Quantum Computation with Diatomic Bits in Optical Lattices

We propose a scheme for scalable and universal quantum computation using diatomic bits with conditional dipole-dipole interaction, trapped within an optical lattice. The qubit states are encoded by the scattering state and the bound heteronuclear molecular state of two ultracold atoms per site. The conditional dipole-dipole interaction appears between neighboring bits when they both occupy the molecular state. The realization of a universal set of quantum logic gates, which is composed of single-bit operations and a two-bit controlled-NOT gate, is presented. The readout method is also discussed.Comment: 5 pages, 1 eps figure, accepted for publication in Phys. Rev.

Land use intensity indirectly affects ecosystem services mainly through plant functional identity in a temperate forest

Land‐use change is known to affect biodiversity, and there is increasing concern regarding how these changes may impact the provision of ecosystem services. Although functional composition (diversity and identity) could influence ecosystem properties and services at the community level, there is little quantitative understanding of these relationships in the field. Here, we evaluate the direct and indirect effects (through ecosystem properties) of biodiversity on the provision of multiple ecosystem services in native mixed forest in north‐west Patagonia, and how land‐use intensity influences these relationships. We used structural equation modelling to test hypotheses regarding the relationship between understorey plant functional composition, two ecosystem properties, four ecosystem services and silvopastoral use intensity (SUI). We also evaluated two alternative models to assess the mechanism behind biodiversity and ecosystem properties relationships (biomass ratio and niche complementarity). Finally, we performed pairwise correlations to identify synergies and trade‐offs between ecosystem services. SUI affected functional composition, and the provision of three out of four ecosystem services was indirectly affected by land‐use intensity through changes in ecosystem properties. We found that this indirect effect of biodiversity on ecosystem services happens mainly through changes in functional identity rather than functional diversity. Under increasing land‐use intensity, functional composition changed towards a community characterized by a resource acquisition strategy. Trade‐offs between ecosystem services (provisioning vs. regulating) were enhanced under high SUI, while synergies where enhanced under low SUI (provisioning vs. cultural). Thus, although the strength of these relationships varied between SUI, its nature (trade‐off or synergy) stayed the same. Our results expand on previous studies by simultaneously considering the effect of land‐use intensification directly on functional composition and on the ecosystem processes underpinning ecosystem services, as well as on the relationship among them. We provide evidence of an indirect effect of land‐use intensification on multiple ecosystem services through biodiversity. Moreover, we found that functional identity is more important than diversity for ecosystem functionality. Land‐use intensification affects biodiversity, and thus, ecosystem properties, but does not change the relationship among ecosystem services.Fil: Chillo, María Verónica. Universidad Nacional de Río Negro. Sede Andina. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vazquez, Diego P.. Albert Ludwigs University Of Freiburg; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Amoroso, Mariano Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Negro. Sede Andina. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural; ArgentinaFil: Bennett, Elena M.. McGill University; Canad

Land-Use Legacies Are Important Determinants of Lake Eutrophication in the Anthropocene

Background: A hallmark of the latter half of the 20 th century is the widespread, rapid intensification of a variety of anthropogenically-driven environmental changes—a ‘‘Great Acceleration.’ ’ While there is evidence of a Great Acceleration in a variety of factors known to be linked to water quality degradation, such as conversion of land to agriculture and intensification of fertilizer use, it is not known whether there has been a similar acceleration of freshwater eutrophication. Methodology/Principal Findings: Using quantitative reconstructions of diatom-inferred total phosphorus (DI-TP) as a proxy for lake trophic state, we synthesized results from 67 paleolimnological studies from across Europe and North America to evaluate whether most lakes showed a pattern of eutrophication with time and whether this trend was accelerated after 1945 CE, indicative of a Great Acceleration. We found that European lakes have experienced widespread increases in DI-TP over the 20 th century and that 33 % of these lakes show patterns consistent with a post-1945 CE Great Acceleration. In North America, the proportion of lakes that increased in DI-TP over time is much lower and only 9 % exhibited a Great Acceleration of eutrophication. Conclusions/Significance: The longer and more widespread history of anthropogenic influence in Europe, the leading cause for the relatively pervasive freshwater eutrophication, provides an important cautionary tale; our current path of intensive agriculture around the world may lead to an acceleration of eutrophication in downstream lakes that could tak

Responses of Mn\u3csup\u3e2+\u3c/sup\u3e Speciation in \u3cem\u3eDeinococcus radiodurans\u3c/em\u3e and \u3cem\u3eEscherichia coli\u3c/em\u3e to γ-Radiation by Advanced Paramagnetic Resonance Methods

The remarkable ability of bacterium Deinococcus radiodurans to survive extreme doses of γ-rays (12,000 Gy), 20 times greater than Escherichia coli, is undiminished by loss of Mn-dependent superoxide dismutase (SodA). D. radiodurans radiation resistance is attributed to the accumulation of low-molecular-weight (LMW) “antioxidant” Mn2+–metabolite complexes that protect essential enzymes from oxidative damage. However, in vivo information about such complexes within D. radiodurans cells is lacking, and the idea that they can supplant reactive-oxygen-species (ROS)–scavenging enzymes remains controversial. In this report, measurements by advanced paramagnetic resonance techniques [electron-spin-echo (ESE)-EPR/electron nuclear double resonance/ESE envelope modulation (ESEEM)] reveal differential details of the in vivo Mn2+ speciation in D. radiodurans and E. coli cells and their responses to 10 kGy γ-irradiation. The Mn2+ of D. radiodurans exists predominantly as LMW complexes with nitrogenous metabolites and orthophosphate, with negligible EPR signal from Mn2+ of SodA. Thus, the extreme radiation resistance of D. radiodurans cells cannot be attributed to SodA. Correspondingly, 10 kGy irradiation causes no change in D. radiodurans Mn2+ speciation, despite the paucity of holo-SodA. In contrast, the EPR signal of E. coli is dominated by signals from low-symmetry enzyme sites such as that of SodA, with a minority pool of LMW Mn2+ complexes that show negligible coordination by nitrogenous metabolites. Nonetheless, irradiation of E. coli majorly changes LMW Mn2+ speciation, with extensive binding of nitrogenous ligands created by irradiation. We infer that E. coli is highly susceptible to radiation-induced ROS because it lacks an adequate supply of LMW Mn antioxidants

Constraints on Extrasolar Planet Populations from VLT NACO/SDI and MMT SDI and Direct Adaptive Optics Imaging Surveys: Giant Planets are Rare at Large Separations

We examine the implications for the distribution of extrasolar planets based on the null results from two of the largest direct imaging surveys published to date. Combining the measured contrast curves from 22 of the stars observed with the VLT NACO adaptive optics system by Masciadri et al. (2005), and 48 of the stars observed with the VLT NACO SDI and MMT SDI devices by Biller et al. (2007) (for a total of 60 unique stars; the median star for our survey is a 30 Myr K2 star at 25 pc), we consider what distributions of planet masses and semi-major axes can be ruled out by these data, based on Monte Carlo simulations of planet populations. We can set this upper limit with 95% confidence: the fraction of stars with planets with semi-major axis from 20 to 100 AU, and mass >4 M_Jup, is 20% or less. Also, with a distribution of planet mass of dN/dM ~ M^-1.16 between 0.5-13 M_Jup, we can rule out a power-law distribution for semi-major axis (dN/da ~ a^alpha) with index 0 and upper cut-off of 18 AU, and index -0.5 with an upper cut-off of 48 AU. For the distribution suggested by Cumming et al. (2007), a power-law of index -0.61, we can place an upper limit of 75 AU on the semi-major axis distribution. At the 68% confidence level, these upper limits state that fewer than 8% of stars have a planet of mass >4 M_Jup between 20 and 100 AU, and a power-law distribution for semi-major axis with index 0, -0.5, and -0.61 cannot have giant planets beyond 12, 23, and 29 AU, respectively. In general, we find that even null results from direct imaging surveys are very powerful in constraining the distributions of giant planets (0.5-13 M_Jup) at large separations, but more work needs to be done to close the gap between planets that can be detected by direct imaging, and those to which the radial velocity method is sensitive.Comment: 46 pages, 17 figures, accepted to Ap

In silico evolution of diauxic growth

The glucose effect is a well known phenomenon whereby cells, when presented with two different nutrients, show a diauxic growth pattern, i.e. an episode of exponential growth followed by a lag phase of reduced growth followed by a second phase of exponential growth. Diauxic growth is usually thought of as a an adaptation to maximise biomass production in an environment offering two or more carbon sources. While diauxic growth has been studied widely both experimentally and theoretically, the hypothesis that diauxic growth is a strategy to increase overall growth has remained an unconfirmed conjecture. Here, we present a minimal mathematical model of a bacterial nutrient uptake system and metabolism. We subject this model to artificial evolution to test under which conditions diauxic growth evolves. As a result, we find that, indeed, sequential uptake of nutrients emerges if there is competition for nutrients and the metabolism/uptake system is capacity limited. However, we also find that diauxic growth is a secondary effect of this system and that the speed-up of nutrient uptake is a much larger effect. Notably, this speed-up of nutrient uptake coincides with an overall reduction of efficiency. Our two main conclusions are: (i) Cells competing for the same nutrients evolve rapid but inefficient growth dynamics. (ii) In the deterministic models we use here no substantial lag-phase evolves. This suggests that the lag-phase is a consequence of stochastic gene expression

The Non-SUSY Baryonic Branch: Soft Supersymmetry Breaking of N=1 Gauge Theories

We study a non-supersymmetric deformation of the field theory dual to the baryonic branch of Klebanov-Strassler. Using a combination of analytical (series expansions) and numerical methods we construct non-supersymmetric backgrounds that smoothly interpolate between the desired UV and IR behaviors. We calculate various observables of the field theory and propose a picture of soft breaking by gaugino masses that is consistent with the various calculations on the string side.Comment: 32 pages plus many appendixes. One figur

Exploring Alternative Futures in the Anthropocene

Many challenges posed by the current Anthropocene epoch require fundamental transformations to humanity’s relationships with the rest of the planet. Achieving such transformations requires that humanity improve its understanding of the current situation and enhance its ability to imagine pathways toward alternative, preferable futures. We review advances in addressing these challenges that employ systematic and structured thinking about multiple possible futures (futures-thinking). Over seven decades, especially the past two, approaches to futures-thinking have helped people from diverse backgrounds reach a common understanding of important issues, underlying causes, and pathways toward optimistic futures. A recent focus has been the stimulation of imagination to produce new options. The roles of futures-thinking in breaking unhelpful social addictions and in conflict resolution are key emerging topics. We summarize cognitive, cultural, and institutional constraints on the societal uptake of futures-thinking, concluding that none are insurmountable once understood