332 research outputs found
Data Set of PLOS Computational Paper PCOMPBIOL-D-18-02181R1
No full textFigures Data of PLOS Computational paper:Modeling of the axon plasma membrane structure and its effects on protein diffusionAuthors: Yihao Zhang, Anastasios V. Tzingounis, and George LykotrafitisCorresponding Author: George Lykotrafitis, Ph.D.University of ConnecticutStorss, CT UNITED STATES</div
The state of modern Greek language as spoken in Victoria
No full textDeposited with permission of the author. © 1986 Dr. Anastasios TamisThis thesis reports a sociolinguistic study, carried out between 1981 and 1984, of the state of the Modern Greek (MG) language in Australia, as spoken by native-speaking first-generation Greek immigrants in Victoria. Particular emphasis is given to the analysis of those characteristics of the linguistic behaviour of these Greek Australians which can be attributed to the contact with English and to other environmental, social and linguistic influence. (For complete abstract open document
New historical evidence for Anastasios Emm. Papas
No full textNo AbstractThe author’s attention has been drawn to the existence of this historicalevidence in the National Archives of Vienna, by his friend the writer EteoclesGregoriadis together with the numbers of the relevant files. Most of the documents were written in the old German script. Thus the author asked for the help of his friend and former colleague at the University of Thessaloniki and director of the Goethe Institute, Graf Kurt v. Posadowsky, for reading andstudying those documents. Without his help this study would have been impossible. This new evidence concerns the sojourn of Anastasios Papas·—son of Emmanuel Papas, leading figure of the Greek Revolution—in Austria andGermany between the 3rd January and 11th March 1822. There is informationabout his short imprisonment in Trieste, after his arival from Vienna. He then visits various towns in Germany and after negotiations with the Philhellene professor Fr. Thiersch in Munich, he purchases large quantities of ammunition to be despatched to Greece. He finally arrives in Greece early in 1824, and takes part—together with his three brothers who were already fighting—in the struggle for the liberation of the common great fartheland
Digital Mammography: From Physical Performance Evaluation To Image Quality Analysis
No full textSince the early 1990s digital X-ray detectors have been used extensively for medical imaging applications, such as Mammography, General Radiography, Computed Tomography, Tomosynthesis, Fluoroscopy, etc. The quality of a radiograph needs to be adequate to provide the required information for a given task. The primary physical parameters that affect image quality are spatial resolution, noise, and contrast. The Modulation Transfer Function (MTF) is the combination of contrast and resolution, the Noise Power Spectrum (NPS) combines the noise and resolution, and the Signal-to-Noise Ratio (SNR) expresses the ratio between signal and noise in large scale objects (i.e. at zero spatial frequency). The combination of SNR, MTF and NPS determines the Detective Quantum Efficiency (DQE) which represents the ability to visualize object details of a certain size and contrast. This study is using image simulation to estimate how the experimentally measured SNR, MTF and NPS of several digital X-ray detectors affect the mammographic image quality. The latter is measured in terms of Contrast-to-Noise Ratio (CNR) and Contrast-Detail (CD) analysis, using synthetic breast and CDMAM phantoms, respectivel
Cdmam_Fit_3: A Graphical User Interface for Mammographic Contrast-Detail Analysis
No full textAccording to the European Guidelines for quality control in digital mammography, mammographic image quality is expressed in terms of threshold contrast visibility using clinical exposure settings. The threshold contrast is defined as the lowest contrast value for which the objects are visible. The Contrast-Detail MAMmography (CDMAM) phantom is commonly used for the contrast-detail analysis, i.e. the detection of small thickness and low contrast objects. An automated scoring software tool (called CDCOM) was recently developed to evaluate the CDMAM radiographs. However, the CDCOM program does not determine the threshold contrast and further analysis is required by the user. This work presents a MATLAB-based graphical user interface (GUI), called CDMAM_fit_3, that a) reads and converts the original CDCOM data to a probability matrix, b) applies a psychometric curve fit to the data, c) predicts the human readout, d) compares the predicted results with the acceptable and achievable limits (provided by the European Guidelines) and e) saves the output data in various formats (i.e. txt, csv, xls, xlsx and xlsm). An executable version of the CDMAM_fit_3 can be used by the user without any programming and data processing knowledg
High Resolution Active Pixel Sensor X-Ray Detectors for Digital Breast Tomosynthesis
No full textCurrent large area x-ray detectors for digital breast tomosynthesis (DBT) are based on the amorphous silicon (a-Si:H) passive pixel sensor (PPS) technology. However, PPS detectors suffer from a limited resolution and high electronic noise. In this dissertation, we propose high resolution large area active pixel sensor (APS) x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) and amorphous In-Sn-Zn-O (a-ITZO) thin-film transistor (TFT) technologies to improve the imager resolution and noise properties.
We evaluated the two-dimensional (2D) x-ray imaging performance as measured by the modulation transfer function (MTF), noise power spectrum (NPS) and detective quantum efficiency (DQE) for both 75 µm (Dexela 2923 MAM) and 50 µm pixel pitch (DynAMITe) CMOS APS x-ray detectors. Excellent imaging performance (DQE in the range of 0.7 – 0.3) has been achieved over the entire spatial frequency range (0 – 6.7 mm-1) at low air kerma below 10 µGy using the 75 µm pixel pitch Dexela 2923 MAM detector. The 50 μm pixel pitch DyAMITe detector has further extended the spatial resolution of the detector to 10 mm-1 with a low electronic noise of 150 e-. Also, a 2D cascaded system analysis model has been developed to describe the signal and noise transfer for the CMOS APS x-ray imaging systems. We also implemented three-dimensional (3D) cascaded system analysis to simulated the 3D MTF, NPS and DQE characteristics using DBT radiation conditions and acquisition geometries. The 3D cascaded system analysis for the DynAMITe detector was integrated with an object task function, a medical imaging display model, and the human eye contrast sensitivity function to calculate the detectability index and area under the ROC curve (AUC). It has been demonstrated that the display pixel pitch and zoom factor should be optimized to improve the AUC for detecting high contrast objects such as microcalcifications. Also, detector electronic noise of smaller than 300 e- and a high display maximum luminance (>1000 cd/cm2) are desirable to distinguish microcalcifications of 150 µm or smaller in size. For low contrast object detection, a medical imaging display with a minimum of 12 bits gray levels is needed to realize accurate luminance levels. A wide projection angle range (≥ ±30°) combined with the image gray level magnification could improve the detectability for low contrast objects especially when the anatomical background noise is high.
CMOS APS x-ray detectors demonstrate both a high pixel resolution and low electronic noise, but are challenging to be fabricated in a large detector size greater than the wafer scale. Alternatively, current-mode APS (C-APS) based on a-ITZO TFTs was proposed for DBT due to the high gain, low noise, and capability to realize a large detector area. Specifically, we fabricated a-ITZO TFTs and achieved a high field-effect mobility of >30 cm2/Vs. We have also evaluated the electrical performance of a 50 µm pixel pitch a-ITZO TFT C-APS combined with an a-Si:H p+-i-n+ photodiode using SPICE simulation. The proposed C-APS circuit demonstrates a high charge gain of 885 with data line loadings considered. A pixel circuit layout and fabrication process have also been suggested. Finally, noise analysis has been applied to the a-ITZO TFT C-APS. A low electronic noise of around 239 e- has been established.
The research presented in this thesis indicates that APS x-ray detectors based on both CMOS and a-ITZO TFT technologies are promising for next generation DBT systems.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/136983/1/zhaocm_1.pd
X-ray Performance Evaluation of the Dexela CMOS APS X-ray Detector Using Monochromatic Synchrotron Radiation in the Mammographic Energy Range
No full textDigital detectors based on complementary metaloxide-semiconductors (CMOS) active pixel sensor (APS) technology have been introduced recently in many scientific applications. This work is focused on the X-ray performance evaluation of a novel CMOS APS detector in low energy medical imaging applications using monochromatic synchrotron radiation (i.e., 17–35 keV), which also allows studying how the performance varies with energy. The CMOS sensor was coupled to a Thallium-activated structured cesium iodide (CsI:Tl) scintillator and the detector’s X-ray performance evaluation was carried out in terms of sensitivity, presampling modulation transfer function (pMTF), normalized noise power spectrum (NNPS) and the resulting detective quantum efficiency (DQE). A Monte Carlo simulation was used to validate the experimentally measured low frequency DQE. Finally, the effect of iodine’s secondary generated K-fluorescence X-rays on pMTF and DQE results was evaluated. Good agreement (within 5%) was observed between the Monte Carlo and experimentally measured low frequency DQE results. A CMOS APS detector was characterized for the first time over a wide range of low energies covering the mammographic spectra. The detector’s performance is limited mainly by the detectability of the scintillator. Finally, we show that the current data could be used to calculate the detector’s pMTF, NNPS and DQE for any mammographic spectral shape within the investigated energies
Financial Education and Decision Making Processes
No full textAbstractThe present paper aims to examine whether students of financial studies, who are, therefore, most likely to pursue a career in stock market, demonstrate tendenc ies of irrational behaviour during decis ion making when exposed to dilemmas.In detail, based on questions drawn from the literature of Behavioural F inance, the study attempts to explore whether biases, emotions and overall behaviour are likely to deter rational choices and also whether the acquis ition of financ ial knowledge enables generating rational thinking and decisions. The findings of the empirical research, based on a sample of 84 students, seem to support the princ iples of the Behavioural F inance theory, according to which decis ion making is contingent upon emotions that are likely to result in systematic errors
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