Quantum mechanical description of Stern-Gerlach experiments

The motion of neutral particles with magnetic moments in an inhomogeneous magnetic field is described in a quantum mechanical framework. The validity of the semi-classical approximations which are generally used to describe these phenomena is discussed. Approximate expressions for the evolution operator are derived and compared to the exact calculations. Focusing and spin-flip phenomena are predicted. The reliability of Stern-Gerlach experiments to measure spin projections is assessed in this framework.Comment: 12 pages, 7 eps figures included, revtex, submitted to PR

Preventive conservation plan for library buildings in La Plata, Argentina

This summary shows the advances of a project called “Development of building environmental management and continuous monitoring for preventive conservation in UNLP libraries” which is now taking place in the libraries of the National University of La Plata. It is essential to know the hygrothermal condition inside the book deposits, as one of the first preventive measures to become aware of the state of conservation of the books. The aim of the study is to propose a systematic environmental monitoring method to verify compatibility between measured parameters and optimal preservation conditions. Annual monitoring campaign was performed in twelve libraries with diverse results according to the characteristics of the envelope and HVAC systems. It is the first time that a formal monitoring campaign has taken place in these library buildings. We met staff well disposed and eager to achieve better results. We provide a standard report model suitable for the institutions as a decision-making tool, with simultaneous analysis of temperature and relative humidity, according to the local climate.Facultad de Arquitectura y Urbanism

Multiscale understanding of tricalcium silicate hydration reactions

Tricalcium silicate, the main constituent of Portland cement, hydrates to produce crystalline calcium hydroxide and calcium-silicate-hydrates (C-S-H) nanocrystalline gel. This hydration reaction is poorly understood at the nanoscale. The understanding of atomic arrangement in nanocrystalline phases is intrinsically complicated and this challenge is exacerbated by the presence of additional crystalline phase(s). Here, we use calorimetry and synchrotron X-ray powder diffraction to quantitatively follow tricalcium silicate hydration process: i) its dissolution, ii) portlandite crystallization and iii) C-S-H gel precipitation. Chiefly, synchrotron pair distribution function (PDF) allows to identify a defective clinotobermorite, Ca11Si9O28(OH)2.8.5H2O, as the nanocrystalline component of C-S-H. Furthermore, PDF analysis also indicates that C-S-H gel contains monolayer calcium hydroxide which is stretched as recently predicted by first principles calculations. These outcomes, plus additional laboratory characterization, yielded a multiscale picture for C-S-H nanocomposite gel which explains the observed densities and Ca/Si atomic ratios at the nano- and meso- scales.This work has been supported by Spanish MINECO through BIA2014-57658-C2-2-R, which is co-funded by FEDER, BIA2014-57658-C2-1-R and I3 (IEDI-2016-0079) grants. We also thank CELLS-ALBA (Barcelona, Spain) for providing synchrotron beam time at BL04-MSPD beamline

Dynamics of scalar perturbations in f(R, T) gravity [Phys. Rev. D 87, 103526 (2013), publisher's note]

Es una nota del editorDepto. de Física TeóricaFac. de Ciencias FísicasTRUEpu

Super-poissonian photon statistics and correlations between pump and probe fields in Electromagnetically Induced Transparency

We have measured the photon statistics of pump and probe beams after interaction with Rb atoms in a situation of Electromagnetically Induced Transparency. Both fields present super-poissonian statistics and their intensities become correlated, in good qualitative agreement with theoretical predictions in which both fields are treated quantum-mechanically. The intensity correlations measured are a first step towards the observation of entanglement between the fields.Comment: 4 pages, two-column, 4 figures, first submitted to PRL on Aug. 6, 200

Enfermedades fungosas del haba (Vicia faba L.) en Boyacá

Se realizó un reconocimiento de las enfermedades fungosas que afectan los cultivos de haba (Vicia faba L.) en la zona productora del departamento de Boyacá. Incluyó 38 municipios y 8 corregimientos entre los 1900 y 3040 m de altitud. Los trabajos de laboratorio fueron realizados en la Facultad de Agronomía U.P.T.C. de Tunja y en Tibaitatá ICA, al igual que trabajos de invernadero. Se encontró que la enfermedad más importante por su amplia distribución y daños producidos es la pudrición gris Botrytis cinerea (Pers) Fries, que afecta las hojas, flores, legumbres y tallos, llegando a producir defoliación total y muerte de la planta. La roya, Uromyces vicia-fabae (Pers) se reconoció en 32 localidades, es enfermedad potencialmente peligrosa, que reduce las plantas defoliadas. La mancha chocolate Botrytis fabae Sard enfermedad poco distribuida, reduce la superficie fotosintetizante y por lo tanto influye en la reducción de la producción. El marchitamiento Fusarium oxysporum se encontró distribuido en el clima más templado donde se cultiva hace muchos años. Se encontraron otras afecciones radicales inducidas por hongos del género Fusarium y caracterizados por pudriciones. Se concluye que la incidencia de enfermedades se debe a deficiente preparación del suelo, fertilización inadeacuada, drenajes y riegos deficientes, ausencia de rotación de cultivos, semilla no certificada ni mejorada y falta de divulgación de estas técnicasHaba-Vicia fab

Role and dynamics of the ribosomal protein p0 and its related trans-acting factor Mrt4 during ribosome assembly in Saccharomyces cerevisiae

Mrt4 is a nucleolar component of the ribosome assembly machinery that shares notable similarity and competes for binding to the 25S rRNA GAR domain with the ribosomal protein P0. Here, we show that loss of function of either P0 or Mrt4 results in a deficit in 60S subunits, which is apparently due to impaired rRNA processing of 27S precursors. Mrt4, which shuttles between the nucleus and the cytoplasm, defines medium pre-60S particles. In contrast, P0 is absent from medium but present in late/cytoplasmic pre-60S complexes. The absence of Mrt4 notably increased the amount of P0 in nuclear Nop7–TAP complexes and causes P0 assembly to medium pre-60S particles. Upon P0 depletion, Mrt4 is relocated to the cytoplasm within aberrant 60S subunits. We conclude that Mrt4 controls the position and timing of P0 assembly. In turn, P0 is required for the release of Mrt4 and exchanges with this factor at the cytoplasm. Our results also suggest other P0 assembly alternatives

Changes of the Neutron Flux of the Nuclear Reactor Triga Mark III Since the Conversion from High to Low 235U Enrichment

The neutron flux of the Triga Mark III research reactor was studied using nuclear track detectors. The facility of the National Institute for Nuclear Research (ININ), operates with a new core load of 85 LEU 30/20 (Low Enriched Uranium) fuel elements. The reactor provides a neutron flux around 2 × 1012 n cm-2s-1 at the irradiation channel. In this channel, CR-39 (allyl diglycol policarbonate) Landauer® detectors were exposed to neutrons; the detectors were covered with a 3 mm acrylic sheet for (n, p) reaction. Results show a linear response between the reactor power in the range 0.1 - 7 kW, and the average nuclear track density with data reproducibility and relatively low uncertainty (±5%). The method is a simple technique, fast and reliable procedure to monitor the research reactor operating power levels

Study of the near-barrier scattering of 8 He on 208 Pb

The structure and dynamics of 8He have been studied through the collision process with a 208 Pb target at energies of 22 and 16 MeV, above and below the Coulomb barrier, respectively. The energy and angular distributions of the elastically scattered 8He and the 6,4He fragments were measured. In this paper, we discuss the method used to determine the effective position of the beam spot on the reaction target and the scattering and solid angles of each pixel of the detector array.Ministerio de Economía y Competitividad PA2010-22131-C021-01, FPA2014-59954-C3-1-PMinistry of Science and Higher Education of Poland N202 03363European Science Foundation EUI2009-0416