2,982 research outputs found
The Effects of Individual Differences on Cued Antisaccade Performance
In the antisaccade task, pre-cueing the location of a correct response has the paradoxical effect of increasing errors. It has been suggested that this effect occurs because participants adopt an "antisaccade task set" and treat the cue as if was a target - directing attention away from the precue and towards the location of the impending target. This hypothesis was tested using a mixed pro / antisaccade task. In addition the effects of individual differences in working memory capacity and schizotypal personality traits on performance were examined. Whilst we observed some modest relationships between these individual differences and antisaccade performance, the strongest predictor of antisaccade error rate was uncued prosaccade latency
Arylation Of β,γ-unsaturated Lactones By A Heck-matsuda Reaction: An Unexpected Route To Aryldiazene Butenolides And Pyridazinones
The palladium catalysed coupling of aryldiazonium salts with β-γ-unsaturated lactones under basic conditions has been investigated. Both (3H)-furanone and α-angelicalactone were evaluated as substrates in the Heck Matsuda reaction but both failed to afford the desired arylated butenolides. Under basic conditions, β-γ-unsaturated lactones generate highly nucleophilic enolates that preferentially undergo azo coupling reactions with arenediazonium salts to afford aryldiazene butenolides. The electronic and steric effect of the substituents on the aryldiazonium salt in the azo coupling reaction is described. Aryldiazene-lactone derivatives were obtained in good yields from a highly facile and straightforward procedure. An aminoisomaleimide was formed from (3H)-furanone and cyclised to the corresponding pyridazinones in modest yield.331020702074Tsuji, J., (1997) Palladium Reagents and Catalysts: Innovations in Organic Synthesis, , 1st ed., Wiley: LondonShibasaki, M., Vogl, E.M., Ohshima, T., (2004) Adv. Synth. Catal., 346, p. 1533. , For reviews seeDounay, A.B., Overman, L.E., (2003) Chem. Rev., 103, p. 2945Siqueira, F.A., Taylor, J.G., Correia, C.R.D., (2010) Tetrahedron. Lett., 51, p. 2102. , For selected examples seeMoro, A.V., Cardoso, F.S.P., Correia, C.R.D., (2009) Org. Lett., 11, p. 3642Pastre, J.C., Correia, C.R.D., (2009) Adv. Synth. Catal., 351, p. 1217Machado, A.H.L., De Sousa, M.A., Patto, D.C.S., Azevedo, L.F.S., Bombonato, F.I., Correia, C.R.D., (2009) Tetrahedron. Lett., 50, p. 1222Moro, A.V., Cardoso, F.S.P., Correia, C.R.D., (2008) Tetrahedron. Lett., 49, p. 5668Coy, E.D., Jovanovic, L., Sefkow, M., (2010) Org. Lett., 12, p. 1976. , For selected examples seeCacchi, S., Fabrizi, G., Goggiamani, A., Sferrazza, A., (2009) Synlett, 8, p. 1277Bartoli, G., Cacchi, S., Fabrizi, G., Goggiamani, A., (2008) Synlett, 16, p. 2508Barbero, M., Cadamuro, S., Dughera, S., (2006) Synthesis, 20, p. 3443Kikukawa, K., Matsuda, T., (1977) Chem. Lett., p. 159Sengupta, S., Bhattacharyya, S., (2001) Tetrahedron. Lett., 42, p. 2035Kikukawa, K., Nagira, K., Wada, F., Matsuda, T., (1981) Tetrahedron., 37, p. 31Kikukawa, K., Matsuda, T., (1977) Chem. Lett., p. 159Hyde, A.M., Buchwald, S.L., (2009) Org. Lett., 11, p. 2663Szele, I., Zollinger, H., (1983) Top. Curr. Chem., 112, p. 1Otto, D., (1907) Berichte der Deutschen Chemischen Gesellschaft, 40, p. 2404Shapiro, D., Segal, H., Flowers, H.M., (1958) J. Am. Chem., 80, p. 1194. , For examples seeVenturello, C., D'Aloisio, R., (1979) Synthesis, 4, p. 283Garst, M.E., Lukton, D., (1980) Synth. Commun., 10, p. 155Blank, O., Wetzel, A., Ullrich, D., Heinrich, M.R., (2008) Eur. J. Org. Chem., 18, p. 3179Jackson, A., Joule, J.A., (1967) Chem. Commun., 9, p. 459. , For examples seeShawali, A.S., El-Galil, A.M., (1971) Tetrahedron., 27, p. 4305Bestmann, H.J., Schmid, G., Sandmeier, D., (1980) Tetrahedron. Lett., 21, p. 2939Atlan, V., Kaim, L., Supiot, C., (2000) Chem. Commun., 15, p. 1385Tsou, K.C., Barnett, R.J., Seligman, A.M., (1955) J. Am. Chem. Soc., 77, p. 4613. , first aminoisomaleimide synthesis was reported in 1955 by Tsou and formed by intramolecular condensation of an N-substituted maleamic acid using trifuroacetic anhydride as dehydrating agentNaesman, J.A.H., Pensar, K.G., (1985) Synthesis, 8, p. 786Kraus, G.A., Roth, B., (1977) Tetrahedron. Lett., 18, p. 3129. , Dimerisation and polymerisation of butenolides has been previously reportedParnarouskis, M., Rubinstein, H., (1976) J. Heterocycl. Chem., 13, p. 423Meier, K.D., Ringier, B.H., Druey, J., (1954) Helv. Chim. Acta, 37, p. 523Seymour, D., (1955) J. Chem. Soc., p. 852Baloniak, S., Mroczkiewicz, A., Katrusiak, A., (1996) Pol. J. Chem., 70, p. 1274Tartar, A., Melnyk, P., (1996) Tetrahedron. Lett., 37, p. 4145Conley, N.R., Hung, R.J., Willson, C.G., (2005) J. Org. Chem., 70, p. 4553Johnston, A.K., Allcock, R.W., Jiang, Z., Collier, I.D., Blakli, H., Rosair, G.M., Bailey, P.D., Adams, D.R., (2008) Org. Biomol. Chem., 6, p. 175Natarajan, S.R., Heller, S.T., Nam, K., Singh, S.B., Scapin, G., Patel, S., Thompson, J.E., O'Keefe, S.J., (2006) Bioorg. Med. Chem. Lett., 16, p. 5809Dal Piaz, P., Vergelli, C., Castellana, M.C., Gioavannoni, M.P., Pieretti, S., (2002) J. Heterocycl. Chem., 39, p. 523Matyus, P., (1998) J. Heterocycl. Chem., 35, p. 1075Jones, J.B., Barker, J.N., (1970) Can. J. Chem., 48, p. 1574. , This reaction is known to occur under basic conditionsLukes, R., Syhora, K., (1954) Collect. Czech. Chem. Commun., 19, p. 1205David, P., Langlois, H.W., (1948) J. Am. Chem. Soc., 70, p. 2624Herbst, W., Hunger, K., (1978) Prog. Org. Coat, 6, p. 10
T-duality in M-theory and supermembranes
The (q_1,q_2) SL(2,Z) string bound states of type IIB superstring theory
admit two inequivalent (T-dual) representations in eleven dimensions in terms
of a fundamental 2-brane. In both cases, the spectrum of membrane oscillations
can be determined exactly in the limit , where is the
type IIA string coupling. We find that the BPS mass formulas agree, and
reproduce the BPS mass spectrum of the string bound state. In the
non-BPS sector, the respective mass formulas apply in different corners of the
moduli space. The axiomatic requirement of T-duality in M-theory permits to
derive a discrete mass spectrum in a (thin torus) region where standard
supermembrane theory undergoes instabilities.Comment: harvmac, 9 page
Ultraviolet Complete Electroweak Model Without a Higgs Particle
An electroweak model with running coupling constants described by an energy
dependent entire function is utraviolet complete and avoids unitarity
violations for energies above 1 TeV. The action contains no physical scalar
fields and no Higgs particle and the physical electroweak model fields are
local and satisfy microcausality. The and masses are compatible with a
symmetry breaking , which
retains a massless photon. The vertex couplings possess an energy scale
TeV predicting scattering amplitudes that can be tested at the
LHC.Comment: 19 pages, no figures, LaTex file. Equation and text corrected.
Reference added. Results remain the same. Final version published in European
Physics Journal Plus, 126 (2011
Development of the Maree Career Matrix : a new interest inventory
In this article, the authors report on the development of an interest inventory (the
Maree Career Matrix) for South Africans with a minimum of Grade 9 second
language English or Afrikaans proficiency. The instrument was completed by
1106 learners in Grade 11 in the Gauteng, Mpumalanga, and North West
provinces of South Africa. Rasch analysis was done; inter-category correlations,
reliability coefficients, and differential item functioning values were calculated;
and validity and norm tables were established. We concluded that the Maree
Career Matrix is easy to use and has good psychometric qualities, takes
relatively little time to administer, provides reliable and valid results, is
standardised, and can be applied to large groups with relative ease. Additional
research is needed to gather data on the profiles of people in other age brackets
and to trace their progress, the aim being to further investigate and enhance the
predictive value of the Maree Career Matrix.http://sap.sagepub.comhb2016Educational Psycholog
D-Brane Probe and Closed String Tachyons
We consider a D-brane probe in unstable string background associated with
flux branes. The twist in spacetime metric reponsible for the supersymmetry
breaking is shown to manifest itself in mixing of open Wilson lines with the
phases of some adjoint matter fields, resulting in a nonlocal and
nonsupersymmetric form of Yang-Mills theory as the probe dynamics. This
provides a setup where one can study fate of a large class of unstable closed
string theories that include as a limit type 0 theories and various orbifolds
of type II and type 0 theories. We discuss the limit of orbifold
in some detail and speculate on couplings with closed string tachyons.Comment: LaTeX, 17 pages, typos fixed, references update
Partial Regularity of solutions to the Four-dimensional Navier-Stokes equations at the first blow-up time
The solutions of incompressible Navier-Stokes equations in four spatial
dimensions are considered. We prove that the two-dimensional Hausdorff measure
of the set of singular points at the first blow-up time is equal to zero.Comment: 19 pages, a comment regarding five or higher dimensional case is
added in Remark 1.3. accepted by Comm. Math. Phy
Validation of a simple canopy conductance model for estimating transpiration of different citrus species under non-limiting soil water conditions
XXXI International Horticultural Congress (IHC2022): International Symposium on Water: a Worldwide Challenge for Horticulture!Please read abstract in the article.South Africa’s Water Research Commission and Citrus Research International.https://www.ishs.org/acta-horticulturae2023-07-31hj2024Plant Production and Soil ScienceSDG-02:Zero Hunge
Optimizing tuning masses for helicopter rotor blade vibration reduction including computed airloads and comparison with test data
The development and validation of an optimization procedure to systematically place tuning masses along a rotor blade span to minimize vibratory loads are described. The masses and their corresponding locations are the design variables that are manipulated to reduce the harmonics of hub shear for a four-bladed rotor system without adding a large mass penalty. The procedure incorporates a comprehensive helicopter analysis to calculate the airloads. Predicting changes in airloads due to changes in design variables is an important feature of this research. The procedure was applied to a one-sixth, Mach-scaled rotor blade model to place three masses and then again to place six masses. In both cases the added mass was able to achieve significant reductions in the hub shear. In addition, the procedure was applied to place a single mass of fixed value on a blade model to reduce the hub shear for three flight conditions. The analytical results were compared to experimental data from a wind tunnel test performed in the Langley Transonic Dynamics Tunnel. The correlation of the mass location was good and the trend of the mass location with respect to flight speed was predicted fairly well. However, it was noted that the analysis was not entirely successful at predicting the absolute magnitudes of the fixed system loads
Hydrodynamic Synchronisation of Model Microswimmers
We define a model microswimmer with a variable cycle time, thus allowing the
possibility of phase locking driven by hydrodynamic interactions between
swimmers. We find that, for extensile or contractile swimmers, phase locking
does occur, with the relative phase of the two swimmers being, in general,
close to 0 or pi, depending on their relative position and orientation. We show
that, as expected on grounds of symmetry, self T-dual swimmers, which are
time-reversal covariant, do not phase-lock. We also discuss the phase behaviour
of a line of tethered swimmers, or pumps. These show oscillations in their
relative phases reminiscent of the metachronal waves of cilia.Comment: 17 pages, 8 figure
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