Hybrid Al2O3-CH3NH3PbI3 Perovskites towards Avoiding Toxic Solvents

We report the synthesis of organometal halide perovskites by milling CH3NH3I and PbI2 directly with an Al2O3 scaffold to create hybrid Al2O3-CH3NH3PbI3 perovskites, without the use of organic capping ligands that otherwise limit the growth of the material in the three dimensions. Not only does this improve the ambient stability of perovskites in air (100 min versus 5 min for dimethylformamide (DMF)-processed material), the method also uses much fewer toxic solvents (terpineol versus dimethylformamide). This has been achieved by solid-state reaction of the perovskite precursors to produce larger perovskite nanoparticles. The resulting hybrid perovskite–alumina particles effectively improve the hydrophobicity of the perovskite phase whilst the increased thermal mass of the Al2O3 increases the thermal stability of the organic cation. Raman data show the incorporation of Al2O3 shifts the perovskite spectrum, suggesting the formation of a hybrid 3D mesoporous stack. Laser-induced current mapping (LBIC) and superoxide generation measurements, coupled to thermogravimetric analysis, show that these hybrid perovskites demonstrate slightly improved oxygen and thermal stability, whilst ultra-fast X-ray diffraction studies using synchrotron radiation show substantial (20×) increase in humidity stability. Overall, these data show considerably improved ambient stability of the hybrid perovskites compared to the solution-processed material

100 Cartas para Paulo Freire de quienes pretendemos Enseñar

Realizar un texto colectivo como “100 Cartas para Paule Freire de quienes pretendemos Enseñar”, es un desafío al reunir el aprehender desde el sentido profesional de la educación y con el espíritu de transformación, desde la educación como un espacio endógeno de revolución y exógeno a las comunidades y sociedades, en busca de un sentido de identidad. Hoy desde una crítica decolonial, antirracista, feminista y ecologica en la construcción de un sentido real que busque enfrentar el sistema hegemónico y destructivo que se ha impuesto con explotación, sangre y libertades de nuestro pueblo

Reproducibility of fluorescent expression from engineered biological constructs in E. coli

We present results of the first large-scale interlaboratory study carried out in synthetic biology, as part of the 2014 and 2015 International Genetically Engineered Machine (iGEM) competitions. Participants at 88 institutions around the world measured fluorescence from three engineered constitutive constructs in E. coli. Few participants were able to measure absolute fluorescence, so data was analyzed in terms of ratios. Precision was strongly related to fluorescent strength, ranging from 1.54-fold standard deviation for the ratio between strong promoters to 5.75-fold for the ratio between the strongest and weakest promoter, and while host strain did not affect expression ratios, choice of instrument did. This result shows that high quantitative precision and reproducibility of results is possible, while at the same time indicating areas needing improved laboratory practices.Peer reviewe

Forward rapidity J/ψ production as a function of charged-particle multiplicity in pp collisions at s \sqrt{s} = 5.02 and 13 TeV

International audienceThe production of J/ψ is measured as a function of charged-particle multiplicity at forward rapidity in proton-proton (pp) collisions at center-of-mass energies $\sqrt{s}$ = 5.02 and 13 TeV. The J/ψ mesons are reconstructed via their decay into dimuons in the rapidity interval (2.5 < y < 4.0), whereas the charged-particle multiplicity density (dN$_{ch}$/dη) is measured at midrapidity (|η| < 1). The production rate as a function of multiplicity is reported as the ratio of the yield in a given multiplicity interval to the multiplicity-integrated one. This observable shows a linear increase with charged-particle multiplicity normalized to the corresponding average value for inelastic events (dN$_{ch}$/dη/〈dN$_{ch}$/dη〉), at both the colliding energies. Measurements are compared with available ALICE results at midrapidity and theoretical model calculations. First measurement of the mean transverse momentum (〈p$_{T}$〉) of J/ψ in pp collisions exhibits an increasing trend as a function of dN$_{ch}$/dη/〈dN$_{ch}$/dη〉 showing a saturation towards high charged-particle multiplicities.[graphic not available: see fulltext

Neutral to charged kaon yield fluctuations in Pb – Pb collisions at sNN\sqrt{s_{\rm NN}} = 2.76 TeV

We present the first measurement of event-by-event fluctuations in the kaon sector in Pb – Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with the ALICE detector at the LHC. The robust fluctuation correlator ν$_{dyn}$ is used to evaluate the magnitude of fluctuations of the relative yields of neutral and charged kaons, as well as the relative yields of charged kaons, as a function of collision centrality and selected kinematic ranges. While the correlator ν$_{dyn}$[K$^+$,K$^−$] exhibits a scaling approximately in inverse proportion of the charged particle multiplicity, ν$_{dyn}$[K$_S^0$,K$^\pm$] features a significant deviation from such scaling. Within uncertainties, the value of ν$_{dyn}$[K$_S^0$,K$^\pm$] is independent of the selected transverse momentum interval, while it exhibits a pseudorapidity dependence. The results are compared with HIJING, AMPT and EPOS–LHC predictions, and are further discussed in the context of the possible production of disoriented chiral condensates in central Pb – Pb collisions

First study of the two-body scattering involving charm hadrons

This article presents the first measurement of the interaction between charm hadrons and nucleons. The two-particle momentum correlations of $pD^-$ and $\bar{p}D^+$ pairs are measured by the ALICE Collaboration in high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV. The data are compatible with the Coulomb-only interaction hypothesis within (1.1–1.5)σ. The level of agreement slightly improves if an attractive nucleon $(N)\bar{D}$ strong interaction is considered, in contrast to most model predictions which suggest an overall repulsive interaction. This measurement allows for the first time an estimation of the 68% confidence level interval for the isospin I=0 inverse scattering length of the $N\bar{D}$ state $f_{0,I=0}^{-1}$∈[-0.4,0.9] fm$^{-1}$, assuming negligible interaction for the isospin I=1 channel

W±^\pm-boson production in p−-Pb collisions at sNN=8.16\sqrt{s_{NN}} = 8.16 TeV and PbPb collisions at sNN=5.02\sqrt{s_{NN}} = 5.02 TeV

The production of the W$^{±}$ bosons measured in p–Pb collisions at a centre-of-mass energy per nucleon–nucleon collision $\sqrt{s_{\textrm{NN}}}$ = 8.16 TeV and Pb–Pb collisions at $\sqrt{s_{\textrm{NN}}}$ = 5.02 TeV with ALICE at the LHC is presented. The W$^{±}$ bosons are measured via their muonic decay channel, with the muon reconstructed in the pseudorapidity region −4 10 GeV/c. While in Pb–Pb collisions the measurements are performed in the forward (2.5 10$GeV/$c$. While in Pb$-$Pb collisions the measurements are performed in the forward ($2.5 < y^\mu_{\rm cms} < 4$) rapidity region, in p$-$Pb collisions, where the centre-of-mass frame is boosted with respect to the laboratory frame, the measurements are performed in the backward ($-4.46 < y^\mu_{\rm cms} < -2.96$) and forward ($2.03 < y^\mu_{\rm cms} < 3.53$) rapidity regions. The W$^{-}$and W$^{+}$production cross sections, lepton-charge asymmetry, and nuclear modification factors are evaluated as a function of the muon rapidity. In order to study the production as a function of the p$-$Pb collision centrality, the production cross sections of the W$^{-}$and W$^{+}$bosons are combined and normalised to the average number of binary nucleon$-$nucleon collision$\langle N_\mathrm{coll} \rangle$. In Pb$-$Pb collisions, the same measurements are presented as a function of the collision centrality. Study of the binary scaling of the W$^\pm$-boson cross sections in p$-$Pb and Pb$-$Pb collisions is also reported. The results are compared with perturbative QCD (pQCD) calculations, with and without nuclear modifications of the Parton Distribution Functions (PDFs), as well as with available data at the LHC. Significant deviations from the theory expectations are found in the two collision systems, indicating that the measurements can provide additional constraints for the determination of nuclear PDF (nPDFs) and in particular of the light-quark distributions

Study of charged particle production at high pT using event topology in pp, p–Pb and Pb–Pb collisions at <math altimg="si1.svg"><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi mathvariant="normal">NN</mi></mrow></msub></mrow></msqrt><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mn>5.02</mn></math>TeV

International audienceThis letter reports measurements which characterize the underlying event associated with hard scatterings at mid-pseudorapidity (|η|&lt;0.8) in pp, p–Pb and Pb–Pb collisions at centre-of-mass energy per nucleon pair, sNN=5.02TeV. The measurements are performed with ALICE at the LHC. Different multiplicity classes are defined based on the event activity measured at forward rapidities. The hard scatterings are identified by the leading particle defined as the charged particle with the largest transverse momentum (pT) in the collision and having 8 &lt;pT&lt;15GeV/c. The pT spectra of associated particles (0.5 ≤pT&lt;6GeV/c) are measured in different azimuthal regions defined with respect to the leading particle direction: toward, transverse, and away. The associated charged particle yields in the transverse region are subtracted from those of the away and toward regions. The remaining jet-like yields are reported as a function of the multiplicity measured in the transverse region. The measurements show a suppression of the jet-like yield in the away region and an enhancement of high-pT associated particles in the toward region in central Pb–Pb collisions, as compared to minimum-bias pp collisions. These observations are consistent with previous measurements that used two-particle correlations, and with an interpretation in terms of parton energy loss in a high-density quark gluon plasma. These yield modifications vanish in peripheral Pb–Pb collisions and are not observed in either high-multiplicity pp or p–Pb collisions