[ by Larry Goldfarb ] JPMorgan Chase continues to grow and upgrade its securities unit even in the face of enormous regulatory scrutiny over the multibillion-dollar trading losses by its Chief Investment Office.  The bank announced in an internal email that it had named Joseph Walker as Senior Vice Chairman of its investment banking unit. Mr. Walker, who previously spent 22 years working at JPMorgan before leaving the firm in 2001, will be based in New York and start later this month.  In his earlier stint with JPMorgan, he had worked both in Asia and in New York.  He served in different roles, co-leading the bank’s M&A business in the late 1990's, and was global head of technology, media and telecommunications investment banking from 1998 to 2000. After leaving JPMorgan in 2001, Mr. Walker served as a senior adviser to General Motors, then later co-founded the advisory firm, KW Advisors. Investment Bank CEO James Staley said he's delighted that Joe has decided to return to JPMorgan - he is someone respected by clients and peers, has extensive experience and talent.  [Dealbook, 5/23]