An analysis of the relationships between articulation and auditory discrimination in kindergarten children

Thesis (Ed.M.)--Boston Universit

Rotation and Macroturbulence in Metal-poor Field Red Giant and Red Horizontal Branch Stars

We report the results for rotational velocities, Vrot sin i, and macroturbulence dispersion, zeta(RT), for 12 metal-poor field red giant branch stars and 7 metal-poor field red horizontal branch stars. The results are based on Fourier transform analyses of absorption line profiles from high-resolution (R ~ 120,000), high-S/N (~ 215 per pixel) spectra obtained with the Gecko spectrograph at CFHT. We find that the zeta(RT) values for the metal-poor RGB stars are very similar to those for metal-rich disk giants studied earlier by Gray and his collaborators. Six of the RGB stars have small rotational values, less than 2.0 km/sec, while five show significant rotation, over 3 km/sec. The fraction of rapidly rotating RHB stars is somewhat lower than found among BHB stars. We devise two empirical methods to translate the line-broadening results obtained by Carney et al. (2003, 2008) into Vrot sin i for all the RGB and RHB stars they studied. Binning the RGB stars by luminosity, we find that most metal-poor field RGB stars show no detectable sign, on average, of rotation. However, the most luminous stars, with M(V) <= -1.5, do show net rotation, with mean values of 2 to 4 km/sec, depending on the algorithm employed, and these stars also show signs of radial velocity jitter and mass loss.Comment: accepted for publication in the Astronomical Journa

Four Logics and a Protocol

The Internet Protocol (IP) is the protocol used to provide connectionless communication between hosts connected to the Internet. It provides a basic internetworking service to transport protocols such as Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). These in turn provide both connection-oriented and connectionless services to applications such as file transfer (FTP) and WWW browsing. In this paper we present four separate specifications of the interface to the internetworking layer implemented by IP using four types of logic: classical, constructive, temporal and linear logic

Calibration strategies for use of the nanoDot OSLD in CT applications.

Aluminum oxide based optically stimulated luminescent dosimeters (OSLD) have been recognized as a useful dosimeter for measuring CT dose, particularly for patient dose measurements. Despite the increasing use of this dosimeter, appropriate dosimeter calibration techniques have not been established in the literature; while the manufacturer offers a calibration procedure, it is known to have relatively large uncertainties. The purpose of this work was to evaluate two clinical approaches for calibrating these dosimeters for CT applications, and to determine the uncertainty associated with measurements using these techniques. Three unique calibration procedures were used to calculate dose for a range of CT conditions using a commercially available OSLD and reader. The three calibration procedures included calibration (a) using the vendor-provided method, (b) relative to a 120 kVp CT spectrum in air, and (c) relative to a megavoltage beam (implemented with 60 Co). The dose measured using each of these approaches was compared to dose measured using a calibrated farmer-type ion chamber. Finally, the uncertainty in the dose measured using each approach was determined. For the CT and megavoltage calibration methods, the dose measured using the OSLD nanoDot was within 5% of the dose measured using an ion chamber for a wide range of different CT scan parameters (80-140 kVp, and with measurements at a range of positions). When calibrated using the vendor-recommended protocol, the OSLD measured doses were on average 15.5% lower than ion chamber doses. Two clinical calibration techniques have been evaluated and are presented in this work as alternatives to the vendor-provided calibration approach. These techniques provide high precision for OSLD-based measurements in a CT environment

Diagnosing students' difficulties in learning mathematics

This study considers the results of a diagnostic test of student difficulty and contrasts the difference in performance between the lower attaining quartile and the higher quartile. It illustrates a difference in qualitative thinking between those who succeed and those who fail in mathematics, illustrating a theory that those who fail are performing a more difficult type of mathematics (coordinating procedures) than those who succeed (manipulating concepts). Students who have to coordinate or reverse processes in time will encounter far greater difficulty than those who can manipulate symbols in a flexible way. The consequences of such a dichotomy and implications for remediation are then considered

Book Reviews

Book reviews by Edward F. Barrett, Edward J. Gray, David T. Link, James K. Stucko, and Thomas M. Clusserath

Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars

We report the results for rotational velocities, Vrot sin i, and macroturbulence dispersions, ζRT, for 12 metal-poor field red giant branch (RGB) stars and 7 metal-poor field red horizontal branch (RHB) stars. The results are based on Fourier transform

Large scale emergent properties of an autocatalytic reaction-diffusion model subject to noise

The non-equilibrium dynamic fluctuations of a stochastic version of the Gray-Scott (GS) model are studied analytically in leading order in perturbation theory by means of the dynamic renormalization group. There is an attracting stable fixed point at one-loop order, and the asymptotic scaling of the correlation functions is predicted for both spatial and temporally correlated noise sources. New effective three-body reaction terms, not present in the original GS model, are induced by the combined interplay of the fluctuations and nonlinearities.Comment: 13 pages, 2 figure

Self-heating effect in intrinsic tunneling spectroscopy of HgBr2 intercalated Bi2.1Sr1.4Ca1.5Cu 2O8+δ single crystals

We report tunneling results in intrinsic Josephson junction (IJJ) stacks fabricated in the form of square micromesas on HgBr2 intercalated Bi2.1Sr1.4Ca1.5Cu2O 8+δ (Bi2212) single crystals using photolithography and Ar ion milling techniques. Self-heating is the most common problem encountered in interlayer tunneling and it is likely to reduce the reliability of IJJ data. Although intercalation reduces heating a hundredfold, it still needs to be minimized substantially in order to approach the authentic superconducting energy gap observed by tunneling using more conventional junctions. We report tunneling characteristics of two mesas with the same height but different sizes (5 × 5 μm2 and 10 × 10 μm2) to show that heating effects are strongly related to IJJ stack size. For the smaller mesa, we observed an energy gap close to that seen in single SIN (S: superconductor, I: insulator, N: normal metal) and SIS break junctions as well as the dip and hump structures at high bias. The subgap data of 5 × 5 μm2 mesa were successfully fit with a momentum averaged d-wave model using convenient parameters. Thus our data is consistent with the predominant pairing symmetry suggested by point contact tunneling, break junction, scanning tunneling microscopy/spectroscopy and angle resolved photoemission measurements in Bi2Sr2CaCu2O8+δ