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Ring

Distribution by Scientific Domains
Chemistry66%
Life Sciences9%
Medical Sciences8%
Polymers and Materials Science6%
Physics and Astronomy3%
Engineering2%
7 Other Domains6%
Distribution within Chemistry
Crystallography31%
Organic Chemistry21%
General & Introductory Chemistry15%
Inorganic Chemistry4%
Analytical Chemistry3%
28 Other Subdomains23%

Kinds of Ring

  • Seven-Member ring
  • Six-Member ring
  • annual ring
  • arene ring
  • aromatic ring
  • arterial ring
  • artery ring
  • aryl ring
  • b ring
  • benzene ring
  • benzenoid ring
  • c ring
  • carbocyclic ring
  • carbon ring
  • central ring
  • chelate ring
  • concentric ring
  • contractile ring
  • cp ring
  • cyclobutane ring
  • cyclohexane ring
  • cyclopentadienyl ring
    		•
  • cyclopropane ring
  • endothelium-intact ring
  • epoxide ring
  • five-membered chelate ring
  • five-membered ring
  • four-membered chelate ring
  • four-membered ring
  • furan ring
  • furanose ring
  • fused ring
  • growth ring
  • guanine ring
  • heterocyclic ring
  • imidazole ring
  • indole ring
  • inguinal ring
  • isoalloxazine ring
  • isolated aortic ring
  • lactam ring
  • lactone ring
  • liesegang ring
  • membered ring
    		•
  • molecular ring
  • naphthalene ring
  • nerve ring
  • outer ring
  • oxazine ring
  • oxazoline ring
  • oxirane ring
  • phenolic ring
  • phenyl ring
  • phenylene ring
  • piperazinedione ring
  • piperidine ring
  • porphyrin ring
  • pyran ring
  • pyrazine ring
  • pyrazole ring
  • pyridine ring
  • pyridyl ring
  • pyrimidine ring
  • pyrrole ring
  • pyrrolidine ring
  • quantum ring
    		•
  • quinoline ring
  • raschig ring
  • rat aortic ring
  • seven-membered ring
  • six-membered chelate ring
  • six-membered heterocyclic ring
  • six-membered ring
  • storage ring
  • substituted benzene ring
  • sugar ring
  • tetrahydropyran ring
  • tetrazole ring
  • thienyl ring
  • thiophene ring
  • three-membered ring
  • tracheal ring
  • tree ring
  • triazole ring
  • tricyclic ring
  • vascular ring

    • Terms modified by Ring

  • ring atom
  • ring b
  • ring c
  • ring cell
  • ring cell carcinoma
  • ring channel
  • ring chromosome
  • ring cleavage
  • ring closing metathesis
  • ring closure
  • ring closure reaction
  • ring component
  • ring compound
    		•
  • ring conformation
  • ring contraction
  • ring current
  • ring d
  • ring domain
  • ring electrode
  • ring expansion
  • ring expansion reaction
  • ring finger
  • ring formation
  • ring fused
  • ring intermediate
  • ring junction
    		•
  • ring lead
  • ring moiety
  • ring motif
  • ring nitrogen atom
  • ring opening
  • ring opening polymerization
  • ring opening reaction
  • ring orientation
  • ring plane
  • ring portion
  • ring position
  • ring proton
  • ring resonator
    		•
  • ring segment
  • ring size
  • ring strain
  • ring structure
  • ring substituent
  • ring substitution
  • ring system
  • ring transformation
  • ring unit
  • ring width

    • Selected Abstracts

    ORTH/VIM proteins that regulate DNA methylation are functional ubiquitin E3 ligases

    THE PLANT JOURNAL, Issue 5 2008
    Edward Kraft
    Summary Appropriate methylation of genomes is essential for gene regulation. Here, we describe the six-member ORTHRUS (ORTH) gene family of Arabidopsis thaliana that plays a role in DNA methylation in vivo. ORTH1, ORTH5 are predicted to encode proteins that contain one plant homeodomain (PHD), two really interesting new gene (RING) domains, and one set ring associated (SRA) domain, whereas ORTHlike-1 encodes a protein with only one RING and SRA domain. cDNAs for ORTH1, ORTH2, ORTH5 and ORTHlike-1 were isolated, and when expressed as glutathione- S -transferase (GST) fusion proteins, were capable of promoting ubiquitylation in vitro with the E2 AtUBC11. ORTH1 promotes ubiquitylation when paired with additional AtUBC8 family members. ORTH1 proteins with substitutions in metal,ligand binding residues in each ORTH1 RING domain individually, and ORTH1 truncation derivatives lacking one or both RING domains, were tested for their ability to catalyze ubiquitylation in vitro. In these assays, either ORTH1 RING domain is capable of promoting ubiquitylation. The PHD alone is not active as an E3 ligase, nor is it required for ligase activity. GFP-ORTH1 and GFP-ORTH2 are nuclear-localized in transgenic Arabidopsis plants. Overexpression of ORTH1 or ORTH2 in Arabidopsis leads to an altered flowering time. Inspection of DNA methylation at FWA and Cen180 repeats revealed hypomethylation when ORTH proteins were overexpressed. Once initiated, a late-flowering phenotype persisted in the absence of the ORTH transgene, consistent with epigenetic effects at FWA. We conclude that ORTH proteins are E3 ligases mediating DNA methylation status in vivo. [source]

    OCCURRENCE OF VASCULAR RINGS IN EX-PRETERM TWINS

    JOURNAL OF PAEDIATRICS AND CHILD HEALTH, Issue 8 2004
    A Turner Dr
    No abstract is available for this article. [source]

    THE ,LORDS OF THE RINGS': AN ANALYTICAL APPROACH TO THE RIDDLE OF THE ,KNOSSIAN REPLICA RINGS'

    BULLETIN OF THE INSTITUTE OF CLASSICAL STUDIES, Issue 1 2009
    YUVAL GOREN
    No abstract is available for this article. [source]

    Vom Minnesang in der Datenbank

    FORSCHUNG, Issue 4 2003
    Armin Schlechter Dr.
    Die mittelalterlichen deutschen Handschriften der Universitätsbibliothek Heidelberg sind kulturhistorische Zeugnisse von Rang. Durch umfassende Katalogisierung wird die Sammlung für die Forschung neu erschlossen [source]

    Detection of glycolate oxidase gene glcD diversity among cultured and environmental marine bacteria

    ENVIRONMENTAL MICROBIOLOGY, Issue 10 2006
    W. W. Y. Lau
    Summary Of eight laboratory cultures of marine ,- and ,- Proteobacteria tested, growth on glycolate as a sole carbon source was detected for only three species: Pseudomonas stutzeri, Oceanimonas doudoroffii and Roseobacter sp. isolate Y3F. Degenerate polymerase chain reaction (PCR) primers were designed to amplify glcD, which encodes the D-subunit of the enzyme glycolate oxidase; glcD could be amplified only from those cultures that grew on glycolate. The PCR primers were used to explore glcD diversity in four field samples collected from different ocean environments: an Atlantic Gulf Stream Ring, sampled above and below the thermocline and two Pacific coastal sites, Parks Bay and San Juan Channel, WA. Environmental glcD sequences belonged to six major bacterial phylogenetic groups, with most sequences forming novel clades with no close relatives. Different patterns of glcD diversity were observed within and between the two nutrient regimes. Comparison of glcD and 16S rDNA diversity and analyses of available bacterial genomes and a metgenomic library from the Sargasso Sea show that glycolate-utilizing potential exists in only a subset of bacteria. Glycolate is produced in marine environments mainly by phytoplankton. Examination of glcD diversity will aid in understanding the influence of phytoplankton on bacterial community structure. [source]

    A Ruthenium(II)-Complexed Rotaxane Whose Ring Incorporates a 6,6,-Diphenyl-2,2,-bipyridine: Synthesis and Light-Driven Motions

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2005
    Jean-Paul Collin
    Abstract By incorporating a 6,6'-diphenyl-2,2'-bipyridine (dpbipy) fragment in a ring, endo coordination of a ruthenium(II) center is performed selectively and almost quantitatively. The threaded system, containing a helical fragment, could be fully characterized. When the terminal functions of the rod-shaped helical complex threaded through the macrocycle are phenol groups, the complete rotaxane is prepared by the classical Williamson stoppering reaction in moderate yield. Light-induced motions of the unstoppered system (pseudorotaxane) and the real rotaxane have been studied. Under visible light irradiation, quantitative decoordination of the dpbipy-containing ring is observed, leading to the separate fragments (ring and helical thread) or to a new rotaxane (uncoordinated ring threaded by the dumbbell). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    Dye-Sensitized Solar Cells Based on a Novel Fluorescent Dye with a Pyridine Ring and a Pyridinium Dye with the Pyridinium Ring Forming Strong Interactions with Nanocrystalline TiO2 Films

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2010
    Yousuke Ooyama
    Abstract As new-type donor,acceptor ,-conjugated dyes capable of forming a strong interaction between the electron-acceptor moiety of the sensitizers and a TiO2 surface, fluorescent dye OH11 and pyridinum dye OH12 with a pyridine and pyridinium ring as the electron-accepting group, respectively, have been designed and synthesized as photosensitizers for use in dye-sensitized solar cells (DSSCs). The fluorescent dye OH11 exhibits an absorption band at around 410 nm and a fluorescence band at around 530 nm. On the other hand, the pyridinum dye OH12 shows an absorption maximum at around 560 nm, assigned to a strong intramolecular charge-transfer excitation from the dibutylamino group to the pyridinium ring. The short-circuit photocurrent densities of the DSSCs prepared by using OH11 and OH12 are 4.33 and 1.74mA cm,2, and the solar energy-to-electricity conversion yields are 1.33 and 0.51,%, respectively, under simulated solar light [AM (air mass) 1.5, 100 mW,cm,2]. The open-circuit photovoltage for OH11 (525 mV) is higher than that of OH12 (444 mV). The effects of the configuration of the dyes on the TiO2 surface and of their chemical structures on the photovoltaic performances are discussed on the basis of semi-empirical molecular orbital calculations (AM1 and INDO/S), spectral analyses and cyclic voltammetry. [source]

    Dihydroazulene Photoswitches: The First Synthetic Protocol for Functionalizing the Seven-Membered Ring

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2009
    Michael Åxman Petersen
    Abstract The first synthetic protocol for functionalizing the dihydroazulene (DHA) photoswitch in its seven-membered ring has been developed. This protocol is based on regioselective bromination, followed by regioselective elimination of HBr, and finally a palladium-catalyzed cross-coupling reaction with a terminal alkyne. The position of functionalization (C-7) was confirmed by X-ray crystal structure analysis. Light-induced ring opening of this compound to its vinylheptafulvene (VHF) isomer followed by thermal ring closure provides a mixture of two DHA regioisomers in a ratio that depends on the wavelength of irradiation and solvent polarity.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Application of 7- endo - trig Pictet,Spengler Cyclization to the Formation of the Benzazepine Ring: Synthesis of Benzazepinoindoles,

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2009
    Sudhir K. Sharma
    Abstract The preparation of benzazepinoindoles, fused heterocycles with a benzazepine moiety, was accomplished through an intramolecular 7- endo - trig Pictet,Spengler cyclization. The precursors comprising C-3- or C-2-linked o -aminobenzylindoles required for the cyclization were obtained either by treating indoles with o -nitrobenzyl bromide followed by reduction of the nitro group or by treating 2-nitrophenylacetic acid with DCC/DMAP followed by reduction of the aryl nitro functionality. Resulting substrates 5 and 6 were then subjected to the 7- endo - trig Pictet,Spengler reaction with a variety of aldehydes and ketones to furnish new polycyclic structures benzazepinoindoles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Sequential 1,3-Dipolar Cycloaddition of Nitrones to ,-(2-Aminophenyl) ,,,-Ynones and Cyclocondensation: A New Entry to the Isoxazolino[4,5- c]quinoline Ring

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2009
    Giorgio Abbiati
    Abstract The reaction of ,-(2-aminophenyl) ,,,-ynones with N -methyl nitrones provides a simple and efficient entry to the isoxazolino[4,5- c]quinoline ring system through a sequential 1,3-dipolar cycloaddition/annulation process. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Synthesis of New Camptothecin Analogues with the E-Lactone Ring Replaced by ,,,-Cyclohexenone

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2006
    Valeriy A. Bacherikov
    Abstract The total synthesis of racemic camptothecin analogues 12a and 12b, in which the E-lactone ring has been replaced by an ,,,-cyclohexenone ring and the ethyl and hydroxy substituents have been retained, was achieved by first preparing the ABCD fragments 31a and 31b, which were then converted into the tetracyclic triol 36a and 36b by osmium-mediated dihydroxylation. Compounds 36a and 36b were oxidized in one-pot reactions, followed by intramolecular aldol condensation to furnish the desired pentacyclic 12a and 12b, which retained topoisomerase I inhibitory activity and exhibited cytotoxicity to tumor cell growth in culture.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Synthesis of 2,4-Diaryl-3,4-dihydro-2H - naphth[2,1- e][1,3]oxazines and Study of the Effects of the Substituents on Their Ring - Chain Tautomerism

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2004
    István Szatmári
    Abstract A number of 2-(,-amino-Y-substituted-benzyl)-1-naphthol hydrochlorides were prepared by a convenient Mannich-type aminoalkylation. 2,4-Diaryl-3,4-dihydro-2H -naphth[2,1- e][1,3]oxazines were prepared through the ring-closure reactions of the starting aminonaphthols with aromatic aldehydes, which proved to furnish three-component (ring1,open,ring2) tautomeric mixtures in CDCl3 at 300 K. The electronic effects of the 2-aryl groups on the ratios of the ring - chain tautomeric forms at equilibrium could be described by Equation (1). Study of the effects of substituents X and Y on the tautomeric equilibria [by the aid of the multiple linear regression analysis of Equations (2) and (3)] revealed that the trans -chain equilibrium constants are significantly influenced by the inductive effect (,F) of substituent Y on the 4-phenyl ring. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Formation of the B Ring in Steroids and Hopanoids from Squalene

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2004
    B. Andes Hess Jr.
    Abstract A theoretical conformational study based on density functional calculations provides evidence that the sterol and nonsterol cyclizations of squalene to triterpenes are controlled by conformational effects as has been previously suggested. It was found that different conformers of a model system of squalene give rise to the chair,boat conformation found in the steroids and the chair,chair conformation of the pentacyclic 3-deoxytriterpenes for their A and B rings. It is suggested that the enzymes play a key role in holding the substrate in the proper orientation for these cyclizations to occur. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Test of the CPT symmetry using laser spectroscopy on antiprotonic atoms

    FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2-3 2003
    2Article first published online: 26 FEB 200, D. Horváth
    Antiprotons stopped in helium get trapped in long-living orbits making possible to study their atomic transitions via laser spectroscopy. These measurements started at CERN, Geneva, 10 years ago at the Low Energy Antiproton Ring and now continue at CERN's Antiproton Decelerator. The main result of the ASACUSA experiment is an improvement in the measurement of the antiproton mass and charge, which tests the CPT invariance when compared with those of the proton. [source]

    A New Light-Path Setup Scheme for Dynamic Traffic in Ring-based Optical Networks

    IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2009
    Yusuke Sato Non-Member
    Abstract A simple and fast ring management token (RMT) wavelength reservation method for dynamic traffic in multi-ring wavelength-routed networks is proposed. The RMT is an agent that can control and manage the used wavelength in the network efficiently. We show that the proposed scheme achieves a high performance in terms of setup delay and loss probability. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

    Use of Biodegradable Annuloplasty Ring For Pediatric Valvuloplasty Operations

    JOURNAL OF CARDIAC SURGERY, Issue 2 2008
    Mustafa Cikirikcioglu M.D., Ph.D.
    No abstract is available for this article. [source]

    Stability studies of oxazolidine-based compounds using 1H NMR spectroscopy

    JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2010
    Gerard P. Moloney
    Abstract A series of oxazolidine-based compounds with a variety of substituents in positions 2 and 3 was synthesized and their stability studied. Ring opened intermediates formed on addition of limiting amounts of D2O to oxazolidine solutions, as observed by NMR. As the hydrolysis reactions proceeded, a series of novel dimeric ,-amino alcohol compounds formed via an internal reaction between ephedrine and the ring opened intermediates. 2-Phenyl substituted oxazolidine compounds containing electron withdrawing nitro substituents were more rapidly hydrolyzed than the unsubstituted derivative and methoxy substituted compounds, with the nitro substituents appearing to stabilize the ring opened intermediates. Two oxazolidine derivatives, with a methyl and proton at position 2, were found to be more stable to oxazolidine hydrolysis than the 2-phenyl substituted compounds. Oxazolidines incorporating phenyl substituents at position 3 were synthesized and found to be less stable than those incorporating a methyl substituent at position 3. These fundamental structure,activity relationships may be useful when choosing oxazolidine derivatives as synthetic intermediates and as prodrugs for the delivery of compounds containing either ,-amino alcohol or aldehyde components. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3362,3371, 2010 [source]

    RT-PCR Detection of Odontoglossum ringspot virus, Cymbidium mosaic virus and Tospoviruses and Association of Infections with Leaf-Yellowing Symptoms in Phalaenopsis

    JOURNAL OF PHYTOPATHOLOGY, Issue 5 2008
    K. Yamane
    Abstract Leaf-yellowing symptoms in Phalaenopsis are most important effects in its commercial production in Japan and their cause has not yet been clarified. In the present study, Odontoglossum ringspot virus (ORSV), Cymbidium mosaic virus (CymMV) and tospoviruses were evaluated by reverse transcription-polymerase chain reaction (RT-PCR) in Phalaenopsis showing leaf-yellowing symptoms. Ring, spot, mosaic, necrosis and other symptom types were observed in 42%, 24%, 25%, 16% and 44% of the tested plants respectively. ORSV was detected in 55% of the plants, particularly in 35 of 42 plants with ring symptoms. CymMV was detected in 34% of the plants, particularly in 18 of 25 plants with mosaic symptoms. Plants co-infected with both viruses tended to show severe symptoms. In spite of systemic infection by inoculation of ORSV, no clear ring symptoms were observed in any plant for 6 months. Symptoms of leaf-yellowing were significantly reduced after 3 months. These results suggest that the symptoms can be associated with the viruses but occurred and alleviated over time and by changes in the environmental conditions. No tospoviruses were detected in 70 tested plants. ORSV and CymMV were simultaneously detected by RT-PCR using reported primers for ORSV and newly designed primers for CymMV using an efficient direct tube RNA extraction technique providing more cost-effective RT-PCR screening. No viruses were detected by RT-PCR in several plants showing spot or ring symptoms, suggesting the presence of other causal agents related to these symptoms. [source]

    Potential of Trichoderma harzianum and T. atroviride to Control Botryosphaeria berengeriana f. sp. piricola, the Cause of Apple Ring Rot

    JOURNAL OF PHYTOPATHOLOGY, Issue 4-5 2002
    G. KEXIANG
    Abstract Trichoderma harzianum T88 and T. atroviride T95 were tested for their efficacy in controlling apple ring rot (caused by Botryosphaeria berengeriana f. sp. piricola) in vitro and in the field. Isolates of T88 and T95 produced both volatile and non-volatile antibiotics that suppressed mycelial growth of the pathogen. Light and scanning electron microscopy showed that mycoparasitism by Trichoderma spp. of B. berengeriana f. sp. piricola resulted in penetration and disruption of hyphal cells, and thinning of cytoplasm of the pathogen. The culture filtrates of T88 and T95 in Czapek's liquid medium suppressed conidial germination of the pathogen, and the germination level was negatively correlated with the duration of culture of Trichoderma. In inoculation tests, 32 days after simultaneous inoculation or preinoculation with B. berengeriana f. sp. piricola and Trichoderma spp., the incidence of infected apple shoots was reduced, respectively, by 65.3,76.4% and 62.5,76.4%, and the index of infection reduced by 36.9,38.9 and 40.7,44.4, The effect of inoculating B. berengeriana f. sp. piricola 3 days after the antagonists were inoculated was greater (81.4,88.8%) than simultaneous inoculation (72.2,77.8%). Re-isolation from inoculated apple shoots demonstrated that the pathogen had been suppressed by Trichoderma. The ability to re-isolate the pathogen from apple after co-inoculation and pre-inoculation with Trichoderma spp. was reduced by 27.0,42.3% and 22.2,47.1%, respectively. The biocontrol field trial suggested that the B. berengeriana f. sp. piricola canker on apple shoots and stems and rotting fruit had been efficiently controlled by the application of spore suspensions of T. harzianum T88 and T. atroviride T95. The efficacy of control by Trichoderma is thus similar to that of routine chemical control. [source]

    Developing 100,ps-resolved X-ray structural analysis capabilities on beamline NW14A at the Photon Factory Advanced Ring

    JOURNAL OF SYNCHROTRON RADIATION, Issue 4 2007
    Shunsuke Nozawa
    NW14A is a newly constructed undulator beamline for 100,ps time-resolved X-ray experiments at the Photon Factory Advanced Ring. This beamline was designed to conduct a wide variety of time-resolved X-ray measurements, such as time-resolved diffraction, scattering and X-ray absorption fine structure. Its versatility is allowed by various instruments, including two undulators, three diffractometers, two pulse laser systems and an X-ray chopper. The potential for the detection of structural changes on the 100,ps time scale at NW14A is demonstrated by two examples of photo-induced structural changes in an organic crystal and photodissociation in solution. [source]

    Amine Modifiers with an s-Triazine Ring for Unsaturated Polyester Resins, 2,

    MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10-11 2007
    Mono-, Multihydroxyalkyl Modifiers
    Abstract The paper deals with the synthesis of amine modifiers for unsaturated polyester resins obtained from N -phenyl-2-amineethanol and 2,4-dichloro-6-methoxy-1,3,5-triazine (modifier A), 2-chloro-4,6-dimethoxy-1,3,5-triazine (modifier B) or with cyanuric chloride (modifier C). Properties of amine modifiers for unsaturated polyester resins are presented. The modifiers were incorporated into resins at the polycondensation stage. [source]

    Radiofrequency Ablation of a Posteroseptal Atrioventricular Accessory Pathway in a Left-Sided Tricuspid Ring with Ebsteinlike Anomaly in a Patient with Congenitally Corrected Transposition of the Great Arteries

    PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2000
    JOSEF BRUGADA
    Radiofrequency ablation successfully eliminated a posteroseptal accessory pathway in a left-sided tricuspid ring with Ebsteinlike anomaly in a patient with a congenially corrected transposition of the great arteries. [source]

    Contraceptive Ring Found Safe, Effective; Most Users Would Recommend It

    PERSPECTIVES ON SEXUAL AND REPRODUCTIVE HEALTH, Issue 1 2003
    Article first published online: 23 JAN 200
    No abstract is available for this article. [source]

    Multidimensional Reaction Coordinate for the Excited-state H-atom Transfer in Perylene Quinones: Importance of the 7-Membered Ring in Hypocrellins A and B

    PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2000
    Anindya Datta
    ABSTRACT The excited-state intramolecular H-atom transfer reactions of hypocrellins B and A are compared by using time-resolved absorption and fluorescence upconversion techniques. The hypocrellin B photophysics are well described by a simple model involving one ground-state species and excited-state forward and reverse H-atom transfer with a nonfluorescent excited state. We suggest that excited-state conformational changes are coupled to the H-atom transfer in hypocrellin B just as gauche/anti changes are coupled to the H-atom transfer in hypocrellin A. [source]

    Four Hats in the Ring: The 1912 Election and the Birth of Modern American Politics , By Lewis L. Gould

    THE HISTORIAN, Issue 2 2010
    Thomas McInerney
    No abstract is available for this article. [source]

    Vaginal Ring and Round Ligament of the Uterus in the Female Cat

    ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 4 2009
    A. Watson
    Summary The peritoneum was examined for the existence of a vaginal ring and the round ligament of the uterus was dissected through the inguinal region in eleven embalmed adult female cats. In all cats, there was no evidence of a peritoneal evagination into the inguinal canal. There was no vaginal ring and no vaginal process. The round ligament of the uterus passed through the inguinal canal and disintegrated in the fascia a short distance beyond the superficial inguinal ring. [source]

    Preparation of Ligand-Stabilized [P4O4]2+ by Controlled Hydrolysis of a Janus Head Type Diphosphorus Trication,

    ANGEWANDTE CHEMIE, Issue 35 2010

    Auf zu neuen Ufern: Die stufenweise Hydrolyse eines Diphosphor-Trikations ist eine effiziente Methode, ein ungewöhnliches ligandenstabilisiertes Dikation mit einem neuartigen kationischen [P4O4]2+ -Gerüst herzustellen (siehe Schema, grau C, Blau N, rot O, orange P). Diese Reaktion unterstreicht das Potenzial des Diphosphor-Trikations als Quelle für Phosphor-Bausteine, mit denen neuartige kationische Ring- und Clustersysteme aufgebaut werden können. [source]

    Magnetische Suszeptibilitätsmessung und 57Fe-Mößbauer- Spektroskopie an einem ferromagnetischen FeIII4Dy4 -Ring,

    ANGEWANDTE CHEMIE, Issue 30 2010
    Dirk Schray
    Die ferromagnetische Wechselwirkung in einem Fe4Dy4 -Einzelmolekülmagnet wurde mit einer Kombination aus magnetischen Suszeptibilitätsmessungen (siehe Diagramm; der Einschub zeigt die Kernstruktur des Clusters) und 57Fe-Mößbauer-Spektroskopie untersucht. [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]

    Lithiation,Electrophilic Substitution of N -Thiopivaloylazetidine,

    ANGEWANDTE CHEMIE, Issue 16 2010
    David
    Sechzehn und vier: Die wenig erforschte N -Thiopivaloyl-Gruppe ist entscheidend für die effiziente ,-Lithiierung eines Azetidinrings und die anschließende Einführung verschiedenartiger Elektrophile. In Gegenwart chiraler Liganden gelangen die ersten enantioselektiven elektrophilen Substitutionen an einem viergliedrigen Ring. [source]