Organic Agriculture in Saudi Arabia - Sector Study 2012

This publication compiles the facts and figures of the organic sector in Saudi Arabia. It is a valuable resource for local stakeholders and interested trading companies. The publication is resulting from a collaboration between GIZ (Deutsche Gesellschaft für Internationale Zusammenarbeit) and FiBL together with its partners of the Saudi Ministry of Agriculture and Saudi Organic Farming Association (SOFA)

New high-z BL Lacs using the photometric method with Swift and SARA

BL Lacertae (BL Lac) objects are the prominent members of the third {\it Fermi} Large Area Telescope catalog of $\gamma$-ray sources. Half of the BL Lac population ($\sim$ 300) lack redshift measurements, which is due to the absence of lines in their optical spectrum, thereby making it difficult to utilize spectroscopic methods. Our photometric drop-out technique can be used to establish the redshift for a fraction of these sources. This work employed 6 filters mounted on the $Swift$-UVOT and 4 optical filters on two telescopes, the 0.65 m SARA-CTIO in Chile and 1.0 m SARA-ORM in the Canary Islands, Spain. A sample of 15 sources was extracted from the $Swift$ archival data for which 6 filter UVOT observations were conducted. By complementing the {\it Swift} observations with the SARA ones, we were able to discover two high redshift sources: 3FGL J1155.4-3417 and 3FGL J1156.7-2250 at $z=1.83^{+0.10}_{-0.13}$ and $z=1.73^{+0.11}_{-0.19}$ , respectively, resulting from the dropouts in the powerlaw template fits to these data. The discoveries add to the important (26 total) sample of high-redshift BL Lacs. While the sample of high-z BL Lacs is still rather small, these objects do not seem to fit well within known schemes of the blazar population and represent the best probes of the extragalactic background light.Comment: 10 pages, 6 figures (accepted by ApJ

The role of financial markets and innovation in productivity and growth in Europe

The extended period of limited growth experienced until recently in many European countries raises the issue as to which policies could be most effective in improving their economic performance. This paper argues that further financial sector reforms may be a valuable complement to ongoing efforts to reform labour and product markets. There is a long-standing view in the economic literature that well-functioning financial systems allow economies to exploit the benefits of innovation in terms of productivity and growth. Moreover, measured productivity differentials between Europe and the United States seem to originate particularly in the financial sector and from sectors that are particularly dependent on external financing. Building on and summarising the existing literature, this paper first introduces a number of concepts that are important for financial sector analyses and policies. Second, it presents a selection of indicators describing the efficiency and development of the European financial system from the perspective of a variety of dimensions. Third, an attempt is made to estimate the extent to which greater financial efficiency might improve the allocation of productive capital in Europe. While in the recent past the research and policy debate in Europe has focused on fostering financial integration, the present paper puts the main emphasis on financial development or modernisation in the context of the finance and growth literature. The results suggest that there are a number of ways in which the financial market framework conditions in Europe can be improved to increase the contribution of the financial system to innovation, productivity and growth. The most robust conclusions can be drawn for certain aspects of corporate governance, the efficiency of legal systems in resolving conflicts in financial transactions and some structural features of European bank sectors. For example, econometric estimations indicate that improving these conditions is likely to increase the size of capital markets – a summary measure of overall financial development – and thereby enhance the speed with which the financial system helps to reallocate capital from declining sectors to sectors with good growth potentials

A new measurement of the Hubble constant and matter content of the Universe using extragalactic background light γ\gamma-ray attenuation

The Hubble constant $H_{0}$ and matter density $\Omega_{m}$ of the Universe are measured using the latest $\gamma$-ray attenuation results from Fermi-LAT and Cherenkov telescopes. This methodology is based upon the fact that the extragalactic background light supplies opacity for very high energy photons via photon-photon interaction. The amount of $\gamma$-ray attenuation along the line of sight depends on the expansion rate and matter content of the Universe. This novel strategy results in a value of $H_{0}=67.4_{-6.2}^{+6.0}$~km~s$^{-1}$~Mpc$^{-1}$ and $\Omega_{m}=0.14_{-0.07}^{+0.06}$. These estimates are independent and complementary to those based on the distance ladder, cosmic microwave background (CMB), clustering with weak lensing, and strong lensing data. We also produce a joint likelihood analysis of our results from $\gamma$ rays and these from more mature methodologies, excluding the CMB, yielding a combined value of $H_{0}=66.6\pm 1.6$~km~s$^{-1}$~Mpc$^{-1}$ and $\Omega_{m}=0.29\pm 0.02$.Comment: 9 pages, 6 figures, 1 table. Accepted by Ap

A Spitzer view of protoplanetary disks in the gamma Velorum cluster

We present new Spitzer Space Telescope observations of stars in the young ~5 Myr gamma Velorum stellar cluster. Combining optical and 2MASS photometry, we have selected 579 stars as candidate members of the cluster. With the addition of the Spitzer mid-infrared data, we have identified 5 debris disks around A-type stars, and 5-6 debris disks around solar-type stars, indicating that the strong radiation field in the cluster does not completely suppress the production of planetesimals in the disks of cluster members. However, we find some evidence that the frequency of circumstellar primordial disks is lower, and the IR flux excesses are smaller than for disks around stellar populations with similar ages. This could be evidence for a relatively fast dissipation of circumstellar dust by the strong radiation field from the highest mass star(s) in the cluster. Another possibility is that gamma Velorum stellar cluster is slightly older than reported ages and the the low frequency of primordial disks reflects the fast disk dissipation observed at ~5 Myr.Comment: Accepted for publication in the Astrophysical Journal: 32 pages; 11 Figure

Probing the EBL evolution at high redshift using GRBs detected with the Fermi-LAT

The extragalactic background light (EBL), from ultraviolet to infrared wavelengths, is predominantly due to emission from stars, accreting black holes and reprocessed light due to Galactic dust. The EBL can be studied through the imprint it leaves, via $\gamma$-$\gamma$ absorption of high-energy photons, in the spectra of distant $\gamma$-ray sources. The EBL has been probed through the search for the attenuation it produces in the spectra of BL Lacertae (BL Lac) objects and individual $\gamma$-ray bursts (GRBs). GRBs have significant advantages over blazars for the study of the EBL especially at high redshifts. Here we analyze a combined sample of twenty-two GRBs, detected by the Fermi Large Area Telescope between 65 MeV and 500 GeV. We report a marginal detection (at the ~2.8 $\sigma$ level) of the EBL attenuation in the stacked spectra of the source sample. This measurement represents a first constraint of the EBL at an effective redshift of ~1.8. We combine our results with prior EBL constraints and conclude that Fermi-LAT is instrumental to constrain the UV component of the EBL. We discuss the implications on existing empirical models of EBL evolution.Comment: on behalf of the Fermi-LAT collaboration, accepted for publication on Ap

The origin of the cosmic gamma-ray background in the MeV range

There has been much debate about the origin of the diffuse $\gamma$--ray background in the MeV range. At lower energies, AGNs and Seyfert galaxies can explain the background, but not above $\simeq$0.3 MeV. Beyond $\sim$10 MeV blazars appear to account for the flux observed. That leaves an unexplained gap for which different candidates have been proposed, including annihilations of WIMPS. One candidate are Type Ia supernovae (SNe Ia). Early studies concluded that they were able to account for the $\gamma$--ray background in the gap, while later work attributed a significantly lower contribution to them. All those estimates were based on SN Ia explosion models which did not reflect the full 3D hydrodynamics of SNe Ia explosions. In addition, new measurements obtained since 2010 have provided new, direct estimates of high-z SNe Ia rates beyond $z\sim$2. We take into account these new advances to see the predicted contribution to the gamma--ray background. We use here a wide variety of explosion models and a plethora of new measurements of SNe Ia rates. SNe Ia still fall short of the observed background. Only for a fit, which would imply $\sim$150\% systematic error in detecting SNe Ia events, do the theoretical predictions approach the observed fluxes. This fit is, however, at odds at the highest redshifts with recent SN Ia rates estimates. Other astrophysical sources such as FSRQs do match the observed flux levels in the MeV regime, while SNe Ia make up to 30--50\% of the observed flux.Comment: 40 pages, 13 Figures, accepted to be published in Ap

Models for Dusty Lyman alpha Emitters at High Redshift

Models are presented for the Lyman alpha emission of dusty high-redshift galaxies by combining the Press-Schechter formalism with a treatment of the inhomogeneous dust distribution inside galaxies. It is found that the amount of Lyman alpha radiation escaping from the galaxies strongly depends on the time over which the dust is produced through stellar activity, and on the ambient inhomogeneity of the HII regions that surround the ionizing OB stars. Good agreement is found with recent observations, as well as previous non-detections. Our models indicate that the dust content builds up in no more than approximately 5x10^8 yr, the galactic HII regions are inhomogeneous with a cloud covering factor of order unity, and the overall star formation efficiency is at least about 5%. It is predicted that future observations can detect these Lyman alpha galaxies upto redshifts of about 8.Comment: 16 pages, 4 figures, submitted to Ap

A hybrid multiagent approach for global trajectory optimization

In this paper we consider a global optimization method for space trajectory design problems. The method, which actually aims at finding not only the global minimizer but a whole set of low-lying local minimizers(corresponding to a set of different design options), is based on a domain decomposition technique where each subdomain is evaluated through a procedure based on the evolution of a population of agents. The method is applied to two space trajectory design problems and compared with existing deterministic and stochastic global optimization methods