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Synthesis of the C11-C23 Fragment of the Potent Antitumor Agent Dictyostatin

DIAS, Luiz C.; LIMA, Dimas J. P.; GONCALVES, Caroline C. S.; ANDRICOPULO, Adriano Defini
Fonte: WILEY-BLACKWELL Publicador: WILEY-BLACKWELL
Tipo: Artigo de Revista Científica
Português
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We wish to report here our initial efforts toward the total synthesis of the potent antitumor agent dictyostatin, describing a short and efficient synthesis of the C11-C23 fragment. ( (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009); Universidade Estadual de Campinas (UNICAMP); FAEP-UNICAMP; FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Novel C11 amino derivatives of cryptolepine : synthesis and in vitro studies with DNA and haeme

Lavrado, João Paulo Martins Ferreira, 1978-
Fonte: Universidade de Lisboa Publicador: Universidade de Lisboa
Tipo: Tese de Doutorado
Publicado em //2010 Português
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Tese de doutoramento, Farmácia (Química Farmacêutica e Terapêutica), Universidade de Lisboa, Faculdade de Farmácia, 2010; Malaria is one of the most widespread infectious diseases of our time. The global malaria map has been shrinking over the past 60 years, but today more people are at risk of suffering from malaria than any other time in history. In the past few years malaria has once again attracted more attention, partly because it is recognized that malaria spread in sub-Saharan Africa has increased in the recent years, mainly due to the development of drug resistances. Cryptolepine (1), is an indoloquinoline alkaloid, extracted from the West African climbing shrub Cryptolepis sanguinolenta (Lindl.) Schltr, a traditional herb used in folk medicine for the treatment of malaria. Several authors hypothesized that the mechanism of action of cryptolepine could be by inhibition of haemozoin formation in the digestive vacuole (DV) of the parasite, however in a microscopic fluorescence study, the indoloquinoline chromophore, was suggested to accumulate into specific parasite structures that could correspond to the parasite nuclei, and thus justifying its activity due to cytotoxic effects on DNA and topoisomerase II activity. Cryptolepine derivatives (3) have been synthesized through the incorporation of basic side-chains in the C-11 position of the 10H-indolo[3...

Cl- and regulation of pH by MDCK-C11 cells

Tararthuch,A.L.; Fernandez,R.; Malnic,G.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2007 Português
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The interaction between H+ extrusion via H+-ATPase and Cl- conductance was studied in the C11 clone of MDCK cells, akin to the intercalated cells of the collecting duct. Cell pH (pHi) was measured by fluorescence microscopy using the fluorescein-derived probe BCECF-AM. Control recovery rate measured after a 20 mM NH4Cl acid pulse was 0.136 ± 0.008 pH units/min (dpHi/dt) in Na+ Ringer and 0.032 ± 0.003 in the absence of Na+ (0 Na+). With 0 Na+ plus the Cl- channel inhibitor NPPB (10 µM), recovery was reduced to 0.014 ± 0.001 dpHi/dt. 8-Br-cAMP, known to activate CFTR Cl- channels, increased dpHi/dt in 0 Na+ to 0.061 ± 0.009 and also in the presence of 46 nM concanamycin and 50 µM Schering 28080. Since it is thought that the Cl- dependence of H+-ATPase might be due to its electrogenic nature and the establishment of a +PD (potential difference) across the cell membrane, the effect of 10 µM valinomycin at high (100 mM) K+ was tested in our cells. In Na+ Ringer, dpHi/dt was increased, but no effect was detected in 0 Na+ Ringer in the presence of NPPB, indicating that in intact C11 cells the effect of blocking Cl- channels on dpHi/dt was not due to an adverse electrical gradient. The effect of 100 µM ATP was studied in 0 Na+ Ringer solution; this treatment caused a significant inhibition of dpHi/dt...

Towards the total synthesis of Stawamycin. Synthesis of C11-C21 fragment

Dias,Luiz C.; Jardim,Luciana S. A.; Ferreira,Andrea A.; Soarez,Helena U.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2001 Português
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The carbocyclic (C11-C21) fragment of Stawamycin has been prepared by a sequence involving 11 steps (10% overall yield) from methyl (R)-(-)-3-hydroxy-2-methylpropionate. Key steps are Pd-catalyzed Stille coupling reaction between a vinyl iodide and a vinylstannane followed by an intramolecular Diels-Alder cycloaddition reaction to afford the desired adduct as the major isomer together with three other possible adducts in 78% overall yield.

Antagonistic Activity of Lactobacillus plantarum C11: Two New Two-Peptide Bacteriocins, Plantaricins EF and JK, and the Induction Factor Plantaricin A

Anderssen, Erlend L.; Diep, Dzung Bao; Nes, Ingolf F.; Eijsink, Vincent G. H.; Nissen-Meyer, Jon
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/1998 Português
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Six bacteriocinlike peptides (plantaricin A [PlnA], PlnE, PlnF, PlnJ, PlnK, and PlnN) produced by Lactobacillus plantarum C11 were detected by amino acid sequencing and mass spectrometry. Since purification to homogeneity was problematic, all six peptides were obtained by solid-phase peptide synthesis and were tested for bacteriocin activity. It was found that L. plantarum C11 produces two two-peptide bacteriocins (PlnEF and PlnJK); a strain-specific antagonistic activity was detected at nanomolar concentrations when PlnE and PlnF were combined and when PlnJ and PlnK were combined. Complementary peptides were at least 103 times more active when they were combined than when they were present individually, and optimal activity was obtained when the complementary peptides were present in approximately equal amounts. The interaction between complementary peptides was specific, since neither PlnE nor PlnF could complement PlnJ or PlnK, and none of these peptides could complement the peptides constituting the two-peptide bacteriocin lactococcin G. Interestingly, PlnA, which acts as an extracellular signal (pheromone) that triggers bacteriocin production, also possessed a strain-specific antagonistic activity. No bacteriocin activity could be detected for PlnN.

Characterization of the locus responsible for the bacteriocin production in Lactobacillus plantarum C11.

Diep, D B; Håvarstein, L S; Nes, I F
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1996 Português
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Lactobacillus plantarum C11 secretes a small cationic peptide, plantaricin A, that serves as induction signal for bacteriocin production as well as transcription of plnABCD. The plnABCD operon encodes the plantaricin A precursor (PlnA) itself and determinants (PlnBCD) for a signal transducing pathway. By Northern (RNA) and sequencing analyses, four new plantaricin A-induced operons were identified. All were highly activated in concert with plnABCD upon bacteriocin induction. Two of these operons (termed plnEFI and plnJKLR) each encompass a gene pair (plnEF and plnJK, respectively) encoding two small cationic bacteriocin-like peptides with double-glycine-type leaders. The open reading frames (ORFs) encoding the bacteriocin-like peptides are followed by ORFs (plnI and -L, respectively) encoding cationic hydrophobic proteins resembling bacteriocin immunity proteins. On the third operon (termed plnMNOP), a similar bacteriocin-like ORF (plnN) and a putative immunity ORF (either plnM or -P) were identified as well. These findings suggest that two bacteriocins of two-peptide type (mature PlnEF and PlnJK) and a bacteriocin of one-peptide type (mature PlnN) could be responsible for the observed bacteriocin activity. The last operon (termed plnGHSTUV) contains two ORFs (plnGH) apparently encoding an ABC transporter and its accessory protein...

The gene encoding plantaricin A, a bacteriocin from Lactobacillus plantarum C11, is located on the same transcription unit as an agr-like regulatory system.

Diep, D B; Håvarstein, L S; Nissen-Meyer, J; Nes, I F
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1994 Português
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Purification and amino acid sequencing of plantaricin A, a bacteriocin from Lactobacillus plantarum C11, revealed that maximum bacteriocin activity is associated with the complementary action of two almost-identical peptides, alpha and beta (J. Nissen-Meyer, A. G. Larsen, K. Sletten, M. Daeschel, and I. F. Nes, J. Gen. Microbiol. 139:1973-1978, 1993). A 5-kb chromosomal HindIII restriction fragment containing the structural gene of plantaricin A was cloned and sequenced. Only one gene encoding plantaricin A was found. The gene, termed plnA, encodes a 48-amino-acid precursor peptide, of which the 22 and 23 C-terminal amino acids correspond to the purified peptides. Northern (RNA) blot analysis demonstrated that a probe complementary to the coding strand of the plantaricin A gene hybridized to a 3.3-kb mRNA transcript. Further analysis of the 3.3-kb transcript demonstrated that it contains three additional open reading frames (plnB, plnC and plnD) downstream of plnA. The DNA sequences of plnB, plnC, and plnD revealed that their products closely resemble members of bacterial two-component signal transduction systems. The strongest homology was found to the accessory gene regulatory (agr) system, which controls expression of exoproteins during post-exponential growth in Staphylococcus aureus. The finding that plnABCD are transcribed from a common promoter suggests that the biological role played by the bacteriocin is somehow related to the regulatory function of the two-component system located on the same operon.

Purinergic inhibition of Na+,K+,Cl− cotransport in C11-MDCK cells: Role of stress-activated protein kinases

Akimova, Olga A.; Taurin, Sebastien; Dulin, Nickolai O.; Orlov, Sergei N.
Fonte: Springer Netherlands Publicador: Springer Netherlands
Tipo: Artigo de Revista Científica
Português
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Previously, we observed that sustained activation of P2Y1 leads to inhibition of Na+,K+,Cl− cotransport (NKCC) in C11 cells resembling intercalated cells from collecting ducts of the Madin-Darby canine kidney. This study examined the role of stress-activated protein kinases (SAPK) in NKCC inhibition triggered by purinergic receptors. Treatment of C11 cells with ATP led to sustained phosphorylation of SAPK such as JNK and p38. Activation of these kinases also occurred in anisomycin-treated cells. Surprisingly, we observed that compounds SP600125 and SB202190, known as potent inhibitors of JNK and p38 in cell-free systems, activated rather than inhibited phosphorylation of the kinases in C11 cells. Importantly, similarly to ATP, all the above-listed activators of JNK and p38 phosphorylation inhibited NKCC. Thus, our results suggest that activation of JNK and/or p38 contributes to NKCC suppression detected in intercalated-like cells from distal tubules after their exposure to P2Y1 agonists.

Total Synthesis and Evaluation of Cytostatin, its C10–C11 Diastereomers, and Additional Key Analogues: Impact on PP2A Inhibition

Lawhorn, Brian G.; Boga, Sobhana B.; Wolkenberg, Scott E.; Colby, David A.; Gauss, Carla-Maria; Swingle, Mark R.; Amable, Lauren; Honkanen, Richard E.; Boger, Dale L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 27/12/2006 Português
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The total synthesis of cytostatin, an antitumor agent belonging to the fostriecin family of natural products is described in full detail. The convergent approach relied on a key epoxide opening reaction to join the two stereotriad units and a single-step late stage, stereoselective installation of the sensitive (Z,Z,E)-triene through a β-chelation controlled nucleophilic addition. The synthetic route provided rapid access to the C4–C6 stereoisomers of the cytostatin lactone, which were prepared and used to define the C4–C6 relative stereochemistry of the natural product. In addition to the natural product, each of the C10–C11 diastereomers of cytostatin was divergently prepared (11 steps from key convergence step) by this route and used to unequivocally confirm the relative and absolute stereochemistry of cytostatin. Each of the cytostatin diastereomers exhibited a reduced activity towards inhibition of PP2A (>100-fold), demonstrating the importance of the presence and stereochemistry of the C10-methyl and C11-hydroxy groups for potent PP2A inhibition. Extensions of the studies provided dephosphocytostatin (40), sulfocytostatin (67, a key analogue related to the natural product sultriecin), 11-deshydroxycytostatin (78), and 72 lacking the entire C12–C18 (Z...

Enantioselective Gas Chromatographic Separation of Racemic N-alkylated Barbiturates: Application of C11-Chirasil-Dex as Chiral Stationary Phase in GC

Ghanem, Ashraf
Fonte: Libertas Academica Publicador: Libertas Academica
Tipo: Artigo de Revista Científica
Publicado em 18/09/2007 Português
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Chirasil-β-Dex containing an undecamethylene spacer (C11-Chirasil-Dex) was synthesized and used as chiral stationary phase (CSP) in enantioselective gas chromatography (GC). The versatility of the new stationary phase in the simultaneous enantiomeric separation of a set of N-alkylated barbiturates is demonstrated.

Isolation of C11 Cyclopentenones from Two Didemnid Species, Lissoclinum sp. and Diplosoma sp.

Ogi, Takayuki; Margiastuti, Palupi; Teruya, Toshiaki; Taira, Junsei; Suenaga, Kiyotake; Ueda, Katsuhiro
Fonte: Molecular Diversity Preservation International Publicador: Molecular Diversity Preservation International
Tipo: Artigo de Revista Científica
Publicado em 17/12/2009 Português
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A series of new C11 cyclopentenones 1–7 was isolated, together with four known metabolites 9/10, 12 and 13, from the extract of the didemnid ascidian Lissoclinum sp. The other didemnid ascidian Diplosoma sp. contained didemnenones 1, 2 and 5, and five known metabolites 8–12. The structures of 1–7 were elucidated by spectroscopic analyses. Cytotoxicity of the isolated compounds was evaluated against three human cancer cell lines (HCT116, A431 and A549).

Shear stress-induced volume decrease in C11-MDCK cells by BK-α/β4

Holtzclaw, J. David; Liu, Liping; Grimm, P. Richard; Sansom, Steven C.
Fonte: American Physiological Society Publicador: American Physiological Society
Tipo: Artigo de Revista Científica
Português
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Large-conductance, calcium-activated potassium channels (BK) are expressed in principal cells (PC) and intercalated cells (IC) in mammalian nephrons as BK-α/β1 and BK-α/β4, respectively. IC, which protrude into the lumens of tubules, express substantially more BK than PC despite lacking sufficient Na-K-ATPase to support K secretion. We previously showed in mice that IC exhibit size reduction when experiencing high distal flows induced by a high-K diet. We therefore tested the hypothesis that BK-α/β4 are regulators of IC volume via a shear stress (τ)-induced, calcium-dependent mechanism, resulting in a reduction in intracellular K content. We determined by Western blot and immunocytochemical analysis that C11-Madin-Darby canine kidney cells contained a predominance of BK-α/β4. To determine the role of BK-α/β4 in τ-induced volume reduction, we exposed C11 cells to τ and measured K efflux by flame photometry and cell volume by calcein staining, which changes inversely to cell volume. With 10 dynes/cm2, calcein intensity significantly increased 39% and monovalent cationic content decreased significantly by 37% compared with static conditions. Furthermore, the shear-induced K loss from C11 was abolished by the reduction of extracellular calcium...

Activation of P2Y receptors causes strong and persistent shrinkage of C11-MDCK renal epithelial cells

Koltsova, Svetlana V.; Platonova, Alexandra; Maksimov, Georgy V.; Mongin, Alexander A.; Grygorczyk, Ryszard; Orlov, Sergei N.
Fonte: American Physiological Society Publicador: American Physiological Society
Tipo: Artigo de Revista Científica
Português
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Purinergic receptors activate diverse signaling cascades and regulate the activity of cell volume-sensitive ion transporters. However, the effects of ATP and other agonists of P2 receptors on cell volume dynamics are only scarcely studied. In the present work, we used the recently developed dual-image surface reconstruction technique to explore the influence of purinergic agonists on cell volume in the C11-Madin-Darby canine kidney cell line resembling intercalated cells from kidney collecting ducts. Unexpectedly, we found that ATP and UTP triggered very robust (55–60%) cell shrinkage that lasted up to 2 h after agonist washout. Purinergic regulation of cell volume required increases in intracellular Ca2+ and could be partially mimicked by the Ca2+-ionophore ionomycin or activation of protein kinase C by 4β-phorbol 12-myristate 13-acetate. Cell shrinkage was accompanied by strong reductions in intracellular K+ and Cl− content measured using steady-state 86Rb+ and 36Cl− distribution. Both shrinkage and ion efflux in ATP-treated cells were prevented by the anion channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and by the BKCa channel inhibitors charybdotoxin, iberiotoxin, and paxilline. To evaluate the significance of cell-volume changes in purinergic signaling...

Genome Sequences of Three Leuconostoc citreum Strains, LBAE C10, LBAE C11, and LBAE E16, Isolated from Wheat Sourdoughs

Laguerre, Sandrine; Amari, Myriam; Vuillemin, Marlène; Robert, Hervé; Loux, Valentin; Klopp, Christophe; Morel, Sandrine; Gabriel, Bruno; Remaud-Siméon, Magali; Gabriel, Valérie; Moulis, Claire; Fontagné-Faucher, Catherine
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /03/2012 Português
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Leuconostoc citreum is a key microorganism in fermented foods of plant origin. Here we report the draft genome sequence for three strains of Leuconostoc citreum, LBAE C10, LBAE C11, and LBAE E16, which have been isolated from traditional French wheat sourdoughs.

Identification of Critical Genes for Growth in Olive Brine by Transposon Mutagenesis of Lactobacillus pentosus C11

Perpetuini, G.; Scornec, H.; Tofalo, R.; Serror, P.; Schirone, M.; Suzzi, G.; Corsetti, A.; Cavin, J. F.; Licandro-Seraut, H.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /08/2013 Português
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Olive brine represents a stressful environment due to the high NaCl concentration, presence of phenolic compounds known as antimicrobials, and low availability of nutrients. Thus, only a few strains of lactic acid bacteria (LAB) are adapted to grow in and ferment table olives. To identify the mechanisms by which these few strains are able to grow in olive brine, Lactobacillus pentosus C11, a particularly resistant strain isolated from naturally fermented table olives, was mutagenized by random transposition using the Pjunc-TpaseIS1223 system (H. Licandro-Seraut, S. Brinster, M. van de Guchte, H. Scornec, E. Maguin, P. Sansonetti, J. F. Cavin, and P. Serror, Appl. Environ. Microbiol. 78:5417–5423, 2012). A library of 6,000 mutants was generated and screened for adaptation and subsequent growth in a medium, named BSM (brine screening medium), which presents the stressful conditions encountered in olive brine. Five transposition mutants impaired in growth on BSM were identified. Transposition occurred in two open reading frames and in three transcription terminators affecting stability of transcripts. Thus, several essential genes for adaptation and growth of L. pentosus C11 in olive brine were identified.

Síntese do fragmento C11-C26 do potente agente antitumoral (-)-dictiostatina; Synthesis of the C11-C26 fragment of the potent antitumor agent dictyostatin

Dimas José da Paz Lima
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 29/07/2010 Português
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A (-)-dictiostatina (1) é uma macrolactona de origem marinha, que foi isolada por Pettit e col. em 1994 da esponja Spongia sp. e posteriormente, por Wright e col. a partir da esponja Lithistida. A (-)-dictiostatina (1) exibe uma potente atividade antitumoral, inibindo a proliferação de células cancerígenas em concentração nanomolar. Descrevemos aqui, nossos resultados na preparação do fragmento C11-C26 (1.72) da (-)-dictiostatina (1). A síntese deste fragmento envolveu as reações aldólicas do tipo syn na preparação dos adutos aldólicos 54 e 1.38, hidrogenação catalítica para a formação do centro C16 na lactona 1.6, reação de HWE entre os fragmentos 1.23 e 1.33 conduzindo de forma eficiente a enona 1.40, redução 1,3-syn nas condições de Narasaka e por fim reação de Wittig para estabelecer as ligações duplas (C23-C26). A síntese do fragmento C11-C26 (1.72) foi concluída de maneira eficiente, envolvendo 26 etapas e rendimento global de 5,5% a partir do éster de Roche (rota linear mais longa). Esta rota é, em princípio, aplicável na preparação deste fragmento e análogos numa escala maior.; The macrolactone (-)- dictyostatin (1) exhibits potent antitumor activity and inhibits the growth of a variety of cancer cell lines at low nanomolar levels. This compound was first isolated in small amounts by Pettit et al. in 1994 from a marine sponge of the genus Spongia sp...

Impaired 2',3'-dideoxy-3'-thiacytidine accumulation in T-lymphoblastoid cells as a mechanism of acquired resistance independent of multidrug resistant protein 4 with a possible role for ATP-binding cassette C11.

Turriziani, O; Schuetz, J D; Focher, F; Scagnolari, C; Sampath, J; Adachi, M; Bambacioni, F; Riva, E; Antonelli, G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/11/2002 Português
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26.95%
Cellular factors may contribute to the decreased efficacy of chemotherapy in HIV infection. Indeed, prolonged treatment with nucleoside analogues, such as azidothymidine (AZT), 2',3'-deoxycytidine or 9-(2-phosphonylmethoxyethyl)adenine, induces cellular resistance. We have developed a human T lymphoblastoid cell line (CEM 3TC) that is selectively resistant to the antiproliferative effect of 2',3'-dideoxy-3'-thiacytidine (3TC) because the CEM 3TC cells were equally sensitive to AZT, as well as the antimitotic agent, vinblastine. The anti-retroviral activity of 3TC against HIV-1 was also severely impaired in the CEM 3TC cells. Despite similar deoxycytidine kinase activity and unchanged uptake of nucleosides such as AZT and 2'-deoxycytidine, CEM 3TC had profoundly impaired 3TC accumulation. Further studies indicated that CEM 3TC retained much less 3TC. However, despite a small overexpression of multidrug resistance protein (MRP) 4, additional studies with cells specifically engineered to overexpress MRP4 demonstrated there was no impact on either 3TC accumulation or efflux. Finally, an increased expression of the MRP5 homologue, ATP-binding cassette C11 (ABCC11) was observed in the CEM 3TC cells. We speculate that the decreased 3TC accumulation in the CEM 3TC might be due to the upregulation of ABCC11.

Report from the IUPAP Commission on Particles and Fields (C11)

Herten, Gregor
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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The Commission 11 (C11) on Particles and Fields of the International Union of Pure and Applied Physics (IUPAP) supervises the organization of the main conferences in particle physics. In the period 2007-2008 it has been active in the oversight and venue selection for the ICHEP and Lepton Photon Conferences, establishment of the new conference on Technology and Instrumentation in Particle Physics (TIPP), the selection of the prize winners for the IUPAP Young Scientist Prize in Particle Physics and the establishment of a working group on the "Assessment of Individual Achievements in Large Collaborations in Particle Physics".; Comment: Plenary talk at ICHEP08, Philadelphia, August 2008, 4 pages

Overhauling SC atomics in C11 and OpenCL

Wickerson, John; Batty, Mark; Donaldson, Alastair F.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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Despite the conceptual simplicity of sequential consistency (SC), the semantics of SC atomic operations and fences in the C11 and OpenCL memory models is subtle, leading to convoluted prose descriptions that translate to complex axiomatic formalisations. We conduct an overhaul of SC atomics in C11, reducing the associated axioms in both number and complexity. A consequence of our simplification is that the SC operations in an execution no longer need to be totally ordered. This relaxation enables, for the first time, efficient and exhaustive simulation of litmus tests that use SC atomics. We use our improved C11 model to present the first rigorous memory model formalisation for OpenCL (which extends C11 with support for heterogeneous many-core programming). In the OpenCL setting, we refine the SC axioms still further to give a sensible semantics to SC operations that employ a 'memory scope' to restrict their visibility to specific threads. Our overhaul requires slight strengthenings of both the C11 and the OpenCL memory models, causing some behaviours to become disallowed. We argue that these strengthenings are natural, and prove that all of the formalised C11 and OpenCL compilation schemes of which we are aware (Power and x86 for C11...

Highly Excited States in C11. Elastic Scattering of Protons by B10

Overley, J. C.; Whaling, Ward
Fonte: Instituto de Tecnologia da Califórnia Publicador: Instituto de Tecnologia da Califórnia
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 01/10/1962 Português
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Excitation functions for the elastic scattering of protons by B10 have been measured at center-of-mass scattering angles near 90°, 125°, and 160° for proton energies between Ep=0.15 MeV and Ep=3.0 MeV. Scattering angular distributions were measured at 43 selected energies in this range. An excitation function for the reaction B10(p, α0)Be7 was also measured between Ep=1.5 MeV and Ep=2.6 MeV at a laboratory angle of 90°. The atomic stopping cross section of boron for protons has been determined between Ep=0.1 MeV and Ep=3.0 MeV. The elastic scattering excitation functions exhibit conspicuous anomalies at Ep=1.50 MeV and Ep=2.180 MeV. The α0 transition to the ground state of Be7 is also resonant at Ep=2.180 MeV. The behavior of the cross sections in these regions has been analyzed in terms of compound states of C11. Satisfactory agreement is achieved with level assignments of Jπ=7/2+ with ER=1.50 MeV, Γp=90 keV, ΓT=250 keV; and Jπ=9/2+ with ER=2.180 MeV, Γp=100 keV, Γα0=100 kev, and ΓT=200 keV. Although complete analysis of the scattering is hindered by the influence of unknown background processes, the negative parity assignment for the previously reported state at Ep=1.17 MeV, derived from other reaction experiments...