Investigation of plasma accelerator /cyclotron resonance propulsion system/ Final report

Electron cyclotron resonance plasma accelerators for space propulsion system

Microwave Driven Magnetic Plasma Accelerator Studies (CYCLOPS)

A microwave-driven cyclotron resonance plasma acceleration device was investigated using argon, krypton, xenon, and mercury as propellants. Limited ranges of propellant flow rate, input power, and magnetic field strength were used. Over-all efficiencies (including the 65% efficiency of the input polarizer) less than 10% were obtained for specific impulse values between 500 and 1500 sec. Power transfer efficiencies, however, approached 100% of the input power available in the right-hand component of the incident circularly polarized radiation. Beam diagnostics using Langmuir probes, cold gas mapping, r-f mapping and ion energy analyses were performed in conjunction with an engine operating in a pulsed mode. Measurements of transverse electron energies at the position of cyclotron resonant absorption yielded energy values more than an order of magnitude lower than anticipated. The measured electron energies were, however, consistent with the low values of average ion energy measured by retarding potential techniques. The low values of average ion energy were also consistent with the measured thrust values. It is hypothesized that ionization and radiation limit the electron kinetic energy to low-values thus limiting the energy which is finally transferred to the ion. Thermalization by electron-electron collision was also identified as an additional loss mechanism. The use of light alkali metals, which have relatively few low lying energy levels to excite, with the input power to mass ratio selected so as to limit the electron energies to less than the second ionization potential, is suggested. It is concluded, however, that the over-all efficiency for such propellants would be less than 40 per cent

Évaluation des nouveaux critères de classification pour le syndrome PFAPA

La fièvre est un motif de consultation fréquent en âge pédiatrique. La plupart du temps, elle est associée à d’autres symptômes ou signes cliniques évoquant une infection virale ou bactérienne. Ces expériences permettent aux enfants de se constituer un système immunitaire efficace contre les pathogènes rencontrés par le biais de formation d’anticorps et de lymphocytes-mémoire. Ce même principe est exploité lors des vaccinations où le pathogène injecté est mort ou atténué, ne provoquant donc pas la maladie. Dans ce cas, la fièvre est le reflet de l’activation du système immunitaire. Lorsque les infections sont plus fréquentes, plus sévères et dues à des pathogènes dits atypiques, une immunodéficience doit être recherchée par exemple par dosage d’anticorps post-vaccinaux. Dans les situations où les épisodes de fièvre sont répétitifs et difficilement attribuables à un état infectieux, l’origine inflammatoire est évoquée. Le diagnostic différentiel s’étend alors aux fièvres récurrentes d’origine inflammatoire, dont le syndrome PFAPA qui est statistiquement le plus fréquent dans la population pédiatrique (1). Le syndrome PFAPA a été décrit pour la première fois en 1987 par Marshall et al. Il établit un set de critères qui est à l’origine de l’acronyme (en anglais) : Periodic Fever, cervical Adenitis, Pharyngitis, Aphtous stomatitis. Quelques années plus tard, se basant sur l’observation d’une centaine de patients, Thomas et al. proposent de compléter les critères, d’où s’en suivent ceux de Marshall modifiés (2) : • Épisodes fébriles récidivant à des intervalles réguliers avec début précoce (âge < 5ans) • Symptômes en l’absence d’infection des voies aériennes supérieures avec au minimum un signe clinique parmi stomatite aphteuse, lymphadénite cervicale et pharyngite • Exclusion de la neutropénie cyclique • Intervalles entre les épisodes complètement asymptomatiques • Croissance et développement normaux Ces critères ont été utilisés mais jamais validés pour le diagnostic de PFAPA durant ces trois dernières décennies. D’ailleurs, une enquête récente montre une pauvre adhérence des médecins dans l’application de ceux-ci dans leur pratique quotidienne. Parmi les raisons évoquées, une faible spécificité est mise en évidence car ces critères sont souvent remplis par les fièvres récurrentes d’origine monogénique comme la fièvre méditerranéenne familiale (FMF), le TNF receptor-associated periodic syndrome (TRAPS), le cryopirin-associated periodic syndrome (CAPS) ou encore la déficience en mévalonate kinase (MKD) (3). Le diagnostic de PFAPA est donc souvent posé après exclusion des autres origines de fièvre récurrente et présente vraisemblablement un retard diagnostic non négligeable. 4 En 2017, une large étude a été menée par Vanoni et al. dans le but d’établir un nouveau set de critères, basé sur un consensus d’experts. Une approche multiphasique selon la technique Delphi a été utilisée et proposée à échelle internationale à plus d’une centaine d’experts dans le domaine. La première phase demandait de lister toute variable considérée pertinente pour le diagnostic de PFAPA. Les variables les plus citées ont ensuite été proposées lors de la seconde phase où les experts étaient amenés à en choisir dix, puis à les classer selon un ordre d’importance en leur donnant un score de 1 à 10. En tenant compte de la fréquence de citation et de la moyenne du score, les meilleures variables ont été retenues. Chacune d’entre elles a ensuite été soumise à une évaluation de son lien à la maladie par régression logistique univariée sur un collectif de patients issus du registre Eurofever. Ainsi, plusieurs sets de classification ont pu être générés et le meilleur a été discuté lors d’une conférence de consensus international (3). Les nouveaux critères de classification pour le syndrome PFAPA sont les suivants : • Durée des épisodes fébriles 3-6 jours • Périodicité • Adénopathies cervicales • Pharyngite • Absence de diarrhée • Absence d’arthrite • Absence de douleur thoracique • Absence d’éruption cutanée Le syndrome PFAPA est caractérisé par la satisfaction de sept critères sur huit au minimum. Ce travail est une étude rétrospective visant à évaluer les nouveaux critères de classification du syndrome PFAPA en les appliquant à la cohorte européenne JIRcohorte

Biliary complications after liver transplantation: A computed tomography and magnetic resonance imaging pictorial review

Biliary complications are the most common complications after liver transplantation. Computed tomography (CT) and magnetic resonance imaging (MRI) are cornerstones for timely diagnosis of biliary complications after liver transplantation. The diagnosis of these complications by CT and MRI requires expertise, mainly with respect to identifying subtle early signs to avoid missed or incorrect diagnoses. For example, biliary strictures may be misdiagnosed on MRI due to size mismatch of the common ducts of the donor and recipient, postoperative edema, pneumobilia, or susceptibility artifacts caused by surgical clips. Proper and prompt diagnosis of biliary complications after transplantation allows the timely initiation of appropriate management. The aim of this pictorial review is to illustrate various CT and MRI findings related to biliary complications after liver transplantation, based on time of presentation after surgery and frequency of occurrence

Technology Directions for the 21st Century, volume 1

For several decades, semiconductor device density and performance have been doubling about every 18 months (Moore's Law). With present photolithography techniques, this rate can continue for only about another 10 years. Continued improvement will need to rely on newer technologies. Transition from the current micron range for transistor size to the nanometer range will permit Moore's Law to operate well beyond 10 years. The technologies that will enable this extension include: single-electron transistors; quantum well devices; spin transistors; and nanotechnology and molecular engineering. Continuation of Moore's Law will rely on huge capital investments for manufacture as well as on new technologies. Much will depend on the fortunes of Intel, the premier chip manufacturer, which, in turn, depend on the development of mass-market applications and volume sales for chips of higher and higher density. The technology drivers are seen by different forecasters to include video/multimedia applications, digital signal processing, and business automation. Moore's Law will affect NASA in the areas of communications and space technology by reducing size and power requirements for data processing and data fusion functions to be performed onboard spacecraft. In addition, NASA will have the opportunity to be a pioneering contributor to nanotechnology research without incurring huge expenses

Intraductal papillary mucinous neoplasms of the pancreas: Uncommon imaging presentation, evolution and comparison of guidelines

Pancreatic cystic lesions are often asymptomatic, incidentally detected and include a range of entities with varying degrees of concern for malignancy. Among these, intraductal papillary mucinous neoplasms (IPMN) are considered premalignant pancreatic lesions, with a broad pathological spectrum ranging from lesions without dysplasia, which can be managed conservatively, to malignant lesions that require surgical resection. The increasing use of CT and MRI has led to increased recognition of this entity incidentally, with branch-duct IPMN representing the most common subtype and the most challenging lesions in terms of patient management. The main imaging modality involved in diagnosis and surveillance of IPMN is MRI. Radiologists play an important role in the management of patients with IPMN, including lesion detection, characterization, follow-up and prognostication, allowing early MRI identification of features that are concerning for malignancy. The main aim of this pictorial review is to illustrate MRI features of IPMN and to discuss risk stratification scores based on different guidelines, with a main focus on branch-duct IPMN. The secondary aims include the presentation of common and uncommon imaging evolution of BD-IPMN as well as the discussion on current controversies on the appropriate management of IPMN

Surgical complications after pancreatic transplantation: A computed tomography imaging pictorial review

pancreatic transplantation should start with the evaluation of the arterial Y-graft, the venous anastomosis and the duodenojejunostomy. With regard to complications, CT allows for the identification of vascular complications, such as thrombosis or stenosis of blood vessels supplying the graft, the detection of pancreatic fluid collections, including pseudocysts, abscesses, or leaks, the assessment of bowel complications (anastomotic leaks, ileus or obstruction), and the identification of bleeding. The aim of this pictorial review is to illustrate CT findings of surgical-related complications after pancreatic transplantation. The knowledge of surgical techniques is of key importance to understand postoperative anatomic changes and imaging evaluation. Therefore, we first provide a short summary of the main techniques of pancreatic transplantation. Then, we provide a practical imaging approach to pancreatic transplantation and its complications providing tips and tricks for the prompt imaging diagnosis on CT.Pancreatic transplantation is considered by the American Diabetes Association and the European Association for the Study of Diabetes an acceptable surgical procedure in patients with type 1 diabetes also undergoing kidney transplantation in pre-final or end-stage renal disease if no contraindications are present. Pancreatic transplantation, however, is a complex surgical procedure and may lead to a range of postoperative complications that can significantly impact graft function and patient outcomes. Postoperative computed tomography (CT) is often adopted to evaluate perfusion of the transplanted pancreas, identify complications and as a guide for interventional radiology procedures. CT assessment afte

Mandibular reconstruction with bridging customized plate after ablative surgery for ONJ: A multi‐centric case series

Purpose: Computer‐aided methods for mandibular reconstruction have improved both functional and morphological results in patients who underwent segmental mandibular resection. The purpose of this study is to evaluate the overlaying of virtual planning in terms of measures of the Computer Assisted Design/Computer Assisted Manufacturing CAD/CAM plate for mandibular reconstruction in patients who are ineligible for the insertion of reconstructing the titanium plate supported by fibular free flap, due to their poor health status, or in the presence of specific contraindications to autologous bone flap harvest. Materials and methods: The retrospective study performed analyzed the results of nine patients. The patients were treated at the Maxillofacial Surgery Unit of Policlinico S. Orsola of Bologna, Italy, and Policlinico San Marco, Catania, Italy, from April 2016 to June 2021. Superimposition between planning and post operative Computed Tomography CT scan was performed to assess the accuracy. Results: All reconstructive procedures were carried out successfully. No microsurgery‐related complications occurred. In two cases, we had plate misplacement, and in one case, plate exposure that led to plate removal. The average accuracy of the series assessed after CT superimposition, as previously described, was 0.95 mm. Conclusions: Considering that microvascular bone transfer is a high‐risk procedure in BRONJ patients, we can conclude that the positioning of a customized bridging mandibular prosthesis (CBMP), whether or not it is associated with a microvascular soft tissue transfer, is a safe technique in terms of surgical outcome and feasibility

Technology Directions for the 21st Century

The Office of Space Communications (OSC) is tasked by NASA to conduct a planning process to meet NASA's science mission and other communications and data processing requirements. A set of technology trend studies was undertaken by Science Applications International Corporation (SAIC) for OSC to identify quantitative data that can be used to predict performance of electronic equipment in the future to assist in the planning process. Only commercially available, off-the-shelf technology was included. For each technology area considered, the current state of the technology is discussed, future applications that could benefit from use of the technology are identified, and likely future developments of the technology are described. The impact of each technology area on NASA operations is presented together with a discussion of the feasibility and risk associated with its development. An approximate timeline is given for the next 15 to 25 years to indicate the anticipated evolution of capabilities within each of the technology areas considered. This volume contains four chapters: one each on technology trends for database systems, computer software, neural and fuzzy systems, and artificial intelligence. The principal study results are summarized at the beginning of each chapter