Analysis of the coupling between the apparent time scale of thermal degradation and sample size

Sample size sensitivity of thermal gravimetric analysis (TGA) presents a serious handicap in the obtaining of reliable thermal stability data for high-temperature applications. For example, predictions of the apparent time for degradation during an isothermal experiment based on the results obtained using a 10 μm thick specimen can be off by an order of magnitude when applied to a product with a thickness of 10 cm. To address this effect, TGA experiments studying the thermal degradation of poly(methyl methacrylate) were conducted. Analysis of the experimental data resulted in the development of a relationship between the apparent time scale of the thermal degradation and the specimen thickness. Origins of the new dependence were traced to the change of the diffusivity resulting from material volatilization. Implications of the coupling between these two events for the analysis of thermal stability for new polymeric materials are discussed, and required changes in the current methodology are outlined.     

Thermo-mechanical and microstructural characterisation of sodium-poly(sialate-siloxo) (Na-PSS) geopolymers

The thermo-mechanical and microstructural character of sodium-poly(sialate-siloxo) (Na-PSS) geopolymers synthesised from dehydroxylated kaolinite (metakaolinite) have been investigated. Thermal analysis by means of TG–DTA showed a single endothermic peak at 135–140 °C due to dehydration (water evolution) from the geopolymer framework. Thermal expansion measurements show that geopolymer suffers 2% shrinkage below 250 °C and is then dimensionally stable up to 800 °C. The inclusion of aggregate (α-quartz or granite) was found to reduce the shrinkage by 1% although the presence of the quartz limits the working temperature range of the composite due a to disruptive phase change. Thermal conductivity and compressive strength of Na-PSS geopolymers varied with change in chemical composition of the geopolymer as well as the amount and type of aggregate. Investigation of the microstructure by electron microscopy showed that the ratio of the starting materials influences the homogeneity of the geopolymer microstructure, which in turn leads to differences in thermal conductivity and compressive strength.     

Learning and classification of monotonic ordinal concepts

Ordinal reasoning plays a major role in human cognition. This paper identifies an important class of classification problems of patterns taken from ordinal domains and presents efficient, incremental algorithms for learning the classification rules from examples. We show that by adopting a monotonicity assumption of the output with respect to the input, inconsistencies among examples can be easily detected and the number of possible classification rules substantially reduced. By adopting a conservative classification criterion, the required number of rules further decreases. The monotonicity and conservatism of the classification also enable the resolution of conflicts among inconsistent examples and the graceful handling of don't knows and don't cares during the learning and classification phases. Two typical examples in which the suggested classification model works well are given. The first example is taken from the financial domain and the second from machining.     

Characterization of Ceramic Materials with BIGDIFF: A Synchrotron Radiation Debye-Scherrer Powder Diffractometer

Experiments have been conducted to evaluate the potential of the BIGDIFF Debye–Scherrer diffractometer (radius of 573 mm) for characterizing ceramic materials using synchrotron radiation. The instrument has been tested at a wavelength of 0.1538 nm (1.5378), under in vacuo conditions, with standard reference materials and an alumina-matrix ceramic specimen using capillary-mounted (diameter of 0.5 mm) powdered material. The diffraction patterns that have been recorded with imaging plates over a period of 15 min provide phase detectability that is clearly superior to Bragg-Brentano laboratory X-ray diffractometry data that is collected in 1 h. The superiority of BIGDIFF for the analysis of phase composition becomes very pronounced for trace phases (,1%). The sharper definition of the Bragg peaks with BIGDIFF synchrotron radiation data also leads to improved estimates of nonlinear residual strain and crystallite size data. The superior performance of BIGDIFF is principally due to (i) the intensity of the synchrotron radiation incident beam that is achieved with high collimation and monochromaticity (E/ΔE 10⁴), (ii) the large ratio of the camera radius to the capillary radius, and (iii) the spatial resolution and dynamic range of the imaging plates.     

Stable Isotopes of Carbon and Oxygen as a Possible New Tool for Estimating Firing Temperatures of Ancient Pottery

The ratios of the stable isotopes of carbon (¹³C/¹²C) and oxygen (¹⁸O/¹⁶O) in calcite in clays that contain carbonate and that were fired at temperatures between 500 and 700 °C displayed a good correlation with the firing temperature for both isotopes. The isotopic composition indicated that the original carbonate was either completely decomposed or that it exchanged with environmental CO₂ to obliterate the original isotopic signature. The isotopic effects seem to be kinetically controlled. The isotope thermometer is used to compare refiring temperatures of pottery which was fired under controlled conditions. The differences between calculated and actual temperatures did not exceed 132 °C and in most cases was about 50 °C or less. Isotopic analysis of pottery from Tel Miqne-Ekron and Deir el Balah, dated to the 13th–12th centuries BC, gave an average ancient firing temperature of about 600 °C. If shown to be of general validity, then perhaps this technique can be used also for estimating preparation temperatures of ancient mortar, especially when preserved in dry climates where later changes would be minimized.     

Coronary artery perforation with rotational coronary atherectomy]

We tried to determine whether women with a urinary tract infection (UTI) were more likely to have had a recent pelvic examination than were women seen for other reasons. We compared 56 women who were diagnosed as having a UTI with 49 controls who had an unrelated complaint (sinusitis). Significantly more women with UTIs had received a pelvic examination within the preceding 2 months (43% vs 16%, P = .01). We conclude that having a pelvic examination is associated with an increased risk of a UTI developing within the following 2 months. This may be due to physical factors related to the examination or to risk factors related to the patients' reasons for obtaining a pelvic examination. Further study is needed to determine if the pelvic examination is an independent risk factor. If so, established preventive measures could reduce this risk.     

Lay persons' sensitivity to statistical information: The case of high perceived applicability.

Six experimental studies were conducted to test the notion that lay persons are insensitive to statistical information when they are in the presence of individuating information allowing judgment by representativeness. Ss were 174 Israeli undergraduates and 259 members of the Israel Defense Forces. Two experiments examined the effects of reliability information on the regressiveness of predictions and on judgmental confidence. Two additional experiments examined the effects on confidence of informational redundancy. The final 2 studies examined Ss' capacity to reason in accordance with the notion of statistical information when its situational applicability is made apparent. On the basis of this and previous evidence, it is concluded that statistical rules seem to be used in accordance with the same rules that govern the use of nonstatistical rules, such as the "representativeness" rule and other rules of various contents. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

TSL—A Texture Synthesis Language

TheTexture Synthesis Language (TSL) is a new high-level graphics language which provides tools for defining and generating regular and random (irregular) synthetic textures. The textures are used to fill in planar regions or can be mapped onto other surfaces. The building block for generating textures is a texture tile, i.e., a rectangular matrix oftexels (texture elements). The programmer constructs texture tiles utilizing predefined constant tiles, user-defined tiles, and texel-based operations. Tiles can be transformed and combined in various ways, and can then be used to tessellate planar polygons.This work was partially supported by the National Science Foundation under grant DCR-86-03603     

Introduction to the special issue on the self and social identity.

This article describes the special issue of the Journal of Personality and Social Psychology (JPSP), which is the result of a joint undertaking by the three sections of JPSP. This makes it different from previous special sections or issues of the journal in that rather than relying on the generous services of a guest editor, the same editorial team that handles the regular journal issues has originated this special issue, as well, thus conveying a sense of "business as usual." Our major reason for the present initiative was to highlight the essential unity of personality and social psychology as a field of science. The topic choice for the present special issue was dictated by its relevance and interest to the field of personality and social psychology as a whole, across its various partitions and subdivisions. The articles in the special issue amply reflect the naturalness with which the self and social identity theme transcends the boundaries of JPSP sections. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Continuous simulation of a car-following equation

Traffic behavior along an urban roadway is explored using a continuous simulation model of a leader-follower pair of vehicles. The model employs a non-linear car-following differential equation that characterizes the motion of the pair. The implementation of the conceptual model is programmed in the continuous simulation language, MIMIC. In analyzing the results, an emphasis is placed on the formulation of a simple exponential expression that describes the pair motion. This exponential formula may replace the traditional differential equation in sketching pair behavior and platoon dispersion in traffic systems and simulation models.