2,416 research outputs found

    Consumer Price Index Data Quality: How Accurate is the U.S. CPI?

    Get PDF
    The Consumer Price Index (CPI) is an estimate of the average change in prices over time paid by urban consumers for a market basket of consumer goods and n the United States. The CPI is used extensively in many different ways, including three major uses: to adjust historical data, to escalate federal payments and tax brackets, and to adjust rents and wages. It directly affects the lives of Americans, so it must be as accurate as possible. But how accurate is it? If, for example, the CPI measures annual inflation as 2.3 percent, how confident can we be in that estimate? This issue of BEYOND THE NUMBERS looks at some different ways the U.S. Bureau of Labor Statistics (BLS) has responded to questions about the accuracy and precision of the CPI. The first section examines the sampling error of the CPI, and the second section discusses possible sources of bias in the index

    A reflective essay about my preparation for education administration

    Get PDF
    The power that schools have to positively impact students\u27 lives and futures is amazing to me. Leading a staff, student body, and a community into positive relationships with one another can be a challenging task and service. Accomplishing this task can be rewarding. Schools exist to promote learning. Learning takes place throughout one\u27s lifetime. The opportunity to lead a school is the opportunity to positively impact lives in the present, as well as the future

    Relationship between religious beliefs and the accounting and economic practices of a society: evidence from the Dead Sea scrolls

    Get PDF
    This study explores the Dead Sea Scrolls to demonstrate how Essene socio-religious values shaped their accounting and economic practices during the late Second Temple period (ca. first century BCE to 70 CE). Our primary focus is on the accounting and commercial responsibilities of a leader within their community †“ the Examiner. We contend that certain sectarian accounting practices may be understood as ritual/religious ceremony and address the performative roles of the Essenes\u27 accounting and business procedures in light of their purity laws and eschatological beliefs. Far from being antithetical to religious beliefs, we find that accounting actually enabled the better practice and monitoring of religious behavior. We add to the literature on the interaction of religion with the structures and practices of accounting and regulation within a society

    Electron and Proton Acceleration Using the 30 TW, 30 fs Hercules Laser.

    Full text link
    This thesis presents experimental measurements of energetic particles accelerated from a high intensity, short pulse interaction with underdense and overdense plasmas. From the interaction of a 40 TW laser pulse with an underdense He plasma, high energy (150 MeV), highly directional (simsim10 mrad) relativistic electron beams are used to perform photonuclear activation (gammagamma,n) of carbon and copper and photofission (gammagamma,f) of uranium. Monte-Carlo simulations show the bremsstrahlung produced by these quasi-monoenergetic electrons in heavy converters includes a large number of MeV gammagamma-rays used to excite the giant dipole resonance. Due to the quasi-monoenergetic nature of the wakefield accelerated electrons, photonuclear activation was enhanced between one to two orders of magnitude compared to previous experiments. In a separate series of experiments proton generation from the interaction of a high intensity, high contrast laser incident upon submicron foils was described. The maximum proton energy from transparent dielectrics is shown to depend on the hydrogen content of the target material and not on the targets thickness. PIC simulations are used to show a two stages acceleration mechanism consisting of: (1) proton acceleration due to a ponderomotively induced charge separation at the front surface and (2) an additional acceleration due to the target normal sheath. The observed effect was experimentally distinguished through target selection of hydrogen and non-hydrogen containing materials. It was observed that the maximum proton energy for hydrogen containing targets such as Mylar and CH was two times higher than for non-hydrogen containing targets such as Si3_{3}N4_{4}. Finally, a relativistic plasma shutter technique was proposed and tested to further increase the laser contrast. This is done by placing a thin foil before the target with a unique thickness such that the leading edge of the laser fully ionizes the foil causing it to expand into an underdense plasma. PIC simulations show a high intensity, high contrast laser strongly deforms a thin target (<< 70 nm) causing the accelerated protons to shift away from the target normal and towards the laser axis. The protons characteristic shift toward the laser axis was observed after inserting a plasma shutter before a 50 nm target.Ph.D.Applied PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/58499/1/reedsa_1.pd

    Seismic Anisotropy and Mantle Dynamics Beneath the Malawi Rift Zone, East Africa

    Get PDF
    SKS, SKKS, and PKS splitting parameters measured at 34 seismic stations that we deployed in the vicinity of the Cenozoic Malawi Rift Zone (MRZ) of the East African Rift System demonstrate systematic spatial variations with an average splitting time of 1.0 ± 0.3 s. The overall NE-SW fast orientations are consistent with absolute plate motion (APM) models of the African Plate constructed under the assumption of no-net rotation of the global lithosphere and are inconsistent with predicted APM directions from models employing a fixed hot spot reference frame. They also depart considerably from the trend of most of the major tectonic features. These observations, together with the results of anisotropy depth estimation using the spatial coherency of the splitting parameters, suggest a mostly asthenospheric origin of the observed azimuthal anisotropy. The single-layered anisotropy observed at 30 and two-layered anisotropy observed at 4 of the 34 stations can be explained by APM-related simple shear within the rheologically transitional layer between the lithosphere and asthenosphere, as well as by the horizontal deflection of asthenospheric flow along the southern and western edges of a continental block with relatively thick lithosphere revealed by previous seismic tomography and receiver function investigations. This first regional-scale shear wave splitting investigation of the MRZ suggests the absence of rifting-related active mantle upwelling or small-scale mantle convection and supports a passive-rifting process for the MRZ

    The Mantle Transition Zone beneath the Afar Depression and Adjacent Regions: Implications for Mantle Plumes and Hydration

    Get PDF
    The Afar Depression and its adjacent areas are underlain by an upper mantle marked by some of the world\u27s largest negative velocity anomalies, which are frequently attributed to the thermal influences of a lower-mantle plume. In spite of numerous studies, however, the existence of a plume beneath the area remains enigmatic, partially due to inadequate quantities of broad-band seismic data and the limited vertical resolution at the mantle transition zone (MTZ) depth of the techniques employed by previous investigations. In this study, we use an unprecedented quantity (over 14 500) of P-to-S receiver functions (RFs) recorded by 139 stations from 12 networks to image the 410 and 660 km discontinuities and map the spatial variation of the thickness of the MTZ. Non-linear stacking of the RFs under a 1-D velocity model shows robust P-to-S conversions from both discontinuities, and their apparent depths indicate the presence of an upper-mantle low-velocity zone beneath the entire study area. The Afar Depression and the northern Main Ethiopian Rift are characterized by an apparent 40- 60 km depression of both MTZ discontinuities and a normal MTZ thickness. The simplest and most probable interpretation of these observations is that the apparent depressions are solely caused by velocity perturbations in the upper mantle and not by deeper processes causing temperature or hydration anomalies within the MTZ. Thickening of the MTZ on the order of 15 km beneath the southern Arabian Plate, southern Red Sea and western Gulf of Aden, which comprise the southward extension of the Afro-Arabian Dome, could reflect long-term hydration of the MTZ. A 20 km thinning of the MTZ beneath the western Ethiopian Plateau is observed and interpreted as evidence for a possible mantle plume stem originating from the lower mantle

    Forced Convective Diffusion and Interphase Heat and Mass Transfer: Computations of Radial Functions, Temperature and Concentration Fields, and Presentation of Local and Average Nusselt and Sherwood Numbers

    Get PDF
    Theoretical calculations have been carried out for forced convective transport for uniform streaming and uniaxial and biaxial extensional axisymmetric flows past single spheres. Homogeneous and heterogeneous chemical reactions, both of first and of second order have also been or are presently being treated. Orthogonality and other properties of Legendre functions have been used, together with introduction of an eigenfunction expansion, to reduce the mathematical description from a partial differential equation with variable coefficients, which is nonlinear for homogeneous second order chemical reactions, to a system of coupled ordinary differential equations for the radial modes. The numerical solutions of the latter have been obtained using the robust, adaptive grid algorithm of Pereyra and Lentini. Plots of the radial functions for given Peclet and Damkohler numbers give insight into the role and interaction of L and of r∞ (the number of terms necessary for convergence of the expansion and the finite radius at which the boundary conditions at infinity are imposed). From the radial modes, local and average Nusselt and Sherwood numbers, as well as the temperature and concentration fields, can be obtained. Plots of radial function families provide new insights that complement physicochemical understanding gained from isocontour plots of the temperature and concentration fields. Plots of local interphase transfer coefficients reflect the behavior of the flux field over the sphere surface and show how the average coefficients arise

    No Thermal Anomalies in the Mantle Transition Zone beneath an Incipient Continental Rift: Evidence from the First Receiver Function Study Across the Okavango Rift Zone, Botswana

    Get PDF
    Mechanisms leading to the initiation and early-stage development of continental rifts remain enigmatic, in spite of numerous studies. Among the various rifting models, which were developed mostly based on studies of mature rifts, far-field stresses originating from plate interactions (passive rifting) and nearby active mantle upwelling (active rifting) are commonly used to explain rift dynamics. Situated atop of the hypothesized African Superplume, the incipient Okavango Rift Zone (ORZ) of northern Botswana is ideal to investigate the role of mantle plumes in rift initiation and development, as well as the interaction between the upper and lower mantle. The ORZ developed within the Neoproterozoic Damara belt between the Congo Craton to the northwest and the Kalahari Craton to the southeast. Mantle structure and thermal status beneath the ORZ are poorly known, mostly due to a complete paucity of broadband seismic stations in the area. As a component of an interdisciplinary project funded by the United States National Science Foundation, a broad-band seismic array was deployed over a 2-yr period between mid-2012 and mid-2014 along a profile 756 km in length. Using P-to-S receiver functions (RFs) recorded by the stations, the 410 and 660 km discontinuities bordering the mantle transition zone (MTZ) are imaged for the first time. When a standard Earth model is used for the stacking of RFs, the apparent depths of both discontinuities beneath the Kalahari Craton are about 15 km shallower than those beneath the Congo Craton. Using teleseismic Pand S-wave traveltime residuals obtained by this study and lithospheric thickness estimated by previous studies, we conclude that the apparent shallowing is the result of a 100-150 km difference in the thickness of the lithosphere between the two cratons. Relative to the adjacent tectonically stable areas, no significant anomalies in the depth of the MTZ discontinuities or in teleseismic P- and S-wave traveltime residuals are found beneath the ORZ. These observations imply an absence of significant thermal anomalies in the MTZ and in the upper mantle beneath the incipient rift, ruling out the role of mantle plumes in the initiation of the ORZ. We propose that the initiation and development of the ORZ were the consequences of relative movements between the South African block and the rest of the African plate along a zone of lithospheric weakness between the Congo and Kalahari cratons. An area of thinner-than-normal MTZ is found at the SW corner of the study area. This anomaly, if confirmed by future studies, could suggest significant transferring of heat from the lower to the upper mantle

    Longitudinal Evaluation of Sealing Molars with and without Incipient Dental Caries in a Public Health Program

    Full text link
    Objectives: This study undertook a retrospective evaluation of the effect of sealants on the caries experience of initially sound and incipient permanent first molar pit and fissure surfaces. Methods : Records of children with complete five-year records were obtained from a school-based dental sealant program in a fluoridated community. Sealants were placed on 677 tooth surfaces in 96 children; 120 tooth surfaces in 17 children who received baseline examinations were not sealed because of lack of caregiver consent. Tooth surfaces were initially diagnosed as being sound or having incipient lesions, and evaluated for caries status after five years. Results : For initially incipient surfaces the five-year decay rate was 10.8 percent (41 of 380 surfaces) for sealed surfaces and 51.8 percent (29 of 56 surfaces) for nonsealed surfaces with an odds ratio of 8.88 (95% Cl=4.56, 17.35). Initially sound surfaces had a decay rate of 8.1 percent (24 of 297 surfaces) for sealed surfaces and 12.5 percent (8 of 64 surfaces) for nonsealed surfaces with an odds ratio of 1.63 (95% Cl=0.63, 4.08). The two odds ratios were significantly different. Conclusions : Initially sound tooth surfaces were unlikely to become decayed in five years, and did not benefit greatly from the application of sealants. Within the limitations of this study, there were clear efficiencies in sealing incipient, but not sound, surfaces. The targeting of teeth with incipient caries for sealants is therefore recommended.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66270/1/j.1752-7325.1995.tb02358.x.pd
    • …
    corecore