Some equations in Appendix B need to be corrected. Equation ͑B1͒ should be replaced by rot ϭ8 s ab 2 e r . ͑B1͒Equations ͑B2͒ and ͑B5͒ are missing a factor r 2 on the right-hand side. Equation ͑B4͒ should be replaced byWith these changes, all further results apply.
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