bluuebunny/crossref_metadata_2025 huggingface dataset:
A toxicokinetic analysis in a patient with acute glufosinate poisoning
Authors: Hirose Y , Kobayashi M , Koyama K , Kohda Y , Tanaka T , Honda H , Hori Y , Yoshida K , Kikuchi M
Published: April 2003

Incidents of poisoning in humans caused by the ingestion of the glufosinate ammonium containing herbicides are gradually increasing in Japan. This poisoning is characterized by various neurological symptoms such as disturbances of consciousness, convulsions and apnea which appear after an asymptomatic interval of several hours. We studied the toxicokinetics of glufosinate in a patient with this poisoning successfully treated without extracorporeal hemopurification. A 65-year-old male ingested BASTA, which contains 20% w/v of glufosinate ammonium, about 300 ml, more than the estimated human toxic dose. Four and a half hours after ingestion, he showed speech ataxia and systemic tremor. He was prophylactically intubated before the occurrence of serious respiratory failure. After 5 days of artificial ventilation he was extubated and discharged without any sequelae. We studied the serial change of serum glufosinate concentration every 3-6 h and assessed the urinary excretion of glufosinate every 24 h. The absorbed amount of glufosinate was estimated from the cumulative excreted in urine. Toxicokinetic analysis was performed using the two-compartment model. The changes in serum glufosinate concentration exhibited T1/2α of 1.84 and T1/2α of 9.59 h. The apparent distribution volume at b-phase and the total body clearance were 1.44 l/kg and 86.6 ml/min, respectively. Renal clearance was estimated to be 77.9 ml/ min. The indication for extracorporeal hemopurification for this poisoning has been discussed.
Lead and calcium transport in human erythrocyte
Authors: Calderón-Salinas J V , Quintanar-Escorcia M A , González-Martínez M T , Hernández-Luna C E
Published: April 2003

In this paper we report the lead (Pb) and calcium (Ca) uptake by erythrocyte ghosts. In both cases the transport was carried out by a passive transport system with two kinetic components (Michaelis-Menten and Hill). Pb and Ca were capable of inhibiting the transport of the other metal in a non-competitive way. Under hyperpolarization, the uptakes of Ca and Pb were enhanced and the Michaelis-Menten component prevailed. Both Ca and Pb uptakes were inhibited by N-ethyl-maleimide to the same extent. These results indicate that Pb and Ca share the same permeability pathway in human erythrocytes and that this transport system is electrogenic.
Biological monitoring exposure of workers from plant producing carbon electrodes: quantification of benzo[a]pyrene DNA adducts in leukocytes, by a 32P-postlabelling method and an immunoassay
Authors: Arnould J P , Pfohl-Leszkowicz A , Bach V , Libert J P , Belegaud J
Published: April 2003

The levels of benzo[a]pyrene were monitored for blood DNA-benzo[a]pyrene adducts in 17 workers from a plant producing carbon electrodes, with high exposure to benzo[a]pyrene (575-902-1149 ng m-3). Two different techniques, a 32P-postlabelling method and a competitive immunoassay using polyclonal antibodies obtained from rabbits immunised with DNA modified by benzo[a]pyrenetrans-7,8-dihydrodiol-9,10-epoxide were used. For each worker, urinary 1-hydroxypyrene, a potential indicator of exposure to polycyclic aromatic hydrocarbons, was measured. The effect of tobacco by urinary cotinine measurement was also considered. The postlabelling and immunoassay detection limits for DNA-benzo[a]pyrene adducts were respectively 0.15 and 10 fmol 50 ug-1 of DNA. The results obtained by the two methods demonstrated a good detection of DNA-benzo[a]pyrene adducts, but no direct relationship between the quantity of adducts and the concentration of benzo[a]pyrene in air-borne was noted in the studied plant.

The levels of DNA-benzo[a]pyrene adducts obtained by immunoassay were significantly higher than those obtained by the 32P-postlabelling (P50.001). For several workers, variations due to professional or non professional factors must be taken into account in interpreting the results. In conclusion, the two methods used proved very efficient in determining DNA-benzo[a]pyrene adducts, and may be useful in monitoring human exposure to known and previously unidentified environmental genotoxic agents.
Antibody forming cell response to nickel and nickel-coated fly ash in rats
Authors: Dogra S , Khanna A K , Kaw J L
Published: April 2003

The potential of nickel as nickel chloride, native fly ash and Ni-coated fly ash to alter pulmonary and systemic immune response was evaluated upon intratracheal (I/T) exposure of rats. The animals were sensitised with sheep red blood cells (SRBC) through I/T and intraperitoneal (I/P) routes. Nickel exposure resulted in a decrease in the number of antibody forming cells (AFC) in lung associated lymph nodes (LALN) and spleen. In rats exposed to native fly ash there was a reduction in the number of AFC in LALN but not in spleen. The results did not demonstrate any significant difference in the immunosuppression of fly ash and Ni-coated fly ash exposed rats. The decrease in AFC formation in Ni-coated fly ash exposed animals was of a lesser magnitude than in rats exposed to Ni-alone.
Acute overdose due to benzydamine
Authors: Gómez-López Lilian , Hernández-Rodrîguez José , Pou Jordi , Nogué Santiago
Published: April 2003

Benzydamine is a nonsteroidal anti-inflammatory drug, currently available as mouthwash, aerosol, dermal cream, vaginal douche preparation, pills and otic drops. Up to now no cases of poisoning due to this drug have been reported. A 6-year-old girl with an accidental poisoning with benzydamine is described. The episode consisted of hallucinosis without other symptoms and resolved spontaneously in 17 h.
Formation of a carcinogenic aromatic amine from an azo dye by human skin bacteria in vitro
Authors: Platzek T , Lang C , Grohmann G , Gi U-S , Baltes W
Published: April 2003

Azo dyes represent the major class of dyestuffs. They are metabolised to the corresponding amines by liver enzymes and the intestinal microflora following incorporation by both experimental animals and humans. For safety evaluation of the dermal exposure of consumers to azo dyes from wearing coloured textiles, a possible cleavage of azo dyes by the skin microflora should be considered since, in contrast to many dyes, aromatic amines are easily absorbed by the skin. A method for measuring the ability of human skin flora to reduce azo dyes was established. In a standard experiment, 361011 cells of a culture of Staphylococcus aureus wereincubatedinsyntheticsweat (pH 6.8, final volume 20 mL) at 288C for 24 h with Direct Blue 14 (C.I. 23850, DB 14). The reaction products were extracted and analysed using HPLC. The reduction product o-tolidine (3,3'-dimethylbenzidine, OT) could indeed be detected showing that the strain used was able to metabolise DB 14 to the corresponding aromatic amine. In addition to OT, two further metabolites of DB 14 were detected. Using mass spectrometry they were identified as 3,3'-dimethyl-4-amino-4'-hydroxybiphenyl and 3,3'-di methyl-4-aminobiphenyl. The ability to cleave azo dyes seems to be widely distributed among human skin bacteria, as, under these in vitro conditions, bacteria isolated from healthy human skin and human skin bacteria from strain collections also exhibited azo reductase activity. Further studies are in progress in order to include additional azo dyes and coloured textiles. At the moment, the meaning of the results with regard to consumer health cannot be finally assessed.
A comparison of the efficacy of a new asymmetric bispyridinium oxime BI-6 with presently used oximes and H oximes against sarin by in vitro and in vivo methods
Authors: Kassa J , Cabal J
Published: April 2003

1 The reactivating and therapeutic efficacy of a new acetylcholinesterase reactivator, designated BI-6 (1-/2-hydroxyiminomethylpyridinium/-4-/carbamoylpyridinium/-2-butene dibromide), against organophosphate sarin was compared with presently used oximes (pralidoxime, obidoxime, methoxime) and H oximes (HI-6, HLö-7) by in vitro and in vivo methods. 2 Our results confirm that the new oxime BI-6 is a significantly more efficacious acetylcholinesterase reactivator than currently available pralidoxime and obidoxime but not as effective as H oximes (HI-6, HLö-7) in vitro as well as in vivo. In addition, the oxime BI-6 is able to protect supralethal sarin poisoned rats at human-relevant doses. 3 Our data also suggest that the potency of oximes tested to reactivate sarin-inhibited acetylcholinesterase in vitro closely corresponds to their reactivating efficacy in vivo and their ability to protect rats poisoned with supralethal doses of sarin.
Inhibitory effects of H2-receptor antagonists on platelet function in vitro
Authors: Nakamura K , Kariyazono H , Shinkawal T , Yamaguchi T , Yamashita T , Ayukawal O , Moriyama Y , Yotsumoto G , Toyohira H , Taira A , Yamada K
Published: April 2003

1 To evaluate in vitro inhibitory effects of four types of histamine H2-receptor antagonist (H2-receptor antagonists), famotidine, roxatidine, cimetidine and ranitidine, on platelet function, we examined aggregating potency and P-selectin levels with agonist-induced aggregation. Ranitidine and cimetidine inhibited, in concentration of 0.35 mM, the secondary aggregation induced by 5 pM adenosine diphosphate (ADP), the aggregation induced by 1,g/mL collagen and 3 gM arachidonic acid. All of H2-receptor antagonists inhibited, in concentration of 1.4 mm, the aggregation induced by ADP, collagen and arachidonic acid. Ranitidine and cimetidine reduced markedly, in same concentration, P-selectin levels after induction of aggregation by 5 gm ADP, 1 ig/xmL collagen and 3 gM arachidonic acid. When classified by the strength of inhibitory action, ranitidine and cimetidine were strong, followed by famotidine and roxatidine. 2 It is considered that inhibitory effects of H.-receptor antagonists on platelet function are weaker than those of acetylsalicylic acid (ASA), since ASA inhibited platelet aggregation in concentration of 100 MM. 3 No relationship was observed between inhibitory effects of H2-receptor antagonists on platelet aggregation induced by above agonists and the presence or absence of imidazole ring in the chemical structure.
Expression of Macrophage Inflammatory Protein-1β in Human Endometrium: Its Role in Endometrial Recruitment of Natural Killer Cells
Authors: Kitaya Kotaro , Nakayama Takeshi , Okubo Tomoharu , Kuroboshi Haruo , Fushiki Shinji , Honjo Hideo
Published: April 2003

Human endometrium is infiltrated by natural killer (NK) cells throughout the menstrual cycle. The number of endometrial NK cells is low in the proliferative phase, but acutely increases after ovulation, and reaches a peak in the late secretory phase, suggesting that endometrium recruits these leukocytes selectively from circulating peripheral blood. We investigated the expression of macrophage inflammatory protein (MIP)-1β, a potential chemoattractant for NK cells, in the endometrium. RT-PCR and ELISA revealed that MIP-1β is expressed in the endometrium throughout the menstrual cycle at both the message and protein levels. MIP-1β expression is stronger in the secretory phase endometrium than in the proliferative phase endometrium. Immunohistochemistry revealed that MIP-1β is localized in the surface epithelial cells, glandular epithelial cells, and perivascular stromal cells throughout the menstrual cycle. Stromal cells in a wider perivascular area became immunoreactive in the secretory phase. There was a strong correlation between the endometrial MIP-1β concentration and the number of endometrial NK cells. Progesterone significantly induced MIP-1β secretion from cultured endometrial stromal cells, whereas 17β-estradiol had a weak effect. These results suggest that endometrial MIP-1β may be involved in the recruitment of NK cells from circulating peripheral blood.
Testosterone Dose-Dependently Increases Maximal Voluntary Strength and Leg Power, but Does Not Affect Fatigability or Specific Tension
Authors: Storer Thomas W. , Magliano Lynne , Woodhouse Linda , Lee Martin L. , Dzekov Connie , Dzekov Jeanne , Casaburi Richard , Bhasin Shalender
Published: April 2003

Testosterone supplementation in men increases fat-free mass, but whether measures of muscle performance, such as maximal voluntary strength, power, fatigability, or specific tension, are improved has not been determined. Furthermore, the extent to which these measures of muscle performance are related to testosterone dose or circulating concentration is unknown. To examine the relationship between testosterone dose and muscle performance, 61 healthy, eugonadal young men (aged 18–35 yr) were randomized to 1 of 5 groups, each receiving a long-acting GnRH agonist to suppress endogenous testosterone production plus weekly injections of 25, 50, 125, 300, or 600 mg testosterone enanthate for 20 wk. These doses produced mean nadir testosterone concentrations of 253, 306, 542, 1345, and 2370 ng/dl, respectively. Maximal voluntary muscle strength and fatigability were determined by a seated leg press exercise. Leg power was measured using a validated leg power instrument. Specific tension was estimated by the ratio of one repetition maximum muscle strength to thigh muscle volume determined by magnetic resonance imaging. Testosterone administration was associated with a dose-dependent increase in leg press strength and leg power, but muscle fatigability did not change significantly during treatment. Changes in leg press strength were significantly correlated with total (r = 0.46; P = 0.0005) and free (r = 0.38; P = 0.006) testosterone as was leg power (total testosterone: r = 0.38; P = 0.007; free testosterone: r = 0.35; P = 0.015), but not muscle fatigability. Serum IGF-I concentrations were not significantly correlated with leg strength, power, or fatigability. Specific tension did not change significantly at any dose. We conclude that the effects of testosterone on muscle performance are specific; it increases maximal voluntary strength and leg power, but does not affect fatigability or specific tension. The changes in leg strength and power are dependent on testosterone dose and circulating testosterone concentrations and exhibit a log-linear relationship with serum total and free testosterone. Failure to observe a significant testosterone dose relationship with fatigability suggests that testosterone does not affect this component of muscle performance and that different components of muscle performance are regulated by different mechanisms.
Preparation of Ordered Macroporous Sr0.5Sm0.5CoO3 as Cathode for Solid Oxide Fuel Cells
Authors: Chen Fanglin , Xia Changrong , Liu Meilin
Published: April 2003

Ordered macroporous Sr0.5Sm0.5CoO3 structrures with an average pore size of 140 nm have been prepared using close-packed arrangement of monodispersed polystyrene spheres as templates. A fuel cell using ordered macroporous Sr0.5Sm0.5CoO3 as the cathode, gadolinia-doped ceria (GDC) film as the electrolyte, and GDC–NiO as the anode generated maximum power densities of 150, 196 and 267 mW/cm2 at 500, 550 and 600 °C, respectively.
Photoisomerization of Persilyl-Substituted Silacyclopropene: Formation of Stable Persilyl-Substituted 1-Silaallene, and Its Reactivity
Authors: Ichinohe Masaaki , Tanaka Takashi , Sekiguchi Akira
Published: April 2003

Persilyl-substituted silacyclopropenes, (R3Si)2SiC2(SiMe3)2 (1a: R3Si = iPr3Si, 1b: R3Si = tBu2MeSi), were photochemically isomerized to 1-silaallene derivatives, (R3Si)2Si=C=C(SiMe3)2  2, at wavelengths longer than 340 nm. These compounds subsequently photoisomerized to acetylene derivatives, (R3Si)2(Me3Si)Si–C≡C–SiMe3  3, as a final product. The existence of 1-silaallene 2 was demonstrated spectroscopically as well as by a trapping reaction with water.
An Efficient Enantioselective Preparation of (S,S)-1,2-Bis(1-hydroxyalkyl)benzene
Authors: Asami Masatoshi , Wada Masaaki , Furuya Sanae
Published: April 2003

(S,S)-1,2-Bis(1-hydroxyalkyl)benzenes were obtained in >99% ee’s with high diastereoselectivity by the enantioselective addition of dialkylzinc to (S)-2-[1-(4-methoxybenzyloxy)alkyl]benzaldehyde (86% ee) in the presence of a catalytic amount of (S)-2-(4-methylpiperazin-1-ylmethyl)indoline.
Direct Synthesis of MCM-41 Mesoporous Aluminosilicates Containing Au Nanoparticles in Aqueous Solution
Authors: Lin Hong-Ping , Chi Yu-Shan , Lin Jiunn-Nan , Mou Chung-Yuan , Wan Ben-Zu
Published: April 2003

A mesoporous MCM-41 aluminosilicate containing Au nanoparticles catalyst of high surface area and porosity has been conveniently prepared in a simple embedding approach.
Aqueous Solution-Based Ceramic Thin Film Deposition Using Organic Polymers with Amide Groups
Authors: Kozuka Hiromitsu , Kishimoto Tomoko
Published: April 2003

An aqueous solution-based dip-coating technique was presented for ceramic thin film deposition. Organic polymers with amide groups such as polyvinylpyrrolidone, polyvinylacetamide and polyacrylamide, incorporated in aqueous solutions of metal salts, were demonstrated to offer much better wetting of the substrates and gel film formability. Transparent, crack-free TiO2 and ZrO2 thin films of 0.07–0.1 µm in thickness could be obtained from aqueous solutions of Ti(SO4)2 and ZrCl2O, respectively, containing these organic polymers.
Reductive Aldol Reaction of a-Imino Esters Promoted by Titanium Tetraiodide: Selective Synthesis of α-Amino-β-hydroxyesters
Authors: Shimizu Makoto , Takeuchi Yuka , Sahara Tetsuya
Published: April 2003

Under the influence of titanium tetraiodide reductive aldol reaction of N-tosylimines, derived from ethyl glyoxylate, with aldehydes proceeded to give α-amino-β-hydroxyesters in good yields.
Rhodium(I)-Catalyzed Acylation of Alkyne with Acylsilane: Transformation of 5- or 6-Alkynoylsilane to α-Alkylidenecycloalkanone
Authors: Yamane Motoki , Amemiya Takuma , Narasaka Koichi
Published: April 2003

Rhodium(I)-catalyzed intramolecular acylation of alkynyl group proceeds by the use of acylsilanes having an alkynyl moiety. 5- and 6-Alkynoylsilanes are converted to α-alkylidenecycloalkanones by treatment with [RhCl(CO)2]2 in the presence of acetic acid via transmetallation between the acylsilane moiety and a rhodium(I) complex.
Synthesis and Transfection Capability of Multi-Functionalized Fullerene Polyamine
Authors: Isobe Hiroyuki , Tomita Naoki , Jinno Shigeki , Okayama Hiroto , Nakamura Eiichi
Published: April 2003

A new fullerene transfection reagent bearing multiple-functional groups has been synthesized by diastereoselective double cycloaddition reaction. The highly oxygenated reagent transfers extra-cellular DNA into mammalian cells with the efficiency comparable to that of a nor-analogue.
Synthesis of Bromohydrosilanes: Reactions of Hydrosilanes with CuBr2 in the Presence of CuI
Authors: Kunai Atsutaka , Ochi Takahiko , Iwata Arihiro , Ohshita Joji
Published: April 2003

Reactions of hydrosilanes, R4−nSiHn (R = alkyl or phenyl, n = 1–3), with 2 equiv of CuBr2 in the presence of a catalytic amount of CuI led to selective replacement of an H–Si bond with a Br–Si bond giving R3SiBr, R2SiHBr, or RSiH2Br, while treatment of R2SiH2 and RSiH3 with 4 equiv of the reagent produced R2SiBr2 and RSiHBr2, respectively. Similar reaction of Het2SiSiEt2H afforded Het2SiSiEt2Br.
Copper(I) Chelate Complexes with Novel π-Conjugated 1,2-Bis(2-pyridylethynyl)benzene Ligands: Synthesis, Structure, and Reactivity
Authors: Kawano Tomikazu , Kuwana Jun , Shinomaru Tatsuji , Du Chong-Xu , Ueda Ikuo
Published: April 2003

Novel π-conjugated nitrogen ligands, 1,2-bis(2-pyridylethynyl)benzenes, and their Cu(I) complexes have been synthesized and structurally characterized: the reactivity of the complexes for radical cyclization has also been examined.
Conformational Change Forced by Cesium Ion Complexation in Crystal Violet Derivative Possessing Tris(monoaza-15-crown-5) Structure
Authors: Uda Ryoko M , Oue Masatoshi , Kimura Keiichi
Published: April 2003

A Crystal Violet derivative incorporating a tris(monoaza-15-crown-5) structure exhibits an anomalous absorbance change in the absorption spectrum of its acetonitrile solution, which was induced only by cesium ion but not by other alkali metal ions. A consideration about its complex conformation explains the cesium ion specificity and a molecular orbital calculation suggests the correlation between the conformation and absorbance.
Synthesis of PPV-Based Conjugated Oligomer Containing Tropone in Main Chain
Authors: Takagi Koji , Nishikawa Yukimi , Kunisada Hideo , Yuki Yasuo
Published: April 2003

The synthesis of a tropone-containing PPV-based conjugated oligomer by the Wittig polycondensation was investigated, where the tropone unit was introduced as the conjugated segment. Although the NMR and IR studies revealed the low molecular weight of the resulting product, no side reaction toward the carbonyl group in the tropone ring occurred to maintain the tropone structure as evidenced by the MALDI(Matrix-Assisted Laser Desorption Ionization)-TOFMS spectrum. The UV–vis and PL spectra gave preliminary information on the optical property of the tropone-containing conjugated oligomer.
Unique Fluorescent Properties of 1-Aryl-3,4-diphenylpyrido[1,2-a]benzimidazoles
Authors: Hirano Keisuke , Oderaotoshi Yoji , Minakata Satoshi , Komatsu Mitsuo
Published: April 2003

Novel fluorophores, 1-aryl-3,4-diphenylpyrido[1,2-a]benzimidazoles were synthesized. They emit intense blue to green fluorescence in solution (Φ: ca. 0.7) and show weak negative solvatofluorochromism by about 10 nm which was caused by the combination of π–π* and n–π* transitions. In the powdered form, they emit intense fluorescence whose intensity is at least two times stronger than that of Alq3.
Porphyrin Polygons: A New Synthetic Strategy for Cyclic Porphyrin Oligomers Utilizing a Porphyrin Double Decker Structure
Authors: Ikeda Masato , Sugasaki Atsushi , Kubo Yohei , Sugiyasu Kazunori , Takeuchi Masayuki , Shinkai Seiji
Published: April 2003

A novel synthetic scheme for constructing cyclic porphyrin oligomers is presented: bisporphyrin derivative 1 reacts with La(acac)3 in 1,2,4-trichlorobenzene to yield porphyrin polygons, such as cyclic dimer 12·2La(III) and cyclic trimer 13·3La(III).
Microporous Structure of Titanium Oxide Prepared by a Salt Catalytic Sol–Gel Process
Authors: Tanaka Kazuhiko , Murakami Yasushi , Imai Tomohito , Matsumoto Taki , Furuno Shinsuke , Sugimoto Wataru , Takasu Yoshio
Published: April 2003

A microporous structure (dpore < 1 nm) of titanium oxide was synthesized by a salt catalytic sol–gel process of dilute titanium tetra-n-butoxide (Ti(n-C4H9O)4) and H2O solution without any template molecule. The specific surface area of titanium oxide after the calcinations at 300–350 °C was 310 m2 g−1. It decreased significantly by calcinations above 400 °C because the microporous structure collapsed with crystallization into anatase.
Structure of the First Tetranuclear Ni(II) Complex Derived from N-(2-hydroxybenzylidene)-4,6-O-ethylidene-β-d-glucopyranosylamine
Authors: Sah Ajay K , Rao Chebrolu P , Saarenketo Pauli K , Rissanen Kari
Published: April 2003

In order to understand the binding nature of the glycosylamines possessing imine functionality, a novel tetranuclear Ni(II) complex of N-(2-hydroxybenzylidene)-4,6-O-ethylidene-β-d-glucopyranosylamine having twisted Ni4O4 cubane core was synthesized and structurally characterized.
Synthesis of New Photoresponsive Polymers Containing Trifluoromethyl-Substituted Norbornadiene Moieties
Authors: Nagai Takabumi , Shimada Miwa , Nishikubo Tadatomi
Published: April 2003

Polymers containing trifluoromethyl (CF3)-substituted donor−acceptor NBD moieties in the side chain or in the main chain were synthesized by substitution or addition with CF3-NBD-carboxylic acid derivatives, or by polycondensation of CF3-NBD-dicarboxylic acid derivatives, and the durability of the resulting polymers was examined.
Molybdenum Hydrido Complex Containing a Novel Quinquidentate (P,P,Ge,P,P) Ligand
Authors: Minato Makoto , Hirabayashi Ryo , Matsumoto Takaomi , Yamaguchi Yoshitaka , Ito Takashi
Published: April 2003

The reaction of [MoH4(Ph2PCH2CH2PPh2)2] with PhGeH3 or Ph2GeH2 resulted in the formation of a novel molybdenum–germyl complex [MoH3{[Ph2PCH2CH2P(Ph)C6H4-o]2(Ph)Ge-P,P,P,P,Ge}] (4) with a quinquidentate ligand comprised of a P∼P∼Ge∼P∼P framework, where activation of Ge–H bonds, two C–H bonds, and, in the case of Ph2GeH2, a Ge–C bond took place concurrently.
Synthesis and Fluorescence Emission Behavior of anti-[2.3](3,10)Phenanthrenophane: Overlap between Phenanthrene Rings Required for Excimer Formation
Authors: Nakamura Yosuke , Fujii Takahiro , Nishimura Jun
Published: April 2003

Novel anti-[2.3](3,10)phenanthrenophane 3, prepared by the intramolecular [2 + 2] photocycloaddition of 1,3-bis(3-vinyl-10-phenanthryl)propane, exhibited monomer fluorescence. This is in a remarkable contrast with the excimer fluorescence emission from anti-[2.3](3,9)phenanthrenophane 2 with slightly larger overlap between phenanthrene rings than in anti-3.
Pyrolyse organischer Verbindungen im Mikrowellenofen
Authors: Lühken Arnim , Bader Hans Joachim
Published: April 2003

DIE PYROLYSE CHEMISCHER VERBINDUNGEN wird im Chemieunterricht in unterschiedlichen Zusammenhängen thematisiert und sollte deshalb auch im Experiment nachvollzogen werden. Beispiele aus dem Bereich der Organischen Chemie sind das Cracken von Erdöl zur Gewinnung von Benzin und die thermische Zersetzung von Ethanol zur Darstellung von Ethen. In der Anorganischen Chemie sind pyrolytische Vorgänge ebenfalls von Bedeutung, werden jedoch meist als Calcinieren oder Brennen bezeichnet.

Mit zunehmender Relevanz der Themen „Umweltschutz, Stoffkreisläufe und Recycling”︁ wurden von verschiedenen Autoren auch Experimente zur Pyrolyse von Kunststoffen und Altreifen zur Demonstration des rohstofflichen Recycling ausgearbeitet [z.B. 1‐3].

In den Versuchsvorschriften zur Pyrolyse organischer Verbindungen wird das Ausgangsmaterial meist mit einem Wärmeüberträger (z.B. Sand) vermengt und über der Flamme eines oder mehrerer Gasbrenner unter Luftausschluss erhitzt. Die Thermolyse geschieht dann meist an einem ebenfalls erhitzten Festkörper‐Katalysator. Als problematisch erweist sich bei der Durchführung dieser Versuchsvorschriften eine ausreichende Wärmezufuhr für die vollständige Pyrolyse der Materialmenge, da die Wärmeübertragung nicht optimal gelingt.

In diesem Beitrag wird eine Methode beschrieben, deren Besonderheit zunächst die Zufuhr der zur Pyrolyse erforderlichen Wärmeenergie durch Mikrowellenstrahlung ist. Dadurch gelingt ein schnelles und gleichmäßiges Erhitzen des Pyrolysematerials. Das eingesetzte Medium zur Wärmeübertragung und dessen hohe Temperatur bedingen ein Produktspektrum, das sich überraschend von dem der klassischen Pyrolyse unterscheidet und zu interessanten Fragestellungen und didaktischen Aspekten führt.
Analytical SPLITT cell fractionation: Linearity and resolution study
Authors: Contado Catia , Dondi Francesco
Published: April 2003

In this paper the analytical SPLITT (split flow thin cell) procedure is used to characterize the percentage composition of micronic polydisperse particulate samples at a given cut‐off size. The linearity and resolution of the separation method have been tested using specifically prepared starch samples, in order to compare the analytical process with two continuous (preparative) SPLITT procedures. Linearity has been checked by injecting a series of suspensions (at different concentrations) under five different flow rate conditions. Retrieval factors F were evaluated to verify the relative amount of sample exiting the cell outlets. The effective resolution has been assessed by inspecting the SPLITT fractions with an optical microscope, counting the granules, and evaluating the percentage of granules of expected size. It has been found that the resolution is very good (around 90%) and independent of sample distribution. It is seen from the comparison that in the analytical SPLITT mode sample resolution is usually around 85–90% and it is significantly better than that of the continuous SPLITT modes, thus making the analytical mode valuable in characterizing polydisperse samples. The method was tested for the characterization of a commercial starch sample.
Optimization of headspace sampling using solid‐phase microextraction for chloroanisoles in cork stoppers and gas chromatography–ion‐trap tandem mass spectrometric analysis
Authors: Bianchi Federica , Careri Maria , Mangia Alessandro , Musci Marilena
Published: April 2003

In a study aiming to characterize cork off‐flavour for quality control purposes, chloroanisoles were extracted and identified from cork stoppers by means of solid‐phase microextraction (SPME)–gas chromatography–ion‐trap mass spectrometry (GC–ITMS). An experimental design procedure was used to investigate the effects of some experimental parameters on the SPME of 2,4‐dichloroanisole, 2,6‐dichloroanisole, and 2,4,6‐trichloroanisole from cork stoppers by using a Carboxen‐PDMS 75 μm fibre. Variables such as extraction temperature, extraction time, and percentage of ethanol added to the matrix were optimized to improve extraction efficiency of chloroanisoles onto SPME fibre. Instrumental analysis was performed by GC–ITMS in the MS/MS mode. Preliminary analyses on standard solutions allowed selection of the appropriate ionization mode (i. e. electron impact or chemical ionization), providing for each analyte the highest instrumental response. In order to find polynomial functions describing the relationships between variables and responses, the analytical responses, i.e. the chromatographic peak areas, were processed by using the backward multiple regression analysis. For all the analytes the operating conditions providing the highest extraction yield inside the experimental domain considered were found.
HPLC of humic substances fractionated by Flow FFF
Authors: Benincasa Maria‐Anna , Cartoni Giampaolo , Imperia Nadia
Published: April 2003

This communication reports a study of the effect of ionic strength and electrolyte composition on fractions, separately collected by flow FFF, of a mixture of humic substances. Reverse phase HPLC analysis of three early eluting fractions suggests that the components released by the column behave as organic acids. The baseline‐resolved peaks of the first two fractions, subject to higher retention in solutions of lower pH and/or higher polarity, substantiate this suggestion. The fraction with larger components, as measured by flow FFF, also appears to contain acidic species. Their retention level, however, may not be accurately modulated by varying the mobile phase properties as these species are either totally retained in acidic phases or released before the void peak at pH ≥ 4.2. Besides showing the effective separation achieved in the flow FFF channel, this study reveals the pronounced difference in the physicochemical properties of some components of a humic mixture even with very close particle size.
Novel Biodegradable and Thermosensitive Dex‐AI/PNIPAAm Hydrogel
Authors: Zhang Xian‐Zheng , Wu Da‐Qing , Sun Guo‐Ming , Chu Chih‐Chang
Published: April 2003

The dextran‐allyl isocyanate/poly(N‐isopropylacrylamide) (Dex‐AI/PNIPAAm) hydrogel was designed and prepared by copolymerization of the modified dextran with N‐isopropylacrylamide (NIPAAm). This novel Dex‐AI/PNIPAAm hydrogel is biodegradable and intelligent due to its biodegradable dextran linkage and thermosensitive PNIPAAm moiety. With an increase in dextran content, it exhibits the increased lower critical solution temperature (LCST) and decreased porous microstructure. Also, the thermosensitivity of this hydrogel is also controllable and adjustable depending on the different compositions.

SEM micrographs of the Dex‐AI/PNIPAAm hydrogels.

magnified image

SEM micrographs of the Dex‐AI/PNIPAAm hydrogels.
Conical diffraction by periodic structures: Variation of interfaces and gradient formulas
Authors: Elschner J. , Schmidt G.
Published: April 2003

This paper studies the dependence of solutions to conical diffraction problems upon geometric parameters of non–smooth profiles and interfaces between different materials of diffractive gratings. This problem arises in the design of those optical devices to diffract time–harmonic oblique incident plane waves to a specified far–field pattern. We prove the stability of solutions and give analytic formulas for the derivatives of reflection and transmission coefficients with respect to Lipschitz perturbations of interfaces. These derivatives are expressible as contour integrals involving the direct and adjoint solutions of conical diffraction problems.
On 1–dimensional dissipative Schrödinger–type operators their dilations and eigenfunction expansions
Authors: Kaiser H.–Ch. , Neidhardt H. , Rehberg J.
Published: April 2003

We study in detail Schrödinger–type operators on a bounded interval of R with dissipative boundary conditions. The characteristic function of this operator is computed, its minimal self–adjoint dilation is constructed and the generalized eigenfunction expansion for the dilation is developed. The problem is motivated by semiconductor physics.
Strategien zur Verbesserung der Fahrdynamik durch aktive Stelleingriffe an den Rädern
Authors: Heinzl Ph. , Plöchl M. , Lugner P.
Published: April 2003

Durch aktive Eingriffe eines Regelungssystems in die Fahrdynamik eines Kraftfahrzeugs können kritische Fahrsituationen verhindert oder der Fahrer bei der Bewältigung dieser unterstützt werden. Ein solches System beeinflußt in der Regel aktiv die Gierbewegung des Fahrzeugs. Als Erweiterung scheint es aber sinnvoll, auch den Schwimmwinkel des Fahrzeugs zu regeln. Dieser kombinierten Regelung ist ein ABS überlagert, das die vom Fahrer oder Regler vorgegebenen Bremsmomente beschränkt.

Der simulierte Regelkreis besteht aus einem Fahrzeugmodell mit ausreichend genau abgebildeten Reifenkräften, aus einem Zustandsbeobachter zur Schätzung des Schwimmwinkels und einem Gleitregler (sliding control). Der Ausgang des Reglers ist eine Kombination zweier der drei möglichen Stelleingriffe: Zusatzlenken der Vorderräder, der Hinterräder und im Falle des einseitigen Zusatzbremsens ein zusätzliches Giermoment. Die Simulationsergebnisse der Fahrmanöver ‘Lenkwinkelsprung’ und ‘Bremsen in der Kurve’ veranschaulichen die Verbesserung der aktiven Fahrsicherheit durch alle drei möglichen Regelstrategien; bei starkem Kurvenbremsen verhält sich die Kombination Zusatzlenken der Vorderräder und Zusatzbremsen ungünstiger als die beiden anderen Kombinationen zufolge der Stellgrößenbeschränkung des übergeordneten ABS.
Low‐rank approximation of FE matrix inverses for operators with jumping coefficients
Authors: Bebendorf M. , Hackbusch W.
Published: April 2003

This article deals with the existence of blockwise low‐rank approximants, so called ℋ︁‐matrices, to inverses of FE matrices in the case of uniformly elliptic operators with L∞‐coefficients. Unlike operators arising from boundary element methods for which the ℋ︁‐matrix theory has been extensively developed the inverses of these operators do not benefit from the smoothness of the kernel function. However, it will be shown that this does not affect the existence of low‐rank approximants. Numerical examples show the correctness of our estimates.
A Scharfetter–Gummel Type Discretization of the Quantum Drift Diffusion Model
Authors: Pinnau René
Published: April 2003

We derive a generalized Scharfetter–Gummel discretization of the Quantum Drift Diffusion Model in one space dimension. The scheme relies on the introduction of a generalized potential which identifies the quantum drift term. Further, the new scheme is stable in the semiclassical limit recovering the SG scheme for the classical drift diffusion equations. Numerical results for a ballistic diode are presented.
Instability of Unbalance Excited Synchronous Forward Whirl at Rotor‐Stator‐Contact
Authors: Ehehalt Ulrich , Markert Richard
Published: April 2003

Normally rotor unbalance causes synchronous forward whirl of rotor‐stator systems, even if rub occurs due to rotorstatorcontact. This synchronous forward whirl has to be stable in order to avoid destructive self‐excited dry friction backward whirl, chaotic motions or sub‐ and superharmonic vibrations. However, friction between rotor and stator can cause the synchronous forward whirl to become unstable within certain rotor speed ranges. In the present paper the stability of the synchronous forward whirl caused by unbalance is investigated for rotor motions under contact with the stator. To analyse the stability of synchronous forward whirl the equations of motion are linearised around the stationary synchronous motion. The characteristic polynomial of the perturbations is calculated and the stability is checked by the Hurwitz criterion.
Prevention of Stick‐Slip Vibrations by Passive Normal Force Control
Authors: Rudolph Martin , Popp Karl
Published: April 2003

The classical stick‐slip oscillator is extended by an additional degree of freedom which couples the slipping motion to the normal force. Using this, the effective friction force can be altered without changing the friction‐velocity characteristic. The paper deals with the optimization problem of finding parameters of the additional system that prevent stick‐slip motion or minimize the amplitude of the residual limit cycle. Another goal is to increase the decay rate of vibration. Results were achieved by numerical integration based on analytical investigations.
Vertikaldynamik von Straßenfahrzeugen mit Gas‐Feder‐Dämpfer‐Elementen
Authors: Duwensee Maik , Heim Andreas , Woernle Christoph
Published: April 2003

Gas‐Feder‐Dämpfer‐Elemente (GFD) sind Luftfedern, die mittels pneumatischer Drosseln bedämpft werden, wodurch separate Schwingungsdämpfer entfallen. Sie stellen ein neues Bauelement zur Aufbaufederung und Dämpfung im Fahrzeug dar. Um sie der Simulation z.B. in einem Viertelfahrzeug‐Schwingungsmodell zugänglich zu machen, muss ihr Verhalten mathematisch modelliert werden. Ihr Steifigkeits‐ sowie Dämpfungsverhalten bei unterschiedlichen Anregungsfrequenzen wird vorgestellt.
Erzwungene Schwingungen von elastischen Mehrkörpersystemen mit Reibkontakten
Authors: Genzo A. , Sextro W. , Popp K.
Published: April 2003

Im Folgenden wird eine Berechnungsmethode vorgestellt, die es erlaubt, das räumliche Schwingungsverhalten eines elastischen Mehrkörpersystems (EMKS) mit Reibkontakten in rechenzeit‐ und speicherplatzsparender Form zu analysieren. Der von trockener Reibung und Mikroschlupf geprägte, nichtlineare Dämpfungsmechanismus in den Reibkontakten eines EMKS wird dabei realitätsnahe abgebildet. Die Plausibilität der mit der Methode gewonnenen Berechnungsergebnisse wird beispielhaft an einem einfachen EMKS, einem in Längsrichtung geteilten, einseitig eingespannten Balken gezeigt. Für den geteilten Balken werden die Frequenzgänge des Torsionswinkels um die Längsachse und der Auslenkung um die biegeweiche Achse berechnet.
Adaptive Schwingungskompensation eines Parallelroboters
Authors: Schüller J. , Rose M. , Sachau D.
Published: April 2003

Bei der Entwicklung von Parallelrobotern stehen vor allem hohe Geschwindigkeiten und Beschleunigungen im Vordergrund, wie sie im Anwendungsfeld der Handhabung und Montage erforderlich sind. Das Streben nach immer leichteren Bauweisen bedingt hierdurch zwangsläufig eine größere Schwingungsanfälligkeit der einzelnen Elemente. In diesem Zusammenhang wird eine ebene und geschlossene kinematische Kette als Vorstudie zur Parallelrobotik untersucht. Mit adaptiven Stäben wird eine aktive Schwingungsreduktion des Robotors realisiert. Das System liegt als elastisches Mehrkörpermodell vor. Anhand der linearisierten Systemgleichungen wird die Beobachtbarkeit und die Steuerbarkeit der Struktur in verschiedenen Posen betrachtet. Mit einer prädiktiv adaptiven Zustandsregelung wird eine aktive Schwingungskompensation des Ende.ektors erreicht und in der nichtlinearen Simulation überprüft.
Construction of polyconvex, anisotropic free‐energy functions
Authors: Schröder J. , Neff P.
Published: April 2003

The existence of minimizers of some variational principles in finite elasticity is based on the concept of quasiconvexity, introduced by Morrey [6]. This integral inequality is rather complicated to handle. Thus, the sufficient condition for quasiconvexity, the polyconvexity condition in the sense of Ball [1], is a more important concept for practical applications, see also Ciarlet [4] and Dacorogna [5]. In the case of isotropy there exist some models which satisfy this condition. Furthermore, there does not exist a systematic treatment of anisotropic, polyconvex free‐energies in the literature. In the present work we discuss some aspects of the formulation of polyconvex, anisotropic free‐energy functions in the framework of the invariant formulation of anisotropic constitutive equations and focus on transverse isotropy.
Zum reversiblen thermomechnischen Kopplungseffekt bei idealen Kristallen
Authors: Schweizer B. , Wauer J.
Published: April 2003

Durch eine spezielle Analyse von Gitterschwingungen wird der thermomechanische Kopplungseffekt (Gough‐Joule‐Effekt) bei Festkörpern untersucht. Verwendet wird ein nichtlineares, unkorreliertes Teilchenmodell, das sog. Einstein‐Modell. Die Berechnung beschränkt sich auf ideale Kristalle mit nur einer Sorte von Gitterteilchen (Debyescher Festkörper). Ein Vergleich zwischen der bekannten makroskopischen Theorie und den hier vorgestellten mikroskopischen Ergebnissen wird gezogen.
Numerische Berechnung von Mikrostrukturen bei inelastischen Materialien mittels relaxierter Energien
Authors: Hoppe U. , Hackl K.
Published: April 2003

Die Verwendung eines inkrementellen Variationsprinzips ermöglicht die Berechnung der Mikrostrukturentwicklung bei inelastischen Materialien. Das Berechnungsverfahren beruht auf einer partiellen Rang‐1‐Konvexifizierung der reduzierten Energiefunktion und wird numerisch als globales Minimierungsproblem umgesetzt. Die Schwierigkeiten hinsichtlich der globalen Minimierung werden diskutiert.
A unified tensorial driving force for phase transitions – calculation of the onset of the transformation
Authors: Oberste‐Brandenburg C.
Published: April 2003

The transformation kinetics during phase transitions in solids are often described by a pair of scalar variables for both the thermodynamic force and flux. Based on the use of the Eshelby‐Tensor as the thermodynamic driving force for the phase‐transition, a tensorial measure is introduced which is used as the associated thermodynamic flux. Based on the assumption that the process maximizes the dissipation, these measures are used to describe the transformation kinetics during the phase transition. The tensorial description reduces to a description with the Gibbs‐energy as the driving force and the mass change of the phases as the thermodynamic flux for a hydrostatic stress state.

These considerations serve as the base for a phenomenological material‐law which describes the austenite‐martensite transformation in steels. In order to incorporate the different behavior of the phases, they are modeled independently. The model have been implemented into a finite‐element‐code which allows thermodynamically coupled calculations. A quenching‐test of a cylindrical specimen under biaxial mechanical load is simulated. The influence of the sequence of the change of the thermomechanical load in the stress‐temperature space (temperature→stress vs. temperature→stress) is studied. Furthermore, the influence of the direction of the applied stress is presented.
Simulation des Ausbreitungsverhaltens mikrostrukturell kurzer Ermüdungsrisse
Authors: Schick A. , Fritzen C.‐P.
Published: April 2003

Es wird ein Fließstreifenmodell zur Simulation des Stadium‐I‐Risswachstums vorgestellt. Das Randwertproblem wird numerisch über Randelemente gelöst, die auf der Versetzungstheorie basieren. Das Modell kann sowohl geometrisches Rissschließen als auch Lastreihenfolgeeffekte berücksichtigen.
A Thermo‐Mechanical Formulation Describing the Frictional Behavior of Rubber
Authors: Hofstetter K. , Eberhardsteiner J. , Mang H.A.
Published: April 2003

In this paper mechanical and thermal phenomena during the sliding motion of a rubber block on a rough surface are investigated. The presented formulation describes the frictional behavior of rubber on a macroscopic scale. Thus, it is not necessary to consider the roughness of the surface explicitly. Only macroscopic characteristics of the involved solids are required for the contact formulation. For the purpose of parameter identification and model verification, experiments have been carried out. The results from numerical simulations by means of the Finite Element Method (FEM) agree well with the experimental results.
Volumenabhängige hydrostatische Druckbelastung in der nichtlinearen FE‐Analyse
Authors: Rumpel T. , Schweizerhof K.
Published: April 2003

Für dünnwandige Schalen‐ und Membranstrukturen ist die Wechselwirkung einer hydrostatischen Druckbelastung mit dem sich durch eine Belastung ergebenden Strukturverformungen sowohl für Stabilitätsbetrachtungen wie auch bei großen Deformationen von entscheidender Bedeutung. Über das Prinzip der virtuellen Arbeit wird die hydrostatische Druckbelastung in die schwache Gleichgewichtsformulierung der elastomechanischen Kräfte eingeführt. Wird für die sich in einem elastischen Behälter befindlichen Flüssigkeit Volumenerhaltung gefordert, so kann die resultierende Spiegelhöhenänderung berechnet werden. Die beschreibenden nichtlinearen Gleichungen sind für eine Lösung mittels Newtonverfahren zu linearisieren. Eine Finite Element Diskretisierung führt auf eine Laststeifigkeitsmatrix und das zugehörige Residuum der volumenabhängigen Druckkraft. Wesentlich ist, das keine Diskretisierung der Flüssigkeit erforderlich ist. An einem numerischen Beispiel wird die Effektivität des Verfahrens vorgestellt.
Identification of the Nonlinear Restoring Force Characteristic of a Rubber Mounting
Authors: Bruns J.‐U. , Lindner M. , Popp K.
Published: April 2003

This paper is concerned with the identification of the nonlinear restoring force characteristic of a rubber mounting that is part of an oscillator which is subjected to harmonic force excitation. A linearity test is successfully applied to the experimental data to detect the nonlinear behaviour of the system. It is shown that the results of linear system identification depend on the level of excitation force applied. Furthermore, the frequency response functions of the identified linear models only poorly match the measured ones. In consequence, a parametric nonlinear spring characteristic is introduced into the linear model. It is demonstrated that only one set of parameters is required to explain the system behaviour at different levels of excitation force. Also, each of the measured frequency response functions is matched more closely by the calculated frequency response of the nonlinear model.
Stability analysis of the constant temperature anemometer with frequency depended amplifier gain
Authors: šajn V. , Kosel F.
Published: April 2003

In this paper we are concerned with the stability and the dynamic response of the constant temperature anemometer. The amplifier of the presented hot–wire anemometer has one pole with high time constant, which affect the presented amplifier to behave in the anemometer working frequency bandwidth with the frequency depended gain. For precise description of the anemometer dynamical response the used transfer function of the amplifier is first order of zeros and third order of poles. The hot–wire response to the sine‐wave voltage perturbation was calculated and measured. The root curves of the transfer function were presented.