Detecting 6 MV X-rays using an organic photovoltaic device

An organic photovoltaic (OPV) device has been used in conjunction with a flexible inorganic phosphor to produce a radiation tolerant, efficient and linear detector for 6 MV X-rays. The OPVs were based on a blend of poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM). We show that the devices have a sensitivity an order of magnitude higher than a commercial silicon detector used as a reference. Exposure to 360 Grays of radiation resulted in a small (2%) degradation in performance demonstrating that these detectors have the potential to be used as flexible, real-time, in vivo dosimeters for oncology treatments.     

Learning contextual relationships in mammograms using a hierarchical pyramid neural network

This paper describes a pattern recognition architecture, which we term hierarchical pyramid/neural network (HPNN), that learns to exploit image structure at multiple resolutions for detecting clinically significant features in digital/digitized mammograms. The HPNN architecture consists of a hierarchy of neural networks, each network receiving feature inputs at a given scale as well as features constructed by networks lower in the hierarchy. Networks are trained using a novel error function for the supervised learning of image search/detection tasks when the position of the objects to be found is uncertain or ill defined. We have evaluated the HPNN's ability to eliminate false positive (FP) regions of interest generated by the University of Chicago's (UofC) Computer-aided diagnosis (CAD) systems for microcalcification and mass detection. Results show that the HPNN architecture, trained using the uncertain object position (UOP) error function, reduces the FP rate of a mammographic CAD system by approximately 50% without significant loss in sensitivity. Investigation into the types of FPs that the HPNN eliminates suggests that the pattern recognizer is automatically learning and exploiting contextual information. Clinical utility is demonstrated through the evaluation of an integrated system in a clinical reader study. We conclude that the HPNN architecture learns contextual relationships between features at multiple scales and integrates these features for detecting microcalcifications and breast masses.     

An integrated microfabricated cell sorter

We have developed an integrated microfabricated cell sorter using multilayer soft lithography. This integrated cell sorter is incorporated with various microfluidic functionalities, including peristaltic pumps, dampers, switch valves, and input and output wells, to perform cell sorting in a coordinated and automated fashion. The active volume of an actuated valve on this integrated cell sorter can be as small as 1 pL, and the volume of optical interrogation is approximately 100 fL. Different algorithms of cell manipulation, including cell trapping, were implemented in these devices. We have also demonstrated sorting and recovery of Escherichia coli cells on the chip.     

Nine-analyte detection using an array-based biosensor

A fluorescence-based multianalyte immunosensor has been developed for simultaneous analysis of multiple samples. While the standard 6 x 6 format of the array sensor has been used to analyze six samples for six different analytes, this same format has the potential to allow a single sample to be tested for 36 different agents. The method described herein demonstrates proof of principle that the number of analytes detectable using a single array can be increased simply by using complementary mixtures of capture and tracer antibodies. Mixtures were optimized to allow detection of closely related analytes without significant cross-reactivity. Following this facile modification of patterning and assay procedures, the following nine targets could be detected in a single 3 x 3 array: Staphylococcal enterotoxin B, ricin, cholera toxin, Bacillus anthracis Sterne, Bacillus globigii, Francisella tularensis LVS, Yersiniapestis F1 antigen, MS2 coliphage, and Salmonella typhimurium. This work maximizes the efficiency and utility of the described array technology, increasing only reagent usage and cost; production and fabrication costs are not affected.     

OLES: an instrument for refining the design of e-learning environments

Abstract Designing and implementing effective e-learning is a complex process, which involves many factors. Lecturers need to constantly consider, evaluate and adjust these factors to provide effective e-learning environments for students. In this paper, we report on the design and development of the Online Learning Environment Survey (OLES), an instrument which can be used to gather and represent data on students' 'actual' (experienced) and 'preferred' (ideal) learning environments. We describe the use of this instrument in blended learning environments with university classes, illustrating how OLES can be used by educators striving for good practice in the design of effective online learning environments.     

Dynamics and control in component‐based agent models

Dynamics are an important aspect of agent models. Control of dynamics requires specific methods of specification that have their own specific semantics. This paper addresses specification and semantics of dynamics and control in component‐based agent models. Specification is based on a dedicated formal design specification language for agent models. Semantics of the dynamics are defined using temporal traces with composite states. It is shown in what manner control aspects can be specified, and what their semantics is in terms of the temporal traces. An agent model for controlled diagnostic reasoning processes is used to illustrate the approach. © 2002 Wiley Periodicals, Inc.     

Chromatic contrast sensitivity: the role of absolute threshold and gain constant in differences between the fovea and the periphery

A model of foveal achromatic and chromatic sensitivity [Vision Res. 36, 1597 (1996)] was extended to the peripheral visual field. Threshold-versus-illuminance functions were analyzed to determine effects of eccentricity on absolute thresholds and gain constants of chromatic and luminance mechanisms. The resulting peripheral model successfully predicted peripheral contrast sensitivity as a function of wavelength, for both white and 500-nm backgrounds. We conclude that the short-wavelength-sensitive cone opponent mechanism may mediate thresholds in Sloan's notch in the normal periphery and that interpretation of reduced chromatic sensitivity in the periphery requires an explicit model of how eccentricity affects both the gain constant and the absolute threshold.     

"Choice processing in emotionally difficult decisions": Correction.

Reports an error in the article "Choice Processing in Emotionally Difficult Decisions' by Mary Frances Luce, James R. Bettman, and John W. Payne (Journal of Experimental Psychology: Learning, Memory, and Cognition, 1997, Vol. 23, No. 2, pp. 384–405; see record 1997-03378-007). In Table 7 on page 396, the high conflict/low trade-off difficulty mean for the PATTERN variable was printed as -0.13, but the actual mean is 0.13. A portion of the original abstract follows: Extends the standard effort-accuracy approach to explaining task influences on decision processing by arguing that coping goals will interact with effort-minimization goals for negatively emotion-laden decision tasks. These coping goals may involve both a desire to process in a thorough, accurate manner and a desire to avoid particularly distressing aspects of processing. The authors hypothesized and found in 3 experiments that decision processing under increasing negative emotion both becomes more extensive and proceeds more by focusing on one attribute at a time. In particular, increased negative emotion leads to more attribute-based processing at the beginning of the decision process. The results are inconsistent with views that negative emotion acts only as an incentive or only as a source of decision complexity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)