bluuebunny/crossref_metadata_2025 huggingface dataset:
Q‐ und R‐Matten aus Kunststoff für Bewehrungsaufgaben in der Geotechnik
Authors: Heerten Georg
Published: September 2004

Wachsende Güterströme und Warenverkehre im Zentrum eines wachsenden Europas und zunehmender Warenaustausch als Folge der Globalisierung der Weltwirtschaft stellen erhebliche Anforderungen an den Erhalt und Ausbau leistungsfähiger Infrastruktursysteme (Straße, Schiene, Wasserstraße). Nachhaltigkeitskonzepte bei der Bautätigkeit und Finanzierungsprobleme der öffentlichen Auftraggeber sind aktuelle Randbedingungen, denen mit Geokunststoff‐Bauweisen optimal Rechnung getragen werden kann. Es können neben den technischen auch die ökonomischen und ökologischen Vorteile – Baukosten sparen, Baustoffressourcen schonen – parallel genutzt werden. Eine Stützwand als “Bewehrte‐Erde‐Konstruktion” kann ganz erheblich kostengünstiger als eine Stahlbeton‐Stützmauer hergestellt werden. Die Ertüchtigung von wenig tragfähigen Böden mit flächig angeordneten Bewehrungslagen und/oder pfahlartigen geokunststoffummantelten Bodensäulen vermeidet umfangreichen Bodenaustausch, spart Kosten, verhindert umfangreichen Transport von Bodenmassen mit LKWs. Hierdurch werden knappe Baustoffressourcen wie Sand und Kies geschont sowie eine z. T. erhebliche Entlastung örtlicher Verkehrswege bewirkt.
Oberflächenabdichtungen aus PE‐HD‐Dichtungsbahnen für Altdeponien
Authors: Müller Werner
Published: September 2004

Bis Mitte 2005 müssen schätzungsweise 250 alte Hausmülldeponien geschlossen werden, die nicht dem Stand der Technik entsprechen. Danach muß irgendwann eine Sicherung erfolgen. Wo dies im Einzelfall kontrollierbar möglich ist, kann man versuchen, den Deponiekörper anaerob ausreagieren zu lassen oder aerob zu stabilisieren. An einer zusätzlichen technischen Barriere wird jedoch auch dann kaum ein Weg vorbeiführen. Einfache, aber hochwirksame technische Abdichtungen können auch auf der Oberfläche einer Deponie errichtet werden. Für die dort wirksamen Beanspruchungen sind Abdichtungen mit ausgewählten PE‐HD‐Dichtungsbahnen besonders geeignet. Eine Zulassung der Produkte für diesen Anwendungszweck ist erforderlich, da PE‐HD‐Werkstoffe, aber auch Dichtungsbahnen, die aus dem gleichen PE‐HD‐Werkstoff unterschiedlich gefertigt wurden, sich in ihren Eigenschaften drastisch unterscheiden können.
Geogitterbewehrte Dämme auf pfahlähnlichen Elementen: Grundlagen und Projekte
Authors: Alexiew Dimiter
Published: September 2004

Dämme auf weichem Untergrund, die durch vertikale pfahlähnliche Elemente und hochfeste horizontale geosynthetische Bewehrungen getragen werden, haben einige Vorteile gegenüber direkt (flach) gegründeten Dämmen: es ist keine Konsolidierungszeit erforderlich, die Dammsetzungen sind äußerst gering, man braucht keinen zusätzlichen Import oder Export von Dammboden zur vorläufigen Überlastung oder zur Setzungskompensation, unter Betrieb sind die Dämme praktisch setzungs‐ und wartungsfrei etc. Während der letzten Jahre nimmt die Anwendung solcher Systeme weltweit rapide zu.

Erste Berechnungsverfahren gibt es seit Ende der 80er Jahre. Sie haben inzwischen eine signifikante Entwicklung durchgemacht. Die wichtigeren davon werden kurz dargestellt mit Hinweisen auf deren Spezifik, Grenzen, Vor‐ und Nachteile. Es werden weiterhin einige ausgeführte Projekte aus den letzten 10 Jahren und aus verschiedenen Ländern beschrieben, die spezifische und innovative Lösungen beinhalten, um das heute Machbare, die Erfahrungen und den praktischen Stand der Technik darzustellen.
Zum Einsatz von Geokunststoffen bei der Flachgründung von Windenergieanlagen
Authors: Aydogmus Taner , Dohmel Denise , Schümann Christian
Published: September 2004

Für die Gründung der zunehmend größeren und leistungsstärkeren Windenergieanlagen ist aus wirtschaftlichen Gesichtspunkten eine Flachgründung anzustreben. Als besonders geeignete Baugrundverbesserungsmaßnahme für derartige Flachgründungen auf setzungsempfindlichen Weichschichten erwies sich der Tragschichteinbau (bewehrt und unbewehrt). Zur weiteren Erhöhung der Tragfähigkeit können in das Tragschichtpolster zusätzliche Bewehrungselemente aus Geokunststoffen eingebaut werden, wodurch eine günstigere Lastverteilung in den Untergrund erreicht, Spannungsspitzen abgebaut und die resultierenden Setzungen vergleichmäßigt werden. Zur Untersuchung der tragfähigkeits‐ und standsicherheitserhöhenden Eigenschaften von Geokunststoffen bei bewehrten Gründungspolstern unter flachgegründeten Windenergieanlagen in wenig tragfähigem Boden wurden im Rahmen dieser Studie numerische Untersuchung mit dem Programmsystem PLAXIS 2d, Version 8.2, durchgeführt, wobei sowohl der separate Beitrag des Füllbodens bzw. des Bewehrungselements ermittelt wurde. Es konnte nachgewiesen werden, daß die Anwendung von Geokunststoffen bei bewehrten Gründungspolstern einen signifikanten Sicherheitszuwachs sowie eine damit einhergehende Verkippungsreduzierung zur Folge hat.
Bestimmung von dynamischen Spannungen in Kunststoffbewehrte‐Erde‐Konstruktionen unter Zuhilfenahme von Kegelmodellen
Authors: Herold Andreas , Tamáskovics Nándor
Published: September 2004

Die Berücksichtigung von vorwiegend nichtruhenden Belastungen aus Verkehr, bauzeitlichen Anregungen oder Maschinenfundamenten wird normalerweise über quasi statische oder statische Modelle abgedeckt. In Einzelfällen kann es erforderlich sein, speziellere und genauere Kenntnisse über den Verlauf der dynamischen Spannungen, Verformungen, Geschwindigkeiten oder Beschleunigungen über die Tiefe zu erhalten. Im allgemeinen sind hier komplizierte Berechnungen im Zeit‐ oder Frequenzbereich mit entsprechenden kontinuumsmechanischen Modellen vorzusehen. Der vorliegende Beitrag beschäftigt sich mit der Anwendung von Kegelmodellen für diese spezielle Aufgabenstellung. Vorgestellt werden der theoretische Ansatz, die praktische Umsetzung sowie Vergleiche mit Meßergebnissen aus der Praxis. Mit der Anwendung des vorgestellten Berechnungsverfahrens ist die praktische Ermittlung von dynamischen Zusatzbelastungen in Geokunststofflage einer Kunststoffbewehrten‐Erde‐Konstruktion unter bevorzugt nichtruhenden Belastungen möglich.
Zum Sicherheitspotential des geotextilbewehrten Gründungspolsters gegenüber Setzungen
Authors: Gödecke Heinz‐Joachim , Schuler Günter , Gödecke Jörg‐Henrik
Published: September 2004

Zur Überbauung problematischer Gründungsflächen mit lokal möglichen Schwächezonen oder Hohlräumen im Untergrund werden oftmals setzungsausgleichende Polsterschichten mit zugfester Geotextilbewehrung eingesetzt und zunehmend Sicherheitsbetrachtungen hinsichtlich der möglichen Setzungen gefordert. Dafür hat sich in unserer Praxis – bei erfreulich begrenztem Rechenaufwand und simpler Programmierung – eine einfache bodenmechanische Modellbetrachtung mit daraus abgeleiteter Näherungsberechnung als hilfreich erwiesen. Nachfolgend wird das bodenmechanische Modell einer idealisiert kegel‐ und zylinderförmigen Auflockerungszone hinsichtlich der Sicherheitsreserve gegenüber Setzungen vorgestellt. Danach wird auf die Möglichkeit zur weiteren Setzungsbegrenzung mittels zugfester Geotextilbewehrung eingegangen, und zwar unter Rückgriff auf das ebenfalls sehr praxisorientierte Näherungsverfahren von Rafael [2]. Ein beispielhaftes Berechnungsergebnis zeigt eine brauchbare Übereinstimmung mit versuchsmäßig beobachteten Meßwerten. Zu berücksichtigen ist, daß die wie vor ermittelte Auflockerungs‐ und Setzungsmulde im Fall statischer und insbesondere dynamischer Belastungen zusätzliche Setzungen erfährt, für deren Ermittlung – unter Berücksichtigung der neuen Steifemodulzustände im Auflockerungszustand – erprobte klassische Berechnungsverfahren zur Verfügung stehen.
Anwendung eines flexiblen Planungskonzepts für die Realisierung einer komplexen Baugrubensicherungsmaßnahme
Authors: Thurner Robert , Lechner Peter , Falk Eduard
Published: September 2004

Am Beispiel der Baugrube “Admonterhof” im historischen Zentrum von Graz wird gezeigt, wie ein Konzept im Sinne der Beobachtungsmethode nicht nur zum technischen, sondern auch zum wirtschaftlichen Erfolg eines ungewöhnlich problematischen Bauvorhabens beitragen kann. Von dem nicht alltäglichen Wunsch ausgehend, unter einem denkmalgeschützten Gebäude eine bis zu 20 m tiefe Baugrube herzustellen, war eine Serie von wesentlichen Fragestellungen zu diskutieren: eine weitgehend bewegungsarme Abfangung des Altbestands über einen Stahlbetonträgerrost, dessen Auflagerung auf Großbohrpfählen und kleinkalibrigen Stahlrohr‐Pfählen mit einer Möglichkeit des aktiven Ausgleichs von Setzungsdifferenzen, die generelle Baugrubensicherung in nicht überbauten Bereichen mit überschnittenen Bohrpfählen, die Unterfangung von unterschiedlich strukturierten Bestandsgebäuden mittels Düsenstrahlverfahren, die Erkundung des Verlaufs und der Durchlässigkeit einer in einem Teil der Baugrube einfallenden Felsschicht, die Sicherung im Bereich des mit stark variierenden mechanischen Eigenschaften unterschiedlich festen Tertiärs und nicht zuletzt die Kontrolle des Grundwasserzutritts bei mehr als 10m Spiegeldifferenz.
Empfehlungen des Arbeitskreises 6.1 “Geotechnik der Deponiebauwerke” der Deutschen Gesellschaft für Geotechnik e. V.
Authors: Witt Karl Josef , Ramke Hans‐Günter
Published: September 2004

Der Arbeitskreis Geotechnik der Deponiebauwerke (früher Geotechnik der Deponien und Altlasten) hat in den Empfehlungsgruppen E 1 bis E 5 bisher 75 Empfehlungen veröffentlicht. Die jährliche Publikation wird fortgesetzt durch die aktualisierte Fassung der Empfehlungen E 2‐1 “Geotechnische Planung für Deponien” und E 1‐3 “Geophysikalische Standortuntersuchung” sowie durch einen neuen Empfehlungsentwurf E 5‐10 “Aufgaben und Qualifikation einer fremdprüfenden Stelle für mineralische Komponenten in Abdichtungssystemen”. Auf weitere überarbeitete Empfehlungen wird hingewiesen.
Fluorescent peptide probes for in vivo diagnostic imaging
Authors: Tung Ching‐Hsuan
Published: September 2004

Recently, many novel peptide‐based near‐infrared (NIR) fluorescent molecular probes have been developed for in vivo biomedical imaging. To report specific information of biological targets, the probes were individually designed according to the unique property or functions of their targets. These peptide‐based probes can be classified into targeting, crosslinking, and enzyme‐activatable probes. Several of them have been tested in various in vitro and in vivo models, and the obtained imaging information has been applied to disease detection, medical diagnosis, and drug evaluations. © 2004 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2004
New drying process for lactic bacteria based on their dehydration behavior in liquid medium
Authors: Mille Yannick , Obert Jean‐Philippe , Beney Laurent , Gervais Patrick
Published: September 2004

This study describes the different stages of optimization in an original drying process for lactic acid bacteria that allows the retrieval of dried samples of Lactobacillus plantarum with maximum viability. The process involves the addition of casein powder to bacterial pellets, followed by mixing and then air‐drying in a fluidized bed dryer. The effects on bacterial viability of the aw of the casein powder and the kinetics of aw variation in the fluidized bed dryer are considered. These parameters were first studied in a water–glycerol solution and the results were then applied to the drying process. Data from the study in liquid medium were reliable in the fluidized drying stage, insofar as optimal viability was achieved for similar dehydration times (16–50 min in liquid medium, and 30 min in the fluidized bed dryer). However, when the powder was mixed rapidly with bacteria, the level of destruction differed from that observed in liquid medium. Viability was up to 70% when the aw of water–glycerol was 0.55, whereas it was only 2.1% when the aw of the casein–bacterial mix was 0.64. The predictive capacity of dehydration in liquid medium is discussed with regard to the permeability of cells to external solutes. The new process allowed 100% survival of L. plantarum after complete drying (final aw < 0.2). However, when used for the desiccation of L. bulgaricus, these parameters achieved a viability of less than 10%. © 2004 Wiley Periodicals, Inc.
Genomic data for alternate production strategies. I. Identification of major contaminating species for Cobalt+2 immobilized metal affinity chromatography
Authors: Cai Ying , Moore Misty , Goforth Robyn , Henry Ralph , Beitle Robert
Published: September 2004

Recent advances in technology have allowed for the identification of complex protein mixtures in a rapid fashion. This report highlights the use of 2D gel electrophoresis, mass spectrometry, and database analysis to determine contaminating species of the Escherichia coli genome that are present during immobilized metal affinity chromatography (IMAC), highlighting Co2+ as the affinity ligand. Four proteins (triosephosphate isomerase, alpha galactosidase, Hsp90, and glucosamine 6‐phosphate synthase) constitute the majority of E. coli proteins that bind and potentially may coelute during chromatography. Results are discussed within the context of changes that when implemented could lead to an increase in IMAC efficiency, not by altering column conditions, but rather by changing the nature of the nuisance proteins that principally reduce column capacity and extend processing times. Such a study illustrates the use of proteome data to aid in bioprocess design. © 2004 Wiley Periodicals, Inc.
Dynamics of gene silencing by RNA interference
Authors: Raab R. Michael , Stephanopoulos Gregory
Published: September 2004

The large number of candidate genes identified by modern high‐throughput technologies require efficient methods for generating knockout phenotypes or gene silencing in order to study gene function. RNA interference (RNAi) is an efficient method that can be used for this purpose. Effective gene silencing by RNAi depends on a number of important parameters, including the dynamics of gene expression and the RNA dose. Using mouse hepatoma cells, we detail some of the principal characteristics of RNAi as a tool for gene silencing, such as the RNA dose level, RNA complex exposure time, and the time of transfection relative to gene induction, in the context of silencing a green fluorescent protein reporter gene. Our experiments demonstrate that different levels of silencing can be attained by modulating the dose level of RNA and the time of transfection and illustrate the importance of a dynamic analysis in designing robust silencing protocols. By quantifying the kinetics of RNAi‐based gene silencing, we present a model that may be used to help determine key parameters in more complex silencing experiments and explore alternative gene silencing protocols. © 2004 Wiley Periodicals, Inc.
Physicochemical surface properties of brewing yeast influencing their immobilization onto spent grains in a continuous reactor
Authors: Brányik Tomáš , Vicente António , Oliveira Rosário , Teixeira José
Published: September 2004

Immobilization of brewing yeast onto a cellulose‐based carrier obtained from spent grains, a brewing byproduct, by acid/base treatment has been studied in a continuously operating bubble‐column reactor. The aim of this work was to study the mechanisms of brewing yeast immobilization onto spent grain particles through the information on physicochemical surface properties of brewing yeast and spent grain particles. Three mechanisms of brewing yeast immobilization onto spent grains carrier were proposed: cell‐carrier adhesion, cell‐cell attachment, and cell adsorption (accumulation) inside natural shelters (carrier's surface roughness). The possibility of stable cell‐carrier adhesion regarding the free energy of interaction was proved and the relative importance of long‐range forces (Derjaguin‐Landau‐Verwey‐Overbeek theory) and interfacial free energies was discussed. As for the cell‐cell attachment leading to a multilayer yeast immobilization, a physicochemical interaction through localized hydrophobic regions on cell surface was hypothesized. However, neither flocculation nor chain formation mechanism can be excluded so far. The adsorption of brewing yeast inside sufficiently large crevices (pores) was documented with photomicrographs. A positive effect of higher dilution rate and increased hydrophobicity of base‐treated spent grains on the yeast immobilization rate has also been found. © 2004 Wiley Periodicals, Inc.
Effects of cyclodextrins, humic substances, and rhamnolipids on the washing of a historically contaminated soil and on the aerobic bioremediation of the resulting effluents
Authors: Berselli Sara , Milone Gabriella , Canepa Pietro , Di Gioia Diana , Fava Fabio
Published: September 2004

Nontoxic and biodegradable pollutant‐mobilizing agents, instead of chemical surfactants, were tested in the washing of an actual‐site chloroaromatic‐contaminated soil. A soil historically contaminated by chlorinated anilines and benzenes, thiophenes and several polycyclic aromatic hydrocarbons was subjected to washing by suspending it (15% w/v) in water or in water with 1.0% (w/v) β‐clodextrin (β‐CD), hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD), rhamnolipid (RL), dissolved humic substances (HS), or Triton X‐100 (TX) in shaken batch reactors for 24 hr. The resulting wastewaters were amended with nutrients and treated aerobically in shaken reactors for 65 days. The biogenic agents markedly enhanced (by 237%, β‐CD; 265%, HP‐β‐CD; 400%, RL; 566%, HS) the capability of water of eluting organic pollutants from the soil. TX enhanced the overall pollutant removal by about 660%; however, a lower depletion of the initial soil ecotoxicity, along with a more extensive impact on the soil organic matter, was observed. Furthermore, TX adversely affected the bioremediation of the resulting effluent by apparently inducing a premature decrease of specialized bacterial biomass. By contrast, the biogenic agents, and in particular HS and RL, sustained the biodegradation and dechlorination of pollutants by apparently enhancing the availability of specialized bacteria in the reactors. Thus, the biogenic agents proposed here seem to be promising nontoxic and nonaggressive soil washing agents for the integrated physicochemical (washing) and biological (aerobic posttreatment) restoration of poorly bioremediable (chloro) organics‐contaminated soils. © 2004 Wiley Periodicals, Inc.
Dibenzothiophene biodesulfurization pathway improvement using diagnostic GFP fusions
Authors: Reichmuth David S. , Blanch Harvey W. , Keasling Jay D.
Published: September 2004

The dibenzothiophene biodesulfurization pathway has shown significant potential for improving the processing of sulfur‐containing fossil fuels. However, the rate of desulfurization is limited by the last enzyme in the pathway, DszB. Genetic constructs designed to produce increased DszB activity were not functional due to low production of DszB, even when using a consensus ribosome binding site. To increase DszB production, the untranslated region 5′ of dszB was mutated using degenerate oligonucleotides and translational fusions with gfp to detect increased translation of dszB. After screening only 96 mutants, several showed increased green fluorescence and two showed increased DszB activity. When cotransformed with the full dszABC operon, the mutant dszB increased the rate of desulfurization ninefold relative to that using the native dszB. © 2004 Wiley Periodicals, Inc.
9,10‐Anthraquinones and Other Biologically Active Compounds from the Genus Rubia
Authors: Singh Ram , Geetanjali  , Chauhan S. M. S.
Published: September 2004

The secondary metabolites isolated from Rubia species, their biological activities, and colouration properties have been reviewed. Over 150 chemical constituents belonging to different classes of bioactive compounds such as anthraquinones and their glycosides, naphthoquinones and glycosides, terpenes, bicyclic hexapeptides, iridoids, and carbohydrates are listed together with their source(s) and corresponding references.
Synthesis, Cytotoxicity, and Apoptosis Induction in Human Tumor Cells by Geiparvarin Analogues
Authors: Viola Giampietro , Vedaldi Daniela , dall'Acqua Francesco , Basso Giuseppe , Disarò Silvia , Spinelli Monica , Cosimelli Barbara , Boccalini Marco , Chimichi Stefano
Published: September 2004

A series of geiparvarin analogues modified on the unsaturated alkenyloxy bridge, where a H‐atom replaced the 3′‐Me group, were synthesized and evaluated against a panel of human tumor cell lines in vitro. These compounds demonstrated a stronger increase in growth inhibitory activity when compared to the parent compound geiparvarin (8). In particular, the activity increased even further in the series of demethylated compounds when a Me substituent in the coumarin moiety is introduced. On the contrary, the same modifications exerted on the parent compound led to an activity reduction. Interestingly, the new derivatives proved to be fully inhibitory to drug‐resistant cell lines, thus suggesting that they are not subject to the pump‐mediating efflux of antitumor drugs. On the basis of their cytotoxic profiles, the most‐active compounds were selected for further biological evaluation. The extracellular acidification rate by the new geiparvarin analogues was measured with the CytosensorTM microphysiometer. The new derivatives significantly increased the acidification rate during the 24–48 h of incubation in a concentration‐dependent manner. Cell‐cycle analysis, evaluated by flow cytometry, revealed a strong apoptotic induction by these compounds confirmed by DNA laddering and observation by electron microscopy. Interestingly, the apoptotic pathway did not appear to be mediated by the activation of caspase‐3.
Electroreduction of Oxygen by Cytochrome c Oxidase Immobilized in Electrode‐Supported Lipid Bilayer Membranes
Authors: Su Lianyong , Hawkridge Fred M. , Rhoten Melissa C.
Published: September 2004

Cytochrome c oxidase is the terminal enzyme in mammalian respiration, and one of its main functions is to catalyze the reduction of oxygen under physiological conditions. Direct reduction of oxygen at electrodes requires application of substantial overpotentials. In this work, bovine cytochrome c oxidase has been immobilized in electrode‐supported lipid bilayer membranes to investigate the electroreduction of oxygen under flow conditions. The effect that temperature, solution pH, and solution composition have on the reduction of oxygen by this novel enzyme‐modified electrode is reported. Results indicate that the electroreduction of oxygen is most pronounced at low pH (6.4) and elevated temperature (38°). At an applied potential of −350 mV vs. Ag/AgCl (1M KCl), a current density of ca. 7 μA/cm2 was obtained. The current responses obtained at these electrodes are stable over a period of ca. 10–14 days (10–15% decrease in response). The cytochrome c oxidase‐modified electrodes described here could potentially be used for the direct electroreduction of oxygen to water in a biofuel cell.
Cholinesterase‐Inhibiting Withanolides from Ajuga bracteosa
Authors: Riaz Naheed , Malik Abdul , Aziz‐ur‐Rehman  , Nawaz Sarfraz Ahmad , Muhammad Pir , Choudhary M. Iqbal
Published: September 2004

Three new withanolides, bracteosin A (=(22R)‐5β,6β : 22,26‐diepoxy‐4β,28‐dihydroxy‐3β‐methoxyergost‐24‐ene‐1,26‐dione; 1), bracteosin B (=(22R)‐5β,6β : 22,26‐diepoxy‐4β,28‐dihydroxy‐3β‐methoxy‐1,26‐dioxoergost‐24‐en‐19‐oic acid; 2), and bracteosin C (=(22R)‐22,26‐epoxy‐4β,6β,27‐trihydroxy‐3β‐methoxyergost‐ 24‐ene‐1,26‐dione; 3), have been isolated from the whole plants of Ajuga bracteosa. Their structures were deduced by spectral analysis, including 1D‐ and 2D‐NMR techniques. In addition, dihydroclerodin‐1, clerodinin A, lupulin A, and dihydroajugapitin have also been isolated for the first time from this species. Compounds 1–3 exhibited evident inhibitory potential against cholinesterase enzymes in a concentration‐dependent fashion.
Nine New Isoxuxuarine‐Type Triterpene Dimers from Maytenus chuchuhuasca
Authors: Shirota Osamu , Sekita Setsuko , Satake Motoyoshi , Morita Hiroshi , Takeya Koichi , Itokawa Hideji
Published: September 2004

Nine new isoxuxuarine‐type triterpene dimers, named isoxuxuarines Bα (1), Bβ (2), 7,8‐dihydro‐Bα (3), Cα (4), Cβ (5), 7,8‐dihydro‐Cα (6), Dα (7), Dβ (8), and 7,8‐dihydro‐Dα (9), were isolated from the South American medicinal plant ‘xuxuá’ (Maytenus chuchuhuasca). The structures were elucidated on the basis of several spectroscopic analyses, including 2D‐NMR experiments, MS spectra, and CD spectral studies. The isolations and structure elucidations of the new triterpene dimers are presented, and a rationale for the divergent formation of the regiochemical and stereochemical isomers of triterpene dimers is discussed.
From Earth's Primitive Atmosphere to Chiral Peptides – The Origin of Precursors for Life
Authors: Plankensteiner Kristof , Reiner Hannes , Rode Bernd M.
Published: September 2004

To re‐enact the long way to the origin of life with today's chemical methods, many steps have to be investigated in the light of a primordial scenario deduced from geochemical research. After the formation of our planet and its atmosphere, prebiotic chemical evolution started its course with the formation of the first building blocks for the formation of biomolecules. In the case of proteins, those building blocks were amino acids that had to be formed in the primitive atmosphere, and then had to react to peptides and proteins as the main pillar of first life. In this paper, we describe the processes in the primordial atmosphere according to contemporary geochemical knowledge leading to the synthesis of amino acids until the formation of homochiral peptides, and, thus, show a plausible pathway towards the origin of life.
Bimetallic Complexes of Spiro‐Azacrown Ligands as Catalysts of Phosphoester and Phosphoric Anhydride Cleavage
Authors: Wang Qi , Mikkola Satu , Lönnberg Harri
Published: September 2004

The ability of bimetallic homo‐ and heteronuclear complexes of two spiro‐linked ligands, viz. a biazacrown (i.e., 2,6,10,14,18,22‐hexaazaspiro[11.11]tricosane (1)) and an azacrowncrown ether (i.e., 14,17,20,23,26‐pentaoxa‐2,6,10‐triaza‐spiro[11.15]heptacosane (2)), to promote the cleavage of the phosphoester linkage of dinucleoside 3′,5′‐phosphates and the phosphoric anhydride bridge of dinucleoside 5′,5′‐triphosphates was studied. In both reactions, the bimetallic homonuclear Cu2+ and Zn2+ complexes were better catalysts than their monometallic counterparts. The acceleration was two‐ to five‐fold with the phosphoester cleavage and 3‐ to 20‐fold with the phosphoric anhydride cleavage. Interestingly, the most‐efficient catalyst of the phosphoester cleavage was the heterodinuclear Ni2+,Zn2+ complex of 1, the catalytic activity of which was up to 5‐ and 100‐fold that of the homodinuclear Zn2+ and Ni2+ complexes, respectively. Moreover, this cooperative acceleration was observed to depend on the identity of the 5′‐linked nucleoside: 3′,5′‐UpU and 3′,5′‐ApU were cleaved much faster than 3′,5′‐UpA, and no cooperative acceleration was observed with 3′,5′‐ApA. The reaction was second‐order in hydroxide ion concentration, suggesting that a double deprotonation took place on going from the initial to the transition state. Evidently, in addition to deprotonation of the attacking 2′‐OH group, N(3)H of the 5′‐linked uridine was displaced by one of the metal ions of the cleaving agent. With the phosphoric anhydride cleavage, no similar cooperativity of two different metal ions was observed, but the greatest rate‐acceleration was achieved with the homodinuclear Cu2+ complexes.
Resolution of Binary Mixtures of Rifamycin SV and Rifampicin by UV/VIS Spectroscopy and Partial Least‐Squares Method (PLS)
Authors: Lomillo M. Asunción Alonso , Domínguez Renedo Olga , Arcos Martínez M. Julia
Published: September 2004

A procedure is proposed for the joint determination of rifamycin SV and rifampicin by UV/VIS spectroscopy. A partial least‐squares regression (PLS) was used for the resolution of the overlapping spectrophotometric signals from mixtures of the two drugs. The application of a genetic algorithm to select some of the predictor variables allows one to considerably reduce the number of experimental variables, as well as to improve the prediction capacity of the PLS model constructed with these selected potentials. Finally, the methods were applied to the determination of these drugs in biological samples.
13C‐CPMAS and 1H‐NMR Study of the Inclusion Complexes of β‐Cyclodextrin with Carvacrol, Thymol, and Eugenol Prepared in Supercritical Carbon Dioxide
Authors: Locci Emanuela , Lai Simona , Piras Alessandra , Marongiu Bruno , Lai Adolfo
Published: September 2004

β‐Cyclodextrin (β‐CD) inclusion complexes with carvacrol (1), thymol (2), and eugenol (3) (components of essential oils of vegetable origin) were prepared by the supercritical CO2 technique, and their structural characterization was achieved by means of 1H‐NMR in aqueous solution and 13C‐CPMAS NMR in the solid state. Evidence of the formation of the inclusion complexes for all the examined systems was obtained by 1H‐NMR in solution, while 2D‐ROESY‐NMR experiments were used to investigate the geometry of inclusion. In addition, the dynamics of these inclusion complexes in the kHz timescale was investigated by analysis of the 1H and 13C spin‐lattice relaxation times in the rotating frame.
A Novel Carbazole Derivative, BMVC: a Potential Antitumor Agent and Fluorescence Marker of Cancer Cells
Authors: Chang Cheng‐Chung , Kuo I‐Chun , Lin Jing‐Jer , Lu Yu‐Cheng , Chen Chin‐Tin , Back Hong‐Tsun , Lou Pei‐Jen , Chang Ta‐Chau
Published: September 2004

We have investigated a novel compound, 3,6‐bis[2‐(1‐methylpyridinium)vinyl]carbazole diiodide (BMVC), for inhibiting telomerase activity and distinguishing human lung H1299 and oral Ca9‐22 cancer cells from lung IMR90 and skin Detroit‐551 normal fibroblast cells. The telomeric repeat amplification protocol (TRAP) assay shows that the concentration of BMVC that inhibits 50% of the telomerase activity (IC50) is ca. 0.05 μM. On the other hand, the cell‐viability assay indicates that the cytotoxicity was less than 15% to the H1299 and Ca9‐22 cancer cells, and almost negligible to the MRC‐5 and Detroit‐551 normal cells after incubation with 0.5 μM BMVC for 72 h. The low concentration of 0.05 μM of BMVC can inhibit telomerase activity but does not have general toxic effects to normal cells, implying that BMVC is a promising telomerase inhibitor. Moreover, wide‐field fluorescence images of 0.1 μM BMVC‐treated cells show bright fluorescence spots in the nuclei of the most H1299 and Ca9‐22 cancer cells. Interestingly, similar fluorescence spots are hardly observed in the nuclei of the IMR90 and Detroit‐551 normal cells, implying that BMVC might be a useful marker to distinguish tumor cells and normal cells.
Antimicrobial Activity of Hydrophobic Xanthones from Cudrania cochinchinensis against Bacillus subtilis and Methicillin‐Resistant Staphylococcus aureus
Authors: Fukai Toshio , Oku Yukio , Hou Ai‐Jun , Yonekawa Makiko , Terada Sumio
Published: September 2004

Ten xanthones with one or two isoprenoid groups and a prenylated benzophenone isolated from roots of Cudrania cochinchinensis (Moraceae) were tested for their antimicrobial activities against Bacillus subtilis and methicillin‐resistant Staphylococcus aureus (MRSA). Among these compounds, gerontoxanthone H exhibited considerable antibacterial activity against B. subtilis (MIC=1.56 μg/ml). Four xanthones, gerontoxanthone I, toxyloxanthone C, cudraxanthone S, and 1,3,7‐trihydroxy‐2‐prenylxanthone, showed weak antibacterial activity against the bacterium (MICs=3.13–6.25 μg/ml). These compounds also exhibited similar MIC values against methicillin‐sensitive S. aureus, MRSAs, and Micrococcus luteus.
Comparative Metabolism of α‐ and β‐Peptides in the Insect Heliothis virescens and in Plant Cells of Black Mexican Sweet Maize
Authors: Lind Rob , Greenhow Daren , Perry Simon , Kimmerlin Thierry , Seebach Dieter
Published: September 2004

The tripeptide H‐Val‐Ala‐Leu‐OH and the N‐Ac‐tetrapeptide amide Ac‐Thr‐Lys‐Trp‐Phe‐NH2, and their β‐peptidic counterparts H‐β3hVal‐β3hAla‐β3hLeu‐OH and Ac‐β3hThr‐(S)β2hLys‐β3hTrp‐β3hPhe‐NH2, respectively, have been injected into Heliothis virescens larvae and added to cell cultures of black mexican sweet maize. The body liquids of the larvae and the supernatant of the plant cell cultures were sampled 0, 2, 3, 6, 17, and/or 24 h after application and analyzed by LC/MS. While the two α‐peptides were degraded rapidly in these environments, the concentration of the β‐peptides was found to decrease very slowly. Thus, ca. 60% of the original amount of the β‐tetrapeptide was detected in the liquids of the insect after 24 h. The plant cells did not seem to make use of the β‐peptides at all, whereas, the α‐tripeptide completely disappeared from the supernatant after 3 h. Thus, we have demonstrated, for the first time, the high stability of β‐peptides against degradation and metabolism in an insect and a plant. Especially remarkable is the persistence of the β‐tetrapeptide with its functionalised and, thus, ‘metabolisable’ side chains of Thr, Lys, Trp, and Phe in the insect larvae, which are known to have a high level of activity of oxidizing enzymes. The results described here match those of ADME investigations with radioactively labeled β‐peptides in rats, where essentially complete stability has been observed, while environmental microorganisms have been found to biodegrade β‐peptides, albeit slowly. Possible implications of these findings for biomedical and pest‐control applications are proposed.
CO2 in Supramolecular Chemistry: Preparation of Switchable Supramolecular Polymers
Authors: Xu Heng , Rudkevich Dmitry M.
Published: September 2004

CO2 gas was used to construct novel types of supramolecular polymers. Self‐assembling nanostructures 11 and 13 were prepared, which employ both hydrogen bonding and dynamic, thermally reversible carbamate bonds. As precursors, calixarene ureas 1 and 2 were synthesized, which strongly aggregate/dimerize (KD≥106 M−1 per capsule) in apolar solution with the formation of self‐assembling capsules 7 and linear polymeric chains 8, respectively, and also possess “CO2‐philic” primary amino groups on the periphery. CO2 effectively reacts with molecules 7 and 8 in apolar solvents and cross‐links them with the formation of multiple carbamate salt bridges. Oligomeric aggregate 11 and three‐dimensional polymeric network 13 were prepared and characterized by 1H and 13C NMR spectroscopy. The morphology of supramolecular gel 13 was studied by scanning electron microscopy. Addition of a competitive solvent destroyed the hydrogen bonding in assembling structures 11 and 13, but did not influence the carbamate linkers; carbamate salts 12 and 14, respectively, were obtained. On the other hand, thermal release of CO2 from 11 and 13 was easily accomplished (1 h, 100 °C) while retaining the hydrogen‐bonding capsules. Thus, three‐dimensional polymeric network 13 was transformed back to linear polymeric chain 8 without breaking up. Encapsulation and storage of solvent molecules by 11 and 13 was demonstrated. This opens the way for switchable materials, which reversibly trap, store, and then release guest molecules. A two‐parameter switch and control over hydrogen bonding and CO2–amine adducts was established.
Polymeric Nanoparticles from Rapid Expansion of Supercritical Fluid Solution
Authors: Sun Ya‐Ping , Meziani Mohammed J. , Pathak Pankaj , Qu Liangwei
Published: September 2004

In this concept paper we highlight applications of supercritical fluid technology in particle formation and production, especially some recent advances in the rapid expansion of supercritical solutions (RESS) processing technique. We also highlight the simple but significant modification to the traditional RESS by using a liquid solvent or solution at the receiving end of the supercritical solution expansion, or the rapid expansion of a supercritical solution into a liquid solvent (RESOLV), and applications of the technique to the preparation of nanoparticles. In particular, successes and challenges in the use of RESOLV for nanoscale (<100 nm) polymeric particles and the subsequent protection of the suspended nanoparticles from agglomeration are discussed.
Vinyl Sulfoxides as Stereochemical Controllers in Intermolecular Pauson–Khand Reactions: Applications to the Enantioselective Synthesis of Natural Cyclopentanoids
Authors: Rodríguez Rivero Marta , Alonso Inés , Carretero Juan C.
Published: September 2004

The use of sulfoxides as chiral auxiliaries in asymmetric intermolecular Pauson–Khand reactions is described. After screening a wide variety of substituents on the sulfur atom in α,β‐unsaturated sulfoxides, the readily available o‐(N,N‐dimethylamino)phenyl vinyl sulfoxide (1 i) has proved to be highly reactive with substituted terminal alkynes under N‐oxide‐promoted conditions (CH3CN, 0 °C). In addition, these Pauson–Khand reactions occurred with complete regioselectivity and very high diastereoselectivity (de=86–>96 %, (S,RS) diastereomer). Experimental studies suggest that the high reactivity exhibited by the vinyl sulfoxide 1 i relies on the ability of the amine group to act as a soft ligand on the alkyne dicobalt complex prior to the generation of the cobaltacycle intermediate. On the other hand, both theoretical and experimental studies show that the high stereoselectivity of the process is due to the easy thermodynamic epimerization at the C5 center in the resulting 5‐sulfinyl‐2‐cyclopentenone adducts. When it is taken into account that the known asymmetric intermolecular Pauson–Khand reactions are limited to the use of highly reactive bicyclic alkenes, mainly norbornene and norbornadiene, this novel procedure constitutes the first asymmetric version with unstrained acyclic alkenes. As a demonstration of the synthetic interest of this sulfoxide‐based methodology in the enantioselective preparation of stereochemically complex cyclopentanoids, we have developed very short and efficient syntheses of the antibiotic (−)‐pentenomycin I and the (−)‐aminocyclopentitol moiety of a hopane triterpenoid.
Insights into the Reaction of Transplatin with DNA and Proteins: Methionine‐Mediated Formation of Histidine–Guanine trans‐Pt(NH3)2 Cross‐Links
Authors: Marchán Vicente , Pedroso Enrique , Grandas Anna
Published: September 2004

Simultaneous exposure of transplatin to polypeptides and DNA was mimicked by using a model peptide–oligonucleotide conjugate. Initially formed methionine–guanine chelates evolved into adducts with histidine–guanine trans‐Pt(NH3)2 cross‐links that differed in constitution and stability from those formed by reaction of the same conjugate with the anticancer drug cisplatin. This finding may be due to different capacities of the two diamminedichloroplatinum(II) complexes to interfere with biological processes and may explain their differing cytotoxicities.
CC Bond Insertion of a Complexed Phosphinidene into 1,6‐Methano[10]annulene
Authors: Bulo Rosa E. , Trion Linda , Ehlers Andreas W. , de Kanter Fransiscus J. J. , Schakel Marius , Lutz Martin , Spek Anthony L. , Lammertsma Koop
Published: September 2004

Reaction of electrophilic phosphinidene complex [MePW(CO)5] with 1,6‐methano‐[10]annulene results in the sole formation of the isomeric CC insertion products 6 c (main) and 6 d (minor). The single‐crystal X‐ray structure of the complexed 1,7‐methano‐3‐phospha[11]annulene (6 c) shows a syn‐W(CO)5 group at the exo bent phosphorus. The structure displays CC bond alternation without bonding between the bridgehead carbon atoms. Density functional theory calculations indicate 6 c to result from a concerted disrotatory ring opening of an undetected tricyclic exo–syn phosphirane intermediate. The endo–anti phosphirane cannot undergo ring expansion, due to the high barrier that is associated with an intramolecular antara–antara retro Diels–Alder reaction. The stabilizing effect of transition‐metal coordination is discussed.
Towards Organo‐Click Chemistry: Development of Organocatalytic Multicomponent Reactions Through Combinations of Aldol, Wittig, Knoevenagel, Michael, Diels–Alder and Huisgen Cycloaddition Reactions
Authors: Ramachary Dhevalapally B. , Barbas Carlos F.
Published: September 2004

Here we report on our studies on combinations of amino acids and copper(I) for catalyzing multicomponent reactions (MCRs). We aimed to prepare both diene and dienophiles simultaneously, under very mild and environmentally friendly conditions, thus giving the constituents for a stereocontrolled Diels–Alder reaction, which in turn yields compounds 4 to 8. A diversity‐oriented synthesis of polysubstituted spirotriones 4 to 6 were assembled from simple substrates like 1‐(triphenylphosphanylidene)‐propan‐2‐one, two aldehydes, and cyclic‐1,3‐diketones through Wittig/Knoevenagel/Diels–Alder and aldol/Knoevenagel/Diels–Alder reaction sequences in one pot under stereospecific organocatalysis. Chemical diversity libraries of polysubstituted spirotrione‐1,2,3‐traizoles 8 were assembled from simple substrates by means of Wittig/Knoevenagel/Diels–Alder/Huisgen cycloaddition reaction sequences in one pot under stereospecific organo/CuI catalysis. Functionalized dispirolactones such as 6 are biologically active antioxidants and radical scavengers, and spirotrione‐1,2,3‐traizoles 8 have found wide applications in chemistry, biology, and materials science. Experimentally simple and environmentally friendly, organocatalytic, asymmetric four‐component Diels–Alder (AFCDA) reactions of 1‐(triphenylphosphanylidene)‐ propan‐2‐one, two different aldehydes, and cyclic‐1,3‐diketones produced diastereospecific and highly enantioselective substituted spirotriones 4 by means of a Wittig/Knoevenagel/Diels–Alder reaction sequence in one pot. Additionally we have developed an organocatalytic, asymmetric three‐component Michael (ATCM) reaction of 1‐(triphenylphosphanylidene)‐propan‐2‐one, aldehyde, and cyclic‐1,3‐diketones that produced Michael adducts 15, 16 through a Wittig/Michael reaction sequence in a highly enantioselective one‐pot process.
The management of ductal carcinoma in situ in North America and Europe
Authors: Ceilley Elizabeth , Jagsi Reshma , Goldberg Saveli , Kachnic Lisa , Powell Simon , Taghian Alphonse
Published: September 2004

BACKGROUND

The goal of the current study was to understand and document contemporary treatment approaches in the management of ductal carcinoma in situ (DCIS).

METHODS

An original questionnaire was designed to assess radiation oncologists' management of breast carcinoma, including 26 questions specifically addressing DCIS. A postal survey was conducted of members of the American and European Societies of Therapeutic Radiology and Oncology. The results of 702 responses from North America were compared with 435 responses from Europe, to determine treatment recommendations and variability by type of institution and geographic region.

RESULTS

There were strong correlations between the grade of DCIS and/or the margin status and the use of radiotherapy (RT; P < 0.0001). For Grade 3 DCIS, RT was recommended regardless of the margin status. Opinions were split in the treatment of low‐grade DCIS with 10‐mm margins. North American respondents were more likely to recommend RT for low‐grade DCIS than their European counterparts (P < 0.0001). Within the United States, there were significant regional variations in physician recommendations for tamoxifen (P < 0.001), but not in the tendency to recommend RT. North American academic physicians were less likely to recommend RT for favorable DCIS than nonacademic physicians (P < 0.01).

CONCLUSIONS

There were marked differences in physician opinions regarding the management of DCIS, with significant international differences in patterns of care. The survey quantified and highlighted areas of agreement and controversy regarding the use of RT and tamoxifen in the management of DCIS. It provided support for large international trials to evaluate the optimal management of DCIS in the areas identified as most controversial. Cancer 2004. © 2004 American Cancer Society.
Unexpectedly frequent hepatitis B reactivation by chemoradiation in postgastrectomy patients
Authors: Cheng Jason Chia‐Hsien , Liu Mei‐Ching , Tsai Stella Y. , Fang Wei‐Tse , Jer‐Min Jian James , Sung Juei‐Low
Published: September 2004

BACKGROUND

Postgastrectomy patients undergoing chemoradiation risk chemoradiation‐induced liver disease (CRILD). The objectives of this study were to investigate dosimetric implications and assess biologic susceptibility to CRILD in these patients.

METHODS

Sixty‐two patients with Stage IB–IV gastric/gastroesophageal adenocarcinoma without metastases underwent radical total/subtotal gastrectomy; regional lymph node dissection; and postoperative, adjuvant, concomitant chemoradiotherapy (CCRT). Among these, 8 patients developed CRILD (defined as Grade 3–4 liver toxicity), and 11 patients were chronic hepatitis B virus (HBV) carriers (HBV+). Chemotherapy consisted of 1 cycle of etoposide, leucovorin, and 5‐fluorouracil (ELF); followed by 5 weekly high doses of 5‐fluorouracil (2000–2600 mg/m2) and leucovorin concurrent with radiotherapy (median dose, 45 grays [Gy] to the tumor bed/regional lymphatics); followed by 3 cycles of ELF separated by a 21‐day interval. Patients were followed for ≥ 4 months after CCRT. Patient‐related and dosimetric factors were correlated with CRILD.

RESULTS

HBV+ status was the only independent factor associated with CRILD. HBV+ patients had a higher CRILD incidence (6 of 11 patients vs. 2 of 51 patients; P < 0.001). HBV‐negative patients with CRILD were recipients of a higher mean liver dose (MLD) (23.8 Gy vs. 15.2 Gy; P = 0.009) and a higher volume fraction of liver that received > 30 Gy (36.5% vs. 19.7%; P = 0.009) compared with noncarriers without CRILD, but no MLD difference was found between HBV+ patients with or without CRILD. Moreover, in four of six carriers with CRILD, HBV infection was reactivated during CRILD. Two of the toxicities were fatal.

CONCLUSIONS

HBV carriers had a higher incidence of CRILD after postgastrectomy CCRT, probably related to HBV reactivation. Dosimetric parameters modulated the risk of CRILD in noncarriers, but not in carriers. These factors deserve attention in CRILD/HBV+ patients, and the underlying pathogenesis warrants investigation. Cancer 2004. © 2004 American Cancer Society.