Diffusion Time / Fick's Law Estimator (biological scale) implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t7-116

Effect

Computation or source lookup only

Input and validation requirements

The zero-diffusion-coefficient input produces an undefined division by zero, and the specification does not state an input-rejection rule. Negative D also yields a mathematically defined but physically invalid negative diffusion time.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "distance": 10,
    "distance_unit": "µm",
    "preset": "O2 in water at 25 °C"
  },
  "expected_outputs": {
    "diffusion_time_s": 0.025,
    "diffusion_time_ms": 25
  },
  "reference_data": {
    "preset": "O2 in water at 25 °C",
    "D_m2_per_s": 2e-9,
    "source_convention": "widely tabulated standard value; dilute aqueous oxygen diffusion coefficient at approximately 25 °C"
  },
  "working": "Convert distance: x = 10 µm × 10^-6 m/µm = 1.0×10^-5 m. Square it: x² = (1.0×10^-5)² = 1.0×10^-10 m². Denominator: 2D = 2×(2.0×10^-9) = 4.0×10^-9 m²/s. Time: t = (1.0×10^-10)/(4.0×10^-9) s = 2.5×10^-2 s = 0.025 s. Convert: 0.025×1000 = 25 ms."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche7/tranche7-results.json