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Fast and simultaneous forward and reverse blood grouping has long remained elusive. Forward blood grouping detects antigens on red blood cells, whereas reverse grouping identifies specific antibodies present in plasma. We developed a paper-based assay using immobilized antibodies and bromocresol green dye for rapid and reliable blood grouping, where dye-assisted color changes corresponding to distinct blood components provide a visual readout. ABO antigens and five major Rhesus antigens could be detected within 30 s, and simultaneous forward and reverse ABO blood grouping using small volumes (100 μl) of whole blood was achieved within 2 min through on-chip plasma separation without centrifugation. A machine-learning method was developed to classify the spectral plots corresponding to dye-based color changes, which enabled reproducible automatic grouping. Using optimized operating parameters, the dye-assisted paper assay exhibited comparable accuracy and reproducibility to the classical gel-card assays in grouping 3550 human blood samples. When translated to the assembly line and low-cost manufacturing, the proposed approach may be developed into a cost-effective and robust universal blood-grouping platform.

Several studies have attempted to determine the lower limit of atmospheric oxygen under which combustion can occur; however, none have been conducted within a fully controlled and realistic atmospheric environment. We performed experimental burns (using pine wood, moss, matches, paper, and a candle) at 20°C in O 2 concentrations ranging from 9 to 21% and at ambient and high CO 2 (2000 parts per million) in a controlled environment room, which was equipped with a thermal imaging system and full atmospheric, temperature, and humidity control. Our data reveal that the lower O 2 limit for combustion should be increased from 12 to 15%. These results, coupled with a record of Mesozoic paleowildfires, are incompatible with the prediction of prolonged intervals of low atmospheric O 2 levels (10 to 12%) in the Mesozoic.

A new polyethylene paper may be marked on a hard surface with an ordinary oversize ball-point pen or dull pencil point. Where the paper is marked, a raised-line imprint appears on the same side of the paper as that used for writing. This imprint may be both felt and seen. Newly blinded and partially sighted persons are able to read ordinary Arabic letters and numerals after a few trials.