Scaffold with gradually changing porosity


  • Scaffold with gradually changing porosity creates better mechanical conditions for bone healing than with uniform structure.(In a medical context, a scaffold is a 3D porous structure made from biomaterials that acts as a temporary support).


  • The Functionally Graded (FG) scaffold is a scaffold where the porosity, stiffness, or composition varies smoothly across its volume to better match how natural bone behaves.


  • Scaffolds with increasing porosity (more holes) toward the metal plate transferred stress better, The improvements were strongest for titanium Ti-6Al-4V material. The more gradual the porosity change, the better the mechanical distribution inside the scaffold.


  • The authors used Finite Element Analysis (FEA).


  • To control porosity, they create a third order polynomial relation between strut thickness (S) (thickness of the bars of the lattice) and porosity(n).

  • This relationship was used to design scaffolds with precise porosity gradients.


  • They measured octahedral shear strain (ε_oct) : this measure combines tension, compression, and shear effects into one value.

  • Uniform scaffolds with 50% porosity exhibited relatively low octahedral shear strain values, particularly adjacent to the fixation plate, indicating regions of stress shielding while Functionally Graded scaffolds show progressively higher strain levels and more extensive strain distribution within the scaffold.


Icy moon’s ice shell and subsurface ocean circulation

On an icy moon like Europa or Enceladus, the ice shell above the water may vary in thickness. The ice is thicker at the equator and thinner at the poles, this slope produces pressure and temperature differences at the ice–ocean boundary.

These differences create density (buoyancy) gradients in the upper ocean, which drives currents and baroclinic eddies (swirling motions) in the ocean.


In subsurface oceans (like on Europa or Enceladus), vertical mixing stirs heat between deep and shallow layers. This energizes baroclinic eddies, swirling flows caused by sloping density layers. Together, they create a circulation loop that transports heat from polar regions (thin ice) toward the equator (thick ice). But when topography (the shape of the seafloor or ice base) dominates, it can either suppress or enhance this heat flow depending on how dense layers are arranged.


ocean flow is modeled using the Boussinesq approximation model.


The differential rotation velocity of an ice shell or core depends on tidal, gravitational, and rotational forces. differential rotation velocity is very low — meaning the ice shell and the underlying ocean rotate almost together, with only tiny relative motion.


Source: https://arxiv.org/html/2510.25988v1


How Oort Cloud comets stay active even billions of kilometers from the Sun


  • Smaller comets appear CO₂-rich while large ones are CO-dominated.


  • Small comets lose all of their CO ice early in their lives, while they are orbiting near Neptune. From the model, a comet smaller than 4 km in diameter completely loses its CO.


  • Larger comets don’t lose all their CO, they become CO-poor only in their upper layers, CO ice survives deep below the surface around 500 m during the some million years near Neptune. 


  • For comets that have CO buried deep inside, when they move outward into the cold Oort Cloud their surface cools, and CO gas from the interior travels outward and refreezes near the surface. When they return toward the Sun, this refrozen CO layer becomes the main source of activity.


  • CO sublimation (turning directly from solid to gas) begins around 50 AU for a 10 km comet and even 150 AU for a 50 km comet. CO₂ activity starts closer to the Sun around 13 AU. Crystallization of amorphous water ice (which releases trapped gases) begins around 7 AU, causing strong outgassing bursts.


  • They calculated Solar heating (via boundary conditions at the surface), Internal heat transport, Sublimation and condensation, Crystallization of amorphous ice, radioactive energy release.


  • The second term on the left-hand side represents the transfer of heat by conduction and advection by flowing volatiles, if present, and the terms on the right-hand side include the rates of absorption/release of latent heat by sublimation/condensation in pores and radioactive energy release.


Engulfment of planet to Kepler 56


  • Kepler-56 is a red giant star, its outer layer spins faster and at a different orientation than its core.


  • Kepler-56’s fast spin cannot be explained just by the tidal pull of its two known planets. Two known planets orbiting Kepler-56 are too far away and too light to transfer enough angular momentum (AM) to make the star’s outer layer spin so fast.


  • Unusually fast rotation of the envelope and misaligned its core and envelope spin of star Kepler-56 might be due to the star once swallowing a close-orbiting hot Jupiter giant planet. It's called planetary engulfment.


  • Tidal torque depends on star radius and mass, orbital period, planet mass, Tidal quality factor Q.

  • Equation of Angular momentum gained by the star when it engulfs

  • Researchers used-

  • MESA code (Modules for Experiments in Stellar Astrophysics) to track how the star’s structure and rotation evolve,

  • Tidal interaction equations to estimate angular momentum transfer from known planets,

  • Engulfment simulation to calculate spin-up from swallowing a planet,

  • Obliquity damping to Study how the spin tilt changes with time.


Source: https://arxiv.org/html/2510.25680v1


Scattering coefficient (μs) method for blood clotting

Researchers compared their new scattering coefficient (μs) method with the traditional optical density (OD) method for clotting blood.

The Optical Density method measures the concentration of substances in the plasma by quantifying how much light it absorbs. 


They used Beer–Lambert law. 

μs is the scattering coefficient

P0 = transmitted power through buffer (no plasma scatterers)

P(t) transmitted optical power through the plasma

d  thickness of glass


When a graph of Scattering coefficient vs time is drawn, a temporal timing shift occurs compared to Optical Density measurements. It shows a function of plasma concentration.


As blood plasma changes from a liquid to a gel (clot), the scattering coefficient μₛ increases steadily  means the structure inside the plasma (fibrin fibers and networks) becomes more complex and scatters light more strongly.


Here μₛ method provides extra information such as specific times (t50%, t90%), time difference (Δt), and the clot formation rate (CFR), and structure of clot formation.


Source: https://iopscience.iop.org/article/10.1088/2057-1976/ae103c


Subscribe to: Comments (Atom)