On the Birth of Isolas

Isolas are isolated, closed curves of solution branches of nonlinear problems. They have been observed to occur in the buckling of elastic shells, the equilibrium states of chemical reactors and other problems. In this paper we present a theory to describe analytically the structure of a class of isolas. Specifically, we consider isolas that shrink to a point as a parameter τ of the problem, approaches a critical value τ_0. The point is referred to as an isola center. Equations that characterize the isola centers are given. Then solutions are constructed in a neighborhood of the isola centers by perturbation expansions in a small parameter ε that is proportional to (τ-τo), with a appropriately determined. The theory is applied to a chemical reactor problem

The Aluminum Concentration in Human Postmortem Lung Tissue from Smokers and Nonsmokers as Determined by Neutron Activation Analysis

Author Institution: Department of Biology, University of AkronANTHONY, ROBERT E. AND KELLER, ROGER F. The Aluminum Concentration in Human Postmortem Lung Tissue from Smokers and Nonsmokers as Determined by Neurton Activation Analysis. Ohio J. Sci. 75: 56, 1975

Accurate Cylindrical-Coordinate Numerical Models For The Analysis Of Hydrologic Tests

Analytical solutions to well hydraulic problems have restrictive assumptions that often do not match real world conditions. Although numerical models more closely match reality, they either ran too slowly to be practical or lacked accuracy because of coarse grid spacing and large time steps. Advances in computer power over the last few decades now allow for accurate, fast numerical models that handle complex flow systems. The purpose of this dissertation was to develop flexible and accurate numerical modeling codes for the simulation of hydrologic tests. One of these numerical modeling codes, the Slug Test Simulator (STS), was designed for the mechanics of a single well test, or slug test. STS can handle a variety of conditions including unconfined flow, partial penetration, layered heterogeneities, and the presence of a homogeneous well skin like existing codes. This program also extends on the capabilities of earlier codes with its ability to simulate a heterogeneous skin where K can vary in both the radial and vertical directions. STS has a clear user interface, can display graphical results, and allows the user to determine hydraulic conductivity through a trial-and-error curve-matching process. Comparisons of STS to the Cooper-Bredehoeft-Papadopulos analytical solution and the Kansas Geological Survey (KGS) semi-analytical solution produced near-identical curves under a wide variety of conditions. Numerous analytical studies have shown that the well skin is an important factor in the underestimation of hydraulic conductivity in slug tests. STS allows for the exploration of the well skin issue under conditions too complex for analytical models. Model trials revealed two key discoveries: 1) if any layers within the skin have the same hydraulic conductivity as the surrounding formation, flow is concentrated within these conduits and the resultant head response approaches the case when no skin is present; and 2) the two most important properties in determining the overall influence of the skin are specific storage and skin thickness. The first discovery suggests that extensive development activities can essentially eliminate any well skin impacts. Other factors such as partial penetration, the placement of the well screen, and anisotropy play insignificant roles in resultant head responses. Recent research is focusing on alternative direct- push (DP) methodologies to determine hydrologic properties. DP offers advantages over traditional well tests, but may yield inaccurate results if the screen becomes clogged during pushing activities. The Kansas Geological Survey (KGS) developed a new DP technique, the Direct-Push Permeameter (DPP), to overcome this limitation. Existing analytical or numerical models cannot address the specialized nature of DPP tests so a second numerical modeling code, the Direct Push Permeameter Simulator (DPSS), was developed. DPPS was generated by modifying STS so both numerical codes are similar in many ways, particularly with their flexibility and accuracy. The codes differ in how they handle vertical layering, the boundary conditions at the well, and the spreadsheet interfaces. DPPS was able to produce near-identical curves in comparison to the Theis analytical solution. DPPS was also able to reasonably recreate DPP field data conducted at two sites with distinctly different media properties. The GEMS and Nauen sites had an average error of 14.2% and 3.1%, respectively between the field data and DPPS simulations

Dependency structure matrix modelling for stakeholder value networks

This paper develops a qualitative/quantitative network approach, namely a “Stakeholder Value Network”, to understand the impacts of both direct and indirect relationships between stakeholders on the success of large engineering projects. Specifically, this paper explores the feasibility and benefit of applying the Dependency Structure Matrix (DSM) as the modelling platform for Stakeholder Value Networks. Further, an efficient algorithm is designed for computing indirect stakeholder influence and implemented in a case study for a multinational energy project. The results derived from this analysis are able to answer three fundamental questions for stakeholder management: What are the critical paths/themes for a project to engage other stakeholders? Who are the most important stakeholders for a project? How can the complexity of a large relationship network be reasonably managed

Early formation of the Moon 4.51 billion years ago

Establishing the age of the Moon is critical to understanding solar system evolution and the formation of rocky planets, including Earth. However, despite its importance, the age of the Moon has never been accurately determined. We present uranium-lead dating of Apollo 14 zircon fragments that yield highly precise, concordant ages, demonstrating that they are robust against postcrystallization isotopic disturbances. Hafnium isotopic analyses of the same fragments show extremely low initial 176Hf/177Hf ratios corrected for cosmic ray exposure that are near the solar system initial value. Our data indicate differentiation of the lunar crust by 4.51 billion years, indicating the formation of the Moon within the first ~60 million years after the birth of the solar system

Diffraction Considerations for Planar Detectors in the Few-Mode Limit

Filled arrays of bolometers are currently being employed for use in astronomy from the far-infrared through millimeter parts of the electromagnetic spectrum. Because of the large range of wavelengths for which such detectors are applicable, the number of modes supported by a pixel will vary according to the specific application of a given available technology. We study the dependence of image fidelity and induced polarization on the size of the pixel by employing a formalism in which diffraction due to the pixel boundary is treated by propagating the second-order statistical correlations of the radiation field through a model optical system. We construct polarized beam pattern images of square pixels for various ratios of p/\lambda where p is the pixel size and \lambda is the wavelength of the radiation under consideration. For the limit in which few modes are supported by the pixel (p/\lambda<1), we find that the diffraction due to the pixel edges is non-negligible and hence must be considered along with the telescope diffraction pattern in modeling the ultimate spatial resolution of an imaging system. For the case in which the pixel is over-moded (p/\lambda>1), the geometric limit is approached as expected. This technique gives a quantitative approach to optimize the imaging properties of arrays of planar detectors in the few-mode limit.Comment: 20 pages, 8 figure

Pain Assessment After Anterior Cruciate Ligament Reconstruction: Bone-Patellar Tendon-Bone Versus Hamstring Tendon Autograft.

BACKGROUND: Anterior cruciate ligament (ACL) reconstruction is a common outpatient procedure that is accompanied by significant postoperative pain. PURPOSE: To determine differences in acute pain levels between patients undergoing ACL reconstruction with bone-patellar tendon-bone (BTB) versus hamstring tendon (HS) autograft. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A total of 70 patients who underwent primary ACL reconstruction using either BTB or HS autografts consented to participate. The primary outcome of the study was postoperative pain levels (visual analog scale), which were collected immediately after surgery and for 3 days postoperatively. Secondary outcome measures included opioid consumption (intravenous morphine equivalents), hours slept, patient satisfaction, reported breakthrough pain, and calls to the physician. RESULTS: Patients treated with BTB had increased pain when compared with those treated with HS in the acute postoperative period (mean ± SD: day 0, 6.0 ± 1.7 vs 5.2 ± 2.0 [P = .066]; day 1, 5.9 ± 1.7 vs 4.9 ±1.7 [P = .024]; day 2, 5.2 ± 1.9 vs 4.1 ± 2.0 [P = .032]; day 3, 4.8 ± 2.1 vs 3.9 ± 2.3 [P = .151]). There were also significant increases in reported breakthrough pain (day 0, 76% vs 43% [P = .009]; day 1, 64% vs 35% [P = .003]) and calls to the physician due to pain (day 1, 19% vs 0% [P = .041]) in the BTB group. There were no significant differences in narcotic requirements or sleep disturbances. Overall, the BTB group reported significantly less satisfaction with pain management on days 0 and 1 (P = .024 and .027, respectively). CONCLUSION: A significant increase in acute postoperative pain was found when performing ACL reconstruction with BTB compared with HS. Patients treated with BTB were more likely to have breakthrough pain, decreased satisfaction with their pain management, and to contact their physician due to pain. These findings suggest a difference in early postoperative pain between the 2 most common graft options for ACL reconstruction. Patients should be informed of the differences in acute postoperative pain when deciding on graft choice with their physician

A Deeper Look at Leo IV: Star Formation History and Extended Structure

We present MMT/Megacam imaging of the Leo~IV dwarf galaxy in order to investigate its structure and star formation history, and to search for signs of association with the recently discovered Leo~V satellite. Based on parameterized fits, we find that Leo~IV is round, with $\epsilon < 0.23$ (at the 68\% confidence limit) and a half-light radius of $r_{h} \simeq 130$ pc. Additionally, we perform a thorough search for extended structures in the plane of the sky and along the line of sight. We derive our surface brightness detection limit by implanting fake structures into our catalog with stellar populations identical to that of Leo~IV. We show that we are sensitive to stream-like structures with surface brightness $\mu_{r}\lesssim29.6$ mag arcsec$^{-2}$, and at this limit, we find no stellar bridge between Leo IV (out to a radius of $\sim$0.5 kpc) and the recently discovered, nearby satellite Leo V. Using the color magnitude fitting package StarFISH, we determine that Leo~IV is consistent with a single age ($\sim$14 Gyr), single metallicity ($[Fe/H]\sim-2.3$) stellar population, although we can not rule out a significant spread in these value. We derive a luminosity of $M_{V}=-5.5\pm0.3$. Studying both the spatial distribution and frequency of Leo~IV's 'blue plume' stars reveals evidence for a young ($\sim$2 Gyr) stellar population which makes up $\sim$2\% of its stellar mass. This sprinkling of star formation, only detectable in this deep study, highlights the need for further imaging of the new Milky Way satellites along with theoretical work on the expected, detailed properties of these possible 'reionization fossils'.Comment: 26 pages, 14 figures, emulateapj format, ApJ accepted versio