bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elektronendichteverschiebungen und Reaktionskonstanten mit entgegengesetzten Vorzeichen bei der Analyse von Dediazonierungsreaktionen mit Hilfe dualer Substituentenparameter
Authors: Glaser Rainer , Horan Christopher J. , Zollinger Heinrich 
Published: July 2007

Warum gibt es nur so wenige Ausnahmen von der Tatsache, daß ρR/ρF= λ positiv ist? Anhand der Dediazonierung substituierter Benzoldiazonium‐Ionen, eines prominenten Beispiels für die wenigen Reaktionen, bei denen die Reaktionskonstanten ρRund ρF[Gl. (1)] entgegengesetztes Vorzeichen haben, wurde versucht, diese Frage zu beantworten. Die Ergebnisse stützen das Bindungsmodell, nach dem die C‐N‐Bindung aus dem synergetischen Zusammenspiel von dativer N → C‐σ‐Bindung und C → N‐π‐Rückbindung resultiert, und führen zu detaillierten Aussagen über die Elektronenstruktur, die mit physikalisch‐organischen Studien allein nicht möglich sind.magnified image
Sb8R4, R = (Me3Si)2CH ‐ ein polycyclisches Organostiban
Authors: Breunig Hans Joachim , Rösler Roland , Lork Enno 
Published: July 2007

Bei der Reaktion von RSbCl2 mit Magnesium in Tetrahydrofuran entstand neben Sb4R4 und Sb3R3 auch die Titelverbindung 1. Eine Röntgenstruktur‐analyse der gelben Kristalle von 1 ergab, daß der Sb8‐Käfig dem P8‐Ausschnitt aus der Struktur des Hittorfschen Phosphors entspricht und strukturell mit Realgar (As4S4) verwandt ist.magnified image
Künstlicher Phototropismus: reversible Photoseparation von selbstorganisierten Komplexen
Authors: Benniston Andrew C. , Harriman Anthony , Yufit Dimitri S. 
Published: July 2007

Sorgfältiges Abstimmen der Energieniveaus ermöglicht die Photoseparation in einem engen Einschlußkomplex (siehe unten). Durch optische Anregung des intermediär auftretenden (nicht komplexierten) Gastmoleküls kommt es während der diffusiven Ladungsrekombination zu starker Fluoreszenz.magnified image
Kupferpnictogenide als selektive Reagentien: ein neuer Zugang zu funktionalisierten Phosphanen und Arsanen
Authors: Meyer Christian , Grützmacher Hansjörg , Pritzkow Hans 
Published: July 2007

Mit einem Bipyridin‐, Phenanthrolinoder Neocuproin‐Coliganden läßt sich die Reaktivität von Kupferpnictogenidkomplexen gegenüber Organohalogenverbindungen fein abstimmen, so daß funktionalisierte Phosphane wie 1 und Arsane sowie auch gemischte Phosphanylarsane wie 2 selektiv erhalten werden.magnified image
Ungewöhnliche Regioselektivität bei der reduktiven Kupplung von Alkinen und Allenen über Hydrozirconierung und Zinca‐Claisen‐Umlagerung
Authors: Suzuki Keisuke , Imai Takahiro , Yamanoi Shigeo , Chino Masao , Matsumoto Takashi 
Published: July 2007

Das α‐Addukt ist das alleinige Produkt bei der Kupplung von Vinyl‐ und Allylzirconium‐Verbindungen mit ZnCl2 (siehe unten), wenn keine MgII‐Salze zugegen sind. Die Zirconiumverbindungen werden in situ aus Alkinen und Allenen gebildet, und die gesamte Reaktion eröffnet einen neuen präparativen Zugang zur Vitamin‐E‐Seitenkette durch asymmetrische Induktion in 1,5‐Stellung. R1 = CH2OCPh3, R2 = CHMeCH2OCH2OMe, “Zr” = [Cp2Zr(H)Cl].magnified image
Elektrostatisch induzierte Bildung mehrschichtiger Membranen bei Riesenvesikeln
Authors: Menger Fredric M. , Keiper Jason S. 
Published: July 2007

Zwei Riesenvesikel mit entgegengesetzter Ladung heften sich bei Berührung aneinander, was sich durch Phasenkontrast‐Mikroskopie beobachten läßt. Eine der Vesikel platzt anschließend und umhüllt die andere als entgegengesetzt geladene Schicht (siehe schematische Darstellung unten). Dieser Vorgang läßt sich wiederholen und so zur Herstellung alternierend geladener mehrschichtiger Membranen nutzen.magnified image
Hexaaryltetrasilabuta‐1,3‐dien: eine Verbindung mit konjugierten Si‐Si‐Doppelbindungen
Authors: Weidenbruch Manfred , Willms Stefan , Saak Wolfgang , Henkel Gerald 
Published: July 2007

Unerwartet einfach wurde die Titelverbindung 2, das erste Tetrasilabuta‐1,3‐dien, durch Lithiierung des Disilens 1, partielle Bromierung mit einem Bromaren und intermolekulare Lithiumbromid‐Abspaltung in Form rotbrauner Kristalle erhalten. Die Konjugation der beiden Si‐Si‐Doppelbindungen von 2 wurde anhand des Elektronenspektrums sowie röntgenstrukturanalytisch nachgewiesen. Mes = 2,4,6‐Me3C6H2, Tip = 2,4,6‐iPr3C6H2.magnified image
Eine konvergente Synthese von (+)‐Parviflorin, (+)‐Squamocin K und (+)‐(5S)‐5‐Hydroxyparviflorin
Authors: Trost Barry M. , Calkins Trevor L. , Bochet Christian G. 
Published: July 2007

30 der 35 Kohlenstoffatome des Acetogenins (+)‐Parviflorin (Squamocin E) 1 stammen in dessen hochgradig konvergenter Synthese ausgehend von einem leicht zugänglichen Alkohol aus diesem Baustein. Die übrigen fünf werden mit einem aus Milchsäure erhältlichen Alkin eingeführt. Schlüsselschritt dieser generellen Strategie zu Bistetra hydrofuran‐Acetogeninen ist eine Ru‐katalysierte Alder‐En‐Verknüpfung des Alkins mit einem aus zwei Bausteinen des Alkohols hergestellten Bistetrahydrofuran.magnified image
Selbstorganisation von Clustern mit Hilfe von Wasserstoffbrückenbindungen: Röhrenstruktur eines Cu4L4‐Cubans
Authors: Oshio Hiroki , Saito Yuki , Ito Tasuku 
Published: July 2007

Ein High‐spin‐Grundzustand kennzeichnet den Cubankomplex, der aus CuII und dem Hydroxygruppen enthaltenden Brückenliganden 2‐(4‐Hydroxysalicylidenamino)ethanol erhalten wurde. Zudem sind die Cluster im Kristall röhrenförmig angeordnet (siehe rechts), was auf die Bildung von Wasserstoffbrückenbindungen zurückzuführen ist.magnified image
Ein Calixaren mit vier Peptidschleifen: ein Antikörper‐Mimeticum zur Erkennung von Proteinoberflächen
Authors: Hamuro Yoshitomo , Calama Mercedes Crego , Park Hyung Soon , Hamilton Andrew D. 
Published: July 2007

Vier konformativ eingeschränkte Peptide mit der Sequenz Gly‐Asp‐Gly‐Asp sind an ein zentrales Calixarengerüst gebunden (siehe unten) und bilden so eine große Kontaktfläche für die Wechselwirkung mit Proteinen. Dieses Antikörper‐Mimeticum bindet nicht nur stark an die Oberfläche von Cytochrom c, es unterdrückt auch dessen Wechselwirkung mit reduzierenden Agentien.magnified image
Ladungsübertragung durch den DNA‐Basenstapel
Authors: Holmlin R. Erik , Dandliker Peter J. , Barton Jacqueline K. 
Published: July 2007

AbstractSeit dem ersten Strukturvorschlag für die DNA‐Doppelhelix besteht eine Diskussion darüber, ob die Stapelung der DNA‐Basen eine effiziente, weitreichende Ladungsübertragung ermöglicht. Die Konsequenzen einer solchen Radikalstellenwanderung durch die DNA sollten für das Verständnis von Carcinogenese und Mutagenese in Betracht gezogen werden. Die DNA zeichnet sich im Innern der Helix durch eine stapelförmige Anordnung von heterocyclischen, aromatischen Basenpaaren aus; sie ist ein einmaliges System zur Erforschung des Elektronentransfers. In unserer Arbeitsgruppe wurden Metallkomplexe entwickelt, die zwischen die Basenpaare der DNA‐Helix intercalieren und die es ermöglichen, DNA‐vermittelten Elektronentransfer zu untersuchen. In diesem Aufsatz beschreiben wir einige von uns durchgeführte Elektronentransferreaktionen, die durch den DNA‐Basenstapel vermittelt werden. In einigen dient die DNA als Brücke, und mit spektroskopischen Verfahren können wir untersuchen, wie der Basenstapel DNA‐gebundene Donoren und Acceptoren koppelt. Die Untersuchungen deuten auf eine hohe Empfindlichkeit der Kopplung gegenüber der DNA‐Intercalation hin. Wenn der DNA‐Basenstapel Donoren und Acceptoren effektiv miteinander verbindet, kann er auch als ausgezeichneter Elektronentransferkanal der DNA selbst dienen, allerdings in Reaktionen, die von entfernten Positionen ausgelöst wurden. Wir haben auch viele Versuche zur oxidativen DNA‐Schädigung durchgeführt, die von einem in größerer Entfernung an der Helix fixierten Oxidationsmittel initiiert wird. Die Ladungsübertragungen hängen sehr von der DNA‐Intercalation und von der Integrität des Basenstapels ab, aber nicht von der Entfernung. Auch die als DNA‐Schädigung physiologisch bedeutsame Bildung von Thymindimeren kann in einer durch Elektronentransfer initiierten Reaktion rückgängig gemacht werden. Über größere Entfernungen vermittelte chemische Reaktionen werden also durch die DNA‐Doppelhelix ermöglicht.
Sukzessive Reaktion von Bis(iodzinkio)methan mit zwei unterschiedlichen Elektrophilen
Authors: Utimoto Kiitiro , Toda Narihiro , Mizuno Takeshi , Kobata Masami , Matsubara Seijiro 
Published: July 2007

[Pd2(dba)3] katalysiert in Gegenwart von Trifurylphosphan (TFP) die sukzessive Umsetzung von CH2(ZnI)2 mit verschiedenen Elektrophilen [G1. (a)]. Die homologe Zn2‐Verbindung CH3CH(ZnI)2 reagiert im 1. Schritt analog mit Cinnamylchlorid; für die Kupplung mit Allylbromid im zweiten Schritt ist aber CuCN/LiCN in stöchiometrischen Mengen nötig. CH2(ZnI)2+RXRCH2ERXPhCHCHCH2Cl, n‐C8H17CCCH2Br, C2H5CCCH(n‐C5H11)Br EXDCl/D2O, CH2CHCH2Br, PhCOCl. (a)magnified image
Enantioselektive Synthese von Altohyrtin C (Spongistatin 2): Synthese des EF‐Bis‐(tetrahydropyran)‐Fragments
Authors: Evans David A. , Trotter B. Wesley , Côté Bernard , Coleman Paul J. 
Published: July 2007

Die erste Totalsynthese eines Spongipyran‐Makrolids, des Altohyrtins C (Spongistatin 2; siehe unten), wurde erfolgreich abgeschlossen. Die aus Meeresschwämmen isolierten Spongipyrane gehören zu den stärksten cytotoxischen Verbindungen und wirken gegen mehrere menschliche Krebszellinien. Während die vorgeschlagenen Strukturen für die unabhängig isolierten Altohyrtine und Spongistatine im wesentlichen gleich sind, unterscheiden sie sich in der relativen Konfiguration der Untereinheiten. Durch die Totalsynthese wurde nun die vorgeschlagene Struktur der Altohyrtine bestätigt und nachgewiesen, daß Altohyrtin C und Spongistatin 2 identisch sind.magnified image
Preparation and characterization of poly(vinylidene fluoride) hollow fiber membranes for vacuum membrane distillation
Authors: Wu Bing , Li K. , Teo W. K. 
Published: July 2007

AbstractVarious asymmetric microporous poly(vinylidene fluoride) (PVDF) hollow fiber membranes with different pore sizes and effective porosities were prepared by the phase inversion method using dimethylacetamide (DMAc) as solvent and LiCl and water as additives. The membranes were characterized using scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) for its microstructure and surface pore size. A gas permeation method was also applied for determining and comparing the effective surface porosity and mean pore size of the different membranes. Moreover, the contact angle with water, critical entry pressure (CEP) of water and collapsing pressure of the PVDF hollow fibers were also determined. Five membrane modules were prepared using the spun hollow fibers and applied in removing 1,1,1‐trichloroethane (TCA) from its aqueous solution by vacuum membrane distillation (VMD) process. The effects of dope composition and spinning conditions on hollow fiber morphology and TCA separation by VMD process are examined. Post‐treating of the spun fibers by solvent exchange using ethanol produced membranes exhibiting higher porosity and higher permeability. A highly porous hollow fiber membrane with a smaller mean pore size can achieve both high TCA permeation flux and high separation factor. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Synthesis, Physicochemical and Anticonvulsant Properties of New N‐4‐Arylpiperazin‐1‐yl Amides of (2‐Aza‐1,3‐dioxospiro[4.4]non‐2‐yl)‐ and [4.5]dec‐2‐yl)‐propionic Acid
Authors: Obniska Jolanta , Kaminski Krzysztof , Hondo Lukasz , Zejc Alfred 
Published: July 2007

AbstractIn continuation of the search of new anticonvulsants, a series of N‐4‐arylpiperazin‐1‐yl 2‐aza‐1,3‐dioxospiro[4.4]non‐2‐yl‐ (5–8) and [4.5]dec‐2‐yl‐ (9–15) propionamides, structurally related to the previously described N‐4‐arylpiperazin‐1‐yl amides of 2‐aza‐1,3‐dioxospiro[4.5]dec‐2‐yl‐acetic acid, were synthesized. The designed compounds 5–15 were prepared by condensation of the formerly obtained (2‐aza‐1,3‐dioxospiro[4.5]dec‐2‐yl)‐ (3) and (2‐aza‐1,3‐dioxo[4.4]non‐2‐yl)‐(4) propionic acids with the appropriately substituted 4‐arylpiperazines, in the presence of the N,N‐carbonyldiimidazole (CDIM) reagent. All the compounds were tested for their anticonvulsant activity in the maximum electroshock seizure (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure threshold tests. Several compounds 7–10, 13 and 14 revealed protection in the MES screening.
Organocatalytic Asymmetric Nitroaldol Reaction: Cooperative Effects of Guanidine and Thiourea Functional Groups
Authors: Sohtome Yoshihiro , Takemura Nobuko , Takada Keisuke , Takagi Rika , Iguchi Toshitsugu , Nagasawa Kazuo 
Published: July 2007

AbstractCatalytic enantio‐ and diastereoselective nitroaldol reactions were explored by using designed guanidine–thiourea bifunctional organocatalysts under mild and operationally simple biphasic conditions. These catalytic asymmetric reactions have a broad substrate generality with respect to the variety of aldehydes and nitroalkanes. Based on this catalytic nitroaldol process, straightforward syntheses of cytoxazone and 4‐epi‐cytoxazone were achieved. These catalytic nitroaldol reactions require KI as an additive for highly asymmetric induction; it operates by inhibiting the retro mode of the reaction. On the basis of studies of structure and catalytic‐activity relationships, a plausible guanidine–thiourea cooperative mechanism and a transition state of the catalytic reactions are proposed. Drastic substituent effects on the catalytic properties of this catalyst may lead to the development of new chiral surfactants.
A Two‐Dimensional Coordination Compound as a Zinc Ion Selective Luminescent Probe for Biological Applications
Authors: Dhara Koushik , Karan Santanu , Ratha Jagnyeswar , Roy Partha , Chandra Goutam , Manassero Mario , Mallik Biswanath , Banerjee Pradyot 
Published: July 2007

AbstractA 2D coordination compound {[Cu2(HL)(N3)]⋅ClO4}∞ (1; H3L=2,6‐bis(hydroxyethyliminoethyl)‐4‐methyl phenol) was synthesized and characterized by single‐crystal X‐ray diffraction to be a polymer in the crystalline state. Each [Cu2(HL)(N3)]+ species is connected to its adjacent unit by a bridging alkoxide oxygen atom of the ligand to form a helical propagation along the crystallographic a axis. The adjacent helical frameworks are connected by a ligand alcoholic oxygen atom along the crystallographic b axis to produce pleated 2D sheets. In solution, 1 dissociates into [Cu2(HL)2(H3L)]⋅2H2O (2); the monomer displays high selectivity for Zn2+ and can be used in HEPES buffer (pH 7.4) as a zinc ion selective luminescent probe for biological application. The system shows a nearly 19‐fold Zn2+‐selective chelation‐enhanced fluorescence response in the working buffer. Application of 2 to cultured living cells (B16F10 mouse melanoma and A375 human melanoma) and rat hippocampal slices was also studied by fluorescence microscopy.
Knowledge, probability, and credibility
Authors: Schum David A. 
Published: July 2007

AbstractThis paper concerns study of the credibility of human sources of evidence and its relation to the inferential value of testimony they provide. From a certain view of 'knowledge' in epistemology comes the suggestion that credibility assessment can be construed as a cascaded inference in which attributes of human source credibility are identified. Scholarship from evidence law in jurisprudence suggests an evidential basis for credibility assessment in terms of these attributes. Applying Bayes' rule to this cascaded inference offers a way of expressing and combining credibility‐related beliefs in the process of assessing the inferential value of evidence.
The need for contextual and technical knowledge in judgmental forecasting
Authors: Sanders Nada R. , Ritzman Larry P. 
Published: July 2007

AbstractThe purpose of this research is to assess the extent to which judgmental forecasts are improved by having more contextual and technical knowledge. Contextual information is knowledge gained by practitioners through experience on the job, consisting of general forecasting experience in the industry as well as specific product knowledge. Technical knowledge is knowledge about data analysis and formal forecasting procedures, including information on how to analyze data judgmentally. We directly compared judgmental forecasts of business practitioners with those generated by students, using 22 real‐world time series. The practitioners had considerable contextual but no technical knowledge. The students had no contextual but two different levels of technical knowledge. We also generated forecasts with statistical methods to benchmark performance. Results show that contextual knowledge is particularly important in making good judgmental forecasts, while technical knowledge has little value. Practitioner forecasts are better than student forecasts in almost all comparisons. A decisive factor affecting forecast performance appears to be data variability, measured by the coefficient of variation of the time‐series data. As the variability of a time series increases, the performance of all forecasts deteriorates, but judgmental forecasts by practitioners become more preferable. Statistical methods have difficulty achieving reasonable forecasts when the data are more variable, whereas judgemental forecasts reinforced by contextual information do relatively well. Data variability is one explanation for the mixed findings of past studies, relative to how well statistical techniques compare with judgment as a forecasting method.
The effect of explicit probabilities on decision weights and on the reflection effect
Authors: Erev Ido , Wallsten Thomas S. 
Published: July 2007

AbstractAn experiment is presented that explores the finding that a request to judge probabilities can bias subsequent decisions (Erev et al., 1993). Subjects chose among gambles whose outcomes were determined by the occurrence of events in a video game environment. The probabilities of the events could be assessed based on the visual display. In the no‐probabilities condition the subjects simply indicated their choices. In the subjective‐probability condition subjects first estimated probabilities and then made choices. In the objective‐probability condition, subjects saw the actual probabilities instead of the events when making their choices. The results suggest that the availability of explicit probabilities (both subjective and objectives) decreases the subjects sensitivity to the outcome dimension and, hence, increases the reflection effect; i.e. subjects in the subjective‐and objective‐probability conditions showed stronger risk aversion when the gambles involved possible profit and stronger risk seeking when the gambles involved possible losses than in the no‐probabilities condition. In addition, the subjective assessments impaired the quality of the decisions in term of the subjects expected profit. Theoretical and practical implications of the results are discussed.
What is wrong with Allais' Certainty Effect?
Authors: Li Shu 
Published: July 2007

AbstractSeveral choice situations are constructed to explore whether the violation of expected utility theory in an Allais paradox choice situation can be attributed to what Tversky and Kahneman (1986) describe as the Allais certainty effect. Problems are developed where the Allais certainty effect would be expected to occur but results show it does not. Other problems demonstrate that the Allais ‘paradox’ is observed in the absence of the Allais certainty effect. The study concludes that, although expected utility theory is known to be wrong through the Allais paradox, the Allais certainty effect does not appear to be able to rescue it.
Ambiguity seeking in multi‐attribute decisions: Effects of optimism and message framing
Authors: Bier Vicki M. , Connell Brad L. 
Published: July 2007

AbstractThis paper investigates the influence of message framing and personality variables on preferences over ambiguity in the context of multi‐attribute decision scenarios. Undergraduate subjects responded to scenarios in which one of two medical treatments was associated with ambiguous probabilities of treatment effects. Probabilities were either positively or negatively framed. Subjects indicated their degree of preference for one treatment over the other. Subjects' optimism, trait anxiety, health locus of control, need for cognitive structure, and current mood were measured. In two separate studies, subjects preferred ambiguity when probabilities were positively framed, and were neutral toward ambiguity when probabilities were negatively framed. Also, in both studies the preference for ambiguity in positively framed scenarios was greater for more optimistic subjects. The unexpected finding of ambiguity seeking may be associated with the use of different decision strategies in multi‐attribute versus single‐attribute decisions.
Shattering the illusion of control: Multi‐shot versus single‐shot gambles
Authors: Koehler Jonathan J. , Gibbs Brian J. , Hogarth Robin M. 
Published: July 2007

AbstractThe illusion of control refers to a phenomenon whereby people believe their chances of success at a task are greater than would be warranted by objective analysis. This article raises two questions. First, how robust is the illusion of control? Second, how might the illusion be ‘shattered?’ Previous experimental demonstrations involved situations that can be likened to unique or single‐shot gambles. If, however, the phenomenon is robust, it should occur in repeated or multi‐shot gambles in which the outcome depends on a series of gambles involving the same underlying random process. It should also appear in single‐shot gambles that are framed so as to superficially resemble multi‐shot gambles. We label this the strong illusion of control hypothesis. On the other hand, because people have a better appreciation of probabilistic concepts in tasks they are able to represent as relative frequencies, the introduction of a multi‐shot or ‘pseudo‐multi‐shot’ context might cue people to the random nature of the task, thereby shattering the illusion. The weak illusion of control hypothesis holds that the illusion of control will occur in single‐shot but not in multi‐shot or pseudo‐multi‐shot gambles. Two studies are reported that support the weak hypothesis. Alternative explanations are considered and implications are discussed.
Decision making in a dynamic situation: The effect of false alarms and time pressure
Authors: Kerstholt José H. 
Published: July 2007

AbstractAn experiment was conducted to investigate the effect of a priori probability of false alarms and time pressure on decision‐making behaviour in a dynamic task environment. In order to assess whether strategy selection in a dynamic task environment would be adaptive, we modelled the task mathematically, and compared actual decision strategies to the optimal ones. In addition to the selected strategy, we also studied decision‐making behaviour at a lower operational level, reflecting the amount of effort subjects are willing to spend on the decision process. Subjects were required to monitor the fitness level of a simulated athlete, who was running a race, and had to provide treatments whenever the athlete's fitness level suggested a real physiological problem. When a decline of the athlete's fitness was caused by a false alarm, a spontaneous recovery would occur after some time, without any need for intervention. Time pressure was manipulated by the rate at which the athlete's fitness level declined. Overall, subjects did not select the most efficient strategy: they dominantly selected information before applying an action, even though it would have been more profitable, and less effortful, just to apply actions. At the operational level, subjects appeared to invest less effort when the probability of false alarms increased and to invest more effort when time pressure increased. However, in contrast to the outcomes of our mathematical model, subjects adjusted the amount of intervention to the a priori probability of false alarms and not to time pressure. Together, the results indicate that the selection of a decision strategy in a dynamic task is less adaptive then is generally concluded from studies with static tasks.