438 research outputs found
Realidade X Fantasia:: Sua influência no raciocínio dedutivo
Many studies have shown the importance of mode ofpresentation in tasks aimed at evaluating cognitive performance.In three experiments concerning the understanding of syllogisticproblems whose content runs counter to subjects' practical worldknowledge, we examined the hypothesis that the presence of thetoys in a make-believe condition, would significantly improve children'sperformance, since encoding of the premisses would be facilitated.Experiments I, II and III showed that, as in the study of Dias& Harris (submited), children's performance was significantly betterwhen the premisses were presented in a make-believe play moderather than in the standard verbal mode. The make-believe contextof play is what facilitates children's reasoning, when the premissesof the problems run counter to their experience.A importância do modo de apresentação das tarefas para avaliar o desempenho cognitivo tem sido enfatizada em muitos estudos. Em três experimentos sobre a compreensão de problemas silogísticos com conteúdos contrários à experiência do dia-a-dia das crianças analisou-se até que ponto a visibilidade de brinquedos durantea tarefa onde brincadeiras eram incluídas, seria um fator fundamental no desempenho na medida' em que favoreceria a memorização das premissas. Os Experimentos I, II e III demonstraram que, como no estudo de Dias e Harris (submetido), o desempenho das crianças era significativamente melhor quando as premissas eram apresentadas dentro de um contexto de brincadeira do que quando eram apresentadas de modo verbal comum. O contexto de faz-de-conta mais do que a visível presença dos brinquedos durante a apresentação é que facilita o raciocínio das crianças quando as premissas dos problemas vão de encontro à suas experiências
Regras morais e convencionais no raciocínio de crianças
A make-believe mode can help children to construct a selfcontainedworld within which they accept premises and conclusions thathave no counterpart in their everyday experience (Dias e Harris, 1988a,b, c; no prelo a e b). Thus, we asked if the construct of that make-believeworld would have the same effect in syllogistic problems that convene either moral or conventional rules. The results show that neither of thepopulations studied (Brazilian and English children from medium SESfamilies and Brazilian children from Orphanages) distinguish betweenmoral and conventional rules as found by Turiel (1983). The make-believemode helped the performance of children from medium SES familes.However, children from Orphanages Showed similar reasoning under thetwo types of context, as children did with known fact premises that agreedwith subject's experience (see Hawkins, Pea, Glick & Scribner, 1984;Dias e Harris, 1988a, b). For these children premises that contravenemoral or conventional rules to the two other populations, seems beaccepted as empirically true without need of the make-believe play.RESUMO - Uma apresentação de brincadeira de faz-de-conta pode ser usada para induzir crianças a criarem um mundo independente, onde os eventos podem ocorrer diferentemente daqueles do mundo empírico, facilitando assim a ocorrência de raciocínio dedutivo com base em premissas contrárias aos fatos (Dias e Harris, 1988a, b, c; no prelo a e b). Analisou-se então, se a criação deste mundo de faz-de-conta proporciona o mesmo efeito em problemas silogísticos que contêm premissas contrárias aos dorhfnios morais ou convencionais. Os resultados mostram que, em nenhuma das três amostras estudadas (crianças brasileiras e inglesas de NSE médio, e crianças brasileiras de orfanatos), houve distinção entre regras morais e convencionais como encontrado por Turiel (1983). O contexto de brincadeira favoreceu, como nos estudos anteriores, o desempenho das crianças inglesas e brasileiras de NSE médio. No entanto, as crianças brasileiras de orfanatos raciocinaram similarmente em ambos os contextos, como acontece quando o conteúdo dos problemas está de acordo com a experiência dos sujeitos (ver Hawkins, Pea, Giick & Scríbner, 1984; Dias e Harris, 1988a, c). Para estas crianças, afirmações que representam violações de regras morais, convencionais ou empíricas para as outras amostras, pareciam ser aceitas como verdades empíricas, facilitando seu desempenho mesmo em problemas apresentados verbalmente, sem necessidade do contexto de brincadeira
Understanding the genetic basis of potato development using a multi-trait QTL analysis
Understanding the genetic basis of plant development in potato requires a proper characterization of plant morphology over time. Parameters related to different aging stages can be used to describe the developmental processes. It is attractive to map these traits simultaneously in a QTL analysis; because the power to detect a QTL will often be improved and it will be easier to identify pleiotropic QTLs. We included complex, agronomic traits together with plant development parameters in a multi-trait QTL analysis. First, the results of our analysis led to coherent insight into the genetic architecture of complex traits in potato. Secondly, QTL for parameters related to plant development were identified. Thirdly, pleiotropic regions for various types of traits were identified. Emergence, number of main stems, number of tubers and yield were explained by 9, 5, 4 and 6 QTL, respectively. These traits were measured once during the growing season. The genetic control of flowering, senescence and plant height, which were measured at regular time intervals, was explained by 9, 10 and 12 QTL, respectively. Genetic relationships between aboveground and belowground traits in potato were observed in 14 pleiotropic QTL. Some of our results suggest the presence of QTL-by-Environment interactions. Therefore, additional studies comparing development under different photoperiods are required to investigate the plasticity of the crop
Search for lepton-flavor violation at HERA
A search for lepton-flavor-violating interactions and has been performed with the ZEUS detector using the entire HERA I
data sample, corresponding to an integrated luminosity of 130 pb^{-1}. The data
were taken at center-of-mass energies, , of 300 and 318 GeV. No
evidence of lepton-flavor violation was found, and constraints were derived on
leptoquarks (LQs) that could mediate such interactions. For LQ masses below
, limits were set on , where
is the coupling of the LQ to an electron and a
first-generation quark , and is the branching ratio of
the LQ to the final-state lepton ( or ) and a quark . For
LQ masses much larger than , limits were set on the four-fermion
interaction term for LQs that couple to an electron and a quark
and to a lepton and a quark , where and are
quark generation indices. Some of the limits are also applicable to
lepton-flavor-violating processes mediated by squarks in -Parity-violating
supersymmetric models. In some cases, especially when a higher-generation quark
is involved and for the process , the ZEUS limits are the most
stringent to date.Comment: 37 pages, 10 figures, Accepted by EPJC. References and 1 figure (Fig.
6) adde
Multijet production in neutral current deep inelastic scattering at HERA and determination of alpha_s
Multijet production rates in neutral current deep inelastic scattering have
been measured in the range of exchanged boson virtualities 10 < Q2 < 5000 GeV2.
The data were taken at the ep collider HERA with centre-of-mass energy sqrt(s)
= 318 GeV using the ZEUS detector and correspond to an integrated luminosity of
82.2 pb-1. Jets were identified in the Breit frame using the k_T cluster
algorithm in the longitudinally invariant inclusive mode. Measurements of
differential dijet and trijet cross sections are presented as functions of jet
transverse energy E_{T,B}{jet}, pseudorapidity eta_{LAB}{jet} and Q2 with
E_{T,B}{jet} > 5 GeV and -1 < eta_{LAB}{jet} < 2.5. Next-to-leading-order QCD
calculations describe the data well. The value of the strong coupling constant
alpha_s(M_Z), determined from the ratio of the trijet to dijet cross sections,
is alpha_s(M_Z) = 0.1179 pm 0.0013(stat.) {+0.0028}_{-0.0046}(exp.)
{+0.0064}_{-0.0046}(th.)Comment: 22 pages, 5 figure
Measurement of (anti)deuteron and (anti)proton production in DIS at HERA
The first observation of (anti)deuterons in deep inelastic scattering at HERA
has been made with the ZEUS detector at a centre-of-mass energy of 300--318 GeV
using an integrated luminosity of 120 pb-1. The measurement was performed in
the central rapidity region for transverse momentum per unit of mass in the
range 0.3<p_T/M<0.7. The particle rates have been extracted and interpreted in
terms of the coalescence model. The (anti)deuteron production yield is smaller
than the (anti)proton yield by approximately three orders of magnitude,
consistent with the world measurements.Comment: 26 pages, 9 figures, 5 tables, submitted to Nucl. Phys.
Photoproduction of mesons associated with a leading neutron
The photoproduction of mesons associated with a leading
neutron has been observed with the ZEUS detector in collisions at HERA
using an integrated luminosity of 80 pb. The neutron carries a large
fraction, {}, of the incoming proton beam energy and is detected at
very small production angles, { mrad}, an indication of
peripheral scattering. The meson is centrally produced with
pseudorapidity {
GeV}, which is large compared to the average transverse momentum of the neutron
of 0.22 GeV. The ratio of neutron-tagged to inclusive production is
in the photon-proton
center-of-mass energy range { GeV}. The data suggest that the
presence of a hard scale enhances the fraction of events with a leading neutron
in the final state.Comment: 28 pages, 4 figures, 2 table
Measurement of beauty production in deep inelastic scattering at HERA
The beauty production cross section for deep inelastic scattering events with
at least one hard jet in the Breit frame together with a muon has been
measured, for photon virtualities Q^2 > 2 GeV^2, with the ZEUS detector at HERA
using integrated luminosity of 72 pb^-1. The total visible cross section is
sigma_b-bbar (ep -> e jet mu X) = 40.9 +- 5.7 (stat.) +6.0 -4.4 (syst.) pb. The
next-to-leading order QCD prediction lies about 2.5 standard deviations below
the data. The differential cross sections are in general consistent with the
NLO QCD predictions; however at low values of Q^2, Bjorken x, and muon
transverse momentum, and high values of jet transverse energy and muon
pseudorapidity, the prediction is about two standard deviations below the data.Comment: 18 pages, 4 figure
Measurement of charm fragmentation ratios and fractions in photoproduction at HERA
The production of D^*+, D^0, D^+, D_s^+ and Lambda_c^+ charm hadrons and
their antiparticles in ep scattering at HERA was measured with the ZEUS
detector using an integrated luminosity of 79 pb^-1. The measurement has been
performed in the photoproduction regime with the exchanged-photon virtuality
Q^2 < 1 GeV^2 and for photon-proton centre-of-mass energies in the range 130 <
W < 300 GeV. The charm hadrons were reconstructed in the range of transverse
momentum p_T(D, Lambda_c) > 3.8 GeV and pseudorapidity |eta(D, Lambda_c)| <
1.6. The production cross sections were used to determine the ratio of neutral
and charged D-meson production rates, R_u/d, the strangeness-suppression
factor, gamma_s, and the fraction of charged D mesons produced in a vector
state, P_v^d. The measured R_u/d and gamma_s values agree with those obtained
in deep inelastic scattering and in e^+e^- annihilations. The measured P_v^d
value is smaller than, but consistent with, the previous measurements. The
fractions of c quarks hadronising as a particular charm hadron, f(c -> D,
Lambda_c), were derived in the given kinematic range. The measured open-charm
fragmentation fractions are consistent with previous results, although the
measured f(c -> D^*+) is smaller and f(c -> Lambda_c^+) is larger than those
obtained in e^+e^- annihilations. These results generally support the
hypothesis that fragmentation proceeds independently of the hard sub-process.Comment: 29 pages, 5 figures, 6 tables; minor text revision
Observation of isolated high-E_T photons in deep inelastic scattering
First measurements of cross sections for isolated prompt photon production in
deep inelastic ep scattering have been made using the ZEUS detector at the HERA
electron-proton collider using an integrated luminosity of 121 pb^-1. A signal
for isolated photons in the transverse energy and rapidity ranges 5 < E_T^gamma
< 10 GeV and -0.7 < eta^gamma < 0.9 was observed for virtualities of the
exchanged photon of Q^2 > 35 GeV^2. Cross sections are presented for inclusive
prompt photons and for those accompanied by a single jet in the range E_T^jet
\geq 6 GeV and -1.5 \leq eta^jet < 1.8. Calculations at order alpha^3alpha_s
describe the data reasonably well.Comment: 16 pages, 5 figure
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