601 research outputs found

    Expression patterns of class I KNOX and YABBY genes in Ruscus aculeatus (Asparagaceae) with implications for phylloclade homology

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    金沢大学大学院自然科学研究科生物多様性動態学金沢大学理学部STM (RaSTM) and YAB2 (RaYAB2) homologues were isolated from Ruscus aculeatus (Asparagaceae, monocots), and their expressions were analyzed by real-time polymerase chain reaction (PCR) to assess hypotheses on the evolutionary origin of the phylloclade in the Asparagaceae. In young shoot buds, RaSTM is expressed in the shoot apex, while RaYAB2 is expressed in the scale leaf subtending the shoot bud. This expression pattern is shared by other angiosperms, suggesting that the expression patterns of RaSTM and RaYAB2 are useful as molecular markers to identify the shoot and leaf, respectively. RaSTM and RaYAB2 are expressed concomitantly in phylloclade primordia. These results suggest that the phylloclade is not homologous to either the shoot or leaf, but that it has a double organ identity. © Springer-Verlag 2007

    A case of giant saphenous vein graft aneurysm followed serially after coronary artery bypass surgery

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    Saphenous vein graft aneurysm (SVGA) is one of the chronic complications after coronary aorta bypass grafting (CABG) and may be caused by atherosclerosis-like phenomena of the vein graft, weakness around the vein valve, rupturing of the suture of the graft anastomosis, or perioperative graft injury. We describe a case of a large, growing saphenous vein graft aneurysm that was followed serially by chest radiography and computed tomography. Eighteen years after CABG, an SVGA (23 × 24 mm) was incidentally detected. The patient was asymptomatic and was followed conservatively. Four years later, coronary computed tomographic angiography showed that the giant aneurysm had grown to 52.1 by 63.8 mm and revealed a second, smaller aneurysm. Finally, the SVG was ultimately resected without bypass via off-pump surgery. Therefore, this case suggested that aggressive treatment that includes surgical intervention should be considered before the aneurysm becomes larger, even if it is asymptomatic

    Higher-order correlations between different moments of two flow amplitudes in Pb-Pb collisions at sNN=5.02\sqrt{s_{\rm NN}}=5.02 TeV

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    International audienceThe correlations between different moments of two flow amplitudes, extracted with the recently developed asymmetric cumulants, are measured in Pb-Pb collisions at sNN=5.02\sqrt{s_{\rm NN}} = 5.02 TeV recorded by the ALICE detector at the LHC. The magnitudes of the measured observables show a dependence on the different moments as well as on the collision centrality, indicating the presence of non-linear response in all even moments up to the eighth. Furthermore, the higher-order asymmetric cumulants show different signatures than the symmetric and lower-order asymmetric cumulants. Comparisons with state-of-the-art event generators using two different parameterizations obtained from Bayesian optimization show differences between data and simulations in many of the studied observables, indicating a need for further tuning of the models behind those event generators. These results provide new and independent constraints on the initial conditions and transport properties of the system created in heavy-ion collisions

    First measurement of the t|t|-dependence of incoherent J/ψ\psi photonuclear production

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    International audienceThe first measurement of the cross section for incoherent photonuclear production of J/ψ\psi vector meson as a function of the Mandelstam t|t| variable is presented. The measurement was carried out with the ALICE detector at midrapidity, y<0.8|y|<0.8, using ultra-peripheral collisions of Pb nuclei at a centre-of-mass energy per nucleon pair sNN=5.02\sqrt{s_{\mathrm{NN}}} = 5.02 TeV. This rapidity interval corresponds to a Bjorken-xx range (0.3(0.3-1.4)×1031.4)\times 10^{-3}. Cross sections are reported in five t|t| intervals in the range 0.04<t<10.04<|t|<1~GeV2^2 and compared to the predictions of different models. Models that ignore quantum fluctuations of the gluon density in the colliding hadron predict a t|t|-dependence of the cross section much steeper than in data. The inclusion of such fluctuations in the same models provides a better description of the data

    Data-driven precision determination of the material budget in ALICE

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    The knowledge of the material budget with a high precision is fundamental for measurements of direct photon production using the photon conversion method due to its direct impact on the total systematic uncertainty. Moreover, it influences many aspects of the charged-particle reconstruction performance. In this article, two procedures to determine data-driven corrections to the material-budget description in ALICE simulation software are developed. One is based on the precise knowledge of the gas composition in the Time Projection Chamber. The other is based on the robustness of the ratio between the produced number of photons and charged particles, to a large extent due to the approximate isospin symmetry in the number of produced neutral and charged pions. Both methods are applied to ALICE data allowing for a reduction of the overall material budget systematic uncertainty from 4.5% down to 2.5%. Using these methods, a locally correct material budget is also achieved. The two proposed methods are generic and can be applied to any experiment in a similar fashion.The knowledge of the material budget with a high precision is fundamental for measurements of direct photon production using the photon conversion method due to its direct impact on the total systematic uncertainty. Moreover, it influences many aspects of the charged-particle reconstruction performance. In this article, two procedures to determine data-driven corrections to the material-budget description in ALICE simulation software are developed. One is based on the precise knowledge of the gas composition in the Time Projection Chamber. The other is based on the robustness of the ratio between the produced number of photons and charged particles, to a large extent due to the approximate isospin symmetry in the number of produced neutral and charged pions. Both methods are applied to ALICE data allowing for a reduction of the overall material budget systematic uncertainty from 4.5% down to 2.5%. Using these methods, a locally correct material budget is also achieved. The two proposed methods are generic and can be applied to any experiment in a similar fashion

    Measurement of Non-prompt D0\rm D^0-meson Elliptic Flow in Pb-Pb Collisions at sNN\sqrt{s_{\rm NN}} = 5.02 TeV

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    International audienceThe elliptic flow (v2v_2) of D0\rm D^0 mesons from beauty-hadron decays (non-prompt D0\rm D^0) was measured in midcentral (30-50%) Pb-Pb collisions at a centre-of-mass energy per nucleon pair sNN\sqrt{s_{\rm NN}} = 5.02 TeV with the ALICE detector at the LHC. The D0\rm D^0 mesons were reconstructed at midrapidity (y<0.8|y|<0.8) from their hadronic decay D0Kπ+\mathrm{D^0 \to K^-\pi^+}, in the transverse momentum interval 2<pT<122 < p_{\rm T} < 12 GeV/cc. The result indicates a positive v2v_2 for non-prompt D0\rm D^0 mesons with a significance of 2.7σ\sigma. The non-prompt D0\rm D^0-meson v2v_2 is lower than that of prompt non-strange D mesons with 3.2σ\sigma significance in 2<pT<82 < p_{\rm T} < 8 GeV/cc, and compatible with the v2v_2 of beauty-decay electrons. Theoretical calculations of beauty-quark transport in a hydrodynamically expanding medium describe the measurement within uncertainties

    Skewness and kurtosis of mean transverse momentum fluctuations at the LHC energies

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    International audienceThe first measurements of skewness and kurtosis of mean transverse momentum (pT\langle p_\mathrm{T}\rangle) fluctuations are reported in Pb-Pb collisions at sNN\sqrt{s_\mathrm{NN}} = 5.02 TeV, Xe-Xe collisions at sNN\sqrt{s_\mathrm{NN}}== 5.44 TeV and pp collisions at s=5.02\sqrt{s} = 5.02 TeV using the ALICE detector. The measurements are carried out as a function of system size dNch/dηη<0.51/3\langle \mathrm{d}N_\mathrm{ch}/\mathrm{d}\eta\rangle_{|\eta|<0.5}^{1/3}, using charged particles with transverse momentum (pTp_\mathrm{T}) and pseudorapidity (η\eta), in the range 0.2<pT<3.00.2 < p_\mathrm{T} < 3.0 GeV/cc and η<0.8|\eta| < 0.8, respectively. In Pb-Pb and Xe-Xe collisions, positive skewness is observed in the fluctuations of pT\langle p_\mathrm{T}\rangle for all centralities, which is significantly larger than what would be expected in the scenario of independent particle emission. This positive skewness is considered a crucial consequence of the hydrodynamic evolution of the hot and dense nuclear matter created in heavy-ion collisions. Furthermore, similar observations of positive skewness for minimum bias pp collisions are also reported here. Kurtosis of pT\langle p_\mathrm{T}\rangle fluctuations is found to be in good agreement with the kurtosis of Gaussian distribution, for most central Pb-Pb collisions. Hydrodynamic model calculations with MUSIC using Monte Carlo Glauber initial conditions are able to explain the measurements of both skewness and kurtosis qualitatively from semicentral to central collisions in Pb--Pb system. Color reconnection mechanism in PYTHIA8 model seems to play a pivotal role in capturing the qualitative behavior of the same measurements in pp collisions

    Photoproduction of K+^{+}K^{-} pairs in ultra-peripheral collisions

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    International audienceK+^{+}K^{-} pairs may be produced in photonuclear collisions, either from the decays of photoproduced ϕ(1020)\phi (1020) mesons, or directly as non-resonant K+^{+}K^{-} pairs. Measurements of K+^{+}K^{-} photoproduction probe the couplings between the ϕ(1020)\phi (1020) and charged kaons with photons and nuclear targets. We present the first measurement of coherent photoproduction of K+^{+}K^{-} pairs on lead ions in ultra-peripheral collisions using the ALICE detector, including the first investigation of direct K+^{+}K^{-} production. There is significant K+^{+}K^{-} production at low transverse momentum, consistent with coherent photoproduction on lead targets. In the mass range 1.1<MKK<1.41.1 < M_{\rm{KK}} < 1.4 GeV/c2c^2 above the ϕ(1020)\phi (1020) resonance, for rapidity yKK<0.8|y_{\rm{KK}}|<0.8 and pT,KK<0.1p_{\rm T,KK} < 0.1 GeV/cc, the measured coherent photoproduction cross section is dσ/dy\mathrm{d}\sigma/\mathrm{d}y = 3.37 ± 0.61\pm\ 0.61 (stat.) ± 0.15\pm\ 0.15 (syst.) mb. The centre-of-mass energy per nucleon of the photon-nucleus (Pb) system WγPb,nW_{\gamma \mathrm{Pb, n}} ranges from 33 to 188 GeV, far higher than previous measurements on heavy-nucleus targets. The cross section is larger than expected for ϕ(1020)\phi (1020) photoproduction alone. The mass spectrum is fit to a cocktail consisting of ϕ(1020)\phi (1020) decays, direct K+^{+}K^{-} photoproduction, and interference between the two. The confidence regions for the amplitude and relative phase angle for direct K+^{+}K^{-} photoproduction are presented

    Photoproduction of K+^{+}K^{-} pairs in ultra-peripheral collisions

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    International audienceK+^{+}K^{-} pairs may be produced in photonuclear collisions, either from the decays of photoproduced ϕ(1020)\phi (1020) mesons, or directly as non-resonant K+^{+}K^{-} pairs. Measurements of K+^{+}K^{-} photoproduction probe the couplings between the ϕ(1020)\phi (1020) and charged kaons with photons and nuclear targets. We present the first measurement of coherent photoproduction of K+^{+}K^{-} pairs on lead ions in ultra-peripheral collisions using the ALICE detector, including the first investigation of direct K+^{+}K^{-} production. There is significant K+^{+}K^{-} production at low transverse momentum, consistent with coherent photoproduction on lead targets. In the mass range 1.1<MKK<1.41.1 < M_{\rm{KK}} < 1.4 GeV/c2c^2 above the ϕ(1020)\phi (1020) resonance, for rapidity yKK<0.8|y_{\rm{KK}}|<0.8 and pT,KK<0.1p_{\rm T,KK} < 0.1 GeV/cc, the measured coherent photoproduction cross section is dσ/dy\mathrm{d}\sigma/\mathrm{d}y = 3.37 ± 0.61\pm\ 0.61 (stat.) ± 0.15\pm\ 0.15 (syst.) mb. The centre-of-mass energy per nucleon of the photon-nucleus (Pb) system WγPb,nW_{\gamma \mathrm{Pb, n}} ranges from 33 to 188 GeV, far higher than previous measurements on heavy-nucleus targets. The cross section is larger than expected for ϕ(1020)\phi (1020) photoproduction alone. The mass spectrum is fit to a cocktail consisting of ϕ(1020)\phi (1020) decays, direct K+^{+}K^{-} photoproduction, and interference between the two. The confidence regions for the amplitude and relative phase angle for direct K+^{+}K^{-} photoproduction are presented
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