3-Aminopropyl-Triethoxysilane Functionalized Graphene Oxide for Silane-Based Consolidation Treatments to Increase Mortar Performances.

The influence of chemically converted GO (graphene oxide) functionalized with APTES (3-aminopropyl-triethoxysilane) and unfunctionalized GO, dispersed in ethanolic solution of TEOS (tetraethyl orthosilicate), on the performances of the mortar samples, such as capillary water absorption and compressive strength was evaluated. The effect of the GO based nanomaterials (GO and GO functionalized with APTES) on the mortar microstructure was investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The multifunctionality of the mortar brushed with GO based nanomaterials consolidation suspension was proved by the results (i) of the mechanical tests which show an improvement of the compressive strength and (ii) the capillary water absorption results which indicate the decreasing of the water penetration speed. For the mortar samples brushed with GO consolidation suspension, an increase value for the compressive strength of approximately twice compared to the untreated control samples and a decreased value for the capillary absorption water coefficient with one order of magnitude in comparison with the untreated control samples were obtained.

Connecting Dissipation and Phase Slips in a Josephson Junction between Fermionic Superfluids.

We study the emergence of dissipation in an atomic Josephson junction between weakly coupled superfluid Fermi gases. We find that vortex-induced phase slippage is the dominant microscopic source of dissipation across the Bose-Einstein condensate-Bardeen-Cooper-Schrieffer crossover. We explore different dynamical regimes by tuning the bias chemical potential between the two superfluid reservoirs. For small excitations, we observe dissipation and phase coherence to coexist, with a resistive current followed by well-defined Josephson oscillations. We link the junction transport properties to the phase-slippage mechanism, finding that vortex nucleation is primarily responsible for the observed trends of conductance and critical current. For large excitations, we observe the irreversible loss of coherence between the two superfluids, and transport cannot be described only within an uncorrelated phase-slip picture. Our findings open new directions for investigating the interplay between dissipative and superfluid transport in strongly correlated Fermi systems, and general concepts in out-of-equilibrium quantum systems.

Repulsive Fermi Polarons in a Resonant Mixture of Ultracold

We employ radio-frequency spectroscopy to investigate a polarized spin mixture of ultracold ^{6}Li atoms close to a broad Feshbach scattering resonance. Focusing on the regime of strong repulsive interactions, we observe well-defined coherent quasiparticles even for unitarity-limited interactions. We characterize the many-body system by extracting the key properties of repulsive Fermi polarons: the energy E_{+}, the effective mass m^{*}, the residue Z, and the decay rate Γ. Above a critical interaction, E_{+} is found to exceed the Fermi energy of the bath, while m^{*} diverges and even turns negative, thereby indicating that the repulsive Fermi liquid state becomes energetically and thermodynamically unstable.

Spatial entanglement of bosons in optical lattices.

Entanglement is a fundamental resource for quantum information processing, occurring naturally in many-body systems at low temperatures. The presence of entanglement and, in particular, its scaling with the size of system partitions underlies the complexity of quantum many-body states. The quantitative estimation of entanglement in many-body systems represents a major challenge, as it requires either full-state tomography, scaling exponentially in the system size, or the assumption of unverified system characteristics such as its Hamiltonian or temperature. Here we adopt recently developed approaches for the determination of rigorous lower entanglement bounds from readily accessible measurements and apply them in an experiment of ultracold interacting bosons in optical lattices of ~10(5) sites. We then study the behaviour of spatial entanglement between the sites when crossing the superfluid-Mott insulator transition and when varying temperature. This constitutes the first rigorous experimental large-scale entanglement quantification in a scalable quantum simulator.

Quasiparticle dynamics in a bose insulator probed by interband bragg spectroscopy.

We investigate experimentally and theoretically the dynamical properties of a Mott insulator in decoupled one-dimensional chains. Using a theoretical analysis of the Bragg excitation scheme, we show that the spectrum of interband transitions holds information on the single-particle Green's function of the insulator. In particular, the existence of particle-hole coherence due to quantum fluctuations in the Mott state is clearly seen in the Bragg spectra and quantified. Finally, we propose a scheme to directly measure the full, momentum-resolved spectral function as obtained in the angle-resolved photoemission spectroscopy of solids.

Exploring correlated 1D bose gases from the superfluid to the mott-insulator state by inelastic light scattering.

We report the Bragg spectroscopy of interacting one-dimensional Bose gases loaded in an optical lattice across the superfluid to the Mott-insulator phase transition. Elementary excitations are created with a nonzero momentum and the response of the correlated 1D gases is in the linear regime. The complexity of the strongly correlated quantum phases is directly displayed in the spectra which exhibit novel features. This work paves the way for a precise characterization of the state of correlated gases in optical lattices.

Noise correlation spectroscopy of the broken order of a Mott insulating phase.

We use a two-color lattice to break the homogeneous site occupation of an atomic Mott insulator of bosonic 87Rb. We detect the disruption of the ordered Mott domains via noise correlation analysis of the atomic density distribution after time of flight. The appearance of additional correlation peaks evidences the redistribution of the atoms into a strongly inhomogeneous insulating state, in quantitative agreement with the predictions.

Ultracold atoms in a disordered crystal of light: towards a bose glass.

We use a bichromatic optical lattice to experimentally realize a disordered system of ultracold strongly interacting 87Rb bosons. In the absence of disorder, the atoms are pinned by repulsive interactions in the sites of an ideal optical crystal, forming one-dimensional Mott-insulator states. We measure the excitation spectrum of the system as a function of disorder strength and characterize its phase-coherence properties with a time-of-flight technique. Increasing disorder, we observe a broadening of the Mott-insulator resonances and the transition to a state with vanishing long-range phase coherence and a flat density of excitations, which suggest the formation of a Bose-glass phase.

Influence of statins on postoperative wound complications after inguinal or ventral herniorrhaphy.

The lipid-lowering agents, statins, are the most commonly prescribed class of drugs in the western world. Because of their widespread use, many patients undergo surgical procedures while on statins. Statins, in addition to cholesterol-lowering effects, also have anticoagulant, immunosuppressive, and antiproliferative properties that may affect the risk of local wound complications. This study investigated the relationship between statins and postoperative wound complications in a large cohort of patients undergoing inguinal or ventral hernia repair. Data mining was performed in the Veterans Integrated Service Network (VISN)16 Data Warehouse. This database contains clinical and demographic information about all veterans cared for at the ten VA Medical Centers that comprise the South Central VA Healthcare Network in the mid-south region of the US. Aggregate data (age, body mass index, smoking history, gender, race, history of diabetes, statin use, and postoperative wound complications) were obtained for all patients who underwent inguinal or ventral hernia repair during the period October 1, 1996-November 30, 2004. During the period of the query, 10,782 patients (10,676 male, 106 female), 1,242 (11.5%) of whom received statins, underwent herniorrhaphy. Statin use did not affect the risk of wound infection or delayed wound healing. Statin use was, however, associated with an increased rate of local postoperative bleeding complications (P=0.01). When the type of hernia, age, smoking, diabetes, and body mass index were included in a multivariate analysis, statins remained borderline significant as an independent predictor of wound hematoma/postoperative bleeding (P=0.04), odds ratio 1.6 (95% CI 1.03-2.44). Patients who undergo inguinal herniorrhaphy while on statins have an increased risk of postoperative wound hematoma/hemorrhage. Focus on additional factors that may affect the propensity to postoperative bleeding and on meticulous intraoperative hemostasis are particularly important in such patients.

Effect of optical disorder and single defects on the expansion of a Bose-Einstein condensate in a one-dimensional waveguide.

We investigate the one-dimensional expansion of a Bose-Einstein condensate in an optical guide in the presence of a random potential created with optical speckles. With the speckle the expansion of the condensate is strongly inhibited. A detailed investigation has been carried out varying the experimental conditions and checking the expansion when a single optical defect is present. The experimental results are in good agreement with numerical calculations based on the Gross-Pitaevskii equation.

Bose-Einstein condensate in a random potential.

An optical speckle potential is used to investigate the static and dynamic properties of a Bose-Einstein condensate in the presence of disorder. With small levels of disorder, stripes are observed in the expanded density profile and strong damping of dipole and quadrupole oscillations is seen. Uncorrelated frequency shifts of the two modes are measured and are explained using a sum-rules approach and by the numerical solution of the Gross-Pitaevskii equation.

Observation of dynamical instability for a Bose-Einstein condensate in a moving 1D optical lattice.

We have experimentally studied the unstable dynamics of a harmonically trapped Bose-Einstein condensate loaded into a 1D moving optical lattice. The lifetime of the condensate in such a potential exhibits a dramatic dependence on the quasimomentum state. This is unambiguously attributed to the onset of dynamical instability, after a comparison with the predictions of the Gross-Pitaevskii theory. Deeply in the unstable region we observe the rapid appearance of complex structures in the atomic density profile, as a consequence of the condensate phase uniformity breakdown.

Optically induced lensing effect on a Bose-Einstein condensate expanding in a moving lattice.

We report the experimental observation of a lensing effect on a Bose-Einstein condensate expanding in a moving 1D optical lattice. The effect of the periodic potential can be described by an effective mass dependent on the condensate quasimomentum. By changing the velocity of the atoms in the frame of the optical lattice, we induce a focusing of the condensate along the lattice direction. The experimental results are compared with the numerical predictions of an effective 1D theoretical model. In addition, a precise band spectroscopy of the system is carried out by looking at the real-space propagation of the atomic wave packet in the optical lattice.

Collective excitations of a trapped Bose-Einstein condensate in the presence of a 1D optical lattice.

We study low-lying collective modes of an elongated 87Rb condensate produced in a 3D magnetic harmonic trap with the addition of a 1D periodic potential which is provided by a laser standing wave along the axial direction. While the transverse breathing mode remains unperturbed, quadrupole and dipole oscillations along the optical lattice are strongly modified. Precise measurements of the collective mode frequencies at different heights of the optical barriers provide a stringent test of the theoretical model recently introduced [M. Krämer, Phys. Rev. Lett. 88, 180404 (2002)]].

[Transparency in public sector acquisitions. The case of hospitals in the City of Buenos Aires]. / Transparencia en las adquisiciones del sector público: el caso de los hospitales de la Ciudad de Buenos Aires.

This paper deals with corruption and the lack of transparency in public sector purchases as well as with the main instruments to obtain adequate results in purchase negotiation.Firstly, we discuss how corruption causes concern to national governments, international organizations, academic centers, non-governmental organizations and society in general. The consequences of corruption in Argentina and other Latin American countries are highlighted, especially the effect of corruption on economic growth and the way it creates economic inefficiency and inequality.Secondly, the database created by the Subsecretary of Strategic Management of the Autonomous Government of the City of Buenos Aires is analyzed. The central purpose of this study is to evaluate the impact of the Administrative Reform of 1998 on the prices of 24 products acquired by 13 general acute care hospitals from 1998-1999. The weighted prices, the number of units purchased and the total number of contracts given in this period, as well as the products with the greatest utilization rate, are analyzed. Multivariante analysis was used to identify hospitals with appropriate activity and efficient budget administration (activity and negotiation indicators). Price development was analyzed using the regression technique (ordinary least squares), which demonstrated an 8% reduction in prices for the year 1999. The contribution of each hospital to this variation is presented using dummy variables. Thus, six of the 13 hospitals significantly contributed to the decrease in prices. Of these six, three hospitals also contributed to reduction in price dispersion. The results obtained allow us to conclude that, if public hospitals have adequate purchase negotiation instruments and a uniform legal framework, they can achieve a good level of activity. Furthermore, public hospitals can contribute to reductions in price and price dispersion, at the same time as improving efficiency in the assignation and utilization of resources.

Transparencia en las adquisiciones del sector público: el caso de los hospitales de la Ciudad de Buenos Aires / Transparency in public sector acquisitions. The case of hospitals in the City of Buenos Aires

El presente trabajo trata el tema de la corrupción y falta de transparencia en las adquisiciones del sector público y los instrumentos que pueden colaborar para obtener resultados positivos en la gestión de compras. En primer lugar, se plantea el estado actual de la discusión del tema y la preocupación que manifiestan los gobiernos, los organismos internacionales, los centros académicos , las organizaciones no gubernamentales y la sociedad civil ante el avance de la corrupción. Se destaca la importancia del tema en Argentina y en otros países latinoamericanos, sobre todo su impacto en el crecimiento económico y las ineficiencias e inequidades que crea en la economía. En segundo término, se analiza la base de datos generada por la Subsecretaría de Gerenciamiento Estratégico del Gobierno Autónomo de la Ciudad de Buenos Aires. El objetivo central es evaluar el impacto de la Reforma Administrativa (1998) en los precios de 24 productos adquiridos por 13 hospitales generales de agudos durante el período 19981999.Se analizan los precios ponderados, las cantidades adquiridas y los montos de las contrataciones para el citado período y el conjunto de productos de mayor tasa de utilización. Se utilizó el análisis factorial multivariante a fin de identificar aquellos establecimientos asistenciales que tuvieron un buen nivel de actividad y a la vez un buen manejo presupuestario (indicadores de actividad y gestión).El análisis del comportamiento de los precios se realiza a través de una serie de regresiones que permiten demostrar que los precios bajaron un 8 por ciento en 1999. La contribución de cada hospital a esta variación se modela con variables dicotómicas. Así, 6 de los 13 hospitales aportan significativamente a la reducción de precios, de los cuales 3 contribuyen además a la baja en la dispersión de precios. Los resultados obtenidos permiten concluir que si los establecimientos asistenciales públicos cuentan con instrumentos de gestión de compra claros y precisos y con una normativa homogénea y uniforme, pueden lograr un buen nivel de acti vidad. Además, pueden contribuir a la baja de precios y la disminución de la dispersión de los mismos, a la vez que mejoran la eficiencia en la asignación y utilización de los recursos (AU)

This paper deals with corruption and the lack of transparency in public sector purchases as well as with the main instruments to obtain adequate results in purchase negotiation. Firstly, we discuss how corruption causes concern to national governments, international organizations, academic centers, non-governmental organizations and society in general. The consequences of corruption in Argentina and other Latin American countries are highlighted, especially the effect of corruption on economic growth and the way it creates economic inefficiency and inequality. Secondly, the database created by the Subsecretary of Strategic Management of the Autonomous Government of the City of Buenos Aires is analyzed. The central purpose of this study is to evaluate the impact of the Administrative Reform of 1998 on the prices of 24 products acquired by 13 general acute care hospitals from 1998-1999. The weighted prices, the number of units purchased and the total number of contracts given in this period, as well as the products with the greatest utilization rate, are analyzed. Multivariante analysis was used to identify hospitals with appropriate activity and efficient budeget administration (activity and negotiation indicators). Price development was analyzed using the regression technique (ordinary least squares), which demonstrated an 8% reduction in prices for the year 1999. The contribution of each hospital to this variation is presented using dummy variables. Thus, six of the 13 hospitals significantly contributed to the decrease in prices. Of these six, three hospitals also contributed to reduction in price dispersion. The results obtained allow us to conclude that, if public hospitals have adequate purchase negotiation instruments and a uniform legal framework, they can achieve a good level of activity. Furthermore, public hospitals can contribute to reductions in price and price dispersion, at the same time as improving efficiency in the assignation and utilization of resources (AU)

Expansion of a coherent array of Bose-Einstein condensates.

We investigate the properties of a coherent array containing about 200 Bose-Einstein condensates produced in a far detuned 1D optical lattice. The density profile of the gas, imaged after releasing the trap, provides information about the coherence of the ground-state wave function. The measured atomic distribution is characterized by interference peaks. The time evolution of the peaks, their relative population, as well as the radial size of the expanding cloud are in good agreement with the predictions of theory. The 2D nature of the trapped condensates and the conditions required to observe the effects of coherence are also discussed.

Time-domain atom interferometry across the threshold for Bose-Einstein condensation.

We have performed time-domain interferometry experiments with matter waves trapped in a harmonic potential above and below the Bose-Einstein phase transition, by means of the method of separated oscillating fields, with a variable time delay T. We observe the oscillations of the population between two internal Zeeman states versus the delay T to be rapidly depleted both below and slightly above Bose-Einstein condensation. We give a quantitative explanation in terms of the phase evolution due to the entanglement between the internal and external degrees of freedom.

Josephson junction arrays with Bose-Einstein condensates.

We report on the direct observation of an oscillating atomic current in a one-dimensional array of Josephson junctions realized with an atomic Bose-Einstein condensate. The array is created by a laser standing wave, with the condensates trapped in the valleys of the periodic potential and weakly coupled by the interwell barriers. The coherence of multiple tunneling between adjacent wells is continuously probed by atomic interference. The square of the small-amplitude oscillation frequency is proportional to the microscopic tunneling rate of each condensate through the barriers and provides a direct measurement of the Josephson critical current as a function of the intermediate barrier heights. Our superfluid array may allow investigation of phenomena so far inaccessible to superconducting Josephson junctions and lays a bridge between the condensate dynamics and the physics of discrete nonlinear media.

Superfluid and dissipative dynamics of a Bose-Einstein condensate in a periodic optical potential.

We create Bose-Einstein condensates of 87Rb in a static magnetic trap with a superimposed blue-detuned 1D optical lattice. By displacing the magnetic trap center we are able to control the condensate evolution. We observe a change in the frequency of the center-of-mass oscillation in the harmonic trapping potential, in analogy with an increase in effective mass. For fluid velocities greater than a local speed of sound, we observe the onset of dissipative processes up to full removal of the superfluid component. A parallel simulation study visualizes the dynamics of the Bose-Einstein condensate and accounts for the main features of the observed behavior.