The 1 st Cumulant or moment (a 1) is used to calculate the intensity weighted Z average mean size and the 2 nd moment (a 2) is used to calculate a parameter defined as the polydispersity index (PdI). It is important to note here, that the Cumulants analysis algorithm does not yield a distribution â it gives only the intensity weighted Z average and the polydispersity index.
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In English, A* to C grades increased 3.7 percentage points to 65.4%. In maths, those achieving a C grade or better increased from 62.4% to 63.3%. There were improvements in A* to C grades for physics, chemistry and biology. But fewer pupils taking the double science GCSE achieved good grades.The numbers of exam entries for separate sciences-physics, chemistry and biology-had all fallen. Exam boards say that this year's results have been influenced by the changing age ranges of those taking GCSEs.here were improvements in A* to C grades for physics, chemistry and biology. But fewer pupils taking the double science GCSE achieved good grades. The numbers of exam entries for separate sciences-physics, chemistry and biology-had all fallen.