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Infinite-layer (IL) nickelates are an emerging family of superconductors whose similarities and differences to cuprate superconductors are under intense debate. To date, the IL phase of nickelates can only be reached via topotactic oxygen reduction of the perovskite phase, using H$_2$ gas or reducing agents such as CaH$_2$. While the topotactic reduction method has been widely employed on thin film and polycrystalline powder samples, the reduction of La$_{1-x}$Ca$_x$NiO$_3$ single-crystals with lateral dimensions up to 150 $\mu$m was achieved only recently, using an indirect contact method with CaH$_2$. Here we report the topotactic transformation of much larger LaNiO$_3$ crystals with lateral dimensions of more than one millimeter, via direct contact with CaH$_2$. We characterize the crystalline, magnetic, and electronic properties of the obtained IL LaNiO$_{2}$ crystals by powder and single-crystal x-ray diffraction (XRD), magnetometry, electrical transport, and x-ray photoelectron spectroscopy (XPS) measurements. The amount of incorporated topotactic hydrogen due to the reduction process is determined by a gas extraction method. In addition, we investigate the evolution of the lattice parameters under hydrostatic pressure up to 12 GPa, using high-resolution synchrotron XRD. Furthermore, we provide a direct comparison of several physical properties of the LaNiO$_{2}$ crystals to their powder and thin film counterparts.

co-auteur étranger; International audience; The additional work we have done using our new laser heating in the diamond anvil cell system since the publication of Andrault et al. (Phys Chem Mineral 47(2), 2020) leads us to the conclusion that there was a systematic bias in the determination of temperature. First, the temperature of the W-lamp used for the calibration of the optical system was overestimated by ~ 22 K at 2273 K. Then, we made the assumption that hot SiO2 was a grey-body (constant emissivity ε(λ)), while the available measurements suggest instead that ε(λ) of SiO2 is similar to that of tungsten. Applying these two corrections lowers the SiO2 melting temperatures significantly. In LMV, we performed a new experimental determination of the SiO2 melting temperature, at 5000 (200) K and ~ 70 (4) GPa, which is well compatible with the amplitude of the correction proposed. The reevaluation of the melting temperature profile does not affect largely the interpretations or the main conclusions presented in Andrault et al. (Phys Chem Mineral 47(2), 2020). Within the stability field of stishovite, the melting curve still presents a relatively sharp change of slope at P-T recalculated as ~ 40 GPa and ~ 4800 K. It is related to a change of the melt structure. At higher pressures, the melting curve is almost flat up to the subsolidus transition from stishovite to the CaCl2-form around 85 GPa, where the slope of the melting curve increases again up to ~ 120 GPa. We present corrected figures and tables of the original publication.

International audience; The martensitic transformation is a fundamental physical phenomenon at the origin of important industrial applications. However, the underlying microscopic mechanism, which is of critical importance to explain the outstanding mechanical properties of martensitic materials, is still not fully understood. This is because for most martensitic materials the transformation is a fast process that makes in situ studies extremely challenging. Noble solids krypton and xenon undergo a progressive pressure-induced face-centered cubic (fcc) to hexagonal close-packed (hcp) martensitic transition with a very wide coexistence domain. Here, we took advantage of this unique feature to study the detailed transformation progress at the atomic level by employing in situ x-ray diffraction and absorption spectroscopy. We evidenced a four-stage pathway and suggest that the lattice mismatch between the fcc and hcp forms plays a key role in the generation of strain. We also determined precisely the effect of the transformation on the compression behavior of these materials.

Frontiers in electronic materials 2, 837651 (2022). doi:10.3389/femat.2022.837651, The search for room temperature superconductivity has accelerated in the last few years driven by experimentally accessible theoretical predictions that indicated alloying dense hydrogen with other elements could produce conventional superconductivity at high temperatures and pressures. These predictions helped inform the synthesis of simple binary hydrides that culminated in the discovery of the superhydride LaH10 with a superconducting transition temperature Tc of 260 K at 180 GPa. We have now successfully synthesized a metallic La-based superhydride with an initial Tc of 294 K. When subjected to subsequent thermal excursions that promoted a chemical reaction to a higher order system, the Tc onset was driven irreversibly to 556 K. X-ray characterization confirmed the formation of a distorted LaH10 based backbone that suggests the formation of ternary or quaternary compounds with substitution at the La and/or H sites. The results provide evidence for hot superconductivity, aligning with recent predictions for higher order hydrides under pressure., Published by Frontiers Media, Lausanne

Knowledge on the temperature distribution in high pressure and temperature devices is important for the interpretation of data and can often not be obtained from experiments. Here, we report on the thermal characteristics of the most employed Paris–Edinburgh press assemblies for in-situ X-ray purposes using finite element calculations. The maximal horizontal T variations in the sample are found to be small and amount maximal 50 K at 2500 K. Temperature differences between the sample and the calibrant material are in the same order of magnitude only if the latter is placed well centred on the sample capsule. The present (pure thermal) calculations can only partly reproduce the discrepancies between experimentally determined input power to T relations (1000 K at 350 W) indicating that different deformation behaviours of assemblies may play a crucial role. Based on the obtained results we present an optimized assembly in terms of sample temperature and gradients.

In the framework of Clean Sky 2 LPA (Large Passenger Aircraft) Platform 1 program, CIRA is the leader of the WP1.3.5 aiming at developing an advanced Autopilot, and a dedicated testing framework for supporting the Dynamically Scaled Vehicle flight demonstrations. The presented Autopilot not only includes basic features like other commercial products, but also introduces new characteristics specifically designed for supporting scaled flight testing on unconventional A/C (aircraft) configurations, allowing implementation of advanced control laws architectures and strategies. To facilitate the flight testing, the framework integrates a dedicated SW function for automated tests, so avoiding,as much as possible, manual piloting and increasing test condition repeatability. Moreover, to facilitate future modifications, the framework includes a library of Simulink modules including basic guidance and control modules, and makes available to the final user the possibility to use a simple procedure for efficiently and reliably generating embedded real time code to be deployed on the on-board HW. Finally, the functional architecture has been designed to be compatible with the highest levels of autonomy with the aim to be easily integrated with additional autonomous functions, so to support future UAS (Unmanned Aerial Systems) operations. This goal has been pursued by developing a modular and scalar architecture and by adding the capability to execute complex automatic functions based on a simple flight instruction list defined by the remote pilot or the ground operator. To this end, the developed programming meta-language would allow performing mission tasks with better efficiency and effectiveness. For supporting and referencing these activities, a specific state of art study on autonomy classification has been conducted as well.

The crystalline A17 layered structure of Phosphorus, commonly indicated as Black Phosphorus, was first high pressure synthesized by Bridgman back in 1914 [1] and is currently attracting a growing attention from the community of chemists, physicists and materials scientist due to the appealing properties of its monolayer counterpart named Phosphorene [2]. Recently, high pressure studies have reported the observation of a pseudo simple cubic structure (p-sc) in the phase diagram of Phosphorus up to 30 GPa. This observation significantly raises the pressure limit for the layered structures of P and opens new perspectives for their stabilization and functionalization, possibly leading to the recovery of new materials at ambient conditions [3- 4]. On the other side, the experimental report of superconductivity in compressed PH 3 [5], with still no structural characterization and ascribed to the formation of different chemical species at high pressure in analogy to H 2 S, has been so far stimulating experimental and theoretical efforts to investigate the stability of different systems containing Phosphorus and Hydrogen at high pressure which can be responsible for such behavior [6,7]. In this study we investigated the chemical reactivity of black Phosphorus and molecular Hydrogen under high pressure and high temperature conditions, which were generated using a membrane Diamond Anvil Cell (DAC) in combination with laser heating. The sample was probed by means of synchrotron X-ray diffraction at ESRF-ID27 and by FTIR and Raman spectroscopy at LENS. A detailed Raman analysis of the sample with micron sized spatial resolution was performed in different spectral regions. The visual inspection of the sample after laser heating below the melting line and within the phase boundary of the A17 structure, clearly showed the consumption of Phosphorus. Correspondingly, the analysis of the experimental XRD and spectroscopic data indicated the formation of different reaction products containing P-H bonds, particularly PH 3 and H-functionalized Phosphorus fragments. A further increase in pressure after laser heating was responsible for the crystallization of a solid product identified as a van der Waals compound made of PH 3 and H 2 , whose crystal structure was accurately determined from single crystal data. The identification of this compound, representing so far a missing piece, consistently fills a gap in the periodic table for Phosphorus, in agreement with analogous compounds reported in literature formed by the hydrides of Carbon (CH 4 ), Sulphur (H 2 S), Selenium (H 2 Se) and Iodine (HI) in the presence of H 2 [8-11]. Furthermore, the observation of this compound provides new experimental evidence for the formation of unexpected chemical species originating from the high pressure chemistry of Phosphorus and Hydrogen, possibly shedding new light on the high pressure superconductivity of Phosphorus hydrides. Acknowledgments: Thanks are expressed to EC through the European Research Council (ERC) for funding the project PHOSFUN "Phosphorene functionalization: a new platform for advanced multifunctional materials" (Grant Agreement No. 670173) through an ERC Advanced Grant. [1] P. W. Bridgman, J. Am. Chem. Soc. 1914, 36, 1344. [2] M. Peruzzini et al., Eur. J. Inorg. Chem. 2019, 1476. [3] D. Scelta et al., Angew. Chem. Int. Ed. 2017, 56, 14135. [4] D. Scelta et al., Chem. Commun. 2018, 54, 10554. [5] A. P. Drozdov et al., arXiv:1508.06224 (2015). [6] T. Bi et al., Angew. Chem. Int. Ed. 2017, 56, 10192. [7 M. Liu et al. J. Raman Spectrosc. 2018, 49, 721. [8] M. S. Somayazulu et al., Science 1996, 271, 1400. [9] T. A. Strobel et al. Phys. Rev. Lett. 2011, 107, 255503 . [10] E. J. Pace et al., J. Chem. Phys. 2017, 147, 184303. [11] Binns J. et al., Phys. Rev. B 2018, 97, 024111.

BaFe

The decay of Λ -hypernuclei without π emission, known as Non-Mesonic Weak Decay (NMWD), gives an effective tool to investigate Δ S = 1 four-baryon interactions. It was theoretically suggested that the two-nucleon induced mechanism could play a substantial role in reproducing the observed NMWD decay rates and nucleon spectra, but at present no direct evidence of such a mechanism has been obtained. The FINUDA experiment, exploiting the possibility to detect both charged and neutral particles coming from the hypernucleus decay, has allowed us to deduce the relative weight of the two nucleon induced decay rate to the total NMWD rate. The value of Γ 2 N / Γ NMWD = 0.21 ± 0.07 stat − 0.02 sys + 0.03 sys has been deduced, well consistent with the previous determinations.

New spectra from the FINUDA experiment of the Non Mesonic Weak Decay (NMWD) proton kinetic energy for 9(Lambda)Be, 11(Lambda)B, 12(Lambda)C, 13(Lambda)C, 15 (Lambda)N and 16(Lambda)O are presented and discussed along with the published data on 5(Lambda)He and 7(Lambda)Li. Exploiting the large mass number range and the low energy threshold (15 MeV) for the proton detection of FINUDA, an evaluation of both Final State Interactions (FSI) and the two nucleon induced NMWD contributions to the decay process has been done. Based on this evaluation, a linear dependence of FSI on the hypernuclear mass number A is found and for the two nucleon stimulated decay rate the experimental value of Gamma2/Gammap=0.43+-0.25 is determined for the first time. A value for the two nucleon stimulated decay rate to the total decay rate Gamma2/GammaNMWD=0.24+-0.10 is also extracted., 11 pages and 2 figures

Recently, simple carbon based polymers have been synthesized at high pressures in silicalite, a pure SiO2 zeolite with a 3D system of mutually interconnected microchannels. These protocols permitted otherwise unstable polymers to be stabilized and protected from the atmosphere and to obtain an entirely novel class of nanocomposites with modified physical properties. In these 3-D systems, channel interconnection may prevent ideal, isolated polymer chains to be obtained. In this work, the high pressure (5-10 GPa) synthesis of two archetypal, linear polymers polyacetylene (PA) and polycarbonyl (pCO) in the 1D channel system of the pure SiO2 zeolite ZSM-22 (TON) has been performed. The two resulting nanocomposites PA/TON and pCO/TON are organic/inorganic composite materials, which are good candidates as highly directional semiconductors and high energy density materials, respectively. The synthesis was performed in diamond anvil cells, starting from dense C2H2 and CO, confined in ZSM-22, and the nanocomposites were recovered at ambient conditions. The monomer polymerization was proven by IR spectroscopy and synchrotron X-ray diffraction measurements. DFT calculations were performed in order to obtain insight about the configurations of the 1D embedded polymers.

The non-mesonic weak decay of Λ-hypernuclei is studied within a microscopic diagrammatic approach which includes, for the first time, the effect or the Δ-baryon resonance. We adopt a nuclear matter formalism extended to finite nuclei via the local density approximation, a one-meson exchange weak transition potential, a Bonn nucleon–nucleon strong potential and a Δ N → N N strong potential based on the Landau–Migdal theory. Ground state correlations and final state interactions (FSI), at second order in the baryon–baryon strong interaction, are introduced on the same footing for all the isospin channels of one- and two-nucleon induced decays. Weak decay rates and single and double-coincidence nucleon spectra are predicted for C Λ 12 and compared with recent KEK and FINUDA data. The Δ ( 1232 ) introduces new FSI-induced decay mechanisms which lead to an improvement when comparing the obtained nucleon spectra with data, while it turns out to have a negligible effect on the decay rates. Discrepancies with experiment remain only for emission spectra involving protons, but are mostly restricted to double-nucleon correlations in the non-back-to-back kinematics.

We investigated the high-pressure behaviour of Fe3+-bearing hydrous phase-X, (K1.307Na0.015)(Mg1.504Fe 0.373 3+ Al0.053Ti 0.004 4+ )Si2O7H0.36, up to 34 GPa at room temperature by synchrotron X-ray powder diffraction. The lattice parameters behave anisotropically, with the [001] direction stiffer than [100]. In the 10−4 to 22 GPa pressure range, the axial bulk moduli are K 0a = 112(3) GPa and K′ = 4, and K 0c = 158(2) GPa and K′ = 4, and the anisotropy of the lattice parameters is β0c :β0a = 0.71:1. The cell volumes are fitted by a second-order Birch–Murnaghan equation of state giving a bulk modulus of K 0 = 127(1) GPa and K′ = 4 in the same pressure range. After 22 GPa, a discontinuity in volume and lattice parameters can be recognized. Sample did not become amorphous up to 34 GPa. The coupled substitution K + Mg = [] + Fe3+ has only a limited influence on the bulk modulus and structural stability of phase-X.

The ratio N n n / N n p between the number of neutron–neutron and neutron–proton pairs emitted in the non–mesonic weak decay of Λ–hypernuclei is calculated within a nuclear matter formalism extended to C Λ 12 via the local density approximation. The single–nucleon emission spectra, N p and N n , are also evaluated. Our formalism takes care of both ground state correlations (gsc) and final state interactions (FSI). The evaluation of N n n / N n p — which, unlike Γ n / Γ p ≡ Γ ( Λ n → n n ) / Γ ( Λ p → n p ) , is an actual observable quantity in non–mesonic decay — is performed within a fully microscopic model where a proper treatment of FSI, gsc and ground state normalization is considered. All the isospin channels contributing to one– and two–nucleon induced decays are included. Our final result for the coincidence number ratio, N n n / N n p = 0.374 , is in agreement with the KEK–E508 datum, ( N n n / N n p ) exp = 0.40 ± 0.10 .

A theoretical review is presented of hypernuclear weak decay, with special emphasis on the non–mesonic modes. We focus on recent progress which lead to the solution of long–standing puzzles on the Γ n / Γ p ratio and on the asymmetry parameter. Perspectives for the future are also indicated.

The contribution of Pauli exchange terms to the two--nucleon induced non--mesonic weak decay of $^{12}_\Lambda$C hypernuclei, $\Lambda NN\to nNN$ ($N=n$ or $p$), is studied within a nuclear matter formalism implemented in a local density approximation. We have adopted a weak transition potential including the exchange of the complete octets of pseudoscalar and vector mesons as well as a residual strong interaction modeled on the Bonn potential. The introduction of exchange terms turns out to reduce the two--nucleon induced non--mesonic rate by 18% and, jointly with an increase in the one--nucleon induced rate by the same magnitude, reveals to be significant for an accurate determination of the full set of hypernuclear non--mesonic decay widths in theoretical and experimental analyses., Comment: 14 pages, 3 figures

The physics of the weak decay of hypernuclei is briefly reviewed from a theoretical point of view. Special regard is devoted to the recent progress concerning the determination of the non-mesonic decay widths and the asymmetry parameters. Convincing evidence has been achieved for a solution of the long-standing puzzle on the ratio Γ n / Γ p . Very recently, it has been shown that the exchange of a ππ pair in the weak mechanism plays a crucial role in explaining the discrepancies between theory and experiment on the decay asymmetries.

We report in-plane resistivity and elastic constant C33 measurements on the Na0.8CoO2 and Na0.5CoO2 systems. An ordering transition is found at T0=280 K for Na0.8CoO2. The temperature dependence of the elastic constant C33 propagating perpendicular to the CoO2 layers is interpreted, in a phenomenological approach, as being due to the anharmonicity of atomic vibrations. The effective Gruneisen parameter γeff deduced directly from the temperature dependence of C33 exhibits important changes at the charge ordering, magnetic and metal-insulator phase transitions.

High-pressure polymerization of simple molecules (C2H2, C2H4, C6H6, CO2, N2, etc.) is a hot topic in chemistry, condensed matter physics, and materials science [Chelazzi, Ceppatelli]. For instance, polyacetylene (PA) is the textbook system for monodimensional, conducting polymers, while polyCO (pCO) is regarded as a very promising high energy density material. In our studies, we have tried to exploit the effect of high density and highly confined conditions in controlled dimensionality to drive reactivity and to obtain stable, linear polymer chains embedded in protecting host systems with the purpose of synthesizing new materials with strong directional properties. We have selected two different synthetic, non catalytic and electrically neutral pure SiO2 zeolites, silicalite and ZSM-22 (TON). Silicalite has a 3D pore network, due to the mutual intersection of two different sets of nano-channels with a diameter of about 5.5 Å [Artioli]; ZSM-22 (TON) has a 1D structure, and a single set of elliptical shaped linear channels (4.6 x 5.7 Å) [Di Renzo]. Driving the polymerization of ethylene, acetylene and CO inside silicalite, using only relatively low pressure conditions (between 5 and 10 GPa) or mild UV laser irradiation (few milliwatts of 350 nm wavelength radiation), we obtained products termed PESIL (PolyEthylene filled SILicalite) [Santoro], PASIL (PolyAcetylene filled SILicalite) [Scelta] and pCOSIL (pCO filled SILicalite) [Santoro2]. Then we have studied the polymerization of acetylene and CO inside TON. From these reactions, we obtained two new materials called PA/TON (PolyAcetylene filled TON) and pCO/TON (polyCO filled TON), where the guest polymers have a strict planar conformation, which is most likely due to the elliptical shape of the host channels, and are mainly in the cis- configuration, although PA is affected by some degree of disorder within the plane. Remarkably, confined pCO is chemically ordered in contrast to bulk pCO observed so far, which is structurally and chemically disordered. On a general ground, our protocols indicate new chemical routes for synthesizing advanced nanocomposite materials with directional properties, where an inorganic scaffold drives the formation, supports, and protects from the atmosphere an embedded organic polymer with selected low dimensionality. We have performed our experiments using membrane Diamond Anvil Cells (mDAC), working with optical (FTIR, micro-Raman) and structural (x-ray diffraction, XRD) techniques. In order to investigate different regions in nanocomposite samples, we have exploited high spatial resolution techniques provided by synchrotron radiation facilities (micro-FTIR and micro-XRD). Computational methods (DFT based calculation) have been used to model the properties of our nanocomposites products. [Chelazzi] D. Chelazzi, et al. High-pressure synthesis of crystalline polyethylene using optical catalysis. Nat. Mater. 2004, 3, 470-475. [Ceppatelli] M. Ceppatelli, et al. Fourier trans-form infrared study of the pressure and laser induced polymerization of solid acetylene. J. Chem. Phys. 2000, 113, 5991-6000. [Artioli] G. Artioli, et al. Neutron powder diffraction study of orthorhombic and monoclinic defective silicalite. Acta Cryst. B, 56, 2-10, 2000. [Di Renzo] F. Di Renzo, et al. Crystallization kinetics of zeolite TON. Zeolites 1991, 11, 539-548. [Santoro] M. Santoro, et al. A. High-pressure synthesis of a polyethylene/zeolite nano-composite material. Nat. Commun. 2013, 4, 1557, DOI: 10.1038/ncomms2564. [Scelta] D. Scelta, et al. High Pressure Polymerization in a Confined Space: Conjugated Chain/Zeolite Nanocomposites. Chem. Mater. 2014, 26, 2249-2255. [Santoro2] M. Santoro, et al. High Pressure Synthesis of All-Transoid Polycarbonyl [--(C?O)--]n in a Zeolite. Chem. Mater. 2015, 27, 6486-6489.

No abstract available.

We have measured the electrical resistance of an Nb0.53Ti0.47 alloy sample as a function of temperature T (4–300 K) and pressure ( T 2 term whose coefficient decreases with pressure. It is linearly dependent on the residual resistance, that also decreases with pressure, in strong agreement with a Koshino–Taylor origin, i.e. inelastic carrier scattering against impurities.

We study the Cr1-xRex phase diagram finding that its phase transition temperature towards an antiferromagnetic order TN follows a quantum [(xc-x)/xc]ψ law, with ψ=1/2, from the quantum critical point (QCP) at xc=0.25 up to TN≈600K. We compare this system to others in order to understand why this elemental material is affected by the QCP up to such unusually high temperatures. We determine a general criterion for the crossover, as a function of an external parameter such as concentration, from the region controlled solely by thermal fluctuations to that where quantum effects become observable. The properties of materials with low coherence lengths will thus be altered far away from the QCP. Fil: Freitas, D. C.. Université Grenoble Alpes; Francia. Centro Brasileiro de Pesquisas Físicas; Brasil Fil: Rodiere, P.. Université Grenoble Alpes; Francia Fil: Nuñez, Matias. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Garbarino, G.. European Synchrotron Radiation Facility; Francia Fil: Sulpice, A.. Université Grenoble Alpes; Francia Fil: Marcus, J.. Université Grenoble Alpes; Francia Fil: Gay, F.. Université Grenoble Alpes; Francia Fil: Continentino, M. A.. Centro Brasileiro de Pesquisas Físicas; Brasil Fil: Regueiro Nuñez, Manuel. Université Grenoble Alpes; Francia

Recent proposals to test Bell's inequalities with entangled pairs of pseudoscalar mesons are reviewed. This includes pairs of neutral kaons or B-mesons and offers some hope to close both the locality and the detection loopholes. Specific difficulties, however, appear thus invalidating most of those proposals. The best option requires the use of kaon regeneration effects and could lead to a successful test if moderate kaon detection efficiencies are achieved., Comment: 19 pages, 1 figure. Contribution to the Festschrift in honor of Prof. E. Santos for his 70th birthday

We analyse the recent claim that a violation of a Bell's inequality has been observed in the $B$--meson system [A. Go, {\em Journal of Modern Optics} {\bf 51} (2004) 991]. The results of this experiment are a convincing proof of quantum entanglement in $B$--meson pairs similar to that shown by polarization entangled photon pairs. However, we conclude that the tested inequality is not a genuine Bell's inequality and thus cannot discriminate between quantum mechanics and local realistic approaches., 5 pages

As vascular endothelial growth factor (VEGF), interleukin-3 (IL-3), released into the tumor microenvironment stimulates motogenic and mitogenic activity of normal and transformed cells. In the present study, we investigate the effects of IL-3 and VEGF on neoplastic vascular growth. Engagement of IL-3 receptor beta common (IL-3R beta c) contributes to both IL-3- and VEGF-induced Rac1 activation, cell migration and in vitro tube-like structure formation as shown by the expression of the dominant-negative IL-3R beta c construct (Delta455). In normal and transformed endothelial cells (EC) as well as in HEK 293 cells expressing KDR and IL-3R, VEGF and IL-3 treatment induces the formation of a KDR/IL-3R beta c complex. Moreover, as shown by the IL-3R Delta455 mutant or by the kinase dead KDR, functional receptors are required for this interaction. Consistent with the contribution of IL-3R beta c in both IL-3- and VEGF-mediated angiogenic signal, a reduced number of vessels inside tumors are found in mice injected with cells expressing the IL-3R Delta455 mutant. Thus, these findings provide a novel mechanism through which IL-3 and VEGF support cell survival and tumor neovascularization.

Theoretical descriptions of the non-mesonic weak decay of Λ-hypernuclei are unable to reproduce the experimental values of the ratio Γ n / Γ p ≡ Γ ( Λ n → n n ) / Γ ( Λ p → n p ) . In this contribution we discuss a new approach to this problem. We have incorporated a one-meson-exchange model for the Λ N → n N transition in finite nuclei in an intranuclear cascade code for the calculation of double-coincidence nucleon distributions corresponding to the non-mesonic decay of 5ΛHe and 12ΛC. The two-nucleon induced decay mechanism, Λ n p → n n p , has been taken into account within a local density approximation scheme using a one-pion-exchange model supplemented by short range correlations. A weak decay model independent analysis of preliminary KEK coincidence data for 5ΛHe allows us to extract Γ n / Γ p = 0.39 ± 0.11 when the two-nucleon induced channel is neglected (i.e., Γ 2 = 0 ) and Γ n / Γ p = 0.26 ± 0.11 when Γ 2 / Γ 1 = 0.2 .

We previously demonstrated that integrin-dependent adhesion activates STAT5A, a well known target of IL-3–mediated signaling. Here, we show that in endothelial cells the active β1 integrin constitutively associates with the unphosphorylated IL-3 receptor (IL-3R) β common subunit. This association is not sufficient for activating downstream signals. Indeed, only upon fibronectin adhesion is Janus Kinase 2 (JAK2) recruited to the β1 integrin–IL-3R complex and triggers IL-3R β common phosphorylation, leading to the formation of docking sites for activated STAT5A. These events are IL-3 independent but require the integrity of the IL-3R β common. IL-3 treatment increases JAK2 activation and STAT5A and STAT5B tyrosine and serine phosphorylation and leads to cell cycle progression in adherent cells. Expression of an inactive STAT5A inhibits cell cycle progression upon IL-3 treatment, identifying integrin-dependent STAT5A activation as a priming event for IL-3–mediated S phase entry. Consistently, overexpression of a constitutive active STAT5A leads to anchorage-independent cell cycle progression. Therefore, these data provide strong evidence that integrin-dependent STAT5A activation controls IL-3–mediated proliferation.

DC electrical current-dependent resistance and pulsed current–voltage characteristics as a function of temperature of mixed valent Mn oxide-based La 5 / 8 - y Pr y Ca 0.375 MnO 3 ( y = 0.35 ) single crystals are reported. We find that the low-temperature regime of this material is strongly current dependent. For small current densities ( ∼ 10 μ A / cm 2 ) , the metal–insulator transition related to the low-temperature enlargement of the ferromagnetic fraction is not observed down to 10 K. Higher current densities causes a large decrease of the resistance, which is temperature dependent and exhibits memory effects. Our results are interpreted within a scenario of strong competition between charge and ferromagnetic ordering.

We have studied the effect of irreversibility induced by repeated thermal cycles on the electric transport and magnetization of polycrystalline samples of La0.5Ca0.5MnO3 and La0.325Pr0.3Ca0.375MnO3. An increase of the resistivity and a decrease of the magnetization at different temperature ranges after cycling is obtained in the temperature range between 300 K and 30 K. Both compounds are known to exhibit intrinsic submicrometric coexistence of phases and undergo a sequence of phase transitions related to structural changes. Changes induced by thermal cycling can be partially inhibited by applying magnetic field and hydrostatic pressure. Our results suggest that the growth and coexistence of phases with different structures gives rise to microstructural tracks and strain accommodation, producing the observed irreversibility. Irrespective of the actual ground state of each compound, the effect of thermal cycling is towards an increase of the amount of the insulating phase in both compounds., to appear in Journal of Alloys and Compounds (2003)

Objective— To characterize the molecules and the mechanisms regulating the neoangiogenetic process in advanced atherosclerotic plaques. Methods and Results— Western blot and immunofluorescence analysis of atherosclerotic specimens demonstrated that unlike neovessels from early lesions that expressed vascular endothelial growth factor (VEGF) and angiopoietin1 (Angio1), vessels from advanced lesions expressed VEGF and angiopoietin 2 (Angio2). Moreover, only few neovessels from advanced lesions showed a positive immunostaining for proliferating cell nuclear antigen. Angio1-elicited and Angio2-elicited intracellular events in endothelial cells (EC) demonstrated that while Angio1 triggered Erk1/Erk2 mitogen activated protein kinases (MAPK) and Akt activation, Angio2 (50 ng/mL) induced STAT5 activation and p21 waf expression and increased the fraction of cells in G1. Both Angio2-mediated events were abrogated by expressing a dominant negative STAT5 construct (ΔSTAT5). Consistent with the expression of Angio2 in neovessels of advanced lesions a transcriptionally active STAT5 was detected. Moreover, co-immunoprecipitation experiments revealed the presence of a STAT5/Tie2 molecular complex in neointima vessels from advanced, but not from early, lesions. Conclusions— In advanced lesions, the activation of the Tie2-mediated STAT5 signaling pathway may negatively regulate vessel growth.

We present the results of the Meson-Exchange model of Refs. [1,2] for the nonmesonic weak decay of single- and double-Λ hypernuclei. The results shown here include the total nonmesonic ( π NM ) decay rate, partial decay rates ( i. e. decays induced separately by neutrons, π Λn , protons, π Λp , and Λs, π ΛΛ ), the kinetic energy correlation of np coincidence pairs emitted in the decay of Λ 5 He, and A , the longitudinal asymmetry in the distribution of final protons coming from the decay of polarized hypernuclei.

A quantitative formulation of Bohr's complementarity principle and interferometric duality is discussed and applied to the neutral kaon system. Recent measurements by the CPLEAR Collaboration can be easily interpreted in terms of ``neutral kaon interferometry'' illustrating and confirming those basic principles of quantum mechanics.

In this review we discuss the present status of strange nuclear physics, with special attention to the weak decay of Lambda hypernuclei. The models proposed for the evaluation of the Lambda decay widths are summarized and their results are compared with the data. Despite the recent intensive investigations, the main open problem remains a sound theoretical interpretation of the large experimental values of the ratio G_n/G_p. Although recent works offer a step forward in the solution of the puzzle, further efforts must be invested in order to understand the detailed dynamics of the non-mesonic decay. Even if, by means of single nucleon spectra measurements, the error bars on G_n/G_p have been considerably reduced very recently at KEK, a clean extraction of G_n/G_p is needed. What is missing at present, but planned for the next future, are measurements of 1) nucleon energy spectra in double coincidence and 2) nucleon angular correlations: such observations allow to disentangle the nucleons produced in one- and two-body induced decays and lead to a direct determination of G_n/G_p. For the asymmetric non-mesonic decay of polarized hypernuclei the situation is even more puzzling. Indeed, strong inconsistencies appear already among data. A recent experiment obtained a positive intrinsic Lambda asymmetry parameter, a_{Lambda}, for 5_{Lambda}He. This is in complete disagreement with a previous measurement, which obtained a large and negative a_{Lambda} for p-shell hypernuclei, and with theory, which predicts a negative value moderately dependent on nuclear structure effects. Also in this case, improved experiments establishing with certainty the sign and magnitude of a_{Lambda} for s- and p-shell hypernuclei will provide a guidance for a deeper understanding of hypernuclear dynamics and decay mechanisms.

The pressure-dependent diffraction response of the superconducting phase-separated ${Cs}_{0.72}$${Fe}_{1.57}$${Se}_{2}$ (${T}_{\mathrm{c}}$ = 28.5 K) has been studied at room temperature using synchrotron radiation up to the pressure of 19 GPa. The main and secondary phases of ${Cs}_{0.72}$${Fe}_{1.57}$${Se}_{2}$ have been observed in the whole pressure range. The main ordered phase has been found to undergo an order-disorder transition in the Fe sublattice at $P$ = 11 GPa with the corresponding kinetics on the order of hours. Contrary to the analogous temperature-induced transition, the secondary phase has not been suppressed suggesting that its stability pressure range is higher than 19 GPa or the corresponding transformation kinetics is too slow at room temperature. Together with the previously reported pressure-dependent resistivity and magnetic susceptibility measurements, this work indicates that superconductivity in the ${A}_{x}$${Fe}_{2\ensuremath{-}y}$${Se}_{2}$ ($A$: alkali metals) phases could be related to the Fe-vacancy ordering in the main phase.

The possible application of the barocaloric effect to produce solid state refrigerators is a topic of interest in the field of applied physics. In this work, we present experimental data about the influence of external pressure on the magnetic properties of a manganite with phase separation. Using the Jahn Teller effect associated with the presence of the charge ordering we were able to follow the transition to the ferromagnetic state induced by pressure. We also demonstrated that external pressure can assist the ferromagnetic state, decreasing the magnetic field necessary to generate the magnetic transition., Acepted to be published in Applied Physics Letters

The predictions of local realistic theories for the observables concerning the evolution of a $K^0\bar{K}^0$ quantum entangled pair (created in the decay of the $\phi$-meson) are discussed. It is shown, in agreement with Bell's theorem, that the most general local hidden-variable model fails in reproducing the whole set of quantum-mechanical joint probabilities. We achieve these conclusion by employing two different approaches. In a first one the local realistic observables are deduced from the most general premises concerning locality and realism, and Bell-like inequalities are not employed. The other approach makes use of Bell's inequalities. Within the former scheme, under particular conditions for the detection times, the discrepancy between quantum mechanics and local realism for the time-dependent asymmetry turns out to be not less than 20%. The same incompatibility can be made evident by means of a Bell-type test by employing both Wigner's and (once properly normalized probabilities are used) Clauser-Holt-Shimony-Holt's inequalities. Because of the relatively low experimental accuracy, the data obtained by the CPLEAR collaboration for the asymmetry parameter do not allow for a decisive test of local realism. Such a test, both with and without the use of Bell's inequalities, should be feasible in the future at the Frascati $\Phi$-factory., Comment: 36 pages, 4 figures

By employing recent data on non-mesonic decay of s-shell Lambda-hypernuclei we study, within the phenomenological model of Block and Dalitz, the validity of the Delta I=1/2 rule in the Lambda N--> NN process. Due to the low experimental precision, a possible violation of this rule can be neither proved nor excluded at present with sufficient accuracy: a pure Delta I=1/2 transition amplitude is excluded at 40% confidence level.

Tritium present in the environment gradually decreased in the last decades and nowadays it has reached extremely low activity concentrations. The purpose of the present work is the implementation of a tritium enrichment system in water samples using electrolytic techniques and pure nickel and iron electrodes. In the present work a mean tritium enrichment factor of 13.0 +/- 3.2 was obtained. This result should allow to reach a minimum detectable activity of tritium in water samples of about 1 tritium unit (TU) or less. The present enrichment system necessitates further adjustments and improvements, such as a cooling system in order to reduce the tritium losses due to evaporation.