Mixed Land Use and Obesity: An Empirical Comparison of Alternative Land Use Measures and Geographic Scales

Obesity is a growing epidemic in the United States. Walkable neighborhoods, characterized as having the three Ds of walkability (population Density, land use Diversity, and pedestrian-friendly Design), have been identified as a potentially promising factor to prevent obesity for residents. Past studies examining the relationship between obesity and walkability vary in geographic scales of neighborhood definitions and methods of measuring the three Ds. To better understand potential influences of these sometimes arbitrary choices, we test how four types of alternative measures of land use diversity measured at three geographic scales relate to body mass index for 4,960 Salt Lake County adults. Generalized estimation equation models demonstrate that optimal diversity measures differed by gender and geographic scale and that integrating walkability measures at different scales improved the overall performance of models.     

ICE THICKNESS,ABLATION, AND OTHER GLACIOLOGICAL MEASUREMENTS ON UPPER FREMONT GLACIER,WYOMING

Glaciological investigations of the Upper Fremont Glacier in the Wind River Range of Wyoming were conducted during 1990–1991. The glaciological data will provide baseline information for monitoring future changes to the glacier and support ongoing research utilizing glacial-ice-core composition to reconstruct paleoenvironmental records. Ice thickness, determined by radio-echo sounding, ranged from 60 to 172 m in the upper half of the glacier. Radio-echo sounding of ice thickness at one point was confirmed by drilling 159.7 m to bedrock. The difference between radio-echo sounding depth and measured drilling depth was about 4 m. Annual ablation (including snow, firn, and ice) measured for the 1990–1991 period averaged about 0.93 m/a. Densification proceeds rapidly on Upper Fremont Glacier. Measured densities in the near-surface parts of the glacier ranged from 4.4 x 10⁵ g/m³ at the surface to larger than 8.5 x 10⁵ g/m³ at depths exceeding 14 m. Surface ice velocity and direction were monitored from July 1990 to August 1991. Ice velocity decreased in a downslope direction. The largest measured velocity was about 3.1 m/a and the smallest was 0.8 m/a. The yearly mean air temperature of the study site during the period from July 11, 1990 to July 10, 1991 was -6.9°. Borehole temperatures from 10-m depths are 0 ± 0.4°. The warmer borehole temperatures relative to the yearly mean air temperature may be caused by the latent heat of freezing, as meltwater from the surface percolates into the glacier and refreezes. [Key words: glaciers, Wyoming, Wind River Range, ice thickness, ablation rates.]     

Stable isotope constraints on the fluid source of hydrothermal breccia pipes in the Tankwa Karoo depocentre,South Africa: Breakdown of authigenic minerals during sill intrusion

The Karoo Basin covers much of South Africa and is an area of prospective shale gas exploration, with the Whitehill Formation the target shale unit. However, the sedimentary succession, including the Whitehill, has been intruded by a series of sills and dykes associated with the Karoo Large Igneous Province (~183 Ma), which are expected to have modified the thermal history of the basin dramatically. Here, we investigate a secondary effect of these intrusions: a series of hydrothermal vent complexes, or breccia pipes, focusing on using O, H, and C isotopes to constrain the origin and evolution of fluids produced during the intrusion of basaltic sills. A cluster of breccia pipes have been eroded down to the level of the Ecca Group at Luiperdskop on the western edge of the Karoo basin; a small isolated pipe of similar appearance crops out 13 km to the east. The Luiperdskop pipes are underlain by a Karoo dolerite sill that is assumed to provide the heat driving fluidization. The pipes consist of fine‐grained matrix and about 8% clasts, on average, of mostly sedimentary material; occasional large rafts of quartzite and dolerite are also present. The presence of clasts apparently from the Dwyka Group is consistent with the depth of formation of the pipes being at, or near, the base of the Karoo Supergroup, between 400 and 850 m below present surface. The presence of chlorite as the dominant hydrous mineral is consistent with an emplacement temperature between 300 and 350°C. The major and trace element, and O‐ and H‐isotope composition of the Tankwa breccias is homogenous, consistent with them being derived from the same source. The δ¹⁸O values (vsVSMOW) of the breccias are relatively uniform (7.1‰–8.7‰), and are similar to that of the country rock shale, and both are lower than expected for shale. The water content of the breccia is between 2.7 and 3.1 wt.% and the δD values range from ?109‰ to ?144‰. Calcite in vesicles has δ¹³C and δ¹⁸O (VSMOW) values of ?4.2‰ and 24.0‰, respectively. The low δD value of the breccia rocks does not appear to be due to the presence of methane in the fluid. Instead, it is proposed that low δD and δ¹⁸O values are the result of the fluid being derived from the breakdown of clay minerals that formed and were deposited at a time of cold climate at ~290 Ma.     

A parameterization of the boundary layer of a tropical cyclone

In an earlier paper by one of the authors (Smith, 1968), a momentum integral method was developed to parameterize the gross constraint imposed by the surface boundary layer of a steady, axisymmetric, tropical cyclone on the meridional circulation within the vortex itself. Specifically, the method provides an effective means of estimating the radial variation of mean upflow/downflow induced by the boundary layer, compatible with a prescribed radial variation of azimuthal velocity just above the boundary layer,V _gr. However, it relies on a judicious choice of vertical profiles of radial and azimuthal velocity components within the boundary layer. An especially suitable set of profiles is discussed herein; these are Ekman-like profiles in which turbulent mixing is characterized by a vertically constant eddy diffusivityK _M , matched to a constant stress sublayer just above the sea surface. An attractive feature of the formulation is that a suitable value forK _M as a function of radius, which is extremely difficult to extract from observational data, can be calculated when the state of the sea surface, described by a roughness lengthZ ₀, is prescribed. Although observations ofZ ₀ at high wind speeds are not yet available, the effect of radial variations in sea surface roughness can be assessed and it is shown that these affect the upflow to a significant degree.     

The impact of the friction of distance on the early settlement and development of Eyre Peninsula,South Australia

The cost of overcoming distance has played and continues to play an important role in the evolution of Australia's space‐economy. This paper examines the impact of the ‘friction of distance’, as well as the quality of the resource base, on the settlement and development of Eyre Peninsula in South Australia. A series of maps portraying the spread of pastoralism and then agriculture on Eyre Peninsula reveals clearly the importance of ‘accessibility’ in influencing the pattern and timing of settlement. It was not until well into this century that all the potentially agricultural land in the interior was occupied, for this required the construction of a railway and water pipeline up the centre of the peninsula.     

COMPARING TRADITIONAL METHODS FOR SELECTING CLASS INTERVALS ON CHOROPLETH MAPS*

The most common goal when classing data for choropleth maps is to create homogeneous classes which contain similar data values. None of the four traditional data classing methods examined here (quartile, equal interval, standard deviation, and natural breaks) consistently generalized the experimental data sets into homogeneous classes. These methods were most accurate for data sets with specific distributional characteristics, but none classed all of any type of distribution accurately. Only the optimization method produced reliable and accurate results for all of the experimental data.     

Palaeomagnetic study of the (Lower Cambrian) Longmyndian sediments and tuffs, Welsh Borderlands

Summary. This study covers detailed thermal, chemical and alternating field demagnetization from 50 sites distributed through all units of the Longmyndian sedimentary succession (with the exception of the Stretton Shales), and eight sites in the tuff bands comprising the Batch Volcanics. The resultant effect of treatment is to remove a low blocking temperature steep component and isolate a coherent remanence direction D = 116°, I = 76° the total NRM is composite and not an adequate indicator of the palaeofield. Chemical demagnetization indicates that both hematite and magnetite grains contribute to this component and these two phases are magnetized in the same direction. A negative fold test shows that this remanence was acquired during or after the Longmyndian folding. Formation of the major magnetic constituent, authigenic magnetite, is linked to dewatering during rapid uplift following the folding which is dated by both the Rb–Sr and fission track methods at c . 525 Ma. The study defines a palaeopole of this age remote from the later APW path for Britain and links the Late Precambrian–Lower Cambrian path defmed from basement rocks of England and Wales with the Ordovician and younger results. Palaeomagnetic results from tuff bands within the sediments and Lower Silurian age intrusions cutting the outcrop are also reported.