Domain: Healthcare — Clinical Laboratory Science
Target concept: Centrifugation and Examination of Cerebrospinal Fluid Samples

Video generation prompt: Take 2 mL of cerebrospinal fluid from a healthy adult and add it to a centrifuge tube. Set the centrifuge speed to 1500 r/min and centrifuge for 5 minutes. Remove the tube and observe the clarity of the supernatant and the sediment at the bottom of the tube.

Evaluation guide:
(i) Target concept: Low-speed centrifugation of a CSF sample from a healthy adult separates it into a clear, colorless supernatant with no cellular pellet visible to the naked eye, because normal CSF contains far too few cells (roughly 0-5 white cells per microliter, essentially no red cells) to form a macroscopic pellet at 1500 r/min for 5 minutes.
Minimum mechanism: CSF must look clear and colorless before spinning; the tube must undergo an actual spin cycle (lid closed, rotor turning) for the stated time/speed; after the spin, the supernatant must still look clear and colorless and the bottom of the tube should show no discernible pellet; any grossly visible pellet, clot, or cloudiness would indicate a pathological sample, not a healthy one.
(ii) Storyline: [Frame 0–2] Hand holds a syringe/pipette drawing clear fluid, then dispenses it into a centrifuge tube (meniscus forms, no splashing). [Frame 3–4] Tube is placed upright into the centrifuge, lid closes, rotor begins turning smoothly. [Frame 5–6] Centrifuge stops, lid opens, hand retrieves the tube and holds it upright against a plain background. [Frame 7–9] Static hold: camera centered on the tube's full height: the liquid looks clear and colorless from top to bottom, with no distinct layer or pellet visible at the base. Perspective is fixed frontal view; no occlusion of the tube bottom; lighting is even so no glare is mistaken for sediment.

Manual:
Experimental Procedure
1. Draw 2 mL clear, colorless cerebrospinal fluid from a healthy adult.
2. Transfer it into a sterile, transparent, round-bottom centrifuge tube.
3. Place tube in centrifuge, close lid, set to 1500 r/min, run for 5 min.
4. Remove tube, hold upright, and observe.
Observation of Experimental Phenomena
Supernatant is clear and colorless; no cellular pellet is visible at the bottom of the tube — a healthy adult's CSF contains too few cells to form a pellet the eye can detect after this brief 1500 r/min spin.
Summary of Experimental Principles
Centrifugation separates any cells or debris present from the fluid portion of CSF. In a healthy adult, the normal cell count (roughly 0-5 white cells/microliter, no red cells) is too low to produce a pellet visible without a microscope, so the defining sign of a healthy sample is a clear, colorless supernatant with no macroscopically visible sediment. A grossly visible pellet, clot, or cloudy supernatant instead points to a pathological process such as infection, hemorrhage, or a traumatic collection.

Prompt Grounding rubric:
level_1: No CSF sample, no centrifuge tube, and no centrifuge machine are shown, or the scene is dominated by unrelated objects (a blood-collection tube, a urine cup, a microscope slide) instead; none of the steps in the prompt (adding CSF, centrifuging, observing) are recognizable.
level_2: Only one of the three required objects appears (the tube, or the CSF liquid, or the centrifuge) with no clear action carried out: no liquid transfer into the tube, no centrifuge cycle shown running, and no post-spin handling of the tube for inspection.
level_3: The CSF sample, the centrifuge tube, and the centrifuge machine are all shown, and at least two of the three actions appear in the right order: (a) CSF is transferred into the tube, (b) the tube is placed in the centrifuge which is shown running (lid closed, motion visible), (c) the tube is taken out and held up for viewing; at most one of these three steps is missing or out of order.
level_4: All three objects are present and all three actions (filling the tube with CSF, running the centrifuge with the tube inside, and removing the tube to hold it for direct viewing) appear in the correct order with nothing swapped (no serum standing in for CSF, no conical tube standing in for a round-bottom centrifuge tube) and nothing skipped or repeated.
level_5: Everything in score 4 holds, and additionally: the CSF looks clear and colorless, the tube looks sterile and transparent, and the centrifuge looks like a real clinical bench-top unit; the three actions run back-to-back with no gaps, repeats, or jump cuts; it is visibly the same physical tube before and after the spin (same size, same cap); when the tube is held up for observation at the end, the camera has an unobstructed view of the tube's full length from top to bottom.

Scientific and Causal Correctness rubric:
level_1: The liquid in the tube looks turbid, yellow, pink, or cloudy rather than clear and colorless, or a large, obvious clump fills much of the tube; either finding is wrong for a healthy adult's CSF.
level_2: The supernatant is clear, but something else is off: a chunky, floating, or loosely suspended sediment is shown (rather than either no visible sediment or, at most, an extremely faint haze), or the liquid shows a color tint of any kind.
level_3: The supernatant looks clear and colorless from top to bottom, and the bottom of the tube shows no obvious clump, chunk, or discrete pellet that a bystander would point to and call the sediment, consistent with the very low cell count of a healthy adult's CSF.
level_4: Everything in score 3 holds, and additionally: there is no visible cloudiness, streaking, or floating debris anywhere in the column of liquid; the tube looks the same clear, colorless liquid at the end of the video as a healthy CSF sample would, with nothing at the bottom resembling a compact pellet.
level_5: Everything in score 4 holds, and additionally: the tube, held up to the light at the end, shows a uniformly clear, colorless liquid with no discernible sediment line, haze, or particulate anywhere, matching what a real healthy-adult CSF sample looks like after a brief low-speed spin.

Spatiotemporal Consistency rubric:
level_1: The tube appears to jump into the centrifuge without ever being placed there; the room lighting suddenly swings from bright to dark between two frames with no explanation; the tube visibly cracks or breaks apart mid-sequence; the tube looks different (different scratches, different label) before and after the spin, as if it were swapped for another tube.
level_2: The tube rotates far more than expected between shots with no hand ever touching it; the centrifuge lid opens or closes with no visible mechanical motion; the hand holding the tube at the end enters from the opposite side compared to the start, as if mirrored; the lighting flickers noticeably a few times, even though nothing else breaks.
level_3: The tube, the centrifuge, and the hand all keep believable size, shape, and position across the clip; the tube stays upright while spinning, without visibly tipping, shaking, or blurring from vibration; the lighting looks the same in the early and late parts of the clip, with no sudden bright or dark jump; the camera doesn't cut from an overhead angle straight to eye-level (or the reverse) without any transition; the tube's motion into and out of the centrifuge follows a natural approach by hand rather than snapping into place.
level_4: Everything in score 3 holds, and additionally: the tube's size, label position, and fill level stay consistent across every step; the centrifuge's spin looks smooth and continuous rather than jerky or stuttering; the tube's label faces the same way throughout, so its orientation doesn't silently change; the lighting and shadows on the tube look steady rather than drifting brighter or dimmer over the course of the clip; the background doesn't shift oddly relative to the tube between shots.
level_5: Everything in score 4 holds, and additionally: any visible surface detail on the tube (scratches, the meniscus curve, the label) looks the same in every frame where it's visible; the centrifuge speeds up and slows down in a believable way, without snapping instantly to full speed or stopping dead; the hand's grip on the tube looks natural and consistent across every time it appears; there is no visible shakiness, warping, or depth mismatch between the tube and its surroundings.