Graduate admissions criteria of leading psychology departments.

As a follow-up to a previous comment by J. E. Purdy et al (see record 1988-02765-001), the authors present the responses of 78% of the directors of top graduate programs to a questionnaire assessing the importance of information in applications for admission to graduate study, of the Graduate Record Examination scores, grade point average (GPA), letters of recommendation, research and clinical experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multivariate Decision Trees

Unlike a univariate decision tree, a multivariate decision tree is not restricted to splits of the instance space that are orthogonal to the features' axes. This article addresses several issues for constructing multivariate decision trees: representing a multivariate test, including symbolic and numeric features, learning the coefficients of a multivariate test, selecting the features to include in a test, and pruning of multivariate decision trees. We present several new methods for forming multivariate decision trees and compare them with several well-known methods. We compare the different methods across a variety of learning tasks, in order to assess each method's ability to find concise, accurate decision trees. The results demonstrate that some multivariate methods are in general more effective than others (in the context of our experimental assumptions). In addition, the experiments confirm that allowing multivariate tests generally improves the accuracy of the resulting decision tree over a univariate tree.     

Interlamellar spacing in discontinuous precipitation

After reviewing the behavior of a number of systems exhibiting discontinuous precipitation, the theoretical treatment of the process is discussed, with emphasis on the problem of the interlamellar (or inter-rod) spacing. The case of the minimum, or critical, spacing is discussed for lamellar and rod products, as is a possible criterion for the maximum accessible spacing. The problem of the optimal spacing is then addressed, mainly from an experimental point-of-view. Experimental data for Al-Zn and Mg-Al alloys are analyzed and related to the discussion. This paper is based on a presentation made at the symposium “Establishment of Microstructural Spacing during Dendritic and Cooperative Growth” held at the annual meeting of the AIME in Atlanta, Georgia on March 7, 1983 under the joint sponsorship of the ASM-MSD Phase Transformations Committee and the TMS-AIME Solidification Committee. formerly with the Department of Metallurgy and Materials Science, McMaster University.     

Quality assurance of serial tomotherapy for head and neck patient treatments

PURPOSE: A commercial serial tomotherapy intensity-modulated radiation therapy (IMRT) treatment planning (Peacock, NOMOS Corp., Sewickley, PA) and delivery system is in clinical use. The dose distributions are highly conformal, with large dose gradients often surrounding critical structures, and require accurate localization and dose delivery. Accelerator and patient-specific quality assurance (QA) procedures have been developed that address the localization, normalization, and delivery of the IMRT dose distributions. METHODS AND MATERIALS: The dose distribution delivered by serial tomotherapy is highly sensitive to the accuracy of the longitudinal couch motion. There is also an unknown sensitivity of the dose distribution on the dynamic mutlileaf collimator alignment. QA procedures were implemented that assess these geometric parameters. Evaluations of patient positioning accuracy and stability were conducted by exposing portal films before (single exposure) and after (single or double exposure) treatments. The films were acquired with sequential exposures using the largest available fixed multileaf portal (3.36 x 20 cm2). Comparison was made against digitally reconstructed radiographs generated using independent software and appropriate beam geometries. The delivered dose was verified using homogeneous cubic phantoms. Radiographic film was used to determine the localization accuracy of the delivered isodose distributions, and ionization chambers and thermoluminescent dosimetry (TLD) chips were used to verify absolute dose at selected points. Ionization chamber measurements were confined to the target dose regions and TLD measurements were obtained throughout the irradiated volumes. Because many more TLD measurements were made, a statistical evaluation of the measured-to-calculated dose ratio was possible. RESULTS: The accelerator QA techniques provided adequate monitoring of the geometric patient movement and dynamic multileaf collimator alignment and positional stability. The absolute delivered dose as measured with the ionization chamber varied from 0.94 to 0.98. Based on these measurements, the delivered monitor units for both subsequent QA measurements and patient treatments were adjusted by the ratio of measured to calculated dose. TLD measurements showed agreement, on average, with the ionization chamber measurements. The distribution of TLD measurements in the high-dose regions indicated that measured doses agreed within 4.2% standard deviation of the calculated doses. In the low-dose regions, the measured doses were on average 5% greater than the calculated doses, due to a lack of leakage dose in the dose calculation algorithm. CONCLUSIONS: The QA system provided adequate determination of the geometric and dosimetric quantities involved in the use of IMRT for the head and neck. Ionization chamber and TLD measurements provided accurate determination of the absolute delivered dose throughout target volumes and critical structures, and radiographic film yielded precise dose distribution localization verification. Portal film acquisition and subsequent portal film analysis using 3.36 x 20 cm2 portals proved useful in the evaluation of patient immobilization quality. Adequate bony landmarks were imaged when carefully selected portals were used.     

A double flow cytometric tag allows tracking of the dynamics of cell cycle progression of newborn Saccharomyces cerevisiae cells during balanced exponential growth

Studies on the dynamics of growth of single eukaryotic cells and their relationships with cell cycle regulations are generally carried out following cell synchronization procedures or, on a relatively low number of cells, by time-lapse studies. Establishment of both time-lapse studies and synchronous cell populations usually requires elaborate experimental efforts and is prone to perturb the physiological state of the cell. In this paper we use a new flow cytometric approach which allows, in asynchronous growing Saccharomyces cerevisiae populations, tagging of both the cell age and the cell protein content of a cohort of daughter cells at the different cell cycle set points. Since the cell protein content is a good estimation of the cell size, it is possible to follow the kinetics of the cell size increase during cell cycle progression. The experimental findings obtained indicate an exponential increase of the cell size during growth, that the daughter and the parent subpopulations grow with the same specific growth rate, that the average cell size increase rate of each individual cell is almost identical to the specific growth rate of the overall population and provide the opportunity to estimate the cell cycle length for the daughter cell population as well as the identification of the complex structure of asynchronously growing yeast populations.     

Interpersonal concomitants and antecedents of depression among college students.

Depressed college students were compared with other-psychopathology and normal controls regarding the relationship they developed with dormitory roommates during a 9-month period. Diagnostic status was periodically assessed via SADS interviews, thus also permitting identification of new cases of depression during the year. Psychosocial characteristics found to be uniquely associated with current depression were: (a) low social contact with roommates, (b) low enjoyability of these contacts, and (c) high life-event stress. Roommates of depressives reported low enjoyability of the relationship and high levels of aggressive behavior towards the depressive. No features were found to be uniquely associated with new cases before they became depressed; however, several antecedents of general psychopathology were identified. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Government—Media—Audiences: Private Sector Participation in Public Service Broadcasting: The Case of Kenya

Commercial advertising and religious broadcasts are allowed in order to raise revenues, but at the same time the public broadcasting organization must ensure that the stability of the state is not threatened by alternative voices.     

In situ observations of chemically induced grain-boundary migration and discontinuous precipitation in the aluminum-zinc system

In situ observations are reported for chemically induced grain-boundary migration (CIGM) and discontinuous precipitation (DP) in the Al-Zn system. In each case, it is found that the migration of the grain boundary is a steady continuous process, at least on the scale of the resolution of the electron optical techniques employed. However, there are significant differences; the grain-boundary velocities are such that a diffusion field must exist in the parent crystal for the case of CIGM but little or no volume diffusion penetration for steady DP. For CIGM, it is argued that the coherency strain energy in the diffusion field is sufficient for the development of a small residual chemical force; for steady DP, a large fraction of the total chemical force is available to act directly across the grain boundary. In the latter case, agreement is obtained between observed and calculated dynamic boundary shapes, using a method in which the chemical force (corrected for losses due to continuous precipitation in the parent phase) is balanced against capillary forces. Formerly with McMaster University     

Infra-red spectra of perfluorinated cation-exchanged membranes

Assignment of the i.r. spectrum of Nafion cation exchange membranes was made possible by use of i.r. absorption and reflectance (ATR) spectroscopy. Shifts in the water and sulphonic vibrations occurring upon exchange of various counterions were compared with those occurring in a polyethylene sulphonic acid and polystyrene sulphonic acid membrane. The type of binding of the cations and the possibility of cluster formation are discussed. A dimeric iron unit FeOFe was identified in the Nafion membrane.