Studies of Ground Conductivity in the Territory of Alaska

The effective ground conductivity of Alaska has been determined by a comparison of experimental and theoretical field strengths. The experimental field strengths have been obtained by use of an airborne receiver, flown along radial paths from a large number of CAA radio ranges and beacons. The surface wave attenuation factor was computed for both a plane and a curved, homogeneous earth by methods presented by Norton. The experimentally determined relative field strengths were plotted as a function of distance and were compared with a family of curves for assumed values of conductivity and dielectric constant. From this comparison, that value of conductivity that best fits the experimental data is taken as the effective conductivity over the path. An investigation of the effect at dielectric constant on the transmitted signal shows that, within the frequency range used, a change of dielectric constant from 1 to 20 has but little effect on the attenuation of the transmitted signal for values of conductivity between 1 and 5 mmho/m. The experimental results indicate that for most sections of Alaska, the effective conductivity falls within this range. In some cases the earth was not homogeneous over the entire flight path as evidenced by changes in the slope of the field strength vs distance curves. In such cases, the data were replotted with an initial point at the discontinuity and new theoretical curves were drawn for each section of the field strength vs distance curves. Investigation of the variation of effective conductivity with change of frequency and at different seasons was made. In addition, wave tilt methods of determining the conductivity were used. A 'Ground Constants Measuring Set' was obtained from the Signal Corps and measurements were made in selected areas in Alaska. Attempts were made to use 1height-gain' and 'mutual coupling of loops' techniques but these were not successful. An investigation of anomolous propagation in the vicinity of Point Barrow was made. It was determined that this anomolous propagation appears to be the result of a layered earth. In addition to the anomolous propagation in the vicinity of Point Barrow, there appears to be similar anomolies in the vicinity of Kotzebue, Galena, Bethel and Port Heiden. From the above investigations a map showing the effective conductivity of Alaska as determined by the attenuation method is presented.Navy Department Bureau of Ships NObsr 72528 NE 120308 Subtask No. 6ABSTRACT -- PART I A. Purpose -- B. General Factual Data -- C. Detail Factual Data -- PART II -- A, Conclusions -- APPENDIX IYe

Strategies to Increase the Number of Minority Teachers in the Public Schools

There can be very little argument that in recent years the teaching profession has become whiter and whiter as fewer minorities and people of color have entered and remained in the teaching profession, and as such, the percentage of white Americans in the field has continued to increase. Out of the approximately 2.3 million K-12 teachers in 1987, only 10.3 percent were minority group members. Current estimates report that by the mid 1990s this number will be further reduced to about five percent.[1] If this trend is not reversed, the teaching profession will be close to being entirely white by early in the twenty-first century. The fact that this is occurring at a time when minority populations of students in these same schools are dramatically increasing makes this situation even more confounding. Table 1 illustrates the relative populations by ethnicity of students and teachers in the public schools today.[2] As can be seen from this table, the relative population of the teaching force is not even close to being representative of the composition of the student body in terms of ethnicity

Tailcone on orbiter altitude attainable at the maximum ALT interface airspeed

A preflight analysis performed for verification of the ALT mated vehicle incidence angle which maximizes the post separation altitude attainment by the orbiter at the maximum approach and landing test (ALT) interface airspeed (300 KEAS) is discussed. In the analysis, altitude versus airspeed profiles are generated for each of the three incidence angles that include and bound the recommended incidence angle for both the forward and the aft cg tailcone on orbiter configurations. Results show that the recommended incidence angles maximize the orbiter post separation altitude attainable within an acceptable tradeoff between separation clearance capability and orbiter structural constraints. Within constraints, the incidence angle that maximizes the orbiter altitude at the maximum ALT interface airspeed for both the forward and aft cg orbiter tailcone on configurations is 6.0 deg. The requirement for a parametric analysis of orbiter altitude attainable at the maximum ALT interface airspeed is stated along with the specifications, assumptions, and analytical approach used to determine orbiter altitude attainable at the maximum ALT interface airspeed

Life, The Universe, and Nothing: Life and Death in an Ever-Expanding Universe

Current evidence suggests that the cosmological constant is not zero, or that we live in an open universe. We examine the implications for the future under these assumptions, and find that they are striking. If the Universe is cosmological constant-dominated, our ability to probe the evolution of large scale structure will decrease with time ---presently observable distant sources will disappear on a time-scale comparable to the period of stellar burning. Moreover, while the Universe might expand forever, the integrated conscious lifetime of any civilization will be finite, although it can be astronomically long. We find that this latter result is far more general. In the absence of possible exotic and uncertain strong gravitational effects, the total information recoverable by any civilization over the entire history of our universe is finite, and assuming that consciousness has a physical computational basis, life cannot be eternal.Comment: 23 pages, latex, submitted to Ap.

Universal Limits on Computation

The physical limits to computation have been under active scrutiny over the past decade or two, as theoretical investigations of the possible impact of quantum mechanical processes on computing have begun to make contact with realizable experimental configurations. We demonstrate here that the observed acceleration of the Universe can produce a universal limit on the total amount of information that can be stored and processed in the future, putting an ultimate limit on future technology for any civilization, including a time-limit on Moore's Law. The limits we derive are stringent, and include the possibilities that the computing performed is either distributed or local. A careful consideration of the effect of horizons on information processing is necessary for this analysis, which suggests that the total amount of information that can be processed by any observer is significantly less than the Hawking-Bekenstein entropy associated with the existence of an event horizon in an accelerating universe.Comment: 3 pages including eps figure, submitted to Phys. Rev. Lett; several typos corrected, several references added, and a short discussion of w <-1 adde

Avoidable Hospitalizations

Georgia Health Policy Center worked to improve health care in eight of the most rural, medically under served states in the country. The Center conducted research and provided strategic planning for eight Southern states: Alabama, Arkansas, Georgia, Louisiana, Mississippi, South Carolina, East Texas and West Virginia

High-resolution Satellite Imaging of the 2004 Transit of Venus and Asymmetries in the Cytherean Atmosphere

This paper presents the only space-borne optical-imaging observations of the 2004 June 8 transit of Venus, the first such transit visible from Earth since AD 1882. The high-resolution, high-cadence satellite images we arranged from NASA's Transition Region and Coronal Explorer (TRACE) reveal the onset of visibility of Venus's atmosphere and give further information about the black-drop effect, whose causes we previously demonstrated from TRACE observations of a transit of Mercury. The atmosphere is gradually revealed before second contact and after third contact, resulting from the changing depth of atmospheric layers refracting the photospheric surface into the observer's direction. We use Venus Express observations to relate the atmospheric arcs seen during the transit to the atmospheric structure of Venus. Finally, we relate the transit images to current and future exoplanet observations, providing a sort of ground truth showing an analog in our solar system to effects observable only with light curves in other solar systems with the Kepler and CoRoT missions and ground-based exoplanet-transit observations