1,720,973 research outputs found
Solution-Grown Organic and Perovskite X-Ray Detectors: A New Paradigm for the Direct Detection of Ionizing Radiation
Full text linkThe recent years witnessed an unprecedented enhancement in improved functionality materials and in the sophistication of solution-based device fabrication techniques. Such significant advancements lead to unexpected and effective opportunities for the utilization of solution-grown organic materials and perovskites in the detection of ionizing radiation. This review presents an updated overview of the recently reported top performing and more innovative organic/perovskite-based X-ray detectors, providing a comparison and a critical discussion on the different materials’ properties and performance. Solution-growth methods that allow to obtain detector grade electronic materials are discussed, focusing on the growth both of single crystals and of thin/thick films and foreseeing the implementation of large-area, organic/hybrid-, and perovskite-based radiation detectors. Insights into the X-ray detection mechanisms are provided, detailing the fundamental processes involved in the charge collection and in the photoconductive gain model, together with the typical figures of merit that describe radiation detector performance
Ultra-Stable and Robust Response to X-Rays in 2D Layered Perovskite Micro-Crystalline Films Directly Deposited on Flexible Substrate
Full text link2D layered hybrid perovskites have recently attracted an increasing interest as active layers in LEDs and UV–Vis photodetectors. 2D perovskites crystallize in a natural self-assembled quantum well-like structure and possess several interesting features among which low-temperature (<100 °C) synthesis and low defect density. Here are presented solid-state ionizing radiation direct detectors based on the 2D layered hybrid perovskite PEA2PbBr4 (PEA = C6H5C2H4NH3+) deposited from solution using scalable techniques and directly integrated onto a pre-patterned flexible substrate in the form of micro-crystalline films displaying crystal-like behavior, as evidenced by the ultra-fast (sub-microsecond) and good detection performances under UV light. The effective detection of X-rays (up to 150 kVp) is demonstrated with sensitivity values up to 806 μC Gy−1 cm−2 and Limit of Detection of 42 nGy s−1, thus combining the excellent performance for two relevant figures of merit for solid-state detectors. Additionally, the tested devices exhibit exceptionally stable response under constant irradiation and bias, assessing the material robustness and the intimate electrical contact with the electrodes. PEA2PbBr4 micro-crystalline films directly grown on flexible pre-patterned substrate open the way for large-area solid-state detectors working at low radiation flux for ultra-fast X-ray imaging and dosimetry
Detection of X-Rays by Solution-Processed Cesium-Containing Mixed Triple Cation Perovskite Thin Films
No full textMaterials and technology development for designing innovative and efficient X-ray radiation detectors is of utmost importance for a wide range of applications ranging from security to medical imaging. Here, highly sensitive direct X-ray detectors based on novel cesium (Cs)-based triple cation mixed halide perovskite thin films are reported. Despite being in a thin film form, the devices exhibit a remarkably high X-ray sensitivity of (3.7 ± 0.1) μC Gy−1 cm−2 under short-circuit conditions. At a small reverse bias of 0.4 V, the sensitivity further increases by orders of magnitude reaching a record value of (97 ± 1) μC Gy−1 cm−2 which surpasses state-of-the-art inorganic large-area detectors (a-Se and poly-CZT). Based on detailed structural, electrical, and spectroscopic investigations, the exceptional sensitivity of the triple cation Cs perovskite is attributed to its high ambipolar mobility-lifetime product as well as to the formation of a pure stable perovskite phase with a low degree of energetic disorder, due to an efficient solution-based alloying of individual n- and p-type perovskite semiconductors
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Abundance of mRNA of Apolipoprotein B100, Apolipoprotein E,and Microsomal Triglyceride Transfer Protein in Liverfrom Periparturient Dairy Cows
No full textLimited secretion of very low density lipoproteins (VLDL) in dairy cows is strongly related to fatty liver and other metabolic disorders in the early postpartum. Currently, there is limited information on which roles apolipoprotein B100 (ApoB100), apolipoprotein E (ApoE), and microsomal triglyceride transfer protein (MTP) play in that VLDL limitation. To our knowledge, no studies have simultaneously measured ApoB100, ApoE, and MTP mRNA in periparturient dairy cows. Therefore, a trial was conducted to assess liver gene expression of these proteins in transition dairy cows and to evaluate the relationships between their expression and metabolic status. Eight multiparous Holstein cows were monitored during the transition period. To evaluate metabolic and nutritional status, body condition score was registered, and plasma indexes of energy metabolism and VLDL were determined from 35 d before to 35 d after calving. Liver biopsies were performed on d −35, 3, and 35 relative to day of calving, and gene expression of ApoB100, ApoE, and MTP were determined on liver tissue. Body condition, plasma glucose and VLDL decreased, and plasma NEFA and BHBA increased after calving. Compared with values of d −35, on d 3 after calving the ApoB100 mRNA synthesis was lower, whereas MTP and ApoE mRNA abundance were higher. Negative correlation (r=−0.57) between plasma NEFA concentration and ApoB100 mRNA abundance, and positive correlation between ApoB100 mRNA abundance and plasma cholesterol (r=0.65) and plasma albumins (r=0.52) were detected at 3 d postpartum. Data on changes of gene expression of the 3 main proteins involved in the regulation of synthesis and secretion of VLDL in the liver suggest that decreased mRNA for ApoB100 may be consistent with decreased synthesis and/or secretion of VLDL from liver during the peripart-urient period
Morphology and mobility as tools to control and unprecedentedly enhance X-ray sensitivity in organic thin-films
Full text linkOrganic semiconductor materials exhibit a great potential for the realization of large-area solution-processed devices able to directly detect high-energy radiation. However, only few works investigated on the mechanism of ionizing radiation detection in this class of materials, so far. In this work we investigate the physical processes behind X-ray photoconversion employing bis-(triisopropylsilylethynyl)-pentacene thin-films deposited by bar-assisted meniscus shearing. The thin film coating speed and the use of bis-(triisopropylsilylethynyl)-pentacene:polystyrene blends are explored as tools to control and enhance the detection capability of the devices, by tuning the thin-film morphology and the carrier mobility. The so-obtained detectors reach a record sensitivity of 1.3 · 104 μC/Gy·cm2, the highest value reported for organic-based direct X-ray detectors and a very low minimum detectable dose rate of 35 μGy/s. Thus, the employment of organic large-area direct detectors for X-ray radiation in real-life applications can be foreseen
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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