Ground-water resources of the Oakland Park area of eastern Broward County, Florida

The Oakland Park area obtains its water from the Biscayne aquifer, S composed of very permeable and porous, sandy limestones. The per- 3 meability of the aquifer increases with depth, and wells in the area <\ generally obtain water at depths ranging from 60 to 80 feet, or between S 100 and 200 feet, depending on the quantity of water desired. The data presented in this paper can be used for further development of water and wise management of resources in the area. Large quantities S of ground water are still available at Oakland Park, if salt-water encroachment can be controlled. The data in this study provide the necessary information to begin an effective water management program. (PDF has 49 pages

A constitutive model with damage for high temperature superalloys

A unified constitutive model is searched for that is applicable for high temperature superalloys used in modern gas turbines. Two unified inelastic state variable constitutive models were evaluated for use with the damage parameter proposed by Kachanov. The first is a model (Bodner, Partom) in which hardening is modeled through the use of a single state variable that is similar to drag stress. The other (Ramaswamy) employs both a drag stress and back stress. The extension was successful for predicting the tensile, creep, fatigue, torsional and nonproportional response of Rene' 80 at several temperatures. In both formulations, a cumulative damage parameter is introduced to model the changes in material properties due to the formation of microcracks and microvoids that ultimately produce a macroscopic crack. A back stress/drag stress/damage model was evaluated for Rene' 95 at 1200 F and is shown to predict the tensile, creep, and cyclic loading responses reasonably well

Achieving accurate FTIR measurements on high performance bandpass filters

The sources of ordinate error in FTIR spectrometers are reviewed with reference to measuring small out-of-band features in the spectra of bandpass filters. Procedures for identifying instrumental artefacts are described. It is shown that features well below 0.01%T can be measured reliably

That Christmas Poinsettia

Here are some tips on caring for poinsettias during and after the holdiay season. It takes some doing, but you may want to try to grow the plants on through the year and have your own poinsettia plants for next Christmas

The geoarchaeology of Dust Cave: a Late Paleoindian through Middle Archaic site in the western Middle Tennessee River Valley

This dissertation uses a geoarchaeological perspective in order to reconstruct the depositional history of Dust Cave. Dust Cave, located in the western Middle Tennessee River Valley, is a complex Late Paleoindian through Middle Archaic site. The cave contains uniquely well-preserved artifacts, and one of the earliest well-dated archaeological sequences in the southeastern US. The depositional history addresses the relationship of Dust Cave to the regional geomorphology and builds a contextual framework based on the cave\u27s microenvironment. Microenvironmental conditions directly affected both the organization of human activity and its preservation. The methodology employed consists of detailed macrostratigraphic field observations and micromorphological analyses of more than 130 sediment thin sections. Micromorphology is the most appropriate technique for the cave environment where fine-scale variation among the deposits is preserved and data from the anthropogenic sediments have the potential to inform about human activity. The zones are organized chronologically based on 46 radiocarbon ages and diagnostic artifacts. When Late Paleoindian peoples began to occupy Dust Cave ca. 10,500 B.P. it had recently been flushed of sediment from a phreatic aquifer at the rear of the cave. The entrance chamber contained only a thin veneer of reworked alluvium overlying the bedrock floor in a ~10 m wide and nearly 8 m deep room with a 5 m high ceiling. Intermittent overbank deposition with limited reworked aeolian sediments and autochthonous sediments accumulated in the cave for the next ca. 2,000 years. During this time Late Paleoindian and Early Archaic peoples seasonally inhabited the cave. Microtopographic surface variation and the periodic resurgence of phreatic drainages controlled the organization and preservation of anthropogenic sediments. After ca. 8,500 B.P., when the floodplain began to stabilize, alluvial sediments were no longer actively contributing to the cave. Sedimentation over the next 3,000 years was primarily the result of human activity, which continues until ca. 5,200 B.P. when the cave is no longer habitable. Several interesting aspects of the depositional history are revealed including relic cold features deep in the sequence and the identification and distribution of prepared surfaces. These discrete anthropogenic structures have significant implications for technology and site formation

Force-detected nuclear double resonance between statistical spin polarizations

We demonstrate nuclear double resonance for nanometer-scale volumes of spins where random fluctuations rather than Boltzmann polarization dominate. When the Hartmann-Hahn condition is met in a cross-polarization experiment, flip-flops occur between two species of spins and their fluctuations become coupled. We use magnetic resonance force microscopy to measure this effect between 1H and 13C spins in 13C-enriched stearic acid. The development of a cross-polarization technique for statistical ensembles adds an important tool for generating chemical contrast in nanometer-scale magnetic resonance.Comment: 14 pages, 4 figure

Added mass of a pair of discs at small separation

Inviscid irrotational flow around a pair of coaxial disks is c onsidered in the limit in which the distance 2 h between the disks is small compared to their radius a . The disks have zero thickness and accelerate away from one another along their common axis. Th e added mass M of each accelerating disk is increased by the presence of the other disk. Analytic predictions are obtained when h/a ≪ 1 , with M ∼ πa/ (8 h ) − ln( h/a ) / 2 + 0 . 77875 + · · · . The term O ( a/h ) can be obtained by means of an inviscid analysis of approximately unidirectional flo w within the gap between the disks, but the correction terms have not been reported previously. The irrotational flow problem satisfies Neu- mann boundary conditions on the surface of the disks, but is o therwise analogous to the Dirichlet problem of the capacitance of a pair of charged disks, which h as been the subject of much study and controversy