Calibration of dosemeters used in mammography with different X ray qualities: Euromet Project No. 526

The effect of different X ray radiation qualities on the calibration of mammographic dosemeters was investigated within the framework of a EUROMET (European Collaboration in Measurement Standards) project. The calibration coefficients for two ionization chambers and two semiconductor detectors were established in 13 dosimetry calibration laboratories for radiation qualities used in mammography. They were compared with coefficients for other radiation qualities, including those defined in ISO 4037-1, with first half value layers in the mammographic range. The results indicate that the choice of the radiation quality is not crucial for instruments with a small energy dependence of the response. However, the radiation quality has to be chosen carefully if instruments with a marked dependence of their response to the radiation energy are calibrate

ELECTRICAL MEASUREMENTS AT THE MICRO SCALE: AIR BREAKDOWN AND Si COULOMB BLOCKADE DEVICES

In this thesis I describe the work performed in two different areas of research, electrical breakdown of air for small electrode separations and measurements of silicon (Si)-based tunable-barrier single electron transistors (SETs). In this work, I describe a new method for measuring the breakdown of air for the range of electrode separation of interest. This method has several advantages compared to ones found in the literature, namely it allows for a measurement of electrode separation before each breakdown measurement; it has a parallel plate geometry and the surface roughness of the electrodes used is very small. Using the results obtained with this method I have made a quantitative comparison between the predictions of the standard theory of the field (field emission of electrons) and our data, something that has not been done before. In this thesis I describe analytically both the theory and the analysis of our data. I conclude that the standard theory used in this field fails for the range of electrode separations of interest (400 nm to 45 μm). Also, I describe electrical measurements performed on a Si-based tunable-barrier device fabricated in the group of Neil Zimmerman at the National Institute of Standards and Technology (NIST) using the fabrication facilities of Cornell University. I demonstrate that this device can be operated as an SET. I continue by describing measurements of the charge offset drift (Q0(t)) for this device and show that it is almost 3 orders of magnitude smaller than in metal devices, and comparable to previously measured Si devices of this type. All of the previously measured devices originated from the same fabrication source, NTT, Japan. Our ability to demonstrate the same low drift in devices fabricated at Cornell, USA, indicates that the small values of Q0(t) is a robust property of Si-based devices, and not sensitive to the details of fabrication

A general purpose electroanalytical system based on a microcomputer controlled coulostatic generator

Thesis (Ph. D.)--Michigan State University. Department of Chemistry, 1978Includes bibliographical references (pages 181-184

An enhanced gas ionization sensor from Y-doped vertically aligned conductive ZnO nanorods

A stable and highly sensitive gas ionization sensor (GIS) constructed from vertically aligned, conductive yttrium–doped ZnO nanorod (YZO NR) arrays is demonstrated. The conductive YZO NRs are synthesized using a facile one-pot hydrothermal method. At higher Y/Zn molar ratio, the aspect ratio of the YZO NRs is increased from 11 to 25. Doping with yttrium atoms decreases the electrical resistivity of ZnO NRs more than 100 fold. GIS measurements reveal a 6-fold enhancement in the sensitivity accompanied with a significant reduction in breakdown voltage from the highly conductive YZO NRs. Direct correlations between the resistivity of the NRs and GIS characteristics are established

21-(4-Methyl­phenyl­sulfon­yl)-4,7,13,16-tetra­oxa-1,10,21-triaza­bicyclo­[8.8.5]tricosane-19,23-dione: an N-tosyl­ated macrobicyclic dilactam

The macrobicyclic title compound, C23H35N3O8S, contains two tertiary amide bridgehead N atoms and a toluene­sulfonamide N atom in the center of the five-atom bridging strand. The mol­ecule has a central cavity that is defined by the 18-membered ring identified by the N2O4 donor atom set and two 15-membered rings with N3O2 donor atom sets. The toluene­sulfonamide N atom adopts an exo orientation with respect to the central cavity, and the tosyl group is oriented on one side of the aza-bridging strand that connects the bridgehead N atoms

Hydrotherapy (Project Hydriades)

Natural resources are being used for the maintenance of health. According to the Law 3498/2006 of the Greek Parliament the natural health spas must be validated for their therapeutic properties. The Association of Municipalities and Communities of Health Springs of Greece signed a contract with the Research Committee of the Aristotle University of Thessaloniki, Greece, in order to conduct the research programme: ‘Study for the documentation of the therapeutic properties of the thermomineral waters’. The main aim of the project is: (1) the study of biological and therapeutic parameters of the natural health sources, (2) the identification of the indications and contraindications of hydrotherapy. Aims parallel to the main ones have been also set

Attenuated Glial Reactivity on Topographically Functionalized Poly(3,4-Ethylenedioxythiophene):P-Toluene Sulfonate (PEDOT:PTS) Neuroelectrodes Fabricated by Microimprint Lithography

Following implantation, neuroelectrode functionality is susceptible to deterioration via reactive host cell response and glial scar-induced encapsulation. Within the neuroengineering community, there is a consensus that the induction of selective adhesion and regulated cellular interaction at the tissue–electrode interface can significantly enhance device interfacing and functionality in vivo. In particular, topographical modification holds promise for the development of functionalized neural interfaces to mediate initial cell adhesion and the subsequent evolution of gliosis, minimizing the onset of a proinflammatory glial phenotype, to provide long-term stability. Herein, a low-temperature microimprint-lithography technique for the development of micro-topographically functionalized neuroelectrode interfaces in electrodeposited poly(3,4-ethylenedioxythiophene):p-toluene sulfonate (PEDOT:PTS) is described and assessed in vitro. Platinum (Pt) microelectrodes are subjected to electrodeposition of a PEDOT:PTS microcoating, which is subsequently topographically functionalized with an ordered array of micropits, inducing a significant reduction in electrode electrical impedance and an increase in charge storage capacity. Furthermore, topographically functionalized electrodes reduce the adhesion of reactive astrocytes in vitro, evident from morphological changes in cell area, focal adhesion formation, and the synthesis of proinflammatory cytokines and chemokine factors. This study contributes to the understanding of gliosis in complex primary mixed cell cultures, and describes the role of micro-topographically modified neural interfaces in the development of stable microelectrode interfaces