Memory for Light as a Quantum Process

We report complete characterization of an optical memory based on electromagnetically induced transparency. We recover the superoperator associated with the memory, under two different working conditions, by means of a quantum process tomography technique that involves storage of coherent states and their characterization upon retrieval. In this way, we can predict the quantum state retrieved from the memory for any input, for example, the squeezed vacuum or the Fock state. We employ the acquired superoperator to verify the nonclassicality benchmark for the storage of a Gaussian distributed set of coherent states

Invariant Killing spinors in 11D and type II supergravities

We present all isotropy groups and associated $\Sigma$ groups, up to discrete identifications of the component connected to the identity, of spinors of eleven-dimensional and type II supergravities. The $\Sigma$ groups are products of a Spin group and an R-symmetry group of a suitable lower dimensional supergravity theory. Using the case of SU(4)-invariant spinors as a paradigm, we demonstrate that the $\Sigma$ groups, and so the R-symmetry groups of lower-dimensional supergravity theories arising from compactifications, have disconnected components. These lead to discrete symmetry groups reminiscent of R-parity. We examine the role of disconnected components of the $\Sigma$ groups in the choice of Killing spinor representatives and in the context of compactifications.Comment: 22 pages, typos correcte

Strain in epitaxial MnSi films on Si(111) in the thick film limit studied by polarization-dependent extended x-ray absorption fine structure

We report a study of the strain state of epitaxial MnSi films on Si(111) substrates in the thick film limit (100-500~\AA) as a function of film thickness using polarization-dependent extended x-ray absorption fine structure (EXAFS). All films investigated are phase-pure and of high quality with a sharp interface between MnSi and Si. The investigated MnSi films are in a thickness regime where the magnetic transition temperature $T_\mathrm{c}$ assumes a thickness-independent enhanced value of $\geq$43~K as compared with that of bulk MnSi, where $T_\mathrm{c} \approx 29~{\rm K}$. A detailed refinement of the EXAFS data reveals that the Mn positions are unchanged, whereas the Si positions vary along the out-of-plane [111]-direction, alternating in orientation from unit cell to unit cell. Thus, for thick MnSi films, the unit cell volume is essentially that of bulk MnSi --- except in the vicinity of the interface with the Si substrate (thin film limit). In view of the enhanced magnetic transition temperature we conclude that the mere presence of the interface, and its specific characteristics, strongly affects the magnetic properties of the entire MnSi film, even far from the interface. Our analysis provides invaluable information about the local strain at the MnSi/Si(111) interface. The presented methodology of polarization dependent EXAFS can also be employed to investigate the local structure of other interesting interfaces.Comment: 11 pages, 10 figure

Culture Medium Factorial Design Optimization for Fibrinolytic Enzymes Production by Bionectria sp.

Thrombotic diseases can be clinically treated with fibrinolytic enzymes and many attempts have been made at laboratory level to increase fibrinolytic enzymes production from microbial sources and to reduce the process cost, including culture medium design, optimization of environmental conditions, and over expression with genetically modified strains. In this contribution we present the optimization of culture medium composition and incubation temperature for fibrinolytic enzyme production by Bionectria sp., a selected fungal strain from Las Yungas (Tucumán). Optimization was carried out at Erlenmeyer scale (100-mL working volume) via factorial design methodology. All trials included a common mineral base (%, w/v: NaCl 0.2, KH2PO4 0.05, MgSO4·7H2O 0.05). According to four factorial designs it could be demonstrated the convenience of using soy peptone as N-source, glucose as C-source, and the possibility to eliminate starch, meat peptone and meat extract from original medium composition, whilst 25°C was selected as the optimal incubation temperature. Results showed that culture medium could be successfully optimized by factorial design, achieving a reduction in the production process costs by means of a decrease in culture medium components, the improvement in culture broth rheology, mycelial morphology and mass/energy transfer, and the subsequent two-fold enhancement in productivity.Fil: Arnau, Victor Gonzalo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Rovati, Jose Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Figueroa, L. I. C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Fariña, Julia Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaXLVI Reunión Anual Sociedad Argentina de Investigaciones Bioquímicas y MolecularesPuerto Madryn, Chubut, ArgentinaArgentinaSociedad Argentina de Investigaciones Bioquímicas y Moleculare

Aplicación de diseño factorial completo para la otpimización del medio de cultivo para la remoción de Cr(VI) por levaduras autóctonas

La contaminación con cromo aumenta incesantemente debido a la continua industrialización y al mal manejo de los residuos. Entre los distintos estados de oxidación, el Cr (VI) es el más tóxico debido a su carácter cancerígeno y mutagénico. La reducción microbiana de Cr(VI) ofrece una alternativa económicamente rentable y ecológicamente viable. Con el fin de reducir los costos operativos en un proceso a gran escala, se estudió la composición y concentración de los componentes del medio de cultivo. Se trabajó con un diseño estadístico del tipo factorial completo para optimizar la remoción de Cr(VI) (1 mM concentración inicial) a las 24 h con las levaduras Cyberlindnera jadinii M9 y Wickerhamomyces anomalus M10. Se estudió y modeló la interacción entre las variables: SO 4(NH4)2, CaCl2, NaCl e inóculo para M9, y: sacarosa, KHPO4 e inóculo, para M10. En ambas cepas se alcanzo la remoción total de Cr(VI) a las 24 h de cultivo. También, se evaluó la tendencia a la máxima remoción a las 12 h. La combinación óptima predicha se confirmó experimentalmente, alcanzando un máximo de 73,91% y 87,32% para M9 y M10, respectivamente. En el caso de M9, NaCl pudo ser excluido de la fórmula del medio de cultivo. La composición resultante del medio de cultivo optimizado para M9 es (en g/L): sacarosa, 60; KHPO 4, 1; extracto de levadura, 1; Mg(SO4)2, 0,5; SO4(NH4)2, 1,05; CaCl2 0,12; inóculo 20% y para M10 resultante es (en g/L): sacarosa, 90; KHPO4, 1,2; SO4(NH4)2, 1,2; extracto de levadura, 1; Mg(SO4)2, 0,5; CaCl2, 0,1; NaCl, 0,1; inóculo 20%. Estos resultados indican que un alto porcentaje de remoción de Cr(VI) puede alcanzarse en un corto tiempo de cultivo empleando un medio de simple composición, el cual podría usarse en el desarrollo de un proceso a gran escala.Fil: Cruz, Elías L.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Fernandez, Pablo Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Figueroa, L. I. C. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaXXXI Jornadas Científicas de la Asociación de Biología de TucumánTucumánArgentinaAsociación de Biología de Tucumá

Machine learning to identify ICL and BCG in simulated galaxy clusters

Nowadays, Machine Learning techniques offer fast and efficient solutions for classification problems that would require intensive computational resources via traditional methods. We examine the use of a supervised Random Forest to classify stars in simulated galaxy clusters after subtracting the member galaxies. These dynamically different components are interpreted as the individual properties of the stars in the Brightest Cluster Galaxy (BCG) and IntraCluster Light (ICL). We employ matched stellar catalogues (built from the different dynamical properties of BCG and ICL) of 29 simulated clusters from the DIANOGA set to train and test the classifier. The input features are cluster mass, normalized particle cluster-centric distance, and rest-frame velocity. The model is found to correctly identify most of the stars, while the larger errors are exhibited at the BCG outskirts, where the differences between the physical properties of the two components are less obvious. We investigate the robustness of the classifier to numerical resolution, redshift dependence (up to z = 1), and included astrophysical models. We claim that our classifier provides consistent results in simulations for z 0.1 R-200) is significantly affected by uncertainties in the classification process. In conclusion, this work suggests the importance of employing Machine Learning to speed up a computationally expensive classification in simulations

Darboux Transformations for Supersymmetric Korteweg - de Vries Equations

\hspace{.2in}We consider the Darboux type transformations for the spectral problems of supersymmetric KdV systems. The supersymmetric analogies of Darboux and Darboux-Levi transformations are established for the spectral problems of Manin-Radul-Mathieu sKdV and Manin-Radul sKdV. Several B\"acklund transformations are derived for the MRM sKdV and MR sKdV systems.Comment: Latex, 8 pages AS-ITP-94-4

Perpendicular magnetic anisotropy and intralayer interactions in a single layer of CoPt nanoparticles

The multilayer films Al2O3/tCo Co/tPt Pt]N, produced by sequential deposition of Co and Pt on alumina consist in layers of CoPt alloyed nanoparticles. They show perpendicular magnetic anisotropy (PMA) below a freezing temperature Tf, an asperomagnetic-like phase below that temperature, and hard ferromagnetic ordering below a transition temperature T1 < Tf. A single layer granular film (N = 1) with deposition thicknesses tCo=0.7 nm, tPt=1.5 nm and particle diameter of 3 nm is presently studied. SQUID magnetometry shows that a single layer presents the three phases as well. Para-, aspero-and ferromagnetic phases are observed upon lowering the temperature, with transition temperatures Tf ˜ 375 K and T1 ˜ 200 K, respectively. In addition, the PMA persists, proving that there is no interlayer coupling in the multilayer system. SQUID results also reveal a core-shell structure in the CoPt nanoparticles

Classical N=2 W-superalgebras From Superpseudodifferential Operators

We study the supersymmetric Gelfand-Dickey algebras associated with the superpseudodifferential operators of positive as well as negative leading order. We show that, upon the usual constraint, these algebras contain the N=2 super Virasoro algebra as a subalgebra as long as the leading order is odd. The decompositions of the coefficient functions into N=1 primary fields are then obtained by covariantizing the superpseudodifferential operators. We discuss the problem of identifying N=2 supermultiplets and work out a couple of supermultiplets by explicit computations.Comment: 19 pages (Plain TeX), NHCU-HEP-94-1