Metadata and Buckets in the Smart Object, Dumb Archive (SODA) Model

We present the Smart Object, Dumb Archive (SODA) model for digital libraries (DLs), and discuss the role of metadata in SODA. The premise of the SODA model is to push down many of the functionalities generally associated with archives into the data objects themselves. Thus the data objects become smarter , and the archives dumber . In the SODA model, archives become primarily set managers, and the objects themselves negotiate and handle presentation, enforce terms and conditions, and perform data content management. Buckets are our implementation of smart objects, and da is our reference implementation for dumb archives. We also present our approach to metadata translation for buckets

Deterministic mechanical model of T-killer cell polarization reproduces the wandering of aim between simultaneously engaged targets

T-killer cells of the immune system eliminate virus-infected and tumorous cells through direct cell-cell interactions. Reorientation of the killing apparatus inside the T cell to the T-cell interface with the target cell ensures specificity of the immune response. The killing apparatus can also oscillate next to the cell-cell interface. When two target cells are engaged by the T cell simultaneously, the killing apparatus can oscillate between the two interface areas. This oscillation is one of the most striking examples of cell movements that give the microscopist an unmechanistic impression of the cell's fidgety indecision. We have constructed a three-dimensional, numerical biomechanical model of the molecular-motor-driven microtubule cytoskeleton that positions the killing apparatus. The model demonstrates that the cortical pulling mechanism is indeed capable of orienting the killing apparatus into the functional position under a range of conditions. The model also predicts experimentally testable limitations of this commonly hypothesized mechanism of T-cell polarization. After the reorientation, the numerical solution exhibits complex, multidirectional, multiperiodic, and sustained oscillations in the absence of any external guidance or stochasticity. These computational results demonstrate that the strikingly animate wandering of aim in T-killer cells has a purely mechanical and deterministic explanation. © 2009 Kim, Maly

Pseudogap effects induced by resonant pair scattering

We demonstrate how resonant pair scattering of correlated electrons above T_c can give rise to pseudogap behavior. This resonance in the scattering T-matrix appears for superconducting interactions of intermediate strength, within the framework of a simple fermionic model. It is associated with a splitting of the single peak in the spectral function into a pair of peaks separated by an energy gap. Our physical picture is contrasted with that derived from other T-matrix schemes, with superconducting fluctuation effects, and with preformed pair (boson-fermion) models. Implications for photoemission and tunneling experiments in the cuprates are discussed.Comment: REVTeX3.0; 4 pages, 4 EPS figures (included

Vibration Isolation for Launch of a Space Station Orbital Replacement Unit

Delivery of Orbital Replacement Units (ORUs) to on-orbit destinations such a the International Space Station (ISS) and the Hubble Space Telescope is an important component of the space program. ORUs are integrated on orbit with space assets to maintain and upgrade functionality. For ORUs comprised of sensitive equipment, the dynamic launch environment drives design and testing requirements, and high frequency random vibrations are generally the cause for failure. Vibration isolation can mitigate the structure-borne vibration environment during launch, and hardware has been developed that can provide a reduced environment for current and future launch environments. Random vibration testing of one ORU to equivalent Space Shuttle launch levels revealed that its qualification and acceptance requirements were exceeded. An isolation system was designed to mitigate the structure-borne launch vibration environment. To protect this ORU, the random vibration levels at 50 Hz must be attenuated by a factor of two and those at higher frequencies even more. Design load factors for Shuttle launch are high, so a metallic load path is needed to maintain strength margins. Isolation system design was performed using a finite element model of the ORU on its carrier with representative disturbance inputs. Iterations on the modelled to an optimized design based on flight proven SoftRide MultiFlex isolators. Component testing has been performed on prototype isolators to validate analytical predictions

Experimental Metrics for Identifying Origins of Combustion Variability during Spark-Assisted Compression Ignition

Spark-assisted compression ignition, SACI, can be used to control the combustion phasing of compression-ignition gasoline engines. However, implementation of this technique can be confounded by cyclic variability. The purpose of this paper is to define experimental metrics that describe the SACI process and to demonstrate the use of these metrics for identifying the source(s) of cyclic variability during the SACI process. This study focused on a light load condition (7 mg/cycle, 200 kPa i.m.e.p.), where spray-guided direct fuel injection with spark ignition and an exhaust-rebreathing strategy was employed to achieve flame propagation, which led to compression ignition. This study employed a combination of measurements including pressure-based heat-release analysis, spark-discharge voltage/current measurements, and cycle-resolved combustion imaging. Based on these measurements, four distinct combustion periods were identified; namely, the spark discharge, the early kernel growth (EKG), flame propagation, and the compression ignition periods. Metrics were defined to characterize each period and used to identify the contribution of each period to the cyclic variability of the main heat release. For the light load condition studied here, the EKG period had the largest effect on the crank angle (CA) position of 50 per cent mass burned, CA50. The spark-discharge event may affect CA50 indirectly through its influence on EKG. However, this could not be definitively assessed here since the camera was incapable of recording both the spark-discharge event and the flame images during cycles of the same tests.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86770/1/Sick18.pd

Magnetic Field Effects in the Pseudogap Phase: A Competing Energy Gap Scenario for Precursor Superconductivity

We study the sensitivity of T_c and T^* to low fields, H, within the pseudogap state using a BCS-based approach extended to arbitrary coupling. We find that T^* and T_c, which are of the same superconducting origin, have very different H dependences. This is due to the pseudogap, \Delta_{pg}, which is present at the latter, but not former temperature. Our results for the coherence length \xi fit well with existing experiments.We predict that very near the insulator \xi will rapidly increase.Comment: 4 pages, 4 figures, RevTe

Coulomb Correlations and Pseudo-gap Effects in a Pre-formed Pair Model for the Cuprates

We extend previous work on pre-formed pair models of superconductivity to incorporate Coulomb correlation effects. For neutral systems, these models have provided a useful scheme which interpolates between BCS and Bose Einstein condensation with increasing coupling and thereby describes some aspects of pseudo-gap phenomena. However, charge fluctuations (via the plasmon, $\omega_p$) significantly modify the collective modes and therefore the interpolation behavior. We discuss the resulting behavior of the pseudo-gap and thermodynamic quantities such as $T_c$, $\chi$ and $C_v$ as a function of $\omega_p$.Comment: 4 pages RevTeX, 3 ps figures included (Submitted to Physical Review B August 27, 1996