Very severe aortic valve stenosis: Diagnostic value of computed tomography aortic valve calcium scoring.

Background: (A) Very severe aortic valve stenosis (VSAS; Vmax ≥ 5 ​m/s, MPG ≥60 ​mmHg) is a critical condition with unfavorable clinical outcomes. Guidelines regard VSAS as one criterion for considering valve replacement in asymptomatic patients. (B) Guidelines recommend the use of aortic valve calcium (AVC) scoring as a parameter to differentiate between moderate and severe aortic valve stenosis (SAS).

Can Radiological Renal Artery Parameters Predict Acute Kidney Injury in Infective Endocarditis Surgery?-From Imaging to Outcomes.

Infective endocarditis (IE) poses significant challenges in cardiovascular medicine, often necessitating valvular surgery to manage severe complications. Postoperative acute kidney injury (AKI) is a notable complication affecting patient outcomes. While clinical and procedural factors have been well studied, the role of radiological renal artery parameters in AKI risk remains underexplored.

Past extent of lunar permanently shadowed areas.

As the Moon migrated away from Earth, it experienced a major spin axis reorientation. Permanently shadowed regions (PSRs), which are thought to have trapped ices and are a main focus of lunar exploration, appeared and grew after this (Cassini state) transition and are often younger than their host craters. Here, we calculate the lunar spin axis orientation and the extent of PSRs based on recent advances for the time evolution of the Earth-Moon distance.

Potential Themis Family Asteroid Contribution to the Jupiter-Family Comet Population.

Recent dynamical analyses suggest that some Jupiter family comets (JFCs) may originate in the main asteroid belt instead of the outer solar system. This possibility is particularly interesting given evidence that icy main-belt objects are known to be present in the Themis asteroid family. We report results from dynamical analyses specifically investigating the possibility that icy Themis family members could contribute to the observed population of JFCs.

Non-gravitational acceleration in the trajectory of 1I/2017 U1 ('Oumuamua).

'Oumuamua (1I/2017 U1) is the first known object of interstellar origin to have entered the Solar System on an unbound and hyperbolic trajectory with respect to the Sun. Various physical observations collected during its visit to the Solar System showed that it has an unusually elongated shape and a tumbling rotation state and that the physical properties of its surface resemble those of cometary nuclei, even though it showed no evidence of cometary activity. The motion of all celestial bodies is governed mostly by gravity, but the trajectories of comets can also be affected by non-gravitational forces due to cometary outgassing.

Pitted terrains on (1) Ceres and implications for shallow subsurface volatile distribution.

Prior to the arrival of the Dawn spacecraft at Ceres, the dwarf planet was anticipated to be ice-rich. Searches for morphological features related to ice have been ongoing during Dawn's mission at Ceres. Here we report the identification of pitted terrains associated with fresh Cerean impact craters.

Extensive water ice within Ceres' aqueously altered regolith: Evidence from nuclear spectroscopy.

The surface elemental composition of dwarf planet Ceres constrains its regolith ice content, aqueous alteration processes, and interior evolution. Using nuclear spectroscopy data acquired by NASA's Dawn mission, we determined the concentrations of elemental hydrogen, iron, and potassium on Ceres. The data show that surface materials were processed by the action of water within the interior.

The geomorphology of Ceres.

Analysis of Dawn spacecraft Framing Camera image data allows evaluation of the topography and geomorphology of features on the surface of Ceres. The dwarf planet is dominated by numerous craters, but other features are also common. Linear structures include both those associated with impact craters and those that do not appear to have any correlation to an impact event.

Two-dimensional description of surface-bounded exospheres with application to the migration of water molecules on the Moon.

On the Moon, water molecules and other volatiles are thought to migrate along ballistic trajectories. Here, this migration process is described in terms of a two-dimensional partial differential equation for the surface concentration, based on the probability distribution of thermal ballistic hops. A random-walk model, a corresponding diffusion coefficient, and a continuum description are provided.

Dynamics of ice ages on Mars.

Unlike Earth, where astronomical climate forcing is comparatively small, Mars experiences dramatic changes in incident sunlight that are capable of redistributing ice on a global scale. The geographic extent of the subsurface ice found poleward of approximately +/-60 degrees latitude on both hemispheres of Mars coincides with the areas where ice is stable. However, the tilt of Mars' rotation axis (obliquity) changed considerably in the past several million years.

Theory of ground ice stability in sublimation environments.

Permanently stable ground ice is found beneath a permanently frost free surface on Mars, and similar conditions exist in the Antarctic Dry Valleys. This phenomenon is due to a balance of the vapor pressure of the ice with the atmospheric humidity in the presence of large amplitude temperature oscillations. An exactly solvable model example shows that the fraction of time the atmosphere needs to be saturated to stabilize the ice decreases with temperature amplitude.

Drainage basins and channel incision on Mars.

Measurements acquired by the Mars Orbiter Laser Altimeter on board the Mars Global Surveyor indicate that large drainage systems on Mars have geomorphic characteristics inconsistent with prolonged erosion by surface runoff. We find the topography has not evolved to an expected equilibrium terrain form, even in areas where runoff incision has been previously interpreted. By analogy with terrestrial examples, groundwater sapping may have played an important role in the incision.

Front formation in an active scalar equation.

We study the formation of thermal fronts in an active scalar equation that is similar to the Euler equation. For a particular initial condition, an earlier candidate for finite-time blowup, the front forms in a generalized self-similar way with constant hyperbolicity at the center. The behavior belongs to a class of scenarios for which finite-time blowup is impossible.

Statistics of velocity gradients in two-dimensional Navier-Stokes and ocean turbulence.

Probability density functions and conditional averages of velocity gradients derived from upper ocean observations are compared with results from forced simulations of the two-dimensional Navier-Stokes equations. Ocean data are derived from TOPEX satellite altimeter measurements. The simulations use rapid forcing on large scales, characteristic of surface winds.

Basins of attraction on random topography.

We investigate the consequences of fluid flowing on a continuous surface upon the geometric and statistical distribution of the flow. We find that the ability of a surface to collect water by its mere geometrical shape is proportional to the curvature of the contour line divided by the local slope. Consequently, rivers tend to lie in locations of high curvature and flat slopes.

Energy spectra of steady two-dimensional turbulent flows.

The power spectrum is measured in direct numerical simulations of the two-dimensional Navier-Stokes equation and other two-dimensional flows with white-in-time forcing at large scales. For the Navier-Stokes equation the energy spectrum in the inertial range approaches k(-3) with increasing Reynolds number, with possible logarithmic corrections. A family of two-dimensional flows, including the surface quasigeostrophic equation, allows us to vary the locality of the "enstrophy" transfer, where enstrophy is the mean square of the convected quantity.

Universality of probability distributions among two-dimensional turbulent flows.

We study statistical properties of two-dimensional turbulent flows. Three systems are considered: the Navier-Stokes equation, surface quasigeostrophic flow, and a model equation for thermal convection in the Earth's mantle. Direct numerical simulations are used to determine one-point fluctuation properties.