Question: What is the name of this White House Cheif of Staff, born in 1950, who assumed the role at the same time as Elaine Duke became Secretary of Homeland Security?

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<P2-S0> Kirstjen M. Nielsen is a government official and national security expert who currently serves as Principal Deputy White House Chief of Staff to U.S. President Donald Trump since September 6, 2017. <P2-S1>  She informally performed the role of Deputy Chief of Staff since the time John F. Kelly became White House Chief of Staff on July 31, 2017. <P2-S2>  Nielsen had previously served as Kelly's Chief of Staff at the Department of Homeland Security. <P2-S3>  She is the founder and former President of Sunesis Consulting. <P2-S4>  Prior to serving in the Trump administration, she was a senior fellow and member of the Resilience Task Force of the Center for Cyber & Homeland Security think tank at the George Washington University and served on the Global Risks Report Advisory Board of the World Economic Forum. <P2-S5>  She holds degrees from the Georgetown School of Foreign Service and the University of Virginia Law School. John Francis Kelly (born May 11, 1950) is the current White House Chief of Staff for U.S. President Donald Trump, previously serving as U.S. Secretary of Homeland Security in the same administration. <P1-S0> Alan D. Bersin (born October 15, 1946) served as the acting Commissioner of U.S. Customs and Border Protection (CBP). <P1-S1>  Acting Commissioner Bersin was placed by President Barack Obama on March 27, 2010 as a recess appointment. <P1-S2>  As Acting Commissioner, Mr. Bersin oversaw the operations of CBP’s 57,000-employee work force and managed an operating budget of more than $11 billion. <P1-S3>  Bersin formerly served as the Department of Homeland Security Assistant Secretary for International Affairs and Special Representative for Border Affairs, informally known as the "Border Czar." <P1-S4>  Bersin currently serves as Assistant Secretary of International Affairs and Chief Diplomatic Officer for the Department of Homeland Security, a position he assumed on January 3, 2012. <P1-S5>  According to the Department of Homeland Security website, in this position Bersin "oversees the Department's international engagement and serves as the principal advisor to Secretary Janet Napolitano on all international affairs". Michael G. Masters was Executive Director of the Department of Homeland Security and Emergency Management for Cook County, Illinois.  He also serves on the Secretary of the Department of Homeland Security’s Faith Based Security and Communications Advisory Committee, as the Vice-Chair of the Secretary’s Homeland Security Advisory Council’s Grants Review Task Force and on the Secretary’s Homeland Security Advisory Council’s Foreign Fighter Task Force. The United States Secretary of Homeland Security is the head of the United States Department of Homeland Security, the body concerned with protecting the U.S. and the safety of U.S. citizens.  The secretary is a member of the President's Cabinet.  The position was created by the Homeland Security Act following the attacks of September 11, 2001.  The new department consisted primarily of components transferred from other cabinet departments because of their role in homeland security, such as the Coast Guard, the Federal Protective Service, U.S. Customs and Border Protection (which includes the Border Patrol), U.S. Immigration and Customs Enforcement (which includes Homeland Security Investigations), the Secret Service, and the Federal Emergency Management Agency (FEMA).  It did not, however, include the FBI or the CIA. The Assistant to the President for Homeland Security and Counterterrorism, commonly referred to as the Homeland Security Advisor and occasionally holding the title of Deputy National Security Advisor for Homeland Security and Counterterrorism, is a senior aide in the Executive Office of the President, based in the West Wing of the White House, who serves as the chief in-house advisor to the President of the United States on homeland security and counterterrorism issues.  The Homeland Security Advisor is a statutory member of the Homeland Security Council.  Serving at the pleasure of the President, the Homeland Security Advisor does not require Senate confirmation for appointment to the office. Elaine Costanzo Duke (born 1958) is an American civil servant who is the current Acting United States Secretary of Homeland Security.  On January 30, 2017, she was nominated by President Donald Trump to become the United States Deputy Secretary of Homeland Security under John F. Kelly.  She became acting Secretary of Homeland Security on July 31, 2017, when John F. Kelly assumed the office of White House Chief of Staff. The Council of Governors is a United States council of state and federal officials that was established to "advise the Secretary of Defense, the Secretary of Homeland Security, and the White House Homeland Security Council on matters related to the National Guard and civil support missions"<ref name="pl/110/181">Pub.L.  110–181 </ref> and to "strengthen further the partnership between the Federal Government and State Governments to protect [the United States] against all types of hazards".  The Council is tasked to review "such matters as involving the National Guard of the various States; homeland defense; civil support; synchronization and integration of State and Federal military activities in the United States; and other matters of mutual interest pertaining to National Guard, homeland defense, and civil support activities." Thomas P. "Tom" Bossert (born March 25, 1975) is an American lawyer and Republican White House staffer, currently serving President Donald Trump as Homeland Security Advisor.  Immediately before, he was fellow at the Atlantic Council and prior to that he served as Deputy Homeland Security Advisor to President George W. Bush.  In that capacity, he co-authored the 2007 National Strategy for Homeland Security.  Prior to that, Bossert held positions in the Federal Emergency Management Agency, the Small Business Administration, the Office of the Independent Counsel, and the House of Representatives.  He also was appointed as the Director of Infrastructure Protection under Bush, overseeing the security of critical U.S. infrastructure, a post he held for two years.  Following that, he was appointed the Senior Director for Preparedness Policy within the Executive Office of the President. Daniel J. Kaniewski is the Deputy Administrator for National Preparedness at the Federal Emergency Management Agency (FEMA).  Prior to being confirmed by the United States Senate for his role at FEMA, Kaniewski was vice president for global resilience at AIR Worldwide, a catastrophe risk modeling and consulting services firm, and a senior fellow at George Washington University's Center for Cyber and Homeland Security.  He has also served as the Mission Area Director for Resilience and Emergency Preparedness/Response at the Homeland Security Studies and Analysis Institute and as an adjunct assistant professor at the Georgetown University School of Foreign Service.  Earlier in his career, Kaniewski served on the White House staff, first as Director of Response and Recovery Policy and later as Special Assistant to the President for Homeland Security and Senior Director for Response Policy.  Kaniewski began his career in homeland security as a firefighter and paramedic.

Supporting sentences:
 On January 30, 2017, she was nominated by President Donald Trump to become the United States Deputy Secretary of Homeland Security under John F. Kelly.  She became acting Secretary of Homeland Security on July 31, 2017, when John F. Kelly assumed the office of White House Chief of Staff. John Francis Kelly (born May 11, 1950) is the current White House Chief of Staff for U.S. President Donald Trump, previously serving as U.S. Secretary of Homeland Security in the same administration.