Opacity of electromagnetically induced transparency for quantum fluctuations

We analyze the propagation of a pair of quantized fields inside a medium of three-level atoms in $\Lambda$ configuration. We calculate the stationary quadrature noise spectrum of the field after propagating through the medium, in the case where the probe field is in a squeezed state and the atoms show electromagnetically induced transparency (EIT). We find an oscillatory transfer of the initial quantum properties between the probe and pump fields which is most strongly pronounced when both fields have comparable Rabi frequencies. This implies that the quantum state measured after propagation can be completely different from the initial state, even though the mean values of the field are unaltered

Observation of ground-state quantum beats in atomic spontaneous emission

We report ground-state quantum beats in spontaneous emission from a continuously driven atomic ensemble. Beats are visible only in an intensity autocorrelation and evidence spontaneously generated coherence in radiative decay. Our measurement realizes a quantum eraser where a first photon detection prepares a superposition and a second erases the "which-path" information in the intermediate state.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Letter

Large Isospin mixing in phi radiative decay and the spatial size of the f0(980)- a0(980) meson

The measured rate for phi to gamma f0(980) appears to be larger than allowed on rather general grounds. We show that mixing between the f0(980) and a0(980), due to their dynamical interaction with the nearby KKbar thresholds, radically affects some existing predictions of their production in phi radiative decay. We predict that Gamma(phi to gamma f0)/Gamma(phi to gamma a_0) approx 3; that sum (b.r.(phi to gamma f0) + b.r. (phi to gamma a_0)) < 5 x 10^-4 with probable individual branching ratios 2 x 10^-4 and 0.7 x 10^-4 respectively.Comment: 7 pages, Late

A model for the spatiotemporal organization of DNA replication in Saccharomyces cerevisiae

DNA replication in eukaryotes is considered to proceed according to a precise program in which each chromosomal region is duplicated in a defined temporal order. However, recent studies reveal an intrinsic temporal disorder in the replication of yeast chromosome VI. Here we provide a model of the chromosomal duplication to study the temporal sequence of origin activation in budding yeast. The model comprises four parameters that influence the DNA replication system: the lengths of the chromosomes, the explicit chromosomal positions for all replication origins as well as their distinct initiation times and the replication fork migration rate. The designed model is able to reproduce the available experimental data in form of replication profiles. The dynamics of DNA replication was monitored during simulations of wild type and randomly perturbed replication conditions. Severe loss of origin function showed only little influence on the replication dynamics, so systematic deletions of origins (or loss of efficiency) were simulated to provide predictions to be tested experimentally. The simulations provide new insights into the complex system of DNA replication, showing that the system is robust to perturbation, and giving hints about the influence of a possible disordered firing

Tussock grasses as shelters for overwintering arthropods in Pampean agroecosystems: effects of plant size, clustering and architecture

Las gramíneas perennes son utilizadas como refugios por numerosas especies de artrópodos invernantes de la región pampeana. Las características estructurales y el tamaño de las plantas, así como su disposición espacial, condicionarían la disponibilidad de hábitat o de refugio y en consecuencia la selección de las mismas por artrópodos invernantes. En este trabajo evaluamos la influencia del tamaño, agrupamiento y modificación de la arquitectura de plantas de Schizachyrium condensatum sobre la abundancia y riqueza de artrópodos invernantes en su interior. En un borde de un área agrícola de la Pampa Ondulada se dispusieron plantas de distinto tamaño: desde 110 cm de altura (plantas grandes) a 70 cm de altura (plantas pequeñas), de manera aislada o en grupos de 5 plantas, a las cuales se les modificó o no su arquitectura (abiertas o cerradas). Luego de la temporada invernal, se extrajeron los artrópodos y se determinó la abundancia y riqueza de morfoespecies en cada planta. Dos especies predadoras de la familia Coccinellidae, Hippodamia convergens y Coccinella ancoralis, representaron el 90% de la abundancia total concentrándose mayoritariamente en las plantas grandes agrupadas-cerradas. En las plantas grandes/cerradas se registró más del doble de la abundancia de artrópodos que en las plantas grandes/abiertas; en las plantas pequeñas no hubo efectos debido a la arquitectura. Se registró similar riqueza de especies de artrópodos entre plantas pequeñas/aisladas y plantas pequeñas agrupadas; en las plantas grandes/agrupadas se detectó casi el doble de especies de artrópodos que en las plantas grandes/aisladas. Estos resultados muestran que el tamaño pequeño, así como la apertura y el aislamiento de las plantas grandes, influyen negativamente sobre la selección de los sitios de refugio de coccinélidos invernantes. En consecuencia, planteamos la importancia de la conservación de las gramíneas perennes en los bordes de áreas agrícolas como refugios que asegurarían la permanencia de coccinélidos afidófagos en las proximidades de los campos de cultivo durante el período invernal.Perennial grasses are used as overwintering shelters by several arthropod species in the Pampa region. Plant size, structure, and clustering may condition habitat or shelter availability, and therefore their selection by overwintering arthropods. We analyzed the influence of clustering, size and architecture modification of Schizachyrium condensatum plants on the abundance and richness of these arthropods dwelling inside these plants. We set up plants of different sizes, from large (110 cm tall) to small (70 cm tall), along the edge of a field crop in the Rolling Pampas. They were planted isolated or in groups of five plants, with or without architecture modification (open or closed). After the winter season, overwintering arthropods were removed and the abundance and richness of morphospecies were calculated for each plant. Two predator species from the Coccinellidae family, Hippodamia convergens and Coccinella ancoralis, represented almost 90% of total abundance in large, grouped and closed plants. In large closed plants there was almost twice the abundance of arthropods than in large open plants. In small plants there was no effect due to architecture. In small plants there was similar arthropod richness between isolated and grouped plants, whereas in large plants there was almost twice the species in grouped than in isolated plants. Our results show that small plant size, as well as opening and isolation for large plants, negatively affected the choice of wintering sites for coccinelids. Therefore, we highlight the importance of conserving perennial grasses in the edges of agricultural areas as they allow the persistence of aphidofagous coccinelids in the surroundings of crop fields during wintering periods and thus contribute to the sustainability of the beneficial faunaFil: Cánepa, María E.. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; ArgentinaFil: Montero, Guillermo A.. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; ArgentinaFil: Barberis, Ignacio Martín. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe; Argentin

The influence of pulsed redox conditions on soil phosphorus

The effects of eleven pulsed reduction-oxidation cycles (20 and 2 days respectively) on soil phosphorus (P) dynamics are compared for 12 soils having contrasting properties and overfertilised with respect to P. Incubation conditions simulated transient waterlogging of the soil profile and involved repeated sampling and analysis of both the solution and solid phase P forms. An initial increase in P concentration occurred upto and including the fourth full cycle was followed by a sharp decline in concentration for all but one soil. Accompanying changes in the main extractable forms of P, which appeared to be cumulative, could be summarised as a general decline in the organic P fraction and an overall increase in amorphous associated inorganic forms of P. The fact that up to 60% of the total soil P was demonstrated to change its sensitivity for a particular extractant suggests that these operationally defined P forms can experience substantial transformations. There was also a suggestion that certain changes in P forms may not be reversible. While the laboratory conditions represent an extreme situation changes in timing and frequency of intense precipitation events, as predicted in many climate change scenarios, may increase the risk of episodic soil waterlogging. The potential onset of reducing conditions even for periods of less than twenty days will influence soil P dynamics and short-term bioavailable P. Various mechanisms are involved but the robustness of sequential extraction procedures and general soil test methods (e.g. Olsen) for quantifying and reliably distinguishing specific soil P forms/associations are questioned

Fkh1 and Fkh2 associate with Sir2 to control CLB2 transcription under normal and oxidative stress conditions

The Forkhead (Fkh) box family of transcription factors is evolutionary conserved from yeast to higher eukaryotes and its members are involved in many physiological processes including metabolism, DNA repair, cell cycle, stress resistance, apoptosis, and aging. In budding yeast, four Fkh transcription factors were identified, namely Fkh1, Fkh2, Fhl1, and Hcm1, which are implicated in chromatin silencing, cell cycle regulation, and stress response. These factors impinge transcriptional regulation during cell cycle progression, and histone deacetylases (HDACs) play an essential role in this process, e.g., the nuclear localization of Hcm1 depends on Sir2 activity, whereas Sin3/Rpd3 silence cell cycle specific gene transcription in G2/M phase. However, a direct involvement of Sir2 in Fkh1/Fkh2-dependent regulation of target genes is at present unknown. Here, we show that Fkh1 and Fkh2 associate with Sir2 in G1 and M phase, and that Fkh1/Fkh2-mediated activation of reporter genes is antagonized by Sir2. We further report that Sir2 overexpression strongly affects cell growth in an Fkh1/Fkh2-dependent manner. In addition, Sir2 regulates the expression of the mitotic cyclin Clb2 through Fkh1/Fkh2-mediated binding to the CLB2 promoter in G1 and M phase. We finally demonstrate that Sir2 is also enriched at the CLB2 promoter under stress conditions, and that the nuclear localization of Sir2 is dependent on Fkh1 and Fkh2. Taken together, our results show a functional interplay between Fkh1/Fkh2 and Sir2 suggesting a novel mechanism of cell cycle repression. Thus, in budding yeast, not only the regulation of G2/M gene expression but also the protective response against stress could be directly coordinated by Fkh1 and Fkh2. © 2013 Linke, Klipp, Lehrach, Barberis and Krobitsch