WIMP searches with gamma rays in the Fermi era: challenges, methods and results

The launch of the gamma-ray telescope Fermi Large Area Telescope (Fermi-LAT) started a pivotal period in indirect detection of dark matter. By outperforming expectations, for the first time a robust and stringent test of the paradigm of weakly interacting massive particles (WIMPs) is within reach. In this paper, we discuss astrophysical targets for WIMP detection and the challenges they present, review the analysis tools which have been employed to tackle these challenges, and summarize the status of constraints on and the claimed detections in the WIMP parameter space. Methods and results will be discussed in comparison to Imaging Air Cherenkov Telescopes. We also provide an outlook on short term and longer term developments.Comment: 72 pages, 7 figures, Invited review for Journal of Experimental and Theoretical Physics,v3: added a few references, addressed referee comment

Quantitative measurement of the surface charge density

We present a method of measuring the charge density on dielectric surfaces. Similar to electrostatic force microscopy we record the electrostatic interaction between the probe and the sample surface, but at large tip-sample distances. For calibration we use a pyroelectric sample which allows us to alter the surface charge density by a known amount via a controlled temperature change. For proof of principle we determined the surface charge density under ambient conditions of ferroelectric lithium niobate

Impact of Electrostatic Forces in Contact Mode Scanning Force Microscopy

In this $\ll$ contribution we address the question to what extent surface charges affect contact-mode scanning force microscopy measurements. % We therefore designed samples where we could generate localized electric field distributions near the surface as and when required. % We performed a series of experiments where we varied the load of the tip, the stiffness of the cantilever and the hardness of the sample surface. % It turned out that only for soft cantilevers could an electrostatic interaction between tip and surface charges be detected, irrespective of the surface properties, i.\,e. basically regardless its hardness. % We explain these results through a model based on the alteration of the tip-sample potential by the additional electric field between charged tip and surface charges

AN ANALYSIS OF THE COMPARATIVE ADVANTAGE AND POLICY INCENTIVES OF COMMERCIAL WHEAT PRODUCTION IN SOUTH AFRICA

Despite the fact that all direct and indirect measures of subsidisation and protection have been removed, commercial agriculture is still widely considered to be subsidised, privileged and uncompetitive. This paper shows how the process of deregulation has in fact changed the situation. The paper reports on the comparative advantage in the production of wheat in South Africa and reveals the various distortionary effects, if any, of the policy environment on the production of wheat in the country prior to 1997. The paper concludes that South Africa has a strong comparative advantage in the production of wheat, especially, in the inland areas. Favourable climatic and soil factors as well as abundant and relatively cheaper domestic factors of production may be some of the reasons for this strong comparative advantage. The inland areas have better RCRs due to higher inland transportation costs. However, wheat production under irrigation seems to have no comparative advantage. This is mainly due to the implicit subsidy on irrigation water.Agricultural and Food Policy, Crop Production/Industries,

Natural Gas and Inequality in Bolivia after Nationalization

The high oil prices and the sharp increases in royalties mean that the natural gas boom in Bolivia has become very important for the economy. This paper uses a Computable General Equilibrium (CGE) model to assess the impacts of this boom on key macroeconomic variables as well as the distribution of incomes in the society. From a macroeconomic perspective, the natural gas boom is a blessing, adding around 1 percentage point to GDP growth rates for at least a decade, and sharply increasing government revenues available for public spending and investment. However, the poorest segments of the population (rural small-holders and urban informals) suffer actual reductions in their real incomes, compared to the counterfactual scenario without the gas boom. This means that the natural gas boom not only causes an increase in inequality but also an increase in poverty. The paper finishes with some policy recommendations on how to counteract the negative side effects of the natural gas boom.Natural Gas, Inequality, CGE model, Bolivia

Sol-Gel Derived Ferroelectric Nanoparticles Investigated by Piezoresponse Force Microscopy

Piezoresponse force microscopy (PFM) was used to investigate the ferroelectric properties of sol-gel derived LiNbO$_3$ nanoparticles. To determine the degree of ferroelectricity we took large-area images and performed statistical image-analysis. The ferroelectric behavior of single nanoparticles was verified by poling experiments using the PFM tip. Finally we carried out simultaneous measurements of the in-plane and the out-of-plane piezoresponse of the nanoparticles, followed by measurements of the same area after rotation of the sample by 90$^{\circ}$ and 180$^{\circ}$. Such measurements basically allow to determine the direction of polarization of every single particle

SUPPLY RESPONSE, DEMAND AND STOCKS FOR SOUTHERN AFRICAN BEEF

Livestock Production/Industries,

Rapidity particle spectra in sudden hadronization of QGP

We show that the remaining internal longitudinal flow of colliding quarks in nuclei offers a natural explanation for the diversity of rapidity spectral shapes observed in Pb--Pb 158AGeV nuclear collisions. Thus QGP sudden hadronization reaction picture is a suitable approach to explain the rapidity spectra of hadrons produced.Comment: 3 pages including 2 figure