Photoluminescence Spectroscopy of 4H- and 6H-SiC

Typical undoped bulk grown SiC shows n- or p-type conductivity due to residual impurities such as nitrogen, boron, or aluminum. In order to produce high resistivity material, vanadium can be used as a compensating dopant. Since vanadium is an amphoteric dopant in SiC, it produces either a donor state, VSi4+(3d1) → VSi5+(3d0), or an acceptor state, VSi4+(3d1) → VSi3+(3d2). Thus, vanadium doping can compensate both n- and p-type conductivity. In this work, vanadium doped and undoped 4H- and 6H-SiC grown by the sublimation method have been studied using low temperature photoluminescence (PL). It was found that the luminescence observed between 0.85 to 0.95 eV of the intra-3d-shell transition of VSi4+(3d1) increased by an order of magnitude in samples intentionally doped with vanadium compared to samples unintentionally doped. In addition, the dominant visible-region luminescence was attributed to titanium which is an isoelectronic trap in SiC. The presence of a broad peak centered at approx. 1.90 eV in some samples is believed to be attributed to donor-acceptor pair recombination between a TiSi-Nc complex donor and the boron defect complex acting as an acceptor. Finally, the TiSi-Nc complex donor location in the bandgap of 6H-SiC is estimated to be Ec-0.54 eV

The United States Chiropractic Workforce: An alternative or complement to primary care?

UnlabelledBackgroundIn the United States (US) a shortage of primary care physicians has become evident. Other health care providers such as chiropractors might help address some of the nation's primary care needs simply by being located in areas of lesser primary care resources. Therefore, the purpose of this study was to examine the distribution of the chiropractic workforce across the country and compare it to that of primary care physicians.MethodsWe used nationally representative data to estimate the per 100,000 capita supply of chiropractors and primary care physicians according to the 306 predefined Hospital Referral Regions. Multiple variable Poisson regression was used to examine the influence of population characteristics on the supply of both practitioner-types.ResultsAccording to these data, there are 74,623 US chiropractors and the per capita supply of chiropractors varies more than 10-fold across the nation. Chiropractors practice in areas with greater supply of primary care physicians (Pearson's correlation 0.17, p-value < 0.001) and appear to be more responsive to market conditions (i.e. more heavily influenced by population characteristics) in regards to practice location than primary care physicians.ConclusionThese findings suggest that chiropractors practice in areas of greater primary care physician supply. Therefore chiropractors may be functioning in more complementary roles to primary care as opposed to an alternative point of access

Distribution and numbers of narwhals (Monodon monoceros) in Baffin Bay and Davis Strait

Aerial surveys were conducted over Baffin Bay during May-October 1978-79 and off West Greenland and over southern Baffin Bay, Davis Strait and Hudson Strait during March 1981-82. Narwhals (Monodon monoceros) were dispersed throughout the pack ice in northern Davis Strait and Baffin Bay during late winter and spring and moved into nearshore areas in and adjacent to Lancaster Sound during late June and July. Important summering areas were identified in Buchan Gulf, Eclipse Sound, Admiralty Inlet, Prince Regent Inlet and Peel Sound, and possibly in Smith Sound and Home Bay, but there was considerable variation in the numbers of narwhals entering these areas each year. Narwhals remained in nearshore areas until late September or early October when they moved south in advance of and with the newly-forming pack ice. During autumn narwhals tended to migrate in large herds, moving both along the coast of Baffin Island and through offshore waters. Our best estimates of the size of the narwhal population have come from surveys conducted in late spring when the whales are widely dispersed among the offshore pack ice. An estimated 34 363 (± SE 8282) narwhals were present in offshore areas of Baffin Bay that were surveyed four times in May-July 1979. This late spring estimate included narwhals that later summered on both the east and west sides of Baffin Bay and Davis Strait, but excluded animals that summered in northern Hudson Bay. It does not include animals outside the survey area nor is it corrected to account for animals below the surface. Our aerial survey data indicate that 7.8-9.0% of narwhals in summering areas were calves. An estimate of calving rate is 0.29 calves/adult female/year based on sightings of I-month-old calves without considering mortality between birth and the survey date. The mortality rate of calves from I month to 13 months of age is estimated as approximately 17%

Oscillation pressure device for dynamic calibration of pressure transducers

Method and apparatus for obtaining dynamic calibrations of pressure transducers. A calibration head (15), a flexible tubing (23) and a bellows (20) enclose a volume of air at atmospheric pressure with a transducer (11) to be calibrated subject to the pressure inside the volume. All of the other apparatus in the drawing apply oscillations to bellows (20) causing the volume to change thereby applying oscillating pressures to transducer (11) whereby transducer (11) can be calibrated

Geology and Ground-Water Resources of the Kansas River Valley Between Lawrence and Topeka, Kansas

The Kansas River Valley between Lawrence and Topeka is an important industrial and agricultural area in eastern Kansas. Both Topeka and Lawrence are built principally on the south bluffs of the valley. The valley is divided topographically into flood plain and Newman terrace. An old dissected terrace is preserved in many places along the margins of the valley, and in other places steeper bedrock escarpments flank the valley. Limestone, shale, siltstone, and sandstone of Pennsylvanian age crop out in the mapped area and dip gently westward. These rocks are the source for small but important quantities of domestic water. Unconsolidated Pleistocene sediments are the only other rocks exposed. Earliest Pleistocene sediments are small deposits of pre-Kansan and early Kansan sands and limestone-chert gravels. Till and outwash of Kansan age are widespread north of Kansas River. Till is impervious and adversely affects groundwater motion, but outwash gravel supplies water to a few wells and to two springs. Colluvium and terrace deposits of post-Kansan age are present along tributaries to the main valley but are not important sources of water. Late Wisconsinan and Recent alluvial fills are the only sources of large quantities of water. In the Kansas River Valley the alluvium reaches a maximum thickness of 89 feet. Industry uses about 75 percent of the 12,852,000 to 15,552,000 gallons of water pumped from wells daily. Use for irrigation ranges from none to more than 2,500,000 gallons a day, quantity depending upon time of year and precipitation. Municipal use is about 3,000,000 gallons of water a day. Wells near the river receive direct recharge by river water, but the main alluvial fill is recharged by rain water and water draining from the uplands. No shortage of ground water exists and proper spacing of future wells will allow substantial increase in the amount of ground water available for utilization in the area. Quality of the water is generally good, the most objectionable property of the water being a high carbonate hardness which is a common constituent of most well water in central United States. Well logs, water-table measurements, chemical analyses, and well yields are tabulated. Maps, cross sections, and profiles present other ground-water and geologic data

Biodiesel Mandate Laws in Argentina and Brazil: An Estimation of Soybean Oil Foregone Export Revenues

Replaced with revised version of paper 02/22/08.Research and Development/Tech Change/Emerging Technologies,

Demographic Influences on Consumer Ethnocentrism: A Two-Study Analysis Demonstrating How Industry-Specific Personal Characteristics Impact the Occupation, Education, Marital Status, Sex and Race Dynamic

Two national surveys were conducted in the United States to test the influence of seven demographic variables on consumer ethnocentrism. Study 1 suggests a social class influence (education and occupation) on consumer ethnocentrism towards automobile brands in the United States, plus a significant relationship between marital status and consumer ethnocentrism. Study 2 tests the impact of U.S. automobile industry-specific knowledge, beliefs, and job-related behavior on ethnocentrism using similar demographic variables. Without considering industry-specific measures, occupation again significantly impacts consumer ethnocentricity among participants. However, when industry-specific measures are included, the underlying influence of gender and race on consumer ethnocentrism is revealed

Lucas' Theorem for Prime Powers

Lucas' theorem on binomial coefficients states that (AB)≡(arbr)⋯(a1b1)(a0b0)(mod p) where p is a prime and A = arpr + ⋯ + a0p + a0, B = brpr + ⋯ + b1p + b0 + are the p-adic expansions of A and B. If s ⩾ 2, it is shown that a similar formula holds modulo ps where the product involves a slightly modified binomial coefficient evaluated on blocks of s digits.

Spring 1982 Conference Issue

Turf Clippings (page 3) How the RPAR Process is Working (4) Cellular and Genetic Engineering Techniques Applied Towards the Improvement of Turfgrass (7) Fifty-First Annual Turf Conference and Sixth Industrial Show (10) Natural Versus Artificial Turf--an Economical Alternative (13) Fertility Assay of Sands (17