2005

A method for automatic lineage assignment of acute leukemias was developed. Input are eight list mode data files acquired with a FACScan flow cytometer. For each cell, four parameters are measured: forward light scatter, orthogonal light scatter, fluorescein fluorescence, and phycoerythrin fluorescence. Eight data files are acquired in the following sequence: unstained, isotype controls, CD10/CD19, CD20/CD5, CD3/CD22, CD7/CD33, HLADR/CD13, and CD34/CD38. First, each of the data files 3 to 8 are clustered independently employing an algorithm based on nearest neighbors. Next, the clusters are associated across the data files to form cell populations, using the assumption of light scatter invariance across tubes for each population. The mean positions of each cell population are fed into a decision tree. The decision tree first identifies normal cell populations, i.e., monocytes, neutrophils, eosinophils, basophils, NK cells, T‐lymphocytes, and B‐lymphocytes. After elimination of the normal cell populations from the data space, the residual cell populations are classified as B‐lineage ALL, T‐lineage ALL, AML, AUL, B‐CLL, or unknown. The effectiveness of this novel approach is shown with case studies of B‐lymphoid, T‐lymphoid, and Myeloid acute leukemias. © 1993 Wiley‐Liss, Inc.
Identification and quantitation of apoptotic cells following anti‐CD3 activation of murine G0 T cells
Authors: Chrest Francis J. , Buchholz Meredith A. , Kim Young Ho , Kwon Taeg‐Kyu , Nordin Albert A.
Published: August 2005

Multiparameter flow cytometry and cell sorting were used to examine the process of apoptosis after activation of murine resting T cells with immobilized anti‐CD3. Activated T cells treated with Hoechst 33342 (HO‐33342) and analyzed by flow cytometry showed two major cell populations of high and low fluorescence. These populations were sorted and the DNA extracted and subjected to electrophoresis. Electrophoresis of DNA extracted from T cells showing a low level of HO‐33342 fluorescence (HO‐Low) resulted in a typical ladder pattern characteristic of internucleosomal DNA degradation associated with apoptosis, whereas the cellular DNA of the cells showing a high level of fluorescence (HO‐High) showed a narrow high molecular weight band. Multiparameter analysis further indicated that cells with HO‐High characteristics possessed corresponding high‐FSC/low‐SSC properties, whereas HO‐Low cells formed a cluster of low‐FSC/high‐SSC cells. Analysis of the DNA extracted from cells sorted on the basis of scatter properties alone confirmed that the low‐FSC/high‐SSC population contained the apoptotic cells and that the high‐FSC/low‐SSC population was comprised of viable cells. This methodology allowed us to determine the percentage of apoptotic cells following anti‐CD3 activation at various time points and to discriminate them from those in cell cycle. We could further quantitate the number of apoptotic versus viable CD4+ and CD8+ cells in the cell cycle. © 1993 Wiley‐Liss, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Optimal detection of apoptosis by flow cytometry depends on cell morphology
Authors: Zamai L. , Falcieri E. , Zauli G. , Cataldi A. , Vitale M.
Published: August 2005

Flow cytometry has recently become a choice technique for the quantitative analysis of apoptosis. Monoparametric DNA analysis usually allows identification of apoptotic cells as a “subdiploid” peak. Progression through apoptosis leads to chromatin condensation, nuclear fragmentation and eventually to cell disruption. Thus, a major problem for the flow cytometric analysis of apoptotic populations is discrimination between debris and apoptotic cells. Here we demonstrate that the best parameter on which to make such a distinction is the DNA content, no matter what type of cell is studied. In contrast, discrimination between apoptotic, non‐apoptotic cells, and debris is possible on the basis of scattering signals only in few selected cases, depending on the morphology of the intact cells. © 1993 Wiley‐Liss, Inc.
Rapid method for cell cycle analysis in a predatory marine dinoflagellate
Authors: Whiteley A. S. , Burkill P. H. , Sleigh M. A.
Published: August 2005

Oxyrrhis marina (Dujardin) is a predatory marine dinoflagellate that feeds phagocytically on live phytoplanktonic “prey” cells from the surrounding environment. A rapid method was developed to separate the cell cycle characteristics of these predators from their prey cells in order to study the cell cycle dynamics of this organism.

Nuclei from Oxyrrhis were isolated in low salt buffer (PBS) using detergent and mechanical agitation and the DNA stained with Hoechst 33258 in a one step procedure. The method permitted the isolation of nuclei from the Oxyrrhis cells with > 95% efficiency.

Discrimination between prey cell nuclei and those of Oxyrrhis was achieved during flow cytometric analysis which yielded routinely G1 CVs of 3–6% for exponentially growing cell populations and 2–3% for stationary phase cells.

The method was used to demonstrate the changes in cell cycle dynamics during the exponential and stationary phases of growth. Results indicated that in contrast to most mammalian and phytoplankton cell types Oxyrrhis spent the major portion (ca. 50%) of its cell cycle in G2 + M when actively dividing. Analysis of stationary phase populations also suggests that specific cell cycle control (or restriction) points were present in both G1 and G2 in this species. © 1993 Wiley‐Liss, Inc.
Measurement of intracellular pH using flow cytometry with carboxy‐SNARF‐1
Authors: Wieder Eric D. , Hang Haiying , Fox Michael H.
Published: August 2005

The new intracellular pH (pHi) dye carboxy‐seminaphthorhodafluor (SNARF‐1) was compared to the established dye 2,3‐dicyanohydroquinone (DCH) using flow cytometry. Both dyes give high‐resolution pHi measurements. SNARF‐1 remains trapped within cells much longer than DCH, so that pHi can be monitored during and after treatments with chemicals or hyperthermia. The toxicity of the dyes is similar, and both dyes can be used at concentrations that result in low toxicity to cells. Adequate staining of cells with SNARF‐1 is dependent on the cell concentration. The absolute pHi values indicated by SNARF‐1 are higher than values measured with DCH. However, the trends measured by both dyes are consistent, and both are useful for making pHi measurements. © 1993 Wiley‐Liss, Inc.
μ‐η1:η1‐N,N′‐Imidazolidine‐Bridged Dicopper(II/III) Complexes of a New Dinucleating μ‐Bis(tetradentate) Schiff Base Ligand: Synthesis, Structural Characterization, 1H NMR Spectroscopy, and Magnetic Coupling
Authors: Bera Manindranath , Wong Wing Tak , Aromí Guillem , Ray Debashis
Published: August 2005

The dicopper oxidation state in the title of the original article1 is erroneously given as (II/III); however, it should be (II/III) as shown in the correct title above.
Reaction of 1,3,5‐Triazacyclohexanes with TiCl4: Formation of Cationic Complexes (Eur. J. Inorg. Chem. 16/2005)
Authors: Köhn Randolf D. , Kampe Philip , Kociok‐Köhn Gabriele
Published: August 2005

The cover picture shows the first crystallographically characterized cationic triazacyclohexane complex of titanium. The hydrogen atoms of the ring‐CH2 groups engage in C−H···Cl interactions with the anion (only the shortest shown) and give rise to two characteristic doublets in the 1H NMR spectrum with shifts that are highly dependent on the N‐substituents, solvent and anion. The cationic complex is readily formed by the treatment of triazacyclohexanes with excess TiCl4 which often results in large crystals containing the Ti2Cl9 anion. Details are discussed in the article by R. D. Köhn et al. on p. 3217 ff.
Palladium(II) Chloride and a (Dipyridin‐2‐ylmethyl)amine‐Derived Palladium(II) Chloride Complex as Highly Efficient Catalysts for the Synthesis of Alkynes in Water or in NMP and of Diynes in the Absence of Reoxidant
Authors: Gil‐Moltó Juan , Nájera Carmen
Published: August 2005

The (dipyridin‐2‐ylmethyl)amine‐derived palladium chloride complex 1 and PdCl2 are efficient catalysts for cross‐coupling reactions between terminal alkynes and aryl iodides or bromides under modified Sonogashira–Cassar–Heck conditions. The alkynylation can be performed under copper‐free conditions in water at reflux or at room temperature under air with pyrrolidine as base and tetra‐n‐butylammonium bromide (TBAB) as additive, with TONs of up to 7 × 104 and TOFs(h–1) of up to 6666. Terminal alkynes can be arylated in NMP as well under copper‐ and amine‐free conditions at 110 °C or room temperature, with tetra‐n‐butylammonium acetate (TBAA) acting as base with TONs up to 2 × 105 and TOFs (h–1) up to 66 666. In general, complex 1 displays a slightly higher efficiency than PdCl2 as catalyst and maintains the same activity after five consecutive runs. Alternatively, these alkynylation processes can be carried out under microwave heating conditions. The homocoupling of terminal alkynes to the corresponding 1,3‐diynes proceeds under phosphane‐free conditions with the (dipyridin‐2‐ylmethyl)amine‐derived palladium chloride complex 1 or with PdCl2 as catalysts and with CuI as cocatalyst in NMP with use of either TBAA or pyrrolidine as bases. This Glaser‐type reaction can be performed at 110 °C or at room temp. in the presence of air without the use of a reoxidant. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Biocompatible needle‐type glucose sensor with potential for use in vivo
Authors: Chen Chien‐Yuan , Su Yuan‐Chi , Ishihara Kazuhiko , Nakabayashi Nobuo , Tamiya Eiichi , Karube Isao
Published: August 2005

A biocompatible material with diffusion‐limiting properties [(MPC‐co‐BMA)‐CA] was prepared by mixing the copolymer of 2‐methacryloyloxyethyl phosphorylcholine and n‐butyl methacrylate (MPC‐co‐BMA) with cellulose acetate (CA). Investigation of the biocompatibility showed that, compared with CA, relatively few platelets bound to it and no morphological change was observed. This material was dipcoated as the outermost layer onto the working electrode of a needle‐type glucose sensor. The sensor showed a rapid response (<120 seconds in batch operation), good reproducibility (RSD < 5%), good stability (more than 36 hours in control serum continuously), and a very wide dynamic range (0–1000 mg/dl glucose). It was used to determine glucose in serum. The data obtained from the sensor showed good agreement (R > 0.95) with that from a clinical autoanalyzer.
Selective biocatalytic measuring cell for flow injection analysis
Authors: Tarcali József , Nagy Géza , Pungor Ernö
Published: August 2005

A flow‐through measuring cell developed for flow injection analysis (FIA) measurements is described. The cell works detecting amperometrically the hydrogen peroxide formed in an enzyme‐catalyzed oxidation reaction of different substrates. The electrode consists of a thin, hollow dialysis fiber introduced into the flow analysis channel, an enzyme solution film pumped inside the fiber, and a cellulose acetate protective layer‐coated thin platinum wire‐base sensor housed inside the hollow fiber. The measuring cell for two different model compounds, glucose and ethanol, was well applicable for the concentration determinations in small volume solution aliquots. Important advantages of the cell are its versatility and its easy activation for measurements.
Anodic stripping voltammetric analysis of selenium: Comparison of electrode geometries
Authors: Hrehocik Michele E. , Lundgren Jeffrey S. , Bowyer Walter J.
Published: August 2005

Gold macrodisk, microdisk, and microband electrodes are compared for the anodic stripping voltammetry of Se(IV). All of these electrodes show a stripping peak at 0.79 V with a width at half height of 80–90 mV. The linear dynamic range, limit of detection, sensitivity, and precision are compared when using the three electrodes. Although flux at the microelectrodes is greater than at the macroelectrode, the limit of detection is similar for all three geometries. The linear dynamic range is smallest when using the microdisk electrode. The precision of the peak current is best with the macrodisk electrode. Although microelectrodes enjoy many advantages in analyses based on reversible systems, these advantages are not always realized with irreversible systems.
Hydrodynamically generated amperometric difference currents using parallel flow streams
Authors: Zhu Caobin , Curran David J.
Published: August 2005

An alternative approach to hydrodynamic modulation in flow streams has been designed which is not influenced by the rate of relaxation of the diffusion layer. Reticulated vitreous carbon flow through working electrodes was used in gravity‐driven dual‐flow lines. Two working electrodes were used, one in each of two independent flow lines. Each flow line contained a complete electrochemical cell, and the working electrode of each cell was maintained at the same potential. The flow rates were different in each flow line, but the solution of analyte was the same. The difference current between the two working electrodes was measured using operational amplifier circuitry. Criteria for the selection of flow rates are presented. The dual‐flow stream has the advantages of real‐time background correction and automatic offset of solid electrode surface or history effects. Hydroquinone was used as a test system, and detection limits were in the subnanomolar region.
Adsorptive stripping measurements of bismuth
Authors: Wang Joseph , Lu Jianmin , Setiadji Rossi
Published: August 2005

A very sensitive stripping procedure for trace measurements of bismuth, based on the adsorptive accumulation of the bismuth‐cupferron complex onto the mercury working electrode, is described. The optimized conditions include a sulfuric acid (5 × 10−4 M) medium, containing 2.5 × 10−5 M cupferron, and an accumulation potential of −0.10 V. Both voltammetric and potentiometric stripping modes can be employed to probe the reduction of the accumulated complex. The limit of detection after 10 minutes preconcentration is 6 ng L−1 (3 × 10−11 M), and the relative standard deviation at the 2 × 10−8 M level is 1.6%. Most cations, including antimony, do not interfere in the determination of bismuth. Simultaneous measurements of bismuth, titanium, and uranium are illustrated.
The transfer coefficient of the electrochemical reduction of cephalosporins and cefamycins
Authors: Muñoz E. , Avila J. L. , Doctor J. Pérez , Camacho L.
Published: August 2005

The electrochemical reduction at a mercury electrode of three cephalosporins and one cefamycin bearing a common R3 substituent was studied. The first one‐electron transfer of the reduction process was found to be the rate‐determining step in all four cases. In addition, the process took place via species adsorbed on the electrode. The analysis of the voltammetric peaks obtained in the absence of diffusion allowed us to establish the variation of the apparent transfer coefficient, αap, throughout the peak. This was found to be a linear function of the faradic current, which is consistent with the assumption that the free energy of adsorption of the antibiotics is a linear function of the coverage. In addition, the transfer coefficient was found to be markedly dependent on the nature of substituent R‐and on the character of the cephalosporin or cefamycin.
Polarographic behavior of 8‐chlorotheophylline and its determination in dosage forms
Authors: Gil E. Pinilla , Blázquez L. Calvo , Carra R. M. García‐Moncó , Misiego A. Sánchez
Published: August 2005

The electroanalytical behavior of 8‐chlorotheophylline has been investigated by cyclic voltammetry on a hanging mercury drop electrode (HMDE) and by differential pulse polarography on a dropping mercury electrode (DME). The differential pulse polarography approach offers a simple and yet reliable method for the determination of 8‐chlorotheophylline in pharmaceutical preparations with good accuracy and precision.
A highly sensitive and selective catalytic oscillopolarographic method for the determination of ultratrace amounts of molybdenum
Authors: Zhi‐Liang Jiang , Guo‐Zhong Dai
Published: August 2005

A very sensitive and selective single‐sweep oscillopolarographic method has been developed for determining trace molybdenum down to 0.06 ng/ml. In the presence of 0.040M mandelic acid‐0.10% OP emulsifier‐0.10M potassium chlorate‐1.0M sulfuric acid Mo(VI) exhibits a very sensitive and sharp polarographic catalytic adsorptive wave at −0.10 V (vs. SCE). The oscillopolarographic behavior and the influence of foreign ions were studied. Molybdenum in human hair, ore, and steel samples were analyzed by this method, and excellent results were obtained.
An image warping approach to spatio‐temporal modelling
Authors: Aberg Sofia , Lindgren Finn , Malmberg Anders , Holst Jan , Holst Ulla
Published: August 2005

In this article we present a spatio‐temporal dynamic model that can be realized using image warping. Image warping is a non‐linear deformation which maps every point in one image plane to a point in another image plane. Using thin‐plate splines, these deformations are defined by how a small set of points is mapped, making the method computationally tractable. In our case the dynamics of the process is modelled by thin‐plate spline deformations and how they vary in time. Thus we make no assumption of stationarity in time. Finding the deformation between two images in the space–time series is a trade‐off between a good match of the images and a smooth, physically plausible, deformation. This is formulated as a penalized likelihood problem, where the likelihood measures how good the match is and the penalty comes from a prior model on the deformation. The dynamic model we suggest can be used to make forecasts and also to estimate the uncertainties associated with these. An introduction to image warping and thin‐plate splines is given as well as an application where the methodology is applied to the problem of nowcasting radar precipitation. Copyright © 2005 John Wiley & Sons, Ltd.
Periodic finite elements in two‐layer tidal flow
Authors: Kawahara Mutsuto , Morihir Michio , Kataoka Shinji , Hasegawa Ken'Ichi
Published: August 2005

The aim of this paper is to present the finite element method and its application to quasi‐steady periodic two‐layer tidal flow in estuaries and coastal seas. Formulating the weighted residual equations, using quadratic polynomials for velocity and linear polynomials for water elevation as interpolation functions and employing the periodic Galerkin method, the nonlinear simultaneous equations can be derived. The present method is used for the simulation analysis of the Niigata Port redevelopment planning.
A simple method to generate high‐order accurate convection operators for explicit schemes based on linear finite elements
Authors: Donéa J. , Giuliani S.
Published: August 2005

A simple method is proposed to generate high‐order accurate convection operators for lumped‐explicit schemes based on linear or multilinear finite elements. The basic idea is to reduce the truncation error on the first‐order spatial derivatives by exploiting the consistent mass matrix of the finite element method in a purely explicit multistep procedure. The effectiveness of the method is demonstrated on pure convection problems in one and two dimensions.
Computation of wave fields in the ocean around an Isaland
Authors: Skovgaard Ove , Jonsson Ivar G.
Published: August 2005

A linear wave equation correct to first order in bed slope is used to calculate the wave field in the sea around an idealized island. This is of circular cylindrical shape and is situated on a paraboloidal shoal in an ocean of constant depth (Figure 1). The sides of the island are assumed fully reflecting. The incident waves are plane and periodic. Wave periods up to 30 min are investigated, and the Coriolis force is neglected. The solution of the wave equation is represented by a finite Fourier series, and a large number of very accurate numerical computations are carried through. The results appear partly in figures showing amplitude and phase angle curves (in some cases extending to the water area of constant depth outside the shoal), partly in figures showing amplitude vs wave period in fixed points. Comparison with solutions to the linearized long‐wave equation is made, and the validity range of the corresponding shallow water theory is given. The influence of the shoal is studied by investigating the wave field around an island in an ocean of constant depth. New criteria are given for the applicability of a geometrical optics approach (i. e. refraction). Complete numerical refraction solutions for points at the shoreline (corresponding to many wave orthogonals ending at the point) for shallows water waves, as for the general case, demonstrate the inadequacy of this approach for long‐period waves (seismic seawaves: tsunamis). All non‐linear effects, including dissipation, are excluded.
Aspects of large eddy simulation of homogeneous isotropic turbulence
Authors: Antonopoulos‐Domis M.
Published: August 2005

HOMTY, a code for Large Eddy Simulation of homogeneous isotropic turbulence is proven by successful simulation of two experiments. The role of each term in the equations of motion and the concept of filtering is examined. It is shown that ‘prefiltering’ is unnecessary, and the resulting additional term in the equations, instead of transferring energy to the subgrid scales, backscatters energy from the resolved large wavenumerbers to the small ones. The kinetic energy decay exponent is shown to depend on the low wavenumber part of the velocity spectrum. Pressure statistics are computed and found to be in agreement with previous computations.
Modelling flow over a backward–facing step using the F.E.M. and the two‐equation model of turbulence
Authors: Taylor C. , Thomas C. E. , Morgan K.
Published: August 2005

Flow over a downstream‐facing step is predicted using the F.E.M. A two‐equation model of turbulence is employed where the transport of turbulence kinetic energy and dissipation rate are depicted using transport‐type equations, i.e. the two‐equation model of turbulence. The results obtained are compared with other models and experimental results. Generally, the model was found to be under‐predictive with regard to the reattachment length when previous empirical data was used in the transport equations.
A generalized variational formulation for convective heat transfer
Authors: Keramidas George A.
Published: August 2005

The Scope of this paper is to develop the basic equations for a variational formulation which can be used to solve problems related to convection and/or diffusion dominated flows. The formulation is based on the introduction of a generalized quantity defined as the hear displacement. The governing equation is expressed in terms of this quantity and a variational formulation is developed which leads to a system of equations similar in form to Lagrange's equations of mechanics. These equations can be used for obtaining approximate solutions, though they are of particular interest for application of the finite element method.

As an example of the formulation two finite element models are derived for solving convectiondiffusion boundary value problems. The performance of the two models is investigated and numerical results are given for different cases of convection and diffusion with two types of boundary conditions. The applications of the developed formulations are not limited to convection‐diffusion problems but can also be applied to other types of problems such as mass transfer, hydrodynamics and wave propagation.
An approximately divergence‐free 9‐node velocity element (with variations) for incompressible flows
Authors: Griffiths D. F.
Published: August 2005

Explicit basis functions are constructed for 9‐node biquadratic velocity fields which guarantee that a weak form of the continuity equation is satisfied. The corresponding pressure approximations are either piecewise constant, piecewise linear or piecewise bilinear. These results are extended to give bases for bilinear velocity/piecewise constant pressure elements and also to some three‐dimensional brick elements.
Old and new finite elements for incompressible flows
Authors: Fortin Michel
Published: August 2005

This paper presents some seemingly new elements for the computation of two and three‐dimensional incompressible flow. We want to obtain elements satisfying the Babǔska‐Brezzi condition for mixed methods and thus introducing no spurious pressure modes (cf. Sani et al.1). In order to present clearly the advantages and disadvantages of our new elements we compare them on a qualitative basis with more standard ones. Of particular importance for incompressible flow is the size and shape of vortices that can be produced by the elements. We shall try to describe this as precisely as possible. The conclusion is that the elements introduced here should be quite competitive on a cost/precision scale.
The Lagrangian approach of advective term treatment and its application to the solution of Navier—Stokes equations
Authors: Huffenus J. P. , Khaletzky D.
Published: August 2005

A one‐dimensional transport test applied to some conventional advective Eulerian schemes shows that linear stability analyses do not guarantee the actual performances of these schemes. When adopting the Lagrangian approach, the main problem raised in the numerical treatment of advective terms is a problem of interpolation or restitution of the transported function shape from discrete data. Several interpolation methods are tested. Some of them give excellent results and these methods are then extended to multi‐dimensional cases.

The Lagrangian formulation of the advection term permits an easy solution to the Navier‐Stokes equations in primitive variables V, p, by a finite difference scheme, explicit in advection and implicit in diffusion.

As an illustration steady state laminar flow behind a sudden enlargement is analysed using an upwind differencing scheme and a Lagrangian scheme. The importance of the choice of the advective scheme in computer programs for industrial application is clearly apparent in this example.
Numerical predictions of the laminar flow over a normal flat plate
Authors: Castro I. P. , Cliffe K. A. , Norgett M. J.
Published: August 2005

Finite‐difference and finite‐element techniques have been used to calculate the steady laminar flow over a flat plate normal to an air stream, up to a Reynolds number, Re, based on the plate half‐width, of 100. The boundary conditions simulate a central splitter plate downstream of the body, to prevent vortex shedding, so the flow is characterized by a closed recirculation region which grows with increasing Re but at Re = O(100) is very similar in size to the turbulent recirculating region that occurs in the corresponding high Reynolds‐number flow. Motivation came, in part, from the increasing efforts of turbulence modellers to calculate complex turbulent flows (containing elliptic regions) and our belief that the numerical methods commonly employed for such work can be inaccurate. The predictions are compared with each other and with some expectations based on classic solutions of the Navier‐Stokes equations, and the nature of the numerical errors is demonstrated. It is concluded that effort comparable with that expended in developing turbulence models should be directed to developing higher‐order numerical methods, before the numerical accuracy of predictions of, for example, bluff‐body flows can be made sufficiently high to sustain detailed discussion of the adequacy of turbulence models in such situations.