Source: https://guthlabs.ai/docs/instruments/cell-bacterial-doubling-time-calculator/implementation/

instrument implementation / implementation-contract

# Cell/Bacterial Doubling Time Calculator implementation

A source-bound implementation contract for Cell/Bacterial Doubling Time Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## 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**: t4-122

**Effect**: Computation or source lookup only

## Input and validation requirements

The formulas encounter undefined results for nonpositive or zero starting counts and at exactly zero net growth. A calculator that accepts N0=0 or emits a finite doubling time when N=N0 would fail this adversarial set.

## 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": {
    "N0": 100,
    "N": 800,
    "elapsed_time": 6,
    "time_unit": "hours"
  },
  "expected_outputs": {
    "doubling_time": 2,
    "growth_rate_mu": 0.34657359028,
    "doublings": 3
  },
  "working": "N/N0 = 800/100 = 8. ln(8) = 2.07944154168 and ln(2) = 0.69314718056. td = 6 × 0.69314718056 / 2.07944154168 = 2 hours. μ = 2.07944154168 / 6 = 0.34657359028 h^-1. Doublings = ln(8)/ln(2) = 2.07944154168/0.69314718056 = 3."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/cell-bacterial-doubling-time-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/cell-bacterial-doubling-time-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/cell-bacterial-doubling-time-calculator/qualification/>)

## Sources and evidence

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

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`