Domain: Healthcare — Clinical Laboratory Science
Target concept: Blood Sample Centrifugation Technique

Video generation prompt: Take 2 mL of fresh venous blood and inject it into an anticoagulant tube. Gently invert the tube three times to mix thoroughly. Place the tube in a centrifuge, set the speed to 3000 r/min, and centrifuge for 5 minutes. Remove the tube and hold it upright.

Evaluation guide:
(i) Target concept: Density-based separation of whole blood via centrifugation in presence of EDTA anticoagulant.
Minimum mechanism: Blood must remain unclotted (EDTA chelates Ca²⁺), tube must be rotated to generate radial acceleration, and sufficient time/speed must elapse for complete sedimentation of RBCs and formation of discrete interfaces.
(ii)Storyline: [Frame 0–2s] Venous blood enters anticoagulant tube → visible meniscus forms, uniform dark red color. [Frame 2–4s] Tube inverted three times: liquid displaces fully each time, meniscus deforms, no air entrapment. [Frame 4–6s] Tube placed upright into centrifuge rotor; lid closes; rotor begins smooth acceleration. [Frame 6–8s] Continuous rotation visible; no vibration or wobble. [Frame 8–10s] Tube removed, held still and vertical; three-layer stratification appears instantly and remains stable; interfaces are horizontal, sharp, and span full tube diameter. All phases observed from fixed frontal angle with consistent lighting and no occlusion.

Manual:
Experimental Procedure
1. Inject 2 mL fresh venous blood into lavender-top anticoagulant tube.
2. Gently invert tube three times to mix blood and EDTA.
3. Place tube upright in centrifuge rotor.
4. Centrifuge at 3000 r/min for 5 minutes.
5. Remove tube and hold vertically for observation.
Observation of Experimental Phenomena
Three distinct horizontal layers: pale yellow translucent plasma (top), thin whitish-gray buffy coat (middle), deep red opaque RBCs (bottom) — with sharp, continuous interfaces.
Summary of Experimental Principles
Anticoagulant (EDTA) prevents clotting; centrifugal force separates components by density: plasma (lowest density), buffy coat (WBCs/platelets), RBCs (highest density).

Prompt Grounding rubric:
level_1: No anticoagulant tube is shown; no venous blood is visible; no centrifuge appears; there's no inversion motion; no centrifugation takes place; nothing resembling layered blood ever appears.
level_2: At least the tube or the blood is visible, but none of the required actions happen: the tube is never inverted, never placed in a centrifuge, the centrifuge never runs, and no layered result appears.
level_3: The anticoagulant tube, fresh venous blood, and a centrifuge are all shown; at least three of these five steps are clearly depicted: blood is drawn or injected into the tube, the tube is inverted two or more times, the tube is placed into the centrifuge, the centrifuge visibly runs, and the tube is removed with a layered result visible, but two or more of these steps are missing, out of order, or impossible to confirm (for example, the inversion isn't shown, the centrifuge lid is closed with no visible motion, or the final layering is blocked from view).
level_4: All five steps appear in the right order: 2 mL of fresh venous blood goes into the anticoagulant tube; the tube is gently inverted exactly three times with a visible wrist motion and liquid sloshing inside; the tube is placed upright into the centrifuge rotor; the centrifuge spins continuously for the full duration with visible motion; the tube is removed and held upright, showing distinct layers, but one small flaw remains, such as an illegible tube label, background clutter partly hiding a layer boundary, or brief motion blur during inversion that doesn't otherwise break the continuity.
level_5: All five objects show their correct visual details: the anticoagulant tube has a lavender top (EDTA), the blood looks dark red before centrifugation, the centrifuge looks like a standard clinical benchtop model with visible rotor slots; and all five actions happen in the exact order given, fully visible throughout: injecting the blood, three complete inversions, placing the tube in the centrifuge, the centrifuge running, removing the tube, and holding it upright to reveal sharp, continuous layers (plasma, buffy coat, red cells), with no blocked view, no cuts, no lighting changes, no objects swapped out, and no jumps in time.

Scientific and Causal Correctness rubric:
level_1: No plausible layering appears at all; the blood looks the same color throughout with no separation into plasma and red cells; there's no distinguishable buffy coat; the liquid stays uniformly red or uniformly yellow with no visible boundary lines.
level_2: Some layering shows up, but it breaks basic physiology: for example, only two layers appear with no buffy coat at all; the plasma layer looks thicker than the red-cell layer; the red-cell layer looks bright red instead of dark red (suggesting hemolysis); the plasma looks cloudy or murky (suggesting clotting or contamination); or the layers appear instantly with no inversion step ever shown.
level_3: Three layers are visible (plasma on top, a thin buffy coat band in the middle, red cells on the bottom), but at least one doesn't look right: the plasma isn't pale yellow/straw-colored, the buffy coat isn't a thin whitish-gray band clearly distinguishable from the layers above and below it, or the red cells aren't a uniform deep red; or the inversion step shows no visible swirling or surface movement; or there's no visible difference between the tube's contents before and after centrifugation.
level_4: All three layers show the right colors and reasonable proportions: pale yellow, translucent plasma; a narrow, distinct, whitish-gray buffy coat clearly thinner than either layer beside it; deep red, uniform red cells; the inversion step shows visible liquid movement and surface disturbance; centrifugation clearly causes the shift from unlayered to layered, but one small inconsistency remains, such as the buffy coat looking a bit wider than a thin band should, or the plasma having a faint haze without losing its overall transparency.
level_5: Before centrifugation: the tube holds uniformly dark red, unclotted-looking blood with an intact surface and no visible sediment. During inversion: the liquid visibly swirls, no air pockets get trapped, and the surface moves smoothly. After centrifugation: sharp, level, continuous boundaries separate three visually distinct layers: pale yellow, fully clear plasma; a thin, crisp, whitish-gray buffy coat clearly the narrowest of the three layers; and dense, opaque, uniform dark-red red cells, with no blurring or mixing at the boundaries, proportions consistent with a several-minute high-speed spin, and no sign of hemolysis, clotting, or cloudiness.

Spatiotemporal Consistency rubric:
level_1: The tube abruptly vanishes and then reappears somewhere else; the centrifuge's position or orientation changes between shots with no transition; the lighting suddenly switches character mid-clip (for example, daylight in one frame and warm indoor light in the next); a shadow points a different way than it did a moment earlier with no light source moving; the tube spins on its own with no hand touching it.
level_2: There are jarring cuts that skip over key actions (for instance, no hand is ever shown placing the tube into the centrifuge); the inversion is shown only as a jump-cut with no continuous motion; the layered result appears without ever showing the tube being taken out of the centrifuge; the centrifuge starts or stops spinning instantly with no visible speeding up or slowing down.
level_3: Everything happens from one fixed camera angle; nothing in the scene teleports; the lighting stays the same throughout and any shadows stay pointed the same direction; all motion looks physically reasonable (the inversion follows a natural wrist motion, the centrifuge spins up smoothly), but there's one small hiccup, such as a brief freeze-frame during inversion, a slight camera jerk when the tube is removed, or the tube's base being briefly hidden from view while the layers are being shown.
level_4: All motion flows continuously and matches how a person's hand and wrist actually move: the inversion shows smooth wrist rotation with the liquid sloshing in sync; the centrifuge visibly speeds up and slows down rather than snapping to full speed; the hand's grip on the tube stays consistent as it goes in and comes out; there's no lighting flicker, no warped perspective, and no object suddenly changing size, but one small, non-critical thing happens, like slight blur on the spinning centrifuge lid without losing sight of the rotor, or a strand of hair or clothing briefly drifting into frame without covering anything important.
level_5: The camera never moves or changes framing; every object's position, orientation, and lighting stay exactly consistent for the whole clip; the hand's motions look fluid and anatomically natural; the liquid moves the way a real fluid would, with no floating or hanging in place unnaturally; the centrifuge spins steadily with no visible wobble; and once the tube is removed, the layering is visible right away and stays visible without delay, obstruction, or repositioning.