Transient response for interaction of two dynamic bodies

During the launch sequence of any space vehicle complicated boundary interactions occur between the vehicle and the launch stand. At the start of the sequence large forces exist between the two; contact is then broken in a short but finite time which depends on the release mechanism. The resulting vehicle response produces loads which are very high and often form the design case. It is known that the treatment of the launch pad as a second dynamic body is significant for an accurate prediction of launch response. A technique was developed for obtaining loads generated by the launch transient with the effect of pad dynamics included. The method solves uncoupled vehicle and pad equations of motion. The use of uncoupled models allows the simulation of vehicle launch in a single computer run. Modal formulation allows a closed-form solution to be written, eliminating any need for a numerical integration algorithm. When the vehicle is on the pad the uncoupled pad and vehicle equations have to be modified to account for the constraints they impose on each other. This necessitates the use of an iterative procedure to converge to a solution, using Lagrange multipliers to apply the required constraints. As the vehicle lifts off the pad the coupling between the vehicle and the pad is eliminated point by point until the vehicle flies free. Results obtained by this method were shown to be in good agreement with observed loads and other analysis methods. The resulting computer program is general, and was used without modification to solve a variety of contact problems

Decay of geodesic acoustic modes due to the combined action of phase mixing and Landau damping

Geodesic acoustic modes (GAMs) are oscillations of the electric field whose importance in tokamak plasmas is due to their role in the regulation of turbulence. The linear collisionless damping of GAMs is investigated here by means of analytical theory and numerical simulations with the global gyrokinetic particle-in-cell code ORB5. The combined effect of the phase mixing and Landau damping is found to quickly redistribute the GAM energy in phase-space, due to the synergy of the finite orbit width of the passing ions and the cascade in wave number given by the phase mixing. When plasma parameters characteristic of realistic tokamak profiles are considered, the GAM decay time is found to be an order of magnitude lower than the decay due to the Landau damping alone, and in some cases of the same order of magnitude of the characteristic GAM drive time due to the nonlinear interaction with an ITG mode. In particular, the radial mode structure evolution in time is investigated here and reproduced quantitatively by means of a dedicated initial value code and diagnostics.Comment: Submitted to Phys. Plasma

Investigating the Features of the M170 in Congenital Prosopagnosia

Face perception generates specific neural activity as early as 170 ms post-stimulus onset, termed the M170 when measured with Magnetoencephalography (MEG). We examined the M170 in six people with congenital prosopagnosia (CP) and 11 typical controls. Previous research indicates that there are two neural generators for the M170 (one within the right lateral occipital area - rLO and one within the right fusiform gyrus - rFG), and in the current study we explored whether these sources reflect the processing of different types of information. Individuals with CP showed face-selective M170 responses within the rLO and right rFG, which did not differ in magnitude to those of the controls. To examine possible links between neural activity and behavior we correlated the CPs' MEG activity generated within rLO and rFG with their face perception skills. The rLO-M170 correlated with holistic/configural face processing, whereas the rFG-M170 correlated with featural processing. Hence, the results of our study demonstrate that individuals with CP can show an M170 that is within the normal range, and that the M170 in the rLO and rFG are involved in different aspects of face processing

Opportunities for optics in integrated circuits applications

Optics potentially addresses two key problems in electronic chips and systems: interconnects and timing. Short optical pulses (e.g., picoseconds or shorter) offer particularly precise timing. Results are shown for optical and electrical four-phase clocking, with <1 ps rms jitter for the optical case

An Information Theoretic Approach to Characterizing the Attention Shifts in the Fruit Fly During Flight

To successfully navigate the complex visual world, animals must extract relevant information from the deluge of light-carried signals that arrive at their eyes. Early vision filters are passive, energy-saving gates that block out irrelevant signals. The remaining incoming signals are then subject to active filtering by visual attention systems which are energetically expensive, especially for smaller animals, which are subject to similar survival challenges as larger animals. Among visual behaviors performed by insects, flight stabilization demands one of the highest rates of information uptake. Flying insects must quickly respond to flight disturbances to avoid navigation errors and collisions. Active flight is energy-intensive, but the variable environmental and flight conditions make passive filtering unreliable to infer self-motion. Dipterans (flies and mosquitoes) are a prosperous order of insects that owe their success to impressive flying skills. Though many visual adaptations for flight have been well characterized, little research has been dedicated to the active attention processes required for flight stabilization. In this dissertation, I investigated how the visual attention systems of fruit flies work to maximize relevant information uptake during flight. I have focused on three main questions: (1) Do flies shift attention away from regions impacted heavily by motion-blur? (2) Do flies’ attention systems prioritize regions with higher quality images? (3) Does the attention system only filter noisy regions, or does it weigh the regional image quality against other sources of information present? I used a virtual reality flight arena to convince stationary, tethered fruit flies that they were actually flying. I tested whether flies were attentive to visual regions by showing local perturbations and measuring corrective steering responses. I found that fast-flying flies (1) shift their attention to the slower frontal parts of their visual field; (2) shift their attention forward when flying in dim and low contrast environments; (3) weigh other relevant information with image clarity. My findings provide a better understanding of how the energy-limited visual systems of fruit flies can process all the information required to stabilize flight

Words Formed by Radio Call Letters

Call letters are assigned to AM radio stations by the Federal Communications Commission: four letters beginning with W in the eastern US, four letters beginning with K in the western US. (In the early days of radio, three letters were also assigned, and a few radio stations of this kind can still be found.) it is interesting to ask whether or not AM radio station owners have a preference for call letters which form common English words. According to the 1979 Broadcasting Yearbook, an industry source on broadcasting data put out by Broadcasting Publications, Inc. of Washington, D. C., there are 4547 commercial Am stations operating in the US (as of December 1978). Of these, the following 72 stations have call letters which form four-letter words found in boldface type in the Merriam-Webster Pocket Dictionary

Implications of new public management and modernization policies within the national probation service : an interpretative approach

This thesis focuses on the implications of New Public Management and Modernization reform policies in the National Probation Service. In an attempt to understand how National Probation Service employees .make sense of those reforms, actors' organizational context, their organizational identity and roles have been explored. The study takes interpretivist, qualitative approach. It is based on ethnographic data, collected over a one-year period in an English regional probation service (RPA). In the course of the fieldwork, forty. five employees were interviewed. Data were also collected through participant observation, and analysis of formal documents. Empiric,al and theoretical contributions emerge from this thesis. The former relate to control, organizational identity, and role issues in the probation service, while the latter relate to resistance

Zinc transporter 8 and MAP3865c homologous epitopes are recognized at T1D onset in Sardinian children

Our group has recently demonstrated that Mycobacterium avium subspecies paratuberculosis (MAP) infection significantly associates with T1D in Sardinian adult patients. Due to the potential role played by MAP in T1D pathogenesis, it is relevant to better characterize the prevalence of anti-MAP antibodies (Abs) in the Sardinian population, studying newly diagnosed T1D children. Therefore, we investigated the seroreactivity against epitopes derived from the ZnT8 autoantigen involved in children at T1D onset and their homologous sequences of the MAP3865c protein. Moreover, sera from all individuals were tested for the presence of Abs against: the corresponding ZnT8 C-terminal region, the MAP specific protein MptD, the T1D autoantigen GAD65 and the T1D unrelated Acetylcholine Receptor. The novel MAP3865c281–287 epitope emerges here as the major C-terminal epitope recognized. Intriguingly ZnT8186–194 immunodominant peptide was cross-reactive with the homologous sequences MAP3865c133–141, strengthening the hypothesis that MAP could be an environmental trigger of T1D through a molecular mimicry mechanism. All eight epitopes were recognized by circulating Abs in T1D children in comparison to healthy controls, suggesting that these Abs could be biomarkers of T1D. It would be relevant to investigate larger cohorts of children, followed over time, to elucidate whether Ab titers against these MAP/Znt8 epitopes wane after diagnosis

Final Project 3.0: A Student Virtual World Conference on the Future of Collaboration

There is currently little research of any kind on enterprise virtual worlds or using these collaborative tool ecosystems for geographically distributed education in organizational studies. In 2013, a group of multidisciplinary graduate students created and executed a conference in a 3D virtual world as a class project. The topics presented in the conference were crowdsourcing and mobile virtual worlds, but the overall experience resulted in learning well beyond those topics. The project team encountered a significant learning curve over planning and executing in person meetings as well as technical challenges that would threaten the success of the project. This paper describes the end-to-end process taken by the team to plan and execute the conference, and shows the challenges, successes, and the lessons learned that can be applied to future conferences in 3D virtual worlds, which promise incredible potential for improving collaboration across businesses