BASIN RESEARCH, Issue 3 2006
P.A. Cowie
ABSTRACT In order to better understand the evolution of rift-related topography and sedimentation, we present the results of a numerical modelling study in which elevation changes generated by extensional fault propagation, interaction and linkage are used to drive a landscape evolution model. Drainage network development, landsliding and sediment accumulation in response to faulting are calculated using CASCADE, a numerical model developed by Braun and Sambridge, and the results are compared with field examples. We first show theoretically how the ,fluvial length scale', Lf, in the fluvial incision algorithm can be related to the erodibility of the substrate and can be varied to mimic a range of river behaviour between detachment-limited (DL) and transport-limited (TL) end-member models for river incision. We also present new hydraulic geometry data from an extensional setting which show that channel width does not scale with drainage area where a channel incises through an area of active footwall uplift. We include this information in the coupled model, initially for a single value of Lf, and use it to demonstrate how fault interaction controls the location of the main drainage divide and thus the size of the footwall catchments that develop along an evolving basin-bounding normal fault. We show how erosion by landsliding and fluvial incision varies as the footwall area grows and quantify the volume, source area, and timing of sediment input to the hanging-wall basin through time. We also demonstrate how fault growth imposes a geometrical control on the scaling of river discharge with downstream distance within the footwall catchments, thus influencing the incision rate of rivers that drain into the hanging-wall basin. Whether these rivers continue to flow into the basin after the basin-bounding fault becomes fully linked strongly depends on the value of Lf. We show that such rivers are more likely to maintain their course if they are close to the TL end member (small Lf); as a river becomes progressively more under supplied, i.e. the DL end member (large Lf), it is more likely to be deflected or dammed by the growing fault. These model results are compared quantitatively with real drainage networks from mainland Greece, the Italian Apennines and eastern California. Finally, we infer the calibre of sediments entering the hanging-wall basin by integrating measurements of erosion rate across the growing footwall with the variation in surface processes in space and time. Combining this information with the observed structural control of sediment entry points into individual hanging-wall depocentres we develop a greater understanding of facies changes associated with the rift-initiation to rift-climax transition previously recognised in syn-rift stratigraphy. [source]

Gold(I)-Catalyzed Cascade for Synthesis of Pyrrolo[1,2- a:2,,1,- c]-/Pyrido[2,1- c]pyrrolo[1,2- a]quinoxalinones

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010
Yu Zhou
Abstract An efficient and convenient method was developed for the one-pot construction of the complex polycyclic heterocycles pyrrolo[1,2- a:2,,1,- c]-/pyrido[2,1- c]pyrrolo[1,2- a]quinoxalinones from two simple starting materials via a gold(I)-catalyzed domino reaction. This strategy presents an atom economical and environmentally friendly transformation, in which two new CN bonds and one new CC bond are formed in a one-pot reaction process. [source]

Deracemisation of Mandelic Acid to Optically Pure Non-Natural L -Phenylglycine via a Redox-Neutral Biocatalytic Cascade

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2010
Verena Resch
Abstract A biocatalytic redox-neutral reaction cascade was designed for the deracemisation of racemic mandelic acid to yield optically pure L -phenylglycine employing three enzymes. The cascade consisted of three steps: a racemisation, an enantioselective oxidation and a stereoselective reductive amination. The enantioselective oxidation of D -mandelic acid to the corresponding oxo acid was coupled with the stereoselective reductive amination of the latter; thus the oxidation as well as the reduction reactions were performed simultaneously. The formal hydrogen abstracted in the first step , the oxidation , was consumed in the reductive amination allowing a redox-neutral cascade due to a cascade-internal cofactor recycling. The enantiomers of the starting material were interconverted by a racemase (mandelate racemase) ensuring that in theory 100% of the starting material can be transformed. Using this set-up racemic mandelic acid was transformed to optically pure L -phenylglycine (ee >97%) at 94% conversion without the requirement of any additional redox reagents in stoichiometric amounts. [source]

Gold-Catalyzed Intramolecular Alkyne Cycloisomerization Cascade: Direct Synthesis of Aryl-Annulated[a]carbazoles from Aniline-Substituted Diethynylarenes

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010
Kimio Hirano
Abstract Aniline-substituted diethynylarenes, which are readily synthesized through Sonogashira coupling reactions from commercially available 1,2-dihaloarenes, directly produce aryl- and heteroaryl-annulated[a]carbazoles by the gold-catalyzed intramolecular cascade hydroamination/cycloisomerization without producing theoretical by-products. This new atom-economical route is easily applicable to various aryl-annulated[a]carbazoles containing an alkyl, aryl or ester substituent. [source]

Expanding the Suzuki,Heck-Type Coupling Cascade: A New Indeno[1,2,3]-Annelation of Polycyclic Aromatic Hydrocarbons

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009
Jennifer
Abstract Fluoranthene derivatives can be constructed in a single operation by a palladium-catalyzed cascade reaction sequence, starting from a peri -dichloronaphthalene derivative and various arylboronic acids. [source]

Synthesis of Aliphatic (S)-,-Hydroxycarboxylic Amides using a One-Pot Bienzymatic Cascade of Immobilised Oxynitrilase and Nitrile Hydratase

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009
Sander van Pelt
Abstract A one-pot bienzymatic cascade combining a hydroxynitrile lyase (Manihot esculenta, E.C. 4.1.2.10) and a nitrile hydratase (Nitriliruptor alkaliphilus, E.C. 4.2.1.84) for the synthesis of enantiopure aliphatic ,-hydroxycarboxylic amides from aldehydes is described. Both enzymes were immobilised as cross-linked enzyme aggregates (CLEAs). Stability tests show that the nitrile hydratase CLEAs are sensitive to water-immiscible organic solvents as well as to aldehydes and hydrogen cyanide (HCN), but are remarkably stable and show useful activity in acidic aqueous environments of pH,4,5. The cascade reactions are consequently carried out by using a portionwise feed of HCN and moderate concentrations of aldehyde in acidic aqueous buffer to suppress the uncatalysed hydrocyanation background reaction. After optimisation, this method was used to synthesise five different kinds of aliphatic ,-hydroxycarboxylic amides from the corresponding aldehydes with good yields and with enantiomeric purities comparable to those obtained for the ,-hydroxynitriles in the microaqueous hydrocyanation using hydroxynitrile lyase and an excess of HCN. [source]

Systemic Regulation of Distraction Osteogenesis: A Cascade of Biochemical Factors,,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2002
S. Weiss M.D.
Abstract This study investigates the systemic biochemical regulation of fracture healing in distraction osteogenesis compared with rigid osteotomy in a prospective in vivo study in humans. To further clarify the influence of mechanical strain on the regulation of bone formation, bone growth factors (insulin-like growth factor [IGF] I, IGF binding protein [IGFBP] 3, transforming growth factor [TGF] ,1, and basic FGF [bFGF]), bone matrix degrading enzymes (matrix-metalloproteinases [MMPs] 1, 2, and 3), human growth hormone (hGH), and bone formation markers (ALP, bone-specific ALP [BAP], and osteocalcin [OC]) have been analyzed in serum samples from 10 patients in each group pre- and postoperatively. In the distraction group, a significant postoperative increase in MMP-1, bFGF, ALP, and BAP could be observed during the lengthening and the consolidation period when compared with the baseline levels. Osteotomy fracture healing without the traction stimulus failed to induce a corresponding increase in these factors. In addition, comparison of both groups revealed a significantly higher increase in TGF-,1, IGF-I, IGFBP-3, and hGH in the lengthening group during the distraction period, indicating key regulatory functions in mechanotransduction. The time courses of changes in MMP-1, bone growth factors (TGF-,1 and bFGF), and hGH, respectively, correlated significantly during the lengthening phase, indicating common regulatory pathways for these factors in distraction osteogenesis. Significant correlation between the osteoblastic marker BAP, TGF-,1, and bFGF suggests strain-activated osteoblastic cells as a major source of systemically increased bone growth factors during callus distraction. The systemic increase in bFGF and MMP-1 might reflect an increased local stimulation of angiogenesis during distraction osteogenesis. [source]

Alcohol-Induced Neurodegeneration: When, Where and Why?

ALCOHOLISM, Issue 2 2004
Fulton T. Crews
Abstract: This manuscript reviews the proceedings of a symposium organized by Drs. Antonio Noronha and Fulton Crews presented at the 2003 Research Society on Alcoholism meeting. The purpose of the symposium was to examine recent findings on when alcohol induced brain damage occurs, e.g., during intoxication and/or during alcohol withdrawal. Further studies investigate specific brain regions (where) and the mechanisms (why) of alcoholic neurodegeneration. The presentations were (1) Characterization of Synaptic Loss in Cerebella of Mature and Senescent Rats after Lengthy Chronic Ethanol Consumption, (2) Ethanol Withdrawal Both Causes Neurotoxicity and Inhibits Neuronal Recovery Processes in Rat Organotypic Hippocampal Cultures, (3) Binge Drinking-Induced Brain Damage: Genetic and Age Related Effects, (4) Binge Ethanol-Induced Brain Damage: Involvement of Edema, Arachidonic Acid and Tissue Necrosis Factor , (TNF,), and (5) Cyclic AMP Cascade, Stem Cells and Ethanol. Taken together these studies suggest that alcoholic neurodegeneration occurs through multiple mechanisms and in multiple brain regions both during intoxication and withdrawal. [source]

Hybrid Lethality in Interspecific F1 Hybrid Nicotiana gossei×N. tabacum Involves a MAP-Kinases Signalling Cascade

PLANT BIOLOGY, Issue 3 2007
M. Mino
Abstract: A cultured cell line, GTH4 (Nicotiana gossei Domin ×N. tabacum L.), which exhibits hybrid lethality, died at 26 °C, but not at 37 °C. Pharmacological experiments using inhibitors of protein phosphatases and protein kinases indicated the involvement of a protein kinase signalling pathway in the cell death process. Immunoblot analysis revealed that salicylic acid-induced protein kinase (SIPK) was phosphorylated soon after the shift in temperature from 37 °C to 26 °C. Cultured cells of the hybrid of N. gossei× transgenic N. tabacum harboring a steroid (dexamethasone; DEX)-inducible NtMEK2DD or NtMEK2KR, constitutively active and inactive forms of NtMEK2, respectively, were established. Induction of NtMEK2DD by DEX in the hybrid cells induced the activation of SIPK, the generation of hydrogen peroxide (H2O2), and cell death at 37 °C. The activation of SIPK, generation of H2O2, and cell death at 26 °C were compromised by DEX treatment in hybrid cells harbouring NtMEK2KR. This study provides evidence for the involvement of MAPK signalling in the regulation of cell death in hybrids. [source]

Clay-Turbid Interactions May Not Cascade,A Reminder for Lake Managers

RESTORATION ECOLOGY, Issue 2 2005
Jukka Horppila
Abstract Food web management is a frequently used lake restoration method, which aims to reduce phytoplankton biomass by strengthening herbivorous zooplankton through reduction of planktivorous fish. However, in clay-turbid lakes several factors may reduce the effectivity of food web management. Increasing turbidity reduces the effectivity of fish predation and weakens the link between zooplankton and phytoplankton. Therefore, the effects of fish stock manipulations may not cascade to lower trophic levels as expected. Additionally, in clay-turbid conditions invertebrate predators may coexist in high densities with planktivorous fish and negate the effects of fish reductions. For instance, in the stratifying regions of the clay-turbid Lake Hiidenvesi, Chaoborus flavicans is the main regulator of cladocerans and occupies the water column throughout the day, although planktivorous Osmerus eperlanus is very abundant. The coexistence of chaoborids and fish is facilitated by a metalimnetic turbidity peak, which prevents efficient predation by fish. In the shallow parts of the lake, chaoborids are absent despite high water turbidity. We suggest that, generally, the importance of invertebrate predators in relation to vertebrate predators may change along turbidity and depth gradients. The importance of fish predation is highest in shallow waters with low turbidity. When water depth increases, the importance of fish in the top-down regulation of zooplankton declines, whereas that of chaoborids increases, the change along the depth gradient being moderate in clear-water lakes and steep in highly turbid lakes. Thus, especially deep clay-turbid lakes may be problematic for implementing food web management as a restoration tool. [source]

Cyclohexyne Cycloinsertion by an Annulative Ring Expansion Cascade,

ANGEWANDTE CHEMIE, Issue 24 2010
Christian
Cyclohexin steigt in den Ring! Unter Verwendung von Cyclohexin wurden auf einfache Weise Polycyclen mit mittelgroßen Ringen synthetisiert. Die Insertion in cyclische Ketone eröffnet einen schnellen Zugang zu Bausteinen mit hoher Funktionalisierungsdichte. [source]

Stereoselective One-Pot Synthesis of 1-Aminoindanes and 5,6-Fused Azacycles Using a Gold-Catalyzed Redox-Pinacol-Mannich-Michael Cascade,

ANGEWANDTE CHEMIE, Issue 9 2010
Hyun-Suk Yeom
Mannich und mehr: Eine Sequenz aus intramolekularer Redox-, Pinacol-, Mannich- und Michael-Reaktion führt unter Goldkatalyse zu verschiedenartigen Strukturen mit quartären Kohlenstoffzentren, z.,B. Spirocyclen, 1-Aminoindanen und anellierten 5,6-Azabicyclen. Die Reaktion zeichnet sich durch vollständige Atomökonomie, hohe Diastereoselektivität und eine erstaunliche Effizienz aus. [source]

Construction of Fused Heterocyclic Architectures by Formal [4+1]/[3+2] Cycloaddition Cascade of Sulfur Ylides and Nitroolefins,

ANGEWANDTE CHEMIE, Issue 50 2009
Liang-Qiu Lu
Kontrollierte Ringschlüsse: Eine Kaskade aus formaler [4+1]- und [3+2]-Cycloaddition erzeugt aus Schefel-Yliden und Nitroolefinen mit anhängenden Alkenfunktionen anellierte polycyclische Heterocyclen in guten Gesamtausbeuten und mit ausgezeichneter Diastereoselektivität (siehe Schema). Eine katalytische Variante dieser Reaktion wird auch vorgestellt. [source]

A Dialdehyde Cyclization Cascade: An Approach to Pleuromutilin,

ANGEWANDTE CHEMIE, Issue 49 2009
Matthew
Nacheinander reagieren die Aldehydgruppen von 1 beim Aufbau des Gerüsts 2 des antibakteriellen Naturstoffs Pleuromutilin in einer SmI2 -vermittelten Cyclisierungskaskade, die vollständig diastereoselektiv zwei Ringe und vier benachbarte Stereozentren liefert. [source]

ChemInform Abstract: Facile Synthesis of Benzofulvene Derivatives from Baylis,Hillman Adducts: In-Mediated Barbier Reaction Combined with Pd(0)-Catalyzed Intramolecular Heck-Elimination Cascade.

CHEMINFORM, Issue 40 2010
Ko Hoon Kim
Abstract Precursors (V), (VIII), and (XI), derived from Baylis,Hillman adducts via bromination, Barbier reaction with aldehydes and acetylation, are subjected to Pd-catalyzed conditions A) or B). [source]

ChemInform Abstract: Gold-Catalyzed Dealkoxylative Carbocyclization/[3 + 3] Annulation Cascade of Acetal,Allene or Ketal,Allene Substrates.

CHEMINFORM, Issue 37 2010
Tse-Min Teng
Abstract Acetal-allene or ketal-allene compounds undergo the title cascade reaction with 2-substituted allylsilanes, a phenol, or enolizable ketones to give a wide variety of tri- and tetracyclic carbocycles as well as oxapolycyclic compounds with good stereocontrol in general. [source]

ChemInform Abstract: Synthesis of 4-Allylquinazolines from N-(2-Cyanoaryl)amides via the In-Mediated Allylation of Nitrile and Dehydrative Cyclization Cascade.

CHEMINFORM, Issue 36 2010
Sung Hwan Kim
Abstract The sequence yields 4-allylquinazolines (III) and (V). [source]

ChemInform Abstract: Palladium-Catalyzed Carboxamidation Reaction and Aldol Condensation Reaction Cascade: A Facile Approach to Ring-Fused Isoquinolinones.

CHEMINFORM, Issue 12 2009
Gagan Chouhan
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Enantioselective Organocatalytic Reactions of 4-Hydroxycoumarin and 4-Hydroxypyrone with ,,,-Unsaturated Aldehydes , An Efficient Michael Addition-Acetalization Cascade to Chromenones, Quinolinones and Pyranones.

CHEMINFORM, Issue 2 2009
Magnus Rueping
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Gold-Catalyzed Double Migration,Benzannulation Cascade Toward Naphthalenes.

CHEMINFORM, Issue 35 2008
Alexander S. Dudnik
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Enantioselective Synthesis of Bicyclo[2.2.2]octenones Using a Copper-Mediated Oxidative Dearomatization/[4 + 2] Dimerization Cascade.

CHEMINFORM, Issue 29 2008
Suwei Dong
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Synthetic Studies on the MARDi Cascade: Stereoselective Synthesis of Heterocyclic Seven-Membered Rings.

CHEMINFORM, Issue 7 2007
Yoann Coquerel
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

A Versatile Aminobenzannulation Method Based on the Deprotonation of 2-(1-Alkynyl)benzaldimines and Similar 2-Aza-2,4-heptadienyl-6-ynes: A Multistep Rearrangement Cascade.

CHEMINFORM, Issue 5 2005
Pramod Sagar
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

A New Strategy Toward Indole Alkaloids Involving an Intramolecular Cycloaddition/Rearrangement Cascade.

CHEMINFORM, Issue 39 2004
Albert Padwa
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

A 4-exo-Dig Cyclocarbopalladation/8, Electrocyclization Cascade: Expeditious Access to the Tricyclic Core Structures of the Ophiobolins and Aleurodiscal.

CHEMINFORM, Issue 36 2004
Bahaa Salem
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Synthesis of Carbo- and Heterocycles via a Palladium-Catalyzed Allene Insertion,Nucleophile Incorporation,Michael Addition Cascade.

CHEMINFORM, Issue 52 2003
Xinjie Gai
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Cascade [4 + 1] Radical Annulations of 2,6-Disubstituted Phenyl Isonitriles with N-Propargyl-6-iodopyridones: Scope, Mechanism and Regioselective Synthesis of 7,9-Disubstituted Camptothecin Analogues.

CHEMINFORM, Issue 48 2003
Wu Du
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Biocatalytic Asymmetric Rearrangement of a Methylene-Interrupted Bis-epoxide: Simultaneous Control of Four Asymmetric Centers Through a Biomimetic Reaction Cascade

CHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2004
Silvia M. Glueck
Abstract Asymmetric enzyme-catalyzed hydrolysis of methylene-interrupted bis-epoxides 1,a and 1,b catalyzed by bacterial epoxide hydrolases furnished tetrahydrofuran derivatives 2,a and 2,b through a hydrolysis,rearrangement cascade. Whereas racemic bis-oxiranes 1,b,d underwent kinetic resolution with moderate stereoselectivities to yield products with up to 92,% ee and 66,% de: meso -bis-oxirane cis,cis- 1,a was transformed into (6R,7R,9S,10S)- 2,a in 94,% ee and 89,% de at high conversion (85,%) by Rhodococcus sp. CBS 717.73 as the major product. The reaction sequence resembles a biomimetic reaction cascade and provides an efficient entry into the structural core of annonaceous acetogenins with simultaneous control of four stereocenters. [source]

Evaluating Enzyme Cascades for Methanol/Air Biofuel Cells Based on NAD+ -Dependent Enzymes

ELECTROANALYSIS, Issue 7-8 2010

Abstract Previous work by the group has entailed encapsulating enzymes in polymeric micelles at bioelectrode surfaces by utilizing hydrophobically modified Nafion membranes, which are modified in order to eliminate the harsh acidity of Nafion while tailoring the size of the polymer micelles to optimize for the encapsulation of an individual enzyme. This polymer encapsulation has been shown to provide high catalytic activity and enzyme stability. In this study, we employed this encapsulation technique in developing a methanol/air biofuel cell through the combined immobilization of NAD+ -dependent alcohol dehydrogenase (ADH), aldehyde dehydrogenase (AldDH) and formate dehydrogenase (FDH) within a tetrabutylammonium bromide (TBAB) modified Nafion to oxidize methanol to carbon dioxide with poly(methylene green) acting as the NADH electrocatalyst electropolymerized on the surface of the electrode. The methanol biofuel/air cell resulted in a maximum power density of 261±7.6,,W/cm2 and current density of 845±35.5,,A/cm2. This system was characterized for the effects of degree of oxidation, temperature, pH, and concentration of fuel and NAD. [source]

Decomposition Cascades of Dicoordinate Copper(I) Chalcogenides

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2007
Heiko Jacobsen
Abstract Cu,E, Si,E, and Cu,P bond energies of R3PCuESiR3 and CuESiR3 complexes (E = O, S, Se) have been investigated using PBE density-functional calculations, and including empirical corrections for dispersive interactions (DFT-D). The bond energies have been used to investigate likely pathways of molecular decomposition. The energy profile for thermal decomposition is to a large degree independent of the nature of the phosphane ligands and silyl groups. Oxides, sulfides, and selenides have qualitatively the same thermal decomposition profile. Thermal decomposition is not likely to produce copper chalcogenide units CuE, but elemental copper Cu instead. Consideration of intermolecular van der Waals attraction suggests that the linear geometry of system tBu3PCuOSiPh3 as found in the crystal is most likely due to crystal packing and intermolecular forces.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]