1,721,020 research outputs found
A dose calculation model application for indoor exposure to two-layer walls gamma irradiation: The case study of ceramic tiles
No full textA calculation model for determining the indoor dose due to building materials with significant concentration of radioactivity has been applied to the case study of ceramic tiles; the model allows the contribution of bearing walls and wall covering materials to be calculated. The model is implemented in FORTRAN 77 and provides a quantification of the gamma radiation field (in terms of external dose rate in air, nGyh-1) inside a room with known dimensions. Application model results have been validated both by comparison with the results obtained by other authors and by experimental measurements. Model sensitivity and performances have been analysed and lastly the case studies focused on ceramic tiles have been proposed
Calibrated Hydraulic Resistance Adjuncts for Carbon Dioxide Angiography Optimization
Full text linkAbstract: Background: Despite the growing interest in CO2 angiography, some mechanical aspects related to CO2 injection still need to be deepened, and some improvements are still possible. This work explores the possibility of optimizing gas injection into small-sized arteries. Since the image quality depends on how the gas fills the vessel and is strongly dependent on injection flow, the possibility of controlling the flow is mandatory to obtain good results. To better control the flow, we propose to adjunct small tubes with known hydraulic resistances in parallel to the injection catheter, allowing the generation of the desired injection flow by modulating the injection pressure. Methods: Using a mechanical mock of the cardiovascular system, we measured pressures and flows of interest and acquired the optical images of the vessel during gas injections. We performed a simulation with four different calibrated adjunct resistances in various injection pressure conditions, with and without saline flushing. Results: Our tests demonstrated that the optimized injection of the gas maintains the same procedure durations and reduces the gas volume and the local pressure increase, avoiding the local gas “explosion” in the injection site. Conclusions: Our proposal appears effective and paves the way for research into optimizing clinical CO2 angiography procedures
Semi-empirical model for fluorescence lines evaluation in diagnostic x-ray beams
No full textDiagnostic x-ray beams are composed of bremsstrahlung and discrete fluorescence lines. The aim of this study is the development of an efficient model for the evaluation of the fluorescence lines. The most important electron ionization models are analyzed and implemented. The model results were compared with experimental data and with other independent spectra presented in the literature. The implemented peak models allow the discrimination between direct and indirect radiation emitted from tungsten anodes. The comparison with the independent literature spectra indicated a good agreement
BIOMECHANICAL CHARACTERIZATION OF SPONTANEOUS AND INDUCED MOTILITY IN SMALL ANIMALS’ GASTROINTESTINAL TISSUE FOR HUMAN NUTRACEUTICAL AND PHARMACEUTICAL PURPOSES
No full textThe correct evaluation of the effects of a new drug or molecule on the tissues it interacts with is essential for fully understanding its benefits and side effects. To date, there is a lack of accurate biomechanical characterization of gastrointestinal tissues, with the effects of active ingredients primarily assessed based on clinical outcomes. While we know a drug is effective, we often fail to understand the underlying mechanisms. Investigating the effects of these substances at the tissue level would improve our understanding of their biochemical and biomechanical properties, allowing the development of more effective drugs or identifying natural molecules with similar benefits but reduced side effects and costs. This study aims to characterize the biomechanical properties of gastrointestinal tissues from small animals. It presents a methodological overview and application using guinea pigs. The research involves biological sample preparation, assessment of spontaneous and induced motility, and evaluation of passive elastic behavior. The study focuses on tissues extracted ex vivo from the ileum and colon of healthy guinea pigs, analyzing their behavior in longitudinal and circular directions. Stress–strain curves were generated for circular samples. Our findings demonstrate the reliability of the proposed method for predicting the activity of compounds and extracts. The clinical efficacy of Otilonium Bromide (OB), tested in our models, highlights the method’s validity. This evidence supports biomechanical characterization as a complementary approach to clinical outcomes, enhancing our understanding of how active ingredients affect gastrointestinal function
X-ray Spectroscopy with a portable Compton Selection chamber: detector design and results.
No full textIn this paper a practical solution to perform spectral analysis of diagnostic X-ray beams is described, based on a miniaturized Compton selection chamber (CSC) using a Si-PIN detector. Results are compared with those obtained with a first prototype of CSC based on nitrogen cooled high purity germanium (HPGe) detector. With this method, the direct X-ray spectrum is Compton scattered inside the CSC, collected by a solid-state detector and reconstructed using a simplified scattering matrix experimentally determined. The results obtained will be compared with a reference standard, represented by direct spectra acquired with an HPGe detector in a laboratory facility, not applicable for on-field measurements
Wireless Endocardial Atrial (and Ventricular) Sensing with no Implanted Power Source: a Proposal
No full textCardiac electrical activity is mainly evaluated by monitoring the electrical biosignals. This requires a long-lasting power supply to make implantable devices cost-effective and efficient. Since the current trend is to implant catheter-free stand-alone electrodes (implantable cardiac monitors), the need for smaller devices is at odds with the need for long-life batteries. To avoid these problems, we propose a passive endocardial sensor able to monitor the movement of the considered chamber based on a permanent magnet shaped for implantation in the internal chamber of the heart (i.e. the right atrium) and an external gauss meter unit to measure sensor-induced magnetic field variations. Since the magnet is permanent, no replacement is needed after the first implant, thereby reducing the risks linked to invasive procedures, and the battery in the external device can be substituted more easily. To test our idea we used a permanent magnet mounted on the tip of a commercial catheter for heart mapping together with a dedicated gauss meter built in our laboratory. The device was tested in vitro and the magnetic field variations were acquired and measured in different conditions of movement and distances. The results demonstrate the feasibility of our approach and open an interesting new scenario where permanent magnets can be used to monitor the mechanical behaviour of the heart
Understanding the basic concepts of CO2 angiography
No full textThe diagnostic quality of carbon dioxide angiography depends both on optimal setting of
radiological aspects (X-ray emission and image post-processing) and on the mechanical behavior
of the injected gas bubbles. The gas behavior differs in large cavities (d>12 mm), medium sized
vessels (d>6 mm), and small diameter vessels (d<6mm): to optimize the result the operator has
to adapt his action to the physical rules governing the phenomenon in the particular situation.
In most cases, it is impossible to fill a vessel completely with gas, and to obtain an adequate
angiogram, the gas volume and injection pressure must be properly selected, patient’s position
must be adjusted and radiological image optimization algorithms, like Digital Subtraction
Angiography (DSA) and stacking, must be applied. In this optimization process, the cultural and
practical intervention of a medical physicist is fundamental. Obtaining a good quality CO2
angiogram is not only a matter of medical operator experience or radiological system performance,
but involves matching a wide knowledge of medical physics to particular pathophysiological
conditions and to unusual measurement tests. Most medical physicists are used to dealing mainly
with radiological problems, and other physical aspects are considered beyond their interest. In CO2
angiography, non-radiological aspects strongly interfere with radiological issues and an optimal
result can only be obtained by tackling the two simultaneously
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
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
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