Large-scale aeroacoustic research feasibility and conceptual design of test-section inserts for the Ames 80- by 120-foot wind tunnel

An engineering feasibility study was made of aeroacoustic inserts designed for large-scale acoustic research on aircraft models in the 80 by 120 foot Wind Tunnel at NASA Ames Research Center. The advantages and disadvantages of likely designs were analyzed. Results indicate that the required maximum airspeed leads to the design of a particular insert. Using goals of 200, 150, and 100 knots airspeed, the analysis indicated a 30 x 60 ft open-jet test section, a 40 x 80 ft open jet test section, and a 70 x 100 ft closed test section with enhanced wall lining, respectively. The open-jet inserts would be composed of a nozzle, collector, diffuser, and acoutic wedges incorporated in the existing 80 x 120 test section. The closed test section would be composed of approximately 5 ft acoustic wedges covered by a porous plate attached to the test section walls of the existing 80 x 120. All designs would require a double row of acoustic vanes between the test section and fan drive to attenuate fan noise and, in the case of the open-jet designs, to control flow separation at the diffuser downstream end. The inserts would allow virtually anechoic acoustic studies of large helicopter models, jets, and V/STOL aircraft models in simulated flight. Model scale studies would be necessary to optimize the aerodynamic and acoustic performance of any of the designs. In all designs studied, the existing structure would have to be reinforced. Successful development of acoustically transparent walls, though not strictly necessary to the project, would lead to a porous-wall test section that could be substituted for any of the open-jet designs, and thereby eliminate many aerodynamic and acoustic problems characteristic of open-jet shear layers. The larger size of the facility would make installation and removal of the insert components difficult. Consequently, scheduling of the existing 80 x 120 aerodynamic test section and scheduling of the open-jet test section would likely be made on an annual or longer basis. The enhanced wall-lining insert would likely be permanent. Although the modifications are technically feasible, the economic practicality of the project was not evaluated

Arctic Ice and the Ecological Ascent of the Dinosaurs

Despite the extremely high levels of atmospheric CO2 (+2000 ppm) in the Late Triassic and earliest Jurassic (~232-199 million years ago), there is evidence of seasonally freezing conditions in the Arctic of that time. This evidence consists of abundant icerafted debris in lake sediments. Based on phylogenetic bracket analysis, dinosaurs at this time were insulated, and could take advantage of the rich Arctic deciduous and evergreen vegetation, even under freezing winter conditions. Transient volcanic winters caused by the eruptions of the Central Atlantic Magmatic Province led to a mass extinction at 201.6 million years ago, at the close of the Triassic, that decimating all medium- to large-sized non-dinosaurian, uninsulated animals on land. In contrast, the insulated dinosaurs, already adapted to cold temperatures, not only survived but underwent a rapid adaptive radiation and ecological expansion in the Jurassic, taking over regions formerly dominated by large uninsulated reptiles

A Panel of Price Indices for Housing, Other Goods, and All Goods for All Areas in the United States 1982-2008

This paper produces a panel of price indices for housing, other produced goods, and all produced goods for each metropolitan area in the United States and the non-metropolitan part of each state from 1982 through 2008 that can be used for estimating behavioral relationships, studying the workings of markets, and assessing differences in the economic circumstances of people living in different areas. Our general approach is to first produce cross-sectional price indices for a single year 2000 and then use BLS time-series price indices to create the panel. Our geographic housing price index for 2000 is based on a large data set with detailed information about the characteristics of dwelling units and their neighborhoods throughout the United States that enables us to overcome many shortcomings of existing interarea housing price indices. For most areas, our price index for all goods other than housing is calculated from the price indices for categories of non-housing goods produced each quarter by the Council for Community and Economic Research. In order to produce a non-housing price index for areas of the United States not covered by their index, we estimate a theoretically-based regression model explaining differences in the composite price index for non-housing goods for areas where it is available and use it to predict a price of other goods for the uncovered areas. The overall consumer price index for all areas is based on the preceding estimates of the price of housing and other goods. The paper also discusses existing interarea price indices available to researchers, and it compares the new housing price index with housing price indices based on alternative methods using the same data and price indices based on alternative data sets. Electronic versions of the price indices are available online.Interarea price indices, interarea housing price indices, geographic cost-of-living differences, geographic price differences

Milankovitch climate forcing in the tropics of Pangaea during the Late Triassic

During the Late Triassic, the Newark rift basin of Eastern North America was in the interior of tropical (2.5–9.5°N) Pangaea. Strikingly cyclical lacustrine rocks comprise most of the 6770 m of continuous core recovered from this basin by the Newark Basin Coring Project. Six of the seven drill cores (each from 800 to 1300 m long) from this project are used to construct a composite lake-level curve that provides a much needed record of long term variations in continental tropical climate. The correlations on which the composite section is based show complete agreement between lake level cycles and independent magnetic polarity boundary isochrons. The main proxy of lake level and hence climate used to construct this lake level curve is a classification of water-depth related sedimentary structures and fabrics called depth ranks. We then use Fourier frequency analysis (both FFT and multitaper methods) and joint time-frequency approaches to resolve the periodic properties of the cyclicity and the secular drift in those properties. A consistent hierarchy in frequencies of the lake level cycles is present throughout the Late Triassic (and earliest Jurassic) portions of the cores, an interval of about 22 m.y. Calibration of the sediment accumulation rate by a variety of methods shows that these thickness periodicities are consistent with an origin in changes in precipitation governed by celestial mechanics. The full range of precession-related periods of lake level change are present, including the two peaks of the ∼20,000 year cycle of climatic precession, the two peaks of the ∼100,000 year eccentricity cycle, the single peak of the 412,900 year eccentricity cycle, and the ∼2,000,000 year eccentricity cycle. There is also good correspondence in the details of the joint-time frequency properties of lake level cycles and astronomical predictions as well. Even in an ice-free world, the tropical climate of Pangaea responded strongly to astronomical forcing, suggesting that precession-dominated climatic forcing probably always has been a prominent feature of tropical climate

A review of the reptile and amphibian assemblages from the Stormberg of southern Africa, with special emphasis on the footprints and the age of the Stormberg

The Molteno, Elliot, and Clarens formations comprise the continental Stormberg Group of the Karoo Basin of South Africa and Lesotho. The Molteno Formation contains a well preserved macro- and microfloral assemblage but apparently no vertebrates; the Elliot and Clarens formations contain abundant vertebrates but virtually no floral remains. The vertebrate taxa represented by skeletal remains are listed and divided into two assemblages - the lower Stormberg (lower Elliot) and upper Stormberg (upper Elliot and Clarens) assemblages. The abundant, diagnosable footprint taxa are revised and their names reduced to eight genera. These ichnotaxa also fall into two biostratigraphic zones that parallel the skeletal assemblages. Comparison of the faunal assemblages with those of the European type section strongly suggests that the lower Stormberg assemblage is Late Triassic (Carnian- Norian) in age while the upper Stormberg assemblage is Early Jurassic (Hettangian-Pliens- bachian) in age. Comparisons with other continental assemblages from other areas suggest that the upper Stormberg (upper Elliot and Clarens formations) assemblage broadly correlates with the upper Newark Supergroup of eastern North America, the Glen Canyon of the southwestern United States, and the lower Lufeng Series of China- all thought to be of Early Jurassic age on the basis of floral and/or radiometric evidence. Based on these correlations, previously published paleobiogeographic maps are revised; these show a shift from Late Triassic floral and faunal provinciality to Early Jurassic homogeneity. This shift was synchronous with a widening of the equatorial arid zone.National Science Foundation, US

Implications of astronomical climate cycles to the chronology of the Triassic

A high resolution climate record from a thick, continuous sedimentary sequence in the Newark basin provides the basis for an astronomically calibrated time scale for the Late Triassic. The astronomical vernier, indexed to radiometric dates that indicate an age of 202 Ma for the Triassic/Jurassic boundary, suggests that the Late Triassic was about 31 m.y. long, or constituted about 2/3 of the entire Triassic. A detailed geomagnetic polarity time scale developed in conjunction with the cycle stratigraphy provides a mechanism to extend the astronomical chronology to other sections in the world

High-resolution early Mesozoic Pangean climatic transect in lacustrine environments

Analysis of 6700 m of core from the Newark rift basin in New Jersey, USA provides a high-resolution astronomically calibrated magnetic polarity time scale for the Late Triassic and Early Jurassic spanning about 33 million years. This time scale, and its application elsewhere, allows a significant simplification of the pattern of climate-sensitive facies in the early Mesozoic basins of the central and north Atlantic margins. Coals and deep-water lacustrine deposits were produced at the paleoequator (Richmond-type sequences), while strikingly cyclical lacustrine and playa deposits were produced \00 to the north and south (Newark-type lacustrine sequences). At 10-30 ON, eolian dunes, playas sediments and evaporites were deposited (Fundy-type sequences). Farther north, shallow-water lacustrine red beds were deposited (Fleming Fjord-type sequences), while yet farther north (-40°), perennial-lake black mudstones and coals again dominated in the humid temperate zone (Kap Stewart-type sequences). Central Pangea drifted north about 10° during the Late Triassic, and the vertical sequence of climate-sensitive facies in individual basins changed as the basins passed through different climate zones. This simple zonal climate pattern explains most first-order changes in overall lacustrine sequences seen in the rift zone. Lakelevel cycles of Milankovitch origin change in a predicable way with the latitudinal shifts in climate and lacustrine style. Roughly \0 ky precessional cycles dominate within a few degrees of the equator, while -20 ky precessional cycles are dominant northward to about 30 ON where 40 ky obliquity cycles become evident in lake-level records

Early Jurassic magnetostratigraphy and paleolatitudes from the Hartford continental rift basin (eastern North America) . . .

To determine whether the ~200 Ma central Atlantic magmatic province (CAMP) coincides with a normal polarity bias and a purported abrupt change in polar wander at the J1 cusp, we collected samples for paleomagnetic study from 80 sites distributed over a ~2500-m-thick section of sedimentary units that are interbedded with and overlie CAMP lavas in the Hartford basin, which together represent the initial 2.4 Ma of the Jurassic according to cycle stratigraphic analysis. Characteristic directions carried by hematite were isolated by thermal demagnetization in 71 sites and define a coherent magnetostratigraphy supported by a positive reversal test and an interbasin fold test. Despite a pronounced overall normal polarity bias (only three relatively short reverse polarity intervals could be confirmed in the sampled section), normal polarity Chron H24n that encompasses the CAMP extrusive zone is no more than 1.6 Ma in duration. Elongation/inclination analysis of the 315 characteristic directions, which have a flattened distribution, produces a result in agreement with a published mean direction for the CAMP volcanic units as well as published results similarly corrected for inclination error from the Newark basin. The three data sets (CAMP volcanics, Newark corrected sediments, and Hartford corrected sediments) provide a 201 Ma reference pole for eastern North America at 67.0°N, 93.8°E, A_95 = 3.2°. Paleopoles from the Moenave and Wingate formations from the Colorado Plateau that virtually define the J1 cusp can be brought into agreement with the 201 Ma reference pole with corrections for net clockwise rotation of the plateau relative to eastern North America and presumed sedimentary inclination error. The corrected data show that apparent polar wander for North America proceeds directly toward higher latitudes over the Late Triassic and Early Jurassic with no obvious change that can be associated with CAMP

Astrochronostratigraphic polarity time scale (APTS) for the Late Triassic and Early Jurassic from continental sediments and correlation with standard marine stages

Paleomagnetic and cycle stratigraphic analyses of nearly 7000 m of section from continuous cores in the Newark basin and an overlapping 2500 meter-thick composite outcrop and core section in the nearby Hartford basin provide an astrochronostratigraphic polarity time-scale (APTS) for practically the entire Late Triassic (Carnian, Norian and Rhaetian) and the Hettangian and early Sinemurian stages of the Early Jurassic (233 to 199 Ma in toto). Aperiodic magnetic polarity reversals make a distinctive pattern of normal and reverse chrons for correlation, ideally paced by the periodic timing of orbital climate cycles, and anchored to million years ago (Ma) by high-precision U-Pb zircon dates from stratigraphically-constrained basalts of the Central Atlantic Magmatic Province (CAMP). Pinned by the CAMP dates, the Newark-Hartford APTS is calibrated by sixty-six McLaughlin cycles, each a reflection of climate forcing by the long astronomical eccentricity variation with the stable 405 kyr period, from 199.5 to 225.8 Ma and encompassing fifty-one magnetic polarity intervals, making it one of the longest continuous astrochronostratigraphic polarity time-scales available in the Mesozoic and Cenozoic. Extrapolation of sediment accumulation rates in fluvial sediments in the basal Newark section extends the sequence an additional fifteen polarity intervals to 232.7 Ma. The lengths of the 66 polarity chrons vary from 0.011 Myr (Chron E23r) to 1.63 Myr (Chron H24n) with an overall mean duration of 0.53 Myr. The oldest CAMP basalts provide a zircon U-Pb-based estimated age of 201.5 Ma for the base of the stratigraphically superjacent McLaughlin cycle 61 and 201.6 Ma using cycle stratigraphy for the onset of the immediately subjacent Chron E23r. The calibration age of 201.5 Ma for the base of McLaughlin cycle 61 is remarkably consistent with the calculated phase of the 498th long eccentricity cycle counting back using a period of 405 kyr from the most recent peak at 0.216 Ma. Accordingly, we suggest a nomenclature (Ecc405:k, where k is the cycle number or fraction thereof) to unambiguously assign ages from the astrochronostratigraphy. Magnetostratigraphic correlation of key Tethyan sections with diagnostic marine biostratigraphic elements to the Newark-Hartford APTS allows determination of numerical ages of standard marine stages, as follows: 227 Ma for the Carnian/Norian boundary, 205.5 Ma for the Norian/Rhaetian boundary (using a chemostratigraphic criterion, or about 4 Myr older for alternative criteria), 201.4 Ma for the Triassic/Jurassic boundary, and 199.5 Ma for the Hettangian/Sinemurian boundary. These age estimates are in excellent agreement with available constraints from high-precision U-Pb zircon dating from the Pucara Basin of Peru and along with the presence of the short Chron E23r in several basins argue strongly against suggestions that millions of years of Rhaetian time is missing in a cryptic hiatus or unconformity that supposedly occurs just above Chron E23r in the Newark Supergroup basins. It is more parsimonious to explain the apparent temporal delays in appearances and disappearances of palynoflora, conchostracans, and other endemic taxa in continental deposits as a reflection of demonstrated continental drift across climate belts and the misinterpretation of ecostratigraphy as chronostratigraphy. The Newark-Hartford APTS provides a chronostratigraphic template for continuing efforts at correlation of Late Triassic and Early Jurassic continental and marine sections throughout the world, including integration with atmospheric pCO2 measurements from paleosol carbonates and carbon isotopic measurements from marine carbonates to better understand the global carbon cycle as well as understanding the causes of and recovery from the end-Triassic mass extinction

Late Triassic-earliest Jurassic geomagnetic polarity reference sequence from cyclic continental sediments of the Newark rift basin

The global nature of geomagnetic polarity reversals has made magnetostratigraphy an essential tool for precise correlation between widely distributed sections of rocks of different lithological and biotic facies. The best documented history of geomagnetic polarity reversals is for the Jurassic to Recent and is based on the analysis of numerous marine magnetic anomaly profiles from the global ocean (e.g., Cande and Kent, 1992; Gradstein et al., 1994). The relative spacing of polarity intervals established from the anomaly patterns is calibrated in time by correlation to magnetostratigraphic sections with biostratigraphy, radiometric dates, and cyclostratigraphy. Because of the absence of seafloor and hence marine magnetic anomalies, a precise geomagnetic polarity reference scale for pre-Jurassic time has been more difficult to develop. There has already been significant progress made for the Late Triassic by assembling relatively condensed or discontinuous marine (e.g., Gallet et al., 1992; 1993) and continental (e.g.. Molina-Garza et at., 1991) sedimentary sections, but thick, continuous magnetostratigraphic sections with good chronostratigraphic control are needed to construct a high resolution reference scale