Summability of Superstring Theory

Several arguments are given for the summability of the superstring perturbation series. Whereas the Schottky group coordinatization of moduli space may be used to provide refined estimates of large-order bosonic string amplitudes, the super-Schottky group variables define a measure for the supermoduli space integral which leads to upper bounds on superstring scattering amplitudes.Comment: 11 pages, TeX. A remark about C-cycles and dividing cycles and two references have been added to the pape

The influence of local community stakeholders in megaprojects: Rethinking their inclusiveness to improve project performance

This paper organizes and synthesizes different extant research streams through a systematic literature review to identify connections and major assumptions on the influence of stakeholders in major Public Infrastructure and Construction projects (PIC), at the local community level. Findings suggest that research on stakeholder management has focused strongly on those stakeholders able to control project resources, whilst the effect on the legitimate ‘secondary stakeholders’, such as the local community, remains widely unexplored. Due to the unavoidable impact of major PIC on both people and places, it is suggested that seeking local community opinions in the initiation phase of the project and monitoring the megaproject impact at the local level can help to improve project performance. The output provides scholars and practitioners with future research directions and practical implications for an inclusive stakeholder management approach in construction megaprojects

Scattering lengths and universality in superdiffusive L\'evy materials

We study the effects of scattering lengths on L\'evy walks in quenched one-dimensional random and fractal quasi-lattices, with scatterers spaced according to a long-tailed distribution. By analyzing the scaling properties of the random-walk probability distribution, we show that the effect of the varying scattering length can be reabsorbed in the multiplicative coefficient of the scaling length. This leads to a superscaling behavior, where the dynamical exponents and also the scaling functions do not depend on the value of the scattering length. Within the scaling framework, we obtain an exact expression for the multiplicative coefficient as a function of the scattering length both in the annealed and in the quenched random and fractal cases. Our analytic results are compared with numerical simulations, with excellent agreement, and are supposed to hold also in higher dimensionsComment: 6 pages, 8 figure

Protein structure determination via an efficient geometric build-up algorithm

Abstract Background A protein structure can be determined by solving a so-called distance geometry problem whenever a set of inter-atomic distances is available and sufficient. However, the problem is intractable in general and has proved to be a NP hard problem. An updated geometric build-up algorithm (UGB) has been developed recently that controls numerical errors and is efficient in protein structure determination for cases where only sparse exact distance data is available. In this paper, the UGB method has been improved and revised with aims at solving distance geometry problems more efficiently and effectively. Methods An efficient algorithm (called the revised updated geometric build-up algorithm (RUGB)) to build up a protein structure from atomic distance data is presented and provides an effective way of determining a protein structure with sparse exact distance data. In the algorithm, the condition to determine an unpositioned atom iteratively is relaxed (when compared with the UGB algorithm) and data structure techniques are used to make the algorithm more efficient and effective. The algorithm is tested on a set of proteins selected randomly from the Protein Structure Database-PDB. Results We test a set of proteins selected randomly from the Protein Structure Database-PDB. We show that the numerical errors produced by the new RUGB algorithm are smaller when compared with the errors of the UGB algorithm and that the novel RUGB algorithm has a significantly smaller runtime than the UGB algorithm. Conclusions The RUGB algorithm relaxes the condition for updating and incorporates the data structure for accessing neighbours of an atom. The revisions result in an improvement over the UGB algorithm in two important areas: a reduction on the overall runtime and decrease of the numeric error.Peer Reviewe

Rural Income Generating Activities: A Cross Country Comparison

This paper uses a newly constructed cross country database composed of comparable variables and aggregates from household surveys to examine the full range of income generating activities carried out by rural households in order to determine: 1) the relative importance of the gamut of income generating activities in general and across wealth categories; 2), the relative importance of diversification versus specialization at the household level; and 3) the influence of rural income generating activities on poverty and inequality. Analysis of the RIGA cross country dataset paints a clear picture of multiple activities across rural space and diversification across rural households. This is true across countries in all four continents, though less so in the African countries included in the dataset. For most countries the largest share of income stems from off farm activities, and the largest share of households have diversified sources of income. Diversification, not specialization, is the norm, although most countries show significant levels of household specialization in non-agricultural activities as well. Nevertheless, agricultural based sources of income remain critically important for rural livelihoods in all countries, both in terms of the overall share of agriculture in rural incomes as well as the large share of households that still specialize in agricultural sources of income.Community/Rural/Urban Development, Consumer/Household Economics,

Rural Household Access to Assets and Agrarian Institutions: A Cross Country Comparison

Agriculture is at the core of the livelihoods of a large share of rural households throughout the developing world. Agricultural growth is a major engine for overall economic growth and possibly the single most important pathway out of poverty in the rural space. This paper characterizes household access to assets and agrarian institutions of households engaged in agricultural activities in a sample of developing countries. The evidence presented in the paper draws from 15 nationally representative household surveys from four regions of the developing world. We find that the access of rural households to a range of agricultural-specific assets (including land and livestock) and institutions is in general low, though highly heterogeneous across countries, and by categories of households within countries. A large share of rural agricultural households do not use or have access to basic productive inputs, agricultural support services or output markets, and in general it is the landless and the smallest landowners who suffer significantly more from this lack of access. We relate this to the households' ability to engage successfully in commercial farming and find consistent supporting evidence for the hypothesis that this lack of access is significantly constraining their potential to engage successfully in agriculture.rural non farm, assets, agrarian institutions, household surveys, Consumer/Household Economics, O13, O57, Q12,

A new method for the determination of the growth rate from galaxy redshift surveys

Given a redshift survey of galaxies with measurements of apparent magnitudes, we present a novel method for measuring the growth rate $f(\Omega)$ of cosmological linear perturbations. We use the galaxy distribution within the survey to solve for the peculiar velocity field which depends in linear perturbation theory on $\beta=f(\Omega)/b$, where $b$ is the bias factor of the galaxy distribution. The recovered line-of-sight peculiar velocities are subtracted from the redshifts to derive the distances, which thus allows an estimate of the absolute magnitude of each galaxy. A constraint on $\beta$ is then found by minimizing the spread of the estimated magnitudes from their distribution function. We apply the method to the all sky $K = 11.25$ Two-MASS Redhsift Survey (2MRS) and derive $\beta=0.35\pm 0.1$ at $z\sim 0$, remarkably consistent with our previous estimate from the velocity-velocity comparison. The method could easily be applied to subvolumes extracted from the SDSS survey to derive the growth rate at $z \sim 0.1$. Further, it should also be applicable to ongoing and future spectroscopic redshift surveys to trace the evolution of $f(\Omega)$ to $z\sim1$. Constraints obtained from this method are entirely independent from those obtained from the two-dimensional distortion of $\xi(s)$ and provide an important check on $f(\Omega)$, as alternative gravity models predict observable differences.Comment: 9pages, 1figure Typos corrected. A slight change in the Discussion and Acknowledgemen

Non-invasive imaging using reporter genes altering cellular water permeability

Non-invasive imaging of gene expression in live, optically opaque animals is important for multiple applications, including monitoring of genetic circuits and tracking of cell-based therapeutics. Magnetic resonance imaging (MRI) could enable such monitoring with high spatiotemporal resolution. However, existing MRI reporter genes based on metalloproteins or chemical exchange probes are limited by their reliance on metals or relatively low sensitivity. Here we introduce a new class of MRI reporters based on the human water channel aquaporin 1. We show that aquaporin overexpression produces contrast in diffusion-weighted MRI by increasing tissue water diffusivity without affecting viability. Low aquaporin levels or mixed populations comprising as few as 10% aquaporin-expressing cells are sufficient to produce MRI contrast. We characterize this new contrast mechanism through experiments and simulations, and demonstrate its utility in vivo by imaging gene expression in tumours. Our results establish an alternative class of sensitive, metal-free reporter genes for non-invasive imaging

Calibration Observations of Fomalhaut with the VLTI

An investigation of the stability of the transfer function of the European Southern Observatory's Very Large Telescope Interferometer has been carried out through observations of Fomalhaut over a wide range in hour angle. No significant variation in the transfer function was found for the zenith angle range 5-70 degrees. The projected baseline varied between 139.7 m and 49.8 m during the observations and, as an integral part of the determination of the transfer function, a new accurate limb-darkened angular diameter for Fomalhaut has been established. This has led to improved values for the emergent flux, effective temperature, radius and luminosity.Comment: 6 pages, 4 figures, uses an.cls, accepted for publication in Astron. Nach

Damping of giant resonances in asymmetric nuclear matter

The giant collective modes in asymmetric nuclear matter are investigated within a dynamic relaxation time approximation. We derive a coupled dispersion relation and show that two sources of coupling appear: (i) a coupling of isoscalar and isovector modes due to different mean-fields acting and (ii) an explicit new coupling in asymmetric matter due to collisional interaction. We show that the latter one is responsible for a new mode arising besides isovector and isoscalar modes.Comment: Varenna conference proceeding