Guar gum, a plant colloid, costs less than agar and is better suited for growing thermophilic bacteria, but is also more difficult to handle, being more viscous and less transparent. The bacterial polysaccharide xanthan is cheaper as well but forms weaker jellies that, as with carrageenan, might result in puncturing its surface. Other colloids, like alginate (from brown seaweed) and gellan gum (from a bacterium), don’t set solely based on temperature and require additives for gelation. These additives might interfere with microbial growth and make the preparation of those jellies less handy than agar plates.
“我们需要的是立足于实际又胸怀长远目标的实干，而不需要不甘寂寞、好高骛远的空想；我们需要的是一步一个脚印的实干精神，而不需要新官上任只烧三把火希图侥幸成功的投机心理；我们需要的是锲而不舍的韧劲，而不需要‘三天打鱼，两天晒网’的散漫。”
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Under certain circumstances, it’s possible to modify ordered dithering so that it can better handle colour information. This requires that we use a palette that is regularly distributed in colour space. A regular palette is composed of all possible combinations of red, green and blue tristimulus values, where each colour component is partitioned into a number of equally spaced levels. For example, 6 levels of red, green and blue totals 6³ = 216 unique colours, equivalent to the common web-safe palette.
"I believe we've had a problem here," said Swigert. Lovell had to repeat the message to a stunned Mission Control: "Houston, we've had a problem."