Plate-specific gain map correction for the improvement of detective quantum efficiency in computed radiography.

PURPOSE: The purpose of this work is to improve the noise power spectrum (NPS), and thus the detective quantum efficiency (DQE), of computed radiography (CR) images by correcting for spatial gain variations specific to individual imaging plates. CR devices have not traditionally employed gain-map corrections, unlike the case with flat-panel detectors, because of the multiplicity of plates used with each reader. The lack of gain-map correction has limited the DQE(f) at higher exposures with CR. This current work describes a feasible solution to generating plate-specific gain maps. METHODS: Ten high-exposure open field images were taken with an RQA5 spectrum, using a sixth generation CR plate suspended in air without a cassette. Image values were converted to exposure, the plates registered using fiducial dots on the plate, the ten images averaged, and then high-pass filtered to remove low frequency contributions from field inhomogeneity. A gain-map was then produced by converting all pixel values in the average into fractions with mean of one. The resultant gain-map of the plate was used to normalize subsequent single images to correct for spatial gain fluctuation. To validate performance, the normalized NPS (NNPS) for all images was calculated both with and without the gain-map correction. Variations in the quality of correction due to exposure levels, beam voltage/spectrum, CR reader used, and registration were investigated. RESULTS: The NNPS with plate-specific gain-map correction showed improvement over the noncorrected case over the range of frequencies from 0.15 to 2.5 mm(-1). At high exposure (40 mR), NNPS was 50%-90% better with gain-map correction than without. A small further improvement in NNPS was seen from carefully registering the gain-map with subsequent images using small fiducial dots, because of slight misregistration during scanning. Further improvement was seen in the NNPS from scaling the gain map about the mean to account for different beam spectra. CONCLUSIONS: This study demonstrates that a simple gain-map can be used to correct for the fixed-pattern noise in a given plate and thus improve the DQE of CR imaging. Such a method could easily be implemented by manufacturers because each plate has a unique bar code and the gain-map for all plates associated with a reader could be stored for future retrieval. These experiments indicated that an improvement in NPS (and hence, DQE) is possible, depending on exposure level, over a wide range of frequencies with this technique.

Exact analytical expressions for the potential of electrical double layer interactions for a sphere-plate system.

Exact, closed-form analytical expressions are presented for evaluating the potential energy of electrical double layer (EDL) interactions between a sphere and an infinite flat plate for three different types of interactions: constant potential, constant charge, and an intermediate case as given by the linear superposition approximation (LSA). By taking advantage of the simpler sphere-plate geometry, simplifying assumptions used in the original Derjaguin approximation (DA) for sphere-sphere interaction are avoided, yielding expressions that are more accurate and applicable over the full range of κa. These analytical expressions are significant improvements over the existing equations in the literature that are valid only for large κa because the new equations facilitate the modeling of EDL interactions between nanoscale particles and surfaces over a wide range of ionic strength.

Consumption of cyanogenic bamboo by a newly discovered species of bamboo lemur

Three species of bamboo‐eating lemurs were found to be sympatric in the southeastern rain forests of Madagascar. Sympatric species generally differ in habitat utilization or diet, but these three closely related bamboo lemurs lived in the same habitat and all ate bamboo. Behavioral observation revealed that they did select different parts of the bamboo, and chemical analyses confirmed that there was a difference in the secondary compound content present in those selections. The growing tips of Cephalostachyum ef uiguieri selected by the golden bamboo lemur (Hapalemuraureus) contained 15 mg of cyanide per 100 g fresh weight bamboo while the leaves of C. perrieri selected by the gentle bamboo lemur (H. griseus)and the mature culms of C. cf uiguieri selected by the greater bamboolemur (H. simus) did not contain cyanide. Since each individual golden bamboo lemur ate about 500 g of bamboo per day, they daily ingestedabout 12 times the lethal dose of cyanide. The mechanism by which this small primate avoids the acute and chronic symptoms of cyanide poisioning is unknown. Copyright © 1989 Wiley‐Liss, Inc., A Wiley Company

Commandeering Aesop’s Bamboo Canon: A 19th Century Confederacy of Creole Fugitive Fables

In my thesis, “Commandeering Aesop’s Bamboo Canon: A 19th Century Confederacy of Creole Fugitive Fables,” I ask and answer the ‘Who? What? Where? When? Why?” of Creole Literature using the 19th century production of Aesopian fables as clues to resolve a set of linguistic, historical, literary, and geographical enigmas pertaining the ‘birth-place(s)’ of Creolophone Literatures in the Caribbean Sea, North and South America, as well as the Indian Ocean. Focusing on the fables in Martinique (1846), Reunion Island (1826), and Mauritius (1822), my thesis should read be as an attempt capture the links between these islands through the creation of a particular archive defined as a cartulary-chronicle, a diplomatic codex, or simply a map in which I chart and trace the flight of the founding documents relating to the lives of the individual authors, editors, and printers in order to illustrate the articulation of a formal and informal confederation that enabled the global and local institutional promotion of Creole Literature. While I integrate various genres and multi-polar networks between the authors of this 19th century canon comprised of sacred and secular texts such as proclamations, catechisms, and proverbs, the principle literary genre charted in my thesis are collections of fables inspired by French 17th century French Classical fabulist, Jean de la Fontaine. Often described as the ‘matrix’ of Creolophone Literature, these blues and fables constitute the base of the canon, and are usually described as either ‘translated,’ ‘adapted,’ and even ‘cross-dressed’ into Creole in all of the French Creolophone spaces. My documentation of their transnational sprouting offers proof of an opaque canonical formation of Creole popular literature. By constituting this archive, I emphasize the fact that despite 200 years of critical reception and major developments and discoveries on behalf of Creole language pedagogues, literary scholars, linguists, historians, librarians, archivist, and museum curators, up until now not only have none have curated this literature as a formal canon. I also offer new empirical evidence in order to try and solve the enigma of “How?” the fables materially circulated between the islands, and seek to come to terms with the anonymous nature of the texts, some of which were published under pseudonyms. I argue that part of the confusion on the part of scholars has been the result of being willfully taken by surprise or defrauded by the authors, or ‘bamboozled’ as I put it. The major paradigmatic shift in my thesis is that while I acknowledge La Fontaine as the base of this literary canon, I ultimately bypass him to trace the ancient literary genealogy of fables to the infamous Aesop the Phrygian, whose biography – the first of a slave in the history of the world – and subsequent use of fables reflects a ‘hidden transcript’ of ‘masked political critique’ between ‘master and slave classes’ in the 4th Century B.C.E. Greece.

This archive draws on, connects and critiques the methodologies of several disciplinary fields. I use post-colonial literary studies to map the literary genealogies Aesop; use a comparative historical approach to the abolitions of slavery in both the 19th century Caribbean and the Indian Ocean; and chart the early appearance of folk music in early colonial societies through Musicology and Performance Studies. Through the use of Sociolinguistics and theories of language revival, ecology, and change, I develop an approach of ‘reflexive Creolistics’ that I ultimately hope will offer new educational opportunities to Creole speakers. While it is my desire that this archive serves linguists, book collectors, and historians for further scientific inquiry into the innate international nature of Creole language, I also hope that this innovative material defense and illustration of Creole Literature will transform the consciousness of Creolophones (native and non-native) who too remain ‘bamboozled’ by the archive. My goal is to erase the ‘unthinkability’ of the existence of this ancient maritime creole literary canon from the collective cultural imaginary of readers around the globe.