Godel-type space-time metrics

A simple group theoretic derivation is given of the family of space-time metrics with isometry group SO(2,1) X SO(2) X R first described by Godel, of which the Godel stationary cosmological solution is the member with a perfect-fluid stress-energy tensor. Other members of the family are shown to be interpretable as cosmological solutions with a electrically charged perfect fluid and a magnetic field.Comment: Heavly rewritten respect to the orginal version, corrected some typos due to files transfer in the last submitted versio

Composition and Structure of Two Old-growth Forest Ecosystem Types of Southeastern Ohio

Author Institution: School of Natural Resources, Ohio Agricultural Research and Development Center, The Ohio State UniversityLess than 1% of the pre-European settlement forest in Ohio currently remains, mostly as small and scattered woodlots. Consequently, few studies have been undertaken to quantify the composition and structure of Ohio’s old-growth forests using a landscape ecosystem perspective. We used an existing multifactor ecosystem classification system developed for the Wayne National Forest in southeastern Ohio to compare the composition and structure of two old-growth forest ecosystem types, located on contrasting north-facing and south-facing middle slopes. No differences in physiography were observed among the stands other than aspect; however, the north-facing old-growth ecosystem type had a greater A horizon thickness and a higher pH than the south-facing old-growth ecosystem type. Mixed-oaks dominate the south-facing ecosystem type, while sugar maple, American beech and northern red oak dominate the north-facing ecosystem type. No differences were detected in stand structural components. Similar trends were observed for the ground-flora layer; specifically, we observed differences in groundflora composition between the two ecosystem types but no differences in total percent cover or species richness. Finally, the composition and structure of coarse woody debris differed between the contrasting ecosystem types. Maple and oak snags and fallen logs dominate the north-facing ecosystem while oak standing snags and fallen stems are typically observed in the south-facing ecosystem. Few differences between the two ecosystem types were detected in coarse woody debris structure, except that snag density tends to be higher in the south-facing old-growth ecosystem and log density and volume tends to be higher in the north-facing ecosystem (P <0.10). Through the use of this ecosystem approach, we can begin to quantify the ecological factors regulating the composition and structure of old-growth communities, improving our ability to effectively manage and restore these rare ecosystems

A near-infrared pyramid wavefront sensor for Keck adaptive optics: real-time controller

A new real-time control system will be implemented within the Keck II adaptive optics system to support the new near-infrared pyramid wavefront sensor. The new real-time computer has to interface with an existing, very productive adaptive optics system. We discuss our solution to install it in an operational environment without impacting science. This solution is based on an independent SCExAO-based pyramid wavefront sensor realtime processor solution using the hardware interfaces provided by the existing Keck II real-time controller. We introduce the new pyramid real-time controller system design, its expected performance, and the modification of the operational real-time controller to support the pyramid system including interfacing with the existing deformable and tip-tilt mirrors. We describe the integration of the Saphira detector-based camera and the Boston Micromachines kilo-DM in this new architecture. We explain the software architecture and philosophy, the shared memory concept and how the real-time computer uses the power of GPUs for adaptive optics control. We discuss the strengths and weaknesses of this architecture and how it can benefit other projects. The motion control of the devices deployed on the Keck II adaptive optics bench to support the alignment of the light on the sensors is also described. The interfaces, developed to deal with the rest of the Keck telescope systems in the observatory distributed system, are reviewed. Based on this experience, we present which design ideas could have helped us integrate the new system with the previous one and the resultant performance gains

Ecological forestry at National Wildlife Refuges: experiences from

ABSTRACT Although land management over much of the history of the U.S. Fish and Wildlife Service&apos;s National Wildlife Refuge System (NWRS) has emphasized single-species management, recent policy has encouraged land managers to focus on broader ecosystem restoration goals. One framework for forest ecosystem management that is becoming more popular in the NWRS and other federal and state resource agencies has been termed &quot;ecological forestry&quot;-an approach to forest ecosystem management where the focus is on incorporating an understanding of the outcomes of natural disturbances and stand development processes into designing silvicultural practices. This approach stresses understanding the effects of natural disturbances on biological legacies, structural and compositional heterogeneity, and the recovery periods between disturbance events (including how this recovery period influences stand complexity). Recently, resource managers and ecologists from Seney National Wildlife Refuge, The Ohio State University, and Central Michigan University have partnered to examine how these guiding principles can be integrated into NWRS forest ecosystem management. Specifically, we are partnering to develop management strategies to help: 1) restore the once extensive mixed-pine forest ecosystems of eastern Upper Michigan; 2) mitigate the effects of the beech-bark disease complex on American beech (Fagus grandifolia Ehrh.), a foundation species in northern hardwood forests of eastern North America; and 3) promote more natural forest patterns for wildlife species of young jack pine (Pinus banksiana Lamb.) forest ecosystems, including the federally endangered Kirtland&apos;s warbler (Dendroica kirtlandii). These efforts are ongoing and will continue to be monitored over time. However, initial collaborations suggest that the NWRS provides an excellent crucible to study the application of ecological forestry principles and develop novel ways to manage forest ecosystems

Analytic Quantization of the QCD String

We perform an analytic semi-classical quantization of the straight QCD string with one end fixed and a massless quark on the other, in the limits of orbital and radial dominant motion. We compare our results to the exact numerical semi-classical quantization. We observe that the numerical semi-classical quantization agrees well with our exact numerical canonical quantization.Comment: RevTeX, 10 pages, 9 figure