Tunable coupling to a mechanical oscillator circuit using a coherent feedback network

We demonstrate a fully cryogenic microwave feedback network composed of modular superconducting devices connected by transmission lines and designed to control a mechanical oscillator coupled to one of the devices. The network features an electromechanical device and a tunable controller that coherently receives, processes and feeds back continuous microwave signals that modify the dynamics and readout of the mechanical state. While previous electromechanical systems represent some compromise between efficient control and efficient readout of the mechanical state, as set by the electromagnetic decay rate, the tunable controller produces a closed-loop network that can be dynamically and continuously tuned between both extremes much faster than the mechanical response time. We demonstrate that the microwave decay rate may be modulated by at least a factor of 10 at a rate greater than $10^4$ times the mechanical response rate. The system is easy to build and suggests that some useful functions may arise most naturally at the network-level of modular, quantum electromagnetic devices.Comment: 11 pages, 6 figures, final published versio

Novel instrumented frame for standing exercising of users with complete spinal cord injuries

This paper describes a Functional Electrical Stimulation (FES) standing system for rehabilitation of bone mineral density (BMD) in people with Spinal Cord Injury (SCI). BMD recovery offers an increased quality of life for people with SCI by reducing their risk of fractures. The standing system developed comprises an instrumented frame equipped with force plates and load cells, a motion capture system, and a purpose built 16-channel FES unit. This system can simultaneously record and process a wide range of biomechanical data to produce muscle stimulation which enables users with SCI to safely stand and exercise. An exergame provides visual feedback to the user to assist with upper-body posture control during exercising. To validate the system an alternate weight-shift exercise was used; 3 participants with complete SCI exercised in the system for 1 hour twice-weekly for 6 months. We observed ground reaction forces over 70% of the full body-weight distributed to the supporting leg at each exercising cycle. Exercise performance improved for each participant by an increase of 13.88 percentage points of body-weight in the loading of the supporting leg during the six-month period. Importantly, the observed ground reaction forces are of higher magnitude than other studies which reported positive effects on BMD. This novel instrumentation aims to investigate weight bearing standing therapies aimed at determining the biomechanics of lower limb joint force actions and postural kinematics

Polynomial Identities, Indices, and Duality for the N=1 Superconformal Model SM(2,4\nu)

We prove polynomial identities for the N=1 superconformal model SM(2,4\nu) which generalize and extend the known Fermi/Bose character identities. Our proof uses the q-trinomial coefficients of Andrews and Baxter on the bosonic side and a recently introduced very general method of producing recursion relations for q-series on the fermionic side. We use these polynomials to demonstrate a dual relation under q \rightarrow q^{-1} between SM(2,4\nu) and M(2\nu-1,4\nu). We also introduce a generalization of the Witten index which is expressible in terms of the Rogers false theta functions.Comment: 41 pages, harvmac, no figures; new identities, proofs and comments added; misprints eliminate

Outcomes of acute intraoperative surgical conversion during endovascular aortic aneurysm repair

PurposeOutcomes and predictors of acute surgical conversion during endovascular aortic aneurysm repair (EVAR) were examined using the American College of Surgeons-National Safety and Quality Improvement Project (ACS-NSQIP) Database (2005 to 2008).MethodsAcute intraoperative surgical conversions occurring during elective EVAR were identified using Current Procedural Terminology codes. Nonemergent EVAR and primary open surgical repairs of infrarenal aneurysms were examined for comparison. Perioperative morbidity was categorized as wound, pulmonary, venous thromboembolic, genitourinary, cardiovascular, operative, and septic. Mortality, overall morbidity, and length of stay (LOS) were examined.ResultsWe identified 72 acute conversions, 2414 open repairs, and 6332 EVAR without acute conversion. Demographics and comorbidities were generally similar among operative groups. Mean operative time was 274 minutes for acute conversion vs 226 minutes for primary open repair and 162 minutes for EVAR (conversion vs EVAR and open repair vs EVAR P < .0001 for each; conversion vs open repair P = .0014; analysis on rank operative time). Blood transfusion was required in 69% of acute conversions (mean volume, 6.0 units) vs 73% of open repairs (mean volume, 3.3 units) and 12% of EVARs (mean volume, 2.6 units; P < .0001 for each pair-wise comparison; analysis on rank number of units among those transfused). Major morbidity was 28% for acute conversions, 28% for open repairs, and 12% for EVARs. Mortality was 4.2% for acute conversions, 3.2% for open repairs, and 1.3% for EVARs. Median (quartile 1, quartile 3) LOS was 7 (5, 9) days for acute conversion and open repair, and 2 (1, 3) days for EVAR. Morbidity and mortality were significantly higher for acute conversion and open repair vs EVAR. The OR (95% confidence interval) for morbidity was 2.9 (1.7-4.8) after conversion and 2.8 (2.5-3.2) after open repair (P < .0001 for both) and for mortality was 3.4 (1.0-10.9; P = .0437) for conversion and 2.5 (1.9-3.5; P < .0001) for open repair. Morbidity and mortality were similar between acute conversion and open repair. A similar pattern among repair groups was demonstrated for LOS, with similar LOS for acute conversions and open repair, which were significantly longer than those observed for EVAR. No significant demographic or medical risk factor predictors of acute conversion during EVAR were identified.ConclusionAcute surgical conversion was a rare complication affecting 1.1% of EVAR cases, with no broadly identifiable at-risk population. When conversion did occur, morbidity and mortality rates paralleled those observed for elective open repair

Stippling by Example

In this work, we focus on stippling as an artistic style and discuss our technique for capturing and reproducing stipple features unique to an individual artist. We employ a texture synthesis algorithm based on the gray-level co-occurrence matrix (GLCM) of a texture field. This algorithm uses a texture similarity metric to generate stipple textures that are perceptually similar to input samples, allowing us to better capture and reproduce stipple distributions. First, we extract example stipple textures representing various tones in order to create an approximate tone map used by the artist. Second, we extract the stipple marks and distributions from the extracted example textures, generating both a lookup table of stipple marks and a texture representing the stipple distribution. Third, we use the distribution of stipples to synthesize similar distributions with slight variations using a numerical measure of the error between the synthesized texture and the example texture as the basis for replication. Finally, we apply the synthesized stipple distribution to a 2D grayscale image and place stipple marks onto the distribution, thereby creating a stippled image that is statistically similar to images created by the example artist

The effect of functional electrical stimulation-assisted posture-shifting in bone mineral density: case series-pilot study

Study design A training intervention study using standing dynamic load-shifting Functional Electrical Stimulation (FES) in a group of individuals with complete spinal cord injury (SCI) T2 to T10. Objectives Investigate the effect of FES-assisted dynamic load-shifting exercises on bone mineral density (BMD). Setting University Lab within the Biomedical Engineering Methods Twelve participants with ASIA A SCI were recruited for this study. Three participants completed side-to-side load-shifting FES-assisted exercises for 29 ± 5 weeks, 2× per week for 1 h, and FES knee extension exercises on alternate days 3× per week for 1 h. Volumetric Bone Mineral density (vBMD) at the distal femur and tibia were assessed using peripheral quantitative computed tomography (pQCT) before and after the intervention study. Results Participants with acute and subacute SCI showed an absolute increase of f trabecular vBMD (vBMDTRAB) in the proximal (mean of 26.9%) and distal tibia (mean of 22.35%). Loss of vBMDTRAB in the distal femur was observed. Conclusion Improvements in vBMDTRAB in the distal tibia were found in acute and subacute SCI participants, and in the proximal tibia of acute participants, when subjected to anti-gravity FES-assisted load-bearing exercises for 29 ± 5 weeks. No vBMD improvement in distal femur or tibial shaft were observed in any of the participants as was expected. However, improvements of vBMD in the proximal and distal tibia were observed in two participants. This study provides evidence of an improvement of vBMDTRAB, when combining high-intensity exercises with lower intensity exercises 5× per week for 1 h

The Influence of Molecular Adsorption on Elongating Gold Nanowires

Using molecular dynamics simulations, we study the impact of physisorbing adsorbates on the structural and mechanical evolution of gold nanowires (AuNWs) undergoing elongation. We used various adsorbate models in our simulations, with each model giving rise to a different surface coverage and mobility of the adsorbed phase. We find that the local structure and mobility of the adsorbed phase remains relatively uniform across all segments of an elongating AuNW, except for the thinning region of the wire where the high mobility of Au atoms disrupts the monolayer structure, giving rise to higher solvent mobility. We analyzed the AuNW trajectories by measuring the ductile elongation of the wires and detecting the presence of characteristic structural motifs that appeared during elongation. Our findings indicate that adsorbates facilitate the formation of high-energy structural motifs and lead to significantly higher ductile elongations. In particular, our simulations result in a large number of monatomic chains and helical structures possessing mechanical stability in excess of what we observe in vacuum. Conversely, we find that a molecular species that interacts weakly (i.e., does not adsorb) with AuNWs worsens the mechanical stability of monatomic chains.Comment: To appear in Journal of Physical Chemistry