Abstract: Use in a gas oil fuel composition, which preferably comprises a Fischer-Tropsch derived fuel, of a compound according to formula (I): wherein: R1 to R5 are each independently hydrogen or a C1-10 alkyl group, where such alkyl groups may be the same as or different from one another; X is a nitrogen- or oxygen-containing group, for the purpose of reducing the cetane number of said fuel composition; preparation of such a fuel composition; and operating a fuel consuming system.

Abstract: A trust manager examines each new class before it is allowed to execute by examining a policy file which includes data structures defining security policies of the user system, a certificate repository for storing a plurality of certificates, a certificate being a data record which is digitally signed and which certifies claims relevant to a security evaluation, a code examiner adapted to analyze the portion of code to determine potential resource use of the portion of code and a trust evaluator adapted to evaluate certificate requirements of the portion of code based on policy rules extracted from the policy file and the potential resource use specified by the code examiner. The trust evaluator also determines, from certificates from the certificate repository and a code identifier identifying the portion of code, whether execution of the portion of code is allowed by the policy rules given the potential resource use, the code supplier and applicable certificates.