Improving the Angular Resolution of EGRET and New Limits on Supersymmetric Dark Matter Near the Galactic Center

Using the EGRET data and an improved point source analysis, including an energy dependent point spread function and an unbinned maximum likelihood technique, we have been able to place considerably lower limits on the gamma ray flux from the galactic center region. We also test this method on known sources, the Crab and Vela pulsars. In both cases, we find that our method improves the angular precision of EGRET data over the 3EG catalog. This new limit on gamma rays from the galactic center can be used to test models of annihilating supersymmetric dark matter and galactic halo profiles. We find that the present EGRET data can limit many supersymmetric models if the density of the galactic dark matter halo is cuspy or spiked toward the galactic center. We also discuss the ability of GLAST to test these models.Comment: 6 pages, 4 figure

The map equation

Many real-world networks are so large that we must simplify their structure before we can extract useful information about the systems they represent. As the tools for doing these simplifications proliferate within the network literature, researchers would benefit from some guidelines about which of the so-called community detection algorithms are most appropriate for the structures they are studying and the questions they are asking. Here we show that different methods highlight different aspects of a network's structure and that the the sort of information that we seek to extract about the system must guide us in our decision. For example, many community detection algorithms, including the popular modularity maximization approach, infer module assignments from an underlying model of the network formation process. However, we are not always as interested in how a system's network structure was formed, as we are in how a network's extant structure influences the system's behavior. To see how structure influences current behavior, we will recognize that links in a network induce movement across the network and result in system-wide interdependence. In doing so, we explicitly acknowledge that most networks carry flow. To highlight and simplify the network structure with respect to this flow, we use the map equation. We present an intuitive derivation of this flow-based and information-theoretic method and provide an interactive on-line application that anyone can use to explore the mechanics of the map equation. We also describe an algorithm and provide source code to efficiently decompose large weighted and directed networks based on the map equation.Comment: 9 pages and 3 figures, corrected typos. For associated Flash application, see http://www.tp.umu.se/~rosvall/livemod/mapequation

Irrigated Acreage Projections in Georgia

Irrigated acreage is an important indicator for agricultural water demand which is a major category of water use. Three methodologies were applied in this study to project irrigated acreage of major crops in Georgia from 2010 to 2050. These three methodologies show consistent results. Total irrigated acreage of major crops in Georgia is projected to increase for the next 40 years. The acreage projection results provide useful information for Georgia agricultural policy makers and farmers. However, the methodologies used in the study have some limitations. They can only be used under certain assumptions. Thus, better methodologies are needed for future related research.Irrigated acreage projection, acreage response elasticities, Crop Production/Industries, Environmental Economics and Policy, Farm Management, Resource /Energy Economics and Policy,

Land Use Change and Ecosystem Valuation in North Georgia

A model of land allocation at the aggregate watershed level was developed assuming profit/net benefit maximization under risk neutrality. The econometric land use model was analyzed as an equation by equation SURE model as all the independent variables were the same for both equations. In analyzing effect of land use change on water quality, we took year 2005 as our baseline and postulated three land use scenarios. We applied Benefit Transfer techniques to value water quality changes resulting from land use change and estimated lower bounds for WTP to improve water quality to meet the FCB criterion for drinking water supply and fishing waters and BOD (DO) criteria for fishing waters. Water quality modeling revealed that land use change would result in increased runoff, and associated increase in FCB and BOD/DO violations. But the BOD/DO violations could be curtailed by managing urban growth as evidenced absence of BOD violations in the managed growth scenario. Our study finds there may be problems of FCB under all postulated future land use scenarios. The findings also support existing literature that there are problems with FCB violation in the study area at the moment. Finally, it seems that the people of UCRB would be willing to pay a lower bound value between USD 15,785,740 and USD 16,141,230 per year to create and maintain quality standards for fishing and drinking water supply.Ecosystem, Economic value, North Georgia, land use, land use change, fish, water quality, structural time series, willingness to pay, benefit transfer, forecasting, vector autoregression, Upper Chattahoochee River, Environmental Economics and Policy, Land Economics/Use,

Effects of the Generalized Uncertainty Principle on the Inflation Parameters

We investigate the effects of the generalized uncertainty principle on the inflationary dynamics of the early universe in both standard and braneworld viewpoint. We choose the Randall-Sundrum II model as our underlying braneworld scenario. We find that the quantum gravitational effects lead to a spectral index which is not scale invariant. Also, the amplitude of density fluctuations is reduced by increasing the strength of quantum gravitational corrections. However, the tensor-to-scalar ratio increases by incorporation of these quantum gravity effects. We outline possible manifestations of these quantum gravity effects in the recent and future observations.Comment: 11 pages, revised version with new references, Accepted for publication in IJMP

Assessing the Effects of Climate Change on Farm Production and Profitability: Dynamic Simulation Approach

In this paper, a dynamic optimization model was developed to simulate how farm-level realized price and profitability respond to yield change which was induced by climate change. Producers' acreage response was included in the dynamic model considering crop rotation effect. In the crop rotation model, a modified Bellman equation was used to dynamically optimize the net present value of farm profit for a five-year interval. This simulation process was repeated through the year 2050. Then yield, price, and acreage response were compiled to generate realized profit. Results generally indicated that reduction in crop yields due to climate change results in reduced farm profitability for most of the states studied. Predicted climate change is more likely to pose a problem for agricultural production and profitability in the southern U.S. states as compared to the northern U.S. states. Our results also suggest that acreage response alone is not sufficient to ameliorate the potential negative effects of global climate change on agricultural production and profitability. The results of this research are expected to provide a foundation for future related research to aid producers' crop rotation decisions in an unstable price environment.Dynamic simulation model, Acreage response, Crop rotation, Expected price, Realized price, Agricultural Finance, Crop Production/Industries, Environmental Economics and Policy, Farm Management, Land Economics/Use, Production Economics, Productivity Analysis, Risk and Uncertainty,

Childhood predictors of successful self-reported delinquents

The main aim of this research is to investigate the childhood predictors of successful self-reported delinquents, defined as those who were not convicted. In the Cambridge Study in Delinquent Development (CSDD), 411 London males have been followed up from age 8 to age 61. Self-reported offending was measured for the whole sample for ages 10–14, 15–18, 27–32, and 42–47, for five crimes: burglary, theft of a vehicle, theft from a vehicle, shoplifting, and vandalism. The prevalence of self-reported offending was 64% at ages 10–18 and 11% at ages 27–47, compared with the prevalence of convictions of 23% and 8% respectively. Successful self-reported delinquents were defined as those who offended between ages 10 and 18 but were not convicted up to age 26; 126 successful delinquents were compared with 120 convicted delinquents. Sixteen childhood factors, including attainment, self-control, socioeconomic, parental, family and behavioural factors, predicted successful self-reported delinquents. The most important independent predictors were committing less serious and fewer offences as well as high school attainment, unconvicted parents, low risk-taking, and unseparated families

A proposed new policy for planetary protection

A critical review of the present policy was conducted with emphasis on its application to future planetary exploration. The probable impact of recent data on the implementation of the present policy was also assessed. The existing policy and its implementation were found to: be excessive for certain missions (e.g., Voyager), neglect the contamination hazard posed by the bulk constituent organics of spacecraft, be ambiguous for certain missions (e.g., Pioneer Venus), and treat all extraterrestrial sample return missions alike. The major features of the proposed policy are planet/mission combinations, a qualitative top level statement, and implementation by exception rather than rule. The concept of planet/mission categories permits the imposition of requirements according to both biological interest in the target planet and the relative contamination hazard of the mission type