Deuterated water found on saturn moons

D/H (Deuterium to Hydrogen atoms)ratio of ice on saturn moons is 1.5 times than Vienna Standard Mean Ocean Water . 4.14 μm O-D absorption line was detected.

The reflectance spectrum radiative transfer model was used here. It tells us what planetary or moon surface is made of and how light interacts with it.


Basic radiative transfer equation:

I λ intensity of light at wavelength 

s  path through the material

αλ absorption coefficient

jλ emission or scattering source term


In planetary science, the Hapke model is widely used for bidirectional reflectance of a particulate surface.

B(g) = opposition effect function (brightening at small phase angles)

P(g) = particle phase function (angular scattering)

H(μ) = multiple scattering function



Source: AI chat GPT and https://arxiv.org/html/2510.14859v1#S5


Use of Piecewise linear transformation for filter in telescope

Each instrument has its own set of filters (wavelength bands) that measure light in slightly different ways. For example:JWST, Roman, the Euclid, the Hubble Telescope.

The libraries researchers used include:

  • CALSPEC (HST calibration stars)
  • IRTF and X-Shooter Spectral Libraries
  • E-IRTF (extended version for cooler stars)

Each library covers different temperature, metallicity (chemical composition), and luminosity classes — together they give a wide coverage of the HR diagram.


Synthetic magnitude is calculated as

F(λ): star’s flux (how much light it emits per wavelength).

T(λ): filter transmission function, show how transparent the filter is at each wavelength.


Continuous Piecewise linear transformation function is calculated as

It is used for fitting or converting magnitudes between different near-infrared (NIR) filters — such as those from JWST, Roman, and Euclid telescopes

Researchers-

  • Collected star spectra from multiple libraries
  • Simulated how each star looks through each telescope’s filters
  • Built mathematical relationships color–magnitude equations
  • Used regression to fit coefficients and calculated error
  • Checked across star types (HR diagram)
  • Applied to TRGB method (red giants branch) measures distance


https://iopscience.iop.org/article/10.3847/1538-3881/adfddb#ajadfddbs1





Structure change of glass when pressurize

The study was done on the structure change of glass at intermediate distances, 5–20 angstroms, it was pressurized upto 100 GPa.

At lower pressures, atoms around a central Si tend to show tetrahedral symmetry (SiO₄).

As pressure increases, the atomic structure in silica glass goes through two stages of reorganization.


Researchers plotted ξ (correlation length) versus pressure graph, it shows two maxima.

During the first maxima Si is bonded with 5 Oxygen. Second maximum (at higher pressure) Si–O units shift to 6-coordination octahedral and cubic.


Different parameters calculated here are:

  • pair correlation function- It shows the typical distances between Si–O, O–O, and Si–Si atoms, and how these change when the glass is squeezed.

  • Coordination number-how many O bond with Si

  • Correlation Length- the distance over which the positions of atoms or material's properties are "correlated" with each other. Beyond this length, the atomic arrangement of the material becomes statistically independent and appears random. 

  • Four-Point Correlation Function

  • Spherical Harmonic coefficient-It tells how strong symmetry shapes are like tetrahedral or cubic.


https://arxiv.org/html/2510.13178v1




RuS2 low thermal conductivity

 

Microstructural disorder is the main reason RuS₂ has low thermal conductivity.

However, internal effects like stronger phonon–phonon Umklapp scattering also play a smaller role. 


When two phonons collide, their combined momentum goes outside the crystal’s Brillouin zone (the allowed region for vibrations). Umklapp scattering reverses the direction of phonon motion, it acts like friction for heat. Every time this happens, part of the heat flow is canceled or redirected, so less heat is carried forward.


At low temperatures, phonons don’t have enough energy to reach outside the Brillouin zone — so Umklapp processes are rare so heat moves easily. At high temperatures, phonons have more energy → more collisions → more Umklapp scattering → thermal conductivity drops. 


The Debye–Callaway model shows that grain boundary and defect scattering in RuS₂ are about ten times stronger than in FeS₂. Equation of Debye–Callaway model of thermal conductivity

θD​ = Debye temperature 

v is the average phonon sound velocity, ω is the phonon frequency, τ is the relaxation time.

A describes the intensity of scattering by point defects,

B is proportional to the intensity of phonon-phonon Umklapp scattering 

D is the characteristic distance between diffusive boundary scattering events

https://iopscience.iop.org/article/10.1088/1361-648X/ae0b21


Coherent Absorption and Image


In experiments, researchers used a conductor–dielectric–conductor (CDC) Fabry-Pérot cavity. 


Fabry–Pérot cavity is basically a sandwich: a layer of dielectric (non-conducting material) between two reflective (or semi-reflective) surfaces. They use silicon nitride (SiN) as the dielectric layer, and thin metal bilayers (Cr/Au) as the conductive layers.


They shine coherent light from both sides (i.e. two laser beams with a controllable phase difference) of CDC material. The structure reveals hidden color information via how much it absorbs light depending on the relative phase.


You can store information (like images, patterns, or codes) in a thin film. The information is invisible under normal light but can be decoded using coherent, phase-controlled illumination. 


Adb: Total absorption when two coherent beams are shining on the structure from opposite sides

Asb: Absorption with single-beam illumination

d: Thickness of the dielectric layer

k=2​π​n/λ, λ the wavelength in vacuum

cosϕ → interference due to the phase difference between the two beams.


https://arxiv.org/html/2510.13637v1


Speckle-based X-ray method for kidney stone


When the X-rays pass through a sample (like a kidney stone), the speckle pattern changes depending on the stone’s internal structure. By carefully measuring how the speckle pattern shifts or blurs, scientists calculate how much scattering happened. 

The rectangular grid mask and Fokker–Planck method were identified as the most effective combination for reliable kidney stone classification. The method successfully separated kidney stones into three groups - ammonium urate, calcium-based, and cystine/struvite stones.


It is Non-invasive method- means that the method does not enter or harm the body- there’s no surgery, no needles, and no instruments placed inside.


(Fokker–Planck method describes how a probability distribution changes over time. It is a partial differential equation.) 


Source: https://iopscience.iop.org/article/10.1088/1361-6560/ae09ed




Subscribe to: Comments (Atom)