bluuebunny/crossref_metadata_2025 huggingface dataset:
The Globus Pallidus, Deep Brain Stimulation, and Parkinson's Disease
Authors: Dostrovsky Jonathan O. , Hutchison William D. , Lozano Andres M.
Published: July 2003

Parkinson's disease (PD) is caused by the degeneration of the dopaminergic neurons in the substantia nigra. Loss of dopaminergic innervation leads to hyperactivity in the internal segment of the globus pallidus (GPi), the main output nucleus of the basal ganglia and to a profound disturbance in the function of motor circuits. Lesions of the GPi (or in its upstream modulator, the subthalamic nucleus) can greatly improve the motor symptoms of PD presumably by reducing this pathological activity. Paradoxically, high-frequency electrical stimulation of the GPi (deep brain stimulation, DBS) mimics the effects of pallidotomy and has become an accepted therapeutic technique. The mechanisms underlying the beneficial effects of pallidal DBS are not known. Various mechanisms that might account for inhibiting or disrupting the pathological pallidal outflow by high-frequency DBS have been proposed ranging from depolarization block to stimulation-evoked release of GABA, and these are discussed.
Cover Picture: A Giant Conjugated Molecular Ring (Angew. Chem. Int. Ed. 27/2003)
Authors: Mayor Marcel , Didschies Claudia
Published: July 2003

As a circular path for electrons a giant macrocycle with a periphery consisting of exclusively conjugation‐active units has been designed. With a diameter of 12 nm it is probably the largest synthesized, shape‐persistent, and monodisperse cyclic structure to date. In addition, the front wheel of a bicycle is shown, the 16‐fold symmetry of which inspired the design of the molecule. For more information on this molecule see the Communication by M. Mayor and C. Didschies on page 3176 ff.
Die Reaktion von Kaliumhydrogensulfid mit Ethylbromid in ethanolischen Lösungen ‐ ein geeignetes Beispiel zur Einführung des SN2‐Reaktionsmechanismus
Authors: Friedrich Jens , Brockmann Melanie , Jansen Walter
Published: July 2003

DIE REAKTION VON KALIUMHYDROGENSULFID mit Ethylbromid in ethanolischer Lösung wurde kinetisch und analytisch untersucht. Abhängig von den Reaktionsbedingungen ist als Hauptprodukt Ethanthiol nachweisbar; Triethylsulfoniumbromid dürfte als Nebenprodukt vermutlich aus dem intermediär vorliegenden Diethylsulfid durch Reaktion mit Ethylbromid entstehen. Aus Leitfähigkeitsmessungen kann eine Kinetik 2. Ordnung ermittelt werden. Eine plausible Erklärung ist die bimolekulare Reaktion von Hydrogensulfid‐Ionen und Ethylbromid‐Molekülen. Zum Vergleich wurde die Reaktion von Kaliumsulfid mit Ethylbromid untersucht: In diesem Fall kann die Bildung von Diethylsulfid als Hauptprodukt sowie Ethanthiol und Triethylsulfoniumbromid als Nebenprodukte nachgewiesen werden. Die untersuchten Umwandlungen sind als mechanistische Modellrektionen für die nukleophile Substitution u.E. geeigneter als die Reaktion von Alkylhalogeniden mit Hydroxid‐Ionen. Informativ ist ein Vergleich zwischen Reaktionen der S‐Nukleophile und den bereits veröffentlichten Ergebnissen über O‐Nukleophile.
Gebacken ist nicht ungefährlich
Authors: Hardam Werner
Published: July 2003

SEITDEM IM JAHRE 2001 die Substanz Acrylamid in alltäglichen Lebensmitteln entdeckt wurde, sind viele Verbraucher verunsichert; die Substanz soll besonders in Kartoffelchips, in Pommes frites, im Müsli, in Corn Flakes sowie in Keksen und Brot vorkommen [1, 2]. Es wurde herausgefunden, dass es sich bei den getesteten Produkten fast immer um pflanzliche Produkte handelt, die viele Kohlenhydrate enthalten und sehr stark gebacken, getoastet oder frittiert werden. In gekochten Speisen tritt die Substanz nicht auf. Insbesondere kommt in erhitzten Kartoffelerzeugnissen eine erhöhte Acrylamid‐Konzentration vor. Grob gilt: Je intensiver die Braunfärbung, desto höher die Acrylamid‐Belastung. Acrylamid gilt aufgrund von Tierversuchen (Ratten, Kaninchen) als krebserregend und erbgutschädigend; die Wirkung auf den menschlichen Organismus ist bisher unbekannt.
Effective radial Liapunov exponent for the radial diffusion of test electrons
Authors: Maluckov A. , Nakajima N. , Okamoto M. , Murakami S. , Kanno R.
Published: July 2003

The radial diffusion of test electrons in the bounded magnetic field region with irregularities is a realization of the magnetic (deterministic) and collisional (statistical) stochasticities. To clarify the development of stochasticities the effective radial Liapunov exponent Ler, the number of the electron trajectories (magnetic field lines) with positive radial Liapunov exponent Np, the distribution of the radial Liapunov exponent, Kolmogorov entropy and 3D Liapunov exponent are calculated numerically. In the absence of collisions the overlapping among magnetic islands (generation of the global stochasticity) is indicated by the qualitative change from negative to positive Ler in the long time limit. The fact that Np < N, where N is the number of test electrons, is the sign of sticking to the magnetic field structures. From the viewpoint of the radial Liapunov exponents both stochasticities manifest similarly. It is shown that the distribution of the radial Liapunov exponents is not the elementary one, except in the region of the extremely frequent collisions and partially destroyed magnetic field. Transition of the radial diffusion from the strange to the standard diffusion [1] is related with neglecting sticking of the electrons to the magnetic field structures by enough frequent collisions.
Trivelpiece‐Gould mode produced gas‐discharges in a diffusion‐controlled regime
Authors: Schlüter H. , Shivarova A. , Tarnev Kh.
Published: July 2003

The study presents a numerical fluid‐plasma model of waveguide discharges sustained by travelling azimuthallysymmetric Trivelpiece‐Gould modes. The results describe weakly‐magnetized (ω ≥ Ωe) plasma production in a diffusion‐controlled regime (ω being the wave frequency, Ωe the electron gyro‐frequency). However, with respect to the influence of the external magnetic field on the transverse ambipolar‐diffusion coefficient, cases of both weak and strong impact of the magnetic field are covered. In its electrodynamical part, the model involves detailed description of the behaviour of the Trivelpiece‐Gould waves in radially‐inhomogeneous collisional plasmas. The gas‐discharge part of the model specifies plasma production in an argon gas. The results are for the self‐consistent structure of the discharge composed out of the interrelated variations of wavenumber, space damping rate, plasma density, electron temperature and power absorbed on average by an electron. The analysis is in terms of influence of gas‐pressure and magnetic‐field changes.
The vacuum arc cathode spot and plasma jet: Physical model and mathematical description
Authors: Beilis I. I.
Published: July 2003

A physical model of the cathode processes and flow of material eroded from the cathode of a vacuum arc is formulated. The model considers the plasma jet and the plasma generation regions, and provides electrical current continuity at the metal‐plasma boundary in the cathode spot. Based on an analysis of the kinetics of cathodic evaporation and plasma flow in the hydrodynamic region, a closed system of equations is obtained. Boundary conditions for the cathodic plasma expansion are formulated. The system of equations allows to compute the spot parameters (cathode potential drop, cathode material erosion rate, plasma parameters ‐velocity, density, temperature, e.t.c) using a self‐consistent description of the plasma flow in the cathode spot and cathode jet regions. The calculations for spot currents 1 ‐ 20 A show that the cathode potential drop increases, erosion rate decreases with spot current and spot life time decreasing.
Iron(III) Chelation: Tuning of the pH Dependence by Mixed Ligands
Authors: Albrecht‐Gary Anne‐Marie , Blanc Sylvie , Biaso Frederic , Thomas Fabrice , Baret Paul , Gellon Gisele , Pierre Jean‐Louis , Serratrice Guy
Published: July 2003

The iron(III) chelating properties of two heteropodands with 8‐hydroxyquinoline and catechol binding groups were examined and compared to those of the corresponding homopodal analogues, O‐TRENSOX and TRENCAMS. Like the parent homopodands, the two heteropodands are based on the TREN scaffold and the chelating units are connected by amide groups, TRENSOX2CAMS having two 8‐hydroxyquinoline and one catechol arms and TRENSOXCAMS2 one 8‐hydroxyquinoline and two catechol moieties. The aqueous coordination chemistry of these ligands was examined by potentiometric and spectrophotometric methods in combination with 1H NMR spectroscopy. The respective pFeIII values showed a cooperative effect of the mixed chelating units. Moreover, the pFeIII dependence on pH showed that the mixed ligands exhibit a higher complexing ability than the parent ligands over the pH range 5−9 which is of biological relevance. This result could be of great interest for medical applications. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Syntheses and Crystal Structures of Two Novel Zinc(II) Coordination Polymers
Authors: Tao Jun , Yin Xin , Jiang Yun‐Bao , Yang Le‐Fu , Huang Rong‐Bin , Zheng Lan‐Sun
Published: July 2003

Two novel zinc(II) coordination polymers, [Zn3(μ3‐OH)2(nip)2] (1) and [Zn2(nip)2(4,4′‐bpy)3·(OH2)] (2) (H2nip = 5‐nitroisophthalic acid, 4,4′‐bpy = 4,4′‐bipyridyl), were obtained by the hydrothermal reactions of zinc nitrate, 5‐nitroisophthalate (nip) (for 1) and zinc nitrate, 5‐nitroisophthalate and 4,4′‐bipyridyl (for 2). Complex 1 displays a two‐dimensional structure that is built from [Zn3(μ3‐OH)2]n chains, while complex 2 is a three‐dimensional structure formed by the interpenetration of two‐dimensional hydrogen‐bonded bilayers. The photoluminescent properties of complex 1 have also been investigated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Second‐Order Nonlinear Optical Properties of Tetraaza‐Coordinated Nickel(II) Complexes
Authors: Di Bella Santo , Fragalà Ignazio
Published: July 2003

In this contribution, we report the design and theoretical analysis, using the INDO/SCI‐SOS quantum chemical formalism, of novel molecular architectures based on planar [N4]‐, (2‐aminobenzylideneiminato)‐ and tetraazamacrocycle‐coordinated nickel(II) complexes, having second‐order nonlinear optical (NLO) properties. Calculations indicate that these molecules possess comparable, or even larger, second‐order nonlinearity to the bis(salicylaldiminato)NiII Schiff‐base analogues. The nonlinearity of substituted complexes is dominated by the nature and position of substituents on the tribenzo[b,f,l] and/or cyclotetradecine rings, and is determined by the relative directions of the ground‐ and excited‐state dipole moments. Moreover, substitution with acceptor groups in the dibenzo[b,l] rings involves a significant octupolar contribution to optical nonlinearity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
New Tris(pyrazolyl)triazine and Pyrazolylpyridine Gold(I) and Palladium(II) Derivatives Based on the 3,5‐Bis(4‐butoxyphenyl)pyrazole Group − Architectures with Different Types of Bonding Interactions
Authors: Claramunt Rosa M. , Cornago Pilar , Cano Mercedes , Heras José V. , Gallego M. Luz , Pinilla Elena , Torres M. Rosario
Published: July 2003

The 3,5‐bis(4‐butoxyphenyl)pyrazolyl group (Pzbp2) has been used as a building block for mono‐ and polymetallic derivatives of 2,4,6‐tris[3,5‐bis(4‐butoxyphenyl)pyrazol‐1‐yl]‐1,3,5‐triazine (TPzbp2Tz, 1), 2‐[3,5‐bis(4‐butoxyphenyl)pyrazol‐1‐yl]pyridine (Pzbp2Py, 2), and 3,5‐bis(4‐butoxyphenyl)pyrazole (HPzbp2, 3) ligands. The synthesis and characterisation of the new hexadentate ligand 1 are described, together with the chemistry of its metal complexes containing [Pd(η3‐C3H5)]+ and [Au(PPh3)]+ fragments. The related complexes containing Pzbp2Py (2) were also studied and their structural characteristics were compared to those of the TPzbp2Tz species. The role of the counter‐ion on the supramolecular assembly of complexes containing the HPzbp2 ligand 3 was made clear by the X‐ray structures of [Pd(η3‐C3H5)(HPzbp2)2](BF4) and [Au(HPzbp2)(PPh3)](NO3). Hydrogen bonds and/or bonding interactions are responsible for pseudohelical one‐dimensional polymers or supramolecular columnar arrays, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis, Crystal Structure and Fluorescence of Two Novel Mixed‐Ligand Cadmium Coordination Polymers with Different Structural Motifs
Authors: Luo Junhua , Hong Maochun , Wang Ruihu , Cao Rong , Han Lei , Lin Zhenzhong
Published: July 2003

Two novel cadmium(II) coordination compounds, [Cd(bpe)1.5(NO2‐BDC)]·0.25H2O (1) and [Cd(bpp)(NO2‐BDC)(H2O)]·0.25H2O (2) [NO2‐BDCH2 = 5‐nitro‐1,3‐benzenedicarboxylic acid, bpe = 1,2‐bis(4‐pyridyl)ethane, bpp = 1,3‐bis(4‐pyridyl)propane] have been hydrothermally synthesized by reaction of cadmium chloride and NO2‐BDC with the homologous ligands bpe and bpp, respectively. The former compound displays a remarkable three‐dimensional architecture sustained by the catenation of 2D bilayers, while the latter exhibits a unique twofold interpenetrating three‐dimensional architecture. The thermal and fluorescence properties associated with their crystal structures have been measured. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Cover Picture: Rhodium and Ruthenium Complexes of 1,1′‐Bis(phosphetano)ferrocenes: Structural Characterisation and Catalytic Behaviour (Eur. J. Inorg. Chem. 14/2003)
Authors: Marinetti Angela , Labrue Francis , Pons Bénédicte , Jus Sébastien , Ricard Louis , Genêt Jean‐Pierre
Published: July 2003

The cover picture shows the X‐ray crystal structures of ruthenium and rhodium complexes of chiral 1,1′‐bis(phosphetano)ferrocenes. These diphosphanes rank among the ligands inducing excellent enantioselectivities in rhodium‐promoted hydrogenations of prochiral olefins. X‐ray crystal structures of their metal complexes afford information about their coordinating behaviour and preferred conformations in catalytically active species. Details are discussed in the article by A. Marinetti et al. on p. 2583 ff.
Information seeking and reciprocity: a transformational analysis
Authors: Gallucci Marcello , Perugini Marco
Published: July 2003

The motivation to reciprocate is analyzed within the framework of interdependence theory, with focus on the process of transformation of situations. A model of transformation is presented for the motivation to reciprocate and hypotheses regarding allocation behavior and information seeking are derived. The hypotheses are tested in two experiments implementing a game where participants allocate payoff to self and other in a sequential way, with one participant able to gather costly information regarding the other's previous behavior. Individual differences in the motivation to reciprocate are assessed with the Personal Norm of Reciprocity questionnaire. Results show that participants with high motivation to reciprocate seek information regarding other's past behavior, and react to this information as the norm of reciprocity prescribes. Participants with low motivation to reciprocate prefer information regarding the future of the interaction (Study 1), or no information (Study 2), and behave in a more selfish way. Results are discussed with respect of (1) the transformation of situation process, (2) the role of reciprocity as an interpersonal motive, and (3) the validity of the individual differences measure. Copyright © 2003 John Wiley & Sons, Ltd.
Ingroup identification moderates stereotype change in reaction to ingroup deviance
Authors: Hutchison Paul , Abrams Dominic
Published: July 2003

An experiment (N = 98) investigated the moderating effect of ingroup identification on reactions to deviant ingroup members. We measured psychology students' level of identification with the group ‘psychologists’ and presented them with information about either a normative or deviant psychologist. Participants completed an ingroup stereotype measure either before or after reading about and evaluating the target psychologist. High identifiers expressed a more positive stereotype of the ingroup after, compared to before, reading about a deviant ingroup member. High identifiers also expressed a more positive stereotype of the ingroup after reading about a deviant than after reading about a normative ingroup member. By contrast, low identifiers' stereotype judgements were relatively unaffected by the target information. The target evaluation ratings indicate that high identifiers were more positive than low identifiers towards the normative ingroup member, but were more negative than low identifiers towards the deviant. The results point to the greater motivational demands on high identifiers to maintain a positive image of the group. Copyright © 2003 John Wiley & Sons, Ltd.
Why inconsistent leadership is regarded as procedurally unfair: the importance of social self‐esteem concerns
Authors: De Cremer David
Published: July 2003

Three experimental studies examined to what extent leader's consistent use of procedures constitutes an important procedural fairness rule and influences people's reactions as a function of social self‐esteem. In line with a recent claim that more attention should be devoted to different procedural fairness rules (Brockner, Ackerman, & Fairchild, 2001), the findings of Study 1 demonstrated that inconsistent leaders were evaluated as less procedurally fair and influenced feelings of uncertainty about oneself in ongoing interpersonal interactions. Study 2 showed that manipulating leader's consistency influenced people's procedural fairness judgments and willingness to replace the leader, but only among those low in social self‐esteem (SSE). Finally, Study 3, using another consistency manipulation, demonstrated that variations in consistency made participants feel bad about themselves, particularly when they were low in SSE. These findings are discussed in light of research on relational models of justice and sociometer theory. Copyright © 2003 John Wiley & Sons, Ltd.
Von der Wiedergeburt einer großen Bibliothek
Authors: Künast Hans‐Jörg , Zäh Helmut
Published: July 2003

In detektivischer Kleinarbeit wird die Bücher‐ und Handschriftensammlung des Augsburger Stadtschreibers Konrad Peutinger rekonstruiert. Der Zeitgenosse Luthers baute eine der bedeutendsten Humanistenbibliotheken seiner Zeit auf
Wie Modelle die Realität beschreiben
Authors: Diehl Barbara
Published: July 2003

Die Wissenschaftsphilosophin Daniela Bailer‐Jones
Die Heuschrecke und der Kurvenflug
Authors: Kutsch Wolfram , Berger Sebastian , Fischer Hanno
Published: July 2003

Mit Hilfe miniaturisierter Daten‐Fernübertragung untersuchen Biologen die Flugbewegungen freifliegender Wüstenheuschrecken und anderer Insekten. Computergestützte Videotechnik rekonstruiert Verhaltensabläufe
Die Arbeitslosen und die Solidarität
Authors: Hamann Silke , Karl Astrid
Published: July 2003

Die grassierende Massenarbeitslosigkeit und die Diskussion um die Zukunft sozialer Sicherung werfen viele Fragen auf. Wie sozialstaatliche Leistungen für Arbeitslose in der Bevölkerung akzeptiert werden, beantwortet eine Studie
Influence of β‐Alanine on Hairpin Polyamide Orientation in the DNA Minor Groove
Authors: Rucker Victor C. , Melander Christian , Dervan Peter B.
Published: July 2003

Antiparallel polyamides containing 1H‐pyrrole, 1H‐imidazole, and 3‐hydroxy‐1H‐pyrrole amino acids display a preference for minor‐groove binding oriented NC with respect to the 5′‐3′ direction of the DNA helix. We find that replacement of a central Py/Py pair with a β/β pair within a ten‐ring hairpin relaxes the orientation preference and, for some DNA sequences, causes the polyamide to prefer the opposite CN orientation. Substitution of the achiral γ‐aminobutanoic acid (γ) with either (R)(or S)‐2‐(acetylamino)‐4‐aminobutanoic acid moderates the orientation preference of the 2‐β‐2‐hairpin.
Synthesis and Glycosidase Inhibitory Activities of 5‐(1′,4′‐Dideoxy‐1′,4′‐imino‐D‐erythrosyl)‐2‐methyl‐3‐furoic Acid (=5‐[(3S,4R)‐3,4‐Dihydroxypyrrolidin‐2‐yl]‐2‐methylfuran‐3‐carboxylic Acid) Derivatives: New Leads as Selective α‐L‐Fucosidase and β‐Galactosidase Inhibitors
Authors: Moreno‐Vargas Antonio J. , Robina Inmaculada , Demange Raynald , Vogel Pierre
Published: July 2003

The García‐González reaction of D‐glucose and ethyl acetoacetate generated ethyl 5‐[(1′S)‐D‐erythrosyl]‐2‐methyl‐3‐furoate (5), which was converted to ethyl 5‐[(1′R)‐1′,4′‐dideoxy‐1′,4′‐imino‐D‐erythrosyl]‐2‐methyl‐3‐furoate (3c) and to ethyl 5‐[(1′S)‐1′,4′‐dideoxy‐1′,4′‐imino‐D‐erythrosyl]‐2‐methyl‐3‐furoate (4c). Similar methods were developed to generate other carboxylic acid derivatives such as methyl (see 3e and 4e), isopropyl (see 3f), and butyl esters (see 3g), S‐phenyl (see 3a) and S‐ethyl thioesters (see 3m), N‐benzylcarboxamides 3b and 4b, glycine‐derived amide 3h, and N‐phenyl (see 3i), N‐isopropyl (see 3j and 4j), N,N‐diethyl‐ (see 3k and 4k), and N‐ethyl‐carboxamides (see 3l). All the new 5‐(1′,4′‐dideoxy‐1′,4′‐imino‐D‐erythrosyl)‐3‐furoic acid (=5‐[(3S,4R)‐3,4‐dihydroxypyrrolidin‐2‐yl)furan‐3‐carboxylic acid) derivatives 3 and 4 were assayed for inhibitory activity towards 25 commercially available glycosidases. Derivative 3a with a S‐phenyl thioester group is a good and selective α‐L‐fucosidase inhibitor (Ki=2–4 μM), whereas 4b (with a N‐benzylcarboxamide group) is a good β‐galactosidase inhibitor.
On the Reaction of Thiazole‐2,4‐diamines with Isothiocyanates – Preparation and Transformation of 2,4‐Diaminothiazole‐5‐carbothioamides
Authors: Hahnemann Cornelia , Hartmann Horst
Published: July 2003

In the reaction of thiazole‐2,4‐diamines 8 with isothiocyanates 1, 2,4‐diaminothiazole‐5‐carbothioamides 9, 10, 18, and 19 as well as thiazolo[4,5‐d]pyrimidine‐7(6H)‐thiones 21 were formed. The carbothioamides 9, 10, and 18 were transformed by reaction with different types of monofunctional and bifunctional electrophiles into hitherto unknown acceptor‐substituted 4,4′‐([2,5′‐bithiazole]‐2′,4′‐diyl)bis[morpholines] 24 and 29, the 2′,4′‐bis(dialkylamino)[2,5′‐bithiazol]‐4‐(5H)‐ones 30, and the 4‐substituted 2′,4′‐bis(dialkylamino)‐2,5′‐bithiazoles 31. From 30 and 31 new 4‐mono‐ or 4,5‐disubstituted 2′,4′‐bis(dialkylamino)‐2,5′‐bithiazoles 34, 35, 38, and 39 as well as 5‐substituted 2′,4′‐bis(dialkylamino)[2,5′‐bithiazol]‐4(5H)‐ones 33, 36, and 37 were prepared.
Cytotoxic Constituents of Piper sintenense
Authors: Chen Jih‐Jung , Duh Chang‐Yih , Huang Hung‐Yi , Chen Ih‐Sheng
Published: July 2003

A new pyridone alkaloid, 5,6‐dihydro‐5‐hydroxy‐1H‐pyridin‐2‐one (1), and a new ester, sintenin (=3‐(3,4‐dimethoxyphenyl)propyl 3‐(3,4‐dimethoxyphenyl)propanoate 2), together with three known compounds, 5,6‐dihydro‐1H‐pyridin‐2‐one (3), d‐sesamin (=5,5′‐(3a,4,6,6a‐tetrahydro‐1H,3H‐furo[3,4‐c]furan‐1,4‐diyl)bis[1,3‐benzodioxole]; 4), and (E)‐phytol (=3,7,11,15‐tetramethylhexadec‐2‐en‐1‐ol; 5) have been isolated from the whole plant of Piper sintenense. The structures of the two new compounds were determined through spectral analyses. Among twenty isolates obtained so far, four compounds exhibited effective cytotoxicities against P‐388, HT‐29, or A549 cell lines in vitro.
Five Novel Taccalonolides from the Roots of the Vietnamese Plant Tacca paxiana
Authors: Mühlbauer Andrea , Seip Stephan , Nowak Alexander , Tran Van Sung
Published: July 2003

Chemical investigation of the roots of the Vietnamese plant Tacca paxiana resulted in the isolation of five new steroidal compounds, taccalonolide R (6), S (7), T (8), U (9), and V (10). Their structures were established on the basis of NMR and mass‐spectral data. In addition, the five known taccalonolides A (1), B (2), E (3), K (4), and N (5) were also isolated and identified.
Synthesis of 5′‐O‐(2‐Azido‐2‐deoxy‐α‐D‐glycosyl)nucleosides and Their Antitumor Activities
Authors: Zhang Gui‐Sheng , Chen Jie , Min Ji‐Mei , Zhang Li‐He
Published: July 2003

The 1,3,4,6‐tetra‐O‐acetyl‐2‐azido‐2‐deoxy‐β‐D‐mannopyranose (4) or the mixture of 1,3,6‐tri‐O‐acetyl‐2‐azido‐2‐deoxy‐4‐O‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐galactopyranosyl)‐β‐D‐mannopyranose (10) and the corresponding α‐D‐glucopyranose‐type glycosyl donor 9/10 reacted at room temperature with protected nucleosides 12–15 in CH2Cl2 solution in the presence of BF3⋅OEt2 as promoter to give 5′‐O‐(2‐azido‐2‐deoxy‐α‐D‐glycosyl)nucleosides in reasonable yields (Schemes 2 and 3). Only the 5′‐O‐(α‐D‐mannopyranosyl)nucleosides were obtained. Compounds 21, 28, 30, and 31 showed growth inhibition of HeLa cells and hepatoma Bel‐7402 cells at a concentration of 10 μM in vitro.
Intercalating Nucleic Acids with Pyrene Nucleotide Analogues as Next‐Nearest Neighbors for Excimer Fluorescence Detection of Single‐Point Mutations under Nonstringent Hybridization Conditions
Authors: Christensen Ulf B. , Pedersen Erik B.
Published: July 2003

Fluorescence and hybridization specificity is reported for intercalating nucleic acids (INAs), which are here oligodeoxynucleotides (ODNs) synthesized with insertions using (S)‐1‐[bis(4‐methoxyphenyl)(phenyl)methoxy]‐3‐[(pyren‐1‐yl)methoxy]propan‐2‐ol phosphoramidites. It is shown that an INA with two insertions placed as next‐nearest neighbors can be used for discrimination between nucleic acids and their single‐point mutants. Quenching of an excimer band at 480 nm is observed upon hybridizing to a complementary sequence, whereas the excimer band is present when the nucleobase pair between the two pyrene moieties is mismatched. It is the first example of a solution based on fluorescence detection of single‐point mutants that uses excimer formation and does not rely on stringent hybridization conditions. Furthermore, it is shown that INAs with pyrene insertions retain their sequence specificity in thermal melting.
Evidence from Circular Dichroism and from Melting Behavior for Helix‐Inducing Complexation of a Designed β3‐Pentadecapeptide with DNA Duplexes. Preliminary Communication
Authors: Kimmerlin Thierry , Namoto Kenji , Seebach Dieter
Published: July 2003

Inspired by naturally occurring DNA‐binding proteins and their artificial α‐peptidic mimics reported to date, a research project was initiated aiming at creating a new class of β‐peptides capable of binding to and ultimately regulating the functions of DNA. As an initial foray, a β3‐pentadecapeptide 1, which bears H‐bonding Asn side chains and positively charged Lys side chains, was designed and synthesized on the solid support. DNA‐Complexation studies by means of circular dichroism and DNA‐melting‐temperature measurements revealed the first preliminary indications that support the existence of ordered interactions between β‐peptides and DNA.
Synthesis and Characterization of Ruthenium Complexes with Substituted Pyrazino[2,3‐f][1,10]‐phenanthroline (=Rppl; R=Me, COOH, COOMe)
Authors: Delgadillo Alvaro , Romo Paola , Leiva Ana Maria , Loeb Bárbara
Published: July 2003

A series of substituted pyrazino[2,3‐f][1,10]‐phenanthroline (Rppl) ligands (with R=Me, COOH, COOMe) were synthetized (see 1–4 in Scheme 1). The ligands can be visualized as formed by a bipyridine and a quinoxaline fragment (see A and B). Homoleptic [Ru(R1ppl)3](PF6)2 and heteropleptic [Ru(R1ppl){(R2)2bpy}2](PF6)2 (R1=H, Me, COOMe and R2=H, Me) metal complexes 5–7 and 8–13, respectively, based on these ligands were also synthesized and characterized by conventional techniques (Schemes 2 and 3, resp.). In the heteroleptic complexes, the R1‐ppl ligand reduces at a less‐negative potential than the bpy ligand, reflecting the acceptor property conferred by the quinoxaline moiety. The potentiality of some of these complexes as solar‐cell dyes is discussed.
Oxidative Fragmentations of the 5α‐ and 5β‐Hydroxy‐B‐norcholestan‐ 3β‐yl Acetates
Authors: Bjelaković Mira S. , Lorenc Ljubinka B. , Pavlović Vladimir D. , Tinant Bernard , Declercq Jean‐Paul , Kalvoda Jaroslav
Published: July 2003

Oxidations of 5α‐hydroxy‐B‐norcholestan‐3β‐yl acetate (8) with Pb(OAc)4 under thermal or photolytic conditions or in the presence of iodine afforded only complex mixtures of compounds. However, the HgO/I2 version of the hypoiodite reaction gave as the primary products the stereoisomeric (Z)‐ and (E)‐1(10)‐unsaturated 5,10‐seco B‐nor‐derivatives 10 and 11, and the stereoisomeric (5R,10R)‐ and (5S,10S)‐acetals 14 and 15 (Scheme 4). Further reaction of these compounds under conditions of their formation afforded, in addition, the A‐nor 1,5‐cyclization products 13 and 16 (from 10) and 12 (from 11) (see also Scheme 6) and the 6‐iodo‐5,6‐secolactones 17 and 19 (from 14 and 15, resp.) and 4‐iodo‐4,5‐secolactone 18 (from 15) (see also Scheme 7). Oxidations of 5β‐hydroxy‐B‐norcholestan‐3β‐yl acetate (9) with both hypoiodite‐forming reagents (Pb(OAc)4/I2 and HgO/I2) proceeded similarly to the HgO/I2 reaction of the corresponding 5α‐hydroxy analogue 8. Photolytic Pb(OAc)4 oxidation of 9 afforded, in addition to the (Z)‐ and (E)‐5,10‐seco 1(10)‐unsaturated ketones 10 and 11, their isomeric 5,10‐seco 10(19)‐unsaturated ketone 22, the acetal 5‐acetate 21, and 5β,19‐epoxy derivative 23 (Scheme 9). Exceptionally, in the thermal Pb(OAc)4 oxidation of 9, the 5,10‐seco ketones 10, 11, and 22 were not formed, the only reaction being the stereoselective formation of the 5,10‐ethers with the β‐oriented epoxy bridge, i.e. the (10R)‐enol ether 20 and (5S,10R)‐acetal 5‐acetate 21 (Scheme 8). Possible mechanistic interpretations of the above transformations are discussed.
Synthesis of 6‐Amino Acid Substituted Derivatives of the Highly Potent Analgesic 14‐O‐Methyloxymorphone
Authors: Schütz Johannes , Brandt Wolfgang , Spetea Mariana , Wurst Klaus , Wunder Gerhard , Schmidhammer Helmut
Published: July 2003

The novel morphinans 13–18, which carry amino acid substituents at C(6), with potentially limited access to the central nervous system were prepared in two steps from 14‐O‐methyloxymorphone (5). Reductive amination with amino acid tert‐butyl esters gave compounds 7–12, which were hydrolyzed with tetrafluoroboric acid. Structure elucidation (including X‐ray analysis), preliminary μ‐opioid receptor binding studies, and calculations of pharmacokinetic parameters were carried out.
Polyprenylated Phloroglucinol Derivatives from Hypericum sampsonii
Authors: Lin Yun‐Lian , Wu Yu‐San
Published: July 2003

Six new prenylated phloroglucinol derivatives, hypersampsones A–F (1–6), were isolated from the aerial part of Hypericum sampsonii, together with 2,4,6‐trihydroxybenzophenone, 2,4,6‐trihydroxybenzophenone 4‐O‐geranyl ether, 2,4,6‐trihydroxybenzophenone 3‐C‐geranyl ether, sampsoniones D and H. Their structures were elucidated by spectroscopic methods, mainly 1D‐ and 2D‐NMR spectroscopy and mass spectrometry.
Atropisomeric PˆN Ligands for the Palladium‐Catalyzed Copolymerization of Styrene with Carbon Monoxide. Preliminary Communication
Authors: Gsponer Achim , Consiglio Giambattista
Published: July 2003

Achiral and chiral cationic palladium catalysts, modified with atropisomeric PˆN ligands with different steric and electronic properties, can efficiently produce poly(styrene‐alt‐CO) with essentially complete regioregularity and variable tacticity, depending on the ligand geometry; the electronic effect on catalytic activity depends on the geometry of the ligand.
Synthesis, Separation, and Theoretical Studies of Chiral Biphenyl Lignans (α‐ and β‐DDB)
Authors: Chang Junbiao , Chen Rongfeng , Guo Ruiyun , Dong Chunhong , Zhao Kang
Published: July 2003

Two biphenyl lignans, α‐ and β‐DDB (1 and 2, respectively) were efficiently synthesized without contamination by other regio‐isomers. The different yields of the Ullmann coupling reactions for the synthesis of 1 and 2 were rationalized by calculating steric hindrance, stability, entropy change, and heat‐of‐formation values. The enantiomers of 1 and 2 were readily separated by HPLC on a chiral stationary phase. Their configurations were assigned based on the Cotton effect of the authentic natural products.
Abundance and Vertical Distribution of the Phytobenthic Community within a Pool and Riffle Sequence of an Alpine Gravel Stream
Authors: Müllner Alexandra N. , Schagerl Michael
Published: July 2003

In the 2nd order mountain brook “Oberer Seebach” (Austria), diatoms and cyanoprokaryotes dominate the microphytobenthos, with the diatoms forming the richest species group.

Comparative investigations of different habitats clearly show seasonal variations in algal species composition and biomass throughout the year. Pool habitats hold a higher number of taxa than riffle sites. In addition, phytobiomass is two‐ to nearly fourfold higher in pools. Based on investigations of the chlorophyll‐a vertical profiles within the coarse gravel sediments, the light discontinuity layer was determined to be situated at 7–10 cm sediment depth. Vertical distribution showed a maximum of taxa a few centimeters below the sediment surface. The same diatom taxa were found throughout all sampling dates, sediment depths and sampling sites.

The results of exposed perforated metal tubes clearly indicate that the occurrence of phytobenthos in aphotic zones is primarily controlled by saltatory movements of the upper sediment layers driven by discharge.
Benthic Invertebrates and Metabolism of West Carpathian (Slovakia) Rivers
Authors: Šporka Ferdinand , Krno Il'ja
Published: July 2003

We examined benthic invertebrates and metabolism on the basis of the annual sampling of 9 types of running waters in the West Carpathians. Headwaters in general represent typical heterotrophic systems, except where they are high mountain streams, which are autotrophic. Lower down, the upper reaches of brooks are transition zones between heterotrophic and autotrophic systems. After the transition to an autotrophic system (which depends mainly on the primary producers) there is a considerable decrease in secondary production. Production is higher in the rivers of the Carpathian basin, as well as lower down the valley (submontane rivers and lower tributaries of submontane streams) where, within the autotrophic systems, there is a shift of metabolism from the bottom to the water column. The temperature days, altitude and slope of the stream and concentration of calcium influence production of macrozoobenthos.
The Choice of Standardisation Reveals a Significant Influence on the Dynamics of Bacterial Abundance in Newly Deposited River Sediments
Authors: Farnleitner Andreas H. , Kasimir Georg D. , Kavka Gerhard G. , Zechmeister Thomas C. , Mach Robert L. , Kirschner Alexander K. T.
Published: July 2003

After a high water event of the River Danube in April 1994, bacterial cell numbers were determined in newly formed deposits in a backwater near Hainburg (Lower Austria) within a time course of 140 days. This data set shows that expressing bacterial numbers per fresh sediment volume, per sediment dry mass, or per pore‐water fluid volume, respectively, yield significantly different results and ecological conlusions. These findings refer particularly to intra‐study and time‐course comparisons as presented in our case. Bacterial cell numbers expressed per gram sediment dry mass revealed statistically significant differences between the beginning and the end of the study, whereas expressed per cm3 of fresh sediment or fluid volume of sediment pore water, no statistical difference could be detected. It is argued that these differences were caused by physical sediment compaction and mineralisation processes over the considered time‐course. Such mechanisms may simulate biological activity if some basic sediment parameters are neglected and thus standardisation has to be done with caution for the particular situation being observed.
Vertical Distribution of Benthic Macroinvertebrates in Riffles versus Deep Runs with Differing Contents of Fine Sediments (Weidlingbach, Austria)
Authors: Weigelhofer Gabriele , Waringer Johann
Published: July 2003

Due to the erosiveness of their sediments, sandstone streams transport high loads of fine particles. The catchment of the Weidlingbach, a 12 km long tributary of the Danube northwest of Vienna, is dominated by calcareous sandstone, marl and slate. Mean sediment grain size ranges from 29.3 to 31.0 mm, and mean pore volume is approximately 20%. The third order study site is divided into a wide, shallow riffle section with high accumulations of fine sediments in the hyporheic zone and a narrow, deep run section with a lower percentage of fine sediments. Invertebrates were sampled to a sediment depth of 60 cm every second month using the freeze‐coring‐technique with electropositioning.

Hyporheic invertebrate densities were significantly higher in sediments of the run than in those of the riffle section. Generally, hyporheic abundances decreased with increasing depth; however, the decline was more distinct within the riffle than the run section. Furthermore, we observed a strong negative correlation between the percentage of fine sediments (<2 mm) and hyporheic invertebrate densities.
The Development of a System to Assess the Ecological Quality of Streams Based on Macroinvertebrates – Design of the Sampling Programme within the AQEM Project
Authors: Hering Daniel , Buffagni Andrea , Moog Otto , Sandin Leonard , Sommerhäuser Mario , Stubauer Ilse , Feld Christian , Johnson Richard , Pinto Paulo , Skoulikidis Nikos , Verdonschot Piet , Zahrádková Svetlana
Published: July 2003

The EU Water Framework Directive (WFD) requires river assessment systems based on benthic invertebrates. The AQEM project is developing, at a European scale, such a methodology, based on a comparison of communities of reference streams and degraded streams. The project is focussing on three main impact types: morphological degradation, organic pollution and acidification.

This paper presents the outline of the AQEM project with special emphasis on:

– an overview of assessment systems with benthic invertebrates presently applied in Europe

– an overview of stream typology approaches in Europe

– the selection process of the stream types investigated in AQEM

– the criteria used to select reference sites

– the design of the sampling programme

– the microhabitat‐based sampling method applied in AQEM

– the links and possibilities of integration between AQEM and existing assessment systems.
Organic Matter Dynamics and Invertebrate Functional Groups in a Mountain Stream in the West Tatra Mountains, Poland
Authors: Galas Joanna , Dumnicka Elżbieta
Published: July 2003

Investigations were carried out at two sites on a low order mountain stream in order to characterise the role of macroinvertebrates in organic matter decomposition. Total benthic organic matter content ranged from 6 to 1304 g AFDM m−2. The fine fraction constituted more than 50% of the total POM at both sites in all seasons, except for autumn. In transported POM the coarse fraction dominated and its highest values were noted in May, after the snow melt season. The density of bottom fauna was five times higher on the sandy‐gravel bottom than on the stony bottom. In both habitats, gathering collectors and scrapers were most abundant; shredders constituted only a few percent of the benthic community in the stony habitat. Our results indicate that the role of shredders is small, and mechanical fragmentation and microbial activity are mainly responsible for fine particle formation.
Spatial Autocorrelation and Fractal Dimension of Alga Species Assemblage in a Gravel Stream of Central Europe
Authors: Komárek Ondrřej
Published: July 2003

The relationship of benthic diatom species to sampling scale was studied in two Moravian rivers that differ in substrate and discharge. Number of cells per mm2 of each species was used for statistical analysis. The distribution of abundance of benthic algae follows a fractal pattern, because it exhibits the same detail over a continuum of scales. DCA first axis score, variogram and fractal dimension were used for spatial autocorrelation estimation. The fractal dimensions obtained are generally close to 2, implying weak spatial dependence. The fractal dimension was not a constant function of scale, implying that patterns of spatial variation at one scale cannot be extrapolated to other scales. The results suggest that appropriate distances among samples of benthic algae must be considered.
Clogging Processes in Hyporheic Interstices of an Impounded River, the Danube at Vienna, Austria
Authors: Blaschke Alfred Paul , Steiner Karl‐Heinz , Schmalfuss Roland , Gutknecht Dieter , Sengschmitt Dieter
Published: July 2003

Stream‐aquifer interactions are influenced significantly by riverbed clogging processes. Detailed field observations have been made in the “Freudenau reservoir” of the Danube at Vienna. Different types of clogged layers have been observed. Multi‐level‐piezometers below the riverbed indicate that the overall clogging process consists of several clogging cycles of a few weeks each initiated by floods until a stable state is reached. Minor flood events cause a temporary increase in the leakage coefficient followed by a new decrease approaching the original level after a few weeks. Major flood events tended to add a sediment layer which re‐initiated the clogging process leading over to a lower level of the leakage coefficient. The computation of the water balance of the two reservoirs of the New Danube indicated a reduction of the seepage rate by about 40% to 60% over a period of 4.5 years. Undisturbed riverbed sediment samples taken by an innovative freeze‐panel‐sampling method demonstrate that the depth of the clogged layer is about 2 cm for two of the clogging types (external clogging and armour layer clogging). Video techniques were used to identify the different types of clogged layers and their variability in time and space. Additionally, this technique facilitated observations of macrozoobenthos organism activities in the hyporheic interstices.
Retention of Coarse Particulate Organic Matter on the Sediments of Njoro River, Kenya
Authors: Magana Adiel Micheni , Bretschko Gernot
Published: July 2003

Retention of benthic organic matter (BOM) on the sediment surface of the Njoro River, Kenya was investigated between February 1998 and June 1999 at two sites, differing in channel morphology and riparian vegetation density and composition i.e. open‐canopy and closed‐canopy sites. Monthly accumulation of benthic organic matter (BOM) was highly variable, ranging from 97.3 to 6691.8 and from 206.6 to 1936.3 g ash free dry weight m−2 (AFDW) with a mean ± CL of 1133.3 ± 794.5 and 834.9 ± 275.8 g AFDW m−2 at the closed and open canopy sites, respectively. Pools retained higher amounts of particulate organic matter than riffles. Surprisingly, differences in retention of BOM at the two sites were not significant. Temporal distribution of benthic organic matter showed no distinct relationship with throughfall and bank runoff input patterns of particulate organic matter. Wood debris comprised 47% and 36% while leaves comprised 34% and 31% of the total BOM at the closed and open canopy sites, respectively; the rest was fruits and fine benthic organic matter (FBOM > 0.1 mm but < 1 mm). Out of 19 plant species recorded at both sites, only 8 species reflected their contribution in BOM with Syzygium cordatum contributing over 80% of the identifiable leaf litter. It is presumed that the variations in spatial and temporal distribution of BOM at the two sites is due to differences in discharge regimes, retention structures and riparian vegetation characteristics.
Biocompatibility and other properties of acrylic bone cements prepared with antiseptic activators
Authors: de la Torre B. , Fernández M. , Vázquez B. , Collía F. , de Pedro J. A. , López‐Bravo A. , San Román J.
Published: July 2003

Acrylic bone cements prepared with activators of reduced toxicity have been formulated with the aim of improving the biocompatibility of the final material. The activators used were N,N‐dimethylaminobenzyl alcohol (DMOH) and 4,4′‐dimethylamino benzydrol (BZN). The toxicity, cytotoxicity, and antiseptic action of these activators were first studied. DMOH and BZN presented LD50 values 3–4 times higher than DMT, were less cytotoxic against polymorphonuclear leucocytes, and possessed an antimicrobial character, with a high activity against the most representative microorganisms involved in postoperative infections. The properties of the acrylic bone cements formulated with DMOH and BZN were evaluated to determine the influence of these activators on the curing process and the physicochemical characteristics of the cements. A decrease of the peak temperature was observed for the curing with DMOH or BZN with respect to that of one commercially available formulation (CMW 3). However, residual monomer content and mechanical properties in tension and compression were comparable to those of CMW 3. The biocompatibility of acrylic bone cements containing DMOH or BZN was studied and compared with CMW 3. To that end, intramuscular and intraosseous implantation procedures were carried out and the results were obtained from the histological analysis of the surrounding tissues at different periods of time. Implantation of rods of cement into the dorsal muscle of rats showed the presence of a membrane of connective tissue, which increased in collagen fibers with time of implantation, for all formulations. The intraosseous implantation of the cements in the dough state in the femur of rabbits, revealed a higher and early osseous neoformation, with the presence of osteoid material surrounding the rest of the cured material, for the cement prepared with the activator BZN in comparison with that obtained following the implantation of the cement cured with DMOH or DMT (CMW 3). © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 66B: 502–513, 2003
Long‐term wear of ceramic matrix composite materials for hip prostheses under severe swing phase microseparation
Authors: Stewart Todd D. , Tipper Joanne L. , Insley Gerard , Streicher Robert M. , Ingham Eileen , Fisher John
Published: July 2003

The purpose of this study was to evaluate the long‐term wear performance of alumina matrix composite (AMC) heads against alumina matrix composite inserts and alumina matrix composite heads against alumina (Al) inserts with the use of a hip‐joint simulator incorporating severe swing phase joint microseparation. The wear of AMC on Al produced an average wear rate of 0.61 mm3/million cycles over the 5‐million‐cycle test duration. The wear of AMC on AMC produced an average wear rate of 0.16 mm3/million cycles over the 5‐million‐cycle test duration. Both the AMC on alumina and AMC on AMC produced significantly lower wear than previously tested HIPed alumina, where an average wear rate of 1.84 mm3/million cycles was reported over 5 million cycles. The wear mechanisms and wear debris of AMC on AMC and AMC on Al were similar to those observed in previous alumina retrieval studies with stripe wear caused by intragranular fracture and wear debris consisting of predominantly uniform 10–20‐nm‐sized particles and a few irregular particles up to 3 μm in size. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 66B: 567–573, 2003