bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface‐enhanced Raman scattering of CO2 dissolved in aqueous colloidal solutions of silver and gold
Authors: Kneipp Katrin , Wang Yang , Berger Andrew J. , Dasari Ramachandra R. , Feld Michael S.
Published: May 2005

The observation of surface‐enhanced Raman scatterings (SERS) from CO2 molecules dissolved in aqueous solutions of silver and gold colloids measured with 850 nm near‐IR excitation is reported. Different types of surface enhancement and surface‐enhanced Raman spectra were observed. The SERS spectrum of CO2 on colloidal gold is in good agreement with the spectrum of CO2 dissolved in water. Two different types of SERS spectra were found for CO2 on colloidal silver. They can be assigned to physisorbed and/or weakly chemisorbed CO2 molecules and to strongly bonded CO2 ‐ negatively charged surface radicals, respectively. The enhancement factor for the stretching mode of carbon dioxide is estimated to be of the order of 102−104, depending on the kinds of metal and types of adsorption, which demonstrates that SERS on colloidal silver or gold particles in solution offers possibilities for detecting CO2 dissolved in liquids at low concentrations.
Resonance Raman detection of two conformers for the cyanide adduct of cytochrome c peroxidase and their pH dependence
Authors: Rajani Cynthia , Kincaid James R.
Published: May 2005

The resonance Raman spectra of the adducts of cytochrome c peroxidase with four cyanide isotopomers (12C14N−, 13C14N−, 12C15N− and 13C15N−) are presented. The spectra reveal the presence of two conformers, an essentially linear conformer whose v(Fe—C) and δ(FeCN) modes occur at 445 cm−1 and 407 cm−1, respectively (at pH 10) and a bent conformer which exhibits two modes at 355 cm−1 and 445 cm−1 (at pH 10). At pH values below 7, the linear form v(Fe—C) shifts to ∼455 cm−1 in response to protonation of the distal histidyl imidazole (which strengthens the Fe—C bond). The stretching mode of the bent form experiences only a slight shift. This smaller shift of the bent form is consistent with the proposal that the bent form originates as a consequence of hydrogen bond formation with the off‐axis proton donor group of arginine (which is protonated at both pH values). The overall spectral response to pH changes reflects interactions with the bound ligand which may be important for heterolytic bond cleavage.
Raman study of the phase transition in LiTa0.9Nb0.1O3 single crystal
Authors: Ge Yun‐Cheng , Zhao Chao‐Zhong
Published: May 2005

The Raman spectra of LiTa0.9Nb0.1O3 single crystal were studied as a function of temperature between 300 and 1000 K. When heated above 900 K, the crystals transform from the ferroelectric phase to the paraelectric phase, and the Raman data suggest that the phase transition is second order. The softening of an A1 mode was observed, but the ‘soft mode’ hardened at 120 cm−1. The mechanism of the phase transition is likely to be of the order‐disorder type.
Dynamic rheological behavior of wheat glutens during heating
Authors: Hayta Mehmet , Schofield J David
Published: May 2005

Creep and dynamic rheological tests indicated that addition of redox additives directly into gluten or into flour before gluten extraction resulted in differences in rheological parameters. Heating from 30 to 50 °C caused a decrease in elastic modulus whereas heating above 50 °C strengthened the structure as evidenced by an increase in elastic modulus. Higher elastic modulus and lower creep compliance values suggested that Hereward gluten was more highly cross‐linked than Riband gluten. Glutenin seemed to be affected more than gliadin during temperature sweep experiments. Both oxidising and reducing reagents showed similar weakening effects on gluten irrespective of addition into flour or gluten. Treatment with oxidising reagents, particularly bromate, slightly delayed the temperature for the increase in elastic modulus as assessed by temperature sweep experiments. The identical effect of reducing and oxidising reagents may be attributable to the differences in mode of action and intrinsic material properties. Copyright © 2005 Society of Chemical Industry
Surface glycosyltransferases on cultured mouse fibroblasts
Authors: Roth Stephen , Patteson Anne , White Diane
Published: May 2005

Previous work has suggested the presence of galactosyltransferases on the outer surface of the plasma membrane of a malignant and a nonmalignant cell line. This paper summarizes data indicating that three other classes of glycosyltransfeases are similarly located on cell surfaces. In addition to the original two cell lines examined, BALB/c 3T3 and BALB/c 3T12, two other lines of BALB/c origin have been investigated. These are the SV40–transformed 3T3 line and one of the revertants of the virally infected cells that is no longer malignant but retains a viral genome.
Assessment of physiological integrity of sonicated retinal rod membranes
Authors: Shichi Hitoshi , Shelton Emma
Published: May 2005

As the size of rod membrane fragments was reduced by sonication or by addition of the detergent Emulphogene, the intensity of the circular dichroism (CD) bands (210 and 221 nm) increased progressively with a blue shift in position. The intensity of the visible CD bands (340 and 495 nm) was also increased by sonication. Since the intensity increase of the CD bands was related to a reduction in turbidity, the anomalous CD features of intact membranes could be attributed to optical artifacts caused by the particulate nature of the material.

Because the magnitude of the CD bands at 221 nm and 340 nm was essentially identical for the sonic suspension and detergent‐clarified solution, the adequacy of sonic suspensions can be assured by checking whether detergent affects the intensity of these bands.

Suspensions of sonicated rod membranes, purified on Agarose, contained vesicles of 112 nm in average diameter. The morphology and size of the vesicles did not change upon photobleaching of rhodopsin. The vesicles retained such rod membrane properties as conformational insensitivity to photobleaching of the retinal chromophore, thermal stability, and pigment regenerability. Thus, the physiological integrity of rod membranes was maintained by the sonicated vesicles.

From the most reliable estimate of the molecular ellipticity at 221 nm, the helical content of membrane‐bound rhodopsin was determined to be approximately 47%.
Characterization of the active transport of chlorotetracycline in Staphylococcus aureus by a florescence technique
Authors: Dockter Michael E. , Magnuson James A.
Published: May 2005

The antibiotic chlorotetracycline (CTC) is used as a fluorescent chelate probe to investigate its active transport in respiring Staphylococcus aureus cells. CTC chelation to magnesium or calcium leads to fluorescence enhancement. This enhancement is further increased when the polarity of its environment is decreased, as occurs when the complex moves from an aqueous environment into a membrane. Upon addition of CTC to a dispersion of S. aureus cells, a time dependent fluorescence enhancement is detected which is a monitor of the transport of the CTC‐divalent cation complex into the membrane. This uptake has been shown to be energy dependent and exhibits saturation kinetics with an apparent Km of 107 ± 20 μM by the same technique. The initial rates of antibiotic uptake are shown to have a pH optimum between 5.5 and 6.5. The effects of exogenously added EDTA and paramagnetic Mn2+ indicate that the CTC‐divalent cation complex is transported to the inside of the membrane. Exogenously added magnesium inhibits the accumulation process. This implies that the membrane CTC binding site involves a divalent cation sequestered away from the surface of the membrane, and only free CTC is bound to that site. The uptake of CTC is also temperature dependent with a maximal rate at 40°. Arrhenius plots of the initial fluorescence enhancement rates are found to be biphasic with a 27° transition temperature. The break in the plots presumably reflects an order‐disorder transition involving the fatty acids of the cell membrane. Thus, transport of the CTC involves movement through the fatty acid region of the membrane. This movement is facilitated by the more fluid state of the membrane above the transition temperature.
Accessibility of the carbohydrate moiety of membrane‐bound rhodopsin to enzymatic and chemical modification
Authors: Shaper Joel H. , Stryer Lubert
Published: May 2005

Galactose was specifically inserted into the carbohydrate moiety of rhodopsin by incubating retinal disk membranes with UDP‐galactose: N‐acetylglucosamine galactosyltransferase. The stoichiometry of labeling ranged from 1.2 to 1.8 (average = 1.5) residues of galactose per molecule of rhodopsin, indicating that some or all of the oligosaccharide chains of membrane‐bound rhodopsin are readily accessible to enzymatic modification. These modified membranes were treated with galactose oxidase to generate an aldehyde at the C‐6 position of the inserted galactose units. The enzymatically‐oxidized membranes were then reacted with dansyl hydrazide to yield a fluorescent hydrazone which is sufficiently stable to permit spectroscopic analysis. This procedure for the specific attachment of a spectroscopic probe should be applicable to a wide variety of membrane glycoproteins.
Hormonal regulation of membrane phenotype
Authors: Carlson Sarah A. , Gelehrter Thomas D.
Published: May 2005

Incubation of rat hepatoma cells (HTC) in tissue culture with glucocorticoids alters several membrane properties characteristic of transformed cells, without affecting the growth rate of these cells. Variant cell lines resistant to dexamethasone inhibition of plasminogen activator production have been isolated using an agar‐fibrin overlay technique to detect plasminogen activator production by individual colonies of HTC cells. The resistance to dexamethasone is not secondary to abnormal or absent glucocorticoid receptors, but due to a lesion in a later step in hormone action specific for plasminogen activator. These variants should prove useful for the study of the mechanism of steroid action as well as for the analysis of the role of proteases in the hormonal regulation of membrane function.
Active calcium transport via coupling between the enzymatic and the ionophoric sites of Ca2+ + Mg2+‐ATPase
Authors: Shamoo Adil E. , Scott Terrence L. , Ryan Thomas E.
Published: May 2005

The 20K dalton fragment of Ca2+ + Mg2+‐ATPase obtained from the tryptically digested sarcoplasmic reticulum has been further purified using Bio‐Gel P‐100. This removed low‐molecular‐weight UV‐absorbing and positive Lowry‐reacting contaminants. The ionophoric activity of the 20K fragment in both oxidized cholesterol and phosphatidylcholine: cholesterol membranes is unaltered by this further purification. The 20K selectivity sequence in phosphatidylcholine: cholesterol membranes is Ba2+ > Ca2+ > Sr2+ > Mn2+ Mg2+.

Digestion of intact sarcoplasmic reticulum vesicles with trypsin, which results in the dissection of the hydrolytic site (30K) from the ionophoric site (20K), is shown to disrupt energy transduction between ATP hydrolysis and calcium transport. This further implicates the 20K dalton fragment as a calcium transport site.

These data and previous evidence are discussed in terms of a proposed model for the ATPase molecular structure and the mechanism of cation transport in sarcoplasmic reticulum.
Energetics of galactose, proline, and glutamine transport in a cytochrome‐deficient mutant of salmonella typhimurium
Authors: Singh A. P. , Bragg P. D.
Published: May 2005

The effect of inhibitors and uncouplers on the osmotic shock‐sensitive transport systems for glutamine and galactose (by the β‐methyl galactoside permease) was compared to their effect on the osmotic shock‐resistant proline and galactose permease systems in cytochrome‐deficient cells of Salmonella typhimurium SASY28. Both osmotic shock‐sensitive and ‐resistant systems were sensitive to uncouplers and to inhibitors of the membrane‐bound Ca2+, Mg2+‐activated adenosine triphosphatase. This suggests that uptake by both types of systems is energized in these cells by an electrochemical gradient of protons formed by ATP hydrolysis through the ATPase.
Homogeneous antibodies directed against human cell surface antigens: I. The mouse spleen fragment culture response to T and B cell lines derived from the same individual
Authors: Lampson Lois A. , Royston Ivor , Levy Ronald
Published: May 2005

The use of the mouse spleen fragment culture system is extended to the production of antibodies to human lymphoblastoid cell lines. These antibodies were tested for reactivity against the immunizing cell line, and against a second cell line which had been derived from the same human blood sample. Many of the antibodies were found to discriminate between the 2 isogenic lines. These results demonstrate the potential of the mouse spleen fragment culture system to provide homogeneous reagents which detect distinguishing markers on closely related human cells.
Chemical and immunological studies of cell surfaces from normal and transformed cells
Authors: Grimes W. J. , Van Nest Gary A. , Kamm Arthur R.
Published: May 2005

Immunological and chemical studies of cell surfaces from normal and transformed BALB/c fibroblasts have shown alterations associated with transformation. The cells studied include normal lines which do not cause tumors when injected into BALB/c mice, viral transformants, and spontaneous transformants which cause tumors that either regress or grow progressively, killing the host. The spontaneously transformed progressors include cell lines which are immunogenic and nonimmunogenic as determined by the ability of tumor excision to protect an animal from subsequent rechallenge by tumor cells. Tumor‐bearing mice produce lymphocytes which are nonspecifically cytotoxic for all the normal and transformed lines. Some of the cell lines induce specific antibody formation in BALB/c hosts. Antisera have been prepared in rabbits which are specific for the transformed cell lines. These antisera can be used to determine specific surface changes on the transformed cells. Chemical studies have shown glycolipid alterations between the normal cells and some, but not all, of the transformants. Glycoproteins labeled by lactoperoxidase‐125 I or [3H] glucosamine were compared by SDS gel electrophoresis. Results from these studies do not show changes associated with malignancy. Individual glycoprotein regions from gels were treated with pronase, and the glycopeptides compared by Sephadex G‐50 chromatography. Alterations in glycopeptides from several cellular glycoproteins are the only changes which appear to be associated with malignancy.
Lectin affinity chromatography of cell surface proteins of novikoff tumor cells
Authors: Glenney John R. , Walborg Earl F.
Published: May 2005

Novikoff hepatocellular carcinoma cells were radioiodinated by a cell surface‐specific method using lactoperoxid ase/125I. The iodinated proteins were solubilized in 0.5% Nonidet P‐40 and subjected to affinity chromatography on Sepharose‐conjugated lectins (Ricinus communis agglutinins I or II, soybean agglutinin, concanavalin A, or wheat germ agglutinin) and analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Almost all the iodinated proteins bound to one or more of the Sepharose‐conjugated lectins, presumptive evidence that these peptides are glycosylated. Lectin affinity chromatography resolved defined subsets of iodinated glycoproteins and suggested that certain glycoproteins could be fractionated on the basis of heterogeneity of their heterosaccharide moieties. Incubation of the iodinated cells with neuraminidase resulted in increased binding of iodinated proteins to Sepharose‐conjugated Ricinus communis agglutinins I and II and soybean agglutinin and decreased binding to Sepharose‐conjugated wheat germ agglutinin. Binding of iodinated proteins to concanavalin A was unaffected by neuraminidase treatment of the cells. These studies demonstrate the utility of lectins for the multicomponent analysis of plasma membrane proteins.
Growth control of normal and transformed cells
Authors: Riddle Veronica G. H. , Pardee Arthur B. , Rossow Peter W.
Published: May 2005

Both serum factors and protein synthesis are required for normal cell growth. Swiss 3T3 cells require the serum growth factors insulin and EGF (epidermal growth factor) during the initial part of the G1 period, until they pass a restriction point about 2 h before the initiation of DNA synthesis. Concentration of cycloheximide that inhibit protein synthesis by as much as 70% dramatically lengthen the cell cycle before the restriction point, while the cell cycle after the restriction point remains nearly constant. These results are consistent with a model in which labile proteins are required for transit of cells past the serum‐sensitive restriction point. The relation of these findings to the growth control of transformed cells is discussed.
Tumorigenicity of revertants from an SV40‐transformed line
Authors: Steinberg Bettie M. , Rifkin Daniel , Shin Seung‐il , Boone Charles , Pollack Robert
Published: May 2005

A syndrome of in vitro properties correlates with the tumorigenicity of SV40‐transformed rodent cells. These properties are plasminogen activator production, loss of large actin cables, and anchorage‐independent growth. An established rat fibroblast line, its SV40 transformant, several T‐antigen negative revertants, and a spontaneous retransformant isolated form one of the revertants were analyzed in vivo for their tumorigenicity and in vitro for the syndrome. The two transformed lines were highly tumorigenic, and had clearly abnormal in vitro properties. The parental rat line was weakly tumorigenic in nude mice and demonstrated a slightly transformed response in the in vitro assays. The revertants were completely nontumorigenic. Expression of the in vitro syndrome was not uniform for all revertants; however, most cell lines maintained the correlation of the syndrome and tumorigenicity.
Averages of glutamine synthetase molecules as obtained with various stain and electron dose conditions
Authors: Kessel M. , Frank J. , Goldfarb W.
Published: May 2005

Averaged projections of individual glutamine synthetase molecules have been obtained by using electron microscopy and image processing. The methodology of correlation averaging under low dose conditions is described in detail. Because of their low signal‐to‐noise ratio, images made under low dose conditions cannot be directly interpreted in terms of high resolution features. Computer averaging of these images reveals a division of the subunit projection into two domains whose sizes agree with results of Lei et al [2] limited proteolysis experiments.
Developmental regulation of glycoprotein biosynthesis in dictyostelium
Authors: Ivatt Raymond J. , Das O. Prem , Henderson Ellen J. , Robbins Phillips W.
Published: May 2005

We have examined the glycoprotein‐linked oligosaccharides assembled during the life cycle of Dictyostelium discoideum, and found their expression to be dramatically dependent upon the stage of development. During early development mature glycans have a high mannose character, and a substantial proportion acquire a fucose residue that correlates with endo‐H resistance. One‐third of the glycans also acquire sulfate residues. These glycans diminish in importance during aggregation.

The mature glycans expressed during late development contain fewer mannose residues, from five to ten mannose residues, and are characterized by the absence of sulfate residues and by the presence of fucose residues on endo‐H‐sensitive glycans. These glycans make their appearance coincident with the construction of tips on tight cell mounds. At this stage glycans characteristic of both early and late stages occur simultaneously.

Developmental regulation of the wide array of protein‐linked glycans expressed during the life cycle of Dictyostelium discoideum may be as simple as the controlled transition from a group of structures that are assembled by the vegetative cells to a group of structures that are assembled by the terminally differentiating cells. The potential biological significance of this transition is discussed.
Long‐term epidermal growth factor–receptor internalization and processing in quiescent human fibroblasts
Authors: King A. Christie , Cuatrecasas Pedro
Published: May 2005

Epidermal growth factor is internalized into cells and concomitantly induces a massive clearance of up to 90% of its total surface receptors. The hormone‐receptor complex is delivered to lysosomes and degraded or inactivated. Lysosomotropic alkylamines block the degradation but not the binding‐or internalization of ligand‐receptor complexes and thus their presence results in a marked potentiation of intracellular accumulation of epidermal growth factor. We have used these alkylamines as pharmacological tools to trap internalized 125I‐labeled epidermal growth factor and now report that the residual population of epidermal growth factor receptors remaining on human fibroblasts after completion of the receptor clearance process is not only accessible for ligand binding but also directs the continued internalization and degradation of this growth factor over prolonged periods of time. We also show that down regulation of epidermal growth factor receptors does not result in desensitization of cells to the mitogenic response.
Die Wasserstoffentwicklungsreaktion an Titanhydriden
Authors: Brauer E. , Nann E.
Published: May 2005

Die Wasserstoffentwicklung an Titanhydriden erfolgt nach einem gekoppelten Entladung‐Rekombination‐Mechanismus, wobei zu berücksichtigen ist, daß ein Teil des sich entwickelnden Wasserstoffs in das Metall diffundieren kann. Die Geschwindigkeit der in mehreren Stufen ablaufenden Hydridbildung und Diffusion ist abhängig vom Bedeckungsgrad, der Rekombination der Wasserstoffatome und vom Wasserstofftransport in das Metall, der geschwindigkeitsbestimmend wird, wenn das System sich vom Gleichgewicht entfernt. Für die Untersuchungen (quasistationär und kinetisch) wurde auf dem Metall eine einheitliche Hydridschicht erzeugt, und zwar durch Beizen in konz. Salzsäure oder durch kathodische Polarisation. Die identifizierten Hydride ‐ TiH2, TiH und TiH1,96zeigen unterschiedliche Überspannung, die auch von der Gasbespülung beeinflußt wird.
High temperature corrosion of nickel‐chromium alloys containing refractory sulphide‐forming elements in sulphur/oxygen environments – theoretical considerations
Authors: Strafford K. N. , Winstanley G. R. , Harrison J. M.
Published: May 2005

Despite the fact that combustion atmospheres in gas turbines are normally strongly oxidizing, microexamination of corroded alloys often not only reveals an anticipated external oxide scale and a degree of internal oxidation, but also a significant amount of sulphide phase(s), particularly after turbine operation in marine situations. Thus a degree of selective sulphidation as well as oxidation occurs. While the exact method of the further propagation of the corrosion product(s) is subject to doubt, it is possible that subsequent oxidation of these sulphide particles may be a factor. It is clear, however, that a necessary prerequisite for the reduction of this complex form of attack is the elimination of or control oh the sulphidation which occurs concurrently with oxidation. The theory underlying the possible development of sulphidation resistant alloys via. selective sulphidation of specific alloying element additions is reviewed. On this basis a number of alloying elements, which can form so‐called refractory sulphides of high melting point, and which hitherto have been largely ignored, are put forward in discussion as being potentially useful as additions to Ni‐based alloys for the inhibition of attack in sulphur/oxygen environments. In this assessment thermodynamic data for these refractory sulphides have been calculated and are quoted.
Beitrag zum Mechanismus der Lochfraßkorrosion des Nickels
Authors: Toušek J.
Published: May 2005

Die Lochfraßkorrosion von Nickel wurde in Abhängigkeit von Zeit, pH, Potential und Konzentration in verschiedenen Salzlösungen gemessen. Dabei zeigt sich, daß die Lochzahl zeitlich von der Konzentration der Salze abhängt, wobei die Zeitabhängigkeit linear oder parabolisch sein kann. Die Potentialabhängigkeit der Lochzahl folgt wieder einem Expotentialgesetz. Von den untersuchten Salzen wirken vor allem die Chloride lochfraßerzeugend;. ihre Wirkung wird durch Nitrate teil‐ weise stark stimuliert. Auch Sulfate beeinflussen die Wirkung der Chloride, jedoch in verschiedenen Konzentrationsbereichen unterschiedlich. Aufgrund der Ergebnisse werden mögliche Mechanismen der Lochbildung und des Lochwachstums erörtert.
Einfluß des Molybdängehaltes niedriglegierter Stähle auf die Spannungsrißkorrosion in Nitratlösungen unter CERT‐Belastung
Authors: Büuning A. , Dahl W. , Schwenk W.
Published: May 2005

Mit Hilfe von CERT‐Versuchen (\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \varepsilon \limits^. = 10^{ - 6} {\rm s}^{ - {\rm 1}} $\end{document}) wurden in NaNO3‐Lösungen der Konzentration 0,1 bis 5 mol/L und der Temperatur 25 bis 90°C Untersuchungen kritischer Parameter der Spannungsrißkorrosion durchgeführt. Die Werkstoffe waren 15 Mo 3, LStE 36 sowie zwei Versuchsschmelzen mit 0,08% C und 0 bzw. 1% Mo. Die Auswertung der gebrochenen Proben erfolgte metallografisch. Dabei zeigten sich verschiedenartige Angriffsformen, die danach unterschieden wurden, ob interkristalline Schädigungen vorlagen oder nicht.

Interkristalline Angriffsformen treten in Potentialbereichen auf, deren negatives Grenzpotential um U11 = −0.2 V nahezu nicht von den Versuchparametern und auch nicht vom Werkstoff abhängt. In diesem Bereich liegt auch das Ruhepotential. Bei freier Korrosion zeigen alle Proben im Medium mit 5 M NaNO3 bei 90°C interkristalline Risse. Sonst zeigt nur die grobkorngeglühte, Mo‐freie Schmelze auch bei kleinerer Konzentration Risse. Das positive Grenzpotential um UH = 0 bis 0,5 V ist vom Werkstoff und von den Mediumparametern abhängig. Bei UH = 0,8 V erfolgt wieder interkristalliner Angriff. Es ist anzunehmen, daß mit ansteigenden Temperaturen der Beständigkeitsbereich für Spannungsrißkorrosion bei UH = 0,5 bis 0,8 V verschwindet, wie dies bei Ca(NO3)2‐Lösungen nach DIN 50 915 bekannt ist und bei der Mo‐freien Schmelze bereits bei 90°C beobachtet wurde. Dieser Beständigkeitsbereich zeigt keinen Zusammenhang mit anderen Korrosionsarten.

Hinsichtlich der Mediumparameter hat die Konzentration praktisch keinen, die Temperatur aber einen großen Einfluß, wobei die Werkstoffe besser durch kritische Temperaturen als durch kritische Potentialbereiche für Spannungsrißkorrosion beschrieben werden können. Wenn im Einzelfall eine Rangordnung der Werkstoffbeständigkeit wegen einer Potentialabhängigkeit nicht einheitlich angebbar ist, so läßt sich aber anhand der Ausdehnung der Beständigkeitsfelder folgende Rangfolge für ansteigende Beständigkeit angeben: Mo‐freie Schmelze → LStE36 → 15 Mo 3 → Mo‐haltige Schmelze. Der Einfluß des Mo wird auf den hohen Gehalt des Bainit im Gefüge zurückgeführt.
Mikrobielle Zerstörung keramischer Werkstoffe
Authors: Sand W. , Bock E.
Published: May 2005

Generell ist festzustellen, daß der biologische Test des Widerstandsverhaltens eines Werkstoffes nicht durch chemische oder physikalische Testverfahren ersetzt oder gar ausgeschlossen werken kann. Der Biotest schließt die Untersuchung der Wechselwirkungen zwischen Organismen und Umwelt, in diesem Fall des Werkstoffes als Substratum (Unterlage) ein. Im Falle der biogenen Schwefelsäurekorrosion führte dies bei gleichen Voraussetzungen zu erheblichen Unterschieden im Widerstand der Prüfkörper. Parallel dazu durchgeführte chemische Untersuchungen mit Schwefelsäure bei einem pH‐Wert um 1,5 zeigten nur geringe Unterschiede. Im Falle eines biologischen Angriffes erlaubt der Einsatz von Simulationsanlagen, aus vielen Werkstoffen die für einen Einsatz geeigneten herauszufinden.
Mikrobielle Materialzerstörung von Wandanstrichen und Klebstoffen
Authors: Brill H.
Published: May 2005

Farben, Lacke und Putze sowie Klebstoffe enthalten Inhaltsstoffe, die dem mikrobiellen Abbau ausgesetzt sind. Deshalb verursachen das Wachstum von Bakterien, Hefen und Schimmelpilzen sowie Grünalgen, Schäden an diesen Produkten, die schon im Gebinde oder erst, nachdem sie ausgebracht wurden, auftreten können. Folgeerscheinungen sind z.B. Verfärbungen, Veränderungen der rheologischen Eigenschaften, pH‐Veränderungen, Gasentwicklungen und Faulgerüche. Um diese Materialien, die meistens Dispersionen sind, vor der biogenen Zerstörung zu schützen, können die verschiedensten Verfahren eingesetzt werden. Die gebräuchlichsten sind gegenwärtig die chemische Konservierung sowie eine geeignete Produktionshygiene, die durch bauliche, apparative und organisatorische Maßnahmen verbessert werden kann. Die notwendigen Forschungsziele werden in diesem Bereich überwiegend durch die produzierende Industrie gesetzt. Hier soll nur die Entwicklung von standardisierten Prüfverfahren und von umweltschonenden Produkten genannt werden.
Corrosion caused by the atmosphere on 1050 aluminum in the Basque country
Authors: Elola A. S. , Otero T. F. , Porro A.
Published: May 2005

After exposing aluminium samples to five atmospheres (rural. industrial and marine‐industrial) in the Basque Country, the number and depth of the pits formed for different exposure times were measured. During the four years of exposure, sulphur dioxide and chloride ion levels, together with relative humidity and temperature, were determined.

From these results, a linear increase of the pit density with time and a bilogarithmic one of the pit depth with time, were determined. An important effect of the synergistic action of SO2and chloride in the formation and growth of pits was found.

A statistical treatment is proposed to predict the pit density to be formed when the 1050 aluminum is exposed to the atmosphere.
Korrosionsschutz – Antworten auf eine Herausforderung. Zur Gründung der Gesellschaft für Korrosionsschutz GfKORR
Authors: Gramberg U.
Published: May 2005

Korrosionsauswirkungen können die Sicherheit und Wirtschaftlichkeit von Anlagen erheblich beeinträchtigen. Ältere Erhebungen in verschiedenen Staaten führten beispielsweise zu jährlichen Korrosionsschätzkosten in Höhe von 4% des Bruttosozialprodukts von Volkswirtschaften oder von 4% des Umsatzes in der Chemieindustrie. Korrosionskosten lassen sich in Schutz‐ und Schadenskosten unterteilen. Wenn man beide gegenläufigen Anteile in Abhängigkeit vom Schutzaufwand addiert, so ergibt sich eine Kostenkurve mit Minimum. Dieses repräsentiert die unvermeidbaren Kosten, letztlich zurückzuführen auf die thermodynamische Instabilität der meisten technisch eingesetzten Werkstoffe. Die Erhebungen haben ferner gezeigt, daß die realistischen Korrosionskosten im Mittel um 25% höher anzusetzen sind als die unvermeidbaren Kosten, zurückzuführen auf eine ungenügende Umsetzung des verfügbaren Korrosionsschutzwissens. Die Industrie sollte daher das vorhandene Wissen wirtschaftlich flächendeckend umsetzen und anwendungsorientierte Weiterentwicklung betreiben. Seitens der Staaten sollten die Korrosionsforschung gefördert und das Korrosionswissen auf allen Ebenen technischer Lehranstalten weitervermittelt werden. Weitere wichtige Aufgaben wie Erfahrungsaustausch, Projektinitiierung, Normung und zertifizierte Ausbildung müssen dagegen von anderen Organisationen übernommen werden. Dies werden die wesentlichen Ziele der neuen Gesellschaft für Korrosionsschutz GfKORR sein, die im November 1995 durch Fusion von AGK‐GKKs und VDKORR entstand.
Effect of Alkyl Groups of Latent Cationic Catalysts on Cure and Dynamic Mechanical Behaviors of Epoxy Resins
Authors: Park Soo‐Jin , Heo Gun‐Young
Published: May 2005

Summary: The latent thermal cationic initiators, benzyl‐2,5‐dimethylpyrazinium hexafluoroantimonate (BDPH) and benzyl‐2‐ethylpyrazinium hexafluoroantimonate (BEPH), were synthesized to investigate the effect of substituted alkyl groups on cure and dynamic mechanical behaviors of difunctional epoxy system. The cure temperature and activation energy of the diglycidyl ether of bisphenol A (DGEBA)/BDPH were higher than those of the DGEBA/BEPH, resulting from the steric hindrance of the substituted groups. The cross‐linking density of the DGEBA/BDPH was higher than that of the DGEBA/BEPH, whereas the Tg's of both specimens are similar. This may be explained by the free volume and the intermolecular hydrogen bonding induced by the hydrogen of the substituted methyl groups. Consequently, the position and number of the substituted groups of the latent thermal initiator were very important in the control of the latent thermal and dynamic mechanical behaviors of the epoxy resin.

Dynamic DSC curves of DGEBA cured by each initiator.

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Dynamic DSC curves of DGEBA cured by each initiator.
Dye Diffusion in Polymer Films Subjected to Supercritical CO2: Confocal Raman Microscopy and Modelling
Authors: Fleming Oliver S. , Stepanek Frantisek , Kazarian Sergei G.
Published: May 2005

Summary: Poly(ethylene terephthalate) films impregnated with Disperse Red 1 from a supercritical CO2 solution were studied using confocal Raman microscopy. Depth profiles of films dyed for different periods of time were measured using the oil immersion approach and concentration‐depth plots of the relative dye concentration were generated. A one‐dimensional Fickian diffusion model was used to evaluate the diffusion coefficient of the dye from the Raman microscopy data using a non‐linear least squares regression. The calculated diffusion coefficient at 200 bar and 80 °C was 6.75 ± 1.01 × 10−14 m2 · s−1.

Typical example of Raman spectra acquired during depth profiling.

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Typical example of Raman spectra acquired during depth profiling.
Microstructural Characterization of Molecular Weight Fractions of Ethylene/1,7‐Octadiene Copolymers Made with a Constrained Geometry Catalyst
Authors: Sarzotti Deborah M. , Narayan Abhishek , Whitney Philip M. , Simon Leonardo C. , Soares João B. P.
Published: May 2005

Summary: Ethylene was copolymerized with 1,7‐octadiene (OD) using a methylaluminoxane (MAO) activated constrained geometry catalyst (dimethylsilyl(N‐tert‐butylamido)(tetramethylcyclopentadienyl)titanium dichloride; CGC‐Ti) at 140 °C in toluene. The polymerization activity increased with the addition of small amounts of OD, reached a maximum, and then decreased at higher OD concentrations. The vinyl‐bond content of the polymers increased with increasing diene in the feed. Increasing OD concentrations led to the production of long chain branched (LCB) polyethylene (PE). Both 1,3‐cycloheptane (CY7) and 1,5‐cyclononane (CY9) units were identified in the copolymers, with the dominant CY9 structure accounting for approximately 53% percent of all rings. Selected copolymers were fractionated by molecular weight using a solvent/non‐solvent technique to obtain their detailed microstructure. The relative amounts of CY7 and CY9 structures were not a function of molecular weight. The number of vinyl functionalities decreased with increasing molecular weight, while the number of branches increased, indicating the incorporation of macromonomers with pendant or terminal vinyl groups.

Molecular weight distributions of ethylene homopolymer and three fractions.

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Molecular weight distributions of ethylene homopolymer and three fractions.
Zerstörungsfreie Messung der Einzeldicken von Schichtsystemen nach dem Wirbelstrom‐Verfahren
Authors: Ott Albert
Published: May 2005

Die Arbeit beschreibt die theoretische, meßtechnische und gerätetechnische Seite eines Wirbelstromverfahrens zur zerstörungsfreien Schichtdickenmessung an Schichtsystemen. Es werden Beispiele für Auswertediagramme mit Meßbeispielen angegeben und quantitativ bewertet.
Temperaturmessung an schwingend beanspruchten Werkstoffen
Authors: Stärk Klaus F.
Published: May 2005

Die technischen Werkstoffe haben einen polykristallinen Aufbau mit mikroskopisch sehr inhomogenem Aufbau. Bei zyklischer Beanspruchung treten unregelmäßig verteilte und unterschiedlich große plastische Dehnungsamplituden auf, die meßtechnisch nicht zugänglich sind; Aufnahmen von Mikrogefügen und Kornstrukturen machen dies deutlich. Ein einfaches statistisches Rechenmodell erleichtert das ingenieurmäßige Verständnis von den Verteilungsmöglichkeiten elastisch‐plastischer Verformungen im schwingbeanspruchten Werkstoff. Mit der Messung der durch Dissipation im Werkstoff entstehenden Wärme lassen sich neue Erkenntnisse zur Schwingfestigkeit und der Ermüdung der metallischen Werkstoffe gewinnen. In Beispielen wird auf Temperaturmessungen im Kerbgrund zur Anrißbestimmung bei hohen Prüffrequenzen sowie an glatten, zylindrischen Proben auf die genaue Bestimmung der spezifischen Wärmemenge pro Schwingspiel zur Beanspruchungsanalyse hingewiesen.
High Temperature Corrosion on high temperature materials – Metallographic, scanning electron microscopic and microanalytical tests
Authors: Thien Volker , Voss Wolfgang , Schmitz Friedhelm
Published: May 2005

High temperature corrosion – oxidative damage of metallic materials from hot gas and other fluid and solid components – shortens the life of gas turbines. By comparing the results of laboratory tests under constant conditions with the results of the operation of gas turbines the facts of failure should be clarified.

Metallographie examinations, but especially SEM, Microprobe and AES help to clear the facts of failures in the microscopic zones. These tests will help when selecting materials and their protective coatings with the purpose of higher rentability of the plant.
Metallische Adhäsion unter trockener Reibung
Authors: Woska R. , Barbehön J.
Published: May 2005

Das Studium der zahlreichen Theorien über die Entstehung und Wirkung der metallischen Adhäsion zeigt, daß der adhäsive Reibungs‐ und Verschleißmechanismus im wesentlichen ein physikalisch‐chemisches Problem darstellt. Die metallische Adhäsion ist als das Ergebnis des Zusammenspiels aller thermischen, elektrischen und durch Sorptionsvorgänge bedingte Wechselwirkungen zwischen den Grenzflächenatomen zweier gepaarter Metalloberflächen aufzufassen. Die für den allgemeinen Maschinenbau relevanten mechanischen Werkstoffeigenschaften, sowie die aufgebrachten Belastungen, stellen lediglich zusätzliche Einflußparameter dar, mit deren Kenntnis allein sich das Adhäsionsverhalten nicht diskutieren läßt.
Lokale Last‐ und Eigenspannungsverteilungen an rißbehafteten Oberflächen nach Korrosionsermüdung von vergütetem Ck 45
Authors: Herzog R. , Scholtes B. , Wohlfahrt H.
Published: May 2005

Korrosionsermüdung im aktiven Zustand führt bei metallischen Werkstoffen zu einer großen Zahl kleiner Anrisse und Korrosionsgrübchen. Die vorliegende Arbeit beschäftigt sich mit der Auswirkung dieser Schädigungsmerkmale auf die lokale Verteilung von Last‐ und Eigenspannung. Untersucht wurde Ck 45 im vergüteten Zustand, der abschließend CBN‐geschliffen war. Die Ergebnisse zeigen, daß lokal sehr inhomogene Spannungsverteilungen auftreten. Korrosionsgrübchen bewirken in ihrer Umgebung eine Relaxation bearbeitungsbedingter Eigenspannungen, unter Last treten aufgrund ihrer Kerbwirkung höchste Beanspruchungen auf.
Effect of film thickness on the selectivity of cyanosilicone capillary columns
Authors: Sidisky Leonard M. , Rijks Jacques A.
Published: May 2005

Data presented herein show that the film thickness of a polar stationary phase, SP‐2380, affects column selectivity under isothermal analysis conditions. The expected linear relationship between film thickness and solute capacity factors (k), as predicted by the partition coefficient equation, was confirmed experimentally. However, selectivity, as determined by ECL values for the fatty acid methyl esters, does not remain constant. As the film thickness is increased from 0.10 μm to 0.20 μm, 0.30 μm, and 0.50 μm, there is an increase in effective column polarity. This increase mimics the polarity shift seen when comparing a 90% bis‐cyanopropyl/10% cyanopropyl phenyl polysiloxane capillary column to a 100% bis‐cyanopropyl polysiloxane column of the same film thickness (0.20 μm) under isothermal conditions. The increase in selectivity over the film thickness range studied is revealed by ECL values for an unsaturated C18:3 ester relative to an unsaturated C20:1 ester and saturated esters, C18:0(methyl stearate), (C20:)(methyl arachidate), and C22:0(methyl behenate). As the film thickness increased, the C18:3 ester eluted farther from the C20:0 ester and changed from eluting before the C20:1 ester to eluting after the C20:1 ester and closer to the C22:0 ester.

The effective polarity increase also reduced the retention time for all of the saturated FAMEs, compared to their respective unsaturated counterparts. Possible causes of the differences in selectivity among these columns include a lessening of the surface adsorption and increased partitioning with the thicker stationary phase film.
Optimization of the resolution of PTH‐amino acids through control of surfactant concentration in micellar electrokinetic capillary chromatography: SDS vs. brij 35/SDS micellar systems
Authors: Little Edward L. , Foley Joe P.
Published: May 2005

The effect of surfactant concentration on resolution in micellar electrokinetic capillary chromatography (MECC) was investigated using several phenylthiohydantoin (PTH) derivatized amino acids as test solutes. Two aqueous micellar systems were employed: sodium dodecyl sulfate (SDS) and a mixed micellar system consisting of SDS and polyoxyethylene(23)dodecanol (Brij® 35). In the SDS system, the tmc/to ratio (elution range) increased significantly with increasing surfactant concentration, making the determination of the optimal concentration, which is dependent on tmc/to, difficult. In contrast, in the Brij 35/SDS system the tmc/to ratio decreased only slightly with increasing concentration of Brij 35. Whereas the SDS and Brij 35/SDS systems are better suited for moderately hydrophobic and hydrophilic solutes, respectively, neither is well‐suited for hydrophobic solutes without organic modifiers. The narrower elution range (lower tmc/to) observed for the Brij 35/SDS micellar system was compensated by several potentially important advantages over the pure SDS system, including significantly higher efficiencies (2–3 times) and lower operating currents. Differences in selectivity and retention mechanisms among solutes and surfactant systems are also discussed.
Conformations of bryonolic acid and its derivatives in CDCl3 solution by 1H and 13C NMR spectroscopy
Authors: Kamisako Wasuke , Suwa Kiyoko , Honda Chie , Isoi Koichiro , Nakai Hiroshi , Shiro Motoo , Machida Katsunosuke
Published: May 2005

Comparison of the 1H and 13C chemical shift data of bryonolic acid (D : C‐friedoolean‐8‐en‐3β‐ol‐29‐oic acid) and its derivatives (13 species) revealed that the conformational features of these compounds in CDCl3 solution depend on whether the functional groups at C‐29 are trigonal, such as COOCH3, or tetrahedral, such as CH2OH. In order to study the conformational features of these two groups of compounds, vicinal coupling constants between the protons on the E rings of the methyl ester of D : C‐friedoolean‐8‐en‐29‐oic acid, D : C‐friedoolean‐8‐en‐29‐oic and its acetate were measured. Comparison of the results with the steric geometries to be expected from the molecular mechanics calculation for the E‐ring moieties of these derivatives in the S form (D‐E rings: boat‐boat form) and the F form (D‐E rings: chair‐chair form) led to the conclusion that the compounds having a trigonal functional group at C‐29 mainly adopt the S form, and those having a tetrahedral functional group at C‐29 are present as mixtures of the S and F form in equilibrium in the solutions.
15N and 17O NMR chemical shift calculations using the MNDO/GIAO method
Authors: Xiaozeng You , Weixiong Wu
Published: May 2005

The previously reported finite perturbation MNDO/GIAO method was ued to calculate nuclear magnetic shielding constants. A set of atomic MNDO parameters for nitrogen and oxygen was chosen by comparing calculated and experimental chemical shifts for compounds containing N and O atoms. The agreement of the trends within these compounds was satisfactory.
1H NMR spectra of cis‐2,6‐diphenylpiperidines and cis‐2,6‐diphenyl‐4‐piperidones
Authors: Arumugam N. , Sundharavadivelu M. , Sivasubramanian S. , Wilson D. A.
Published: May 2005

1H NMR spectra of t‐3‐ethyl‐r‐2,c‐6‐diphenylpiperidine, t‐3‐ethyl‐r‐2,c‐6‐diphenyl‐4‐piperidone and several related compounds have been obtained in deuteriochloroform and deuteriotrifluoroacetic acid solutions, and compared with the spectra of their hydrochlorides in deuteriochloroform‐hexadeuteriodimethyl sulphoxide solutions. The effects of the structural changes 4‐CH2 → have been observed on the chemical shifts of ring and substituent protons, and on the non‐equivalence of the diastereotopic protons of the ethyl groups.
Theoretical IPPP analysis of 13C‐31 P through‐space indirect couplings in phosphorus‐substituted alkenes
Authors: Diz A. C. , Giribet C. G. , de Azúa M. C. Ruiz , Contreras R. H. , Aucar G. A.
Published: May 2005

A refined version of the IPPP‐INDO method was used to analyse the difference between cis and trans 13C‐31P couplings in phosphorus‐substituted alkenes. A large through‐space transmission of the Fermi contact term is predicted for the cis 13C‐31P coupling. With the new version of the IPPP method it was assessed how different orbitals, describing chemically intuitive bonds, lone pairs and antibonding orbitals, contribute to the Fermi contact term. The importance of the P lone pair and C‐H bonds was clearly determined. The antibonding orbitals, which are very important but rarely mentioned, are also discussed.
Two‐dimensional NMR spectra of sesquiterpenes. I—NOESY study of caryophyllenes from Inula spiraeifolia
Authors: Vajs Vlatka , Jeremić Dragoslav , Milosavljević Slobodan , Macura Slobodan
Published: May 2005

The application of two‐dimensional NOE NMR spectroscopy (NOESY) for the stereochemical assignment of isomeric 14‐acetoxy‐13‐hydroxy‐ and 13‐acetoxy‐14‐hydroxy‐5,6‐caryophyllen‐7‐ones, and their acetylation products, is reported.
Investigation of association in purine—pyrimidine aqueous systems by 1H NMR chemical shift
Authors: Aradi Ferenc , Földesi Andras
Published: May 2005

The association behaviour of purine and pyrimidine has been studied in deuterium oxide at 35°C by measuring the concentration‐dependent selective changes in the chemical shifts of the CH protons. A satisfactory interpretation of the cross‐interaction, i.e. the mutually induced upfield shifts in mixed solution, required the extension of the 1:1 hetero‐association model by taking into account the self‐association of both compounds. The self‐association and the hetero‐association parameters have been determined on the basis of two‐state and three‐state models. The equilibrium constants give a decreasing tendency for association within the series purine‐purine (0.82 ± 0.08 1 mol−1) > purine‐pyrimidine (0.54 ± 0.06 1 mol−1) > pyrimidine‐pyrimidine (0.050 ± 0.002 1 mol−1), and the values of the dimer upfield shifts suggest that the association processes are dominated by the interaction of the six‐membered rings.