Inside, the warehouse was a big open hall, divided into metal cages piled high with different grades of insulating material.

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The seats are covered in yet softer and more exclusive Valcona leather (color-matching two different grades of leather is itself something of a technical feat).

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They claim pupils sitting the exams in one part of the year got different grades for the same marks obtained by those in another part of the year.

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Late and dramatic changes to GCSE grade boundaries, which left many pupils with the same mark on different grades, are the subject of a legal challenge by heads, local authorities, pupils and teachers.

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In a report on the Foreign and Commonwealth Office's performance last year, the committee said promotions to different grades in the Diplomatic Service were judged on the basis of general competencies, including leadership and management abilities.

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"We did not find strong evidence that the effect of work stress on heart disease is worse for those in lower grades - the effect of stress was pretty much the same across different grades, " said Dr Chandola.

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But it appears that relatively few students have used this to find different places with their higher grades.

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With good grades you can choose different, better paths.

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When a stone is identified as a borderline case between two grades, the system uses an optimisation technique, called a genetic algorithm, to explore the different ways in which the stone could be cut to maximise its value.

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