Structural Stability and Renormalization Group for Propagating Fronts

A solution to a given equation is structurally stable if it suffers only an infinitesimal change when the equation (not the solution) is perturbed infinitesimally. We have found that structural stability can be used as a velocity selection principle for propagating fronts. We give examples, using numerical and renormalization group methods.Comment: 14 pages, uiucmac.tex, no figure

Procedural and Mid-Term Outcomes of Coronary Protection During Transcatheter Aortic Valve Replacement in Patients at Risk of Coronary Occlusion: Insight From a Single-Centre Retrospective Analysis

BACKGROUND: Detailed procedural analysis and long-term data is limited for coronary protection (CP) during transcatheter aortic valve replacement (TAVR) for patients with high anatomical risk for coronary occlusion (CO). We aim to assess the procedural and mid-term outcomes of CP during TAVR. METHODS: We retrospectively analyzed patients who underwent TAVR at Henry Ford Hospital, USA from January 2015 to August 2019 and identified those considered at risk of CO and underwent pre-emptive CP with or without subsequent chimney stenting (i.e. coronary stenting with intentional protrusion into the aorta). Procedural features, immediate and mid-term clinical outcomes were reviewed. RESULTS: Twenty-five out of 1166 (2.1%) patients underwent TAVR with CP, including 10 (40%) valve-in-valve procedures. Twenty-eight coronary arteries (Left: n = 11, Right: n = 11; Left + Right: n = 3) were protected. Eleven coronaries (39.3%) were electively chimney -stented due to angiographic evidence of coronary impingement (63.6%), tactile resistance while withdrawing stent (27.3%) and electrocardiogram change (9.1%). Twenty-four patients (24/25, 96%) had successful TAVR without CO. Procedure-related complications included stent-balloon entrapment (n = 1), stent entrapment (n = 1) and occlusive distal stent edge dissection (n = 1). After a mean follow-up of 19.1 months, there was 1 cardiac death but no target vessel re-intervention or myocardial infarction. CONCLUSIONS: Our study found that angiographic evidence of coronary impingement (63.6%) was the most common reason for stent deployment during TAVR with CP. The mid-term clinical outcome of CP with TAVR was favorable

Renormalization Group Theory And Variational Calculations For Propagating Fronts

We study the propagation of uniformly translating fronts into a linearly unstable state, both analytically and numerically. We introduce a perturbative renormalization group (RG) approach to compute the change in the propagation speed when the fronts are perturbed by structural modification of their governing equations. This approach is successful when the fronts are structurally stable, and allows us to select uniquely the (numerical) experimentally observable propagation speed. For convenience and completeness, the structural stability argument is also briefly described. We point out that the solvability condition widely used in studying dynamics of nonequilibrium systems is equivalent to the assumption of physical renormalizability. We also implement a variational principle, due to Hadeler and Rothe, which provides a very good upper bound and, in some cases, even exact results on the propagation speeds, and which identifies the transition from ` linear'- to ` nonlinear-marginal-stability' as parameters in the governing equation are varied.Comment: 34 pages, plain tex with uiucmac.tex. Also available by anonymous ftp to gijoe.mrl.uiuc.edu (128.174.119.153), file /pub/front_RG.tex (or .ps.Z

INITIAL EXPERIENCE WITH LITHOTRIPSY FOR MITRAL BALLOON VALVULOPLASTY

Background: Mitral annular calcification (MAC) causes degeneration of the mitral valve function. Since these patients are poor surgical candidates, options are limited to percutaneous solutions. Use of balloon lithotripsy (BL) to augment mitral balloon valvuloplasty (MBV) is a novel technique for treatment of MAC-related mitral stenosis (MS). Methods: Single-center retrospective review of 35 consecutive MBV for MAC cases at Henry Ford from 3/2013 to 4/2021. Outcome variables are reported as median and interquartile ranges (IQR). Chi-squared and Wilcoxon-signed rank tests were used to compare categorical and continuous variables respectively using 95% confidence intervals for statistical significance. Procedural success was defined as a final mitral valve area ≥1.5 cm2 or ≥50% reduction in gradient. Results: Of 35 MBV cases done for MAC, 5 utilized lithotripsy balloons to augment valvuloplasty results (Table). Mean baseline gradients were similar and right ventricular systolic pressures trended higher for BL cases. Cases utilizing lithotripsy were longer and utilized more fluoroscopy time but the final invasive gradient trended lower (non-BL 7mmHg [4, 9] vs. BL 1 mmHg [0,5] p=0.113), therefore, higher rates of procedural success were seen (non-BL 47% vs. BL 80%, p=0.2). Survival analysis was hampered due to loss of follow-up in the BL group. Conclusion: BL appears to augment immediate valvuloplasty results. Further studies regarding the durable impact of balloon lithotripsy on MBV are warranted

Molecular evolution in Panagrolaimus nematodes: origins of parthenogenesis, hermaphroditism and the Antarctic species P. davidi

10.1186/1471-2148-9-15BMC Evolutionary Biology911

Pearling and Pinching: Propagation of Rayleigh Instabilities

A new category of front propagation problems is proposed in which a spreading instability evolves through a singular configuration before saturating. We examine the nature of this front for the viscous Rayleigh instability of a column of one fluid immersed in another, using the marginal stability criterion to estimate the front velocity, front width, and the selected wavelength in terms of the surface tension and viscosity contrast. Experiments are suggested on systems that may display this phenomenon, including droplets elongated in extensional flows, capillary bridges, liquid crystal tethers, and viscoelastic fluids. The related problem of propagation in Rayleigh-like systems that do not fission is also considered.Comment: Revtex, 7 pages, 4 ps figs, PR

Remote Sensing Experiments Using the Rogue-alpha,beta CubeSats as a Constellation: High Frame Rate Environmental Observations from Agile, Taskable, Infrared and Visible Sensors in Low Earth Orbit

The Aerospace Corporation’s Rogue-alpha,beta program built and launched two 3-Unit CubeSats in 18-months, each equipped with modified commercial infrared camera payloads, visible context cameras, laser communications and precision pointing capabilities. Launched on November 2, 2019, the two spacecraft (Rogue-alpha and beta) were boosted and released from the International Space Station Cygnus NG-12 robotic resupply spacecraft on January 31, 2020 into a circular 460-km, 52° inclined orbit. The primary Rogue IR sensor is a 1.4-micron band, 640x512 pixel, 28° field of view, InGaAs short wavelength infrared (SWIR) camera. It is accompanied by a panchromatic, 10-megapixel, 37° field of view visible context camera. In addition, the narrow- and wide-field-of-view star sensors may also be utilized as nighttime sensors. During the first two years of spaceflight, the Rogue satellites conducted a series of experiments using both spacecraft to conduct cooperative remote sensing observations and to test the capabilities of the 1.4-micron water overtone band. These included: 1) fore-aft pointing using two spacecraft for stereo observations of cloud structure and altitude, 2) horizon-pointed imaging in all directions relative to the spacecraft orbit (fore, aft, port, and starboard) to maximize the imaged field of view, 3) pre-programmed point-and-stare imaging, 4) nadir-pointed operations for vicarious calibration with other satellites. All of these modes of operation are usually conducted in multi-frame collections at 1-20 frames-per-second for dozens to thousands of frames. During the mission we investigated different modes of collecting data, taking advantage of the evolving orbital spacing of the pair of CubeSats. Initial close satellite spacing allowed along-track fore-aft stereo observations of weather formations, as well as pre-programmed tip-and-queue observations, and sequential point-and-stare experiments aimed at collecting minutes of data on targets of interest. Cloud altitude was measured on weather events by simultaneous stereo observations, and by mono observations using the changing view angles during a constant point along track or slewing during a pass. Observations were collected on hurricanes, typhoons, thunderstorms, monsoon storms, and forecasted tornadic weather. Unique observations of severe wildfires were collected, exploring the capability for our 1.4micron band to detect fires during daytime, and to characterize pyrocumulonimbus clouds. Nighttime observations were also made of human lighting, infrared sources, and moonlight-illuminated clouds, including observations utilizing the Rogue satellites’ star sensors for remote sensing tests. These experiments collectively explored the possibilities for dynamically tasked, high-frame-rate, low-earth-orbit sensors to carry out weather and environmental monitoring missions in ways that differ from traditional scanned or push-broom satellite sensor systems. We will present a summary of our tasking ConOps, observations of weather events and fires, and highlight results and techniques for cloud height characterization by our two CubeSat constellation during its first two years on orbit. Our results with two satellites demonstrate possibilities for future missions using cooperative tasking in larger constellations of dynamically tasked sensors in low Earth orbit

Wake response to an ocean-feedback mechanism: Madeira Island case study

This discussion focused on the numerical study of a wake episode. The Weather Research and Forecasting model was used in a downscale mode. The current literature focuses the discussion on the adiabatic dynamics of atmospheric wakes. Changes in mountain height and consequently on its relation to the atmospheric inversion layer should explain the shift in wake regimes: from a 'strong-wake' to a 'weak-wake' scenario. Nevertheless, changes in SST variability can also induce similar regime shifts. Increase in evaporation, contributes to increase convection and thus to an uplift of the stratified atmospheric layer, above the critical height, with subsequent internal gravity wave activity.Comment: Under review proces

The Speed of Fronts of the Reaction Diffusion Equation

We study the speed of propagation of fronts for the scalar reaction-diffusion equation $u_t = u_{xx} + f(u)$\, with $f(0) = f(1) = 0$. We give a new integral variational principle for the speed of the fronts joining the state $u=1$ to $u=0$. No assumptions are made on the reaction term $f(u)$ other than those needed to guarantee the existence of the front. Therefore our results apply to the classical case $f > 0$ in $(0,1)$, to the bistable case and to cases in which $f$ has more than one internal zero in $(0,1)$.Comment: 7 pages Revtex, 1 figure not include