University of Maryland, Baltimore County

About: University of Maryland, Baltimore County is a education organization based out in Baltimore, Maryland, United States. It is known for research contribution in the topics: Population & Aerosol. The organization has 8749 authors who have published 20843 publications receiving 795706 citations. The organization is also known as: UMBC.

Fermi lat discovery of extended gamma-ray emission in the direction of supernova remnant w51c

Abstract: The discovery of bright gamma-ray emission coincident with supernova remnant (SNR) W51C is reported using the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. W51C is a middle-aged remnant (~10^4 yr) with intense radio synchrotron emission in its shell and known to be interacting with a molecular cloud. The gamma-ray emission is spatially extended, broadly consistent with the radio and X-ray extent of SNR W51C. The energy spectrum in the 0.2-50 GeV band exhibits steepening toward high energies. The luminosity is greater than 1x10^{36} erg/s given the distance constraint of D>5.5 kpc, which makes this object one of the most luminous gamma-ray sources in our Galaxy. The observed gamma-rays can be explained reasonably by a combination of efficient acceleration of nuclear cosmic rays at supernova shocks and shock-cloud interactions. The decay of neutral pi-mesons produced in hadronic collisions provides a plausible explanation for the gamma-ray emission. The product of the average gas density and the total energy content of the accelerated protons amounts to 5x10^{51}(D/6kpc)^2 erg/cm^3. Electron density constraints from the radio and X-ray bands render it difficult to explain the LAT signal as due to inverse Compton scattering. The Fermi LAT source coincident with SNR W51C sheds new light on the origin of Galactic cosmic rays.

Does secure land tenure save forests? A meta-analysis of the relationship between land tenure and tropical deforestation

Abstract: Deforestation and degradation are tied to a complex array of socioeconomic and political factors. Many assume that among the most important of these are the particular bundles of rights regulating who can benefit from land (tenure form) and the overall assurance that those rights will be upheld (tenure security). This paper reviews literature that connects forest outcomes and land tenure to better understand broad interactions between tenure form, security and forest change. Papers from economic theory suggest tenure is embedded in a broader socioeconomic context, with the potential for either a positive or negative conservation impact on forested land. Empirically, we find 36 publications that link land cover change to tenure conditions while also controlling for other plausibly confounding variables. Publications often investigate more than one site and more than one form of tenure, so from these we derive 118 cases linking forest change with a specific tenure form in a particular location. From these cases, we find evidence that protected areas are associated with positive forest outcomes and that land tenure security is associated with less deforestation, regardless of the form of tenure. We conclude with a call for more robust identification of this relationship in future research, as well as set of recommendations for policymakers, particularly as forest carbon incentive programs such as REDD integrate further into national policies.

Female song is widespread and ancestral in songbirds.

Abstract: Bird song has historically been considered an almost exclusively male trait, an observation fundamental to the formulation of Darwin's theory of sexual selection. Like other male ornaments, song is used by male songbirds to attract females and compete with rivals. Thus, bird song has become a textbook example of the power of sexual selection to lead to extreme neurological and behavioural sex differences. Here we present an extensive survey and ancestral state reconstruction of female song across songbirds showing that female song is present in 71% of surveyed species including 32 families, and that females sang in the common ancestor of modern songbirds. Our results reverse classical assumptions about the evolution of song and sex differences in birds. The challenge now is to identify whether sexual selection alone or broader processes, such as social or natural selection, best explain the evolution of elaborate traits in both sexes.

The relationship between internet activities and depressive symptoms in a sample of college freshmen.

Abstract: An Internet survey of college freshmen at a mid-Atlantic mid-sized university was conducted during the spring of 2002 to determine the impact of Internet activities on social support and well-being. Results obtained from the survey allow examination of the impact of amount of time performing different types of Internet activities on depressive symptoms, as measured by the Iowa version of the Center for Epidemiologic Studies Depression Scale (CES-D) via a semi-elasticity ordinary least squares regression model. Results indicate that increased e-mail and chat room/instant messaging (IM) hours are associated with decreased depressive symptoms, while increased Internet hours for shopping, playing games, or research is associated with increased depressive symptoms. The implications of these results for institutions of higher education, and Internet and health researchers are discussed.

Gamma-ray emission from the shell of supernova remnant W44 revealed by the Fermi LAT

Abstract: Recent observations of supernova remnants (SNRs) hint that they accelerate cosmic rays to energies close to ~1015 electron volts. However, the nature of the particles that produce the emission remains ambiguous. We report observations of SNR W44 with the Fermi Large Area Telescope at energies between 2 × 108 electron volts and 3 × 1011 electron volts. The detection of a source with a morphology corresponding to the SNR shell implies that the emission is produced by particles accelerated there. The gamma-ray spectrum is well modeled with emission from protons and nuclei. Its steepening above ~109 electron volts provides a probe with which to study how particle acceleration responds to environmental effects such as shock propagation in dense clouds and how accelerated particles are released into interstellar space.