bluuebunny/crossref_metadata_2025 huggingface dataset:
Micromixing in fermentors: Metabolic changes in Saccharomyces cerevisiae and their relationship to fluid turbulence
Authors: Dunlop E. H. , Ye S. J.
Published: May 2005

Even when microorganisms are grown in highly agitated fermentors, calculation predicts a mismatch between the microscale of the turbulence (where the smallest eddy is typically 50–300 μm diameter) and the cellular dimensions (1–5 μm). The cell thus spends substantial portions of time in an apparently stagnant eddy, depleted of nutrients. The local fluid microscales were measured in a laboratory fermenter to confirm this. Using S. cerevisiae in continuous culture, it is shown that the local microscales influence cell metabolism dramatically. The issues addressed in this study are thus micromixing and microsegregation of reactants and how they influence cell yield.
An HPLC assay for rat liver ferrochelatase activity
Authors: Li Famei , Lim Chang Kee , Peters Timothy J.
Published: May 2005

A rapid, reliable, sensitive and reproducible HPLC method was developed for the assay of ferrochelatase activity in rat liver. The assay was carried out aerobically with Zn2+ and mesoporphyrin or protoporphyrin IX as substrates. Zn‐porphyrins formed were extracted with dimethyl sulphoxide/methanol (30:70, v/v) containing Zn‐deuteroporphyrin as the internal standard for separation and quantification by reversed‐phase chromatography. The Km for mesoporphyrin was 5.9 μM, for protoporphyrin IX 8.8 μM and for zinc 6.0 μM. The specific activities were 33.1 ± 5.0 nmol Zn‐mesoporphyrin or 13.4 ± 2.0 nmol Zn‐protoporphyrin formed per hour per mg of protein for mitochondria and 12.3 ± 2.2 nmol Zn‐mesoporphyrin or 4.6 ± 0.9 nmol Zn‐protoporphyrin per hour per mg of protein for liver homogenate.
Fluorometric analysis of urinary chondroitin sulfate isomers by HPLC using dansylhydrazine as a prelabeling reagent
Authors: Shinomiya Kazufusa , Yamanashi Shigeyuki , Imanari Toshio
Published: May 2005

Chondroitin sulfate isomers (ChS isomers) were digested with chondroitinase ABC, and the unsaturated disaccharides produced were converted into fluorescent dansylhydrazine derivatives and analyzed by HPLC. The proposed method was applied to the determination of relative amounts of ChS isomers in normal human urine and analytical results showed that chondroitin‐6‐sulfate and chondroitin‐4‐sulfate were excreted in large amounts. Moreover, this method was used for the identification of urinary ChS isomers which were extracted from a cellulose acetate strip after carrying out electrophoresis.
High performance liquid chromatographic determination of Picumast and two active metabolites in plasma using on‐line sample preparation
Authors: Besenfelder E.
Published: May 2005

A method for determining Picumast, an antiallergic drug, in plasma by HPLC and column switching has been developed. The system consisted of two precolumns, an analytical column, three pumps, an autosampler and a fluorescence detector. The precolumns (17 × 4.6 mm i.d.) were packed with LiChroprep RPR (a moderately polar reversed phase) and the analytical column with Nucleosil ODS (RP 18, 5 μm). The columns were connected according to the alternating precolumn technique. The mobile phase consisted of 30% CH3CN/70% 0.05M KH2PO4, pH 2.5, with a flow gradient. Detection wavelengths were 333 nm for excitation and 383 nm for emission. The retention times of Picumast, M1 and M2 were 12, 3.6 and 4.0 min, respectively. Total run time was 15 min. The limit of detection was 3 ng/mL for M1 and 1 ng/mL for M2 and Picumast using an injection volume of 150 μL. The recoveries vary between 89% and 97% with standard deviations between 2.4 and 3.3%.
Enantiomeric analysis of phenylpropanolamine in plasma via resolution of dinitrophenylurea derivatives on a high performance liquid chromatographic chiral stationary phase
Authors: Doyle Thomas D. , Brunner Charlotte A. , Vick James A.
Published: May 2005

Racemic phenylpropanolamine was resolved on a high performance liquid chromatographic (HPLC) chiral stationary phase (CSP) as the 3,5‐dinitrophenyl ureide derivative. The CSP was prepared by a simple in situ procedure in which (R)‐(1‐naphthyl)ethyl isocyanate was bound to aminopropyl silanized silica through a urea linkage. The enantiomeric ureides were prepared by a room‐temperature, 60‐second procedure, accomplishing simultaneous extraction and derivatization and utilizing achiral 3,5‐dinitrophenyl isocyanate as reagent. Baseline resolution was readily achieved under normal phase conditions, with a separation factor (α) of 1.16 and a resolution factor (Rs) of 2.2. Elution was complete within 10 min. A limit of detection, by UV at 235 nm, of 250 pg per isomer was established. Feasibility of the procedure for plasma determinations was demonstrated by assay of samples from a canine subject.
Purification of two murine monoclonal antibodies of the IgM class by hydroxylapatite chromatography and gel filtration
Authors: Henniker A. J. , Bradstock K. F.
Published: May 2005

A two‐step method using hydroxylapatite chromatography and gel filtration is described for the purification of two murine monoclonal antibodies of the IgM class. Ascites fluid from each hybridoma was diluted in sodium phosphate buffer (0.01 M, pH 6.8), loaded onto a hydroxylapatite column and eluted with a stepwise sodium phosphate gradient. The immunoreactive protein peaks were concentrated and subjected to gel filtration using either Sephadex G‐200 or Sephacryl S‐200HR. The biological activity of the end‐products was confirmed by complement lysis assay and by indirect immunofluorescence and flow cytometry. The purity of the end‐products as assessed by SDS polyacrylamide gel electrophoresis and densitometry was at least 90%. The methods described produced immunoreactive material with a high level of purity. The procedure for each antibody was reproducible and provides a reliable method for purification of monoclonal antibodies of the IgM class.
Determination of acetazolamide in dosage forms by high performance liquid chromatography
Authors: Gomaa Z. S.
Published: May 2005

A high performance liquid chromatographic assay for the quantitation of acetazolamide in both tablet and injection form is described. Acetazolamide is extracted with 0.005 M NaOH solution containing 0.3 mg/mL sulphadiazine (internal standard).A commercially available μ‐Bondapak C18 cartridge column was used for the separation together with a mobile phase made of acetonitrile, methanol and sodium acetate buffer mixture (10:2:88) (pH 4) at a flow‐rate of 4 mL/min. Retention times of about 2.50 and 3.36 min were obtained for the drug and the internal standard, respectively.
Plasma concentrations of β‐carotene, vitamin A and vitamin E after β‐carotene and vitamin E intake
Authors: Postaire E. , Kouyate D. , Rousset G. , Regnault C. , Lati E. , Bejot M. , Gossioux P. , Hazebroucq G.
Published: May 2005

We have studied the metabolism (absorption) of β‐carotene and vitamin E by assigning eleven volunteers to receive daily two capsules of OENOBIOL, each containing 15 mg of β‐carotene and 15 mg of vitamin E, over 60 days. The β‐carotene, vitamin E and vitamin A plasma levels were then determined using new methods developed in our laboratory. After two months, the actively treated group's median β‐carotene and vitamin E levels were significantly higher than those of a control group. However, no significant change between treated and control groups in the mean of vitamin A (retinol) plasma levels were observed. Treatment with β‐carotene, a vitamin A precursor, does not significantly modify the vitamin A levels. This conclusion had already been observed and it is assumed that a plasma level of β‐carotene equal or higher than 0.3 mg/L reflects a nutritional intake of provitamins sufficient to support homeostasis of retinol (Brubacher et al., 1982).
Separation of human pancreatic carboxypeptidase A isoenzymes by high performance liquid chromatography
Authors: Linder D. , Linder M. , Schade H. , Sziegoleit A.
Published: May 2005

Human pancreatic carboxypeptidase A, which was isolated from a pool of necrobiotic pancreae, crystallized spontaneously and appeared homogeneous in sodium dodecylsulphate polyacrylamide gel electrophoresis. Reversed phase high performance liquid chromatography of the dissolved crystals, however, revealed the presence of two distinct isoenzymes, which were shown by aminoterminal sequence analysis to be only 61% homologeous in their 31 amino terminal amino acids. On the other hand, amino terminal sequences of the isoenzymes were found to be 79% and 87% homologeous with CAP 1 and CPA 2 of the rat, respectively. Thus, the presence of two distinct pancreatic carboxypeptidase A isoenzymes could be clearly demonstrated for the first time in human tissue.
Purity evaluation of aprotinin by high performance liquid chromatography
Authors: Dimov N. , Simeonov S.
Published: May 2005

A separation to the baseline isocratic technique has been developed for the evaluation of the purity of aprotinin by internal normalization. The column used was a 30 nm pore diameter butyl‐bonded silica stationary phase. An exact relationship was found to give an adequate description of the retention of aprotinin using acetonitrile concentrations of 17–22% and NaCIO4 concentrations of 5–50 mmol. It can be used to optimize the mobile phase content for the particular user column and to compensate for possible variations in the retention time of aprotinin, analysed on different batches of butyl‐bonded stationary phases.
Determination of 5,10,15,20‐tetra‐(m‐hydroxyphenyl) chlorin in tissues by high performance liquid chromatography
Authors: Wang Qiang , Altermatt H. J. , Ris H.‐B. , Reynolds Brenda E. , Stewart J. C. M. , Bonnett R. , Lim C. K.
Published: May 2005

A procedure for the extraction and high performance liquid chromatographic (HPLC) determination of the photodynamic therapeutic agent 5,10,15,20‐tetra(m‐hydroxyphenyl)chlorin in human, rat and mouse tissues following intravenous administration of the drug is described. The tissue (tumour, skin, muscle and liver) was homogenized and extracted into a mixture of methanol:dimethyl sulphoxide:water (32:8:1 by vol.) containing, 5,10,15,20‐tetra(p‐hydroxyphenyl)chlorin as the internal standard. The precipitated proteins were removed by centrifugation and the supernatant was separated by reversed phase HPLC on a Hypersil‐ODS column with 77% (v/v) acetonitrile in 0.1% trifluoroacetic acid as the mobile phase. The solute was detected with high sensitivity and specificity by a UV‐VIS detector set at 423 nm.
FT‐IR spectroscopic studies on molecular interactions of cryoprotectant agents with bacteria
Authors: Zeroual Widad , Millot Jean Marc , Choisy Claude , Manfait Michel
Published: May 2005

Fourier transform infrared spectroscopy was used to investigate, without any destructive interference, interactions of the cryoprotective agents, glycerol and dimethyl sulfoxide withBradyrhizobium japonicum. The intracellular spectrum of glycerol, obtained by subtracting the spectrum of control bacteria from that of glycerol‐treated bacteria, showed no differences in infrared features compared to that of pure glycerol. This was not the case when dimethyl sulfoxide treatment was used. The intracellular spectrum displayed important modifications compared to that of the pure chemical. Spectral analysis showed that glycerol and dimethyl sulfoxide uptake required only a few minutes. Moreover, the infrared features resulting from the presence of pure glycerol, in bacteria, were still existent for up to 2 or 3 hours after thawing process. The deconvoluted Amide I and Amide II bands of bacterial proteins reflected important changes in secondary structure after treatment of bacteria with dimethyl sulfoxide (increase in β‐sheet and loss of random coil content). In contrast to glycerol, the cryoprotective action of dimethyl sulfoxide probably involves interactions with a wide range of intrabacterial species. © 1995 John Wiley & Sons, Inc.
Haemosiderin and tissue damage
Authors: Weir Malcolm P. , Gibson John F. , Peters Timothy J.
Published: May 2005

High levels of haemosiderin occur in iron overload syndromes such as idiopathic haemochromatosis or secondary iron overload in thalassaemic patients; haemosiderin is the predominant iron‐storage compound in such cases. It consists of a large aggregate of FeOOH cores, many of which have an incomplete shell of protein, and is probably derived from ferritin by lysosomal proteolysis. In addition, some chemical degradation of the ferritin cores appears to occur on conversion to haemosiderin. Other biochemical components are phosphate and magnesium, which may be adsorbed to the core surface, and perhaps certain lipids. Haemosiderin may have a central role, either directly or indirectly, in iron cytotoxicity and therefore the chemistry and biochemistry of this material warrants further study.
The Clara cell and pulmonary surfactant: A study using selective chemical ablation
Authors: Cottrell R. C. , Foster J. R. , Pelling D. , Herod I. A. , Lee V. S. , Purchase R. , Bayley D. , Miller K.
Published: May 2005

Administration of 3‐hydroxymethylfuran‐N‐ethylcarbamate (HFC) to female hamsters via the jugular vein under pentobarbitone anaesthetic at 20 mg per kg body weight produced pronounced necrosis of the Clara cells without apparent morphological effect on other cell types as judged by transmission electron microscope examination. The surfactant material recoverable by minimal lavage followed by purification by sucrose gradient ultracentrifugation increased, reaching a maximum around 48 h after treatment. At this time static pressure/volume measurements on isolated lungs indicated an increase in airway surface compliance. Lavageable surfactant phospholipid composition was examined by 31P nuclear magnetic resonance (n.m.r.). The distribution of phospholipids between the various classes was unchanged by HFC treatment. No change in the total lung surfactant pool size was seen. These results are discussed in relation to the possible roles of the Clara cell in influencing airway surfactant levels.
Localization of putative gonadotrophin releasing hormone receptor protein in the anterior pituitary
Authors: Zolman Joseph C. , Theodoropoulos Theodor J.
Published: May 2005

Specific binding of a fully biologically active 125I‐gonadotrophin releasing hormone (GnRH) to isolated anterior pituitary cells is time dependent, saturable and the concentration dependent binding curves exhibit positive cooperativity. Binding to intact or solubilized plasma membranes and an affinity purified GnRH receptor protein reveals in all instances multiple high affinity binding sites. Thus, GnRH receptor protein appears to be an intrinsic constituent of the cell membrane, and perhaps, other membranous organelles. To investigate the latter, the binding of 125I‐GnRH to various subcellular fractions was studied and its affinity and time requirements determined. GnRH binding to plasma membranes and secretory granules was to multiple high affinity sites, while that to nuclei and microsomes was to a single high affinity site. Binding was 1.83 ± 0.07, 0.78 ± 0.04, 0.31 ± 0.03 and 0.27 ± 0.03 fmol μg−1 protein for isolated plasma membranes, secretory granules, microsomes and nuclei, respectively, after 30 min incubation with 10−9 M GnRH. The magnitude of binding to microsomes did not change during the incubation period. It did not show any decrease (p > 0.5) in isolated nuclei and plasma membranes, except for the 24 h time period, when a significant drop (p < 0.001) was seen. Binding to the secretory granule fraction culminated at 15 min and then decreased (p < 0.001) steadily to a non‐detectable level at 24 h. Thus GnRH receptor protein or its portion may be an integral part of some membranous particles in the anterior pituitary cells. A single, low‐capacity binding site may, or may not suggest the presence of a structurally incomplete form of the receptor protein in microsomes and nuclei. Binding to the secretory granules fraction exhibited only a relatively minor temporal difference compared to the plasma membrane, which may have resulted from an inappropriate conformational state of the receptor protein. Only the binding to the plasma membrane exhibited appropriately both the affinity and temporal requirements of the intact GnRH receptor protein in vitro and in vivo.
In vitro trophic effects of synthetic ACTH1–24
Authors: Jolink D. , Drexhage H. A. , van der Gaag R. D.
Published: May 2005

In vitro trophic effects of adrenocorticotrophin1–24 (ACTH1–24, Synacthen) on adrenal cells were studied, using an in vitro assay system of guinea‐pig adrenal segments kept in organ culture. Two separate methods for detecting growth activity were used, namely the measurement of thymidine kinase and a nucleic acid cytophotometric method. Synthetic ACTH was able to induce growth in the adrenal explants at very low concentrations (10–25 fg ml−1). Biphasic dose‐response curves were obtained, comparable to those described for other cytochemical bioassays. The principles of this assay system may allow the development of a new bioassay for the measurement of plasma concentrations of ACTH or antibodies mimicking the growth effect of this trophic hormone.
Scanning cytophotometric analysis of myocardial nucleic acid and chromatin changes in soman toxicated rabbits
Authors: Martin Lee J. , Doebler Jeffrey A. , Swisher John W. , Anthony Adam , Shih Tsung‐Ming
Published: May 2005

Myocardial nucleic acid responses were analysed in New Zealand White rabbits 20 min–1 h and 6–8 h following single subcutaneous injections of soman (20, 30, or 40 μg kg−1). Scanning‐integrating microdensitometry was used to quantify Azure B‐RNA and Feulgen–DNA (F‐DNA) levels, and changes in the suseptibility of chromatin to Feulgen acid hydrolysis (F‐DNA reactivity) of individual ventricular myocardial cells. With a dosage of 20 μg kg−1 soman, no RNA alterations were evidenced at 1 h whereas at 6–8 h myocardial cells exhibited higher RNA levels and an increase in F‐DNA reactivity of chromatin. With dosages of 30 and 40 μg kg−1 soman there was an augmentation in RNA levels and in the acid hydrolysability of nuclear chromatin at both 20 min–1 h and 6–8 h. It is postulated that the observed cellular transformations represent a compensatory augmentation in myocardial metabolic functioning presumably in response to an increased functional demand on the ventricular myocardium. The absence of cytopathic or cytochemical evidence of impairment in nucleic acid metabolism is inconsistent with the premise that soman exerts direct cytotoxic effects on rabbit myocardium.
Synthesis and levels of organic phosphates in erythrocytes during avian development: Specific formation of BPG and IP5 in two distinct populations from young chicks
Authors: Ruiz‐Ruano A. , Martin M. , Luque J.
Published: May 2005

Two generations of red cells (embryonic and definitive), different types of haemoglobins, and special organic phosphates involved in the control of haemoglobin oxygenation (2:3‐bisphosphoglycerate, BPG, and inositol‐5‐phosphate, IP5), have been found progressively during development of the chick. Levels of both organic phosphates, as well as activities of the enzymes involved in BPG synthesis (2:3‐bisphosphoglycerate synthase, BPGM) and IP5 formation (phytase), were studied in the erythrocyte populations from embryo, young and adult chickens. Measurement of specific activities of BPGM and phytase in the two subpopulations present in young chickens showed that these phosphates could be specifically and predominantly formed in these two red cell populations.
Induction of cytochrome(s) P450‐dependent drug metabolism in cultured MH1C1 hepatoma cells
Authors: Ferro Margherita , Bassi Anna M. , Marinari Umberto M. , Nanni Giorgio , Chiarpotto Elena , Poli Giuseppe , Dianzani Mario U.
Published: May 2005

A cell line derived from a Morris hepatoma, MH1C1, was examined for its in vitro expression of monooxygenases. These cells were found to contain different forms of cytochrome P450, as shown by the response to inducers, namely phenobarbital (PB), 3‐methylcholanthrene (MC) and metyrapone (MP). MH1C1 cell monolayers exposed to PB or MC showed an increase in the concentration of two spectrally distinct forms of cytochrome P450. The PB and MC treatments elicited enzyme activities towards the substrates aminopyrine and benzo(a)pyrene, respectively. The cell treatment with metyrapone led to a simultaneous stimulation of aminopyrine demethylase and benzo(a)pyrene hydroxylase activities, so underlining the peculiar features of this inducer.
Cell cycle effects of hypertonic stress on various human cells in culture
Authors: Pellicciari C. , Filippini C. , De Grada L. , Conti A. M. Fuhrman , Romanini M. G. Manfredi
Published: May 2005

Long‐term exposure to hypertonic (HT) culture media has been found to perturb the cell cycle and change gene expression in various animal cell types. A lower growth rate, with exit of cells from the cycling compartment has been observed previously in human transformed EUE. cells. The aim of this study was to investigate if the kinetic changes after long‐term HT stress, were typical of transformed cells or could be also found in primary cultures of normal cells. Human transformed cells from normal and neoplastic tissues, and normal human cells of epithelial and connective origin have been studied. After the incorporation of bromodeoxyuridine (BrdUrd), the frequency of S‐phase cells was estimated by dual‐parameter flow cytometry of DNA content versus BrdUrd immuno‐labelling; the total growth fraction was also estimated, after immunolabelling with an anti‐PCNA antibody. We also investigated, by polyacrylamide gel electrophoresis, changes in the amount of a 35 kDa protien band, which increased in EUE cells grown in an HT medium, and which may be directly involved in cell resistance to hypertonicity. Lower BrdUrd labelling indices and higher frequencies of cells in the G0/1 range of DNA content were common features of all the cells in HT media, irrespective of their tissue of origin; other cycle phases may also be involved, depending on the cell type considered. The mechanisms by which cells cope with the HT environment could however, differ, since only some cell types showed an increase of the 35 kDa stress protein found originally in HT EUE cells.
Effects of choline and ethanolamine on the synthesis and breakdown of the inositol phospholipid (PI) system in Tetrahymena
Authors: Kovács P. , Csaba G.
Published: May 2005

Lower concentrations of choline chloride and ethanolamine (10−3 M; 10−5 M) increased phosphatidyl inositol (PI), phosphatidyl inositol monophosphate (PIP) and phosphatidyl inositol bisphosphate (PIP2) level of Tetrahymena, while higher concentrations (10−2 M) decreased them. These two substances also influenced, however in a less obvious way, the transformation of inositol phospholipids. The experiments draw attention to the sensitivity of the precursors of the second messenger system at a phylogenetically low level.
Real‐time filtering of data from mobile, passive remote infrared sensors with principal component models of background
Authors: Brown S. D.
Published: May 2005

Real‐time monitoring of pollutant levels from a mobile measuring platform requires fast, flexible data analysis methods. This paper reports a method for rapid analysis of passive remotely sensed infrared data with the aid of a Kalman filter. The background spectra produced by emission from the atmosphere are modelled at the start of the data collection sequence with a simple principal components model obtained by eigenanalysis of the initial ‘blank’ data taken with the spectrometer. The species of interest are included in the state space model by a separate measurement of their infrared spectra. It is demonstrated that for best filter performance in detecting the simulated pollutant species SF6 in the atmosphere, a filter model with two principal components describing the emission background works best. The filter ‘maps’ of SF6 closely follow the integrated spectral intensities measured after removal of suitable backgrounds.
Expectation–maximization algorithm for regression, deconvolution and smoothing of shot‐noise limited data
Authors: Bialkowski S. E.
Published: May 2005

A simple algorithm for deconvolution and regression of shot‐noise‐limited data is illustrated in this paper. The algorithm is easily adapted to almost any model and converges to the global optimum. Multiple‐component spectrum regression, spectrum deconvolution and smoothing examples are used to illustrate the algorithm. The algorithm and a method for determining uncertainties in the parameters based on the Fisher information matrix are given and illustrated with three examples. An experimental example of spectrograph grating order compensation of a diode array solar spectroradiometer is given to illustrate the use of this technique in environmental analysis. The major advantages of the EM algorithm are found to be its stability, simplicity, conservation of data magnitude and guaranteed convergence.
Box–Cox transformations in the analysis of compositional data
Authors: Rayens William S. , Srinivasan Cidambi
Published: May 2005

The statistical analysis of compositional data is of fundamental importance to practitioners in general and to chemists in particular. The existing methodology is principally due to Aitchison, who effectively uses two transformations, a ratio followed by the logarithmic, to create a useful, coherent theory that in principle allows the plethora of normal‐based multivariate techniques to be used on the transformed data. This paper suggests that the well‐known class of Box–Cox transformations can be employed in place of the logarithmic to significantly improve the existing methodology. This is supported in part by showing that one of the most basic problems that Aitchison managed to overcome, namely the specification of an interpretable covariance structure for compositional data, can be resolved, or nearly resolved, once the ratio transformation has been applied. Hence the resolution is not directly dependent on the logarithmic transformation. It is then verified that access to the general Box–Cox family will allow a more accurate use of the normal‐based multivariate techniques, simply because better fits to normality can be achieved. Finally, maximum likelihood estimation and some associated asymptotics are employed to construct confidence intervals for ratios of the true, unknown compositional constituents. Heretofore this had not been done even in the context of the logarithmic transformation. Applications to real data are presented.
Finding causes of outliers in multivariate environmental data
Authors: Garner Forest C. , Stapanian Martin A. , Fitzgerald Kirk E.
Published: May 2005

Multivariate outliers in environmental data sets are often caused by atypical measurement error in a single variable. From a quality assurance perspective it is important to identify these variables efficiently so that corrective actions may be performed. We demonstrate a procedure for using two multivariate tests to identify which variable ‘caused’ each outlier. The procedure is tested with simulated data sets have have the same correlation structure as selected water chemistry variables from a survey of lakes in the Western United States. The success rates are evaluated for three of the variables for sample sizes of 50 and 100, significance levels of 0.01 and 0.05 and various amounts of mean shift. The procedure works best for highly correlated variables.
Estimation of errors in absorbance ratio measurements
Authors: Sharaf Muhammad , Arroy Gary , Perkins Ron
Published: May 2005

Ratio measurements are commonly used to address a variety of analytical problems in environmental, forensic and pharmaceutical laboratories. In absorbance ratioing techniques, analytical chemists rely on the spectral features of the analyte(s) of interest. The absorbances at two wavelengths are monitored and the ratio of these two absorbances is computed. This ratio is then used to confirm the identity of the analyte(s) of interest, the purity of a product of the overlap of chromatographic peaks. These decisions often have far‐reaching consequences (e.g. the identification of the source, biogenic or petrogenic, of hydrocarbons in biological tissues or water). Given the cost and the liabilities associated with such decisions, it is unfortunate that these ratios are seldom reported with any statistical confidence. The purpose of this study is to delineate the parameters that affect absorbance ratio measurements. The models that can be used to estimate the statistical confidence in these measurements are derived and evaluated experimentally. The results show that these models can estimate the relative standard deviations in absorbance ratios accurately. They can also estimate the effect of signal‐to‐noise ratio and the choice of wavelengths on the precision of absorbance ratios.
On confidence intervals for the product of three means of three normally distributed populations
Authors: Yfantis E. A. , Flatman G. T.
Published: May 2005

In many environmental applications, such as exposure assessment and risk modelling, the desired estimate is a random variable computed as the product of three independently distributed random variables. These variables may not necessarily have the same mean and variance. The method for finding the 100(1 − α)% confidence interval for the mean of the product random variable has been proposed by some practitioners as the product of the 100(1 − α)% confidence interval of the three means. In this paper we show that the distribution of the product of three independent normal variables is not normal. We find the mean and variance of the product distribution. Further, we show that although the mean of the product is equal to the product of the means, the product of the three confidence intervals is not a good approximation of the confidence intervals for the mean of the product variable. The confidence interval of the mean of the product variable may be estimated by computer simulation. An algorithm for estimating the confidence interval for the mean of the product random variable is given. The program implementing this algorithm is given as an appendix.
Error analysis of the generalized rank annihilation method
Authors: Booksh Karl , Kowalski Bruce R.
Published: May 2005

The effects of correlated and uncorrelated random errors on the precision of predicted quantitative and qualitative information obtained by analysis with the generalized rank annihilation method (GRAM) are shown. These are discussed in terms of propagation of errors through the algorithm. The effects of colinearity, noise level and noise distribution are compared and discussed.
Application of a genetic algorithm to feature selection under full validation conditions and to outlier detection
Authors: Leardi Riccardo
Published: May 2005

Genetic algorithms have been proved to be a very efficient method in the feature selection problem. However, as for every other method, if the validation of the results is performed in an incomplete way, erroneous conclusions can be drawn. In this paper a development of a previous genetic algorithm is presented so that a full validation of the results can be obtained. Furthermore, this algorithm has been shown to perform very well also as an outlier detector, allowing easy identification of the presence of outliers even in cases where the ‘classical’ techniques fail.
Factor Analysis of Deuterium Isotope Effects on 13C NMR Chemical Shifts in Schiff Bases
Authors: Dominiak Paulina M. , Filarowski Aleksander , Hansen Poul Erik , Woźniak Krzysztof
Published: May 2005

We have analyzed deuterium isotope effects on 13C chemical shifts in a series of o‐hydroxy Schiff bases by applying factor analysis. Two orthogonal factors were obtained that explain about 80 and 10 % of the variance of the data. The numerical values of these factors can be related to 1H NMR chemical shifts of the proton involved in the intramolecular bonds δ(XH) (X=O or N). Such a relation allows one to identify clusters of compounds with different tautomeric forms of hydrogen bonding. Application of a similar approach to solution 13C NMR chemical shifts produces three important factors, which have a different structure to factors describing isotope effects. This illustrates well the different nature of chemical shifts and isotope effects. The three factors explain about 54, 15, and 13 % of variance. They can be rationalized and are strongly related to the electronic properties and location of substituents.
The DMAP‐Catalyzed Acetylation of Alcohols—A Mechanistic Study (DMAP=4‐(Dimethylamino)pyridine)
Authors: Xu Shangjie , Held Ingmar , Kempf Bernhard , Mayr Herbert , Steglich Wolfgang , Zipse Hendrik
Published: May 2005

The acetylation of tert‐butanol with acetic anhydride catalyzed by 4‐(dimethylamino)pyridine (DMAP) has been studied at the Becke3 LYP/6‐311+G(d,p)//Becke3 LYP/6‐31G(d) level of theory. Solvent effects have been estimated through single‐point calculations with the PCM/UAHF solvation model. The energetically most favorable pathway proceeds through nucleophilic attack of DMAP at the anhydride carbonyl group and subsequent formation of the corresponding acetylpyridinium/acetate ion pair. Reaction of this ion pair with the alcohol substrate yields the final product, tert‐butylacetate. The competing base‐catalyzed reaction pathway can either proceed in a concerted or in a stepwise manner. In both cases the reaction barrier far exceeds that of the nucleophilic catalysis mechanism. The reaction mechanism has also been studied experimentally in dichloromethane through analysis of the reaction kinetics for the acetylation of cyclohexanol with acetic anhydride, in the presence of DMAP as catalyst and triethylamine as the auxiliary base. The reaction is found to be first‐order with respect to acetic anhydride, cyclohexanol, and DMAP, and zero‐order with respect to triethyl amine. Both the theoretical as well as the experimental studies strongly support the nucleophilic catalysis pathway.
Entwicklungslinien im Bau von Wärmeaustauschern
Authors: Grassmann P.
Published: May 2005

Wärmeaustauscher für große Luftzerlegungsanlagen oder Gasturbinen sowie Kühler von Flugzeugen verlangen möglichst hohen Wärmeübergang bei möglichst niedrigem Druckabfall. Da die gleiche Aufgabe auch häufig in der Verfahrenstechnik gestellt wird, können die in neuerer Zeit zur Lösung dieses Problems beschrittenen Wege auch für den Chemie‐Ingenieur richtungsweisend sein. Auch Bewertungsmaßstäbe, durch die das Verhältnis von Wärmeübergang zu Druckverlust gekennzeichnet wird, verdienen in diesem Zusammenhang Beachtung. Die Kühlung von Raketentriebwerken erfordert die sichere Beherrschung von Wärmestromdichten bis etwa 10 · 605 kcal/m2h. Besonders durch die Entwicklung der Atombrenner wurde der Wärmeübergang an flüssige Metalle genauer erforscht. Diese Untersuchungen sind wegen der sehr kleinen Prandtlzahlen flüssiger Metalle auch für die Theorie des Wärmeübergangs wichtig.
Schwingungstechnik in der chemischen Industrie
Authors: Dunker H. W.
Published: May 2005

Die Schwingungstechnik hat in den letzten Jahren auch in der chemischen Industrie ständig an Bedeutung gewonnen. Einmal ergaben sich in vorhandenen Anlagen bei Erweiterungen Schwierigkeiten, so daß man auf neue Erkenntnisse der Schwingungstechnik angewiesen war, zum anderen aber wollte man auch bei Neuplanungen die Vorteile schwingungstechnischer Gründung von Maschinen von vornherein ausnutzen. Im folgenden wird eine Übersicht gegeben über die sich bietenden Probleme und deren praktische Lösungen, wie sie mit Erfolg bereits verwirklicht sind oder z. Zt. verwirklicht werden.
Zur Physik der Pulverdispersoide
Authors: Nassenstein H.
Published: May 2005

Im folgenden werden die Grundzüge der Physik der Festkörper, soweit sie zum Verständnis der Pulverdispersoide notwendig sind, behandelt. Der Einfluß von mechanischem Zerkleinerungsgrad, Eigengewicht, Kristallstruktur und ‐oberfläche auf das Verhalten von Pulvern wird dargelegt.
Über die Technologie und Verfahrenstechnik der Herstellung von Antibiotika
Authors: Öppinger Heinz , Schaefer Heinz
Published: May 2005

Am Beispiel des Penicillin wird die großtechnische Herstellung der Antibiotika behandelt. Besonderheiten, die sich für die Reinigung von Streptomycin und Aureomycin aus ihren chemischen Eigenschaften ergeben, werden berücksichtigt.
Neuzeitlicher Straßenbau in chemischen Betrieben
Authors: Holzapfel Adolf
Published: May 2005

Die Werkstraße hat zumindest zwei Funktionen zu erfüllen: Abwicklung des Verkehrs und Unterbringung der Versorgungsleitungen. Es wird dargelegt, wie die Aufteilung des oberirdischen und des unterirdischen Querschnittes den baulichen und betrieblichen Belangen am besten gerecht wird.
Die Gelatinekapsel, ihre Herstellung und ihre Verwendung
Authors: Kipphan Karl
Published: May 2005

Ein neues vollkontinuierliches Herstellungsverfahren von Gelatinekapseln führte zu wesentlicher Qualitätsverbesserung und Verbilligung der Kapsel und erlaubt genauere Dosierung der Füllung.
Bestimmung des Feinstaubgehalts der Luft Eine Übersicht über Meßgeräte und Meßverfahren
Authors: Hasenclever D.
Published: May 2005

Es gibt zur Zeit 30 Staubmeßgeräte, von denen jedes oft einen nur engen, ganz bestimmten Anwendungsbereich hat. Bei Benutzung eines an sich richtig arbeitenden Meßgerätes unter falschen Voraussetzungen kommt man zu Meßergebnissen, die zu Fehlurteilen führen. Der Überblick über die derzeitigen Geräte zur Messung von gesundheitsschädlichen Stäuben unter 5 μ Dmr. behandelt zugleich den jeweiligen Anwendungsbereich der verschiedenen Meßverfahren.
Wärmeübergang an nicht‐Newtonsche Flüssigkeiten bei laminarer Rohrströmung
Authors: Grigull U.
Published: May 2005

Für eine strukturviscose Flüssigkeit, deren Reibungsgesetz dem Potenzansatz nach Ostwald/de Waele entspricht, sowie für eine Paste nach Bingham werden die Temperaturverteilungen und die Nußelt‐Zahlen der laminaren Rohrströmung angegeben. Als Randbedingung dient der Fall konstanter Wärmestromdichte an der Wand bzw. eine linear mit der Rohrlänge ansteigende Wandtemperatur. Die Stoffwerte werden als temperaturunabhängig angenommen.
Titan im chemischen Apparatebau
Authors: Fischer R. W. , Van Kann H.
Published: May 2005

Die fortschreitende technische Entwicklung besonders auch in der chemischen Industrie macht die Verwendung von immer hochwertigeren Werkstoffen erforderlich. Das neue Metall Titan eröffnet dem chemischen Apparatebau zahlreiche Möglichkeiten durch seine Korrosionsbeständigkeit in Verbindung mit den besonderen mechanischen Eigenschaften. Die Titan‐Legierungen brauchen hier nicht ausführlich behandelt zu werden, da noch keine auf dem Markt ist, deren Korrosionsbeständigkeit den unlegierten Titan‐Sorten überlegen ist.
Über die Methodik des Fraktionenschneidens bei der Chromatographie und einen verbesserten photoelektrischen Fraktionensammler
Authors: Grubhofer N. , Lwowski W.
Published: May 2005

Die verschiedenen technischen Möglichkeiten für die Konstruktion eines Fraktionensammlers werden kritisch miteinander verglichen, wobei sich die Feststellung ergibt, daß das ursprünglich von Stein und Moore angegebene Verfahren am meisten Vorteile bietet. In Anlehnung an dieses Vorbild wird ein Fraktionensammler beschrieben, welcher im wesentlichen folgende Verbesserungen aufweist: Photoelektrische Anlage und Verstärker stark vereinfacht, Flüssigkeit berührt nach dem Austritt aus der Säule keinen Teil des Gerätes, Zähler mit Untersetzer neu konstruiert und umschaltbar auf Zeitdosierung, leicht auswechselbare Fraktionenteller.
Verwertungsmöglichkeiten kohlenoxydhaltiger Abgase zur Synthese von Kohlenwasserstoffen
Authors: Kölbel Herbert
Published: May 2005

Da sich synthetisch hergestellte Kohlenwasserstoffe wegen ihrer Reinheit und einheitlichen geradkettigen Struktur hervorragend als Ausgangsstoffe für die Petro‐Chemie eignen, wird im folgenden untersucht, ob sich nicht billige kohlenoxydhaltige Abgase für die Kohlenwasserstoff ‐ Synthese eignen. Hierfür kommen die kohlenoxyd‐reichen Abgase aus der Carbid‐Erzeugung mit bis zu 90% CO und die kohlenoxyd‐armen Gichtgase der Eisenverhüttung mit 30 bis 35% CO in Frage.
Gerät zur kontinuierlichen Messung des Nitriervermögens von Nitriersäuren
Authors: Krupp H. , Letschert W.
Published: May 2005

Es wird ein neues Meßgerät beschrieben, das die bei der Reaktion zwischen Nitriersäure und Benzol auftretende Wärmetönung mißt und somit das Nitriervermögen von Nitriersäuren fortlaufend bestimmt.
Zusammenhang zwischen Druckverlust und Rektifizierwirkung in Füllkörperkolonnen
Authors: Brauer H.
Published: May 2005

Druckverlust und Rektifizierwirkung wurden in Abhängigkeit von der Flüssigkeitsbelastung bei 13 verschiedenen Füllkorperarten in einer Füllkörpersäule von 37 mm Dmr. und 1 m Packungshöhe gemesen. Als Testgemisch diente n‐Heptan/Methylcyclohexan. Die Druckverlust‐ und die Rektifizierkurven, aufgetragen über dem Flüssigkeitsstrom, zeigen bei denselben Flüssigkeitsbelastungen Knickpunkte, woraus sich ein logarithmisches Geradliniengesetz zwischen der theoretischen Bodenzahl und dem Druckverlust ergibt.
Grundsätzliches über Wartung von pH‐Meßanlagen
Authors: Lieneweg Fritz
Published: May 2005

Um in Betrieben zuverlässige pH‐Messungen zu gewährleisten, müssen schon beim Planen der Anlage sorgfältige Überlegungen und Voruntersuchungen angestellt werden. Während des Betriebes sind eine Reihe von Wartungsmaßnahmen nötig, die sich nicht nur auf die Elektrodenketten, sondern auch auf die pH‐Meßzusätze bzw. pH‐Meter einschließlich Verstärker und auf die Zuleitungen zwischen pH‐Geber und Meßzusatz erstrecken. Auch das Verhalten des pH‐Gebers selbst ist zu prüfen. Es wird gezeigt, daß für die Wartung von pH‐Meßanlagen unabhängig von der Wahl und Art der Elektrodenkette und des Verstärkers im Meßzusatz bzw. pH‐Meter grundsätzlich gleichartige Gesichtspunkte maßgebend sind. Diese werden sowohl für Meßanlagen mit Glas‐Elektroden als auch für Meßanlagen mit Metall/Metalloxyd‐Elektroden (z. B. Antimon‐Elektroden) aufgezeigt.
Laboratorien für Radioisotope
Authors: Schanze Ulrich O.
Published: May 2005

Für Arbeiten mit radioaktiven Isotopen, die sich als wertvolle Hilfsmittel in allen Zweigen der Naturwissenschaft und Technik erwiesen haben, sind spezielle Geräte und Schutzmaßnahmen erforderlich. Deshalb soll hier über Isotopen‐Laboratorien berichtet werden, wie sie besonders für chemische und ähnliche Zwecke geeignet erscheinen.
Über die Vorausberechnung chemischer Reaktionsapparate
Authors: Schoenemann K. , Hofmann Hanns
Published: May 2005

An drei speziellen Beispielen für eine Gasphase‐, Flüssigphase‐ und Gemischtphase‐Reaktion werden die Möglichkeiten für eine Vorausberechnung von Reaktionsapparaten für die chemische Industrie summarisch aufgezeigt. Der Beitrag soll vor allem im Hinblick auf die zunehmende Bedeutung der kontinuierlich‐katalytischen Arbeitsweise zu einer verstärkten Anwendung der technischen Reaktionskinetik anregen, zumal sich dieses gesamte Gebiet mit wenigen Grundgesetzen beherrschen läßt.
Thermodynamik technischer Methan‐Reaktionen (am Beispiel der Bildung von Acetonitril aus Methan und Chlorcyan)
Authors: Fuchs W. , Andres K. H. , Plenz J. , Veiser O.
Published: May 2005

Nach einer thermodynamischen Behandlung der Umsetzungsmöglichkeiten zwischen Methan mit verschiedenen Elementen, einigen anorganischen sowie organischen Verbindungen wird die Umsetzung zwischen Methan und Chlorcyan zu Acetonitril eingehend behandelt. Dabei wird der Einfluß der Temperatur, der Strömungsgeschwindigkeit sowie des Mischungsverhältnisses auf die Ausbeute untersucht.
Betriebsüberwachung durch kontinuierliche Ultrarot‐Gasanalyse. Ein Betriebsgerät mit einem Strahlengang und Wechseldruckmodulation des Meßgases
Authors: Hummel Heinz
Published: May 2005

Es wird ein UR‐Gasanalysator mit einem Strahlengang beschrieben. Durch Erzeugung eines konstanten Wechseldruckes in einer Meßküvette wird eine Wechselstrahlung gewonnen, welche mit einem Wechselstrahlungsempfänger und einem nachgeschalteten Wechselspannungsverstärker gemessen wird.
Zur Darstellung der Leistungsaufnahme von Rührern
Authors: Siemes W. , Rahmel W. , Thrun E.
Published: May 2005

Die Darstellung der Leistungsaufnahme von Rührern mit Hilfe der konventionellen Kennzahlen führt teilweise zu Schwieriakeiten bei der Ermittlung der Leistungsfunktion. Die Einführung neuer Kenngrößen beseitigt diese Schwierigkeiten, wie an einigen Beispielen gezeigt wird. Dabei ergibt sich eine für Newtonsche Flüssigkeiten anscheinend im gesamten Bereich technischer Rührvorgänge gültige Beziehung zwischen diesen Kennzahlen.
Konstruktion und Betrieb des Drehrohres, dargestellt am Beispiel des Zement‐Drehofens
Authors: Milowiz Kurt
Published: May 2005

Das Drehrohr wird in der Verfahrenstechnik als Kugelmühle für Trocken‐ und Naßmahlung, Stabmühle, Mischtrommel, Trommelscheider, Wärmeaustauscher, Kühler oder Röhrentrockner und in seinen größten Abmessungen als Drehrohrofen angewendet. Am Beispiel des Zement‐Drehofens werden die konstruktiven Probleme beim Antrieb und der Lagerung erörtert. Abschließend werden praktische Erfahrungen bei der Wartung der Öfen mitgeteilt.
Erforschung extrem schneller Vorgänge. Bericht von der IV. Internationalen Tagung für Kurrzzeitphotographie und Hochfrequenzkinematographie
Authors: Thomer G. , Schall R.
Published: May 2005

Es gibt ‐ über die ganze Welt verteilt ‐ nur etwa zehntausend lngenieure und Physiker, die sich mit der Erforschung extrem schneller Vorgänge befassen. Alle Zwei Jahre versammeln sich einige Hundert von ihnen, um in einer internationalen Tagung neue Fors chungsergebnisse, auf apparativem Gebiet wie auch auf dem Sektor der Anwenungen, auszutauschen. Die IV. Tagung dieser Art, die vom 22. bis 26. September 1958 in Köln stattfand, war deshalb besonders interessant, weil zum ersten Mal Forscher ausder Sowjetunion, wo die Kurzzeitphotographie im Zusammenhang mit der Entwicklung von Raketen, nuklearen Waffen und Fusionsreaktoren beträchtlich vorangetrieben wurde, ihre neuen Geräte vorstellten und die westlichen Kollegen mit den von ihnen erzielten Leistungen überraschten.
Umlaufhomogenisierung als neues Verfahren
Authors: Berg G. P. W.
Published: May 2005

Bei der Kreislaufmahlung und der später entwickelten Umlaufhomogenisierung wird dem Zerkleinerungs‐ bzw. Mischvorgang ein Trennvorgang nachgeschaltet, wodurch eine Energieersparnis erreicht wird.
Optimalprinzipien für die Anreicherung von schwerem Wasser in Heiß‐Kalt‐Kolonnen Teil II: Die Anreicherungskaskade, das Abstreifsystem und die Übertragungskolonne
Authors: Bier K.
Published: May 2005

Die in einer früheren Arbeit angestellten Optimalbetrachtungen über die Anreicherung von schwerem Wasser in Heiß‐Kalt‐Kolonnen werden auf eine aus mehreren Heiß‐Kalt‐Kolonnenpaaren bestehende Trennkaskade ausgedehnt. Außerdem werden die mit der Erhöhung der Deuterium‐Ausbeute durch ein als Abstreifsystem wirkendes HeißKalt‐Kolonnenpaar und die mit dem Einsatz einer Übertragungskolonne zusammenhängenden Fragen diskutiert.
Verwendung radioaktiver Stoffe in der Verfahrenstechnik
Authors: Götte Hans
Published: May 2005

In den letzten Jahren hat sich der Anwendungsbereich für radioaktive Stoffe in der Chemie und Technik stark erweitert. Es werden einige Beispiele beschrieben, wie die Messung von Strömungsgeschwindigkeiten in Rohren, die Markierung von Grenzzonen zwischen verschiedenen Chargen, die Bestimmung von Mischungsvorgängen sowie von Durchlaufzeiten, Volumen und Durchsatz bei technischen Prozessen.
Anlagen zur Druckdestillation von Ammoniak‐Wasser
Authors: Niebergall W.
Published: May 2005

Die bei den verschiedenen Verfahren benutzten Schaltungen und Anordnungen der Druckdestillation von Ammoniak‐Wasser werden beschrieben; dabei wird auch die Frage behandelt, ob für die Beheizung der Kolonne unmittelbare Dampfeinblasung in den Kolonnensumpf oder ein besonderer Wärmeaustauscher zweckmäßiger ist. Zur Berechnung derartiger Ammoniak‐Kolonnen, insbesondere zur Bestimmung der Rücklaufwärme und der theoretischen Bodenzahl von Abtriebs‐ und Verstärkungssäule, läßt sich mit Vorteil das bekannte i,ζ‐Diagramm von Merkel und Bosnjakovic verwenden.