1,094 research outputs found
Two particle correlations inside one jet at "Modified Leading Logarithmic Approximation" of Quantum Chromodynamics; I: exact solution of the evolution equations at small x
We discuss correlations between two particles in jets at high energy
colliders and exactly solve the MLLA evolution equations in the small x limit.
We thus extend the Fong-Webber analysis to the region away from the hump of the
single inclusive energy spectrum. We give our results for LEP, Tevatron and LHC
energies, and compare with existing experimental data.Comment: LaTeX, 49 pages, 57 .eps figures + one log
Addition Of Chiral And Achiral Allyltrichlorostannanes To Chiral α-alkoxy Aldehydes
Achiral and chiral allyltrichlorostannanes reacted with chiral α-alkoxy aldehydes to give the corresponding homoallylic alcohols with moderate to good levels of 1,4-syn-diastereoselection.204802812Fleming, I., Barbero, A., Walter, D., (1997) Chem. Rev., 97, p. 2063Nishigaichi, Y., Takuwa, A., Naruta, Y., Maruyama, K., (1993) Tetrahedron, 49, p. 7395Panek, J.S., Xu, F., Rondon, A.C., (1998) J. Am. Chem. Soc., 120, p. 4113Zhu, B., Panek, J.S., (2001) Eur. J. Org. Chem., 9, p. 1701Huang, H.B., Spande, T.F., Panek, J.S., (2003) J. Am. Chem. Soc., 125, p. 626Keck, G.E., Abbott, D.E., (1984) Tetrahedron Lett, 25, p. 1883Maguire, R.J., Mulzer, J., Bats, J.W., (1996) J. Org. Chem., 61, p. 6936Denmark, S.E., Stavenger, R.A., (1998) J. Org. Chem., 63, p. 9524Trost, B.M., Urabe, H., (1990) J. Org. Chem., 55, p. 3982Nishigaishi, Y., Takuwa, A., Jodai, A., (1991) Tetrahedron Lett, 32, p. 2383Almendros, P., Gruttadauria, M., Helliwell, M., Thomas, E.J., (1997) J. Chem. Soc. Perkin Trans. I, p. 2549Deka, D.C., Helliwell, M., Thomas, E.J., (2001) Tetrahedron, 57, p. 10017Martin, N., Thomas, E.J., (2001) Tetrahedron Lett, 42, p. 8373Kumar, P., Thomas, E.J., Tray, D.R., (2001) J. Braz. Chem. Soc., 12, p. 623Gruttadauria, M., Thomas, E.J., (1995) J. Chem. Soc. Perkin Trans. I, p. 1469Nishigaichi, Y., Kuramoto, H., Takuwa, A., (1995) Tetrahedron Lett, 36, p. 3353Dias, L.C., Giacomini, R., (1998) J. Braz. Chem. Soc., 9, p. 357Dias, L.C., Giacomini, R., (1998) Tetrahedron Lett, 39, p. 5343Dias, L.C., Meira, P.R.R., Ferreira, E., Org. Lett., 1999, p. 1335. , See also: "NMR Spectra and Structures of Organotin Compounds," V. S. Petrosyan, Progr. in NMR Spectr. 1978, 11, 115Dias, L.C., Meira, P.R.R., (2000) Synlett, p. 37Dias, L.C., Ferreira, E., (2001) Tetrahedron Lett, 42, p. 7159Dias, L.C., Ferreira, A.A., Diaz, G., (2002) Synlett, p. 1845Dias, L.C., Diaz, G., Ferreira, A.A., Meira, P.R.R., Ferreira, E., (2003) Synthesis, p. 603Dias, L.C., Giacomini, R., Meira, P.R.R., Ferreira, E., Ferreira, A.A., Diaz, G., dos Santos, D.R., Steil, L.J., (2003) Arkivoc, 10, p. 240Dias, L.C., dos Santos, D.R., Steil, L.J., (2003) Tetrahedron Lett, 44, p. 6861(2002) Org. Lett., 4, p. 4325. , We have recently described a very efficient, synthetically useful 1, 4-anti-1, 5-anti boron-mediated aldol reaction of chiral α-methyl-β-alkoxy methyl ketone with achiral aldehydes: Dias, L.C., Baú, R.Z., de Sousa, M.A., Zukerman-Schpector, JDenmark, S.E., Wilson, T., Willson, T.M., (1988) J. Am. Chem. Soc., 110, p. 984Denmark, S.E., Weber, E.J., Wilson, T., Willson, T.M., (1989) Tetrahedron, 45, p. 1053Denmark, S.E., Almstead, N.G., (1992) Tetrahedron, 48, p. 5565Denmark, S.E., Almstead, N.G., (1993) J. Am. Chem. Soc., 115, p. 3133Dias, L.C., Fattori, J., Perez, C.C., (2008) Tetrahedron Lett, 49, p. 557Dias, L.C., Fattori, J., Perez, C.C., Oliveira, V.M., Aguilar, A.M., (2008) Tetrahedron, 64, p. 5891Kim, D., Lee, J., Shim, P.J., Lim, J.I., Doi, T., Kim, S., (2002) J. Org. Chem., 67, p. 772noteShambayati, S., Schreiber, S.L., Blake, J.F., Wierschke, S.G., Jorgensen, W.L., (1990) J. Am. Chem. Soc., 112, p. 697noteChérest, M., Felkin, H., Prudent, N., (1968) Tetrahedron Lett, 18, p. 2199Anh, N.T., Eisenstein, O., (1977) Nouv. J. Chem., 1, p. 61noteBatey, R.A., Thadani, A.N., Smil, D.V., Lough, A.J., (2000) Synthesis, 7, p. 990Heathcock, C.H., Pirrung, M.C., Sohn, J.E., (1979) J. Org. Chem., 44, p. 4294Landmann, B., Hoffmann, R.W., (1987) Chem. Ber., 120, p. 331Dias, L.C., Ferreira, M.A.B., Tormena, C.F., (2008) J. Phys. Chem. A, 112, p. 232Sames, D., Liu, Y., De Young, L., Polt, R., (1995) J. Org. Chem., 60, p. 2153Lombardo, M., Morganti, S., Trombini, C., (2003) J. Org. Chem., 68, p. 997notenotenot
Systematics of Coupling Flows in AdS Backgrounds
We give an effective field theory derivation, based on the running of Planck
brane gauge correlators, of the large logarithms that arise in the predictions
for low energy gauge couplings in compactified AdS}_5 backgrounds, including
the one-loop effects of bulk scalars, fermions, and gauge bosons. In contrast
to the case of charged scalars coupled to Abelian gauge fields that has been
considered previously in the literature, the one-loop corrections are not
dominated by a single 4D Kaluza-Klein mode. Nevertheless, in the case of gauge
field loops, the amplitudes can be reorganized into a leading logarithmic
contribution that is identical to the running in 4D non-Abelian gauge theory,
and a term which is not logarithmically enhanced and is analogous to a two-loop
effect in 4D. In a warped GUT model broken by the Higgs mechanism in the
bulk,we show that the matching scale that appears in the large logarithms
induced by the non-Abelian gauge fields is m_{XY}^2/k where m_{XY} is the bulk
mass of the XY bosons and k is the AdS curvature. This is in contrast to the UV
scale in the logarithmic contributions of scalars, which is simply the bulk
mass m. Our results are summarized in a set of simple rules that can be applied
to compute the leading logarithmic predictions for coupling constant relations
within a given warped GUT model. We present results for both bulk Higgs and
boundary breaking of the GUT gauge group.Comment: 22 pages, LaTeX, 3 figures. Comments and references adde
Evolutionary trait‐based approaches for predicting future global impacts of plant pathogens in the genus Phytophthora
Plant pathogens are introduced to new geographical regions ever more frequently as global connectivity increases. Predicting the threat they pose to plant health can be difficult without in‐depth knowledge of behaviour, distribution and spread. Here, we evaluate the potential for using biological traits and phylogeny to predict global threats from emerging pathogens.
We use a species‐level trait database and phylogeny for 179 Phytophthora species: oomycete pathogens impacting natural, agricultural, horticultural and forestry settings. We compile host and distribution reports for Phytophthora species across 178 countries and evaluate the power of traits, phylogeny and time since description (reflecting species‐level knowledge) to explain and predict their international transport, maximum latitude and host breadth using Bayesian phylogenetic generalised linear mixed models.
In the best‐performing models, traits, phylogeny and time since description together explained up to 90%, 97% and 87% of variance in number of countries reached, latitudinal limits and host range, respectively. Traits and phylogeny together explained up to 26%, 41% and 34% of variance in the number of countries reached, maximum latitude and host plant families affected, respectively, but time since description had the strongest effect.
Root‐attacking species were reported in more countries, and on more host plant families than foliar‐attacking species. Host generalist pathogens had thicker‐walled resting structures (stress‐tolerant oospores) and faster growth rates at their optima. Cold‐tolerant species are reported in more countries and at higher latitudes, though more accurate interspecific empirical data are needed to confirm this finding.
Policy implications. We evaluate the potential of an evolutionary trait‐based framework to support horizon‐scanning approaches for identifying pathogens with greater potential for global‐scale impacts. Potential future threats from Phytophthora include Phytophthora x heterohybrida, P. lactucae, P. glovera, P. x incrassata, P. amnicola and P. aquimorbida, which are recently described, possibly under‐reported species, with similar traits and/or phylogenetic proximity to other high‐impact species. Priority traits to measure for emerging species may be thermal minima, oospore wall index and growth rate at optimum temperature. Trait‐based horizon‐scanning approaches would benefit from the development of international and cross‐sectoral collaborations to deliver centralised databases incorporating pathogen distributions, traits and phylogeny
Diffusion of gold nanoclusters on graphite
We present a detailed molecular-dynamics study of the diffusion and
coalescence of large (249-atom) gold clusters on graphite surfaces. The
diffusivity of monoclusters is found to be comparable to that for single
adatoms. Likewise, and even more important, cluster dimers are also found to
diffuse at a rate which is comparable to that for adatoms and monoclusters. As
a consequence, large islands formed by cluster aggregation are also expected to
be mobile. Using kinetic Monte Carlo simulations, and assuming a proper scaling
law for the dependence on size of the diffusivity of large clusters, we find
that islands consisting of as many as 100 monoclusters should exhibit
significant mobility. This result has profound implications for the morphology
of cluster-assembled materials
Dietary supplementation of heat-treated Gracilaria and Ulva seaweeds enhanced acute hypoxia tolerance in gilthead sea bream (Sparus aurata)
Intensive aquaculture practices involve rearing fish at high densities. In these conditions, fish may be exposed to suboptimal dissolved O2 levels with an increased formation of reactive O2 species (ROS) in tissues. Seaweeds (SW) contain biologically active substances with efficient antioxidant capacities. This study evaluated the effects of dietary supplementation of heat-treated SW (5% Gracilaria vermiculophylla or 5% Ulva lactuca) on stress bioindicators in sea bream subjected to a hypoxic challenge. 168 fish (104.5 g average weight) were distributed in 24 tanks, in which eight tanks were fed one of three experimental diets for 34 days: (i) a control diet without SW supplementation, (ii) a control diet supplemented with Ulva, or (iii) a control diet with Gracilaria. Thereafter, fish from 12 tanks (n=4 tanks/dietary treatment) were subjected to 24 h hypoxia (1.3 mg O2 l-1) and subsequent recovery normoxia (8.6 mg O2 l-1). Hypoxic fish showed an increase in hematocrit values regardless of dietary treatment. Dietary modulation of the O2-carrying capacity was conspicuous during recovery, as fish fed SW supplemented diets displayed significantly higher haemoglobin concentration than fish fed the control diet. After the challenge, survival rates in both groups of fish fed SW were higher, which was consistent with a decrease in hepatic lipid peroxidation in these groups. Furthermore, the hepatic antioxidant enzyme activities were modulated differently by changes in environmental O2 condition, particularly in sea bream fed the Gracilaria diet. After being subjected to hypoxia, the gene expression of antioxidant enzymes and molecular chaperones in liver and heart were down regulated in sea bream fed SW diets. This study suggests that the antioxidant properties of heat-treated SW may have a protective role against oxidative stress. The nature of these compounds and possible mechanisms implied are currently being investigated. © 2017. Published by The Company of BiologistsThe authors are grateful to Pedro Eloi, Fernando Magalhães and Carlos Morais (ICBAS-UP) for fish maintenance. We would like to thank Kevin Tromp (WIAS-WU), Luis Pereira, Francisca Silva-Brito, and Filipa Fontinha for technical assistance during sampling and analysis (CIIMAR-UP). The authors would like to express gratitude to Rui Pereira (ALGA plus), Jorge Dias (Sparos Lda.), Jon Svendsen and Maria João Peixoto (CIIMAR-UP) for technical advic
FGF receptor genes and breast cancer susceptibility: results from the Breast Cancer Association Consortium
Background:Breast cancer is one of the most common malignancies in women. Genome-wide association studies have identified FGFR2 as a breast cancer susceptibility gene. Common variation in other fibroblast growth factor (FGF) receptors might also modify risk. We tested this hypothesis by studying genotyped single-nucleotide polymorphisms (SNPs) and imputed SNPs in FGFR1, FGFR3, FGFR4 and FGFRL1 in the Breast Cancer Association Consortium.
Methods:Data were combined from 49 studies, including 53 835 cases and 50 156 controls, of which 89 050 (46 450 cases and 42 600 controls) were of European ancestry, 12 893 (6269 cases and 6624 controls) of Asian and 2048 (1116 cases and 932 controls) of African ancestry. Associations with risk of breast cancer, overall and by disease sub-type, were assessed using unconditional logistic regression.
Results:Little evidence of association with breast cancer risk was observed for SNPs in the FGF receptor genes. The strongest evidence in European women was for rs743682 in FGFR3; the estimated per-allele odds ratio was 1.05 (95 confidence interval=1.02-1.09, P=0.0020), which is substantially lower than that observed for SNPs in FGFR2.
Conclusion:Our results suggest that common variants in the other FGF receptors are not associated with risk of breast cancer to the degree observed for FGFR2. © 2014 Cancer Research UK
Emergence of resistance to colistin during the treatment of bloodstream infection caused by Klebsiella pneumoniae carbapenemase-producing Klebsiella pneumoniae
We report the emergence of colistin resistance in Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae after 8 days of colistin-based therapy, resulting in relapse of bloodstream infection and death. Disruption of the mgrB gene by insertion of a mobile genetic element was found to be the mechanism, which was replicated in vitro after exposure to subinhibitory concentrations of colistin and meropenem
Study of the production of and hadrons in collisions and first measurement of the branching fraction
The product of the () differential production
cross-section and the branching fraction of the decay () is
measured as a function of the beauty hadron transverse momentum, ,
and rapidity, . The kinematic region of the measurements is and . The measurements use a data sample
corresponding to an integrated luminosity of collected by the
LHCb detector in collisions at centre-of-mass energies in 2011 and in 2012. Based on previous LHCb
results of the fragmentation fraction ratio, , the
branching fraction of the decay is
measured to be \begin{equation*} \mathcal{B}(\Lambda_b^0\rightarrow J/\psi
pK^-)= (3.17\pm0.04\pm0.07\pm0.34^{+0.45}_{-0.28})\times10^{-4},
\end{equation*} where the first uncertainty is statistical, the second is
systematic, the third is due to the uncertainty on the branching fraction of
the decay , and the
fourth is due to the knowledge of . The sum of the
asymmetries in the production and decay between and
is also measured as a function of and .
The previously published branching fraction of , relative to that of , is updated.
The branching fractions of are determined.Comment: 29 pages, 19figures. All figures and tables, along with any
supplementary material and additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-032.htm
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