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Search Results: 1 - 10 of 32503 matches for " John Stang "
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Microwave Breast Imaging System Prototype with Integrated Numerical Characterization
Mark Haynes,John Stang,Mahta Moghaddam
International Journal of Biomedical Imaging , 2012, DOI: 10.1155/2012/706365
Abstract: The increasing number of experimental microwave breast imaging systems and the need to properly model them have motivated our development of an integrated numerical characterization technique. We use Ansoft HFSS and a formalism we developed previously to numerically characterize an S-parameter- based breast imaging system and link it to an inverse scattering algorithm. We show successful reconstructions of simple test objects using synthetic and experimental data. We demonstrate the sensitivity of image reconstructions to knowledge of the background dielectric properties and show the limits of the current model. 1. Introduction A number of experimental systems for microwave breast imaging have been developed in recent years. These systems test full-wave inverse scattering algorithms [1–4] as well as synthetic aperture beam focusing techniques [5]. While imaging algorithms abound in the literature, techniques to properly model, characterize, and calibrate these systems have lagged behind algorithm development. Investigators have started to identify characterization as a major task, which must be addressed in order to fully evaluate the efficacy of microwave imaging for breast cancer detection. Part of this evaluation involves separating modeling errors from intrinsic algorithm artifacts in the final images. Thus, there is a need for accurate models of experimental systems, as well as methods that efficiently incorporate these models into the imaging algorithms. The task of characterizing a microwave breast imaging system for inverse scattering, as compared to a free-space system, is complicated by several factors. Specifically, the antennas are not isolated in the background media but exist as part of the surrounding structure. Also, compact arrangements of many antennas create a cavity-like imaging geometry, and the transmitter incident fields include all background multiple scattering. Finally, the antennas and object are in each others near-fields, so object-cavity scattering should be modeled. In trying to characterize breast imaging systems, investigators have turned to full numerical simulation. The antenna cavity in [6] was modeled using Ansoft HFSS and only used for antenna design and sensitivity analysis. In [7], dipole sources of an inverse scattering experiment were modeled with HFSS and calibration constants used to scale the antenna incident fields. HFSS has also been used to obtain antenna incident fields in a near-field and open, antenna setup [8]; however, ad hoc methods have been used to calibrate the scattered field S-parameter data for
1st H ndel School of Modern Epidemiology in Halle, October 3-6, 2005 with Prof. Kenneth J. Rothman
Stang, Andreas
GMS Medizinische Informatik, Biometrie und Epidemiologie , 2005,
Abstract: The H ndel School of Modern Epidemiology is dedicated to the education of scientists and students who have a particular interest in modern epidemiologic methods. The school is named after the famous Georg Friederich H ndel who was born in Halle (Saale) in 1685. The H ndel School will be held once per year in October. This year's opening school was given by Prof. Kenneth J. Rothman from Boston University. The course covered several methodological topics that attracted a wide range of scientists and students from seven European countries. The next year's H ndel School lecturer will be Prof. Albert Hofman, Erasmus University, Rotterdam, who will cover modern methods of clinical epidemiology.
Fluctuating exciton localisation in giant pi-conjugated spoked-wheel macrocycles
Vikas Aggarwal,Alexander Thiessen,Alissa Idelson,Daniel Kalle,Dominik Wuersch,Thomas Stang,Florian Steiner,Stefan-S. Jester,Jan Vogelsang,Sigurd Hoeger,John M. Lupton
Physics , 2015,
Abstract: Conjugated polymers offer potential for many diverse applications but we still lack a fundamental microscopic understanding of their electronic structure. Elementary photoexcitations - excitons - span only a few nanometres of a molecule, which itself can extend over microns, and how their behaviour is affected by molecular dimensions is not fully understood. For example, where is the exciton formed within a conjugated segment, is it always situated on the same repeat units? Here, we introduce structurally-rigid molecular spoked wheels, 6 nanometres in diameter, as a model of extended pi-conjugation. Single-molecule fluorescence reveals random exciton localisation, leading to temporally-varying emission polarisation. Initially, this random localisation arises after every photon absorption event because of temperature independent spontaneous symmetry breaking. These fast fluctuations are slowed to millisecond timescales following prolonged illumination. Intramolecular heterogeneity is revealed in cryogenic spectroscopy by jumps in transition energy, however, emission polarisation can also switch without a spectral jump occurring, implying long-range homogeneity in local dielectric environment.
Quantifying human vulnerability in rural areas: case study of Tutova Hills (Eastern Romania)
I. C. Stang,A. Grozavu
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2012, DOI: 10.5194/nhess-12-1987-2012
Abstract: This paper aims to assess the vulnerability at regional level, the model and the proposed indicators being explicitly intended for an essentially rural region, in this case–Tutova Hills (Eastern Romania). Five categories of variables were taken into account to define the vulnerability components: rural habitat, demographic features, agriculture, environmental quality and emergency situations. For each one, five variables were analyzed and ranked based on the level of determination or subordination. In order to ensure the flexibility of the model and to avoid the criteria duplication in assessing vulnerability, only a single indicator of each category was retained and included in analysis: total number of inhabitants, dependency ratio, weight of arable land on slope categories, weight of land under forestry and road accessibility of villages. The selected indicators were mathematically processed in order to maximize their relevance and to unitary express the results in the spread 0–1. Also, values of each indicator were grouped into four classes, corresponding to the level of vulnerability: low, medium, high and very high. A general index was obtained through the integration of vulnerability factors in an equation based on the geometric mean. Spatial analysis was based on features of the MicroImages TNTmips 7.3. software, which allow the vulnerability mapping. This approach argues and states that vulnerability assessment through indicator-based methods can be made only according to the level and scale of analysis and related to natural or human conditions of a region.
Interactions between teaching assistants and students boost engagement in physics labs
Jared B. Stang,Ido Roll
Physics , 2013, DOI: 10.1103/PhysRevSTPER.10.020117
Abstract: Through in-class observations of teaching assistants (TAs) and students in the lab sections of a large introductory physics course, we study which TA behaviors can be used to predict student engagement and, in turn, how this engagement relates to learning. For the TAs, we record data to determine how they adhere to and deliver the lesson plan and how they interact with students during the lab. For the students, we use observations to record the level of student engagement and pre- and post-tests of lab skills to measure learning. We find that the frequency of TA-student interactions, especially those initiated by the TAs, is a positive and significant predictor of student engagement. Interestingly, the length of interactions is not significantly correlated with student engagement. In addition, we find that student engagement was a better predictor of post-test performance than pre-test scores. These results shed light on the manner in which students learn how to conduct inquiry and suggest that, by proactively engaging students, TAs may have a positive effect on student engagement, and therefore learning, in the lab.
Burn Injuries in Elderly—A Retrospective Analysis of a Ten Year Period  [PDF]
Frank Siemers, Eirini Liodaki, Karl L. Mauss, Felix H. Stang, Tobias von Wild, Peter Mailaender
Modern Plastic Surgery (MPS) , 2012, DOI: 10.4236/mps.2012.22004
Abstract: Objective: Geriatric patients represent a separate group in the treatment of burn injury regarding pathogenesis, pathophysiology and therapeutic procedure. Methods: From 2000 to 2010 on our burn unit 53 patients aged over 60 years were treated. The mean age of the 27 women and 26 men was 76 years (60 - 102 years), with an average of 33.2% of total burn surface area. 25 patients (47.2%) had severe inhalation injury, 77.4% of the patients suffered full thickness burn injuries. Mean ABSI Score was 12. Relevant additional diseases were coronary heart disease, heart insufficiency, hypertension, COPD, adiposity and chronic alcoholism. Results: 22 patients were treated by early operative intervention (day 0 - 4), 13 of these patients survived further process. In 17 cases first operative procedure could take place only at a later date, 14 patients deceased before operation. 26 patients developed pneumonia. The total morbidity amounted to 26 of 53 patients (49%). A total of 19 injured with a burn index over 80 survived. 9 of them had an index of more than 100. Usual indices as the “Zellweger Index” and the ABSI-Score are not adequate to determine the prognosis of thermal injuries in the elderly. Conclusion: The treatment of elderly with burn trauma is affected by many factors. Compared to younger patients the increased incidence of an inhalation injury is decisive for the prognosis of older patients. The frequency of pre-existing diseases is clearly largely than with younger burn injured patients. These prognostically relevant parameters were not sufficiently considered by established score systems.
Biocompatibility of Different Nerve Tubes
Felix Stang,Gerburg Keilhoff,Hisham Fansa
Materials , 2009, DOI: 10.3390/ma2041480
Abstract: Bridging nerve gaps with suitable grafts is a major clinical problem. The autologous nerve graft is considered to be the gold standard, providing the best functional results; however, donor site morbidity is still a major disadvantage. Various attempts have been made to overcome the problems of autologous nerve grafts with artificial nerve tubes, which are “ready-to-use” in almost every situation. A wide range of materials have been used in animal models but only few have been applied to date clinically, where biocompatibility is an inevitable prerequisite. This review gives an idea about artificial nerve tubes with special focus on their biocompatibility in animals and humans.
New contraceptive eligibility checklists for provision of combined oral contraceptives and depot-medroxyprogesterone acetate in community-based programmes
Stang,Amanda; Schwingl,Pamela; Rivera,Roberto;
Bulletin of the World Health Organization , 2000, DOI: 10.1590/S0042-96862000000800011
Abstract: community-based services (cbs) have long used checklists to determine eligibility for contraceptive method use, in particular for combined oral contraceptives (cocs) and the 3-month injectable contraceptive depot-medroxyprogesterone acetate (dmpa). as safety information changes, however, checklists can quickly become outdated. inconsistent checklists and eligibility criteria often cause uneven access to contraceptives. in 1996, who produced updated eligibility criteria for the use of all contraceptive methods. based on these criteria, new checklists for cocs and dmpa were developed. this article describes the new checklists and their development. several rounds of expert review produced checklists that were correct, comprehensible and consistent with the eligibility requirements. nevertheless, field-testing of the checklists revealed that approximately half (48%) of the respondents felt that one or more questions still needed greater comprehensibility. these findings indicated the need for a checklist guide.in march 2000, who convened a meeting of experts to review the medical eligibility criteria for contraceptive use. the article reflects also the resulting updated checklist.
Paired teaching for faculty professional development in teaching
Jared B. Stang,Linda E. Strubbe
Physics , 2015,
Abstract: Paired (or co-)teaching is an arrangement in which two faculty are collaboratively responsible for all aspects of teaching a course. By pairing an instructor experienced in research-based instructional strategies (RBIS) with an instructor with little or no experience in RBIS, paired teaching can be used to promote the adoption of RBIS. Using data from post-course interviews with the novice instructors of four such arrangements, we seek to understand the factors that make for effective professional development in teaching via paired teaching. Learning about teaching for the novice instructors was found to be mediated both by the approach of the novice instructor to the paired teaching and the previous teaching experience of the novice instructor. Additionally, the structure of the pair-taught course and the sequence of teaching assignments for the novice instructor both play roles in lowering the barrier to novice instructors adopting RBIS.
Pr vention und Gesundheitsf rderung im Medizinstudium: Querschnittstudie zu Pr ferenzen, Haltungen und Vorkenntnissen von Studierenden [Prevention and health promotion in undergraduate medical education: Preferences, attitudes and previous knowledge of medical students - a cross-sectional study]
Klement, Andreas,Bretschneider, Kristin,Lautenschl?ger, Christine,Stang, Andreas
GMS Zeitschrift für Medizinische Ausbildung , 2011, DOI: 10.3205/zma000729
Abstract: [english] Objective: The interdisciplinary topic "prevention and health promotion" (Q10) was introduced into the medical training in Germany by the new medical licensing regulations in 2004. For the conception of an effective curriculum, it is helpful to know student preferences concerning teaching-formats, attitudes and self-estimated previous knowledge. Little is known concerning student perception of “prevention and health promotion” in Germany. Thus, this explorative cross-sectional study aims to provide a first step for closing this gap.Methods: Medical students (n=220) in the fifth academic year were asked to fill in a standardized questionnaire prior to the Q10 curriculum. Questions focused on preferences for teaching and testing formats and self-estimated previous knowledge as well as on rating the importance of prevention topics and health risks. The questions were multiple choice, five-point Likert scales and open-ended questions. Results: A total of 94 students filled questionnaires (42% response rate). Prevention and health promotion was rated as “important” or “very important” for their “own medical professionalism” by 68% of students. Ratings showed preferences for self-directed teaching and learning strategies, including case-based learning, and 78% wished for predominantly oral examinations. The self-estimated knowledge about prevention and health promotion is rated as “rather poor”. The most favored training aim was “decision making within the physician-patient-relationship”. Regarding medical health consultation, students frequently estimate “lifestyle factors” and “psychological disease” as being "very important". Conclusion: Students’ self-estimated poor previous knowledge of prevention and health promotion creates special challenges for curriculum development. High ratings of relevance assigned to prevention-related topics point to a motivational potential which should be utilized through suitable selection of teaching and testing formats to achieve effective and practice-relevant instructional content. [german] Einleitung: Der interdisziplin re Querschnittsbereich Pr vention und Gesundheitsf rderung“(Q10) wurde durch die neue rztliche Approbationsordnung 2004 in die medizinische Ausbildung eingeführt. Für eine effektive Unterrichtskonzeption sind Bestands- und Bedarfsanalysen der Zielgruppe erforderlich. Bisher ist jedoch zu pr ventionsbezogenen studentischen Pr ferenzen für Unterrichtsformate, Haltungen und selbst eingesch tzten Vorkenntnissen im deutschen Sprachraum wenig bekannt. Unsere explorierende Querschnitts-Erhebung biete
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