Hamiltonian and physical Hilbert space in polymer quantum mechanics

In this paper, a version of polymer quantum mechanics, which is inspired by loop quantum gravity, is considered and shown to be equivalent, in a precise sense, to the standard, experimentally tested, Schroedinger quantum mechanics. The kinematical cornerstone of our framework is the so called polymer representation of the Heisenberg-Weyl (H-W) algebra, which is the starting point of the construction. The dynamics is constructed as a continuum limit of effective theories characterized by a scale, and requires a renormalization of the inner product. The result is a physical Hilbert space in which the continuum Hamiltonian can be represented and that is unitarily equivalent to the Schroedinger representation of quantum mechanics. As a concrete implementation of our formalism, the simple harmonic oscillator is fully developed.Comment: 19 pages, 2 figures. Comments and references added. Version to be published in CQ

Implications of Halo Inside-out Growth on the X-Ray Properties of Nearby Galaxy Systems within the Preheating Scenario

We present an entirely analytic model for a preheated, polytropic intergalactic medium in hydrostatic equilibrium within a NFW dark halo potential in which the evolution of the halo structure between major merger events proceeds inside-out by accretion. This model is used to explain, within a standard $\Lambda$CDM cosmogony, the observed X-ray properties of nearby relaxed, non-cooling flow groups and clusters of galaxies. We find that our preferred solution to the equilibrium equations produces scaling relations in excellent agreement with observations, while simultaneously accounting for the typical structural characteristics of the distribution of the diffuse baryons. In the class of preheating models, ours stands out because it offers a unified description of the intrahalo medium for galaxy systems with total masses above \sm 2\times 10^{13}\msun, does not produce baryonic configurations with large isentropic cores, and reproduces faithfully the observed behavior of the gas entropy at large radii. All this is achieved with a moderate level of energy injection of about half a keV, which can be easily accommodated within the limits of the total energy released by the most commonly invoked feedback mechanisms, as well as with a polytropic index of 1.2, consistent with both many observational determinations and predictions from high-resolution gas-dynamical simulations of non-cooling flow clusters. More interestingly, our scheme offers a physical motivation for the adoption of this specific value of the polytropic index, as it is the one that best ensures the conservation after halo virialization of the balance between the total specific energies of the gas and dark matter components for the full range of masses investigated.Comment: 18 pages, 11 figures, accepted for publication in the Astrophysical Journa

Fractal space-times under the microscope: A Renormalization Group view on Monte Carlo data

The emergence of fractal features in the microscopic structure of space-time is a common theme in many approaches to quantum gravity. In this work we carry out a detailed renormalization group study of the spectral dimension $d_s$ and walk dimension $d_w$ associated with the effective space-times of asymptotically safe Quantum Einstein Gravity (QEG). We discover three scaling regimes where these generalized dimensions are approximately constant for an extended range of length scales: a classical regime where $d_s = d, d_w = 2$, a semi-classical regime where $d_s = 2d/(2+d), d_w = 2+d$, and the UV-fixed point regime where $d_s = d/2, d_w = 4$. On the length scales covered by three-dimensional Monte Carlo simulations, the resulting spectral dimension is shown to be in very good agreement with the data. This comparison also provides a natural explanation for the apparent puzzle between the short distance behavior of the spectral dimension reported from Causal Dynamical Triangulations (CDT), Euclidean Dynamical Triangulations (EDT), and Asymptotic Safety.Comment: 26 pages, 6 figure

Myxobolus sp. and Henneguya sp. (Cnidaria: Myxobolidae) natural co-infection in the kidney of Piaractus mesopotamicus(Characiformes: Serrasalmidae)

This study evaluated the myxozoan infection and histopathology of the kidney of freshwater fish Piaractus mesopotamicus from intensive fish farming in Brazil. A total of 55 fish were examined for myxozoan infection. Infected organs were processed by usual histology and stained with hematoxylin-eosin (H&E) and Ziehl-Neelsen (ZN). From the total of 55 fish analyzed, 47 (85.45%) presented myxospores, being 9.09% (5/55) only with Myxobolus sp., 5.45% (3/55) only with Henneguya sp., and 70.91% (39/55) presenting both parasites. The presence of myxospores was associated with histological alterations in both stromal and renal parenchyma. Myxospores were found mostly in the peritubular interstitial tissue and in low intensity in the glomerulus which caused nuclear hypertrophy and loss of Bowman space. An increase in the glomerular tuft and a reduction in the lumen of the collector tubules were also observed, besides the high number of melanomacrophage cells in the glomerulus. This study reports for the first time detection of myxozoan mixed infection in one organ of pacu and discuss the possible transportation of myxospores in the circulating blood

Induction of somatic embryogenesis in recalcitrant sweetpotato (Ipomoea batatas L.) cultivars

Genetic transformation is considered as one of the most promising options for improvement of crop traits. Current transformation methods for sweetpotato depend on plant regeneration through organogenesis or somatic embryogenesis. Somatic embryogenesis and plant regeneration at a high frequency has been  restricted to a few sweetpotato varieties. Three auxins namely: 2,4-dichlorophenoxyacetic acid (2,4-D),  4-fluoroamphetamine (4-FA) and 4,5-trichlorophenoxyacetic acid (2,4,5-T) were investigated in this study for enhancing somatic embryogenesis from various plant organs of recalcitrant African sweetpotato cultivars.  2,4-D was found to be the best (p . 0.05) for induction of embryogenic callus. Cultivar Bwanjule had the highest  (20.2%) embryogenic callus frequency among the five African cultivars tested. The highest number of plants in this study was regenerated from the non-African cultivar variety Jonathan on media supplemented with 0.2 mg Zeatin. The emergence of roots from callus of recalcitrant Ugandan cultivars and the comparable high embryogenic responses in this work demonstrate the potential for regenerating plants from African  cultivars that have not been regenerated before. The regeneration of roots in this work could be useful for the initiation of root cultures. The most important application of this work is in genetic transformation of sweet potato, particularly for improvement of resistance to weevils.Key words: Embryogenesis, plant growth regulators, plant regeneration, Ipomoea batatas

The participatory market chain approach: stimulating pro-poor market-chain innovation

Innovation in the food and agriculture sector is frequently short-circuited by a lack of trust and communication between actors in the market chain. To overcome these problems and stimulate innovation, the Participatory Market Chain Approach (PMCA) brings together small farmers, market agents, and service providers for an intense process of facilitated interaction. The PMCA uses a flexible three-stage participatory process to improve communication, build trust, and facilitate collaboration among participants so that they can jointly identify, analyze, and exploit new market opportunities. The PMCA focuses on innovation in products, technologies, and ways of working together. By carefully selecting market chains and partners, and building in social responsibility, the PMCA can lead to favourable outcomes and impacts for poor farmers, typically the weakest link in the chain. The PMCA requires facilitation and technical support from professionals with good social skills, research experience, and marketing knowledge, based in a neutral research and development organization. To ensure that impacts are sustained, the PMCA is best used as part of a broader programme of market chain development

The benefits of being seen to help others: indirect reciprocity and reputation-based partner choice

When one individual helps another, it benefits the recipient and may also gain a reputation for being cooperative. This may induce others to favour the helper in subsequent interactions, so investing in being seen to help others may be adaptive. The best-known mechanism for this is indirect reciprocity (IR), in which the profit comes from an observer who pays a cost to benefit the original helper. IR has attracted considerable theoretical and empirical interest, but it is not the only way in which cooperative reputations can bring benefits. Signalling theory proposes that paying a cost to benefit others is a strategic investment which benefits the signaller through changing receiver behaviour, in particular by being more likely to choose the signaller as a partner. This reputation-based partner choice can result in competitive helping whereby those who help are favoured as partners. These theories have been confused in the literature. We therefore set out the assumptions, the mechanisms and the predictions of each theory for how developing a cooperative reputation can be adaptive. The benefits of being seen to be cooperative may have been a major driver of sociality, especially in humans. This article is part of the theme issue ‘The language of cooperation: reputation and honest signalling’

Thermoelectric Performance of various Benzo-difuran Wires

Using a first principles approach to electron transport, we calculate the electrical and thermoelectrical transport properties of a series of molecular wires containing benzo-difuran subunits. We demonstrate that the side groups introduce Fano resonances, the energy of which is changing with the electronegativity of selected atoms in it. We also study the relative effect of single, double or triple bonds along the molecular backbone and find that single bonds yield the highest thermopower, approximately 22$\mu$V/K at room temperature, which is comparable with the highest measured values for single-molecule thermopower reported to date.Comment: 7 pages, 8 figure