The Energy Balance of Corn Ethanol: An Update

Studies conducted since the late 1970s have estimated the net energy value (NEV) of corn ethanol. However, variations in data and assumptions used among the studies have resulted in a wide range of estimates. This study identifies the factors causing this wide variation and develops a more consistent estimate. We conclude that the NEV of corn ethanol has been rising over time due to technological advances in ethanol conversion and increased efficiency in farm production. We show that corn ethanol is energy efficient as indicated by an energy output:input ratio of 1.34.ethanol, net energy balance, corn production, energy, Crop Production/Industries, Resource /Energy Economics and Policy,

Galaxy Cluster Formation from the Large-scale Structure: A Case Study of the Abell 2125 Complex at z=0.247

The structure of the universe is believed to have formed by clustering hierarchically from small to large scales. Much of this evolution occurs very slowly but at a few special times more, rapid, violent activity may occur as major subunits collide at high velocities. The Abell 2125 complex (z=0.247) appears to be undergoing such an event as shown by modeling of the optical velocity field and by the detection with the VLA of an unusually large number of associated radio active galaxies. We present an 80 ksec Chandra imaging of Abell 2125, together with extensive complementary multi-wavelength data. We show direct evidence for galaxy transformation and destruction during the cluster formation. The Chandra data unambiguously separate the X-ray contributions from discrete sources and large-scale diffuse gas in the Abell 2125 complex, which consists of various merging clusters/groups of galaxies and low-surface brightness emission. This enables us to study processes affecting galaxy evolution during this special time from scales of Mpc down to a few kpc. The overall level of activity plus the special time for the cluster-cluster merger suggests that an important phase of galaxy evolution can take place during such events.Comment: 4 pages plus 4 figures. To appear in proceedings of IAU CColloquium No. 195: Outskirts of Galaxy Clusters: Intense Life in the Suburbs. A high resolution version may be found at http://www.astro.umass.edu/~wqd/papers/iau195.ps.g

X-raying Abell 2125 -- a Large-scale Hierarchical Complex of Galaxies and Hot Gas

We present an 82 ksec Chandra ACIS-I observation of a large-scale hierarchical complex, which consists of various clusters/groups of galaxies and low-surface brightness X-ray emission at z = 0.247. This high-resolution {\sl Chandra} observation allows us for the first time to separate unambiguously the X-ray contributions from discrete sources and large-scale diffuse hot gas. We detect 99 X-ray sources in a $17^\prime \times 17^\prime$ field. Ten of these sources are identified as members of the complex and are mostly radio-bright. Whereas unresolved X-ray sources tend to be associated with galaxies in intermediate density environments, extended X-ray emission peak at bright radio galaxies in the central cluster. In particular, a distinct X-ray trail appears on one side of the fast-moving galaxy C153, clearly due to ram-pressure stripping. The diffuse X-ray emission from the central cluster can be characterized by a thermal plasma with a characteristic temperature of $3.2_{-0.4}^{+0.5}$ keV and a heavy element abundance of $0.24_{-0.12}^{+0.15}$ solar (90% confidence uncertainties). In comparison, a patch of low-surface brightness X-ray emission apparently originates in relatively low density intergalactic gas with a characteristic temperature of $0.98_{-0.27}^{+0.22}$ keV and an abundance of $\lesssim 0.09$ solar. The Chandra observation, together with extensive multi-wavelength data, indicates that the complex represents a projection of several galaxy sub-structures, which may be undergoing major mergers. We discuss the dynamic states of the complex and its sub-structures as well as properties of X-ray-emitting galaxies and the relationship to their environments.Comment: 18 pages plus figures, to be published in ApJ. A complete high resolution version can be found at http://www.astro.umass.edu/~wqd/papers/a2125

A new 111 type iron pnictide superconductor LiFeP

A new iron pnictide LiFeP superconductor was found. The compound crystallizes into a Cu2Sb structure containing an FeP layer showing superconductivity with maximum Tc of 6K. This is the first 111 type iron pnictide superconductor containing no arsenic. The new superconductor is featured with itinerant behavior at normal state that could helpful to understand the novel superconducting mechanism of iron pnictide compounds.Comment: 3 figures + 1 tabl